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Original Article

Korean Journal of Medical Physics 2009; 20(1): 7-13

Published online March 25, 2009

Copyright © Korean Society of Medical Physics.

Chamber to Chamber Variations of a Cylindrical Ionization Chamber for the Calibration of an 192Ir Brachytherapy Source Based on an Absorbed Dose to Water Standards

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

Seong Hoon Kim*, Hyundo Huh, Sang Hyun Choi, Chan Hyeong Kim,Chul Hee Min, Dong Oh Shin§, Jinho Choi

김성훈*ㆍ허현도ㆍ최상현ㆍ김찬형ㆍ민철희ㆍ신동오§ㆍ최진호

*Department of Radiation Oncology, Hanyang University Hospital, Department of Radiation Oncology, Inhwa University Hospital, Department of Nuclear Engineering, Hanyang University, §Department of Radiation Oncology, Kyung Hee University Hospital, Seoul, Department of Radiation Oncology, Gachon University of Medicine and Science, Incheon, Korea

*한양대학병원 방사선종양학과, 인하대학병원 방사선종양학과, 한양대학교 원자력공학과, §경희의료원 방사선종양학과, 가천의과대학 방사선종양학교실

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

k _{Q,Q _{o}}

is needed. In this study

k _{Q,Q _{o}}

s 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
k _{Q,Q _{0}} ^{g e n}
, the chamber to chamber variations were within a maximum deviation of 0.5% with the individual

k _{Q,Q _{0}} ^{i n d}

. 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.

KeywordsBeam quality correction factor, Absorbed dose to water, Ionization chamber, Primary standards

Korean Society of Medical Physics

Vol.35 No.1
March 2024

pISSN 2508-4445
eISSN 2508-4453
Formerly ISSN 1226-5829

Frequency: Quarterly

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