Sookpeng Supawitoo, Martin Colin J, Cheebsumon Patsuree, Pengpan Thanyawee
Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok 65000, Thailand.
J Radiol Prot. 2017 Mar 20;37(1):84-96. doi: 10.1088/1361-6498/37/1/84. Epub 2016 Dec 15.
Automatic tube current modulation (ATCM) systems to aid in optimizing dose and image noise have become standard on computed tomography (CT) scanners over the last decade. ATCM systems of the main vendors modulate tube current in slightly different ways, with some using a control parameter related to image noise (e.g. Toshiba, GE) while others use a quality reference image mAs (e.g. Siemens). The translation of clinical protocols including ATCM operation between CT scanners from different manufacturers in order to obtain similar levels of image quality with optimized exposure variables has become an important issue. In this study, cylindrical phantoms of different sizes representing small, average and large patients, have been combined into one phantom, which has been scanned on Siemens, Toshiba and GE CT scanners with the full ranges of ATCM image quality settings. The volume weighted CT dose index (CTDI) and image noise over each section of the phantom were recorded for every setting. Relationships between the image quality level settings, and CTDI and measured image noise were analysed in order to investigate ATCM performance. Equations were developed from fits of the data to enable CTDI and image noise to be expressed in terms of the image quality parameters for different size phantoms on each scanner. The Siemens scanner protocol was chosen as the reference, as it avoided high doses for large patients, while allowing full modulation of tube current for patients of all sizes, and so was considered to provide optimized performance. The equations derived were used to equate the noise parameters on Toshiba and GE scanners to the quality reference mAs on the Siemens scanner, so that clinical protocols incorporating similar levels of optimization could be obtained on the three CT scanners.
在过去十年中，有助于优化剂量和图像噪声的自动管电流调制（ATCM）系统已成为计算机断层扫描（CT）扫描仪的标准配置。主要供应商的ATCM系统以略有不同的方式调制管电流，一些使用与图像噪声相关的控制参数（如东芝、通用电气），而另一些则使用质量参考图像毫安秒（如西门子）。为了在不同制造商的CT扫描仪之间获得具有优化曝光变量的相似图像质量水平，包括ATCM操作在内的临床协议的转换已成为一个重要问题。在本研究中，代表小、中、大患者的不同尺寸的圆柱形体模被组合成一个体模，并在西门子、东芝和通用电气CT扫描仪上使用ATCM图像质量设置的全范围进行扫描。记录每个设置下体模各部分的体积加权CT剂量指数（CTDI）和图像噪声。分析图像质量水平设置与CTDI和测量图像噪声之间的关系，以研究ATCM性能。通过对数据的拟合得出方程，以便能够根据每台扫描仪上不同尺寸体模的图像质量参数来表示CTDI和图像噪声。选择西门子扫描仪协议作为参考，因为它避免了给大患者使用高剂量，同时允许对所有尺寸的患者完全调制管电流，因此被认为提供了优化的性能。导出的方程用于将东芝和通用电气扫描仪上的噪声参数与西门子扫描仪上的质量参考毫安秒相等，以便在三台CT扫描仪上获得包含相似优化水平的临床协议。
