title: Investigation of an anisotropic tortuosity in a biot model of ultrasonic propagation in cancellous bone.
abstract: The modeling of ultrasonic propagation in cancellous bone is relevant to the study of clinical bone assessment. Historical experiments revealed the importance of both the viscous effects of bone marrow and the anisotropy of the porous microstructure. Of those propagation models previously applied to cancellous bone, Biot's theory incorporates viscosity, but has only been applied in isotropic form, while Schoenberg's anisotropic model does not include viscosity. In this paper we present an approach that incorporates the merits of both models, by utilizing the tortuosity, a key parameter describing pore architecture. An angle-dependent tortuosity for a layered structure is used in Biot's theory to generate the "Stratified Biot Model" for cancellous bone, which is compared with published bone data. While the Stratified Biot model was inferior to Schoenberg's model for slow wave velocity prediction, the proposed model improved agreement fast wave velocity at high propagation angles, particularly when sorted for porosity. An attempt was made to improve the fast wave agreement at low angles by introducing an angle-dependent Young's Modulus, which, while improving the agreement of predicted fast wave velocity at low angles, degraded agreement at high angles. In this paper the utility of the tortuosity in characterizing the architecture of cancellous bone is highlighted.
authors.affiliation: Institute of Sound and Vibration Research, University of Southampton, Southampton, S017 IBJ, United Kingdom.
authors.forename: Elinor R
authors.initials: ER
authors.lastname: Hughes
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Leighton
authors.forename: Paul R
authors.initials: PR
authors.lastname: White
authors.forename: Graham W
authors.initials: GW
authors.lastname: Petley
mesh_terms: D000162:Acoustics; D000818:Animals; D016880:Anisotropy; D001844:Bone Conduction / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D002417:Cattle; D008954:Models, Biological; D014465:Ultrasonics; D014463:Ultrasonography