title: Regional variation in T1ρ and T2 times in osteoarthritic human menisci: correlation with mechanical properties and matrix composition.
abstract: OBJECTIVE
  Changes in T1ρ and T2 magnetic resonance relaxation times have been associated with articular cartilage degeneration, but similar relationships for meniscal tissue have not been extensively investigated. This work examined relationships between T1ρ and T2 measurements and biochemical and mechanical properties across regions of degenerate human menisci.
  
  
  METHODS
  Average T1ρ and T2 relaxation times were determined for nine regions each of seven medial and 13 lateral menisci from 14 total knee replacement patients. Sulfated glycosaminoglycan (sGAG), collagen and water contents were measured for each region. Biomechanical measurements of equilibrium compressive, dynamic compressive and dynamic shear moduli were made for anterior, central and posterior regions.
  
  
  RESULTS
  T1ρ and T2 times showed similar regional patterns, with longer relaxation times in the (radially) middle region compared to the inner and outer regions. Pooled over all regions, T1ρ and T2 times showed strong correlations both with one another and with water content. Correlations with biochemical content varied depending on normalization to wet or dry mass, and both imaging parameters showed stronger correlations with collagen compared to sGAG content. Mechanical properties displayed moderate inverse correlations with increasing T1ρ and T2 times and water content.
  
  
  CONCLUSIONS
  Both T1ρ and T2 relaxation times correlated strongly with water content and moderately with mechanical properties in osteoarthritic menisci, but not as strongly with sGAG or collagen contents alone. While the ability of magnetic resonance imaging (MRI) to detect early osteoarthritic changes remains the subject of investigation, these results suggest that T1ρ and T2 relaxation times have limited ability to detect compositional variations in degenerate menisci.
authors.affiliation: Department of Bioengineering, Stanford University, Stanford, CA 94305-4038, USA. minsunson@gmail.com
authors.forename: M
authors.initials: M
authors.lastname: Son
authors.forename: S B
authors.initials: SB
authors.lastname: Goodman
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: B A
authors.initials: BA
authors.lastname: Hargreaves
authors.forename: G E
authors.initials: GE
authors.lastname: Gold
authors.forename: M E
authors.initials: ME
authors.lastname: Levenston
mesh_terms: D000368:Aged; D001834:Body Water / Q000378:metabolism; D002358:Cartilage, Articular / Q000737:chemistry / Q000473:pathology*; D003094:Collagen / Q000378:metabolism; D005260:Female; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008592:Menisci, Tibial / Q000737:chemistry / Q000473:pathology*; D008875:Middle Aged
chemical_list: D006025:Glycosaminoglycans; C013786:A73025; D003094:Collagen