Department of Radiological Sciences, Faculty of Health Sciences, Morinomiya University of Medical Sciences, 1-26-16 Nankokita, Suminoe-ku, Osaka, 559-8611, Japan.
Radiology Department, Medical Technology Division, Osaka General Medical Center, 3-1-56 Bandai-higashi, Sumiyoshi-ku, Osaka, 558-8558, Japan.
Radiol Phys Technol. 2022 Dec;15(4):349-357. doi: 10.1007/s12194-022-00674-2. Epub 2022 Aug 29.
In many digital X-ray imaging systems, although air kerma on a surface of each detector is used, a standardized dose index called an exposure index (EI) has been proposed by the IEC, which is expected to be utilized for dose management. In clinical practices, EI is effectively utilized using a deviation index (DI), which is a deviation between a target EI (EI) set for each imaging region and an EI of the acquired image. However, an important issue in clinical uses of EI is a suppression of excessive doses. It is difficult to achieve a reliable reduction in exposure doses by indicating DI. In this study, physical image characteristics of detectors, visual detectability by charts, and observer experiments using a chest phantom were examined to determine upper (DImax) and lower (DImin) limits of the EI and DI to achieve a reliable dose reduction in chest examinations. As the result, the tolerance ranges indicated by DImax and DImin, which were set based on the results of physical and visual evaluations, proved to be almost consistent with the distribution of EI values in 735 clinical images taken with a photo-timer control in real clinical practices.
在许多数字 X 射线成像系统中，尽管使用了每个探测器表面的空气比释动能，但 IEC 已经提出了一个称为曝光指数 (EI) 的标准化剂量指标，预计将用于剂量管理。在临床实践中，使用偏差指数 (DI) 有效地利用了 EI，DI 是为每个成像区域设置的目标 EI (EI) 与获取的图像的 EI 之间的偏差。然而，EI 在临床应用中的一个重要问题是抑制过量剂量。通过指示 DI 很难实现可靠的曝光剂量降低。在这项研究中，检查了探测器的物理图像特征、图表的视觉可检测性以及使用胸部体模的观察者实验，以确定达到胸部检查可靠剂量降低的 EI 和 DI 的上限 (DImax) 和下限 (DImin)。结果表明，基于物理和视觉评估结果设置的 DImax 和 DImin 的容差范围与实际临床实践中使用光定时器控制拍摄的 735 张临床图像中 EI 值的分布几乎一致。
