Proton therapy in combination with PET as monitor: a feasibility study

To evaluate the possibility of combining proton therapy with positron emission tomography (PET) as a therapy monitor and as a tool for in situ dosimetry during therapy, proton activation experiments have been performed using a 55-MeV proton beam on two different materials. The three-dimensional measurements of the induced activity with PET are compared with the calculated dose distribution and with model calculations. It is concluded that the radioactivity induced by proton beams in tissue-like (consisting mainly of C, N and O) materials can be measured accurately by means of PET. It is expected that the rather low amount of activity created during a therapy treatment can be detected with sufficient accuracy; in particular, the region preceding the Bragg peak in the dose distribution can be monitored quite well with this method