Water-jet-cooled Nd:YAG laser coagulation: selective destruction of rat liver metastases.

The photocoagulating properties of the water-jet-cooled Nd:YAG laser (1,064 nm) have been studied in a rat tumor model. A colon carcinoma CC531 was implanted in the liver; 20 days after inoculation, laser therapy was performed with 600 J, 850 J, 1,200 J, 1,700 J, or 2,400 J at a power setting of either 10 or 20 W. Liver damage was determined in tissue specimen on day 1 after treatment and by serum levels of alanine aminotransferase and aspartate aminotransferase on day 1 and 2. Tissue specimen of day 36 were used to evaluate tumor remission. Liver function was assessed by antipyrine clearance on day 2. Light microscopic examination on day 1 showed coagulative necrosis up to 10 mm in diameter at 1,700 J and 20 W. At 20 W, liver damage was 22% larger than at 10 W (P = 0.0001). A significant relationship was found between laser energy and liver damage with complete tumor destruction in all animals at 2,400 J. No deterioration in liver function was found. The results of this study show the ability of the water-jet-cooled Nd:YAG laser to produce tumor coagulation necrosis with minor liver damage.