Verkruysse W, Nilsson A M, Milner T E, Beek J F, Lucassen G W, van Gemert M J
Laser Centre, University of Amsterdam, The Netherlands.
Photochem Photobiol. 1998 Mar;67(3):276-81.
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.
光学特性是葡萄酒色斑激光治疗模型中的重要参数。在本研究中，我们调查了在0.5毫秒激光脉冲期间血液光学特性是否会发生变化。用激光脉冲（辐照剂量2 - 12 J/cm²，波长586 nm，脉冲长度0.5毫秒）对三名志愿者的血液进行体外照射。使用双积分球测量的反射系数和透射系数在脉冲的第一部分略有下降。在2.9 J/cm²的辐照剂量下，反射率增加，与脉冲的总辐照剂量无关。这是由血液凝固引起的。在6.3 J/cm²附近反射率再次突然增加且透射率显著增加，并伴有“爆裂”声，表明由于血液汽化导致气泡迅速膨胀。使用血液的多层模型将计算的透射系数曲线与测量值拟合，并确定与温度相关的血液光学吸收。结果表明热扩散的影响较小。温度从20℃升高到100℃时吸收增加2.5倍，准确描述了高达2.9 J/cm²的测量透射系数。
