Impact of treatment planning using a structure block function on the target and organ doses related to patient movement in cervical esophageal cancer: A phantom study
Impact of treatment planning using a structure block function on the target and organ doses related to patient movement in cervical esophageal cancer: A phantom study
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DOI：
10.1002/acm2.12582
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发表时间：
2019-05-01
影响因子：
2.1
通讯作者：
Kodaira, Takeshi
中科院分区：
文献类型：
--
作者：
Shimizu, Hidetoshi;Sasaki, Koji;Kodaira, Takeshi
螺旋断层治疗（HT）可以通过剂量优化来限制光束穿过计算机断层扫描（CT）图像的虚拟轮廓，减少对危险器官（OARs）的剂量。束流约束限制了入射束流角；因此，适当的计划靶体积（PTV）范围可能不同于没有束流限制的标准治疗计划，这取决于患者在给药期间的运动情况。由于病人运动而引起的剂量分布变化，在有束束限制的治疗计划中尚未得到描述。本研究通过系统地移动幻体，量化了当束束限制应用于HT治疗方案时靶区和桨区剂量分布的变化。针对RANDO幻象的CT图像，设计有和没有束束限制模式（分别为定向阻断（DB）和非阻断（NB））的宫颈癌治疗方案。DB模式的PTV余量设置与NB模式相同（5mm）。CT图像在左右、前后、上下方向有意移动+/- 1、+/- 2、+/- 3个体素，并利用NB或DB模式的影响量重新计算每个位置的剂量分布。当幻相移位与NB模式处于相同的PTV边缘时，DB模式下靶、肺、心和脊髓的剂量变化与NB模式下的剂量变化较小。总之，本研究中使用的虚拟轮廓形状可以提供安全的分娩，即使患者在与NB模式相同的PTV边缘内运动。
Helical tomotherapy (HT) can restrict beamlets passing through the virtual contour on computed tomography (CT) image in dose optimization, reducing the dose to organs at risk (OARs). Beamlet restriction limits the incident beamlet angles; thus, the proper planning target volume (PTV) margin may differ from that of the standard treatment plan without beamlet restriction, depending on the patient's movement during dose delivery. Dose distribution changes resulting from patient movement have not been described for treatment plans with beamlet restriction. This study quantified changes in dose distribution to the target and OARs when beamlet restriction is applied to cervical esophageal cancer treatment plan using HT by systematically shifting a phantom. Treatment plans for cervical esophageal cancers with and without beamlet restriction modes [directional block (DB) and nonblock (NB), respectively] were designed for CT images of the RANDO phantom. The PTV margin for the DB mode was set to be the same as that for the NB mode (5 mm). The CT image was intentionally shifted by +/- 1, +/- 2, and +/- 3 voxels in the left-right, anterior-posterior, and superior-inferior directions, and the dose distribution was recalculated for each position using the fluence for the NB or DB mode. When the phantom shift was within the same PTV margin as the NB mode, changes in doses to the targets, lungs, heart, and spinal cord in the DB mode were small as those in the NB mode. In conclusion, the virtual contour shape used in this study would provide safe delivery even with patient movement within the same PTV margin as for the NB mode.