title: Reduction of metal artifact in single photon-counting computed tomography by spectral-driven iterative reconstruction technique.
abstract: OBJECTIVE
  The exciting prospect of Spectral CT (SCT) using photon-counting detectors (PCD) will lead to new techniques in computed tomography (CT) that take advantage of the additional spectral information provided. We introduce a method to reduce metal artifact in X-ray tomography by incorporating knowledge obtained from SCT into a statistical iterative reconstruction scheme. We call our method Spectral-driven Iterative Reconstruction (SPIR).
  
  
  METHODS
  The proposed algorithm consists of two main components: material decomposition and penalized maximum likelihood iterative reconstruction. In this study, the spectral data acquisitions with an energy-resolving PCD were simulated using a Monte-Carlo simulator based on EGSnrc C++ class library. A jaw phantom with a dental implant made of gold was used as an object in this study. A total of three dental implant shapes were simulated separately to test the influence of prior knowledge on the overall performance of the algorithm. The generated projection data was first decomposed into three basis functions: photoelectric absorption, Compton scattering and attenuation of gold. A pseudo-monochromatic sinogram was calculated and used as input in the reconstruction, while the spatial information of the gold implant was used as a prior. The results from the algorithm were assessed and benchmarked with state-of-the-art reconstruction methods.
  
  
  RESULTS
  Decomposition results illustrate that gold implant of any shape can be distinguished from other components of the phantom. Additionally, the result from the penalized maximum likelihood iterative reconstruction shows that artifacts are significantly reduced in SPIR reconstructed slices in comparison to other known techniques, while at the same time details around the implant are preserved. Quantitatively, the SPIR algorithm best reflects the true attenuation value in comparison to other algorithms.
  
  
  CONCLUSIONS
  It is demonstrated that the combination of the additional information from Spectral CT and statistical reconstruction can significantly improve image quality, especially streaking artifacts caused by the presence of materials with high atomic numbers.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Strasse 22, 81675 Munich, Germany.
authors.forename: Radin A
authors.initials: RA
authors.lastname: Nasirudin
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Strasse 22, 81675 Munich, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Mei
authors.forename: Petar
authors.initials: P
authors.lastname: Penchev
authors.affiliation: Institut für Medizinische Physik und Strahlenschutz, Technische Hochschule Mittelhessen, Wiessenstrasse 14, 35390 Giessen, Germany.
authors.forename: Petar
authors.initials: P
authors.lastname: Panchev
authors.affiliation: Chair for Biomedical Physics and Institute for Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Fehringer
authors.affiliation: Chair for Biomedical Physics and Institute for Medical Engineering, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany.
authors.forename: Franz
authors.initials: F
authors.lastname: Pfeiffer
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Strasse 22, 81675 Munich, Germany.
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Rummeny
authors.affiliation: Institut für Medizinische Physik und Strahlenschutz, Technische Hochschule Mittelhessen, Wiessenstrasse 14, 35390 Giessen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Fiebich
authors.affiliation: Department of Diagnostic and Interventional Radiology, Technische Universität München, Ismaninger Strasse 22, 81675 Munich, Germany.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Noël
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008670:Metals / Q000737:chemistry*; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D017785:Photons; D019736:Prostheses and Implants; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface; D014965:X-Rays
chemical_list: D008670:Metals