Defocus-gradient corrected back-projection

• Published in: Ultramicroscopy Vol. 84; no. 1; pp. 57 - 64
• Main Authors: Jensen, Grant J, Kornberg, Roger D
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.07.2000; Elsevier Science
• Subjects: Algorithms; Computer simulation; Cryoelectron Microscopy; Data processing; DNA - chemistry; DNA - ultrastructure; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - ultrastructure; Electron microscopy; Electron, positron and ion microscopes, electron diffractometers and related techniques; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Image analysis; Image processing; Image Processing, Computer-Assisted - methods; Image reconstruction; Image reconstruction; tomography; Imaging and optical processing; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Models, Theoretical; Optical resolving power; Optics; Physics; TATA Box; TATA-Box Binding Protein; Three-dimensional reconstruction; Transcription Factor TFIIB; Transcription Factors - chemistry; Transcription Factors - ultrastructure; Transfer functions; Data processing; Image processing; 005; 041; Three-dimensional reconstruction; Viruses; Computerized simulation; Electron microscopy; Image reconstruction; Analytical method
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/S0304-3991(00)00005-X

Three-dimensional reconstructions of icosahedral viruses from cryoelectron microscope images have reached resolutions where the microscope depth of field is a significant resolution-limiting factor. An analytical treatment presented here shows how the depth of field limitation can be understood as an envelope function which gradually attenuates the signal, starting well before the numerical depth of field is actually reached. A simple modification to the well-known back-projection reconstruction algorithm is described, called the defocus-gradient corrected back-projection, which computationally corrects for the contrast transfer function along a defocus gradient. Computer simulations demonstrate how the algorithm effectively eliminates the depth of field limitation.