【摘要】 蒙特卡罗法(MC)广泛用于模拟光在皮肤组织中的传播。发展了基于四面体网格的蒙特卡罗(TMC)方法,提出了距离阈值的概念避免数值耗散导致的错误能量沉积。通过计算带有单根血管的两层皮肤模型比较了几何蒙特卡罗(GMC)、基于结构化网格的蒙特卡罗(VMC)和TMC。GMC通过数学定义组织界面,避免了离散,精度最高,但不适用于复杂的界面。VMC实施简单,但是对曲折表面的离散会导致显著的误差。TMC使用边界适应性较好的四面体单元在计算的精度和灵活性上找到了平衡。计算结果表明,TMC法对几何形状的空间适应性远强于VMC,在复杂界面区域的误差仅为VMC法的10%~25%,是一种理想的边界区域离散化的方法。更多还原

【Abstract】 The Monte Carlo(MC) method is widely used in simulating light propagation in skin tissues. A tetrahedron-based Monte Carlo(TMC) method is developed. Energy deposition error due to numerical dissipation can be avoided by the definition of distance threshold. Laser propagation in a two-layered skin model with single blood vessel is simulated to compare geometry-based MC(GMC), voxel-based MC(VMC) and TMC. In GMC, the interface is defined mathematically without any discretization. It is the most accurate but not applicable to more complicated domains. The implement of VMC is simple but it may lead to non- neglected error due to zigzag polygonal interface. TMC provides balance between accuracy and flexibility in the treatment of photon-boundary interaction by the boundary adaptive tetrahedron cells. Numerical results reveal that space adaptability of geometrical shape of TMC is much stronger than that of VMC. Photon energy deposition error by TMC in complex interfacial region is 10%~25% of that by VMC. These results show that TMC is superior in the discretization of tissue boundaries.更多还原