In-vivo quantitative structural imaging of the human midbrain and the superior colliculus at 9.4T
In-vivo quantitative structural imaging of the human midbrain and the superior colliculus at 9.4T
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DOI：
10.1016/j.neuroimage.2018.04.071
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发表时间：
2018-08-15
期刊：
影响因子：
5.7
通讯作者：
Hagberg, Gisela E.
中科院分区：
文献类型：
--
作者：
Loureiro, Joana R.;Himmelbach, Marc;Hagberg, Gisela E.
我们通过9.4T的体内磁共振成像（MRI）探索了上丘（SC）的解剖细节。高信噪比可以获得高分辨率的多模态图像，体素大小在176 x 132 x 600 μ m和（800）(3)μ m之间。在14名健康志愿者中进行了纵向松弛率R1，有效横向松弛率R2*和磁化率QSM的定量映射。在原始空间和归一化到共同脑空间（MNI）后对图像进行分析。在中脑的突出区域评估受试者间的变异系数（CoV），在MNI空间的SC R2*图中达到了最好的重现性（CoV为5%），而在QSM图中，无论脑空间如何，CoV仍然很高。为了研究是否可以检测到更复杂的神经生物学结构特征，我们沿着背尾轴在不同水平的SC上评估了通过SC层向红核（RN）的深度剖面。该分析显示定量MRI参数的改变与之前死后SC细胞和骨髓结构的组织学研究一致。总的来说，R1图在以存在丰富髓鞘纤维为特征的区域呈高强度，可能能够检测到与导水管周围灰色相邻的SC的深白色第七层。虽然R1地图未能揭示更精细的细节，可能是由于这种模式使用的相对粗糙的空间采样，这些可以在R2*地图和QSM中恢复。在SC的中央部分沿其上尾轴，在SC表面以下2mm处观察到R2*值升高和敏感性值降低，可能反映了浅视层（III层）的髓鞘纤维。在更深层，R2*的第二次增加与QSM的顺磁位移平行，这表明SC表面以下约3mm处存在富含铁的层，归因于由多极神经元组成的中间灰色层（IV）。这些结果与组织标本和动物研究的观察结果相吻合，表明9.4T高分辨率多模态MRI可以揭示SC体内的一些微观结构特征。
We explored anatomical details of the superior colliculus (SC) by in vivo magnetic resonance imaging (MRI) at 9.4T. The high signal-to-noise ratio allowed the acquisition of high resolution, multi-modal images with voxel sizes ranging between 176 x 132 x 600 mu m and (800)(3)mu m. Quantitative mapping of the longitudinal relaxation rate R1, the effective transverse relaxation rate R2*, and the magnetic susceptibility QSM was performed in 14 healthy volunteers. The images were analyzed in native space as well as after normalization to a common brain space (MNI). The coefficient-of-variation (CoV) across subjects was evaluated in prominent regions of the midbrain, reaching the best reproducibility (CoV of 5%) in the R2* maps of the SC in MNI space, while the CoV in the QSM maps remained high regardless of brain-space. To investigate whether more complex neurobiological architectural features could be detected, depth profiles through the SC layers towards the red nucleus (RN) were evaluated at different levels of the SC along the rostro-caudal axis. This analysis revealed alterations of the quantitative MRI parameters concordant with previous post mortem histology studies of the cyto-and myeloarchitecture of the SC. In general, the R1 maps were hyperintense in areas characterized by the presence of abundant myelinated fibers, and likely enabled detection of the deep white layer VII of the SC adjacent to the periaqueductal gray. While R1 maps failed to reveal finer details, possibly due to the relatively coarse spatial sampling used for this modality, these could be recovered in R2* maps and in QSM. In the central part of the SC along its rostro-caudal axis, increased R2* values and decreased susceptibility values were observed 2 mm below the SC surface, likely reflecting the myelinated fibers in the superficial optic layer (layer III). Towards the deeper layers, a second increase in R2* was paralleled by a paramagnetic shift in QSM suggesting the presence of an iron-rich layer about 3 mm below the surface of the SC, attributed to the intermediate gray layer (IV) composed of multipolar neurons. These results dovetail observations in histological specimens and animal studies and demonstrate that high-resolution multi-modal MRI at 9.4T can reveal several microstructural features of the SC in vivo.