Monitoring Proton Therapy Through In-Beam PET: An Experimental Phantom Study

In this work, we investigate the use of a PET system to monitor the proton therapy. The monitoring procedure is based on the comparison between the β+activity generated in the irradiated volume during the treatment, with the β+activity distribution obtained with Monte Carlo simulation. The dedicated PET system is a dual head detection system; each head is composed of nine scintillating LYSO crystal matrices read out independently with a custom modularized acquisition system. Our experimental data were acquired at the Cyclotron Centre Bronowice, Institute Nuclear Physics in Krakow, Poland and were simulated with the FLUKA Monte Carlo code. Homogeneous and heterogeneous plastic phantoms were irradiated with monoenergetic 130-MeV protons. The capabilities of our PET system to distinguish different irradiated materials were investigated, and the proton pencil beams were used as probes. Our focus was to analyze the activity width and the total activity event number in several cases. Irradiations were performed using either single pencil beams one at a time, or two pencil beams during the same data taking. The comparison of 1D activity profile for experimental data and MC simulation were always in good agreement showing that, the treatment quality assessment in proton therapy can be based on β+ activity measurements.