EPI-signal fluctuations at the cardiac frequency: A tissue-specific quantification of inflow, displacement and potential oxygenation effects over the cardiac cycle.

The impact and transmission mechanisms of the cardiac arterial pressure wave into brain tissue are not fully understood. It is hypothesised that age-related arterial stiffening and increased CBF pulsatility leads to propagation of the arterial wave further down the vascular tree causing tissue damage. Here we quantify inflow ($$$S_0$$$) and displacement/oxygenation ($$$T_2^*$$$) induced fluctuations of the EPI-signal at the cardiac frequency. We relate the EPI-signal phase at the cardiac frequency to the fluctuations of $$$S_0$$$ and $$$T_2^*$$$ over the cardiac cycle in the arteries, veins and tissue.