Forward and backprojection model (FP/BP)

Abstract

The forward projection (FP) operation is the mathematical model of the physical data acquisition process in computed tomography and tomosynthesis. The backprojection (BP) operation is the corresponding reverse model. The forward- and backprojection pair is a key module in reconstruction algorithms. In any iterative reconstruction algorithm this pair is used during each iteration at least once, therefore an optimal practical implementation is required to be fast, accurate and memory efficient. For the practical numerical implementation of the forward and backprojections, a continuous object has to be discretized, i.e. it has to be represented by a finite number of parameters.