Computer simulation of convection and diffusion effects on velocity estimations from X-ray contrast density time curves

Abstract

The problem of velocity measurement in X-ray angiography using the leading edge of the contrast bolus is considered. The velocity obtained from the ratio of the temporal derivative to the spatial derivative of the contrast concentration curves is shown to reflect the transport velocity, which is the basis for an estimate of the true blood velocity in X-ray angiography. The contrast distribution along the vessel cross section affects the value of transport velocity. Under laminary flow conditions, the measured transport velocity of the leading edge has been found to be between the average and the peak (central) fluid velocities. Simulation studies of the bolus in laminar flow through a straight tube are presented in this paper to provide further proof of the higher transport velocity of the bolus leading edge. The simulation studies confirm observations made previously from X-ray images of contrast passage through simple tubes.