title: Multiple echo multi-shot diffusion sequence.
abstract: OBJECTIVE
  To measure both transversal relaxation time (T2 ) and diffusion coefficients within a single scan using a multi-shot approach. Both measurements have drawn interest in many applications, especially in skeletal muscle studies, which have short T2 values. Multiple echo single-shot schemes have been proposed to obtain those variables simultaneously within a single scan, resulting in a reduction of the scanning time. However, one problem with those approaches is the associated long echo read-out. Consequently, the minimum achievable echo time tends to be long, limiting the application of these sequences to tissues with relatively long T2 .
  
  
  METHODS
  To address this problem, we propose to extend the multi-echo sequences using a multi-shot approach, so that to allow shorter echo times. A multi-shot dual-echo EPI sequence with diffusion gradients and echo navigators was modified to include independent diffusion gradients in any of the two echoes.
  
  
  RESULTS
  The multi-shot approach allows us to drastically reduce echo times. Results showed a good agreement for the T2 and mean diffusivity measurements with gold standard sequences in phantoms and in vivo data of calf muscles from healthy volunteers.
  
  
  CONCLUSIONS
  A fast and accurate method is proposed to measure T2 and diffusion coefficients simultaneously, tested in vitro and in healthy volunteers.
authors.affiliation: Biomedical Engineering Department, Universidad de Valparaíso, Valparaíso, Chile.
authors.forename: Steren
authors.initials: S
authors.lastname: Chabert
authors.forename: César
authors.initials: C
authors.lastname: Galindo
authors.forename: Cristian
authors.initials: C
authors.lastname: Tejos
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Uribe
mesh_terms: D000328:Adult; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
keywords: diffusion MRI; multiple echoes; multiple shot; transversal relaxation time