Advanced Topics in Neuro MRI Pt.1 Flashcards
What is Diffusion?
The flow of energy or matter from a high concentration to low concentration, resulting in a homogenous distribution
True or false. Diffusion weighted imaging (DWI) is a type of contrast-weighting in MRI.
True
In DWI the contrast difference between the tissues is based on the difference in the _________ diffusion in those tissues.
water molecule
If cells swell they hinder the path of the intercellular diffusion and hence increase/reduce the diffusion coefficient. So __ or __ can be detected.
reduce; swelling or inflammation
What sequences are used in DWI?
fast sequences; usually done with fast EPI sequence
What is apparent diffusion coefficient (ADC)?
The signal intensity that is dependent on the strength of the gradients and the diffusion coefficient; ADC can be measured if we have signal from two different gradients
What are some clinical applications of DWI? (when is it used)?
strokes, abcesses, tumors, lymphoma
When there is low diffusion (little to no motion of water molecules), then what color is the does the water signal appear as?
white
Is diffusion isotropic or anisotropic?
anisotropic
What is Diffustion Tensor Imaging (DTI)?
The type of measurement where you measure diffusion along many directions (one at a time)
What is anisotropy?
diffusion rate depends on direction
Anisotropic diffusion can be expressed by a _.
tensor
Higher number of diffusion direction =
better accuracy of directionality of diffusion, but longer acquisition time
What are the colors for direction and what do they represent?
Green = Anterior-Posterior
Red = Right-Left
Blue = Superior-Inferior
Other colors = combination of directions
What is fiber tracking?
colorful lines that show how diffusion propagates in the brain and are thought to be white matter fibers
