A system, apparatus and method are provided for measuring and removing the influence of pulsatility on contrast agent flow in a region of interest of a vascular system of a patient. Once the change of blood speed over the cardiac cycle is known (pulsatility), this influence is removed from acquired image sequence for outcome control such that 'quasi-stationary', regular flow acquisition is passed on to subsequent visualization and analysis processes. A contrast agent injector is also provided that simultaneously measures and uses ECG to inject a known contrast agent at a fixed point over the cardiac cycle or such that a known amount of contrast agent will arrive at a known time at a region of interest in the vasculature of a patient, thus controlling one of the main unwanted variables in an acquisition of blood flow sequences.