3.2.3 brain-scanning techniques Flashcards
1
Q
what are the main brain scanning techniques?
A
- PET
- CT
- fMRI
2
Q
how do CT scans work?
A
- Can be used to take images of any part of the body.
- Scans of the brain involve multiple X-ray beams passing into the head from different angles.
- Produces a detailed, 3D image of the structure of the brain.
3
Q
what are the strengths of using a CT scan?
A
- Useful to see areas of brain damage or tumors (can help with accuracy of surgery) but gives no info about how the brain is functioning.
- Non-invasive/painless (no tracers need to be injected)
- Reliable because it’s replicable - the same procedure can be carried out in exactly the same way each time.
4
Q
what are the weaknesses of using a CT scan?
A
- Radiation poses a potential risk to health - pregnant women are not allowed to have a CAT scan in case of damage to the unborn baby.
- Only measures structure and layout of the brain (eg. damage to the frontal lobe), doesn’t record brain activity and so is less detailed than MRI/PET
5
Q
PET scans
how does it work?
A
- Patient is injected with small amount of radioactive tracer (radioactive atom attached to glucose- energy for the brain)
- Task may be given to stimulate the brain and encourage activity.
- Brain uses up glucose, the radioactive atoms start to break down, emitting positrons.
- Gamma rays are produced by this process and picked up by the scanner.
red/yellow - most active, blue - least active
6
Q
strengths of using a PET scan
A
- Produces accurate (valid) and objective images of brain activity. Therefore ensures accurate conclusions/predictions can be made
- Reliable because of replicability, the same procedure can be carried out in exactly the same way each time standardised procedure. high is red low is blue produces same comparable images interpreted same by all researchers
7
Q
weaknesses of using a PET scan
A
- More invasive compared to CAT/fMRI scans due to injection of radioactive substance, although low levels of substance therefore low risk to health
- Produces broad images of colour, detail may be unclear in some images, hard to distinguish between warm and cold colours based on brain activity.
- Low ecological validity as scans take place in an artificial setting, and tasks to stimulate brain activity can be artificial, therefore do not measure true to life brain activity.
8
Q
fMRI scans
A
Scanner produces a picture of brain activity by measuring blood flow
- Head is placed inside a large electromagnet.
- Once inside the magnetic field the nuclei within hydrogen molecules in water align themselves with the direction of the magnetic field
- As activity increases in the brain, blood flow increases in the active areas to keep up with the demand for oxygen
- Haemoglobin repels a magnetic field when carrying oxygen, but when it is deoxygenated it follows the direction of the magnetic field. These are the changes the scanner picks up to create an image.
doesn’t use radiation unlike pet and cat
9
Q
strengths of fMRI scans
A
- There is no risk to health due to radiation, therefore safer than CAT and PET
- Non-invasive. Unlike some other imaging techniques, fMRI does not require the injection of radioactive tracers or exposure to radiation. This makes it safer for repeated use
- Valid because it is accurate and precise, produces high resolution images which shows structure AND function/activity
- Reliable because it’s replicable - the same procedure can be carried out in exactly the same way each time.
10
Q
weaknesses of fMRI scans
A
- Not suitable for all - if an individual has a cardiac pacemaker or surgical implants due to powerful magnetic field.
- Anyone who is claustrophobic or unnerved by loud noises and confined spaces may become quite distressed having to lie flat and still within the large tube.
- Artificial setting so lowers ecological validity, brain activity is not natural due to situation being different from everyday life
