Gullberg G T, Huesman R H, Malko J A, Pelc N J, Budinger T F
Phys Med Biol. 1985 Aug;30(8):799-816. doi: 10.1088/0031-9155/30/8/004.
A new ray-driven projector-backprojector which can easily be adapted for hardware implementation is described and simulated in software. The projector-backprojector discretely models the attenuated Radon transform of a source distributed within an attenuating medium as line integrals of discrete pixels, obtained using the standard sampling technique of averaging the emission source or attenuation distribution over small square regions. Attenuation factors are calculated for each pixel during the projection and backprojection operations instead of using precalculated values. The calculation of the factors requires a specification of the attenuation distribution, estimated either from an assumed constant distribution and an approximate body outline or from transmission measurements. The distribution of attenuation coefficients is stored in memory for efficient access during the projection and backprojection operations. The reconstruction of the source distribution is obtained by using a conjugate gradient or SIRT type iterative algorithm which requires one projection and one backprojection operation for each iteration.
描述了一种新型的射线驱动投影仪-反投影仪，它易于适配硬件实现，并在软件中进行了模拟。该投影仪-反投影仪将分布在衰减介质中的源的衰减拉东变换离散地建模为离散像素的线积分，这些像素是使用标准采样技术获得的，即将发射源或衰减分布在小正方形区域上进行平均。在投影和反投影操作期间，为每个像素计算衰减因子，而不是使用预先计算的值。这些因子的计算需要指定衰减分布，该分布可以从假定的恒定分布和近似身体轮廓估计，也可以从透射测量估计。衰减系数的分布存储在内存中，以便在投影和反投影操作期间进行高效访问。源分布的重建通过使用共轭梯度或SIRT类型的迭代算法获得，每次迭代需要一次投影和一次反投影操作。
