Abstract:
A method of fabricating a stimulation lead by supplying a lead body with a plurality wire conductors extending the length of the lead body and being within insulative material therein; providing a plurality of terminals and electrodes on the ends of the lead body, wherein the plurality of terminals and electrodes are electrically coupled, wherein the providing comprises: (i) positioning a conductive band about the lead body that is adapted to be clasped about the lead body; (ii) positioning a conductor wire between an exterior surface of the first end and an interior surface of the second end of the conductive band; (iii) closing overlapping ends of the conductive band about the conductor wire; and (iv) welding the ends to seal the conductive band about the lead body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/290,656, filed Dec. 29, 2009, which is incorporated herein by reference. 
    
    
     TECHNICAL HELD 
     This application is generally related to a stimulation lead for application of electrical pulses to tissue of a patient and method for fabricating a stimulation lead. 
     BACKGROUND 
     Neurostimulation systems are devices that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is the most common type of neurostimulation. In SCS, electrical pulses are delivered to nerve tissue in the spine typically for the purpose of chronic pain control. Applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions which can effectively mask the transmission of non-acute pain sensations to the brain. 
     Neurostimulation systems generally include a pulse generator and one or more leads. The pulse generator is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses, control circuitry, communication circuitry, a rechargeable battery, etc. The pulse generating circuitry is coupled to one or more stimulation leads through electrical connections provided in a “header” of the pulse generator. 
     Each stimulation lead includes a lead body of insulative material that encloses wire conductors. The distal end of the stimulation lead includes multiple electrodes that are electrically coupled to the wire conductors. The proximal end of the lead body includes multiple terminals, which are also electrically coupled to the wire conductors, that are adapted to receive electrical pulses. The distal end of a respective stimulation lead is implanted at the location adjacent or within the tissue to be electrically stimulated. The proximal end of the stimulation lead is connected to the header to the pulse generator or to an intermediate “extension” lead. 
     The manufacture of stimulation leads is a relatively complex process. Some manufacturing techniques involve wrapping conductor wires with insulative coatings about a mandrel in a helical manner to form a lead body. An example of a system adapted to perform such winding is shown in U.S. Pat. No. 7,287,366, entitled “Method for producing a multielectrode lead,” which is incorporated herein by reference. Upon fabrication of a lead body electrodes and terminals are provided to the lead body. A variety of techniques exist for electrode and terminal fabrication. Some known techniques involve employing a “blind weld” to electrically couple a respective electrode to a wire of the lead body. 
     SUMMARY 
     In one embodiment, a method of fabricating a stimulation lead for applying electrical pulses to tissue of a patient, comprises: supplying a lead body, wherein the lead body comprises a plurality of wire conductors extending from a proximal end of the lead body to a distal end of the lead body, and the plurality of conductor wires are disposed within insulative material of the lead body; and providing a plurality of terminals and electrodes on the proximal end and the distal end of the lead body respectively, wherein the plurality of terminals and electrodes are electrically coupled through the plurality of wire conductors; wherein the providing comprises: (i) positioning a conductive band about the lead body, wherein the conductive band comprises a first end and a second end and the first end and second end are adapted to be clasped together; (ii) positioning a conductor wire between an exterior surface of the first end and an interior surface of second end of the conductive band; (iii) closing the first end and second end of the conductive band about the conductor wire wherein the first end and second end are disposed in an overlapping arrangement; and (iv) welding the first end and second end to seal the conductive band about the lead body. 
     The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a process for fabricating a lead body according to one representative embodiment. 
         FIG. 2  depicts a mandrel for use in fabricating a lead body. 
         FIG. 3  depicts a segment of a lead body fabricated according to one representative embodiment. 
         FIG. 4  depicts a cross-sectional view of a lead body assembly according to one representative embodiment. 
         FIG. 5  depicts a lead body fabricated according to one representative embodiment. 
         FIG. 6  depicts a cross-sectional view of a conductive band in an open configuration according to one representative embodiment. 
         FIG. 7  depicts a cross-sectional view of a conductive band in a dosed configuration according to one representative embodiment. 
         FIG. 8  depicts an isometric view of a conductive band with a conductor placed within the conductive band according to one representative embodiment. 
         FIG. 9  depicts a process for providing an electrode or a terminal on a lead body during fabrication of a stimulation lead according to one representative embodiment. 
         FIG. 10  depicts a stimulation lead according to one representative embodiment. 
         FIG. 11  depicts a stimulation system according to one representative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment, a process for fabricating lead body material for stimulation leads begins with a continuous core material  10  shown in  FIG. 1 . In one embodiment, the core material  10  is a polytetrafluoroethylene (PTFE) coated stainless steel mandrel wire  12  (shown in  FIG. 2 ), although additional insulative layers may also be provided according to other embodiments. Referring again to  FIG. 1 , the core material  10  is then helically wrapped with a set of insulated wires  14  at a wire wrapping system  15 . Systems for helically winding wires for fabrication of a lead body are disclosed in U.S. Provisional Application Ser. No. 61/247,264, entitled “System and method for fabricating a stimulation lead,” and U.S. Pat. No. 7,287,366, entitled “Method for producing a multi-electrode lead,” which are incorporated herein by reference. 
     Each of the wires  14  may include one or more layers of insulation. In one embodiment, each wire  14  comprises an inner thin layer of perfluoroalkoxy (PFA) and outer thicker layer of a thermoplastic silicone polycarbonate urethane (e.g., CARBOSIL™). While eight insulated wires are used in one embodiment, those skilled in the art will recognize that any suitable number of wires may be wrapped onto mandrel  12  according to other embodiments. In other embodiments, additional layers of wires  14  may be wound over the initial layer(s) of wires. 
     In one preferred embodiment, wires  14  are wrapped about core material  10  in an axially repeating pattern of groups  301  of closely spaced wires with each group  301  separated by distance  302  that is larger than the spacing between adjacent wires within each group ( FIG. 3 ). The distance between groups in  FIG. 3  is by way of example and any suitable distance may be employed according to some embodiments. 
     Referring again to  FIG. 1 , core material  10 , now comprising mandrel  12  and helically wrapped insulated wires  14  may now be spooled and later unspooled (not shown) or fed directly to the next step in the process. In the next step, core material  10  may be selectively and repeatedly heated in a reflow oven  18 . The wires  14  are heated to a temperature that causes the insulation of insulated wires  14  to approach or achieve a phase change, thereby becoming soft and adherent and ultimately fusing together, by heating, melting and re-solidifying after removal from reflow oven  18 . 
     At this point, the core material  10 , now comprising mandrel  12  having insulated wires  14  at least partially fused about it, may now be spooled (step  19 ) onto a spool and stored for later work. Alternatively, step  19  is not performed and core material  10  proceeds directly to the remaining steps. Continuous core material  10  is cut (step  24 ) into individual lead bodies  21 . Each individual lead body  21  may have a length of from about 10 cm (4 in) to about 150 cm (60 in). 
     After the lead bodies  21  have been cut to length, mandrel  12  is removed in a mandrel removal step  28 . This task may be facilitated by a coating of mandrel  12  that will ease removal, such as a PTFE coating. The mandrel removal step  28  may be a simple hand operation by a human worker. 
     Next, in an electrode creation step  30 , electrodes are provided on the distal end of the lead body. In step  32 , terminals are provided on the proximal end of the lead body. Electrode and terminal fabrication are further discussed below. 
       FIG. 4  depicts a cross-sectional view of lead body assembly  400  according to one representative embodiment. Lead body assembly  400  comprises stainless steel mandrel  420  which is coated with layer  401  of PTFE. Inner layer  402  of CARBOSIL™ is extruded or otherwise provided over the inner layer of PTFE. The mandrel  420  with layers  401  and  402  is utilized as core material  10  in wire wrapping system  15 . Each wire  410  (only one wire is annotated for the sake of clarity) is preferably stranded wire coated with a thin layer of PFA and a thicker layer of CARBOSIL™. Wire wrapping system  15  wraps a plurality of wires  410  about mandrel  420 , layer  401 , and layer  402  in the manner discussed above. An outer layer  403  of CARBOSIL™ is also provided. Shrink wrap tubing  404  is then provided on the exterior of the assembly. 
     Lead body  400  is cut to length and lead body assembly  400  is subjected to heating above the melting point of the thermoplastic material. The heat and pressure (e.g., from heat shrinkable tubing) causes the thermoplastic insulative material (e.g., the CARBOSIL™ material) to flow. After the thermoplastic material is cooled, the thermoplastic material re-solidifies into a lead body  500  of fused insulative material enclosing the respective conductors  410 . Also, as shown in  FIG. 16 , gap  610  is provided within lead body  500  where no conductors are located within gap  610 . That is, gap  610  is entirely filled with insulative material. 
     In one embodiment, the lead body is fabricated so that the lead body is capable of elastic elongation under relatively low stretching forces. Also, after removal of the stretching force, the lead body is capable of resuming its original length and profile. For example, in one embodiment, relatively low durometer, elastic polymer material is used for the material of the lead body. The combination of the selection of the materials, the helically wrapping of the wires, and the repeating groups of wires with separating gaps enables the stretching according to the relatively low stretching forces. For example, the lead body may stretch 10%, 20%, 25%, 35%, or even up to 50% at forces of about 0.5, 1.0, and/or 2.0 pounds of stretching force. For additional description of a lead body capable of elastic elongation, reference is made to U.S. Patent Publication No. 2007/0282411, entitled “COMPLIANT ELECTRICAL STIMULATION LEADS AND METHODS OF FABRICATION,” which is incorporated herein by reference. Although some specific lead body fabrication techniques are discussed herein, any suitable processes may be employed for lead fabrication. Alternative example lead fabrication processes are discussed in U.S. Pat. Nos. 5,555,618 and 6,216,045, which are incorporated herein by reference. 
     Lead body  500  is then cut into appropriate lengths and electrodes and terminals are provided. 
       FIG. 6  depicts a cross-sectional view of conductive band  600  according to one representative embodiments. Conductive band  600  may be employed to provide the electrodes and/or terminals of a stimulation lead. Conductive band  600  may be fabricated using any suitable conductive material. In one specific embodiment, conductive band  600  is fabricated using a platinum iridium ahoy. Conductive ring is not a single continuously connected ring of material. Instead, band  600  comprises first end  601  and second end  602 . First end  601  and second end  602  are moveable. Conductive band  600  may be placed in an open position as shown in  FIG. 6 . Conductive bands  600  is also adapted to be placed in a dosed position as shown in  FIG. 7  with first end  601  and second end  602  disposed in an overlapping arrangement. 
     Referring to  FIG. 6 , conductive band  600  comprises opposing surface features  603  and  604 . Surface feature  603  is disposed on an “exterior” side of end  601  and surface feature  604  is disposed on an “interior” side of end  602 . Surface features  603  and  604  may be formed using suitable miffing or laser etching techniques. Surface features  603  and  604  are adapted to interconnect or mate with each other. In one embodiment, surface features  603  and  604  comprise a saw-tooth pattern. Also, in one embodiment, band  600  is implemented to possess a spring-characteristic which provides a biasing force to press surface features  603  and  604  against each other when band  600  is placed in the dosed position. 
     Surface features  603  and  604  optionally include sub-features  605  and  606 , respectively. Sub-features  605  and  606  are adapted to clamp about a conductive wire when band  600  is placed in the closed position.  FIG. 7  depicts conductive band  600  in the closed position. As shown in  FIG. 7 , conductive band  600  includes recess  701  (formed by sub-features  605  and  606 ). Recess  701  is adapted to the size of a suitable conductive wire for electrical connection with conductive band  600  when conductive band  600  is integrated with the lead body.  FIG. 8  depicts an isometric view of conductive band  600  in the dosed position with conductive wire  801  crimped within recess  701 . After wire  801  is placed within conductive band  600  is this manner, laser or other suitable welding is preferably applied to permanently seal conductive band  600 . 
       FIG. 9  depicts a process for providing an individual terminal or electrode on a lead body of a stimulation lead under fabrication. The process of  FIG. 9  may be repeated for each of the electrodes and/or terminals to be provided on the end-product stimulation lead. 
     In  901 , insulative material is removed from the lead body to expose a conductor wire of lead body. The insulative material may be removed using any suitable technique. Manual operations may be employed. In another embodiment, a suitable laser may be employed to ablate insulative material from the lead body. 
     In  902 , a length of the exposed wire is freed from the lead body. Alternatively, a jumper wire may be attached to the exposed portion of the conductor wire of the lead body (see e.g., U.S. Pat. No. 6,952,616, entitled “Medical lead and method for electrode attachment,” which is incorporated herein by reference). 
     In  903 , conductive band  600  is provided about the lead body adjacent to the exposed wire of the lead body. 
     In  904 , the exposed wire or the jumper wire is placed within conductive band  600 . Conductive band  600  is then dosed about the wire ( 905 ) and around the lead body. In some embodiments, the wire is positioned within an interior aperture or recess  701  of conductive band  600  when the conductive band is dosed. Conductive band  600  is subjected to laser welding or other suitable welding to permanently seal the conductive band about the lead body ( 906 ). 
     It is believed that the electrode fabrication according to some embodiments may provide one or more advantageous. For example, a “blind” weld is not required for some embodiments. Also, the welding technique of some embodiments is less technique dependent and may result in greater manufacturing yields. Moreover, it is believed that the mechanical characteristics involved with the conductor wire and the conductive band for some embodiments may be more robust than other known attachment techniques. Also, since crimping is not necessarily employed, less scrap material may be used for some embodiments. 
       FIG. 10  depicts percutaneous lead  1000  fabricated according to some embodiments. Lead  1000  comprises a plurality of electrodes and terminals fabricated using conductive bands  600  according to some representative embodiments. Although lead  1000  is shown to be fabricated as a “percutaneous lead,” other lead designs may also be employed such as paddle-style leads where only the terminals are fabricated using conductive bands  600 . Also, not all of the electrodes of a stimulation lead need involve the use of band  600 . For example, a conventional “tip” electrode design could be employed for the most distal electrode of lead  1000  if desired for a particular medical therapy. Further, although some embodiments have discussed fabrication of neurostimulation leads, other medical leads may be fabricated according to other embodiments, such as cardiac leads, mapping leads, ablation leads, etc. 
       FIG. 11  depicts stimulation system  1150  that generates electrical pulses for application to tissue of a patient according to one embodiment. In one embodiment, system  1150  is adapted to generate electrical pulses and deliver the pulses to tissue of the patient. For example, system  1150  may be adapted to stimulation spinal cord tissue, peripheral nerve tissue, deep brain tissue, cortical tissue, cardiac tissue, digestive tissue, pelvic floor tissue, or any other suitable tissue within a patient&#39;s body. 
     System  1150  includes implantable pulse generator  1100  that is adapted to generate electrical pulses for application to tissue of a patient. Implantable pulse generator  1100  typically comprises a metallic housing that encloses pulse generating circuitry  1102 , controller  1101 , charging coil (not shown), battery  1103 , far-field and/or near field communication circuitry (not shown), battery charging circuitry  1104 , etc. of the device. Although an implantable pulse generator is shown for the embodiment of  FIG. 11 , an external pulse generator (e.g., a “trial” stimulator) may alternatively be employed. The controller  1101  typically includes a microcontroller or other suitable processor for controlling the various other components of the device. Software code is typically stored in memory of the pulse generator  1100  for execution by the microcontroller or processor to control the various components of the device. 
     A processor and associated charge control circuitry for an implantable pulse generator is described in U.S. Patent Publication No. 20060259098, entitled “SYSTEMS AND METHODS FOR USE IN PULSE GENERATION,” which is incorporated herein by reference. Circuitry for recharging a rechargeable battery of an implantable pulse generator using inductive coupling and external charging circuits are described in U.S. patent Ser. No. 11/109,114, entitled “IMPLANTABLE DEVICE AND SYSTEM FOR WIRELESS COMMUNICATION,” which is incorporated herein by reference. 
     An example and discussion of “constant current” pulse generating circuitry is provided in U.S. Patent Publication No. 20060170486 entitled “PULSE GENERATOR HAVING AN EFFICIENT FRACTIONAL VOLTAGE CONVERTER AND METHOD OF USE,” which is incorporated herein by reference. One or multiple sets of such circuitry may be provided within pulse generator  1100 . Different pulses on different electrodes may be generated using a single set of pulse generating circuitry using consecutively generated pulses according to a “multi-stimset program” as is known in the art. Alternatively, multiple sets of such circuitry may be employed to provide pulse patterns that include simultaneously generated and delivered stimulation pulses through various electrodes of one or more stimulation leads as is also known in the art. Various sets of parameters may define the pulse characteristics and pulse timing for the pulses applied to various electrodes as is known in the art. Although constant current pulse generating circuitry is contemplated for some embodiments, any other suitable type of pulse generating circuitry may be employed such as constant voltage pulse generating circuitry. 
     Stimulation system  1150  further comprises one or more stimulation leads  1120 . Stimulation lead  1120  comprises a lead body of insulative material about a plurality of conductors that extend from a proximal end of lead  1120  to its distal end. The conductors electrically couple a plurality of electrodes  600  to a plurality of terminals (not shown) of lead  1120 . The terminals are adapted to receive electrical pulses and the electrodes  600  are adapted to apply stimulation pulses to tissue of the patient. Also, sensing of physiological signals may occur through electrodes  600 , the conductors, and the terminals. Additionally or alternatively, various sensors (not shown) may be located near the distal end of stimulation lead  1120  and electrically coupled to terminals through conductors within the lead body  1111 . 
     Stimulation system  1150  optionally comprises extension lead  1110 . Extension lead  1110  is adapted to connect between pulse generator  1100  and stimulation lead  1120 . That is, electrical pulses are generated by pulse generator  1100  and provided to extension lead  1110  via a plurality of terminals (not shown) on the proximal end of extension lead  1110 . The electrical pulses are conducted through conductors within lead body  1111  to housing  1112 . Housing  1112  includes a plurality of electrical connectors (e.g., “Bal-Seal” connectors) that are adapted to connect to the terminals of lead  1120 . Thereby, the pulses originating from pulse generator  1100  and conducted through the conductors of lead body  1111  are provided to stimulation lead  1120 . The pulses are then conducted through the conductors of lead  1120  and applied to tissue of a patient via electrodes  600 . 
     In practice, stimulation lead  1120  is implanted within a suitable location within a patient adjacent to tissue of a patient to treat the patient&#39;s particular disorder(s). The lead body extends away from the implant site and is, eventually, tunneled underneath the skin to a secondary location. Housing  1112  of extension lead  1110  is coupled to the terminals of lead  1120  at the secondary location and is implanted at that secondary location. Lead body  1111  of extension lead  1110  is tunneled to a third location for connection with pulse generator  1100  (which is implanted at the third location). 
     Controller device  1160  may be implemented to recharge battery  1103  of pulse generator  1100  (although a separate recharging device could alternatively be employed). A “wand”  1165  may be electrically connected to controller device through suitable electrical connectors (not shown). The electrical connectors are electrically connected to coil  1166  (the “primary” coil) at the distal end of wand  1165  through respective wires (not shown). Typically, coil  1166  is connected to the wires through capacitors (not shown). Also, in some embodiments, wand  1165  may comprise one or more temperature sensors for use during charging operations. 
     The patient then places the primary coil  1166  against the patient&#39;s body immediately above the secondary coil (not shown), i.e., the coil of the implantable medical device. Preferably, the primary coil  1166  and the secondary coil are aligned in a coaxial manner by the patient for efficiency of the coupling between the primary and secondary cons. Controller  1160  generates an AC-signal to drive current through coil  1166  of wand  1165 . Assuming that primary coil  1166  and secondary coil are suitably positioned relative to each other, the secondary coil is disposed within the field generated by the current driven through primary coil  1166 . Current is then induced in secondary coil. The current induced in the coil of the implantable pulse generator is rectified and regulated to recharge battery  1103  by charging circuitry  1104 . Charging circuitry  1104  may also communicate status messages to controller  1160  during charging operations using pulse-loading or any other suitable technique. For example, controller  1160  may communicate the coupling status, charging status, charge completion status, etc. 
     External controller device  1160  is also a device that permits the operations of pulse generator  1100  to be controlled by user after pulse generator  1100  is implanted within a patient, although in alternative embodiments separate devices are employed for charging and programming. Also, multiple controller devices may be provided for different types of users (e.g., the patient or a clinician). Controller device  1160  can be implemented by utilizing a suitable handheld processor-based system that possesses wireless communication capabilities. Software is typically stored in memory of controller device  1160  to control the various operations of controller device  1160 . Also, the wireless communication functionality of controller device  1160  can be integrated within the handheld device package or provided as a separate attachable device. The interface functionality of controller device  1160  is implemented using suitable software code for interacting with the user and using the wireless communication capabilities to conduct communications with IPG  1100 . 
     Controller device  1160  preferably provides one or more user interfaces to allow the user to operate pulse generator  1100  according to one or more stimulation programs to treat the patient&#39;s disorder(s). Each stimulation program may include one or more sets of stimulation parameters including pulse amplitude, pulse width, pulse frequency or inter-pulse period, pulse repetition parameter (e.g., number of times for a given pulse to be repeated for respective stimset during execution of program), etc. IPG  1100  modifies its internal parameters in response to the control signals from controller device  1160  to vary the stimulation characteristics of stimulation pulses transmitted through stimulation lead  1120  to the tissue of the patient. Neurostimulation systems, stimsets, and multi-stimset programs are discussed in PCT Publication No. WO 01/93953, entitled “NEUROMODULATION THERAPY SYSTEM,” and U.S. Pat. No. 7,228,179, entitled “METHOD AND APPARATUS FOR PROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” which are incorporated herein by reference. 
     Although certain representative embodiments and advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate when reading the present application, other processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the described embodiments may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.