An investigation of the dose distribution effect related with collimator angle in volumetric arc therapy of prostate cancer.
An investigation of the dose distribution effect related with collimator angle in volumetric arc therapy of prostate cancer.
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DOI：
10.4103/0971-6203.181635
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发表时间：
2016-04
影响因子：
0.9
通讯作者：
Ozturk ST
中科院分区：
文献类型：
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作者：
Tas B;Bilge H;Ozturk ST
旨在研究 11 名计划接受单弧和双弧体积调制弧治疗 (VMAT) 的前列腺癌患者在改变准直器角度时计划靶区 (PTV) 和危及器官 (OAR) 的剂量体积变化。单弧和双弧 VMAT 治疗计划是使用 Monaco5.0® 创建的，准直器角度设置为 0°。所有计划均将 7600 cGy 剂量标准化为临床靶体积 (CTV) 体积的 95%。单弧 VMAT 计划使用不同的准直器角度（0°、15°、30°、45°、60°、75° 和 90°）重新优化，双弧 VMAT 计划（0–0°、15°–345、30–330°、45–315°、60–300°、75–285°、 90–270°）使用相同的优化参数。为了进行比较，计算并分析了异质性指数（HI）、剂量体积直方图和 95% PTV 体积的最小剂量（D95 PTV）等参数。使用二维离子室阵列 IBA Matrixx® 和三维 IBA Compass® 程序验证了最佳计划。通过γ指数（3%/3 mm）分析进行计算与测量的比较。具有 15° 准直器角度的单弧 VMAT 具有更高的 D95 (PTV)。对于双弧，VMAT 准直器角度为 60–300° 和 75–285°。然而，75-285° 准直器角度获得的直肠剂量较低。与膀胱和股骨头等其他 OAR 相比，没有显着的剂量差异。当我们比较单弧 VMAT 和双弧 VMAT 的 D95 (PTV) 时，我们确定双弧 VMAT 具有 2.44% 的高覆盖率和较低的 HI。所有计划均以超过 97% 的分数通过了 γ 指数 (3%/3 mm) 分析，并且使用双弧 VMAT 时，CTV 的平均 γ 指数为 0.36，PTV 的平均 γ 指数为 0.32。通过 Wilcoxon 符号秩检验统计，这些结果具有显着性。结果表明，由于靶标和 OAR 的几何形状，靶标和 OAR 剂量的剂量覆盖范围也很大程度上取决于准直器角度。根据结果，我们决定在我们的诊所为前列腺癌患者规划双弧 VMAT 和 75°–285° 准直器角度。
To investigate the dose-volume variations of planning target volume (PTV) and organ at risks (OARs) in eleven prostate cancer patients planned with single and double arc volumetric modulated arc therapy (VMAT) when varying collimator angle. Single and double arc VMAT treatment plans were created using Monaco5.0® with collimator angle set to 0°. All plans were normalized 7600 cGy dose to the 95% of clinical target volume (CTV) volume. The single arc VMAT plans were reoptimized with different collimator angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°), and for double arc VMAT plans (0–0°, 15°–345, 30–330°, 45–315°, 60–300°, 75–285°, 90–270°) using the same optimization parameters. For the comparison the parameters of heterogeneity index (HI), dose-volume histogram and minimum dose to the 95% of PTV volume (D95 PTV) calculated and analyzed. The best plans were verified using 2 dimensional ion chamber array IBA Matrixx® and three-dimensional IBA Compass® program. The comparison between calculation and measurement were made by the γ-index (3%/3 mm) analysis. A higher D95 (PTV) were found for single arc VMAT with 15° collimator angle. For double arc, VMAT with 60–300° and 75–285° collimator angles. However, lower rectum doses obtained for 75–285° collimator angles. There was no significant dose difference, based on other OARs which are bladder and femur head. When we compared single and double arc VMAT's D95 (PTV), we determined 2.44% high coverage and lower HI with double arc VMAT. All plans passed the γ-index (3%/3 mm) analysis with more than 97% of the points and we had an average γ-index for CTV 0.36, for PTV 0.32 with double arc VMAT. These results were significant by Wilcoxon signed rank test statistically. The results show that dose coverage of target and OAR's doses also depend significantly on the collimator angles due to the geometry of target and OARs. Based on the results we have decided to plan prostate cancer patients in our clinic with double arc VMAT and 75°–285° collimator angles.