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Proceedings Paper

Time resolved detection of tissue denaturation during retinal photocoagulation
Author(s): Kerstin Schlott; Jens Langejürgen; Marco Bever; Stefan Koinzer; Reginald Birngruber; Ralf Brinkmann
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Paper Abstract

The retinal photocoagulation is an established treatment method for different retinal diseases. The extent of the thermal coagulations depends strongly on the generated temperature increase. Until now the dosage is based on a pool of experience of the treating physicians as well as the appearance of the whitish lesions on the retina. The temperature course during photocoagulation can be measured in real-time by optoacoustics. A frequency-doubled Q-switched Nd:YLF laser (523nm, 75 ns) is used for optoacoustic excitation and a continuous-wave Nd:YAG laser (532nm) with adjustable irradiation time and power for heating of the fundus tissue. The onset of coagulation is determined by a photodiode that is placed directly behind enucleated porcine eyes, which served as a model. The onset of coagulation is observed clearly when scattering sets in. The required power for coagulation increases exponentially with decreasing irradiation time. The first results on rabbit eyes in vivo indicate that the onset of coagulation defined by just barely visibile lesions at a slit lamp sets in at an ED50 threshold temperature of 63°C for an irradiation time of 400 ms. In conclusion, optoacoustics can be used to determine temperatures during retinal laser treatments in real-time. This allows evaluating the time-temperature-dependence of retinal coagulation in vivo.

Paper Details

Date Published: 17 July 2009
PDF: 8 pages
Proc. SPIE 7373, Therapeutic Laser Applications and Laser-Tissue Interactions IV, 73730E (17 July 2009); doi: 10.1117/12.831877
Show Author Affiliations
Kerstin Schlott, Medizinisches Laserzentrum Lübeck GmbH (Germany)
Univ. zu Lübeck (Germany)
Jens Langejürgen, Univ. zu Lübeck (Germany)
Marco Bever, Medizinisches Laserzentrum Lübeck GmbH (Germany)
Stefan Koinzer, Uni. Kiel (Germany)
Reginald Birngruber, Univ. zu Lübeck (Germany)
Medizinisches Laserzentrum Lübeck GmbH (Germany)
Ralf Brinkmann, Univ. zu Lübeck (Germany)
Medizinisches Laserzentrum Lübeck GmbH (Germany)

Published in SPIE Proceedings Vol. 7373:
Therapeutic Laser Applications and Laser-Tissue Interactions IV
Ronald Sroka; Lothar D. Lilge, Editor(s)

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