title: Efficacy and predictability of soft tissue ablation using a prototype Raman-shifted alexandrite laser.
abstract: Previous research showed that mid-infrared free-electron lasers could reproducibly ablate soft tissue with little collateral damage. The potential for surgical applications motivated searches for alternative tabletop lasers providing thermally confined pulses in the 6- to-7-µm wavelength range with sufficient pulse energy, stability, and reliability. Here, we evaluate a prototype Raman-shifted alexandrite laser. We measure ablation thresholds, etch rates, and collateral damage in gelatin and cornea as a function of laser wavelength (6.09, 6.27, or 6.43 µm), pulse energy (up to 3 mJ/pulse), and spot diameter (100 to 600 µm). We find modest wavelength dependence for ablation thresholds and collateral damage, with the lowest thresholds and least damage for 6.09 µm. We find a strong spot-size dependence for all metrics. When the beam is tightly focused (~100-µm diameter), ablation requires more energy, is highly variable and less efficient, and can yield large zones of mechanical damage (for pulse energies>1 mJ). When the beam is softly focused (~300-µm diameter), ablation proceeded at surgically relevant etch rates, with reasonable reproducibility (5% to 12% within a single sample), and little collateral damage. With improvements in pulse-energy stability, this prototype laser may have significant potential for soft-tissue surgical applications.
authors.affiliation: Vanderbilt University, Department of Physics and Astronomy, 6301 Stevenson Center, Nashville, Tennessee 37235, United States.
authors.forename: John A
authors.initials: JA
authors.lastname: Kozub
authors.affiliation: Vanderbilt University Medical Center, Department of Ophthalmology and Vanderbilt Eye Institute, 2311 Pierce Avenue, Nashville, Tennessee 37232, United States.
authors.forename: Jin-H
authors.initials: JH
authors.lastname: Shen
authors.affiliation: Vanderbilt University Medical Center, Department of Ophthalmology and Vanderbilt Eye Institute, 2311 Pierce Avenue, Nashville, Tennessee 37232, United States.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Joos
authors.affiliation: Vanderbilt University Medical Center, Department of Ophthalmology and Vanderbilt Eye Institute, 2311 Pierce Avenue, Nashville, Tennessee 37232, United States.
authors.forename: Ratna
authors.initials: R
authors.lastname: Prasad
authors.affiliation: Vanderbilt University, Department of Physics and Astronomy, 6301 Stevenson Center, Nashville, Tennessee 37235, United States.
authors.forename: M Shane
authors.initials: MS
authors.lastname: Hutson
mesh_terms: D003315:Cornea / Q000473:pathology* / Q000601:surgery*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D066298:In Vitro Techniques; D053685:Laser Therapy / Q000295:instrumentation*; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D010865:Pilot Projects; D013059:Spectrum Analysis, Raman / Q000295:instrumentation*; D016896:Treatment Outcome