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Abstract：
Background Geometrical and anatomical variations occur during the brachytherapy of carcinoma cervix and dose optimization is necessary for every fraction of high‑dose rate intracavitary brachytherapy (HDR-ICBT) for carcinoma of the cervix. A single planned treatment is usually delivered for multiple fractions without consideration of inter-fractional applicator positioning variations and organ motion, which may lead to substantial differences between the planned and delivered doses. Aim and objectives This study was aimed at evaluating the inter-fractional variation in volume and radiation dose to organs at risk during ICBT for cervical cancer. Furthermore, the doses to high-risk clinical target volume (HRCTV) and the role of adaptive planning in ICBT were assessed. Materials and methods Twenty-two patients with carcinoma of the cervix Stage IB2-IVA receiving ICBT were enrolled in the study. All the patients were treated with ICBT four fractions in two applications. For the first application, magnetic resonance imaging-based planning was done, and for the next three fractions, computed tomography (CT) scans were done before every treatment fraction. The CT images were contoured and replanned by keeping the First (I) fraction of each application as the reference. Dose-volume histograms (DVH) were generated, and details of D2cc (DVH on a volume of 2cc) of bladder, rectum, and sigmoid colon (organs at risk-OAR) and D90 HRCTV (dose covering 90%) were documented. Results In patients receiving ICBT, variations in OAR D2cc ranged from 1.5 to 2.5Gy for the bladder (p- 0.001), from 2.0 to 3.2Gy (p-0.005) for the rectum and from 1.5 to 3.5Gy for the sigmoid colon (p 0.103). The p-value was significant for D2cc when compared with the OAR volume for the bladder and rectum in both applications, whereas it was not significant for the sigmoid colon. The percentage change in HRCTV coverage was 7% in the first application and by 16% in the second application because of adaptive planning. Conclusion Significant variations in doses received by D2cc of the bladder and rectum as well as significant improvement in HRCTV coverage between the fractions were observed because of replanning. Hence, image-guided HDR-ICBT should be incorporated with adaptive planning when delivering in multiple fractions.
摘要：
背景技术在宫颈癌的近距离放射治疗期间会发生几何和解剖学变化，并且对于宫颈癌的高剂量率腔内近距离放射治疗（HDR-ICBT）的每个部分，剂量优化都是必要的。一个单一的计划治疗通常是交付多个部分，而不考虑部分间的施药器定位变化和器官运动，这可能导致计划剂量和递送剂量之间的实质性差异。目的和目的本研究旨在评估宫颈癌ICBT期间对有风险器官的体积和辐射剂量的分数间变化。此外，评估了高危临床目标体积(HRCTV)的剂量和适应性计划在ICBT中的作用.材料和方法本研究纳入了22例接受ICBT治疗的IB2-IVA宫颈癌患者。所有患者均在两次应用中接受了ICBT四个部分的治疗。对于第一个应用程序，进行了基于磁共振成像的规划，接下来的三个部分，每次治疗前都进行计算机断层扫描(CT)扫描.通过保持每个应用的第一(I)部分作为参考,对CT图像进行轮廓化和重新扫描。产生剂量-体积直方图(DVH),以及膀胱D2cc（体积为2cc的DVH）的详细信息，直肠,记录了乙状结肠（OAR危险器官）和D90HRCTV（剂量覆盖90％）。结果在接受ICBT的患者中，膀胱OARD2cc的变化范围为1.5至2.5Gy（p-0.001），直肠从2.0到3.2Gy（p-0.005），乙状结肠从1.5到3.5Gy（p0.103）。在两种应用中，与膀胱和直肠的OAR体积相比，D2cc的p值显着。而乙状结肠则不显著。由于自适应规划，第一次应用的HRCTV覆盖率变化百分比为7％，第二次应用的变化百分比为16％。结论由于重新计划，观察到膀胱和直肠的D2cc接受的剂量显着变化，以及各部分之间HRCTV覆盖率的显着改善。因此，图像引导的HDR-ICBT应与自适应规划相结合，以多个部分交付。
