Minimal Invasive Laser Surgery Supported by Fluorescence Spectroscopical Diagnostics
Applying Tm:YAG laser pulses to biological tissue results in rather high ablation rates with moderate thermal side effects, since its wavelength of 2.01 μm coincides with a strong absorption band of water. The pulse duration of the employed system in the free running mode has been measured to be 400–1600 μs. Optical fibers of 600 μm core diameter have been used to guide the laser radiation at typically 80% transmission rate. The energy was set to 0.5–1.5 J. The ablation process is accompanied by microplasma formation and intense fluorescence emission. This fluorescence is probed by a second fiber, detected by an intensified optical multichannel analyzer, and displayed and recorded on-line via a PC-based frame grabber system. First results on fluorescence spectra taken from different tissue samples are presented. Bone tissue spectra show, for example Calcium lines even if the samples are irradiated in aqueous solution. Long pulse measurements at 2.94 μm with an Er:YAG laser and investigations with Q-switched pulses from the Tm:YAG laser system are in preparation.
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