POTENTIAL OF SUPER PULSE DIODE AND FIBER LASERS FOR TREATMENT OF SOFT AND HARD TISSUES IN MEDICAL APPLICATIONS

摘要

Lasers are becoming energy sources of choice for many medical applications. Ability to deliver sufficiently high energy in a short pulse while maintaining required average power ("super pulse") is crucial for a number of surgical procedures. Recent technological advances have made possible implementation of Super Pulse (SP) regimes in Laser Diodes (LD) and Fiber Lasers (FL). This capability may offer numerous advantages over existing techniques. In this work, we have conducted thorough evaluation of two prototype super-pulse LD and FL systems, respectively designed for dentistry (treatment of soft tissues) and urology (lithotripsy), through their comparison with the corresponding "gold standard" commercial systems. Prototype super-pulse LD system for dentistry provided up to 25 W average and up to 150 W peak power at ～980 nm wavelength. The laser was operated in various modes of control including those with thermal feedback. The following characteristics of the system performance were evaluated: 1) Speed and depth of cutting; 2) Degree of charring and dimensions of coagulative margin. The SP laser diode system was compared with industry-leading conventional diode and CO_2 devices. The results indicated that the super-pulse diode laser system yielded increase in speed of controlled cutting by a factor of 2 in comparison with the conventional diode laser and approaching that of CO_2 device. Prototype super-pulse Thulium (Tm) FL system for lithotripsy was capable of operation with up to 50 W average and 500 W peak power at ～1940 nm wavelength. The in vitro experimental setup included a specially designed cuvette allowing quantitative assessment of size distribution of stone fragments and evaluation of the ablation rate. Magnitude of the retropulsion effect was measured as well. The SP Tm fiber laser system was compared with leading Ho:YAG system on the market. The two systems were matched in terms of average power and/or pulse energy. Ablation rate measurements revealed that, depending on stone composition and laser settings, the Tm laser provided between 1.2 and 4.3 times faster ablation than the Ho system. The temperature rise in the cuvette was nearly equal for the two lasers. The average retropulsion distance after a single pulse was substantially shorter with the Tm laser. The results obtained suggest that super-pulse technology implemented in laser diodes and fiber lasers may have significant potential for creating a new standard of care in the field of precision soft and hard tissue surgery in various specialties of medicine.