title: Evaluation of a metal artefact reduction tool on different positions of a metal object in the FOV.
abstract: OBJECTIVE
  To evaluate the action of a metal artefact reduction (MAR) tool when artefact-generator metal object is at different positions in the field of view (FOV).
  
  
  METHODS
  A cylindrical utility wax phantom, with a metal alloy sample inside, was made. The phantom was positioned centrally and peripherally in the FOV for image acquisition, with and without the MAR tool activation. The standard deviation values (image noise levels) from areas around the metal sample and the control area were obtained. The numbers were compared by Student's t-test (α = 0.05).
  
  
  RESULTS
  When the tool was activated, a significant difference of image noise was observed for central and peripheral positioning, for both control area (p = 0.0012) and metal area (p = 0.03), and a smaller level of noise was observed for images with phantoms in central positioning. A decrease in image noise with the tool activated was found only in phantoms with the metal object positioned centrally in the FOV.
  
  
  CONCLUSIONS
  For the MAR tool to be effective, the artefact-generator object needs to be in the central region of the FOV.
authors.affiliation: Department of Oral Diagnosis, Area of Oral Radiology, Piracicaba Dental School, University of Campinas, Piracicaba, Sao Paulo, Brazil.
authors.forename: Polyane M
authors.initials: PM
authors.lastname: Queiroz
authors.affiliation: Department of Oral Diagnosis, Area of Oral Radiology, Piracicaba Dental School, University of Campinas, Piracicaba, Sao Paulo, Brazil.
authors.forename: Gustavo M
authors.initials: GM
authors.lastname: Santaella
authors.affiliation: Department of Oral Diagnosis, Area of Oral Radiology, Piracicaba Dental School, University of Campinas, Piracicaba, Sao Paulo, Brazil.
authors.forename: Thais D J
authors.initials: TD
authors.lastname: da Paz
authors.affiliation: Department of Oral Diagnosis, Area of Oral Radiology, Piracicaba Dental School, University of Campinas, Piracicaba, Sao Paulo, Brazil.
authors.forename: Deborah Q
authors.initials: DQ
authors.lastname: Freitas
mesh_terms: D016477:Artifacts; D054893:Cone-Beam Computed Tomography; D008670:Metals; D019047:Phantoms, Imaging; D011861:Radiography, Dental / Q000379:methods*
chemical_list: D008670:Metals
keywords: CBCT; artefacts