title: Precise size evaluation of extraocular muscles using fat-suppressed fast T1-weighted gradient-recalled echo imaging and multiple gaze fixation targets.
abstract: OBJECTIVE
  We studied the feasibility of the precise size measurement of extraocular muscles using fast magnetic resonance imaging sequences and gaze fixation targets.
  
  
  METHODS
  We recruited 20 healthy volunteers and optimized fat-suppressed fast T1-weighted gradient-recalled echo (FS T1-GRE) and single-shot fast spin-echo (SSFSE) imaging for evaluating extraocular muscles. With each eye at 40° abduction and adduction, we scanned the short-axis plane at the maximum diameter of the bilateral lateral and medial rectus muscles and measured the maximal cross-sectional area of the muscles during extension and contraction. We evaluated interobserver reproducibility and variability between the size measurements using the two MR sequences and the measurement reproducibility using FS T1-GRE imaging.
  
  
  RESULTS
  The interobserver reproducibility in the muscle size measurements using FS T1-GRE and SSFSE imaging was excellent (r = 0.93-0.94) and moderate to good (r = 0.54-0.75), respectively. The interobserver variability was less with FS T1-GRE than SSFSE imaging (p < 0.01). The reproducibility of the size measurement using FS T1-GRE was good to excellent (r = 0.78-0.92).
  
  
  CONCLUSIONS
  FS T1-GRE imaging with the subject staring at each of multiple targets is useful for evaluating precisely the size of extraocular muscles.
authors.affiliation: Department of Clinical Radiology, Hiroshima University Hospital, Hiroshima, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Keizo
authors.initials: K
authors.lastname: Tanitame
authors.forename: Kazushi
authors.initials: K
authors.lastname: Yokomachi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Akiyama
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kaichi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Awai
mesh_terms: D000328:Adult; D003627:Data Interpretation, Statistical; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D005403:Fixation, Ocular; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009801:Oculomotor Muscles / Q000033:anatomy & histology*; D015203:Reproducibility of Results