title: Prospects for quantitative computed tomography imaging in the presence of foreign metal bodies using statistical image reconstruction.
abstract: X-ray computed tomography (CT) images of patients bearing metal intracavitary applicators or other metal foreign objects exhibit severe artifacts including streaks and aliasing. We have systematically evaluated via computer simulations the impact of scattered radiation, the polyenergetic spectrum, and measurement noise on the performance of three reconstruction algorithms: conventional filtered backprojection (FBP), deterministic iterative deblurring, and a new iterative algorithm, alternating minimization (AM), based on a CT detector model that includes noise, scatter, and polyenergetic spectra. Contrary to the dominant view of the literature, FBP streaking artifacts are due mostly to mismatches between FBP's simplified model of CT detector response and the physical process of signal acquisition. Artifacts on AM images are significantly mitigated as this algorithm substantially reduces detector-model mismatches. However, metal artifacts are reduced to acceptable levels only when prior knowledge of the metal object in the patient, including its pose, shape, and attenuation map, are used to constrain AM's iterations. AM image reconstruction, in combination with object-constrained CT to estimate the pose of metal objects in the patient, is a promising approach for effectively mitigating metal artifacts and making quantitative estimation of tissue attenuation coefficients a clinical possibility.
authors.affiliation: Department of Radiation Oncology, Washington University, St. Louis, Missouri 63110, USA. jfwilliamson@vcu.edu
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Williamson
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Whiting
authors.forename: Jasenka
authors.initials: J
authors.lastname: Benac
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Murphy
authors.forename: G James
authors.initials: GJ
authors.lastname: Blaine
authors.forename: Joseph A
authors.initials: JA
authors.lastname: O'Sullivan
authors.forename: David G
authors.initials: DG
authors.lastname: Politte
authors.forename: Donald L
authors.initials: DL
authors.lastname: Snyder
mesh_terms: D000465:Algorithms; D001918:Brachytherapy / Q000379:methods; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008670:Metals; D015233:Models, Statistical; D019047:Phantoms, Imaging; D017785:Photons; D012542:Scattering, Radiation; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014965:X-Rays
chemical_list: D008670:Metals