Thresholds for inertial cavitation in Albunex suspensions under pulsed ultrasound conditions

Stabilized microbubbles used as echo-contrast agents can be destroyed by ultrasonic irradiation. We have identified two pressure thresholds at which these microbubbles undergo inertial cavitation (here, defined as the collapse of gas bubbles followed by emission of an acoustic broadband noise). The...

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Bibliographic Details
Published in:IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2001-01, Vol.48 (1), p.161-170
Main Authors: Chang, P.P., Wen-Shiang Chen, Mourad, P.D., Poliachik, S.L., Crum, L.A.
Format: Article
Language:English
Subjects:
Acoustic emission
Acoustic measurements
Acoustic noise
Acoustic pulses
Acoustic scattering
Acoustical measurements and instrumentation
Acoustics
Albumins - chemistry
Biological and medical sciences
Cardiovascular system
Cavitation
Contrast agents
Contrast Media - chemistry
Drug Delivery Systems
Exact sciences and technology
Frequency
Fundamental areas of phenomenology (including applications)
Hemolysis
Humans
Inertial
Investigative techniques, diagnostic techniques (general aspects)
Medical sciences
Microorganisms
Microspheres
Physics
Pressure
Pulse measurements
Suspensions
Thresholds
Ultrasonic imaging
Ultrasonic investigative techniques
Ultrasonic variables measurement
Ultrasonography - methods
Ultrasound
Underwater sound
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Summary:Stabilized microbubbles used as echo-contrast agents can be destroyed by ultrasonic irradiation. We have identified two pressure thresholds at which these microbubbles undergo inertial cavitation (here, defined as the collapse of gas bubbles followed by emission of an acoustic broadband noise). The first threshold (P1) corresponds to the pressure at which all the microbubbles in a cavitation field lose their property as an effective scatterer because of fragmentation or deflation. The second threshold (P2) is associated with the acoustic reactivation of the remnants of the contrast agents and is related to the onset of more violent inertial cavitation. P1 and P2 were measured as a function of the concentration of Albunex(R) (Molecular Biosystems Inc., San Diego, CA) contrast agent, the number of transmitting acoustic cycles, and the pulse repetition frequency (PRF). The ultrasound frequency used was 1.1 MHz, and the peak negative acoustic pressures ranged from 0 to 8 MPa. Our results, measured in Isoton(R) II (Coulter Diagnostics, Miami, FL) and whole blood solutions, showed that P1 increased with increasing Albunex(R) concentration and decreased with increasing PRF, whereas P2 decreased with increasing Albunex(R) concentration and was independent of the PRF. Both P1 and P2 decreased with increasing number of acoustic cycles N for N10. Ultrasound images of Albunex(R) acquired by a commercial scanner showed echo enhancement not only at pressure levels below P1 but also at levels above P2. The threshold P2 was achieved at ultrasound energies above the diagnostic level. Inertial cavitation produced at P2 was associated with a higher level of hemolysis compared with P1. The results of this investigation have potential significance for both diagnostic and therapeutic ultrasound applications.
ISSN:0885-3010
1525-8955
DOI:10.1109/58.895927