Unit of Medical Physics, Pisa University Hospital "Azienda Ospedaliero-Universitaria Pisana", Pisa, Italy.
Diagnostic and Interventional Radiology, University of Pisa, Pisa, Italy.
PLoS One. 2021 Jan 14;16(1):e0245374. doi: 10.1371/journal.pone.0245374. eCollection 2021.
Nowadays, given the technological advance in CT imaging and increasing heterogeneity in characteristics of CT scanners, a number of CT scanners with different manufacturers/technologies are often installed in a hospital centre and used by various departments. In this phantom study, a comprehensive assessment of image quality of 5 scanners (from 3 manufacturers and with different models) for head CT imaging, as clinically used at a single hospital centre, was hence carried out. Helical and/or sequential acquisitions of the Catphan-504 phantom were performed, using the scanning protocols (CTDIvol range: 54.7-57.5 mGy) employed by the staff of various Radiology/Neuroradiology departments of our institution for routine head examinations. CT image quality for each scanner/acquisition protocol was assessed through noise level, noise power spectrum (NPS), contrast-to-noise ratio (CNR), modulation transfer function (MTF), low contrast detectability (LCD) and non-uniformity index analyses. Noise values ranged from 3.5 HU to 5.7 HU across scanners/acquisition protocols. NPS curves differed in terms of peak position (range: 0.21-0.30 mm-1). A substantial variation of CNR values with scanner/acquisition protocol was observed for different contrast inserts. The coefficient of variation (standard deviation divided by mean value) of CNR values across scanners/acquisition protocols was 18.3%, 31.4%, 34.2%, 30.4% and 30% for teflon, delrin, LDPE, polystyrene and acrylic insert, respectively. An appreciable difference in MTF curves across scanners/acquisition protocols was revealed, with a coefficient of variation of f50%/f10% of MTF curves across scanners/acquisition protocols of 10.1%/7.4%. A relevant difference in LCD performance of different scanners/acquisition protocols was found. The range of contrast threshold for a typical object size of 3 mm was 3.7-5.8 HU. Moreover, appreciable differences in terms of NUI values (range: 4.1%-8.3%) were found. The analysis of several quality indices showed a non-negligible variability in head CT imaging capabilities across different scanners/acquisition protocols. This highlights the importance of a physical in-depth characterization of image quality for each CT scanner as clinically used, in order to optimize CT imaging procedures.
如今，随着 CT 成像技术的进步和 CT 扫描仪特性的日益多样化，许多具有不同制造商/技术的 CT 扫描仪经常安装在医院中心，并由各个部门使用。在这项体模研究中，对 5 台扫描仪（来自 3 个制造商，具有不同型号）的头部 CT 成像图像质量进行了全面评估，这些扫描仪在我们医院的一个单一中心临床使用。使用我们机构的各个放射科/神经放射科工作人员为常规头部检查使用的扫描协议（CTDIvol 范围：54.7-57.5 mGy）对 Catphan-504 体模进行螺旋和/或顺序采集。通过噪声水平、噪声功率谱（NPS）、对比噪声比（CNR）、调制传递函数（MTF）、低对比度检测（LCD）和非均匀性指数分析评估每个扫描仪/采集协议的 CT 图像质量。噪声值在扫描仪/采集协议之间的范围为 3.5 HU 至 5.7 HU。NPS 曲线在峰值位置（范围：0.21-0.30 mm-1）方面有所不同。对于不同的对比插件，观察到 CNR 值随扫描仪/采集协议的显著变化。不同对比插件的 CNR 值的变异系数（标准差除以平均值）在扫描仪/采集协议之间分别为 18.3%、31.4%、34.2%、30.4%和 30%。对于特氟龙、聚甲醛、LDPE、聚苯乙烯和丙烯酸插件，在扫描仪/采集协议之间的 MTF 曲线存在显著差异，MTF 曲线的变异系数为 f50%/f10%，在扫描仪/采集协议之间为 10.1%/7.4%。不同扫描仪/采集协议的 LCD 性能存在显著差异。对于典型的 3 毫米物体大小的对比度阈值范围为 3.7-5.8 HU。此外，在 NUI 值（范围：4.1%-8.3%）方面也存在明显差异。对多个质量指标的分析表明，不同扫描仪/采集协议之间头部 CT 成像能力存在不可忽视的变异性。这凸显了对临床使用的每个 CT 扫描仪进行深入的物理图像质量特性分析的重要性，以优化 CT 成像程序。
