title: Real-time sonoelastography using an external reference material: test-retest reliability of healthy Achilles tendons.
abstract: OBJECTIVE
  To establish the test-retest reliability of sonoelastography (SE) on healthy Achilles tendons in contracted and relaxed states using an external reference system.
  
  
  METHODS
  Forty-eight Achilles tendons from 24 healthy volunteers were assessed using ultrasound and real-time SE with an external reference material. Tendons were analyzed under relaxed and contracted conditions. Strain ratios between the tendons and the reference material were calculated. The intraclass correlation coefficient (ICC2.k) and Bland-Altman plot were used to assess test-retest reliability.
  
  
  RESULTS
  The reliability of SE measurements under relaxed conditions ranged from high to very high, with an ICC2.k of 0.84 (95 % CI: 0.64-0.92) for reference material, 0.91 (95 % CI: 0.83-0.95) for Achilles tendons and 0.95 (95 % CI: 0.91-0.97) for Kager fat pads (KFP). The ICC2.k value for skin was 0.30 (95 % CI: -0.26 to 0.61). Reliability for measurements in the contracted state ranged from high to very high, with an ICC2.k of 0.93 (95 % CI: 0.87-0.96) for reference material, 0.72 (95 % CI: 0.50-0.84) for skin, 0.93 (95 % CI: 0.87-0.96) for Achilles tendons, and 0.81 (95 % CI: 0.66-0.89) for KFP. Reliability of the strain ratio (tendon/reference) under relaxed conditions was high with an ICC2.k of 0.87 (95 % CI: 0.75-0.93), and in the contracted state, it was very high with an ICC2.k of 0.94 (95 % CI: 0.90-0.97).
  
  
  CONCLUSIONS
  Sonoelastography using an external reference material is a reliable and simple technique for the assessment of the elasticity of healthy Achilles tendons. The use of an external material as a reference, along with strain ratios, could provide a quantitative measure of elasticity.
authors.affiliation: Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland. alessandro.schneebeli@supsi.ch.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Schneebeli
authors.affiliation: Servizio di Radiologia, Ospedale Regionale di Lugano, Ente Ospedaliero Cantonale (EOC), Lugano, Switzerland.
authors.forename: Filippo
authors.initials: F
authors.lastname: Del Grande
authors.affiliation: Servizio di Radiologia, Ospedale Regionale di Lugano, Ente Ospedaliero Cantonale (EOC), Lugano, Switzerland.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Vincenzo
authors.affiliation: Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland.
authors.forename: Corrado
authors.initials: C
authors.lastname: Cescon
authors.affiliation: Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Landquart, Switzerland.|Thim van der Laan AG, University College Physiotherapy, Landquart, Switzerland.|Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Brussels, Belgium.
authors.forename: Ron
authors.initials: R
authors.lastname: Clijsen
authors.affiliation: ESAOTE S.p.A., Genoa, Italy.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Biordi
authors.affiliation: Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland.
authors.forename: Marco
authors.initials: M
authors.lastname: Barbero
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging*; D000328:Adult; D054459:Elasticity Imaging Techniques; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D014463:Ultrasonography; D055815:Young Adult
keywords: Achilles tendon; Reliability; Sonoelastography