This study aimed to evaluate multi-leaf collimator (MLC) positional accuracy by using an electronic portal imaging device (EPID) and radiochromic EBT3 film. Furthermore, the MLC’s positional accuracy at different gantry and collimator angles of a Siemens ONCOR linear accelerator (linac) was evaluated. A picket fence test was performed to evaluate the MLC’s positional accuracy at various gantry and collimator angles of the linac. The EPID and the EBT3 films were sequentially irradiated seven times at 2-cm intervals by making a rectangular field (0.3 × 19 cm 2 ). The full-width at half-maximum (FWHM) of each band (field) was calculated for all leaves by using inhouse software. Then, variations between the actual and the planned leaf locations were obtained by using the EPID and the EBT3 film at various gantry and collimator angles. The mean FWHM, acquired using the EPID and the EBT3 film ranged from 2.331 - 3.647 mm and 2.059 - 4.001 mm, respectively. Variations between the actual and the planned leaf locations were found to be affected by changes in the collimator and the gantry angles. Moreover, a -0.060 - 1.588 mm difference we seen between the result obtained from the EBT3 film and that obtained from the EPID. The mean FWHM, at most angles, for the EBT3 film was larger than that for the EPID. The findings showed average deviations for the EPID (0.001 - 0.669 mm) and EBT3 film (0.007 - 1.001 mm); these values agreed within the tolerance level (±1 mm). Furthermore, good agreement was found between the results obtained from the EPID and the EBT3 film; these two dosimetric methods can be used interchangeably, but each must be chosen considering its advantages and disadvantages.

中文翻译：

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使用放射变色 EBT3 薄膜和电子入口成像设备评估多叶准直器位置精度

本研究旨在通过使用电子门户成像设备 (EPID) 和辐射变色 EBT3 薄膜来评估多叶准直器 (MLC) 的定位精度。此外，还评估了西门子 ONCOR 直线加速器 (linac) 在不同机架和准直器角度下的 MLC 位置精度。进行了栅栏测试以评估 MLC 在直线加速器的各种龙门和准直器角度下的定位精度。EPID 和 EBT3 膜通过制作矩形场（0.3 × 19 cm 2 ）以 2 cm 的间隔依次照射 7 次。使用内部软件计算所有叶子的每个带（场）的半峰全宽（FWHM）。然后，通过在各种机架和准直器角度使用 EPID 和 EBT3 膜，获得实际和计划叶片位置之间的变化。平均 FWHM，使用 EPID 和 EBT3 薄膜获得的范围分别为 2.331 - 3.647 毫米和 2.059 - 4.001 毫米。发现实际和计划叶片位置之间的变化受准直器和机架角度变化的影响。此外，我们看到从 EBT3 薄膜获得的结果与从 EPID 获得的结果之间存在 -0.060 - 1.588 毫米的差异。在大多数角度，EBT3 膜的平均 FWHM 大于 EPID 的平均 FWHM。结果显示 EPID (0.001 - 0.669 mm) 和 EBT3 薄膜 (0.007 - 1.001 mm) 的平均偏差；这些值在公差水平 (±1 mm) 内达成一致。此外，从 EPID 和 EBT3 薄膜获得的结果之间发现了良好的一致性；这两种剂量测定方法可以互换使用，但必须根据各自的优点和缺点进行选择。