CT scans and MRIs are both used to capture images within your body.

The biggest difference is that MRIs (magnetic resonance imaging) use radio waves and CT (computed tomography) scans use X-rays.

While both are relatively low risk, there are differences that may make each one a better option depending on the circumstances.

Using radio waves and magnets, MRIs are used to view objects inside your body.

They’re frequently used to diagnose issues with your:

A constant magnetic field and radio frequencies bounce off of the fat and water molecules in your body. Radio waves are transmitted to a receiver in the machine which is translated into an image of the body that can be used to diagnose issues.

An MRI is a loud machine. Typically, you’ll be offered earplugs or headphones to make the noise more bearable.

You’ll also be asked to lay still while the MRI is taking place.

A CT scan is a form of X-raying that involves a large X-ray machine. CT scans are sometimes called CAT scans.

A CT scan is typically used for:

  • bone fractures
  • tumors
  • cancer monitoring
  • finding internal bleeding

During a CT scan, you’ll be asked to lay down on a table. The table then moves through the CT scan to take cross-sectional pictures inside your body.

CT scans are more widely used than MRIs and are typically less expensive.

MRIs, however, are thought to be superior in regards to the detail of the image. The most notable difference is that CT scans use X-rays while MRIs do not.

Other differences between MRI and CT scans include their risks and benefits:

Risks

Both CT scans and MRIs pose some risks when used. The risks are based on the type of imaging as well as how the imaging is performed.

CT scan risks include:

  • harm to unborn babies
  • a very small dose of radiation
  • a potential reaction to the use of dyes

MRI risks include:

  • possible reactions to metals due to magnets
  • loud noises from the machine causing hearing issues
  • increase in body temperature during long MRIs
  • claustrophobia

You should consult a doctor prior to an MRI if you have implants including:

Benefits

Both MRIs and CT scans can view internal body structures. However, a CT scan is faster and can provide pictures of tissues, organs, and skeletal structure.

An MRI is highly adept at capturing images that help doctors determine if there are abnormal tissues within the body. MRIs are more detailed in their images.

Most likely, your doctor will give you a recommendation based on your symptoms whether you should get an MRI or CT scan.

If you need a more detailed image of your soft tissue, ligaments, or organs, your doctor will commonly suggest an MRI.

Such cases include:

If you need a general image of an area like your internal organs, or due to a fracture or head trauma, a CT scan will commonly be recommended.

While there are more risks associated with MRI scans, both CT scans and MRI scans are relatively low risk. Both offer important information to help your doctor properly diagnose specific conditions.

Most likely, your doctor will tell you which one they recommend. Be sure to ask questions and discuss any concerns with your doctor, so you can be comfortable with the choice they recommend.