1. A computer implemented method for improving a three-dimensional (3D) tomographic reconstruction of a sample, said method comprising: removing uncorrelated noise in said 3D reconstruction with COMET or other regularization techniques; and removing correlated noise in said 3D tomographic reconstruction by applying an Extended Field Iterative Reconstruction Technique (EFIRT) procedure, said EFIRT procedure comprising performing a set of successive tomographic reconstructions on an extended field larger than a region of interest (ROI) and extracting and averaging the ROI from said set of successive tomographic reconstructions, wherein the set of successive tomographic reconstructions is performed by increasing a volume of the extended field for each successive tomographic reconstruction.