Comparative investigations of the effects of the neodymium:YAG laser at 1.06 microns and 1.32 microns on tissue.

The beneficial deep homogeneous coagulation of neodymium (Nd):YAG laser radiation at 1.06 microns owing to low absorption and high scattering in tissue has been documented widely. For another Nd:YAG laser wavelength at 1.32 microns the absorption coefficient of water and saline is approximately ten times higher than at 1.06 microns. This results in more efficient energy conversion into heat in tissue at 1.32 microns. The extinction coefficient in blood at 1.32 microns is only one-third of that at 1.06 microns. We would expect this to result in less heat dissipation by blood and deeper penetration in tissue at 1.32 microns. Nevertheless, at this wavelength scattering also contributes to an effective, uniform distribution of the laser light in the tissue. Animal experiments have been done to examine the effect of wavelength, irradiation time, and beam geometry on tissue damage and to assess its possible clinical uses. The results imply that the 1.32 microns wavelength will produce further indications for the use of the Nd:YAG laser in surgery.