Optimizing Laser Parameters for Precise Working Depths in Liver-Tissue Applications

The aim of this thesis study is to determine optimum safe working parameters by investigating application times of 980, 809, 635 and 450 nm wavelength diode lasers to the liver tissue surface in CW and direct contact mode. In the first part, the irradiation times of the lasers up to coagulation or carbonization formation were measured and energy values of each time were calculated. Average groups were performed to t-test analysis (p<0.05). In second part, temperature changes were measured with two laser groups as 809 nm at 4 W - 6 sec and 980 nm at 2 W - 12 sec on the tissue. In the findings, average coagulation and carbonization thereshold times ranges were 0.54 – 5.68 sec and 2.89 – 11.65 sec at 1 - 8 W in 980 nm; 1.62 – 14.96 sec and 5.13 – 12.53 sec at 1 - 6 W in 809 nm and 0.33 – 1 sec at 0.5 - 1 W and 0.34 – 1.31 sec at 1 - 3 W in 450 nm, respectively. Energy ranges were 2.92 – 5.68 joule and 18.04 – 23.3 joule in 980 nm; 9.74 – 23.3 joule and 20.41 – 38.06 joule at 809 nm and 0.33 – 0.5 joule and 1.01 – 1.33 joule at 450 nm in coagulation and carbonization, respectively. Temperature changes were found as 29.26 ± 10.46 ºC in 980 nm and 31.86 ± 8.41 ºC in 809 nm. In conclusion, 980 nm was found to have the safest operating parameters for future laser applications due to its high thereshold difference between coagulation and carbonization at applied powers.