The Physics of Patient Care

In the last 25 years, new technology has exploded the possibilities in radiation oncology. The development of 3-D X-ray imaging (CT scan) gave doctors better images to choose the best treatment for their patients. Now they can also incorporate positron emission tomography (PET) and magnetic resonance imaging (MRI) into their decision process. And in 14 centers in the U.S., including Penn, physicians can use one of the most sophisticated weapons against cancer, proton therapy.

But what does it take to translate new discoveries in physics into new treatments for patients? After learning their way around both physics labs and hospitals, Penn’s medical physics students set forth to answer that question.

Medical physicists are trained to create and monitor these technologies, with the ultimate charge of ensuring the safety of the patient. Penn’s medical physics program in Professional and Liberal Education gathers its faculty from the Department of Physics and Astronomy, the Perelman School of Medicine, and the School of Engineering and Applied Science. “Students learn that biologists do research totally differently than physicists, that engineers are different,” says Assistant Professor of Radiation Oncology Stephen Avery, the program director. “But we work together as a team and students learn how we integrate knowledge from the different schools to answer a common question.”

Along with a clinical practicum, Penn’s medical physics program emphasizes research and requires students to do a capstone project before they graduate. Their projects are as varied as their faculty. They’re developing better contrast agents, including research with biomedical engineers to see how gold nanoparticles would enhance imaging and treatment. Students are working with Joel Karp, a professor of radiologic physics, to develop a time-of-flight PET scanner which can offer better resolution by calibrating for the size of the patient. Others are using 3-D printing to create individualized supports to exactly position patients.

Penn’s Roberts Proton Therapy Center gives students a special advantage. The therapy is so new that there’s still much to learn. Because protons stop at a specific place, the treatment spares more tissue than conventional radiation treatments. This is especially important for children, in whom it decreases the probability of second malignancies.

Students are collaborating on projects to develop methods to verify that the proton stops where it is supposed to by using PET technology and Compton cameras that detect gamma rays, or measuring thermo-acoustic signals. Beyond that, they’re trying to increase the potency of the treatment. Since the proton delivers its highest dose at the point where it stops, students and faculty are looking at whether it might be more effective to stop the proton in the middle of the target area, and send another proton from the other side to do the same.

Medical physics students are also working with researchers to investigate the use of diffusion tensor imaging (DTI) as a tool for monitoring treatment of proton therapy. One potential use of DTI is as a biomarker to evaluate the effectiveness of treatment alterations for reducing radiation therapy-induced toxicity in the brain. This would be especially valuable for pediatric patients.

“These approaches are all from basic physics; it’s just that we’re applying it to medicine,” says Avery. “We want someone who is going to be innovative, really be a leader. We want our students to push the field forward.”