Recording of Presentation
Speaker: Josefina Maranzano, MD. PhD.
Assistant Professor, Department of Anatomy, Université du Québec à Trois-Rivières
Adjunct Professor, Neurology and Neurosurgery, McGill University
Talk Abstract: MRI-histology correlation studies of the ex vivo brain mostly employ fresh, extracted (ex situ) specimens, aldehyde fixed by immersion. This method entails manipulation of the fresh brain during extraction, introducing several disadvantages: deformation of the specimen prior to MRI acquisition; introduction of air bubbles in the sulci, creating artifacts; and uneven or poor fixation of the deeper regions of the brain.
We propose a new paradigm to scan the ex vivo brain, exploiting a technique used by anatomists: fixation by whole body perfusion, which implies fixation of the brain in situ. This allows scanning the brain surrounded by fluids, meninges, and skull, thus preserving the structural relationships of the brain in vivo and avoiding the disadvantages of ex situ scanning. Hence, our study aimed to assess: 1) whether months of in situ fixation results in a loss of fluid around the brain, 2) whether in situ fixation modifies antigenicity for myelin and neuron specific markers, and 3) whether in situ fixation improves the registration of ex vivo brain images to standard neuroanatomical templates in pseudo-Talairach space.
Our initial results show that most specimens retain fluids in the subarachnoid and ventricular spaces; that all T1-weighted images were successfully processed through a validated pipeline used with in vivo MRIs without any modification to run on the ex vivo-in situ scans, successfully registering to a standard brain template, more accurately than an ex vivo-ex situ scan. Further, all specimens exhibited positive antigenicity for myelin and neuron specific antigens.
We conclude that MRI and histology study of the ex vivo-in situ brain fixed by perfusion is feasible and allows for in situ MRI imaging for at least 10 months post-mortem prior to histology analyses.