High dose rate brachytherapy source measurement intercomparison

This work presents a comparison of air kerma rate (AKR) measurements performed by multiple radiotherapy centres for a single HDR ¹⁹²Ir source. Two separate groups (consisting of 15 centres) performed AKR measurements at one of two host centres in Australia. Each group travelled to one of the host centres and measured the AKR of a single ¹⁹²Ir source using their own equipment and local protocols. Results were compared to the ¹⁹²Ir source calibration certificate provided by the manufacturer by means of a ratio of measured to certified AKR. The comparisons showed remarkably consistent results with the maximum deviation in measurement from the decay-corrected source certificate value being 1.1%. The maximum percentage difference between any two measurements was less than 2%. The comparisons demonstrated the consistency of well-chambers used for ¹⁹²Ir AKR measurements in Australia, despite the lack of a local calibration service, and served as a valuable focal point for the exchange of ideas and dosimetry methods.