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

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 (1)ADC、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^-3mm²/s、(1.70±0.34)×10^-3mm²/s、(1.20±0.32)×10^-3mm²/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^-3mm²/s、(5.10±0.96)×10^-3mm²/s、(3.70±0.76)×10^-3mm²/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^-3mm²/s、4.49×10^-3mm²/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。

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

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 grade Ⅰ and 17 with grade Ⅱ)and high-grade group(19 with grade Ⅲ and 15 with grade Ⅳ)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. Results (1)There 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^-3mm²/s,(1.70±0.34)×10^-3mm²/s, and(1.20±0.32)×10^-3mm²/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^-3mm²/s,(5.10±0.96)×10^-3mm²/s, and(3.70±0.76)×10^-3mm²/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). (2)ROC analysis showed that the cut-off values of ADC, MD, MK, Ka and Kr in predicting pathological grade of ccRCC were 1.50×10^-3mm²/s, 4.49×10^-3mm²/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.