Destruction of contrast microbubbles used for ultrasound imaging and drug delivery

Abstract

Microbubble contrast agent destruction by ultrasound pulse is useful in real‐time blood‐flow velocity measurement, stimulating arteriogenesis, or targeted drug delivery. We investigated in vitro destruction of contrast agent Definity (Bristol Meyer‐Squibb Imaging, North Billerica, MA) by measuring attenuation of ultrasound through it. The measurement is performed with single‐cycle bursts for varying pressure amplitudes at 50‐, 100‐, and 200‐Hz pulse repetition frequencies (PRF). At low excitation levels, the attenuation increases with time, indicating an increase in bubble size due to ingress of dissolved air from the surrounding liquid. With increased excitation levels, the attenuation level decreases with time, indicating destruction of microbubbles. A critical pressure amplitude (1.2 MPa) was found for all three PRFs, below which there is no significant bubble destruction. Above the critical excitation level, the rate of destruction depends on excitation levels. But, at high pressure amplitudes destruc...