Design and Experimental Validation of Series-Resonated Helmholtz Coil System for Magnetic Nanoparticle Hyperthermia

Abstract

This paper investigates the application of the Helmholtz coil (HH coil) to magnetic hyperthermia (MH) using magnetic nanoparticles (MNPs), aiming to overcome the limitations of conventional circular or solenoidal coils in generating alternating magnetic fields (AMFs) for MNP-based MH. The proposed HH coil is designed to produce a stronger and more spatially uniform magnetic field under the same current, thereby minimizing coil heating and enabling effective treatment of larger target regions. To realize a compact and low-voltage system, magnetic coupling characteristics, coil connection methods, and a series resonance technique are explored for integration into an H-bridge coil driver. The performance of the HH coil and driver circuit is verified through both simulations and experimental measurements. Furthermore, in in-vitro experiments, the thermal conversion efficiency is validated using a 13 nm Fe3O4 MNP suspension (1 mL, 40 mg/mL). At an excitation frequency of 3 MHz and a magnetic flux density of 0.7 mT, the system achieves a maximum temperature change rate of 0.9 °C/15 s and a specific absorption rate (SAR) of 6.27 W/g, demonstrating the effectiveness and applicability of the proposed system for MNP-based MH. Finally, the proposed system was validated through in-vivo experiments, where localized heating was observed in the MNP-injected mouse brain under AMF, demonstrating its feasibility for practical MH applications. © 2016 IEEE.