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 (ε₃₃^S,/ε₀) from 1200 to 2000 were observed.