Effects of Wavelength, Pulse Duration and Pulse Repetition Frequency of theInteractions and Desorption of Brain Tissue

摘要

We report a phenomenological study of the effects of 532 and 308 nm laser lightat nanosecond and picosecond pulse durations and at two different repetition rates on a rat-brain model. The quality and morphology of each ablation well and of its relationship with the laser parameters were made. Special attention was paid to unusual shapes of the cavity, such as 'keyholes,' and the effect of focussing on cavity shape was investigated. Neurosurgical applications of laser-tissue interactions have been directed to (1) singlet oxygen-mediated tumoricidal photodynamic therapy via excitation of various fluorescing compounds by fiber-delivered monochromatic light, and (2) precision tissue ablation, predominantly using the CO2, Nd:YAG and KTP-532 lasers via microslade-directed intramicroscopic system. While the successful application of photodynamic therapy techniques to central nervous system tissue requires fabrication of an efficient but relatively nontoxic agent with excitatory wavelengths suitable for maximal light penetration through brain parenchyma, precision ablation of central nervous system tissue requires the experimental identification of combinations of laser light wavelengths, pulse and power characteristics that are optimized for clinical use. This in turn requires a fundamental understanding of the processes leading to the laser irradiation-induced desorption of brain tissue.