Department of Radiation Therapy, Osaka Police Hospital, Osaka City, Japan.
J Appl Clin Med Phys. 2012 Jul 5;13(4):3763. doi: 10.1120/jacmp.v13i4.3763.
EBT2 film is widely used for quality assurance in radiation therapy. The purpose of this study was to investigate the homogeneity of EBT2 film among various lots, and the dose dependence of heterogeneity. EBT2 film was positioned in the center of a flatbed scanner and scanned in transmission mode at 75 dpi. Homogeneity was investigated by evaluating gray value and net optical density (netOD) with the red color channel. The dose dependence of heterogeneity in a single sheet from five lots was investigated at 0.5, 2, and 3 Gy. Maximum coefficient of variation as evaluated by netOD in a single film was 3.0% in one lot, but no higher than 0.5% in other lots. Dose dependence of heterogeneity was observed on evaluation by gray value but not on evaluation by netOD. These results suggest that EBT2 should be examined in each lot number before clinical use, and that the dose calibration curve should be constructed using netOD.
EBT2 膜广泛应用于放射治疗中的质量保证。本研究旨在研究不同批次的 EBT2 膜的均匀性和不均匀性的剂量依赖性。将 EBT2 膜置于平板扫描仪的中心，以 75dpi 的传输模式进行扫描。通过评估红色通道的灰度值和净光密度（netOD）来研究均匀性。在 0.5、2 和 3Gy 下，研究了来自五个批次的单个薄片的不均匀性的剂量依赖性。在一个批次中，单个膜的 netOD 评估的最大变异系数为 3.0%，但在其他批次中不高于 0.5%。通过灰度值评估观察到不均匀性的剂量依赖性，但通过 netOD 评估未观察到。这些结果表明，在临床使用前应检查每个批次的 EBT2，并使用 netOD 构建剂量校准曲线。
