Although the CO2 laser radiation has a very short absorption length in living tissue, it can still cause extended damage around the incision. In order to reduce thermal damage in the tissue, one can optimize the irradiation parameters of the laser. Anoter method for reducing the thermal damage is to find a way to cool the tissue. We were able to show that the thermal damage surrounding a crater made by a pulsed CO2 laser may be reduced by irradiating the tissue under water. However, we first had to overcome the high absorption of the water layer. We used a pulsed laser beam of high energy and high repetition rate to create a stationary cavity in the liquid. Through this cavity the beam is transmitted to the material to be treated. Using a simplifid model, we found that the height of the cavity depends on the repetition rate and pulse energy of the beam but not on the pulse width. We also found that the temperature rise in the liquid surrounding the cavity increases with pulse width. In a series of experiments performed in bovine cornea, we found that the thermal damage surrounding the incision caused by a CO2 laser beam was significantly reduced when the tissue was irradiated under water, applying the cavity mode of beam transfer.

Date Published: 1 June 1990
PDF: 7 pages
Proc. SPIE 1202, Laser-Tissue Interaction, (1 June 1990);

Published in SPIE Proceedings Vol. 1202:
Laser-Tissue Interaction
Steven L. Jacques, Editor(s)