Brain scans

• What does EEG involve?

  Recording of electrical activity along the scalp produced by firing of neurons within brain over a short period of time (20-40 mins). Recorded from multiple electrodes placed on scalp.
• Advantages of EEG:

  Non-invasive & can be used with children/claustrophobic patients.
• Disadvantages of EEG:

  Doesn't show you structural information inside brain.
• Advantages of PET scans:


  Provides an image of brain activity.
• Disadvantages of PET scans:

  Expensive & radioactive material used.
• Disadvantages of CAT scans:

  Uses radiation, & more radiation than normal x-rays. May not be suitable for children or those prone to cancer. Only provides information about structure of brain, not function/activity.
• Advantages of CAT scans:

  Quality of images is higher than normal x-rays, useful for revealing abnormal structures, e.g, tumours or brain damage.
• Advantages of MRI scans:


  No x-rays or radioactive material used, provides detailed view of the brain in different dimensions, safe, painless, non-invasive, no special preparation (except removal of all metal) is required from the patient.
• Disadvantages of MRI scans:

  Expensive, can't be used in patients with metallic devices like pacemakers, can't be used with uncooperative (or claustrophobic) patients as they must lie still.
• What is a CAT scan?

  Series of X-ray beams passed through head, creating 2D or 3D cross-sectional images showing structure not function. Dye injected in patient as contrast material. Placed into CAT scan machine-takes pictures (10-20 mins).
• What is a PET scan?

  Positron emission tomography. Focuses on brain function. Produces computer-generated pictures of brain. Tracer taken into body that emits radioactivity (usually glucose). Tracer can be picked up by producing positrons which gives signals that are recorded. Shows up as brain activity which can then be interpreted. Scan measures blood flow & O2 use. Can identify which parts of brain do what through patients doing activity, e.g, talking.
• What is an MRI scan?


  Magnetic Resonance Imaging. Looks at structure of brain. Uses magnetic & radio waves. Patient lies in large cylinder magnet, radio waves sent through body, affecting body's atoms. Scanner picks up signals as atoms move back into position. Computer turns signals into pictures.