Stahl R, Dietrich O, Teipel S, Hampel H, Reiser M F, Schoenberg S O
Institut für Klinische Radiologie--Grosshadern, Klinikum der Universität München, Munich.
Radiologe. 2003 Jul;43(7):566-75. doi: 10.1007/s00117-003-0925-4.
Alzheimer disease (AD) causes cortical degeneration with subsequent degenerative changes of the white matter. The aim of this study was to investigate the extent of white matter tissue damage of patients with Alzheimer's disease in comparison with healthy subjects using diffusion tensor MRI (DTI). The value of integrated parallel imaging techniques (iPAT) for reduction of image distortion was assessed.
We studied 9 patients with mild AD and 10 age and gender matched healthy controls. DTI brain scans were obtained on a 1.5 tesla system (Siemens Magnetom Sonata) using parallel imaging (iPAT) and an EPI diffusion sequence with TE/TR 71 ms/6000 ms. We used an 8-element head coil and a GRAPPA reconstruction algorithm with an acceleration factor of 2. From the tensor, the mean diffusivity (D), the fractional anisotropy (FA), and the relative anisotropy (RA) of several white matter regions were determined.
FA was significantly lower (p <0,05) in the white matter of the genu of corpus callosum from patients with AD than in the corresponding regions from healthy controls. There was a trend observed for slightly higher ADC values in the AD group (p=0,06). No significant changes were observed in the regions of the splenium, internal capsule, pericallosal areas, frontal, temporal, parietal, and occipital lobe. The images obtained with iPAT contained substantially less susceptibility artefacts and were less distorted than images acquired with non-parallel imaging technique.
DTI is a method with potential to assess early stages of white matter damage in vivo. The altered FA and ADC values in the genu of corpus callosum of patients with AD presumably reflect the microscopic white matter degeneration. Acquisition time can be reduced by iPAT methods with less image distortion from susceptibility artefacts resulting in a more accurate calculation of the diffusion tensor.
阿尔茨海默病（AD）会导致皮质变性，随后白质出现退行性变化。本研究的目的是使用扩散张量磁共振成像（DTI），比较阿尔茨海默病患者与健康受试者白质组织损伤的程度。评估了集成并行成像技术（iPAT）减少图像失真的价值。
我们研究了9例轻度AD患者和10名年龄及性别匹配的健康对照者。在1.5特斯拉系统（西门子Magnetom Sonata）上使用并行成像（iPAT）和TE/TR为71 ms/6000 ms的EPI扩散序列进行DTI脑部扫描。我们使用8通道头部线圈和加速因子为2的GRAPPA重建算法。从张量中确定几个白质区域的平均扩散率（D）、分数各向异性（FA）和相对各向异性（RA）。
AD患者胼胝体膝部白质的FA显著低于健康对照者的相应区域（p<0.05）。AD组的表观扩散系数（ADC）值有略高的趋势（p=0.06）。在胼胝体压部、内囊、胼周区域、额叶、颞叶、顶叶和枕叶区域未观察到显著变化。与使用非并行成像技术获取的图像相比，iPAT获取的图像中磁敏感伪影明显更少，失真也更小。
DTI是一种有潜力在体内评估白质损伤早期阶段的方法。AD患者胼胝体膝部FA和ADC值的改变可能反映了微观白质变性。iPAT方法可以减少采集时间，同时减少磁敏感伪影导致的图像失真，从而更准确地计算扩散张量。
