中文摘要：

扩散方程模型被广泛应用于光学CT图像的重建中，其精确性直接关系到所成图像的质量。为了研究扩散方程模型对近红外光子输运过程描述的精确性及其适用范围，本研究应用Monte Carlo（MC）模拟方法，分别给出了强、弱两类散射介质中光学CT正向问题的数值模拟结果，并将其与基于扩散方程的数值计算结果进行了比较。实验结果表明，扩散方程可以较为准确地描述光子在强散射介质中的输运过程；但对弱散射介质扩散方程模型却存在较大的误差，因而不适用于该种情况下的图像重建。

英文摘要：

Diffusion equation is now widely used in optical tomographic image reconstruction and the precision of this model has great impact on the quality of reconstructed images. In order to study the validity scope and the accuracy of this model, Monte Carlo （MC） simulation results are presented respectively for strong and weak scattering tissues along with some comparisons between the MC results and the results obtained from the finite element method （FEM）. Experimental results show that the diffusion equation based model is valid to describe the photon transportation process in strong scattering tissues, while relatively larger errors exist for the weak scattering tissues and hence it is not valid for that case.