Practical experience commissioning MRI-compatible tandem and ring applicators for use with the Bravos HDR afterloader.

Five complete MR-conditionally approved ring sets, including fifteen tandems, and two additional rings, were commissioned at an institution intending to use them in an MRI planning environment with a Bravos HDR brachytherapy remote afterloader. Channel length, radiograph, autoradiograph, ring offset, and treatment interrupt measurements were performed, and applicators were assessed in both CT and MRI. During commissioning, one ring was found to be defective and was returned to the manufacturer for a replacement. The eventual complete applicator suite (including the replacement ring) was found to follow the manufacturer-provided specifications, including those delineated in vendor-provided 3D virtual models and those defined within the manufacturer's instructions for use documentation. Based on this work, an offset correction of -0.4 cm will be used for all tested rings using the Bravos system's internal distal dwell position correction feature during treatment preparation. This study reiterated the requirement for careful commissioning of each applicator intended for clinical service considering the intended use and the planned clinical environment and work processes.