The 1.320 micron Nd-YAG laser. Experimental study of a new wavelength adapted to neurosurgery

The authors present a new laser wavelength for neurosurgery: the 1.32 micron Nd-YAG laser. Schematically, it combines the advantages of both the 1.06 micron Nd-YAG laser and the CO2 laser. As for nervous tissue it has the same physico-thermal properties as the CO2 laser: an important absorption and little thermal diffusion. Like the 1.06 Nd-YAG laser, the 1.32 Nd-YAG has very good maneuverability, because its beam is conducted through optical fibers. Experimental studies have been made on rats. They consisted of comparison between the thermal effects and the consequent histological lesions of three lasers: 1.32 micron Nd-YAG, 1.06 micron Nd-YAG, CO2. 145 impacts on the cortex of 45 rats have been studied. Each shot was registered with an infrared camera, measuring the cortex surface temperature around the impact. The signals were digitalized; they allowed us to obtain a numerical image and the profile of temperature for each shot, as well as the development of temperature of each point of the profile. These results have been correlated with the histological data. It appears that for equivalent efficient outputs, the cortical lesions, 8 days after the shots, were similar for the 1.32 Nd-YAG laser and the CO2 laser. For instance, the depth of the coagulation necrosis varied from 200 to 250 microns after CO2 laser impacts (P = 3W; t = 0 05s; Fluence = 5 Joules/cm2), and from 210 to 260 microns after 1.32 Nd-YAG laser impacts (P = 5-14W; t = 0.4s; F = 50-170 J/cm2).(ABSTRACT TRUNCATED AT 250 WORDS)