Research On High Power 532nm Laser And Its Application In Urological Surgery

With the improvement of our living standards and the rapid increase of agingpopulation, disease of urinary system, such as benign prostate hyperplasia (BPH), urethrastricture, bladder tumor, is seen with an increasing frequency in elderly men. The lowerurinary tract symptoms (LUTS) have become a common and multiple disease thatsignificantly affect man's health. Therefore it is very important to treat the disease ofurinary system. At present, the main treatment ways include: open surgery, transurethralresection of the prostate (TURP), thermal coagulation, 2100nm Ho: YAG laser treatment or1064nm Nd: YAG laser ablation and so on. There are a lot of side effects in theconventional ways.The high power KTP (potassium-Titanyl-Phosphate)-Nd: YAG (Neodymium: Yttrium-Aluminum-Garent) 532nm green laser is the best procedure for removal of disease tissue inurological surgery. The clinical result showed that green laser surgical procedures haveachieved a quicker operation times, a shorter post-operation catherization of the urethratimes (only 2-3days), good hemostasia and the lower levers of adverse side effects. It isnecessary to research high power 532um laser and its application in urological surgery.In this thesis the development of the high power 532nm laser system and itsapplication in urological surgery, specially on prostate, were reviewed. The key scientifictechnology of high power 532nm laser was expressed and the high power 532nm lasersystem was developed and tested. The animal test and clinical results were presented. Thethesis mainly includes:(1) The key technology of KTP intracavity-doubled Nd: YAG laser was discussedtheoretically. The effective nonlinear coefficient of typeⅡphase matching is larger thanthat of typeⅠphase matching. The appropriate crystal angle, cooling water temperature andresonant cavity length can increase KTP double efficiency, and the power of secondharmonic can be improved with the increase of fundamental beam power.(2) The high power 532nm laser system was researched and stable laser system wasachieved. The high effective IGBT switched electric source can provide 60A-120A current,1ms-20ms pulse width and 1Hz-100Hz pulse frequency. The Nd: YAG laser was pumpedby a Xenon lamp and produced 80W of optical fiber end power at 532nm, when it was intracavity doubed with KTP crystal and accousto-optic Q switched at 40 kHz. Thecoupling system of side-firing optical fiber was designed. The laser light was deflected60°-90°with respect to the axis of the fiber and the fiber coupling efficiency was 78%. Theoutput power instability was±1%, and the output power reproducibility was±2%.(3) The experiment of domestically manufactured green laser vaporization of animaltissue under water was carried out. The 532nm laser was used to vaporize porcine muscles,porcine livers and fresh canine prostate in air and/or under water. 1064nm laservaporization porcine muscles under water and in air were also presented. The experimentresults showed that the better vaporization effect and less necrosis depth were obtained with532nm laser than that with 1064nm laser both in air or under water. 532nm laser withpower as low as 30W can vaporize the tissues which contain mostly oxyhemoglobin. Withthe laser power increasing, the vaporization depth and vaporization width increasedsignificantly, and the necrosis was remained 1mm to 2mm deep to the vaporization zone.(4) The domestically manufactured 532nm laser vaporization in human urologicaltissue was performed clinically. The laser prostatectomy was performed in 15 BPHs. This532nm laser system was also used to treat 12 strictures and 9 urothelial tumors. Theseprocedures were similar. All patients received spinal anesthesia. Isotonic saline at roomtemperature was used as irrigation solution. Postoperative insertion of an indwellingcatheter was mandatory. The clinical results showed that these surgical procedures haveachieved a quicker operation times, a shorter post-operation catherization of the urethratimes, good hemostasia and the lower levers of adverse side effects. The conclusion can bedrawn that green laser vaporization of tissue is a treatment method that can be adopted totreat patients with BPH, strait urethra, bladder tumor etc urology diseases, and be safe andeffective, especially can be used in patients at high risk of anesthesia.