Clinical implementation of intensity-modulated arc therapy (IMAT) for rectal cancer
Clinical implementation of intensity-modulated arc therapy (IMAT) for rectal cancer
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DOI：
10.1016/j.ijrobp.2004.04.016
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发表时间：
2004-11-01
影响因子：
7
通讯作者：
De Neve, W
中科院分区：
文献类型：
--
作者：
Duthoy, W;De Gersem, W;De Neve, W
目的：在直肠癌患者中，术前或术后联合放疗和化疗是公认的治疗方法。晚期小肠(SB)毒性是一种令人担忧的副作用，并以体积依赖的方式限制辐射剂量的增加。为了减少大剂量Sb的照射剂量，从而减少Sb的毒性，制定了强度调制弧光治疗(IMAT)的计划策略，并在临床上实施了IMAT。我们报告了前7例患者的治疗计划，比较了IMAT与传统3D计划(3D)的差异，以及IMAT交付的可行性。方法与材料：7例直肠癌患者，术前(n=4)或术后(n=3)接受放射治疗，均同意接受IMAT治疗。所有患者均行俯卧位CT扫描。CT和MRI融合后，在放射科医生的帮助下，勾画出临床靶区。对于IMAT计划，弧形是使用基于解剖学的分割工具生成的。ARC的优化是通过权重优化(WO)和叶位优化(LPO)完成的，这两种优化都适用于IMAT目的。3D计划采用一个后方和两个侧方楔形梁，其轮廓被塑造成与规划目标体积(PTV)的束眼投影相一致的形状。波束WO采用约束矩阵求逆方法。在剂量-体积直方图分析中，所有计划均归一化为45GyPTV中位剂量。在人形体模上的聚合物凝胶剂量学(PGD)被用于验证全链(计划到交付)。IMAT治疗由Elekta SliPlus直线加速器使用与临床模式相同的联锁级别的原型软件进行。结果：IMAT计划产生3~6个弧形，平均传送时间6.3min，平均456个监测单位(MIU)，180cGy次/次。在3D和IMAT计划中，PTV的最小剂量没有显著差异。IMAT平面的不均质性最高(14.1%)，3D平面的不均质性最低(9.9%)。IMAT计划对SB的平均剂量(12.4GY)明显低于3D计划(17.0GY)。IMAT计划的SB接受剂量低于任何剂量水平的体积低于3D计划。IMAT计划的积分剂量低于3D计划(分别为244J和262J，45GY)。结论：IMAT计划可在5-10分钟的时间内提供给药，并且给SB的剂量比3D计划低，且不会在PTV中产生明显的剂量不足。PGD显示IMAT投放与3D投放一样准确。(C)2004年爱思唯尔公司。
Purpose: In rectal cancer, combined radiotherapy and chemotherapy, either pre- or postoperatively, is an accepted treatment. Late small bowel (SB) toxicity is a feared side effect and limits radiation-dose escalation in a volume-dependent way. A planning strategy for intensity- modulated are therapy (IMAT) was developed, and IMAT was clinically implemented with the aim to reduce the volume of SB irradiated at high doses and thus reduce SB toxicity. We report on the treatment plans of the first 7 patients, on the comparison of IMAT with conventional 3D planning (3D), and on the feasibility of IMAT delivery.Methods and Materials: Seven patients, who were referred to our department for preoperative (n = 4) or postoperative (n = 3) radiotherapy for rectal cancer, gave written consent for IMAT treatment. All patients had a planning CT in prone position. The delineation of the clinical target volume was done after fusion of CT and MRI, with the help of a radiologist. For the IMAT plan, arcs were generated using an anatomy-based segmentation tool. The optimization of the arcs was done by weight optimization (WO) and leaf position optimization (LPO), both of which were adapted for IMAT purposes. The 3D plans used one posterior and two lateral wedged beams, of which the outlines were shaped to the beam's-eye view projection of the planning target volume (PTV). Beam WO was done by constrained matrix inversion. For dose-volume histogram analysis, all plans were normalized to 45 Gy as median PTV dose. Polymer gel dosimetry (PGD) on a humanoid phantom was used for the validation of the total chain (planning to delivery). IMAT treatments were delivered by an Elekta SliPlus linear accelerator using prototype software with the same interlock class as in clinical mode.Results: The IMAT plan resulted in 3 to 6 arcs, with a mean delivery time of 6.3 min and a mean of 456 monitor units (MIU) for a 180 cGy fraction. The minimal dose in the PTV was not significantly different between 3D and IMAT plans. Inhomogeneity was highest for the IMAT plans (14.1 %) and lowest for the 3D plans (9.9 %). Mean dose to the SB was significantly lower for the IMAT plans (12.4 Gy) than for the 3D plans (17.0 Gy). The volume of SB receiving less than any dose level was lower for the IMAT plans than for 3D plans. Integral dose was lower in the IMAT plans than for the 3D plans (respectively 244 J and 262 J to deliver 45 Gy). Differences between the PGD measured dose and the calculated dose were as small for IMAT as for 3D treatments.Conclusion: IMAT plans are deliverable within a 5-10-minute time slot, and result in a lower dose to the SB than 3D plans, without creating significant underdosages in the PTV. PGD showed that IMAT delivery is as accurate as 3D delivery. (C) 2004 Elsevier Inc.