title: Validation of a generic approach to muscle water T2 determination at 3T in fat-infiltrated skeletal muscle.
abstract: OBJECTIVE
  To introduce a novel method for skeletal muscle water T2 determination in fat-infiltrated tissues, using a tri-exponential fit of the global muscle signal decay.
  
  
  METHODS
  In all, 48 patients with various neuromuscular diseases were retrospectively selected and their thigh muscles analyzed. Each patient was imaged using a multispin-echo (MSME) sequence with a 17-echo train. The transmit field (B1+) inhomogeneities were evaluated using the actual flip angle imaging method toward voxel sorting. Muscle water T2 was quantified using a tri-exponential signal decay model. The difference between water T2 of voxels within the same muscle but having different fat ratio was analyzed using nonparametric statistical tests. In addition, we evaluated the correlation between fat ratio and T2 values obtained using both a mono- and tri-exponential approach.
  
  
  RESULTS
  The results showed that muscle water T2 values obtained using a tri-exponential approach combined with B1+ map-based voxel sorting were independent of the fat infiltration degree inside the muscle (R(2) < 0.03). This was not the case using the mono-exponential model, which measured different T2s between voxels of the same muscle but with various fat ratio (R(2) > 0.67; P < 10e(-4) ).
  
  
  CONCLUSIONS
  The tri-exponential model is an accurate tool to monitor muscle tissue disease activity devoid of bias introduced by fat infiltration.
authors.affiliation: Institute of Myology, NMR Laboratory, Paris, France; CEA, I2BM MIRCen IdM NMR Laboratory, Paris, France.
authors.forename: Noura
authors.initials: N
authors.lastname: Azzabou
authors.forename: Paulo
authors.initials: P
authors.lastname: Loureiro de Sousa
authors.forename: Ericky
authors.initials: E
authors.lastname: Caldas
authors.forename: Pierre G
authors.initials: PG
authors.lastname: Carlier
mesh_terms: D000273:Adipose Tissue; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013848:Thigh / Q000473:pathology; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water
keywords: B1 transmit based sorting; fat infiltration; muscle T2; tri-exponential fit