Modelling the effects of cardiac pulsations in arterial spin labelling.

It has recently been demonstrated experimentally that cardiac pulsations seem significantly to affect the arterial spin labelling (ASL) signal. In this paper, we introduce a new theoretical model to examine this effect. Existing models of ASL do not take such effects into account since they model the transit of the ASL signal assuming uniform plug flow with a single transit delay. In this study, we model cardiac pulsations through the coupling of the Navier-Stokes equations with the three-dimensional mass transport equation. Our results complement the experimental findings and suggest that the ASL signal does depend on the timing of the onset of the cardiac cycle relative to the tagging and imaging locations. However, cardiac pulsatility only appears to have a small effect on the quantification of perfusion estimates.