‘End to end’ dosimetry audit for HDR brachytherapy

Abstract

Purpose: A dosimetric audit of Ir-192 high dose rate (HDR) brachytherapy remote afterloading units was carried out in 2019. All six brachytherapy departments on the island of Ireland participated in an end-to-end test and in a review of local HDR dosimetry procedures. Materials and methods: A 3D-printed customised phantom was created to position the following detectors at known distances from the HDR source: a Farmer ionization chamber, GafChromic film and thermoluminescent dosimeters (TLDs). Dedicated HDR applicator needles were used to position an Ir-192 source at 2 cm distance from these detectors. The end-to-end dosimetry audit pathway was performed at each host site and included the stages of imaging, applicator reconstruction, treatment planning and delivery. Deviations between planned and measured dose distributions were quantified using gamma analysis methods. Local procedures were also discussed between auditors and hosts.