X-rays are a type of radiation, and when they pass through the body, dense objects such as bone block the radiation and appear white on the x-ray film, while less dense tissues appear gray and are difficult to see. X-rays are typically used to diagnose and assess bone degeneration or disease, fractures and dislocations, infections, or tumors.
Organs and tissues within the body contain magnetic properties. MRI, or magnetic resonance imaging, combines a powerful magnet with radio waves (instead of x-rays) and a computer to manipulate these magnetic elements and create highly detailed images of structures in the body. Images are viewed as cross sections or "slices" of the body part being scanned. There is no radiation involved as with x-rays. MRI scans are frequently used to diagnose bone and joint problems.
A computed tomography (CT) scan (also known as CAT scan) is similar to an MRI in the detail and quality of image it produces, yet the CT scan is actually a sophisticated, powerful x-ray that takes 360-degree pictures of internal organs, the spine, and vertebrae. By combining x-rays and a computer, a CT scan, like an MRI, produces cross-sectional views of the body part being scanned. In many cases, a contrast dye is injected into the blood to make the structures more visible. CT scans show the bones of the spine much better than MRI, so they are more useful in diagnosing conditions affecting the vertebrae and other bones of the spine.