Brain Imaging Flashcards
How do CT scanners work
Use radiation in form of beams of X rays to produce cross-section images of the brain
-dense structures in brain absorb more radiation so show up as darker colour than less dense structures
Does CT show functions of brain structures and how can this be inferred
Doesn’t show functions of brain structures but if CT scan shows diseased/damaged brain structure and the patient has lost some function means the function of that part of the brain can be worked out
Uses of CT scanners
-used to diagnose medical problems as they show damaged/diseases areas of the brain
-can show extent and location of bleeding (stroke) as blood has dif density to brain tissue so shows up lighter colour, can work out which blood vessels have been damaged and what brain functions likely to be affected
Limitations of CT scanners
-potentially dangerous as use radiation in the form of X rays, can cause mutations in DNA which can lead to cancer
-lower resolution than MRI
-can have side effects from contrast medium
What does CT stand for
Computed tomography scanner
How does MRI work
Uses really strong magnetic field and radio waves to produce cross-section images of the brain
Advantage of MRI over CT
Gives higher quality images for soft tissue types than CT and better resolution between tissue types
Uses of MRI
-clearly see dif between normal and diseased/damaged tissue eg tumour cells respond differently to magnetic field than healthy cells and are lighter in colour, shows exact size and location of tumour to decide most effective treatment
-can work out brain function by looking at damaged areas and which functions affected
How does fMRI work
-shows changes in brain activity as they happen
-more oxygenated blood flows to active areas of brain(to supply neurones with oxygen and glucose)
-oxygenated haemoglobin responds differently to magnetic field than deoxygenated haemoglobin, signal returned to scanner stronger from oxygenated blood
Advantages of fMRI
-gives detailed high resolution picture of brains structure
-can be used to show function
How does fMRI show function of brain structures
-if function carried out whilst in scanner the part of the brain involved with that function will be more active
Uses of fMRI
-show damaged/diseases areas of brain and allow you to study conditions caused by abnormal activity in the brain (as some conditions don’t have obvious structural cause) eg can take fMRI before and during seizure to pinpoint which part of brain not working properly and find cause
What does fMRI stand for
Functional magnetic resonance imaging
What does PET stand for
Positron emission tomography
How does PET scanner work
-shows how active dif areas of the brain are
-radioactive tracer (eg radioactively labelled glucose can be used to look at glucose metabolism) introduced into body and absorbed into tissues, scanner detects the radioactivity of the tracer to build up map of radioactivity in the body
