Air‐kerma strength determination of a high dose rate brachytherapy source

The increased demand for high dose rate (HDR) brachytherapy as an alternative to external beam radiotherapy has led to the introduction of a HDR brachytherapy isotope . This source offers a dose rate similar to HDR sources, at about one fourth the effective photon energy. This work presents the calibration of this source in terms of air‐kerma strength, based on an adaptation of the current, National Institute of Standards and Technology traceable, in air measurement technique currently used for HDR sources. Several additional measurement correction factors were required, including corrections for air scatter, air attenuation, and ion recombination. A new method is introduced for determining the ion chamber calibration coefficient . An uncertainty analysis was also performed, indicating an overall measurement expanded uncertainty in the air‐kerma strength of 2.2%.