New Method to Control Excess Radiation

October 14, 2015    |  

Scientists from the University of Maryland School of Medicine (UMSOM) have developed a new imaging technique that allows them to better visualize and measure the location of radiation in the body during cancer treatment. The technique could improve the safety of some radiation treatments because it will help doctors reduce the amount of harmful radiation that affects the healthy tissue surrounding tumors.

The results are published in the latest issue of Physics in Medicine and Biology.

“This is potentially a big step forward for radiotherapy,” said the technique’s lead developer, Jerimy C. Polf, PhD, an assistant professor in the Department of Radiation Oncology at the School of Medicine. “Using this approach we can better verify that we’re hitting only the area that we want to hit.”

The imaging technique works with proton beam radiotherapy, which uses protons traveling at about two-thirds the speed of light to precisely deliver beams of radiation to tumors.

For certain kinds of cancer, the radiation dose delivered by the treatment beam to healthy tissues around the tumor remains a serious issue. For example, when treating lung cancer, doctors must be very careful to avoid delivering radiation to the heart, which is just inches away from the lungs.

Polf’s invention measures a secondary form of radiation known as gamma rays that are created when the proton treatment interacts with tissues in the body. A sophisticated computer program uses these measurements to generate real-time three-dimensional images of how and where the gamma rays are created in the body. Since the gamma rays are created by the proton treatment beam, and are only emitted along the path of the beam, the image of the gamma ray emission reveals the path of the proton beam as it passes through the patient.

Currently, doctors use complex equations that include the patient’s physical dimensions to predict the path of the proton beam through the body. These calculations are precise, but can be inexact. Polf says the new technique can greatly improve the accuracy and precision of proton treatment delivery. “In the past, we didn’t have as much information as we would have liked, but with this new technique we will be able to actually see the beam during the treatment delivery” he says.

With this added imaging information, clinicians can more accurately target the tumor and may be able to increase the amount of radiation they use on tumors. With a better understanding of exactly where the radiation is going, they can increase the power of the cancer-killing radiation dose delivered with proton therapy.

Polf worked on the effort with scientists at the University of Texas MD Anderson Cancer Center in Houston, Texas, and H3D, a company based in Ann Arbor, Mich. Cancer patients at UMSOM will be involved in clinical trials using the technique.

Polf’s work is especially timely because UMSOM will soon begin offering proton therapy when it opens the Maryland Proton Treatment Center (MPTC) this winter. The center will use a highly precise form of radiation therapy known as pencil beam scanning (PBS), which targets tumors while significantly decreasing radiation doses to healthy tissue.

The new facility will offer PBS as the sole modality of proton treatment. The treatment works well for many kinds of tumors, including those found in the brain, breast, esophagus, lung, head and neck, prostate, liver, spinal cord, and gastrointestinal system. It is also an important option for children with cancer.

During treatment, a tiny pencil-sized spot of protons is used to target the tumor point by point and layer by layer. Protons can be aimed very precisely and, unlike conventional forms of radiation treatment, significantly minimize the radiation dose to nearby healthy tissue, reducing side effects and reducing recovery time.

The 110,000-square-foot, $200 million center is expected to treat up to 2,000 patients a year. It will be one of less than 15 proton therapy centers in the country, and the first in this area.

“This innovation will further improve on an already cutting-edge technology,” said Dean E. Albert Reece, MD, PhD, MBA, who is also vice president of medical affairs at the University of Maryland and the John Z. and Akiko Bowers Distinguished Professor at UMSOM. “This is another example of how our faculty are combining technology and medicine to save even more lives and make disease treatment even more safe and effective.”