There are many therapeutic devices based on the use of an electromagnetic field, and various intensities of electric current are applied. The spectrum of the electromagnetic rays generated by these devices is very wide, so – naturally – the consequent biological effects are also different.
Just to give a general picture, let us look at the most frequently used devices, instruments and procedures:
The most frequent and simplest are permanent magnets, made of various alloys.
Magnets with a stationary magnetic field have been used in the past for faith healing. They are, in fact, the predecessors of the devices used for treatment today; however, modern devices work with a pulse magnetic field that is biologically more efficient.
At present, permanent magnets are usually made of an alloy, consisting of barium and iron (ferrite magnets, baric ferrite) or with samarium, cobalt or neodymium.
Neodymium magnets NdFeB (neodymium –iron – boron) are the strongest magnets. The basic material is processed by sintering. NdFeB magnets are vulnerable to corrosion so the surface is usually finished with nickel, zinc or epoxy resin; alternatively, the surface may be finished by passivation.
Permanent magnets are normally applied directly onto the body. A standard magnet made of ferrite (the type you know from bulletin boards) will – at a distance of 1 cm from the surface – generate magnetic induction ranging from approx. 30 to 70 mT (militesla), which is a thousand times higher than the Earth´s magnetic field. At a distance of approx. 30 cm from the magnet surface, the field is just about the same as the Earth´s field.
Magnetofors – Magnetofors are foils made of a soft plastic material in which soft ferromagnetic particles are integrated; they are magnetised in such a way that the whole thing resembles a checkerboard. The induction on the surface is under 40 mT; however, as the thickness is very low, there is a considerable gradient, so at a distance of 5 cm the magnetic induction is rather a fraction of the induction on the surface.
Biolamps – The concept of the biolamp is based on polarised light that – unlike the laser – is neither monochromatic nor coherent. The effects and indications are similar to the laser; however, the performance and the ability to penetrate into the tissues are different. As regards bio-lamps, penetration into the tissue is not very deep.
Low-frequency current 0 to 1000 Hz. The low-frequency current (0 – 1000 Hz) used in physiotherapy is generated by interruption of the galvanic current, by modification of the network alternating current, or electronically. Such currents are applied using electrodes.
Diadynamic current – Diadynamic current is frequently used in low-frequency therapy. This is based on application of a low-frequency sinus mono-phase current mounted on the galvanic component. The current is also applied by means of electrodes. The procedure causes tissue warming.
Contact-free high-frequency therapy – In contact-free high-frequency therapy, an alternating current is used, at a frequency above 100 kHz, up to 300 GHz. As for the procedures, short-wave diathermy, capacitive dielectrothermy, and inductive inductothermy are used. One of the effects of these methods is that the electromagnetic energy is converted into thermal energy, which results in warming of the tissues exposed.
Distance electrotherapy – This method uses an electric current generated in the deep layers of the tissue by means of electromagnetic induction. Considering the physical mechanisms, this is a transitional stage between electrotherapy and magnetotherapy. Unlike magnetotherapy, with a magnetic field serving as the therapeutic means, with distance electrotherapy, the electric component of the electromagnetic field is used.
Magnetotherapy – Magnetotherapy is classed as a contact-free electrotherapeutic method. In the case of magnetotherapy, the electric component of the electromagnetic field in the tissues (the electric voltage and the electric current) is (on average) 100 times lower, compared to traditional (contact) electrotherapy. It is used for therapeutic purposes due to the general biological effects of the magnetic component of the electromagnetic field.
A magnetic field is generated around every conductor through which an electric current flows; its properties depend on the parameters of the electric current. The phenomenon is known as electromagnetic induction.
The magnetic field may be static, alternating or pulse. In the case of pulse magnetic fields, the frequency is important. We can distinguish the following pulse magnetic fields:
– from 0 to 100 or 150 Hz
9 to 250 MHz, connected in groups of low frequency (40 to 640 Hz)
As regards low-frequency magnetotherapy, the thermal effect is not primarily used for its therapeutic effects: this makes the method different from high-frequency magnetotherapy (especially the capacitive method).
By the way, this means that low-frequency pulse magnetotherapy is applicable even with people who use metal prostheses or have implants installed in their bodies.
Many devices and instruments have been designed and developed for magnetotherapeutic purposes. Recently, many of them have applied the latest technology, presenting numerous so-called medical programmes. However, they have been rather bulky and difficult to operate, some of them using higher frequencies or frequencies whose potential effects are not really known. Therefore, the first important thing is to choose a suitable device for applying pulse magnetotherapy and secondly, one should not confuse high- and low-frequency magnetotherapy and their features, including the intensity of the magnetic field required (see also the chapter entitled Therapeutic effects of the magnetic field).
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