Department of Vision Sciences, University of Alabama at Birmingham, Birmingham, AL, USA.
Biol Psychiatry. 2013 Feb 1;73(3):289-94. doi: 10.1016/j.biopsych.2012.07.035. Epub 2012 Sep 12.
Magnetic resonance imaging (MRI) has multiple contrast mechanisms. Like various staining techniques in histology, each contrast type reveals different information about the structure of the brain. However, it is not always clear how structures visible in MRI correspond to structures previously identified by histology. The purpose of this study was to determine if magnetic transfer contrast (MTC) or T2 contrast MRI was better at delineating the substantia nigra (SN).
MRI scans were acquired in vivo from two nonhuman primates (NHPs). The NHPs were subsequently euthanized, perfused, and their brains sectioned for histologic analyses. Each slice was photographed before sectioning. Each brain was sectioned into approximately 500 sections, 40 μm each, encompassing most of the cortex, midbrain, and dorsal parts of the hindbrain. Levels corresponding to anatomic MRI images were selected. From these, adjacent sections were stained using Kluver-Barrera (myelin and cell bodies) or tyrosine hydroxylase (dopaminergic neurons) immunohistochemistry. The resulting images were coregistered to the block-face images using a moving least squares algorithm with similarity transformations. MR images were similarly coregistered to the block-face images, allowing the structures on MRI to be identified with structures on the histologic images.
We found that hyperintense (light) areas in MTC images were coextensive with the SN as delineated histologically. The hypointense (dark) areas in T2-weighted images were not coextensive with the SN but extended partially into the SN and partially into the cerebral peduncles.
MTC is more accurate than T2-weighting for localizing the SN in vivo.
磁共振成像（MRI）具有多种对比机制。就像组织学中的各种染色技术一样，每种对比类型都能揭示大脑结构的不同信息。然而，MRI 中可见的结构与组织学先前确定的结构如何对应并不总是清楚的。本研究的目的是确定磁共振转移对比（MTC）或 T2 对比 MRI 是否更能描绘黑质（SN）。
对两只非人类灵长类动物（NHP）进行体内 MRI 扫描。随后对 NHP 进行安乐死、灌注，并对其大脑进行切片进行组织学分析。在切片之前对每个切片进行拍照。每个大脑被切成大约 500 个切片，每个 40μm，涵盖了大部分皮层、中脑和后脑的背侧部分。选择对应于解剖 MRI 图像的水平。从这些水平中，选择相邻的切片用 Kluver-Barrera（髓鞘和细胞体）或酪氨酸羟化酶（多巴胺能神经元）免疫组织化学染色。将所得图像使用具有相似变换的移动最小二乘法算法与块面图像进行配准。MR 图像也以类似的方式与块面图像配准，从而可以在组织学图像上识别 MRI 上的结构。
我们发现 MTC 图像中的高信号（亮）区域与组织学上描绘的 SN 是一致的。T2 加权图像中的低信号（暗）区域与 SN 不一致，但部分延伸到 SN 并部分延伸到大脑脚。
MTC 比 T2 加权更准确地定位体内 SN。
