Medical College of Wisconsin
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Investigating microstructural changes between in vivo and perfused ex vivo marmoset brains using oscillating gradient and b-tensor encoded diffusion MRI at 9.4 T. Magn Reson Med 2025 Feb;93(2):788-802

Date

09/26/2024

Pubmed ID

39323069

Pubmed Central ID

PMC11604852

DOI

10.1002/mrm.30298

Scopus ID

2-s2.0-85205058687 (requires institutional sign-in at Scopus site)   6 Citations

Abstract

PURPOSE: To investigate microstructural alterations induced by perfusion fixation in brain tissues using advanced diffusion MRI techniques and estimate their potential impact on the application of ex vivo models to in vivo microstructure.

METHODS: We used oscillating gradient spin echo (OGSE) and b-tensor encoding diffusion MRI to examine in vivo and ex vivo microstructural differences in the marmoset brain. OGSE was used to shorten effective diffusion times, whereas b-tensor encoding allowed for the differentiation of isotropic and anisotropic kurtosis. Additionally, we performed Monte Carlo simulations to estimate the potential microstructural changes in the tissues.

RESULTS: We report large changes (˜50%-60%) in kurtosis frequency dispersion (OGSE) and in both anisotropic and isotropic kurtosis (b-tensor encoding) after perfusion fixation. Structural MRI showed an average volume reduction of about 10%. Monte Carlo simulations indicated that these alterations could likely be attributed to extracellular fluid loss possibly combined with axon beading and increased dot compartment signal fraction. Little evidence was observed for reductions in axonal caliber.

CONCLUSION: Our findings shed light on advanced MRI parameter changes that are induced by perfusion fixation and potential microstructural sources for these changes. This work also suggests that caution should be exercised when applying ex vivo models to infer in vivo tissue microstructure, as significant differences may arise.

Author List

Santini T, Shim A, Liou JJ, Rahman N, Varela-Mattatall G, Budde MD, Inoue W, Everling S, Baron CA

Author

Matthew Budde PhD Associate Professor in the Neurosurgery department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Anisotropy
Brain
Callithrix
Computer Simulation
Diffusion Magnetic Resonance Imaging
Diffusion Tensor Imaging
Female
Image Processing, Computer-Assisted
Male
Monte Carlo Method
Perfusion