A laminar flow model for 3D time-of-flight MR angiography

A theoretical flow model for laminar flow has been developed by Chen and Hedges (1997). A theoretical flow model for plug flow previously developed by using the Bloch equation was used by Parker et al. (1991) in their paper about MOTSA technique. Both models assume constant flow through a tube of constant circular cross section. However, the plug flow model is used to simulate the signal from the center portion of the flow, which has almost unique flow velocity; while the laminar flow model is used to simulate the average signal from the whole cross section, which has a distribution of flow velocities. For detection of small vessels of width close to the voxel width, the laminar model is more appropriate. Phantom and human subject studies validate the use of laminar flow model for cross-sectional average signal for small vessels.