Time-of-flight NMR imaging of plug and laminar flow

Moving spins have a significant effect upon the received MRI signal, which is seen, depending upon the pulse sequence utilized, as a modulation in signal intensity and/or phase relative to that of stationary spins. This can be used in MRI to distinguish between blood vessels and stationary anatomic structures. Monoplanar time-of-flight techniques use pulse sequences which modulate the signal intensity from spins in a vessel flowing perpendicularly through a slice. Here the authors develop expressions for the signal intensity of two pulse sequences which are expected to give optimum contrast for imaging flowing blood free of overlying non-vascular anatomy. This imaging technique would provide a means for imaging blood vessels without the use of ionizing radiation or contrast injection; furthermore, it provides information about the presence of flow in vessels. As such, it may be promising as a method to evaluate vessels which are not accessible to standard angiographic imaging