PDF(Pubmed)
Abstract：
OBJECTIVE: To investigate the operation principles of the automatic tube current modulation (ATCM) of a modern GE healthcare CT scanner, and the impact of related settings on image quality and patient dose.
METHODS: A dedicated phantom (Mercury 4.0) was scanned using two of the most frequently used clinical scanning protocols (chest and abdomen-pelvis). The preset protocol settings were used as starting points (reference conditions). Scan direction, scan mode (helical vs. axial), total beam width, tube potential (kVp), and ATCM settings were then modified individually to understand their impact on radiation dose and image quality. Regarding the ATCM settings, the SmartmA minimum and maximum mA limits, and the noise index (NI) values were varied. As surrogates of patient dose, the CTDIvol and DLP values of each scan were used. As surrogates of image quality were used the image noise and the detectability index (d\') of five different materials (air, solid water, polystyrene, iodine, and bone) embedded in the Mercury phantom calculated with the ImQuest software.
RESULTS: The scanning direction did not have any effect on ATCM curves, unlike what has been observed in CT scanners from other manufacturers. Total beam width does matter, however, the SmartmA limit settings and kVp selection had the greatest impact on image quality and dose. It was seen that improper minimum mA limit settings practically invalidated the ATCM operation. In contrast, when full modulation was allowed without restrictions, noise standard deviation, and detectability index became much more consistent across the wide range of phantom diameters. For lower kVp settings an impressive dose reduction was observed that requires further investigation.
CONCLUSIONS: SmartmA is a tool that if not properly used may increase the patient doses considerably. Therefore, its settings should be carefully adjusted for each preset different clinical protocol.
METHODS: A dedicated phantom (Mercury 4.0) was scanned using two of the most frequently used clinical scanning protocols (chest and abdomen-pelvis). The preset protocol settings were used as starting points (reference conditions). Scan direction, scan mode (helical vs. axial), total beam width, tube potential (kVp), and ATCM settings were then modified individually to understand their impact on radiation dose and image quality. Regarding the ATCM settings, the SmartmA minimum and maximum mA limits, and the noise index (NI) values were varied. As surrogates of patient dose, the CTDIvol and DLP values of each scan were used. As surrogates of image quality were used the image noise and the detectability index (d\') of five different materials (air, solid water, polystyrene, iodine, and bone) embedded in the Mercury phantom calculated with the ImQuest software.
RESULTS: The scanning direction did not have any effect on ATCM curves, unlike what has been observed in CT scanners from other manufacturers. Total beam width does matter, however, the SmartmA limit settings and kVp selection had the greatest impact on image quality and dose. It was seen that improper minimum mA limit settings practically invalidated the ATCM operation. In contrast, when full modulation was allowed without restrictions, noise standard deviation, and detectability index became much more consistent across the wide range of phantom diameters. For lower kVp settings an impressive dose reduction was observed that requires further investigation.
CONCLUSIONS: SmartmA is a tool that if not properly used may increase the patient doses considerably. Therefore, its settings should be carefully adjusted for each preset different clinical protocol.
摘要：
目的：研究现代GE医疗保健CT扫描仪的自动管电流调制（ATCM）的操作原理，以及相关设置对图像质量和患者剂量的影响。
方法：使用两种最常用的临床扫描方案（胸部和腹部骨盆）扫描专用体模（Mercury4.0）。预设的协议设置用作起点(参考条件)。扫描方向,扫描模式(螺旋与轴向)，总光束宽度，管电位（kVp），然后分别修改ATCM设置，以了解它们对辐射剂量和图像质量的影响。关于ATCM设置，SmartmA最小和最大mA限制，和噪声指数（NI）值变化。作为患者剂量的替代品，使用每次扫描的CTDIvol和DLP值.作为图像质量的替代，使用了五种不同材料(空气，固体水,聚苯乙烯,碘，和骨骼）嵌入在使用ImQuest软件计算的Mercury幻影中。
结果：扫描方向对ATCM曲线没有任何影响，与其他制造商的CT扫描仪不同。总光束宽度确实很重要，然而,SmartmA限值设置和kVp选择对图像质量和剂量影响最大.可以看出，不正确的最小mA限制设置实际上使ATCM操作无效。相比之下,当不受限制地允许全调制时，噪声标准偏差，和可检测性指数变得更加一致，在广泛的体模直径范围内。对于较低的kVp设置，观察到令人印象深刻的剂量减少，需要进一步研究。
结论：SmartmA是一种工具，如果使用不当，可能会大大增加患者的剂量。因此,应针对每个预设的不同临床方案仔细调整其设置.
方法：使用两种最常用的临床扫描方案（胸部和腹部骨盆）扫描专用体模（Mercury4.0）。预设的协议设置用作起点(参考条件)。扫描方向,扫描模式(螺旋与轴向)，总光束宽度，管电位（kVp），然后分别修改ATCM设置，以了解它们对辐射剂量和图像质量的影响。关于ATCM设置，SmartmA最小和最大mA限制，和噪声指数（NI）值变化。作为患者剂量的替代品，使用每次扫描的CTDIvol和DLP值.作为图像质量的替代，使用了五种不同材料(空气，固体水,聚苯乙烯,碘，和骨骼）嵌入在使用ImQuest软件计算的Mercury幻影中。
结果：扫描方向对ATCM曲线没有任何影响，与其他制造商的CT扫描仪不同。总光束宽度确实很重要，然而,SmartmA限值设置和kVp选择对图像质量和剂量影响最大.可以看出，不正确的最小mA限制设置实际上使ATCM操作无效。相比之下,当不受限制地允许全调制时，噪声标准偏差，和可检测性指数变得更加一致，在广泛的体模直径范围内。对于较低的kVp设置，观察到令人印象深刻的剂量减少，需要进一步研究。
结论：SmartmA是一种工具，如果使用不当，可能会大大增加患者的剂量。因此,应针对每个预设的不同临床方案仔细调整其设置.
