title: Optimal diffusion weighting for in vivo cardiac diffusion tensor imaging.
abstract: OBJECTIVE
  To investigate the influence of the diffusion weighting on in vivo cardiac diffusion tensor imaging (cDTI) and obtain optimal parameters.
  
  
  METHODS
  Ten subjects were scanned using stimulated echo acquisition mode echo planar imaging with six b-values, from 50 to 950 s·mm(-2) , plus b = 15 s·mm(-2) reference. The relationship between b-value and both signal loss and signal-to-noise ratio measures was investigated. Mean diffusivity, fractional anisotropy, and helical angle maps were calculated using all possible b-value pairs to investigate the effects of diffusion weighting on the main and reference data.
  
  
  RESULTS
  Signal decay at low b-values was dominated by processes with high apparent diffusion coefficients, most likely microvascular perfusion. This effect could be avoided by diffusion weighting of the reference images. Parameter maps were improved with increased b-value until the diffusion-weighted signal approached the noise floor. For the protocol used in this study, b = 750 s·mm(-2) combined with 150 s·mm(-2) diffusion weighting of the reference images proved optimal.
  
  
  CONCLUSIONS
  Mean diffusivity, fractional anisotropy, and helical angle from cDTI are influenced by the b-value of the main and reference data. Using optimal values improves parameter maps and avoids microvascular perfusion effects. This optimized protocol should provide greater sensitivity to pathological changes in parameter maps.
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Scott
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Pedro F A D C
authors.initials: PF
authors.lastname: Ferreira
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Nielles-Vallespin
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Gatehouse
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Laura-Ann
authors.initials: LA
authors.lastname: McGill
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Philip
authors.initials: P
authors.lastname: Kilner
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: Dudley J
authors.initials: DJ
authors.lastname: Pennell
authors.affiliation: NIHR Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK.|National Heart and Lung Institute, Imperial College, London, UK.
authors.forename: David N
authors.initials: DN
authors.lastname: Firmin
mesh_terms: D000328:Adult; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D056324:Diffusion Tensor Imaging; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006352:Heart Ventricles / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D055815:Young Adult
keywords: DTI; b-value; cardiac diffusion; diffusion weighting; microvascular perfusion