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10 June 2004 Hollow waveguide delivery of ultrashort pulses for tissue ablation
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Tissue ablation with pulses in the femtosecond regime is generally more efficient and causes less collateral and thermal damage to the surrounding tissue compared to ablation with longer pulsewidths. A compact, flexible fiber delivery system that could transmit these pulses would be advantageous over free-space beam delivery, since it would allow ultrashort pulse tissue ablation in vivo. However, the extremely high intensities associated with ultrashort pulses have deleterious effects in conventional silica fibers such as nonlinearities and fiber damage. Hollow silica waveguides with a silver inner coating essentially guide the pulses in air, thereby avoiding many of these problems. The transmission characteristics of four hollow waveguides with bore diameters of 300, 500, 750 and 1000μm and lengths up to 1m were tested using pulses from a femtosecond regime Ti:Sapphire laser operating with input pulses <150fs duration and energy up to 700 microjoules at a repetition rate of 1kHz. Coupling was primarily to the HE11 mode and straight and bending losses were measured. Beam profiles were also taken at the output of straight and bent waveguides. Autocorrelation measurements show minimal pulse broadening for straight waveguides and increasing pulsewidth with waveguide bend. Diffractive micro-optics were used to focus the output and ablation of fresh cadaveric porcine liver and heart tissues was accomplished using an x-y-z translational stage moving at 1 mm/second. Targeted tissues were then processed for light and electron microscopic examination. Light and scanning electron microscopy demonstrated near a-thermal ablation with depth correlating to energy application.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael N. Nguyen, Bryan S. Irwin, Russell G. Higbee D.V.M., Waleed S. Mohammed, Eric G. Johnson, Kenneth E. Bartels D.V.M., William L. Warren, and Kenneth H. Church "Hollow waveguide delivery of ultrashort pulses for tissue ablation", Proc. SPIE 5317, Optical Fibers and Sensors for Medical Applications IV, (10 June 2004);

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