Never Had a CT or MRI? Here's What to Expect

CTs use X-rays to create 3-D images; MRIs produce two-dimensional images with electromagnetic waves.

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Even after you're admitted, you might get a CT or MRI scan, so here's what you need to know.

A CT (computed tomography) scanner takes multiple X-rays of your body and assembles the "slices," as thin as 1/50th of an inch, into a 3-D image. You will get an IV injection of a contrast dye first, to highlight the tissue of interest. Then you'll lie flat on a table and positioned inside a ring like a large doughnut.

A magnetic resonance imaging (MRI) scanner produces two-dimensional images from electromagnetic waves. You will be secured to a platform and pushed inside a body-length tube, perhaps after an injection of contrast dye. If offered headphones, with or without music, use them to muffle the jackhammerlike racket. It could take an hour or longer; you'll have to keep still and hold your breath on cue.

You can get a sedative if you're apprehensive, and a panic button will signal the staff to pull you out. At Sentara Heart Hospital in Norfolk, Va., the room is spritzed with a vanilla-scented spray that calms some patients, and glasses with angled lenses are provided for a view to the outside world. The electromagnetic waves are harmless but can affect metal objects in the body—patients with a pacemaker or other metallic implants should tell the radiologist.

This story was originally reported on 7/15/07.