Nguyen Tran Thi Thao, Arimura Hidetaka, Asamura Ryosuke, Hirose Taka-Aki, Ohga Saiji, Fukunaga Jun-Ichi
Division of Medical Quantum Science, Department of Health Sciences, Graduate School of Medical Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Japan Society for the Promotion of Science, 5-3-1, Kojimachi, Chiyoda-ku, Tokyo, 102-0083, Japan.
Radiol Phys Technol. 2019 Jun;12(2):137-148. doi: 10.1007/s12194-019-00502-0. Epub 2019 Feb 25.
This study compared dosimetric indices of volumetric-modulated arc therapy (VMAT) with intensity-modulated radiation therapy (IMRT) accounting for cold spots in prostate cancer plans. IMRT plans were retrospectively generated from 30 prostate cancer patients with ten cases for each risk group, who received VMAT plans. The mean, maximum, and minimum doses, and conformity and homogeneity indexes were evaluated for planning target volume (PTV) and the mean dose and V20-V70 for organs at risk (OAR) including the rectum, bladder, right and left femoral heads, and rectum overlapped with PTV (ROP) regions. The numbers and volume percentages of cold spots within PTVs and ROP regions were measured using in-house software. Three-dimensional probabilistic distributions of the probability and distributions of cold spots were generated using a centroid matching technique for visualization and analysis. There was a statistically better dose conformity in the PTV, rectum, and bladder dose-sparing in VMAT compared to that in the IMRT plans, whereas VMAT had statistically worse target dose homogeneity, and right and left femoral head dose-sparing than those of the IMRT plans. The average volume percentage of cold spots per PTV for the VMAT was 4.37 ± 2.68%, which was smaller than the 5.72 ± 1.84% observed for IMRT plans (P = 0.007). The volume percentage of cold spots per ROP for the VMAT did not significantly differ from those for the IMRT plans. Compared with IMRT, the VMAT plans achieved better PTV dose conformity, OAR dose-sparing, and smaller cold spots in the treatment of prostate cancer.
本研究比较了容积调强弧形放疗（VMAT）与调强放射治疗（IMRT）的剂量学指标，同时考虑了前列腺癌计划中的冷点。IMRT计划是从30例前列腺癌患者中回顾性生成的，每个风险组10例，这些患者均接受了VMAT计划。对计划靶区（PTV）的平均剂量、最大剂量和最小剂量以及适形度和均匀性指数进行了评估，对包括直肠、膀胱、左右股骨头以及与PTV重叠区域（ROP）的危及器官（OAR）的平均剂量和V20-V70进行了评估。使用内部软件测量PTV和ROP区域内冷点的数量和体积百分比。使用质心匹配技术生成冷点概率的三维概率分布和分布情况，以进行可视化和分析。与IMRT计划相比，VMAT在PTV、直肠和膀胱剂量 sparing方面的剂量适形度在统计学上更好，而VMAT在靶区剂量均匀性以及左右股骨头剂量 sparing方面在统计学上比IMRT计划更差。VMAT每个PTV的冷点平均体积百分比为4.37±2.68%，低于IMRT计划观察到的5.72±1.84%（P = 0.007）VMAT每个ROP的冷点体积百分比与IMRT计划相比无显著差异。与IMRT相比，VMAT计划在前列腺癌治疗中实现了更好的PTV剂量适形度、OAR剂量 sparing和更小的冷点。
