Magnetic Resonance Imaging (MRI)
What is an MRI?
Magnetic resonance imaging (MRI) is a diagnostic imaging test that uses a powerful magnet, radio waves and a computer to create detailed images of the inside of the body. An MRI scan is noninvasive, painless and does not use radiation.
MRI imaging is especially useful for evaluating:
- Abdomen and pelvis
- Brain and spinal cord
- Heart and blood vessels
- Joints, muscles and soft tissue
Because an MRI machine provides high-resolution images, it helps providers diagnose injuries, tumors, neurological disorders and organ abnormalities without surgery.
What is an MRI with Contrast?
Not all patients require contrast for an MRI. When needed, contrast helps certain organs, blood vessels or tissues stand out, providing clearer images for evaluating disease or injury.
Contrast is administered in one of two ways:
- Intravenously (IV): A small needle delivers the contrast agent into a vein in the arm or hand.
- Orally: The patient swallows the contrast solution before the scan.
MRI vs. CT Scan: What’s the Difference?
Both MRI and computed tomography (CT) scans are advanced diagnostic imaging tools. The primary difference is:
- CT scans use X-rays (ionizing radiation)
- MRI uses magnets and radio waves
An MRI scan is better at detecting subtle differences in soft tissue, making it ideal for evaluating the brain, ligaments, cartilage and organs. A CT scan may be recommended if bone and soft tissue are being evaluated or you can’t undergo MRI due to metal implants or certain pacemakers.
Unlike CT scans, MRI does not expose you to radiation.
Is an MRI Safe?
MRI is considered very safe for most patients. Because it doesn’t use ionizing radiation, it’s often preferred for repeated imaging.
However, patients with certain implanted medical devices — such as pacemakers, aneurysm clips or cochlear implants — must be evaluated before scheduling an MRI. Always inform your provider and technologist about any implants or metal in your body.
How Does an MRI Work?
Understanding how an MRI works can help reduce anxiety and make the process easier.
Most MRI scans are performed in large, tube-shaped machines that use powerful magnets and radio waves to create detailed images. During the MRI procedure, you lie on a table that slides into the tunnel of the machine. Only the area being examined needs to be centered in the magnet. For example, your head for a brain MRI or your knees for a knee MRI.
During the scan, you may hear tapping, clicking or knocking noises from the machine as it produces images. You’ll receive headphones to reduce noise and hear instructions from the MRI technologist. Holding still is essential for a clear scan, especially the body part being imaged. If you need to stretch or adjust, you can do so between image sequences.
The technologist monitors you throughout the MRI procedure and communicates via intercom. You can speak to them at any time, though it’s best to wait until between scans to avoid motion that could affect image quality.
What Does an MRI Show or Diagnose?
An MRI scan produces detailed images that help diagnose a wide range of medical conditions.
Because MRI imaging provides exceptional detail of soft tissue, it’s considered the gold standard for diagnosing many neurological conditions.
MRI imaging can detect abnormalities in the:
- Kidneys
- Liver and bile ducts
- Pancreas
- Prostate
- Spleen
- Uterus and ovaries
MRI is commonly used for:
- Bone infections
- Soft tissue or bone tumors
- Spine disc problems
- Torn ligaments or cartilage
MRI is the most frequently used imaging test of the brain and spinal cord. A brain MRI provides highly detailed images that allow healthcare providers to identify areas where changes have occurred or where the brain may not be functioning properly.
A brain MRI is often used to evaluate symptoms such as:
- Changes in vision
- Hearing loss
- Persistent headaches
- Seizures
- Weakness or numbness
Conditions commonly diagnosed with a brain MRI include:
- Brain tumors
- Inflammation or infection
- Multiple sclerosis (MS)
- Stroke
- Structural abnormalities
Functional MRI (fMRI)
A functional MRI (fMRI) measures brain activity. During an fMRI, you may be asked to perform simple tasks, such as move your arms or perform a simple math problem. This test helps evaluate brain injuries, Alzheimer’s disease and areas responsible for speech or movement.
An MRI of the breasts is often used with mammography to detect breast cancer, particularly in women with dense breast tissue or increased risk.
A cardiac MRI can evaluate:
- Aortic aneurysms or dissections
- Blood vessel inflammation or blockages
- Damage from heart attack or heart disease
- Heart chamber size and function
- Thickness and movement of the heart’s walls
How to Prepare for an MRI
Preparing for an MRI exam is usually simple. In most cases, you can eat and drink normally and continue taking your regular medications unless your provider gives you different instructions.
MRI and Metal
Before your MRI scan, you’ll typically change into a gown and remove any items that could interfere with the magnetic imaging. Any materials that could be affected by the magnetic field should be left at home or given to the staff for safekeeping. This includes items such as:
- Bobby pins
- Coins
- Cosmetics that contain metal particles
- Credit cards
- Dentures
- Eyeglasses
- Hairpins
- Hearing aids
- Jewelry
- Keys
- Pocketknives
- Underwire bras
- Watches
- Wigs
Because MRI uses a powerful magnet, it’s critical to inform your physician and MRI technologist about any metallic devices or implants in your body. These may include:
- Aneurysm clips
- Cochlear implants or stimulating devices
- Dental braces
- Embedded shrapnel or metal fragments
- Pacemakers and/or pacer wires
If you have an implant, bring your manufacturer’s information card to your MRI appointment if available. This helps confirm whether the device is MRI-safe.
Proper MRI preparation ensures your scan is safe, accurate and completed without delays.
FAQs
Most MRI scans last 30 to 60 minutes. The time depends on the body part being examined, complexity of the condition and whether contrast dye is used.
In most cases, yes. However, fasting may be required before an MRI with contrast to reduce nausea and ensure clear images. Always follow the instructions from your provider or the imaging center.
Contrast can upset the stomach. Fasting before an MRI with contrast reduces the risk of nausea, vomiting and potential aspiration while lying flat.
No. MRI does not use ionizing radiation like X-rays or CT scans.
MRI is not associated with cancer risk because it does not use ionizing radiation.
Yes. An MRI is considered safe during any trimester of pregnancy when medically necessary. Tell your health care provider if you are, or might be, pregnant.
Yes. Most modern braces are made of non-magnetic materials such as stainless steel or titanium, which are generally safe during an MRI scan.
Always inform your orthodontist and your healthcare provider before your MRI appointment, so the imaging team can determine whether any special precautions are needed.
The cost of an MRI depends on the body part being scanned, whether contrast is used and your insurance coverage. Contact your insurance provider or imaging center for specific pricing information.
Find an MRI Location Near You
If you’re searching for an MRI location near you, UnityPoint Health offers advanced MRI imaging services at convenient locations.
Most MRI exams require a provider referral. Talk with your healthcare provider to schedule your MRI appointment and determine which type of imaging is right for you.