Development of a Compact Dose Verification System Using a Fluorescent Screen for Carbon-Ion Therapy

For quality assurance (QA) of therapeutic ion beams, a QA tool having high spatial resolution and quick verification is required. An imaging system with a fluorescent screen is suitable for the QA procedure. We developed a compact and quick verification system (NQA-SCN) using a fluorescent screen with a charge-coupled device (CCD) camera for the sake of two-dimensional dosimetry. The NQA-SCN can be attached to the irradiation port and the water column. Several types of corrections were applied to the raw image obtained by using the NQA-SCN. Our goal is to use the NQA-SCN for three-dimensional dose verification. However, in carbon-ion therapy, the fluorescent light is decreased by the quenching effect due to the increased linear energy transfer (LET) in the Bragg peak. For three-dimensional dose verification, as a first approach, we investigated the quenching effect of a carbon-ion beam in water. Also, to evaluate the performance of NQA-SCN, we carried out experiments concerning QA procedures