Comparison of Holmium:YAG and Thulium Fiber lasers on soft tissue : an ex vivo study.

Objective To assess the fiber-tissue interaction through ablation, coagulation, and carbonization characteristics of the Ho:YAG laser and Super Pulsed Thulium Fiber Laser (TFL) in a non-perfused porcine kidney model. To assess the degradation of laser fibers during soft tissue treatment. Methods A 50W TFL generator was compared to a 120W Ho:YAG laser. The laser settings that can be set identically between the two lasers (pulse energy and frequency), and clinically relevant for prostate laser enucleation, were identified and used for tissue incisions on fresh non-frozen porcine kidneys. For each parameter were also tested the short, medium and long pulse durations for the Ho:YAG generator, and the different peak powers 150W, 250W and 500W for the TFL. Laser incisions were performed with 550μm stripped laser fiber fixed on a robotic arm at a distance of 0.1mm with the tissue surface and at a constant speed of 10mm/s. Histological analysis was then performed, evaluating: incision shape, incision depth and width, axial coagulation depth, presence of carbonization. Degradation of the laser fiber was defined as reduction of laser fiber tip length after laser activation. Results Incision depths and areas of coagulation were greater with the Ho:YAG laser compared to the TFL. While no carbonization zone was found with the Ho:YAG laser, this was constant with the TFL. While a fiber tip degradation was constantly observed with Ho:YAG laser, except in the case of a long pulse duration and low pulse energy (0.2J), this was not the case with TFL. Conclusion TFL appears to be an efficient alternative to Ho:YAG laser for soft tissue surgery. The histological analysis found greater tissue penetration with the Ho:YAG laser and different coagulation properties between the two lasers. These results need to be investigated in vivo to assess the clinical impact of these differences and find the optimal settings for laser prostate enucleation.