磁共振DWI及DTI在肾透明细胞癌与乏脂性肾血管平滑肌脂肪瘤鉴别中的价值

目的探讨磁共振扩散加权成像(DWI)及扩散张量成像(DTI)在肾透明细胞癌(ccRCC)与乏脂性肾血管平滑肌脂肪瘤(MFAML)鉴别诊断中的价值。方法回顾性搜集行腹部MRI检查、经手术病理证实为ccRCC及MFAML的患者共55例(ccRCC 42例,MFAML 13例)。两组患者均行1.5T(GE 1.5T Signa HDXT,美国)MRI常规T1WI、T2WI扫描、LAVA增强扫描、DWI(b=0,600 s/mm^2)、DTI序列扫描(b=0,600 s/mm^2,在6个方向)。由两位放射科医师采用双盲法进行图像分析和测量。在ADW4.6工作站上应用Functool后处理软件进行后处理,使用DWI序列生成ADC图,使用DTI序列生成ADC图和FA图,分别在相应的ADC图和FA图中的ccRCC及MFAML病灶实质部分放置ROI,测量各ROI的ADC值及FA值,对两次测量结果的平均值进行统计分析。应用组内相关系数(ICC)检验两观察者所测数据一致性。使用独立样本t检验比较DWI的ADC值(ADCDWI)及DTI的ADC值(ADCDTI)在ccRCC与MFAML之间的差异,使用Mann-Whitney U检验比较FA值在ccRCC与MFAML之间的差异。应用ROC曲线分析DWI的ADCDWI值及DTI参数中ADCDTI值、FA值对鉴别ccRCC与MFAML的诊断效能,并且分析ADCDWI、ADCDTI及FA值三者联合诊断对鉴别ccRCC与MFAML的效能。结果两位观察者测量各参数的一致性良好。ccRCC的ADCDWI值显著高于MFAML(1.93±0.44)×10^-3mm^2/s与(1.40±0.29)×10^-3mm^2/s,P<0.001],ccRCC的ADCDTI值显著高于MFAML(2.06±0.45)×10^-3mm^2/s与(1.63±0.33)×10^-3mm^2/s,P=0.002],但ccRCC的FA值显著低于MFAML(0.20±0.07)与(0.31±0.20),P=0.020]。ADCDWI值对鉴别ccRCC与MFAML的曲线下面积为0.845,阈值为1.63×10^-3mm^2/s时,其诊断ccRCC排除MFAML的敏感性和特异性分别为71.4%、84.6%;ADCDTI值对鉴别两者的曲线下面积为0.788,阈值为1.77×10^-3mm^2/s时,其诊断ccRCC排除MFAML的敏感性和特异性分别为76.2%、76.9%;FA值对鉴别两者的曲线下面积为0.722,阈值为0.27时,其诊断ccRCC排除MFAML的敏感性和特异性分别为88.1%、53.8%。应用ADCDTI与FA联合诊断鉴别ccRCC和MFAML的效能具有较高的诊断效能,ROC曲线下面积达到0.811,并且诊断特异性达到92.3%。结论磁共振DWI及DTI均能有效鉴别ccRCC与MFAML。其中,ADCDWI对鉴别两者有更高的诊断效能及诊断特异性。应用DWI及DTI的参数进行联合诊断更能提高对两者的诊断效能及敏感性。

Diffusion Weighted Imaging and Diffusion Tensor Imaging in the Differential Diagnosis of Clear Cell Renal Cell Carcinoma and Minimal Fat Angiomyolipoma

Objective To evaluate and compare diffusion weighted imaging(DWI)and diffusion tensor imaging(DTI)in differentiating clear cell renal cell carcinoma(ccRCC)and minimal fat angiomyolipoma(MFAML).Methods Fifty-five histopathology proven ccRCC and MFAML patients(42 cases of ccRCC and 13 cases of MFAML),were retrospectively enrolled in this study.All the patients were performed abdominal MRI exams on 1.5 T scanner(GE 1.5 T Signa HDXT,America)from April 2012 to January 2018 in a protocol containing the routine T1WI,T2WI,LAVA,DWI(b=0,600 s/mm2)and DTI(b=0,600 s/mm2,in 6 directions).MR images were reviewed and analyzed by two radiologists in a double-blind manner with the value of ADC from DWI,the value of ADC and FA from DTI measured using the Functool on GE ADW 4.6 workstation.For every ROI,the ADC values and FA values were measured.ROIs were drawn twice in tumor parenchyma that was greater than 1/3 of the tumor avoiding of hemorrhagic and necrotic part,then the average value was calculated for analysis.The data from two observers was analyzed with intra-class correlation coefficients(ICC)to assess inter-observer agreement,if the values were concordant,the average data from them was calculated for further statistical analysis.The differences of ADC values of DWI(ADCDWI)and the ADC values of DTI(ADCDTI)between ccRCC and MFAML were compared by independent t-test.The Mann-Whitney U test was used to compare the differences of the FA values of DTI between ccRCC and MFAML.The ROC curves of all parameters were used to analyze and compare the diagnostic value of DWI and DTI in differentiating ccRCC and MFAML.Results The inter-observer agreements were good(ICC>0.75).The ADCDWI value of ccRCC was statistically higher than that of MFAML(1.93±0.44)×10^-3mm^2/s vs.(1.40±0.29)×10^-3mm^2/s,P<0.001],and The ADCDTI value of ccRCC was statistically higher than that of MFAML(2.06±0.45)×10^-3mm^2/s vs.(1.63±0.33)×10^-3mm^2/s,P=0.002].But the FA value of ccRCC was statistically lower than that of MFAML(0.20±0.07)vs.(0.31±0.20),P=0.020].The area under the ROC curve of ADCDWI was 0.845,and there was a sensitivity of 71.4%,a specificity of 84.6%and the threshold of 1.63×10^-3mm^2/s for differentiating ccRCC from MFAML.The AUC of ADCDTI was 0.788,sensitivity 76.2%and specificity 76.9%.The ADCDTI threshold for differentiating ccRCC from MFAML was 1.77×10^-3mm^2/s.The AUC of FA was 0.722,and there was a sensitivity of 88.1%,a specificity of 53.8%and the threshold of 0.27 for differentiating ccRCC from MFAML.The combined diagnosis of ccRCC and MFAML with ADCDWI and FA values is better than that with ADCDWI,ADCDTI and FA values,which showed the highest efficiency when the area under the ROC curve was 0.863.The specificity for diagnosing ccRCC except for MFAML was up to 100.0%.Conclusion MRI DWI and DTI can effectively discriminate ccRCC and MFAML,and the ADC value of DWI has higher diagnostic efficacy and specificity.All parameters have high diagnostic efficiency,of which FA value was the highest.The application of DWI and DTI parameters for combined diagnosis can increase diagnostic efficacy and sensitivity.