Abstract
As the global population continues to age, understanding how cerebral blood flow changes with healthy aging is important to determine physiology from pathology. However, the study of cerebral blood flow (CBF) regulation in humans is complex as the encapsulation of the brain in the skull makes the brain's vasculature difficult to image. Furthermore, studies of cerebrovascular anatomy suggest that over 50% of humans do not have standard anatomical configurations. Thus, inferences regarding CBF regulation in an individual with the standard anatomical configuration may not translate to others. This dissertation will describe 1) the effect of aging on cerebrovascular function 2) the age-related changes in CBF in adults with a cerebral anatomical variation (vertebral artery hypoplasia) and 3) the prevalence of vertebral artery hypoplasia in a larger cohort of cognitively unimpaired adults with enriched risk for Alzheimer's disease. Using in vivo standard (transcranial Doppler ultrasound) and novel (4D flow phase contrast MRI) imaging techniques, the results from these studies suggest that there are age-related differences in cerebrovascular function. In addition, an anatomical variation in the posterior circulation (vertebral artery hypoplasia) impacts the age-related differences in regional cerebral blood flow. Furthermore, vertebral artery hypoplasia is associated with lower global cerebral blood flow even after adjusting for vascular risk factors. Taken together, these findings suggest that cerebral anatomical variations may affect the age-related changes in cerebral blood flow regulation and could be considered a risk factor for cerebral hypoperfusion.