中文摘要：

目的探讨单指数、双指数及拉伸指数DWI模型在肾乏脂肪性错构瘤与肾透明细胞癌鉴别诊断中应用价值。方法回顾性分析131例经病理证实为肾乏脂肪性错构瘤（27例）与透明细胞肾癌（104例）的临床资料,所有病人均在3.0 T MRI上接受多b值DWI检查（b值为0~1700 s/mm^2）。基于单指数模型计算出各向同性的表观扩散系数（ADC）;应用双指数模型计算出假扩散系数（D_p）,纯扩散系数（D_t）和灌注分数（f_p）;应用拉伸指数模型计算出水分子扩散异质性指数（α）扩散分布系数（DDC）。所有扩散参数在乏脂肪性错构瘤与肾透明细胞癌两组中的比较采用Student’s t检验进行分析。同时采用ROC曲线及组内相关系数等方法比较诊断效能。结果肾乏脂肪性错构瘤组的ADC,Dt,α值显著低于肾透明细胞癌组,差异有统计学意义（P〈0.001）;虽然D_p,f_p及DDC值略高于肾透明细胞癌组,差异无统计学意义（P=0.136,0.090,0.424）。鉴别两类肿瘤,α（0.953）和D_t（0.964）的曲线下面积（AUC）都显著高于ADC（0860）,D_p（0.605）,f_p（0.596）及DDC（0.477）的AUC值（P〈0.001）。结论与传统扩散参数相比,水分子扩散异质性指数（α）与D_t在鉴别乏脂肪性错构瘤与透明细胞肾癌可以提供更多信息并提高诊断敏感性与特异性。

英文摘要：

Objective To explore various diffusion parameters obtained from monoexponential,biexponential,and stretched exponential diffusion-weighted imaging（DWI） models in differentiating between clear cell renal cell carcinoma（cc RCC） and minimal fat angiomyolipoma（MFAML）.Methods The clinical data of 131 patients with pathologically confirmed MFAML（27） or cc RCC（104） were analyzed retrospectively.All patients underwent DWI with multiple b values of 0-1700 s/mm^2 on a 3.0 T MR system.An isotropic apparent diffusion coefficient（ADC） was calculated from DWI using a monoexponential model.Pseudo-ADC（D_p）,true ADC（D_t）,and perfusion fraction（f_p） were calculated from DWI using a biexponential model.A water molecular diffusion heterogeneity index（α） and distributed diffusion coefficient（DDC） were calculated from DWI using a stretched exponential model.All parameters were compared between cc RCC and MFAML by the Student ＇ s t test,receiver operating characteristic（ROC） curve and intraclass correlation coefficient analysis.Results ADC,Dt,and α values of MFAML were significantly lower（P〈0.001） whereas Dp,fp,and DDC values were insignificantly higher（P〉 0.05） than that of cc RCC.The areas under the ROC curves（AUCs） for both α（0.953）and D_t（0.964） were significantly higher（P〈0.001） than those for ADC（0.860）,D_p（0.605）,f_p（0.596）,and DDC（0.477） in the differentiation of cc RCC from MFAML.Conclusion Dtand α may improve the differentiation between MFAML and cc RCC compared with conventional diffusion parameters.