title: Gender differences in MR muscle tractography.
abstract: BACKGROUND
  Tractography of skeletal muscle can clearly reveal the 3-dimensional course of muscle fibers, and the procedure has great potential and could open new fields for diagnostic imaging. Studying this technique for clinical application, we noticed differences in the number of visualized tracts among volunteers and among muscles in the same volunteer. To comprehend why the number of visualized tracts varied so that we could acquire consistently high quality tractography of muscle fiber, we started to examine whether differences in individual parameters affected tractography visualization.
  
  
  OBJECTIVE
  To determine whether there are gender- and age-specific differences that differentiate the muscles by gender and age in MR tractography of skeletal muscle fiber.
  
  
  METHODS
  We divided 33 healthy volunteers by gender and age among 3 groups, A (13 younger men, aged 20 to 36 years), B (11 younger women, 25 to 39 years), and C (9 older men, 50 to 69), and we obtained from each volunteer tractographs of 8 fibers, including the bilateral gastrocnemius medialis (GCM), gastrocnemius lateralis (GCL), soleus (SOL), and anterior tibialis (AT) muscles. We classified the fibers into 5 grades depending on the extent of visualized tracts and used Mann-Whitney U-test to compare scores by gender (Group A versus B) and age (Group A versus C).
  
  
  RESULTS
  Muscle tracts were significantly better visualized in women than men (median total visual score, 34 versus 24, P<0.05). In particular, the SOL muscles showed better visualization in the right (4.0 in women, 1.0 in men, P<0.05) and left (3.0 in women, 1.0 in men, P<0.05). Difference by age was not significant. The GCL was the highest scored muscle in all groups.
  
  
  CONCLUSIONS
  Our results suggest that group differences, especially by gender, affected visualization of tractography of muscle fiber of the calf.
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: Akira
authors.initials: A
authors.lastname: Kunimatsu
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kono
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kujiraoka
authors.forename: Jyunichi
authors.initials: J
authors.lastname: Sonobe
authors.forename: Manabu
authors.initials: M
authors.lastname: Minami
mesh_terms: D000328:Adult; D000368:Aged; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D035002:Lower Extremity; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D012727:Sex Characteristics; D014463:Ultrasonography; D055815:Young Adult