Patient education: MRI scan (The Basics)

What is an MRI scan? — MRI stands for "magnetic resonance imaging." It is a test that creates pictures of the inside of the body. This is done with a special machine that uses a strong magnet (figure 1).

There are different types of MRI machines:

●Standard – This type looks like a narrow tube. You lie down on a table that slides into the scanner through the opening at 1 end.

●Wide-bore – This type is also shaped like a tube, but the opening is bigger and there is more space inside. This might be a better option for people who get very nervous in small spaces or who are larger.

●Open – This type has no sides. Open scanners usually do not create as clear pictures as the other types. But they might be used in some situations.

MRI can be used to look at different areas of the body, such as the:

●Brain and spinal cord

●Organs in the chest, belly, or pelvis

●Heart and blood vessels

●Bones and joints

●Breasts

The test can be used to check for problems in a specific part of the body. It can also be used to monitor a known condition or see if treatment is working.

Sometimes, a special dye called "contrast" is used during an MRI. The dye most often used for this is called "gadolinium." It is injected into one of your veins through a thin tube called an "IV." This helps make the pictures clearer.

How do I prepare for an MRI? — The doctor or nurse will tell you if you need to do anything special to prepare.

They will also ask you about your "health history." This involves asking you questions about any health problems you have or had in the past, past surgeries, and any medicines you take. Tell them about:

●Any medicines you are taking – This includes any prescription or "over-the-counter" medicines you use, plus any herbal supplements you take. It helps to write down and bring a list of any medicines you take, or bring a bag with all of your medicines with you.

●Any allergies you have

●Any metal in your body – This includes medical devices like pacemakers, artificial joints, ear implants, or IUDs (a type of birth control). It also includes any hardware like pins, screws, metal plates, or staples that might have been used in surgery, for example, to fix a broken bone. The MRI scanner uses a big magnet to create images. If you have metal in your body, your doctor will talk to you about whether it is safe to have an MRI.

●Any other devices or materials on your body – These include things like insulin pumps, medicine patches, piercings, and dentures. You will also be asked if you have any tattoos or permanent makeup. These can affect the pictures from an MRI scan.

●Whether you could be pregnant – An MRI scan can be done during pregnancy if needed. But your doctor might want to delay the test until after your baby is born. If they do need to do an MRI scan, they will probably not use gadolinium dye, as this might not be safe for a developing baby. If you are breastfeeding, tell your doctor.

●If you get nervous in small spaces – Some MRI machines are narrow. If small spaces make you feel nervous or anxious, tell your doctor. You might be able to request a "wide-bore" scanner with more space inside. If needed, your doctor can also prescribe medicine to help you stay calm during the procedure. If you might not be able to lie still for the entire test, your doctor will talk to you about other options, such as sedation.

Ask the doctor or nurse if you have questions or if there is anything that you do not understand.

What happens during an MRI? — When it is time for the procedure:

●You will change into a hospital gown and remove any metal objects from your body. These include jewelry, glasses, dentures, and hearing aids.

●You might get an "IV," which is a thin tube that goes into a vein.

●You will get ear plugs or headphones to wear. This is because the MRI machine is very loud, and the sound can damage your ears if you don't have ear protection. Wearing ear plugs or headphones will help make you more comfortable. You might also be able to listen to music if you want.

●If your doctor prescribed medicine to help you stay calm during the MRI, you will take this before the scan.

●The person doing the MRI (called a "technician") will use your IV to inject the special dye into your vein, if you are getting it.

●You will lie on the narrow table of the MRI machine. The table slides into the scanner. The technician will not be in the room with you, but they will be nearby and able to see you and talk to you.

●You will need to lie very still during the MRI scan, so the images are clear. You might also be asked to do other things, like hold your breath for a few seconds. The machine does not touch you, and the test does not hurt.

●An MRI scan usually takes between 20 and 60 minutes. This depends on how many pictures your doctor wants to see.

●When the procedure is over, the table will slide back out of the machine.

What happens after an MRI? — If you had an IV, it will be removed. In most cases, you can go home right away after your MRI scan.

If you got medicine to help you stay calm during the test, someone will need to take you home afterward.

What are the risks of an MRI? — Your doctor will talk to you about all of the possible risks, and answer your questions. Possible risks include:

●Minor or serious allergic reaction to the dye

●Kidney damage from the dye

●Radiation exposure – MRI exposes you to some radiation. In general, exposure to radiation very slightly raises a person's risk of developing cancer later in life. But the amount of radiation during an MRI is very small. The overall risk increases if you have to get many imaging tests over time.

What else should I know? — You might get your results the same day, or it might take a little longer for them to be read by an expert. Your doctor or nurse will let you know when to expect your results.

If your MRI scan shows any abnormal results, your doctor or nurse will talk to you about what to do next.

More on this topic

Patient education: Magnetic resonance angiography (The Basics)
Patient education: CT scan (The Basics)