When Do I Need an MRI?

Medically Reviewed by Sabrina Felson, MD on February 07, 2021

An MRI (magnetic resonance imaging) lets your doctor see the organs, bones, and tissues inside your body without having to do surgery. This test can help diagnose a disease or injury.

You might need an MRI if an X-ray or CT scan didn't give enough information about your condition. An MRI can also show your doctor whether treatment has helped you.

What Conditions Can an MRI Diagnose?

The purpose of the MRI depends on what part of your body is being imaged.

An MRI of the brain and spinal cord helps your doctor diagnose:

A special kind of MRI called a functional MRI (fMRI) checks brain activity by measuring blood flow to certain areas of your brain. An fMRI can show the active areas of your brain while you do a task. Your doctor can use this test to see damage from Alzheimer's disease or a brain injury, or if they need to map brain functions before you get surgery for epilepsy or brain tumors.

A heart and blood vessel MRI helps diagnose:

  • Blockages or swelling in blood vessels
  • Damage from a heart attack
  • Heart valve problems
  • Pericarditis (inflammation of the tissue that surrounds the heart)
  • Problems with the aorta (main artery in the body)
  • Problems with the structure of the heart's walls and chambers
  • Tumors inside the heart’s chambers

An MRI of the bones and joints looks for:

  • Arthritis
  • Bone infections
  • Tumors involving the bones or joints
  • Damage to joints, such as torn cartilage, ligaments, or tendons
  • Herniated discs or spinal cord compression
  • Fractures that can't be seen on X-rays

An MRI of the breast is done to:

  • Screen for breast cancer in women who have a high risk for developing the disease
  • See how large the tumor is and how far it has spread in women who've been diagnosed with breast cancer
  • Find out whether the cancer has come back after it has been treated with surgery or chemotherapy
  • See whether implants have ruptured

You can also have an MRI to check for disease and other problems in these organs:

Before Your MRI

Before you have an MRI, find out why your doctor has chosen this test. Ask these questions:

  • Why do I need an MRI?
  • Is an MRI the best way to check on my condition?
  • How will the results affect my treatment?
  • What are the risks?
  • Do the benefits of this test outweigh the risks to me?

Make sure you understand the reasons for the test. Find out how it will help direct your treatment.

WebMD Medical Reference



American Academy of Orthopaedic Surgeons: "X-rays, CT Scans and MRIs."

Harvard Medical School: "What you need to ask before getting an imaging test."

Mayo Clinic: "MRI: Why it's done."

National Heart, Lung, and Blood Institute: "Cardiac MRI." "Chest MRI."

Radiological Society of North America: "Magnetic Resonance Imaging (MRI) -- Body," "Magnetic Resonance Imaging (MRI) -- Breast," "Magnetic Resonance Imaging (MRI) -- Chest," "Magnetic Resonance Imaging (MRI) -- Knee."

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