Numerical study of nanofluid infusion in deformable tissues for hyperthermia cancer treatments.

Direct infusion by means of needles is one of the widely used methods for the delivery of nanoparticles in tumors for hyperthermia cancer treatments. During an infusion process, infusion-induced deformation can substantially affect the dispersion of the nanoparticles injected in a biological tissue. In this study, a poroelastic model is developed to investigate fluid transport and flow-induced tissue deformation in a tumor during an infusion process. A surface tracking technique is employed to predict the shape of nanofluid spreading after injection. The model is then used to simulate the formation of backflow and the change of tissue porosity due to the deformation. Specifically, we quantify the influence of the backflow on the spreading shape of the nanofluid and its dependence on injection parameters such as infusion rates, needle diameters, and tumor elastic properties. It is found that backflow is an important factor causing an irregular distribution of the nanofluid injected in a tumor. A higher infusion rate, larger needle diameter, and lower elastic modulus yield a longer backflow length and cause a more irregular spreading shape of the nanofluid. The infusion-induced tissue deformation also leads to a pore swelling and an increase of the porosity in the vicinity of the needle tip and the needle outer surface. It is anticipated that the increased pore size may facilitate the particle penetration in a tumor. To achieve a controlled heat generation, the injection parameters should be selected judiciously with the consideration of tumor sizes, tumor properties, and thresholds at which tumors break under the infusion pressure.