Magnetic Resonance Imaging (MRI) is a scan that uses a strong magnet, radio waves and a computer to create detailed images of your body. It is a safe and painless way for doctors to get a closer look at bones, organs and tissues inside your body. It is used to help diagnose diseases and many other medical conditions.
An MRI is somewhat like an X-ray (which is used for pictures of your bones) or a CT scan (also called a CAT scan or computed tomography scan, and is used for pictures of bones, muscles and organs) because it can provide images of internal body structures. It is more like a CT scan than an X-ray. Many people get the two scans confused because the equipment used for each is very similar. Plus, both an MRI and CT scan produce images of your bones, organs, and other internal tissues. Here is how they are different:
- An MRI uses a magnetic field to generate an image. This means you aren’t exposed to radiation. No studies have linked MRIs to any harmful health effects. A CT scan uses radiation to make an image. Repeated exposure can be harmful.
- An MRI scan takes longer to perform (30 to 60 minutes, on average). A CT scan is quick (around 5 to 10 minutes).
- An MRI provides a clearer picture of abnormal tissues. It is a better scan for looking at ligaments and tendons, your spinal cord and other soft tissues. A CT scan can give you a higher-quality picture of bones and is better for diagnosing chest and lung problems, as well as detecting some cancers.
- An MRI is more expensive than a CT scan. On average, an MRI can cost from $1,200 to $4,000. A CT scan typically costs less than an MRI. The average cost for a CT scan is $1,200 to $3,200.
There are many reasons your doctor may order an MRI. Generally, an MRI can help your doctor identify what is causing your health issue so that he or she can diagnose you accurately and prescribe a treatment plan.
Depending on your symptoms, an MRI will scan a specific portion of your body to diagnose:
- heart damage
- lung damage
- problems with your eyes or ears
- sports injuries
- problems with your spine, including disc (rubbery cushions between your backbones) problems or spinal tumors
- problems with your veins or arteries
- brain abnormalities, such as tumors, and dementia
- abdominal/digestive tract problems
- bone diseases and conditions
- pelvic problems (in women) or prostate problems (in men)
Path to improved health
If your primary care doctor determines that you should have an MRI, their office staff will most likely call to schedule an appointment for you. Many insurance companies require office staff to call on your behalf to get the scan approved. You will go to a hospital or radiology center for the scan.
Your doctor may ask you not to eat or drink anything a few hours before the MRI, depending on what part of your body you are having scanned. You should mention this when you call to make the appointment.
Your doctor also may request that you have an MRI with contrast. This means that a contrast agent (think of it as a dye) will be injected into your body just before the scan. The injection of contrast is most often done through an IV (intravenously, through a vein) that is placed in the back of your hand or the inside of your elbow. The contrast will improve the quality of the images and provide more detail in some instances.
You cannot wear jewelry or have metal of any kind on your body (such as on your clothes) during the MRI. In fact, you may be asked to walk through a metal detector before having an MRI. Additionally, if you have metal inside your body, you may not be able to have an MRI. Discuss this with your doctor before scheduling an MRI if you are pregnant or breastfeeding, or if you have:
- cochlear implants
- a pacemaker
- metal plates, screws, or rods
- artificial heart valves
- an intrauterine device (IUD)
- a drug pump implant
- artificial joints
- dental fillings, bridges or other metal dental work
- worked in the metal working industry (and could have metal dust in your eyes)
MRIs are painless. The only “challenge,” for adults and especially for children, will be lying completely still for the scan. Any movement could result in blurred images, just as they would with a typical camera. The amount of time for the scan will vary, depending on what you are having scanned. Normally, scans last between 15 minutes to an hour.
The MRI machine itself looks like a big donut with a table attached to it. You’ll be asked to lie on the table and a lab assistant or technician will help you into a comfortable position and explain what you can expect during the scan. When you’re ready, the table will slide into the doughnut-shaped opening of the machine. Your whole body does not go in the machine, only the half or part that needs to be scanned.
One thing you’ll need to know is that the machine is noisy. It makes a lot of different noises, and some of them are extremely loud. Some patients say it sounds like a sledgehammer. For this reason, you will be offered headphones. You can listen to music or sometimes even watch a movie. You’ll also be able to hear the radiology technician give you instructions or check on you through the headphones.
If you feel uneasy about the scan, you can request that the technician give you a “panic button” to hold during the process. Pressing the button will signal the technician that you would like to stop the scan and come out of the machine.
You can also invite a friend or loved one to be with you in the room during the scan, which is very helpful for children’s scans but also makes some adults more comfortable, as well. This person also will not be allowed to wear jewelry or metal and will have to go through the same screening process as the person being scanned.
A radiologist (a doctor who specializes in medical imaging) will review the images and send a report to your referring doctor. Your doctor will receive a full report a day or two following the test and can go over the results with you.
Things to consider
Even though having an MRI is safe and painless, it can be a difficult test for persons who are claustrophobic. The MRI machine is never completely closed, but just being even partially in an enclosed area is enough to fill some people with dread. In these cases, it may be possible to use an “open” MRI machine for the scan.
Open MRI machines are, as the name suggests, more open and less confining than the traditional machines. They have larger openings and do not completely surround your body. This makes them a better alternative not only for claustrophobic patients, but also for obese patients or normal-sized males who have larger shoulders.
Small children who are incapable are being still for the duration of the scan may require sedation prior to having an MRI. In this case, an anesthesiologist would provide the sedation and stay (in addition to a nurse) to monitor the patient before, during, and after the scan. Sedation is also sometimes used for patients who are extremely claustrophobic.
If your MRI requires contrast, your radiologist will monitor you for allergies during the procedure. Severe reactions to the contrast agent are rare, but could happen. In those cases, the radiology department is well-trained on how to handle your allergic reaction.
Questions for your doctor
- Why are you ordering an MRI?
- How long will my MRI take?
- Should I fast before my MRI appointment?
- Will the MRI technician need to use contrast material?
- I have metal dental work. Can I have an MRI?
- Can I have an MRI if I am pregnant/breastfeeding?
- When will you have my results?
- Will you notify me of my test results even if they are normal?
- I am claustrophobic. Can I have an open MRI?
- Will my child need to be sedated before having an MRI?
- Does having an MRI increase my chances for getting cancer?
Copyright © American Academy of Family Physicians
This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.