3-DIMENSIONAL RECONSTRUCTION FROM REDUCED SETS OF VERY NOISY IMAGES ACQUIRED FOLLOWING A SINGLE-AXIS TILT SCHEMA - APPLICATION OF A NEW 3-DIMENSIONAL RECONSTRUCTION ALGORITHM AND OBJECTIVE COMPARISON WITH WEIGHTED BACKPROJECTION

In this work we propose a reconstruction algorithm (ART with blobs) th at has not been previously used in electron Tomography and we compare it with the standard method in the field (weighted back projection, WB P). We assume that only a limited set of very noisy images, collected around a single axis tilt, is available; which is a typical situation in Electron Tomography. In general, the reconstruction problem is unde rdetermined (due to the limited number of projections) and the data ar e inconsistent (due to the high level of noise). The evaluation of the results is performed in a rigorous way by a task-oriented approach wh ich makes use of numerical observers. ART with blobs outperforms WBP f or a number of key tasks. Results are presented both for simplified li ne integral data and for realistic simulations of macromolecular struc tures embedded in amorphous ice. (C) 1997 Academic Press.