The Development of Cooling Laser Irradiation Device

The Nd-YAG laser, which is known to penetrate tissues well and is within the infrared wavelength, mainly produce tissue coagulation and vaporization with heat. Through preliminary experiments, it was found that by cooling the tissue surface, only the deep area forms the various shapes of laser coagulation corresponding to different irradiation pattern and different cooling environment, even though no change can be detected on the tissue surface with naked eyes. The device manufactured for this research, named Cooling Laser Irradiation Device, consists laser irradiation part, water circulation pump with a constant temperature apparatus, and a super-high sensitivity video monitor. This device selectively forms desired shape of coagulation in the deep tissues while the surface remains undamaged. Under video observation, the convex lens tip can slide smoothly over the concerned lesion while maintaining contact with the surface tissue. Adjustable irradiation pattern of the laser beam can be applied to the tissue surface while its temperature is controlled by the flow velocity and temperature of the cooling water. With the use of the Cooling Laser Irradiation Device, the temperature distribution of the deep tissue was analyzed using multiple thermo-coupling system. In the future, this device will contribute significantly in the development of less, or even non-invasive surgery.