Primary investigations on defined thermal effects on soft tissue using a diode pumped Er:YAG laser system

Flashlamp pumped Erbium lasers are successfully used clinical for soft and hard tissue ablation. Especially for soft tissue ablation the limited repetition rate is a disadvantage (bleeding; perforation instead of cutting). Now diode pumped solid state (DPSS) Er:YAG laser systems (Pantec Engineering AG) are available, with mean laser power up to 50 W and pulse repetition rate up to 2 kHz. The aim of this study is to investigate the potential of this laser system for increased and defined soft tissue coagulation/manipulation at various irradiation parameters, in particular at repetition rates exceeding 100 Hz. Firstly, an appropriate experimental set-up was realized with laser system, focusing unit, computer-controlled linear stage with sample holder and shutter unit to move the sample (fresh chicken breast) with a defined velocity while irradiation by various laser parameters. While irradiation the tissue effects were recorded by a video camera, adapted on a surgical microscope. After irradiation, the samples were analyzed by light microscopy. In addition, histological sections were prepared and microscopically analyzed. Mainly depending on the fluence, the thermal effect can be limited to coagulation without carbonization. In addition, tissue melting can be observed. The coagulation depth increases with increasing pulse repetition rate and decreasing movement velocity from about 30 mu m to above 1 mm. In conclusion, the results of the in vitro studies show that the diode pumped, pulsed Er:YAG laser has the potential to provide one system both, for high efficient hard and soft tissue ablation as well as for soft tissue coagulation and fusion.