Li Tie-Qiang, van Gelderen Peter, Merkle Hellmut, Talagala Lalith, Koretsky Alan P, Duyn Jeff
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA.
Neuroimage. 2006 Sep;32(3):1032-40. doi: 10.1016/j.neuroimage.2006.05.053. Epub 2006 Jul 18.
MRI at high magnetic field strength potentially allows for an increase in resolution and image contrast. The gains are particularly dramatic for T(2)()-weighted imaging, which is sensitive to susceptibility effects caused by a variety of sources, including deoxyhemoglobin, iron concentration, and tissue microstructure. On the other hand, the acquisition of high quality whole brain MRI at high field is hampered by the increased inhomogeneity in B(o) and B(1) fields. In this report, high-resolution gradient echo MRI was performed using an 8-channel detector to obtain T(2)()-weighted images over large brain areas. The high SNR achieved with the multi-channel array enabled T(2)()-weighted images of the brain with an unprecedented spatial resolution of up to 0.2 x 0.2 x 0.5 mm(3). This high resolution greatly facilitated the detection of microscopic susceptibility effects. In addition to the expected contrast between gray, white matter, cerebral spinal fluid, and veins, a large degree of heterogeneity in contrast was observed throughout the white matter of normal brain. The measured T(2)() values in white matter varied as much as 30% with some of the variation apparently correlating with the presence of large fiber bundles.
高磁场强度下的磁共振成像（MRI）有可能提高分辨率和图像对比度。对于T(2)()加权成像而言，这种提升尤为显著，该成像对多种来源引起的磁化率效应敏感，这些来源包括脱氧血红蛋白、铁浓度和组织微观结构。另一方面，高场强下高质量全脑MRI的采集受到B(o)和B(1)场中不均匀性增加的阻碍。在本报告中，使用8通道探测器进行高分辨率梯度回波MRI，以获取大面积脑区的T(2)()加权图像。多通道阵列实现的高信噪比使得能够获得空间分辨率高达0.2×0.2×0.5 mm(3)的前所未有的脑T(2)()加权图像。这种高分辨率极大地促进了微观磁化率效应的检测。除了灰质、白质、脑脊液和静脉之间预期的对比度外，在正常脑白质中还观察到很大程度的对比度异质性。白质中测得的T(2)()值变化高达30%，其中一些变化显然与大纤维束的存在相关。
