【摘要】 提出一种几何蒙特卡洛方法(GMC),利用光子位置与物质界面间的几何关系在整个计算区域而非单个网格内计算光子传输。计算区域无网格离散,光在物质界面处的传播严格依据其实际过程进行,消除了网格蒙特卡洛方法(VMC)中的光传播误差并大幅提高了计算速度。对于包含单根血管的情况,采用10μm网格,GMC的计算速度约为VMC的25倍。利用GMC方法计算了激光在多根同轴血管簇皮肤组织模型中的能量沉积,发现血液体积分数不变时,血液能量吸收特性对血管分布的依赖性随着血管数量的增加而降低。当血管数量为20根时,不同血管分布下血液能量吸收最大变动率不超过4%。这表明可以通过假设的血管分布开展研究而无需考虑真实的复杂血管结构,具有重要的实际应用意义。更多还原

【Abstract】 A three-dimensional geometric Monte Carlo(GMC) method is proposed. By taking advantage of the geometrical relationship between the photon position and the interface, GMC can simulate the photon transportation in the whole domain rather than a voxel. Discrete voxels are unnecessary and the photon motion is calculated according to the geometrical optics. Therefore the optical transmission error induced by the voxel Monte Carlo(VMC) method can be eliminated. Also, the computation time consumed by GMC is dramatically shortened, and GMC is about 25 times faster than VMC with voxel grid size of 10 microns for the single vessel situation. Through the calculation of the energy deposition in a tissue model with the multi-coaxial vessel cluster, it is found that the dependence of energy absorption on the vessel distribution will recede when the vessel number increases at a certain blood volume fraction(BVF). The largest deviation of blood energy absorption is 4% with 20 vessels when BVF is 5%. This implies that artificial vascular distribution can be used to predict the real absorption characteristics with the same blood volume fraction instead of difficult measurement of real complex distribution of blood vessels,which is of great practical importance for the clinical treatment.更多还原