MRI stands for magnetic resonance imaging. MRI involves the use of a magnetic field. Brief alterations in this magnetic field cause your body to send out radio waves which are then captured by the scanner and converted to images (photos). The bed you must lie on in the MRI scanner moves forward in very small steps, and a photo is taken at each step. Each photo shows an image of the organs and other parts of the body at that spot. These images are called slices. All the slices together provide a good image of the inside of your body; thus, the structure, form, size, and location of everything in your body becomes visible. An MRI scan makes a great deal of noise. It makes a loud, ticking sound; therefore, wearing a pair of headphones can make the experience more pleasant. This test takes a long time, between 15 and 45 minutes, depending on the area being examined. During the scan, you must lie very still. This can be quite difficult if the scan takes a while. If you are very young or have difficulty lying still, the MRI can also be performed under anesthesia.