What are the differences between time-of-flight and velocity-encoded MRA?
The velocity-encoded MRA uses velocity of the vessels to show contrast where as TOF uses spin suppression to arise to a contrast image by suppressing signals from the spin within an imaging plane so that voxels with inflowing spins have high signals. 13. What does diffusion imaging measure? What is the ADC, and what does it represent? Diffusion imaging uses the movement or amplitude of diffusion to create a MR signal. ADC is apparent diffusion coefficient, which is the quantification of diffusivity assuming isotropic (equal) diffusion. 14. Why might diffusion be anisotropic? What does FA represent? Diffusion may be anisotropic (unequal) because certain tissue may have a higher preference for water molecules. FA is the preference for molecules to diffuse in an anisotropic manner. 15. What does perfusion MRI measure? Perfusion MRI measures how the blood is delivered to the body (i.e. through capillaries). Perfusion MRI can use both exogenous and endogenous contrast. Exogenous contrast us
