遗忘型轻度认知损害患者海马三维磁共振影像特点

Characteristics of hippocampal 3-dimensional magnetic resonance imaging in anmestic mild cognitive impairment

目的运用基于海马表面的形态分析技术，探讨遗忘型轻度认知损害（aMCI）患者的海马三维MRI特点。方法对15例aMCI患者和16名年龄及教育程度相匹配的对照，行头颅三维MRI扫描，数据采集后采用InsightSNAP1．4．1软件在可视三维窗口下选取冠状位逐层勾勒海马轮廓，计算机自动计算海马体积后，进行两组间海马体积的统计学分析；将海马磁共振影像经过三维网格重建，其曲面网格参数化为400×200的点，将各点到中轴线的径向距离进行两组间比较，获得左右海马径向距离t值图；再经多重比较校正后，获得aMCI组与健康对照组间的三维海马形态差异图。结果左侧海马标化平均体积aMCI组（3247．5±600．2）mm^3、健康对照组（3467．9±451．3）mm^3，两者差异无统计学意义（t=1．161，P=0．255）。右侧海马标化平均体积aMCI组（3416．8±699．1）mm^3、健康对照组（3469．1±358．9）mm^3，两者差异亦无统计学意义（U=0．178，P=0．859）。运用基于海马表面的形态分析技术得到两组间三维海马形态差异图，结果显示aMCI组与健康对照组相比双侧海马的外侧及下表面（组织学上的CA1区和下托）明显萎缩。结论aMCI患者海马体积未见显著性减小，但通过基于海马表面的形态分析，发现aMCI患者的海马部分区域形态有一定程度的萎缩，以双侧海马外侧及下表面的区域性萎缩为主。这一结果可能反映了aMCI的早期影像学标志。

Objective To identify the characteristics of hippocampal 3-dimensional MRI in patients diagnosed as having subtypes of amnestic mild cognitive impairment （ aMCI ） using hippocampal surfacebased analytic technique. Methods Fifty aMCI patients and 16 healthy controls who were equivalent in age and education （NC） were recruited. Every subject carried out a 3-dimensional MRI scan. After the imaging data were acquired, the borders of the hippocampus were manually traced in coronal view using the software of InsightSNAP1.4. 1. Hippocampal volume was computed automatically and statistically analysed. Hippocampal 3-dimension MRI were transformed into 3-dimension parametric surface mesh models of 400 × 200 grids. Hippocampal radial distance measures which was the distance from the surface point to the central axis were statistically compared between two groups. The radial atrophy significance maps were acquired and adjusted for multiple comparisons. Hippocampal morphological difference maps of aMCI in contrast with NC were acquired. Results The average normalized volume of left hippocampus were （3247.5 ±600. 2 ） mm^3 in aMCI patients and （ 3467.9±451.3 ）mm^3 in NC subjects. The average normalized volume of right hippocampus were （3416. 8±699. 1 ） mm^3 in aMCI patients and （3469.1±358. 9） mm^3 in NC subjects. Comparison of hippocampal volume did not differ significantly between aMCI patients and NC subjects （ t = 1. 161, P = 0. 255 ; U = 0. 178, P = 0. 859 ） . By using hippocampal surface-based morphologic analytic technique, 3-dimension hippocampal morphological difference maps between two groups were acquired,showing significant atrophy on the lateral and inferior hippocampal surface which corresponded to CA1 and subiculum hippocampal subfields bilaterally in aMCI patients compared with NC subjects. Conclusions aMCI patients do not have significant volume loss in the hippocampus. Through hippocampal surface-based morphologic analyses, partial regional atrophy of hippocampus at some degree is found, mainly localizing in the lateral and inferior hippocampal regions which correspond to CA1 and subiculum hippocampal subfields bilaterally in aMCI compared with NC. These results may reflect the early image marker in aMCI.