AuthorR. Leiderman, P. E. Barbone, A.A. Oberai and J.C. Bamber
TitleCoupling between elastic strain and interstitial fluid flow: Ramifications for poroelastic imaging
JournalPhysics and Medicine in Biology
AbstractAbstract. We study the e_ects of interstitial uid ow and interstitial uid drainage on the spatio-temporal response of soft tissue strain. The motivation stems from the ability to measure in vivo strain distributions in soft tissue via elastography, and the desire to explore the possibility of using such techniques to investigate soft tissue uid ow. Our study is based upon a mathematical model for soft tissue mechanics from the literature. It is a simple generalization of biphasic theory that includes coupling between the uid and solid phases of the soft tissue, and crucially, uid exchange between the interstitium and the local microvasculature. We solve the mathematical equations in two dimensions by the _nite element method (FEM). The _nite element implementation is validated against an exact analytical solution that is derived in the appendix. Realistic input tissue properties from the literature are used in conjunction with FEM modeling to conduct several computational experiments. The results of these lead to the following conclusions: (i) di_erent hypothetical ow mechanisms lead to di_erent patterns of strain relaxation with time; (ii) representative tissue properties show uid drainage into the local microvasculature to be the dominant ow-related stress/strain relaxation mechanism; (iii) the relaxation time of strain in solid tumors due to drainage into the microvasculature is on the order of 5_10 sec:; (iv) under realistic applied pressure magnitudes, the magnitude of the strain relaxation can be as high as approximately 0:4% strain (4; 000 microstrains), which is well within the range of strains measurable by elastography.
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