Iterative reconstruction refers to iterative algorithms used to reconstruct 2D and 3D images in certain imaging techniques.For example, in computed tomography an image must be reconstructed from projections of an object. Here, iterative reconstruction techniques are usually abetter, but computationally more expensive alternative to the common filtered back projection (FBP) method, which directly calculates the image ina single reconstruction step. In recent research works, scientists have shown that extremely fast computations and massive parallelism is possible for iterative reconstruction, which makes iterative reconstruction practical for commercialization.