title: Accuracy of 3D dual echo steady state (DESS) MR arthrography to quantify acetabular cartilage thickness.
abstract: OBJECTIVE
  To deploy and quantify the accuracy of 3D dual echo steady state (DESS) MR arthrography with hip traction to image acetabular cartilage. Clinical magnetic resonance imaging (MRI) sequences used to image hip cartilage often have reduced out-of-plane resolution and may lack adequate signal-to-noise to image cartilage.
  
  
  METHODS
  Saline was injected into four cadaver hips placed under traction. 3D DESS MRI scans were obtained before and after cores of cartilage were harvested from the acetabulum; the two MRIs were spatially aligned to reference core positions. The thickness of cartilage cores was measured under microscopy to serve as the reference standard. 3D reconstructions of cartilage and subchondral bone were generated using automatic and semiautomatic image segmentation. Cartilage thickness estimated from the 3D reconstructions was compared to physical measurements using Bland-Altman plots.
  
  
  RESULTS
  As revealed by the automatic segmentation mask, saline imbibed the joint space throughout the articulating surface, with the exception of the posteroinferior region in two hips. Locations where air bubbles were introduced and regions of suspected low density bone disrupted an otherwise smooth automatic segmentation mask. Automatic and semiautomatic segmentation yielded a bias ± repeatability coefficient (95% limits of agreement) of 0.10 ± 0.51 mm (-0.41 to 0.61 mm) and 0.06 ± 0.43 mm (-0.37 to 0.49 mm), respectively.
  
  
  CONCLUSIONS
  Cartilage thickness can be estimated to within ∼0.5 mm of the physical value with 95% confidence using 3D reconstructions of 3D DESS MR arthrography images. Manual correction of the automatic segmentation mask may improve reconstruction accuracy.
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah, USA.|Department of Orthopaedics, University of Utah, Salt Lake City, Utah, USA.
authors: Christine L
authors: CL
authors: Abraham
authors: Department of Radiology, University of Utah, Salt Lake City, Utah, USA.|Department of Electrical and Computer Engineering, Brigham Young University, Provo, Utah, USA.
authors: Neal K
authors: NK
authors: Bangerter
authors: Department of Orthopaedics, University of Utah, Salt Lake City, Utah, USA.
authors: Lance S
authors: LS
authors: McGavin
authors: Department of Orthopaedics, University of Utah, Salt Lake City, Utah, USA.
authors: Christopher L
authors: CL
authors: Peters
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah, USA.|Department of Orthopaedics, University of Utah, Salt Lake City, Utah, USA.
authors: Alex J
authors: AJ
authors: Drew
authors: Department of Radiology, University of Utah, Salt Lake City, Utah, USA.
authors: Christopher J
authors: CJ
authors: Hanrahan
authors: Department of Bioengineering, University of Utah, Salt Lake City, Utah, USA.|Department of Orthopaedics, University of Utah, Salt Lake City, Utah, USA.
authors: Andrew E
authors: AE
authors: Anderson
mesh_terms: D000077:Acetabulum / Q000033:anatomy & histology*; D000328:Adult; D001175:Arthrography / Q000379:methods*; D002102:Cadaver; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio
keywords: DESS MRI; cartilage imaging; cartilage thickness; hip; osteoarthritis