Technical evaluation of magnetic resonance imaging and spectroscopy will be performed on subjects who are eligible and willing to volunteer to have a research MRI performed. These studies may involve the intravenous administration of commercially available MR contrast media. Some scans may require inhaled carbogen (95% oxygen and 5% carbon dioxide) and hyperoxia (100% oxygen) as a contrast media. 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.