Effect of extracellular space preservation and partial delipidation on ex vivo brain MRI tissue contrast and microstructure

Motivation: Accurate tissue preservation is crucial for ex vivo MRI as it better reflects living tissue and allows for more reliable comparison with histopathology. Goal(s): To evaluate the impact of different tissue preparation techniques, including extracellular space (ECS) preservation and partial delipidation, on MRI-derived microstructure measures. Approach: dMRI on ECS-preserved and partially-cleared mouse brains was compared against conventionally fixed tissue imaging. DTI and standard model imaging with dot compartment metrics were evaluated. Results: ECS-preserved brain had higher mean diffusivity and extracellular signal fraction and reduced dot compartment fraction. The partially cleared mouse brain showed increased diffusivity without affecting T2 and T2* values. Impact: Incorporating advanced tissue preparation methods in ex vivo MRI studies will improve accuracy of histopathologic correlations and translational relevance to in vivo imaging interpretation.