Funama Yoshinori, Awai Kazuo, Liu Duo, Oda Seitaro, Yanaga Yumi, Nakaura Takeshi, Kawanaka Koichi, Shimamura Masamichi, Yamashita Yasuyuki
Department of Radiological Sciences, School of Health Sciences, Kumamoto University, Kumamoto, Japan.
J Comput Assist Tomogr. 2009 Jan-Feb;33(1):49-53. doi: 10.1097/RCT.0b013e31815e6291.
To investigate the effect of the radiation dose (tube current second product) and the attenuation value of nodules with ground-glass opacity (GGO) on their detectability at multidetector computed tomography (MDCT).
We scanned a chest CT phantom that included simulated GGO nodules with an MDCT scanner. The attenuation value of the simulated lung parenchyma was -900 Hounsfield units (HU); it was -800 and -650 HU for the simulated GGO nodules. We used a tube current second product of 180 mA as the standard and 21, 45, 60, and 90 mAs as the low-dose and performed receiver operating characteristic analysis to compare the performance of 5 radiologists in detecting GGO nodules at each milliampere. To assess the detectability of GGO nodules on human lung images, the observers were presented with 38 GGO nodules from 15 patients. The 5 radiologists independently reviewed chest CT images at 21 and 45 mAs.
In the phantom study, the Az value for GGO nodules with a CT number of -800 HU was significantly lower at 21 than 180 effective mA (0.86 vs. 0.96; P < 0.01). There was no statistically significant difference in the Az value of GGO nodules with a CT number of -650 HU, irrespective of milliamperes used (P = 0.165). In the clinical study, 39.5% and 25.8% of GGO were missed at 21 and 45 mAs, respectively.
At MDCT, GGO nodules with a CT number of -650 HU or less were difficult to detect at the lower milliampere settings (21 and 45 mAs).
探讨辐射剂量（管电流秒积）及磨玻璃密度（GGO）结节的衰减值对其在多排螺旋计算机断层扫描（MDCT）上可检测性的影响。
我们使用MDCT扫描仪对包含模拟GGO结节的胸部CT体模进行扫描。模拟肺实质的衰减值为-900亨氏单位（HU）；模拟GGO结节的衰减值为-800 HU和-650 HU。我们将180 mA的管电流秒积作为标准，将21、45、60和90 mAs作为低剂量，并进行了接受者操作特征分析，以比较5名放射科医生在每个毫安下检测GGO结节的性能。为了评估GGO结节在人体肺部图像上的可检测性，向观察者展示了来自15名患者的38个GGO结节。5名放射科医生分别在21和45 mAs下独立复查胸部CT图像。
在体模研究中，CT值为-800 HU的GGO结节在21有效毫安时的Az值显著低于180有效毫安时（0.86对0.96；P<0.01）。无论使用的毫安数是多少，CT值为-650 HU的GGO结节的Az值均无统计学显著差异（P = 0.165）。在临床研究中，分别有39.5%和25.8%的GGO在21和45 mAs时被漏诊。
在MDCT上，CT值为-650 HU或更低水平的GGO结节在较低毫安设置（21和45 mAs）下难以检测到。
