Evaluation of capacitive micromachined ultrasonic transducers for passive monitoring of microbubble-assisted ultrasound therapies

Abstract

Passive cavitation detection can be performed to monitor microbubble activity during brain therapy. Microbubbles under ultrasound exposure generate a response characterized by multiple nonlinear emissions. Here, the wide bandwidth of capacitive micromachined ultrasonic transducers (CMUTs) was exploited to monitor the microbubble signature through a rat skull and a macaque skull. The intrinsic nonlinearity of the CMUTs was characterized in receive mode. Indeed, undesirable nonlinear components generated by the CMUTs must be minimized as they can mask the microbubble harmonic response. The microbubble signature at harmonic and ultra-harmonic components (0.5-6 MHz) was successfully extracted through a rat skull using moderate bias voltage.

Lumped-Parameter Equivalent Circuit Modeling of CMUT Array Elements

“…To close this section, it is interesting to discuss other possible exploitation of the lumped-element representation which, even if evident, provides a clear insight into the parameters that are relevant to the desired application. In addition to the common pulse-echo imaging applications, therapeutic applications [62] and passive acoustic imaging [63], [64] could be adressed specifically. For therapeutic purposes, the output quantity is the mean radiated acoustic power only.…”