title: Metallic artefacts in MR imaging: effects of main field orientation and strength.
abstract: OBJECTIVE
  To determine the effect of metallic implant positioning on magnetic resonance (MR) imaging artefacts, and to determine the optimal imaging parameters for minimization of metallic artefacts.
  
  
  METHODS
  In a phantom and in three joints with non-ferromagnetic metallic implants imaged at 1.5 and/or at 0.2 T, we examined the influence of the static magnetic field (B(0)) strength and orientation, frequency-encoding direction, and type of imaging sequence on metallic artefacts.
  
  
  RESULTS
  The impact of artefacts caused by metallic objects depends mainly on the relationship between the anatomy of interest and the orientation of the object relative to the direction of B(0). The main field strength plays a less important role, but its orientation depends on the type of MR imager.
  
  
  CONCLUSIONS
  MR artefacts can be easily minimized by optimally positioning patients with metallic implants in the magnet. Knowledge of how this influences MR imaging is helpful in patient selection and guiding limb positioning.
authors.affiliation: Department of Radiology, University of California at San Francisco, San Francisco, California 94117-1349, USA. ali.guermazi@oarg.ucsf.edu
authors.forename: A
authors.initials: A
authors.lastname: Guermazi
authors.forename: Y
authors.initials: Y
authors.lastname: Miaux
authors.forename: S
authors.initials: S
authors.lastname: Zaim
authors.forename: C G
authors.initials: CG
authors.lastname: Peterfy
authors.forename: D
authors.initials: D
authors.lastname: White
authors.forename: H K
authors.initials: HK
authors.lastname: Genant
mesh_terms: D016477:Artifacts; D006801:Humans; D007595:Joint Prosthesis; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics; D008670:Metals; D014953:Wrist
chemical_list: D008670:Metals