Collimator rotation in volumetric modulated arc therapy for craniospinal irradiation and the dose distribution in the beam junction region.
Collimator rotation in volumetric modulated arc therapy for craniospinal irradiation and the dose distribution in the beam junction region.
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DOI：
10.1186/s13014-015-0544-z
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发表时间：
2015-11-19
期刊：
影响因子：
--
通讯作者：
Pei H
中科院分区：
文献类型：
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作者：
Li Q;Gu W;Mu J;Yin W;Gao M;Mo J;Pei H
本研究的目的是调查的作用，束准直器旋转的体积调制弧治疗（VMAT）的颅脊髓照射（CSI），以及对剂量分布的影响，在束结。选择了6名成年患者进行研究。为每名患者生成6个具有不同准直器角度的VMAT计划。患者均采用仰卧位双束等中心治疗。通过分析计划靶体积（PTV）和危及器官（OAR）的剂量-体积直方图（DVH）数据以及靶区的符合性指数（CI）和均匀性指数（HI）对计划进行评价。仔细检查束结中的剂量分布，并在体模中进行实验验证，使用离子室阵列和薄膜进行测量。不同射束准直器角度的计划的HI和CI的平均值没有显著差异。45°准直器的计划的节段数、监测单元数和递送时间明显高于其他准直器角度的计划。当两组射束的准直器角度设置为0°时，在结区测得1 mm的低剂量间隙。通过将准直器角度设置为45°，仅需两个等中心点即可治疗长度达90 cm的靶。无论准直器角度是否为0°，计划的HI和CI几乎相同。至少一组射束的准直器角度应偏离0°，以避免射束结区的剂量间隙。本文的在线版本（doi：10.1186/s13014-015-0544-z）包含补充材料，可供授权用户使用。
The purpose of this study was to investigate the role of beam collimator rotation in Volumetric Modulated Arc Therapy (VMAT) for craniospinal irradiation (CSI), and the impact on dose distribution in the beam junctions. Six adult patients were selected for the study. Six VMAT plans with different collimator angles were generated for each patient. The patients were treated in supine position with two beam isocenters. The plans were evaluated by analysis of Dose-Volume Histogram (DVHs) data for planning target volume (PTV) and organs at risk (OAR), and conformity index (CI) and homogeneity index (HI) for the target. Dose distributions in the beam junctions were examined carefully and experimentally validated in phantom, with measurement using an ion chamber array and film. The mean values of HI and CI for the plans with different beam collimator angles were not significantly different. The numbers of segments, monitor units (MUs) and the delivery time of the plans with 45° beam collimator were obviously higher than those in plans with other beam collimator angles. When collimator angle for both sets of beams were set at 0°, there was a 1 mm low dose gap measured in the junction region. By setting the collimator angle to 45°, only two isocenters were needed for the treatment of a target with the length up to 90 cm. The HI and CI of the plans were almost the same, regardless if the collimator angles were at 0°. The collimator angles for at least one set of beams should be off 0° in order to avoid a dose gap in the beam junction region. The online version of this article (doi:10.1186/s13014-015-0544-z) contains supplementary material, which is available to authorized users.