High frequency transducer arrays for medical imaging

This paper discusses the design, fabrication, testing, and simulated imaging performance of high frequency linear arrays. Both a 2-2 PZT composite array with a fine spatial scale and a PbTiO3 array have been investigated at 30 MHz. The composite array demonstrated a seven-fold increase in sensitivity over the PbTiO3 array, as well as increased bandwidth and reduced crosstalk. The electrical impedance magnitude of the composite array was 56 ohms at 30 MHz, and the measured insertion loss was -14 dB. Simulated results demonstrate excellent lateral and axial resolution when imaging a phantom using a synthetic aperture approach. A 35 MHz device is also under development. An interconnect method using a flex circuit and sputtered metal films is used to electrically connect to each element. A curve fitting technique was then used to characterize elements of the array. Electromechanical coupling coefficients from 0.55 to 0.62 and clamped relative permittivities (epsilon(33)(S)'/epsilon(0)) from 1200 to 2000 were observed.