Department of Radiological Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, Thailand.
Department of Clinical Physics and Bio-engineering, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
J Radiol Prot. 2021 Nov 1;41(4). doi: 10.1088/1361-6498/abebb4.
The effects of tube potential selection with a computed tomography (CT) automatic tube current modulation (ATCM) system on radiation dose and image quality have been investigated on a Canon CT scanner. The use of different values of tube voltage for imaging, and the appropriate settings of the ATCM system, were evaluated. The custom-made phantom consisted of three sections of different sizes with inserts of various materials. It was scanned using tube potentials of 80-140 kV and different image quality ATCM settings. CTDIand image quality in terms of noise, contrast, and contrast-to-noise ratio (CNR) for air, polyethylene (PE), acrylic, polyoxymethylene (POM) and polyvinylchloride (PVC) were analysed. A figure of merit (FOM) was estimated by combining CNR and CTDI. CTDIvalues were similar for all values of tube voltage and individual image quality ATCM settings when tube current was not restricted by the maximum value. The contrasts were independent of ATCM image quality setting, but CNR increased at the higher image quality level as image noise decreased. Both contrast and CNR decreased with increasing tube voltage for PVC and PE, but increased for POM and acrylic. PVC was the only insert material for which there was a significant improvement in contrast at lower tube potentials. FOM indicated that standard (SD = 10) and low dose (SD = 12.5) ATCM settings might be appropriate. The optimum tube voltage settings for imaging the PVC was 80-100 kV, but not for the lower contrast POM and acrylic, for which the standard tube voltage setting of 120 kV was better. The tube potential should be carefully set to gain radiological protection optimisation and keep the radiation dose as low as possible. Results indicate that 100 kV is likely to be appropriate for imaging small and medium-sized Thai patients when iodine contrast is used.
本研究旨在探讨佳能 CT 扫描仪中 CT 自动管电流调制（ATCM）系统下管电流选择对辐射剂量和图像质量的影响。评估了不同管电压值在成像中的应用，以及 ATCM 系统的适当设置。定制的体模由三个不同大小的部分组成，其中插入了不同的材料。使用管电压 80-140kV 以及不同的图像质量 ATCM 设置进行扫描。分析了空气、聚乙烯（PE）、亚克力、聚甲醛（POM）和聚氯乙烯（PVC）的 CTDI 和噪声、对比度、对比噪声比（CNR）等图像质量。通过结合 CNR 和 CTDI 来估计一个质量指标（FOM）。当管电流不受最大限制时，所有管电压值和单个图像质量 ATCM 设置的 CTDI 值相似。对比度与 ATCM 图像质量设置无关，但随着图像噪声的降低，CNR 增加。对于 PVC 和 PE，对比度和 CNR 随管电压的增加而降低，但对于 POM 和亚克力，对比度和 CNR 增加。PVC 是唯一一种在较低管电压下对比度有显著提高的插入材料。FOM 表明标准（SD=10）和低剂量（SD=12.5）ATCM 设置可能是合适的。对于 PVC 成像，标准管电压设置 120kV 可能更合适，而对于对比度较低的 POM 和亚克力，则需要选择最佳的管电压设置。为了获得最佳的放射防护优化并尽可能降低辐射剂量，应仔细选择管电压。结果表明，当使用碘对比剂时，100kV 可能适用于对泰国中小体型患者进行成像。
