Topological tree-analysis of the microvascular system in macaque visual cortex

For a profound understanding of functional brain imaging in research and in clinical applications, investigations of neurovascular coupling are mandatory. Three-dimensional tree-analysis of cortical vasculature elucidates the structural aspects of neurovascular coupling such as the organization of the cortical vasculature and network topology. Here we report a technique to obtain high resolution tomographic images of the cerebral vasculature, accurate reconstructions of the whole vasculature and extraction of vessel attributes to reliably quantitate large vascular networks. Non-human primate (Macaca mulatta) brains were collected and processed. Samples were punched from the primary visual cortex and scanned at the material science beamline of the Swiss Light Source to yield X-ray tomographic images for 3D reconstruction of the vasculature. Key vessel parameters have been evaluated for different levels of analysis (from single samples to grouped data). The diameter and length distributions of the cortical vessels indicated a high percentage of capillaries. Layer 4cβ had the highest density of capillary and noncapillary vessels in comparison to the other cortical layers. Mean volume fraction was 2.5 for cortical gray matter. Extravascular distance measure yielded an average mesh size of 56 μm. Branching pattern analyses have been performed for single vessels extracted from whole networks for investigation of network geometry. In conclusion, these results indicate the reliability of the technique in studying cortical vasculature. The results were in good agreement with histological data as well as with data from the literature. Quantitative three-dimensional morphometry of vascular networks is critical for future blood flow modeling in the cerebral cortex