4D Cone-beam CT reconstruction using a motion model based on principal component analysis.

Purpose: To provide a proof of concept validation of a novel 4D cone-beam CT (4DCBCT) reconstruction algorithm and to determine the best methods to train and optimize the algorithm.

Methods: The algorithm animates a patient fan-beam CT (FBCT) with a patient specific parametric motion model in order to generate a time series of deformed CTs (the reconstructed 4DCBCT) that track the motion of the patient anatomy on a voxel by voxel scale. The motion model is constrained by requiring that projections cast through the deformed CT time series match the projections of the raw patient 4DCBCT.

Stable stationary vortices and traveling oscillatory vortices in a stenotic fluid-flow channel.

A shearing zonal flow of viscous fluid near a boundary perturbation can generate vortices that either remain attached near the boundary or detach to be abruptly carried downstream. At low speed a stationary attached vortex develops downstream from the perturbation. At higher speeds an array of traveling vortices forms, with successive rolls rotating in opposite directions.