MRI (Magnetic Resonance Imaging): What It Is, Types & Results (2024)

What is an MRI?

An MRI (magnetic resonance imaging) scan is a painless test that produces very clear images of the organs and structures inside your body. MRI uses a large magnet, radio waves and a computer to produce these detailed images. It doesn’t use X-rays (radiation).

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Because MRI doesn’t use X-rays or other radiation, it’s the imaging test of choice when people will need frequent imaging for diagnosis or treatment monitoring, especially of their brain.

What is an open MRI?

An open (or “open bore”) MRI refers to the type of machine that takes the images. Typically, an open MRI machine has two flat magnets positioned over and under you with a large space between them for you to lie. This allows for open space on two sides and alleviates much of the claustrophobia many people experience with closed-bore MRI machines.

However, open MRIs don’t take as clear images as closed-bore MRI machines. Closed-bore MRI machines have a ring of magnets that forms an open hole or tube in the middle where you’d lie to get the images. Closed-bore MRIs are narrow with tight head-to-ceiling space. This can cause anxiety and discomfort for some people, but these MRI machines take the best quality images.

If you’re nervous about your MRI scan or have a fear of closed spaces, talk to your healthcare provider. If needed, your provider will discuss options for sedatives (medicines to make you feel relaxed) or even anesthesia if necessary.

What is an MRI with contrast?

Some MRI exams use an injection of contrast material. The contrast agent contains gadolinium, which is a rare earth metal. When this substance is present in your body, it alters the magnetic properties of nearby water molecules, which enhances the quality of the images. This improves the sensitivity and specificity of the diagnostic images.

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Contrast material enhances the visibility of the following:

  • Tumors.
  • Inflammation.
  • Infection.
  • Blood supply to certain organs.
  • Blood vessels.

If your MRI requires a contrast material, a healthcare provider will insert an intravenous catheter (IV line) into a vein in your hand or arm. They’ll use this IV to inject the contrast material.

Contrast materials are safe drugs. Side effects ranging from mild to severe do occur, but severe reactions are very rare.

What’s the difference between an MRI scan and a CT scan?

Magnetic resonance imaging (MRI) uses magnets, radio waves and a computer to create images of the inside of your body, whereas computed tomography (CT) uses X-rays and computers.

Healthcare providers often prefer to use MRI scans instead of CT scans to look at the non-bony parts or soft tissues inside your body. MRI scans are also safer since they don’t use the damaging ionizing radiation of X-rays.

MRI scans also take much clearer pictures of your brain, spinal cord, nerves, muscles, ligaments and tendons than regular X-rays and CT scans.

However, not everyone can undergo an MRI. The magnetic field of MRI can displace metal implants or affect the function of devices such as pacemakers and insulin pumps. If this is the case, a CT scan is the next best option.

MRI scanning is usually more expensive than X-ray imaging or CT scanning.

What does an MRI show?

Magnetic resonance imaging (MRI) produces detailed images of the inside of your body. Healthcare providers can “look at” and evaluate several different structures inside your body using MRI, including:

  • Your brain and surrounding nerve tissue.
  • Organs in your chest and abdomen, including your heart, liver, biliary tract, kidneys, spleen, bowel, pancreas and adrenal glands.
  • Breast tissue.
  • Your spine and spinal cord.
  • Pelvic organs, including your bladder and reproductive organs (uterus and ovaries in people assigned female at birth and the prostate gland in people assigned male at birth).
  • Blood vessels.
  • Lymph nodes.

When would I need an MRI?

Healthcare providers use magnetic resonance imaging (MRI) to help diagnose or monitor the treatment for many different conditions. There are also different types of MRIs based on which area of your body your provider wants to examine.

Brain and spinal cord MRIs can help evaluate and diagnose the following conditions:

  • Brain aneurysms.
  • Brain tumors and spinal tumors.
  • Brain and spine injuries from trauma.
  • Compression or inflammation of spinal cord and nerves (pinched nerve).
  • Multiple sclerosis (MS).
  • Spinal cord conditions.
  • Spine anatomy and alignment.
  • Stroke.

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Providers use cardiac (heart) MRIs for several reasons, including:

  • To evaluate the anatomy and function of your heart chambers, heart valves, size of and blood flow through major vessels and the surrounding structures.
  • To diagnose cardiovascular conditions, such as tumors, infections and inflammatory conditions.
  • To evaluate the effects of coronary artery disease, such as limited blood flow to your heart muscle and scarring within your heart muscle after a heart attack.
  • To evaluate the anatomy and function of the heart and blood vessels in children and adults with congenital heart disease.

Body MRIs can evaluate structures and diagnose several conditions, including:

  • Tumors in your chest, abdomen or pelvis.
  • Liver diseases, such as cirrhosis, and issues with your bile ducts and pancreas.
  • Inflammatory bowel disease, such as Crohn's disease and ulcerative colitis.
  • Malformations of blood vessels and inflammation of the vessels (vasculitis).
  • A developing fetus in your uterus.

MRIs of bones and joints can help evaluate:

  • Bone infections (osteomyelitis).
  • Bone tumors.
  • Disk abnormalities in your spine.
  • Joint issues caused by injuries.

Healthcare providers sometimes use breast MRIs with mammography to detect breast cancer, especially in people who have dense breast tissue or who might be at high risk of breast cancer.

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Is an MRI safe?

An MRI scan is generally safe and poses almost no risk to the average person when appropriate safety guidelines are followed.

The strong magnetic field the MRI machines emit is not harmful to you, but it may cause implanted medical devices to malfunction or distort the images.

There’s a very slight risk of an allergic reaction if your MRI requires the use of contrast material. These reactions are usually mild and controllable by medication. If you have an allergic reaction, a healthcare provider will be available for immediate assistance.

Healthcare providers generally don’t perform gadolinium contrast-enhanced MRIs on pregnant people due to unknown risks to the developing baby unless it’s absolutely necessary.

Who shouldn’t get an MRI?

In most cases, an MRI exam is safe for people with metal implants, except for a few types. Unless the device you have is certified as MRI safe, you might not be able to have an MRI. These devices may include:

  • Metallic joint prostheses.
  • Some cochlear implants.
  • Some types of clips used for brain aneurysms.
  • Some types of metal coils placed within blood vessels.
  • Some older cardiac defibrillators and pacemakers.
  • Vagal nerve stimulators.

If your healthcare provider recommends an MRI scan, they’ll ask detailed questions about your medical history and any medical devices or implants you may have in or on your body.

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MRI (Magnetic Resonance Imaging): What It Is, Types & Results (2024)
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