Synchronized sine-sweep imaging for uncoupling nonlinear signatures during pulse compression

Cavitation mapping is a reliable tool to monitor therapeutic ultrasound applications based in microbubbles. However, when the temporal duration of the transmitted pulses is long, the acoustic emission of the bubbles extends in time, and it becomes difficult to generate sharp acoustic cavitation images. In this work, we present a method based on long synchronized sine-sweep pulses that enable the separation of individual impulse responses to produce sharp cavitation images and increases the signal-to-noise ratio. By uncoupling nonlinear signatures, the method allows the separation of pulse-compressed impulse responses for the linear response and for each harmonic component. In this way, using synchronized sine-sweep, the cavitation of microbubbles under the action of a therapeutic transducer can be mapped with accuracy and with a robust signal-to-noise ratio. This pulse compression method enables the harmonic localization for nonlinear cavitation mapping, enabling the individual imaging of nonlinear signatures of cavitating bubbles. The cavitation images allow to identify the real focal spot of a therapeutic transducer, and the nonlinear signatures offers quantitative information about the stable or inertial regime of the cavitating bubble.