Stepping out from behind the machines

With radiation dose a growing concern, medical physicists see a more prominent role in patient care

A potentially valuable new partner in today’s shift toward value- and evidence-based medicine is someone you should know, but probably don’t. Grounded in science, innovation and data, the medical physicist has the skills and the calling to positively affect the value equation of quality, safety and cost, but instead is often relegated to a technical role in radiation medicine.

Most people are only likely to know about medical physicists if one is a friend or they have had cancer and undergone radiation therapy. Even then, they are unlikely to understand the practitioner’s skill set and role in medicine. A bigger issue is that the same lack of recognition exists among the folks who work in a hospital. Physicians and staff in radiology and radiation oncology are aware of medical physicists, but some only know them as their physics teachers. Physicians from other specialties, nurses and other healthcare staff are much less likely to be familiar with – or even aware of – the existence of medical physicists, let alone the value that they provide.

This is a significant oversight, if for no other reason than the central role medical physicists play in the effort to gain control over radiation exposure. The use of CT scans nearly tripled from 1996 to 2010, according to a study published in the Journal of the American Medical Association that was based on data from patients in six large HMOs. The researchers found that 2.5% of the patients were exposed to 20 to 50 millisieverts of radiation in 2010, a level that the International Commission on Radiological Protection says is excessive. Another 1.4% of the patients were exposed to more than 50 millisieverts, which the U.S. Nuclear Regulatory Commission says is unsafe. About 10% of all CT examinations are performed in children, who have generally higher sensitivity to radiation due to growing tissues. A 2012 study from the National Institutes of Health showed a correlation between CT scans in children and their subsequent risk of developing cancer.

A call for accountability

These risks, while hard to fully quantify, have garnered a great deal of attention in recent years from the scientific community, regulators and the public. There has been a call for accountability for both the frequency of medical imaging examinations involving ionizing radiation and the magnitude of radiation exposure involved.

Since July 2015, the Joint Commission has mandated that providers document radiation dose on every study produced during a CT examination. The radiation dose must be exam-specific, summarized by series or anatomic area, and documented in a retrievable format. The provider must also review incidents where the radiation dose emitted by the CT imaging system during diagnostic exams exceeded expected dose ranges identified in imaging protocols.

Dose monitoring, a tool to standardize dose and image quality across systems, is central to the medical physicist role. It is a complex task, given that even in mid-sized hospitals, there are often multiple CT makes and models, and protocols vary widely. There is also no standard metric of radiation burden. The most commonly implemented metric is volume CT dose index, which reflects the radiation output of a CT system in units of dose to a standard-sized object. While effective in characterizing the system output for CT protocols in terms of dose, CT dose index fails to represent all protocols and to fully account for individual patient attributes. A metric called size-specific dose estimate was developed to address the dependency of radiation dose on a patient's overall size. While an improvement, it shares the other limitations of CT dose index by not accounting for factors such as body shape, organ location and orientation and tissue composition. And after all, such metrics are technology-focused, while quantities of patient radiation exposure should be reflective of the burden to the patient – the only way that radiation risk can be put in context of other risks and benefits of medical intervention.

A vast amount of expertise

The solutions for dose measurement, monitoring and optimization will come from medical physicists, who were the progenitors of the disciplines of radiology and radiation oncology. Medical physicists have strong analytical and problem-solving skills, technical expertise in physics and biomedical sciences, and knowledge of clinical processes and workflow, including imaging science and radiation therapy planning and delivery. Medical physicists have also committed enormous effort into the highly demanding areas of safety and compliance testing of both therapeutic and diagnostic equipment.

Other areas where they play a major role in the hospital include:

• Ensuring that 4D computed tomography in radiation therapy, a highly complex procedure, is done appropriately, giving higher doses to tumors while minimizing toxicity to the surrounding normal tissues.

• Overcoming the technical, physical and biological uncertainties in the newer multimodality methodologies that join in various iterations of CT, nuclear medicine, positron emission tomography, magnetic resonance imaging and optical imaging.

• Integrating, analyzing and ensuring integrity of the data on dosing and image quality from an array of imaging devices.

A new role in direct patient care

You may think medicine as a discipline should rely on all basic sciences that can improve its processes and deliveries. Biology and chemistry have established that contribution. Physics likewise should serve as an integral component of medicine. The profession of medical physics has matured to where national accreditation and certification processes have been implemented and widely recognized. Now, members of the American Association of Physicists in Medicine are focused on the next step in our evolution: a bigger role in direct patient care.

In some places, this has started already. Radiation therapy medical physicists at University of California, San Diego meet with patients at the beginning of the radiation therapy process and provide them with an overview of their treatment plan. They are available to answer questions throughout the process, including the impact of radiation dose.

The new-age medical physicist looks to communicate his or her value by engaging routinely with diverse members of the healthcare team, including participating in such interdisciplinary functions as tumor boards, chart rounds and quality and safety committees.

Medical physicists have the skills, background and desire to improve the practice of evidence-based medicine while keeping patients safe. They just need the chance to step out from behind the scanners and introduce themselves.

Ehsan Samei, PhD, is a professor at Duke University, Durham, N.C., where he leads the Medical Physics Graduate Program and the Clinical Imaging Physics Group. He is the chairman of the American Association of Physicists in Medicine Medical Physics 3.0 initiative.

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