title: Influence of pulse sequence parameters at 1.5 T and 3.0 T on MRI artefacts produced by metal-ceramic restorations.
abstract: OBJECTIVE
  Susceptibility artefacts from dental materials may compromise MRI diagnosis. However, little is known regarding MRI artefacts of dental material samples with the clinical shapes used in dentistry. The present phantom study aims to clarify how pulse sequences and sequence parameters affect MRI artefacts caused by metal-ceramic restorations.
  
  
  METHODS
  A phantom consisting of nickel-chromium metal-ceramic restorations (i.e. dental crowns and fixed bridges) and cylindrical reference specimens immersed in agar gel was imaged in 1.5 and 3.0 T MRI scanners. Gradient echo (GRE), spin echo (SE) and ultrashort echo time (UTE) pulse sequences were used. The artefact area in each image was automatically calculated from the pixel values within a region of interest. Mean values for similar pulse sequences differing in one parameter at a time were compared. A comparison between mean artefact area at 1.5 and 3.0 T, and from GRE and SE was also carried out. In addition, a parametric correlation between echo time (TE) and artefact area was performed.
  
  
  RESULTS
  A significant correlation was found between TE and artefact area in GRE images. Higher receiver bandwidth significantly reduced artefact area in SE images. UTE images yielded the smallest artefact area at 1.5 T. In addition, a significant difference in mean artefact area was found between images at 1.5 and 3.0 T field strengths (p = 0.028) and between images from GRE and SE pulse sequences (p = 0.005).
  
  
  CONCLUSIONS
  It is possible to compensate the effect of higher field strength on MRI artefacts by setting optimized pulse sequences for scanning patients with metal-ceramic restorations.
authors.affiliation: 1 Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA.|2 Department of Radiology, Harvard Medical School, Boston, MA, USA.
authors.forename: A R G
authors.initials: AR
authors.lastname: Cortes
authors.affiliation: 3 Department of Stomatology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Abdala-Junior
authors.affiliation: 3 Department of Stomatology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: M
authors.initials: M
authors.lastname: Weber
authors.affiliation: 3 Department of Stomatology, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: E S
authors.initials: ES
authors.lastname: Arita
authors.affiliation: 1 Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, USA.|2 Department of Radiology, Harvard Medical School, Boston, MA, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Ackerman
mesh_terms: D016477:Artifacts; D002858:Chromium Alloys / Q000737:chemistry*; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry*; D003830:Denture, Partial, Fixed; D006801:Humans; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000379:methods*; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D019047:Phantoms, Imaging
chemical_list: D002858:Chromium Alloys; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain
keywords: artifact; magnetic resonance imaging; metal-ceramic restorations; pulse sequence