Thermal tissue damage analysis for magnetothermal neuromodulation and lesion size minimization

The study of temperature profiles within the central nervous system (CNS) when exposed to an alternating magnetic field (AMF) as a plausible therapy for neuropsychiatric disorders is crucial. This new procedure can be a better alternative for conventional permanent implanted electrodes treatment for CNS diseases such as Parkinson's disease (PD). Hyperthermic treatments are highly dependent on biomaterial thermophysical properties, magnetic nanoparticle (MNP) solution and magnetic field characteristics. This manuscript aims to ascertain the optimum conditions for magnetothermal neuromodulation. Hence, we employ a comprehensive modeling and utilize finite element method (FEM) for simulations to obtain the temperature distribution across the exposed tissue by which the lesion size is evaluated. The results are compared against experimental data in the literature. Local temperature distribution demonstrates an elevated temperature of 57 °C particularly, at the center of the injected solution after exposure. It is shown that a high fraction of the tissue around the injected magnetic nanoparticle solution is damaged mainly due to crossing the safe temperature domain (43 °C < T_tissue < 50 °C). In this investigation, we advance an optimized approach to a theoretical model of neuromodulation, based on Pennes’ equation, that includes a novel stimulation constraint. We establish several new results with this technique; in particular, we demonstrate: the method can be utilized to compute optimized parameter values. Consequently, the minimum necessary activation temperature for magnetothermal stimulation is achieved. Meanwhile, the underlying biomaterial is maintained at low levels of thermal-induced damage.

Statement of Significance

The invasiveness of conventional therapy for neurodegenerative diseases has prompted neuroscientists to discover a new treatment with the least side effects. Magnetothermal stimulation as a great potential alternative, utilizes nano-transducers to convert magnetic field energy to heat and activate targeted neurons. This technique has exhibited promising test results that ameliorates the symptoms. This manuscript by employing an optimization method and damage analysis, establishes the methodology to diminish the adverse impacts of magnetothermal stimulation. The optimum stimulation was established which satisfies the neuron activation requirement while causing the least damage on the targeted brain tissue.