光能量在生物组织中传输的蒙特卡罗研究

Study on Optical Energy Transmission in Biotic Tissues by Monte Carlo Method

生物组织是一种高散射随机介质,高散射随机介质中光传播问题的研究对于激光生物医学诊断和治疗具有十分重要的意义。采用蒙特卡罗方法模拟了准直光束在生物组织中的传播与分布规律,分析了轴向和组织内部的光能量分布及上下表面的反射或透射、光学参数(各向异性因子-g因子、反照率albedo、吸收系数μa)对光能量分布随深度变化的影响。结果表明:轴向光能量在离中心越近的地方,随深度变深下降越快,并在近表面处有一峰值;g因子对从上下表面损失的光能量影响显著;g因子减小,前向穿透能力减弱,穿透深度随之减小,光能量变化越来越分散;固定吸收系数时,反照率的变化在深度较浅和较深处的影响不同。

Biotic tissues are a kind of highly scattering random media; studies on laser light propagation in biotic tissues play an important role in bio-medical diagnostics and therapeutics. The propagation and distribution of infinitely narrow photon beam in tissues are simulated by Monte Carlo method in this paper. Also presented are the energy distribution with regard to depths,light distribution in tissues,reflection and transmittance on the upper and lower surface. The optical parameters adopted in this study are g,albedo and μa,which have influence on energy distribution. The results show：The energy distribution decreases more quickly with the increase of depths and reveals a peak value close to the surface; g factor plays an important part in the lost energy on the upper surface and lower surface; the decrease of g factor causes weaking of the forward moving ability,so the penetration depth becomes smaller and the energy becomes dispersive; variation of albedo has distinct effect on the shallow and deep tissues.