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Comparison of192Ir air kerma calibration coefficients derived at ARPANSA using the interpolation method and at the National Physical Laboratory using a direct measurement

  • D. Butler
  • A. Haworth
  • T. Sander
  • S. Todd
Scientific Note

Abstract

The reference air kerma rate from192Ir High Dose Rate (HDR) brachytherapy sources can be measured using a suitably calibrated Farmer chamber and an appropriate in-air calibration jig. When a primary standard for192Ir gamma rays is available, a calibration coefficient for the chamber and jig combination can be determined directly. In Australia, due to the absence of such a standard, the chamber must be calibrated by interpolation of the response in60Co and in a kilovoltage x-ray beam. Corrections for the effect of the jig, scatter and beam non-uniformity must then be measured or calculated before the reference air kerma rate can be determined. We compare the air-kerma calibration coefficient of a PTW 30010 PMMA/Al Farmer chamber (referred to as Farmer chamber throughout this report) obtained from the192Ir primary standard at the National Physical Laboratory in the UK with the corresponding coefficient obtained by interpolating Australian calibrations using60Co and 250 kV x-rays and determining suitable correction factors. The resulting chamber/jig calibration coefficients differ by 0.2% which is well within the combined standard uncertainties of 1.2% and 0.6% reported by ARPANSA and NPL respectively.

Key words

192Ir HDR brachytherapy dosimetry comparison 

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Copyright information

© Australasian College of Physical Scientists and Engineers in Medicine 2008

Authors and Affiliations

  1. 1.Australian Radiation Protection and Nuclear Safety AgencyYallambieAustralia
  2. 2.Peter MacCallum Cancer CentreMelbourneAustralia
  3. 3.School of Applied SciencesRMIT UniversityMelbourneAustralia
  4. 4.National Physical LaboratoryTeddingtonUK

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