Fractal analysis of ischemic stroke: From microscale to macroscale from simulation to laboratory experiments

Ischemic stroke, a cerebral vascular accident, is induced by occlusion of blood vessels in the brain. Decreased cerebral blood flow (CBF) or even complete loss of blood supply results in cellular damage or cell death. Quantitative evaluation of the relationship between blood vessel occlusion (i.e., CBF reduction) and neuronal damage is important to investigate the mechanism and therapeutic efficacy in cerebral ischemic studies.If the brain is considered as an information processing system , there must exist a global parameter(s) to describe or regulate this accident on brain vessels. Fractal dimension, one of parameters in fractal analysis, describes the complexity of a system or a process and may be adopted to describe the CBF properties, evaluate the neuronal damage, and connect these signals. This dissertation presents a novel method to correlate the CBF reduction with neuronal damage by using fractal analysis.Firstly, a virtual cerebral vasculature system has been established. A programmable fractal-growing based system has been generated to simulate the cerebral blood supply network. A virtual valve to imitate the blood vessel occlusion could be placed and adjusted in the system to indicate the location and degree of occlusion. Fractal analysis has been performed on the virtual system and experimental CBF data acquired by autoradiographic and laser Doppler imager techniques to measure the blood flow distribution.A correspondence between microscale and macroscale immunohistopathology has been established to quantitatively evaluate the cellular activities in microscale brain sections (image acquired within one microscopic view) under low microscopic magnification, extract the information of cellular activities from macroscale image (image of a whole brain section), and quantify this information into the intensity value of an image. Distribution of immuno-positives on macroscale brain sections has been characterized by fractal analysis.Finally, the relationship between CBF reduction and the consequent neuronal damage will be evaluated. Correlative study of the fractal dimensions discloses the correspondence between CBF decrease and neuronal immuno-positive expression. An analytical description for the experimental ischemic stroke based on fractal parameters has been achieved