title: Quantitative Ultrasound Elastography With an Acoustic Coupler for Achilles Tendon Elasticity: Measurement Repeatability and Normative Values.
abstract: OBJECTIVE
  The purposes of this study were to measure intraobserver and interobserver repeatability of quantitative elastography using an acoustic coupler for the Achilles tendon, to compare elastographic values among different age groups, and to assess the correlation between quantitative and conventional qualitative measurements.
  
  
  METHODS
  One hundred asymptomatic Achilles tendons of 50 volunteers were examined. For quantitative elastography, the strain value of the tendon was divided by that of the acoustic coupler with a known Young modulus, and the strain ratio was calculated. B-mode image assessment and qualitative elastography were also performed. Intraobserver repeatability and interobserver repeatability of strain ratio measurements were calculated. The strain ratios were compared among age groups by the Kruskal-Wallis test. Additionally, strain ratios for each B-mode grade and qualitative elastographic grade were compared by the Wilcoxon signed rank test.
  
  
  RESULTS
  Intraobserver repeatability intraclass correlation coefficient (1, 3) values were 0.87 and 0.93, respectively. The correlation coefficient between the observers' measurements was 0.61. The strain ratio for the 30s age group was 0.27, which was significantly lower than the values for the other age groups (P < .001). Although 97 of 100 tendons were normal on B-mode evaluations, 36 of the 97 tendons were degenerated on qualitative elastography and also had higher strain ratio values than normal tendons.
  
  
  CONCLUSIONS
  Quantitative elastography using an acoustic coupler is a reproducible technique for measuring the elasticity of the Achilles tendon. It may detect early tendon degeneration that is not depicted on B-mode imaging.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.).
authors.forename: Yohei
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.). y-satoshi@mvb.biglobe.ne.jp.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.).
authors.forename: Takahisa
authors.initials: T
authors.lastname: Sasho
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.).
authors.forename: Taisuke
authors.initials: T
authors.lastname: Fukawa
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.).
authors.forename: Yorikazu
authors.initials: Y
authors.lastname: Akatsu
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.).
authors.forename: Kengo
authors.initials: K
authors.lastname: Nagashima
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical and Pharmaceutical Sciences, Chiba University, Chiba, Japan (Y.Y., S.Y., T.S., T.F., Y.A., K.T.); and Clinical Research Center, Chiba University Hospital, Chiba, Japan (K.N.).
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000502:physiology*; D000162:Acoustics / Q000295:instrumentation*; D000328:Adult; D000368:Aged; D055119:Elastic Modulus / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007564:Japan; D008875:Middle Aged; D015588:Observer Variation; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology; D014159:Transducers
keywords: Achilles tendon; elastography; musculoskeletal ultrasound; sonography