Therapeutic ultrasound phased arrays: practical consideration and design strategies

Focused high-intensity ultrasound is used for a wide range of therapeutic applications including hyperthermia cancer therapy, myocardial ablation, drug delivery/drug activation, and ultrasound surgery. Although many different applicators are capable of generating acceptable power levels for ultrasound therapy, multiple element arrays offer the most flexible option for ultrasound power delivery. The various engineering and economic trade-offs, which optimize the phased array aperture with respect to the channel count, usually result in element sizes which are far from ideal. These array elements excite lateral modes, which reduce the electric to acoustic efficiency significantly (down to 10-20%). This problem can be solved with piezo-composite technology. Piezo-composite transducers resonate cleanly in the thickness mode with 55-65% efficiency, producing sufficient power for thermal therapy.