High bandwidth, high density arrays for advanced ultrasound imaging

Nowadays, advanced ultrasound imaging such as contrast agent imaging, harmonic imaging, coded excitation or pulse inversion techniques require from ultrasound arrays higher performances than the standard state of the art. Then, higher bandwidth, higher resolution and better sensitivity have to be reached in order to improve image quality. In order to overtake standard performances, we use multilayer stack of passive materials with a volume controlled impedance gradient as acoustic front matching adaptation with 1-3 piezocomposite to develop both single element transducers and high density arrays exhibiting very high fractional bandwidth. The 3.5 MHz high density array manufactured with innovative matching design presents outstanding performances as compared to state of the art: 90% to 95% bandwidth distribution on all array elements, a minimized -1.2 dB sensitivity loss and an excellent -20 dB pulse duration equal to 2.3 /spl lambda/. We have reported results on a 3.5 MHz high density array, but this high bandwidth design could also be applied to higher pitch configurations or higher frequency design.