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Proceedings Paper

Thermal imaging of laser-tissue interaction using color Schlieren techniques quantified by ray-tracing simulation
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Paper Abstract

In various studies the use of a color Schlieren technique to visualize the dynamic thermal effects of lasers in an aqueous environment has proven to be very useful. Besides for the research, this setup has also proven to be very successful for education and demonstration purposes. This 'pseudo thermal imaging' technique has also been applied to study the behavior of diathermia devices and ultrasound resectors used in surgery. Since, the images reflect gradients in refractive index induced by thermal gradients, they can not simply be converted and interpreted as thermal images. In order to understand the pathway of light through thermal gradients, a ray-trace program was developed. The program is capable of visualizing the path of light rays through simulated thermal gradients as well as generating an image, which can be compared with the 'real' images from the color Schlieren setup. For calibration, the program was successfully tested on well defined optical configurations such as spherical and index-gradient lenses. Images calculated using data from a temperature profile measured with a small thermocouple appeared to be almost similar to the actual Schlieren image. Matching the calculated and actual image was possible by either assuming a minimal error in the temperature measurements or in the temperature dependence of the refractive index. The ray-trace program has been a helpful tool to quantify the absolute temperatures in color images from simple geometries. Expanding the code might enable the quantification of more complex temperature gradients. Such information is valuable for the clinical application of energy source such as lasers.

Paper Details

Date Published: 14 June 1999
PDF: 10 pages
Proc. SPIE 3601, Laser-Tissue Interaction X: Photochemical, Photothermal, and Photomechanical, (14 June 1999); doi: 10.1117/12.349999
Show Author Affiliations
Rudolf M. Verdaasdonck, Univ. Hospital Utrecht (Netherlands)
Rogier Lodder, Univ. Hospital Utrecht (Netherlands)
Christiaan F. P. van Swol, Univ. Hospital Utrecht (Netherlands)
Matthijs C. M. Grimbergen, Univ. Hospital Utrecht (Netherlands)

Published in SPIE Proceedings Vol. 3601:
Laser-Tissue Interaction X: Photochemical, Photothermal, and Photomechanical
Steven L. Jacques; David H. Sliney; Gerhard J. Mueller; Gerhard J. Mueller; Andre Roggan; Andre Roggan; David H. Sliney, Editor(s)

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