3D RECONSTRUCTION IN ELECTRON-MICROSCOPY USING ART WITH SMOOTH SPHERICALLY SYMMETRICAL VOLUME ELEMENTS (BLOBS)

Algebraic reconstruction techniques (ART) are iterative procedures for solving systems of linear equations. They have been used in tomograph y to recover objects from their projections. In this work we apply an ART approach in which the basis functions used to describe the objects are not based on voxels, but are much smoother functions named ''blob s'', The data collection studied in this work follows the so-called '' conical tilt geometry'' that is commonly used in many applications of three-dimensional electron microscopy of biological macromolecules. Th e performance of ART with blobs is carefully compared with a currently well-known three dimensional (3D) reconstruction algorithm (weighted backprojection) using a methodology which assigns a level of statistic al significance to a claim of relative superiority of one algorithm ov er another for a particular task. The conclusion we reach is that ART with blobs produces high-quality reconstructions and is, in particular , superior to weighted backprojection in recovering features along the ''vertical'' direction. For the exact implementation recommended in t his paper, the computational costs of ART are almost an order of magni tude smaller than those of WBP. (C) 1998 Elsevier Science B.V. All rig hts reserved.