title: [Artifacts from dental metal alloys in magnetic resonance imaging].
abstract: OBJECTIVE
  To evaluate the artifact sizes at 3.0 T compared to at 1.5 T caused by three kinds of metallic dental materials, and to evaluate the influences of different magnetic resonance imaging (MRI) sequences on the artifact.
  
  
  METHODS
  Samples of metal-ceramic crown of three kinds of dental materials (Ni-Cr alloy, Co-Cr alloy, and gold alloy) were placed in a cylindrical plastic vessel filled with agarose gel. Acrylic resin crown was used as control. Images were performed by means of 1.5 T and 3.0 T MRI apparatus with 4 different sequences commonly used in brain MRI sequences. Artifact diameter was calculated and compared quantitatively. A 4 x 4 x 2 factorial design was applied to determine the effects on the MRI artifact of different metal materials, different sequences, and different magnetic field strengths.
  
  
  RESULTS
  ANOVA of factorial design showed that the influences of material, magnetic field strength, and sequence were all significantly different( materials: F = 124.796, df = 3, P = 0.000; magnetic field strength: F = 9.367, df = 1, P = 0.003; sequence: F = 3.020, df = 3, P = 0.036). Among the 3 kinds of alloys, the gold alloy produced the least artifact. Among the 4 imaging sequences, fast spin echo (FSE) produced the least artifact. The artifact sizes increased at 3.0 T compared to at 1.5T. Interactions among the 3 factors did not influence the artifacts significantly (P > 0.05).
  
  
  CONCLUSIONS
  Selection of specific metal material and imaging sequence can minimize the metal artifacts in MRI. The increment of artifacts at 3.0 T is only by 10% compared to that at 1.5 T. But 3.0 T MRI system has great advantages, so it is eligible on patients with metal restoration.
authors.affiliation: Department of Stomatology, Sir Run Run Shaw Hospital of Zhejiang University Medical College, Hangzhou 310016, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Cao
authors.forename: Li-li
authors.initials: LL
authors.lastname: Chen
authors.forename: Xiang-yang
authors.initials: XY
authors.lastname: Gong
mesh_terms: D016477:Artifacts; D003722:Dental Alloys / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*
chemical_list: D003722:Dental Alloys