Motion-Correction Enabled Ultra-High Resolution In-Vivo 7T-MRI of the Brain

ObjectivesTo demonstrate the image quality that can be obtained for multiple contrasts using ultra-high resolution MRI (highest nominal resolution: 350 μm isotropic) at 7T using appropriate motion-correction.Materials and MethodsAn MRI-based fat-excitation motion navigator (which requires no additional hardware) was incorporated into T1-weighted (MP2RAGE, 350 μm nominal isotropic resolution, total scan time 124 mins over 2 sessions. The MP2RAGE also provides quantitative T1-maps), 3D-TSE (380 μm nominal isotropic resolution, total scan time 58 mins) and T2*-weighted protocols (3D-GRE, 380 μm nominal isotropic resolution, total scan time 42 mins) on a 7T MR system. Images from each contrast are presented from a single healthy adult male volunteer (34 years) for direct comparison. The subject provided written consent in accordance with the local review board.ResultsImages of various brain structures are revealed at unprecedented quality for in-vivo MRI. The presented images permit, for example, to delimit the internal structure of the basal ganglia and thalamus. The single digitationes of the hippocampus are visible, and the gyrus dentatus can be visualized. Intracortical contrast was also observed in the neocortex, including the stria of Gennari of the primary visual cortex.ConclusionsAppropriate motion-correction allows MRI scans to be performed with extended scan times enabling exceptionally high resolution scans with high image quality, with the use of a 7T scanner allowing large brain coverage for 350–380 μm isotropic voxels with total scan times for each contrast ranging from 42 to 124 minutes.研究目标：展示在7T磁共振系统中，采用适配的运动校正（motion-correction）技术，可获得多对比度超高分辨率磁共振成像（MRI，Magnetic Resonance Imaging）的图像质量，该成像的标称最高各向同性分辨率可达350 μm。材料与方法：本研究在7T磁共振系统中，将无需额外硬件的脂肪激发运动导航器（fat-excitation motion navigator）集成至三种成像协议中：T1加权成像（T1-weighted, MP2RAGE，标称各向同性分辨率350 μm，总扫描时长124分钟，分2次完成；该序列可同步生成定量T1图谱）、三维快速自旋回波序列（3D-TSE，标称各向同性分辨率380 μm，总扫描时长58分钟）以及T2*加权成像协议（三维梯度回波序列3D-GRE，标称各向同性分辨率380 μm，总扫描时长42分钟）。所有对比度图像均来自一名34岁健康成年男性志愿者，以实现不同序列成像结果的直接对比。受试者已按照当地伦理审查委员会的要求签署书面知情同意书。结果：本研究获得的活体磁共振成像图像展现出前所未有的质量，清晰勾勒出多种脑组织结构。例如，该图像可清晰分辨基底神经节与丘脑的内部细微结构；海马体的单个指状突起清晰可见，齿状回也可被可视化呈现；新皮层中亦可观察到皮层内对比度信号，包括初级视觉皮层内的詹纳里纹（stria of Gennari）。结论：适配的运动校正技术可支持更长时长的磁共振扫描，从而实现兼具超高分辨率与优异图像质量的成像；搭配7T磁共振扫描仪，可实现350~380 μm各向同性体素的全脑覆盖，且各对比度序列的总扫描时长介于42~124分钟之间。