7 August 1992 Influence of holmium:YSGG intensity on bubble formation in saline and in tissue
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Proceedings Volume 1646, Laser-Tissue Interaction III; (1992) https://doi.org/10.1117/12.137473
Event: OE/LASE '92, 1992, Los Angeles, CA, United States
Abstract
Previous studies of mid-infrared ablation of tissue showed blast damage to adjacent tissue in the form of large fissures extending from the crater wall. We hypothesized that these fissures are due to the forceful expansion of a water vapor bubble within tissue. Time resolved flash photography documented an expanding vapor bubble within the tissue by the elevation of the tissue surface. The aim of this study was to determine the relation between the intensity of holmium:YSGG laser irradiation and bubble dimension in saline and in tissue. The influence of the spatial distribution of the intensity was determined by delivering 200 to 500 mJ laser pulses through a 320 micrometers and 600 micrometers diameter bare fiber, which was in light contact with porcine aorta. A holmium:YSGG laser pulse is a superposition (500 microsecond(s) long) of microsecond pulses. The first part of the laser pulse contains the most intense spikes. To determine the influence of the high peak power spikes on bubble formation, the first part of a 650 mJ laser pulse was absorbed. The modified laser pulse (400 mJ) was smoother and 75 microsecond(s) shorter than the original 400 mJ laser pulse. Increasing the fiber tip area by a factor of 3.5 (600 micrometers vs. 320 micrometers diameter) resulted in a decrease in the diameter of tissue elevation by only a factor of 1.25, indicating that the delivered energy determined the extent of tissue elevation. Elimination of the high peak power of the first part of the laser pulse did not decrease the dimension of the bubble in saline and of the tissue elevation. Therefore we anticipate that the extent of the blast damage in tissue cannot be reduced substantially by either reducing the fluence or by quenching high peak power spikes of the laser pulse.
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Ton G. J. M. van Leeuwen, Ton G. J. M. van Leeuwen, Rudolf M. Verdaasdonck, Rudolf M. Verdaasdonck, Cornelius Borst, Cornelius Borst, } "Influence of holmium:YSGG intensity on bubble formation in saline and in tissue", Proc. SPIE 1646, Laser-Tissue Interaction III, (7 August 1992); doi: 10.1117/12.137473; https://doi.org/10.1117/12.137473
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