title: Correlation of signal attenuation-based quantitative magnetic resonance imaging with quantitative computed tomographic measurements of subchondral bone mineral density in metacarpophalangeal joints of horses.
abstract: OBJECTIVE
  To evaluate the ability of signal attenuation-based quantitative magnetic resonance imaging (QMRI) to estimate subchondral bone mineral density (BMD) as assessed via quantitative computed tomography (QCT) in osteoarthritic joints of horses.
  
  
  METHODS
  20 metacarpophalangeal joints from 10 horse cadavers.
  
  
  METHODS
  Magnetic resonance (MR) images (dorsal and transverse T1-weighted gradient recalled echo [GRE] and dorsal T2*-weighted GRE fast imaging employing steady-state acquisition [T2*-FIESTA]) and transverse single-slice computed tomographic (CT) images of the joints were acquired. Magnetic resonance signal intensity (SI) and CT attenuation were quantified in 6 regions of interest (ROIs) in the subchondral bone of third metacarpal condyles. Separate ROIs were established in the air close to the joint and used to generate corrected ratios and SIs. Computed tomographic attenuation was corrected by use of a calibration phantom to obtain a K(2)HPO(4)-equivalent density of bone. Correlations between QMRI performed with different MR imaging sequences and QCT measurements were evaluated. The intraobserver repeatability of ROI measurements was tested for each modality.
  
  
  RESULTS
  Measurement repeatability was excellent for QCT (R(2) = 98.3%) and QMRI (R(2) = 98.8%). Transverse (R(2) = 77%) or dorsal (R(2) = 77%) T1-weighted GRE and QCT BMD measurements were negatively correlated, as were dorsal T2*-FIESTA and QCT (R(2) = 80%) measurements. Decreased bone SI during MR imaging linearly reflected increased BMD.
  
  
  CONCLUSIONS
  Results of this ex vivo study suggested that signal attenuation-based QMRI was a reliable, clinically applicable method for indirect estimation of subchondral BMD in osteoarthritic metacarpophalangeal joints of horses.
authors.affiliation: Département des Biomédecine, Faculté de Médecine Vétérinaire, Université de Montréal, St-Hyacinthe, QC J2S 7C6, Canada.
authors.forename: Julien
authors.initials: J
authors.lastname: Olive
authors.forename: Marc-André
authors.initials: MA
authors.lastname: d'Anjou
authors.forename: Kate
authors.initials: K
authors.lastname: Alexander
authors.forename: Guy
authors.initials: G
authors.lastname: Beauchamp
authors.forename: Christine L
authors.initials: CL
authors.lastname: Theoret
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology*; D002102:Cadaver; D005552:Forelimb / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D007596:Joints / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000662:veterinary*; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000662:veterinary*