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What is the Difference Between MRI and CT?

What is an MRI?

MRI stands for magnetic resonance imaging. An MRI is a special imaging modality that allows a doctor to see the soft tissue of any extremity or body part that needs to be examined. MRI machines are large, tubular magnets that you lie inside. While you are lying in the machine, the magnetic field temporarily moves the hydrogen atoms in your body. Radio waves are then used to make these atoms produce minute signals which can create an image of the interior of the body.

Even 3-D images can be produced by an MRI machine.


What are MRI images used for?

Such images may include those of tendons, ligaments, bones, organs and blood vessels. It really is a great way of looking at soft tissue injuries, diseases and disorders, without having to open up the body to see what is going on inside. With these images, doctors can evaluate and diagnose a wide range of conditions including cancers, tumors, heart and vascular diseases, muscular and bone injuries and many more.  


What is a CT scan?

A computerized tomography scan, or CT scan, is a special type of X-ray which uses a computerized program to look at axial images of a person’s body part. The computer processing program combines a series of X-ray images that were taken at different angles to produce a cross-sectional image.


What are CT scans used for?

CT images are used to examine internal structures and view their shape, size, density and texture. They can even show organs functioning, blood vessels filling and metabolic activity. Since the scan shows such detail, doctors can use it to identify and diagnose a medical problem.

They can be used to diagnose an infection, locate an exact area of the body that needs to be reached, study blood vessels and identify tumors, cysts or other masses.  


  • CT images typically look at the head, abdomen, spine, pelvis and chest.
  • MRI images usually are used on soft tissues, tendons, ligaments and joints.
  • CT scans use X-rays and ionizing radiation, while MRI images use X-rays and magnets.
  • A CT scan can take just five minutes, and an MRI might take 30 minutes to complete.
  • CT scans carry greater risks than MRIs due to the radiation exposure. 
  • MRI machines are more closed in as compared to CT machines. Therefore, claustrophobics prefer a CT scan over an MRI.
  • Since MRIs use a magnetic force, you cannot get one if you have a metal implant. 
  • If you are heavier than 450 pounds, you might not be able to fit in a CT scanner. If you weigh more than 350 pounds, you may be too large for an MRI machine. 
  • Getting a CT scan is not as expensive as getting an MRI is.
  • CT machines were invented in 1971, while MRI machines were invented 10 years later, in 1981.