中文摘要：

高分辨率单光子发射计算机断层成像（SPECT）是临床和小动物影像的重要技术之一。对SPECT的系统传输矩阵进行建模,并结合于迭代重建算法中,是提高系统空间分辨率的有效手段。本文基于实验室自主研发的多针孔小动物SPECT系统,研究了一种蒙特卡罗模拟和解析模型相结合的系统传输矩阵精确计算方法。该方法是基于多点源模拟的投影数据,结合数据再估计方法和高斯拟合方法提取点扩展函数（PSF）特征参数,并结合解析形式的系统物理模型,从而计算任意位置的精确PSF。通过对四点源模拟投影数据分别用纯解析方法和蒙特卡罗模拟与解析模型相结合的方法进行计算,并对所得的系统传输矩阵进行重建对比,验证了蒙特卡罗模拟与解析模型相结合方法对图像分辨率的改善效果。进一步比较了不同点源排列的重建效果,获得了优化的点源排布方案。相对于基于实验方法测量系统传输矩阵,本方法能以更合理的代价实现系统传输矩阵的精确建模,并能有效提高系统空间分辨率。

英文摘要：

High resolution single photon emission computed tomography （SPECT） is a very important technology in clinical and small animal imaging. It has been proved that by modeling the system matrix of SPECT and using the iterative reconstruction algo- rithm, the spatial resolution can be improved efficiently. In this research, a method which combines Monte Carlo simulation and analytical model to calculate accurate system matrix was studied based on the small animal SPECT system. After the simulated point source projection data were acquired, the feature parameters of point spread function （PSF） were extracted by Gaussian fitting. Using the analytical model and the parameters make calculating the accurate PSF of any position in this system possible. In the reconstruction results of using two different system matrixes, one only used the ana lyticaI model and the other used the new method. The results vaIidate that the method proposed in this paper improves the spatial resolution of image. Furthermore, the influ- ence between different point source arrangements was studied in order to acquire a better arrangement. With respect to the method based on the experiment, this method can accurately realize the modeling of system matrix and improve the spatial resolution of image in a more appropriate way.