title: 3D-T1rho-relaxation mapping of articular cartilage: in vivo assessment of early degenerative changes in symptomatic osteoarthritic subjects.
abstract: OBJECTIVE
  To determine the in vivo feasibility of quantifying early degenerative changes in patellofemoral joint of symptomatic human knee using spin-lattice relaxation time in the rotating frame (T(1rho)) magnetic resonance imaging (MRI).
  
  
  METHODS
  All the MRI experiments were performed on a 1.5 T whole-body GE Signa clinical scanner using a custom built 15-cm diameter transmit-receive quadrature birdcage radiofrequency coil. The T(1rho)-prepared magnetization was imaged with a three-dimensional gradient-echo pulse sequence pre-encoded with a three-pulse cluster consisting of two hard 90 degrees pulses and a low power spin-lock pulse. Quantitative T(1rho) relaxation maps of asymptomatic (n = 8 males), and six symptomatic human volunteers (four men, two women) were computed using a appropriate signal expression.
  
  
  RESULTS
  All six symptomatic volunteers showed elevation in T(1rho) relaxation times when compared with asymptomatic subjects. In symptomatic population, the T(1rho) relaxation times varied from 63 +/- 4 ms to 95 +/- 12 ms (mean +/- standard deviation) depending on the degree of cartilage degeneration. The increase in T(1rho) of symptomatic population was statistically significant (n = 6, P <.002) when compared with corresponding asymptomatic population. However, in asymptomatic population the relaxation times varied only from approximately 45 to 55 ms (n = 8, age range 22-45 years).
  
  
  CONCLUSIONS
  Preliminary results demonstrated the in vivo feasibility of quantifying early biochemical changes in symptomatic osteoarthritis subjects employing T(1rho)-weighted MRI on a 1.5 T clinical scanner. This study on limited number of symptomatic population shows that T(1rho)-weighted MRI provides a noninvasive marker for quantitation of early degenerative changes of cartilage in vivo. However, further studies are needed to correlate early osteoarthritis determined from arthroscopy with T(1rho) in a large symptomatic population.
authors.affiliation: Metabolic Magnetic Resonance Resource and Computing Center (MMRRCC), Department of Radiology, B1, Stellar-Chance Laboratories, University of Pennsylvania Medical Center, Philadelphia, PA 19104-6100, USA. regatte@mail.mmrrcc.upenn.edu
authors.forename: Ravinder Reddy
authors.initials: RR
authors.lastname: Regatte
authors.forename: Sarma V S
authors.initials: SV
authors.lastname: Akella
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Wheaton
authors.forename: Gwen
authors.initials: G
authors.lastname: Lech
authors.forename: Arijitt
authors.initials: A
authors.lastname: Borthakur
authors.forename: J Bruce
authors.initials: JB
authors.lastname: Kneeland
authors.forename: Ravinder
authors.initials: R
authors.lastname: Reddy
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D005269:Femur / Q000473:pathology; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis*; D010329:Patella / Q000473:pathology