Design and evaluation of a transrectal phased piezoelectric micromachined ultrasound transducer (pmut) array for thermal treatment of prostate cancer

This paper describes a simulation study of designing a two-dimensional (2D) ultrasound phased piezoelectric micromachined ultrasound transducer (PMUT) arrays to be used for thermal treatment of prostate cancer.With 2D phased PMUT arrays, the location of the focal point can be precisely controlled by varying the elements' driving information (phase and power) which gives the ability to generate focal points and steer them electronically in a three-dimensional volume. Compared to piezoelectric (PZT) ultrasound transducers, PMUTs cost less, need less power to drive, smaller in size, and better in acoustic impedance matching. Different frequency/diameter pairs were considered in the study. For each frequency/diameter pair, different 2D arrays of size m x m was considered where each element in the array was considered a thin circular clamped plate. For each case, the maximum depth of penetration (DOP) and the maximum possible steering angle were reported. Optimal designs, that took into consideration PMUT parameters and prostate physical parameters, were sought. The study concluded that in order to achieve a PMUT array design that can generate focal points and fully steer them in the whole prostate (a steering angle of at least 21.25° and a maximum DOP of at least 4.5 cm), the optimal PMUT design must operate at a frequency less than 0.75 MHz and it must include at least 90 x 90 elements. Thus, the proposed technique allows for far distance ablation non-invasively and with higher steering angle ranges by using small size PMUT array.