slew Rate and ICES

Two presenters at the PEMFcon October 2024 meeting claimed that higher slew rates were better than slow rates. The slew rate is the change in voltage with time. Whys is this important? Robert Dennis of Pulse Health was at the center of some of the early research. This post also intrudes Pulse Health ICES technology.

An Analogy

Acceleration is the change in velocity with time.

We have to remember that it is not BF that goes flying when we floor the accelerator but rather the car relative to BF. Now we’re going at a pretty good clip on the freeway. BF is sitting happy on the passenger’s seat. The car ahead of us has a tire blow out. To avoid an accident requires an immediate and very fast stop. Poor little BF goes flying again. This narrative is going to stop here because imperfections in the analogy. It should be intuitive that the rate of applying a force as well as the rate of removing a force matters.

We can easily get mired into the rabbit hole of differences between electric and magnetic components of electromagnetic fields. The featured image features all three and an image of what it means for an ion to move through an electric field. The difference between an electric field and a magnetic field is all about degrees of separation. In electric fields the charges are separated by space. In magnetic fields they are within the same atom. This sites icon on the upper left is a dog jumping through a magnetic field generated by electrons flowing through a coil. A must see cartoon of electrons leapfrogging around metal atom nuclei brings home this concept. There is just something special about electrons moving in a coil that generates the N/S or +/- polarity of a magnetic field.

Quotes from EMF Portal

Electric field is created between charge carriers, when an electrical voltage is present due to electrical charge difference. This is also the case when no current flows. The electric field strength is given in units of volts per meter (V/m). It increases with higher voltage and decreases with growing distance from the source.

Magnetic field may arise from moving charges…The strength of the magnetic field is measured in current per meter (A/m), and referred to as the magnetic field strength H. In contrast to the electric field strength E, the magnetic field strength does not represent the total electromagnetic force of the magnetic field, since this force will depend not only on the current intensity, but also on the material that is penetrated by the magnetic field. Thus, to describe the strength of the magnetic field in matter, the magnetic flux density B is used with the unit Tesla (T). The magnetic flux density is often also referred to as magnetic induction. The magnetic flux density B is linked to the magnetic field strength H by a material constant, the magnetic permeability µ.

B = µ × H In simple terms, the magnetic permeability µ (also called magnetic conductivity) is a measure of the permeability of materials for magnetic fields.

Electromagnetic Fields Electric field (E) and magnetic field (H) of a propagating, linearly polarized electromagnetic wave over time (t). E and H are in phase and at 90 degrees to each other and mutually generate one another. The power flux density S of the electromagnetic field consists of energy fractions of the electric and magnetic field components and is measured in watts per square meter (W/m²). The field strength decreases with increasing distance from the field source.

Inductively coupled electrical stimulation

Remember high school physic and the use of those curly wires called inductors to take the high voltage power lines down to a voltage we can use in our homes without cooking our appliances? Creating a coupled inductor with two discrete inductors

This technology was initially developed at NASA’s Johnson Space Center. Inductively coupled in twin coils is explained in Fig1 of ref [3].

wave form and density of cultured muscle cells. [1]

For Experimental Series #1, all pulses were delivered at 10 Hz (except the DC), The applied fields alternated symmetrically between positive and negative at 10 Hz (except DC, which was always positive). In Part 1 the endpoint was C2C12 muscle cell line cell density scored 0-5 with 5 being the most dense. Six different wave forms were examined.

• A sinusoid, density score 0. Control, also density score 0.
• B “DC” steady fixed magnetic field, density score 0
• C triangle, saw tooth and triangle 0-1 density.
• D saw tooth, which is a skewed or asymmetric triangle, which means that ramping up is slower than ramping down.
• E square wave, 50 msec, density score 3-5.
• F delta pulse, 0.2 msec, which is a really short lived spike of which there are six pulses in the same unit time there are three with the square wave. density score 204

The discussion covered the difficulty of creating authentic square wave and the establishment of extracellular matrix as the mechanism of action of said square waves. Some of these data were presented at PEMFcon.

Part 2 bone healing and wave form [2]

Part 2 used two wave forms: delta spikes and a combination of saw tooth waves in a square wave configuration. delta waves. Bone gaps were surgically created in rabbits. Cuffs were used to apply the PEMF. Control rabbits, 9%, showed some regeneration. None of the control rabbits showed extensive regeneration.

	Pulse	Peak	Rising	Falling	some bone regeneration	extensive regeneration
Small Cuff	100 μs	10.1 G	101 kG/s	-28 kG/s	100%	40%
Large Cuff	200 μs	9.6 G	48 kG/s	-54 kG/s	67%	0%

The hopeful but incomplete nature of this study was part of discussion. The author concluded that the key parameter for biological effectiveness of PEMF was determined to be magnetic slew rate (dB/dt). The minimum threshold of this parameter for clinical effectiveness for regeneration of bone tissue after orthopedic injury was found to be ~ 100 kG/s. This magnetic slew rate, when sustained for 100 μs at a pulse rate of 10 Hz, was found to be effective both for pain reduction as well as to induce bone regeneration in a critical defect gap.

Improving on the ICES design [3]

1. Fig 1 oppositely polarized magnetic fields, resulting in the formation of magnetic arcs, spanning from coil to coil with each pulse.
2. Fig 2 map of N/S polarities created by the coils.
3. Fig 3 stacking the twin coils. In this configuration, where the separation distance between the coils h is equal to (or less than) the radius r of the coils, a nearly uniform magnetic field is formed between the coils, illustrated by the parallel and equally-spaced flux lines (green) in the region between the coils.
4. Fig 4 and Fig 5 mouse cage models
5. Fig 6 the two Micropulse coils in different configurations.
6. Fig 7 typical rise and fall of ICES device in units of Gauss per mcro sec.
7. Fig 8 Gauss at 50% at less than 10 mm from the coils.
8. Fig 9, The slew rate gets slower the further from the coils.
9. Fig.10 The wave form within stacked coils with peak field intensity up to 0.025 T.

There was some in the discussion on the drop off of magnetic field with distance in he rodent cage.

Seed germination [4]

This particular paper seemed to dismiss the role of Cryptochromes in seed germination, magnetic field sensing, and blue light sensing. Variability among plant species was observed.

Part 5 of the Inductively Coupled Electrical Stimulation series got into the issue of there being just too many possible variables in PEMF [5] If there were some sort of feed back to couple tissue response to wave form variables…

Physiostim “gold standard” vs novel high slew rate device [6]

osteogenesis distraction OD) is a process in which a portion of bone is cut away and the callus allowed to grow in.

• Physio-Stim PEMF signal has a fundamental burst frequency of 15 Hz, pulse frequency of 3.85 kHz, and slew rate of 10 T/s. The FSA approved time is 3 hours per day.
• The Orthofix Medical has the same burst and pulse frequencies but a higher slew rate, theoretically resulting in a higher energy input to the target tissue. The times ere 30 min, 1 hour, and 3 hours per day.

. The Orthofix high slew rate PEMF device produced stronger chondrogenesis and bone mineralization than that of a classic PEMF device in a rat model.

Tumor membranes revisited [7] or not, concluding remarks

The ability of pulsed magnetic fields to cause membrane leaks was addressed on PEMF and membrane leaks on this site. These authors applied 20 mT magnetic fields in the msec time frame. , if dB/dt is high enough, applying a magnetic field pulse should generate a torsional electromotive force (EMF) on any charge-carrying elements of the cell surface, so long as the charge density is high enough. This effect may operate through Faraday’s law of induction. [7] Is a flow of ions turning “wrench” or is the magnetic field turning the wrench itself? The featured image for this post illustrates the fine points of electric and magnetic fields, electromagnetic waves….. and ….. the any time a charged anything moves through a biological medium, there is interaction with other charged groups. Pulse Health makes a very big deal about their device NOT being FDA approved. It certainly seems obvious why it is so hard to get FDA approval for anything PEMF. Pulse Health does have a wide range of models with lot of programs for their more expensive units. A portal allows users to compare notes.

References

1. Dennis, Robert. (2019). Inductively Coupled Electrical Stimulation – Part I: Overview and First Observations. The Journal of Science and Medicine e. 1. 20-35. 10.37714/josam.v1i1.5. free paper
2. Dennis Robert. Inductively Coupled Electrical Stimulation – Part 2: Optimization of
   parameters for orthopedic injuries and pain. The Journal of Science and Medicine. 2020; free paper
   1(2)DOI
3. Dennis Robert. Inductively Coupled Electrical Stimulation – Part 3: PEMF Systems for use in Basic Research with Laboratory Animals and In Vitro. The Journal of Science and Medicine. 2020; 2(3)DOI free paper
4. Dennis Robert, Tommerdahl Anna, Dennis Andromeda. Inductively Coupled Electrical Stimulation – Part 4: Effect of PEMF on seed germination; evidence of triphasic inverse hormesis. The Journal of Science and Medicine. 2021; 2(4)DOI
5. Dennis, Robert. (2021). Inductively Coupled Electrical Stimulation – Part 5: How many types of PEMF are there? A model and Excel Calculator. The Journal of Science and Medicine. 3. 10.37714/josam.v3i2.67. Research Gate.
6. Li Y, Yang Y, Wang M, Zhang X, Bai S, Lu X, Li Y, Waldorff EI, Zhang N, Lee WY, Li G. High slew rate pulsed electromagnetic field enhances bone consolidation and shortens daily treatment duration in distraction osteogenesis. Bone Joint Res. 2021 Dec;10(12):767-779. PMC free paper
7. Ashdown CP, Johns SC, Aminov E, Unanian M, Connacher W, Friend J, Fuster MM. Pulsed Low-Frequency Magnetic Fields Induce Tumor Membrane Disruption and Altered Cell Viability. Biophys J. 2020 Apr 7;118(7):1552-1563. PMC free paper
8. Hubbard DK, Dennis RG. Pain relief and tissue healing using PEMF therapy: a review of stimulation waveform effects. Asia Health Care Journal. 2012; 1(1):26-35.