title: Real-time ultrasound elastography of the normal Achilles tendon: reproducibility and pattern description.
abstract: OBJECTIVE
  To investigate the feasibility and reproducibility of real-time freehand ultrasound elastography (RTE) of the normal Achilles tendon and to describe its elastographic appearances.
  
  
  METHODS
  Fifty normal Achilles tendons were prospectively examined using RTE performed by tissue compression using the hand-held transducer. The information was colour-coded (red=soft, green=medium, blue=hard) and superimposed on the B-mode image. Each tendon was examined three times transversely and longitudinally by two radiologists and the ratio between tendon and retro-Achilles fat strain (strain index) was calculated. The reproducibility of the elastograms was assessed qualitatively and quantitatively using the strain index inter and intra observer variation coefficient (intra/inter-CV and intra/inter-CC, respectively).
  
  
  RESULTS
  All tendons were clearly visualized on the elastograms. Nineteen tendons (19/50, 38%) appeared homogeneously green/blue (type 1). Thirty-one tendons (31/50, 62%) appeared green with longitudinal red stripes (type 2). The intra- and inter-CC values of the strain index were lower for the transverse plane than for the longitudinal plane (0.43, 0.45, 0.41 and 0.78, 0.66, 0.51, respectively). The intra-CV and inter-CV values were higher for the transverse than for the longitudinal plane measurements (39%, 37%, 30% and 30.50%, 30.10%, 29.60%, respectively).
  
  
  CONCLUSIONS
  RTE of the normal Achilles tendon is a feasible method. The reproducibility of the strain index is good and higher for longitudinal elastograms. Qualitative assessment enables the discrimination of two distinct elastographic patterns. Further studies are required to assess the clinical value of this method.
authors.affiliation: Department of Radiology, University Hospital, Heraklion, Greece. drakonaki@yahoo.gr
authors.forename: E E
authors.initials: EE
authors.lastname: Drakonaki
authors.forename: G M
authors.initials: GM
authors.lastname: Allen
authors.forename: D J
authors.initials: DJ
authors.lastname: Wilson
mesh_terms: D000125:Achilles Tendon / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D000328:Adult; D004548:Elasticity; D054459:Elasticity Imaging Techniques / Q000379:methods* / Q000706:statistics & numerical data; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D055815:Young Adult