Architectures for Multi-Electrode Implantable Stimulator Devices Having Minimal Numbers of Decoupling Capacitors
Architectures for implantable stimulators having N electrodes are disclosed. The architectures contains X current sources, or DACs. In a single anode/multiple cathode design, one of the electrodes is designated as the anode, and up to X of the electrodes can be designated as cathodes and independently controlled by one of the X DACs, allowing complex patient therapy and current steering between electrodes. The design uses at least X decoupling capacitors: X capacitors in the X cathode paths, or one in the anode path and X−1 in the X cathode paths. In a multiple anode/multiple cathode design having X DACs, a total of X−1 decoupling capacitors are needed. Because the number of DACs X can typically be much less than the total number of electrodes (N), these architectures minimize the number of decoupling capacitors which saves space, and ensures no DC current injection even during current steering.
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The present invention relates generally to multi-electrode implantable stimulator devices.
BACKGROUNDImplantable stimulation devices generate and deliver electrical stimuli to nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators to treat motor and psychological disorders, occipital nerve stimulators to treat migraine headaches, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder sublaxation, etc. Implantable stimulation devices may comprise a microstimulator device of the type disclosed in U.S. Patent Application Publication 2008/0097529, or a spinal cord stimulator of the type disclosed in U.S. Patent Application Publication 2007/0135868, or other forms.
Microstimulator devices typically comprise a small, generally-cylindrical housing which carries electrodes for producing a desired electric stimulation current. Devices of this type are implanted proximate to the target tissue to allow the stimulation current to stimulate the target tissue to provide therapy. A microstimulator's case is usually on the order of a few millimeters in diameter by several millimeters to a few centimeters in length, and usually includes or carries stimulating electrodes intended to contact the patient's tissue. However, a microstimulator may also or instead have electrodes coupled to the body of the device via a lead or leads.
Some microstimulators 2 in the prior art contain only one two electrodes, such as is shown in
A current source or DAC could also be coupled to the anode. However, as shown, the anode is coupled to a compliance voltage, V+, of sufficient strength to provide the current, Iout, programmed into the DAC 20. This compliance voltage can be generated from a battery voltage, Vbat, provided by a battery 12 in the microstimulator 2. A DC-DC converter 22 is used to boost Vbat to the desired compliance voltage V+, and is controlled by a V+ monitor and adjust circuitry 18. Because such circuitry for compliance voltage generation is well known, and not directly germane to the issues presented by this disclosure, further elaboration is not provided.
Also shown in
Although two decoupling capacitors 42 and 44 are shown in
Bi-electrode microstimulators 2 benefit from simplicity. Because of their small size, such microstimulators 2 can be implanted at site requiring patient therapy, and without leads to carry the therapeutic current away from the body as mentioned previously. However, such bi-electrode microstimulators lack therapeutic flexibility: once implanted, the single cathode/anode combination will only recruit nerves in their immediate proximity, which generally cannot be changed unless the position of the device is manipulated in a patient's tissue.
To improve therapeutic flexibility, microstimulators having more than two electrodes have been proposed, and such devices are referred to herein as “multi-electrode” microstimulators to differentiate them from bi-electrode microstimulators discussed above. When increasing the number of electrodes in this fashion, the electrodes can be selectively activated once the device is implanted, providing the opportunity to manipulate therapy without having to manipulate the position of the device.
Exemplary multi-electrode microstimulators 4, 6, and 8 are shown in
In the embodiment of
Also shown in
The embodiment of
The embodiments of
However, the designs of
An embodiment disclosed in the above-referenced '529 Publication capable of current steering is shown in
Unfortunately, microstimulator 8 of
As seen in
Because the SCS 10 has individually-controllable DACs dedicated to each of the electrodes, current can readily be steered between the two electrodes. That is, two or more of the electrodes can act as cathodes (sinks) and/or two or more of the electrodes can act as anodes (sources) at one time. Moreover, because each electrode is hardwired to a decoupling capacitor C1-Cn, there is no risk of direct DC current injection into the tissue R of the patient, even during current steering.
The SCS 10 system therefore has many favorable functional benefits. However, the requirement that each of the N electrodes be hardwired to a dedicated decoupling capacitor means that N decoupling capacitors must be provided. As mentioned before, these capacitors can take up significant space in the case of the implantable stimulator. This may not be as critical of a concern where the implantable stimulator is an SCS 10 for example, because as mentioned, that type of device can generally support a larger case. However, where a small-sized microstimulator is concerned, the requirement of N capacitors for each of the N electrodes is prohibitive.
Accordingly, the inventor believes that the implantable stimulator art, and particularly the multi-electrode microstimulator art, would benefit from an architecture that would minimize device size and ensure patient safety. Specifically desirable would be a design that would minimize the number of decoupling capacitors required, but which would still prevent DC current injection even during current steering. Embodiments of such a solution are provided herein.
Architectures for implantable stimulators having N electrodes are disclosed. The architectures contains X current sources, or DACs. In a single anode/multiple cathode design, one of the electrodes is designated as the anode, and up to X of the electrodes can be designated as cathodes and independently controlled by one of the X DACs, allowing complex patient therapy and current steering between electrodes. The design uses at least X decoupling capacitors: X capacitors in the X cathode paths, or one in the anode path and X−1 in the X cathode paths. In a multiple anode/multiple cathode design having X DACs, a total of X−1 decoupling capacitors are needed. Because the number of DACs X can typically be much less than the total number of electrodes (N), these architectures minimize the number of decoupling capacitors which saves space, and ensures no DC current injection even during current steering.
A first embodiment of an improved multi-electrode stimulator 100 is shown in
Stimulators 100 and 100′ comprises N electrodes, E1-En. In the configurations shown, any one of the electrodes can be programmed as the anode, and one or more of the other electrodes can be programmed as cathodes. As best shown in
Recovery switches 64 and 66a-66x are shown in
In the both of stimulators 100 and 100′, there are X DACs 20a-20x, and X switch matrices 81a-x for coupling those DACs to any of the electrodes E1-En. Each switch matrix 81 comprises N cathode selection switches 621-n to couple a given DAC 20 to any of the N electrodes. For example, if it was desired to couple DAC 20b to electrode E1, thus designating electrode E1 as a cathode, then selection switch 62b1 in switch matrix 81b would be selected.
Because there are X DACs 20a-20x, a maximum of X electrodes can act as cathodes at any given time. (Actually, it is possible that more than X electrodes can act as cathodes so long as some of these cathodes share one of the DACs, but this possibility is not further discussed). Moreover, the current at each of those X cathode electrodes can be individually and simultaneously controlled. It would normally be the case that X (the number of DACs, or the maximum number of cathodes) is smaller than N (the number of electrodes). This is true because it is generally only desired to allow some subset of the electrodes (as opposed to all electrodes) act as cathodes at a given time. For example, in a microstimulator having N=8 electrodes, it might be desirable to at most designate X=3 cathodes at one time. In an even simpler example illustrated in
Unlike the microstimulator 8 of
Specifically, in each of stimulators 100 and 100′, only X decoupling capacitors (i.e., equal to the number of DACs) are required to ensure no DC current injection. In the improved stimulator 100 of
Even when only X total capacitors are used, the improved stimulators 100 and 100′ guarantee no DC current injection in any path, even during current steering. This can be noticed from the different scenarios illustrated in
Starting with stimulator 100 and
Scenarios II and III include the selection of additional cathode electrodes, such that, generically speaking, one anode and Y cathodes are simultaneously designated as a given time. However, because each of the cathode paths includes a capacitor, and hence draws no DC current, then the current in the single anode path (Idca) must again equal 0.
In stimulator 100′ of
This can be noticed from the different scenarios illustrated in
Scenarios III to V illustrates the selection of additional cathode electrodes, such that, generically speaking, one anode and Y cathodes are simultaneously designated as a given time. Scenarios III and IV select two cathode electrodes Ey and Ez as cathodes, which could be a permanent therapy setting for a given patient or could be a temporary setting such as occurs during current steering between electrodes. In Scenario III, DACs 20a and 20b are used, each having a capacitor 44a and 44b. As capacitors are present in the anode path and both cathode paths, it is elementary that no DC current injection is possible. In scenario IV, DAC 20x, which lacks a capacitor, is used, along with DAC 20b, which includes a capacitor 44b. In this case, the DC current in the anode path is Idca=0 by virtue of anode capacitor 42. The DC current in the cathode path established by DAC 20b is Idcc1=0 by virtue of cathode capacitor 44b. Because the sum of the DC currents must equal 0 at the common node established by the patent's tissue R, the DC current in the cathode path established by DAC 20x (Idcc2) is 0, even though that path lacks a decoupling capacitor. Scenario V furthers this example by the addition of yet another cathode path, but still the DC current in the cathode path established by DAC 20x (Idcc3) is 0.
To summarize, in stimulator 100′, the cathode path established by DAC 20x need not contain a decoupling capacitor because all other paths to the patient's tissue R, i.e., the anode path and all other cathode paths, will contains a decoupling capacitor. Therefore, the circuitry is guaranteed to have no DC current injection into the patient's tissue, despite the lack of a decoupling capacitor in DAC 20x's cathode path.
While there is a size benefit to using only X capacitors, it should be noted that X+1 capacitors can also be used in another embodiment, such as stimulator 100″ shown in
To this point in the disclosure, it has been assumed that the improved stimulators 100 or 100′ comprise a single anode/multiple cathode design. However, and as shown in
To this point in the disclosure, embodiments of the invention have been illustrated in either single anode/multiple cathode or multiple anode/single cathode configurations. However, the invention is also extendable to a multiple anode/multiple cathode configuration, such as is shown in stimulator 110 of
Multiple anode/multiple cathode stimulator 110 comprises at least X−1 decoupling capacitors. This means a decoupling capacitor can be missing from any of the X NDACs 20 or PDACs 21 illustrated, but as shown, the capacitor is missing from the anode path coupled to the last PDAC 21j. Thus, in the illustrated example, there are I cathode path capacitors, and J−1 anode path capacitors, for a total of X−1 capacitors.
Even though a capacitor is missing from PDAC 21j's anode path, the design is still guaranteed to allow no DC current injection at any electrode, because once again, the presence of capacitors in all other anode and cathode paths prevents this. The scenario illustrated in
Because only X−1 decoupling capacitors are required in the stimulator 110 of
Like stimulator 110, multiple anode/multiple cathode stimulator 120 comprises at least X−1 decoupling capacitors, as shown in
The disclosed stimulators improves upon the prior art. Because they contains a smaller number of DACs (X) relative to the number of electrodes (N), and accordingly contains a smaller number of decoupling capacitors (either X−1, X, or X+1 depending on the embodiment considered), the stimulator can be incorporated into a relatively small case. This facilitates use as a multi-electrode microstimulator for example, or allows a spinal cord stimulator case to be made that much smaller. Moreover, the disclosed designs guarantee no DC current injection, even during current steering, i.e., during the simultaneous activation of more than one cathode and/or more than one anode.
This disclosure has referred to “anodes” as being sources of current and “cathodes” as sinks of current. However, because this designation is relative, an “anode” can also refer to a sink of current and a “cathode” can also refer to a source of current. Therefore, as used herein, “anode” and “cathode” should simply be understood as having opposite polarities.
While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the literal and equivalent scope of the invention set forth in the claims.
Claims
1. An implantable medical device, comprising:
- a plurality of N electrodes, wherein only one first of the electrodes is designated as either a cathode or an anode having a first current path, and wherein a second plurality of the other of the electrodes are designatable as the other of cathodes or anodes each having a second current path;
- a plurality of X current sources, each current source being coupleable to one of the second electrodes, wherein X is less than N; and
- a plurality of at least X capacitors, wherein the at least X capacitors are placed in the first or second current paths.
2. The device of claim 1, wherein the device comprises X+1 capacitors such that each of the first or second current paths contains a capacitor.
3. The device of claim 1, wherein the device comprises only X capacitors such that only one of the first or second current paths contains no capacitor.
4. The device of claim 3, wherein the X capacitors are placed in the second current paths such that only the first current path contains no capacitor.
5. The device of claim 3, wherein X−1 of the capacitors are placed in the second current paths and one of the capacitors is placed in the first current path such that only one of the second current paths contains no capacitor.
6. The device of claim 1, wherein the first electrode comprises an anode, and wherein the second electrodes are designatable as cathodes.
7. The device of claim 1, wherein the first electrode comprises a cathode, and wherein the second electrodes are designatable as anodes.
8. The device of claim 1, wherein the first electrode can be selected from any of the N electrodes.
9. The device of claim 1, wherein the first electrode comprises a dedicated one of the N electrodes.
10. A method for operating an implantable medical device having a plurality of electrodes, comprising:
- simultaneously designating only one first electrode as either a cathode or anode thereby establishing a first current path, and a plurality of Y second electrodes as the other of the cathodes or anodes thereby establishing Y second current paths; and
- placing only Y capacitors in the first or second current paths, wherein only one of the first or second current paths contains no capacitor.
11. The method of claim 10, wherein the Y capacitors are placed in the second current paths such that the first current path contains no capacitor.
12. The method of claim 10, wherein Y−1 of the capacitors are placed in the second current paths and one of the capacitors is placed in the first current path such that only one of the second current paths contains no capacitor.
13. The method of claim 10, wherein the first electrode is designated as an anode, and wherein the second electrodes are designated as cathodes.
14. The method of claim 10, wherein the first electrode is designated as an cathode, and wherein the second electrodes are designated as anodes.
15. The method of claim 10, wherein the first electrode can be selected from any of the plurality of electrodes.
16. The method of claim 10, wherein the first electrode comprises a dedicated one of the plurality of electrodes.
17. The method of claim 10, wherein the second electrodes are designated by coupling each to a current source.
18. An implantable medical device, comprising:
- a plurality of N electrodes, wherein at least one first electrode is designatable as either a cathode or an anode having a first current path, and wherein at least one second electrodes is designatable as the other of cathodes or anodes having a second current path;
- a plurality of J anode current sources, each anode current source being coupleable to one of the first electrodes; and
- a plurality of I cathode current sources, each cathode current source being coupleable to one of the second electrodes; and
- a plurality of at least J+I−1 capacitors, wherein the at least J+I−1 capacitors are placed in the first and second current paths.
19. The device of claim 18, wherein J is less than N and wherein I is less than N.
20. The device of claim 18, wherein the device comprises J+I capacitors such that each of the first or second current paths contains a capacitor.
21. The device of claim 18, wherein the device comprises only J+I−1 capacitors such that only one of the first or second current paths contains no capacitor.
22. The device of claim 18, wherein the at least one first electrode is designatable as an anode, and wherein the at least one second electrode is designatable as a cathodes.
23. The device of claim 18, wherein the at least one first electrode can be selected from any of the N electrodes.
24. The device of claim 18, wherein each of the J anode current sources are coupleable to any of the first electrodes by a switch matrix, and wherein each of the I cathode current sources are coupleable to any of the second electrodes by a switch matrix.
25. The device of claim 18, wherein the J anode current sources are coupled to a compliance voltage, and wherein the I cathode current sources are coupled to a reference voltage.
26. The device of claim 18, wherein J equals I.
27. An implantable medical device, comprising:
- a plurality of N electrodes, wherein at least one first electrode is designatable as either a cathode or an anode having a first current path, and wherein at least one second electrodes is designatable as the other of cathodes or anodes having a second current path;
- a plurality of X current sources, each current source being programmable as either a anode current source coupleable to one of the first electrodes, or as a cathode current source coupleable to one of the second electrodes;
- a plurality only X−1 capacitors, wherein the X−1 capacitors are placed in the first and second current paths such that only one of the first or second current paths contains no capacitor.
28. The device of claim 27, wherein X is less than N.
29. The device of claim 27, wherein the at least one first electrode is designatable as an anode, and wherein the at least one second electrode is designatable as a cathodes.
30. The device of claim 27, wherein the at least one first electrode can be selected from any of the N electrodes.
31. The device of claim 27, wherein each of the X current sources are coupleable to any of the N electrodes by a switch matrix.
32. A method for operating an implantable medical device having a plurality of electrodes, comprising:
- simultaneously designating at least one P first electrode as either a cathode or anode thereby establishing P first current paths, and a plurality of Q second electrodes as the other of the cathodes or anodes thereby establishing Q second current paths;
- placing only P+Q−1 capacitors in the first or second current paths, wherein only one of the first or second current paths contains no capacitor.
33. The method of claim 32, wherein the P first electrodes and the Q second electrodes can be selected from any of the plurality of electrodes.
34. The method of claim 32, wherein each of the P first electrodes are coupled to a first current source of a first polarity and wherein each of the Q second electrodes are coupled to a second current source of a second polarity opposite the first polarity.
35. The method of claim 32, wherein the first current sources are coupled to a compliance voltage, and wherein the second current sources are coupled to a reference voltage.
Type: Application
Filed: Apr 17, 2009
Publication Date: Oct 21, 2010
Applicant: Boston Scientific Neuromodulation Corporation (Valencia, CA)
Inventors: Jordi Parramon (Valencia, CA), Rafael Carbunaru (Valley Village, CA)
Application Number: 12/425,505