Patients under deep sedation and general anesthesia lose heat to their surrounding environment. Hypothermia after anesthesia is associated with worse patient outcomes, including increased number of infections and cardiovascular complications. Cardiac MRI scans performed for patients who require general anesthesia can cause a loss of body heat.

Several mechanisms exist for reducing hypothermia under anesthesia including forced air warmers, fluid warmers, radiant warmers, and chemical warmers. Unfortunately, there are no MRI-compatible systems which allow patient warming and prevention of hypothermia in anesthetized patient in the MRI-scanner.

This study is testing a non-invasive device that warms patients under clinically indicated general anesthesia in the MRI scanner. This device will keep in the heat made by the MRI scanner.

A. Each group will receive the usual clinical care for having an MRI under general anesthesia:

1. General anesthesia. The type of anesthesia used will be determined by the individual anesthesiologist, and will be the safest technique possible to allow for the desired MRI images to be obtained.
2. All participants will be covered with 1-2 warm blankets before receiving anesthesia and while in the scanner as part of standard warming measures.
3. All participants will have continuous temperature monitoring during the scan.

B. Participants will be randomized to one of the three

1. 20 subjects will receive the standard of care which is 1-2 warm blankets. This group is called the control group.
2. 20 study subjects will have the MRI-safe bore covering applied. This includes a clear covering sheet positioned over the openings of the MRI scanner.
3. 20 study subjects will have the MRI-safe bore covering applied, and in addition one opening of the covering sheet will be connected to a "Bair hugger" ( an approved device which blows warm air). The second opening will act as a vent to let air out of the MRI scanner bore. The Bair hugger will be programmed to deliver forced air at 38 degrees Celsius (approximately 100 degrees Fahrenheit) into the contained space within the MRI scanner.

Body temperature will be monitored continuously and documented in the electronic anesthesia record. The temperature of the forced air will be adjusted to maintain a goal body temperature of 36-38 degrees Celsius (96.8- 100.4 degrees Fahrenheit).

Image quality will be evaluated by the MRI-technologist and MRI -cardiologist subjectively.

Inclusion Criteria:

1. Children < 7 years of age.
2. Undergoing medically necessary cardiovascular MRI under general anesthesia

Exclusion Criteria:

1.Patients with fever (temperature >38.5 degrees Celsius) or condition which require active cooling at the time of MRI