Intensity distribution segmentation in ultrafast Doppler and scanning laser confocal microscopy for evaluate vascular changes associated with aging and neurodegeneration

Abstract

Ultrafast Doppler (μDoppler) and scanning laser confocal microscopy (SLCM) are powerful imaging modalities that can measure in vivo cerebral blood volume (CBV) and vascular structure, respectively. In the brain, the hippocampus plays an important role in learning and memory, requiring high-neuronal oxygenation. Understanding the relationship between blood flow and vascular structure - and how it changes with aging or neurodegeneration - is physiologically and anatomically relevant. We apply both imaging modalities to a cross-sectional and longitudinal study of hippocampi vasculature in wild-type (Wt) and Trembler-J (TrJ) mice brains, a biological model of Charcot-Marie-Tooth (CMT) neurological syndrome. For aging study, we introduce a segmentation of CBV distribution obtained from μDoppler and show that this mice-independent and mesoscopic measurement is correlated with vessel volume fraction (VVF) distribution obtained from SLCM-e.g., high CBV relates to specific vessel locations with large VVF, in wild-type mice. Moreover, we find significant changes in CBV distribution and vasculature due to aging (5 vs. 21 month-old mice), highlighting the sensitivity of our approach. Overall, we are able to associate CBV with vascular structure - and track its longitudinal changes - at the artery-vein, venules, arteriole, and capillary levels. Under neurodegeneration conditions (Trembler-J mice), the same strategy was applied. Recently, the same strategy was used to understand the vascular component in Trembler-J. μDoppler analysis indicated that the TrJ hippocampus showed hyperperfusion to the Wt mice hippocampus. These preliminary but consistent data open up a different and new perspective to explore vascular components in CMT diseases. We believe that this approach can be a powerful tool for studying other acute (e.g., brain injuries), progressive (e.g., neurodegeneration) or induced pathological changes.