물흡수선량 표준에 기반한 192Ir 근접치료 선원 교정 시 원통형 이온함의 이온함 간 변화

Abstract

This work is for the preliminary study for the calibration of an 192Ir brachytherapy source based on an absorbed dose to water standards. In order to calibrate brachytherapy sources based on absorbed dose to water standards using a clyndirical ionization chamber, the beam quality correction factor kQ,Q0 is needed. In this study kQ,Q0s were determined by both Monte carlo simulation and semiexperimental methods because of the realistic difficulties to use primary standards to measure an absolute dose at a specified distance. The 5 different serial numbers of the PTW30013 chamber type were selected for this study. While chamber to chamber variations ran up to maximum 4.0% with the generic kgenQ,Q0, the chamber to chamber variations were within a maximum deviation of 0.5% with the individual kindQ,Q0. The results show why and how important ionization chambers must be calibrated individually for the calibration of 192Ir brachytherapy sources based on absorbed dose to water standards. We hope that in the near future users will be able to calibrate the brachytherapy sources in terms of an absorbed dose to water, the quantity of interest in the treatment, instead of an air kerma strength just as the calibration in the high energy photon and electron beam.