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Proceedings Paper

Cellular tolerance to pulsed heating
Author(s): Dimitrii Simanovski; M. Sarkar; A. Irani; C. O'Connell-Rodwell; C. Contag; H. Alan Schwettman; D. Palanker
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Paper Abstract

Many laser therapies involve significant heating of tissue with pulses varying from picoseconds to minutes in duration. In some of the applications heating is a primary goal, while in others it is an undesirable side effect. In both cases, if a hyperthermia is involved, the knowledge about the threshold temperature leading to irreversible cellular damage is critically important. We study the dependence of the threshold temperature on duration of the heat exposure in the range of 0.3 ms to 5 seconds. Thin layer of cells cultured in a Petri dish was exposed to a pulsed CO2 laser radiation. Laser beam was focused onto sample providing Gaussian intensity distribution in the focal plane with a beam diameter (2w) 2-10 mm. Surface temperature in the central part of the focal spot (1mm in diameter) was measured by thermal infrared (IR) emission from the sample, recorded with a fast IR detector. For pulses shorter than 1 s the temperature profile across the focal spot was found to closely correspond to the radial distribution of the laser beam intensity, thus allowing for accurate determination of temperature at any given distance from the center of the spot. Immediate cellular damage was assessed using vital staining with the live/dead fluorescent assay. Threshold temperatures were found to vary from 65 °C at 5 s of heating to 160 °C at pulses of 0.3 ms in duration. The shorter end of this range was limited by vaporization, which occurs during the laser pulse and results in mechanical damage to cells. Dependence of the maximal temperature on pulse duration could be approximated by Arrhenius law with activation energy being about 1 eV.

Paper Details

Date Published: 15 April 2005
PDF: 6 pages
Proc. SPIE 5695, Optical Interactions with Tissue and Cells XVI, (15 April 2005); doi: 10.1117/12.601774
Show Author Affiliations
Dimitrii Simanovski, Stanford Univ. (United States)
M. Sarkar, Stanford Univ. (United States)
A. Irani, Stanford Univ. (United States)
C. O'Connell-Rodwell, Stanford Univ. (United States)
C. Contag, Stanford Univ. (United States)
H. Alan Schwettman, Stanford Univ. (United States)
D. Palanker, Stanford Univ. (United States)


Published in SPIE Proceedings Vol. 5695:
Optical Interactions with Tissue and Cells XVI
Steven L. Jacques; William P. Roach, Editor(s)

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