Magnetic resonance imaging, known as MRI, uses strong magnets to generate images of the body. This technology is currently the best way for radiologists to diagnose tumors of the brain.
MRI uses a very strong magnetic field; thus, any metal object will be pulled into the magnet. The technician who performs the MRI will ask if you have any metal implanted in your body, such as a heart pacemaker, implanted port/infusion catheter, prosthetic joints, metal plates, pins, or surgical staples.
You will also be asked if you have a bullet or shrapnel in your body or have ever worked with metal. If there is any question of metal fragments, you may be asked to have an x-ray to detect their possible presence. You will be asked to remove hairpins, jewelry, eyeglasses, hearing aids, and removable dental work.
The conventional MRI unit is a closed cylindrical magnet in which the patient needs to lie completely still for several minutes at a time. The patient is placed on a sliding table and a radio antenna device, called a surface coil, is positioned around the upper part of the head. The technician will leave the room, but is able to communicate with you by using an intercom system.
In general, the test can take 15-45 minutes, depending on how detailed the requested study must be. Some people may feel confined or claustrophobic. If this is a concern for you, please ask your primary care doctor to give you a sedative. Most bothersome to many people is the loud tapping or knocking noises heard at certain times during the test. The technician will offer you ear plugs to help.
Sometimes an injection of contrast material through an IV line (intra-venous; into a vein) is needed. MRI contrast material is less likely to produce an allergic reaction than the iodine-based material used during CT (computed tomography) scans, and the potential for kidney damage is not a concern. Some people may experience a cool sensation at the injection site.