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Proceedings Paper

Optoacoustic temperature determination and automatic coagulation control in rabbits
Author(s): Kerstin Schlott; Stefan Koinzer; Lars Ptaszynski; Susanne Luft; Alex Baade; Marco Bever; Johann Roider M.D.; Reginald Birngruber; Ralf Brinkmann
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Paper Abstract

Retinal laser photocoagulation is an established treatment method for many retinal diseases like macula edema or diabetic retinopathy. The selection of the laser parameters is so far based on post treatment evaluation of the lesion size and strength. Due to local pigment variations in the fundus and individual transmission the same laser parameters often lead to an overtreatment. Optoacoustic allows a non invasive monitoring of the retinal temperature increase during retinal laser irradiation by measuring the temperature dependent pressure amplitudes, which are induced by short probe laser pulses. A 75 ns/ 523 nm Nd:YLF was used as a probe laser at a repetition rate of 1 kHz, and a cw / 532 nm treatment laser for heating. A contact lens was modified with a ring-shaped ultrasonic transducer to detect the pressure waves at the cornea. Temperatures were collected for irradiations leading to soft or invisible lesions. Based on this data the threshold for denaturation was found. By analyzing the initial temperature increase, the further temperature development during irradiation could be predicted. An algorithm was found to calculate the irradiation time, which is needed for a soft lesion formation, from the temperature curve. By this it was possible to provide a real-time dosimetry by automatically switching off the treatment laser after the calculated irradiation time. Automatically controlled coagulations appear softer and more uniformly.

Paper Details

Date Published: 16 February 2011
PDF: 8 pages
Proc. SPIE 7885, Ophthalmic Technologies XXI, 78850T (16 February 2011); doi: 10.1117/12.875104
Show Author Affiliations
Kerstin Schlott, Medical Laser Ctr. Luebeck (Germany)
Stefan Koinzer, Univ. of Schleswig-Holstein (Germany)
Lars Ptaszynski, Medical Laser Ctr. Luebeck (Germany)
Susanne Luft, Univ. of Luebeck (Germany)
Alex Baade, Medical Laser Ctr. Luebeck (Germany)
Marco Bever, Medical Laser Ctr. Luebeck (Germany)
Johann Roider M.D., Univ. of Schleswig-Holstein (Germany)
Reginald Birngruber, Medical Laser Ctr. Luebeck (Germany)
Univ. of Luebeck (Germany)
Ralf Brinkmann, Medical Laser Ctr. Luebeck (Germany)
Univ. of Luebeck (Germany)

Published in SPIE Proceedings Vol. 7885:
Ophthalmic Technologies XXI
Fabrice Manns; Per G. Söderberg; Arthur Ho, Editor(s)

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