WARF: P08157US

Measurement of Stress, Strain and Stiffness in Functionally Loaded Tissues


Ray Vanderby, Hirohito Kobayashi

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a system and method to directly measure stress, strain and stiffness of functionally loaded tissues.
OVERVIEWTissue stresses and strains are important measures of biomechanical function. Tissue stiffness aids in determining whether tissue is healthy, damaged, healing or pathological in some other way. Ultrasound “acoustoelasticity,” as described by WARF reference number P06115US, provides a method of computing material properties using mathematical relationships between sound propagation and material properties.

This technique allows the determination of axial strain but not axial stress or stiffness. Although it is possible to measure axial properties by shifting the direction of the tranducers used along the axis of measurement, this solution is not practical with in situ tendons and ligaments. A method is needed to directly measure stress, strain and stiffness of functionally loaded tissues, which are orthogonal to the principal direction of the transducer system.
THE INVENTIONUW-Madison researchers have developed an apparatus and technique that can provide axial properties of material when only lateral access is available for ultrasound probes. The device provides a transverse directed ultrasonic transducer that determines transverse properties using the acoustoelastic techniques described in WARF reference number P06115US. The inclusion of a pair of angled transducers, one of which is a transmitter and the other a receiver, provides an angled measurement of both transverse and axial properties. Mathematical combination of these two measurements allows extraction of isolated axial properties.
  • Determination of non-linear tissue stiffness from multiple levels of tissue loading as well as the stress and strain in the tissue at each level of loading
  • Applicable to materials other than soft tissues
  • Returns stress, strain and stiffness measurements in real-time without requiring extensive image analysis as with elastography
  • Expandable to measure more complexly loaded tissues in multiple directions
  • Non-invasive, low-risk procedure using relatively inexpensive instrumentation
Contact Information
For current licensing status, please contact Jeanine Burmania at or 608-960-9846.
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