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Original Article

Korean Journal of Medical Physics 2006; 17(4): 232-237

Published online December 25, 2006

Copyright © Korean Society of Medical Physics.

The Development of Air-kerma Strength Calculation Algorithm in Terms of the Absorbed Dose to Water for HDR Ir-192 Source

기준점에서의 물 흡수선량을 이용한 Ir-192 선원의 공기커마 세기 계산을 위한 알고리즘 개발

HyunDo Huh*, WooChul Kim*, John J K Loh*, Suk Lee, SangHoon Lee, SamJu Cho, DongOh Shin§, Jinho Choi, Sooil Kwon, SeongHoon Kim

허현도*·김우철*·노준규*·이석·이상훈·조삼주·신동오§·최진호·권수일·김성훈

*Department of Radiation Oncology, College of Medicine, Inha University, Incheon; Department of Medical Physics, Kyonggi University, Suwon; Department of Radiation Oncology, College of Medicine, Korea University, Seoul; §Department of Radiation Oncology, Medicine, College of Medicine, KyungHee University, Department of Radiation Oncology, Gacheon Medical School, Gil Medical Center, Incheon; Department of Radiation Oncology, College of Medicine, Hanyang University, Seoul, Korea

*인하대학교 의과대학 방사선종양학교실, 경기대학교대학원 의학물리학과, 고려대학교 의과대학 방사선종양학교실, §경희대학교 의과대학 방사선종양학교실, 가천의과학대학교 방사선종양학교실, 한양대학교 의과대학 방사선종양학교실

Abstract

The aim of this study was to develop the calculation algorithm of source strength of Ir-192 source in terms of the absorbed dose to water instead of an apparent activity (Ci). For this work the Multi Purpose Brachytherapy Phantom(MPBP) was developed, which was designed to locate the source and the chamber precisely at a specific position inside the water phantom. The reference point of measurement was set at the 5 cm distance along the transverse axis of the source. For a brachytherapy source calibration, the absorbed dose to water calibration factor (ND,W,Q) of an ionization chamber were determined and then apply standard protocols of absorbed dose to water. The calibration factor (ND.W,Q) of the ion chamber (TM30013, PTW, Germany) was determined using the EGSnrcCPP Monte Carlo Code. The calculated calibration factor (ND,W,Q) was 5.28 cGy/nC. The calculated factor was then used to determine the absorbed dose to water from which the air kerma strength for an Ir-192 source can be easily derived at the reference point (5 cm). The calculated air kerma strength showed discrepancies of -0.6% to +1.8% relative to the air kerma strength provided by the vendor. In this work we demonstrated that the air kerma strength (Sk) could be determined from the absorbed dose to water calibration factor for Ir-192 source. In addition, this source calibration method could be applied directly to the dose calculation formalism of AAPM report TG-43.

KeywordsAir-kerma strength, Apparent activity, Algorithm, Calibration factor

Korean Society of Medical Physics

Vol.35 No.2
June 2024

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

Frequency: Quarterly

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