title: Magnetic resonance imaging artifacts caused by aneurysm clips and shunt valves: dependence on field strength (1.5 and 3 T) and imaging parameters.
abstract: OBJECTIVE
  To evaluate artifact sizes at 3 T compared to at 1.5 T, and to evaluate the influence of scanning parameters with respect to artifact size on a 3-T magnetic resonance imaging (MRI) system.
  
  
  METHODS
  Two aneurysm clips and five shunt valves were imaged in a water phantom at 1.5 and 3 T. At 3 T the influence of bandwidth (spin echo (SE) images) and echo time (gradient echo (GRE) images) on artifact size (area and extension in two orthogonal directions) was investigated.
  
  
  RESULTS
  Artifact sizes increased substantially (typically 5-10 mm) at 3 T, compared to at 1.5 T, for implants entirely made of metallic materials, whereas the increase was the size less prominent (0-5 mm) for implants only partly containing metal. Artifact areas could be altered by changing the bandwidth or the echo time to about the same extent as it was affected by the increased field strength.
  
  
  CONCLUSIONS
  Artifact sizes increase at 3 T, compared to at 1.5 T, depending on the type and composition of the implant, but can be substantially reduced by altering the imaging parameters. Optimization of imaging protocols to minimize artifacts is therefore important at higher field strengths.
authors.affiliation: MR Department, Lund University Hospital, Lund, Sweden. Johan.Olsrud@med.lu.se
authors.forename: Johan
authors.initials: J
authors.lastname: Olsrud
authors.forename: Jimmy
authors.initials: J
authors.lastname: Lätt
authors.forename: Sara
authors.initials: S
authors.lastname: Brockstedt
authors.forename: Bertil
authors.initials: B
authors.lastname: Romner
authors.forename: Isabella M
authors.initials: IM
authors.lastname: Björkman-Burtscher
mesh_terms: D016477:Artifacts; D002557:Cerebrospinal Fluid Shunts / Q000295:instrumentation*; D002532:Intracranial Aneurysm / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008670:Metals; D019047:Phantoms, Imaging; D019736:Prostheses and Implants; D013525:Surgical Instruments
chemical_list: D008670:Metals