Hybrid multi/single layer array transducers for increasedsignal-to-noise ratio

摘要

In medical ultrasound imaging, two-dimensional (2-D) arrayntransducers are necessary to implement dynamic focusing in twondimensions, phase correction in two dimensions and high speed volumetricnimaging. However, the small size of a 2-D array element results in ansmall clamped capacitance and a large electrical impedance, whichndecreases the transducer signal-to-noise ratio (SNR). We have previouslynshown that SNR is improved using transducers made from multi-layer PZT,ndue to their lower electrical impedance. In this work, we hypothesizenthat SNR is further increased using a hybrid array configuration: in thentransmit mode, a 10 Ω electronic transmitter excites a 10 Ωnmulti-layer array element; in the receive mode, a single layer elementndrives a high impedance preamplifier located in the transducer handle.nThe preamplifier drives the coaxial cable connected to the ultrasoundnscanner. For comparison, the following control configuration was used:nin the transmit mode, a 50 Ω source excites a single layernelement, and in the receive mode, a single layer element drives ancoaxial cable load. For a 5×102 hybrid array operating at 7.5 MHz,nmaximum transmit output power was obtained with 9 PZT layers accordingnto the KLM transmission line model. In this case, the simulatednpulse-echo SNR was improved by 23.7 dB for the hybrid configurationncompared to the control. With such dramatic improvement in pulse-echonSNR, low voltage transmitters can be used. These can be fabricated onnintegrated circuits and incorporated into the transducer handle