Purpose:
This study investigated reliable vaginal mucosa dose-volume histogram (DVH) metrics in gynecologic template interstitial high-dose-rate brachytherapy (HDR-BT) for the purpose of standardized dose reporting.

Material and methods:
Gynecologic template (Syed/Neblett) interstitial HDR-BT patients treated from September 2016 to November 2022 at the study institute were included in the cohort. Each patient implant included a vaginal mucosa contour defined by a 5 mm expansion from vaginal cylinder, then another volume with clinical target volume subtracted. DVH metrics were investigated between D_0.1cc to D_4cc. Clinical plans were re-calculated using Monte Carlo (MC) simulations both in heterogeneous material and in water.

Results:
The patient cohort included 61 patients with clinical plans using conventional homogeneous dose calculation (TG43). Heterogeneous vs. water MC dose differences were between –1.1% and –1.4% for all metrics investigated. DVH metrics D_1cc and smaller resulted in > 5% discrepancies between TG43 and MC dose (to water) calculation due to the proximity of source positions in/nearby the vaginal mucosa. Reliability improved when DVH metric volume was larger (D_2cc and D_4cc). Both D_2cc and D_4cc presented very high linear correlation between TG43 and MC reported doses for the vagina, and average ± standard deviation dose difference was 4.6 ±2.9% and –3.0 ±1.9%, respectively. Dose differences decreased when the clinical target volume was removed: –1.5 ±3.5% and –0.8 ±2.1% for D_2cc and D_4cc, respectively.

Conclusions:
For perineal template gynecologic HDR-BT procedures, the 2 cc volume is the smallest representative volume that reliably reports vaginal dose and at minimum should be reported to establish dose and outcome evaluation.



中文翻译：

---

使用蒙特卡罗模拟评估妇科模板间质高剂量率近距离放射治疗的阴道粘膜剂量

目的：
本研究调查了妇科模板间质高剂量率近距离放射治疗 (HDR-BT) 中可靠的阴道粘膜剂量体积直方图 (DVH) 指标，以实现标准化剂量报告。

材料和方法：
2016年9月至2022年11月在研究机构接受治疗的妇科模板（Syed/Neblett）间质性HDR-BT患者被纳入队列。每个患者植入物都包括由阴道圆柱体延伸 5 毫米定义的阴道粘膜轮廓，然后减去临床目标体积的另一个体积。DVH 指标在 D _0.1cc至 D _4cc之间进行了研究。使用蒙特卡罗 (MC) 模拟在异质材料和水中重新计算临床计划。

结果：
患者队列包括 61 名使用传统均质剂量计算 (TG43) 进行临床计划的患者。对于所有调查的指标，异质 MC 与水 MC 剂量差异在 –1.1% 和 –1.4% 之间。由于阴道粘膜内/附近的源位置接近，DVH 指标 D _{1cc及更小导致 TG43 和 MC 剂量（对水）计算之间存在 > 5% 的差异。}当 DVH 公制体积较大（D _2cc和 D _4cc）时，可靠性会提高。D _2cc和 D _4cc在 TG43 和 MC 报告的阴道剂量之间呈现出非常高的线性相关性，平均±标准偏差剂量差异分别为 4.6 ±2.9% 和 –3.0 ±1.9%。当临床目标体积被移除时，剂量差异减小：D _2cc和 D _4cc分别为 –1.5 ±3.5% 和 –0.8 ±2.1%。

结论：
对于会阴模板妇科 HDR-BT 手术，2 cc 体积是可靠报告阴道剂量的最小代表体积，并且至少应报告以建立剂量和结果评估。