The method of laser intracorporal lithotripsy is now being used in medical practice1 .In this method, laser radiation destroying the stones is transported into human body through fibers.The necessary condition for efficient destruction is that laser radiation is absorbed in the stone material4. However, the lasers used for this purpose, in particular, dye lasers, alexandrite and neodimium lasers, emit in visible and near infra-red ranges where many types of stones absorb slightly and cannot be destroyed by laser radiation.Another option is to use erbium lasers for intracorporal lithotripsy whose wavelengths are about 3 micron and their radiation is strongly absorbed in water and almost in every type of stones6.In our previous work we have studied destruction of gall stones by the radiation of Er:Cr:YSGG laser with the wavelength 2.79 micron without fibers5. The radiation was focused into spots 0.2 to 0.4 mm onto stones. it was demonstrated that fragmentation of stones by this radiation runs very efficiently.in this paper we report the results on destruction of several types of stones in aqueous media by radiation of Er:YSGG laser transported through fibers, i.e. under the conditions simulating those of human body. The lasers operated in both Q-switched mode and in free Easing.For experiments, we have used fluoride and quartz fibers with core diameters 0.2 and 0.4 mm respectively.Fluoride fiber as long as about one meter transmits not less than 80% of incident radiation and exhibits good strength (it survives bending with curvature radius about 2 cm) . Quartz-quartz fiber with polymer cladding was made of dried quartz in Institute of General Physics. Transmission of a 0.5-rn piece was up to 50%.The laser used Cr:Er:YSGG rod (diameter 4 mm, length 75 mm) , concentrations of Cr and Er ions were 2.1020 and 4.7.1021 cm3 respectively. Both free lasing and Q-switched modes were tried, pulse durations being about 100 microsecond and 100 nanosecond respectively. Repetition rates were from I to S Hz. Radiation was put into fibers with use of a fluoride lens with focal length 20 mm.Urinal stones can be destroyed either by direct effect of laser radiation1 or by the acoustic shock waves3 produced when laser radiation gets absorbed in a thin layer of water near the fiber end face. When the fiber end face touches the stone, direct ablation mechanism is dominant and a slight pressing of the fiber against the stone results in a sort of drilling. If the distance between the fiber end face and the stone surface is greater than the thickness of the water layer that can be made transparent by laser radiation1, the destruction runs due to the shock waves. Also, the two factors can appear simultaneously for certain values of the distance.The mass of material Aj'n removed by ablation was determined from the volume of cavities produced by laser radiation and the stone's density, the volumes having been measured using a microscope. Fig.1 shows the dependence of the reciprocal efficiency of destruction 1/,(Y'Arn versus the laser pulse ene...
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