104. FMRI: APPARENT DIFFUSION COEFFICIENT (ADC) Flashcards
- What do the different colours in this Apparent Diffusion Coefficient image represent?
DARK REGIONS:
- the water is diffusing slower
- the movement is more restricted
- there are more obstacles present
- the viscosity is increased
- the Apparent Diffusion Coefficient is low
- this is where the stroke will be found
BRIGHT REGIONS:
- the water is diffusing faster
- the movement is less restricted
- there are less obstacles present
- the viscosity is decreased
- the Apparent Diffusion Coefficient is high
NB:
- this is a left Middle Cerebral Artery Stroke
- What is the relation between the intensity of the pixels and the extent of the diffusion?
- they are proportional
- an increase in one leads to an increase in the other
- What do the different colours in this Diffusion Weighted image represent?
BRIGHT REGIONS:
- there is decreased water diffusion
- the Diffusion Weighted Image signal is high
- this is where the stroke will be found
DARK REGIONS:
- there is increased water diffusion
- the Diffusion Weighted Image signal is low
- What do we use the very strong multidirectional gradients for?
- we use them to Map White Tracts
THIS IS BECAUSE:
- they have a lower Apparent Diffusion Coefficient than
the surrounding Grey Matter
THIS TECHNIQUE IS CALLED:
- Diffusion Tensor Imaging
- DTI
- What kind of structures can we image using Diffusion Tensor Imaging (DTI)?
- any structures that include fibres
EXAMPLE:
- muscles
- skeletal muscles
- left ventricle
- What do the different colours in this image represent?
EACH COLOUR:
- represents the different direction that the molecule
(fibre) travels in
BLUE:
- the fibres travel along the Z-Axis
- this is Superior and inferior movement
RED:
- the fibres travel along the X-Axis
- this is transverse movement
GREEN:
- the fibres travel along the y-axis
- they travel in the anterior and posterior direction
- Define: Perfusion.
- this measures the quality of the Vascular Supply to a
tissue
IT CAN ALSO BE USED:
- to measure tissue activity
- What method does Perfusion make use of?
- it uses a Bolus injection of Gadolinium
- Gadolinium is a contrast agent that is used in MRI
- this is done during ultrafast T2* Acquisition
- What does the Gadolinium Contrast Agent do?
- it causes the temporary decreases in the T2*
- this happens in and around the microvascular regions
- these are made up of many tiny vessels
- these regions have a lot of contrast
- What happens after we have obtained Perfusion data?
WE CAN DETERMINE:
- the blood volume
- the transit time
- the measurement of perfusion
- What can be seen in this image?
- this is the Perfusion Curve
- it is called the Time Intensity Curve
- When do we take different Time Intensity Curves?
- we take them during and after the Gadolinium
injections - they are combined together to create a Cerebral Blood
Volume (CBV) map
- What do we use Perfusion imaging for?
- it is used to evaluate Ischaemic diseases
- this is when an organ does not get enough Blood
Supply - it is also used to look at Metabolism
- What do the different colour regions in Cerebral Blood Volume Maps indicate?
DARK REGIONS:
- show that there is low perfusion
- these are the areas where we will find a stroke
BRIGHT REGIONS:
- show the areas of high perfusion
- this is where we will usually find malignant tumours
- Label this image?
STRUCTURE 1:
- Diffusion
- the bright region indicates the area of low diffusion
- this is where we will see a stroke
STRUCTURE 2:
- Perfusion
STRUCTURE 3:
- this is a combination area of perfusion and diffusion
- this is where the stroke is occurring
- Label these images?
STRUCTURE 1:
- this is a T2 Weighted image
- it cannot detect the stroke
STRUCTURE 2:
- cannot detect the stroke
STRUCTURE 3:
- this is a Diffusion Weighted Image
- the areas of decreased diffusion are bright
- this is where the stroke is
STRUCTURE 4:
- this is a Perfusion Image
- the areas of decreased diffusion are dark
- this is where the stroke is taking place
