Brain Scanning Techniques Flashcards
What is a CAT scan
X-rays and a computer create detailed structural images of body/brain
Large doughnut shaped scanner rotates around an individual
CAT scan image
cross section of body/ brain combined to form detailed picture
Strength of CAT scan
Reveals abnormal brain
traditional X-rays
structures (e.g. tumours)
Image quality much higher than that of
traditional X-rays
Weakness of CAT scan
-Needs more radiation than radiation than
traditional X-rays
More detailed/complex the scan, the more radiation than radiation exposure (cannot be used often)
-Only provides information about brain structure
Still images, not ‘live’ brain activity (unlike PET and fMRI), so limited use in research
What is a PET scan
Measures metabolic activity in the brain (i.e. most active areas).
Injection of small amount of radioactive glucose given. Most active areas use more of it, coloured red or yellow on the scan, with least active areas represented as blue
Strengths of PET scan
-Shows the ‘live’ brain in
action
Useful for research links biological activity to behaviour
- Shows specific brain areas linked to experience
Evidence of localisation of function (e.g. identifies brain area linked to thinking about something).
Weaknesses of PET scan
-Sometimes the results are not easy to interpret
-Ethical issue (injection of radioactive glucose)
Radiotracers can cause tissue damage, so used just once every six months - limited usefulness
What is an fMRI scan
Radio waves measure blood oxygen levels in the brain (most active areas use most oxygen so blood is directed to these areas)
Activity is picked up through radio signals which produce a series of images of successive ‘slices’ turned into a 3D image by a computer
Strengths of fMRI
-Shows which areas of the
brain are being used.
-Does not use radiation.
Safer than PET and CA.
-fMRI images very clear
Can show brain activity to the millimetre
Weaknesses of fMRI
-Person has to stay perfectly still in the scanner.
Difficult for some (e.g. children), so limits the use of fMRI with some kinds of research.
-5-second delay between brain activity and image.
Can cause problems trying to interpret the information.
How does PET scan work
Inject radioactive glucose metabolism, releasing beta+ particles (positively charged electron)
When they collide they annihilate one another, no more e- or positrons producing a gamma ray
Gamma ray picked up by scanner
How does fMRI work
Haemoglobin carrying O2 is diamagnetic (repels magnetic field)
Haemoglobin with an attached is paramagnetic molecules (follows magnetic field)
Use radio burst to higgle molecules and then they reveal its state
