The Physics of Imaging

No longer working only behind the scenes, today’s medical physicists are providing clinical guidance to improve patient care.


June 2015
When the radiology department at Cincinnati Children’s Hospital hired a full-time medical physicist about three years ago, the chief of thoracic imaging, Alan S. Brody, MD, didn’t expect the move to significantly impact the department’s operations. Brody, who is also a professor of radiology and pediatrics at the University of Cincinnati College of Medicine, assumed the physicist would work primarily on special projects and calibrate the department’s imaging equipment to meet federal and state regulations. While he supported the hire, Brody wondered whether that was enough work to justify having a medical physicist on staff full time.
But once Keith J. Strauss, MS, FACR, clinical imaging physicist, began working with the department’s radiologists and technologists to optimize dose and enhance image quality beyond the regulatory mandates, Brody soon realized that he had misunderstood what an on-staff medical physicist could do for the department. “I thought a medical physicist did measurements when there was a regulatory need or when someone in the department wanted to better understand radiation dose,” Brody explains. “But our medical physicist has taken an active role in the department and has identified new techniques that have dramatically decreased dose and improved the consistency of our image quality.”
 Brody’s assumptions about the role of medical physicists in radiology are not uncommon. In the past, medical physicists have worked largely behind the scenes — evaluating imaging equipment after hours and issuing reports in much the same way that radiologists issue imaging reports to referring physicians. They traditionally have not collaborated closely with radiologists and other practice members to reduce dose and improve image quality, but that is changing. “As a profession, we are trying to increase our visibility and move from an environment where we are known as the purely technological people to a place where we use our knowledge in a consultative way to help in patient care,” says Robert J. Pizzutiello Jr., MS, FACR, senior vice president of imaging at Landauer Medical Physics, headquartered in Greenwood, Ill., and president and residency program director at Upstate Medical Physics, PC., in Victor, N.Y.

Where Physicists Work

Most medical physicists work in radiation oncology, with only about 25 percent in diagnostic imaging. Imaging medical physicists work either in-house at an institution or as consultants who serve many institutions at once. In-house medical physicists typically work for large hospitals or practices, while consultants tend to serve smaller institutions. “It takes a pretty sizable institution to make it cost-effective to have a medical physicist on staff full time,” says Richard A. Geise, PhD, FACR, a medical physicist who works part-time at Abbott Northwestern Hospital in Minneapolis and as a consultant for several hospitals, clinics, and radiology groups in the Twin Cities area. “So as health care organizations become larger and have more of an umbrella parent organization over multiple hospitals, these facilities might hire a physicist or multiple physicists to support all of the hospitals within their systems.”
Some institutions may wonder whether it’s best to hire an in-house or a consulting medical physicist. Pizzutiello, who founded the consulting group Upstate Medical Physics, notes that each approach has its advantages. “In-hospital physicists have a more intimate knowledge of all the people, processes, and equipment at a single location,” he says. “Consultants, on the other hand, know how different processes and equipment have worked across facilities.” Pizzutiello adds that both in-house and consulting medical physicists can participate in CT protocol optimization. “Our consulting group has been helping clients optimize CT protocols since 2010, and I know many others who have expanded into this more consultative role,” he says. From a radiologist’s perspective, Brody says that either a full-time or consulting medical physicist can make an important difference as long as he or she is available for both regulatory needs and to answer clinical questions.

"We have a high degree of respects for our physicists because this is very detailed physics up to the nuclear reactor level." — Geoffrey R. Bodeau, MD


Whether in-house or consulting, the most basic job of medical physicists is to ensure that institutions meet the scores of imaging regulations that state and federal governments impose. These include the United States Nuclear Regulatory Commission’s ALARA dose requirements and the Joint Commission’s new mandate requiring hospitals to have medical physicists evaluate the performance of their CT imaging equipment annually (which follows the ACR’s longstanding accreditation requirements). Some medical physicists also engage in clinical care, which can significantly improve image quality and patient safety. “As an in-house medical physicist, I make sure the compliance issues are met, but the majority of my time is spent helping the technologists and the radiologists leverage the strengths of their imaging equipment to get better images and properly manage dose levels,” Strauss says. 

What Physicists Do

No matter the setting, medical physicists work with radiologists and technologists to achieve three primary goals: ensure image quality, develop radiation safety procedures, and optimize dose. “I apply physics principles of imaging to come up with a plan to improve the process the department uses to create the images,” Strauss explains. “Depending on the situation, the idea might be that we’re improving image quality and maintaining dose or maybe we’re trying to maintain image quality and reduce dose — or maybe we’re trying to do both.”


While medical physicists sometimes have to assess imaging equipment during off hours to keep from disrupting patient exams, they are becoming more visible by advising radiologists and technologists on quality-improvement techniques. Once they understand how the department is using its imaging equipment, medical physicists have the expertise to develop protocol improvements that others in the department may not consider. “We have a high degree of respect for our physicists because this is very detailed physics up to the nuclear reactor level,” says Geoffrey R. Bodeau, MD, medical director of nuclear medicine at Abbott Northwestern Hospital. “As doctors, we appreciate the fact that they really know this stuff inside and out, and we realize that the work of the hospital couldn’t go on without them.”


At Cincinnati Children’s Hospital, for instance, Strauss developed a completely new way for determining X-ray dose after examining some of the department’s plain films. Brody explains that the department was using age and weight to determine dose. But when Strauss analyzed the techniques the technologists were using, he noticed that the same techniques were used for tall, thin patients as short, stocky patients, which leads to inconsistent dose levels for identical exams for patients of the same age. To more accurately and consistently determine dose, Strauss recommended using body thickness rather than age and weight. “As a result, we’re producing higher quality images and decreasing dose in some cases, which is fantastic,” Brody says.


Physicists' Additional Roles

Medical physicists also play several other important roles inside of health care institutions. For instance, medical physicists may advise institutions on equipment purchasing decisions. They may also assist with facility design to determine how much lead shielding is necessary to prevent radiation from escaping through the walls of an exam room. “There are all of these calculations that radiologists wouldn’t necessarily think of, but medical physicists have the expertise to help make sure our facilities are safe for patients, radiologists, technologists, and the general public,” Bodeau says. Medical physicists are also trained to assist in emergency situations such as radioactive material spills and terrorist attacks involving nuclear reactor byproducts.


At the ACR, medical physicists are involved in several initiatives, including ACR Select™ (the electronic version of the ACR Appropriateness Criteria®) and the ACR Dose Index Registry™ (a data registry that allows institutions to compare their CT dose levels to regional and national values). They also assist with the ACR’s accreditation program and the technical standards and practice parameters related to radiation issues and safety. “We’re able to look at these programs from the medical physics perspective and contribute to their development and ongoing operation,” Pizzutiello says. “For example, in all of the accreditation programs not only does a radiologist assess the clinical images, but a medical physicist also evaluates the phantom images and physics reports to ensure they meet the accreditation standards.”


Still, medical physicists’ most important role is working directly with radiologists and technologists to improve patient care. Strauss says that radiologists can help medical physicists fulfill this role by encouraging their institutions to hire medical physicists to do more than simply address regulatory requirements. “There are many institutions that want to take care of the compliance issues but aren’t necessarily willing to spend the time, money, and effort needed to optimize things as much as they could,” he says. “Radiologists should advocate for hiring medical physicists as part of their institutions’ overall efforts to improve patient care.”


By Jenny Jones, freelance writer for the ACR Bulletin


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