Preliminary studies towards the development of an in-vivo dosimetry system for radiation therapy

Effort has been centered upon developing a new-vivo dosimetry system based upon solid state nuclear track detector CR-39. Mostly in-vivo dosimetry is done with the help of thermoluminescence dosimeters. In-vivo dosimetry means confirming die calculated dose distribution within die body by actually measuring it at different parts of the body. The need for a new dosimetry system was felt due to the high cost of the TLD/sub s/ and its reading system. Further the easy availability and low cost of CR-39 detectors enticed its use as a gamma ray dosimeter. For using CR-39 as a gamma ray dosimeter, its response/bulk etching rate should vary linearly with the dose of the gamma radiation. In this context doses in the range of 0-18 Gy. were given to the detectors and the variation of bulk etch rate was measured. It was found that there is some relationship between dose and the bulk etch rate up to a dose of 14 Gy. In addition to this the effect of dose fractionation was also studied which showed that there is no or very little effect of dose fractionation (as compared to the dose given all at once) on the bulk etch rate of the CR-39 track detectors. (author)