1. A method for ultrasonic flow parameter imaging comprising the following steps: transmitting a timed sequence of spatially diverging ultrasonic transmit beams from a transducer array into a region of interest in a body at a pulse repetition frequency; converting ultrasound wave energy returned to said array into electronic signals; beamforming said electrical signals to simultaneously form a respective set of receive beams following each transmission, each set of receive beams consisting of multiple lines through respective spatial positions in the region of interest; calculating a respective mean velocity value for each receive beam; calculating a respective value of a given flow parameter for each receive beam, a respective set of flow parameter values being calculated from the respective set of mean velocity values; and displaying a respective visual value for each calculated flow parameter value in a spatial relationship that generally corresponds to the spatial relationship of said spatial positions in said body, thereby forming a respective flow parameter image.