title: Magnetic resonance imaging of knee cartilage using a water selective balanced steady-state free precession sequence.
abstract: OBJECTIVE
  To compare an optimized water selective balanced steady-state free precession sequence (WS-bSSFP) with conventional magnetic resonance (MR) sequences in imaging cartilage of osteoarthritic knees.
  
  
  METHODS
  Flip angles of sagittal and axial WS-bSSFP sequences were optimized in three volunteers. Subsequently, the knees of 10 patients with generalized osteoarthritis were imaged using sagittal and axial WS-bSSFP and conventional MR imaging techniques. We calculated contrast-to-noise ratios (CNR) between cartilage and its surrounding tissues to quantitatively analyze the various sequences. Using dedicated software we compared, in two other patients, the accuracy of cartilage volume measurements with anatomic sections of the tibial plateau.
  
  
  RESULTS
  CNRtotal eff (CNR efficiency between cartilage and its surrounding tissue) using WS-bSSFP was maximal with a 20-25 degrees flip angle. CNRtotal eff was higher in WS-bSSFP than in conventional images: 6.1 times higher compared to T1-weighted gradient echo (GE) images, 5.1 compared to proton-density (PD) fast spin echo (FSE) images, and 4.8 compared to T2-weighted FSE images. The mean difference of cartilage volume measurement on WS-bSSFP and anatomic sections was 0.06 mL compared to 0.24 mL for T1-GE and anatomic sections.
  
  
  CONCLUSIONS
  A WS-bSSFP sequence is superior to conventional MR imaging sequences in imaging cartilage of the knee in patients with osteoarthritis.
authors.affiliation: Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands. P.R.Kornaat@lumc.nl
authors.forename: Peter R
authors.initials: PR
authors.lastname: Kornaat
authors.forename: Joost
authors.initials: J
authors.lastname: Doornbos
authors.forename: Aart J
authors.initials: AJ
authors.lastname: van der Molen
authors.forename: Margreet
authors.initials: M
authors.lastname: Kloppenburg
authors.forename: Rob G
authors.initials: RG
authors.lastname: Nelissen
authors.forename: Pancras C W
authors.initials: PC
authors.lastname: Hogendoorn
authors.forename: Johan L
authors.initials: JL
authors.lastname: Bloem
mesh_terms: D000368:Aged; D002358:Cartilage, Articular / Q000473:pathology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000473:pathology*; D012016:Reference Values