Optical Absorption of Blood Depends on Temperature during a 0.5 ms Laser Pulse at 586 nm

• Published in: Photochemistry and photobiology Vol. 67; no. 3; pp. 276 - 281
• Main Authors: Verkruysse, Wim, Nilsson, Annika M. K., Milner, Thomas E., Beek, Johan F., Lucassen, Gerald W., van Gemert, Martin J. C.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.1998
• Subjects: Absorption; Blood - radiation effects; Humans; Laser Therapy; Port-Wine Stain - surgery; Spectrophotometry; Temperature
• ISSN: 0031-8655; 1751-1097; 1751-1097
• DOI: 10.1111/j.1751-1097.1998.tb05199.x

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°C, accurately describes transmission coefficients measured up to 2.9 J cm−2.