Dynamic multileaf-collimator (DMLC) and volumetric modulation arc therapy (VMAT) were compared carefully in radiotherapy for esophagus cancer (EC) with the help of a new plan quality index: chair homogeneity index (CHI). Thirty-five patients with EC who underwent RT were enrolled. The prescription for the planning tumor volume (PTV) was 54Gy/25f and for the boost volume was 60Gy/25f. Two plans were designed for each patient: DMLC and VMAT. The dose-volume constraints were the same for two kinds of plans of each patient. CHI was an index developed by us and described the dose heterogeneity in the PTV but excluding the Boost (P–B). Heterogeneity index (HI), conformity index (CI) and other plan qualities indexes were also collected. The mean CHIs of PTV and P–B were 1.70 and 1.79 in DMLC, significantly higher than 0.82 and 0.86 in VMAT, respectively. The mean HIs of PTV and PTV-Boost were 17.79% and 15.55% in DMLC, slightly higher than 19.33% and 16.83% in VMAT, respectively. From the data aforementioned, DMLC is superior to VMAT in the treatment for EC. The high values of CHI in plans with DMLC proposed that DMLC achieve a more ideal dose distribution inside a compound target than VMAT.

中文翻译：

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椅子均匀性指数的应用：DMLC相对于VMAT在食管癌放疗中的优势

借助新的计划质量指数：治疗椅均匀性指数 (CHI)，对食管癌 (EC) 放射治疗中的动态多叶准直器 (DMLC) 和体积调制弧疗法 (VMAT) 进行了仔细比较。纳入了 35 名接受 RT 的 EC 患者。计划肿瘤体积 (PTV) 的处方为 54Gy/25f，增强体积为 60Gy/25f。为每位患者设计了两个计划：DMLC 和 VMAT。每个患者的两种计划的剂量体积限制是相同的。 CHI 是我们开发的一个指数，描述了 PTV 中的剂量异质性，但不包括 Boost (P-B)。还收集了异质性指数（HI）、一致性指数（CI）和其他计划质量指数。 DMLC 中 PTV 和 P-B 的平​​均 CHI 分别为 1.70 和 1.79，显着高于 VMAT 中的 0.82 和 0.86。 DMLC 中 PTV 和 PTV-Boost 的平均 HI 分别为 17.79% 和 15.55%，略高于 VMAT 中的 19.33% 和 16.83%。从上述数据来看，DMLC在治疗EC方面优于VMAT。 DMLC 计划中的 CHI 值较高，表明 DMLC 在复合靶区内实现了比 VMAT 更理想的剂量分布。