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Title:
SYSTEMS AND METHODS FOR AN ADAPTIVE HIGH POWERED PULSED TRANSCRANIAL MAGNETIC STIMULATOR
Document Type and Number:
WIPO Patent Application WO/2017/132750
Kind Code:
A1
Abstract:
The present disclosure relates to a system and method for providing an enhanced TMS system that significantly improves upon the application of TMS for currently treated disease states. In another aspect, there is provided a system for applying high-powered magnetic flux density. The system comprises one or a plurality of high voltage capacitor charging power supplies, a high voltage capacitor bank, an H-bridge integrated gate bipolar transistor (IGBT) switching circuitry with intelligent gate driving circuitry, integrated cooling, a microcontroller with complex waveform capability for triggering the IGBTs, including an optical interface to reduce EMI effects, snubber circuits to suppress voltage transients arising from the IGBTs, a discharging system that absorbs residual energy upon completion of treatment or when the system is halted for safety purposes, a coil assembly with integrated cooling, and a real-time feedback circuit to verify the integrity of the output waveforms and institute corrections in the event of any deviations in electrical parameters or halt the system if parameters fall outside of safety limits.

Inventors:
SAFAVI-NAEINI ALI SAFIEDDIN (CA)
LOTFINEYESTANAK ABBASALI (CA)
GHASEMI MASSOUD (CA)
DOUCET KEITH (CA)
GLASS IAIN (CA)
Application Number:
PCT/CA2017/000026
Publication Date:
August 10, 2017
Filing Date:
February 06, 2017
Export Citation:
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Assignee:
NEUHORIZON MEDICAL CORP (CA)
International Classes:
A61N2/04
Foreign References:
CA2915928A12014-12-24
US20090018384A12009-01-15
US20100087699A12010-04-08
US20150367141A12015-12-24
Attorney, Agent or Firm:
NAHM, Tai, W. (CA)
Download PDF:
Claims:
CLAIMS:

1. A system for applying pulsed transcranial magnetic stimulation (TMS), comprising: a cascadable high voltage source; a bank of cascadable high voltage capacitors; an integrated gate bipolar transistor (IGBT) switching network with intelligent gate drivers; and a microcontroller adapted to generate complex waveforms obtained from a combination of pulse waveforms of varying shape for triggering the IGBTs; whereby the IGBTs are adapted to drive a coil assembly which generates a magnetic flux density (B) greater than 2.5 Tesla and duty cycles exceeding 25%.

2. The system of claim 1 , wherein the IGBTs include snubber circuits to suppress voltage transients arising from the IGBTs.

3. The system of claim 2, wherein the system further comprises a real-time feedback circuit to verify the integrity of the output waveforms and institute corrections in the event of any deviations in electrical parameters or halt the system if parameters fall outside of safety limits.

4. The system of claim 1 , further comprising a discharging system that absorbs residual energy upon completion of a treatment cycle, or when the system is halted for safety purposes.

5. The system of claim 1 , wherein the high voltage supply and capacitor bank are cascaded to provide greater power and/or wider pulse widths in stages.

6. The system of claim 1 wherein the system is adapted to generate a magnetic flux density of up to 4.2 Tesla at a duty cycle of 50% for operation periods exceeding half an hour.

7. The system of claim 1 wherein the system is adapted to generate up to a PRF of 100 Hz.

8. The system of claim 1 wherein the microcontroller is adapted to generate rectangular (symmetric and asymmetric), triangular, sinusoidal, or trapezoidal pulse waveforms with slow, medium and fast rise times, to drive the coil assembly in each pulse repetition interval (PRI) to PRI basis, where PRI=1/PRF.

9. The system of claim 8, wherein the microcontroller is adapted to combine any two types of pulse waveforms to create a unique hybrid shape, on a PRI to PRI basis.

10. The system of claims 8 wherein the width of each pulse shape ranges from about 60 to about 200 microseconds, creating pulse waveform periods of up to 400 microseconds on a PRI to PRI basis.

11. The system of claim 8 wherein each pulse waveform is monophasic or biphasic in either normal or reverse current directions on a PRI to PRI basis.

12. The system of claim 8 wherein the pulse waveforms are generated in paired, tri or quad sequences within each PRI, on a PRI to PRI basis.

13. The system of claim 12 wherein each pulse waveform is independently controlled in amplitude, pulse width and time delay between pulses on a PRI to PRI basis.

14. The system of claim 12 wherein the pulse waveforms are applied to optical couplers to minimize the effects of EMI from the high magnetic field emanating from the coil and transmission lines within the system.

15. The system of claim 13 wherein the amplitude is fixed or ramp up or down with a specific slope and min and max settings on a PRI to PRI basis.

16. The system of claim 1 , wherein the coil assembly comprises braided or Litz wiring of minimum dimensions of 15x5 mm.

17. The system of claim 1 wherein the coil assembly comprises perforated spiral walls, corrugated channels, and an inner wall cone design to increase water flow across the conductors for increased heat transfer.

18. The system of claim 1 wherein the IGBTs include integrated cooling.

19. The system of claim 18, wherein the IGBTs include intelligent drivers to monitor switching behavior for optimized performance and to detect short circuit conditions.

20. The system of claim 1 further comprising paired copper plates, separated by a minimum of 10 mm to prevent arcing and minimize electromagnetic interference.

21. The system of claim 1 further comprising a Hall effect current transducer to provide real-time feedback to the microcontroller to optimize each waveform.

22. The system of claim 1 wherein a discharging circuit is applied each time the system is halted.

Description:
SYSTEMS AND METHODS FOR AN ADAPTIVE HIGH POWERED PULSED

TRANSCRANIAL MAGNETIC STIMULATOR

FIELD

[0001] The present invention is directed to systems and methods for creating a high- powered, adaptive, highly efficient, scalable multi-waveform pulsed repetitive Transcranial Magnetic Stimulator (rTMS) system for improved treatment efficacy and safety.

BACKGROUND

[0002] Transcranial Magnetic Stimulation (TMS) is a non-invasive therapeutic technique that uses a focused, high-powered magnetic pulsed field emanating from coil windings to induce neural action potentials in the brain to address a variety of neurological and physiological applications.

[0003] TMS therapy, which has been FDA approved for treatment of major depressive disorder (MDD), holds promise for a wide range of disease states including, Schizophrenia, Parkinson, Tourette's Syndrome, Alzheimer's, Amyotrophic Lateral Sclerosis, Multiple Sclerosis, Attention Deficit/Hyperactivity Disorder, Obesity, Bipolar Disorder, Post Traumatic Stress Disorder (PTSD), anxiety disorders, etc.

[0004] The basic building blocks of a TMS system include a charging circuit that feeds into an array of high voltage capacitors bank, and solid state switches that channel the high powered current from the high voltage capacitor bank to a coil for magnetic field stimulation into the brain.

[0005] Repetitive TMS (rTMS) involves the generation of a train of high powered magnetic pulses with varying transmission parameters, including pulse width, pulse repetition rate, frequency and power level, to elicit specific excitatory or inhibitory neurological effects within the brain.

[0006] Current rTMS systems lack in several principal areas preventing optimal application or, in many cases, rendering treatment ineffective. As well, the operational constraints associated with current systems can lead to patient discomfort and heightened anxiety during treatment, negatively impacting efficacy.

[0007] Specifically, existing rTMS systems exhibit relatively low magnetic flux density levels (approximately 2.5 Tesla), feature poor thermal management capability, resulting in limited duty cycles and subsequent reduced per-session treatment times, possess limited waveform versatility and agility, and lack real-time stimulant feedback for treatment optimization.

[0008] Therefore, what is needed is an improved system and methods for addressing at least some of the limitations in the prior art.

SUMMARY

[0009] The present invention relates to systems and methods for providing an enhanced TMS system that significantly improves upon the application of TMS for currently treated disease states, such as MDD, and paving the way to treat a plethora of new mental and neurological disorders. Additionally, the presently disclosed systems and methods provide the tools and capability to stimulate the brain in a manner not previously possible.

[0010] In another aspect, there is disclosed a system for applying high-powered magnetic flux density. The system comprises one or a plurality of high voltage capacitor charging power supplies, a high voltage capacitor bank, an H-bridge integrated gate bipolar transistor (IGBT) switching circuitry with intelligent gate driving circuitry, integrated cooling, a microcontroller with complex waveform capability for triggering the IGBTs, including an optical interface to reduce EMI effects, snubber circuits to suppress voltage transients arising from the IGBTs, a discharging system that absorbs residual energy upon completion of treatment or when the system is halted for safety purposes, a coil assembly with integrated cooling, and a real-time feedback circuit to verify the integrity of the output waveforms and institute corrections in the event of any slight deviations in electrical parameters or halt the system if parameters fall outside of safety limits. [0011] In another aspect, a method in accordance with an embodiment comprises generating complex waveforms to stimulate a variety of physiological effects on the neuronal structure of the brain and other parts of the body for unique treatment and research applications.

[0012] In an illustrative embodiment, the system includes the capability to generate a series or train of pulses comprising triangular, rectangular, sinusoidal, trapezoidal (with slow, medium and fast rise times) and a combination of these waves to form unique hybrid profiles.

[0013] In another illustrative embodiment, the pulse trains can be generated for both mono-phasic and biphasic as well as a combination of mono and biphasic stimulation on a pulse-to-pulse basis.

[0014] In another aspect, there is disclosed a method of generating a series or a train of waveforms by employing rectangular pulses to trigger the H-bridge IGBT switch fabric based on specific combinations of pulse width, amplitude and time delays within each Pulse Repetition Interval (PRI).

[0015] In an embodiment, the method generates, on a pulse-to-pulse basis, normal or reverse current directions over a wide range of pulse widths and at various power levels, from steady to ramping at any desired slope, duration and start and stop intensity levels.

[0016] In another embodiment, the method produces multiple pulses within each PRI, including two (pair), three (tri) and four pulses (quad), where each pulse can be independently controlled to exhibit one of the wave shapes described previously, for any amplitude, pulse width, time delay and PRF.

[0017] In another embodiment, the time delay between pulses is programmable ranging from one pulse width up to the PRI, allowing unique neurological stimulants and responses to be produced. Each pulse can be monophasic or biphasic in either the normal or reverse current direction. One example of paired pulse stimulation involves generating an initial high powered monophasic trapezoidal pulse, at 100% of motor evoked potential (MEP), with relatively wide pulse width and fast rise time, to create a washout effect, followed by a biphasic triangular pulse at 75% of MEP 10 milliseconds later, to facilitate measurement of the neurological excitation/inhibition responses of the brain within a specific path.

[0018] In another aspect, there is disclosed a method for generating paired, tri, and quad pulses at pulse repetition frequencies ("PRFs") as high as 100 Hz at pulse widths of up to 200 microseconds.

[0019] In another aspect, there is disclosed an integrated cooling system within the IGBT circuit and coil assembly to facilitate high power at much greater duty cycles than is possible with conventional systems. Current rTMS systems generate 2-2.5 Tesla of magnetic flux density at duty cycles of 25% or less. In comparison, the present system and method in accordance with one embodiment is capable of generating magnetic fields of up to 4.2 Tesla at duty cycles of 50%.

[0020] In another aspect, the present system and method uses a Hall effect current transducer to measure the precise shape and magnitude of the pulse, which is fed back to the microcontroller for real-time optimization to address variances that can occur from parametric drifts arising from the high temperatures over which the system operates. The mechanism is also used to detect any excessive drift, arising from circuit component failures, immediately halting the system if the high-power waveform deviates from specified safety limits.

[0021] In an embodiment, the present system and method uses rectangular braided wiring, configured in a traditional figure eight or O-shape coil assembly, while another embodiment describes the use of rectangular Litz wiring, configured similarly, to achieve more efficient thermal dynamics (due to reduced AC resistance from skin and proximity effects).

[0022] In another embodiment, the coil design includes perforated spiral carbon walls for all coil configurations to allow pressurized coolant liquid to flow across the surface areas of the braided/Litz conductors to promote efficient heat transfer throughout the coil assembly. Relatively large braided wires are employed to promote better heat transfer. The larger conductor also offers the advantage of reduced mechanical stress when the high power is applied, resulting in decreased noise emanating from the coil assembly, and hence providing greater patient comfort during treatment.

[0023] In another aspect, the system incorporates a modular design of the high voltage system and charging capacitor banks, allowing the system to be configured or reconfigured from low power to high power, or to increase waveform pulse widths in the field. This is in contrast to conventional systems that are typically offered on the basis of power categories (e.g. low, medium and high). A user acquiring a low power system initially and desires to upgrade to a higher power system in the future, will be required to acquire a whole new system, having to extract the old system at an inconvenience and cost.

[0024] In this respect, before explaining at least one embodiment of the system and method of the present disclosure in detail, it is to be understood that the present system and method is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The present system and method is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a block diagram illustration of a system in accordance with an embodiment.

[0026] FIGS. 2A and 2B comprise a block diagram illustration of the scalability of the high voltage source and high voltage capacitor bank in accordance with embodiment.

[0027] FIG. 3 is a schematic illustration of the micro-controller interconnecting to the IGBT modules in accordance with an embodiment. [0028] FIG. 4 provides an illustration of the stimulant waveforms required to generate a monophasic triangular pulse in the normal direction in accordance with an embodiment.

[0029] FIG. 5 is an illustration of the stimulant waveforms required to generate a monophasic triangular pulse in the reverse direction in accordance with an embodiment.

[0030] FIG. 6 is an illustration of the stimulant waveforms required to generate a biphasic triangular pulse in accordance with an embodiment.

[0031] FIG. 7 is an illustration of the stimulant waveforms required to generate a monophasic rectangular pulse in accordance with an embodiment.

[0032] FIG. 8 is an illustration of the stimulant waveforms required to generate a biphasic rectangular pulse in accordance with an embodiment.

[0033] FIG. 9 is an illustration of the stimulant waveforms required to generate a biphasic rectangular pulse in the reverse direction in accordance with an embodiment.

[0034] FIG. 10 is an illustration of the stimulant waveforms required to generate a monophasic sinusoidal pulse in accordance with an embodiment.

[0035] FIG. 11 is an illustration of the stimulant waveforms required to generate a biphasic sinusoidal pulse in accordance with an embodiment.

[0036] FIG. 12 is an illustration of the stimulant waveforms required to generate a monophasic trapezoidal pulse with medium rise time in accordance with an embodiment.

[0037] FIG. 13 is an illustration of the stimulant waveforms required to generate a biphasic trapezoidal pulse with medium rise time in accordance with an embodiment.

[0038] FIG. 14 is an illustration of the stimulant waveforms required to generate a biphasic hybrid pulse in accordance with an embodiment.

[0039] FIG. 15 is an illustration of the stimulant waveforms required to generate an asymmetric triangular pulse in accordance with an embodiment. [0040] FIG. 16 is an illustration of the stimulant waveforms required to generate a paired pulse comprising a monophasic trapezoidal wave and biphasic triangular wave within a single PRI in accordance with an embodiment.

[0041] FIG. 17 is an illustrative example of an output waveform comprising four distinct pulse shapes comprising a biphasic hybrid pulse, a monophasic sinusoidal wave, a monophasic trapezoidal wave and biphasic trapezoidal wave within a single PRI in accordance with an embodiment.

[0042] FIG. 18 is an illustration of the feedback mechanism of the generated output power in an embodiment.

[0043] FIGS. 19a and 19b illustrate coil wire and spiral walls within the coil assembly in accordance with an embodiment.

[0044] FIG 20 is an illustration of the coil assembly.

[0045] FIG 21 is an illustration of the bottom of the perforated spiral walls within the coil assembly.

[0046] FIG 22 is an illustration of the coolant system and intelligent drivers for the IGBTs.

[0047] FIG 23 is an illustration of the coolant system in series to IGBTs and coil assembly.

[0048] FIG 24 is an illustration of the paired copper plate buses interconnecting the subsystems.

[0049] FIG 25 is a schematic block diagram of a generic computing device. DETAILED DESCRIPTION

[0050] As noted above, the present disclosure relates to systems and methods for creating a high-powered, adaptive, highly efficient, scalable multi-waveform pulsed integrated Transcranial Magnetic Stimulator (iTMS) system for improved treatment efficacy and safety. In an aspect, there is provided a method for applying iTMS to generate magnetic flux density with greater energy efficiency, lower heat loss/dissipation, and higher waveform flexibility/versatility over conventional rTMS systems. Various illustrative embodiments will now be described with reference to the figures.

[0051] Reference is now made to FIG 1 , which provides a block diagram illustration of one aspect of embodiment of the iTMS system. The overall system comprises a cascadable high voltage source or high voltage power supply (HVPS) 101 , a bank of cascadable high voltage capacitors 102, switching network of IGBTs 103, ultra-compact single channel intelligent gate drivers 113, a microcontroller 104 with optical interfaces 114 to the IGBTs 103, coil assembly 205, snubber circuitry 107, discharging circuitry 108, and integrated liquid coolant 106.

[0052] In an embodiment, the HVPS 101 comprises a single or a multiplicity of capacity charging sources each supplying 6000 J/sec of charging power to the high voltage capacitor bank 102. The output of the capacity charger module provides a constant current to charge multiple capacitors within the high voltage capacitor bank 102 to a predefined voltage amplitude value set by the micro-controller 104.

[0053] In another embodiment, modules in the HVPS can be ganged to increase the total current and corresponding output power to the high voltage capacitor bank 102, which in turn increases the amount of magnetic flux density transmitted by the coil. An illustrative example is given in FIGS. 2A and 2B, which depict a single HVPS module 101 feeding into the high voltage capacitor bank 102 in FIG. 2A, while FIG. 2B depicts a second HVPS 101 a added in parallel and applied to a pair of high voltage diodes 109, 109a. In another aspect of the design, additional capacitors 102a may be added in the high voltage capacitor bank 102 to increase the pulse width of the generated waveforms.

[0054] In an embodiment, the microcontroller 104 adjusts for the extra power and updates a graphical user interface (GUI), as described with respect to generic computer device 1000 further below, accordingly through signaling from the HVPS module. Both HVPS and capacitors can be added in the field by the end user, allowing the system to be configured or reconfigured to build up of power or pulse width as the requirement arises. Also, the HVPS can be connected to any configuration of prime power including one or more single phase or three-phase 110/240V sources.

[0055] In another embodiment, the energy stored in the discharge capacitor bank 102 is released at a rapid rate into an inductive coil 201 through an H-bridge IGBT switching circuit 103.

[0056] The resultant current flowing through the coil 201 produces a time-varying magnetic field, which when applied to the head region of a subject, induces an electrical current into the subject's brain, based upon Faraday's principles of electromagnetic induction. The current creates an electrical potential within the brain leading to a stimulation of neurons that can result in neuronal excitability or inhibition depending on the waveform profile of the magnetic field.

[0057] Applying different waveform shapes and intensity of the magnetic field into the brain induces different and unique neuronal responses that can help address different neurological and mental diseases. The present system and method provides the means for generating complex waveforms, in singular and independently controlled multi pulse transmissions, over significantly higher power levels and longer duty cycles to allow new neurological and mental disease states to be addressed, as well as to improve significantly upon conventional methods of TMS applications for currently treated disorders such as MDD.

[0058] Advantageously, the functionality and capability associated with the present system and method may significantly alter the manner in which rTMS is applied. For example, in the clinical environment, it may dramatically shorten the length time of treatment, increase efficacy and enhance patient comfort. In neurological studies, it may provide the means to excite the brain in a new manner, opening possibilities to new areas of research.

[0059] Making reference to FIG 3, an illustrative embodiment includes a micro-controller 104 that generates up to four (4) rectangular pulse waveforms, 110c, 110a, 110b, and 110d, applied to the IGBT switch fabric through optical interfaces 114a, 114b, 114c, 114d and intelligent IGBT drivers 113a, 113b, 113c and 113d respectively, to produce the desired current waveforms at the coil 201 . The optical drivers help to significantly minimize the effects of EMI emanating from the coil and transmission circuits within the device to the low voltage components residing in the microcontroller 104. The intelligent IGBT drivers comprise circuitry to sense proper operation of the IGBT switches and provide immediate feedback to the microcontroller in the event a short circuit condition arises, in which case the system is halted.

[0060] In another aspect, the present system and method provides the capability of generating waveforms to the coil 201 with pulse repetition frequencies (PRF) from 1 to 100 Hz, at pulse widths ranging from 60 to 200 microseconds for both monophasic and biphasic transmissions in either normal or reverse current direction. As previously noted, wider pulse widths can be obtained by adding additional capacitors in the capacitor bank 102.

MONO PHASIC - Normal Biphasic Norma! Mono Phasic Reverse Bi-Phase Reverse Delay Width Delay Width Delay Width Delay Width

Triangular 100 us Triangular 200 us

5 50 5 50

55 50

55 50

50 5 50

115 0 215

Rectangular 100 us Rectangular 200 us

5 85 5 85

60 85

60 15

5 15 5 15

0 115 0 215

Sinusoidal 200 us Sinusoidal 400 us

5 100 5 100

205 100

205 100

100 5 100

215 0 415

Trapezoid Fast 100 us Trapezoid Fast 200 us

5 60 5 60

105 60

105 40

40 5 40

115 0 215

Trapezoid Med 100 us Trapezoid Med 200 us

5 70 5 70

105 70

105 30

30 5 30

115 0 215

Trapezoid Slow 100 us Trapezoid Slow 200 us

5 80 5 80

105 80

105 20

20 5 20

115 0 215

Table

[0061] Table A describes illustrative parametric combinations of stimulant waveforms 1 to 4 (110a to 110d), applied to the four IGBTs 103a to 103d and corresponding resultant current waveform generated at the coil 201. It is to be understood the parametric combinations provided in the table are a subset example of what the system is capable of producing, and are not meant to be a complete or exhaustive list of the combinations possible. Thus, the present system and method and all of its embodiments are not limited to the listed example waveforms. [0062] As shown in FIG 3, the microcontroller 104 generates a fifth pulse 110e that is applied to the high voltage supply 101 (e.g. of FIG. 1 , or FIGS. 2A and 2B). The purpose of this signal is to mute or disable the output of the high voltage supply 101 when the capacitors in the high voltage capacitor bank 102 release energy to the IGBT circuitry 103. Note waveform 5 (110e) mutes the HVPS 101 when it is in the high state. A slight time margin is applied between waveforms 5 and waveforms 1 -4, to ensure no coupling of HVPS to the IGBTs occurs during active switching.

[0063] Reference is now made to FIG 4 depicting a graphical illustration of a monophasic triangular wave operating in the normal current direction. The triangular waveform in this example of embodiment comprises a pulse width of 100 microseconds, created by two rectangular pulses, waveform 1 (110a) and waveform 4 (110d), each with a pulse width of 50 microseconds. Note if the pulse width of waveforms 1 and 4 exceed 60 microseconds, then the resultant magnetic field exhibits a sinusoidal shape described below. The amplitude for each pulse is equal and set according to the desired magnetic flux density emanating from the coil 201.

[0064] Both waveforms 1 (110a) and 4 (11 Od) are applied to the coil in parallel with an RC circuit 111 (shown in FIG 3), creating a triangular magnetic field with a 100 microsecond pulse width. The waveform 5 (110e) returns to a low state after 115 microseconds in the high state, enabling the HVPS 101 to resume charging of the capacitor bank 102 until the next PRI.

[0065] In another illustrative example shown in FIG 5, the same 100 microsecond triangular waveform is now produced in the reverse direction by employing waveforms 2 (110b) and 3 (1 0c) each with 50 microsecond pulse widths.

[0066] In another non-limiting example, FIG 6 provides an illustration of a biphasic triangular waveform in the normal current direction. In this case, all four waveforms 1-4 (110a to 11 Od) are generated to drive the IGBT switch fabric 103. As shown, waveforms 1 and 4 (110a and 11 Od, respectively) are rectangular pulses featuring a width of 50 microseconds each and delayed 5 microseconds from the rising edge of waveform 5 (110e). Waveforms 2 and 3 (110b and 110c) are rectangular pulses with a width of 50 microseconds, delayed by 55 microseconds from the rising edge of waveform 5 (110e). The resulting magnetic field is a biphasic triangular waveform with a 100 microsecond positive rectangular pulse, and a 100 microsecond negative rectangular pulse, yielding a total waveform period of 400 microseconds.

[0067] In another non-limiting example, FIG 7 provides an illustration of a 100 microsecond monophasic rectangular shaped waveform generated by waveform 1 (110a) with 85 microsecond pulse width and waveform 4 (11 Od) with 15 microsecond pulse width.

[0068] An illustrative example of the biphasic rectangular waveform with pulse width of 100 microseconds for the positive and negative pulses yielding a period of 200 microseconds is shown in FIG 8. In this example, both waveforms 1 and 2 are 85 microseconds wide; with waveform 2 delayed 55 microseconds from waveform 1. Waveforms 3 and 4 are 15 microseconds wide, with waveform 3 delayed 55 microseconds from waveform 4.

[0069] The reverse direction of the biphasic rectangular waveform is shown in the illustrative example of FIG 9. In this case, waveforms 1 and 2, from FIG 8, are interchanged and waveforms 3 and 4 are interchanged.

[0070] Making reference to FIG 10 a non-limited example of the stimulant waves required to produce a 200 microsecond monophasic sinusoidal wave is presented. In this example, waveforms 1 (110a) and 4 (110d) are employed, each with a pulse width of 100 microseconds. It is worth noting, the waveforms required to generate a sinusoidal wave is similar to the waveforms needed to produce a triangular wave depicted in FIG 4, with the exception of pulse width. For both monophasic and biphasic modes, a sinusoidal shape is achieved once the individual waveforms 1 to 4 (110a to 11 Od) possess a pulse width greater than 60 microseconds.

[0071] An illustrative example of a biphasic sinusoidal wave is presented in FIG 11 . The total period of the wave, which comprises a positive and negative sinusoidal shape, each with a pulse width of 200 microseconds, is 400 microseconds. This is achieved by employing all four waveforms (waves 1-4) each having a pulse width of 100 microseconds. Note waveforms 1 (110a) and 4 (110d) are delayed by 5 microseconds from the rising edge of waveform 5 110e, while waveforms 2 110b and 3 110c are delayed by 205 microseconds.

[0072] In an embodiment, another achievable waveform is a Trapezoidal shaped pulse with slow, medium and fast rise times. An illustrative example of a 100 microsecond monophasic trapezoidal wave with medium rise time is presented in FIG 12. In this example, waveforms 1 and 4 are employed with pulse widths of 70 and 30 microseconds, respectively.

[0073] An example of a biphasic trapezoid wave, with a total period of 200 microseconds and medium rise time, is presented in FIG 13. All four waveforms are employed; waves 1 (110a) and 2 (110b) have a pulse width of 70 microseconds while waves 3 (110c) and 4 (110d) comprise a pulse width of 30 microseconds. Waves 1 (110b) and 4 (110c) are delayed by 5 microseconds from the rising edge of waveform 5 (110e) while waveforms 2 (110b) and 3 (110c) are delayed by 105 microseconds.

[0074] In another aspect of the design, a method is described that allows hybrid waveforms to be generated within each PRI, i.e. a paired combination of sinusoidal, rectangular, triangular or trapezoid waveforms. An example of a 200 microsecond biphasic hybrid waveform, featuring a triangular and trapezoidal wave, is shown in FIG 14. The waveform is made up of the following; waves 1 and 4 have a pulse width of 50 microseconds delayed 5 microseconds from wave 5, wave 2 has a 75 microsecond pulse width and delayed 105 microseconds from wave 5 and wave 3 has a 25 microsecond pulse width delayed 105 microseconds from wave 5.

[0075] In another illustrative example of an output waveform produced by the present system and method, FIG 15 depicts a 150 microsecond biphasic asymmetric triangular waveform. All four stimulant waves are employed with the following attributes: waves 1 and 4 are 50 microseconds in width delayed by 5 microseconds from wave 5; waves 2 and 3 are 25 microseconds in width delayed by 80 microseconds from wave 5. [0076] In another illustrative example of an output waveform produced by the present system and method, FIG 16 depicts a paired pulse stream comprising a monophasic trapezoid pulse followed 2 msec later by a biphasic triangular wave. The time delay of the second pulse can range from 1 microsecond to 10 seconds, depending on the PRI of the pulse train. Variable pulse widths can be employed for each wave. In this example the pulse width of the trapezoid is 100 microseconds while the pulse width of the biphasic triangular wave is 50 microseconds. The amplitude of each pulse can be set independently. In this example diagram, the trapezoid pulse is set to 100% of the MEP while the triangular wave is set to 75% of the MEP.

[0077] In another embodiment of the present system and method, in addition to pairing, three (tri) and four (quad) pulses can be generated and manipulated in the same manner as the example paired pulse. FIG 17 shows an illustrative example of an output waveform comprising four distinct pulse shapes comprising a biphasic hybrid pulse, a monophasic sinusoidal wave, a monophasic trapezoidal wave and biphasic trapezoidal wave within a single PRI in accordance with an embodiment.

[0078] In another embodiment, the system employs a feedback mechanism, shown in the illustrative example of FIG 18, comprising a high-powered magnetic field inducer 115 to measure the precise profile of the output wave 112 being applied to the coil 205. The measured signal is fed back to the microcontroller 104, which performs a comparison of the measured signal to the intended or desired waveform and adjusts waves 1 to 4 in the event there are slight variances. Slight variances can arise from the effects of high temperature or natural aging on the electrical components of the system. If the signal deviation is significant, i.e. the output waveform profile falls outside of specified tolerance levels, then the microcontroller 104 immediately shuts down the system.

[0079] Making reference to FIG 19a, another illustrative embodiment describes the use of rectangular braided wiring 201 to convert the high current originating from the IGBT circuit 103 into a high-powered magnetic field. [0080] In an embodiment, the braided wire is inserted into a pair of spiral walls 200 made of carbon material, shown in FIG 19b, for a "figure 8" configuration. Other aspects include coil configurations of single dimension (e.g. 0-shape) and multi-dimension (e.g. coil arrays).

[0081] In another embodiment, the system is designed to generate a magnetic flux density of 3 Tesla using a "figure 8" coil arrangement 200. This flux density is based on a peak current of 9,000 amps and voltage of 2200 V DC for PRFs up to 100 Hz PRF. This is accomplished, in one non-limiting example, by using one 6000 J/s HVPS module 101 , six 60 microfarad capacitors connected in parallel within the high voltage capacitor bank 102. For optimal transfer of magnetic flux density, the Figure 8 coil comprises braided conductors 201 with wire thickness of mm, wire height of 19 mm, inner radius of 12.7 mm, outer radius of 42.3mm, wire turn spacing of 1.6 mm and coil windings of 12 turns in each spiral.

[0082] In another embodiment for an O-shape spiral coil, the system is designed to generate a magnetic flux density of 4.2 Tesla, based on a peak current of 8,000 amps and voltage of 2200 V DC. This is accomplished, in one non limiting example, by using two 6000 J/s HVPS modules 101 , six 60 microfarad capacitors connected in parallel within the high voltage capacitor bank 102, and a braided coil 201 comprising a wire thickness of 1 mm, wire height of 19 mm, inner radius of 10 mm, outer radius of 40 mm, wire spacing of 1 mm and coil windings of 20 turns.

[0083] Another illustrative embodiment describes a coil enclosure design to address the high temperature arising from the coil conductors, as shown in the illustrative example of FIG 20.

[0084] In an embodiment, coolant liquid 211 , comprised of pure distilled water, enters into the coil assembly enclosure 205 through pipe fitting/connector 209.

[0085] The coolant originates from an external chiller unit 106 that, in one example implementation, features a capacity of approximately 29800 BTU/h or 8700 Watts to maintain a liquid temperature of 25°C throughout the coil enclosure 205. [0086] Still referring to FIG 20, in another embodiment of the present system and method, the inner wall 206 of the coil enclosure 205 may be sloped inwards towards the bottom of the enclosure, creating a reduction in volume, which in turn creates a slight centrifugal flow effect 213 to increase water flow and expedite heat transfer.

[0087] Also shown in FIG. 20, is block 204 located between the spiral walls designed to prevent water from flowing or shunting at the top of the enclosure directly from fitting 209 to fitting 208. Instead, the fluid is forced down the first spiral, across the channels 202, up into the second spiral and finally out of the tube fitting 210, to ensure most or all of the dissipated heat is exposed to the coolant.

[0088] In an embodiment, the braided wire enters into the coil assembly through connector 207, attached to sub-enclosure 214, and exits the assembly through connector 208. The sub-enclosure 214 is filled with epoxy like material to contain the liquid within the assembly.

[0089] In another embodiment, making reference to in FIG 21 , the bottom of the spiral walls 200 feature a corrugated design 202 that form channels or canals to allow the fluid to propagate efficiently throughout the enclosure, helping to transfer heat accordingly.

[0090] Also, in another embodiment of the present system and method, the spiral walls, depicted in the illustrative example of figure FIG 21 , consist of densely placed perforations 203 to increase surface exposure of the conductor to the liquid coolant, for increased heat transfer, while ensuring the individual wire strands do not short across the walls.

[0091] In another illustrative embodiment, shown in FIG 22, a pair of coolant plates 305a and 305b are mounted beneath the four IGBTs 103a-103d to help transfer the high temperature heat away from the switching circuit. Temperature probes 306a and 306b are attached to the coolant plates providing feedback to the microcontroller 104 to regulate water flow and temperature settings of the coolant system accordingly.

[0092] The pressurized coolant liquid traverses from the cooling device 300, shown in an illustrative example of FIG 23, to the coolant plates 305a and 305b and then in series to the coil assembly 205. In another illustrative embodiment, the coolant plates and coil assembly modules can be placed in parallel.

[0093] In another illustrative embodiment, a pair of copper plates are employed to interconnect the charging capacitor bank 102, IGBTs 103a-103d and coil 201 as shown in the illustrative example of FIG 24. The transmission plates are rectangular in shape with minimum dimensions of 15x5 mm, to provide a sufficiently large surface area to minimize resistance, which in turn reduces heat dissipation. As shown in FIG. 24, piping 400, 401 may be used to direct cooling fluid over the IGBTs 103 in order to cool the IGBTs 103. Other forms of cooling, including air cooling with fans (not shown), may also be used. In another illustrative embodiment, aluminum plates can be employed.

[0094] In an embodiment, the transmission plates are separated by 10 mm to avoid voltage arcing. Also, in another embodiment, the current flowing through each plate traverses in opposite direction, helping to minimize EMI and spurious spikes through electromagnetic interference cancelation.

[0095] Now referencing FIG 25, the present system and method may be practiced in various computer-implemented embodiments. A suitably configured generic computer device, and associated communications networks, devices, software and firmware may provide a platform for enabling one or more embodiments as described above. By way of example, FIG. 25 shows a generic computer device 1000 that may be operatively connected to microcontroller 104, as discussed above with respect to FIG. 1.

[0096] Generic computer device 1000 may include a central processing unit ("CPU") 1002 connected to a storage unit 1004 and to a random access memory 1006. The CPU 1002 may process an operating system 1001 , application program 1003, and data 1023. The operating system 1001 , application program 1003, and data 1023 may be stored in storage unit 1004 and loaded into memory 1006, as may be required. Computer device 1000 may further include a graphics processing unit (GPU) 1022 which is operatively connected to CPU 1002 and to memory 1006 to offload intensive image processing calculations from CPU 1002 and run these calculations in parallel with CPU 1002. An operator 1007 may interact with the computer device 1000 using a video display 1008 connected by a video interface 1005, and various input/output devices such as a keyboard 1010, mouse 1012, and disk drive or solid state drive 1014 connected by an I/O interface 1009. In known manner, the mouse 1012 may be configured to control movement of a cursor in the video display 1008, and to operate various graphical user interface (GUI) controls appearing in the video display 1008 with a mouse button. The disk drive or solid state drive 1014 may be configured to accept computer readable media 1016. The computer device 1000 may form part of a network via a network interface 1011 , allowing the computer device 1000 to communicate through wired or wireless communications with other suitably configured data processing systems (not shown).

[0097] It will be appreciated that various amendments and modifications may be made to the illustrative embodiments described herein without departing from the scope of the invention, and that the examples provided in the present disclosure are not limiting. Rather, the scope of the invention is defined by the following claims which should be given their broadest interpretation consistent with the scope of the present disclosure.