Effect of laser-induced hydrodynamic dissection of biotissue in operative urology

We study the effects that occur in a physiological solution when laser radiation with a wavelength of 1.94 μm and a power of 60–120 W is delivered into it through an optical fibre. It is shown that as a result of the boiling of the liquid near the fibre end, a laserinduced hydrodynamic effect can be realised, in which a two-phase jet is formed, consisting of heated water and vapour-gas bubbles propagating at a speed of ~1 m s^-1. This jet can be used in medicine for dissecting biological tissues when removing a bladder tumour as a single unit, for dissecting the stricture of the ureter or urethra, and for enucleation of the prostate adenoma (hyperplasia). The use of this effect allows pathological tissue to be accurately separated from the underlying layer, virtually eliminating carbonisation and the formation of viable tumour fragments, which can lead to tumour dissemination. The characteristics of a laser-induced jet, which determine the nature of its effect on biological tissues, are studied experimentally, and the optimal regimes of laser irradiation are found. It is shown that the jet parameters most effective for hydrodynamic dissection of biological tissue are implemented using a radiation power of 120 W at a distance of ~3 mm from the fibre end.