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Category: Clinical Cases

Case 33: parotid mass.

A 73-year-old male with a past medical history including atrial fibrillation and hypertension presented to the ED for admission for planned resection of a parotid mass with ENT. He first noted pain to his right cheek several months prior. Over this period, a mass was noted. The mass continued to grow over time, raising concern for malignancy, and the decision was made to pursue resection of the mass. On presentation, he endorsed significant pain to the right parotid area, but denied any fever, chills, chest pain, SOB, nausea, vomiting, abdominal pain, or dysuria. On physical exam, gross observation revealed diffuse swelling of the patient’s right cheek just anterior to the right tragus with marked tenderness to palpation. The remainder of his exam was unremarkable.

Vitals: BP 160/81 | Pulse 75  | Temp 97.4 °F (36.3 °C)  | Resp 20  | Ht 5' 11" (1.803 m)  | Wt 87.7 kg (193 lb 5.5 oz)  | SpO2 98%  | BMI 26.97 kg/m²

Point of care ultrasound was performed to visualize the mass (right side) and compare it to the contralateral, non-diseased glandular tissue (left side). The following scans were obtained:

Figure 1: Left parotid, transverse view

Figure 2: Left parotid, sagittal view

Figure 3: Right parotid with mass, transverse view

Figure 4: Right parotid with mass, sagittal view

The parotid gland can often be elusive on account of its relatively unremarkable echogenicity. However, using anatomical landmarks, finding the gland and its surrounding structures can be quick and easy. The technique used for obtaining our bedside images for this case is summarized below: 

Figure 5: Scan plane used to obtain sagittal view of the parotid

Figure 6: Scan plane used to obtain transverse view of the parotid

Figure 7: Labeled Anatomy of Parotid Gland (image from teachmeanatomy.info)

The superficial location of the parotid necessitates a high-resolution linear probe for optimal scan resolution. We found that the base of the tragus was an easy and reliable landmark to use as a starting waypoint for obtaining either the transverse or sagittal plane views. This positioning allows for identification of the parotid gland as it wraps around the angle of the mandible. The transverse plane is particularly useful for visualization of the accessory parotid gland, which is known to be the landmark for the parotid (Stenson’s) duct. 2,3   In fact, ultrasound has been shown to successfully diagnose parotid duct obstruction. 4  T he sagittal plane can be useful when searching for an optimal cross-section of Stenson’s duct, especially when it is dilated (e.g. in the case of an obstructing stone).  Should the duct prove difficult to locate, the course and angle of Stenson’s duct may be approximated by drawing an imaginary line from the base of the tragus to the upper lip. 5  Though we were unable to obtain optimal imaging of Stenson’s duct with this patient, we were able successfully locate the accessory parotid gland using the technique described above.

Figure 8: Left parotid gland (PG) with labeled accessory lobe (AL) noted to be just medial and separate from the main gland in the transverse plane

Overall, this case was an excellent exercise in using anatomical landmarks for localization of the parotid gland, review of notable anatomy, and comparison with diseased tissue. This patient underwent successful right superficial parotidectomy in the following days and was discharged on post-op day 1. The pathology report was concerning  for high grade carcinoma with localized spread but clean margins. No lymph node involvement.

1. The parotid gland. TeachMeAnatomy. (n.d.). https://teachmeanatomy.info/head/organs/salivary-glands/parotid/

2. Parotid gland- normal. ULTRASOUNDPAEDIA. (n.d.) https://ultrasoundpaedia.com/parotid-gland-normal/

3. Human Anatomy Lessons. (2022, August 5). Parotid gland. Learn Human Anatomy. https://humananatomyonline.in/2022/08/05/parotid-gland/

4. Goncalves, M., Mantsopoulos, K., Schapher, M., Iro, H., & Koch, M. (2021). Ultrasound in the diagnosis of parotid duct obstruction not caused by sialolithiasis: diagnostic value in reference to direct visualization with sialendoscopy. Dentomaxillofacial Radiology, 50(3), 20200261.

5. Jones J, Howden W, Yu Y, et al. Parotid gland. Reference article, Radiopaedia.org (Accessed on 21 Sep 2023) https://doi.org/10.53347/rID-10448

This post was written by Henry Horita , Lainey Yu, MD, Ben Supat, MD, MPH, and Sukh Singh, MD.  Posted by Ben Supat, MD, MPH.

Case 32: Perforated Gallbladder

A 77-year old man presented to the emergency department with a complaint of appetite loss over the past 15 days. He reported ongoing symptoms for the past 5 months. However, over the previous 15 days, his appetite had been so poor that he only drank 1-2 nutrition drinks per day. He reported a 10-15 lbs weight loss paired with fatigue and weakness. He denied nausea, vomiting, abdominal pain, fevers, and chills. The patient reported normal bowel movements. He denied any significant medical history and had no records in our EMR. He reported an unremarkable colonoscopy 7-8 years ago.

Upon physical examination, he was non-toxic in appearance. Vitals were as follows: 

BP: 155/89 | HR: 105 | RR: 16 | T: 99.8 F | Sp02 100% on RA | 

The patient had no masses, no hepatomegaly, no flank pain, and no tenderness to the abdomen upon palpation. Laboratory evaluation included a CBC which was remarkable for an elevated white blood count of 23,200 with a left shift. The chemistry panel was notable for normal ALT, AST, bilirubin, and creatinine. 

Bedside ultrasound was performed, and the following images were obtained. In examining these images, what do you notice and how would this change your patient management?

Answer and Learning Points

Figure 3: Thickened gallbladder wall and echoic sludge around the cholelithiasis. Gallbladder wall perforation can be visualized at the 2 o’clock position.

Figure 4: Gallbladder wall perforation visualized at the 11 o’clock position.

Figure 5: CT image demonstrating gallbladder wall perforation at the 2 o’clock position as well as pericholecystic fluid.

In the images above, a thickened gallbladder wall with “hole-signs” can be seen, indicating perforation.

Discussion 

Biliary pathology is the third most common cause of acute abdominal pain presenting to the ED [1]. Unfortunately, labs and clinical exam findings, either alone or in combination, are insufficient to reliably rule out biliary pathology [2]. Point-of-care ultrasound (POCUS) in the ED can detect cholelithiasis with a sensitivity and specificity of 89.8% and 88.0%, respectively [3]. Regarding the detection of cholecystitis, ED POCUS features a sensitivity and specificity of  87% and 82%, respectively [4]. In this case, we visualized a perforation and abscess outside the inflamed wall of the gallbladder, illustrating the accuracy and utility of POCUS as a diagnostic tool. 

How to best visualize the gallbladder: 

1. Subcostal sweep: With the marker dot to the patient’s head, place the probe in the subxiphoid/epigastric area. Next, slide the probe slowly to the patient’s right flank until the gallbladder is visualized or one has determined that another view is necessary.

2. Subcostal fanning: With the marker dot to the patient’s right, place the probe in the RUQ abdomen, where one would palpate for a non-ultrasound Murphy’s sign. Fan cephalad to look for the gallbladder in the area under the anterior ribs. 

3. X-7: Start subxiphoid and move the probe approximately 7 cm to the patient’s right, scan in transverse orientation transverse below or through the ribs. If scanning through the ribs, one may need to rotate the probe slightly clockwise to align the probe with the intercostal space.

4. Mid-axillary longitudinal view:  Obtain a view of Morrison's pouch as you would when completing a FAST (marker dot toward the patient’s head, patient supine, and probe placed in the mid axillary line). Remember, the kidney is retroperitoneal. After identifying the hepatorenal interface, slowly fan anteriorly until the gallbladder is directly under the probe. The common bile duct will be parallel and superficial to the portal vein. The inferior vena cava, with its characteristic respiratory variation, will be deep to the portal vein. Use color flow to differentiate the structures, as the common bile duct will not have color flow.

5. Roll the patient: If the above does not yield satisfactory views, roll the patient into a left lateral decubitus position. This will bring the gallbladder to a more anterior location and likely improve visualization of the GB when the steps above are repeated in this new patient position.

Normal Findings:

The upper limit of normal for the adult common bile duct is 6mm up to the age of 60. After this, the upper limit of normal rises an additional 1mm for every decade of life after 60 (e.g. 7mm at 70 years of age). Remember, there is a band of connective tissue called the main lobar fissure (MLF) that anchors both the portal triad and the neck of the gallbladder. Therefore, if you see the portal triad, you can then find the main lobar fissure emanating from the portal triad and track it to the neck of the gallbladder. The converse is true when locating the portal triad after identifying the gallbladder (follow the gallbladder neck, then trace the MLF to the portal triad).

During the examination, measure the thickness of the anterior gallbladder wall. The posterior wall is subject to posterior acoustic enhancement, which may yield an inaccurate measurement. A normal gallbladder wall thickness should measure less than 3 millimeters (mm). This measurement serves as a baseline for evaluating potential abnormalities.

Signs of Cholecystitis: 

Cholecystitis can be diagnosed by observing gallbladder wall thickening greater than 3mm, pericholecystic fluid collection, gallbladder distension, and the presence of a sonographic Murphy's sign (positive when the point of maximal tenderness is identified by pressing the abdomen with the ultrasound probe while the gallbladder is centered on the screen) [5].

The presence of gallstones within the gallbladder lumen can be detected through ultrasound. Gallstones are typically visualized as rounded structures with an bright, anterior outer layer and associated acoustic shadowing (similar to bone). When the stones occupy most of the lumen of the gallbladder, or a gallbladder is contracted around one or more stones, one may appreciate a “Wall Echo Sign”, where the shadowing from the stones obstructs visualization of the posterior wall of the gallbladder. Note that non-calcified stones will not produce shadowing artifacts behind them.

The significance of sludge in ultrasound imaging of the gallbladder can vary depending on the clinical context. Sludge itself can be a precursor to the formation of gallstones. It may indicate an imbalance in the components of bile, such as excess cholesterol or insufficient bile salts, which can lead to the development of gallstones over time. Perforation can be diagnosed by observing gallbladder wall discontinuity or disruption, pericholecystic fluid collection or abscess formation, and signs of free fluid in the abdominal cavity [6].

POCUS is a powerful diagnostic modality for identifying biliary pathology, including cholecystitis, cholelithiasis, and perforation of the gallbladder wall. By following the scanning technique outlined above and identifying findings consistent with biliary pathology, clinicians can obtain accurate diagnoses and facilitate appropriate patient management. POCUS is a valuable tool to use in conjunction with a patient's clinical history, physical examination, and other diagnostic modalities to ensure comprehensive assessment and optimal healthcare outcomes.

1) Cervellin, Gianfranco, Riccardo Mora, Andrea Ticinesi, Tiziana Meschi, Ivan Comelli, Fausto Catena, and Giuseppe Lippi. 2016. “Epidemiology and Outcomes of Acute Abdominal Pain in a Large Urban Emergency Department: Retrospective Analysis of 5,340 Cases.” Annals of Translational Medicine 4 (19): 362.

2) Trowbridge, Robert L., Nicole K. Rutkowski, and Kaveh G. Shojania. 2003. “Does This Patient Have Acute Cholecystitis?” JAMA: The Journal of the American Medical Association 289 (1): 80–86.

3) Ross, Marshall, Michael Brown, Kyle McLaughlin, Paul Atkinson, Jenny Thompson, Susan Powelson, Steve Clark, and Eddy Lang. 2011. “Emergency Physician-Performed Ultrasound to Diagnose Cholelithiasis: A Systematic Review.” Academic Emergency Medicine: Official Journal of the Society for Academic Emergency Medicine 18 (3): 227–35.

4) Summers, Shane M., William Scruggs, Michael D. Menchine, Shadi Lahham, Craig Anderson, Omar Amr, Shahram Lotfipour, Seric S. Cusick, and J. Christian Fox. 2010. “A Prospective Evaluation of Emergency Department Bedside Ultrasonography for the Detection of Acute Cholecystitis.” Annals of Emergency Medicine 56 (2): 114–22.

5) Simeone, J. F., J. A. Brink, P. R. Mueller, C. Compton, P. F. Hahn, S. Saini, S. G. Silverman, G. Tung, and J. T. Ferrucci. 1989. “The Sonographic Diagnosis of Acute Gangrenous Cholecystitis: Importance of the Murphy Sign.” AJR. American Journal of Roentgenology 152 (2): 289–90.

6) Sood BP, Kalra N, Gupta S, et al. Role of sonography in the diagnosis of gallbladder perforation. J Clin Ultrasound. 2002;30(5):270-274. doi:10.1002/jcu.10071

This post was written by  Cameron  Olandt , Ben Supat, MD, MPH, and Colleen Campbell, MD.  Posted by Ben Supat, MD, MPH.

Case 31: A Man with Shortness of Breath

A 77-year-old patient presented to a rural Emergency Department with a chief complaint of shortness of breath a day prior to presentation. Patient also reported that he fell several weeks ago and hurt his ribs. He was subsequently admitted to the hospital and was ultimately treated for pyelonephritis. He endorsed being more sedentary than usual for the next several weeks. On the day of presentation he was lying in bed when he began to suddenly feel short of breath. He denied feeling any chest pain, lightheadedness, dizziness, nausea, vomiting, diarrhea, diaphoresis, jaw or arm pain. His shortness of breath had self resolved prior to coming into the emergency department. On physical examination, the patient was alert and had mild respiratory distress. He was tachycardic and also found to have inspiratory crackles in the right lower lung fields. The remainder of the physical exam was within normal limits.

Upon arrival, vitals were as follows:

BP : 92/70 | HR: 118 | RR: 18 | T: 98.2 | Sp02: 80’s% on RA to 90 % with 15L NRB

Point of care ultrasound was performed and the following images were obtained. In these images, what do you notice and how does this change your patient management?

Figure 1: Parasternal Short Axis view of the left ventricle at the mid-papillary level

Figure 2: A normal parasternal Short Axis view of the left ventricle at the mitral valve level.

Figure 3: Our patient’s Parasternal Short Axis view of the D-sign in the left ventricle.

View shown in the image above is the parasternal short axis. To perform this technique, use the phased array transducer and place it around the 4th intercostal space, next to the sternum, with the probe marker to the patient’s right shoulder. For example:

Figure 4: Placement of probe for Parasternal Long Axis view [1].

Figure 5: Standard long axis view of the left ventricle at the mitral level [2].

Clockwise rotation of the probe (90 degrees) where the indicator is pointing towards the patient's left shoulder will provide a short axis view of the left ventricle. Normal parasternal short axis view in a patient without cardiac dysfunction will include the right ventricle sitting as a semi-circle on top of the circular left ventricle. For example: 

Figure 6: Placement of probe for Parasternal Short Axis view [1].

Figure 7: Standard short axis view of the left ventricle at the mitral level [2].

In our case, the right ventricle is pushing down on the left ventricle, indicating increased right sided pressures. This is the classic “D-sign” of the left ventricle, the septum has become straight due to the right sided pressures. 

Classically, the apical four view is used to diagnose elevated right sided pressures by comparing chamber sizes. However, this view can be challenging at times. In our case, we show the effectiveness of diagnosing right sided pressures using a parasternal short axis view [Figure 3].

We typically observe indications of increased pressures in the pulmonary artery and strain on the right side of the heart. These indications can be identified through the presence of reduced movement in the right ventricular wall, enlargement of the right ventricle and right atrium, abnormal motion of the septum during systole, and a dilated inferior vena cava that does not collapse during respiration.

In our case, POCUS utilizing the parasternal short axis view of the heart indicated the “D-sign”. In a normal heart with proper physiological functioning, the pressure in the left ventricle is higher than the pressure in the right ventricle. As a result, during systole the left ventricle maintains a round shape, causing the intraventricular septum to bulge into the right ventricle. However, if the right ventricle pressures are elevated, the septum becomes straight, changing the shape of the left ventricle into a "D".

 Case Conclusion

Visualization of the D sign led to a high concern for pulmonary embolism. Management of the patient’s hypotension was transitioned from fluid resuscitation to vasopressors, on which he was stabilized. He was then taken for a STAT CTA, showing a large saddle pulmonary embolus. The patient was treated with thrombolytics, and he was transferred to a tertiary care center for higher level of care. There, the patient underwent thrombectomy with removal of significant clot burden as below:

Figure 8: Clots retrieved post-thrombectomy.

His clinical status continued to improve and he was discharged on hospital day 7 with no residual complications. 

In this case, recognition of the D-sign allowed for prompt and effective management of a critically ill patient, and the patient made a full recovery. Key clinical advantages were expediting a difficult diagnosis in a patient who was reportedly asymptomatic at the time of presentation, a rapid transition from fluid resuscitation (which could have worsened his right heart strain) to vasopressor support, and early imaging and thrombolytics before his clinical picture could worsen.

1) Lee V, Dinh V, Ahn J, Deschamps J, Genoba S, Lang A, Tooma D, White S, Krause R. Cardiac Ultrasound (Echocardiography) Made Easy: Step-By-Step Guide. POCUS 101. https://www.pocus101.com/cardiac-ultrasound-echocardiography-made-easy-step-by-step-guide/#Step_1_Parasternal_Long_Axis_PSLA_View. (Accessed May 30, 2023)

2) “Normal Cardiac Anatomy.” n.d. TPA. Accessed August 1, 2023. https://www.thepocusatlas.com/normal-cardiac-anatomy/normal-parasternal-long-axis-plax-view.

This post was written by  Cameron  Olandt , Dr. Daniel Brownstein, Dr. Andrew Lafree, Dr. Colleen Campbell, and Dr. Sukhdeep Singh.  Posted by Dr. Ben Supat.

Case 30: Ultrasound-Guided Extraction of a Foreign Body

A 53-year-old homeless alcoholic female presented to the emergency department with a chief complaint of localized left lower quadrant abdominal pain secondary to a possible gunshot wound. She was unclear but stated she thinks some boys in a gang fired at her two days prior with a possible BB gun. Pertinent medical history included psychiatric history, morbid obesity (BMI>40), chronic alcohol abuse, sepsis and hypoxemic respiratory failure. The patient was clinically intoxicated upon arrival and therefore history was of limited accuracy. 

Upon arrival, patient appeared stable and vitals were as follows:

BP : 121/63 | HR: 73 | RR: 18 | T: 98.4 | Sp02: 98% on RA 

Physical examination revealed a 10x10 cm area of ecchymosis with a central penetrating wound about 2mm, to the left lower quadrant. The patient was tender to palpation around the affected area but there was no significant warmth or erythema to suggest infection. No palpable foreign bodies were identified. There were no signs of peritonitis: the remainder of the abdominal examination was benign and patient had active bowel sounds. She denied vomiting, hematuria, hematochezia, and melena. She also denied shortness of breath, chest pain, and back pain.  

To evaluate the wound for the presence of foreign bodies and for depth of penetration, bedside ultrasound was obtained. What do you see, and how would this change your patient management?

Figure 1: Wound prior to foreign body exploration.

Figure 2: A hyperechoic object with reverberation artifacts and shadow seen at 1cm.

Figure 3: Removal of FB under US guidance using curved hemostats.

Figure 4: Extracted pellet.

In these scans, an echogenic foreign body can be observed 1 cm below the epidermis with associated reverberation and mirror artifact. Using ultrasound guidance, a curved hemostat was used to remove the foreign body after local anesthetic injection. Upon contact with the forceps, the foreign body can be seen fluctuating in position. A rounded edge on the foreign body can be seen on the image.  Importantly, we clearly identified the peritoneal line to be > 4cm deeper than the foreign body and were able to safely determine the foreign body location to be significantly more superficial to the abdominal wall musculature. 

Soft tissue foreign bodies (FB’s) are a common reason for Emergency Department visits, with open wounds producing 4,171,000 visits to United States Emergency Departments in 2020 [1]. However, retained foreign bodies account for 7-15% of cases, particularly those involving the extremities. A granulomatous tissue response commonly known as an FB reaction results as the immune system attempts to isolate the FB from the host [2]. This can lead to serious adverse complications including soft tissue inflammation and infection. The most commonly retained FB materials are metal, glass and wood. Glass accounts for half of missed FB’s on physical examination and radiographs. Although essential, a physician-performed clinical history, physical examination, and wound exploration are not sufficient to exclude a FB from differentials [2]. Thus, imaging plays an essential role in improving patient outcomes that present with FB’s. 

MRI is not a suitable imaging modality, as metallic contents may have hazardous movements due to the magnetic field. Computed tomography (CT) and ultrasound sonography (US) are the most effective imaging modalities. CT and US have similar sensitivity in identifying high-density objects such as stone, metal and glass [3]. Low-density foreign objects such as plastic and wood are remarkably difficult to see in techniques other than US, regardless of superficial or deep impaction. For example, radiographic images have a sensitivity of 7.4% for wood [3,4]. Sensitivity of ultrasound for FB is 80% on average, and it carries a specificity of 85%, with metals being much higher due to noticeable reverberation, and wood is more difficult to detect. However, the sensitivity of US to identify foreign bodies in soft tissues begins to decrease as the depth of the foreign body surpasses 4cm [4]. 

US provides a unique advantage to foreign body detection as it can provide instantaneous and simultaneous visualization of foreign bodies during extraction procedures with minimal risk and no exposure to radiation. In a study of pediatric patients presenting with an FB, sonography performed by EM physicians provided an overall sensitivity of 67% and a specificity of 96.6% [4]. US is inexpensive and provides real-time visualization, however the quality of US images is operator dependent [5].

Table 1 : A List of FB Materials and the Expected US Findings [3].

To perform this technique, scan use the linear probe in the area of the suspected location of the FB.  The FB can be identified by characteristic reverberation or acoustic shadowing, with additional indications being signs of infection, edema, or interruption of the fascial planes. Position the probe so that the FB is visualized in the center of the screen, and mark this area with a surgical pen. Rotate the probe 90 degrees and ensure the FB is in the middle of the US screen. Then mark this area with a surgical pen. Where these markings cross should give you the exact location of the FB such that incision and probing with forceps will result in effective removal of the FB. 

Removing foreign bodies is one of the least favorite procedures in the Emergency Department due to it’s difficulty and low success rates.  Bedside ultrasound is easily performed and is a useful adjunct in the accurate identification of foreign bodies and also can provide real-time guidance in foreign body removal.

1) Cairns C, Kang K. National Hospital Ambulatory Medical Care Survey: 2020 emergency department summary tables. DOI: https://dx.doi.org/10.15620/cdc:121911.

2) Carneiro BC, Cruz IAN, Chemin RN, et al. Multimodality Imaging of Foreign Bodies: New Insights into Old Challenges. Radiographics . 2020;40(7):1965-1986. doi:10.1148/rg.2020200061

3) Haghnegahdar A, Shakibafard A, Khosravifard N. Comparison between Computed Tomography and Ultrasonography in Detecting Foreign Bodies Regarding Their Composition and Depth: An In Vitro Study. J Dent (Shiraz) . 2016;17(3):177-184.

4) Davis J, Czerniski B, Au A, Adhikari S, Farrell I, Fields JM. Diagnostic Accuracy of Ultrasonography in Retained Soft Tissue Foreign Bodies: A Systematic Review and Meta-analysis. Acad Emerg Med. 2015;22(7):777-787. doi:10.1111/acem.12714

5) Rupert J, Honeycutt JD, Odom MR. Foreign Bodies in the Skin: Evaluation and Management. Am Fam Physician . 2020;101(12):740-747.

This post was written by Cameron Olandt, Rachna Subramony, MD, Skyler Sloane, and Colleen Campbell, MD.

Case 29: Perforated Diverticulitis

A 37-year-old female presented to the emergency room with severe, radiating bilateral flank pain lasting one week. Pain was constant and pressure-like. Patient had a past medical history significant for constipation, ovarian cysts, diverticulitis, and a colonic polypectomy. She denied fever, vomiting, and denied melena and hematochezia. Patient had no dysuria, frequency or hematuria. She denied vaginal discharge or odor. Patient was seen and treated by her primary care provider with ciprofloxacin and metronidazole for presumed diverticulitis. When pain failed to improve two days later, patient presented to the Emergency Department.

Upon arrival, her vital signs were as follows:

T 98.2 | BP 109/73 | HR 71 | RR 16 | SPO2 99% on RA |

Her physical exam revealed left paraumbilical and left lower-quadrant tenderness. No masses were palpated. A bedside ultrasound of the abdomen is performed, and the following images were obtained. In examining these images, what do you notice and how would this change your patient management?

In these images/videos, a thickened bowel wall is observed in the distal descending colon and proximal sigmoid. Extensive pericolonic fat stranding is represented by the hyperechoic fat deep to the bowel, with no drainable abscess found.

In the emergency setting, computed tomography (CT) scans are highly accurate and remain the most widely used modality to diagnose diverticulitis, with an overall accuracy of 99% [1]. CT can assist in planning if surgical intervention is needed. An estimated 15-20% of all patients admitted with either complicated or uncomplicated diverticulitis will require surgical intervention during their initial admission, yet that likelihood increases to upwards of 50% for those with complicated diverticulitis [2]. However, concerns of radiation exposure and extended length of stays have led to increased use of point-of-care ultrasound (POCUS) [3].

Cohen et al found that POCUS performed by ultrasonographic-trained emergency physicians, physician assistants, and ultrasonographic fellows had both high sensitivity (92%) and specificity (97%) for diagnosing acute diverticulitis [3]. However, the usage of POCUS for diverticulitis by EM physicians is a new application and not a current widespread practice.

There are 3 POCUS indicators of acute diverticulitis, namely:

1) Thickened bowel wall greater than 5mm surrounding an adjacent diverticulum

2) enhancement of surrounding pericolonic fat

To perform this technique, place the curvilinear probe on the patient in the areas of tenderness and compress the bowel wall. The bowel will be found just deep to the peritoneal line. In diverticulitis, the bowel will appear with a thickened wall >4 mm with a visible diverticulum.

Surrounding hypoechoic edema is often visible. Perforation may appear contiguously to the diverticulitis. Normal bowel will compress fully with the ultrasound probe.

This patient received a CT that confirmed acute flare of diverticulitis with contained perforation involving a short segment in the distal descending colon and proximal sigmoid, with no drainable abscess at this time. She was admitted to medicine with GI and surgery consults following.

1) Sai, V. F., Velayos, F., Neuhaus, J., & Westphalen, A. C. (2012). Colonoscopy after CT diagnosis of diverticulitis to exclude colon cancer: a systematic literature review. Radiology, 263(2), 383–390. https://doi.org/10.1148/radiol.12111869

2) Wieghard N, Geltzeiler CB, Tsikitis VL. Trends in the surgical management of diverticulitis. Ann Gastroenterol. 2015;28(1):25-30.

3) Cohen, A., Li, T., Stankard, B., & Nelson, M. (2020). A Prospective Evaluation of Point-of-Care Ultrasonographic Diagnosis of Diverticulitis in the Emergency Department. Annals of emergency medicine, 76(6), 757–766. https://doi.org/10.1016/j.annemergmed.2020.05.017

This post was written by Cameron Olandt and Colleen Campbell MD RDMS.

Case 28: Nah-bscess

A 35 year old male with a history of IV drug use and HIV on ART presents to the emergency department with pain and redness of his left upper extremity for a few days. He denies systemic symptoms or prior history of abscess.

Vitals: Temp 98.5, HR 93,  BP 122/75, RR20

Physical Exam: Notable for a large, well circumscribed area of induration, erythema, warmth, and  tenderness on the left upper arm. Distal to the lesion, there is intact cap refill and 2+ radial pulse.

A bedside ultrasound was performed. What do you see?

Image 1 is a transverse view of the LUE and demonstrates cobblestoning in the subcutaneous tissue which is suggestive of cellulitis. There is no fluid tracking on the fascial planes, fascial thickening, hyperechoic gas or dirty shadowing to suggest necrotizing fasciitis.

Image 1 also demonstrates a well-circumscribed, anechoic fluid collection concerning for an abscess. However, the lumen-like and well-demarcated appearance deep to the area of cobblestoning also suggests a blood vessel, and so we imaged it with color and pulse-wave doppler.

Image 2 use color doppler and demonstrates turbulent flow within the fluid collection. Superficial and medial to the fluid collection, a vessel can be appreciated with flow towards the ultrasound probe.

Image 3 and 4 use pulse wave doppler and demonstrate areas of both pulsatile and continuous flow in various parts of this structure.

Image 5 demonstrates continuity between a distal pulsatile vessel and the proximal fluid collection. The fluid collection likely represents an arterial aneurysm or arteriovenous fistula, as opposed to an abscess. Taking into consideration the patients history of IV drug use, trauma from repeated injections may have created abnormal structures within the patient’s vasculature.

Conclusion and Learning Points:

1. When there is concern for cellulitis, POCUS is a useful tool to quickly evaluate for drainable fluid collections, as well as to evaluate for necrotizing fasciitis.

2. When evaluating a possible abscess, it is important to confirm that the collection has no pusatility or flow before attempting drainage.

1. Bystritsky R, Chambers H. Cellulitis and Soft Tissue Infections. Ann Intern Med. 2018 Feb 6;168(3):ITC17-ITC32. doi: 10.7326/AITC201802060. Erratum in: Ann Intern Med. 2020 May 19;172(10):708. PMID: 29404597.

2. Paz Maya S, Dualde Beltrán D, Lemercier P, Leiva-Salinas C. Necrotizing fasciitis: an urgent diagnosis. Skeletal Radiol. 2014 May;43(5):577-89. doi: 10.1007/s00256-013-1813-2. Epub 2014 Jan 29. PMID: 24469151.

This post was written by Jeff Hendel, MS4 and Ben Liotta, MD, with further editing by Sukh Singh, MD.

Case 27: Ectopic Pregnancy

A 43 year old female with no past medical history presents to the Emergency Department (ED) with lower abdominal pain for the last three hours. She says she knows she is pregnant from a home pregnancy test, but has not had any appointment with obstetrics and has not had an ultrasound yet. She denies any vaginal bleeding.  

Vitals: BP 120/65 mmHg, HR 85, O2 100% on RA.

She is comfortable appearing, her abdominal exam shows mild tenderness to palpation diffusely in the lower abdomen with no rebound and her pelvic exam shows a closed os with no bleeding.

Her point-of-care urine pregnancy test is positive.

You perform a trans-abdominal bedside ultrasound, what do you see?  What are your next steps?

The first image is a transverse view of the uterus that shows free fluid in the retcouterine pouch (Pouch of Douglas). The second image is another transverse view of the uterus that also shows free fluid in the rectouterine pouch and then fans through to scan the uterus and adnexa. From what we see there is no gestational sac in the uterus and if you look closely there appears to be a heterogenous structure in the left adnexa. The final view is a FAST view in the right upper quadrant, looking at Morrison's Pouch. We see free fluid here as well. 

These findings - a positive pregnancy test, free fluid in the pelvis and no clear intra-uterine pregnancy indicates an ectopic pregnacny until proven otherwise. The next step should be a tranvaginal ultrasound and consultation with Gynecology. 

The transvaginal ultrasound revealed a left-sided ectopic pregnancy, as seen in the following picture. They identified a fetal pole and even a fetal heart rate in the ectopic pregnancy. The patient was taken to the operating room with Gynecology and had a salpingectomy without complications. She was discharged home three days later. 

Learning Points:

• Any female of child-bearing age with abdominal pain should be considered for ectopic pregnancy
• Intra-abdominal free fluid
• No clear intra-uterine pregnancy (patients with ectopic will sometimes still have a "pseudo-gestational sac" that appears similar to a gestational sac, but there will be no yolk sac or fetal pole)
• Heterogenous adnexal structure
• You should not wait for B-HCG measurements to consider ectopic pregnancy, case reports have shown ectopic pregnancies with minimal HCG levels can still rupture (1)

1. Fu, Joyce, et al. Rupture of ectopic pregnancy with minimally detectable beta-human chorionic gonadotropin levels: a report of 2 cases. J Reprod Med . 2007 Jun;52(6):541-2.

This post was written by Charles Murchison MD and Anthony Medak MD, with further editing by Amir Aminlari MD.

Case 26: Genicular Nerve Block for Knee Pain – A Novel Technique

A 68 year old female with no significant past medical history presents to the Emergency Department (ED) with one day of right knee pain after falling off her bicycle onto her right side. She was immediately unable to bear weight on her right leg. 

Vitals: T 98.3, HR 73, RR 18, BP 114/70, SpO2 99%

Right leg exam: mild right knee effusion. No ligamentous laxity. Tenderness to palpation over lateral joint line > medial joint line. Tenderness to palpation over proximal anterior tibia. Knee extension limited due to pain. Neurovascularly intact with soft compartments.

Radiographic imaging demonstrated an isolated right tibial plateau fracture depression of the lateral plateau. The patient reports she is in severe pain but dislikes taking both over-the-counter and opioid pain medications. 

What nerves may be targeted to provide pain relief to her knee while maintaining motor function? What anatomic landmarks should be used on ultrasound to identify the branches of this nerve?

The genicular nerves derive from various major lower extremity nerve branches (femoral, obturator, sciatic, tibial) nerves and provide sensation to the knee capsule and joint. Cadaveric studies suggest that most genicular nerves are easily identifiable landmarks that may be used for therapeutic purposes. 5   Genicular nerve blocks (GNB) are traditionally used in this setting of chronic osteoarthritis knee pain via radiofrequency ablation or perioperative knee pain via ultrasound ( 1-4, 9).

The use of a GNBs in the ED is a novel technique to provide motor-sparing, pain relief for acute knee pain. This 68 year old patient with an isolated lateral tibial plateau fracture reported 4/10 pain over her proximal tibia at rest and 8/10 over her proximal tibia with movement. Written informed consent was obtained for GNBs of her right knee. Anatomic landmarks for the superior lateral (Image A,B) , superior medial (Image C,D), and inferior medial (Image D,E,F) genicular nerves were identified on ultrasound.

The ultrasound probe was placed in the sagittal orientation for each site. The superior lateral genicular nerve was located on ultrasound at the junction of the lateral femoral epicondyle and the epiphysis of the shaft of the femur, adjacent to the superior lateral genicular artery (Image A,B). The superior medial genicular nerve (SMGN) can be identified on ultrasound at the junction of the medial femoral epicondyle and the epiphysis of the shaft of the femur, adjacent to the superior medial genicular artery (Image C, D). The inferior medial genicular nerve (IMGN) can be identified on ultrasound at the junction of the medial tibial epicondyle and the epiphysis of the shaft of the tibia, adjacent to the inferior medial genicular artery (Image E, F, G) (6-8).

Under ultrasound guidance and using sterile technique, the skin was first anesthetized with 1% lidocaine after each site. A 21-gauge, 2 inch echogenic needle was inserted percutaneously and advanced under ultrasound guidance using an out-of-plate technique to inject 1.5 mL of 0.5% bupivacaine around the right superior lateral, superior medial, and inferior medial genicular nerves. 

Learning points

• Genicular nerves derive from several lower extremity nerves and supply sensory innervation to the knee.  
• The superior lateral, superior medial, and inferior medial genicular nerves are commonly targeted for pain relief with chronic knee osteoarthritis and postoperative pain.
• The SLGN, SMGN, IMGN are easily located on ultrasound using anatomic landmarks (junction between epicondyles and epiphysis of the femur and tibia, adjacent to paired genicular arteries).
• To obtain the images, you can use the linear probe in the sagittal location over lateral femoral epicondyle, medial femoral epicondyle, and medial tibial epicondyle.

1. Ahmed, Arif. “Ultrasound-guided radiofrequency ablation of genicular nerves of knee for relief of intractable pain from knee osteoarthritis: a case series.” British Journal of Pain , vol. 12, no. 3, 2017, pp. 145-154, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6058456/. Accessed 18 November 2020.

2. Caldwell, George L. “Reduced Opioid Use After Surgeon-Administered Genicular Nerve Block for Anterior Cruciate Ligament Reconstruction in Adults and Adolescents.” HSS Journal , vol. 15, no. 1, 2019, pp. 42-50, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6384209/. Accessed 18 November 2020.

3. Cankurtaran, Damla. “Comparing the effectiveness of ultrasound guided versus blind genicular nerve block on pain, muscle strength with isokinetic device, physical function and quality of life in chronic knee osteoarthritis: a prospective randomized controlled study.” Korean J Pain , vol. 33, no. 3, 2020, pp. 258 - 266, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7336352/. Accessed 18 November 2020.

4. Erdem, Yusuf. “The Efficacy of Ultrasound-Guided Pulsed Radiofrequency of Genicular Nerves in the Treatment of Chronic Knee Pain Due to Severe Degenerative Disease or Previous Total Knee Arthroplasty.” Med Sci Monit , vol. 25, 2019, pp. 1857 - 1863, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6423735/. Accessed 18 November 2020.

5. Fonkoué, Loïc. “Distribution of sensory nerves supplying the knee joint capsule and implications for genicular blockade and radiofrequency ablation: an anatomical study.” Surgical and Radiologic Anatomy , vol. 41, 2019, 1461–1471(2019), https://link.springer.com/article/10.1007/s00276-019-02291-y#citeas. Accessed 18 November 2020.

6. Güzelküçük, DemIr. “A different approach to the management of osteoarthritis in the knee: Ultrasound guided genicular nerve block.” Pain Medicine , vol. 18, no. 1, pp. 181 - 183, https://academic.oup.com/painmedicine/article/18/1/181/2924744. Accessed 18 November 2020.

7. Kim, Doo-Hwan. “Ultrasound-Guided Genicular Nerve Block for Knee Osteoarthritis: A Double-Blind, Randomized Controlled Trial of Local Anesthetic Alone or in Combination with Corticosteroid.” Pain Physician , vol. 21, 2018, pp. 41 - 51, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6058456/. Accessed 18 November 2020.

8. Protzman, Nicole. “Examining the feasibility of radiofrequency treatment for chronic knee pain after total knee arthroplasty.” PM&R , vol. 6, no. 4, 2014, pp. 373 - 376, https://pubmed.ncbi.nlm.nih.gov/24373908/. Accessed 18 November 2020.

9. Sahoo, Rajendra K. “Genicular nerve block for postoperative pain relief after total knee replacement.” Saudi J Anaesth , vol. 12, no. 2, 2020, pp. 235 - 237, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7164458/. Accessed 18 November 2020.

This post was written by Julia Sobel MD, with editing from Jessica Oswald MD, Charles Murchison MD and Amir Aminlari MD.

Case 25: Aortic Dissection

A 44 year old male with a history of heroin abuse presents to the emergency department with altered mental status.  Per EMS, the patient was found on the street with decreased level of consciousness and poor respiratory effort.  EMS was concerned about opioid overdose, and he was treated with 4mg Narcan, with improvement in his mental status.  

Upon arrival to the ED, he was noted to be agitated and tachypneic with RR in the 40’s.  

Vitals: BP 90/65 mmHg, HR 110, O2 100% on RA, glucose 158.

He is alert and oriented to person, month, and place, but appears agitated and confused.  He denies any complaints other than shortness of breath, and states he felt fine before using heroin.  He denies any past medical history.

Exam notable for tachycardia, diffuse rhonchi throughout all lung fields, 2+ nonpitting lower extremity edema.  He is neurologically intact with 2+ pulses throughout.

A bedside echocardiogram was performed, what do you see?  What are your next steps?

The first two images show a parasternal long-axis view, with a dilated aortic root measuring approximately 4.2cm.  Also notice the pericardial effusion with a homogenous layer that appears fixed to the pericardium.  At the time it was unclear whether this represented a clot within the pericardial sac, or was superficial to it.

Given the dilated aortic root, a suprasternal short-axis view was obtained to assess the proximal aorta, with the short axis view seen on the third image.  A flap was visualized in the aortic lumen, significant for an ascending aortic dissection.  The dissection was then visualized in the abdominal aorta, extending distal to the common iliac arteries, seen in the last images.

The patient was placed on esmolol drip and later required vasopressor support.  CT angiography was obtained, confirming a Type A aortic dissection.  He was transferred to a nearby hospital for emergent repair of his ascending and descending aortic dissection.  

Per the operative report, the patient had developed a significant pericardial effusion by the time he reached the OR, and the visualized homogenous layer above most likely represented a blood clot within the pericardium.

• While CTA remains the gold standard for diagnosis of aortic dissection, POCUS remains a great tool for diagnosing both ascending and descending aortic dissection, particularly in the unstable patient.
• In addition to directly visualizing the dissection flap, TTE can also be used to identify patients with high risk features, such as those with cardiac tamponade, severe aortic dilatation, severe aortic regurgitation, regional wall motion abnormalities, and decreased ejection fraction (1).
• TTE has been shown to have a sensitivity of 78-90% and specificity 87-96% for type A dissection in older studies (2,3), and in more recent studies showing improved sensitivity up to 97-99% (1,4,5) and specificity 100% (4) with improved image quality.
• The suprasternal notch views are particularly useful in evaluating the proximal ascending aorta, and allow the operator to assess for aortic dissection, coarctation, dilatation of the aortic arch, and retrograde flow from the descending aorta.

1. Sobczyk D, Nycz K. Feasibility and accuracy of bedside transthoracic echocardiography in diagnosis of acute proximal aortic dissection. Cardiovasc Ultrasound. 2015;13:15.

2. Evangelista A, Flachskamp FA, Erbel R, Antonini-Canterin F, Vlachopoulos C, Rocchi G, et al. Echocardiography in aortic diseases: EAE recommendations for clinical practice. Eur J Echocardiogr. 2010;11:645–58. doi: 10.1093/ejechocard/jeq056.

3. Nienaber CA, von Kodolitsch Y, Nicolas V, Siglow V, Piepho A, Jaup T, et al. The diagnosis of thoracic aortic dissection by noninvasive imaging procedures. N Engl J Med. 1993;328:1–9. doi: 10.1056/NEJM199301073280101.

4. Cecconi M, Chirillo F, Constantini C, Iacobone G, Lopez E, Zanoli R, et al. The role of transthoracic echocardiography in the diagnosis and management of acute type A aortic syndrome. Am Heart J. 2012;163(1):112–8. doi: 10.1016/j.ahj.2011.09.022.

5. Nazerian, P., Vanni, S., Castelli, M. et al. Diagnostic performance of emergency transthoracic focus cardiac ultrasound in suspected acute type A aortic dissection.  Intern Emerg Med 9, 665–670 (2014). https://doi.org/10.1007/s11739-014-1080-9

This post was written by Rachna Subramony MD, Alex Anshus MD, with editing from Sukhdeep Singh MD, Charles Murchison MD and Amir Aminlari MD.

Case 24: Diverticulitis

A 56 year old male with a history of uncomplicated diverticulitis presented to the emergency room with left lower quadrant pain and loose stools for the last six days. He denies fever, vomiting or blood in hist stool 

Vitals: T 97.3   BP 152/81   HR 91       RR 18      SPO2 97% on RA

You physical exam shows tenderness to palpation in the left lower quadrant with no peritoneal signs. You are on the fence about getting a CT abdomen and pelvis with contrast to look for an abscess versus treating this as uncomplicated diverticulitis. You decide to throw the ultrasound probe on the area of his pain. What do we see in these images? How would this change management?

The three videos and two images show diverticulitis with an abscess or phlegmon beneath the bowel loops. Though CT is the gold standard for diagnosing diverticulitis, ultrasound is relatively sensitive in the diagnosis and has the advantage of being cheap, fast and radiation-free (1). 

When looking for diverticulitis on ultrasound physicians will typically use a "lawn mower" approach to the left abdomen to search for areas of affected bowel. One way to get to the area of interest more quickly is simply ask the patient to point to the area of maximal tenderness and start there, similar to appendicitis or small bowel obstruction. There are a few findings on ultrasound that indicate diverticulitis (2,3):

• Thickening of bowel wall, typically at least 4-5mm
• Echogenic fat surrounding the bowel, which is representative of fat stranding seen on CT
• Diverticulum

Ultrasound is also helpful in looking for abscess, such as in our case. We see there is an area of hypoechogenicity with no color flow, representing likely abscess adjacent to the bowel.  

Our patient ultimately got a CT scan that confirmed he had diverticulitis with abscess. He was admitted to medicine with GI and surgery consults following.

(1) Lameris, W et al. Graded compression ultrasonography and computed tomography in acute colonic diverticulitis: meta-analysis of test accuracy. Eur Radiol. 2008 Nov;18(11):2498-511.

(2) Schwerk, WB et al. Sonography in acute colonic diverticulitis. A prospective stud. Dis Colon Rectum . 1992 Nov;35(11):1077-8

(3) Mazzei M et al. Sigmoid diverticulitis: US findings. Crit Ultrasound J. 2013 Jul 15;5 Suppl 1(Suppl 1):S5.

This post was written by Charles Murchison MD, with editing from Colleen Campbell MD and Amir Aminlari MD.

Ultrasound of the Month Cases

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Utility of the Venous Excess Ultrasound (VEXUS) score to track dynamic change in volume status in patients undergoing fluid removal during haemodialysis – the ACUVEX study

The use of ultrasound assessment, including the Venous Excess Ultrasound (VEXUS) score, is increasingly being utilised as part of fluid status assessment in clinical practice. We aime...

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Roberto Copetti, MD (1954–2024)

Canadian internal medicine ultrasound (cimus) consensus statement: recommendations for mandatory ultrasound competencies for ultrasound-guided thoracentesis, paracentesis, and central venous catheterization.

To develop a Canadian Internal Medicine Ultrasound (CIMUS) consensus statement on recommended mandatory point-of-care ultrasound (POCUS) competencies for ultrasound-guided thoracentesis, paracentesis, and cent...

Lung ultrasound score predicts outcomes in patients with acute respiratory failure secondary to COVID-19 treated with non-invasive respiratory support: a prospective cohort study

Lung ultrasound has demonstrated its usefulness in several respiratory diseases management. One derived score, the Lung Ultrasound (LUS) score, is considered a good outcome predictor in patients with Acute Res...

Integrating a self-directed ultrasound curriculum for the internal medicine clerkship

Incorporating ultrasound into the clinical curriculum of undergraduate medical education has been limited by a need for faculty support. Without integration into the clinical learning environment, ultrasound s...

Point-of-care ultrasound to inform antiviral treatment initiation in chronic hepatitis B virus infection in low-resource settings – the PUSH protocol

Chronic Hepatitis B (CHB) is prevalent worldwide and most related deaths occur in low-resource settings. Antiviral treatment of CHB is indicated in those with significant liver disease and markers of viral rep...

Right ventricular free wall longitudinal strain during weaning from mechanical ventilation using high-flow or conventional oxygen treatment: a pilot study

Medico-legal risks of point-of-care ultrasound: a closed-case analysis of canadian medical protective association medico-legal cases.

Point-of-care ultrasound (POCUS) has become a core diagnostic tool for many physicians due to its portability, excellent safety profile, and diagnostic utility. Despite its growing use, the potential risks of ...

Test characteristics of point-of-care ultrasonography in patients with acute kidney injury

Acute kidney injury is a common disorder that is associated with significant morbidity and mortality. Point-of-care ultrasonography (PoCUS) is an imaging modality performed at the bedside and is used to assess...

Ultrasound contrast agent assisted ultrasonography guidance percutaneous nephrostomy for non-hydronephrotic kidney

Given the limited success rate and considerable challenges associated with conventional ultrasonography (US) guidance for percutaneous nephrostomy (PCN) in non-hydronephrotic kidneys, this study proposed a sol...

The usefulness of point-of-care ultrasound in dehydrated patients in a pediatric emergency department

Dehydration is among the most common causes of Pediatric Emergency Department admission; however, no clinical signs, symptoms, or biomarkers have demonstrated sufficient sensitivity, specificity, or reliabilit...

Evaluation of point-of-care ultrasound training among healthcare providers: a pilot study

The use of Point-of-Care Ultrasound (POCUS) has become prevalent across a variety of clinical settings. Many healthcare professionals have started getting hands-on training. To evaluate the effectiveness of su...

Thoracic ultrasound use in hospitalized and ambulatory adult patients: a quantitative picture

Thoracic ultrasound (TUS) has been established as a powerful diagnostic and monitoring tool in the Intensive Care Unit (ICU). However, studies outside the critical care setting are scarce. The aim of this stud...

Can absence of cardiac activity on point-of-care echocardiography predict death in out-of-hospital cardiac arrest? A systematic review and meta-analysis

The purpose of this systematic review and meta-analysis was to evaluate the accuracy of the absence of cardiac motion on point-of-care echocardiography (PCE) in predicting termination of resuscitation (TOR), s...

Point-of-Care Ultrasound training in undergraduate education in the European Union: current situation and perspectives

Given the widespread use of Point-of-Care UltraSound (PoCUS) in clinical practice, with ultrasound machines becoming more portable and affordable, recommendations and position statements from ultrasound societ...

Assessment of quadriceps muscle mass by ultrasound in the postoperative period of cardiac surgery

Patients undergoing cardiac surgery are exposed to many factors that activate catabolic and inflammatory pathways, which affect skeletal muscle and are, therefore, related to unfavorable hospital outcomes. Giv...

Lung ultrasound and supine chest X-ray use in modern adult intensive care: mapping 30 years of advancement (1993–2023)

In critically ill patients with acute respiratory failure, thoracic images are essential for evaluating the nature, extent and progression of the disease, and for clinical management decisions. For this purpos...

Comparing contamination rates of sterile-covered and uncovered transducers for ultrasound-guided peripheral intravenous lines

Physicians frequently use point-of-care ultrasound for intravenous access and bloodwork in the ED. Recently, AIUM and ACEP released recommendations on ultrasound-guided peripheral intravenous lines (USPIVs), b...

Change in economy of ultrasound probe motion among general medicine trainees

To observe change in economy of 9 ultrasound probe movement metrics among internal medicine trainees during a 5-day training course in cardiac point of care ultrasound (POCUS).

The role of point-of-care ultrasound (POCUS) imaging in clinical outcomes during cardiac arrest: a systematic review

Cardiac arrest in hospital and out-of-hospital settings is associated with high mortality rates. Therefore, a bedside test that can predict resuscitation outcomes of cardiac arrest patients is of great value. ...

Advancement in pleura effusion diagnosis: a systematic review and meta-analysis of point-of-care ultrasound versus radiographic thoracic imaging

Pleural effusion is a fluid buildup in the pleural space that mostly result from congestive heart failure, bacterial pneumonia, malignancy, and pulmonary embolism. The diagnosis of this condition can be challe...

Correction: Utility of ultrasound in managing acute medical conditions in space: a scoping review

The original article was published in The Ultrasound Journal 2023 15 :47

Replacement of fluoroscopy by ultrasonography in the evaluation of hemidiaphragm function, an exploratory prospective study

Dysfunction of the diaphragm may ultimately lead to respiratory insufficiency and compromise patient outcome. Evaluation of diaphragm function is cumbersome. Fluoroscopy has been the gold standard to measure d...

Utility of ultrasound in managing acute medical conditions in space: a scoping review

In long-distance spaceflight, the challenges of communication delays and the impracticality of rapid evacuation necessitate the management of medical emergencies by onboard physicians. Consequently, these phys...

The Correction to this article has been published in The Ultrasound Journal 2024 16 :2

Additional predictive value of optic nerve sheath diameter for neurological prognosis after cardiac arrest: a prospective cohort study

The goal is to estimate the additional value of ultrasonographic optic nerve sheath diameter (ONSD) measurement on days 1–3, on top of electroencephalography (EEG), pupillary light reflexes (PLR), and somatose...

Optic nerve sheath diameter measurement for the paediatric patient with an acute deterioration in consciousness

Ocular Point of Care Ultrasound (PoCUS) is emerging as a valuable utility within emergency medicine. Optic nerve sheath diameter (ONSD) has been demonstrated to correlate closely with intracranial pressure (IC...

Correction: Feasibility of using a handheld ultrasound device to detect and characterize shunt and deep vein thrombosis in patients with COVID-19: an observational study

The original article was published in The Ultrasound Journal 2020 12 :49

Correction: A survey demonstrating that the procedural experience of residents in internal medicine, critical care and emergency medicine is poor: training in ultrasound is required to rectify this

The original article was published in The Ultrasound Journal 2021 13 :20

Internal jugular access using pocket ultrasound in a simulated model: comparison between biplane and monoplane visualization techniques

Ultrasound is the current standard for central venous access due to its advantages in efficiency and safety. In-plane and out-of-plane visualization techniques are commonly used, but there is no clear evidence...

Abscess pulsatility: a sonographic sign of osteomyelitis

Early diagnosis and aggressive treatment of acute osteomyelitis may improve prognosis and prevent further complications. Sonography is useful in the evaluation of osteomyelitis. It can demonstrate early signs ...

The diagnostic accuracy of lung ultrasound to determine PiCCO-derived extravascular lung water in invasively ventilated patients with COVID-19 ARDS

Lung ultrasound (LUS) can detect pulmonary edema and it is under consideration to be added to updated acute respiratory distress syndrome (ARDS) criteria. However, it remains uncertain whether different LUS sc...

Development of a novel observed structured clinical exam to assess clinical ultrasound proficiency in undergraduate medical education

A pilot study was performed to develop and test an observed structured clinical exam (OSCE) for clinical ultrasound in second-year medical students. The goal was to assess a longitudinal clinical ultrasound cu...

Echocardiographic parameters in COVID-19 patients and their association with ICU mortality: a prospective multicenter observational study

Echocardiography has become an integral part of the management of critically ill patients. It helps to diagnose and treat various conditions. COVID-19 patients can develop cardiac dysfunction. We planned to st...

The correlation between epicardial fat thickness and longitudinal left atrial reservoir strain in patients with type 2 diabetes mellitus and controls

Diabetes mellitus (DM) has been documented among the strongest risk factors for developing heart failure with preserved ejection fraction (HFpEF). The earliest imaging changes in patients with DM are the left ...

The association of attentional foci and image interpretation accuracy in novices interpreting lung ultrasound images: an eye-tracking study

It is unclear, where learners focus their attention when interpreting point-of-care ultrasound (POCUS) images. This study seeks to determine the relationship between attentional foci metrics with lung ultrasou...

Transesophageal echocardiography (TEE)-guided transvenous pacing (TVP) in emergency department

Placement of a temporary pacemaker is a vital skill in the emergency setting in patients that present with life-threatening bradycardia. Transvenous pacing is the definitive method of stabilizing the arrhythmi...

Feasibility of chest ultrasound up to 42 m underwater

After recent advancements, ultrasound has extended its applications from bedside clinical practice to wilderness medicine. Performing ultrasound scans in extreme environments can allow direct visualization of ...

Evaluation of commercially available point-of-care ultrasound for automated optic nerve sheath measurement

Measurement of the optic nerve sheath diameter (ONSD) via ultrasonography has been proposed as a non-invasive metric of intracranial pressure that may be employed during in-field patient triage. However, first...

Simultaneous venous–arterial Doppler during preload augmentation: illustrating the Doppler Starling curve

Providing intravenous (IV) fluids to a patient with signs or symptoms of hypoperfusion is common. However, evaluating the IV fluid ‘dose–response’ curve of the heart is elusive. Two patients were studied in th...

Learning curves for point-of-care ultrasound image acquisition for novice learners in a longitudinal curriculum

A learning curve is graphical representation of the relationship between effort, such as repetitive practice or time spent, and the resultant learning based on specific outcomes. Group learning curves provide ...

Point-of-Care-ultrasound in undergraduate medical education: a scoping review of assessment methods

Point-of-Care-Ultrasound (POCUS) curricula have rapidly expanded in undergraduate medical education (UME). However, the assessments used in UME remain variable without national standards. This scoping review c...

Doppler flow morphology characteristics of epiaortic arteries in aortic valve pathologies: a retrospective study on a cohort of patients with ischemic stroke

Neurovascular ultrasound (nvUS) of the epiaortic arteries is an integral part of the etiologic workup in patients with ischemic stroke. Aortic valve disease shares similar vascular risk profiles and therefore ...

Real-time Remote Expert-guided Echocardiography by Medical Students

Echocardiography is a highly specialised examination performed by experienced healthcare professionals. These experienced healthcare professionals may not be available to patients during all hours in rural hea...

Ultrasound findings in Kaposi sarcoma patients: overlapping sonographic features with disseminated tuberculosis

Focused Assessment with Sonography for HIV-associated TB (FASH) is a diagnostic tool for extra-pulmonary tuberculosis (TB) in symptomatic patients with advanced HIV. As Kaposi’s sarcoma (KS) is also prevalent ...

Ultrasound detected increase in optic disk height to identify elevated intracranial pressure: a systematic review

Elevated intracranial pressure (eICP) is a serious medical emergency that requires prompt identification and monitoring. The current gold standards of eICP detection require patient transportation, radiation, ...

Determinants of point-of-care ultrasound lung sliding amplitude in mechanically ventilated patients

Although lung sliding seen by point-of-care ultrasound (POCUS) is known to be affected to varying degrees by different physiologic and pathologic processes, it is typically only reported qualitatively in the c...

Femoral vein pulsatility: a simple tool for venous congestion assessment

Femoral vein Doppler (FVD) is simpler than the VExUS score which is a multimodal scoring system based on combination of IVC diameter, hepatic venous Doppler, portal vein pulsatility and renal vein Doppler, may...

Airway ultrasound to detect subglottic secretion above endotracheal tube cuff

Subglottic secretion had been proven as one of the causes of microaspiration and increased risk of ventilator-associated pneumonia (VAP). The role of ultrasound to detect subglottic secretion has not yet been ...

Intra-and inter-observer variability of point of care ultrasound measurements to evaluate hemodynamic parameters in healthy volunteers

Point-of-care ultrasound (POCUS) is a valuable tool for assessing the hemodynamic status of acute patients. Even though POCUS often uses a qualitative approach, quantitative measurements have potential advanta...

Correction: Empowering the willing: the feasibility of tele-mentored self-performed pleural ultrasound assessment for the surveillance of lung health

The original article was published in The Ultrasound Journal 2022 14 :2

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• Impact case studies

Medical ultrasound: Case Study

Today we take for granted the use of ultrasound for medical examination and diagnosis, but in the 1950s ultrasound was still an emerging technology. NHMRC supported ultrasound research in Australia from its early beginnings, and one of the first ultrasound scanners was developed by NHMRC-funded researchers. 

Co-developed with the Australasian Society for Ultrasound in Medicine (ASUM), this case study focuses on the work of the Ultrasonics Institute (UI) and of pioneering Australian doctors and sonographers who revolutionised the use of medical imaging.

At the beginning of the 20th century the only medical diagnostic imaging tool available to doctors was X-ray. Early X-ray machines had their shortcomings: patients might be required to stand completely still for several minutes of intense radiation exposure in order to obtain a useful image. Consequently, taking X-rays of pregnant women and infants was dangerous. A safer approach to medical imaging was needed. 

In 1943, NHMRC established an Acoustic Testing Laboratory (ATL) in Sydney to undertake war-time research. The laboratory later became the Commonwealth Acoustic Laboratories (CAL) (1947). In 1975, the CAL’s Ultrasonics Research Section became the Ultrasonics Institute (UI). 

Directed by Norman Murray, the laboratory initially focused on hearing support for deafened veterans and children affected by the 1940-41 epidemic of maternal rubella. During the 1950s, Murray became interested in developments in ultrasound to treat Ménière’s disease and Parkinson’s disease, and the diagnostic use of reflected ultrasound to detect and determine the nature of breast tumours.

Early black and white obstetric ultrasound. Source ASUM

Greyscale was a significant improvement on black and white imaging. Obstetric ultrasound in 1978. Source ASUM

Development and Investment

NHMRC funded the establishment of the ATL and the salaries of its staff from 1943-46. In 1946, the Australian Government Department of Health (DoH) took over funding the laboratory. In 1955, NHMRC set up an Ultrasonics Committee, chaired by Murray, to inquire into the control and use of ultrasonic therapy apparatus and establish standards in the measurement of acoustic output. 

In 1958, UK obstetrician Dr Ian Donald first used ultrasound in a clinical setting in Glasgow. Informed by this development, Murray sought to produce such a system in Australia and recommended to NHMRC that CAL employ a full-time scientist to undertake research into this new field of diagnostic medical ultrasound. George Kossoff joined CAL in 1959 as a research physicist and also became a member of NHMRC’s Ultrasonics Committee, as did Dr William Garrett, an obstetrician at Sydney's Royal Hospital for Women (RHW). Kossoff headed the section, which was made up of technical experts working with a variety of medical specialists. By 1963, CAL had become world renowned for its research and development in the field of medical ultrasound.

Between 1970 and 1990, NHMRC funded CAL/UI researchers and others including:

• Professor John McCaffrey : for blood flow studies and to develop an ultrasonic computerised tomography system 
• Professor David Wilcken : for multi-scanning echocardiography (using ultrasound to generate images of the heart)
• Professor Brian Trudinger : for Doppler ultrasound (blood flow volume and velocity studies) of the placenta and fetus
• Professor Thomas Reeve : for characterisation of breast tissue by ultrasound

Technology : In 1961, the first commercially practical Australian ultrasonic scanner (the CAL Echoscope) was built by Kossoff and Dr David Robinson. From 1970, CAL Echoscopes were modified to include greyscale scanning: a world first. This technology represented a significant improvement over the black and white imaging that was previously available. It produced clearer and more detailed images and could reveal soft tissues. 

Obstetrics : In May 1962, the first ultrasound obstetrics examination was performed at the RHW by Robinson, Kossoff and Garrett. In the early 1970s, Garrett led the world in identifying fetal anatomy using ultrasound, and he and Robinson published an early textbook on ultrasound in clinical obstetrics. Professor Robert Gill, a researcher and developer of Doppler ultrasound techniques joined UI in 1975. In 1979, he published the first measurements of blood flow in the umbilical cord in pregnancies, paving the way for Doppler to be used in other studies.

Breast : In 1966, a dedicated breast scanner was installed at the Royal North Shore Hospital (RNSH). Reeve was the clinical consultant. Scientific support was provided by Dr Jack Jellins, and Kaye Griffiths made significant contributions to this work. From 1969, Reeve began developing a comprehensive range of diagnostic interpretative criteria.

Brain : In 1969, Kossoff and Robinson developed an Ultrasonic Neuroscope which produced clear images of the brain. Unlike the previously available methods, this form of imaging posed no risk to the infant. The team, working with Garrett, also used the device to create an atlas of the normal infant brain.

Heart : Wilcken collaborated on the very early development of echocardiography. He, along with Dr Ian McDonald, was one of the first to develop and promote its use in Australia.

The UI Octoson. Source ASUM

Results and Translation

After greyscale became available, one of the early discoveries by Reeve was the different ultrasonic features in benign and malignant solid lesions in the breast. This led to more accurate cancer diagnoses.

The UI team continued to make technical improvements to their scanners. In 1975, Kossoff and Robinson developed the UI Octoson. Ausonics Pty Ltd was established to manufacture it in Sydney. Over the next five years nearly two hundred were sold worldwide. 

In 1987, Trudinger and his team at The University of Sydney published results of the first randomised clinical trial showing the usefulness of umbilical artery Doppler ultrasound to assess fetal well-being in high-risk pregnancies. Much of this work remains in mainstream clinical practice today.

McCaffrey advanced the understanding and implementation of breast cancer screening and of the treatment of early breast cancer. He played a major role in the establishment of breast ultrasound in Australia and internationally.  

Wilcken used echocardiography to visualise mitral valve prolapse (an abnormality of a heart valve) on which he became one of the world’s leading experts. In 1977, he organised the first course in echocardiography. Echocardiography is now an essential part of routine cardiac assessment. 

The skill required of sonographers (i.e. operators of ultrasound scanners) was recognised in Australia early on. The Australasian Society for Ultrasound in Medicine (ASUM) was formed in 1970 as use of ultrasound spread further than the UI. In 1976, Garrett helped set up the Diploma of Diagnostic Ultrasound for doctors and the Diploma of Medical Ultrasound for sonographers.

Health Outcomes and Impact  

As technology advanced, the early ultrasound scanners were superseded by smaller, more portable, electronic, real-time scanners. But the use of ultrasound as an accepted clinical tool was firmly established, as was its excellent safety record.

In the late 1960s and early 1970s, cardiac diagnostics such as ultrasound, along with other factors, resulted in improved survival from chronic heart disease in Australia. By the mid 1990s, use of cardiac and vascular ultrasound was increasing significantly and that growth has continued up until the present time. 

By 1995, ultrasound in pregnancy represented 20% of ultrasound services and was performed in 97% of pregnancies. 

• Evidence from randomised trials during pregnancy had shown that a routine 16-18 week scan in pregnancy reduced perinatal mortality through the detection of fetal abnormalities.
• The use of Doppler ultrasound of the umbilical artery as a clinical guide to management of high-risk pregnancies had been shown to reduce the odds of perinatal death by 38%.

Source: Services Australia

Diagnostic imaging now plays a critical role in a world-class, 21st century health system. 

UI was transferred to CSIRO in 1989, becoming its Ultrasonics Laboratory until 1997. 

In 2004, Australia Post issued a stamp highlighting ultrasound as part of its Australian innovation series. 

Norman Murray

Norman Murray (d 1971) was a pioneer of acoustics research in Australia and the foundation Director of CAL (1947-1967). He chaired NHMRC’s Ultrasonics Committee from 1955-63. 

Dr George Kossoff AO

Dr George Kossoff designed the first Australian ultrasound scanner and later the scan converter that led to the clearest greyscale images seen at the time. He was foundation President of ASUM (1970-72) and President of the World Federation for Ultrasound in Medicine and Biology (1982-85). He was appointed an Officer of the Order of Australia in 1999.

Dr William Garrett AM 

Dr William Garrett (1927–2015) was founding Medical Director of RHW’s Department of Diagnostic Ultrasound and President of ASUM (1972-74). He was appointed a Member of the Order of Australia (AM) in 1985 for service to medicine, particularly the science of obstetric ultrasound.

Dr John McCaffrey

Dr John McCaffrey (1933-2000) was an oncological surgeon at the Royal Brisbane Hospital, where he founded the first public breast screening clinic in Australia. He was a founding member of ASUM and President of ASUM from 1982-83.

Professor David Wilcken

Professor David Wilcken (1927-2020) was a pioneering cardiologist at the Royal Prince Henry Hospital and one of the world’s leading experts on mitral valve prolapse. His later research confirmed the link between smoking and the diseased arteries which lead to heart failure. 

Professor Brian Trudinger

Professor Brian Trudinger was Professor of Obstetrics and Gynecology at Westmead Hospital, The University of Sydney. His ultrasound studies of placental blood flow and its effect on fetal physiology led to a new way of monitoring fetal wellbeing. In 2006, the International Society of Ultrasound in Obstetrics and Gynecology awarded him the Ian Donald Gold Medal.

Dr David Robinson AM 

Dr David Robinson (1939-2010) built Australia's first ultrasound scanner and helped develop greyscale ultrasound scanners. He was President of ASUM (1974-76) and was appointed a Member of the Order of Australia in 2002. The Australasian College of Physical Scientists & Engineers in Medicine (ACPSEM) established a prize to commemorate his contributions to the field of biomedical engineering.

Professor Robert Gill

Professor Robert Gill is a pioneer in Doppler ultrasound technology. As well as scientific publications and papers on his research, he has authored four international patents. He was President of ASUM (1990-91).

Prof Thomas Reeve AC CBE

Professor Thomas Reeve was Surgical Research Fellow in the Unit of Clinical Investigation at RNSH and involved in clinical ultrasound during its early development for the study of the breast, and the thyroid and parathyroid glands. An expert in his field, Professor Reeve was appointed Commander of the Order of the British Empire in 1973, and a Companion of the Order of Australia in 1994.

Kaye Griffiths AM

Kaye Griffiths (1945-2017) was a research sonographer who pioneered two dimensional techniques to examine the brains of young children. She convened the First World Congress of Sonographers in Sydney in 1985. In 2002, she was appointed a Member of the Order of Australia.

This case study was developed in partnership with ASUM. The information and images from which impact case studies are produced may be obtained from a number of sources including our case study partner, NHMRC’s internal records and publicly available materials.

The following sources were used for this case study:

ASUM Bulletins 

• Griffiths KA. An historical look at ultrasound as an Australian innovation on the occasion of the ultrasound stamp issued by Australia Post – 18 May 2004. ASUM Ultrasound Bulletin. 2004 Aug; 7(3): 22–26
• Hassall L. Sonography – the emergence of a profession. ASUM Ultrasound Bulletin. 2007 Aug; 10(3): 29–34
• Kossoff G. How research into medical ultrasound began in Australia. ASUM Bulletin. 2000 Nov; 3(4): 8-13.

Ultrasonics Institute

• Robinson D, Garrett W, Gill R, Griffiths K, Jellins J, Kossoff G, Reeve T, Shepherd I, Wilson L, Warren P. Ultrasonics Institute Australia 1959-1997, A short history of the Ultrasonics Institute (under its various titles) prepared for the historical display at the 2009 Congress of the World Federation for Ultrasound in Medicine and Biology, Sydney, Australia
• Ultrasonics Institute. History of the Ultrasonics Institute: A record of a historical exhibit at the World Congress for Ultrasound in Medicine and Biology, WFUMB'88, Washington DC, October, 1988. Commonwealth Department of Health.
• Campbell S. A Short History of Sonography in Obstetrics and Gynaecology. Facts Views Vis Obgyn. 2013; 5(3): 213–229
• McNay MB, Fleming JEE. Forty years of obstetric ultrasound 1957-1997: from A-scope to three dimensions. Ultrasound Med Biol. 1999 Jan; 25(1): 3-56. DOI: 10.1016/s0301-5629(98)00129-x
• Services Australia, Medicare Group Reports, MBS Group Statistics Reports. Report generated was Category 5,  Diagnostic Imaging Services, for financial years from July 1993 to June 2020. Obtained from http: //medicarestatistics.humanservices.gov.au/statistics/mbs_group.jsp on 30 Apr 2021
• Woo J. A short History of the development of Ultrasound in Obstetrics and Gynecology. Obtained from: https: //www.ob-ultrasound.net/history.html on 19 Nov 2020.
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• Practice Innovations in Emergency Medicine
• Open access
• Published: 01 February 2024

A case report on ultrasound-guided pericardiocentesis with a right parasternal approach: a novel in-plane lateral-to-medial technique

• Najem Abdullah Mohammed 1 , 2 , 3 ,
• Tanweer A. Al-zubairi 1 , 2 &
• Moad H. Al-soumai 1 , 2  

International Journal of Emergency Medicine volume  17 , Article number:  15 ( 2024 ) Cite this article

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Introduction

Emergency pericardiocentesis is a life-saving procedure that is performed to aspirate fluid from the pericardial space in patients who have severe pericardial effusion that is causing hemodynamic compromise. The current gold standard for pericardial fluid aspiration is ultrasound-guided pericardiocentesis. Echocardiography with a low-frequency transducer has generally been used in pericardiocentesis, but this method lacks real-time visualization of the needle trajectory, leading to complications. Therefore, we describe a case involving an ultrasound-guided pericardiocentesis method using a novel in-plane technique with a lateral-to-medial approach via the right parasternal and a high-frequency probe. The method was performed for an infant with cardiac tamponade.

Case presentation

We present a case of a 14-month-old male infant who was brought to the emergency room with a history of cough, shortness of breath, and fever following recurrent chest infections. Despite prior treatments, his condition deteriorated, and signs of cardiac tamponade were evident upon examination. Cardiopulmonary point-of-care ultrasound confirmed the presence of a large pericardial effusion with tamponade. Emergency pericardiocentesis was performed using the novel in-plane technique, resulting in successful fluid aspiration and stabilization of the patient’s condition.

Technique description

The proposed technique involves positioning a high-frequency ultrasound probe over the right parasternal area to obtain real-time visualization of the needle trajectory and surrounding structures, including the sternum, right internal thoracic vessels, pleural sliding end point, pericardial effusion, and myocardium. The needle is inserted laterally to medially at a 45-degree angle, ensuring safe passage between the pleural sliding endpoint and the right internal thoracic vessels while reaching the pericardial effusion.

The presented technique provides real-time visualization of the needle and surrounding structures, which may potentially help to avoid complications and improve accuracy. The proposed technique may potentially enable access for emergency pericardiocentesis and for loculated pericardial effusion that has formed around the right atrium. Nevertheless, further studies with large patient populations are needed.

Cardiac tamponade is a life-threatening condition that is characterized by the collection of fluid in the pericardial sac, which results in cardiac compression and impaired cardiac function. This condition can affect patients of all ages, but due to the smaller anatomical structures of pediatric patients, it poses unique challenges in such cases. Early diagnosis and treatment are essential for successful outcomes [ 1 , 2 , 3 ].

In cases of large, symptomatic pericardial effusion or cardiac tamponade, pericardiocentesis is the most useful therapeutic technique for early therapy or diagnosis [ 3 , 4 ]. Emergency pericardiocentesis is a lifesaving procedure that is used to aspirate fluid from the pericardial space in patients with significant pericardial effusion that has resulted in hemodynamic compromise [ 5 , 6 ]. The introduction of ultrasound-guided procedures has enhanced the technique’s safety and practicability and has contributed to its evolution over time [ 7 , 8 ]. Ultrasound-guided pericardiocentesis has become the gold standard for the aspiration of pericardial fluid. First introduced in 1979 at the Mayo Clinic [ 7 , 8 ], this method has been shown to be effective in comparison to blind or surgical methods [ 9 ].

Over time, this method has been refined into better techniques with different approaches, and with the increasing use of point-of-care cardiac ultrasonography, ultrasound-guided pericardiocentesis has become a viable option in the emergency department [ 10 ]. Several methods have been described, including parasternal, apical, and subxiphoid methods [ 7 , 9 , 10 , 11 ], but the optimal approach for draining pericardial effusion remains controversial. One reason is that procedure selection frequently depends on the patient’s characteristics and the expertise of the hospital [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ].

Conventionally, a low-frequency transducer has been used with echocardiography to diagnose pericardial effusion and determine the optimal puncture site [ 7 , 8 , 9 , 11 ]. However, a few new nonconventional approaches to pericardiocentesis have been described, such as echocardiography-guided pericardiocentesis with a high-frequency transducer [ 12 , 13 , 14 , 15 ], an apical in-plane approach in a sitting position with a high-frequency transducer [ 12 ], and an in-plane medial-to-lateral technique through a left parasternal approach [ 13 ]. Real-time tracking of the needle using a high-frequency transducer enables clinicians to avoid injuring adjacent structures [ 12 , 13 , 16 , 17 ]. The present study describes a new technique for pericardiocentesis using a high-frequency probe through a right parasternal approach. We also share our initial experience using this approach in the emergency room for infants with cardiac tamponade.

A 14-month-old male infant presented with a history of coughs, shortness of breath, and fever 2 weeks prior. The symptoms were preceded by a recurring chest illness in the previous 2 months. He underwent treatment but did not improve. He was brought to the emergency room of our hospital due to breathlessness, irritability, fever, and poor feeding. His vital signs included a temperature of 37.9 °C, respiratory rate of 70 breaths per minute, heart rate of 171 beats per minute, blood pressure of 90/70 mmHg, and SPO2 of 89%.

A physical examination revealed that the patient was ill and irritable. He had pallor, a low-grade temperature, dyspnea, tachycardia, congested neck veins, and a good peripheral pulse. A lung examination revealed small crackles in the left middle zone and limited air entry at the base. The results of a heart exam and other systemic exams were normal. Cardiopulmonary point-of-care ultrasound (POCUS) revealed significant pericardial effusion (Fig.  1 ) and left lung consolidation. A lab investigation revealed positive findings of a high white blood cell count (WBC) with lymphocytosis. His erythrocyte sedimentation rate (ESR) was 70 mm/h.

A , B Pre-procedural echocardiography views (apical 4-chamber and subxiphoid) revealing a large pericardial effusion concentrated maximally around the right atrium (dashed line and star). C Right parasternal ultrasonographic view displaying the pericardial effusion with fibrin strands, the surrounding vital structures (pleura, internal thoracic vessels (ITVs), and myocardium), the diameter of cardiac effusion A , and the path of needle insertion B (the distance from the skin to the pericardial space). D Image demonstrating the position of operator, ultrasound machine, and placement of high-frequency ultrasound probe in the right parasternal area

The patient’s condition worsened because of cardiac tamponade, necessitating an emergency pericardiocentesis. The procedure was performed using an in-plane technique with a lateral-to-medial approach via the right parasternal route with a high-frequency probe. After aspirating 60 ml of pericardial fluid, the patient’s hemodynamics stabilized, and he was monitored for 24 h with repeated cardiac scans (Fig.  3 ). A cytochemical test of the pericardial fluid revealed a high WBC, lymphocytosis, and a high protein level. The patient was then referred to a specific pediatric facility and diagnosed with tuberculosis. After 2 weeks, the patient was brought in for follow-up, and a cardiac scan indicated no pericardial effusion (Fig.  3 ). A repeat follow-up scan was done every month thereafter until the regimen of anti-tuberculosis drugs was completed, and the scans demonstrated no pericardial effusion.

The technique

Pre-procedure (finding the optimal puncture site).

The pericardial effusion was initially evaluated with a (cardiac) phased array probe for size and maximum collection location (Fig.  1 A, B; Supplementary material files, video 1 ). The right parasternal view was then obtained with a high-frequency probe by putting it in a transversal position on the right parasternal area at the 4th intercostal space. The next step was finding and setting up the best view that showed the pericardium near the chest wall, through which the sternum, right internal thoracic vessels (ITVs), the end point of plural sliding, pericardial effusion, and the myocardium (right atrium) could all be easily seen. Measurements of the distance from the skin to the pericardium sac and effusion diameter were then taken (Fig.  1 C; Supplementary files, video 2 ). The technique could be done safely with a pericardial effusion (PE) diameter and distance between the right ITV and plural sliding end points greater than 1 cm in the right parasternal window (Figs. 1 C and 2 A).

A Image demonstrating the operator handling the high-frequency ultrasound probe and needle insertion using in-plane technique with lateral-to-medial approach at a 45-degree angle. B Parasternal sonogram in long-axis view revealing the cardiac effusion diameter A and the distance B from the end point of the pleura sliding to the internal thoracic vessels (ITVs). C Parasternal sonographic long-axis view showing the needle’s path of insertion, which passes between the end point of the pleura laterally to the ITVs and medially to the pericardial sac and was visualized in real time during the procedure

Patient and ultrasound positioning and preparation

All steps should be done under antiseptic conditions. An ultrasound machine was positioned on the left of the patient, who was kept supine throughout the procedure. The operator was on the right, allowing a direct view of the ultrasound screen after optimal adjustment of the ultrasound settings (Fig.  1 C, D). Patients should be sedated to prevent unnecessary movements. The skin overlying the right chest was prepped, and the ultrasound transducer was covered with a sterile sheath.

Identifying the puncture site and surrounding structures

A high-frequency ultrasound probe was placed transversally in the intercostal space of the right parasternal (which was the area where the pre-procedure scan gave the best view). Then, the structures around it were identified, such as the sternum, right internal thoracic vessels, end point of plural sliding, pericardial effusion, and myocardium (right atrium). We then determined the optimal puncture path for drainage (Figs. 1 C and 2 A) (Supplementary material files, video 2 ). The optimal puncture path was defined as the pathway that had the lowest distance between the needle insertion site and the pericardial sac and avoided essential structures.

Needle insertion and confirmation

The operator fixes the liner probe on site with the left hand and the needle in the right hand and then smoothly advances the needle in-plane laterally to medially at a 45-degree angle. This is done with real-time visualization of the needle, which passes between the end point of plural sliding laterally and the right internal thoracic vessels medially to the pericardial effusion. The needle appears as a bright echogenic line in the long-axis view (Fig.  2 C). Once the needle reaches the pericardial space, confirmation is obtained by aspiration of the pericardial cavity, as well as visualization of the tip of the needle in real time during the procedure. By inserting the needle along the superior border of the ribs, it is possible to avoid the intercostal vessels that run along the inferior border [ 18 ].

Fluid drainage

After confirming pericardial access, fluid drainage is initiated. This can be done by attaching a syringe or drainage system to the needle and gently withdrawing the fluid until hemodynamic stabilization is achieved. Throughout the procedure, continuous monitoring of the patient’s hemodynamic status is essential. An immediate improvement in hemodynamic stability is expected after successful pericardiocentesis.

Post-procedure care

After completing the pericardiocentesis, the patient is monitored for any complications or recurrence of pericardial effusion. Close observation and appropriate management are necessary to ensure a favorable outcome. This novel technique was used in an emergency situation with an infant with cardiac tamponade in an emergency room. It was performed at the bedside with the infant in a supine position and sedated, while vital signs and pulse oximetry were monitored. The pericardiocentesis was performed successfully without complications and relieved the hemodynamic instability (Fig.  3 ; Supplementary material files, videos 3 and 4 ).

Cardiac ultrasonographic views following the procedure. A Apical four-chamber (A4C) view showing a decrease in the pericardial effusion (white dot). B Right parasternal view (longitudinal view axis) demonstrating a reduction in diameter of the cardiac effusion (white dot).The patient was referred to a specific pediatric facility and then diagnosed with tuberculosis. C Echocardiography scan and parasternal long-axis view revealing full clearance in pericardial effusion at 2 weeks after pericardiocentesis

This is the first report to describe technical experience of ultrasound-guided pericardiocentesis via the right parasternal route using a novel in-plane technique with a lateral-to-medial approach and a high-frequency ultrasound probe. The use of bedside ultrasound has significantly altered the practice of modern medicine. Greater familiarity with the technology has accelerated the transition of technical skill from novice to expert levels, enhanced performance in commonly encountered procedures, and led to novel approaches to clinical challenges [ 19 , 20 , 21 , 22 ].

In the 1970s, echocardiography-guided pericardiocentesis was developed and later accepted as the gold standard because it had fewer complications, such as liver, myocardium, artery, and lung perforation. Due to a lack of expertise in point-of-care ultrasound, many centers still use blind subxiphoid pericardiocentesis, which has a morbidity rate of about 20% and a mortality rate as high as 6% [ 7 ]. In contrast, 0.339% of echo-guided pericardiocentesis practitioners experience significant complications, while 0.420% experience minor complications [ 9 ].

The standard technique depends on identifying the location and distribution of pericardial fluid and inserting the needle at a site where the greatest amount of fluid is closest to the skin while using the “bubble test” to confirm the correct needle position. This technique is responsible for the low rate of minor and severe complications (3.5% and 1.2%, respectively) [ 9 ]. Alternative procedures with comparable complication rates, including the probe-mounted needle method, have been proposed with similar complications [ 23 ]. Pericardiocentesis guided by computed tomography (CT) is typically reserved for patients with poor acoustic windows and frequently complex, loculated pericardial effusions (typically posterior effusions), which can occur post-operatively and are not readily accessible via standard approaches. However, CT has limitations regarding accessibility and lengthy procedural durations, which were reported to be 65 min on average in one series [ 24 ].

In conventional techniques, low-frequency probes are typically used to route the needle insertion to areas with the greatest fluid accumulation and to ensure that the needle trajectory avoids vital structures [ 7 , 8 , 9 , 11 , 18 , 26 ]. However, the complication rate is 5% [ 9 ]. Real-time visualization of the entire needle trajectory may be challenging with a low-frequency probe, which could result in injury to adjacent vital organs [ 13 , 28 ]. Even with ultrasound guidance, several observational studies have demonstrated that the parasternal approach is preferable to the conventional subxiphoid approach as it offers the most direct, secure, and superficial access to the pericardial space [ 9 , 15 , 26 , 27 ].

The apical or parasternal approach is transpleural and involves a risk of pneumothorax or infection spreading to the pleura and lungs. The subxiphoid approach increases the risk of liver, cardiac, and IVC injuries [ 11 ]. If echocardiography is available in an emergency situation, the intercostal approach can be used to perform urgent pericardiocentesis safely and effectively [ 28 ]. Conventional parasternal access is performed by inserting the needle directly next to the sternum to avoid damaging the ITVs that run about 1 cm laterally [ 23 ]. However, the technique involves a risk for potential complications due to a lack of visualization of the needle’s path and the adjacent anatomical structures.

To address the challenges of real-time visualization, a few new approaches using high-frequency probe US have been described [ 12 , 13 , 14 , 15 ]. High-frequency ultrasound is predominantly used in percutaneous thoracic interventions [ 16 ]. Using a linear probe enhances spatial resolution and reduces artifacts, allowing the operator to avoid injury to vital structures [ 29 ]. Case reports have described parasternal, in-plane, and real-time methods, but they did not describe them as lateral to medial via a right parasternal approach [ 14 , 15 ]. Recently, Osman et al. [ 13 ] described using an in-plane medial-to-lateral approach via the left parasternal route for a small group of patients with a high-frequency probe, for which they reported a 100% success rate with no complications. The benefits of this medial-to-lateral technique include improved vision of the needle route and nearby anatomical structures, which can prevent complications and shorten the procedure duration.

The right parasternal access is beneficial for a number of theoretical reasons. First, the pericardial space around the right atrium is considered the typical site for the maximum collection of pericardial effusions because of gravity and having the lowest pressures of the cardiac chamber of the right atrium during the cardiac cycle. As a result, pericardial fluid accumulation is simpler in this location. Continually accumulating fluid causes the effusion to become circumferential.

Furthermore, because the right atrium has thin walls, it is the most susceptible to invagination due to the presence of a large pericardial effusion. This effect is most pronounced in the supine position, when effusion accumulates posteriorly around the right atrium [ 30 , 31 , 32 , 33 ]. As a result, the effusion diameter around the atrium will increase, and this site becomes the area of maximal fluid collection. Consequently, access to this collection around the right atrium via the right parasternal approach may potentially be easier and more feasible than with other approaches.

Second, loculated PE effusions and hematomas are the most common postoperative complications [ 24 , 34 ]. Hematomas are typically found anteriorly and laterally of the right atrial free wall and could cause isolated compression of any chamber. This could result in hemodynamic collapse, especially if the affected chamber is adjacent to the atrium [ 34 ]. The right parasternal access has a direct path to the pericardial space around the right atrium, which suggests that the proposed technical approach may offer a feasible and valuable access point for loculated effusions or hematomas, which are inaccessible via standard approaches and require surgical intervention or CT-guided pericardiocentesis [ 24 , 34 ].

Due to the parietal pericardium, a thin fibrous structure is closely adjacent to the lateral pleural surfaces [ 35 ]. With a symmetrically expanding pericardial contour around the heart, the pericardial layer comes into contact with the anterior thoracic wall in a large pericardial effusion, displacing the pleura laterally. In the present case, the right parasternal access was chosen because it was the clearest, closest, and safest with the greatest quantity of fluid collection (Fig.  1 ). Successful aspiration of pericardial fluid and stabilization of the patient’s hemodynamics were achieved (Fig.  3 ), suggesting potential benefits of the technique in similar situations.

The parasternal window effusion diameter should to be more than 1 cm to be suitable for the in-plane technique, and the thoracic vessels should to be mapped out with ultrasound before the procedure [ 18 ]. In the proposed approach, the needle advances between the right ITVs medially and the end point of plural sliding laterally. Thus, the distance between them should be sufficient for advancement and control of the needle on its way to the pericardial space while avoiding injury to surrounding structures, as well as complications. Our opinion is that more than 1 cm is a safe distance to perform the procedure (Fig.  2 ).

Many emergency physicians know how to use the in-plane technique for needle guidance with a linear array probe. This makes this less common procedure somewhat similar to more common procedures, such as ultrasound-guided peripheral and central vascular access [ 36 ]. Thus the described technique is potentially promising for emergency and critical-care physicians.

The limitations and challenges

Operator experience and proficiency in ultrasound-guided procedures are essential for ensuring patient safety and favorable outcomes. Although many emergency clinicians use ultrasound-guided procedures on a regular basis, this is not the case for all of them. Another issue is that chest emphysema affects image quality. In addition, the parasternal approach is impractical in cases of cardiac arrest, and the subxiphoid approach is highly preferred [ 13 , 23 , 24 , 25 , 26 , 27 , 28 ]. Lastly, only one clinical case was considered for this technical approach notation. Therefore, this novel approach requires validation with a larger population.

Conclusions

This case report has demonstrated the clinical impact of a new technique, particularly in an emergency situation where alternative approaches may be limited or impractical. The use of real-time visualization potentially improves the accuracy of needle placement and reduces the risk of complications. This case report may serve as a basis for a new technical approach for pericardiocentesis, loculated pericardial effusion, or hematoma around the right atrium. Nevertheless, further research and clinical experience are required to validate the efficacy and prospective benefits with a larger patient population.

Availability of data and materials

Not applicable.

Abbreviations

• Point-of-care ultrasound

Internal thoracic vessels

Computed tomography

Apical four chambers

Parasternal long-axis

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Emergency Department and Intensive Care Unit, Al Zamalh Hospital, Mawia Street, Taiz City, Yemen

Najem Abdullah Mohammed, Tanweer A. Al-zubairi & Moad H. Al-soumai

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NAM set up the theoretical basis, POCUS images and clips for the case, AND the original idea for the procedure; performed the procedure; coordinated the preparation of the manuscript; and conducted critical revisions. MHA provided assistance and support for performing procedures and communicated with parents regarding informed consent. TAA gave advice and was major contributor in writing the manuscript and preparing the images and clips. All authors read and approved the final manuscript.

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NAM is a senior general practitioner in the emergency room at Al Zamalh Hospital; a resident in the general surgery department at Al Thawra General Hospital, Ibb, Yemen; and a POCUS instructor at Yemen POCUS academy. He graduated from the School of Medicine and Health Sciences of Taiz University, Yemen. TAA is a senior general practitioner in the pediatric department at Al Zamalh Hospital, Taiz, Yemen, and graduated from the School of Medicine and Health Sciences, Taiz University, Yemen. MHA is a senior general practitioner in the ICU at Al Zamalh Hospital, Taiz, Yemen; a resident in the general surgery department at Al Thawra General Hospital, Ibb, Yemen; and graduated from the School of Medicine and Health Sciences, Taiz University, Yemen.

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Correspondence to Najem Abdullah Mohammed .

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The authors certify that the study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The study was subjected to ethical review and approved by the ethical standards committee of our hospital (Al Zamalh Hospital, Taiz, Yemen). It also followed the ethical standards of the national ethical committee. In addition, written informed consent was obtained from the parents of the patient.

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The authors certify that they have obtained all appropriate patient consent forms. The form was used to obtain parental consent for the use of images, echocardiography clips, and other clinical information to be reported in the study. The parents understand that the patient’s name and initials will not be published and that due efforts were made for doing so without guarantees.

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Mohammed, N.A., Al-zubairi, T.A. & Al-soumai, M.H. A case report on ultrasound-guided pericardiocentesis with a right parasternal approach: a novel in-plane lateral-to-medial technique. Int J Emerg Med 17 , 15 (2024). https://doi.org/10.1186/s12245-024-00592-7

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DOI : https://doi.org/10.1186/s12245-024-00592-7

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At the time the case was submitted for publication Maulik S Patel had no recorded disclosures.

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Dysuria referred with laboratory findings of urinary tract infection.

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Right kidney shows ill-defined hyperechoic parenchymal areas without vascularity in upper pole and interpolar regions. There is no solid or cystic area in renal parenchyma. Renal artery and vein are patent. There is no calculus or back pressure change. There is urothelial thickening involving renal pelvi-calyceal system.

Left kidney and urinary bladder were normal (images not uploaded).

10th day follow up Ultrasound

Right kidney shows ill-defined hyperechoic parenchymal areas without vascularity in upper pole. There is an avascular anechoic area in lower polar renal parenchyma. Renal artery and vein are patent. There is no calculus or back pressure change. There is urothelial thickening involving renal pelvi-calyceal system.

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Initial ultrasound shows right pyelonephritis. 10th day follow-up ultrasound shows a complication - renal abscess.

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Research Article

The effect of real-time EF automatic tool on cardiac ultrasound performance among medical students

Roles Conceptualization, Data curation, Investigation, Methodology, Project administration, Writing – original draft, Writing – review & editing

* E-mail: [email protected]

Affiliation Joyce and Irving Goldman Medical School, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel

Roles Conceptualization, Formal analysis, Investigation, Methodology, Software, Writing – original draft, Writing – review & editing

Affiliations Joyce and Irving Goldman Medical School, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Clinical Research Center, Soroka University Medical Center and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel

Roles Conceptualization, Data curation, Investigation

Roles Project administration, Writing – review & editing

Affiliations Joyce and Irving Goldman Medical School, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Clinical Research Center, Soroka University Medical Center and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Department of Epidemiology, Biostatistics and Community Health, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva, Israel

Roles Writing – original draft, Writing – review & editing

Affiliation Medical School for International Health in Beer-Sheva, Beer-Sheva, Israel

Roles Project administration, Resources

Affiliation Department of Emergency Medicine, Ben Gurion University of the Negev in Beer- Sheva, Israel

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Resources, Supervision, Writing – original draft, Writing – review & editing

Affiliations Clinical Research Center, Soroka University Medical Center and Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel, Department of Epidemiology, Biostatistics and Community Health, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva, Israel, Medical Intensive Care Unit, Soroka University Medical Center, Beer-Sheva, Israel

• Noam Aronovitz, 
• Itai Hazan, 
• Roni Jedwab, 
• Itamar Ben Shitrit, 
• Anna Quinn, 
• Oren Wacht, 

• Published: March 28, 2024
• https://doi.org/10.1371/journal.pone.0299461
• Peer Review
• Reader Comments

Point-of-care ultrasound (POCUS) is a sensitive, safe, and efficient tool used in many clinical settings and is an essential part of medical education in the United States. Numerous studies present improved diagnostic performances and positive clinical outcomes among POCUS users. However, others stress the degree to which the modality is user-dependent, rendering high-quality POCUS training necessary in medical education. In this study, the authors aimed to investigate the potential of an artificial intelligence (AI) based quality indicator tool as a teaching device for cardiac POCUS performance.

The authors integrated the quality indicator tool into the pre-clinical cardiac ultrasound course for 4th-year medical students and analyzed their performances. The analysis included 60 students who were assigned to one of two groups as follows: the intervention group using the AI-based quality indicator tool and the control group. Quality indicator users utilized the tool during both the course and the final test. At the end of the course, the authors tested the standard echocardiographic views, and an experienced clinician blindly graded the recorded clips. Results were analyzed and compared between the groups.

The results showed an advantage in quality indictor users’ median overall scores (P = 0.002) with a relative risk of 2.3 (95% CI: 1.10, 4.93, P = 0.03) for obtaining correct cardiac views. In addition, quality indicator users also had a statistically significant advantage in the overall image quality in various cardiac views.

Conclusions

The AI-based quality indicator improved cardiac ultrasound performances among medical students who were trained with it compared to the control group, even in cardiac views in which the indicator was inactive. Performance scores, as well as image quality, were better in the AI-based group. Such tools can potentially enhance ultrasound training, warranting the expansion of the application to more views and prompting further studies on long-term learning effects.

Citation: Aronovitz N, Hazan I, Jedwab R, Ben Shitrit I, Quinn A, Wacht O, et al. (2024) The effect of real-time EF automatic tool on cardiac ultrasound performance among medical students. PLoS ONE 19(3): e0299461. https://doi.org/10.1371/journal.pone.0299461

Editor: Antoine Fakhry AbdelMassih, Cairo University Kasr Alainy Faculty of Medicine, EGYPT

Received: July 30, 2023; Accepted: February 9, 2024; Published: March 28, 2024

Copyright: © 2024 Aronovitz et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The minimal data set file we uploaded contains all the data we based our analysis on. The files including the actual POCUS clips cannot be shared publicly as initial ethical permission is now outdated, and also because permission was not granted a-priori. Attached, are the credentials and contact information for the chairman of the ethics committee: Abed N. Azab, Ph.D. Associate Professor of Clinical Pharmacology Head of the Ethics Review Board, Faculty of Health Sciences Recanati School for Community Health Professions Faculty of Health Sciences Ben-Gurion University of the Negev P.O.B 653, Beer-Sheva 84105, Israel Phone: (972)-86479880; Fax: (972)-86477683 Email: [email protected] , [email protected] .

Funding: GE Healthcare© provided the POCUS devices used in this study. Lior Fuchs declares that he works as a consultant for GE Healthcare©. However, it's important to note that GE Healthcare© provided support solely in the form of lending the POCUS systems for the research. They did not play any additional roles in the study design, data collection and analysis, decision to publish, or manuscript preparation. The specific roles of Lior Fuchs are detailed in the 'author contributions' section. It's worth highlighting that this research was conducted independently and not in his capacity as a consultant for GE Healthcare©. Additionally, Lior Fuchs did not receive any financial support or salary from GE Healthcare© for the work he contributed to this research.

Competing interests: I have reviewed the journal’s policy, and the authors of this manuscript have the following competing interests: GE Healthcare© provided the POCUS devices used in this study. Lior Fuchs declares that he is a consultant for GE Healthcare. However, it’s important to note that the company had no access to the idea, to the study’s primary objective, nor to its design, data analysis, or writing. This affiliation does not affect our adherence to PLOS ONE policies regarding data and material sharing. The remaining authors declare that they have no competing interests.

Introduction

Ultrasound imaging is a sensitive, safe, low-cost, and non-invasive tool. Ultrasound devices are more portable due to technological advances, becoming ubiquitous in different clinical settings outside the services of traditionally trained medical imaging specialists. Point-of-care ultrasound (POCUS) is the use of portable ultrasound devices at the bedside by non-radiologists [ 1 ].

Recent studies established the importance of integrating POCUS in bedside physical exams [ 2 – 4 ]. POCUS utilization includes cardiac function evaluation, shock diagnosis and management, image-guided procedures, and many other applications. It enhances internal medicine residents’ skills, as reflected in research covering diagnostic assessment of left ventricle (LV) function, valve diseases, and LV hypertrophy [ 5 ]. A randomized controlled trial showed that early POCUS exams in patients with chest pain and dyspnea reduced time for initiation of appropriate treatments [ 6 ].

The improved diagnostic performance and the positive clinical outcomes attributed to POCUS use, highlight the importance of its integration into medical education [ 7 ]. Most American medical school curricula now integrate ultrasound training [ 3 , 8 ]. However, its highly operator-dependent modality requiring experience creates potential difficulty when implementing ultrasound training, especially for POCUS.

A study reviewing the POCUS-guided diagnosis of aortic aneurysms by emergency department physicians showed markedly varied results correlating with user experience [ 9 ]. An Australian study presented a distinct correlation between user experience and interobserver agreement with expert echocardiographers in transthoracic hemodynamic POCUS evaluation [ 10 ]. Both examples show how essential POCUS integration in medical training is for novice users to gain experience.

Despite the advantages mentioned, POCUS is not yet sufficiently utilized in many clinical settings. One American study conducted in 2020 surveyed POCUS use in all Veterans Affairs medical centers. It showed that the number of physicians using POCUS has not changed significantly between 2015 and 2020 despite the availability of equipment [ 11 ]. The low utilization rates among experienced physicians and the limited experience of novice clinicians underscore the importance of integrating high-quality POCUS training early in medical education as well as implementing a feedback system independent of the user’s personal experience. To address this gap, it is crucial to focus on enhancing technological solutions, supporting inexperienced users in their clinical practices, and developing efficient training methods. In our study, we aimed to evaluate the effectiveness of one such technological solution, the artificial intelligence (AI) quality indicator tool, by assessing the cardiac ultrasound performance of inexperienced POCUS users in both intervention and control groups.

Some POCUS device manufacturers have already added automatic AI-based tools to enhance the performance and imaging abilities of novice and experienced users alike. These companies include but are not limited to Phillips, GE Healthcare, DiA, Pulsnmore, Kosmos, Ultrasight, and Caption Health. The Real-Time quality indicator is part of the Real-Time Ejection Fraction (EF) tool (by GE Healthcare, Venue POCUS family system) designed to execute automated calculations of EF values in the apical 4-chamber position. The tool provides live quality feedback of the apical 4-chamber image through a superimposed colored left ventricular contour line (red—poor, yellow—moderate, or green–good). The quality is based on AI analysis of image quality ( Fig 1 ).

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

Quality indicator contour lines in green, yellow and red, correspond with good, medium and bad quality apical 4 chamber positioning. Republished from [ 12 ] under a CC BY license, with permission from GE HealthCare, original copyright 2021.

https://doi.org/10.1371/journal.pone.0299461.g001

In our study, we aimed to address the shortage of experienced POCUS operators among medical school graduates. Considering previous research indicating that students often struggle with apical cardiac views [ 11 ], we hypothesized that an AI-based quality indicator tool, specifically designed for apical 4- and 5-chamber views, could serve as an effective teaching aid, to improve the cardiac ultrasound skills of novice operators. Our study was designed to compare the success rates and quality of apical views, as well as other cardiac views, between students using the AI-based tool and those using the standard POCUS device, in order to test the added value of integrating such tools in medical education and clinical work.

This is a prospective randomized controlled study in medical education, where the reader of the ultrasound test results was blinded to the study groups.

Study population

The study was conducted at Ben-Gurion University during the pre-clinical cardiac ultrasound course, specifically involving 4 th -year medical students in a 6-year program. Recruitment for this study took place on January 22nd, 2022. The possibility to participate was offered to all students who were enrolled in the POCUS course (a mandatory course in the curriculum). Exclusion criteria included previous POCUS experience or training, failure to sign informed consent and failure to observe group allocation during the training. Further exclusion criteria were applied during data processing after the 6-minute exam was conducted, as specified in the results section. Participating students filled out a personal questionnaire (see full questionnaire, S1 Appendix ) and signed an informed consent form permitting the use of the data collected in the study for research purposes only. The questionnaire included personal and demographic details, extracurricular POCUS training hours, and thoracic anatomy knowledge reflected by the grade received in an academic course. The study was approved by the ethics committee of Ben-Gurion University Faculty of Health Sciences study. ID– 36–2021, November 28, 2021.

Students were divided into 4- to 6-member training groups. In the first training session, we randomly assigned these groups to one of two POCUS training methods. The first group utilized the AI-based quality indicator tool described below (the Auto-EF tool by Venue GE Healthcare). This student group was defined as the intervention group that underwent training and testing using the quality indicator. The second group, defined as the control group, was trained with standard POCUS systems without using the quality indicator tool. Group profiles were analyzed based on demographics and other relevant variables to ensure random assignment and equal representation [ Table 1 ].

https://doi.org/10.1371/journal.pone.0299461.t001

Point of care cardiac ultrasound training course

All participants completed the same 8-hour frontal POCUS course, comprised of two 4-hour sessions focused on obtaining basic transthoracic cardiac views. The first covered basic principles of cardiac ultrasound imaging, sonographic heart anatomy, and common pathologies. The second included hands-on training focused on acquiring various cardiac views. Students were allocated randomly to one of the study groups: the AI-based quality indicating tool and the non-AI group. Apart from using the quality indicator when practicing the apical 4- and 5-chamber views, both groups underwent identical hands-on training courses, including 4 hours of bedside teaching by experienced POCUS instructors. After the formal training hours, the students had access to the POCUS training lab which held ultrasound devices with and without the AI-based tool according to their study group. A healthy model was used during the course’s hands-on, bedside teaching sessions, as well as during the exam.

The AI quality indicator tool

The AI-based quality indicator tool provides real-time, three scale feedback on the quality of the apical 4-chamber image. This tool is part of the automatic EF tool. It presents the user with an LV endocardial border contour line that appears when the AI tool recognizes the apical 4- or 5-chamber views ( Fig 1 ). The contour line can appear in green (best quality), yellow (medium quality), or red (unrecognized structures), according to the image quality determined by the AI algorithm. The algorithm analyzes real-time image quality, anatomical landmark identification, and EF result consistency ( Fig 1 ). As mentioned, the intervention group used the tool during the course, additional training time, and exam. The control group did not use the tool at any point. All students were encouraged to practice outside the eight-hours course but were not mandated to do so. Students were required to document any extra practice hours for later analyses and comparisons between the groups.

The six-minute exam

At the end of the course, we evaluated the students’ POCUS handling skills with the previously established six-minute exam (see exam scoring criteria, S2 Appendix ) [ 11 ]. This exam evaluates skills in obtaining key transthoracic cardiac views. The exam required students from both groups to acquire and store images of identical cardiac views.

Experienced POCUS instructors supervised the exam. Each student had 6 minutes to obtain clips with the POCUS device in a predetermined order of the following views: parasternal long axis; parasternal short axis including aortic valve (AV), mitral valve (MV), and mid-papillary level; apical 4-chamber; apical 5-chamber; apical 2-chamber; subcostal long axis and the inferior vena cava (IVC). All recorded clips were digitally stored for analysis.

After data collection was completed, the blinded review of the clips began. Clips were scrambled, and when reviewed, the quality indicator marker was removed to prevent the identification of the study group by the reviewer. A senior intensive care physician with over ten years of cardiac ultrasound experience performed a blinded rating of clip quality (grading anatomical landmarks acquisition and image quality). The exam score was based on a checklist of anatomical landmarks depicted in each echocardiographic view for a total of 31 points with one point per landmark (see scoring criteria in the exam, S2 Appendix ). Models passed a pretest screening for approval of the cardiac sonographic windows to reduce a bias of models’ anatomical differences.

Additionally, we added another assessment criterion: the image quality score. This was a subjective criterion graded by the senior physician who blindly reviewed and graded all clips based on clinical experience and without restriction to specific landmarks. Overall scan quality scores were given as follows: 0—impossible to ascertain; 1- medium quality, readable image; and 2- good or excellent image.

Statistical analysis

We compared the intervention and control groups’ scores, using non-parametric Mann-Whitney U tests to determine significant differences. We analyzed specific views and quality assessments using t-tests and chi-square tests as appropriate. A Poisson regression analysis assessed the relative risk of achieving a higher than the median score, adjusting for relevant covariates. Furthermore, we calculated Cohen’s D to measure the effect size, providing us with a standardized measure of the magnitude of the observed effects and aiding in interpreting the practical significance of our findings. All analyses were performed using R software version 4.0.2 (R Foundation for Statistical Computing, https://www.R-project.org/ ). We considered P values < 0.05 as statistically significant. Subgroup analyses were performed for gender, ethnicity, age, practice hours, and anatomy exams using the same tests and models.

A total of 100 students participated in the ultrasound training with 40 excluded from our study. Students were excluded if they did not sign the informed consent (n = 4), did not follow group allocation (n = 5), exceeded the 6-minute time limit (n = 15), scored below 15/31 points (n = 7), or a combination of these (n = 7). Details of exclusion according to group allocation are seen in Fig 2 . We added the total score exclusion criterion since it was difficult to ascertain which views they attempted to achieve, rendering the data collected impossible to use. This was the case with 3/33 (9%) of the intervention group students and 11/63 (17.5%) of the control group students. There were no significant differences between the study groups in basic demographic parameters such as sex, age, ethnic background, anatomy exam score, and additional practice hours [ Table 1 ].

https://doi.org/10.1371/journal.pone.0299461.g002

Total score

We found a significant difference between the groups in the total exam score. The intervention group had a median score of 26/31 (83.9%) as compared to 22/31 (71%) in the control group (P = 0.002). Cohen’s D for the difference in total exam score between the groups was 0.890 [ Table 2 ].

https://doi.org/10.1371/journal.pone.0299461.t002

Specific view scores

There were two specific views with significantly different student scores. The first was the parasternal long-axis view with a mean score of 3.48/4 in the intervention group and 2.77/4 in the control group (P = 0.01). Cohen’s D for the difference in the long axis mean score between the groups was 0.536. In this view, the AI-based quality indicator does not function. Median scores were 4 and 3, respectively [ Table 1 ]. The second was the apical 5-chamber view, where the AI-based quality indicator does function, with a mean score of 5.33/6 in the intervention group and 4.21/6 in the control group (P = 0.03) [ Table 2 ]. Cohen’s D for the difference in the apical 5-chamber mean score between the groups was 0.634. In both parasternal long and apical 5-chamber views, all landmarks received higher success rates in the intervention group. The intervention group exhibited a trend of higher performance scores in most other cardiac windows but without statistical significance. In parasternal short views, the mean scores for the intervention and control group were as follows: aortic valve level view 3.05/4 and 2.54/4, respectively (P = 0.13); mitral valve level view 1.48/2 and 1.68/2, respectively (P = 0.4); and mid-papillary level view 1.33/2 for both groups (P>0.9) [ Table 1 ]. Subcostal view mean scores were 2.71/3 and 2.41/3, respectively (P = 0.3); and IVC view mean scores were 1.76/2 and 1.44/2 (P = 0.09). Interestingly, we found no statistically significant differences between the groups in the apical 4-chamber view in which together with apical 5 chamber, the AI tool was designed to function. The mean scores were almost identical, 4.43/5 and 4.44/5 in the intervention and control groups, respectively (P = 0.8).

Quality assessment scores

Blinded overall scan quality assessment scores generated significant differences in favor of the AI-based tool in various cardiac views. Quality indicator users achieved a higher score in the parasternal long axis (P = 0.002), apical 4-chamber (P = 0.003), apical 5-chamber (P = 0.003), subcostal (P = 0.04), and IVC (P = 0.02) views [ Table 3 ]. Cohen’s D for the difference in the quality assessment score between the groups was 0.815 for parasternal long axis, 0.840 for apical 4-chamber, 0.850 for apical 5-chamber, 0.594 in subcostal, and 0.631 for IVC view. We found insignificant differences in the parasternal short aortic valve level (P = 0.1), mid-papillary level (P>0.9), mitral valve level (P>0.9), and apical 2-chamber (P = 0.2) [ Table 3 ].

https://doi.org/10.1371/journal.pone.0299461.t003

The utilization of the automatic tool during the cardiac study did not prolong the scanning time for the clip it was applied to. There was no significant difference in the time required for apical 4-chamber acquisition (measured as the time elapsed between the last clip prior to the apical 4-chamber clip and the time of the optimal apical 4-chamber clip) (P = 0.6). The total test time of the study groups was equal.

Subgroup analysis

We conducted subgroup analyses comparing exam scores and image quality in subgroups based on gender, ethnicity, age, and anatomy exam. We also tested the extracurricular training by students as a covariate for better performance and found it to be equally distributed between the two study groups ( Table 1 ). Our analysis did not reveal any statistically significant differences between the two groups, leaving the automatic tool as the only significant factor that can explain score differences.

Multivariate analysis

The Poisson regression analysis showed that quality indicator users had a relative risk of 2.3 (95% CI: 1.10, 4.93, P = 0.03) for receiving an overall score higher than the median score of 23 compared to the control group.

6-minute exam

The overall 6-minute exam score showed a significant advantage for the intervention group. This general improvement can be broken down into the direct effect of the quality indicator demarcation seen in apical 4- and 5-chamber views and the indirect effect when the quality indicator demarcation was absent in other views. Furthermore, the quality of cardiac views, the anatomical landmarks acquired, and the acquired image quality received significantly higher scores among the intervention compared to control students in most cardiac views, even in cardiac views where the quality indicator demarcation is not active [ Table 3 ].

Nevertheless, although the quality indicator was designed for the apical 4-chamber view, the mean score in this view was not significantly higher in the intervention group. However, the apical 5-chamber, also a compatible view for the tool, received significantly higher scores among the intervention group. A more thorough investigation revealed that the control group lost points during the transition from apical 4-chamber view to apical 5-chamber (worsening LV imaging from 38 (97%) successful depictions to 30 (77%), RV from 33 (85%) to 27 (69%), MV from 39 (100%) to 32 (82%), tricuspid valve (TV) from 30 (77%) to 19 (49%), and atria from 33 (85%) to 27 (69%), respectively). In contrast to the control, the intervention group revealed identical or improved success rates of demonstrating cardiac structures when shifting from apical 4-chamber to apical 5-chamber (RV from 17 (81%) to 18 (86%), MV at 20 (95%) for both, TV at 16 (76%) for both, and atria from 18 (86%) to 19 (90%), respectively) [ Table 2 ].

These results suggest that the quality indicator may assist in maintaining the cardiac landmarks shared by both views when the operator shifts from the apical 4- to 5-chamber view. This may be due to an advantageous probe positioning in the apical 4-chamber view while preparing to shift to apical 5-chamber. It is also possible that the quality indicator helped maintain the proper apical 5-chamber view landmarks despite the more complex positioning when presenting the aortic valve.

In most views other than the apical 4- and 5-chamber, the intervention group had higher mean scores than the control group, despite the tool not being active. These included the parasternal-long axis, parasternal short axis base, apical 2-chamber, subcostal, and IVC presenting views [ Table 1 ]. The parasternal long axis is the only view with a statistically significant improvement. However, the overall mean test score was significantly higher for the intervention group, further supporting the generalized improvement in sonography skills.

Subgroup analysis results had no significant difference in exam scores between groups based on gender, ethnicity, age, self-practice hours outside of the course, and anatomy exam scores.

Our multivariate analysis, however, showed a relative risk of 2.3 (95% CI: 1.10, 4.93, P = 0.03) for higher than the median scores compared to the control group, adjusting for age and sex. This indicates that quality indicator use was associated with a significantly greater likelihood of obtaining a higher general score, attributing the difference between the group scores to the quality indicator.

Quality assessment

We compared the quality of the cardiac images with the help of an independent, experienced clinician blinded to the study group. The blinding was done by removing the automatic EF LV demarcation line to prevent identification of quality indicator use. Unlike in the standardized 6-minute exam scoring, the clinician based it on his general impression, making it potentially the most difficult factor to predict in relation to the quality indicator. The intervention group achieved significant improvement in image quality compared to the control group. In 5 of 9 views, quality indicator users had statistically significant higher image quality grades. The advantageous views included apical 4- and 5-chamber, parasternal long, subcostal, and IVC views. Our explanation for the improved image quality, even in the views without the quality indicator use, is that it assists the users on several levels. First is gaining a better sense of the correct pressure applied on the probe for optimizing image quality. Second is the familiarity with the proper representation of the cardiac images, exposing them to better image standards that later helped them acquire more explicit images in the tool-free cardiac views. Additional factors may be that rather than identifying the correct general positioning and moving on, students using the quality indicator learn to take their time until optimizing the image. This could be done by optimizing patient positioning, adding ultrasound gel etc. This habit will more likely be acquired when receiving repeated feedback requiring quality improvement and landmark depiction. This can also be seen in the time students required for image acquisition, which although not statistically significant, was longer in the intervention group than the control group (1.04 and 0.79 minutes respectively, P = 0.6) [ Table 2 ]. An additional factor which may have had an effect is the fact that the intervention group had a higher number of extracurricular training hours [ Table 1 ]. However, this difference was statistically insignificant, and likely a less probable explanation.

Subgroup analysis did not show a significant difference in image quality scores between groups based on gender, ethnicity, age, practice hours, and anatomy exam scores, supporting the attribution of the improved score to the quality indicator.

These findings suggest a general effect of improved image acquisition that is not limited to the direct effect of the quality indicator demarcation. Previous studies on AI-assisted echocardiography often focused on software used for retrospective image analysis rather than real-time image acquisition and quality improvement [ 13 – 16 ]. In studies where image acquisition was tested, the focus was on comparing novice users to experienced clinicians [ 9 , 10 , 16 ]. Unlike previous studies, this study takes the assisting technology to the realm of medical education, comparing traditional learning methods with a new, real-time, AI-assisted tool. Our research suggests that real-time based feedback for cardiac ultrasound image quality improves image accuracy and quality among inexperienced users. As cardiac POCUS becomes an integral part of the standard physical examination, the demand for higher proficiency will enhance the need and development of such learning tools that enable novice operators to perform high-quality POCUS examinations.

Our research reinforces the established notion that interactive AI-based feedback tools can enhance POCUS performance, particularly in pulmonary and cardiovascular assessments [ 17 , 18 ]. Our study demonstrates that incorporating AI live feedback tools during cardiac POCUS training can significantly enhance training efficiency and outcomes among medical students.

We believe the implications of our findings are twofold: first, in training for quality control, establishing professional standards for student training; and second, in the clinical field, as previous research shows that POCUS integrated automated AI tool integration can support and validate clinical decision-making, particularly among less experienced users [ 19 ]. Regarding the cardiac ultrasound applications explored in this study, we advocate for the integration of these tools into new POCUS systems and in student POCUS training programs. They prove invaluable in helping novice users optimize their imaging capabilities and further enhance the skills of experienced operators. Importantly, our findings indicate that the use of AI-based quality indicator tools did not significantly prolong the time required for image acquisition.

Limitations

Our research has several limitations. The first and perhaps the most significant is that the 6-minute cardiac ultrasound competency exam took place immediately after a brief academic course. This is important as long-term differences (weeks or months after the course rather than days) between the groups are crucial in estimating effective medical education. Another significant limitation is the exclusion of over one-third of the participants from the study that could have caused a selection bias. It is important to stress that this exclusion was due to several reasons, as detailed in the results section. Criteria such as exceeding the time limit made the results incomparable to other users because time is an important factor in the exam, and the exclusion of students who scored ≤15 points was required because these students also had unclear images in their files, to such an extent that it was impossible to ascertain which views they were attempting to capture. Importantly, the excluded students were relatively equally divided between the two groups ( Fig 2 ). Additionally, we tested the intervention group while using the quality indicator. This fact precludes our reporting on whether the tool improved performance in the intervention group even when not using the tool. However, for views other than the apical 4- and 5- chamber (where the tool is not active), results were better in the intervention group.

The study took place in a single university medical school, causing a possible selection bias. The sample may not represent the larger population since the medical school curriculum may differ between institutions. Thus, it may not accurately reflect the tool’s advantage in other medical schools or healthcare settings. Further studies should be conducted on the intervention group without the tool in the future and should include larger sample sizes and additional medical schools.

An AI-based quality indicator integrated into POCUS cardiac views improved the performance of cardiac ultrasound, as measured by the 6-minute exam, among recently trained students compared to students who did not use the tool. Improved scores were observed among the intervention group, even in cardiac views where the automatic tool was inactive. Such tools can assist in the learning process of cardiac ultrasound and should be integrated in new POCUS systems, in addition to expanding their repertoire to include more cardiac views. Further studies should be conducted to estimate their long-term effects on learning.

Supporting information

S1 appendix. research questionnaire..

https://doi.org/10.1371/journal.pone.0299461.s001

S2 Appendix. 6-Minute exam scoring.

https://doi.org/10.1371/journal.pone.0299461.s002

S1 Data set.

https://doi.org/10.1371/journal.pone.0299461.s003

Acknowledgments

This research is part of the qualification requirements for M.D. approval at the Joyce & Irving Goldman Medical School at the Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel.

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• Should all patients with polymyalgia rheumatica have a vascular ultrasound assessment?
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• http://orcid.org/0000-0002-7788-8322 Sharon Cowley 1 , 2 ,
• Patricia Harkins 2 , 3 ,
• Colm Kirby 1 ,
• http://orcid.org/0000-0003-2538-3362 Richard Conway 3 ,
• David J Kane 1 , 2
• 1 Department of Rheumatology , Tallaght University Hospital , Dublin , Ireland
• 2 Trinity College Dublin , Dublin , Ireland
• 3 Department of Rheumatology , St James Hospital , Dublin , Ireland
• Correspondence to Dr Sharon Cowley, Department of Rheumatology, Tallaght University Hospital, Dublin, Ireland; sharoncowley111{at}gmail.com

There is a growing appreciation that both giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are closely interrelated conditions that have significant overlap in aetiology, clinical characteristics and treatment regimens. Subclinical GCA in PMR is becoming increasingly recognised, and there is evolving evidence that this may be a more aggressive disease phenotype than PMR. Ultrasound (US) lends itself well as a screening tool for GCA in PMR; it is inexpensive, non-invasive, widely available, lacks ionising radiation, may be performed at the bedside and is recommended by EULAR as a first-line investigation for suspected GCA. There is insufficient evidence to currently recommend that all patients with PMR should have a US assessment for vascular involvement. However, as clinical and laboratory parameters alone do not accurately diagnose patients with subclinical GCA, we suggest that vascular US will be increasingly performed by rheumatologists in practice to identify these patients with PMR, preferably as part of larger prospective outcome studies.

• Polymyalgia Rheumatica
• Giant Cell Arteritis
• Ultrasonography

https://doi.org/10.1136/ard-2024-225650

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Introduction

Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are closely interrelated conditions in a common spectrum of inflammatory diseases. Their clinical, epidemiological and immunological overlay has been recently described as GCA-PMR spectrum disease (GPSD). 1 Both diseases can occur separately, simultaneously or in a sequential fashion. Both PMR and GCA are characterised by systemic inflammation, have a predominant interleukin (IL)-6 signature, have evidence of a common pathogenic role of IL-17 in vascular intima 2 and shoulder inflammation, 3 respond excellently to glucocorticoids, affect an older population and tend to relapse. 1 GCA is frequently underdiagnosed in patients with PMR and may explain some cases of glucocorticoid-resistant PMR. 4 5 The lack of evidence guiding risk stratification in GPSD at the time of diagnosis to guide a personalised treatment plan is a major unmet need. Currently, the recommendations for PMR management do not advocate for routine imaging to assess for underlying vasculitis. 6 The presence of ultrasound (US) findings consistent with GCA in patients with newly diagnosed PMR not reporting any clinical cranial GCA symptoms is well established. 7 8 A systematic review that included imaging with US, positron emission tomography (PET) and MRI concluded that more than a quarter of PMR may have subclinical GCA on imaging. 9 Recent US studies have confirmed this finding and suggested that this is a different PMR clinical phenotype, resulting in a different treatment protocol. 10 11 A prospective US study that followed patients with PMR for up to 2 years found that those with US-identified subclinical GCA in PMR were almost four times more likely to relapse compared with isolated PMR. 12 This has raised valid questions about whether rheumatologists should now include vascular imaging in management protocols for PMR to assess for vasculitis to accurately assess risk stratification, guide therapy and optimise patient outcomes.

The recent EULAR imaging guidelines in large vessel vasculitis recommend the US of temporal and axillary arteries to be considered as the first imaging modality to investigate mural inflammatory changes in patients with suspected GCA. 13 US has been shown to have high diagnostic validity, is radiation-free, highly patient-acceptable, widely available and inexpensive. Furthermore, the reliability of findings is high among trained experts and is comparable to that of biopsy readings by pathologists. 14 Professional US practice requires reliable training, sufficient experience, clinician accreditation and adequate equipment to be implemented correctly. The presence of a ‘halo’ on the US, present in GCA, is morphologically defined as a dark hypoechoic ring area around the vessel lumen, which is suggestive of oedema from transmural inflammation. Measurement of the intima-media thickness (IMT) and assessment of vessel compressibility, stenosis and occlusion can also be quantified on US. Axillary arteries can also be measured for thickened IMT, may demonstrate a ‘slope sign’ distinct from atherosclerosis with a smooth thickening continuous up to a transitional point where the IMT gradually slopes downwards back to a normal level 15 and may have visible stenosis or occlusion. The halo score has been developed to quantify the extent of vascular inflammation in GCA. It is based on percentiles of halo thickness, correlates with C reactive protein (CRP) and is shown to be associated with a higher risk of ocular ischaemia. 16 Outcome Measures in Rheumatology (OMERACT) has also defined an ultrasonography score for monitoring disease activity in GCA. 17 This score may be used as a monitoring tool and outcome measure in research, particularly in clinical trials. These tools are an exciting development in GCA and have the potential to stratify patients for personalised treatment and provide objective target organ monitoring during follow-up.

Vascular US studies in PMR

Vascular screening of patients with PMR is not a new concept, with the earliest studies looking at the prevalence of US features of vasculitis in PMR at the time of diagnosis completed over 20 years ago. 7 8 Combined, these studies assessed 110 patients and found a prevalence of 7.3% (eight patients) for subclinical GCA. Biopsies were performed on all US-positive patients (eight) and showed a 50% positivity rate for features of GCA. Among those with a negative biopsy (four), three patients did not have the US-identified positive branch with a halo sign sampled due to anatomical reasons and fear of resultant complications. One further patient had stenosis of the common temporal branch seen on biopsy, which may represent either atherosclerosis or inflammation. It is worth noting that a 3% stenosis rate was seen among their normal controls. Axillary or other vascular territories were not investigated in these earlier studies, which may explain the low incidence rate of US-identified subclinical GCA. In addition, US technology had significantly lower image quality 20 years ago.

There has been significant evolution in US technology and vascular imaging definition in recent years. Vascular scanning techniques for GCA diagnosis have been optimised and standardised, 18 along with the development and validation of a US scoring system by OMERACT for monitoring vascular activity in GCA. 17 These advances have led to two robust studies, which were published in 2023 with a combined population of over 400 patients with PMR. 10 11 Both studies prospectively examined consecutively enrolled patients with newly diagnosed PMR without any clinical symptoms of cranial GCA. An almost identical incidence of subclinical GCA was identified in both studies, at 22% and 22.8%, respectively. This represents a much higher positivity rate than previous studies, which may be explained by the inclusion of more vascular territories. There was a high predilection for the extracranial vessels, with over three-quarters of patients in each study exhibiting axillary involvement. These more recent studies have also provided more clinical information on patients with PMR with subclinical GCA. Older age at the time of diagnosis and higher incidence of hip girdle symptoms were more frequently reported in the subclinical GCA group compared with those with pure PMR. 10 11 CRP levels were significantly higher in the subclinical GCA group in Burg et al ’s study, but this finding was not upheld in De Miguel’s larger multicentre study. The sensitivity and specificity of these clinical and laboratory features for the differentiation of subclinical GCA in PMR from isolated PMR were low by comparison with US, which is a more accurate differentiator than relying solely on clinical characteristics ( table 1 ).

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Summary of vascular US in PMR studies

Crucial is longer-term follow-up of patients with subclinical GCA in PMR to determine their clinical course, including risk of relapse, rate of progression to GCA, corticosteroid burden and resultant morbidity. To date, there has only been one follow-up study that has reported on the outcomes of subclinical GCA in PMR, with a median follow-up of 22 months from the time US-identified subclinical GCA was observed. 12 150 patients were included, and it was shown that patients with subclinical GCA in PMR were four times more likely to relapse compared with those with PMR. Interestingly, all relapses, apart from one patient, were minor as classified by EULAR 19 without clinical features of ischaemia, aortic or large vessel dilatation, stenosis or occlusion. This higher relapse rate was observed despite those with subclinical GCA being treated with an initial higher glucocorticoid taper (36.6 mg vs 19.8 mg daily of prednisone, p<0.001). 12 An increased requirement for second-line therapies in the subclinical GCA subgroup was also observed, with methotrexate as the most prescribed treatment. It appears from this study that subclinical GCA in PMR has a more severe phenotype than seen in those with PMR ( table 2 ).

Summary of clinical characteristics of patients with US-detected subclinical GCA

Imaging currently plays a major role in the diagnosis of GCA and has an evolving role in PMR. US vascular imaging is an attractive prospect as it has already been implemented as a recommended first-line investigation for GCA, 13 with many centres having established referral pathways. It also has the potential to be incorporated into a fast-track PMR clinic model, as it can be rapidly performed in an outpatient setting, and recent guidelines have advocated for early specialist input in PMR. 20 US requires a trained specialist using appropriate equipment with standardised operational procedures and settings, which requires adequate funding, training time and proficiency. Incorporation of US vascular screening of patients with PMR in an early specialist referral pathway is not currently recommended, but recent studies increasing our understanding of PMR may pave the way for future recommendations in distinct patients with PMR. Given the high disease burden of PMR in the community, targeted screening will likely be most appropriate to ensure equitable use of time and resources in fast-track PMR clinics.

Emerging evidence shows a high prevalence of subclinical GCA in PMR, affecting up to one in four patients. Indeed, this may be a biased estimation, as only a minority of patients with PMR are referred to secondary care currently, with responders to standard glucocorticoid taper being treated in the community. Conversely, it is unknown if there are missed cases affecting large vessels such as the aorta, which is more difficult to assess in its entirety with US alone. A community-based study that recruited patients from primary care regardless of PMR severity reported a lower prevalence of subclinical GCA in PMR at 17.5%. 21 Vascular US has a superior ability to risk stratify patients with PMR when implemented in addition to clinical history, examination and laboratory investigations. It also appears to correlate well with PET studies. US studies have identified that patients with an older age at diagnosis, reporting an increased frequency of hip or pelvic girdle pain and stiffness, are more at risk of having subclinical GCA in PMR. 11 Positive PET/CT studies have also found that patients with PMR with diffuse bilateral lower limb pain, pelvic girdle pain and lower back pain are positive predictors of vascular involvement in this cohort. 22 Whether there is a role for vascular US interrogation in relapsing or glucocorticoid-refractory PMR remains to be elucidated. These patients have more asthenia, weight loss and fever than those with pure PMR, 23 although this cohort requires more studies to determine the prevalence of vascular involvement.

The medium-term clinical outcome of patients with US-identified subclinical GCA in PMR appears to follow a more severe phenotype with an increased rate of relapse and a higher requirement for glucocorticoids and other disease-modifying treatments. 12 Clinicians may have the most yield from scanning patients with PMR that have predominant hip or pelvic girdle pain (which may represent limb claudication), back pain (which can be a manifestation of aortitis), constitutional symptoms (including fever, night sweats, weight loss and/or anaemia), those with very high ESR/CRP at the outset and patients with poor response to initial PMR dose glucocorticoids. Those with relapsing PMR may also benefit from vascular imaging, particularly if these manifestations are also present. It remains unclear how to manage patients with US-identified vascular changes without profound clinical symptoms, as there are currently no longer-term studies on the impact of subclinical GCA on the prognosis of patients with PMR. There are also no consensus recommendations for either routine or targeted vascular screening of patients with PMR. Similarly, there are no studies to determine the minimum glucocorticoid dose to effectively treat PMR both with and without subclinical vasculitis. We believe those who relapse on higher glucocorticoid doses (≥10 mg) with subclinical vasculitis should be given consideration for the early introduction of a steroid-sparing agent. While the vascular US of all patients with PMR is enticing, given the potentially high yield of positive cases, it is clear that further retrospective and prospective international multicentre studies are needed to identify patients most appropriate for screening. Some such studies are underway, and interim findings suggest male patients with a higher ESR at baseline are most likely to have US findings of subclinical vasculitis. 21 We advocate that rheumatology centres that have both the technology and the clinician sonographers should consider including it in the initial assessment of PMR and, preferably, as part of prospective outcome studies. We acknowledge that long-term studies delineating the natural history of PMR and subclinical GCA are required to establish the optimal therapy and cost-effectiveness of this approach.

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Handling editor Josef S Smolen

Contributors SC is the main author of the article, writing the first draft and making corrections based on co-author feedback. PH, CK, RC and DJK were involved in drafting the manuscript and approving the final version.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests SC: grant support from Novatris, speaker honoria from Janssen and conference attendance support from Abbvie, Janssen and Novartis. CK: conference attendance support from Novartis. PH: grant support from Janssen and Novartis and conference attendance support from Abbvie and Novartis. RC: grant support from Janssen and Novartis and consulting fees/speaker fees from Janssen, Abbvie, Fresenius Kabi, Galapagos, UCB, Viatris, Celltrion, Nordic Pharma and Novartis. DJK: grant support from Novartis and conference attendance support from Abbvie.

Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

Provenance and peer review Not commissioned; externally peer reviewed.

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Ultrasonic imaging: safety considerations

Modern ultrasound imaging for diagnostic purposes has a wide range of applications. It is used in obstetrics to monitor the progress of pregnancy, in oncology to visualize tumours and their response to treatment, and, in cardiology, contrast-enhanced studies are used to investigate heart function and physiology. An increasing use of diagnostic ultrasound is to provide the first photograph for baby's album—in the form of a souvenir or keepsake scan that might be taken as part of a routine investigation, or during a visit to an independent high-street ‘boutique’. It is therefore important to ensure that any benefit accrued from these applications outweighs any accompanying risk, and to evaluate the existing ultrasound bio-effect and epidemiology literature with this in mind. This review considers the existing laboratory and epidemiological evidence about the safety of diagnostic ultrasound and puts it in the context of current clinical usage.

1. Introduction

Modern ultrasound imaging for diagnostic purposes has a wide range of applications. For example, it is used in obstetrics to monitor the progress of pregnancy, in oncology to visualize tumours and their response to treatment, and, in cardiology, contrast-enhanced studies are used to investigate heart function and physiology. An increasing use of diagnostic ultrasound is to provide the first photograph for baby's album—in the form of a souvenir or keepsake scan that might be taken as part of a routine investigation, or during a visit to an independent high-street ‘boutique’.

A fundamental principle of medical ethics is primum non nocere (‘first do no harm’), and this is paraphrased in the Hippocratic Oath that contains a promise to ‘abstain from doing harm’. A second principle is that a procedure can be legitimately carried out if the importance of the objective is in proportion to the risk to the subject. Only if the ratio of risk to benefit is beneficial to the subject can it be considered ethical. The assumption hitherto has always been that ultrasound scans are ‘safe’. There are a number of reasons not to be blasé about ultrasound safety. Firstly, it is well known that ultrasound can be used to produce changes in biological tissue—it is this that drives its use as a therapeutic agent, whether at low powers for physiotherapy or drug delivery, or at higher powers for cancer therapy where instantaneous cell killing is sought. Can we really be sure that the ultrasound pulsing regimes used in ultrasound imaging are not also producing biological changes that may be considered deleterious in the context of an imaging application?

Secondly, as will be seen below, while existing human epidemiological studies of the safety of ultrasound are reassuring, it must be remembered that the scans under consideration for these were all carried out using early clinical scanners, before the increase in output levels that has taken place over the last two decades.

It is important, as ultrasound imaging techniques and applications evolve and new devices become available, to be ever vigilant and to provide ongoing assessment of diagnostic ultrasound usage to ensure that its use can continue to be justified on safety grounds. In what follows, the existing knowledge about the interaction of ultrasound with tissue is reviewed in the context of the safety of ultrasound diagnosis for all applications. That of most concern is imaging of the unborn baby, but the discussion is not restricted to this use of ultrasound. The differences between imaging modes (B-mode, pulsed and colour flow Doppler) lie in the lengths of the pulses used, their repetition frequency and the pressure in the pulses [ 1 ]. The characteristics of each different mode of ultrasound imaging remain essentially the same, irrespective of the target being imaged. What matters in safety terms is the sensitivity of the tissue constituents to the thermal and mechanical effects produced. No medical procedure is completely without risk, and it should be remembered that, while we may not be able to provide evidence of harm from a technique such as ultrasound imaging, we are not able to provide proof of absence of harm—it is, to all intents and purposes, impossible to prove a negative.

2. Interaction of ultrasound with tissue

Ultrasound exposure of tissue is often described as being ‘non-invasive’. While this is correct in terms of the definition of a non-invasive procedure (one for which no break in the skin is created and there is no contact with the mucosa or internal body cavity), it must be remembered that the formation of an ultrasound image necessarily requires the exposure of regions of interest to ultrasonic energy.

As an ultrasound beam propagates through tissue, the energy reduces with depth travelled—that is, it is attenuated. Some energy is reflected by tissue structures in the beam path, and some is absorbed. The required ultrasound image is formed from the scattered energy received at the imaging probe, with the time of its arrival being a measure of the depth of the reflecting structure, and its amplitude giving information about the structure itself. The amount of energy absorbed depends on the composition of the tissue and the frequency of the ultrasound beam. Broadly, bone absorbs more ultrasound energy than soft tissue, and also reflects more strongly. Ultrasound absorption in tissue rises with increasing frequency.

In a plane wave, the relationship between the intensity incident on the surface of tissue ( I 0 ) and the intensity at a depth x into tissue ( I ( x )) may be written as

where μ , the intensity attenuation coefficient, is a sum of contributions from absorption ( μ a ) and scatter ( μ s ) such that μ = μ a + μ s . The contribution of absorption to attenuation may be 60–80% of the total [ 2 ].

The amount of energy reflected by a structure, such as bone, that lies in the ultrasound beam path is determined by the change in acoustic impedance at its surface. The acoustic impedance, Z , is given by Z = ρc , where ρ is the tissue density and c is the speed of sound. The greatest impedance mismatches in clinical ultrasound usage occur at soft tissue–bone and soft tissue–gas interfaces. These are seen as the brightest echoes on an ultrasound image.

The mechanisms of interaction of ultrasound with tissue that may lead to biological effects are often broadly divided into two categories—thermal and non-thermal. In reality, these mechanisms are inter-related since, as will be seen below, tissue heating may facilitate non-thermal effects by reducing the threshold for cavitation, and non-thermal effects such as cavitation may, in turn, affect local tissue heating. For convenience, however, these mechanisms will initially be treated separately in what follows.

2.1. Thermal effects

If there is no heat loss out of the volume by conduction, convection or radiation; this may also be written as

where ρ is the density, C is the heat capacity and d T /d t is the rate of temperature change. By combining these equations, we can get

This relationship allows us to estimate the maximum possible rate of temperature rise for different modes of ultrasound imaging. A recent survey has given the mean spatial peak temporal average intensity ( I SPTA ) as 341 mW cm −2 for B-mode imaging, as 860 mW cm −2 for pulsed Doppler and as 466 mW cm −2 for colour flow Doppler [ 3 ]. Assuming average acoustic and thermal parameters for soft tissue ( μ 0.06 neper cm −1 (0.5 dB cm −1 ) at 1 MHz, and C 4.18 J g −1 o C −1 ), the temperature rises calculated in this way are given in table 1 . Clearly, these are over estimates, as they do not account for thermal conduction, the cooling effects of blood flow, nor for movement of the transducer. Nevertheless, they show the relative heating potential of the different imaging modes. The absorption coefficient of bone is many times that of soft tissues (for example, Duck [ 2 ] gives an average value for brain of 0.6 dB cm −1 MHz −1 and for skull bone of approx. 20 dB cm −1 MHz −1 ), and so the rate of heat deposition at the bone surface is much greater. Tissues at most risk from ultrasound exposures are therefore bone and any soft tissues lying adjacent to it, and especially developing bone.

Table 1.

Estimates of rates of temperature rise in soft tissue for different imaging modes made using equation (2.3). These assume average acoustic and thermal parameters for soft tissue of absorption coefficient, μ a : 0.06 neper cm −1 (0.5 dB cm −1 ) at 1 MHz, and heat capacity, C: 4.18 J g −1 °C −1 .

The temperature rise may be limited by the cooling effects of blood flow in the exposed volume. Highly vascular organs, such as the liver and kidney, are thus more difficult to heat than bone, which is less well perfused. However, in narrow, focused beams such as those used in pulsed Doppler examinations, there is a large temperature gradient across the beam, and so thermal conduction out of the heated volume is likely to be more important than the cooling provided by blood flow [ 4 ]. The temperature rise during many diagnostic ultrasound examinations is also limited by the use of scanned beams, with any point in tissue being interrogated for only a very short time. Significantly elevated temperatures are only likely to be found when stationary beams are used, such as in M-mode, spectral Doppler studies and some colour flow imaging techniques.

The biological significance of a temperature rise depends on both its magnitude and its duration, with higher temperatures requiring shorter times to produce comparable effects. The concept of thermal dose was introduced to allow comparison of the bio-effects arising from different thermal histories. Thermal dose is defined in terms of a time that is given by the equation

where t ref , the thermal dose, is the time at a temperature T ref that will produce a thermal effect equivalent to that from a temperature T maintained for a time t [ 5 – 7 ]. R is a constant that has been shown to be 2 for T > 43°C and 4 for T < 43°C.

It is well known that temperature rises above normal core levels can be teratogenic, although there is some debate as to whether it is the temperature rise or the absolute temperature that is the most important factor in determining the biological effect [ 1 , 8 – 12 ]. There have been many laboratory studies of the effects of heat on the embryo or foetus (usually involving whole body heating), and it is the developing central nervous system that is thought to be the most sensitive to heat [ 1 , 13 , 14 ]. In addition to the rise in temperature and its duration, the stage of development is crucially important in determining the severity of effects produced. For example, mild exposures during the pre-implantation period may lead to foetal death, whereas much larger thermal doses can be tolerated after birth. The teratogenic effects of heat at different stages of development in utero have been reviewed [ 1 , 10 ], and include resorption and death during pre-implantation through abortion; neural tube, heart and vertebral defects in the early embryonic stage; and micro-encephaly, abortion and behavioural deficits in the mid-embryonic and foetal stage. However, it must be remembered that these effects have been seen following whole body heating of both the mother and the offspring, in which a slow temperature rise (approx. 0.5°C min −1 ) is obtained by warming the skin surface using either hot air or warm water. This differs from ultrasound heating in a number of important ways. In whole body heating, the slow rise in core temperature may trigger a measure of thermotolerance by synthesis of relevant heat shock proteins [ 15 ]. Ultrasound heating is very rapid ( table 1 ). In addition, ultrasound exposures in pregnancy only subject a small fraction of the maternal volume to a potential temperature rise, and thus any heating of the embryo is likely to be rapidly dissipated. Exposure of the mineralized bone in the third trimester, however, may result in a more biologically significant temperature rise.

An analysis of published data by Miller & Ziskin [ 12 ] led to the recommendation by many professional bodies that a temperature elevation of 1–1.5°C can be applied indefinitely without concern on safety grounds. This has been revised more recently, with the suggestion that ‘best estimates’ of a threshold for temperature-induced effects give approximately 1.5–2.5°C above normal body temperature held for longer than an hour [ 1 ]. For higher temperatures, the threshold for safety was set by the World Federation of Societies for Ultrasound in Medicine and Biology (WFUMB; http://www.wfumb.org/about/statements.aspx .) to be the thermal equivalent of 43°C for 75 s (a temperature rise of 4°C for 5 min). However, this first analysis, based on data from a number of different species, did not account for differing core temperatures. Church & Miller [ 9 ] have normalized the data to the animals' normal temperature. This reduced the threshold to lie at a temperature rise of 4°C maintained for 30 s.

Although safety training will exhort the ultrasound user to limit temperature during a scan, it is difficult to assess what this might be during an imaging procedure. In order to aid this assessment, the concept of thermal index (TI) has been developed (see below).

2.2. Non-thermal effects

The passage of an ultrasonic pressure wave through tissue also leads to ‘mechanical’ effects. These include acoustic cavitation and phenomena arising from radiation pressure effects, such as acoustic streaming. It is acoustic streaming that is of most concern on safety grounds.

The negative pressure in an ultrasonic pulse can draw gas out of solution in tissue. These gas bubbles grow from existing nuclei in tissue. Evidence for the existence of such nuclei comes from the development of decompression sickness in deep sea divers [ 16 ]. Once a bubble has been formed, it may expand and contract, in what are often termed breathing oscillations, in response to the pressure wave (non-inertial or stable cavitation), or, if at a size that is resonant for the drive frequency of the ultrasound beam, the bubble will expand greatly, followed by rapid contraction (inertial cavitation) and break up. Stable cavitation bubble oscillation may set up microstreaming patterns in fluids in which they form. While this is unlikely to cause significant adverse biological effects, it may alter ionic transport across cell membranes, and may in fact have beneficial therapeutic outcome. Very high temperatures and pressures result from inertial collapse. This can lead to localized tissue damage at the site of the bubble.

The resonant bubble radius ( R 0 ) up to 100 kHz is defined by an equation first derived by Minnaert [ 17 ],

where ω 0 is the angular frequency of the ultrasound field, P 0 is the ambient pressure, ρ 0 is the liquid density and γ is the ratio of the specific heats of the gas within the bubble. Above 100 kHz, surface tension, σ , becomes

For frequencies between 1 and 3 MHz, the resonant bubble size is approximately 4–1 µm.

There is considerable debate as to whether diagnostic ultrasound exposure conditions are able to induce cavitation effects in the absence of extrogenous bubbles (such as those that are used as ultrasound contrast agents (UCAs)). The consensus of opinion is that they are unlikely to occur at significant levels, but the possibility of low-level activity cannot be altogether ruled out [ 1 , 18 ]. Ultrasonically driven cavitation bubbles emit characteristic acoustic signals, which can be detected actively or passively using a piezo-electric sensor (an active sensor ‘pings’ the bubble using an ultrasonic pulse and picks up the returning echo, while a passive sensor solely detects the acoustic emissions that result from bubble oscillations). Considerable effort has gone into determining the threshold acoustic pressure that gives rise to acoustic cavitation in tissue, but, in reality, the validity of published values depends on the sensitivity of the sensor used. Cavitation detection is usually carried out at frequencies above the drive, and the emissions are consequently absorbed strongly in the tissue between the bubble and the detector. In general, the presence of UCAs lowers the threshold for cavitation as they obviate the need to nucleate gas bubbles.

The other often cited non-thermal mechanisms by which ultrasound can produce effects in tissue are those due to radiation pressure and acoustic streaming. The evidence for these mechanisms mediating biological effects is less well established than it is for thermal and cavitational effects.

An ultrasound beam exerts forces on discontinuities in its path. There are two components to these forces: an oscillatory component that time averages to zero and a component with a non-zero time average. The steady component is the radiation force, and arises because of propagation nonlinearities in the sound field. The absorption of energy in liquids in the field leads to a transfer of momentum, and thus fluid movement (acoustic streaming). The velocity gradients near boundaries that are associated with acoustic streaming may be high, and thus the shear stresses that are set up may be significant. Starritt et al . [ 19 ] measured streaming velocities of 14 cm s −1 in water during pulsed Doppler exposures, and 1 cm s −1 during B-mode.

It is important to assess existing reports of ultrasonic bio-effects and safety research critically. There is a huge canon of literature on the topic, but very little directly addresses the exposure of mammalian tissue using clinically relevant devices. Despite this, there is useful information available. A useful first step in understanding a biological effect is to perform tissue culture experiments using cells grown either as a monolayer or in suspension culture. This offers the possibility of looking at the effects of ultrasound on isolated cell populations and using the sophisticated battery of techniques available for studying such systems. However, the aqueous environment in which cells are maintained is likely to promote effects due to cavitation and streaming, and to minimize thermal effects. Experiments carried out in intact tissues (whether in vivo or ex vivo ) provide conditions that are more representative of human exposures, with more relevant tissue heating. Of course, ex vivo tissues, while providing a useful first step (and complying with a researcher's obligation to respect the 3R's of live animal experimentation—replacement, reduction and refinement [ 20 ]) may maximize thermal effects owing to the lack of blood perfusion. In vitro experimentation has the advantage of facilitating good ultrasound dosimetry. It is generally relatively easy to introduce a hydrophone (for example) into the sample holder in order to perform relevant field calibration. This is far more difficult in intact tissue. The ultrasonic exposure conditions within the tissue volume of interest under these circumstances are usually inferred from free-field measurements in a water bath and a knowledge of the acoustic properties of the tissues involved. An additional caveat to interpreting the bio-effects literature is a consideration of scaling. Most safety studies involve exposure of small rodents, which for most clinically relevant ultrasound beams irradiate a large proportion of their total body volume. This must be taken into account when interpreting the effects seen.

3. Machine outputs

One significant problem encountered in interpreting the ultrasound safety literature lies in understanding the exposure conditions used to induce a given effect, in order to relate them to those used clinically. The output of ultrasound transducers is usually measured in terms of the total acoustic power (using some form of radiation balance) and of acoustic pressure (using a hydrophone probe to map the field). Intensity distributions are usually derived from the measured pressure fields. The best papers in the literature describe the exposure conditions fully, giving the acoustic pressure (or intensity) distribution in the volume of interest, the frequency, the exposure time and the pulsing conditions where appropriate. A recent paper has described best practice in this regard [ 21 ]. The aim should be either that the conditions can be reproduced in another laboratory or that they can be related to clinical practice.

Whereas ionizing radiations have well-developed parameters for relating exposure (the amount of ionization produced in air, with units of roentgens) and the dose (the amount of energy deposited per kilogram in the region of interest (units of rads)), medical ultrasound makes no such distinction, with the terms exposure and dose being used (mistakenly) interchangeably. The literature often uses the terms ‘derated’ or ‘ in situ ’ to describe the intensity or pressure level at the point of interest. It is extremely difficult to measure these values in tissue in vivo and so they are usually inferred from a knowledge (or assumption) of the attenuation coefficients of overlying tissues in the beam path.

In a recent study, Martin [ 3 ] conducted a survey of five major ultrasound manufacturers, asking them for output data from current ultrasound systems. The data provided conformed to either US Food and Drug Administration (FDA) or International Electrotechnical Commission (IEC) reporting formats. The data presented were ‘worst case’ values, that is, maximum values measured under free-field conditions in water. No attempt was made to quote ‘ in situ ’ values—that is, the values that would be measured (if this were possible) at the point of interest in the organ being examined. Martin [ 3 ] reported that median I SPTA values for B-mode scanning had increased from 6 mW cm −2 in 1991 to 273 mW cm −2 in 2010; for colour flow from 55 mW cm −2 to 450 mW cm −2 ; and for pulsed Doppler had dropped from 1070 mW cm −2 in 1991 to 749 mW cm −2 in 2010. I SPTA values for B-mode rose from 6 mW cm −2 in 1991 to 67 mW cm −2 in 1995, and from 94 mW cm −2 in 1998 to 273 mW cm −2 in 2010. The comparison was made with surveys published by Duck & Martin [ 22 ], Henderson et al . [ 23 ] and Whittingham [ 24 ]. The change in values of peak negative pressure ( p r ) shows similar increases, but, in this case, there is also a rise for pulsed Doppler: B-mode (2.1 MPa in 1991, 3.7 MPa in 2010) for pulsed Doppler rose from 1.6 MPa in 1991 to 4.2 MPa in 2010, and for colour flow from 2.3 MPa in 1991 to 4.2 MPa in 2010.

4. Animal studies

The ultrasound safety literature is now considerable and wide ranging. It is not appropriate here to try to review it in its entirety, and the reader is directed to excellent summaries such as that produced by AGNIR [ 1 ]. The effects of ultrasound on cells and tissues have been studied at a number of levels—in tissue culture in vitro , in ex vivo tissue preparations and in vivo . Each has its own advantages and disadvantages. In vitro cultures provide a liquid environment for the cells in which thermal effects are likely to be less important than in intact tissues. As pointed out above, in the aqueous media necessary to maintain cell viability, non-thermal mechanisms such as acoustic cavitation and streaming are likely to predominate. Effects that have been studied in cells maintained in culture conditions are lysis, cell division and ultrastructural, chromosomal, cytogenetic and functional changes. While effects have been seen, it is difficult to relate these to clinical diagnostic exposures.

The majority of in vivo studies have used ultrasound exposures more typical of therapy applications than of diagnosis. Very few researchers have used diagnostic ultrasound scanners, or fields representative of those used clinically, to expose tissues. The main difference between these applications lies in the way in which the ultrasound is delivered, with short pulses (1–10 µs duration, pulse repetition frequency approx. 20 kHz) being used for diagnosis, and tone burst (longer than 1 ms) or continuous wave being used for therapy. There is some overlap in pressure amplitudes and intensities used. In what follows, the emphasis will be placed on studies that have used exposures relevant to medical diagnosis. One of the earliest findings was that short exposures of the lungs of rodents, swine and monkeys to ultrasound could lead to peri-alveolar capillary rupture (this is often referred to as lung haemorrhage) [ 25 – 45 ]. The safety implications of these findings are unclear. Similar areas of haemorrhage have been seen where the gas-containing intestine of mouse was exposed [ 46 ]. It has also been reported that diagnostic ultrasound might reduce the number of epithelial cells in the crypts of the mouse small intestine undergoing mitosis, and significantly increase the number of apoptotic cells [ 47 ]. These effects were reported after exposure to 8 MHz B- and colour flow modes.

In general, there have been very few positive findings following ultrasound exposure of mammalian foetuses to ultrasound. Tarantal & Hendrickx [ 48 , 49 ] and Tarantal et al. [ 50 ] used a commercial real-time sector scanner to expose macaques to pulsed 7.5 MHz ultrasound. They found a short-lasting statistically significant reduction in birth weight, and some short-term changes in behaviour. However, these findings have not been convincingly replicated in human epidemiological studies (see below).

Ang et al . [ 51 ] studied the effects of neuronal migration in mice following exposure in utero to diagnostic ultrasound on day 16 of gestation. The brains, removed 10 days after birth, showed no difference in brain size or gross cortical architecture, but there was a statistically significant dose-dependent difference in neuronal dispersion in animals that had been exposed to ultrasound for 30 min or more, with approximately 4 per cent more neurons in the experimental group of animals remaining in the deeper neuronal layers after 60 min of exposure, and not reaching the more superficial layers as had those in the control animals. In extrapolating these results to the human, a number of important factors must be considered. For experimental reasons, the pregnant females required restraint during exposure. This alone influences neuronal migration, as was shown by the increased dispersion in the sham control animals. In considering the ultrasound exposure level itself, it must be remembered that there is very little attenuation in the tissue path overlying the foetal mice, and so the in situ intensity is much higher than might be experienced by the human foetus. In addition, the whole mouse foetus is exposed, whereas only a small proportion of the human foetus would be using these probes. These factors make it difficult to extrapolate to human exposures. It is also not clear whether, in any case, these findings would have any functional significance, as the neurons involved may not persist.

Schneider-Kolsky et al . [ 52 ] performed a study on the effects on learning and memory of ultrasound exposure of foetal chick brain. Their findings suggested that B-mode exposure on day 19 of a 21 day incubation period had no effect on learning or memory, whereas 4–5 min of pulsed Doppler ultrasound did. This study suffers from many of the same limitations as the Ang work. The exposure conditions in ovo are impossible to interpret in relation to the human clinical investigations. It seems probable that significant reflections would be seen within the shell. No morphological studies were carried out.

In summary, it seems clear from the laboratory studies that have been reported that, while acoustic cavitation can lead to lysis of cells exposed in culture conditions because of the low threshold for its induction in this aqueous environment, there is no effect on the reproductive ability of those that survive. This suggests that, unless there is significant cavitation-induced cell lysis in vivo , there should be little concern about damage to cellular DNA. There is evidence from animal studies that where gas bodies are present in tissue, such as in the lung or intestine, some bleeding may occur, although the importance of these findings to clinical safety is not fully understood. Foetal and embryonic studies have generally provided reassuring evidence for safety in the absence of obvious thermal effects. It is clear that the stage of development is an important factor in these studies. One study has demonstrated the potential for alteration of neuronal migration in the mouse brain, and, while the significance of this finding to clinical exposures is not fully understood, there remains the slight possibility that ultrasound may be able to induce subtle effects in the foetal brain [ 53 ].

5. Human epidemiology

As has been made clear above, the area of most concern for the safety of ultrasound lies in exposure of the embryo and foetus. Thus, the vast majority of human epidemiological studies have been on children exposed to ultrasound prenatally.

It is certainly true that ultrasound has been used in obstetrics for several decades without any evidence of harm. Any effects that may have been caused by ultrasound examinations in pregnancy have been sufficiently few to preclude their attribution to the effects of acoustic radiation. However, absence of evidence of harm is not evidence of absence of harm, and it is important to conduct well-designed prospective epidemiological surveys to establish the facts. The current ubiquitous usage of ultrasound for pregnancy screening purposes makes such studies almost impossible now, but there are existing studies in the literature. This area has been reviewed by a number of people, but most recently there has been a World Health Organization systematic review [ 54 ], and a Cochrane review [ 55 ]. A number of different endpoints have been studied. These include birth weight, peri-natal mortality, neurological development, school performance and handedness. Of these, only handedness has shown any association with ultrasound exposure in utero .

Torloni et al . [ 54 ] considered 16 controlled clinical trials (the most rigorous type of epidemiological study), 13 cohort and 12 case–control studies. These were taken from the 6716 titles and abstracts that were screened, of which 61 papers were suitable for review.

The most widely studied adverse event has been birth weight. However, it seems clear that, for all except one study published between 1950 and 2007 (involving approx. 37 000 women), ultrasound exposure in vivo had no significant influence on mean birth weight [ 56 – 67 ]; only one study has given cause for concern [ 63 ]. In this Australian randomized controlled trial, half of the 2843 women studied were offered continuous wave Doppler ultrasound examinations five times in the third trimester. The controls received one diagnostic imaging ultrasound scan at 18 weeks. A statistically significant increase in the number of babies in the Doppler group with a birth weight below the 10th percentile (relative risk 1.35, 95% confidence interval 1.09–1.67) was reported but the difference in mean birth weight between the groups was not significant (25 g). Birth weight difference was not a formal hypothesis in this trial. A subsequent report from this group found no significant difference in mean weight, height, head circumference or other physical measurements at any age (measured separately for girls and boys) in the same group of children [ 68 ].

One of the goals of ultrasound screening in pregnancy is to reduce the rate of peri-natal mortality. In this context, it is arguably more important that mortality is not increased by these investigations. Controlled trials and a cohort study involving approximately 250 000 women have demonstrated a non-significant reduction in perinatal mortality [ 69 ]. Similarly, no association has been found between ultrasound exposure and incidence of pre-term births, admission to neonatal intensive care, and low Apgar scores at 5 min [ 54 ].

Eight studies of childhood malignancies have provided data on more than 14 000 children, with no association being found, even when sub-groups for leukaemia [ 70 – 74 ] and central nervous tissue tumours were considered [ 70 , 75 , 76 ].

There have been four published studies addressing potential harm to the developing foetal brain, as manifested by dyslexia, delayed speech development, impaired vision and hearing and a number of other outcomes. These involved approximately 6000 children in total [ 77 – 81 ]. Although two of these studies, one a case–control study and the other a cohort study, found a possible association between ultrasound exposure and dyslexia, the much larger controlled trials [ 79 – 81 ] found no statistically significant associations. It thus seems unlikely that the foetal brain is damaged by ultrasound exposure in utero [ 54 ].

Salvesen et al . [ 82 ] could find no association between school performance in 8–9 year olds (arithmetic, spelling and reading scores) and in utero ultrasound. A more recent study [ 83 ] found no statistical significance for children aged 15–16 years; although boys tended to have lower grades, this was not statistically significant.

Kieler et al . [ 84 ] found an increased risk of subnormal intellectual performance in 18 year old men who had been exposed to ultrasound prenatally. However, they concluded that confounding socio-geographical factors meant that the ‘study failed to demonstrate a clear association between ultrasound and intellectual performance’. A different study was unable to find an association between ultrasound and schizophrenia [ 83 ].

The only finding that has been consistent over several surveys and epidemiological analyses is that of an increase in non-right handedness in boys exposed to ultrasound in utero . This was first reported by Salvesen et al . [ 85 , 86 ] in 8–9 year olds. These findings were replicated by Kieler et al . [ 87 ]. Meta-analysis of these studies has been conducted [ 54 , 55 , 88 , 89 ]. The Cochrane review did not present gender-specific data, and failed to demonstrate this association; however, the other two papers were able to confirm that one in 20 exposed male foetuses is likely to be non-right handed. The relevance of these findings is hard to gauge. Of course, being left-handed is not problematical, or abnormal in any way. However, it is an interesting question as to what has caused this, if it is indeed a real ultrasonically induced effect. This is an area that clearly would benefit from more investigation.

While the over-riding epidemiological evidence about prenatal exposures to ultrasound is reassuring from a safety viewpoint, it must be remembered that the ultrasound examinations to which these children were subjected involved ultrasound scanners that have long since been superceded. None of these were colour flow or pulsed Doppler examinations, and B-mode outputs have increased by more than an order of magnitude over the intervening years [ 3 ]. We therefore cannot be complacent, and must make sure that good practice is continued to maintain ultrasound imaging's, to date, excellent safety record.

6. Regulations and guidelines

Most professional bodies concerned with diagnostic ultrasound have safety committees which have issued clinical safety statements on topics of relevance to the ultrasound user, and in some cases also guidelines for good practice and safe use (British Medical Ultrasound Society (BMUS), http://www.bmus.org/policies-guides/pg-safetystatements.asp ; American Institute of Ultrasound in Medicine (AIUM), http://www.aium.org/publications/statements.aspx ; European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB), www.efsumb.org ; Australian Society for Ultrasound in Medicine (ASUM), http://www.asum.com.au/site/policies.php ; International Society for ultrasound in Obstetrics and Gynaecology (ISUOG), http://www.isuog.org/ClinicalResources/Statements+and+Guidelines/Safety+Statements/ ; and WFUMB above others).

In Europe, ultrasound imaging manufacturers are required to meet the essential requirements for safety and effectiveness of the Medical Devices Directorate, if their devices are to be sold in the European Union. This entails demonstrating acoustic safety by conforming to IEC standards for declaring output values (IEC 61157, 606-2-37 [ 90 , 91 ]). The situation in the USA is different in that the acoustic output levels are limited by the FDA. The maximum permitted I SPTA is 720 mW cm −2 for all applications other than ophthalmology, in which it is restricted to 50 mW cm −2 . This is known as track 3 for approval, and was introduced in 1992. With the exception of ophthalmology, this maximum level is application independent, and, at that time, the onus for safety was put back onto the user. On-screen labels of two indices, thermal and mechanical, were provided to help judgements about safety to be made. The mechanical index (MI), which is an indicator of the potential for cavitation activity in the absence of UCAs, is defined as

where f is the frequency and p r here is the rarefactional pressure reduced to account for any attenuation that would occur in the tissue path to the measurement point using an attenuation coefficient of 0.3 dB cm −1 MHz −1 . The model used to derive this formula predicts that cavitation is unlikely for MI < 0.7. The FDA track 3 limits MI to a maximum of 1.9.

The TI is defined as the ratio of the acoustic power for the conditions being displayed ( W ) to the power required to raise the temperature by 1 o C ( W deg ),

Three different TIs have been defined, TIS, which is appropriate for soft tissues only; TIB, which is for use when bone lies at the focus; and TIC, for situations where bone lies near the skin surface, such as during neonatal brain scanning. The formulae used to calculate the thermal indices differ with scanned and non-scanned modes, and with different beam apertures (Output Display Standard, ODS [ 92 ]). The FDA track 3 limits TI to a maximum of 1.0 for ophthalmic applications, and 6.0 for all others.

The quid pro quo for this arrangement was that users would be educated in the importance of these indices. However, almost 20 years later, it is disappointing to see that this has not been very successful, with a number of surveys showing that less than 50 per cent of users could answer questions about these indices correctly [ 93 – 95 ]. In a recent survey of obstetric scans conducted within National Health Service (NHS) departments in the UK [ 96 ], maximum TIs observed during scanning were reported as ranging between 0.1 and 2.5 with a mean (± standard deviation) of 0.98 ± 0.69. The maximum TI (2.5) was found during a pulsed Doppler scan. In the same study, MI ranged from 0.2 to 1.6, with a mean of 0.74 ± 0.45. For trans-vaginal scans, TI ranged from 0.1 to 0.4 (mean 0.23 ± 0.15) and MI from 0.4 to 1.0 (mean 0.7 ± 0.22). In a similar survey carried out in an independent ultrasound clinic performing four-dimensional scans, the MI ranged from 0.4 to 1.3 (mean 0.99 ± 0.22) and the TI from 0.1 to 0.5 (mean 0.17 ± 0.08).

The BMUS has published guidelines for the safe use of diagnostic ultrasound. These guidelines tabulate recommended maximum scanning times for obstetric, neonatal and other applications (BMUS website and [ 97 ]). These times are based loosely on the thermal dose, while applying a safety margin, and identify different exposures in terms of the TI displayed. For obstetric scanning these times are

• — 0.7 < TI ≤ 1.0: 60 min
• — 1.0 < TI ≤ 1.5: 30 min
• — 1.5 < TI ≤ 2.0: 15 min
• — 2.0 < TI ≤ 2.5: 4 min
• — 2.5 < TI ≤ 3.0: 1 min

Scans involving TI > 3.0 are not recommended. For scans up to 10 weeks after the last menstrual period TIS should be monitored, whereas, for later scans, it is TIB that is important.

Safety statements from all the professional bodies convey similar messages, namely that there is no reason to withhold diagnostic ultrasound during pregnancy, provided it is performed by fully trained operators. The exception to this is the routine use of Doppler in the first trimester of pregnancy. This is discussed below.

The 2010 Clinical Safety statement from EFSUMB is typical of other such statements and is:

Clinical Safety Statement for Diagnostic Ultrasound ( 2010 ) Diagnostic ultrasound has been widely used in clinical medicine for many years with no proven deleterious effects. However, if used imprudently, diagnostic ultrasound is capable of producing harmful effects. The range of clinical applications is becoming wider, the number of patients undergoing ultrasound examinations is increasing and new techniques with higher acoustic output levels are being introduced. It is therefore essential to maintain vigilance to ensure the continued safe use of ultrasound. Ultrasound examinations should only be performed by competent personnel who are trained and updated in safety matters. It is also important that ultrasound devices are appropriately maintained. Ultrasound produces heating, pressure changes and mechanical disturbances in tissue. Diagnostic levels of ultrasound can produce temperature rises that are hazardous to sensitive organs and the embryo/foetus. Biological effects of non-thermal origin have been reported in animals but, to date, no such effects have been demonstrated in humans, except when a microbubble contrast agent is present. The thermal index (TI) is an on-screen guide to the user of the potential for tissue heating. The mechanical index (MI) is an on-screen guide of the likelihood and magnitude of nonthermal effects. Users should regularly check both indices while scanning and should adjust the machine controls to keep them as low as reasonably achievable (ALARA principle) without compromising the diagnostic value of the examination. Where low values cannot be achieved, examination times should kept as short as possible. Guidelines issued by several ultrasound societies are available. Some modes are more likely than others to produce significant acoustic outputs and, when using these modes, particular care should be taken to regularly check the TI and MI indices. Spectral pulse wave Doppler and Doppler imaging modes (colour flow imaging and power Doppler imaging) in particular can produce more tissue heating and hence higher TI values, as can B-mode techniques involving coded transmissions. Tissue harmonic imaging mode can sometimes involve higher MI values. 3D (three dimensional) imaging does not introduce any additional safety considerations, particularly if there are significant pauses during scanning to study or manipulate the reconstructed images. However, 4D scanning (real-time 3D) involves continuous exposure and users should guard against the temptation to prolong examination times unduly in an effort to improve the recorded image sequence beyond that which is necessary for diagnostic purposes. Ultrasound exposure during pregnancy The embryo/foetus in early pregnancy is known to be particularly sensitive. In view of this and the fact that there is very little information currently available regarding possible subtle biological effects of diagnostic levels of ultrasound on the developing human embryo or foetus, care should be taken to limit the exposure time and the Thermal and Mechanical Indices to the minimum commensurate with an acceptable clinical assessment. Temperature rises are likely to be greatest at bone surfaces and adjacent soft tissues. With increasing mineralisation of foetal bones, the possibility of heating sensitive tissues such as brain and spinal cord increases. Extra vigilance is advised when scanning such critical foetal structures, at any stage in pregnancy. Based on scientific evidence of ultrasound-induced biological effects to date, there is no reason to withhold diagnostic scanning during pregnancy, provided it is medically indicated and is used prudently by fully trained operators. This includes routine scanning of pregnant women. However, Doppler ultrasound examinations should not be used routinely in the first trimester of pregnancy. The power levels used for foetal heart rate monitoring (cardiotocography – CTG) are sufficiently low that the use of this modality is not contra-indicated on safety grounds, even when it is to be used for extended periods. Safety considerations for other sensitive organs Particular care should be taken to reduce the risk of thermal and non-thermal effects during investigations of the eye and when carrying out neonatal cardiac and cranial investigations. Ultrasound contrast agents ( UCA ) These usually take the form of stable gas filled microbubbles, which can potentially produce cavitation or microstreaming, the risk of which increases with MI value. Data from small animal models suggest that microvascular damage or rupture is possible. Caution should be considered for the use of UCA in tissues where damage to microvasculature could have serious clinical implications, such as in the brain, the eye, and the neonate. As in all diagnostic ultrasound procedures, the MI and TI values should be continually checked and kept as low as possible. It is possible to induce premature ventricular contractions in contrast enhance.

7. Contentious issues

7.1. pulsed doppler during first trimester.

Recent papers have advocated the use of routine pulsed Doppler measurement of the cardiac and infra-cardiac regions of every first trimester foetus (11–13 + 6 weeks) [ 98 ]. It has become a contentious issue as to whether this practice should be condoned, and, perhaps more importantly, whether it is, in any case, needed. Although Kagan et al . [ 98 ] have argued for first stage testing in trisomy 21 screening based on maternal age and Doppler ultrasound, equally good results have been obtained using a two-stage nuchal translucency and biochemistry screening programme that does not require the use of pulsed Doppler [ 99 ].

While there is no evidence that pulsed Doppler in early gestation can cause harm, we cannot be completely certain that it is 100 per cent safe; if it were to have an adverse effect, this might be most likely to occur in the most vulnerable stage of foetal life, namely in the first trimester. Good practice would, therefore, suggest advocating restricted, or at least very cautious (rather than routine), use of pulsed Doppler at this time.

7.2. Souvenir scanning

Many professional ultrasound bodies have issued statements to the effect that the use of ultrasound solely for the production of souvenir scans (also known as keepsake or bonding scans) cannot be recommended, citing safety grounds as the basis for this (WFUMB, AIUM, ISUOG and BMUS). At first sight this may seem to contradict the ‘clinical’ safety statements from these same organizations in which routine scans during pregnancy are said to be safe. Of course, an ultrasound scan conducted in a souvenir scanning centre is not inherently more harmful than the same scan conducted for clinical reasons if carried out by a qualified practitioner. The difference between these scanning scenarios lies in the perceived benefit obtained versus any potential risk. A ‘routine’ obstetric ultrasound scan is conducted with the expectation that it will beneficially inform the management of the pregnancy, whereas a souvenir scan is solely for ‘recreational’ purposes. Thus, the clinically indicated scan should confer significant benefit, whereas the souvenir scan should not. A compromise is reached by conceding that providing a ‘souvenir’ image at the end of a clinically indicated scan does not add significantly to any potential risk, and may dissuade the pregnant mother from resorting to a high-street ‘boutique’ with unknown skills and qualifications to obtain such a scan [ 100 , 101 ].

8. Summary and conclusions

The first mention that ultrasound could be used to produce images of the foetal head was probably in a lecture given by Ian Donald in 1959. Since that time, the use of ultrasound in obstetrics has grown rapidly, and has a generally accepted excellent safety record. However, it is impossible to prove zero risk, and the absence of evidence of harm should not be taken as evidence of absence of harm. The epidemiological evidence that exists is reassuring as to the safety of routine ultrasound scanning, but of necessity it only includes subjects who were imaged with devices that were state of the art at the time (mostly early 1980s). No pulsed Doppler or colour flow examinations are included, and the output from modern ultrasound scanners is considerably higher today than it was at that time. It is, therefore, essential to remain vigilant, and to assess new technologies and applications from a safety aspect as they arise.

Above all, ultrasound scans should only be carried out when there is a clinical need, and only by fully trained professionals who understand the modality and its safe use. This is especially vital for obstetric scanning.