Temperature generation of ktp and nd:yag lasers while applied on rat liver

As the laser produces its biological effects on tissue converting the light energy into heat energy, we experimented the effectiveness of KTP laser in cutting liver tissue in comparison to Nd:YAG by recording and evaluating the generated heat during application on rat liver. Eleven -week old male Wistar rats were used in the experiment. Comparisons were made at different energy levels (5-14 watts) at different time limits (1-8 sec). Only noncontact (working distance 5 mm) application was used. The KTP/YAG Surgical Laser System (Laserscope®, California), was used with a 0.4 mm diameter bare fiber for both KTP and Nd:YAG laser delivery. The temperature generation during the application was recorded by a Thermotracer® (TH1000, Nippon Denki Sanei, Tokyo), which had a recordable temperature range from 100 to 600°C. Temperatures at the center of lesions as well as 0.25, 0.50, 0.75, 1.00 and 1.25 mm from the center for every seconds through 1st to 8th were recorded. In case of KTP, temp. at the beginning was much higher than at the 8th sec. As for example the temp at the center of the lesions at 2nd sec. for 5 watt of KTP was 287.53±22.56 whereas for YAG was 129.16±26.02 (P value is <0.001). But the temp at the center at 8th sec for 5 watt of KTP was 327.52±37.12 and that for YAG was 271.28±28 (P values are <0.05). Analysis of the result showed that the KTP had always a rapid and faster rise of temperature at the center than YAG. At the other 5 points of recording, KTP and YAG showed little differences in radiation of temperature laterally. KTP shows a sharper lateral fall of temperature despite a greater temperature at the center than those of YAG. To justify the above results we have experimented the absorption of both lasers light in bile juice, blood, the two major liquid components of liver and blood contents such as plasma and serum. We also studied the absorption and transmission of light in the same materials of different wavelengths by a spectrophotometer. All the results showed a greater and remarkable absorption of KTP laser in blood and bile juice, which causes a greater heat production and less scatter.The above results justified the faster and sharper cutting effects of KTP laser on rat liver in comparison to that of YAG laser.