Development of a SiC semiconductor-based dosimeter for evaluating clinical dose distribution in carbon ion cancer therapy fields

Dosimeters with excellent energy resolution are required to improve quality control and assurance (QA/QC) for heavy-ion cancer therapy, in which multiple species of ions are expected to be used. The conventional ionization chamber that is widely used for QA/QC generally does not support quality discrimination for different radiation species, and several types of energy-dispersive dosimeters are being studied for this application, including silicon semiconductors on insulator devices. Other wide bandgap semiconductors with good radiation hardness, including SiC and diamond, are being studied for use in cancer therapy ion fields. In this study, a 4H-SiC Schottky barrier diode was used for energy-dispersive dosimetry in the clinical carbon therapy field at Gunma University Medical Center for Heavy Ion Beam Medicine. The relative biological effectiveness was estimated from the linear energy transfer spectra for a pristine carbon beam with an energy of 290 MeV/n and a spread-out Bragg peak beam using the linear-quadratic model. The results showed that the SiC-based dosimeter could be used in the detailed characterization of the clinical dose distribution of carbon ion cancer therapy fields.