(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0199992 A1
`Eisenberg et al.
`(43) Pub. Date:
`Sep. 7, 2006
`
`US 2006O199992A1
`
`MAGNETIC STIMULATOR
`
`Publication Classification
`
`Inventors: Solomon R Eisenberg, Newton, MA
`(US); Daniel Mocanu, Braila (RO)
`
`Correspondence Address:
`WEINGARTEN, SCHURGIN, GAGNEBIN &
`LEBOVC LLP
`TEN POST OFFICE SQUARE
`BOSTON, MA 02109 (US)
`
`Appl. No.:
`
`10/549,965
`
`PCT Filed:
`
`Mar. 16, 2004
`
`PCT No.:
`
`PCT/USO4/08007
`
`Related U.S. Application Data
`Provisional application No. 60/455,309, filed on Mar.
`17, 2003.
`
`(51) Int. Cl.
`(2006.01)
`A61N L/00
`(52) U.S. Cl. ................................................................ 600/14
`
`ABSTRACT
`(57)
`At least two coils deliver at least two time-varying magnetic
`fields to a target region within a body. The coils are oriented
`Such that the magnetic fields create intersecting electric
`fields in the target region. The magnetic fields operate at
`different frequencies and thus produce a beat frequency
`signal where the electric fields intersect. The frequencies are
`chosen so a time-varying electric field, or a current induced
`by a time-varying magnetic field, alternating at the beat
`frequency would stimulate excitable tissue located in the
`target region. Some embodiments utilize a novel coil, which
`includes a first conductor and at least one second conductor
`electrically connected to the first conductor at a point. The
`second conductor extends from the point of connection with
`the first conductor to a location spaced from the first
`conductor. At least a portion of the second conductor adja
`cent the point of connection with the first conductor is
`non-parallel to the first conductor.
`
`(54)
`
`(76)
`
`(21)
`(22)
`(86)
`
`(60)
`
`
`
`118
`
`LUMENIS EX1032
`Page 1
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`

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`Patent Application Publication
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`Sep. 7,2006 Sheet 1 of 11
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`US 2006/0199992 Al
`
` FIG.I
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`LUMENIS EX1032
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`Patent Application Publication Sep. 7, 2006 Sheet 2 of 11
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`US 2006/0199992 A1
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`
`
`SIGNAL
`GENERATOR
`
`SIGNAL
`GENERATOR
`
`308
`
`304
`
`FIG. 3
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`Patent Application Publication Sep. 7, 2006 Sheet 3 of 11
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`US 2006/0199992 A1
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`IV- 04
`
`
`
`308
`
`304
`
`FIG. 4
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`Patent Application Publication Sep. 7, 2006 Sheet 4 of 11
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`US 2006/0199992 A1
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`104
`
`116d
`
`106
`
`600
`
`FIG. 6
`
`700
`
`116e
`
`702
`
`708
`
`FIG. 7
`
`704
`
`706 V
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`Patent Application Publication Sep. 7, 2006 Sheet 5 of 11
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`US 2006/0199992 A1
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`
`
`s
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`LUMENIS EX1032
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`Patent Application Publication Sep. 7, 2006 Sheet 6 of 11
`
`US 2006/0199992 A1
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`SIGNAL
`GENERATOR
`
`
`
`SIGNAL
`GENERATOR
`
`FIG. 9
`
`LUMENIS EX1032
`Page 7
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`Patent Application Publication Sep. 7, 2006 Sheet 7 of 11
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`US 2006/0199992 A1
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`
`
`FIG. I.0
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`LUMENIS EX1032
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`ESV/Hd90/
`
`TV/NSDIS
`
`00||| || || |?0400) || || ||
`
`
`
`
`
`
`
`
`
`
`Patent Application Publication Sep. 7, 2006 Sheet 8 of 11
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`US 2006/0199992 A1
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`HETTIOHINOO
`
`TV/NSDIS
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`TV/NSDIS
`
`HO_L\/HEINE SO
`
`II '9IH
`
`TV/NSDIS
`
`LUMENIS EX1032
`Page 9
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`Patent Application Publication Sep. 7, 2006 Sheet 9 of 11
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`US 2006/0199992 A1
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`1218e
`
`
`
`%-12148
`
`12.12b
`
`FIG. 12
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`Patent Application Publication Sep. 7, 2006 Sheet 10 of 11
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`US 2006/0199992 A1
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`
`
`1208
`
`1210
`
`FIG. I.3
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`Patent Application Publication Sep. 7, 2006 Sheet 11 of 11
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`US 2006/0199992 A1
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`1212h
`
`1202
`
`1212k
`
`1210
`FIG. I.4A
`
`1210
`FIG. I.4B
`
`122m
`
`1204
`
`12O2
`
`1206
`
`1210
`
`FIG. I.4C
`
`
`
`1202
`
`1212p
`
`
`
`1210
`
`1204
`
`1212n
`
`1206b
`
`FIG. I.4D
`
`1204
`
`1202
`
`1212
`
`2O6
`
`1210
`
`FIG. I.4E
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`US 2006/01 99992 A1
`
`Sep. 7, 2006
`
`MAGNETIC STIMULATOR
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`0001) This application claims the benefit of U.S. Provi
`sional Application No. 60/455,309, filed Mar. 17, 2003, the
`contents of which are hereby incorporated by reference
`herein.
`
`STATEMENT REGARDING FEDERALLY
`SPONSORED RESEARCH OR DEVELOPMENT
`0002) (Not applicable)
`
`BACKGROUND OF THE INVENTION
`0003) 1. Field of the Invention
`0004 The present invention relates to electrical stimula
`tion of tissues for therapeutic, diagnostic or experimental
`purposes and, more particularly, to systems that use time
`varying magnetic fields to create electric fields or currents
`that stimulate these tissues.
`0005) 2. Related Art
`0006 Electric and magnetic signals are used to stimulate
`regions of bodies for therapeutic, diagnostic and experimen
`tal purposes. For example, motor-control regions deep
`within the brains of Parkinson’s patients are sometimes
`electrically stimulated to arrest shaking (dyskinesia), and
`Some protocols for treating depression call for electrically
`stimulating a certain part of the brain.
`0007 Stimulating a brain with pulsed sinusoidal electri
`cal signals can temporarily block or inhibit a brain function.
`Cognitive neuroscientists have used such stimulation to
`“knockout' or “temporary lesion’ portions of brains to
`experimentally determine or confirm which parts of the
`brains control various body parts or functions.
`0008 Repeated stimulation of a neuron can produce
`long-term changes in the neuron. Low-frequency electrical
`stimulation can cause long-term depression (LTD) of the
`neuron, which diminishes efficiency of intercellular links.
`On the other hand, high-frequency stimulation can cause
`long-term potentiation (LTP) of the neuron. Thus, it may be
`possible to selectively increase or decrease the excitability
`of neurons in discrete brain regions and thereby “program'
`or “reprogram brain neural circuitry. The possibility of
`using LTD and LTP to reprogram brain neural circuitry. Such
`as to enable the brain to perform a function that was lost due
`to a stroke, is presently motivating research in this area.
`0009 Electrical stimulation of tissue below a subjects
`skin is, however, invasive, in that it requires implanting
`electrodes and sometimes involves risks associated with
`anesthesia. Fortunately, magnetic pulses are known to
`induce electric fields and currents that can stimulate excit
`able tissues, such as nerve cells and muscles. Thus, magnetic
`pulses can be used to non-invasively stimulate these tissues.
`A magnetic stimulation field is typically generated by a
`current-carrying coil. Most successful transcranial magnetic
`stimulation (TMS) applications involve figure-8 coils. Cir
`cular coils have also been used, but the currents they induce
`in tissues are typically more diffuse.
`
`0010 With conventional coil designs, magnetic field
`strength drops off sharply with distance from the coil.
`Increasing the magnetic field strength to overcome this
`drop-off can have undesirable side effects, including stimu
`lating or over-stimulating Surface and near-Surface tissue,
`which can cause skin or muscle twitching or pain. Conse
`quently, magnetic stimulation cannot be effectively used
`deeper than about 2-3 cm within a body. Unfortunately,
`many regions of the brain and other potentially beneficial or
`interesting stimulation regions lie deeper than 2-3 cm and
`are, therefore, unreachable by conventional magnetic stimu
`lation technology.
`0011 Furthermore, conventional magnetic stimulation
`technology cannot stimulate a region below a body's Surface
`without also stimulating tissue that lies between the surface
`and the region that is to be stimulated. This lack of ability to
`target or focus magnetic stimulation can pose problems,
`Such as when it is desirable to stimulate a region deep within
`a brain without also stimulating other portions of the brain.
`Thus, the lack of targeting ability, and the related depth
`limitation discussed above, severely limit the number of
`situations in which magnetic stimulation can be used Suc
`cessfully.
`
`BRIEF SUMMARY OF THE INVENTION
`0012 Embodiments of the present invention enable a
`target region of interest to be magnetically stimulated,
`without necessarily stimulating adjacent regions or regions
`that lie between the surface and the target region. Some
`embodiments of the invention utilize at least two time
`varying magnetic fields that create intersecting electric fields
`in the target region. The region where the electric fields
`intersect is called an “intersection region.” The magnetic
`fields, and therefore the electric fields, operate at different
`frequencies and thus produce a beat frequency electric signal
`in the intersection region. Each of the at least two magnetic
`fields operates at a frequency/amplitude combination that
`does not cause significant tissue stimulation. Thus, it is
`possible to use field strengths high enough to penetrate
`deeper within a body than is practical with conventional
`systems. The frequencies are chosen so the difference
`between the frequencies, i.e., the beat frequency, stimulates
`tissue located in the intersection region. More precisely, a
`time-varying electric field, or a current caused by the time
`varying electric field, alternates at the beat frequency and
`stimulates excitable tissue in the intersection region.
`0013 Some embodiments of the invention utilize a novel
`coil configuration to generate a deep-penetrating magnetic
`field. The coil includes a first conductor and at least one
`second conductor electrically connected to the first conduc
`tor at a point. The at least one second conductor extends
`from the point of connection with the first conductor to a
`location spaced from the first conductor. At least a portion of
`the second conductor adjacent the point of connection with
`the first conductor is non-parallel to the first conductor. The
`coil preferably includes a number of second conductors
`spaced evenly around the first conductor. In one embodi
`ment, the second conductor is a cone-shaped surface.
`
`BRIEF DESCRIPTION OF THE SEVERAL
`VIEWS OF THE DRAWINGS
`0014. These and other features, advantages, aspects and
`embodiments of the present invention will become more
`
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`

`

`US 2006/01 99992 A1
`
`Sep. 7, 2006
`
`apparent to those skilled in the art from the following
`detailed description of an embodiment of the present inven
`tion when taken with reference to the accompanying draw
`ings, in which the first digit of each reference numeral
`identifies the figure in which the corresponding item is first
`introduced, and in which:
`0.015
`FIG. 1 is a perspective view of a two-coil embodi
`ment of the present invention being used in a clinical or
`experimental context;
`0016 FIG. 2 is a simplified schematic wiring diagram of
`the embodiment of FIG. 1;
`0017 FIG. 3 is a diagram illustrating a position of an
`intersection region produced by an embodiment, such as the
`one illustrated in FIG. 1;
`0018 FIG. 4 is a diagram illustrating a shift in position
`of the intersection region of FIG.3 as a result of altering one
`magnetic field strength;
`0.019
`FIG. 5 is a diagram illustrating a position of the
`intersection region of FIGS. 3 and 4 as a result of altering
`the angle of the coils;
`0020 FIG. 6 is a top view of a possible orientation of two
`coils and an intersection region, relative to a Subject, accord
`ing to one embodiment of the present invention;
`0021
`FIG. 7 is a top view of a possible orientation of
`four-coils and an intersection region, relative to a subject,
`according to another embodiment of the present invention;
`0022 FIG. 8 is a simplified schematic wiring diagram of
`the embodiment of FIG. 7:
`0023 FIG. 9 is an alternative simplified schematic wir
`ing diagram of the embodiment of FIG. 7:
`0024 FIG. 10 is a perspective view of a four-coil
`embodiment of the present invention being used in a clinical
`or experimental context;
`0.025
`FIG. 11 is a simplified schematic wiring diagram
`the embodiment of FIG. 10;
`0026 FIG. 12 is a diagram of a coil that can be used with
`the embodiments of FIGS. 1 and 10 or with conventional
`magnetic stimulation equipment;
`0027 FIG. 13 is a diagram of an alternative embodiment
`of the coil of FIG. 12; and
`0028 FIGS. 14A, 14B, 14C, 14D and 14E contain dia
`grams of other alternative embodiments of the coil of FIG.
`12.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`0029 Embodiments of the present invention use at least
`two coils to deliver at least two time-varying magnetic fields
`to a body. Each magnetic field induces an electric field and
`electric currents in electrically conductive tissues, such as
`nerves or muscles, within a portion of the body. Each electric
`field and its currents may extend beyond its respective
`magnetic field, because of the conductive nature of the
`tissues.
`0030 The at least two magnetic fields need not neces
`sarily intersect, however the coils are oriented such that the
`
`electric fields or currents intersect in a target region of the
`body. The coils are preferably driven at frequencies and
`amplitudes that do not directly cause significant tissue
`stimulation, but a beat frequency signal produced in a region
`where the electric fields or currents intersect (the intersec
`tion region) alternates at a frequency (the beat frequency)
`that stimulates excitable tissue in the target region.
`0031. In clinical or experimental contexts, it is often
`desirable to precisely orient the coils relative to a body part
`and hold the body part steady, so the electric fields intersect
`in the target region. Sometimes it is necessary to maintain or
`establish a coil(s)-to-body part orientation for a period of
`time during a treatment or repeatedly over a series of
`treatments. Fixtures, such as the one shown at 100 in FIG.
`1, can be used to establish and maintain such a coil(s)-to
`body part orientation. Although the fixture 100 is shown
`being used to hold a head of a subject 102 steady in
`conjunction with stimulating a region within the Subjects
`head, other similar fixtures (not shown) can be used to hold
`other body parts steady in conjunction with stimulating other
`regions within a subject’s body. Alternatively, head-fitting
`coils (so-called “cap' coils) or coils fitted to other body parts
`can be used. In other embodiments, one or both of the coils
`can be hand-held.
`0032. The coils 104 and 106 produce magnetic fields
`(indicated by arrows 108 and 110), which induce respective
`electric fields 112 and 114. As noted, the electric fields 112
`and 114 can extend beyond the respective magnetic fields
`108 and 110 due to the conductive nature of the tissues. The
`coils 104 and 106 are oriented so the electric fields 112 and
`114 intersect in an intersection region 116. The orientation of
`the coils 104 and 106 and the strengths of the magnetic fields
`108 and 110 are selected to position the intersection region
`116 so it corresponds to the target region of the subject 102.
`as described in more detail below. Embodiments of the
`invention preferably use a novel coil design, which is
`described in detail below. Alternatively, conventional fig
`ure-8, circular, Helmholtz, Hesed, cap or other types of coils,
`coil arrays or coil combinations can be used.
`0033. The intersection region 116 shown in this example
`is located within the brain of the subject 102, but the
`intersection region can be located elsewhere in the Subjects
`head or in another portion of the subject’s body. In the
`example shown in FIG. 1, the magnetic fields 108 and 110
`penetrate at least part way through the Subjects head. In
`Some applications, the magnetic fields penetrate the brain. A
`magnetic field is referred to herein as being adjacent a brain
`whether the magnetic field penetrates the brain or is merely
`near the brain.
`0034). Each coil 104 and 106 is driven by a signal
`generator 118 to produce its respective time-varying mag
`netic field 108 and 110. FIG. 2 is a simplified schematic
`diagram of one embodiment of the present invention. Coil
`104 is connected to a first signal generator 118a, preferably
`by a first flexible cable 204, and coil 106 is connected to a
`second signal generator 118b, preferably by a second flex
`ible cable 206. The signal generators 118a and 118b include
`appropriate power Supplies, amplifiers, signal strength con
`trols, frequency controls, timers, coil cooling systems, etc.
`(not shown), as are well-known in the art. Amplitudes of the
`magnetic fields 108 and 110 vary according to the signals
`that drive the respective coils 104 and 106. Preferably, the
`
`LUMENIS EX1032
`Page 14
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`

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`US 2006/01 99992 A1
`
`Sep. 7, 2006
`
`coils 104 and 106 are driven by sinusoidal signals, but other
`waveforms, such as Square waves, are acceptable. The
`magnetic fields 108 and 110, and therefore the stimulation,
`can be applied in pulses or continuously for a period of time.
`The magnetic fields 108 and 110 are preferably pulsed, such
`as alternatingly on for 10 mSec. and off for 90 mSec., to
`allow the coils to cool after each pulse.
`0035) Returning to FIG. 1, each coil 104 and 106 pro
`duces a time-varying magnetic field 108 and 110 that
`alternates at a different frequency. The frequencies are
`preferably between about 5 KHZ and about 100 KHZ,
`although other frequencies below about 5 KHZ or above
`about 100 KHZ are also acceptable. The frequencies and
`amplitudes are preferably chosen so the magnetic fields 108
`and 110, or electric fields or currents they induce, do not
`significantly directly stimulate tissues within the magnetic
`fields.
`0036) The frequencies are also chosen so a time-varying
`electric field (or electric currents created by the electric field)
`alternating at a frequency equal to the difference between the
`two magnetic field frequencies would stimulate excitable
`tissue located within the intersection region 116. The dif
`ference between the two magnetic field frequencies prefer
`ably is between about 10 Hz and about 50 Hz, although
`differences between about 1 Hz, and about 100 Hz or any
`frequency that would stimulate excitable tissue are accept
`able.
`0037 As noted, each magnetic field 108 and 110 induces
`a time-varying electric field 112 and 114. These electric
`fields 112 and 114 interact in the intersection region 116 to
`produce the beat frequency time-varying electric field 120.
`The time-varying electric field 120 alternates at a frequency
`equal to the difference between the magnetic field frequen
`cies, i.e. the beat frequency.
`0038. The location of the intersection region 116 is
`largely determined by the orientation of the coils 104 and
`106 and the strengths of the magnetic fields 108 and 110. As
`shown in FIG. 3, if the coils 104 and 106 are oriented such
`that their respective axes 300 and 302 form an angle 304, the
`intersection region 116a lies along a line 306 that divides the
`angle. The intersection region 116a is displaced along the
`line 306, away from the vertex 308 of the angle 304, toward
`the coils 104 and 106. This displacement and the exact
`location of the line 306 are influenced by tissues, particularly
`conductive tissues, that lie within the magnetic fields and
`electric fields, as well as the coils designs.
`0039) If the magnetic fields 108 and 110 are of equal
`strengths, the line 306 approximately bisects the angle 304
`formed by the coil axes 300 and 302. However, as shown in
`FIG. 4, if one of the magnetic fields (for example, the field
`produced by coil 104) is weaker than the other magnetic
`field, the line 306a and the intersection region 116b are
`displaced toward the axis of the weaker magnetic field and
`further away from the vertex 308.
`0040. In general, as the angle between the coil axes
`increases, the intersection region moves closer to the vertex
`308. To illustrate this point, FIG. 5 illustrates coils 104 and
`106 oriented in opposition, i.e. their respective magnetic
`fields 108 and 110 are aimed at each other along a common
`axis 500. In other words, the coils 104 and 106 are oriented
`180° apart. If the coils 104 and 106 are oriented in opposi
`
`tion, and the magnetic fields are of equal strengths, the
`intersection region 116c lies approximately half way
`between the coils and along the axis 500.
`0041
`Returning to FIG. 1, the arrows representing the
`magnetic fields 108 and 110 indicate directions of the
`respective magnetic fields. The magnetic fields 108 and 110
`are oriented generally toward the target region. The coils 104
`and 106 are oriented, and the strengths of the magnetic fields
`108 and 110 are adjusted, such that the intersection region
`116 is preferably approximately the same size as the region
`of the body that is to be stimulated. However, the intersec
`tion region can be larger or Smaller than the region to be
`stimulated.
`0042. In general, the strength of the beat frequency
`electric field 120 is approximately twice the strength of an
`electric field that would be produced by the weaker of the
`two magnetic fields 108 or 110 alone. Similarly, electric
`currents created by the beat frequency electric field 120 are
`approximately twice the strength of currents that would be
`produced by the electric field produced by the weaker
`magnetic field alone. Thus, conventional calculations can be
`used to determine the strengths of the magnetic fields 108
`and 110 needed to stimulate a target region, given the depth
`of the target region within a body and the desired strength of
`a stimulating electric field to be applied to the target region.
`0043. As noted, the coils are oriented about the subject
`Such that the electric fields intersect in the target region.
`Preferably, the coils are oriented such that the beat frequency
`electric field 120 does not extend outside the target region or
`the amount of this out-of-target region extension is minimal.
`Thus, tissues outside the target region are not stimulated, or
`out-of-target region stimulation is minimal. FIG. 6 is a top
`view of two coils 104 and 106 oriented about a head 600 of
`a subject. The coils 104 and 106 produce magnetic fields that
`ultimately create a beat frequency electric field or currents in
`an intersection region 116d.
`0044) In some embodiments, more than two coils are
`used to produce the intersecting electric fields. For example,
`FIG. 7 shows four coils 700, 702, 704 and 706 oriented
`about a head 708 of a subject to stimulate a target region
`116e. If more than two coils are used, as in this example,
`each of two signal generators can drive one or more of the
`coils. For example, as shown in FIG. 8, the coils 700 and
`704, which are driven by one signal generator 118a, can be
`connected to each other in parallel, and the coils 702 and
`706, which are driven by the other signal generator 118b, can
`be connected to each other in parallel. Alternatively, as
`shown in FIG. 9, the coils 700 and 704 can be connected to
`each other in series, and the other coils 702 and 706 can be
`connected to each other in series.
`0045. As noted, the coils can be Helmholtz or other types
`of coils. For example, the coils 700 and 704 shown in FIG.
`9 can be part of a Helmholtz coil pair, and the other coils 702
`and 706 can be part of another Helmholtz coil pair.
`0046) The coils 700, 702, 704 and 706 can be oriented
`such that all the electric fields produced by the coils inter
`sect. Alternatively, the coils can be oriented Such that pairs
`of electric fields intersect in intersection regions, and the
`intersection regions fully or only partially overlap each
`other, as described in more detail below, with reference to
`FIG 10.
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`US 2006/01 99992 A1
`
`Sep. 7, 2006
`
`0047 Thus far, embodiments that generate magnetic
`fields operating at two different frequencies have been
`discussed. Alternatively, magnetic fields operating at more
`than two different frequencies can be used. Such an arrange
`ment can, for example, be used when it is difficult or
`inconvenient to generate a sufficiently strong or Sufficiently
`targeted beat frequency signal using only two frequencies.
`For example, as shown in FIGS. 10 and 11, each of four
`coils 700, 702, 704 and 706 can be connected to a respective
`signal generator 118a, 118b, 118c and 118d.
`0.048. Two of the signal generators 118a and 118b and
`two of the coils 700 and 702 can operate at a first pair of
`frequencies (F1 and F2) to produce a first pair of electric
`fields that intersect, as described above, to produce a first
`beat frequency signal 120a. The first beat frequency is the
`difference between the first pair of frequencies, i.e. the
`absolute value of (F1-F2).
`0049. The other two signal generators 118c and 118d and
`the other two coils 704 and 706 can operate at a second pair
`of frequencies (F3 and F4), different than the first pair of
`frequencies (F1 and F2), to produce a second pair of electric
`fields that intersect to produce a second beat frequency
`signal 120b. The second beat frequency is the difference
`between the second pair of frequencies, i.e. the absolute
`value of (F3-F4).
`0050. The coils can be oriented such that the two beat
`frequency electric fields 120a and 120b fully or only par
`tially overlap each other. If the beat frequency electric fields
`120a and 120b only partially overlap, the maximum stimu
`lation is provided in a region 1000 where the two beat
`frequency electric fields overlap, and less or no stimulation
`is provided in the remainder of the two beat frequency
`electric fields.
`0051. The considerations described above, with respect
`to a two-frequency system, apply to a system that uses more
`than two frequencies. Each frequency/amplitude combina
`tion is preferably chosen so it does not significantly stimu
`late tissue within the respective field, and the frequencies are
`chosen so beat frequency signals produced by the electric
`fields (or currents) stimulate excitable tissue in one or more
`beat frequency electric fields.
`0.052 The beat frequencies can be identical or they can be
`different from each other. If the beat frequencies are iden
`tical, it is preferable for the beat frequency signals to be in
`phase with each other, so they do not destructively interfere
`with each other. A phase controller 1100 (FIG. 11) can be
`used to maintain a phase relationship among at least Some of
`the signals generated by the signal generators 118a-d, so the
`resulting beat frequency signals are in phase.
`0053 As discussed above, with conventional coil design,
`magnetic field strength drops off sharply with distance from
`the coil. Embodiments of the present invention preferably
`use a novel coil design that provides deeper magnetic field
`penetration than conventional coil designs. In addition, this
`coil can be advantageously used with conventional magnetic
`stimulation equipment. When the coil is used with conven
`tional magnetic stimulation equipment, it is preferably oper
`ated at a frequency between about 10 and 100 Hz, although
`frequencies between about 1 Hz and 1 KHZ, or any fre
`quency that would stimulate excitable tissue, are acceptable.
`0054 FIG. 12 illustrates one embodiment 1200 of such
`a coil. The coil 1200 includes two leads 1202 and 1204, by
`
`which it can be connected to a signal generator (not shown),
`such as via a flexible cable (not shown). One lead 1202 is
`connected to a first conductor 1206, which provides a signal
`path (indicated by arrow 1208) to a point 1210, preferably
`at the end of the first conductor. The first conductor 1206 is
`preferably Substantially straight, although a slightly curved
`first conductor or minor deviations (such as a series of “s'
`shaped segments) are acceptable.
`0055. At least one second conductor (examples of which
`are shown at 1212a-f) provides a signal path (examples of
`which are indicated by arrows 1214a-f) from the point 1210.
`The second conductor 1212 is oriented generally back along
`the signal path 1208 of the first conductor 1206. The second
`conductor 1212 is connected to the second lead 1204, such
`as by a bus 1216. Thus, the second conductor 1212 is
`connected in series with the first conductor 1206. Together,
`the first and second conductors 1206 and 1212 provide a
`continuous signal path through the coil 1200. The first and
`second conductors 1206 and 1212 can be wires or they can
`be made from a single piece of wire bent proximate the point
`1210.
`0056. The second conductor 1212 extends from the point
`1210 of connection with the first conductor 1206 to a
`location (examples of which are shown at 1218a-f) spaced
`from the first conductor. At least a portion of the second
`conductor 1212 adjacent the point 1210 of connection (such
`as the portion between the point 1210 and the location 1218)
`is non-parallel to the first conductor 1206. From the location
`1218, the second conductor extends to the bus 1216,
`although this extension need not be straight. The second
`conductor 1212 forms an angle (an example of which is
`shown at 1220) with the first conductor 1206. This angle
`1220 is preferably between about 10° and about 20°,
`although other angles as Small as about 10 are acceptable.
`Angles up to 45°, 90° or more are also acceptable.
`0057 The coil 1200 preferably includes six second con
`ductors 1212 spaced evenly around the first conductor 1206,
`although fewer (as few as one) or more second conductors
`1212 are acceptable. When more than one second conductor
`is used, electric current flowing along the first conductor
`1206 is approximately evenly divided among the second
`conductors 1212a-f. Thus, the magnetic field Surrounding
`each second conductor 1212 is weaker than the magnetic
`field surrounding the first conductor 1206.
`0.058
`Alternatively, as shown in FIG. 13, the second
`conductor 1212g can be a Surface or a portion of a Surface
`(such as a cone). Bus 1216g can also be a Surface or portion
`thereof.
`0059) Although FIGS. 12 and 13 show second conduc
`tors 1212 that extend substantially straight from the point
`1210 of connection with the first conductor 1206 to the
`location 1218 spaced from the first conductor, other shapes
`(such as an umbrella shape) are also acceptable. Examples
`of other acceptable shapes of second conductors are shown
`in FIGS. 14A-D at 1212h, 1212k, 1212m, 1212n and 1212p.
`As shown in FIG. 14C, there need not be a definite point at
`which the first conductor 1206 connects to the second
`conductor 1212m.
`0060 Although FIGS. 12 and 13 show a substantially
`straight first conductor 1206, other shapes (such as a helical
`coil, as shown in FIG. 14E) are acceptable. Furthermore, as
`shown in FIG. 14D, the first conductor can include more
`
`LUMENIS EX1032
`Page 16
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`

`

`US 2006/01 99992 A1
`
`Sep. 7, 2006
`
`than one Substantially parallel conductor (examples of which
`are shown at 1206a and 1206b), and the second conductors
`(such as 1212n and 1212p) can be connected in series with
`the first conductors. In addition, features shown in FIGS. 12,
`13 and 14A-E can be combined in an embodiment. For
`example, the six-first-conductor embodiment of FIG. 12 can
`be constructed with a coiled second conductor.
`0061 While the invention has been described with ref
`erence to a preferred embodiment, those skilled in the art
`will understand and appreciate that variations can be made
`while still remaining within the spirit and scope of the
`present invention, as described in the appended claims. For
`example, various types of coils (circular, figure-8, Helm
`holtz, etc.) can be combined in a single embodiment. In
`addition, various types or combinations of coils can be
`combined with two or more signal generators.
`
`What is claimed is:
`1. A magnetic stimulator for magnetically stimulating a
`region of a body, comprising:
`a first coil producing a first time-varying magnetic field
`adjacent a brain of the body at a first frequency; and
`a second coil producing a second time-varying magnetic
`field adjacent the brain at a second frequency that is
`different than the first frequency;
`wherein the first and second coils are oriented such that
`the first and second magnetic fields produce a beat
`frequency time-varying electric field in the region of
`the body, the beat frequency being determined by the
`first and second frequencies.
`2. The magnetic stimulator of claim 1, wherein the first
`frequency is within about 100 Hz of the second frequency.
`3. The magnetic stimulator of claim 1, wherein the first
`frequency is within about 50 Hz of the second frequency.
`4. The magnetic stimulator of claim 1, wherein the first
`and second frequencies are each between about 5 KHZ and
`about 100 KHZ.
`5. The magnetic stimulator of claim 1, wherein the beat
`frequency is between about 1 Hz, and about 100 Hz.
`6. The magnetic stimulator of claim 1, wherein the beat
`frequency is between about 10 Hz