Computed Tomography and Magnetic Resonance Imaging

Your doctor will decide which imaging study to perform based on several factors.

• Possible concerns with CT: Allergic reaction to the intravenous (IV) contrast agent, kidney disease or failure, pregnancy.
• These tests use modern computerized image processing techniques that give your doctor a 3D view — an important step in determining the extent of vascular disease and how best to treat it.

• Each test requires an examination while you lie on a motorized bed that is wheeled into a special structure called a gantry with scanner detectors positioned in a circle around it.
• Each test may require an IV contrasting agent that lets your doctor better view certain blood vessels.

There are more differences between CT and MRI than there are similarities.

• All CT exams require the use of an IV contrast agent, but not all MRIs do.
• CT exams take just a few minutes to complete; MRIs may last 20-30 minutes.
• CT exams involve exposure to radiation; MRIs do not.
• Possible concerns with MRI: Presence of a pacemaker or AICD device, stimulators (e.g., for the spine), infusion pumps, certain implants.
• Possible concerns if gadolinium IV contrast agent is ordered as part of the MRI: Allergic reaction to the IV contrast agent, kidney disease or failure, pregnancy.

While CT tests are safe, if repeated exams are planned, you will be exposed to more radiation. However, radiation from a typical CT is about the same amount the average person normally receives each year from the environment. This is called “background radiation.”

• An MRI is considered preferable for repeated examinations.