Influence of heating efficiency-temperature relationships on the temperature self-regulating ability of MNPs in tumor hyperthermia

Magnetic hyperthermia requires sufficient tumor heating while limiting thermal injury to surrounding tissue. A decrease in the specific loss power ( SLP ) of magnetic nanoparticles (MNPs) as temperature ( T ) rises can improve temperature control and enable the MNPs to self-regulate the tumor temperature to the therapeutic range of 42–46°C. However, research on the effects of different SLP - T curves on this temperature self-regulating ability is limited, and a simulation method that incorporates these curves is needed to analyze the tumor temperature field. This study developed magnetic hyperthermia tumor temperature field simulation software, MH-TempFieldSim 1.0, that uses SLP - T curves to calculate the required MNP concentration, tumor temperature distribution, and changes in tumor temperature caused by variations in heating and tissue parameters. The temperature predictions were validated by ex vivo pork liver tissue heating experiments, with relative root mean square deviation ( RRMSD ) values of 0.44–3.40% between the experimental and simulated heating curves. Six reported nonlinear SLP - T curves were then piecewise linearized using the temperature at which SLP starts to decrease ( T 1 ) and the temperature at which the linear decrease reaches zero ( T 2 ). Simulations using the piecewise linearized and nonlinear curves produced similar results, with maximum relative deviations of 4.25% in the required MNP concentrations and 0.775% in the tumor temperatures and their changes. For MNPs with T 2 greater than 46.02°C, decreasing T 1 toward 37°C and T 2 toward 46°C reduced the intratumoral temperature difference and the temperature changes caused by variations in heating and tissue parameters. These improvements required a higher heating power density. When T 2 was sufficiently close to 46°C (46.00–46.02°C in the present model), the maximum intratumoral temperature difference could be reduced to below 2°C, and the change in T center could be limited to below 0.5°C under ±20% changes in heating power density or tumor radius. The software can aid magnetic hyperthermia simulation, and the parameter analysis may provide references for evaluating the temperature self-regulating behavior of MNPs.