8 - SCANNERS USED TO VISUALISE THE BRAIN Flashcards
What are the four types of scanner used to visualise the brain?
Computed Tomography (CT), Magnetic resonance imagining (MRI), functional magnetic resonance imaging (fMRI), Position emission tomography (PET)
What method does the CT scanner use and what does it produce?
It uses radiation (X-rays) to produce cross-section images of the brain.
Why might certain parts of the brain appear lighter when a cross image is given using this type of scanning?
Because denser structures in the brain absorb more radiation than less dense structures so they show up as lighter in colour.
What does and doesn’t the CT scan show?
it shows:
- major structures in the brain
- diseased areas of the brain (therefore can be used in medical diagnosis)
- if there is heavy bleeding in or around the brain (because the blood will be lighter colour on the CT scan as it has different density)
but doesn’t show:
- the functions of the different parts of the brain
What method does the MRI scanner use and what does it produce?
It uses a magnetic field and radio waves to produce cross section images
Does it give better or worse quality images than the CT scan?
Better
What does MRI allow you to clearly see?
The abnormal and normal brain tissue.
What does and doesn’t the MRI scan show?
shows:
- diseased parts of the brain
- brain tumours and their exact size and location (as tumour cells respond differently to magnetic fields and are therefore lighter in colour)
doesn’t show:
- functions of brain
what is the difference between fMRI and MRI scanners?
the fMRI scanner is the same as the MRI scanner but it shows brain activity live (at that moment).
How does it work?
As more oxygenated blood flows to active areas of the brain, and molecules of oxygenated blood respond differently to a magnetic field than those in deoxygenated blood - the signal returned to the scanner is stronger from the oxygenated blood, allowing more active areas of the brain to be identified.
So what does it show? (fMRI)
damaged or diseased areas of the brain and abnormal activity in the brain
What does the PET scanner use?
radioactive material
How does the PET scanner work?
1) A radioactive tracer is introduced into the body and is absorbed into the tissues
2) The scanner detects the radioactivity of the tracer - building a map of radioactivity in the body
What does the PET scan offer?
The ability to give both the structure and the function of the brain in real time.
why is the PET scanner particularly useful in studying disorders that change the brains activity?
Because it can show which parts of the brain are inactive and active
