Department of Neurosurgery, Maastricht University Medical Center, P. Debyelaan 25, Maastricht, 6202 AZ, the Netherlands; School for Mental Health and Neuroscience (MHeNS), Maastricht University Medical Center, P. Debyelaan 25, Maastricht, 6200 MD, the Netherlands.
Department of Neurosurgery, Maastricht University Medical Center, P. Debyelaan 25, Maastricht, 6202 AZ, the Netherlands; School for Mental Health and Neuroscience (MHeNS), Maastricht University Medical Center, P. Debyelaan 25, Maastricht, 6200 MD, the Netherlands.
Neuroimage. 2021 Jul 15;235:118010. doi: 10.1016/j.neuroimage.2021.118010. Epub 2021 Apr 2.
The emerging field of ultra-high field MRI (UHF-MRI, 7 Tesla and higher) provides the opportunity to image human brains at a higher resolution and with higher signal-to-noise ratios compared to the more widely available 1.5 and 3T scanners. Scanning postmortem tissue additionally allows for greatly increased scan times and fewer movement issues leading to improvements in image quality. However, typical postmortem neuroimaging routines involve placing the tissue within plastic bags that leave room for susceptibility artifacts from tissue-air interfaces, inadequate submersion, and leakage issues. To address these challenges in postmortem imaging, a custom-built nonferromagnetic container was developed that allows whole brain hemispheres to be scanned at sub-millimeter resolution within typical head-coils.
The custom-built polymethylmethacrylaat container consists of a cylinder with a hemispheric side and a lid with valves on the adjacent side. This shape fits within common MR head-coils and allows whole hemispheres to be submerged and vacuum sealed within it reducing imaging artifacts that would otherwise arise at air-tissue boundaries. Two hemisphere samples were scanned on a Siemens 9.4T Magnetom MRI scanner. High resolution T2* weighted data was obtained with a custom 3D gradient echo (GRE) sequence and diffusion-weighted imaging (DWI) scans were obtained with a 3D kT-dSTEAM sequence along 48 directions.
The custom-built container proved to submerge and contain tissue samples effectively and showed no interferences with MR scanning acquisition. The 3D GRE sequence provided high resolution isotropic T2* weighted data at 250 μm which showed a clear visualization of gray and white matter structures. DWI scans allowed for dense reconstruction of structural white matter connections via tractography.
Using this custom-built container worked towards achieving high quality MR images of postmortem brain material. This procedure can have advantages over traditional schemes including utilization of a standardized protocol and the reduced likelihood of leakage. This methodology could be adjusted and used to improve typical postmortem imaging routines.
新兴的超高场 MRI（UHF-MRI，7 特斯拉及以上）提供了在比更广泛使用的 1.5 和 3T 扫描仪更高的分辨率和更高的信噪比下对人脑进行成像的机会。对死后组织进行扫描还可以大大增加扫描时间，并减少运动问题，从而提高图像质量。然而，典型的死后神经影像学常规涉及将组织放置在塑料袋中，这会导致组织-空气界面的磁化率伪影、浸没不足和泄漏问题。为了解决死后成像中的这些挑战，开发了一种定制的非铁磁容器，允许以亚毫米分辨率在典型的头部线圈内对整个大脑半球进行扫描。
定制的聚甲基丙烯酸甲酯容器由一个带有半球形侧面的圆柱体和一个带有相邻侧面阀门的盖子组成。这种形状适合于常见的磁共振头部线圈，允许整个半球浸没并在其中进行真空密封，从而减少在空气-组织边界处产生的成像伪影。两个半球样本在西门子 9.4T Magnetom MRI 扫描仪上进行了扫描。使用定制的 3D 梯度回波（GRE）序列获得高分辨率 T2*加权数据，并使用 3D kT-dSTEAM 序列沿 48 个方向获得扩散加权成像（DWI）扫描。
定制的容器被证明能够有效地浸没和容纳组织样本，并且对磁共振扫描采集没有干扰。3D GRE 序列提供了 250μm 的高分辨率各向同性 T2*加权数据，清楚地显示了灰质和白质结构的可视化。DWI 扫描允许通过轨迹重建对结构白质连接进行密集重建。
使用这种定制的容器有助于获得高质量的死后脑组织的磁共振图像。这种方法相对于传统方案具有优势，包括利用标准化方案和降低泄漏的可能性。这种方法可以进行调整并用于改进典型的死后成像常规。
