Abstract: A multi-gated pulsed wave color Doppler imaging system is used to provide accurate non-invasive measurements of liquid flow through a narrowed orifice by using the color Doppler to first measure the velocity of flow along an axis perpendicular to the orifice to provide a first image of the liquid velocity. The first image includes a two-color interface at locations in the image representing locations where the liquid velocity is equal to the aliasing velocity of the color Doppler imaging system. The distance from the two-color interface to the center of the orifice is measured and saved. A second image is obtained along an axis perpendicular to the first axis to represent the flow of liquid to the orifice from the perimeter of the orifice. The distance from a two-color interface to the center of the orifice in the second image is measured. The two measured dimensions are used to model a hemi-ellipsoidal surface proximal to the orifice wherein all points on the surface have the same isovelocity.