The purpose of this study is to assess the applicability of a new SSFP-based BOLD sensitive MRI sequence in evaluating endothelial function. Endothelial function will be tested in a setting of reactive hyperemia in the forearm. In a setting of ischemia-reperfusion, the effect of transient endothelial function impairment will be tested. Comparison with endothelial function assessment by brachial ultrasound (FMD) and finger tip plethysmography (PAT) will be incorporated.