Designing intensity modulated brachytherapy applicator for vaginal cuff applications: Dosimetrical feasibility study

Depending on technological advances in radiotherapy, the use of three-dimensional (3D) treatment planning in brachytherapy (BRT) applications has provided a great advantage in terms of efficacy of treatment in gynecological patients. In this study, it was aimed to design intensity modulated (IM) vaginal cuff applicator which allows IM-BRT applications in gynecologic patients who require vaginal cuff BRT. Applicator, quality assurance phantom and auxiliary fixation devices were modeled in "Sketchup" drawing program and print out from "MakerBot Replicator Z18" 3D printer. The quality control (QC) tests conducted with the aim of testing the clinical use of applicator was carried out in Varian GammaMed Plus iX BRT device and treatment planning simulation processes were performed in BrachyVision treatment planning system (TPS) used in Hacettepe University Department of Radiation Oncology. When the measurement results were analyzed, it was observed that measurements performed in homogenous medium for different measurement conditions were compatible with TPS within 4% differences in point dose measurement. Furthermore, in 2D dosimetry, the number of passing point was found greater than %90 for all measurements using gamma evaluation criteria of 3 mm distance-to-agreement (DTA) and 3% dose difference (DD). In mechanical QC tests it was found that the designed applicator had a positioning accuracy less than 1 mm. In the next stage, prospective studies are planned in an appropriate patient group so that the clinical effectiveness of the applicator can be evaluated.