GSBS Student Chases Details of Stray Neutrons in Proton Therapy

Publishing high-quality research is a major advantage for graduate students in today's climate of financial austerity and intense competition for grants and fellowships.

Rui Zhang, a doctoral student in The University of Texas Graduate School of Biomedical Sciences at Houston (GSBS), recently served as first author of a major paper in the journal Physics in Medicine and Biology--a top-tier publication in the field of radiation physics.

Guided by his advisor, Wayne Newhauser, Ph.D., associate professor in The University of Texas MD Anderson's Department of Radiation Physics, Zhang and his co-authors developed a new analytical model to calculate the dosage of stray neutrons that cancer patients are exposed to while undergoing proton therapy.

"People generally believe that proton therapy will deliver a much lower dose of radiation to the patient, but it recently was found that the stray neutrons generated in proton therapy can induce second cancers," said Zhang, a research assistant in the department. "Those neutron doses are not negligible, so researchers are trying to quantify the stray neutron dose and the corresponding risk and inform the patient about the risk."

Previous studies by the research group found that proton therapy generates a much lower risk of second cancers compared to conventional photon therapy.

Model could help reduce risk of second cancers Developing an analytical model to predict stray neutron exposure during proton therapy has been a long-term goal of radiation physicists. Without an accurate and reliable analytical model, they have had to rely on more time-consuming measurements typically taken in a water phantom, water-filled tanks used to measure and calibrate radiation dosages.

"These measurements are not easy to do, and it is not realistic to do them routinely or for every patient," Zhang said. "By creating an analytical model to calculate the stray neutron dose in proton therapy, we can predict the dose easily by doing some calculations instead of taking many measurements every day."

The accuracy of the new analytical model was found to be comparable to that of widely used neutron simulations and measurements.

Quantifying the whole-body radiation dosages patients receive during proton therapy may ultimately help researchers reduce the risks of radiation-related second cancers. Preventing second cancers is becoming increasingly important as advances in cancer treatment help patients live longer.

Publishing high-quality work before graduation Newhauser said in the current climate of shrinking research funding, graduate students must publish.

"Today it's difficult to get a Ph.D. The time to matriculation has increased, and it is increasingly important that graduate students are able to communicate about their work and generate enthusiasm for it," Newhauser said. "They also must have a record of productivity when they apply for their first research grant because this track record is a very important part of the review process. To be prepared for the real world, students need to know how to publish high-quality papers before they graduate."

Newhauser noted that most of his students have been able to get awards and grants or fellowships, and several already have received federal grants. He said the GSBS has been supportive and a great advocate for the program.

"I am really lucky to start my research career in the GSBS at MD Anderson Cancer Center," Zhang said. "Dr. Newhauser not only helps me with research and science, but also shows me how to become a good scientist and how to build up my own career. I am really grateful for his help."