Featured are methods for non-invasive assessment of vascular reactivity. The methods of the invention use phase contrast magnetic resonance imaging angiography and use the image data thereby acquired to measure shear rate, radius of the vasculature and flow through the vasculature. According to one aspect, such acquisition of image data occurs before and during, an arterial occlusion and according to another aspect such acquisition of image data occurs before during and after arterial occlusion. The disclosed methods of the invention allow for reproducible, non-invasive diagnosis of early stage indicators of atherosclerosis.