title: T2 Relaxation time quantitation differs between pulse sequences in articular cartilage.
abstract: BACKGROUND
  To compare T2 relaxation time measurements between MR pulse sequences at 3 Tesla in agar phantoms and in vivo patellar, femoral, and tibial articular cartilage.
  
  
  METHODS
  T2 relaxation times were quantified in phantoms and knee articular cartilage of eight healthy individuals using a single echo spin echo (SE) as a reference standard and five other pulse sequences: multi-echo SE (MESE), fast SE (2D-FSE), magnetization-prepared spoiled gradient echo (3D-MAPSS), three-dimensional (3D) 3D-FSE with variable refocusing flip angle schedules (3D vfl-FSE), and quantitative double echo steady state (qDESS). Cartilage was manually segmented and average regional T2 relaxation times were obtained for each sequence. A regression analysis was carried out between each sequence and the reference standard, and root-mean-square error (RMSE) was calculated.
  
  
  RESULTS
  Phantom measurements from all sequences demonstrated strong fits (R(2)  > 0.8; P < 0.05). For in vivo cartilage measurements, R(2) values, slope, and RMSE were: MESE: 0.25/0.42/5.0 ms, 2D-FSE: 0.64/1.31/9.3 ms, 3D-MAPSS: 0.51/0.66/3.8 ms, 3D vfl-FSE: 0.30/0.414.2 ms, qDESS: 0.60/0.90/4.6 ms.
  
  
  CONCLUSIONS
  2D-FSE, qDESS, and 3D-MAPSS demonstrated the best fits with SE measurements as well as the greatest dynamic ranges. The 3D-MAPSS, 3D vfl-FSE, and qDESS demonstrated the closest average measurements to SE. Discrepancies in T2 relaxation time quantitation between sequences suggest that care should be taken when comparing results between studies.
authors.affiliation: Radiology, Stanford University, Stanford, California, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Matzat
authors.affiliation: Radiology, Stanford University, Stanford, California, USA.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: McWalter
authors.affiliation: Radiology, Stanford University, Stanford, California, USA.
authors.forename: Feliks
authors.initials: F
authors.lastname: Kogan
authors.affiliation: MR Applied Science Laboratory, GE Healthcare, Menlo Park, California, USA.
authors.forename: Weitian
authors.initials: W
authors.lastname: Chen
authors.affiliation: Radiology, Stanford University, Stanford, California, USA.|Bioengineering, Stanford University, Stanford, California, USA.
authors.forename: Garry E
authors.initials: GE
authors.lastname: Gold
mesh_terms: D000328:Adult; D000465:Algorithms; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: T2 relaxation time mapping; cartilage; magnetic resonance imaging; pulse sequence