Multi-Institutional Study of End-to-End Dose Delivery Quality Assurance Testing for Image-Guided Brachytherapy Using a Gel Dosimeter

• DOI: 10.1016/j.brachy.2022.06.006
• Publication Date: 2022-07-25T12:11:07Z
• Authors: Hidenobu Tachibana; Yusuke Watanabe; Shogo Kurokawa; Takuya Maeyama; Tomoyuki Hiroki; Hideaki Ikoma; Hideaki Hirashima; Hironori Kojima; Takehiro Shiinoki; Yuuki Tanimoto; Hidetoshi Shimizu; Hiroki Shishido; Yoshitaka Oka; Taka-aki Hirose; Masashi Kinjo; Takuya Morozumi; Masahiko Kurooka; Hidekazu Suzuki; Tomohiko Saito; Keiichi Fujita; Ryosuke Shirata; Ryuji Inada; Ryuichi Yada; Mikiko Yamashita; Kazuto Kondo; Takashi Hanada; Tadashi Takenaka; Keisuke Usui; Hiroyuki Okamoto; Hiroshi Asakura; Ryoichi Notake; Toru Kojima; Yu Kumazaki; Shogo Hatanaka; Riki Kikumura; Masaru Nakajima; Ryosei Nakada; Ryusuke Suzuki; Hideyuki Mizuno; Shinji Kawamura; Mistuhiro Nakamura; Tetsuo Akimoto
• Keywords: 03 medical and health sciences; Catheters; 0302 clinical medicine; Radiation Dosimeters; Phantoms, Imaging; Brachytherapy; Humans; Radiotherapy Dosage; Tomography, X-Ray Computed; Radiometry; 3. Good health

To quantify dose delivery errors for high-dose-rate image-guided brachytherapy (HDR-IGBT) using an independent end-to-end dose delivery quality assurance test at multiple institutions. The novelty of our study is that this is the first multi-institutional end-to-end dose delivery study in the world.The postal audit used a polymer gel dosimeter in a cylindrical acrylic container for the afterloading system. Image acquisition using computed tomography, treatment planning, and irradiation were performed at each institution. Dose distribution comparison between the plan and gel measurement was performed. The percentage of pixels satisfying the absolute-dose gamma criterion was reviewed.Thirty-five institutions participated in this study. The dose uncertainty was 3.6% ± 2.3% (mean ± 1.96σ). The geometric uncertainty with a coverage factor of k = 2 was 3.5 mm. The tolerance level was set to the gamma passing rate of 95% with the agreement criterion of 5% (global)/3 mm, which was determined from the uncertainty estimation. The percentage of pixels satisfying the gamma criterion was 90.4% ± 32.2% (mean ± 1.96σ). Sixty-six percent (23/35) of the institutions passed the verification. Of the institutions that failed the verification, 75% (9/12) had incorrect inputs of the offset between the catheter tip and indexer length in treatment planning and 17% (2/12) had incorrect catheter reconstruction in treatment planning.The methodology should be useful for comprehensively checking the accuracy of HDR-IGBT dose delivery and credentialing clinical studies. The results of our study highlight the high risk of large source positional errors while delivering dose for HDR-IGBT in clinical practices.