title: A standardized evaluation of artefacts from metallic compounds during fast MR imaging.
abstract: OBJECTIVE
  Metallic compounds present in the oral and maxillofacial regions (OMRs) cause large artefacts during MR scanning. We quantitatively assessed these artefacts embedded within a phantom according to standards set by the American Society for Testing and Materials (ASTM).
  
  
  METHODS
  Seven metallic dental materials (each of which was a 10-mm3cube embedded within a phantom) were scanned [i.e. aluminium (Al), silver alloy (Ag), type IV gold alloy (Au), gold-palladium-silver alloy (Au-Pd-Ag), titanium (Ti), nickel-chromium alloy (NC) and cobalt-chromium alloy (CC)] and compared with a reference image. Sequences included gradient echo (GRE), fast spin echo (FSE), gradient recalled acquisition in steady state (GRASS), a spoiled GRASS (SPGR), a fast SPGR (FSPGR), fast imaging employing steady state (FIESTA) and echo planar imaging (EPI; axial/sagittal planes). Artefact areas were determined according to the ASTM-F2119 standard, and artefact volumes were assessed using OsiriX MD software (Pixmeo, Geneva, Switzerland).
  
  
  RESULTS
  Tukey-Kramer post hoc tests were used for statistical comparisons. For most materials, scanning sequences eliciting artefact volumes in the following (ascending) order FSE-T1/FSE-T2< FSPGR/SPGR < GRASS/GRE < FIESTA < EPI. For all scanning sequences, artefact volumes containing Au, Al, Ag and Au-Pd-Ag were significantly smaller than other materials (in which artefact volume size increased, respectively, from Ti < NC < CC). The artefact-specific shape (elicited by the cubic sample) depended on the scanning plane (i.e. a circular pattern for the axial plane and a "clover-like" pattern for the sagittal plane).
  
  
  CONCLUSIONS
  The availability of standardized information on artefact size and configuration during MRI will enhance diagnosis when faced with metallic compounds in the OMR.
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Shumei
authors.initials: S
authors.lastname: Murakami
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Rinus G
authors.initials: RG
authors.lastname: Verdonschot
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Miyoshi
authors.initials: M
authors.lastname: Kataoka
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Kakimoto
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Shimamoto
authors.affiliation: 2 3D Craniofacial Image Laboratorium, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Sven
authors.initials: S
authors.lastname: Kreiborg
mesh_terms: D016477:Artifacts; D003764:Dental Materials; D008279:Magnetic Resonance Imaging; D008670:Metals; D019047:Phantoms, Imaging
chemical_list: D003764:Dental Materials; D008670:Metals
keywords: artefacts; dental materials; head and neck imaging; magnetic resonance imaging; radiology