Smithies D J, Lindmo T, Chen Z, Nelson J S, Milner T E
Beckman Laser Institute and Medical Clinic, University of California at Irvine, 92612, USA.
Phys Med Biol. 1998 Oct;43(10):3025-44. doi: 10.1088/0031-9155/43/10/024.
A Monte Carlo model has been developed for optical coherence tomography (OCT). A geometrical optics implementation of the OCT probe with low-coherence interferometric detection was combined with three-dimensional stochastic Monte Carlo modelling of photon propagation in the homogeneous sample medium. Optical properties of the sample were selected to simulate intralipid and blood, representing moderately (g = 0.7) and highly (g = 0.99) anisotropic scattering respectively. For shallow optical depths in simulated intralipid (<3 scattering mean free path (mfp) units), the number of detected backscattered photons followed the extinction-single-backscatter model, and OCT was found to detect only minimally scattered photons. Within this depth range the backscatter positions of detected photons corresponded well with the nominal focus position of the probe. For propagation to deeper positions in intralipid, localization of backscattering was quickly lost due to detection of stray photons, and the number of detected photons remained constant with increasing depth in the non-absorbing medium. For strongly forward-directed scattering in simulated blood, the number of detected photons approached the extinction-single-backscatter model only for very shallow depths (<2 mfp units). However, backscattering positions for detected photons correlated well with the nominal focus position of the probe even for optical depths greater than 40 mfp units.
已经开发出一种用于光学相干断层扫描（OCT）的蒙特卡罗模型。将具有低相干干涉检测功能的OCT探头的几何光学实现方式与光子在均匀样品介质中传播的三维随机蒙特卡罗建模相结合。选择样品的光学特性来模拟脂质乳剂和血液，分别代表中等程度（g = 0.7）和高度（g = 0.99）的各向异性散射。对于模拟脂质乳剂中的浅光学深度（<3个散射平均自由程（mfp）单位），检测到的后向散射光子数量遵循消光-单次后向散射模型，并且发现OCT仅检测到极少散射的光子。在此深度范围内，检测到的光子的后向散射位置与探头的标称焦点位置非常吻合。对于在脂质乳剂中传播到更深的位置，由于杂散光子的检测，后向散射的定位很快就会丢失，并且在非吸收性介质中，检测到的光子数量随着深度的增加而保持恒定。对于模拟血液中的强前向散射，仅在非常浅的深度（<2个mfp单位）下，检测到的光子数量才接近消光-单次后向散射模型。然而，即使对于大于40个mfp单位的光学深度，检测到的光子的后向散射位置也与探头标称焦点位置高度相关。
