Theoretical gas body pulsation in relation to empirical gas-body destabilization and to cell membrane damage thresholds

Contrast agent gas bodies attached to phagocytic monolayer cells pulsate in response to ultrasound exposure and damage the cells above thresholds, which increase in proportion to frequency. This study considered the physical basis for the thresholds and their frequency dependence. Theory for the pul...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2004-12, Vol.116 (6), p.3742-3749
Main Authors: MILLER, Douglas L, CHUNYAN DOU
Format: Article
Language:English
Subjects:
Acoustics
Albumins - adverse effects
Cell Membrane - diagnostic imaging
Cells, Cultured
Contrast Media - adverse effects
Exact sciences and technology
Fluorocarbons - adverse effects
Fundamental areas of phenomenology (including applications)
Gases
Humans
Microbubbles
Models, Theoretical
Phagocytes
Physics
Shear Strength
Ultrasonography, Doppler, Pulsed - adverse effects
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Summary:Contrast agent gas bodies attached to phagocytic monolayer cells pulsate in response to ultrasound exposure and damage the cells above thresholds, which increase in proportion to frequency. This study considered the physical basis for the thresholds and their frequency dependence. Theory for the pulsation was evaluated using empirical pulse waveforms acquired at thresholds for 1.0, 2.25, 3.5, 5.0, 7.5, and 10 MHz. For optimum-sized gas bodies, the amplitudes calculated at the thresholds were about 11% of the initial radii. At the cell membrane damage thresholds, theoretical negative shell stresses were approximately constant with frequency at about 50 MPa. This stress appears to be sufficient to induce failure of the shell, and gas body destabilization was confirmed by increases in transmission of ultrasound pulses through the monolayer and by microscopically-observed shrinkage of the gas bodies. A model of acoustic microstreaming was used to calculate the shear stress during the pulses. The maximum shear stress increased from about 1500 to 4500 Pa from 1 to 10 MHz, sufficient for the cell membrane damage. This theoretical analysis shows that both the gas body destabilization and the cell membrane damage could be expected at similar peak rarefactional pressure amplitudes, with thresholds having the observed proportionality to frequency.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.1823212