Magnetic Resonance Imaging (MRI)
What Is MRI?
Magnetic resonance imaging (MRI) is a type of safe, painless testing that doctors use to see the body's organs and structures. MRI uses a magnetic field and radio waves to create detailed pictures of the body's insides. Unlike CAT scans or X-rays, MRI doesn't use radiation.
An MRI scanner is a large doughnut-shaped magnet that often has a tunnel in the center. You lie on a table that slides into the tunnel. Some hospitals and radiology centers use what are called "open" MRI machines. They have larger openings and are helpful for people who are afraid of being in tight, closed-in spaces.
Why Do You Need It?
MRI helps in several ways:
- It gives clear images of body parts that can't be seen as well with an X-ray, CAT scan, or ultrasound. MRI is helpful for looking at a person's eyes, ears, heart, and circulation system. It also helps doctors see inside joints, cartilage, ligaments, and tendons.
- MRI lets doctors detect problems in the brain, spinal cord, skeleton, chest, lungs, abdomen, pelvis, wrists, hands, ankles, and feet.
- It helps doctors identify infections and conditions that cause swelling inside the body.
- It allows doctors to see when there isn't a problem inside the body — like a tumor, for example. Doctors call this "ruling out" a condition.
Preparing for Your MRI Exam
You don't usually need to do anything special (like fasting) before an MRI exam. Because metal can leave a bright or blank spot on the MRI film, you will need to take off anything you're wearing that has metal in it (like glasses, jewelry, or belts) before you lie on the MRI table.
A specially trained technician (or "tech") operates the MRI machine. He or she may ask if you have any metal clips from surgery or anything else that's metal inside your body. These things might cause a problem near the strong magnetic field.
You won't be able to take your music player or other devices into the MRI room. Electronics can interfere with the equipment.
Some people are given medicine so they fall asleep (called "sedation") during an MRI exam. Sedation is usually used for infants and little kids who can't stay still during MRI. Sometimes MRI techs sedate teens who have trouble relaxing inside the machine.
If you need sedation, your doctor will ask you not to eat or drink for several hours before the MRI. Before you get sedation, tell the MRI tech if you:
- have allergies
- have every had a bad reaction to medicines
- might be pregnant
An MRI exam usually takes between 20 and 90 minutes. How long you stay in the machine depends on the type of study your doctor has ordered and whether the tech needs to re-do any scans.
You'll lie on the scanning table. The technician will move you into position. When you're ready, the table slides into the tunnel and the tech takes the images. Each scan lasts a few minutes.
Some people get a contrast solution as part of an MRI exam. Contrast solution is a liquid that goes inside the body to highlight things like blood vessels. It helps doctors see specific problems that might not show up otherwise.
If you need contrast solution, the tech will probably use an IV to get it inside your body. He or she will ask if you're allergic to any medicines or food before giving you contrast solution.
If you feel cold lying on the MRI table, ask for a blanket before the test starts. You'll need to stay still during the actual MRI so that the images come out clearly. If an image is blurred, it may need to be done over.
The noises that an MRI machine makes can be loud! You can't bring your own player into the MRI room, but some places give you special headphones so you can listen to music.
The headphones also let you talk to the technician. If an MRI system doesn't have headphones, it may have an intercom so the technician can talk to you and tell you what to do during the test. Some machines have a call button that you can press if you need help.
When the exam is over, the technician will help you off the table. If you've been sedated, the tech will wheel the table to a recovery area and you'll stay there until you're ready to stand up.
After the test, you'll probably be able to go back to your normal routine right away. Most sedation wears off in 1-2 hours. Any contrast material should be gone from your body in about 24 hours.
MRIs are safe and easy. Because they use low-energy radio waves instead of radiation, doctors haven't found any health risks. People can get more than one MRI with no side effects.
Because MRI techs ask questions before giving people sedation or contrast solution, it's very rare to have an allergic reaction. If someone does have a reaction, the technician and other staff are trained to handle it.
If you have kidney problems, tell the radiologist and technician before they give you IV contrast solution. In very rare cases, people whose kidneys don't work well can have problems after getting contrast solution.
Getting Your Results
You won't get MRI results right away. A radiologist (a doctor trained to understand MRI scans) needs to look at the images. The radiologist will send a report to your doctor. Your doctor will then call or make an appointment to talk to you about the results and explain what they mean.