Page 250 - Computational Modeling in Biomedical Engineering and Medical Physics

Magnetic stimulation and therapy 239

These results outline processes that could hardly (if possible) be perceived using
other means and support the merit of the numerical simulation as an assistive, valuable
aid in the preparing the TMS and evaluating the main, stimulating effect as well as the
side effects—thermal, mechanical, etc.

7.5 Magnetic therapy

Magnetic field therapy (MFT) is using EMF exposure at 10 100 Hz (up to 170 Hz)
such that the magnetic field component prevails the electric field component.
However, in case of metallic implants, especially those that are fixed in soft tissues
and are not made of antimagnetic materials, the magnetic component may be signifi-
cant. In this frequency range, biological entities are diamagnetic and their molecules
orient to minimize the field energy. In biological tissues, such actions are against the
bonds between atoms, molecules, and ions, which accordingly influence the cellular
processes (Monzel et al., 2017; Fei et al., 2019; Peng et al., 2019).
The physiological response of the body to the application of MT comprises multi-
ple effects: analgesic, antiedematous, trophic (acceleration of healing by growth), vaso-
dilation and muscle relaxation, reduced pain, costs, and duration of treatment
(Markov, 2007; Chalidis et al., 2011; BTL, 2020).
Time-variable magnetic fields are significantly more effective than static magnetic
fields for various therapies, and they can be combined with other physiotherapy proce-
dures or with pharmacotherapy. The vascular tree (including lymph and blood), the
peripheral nerves, the central neural system and its path—the moving conductor—
and, not the least, the individual ions and charges on cellular membranes—the travel-
ing charges—are electrically conductive constituents, such that in variable magnetic
field physiotherapy, the electrodynamics effects are important.
Different types of magnetic field excitations are used: stationary, for increased
bleeding conditions, acute states, postoperative conditions; alternating, for nerves or
muscle distortion, triangular, for cartilages or tendons dysfunctions, and pulse, for bone
diseases. However, for pulse MF it is yet to clarify whether the electric field compo-
nent is more intense, prevailing.
As for TMS and LMS, the MFT uses applicators (electric current-carrying coils) to
provide focused exposure to magnetic field (Markov, 2007; Krawczy et al., 2017;
Physiomed, 2020). The coils function may be enhanced using permanent magnets
embedded within the disc-type applicators. The applicators are placed as close as possi-
ble to the patient’s body, to limit the dispersive magnetic flux. The minimum expo-
sure time is at least 10 min, and the total daily exposure should not exceed 40 min
(BTL, 2020). For best results exposures should be repeated.
In the electrodynamics of conductive moving media and variable magnetic fields, the elec-
tric currents are accompanied by heating effects, and in this section, we are concerned with