A Dose verification method for proton therapy by using a plastic scintillation plate

An interesting issue in proton therapy is how to reduce the time needed for percent depth dose (PDD) measurement and how to prepare a two-dimensional dose measurement tool for a proton scanning beam. Currently, three-dimensional water phantom systems are used for range verification in the scattering beam mode of proton therapy. However, this approach is very slow and is in appropriate for use with a proton scanning beam. At the National Cancer Center in Korea (NCC), we have developed a simple and easy-to-handle range verification system that consists of a plastic scintillation plate, a PMMA (poly methyl methacrylate) phantom, a charge-coupled device camera, and a one-dimensional moving table. In the present study, the linearity of the signal with the dose, the background signal measurement and correction, and the influence of the ionization density on the signal were investigated using our new system. The measured yield depended linearly on the dose, and the dose range measurements had a spatial resolution of about 1 mm.