Modification of Green's one-step-late algorithm for attenuated emission data

Green's one-step-late (OSL) algorithm is a popular image reconstruction algorithm in emission-data tomography, in spite of its convergence issues. One drawback of Green's algorithm is that the algorithm exhibits non-stationary regularization when the algorithm's projector and backprojector model the attenuation effects in single photon emission computed tomography (SPECT). This paper suggests a remedy to improve Green's OSL algorithm so that stationary regularization can be obtained. This paper also observes some similarities between the modified Green's OSL algorithm and the gradient descent algorithm.