Abstract
Despite working in clinically as a vascular sonographer, I had no practical experience with the use of ultrasound contrast agents, but I am fortunate to have had the opportunity to explore the clinical use of contrast-enhanced ultrasound (CEUS) in my research. Now that the US Food and Drug Administration (FDA) has approved this amazing technology for clinical use, I have been asked to share my thoughts on how to get started offering and performing CEUS in a clinic that has not yet done so. I feel strongly that my process for preparing to use CEUS as a researcher is a similar process for those who are new to its clinical use.
Educating yourself on CEUS is a key place to start. Our lab attended several lectures by Dr Richard Barr and Cynthia Peterson, MPH, RDMS, RVT, as a primer for understanding how contrast media behaves and what types of imaging could be expected. After attending these lectures and reviewing multiple evidence-based resources, we sought direct training. At the time, ultrasound contrast was approved for cardiac imaging; therefore, we contacted the echocardiography lab at our hospital and met with the echocardiographers who had vast experience using ultrasound contrast agents. Through these meetings, we learned about their experiences and gained insight into policies and procedures meant to ensure patient safety, while obtaining optimal contrast-enhanced images. Important aspects of the training included how to image using the contrast mode on the ultrasound machine and proper technical parameters, as various parameters influence the image differently when using contrast. In addition, we met with cardiologists and the nursing team to discuss their role in supporting CEUS studies.
Although the use of CEUS may be seemingly simple, we discovered that there were numerous practical and technical things to consider. Among these were the addition of at least one more staff member, consideration for proper storage and handling of the contrast media, timing of the injection with the corresponding imaging, and other logistic obstacles. Following meetings with the echocardiography staff, I contacted the contrast media vendor for additional instruction in preparing and properly storing the pharmaceutical agent, calculating dosing, and other technical considerations. Of particular importance is that although the structure and chemistry of these agents are very similar, contrast media provided by different vendors vary slightly and, as such, cannot be treated the same. It is vital to ensure full understanding of the technical factors for the specific agent being used.
In addition to the contrast vendor, it is advisable to contact your ultrasound equipment vendor to understand settings on their machines and determine what has been working in the field when using their equipment for specific examinations. When using ultrasound contrast, the technical parameters that sonographers are familiar with optimizing every day have a very different effect on an image and the physics that are occurring in vivo. With our vendor, we discussed contrast optimization for output power, frequency, time of examination, and other settings to ensure the ability to capture all of the needed imaging data, while maintaining the safety of the physiologic processes that are occurring within the patient. Vendors at trade shows and even your local sales representative are very helpful. In addition, they are able to elevate your questions to their commercial research staff, to provide even more assistance with equipment constraints.
Once you have a good understanding of the basic applications of CEUS and have explored the technical factors related to the particular agent and machine being used, the final step in preparation is to gather as much information as you can related to the specific clinical purpose of the examination. Although this is new to the United States, there is a wide range of evidence-based papers and published clinical protocols to use as a starting point. I have found that a variety of European and other international documents exist that can help in guiding sonographers to develop their clinical imaging protocols, including the imaging process as well as agent preparation and dosing information. Two such protocols include the following: Claudon M, Dietrich CF, Choi BI, Cosgrove DO, Kudo M, Nolsøe CP, Piscaglia F, Wilson SR, Barr RG, Chammas MC, Chaubal NG. Guidelines and good clinical practice recommendations for contrast enhanced ultrasound (CEUS) in the liver–update 2012. Ultraschall Med. 2013 Feb;34(01):11-29. Piscaglia F, Nolsøe C, Dietrich CA, Cosgrove DO, Gilja OH, Nielsen MB, Albrecht T, Barozzi L, Bertolotto M, Catalano O, Claudon M. The EFSUMB guidelines and recommendations on the clinical practice of contrast enhanced ultrasound (CEUS): update 2011 on non-hepatic applications. Ultraschall Med. 2012 Feb;33(01):33-59.
Ultrasound contrast is a very heavily researched and quickly growing area of radiology; thus, it is important to stay current on technological and pharmacological advancements. In this aspect, I found the International Contrast Ultrasound Society (ICUS) to be an excellent resource. On their website (http://www.icus-society.org/ceus-guidelines), ICUS provides up-to-date peer-reviewed literature to support initial/continuing education, information on various products, consensus statements regarding the use of CEUS, and links to other ultrasound and contrast organizations that are able to assist in the decision-making process.
I also found that it is very important to reach out to experts in the field. In my case, I am indebted to Dr Joshua Rychak, who spoke to me about his experience with CEUS and how certain organs and biological processes could be targeted. I humbled myself to Dr Rychak and was very open about my need to learn and make sure that I was thinking clearly about my use of the contrast media, my imaging protocol, dosing, etc. I was very lucky because he openly shared his expertise with me, and I firmly believe that is the role of scientists in the field. In my current work, I try to model that same openness and willingness to help novice clinicians and researchers in areas that I have deeply studied, as this is the most effective way to advance science and knowledge.
After exhausting all of the resources around us, we still felt like we needed to carefully practice all phases of the examination from mixing the contrast, agitating the preparation, reviewing the dosing schedule, to checking the equipment settings. Practicing and timing of the process is critical to ensure that all steps are followed, leading to a successful examination.
There is a host of other things that need to be considered when using a pharmaceutical agent as part of an examination. Of highest importance is that sonographers pay attention to and document any side effects that are observed following contrast administration. You will want to discuss these potential reactions and your response planning with your echocardiography lab team, explore existing literature, and review the information on chemical properties and possible adverse reactions that are listed on the package insert that comes with your contrast agent. Not only is patient safety paramount in our profession, but documentation of adverse effects is mandated. Most hospitals and larger institutions have a quality assurance committee who will request that all reactions (adverse or otherwise) be documented in the patient’s chart. It is highly recommended that the process of documentation be informed by the vendor, the nursing staff, and the hospital quality assurance committee.
Once you have finalized a protocol for your CEUS examination and reporting process, it is vital that all clinical sonography staff receive training in the important facets of the CEUS imaging process. Although the FDA has approved the use of CEUS for abdominal imaging, it is predicated on the responsible use of the product and an efficacious imaging process. We must be vigilant and very responsible in the use of this new and important imaging tool, as there is no guarantee that misuse or deleterious adverse effects could result in its discontinued approval. It is important that all staff understand the appropriate use and limits for various agents imposed by the FDA. An example of FDA limits is provided by this announcement: http://asecho.org/wordpress/wp-content/uploads/2015/11/PR_221236_LUMASON_Liver-FINAL-FACS-APPROVED-PR-1-APRIL-2016.pdf
In addition to limits of specific agents, additional consideration must be taken when performing examinations on children. Pediatric patients are more likely to experience adverse reactions to contrast agents due to their differing size and internal physiology. As such, the FDA is interested in protecting them from misuse for possible abuse of contrast injections. Additional resources to consult for pediatric CEUS imaging are as follows: Darge K, CEUS Task Force of the Society for Pediatric Radiology. Contrast-enhanced US (CEUS) in children: ready for prime time in the United States. Pediatr Radiol. 2011 Nov 1;41(11):1486. McCarville MB. Contrast-enhanced sonography in pediatrics. Pediatr Radiol. 2011 May 1;41(1):238-42.
Overall, the use of contrast itself is not difficult, but there are many items that should be considered by sonographers who do not have previous experience with contrast-enhanced echocardiography. It is critical to develop a plan prior to agreeing to start performing CEUS examinations. Sonographers should become knowledgeable of not only the scan itself but also the additional processes and requirements that are associated with the use of a pharmaceutical agent. This must be done in order to ensure patient safety and perform a high-quality CEUS examination. When I first decided to begin using ultrasound contrast agents, I did not consider all of the additional factors that went along with it. It was only through trial and error and the use of all of the resources at my disposal that I was able to begin performing CEUS effectively. It is my hope that this editorial provides an understanding of the considerations that must take place prior to injecting a patient with ultrasound contrast for sonographers who are interested in performing CEUS examinations.
Given the importance of preparation, as well as the overwhelming feelings it can cause, below is a quick reference guide listing the recommended actions to be taken by a novice user prior to performing CEUS.
Implementing CEUS Examinations in Your Clinic
Meet with your local echocardiography lab to discuss and begin to familiarize yourself with CEUS imaging and, if possible, observe a contrast scan
Discuss your specific needs and intended applications with the contrast media vendor
Consult with your ultrasound equipment vendor regarding optimization of your system for CEUS
Review evidence-based practice guidelines on CEUS that have been published
Identify a way to keep up on changes and innovations for CEUS (e.g., ICUS web searches)
Elicit support from CEUS experts and develop a clinical protocol for implementation in your setting
Instruct all sonographers in your facility on the established CEUS protocol to ensure consistency and review FDA guidelines
Establish a hospital-approved documentation mechanism for any adverse reactions experienced by patients while using CEUS
Consider publishing unexpected or interesting findings to advance the knowledge of CEUS and further educate colleagues
Closely monitor regulations and evidence-based literature to ensure that your protocols and practice remain current and safe for your specific population and application
