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Proceedings Paper

Optoacoustic online temperature determination during retinal laser photocoagulation
Author(s): Kerstin Schlott; Jens Stalljohann; Benjamin Weber; Jochen Kandulla; Katharina Herrmann; Reginald Birngruber; Ralf Brinkmann
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Paper Abstract

Retinal photocoagulation is an established treatment of different retinal diseases. The treatment relies on a short, local heating of the tissue which induces a denaturation. The resulting scar formation may for example prevent the further detachment of the retina. The extent of the coagulation is besides other parameters mostly dependent on the induced temperature increase. However, until today a temperature based dosimetry for photocoagulation does not exist. The dosage is rather based on the experience of the treating physicians to achieve visible whitish lesions on the retina. In this work a technique is presented, which allows an online temperature monitoring during photocoagulation. If an absorbing material is irradiated with short laser pulses, a thermoelastic expansion of the absorber induces an acoustic wave. Its amplitude is dependent on the temperature of the absorber. For analyzing the applicability of the optoacoustic temperature determination for dosimetry, measurements were performed on enucleated porcine eye globes. The pressure transients are detected by an ultrasonic transducer, which is embedded in an ophthalmologic contact lens. As long as no strong lesions occur, the determined temperatures are almost proportional to the power of the treatment laser. Using a spot diameter of 200 μm and different laser powers, the temperature rise at the end of the 400 ms irradiation was found to be approximately 0.16 °C/mW. The onset of the denaturation was observed around 50°C. The far aim of this project is an automatic regulation of the treatment laser onto a desired temperature course.

Paper Details

Date Published: 13 July 2007
PDF: 8 pages
Proc. SPIE 6632, Therapeutic Laser Applications and Laser-Tissue Interactions III, 66321B (13 July 2007); doi: 10.1117/12.728291
Show Author Affiliations
Kerstin Schlott, Institute of Biomedical Optics, Univ. of Luebeck (Germany)
Jens Stalljohann, Medical Laser Ctr., Luebeck (Germany)
Benjamin Weber, Medical Laser Ctr., Luebeck (Germany)
Jochen Kandulla, Institute of Biomedical Optics, Univ. of Luebeck (Germany)
Katharina Herrmann, Institute of Biomedical Optics, Univ. of Luebeck (Germany)
Reginald Birngruber, Institute of Biomedical Optics, Univ. of Luebeck (Germany)
Medical Laser Ctr., Luebeck (Germany)
Ralf Brinkmann, Institute of Biomedical Optics, Univ. of Luebeck (Germany)
Medical Laser Ctr., Luebeck (Germany)


Published in SPIE Proceedings Vol. 6632:
Therapeutic Laser Applications and Laser-Tissue Interactions III
Alfred Vogel, Editor(s)

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