title: High-resolution diffusion tensor MR imaging for evaluating myocardial anisotropy and fiber tracking at 3T: the effect of the number of diffusion-sensitizing gradient directions.
abstract: OBJECTIVE
  We wanted to evaluate the effect of the number of diffusion-sensitizing gradient directions on the image quality for evaluating myocardial anisotropy and fiber tracking by using in vitro diffusion tensor MR imaging (DT-MRI).
  
  
  METHODS
  The DT-MR images, using a SENSE-based echoplanar imaging technique, were acquired from ten excised porcine hearts by using a 3T MR scanner. With a b-value of 800 s/mm(2), the diffusion tensor images were obtained for 6, 15 and 32 diffusion-sensitizing gradient directions at the midventricular level. The number of tracked fibers, the fractional anisotropy (FA), and the length of the tracked fibers were measured for the quantitative analysis. Two radiologists assessed the image quality of the fiber tractography for the qualitative analysis.
  
  
  RESULTS
  By increasing the number of diffusion-sensitizing gradient directions from 6 to 15, and then to 32, the FA and standard deviation were significantly reduced (p < 0.01), and the number of tracked fibers and the length of the tracked fibers were significantly increased (p < 0.01). The image quality of the fiber tractography was significantly increased with the increased number of diffusion-sensitizing gradient directions (p < 0.01).
  
  
  CONCLUSIONS
  The image quality of in vitro DT-MRI is significantly improved as the number of diffusion-sensitizing gradient directions is increased.
authors.affiliation: Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
authors.forename: Sang Il
authors.initials: SI
authors.lastname: Choi
authors.forename: Joon-Won
authors.initials: JW
authors.lastname: Kang
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Chun
authors.forename: Seong Hoon
authors.initials: SH
authors.lastname: Choi
authors.forename: Tae-Hwan
authors.initials: TH
authors.lastname: Lim
mesh_terms: D000818:Animals; D016880:Anisotropy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology*; D013552:Swine