title: The effect of magnification on sonographically measured nerve cross-sectional area.
abstract: BACKGROUND
  The primary aim of this investigation was to determine whether use of write-zoom magnification affects sonographically determined cross-sectional area (CSA) of peripheral nerves.
  
  
  METHODS
  CSAs of the median (MN) and posterior interosseous (PIN) nerves were measured in 22 limbs from 11 asymptomatic volunteers using both standard imaging and write-zoom magnification. CSA measurements were repeated on the same images 1 week later.
  
  
  RESULTS
  The average CSA of write-zoomed images for the MN was significantly larger at both measurement sessions (week 1: 11.1 mm(2) write-zoom vs. 10.0 mm(2) standard, P = 0.019; week 2: 11.8 mm(2) vs. 10.4 mm(2), P = 0.023). Similar differences were noted for the PIN (week 1: 2.3 mm(2) vs. 1.9 mm(2), P = 0.002; week 2: 2.5 mm(2) vs. 1.9 mm(2), P = 0.001).
  
  
  CONCLUSIONS
  Write-zoom magnification may significantly increase the measured CSA of peripheral nerves. These changes appear to be more substantial when smaller nerves are measured.
authors.affiliation: Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.
authors.forename: Elena J
authors.initials: EJ
authors.lastname: Jelsing
authors.forename: James C
authors.initials: JC
authors.lastname: Presley
authors.forename: Eugene
authors.initials: E
authors.lastname: Maida
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Hangiandreou
authors.forename: Jay
authors.initials: J
authors.lastname: Smith
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002348:Carpal Bones / Q000033:anatomy & histology; D005260:Female; D005542:Forearm / Q000294:innervation; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging*; D008875:Middle Aged; D014463:Ultrasonography / Q000379:methods*; D055815:Young Adult
keywords: carpal tunnel syndrome; cross-sectional area; peripheral nerve; posterior interosseous nerve ultrasound