title: Unicompartmental knee arthroplasty MRI: impact of slice-encoding for metal artefact correction MRI on image quality, findings and therapy decision.
abstract: OBJECTIVE
  To evaluate the impact of slice-encoding for metal artefact correction (SEMAC) on image quality, findings, and therapy decision in patients with unicompartmental knee arthroplasty (UKA).
  
  
  METHODS
  Forty-five painful UKAs were examined at 1.5T-MRI (STIR, proton-density(PD)-weighted sequence, each with SEMAC and high-bandwidth). Artefact size, image quality, anatomic depiction, and clinically relevant findings were compared between SEMAC and high-bandwidth (2 readers). In 30 patients, therapy decision was retrospectively assessed by two orthopaedic surgeons without MRI, with high-bandwidth-MRI, and with SEMAC-MRI.
  
  
  RESULTS
  SEMAC reduced mean artefact size for STIR (11.8 cm(2) vs. 37.7 cm(2)) and PD (16.8 cm(2) vs. 18.9 cm(2)), p < 0.0005 for both comparisons. SEMAC showed more blurring than high-bandwidth, p < 0.0005. STIR-SEMAC revealed more bone marrow oedema (29 vs. 18 patients, p = 0.001, 30 vs. 13 patients, p < 0.0005, for reader 1 and 2 respectively). PD-SEMAC was worse in detecting meniscal lesions (6 missed, p = 0.031, 9 missed, p = 0.004, by reader 1 and 2 respectively) than PD-high-bandwidth. Revision-surgery was chosen in 12 and 11 patients without MRI (surgeon 1 and 2), with high-bandwidth-MRI in 15 and 14 patients, and with SEMAC-MRI in 19 and 14 patients.
  
  
  CONCLUSIONS
  STIR-SEMAC was useful in detecting bone marrow oedema and influenced the orthopaedic surgeons' decisions towards surgery, while PD-SEMAC showed no clinical benefit.
  
  
  CONCLUSIONS
  • Slice-encoding for metal artefact correction (SEMAC) MRI reduces metal-induced artefact size. • STIR SEMAC detects more bone marrow oedema in painful unicompartmental knee arthroplasty. • STIR SEMAC can help the orthopaedic surgeon with decision making. • PD SEMAC suffers from blurring of images, potentially masking relevant meniscal lesions. • PD SEMAC does not improve cartilage lesion detection in the non-operated compartments.
authors: Radiology Department, Balgrist University Hospital, Forchstrasse 340, 8008, Zurich, Switzerland, christoph.agten@balgrist.ch.
authors: Christoph A
authors: CA
authors: Agten
authors: Filippo
authors: F
authors: Del Grande
authors: Sandro F
authors: SF
authors: Fucentese
authors: Samuel
authors: S
authors: Blatter
authors: Christian W A
authors: CW
authors: Pfirrmann
authors: Reto
authors: R
authors: Sutter
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000473:pathology*; D019645:Arthroplasty, Replacement, Knee; D016477:Artifacts; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008670:Metals; D008875:Middle Aged; D010149:Postoperative Pain / Q000473:pathology*; D010820:Physicians; D011446:Prospective Studies; D011522:Protons
chemical_list: D008670:Metals; D011522:Protons
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