Numerical Model Study of In Vivo Magnetic Nanoparticle Tumor Heating.

Abstract

Iron oxide nanoparticles are currently under investigation as heating agents for hyperthermic treatment of tumors. Major determinants of effective heating include the biodistribution and minimum iron oxide loading required to achieve adequate heating at practically achievable magnetic field strengths. These inter-related criteria ultimately determine the practicality of this approach to tumor treatment. Further, in our experience the currently used treatment assessment criterion for hyperthermia treatment-cumulative equivalent minutes at 43 °C, CEM₄₃ -provides an inadequate description of the expected treatment effectiveness. Couple numerical models to experimental measurements to study the relative heating effectiveness described by cell death predictions. FEM numerical models were applied to increase the understanding of a carefully calibrated series of experiments in mouse mammary adenocarcinoma. The numerical model results indicate that minimum tumor loadings between approximately 1.3 to 1.8 mg of Fe per cm³ of tumor tissue are required to achieve the experimentally observed temperatures in magnetic field strengths of 32 kA/m (rms) at 162 kHz. We show that including multiple cell death processes operating in parallel within the numerical models provides valuable perspective on the likelihood of successful treatment. We show and believe that these assessment methods are more accurate than a single assessment figure of merit based only on the comparison of thermal histories, such as the CEM method.