Technical evaluation of magnetic resonance imaging and spectroscopy will be performed on normal volunteers. These studies will be conducted in the NIH MRI systems located in Suburban Hospital in Bethesda, Maryland. These studies may involve the intravenous administration of commercially available MR contrast media and exercise. The results will be used to evaluate the performance of various pulse sequences, gradient coils, and RF coils on human subjects and will provide essential ground work for specific patient protocols.