Time Varied Fields

The scientific literature on the effect of TMFs on biology is much more extensive than for static magnets. Scientists, biologists and engineers still have a conceptual block to the possibility that SMFs can have any effect on biology. They often think that currents and/or heat need to be generated to cause any biologic action. There has been considerable work to show that even SMFs have important biologic effects. But, it is still true that more research has been done on TMFs.

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TMF specifications

As discussed in the section on time variation, TMFs are MFs that are simply turned on or off (pulsed) or more gradually adjusted (sinusoidal). A specific defined pattern is designed into the equipment depending on the intentions of the designer. Like with SMFs designs can vary greatly. I will always attempt to get detailed descriptive information on the design specifications of the apparatus to be able to judge what to expect from treatment.

The important specifics I look at include at the least:

• Signal frequency/frequencies
• Waveform
• Rise time of waveform
• Decay time
• Modulation (if any)
• Field strength/intensities
• Field dimensions and shape
• Coil design
• Control unit or amplifier
• Build-in therapy programs

I also look for any research available on the particular TMF system to determine how it will fit into an overall magnetic therapy program, understanding the advantages and disadvantages of any given system.

Waveforms

The two basic waveforms are pulsed and sinusoidal, or combinations.

Pulsed waves are the most commonly used in treatment systems. Pulsed “waves” can be shaped like spikes, triangles, squares or rectangles. The look of the wave within these groups can vary in unlimited ways. Any of these patterns can be notched (saw-toothed). They can also change polarity. The waves can be any width. They can be combined with sinusoidal patterns and “sit on top of them.”

Various results are expected with each of these designs. Without specific research it is hard to say that anyone is better than another. Research results may have been obtained with any given waveform, but, unless they are compared directly it is hard to say that one form is better than another when applied to a living human body or for a given test system.

The complexity of these wave patterns makes it very difficult to compare results of research and know which systems perform better for given problems. Only rarely have side by side comparisons been made of the waveforms of different systems. This is made even more of a problem because much of the basic research is done outside living tissue, in animals or in laboratories. Results from this research may be applied to humans but until tested the true impact potential is unknown.

Waveform Samples

Lengths of the waves

The higher the frequency the shorter the wave length. The lower the wave frequency, the longer the wave. Longer waves can penetrate through the waves or breadth of a human body more readily. Higher frequency waves tend to be used in more superficial tissues or where the tissue is easily accessible to the applicator. Because of these frequencies, generate heat, unless they are of extremely low intensity, they are generally used to destroy tissue, such as tumors. Eastern Europeans have used very low intensity, millimeter waves to stimulate acupuncture points and other uses. These low intensity millimeter waves do not generate destructive heat.

Frequency (Hz)	Wavelength (M)*	Wave Type	Range Abbreviation
0 Hz	1,000,000,000	Sub Extremely Low Frequency	SELF
3	10,000,000	Extremely Low Frequency (voice range)	ELF
27	100,000	Very Low Frequency to Low Frequency VLF	LF
243	1000	Medium to High Frequency MF	HF
2,187	1	Very High to Ultra High Frequency VHF	UHF
19,683	0.1	Microwave
177,147	0.001	Infra-Red	IR
1,594,323	0.00001	Infra-Red to visible light to Ultraviolet IR	visible – UV
14,348,907	0.0000001- ?0	X-ray – Gamma – Cosmic
*M=meters

Frequency bands

Frequency is defined as cycles per second or Hertz (Hz). They can vary from the single Hz range through to Giga HZ (GHz) levels. They are typically classified into ranges of frequencies. These ranges usually have unique actions studied or found for them. It’s not expected that a single low range frequency (e.g. 6 Hz or a power line frequency of 60Hz) will act the same as a single high frequency range signal, e.g. 60 mega Hz (MHz) or giga Hz (GHz). Broadband signals, which comprise multiple ranges of signals, will be expected to have yet other actions.

Broadband signals could include multiple frequencies, only limited to the imagination or expectation of the designer. For example, they may be 3HZ, 24Hz, 100 Hz, 200 Hz and 500 Hz all produced by the same system, as individual frequencies or a modulated frequencies on top of others. Some systems are designed to place a number of different frequencies into packets or bundles, sometimes called trains in order to exaggerate specific cellular actions.

The reason to design complicated signals like these are the expectation that they will perform the functions found at individual frequencies and in addition will cause “harmonic” interactions at other “harmonic” frequencies. This means that any single frequency system will have harmonic actions anywhere along it’s harmonic scale. The results of harmonics have had little study in biology. I believe they do exist but the effects remain to be better defined.

Magnetic fields have been studied in the following ranges:

• DC -0 hertz (Hz)
• Geomagnetics
• Less than 1 Hz
• 1-100 Hz
• 100-999 Hz
• Kilo Hz (kHz) – (1,000 Hz – 999,999 Hz)
• Mega Hz (MHz) or millions (1,000,000 – 999,999,999) of Hz
• Giga Hz (GHz) – more than 1 billion Hz

Some scientists designate these frequencies in the following bands:

• Extremely low (ELFs)
• Very low (VLFs)
• Infra-red
• Milimeter waves (MMWs)
• Microwaves
• Radiofrequencies (RFs)

Signal width and height

The height and width of an individual wave pulse are felt to influence specific biologic processes accordingly. This is called the rise-time and drop-off rate (or decay rate) of a signal. This is determined by how long it takes an individual wave/pulse signal to reach its peak or to drop down from that peak. The rise time is usually faster than the drop-off time. Some systems are designed with an almost instantaneous rise time, while others take micro- or milli-seconds to reach their peaks or drops. Various systems developers make specific “biologic activity” claims for their particular signal design and are granted patents accordingly.

This graphic shows a specific signal that is built up into a package of frequencies. See the graphic above in the “Waveforms” section.

Energy produced

I will direct a lot of technical attention here since this issue is probably the most critical in understanding how MFs create their actions on the body.
Whether a MF produces current or not will depend on its strength (amplitude), frequency and the tissue volume. Amplitude of the induced electric field within the area of the target penetrated by the magnetic field is proportional to the change in strength (B) and the change in time – t – (dB/dt), i.e., change in induced current (I) or dI/dt in the transmitting coil or applicator) and the radius of the target i.e., the volume distribution of the induced field vs target size. The waveform of E(t) also depends upon dB/dt, which in turn determines the amplitude spectrum, allowing choice of the applied frequency spectrum as a function of the electrical properties of the target (impedance, bandpass).

Electromagnetic effects on biology from relatively weak signals are often due to the time-varying electric field, E(t) and can be induced from an applied time-varying magnetic field, B(t). The majority of electromagnetic clinical devices in present use induce a peak electric field (E) of 1-10 mV/cm at the treatment site, where V is volts.

The voltage and current (I) induced in human limbs and, scaled-up, in the whole body, have to be calculated and projected as possibilities, since living humans can’t be studied directly. The techniques to study humans directly are very invasive and therefore unethical to perform. Experimental models have been created to approximate what would be expected to happen in the human body. The saline in the body changes the electrochemical dynamics significantly vs simple experimental systems. While the magnetic (B) field in laboratory dishes or in vivo is relatively easy to determine, the question of biological effect vs relative orientation of the target and the B field is still unknown.

The distribution of current flow in target tissue depends upon the geometry of both the coil and the tissue. The basic rule is that the voltage induced will act like that from a three-dimensional voltage source, defined by the distribution of magnetic flux within the tissue.

The most commonly used PEMF signals consist of repetitive bursts of symmetric or asymmetric pulse waves, of microsecond to millisecond duration. Peak induced electric fields from PEMF signals are in the mV/cm range at frequencies below 5 kHz. A clinical RF signal typically consists of repetitive bursts of sinusoidal waves in the 13-40 MHz range. RF signals in current clinical use consist of 10-100µs (micro second) bursts of a 27.12 MHz sinusoidal wave repeating at 10-1000 bursts/sec. This signal induces peak electric fields in the V/cm (vs mV) range at 27.12 MHz, an increase between 1000 – 10,000 fold.

Research has shown that even a PEMF magnetic field of 20G, which induces 1 mV/cm in a 1 cm target radius, can produce a bone healing signal. It may be that signals that produce other specific field strengths in different target tissues may have different healing effects. These specificities remain to be determined.

Eventually, we may be able to get to a “dial-a-field” stage in magnetic therapy, with devices that will allow us to dial up what is needed for the problem at hand, whether in the practitioner’s office or the home setting.