Slides in this set
CT scan see INSIDE
Tiny beams of X-rays are passed through
an area of the body, e.g. head
Each beam is attenuated by the density of
the tissue it passes through.
The X-rays which make it through are
detected and measured.
Sometimes special dyes are injected into
the blood or tissues to make certain areas
X-rays opaque so they show up in the scan.…read more
Magnetic resonance diagnose brain
imaging (MRI) strokes, and
infections of the
brain or spine.
Produced using magnetic fields and radio
waves to image the soft tissues
Hydrogen atoms are the most commonly
The signals produced are analysed by a
computer and used to produce an image.…read more
CT vs. MRI
MRI scans produce images that show much
finer detail than CT scans
CT exposes the patient to moderate doses of
radiation, MRI doesn't involve radiation.
The high magnetic radiation in MRI means
that people with pacemaker or metal body
parts cannot enter it.
Both give a historical image of the brain, they
don't show it as it works.…read more
Functional MRI (fMRI) of the active
It monitors the uptake of oxygen in different brain
Deoxyhaemoglobin absorbs the radiowave
signal and re-emits it (oxyhaemoglobin doesn't).
When an area of the brain is active, the blood
flow increases and more oxyhaemoglobin is
delivered to supply the active cells with the
oxygen needed for aerobic respiration.
An active area of the brain absorbs less energy
than a less active area.
Different areas of the brain light up on the images
when they become active.…read more
Disadvantages of fMRI
It is a noisy procedure
The patient's head has to be very still or the
accuracy of the image will be affected
Validity some argue that the blood flow to a
different areas of the brain in response to
different stimuli is not a causal link…read more