PMID: 9523528Apr 2, 1998Paper

Optical absorption of blood depends on temperature during a 0.5 ms laser pulse at 586 nm

Photochemistry and Photobiology
W VerkruysseM J van Gemert

Abstract

Optical properties are important parameters in port wine stain laser treatment models. In this study we investigated whether changes in blood optical properties occur during a 0.5 ms laser pulse. Blood from three volunteers was irradiated in vitro with laser pulses (radiant exposure 2-12 J cm-2, wavelength 586 nm, pulse length 0.5 ms). Reflection and transmission coefficients, measured using double integrating spheres, decreased slightly during the first part of the pulse. At 2.9 J cm-2 radiant exposure, the reflectance increased, independent of total radiant exposure of the pulse. This was caused by blood coagulation. A second sudden increase in reflection and a significant increase in transmission occurred near 6.3 J cm-2 and was accompanied by a "popping" sound, indicating rapid expansion of bubbles due to blood vaporization. A multilayered model of blood was used to fit calculated transmission coefficient curves to the measurements and determine temperature-dependent optical blood absorption. Heat diffusion was shown to be of minor importance. A 2.5-fold increase in absorption for temperatures increasing from 20 to 100 degrees C, accurately describes transmission coefficients measured up to 2.9 J cm-2.

Citations

Apr 1, 1999·Lasers in Surgery and Medicine·T J PfeferA J Welch
Jun 20, 2001·Lasers in Surgery and Medicine·W VerkruysseJ A Spaan
Jun 2, 2000·Journal of Biomechanical Engineering·T J PfeferA J Welch

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