National Cancer Centre Singapore, Division of Radiation Oncology, Singapore; Monash University, Department of Medical Imaging and Radiation Sciences, Clayton, Australia.
Monash University, Department of Medical Imaging and Radiation Sciences, Clayton, Australia.
Med Dosim. 2022;47(1):92-97. doi: 10.1016/j.meddos.2021.09.004. Epub 2021 Nov 2.
Inter-fraction organ variations cause deviations between planned and delivered doses in patients receiving radiotherapy for prostate cancer. This study compared planned (D) vs accumulated doses (D) obtained from daily cone-beam computed tomography (CBCT) scans in high-risk- prostate cancer with pelvic lymph nodes irradiation. An intensity-based deformable image registration algorithm used to estimate contours for D was validated using geometrical agreement between radiation oncologist's and deformable image registration algorithm propagated contours. Spearman rank correlations (r) between geometric measures and changes in organ volumes were evaluated for 20 cases. Dose-volume (DV) differences between D and D were compared (Wilcoxon rank test, p < 0.05). A novel region-of-interest (ROI) method was developed and mean doses were analyzed. Geometrical measures for the prostate and organ-at-risk contours were within clinically acceptable criteria. Inter-group mean (± SD) CBCT volumes for the rectum were larger compared to planning CT (pCT) (51.1 ± 11.3 cmvs 46.6 ± 16.1 cm), and were moderately correlated with variations in pCT volumes, rs = 0.663, p < 0.01. Mean rectum DV for D was higher at V30-40 Gy and lower at V70-75 Gy, p < 0.05. Mean bladder CBCT volumes were smaller compared to pCT (198.8 ± 55 cmvs 211.5 ± 89.1 cm), and was moderately correlated with pCT volumes, rs = 0.789, p < 0.01. Bladder D was higher at V30-65 Gy and lower at V70-75 Gy (p < 0.05). For the ROI method, rectum and bladder D were lower at 5 to 10 mm (p < 0.01) as compared to D, whilst bladder D was higher than D at 20 to 50 mm (p < 0.01). Generated D demonstrated significant differences in organ-at-risk doses as compared to D. A well-constructed workflow incorporating a ROI DV-extraction method has been validated in terms of efficiency and accuracy designed for seamless integration in the clinic to guide future plan adaptation.
分次器官变化导致前列腺癌接受放射治疗的患者计划剂量和实际剂量之间的偏差。本研究比较了高危前列腺癌伴盆腔淋巴结照射患者的计划剂量（D）与每日锥形束 CT（CBCT）扫描获得的累积剂量（D）。一种基于强度的可变形图像配准算法用于估计 D 的轮廓，该算法使用放射肿瘤学家和可变形图像配准算法传播的轮廓之间的几何一致性进行验证。对于 20 例患者，评估了器官体积变化的几何测量值和器官体积变化的 Spearman 秩相关系数（r）。比较了 D 与 D 的剂量体积（DV）差异（Wilcoxon 秩检验，p<0.05）。开发了一种新的感兴趣区域（ROI）方法，并分析了平均剂量。前列腺和危及器官轮廓的几何测量值符合临床可接受标准。与计划 CT（pCT）相比，直肠的组间平均（±SD）CBCT 体积更大（51.1±11.3 cm3 对 46.6±16.1 cm3），与 pCT 体积变化中度相关，rs=0.663，p<0.01。D 时直肠的平均剂量在 30-40 Gy 时较高，在 70-75 Gy 时较低，p<0.05。与 pCT 相比，膀胱的平均 CBCT 体积较小（198.8±55 cm3 对 211.5±89.1 cm3），与 pCT 体积中度相关，rs=0.789，p<0.01。膀胱的 D 在 30-65 Gy 时较高，在 70-75 Gy 时较低，p<0.05。对于 ROI 方法，与 D 相比，直肠和膀胱的 D 在 5 至 10 mm 时较低（p<0.01），而膀胱的 D 在 20 至 50 mm 时高于 D（p<0.01）。与 D 相比，生成的 D 显示出危及器官剂量的显著差异。已验证一种构建良好的工作流程，该工作流程结合 ROI DV 提取方法，在效率和准确性方面具有优势，旨在无缝集成到临床中，以指导未来的计划适应。
