For Radiation Therapy, Seeing is Validation

Radiation oncologists can now see their treatment delivery in action. A new method that captures imaging and real-time video of the beam directly on the patient allows providers to see exactly what they are doing – and to make changes when necessary.

Known as Cherenkov imaging, this technique, developed by the Dartmouth-Hitchcock Norris Cancer Center (NCCC) and Dartmouth spin-off company DoseOptics, LLC, turns radiation therapy into a visual process, says the company’s co-founder.

“Cherenkov imaging provides visualization of the radiation therapy treatment, so that the treatment team can see everything and make adjustments when unexpected things happen,” said Brian Pogue, Ph.D., DoseOptics, LLC, co-founder and co-director of the NCCC Translational Engineering in Cancer Research Program.

When photon or electron radiation beams hit tissue, such as skin, it produces a small light emission from the surface, known as the Cherenkov effect. BeamSite cameras, also developed by DoseOptics, LLC, can capture real-time images of the treatment-beam shape, as well as show intensity levels that are proportional to the radiation dose. That data can be used to verify the accuracy of dose and beam delivery for each daily treatment, he said. Standard quality assurance measure cannot do this, he said.

The NCCC is the first cancer center in the world to install BeamSite Cherenkov imaging cameras into radiotherapy treatment rooms. Based on their initial experiences with the system, a team from Dartmouth published findings recently in The International Journal of Radiation Oncology, Biology, Physics.

To gather their data, the team, led by lead study author Lesley Jarvis, M.D., Ph.D., associate professor of medicine at Dartmouth’s Geisel School of Medicine and member of NCCC’s Translational Engineering in Cancer Research program, followed 64 patients receiving treatment for breast cancer, sarcoma, lymphoma, or other cancers.

Based on their analysis, six patients would have benefited from adjustments. For breast treatments, the Cherenkov images pinpointed instances where treatment delivery introduced dose to the contralateral breast, the arm, or the chin, as well as non-ideal bolus positioning. In addition, investigators found, with sarcoma patients, that there was no unintended exposure to the opposite leg, confirming that inadvertent dose was not a problem.

Although national statistics indicate a roughly 1-percent incidence rate of incorrect radiation therapy delivery, Pogue said, Cherenkov imaging still offers value for patient care.

“Normally, treatments are just fine,” he said. “However, if you cannot see where the beam is, then it is a blind treatment, and the interaction between patients and therapy team is just less natural than it could be if the treatment was visual.”

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