Correction of distance-dependent blurring in projection data for fully three-dimensional electron microscopic reconstruction

We propose a method of correction for distance-dependent blurring, which is one of the limiting factors to achieving higher resolution in 3D reconstructions of biological specimens from 2D projections obtained by an electron microscope. Our proposed correction is based on the frequency-distance relation that has been used successfully in correction of a similar problem in single photon emission tomography and has been suggested for electron microscopy data obtained by rotating a sample around a single axis. We extend these approaches to electron microscopy data that are obtained from arbitrary directions. We develop the theoretical background for a correction method that results in an estimate of a true projection data set, which then can be used to obtain a 3D reconstruction by any currently existing algorithm.