Oncology Center, Osaka University Hospital, Suita, Osaka 565-0871, Japan.
Osaka University Graduate School of Meidcine, Suita, Osaka 565-0871, Japan.
J Radiat Res. 2021 Mar 10;62(2):319-328. doi: 10.1093/jrr/rraa124.
In this study, we evaluated the inter-unit variability of the lateral response artifact for multiple flatbed scanners, focusing on the dual-channel method, and investigated the correction method of the lateral non-uniformity. Four scanners with A3+ paper-size and five scanners with A4 paper-size were evaluated. To generate the dose-response curves, small pieces of the Gafchromic EBT3 and EBT-XD films were irradiated, and five of the pieces were repeatedly scanned by moving them on the scanner to evaluate the lateral non-uniformity. To calculate the dose distribution accounting for the lateral non-uniformity, linear functions of the correction factor, representing the difference between the pixel values at offset position and the scanner midline, were calculated for red and blue color channels at each lateral position. Large variations of the lateral non-uniformity among the scanners were observed, even for the same model of scanner. For high dose, red color showed pixel value profiles similar to symmetric curves, whereas the profiles for low dose were asymmetric. The peak positions changed with dose. With correction of the lateral non-uniformity, the dose profiles of the pyramidal dose distribution measured at various scanner positions and that calculated with a treatment planning system showed almost identical profile shapes at all high-, middle- and low-dose levels. The dual-channel method used in this study showed almost identical dose profiles measured with all A3+ and A4 paper-size scanners at any positions when the corrections were applied for each color channel.
在这项研究中，我们评估了多个平板扫描仪的横向响应伪影的单元间变异性，重点关注双通道方法，并研究了横向不均匀性的校正方法。评估了四台 A3+纸张尺寸的扫描仪和五台 A4 纸张尺寸的扫描仪。为了生成剂量响应曲线，对小块 Gafchromic EBT3 和 EBT-XD 胶片进行了照射，并通过在扫描仪上移动来重复扫描其中的五块，以评估横向不均匀性。为了计算考虑横向不均匀性的剂量分布，针对每个横向位置，针对红色和蓝色颜色通道，计算了校正因子的线性函数，校正因子表示偏移位置处的像素值与扫描仪中线之间的差异。即使对于相同型号的扫描仪，也观察到扫描仪之间的横向不均匀性有很大差异。对于高剂量，红色颜色显示的像素值曲线类似于对称曲线，而低剂量的曲线则不对称。峰位随剂量变化而变化。通过校正横向不均匀性，在各种扫描仪位置测量的金字塔剂量分布的剂量曲线以及使用治疗计划系统计算的剂量曲线，在所有高、中、低剂量水平下，曲线形状几乎完全相同。当针对每个颜色通道进行校正时，本研究中使用的双通道方法在任何位置使用所有 A3+和 A4 纸张尺寸的扫描仪测量时，显示出几乎相同的剂量曲线。
