[Application of stretched exponential diffusion-weighted imaging model in quantitative diagnosis of nonalcoholic...

Objective: To evaluate the feasibility of diffusion parameters obtained from mono-exponential and stretched exponential diffusion-weighted imaging models in staging of nonalcoholic fatty liver disease and compare the diagnosis ability of nonalcoholic steatohepatitis. Methods: Thirty-two 12 -week-old male New Zealand rabbits, about 2.5 kg of each, were randomly divided into five groups. To obtained different severity groups of NAFLD, a variety of diet (from standard to high-fat, high cholesterol chow) were feed for different periods before liver diffusion imaging was performed by using 3.0 T MR imaging system (Discovery 750W GE health care), the value of ADC, stretched exponential model parameters distributed diffusion coefficient (DDC) and α (water molecular diffusion heterogeneity index) were measured. Liver specimens were obtained for pathological grading (NAFLD activity scoring system). The diffusion parameters of each group of NAFLD were compared by ANOVA, LSD-t test was utilized to pairwise comparison between different grades of NAFLD. Spearman rank correlation analysis was used to evaluate the correlation between ADC, DDC, α and different severity groups of NAFLD. ROC curve was compared to evaluate the diagnostic efficiency of MR parameters for NASH. Results: α was significant different between borderline and NASH groups (0.65±0.05 vs 0.72±0.07; P<0.05); ADC and DDC showed no statistical difference between borderline and NASH groups (ADC:(1.09±0.14)×10(-3) vs (1.04±0.24)×10(-3) mm(2)/s; DDC: (0.73±0.08)×10(-3) vs (0.66±0.19)×10(-3) mm(2)/s; P>0.05); ADC and DDC were negatively correlated with NAFLD, and the correlation coefficients were -0.552, -0.596, respectively (P<0.05). α was found to be positively correlated with advancement of NAFLD, the correlation coefficient was 0.729 (P<0.05).In terms of the diagnostic efficiency of NASH, the AUC of ADC, DDC and α were 0.736, 0.784, 0.900, respectively, α was significantly greater than ADC in diagnosis of NASH (P<0.05). Conclusion: Stretched exponential model parameter α (water molecular diffusion heterogeneity index) could be utilized to identify NAFLD. α may provide more information and improve the staging of NASH compared with conventional diffusion parameters.