EXPANDING OUR CLINICAL ROLECynthia H. McCollough, PhD, Rochester, MN

The Evolving Role of the Medical Physicist in CT Imaging

The role of the diagnostic medical physicist continues to evolve toward having a greater role in clinical practice. In CT, for example, a qualified medical physicist is required to participate in protocol reviews as a member of a team comprised of radiologists, technologists and physicists. This triad of expertise provides the needed skills to develop and maintain accurate, dose efficient and clinically appropriate protocols that meet the needs of our patients. Each member of the team brings essential knowledge to the table, with the medical physicist bringing a depth of understanding of the fundamental physics related to, and technical complexity of, the impact of protocol parameters on dose, image quality, and artifact susceptibility. In reflecting upon this topic, I cannot help to consider my own journey.

In 1991, I joined the Mayo Clinic, fresh out of graduate school. From the beginning, my role at Mayo was integrated with the clinical practice. Developing and overseeing an acceptance testing and quality assurance program was of course an expected duty, as were evaluation of equipment for purchases and education of technologists and physicians. However, in the course of getting to know my radiologist and technologist colleagues (and simply finding my way around to our over 20 CT scanners), I made it a habit to walk through each CT area on a daily basis. At first, I simply observed. I was there to learn from them. Later, I began to ask questions. Being careful to come across as curious and not judgmental, I would ask why the slice thickness was 10 mm in some exams and 7 mm in others (yes – those were the typical slice widths in 1991). As I read radiology and physics papers, I understood the clinical implications of partial volume averaging and beam hardening. I ran experiments to create teaching slides on these and other topics, and I worked to make sure that I was testing equipment features that made a difference to our clinical practice. By being present and being clinically oriented, I became a trusted resource. When difficult patients were being scanned, I was often paged to the scanner to assist in tough protocol choices. I became more than the person who tested the scanners and worried about badge readings, I became a part of the team.

Having learned how to be clinically relevant, I provided knowledge to the medical director of CT and technologist supervisor about the capabilities of our various scanner models, so that appropriate triage rules could be set up to make sure that patients with specific needs were scanned on equipment with the necessary feature set. I formed and chaired the "CT Technical Support Committee", which met monthly to discuss all equipment or operator incidents, service needs, and upcoming installations and upgrades. Over a decade ago, I advocated for all of our CT technologists to become CT certified, and provided a year of monthly in-service programs to help prepare our staff for their exam. In that same time frame, the CT physics team took over protocol review and oversight, developing a team-based approach to developing, revising, and evaluating our set of over 300 CT protocols. With my colleagues, we developed a web-based protocol management system and organized at least annual formal protocol reviews with each division (neuro CT, body CT, cardiac CT, etc.) on an annual basis. In short, my CT physics colleagues and I became an integral part of the daily operation of our CT practice, sharing our unique knowledge and expertise with the overall team.

Now, accreditation bodies are requiring these sorts of activities, yet many physicists have not had the opportunity to develop the clinically oriented knowledge needed to support their practice in this manner. For example, most medical physics curricula do not include lectures as to what specific features are important to the radiologist and technologist for a tri-phase liver or pancreas scan and how that protocol needs to differ from a CT urogram, a CT enterography for blood loss or a non-contrast abdomen scan for flank pain. These are things that are learned in the reading room, in detailed conversations with technologists, at the scanner during a complex study, or in clinical sessions at radiologist meetings.

Being so close to the clinical practice of CT, I have spoken frequently at radiologist meetings, helping to explain the physics and technical principles of spiral CT, cardiac CT, or iterative reconstruction in a manner that conveys the information they need and care about, and avoids technical jargon. Now, I serve as a vice-president of the International Society of Computed Tomography, whose purpose is to develop educational content for radiologists, technologists and physicists related to all things CT. If you find yourself wanting to deepen your involvement in clinical practice, I encourage you to attend the ISCT, June 4-7, 2017 in San Francisco, or take advantage of our on-line educational material. Whether ISCT, RSNA, ARRS or another clinical conference, learn about the practice of radiology. Make sure that you understand the differences in exam types, and can understand why exam timing is critical for run-off exams and pulmonary scans. With such knowledge, you position yourself to contribute to the clinical practice(s) that you support in an exciting and rewarding fashion. Nothing beats working with a technologist to acquire a beautiful cardiac exam on an obese patient with an irregular heart rate, and being thanked by the radiologist for helping to provide optimal care for their — and your — patient!

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