2d. Techniques used to study brain Flashcards
CAT scans
Computerized Axial Tomography. Radiology technique that creates clear images of deep internal structures of the body
What can CAT scans see?
Produces detailed images of hard and soft tissues, blood vessels and bones
How does CAT scans work?
Uses cross sectional images that are compiled to form a 3D image. Contrast dye helps highlight certain areas like blood vessels
Uses of CAT scans
Post-trauma head damage, blood clot, tumors, fluid in brain
Advantages of CAT scans
- Less expensive than MRI
- More detailed than xrays
- Widely available
- Very clear
- Fast and non-invasive
Disadvantages of CAT scans
- Exposed to high doses of ionizing radiation
- Requires breath holding
- Pregnant ladies should avoid
MRI
Magnetic resonance imaging
How does MRI work
- Uses strong magnets to create unified field that hydrogen protons follow
- H atoms emit energy when placed in field so machine captures location
Advantages of MRI
- Non-invasive
- No radiation exposure
- High spatial resolution
Disadvantages of MRI
- Metal is attracted to magnet
- Expensive
- Problematic for claustrophobics
- Lot of noise and one has to be still
fMRI
Functional magnetic resonance imaging
What do fMRIs use?
BOLD signals (Blood-oxygen level dependent) where oxy blood repels magnetic fields and deoxy blood is weakly attracted creating a gradient
How do fMRI images look like?
Different colours represent gradient eg. Yellow is low activity and red is high
What idea does fMRI rely on?
Idea that when brain cells use energy, there is more blood flow to that region to provide oxygen
Use of fMRI
LoF and neurobehavioral disorders
Advantages of fMRI
- No radiation exposure
- Able to record signal all over the brain
- Used to localize function
Disadvantages of fMRI
- Localization is complex
- Costly and lengthy
- Metal implants attracted
- Claustrophobia
PET scans
Positron Emission Tomography scans where blood flow is indicator of activity
How does PET work?
Radioactive tracer is ingested and it binds to glucose. Scanner registers frequencies emitted and shows which brain area is more active
Uses of PET
- Cancer cell identification
- Tumours
Advantages of PET
- Spatial resolution
- Small and portable
- Usable on small animals
- Demonstrates biochemical changes
Disadvantages of PET
- Very slow process
- Exposed to radioactivity
EEG
Electroencephalography.
What concept does EEG rely on?
Neurons in our brain use small electrical and chemical impulses to communicate. If large groups of neurons fire at the same time, electric potential can become detectable
Does EEG give structure of brain?
No. Only function
Uses of EEG
Epilepsy, seizures, head injury, encephalitis
How is EEG done
Small electrodes are attached to scalp using glue or cap. Electrodes are connected to an EEG monitor.
Takes two electrical impulses and outputs difference
Advantages of EEG
- Changes can be seen in real time
- Cheaper
- Silent
Disadvantages of EEG
- Only shows current results
- Can trigger epilepsy
- Hard to figure out where electrical activity is coming from
