Lead with improved MRI compatibility

Abstract

A system for providing neurostimulation to a patient includes a pulse generator having a housing. The implantable neurostimulation lead is configured to connect with a pulse generator, and the pulse generator is configured to generate a plurality of electrical pulses for delivering neurostimulation therapy through the lead to a patient when the lead is implanted at a target location. The lead includes one or more conductors extending from a proximal end of the lead to one or more neurostimulation electrodes disposed at or near a distal end of the lead. The lead comprises an energy absorber comprising a carbon nanotube material and extending substantially along the length of the one or more conductors.

Description

Summary of the Invention

[0001] This application discloses an improved neural stimulation lead having one or more additional electromagnetic shielding layers within the lead body. The disclosed neural stimulation lead comprises a shielded or integrated carbon nanotube (CNT) material. The CNT material can be a composite material, and may also include any other type of non-metallic conductive material. Any CNT shielding layer may be further coated with a high-dielectric-constant material such as iron or nickel. The use of electromagnetic shielding layers allows for improved MRI compatibility of the neural stimulation lead.

[0002] Typical neurostimulation leads typically have electrodes at the distal end. At the proximal end, the lead has electrical contacts that connect to an implantable pulse generator (IPG) that generates an electrical signal. Conductors within the lead provide a conductive path along which the electrical signal can be delivered to the neural target for therapeutic purposes. When a patient requires an MRI scan, the entire implanted system (including the IPG and neurostimulation lead) is exposed to a strong electromagnetic (EM) field generated by the MRI scanner. The lead conductors, acting like antennas, absorb electromagnetic energy, particularly radio frequency energy at megahertz frequencies (i.e., 64 MHz or 128 MHz). The EM energy absorbed by the lead can create high thermal stress on the tissue in contact with the electrodes and voltage stress on the IPG device, potentially leading to tissue or device damage. In particular, typical neurostimulation leads dissipate heat at the distal end of the electrodes, creating a point heat source that can potentially harm the patient. Therefore, for at least these reasons, patients with implanted systems are generally not permitted to undergo MRI scans. Therefore, it is desirable to have nerve stimulation leads with improved electromagnetic shielding to reduce absorbed EM energy and better dissipate heat.

[0003] This application discloses a neurostimulation system comprising an improved neurostimulation lead having one or more electromagnetic shielding layers within a lead body. The shielding layers protect the conductors from exposure to electromagnetic energy. The neurostimulation system includes an implantable pulse generator (IPG) with a housing and the improved neurostimulation lead comprising a set of one or more lead conductors. The neurostimulation system as a whole is designed to conduct electrical pulses generated by the IPG through the neurostimulation lead to a target location within a patient's body, thereby providing neurostimulation therapy. In one embodiment, the disclosed neurostimulation lead includes at least one shielding layer comprising a carbon nanotube (CNT) material. Throughout this disclosure, references to CNTs encompass both composite CNT materials and homogeneous CNT materials. For example, the CNT material disclosed herein may be a composite material that also includes any other suitable type of conductive material. Alternatively, CNTs used as heat sinks or shielding layers may be made of homogeneous CNT materials. CNT materials may take the form of elongated cords, yarns, fibers, or filament structures. Alternatively, CNT materials may be sheets, coatings, or membrane structures. Furthermore, in some disclosed embodiments, the CNT shielding material of the nerve stimulation lead may be further coated with a high dielectric constant material such as iron or nickel.

[0004] The disclosed neurostimulation leads can have various forms of CNT shielding, including (but not limited to) shielding layers on individual lead conductors, shielding layers wrapped around the entire group of lead conductors, and CNT materials of fibrous material configured to be integrated with and extend along the length of the lead conductors. One or more forms of CNT shielding can be electrically interconnected to uniformly distribute heat and electromagnetic energy along the structure of the neurostimulator lead. One or more forms of CNT shielding can be further electrically connected to the IPG housing, allowing the housing to receive and dissipate heat and electromagnetic energy. Attached Figure Description

[0005] Figure 1 An example of an implantable neurostimulation system designed to provide neurostimulation therapy to a patient is shown.

[0006] Figure 2 An example of the distal end of a typical neurostimulator lead with four electrodes is shown.

[0007] Figures 3A-3C Examples of conductor coils encapsulated in various EM shielding designs are shown. Figure 3A An example of a coil with a braided carbon nanotube shielding is shown. Figure 3B An example of a coil with a helical / wound carbon nanotube shield is shown, and Figure 3C An example of a coil with a foil / spiral ribbon carbon nanotube shield is shown.

[0008] Figure 4 An example of a neural stimulation lead structure comprising one or more conductors and an integrated carbon nanotube shielding wire is shown.

[0009] Figure 5 A cross-section of an example structure of a neural stimulation lead is shown, which includes one or more conductors, each having a carbon nanotube coating.

[0010] Figure 6 An example of a neurostimulation lead structure with integrated carbon nanotube shielding wire, braided shielding layer, and sheath is shown.

[0011] Figure 7 A side view showing an example of the structure of a neural stimulation lead, which has carbon nanotube fibers interwoven in and outside the lead conductor.

[0012] Figures 8A-8B An example of an interwoven pattern is shown, in which carbon nanotube fibers are interwoven in and outside the lead conductor. Detailed Implementation

[0013] Figure 1 An example of an implantable neurostimulation system 100 designed to provide neurostimulation therapy to a patient is shown. The implantable system 100 includes an implantable pulse generator (IPG) 110 coupled to a neurostimulation lead 120, which includes a group of neurostimulation electrodes 142 at a distal end 140 of the lead 120. The IPG 110 may include a head portion and a feedthrough assembly coupled to both a lead connector stack located in the head and internal circuitry located in the main portion of the IPG 110. In some embodiments, Balsala® employs a connector block, and the connector block may be connected to the feedthrough pins. In some embodiments, the electrode pins are part of a plurality of pins, wherein the remainder of the plurality of pins is not configured for connection to the connector stack, but is inactive, connected to ground, or directly connected to other components such as an antenna.

[0014] In one embodiment, the IPG 110 is encapsulated in a housing 111. In one embodiment, the lead 120 is connected to the IPG 110 and the IPG housing 111 by means of a lead connector 121. The lead 120 may include a lead anchoring portion 141 having a series of radially outwardly extending serrations to anchor the lead 120 and maintain the position of the neurostimulation lead 120 after implantation. In one embodiment, the lead 120 includes one or more conductors 130 (see...). Figure 4In some embodiments, the IPG 110 provides monopolar or bipolar electrical pulses delivered to the target nerve via one or more neurostimulation electrodes 142 (typically four electrodes). In sacral nerve stimulation, the lead 120 is typically implanted through the S3 hole.

[0015] Figure 2 An example of the distal end 140 of a typical neurostimulation lead 120 with four electrodes 142 is shown. A typical neurostimulation lead 120 typically has electrodes 142 at the distal end 140. At the proximal end, the lead 120 has a lead connector 121 (see [link to diagram]). Figure 1 The lead wire 120 is connected to the electrical contacts of the IPG 110 that generates the electrical signal. In one embodiment, the lead conductor 130 in the lead wire 120 provides a conductive path to allow the electrical signal to be delivered to a nerve target via the electrode 142 for therapeutic purposes.

[0016] Figures 3A-3C Examples of conductor coils 330 encapsulated in various EM shielding designs are shown. Figure 3A An example of a conductor coil 330 with a braided CNT shield 312 is shown. Figure 3B An example of a conductor coil 330 with a CNT shield 322 of spiral wire / wound is shown, and Figure 3C An example of a conductor coil 330 with a foil / spiral CNT shield 332 is shown. A braided shielded cable 310 includes a conductor coil 330, a braided CNT shield 312, and a sheath 313. A spiral / wound shielded cable 320 includes a conductor coil 330, a spiral / wound CNT shield 322, and a sheath 313. A foil / spiral shielded cable 330 includes a conductor coil 330, a spiral / wound CNT shield 332, a sheath 313, and a drain wire 314.

[0017] These EM shields can be at least partially composed of carbon nanotube (CNT) materials. In one embodiment, CNTs consist of single layers of carbon atoms in a cylindrical configuration. CNT materials can be manufactured by various methods, but most are typically produced using chemical vapor deposition. The end result of this method is a paper-like ultrathin sheet, which can be further processed into various forms, including but not limited to yarns, sheets, and tapes. Alternatively, CNT materials can be prepared using a suspension solution that can be sprayed or printed onto the deposition surface like conventional ink.

[0018] Although CNTs are non-metallic, they can conduct electricity like metals; however, they still retain the flexibility, low weight, ductility, and corrosion resistance of polymers. When used for electromagnetic shielding, CNTs can be made into shields such as braided shields, wound shields, or spiral tape shields. Figures 3A-3CThe structure of CNT shielding can also be configured in ways other than those disclosed in this application.

[0019] Figure 4 An example of the structure of a neurostimulation lead 120 including one or more conductors 130 and an energy absorber 150 is shown. The energy absorber 150 (which may alternatively be referred to as a “heat sink,” “energy shield,” or “EM energy absorption conduit”) may be a shielded wire integrated with one or more conductors 130, and the energy absorber 150 may be constructed of a material including CNTs. The energy absorber 150 may be configured to serve as an energy absorber and / or energy conduit for the entire system. In one embodiment, the energy absorber 150 conducts absorbed EM energy along its length, avoiding the risk of thermal damage from point source dissipation by moving the EM energy to a safe dissipation site. In another embodiment, the energy absorber 150 may transfer the absorbed EM energy to an IPG housing 111 (see [link to IPG housing 111]). Figure 1 The housing 111 further functions as an energy dissipator. Due to the high IPG-tissue interface impedance, the IPG housing 111 dissipates the absorbed EM energy by first converting the absorbed EM energy into heat at the IPG-tissue interface and then dispersing the heat over the large tissue contact area of ​​the IPG housing. In one embodiment, the energy absorber 150 is connected via a lead connector 121 (see...). Figure 1 ) Transfer EM energy to IPG housing 111.

[0020] Figure 5 An example of a structure for a neurostimulation lead 120 having CNTs coated on each lead conductor 130 is shown. The embodiments disclosed herein relate to methods for fabricating and forming the aforementioned CNT electromagnetic shielding structure / layer 133 in the neurostimulation lead 120. CNTs can be prepared in a liquid suspension. Therefore, they can be used like ink or paint for printing or spraying conductive traces. In some embodiments, the polymer insulating layer 132 of each lead conductor 130 may be coated with a liquid formulation comprising suspended CNT particles. In one embodiment, the process produces a conformal, conductive, and thin CNT coating 133 outside the insulating layer 132, thereby providing electromagnetic interference (EMI) shielding for the conductor core 131. Various types and methods can be used to create the conformal CNT coating 133, including (but not limited to) dispersion, immersion, and injection.

[0021] Figure 6An example of the structure of a neurostimulation lead 120 with an integrated CNT energy absorber 150, a CNT shielding layer 122, and a sheath 123 is shown. In one embodiment, the neurostimulation lead 120 has an outer polymer sheath 123 forming an elongated cylindrical lead body 120. In one embodiment, lead conductors 130 are disposed within the lead body 120, and each lead conductor 130 has its own insulating sheath 132 (see [link to original text]). Figure 5 In another embodiment, each lead conductor 130 may also include a CNT coating 133 (see [link to documentation]). Figure 5 To achieve EMI shielding, a CNT electromagnetic shielding layer 122 can be added to the lead body 120, between the lead conductor 130 and the outer polymer sheath 123. At the proximal end, the CNT shielding layer 122 can be electrically connected to the IPG housing 111 via a lead connector 121. In one embodiment, any EM field can be absorbed by the CNT shielding layer 122 and dissipated through the IPG housing 111. In such an embodiment, the lead conductor 130 within the shielding layer 122 is shielded from any external EM interference. The addition of an integrated CNT shielding wire 150 can further provide shielding against external EM interference while also providing another channel for dissipating any absorbed EM energy. For this purpose, an integrated CNT energy absorber 150 can also be electrically connected to the IPG housing 111 and / or the CNT electromagnetic shielding layer 122. This electrical connection can travel through the lead connector 121.

[0022] Figure 7 A side view showing an example of the structure of a neural stimulation lead 120 is shown, which has CNT fibers 160 interwoven within and outside a lead conductor 130. In one embodiment, the lead conductor 130 and one or more CNT fibers 160 may be interwoven together to form a uniform coil, thereby including the core of the neural stimulation lead 120. The lead conductor 130 and the CNT fibers 160 may be coiled in opposite directions around a length sharing a common axis; for example, the lead conductor 130 may be coiled in a left-handed thread pattern, and the CNT fibers 160 may be coiled in a right-handed thread pattern. To support such a coil pattern, the lead conductor 130 and the CNT fibers 160 may engage with each other at regular intervals along the length of the neural stimulation lead 120.

[0023] Figures 8A-8B An example of an interlaced pattern is shown, in which CNT fibers 160 are interlaced in and out of lead conductor 130. Figure 8A An example of a 1×1 plain weave pattern is shown, while Figure 8BAn example of a 4×4 twill interlaced pattern is shown. In one embodiment, the interlaced CNT fibers 160 and lead conductors 130 in these interlaced patterns can be individual strands. In another embodiment, the interlaced CNT fibers 160 and lead conductors 130 in these interlaced patterns can be a group of strands assembled together in a strip (e.g., Figure 4 ).

Claims

1. A system for providing neural stimulation to a patient, the system comprising: Including the pulse generator in the housing, and An implantable neurostimulation lead, wherein the implantable neurostimulation lead is configured to be connected to the pulse generator; The pulse generator is configured to generate multiple electrical pulses for delivering neurostimulation therapy to the patient via the neurostimulation lead when the lead is implanted at the target location. The implantable neurostimulation lead includes one or more conductors, which extend from the proximal end of the implantable neurostimulation lead to one or more neurostimulation electrodes disposed at or near the distal end of the implantable neurostimulation lead. The implantable neurostimulation lead includes an energy absorber comprising a carbon nanotube material and extending substantially along the length of the one or more conductors; and The energy absorber is configured to absorb electromagnetic energy and conduct electromagnetic energy along the length of the implantable neurostimulation lead.

2. The system according to claim 1, wherein, The housing is connected to the energy absorber and serves as a component of the energy absorber.

3. The system according to claim 2, wherein, The housing is configured to dissipate the electromagnetic energy absorbed and conducted by the energy absorber.

4. The system according to claim 1, wherein, The energy absorber covers the one or more electrodes.

5. A system for providing neural stimulation to a patient, the system comprising: Including the pulse generator in the housing, and An implantable neurostimulation lead, wherein the implantable neurostimulation lead is configured to be connected to the pulse generator; The pulse generator is configured to generate multiple electrical pulses for delivering neurostimulation therapy to the patient via the neurostimulation lead when the lead is implanted at the target location. The implantable neurostimulation lead includes a plurality of conductor wires, which extend from the proximal end of the implantable neurostimulation lead to one or more neurostimulation electrodes disposed at or near the distal end of the implantable neurostimulation lead. The implantable neurostimulation lead includes an energy absorber comprising a carbon nanotube material configured to shield the conductor from electromagnetic energy. The energy absorber is configured to absorb electromagnetic energy and conduct electromagnetic energy along the length of the implantable neurostimulation lead.

6. The system according to claim 5, wherein, The housing is connected to the energy absorber and serves as a component of the energy absorber.

7. The system according to claim 6, wherein, The housing is configured to dissipate the electromagnetic energy absorbed and conducted by the energy absorber.

8. The system according to claim 5, wherein, The carbon nanotube material is a homogeneous carbon nanotube material.

9. The system according to claim 5, wherein, The carbon nanotube material is a composite carbon nanotube material.

10. The system according to claim 5, wherein, The plurality of conductor wires are arranged in a coil extending along the length of the nerve stimulation lead.

11. The system according to claim 10, wherein, The energy absorber is configured as a thin wire embedded in the plurality of conductor wires.

12. The system according to claim 5, wherein, The energy absorber covers the coil of the conductor wire.

13. The system according to claim 12, wherein, The energy absorber includes wires embedded in a plurality of electrode wires.

14. A system for providing neural stimulation to a patient, the system comprising: Including the pulse generator in the housing, and An implantable neurostimulation lead, wherein the implantable neurostimulation lead is configured to be connected to the pulse generator; The pulse generator is configured to generate multiple electrical pulses for delivering neurostimulation therapy to the patient via the neurostimulation lead when the lead is implanted at the target location. The implantable neurostimulation lead includes a plurality of conductors forming a conductor coil, the conductor coil extending from the proximal end of the implantable neurostimulation lead to one or more neurostimulation electrodes disposed at or near the distal end of the implantable neurostimulation lead. The implantable neurostimulation lead includes an energy absorber made of carbon nanotube material. The energy absorber is configured to be at least one wire interwoven into the conductor coil; and The energy absorber is configured to absorb electromagnetic energy and conduct electromagnetic energy along the length of the implantable neurostimulation lead.

15. The system according to claim 14, wherein, The energy absorber and conductor coil are interwoven together in a plain weave pattern.

16. The system according to claim 14, wherein, The energy absorber and conductor coil are interwoven together in a diagonal pattern.

17. The system according to claim 14, wherein, The energy absorber includes multiple lines.

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