title: Ultra-high field diffusion tensor imaging of articular cartilage correlated with histology and scanning electron microscopy.
abstract: OBJECTIVE
  To investigate the relationship of the different diffusion tensor imaging (DTI) parameters (ADC, FA, and first eigenvector (EV)) to the constituents (proteoglycans and collagen), the zonal arrangement of the collagen network, and mechanical loading of articular cartilage.
  
  
  METHODS
  DTI of eight cartilage-on-bone samples of healthy human patellar cartilage was performed at 17.6 T. Three samples were additionally imaged under indentation loading. After DTI, samples underwent biomechanical testing, safranin-O staining for semiquantitative proteoglycan estimation, and scanning electron microscopy (SEM) for depicting collagen architecture.
  
  
  RESULTS
  From the articular surface to the bone-cartilage interface, ADC continuously decreased and FA increased. Cartilage zonal heights calculated from EVs strongly correlated with SEM-derived zonal heights (P < 0.01, r (2)=0.87). Compression reduced ADC in the superficial 30% of cartilage and increased FA in the superficial 5% of cartilage. Reorientation of the EVs indicative of collagen fiber reorientation under the indenter was observed. No significant correlation was found between ADC, FA, and compressive stiffness.
  
  
  CONCLUSIONS
  Correlating ADC and FA with proteoglycan and collagen content suggests that diffusion is dominated by different depth-dependent mechanisms within cartilage. Knowledge of the spatial distribution of the DTI parameters and their variation contributes to form a database for future analysis of defective cartilage.
authors.affiliation: Department of Radiology, New York University Langone Medical Center, Center of Biomedical Imaging, 660 First avenue, 4th floor, New York, NY 10016, USA. Jose.Raya@nyumc.org
authors.forename: José G
authors.initials: JG
authors.lastname: Raya
authors.forename: Andreas P
authors.initials: AP
authors.lastname: Arnoldi
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Weber
authors.forename: Lucianna
authors.initials: L
authors.lastname: Filidoro
authors.forename: Olaf
authors.initials: O
authors.lastname: Dietrich
authors.forename: Silvia
authors.initials: S
authors.lastname: Adam-Neumair
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mützel
authors.forename: Gerd
authors.initials: G
authors.lastname: Melkus
authors.forename: Reinhard
authors.initials: R
authors.lastname: Putz
authors.forename: Maximilian F
authors.initials: MF
authors.lastname: Reiser
authors.forename: Peter M
authors.initials: PM
authors.lastname: Jakob
authors.forename: Christian
authors.initials: C
authors.lastname: Glaser
mesh_terms: D000328:Adult; D016880:Anisotropy; D001696:Biomechanical Phenomena / Q000502:physiology*; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000166:cytology* / Q000648:ultrastructure; D003094:Collagen / Q000032:analysis; D004058:Diffusion; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D010329:Patella / Q000033:anatomy & histology / Q000166:cytology; D011509:Proteoglycans / Q000032:analysis / Q000648:ultrastructure
chemical_list: D011509:Proteoglycans; D003094:Collagen