PLASMA-MEDIATED ABLATION OF BRAIN-TISSUE WITH PICOSECOND LASER-PULSES

Plasma-mediated ablations of brain tissue have been performed using picosecond laser pulses obtained from a Nd:YLF oscillator/regenerative amplifier system. The laser pulses had a pulse duration of 35 ps at a wavelength of 1.053 mum. The pulse energy varied from 90 muJ to 550 muJ at a repetition rate of 400 Hz. The energy density at the ablation threshold was measured to be 20 J/cm2. Comparisons have been made to 19 ps laser pulses at 1.68 mum and 2.92 mum from an OPG/OPA system and to microsecond pulse trains at 2.94 mum from a free running Er:YAG laser. Light microscopy and scanning electron microscopy were performed to judge the depth and the quality of the ablated cavities. No thermal damage was induced by either of the picosecond laser systems. The Er:YAG laser, on the other hand, showed 20 mum wide lateral damage zones due to the longer pulse durations and the higher pulse energies.