Rapid, non-invasive, in vivo measurement of tissue mechanical properties using gravitational loading and a nonlinear virtual fields method

Evans, S. L. ORCID: https://orcid.org/0000-0003-3664-2569, Keenan, B. E. ORCID: https://orcid.org/0000-0001-7787-2892, Hill, J., Zappala, S., Bennion, N. and Avril, S. 2023. Rapid, non-invasive, in vivo measurement of tissue mechanical properties using gravitational loading and a nonlinear virtual fields method. Journal of the Royal Society. Interface 20 (207) , 20230384. 10.1098/rsif.2023.0384

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Abstract

Measuring the mechanical properties of soft tissues in vivo is important in biomechanics and for diagnosis and staging of diseases, but challenging because it is difficult to control the boundary conditions. We present a novel, non-invasive method for measuring tissue properties using gravitational loading. MRI images of an organ in different positions are registered to measure tissue displacements due to gravitational forces in different positions. Considering equilibrium between stresses and gravity, we established a nonlinear virtual fields method to identify the tissue properties. The method was applied to the human brain as a proof of concept, using an Ogden model. Sensitivity analysis showed that the bulk modulus could be identified accurately whilst the shear modulus was identified with greater uncertainty; the strains were too small to identify the strain stiffening exponent. The measured properties agreed well with published in vitro data. The technique offers very promising perspectives, allowing the non-invasive measurement of otherwise inaccessible tissues and providing new information such as the bulk modulus under static loading, which has never previously been measured in vivo.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Engineering
Publisher:	The Royal Society
ISSN:	1742-5689
Date of First Compliant Deposit:	25 September 2023
Date of Acceptance:	19 September 2023
Last Modified:	09 Jan 2024 11:49
URI:	https://orca.cardiff.ac.uk/id/eprint/162738

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