Absorbed dose to water distribution measured around an HDR 192Ir brachytherapy source by thermoluminescent dosimeters

The purpose of this work was to develop a procedure to directly estimate the spatial distribution of the absorbed dose rate to water, (D) over dot(w), around an HDR Ir-192 brachytherapy source. The methodology developed was based on Monte Carlo calculations and measurements in air and in water with thermoluminescent detectors. Variations in detector positioning had a significant influence near the brachytherapy source (20% at 1 cm). The method leads to a mean difference of about 7% with the CLRP TG-43 Parameter Database when the absorbed dose to water is characterized along the transverse plane to the source (from 1 cm to about 11 cm). This mean difference, however, is within an uncertainty of 7.7% over all distances. This method therefore can be used to provide direct estimates of the absorbed dose rate to water for HDR brachytherapy source irradiations which are more realistic than those which use other phantom materials. In addition, measurements are indicative of the source geometry and material composition.