Brain Scanning Techniques Flashcards
EEG: electroencephalography
Give a description of the process
What brain disorders can it be used to detect?
- Electrodes are placed under the scalp to pick up voltage fluctuations
- It is used to provide information about normal electrical activity and the voltage fluctuations have been correlated with the functioning of the cerebral cortex and various types of behaviour
- epilepsy, sleeping disorders,brain death and the depth of anaesthesia during surgery
EEG: electroencephalography
Give a description of the process
What brain disorders can it be used
- Electrodes are placed under the scalp to pick up voltage fluctuations
- It is used to provide information about normal electrical activity and the voltage fluctuations have been correlated with the functioning of the cerebral cortex and various types of behaviour
- epilepsy, sleeping disorders,brain death and the depth of anaesthesia during surgery
Advantages of EEG
+ cheap
+ fast
+ Non invasive
Disadvantages of EEG:
- it’s hard to figure out where in the brain the electrical activity is coming from
CT: computerised tomography
Give a description of the process
1 . Many X-ray images, taken from different angles then combined using sophisticated software
2. This produces high resolution cross sections or tomographic images (‘virtual slices’) which make it possible to see the inside of the body without cutting
Advantages of CT scans
+ more detailed info (high contrast)
+ more readily available than MRI in the uk
+ no ghost images of other structures
Disadvantages of CT scans
- involves does of radiation (may cause cancer)
- very expencive
- requires cooperative or sedated patients
MRI: Magnetic resonance imaging
Give a description of the process
- Uses a powerful magnetic field, radio frequency pulses and a computer to make detailed image of slices through the body
- The magnetic field aligns protons in water molecules
- The images produced are maninly of soft tissue l
Advantages of MRI
\+ does not involve ionising radiation \+ no known side effects \+ Non invasive \+ better soft tissue contrast than CT \+ 3D data
Disadvantages MRI
- very expencive
- Cannot scan patients with metallic implants
- unsuitable for claustrophobic or obese patients
fMRI: functional magnetic resomance imaging
Give a description of the process
1 . uses a strong magnetic field and a wave pulse to construct BOLD (blood oxygen level dependent) images
- fMRI shows the flow of oxygenated blood
- A 3D map is produced where areas in the cortex that are responding to a particular stimuli produce a brighter area in the image
- often used in the study of memory, emotion and language
Advantages of fMRI
\+ does not involve ionising radiation \+ no known side effects \+ Non invasive \+ better soft tissue contrast than CT \+ 3D data
Disadvantages of fMRI
- Very expencive
- Cannot scan patients with metallic implants
- unsuitable for claustrophobic or obese patients
PET: Positron emitting tomography
Give a description of the process
- Uses a radioactive isotope (glucose), with a short half life
- Active areas use more glucose, release more radiation which the computer translates into yellow and red
3 . PET scanners detect biochemical changes in the brain before anatomical changes occur
Mechanism of a PET scanner
- Fluordeoxyglucose (FDG) is injected into the patient and it enters the respiratory pathway
- Like glucose, it Phosphorylated by hexerokinase which is very active in fast growing tumours
- 18 F in FDG replaces an oxygen at on in glucose that is needed for the next step In glucose metabolism so there is no further reaction and FDG is trapped in any cell that takes it up
- 18 F emits a Positron as it decays
- The emitted Positron travels less than 1mm and looses kinetic energy until It collides with an electron
- Particles anhililate with each other and produce gamma rays which are detected in the scanner
