13 July 2004 Ultrafast pulsed lasers: surgical wave of the future?
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A Ti:Sapphire laser operating at 800 nm and 1 kHz repetition rate, was used to investigate the damage induced to fresh cadaveric porcine tissues. The laser was held constant at a focal spot diameter of 100 μm for pulse widths varying from 120-femtoseconds to 7-nanoseconds yielding a maximum fluence of 12.7 J/cm2 irradiation. Polarization optics were used to reduce the energy per pulse to well below tissue ablation threshold fluences. Hollow silica waveguides with a silver inner coating and bore diameters of 300, 500, 750 and 1000 μm were also used for the Ti:Sapphire laser with output pulses <150 fs duration and energy up to 700 μjoules. A high resolution motorized X-Y-Z stage translated the tissue through the beam at 1 mm/sec. A Luxar Novapulse CO2 surgical laser was used as a standard for comparison. Tissues were processed for light, scanning and transmission electron microscopy by standard protocols. Tissue samples were examined for tissue removal rates, thermal damage to adjacent tissue, and cellular disruption for equivalent fluence levels. The Ti:Sapphire laser demonstrated an increase in removal rate along with a decrease in thermal damage as the pulse widths approached the femtosecond regime for a constant fluence. With femtosecond pulses, ablation still occurred below fluences of 2 J/cm2. However, for nanosecond pulses, ablation no longer occurred, showing a decrease in ablation threshold as the pulse width decreases. Because of the reduced thermal effects compared to nanosecond pulses, ultrafast lasers may offer a solution to more precise tissue removal with less damage to surrounding cells as compared to more conventional surgical laser systems.
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Russell G. Higbee, Bryan S. Irwin, Michael N. Nguyen, Kenneth E. Bartels, William L. Warren, "Ultrafast pulsed lasers: surgical wave of the future?", Proc. SPIE 5312, Lasers in Surgery: Advanced Characterization, Therapeutics, and Systems XIV, (13 July 2004); doi: 10.1117/12.529637; https://doi.org/10.1117/12.529637

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