Role of structural anisotropy of biological tissues in poroelastic wave propagation

Abstract

Ultrasound waves have a broad range of clinical applications as a non-destructive testing approach in imaging and in the diagnoses of medical conditions. Generally, biological tissues are modeled as an homogenized equivalent medium with an apparent density through which a single wave propagates. Only the first wave arriving at the ultrasound probe is used for the measurement of the speed of sound. However, the existence of a second wave in tissues such as cancellous bone has been reported and its existence is an unequivocal signature of Biot type poroelastic media. To account for the fact that ultrasound is sensitive to microarchitecture as well as density, a fabric-dependent anisotropic poroelastic ultrasound (PEU) propagation theory was recently developed. Key to this development was the inclusion of the fabric tensor - a quantitative stereological measure of the degree of structural anisotropy of bone - into the linear poroelasticity theory. In the present study, this framework is extended to the propagation of waves in several soft and hard tissues. It was found that collagen fibers in soft tissues and the mineralized matrix in hard tissues are responsible for the anisotropy of the solid tissue constituent through the fabric tensor in the model.

Principal trabecular structural orientation predicted by quantitative ultrasound is strongly correlated with $$\upmu $$ μ FEA determined anisotropic apparent stiffness

“…Recently, many researchers have been investigating the interaction between the anisotropic trabecular macroarchitecture and the quantitative ultrasound propagation (Cardoso and Cowin, 2011, 2012; Cowin and Cardoso, 2011; Han and Rho, 1998; Hosokawa, 2009, 2010, 2011a, b; Hosokawa and Otani, 1998; Lee et al, 2007; Mizuno et al, 2009; Mizuno et al, 2008; Mizuno et al, 2010). In a 3-dimensional volumetric trabecular structure, not only the alignment of the trabeculae but also the “solid/liquid” or “bone/marrow” interfaces play a very important role in scattering, refracting and attenuating the ultrasound wave.…”

Prediction of trabecular bone principal structural orientation using quantitative ultrasound scanning

“…Cardoso and Cowin (Cardoso and Cowin, 2011, 2012; Cowin and Cardoso, 2011) studied the relation between fabric tensor—a measurement of the degree of anisotropy of the trabecular bone—and the wave propagation equations in anisotropic porous media. An angle-dependent model to the classic Biot’s theory (Biot, 1956a, b) to predict the ultrasound velocity in an anisotropic trabecular bone model was also introduced (Lee et al, 2007).…”

Enhanced correlation between quantitative ultrasound and structural and mechanical properties of bone using combined transmission-reflection measurement

“…The anisotropic structure of trabecular bone is the result of adaptation to its mechanical environment according to "Wolff's Law" (Wolff, 1896). Recent studies described the interaction between trabecular bone structural alignment and ultrasound wave (Gluer et al, 1993;Njeh et al, 1997a;Han and Rho, 1998;Hosokawa and Otani, 1998;Nicholson et al, 1998;Hans et al, 1999;Wear, 2000;Lee et al, 2007;Mizuno et al, 2008;Hosokawa, 2009;Mizuno et al, 2009;Hosokawa, 2010;Mizuno et al, 2010;Cardoso and Cowin, 2011;Cowin and Cardoso, 2011;Hosokawa, 2011;Cardoso and Cowin, 2012;Liu et al, 2014). These researchers all came to the same conclusion: that QUS is sensitive enough to pick up the difference of structural and mechanical properties of trabecular bone in different orientations and, generally, provide more comprehensive information of bone "quality" than simply bone "quantity.…”