Spectroscopic MRIs, which measure certain metabolites in the body, helping doctors to diagnose and treat conditions such as cancer or infections.Functional MRIs, which make it possible to measure split-second nerve cell activity in parts of the brain.While MRIs are relatively new technology, advances are continuing to be made. They don't contain iodine and aren't as likely to cause an allergic reaction.Īs with X-rays or CT scans, a radiologist who is trained to read the images will review the results of your MRI and make a report to your doctor or surgeon. The dye or contrast agent used in an MRI is different than those used in computerized tomography scanning. Sometimes a dye or contrast agent is injected into your veins to enhance how certain tissues or blood vessels look in the images. If being in an enclosed space makes you anxious, talk to your doctor before the MRI. It is important to lie still and breathe quietly as movement can blur the images. It typically takes 30 to 90 minutes to do an MRI. You may be given earplugs or music to listen in order to block the noise. You may hear tapping, thumping or other sounds from inside the machine. You won't feel anything as the MRI generates a strong magnetic field around you and directs radio waves at your body. A technician monitors you from another room and can talk to you through a microphone or intercom. When you are having an MRI, you lie on a table that slides into the opening of the magnet. The images can also be put on photographic film. This image can then be seen on a video monitor. A cross-sectional slice through your body at any point can be electronically generated from the picture. The image is a composite, three-dimensional picture of your body. The MRI machine senses the signals and sends them to a computer, which then generates an image. While you are inside the machine, radio waves are sent to your body, which responds by sending faint signals back. Other coils in the unit send and receive radio waves. The strong magnetic field is produced by sending an electric current through wire loops or coils inside the unit. Most MRI machines are large, cylindrical magnets. It may be necessary to use a different type of test or postpone an MRI if you are pregnant. The effects of magnetic fields on fetuses aren't well understood. If you are pregnant or think you may be, be sure to tell the technician before having an MRI. The strong magnetic field created by the MRI unit may interfere with how these devices work. The magnetic field may damage electronic items.ĭo not have an MRI scan if you have an implantable cardioverter defibrillator or pacemaker. Metal may interfere with the magnetic field used to create an MRI image and can cause a safety hazard. If you have metal or electronic devices in your body such as artificial joints or heart valves, a pacemaker or rods, plates or screws holding bones in place, be sure to tell the technician. Identify infections of the bones and jointsīefore an MRI, remove any clothing, wigs, and appliances such as hearing aids, dentures and jewelry that may contain metal or electronics.Identify bone and joint damage from injuries, degenerative disorders and tumors.Find eye or inner ear tissue abnormalities.Identify brain or spinal tumors or other chronic disorders of the nervous system.Diagnose disorders of the central nervous system, such as multiple sclerosis.Magnetic resonance imaging can be used to:
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