The invention provides a method for obtaining a parameter relating to flow from a vessel. The method begins by obtaining ultrasound data, which includes Doppler ultrasound data, from an imaging plane and identifying a vessel cross section within the imaging plane based on the ultrasound data. A shape of the identified vessel cross section is then determined and a vessel axis extending along the length of the vessel is determined based on the shape of the identified vessel cross section, with the assumption of a circular cross section on a plane perpendicular to the vessel axis. A Doppler angle is determined between the vessel axis and the imaging plane and the parameter relating to flow derived based on the Doppler angle, the vessel axis and the Doppler ultrasound data.
