使用7.0T MRI信号强度比和扩散张量成像定量分析小鼠脱髓鞘模型的研究

Quantitative analysis of demyelination mouse model using signal intensity ratio and diffusion tensor imaging at 7.0 Tesla MRI

目的用7.0 T MRI扫描改良双环己酮草酸二腙(cuprizone,CPZ)小鼠多发性硬化(multiple sclerosis,MS)脱髓鞘模型,探讨信号强度比(signal intensity ratio,SIR)联合扩散张量成像(diffusion tensor imaging,DTI)定量检测和分析小鼠MS模型灰、白质脱髓鞘的价值。方法20只小鼠使用随机数字表法分为实验组(n=10)及对照组(n=10),分别使用CPZ-羧甲基纤维素钠(sodium carboxymethyl cellulose,CMCNa)悬浊液及0.5%CMCNa溶液灌胃6周后,在7.0T MRI上对两组小鼠行T_1WI及T_2WI扫描,在空间配准后计算SIR,同时行DTI扫描获取各向异性分数(fractional anisotropy,FA)、平均扩散率(mean diffusivity,MD)等扩散张量参数,并行脑组织病理染色。选择胼胝体(corpus callosum,CC)、双侧大脑皮层(cortex,CTX)、双侧丘脑(thalamus,THA)及双侧海马体(hippocampus,HIP)为感兴趣区(regions of interest,ROI),比较两组SIR、FA、MD及病理染色平均灰度值(mean grayscale value,MGSV)的差异,并行影像及病理参数的两两相关分析及线性拟合。结果与对照组相比,实验组小鼠CC呈明显脱髓鞘改变,SIR及FA值显著降低(P<0.05),而MD值差异无统计学意义,病理MGSV显著升高(P<0.05);其余部位两组SIR、FA、MD值及病理MGSV比较差异均无统计学意义。相关性分析显示SIR、FA值均与MGSV呈负相关,且|r_(SIR)|>|r_(FA)|。结论利用SIR联合DTI可以定量评估MS模型白质脱髓鞘改变。

Objective To assess the value of combined signal intensity ratio(SIR)and diffusion tensor imaging(DTI)measured at 7.0 T MRI in quantitative detection and analysis of gray and white matter demyelination in the modified cuprizone(CPZ)-induced mouse model of multiple sclerosis(MS).Methods A total of 20 mice were randomly divided into experimental group(n=10)and control group(n=10),and were intragastrically administrated with CPZ-carboxymethyl cellulose sodium(CMCNa)suspension and 0.5%CMCNa solution,respectively.In 6 weeks after administration,the mice of both groups were given T1WI and T2WI scanning on 7.0 T MRI,and the SIR value was calculated by linear registration of T1WI and T2WI.Besides,DTI scanning was also conducted in both groups to obtain the diffusion parameters such as fractional anisotropy(FA)and mean diffusivity(MD).Moreover,pathological observation was performed on cerebral tissues after Luxol fast blue staining for mean grayscale value(MGSV).Then corpus callosum(CC),bilateral cerebral cortex(CTX),bilateral thalamus(THA),and bilateral hippocampus(HIP)were selected as the regions of interest(ROI).SIR,FA,MD and MGSV of above regions were subsequently compared between the experimental and control groups.Finally,pairwise correlation analysis and linear fitting were carried out on the MRI metrics and pathological parameters.Results As compared with the control group,the CC region in the experimental group showed significant demyelinating changes,with lower SIR and FA values and higher MGSV(P<0.05),while the MD value showed no statistical significance(P>0.05).However,in terms of other cerebral regions,there were no significant differences between the 2 groups in SIR,FA,MD and MGSV values(P>0.05).Correlation analysis suggested that both SIR and FA values were negatively correlated with MGSV,with|rSIR|>|rFA|.Conclusion SIR combined with DTI can quantitatively evaluate the demyelination changes of white matter in MS model.