Hypo-and hyperthermia effects on macroscopic fluid transport in tumors

Combining the effects of transvascular and interstitial fluid movement with the structural mechanics of a tissue is necessary to properly analyze processes such as nutrient transport in a tumor cell. Furthermore, externally induced heat loads can play a role: for example, cryoablation can be performed by means of hypothermia and hyperthermia can be induced in order to treat some kinds of tumors such as liver tumor. Recently, the study of the effects of hypo-and hyperthermia on fluid flow and mass transport in biological systems by considering the fluid–structure interaction has gained researchers’ attention. In this paper, fluid flow in a tumor mass is analyzed at the macroscopic scale by considering the effects of both solid tissue deformation and temperature via hypo-and hyperthermia. Governing equations are averaged over a representative elementary volume of the living tissue, and written by means of the thermo-poroelasticity theory. Darcy’s law is used to describe fluid flow through the interstitial space, while transvascular transport is described with a generalized Starling’s law. The effects of hypo-and hyperthermia on the living tissue are included with a source term in the tissue momentum equation that considers thermal expansion. This term can be either negative or positive, i.e., hypo-or hyperthermia is herein considered. Governing equations with the appropriate boundary conditions are solved with the finite-element commercial code COMSOL Multiphysics in the steady-state regime. The numerical model is validated with analytical results from previously published results for an isothermal case. Results are presented in terms of pressure, velocity, and temperature fields for various thermal loads and the effects of hypo-and hyperthermia on various physical parameters are analyzed.