title: Spline-based image-to-volume registration for three-dimensional electron microscopy.
abstract: This paper presents an algorithm based on a continuous framework for a posteriori angular and translational assignment in three-dimensional electron microscopy (3DEM) of single particles. Our algorithm can be used advantageously to refine the assignment of standard quantized-parameter methods by registering the images to a reference 3D particle model. We achieve the registration by employing a gradient-based iterative minimization of a least-squares measure of dissimilarity between an image and a projection of the volume in the Fourier transform (FT) domain. We compute the FT of the projection using the central-slice theorem (CST). To compute the gradient accurately, we take advantage of a cubic B-spline model of the data in the frequency domain. To improve the robustness of the algorithm, we weight the cost function in the FT domain and apply a "mixed" strategy for the assignment based on the minimum value of the cost function at registration for several different initializations. We validate our algorithm in a fully controlled simulation environment. We show that the mixed strategy improves the assignment accuracy; on our data, the quality of the angular and translational assignment was better than 2 voxel (i.e., 6.54 angstroms). We also test the performance of our algorithm on real EM data. We conclude that our algorithm outperforms a standard projection-matching refinement in terms of both consistency of 3D reconstructions and speed.
authors.affiliation: Biomedical Imaging Group, Ecole polytechnique fédérale de Lausanne (EPFL), CH-1015 Lausanne VD, Switzerland. Slavika.Jonic@lmcp.jussieu.fr
authors.forename: S
authors.initials: S
authors.lastname: Jonić
authors.forename: C O S
authors.initials: CO
authors.lastname: Sorzano
authors.forename: P
authors.initials: P
authors.lastname: Thévenaz
authors.forename: C
authors.initials: C
authors.lastname: El-Bez
authors.forename: S
authors.initials: S
authors.lastname: De Carlo
authors.forename: M
authors.initials: M
authors.lastname: Unser
mesh_terms: D000465:Algorithms; D001436:Bacteriorhodopsins / Q000737:chemistry / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted / Q000379:methods / Q000706:statistics & numerical data; D008854:Microscopy, Electron / Q000379:methods* / Q000706:statistics & numerical data; D008958:Models, Molecular
chemical_list: D001436:Bacteriorhodopsins