The problem of image restoration in cryo-EM entails correcting for the effects of the Contrast Transfer
Function (CTF) and noise. Popular methods for image restoration include ‘phase flipping’, which corrects
only for the Fourier phases but not amplitudes, and Wiener filtering, which requires the spectral signal to
noise ratio. We propose a new image restoration method which we call ‘Covariance Wiener Filtering’
(CWF). In CWF, the covariance matrix of the projection images is used within the classical Wiener filtering
framework for solving the image restoration deconvolution problem. Our estimation procedure for
the covariance matrix is new and successfully corrects for the CTF. Results with experimental
datasets demonstrate that CWF provides a good way to evaluate the particle images and to see what
the dataset contains even without 2D classification and averaging.

Further Reading:

T. Bhamre, T. Zhang, A. Singer, Denoising and Covariance Estimation of Single Particle Cryo-EM ImagesJournal of Structural Biology, 195 (1), pp. 72-81 (2016). PMID:27129418 [PubMed - in process]