title: Correlation between pennation angle and image quality of skeletal muscle fibre tractography using deterministic diffusion tensor imaging.
abstract: BACKGROUND
  The aim of this study was to ascertain whether a correlation existed between muscle pennation angle and the ability to successfully perform tractography of the lower leg muscle fibres with deterministic diffusion tensor imaging (DTI) in normal volunteers.
  
  
  METHODS
  Fourteen volunteers aged 20-39 (mean 28.2 years old) were recruited. All volunteers were scanned using DTI, and six fibre tractographs were constructed from one lower leg of each volunteer, and the 'fibre density' was calculated in each of the tractographs. The pennation angle is the angle formed by the muscle fibre and the aponeurosis. The average pennation angle (AVPA) and standard deviation of the pennation angle (SDPA) were also measured for each muscle by ultrasonography in the same region as the MRI scan. For all 84 tractography images, the correlation coefficient between the fibre density and AVPA or SDPA was calculated.
  
  
  RESULTS
  Fibre density and AVPA showed a moderate negative correlation (R = -0.72), and fibre density and SDPA showed a weak negative correlation (R = -0.47). With respect to comparisons within each muscle, AVPA and fibre density showed a moderate negative correlation in the gastrocnemius lateralis muscle (R = -0.57).
  
  
  CONCLUSIONS
  Our data suggest that a larger, more variable pennation angle resulted in worse skeletal muscle tractography using deterministic DTI.
authors.affiliation: Department of Radiology, Institute of Clinical Medicine, University of Tsukuba Hospital, Tsukuba, Ibaraki, Japan. yokamoto@md.tsukuba.ac.jp
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Okamoto
authors.forename: Toru
authors.initials: T
authors.lastname: Okamoto
authors.forename: Kujiraoka
authors.initials: K
authors.lastname: Yuka
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hirano
authors.forename: Tomonori
authors.initials: T
authors.lastname: Isobe
authors.forename: Manabu
authors.initials: M
authors.lastname: Minami
mesh_terms: D000328:Adult; D000465:Algorithms; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D055815:Young Adult