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18 January 1995 Acoustic transients in pulsed holmium laser ablation: effects of pulse duration
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Proceedings Volume 2323, Laser Interaction with Hard and Soft Tissue II; (1995)
Event: International Symposium on Biomedical Optics Europe '94, 1994, Lille, France
The goal of this work was to study the influence of pulse duration on acoustic transient generation in holmium laser ablation. For this, the generation and collapse of cavitation bubbles induced by Q-switched and free-running laser pulses delivered under water were investigated. Polyacrylamide gel of 84% water content served as a model for soft tissue. This gel is a more realistic tissue phantom than water because it mimics not only the optical properties but also the mechanical properties of tissue. The dynamics of bubble formation inside the clear gel were observed by 1 ns time resolved flash videography. A polyvinylidenefluoride (PVDF) needle probe transducer measured absolute values of pressure amplitudes. Pressure wave generation by cavitation bubble collapse was observed in all phantoms used. Maximum pressures of more than 180 bars at 1 mm from the collapse center were observed in water and high water-contents gels with a pulse energy of 200 mJ and a 400 micrometers fiber. A strong dependency of the bubble collapse pressure on the pulse duration for constant pulse energy was observed in gel as well as in water. For pulse durations longer than 400 microsecond(s) a 90% reduction of pressure amplitudes relative to 100 microsecond(s) pulses was found. This suggests that optimization of pulse duration offers a degree of freedom allowing us to minimize the risk of acoustical damage in medical applications like arthroscopy and angioplasty.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Thomas Asshauer, Guy P. Delacretaz, E. Duco Jansen, Ashley J. Welch, and Martin Frenz "Acoustic transients in pulsed holmium laser ablation: effects of pulse duration", Proc. SPIE 2323, Laser Interaction with Hard and Soft Tissue II, (18 January 1995);

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