多b值DWI对非酒精性脂肪性肝炎早期诊断价值的实验研究

Early Diagnosis of Nonalcoholic Steatohepatitis by Using Multi-b Values Diffusion-Weighted Imaging

目的探讨多b值扩散加权成像(DWI)参数对非酒精性脂肪性肝病定量分级及早期诊断非酒精性脂肪性肝炎的价值。方法选取32只新西兰大白兔分别采用标准饲料和高脂饲料饲养不同周期以获取不同病理等级非酒精性脂肪性肝病动物模型。所有兔子均行肝脏多b值DWI,采用双指数模型获得定量扩散参数真实扩散系数(D值)、假性扩散系数(D^*值)及灌注分数(f值),同时计算表观扩散系数(ADC值)。搜集肝脏标本,根据非酒精性脂肪性肝病活动性积分(NAS),将非酒精性脂肪性肝病分为正常组、单纯性脂肪肝组、临界组和非酒精性脂肪性肝炎组。采用独立样本T检验比较正常组和非酒精性脂肪性肝病组各参数的差异。非酒精性脂肪性肝病组不同等级间的参数比较采用单因素方差分析,组内两两比较采用LSD-T检验。采用Spearman相关性分析评估各参数与非酒精性脂肪性肝病等级间的相关性,采用受试者工作特征(ROC)曲线预测各参数诊断非酒精性脂肪性肝炎的效能。结果正常组肝脏ADC值、D值、D^*值和f值分别为(1.338±0.222)×10^-3mm^2/s、(0.665±0.109)×10^-3mm^2/s、(18.638±6.169)×10^-3mm^2/s、(38.000±3.040)%,非酒精性脂肪性肝病组ADC值、D值、D^*值和f值分别为(1.105±0.210)×10^-3mm^2/s、(0.791±0.112)×10^-3mm^2/s、(15.622±5.510)×10^-3mm^2/s、(31.857±5.031)%。正常组和非酒精性脂肪性肝病组间ADC值、D值和f值有统计学差异(P为<0.05)。在临界组和非酒精性脂肪性肝炎组间,仅f值有统计学差异(P<0.05)。ADC值和f值与非酒精性脂肪性肝病等级呈负相关,相关系数分别为-0.529、-0.768(P均<0.05),D值与非酒精性脂肪性肝病等级呈正相关,相关系数为0.373(P<0.05)。f值[曲线下面积(AUC)=0.922]诊断非酒精性脂肪性肝炎的效能优于ADC值(AUC=0.727)(P<0.05)。结论多b值DWI定量参数值可用于分级诊断非酒精性脂肪性肝病,其中f值对非酒精性性脂肪性肝炎诊断效能优于传统ADC值。

Objective To explore the diagnosis value of multi-b values diffusion weighted imaging in quantitative strati-fying of nonalcoholic fatty liver disease(NAFLD)including nonalcoholic steatohepatitis(NASH).Methods 32 New Zealand rabbits were fed a variety of diets(from a standard diet to a high fat and high cholesterol diet)for different periods before MR diffusion weighted imaging scanning.Apparent diffusion coefficient(ADC)and IVIM derived parameters(D,D^*,f)were measured.Liver biopsy specimens were obtained and categorized as normal,simple steostsis,borderline and NASH according to NAS scoring system.The diffusion parameters of normal group and NAFLD group were compared by in-dependent sample t test.The difference of values diffusion parameters between different grades of NAFLD were compared by one-way ANOVA.Spearman correlation analysis was used to reveal the correlation between diffusion parameters and different severity groups of NAFLD.ROC curve was compared to evaluate the diagnostic efficiency of MR parameters for NASH.Results ADC and f were significantly lower in NAFLD than normal(1.105±0.210 vs.1.338±0.222×10^-3 mm^2/s,31.857±5.031 vs.38.000±3.040%,respectively)(P<0.05),D was significantly higher in NAFLD than normal(0.791±0.112 vs.0.665±0.109×10^-3 mm^2/s)(P<0.05).fhad significant difference between borderline and NASH(P<0.05).ADC and f showed a negative correlation with the degree of NAFLD with the coefficient of-0.529、-0.768,respectively(P<0.05).f(AUC=0.922)had significantly greater AUC values than ADC(AUC=0.727)in the NASH group and borderline or less severe group(P<0.05).Conclusion Perfusion fraction f extracted from multi-b values dif-fusion weighted imaging can distinguish NASH from borderline,and help in the staging of NASH compared with convention-al diffusion parameter.