Perfusion and hemodynamics in brain imaging across the lifespan

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The brain has limited fuel reserves and must rely on a continuous supply of oxygen and nutrients through blood flow. Perfusion is the process by which nutrients are delivered via arteries to the capillary bed. Perfusion is an integral, dynamic part of brain physiology, during mental processing, during the resting state and during the natural aging process. In the fields of neuroscience and diagnostic imaging, there is tremendous value in developing tools that image in-vivo physiology. Magnetic resonance imaging (MRI) is versatile and non-invasive, therefore an excellent modality to develop new imaging techniques. Perfusion MRI techniques can be used to study the interplay between physiology, function and structure, including cerebral vasculature, grey and white matter. One of the most exciting MRI developments is arterial spin labeling (ASL) because, compared to positron emission tomography (PET) or gadolinium enhanced dynamic susceptibility contrast (DSC) MRI, it is entirely non-invasive. Water molecules in the blood of arteries are "labeled" magnetically and detected downstream at tissue regions of interest, such as in the gray matter. ASL can also be designed to image movement of "tagged" blood water in arteries or veins. As the physics of ASL develops, it can be applied to characterise the natural perfusion patterns across the lifespan of healthy adult humans and it is thus the focus for this grant proposal. Anticipated results are the following: 1) an improved understanding of how blood flow patterns change during aging and cause a decrease in perfusion in the brain's gray matter, 2) a demonstration of the value of ASL when compared to DSC, and 3) development of ASL techniques to improve assessment of white matter.