Daily QA System for the Rotating Gantry for Carbon Ion Therapy at NIRS

At the National Institute of Radiological Sciences (NIRS), we have been commissioning the rotating-gantry system for the carbon-ion radiotherapy. This system is equipped with a three-dimensional pencil beam scanning irradiation system. To ensure the treatment quality, calibration of the primary dose monitor, range check, dose rate check, machine safety check, and some mechanical tests should be performed efficiently. For this purpose, we have developed a measurement system dedicated for quality assurance (QA) of this gantry system. The system consists of an ionization chamber system and a scintillator system. For the ionization chamber system, a Farmer type ionization chamber is inserted into the center of a plastic water phantom. The thickness of the phantom could be changed so that employ both calibration of the output at entrance and output checking at center of the irradiation field. For the scintillator system, the ranges of beams are verified using a CCD camera and a scintillator. From the taken images, maximum gradient points are determined by some image processing and compared with reference data. In this paper, we describe consideration of the daily QA for the rotating-gantry.19th International Conference on Accelerators and Beam Utilization