采用MC法模拟设计了用于SPECT成像的多路平行束(MPB)准直器,将MPB系统重建的模具图像与平行束(PB)系统重建图像进行对比.用OS-EM迭代算法重建图像并计算对比度、信噪比、归一化标准偏差三个指标用于评价图像质量.结果表明:随着迭代次数增加,MPB系统重建图像中热源的对比度高于PB系统,对于小半径热源这个差值更明显,但是冷源的对比度低于PB系统;两个系统有可比较的重建图像收敛速度,随着迭代次数增加,MPB系统的噪声特性略差于PB系统.%A new design of multi-parallel beam collimator is proposed for SPECT imaging by MC simulation.The images obtained by multi-parallel beam svstem and parallel beam system are compared in this paper.The OS-EM algorithm is acted on the image reconstruction.Contrast,signal-to-noise ratio and normalized standard deviation are calculated for the image evaluatiou.The results indicate that,contrasts of hot sources acquired from multi-parallel beam system are bigger than those from parallel beam system which has the same sensitivity as multi-parallel beatn system.And the difference of contrasts between two systems is more obvious for hot source with a smaller radius.While the contrasts of cold sources from multi-parallel beam system are smaller than those from parallel beam system.These two systems have a comparable convergence speed of reconstructed image and the noise performance of multi-parallel beam system is slightly worse than that of parallel beam system.
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