Your frequent questions answered by the experts at Nationwide Children's Hospital.

Q: My son needs to get an MRI later this year and he's scared because the machine looks pretty daunting. How can I explain to him what the machine does and the fact that it's safe?

A: Magnetic Resonance Imagining (MRI) is a method of examining the inside of the body. The MRI scanner has a large donut-shaped magnet with a tunnel inside. The patient lies on a table that slides into the tunnel, and the magnet surrounds the body.

The MRI machine uses magnetic fields and radio frequencies instead of X-rays to produce images. The test is safe and completely painless, though while it is taking pictures, it may make loud tapping or knocking noises. Let your son know that he'll need to remain very still during the procedure.

MRI is used to detect problems in the brain, spinal cord, skeleton, chest, lungs, abdomen, pelvis, wrists, hands, ankles and feet. In some cases, it can provide a clearer image of body parts than an X-ray, CAT scan or ultrasound because MRI can highlight contrasts in soft tissue. MRI can also identify infections, inflammation and tumors.

Your doctor may ask that your child be given contrast solution during the test to help the images show up better on the film. An intravenous infusion (IV) will be started and the contrast solution will be put in the IV. After the contrast is given, the IV will be removed and the scan will continue.

Be sure to consult your son's primary care physician with any other specific MRI questions, or about your son's health in general.

-Dr. William E. Shiels II is Chief of the Department of Radiology at Nationwide Children's Hospital and a Clinical Professor of Radiology and Pediatrics and Category M on the graduate faculty in Biomedical Engineering at The Ohio State University College of Medicine.