神经突方向离散度和密度成像对遗忘型轻度认知障碍脑白质微观结构的研究

A Study on the White matter Microstructure in Amnestic Mild Cognitive Impairment Based on Neurite Orientation Dispersion and Density Imaging

目的采用神经突方向离散度和密度成像(NODDI)研究遗忘型轻度认知障碍(aMCI)患者脑白质微观结构的改变。方法搜集aMCI患者26例和正常对照者(NC)24名进行头部磁共振扩散序列扫描,采用FSL软件计算扩散张量成像(DTI)参数图各向异性分数(FA),采用NODDI_toolbox计算NODDI的参数图神经突密度指数(NDI)和方向离散度指数(ODI)。采用基于纤维束的空间统计分析方法(TBSS)构建FA、NDI和ODI白质纤维骨架图,对两组间骨架图进行双样本t检验;提取有统计学差异的纤维束的参数值,分别与简易智能状态检查量表(MMSE)和蒙特利尔认知评估量表(MoCA)评分做相关性分析。对相关性最强的纤维束的各参数值进行受试者工作特征(ROC)曲线分析。结果与NC组相比较,aMCI组FA值无统计学差异,NDI值在左侧扣带束、双侧钩束、左侧外囊、双侧内囊前肢及后肢、胼胝体压部和双侧上纵束显著降低(P<0.01,TFCE校正),ODI值在双侧扣带束、左侧皮质脊髓束、右侧上纵束显著降低(P<0.01,TFCE校正)。在NDI和ODI参数图中,胼胝体压部NDI值(r=0.351,P=0.012)及右侧上纵束ODI值(r=0.314,P=0.027)与MMSE评分相关性最强;胼胝体压部NDI值(r=0.448,P=0.001)及右侧扣带束ODI值(r=0.348,P=0.013)与MoCA评分相关性最强。ROC曲线下面积(AUC)相比较,胼胝体压部NDI值显著大于FA值(AUC=0.849,0.635,P=0.008),右侧上纵束NDI值与FA值AUC相比较无统计学差异(AUC=0.755,0.574,P=0.050),右侧扣带束ODI值与FA值AUC相比较无统计学差异(AUC=0.736,0.579,P=0.241)。结论MCI阶段存在神经突密度以及树突复杂性的降低,NODDI对白质的变化较DTI敏感,对aMCI的诊断可能较DTI有优势。

Objective To investigate the changes of white matter microstructure in amnestic mild cognitive impairment(aM CI)by using neurite orientation dispersion and density imaging(NODDI).Methods 26 aM CI patients and 24 normal controls(NC)were recruited and underwent MR diffusion sequence brain scanning.The DTI parameter FA was calculated by FSL and NODDI parameters,which included neurite density index(NDI)and orientation dispersion index(ODI),were calculated by NODDI_toolbox.The Tract-Based Spatial Statistics(TBSS)method was used to construct the skeleton images of FA,NDI,ODI and Vcsf for two-sample t-test.The parameter values with significant difference were extracted for correlation analysis with Mini-Mental State examination(MMSE)and Montreal Cognitive Assessment(MoCA)scores.A receiver operating characteristic(ROC)curve was drawn to assess the diagnostic performance of different parameters of fibers with the strongest correlation.Results(1)There was no significant difference in FA value between NC and aM CI groups.Compared with the NC group,the NDI values decreased in aM CI group,including the left cingulum,bilateral uncinate fasciculus,left external capsule,bilateral anterior limb of internal capsule,bilateral posterior limb of internal capsule,splenium of corpus callosum and bilateral superior longitudinal fasciculus(P<0.01,TFCE corrected).The ODI values decreased in aM CI group,including the bilateral cingulum,left corticospinal tract and right superior longitudinal fasciculus(P<0.01,TFCE corrected).(2)The NDI value of the splenium of corpus callosum(r=0.351,P=0.012)and the ODI value of right superior longitudinal fasciculus(r=0.314,P=0.027)showed the strongest correlation with the MMSE score.The NDI value of the splenium of corpus callosum(r=0.448,P=0.001)and the ODI value of right cingulum(r=0.348,P=0.013)showed the strongest correlation with MoCA score.(3)The area under the ROC curve(AUC)of the NDI value of splenium of corpus callosum was larger than FA value(AUC=0.849,0.635,P=0.008).The AUC of the NDI value and FA value of the right superior longitudinal fasciculus had no significant difference(AUC=0.755,0.574,P=0.050).The AUC of the ODI value and FA value of the right cingulum had no significant difference(AUC=0.736,0.579,P=0.241).Conclusion The neurite density and the dendritic complexity decreased in the MCI stage.NODDI is more sensitive to the white matter microstructure changes than DTI and may be superior to DTI in the diagnosis of aM CI.