brain scans Flashcards
neuroimaging
the process of using brain scans to study the structure and functioning of the brain
3 types of brain scans we look at
CAT scans
fMRI scans
PET scans
CAT scans process
- someone lies still while a scanner rotates around them taking x ray images of the brain/body
how long do CAT scans take
a few minutes to 30 minutes
how are pictures formed with CAT scans
by showing which areas of the body blocks x rays and which don’t
- bone and body tissues absorb different amounts depending on their densities
what do CAT scans show
- medical information e.g presence of tumors in the brain
CAT scans strengths
- provide detailed info about brain structure - helps detect abnormalities, e.g tumors
- non invasive and painless
CAT scans weaknesses
- radiation exposure is equal to a year of normal exposure, increasing cancer risk and damage
- not suitable for pregnant people
- only provides structural information, as they only produce still images
how do PET scans work
- individuals are injected with glucose and a radioactive isotope tracer
- as part of the brain is active they will use more glucose
- on scan tracer will appear in areas where brain is working hard
what do positrons on PET scans do
- they are emitted by the tracer
- create signals which are
recorded and displayed as images - this info is sent to a computer
in PeT scans what colours show the most active areas of the brain
red/yellow
in PET scans which colours show the least active areas of the brain
- blue
what is the radioactive atom used in the tracer for PET scans
fluorodeoxyglucose (FDG)
what does fluorodeoxyglucose do
attach to glucose
- as brain uses glucose for energy FDG atoms start to break down emitting positrons
- positrons produce gamma rays which are picked up by the scanner
what does a high concentration of gamma rays mean - pet scans
- high levels of brain activity
- lots of glucose is used up
pet scans strengths
- learn about brain activity and which areas are involved in different cognitive tasks
- diagnose brain diseases where metabolism changes
- can detect alzheimer’s in early stages
- shows brain in action
pet scans weaknesses
- pet machines cost to produce isotopes and is expensive limiting accessibility to this procedure
- short half life isotope means only short tasks can be studied so restricts research
- ethical issues so radioactive glucose is injected = harm
what does fMRI stand for
functional magnetic resonance imaging
how does fMRI scans work
- applying a strong magnetic field to a person, magnetizing their blood
- head is placed inside an electromagnet
- blood magnetized differently depending on whether it’s rich/poor in oxygen
what does the fMRI scan measure
- increased and decreased oxygen levels in the brain
which areas of the brain need more oxygen
active areas
how can we use the idea of oxygenated//deoxygenated blood to show brain activity (fMRI)
- deoxygenated blood follows the magnetic field which is detected by the scanner
- this is blood where oxygen has been used up
- this shows the brain is active as it is using up oxygen
strengths FMRI scan
- safer = no exposure to radiation
- helps detect strokes (medical purposes)
- clearly identifies active brain areas during cognitive tasks
- helps brain research function
FMRI weaknesses
- not suitable for people with pacemakers / who are claustrophobic
- hard to establish a baseline measure as brain is never truly at rest
- brain regions which light up at fMRI could be used for multiple functions, which decreases our understanding of the brain
