Zhang Wu-Zhe, Zhai Tian-Tian, Lu Jia-Yang, Chen Jian-Zhou, Chen Zhi-Jian, Li De-Rui, Chen Chuang-Zhen
Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College, Guangdong, China.
Center of Clinical Oncology, The University of Hongkong-Shenzhen Hospital 1, Shenzhen, China.
PLoS One. 2015 Mar 27;10(3):e0121385. doi: 10.1371/journal.pone.0121385. eCollection 2015.
To compare plans using volumetric-modulated arc therapy (VMAT) with conventional sliding window intensity-modulated radiation therapy (c-IMRT) to treat upper thoracic esophageal cancer (EC).
CT datasets of 11 patients with upper thoracic EC were identified. Four plans were generated for each patient: c-IMRT with 5 fields (5F) and VMAT with a single arc (1A), two arcs (2A), or three arcs (3A). The prescribed doses were 64 Gy/32 F for the primary tumor (PTV64). The dose-volume histogram data, the number of monitoring units (MUs) and the treatment time (TT) for the different plans were compared.
All of the plans generated similar dose distributions for PTVs and organs at risk (OARs), except that the 2A- and 3A-VMAT plans yielded a significantly higher conformity index (CI) than the c-IMRT plan. The CI of the PTV64 was improved by increasing the number of arcs in the VMAT plans. The maximum spinal cord dose and the planning risk volume of the spinal cord dose for the two techniques were similar. The 2A- and 3A-VMAT plans yielded lower mean lung doses and heart V50 values than the c-IMRT. The V20 and V30 for the lungs in all of the VMAT plans were lower than those in the c-IMRT plan, at the expense of increasing V5, V10 and V13. The VMAT plan resulted in significant reductions in MUs and TT.
The 2A-VMAT plan appeared to spare the lungs from moderate-dose irradiation most effectively of all plans, at the expense of increasing the low-dose irradiation volume, and also significantly reduced the number of required MUs and the TT. The CI of the PTVs and the OARs was improved by increasing the arc-number from 1 to 2; however, no significant improvement was observed using the 3A-VMAT, except for an increase in the TT.
比较容积调强弧形放疗（VMAT）计划与传统滑动窗口调强放疗（c-IMRT）计划治疗胸段上段食管癌（EC）的效果。
确定11例胸段上段EC患者的CT数据集。为每位患者生成4种计划：5野c-IMRT（5F）以及单弧VMAT（1A）、双弧VMAT（2A）或三弧VMAT（3A）。原发肿瘤（PTV64）的处方剂量为64 Gy/32 F。比较不同计划的剂量体积直方图数据、监测单位（MU）数量和治疗时间（TT）。
所有计划对PTV和危及器官（OAR）产生的剂量分布相似，不过2A-VMAT和3A-VMAT计划产生的适形指数（CI）显著高于c-IMRT计划。通过增加VMAT计划中的弧数可提高PTV64的CI。两种技术的脊髓最大剂量和脊髓剂量的计划风险体积相似。2A-VMAT和3A-VMAT计划产生的平均肺剂量和心脏V50值低于c-IMRT。所有VMAT计划中肺的V20和V30低于c-IMRT计划，但代价是V5、V10和V13增加。VMAT计划可显著减少MU数量和TT。
2A-VMAT计划似乎在所有计划中最有效地使肺免受中等剂量照射，代价是增加低剂量照射体积，并且还显著减少了所需的MU数量和TT。将弧数从1增加到2可改善PTV和OAR的CI；然而，使用3A-VMAT未观察到显著改善，除了TT增加。
