An immediate after-backprojection filtering method with blob-shaped window functions for voxel-based iterative reconstruction

Blobs have better resolution-noise performance than voxels because of the overlapping of their rotational symmetric basis functions; however, using blobs is more computationally costly than using voxels due to blob overlap. We propose an immediate after-backprojection filtering method (ABF) with blob-shaped window functions for a voxel-based reconstruction. We compared this method with the general voxel-based method (without filtering), the blob-based method, the voxel-based method with between-iteration filtering (BIF) and with post-filtering (POF), using computer simulations. The reconstruction quality was measured by the contrast recovery coefficient (CRC) versus the background noise. It is shown that the ABF method with blob windows is characterized by less image noise and preserved image contrast in comparison with both the general voxel-based method and the voxel-based method with BIF. When using a standard blob window a = 2.0, alpha = 10.4 and m = 2, the ABF method achieves identical CRC-noise features to the blob-based method with "standard" blobs. In addition, the ABF method can be combined with the POF method to achieve better noise-resolution performance than the general voxel-based POF method. The computational cost of the ABF method is slightly greater than that of the general voxel-based method, but much less than the blob-based method.