Anilchandra Attaluri1,2, John Jackowski3, Anirudh Sharma1, Sri Kamal Kandala1,4, Valentin Nemkov3, Chris Yakey3, Theodore L DeWeese1,5, Ananda Kumar6, Robert C Goldstein3, Robert Ivkov1,4,5,7,8. 1. Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA. 2. Department of Mechanical Engineering, Pennsylvania State University, Harrisburg, PA, USA. 3. AMF Life Systems, LLC, Auburn Hills, MI, USA. 4. Deparment of Mechanical Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, USA. 5. Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. 6. Lambda Z Technologies Inc, Baltimore, MD, USA. 7. Institute for NanoBioTechnology, Johns Hopkins University, Baltimore, MD, USA. 8. Deparment of Materials Science and Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, USA.
Abstract
Purpose: We describe a modified Helmholtz induction coil, or Maxwell coil, that generates alternating magnetic fields (AMF) having field uniformity (≤10%) within a = 3000 cm3 volume of interest for magnetic hyperthermia research.Materials and methods: Two-dimensional finite element analysis (2D-FEA) was used for electromagnetic design of the induction coil set and to develop specifications for the required matching network. The matching network and induction coil set were fabricated using best available practices and connected to a 120 kW industrial induction heating power supply. System performance was evaluated by magnetic field mapping with a magnetic field probe, and tests were performed using gel phantoms. Results: Tests verified that the system generated a target peak AMF amplitude along the coil axis of ∼35 kA/m (peak) at a frequency of 150 ± 10 kHz while maintaining field uniformity to >90% of peak for a volume of ∼3000 cm3.Conclusions: The induction coil apparatus comprising three independent loops, i.e., Maxwell-type improves upon the performance of simple solenoid and Helmholtz coils by providing homogeneous flux density fields within a large volume while minimizing demands on power and stray fields. Experiments with gel phantoms and analytical calculations show that future translational research efforts should be devoted to developing strategies to reduce the impact of nonspecific tissue heating from eddy currents; and, that an inductor producing a homogeneous field has significant clinical potential for deep-tissue magnetic fluid hyperthermia.
Purpose: We describe a modified Helmholtz induction coil, or Maxwell coil, that generates alternating magnetic fields (AMF) having field uniformity (≤10%) within a = 3000 cm3 volume of interest for magnetic hyperthermia research.Materials and methods: Two-dimensional finite element analysis (2D-FEA) was used for electromagnetic design of the induction coil set and to develop specifications for the required matching network. The matching network and induction coil set were fabricated using best available practices and connected to a 120 kW industrial induction heating power supply. System performance was evaluated by magnetic field mapping with a magnetic field probe, and tests were performed using gel phantoms. Results: Tests verified that the system generated a target peak AMF amplitude along the coil axis of ∼35 kA/m (peak) at a frequency of 150 ± 10 kHz while maintaining field uniformity to >90% of peak for a volume of ∼3000 cm3.Conclusions: The induction coil apparatus comprising three independent loops, i.e., Maxwell-type improves upon the performance of simple solenoid and Helmholtz coils by providing homogeneous flux density fields within a large volume while minimizing demands on power and stray fields. Experiments with gel phantoms and analytical calculations show that future translational research efforts should be devoted to developing strategies to reduce the impact of nonspecific tissue heating from eddy currents; and, that an inductor producing a homogeneous field has significant clinical potential for deep-tissue magnetic fluid hyperthermia.
Entities:
Keywords:
AC magnetic fields; Maxwell coil; hyperthermia; magnetic nanoparticle hyperthermia; uniform magnetic fields
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