PET Scan name
Position Emission Tomography
Pet Scan Process
Injection / Inhalation of radioactive glucose (scanner detects radioactive material)
Radioactive glucose and oxygen accumulate in brain areas which are metabolically active
PET Scan Example
Rain et al. - used to determine a difference in brain activity in murderers pleading NGRI and ‘normal’ people
- Correlated brain activity / damage to aggressive behaviours and tendencies
PET Scan Strengths
- Reveals chemical information not available with other imaging techniques (can distinguish between benign and malignant tumours)
- Can help plan operations such as brain surgery for epilepsy
PET Scan Weaknesses
- Expensive (unavailable for psych research)
- Invasive (Injection - fear of needles)
- Radioactive (cannot be done regularly & impractical to patient)
- Less precise than MRIs
MRI Name
Magnetic Resonance Imaging
MRI Process
Detects radio frequency signals produced by radio waves in a magnetic field
Large tube containing magnets that patient lies in during the scan
Provides anatomical view of the body (upright)
Can be used to examine almost any part of the body (brain / spinal cord / joints)
RESULTS: help diagnose conditions, plan treatment & assess how effective previous treatment has been
MRI Strengths
- No radioactive material / x-rays used
- Provides detailed view of the brain in different dimensions
- Non-invasive (safe & painless)
- No special prep required (except removal of all metal)
MRI Weaknesses
- Expensive
- Cannot be used by patients with metallic devices (e.g. pacemakers)
- Cannot be used with claustrophobic / uncooperative patients (must lie still)
fMRI Name
Functional Magnetic Resonance Imaging
fMRI Process
Detects changes in haemodynamic response / blood oxygenation levels while the patient performs a task
Produces 3D images of the brain which map the areas active in response to the task
- Possible to draw links between brain activity & mental processes
Haemodynamic Response (fMRI)
- Brain activity requires more oxygenated blood
- More activity requires more oxygenated blood
- Blood flow is directed to active areas
fMRI Strengths
- No radiation (risk-free)
- Non-invasive
- High spatial resolution images (can provide info on localised brain function during the task)
fMRI Weaknesses
- Expensive
- Cannot be used for claustrophobic / uncooperative patients (must lie still)
- Poor temporal resolution images (5 sec lag between neuron firing & image production)
- Only measures blood flow, not specific neuron activity
CT Scan Name
Computer Tomography Scan
CT Scan Process
A series of x-ray beams passed through the head
- Creates cross-sectional images of the brain showing the STRUCTURE not the function
CT Scan Use
- Diagnose conditions (damage to bones / injuries to internal organs / stroke / cancer)
- Guide for further tests / treatment
Helps determine the location, size & shape of a tumour before radiotherapy / needle biopsy - Monitor conditions
Checking size of tumours before & after cancer treatments
CT Scan Strengths
- Very detailed image
- Effective at producing a structural image of the brain
CT Scan Weaknesses
- Invasive (Injection)
- Structural information only
- Impractical (noisy & uncomfortable - IV inserted)
- Takes a few weeks for results to come in
EEG Scan Name
Electroencephalogram Scan
EEG Scan Process
Measures electrical activity in the brain
- Electrodes fixed to a gap are glued to patients scalp
- Records brainwave patterns
- Can detect irregular (arrhythmic) patterns: indicate underlying neurological abnormalities
EEG Scan Example
Dement & Kleitman - EEG Scan used to record stages of sleep
- Effectively allowed researcher to record stages of sleep
EEG Scan Strengths
- Quickly & easily shows irregular brain activity
- High temporal resolution (almost instantaneous feedback on neuronal activity)
EEG Scan Weaknesses
- Recordings produced represent millions of fired neurons (hard to detect the specific firings of neurons in response to one particular event)
- Uncomfortable & messy (electrodes glued)
