Korean J Med Phys.  2009 Mar;20(1):7-13.

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

Affiliations
  • 1Department of Radiation Oncology, Hanyang University Hospital, Korea. dochokim@yahoo.co.kr
  • 2Department of Radiation Oncology, Inhwa University Hospital, Korea.
  • 3Department of Nuclear Engineering, Hanyang University, Korea.
  • 4Department of Radiation Oncology, Kyung Hee University Hospital, Seoul, Korea.
  • 5Department of Radiation Oncology, Gachon University of Medicine and Science, Incheon, Korea.

Abstract

This work is for the preliminary study for the calibration of an (192)Ir 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 kappa(Q,Q0) is needed. In this study kappa(Q,Q0)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 kappa gen(Q,Q0), the chamber to chamber variations were within a maximum deviation of 0.5% with the individual kappa ind(Q,Q0). The results show why and how important ionization chambers must be calibrated individually for the calibration of (192)Ir 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.

Keyword

Beam quality correction factor; Absorbed dose to water; Ionization chamber; Primary standards

MeSH Terms

Brachytherapy
Calibration
Electrons
Water
Water
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