Method and apparatus for ultrasonic beamforming with spatially encoded transmits

The frame rate in medical ultrasound imaging is increased significantly by reducing the number of transmit events per image frame using spatially encoded transmit events in accordance with an invertible encoding matrix. First, M sets of encoded signals are transmitted, one set after the next, from M transmitting elements of a transducer array. For each transmission, all M transmitting elements are activated simultaneously in accordance with the encoding of a particular set of signals. The resulting scattering data are stored for each of the M transmit events, and are subsequently decoded with the inverse of the encoding matrix to obtain individual elemental information. The complete set of scattering data captures the time history of the ultrasound pulses that are transmitted from a single transducer element of the phased array, such as the m-th transmitter element, scattered by the medium under investigation, and subsequently received at the n-th receiver element, for all M transmitters and N receivers. The invertible code is preferably an orthogonal phase code such as a Hadamard code.