Approved research

Assessing the effect of free water on brain microstructure in aging using diffusion MRI

Lay summary

Modern society is currently dealing with an aging population, and an associated decline in brain function is posing a threat towards clinical care in a way that is not yet fully understood. The aim of this research project is to develop a better understanding of how the brain changes through healthy adult aging and to characterize these changes right when they begin, on a microstructural level, before progression into larger-scale changes. Diffusion MRI can characterize brain microstructure by measuring the microscopic diffusion of water molecules through brain tissue. However, the brain is known to shrink with age, allowing for more extracellular free water molecules to diffuse in the brains of older adults. Free water is not reflective of authentic tissue microstructure, so increases in free water at older ages can lead to biases in assessing age-effects with diffusion MRI. This research project will apply 'free water elimination' to diffusion MRI data, allowing for aging microstructure to be assessed strictly within brain tissue itself. Over 36 months of analysis, we will work to identify brain regions where microscopic diffusivity parameters become altered in healthy aging. This analysis will be conducted in both the white matter and gray matter. The gray matter is situated directly next to cerebrospinal fluid and fast-flowing blood, which are forms of free water that make the gray matter particularly susceptible to bias, and thus aging gray matter microstructure has scarcely been studied altogether with diffusion MRI. We will eliminate this free water to allow for the first ever large-scale in-vivo study of gray matter microstructural changes through healthy aging. This will furthermore allow for better distinction of pathological aging, and ultimately allow for health care systems to cater closer to the needs of its aging population.