[Radiochromic Hydrogel Dosimeters]

Radiochromic hydrogel dosimeters are a useful tool for the verification of 3D dose distributions using optical CT scanners which are lower cost and with higher spatial resolution in a limited time than MRI scanners. In this paper, recent development of radiochromic micelle gel and genipin-gelatin gel dosimeters are described. They have the advantage of water equivalency, low or no diffusion property, and lower toxicity. Micelle gels consist of leuco dye, surfactant, radical initiator (halocarbons), and gelling agent. The dose sensitivities are affected by the concentration of each component and the temperature during irradiation. In non-diffusing genipin-gelatin gels, radiation induced bleaching is observed. The dose sensitivity is strongly affected by the concentration of genipin and sulfuric acid and by the blending time with gelatin. Higher dose sensitivity and standardization of the dose evaluation procedure will be the future issue.