title: Evaluation of metal artifacts in clinical MR images of patients with total hip arthroplasty using different metal artifact-reducing sequences.
abstract: OBJECTIVE
  To evaluate the distortion and artifact area of metal in MR images and to compare artifact reduction using different metal artifact-reducing sequences in patients with metal-on-metal (MoM) and non-MoM total hip prostheses.
  
  
  METHODS
  Thirty-six MoM and 15 non-MoM prostheses were examined in a 1.5-T MR scanner using T1-weighted (T1-w) sequences: turbo spin echo (TSE) high-readout bandwidth (hiBW), T1-w; TSE view angle tilting (VAT), T1-w; TSE VAT + slice encoding for metal artifact correction (SEMAC); short tau inversion recovery (STIR) hiBW or matched RF pulses (mRFp). Distortion was quantified using a new method measuring the acetabular roof angle (ARA). The artifact area was defined in the mid-coronal plane of the artifact.
  
  
  RESULTS
  The T1 VAT + SEMAC sequence showed the least distortion compared to T1 VAT and T1-hiBW (150°, 127° and 102°, p < 0.001, in MoM; 152°, 143° and 128°, p ≤ 0.014, in non-MoM). The artifact area was smaller in MoM prostheses using the T1 VAT sequence compared to T1 hiBW and T1 VAT + SEMAC (2506 mm(2), 3160 mm(2) and 3214 mm(2), p < 0.001) and smaller in non-MoM prostheses using T1 VAT compared to T1-hiBW (4296 mm(2) and 4831 mm(2), p = 0.041). STIR-mRFp substantially reduced the artifact size compared with STIR-hiBW (MoM 4559 mm(2) and 6323 mm(2); non-MoM 5625 mm(2) and 8764 mm(2), p < 0.001).
  
  
  CONCLUSIONS
  Metal artifacts in MR imaging examinations of hip prostheses can be evaluated for distortion using a distortion angle (ARA) and the degree of signal artifact as determined by measuring the largest cross-sectional artifact area. T1 VAT + SEMAC showed the least distortion; T1 VAT and STIR-mRFp were most efficient for reduction of the artifact area.
authors.affiliation: Department of Radiology, Lund University, Skåne University Hospital, Inga Marie Nilssonsgata 49, 20502, Malmö, Sweden, gunilla.muller@med.lu.se.
authors.forename: Gunilla M
authors.initials: GM
authors.lastname: Müller
authors.forename: Björn
authors.initials: B
authors.lastname: Lundin
authors.forename: Thord
authors.initials: T
authors.lastname: von Schewelov
authors.forename: Markus F
authors.initials: MF
authors.lastname: Müller
authors.forename: Olle
authors.initials: O
authors.lastname: Ekberg
authors.forename: Sven
authors.initials: S
authors.lastname: Månsson
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D016477:Artifacts; D005260:Female; D006621:Hip Joint / Q000473:pathology* / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D061825:Metal-on-Metal Joint Prostheses; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome