基于单源双能CT平扫图像的纹理分析对肝脓肿和肝转移瘤的鉴别价值

Differentiation of liver abscess and metastatic tumor:based on texture analysis on non-enhanced spectral CT

目的:探讨单源双能CT平扫图像结合纹理分析对肝脓肿和肝转移瘤的鉴别诊断价值。方法:回顾性分析2011年9月-2016年12月采用单源双能CT行CT能谱成像平扫的26例肝脓肿(27个病灶)和29例肝转移瘤(39个病灶)患者的病例资料,所有入组病例均见明显的中心液化区。在AW 4.5工作站上,重建单能量图像(40~70 keV)用于纹理分析,选择病灶囊腔最大层面勾画兴趣区(ROI)。应用灰度直方图及灰度共生矩阵纹理分析方法测定熵值、能量、偏度、方差及逆差矩5个参数。采用独立样本t检验(正态分布)或Mann-Whitney U(非正态分布)比较两组间各参数差异性,绘制受试者操作特征(ROC)曲线,比较各参数诊断效能。选择两个最佳参数进行二元logistics回归分析,比较不同单能量下诊断效能。结果:40 keV、50 keV、60 keV条件下肝脓肿能量及逆差矩小于肝转移瘤,熵值及方差大于肝转移瘤(P均<0.05)。50 keV及60 keV条件下偏度小于肝转移瘤(P均<0.05)。其中50 keV条件下诊断肝转移瘤效能最高,AUC为0.782,敏感度88.9%,特异度69.2%。70 keV条件下肝脓肿方差大于肝转移瘤(P<0.05)。结论:基于单源双能CT平扫图像的纹理分析能够有效鉴别肝脓肿与肝转移瘤,50 keV图像结合纹理分析诊断效能最佳。

Objective:The purpose of this study was to determine the feasibility of texture analysis of non-enhanced CT images for differential diagnosis of liver abscess and metastatic tumor.Methods:55 patients with 66 liver lesions(27 abscess,39 metastatic tumors)underwent spectral CT scans from September 2011 to December 2016.All lesions had a central liquefied necrotic area.The images of monochromatic(40~70keV)were reconstructed on an AW 4.5 workstation for further analysis.The ROI was placed at the maximum level of the cystic,2mm inside along the medial margin of the lesion.Texture features derived from the gray-level histogram and co-occurrence were calculated,including entropy,energy,skewness,variance,inverse difference moment.These parameters of abscess and metastatic tumors were compared by independent sample t-test or Mann-Whitney U.Using binary logistics regression analysis combined with these parameters to establish the predictive model for diagnosingof liver metastatic tumors.The operating characteristic curve of subjects was drawn,and the area under the curve was obtained.Sensitivity and specificity were calculated for the optimal threshold.Results:The energy and inverse difference moment of metastatic tumors were significantly higher than those of liver abscesses at 40keV(P<0.05).The entropy and variance of liver abscesses were significantly higher than that of metastatic tumors at 40keV(P<0.05).The area under curve(AUC)was 0.763.The sensitivity and specificity of liver metastatic tumors except liver abscesses were 85.2%and 59%.The energy,skewness and inverse difference moment of liver metastatic tumors were significantly higher than those of abscess at energy levels ranging from 50keV to 60keV(P<0.05).The entropy and variance of liver abscesses were significantly higher than those of liver metastatic tumors at energy levels ranging from 50keV to 60keV(P<0.05).The area under curve(AUC)was 0.782 in the monochromatic images(50keV),the sensitivity and specificity of liver metastatic tumors except liver abscesses were 88.9%and 69.2%.The area under curve(AUC)was 0.713 in the monochromatic images(60keV),the sensitivity and specificity of liver metastatic tumors except liver abscesses were 66.7%and 74.4%.There were significant differences in variance of the monochromatic images(70keV)between abscess and metastatic tumors.The area under curve(AUC)was 0.684.The sensitivity and specificity of abscesses except metastatic tumors were 66.7%and 66.7%.Conclusions:Texture analysis of non-enhanced CT scan is an effective method in the differential diagnosis of liver abscess and liver metastatic tumors.The monochromatic image(50keV)combined with texture analysis can achieve the best diagnostic performance.