阿尔茨海默病患者脑白质束铁沉积的磁共振相位成像

MR phase imaging in the investigation of the white matter iron deposition in patients with Alzheimer′s disease

目的:利用磁共振相位成像和扩散张量成像(DTI)技术,探讨阿尔茨海默病(AD)患者的脑白质束损伤与相应白质束铁沉积的相关性。方法:对25例AD患者及20例年龄相匹配的健康老年志愿者进行MR扩散张量成像及相位成像。DTI数据经后处理生成平均扩散系数(MD)和部分各向异性(FA)图,分别测量穹窿、胼胝体膝部、胼胝体压部、双侧上下纵束、下额枕束及扣带束后部的FA值和MD值。相位图测量选取与DTI相同层面同样的兴趣区以获取相位值。结果:AD患者穹窿及双侧扣带束后部的相位值及FA值均较对照组明显降低。控制年龄因素后AD组穹窿的FA值与相位值呈明显正相关(偏相关系数r=0.666,P<0.001)。同时AD组左右两侧扣带束FA值与相位值也呈现正相关性,其偏相关系数分别为右侧r=0.436,P=0.033;左侧r=0.458,P=0.022。在正常对照组中未发现DTI参数与相位值的相关性。结论:AD患者的穹窿和双侧扣带束后部区域的铁沉积与FA值减低存在相关性,提示铁质异常沉积可能是AD患者白质损伤的病因之一。

Objective：To investigate the correlation of white matter degeneration and iron accumulation in white matter fibers in patients with Alzheimer′s disease（AD） by using quantitative phase MR imaging and diffusion tensor imaging（DTI）.Methods：25 patients with AD and 20 age-paired healthy volunteer（as controls） participated in this study.MR phase imaging and diffusion tensor imaging were performed for all participants.Eleven sites of white matter fibers in bilateral hemispheres including fornix（Fx）,posterior cingulum（PC）,superior longitudinal fasciculus（SLF）,inferior longitudinal fasciculus（ILF）,frontal occipital fasciculus（IOF）,genu of corpus callosum（GCC）,and splenium of corpus callosum（SCC） were measured on fractional anisotropy（FA） map and mean diffusivity（MD） map of DTI after post-processing.With FA map as a white matter template,phase values on phase imaging were measured on the same region of interest of DTI.Results：Significant decrease of phase values and FA values in Fx and bilateral PC regions were found in AD patients compared with that of normal controls.After age controlled correlation analysis showed that phase value in Fx had a moderate positive correlation with FA value（r=0.666,P=0.000） in AD patients.Meanwhile,phase values in bilateral PC showed positive correlation with FA values,with the right side：r=0.436,P=0.033,the left side r=0.458,P=0.022,respectively.No significant correlation between DTI data and phase value was found in normal controls.Conclusion：Iron accumulation of Fx and PC regions was significantly positively correlated with FA value,indicating that abnormal iron deposition may be one of the causes of the white matter disruption in AD patients.