Magnetic resonance imaging (MRI) is a noninvasive medical test that helps physicians diagnose and treat medical conditions.MR imaging uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. The images can then be examined on a computer monitor, printed or copied to CD. MRI does not use ionizing radiation (x-rays).
MR imaging of the body is performed to evaluate:
organs of the chest, abdomen and pelvis including the heart, liver, biliary tract, kidney, spleen, pancreas and adrenal glands.
pelvic organs including the reproductive organs in the male (prostate and testicles) and the female (uterus, cervix and ovaries).
pelvic and hip bones.
blood vessels (MR Angiography).
Physicians use the MR examination to help diagnose or monitor treatment for conditions such as:
tumors of the chest, abdomen or pelvis.
coronary artery disease and heart problems including the aorta, coronary arteries and blood vessels, by examining the size and thickness of the chambers of the heart and the extent of damage caused by a heart attack or progressive heart disease.
tumors and other abnormalities of the reproductive organs (e.g., uterus, ovaries, testicles, prostate).
causes of pelvic pain in women, such as endometriosis.
functional and anatomical abnormalities of the heart. •diseases of the liver, such as cirrhosis, and that of other abdominal organs (when a complete diagnostic assessment can not be done with other techniques).
congenital arterial and venous vascular anomalies and diseases (e.g., atherosclerosis) of the chest, abdomen and pelvis (MR Angiography).
conditions involving the bile duct, gallbladder and pancreatic ducts (MRCP).
What to do to prepare for your MRI:
Some MRI examinations may require the patient to swallow contrast material or receive an injection of contrast into the bloodstream. The radiologist or technologist may ask if you have allergies of any kind, such as allergy to iodine or x-ray contrast material, drugs, food, the environment, or asthma. However, the contrast material used for an MRI exam, called gadolinium, does not contain iodine and is less likely to cause an allergic reaction.
The radiologist should also know if you have any serious health problems and what surgeries you have undergone. Some conditions, such as severe kidney disease may prevent you from having an MRI with contrast material.
Women should always inform their physician or technologist if there is any possibility that they are pregnant. MRI has been used for scanning patients since the 1980's with no reports of any ill effects on pregnant women or their babies. However, because the baby will be in a strong magnetic field, pregnant women should not have this exam unless the potential benefit from the MRI is assumed to outweigh the potential risks.
If you have claustrophobia (fear of enclosed spaces) or anxiety, you may want to ask your physician for a prescription for a mild sedative.
Jewelry and other accessories should be left at home if possible, or removed prior to the MRI scan. Because they can interfere with the magnetic field of the MRI unit, metal and electronic objects are not allowed in the exam room. These items include:
- jewelry, watches, credit cards and hearing aids, all of which can be damaged.
- pins, hairpins, metal zippers and similar metallic items, which can distort MRI images.
- removable dental work.
- pens, pocketknives and eyeglasses.
- body piercings.
In most cases, an MRI exam is safe for patients with metal implants, except for a few types. People with the following implants cannot be scanned and should not enter the MRI scanning area unless explicitly instructed to do so by a radiologist or technologist who is aware of the presence of any of the following:
- internal (implanted) defibrillator or pacemaker
- cochlear (ear) implant
- some types of clips used on brain aneurysms
You should tell the technologist if you have medical or electronic devices in your body, because they may interfere with the exam or potentially pose a risk. Examples include but are not limited to:
- artificial heart valves
- implanted drug infusion ports
- implanted electronic device, including a cardiac pacemaker
- artificial limbs or metallic joint prostheses
- implanted nerve stimulators
- metal pins, screws, plates or surgical staples
In general, metal objects used in orthopedic surgery pose no risk during MRI. However, a recently placed artificial joint may require the use of another imaging procedure. If there is any question of their presence, an x-ray may be taken to detect the presence of any metal objects.
Patients who might have metal objects in certain parts of their bodies may also require an x-ray prior to an MRI. Dyes used in tattoos may contain iron and could heat up during MRI, but this is rarely a problem. Tooth fillings and braces usually are not affected by the magnetic field but they may distort images of the facial area or brain, so the radiologist should be aware of them.