Application Of Diffusion Weighted Magnetic Resonance Imaging In The Diagnostic Of Focal Renal Tumors

Part I ADC Histogram Analysis:Differentiation of clear cell Renal Cell Carcinoma from non-clear cell Renal Cell Carcinoma at r-Fov DWIObjective:To explore the utility of ADC histogram analysis for differentiation of clear cell renal cell carcinoma?ccRCC?and non-clear cell renal cell carcinoma?non-ccRCC?at r-Fov DWI.Methods:We retrospectively evaluated 66 renal tumors?46 patients with 47 ccRCCs and 18 patients with 19 non-ccRCCs?in 64 patients who underwent preoperative routine renal MRI sequences and r-FOV DWI.The whole-lesion ADC assessments,including ADC mean?ADC median?ADC₅th?ADC₂5th?ADC₇5th?ADC₉5^th?skew and kurtosis,were performed for each patient.All Histogram-derived ADC parameters between ccRCC and non-ccRCC were compared by using the Student's t test or Mann–Whitney U test depending on homogeneity of variance.Receiver operating characteristic analysis was used for assessing the diagnostic performance of ADC histogram in distinguishing the 2 groups.Results:ADC histograms of the non-ccRCC group were mostly skewed positively,while the curves of ccRCC were largely skewed negatively.Mean ADC,median ADC,5th percentile ADC,25th percentile ADC,75th percentile ADC,95th percentile ADC?all P<0.05?were significantly lower in non-ccRCC,while skewness was significantly higher in non-ccRCC?P<0.05?.Kurtosis had no significant difference between those 2 groups?P>0.05?.75th percentile ADC achieved the highest AUC?0.987?in differentiating ccRCC and non-ccRCC,with a cutoff value of 1.81×10^-3mm²/s,and a sensitivity of 100.0%and a specificity of 94.7%.Conclusion:ADC histograms of r-FOV DWI might be helpful for differentiating ccRCC from non-ccRCC,and 75th percentile ADC had the highest diagnostic accuracy.Part II Monoexponential,Biexponential,and Stretched exponential Diffusion-weighted Imaging Models: Quantitative Biomarkers for Differentiating Renal Clear Cell Carcinoma and Minimal Fat AngiomyolipomaObjective: To explore various diffusion parameters obtained from monoexponential,biexponential,and stretched exponential Diffusion-weighted imaging models in differentiating between Minimal Fat Angiomyolipoma?MFAML?and clear cell Renal Cell Carcinoma?cc RCC?.Methods: One hundred and thirty-one patients with pathologically confirmed MFAML?n=27?or cc RCC?n=104?underwent multi-b values DWI?0¹700 sec/mm2?imaging at 3.0T MRI.An isotropic apparent diffusion coefficient?ADC?was calculated from diffusion-weighted images by using a monoexponential model.A pseudo-ADC?Dp?,true ADC?Dt?and perfusion fraction?fp?were calculated from diffusion-weighted images by using a biexponential model.A water molecular diffusion heterogeneity index???and distributed diffusion coefficient?DDC?were calculated from diffusion-weighted images by using a stretched exponential model.All parameters were compared between MFAML and cc RCC by using the Student's t test.Receiver operating characteristic and intraclass correlation coefficient analysis were used for statistical evaluations.Results: ADC,Dt,? values were significantly lower in the MFAML group than in the cc RCC group?P <0.001?.Dp,fp and DDC values were slightly higher in the MFAML group than in the cc RCC group,however,the difference was not significant?P=0.136,0.090 and 0.424,respectively?.The AUC values for both ??0.953?and Dt?0.964?were significantly higher than those for ADC?0860?,Dp?0.605?,fp?0.596?and DDC?0.477?in the differentiation of MFAML from cc RCC?P<0.001?.Conclusions: Dt and ? may provide additional information and could lead to improved differentiation with better sensitivity and specificity between MFAML and cc RCC compared with conventional diffusion parameters.