Encapsulated contrast microbubble radial oscillation associated with postexcitation pressure peaks

• Published in: The Journal of the Acoustical Society of America Vol. 127; no. 2; pp. 1156 - 1164
• Main Authors: Santin, M. D., King, D. A., Foiret, J., Haak, A., O'Brien, W. D., Bridal, S. L.
• Format: Journal Article
• Language: English
• Published: Melville, NY Acoustical Society of America 01-02-2010; American Institute of Physics
• Subjects: Albumins; Algorithms; Bioacoustics; Biological and medical sciences; Cardiovascular system; Computer Simulation; Contrast Media; Fluorocarbons; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Microbubbles; Models, Theoretical; Periodicity; Phospholipids; Pressure; Sulfur Hexafluoride; Time Factors; Ultrasonic investigative techniques; Ultrasonics; Radial vibration; Bubble; Contrast media
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.3277216

This work combines modeling and experiment to assess encapsulated microbubble oscillations associated with broadband pressure peaks detected after microbubble excitation (postexcitation signals). Data were acquired from albumin-shelled and phospholipid-shelled microbubbles using a passive cavitation detector consisting of a confocally aligned 2.8-MHz transmitter and 13-MHz receiver. Microbubbles in weak solutions were insonified with a 5-cycle pulse at a peak rarefactional pressure of
2.0
±
0.2

MPa
. For each microbubble type, at least 100 received signals were identified as individual-microbubble responses. The average broadband noise from signals with postexcitation response was 4.2-7.2 dB higher than from signals without postexcitation. Pressure-time responses for each microbubble type were simulated using the model by
Marmottant
[
J. Acoust. Soc. Am.
118
,
3499-3505
(
2005
)]
, with insonification conditions matching the experiment. Increased broadband noise predicted for microbubbles with postexcitation response was consistent with that observed experimentally (4.0-8.9 dB). The model predicted that postexcitation signals occur only when the radial oscillation exceeds both the shell break-up threshold and twice the initial radius (free bubble inertial cavitation threshold).