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

In almost every single application of ionising radiation, the accurate determination of absorbed radiation energy is of great importance. Radiation sensitive gels were first proposed for non-destructive and non-invasive measurements of the spatial distribution of radiation absorbed dose in 1984. Two different systems were developed but neither of these systems is widely used in practice due to some technical drawbacks. To overcome the problems associated with previous systems a gelatin gel of different composition has been devised and characterised for radiation dosimetry. This system is based on the changes in the optical properties of a transparent gel medium when it is exposed to ionising radiation. The detection material was carefully investigated and the role of each constituent of this system has been studied 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 altered to suit other applications by changing the concentration of the active chemicals. The gel sensitivity, defined as the change in optical density per unit radiation dose, was found to be 70x10-3 cm-1 Gy-1 and the system stability was studied for both pre- and post-irradiation effects. This new formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths