A Multi-Phasic Continuum Damage Mechanics Model of Mechanically Induced Increased Permeability in Tissues
Brian O'Neill, Timothy P. Quinn, Victor F. Frankel, King C. Li
Recently, we have reported enhanced permeability of tissues due to in vivo treatment with pulsed high intensity focused ultrasound (pHIFU). This new therapy has shown promise as a way of increasing the penetration of large drug molecules both out of the vasculature and into the tissue. To date, no clear physical model of tissue exists that can account for these effects. A new model is proposed that clearly establishes the link between tissue structure and fluid flow properties on one hand, and the history of applied mechanical forces on the other. The model draws inspiration from two different theoretical fields of materials science, multi-phase theory and continuum damage mechanics. The theory differs from the traditional bi-phasic solid-fluid model of tissues in that the fluid part here is broken into trapped (moving with the solid) and free (moving through the solid) parts. A damage-like variable links the effective elasticity of the tissue to the ratio of the trapped to free fluids. As the damage increases, the tissue becomes, in effect, less stiff and more permeable. Elastic energy is released, which drives the process. A distribution of energy barriers opposes the process and governs how the fluid is released as damage increases.
high intensity focused ultrasound, therapeutic ultrasound
, Quinn, T.
, Frankel, V.
and Li, K.
A Multi-Phasic Continuum Damage Mechanics Model of Mechanically Induced Increased Permeability in Tissues, Proceedings of the 2005 Fall MRS Meeting, Boston, MA, USA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50254
(Accessed February 23, 2024)