title: Musculoskeletal MR imaging at 4 T and at 1.5 T: comparison of relaxation times and image contrast.
abstract: OBJECTIVE
  To evaluate the relaxation time-based contrast between the main tissues of the musculoskeletal system as measured in the human knee with magnetic resonance imaging at 4 T and 1.5 T.
  
  
  METHODS
  Five volunteers underwent 4-T and 1.5-T imaging. Inversion-recovery series were used to measure T1 values, and T2 values were measured with a spin-echo sequence.
  
  
  RESULTS
  T1 values increased in all tissues with 4-T imaging. Values increased in muscle from 1 to 1.8 seconds, in fat from 0.3 to 0.4 seconds, and in cartilage from 0.8 to 1.5 seconds. T2 values were 10%-20% shorter in all tissues at 4 T.
  
  
  CONCLUSIONS
  Advantages of 4-T imaging compared with 1.5-T imaging include a higher signal-to-noise ratio and an improved signal difference-to-noise ratio. However, any improvement in signal-to-noise ratio at high field strengths can partially be reduced by the increase in the T1 value. The slightly shorter T2 values at 4 T do not affect image contrast.
authors.affiliation: Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Duewell
authors.forename: T L
authors.initials: TL
authors.lastname: Ceckler
authors.forename: K
authors.initials: K
authors.lastname: Ong
authors.forename: H
authors.initials: H
authors.lastname: Wen
authors.forename: F A
authors.initials: FA
authors.lastname: Jaffer
authors.forename: S A
authors.initials: SA
authors.lastname: Chesnick
authors.forename: R S
authors.initials: RS
authors.lastname: Balaban
mesh_terms: D002358:Cartilage, Articular / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement; D007717:Knee / Q000033:anatomy & histology*; D007719:Knee Joint / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008961:Models, Structural; D018482:Muscle, Skeletal / Q000033:anatomy & histology*