HOLLOW WAVE-GUIDES FOR CO2-LASER RADIATION IN OPERATIVE LAPAROSCOPY -AN IN-VITRO STUDY

The purpose of this study was to compare the transmission and incision properties of two different CO2 laser radiation delivery systems: the Hopkins(R) CO2 laser laparoscope and the hollow waveguide, respective ly, in view of a practical use of the latter in laparoscopic surgery, Using a CO2 gas flow rate of 4 L/min, the waveguide delivers CO2 laser power between 10 and 50 watts (W) to tissue with significantly less i ntensity loss than the laparoscope (9-15% and 33-40%, respectively). T he laparoscope emits radiant energy with the most fundamental TEM00 mo de, In contrast, because of loss of coherence and collimation, the out put beam profiles of the waveguide is characterized by a quasi-top-hat function with sharp edges and hot spots randomly distributed over the beam. Histologic tissue analysis on fresh uterine tissue of the pig r evealed significantly greater incision depths for lesions created with the waveguide, and no enlargement of tissue spot-size at higher power settings. The extent of thermal damage adjacent to the laser incision did not differ between the two delivery systems tested, In comparison to the Hopkins(R) laparoscope, the hollow waveguide delivers CO2 lase r radiation with less absorption and without a ''blooming'' effect by the CO2 insufflation gas, These advantageous transmission properties r ender possible higher power and power density at tissue level, and thu s a more precise and efficient cutting in the power range needed for m ost laparoscopic surgical applications.