Source geometry factors for HDR ¹⁹²Ir brachytherapy secondary standard well-type ionization chamber calibrations

Physics in Medicine and Biology
D R ShipleyR F Nutbrown

Abstract

Well-type ionization chambers are used for measuring the source strength of radioactive brachytherapy sources before clinical use. Initially, the well chambers are calibrated against a suitable national standard. For high dose rate (HDR) (192)Ir, this calibration is usually a two-step process. Firstly, the calibration source is traceably calibrated against an air kerma primary standard in terms of either reference air kerma rate or air kerma strength. The calibrated (192)Ir source is then used to calibrate the secondary standard well-type ionization chamber. Calibration laboratories are usually only equipped with one type of HDR (192)Ir source. If the clinical source type is different from that used for the calibration of the well chamber at the standards laboratory, a source geometry factor, k(sg), is required to correct the calibration coefficient for any change of the well chamber response due to geometric differences between the sources. In this work we present source geometry factors for six different HDR (192)Ir brachytherapy sources which have been determined using Monte Carlo techniques for a specific ionization chamber, the Standard Imaging HDR 1000 Plus well chamber with a type 70010 HDR iridium source holder. The cal...Continue Reading

References

Feb 7, 2007·Medical Physics·D GraneroJ Venselaar
Mar 3, 2011·Medical Physics·Domingo GraneroMark J Rivard
Dec 14, 2011·Medical Physics·Brian E RasmussenLarry A Dewerd
Mar 28, 2012·Physics in Medicine and Biology·Pedro AndreoFrancesc Salvat

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