title: Temporal sparsity exploiting nonlocal regularization for 4D computed tomography reconstruction.
abstract: X-ray imaging applications in medical and material sciences are frequently limited by the number of tomographic projections collected. The inversion of the limited projection data is an ill-posed problem and needs regularization. Traditional spatial regularization is not well adapted to the dynamic nature of time-lapse tomography since it discards the redundancy of the temporal information. In this paper, we propose a novel iterative reconstruction algorithm with a nonlocal regularization term to account for time-evolving datasets. The aim of the proposed nonlocal penalty is to collect the maximum relevant information in the spatial and temporal domains. With the proposed sparsity seeking approach in the temporal space, the computational complexity of the classical nonlocal regularizer is substantially reduced (at least by one order of magnitude). The presented reconstruction method can be directly applied to various big data 4D (x, y, z+time) tomographic experiments in many fields. We apply the proposed technique to modelled data and to real dynamic X-ray microtomography (XMT) data of high resolution. Compared to the classical spatio-temporal nonlocal regularization approach, the proposed method delivers reconstructed images of improved resolution and higher contrast while remaining significantly less computationally demanding.
authors.affiliation: The Manchester X-ray Imaging Facility, School of Materials, The University of Manchester, Manchester, UK.|Research Complex at Harwell, Didcot, Oxfordshire, UK.
authors.forename: Daniil
authors.initials: D
authors.lastname: Kazantsev
authors.affiliation: The Manchester X-ray Imaging Facility, School of Materials, The University of Manchester, Manchester, UK.|Research Complex at Harwell, Didcot, Oxfordshire, UK.
authors.forename: Enyu
authors.initials: E
authors.lastname: Guo
authors.affiliation: Neutron Imaging and Activation Group, Paul Scherrer Institut, Switzerland.
authors.forename: Anders
authors.initials: A
authors.lastname: Kaestner
authors.affiliation: School of Mathematics, Alan Turing Building, The University of Manchester, Manchester, UK.
authors.forename: William R B
authors.initials: WR
authors.lastname: Lionheart
authors.affiliation: Unilever Research, Colworth, UK.
authors.forename: Julian
authors.initials: J
authors.lastname: Bent
authors.affiliation: The Manchester X-ray Imaging Facility, School of Materials, The University of Manchester, Manchester, UK.|Research Complex at Harwell, Didcot, Oxfordshire, UK.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Withers
authors.affiliation: The Manchester X-ray Imaging Facility, School of Materials, The University of Manchester, Manchester, UK.|Research Complex at Harwell, Didcot, Oxfordshire, UK.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Lee
mesh_terms: D000465:Algorithms; D000818:Animals; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D051379:Mice; D019047:Phantoms, Imaging; D013977:Tibia / Q000000981:diagnostic imaging
keywords: Iterative reconstruction; X-ray microtomography; big data; material science; nonlocal graphs; p-Laplacian; spatio-temporal regularization; time-lapse