title: Spatial analysis of magnetic resonance T1rho and T2 relaxation times improves classification between subjects with and without osteoarthritis.
abstract: OBJECTIVE
  Studies have shown that functional analysis of knee cartilage based on magnetic resonance (MR) relaxation times is a valuable tool in the understanding of osteoarthritis (OA). In this work, the regional spatial distribution of knee cartilage T1rho, and T2 relaxation times based on texture and laminar analyses was studied to investigate if they provide additional insight compared to global mean values in the study of OA.
  
  
  METHODS
  Knee cartilage of 36 subjects, 19 healthy controls and 17 with mild OA, was divided into 16 compartments. T1rho and T2 relaxation times were studied with first order statistics, eight texture parameters with four different orientations using gray-level co-occurrence matrices and by subdividing each compartment into two different layers: Deep and superficial. Receiver operating characteristic curve analysis was performed to evaluate the potential of each technique to correctly classify the populations.
  
  
  RESULTS
  Although the deep and superficial cartilage layers had in general significantly different T1rho and T2 relaxation times, they performed similarly in terms of subject discrimination. The subdivision of lateral and medial femoral compartments into weight-bearing and non-weight-bearing regions did not improve discrimination. Also it was found that the most sensitive region was the patella and that T1rho discriminated better than T2. The most important finding was that with respect to global mean values, laminar and texture analyses improved subject discrimination.
  
  
  CONCLUSIONS
  Results of this study suggest that spatially assessing MR images of the knee cartilage relaxation times using laminar and texture analyses could lead to better and probably earlier identification of cartilage matrix abnormalities in subjects with OA.
authors.affiliation: Grupo Tecnológico Santa Fe, S.A. de C.V., Mexico City 06140, Mexico. Julio.Carballido@radiology.ucsf.edu
authors.forename: Julio
authors.initials: J
authors.lastname: Carballido-Gamio
authors.forename: Robert
authors.initials: R
authors.lastname: Stahl
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Blumenkrantz
authors.forename: Adan
authors.initials: A
authors.lastname: Romero
authors.forename: Sharmila
authors.initials: S
authors.lastname: Majumdar
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
mesh_terms: D000328:Adult; D002356:Cartilage / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007719:Knee Joint / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis* / Q000473:pathology*; D012372:ROC Curve