Abstract Submitted for the MAR07 Meeting of The American Physical Society Confounding Effect of Spot-Size on the Wavelength-Dependence of Tissue Ablation Metrics1 M. SHANE HUTSON, GILMA ADUNAS, YAOWU

Submitted for the MAR07 Meeting of The American Physical Society Confounding Effect of Spot-Size on the Wavelength-Dependence of Tissue Ablation Metrics1 M. SHANE HUTSON, GILMA ADUNAS, YAOWU XIAO, Vanderbilt University — Tunable free-electron lasers have been used in several previous studies to investigate the mid-IR wavelength-dependence of tissue ablation. These studies gave conflicting results on an important question: do the ablation metrics depend on targeting the laser energy to a water or protein vibration? Here, we investigate the effects of two parameters that varied widely in previous studies – fluence and focused spot-size. We measured ablation threshold, etch depth and collateral damage in porcine corneas for a set of five matched wavelengths – same absorption coefficients, but different primary chromophores. Although the ablation thresholds are similar, the slope of etch depth versus fluence (ablation efficiency) differs by up to a factor of five. These differences are most strongly dependent on the focused spot diameter, not wavelength. When spot sizes are matched, proteintargeting wavelengths still leave less collateral damage, but they remove tissue less efficiently. The confounding roles of fluence and spot size have strong implications for the interpretation of previous wavelength-dependent results. 1Supported by grant FA9550-04-1-0045 from the DoD MFEL Program. M. Shane Hutson Vanderbilt University Date submitted: 21 Nov 2006 Electronic form version 1.4