Tissue-equivalent gel for non-invasive spatial radiation dose measurements

In almost every single application of ionising radiation, the accurate dete rmination of absorbed radiation energy is of great importance. Radiation se nsitive gels were first proposed for non-destructive and non-invasive measu rements of the spatial distribution of radiation absorbed dose in 1984 [1]. Two different systems were developed but neither of these systems is widel y used in practice due to some technical drawbacks. To overcome the problem s associated with previous systems a gelatin gel of different composition h as been devised and characterised for radiation dosimetry. This system is b ased on the changes in the optical properties of a transparent gel medium w hen it is exposed to ionising radiation. The detection material was careful ly investigated and the role of each constituent of this system has been st udied in order to determine the optimum composition. Gel with this formula has a linear dose response in the range 0.1-30 Gy, this range can be altere d to suit other applications by changing the concentration of the active ch emicals. The gel sensitivity, defined as the change in optical density per unit radiation dose, was found to be 70 x 10(-3) cm(-1) Gy(-1) and the syst em stability was studied for both pre- and post-irradiation effects. This n ew formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths. (C) 2000 El sevier Science B.V. All rights reserved.