Volumetric-modulated arc therapy (VMAT) requires highly accurate control of multileaf collimator (MLC) movement, rotation speed of linear accelerator gantry, and monitor units during irradiation. Pretreatment validation and monitoring of these factors during irradiation are necessary for appropriate VMAT treatment. Recently, a gantry mounted transmission detector “Delta⁴ Discover® (D4D)” was developed to detect errors in delivering doses and dose distribution immediately after treatment. In this study, the performance of D4D was evaluated. Simulation plans, in which the MLC position was displaced by 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm from the clinically used original plans, were created for ten patients who received VMAT treatment for prostate cancer. Dose deviation (DD), distance-to-agreement (DTA), and gamma index analysis (GA) for each plan were evaluated by D4D. These results were compared to the results (DD, DTA and GA) measured by Delta⁴ Phantom + (D4P). We compared the deviations between the planned and measured values of the MLC stop positions A-side and B-side in five clinical cases of prostate VMAT during treatment and measured the GA values. For D4D, when the acceptable errors for DD, DTA, and GA were determined to be ≤3%, ≤2 mm, and ≤3%/2 mm, respectively, the minimum detectable errors in the MLC position were 2.0, 1.5, and 1.5 mm based on DD, DTA, and GA respectively. The corresponding minimum detectable MLC position errors were 2.0, 1.0, and 1.5 mm, respectively, for D4P. The deviation between the planned and measured position of MLC stopping point of prostate VMAT during treatment was stable at an average of −0.09 ± 0.05 mm, and all GA values were above 99.86%. In terms of delivering doses and dose distribution of VMAT, error detectability of D4D was comparable to that of D4P. The transmission-type detector “D4D” is thus suitable for detecting delivery errors during irradiation.

中文翻译：

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使用安装在机架上的透射检测器在前列腺 VMAT 治疗期间检测输送错误的可用性

体积调制弧光疗法 (VMAT) 需要高度精确地控制多叶准直器 (MLC) 运动、直线加速器机架的旋转速度和辐照期间的监测单元。在辐照期间对这些因素进行预处理验证和监测对于适当的 VMAT 治疗是必要的。最近，一种安装在机架上的透射探测器“Delta ⁴Discover® (D4D)”的开发是为了检测治疗后立即提供剂量和剂量分布的错误。在本研究中，评估了 D4D 的性能。为 10 名接受 VMAT 治疗的前列腺癌患者创建了模拟计划，其中 MLC 位置从临床使用的原始计划中位移了 0.5、1.0、1.5、2.0、2.5 和 3.0 毫米。D4D 对每个计划的剂量偏差 (DD)、一致性距离 (DTA) 和伽玛指数分析 (GA) 进行了评估。将这些结果与 Delta ⁴测量的结果（DD、DTA 和 GA）进行比较幻影 + (D4P)。我们比较了治疗期间前列腺 VMAT 的五个临床病例中 MLC 停止位置 A 侧和 B 侧的计划值和测量值之间的偏差并测量了 GA 值。对于 D4D，当 DD、DTA 和 GA 的可接受误差分别确定为≤3%、≤2 mm 和≤3%/2 mm 时，MLC 位置的最小可检测误差为 2.0、1.5 和1.5 mm 分别基于 DD、DTA 和 GA。对于 D4P，相应的最小可检测 MLC 位置误差分别为 2.0、1.0 和 1.5 毫米。治疗期间前列腺VMAT MLC停止点的计划位置与实测位置偏差稳定在-0.09±0.05 mm，所有GA值均在99.86%以上。在 VMAT 的递送剂量和剂量分布方面，D4D 的错误检测能力与 D4P 相当。因此，透射型检测器“D4D”适用于检测辐照期间的输送错误。