Computational and Mathematical Methods in Medicine
Volume 2012 (2012), Article ID 979847, 6 pages
http://dx.doi.org/10.1155/2012/979847
Research Article

Quantitative Imaging of Young’s Modulus of Soft Tissues from Ultrasound Water Jet Indentation: A Finite Element Study

Min-Hua Lu,1,2,3 Rui Mao,4 Yin Lu,3 Zheng Liu,3 Tian-Fu Wang,1,2,3 and Si-Ping Chen1,2,3

1National-Regional Engineering Laboratory for Key Technology of Medical Ultrasound, Shenzhen University, Shenzhen 518060, China
2Guangdong Key Laboratory of Biomedical Information Detection and Ultrasound Imaging, Shenzhen University, Shenzhen 518060, China
3Department of Biomedical Engineering, School of Medicine, Shenzhen University, Shenzhen 518060, China
4Shenzhen Key Labratory of Service Computing and Applications, College of Computer Science and Software Engineering, Shenzhen University, Shenzhen 518060, China

Received 2 June 2012; Accepted 8 July 2012

Academic Editor: Huafeng Liu

Copyright © 2012 Min-Hua Lu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Indentation testing is a widely used approach to evaluate mechanical characteristics of soft tissues quantitatively. Young’s modulus of soft tissue can be calculated from the force-deformation data with known tissue thickness and Poisson’s ratio using Hayes’ equation. Our group previously developed a noncontact indentation system using a water jet as a soft indenter as well as the coupling medium for the propagation of high-frequency ultrasound. The novel system has shown its ability to detect the early degeneration of articular cartilage. However, there is still lack of a quantitative method to extract the intrinsic mechanical properties of soft tissue from water jet indentation. The purpose of this study is to investigate the relationship between the loading-unloading curves and the mechanical properties of soft tissues to provide an imaging technique of tissue mechanical properties. A 3D finite element model of water jet indentation was developed with consideration of finite deformation effect. An improved Hayes’ equation has been derived by introducing a new scaling factor which is dependent on Poisson’s ratios v, aspect ratio a/h (the radius of the indenter/the thickness of the test tissue), and deformation ratio d/h. With this model, the Young’s modulus of soft tissue can be quantitatively evaluated and imaged with the error no more than 2%.