Measuring the Elastic Modulus of Small Tissue Samples

Abstract

Independent measurements of the elastic modulus (Young's modulus) of tissue are necessary step in turning elasticity imaging into a clinical tool. A system capable of measuring the elastic modulus of small tissue samples was developed. The system tolerates the constraints of biological tissue, such as limited sample size (< or = 1.5 cm3) and imperfections in sample geometry. A known deformation is applied to the tissue sample while simultaneously measuring the resulting force. These measurements are then converted to an elastic modulus, where the conversion uses prior calibration of the system with plastisol samples of known Young's modulus. Accurate measurements have been obtained from 10 to 80 kPa, covering a wide range of tissue modulus values. In addition, the performance of the system was further investigated using finite element analysis. Finally, preliminary elasticity measurements on canine kidney samples are presented and discussed.

Congruence of Imaging Estimators and Mechanical Measurements of Viscoelastic Properties of Soft Tissues

“…The mean Young's modulus values were 9.9 kPa and 6.6 kPa, respectively (Kemper et al 2004). Significant discrepancies were also found on the reported stiffness of kidney tissue (Erkamp et al 1998;Kruse et al 2000;Nasseri et al 2002;Snedeker et al 2005). The divergent reports of soft tissue properties are mainly caused by the different choices of testing techniques, tissue models, compression frequencies, temperature, sample variation, and other experimental factors.…”

Correspondence of ultrasound elasticity imaging to direct mechanical measurement in aging DVT in rats

“…For tissue specimens that can be excised into large homogeneous pieces, for example, liver and muscle, the traditional approach is uniaxial compression (Chen et al 1996). For small tissue samples (breast and prostate), a majority of existing systems are indentation apparatus (Erkamp et al 1998;Krouskop et al 1998;Samani et al 2003). Their general procedure is to indent the tissue sample in either constrained or unconstrained lateral boundary conditions, record the indenter displacement, simultaneously measure the resulting deformation force, and then convert the slope of force-displacement to Young's modulus via a conversion factor.…”

“…Samani et al (2003) proved that in the linear theory of elasticity, the conversion factor is only related to boundary conditions and deformation geometry. The factor can be determined by theoretical derivation (Hayes et al 1972), finite element simulation (Erkamp et al 1998;Samani et al 2003) or calibration with phantom samples of known Young's modulus (Erkamp et al 1998;Samani et al 2003). The mechanical device presented in (Krouskop et al 1998) is capable of testing tissue samples (breast tissue) prepared in a thin slab.…”

“…The mechanical device presented in (Krouskop et al 1998) is capable of testing tissue samples (breast tissue) prepared in a thin slab. Canine kidney samples were characterized using the system developed by Erkamp et al (1998). Samples were cut into cylinders and constrained on the side and bottom in a mold via gelatin.…”

“…A circular piston indents the center of the sample. Samani et al adapted the basic concept of (Erkamp et al 1998) in designing their system. However, tissue samples (breast tissue) were measured in a block shape.…”