Magnetic resonance imaging (MRI) is a common procedure used to gain detailed images of organs and structures within the body in order to help physicians diagnose a health problem.
The MRI machine is a large, tube-shaped machine that creates a strong magnetic field around the patient. This magnetic field, along with a radiofrequency, alters the natural alignment of hydrogen atoms in the body. Computers then are used to form 2D images of brain, spine, heart, bones, joints and soft tissues such as cartilage, muscles and tendons.
Unlike x-rays or computed tomography (CT scans), MRI doesn’t use radiation. However, due to the use of the strong magnet, MRI can’t be used for people with:
- Implanted pacemakers.
- Some older intracranial aneurysm clips.
- Cochlear implants.
- Certain prosthetic devices.
- Implanted medicine infusion pumps.
- Neurostimulators.
- Bone-growth stimulators.
- Certain intrauterine contraceptive devices (IUDs).
- Any other type of iron-based metal implants.
- Internal metallic objects in certain areas, such as bullets or shrapnel, surgical clips, pins, plates, screws, metal sutures, or wire mesh.
While there generally is no special restriction to diet or activity prior to an MRI procedure, it’s extremely important that you inform the technologist if:
- You are claustrophobic and think that you will be unable to lie still inside the scanning machine, in which case you may be given a sedative.
- You have a pacemaker or have had heart valves replaced.
- You have any type of implanted pump, such as an insulin pump.
- You have metal plates, pins, metal implants, surgical staples, or aneurysm clips.
- You have any metallic fragments anywhere in the body.
- You have permanent eyeliner or tattoos.
- You are pregnant or think you may be pregnant.
- You have ever had a bullet wound.
- You have ever worked with metal (for example, a metal grinder or welder).
- You have any body piercings.
- You have an intrauterine device (IUD).
- You are wearing a medicine patch.
Some MRI procedures will require the use of a contrast dye. If this dye is used, there is a risk for allergic reaction. Patients who are allergic to or sensitive to medicines, contrast dye or iodine should tell their health care providers.
MRI contrast also may have an effect on other conditions such as allergies, asthma, anemia, low blood pressure, kidney disease and sickle cell disease.
Nephrogenic systemic fibrosis (NSF) is a very rare but serious complication of MRI contrast use in people with kidney disease or kidney failure. If a patient has a history of kidney disease, kidney failure, kidney transplant, liver disease, or are on dialysis, be sure to tell the MRI technologist or radiologist before getting the contrast.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your health care provider prior to the procedure.
Published on: July 11, 2016
