This study will examine ways to establish and standardize normal measurements for children, specific to gender, age, and body surface, when using magnetic resonance imaging (MRI). MRI, which was introduced in the 1980s, is being used more frequently for children. In this study, researchers seek to understand how a child's heart is different from that of an adult, when an MRI is used for tests. More children with congenital heart disease are living longer. Researchers are looking for a better way to assess their cardiac anatomy and function, and to compare findings with normal function.

Patients ages 8 to 21 in good health and who do not smoke may be eligible for this study. There will be a blood or urine test to check for pregnancy in female volunteers who have begun menstruating or who are over age 12. Pregnancy test results must be negative for those patients to stay in the study. The MRI technique uses a strong magnetic field and radio waves to obtain images of body organs and tissues. For that procedure, patients will lie still on a table that slides into the enclosed tunnel of the scanner. They will be in the scanner from 20 to 60 minutes. As the scanner takes pictures, patients will hear knocking or beeping sounds, and they will wear earplugs to reduce the noise. Patients will be able to communicate with the MRI staff at all times during the scan. At any time, patients or their parents may ask that the patients be moved out of the machine. If they would like, patients can bring a music CD or listen to a radio station through headphones. Some MRI techniques require monitoring while the patient is undergoing the scan. For monitoring of the heart, an electrocardiogram (EKG) will be performed to make sure that the heart rhythm is normal and that heart disease is not present. Patients may be asked to wear adhesive patches that are attached to wires of the EKG machine on their chests. To monitor breathing, patients may be asked to wear a rubber belt that stretches as they take a breath. So that the best quality images are produced, patients may be asked to hold their breath for about 15 seconds.

During the MRI scan, patients may experience peripheral nerve stimulation, usually experienced as a muscle twitch. It is caused by rapid switching of magnetic fields and is not serious. Patients who feel a muscle twitch should report that sensation to the person performing the scan. It is possible, though unlikely, for a painful sensation to result from nerve stimulation. Patients should immediately report if they have pain so that the scan can be stopped.