Design and development of thulium laser system for medical applications

Abstract

The Thulium (Tm:YAP) laser is suitable for medical applications due to strong absorption in water. In this thesis, a computer controlled Tm:YAP laser system with a power output up to 1 W and emission wavelength of 1980 nm were established. Once the laser system was stabilized, its output power, spot size, and light intensity measurements were performed. The thermal e ects of the laser system on brain, liver, heart, and kidney tissues were macroscopically analyzed. The ablation e ciency of the laser system was experimentally tested on ex-vivo brain tissue. The maximum ablation e ciency was obtained at a power level of 200 mW with a duration of 10 seconds (69 W/cm2). The uence e ect for skin ablation was analyzed by histology on Wistar rat skin tissues during a 4-day healing period. Temperature measurements by thermal camera and thermocouples were investigated to see the temperature e ect of CW and modulated mode of the Tm:YAP laser under skin and on skin surface. The temperature increase was faster and the temperature decrease was found slower in CW mode. The main aim of the study is to explore the welding capabilities of Tm:YAP laser in modulated and CW modes of operation on Wistar rat skin during 21-day healing period. Full-thickness incisions were welded at 100 mW and 5 s (34.6 W/cm2). The results were compared to conventional suture techniques by both histology and tensile strength measurements. After day 4, full closure was obtained for both laser modes, whereas, full closure was not observed till day 4 in suture group. In tensile strength analysis, tensile forces found for both modulated and CW modes of operation were signi cantly higher than the tensile force values found for conventional suture technique. Tm:YAP laser tissue welding possessed signi cantly stronger closure than conventional suture technique.|Keywords : Thulium (Tm:YAP) laser, laser tissue welding, wound healing, skin, brain, ablation, temperature measurement, histology, suturing, tensile strength test.