Development of an easy-to-handle range measurement tool using a plastic scintillator for proton beam therapy.

Proton beam therapy can concentrate the dose on a tumour. In order to offer high-precision proton beam therapy to the patient, it is important to confirm the range every day. At the National Cancer Center Hospital East (NCC), the range measurement tool consists of a water phantom and an ionization chamber. These large and heavy tools take a long time to set up. Therefore, we developed a simple and easy-to-handle range measurement tool for proton beam therapy. This tool consists of a plastic scintillator block and a CCD camera. We recorded visible scintillation light generated by proton irradiation on the scintillator, and could measure the range from the shape of light distribution by using a computer with automatic analysis software installed. We carried out proton irradiation experiments with this tool to examine its performance as a tool of daily range measurements. The precision of the range measurement is within 0.3 mm (sd). The tool can measure possible short-term range variation with 1 s sampling time during the time interval of a typical treatment in a few minutes. We conclude that this tool can measure the range with sufficient resolution in a short time, and is useful for range control in a clinical setting.