Characterization of micromanipulators for CO 2 laser surgery in head and neck: comparison of reflective and refractive optical systems

Abstract

Laser micromanipulators deliver laser energy to difficult to access regions within the head and neck allowing surgeons to perform high precision microsurgical procedures. In this study, the laser spot sizes (as a function of power) produced by a two micromanipulators of different optical design were compared. A CO<SUB>2</SUB> laser and operating microscope (400 mm focal length) was coupled to either a reflective (Cassegrain- like) (Unimax 2000, Reliant Technologies, Inc., Foster City, CA) or refractive micromanipulator (Microslad 719, Sharplan Lasers Inc. Allendale, NJ). The laser spot size was determined by measuring the region of ablation following laser irradiation of dry tongue blades, exposed photopaper, and agar gel using optical micrometry. Laser power was varied from 0.5 to 20 W for pulse durations of 0.1 and 0.5 seconds. A logarithmic relationship between spot size (diameter) and laser power on wood and photopaper was observed for both devices. In agar samples a discontinuity in spot size was observed at 9 W due to the formation of a large ablation crater on the surface of the agar. For a given laser power, the micromanipulator with reflective optics demonstrated overall smaller spot sizes and lower incremental change in spots size with increasing power. These results suggest the reflective micromanipulator tested in this study produced a smaller spot size at all powers tested, and with increasing power the spot size increased more slowly than with the conventional refractive optical device tested.