Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, Japan.
J Radiat Res. 2012 Nov 1;53(6):936-44. doi: 10.1093/jrr/rrs035. Epub 2012 Jul 17.
To develop an easy independent patient-specific quality assurance (QA) method using a benchmark plan for high-dose-rate intracavitary brachytherapy for cervix cancer, we conducted benchmark treatment planning with various sizes and combinations of tandem-ovoid and tandem-cylinder applications with 'ideal' geometry outside the patient. Two-dimensional-based treatment planning was conducted based on the Manchester method. We predicted the total dwell time of individual treatment plans from the air kerma strength, total dwell time and prescription dose of the benchmark plan. In addition, we recorded the height (dh), width (dw) and thickness (dt) covered with 100% isodose line. These parameters were compared with 169 and 29 clinical cases for tandem-ovoid or tandem-cylinder cases, respectively. With regard to tandem-ovoid cases, differences in total dwell time, dh, dt and dw between benchmark and individual plans were on average -0.2% ± 3.8%, -1.0 mm ± 2.6 mm, 0.8 mm ± 1.3 mm and -0.1 mm ± 1.5 mm, respectively. With regard to tandem-cylinder cases, differences in total dwell time, dh(front) (the distance from tandem tip to tandem ring), dt and dw between benchmark and individual plans were on average -1.5% ± 3.1%, -1.5 mm ± 4.9 mm, 0.1 mm ± 1.0 mm and 0.2 mm ± 0.8 mm, respectively. Of two cases, more than 13% differences in total dwell time were observed between benchmark plans and the clinical cases, which turned out to be due to the use of the wrong source position setting. These results suggest that our method is easy and useful for independent verification of patient-specific treatment planning QA.
为了开发一种用于宫颈癌高剂量率腔内近距离治疗的简便独立患者特异性质量保证（QA）方法，我们使用“理想”患者外的子宫颈肿瘤模型，对各种大小的宫旁组织模型进行了包括 tandem-ovoid 和 tandem-cylinder 在内的组合的基准治疗计划。二维治疗计划是基于 Manchester 方法进行的。我们根据基准计划的空气比释动能强度、总驻留时间和处方剂量，预测了各个治疗计划的总驻留时间。此外，我们记录了覆盖 100%等剂量线的高度（dh）、宽度（dw）和厚度（dt）。这些参数分别与 169 个和 29 个 tandem-ovoid 或 tandem-cylinder 病例的临床病例进行了比较。对于 tandem-ovoid 病例，基准计划和个体计划之间的总驻留时间、dh、dt 和 dw 的差异平均为-0.2%±3.8%、-1.0mm±2.6mm、0.8mm±1.3mm 和-0.1mm±1.5mm。对于 tandem-cylinder 病例，基准计划和个体计划之间的总驻留时间、dh（front）（从 tandem 尖端到 tandem 环的距离）、dt 和 dw 的差异平均为-1.5%±3.1%、-1.5mm±4.9mm、0.1mm±1.0mm 和 0.2mm±0.8mm。在这两个病例中，基准计划和临床病例之间的总驻留时间差异超过 13%，这是由于源位置设置错误所致。这些结果表明，我们的方法对于独立验证患者特异性治疗计划 QA 既简单又实用。
