Figures of Merit and Screening Approaches for Evaluating Heat Generation in Magnetic Nanoparticles for Hyperthermia

The heating performance of magnetic nanoparticles for hyperthermia is conventionally evaluated using the specific absorption rate ( SAR nano ), measured under irradiation conditions specific to each laboratory. However, because SAR nano depends strongly on magnetic field amplitude and frequency, values obtained under non-identical conditions may not serve as a fair metric for comparing material performance. This study examines additional indicators, including the heating selectivity ratio between normal tissue and nanoparticles, which reflects side effects, and the specific power factor, which represents device load (equivalent to the specific absorption rate and intrinsic loss power). The results show that the ratio of experimentally generated heat to theoretical maximum heat output provides a more reliable measure of heat generating efficiency, independent of irradiation conditions. Furthermore, conventional measurement conditions often differ from those that maximize heating performance, potentially excluding nanoparticles with high potential. Therefore, a method is introduced to predict heating behavior over a wide parameter range using the blocking temperature and switching magnetic field distribution. For sparsely immobilized nanoparticles, the predicted values were found to be in good agreement with the experimental results, demonstrating that the method can predict the maximum potential of heat generation performance under ideal conditions. On the other hand, the current method could not adequately account for dipolar interactions or particle rotations; hence, further improvements are needed for applications such as nanoparticles concentrated within endosomes. The proposed performance indicators and predictive framework provide a more robust method for evaluating heating performance, thereby accelerating the development of magnetic nanoparticles for hyperthermia applications