Abstract
Using a long-distance microscope imaging system and a technique using a movable lock-in pulse laser, optical measurement demonstrated the behavior of a SonoVue® contrast agent microbubble exposed to a low-amplitude, 478 kHz ultrasound field. The microbubble consisted of the gas SF6 encapsulated by a polymer shell. Eighty-four frames of a microbubble oscillating in response to an ultrasound field were captured in one acoustic cycle. The experimental data on microbubble radius were fitted by the numerical calculations of the Hoff, Yasui, and Keller–Miksis models. The results showed good agreement between the data and the theoretical calculation of the Hoff model using our experimental parameters. In addition, the spectral analysis of the time-radius data indicated that the relative intensity of the second harmonic increased with the increase in acoustic pressure amplitude.