ANYL 123 |
| Ablation of soft tissues with the Vanderbilt University Mark-III Free Electron Laser (FEL) displays a strong wavelength dependence. Tissue is efficiently and speedily removed, with minimal collateral damage, when the laser is tuned to the amide II absorption band of collagen near 6.45 µm. Other wavelengths, particularly those around the OH stretch mode near 3 µm, remove tissue less efficiently and leave greater collateral damage. In order to investigate the origin of this wavelength-dependence, we measured FTIR spectra of the non-volatile components of ablation plumes collected when corneas were exposed to either 2.77 or 6.45 µm radiation. Corneal tissue exhibits the same linear absorbance at these two wavelengths, but with different major chromophores (water and protein, respectively). The FTIR spectra of the plume collected at 6.45 µm clearly shows a new vibrational band around 2218 cm-1, whose intensity strongly depends upon the wavelength and fluence selected for ablation. The intensity also depends strongly on the water content of the tissue prior to ablation. The appearance of this new band suggests the presence of either nitrile or alkyne groups in the ablation plume. Such groups could arise through oxidative degradation of the protein component of cornea. Further biochemical analysis is underway to determine the exact nature of the new chemical species formed and their possible role in the ablation process |
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General Papers
7:00 PM-9:00 PM, Sunday, 13 March 2005 Convention Center -- Sails Pavilion, Poster
Division of Analytical Chemistry |