Study Of Cr, Tm, Ho:YAG Laser System Used In Ureteral Calculi Lithotripsy

The dominating mechanism of the Cr,Tm,Ho:YAG laser lithotripsy is photothermic effect. The laser beam irradiates the calculi and produces high temperature, which leads to the chemical decomposition of the ureteral calculi, and then smashes the calculi. Contrast to other pulse laser lithotrities, which ground on photomechanical effects, such as laser induced plasma and cavitations, Cr,Tm,Ho:YAG laser lithotripter has many advantages. It will be an important therapy to the ureteral calculi.This paper introduces several therapies in current to the ureteral calculi, and discusses the mechanisms and advantages of the Cr,Tm,Ho:YAG laser lithotripter in detail. We analyzed the pump mechanism of the laser crystal and the sensitization effects of Cr3+ ion and Tm3+ ion. The parameters of single ellipse cavity were optimizing designed, and the coupling efficiency along with the pump energy distribution was analyzed. We also chose the material of reflection layer of the pump cavity. We emulated the discharge circuit of the pulse xenon lamp, and designed the PFN (Pulse Forming Network). We studied dynamical resonator and designed the optimum resonator. A semiconductor refrigerator was used in the cooling system and a new idea to seal and dry the laser rod and mirrors was presented and relatively ideal results were obtained when this idea had been applied in the experiments. Based on the above, a Cr,Tm,Ho:YAG laser system for ureteral calculi lithotripsy was successfully made.Based on this laser, we had carried out a number of experiments, and analyzed the effects of some factors upon the output properties of the laser, such as the temperature,the transparent rate of output mirror,the wave shape of discharge,the duration of flash lamp pulse,the pump density and etc. We found out that the output properties of the laser are closer related with the temperature. The effect of temperature variation upon the threshold and slope efficiency of laser is emphatically analyzed. It is discovered that different discharging conditions apparently influences on laser output. The selective absorption of this kind of laser material for pump light and the difference radiation spectrum of the lamp which is related with the discharging conditions result in this kind of phenomenon. At last, the prospective work is put forward.