Excitation and response of surface waves on isotropic and nonisotropic viscoelastic half-spaces with application to medical diagnosis

Abstract

An analytical solution is proposed for the problem of surface wave generation on a viscoelastic half-space by a finite rigid circular disk located on the surface and oscillating normal to it. The solution is an incremental advancement of the work reported in two articles published in the 1950s in the Proceedings of the Royal Society. While the application focus of those articles was seismology, the application of interest here is medical diagnostics. Consequently, the solution is verified experimentally using a viscoelastic phantom with material properties that approximate biological soft tissue. Also, the effect of an inclusion on surface wave behavior within the otherwise isotropic medium is investigated. Measurement of wave motion on the skin surface caused by internal biological functions or external stimuli has been studied by a few researchers for rapid, nonintrusive diagnosis of a variety of medical conditions. Conditions considered include those associated with cardio-vascular dynamics, oedema and other skin ailments, hardened tissue regions, e.g., tumors, and extraluminal air in the abdomen, a.k.a. pneumoperitineum. It is hoped that the developments reported here will advance these techniques and also provide insight into related diagnostic techniques, such as sonoelastic imaging and other vibro-acoustic methodologies. [Work supported by the Whitaker Foundation.]