Progress in Development of HIFU CMUTs for use under MR-guidance

High intensity focused ultrasound (HIFU) guided by magnetic resonance imaging (MRI) is a noninvasive treatment that potentially reduces patient morbidity, lowers costs, and increases treatment accessibility. Traditionally, piezoelectric transducers are used for HIFU, but capacitive micromachined ultrasonic transducers (CMUTs) have many advantages, including fabrication flexibility, low loss, and efficient transmission. We designed, fabricated, and tested HIFU CMUTs for use under MRI guidance and have demonstrated continuous wave (CW) focusing. In this paper, we demonstrate that CMUTs can be designed for therapeutic ultrasound. First, we demonstrate successful unfocused heating of a HIFU phantom to 18.6°C, which was successfully monitored under MR guidance. Second, we demonstrated a focused CMUT array whose beam profile matched with simulation. In the future, we will expand the array and system for upper abdominal cancer therapy.