The present invention relates to a determination of a physiological functional parameter of a living being. Ultrasound image data and Doppler image data of a vessel structure are provided (101) and registered (102). The vessel structure is segmented (103) to generate (104) a representation of the vessel structure. The flow velocity inside a vessel of the vessel structure is determined (105) based on the Doppler image data. A physiological functional parameter determination model defining a value of a functional physiological parameter in dependence of a representation of a vessel structure and a flow velocity inside a vessel of the vessel structure is used (106) to determine (107) the physiological functional parameter inside the vessel of the vessel structure. The representation of the vessel structure and/or the flow velocity values can be constantly updated upon receipt of further input images to provide an estimation of the functional physiological parameter in real-time.
