磁共振相位成像和R2*定量评估阿尔茨海默病脑内铁质沉积

目的：研究显示阿尔茨海默病（AD）患者脑内存在铁质过度沉积,并与B淀粉样变以及氧化应激直接相关。通过磁共振相位值和R2^＊值的测量可以定量评估铁质在脑内的聚积程度。本文的目的在于比较上述两种方法在评估阿尔茨海默脑病患者和年龄匹配的正常老年纽间的差异。方法：阿尔茨海默病患者26例,正常健康老年人24例,前组均经临床神经科医师根据美国国立神经及交流疾病和脑卒中研究院、Alzheimer病及相关疾病协会（NINCDS-ADRDA）关于可能AD拟诊标准作出诊断。采用GESigna HD 1．5T磁共振扫描仪,8通道头线圈,检查序列包括冠状面三维高分辨率梯度回波和快速多回波梯度序列,经后处理获得校正后的相位图和R2。图,在上述两幅功能图上测量相同层面的双侧壳核、苍白球以及双侧海马的头部和体部的参数值。结果：阿尔茨海默脑病组基底节和海马区域的相位值较对照组有明显下降（P〈0．05）。R2^＊值在苍白球部位显示有明显升高（P〈0．05）。右侧海马头部的相位值与MMSE评分具有中等程度相关性（r=0．603,P=0．000）,而与阿尔茨海默病的病程呈负相关（r=-0．677,P=0．013）。以-0．0972作为诊断的最优临界值,诊断阿尔茨海默病的敏感度和特异度分别为95．8％和80．8％。结论：相位成像对于鉴别正常老年人和阿尔茨海默脑病更具敏感度和有效度。研究海马区铁质过多积聚有助于更好地认识阿尔茨海默脑病的病理发展过程和神经精神功能损害的机制。

Quantitative Assessment of Intracerebral Iron Accumulation in Patients with Alzheimer's Disease Using Phase Imaging and R2* Measurement

Objective：Iron accumulates in the Alzheimer＇s disease （AD） brain and is directly associated with β-amy loid pathology and oxidative stress. Both phase imaging and R2^＊ measurement by magnetic resonance imaging （MRI） can be quantitative methods utilized to assess iron deposits in the brain. In this study,we compare noninvasive iron estimates using these two methods in patients with AD and healthy age-matched controls. Methods： 26 AD patients and 24 healthy controls were recruited. A three-dimensional high-resolution, gradient-echo sequence and a multi-echo fast gradient-echo sequence were used to collect phase data and R2^＊ data in the coronal plane. The regions which were evaluated included the bilateral putamen,globus pallidus, the head and the body of hippocampus. Results：Significantly lower phase values in both basal gan glion and hippocampus were revealed in AD group compared to normal controls （P〈0.05）. R2^＊ only demonstrated significantly higher mean values in the globus pallidus （P〈0.05）. Phase value in the right side of the head of the hippocampus had a moderate positive correlation with MMSE score （r= 0. 603, P=0. 000） and a negative correlation with the duration of the disease （r=-0. 677 ,P=0. 013）. Using --0. 0972 as an optimal cutoff value,the sensitivity and specificity for differentiation from AD to normal controls reached 95.8% and 80.8%. Conclusion.. Phase imaging proved more sensitive and efficient for the differentiation between the normal controls and AD patients. Investigation of the excessive accumulation of iron in the hippocampus may help us better understand the pathologic process and neuropsychological dysfunction of AD disease.