钆塞酸二钠增强MR纵向弛豫时间定量成像及弥散加权成像评价肝纤维化的对比研究

A comparative study of gadoxetic acid enhanced T1-mapping and diffusion-weighted imaging in assessing liver fibrosis

目的评估钆塞酸二钠增强MR纵向弛豫时间定量成像(T1-mapping)对肝纤维化的分级诊断价值,并进一步与扩散加权成像(DWI)进行对比。方法建立SD大鼠四氯化碳肝纤维化模型,分为肝纤维化模型组(24只)和正常对照组(6只)。模型组大鼠分为4个亚组,每组6只,皮下注射50%四氯化碳植物油溶液,4个亚组分别注射2、4、6、8周;对照组皮下注射等量橄榄油。对所有大鼠进行钆塞酸二钠增强T1-mapping及DWI成像,测定肝胆特异期(HBP)T1弛豫时间、增强前后T1弛豫时间下降率(Δ%)及表观弥散系数(ADC),并进行肝纤维化病理分级诊断。采用Spearman相关分析评估T1弛豫时间及ADC值与纤维化分级间相关性,采用单因素方差分析(Δ%-T1弛豫时间)或Kruskal-Wallis检验(HBP-T1弛豫时间及ADC值)比较不同肝纤维化分级组间参数差异,进一步采用ROC曲线评估T1弛豫时间及ADC值对轻度-重度肝纤维化、非肝硬化-肝硬化的诊断效能。结果本研究纳入F0～F4级大鼠各6,5,7,5,7只。不同纤维化等级间HBP-T1、Δ%-T1弛豫时间及ADC值比较,差异具有统计学意义(χ~2=25.21,P <0.001;F=19.37,P <0.001;χ~2=18.50,P=0.001)。HBP-T1弛豫时间与纤维化分级呈强正相关性(r=0.927,P <0.001),Δ%-T1弛豫时间及ADC值与纤维化分级呈负相关(r=-0.892,P <0.001及r=-0.778,P <0.001)。HBP-T1弛豫时间及Δ%-T1弛豫时间判断轻重度纤维化比ADC具有更大的曲线下面积(0.949 vs 0.944 vs 0.842),但差异无统计学意义(Z=0.343、1.495,P=0.135、0.732);HBP-T1弛豫时间及Δ%-T1弛豫时间在肝硬化判断上较ADC亦具有更大的曲线下面积(0.988 vs 0.957 vs 0.804),差异具有统计学意义(Z=2.202,P=0.028;Z=2.004,P=0.045)。结论钆塞酸二钠增强T1-mapping成像能较好地评估肝纤维化程度,优于传统DWI成像。

Objective To evaluate the diagnostic value of gadoxetic acid enhanced magnetic resonance T1-mapping in assessing liver fibrosis by comparing with diffusion weighted imaging(DWI).Methods Thirty rats were divided into a CCl4-induced fibrosis group(n=24)and a control group(n=6).The rats in the fibrosis group were further randomly divided into four subgroups(n=6 each)and administered with 50%CCl4 intraperitoneally for 2,4,6,and 8 weeks,respectively.Rats in the control group were administered with the same dose of olive oil.Gadoxetic acid enhanced T1-mapping and DWI were performed,and the hepatobiliary phase(HBP)T1 relaxation time,reduction rate(Δ%),and apparent diffusion coefficient(ADC)were calculated.Spearman correlation analysis was used to assess the correlation between T1 relaxation time,ADC,and fibrosis stage(F),and one-way ANOVA(Δ%-T1)or Kruskal-Wallis test(HBP-T1 and ADC)was used to compare MR parameters between different fibrosis stages.Receiver operating characteristic curve analysis was used to assess the diagnostic performance of T1 relaxation time and ADC in discriminating F≥3 and cirrhosis.Results A total of 6,5,7,5,and 7 rats were diagnosed with F0 to F4,respectively.HBP-T1,Δ%-T1 relaxation time,and ADC differed significantly between fibrosis stages(χ2=25.21,P<0.001;F=19.37,P<0.001;χ2=18.50,P=0.001).HBP relaxation time was positively correlated with fibrosis stage(r=0.927,P<0.001),whileΔ%-T1 relaxation time and ADC were negatively related to fibrosis stage(r=-0.892,P<0.001;r=-0.778,P<0.001).ROC analysis demonstrated the areas under the curves of HBP andΔ%T1 relaxation time were larger than that of ADC(0.949 vs 0.944 vs 0.842)for identifying mild and severe fibrosis,but there was no statistical difference(Z=0.343,1.495;P=0.135,0.732);however,for non-cirrhosis and cirrhosis(0.988 vs 0.957 vs 0.804),there was a significant difference(Z=2.202,P=0.028;Z=2.004,P=0.045).Conclusion Gadoxetic acid enhanced T1-mapping may have higher value than conventional DWI in assessing liver fibrosis.