Pulsed Laser-Induced Thermal Damage in Whole Blood

[+] Author and Article Information
T. Joshua Pfefer, Bernard Choi, Gracie Vargas, Karen M. McNally, A. J. Welch

Biomedical Engineering Program, The University of Texas at Austin, Austin, TX 78712

J Biomech Eng 122(2), 196-202 (Nov 18, 1999) (7 pages) doi:10.1115/1.429642 History: Received June 14, 1999; Revised November 18, 1999
Copyright © 2000 by ASME
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Threshold temperatures of skin and blood constituents as a function of exposure time, using Eq. (2), the rate process data in Table 1, and assuming step changes in temperature. Symbols are for identification purposes only and do not represent specific data points.
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Radiometric temperature distributions for a point near the center of the laser beam (λ=532; τp=10 ms) for six different radiant exposure levels
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Thermal damage levels calculated from radiometric temperature distributions (Fig. 2) using rate process coefficients for: (a) hemoglobin 13; and (b) bulk skin 25. Horizontal lines at Ω=1 indicate the coagulation threshold. Note that minimum and maximum values of Ω (10−10 and 1010) were chosen arbitrarily.
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OCT images documenting the morphology of coagulated regions of whole blood at radiant exposures of: (a) 4.4, (b) 6, (c) 8, and (d) 10 J/cm2 . As labeled in (d), four regions are visible (from top to bottom): glass (black), glass–blood interface (white), coagulated blood (bright speckle), and native blood (darker speckle). The length of size bars corresponds to a distance of approximately 200 μm. The thickness of each coagulum is indicated by a pair of thin lines. The left side of image (d) shows the edge of coagulum. Note that the intensity of the OCT signal in (a) is lower in the coagulum (and higher in the native blood) than in the corresponding regions of the other images.
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The effect of increasing radiant exposure on coagulum thickness (from OCT images) and transmission of coaligned laser beam (λ=635 nm). Error bars represent±one standard deviation. The laser pulse duration was 10 ms.




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