title: Structural and mechanical parameters of trabecular bone estimated from in vivo high-resolution magnetic resonance images at 3 tesla field strength.
abstract: OBJECTIVE
  To evaluate the performance of a new 3 Tesla (T) high-resolution trabecular bone (TB) imaging technique at two resolution regimens in terms of serial reproducibility and sensitivity.
  
  
  METHODS
  The left distal tibial metaphysis of seven healthy volunteers was imaged at three time-points using a FLASE (fast large-angle spin-echo) pulse sequence at 137 x 137 x 410 mum(3) and (160 mum)(3) voxel sizes. Image artifacts, motion degradation, and serial image volume misalignments were controlled to maximize reproducibility of image-derived measures of scale, topology, orientation in terms of structural anisotropy, and finite-element derived Young's and shear moduli. Coefficients of variation (CV) and intraclass correlation coefficients (ICC) for structural and mechanical parameters were evaluated as measures of reproducibility and reliability. The ability of structural and mechanical parameters to distinguish between subjects was tested by analysis of variance.
  
  
  RESULTS
  Reproducibility was generally higher in the anisotropic data (CVs 1-5% versus 1-9% for isotropic images). Anisotropic voxel size yielded greater measurement reliability (ICCs 0.75-0.99, mean = 0.92 versus 0.62-0.99, mean = 0.86) and better discrimination of the seven subjects (75% versus 50% of the possible comparisons were significantly different [P < 0.05]) except for measures of structural anisotropy and topology. Isotropic resolution improved detection of structural orientation and permitted visualization of small perforations in longitudinal trabecular plates not detected at anisotropic resolution.
  
  
  CONCLUSIONS
  Improved image acquisition and processing techniques enhance reproducibility of structural and mechanical parameters derived from high-resolution MRI of metaphyseal bone in the distal tibia.
authors.affiliation: Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA. mikewald@gmail.com
authors.forename: Michael Jeffrey
authors.initials: MJ
authors.lastname: Wald
authors.forename: Jeremy Franklin
authors.initials: JF
authors.lastname: Magland
authors.forename: Chamith Sudesh
authors.initials: CS
authors.lastname: Rajapakse
authors.forename: Felix Werner
authors.initials: FW
authors.lastname: Wehrli
mesh_terms: D000465:Algorithms; D016880:Anisotropy; D003198:Computer Simulation; D055119:Elastic Modulus; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D033081:Shear Strength; D013977:Tibia / Q000033:anatomy & histology* / Q000502:physiology*; D055815:Young Adult