Bahadur Yasir A, Constantinescu Camelia, Hassouna Ashraf H, Eltaher Maha M, Ghassal Noor M, Awad Nesreen A
Department of Radiology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia.
Department of Bio-Medical Physics, King Faisal Specialist Hospital & Research Center, Jeddah, Saudi Arabia.
J Contemp Brachytherapy. 2015 Jan;6(4):362-70. doi: 10.5114/jcb.2014.47816. Epub 2014 Dec 31.
To retrospectively compare the potential dosimetric advantages of a multichannel vaginal applicator vs. a single channel one in intracavitary vaginal high-dose-rate (HDR) brachytherapy after hysterectomy, and evaluate the dosimetric advantage of fractional re-planning.
We randomly selected 12 patients with endometrial carcinoma, who received adjuvant vaginal cuff HDR brachytherapy using a multichannel applicator. For each brachytherapy fraction, two inverse treatment plans (for central channel and multichannel loadings) were performed and compared. The advantage of fractional re-planning was also investigated.
Dose-volume-histogram (DVH) analysis showed limited, but statistically significant difference (p = 0.007) regarding clinical-target-volume dose coverage between single and multichannel approaches. For the organs-at-risk rectum and bladder, the use of multichannel applicator demonstrated a noticeable dose reduction, when compared to single channel, but statistically significant for rectum only (p = 0.0001). For D2cc of rectum, an average fractional dose of 6.1 ± 0.7 Gy resulted for single channel vs. 5.1 ± 0.6 Gy for multichannel. For D2cc of bladder, an average fractional dose of 5 ± 0.9 Gy occurred for single channel vs. 4.9 ± 0.8 Gy for multichannel. The dosimetric benefit of fractional re-planning was demonstrated: DVH analysis showed large, but not statistically significant differences between first fraction plan and fractional re-planning, due to large inter-fraction variations for rectum and bladder positioning and filling.
Vaginal HDR brachytherapy using a multichannel vaginal applicator and inverse planning provides dosimetric advantages over single channel cylinder, by reducing the dose to organs at risk without compromising the target volume coverage, but at the expense of an increased vaginal mucosa dose. Due to large inter-fraction dose variations, we recommend individual fraction treatment plan optimization.
回顾性比较子宫切除术后腔内阴道高剂量率（HDR）近距离放疗中多通道阴道施源器与单通道施源器潜在的剂量学优势，并评估分次重新计划的剂量学优势。
我们随机选择了12例子宫内膜癌患者，她们使用多通道施源器接受辅助性阴道残端HDR近距离放疗。对于每个近距离放疗分次，进行并比较了两个逆向治疗计划（中央通道和多通道加载）。还研究了分次重新计划的优势。
剂量体积直方图（DVH）分析显示，单通道和多通道方法在临床靶体积剂量覆盖方面存在有限但具有统计学意义的差异（p = 0.007）。对于危及器官直肠和膀胱，与单通道相比，使用多通道施源器显示出明显的剂量降低，但仅对直肠具有统计学意义（p = 0.0001）。对于直肠的D2cc，单通道的平均分次剂量为6.1±0.7 Gy，而多通道为5.1±0.6 Gy。对于膀胱的D2cc，单通道的平均分次剂量为5±0.9 Gy，而多通道为4.9±0.8 Gy。分次重新计划的剂量学益处得到了证明：DVH分析显示，由于直肠和膀胱定位及充盈的分次间差异较大，首次分次计划与分次重新计划之间存在较大但无统计学意义的差异。
使用多通道阴道施源器和逆向计划的阴道HDR近距离放疗比单通道圆柱体具有剂量学优势，可在不影响靶体积覆盖的情况下降低危及器官的剂量，但代价是增加阴道黏膜剂量。由于分次间剂量差异较大，我们建议进行个体化分次治疗计划优化。
