Ultrasonic 2D matrix array transducer for volumetric imaging in real time

Matrix array transducers have been developed in this work for cardiac imaging in real-time and 3D. The matrix array transducers have 4,096 (64×64) active elements made of the piezoelectric single crystals, PMN-PT, within 1 inch square. Two different matrix array structures have been developed: (1) fabrication of whole 64×64 elements as a single unit on a PMN-PT plate with a conductive backing, and (2) assembly of eight 64×8 element modules to compose 64×64 channels. Optimal structures of the two matrix array transducer types have been determined through finite element analysis to have their center frequency at 3.5 MHz and fractional frequency bandwidth over 60%. In the single unit structure, it was very difficult to achieve good enough uniformity over the whole 4,096 elements, which was likely to cause serious difficulty in production of the transducer. The acoustic module assembly technique was developed to resolve the problem. In case some elements showed big deviation in performance due to mistakes in fabrication, that particular module containing the bad elements could be easily replaced with a good one. However, the module assembly method necessitated more complicated fabrication processes. Fabricated prototypes of the transducers satisfied the design specifications very well.