A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, P.O. Box 1627, 70211, Neulaniementie 2, Kuopio, Finland.
Department of Radiology, University of Cambridge, Cambridge, UK.
Sci Rep. 2023 Feb 8;13(1):2219. doi: 10.1038/s41598-023-29010-3.
Our study explores the potential of conventional and advanced diffusion MRI techniques including diffusion tensor imaging (DTI), and single-shell 3-tissue constrained spherical deconvolution (SS3T-CSD) to investigate complex microstructural changes following severe traumatic brain injury in rats at a chronic phase. Rat brains after sham-operation or lateral fluid percussion (LFP) injury were scanned ex vivo in a 9.4 T scanner. Our region-of-interest-based approach of tensor-, and SS3T-CSD derived fixel-, 3-tissue signal fraction maps were sensitive to changes in both white matter (WM) and grey matter (GM) areas. Tensor-based measures, such as fractional anisotropy (FA) and radial diffusivity (RD), detected more changes in WM and GM areas as compared to fixel-based measures including apparent fiber density (AFD), peak FOD amplitude and primary fiber bundle density, while 3-tissue signal fraction maps revealed distinct changes in WM, GM, and phosphate-buffered saline (PBS) fractions highlighting the complex tissue microstructural alterations post-trauma. Track-weighted imaging demonstrated changes in track morphology including reduced curvature and average pathlength distal from the primary lesion in severe TBI rats. In histological analysis, changes in the diffusion MRI measures could be associated to decreased myelin density, loss of myelinated axons, and increased cellularity, revealing progressive microstructural alterations in these brain areas five months after injury. Overall, this study highlights the use of combined conventional and advanced diffusion MRI measures to obtain more precise insights into the complex tissue microstructural alterations in chronic phase of severe brain injury.
我们的研究探索了传统和先进的扩散 MRI 技术的潜力，包括弥散张量成像（DTI）和单壳 3 组织约束球分解（SS3T-CSD），以研究大鼠慢性期严重创伤性脑损伤后的复杂微观结构变化。假手术或侧方液压冲击（LFP）损伤后的大鼠脑在 9.4T 扫描仪中进行离体扫描。我们基于感兴趣区域的张量和 SS3T-CSD 衍生的固定体、3 组织信号分数图的方法对脑白质（WM）和灰质（GM）区域的变化均敏感。与基于固定体的指标（如表观纤维密度（AFD）、峰 FOD 幅度和初级纤维束密度）相比，张量指标（如各向异性分数（FA）和径向扩散系数（RD））检测到 WM 和 GM 区域的更多变化，而 3 组织信号分数图揭示了 WM、GM 和磷酸盐缓冲盐水（PBS）分数的明显变化，突出了创伤后复杂的组织微观结构改变。轨迹加权成像显示严重 TBI 大鼠在原发性损伤远端的轨迹形态发生变化，包括曲率减小和平均路径长度减小。在组织学分析中，扩散 MRI 指标的变化与髓鞘密度降低、少突胶质细胞轴突丢失和细胞增多有关，揭示了这些脑区在损伤后五个月的进行性微观结构改变。总的来说，这项研究强调了联合使用传统和先进的扩散 MRI 指标，以更精确地了解严重脑损伤慢性期的复杂组织微观结构改变。
