Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran.
Radiation Oncology Research Center (RORC), Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.
Med Dosim. 2022;47(4):318-324. doi: 10.1016/j.meddos.2022.06.001. Epub 2022 Jul 28.
Vaginal brachytherapy is a standard method for preventing the recurrences of malignancies in the treatment of gynecological cancers. Cylindrical applicators are usually employed in high dose rate cobalt-60 source brachytherapy after abdominal hysterectomy or bilateral salpingo-oophorectomy treatment. The aim of this study is to conduct an assessment of dosimetric properties of single channel, multichannel, and shielded cylinder applicators. This study utilizes a pelvis phantom with three different volumes of bladder and rectum to perform dose measurement around the cylindrical applicators. GAFCHROMIC EBT3 model film was used to measure dose distributions in water phantom around the bladder, rectum, applicator, and CTV. In order to properly compare the performance of the shielded applicator with multichannel and single channel applicators, we consider the both cases of a one-sided CTV and two CTVs placed on both sides of the vagina. Dose-volume histograms analysis shows no statistically significant difference in tumoral region for the two types of CTV between cylindrical applicators. The V, V and D values of target volume were 47.36%. 91.46%, and 3.99Gy for multi-channel cylinder applicator, 60.2%, 95.02%, and 3.99Gy for single channel cylinder applicator, respectively. Statistical analysis reports D, D and D for the multichannel applicator demonstrates a significant dose reduction in bladder compared with single channel. The V, V and D values of target volume were 55.50%. 97.90%, and 3.91Gy for multi-channel cylinder applicator with four active channels (MCC-4), 41.56%, 92.10%. and 4.13Gy for shielded cylinder applicator, respectively. Statistical analysis reports D, D and D for the MCC-4 demonstrates a noticeable dose reduction in bladder and rectum compared with Shielded channel. The results indicate that employing multichannel applicator in vaginal high dose rate cobalt-60 source brachytherapy can reduce the received dose to organs at risk without any significant loss of received dose in CTV, which is contributed to its asymmetric or symmetric dose distribution that depend on which channels are activated.
阴道近距离放疗是妇科癌症治疗中预防恶性肿瘤复发的标准方法。在腹部子宫切除术或双侧输卵管卵巢切除术治疗后，通常使用圆柱形施源器进行高剂量率钴-60 源近距离放疗。本研究旨在评估单通道、多通道和屏蔽圆柱形施源器的剂量学特性。本研究使用具有三个不同膀胱和直肠体积的骨盆体模，在圆柱形施源器周围进行剂量测量。使用 GAFCHROMIC EBT3 模型胶片在膀胱、直肠、施源器和 CTV 周围的水模体中测量剂量分布。为了正确比较屏蔽施源器与单通道和多通道施源器的性能，我们考虑了将单侧 CTV 和放置在阴道两侧的两个 CTV 两种情况。剂量-体积直方图分析表明，在圆柱形施源器中，两种 CTV 类型在肿瘤区域没有统计学上的显著差异。靶体积的 V、V 和 D 值分别为多通道圆柱形施源器的 47.36%、91.46%和 3.99Gy、单通道圆柱形施源器的 60.2%、95.02%和 3.99Gy。统计分析报告多通道施源器的 D、D 和 D 表明与单通道相比，膀胱的剂量显著降低。靶体积的 V、V 和 D 值分别为多通道圆柱形施源器（MCC-4）的 55.50%、97.90%和 3.91Gy、具有四个有源通道的多通道圆柱形施源器（MCC-4）的 41.56%、92.10%和 4.13Gy、屏蔽圆柱形施源器的 41.56%、92.10%和 4.13Gy。统计分析报告 MCC-4 的 D、D 和 D 表明，与屏蔽通道相比，膀胱和直肠的剂量显著降低。结果表明，在阴道高剂量率钴-60 源近距离放疗中使用多通道施源器可以降低危及器官的接受剂量，而不会对 CTV 中的接受剂量造成任何显著损失，这归因于其不对称或对称的剂量分布，这取决于激活的通道。
