Scanning techniques

• CT - Computerised tomography 


  • Person lies still inside a large doughnut-shaped scanner
  • When all images are put together, it builds a detailed image of the brain
  • Creates images of slices of the brain
• Evaluation of CT (1)

  • Strength
  • Useful for revealing abnormal structures such as tumours or structural damage
  • High quality
• Evaluation of CT (2)

  • Weakness
  • Requires radiation - cannot be used often
  • Only provides a still image - does not show live activity
• PET - Positron emission tomography 


  • Measures activity in the brain after injected with a radioactive tracer (glucose)
  • Substance helps the scan see active areas of the brain
  • Shows live activity
• Evaluation of PET (1)

  • Strength
  • Shows live activity which is useful for research
  • Can show localisation of function
  • E.g, we can ask patient's to recall events and we can see what part of the brain is active
• Evaluation of PET (2)

  • Weakness
  • Very expensive - rarely used in research
  • Results can be difficult to interpret
  • As it uses a radioactive substance, it can only be used a few times
• fMRI - Functional magnetic resonance imaging 


  • Works similar to PET, requires no radioactive substance
  • Measures oxygen levels in the brain
  • When an area is active, it uses more oxygen, so more blood is directed which is shown on the scan
• Evaluation of fMRI (1)

  • Strength
  • Shows the brain in action - useful for research
  • Does not use radiation - safe
  • Images are very clear
• Evaluation of fMRI (2)

  • Weakness
  • Expensive to use
  • Only useful if patient stays still - difficult for children
  • 5-second delay in brain activity - difficult to judge