Feasibility Study of Alanine Dosimeter for Carbon-Beam Dosimetry

Alanine dosimeters are useful tools for measuring both kilo-gray level doses and radiation therapy level doses. The National Metrology Institute of Japan is planning to develop a dose measurement service for carbon-beam therapy. The purpose of this study was to verify that the alanine dosimeter could be used for carbon-beam dosimetry. We irradiated the alanine dosimeter with 60Co-gamma rays and a carbon beam using a range of 10–30 Gy. For the gamma-ray irradiation, the alanine dosimeter was placed in a 5 g cm−2 water phantom. For the carbon-beam irradiation, the spread out Bragg peak of the 290 meV/u carbon ion was used, and the dosimeter was located at the centre of the peak region. The alanine spectra obtained under the carbon-beam irradiation were almost the same as the spectra under the gamma-ray irradiation. The alanine dosimeter irradiated with the carbon beam show a smaller signal than that obtained under the gamma-ray irradiation for the same dose. The alanine signal increased as the dose increased over the entire dosage range for both the gamma-ray and carbon-beam irradiation. This result suggests that the alanine dosimeter has potential for carbon-beam dosimetry.