Facultad de Medicina, Universidad Autónoma del Estado de México, Paseo Tollocan s/n esquina Jesús Carranza, Col. Moderna de la Cruz, CP. 50180, Toluca, Estado de Mexico, Mexico.
Med Biol Eng Comput. 2018 Apr;56(4):649-655. doi: 10.1007/s11517-017-1713-z. Epub 2017 Aug 29.
The aim of this work was to develop an event-by-event Monte Carlo code for light transport (called MCLTmx) to identify and quantify ballistic, diffuse, and absorbed photons, as well as their interaction coordinates inside the biological tissue. The mean free path length was computed between two interactions for scattering or absorption processes, and if necessary scatter angles were calculated, until the photon disappeared or went out of region of interest. A three-layer array (air-tissue-air) was used, forming a semi-infinite sandwich. The light source was placed at (0,0,0), emitting towards (0,0,1). The input data were: refractive indices, target thickness (0.02, 0.05, 0.1, 0.5, and 1 cm), number of particle histories, and λ from which the code calculated: anisotropy, scattering, and absorption coefficients. Validation presents differences less than 0.1% compared with that reported in the literature. The MCLTmx code discriminates between ballistic and diffuse photons, and inside of biological tissue, it calculates: specular reflection, diffuse reflection, ballistics transmission, diffuse transmission and absorption, and all parameters dependent on wavelength and thickness. The MCLTmx code can be useful for light transport inside any medium by changing the parameters that describe the new medium: anisotropy, dispersion and attenuation coefficients, and refractive indices for specific wavelength.
这项工作的目的是开发一个用于光传输的事件驱动蒙特卡罗代码（称为 MCLTmx），以识别和量化生物组织内的弹道、扩散和吸收光子，以及它们的相互作用坐标。在散射或吸收过程中，两个相互作用之间的平均自由程长度被计算出来，如果需要，散射角被计算出来，直到光子消失或离开感兴趣区域。使用三层阵列（空气-组织-空气），形成半无限三明治。光源放置在 (0,0,0)，向 (0,0,1) 发射。输入数据包括：折射率、目标厚度（0.02、0.05、0.1、0.5 和 1 厘米）、粒子历史数和 λ，代码从中计算出：各向异性、散射和吸收系数。验证结果与文献报道的结果相比差异小于 0.1%。MCLTmx 代码可区分弹道光子和扩散光子，并在生物组织内计算：镜面反射、漫反射、弹道透射、漫透射和吸收，以及所有依赖于波长和厚度的参数。通过改变描述新介质的参数，MCLTmx 代码可用于任何介质内部的光传输：各向异性、色散和衰减系数，以及特定波长的折射率。
