磁共振扩散加权成像单指数模型与扩散峰度成像模型在61例肾透明细胞癌分级中的对比

Comparison of the value of mono-exponential mode and diffusion kurtosis imaging mode in grading clear cell renal cell carcinoma using magnetic resonance diffusion-weighted imaging

目的探讨磁共振扩散加权成像(DWI)单指数模型和扩散峰度成像(DKI)模型在预测肾透明细胞癌(ccRCC)病理分级中的价值差异。方法前瞻性纳入经病理结果证实的ccRCC患者61例,根据Fuhrman分级将其分为低级别组27例(Ⅰ级10例、Ⅱ级17例)和高级别组34例(Ⅲ级19例、Ⅳ级15例)。患者均行肾脏常规单指数DWI序列和DKI序列扫描,测量参数包括ADC值、各向异性分数(FA)、平均扩散系数(MD)、平均扩散峰度(MK)、轴向扩散峰度(Ka)以及径向扩散峰度(Kr)值。多组间比较采用单因素方差分析(ANOVA),利用独立样本t检验进行两组间均数的比较,使用受试者工作特征(ROC)曲线得出DWI、DKI各参数的曲线下面积(AUC)、敏感度、特异度,并用Delong检验比较各参数的AUC值,以评价各参数对分级的诊断效能。结果①ADC、MD、MK、Ka、Kr值在正常肾实质、低级别及高级别ccRCC间的差异有统计学意义(P<0.05),FA值在3组间的差异无统计学意义(P>0.05)。正常肾实质、低级别及高级别ccRCC的ADC值分别为(2.10±0.16)×10^-3mm^2/s、(1.70±0.34)×10^-3mm^2/s、(1.20±0.32)×10^-3mm^2/s,FA值分别为0.26±0.06、0.26±0.11、0.28±0.14,MD值分别为(6.02±0.43)×10^-3mm^2/s、(5.10±0.96)×10^-3mm^2/s、(3.70±0.76)×10^-3mm^2/s,MK值分别为0.49±0.04、0.57±0.07、0.84±0.20,Ka值分别为0.39±0.04、0.48±0.14、0.65±0.19,Kr值分别为0.53±0.05、0.66±0.18、0.98±0.29。与正常肾实质比较,低级别与高级别ccRCC患者的ADC、MD值均逐渐减低,MK、Ka及Kr值均逐渐升高,差异有统计学意义(P<0.05),FA值差异无统计学意义(P>0.05)。②绘制ROC曲线,得出ADC、MD、MK、Ka及Kr值鉴别低级别、高级别ccRCC的截断值分别为1.50×10^-3mm^2/s、4.49×10^-3mm^2/s、0.71、0.51、0.68,敏感度分别为85.3%、87.5%、79.2%、83.3%、95.8%,特异度分别为75.2%、90.6%、100.0%、85.3%、75.4%;各参数鉴别低级别、高级别ccRCC的AUC分别为ADC值0.831,MD值0.884,MK值0.950,Ka值0.832,Kr值0.874,其中以MK值的AUC最高。结论与单指数扩散模型相比,DKI模型,特别是其衍生出的参数MK,更适合作为ccRCC病理分级预测的成像技术。

Objective To compare the value of diffusion kurtosis imaging(DKI)and diffusion weighted imaging(DWI)mono-exponential mode in grading clear cell renal cell carcinoma(ccRCC).Methods Sixty-one patients with pathologically proven ccRCC were enrolled in this prospective clinical study.The patients were divided into low grade group(10 with gradeⅠand 17 with gradeⅡ)and high-grade group(19 with gradeⅢand 15 with gradeⅣ)according to the Fuhrman classification system.All patients underwent DWI examination by using both mono-exponential mode and DKI mode.The ADC,fractional anisotropy(FA),mean diffusivity(MD),mean kurtosis(MK),axial kurtosis(Ka)and radial kurtosis(Kr)values were measured,respectively.One-way analysis of variance(ANOVA)was used to compare the difference among three groups,and the independent sample t test was used to compare the difference between two groups.The AUC,sensitivity,and specificity of DWI and DKI parameters were calculated by using receiver-operating characteristic(ROC)analysis,then these AUC values were compared by Delong test to evaluate the diagnostic efficacy of the parameters.Results①There were statistical differences in ADC,MD,MK,Ka,and Kr values among the normal renal parenchyma,low-grade and high-grade ccRCC groups(P<0.05).The difference in FA value among the three groups was not statistically significant(P>0.05).The ADC values of the normal renal parenchyma,low-grade and high-grade ccRCC were(2.10±0.16)×10^-3mm^2/s,(1.70±0.34)×10^-3mm^2/s,and(1.20±0.32)×10^-3mm^2/s,FA values were 0.26±0.06,0.26±0.11,and 0.28±0.14,MD values were(6.02±0.43)×10^-3mm^2/s,(5.10±0.96)×10^-3mm^2/s,and(3.70±0.76)×10^-3mm^2/s,MK values were 0.49±0.04,0.57±0.07,and 0.84±0.20,Ka values were 0.39±0.04,0.48±0.14,and 0.65±0.19,Kr values were 0.53±0.05,0.66±0.18,and 0.98±0.29,respectively.Compared with the normal renal parenchyma,the ADC and MD values of patients with low-grade and high-grade ccRCC were gradually decreased,and the MK,Ka,and Kr values were all gradually increased(P<0.05).The difference in FA value was not statistically significant(P>0.05).②ROC analysis showed that the cut-off values of ADC,MD,MK,Ka and Kr in predicting pathological grade of ccRCC were 1.50×10^-3mm^2/s,4.49×10^-3mm^2/s,0.71,0.51,0.68,the sensitivity were 85.3%,87.5%,79.2%,83.3%,95.8%,and the specificity were 75.2%,90.6%,100.0%,85.3%,75.4%,respectively.The area under the curve(AUC)of ADC,MD,MK,Ka and Kr was 0.831,0.884,0.950,0.832 and 0.874,among which the AUC of the MK value was the highest.Conclusion Compared with DWI mono-exponential mode,DKI mode,especially its derived parameter MK,is more suitable to serve as an imaging technique for predicting the pathological grade of ccRCC.