Abstract: 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.

Key words: Clear cell renal cell carcinoma, Diffusion-weighted imaging, Mono-exponential mode, Diffusion kurtosis imaging mode