Abstract
Nd-YAG laser cannot be observed under usual conditions as it is an invisible beam, but it has been recognized that Nd-YAG laser beams could be seen in color by means of a semiconductor TV camera while cautery of early gastric cancer is being performed under gastrofiberscopic observation using the beams. This laser beam observed with the TV was green. The intensity of the green beam seemed to correlate with the output of the laser. Liver of pig and early gastric cancer were observed and recorded on a VTR during the laser cautery. This system made it possible to identify the irradiation focus of the laser. Furthermore, the risk to the eyes of technicians making the observation is extremely small, indicating that this method is very useful.
