Pulsed holmium laser ablation of tissue phantoms: correlation between bubble formation and acoustic transients |
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Authors: | T Asshauer G Delacrétaz ED Jansen AJ Welch M Frenz |
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Institution: | Institut d’Optique Appliquée, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland (Fax: +41-21-693 37 01, E-mail: guy.delacretaz@ioa.dmt.epfl.ch), CH Biomedical Engineering Program, University of Texas at Austin, Austin TX 78712, USA, US Institut für Angewandte Physik, Universit?t Bern, CH-3012 Bern, Switzerland, CH
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Abstract: | 5 Pa served as tissue phantoms to evaluate such effects. Holmium laser pulses (wavelength: 2.12 μm, duration: 180 μs FWHM),
were delivered through 400 and 600 μm diameter optical fibers inserted into cubes of clear gel. Bubble effects were investigated
using simultaneous flash micro-videography and pressure recording for radiant exposures of 20–382 J/cm2.
Bubble formation and bubble collapse induced pressure transients were observed regardless of phantom stiffness. Bubbles of
up to 4.2 mm in length were observed in gels with a Young’s modulus of 2.9×105 Pa at a pulse energy of 650 mJ. An increase of Young’s modulus (reduction in water content) led to a monotonic reduction
of bubble size. In the softest gels, bubble dimensions exceeded those observed in water. Pressure amplitudes at 3 mm decreased
from 100±14 bars to 17±6 bars with increasing Young’s modulus over the studied range. Theoretical analysis suggested a major
influence on bubble dynamics of the mass and energy transfer through the bubble boundary.
Received: 26 August 1996/Revised version: 10 February 1997 |
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Keywords: | PACS: 42 62 Be 62 50 +p 87 45 -k |
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