Evaluation of radioactivity induced by patient-specific devices in proton therapy

Estimating the radioactivity induced by patient-specific devices installed near the patient skin is important, because patients are directly exposed during the treatment. This study evaluated the radioactivity induced by a brass collimator and a PMMA range compensator in a proton beam and identified the radionuclides produced by nuclear interactions with the proton beam and with the patient-specific devices. The total dose rate depended on the radionuclides, which had short decay times and 1 hour later their activities reach about one-fiftieth of the initial values in the cases of both PMMA and brass. Although the radioactivity induced by proton therapy can affect patients during the radiotherapy, the total radiation dose is much smaller than the prescribed dose for cancer treatment, and the treatment time is very short. Therefore, the radioactivity induced by patient-specific devices should be negligible.