Magnetic resonance imaging (MRI) is a sophisticated and highly accurate imaging technique used to diagnose diseases of the brain, spine, skeleton, chest, abdomen, pelvis and blood vessels.
MRI is a completely safe, non-invasive and painless diagnostic procedure. With a large magnet, radio waves and a computer, MRI produces detailed cross-sectional pictures of your internal organs and structures without using ionizing radiation.
During your MRI exam, you will be placed in a strong magnetic field that aligns the nuclear magnetism of protons in your hydrogen atoms, which make up 95 percent of your body.
When a radio wave passes through those protons, they generate a radio signal that is processed by computer in the form of tomographic images. Your doctor will use those images to make an accurate diagnosis and plan your treatment.
How should I prepare?
- Metallic objects limit the accuracy of MRI, and the magnetic field can interfere with some surgically implanted devices.
If any of the following apply to you, tell your doctor:
- Cardiac pacemaker or artificial heart valve
- Metallic implant
- Insulin pump or other infusion pump
- Intrauterine device
- If you are a metal worker
- Inner ear implant
- Previous gunshot wound
- Joint or bone pins
- Permanent tattoos or eyeliner
- Aneurysm clips
- Eat and take any prescription medications as usual, unless your doctor tells you otherwise.
- If you'd like, ask a friend or relative to accompany you to the exam.
- If you are afraid of closed-in spaces, tell your doctor in advance. Your doctor can prescribe a sedative to help you relax. In that case, you will need someone to drive you home after the exam.
- If you feel you will be unable to remain still for 30 to 60 minutes due to pain, please inform your physician.
- Leave items such as watches, credit cards, pocketknives, jewelry, hearing aids or any other metallic items at home or give them to the technologist for safekeeping.
- Avoid wearing eye makeup (many eye shadows contain metallic flakes).
- Plan to arrive 30 minutes before your exam to provide medical and insurance information.
- Please bring previous imaging study results (x-ray, MRI, CT, ultrasound) such as reports, films or CD-roms if available.
What should I expect during the exam?
- An MRI exam generally takes between 30 minutes and an hour. The length of your exam will depend on the type of study your doctor has ordered.
- We want to ensure complete comfort during your exam. The technologist will help you lie on an automatic, cushioned scanning table. You'll be able to select music to listen to during the exam. You'll rest on your back with your head in a cushioned headrest.
- Once you are completely comfortable, the technologist will position a device, called a "coil," over or under the area being scanned. The coil helps produce the clearest picture of the area of interest.
- When you are properly positioned, the table will slide into the opening of the machine and the exam will begin. It's important that you remain as still as possible throughout the exam. You won't feel a thing, but you will hear a muted thumping or knocking sound for several minutes at a time. This is completely normal.
- If you become uncomfortable or have questions at any time, you'll be able to communicate with the technologist through a built-in intercom. When the exam is complete, the technologist will help you off the table and you'll collect your personal belongings.
Will I need an injection?
In some cases, your doctor may order a contrast agent to enhance the images. The agents, which are completely safe and FDA-approved, are injected into a vein in your arm.
What should I expect after the exam?
- A radiologist who specializes in a specific area of the body will review your images.
- The radiologist prepares a diagnostic report to share with your doctor.
- Your doctor will consider this information in context of your overall care, and talk with you about the results.
Go here for frequently asked questions about MRI.