MR扩散峰度成像对非酒精性脂肪性肝病诊断价值

目的探讨扩散峰度成像(DKI)对非酒精性脂肪性肝病(NAFLD)定量分级诊断及早期检出非酒精性脂肪性肝炎(NASH)的价值。方法采用高脂饮食喂养新西兰大白兔,构建不同等级非酒精性脂肪性肝病动物模型。采用3.0 T磁共振、关节表面柔线圈,进行肝脏扩散峰度成像(b=0、400、800 s/mm2)和磁共振扩散加权成像(DWI),分别获取MD值、MK值和ADC值,对所有肝脏标本进行非酒精性脂肪性肝病活动度评分。采用Spearman相关性分析评估不同等级与磁共振参数的相关性。采用ROC明确各磁共振参数诊断不同等级非酒精性脂肪性肝病的效能。采用比较ROC分析不同模型参数在早期诊断非酒精性脂肪性肝炎中的价值。结果ADC值和MD值与非酒精性脂肪性肝病等级程度呈负相关(ρ=-0.52,-0.904;P<0.05)。MK值与疾病等级程度呈正相关(ρ=0.761;P<0.05)。MD值和MK值在临界组和NASH组间差异有统计学意义(MD:1.729±0.114比1.458±0.240μm^2/ms;MK:1.096±0.079比1.237±0.180;P<0.05)。MD值和MK值诊断NASH的ROC曲线下面积分别为0.955和0.905,且均优于ADC值(AUC=0.727)(P<0.05)。结论扩散峰度成像可对非酒精性脂肪性肝病进行分级诊断,且早期诊断非酒精性脂肪性肝炎的价值优于传统磁共振扩散加权成像。

Diagnostic value of non-alcoholic fatty liver disease with MR diffusion kurtosis imaging

Objective To study the feasibility of diffusion kurtosis MR imaging (DKI) for grading nonalcoholic fatty liver disease (NAFLD) and early detection of nonalcoholic steatohepatitis (NASH). Methods High fat diet was used to introduce different severity of NAFLD in rabbit models. Diffusion-weighted MR imaging (DWI) and DKI were performed with a joint surface coil on a 3T MR system. Liver DKI with b values of 0, 400, 800 s/mm2 and DWI were performed. Apparent diffusion coefficient (ADC) was derived from the linear exponential DWI model. Mean diffusion (MD) and mean kurtosis (MK) were derived from the quadratic exponential model of DKI. Correlations between MR parameters and hepatic pathology determined by the NAFLD activity scoring system were analyzed by Spearman rank correlation analysis. Receiver operating characteristic (ROC) analysis was used to determine diagnostic performance of all MR parameters in distinguishing NASH from non-NASH. Results Both the ADC (ρ=-0.529) and MD (ρ=-0.904) had negative correlation with the severity of NAFLD (P<0.05). MK values correlated positively with severity of NAFLD (ρ=0.761, P<0.05). Both MD (1.729±0.144×10-3 mm2/s) and MK (1.096±0.079) values in borderline NASH were significantly different (P<0.05) from that of NASH (1.458±0.240×10-3 mm2/s, 1.237±0.180). The areas under the ROC curves for MD (0.955) and MK (0.905) were both significantly higher than that of ADC (0.736). Conclusion DKI is feasible for grading NAFLD and is superior to DWI in discriminating NASH from non-NASH.