A matrix transducer for 3D Transesophageal Echocardiography with a separate transmit and receive subarray

With 3D Transesophageal echocardiography (3D TEE) the 3D anatomy and function of the heart is visualized. For 3D imaging an ultrasound matrix of several thousands of piezoelectric elements is required. The gastroscopic tube of a transesophageal echocardiography (TEE) probe can accommodate a limited number of cables, since it should remain thin and flexible. Therefore, the number of channels from the transducer should be reduced by using smart signal processing with integrated circuitry in the tip of the probe. The integrated receive circuits require low voltages. To ensure separation from the high voltages required for transmission, the proposed design features a separate transmit and receive subarray. An additional advantage of the two subarray design is that each subarray can be optimized for its specific role. A drawback of separate subarrays is that the axes of the transmit and receive beams do not coincide, making beamforming less straightforward. To reduce the sensitivity to grating lobe artifacts, the transducer is designed for second harmonic imaging. To ensure sufficient frame rate to visualize the movement of the heart valves, wide beam are transmitted (at 3MHz) and in receive (6MHz) microbeamforming is done in the transducer head and parallel beam forming in the mainframe. In this paper we investigate the beamforming using the separate transmit and receive subarray configuration. We focus on the overlap of the transmit and receive beams with parallel beamforming in reception.