Magnetic induction hyperthermia

Abstract

A review of physical principles and experimental data on magnetic hyperthermia are presented. The main principles of magnetic hyperthermia are considered. Results of its application in the therapy of oncology diseases are presented. PHYSICAL PRINCIPLES OF HYPERTHERMIATwo components of ac electromagnetic fields E and H can cause heating of tissues. Based on the Maxwell equations and thermodynamic relations, not only the electrocaloric effect, namely, the heat absorption in substance caused by the electric field component E [6], but also the magnetocaloric effect caused by variations in H can be calculated. These effects are mainly determined by the dielectric (ε and δε/δТ) and magnetic (μ) properties of substances, respectively. Because magnetism of biological objects is negligibly small, biologically compatible nontoxic magnetic nanoparticles (based on magnetite and so on) are used to strengthen the influence of an external magnetic field.Thermodynamic relations for a magnet in a magnetic field are similar to those for a dielectric in an electric field [6]. However, an essential difference is that the magnetic field, unlike the electric field, does no work on charges moving in it, because the Lorentz force is perpendicular to the velocity vector of the moving charge. To calculate a change in the energy of the medium when the magnetic field is switched on, electric fields induced by magnetic field variations should be considered. In their turn, high-frequency electromagnetic fields cause heating due to the electric field component. At low frequencies, this effect is insignificant. At the same time, the role of the magnetic field component in magnet heating is significant only at low frequencies [6]. Therefore, inclusion of electromagnetic induction hyperthermia in a separate class of high-frequency phenomena [1], on the one hand, and of magnetic hyperthermia as a low-frequency influence, on the other hand, though relative, is justified.Low-frequency (less than 100 kHz) electromagnetic fields can cause heating of magnetic nanoparticles at the expense of the magnetocaloric effect [7], magnetic reversal in the presence of a hysteresis loop, and magnetic crystal anisotropy of superparamagnetic particles. Physics of the magnetocaloric effect of this phenomenon is the following: elementary magnetic moments are directed chaotically without magnetic field, and hence the magnetic contribution to the entropy is significant. As the magnetic field increases, the magnetic moments are ordered along the field. As a result, the magnetic entropy component S M decreases. Because the magnetization process is close to adiabatic one, the total entropy S does not change, but the entropy component caused by thermal motion increases. Thus, the ferromagnet temperature increases with the magnetic field. Quantitatively, the temperature change is calculated from the formula From the above formula it follows that the temperature can raise when the magnetic moment М S changes with temperature, since the heat capacity C is always positive. The ...

Flow of a biomagnetic viscoelastic fluid: application to estimation of blood flow in arteries during electromagnetic hyperthermia, a therapeutic procedure for cancer treatment

“…In the method of magnetic hyperthermia for the treatment of cancers/malignant tumors, superparamagnetic gels (with particles whose sizes range is between 8 nm and 10 nm) are preferred [1] . In this particular therapeutic procedure for the treatment of tumors, clinicians use the method of exposing the tumor to a magnetic field at low frequencies (usually less than 200 kHz) by using nanoparticles of ferrite materials.…”

“…Heating is performed by nanoparticles, whereby the temperature level is raised to 45 • C−47 • C. If the nanoparticles are injected directly into the tumor, the possibility of the normal cells remaining unaffected increases considerably. Also, as mentioned in [1], magnetic signal of injected particles enhances magnetic contribution of the blood vessel. In biomedical technology, this is reckoned as a strong advantage of using magnetic nanoparticles.…”

“…However, this is not possible when the patient is treated by using radiotherapy, chemotherapy, or surgery. Basing upon the experimental observation that at a temperature higher than 41 • C, the transformed malignant cells become more sensitive than the normal cells, a better alternative treatment by subjecting the malignant cells to a temperature field higher than 41 • C with the help of ultrasound/microwave technique has been suggested, and thereby a method called electromagnetic hyperthermia has been developed (see [1]). This method consists of injecting a magnetic fluid into an artery that supplies blood directly to the malignant tissues and then subjecting the system to an alternating current (AC) magnetic field.…”

“…For magnetic hyperthermia, the basic principles and available experimental data have been nicely reviewed by Nikiforov [1] . The underlying principle, as per his assertion, in the method of magnetic hyperthermia for the treatment of malignant tumors is to heat a tumor by using iron oxides.…”

The Effect of Spatially Inhomogeneous Electromagnetic Field and Local Inductive Hyperthermia on Nonlinear Dynamics of the Growth for Transplanted Animal Tumors

“…The electro-and magnetocaloric effects are electro-and magneto-thermodynamic phenomenons in which a reversible change in temperature of a suitable material is caused by exposing the material to a changing EF. It was accompanied by changes in transfers from electromagnetic to thermodynamic entropy and enthalpy (Nikiforov, 2007;Crosignani & Tedeschi, 1976). Therefore, we can symbolically included high-frequencies electromagnetic IH in separate class of electro-and magnetocaloric effects.…”