“MRI” stands for magnetic resonance imaging. This diagnostic imaging test uses magnetic fields and radio waves to make three-dimensional pictures of the body without using x-rays.
MRI passes through bone and takes pictures of soft tissue, such as:
- Blood vessels
- The brain
The pictures — called scans — let doctors see very detailed images of the inside of your body.
“MRA” stands for magnetic resonance angiography. An MRA scan gives a view of specific blood vessels (arteries and veins).
You might have an MRA as part of your MRI exam.
Criteria Checklist: Who Can and Can’t Have MRI or MRA Scans
The checklist below helps to show if you can have MRI and MRA scans. Because these tests use highly powerful magnetic fields, it’s crucial that your doctor and testing team know about any metal in your body.
Many items on the checklist below are safe, but some mean that you cannot have an MRI or MRA.
Note all the items that apply:
- You have a history of working with metal.
- You have metal in your eye or have ever had metal removed from your eye.
- You have shrapnel, BBs, or bullets anywhere in your body.
- You have a pacemaker, cardioverter, or defibrillator.
- You have had heart valve replacement or cardiac stents.
- You have aneurysm clips or embolization coil.
- You have hearing devices of any kind.
- You have implants of any kind (for example, dental, breast, penile, or ear).
- You have had surgery in the past 2 months.
- You have fear of tight or enclosed spaces (claustrophobia).
- You think you may be pregnant.
- You have had problems with past MRI or MRA scans.
If any of these items apply to you, tell your testing center before the day of your exam.
Do not assume that your doctor’s office knows about your metal implants or any other items. You are responsible to alert your testing team to these items.
How Do I Prepare for the Test?
MRI exams don’t require any special preparations.
Unless your doctor says otherwise, on the day of your MRI you can:
- Eat and drink fluids.
- Go about your normal routine.
- Take your medicines.
For an MRA exam, your testing center will tell you about any special preparations.
If the test is scanning an area of your body above the shoulder, do not wear:
- Hair products such as mousse, gel, or hair spray
These items may affect the scan.
Tell the doctor or technologist if you have asthma or if you’ve ever had an allergic reaction to:
- A contrast-enhancing agent
If you are large or have a fear of enclosed spaces (claustrophobia), please tell your doctor in advance so he or she can arrange a wide-bore MRI scan.
What Happens Before the MRI or MRA Test?
Plan to arrive 30 minutes before your exam to register.
A staff member may ask you to change into a hospital gown and pants. If so, you must remove all jewelry and store personal belongings in a locker. It’s best to leave all valuables at home.
Some MRI and MRA exams use contrast-enhancing agents.
If you are to receive an enhancing agent, a technologist will insert an intravenous line (IV) in your arm or hand.
The enhancing agent may give you a brief sensation that moves up your arm.
You might get a:
- Warm, flushed feeling.
- Taste of salt or metal in your mouth.
- Feeling of nausea for a few minutes.
This is normal, but you should tell the technologist about these or other reactions.
What Happens During an MRI or MRA Scan?
Most MRI and MRA exams are inside a closed scanner. The magnet is like a tunnel — open at both ends — allowing light and air inside.
The technologist will help you onto a scanning bed. You will lie flat on the bed. The scanning bed will move into the center of the magnet.
Inside the scanner, you should:
- Lie quietly and stay as still as possible, so the pictures are clear.
- Breathe normally.
You’ll have earplugs to block out the machine’s loud knocking noise.
The technologist will be in a room behind a large window and will see and hear you at all times. You’ll be able to talk through an intercom.
The exam usually lasts 1 to 2 hours.
What Happens After the Test?
The technologist will help you off the bed. You may resume your normal diet.
If your MRI or MRA required an enhancing agent, drink plenty of fluids to flush the agent out of your body.
If you have diarrhea for more than a day, call your doctor.
How Do I Get My MRI or MRA Test Results?
A radiologist will study your scans and report the results to your doctor. Your doctor will discuss the results with you.
Ask your doctor or testing center about how to get your test results.
For more information on diagnostic imaging tests, check out our blog post explaining the difference between an X-ray, CT scan, and MRI scan.