title: A high-resolution cardiovascular magnetic resonance diffusion tensor map from ex-vivo C57BL/6 murine hearts.
abstract: BACKGROUND
  The complex cardiac fiber structural organization and spatial arrangement of cardiomyocytes in laminar sheetlets contributes greatly to cardiac functional and contractile ejection patterns. This study presents the first comprehensive, ultra-high resolution, fully quantitative statistical tensor map of the fixed murine heart at isotropic resolution of 43 μm using diffusion tensor (DT) cardiovascular magnetic resonance (CMR).
  
  
  METHODS
  Imaging was completed in approximately 12 hours using a six-directional encoding scheme, in five ex vivo healthy C57BL/6 mouse hearts. The tensor map constructed from this data provides an average description of the murine fiber architecture visualized with fiber tractography, and its population variability, using the latest advances in image tensor analysis and statistics.
  
  
  RESULTS
  Results show that non-normalized cardiac tensor maps are associated with mean fractional anisotropy of 0.25 ± 0.07 and mean diffusivity of 8.9 ± 1.6 × 10⁻⁴mm²/s. Moreover, average mid-ventricular helical angle distributions ranged between -41 ± 3° and +52 ± 5° and were highly correlated with transmural depth, in agreement with prior published results in humans and canines. Calculated variabilities of local myocyte orientations were 2.0° and 1.4°. Laminar sheet orientation variability was found to be less stable at 2.6°. Despite such variations, the murine heart seems to be highly structured, particularly when compared to canines and humans.
  
  
  CONCLUSIONS
  This tensor map has the potential to yield an accurate mean representation and identification of common or unique features of the cardiac myocyte architecture, to establish a baseline standard reference of DTI indices, and to improve detection of biomarkers, especially in pathological states or post-transgenetic modifications.
authors.affiliation: Department of Mechanical and Manufacturing Engineering, Laboratory of Physiology and Biomedical Imaging, School of Engineering, University of Cyprus, 75 Kalipoleos Avenue, Green Park Building, Nicosia, Cyprus. ste.aggeli@gmail.com.
authors.forename: Stelios
authors.initials: S
authors.lastname: Angeli
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, USA. nicholas.befera@duke.edu.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Befera
authors.affiliation: Qatar Robotic Surgery Centre, Qatar Science & Technology Park, Doha, Qatar. jmpeyrat@gmail.com.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Peyrat
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, USA. evan.calabrese@duke.edu.
authors.forename: Evan
authors.initials: E
authors.lastname: Calabrese
authors.affiliation: Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, USA. gjohnson@duke.edu.
authors.forename: George Allan
authors.initials: GA
authors.lastname: Johnson
authors.affiliation: Department of Mechanical and Manufacturing Engineering, Laboratory of Physiology and Biomedical Imaging, School of Engineering, University of Cyprus, 75 Kalipoleos Avenue, Green Park Building, Nicosia, Cyprus. Christakis.Constantinides@gmail.com.|Chi-Biomedical Limited, 36 Parthenonos Street, Apartment 303, Strovolos, 2021, Nicosia, Cyprus. Christakis.Constantinides@gmail.com.
authors.forename: Christakis
authors.initials: C
authors.lastname: Constantinides
mesh_terms: D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D006321:Heart / Q000033:anatomy & histology*; D008297:Male; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000166:cytology*; D032383:Myocytes, Cardiac; D011237:Predictive Value of Tests