We will evaluate new developments in fast magnetic resonance imaging (MRI) of the heart and blood vessels on healthy volunteers. These studies will be conducted in the NIH MRI systems located at the NIH Clinical Center in Bethesda, Maryland. These procedures may involve the intravenous administration of commercially available MR contrast media, supine exercise or the inflation of blood pressure cuffs on the lower extremities during the MRI imaging. The results will be used to evaluate the performance of various research pulse sequences, gradient coils, and radiofrequency receiver coils on human subjects and will provide essential ground work for specific patient protocols, both diagnostic and therapeutic.