On sensitivity and surface temperature of multilayered linear ultrasound phased array for medical imaging: Modeling, prototyping and experiments

The advantages of the multilayer ultrasound transducers (MLT) compared to classic single layer transducers (SLT) are lower electrical impedance and better signal-to-noise ratio (SNR). These properties were emphasised in the last two decades. However, to our knowledge, unbiased receiving relative sensitivity results as well as surface temperature experiments for SLT and MLT based on similar piezoceramics were not reported to date. The present paper comparatively investigates designing and measuring of CTS 3203HD based SLT and MLT transducers for high sensitivity, fine pitch 2.5 - 3.3 MHz 128 elements ultrasound phased array. The effect of a parallel resistor heat sink on decreasing surface temperature is also being addressed. Good correspondence between finite element simulations and measurements was found for all the parameters investigated with differences less than 10 %. The manufactured adhesive bonds were thin enough to be acoustically invisible within the bandwidth of interest. The MLT prototype had a 67 % higher transmit relative efficiency, similar relative receiving sensitivity but for 32% less applied voltage, 4.5 dB better SNR compared to SLT one. Due to a much lower equivalent resistance, MLT elements have a higher current draw than SLT ones. Parallel resistors are decreasing the self-heating and improve the electromechanical performance.