Showing papers by "William B. Armstrong published in 2002"

Ultrashort pulse laser ossicular ablation and stapedotomy in cadaveric bone.

Abstract: Background and Objective: The purpose of this study was to evaluate the ablation of ossicular tissue using a 1,053 nm Ti:Sapphire chirped pulse amplifier laser system configured to deliver ultrashort pulses of 350 femtoseconds (fs) (3.5 x 10 -13 seconds) in cadaver temporal bone. Study Design/Materials and Methods: Ablation of the formalin-fixed incus and stapes was performed using an ultrashort pulse laser (USPL) (0.4 mm beam diameter, pulse fluence of 2.0 J/cm 2 , and pulse repetition rate of 10 Hz). The ablation rate was measured using optical micrometry, and crater surface morphology examined using scanning electron microscopy. Results: The laser produced precise bone ablation at a rate of 1.26 μm/pulse, with almost no evidence of thermal damage, and very little evidence of photomechanical injury. Conclusions: Ultrashort pulse lasers may provide a useful clinical tool for otologic and skull base surgery, where precise hard tissue ablation is required adjacent to critical structures.

The effect of optical design on micromanipulator spot size using CO2 laser irradiation.

Abstract: Objective: The study goal was to compare the laser spot size created using reflective and refractive micromanipulators with a CO 2 laser and to determine the sensitivity of spot size to laser power. Study Design and Setting: A CO 2 laser and operating microscope (400-mm focal length) was coupled to either a reflective (Cassegrain-like) or refractive micromanipulator. Laser spot size was determined by measuring the region of ablation created by laser irradiation of wood (dry tongue depressors), exposed photographic film, and agar gel using optical micrometry. Laser power varied from 0.5 to 20 W with pulse durations of 0.1 and 0.5 second. Results: The reflective micromanipulator demonstrated overall smaller spot sizes for a given laser power and lower incremental change in spot size with increasing power. The reflective design demonstrated less sensitivity to increases in laser power. Conclusions: Micromanipulator optical design can result in significant differences in laser spot size. The reflective device used in this study demonstrated less sensitivity to increasing laser power. (Otolaryngol Head Neck Surg 2002;126:593-597.)