Simpfendorfer Claus, Herts Brian R, Motta-Ramirez Gaspar A, Lockwood Daniel S, Zhou Ming, Leiber Michael, Remer Erick M
Section of Abdominal Imaging, Imaging Institute, Desk Hb6, Cleveland Clinic, Cleveland, OH 44195, USA.
AJR Am J Roentgenol. 2009 Feb;192(2):438-43. doi: 10.2214/AJR.08.1180.
The purpose of this study was to determine whether counts of pixels with subzero attenuation on CT scans can aid in the diagnosis of renal angiomyolipoma with minimal fat.
Of 33 angiomyolipomas identified among 719 renal masses resected from 702 patients over 4 years, 15 masses in 15 patients were prospectively diagnosed on the basis of the presence of fat at MDCT. The 18 patients with minimal-fat angiomyolipoma and a matched (age, sex, tumor size) cohort of patients with renal cell carcinoma were included in this study. Three radiologists independently counted the number of pixels with attenuation less than -10, -20, and -30 HU. Receiver operating characteristic analysis of the number of pixels at each cutoff was used to calculate sensitivity, specificity, and positive predictive value with the following criteria: 1, more than 10 pixels less than -20 HU; 2, more than 20 pixels less than -20 HU; 3, more than 5 pixels less than -30 HU.
Using criterion 1, reader A identified six angiomyolipomas; reader B, five; and reader C, two. The combined sensitivity was 24%; specificity, 98%; and positive predictive value, 69%. Using criterion 2, reader A identified three angiomyolipomas; reader B, four; and reader C, two. The combined sensitivity was 17%; specificity, 100%; and positive predictive value, 100%. Using criterion 3, reader A identified four angiomyolipomas; reader B, four; and reader C, two. The combined sensitivity was 18%; specificity, 100%; and positive predictive value, 100%.
CT findings of more than 20 pixels with attenuation less than -20 HU and more than 5 pixels with attenuation less than -30 HU have a positive predictive value of 100% in detection of angiomyolipoma, but most angiomyolipomas with minimal fat cannot be reliably identified on the basis of an absolute pixel count.
本研究旨在确定CT扫描中衰减值为负的像素计数是否有助于诊断含极少脂肪的肾血管平滑肌脂肪瘤。
在4年期间从702例患者切除的719个肾肿块中识别出33个血管平滑肌脂肪瘤，其中15例患者的15个肿块基于多排螺旋CT（MDCT）上脂肪的存在被前瞻性诊断。本研究纳入了18例含极少脂肪的血管平滑肌脂肪瘤患者以及一组匹配（年龄、性别、肿瘤大小）的肾细胞癌患者。三名放射科医生独立计数衰减值小于-10 HU、-20 HU和-30 HU的像素数量。对每个截断值处的像素数量进行受试者工作特征分析，以计算敏感性、特异性和阳性预测值，标准如下：1. 衰减值小于-20 HU的像素超过10个；2. 衰减值小于-20 HU的像素超过20个；3. 衰减值小于-30 HU的像素超过5个。
采用标准1，A阅片者识别出6个血管平滑肌脂肪瘤；B阅片者识别出5个；C阅片者识别出2个。联合敏感性为24%；特异性为98%；阳性预测值为69%。采用标准2，A阅片者识别出3个血管平滑肌脂肪瘤；B阅片者识别出4个；C阅片者识别出2个。联合敏感性为17%；特异性为100%；阳性预测值为100%。采用标准3，A阅片者识别出4个血管平滑肌脂肪瘤；B阅片者识别出4个；C阅片者识别出2个。联合敏感性为18%；特异性为100%；阳性预测值为100%。
CT表现为衰减值小于-20 HU的像素超过20个以及衰减值小于-30 HU的像素超过5个，在检测血管平滑肌脂肪瘤时阳性预测值为100%，但大多数含极少脂肪的血管平滑肌脂肪瘤无法基于绝对像素计数可靠地识别。
