Noncontact photoacoustic spectroscopy (NCPAS) for photoablation control: data acquisition and analysis using cluster analysis

Holger Specht; Thomas Bende; Benedikt J. Jean M.D.; Wolfgang Fruehauf

doi:10.1117/12.350581

18 June 1999 Noncontact photoacoustic spectroscopy (NCPAS) for photoablation control: data acquisition and analysis using cluster analysis

Holger Specht, Thomas Bende, Benedikt J. Jean M.D., Wolfgang Fruehauf

Author Affiliations +

Proceedings Volume 3591, Ophthalmic Technologies IX; (1999) https://doi.org/10.1117/12.350581
Event: BiOS '99 International Biomedical Optics Symposium, 1999, San Jose, CA, United States

Abstract

Laser photoablation using UV or IR lasers is known to trigger a photo acoustic event. Different target materials can be discriminated by analyzing the photoacoustic signal. In vitro measurements of NCPAS have revealed the necessity to integrate a number of variable elements (tissue hydration, fluence, laser beam diameter, distance to microphone, etc.). This study defines the parameters needed for the initiation of a self learning system for target material recognition. A UV excimer laser (λ=193 nm; Summit Technology, UV 200L) was used to ablate organic polymers (PMMA, PA, PVC), normal and porcine corneal scar tissue, and human cornea in vivo. NCPAS was performed using a microphone (up to 200 kHz) as a detector. During photoablation, the acoustic signal was analyzed by a multiport A/D IBM PC based digital oscilloscope. The data obtained were imported into a Matlab language program and analyzed. NCPAS allows the discrimination of different materials by a characteristically frequency shift of the photoacoustic signal. Detection and online material recognition using NCPAS is a step on the way to a `smart' laser control, based on an artificial neuronal network.

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Holger Specht, Thomas Bende, Benedikt J. Jean M.D., and Wolfgang Fruehauf "Noncontact photoacoustic spectroscopy (NCPAS) for photoablation control: data acquisition and analysis using cluster analysis", Proc. SPIE 3591, Ophthalmic Technologies IX, (18 June 1999); https://doi.org/10.1117/12.350581

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