What is an MRI?
Magnetic resonance imaging (MRI) is a test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body. In many cases MRI gives different information about structures in the body than can be seen with an X-ray, ultrasound, or computed tomography (CT) scan. MRI also may show problems that cannot be seen with other imaging methods.
Magnetic resonance imaging (MRI) is done for many reasons. It is used to find problems such as tumors, bleeding, injury, blood vessel diseases, or infection. MRI also may be done to provide more information about a problem seen on an X-ray, ultrasound scan, or CT scan. Contrast material may be used during MRI to show abnormal tissue more clearly. An ENT specialist may send a patient for an MRI to investigate the:
- Head. MRI can find problems of the the ears and auditory nerves as well as eyes and optic nerves. It can look at the brain for tumors, an aneurysm, bleeding in the brain, nerve injury, and other problems, such as damage caused by a stroke. It can also help to assess tumors and lesions of the salivary glands and other soft tissues of the face.
- neck and Chest. MRI of the chest may also be used to look for esophageal, throat, tracheal and lung cancers as well as other soft tissue abnormalities.
- Blood vessels. Using MRI to look at blood vessels and the flow of blood through them is called magnetic resonance angiography (MRA). It can find problems of the arteries and veins, such as an aneurysm, a blocked blood vessel, or the torn lining of a blood vessel (dissection). Sometimes contrast material is used to see the blood vessels more clearly.
- TMJ. MRI can check for problems of the bones and joints, such problems with the temporomandibular joint, bone marrow problems,bony tumors of the jaw, cartilage problems or infection. MRI may also be used to tell if a bone is broken when X-ray results are not clear.
- Spine. MRI can check the discs and nerves of the spine for conditions such as spinal narrowing (stenosis), disc bulges, and spinal tumors that can cause neck pain.
Before your MRI test, tell your doctor and the MRI technologist if you:
- Are allergic to any medicines. The contrast material used for MRI does not contain iodine. If you know that you are allergic to the contrast material used for the MRI, tell your doctor before having another test.
- Are or might be pregnant.
- Have any metal implanted in your body. This helps your doctor know if the test is safe for you. Tell your doctor if you have:
- Heart and blood vessel devices such as a coronary artery stent, a pacemaker, an ICD (implantable cardioverter-defibrillator), or a metal heart valve.
- Metal pins, clips, or metal parts in your body, including artificial limbs and dental work or braces.
- Any other implanted medical device, such as a medicine infusion pump or a cochlear implant.
- Cosmetic metal implants, such as in your ears, or tattooed eyeliner.
- Had recent surgery on a blood vessel. In some cases, you may not be able to have the MRI test.
- Have an intrauterine device (IUD) in place. An IUD may prevent you from having the MRI test done.
- Become very nervous in confined spaces. You need to lie very still inside the MRI magnet, so you may need medicine to help you relax. Or you may be able to have the test done with open MRI equipment. It is not as confining as standard MRI machines.
- Have any other health conditions, such as kidney problems or sickle cell anemia, that may prevent you from having an MRI using contrast material.
- Wear any medicine patches. The MRI may cause a burn at the patch site.
You may need to arrange for someone to drive you home after the test, if you are given a medicine (sedative) to help you relax.
You will need to take off all or most of your clothes, depending on which area is examined (you may be allowed to keep on your underwear if it is not in the way). You will be given a gown to use during the test. If you are allowed to keep some of your clothes on, you should empty your pockets of any coins and cards (such as credit cards or ATM cards) with scanner strips on them because the MRI magnet may erase the information on the cards.
During the test you usually lie on your back on a table that is part of the MRI scanner. Your head, chest, and arms may be held with straps to help you remain still. The table will slide into the space that contains the magnet. A device called a coil may be placed over or wrapped around the area to be scanned. A special belt strap may be used to sense your breathing or heartbeat. This triggers the machine to take the scan at the right time.
Some people feel nervous (claustrophobic) inside the MRI magnet. If this keeps you from lying still, you can be given a medicine (sedative) to help you relax. Some MRI machines (called open MRI) are now made so that the magnet does not enclose your entire body. Open MRI machines may be helpful if you are claustrophobic, but they are not available everywhere. The pictures from an open MRI may not have as high of a resolution as those from a standard MRI machine.
Inside the scanner you will hear a fan and feel air moving. You may also hear tapping or snapping noises as the MRI scans are taken. You may be given earplugs or headphones with music to reduce the noise. It is very important to hold completely still while the scan is being done. You may be asked to hold your breath for short periods of time.
During the test, you may be alone in the scanner room. But the technologist will watch you through a window. You will be able to talk with the technologist through a two-way intercom.
If contrast material is needed, the technologist will put it in an intravenous (IV) linein your arm. The material may be given over 1 to 2 minutes. Then more MRI scans are done.
An MRI test usually takes half an hour to an hour but can take as long as 2 hours.