共面与非共面的VMAT在肺癌放疗中的剂量学比较

目的:探讨共面与非共面的容积调强（VMAT）技术在中央型肺癌和周围型肺癌中的剂量学差异。 方法:选择14例单一病灶的肺癌患者，其中7例为中央型肺癌、7例为周围型肺癌，分别制定共面的VMAT计划以及非共面的VMAT计划。比较两种计划的靶区适形指数（CI）、均匀性指数（HI）和梯度指数（GI）；危及器官比较:双肺V1、V2.5、V5、V20、Dmean，健侧肺V1和V5，心脏Dmean，食管Dmean，脊髓Dmax，胸壁V30及Dmean。 结果:对于靶区GI、胸壁V30和双肺V20，非共面的VMAT计划均要好于共面的VMAT计划。在中央型肺癌中，差异更加明显，结果具有统计学意义（P<0.05）。双肺及健侧肺的V1中，非共面的VMAT计划高于共面的VMAT计划（P<0.05）。对于心脏Dmean，非共面VMAT计划高于共面的计划，但差异无统计学意义（P>0.05）。非共面VMAT计划的机器跳数高于共面的VMAT计划（P<0.05）。 结论:非共面的VMAT计划较共面的VAMT计划剂量梯度更陡，对于保护胸壁和肺更有优势，在中央型肺癌中更加明显。本研究结果为肺癌的计划设计提供了一种新思路。

Dosimetric comparison of coplanar and non-coplanar volumetric modulated arc therapy for lung cancer

Abstract: Objective To investigate the dosimetric differences between coplanar and non-coplanar volumetric modulated arc therapy (VMAT) in treatment of central type lung cancer and peripheral lung cancer. Methods A total of 14 patients with single lesion of lung cancer, including 7 cases of central type lung cancer and 7 cases of peripheral lung cancer, were selected. Two plans, namely coplanar and non-coplanar VMAT plans, were designed for each patient. The conformity index, homogeneity index and gradient index of target areas were compared, and several indexes of organs-at-risk, including the V1, V2.5, V5, V20, Dmean of lungs, the V1, V5 of contralateral lung, the Dmean of heart, the Dmean of esophagus, the Dmax of spinal cord, and the Dmax, V30 of chest wall, were also compared. Results The gradient index of target areas, the V30 of chest wall, and the V20 of lungs in non-coplanar VMAT plan were superior to those in coplanar VMAT plan, and the differences were more obvious in patients with central type lung cancer, with statistical significances (P<0.05). The V1 of bilateral lungs and contralateral lung was higher in non-coplanar VMAT plan than in coplanar VMAT plan (P<0.05), and the Dmean of heart in non-coplanar VMAT plans was higher than that in coplanar VMAT plans, without any statistical differences (P>0.05). Moreover, the number of monitor units in non-coplanar VMAT plan was higher than that in coplanar VMAT plan (P<0.05). Conclusion Non-coplanar VMAT plan has a steeper dose gradient than coplanar VAMT plan, which is more advantageous for the protection of the chest wall and lung, especially for patients with central type lung cancer, providing a new idea for designing treatment plans of lung cancer.