NMR Biomed. 2026 Nov;39(11):e70411. doi: 10.1002/nbm.70411.
ABSTRACT
Vascular mapping of fixed postmortem human brain tissue remains biologically complex and technically challenging because postmortem changes, including clot contraction and fragmentation, vascular collapse, and fixation-induced alterations, substantially affect vascular MRI contrast. Furthermore, the mechanisms governing vascular contrast in postmortem MRI remain incompletely understood. In this study, we aim to determine the feasibility and reliability of using blood clot formation as a susceptibility contrast source to improve vascular visibility and enable quantitative assessment on ex vivo MRI. Postmortem brain hemispheres and tissue blocks were imaged to assess vascular conspicuity in the cortex, hippocampus, and white matter. Coagulated blood signal was clearly observed within the postmortem brain surface vasculature, with intact clots in small vessels and partial or discontinuous clotting in larger vessels. High-resolution gradient echo (GRE) imaging of tissue blocks enabled detailed reconstruction of local vascular networks, including intrahippocampal vasculature, for vessel density quantification. Quantitative analysis demonstrated markedly shorter T2* values for blood clots (6.6 ± 2.0 ms) compared with gray matter (34.8 ± 8.9 ms) and white matter (19.1 ± 3.6 ms) at 7 T, resulting in appropriate vascular contrast and conspicuity. Histological hematoxylin-eosin and Luxol Fast Blue staining confirmed intravascular clot formation and localization. These findings demonstrate that blood clots can act as an intrinsic contrast for mesoscopic vascular MRI in the postmortem human brain, enabling detailed assessment of microvascular changes and their pathological correlates relevant to vascular contributions to cognitive impairment and dementia.
PMID:42806520 | DOI:10.1002/nbm.70411