Medical Imaging Techniques

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CAT (CT) Scans - Computerised Tomography

  • Uses thousands of narrow beam X-rays rotated around the patient to pass through the tissue from different angles.
  • Each anrrow beam is reduced in strength according to the density of the tissue in its path.
  • The X rays are detected and used to produce an image of the brain in which different soft tissues can be distinguished.


- This method is often cheaper than other scans such as MRI and fMRI.

- Individuals can feel less claustrophobic.

- Can identify brain structure.


- It uses radiation and is not suitable for pregnant women or children.

- Still quite expensive.

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Medical Resonance Imaging (MRI) Scans

  • Uses a magnetic field and radio waves to detect soft tissues.
  • Different tissues respond differently to the magnetic field so produce contrasting signals and distinct regions.
  • It can be used in diagnosis of tumours, strokes, brain injuries and infection.


- Does not use radiation so is suitable for pregnant women and children.

- Can identify brain structure.


- Patients may feel claustrophobic in the scanner.

- Expensive.

- Cannot identify function.

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Functional Magnetic Resonance Imaging (fMRI)

  • Looks at the function of the different areas of the brain by following the uptake of oxygen in active brain areas.
  • Deoxyhaemoglobin absorbs the radio wave signal where as oxyhaemoglobin does not.
  • Increased neural activity in the brain results in an increased demand for oxygen and hense increased blood flow.
  • Less radio signals are absorbed so it will be highlighted according to when they are active.


- Can identify the funciton of the brain as well as the structure.

- Does not use radiation and has virtually no risks.


- Very expensive.

- Patients may feel extremely claustrophobic.

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