MRI and CT Scans - What's The Difference?

18 November 2016
 Categories: Health & Medical , Blog


If you are referred to hospital for a 'scan', you may wonder what type of scan this could be.  The two most commonly used scans are CT and MRI, both of which are used for diagnostics purposes.  So what's the difference between the two and what can you expect to happen when you attend for yours?

CT scans

A CT (Computed Tomography) scan is essentially a form of X-ray. The scanner looks like a long tube through which you are passed on a special bed while the X-rays are taken.  CT scan images show the variances of tissue density within an organ and are used to provide doctors with detailed information about many areas of the body including:

  • the brain and its vessels
  • the eyes
  • the inner ear and sinuses
  • the heart and lungs
  • the skeleton
  • the reproductive systems
  • the bladder
  • the gastrointestinal tract

The scan itself is painless, although you may feel slightly anxious if you don't like confined spaces.  The amount of radiation you'll be exposed to during a CT scan is not harmful.

MRI scans

Whereas CT scanning uses X-ray technology, MRI scanning employs the use of radio frequency pulses and magnetic fields in order to produce in-depth, detailed images of internal body structures, including bone, soft tissues and organs.  The images obtained through MRI scanning are generally thought to be clearer and more definitive that those produced by CT scans.

An MRI scanner looks like a large tube, and you lie on a bed that is pushed back into the scanner.  Throughout the scan, medical staff will observe you and be in communication with you via a speaker in the scanner.  Although the scan itself is painless, it can be claustrophobic and is very noisy compared with a CT scan.  It's extremely important that you keep completely still during your scan.  If you are concerned that you will have a panic attack or be unable to relax, mention this to your clinician and they will arrange for you to have a mild sedative prior to the procedure.

You will be given hearing protectors to wear during the scan.  Because of the magnets used in the scanner, you will be asked to remove any metal items, like jewellery, before you enter the machine.

CT and MRI scans are used routinely in hospitals as part of the diagnostics process.  If you require any further information and advice about how to prepare for your scan, have a chat with the staff in the radiology department at your local hospital or clinic.