Sander, T; Billas, I; Kelly, M; Maughan, D J; Shipley, D R (2024) Changes to the NPL reference air kerma rate primary standard TH100C for high dose rate 192Ir brachytherapy sources. NPL Report. IR 67

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Abstract

The NPL reference air kerma rate (RAKR) primary standard cavity ionisation chamber for high dose rate (HDR) 192Ir brachytherapy sources, designated as TH100C, was originally established in 2004. From 2004 to 2013, the cavity chamber was used to measure the RAKR of Nucletron microSelectron-v1 classic HDR 192Ir sources. This type of source became obsolete at the end of 2013. Since 2014, the cavity chamber has been used for measuring Elekta HDR 192Ir Flexisources instead. Switching from one source type to another required a re-evaluation of some of the primary standard conversion and correction factors in 2014. Additionally, the implementation of new physical data from ICRU report 90 required a recalculation of some of the Monte Carlo (MC) calculated correction factors. Pre-July 2019 calibrations for HDR 192Ir at NPL were based on data from ICRU report 37.

This NPL report is an update to NPL report DQL-RD 004 (Sander and Nutbrown 2006) and summarises the changes made to various primary standard correction factors since 2006. An updated uncertainty budget for the measurement of RAKR of an Elekta HDR 192Ir Flexisource and the calibration of secondary standard ionisation chambers is also presented.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	IR 67
Keywords:	high dose rate; Ir-192; brachytherapy reference; air kerma rate; primary standard; correction factors
Subjects:	Ionising Radiation > Dosimetry
Divisions:	Medical, Marine & Nuclear
Identification number/DOI:	10.47120/npl.IR67
Last Modified:	11 Dec 2024 09:08
URI:	https://eprintspublications.npl.co.uk/id/eprint/10105