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

MRIs (magnetic resonance imaging) and CT or CAT scans (computed tomography) are used to get images of your body and provide more detail than simple X-rays. If you need specialized imaging, it can be helpful to understand the differences between a CT scan vs. an MRI.

In some ways, these two tests are similar. They both show a cross-section  picture of the body, but they accomplish it with different techniques:

• CT scans use many X-rays, taken at different angles, to produce the cross-sectional images
• MRI scans use magnetic fields and radio frequencies

Because of this, each test shows the same parts of the body in different ways and are chosen by doctors depending on the possible diagnosis.

Table of Contents

• Side-by-side comparison
• Costs
• Common uses
• Risks

Side-by-side comparison

MRI vs CT scan costs

• The biggest difference is due to the cost of the machine and also the duration of the exam. MRI takes at least 30 minutes, while a CT scan can be done in as little as 5-15 minutes
• If you choose the cash route, you can get MRI for as little as $250 while you can get a CT scan for about $220 (find a price near you)

Common uses for CT vs MRI scan

1. Abdominal pain – CT is the preferred test. It is more readily available on an emergency basis and is very accurate. Ultrasounds are used for children and pregnant women.
2. Trauma – CT is present in most emergency departments and imaging centers and it is the best at showing bone fractures, blood collection and organ injury.
3. Spine – MRI scans are the best diagnostic imaging techniques for the spinal cord and nerves.
4. Brain – CT is used when speed is important, as in trauma and stroke. MRI is best when the images need to be very detailed, looking for cancer, causes of dementia, epilepsy or neurological diseases, or looking at places where bone might interfere.
5. Chest – CT is much better at examining lung tissue and often used to follow up on abnormal chest x-rays. Low dose CT Scans are available and used with high-risk smokers who need to be screened annually.
6. Joints – MRI is best at showing tendons and ligaments.

MRI scan vs CT scan risks

Both CT scans and MRIs pose some risks when used, so you should ask your doctor for a referral to ensure the imaging procedure is necessary. 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 small dose of radiation (equivalent to ~200 X-rays)
• a potential allergic reaction to the use of dyes

MRI risks include:

• possible reactions to metals due to magnets in the machine
• loud noises from the machine causing hearing issues
• increase in body temperature during scans
• claustrophobia (for closed MRIs)
• You should consult a doctor before an MRI if you have implants including:
  • artificial joints
  • eye implants
  • an IUD
  • a pacemaker

Tips for getting the best price for an MRI scan or a CT scan

• Shop around for the best price (see the facilities in your area)
• Don't hesitate to ask for discounts
• Ask about all the fees. Do they include the cost of scan and the radiologist reading?
• Take your doctor's referral with you to another facility - your referral might be issued to one of the most expensive hospitals in the country
• Check the recommendation of best machine type required for your scan - if you need a simple scan you probably don't need to get it in a state of the art machine