Beamforming for 3D Transesophageal Echocardiography

In this thesis, we study beamforming techniques that offer opportunities for 3D transesophageal echocardiography imaging, especially to achieve higher frame rates. In 3D TEE with a matrix transducer, two main challenges are to connect a large number of elements to a standard ultrasound system and to achieve a high volume rate (>200 Hz). We develop a prototype miniaturized matrix transducer for pediatric patients with micro-beamforming to reduce the channel count. Initially, we propose two dual stage beamforming techniques for 1D arrays to produce high-quality images with reduced channel count: one using fixed focused receive and another with a simple summation in receive (no delays). Because of their inapplicability to the prototype transducer, we propose multiline 3D ultrasound beamforming schemes that utilize the micro-beamforming capabilities. The proposed beamforming schemes use an angle-weighted combination of the neighboring overlapping sub-volumes to suppress the crossover artifacts that are typical for parallel beamforming and produce high-quality images at a high volume rate (~300 Hz). A similar beamforming scheme adapted for a newly designed prototype matrix adult TEE probe is used for in vivo 3D imaging of the heart of a healthy adult pig to produce good quality 3D images at a high frame rate. The proposed 3D beamforming scheme can easily be adapted for matrix probes with micro-beamforming capabilities to produce good quality volume images at a high volume rate, even for a very different layout of the transmit and receive arrays.