Evaluation of Thermal Properties of Ferromagnetic Core for Treatment of Solid Tumors by Electromagnetic Induction Hyperthermia

Abstract

Background: Electromagnetic induction hyperthermia is a promising method to treat the deep-seated tumors such as brain and prostatic tumors. This technique is performed using the induction of electromagnetic waves in the ferromagnetic cores implanted at the solid tumor.

Objective: This study aims at determining the conditions of the optimal thermal distribution in the different frequencies before performing the in vitro cellular study.

Material and methods: In this experimental study, the i-Cu alloy (70.4-29.6; wt%) was prepared and characterized and then the parameters, affecting the amount of induction heating in the ferromagnetic core, were investigated. Self-regulating cores in 1, 3, 6, and 9 arrangements in the water phantom with a volume of 2 cm³ were used as a replacement for solid tumor.

Results: Inductively Coupled Plasma (ICP) analysis and Energy Dispersive X-ray Spectroscopy (EDS) show the uniformity of the alloy after 4 times remeling by vacuum arc remelting furnace. The Vibrating Sample Magnetometer (VSM) shows that the Curie temperature (T_C) of the ferromagnetic core is less than 50 °C. Temperature profile with a frequency of 100-400 kHz for 30 min, was extracted by infrared imaging camera, indicating the increase temperature in the range of 42 °C to 46 °C.

Conclusion: The optimum conditions with used hyperthermia system are supplied in the frequency of 100 kHz, 200 kHz and 400 kHz with 6, 3 and 1 seeds, respectively. It is also possible to induce a temperature up to 50 °C by increasing the number of seeds at a constant frequency and power, or by increasing the applied frequency at a constant number of seeds.

Keywords: Alloys; Electromagnetic Fields; Hyperthermia; Ni-Cu Ferromagnetic Core; Solid Tumor; Water Phantom.

Figure 1

View of hyperthermia system for animal studies and the cross-section sight of the water phantom that placed in the coil.

Figure 2

X-ray diffraction result for the nickel-copper alloy with weight composition (70.4-29.6%).

Figure 3

Results of Energy Dispersive X-ray Spectroscopy (EDS) analysis for Ni-Cu alloy after 4 remelting.

Figure 4

The ratio of magnetization changes to temperature changes dM/dT curve of Ni-Cu alloy measured at magnetic field of 1000 Oe; (inset: Variation of the relative permeability of the Ni-Cu alloy (70.4-29.6 ; wt%) with temperature [ 27 ]).

Figure 5

The extracted temperature-time profiles from the electromagnetic field induction at the central region of phantom (1×1 cm²) with power=1000 W and in different frequencies; (a) 100 kHz, (b) 150 kHz, (c) 200 kHz, (d) 250 kHz, (e) 300 kHz, (f) 350 kHz and (g) 400 kHz.

Figure 6

Suggestion terms for hyperthermia with Ni-Cu ferromagnetic core in power equal 1000 W and different frequency and number of seeds: (a) 1 seed (1S), F=400 kHz, (b) 3 seed (3S), F=200 kHz, (c) 6 seed (6S), F=100 kHz, (d) 9 seed, F=100 kHz.