This study will test new techniques to image the heart, blood vessels, and legs using magnetic resonance imaging (MRI). The techniques will be used to plan and guide treatments using minimally invasive methods.

Healthy normal volunteers 18 years of age and older may be eligible for this study.

For MRI, the subject lies flat on a table that can slide in and out of the scanner, a metal cyclinder. Special antennas, covered in pads, are placed against the subject's body. The scan time can vary from 20 minutes to 2 hours, with most scans lasting between 45 and 90 minutes. The subject may be asked to wear adhesive patches on the chest for monitoring the heart and a belt or finger pad for monitoring breathing. During the test, a contrast agent called gadolinium may be injected. This substance brightens the heart and arteries during the scan, providing a better picture of blood flow.

During the procedure, subjects may be asked to exercise their legs on a machine to evaluate the effects of motion and exercise on the MRI exam.

Large blood pressures cuffs may be placed on either or both thighs or calves to try to measure arterial flow to the legs. The cuffs are inflated to a pressure as high as at least 50 mmHg higher than thesubject's systolic blood pressure (up to 250 mmHg) for up to 10 minutes.

Subjects may be asked to return for repeated scans.