MRI scans use radio waves and strong magnets instead of x-rays. A contrast material is often put into a vein before the scan to better show the details.
MRI scans take longer than CT scans — often up to an hour. And you have to lie inside a narrow tube, which can upset people who don’t like enclosed spaces. (Special, "open" MRI machines can sometimes be used instead.) The machine also makes buzzing and clicking noises that you may find disturbing. Some centers provide earplugs to block this noise out.