Passive detection method for synchronizing with resonant oscillations of bubbles

In medical ultrasound, microbubbles might be grown in a body fluid to create a bolus of high scattering fluid for study of circulatory or urinary tract dynamics. Microbubble creation and growth via rectified diffusion has been investigated for chirps with a temporally decreasing frequency to drive the growing bubbles at resonance. A method is considered for control of the ultrasound frequency and amplitude to maintain the bubbles at a desired size or growth rate. If the frequency of the ultrasound growth or maintenance field can be modulated over a significant portion of a bubble resonance curve, the modulation of the backscattered or transmitted waveform by the resonance can be used to keep the frequency centered on the resonance, and the amplitude can be adjusted to maintain the desired growth rate