Linear energy transfer (LET) spectroscopy and relative biological effect estimation by SiC-based dosimeter at clinical carbon-beam cancer therapy field

A radiation-tolerant silicon carbide (SiC) based dosimeter was developed for the measurement of linear energy transfer (LET) distributions along the Bragg curve for pristine and spread-out Bragg peak (SOBP) clinical carbon beam. Since the conventional ionized chamber is not suitable and effective for LET measurement, several energy-dispersive dosimeters are being developed and tested in the clinical field. While most of the detector lacks radiation hardness against carbon beam, we have utilized wide-bandgap semiconductors of SiC with different epitaxial layers from 25, 69, and 170 μm as a dosimeter for the clinical carbon field at Gunma University Heavy Ion Medical Center (GHMC). LET spectra were obtained not only for pristine carbon beams with an energy of 290 MeV/n but also SOBP conditions. It was confirmed through the changes in LET distribution, primally carbons and fragments are identified, and those energy depositions are successfully obtained by the fabricated SiC dosimeter. The distribution of relative biological effectiveness (RBE) was estimated from LET through biological estimation models. Results suggested that SiC-based dosimeter is successful in being utilized in the detailed characterization of the clinical carbon therapy field.