What is an MRI?
Magnetic resonance imaging (MRI) is a test that uses powerful magnets, radio waves, and a computer to make detailed pictures inside your body.
Your doctor can use this test to diagnose you or to see how well you’ve responded to treatment. Unlike X-rays and CT scans, an MRI doesn’t use radiation.
Why is an MRI performed?
An MRI helps a doctor diagnose a disease or injury, and it can monitor how well you’re doing with a treatment. MRIs can be done on different parts of your body.
An MRI of the brain and spinal cord looks for:
- Blood vessel damage
- Brain injury
- Multiple sclerosis
- Spinal cord injuries
An MRI of the heart and blood vessels looks for:
- Blocked blood vessels
- Damage caused by a heart attack
- Heart disease
- Problems with the structure of the heart
An MRI of the bones and joints looks for:
- Bone infections
- Damage to joints
- Disc problems in the spine
MRI can also be done to check the health of these organs:
- Breasts (women)
- Ovaries (women)
- Prostate (men)
A special kind of MRI called a functional MRI (fMRI) maps brain activity.
This test looks at blood flow in your brain to see which areas become active when you do certain tasks. An fMRI can detect brain problems, such as the effects of a stroke, or for brain mapping if you need brain surgery for epilepsy or tumors. Your doctor can use this test to plan your treatment.
What should I know before receiving an MRI?
Before your MRI exam, you will likely be asked to fill out a screening questionnaire. The International Society for Magnetic Resonance in Medicine (ISMRM) has a sample patient screening form disclaimer icon available on its website. For your safety, answering the questionnaire accurately is extremely important. In particular, make sure you notify the MRI technologist or radiologist if you have any implanted medical devices, such as stents, knee or hip replacements, pacemakers, or drug pumps. Also be sure to tell the technologist if you have any tattoos or drug patches as these can cause skin irritation or burns during the exam. The medical team will need to make sure that these devices can safely enter the MR environment.
Some devices are MR Safe or MR Conditional, meaning that they can be safely used in the MR environment under specific conditions. If you have an implant card for your device, bring it with you to your MRI exam so that you can help the doctor or the MRI technologist identify what type of device you have.
The space where you will lay in an MRI scanner to have your images taken can be a tight fit for some people, especially larger individuals. If you believe that you will feel claustrophobic, tell the MRI technologist or your doctor.
The MRI scanner will make a lot of noise as it takes images. This is normal. You should be offered earplugs and/or headphones to make the noise sound less loud. You may also be able to listen to music through the headphones to make the MRI exam more enjoyable.
If your exam includes a contrast agent, the MRI technologist will place a small intravenous (IV) line in one of your arms. You may feel some coldness when the contrast agent is injected. Be sure to notify the technologist if you feel any pain or discomfort.
Remember, your doctor has referred you to have an MRI because he or she believes the scan will provide useful information. If you have any questions about your procedure, don’t be afraid to ask.
How to prepare for an MRI?
There is little to no preparation required for patients before an MRI scan. On arrival at the hospital, doctors may ask the patient to change into a gown. As magnets are used, it is critical that no metal objects are in the scanner, so the patient will be asked to remove any metal jewelry or accessories that may interfere with the machine.
Sometimes, patients will be injected with intravenous (IV) contrast liquid to improve the appearance of a certain body tissue.
The radiologist will then talk the individual through the MRI scanning process and answer any questions they may have about the procedure.
Once the patient has entered the scanning room, they will be helped onto the scanner to lie down. Staff will ensure that they are as comfortable as possible by providing blankets or cushions.
Earplugs or headphones will be provided to block out the loud noises of the scanner. The latter is very popular with children as they can listen to music to calm any anxiety.
What happens during an MRI?
Before some MRIs, you’ll get contrast dye into a vein in your arm or hand. This dye helps the doctor more clearly see structures inside your body. The dye often used in MRIs is called gadolinium. It can leave a metal taste in your mouth.
You will lie on a table that slides into the MRI machine. Straps might be used to hold you still during the test. Your body might be completely inside the machine. Or, part of your body may stay outside the machine.
The MRI machine creates a strong magnetic field inside your body. A computer takes the signals from the MRI and uses them to make a series of pictures. Each picture shows a thin slice of your body.
You might hear a loud thumping or tapping sound during the test. This is the machine creating energy to take pictures inside your body. You can ask for earplugs or headphones to muffle the sound.
You might feel a twitching sensation during the test. This happens as the MRI stimulates nerves in your body. It’s normal, and nothing to worry about.
The MRI scan should take between 20 and 90 minutes.
What happens after an MRI?
After the scan, a radiologist will examine the images to check whether any further images are required. If the radiologist is satisfied, the patient can go home. The radiologist will prepare a short report for the doctor, who will make an appointment to discuss the results.
If you have any questions about the MRI, please consult with your doctor to better understand your instructions.
Explanation of results
What do my results mean?
A specially trained doctor called a radiologist will read the results of your MRI and send the report to your doctor.
Your doctor will explain the meaning of your test results and what to do next.
Depending on the laboratory and hospital, the normal range for an MRI may vary. Please discuss with your doctor any questions you may have about your test results.
Hello Health Group does not provide medical advice, diagnosis or treatment.
What Is an MRI?. https://www.webmd.com/a-to-z-guides/what-is-an-mri#3-6. Accessed May 2, 2018.
What Patients Should Know Before Having an MRI Exam. https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MRI/ucm482768.htm. Accessed May 2, 2018.
What you should know about MRI scans. https://www.medicalnewstoday.com/articles/146309.php. Accessed May 2, 2018.
Review Date: May 6, 2018 | Last Modified: September 12, 2019