Numerical assessment of a criterion for the optimal choice of the operative conditions in magnetic nanoparticle hyperthermia on a realistic model of the human head

Purpose: This paper presents a numerical study aiming at assessing the effectiveness of a recently proposed optimisation criterion for determining the optimal operative conditions in magnetic nanoparticle hyperthermia applied to the clinically relevant case of brain tumours. Materials and methods: The study is carried out using the Zubal numerical phantom, and performing electromagnetic-thermal co-simulations. The Pennes model is used for thermal balance; the dissipation models for the magnetic nanoparticles are those available in the literature. The results concerning the optimal therapeutic concentration of nanoparticles, obtained through the analysis, are validated using experimental data on the specific absorption rate of iron oxide nanoparticles, available in the literature. Results: The numerical estimates obtained by applying the criterion to the treatment of brain tumours shows that the acceptable values for the product between the magnetic field amplitude and frequency may be two to four times larger than the safety threshold of 4.85 x 10(8)A/m/s usually considered. This would allow the reduction of the dosage of nanoparticles required for an effective treatment. In particular, depending on the tumour depth, concentrations of nanoparticles smaller than 10 mg/mL of tumour may be sufficient for heating tumours smaller than 10 mm above 42 degrees C. Moreover, the study of the clinical scalability shows that, whatever the tumour position, lesions larger than 15 mm may be successfully treated with concentrations lower than 10 mg/mL. The criterion also allows the prediction of the temperature rise in healthy tissue, thus assuring safe treatment. Conclusions: The criterion can represent a helpful tool for planning and optimising an effective hyperthermia treatment.