title: Comparison of shear wave velocity measurements assessed with two different ultrasound systems in an ex-vivo tendon strain phantom.
abstract: OBJECTIVE
  The purpose of this study is to compare the reliability of SW velocity measurements of two different ultrasound systems and their correlation with the tangent traction modulus in a non-static tendon strain model.
  
  
  METHODS
  A bovine tendon was fixed in a custom-made stretching device. Force was applied increasing from 0 up to 18 Newton. During each strain state the tangent traction modulus was determined by the stretcher device, and SW velocity (m/s) measurements using a Siemens S3000 and a Supersonic Aixplorer US machine were done for shear modulus (kPa) calculation.
  
  
  RESULTS
  A strong significant positive correlation was found between SW velocity assessed by the two ultrasound systems and the tangent traction modulus (r = 0.827-0.954, p < 0.001), yet all SW velocity-based calculations underestimated the reference tissue tangent modulus. Mean difference of SW velocities with the S3000 was 0.44 ± 0.3 m/s (p = 0.002) and with the Aixplorer 0.25 ± 0.3 m/s (p = 0.034). Mean difference of SW velocity between the two US-systems was 0.37 ± 0.3 m/s (p = 0.012).
  
  
  CONCLUSIONS
  In conclusion, SW velocities are highly dependent on mechanical forces in the tendon tissue, but for controlled mechanical loads appear to yield reproducible and comparable measurements using different US systems.
authors.affiliation: Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland. andrea.rosskopf@balgrist.ch.|Faculty of Medicine, University of Zurich, Zurich, Switzerland. andrea.rosskopf@balgrist.ch.
authors.forename: Andrea B
authors.initials: AB
authors.lastname: Rosskopf
authors.affiliation: Laboratory for Orthopedic Biomechanics, Orthopedic University Hospital Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.
authors.forename: Elias
authors.initials: E
authors.lastname: Bachmann
authors.affiliation: Laboratory for Orthopedic Biomechanics, Orthopedic University Hospital Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.|Institute for Biomechanics, Swiss Federal Institute of Technology in Zurich (ETHZ), Lengghalde 5, 8092, Zurich, Switzerland.
authors.forename: Jess G
authors.initials: JG
authors.lastname: Snedeker
authors.affiliation: Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Christian W A
authors.initials: CW
authors.lastname: Pfirrmann
authors.affiliation: Radiology, Orthopedic University Hospital Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.|Faculty of Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Buck
mesh_terms: D000818:Animals; D002417:Cattle; D055119:Elastic Modulus / Q000502:physiology; D054459:Elasticity Imaging Techniques / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D066298:In Vitro Techniques; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D033081:Shear Strength / Q000502:physiology; D013314:Stress, Mechanical; D013710:Tendons / Q000000981:diagnostic imaging* / Q000502:physiology*; D013718:Tensile Strength / Q000502:physiology
keywords: Accuracy; Animal model; Shear modulus; Shear wave velocity; Sonoelastography; Stress