What happens when someone has a CAT or MRI scan? Do you feel anything? A CAT scan is a fancy computer x-ray picture, only clearer and more precise. Nothing about a CT scan itself hurts. You lay down on a table which moves you into a large tunnel-like machine. It makes a whirling noise for a couple of minutes and it's over. Magnetic resonance imaging (MRI), like a CT scan, requires you to lay down on a table. Again, a table slides you into a big tunnel-like machine. This scan uses magnets to show the brain in a 3- dimensional view with fine detail. Usually the medical team will provide you with headphones to listen to music during the scan - the music helps soften the thumping noise the scanner makes. You might even fall asleep! The difference between the two scans is like comparing plain Nintendo (the CT scan) to Nintendo 64 (the MRI). A full MRI study of the brain can take anywhere from ‡ to 1 hour; CT scans are less. Answered by Dr. Stewart Goldman, pediatric oncologist, Children's Memorial Hospital, Chicago July, 2007