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ABSTRACT: We study non-spherical oscillations (surface modes) of the coated microbubbles used in ultrasound contrast agents. We show that an acoustic pressure of 100 kPa, at a frequency of 1.7 MHz, is sufficient to excite surface modes for radii between 2 and 4 mum. Surface modes develop as a parametric instability. We derive their evolution equation accounting for the effect of the shell viscoelasticity. We identify a critical radius (1 to 3 mum, depending on the mode number) below which no surface mode can occur
Ultrasonics Symposium, 2006. IEEE; 11/2006
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ABSTRACT: Here we present optical tweezers as a micromanipulation tool for the study of ultrasound contrast agent (UCA) microbubbles. Optical trapping and the resulting manipulation of individual and multiple microbubbles enables the study of their dynamics with controlled boundary conditions. The bubble response to ultrasound is recorded optically using the ultra high-speed Brandaris 128 camera. In our experiments, the amplitude of bubble oscillations was found to be strongly influenced by the vicinity of the sample chamber wall. Experiments with two trapped bubbles also showed a considerable influence of the neighboring bubble on the amplitude of oscillations of the other one
Ultrasonics Symposium, 2006. IEEE; 11/2006
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Ultrasonics Symposium, 2005 IEEE; 10/2005
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ABSTRACT: We have investigated surface vibrations generated by ultrasound excitation of individual unencapsulated micron-sized bubbles. In addition, we present surface modes (n=2 and 3) observed for phospholipid-coated ultrasound contrast agents excited through excitation of radial modes at frequencies between 1 and 4 MHz. Even higher modes of vibration (up to mode 5) are observed for coated microbubbles at insonation frequencies of 10 and 19 MHz. The potential relevance of surface modes for medical ultrasound is discussed, including the possible implications for current theoretical models of ultrasound contrast agents.
Ultrasonics Symposium, 2004 IEEE; 09/2004
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ABSTRACT: The resonance frequencies of individual SonoVue™ contrast agent bubbles were measured optically by recording the radius-time curves of a single microbubble at 24 different frequencies. For these experiments, the Brandaris 128 fast framing camera was operated in a special segmented mode. The resonance frequencies found for SonoVue™ microbubbles are in good agreement with the modified Herring model for coated bubbles indicating that the shell only slightly affects the resonance frequency of this class of contrast bubbles.
Ultrasonics Symposium, 2004 IEEE; 09/2004
