Introduction
The use of vaginal immobilization balloons placed into the vagina for immobilization of tandem and ovoid (T + O) applicator during high-dose-rate (HDR) brachytherapy delivery has been used at our institution, and seems to have improved our patient comfort, decreased procedure time, and minimized applicator misplacement. We aimed to show that these balloons, while originally marketed for single-day use, are safe and maintain applicator positioning/dosimetry when left in situ overnight for treatment delivery on sequential days.

Material and methods
Forty-two paired computed tomography (CT) scans from thirteen patients who underwent T + O HDR treatments on sequential days with vaginal immobilization balloons in situ overnight were retrospectively compared to calculate mean change of balloon volumes and balloon/T + O distance to bony landmarks. Dosimetric planning was retroactively performed on day 2 using CT scan of each pair, and the change in estimated radiation delivery to the bladder and rectum was compared.

Results
No statistically significant overnight changes were found in balloon volumes or anterior balloon positioning. The posterior balloon shifted –0.29 ±0.46 cm (p = 0.03) to the anterior public symphysis and 0.32 ±0.50 cm (p = 0.01) to the right femoral head. The tandem shifted 0.37 ±0.39 cm (p = 0.002) to the pubic symphysis. There was no significant difference found in radiation delivered to the bladder or rectum between the paired scans.

Conclusions
This study showed minimal change in balloon volumes, balloons/T + O positioning, or in radiation dose to bladder and rectum when the applicator remained overnight. These findings support that inflatable vaginal immobilization balloons remaining in situ overnight for additional HDR T + O treatments on sequential days, is safe and provides stable dosimetry.



中文翻译：

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阴道固定球囊在宫颈癌近距离治疗中过夜原位的可重复性

介绍
在我们的机构中​​使用放置在阴道内的阴道固定球囊在高剂量率 (HDR) 近距离放射治疗期间固定串联和卵形 (T + O) 施药器，并且似乎改善了我们的患者舒适度，减少了手术时间，并最大限度地减少了涂药器的错位。我们的目的是证明，这些球囊虽然最初在市场上销售为单日使用，但在原位过夜以连续几天进行治疗时，是安全的，并且可以保持涂药器的定位/剂量测定。

材料与方法
回顾性比较了 13 名连续几天接受 T + O HDR 治疗的患者的 42 对计算机断层扫描 (CT) 扫描，这些患者使用阴道固定球囊在原位过夜，以计算球囊体积的平均变化和球囊/T + O 到骨标志的距离. 在第 2 天使用每对 CT 扫描追溯执行剂量计划，并比较估计的膀胱和直肠辐射输送的变化。

结果
在球囊体积或前球囊定位中未发现具有统计学意义的过夜变化。后球囊移动 –0.29 ±0.46 cm (p = 0.03) 到前公共联合，0.32 ±0.50 cm (p = 0.01) 移动到右侧股骨头。串联移动 0.37 ±0.39 cm (p = 0.002) 到耻骨联合。在成对扫描之间，输送到膀胱或直肠的辐射没有显着差异。

结论
本研究表明，当施放器保持过夜时，球囊体积、球囊/T + O 定位或膀胱和直肠的辐射剂量变化很小。这些发现支持充气阴道固定气球在原位过夜以在连续几天进行额外的 HDR T + O 治疗，是安全的并提供稳定的剂量测定。