In IMRT (Intensity Modulated Radiation Therapy: IMRT) and VMAT (Volumetric Modulated Arc Therapy: VMAT), irradiation dose can be concentrated to a tumor by a complicated time-dependent control of multiple irradiation field segment and position of high energy X-rays. Therefore, dosimetric verification of each patient is significant in order to provide a high quality IMRT and VMAT to patients. However, conventional dosimeters such as ionization chambers, radiochromic films and multi- dimensional detectors cannot measure the time variation of dose distribution.

We consider a new verification system using a plastic scintillator (PS). PS is a material which emits fluorescence, called scintillation light, when it absorbed radiation dose. Time variation of the dose distribution can be measured by acquisition of the scintillation light distribution using a charge coupled device (CCD) camera because the decay time of the scintillation light is very short. In this study, we investigate the contamination effects of Cherenkov radiation from obtained CCD images and the diffusion effects of scintillation light for new dose verification system using PS and CCD camera.