\IIIII
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`1111111111111111111111111111111111111111111111111111111111111111111111111111
`US 20020143377Al
`
`(19) United States
`(12) Patent Application Publication
`Wessman et al.
`
`(10) Pub. No.: US 2002/0143377 Al
`Oct. 3, 2002
`(43) Pub. Date:
`
`(54) LEAD BODY AND METHOD OF LEAD BODY
`CONSTRUCTION
`
`(75)
`
`Inventors: Bradley J. Wessman, Maple Grove,
`MN (US); Peter J. Pohndorf,
`Stillwater, MN (US)
`
`(22) Filed:
`
`Mar. 30, 2001
`
`Publication Classification
`
`(51)
`Int. Cl? ....................................................... A61N l/05
`(52) U.S. Cl. .............................................................. 607/116
`
`Correspondence Address:
`Kevin W. Cyr
`Rider, Bennett, Egan & Arundel
`333 S. Seventh Street
`Suite 2000
`Minneapolis, MN 55402 (US)
`
`(73)
`
`Assignee: MicroNet Medical, Inc., 1839 Buerkle
`Road, White Bear Lake, MN (US)
`
`(21)
`
`Appl. No.:
`
`09/821,919
`
`(57)
`
`ABSTRACT
`
`A lead body and method for lead body manufacture are
`provided having at least one conductor positioned between
`an inner insulator and an outer insulator wherein the outer
`insulator is fused to the inner insulator by heating. Further,
`an insulating spacer may be provided between the conduc(cid:173)
`tors that may be fused to either or both of the outer insulator
`and the inner insulator.
`
`jl_
`
`)6
`
`1 g
`
`Nevro Corp.
`Ex. 1009
`U.S. Patent No. 7,891,085
`
`

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`Patent Application Publication
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`Patent Application Publication
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`Patent Application Publication
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`Patent Application Publication
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`US 2002/0143377 Al
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`Oct. 3, 2002
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`1
`
`LEAD BODY AND METHOD OF LEAD BODY
`CONSTRUCTION
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1 Field of the Invention
`
`[0002] The present invention relates to medical devices
`and more particularly, to a lead body for a medical lead and
`a method for constructing a lead body.
`
`[0003] 2 Discussion of the Related Art
`
`[0004] A variety of medical electrode catheters are avail(cid:173)
`able today for the diagnosis and treatment of various disor(cid:173)
`ders of the cardiovascular and neurological systems. These
`electrode catheters can be used to sense electrical activity
`within the body and to deliver different forms of energy to
`stimulate, ablate, cauterize or pace. Examples of medical
`catheters using electrodes include permanent and temporary
`cardiac pacing leads, electrophysiologic (EP) catheters,
`electrocautery probes and spinal stimulation catheters. Gen(cid:173)
`erally, for all applications, a reduced diameter lead is desired
`to limit the negative steric effects of lead implantation.
`Therefore, a need exists for a reduced diameter lead to
`reduce the negative effects of lead implantation.
`
`In addition, lead size can prevent access to certain
`[0005]
`tissues and structures. In the case of neurostimulation, spinal
`cord stimulation may have a limited effectiveness for certain
`pain conditions. In many cases where spinal cord stimula(cid:173)
`tion is inadequate, spinal or peripheral nerves must be
`specifically stimulated to provide pain relief. However,
`access to spinal and peripheral nerves is limited because of
`the limited space for lead placement within the intervertebral
`foranin. Therefore, with existing technology, access to cer(cid:173)
`tain nerves is best accomplished using a laminectomy pro(cid:173)
`cedure. In a laminectomy procedure, a portion of a vert(cid:173)
`ibrae's lamina is surgically removed to allow placement of
`an electrode adjacent to the target nerve. The surgery fre(cid:173)
`quently results in significant scarring and patient discomfort.
`Therefore, a need exists for a method to manufacture of a
`reduced diameter body lead to provide improve access for
`nerve stimulation.
`
`[0006] Procedurally, spinal or peripheral nerve stimulation
`is more challenging than spinal chord stimulation. The
`spinal and peripheral nerves branch off of the spinal chord
`through the transverse foramen of the vertebrae. Spinal and
`peripheral nerve stimulation is necessary when a region of
`the body is affected that cannot be effectively stimulated via
`the spinal cord. To stimulate these nerves, a lead is inserted
`through the epidural space along the spinal chord and then
`turned laterally outward to track the branching nerves.
`Tracking these nerves requires a lead having a significantly
`smaller diameter than conventional stimulation leads. Fur(cid:173)
`ther, in deep brain stimulation, a reduced diameter lead may
`provide for less traumatic placement of electrodes as well as
`more precise electrical stimulation by allowing electrode
`placement directly adjacent to remote target locations within
`the brain. Therefore, a need exists for the manufacture of a
`reduced diameter lead to improve access in neurological
`applications.
`
`In cardiac applications, a reduced diameter leads
`[0007]
`may provide access to locations within the heart and veins
`that would not otherwise accessible. In addition, smaller
`leads allow more efficient valve function than their standard
`
`diameter counterparts when the lead passes through the
`valves in the heart. Further, smaller leads allow access to
`smaller veins without compromising blood flow. Thus, a
`need exists for a reduced diameter lead configured for
`cardiac pacing.
`
`[0008] Prior methods for the manufacture of lead bodies
`either wound heated conductors into insulating material and
`then passed the lead bodies through a smoothing dye or
`wound conductors over an inner insulator and then extruded
`an outer insulator over the conductors. These methods do not
`allow for the precise control of variables such as conductor
`positioning and pitch during manufacture because the meth(cid:173)
`ods may permit the conductors to float during manufacture.
`Imprecise positioning can result
`in electrical contact
`between adjacent conductors resulting in the particular lead
`body having to be discarded. Therefore, a need exists for a
`method that allows for more precise control and tighter
`tolerances during manufacture. Further, these methods have
`a tendency to destroy outer coverings that may be present on
`the wires during manufacture. Therefore, a need also exists
`for a method of forming a lead body that does not destroy the
`integrity of coverings, such as for example insulators, during
`manufacture.
`
`[0009] The present invention meets the above needs and
`provides other improvements and advantages that will be
`recognized by those skilled in the art upon review of the
`following description and drawings.
`
`SUMMARY OF THE INVENTION
`
`[0010] A lead body in accordance with the present inven(cid:173)
`tion includes an inner insulator, an outer insulator and at
`least one conductor. The conductor is wound between the
`inner insulator and the outer insulator and the outer insulator
`and the inner insulator are fused together. When the lead
`body includes a plurality of conductors, the inner insulator
`may be fused to the outer insulator to electrically isolate the
`conductors from one another. The lead body may further
`include a lead body a lumen extending through the inner
`insulator along the longitudinal axis of the lead body. One or
`more insulating spacers may also be provided between the
`inner and outer insulator to space and/or electrically insulate
`the conductors. The least one insulating spacers may be
`fused to either or both of the inner insulator and the outer
`insulator.
`
`[0011] A lead body in accordance with the present inven(cid:173)
`tion may be manufactured by positioning at least one
`conductor between an outer and an inner insulator and
`fusing the outer and the inner insulators to one another. In
`one embodiment, the inner insulator is disposed about a
`mandrel intermediate a first end and a second end of the
`mandrel. The first end and the second end of the mandrel are
`typically exposed. A first end of the at least one conductor
`is secured to the first end of the mandrel. The at least one
`conductor is then spirally wound around the inner insulating
`material and the second end of the conductor is secured to
`the second end of the mandrel. One or more insulating
`spacers may be provided and spirally wound between the
`conductors. An outer insulating material is then disposed
`around the wound conductor coextensive with the inner
`insulating material. The inner and outer insulators are then
`fused by heating. The fusing may be facilitated by disposing
`shrink-wrap tubing over the outer insulating material and
`
`

`

`US 2002/0143377 Al
`
`Oct. 3, 2002
`
`2
`
`heating the shrink-wrap, the outer insulating material and
`the inner insulating material. The heating shrinks the shrink(cid:173)
`wrap tubing and forces the outer insulating material to
`contact the inner insulating material. The shrink-wrap may
`be removed after the layers have been fused. The fusing may
`also be facilitated by disposing tubing over the outer insu(cid:173)
`lating material, sealing a first end of the tubing, applying a
`partial vacuum to a second end of the tubing, and heating the
`tubing. The vacuum draws the inner and outer insulators into
`contact with one another and the heating fuses the outer
`insulating material to the inner insulating material. The
`mandrel may be removed from the lead body to form a
`lumen or may remain within the lead body.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0012] FIG. lA illustrates a longitudinal cross-section of
`an embodiment of a lead body in accordance with the
`present invention;
`[0013] FIG. lB illustrates a transverse cross-section of the
`embodiment of a lead body as shown in FIG. lA;
`[0014] FIG. 2 illustrates a transverse cross-section of
`another embodiment of a lead body in accordance with the
`present invention;
`[0015] FIG. 3 illustrates a transverse cross-section of yet
`another embodiment of a lead body in accordance with the
`present invention;
`[0016] FIG. 4A illustrates a perspective view of a mandrel
`covered with the inner insulator;
`[0017] FIG. 4B illustrates a perspective view of a mandrel
`covered with the inner insulator having a conductor wound
`over the inner insulator;
`[0018] FIG. 4C illustrates a partial cross-section of an
`embodiment of the present invention prior to fusing the
`outer insulator to the inner insulator; and
`[0019] FIG. 5 illustrates an embodiment of the present
`invention including an insulating spacer.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`[0020] The present invention provides a novel method for
`the manufacture of lead body and provides a novel lead body
`for use in a variety of medical applications. The invention is
`described as the particular embodiments described below for
`exemplary purposes only, those skilled in the art will under(cid:173)
`stand how to apply the present invention to a variety of lead
`bodies. Therefore, the appended claims are not intended to
`be limited to any specific example or embodiment described
`in this patent. Further, in the drawings described below,
`reference numerals are generally repeated where identical
`elements appear in more than one figure.
`
`[0021] A lead body in accordance with the present inven(cid:173)
`tion is illustrated in FIGS. lA and lB. Lead body 10
`includes a lumen 12, an inner insulator 14, at least one
`conductor 16 and an outer insulator 18. Conductor 16 may
`be in the form of a round wire, a square wire, a cable, or
`other elongated form. Conductors 16 are shown as ribbon
`wire having a rectangular cross-section for exemplary pur(cid:173)
`poses only. Further, conductors 16 may be solid wires, a
`drawn-filled-tube or other configuration of conductor that
`
`will be recognized by those skilled in the art. Conductors 16
`are typically composed of stainless steel, MP35N, platinum,
`gold, silver, copper, vanadium or other metal. Further,
`conductors 16 may include a conductor insulator or other
`covering disposed about the individual conductors. Typi(cid:173)
`cally, the conductor insulator is a polymeric or silicone
`based material. Conductors 16 typically extend from a first
`end to a second end of the lead body. Conductors 16 are
`typically wound about the lumen and are insulated from the
`external environment by outer insulator 18 and from the
`lumen by inner insulator 14. Inner insulator 14 and outer
`insulator 18 are fused together during manufacture. The
`fused inner insulator 14 and outer insulator 18 can electri(cid:173)
`cally isolate individual conductors 16 from one another.
`Inner insulator 16 and outer insulator 18 may be the same or
`different materials. The inner insulator 16 and outer insulator
`18 are typically made from an insulating material such as
`polyurethane or silicone rubber. To facilitate fusing during
`manufacture, the materials of inner insulator 16 and outer
`insulator 18 have a similar melting point. The similarity
`between the melting points of inner insulator 16 and outer
`insulator 18 permits fusing of the insulators after softening
`the materials using heat without a substantial disruption in
`their shape from melting. The materials selected for insula(cid:173)
`tors 16 and 18 may have disparate durometers to alter the
`flex characteristics for particular applications. Further, an
`insulating spacer 21, shown in FIG. 5, may be wound
`between the individual conductors during manufacture to
`further electrically isolate adjacent conductors. Insulating
`spacer 21 typically being formed of a material that will fuse
`to inner insulator 16 and outer layer 18 during manufacture.
`
`[0022] FIG. 2 illustrates a transverse cross-section of
`another embodiment of a lead in accordance with the present
`invention. Lead body 20, as shown in FIG. 2, includes a
`lumen 12, an inner insulator 14, at least one inner conductor
`26, an intermediate insulator 17, at least one outer conductor
`36 and an outer insulator 18. Inner conductors 26 and outer
`conductors 36 typically extend from a proximal end of the
`lead body to a distal end of the lead body and may be wound
`in the same or opposite directions within the lead body. Inner
`conductors 26 are typically wound around inner insulator 14
`and are insulated from the outer conductors 36 by interme(cid:173)
`diate insulator 17. Outer insulator 18 electrically isolates the
`conductors from the exterior environment and inner insula(cid:173)
`tor 16 electrically isolates the conductors from the lumen.
`Inner insulator 16, intermediate insulator 17 and outer
`insulator 18 are fused together and function to electrically
`isolate the conductors from one another. In addition, lead
`body 10 may include an insulating spacer 20, as shown in
`FIG. 5, wound between either or both of inner conductors 26
`and outer conductors 36. An insulating spacer 21 between
`inner conductors 26 can be fused between inner insulator 16
`and intermediate layer 17 to electrically isolate adjacent
`conductors. An insulating spacer 21 between outer conduc(cid:173)
`tors 36 can be fused between intermediate layer 17 and outer
`insulator 18 to electrically isolate adjacent conductors. Addi(cid:173)
`tional insulating layers and additional layers of conductors
`may be provided as required by particular applications to
`alter the flexibility, torquability and/or diameter of lead body
`20. When providing multiple layers of conductors only one
`layer of conductors need be conductive, the additional layers
`may be provided in a manner to confer particular physical
`properties to the lead body, such as torqueability. The
`non-conductive materials which can be used may include
`
`

`

`US 2002/0143377 Al
`
`Oct. 3, 2002
`
`3
`
`nylon, polytetrafluoroethylene (PTFE), and other non-con(cid:173)
`ductive materials that may be formed into filaments and
`wound.
`[0023] FIG. 3 illustrates a transverse cross-section of yet
`another embodiment of a lead in accordance with the present
`invention. Lead body 30, as shown in FIG. 3, includes a
`lumen 12, an inner insulator 14, at least one conductor 16,
`an intermediate insulator 17, and an outer insulator 18.
`Conductors 16 typically extend from a first end of to a
`second end of lead body 30. Conductors 16 are typically
`wound around inner insulator 14 and are insulated by
`intermediate insulator 17. Outer insulator 18 may extend for
`the entire length of lead body 30 or for only a portion of the
`length of lead body 30. Outer insulator 18 may function to
`alter either or both of the flex characteristics of lead body 30
`and the diameter along the length of lead body 30 as may be
`required in certain applications. Inner insulator 16, interme(cid:173)
`diate insulator 17 and outer insulator 18 are fused together
`during manufacture. In addition, lead body 30 may include
`an insulating spacer 21, as shown in FIG. 5, wound between
`inner conductors 26. An insulating spacer 20 between con(cid:173)
`ductors 16 can be fused between inner insulator 16 and
`intermediate layer 17 to electrically isolate adjacent conduc(cid:173)
`tors 16. An insulating spacer 21 between outer conductors 36
`can be fused between intermediate layer 17 and outer
`insulator 18 to electrically isolate adjacent conductors. Addi(cid:173)
`tional insulating layers may be provided as required by
`particular applications to alter the flexibility, torquability
`and/or diameter of lead body 30.
`[0024] A lead body in accordance with the present inven(cid:173)
`tion may be manufactured using a process outlined in FIGS.
`4A to 4C. FIG. 4A illustrates an inner insulator 14 is
`disposed about a mandrel 42. Inner insulator 16 may be
`extruded over the mandrel or may otherwise be deposited
`about the mandrel as will be recognized by those skilled in
`the art. For manufacture of reduced diameter leads mandrel
`42 may, for example, be a wire having a diameter ~f around
`0.013 inch. Typically, the mandrel's diameter is selected as
`appropriate for the end use of the particular lead body.
`Further, mandrel 42 may have a variety of cross-sectional
`shapes as required by particular applications. FIG. 4A
`further illustrates a pair of attachment regions 44 provided
`along mandrel 42. Attachment regions 44 provide locations
`for attachment of conductors 16, shown in FIG. 4B, during
`manufacture. Attachment regions 44 are typically exposed
`portions of mandrel 42 without any inner insulator 14 and
`are typically provided at both a first end 46 and a second end
`48 of mandrel 42. Typically, a length of mandrel 42 and
`inner insulator 14 are cut from a spool of insulator covered
`mandrel after a continuous extrusion process prior to form(cid:173)
`ing attachment region 44, although the insulator covered
`mandrel may be constructed in any of a variety of methods
`that will be recognized by those skilled in the art. The length
`of mandrel42 and inner insulator 14 cut from the spool will
`depend on the particular application for the lead body.
`Alternatively, mandrel 42 and inner insulator 14 may be
`prefabricated in the desired length. Typically, attachment
`region 44 is formed by stripping the insulator 16 from
`mandrel 42 after extrusion, although attachment region 44
`may be formed during the deposition of inner insulator 14 on
`mandrel 42. Attachment region 44 provides a region of
`reduced diameter to which the first and second ends of
`conductors 16 will be attached to prevent unwinding during
`manufacture. FIG. 4C illustrates the attachment of the
`
`conductors. A first end of conductors 16 is secured to an
`attachment region 44 at first end 46 of mandrel 42. Con(cid:173)
`ductors 16 may be secured by winding around attachment
`region 44, by adhesives, by shrink tubing, by welding or by
`other methods that will be recognized by those skilled in the
`art. FIGS. 4B and 4C illustrate conductors 16 secured by
`winding for exemplary purposes. The method of securing is
`typically chosen so that the outside diameter of the secured
`conductor ends does not exceed the outside diameter of
`conductors 16 wound over insulator 14. Maintaining an
`equal or smaller diameter for the secured ends of conductors
`16 permits the passing of a length of outer insulator 18 in the
`form of a tube over attachment region 44 for positioning
`over wound conductors 16 and inner insulator 14 as illus(cid:173)
`trated in FIG. 4C. Again referring to FIG. 4B, once the
`proximal end of the conductor are secured, a desired number
`of conductors 16 are wound over inner insulator 14 at a
`desired pitch and tension. Once the winding has reached
`second end 48 of mandrel 42, a second end of conductors 16
`is secured to a second attachment region 44 at second end 48
`to prevent conductors from unwinding during subsequent
`steps of manufacture. In addition to conductors 16 an
`insulating spacer 21, shown in FIG. 5, may be separately or
`simultaneously wound between conductors. Insulating
`spacer 21 can function to maintain the spacing of the wires
`during manufacture and to further insulate the individual
`conductors in the finished lead body. Outer insulator 18 is
`then applied over conductors 16. Typically, outer insulator
`18 is provided in the form of a tube, although the material
`may be provided as a sheet and wrapped around the con(cid:173)
`ductors. Additional layers of conductors and insulators may
`also be provided as outlined above. Once outer insulator 18
`has been provided over conductors 16, outer insulator 18 is
`fused to inner insulator 14 by heating the lead body or
`alternatively, outer insulator 18 is fused to non-conductive
`spacer 20 and non-conductive spacer 20 is fused to inner
`insulator 14 by heating the lead body. Fusing requires the
`heating of the various insulating layers to a point where
`contact between the layers will adhere the adjacent layers.
`To fuse the materials, a shrink-wrap, a vacuum or other
`method may be utilized. Using the shrink-wrap method, a
`shrink-wrap material is disposed about the outermost layer
`of insulating material. The entire assembly is then heated to
`shrink the shrink-wrap and soften the insulating material
`sufficiently to facilitate fusing of the inner insulating mate(cid:173)
`rial with the outer insulating material or alternatively
`between the insulator layers and the non-conductive spacer.
`After heating, the assembly is typically allowed to cool
`before removal of the shrink-wrap material and removal of
`the mandrel. Using the vacuum method, a tube is disposed
`about the outermost layer of insulating material. With one
`end of the tube sealed and the other end of the tube attached
`to a vacuum pump, a partial vacuum is applied and the entire
`assembly is heated to soften the insulating material to
`facilitate fusing. After heating, the assembly is typically
`allowed to cool before removal of the tubing and removal of
`the mandrel.
`
`1. A lead body, comprising:
`
`an inner insulator;
`
`an outer insulator positioned around the inner insulator,
`wherein the outer insulator and the inner insulator are
`fused together;
`
`

`

`US 2002/0143377 Al
`
`Oct. 3, 2002
`
`4
`
`at least one conductor is wound between the inner insu(cid:173)
`lator and the outer insulator.
`2. A lead body, as in claim 1, further comprising a lumen.
`3. A lead body, as in claim 1, comprising a plurality of
`conductors, wherein the inner insulator is fused to the outer
`insulator to electrically isolate the plurality of conductors.
`4. A lead body, as in claim 1, further comprising at least
`one insulating spacer spirally wound about the insulator
`between the wound conductors.
`5. A lead body, as in claim 4, wherein the at least one
`insulating spacer is fused to at least one of the inner insulator
`and the outer insulator.
`6. A lead body, as in claim 1, wherein the inner insulator
`and the outer insulator are composed of a material selected
`from the group of polyurethane and silicone rubber.
`7. A lead body, comprising:
`
`an inner means for insulating;
`
`an outer means for insulating, wherein the outer means for
`insulating is positioned around the inner means for
`insulating, and the outer means for insulating and the
`inner means for insulating are fused together;
`
`at least one means for conducting is wound between the
`inner means for insulating and the outer means for
`insulating.
`8. A lead body, as in claim 7, further comprising a means
`for inserting a stylet longitudinally through the lead body.
`9. A lead body, as in claim 7, comprising a plurality of
`means for conducting, wherein the inner means for insulat(cid:173)
`ing is fused to the outer means for insulating to electrically
`isolate the plurality of conductors.
`10. A lead body, as in claim 7, further comprising at least
`one means for spacing secured between the means for
`conducting.
`11. A lead body, as in claim 10, wherein the means for
`spacing is fused to the inner means for insulating and the
`outer means for insulating.
`12. A lead body, as in claim 7, wherein the inner means
`for insulating and the outer means for insulating are com(cid:173)
`posed of a material selected from the group of polyurethane
`and silicone rubber.
`13. A method for manufacturing a lead body, comprising:
`
`providing a mandrel having an inner insulating material
`disposed intermediate a first end and a second end of
`the mandrel, wherein the mandrel extends beyond the
`inner insulating material at the first end and the second
`end of the mandrel;
`
`securing a first end of at least one conductor to the first
`end of the mandrel;
`
`positioning the at least one conductor spirally around the
`inner insulating material and securing a second end of
`the at least one conductor to the second end of the
`mandrel;
`
`disposing an outer insulating material around the wound
`conductors coextensive with the inner insulating mate(cid:173)
`rial; and
`
`fusing the inner insulator to the outer insulator.
`14. A method, as in claim 13, wherein fusing the inner
`insulator to the outer insulator further comprises:
`
`disposing shrink-wrap tubing over the outer insulating
`material; and
`
`heating the shrink-wrap, the outer insulating material and
`the inner insulating material to shrink the shrink-wrap
`tubing and fuse the outer insulating material to the
`inner insulating material.
`15. A method, as in claim 13, wherein fusing the inner
`insulator to the outer insulator further comprises:
`
`disposing tubing over the outer insulating material;
`
`sealing a first end of the tubing;
`
`applying a partial vacuum to a second end of the tubing;
`and
`
`heating the tubing, wherein the partial vacuum draws the
`outer insulating material and the inner insulating mate(cid:173)
`rial into contact and the heating fuses the outer insu(cid:173)
`lating material to the inner insulating material.
`16. A method, as in claim 13, further comprising remov(cid:173)
`ing the mandrel from the inner insulator to form a lumen.
`17. A method, as in claim 13, further comprising remov(cid:173)
`ing the shrink-wrap material.
`18. A method, as in claim 13, wherein the winding of the
`conductors, comprises spirally winding the conductors.
`19. A method, as in claim 18, further comprising:
`
`providing at least one insulating spacer; and
`
`spirally winding the insulating spacer between the con(cid:173)
`ductors.
`20. A method, as in claim 13, wherein the inner insulator
`and the outer insulator are selected from the group consist(cid:173)
`ing of polyurethane and silicone rubber.
`
`* * * * *
`
`