Sonographers and Contrast-Enhanced Ultrasound

Now that contrast-enhanced ultrasound (CEUS) has been approved in the United States for several abdominal applications in adults and pediatrics, I decided to take a deeper look into the sonographer’s role in CEUS. Traditionally, sonographers perform ultrasound examinations based on a protocol, construct a preliminary ultrasound findings worksheet, and perhaps discuss the findings with a radiologist. And now CEUS has transformed traditional ultrasound and gives physicians and sonographers additional diagnostic information related to the presence and patterns of contrast enhancement.DSC00125

Based on sonographers’ traditional scope of practice, some questions came to mind. What is the training process for sonographers to learn CEUS? How should CEUS images be obtained and stored? How should CEUS findings be communicated?

I envision CEUS training for sonographers broken down into stages, where they begin by learning the basics and eventually transition to where they can perform and record the studies independently. The first stage for sonographers is the ‘CEUS learning curve.’ In this stage, sonographers become familiar with basic CEUS concepts, eg, understanding physics of contrast agents and contrast-specific image acquisition modes, CEUS protocols, and typical patterns of contrast enhancement seen in various organs. In addition, an important part of the training is recognizing contrast reactions, and learning IV placement, documentation and billing related to CEUS.

The next stage involves sonographers performing more patient care and gaining scanning responsibilities. Sonographers place the IV and prepare the contrast agent. The scope of sonographer responsibilities does not generally include contrast injection (although it is reasonable since CT, MR, nuclear medicine, and echocardiography technologists routinely place IV lines and inject contrast). It should be noted that CEUS examination usually requires an additional person (physician, nurse, or another sonographer) to assist with contrast injection while the sonographer performs the ultrasound examination. In the beginning of sonographer training, it is very beneficial to have a radiologist present in the room to guide scanning and appropriate image recording.

In the third stage, a well-trained sonographer is more independent. At the completion of the examination, the sonographer will either send clips or still images to a physician to document the CEUS findings and discuss the procedure. Ideally a worksheet is filled out, comparable to what is done today with “regular” ultrasound.

The majority of CEUS examinations are performed based on pre-determined protocols, usually requiring a 30–60-sec cineloop to document contrast wash-in and arterial phase enhancement. After that continuous scanning should be terminated and replaced with intermittent acquisition of short 5–10-sec cineloops obtained every 30–60 sec to document late phase contrast enhancement. These short clips have the advantage of limiting stored data while providing the interpreting physician with real-time imaging information. Detailed information on liver imaging CEUS protocols could be found in the recently published technical guidelines of the ACR CEUS LI-RADS committee.[i] Some new users might acquire long 2–3-minute cineloops instead, producing massive amounts of CEUS data. As a result, studies can slow down a PACS system if departments are not equipped to deal with large amounts of data. In addition, prolonged continuous insonation of large areas of vascular tissue could result in significant ultrasound contrast agent degradation limiting our ability to detect late wash-out, a critical diagnostic parameter required to diagnose well differentiated HCC. Any solution requires identifying and capturing critical moments, which will be determined by a sonographer’s expertise. Exactly how sonographers can ensure CEUS will successfully capture the most important images is a critical question that must be answered and standardized.

Ideally, leading academic institutions should provide CEUS training for physicians and sonographers. I have seen and attended CEUS continuing medical education courses and they are a great way for physicians and sonographers to learn CEUS imaging. CEUS is a step forward for sonographers and will potentially transform our scope of practice. The technology will advance the importance of sonographers and diagnostic ultrasound, and importantly it will improve the care of our patients.

Acknowledgements:
Dr. Laurence Needleman, MD
Dr. Andrej Lyshchik, MD
Dr. John Eisenbrey, PhD
Joanna Imle, RDMS, RVT

[i] Lyshchik A, Kono Y, Dietrich CF, Jang HJ, Kim TK, Piscaglia F, Vezeridis A, Willmann JK, Wilson SR. Contrast-enhanced ultrasound of the liver: technical and lexicon recommendations from the ACR CEUS LI-RADS working group. Abdom Radiol (NY). 2017 Nov 18. doi: 10.1007/s00261-017-1392-0. [Epub ahead of print]

Has CEUS helped your sonography career? How do you envision CEUS being incorporated in your work? Comment below or let us know on Twitter: @AIUM_Ultrasound.

Corinne Wessner BS, RDMS, RVT is the Research Sonographer for Thomas Jefferson University Hospital in Philadelphia, Pennsylvania. Corinne has an interest in contrast-enhanced ultrasound, ultrasound research, medical education, and sonographer advocacy.

Should You Include CEUS and Elastography in Your Liver US Practice?

Today, the liver is regarded with high importance by our clinical colleagues. The obesity epidemic, with its considerable impact in North America, is associated with severe metabolic disturbances including nonalcoholic fatty liver disease (NAFLD). Further, liver cancer is the only solid organ cancer with an increasing incidence in North America. Where do we as ultrasonographers fit into the imaging scheme to most appropriately deal with these new challenges?

The liver is the largest organ in the body, and certainly the most easily accessed on an abdominal ultrasound (US). It has been the focus of countless publications since the introduction of abdominal ultrasound many decades ago. Exquisite resolution allows for excellent detailed liver evaluation allowing US to play an active role in the study of both focal and diffuse liver disease. Focal liver masses are often incidentally detected on US examinations performed for other reasons and on scans performed on symptomatic patients. Abdominal pain, elevated liver function tests, and nonspecific systemic symptoms may all be associated with liver disease. The introduction of color Doppler to abdominal US scanners many years ago elevated the role of US by allowing for improved capability of US to participate in assessment of the hemodynamic function of the liver as well.

malignant tumor ceus

The well-recognized value of abdominal US, including detailed morphologic liver assessment, has made this examination the most frequent study performed in diagnostic imaging departments worldwide. However, in recent years, US has been relegated to an inferior status relative to CT and MR scan, as their use of intravenous contrast agents has made them the cornerstone modalities for virtually all imaging related to the presence of focal liver masses. As we now live in an era of noninvasive diagnosis of focal liver disease, greyscale US has fallen out of favor, as it is nonspecific for liver mass diagnosis. While US is the recommended modality for surveillance scans in those at risk for development of hepatocellular carcinoma, today, all identified nodules are then investigated further with contrast-enhanced CT and/or MR scan.

In the more recent past, US has been augmented by 2 incredible noninvasive biomarkers: elastography, which measures tissue stiffness, and contrast-enhanced ultrasound, which shows perfusion to the microvascular level for the first time possible with US. These noninvasive additions are invaluable and their adoption in routine US practices may allow the reemergence of US as a major player in the field of liver imaging.

Most conventional US machines today are equipped with the capability to perform elastography, especially with point shear wave techniques (pSWE). In pSWE, an ARFI pulse is used to generate shear waves in the liver in a small (approximately 1 cm3) ROI. B mode imaging is used to monitor the displacement of liver tissue due to the shear waves. From the displacements monitored over time at different locations from the ARFI pulse, the shear wave speed is calculated in meters per second, with higher velocities associating with increased tissue stiffness. The accuracy for the determination of liver fibrosis and cirrhosis with pSWE as compared with gold standard liver biopsy is now indisputable. Because of the great significance of liver fibrosis secondary to fatty liver and the obesity epidemic, the development of this technique as a routinely available study is essential. Because of the frequent selection of US as the first test chosen for any patient suspect to have undiagnosed diffuse liver disease, the opportunity for elastography to be included with the diagnostic morphologic US test should be developed as a routine.

Contrast-enhanced US (CEUS), similarly, is available on most currently available mid- and high-range US systems, allowing for nondestructive low MI techniques to image tumor and liver vascularity following the injection of microbubble contrast agents for US. This allows for a similar algorithmic approach to contrast-enhanced CT and MR scan for noninvasive diagnosis of focal liver masses. CEUS additionally offers unique imaging benefits that include no requirement for ionizing radiation and also imaging without risk of nephrotixity, invaluable in the many patients who present for imaging with high creatinine, preventing injection of both CT and MR contrast agents.

Incorporation of pSWE and CEUS into standard liver US in patients with suspect diffuse or focal liver disease is a cost-effective and highly appropriate consideration as this is readily available, performed without ionizing radiation, and at a considerable cost saving over all other choices.

Can you diagnose a hepatocellular carcinoma or other liver tumor with CEUS?  And, can you determine if a liver is cirrhotic or not?  With the addition of pSWE and CEUS to your liver US capability, yes, you can.

What is your experience with treating liver disease? What aspect is most difficult for you? What other area do you think would benefit from the addition of CEUS? Comment below or let us know on Twitter: @AIUM_Ultrasound.

Stephanie R Wilson is a Clinical Professor at the University of Calgary.