Spinal cord stimulation using monophasic pulses of alternating polarity and passive charge recovery

Abstract

A new waveform for use in an implantable pulse generator or an external test stimulator is disclosed, which waveform simulates an actively driven biphasic pulse and is particularly used to emit low-frequency pulses. The waveform includes a staggered first pulse and a second pulse at each electrode. Each first pulse includes a first monophasic pulse and a first passive charge recovery period. Each second pulse includes a second monophasic pulse with a polarity opposite to the first monophasic pulse and a second passive charge recovery period. Preferably, the amplitude and pulse width of the first monophasic pulse and the second monophasic pulse are equal, or at least charge balanced at each electrode. The first monophasic pulse and the second monophasic pulse imitate the function of a symmetrical biphasic pulse, wherein the first monophasic pulse imitates the function of the first phase of the biphasic pulse, and wherein the second monophasic pulse imitates the function of the second phase of the biphasic pulse.

Description

Technical Field

[0001] The present application relates to implantable medical devices (IMDs), typically spinal cord stimulators, and more particularly to methods of controlling such devices. Background Art

[0002] Implantable neurostimulator devices are devices that generate and deliver electrical stimulation to body nerves and tissues for the treatment of various biological diseases, such as pacemakers for treating cardiac arrhythmias, defibrillators for treating cardiac fibrillation, cochlear stimulators for treating deafness, retinal stimulators for treating blindness, muscle stimulators for producing coordinated limb movements, spinal cord stimulators for treating chronic pain, cortical and deep brain stimulators for treating movement and psychological disorders, and other neurostimulators for treating urinary incontinence, sleep apnea, shoulder subluxation, etc. The following description will generally focus on the use of the present invention in a spinal cord stimulation (SCS) system (such as the system disclosed in U.S. Patent 6,516,227). However, the present invention can be applied to any implantable neurostimulator device system.

[0003] The SCS system generally includes an implantable pulse generator (IPG) 10 shown in FIG. 1 . The IPG 10 includes a generally conductive biocompatible device housing 12 that houses the circuitry of the IPG and a battery 14 for providing power for the operation of the IPG. The IPG 10 is coupled to tissue stimulation electrodes 16 via one or more electrode leads that form an electrode array 17. For example, one or more percutaneous leads 15 having annular or open ring electrodes 16 carried on a flexible body 18 may be used. In another example, a paddle-shaped lead 19 provides an electrode 16 positioned on one of its generally flat surfaces. A guide wire 20 within the lead is coupled to the electrode 16 and to a proximal contact 21 that can be inserted into a lead connector 22 that is secured in a header 23 on the IPG 10 that may include, for example, epoxy. Once inserted, the proximal contacts 21 connect to header contacts 24 within the lead connector 22 , which in turn couple to stimulation circuitry 28 within the housing 12 through feedthrough pins 25 through housing feedthroughs 26 .

[0004] In the IPG 10 shown, there are 32 electrodes (E1 to E32) divided between four percutaneous leads 15, or contained on a single paddle lead 19, and thus the head 23 can include a 2×2 array of 8-electrode lead connectors 22. However, the type and number of leads in the IPG and the number of electrodes are application specific and can therefore vary. The conductive housing 12 can also include electrodes (Ec). In SCS applications, one or more electrode leads are typically implanted in the spine near the dura mater, in the patient's spinal cord, preferably across the patient's spine. The proximal contacts 21 penetrate through the patient's tissue to a distal location, such as the buttocks where the IPG housing 12 is implanted, at which point they are coupled to the lead connector 22. In other IPG examples designed for direct implantation at a site where stimulation is desired, the IPG can be leadless, with the electrodes 16 instead appearing on the body of the IPG 10 for contacting the patient's tissue. In other solutions, one or more IPG leads can be integrated with the IPG 10 and permanently connected to the IPG 10. The goal of SCS therapy is to provide electrical stimulation from electrodes 16 to relieve the patient's symptoms, such as chronic back pain.

[0005] The IPG 10 may include an antenna 27a that allows it to communicate bidirectionally with multiple external devices used to program or monitor the IPG (such as a handheld patient controller or a clinician's programmer described later with reference to FIG. 5). The antenna 27a shown includes a conductive coil within the housing 12, although the coil antenna 27a may also be present in the head 23. When the antenna 27a is configured as a coil, communication with the external device preferably occurs using near-field magnetic induction. The IPG 10 may also include a radio-frequency (RF) antenna 27b. In FIG. 1, the RF antenna 27b is shown within the head 23, but it may also be within the housing 12. The RF antenna 27b may include a patch, a slot, or a wire, and may be operated as a monopole or a dipole. The RF antenna 27b preferably communicates using far-field electromagnetic waves, and may operate according to any number of known RF communication standards, such as Bluetooth, Zigbee, MICS, etc.

[0006] Stimulation in the IPG 10 is typically provided by pulses, as shown in Figures 2A and 2B. The stimulation parameters typically include the amplitude of the pulse (A; whether current or voltage); the frequency of the pulse (F); the pulse width (PW) of the pulse (or its various phases as described below); the electrode 16 (E) activated to provide such stimulation; and the polarity (P) of such activated electrode, i.e., whether the activated electrode acts as an anode that provides (source) current to the tissue or a cathode that absorbs (sink) current from the tissue. These and possibly other stimulation parameters employed together constitute a stimulation program that the IPG 10 can execute to provide stimulation to the patient.

[0007] The pulse in FIG. 2A includes two pulse phases 30a and 30b, each of which is actively driven by the stimulation circuit system 28 shown in FIG. 3. During the first phase 30a, electrode E4 is selected as the anode and thus provides a positive current of amplitude +A to the tissue, while electrode E5 is selected as the cathode and thus absorbs a corresponding negative current of amplitude -A from the tissue. However, more than one electrode can act as an anode at a given time, and more than one electrode can act as a cathode at a given time. It is also possible to stimulate using the housing electrode Ec, as shown in FIG. 3.

[0008] A pulse as shown in FIG. 2A having two actively driven phases 30a and 30b, where phases 30a and 30b have opposite polarities, is generally referred to as a "biphasic" pulse. (There may be a short interphase period between the two phases 30a and 30b during which no current flows, although this is not shown). The use of a biphasic pulse is useful in charge recovery, which may be necessary in view of the capacitance in the current path established between the selected electrodes, as further explained below. Although not shown, each of the phases 30a and 30b can be broken down into a series of higher frequency pulses, which are generally referred to as a "train" of pulses, as is well known.

[0009] The stimulation circuit system 28 shown in FIG. 3 includes one or more current source circuits 40 i and one or more current sink circuits 42 i Source 40 i and absorber 42 i The PDAC 40 may include a digital-to-analog converter (DAC) and may be referred to as a PDAC 40 based on the positive (sourced, anode) and negative (sunk, cathode) currents they source, respectively. i and NDAC 42 i In the example shown, the NDAC / PDAC 40 i / 42 iThe pairs are dedicated (hardwired) to specific electrode nodes ei 39. Each electrode node ei 39 is connected to electrode Ei 16 via a DC blocking capacitor Ci 38 for reasons explained below. The stimulation circuitry 28 in this example also supports the selection of the conductive housing 12 as the electrode (Ec 12), which is typically selected for monopolar stimulation. PDAC 40 i and NDAC 42 i Although not shown, the switch matrix may be provided between one or more PDACs 40. i and electrode node ei 39, and one or more NDACs 42 i The switch matrix allows one or more of the PDACs or one or more of the NDACs to be connected to one or more anode or cathode electrode nodes at a given time.

[0010] The stimulation circuit system 28 is configured by stimulation parameters, which may be provided to the stimulation circuit system 28 by a controller circuit system 29 in the IPG 10. The controller circuit system 29 may include a microcontroller, a microprocessor, a microcomputer, an FPGA, other digital logic structures, etc., which are capable of executing instructions of an electronic device. The controller circuit system 29 may include separate components or may be integrated with an application specific integrated circuit (ASIC) that includes the stimulation circuit system 28 and other circuits required to operate various functions of the IPG 10. The PDAC 40 is controlled by the stimulation parameters. i and NDAC 42 iAppropriate control of allows any of the electrodes 16 to act as an anode or cathode to generate a current I of a specified amplitude through the patient's tissue R, hopefully with a good therapeutic effect. In the example shown, and during the first phase 30a in which electrodes E4 and E5 are selected as anodes and cathodes, respectively, PDAC 404 and NDAC 425 are activated and digitally programmed to generate the desired current A with the correct timing (e.g., according to a specified frequency F and pulse width PWa). During the second phase 30b (PWb), PDAC 405 and NDAC 424 will be activated to reverse the polarity of the current. More than one anode electrode and more than one cathode electrode can be selected at a time, and thus current can flow through tissue R between two or more of the electrodes 16. Power for the stimulation circuit system 28 is provided by the compliance voltage VH, as described in further detail in U.S. Patent Application Publication No. 2013 / 0289665. Other examples of stimulation circuitry and details of various PDAC and NDAC circuits are disclosed in USP 6,181,969, 8,606,362, 8,620,436, US Patent Application Publication Nos. 2018 / 0071520 and 2019 / 0083796. Note that stimulation circuitry 28 is capable of independently setting the current at any of the electrodes - this is sometimes referred to as Multiple Independent Current Control (MICC).

[0011] A DC blocking capacitor Ci 38 is placed in series between each of the electrode nodes ei 39 and the electrode Ei 16 (including the housing electrode Ec 12). The DC blocking capacitor 38 acts as a safety measure to prevent DC current from being injected into the patient, which could occur, for example, if there is a circuit fault in the stimulation circuit system 28. The DC blocking capacitor 38 is typically provided off-chip (outside of one or more ASICs), and may alternatively be provided in or on a circuit board in the IPG 10 used to integrate its various components, as explained in U.S. Patent Application Publication No. 2015 / 0157861.

[0012] As described above, biphasic pulses as shown in FIG. 2A can be used to restore charge stored on capacitors in the current path, particularly the charge stored on the DC blocking capacitor 38. When a constant current I is driven during the first phase 30a, the capacitors (C4 and C5) in the current path will store charge at a rate dV / dt=I / C, and thus a voltage will build up across these capacitors (Vc4 and Vc5). When the polarity of this current is reversed during the second phase 30b, this stored charge is restored, and the voltage across the capacitors preferably returns to zero before the next pulse is issued (i.e., before the next phase 30a). Using biphasic pulses in this manner is sometimes referred to as "active" charge restoration, because the charge stored during the first phase 30a is restored by the current actively driven by the stimulation circuit system 28 during the second phase 30b. During active charge restoration, it is generally preferred that the phases 30a and 30b are charge balanced, that is, the amount of charge passed during the first phase 30a is equal to the amount of charge passed during the second phase 30b. This can be achieved by setting the current amplitude and pulse width to equal values ​​during the two phases (|+A|=|-A|; PWa=PWb). However, this is not strictly necessary, and charge balance can also be achieved if the product of the amplitude and pulse width is equal for the two phases (or more generally, if the areas under their curves are equal).

[0013] It is also possible to provide a stimulation pulse using a monophasic pulse followed by passive charge recovery, as shown in FIG2B . Such a monophasic pulse includes only a single active phase 30 a, which is actively driven as before. Because this phase 30 a will charge the capacitance in the current path as just described, it is also prudent to recover this charge, but this occurs passively without the stimulation circuitry 28 (that is, the PDAC and NDAC) driving active current. Specifically, the passive charge recovery switch 41 i Provided in the stimulation circuit system 28 (FIG. 3). Switch 41 i 39 and a reference potential. In the depicted example, this reference potential comprises the voltage of the battery 14 (Vbat), although another reference potential may be used. After the first pulse phase 30a is issued, the switches 41 iOne or more of the electrodes (whose electrode nodes e4 and e5 participate in all, or at least 414 and 415, of the current provided during the first phase) are closed during the passive charge recovery period 30c (FIG. 2B). This places the capacitor that was charged during the first phase in parallel between the reference potential (Vbat) and the patient's tissue R. As a result, and as shown in FIG. 2B, as the capacitor discharges, a current pulse of opposite polarity will flow at each electrode, which current will decay exponentially at a rate that depends on the circuitry of the IPG and the values ​​of the capacitance and resistance inherent in the tissue R. Preferably, switch 41 i The closure during period 30c lasts for a duration sufficient to effectively restore all of the charge stored on the capacitive element (e.g., capacitor 38) during the first phase 30a. At the end of the passive charge recovery period, switch 41 i Can be turned on again. Passive charge recovery is more fully explained in U.S. Patent Application Publications 2018 / 0071527 and 2018 / 0140831.

[0014] Note that passive charge recovery can also be used with the biphasic pulses shown in FIG2A. Thus, a passive charge recovery period 30c can follow the second active drive phase 30b. Even if the active drive phases 30a and 30b are designed to be charge balanced, non-idealities may result in imperfect charge balance, and thus providing passive charge recovery during phase 30c may be prudent to ensure that charge is fully restored before issuing the next pulse.

[0015] FIG. 4 shows an external trial stimulation environment that can be performed before the IPG 10 is implanted in the patient. During external trial stimulation, stimulation can be attempted on the intended implanted patient without reaching the point where the IPG 10 is to be implanted. Alternatively, a trial electrode array 17' comprising one or more leads (e.g., one or more percutaneous leads 15 or paddle leads 19) is implanted at a target location 34 in the patient's tissue 32, such as within the spine as previously described. The proximal ends of the leads of the trial electrode array 17' leave the incision 36 and are connected to an external trial stimulator (ETS) 40. The ETS 40 typically mimics the operation of the IPG 10, and thus can provide stimulation pulses to the patient's tissue as explained above. For example, see 9,259,574, which discloses a design for an ETS. The ETS 40 is typically worn externally by the patient for a short period of time (e.g., two weeks), which allows the patient and his clinician to experiment with different stimulation parameters to try and find a stimulation program that alleviates the patient's symptoms (e.g., pain). If the external trial stimulation proves successful, the trial electrode array 17' is removed and the complete IPG 10 and electrode array 17 is implanted as described above; if unsuccessful, the electrode array 17' is simply removed.

[0016] Like the IPG 10, the ETS 40 may include one or more antennas to enable bidirectional communication with external devices, as will be further explained with reference to FIG5. Such antennas may include a near-field magnetic induction coil antenna 42a and / or a far-field RF antenna 42b, as previously described. The ETS 40 may also include a stimulation circuit system capable of forming stimulation pulses according to a stimulation program, which may be similar or identical to the stimulation circuit system 28 present in the IPG 10. The ETS 40 may also include a battery (not shown) for operating power.

[0017] FIG5 shows various external devices capable of wirelessly communicating data with the IPG 10 and ETS 40, including a patient-held external controller 45 and a clinician programmer 50. Both of the devices 45 and 50 can be used to send stimulation programs to the IPG 10 or ETS 40—that is, to program their stimulation circuitry to produce pulses with the desired shape and timing described previously. Both devices 45 and 50 can also be used to adjust one or more stimulation parameters of a stimulation program currently being executed by the IPG 10 or ETS 40. Devices 45 and 50 can also receive information from the IPG 10 or ETS 40, such as various status information, etc.

[0018] The external controller 45 may be, for example, as described in U.S. Patent Application Publication 2015 / 0080982, and may include a dedicated controller configured to work with the IPG 10. The external controller 45 may also include a general-purpose mobile electronic device, such as a mobile phone that has been programmed with a Medical Device Application (MDA), thereby allowing it to work as a wireless controller for the IPG 10 or ETS 40, as described in U.S. Patent Application Publication 2015 / 0231402. The external controller 45 includes a user interface, including means for inputting commands (e.g., buttons or icons) and a display 46. The user interface of the external controller 45 enables the patient to adjust stimulation parameters, although it may have limited functionality compared to the more powerful clinician programmer 50 described later.

[0019] The external controller 45 may have one or more antennas capable of communicating with the IPG 10 and the ETS 40. For example, the external controller 45 may have a near-field magnetic induction coil antenna 47a capable of wirelessly communicating with the coil antenna 27a or 42a in the IPG 10 or ETS 40. The external controller 45 may also have a far-field RF antenna 47b capable of wirelessly communicating with the RF antenna 27b or 42b in the IPG 10 or ETS 40. The external controller 45 may also have a controller circuit system 48 capable of executing instructions of an electronic device, such as a microcontroller, microprocessor, microcomputer, FPGA, other digital logic structure, etc. The controller circuit system 48 may, for example, receive adjustments to stimulation parameters by the patient and create a stimulation program to be wirelessly transmitted to the IPG 10 or ETS 40.

[0020] The clinician programmer 50 is further described in U.S. Patent Application Publication 2015 / 0360038 and is only briefly explained here. The clinician programmer 50 may include a computing device 51, such as a desktop computer, a laptop or notebook computer, a tablet computer, a mobile smart phone, a personal data assistant (PDA) type mobile computing device, etc. In FIG. 5 , the computing device 51 is shown as a laptop computer, which includes typical computer user interface devices, such as a screen 52, a mouse, a keyboard, a speaker, a stylus, a printer, etc., all of which are not shown for convenience. Also shown in FIG. 5 are the accessory devices (such as a communication "stick" 54 and a joystick 58) of the clinician programmer 50 that are typically specific to its operation as a stimulation controller, which can be coupled to a suitable port on the computing device 51, such as a USB port 59.

[0021] The antenna used in the clinician programmer 50 for communicating with the IPG 10 or ETS 40 can depend on the type of antenna included in those devices. If the patient's IPG 10 or ETS 40 includes a coil antenna 27a or 42a, the rod 54 can also include a coil antenna 56a to establish near-field magnetic induction communication at a small distance. In this case, the rod 54 can be attached near the patient, such as by placing the rod 54 in a belt or holster that the patient can wear and close to the patient's IPG 10 or ETS 40. If the IPG 10 or ETS 40 includes an RF antenna 27b or 42b, the rod 54, the computing device 51 or both can also include an RF antenna 56b to establish communication with the IPG 10 or ETS 40 at a greater distance. (In this case, the rod 54 may not be necessary). The clinician programmer 50 can also establish communication with other devices and networks (such as the Internet) wirelessly or via a wired link provided at an Ethernet or network port.

[0022] To program stimulation programs or stimulation parameters for the IPG 10 or ETS 40, the clinician interacts with a clinician programmer graphical user interface (GUI) 64 provided on the display 52 of the computing device 51. As will be appreciated by those skilled in the art, the GUI 64 may be presented by executing clinician programmer software 66 on the computing device 51, which may be stored in the non-volatile memory 68 of the device. Those skilled in the art will also recognize that the execution of the clinician programmer software 66 in the computing device 51 may be facilitated by a control circuit system 70 (such as a microprocessor, microcomputer, FPGA, other digital logic structure, etc.) capable of executing programs in the computing device. In addition to executing the clinician programmer software 66 and presenting the GUI 64, such a control circuit system 70 may also be capable of communicating via the antenna 56a or 56b to communicate the stimulation parameters selected via the GUI 64 to the patient's IPG 10.

[0023] exist Figure 6 A portion of the GUI 64 is shown in an example of FIG. Those skilled in the art will appreciate that the details of the GUI 64 will depend on where the clinician programmer software 66 is in its execution, which may depend on previous GUI selections that the clinician has made. Figure 6 GUI 64 is shown at a point that allows stimulation parameters to be set for a patient's IPG 10 or ETS 40. Although GUI 64 is shown as operating in clinician programmer 50, a user interface of external controller 45 may provide similar functionality.

[0024] Shown on the right is an interface in which specific stimulation parameters can be defined for the stimulation program. The values ​​of the stimulation parameters (A; in this example, current, PW, F) associated with the shape of the waveform are shown in the waveform parameter interface 84, including buttons that the clinician can use to increase or decrease these values. The stimulation parameters associated with the electrode 16 (active electrode and its polarity) are adjustable in the electrode parameter interface 86. The electrode parameters are also visible and can be manipulated in the lead interface 92, which displays the electrode array 17 (or 17') roughly in its proper position relative to each other, for example, on the left and right sides of the spine (for simplicity, only two leads are shown). The cursor 94 (or other selection devices such as a mouse pointer) can be used to select a specific electrode in the lead interface 92. The buttons in the electrode parameter interface 86 allow the selected electrode (including the shell electrode Ec) to be designated as an anode, cathode or off. The electrode parameter interface 86 also allows the relative intensity of the anode or cathode current of the selected electrode to be specified as a percentage X. This is particularly useful if more than one electrode acts as an anode or cathode at a given time, as explained in the '038 publication. According to the example waveforms shown in FIGS. 2A and 2B , as shown in the lead interface 92 , electrode E4 has been selected as the only anode sourcing current, and this electrode receives X=100% of the specified anode current +A. Similarly, electrode E5 has been selected as the only cathode sinking current, and this electrode receives X=100% of the cathode current −A. Likewise, more than one electrode may be selected at a time to act as an anode or cathode, where these electrodes share the anode current +A or the cathode current −A. For example, both electrodes E3 and E4 may be selected to act as anodes, where E3 receives 30% of the +A and E4 receives 70% of the +A. The GUI 64 may also include other advanced options not shown, which, for example, allow for setting the duty cycle (on / off time) of the stimulation pulse, setting the rise time at which the stimulation pulse will reach its programmed amplitude (A), specifying the option to use a biphasic waveform and / or passive charge recovery, and the like. Summary of the invention

[0025] A method for programming a stimulator device is disclosed, the stimulator device comprising a plurality of electrode nodes, each electrode node being configured to couple to one of a plurality of electrodes configured to contact tissue of a patient. The method may include programming the stimulator device to provide a repetitive sequence of staggered first pulses and second pulses at at least two of the electrode nodes, thereby creating a stimulation current through the tissue of the patient via the first pulses and the second pulses, wherein, at a first electrode node of at least two of the electrode nodes, each first pulse comprises a first monophasic pulse of a first polarity and a first passive charge recovery pulse of a second polarity opposite to the first polarity, the first passive charge recovery pulse being configured to recover charge stored during the first monophasic pulse, and wherein, at the first electrode node, each second pulse comprises a second monophasic pulse of a second polarity and a second passive charge recovery pulse of the first polarity, the second passive charge recovery pulse being configured to recover charge stored during the second monophasic pulse.

[0026] In one example, the first passive recovery pulse is immediately after the first single-phase pulse in the first pulse at the first electrode node, and wherein the second passive recovery pulse is immediately after the second single-phase pulse in the second pulse at the first electrode node. In one example, the first single-phase pulse has a first amplitude and a first pulse width, and wherein the second single-phase pulse has a second amplitude and a second pulse width. In one example, the first amplitude and the second amplitude include a constant current amplitude. In one example, the first amplitude and the second amplitude are equal, and wherein the first pulse width and the second pulse width are equal. In one example, the first single-phase pulse and the second single-phase pulse are charge balanced at the first electrode node. In one example, the first single-phase pulse and the second single-phase pulse are not charge balanced at the first electrode node. In one example, the stimulator device includes a stimulation circuit system, the stimulation circuit system includes one or more digital-to-analog converters (DACs), and the digital-to-analog converters are configured to actively drive the first single-phase pulse and the second single-phase pulse at the first electrode node. In one example, the stimulation circuit system includes a plurality of passive recovery switches each coupled between one of the electrode nodes and a reference potential, wherein the first passive charge recovery pulse and the second passive charge recovery pulse are formed by closing the passive recovery switch coupled to the first electrode node. In one example, one or more DACs are not configured to actively drive the first passive charge recovery pulse and the second passive charge recovery pulse. In one example, the one or more DACs include one or more positive DACs (PDACs) configured to provide current and one or more negative DACs (NDACs) designed to sink current, wherein the first single-phase pulse is actively driven by at least one of the one or more PDACs at the first electrode node, and wherein the second single-phase pulse is actively driven by at least one of the one or more NDACs at the first electrode node. In one example, the second pulse is centered in time relative to the first pulse at the first electrode node. In one example, the first pulse and the second pulse do not overlap at the first electrode. In one example, at the second electrode node of at least two electrode nodes, each first pulse includes a third single-phase pulse of a second polarity and a third passive charge recovery pulse of a first polarity, the third passive charge recovery pulse being configured to recover the charge stored during the third single-phase pulse, wherein, at the second electrode node, each second pulse includes a fourth single-phase pulse of a first polarity and a fourth passive charge recovery pulse of a second polarity, the fourth passive charge recovery pulse being configured to recover the charge stored during the fourth single-phase pulse. In one example, the first single-phase pulse and the third single-phase pulse coincide in time, and wherein the second single-phase pulse and the fourth single-phase pulse coincide in time. In one example, the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time.In one example, the stimulator device also includes a housing for accommodating a stimulation circuit system, wherein the housing is conductive and includes one of a plurality of electrodes, wherein a second electrode node includes an electrode node coupled to the conductive housing. In one example, an interval period during which no stimulation current flows is between (i) a first monophasic pulse and a first passive charge recovery pulse in each first pulse, and (ii) a second monophasic pulse and a second passive charge recovery pulse in each second pulse. In one example, a first pulse is emitted at a first frequency at a first electrode node, and wherein a second pulse is emitted at a first frequency at a first electrode node. In one example, the stimulator device includes at least one implantable lead, wherein at least some of the electrodes are located on at least one implantable lead. In one example, a first electrode node includes an electrode node coupled to an electrode located on at least one implantable lead. In one example, each electrode node is coupled to its associated electrode by a DC blocking capacitor. In one example, the stimulator device includes an implantable pulse generator or an external test stimulator.

[0027] A stimulator device is disclosed, which may include: a plurality of electrode nodes, each electrode node being configured to couple to one of a plurality of electrodes configured to contact patient tissue; and a stimulation circuit system, which is configured through stimulation parameters to provide a repetitive sequence of staggered first pulses and second pulses at at least two of the electrode nodes, thereby creating a stimulation current through the patient's tissue via the first pulses and the second pulses, wherein, at a first electrode node of at least two electrode nodes, each first pulse includes a first monophasic pulse of a first polarity and a first passive charge recovery pulse of a second polarity opposite to the first polarity, the first passive charge recovery pulse being configured to recover charge stored during the first monophasic pulse, and wherein, at the first electrode node, each second pulse includes a second monophasic pulse of a second polarity and a second passive charge recovery pulse of the first polarity, the second passive charge recovery pulse being configured to recover charge stored during the second monophasic pulse.

[0028] In one example, the first passive recovery pulse is immediately after the first single-phase pulse in the first pulse at the first electrode node, and wherein the second passive recovery pulse is immediately after the second single-phase pulse in the second pulse at the first electrode node. In one example, the first single-phase pulse has a first amplitude and a first pulse width, and wherein the second single-phase pulse has a second amplitude and a second pulse width. In one example, the first amplitude and the second amplitude include a constant current amplitude. In one example, the first amplitude and the second amplitude are equal, and wherein the first pulse width and the second pulse width are equal. In one example, the first single-phase pulse and the second single-phase pulse are charge balanced at the first electrode node. In one example, the first single-phase pulse and the second single-phase pulse are not charge balanced at the first electrode node. In one example, the stimulation circuit system includes one or more digital-to-analog converters (DACs) configured to actively drive the first single-phase pulse and the second single-phase pulse at the first electrode node. In one example, the stimulation circuit system includes a plurality of passive recovery switches each coupled between one of the electrode nodes and a reference potential, wherein the first passive charge recovery pulse and the second passive charge recovery pulse are formed by closing the passive recovery switch coupled to the first electrode node. In one example, one or more DACs are not configured to actively drive the first passive charge recovery pulse and the second passive charge recovery pulse. In one example, the one or more DACs include one or more positive DACs (PDACs) configured to provide current and one or more negative DACs (NDACs) designed to sink current, wherein the first single-phase pulse is actively driven by at least one of the one or more PDACs at the first electrode node, and wherein the second single-phase pulse is actively driven by at least one of the one or more NDACs at the first electrode node. In one example, the second pulse is centered in time relative to the first pulse at the first electrode node. In one example, the first pulse and the second pulse do not overlap at the first electrode. In one example, at the second electrode node of at least two electrode nodes, each first pulse includes a third single-phase pulse of a second polarity and a third passive charge recovery pulse of a first polarity, the third passive charge recovery pulse being configured to recover the charge stored during the third single-phase pulse, wherein, at the second electrode node, each second pulse includes a fourth single-phase pulse of a first polarity and a fourth passive charge recovery pulse of a second polarity, the fourth passive charge recovery pulse being configured to recover the charge stored during the fourth single-phase pulse. In one example, the first single-phase pulse and the third single-phase pulse coincide in time, and wherein the second single-phase pulse and the fourth single-phase pulse coincide in time. In one example, the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time.In one example, the stimulator device also includes a housing for accommodating the stimulation circuit system, wherein the housing is conductive and includes one of a plurality of electrodes, wherein the second electrode node includes an electrode node coupled to the conductive housing. In one example, the interval period in which no stimulation current flows is between (i) the first monophasic pulse and the first passive charge recovery pulse in each first pulse, and (ii) the second monophasic pulse and the second passive charge recovery pulse in each second pulse. In one example, a first pulse is emitted at a first frequency at a first electrode node, and wherein a second pulse is emitted at a first frequency at the first electrode node. In one example, the stimulator device also includes at least one implantable lead, wherein at least some of the electrodes are located on at least one implantable lead. In one example, the first electrode node includes an electrode node coupled to an electrode located on at least one implantable lead. In one example, each electrode node is coupled to its associated electrode by a DC blocking capacitor. In one example, the stimulator device includes an implantable pulse generator or an external test stimulator.

[0029] A non-transitory computer-readable medium is disclosed, comprising instructions for programming a stimulator device, the stimulator device comprising a plurality of electrode nodes, each electrode node being configured to couple to one of a plurality of electrodes configured to contact tissue of a patient, wherein the instructions, when executed, are configured to perform the following method: programming a stimulation circuit system in the stimulator device to provide a repetitive sequence of staggered first pulses and second pulses at at least two of the electrode nodes, thereby creating a stimulation current through the tissue of the patient via the first pulses and the second pulses, wherein, at a first electrode node of at least two of the electrode nodes, each first pulse comprises a first monophasic pulse of a first polarity and a first passive charge recovery pulse of a second polarity opposite to the first polarity, the first passive charge recovery pulse being configured to recover charge stored during the first monophasic pulse, and wherein, at the first electrode node, each second pulse comprises a second monophasic pulse of a second polarity and a second passive charge recovery pulse of the first polarity, the second passive charge recovery pulse being configured to recover charge stored during the second monophasic pulse.

[0030] In one example, the non-transitory computer-readable medium resides in a stimulator device. In one example, the non-transitory computer-readable medium resides in an external device for programming the stimulator device. In one example, the first passive recovery pulse is immediately after the first monophasic pulse in the first pulse at the first electrode node, and wherein the second passive recovery pulse is immediately after the second monophasic pulse in the second pulse at the first electrode node. In one example, the first monophasic pulse has a first amplitude and a first pulse width, and wherein the second monophasic pulse has a second amplitude and a second pulse width. In one example, the first amplitude and the second amplitude include a constant current amplitude. In one example, the first amplitude and the second amplitude are equal, and wherein the first pulse width and the second pulse width are equal. In one example, the first monophasic pulse and the second monophasic pulse are charge balanced at the first electrode node. In one example, the first monophasic pulse and the second monophasic pulse are not charge balanced at the first electrode node. In one example, the second pulse is centered in time relative to the first pulse at the first electrode node. In one example, the first pulse and the second pulse do not overlap at the first electrode. In one example, at a second electrode node of at least two electrode nodes, each first pulse includes a third monophasic pulse of a second polarity and a third passive charge recovery pulse of a first polarity, the third passive charge recovery pulse being configured to recover the charge stored during the third monophasic pulse, wherein, at a second electrode node, each second pulse includes a fourth monophasic pulse of a first polarity and a fourth passive charge recovery pulse of a second polarity, the fourth passive charge recovery pulse being configured to recover the charge stored during the fourth monophasic pulse. In one example, the first monophasic pulse and the third monophasic pulse coincide in time, and wherein the second monophasic pulse and the fourth monophasic pulse coincide in time. In one example, the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time. In one example, the stimulator device further includes a housing for accommodating the stimulation circuit system, wherein the housing is conductive and includes one of a plurality of electrodes, wherein the second electrode node includes an electrode node coupled to the conductive housing. In one example, the inter-period period in which no stimulation current flows is between (i) the first monophasic pulse and the first passive charge recovery pulse in each first pulse, and (ii) the second monophasic pulse and the second passive charge recovery pulse in each second pulse. In one example, the first pulse is emitted at a first frequency at the first electrode node, and wherein the second pulse is emitted at the first frequency at the first electrode node.

[0031] A method for programming a stimulator device is disclosed, the stimulator device comprising a plurality of electrode nodes, each electrode node being configured to couple to one of a plurality of electrodes configured to contact tissue of a patient. The method may include: receiving stimulation parameters for pulses to be generated at at least two of the electrode nodes in the stimulation device at a graphical user interface (GUI) on an external device for programming the stimulation device; automatically deriving a waveform at the external device based on the stimulation parameters, wherein the waveform comprises staggered first pulses and second pulses at at least two electrode nodes, wherein in the automatically derived waveform, at a first electrode node of the at least two electrode nodes, each first pulse comprises a first monophasic pulse of a first polarity, followed by a first passive charge recovery pulse configured to restore charge stored during the first monophasic pulse, and wherein in the automatically derived waveform, at a first electrode node, each second pulse comprises a second monophasic pulse of a second polarity opposite to the first polarity, followed by a second passive charge recovery pulse configured to restore charge stored during the second monophasic pulse.

[0032] In one example, the stimulation parameters do not independently specify the staggered first pulse and the second pulse. In one example, in the automatically derived waveform, at the second electrode node of at least two electrode nodes, each first pulse includes a third monophasic pulse of a second polarity, followed by a third passive charge recovery pulse configured to recover the charge stored during the third monophasic pulse, wherein in the automatically derived waveform, at the second electrode node, each second pulse includes a fourth monophasic pulse of a first polarity, followed by a fourth passive charge recovery pulse configured to recover the charge stored during the second monophasic pulse. In one example, the first monophasic pulse and the third monophasic pulse coincide in time, and wherein the second monophasic pulse and the fourth monophasic pulse coincide in time. In one example, the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time. In one example, the method also includes transmitting the derived waveform to a stimulator device to generate pulses at at least two of the electrode nodes. In one example, when a user selection is received at a GUI, an automatic waveform is derived according to the stimulation parameters.

[0033] A system is disclosed that may include: a stimulator device comprising a plurality of electrode nodes, each electrode node being configured to couple to one of a plurality of electrodes configured to contact tissue of a patient; and an external device for programming the stimulator device, comprising a non-transitory computer-readable medium containing a software program, wherein the software program, when executed on the external device, is configured to: present a graphical user interface (GUI) on the external device, receive at the (GUI) stimulation parameters for pulses to be generated at at least two of the electrode nodes in the stimulator device, automatically derive a waveform based on the stimulation parameters, wherein the waveform comprises staggered first pulses and second pulses at at least two of the electrode nodes, wherein in the automatically derived waveform, at a first electrode node of the at least two electrode nodes, each first pulse comprises a first monophasic pulse of a first polarity, followed by a first passive charge recovery pulse configured to recover charge stored during the first monophasic pulse, and wherein in the automatically derived waveform, at a first electrode node, each second pulse comprises a second monophasic pulse of a second polarity opposite to the first polarity, followed by a second passive charge recovery pulse configured to recover charge stored during the second monophasic pulse.

[0034] In one example, the stimulation parameters do not independently specify the staggered first pulse and the second pulse. In one example, in the automatically derived waveform, at the second electrode node of at least two electrode nodes, each first pulse includes a third monophasic pulse of a second polarity, followed by a third passive charge recovery pulse configured to recover the charge stored during the third monophasic pulse, wherein in the automatically derived waveform, at the second electrode node, each second pulse includes a fourth monophasic pulse of a first polarity, followed by a fourth passive charge recovery pulse configured to recover the charge stored during the second monophasic pulse. In one example, the first monophasic pulse and the third monophasic pulse coincide in time, and wherein the second monophasic pulse and the fourth monophasic pulse coincide in time. In one example, the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time. In one example, the software program is also configured to transmit the derived waveform to the stimulator device when executed on an external device to generate pulses at at least two of the electrode nodes. In one example, the GUI includes user-selectable options to automatically derive the waveform according to the stimulation parameters.

[0035] A non-transitory computer-readable medium is disclosed, comprising instructions for an external device for programming a stimulator device, the stimulator device comprising a plurality of electrode nodes, each electrode node being configured to couple to one of a plurality of electrodes configured to contact tissue of a patient, wherein the instructions, when executed on the external device, are configured to perform the following method: providing input at a graphical user interface (GUI) on the external device to receive stimulation parameters for pulses to be generated at at least two of the electrode nodes in the stimulator device; automatically deriving a waveform at the external device based on the stimulation parameters, wherein the waveform comprises staggered first pulses and second pulses at at least two electrode nodes, wherein in the automatically derived waveform, at a first electrode node of the at least two electrode nodes, each first pulse comprises a first monophasic pulse of a first polarity, followed by a first passive charge recovery pulse configured to recover charge stored during the first monophasic pulse, and wherein in the automatically derived waveform, at a first electrode node, each second pulse comprises a second monophasic pulse of a second polarity opposite to the first polarity, followed by a second passive charge recovery pulse configured to recover charge stored during the second monophasic pulse.

[0036] In one example, the stimulation parameters do not independently specify staggered first and second pulses. In one example, in the automatically derived waveform, at the second electrode node of at least two electrode nodes, each first pulse includes a third monophasic pulse of a second polarity, followed by a third passive charge recovery pulse configured to recover the charge stored during the third monophasic pulse, wherein in the automatically derived waveform, at the second electrode node, each second pulse includes a fourth monophasic pulse of a first polarity, followed by a fourth passive charge recovery pulse configured to recover the charge stored during the second monophasic pulse. In one example, the first monophasic pulse and the third monophasic pulse coincide in time, and wherein the second monophasic pulse and the fourth monophasic pulse coincide in time. In one example, the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time. In one example, when executed on an external device, the instructions also include transmitting the derived waveform to a stimulator device to generate pulses at at least two of the electrode nodes. In one example, when executed on the external device, the instructions further include providing a user selectable option on the GUI to automatically derive a waveform based on the stimulation parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows an implantable pulse generator (IPG) that can be used for spinal cord stimulation (SCS) according to the prior art.

[0038] 2A and 2B illustrate examples of stimulation pulses that may be generated by an IPG using active charge recovery and passive charge recovery, respectively, according to the prior art.

[0039] FIG. 3 shows stimulation circuitry for providing stimulation pulses in an IPG according to the prior art.

[0040] FIG. 4 shows an external trial stimulator (ETS) that may be used to provide stimulation prior to implantation of an IPG according to the prior art.

[0041] FIG. 5 shows various external devices capable of communicating with and programming stimulation in the IPG and ETS according to the prior art.

[0042] Figure 6 A graphical user interface (GUI) of a clinician programmer external device for setting or adjusting stimulation parameters according to the prior art is shown.

[0043] Figure 7 A "sweet spot search" using a movable supra-perception bipole to determine an effective electrode for a patient is shown.

[0044] Figure 8 A sweet spot search is shown where the dipoles consist of virtual poles that do not correspond to the positions of the electrodes in the electrode array.

[0045] Fig. 9 Data correlating lower frequencies with optimal pulse widths that can be used to provide sub-perception stimulation in IPG or ETS are presented.

[0046] Fig.10 It is preferably used to provide Fig. 9 Example of a symmetrical biphasic waveform for a lower frequency stimulus.

[0047] Fig.11 Shows a simulation Fig.10 The functionality of the biphasic waveform is however the first example of a waveform employing a monophasic pulse followed by passive charge recovery.

[0048] Figures 12 to 15 Shows the Fig.11 Other examples of modifications of waveforms.

[0049] Fig.16 Shows the use of Fig.11 waveform to create a virtual pole.

[0050] Fig.17 The external device GUI is shown to allow the clinician to form the pulse into a biphasic pulse ( Fig.10 ), or a monophasic pulse followed by passive charge recovery ( Fig.11 ) options. DETAILED DESCRIPTION

[0051] While spinal cord stimulation (SCS) therapy is an effective means of relieving pain for patients, this stimulation can also cause paresthesias. Paresthesias—sometimes referred to as "supersensory" therapy—are sensations that may accompany SCS therapy, such as tingling, prickling, heat, cold, and more. Generally speaking, the effects of paresthesias are mild, or at least not too severe for the patient. And, for patients whose chronic pain is now under control with SCS therapy, paresthesias are often a reasonable trade-off. Some patients even find paresthesias comfortable and soothing.

[0052] Nevertheless, at least for some patients, SCS therapy would ideally provide complete pain relief without paresthesias - this is often referred to as "sub-perceptual" or sub-threshold therapy that is not felt by the patient. Effective sub-perceptual therapy can relieve pain without paresthesias by delivering stimulation pulses at a higher frequency. Unfortunately, this higher frequency stimulation may require more power, which tends to drain the battery 14 of the IPG 10. For example, see U.S. Patent Application Publication 2016 / 0367822. If the battery 14 of the IPG is a primary cell and is not rechargeable, high frequency stimulation means that the IPG 10 needs to be replaced more quickly. Alternatively, if the IPG battery 14 is rechargeable, the IPG 10 will need to be charged more frequently, or charged for a longer period of time. In any case, it is inconvenient for the patient.

[0053] In SCS applications, it is desirable to determine a therapeutic stimulation program that is effective for each patient. An important part of determining an effective therapeutic stimulation program is determining the "sweet spot" of stimulation within each patient, i.e., selecting which electrodes should be active (E) and with what polarity (P) and relative amplitude (X%) to recruit and thereby treat the neural site in the patient where pain originates. Selecting electrodes close to this painful neural site can be difficult to determine, and experiments are often performed to select the best combination of electrodes to provide treatment for the patient. A sweet spot search for determining electrodes for subsequent therapeutic stimulation is particularly useful in an experimental setting after a patient is first implanted with an electrode array, i.e., after receiving an IPG or ETS, but a sweet spot search can also be performed at any time during the life of the IPG to optimize treatment.

[0054] As described in U.S. Patent Application Publication No. 2019 / 0046800 (the '800 publication), when subperceptual therapy is used, selecting electrodes for a given patient may be more difficult because the patient cannot feel the stimulation, and therefore it may be difficult for the patient to feel whether the stimulation is "masking" his pain, and therefore it may be difficult for the patient to feel whether the selected electrodes are effective. Further, subperceptual stimulation therapy may require a "wash in" period before it may become effective. The wash in period may take a day or more, and therefore the subperceptual stimulation may not be immediately effective, making electrode selection more difficult.

[0055] The '800 publication discloses that the sweet spot search may therefore preferably be conducted using supersensory stimulation, even if the final stimulation treatment provided after the sweet spot search is subsensory. By definition, supersensory treatment allows the patient to feel the stimulation, which enables the patient to provide essentially immediate feedback to the clinician during the sweet spot search as to whether paresthesias appear to be masking his pain well, without the need for a wash-in period. Further, the use of supersensory stimulation during the sweet spot search ensures that electrodes are determined to be well recruited to the neural sites of the patient's pain. As a result, after the sweet spot search is completed and the final subsensory treatment is provided at the determined electrodes, the wash-in of the subsensory treatment may not take as long because the electrodes required for good recruitment have already been reliably determined.

[0056] refer to Figure 7 , briefly describes the sweet spot search described in the '800 publication in a simple example. In this example, it is assumed that the pain site 100 may be within a tissue region 102. Such a region 102 may be inferred by a clinician based on patient symptoms, for example, by understanding which electrodes are close to certain vertebrae (not shown), such as within the T9 to T10 space. Figure 7 , a super-sensitive bipole 104 is selected and applied to the patient at a first position (position 1) in the electrode array 17 or 17'. In this example, the bipole 104 is initially placed near electrodes E2 and E3, where electrode E2 is selected as an anode that will provide a positive current (+A) to the patient's tissue, and where electrode E3 is selected as a cathode that will sink a negative current (-A) from the tissue. The specific stimulation parameters selected when forming the bipole 104 can be selected at the GUI 64 of the clinician programmer 50 or other external device (such as a patient external controller 45) and wirelessly telemetered to the patient's IPG or ETS for execution. The super-sensitive bipole 104 is provided to the patient for a short duration, during which the patient provides feedback to the clinician regarding how well the bipole 104 helps their symptoms. Such patient feedback can include a pain scale rating (which can be input into the GUI 64 of the clinician programmer 50 (or patient controller 45; FIG. 5) (e.g., Figure 7)) and information about the current position of the bipole 102 reflecting the anode and cathode electrode positions. The pain scale rating may include a scale from 1 to 10 using a Numerical Rating Scale (NRS) or Visual Analogue Scale (VAS), where 1 represents no or little pain and 10 represents the worst pain imaginable. If desired, the GUI 64 may include inputs for marking and recording the pain rating and bipolar position.

[0057] After testing the bipole 104 in this first position, the bipole 104 can be moved to a different electrode combination, such as an anode electrode E3 and a cathode electrode E4 (position 2), to again test and record its efficacy. Movement of the bipole can occur in different ways. For example, the GUI can include a dial 112 with arrows that allow the clinician to move the bipole up, down, left, and right in the electrode array 17 or 17', and these arrows can be engaged using the cursor 94. Accessory devices such as a joystick 58 (Figure 5) can also be used to move the bipole 104. The user can also enter text into the GUI to set a new position for the bipole. In the example shown, when it is desired to find an electrode combination that covers the pain area 100, one electrode lead of the bipole 104 is moved downward and the other electrode lead is moved upward, as shown by path 106. In Figure 6 In the example of , given that the pain site 100 is near electrodes E13 and E14, it can be expected that the bipole 104 at these electrodes will provide the best relief for the patient, as reflected by the patient's pain rating. During the optimal point search, it is not necessary to move the bipole in any particular path 106, but rather the bipole 104 can be moved randomly or in other logical ways, perhaps as guided by the patient's input.

[0058] The bipolar 104 can be formed in different ways, and as described in the '800 publication, can be formed using a virtual pole 108 (i.e., a virtual anode or cathode) that is not necessarily located at the physical location of the electrode 16. The virtual pole 108 is further discussed in U.S. Patent Application Publication 2018 / 0243569 (the '569 publication), and therefore the virtual pole 108 is only briefly explained here. If the stimulation circuit system 28 used in the IPG or ETS is capable of independently setting the current at any one of the electrodes, the formation of the virtual pole is assisted, as explained above with reference to FIG. 3.

[0059] When the dummy dipole 104a is used and as Figure 8As shown, the GUI 64 of the clinician programmer 50 (FIG. 4) can be used to define anodes (+) and cathodes (-) 108 at coordinates X, Y in the electrode array 17 or 17'. As explained in the '569 publication, the electrode configuration algorithm 120 programmed into the control circuit system 70 of the clinician programmer 50 (FIG. 5) can calculate which physical electrodes 16 need to be selected based on these locations and based on other tissue modeling information, and at what relative magnitudes to form virtual anodes and virtual cathodes at the specified locations. For example, in Figure 8 , the virtual anode is located at a position between electrodes E2, E3 and E10. The electrode configuration algorithm 120 can then calculate, based on this position, the appropriate share (X%) of the total anode current +A that each of these electrodes will receive (during the first pulse phase 30a) to position the virtual anode at this position. Because the position of the virtual anode is closest to electrode E2, this electrode E2 can receive the largest share of the specified anode current +A (e.g., 75%*+A). Electrodes E3 and E10, which are closer to the position of the virtual anode but farther away, receive smaller shares of the anode current (e.g., 15%*+A and 10%*+A, respectively). Similarly, from the specified positions of the virtual cathodes near electrodes E4, E11 and E12, it can be seen that these electrodes will receive appropriate shares of the specified cathode current A - (e.g., 20%*-A, 20%*-A and 60%*-A, respectively, during the first pulse phase 30a). These polarities will then be reversed during the second phase 30b of the pulse, as shown. Figure 8 In any case, the use of virtual poles in the formation of the bipole 104a allows shaping of the field in the tissue, and many different electrode combinations can be tried during the search for the best point. In this regard, it is not strictly necessary that the (virtual) bipole moves along an ordered path 106 relative to the electrode, and the path can be random, possibly as guided by feedback from the patient.

[0060] The '800 publication explains that once the sweet spot search has been completed and electrodes proximal to the patient's pain site 100 have been identified, these electrodes (or electrodes proximal to them) can be used to provide sub-perceptual therapy to the patient. Significantly, the '800 publication discloses that effective sub-perceptual therapy can occur even at lower frequencies (less than or equal to 10 kHz) using lower amounts of power in the IPG 10 or ETS 40, and that such effectiveness at lower frequencies is also achieved when the pulse width is adjusted to specific values ​​at each frequency. The graph taken from the '800 publication is at Fig.10 It is shown in Fig.10The relationship between this lower frequency and the pulse width noted to provide optimal subperceptual treatment based on empirical testing is shown. The '800 publication analyzes this data in more depth, including identifying specific relationships (curve fits) and frequency / pulse width regions that indicate subperceptual effectiveness. The amplitude A of the stimulation provided at such a frequency and pulse width can be titrated down until subperceptual is achieved. It is assumed that the reader is familiar with the '800 publication, and therefore these details will not be repeated here.

[0061] Of particular interest in the '800 publication is the observation that effective super-perceptual sweet spot searching and effective sub-perceptual treatment can be achieved at very low frequencies (less than or equal to 200 Hz). In the '800 publication, the pulses used during super-perceptual sweet spot searching and / or during sub-perceptual treatment are preferably symmetrical biphasic pulses. That is, and as Fig.10 As shown, the pulse comprises at least two active drive phases 30a and 30b, wherein the amplitude A is the same (but with opposite polarity) during each of these phases, and wherein the pulse width PW is also equal. (Here, it is assumed that Figure 7 Electrodes E13 and E14 near the site of pain 100 form a bipolar). It is assumed that effectiveness is enhanced because each phase 30a and 30b will tend to actively recruit different neural targets in the patient's tissue. That is, a first group of neural targets are recruited during phase 30a, and a second group of (possibly overlapping) neural targets are recruited during phase 30b. Thus, the stimulation coverage is expanded. In addition, the use of symmetrical biphasic pulses is beneficial because, as mentioned above, such pulses are charge balanced, so (ideally) all stored charge is restored at the end of the second phase 30b.

[0062] However, in some IPGs or ETSs, it may be difficult or impossible to form symmetrical biphasic pulses at lower frequencies (e.g., <200 Hz). This is because some IPG / ETS manufacturers may not provide the ability to use dual active drive phases at such low frequencies. Alternatively, the IPG or ETS may only support, and the GUI 64 of the external device may only allow the use of monophasic pulses using passive charge recovery, as explained previously with reference to FIG. 2B . While it may be possible to "trick" such a device into forming symmetrical biphasic pulses at low frequencies, even if such tricking is possible, such tricking is inconvenient and difficult to implement. In short, in the inventor's opinion, some of the teachings of the '800 publication may be difficult to implement when using lower frequencies during super-perceptual sweet spot searches or sub-perceptual treatments.

[0063] To overcome this problem, the inventors disclose the use of a new waveform for use in IPG or ETS that can effectively create the desired effect of actively driven biphasic pulses at a lower frequency, but through the use of monophasic pulses with passive charge recovery. The waveform includes a staggered first pulse and a second pulse at each electrode, so that each electrode emits a first pulse sequence, followed by a second pulse, followed by a first pulse, and so on. Each first pulse includes a first monophasic pulse of a first polarity having a first amplitude and a first pulse width, and a first passive charge recovery period. The first pulse is preferably emitted at a desired frequency (such as less than 200 Hz), which is shown to be useful in, for example, the '800 publication. Each second pulse includes a second monophasic pulse of a second polarity opposite to the first polarity having a second amplitude and a second pulse width, and a second passive charge recovery period. The second pulse is emitted at the same frequency as the first pulse, and each second pulse at each electrode can be centered in time relative to the previous and next first pulses. Preferably, the first and second amplitudes and the first and second pulse widths are equal, or at least it is desirable that the first and second monophasic pulses of opposite polarity at each electrode are charge balanced. The first monophasic pulse and the second monophasic pulse imitate the function of the biphasic pulse, wherein the first monophasic pulse imitates the function of the first phase of the biphasic pulse, and wherein the second monophasic pulse imitates the function of the second phase of the biphasic pulse. Because each of the first pulse and the second pulse includes a monophasic pulse followed by a passive charge recovery period, they are easily formed at a low frequency in a conventional IPG or ETS device.

[0064] Such a waveform is Fig.11 As just explained, the first pulses 130 are emitted at a frequency F. For example, this frequency F may be less than 200 Hz, as is useful, for example, as shown in the '800 publication, although the disclosed waveforms may be used at any desired frequency. Each first pulse 130 includes a monophasic pulse 132 followed by a passive charge recovery period 134 that produces a passive charge recovery pulse. The passive recovery pulse 134 follows the monophasic pulse 132 in the first pulse at the first electrode node, meaning that it is followed by a minimal inter-period period, or otherwise meaning that no pulses are emitted in between, even if the time interval between them is relatively long. The monophasic pulses 132 are actively driven by the stimulation circuitry 28 ( FIG. 3 ), i.e., by one or more PDACs 40 i or NDAC42 iThe monophasic pulse 132 is driven by a single phase pulse 132, depending on whether its polarity is positive or negative. At electrode E13, this monophasic pulse 132 is positive (anodic) with a constant current +A during the pulse width PWa, while at electrode E14, the monophasic pulse is negative (cathodic) with a constant current –A during the pulse width PWa. However, it is not strictly necessary for the monophasic pulse 132 to remain constant over its pulse width PWa. Alternatively, the amplitude of the monophasic pulse 132 may be variable. Further, the monophasic pulse 132 may include a voltage instead of a current, which voltage may be positive or variable.

[0065] The monophasic pulse 132 at each electrode is followed by a passive charge recovery period 134, which results in a pulse that is not actively driven by the stimulation circuitry 28. Instead, during the passive charge recovery period 134, the passive charge recovery switch 41 in the stimulation circuitry 28 (FIG. 3) is switched on. i During the passive charge recovery period 134, all switches 41 are closed (ie, all switches 41 are closed). i , or at least switch 41 13 and 41 14 ). Passive charge recovery 134 occurs over a duration PWb. PWb is preferably long enough to allow all of the charge stored during the monophasic pulse 132 (e.g., +Q at E13, or −Q at E14) to be passively recovered during period 134 (e.g., −Q at E13 or +Q at E14). The duration PWb of the passive charge recovery period 134 may be variable, as the duration required to fully recover the stored charge will depend on the specific capacitances and resistances involved. Although not shown, in each first pulse 130, a short interphase period may separate the monophasic pulse 132 from the passive charge recovery pulse 134.

[0066] The second pulse 140 is interleaved with the first pulse 130 at each of the electrodes. The second pulse 140 is preferably identical to the first pulse 130, but has an opposite polarity. Therefore, the second pulse 140 also includes a monophasic pulse 142 followed by a passive charge recovery period 144. At electrode E13, the monophasic pulse 142 is negative (cathodic) with a constant current -A during the pulse width PWa, while at electrode E14, the monophasic pulse 132 is positive (anodic) with a constant current +A during the pulse width PWa. In this example, at each electrode, the amplitude (A, although different in polarity) of the monophasic pulses 132 and 142 is the same as its pulse width PWa, which means that the monophasic pulses 132 and 142 are symmetrical and the charge is balanced at each electrode. However, as described in the following examples, this is not strictly necessary. As previously described, the passive charge recovery switch 41 may be closed by closing the associated passive charge recovery switch 41. iTo implement a passive charge recovery period 144, this can again occur over a duration PWb, which is again preferably long enough to allow all of the stored charge during the single-phase pulse 142 (e.g., -Q at E13, or +Q at E14) to be passively recovered during period 144 (e.g., +Q at E13 or -Q at E14).

[0067] Because the second pulses 140 are staggered with the first pulses 130 at each electrode, they are also emitted at a frequency F at each electrode. Each second pulse 140 can be perfectly centered in time with respect to the first pulses 130 that come before and after at each electrode. In other words, at each electrode, each second pulse 140 can be emitted after the previous first pulse 130 time ta, and can be emitted before the next first pulse 140 time tb. (As shown, ta and tb can be measured between the start of the monophasic pulses 132 and 142, although other reference points can also be selected.) Fig.11 As shown, if ta=tb, each second pulse 140 can be centered in time, which means that pulses 130 and 140 are emitted at each electrode with a periodic frequency of 2F. However, it is not strictly necessary that the second pulse 140 is centered in time relative to the first pulses on both sides at each electrode, as discussed later.

[0068] When people compare Fig.10 The biphasic waveform and Fig.11 As mentioned above, assuming that Fig.10 The waveform of is effective (particularly at lower frequencies, and particularly when applying sub-perceptual treatment) because both active drive phases 30a and 30b will tend to actively recruit different neural targets in the patient's tissue, thereby expanding the stimulation coverage in the patient's tissue. Fig.11 The same is true when considering pulses 130 and 140 in . Essentially, Fig.10 The first phase 30a of the active drive of the biphasic pulse consists of Fig.11 The first pulse 130 is realized by a single-phase pulse 132. Similarly, Fig.10 The second phase 30b of the active drive of the biphasic pulse consists of Fig.11 The single-phase pulse 142 in the second pulse 130 is realized. Moreover, Fig.11 This stimulation is related to Fig.10 The same effective frequency F occurs in Fig.10 Like the symmetrical biphasic pulse, Fig.11The waveform is also charge balanced, and this charge balancing can occur in two ways. First, the monophasic pulses 132 and 142 can be charge balanced at each electrode. Second, each monophasic pulse 132 and 142 can be charge balanced using its associated passive charge recovery phase 134 and 144. In either case, Fig.11 The waveform fully restores the charge at each electrode within each pulse 130 or 140, or between consecutive pulses 130 and 140.

[0069] Additionally, because the waveform at each electrode consists of a monophasic pulse followed by a passive charge recovery pulse, such pulses can be easily formed in IPG or ETS, which might otherwise not allow the formation of actively driven biphasic pulses at lower frequencies F ( Fig.10 ). In this regard, note that an IPG or ETS typically supports defining different prescribed pulses in different timing channels (TCs). The use of different timing channels allows more complex treatments to be provided by the IPG or ETS, where each timing channel provides its pulses simultaneously with pulses in other timing channels, even if the pulses in these timing channels do not overlap in time. See, for example, USP 9,656,081 which describes the timing channels in the IPG in more detail). When forming Fig.11 When looking at the waveform of FIG. 1 , note that the first pulse 130 can be defined and formed in the first timing channel (TC1), while the second pulse 140 can be defined and formed in the second timing channel (TC2). Alternatively, pulses 130 and 140 can be formed in a single timing channel.

[0070] right Fig.11 Modifications to the waveform are possible, some modifications are in Figures 12 to 16 In Fig.12 , the second pulse 140 is not centered in time with respect to the first pulse 130. Alternatively, the second pulse 140 is issued immediately after the first pulse ends, that is, immediately after the passive charge recovery period 134 of the previous first pulse 130 ends. That is, the second pulse 140 may be issued at a time ta after the previous first pulse 130. In this case, ta will be shorter than tb (the time to the next first pulse 130), and preferably, ta is at least long enough to include the duration (PWa) of the monophasic pulse 132 and the duration (PWb) of the passive charge recovery period 134. Fig.13A similar modification is shown, except that the second pulse 140 is issued as late as possible before the next first pulse 130 begins. In this example, the second pulse 140 begins with enough time to end before the next first pulse 130 is issued at a given electrode. This means that the second pulse begins at least a time tb before the next first pulse, which means that the time tb is at least as long as the duration of the monophasic pulse 142 (PWa) and the passive charge recovery period 144 (PWb) of the second pulse 140. In this case, the time tb will be shorter than the time ta, as shown in FIG. Fig.13 Of course, the second pulse 140 may appear Fig.12 and Fig.13 Anywhere between the extreme values ​​shown.

[0071] exist Fig.14 In the modification of FIG. 1 , the monophasic portions 132 and 142 of the first and second pulses 130 and 140, while having opposite polarities, are not symmetrical in other respects. Specifically, in this example, at electrode E13, the monophasic pulse 142 in the second pulse 140 has a longer duration (PW') and a lower amplitude (-A') than the monophasic pulse 132 (PW, +A) in the first pulse 130. Even though asymmetrical, the monophasic pulses 132 and 142 are still charge balanced at each electrode, i.e., +Q = |-Q|, because in this case PW*+A = PW'*|-A|. As previously described, in general, charge balancing of pulses 132 and 142 can occur if the area under each of these curves is equal (despite having opposite polarities). The same is true at electrode E14, despite the polarity being reversed.

[0072] exist Fig.15 In the modification of , the monophasic pulses 132 and 142 are not charge balanced at each electrode. Specifically, at electrode E13, the monophasic pulse 132 has a charge of +Q, while the monophasic pulse 142 has a charge of -Q'. In this example, |-Q'| is less than Q, which can be affected by making the pulse width (PW') of the monophasic pulse 142 less than the pulse width (PW) of the monophasic pulse 132, or making the amplitude (A') of 142 less than the amplitude (A) of 132, or both. Even though the monophasic pulses 132 and 142 are not charge balanced, each of the first and second pulses 130 and 140 is individually charge balanced when considering their passive recovery periods 134 and 144. When the monophasic pulse 132 provides a charge of +Q, the passive recovery period 134 restores -Q (assuming its duration is long enough). Similarly, when the monophasic pulse 142 provides a charge of -Q', the passive recovery period 144 restores +Q' (again assuming its duration is long enough). Thus, each pulse 130 and 140 is individually charge balanced. Likewise, the same situation occurs at electrode E14, although the polarity is reversed.

[0073] Fig.16 Shows Figures 11 to 15 The waveform may be provided to more than two electrodes, which as previously described is useful for creating stimulation having virtual poles whose locations may not correspond to the physical locations of electrodes 16 in the electrode array. Fig.16 Shown is applied to Fig.11 This modification of the waveform, but also Figures 12 to 15 The waveforms are modified similarly.

[0074] exist Fig.16 As mentioned above ( Figure 8 ) creates a bipolar 104a with poles 108. In this example, the anode 108 is virtual and its position does not correspond to the physical position of the electrode. However, the cathode 108 is positioned at electrode (E14), although this pole 108 can actually be formed at any random position in the electrode array 17 or 17' by dividing the cathode current -A between different electrodes. Considering the position of the virtual anode 108 relative to electrodes E5 and E13, it can be seen that the electrode configuration algorithm 120 explained above has been operated in an associated external device (e.g., clinician programmer 50) to calculate how the anode current +A should be distributed between the electrodes so as to optimally form the virtual anode at the desired location. Specifically, the electrode configuration algorithm 120 has calculated that electrode E13 should receive 75% of the anode current +A, while electrode E5 receives the remaining 25%. Note that the use of the electrode configuration algorithm 120 is not strictly necessary. Alternatively, the user can manually select to use electrodes E13 and E5 as anode electrodes, and can manually select to split the anode current between them at 75% and 25%, for example using Figure 6 GUI 64.

[0075] In any case, the resulting waveform at the electrodes is formed as before, with the first pulse 130 having a monophasic pulse 132 and a passive charge recovery period 134, and the interleaved second pulse 140 having a monophasic pulse 142 and a passive charge recovery period 144. The only difference is the resulting amplitude of the pulse at the activation electrode.

[0076] As previously discussed, the use of the described waveforms is believed to be particularly useful when providing therapeutic sub-perceptual stimulation at lower frequencies. However, the use of the disclosed waveforms is not so limited. For example, the disclosed waveforms may be used during an optimal point search, as previously described with reference to Figure 7 and Figure 8In addition, the use of the disclosed waveforms is not limited to sub-perceptual stimulation or any particular frequency or pulse width. Instead, the waveforms may be used more generally to provide suprasensory stimulation. In fact, for the reasons described above, the use of the disclosed waveforms to provide suprasensory stimulation may be particularly useful during sweet spot searches. The disclosed waveforms (which emulate the function of an actively driven biphasic waveform) Fig.10 )) can be used in other stimulation contexts where biphasic waveforms have traditionally been used.

[0077] Fig.17 shows that it can be used to form a single-phase pulse followed by passive charge recovery. Figures 11 to 16 An optional aspect of the GUI 64 of the clinician programmer 50 for waveforms of the present invention has been included to allow the clinician to select the option of forming a pulse whose stimulation parameters are otherwise specified (e.g., using interfaces 84 and 86) as a biphasic pulse (150) (e.g., as Fig.10 ) or is provided as a monophasic pulse (152) using passive charge recovery (e.g. Fig.11 140). If option 150 is selected, the software 66 will take the input amplitude, pulse width, and frequency information, as well as the activated electrodes, their polarity, and the current fraction (X%), to automatically derive a biphasic waveform with actively driven phases 30a and 30b, as previously explained. Once derived, the stimulation parameters representing this waveform can be sent from the clinician programmer 50 to the IPG or ETS for execution by the stimulation circuitry. If option 152, which is most relevant here, is selected, the software 66 will take those same parameters and automatically derive a waveform with first and second pulses 130 and 140 of opposite polarity, wherein each of the pulses 130 and 140 has an actively driven monophasic pulse 132 and 142 followed by a passive charge recovery pulse 134 and 144, as previously explained. This is true even if the input stimulation parameters (e.g., A, PW, F) do not themselves independently specify interleaved first and second pulses. If necessary, the software 66 can derive these waveforms in a single or multiple (e.g., two) timing channels, as previously explained. Once derived, stimulation parameters representing this waveform may be sent from the clinician programmer 50 to the IPG or ETS for execution by the stimulation circuitry. Although not shown, the GUI 64 may have a plurality of functions for implementing the stimulation parameters previously described in Figures 12 to 16 For example, other options may allow the amplitude and pulse width of the monophasic pulses 132 and 142 to be separately customized (e.g., Fig.14 and Fig.15 ), or adjusting the relative timing of pulses 130 and 140 ( Fig.12 and Fig.13 ).

[0078] Various aspects of the disclosed technology, including programs (such as software program 66) that may be implemented in an IPG or ETS, or that may be implemented in an external device (such as a clinician programmer or external controller), may be formulated and stored as instructions in a computer-readable medium associated with such a device, such as a magnetic, optical, or solid-state memory. The computer-readable medium with such stored instructions may also include a device that can be read by a clinician programmer or external controller, such as in a memory stick or removable disk, and can be provided to the IPG or ETS wirelessly. The computer-readable medium may reside elsewhere. For example, the computer-readable medium may be associated with a server or any other computer device, thereby allowing instructions to be downloaded to a clinician programmer system or external controller or to the IPG or ETS, for example, via the Internet.

[0079] Note that some of the applications from which the present disclosure claims priority relate to concepts related to the disclosed waveforms (e.g., selecting optimal stimulation parameters, and stimulation parameters that induce subperception at lower frequencies in particular). The techniques in the present disclosure may also be used in the context of these priority applications.

Claims

1. A stimulator device comprising: a plurality of electrode nodes, each electrode node configured to couple to one of a plurality of electrodes configured to contact tissue of a patient; as well as stimulation circuitry configured by stimulation parameters to provide a repeating sequence of interleaved first pulses and second pulses at at least two of the electrode nodes to create a stimulation current through tissue of the patient via the first pulses and the second pulses, wherein, at a first electrode node among the at least two electrode nodes, each first pulse comprises a first single-phase pulse of a first polarity and a first passive charge recovery pulse of a second polarity opposite to the first polarity, the first passive charge recovery pulse being configured to recover charge stored during the first single-phase pulse, and wherein, at the first electrode node, each second pulse comprises a second single-phase pulse of the second polarity and a second passive charge recovery pulse of the first polarity, the second passive charge recovery pulse being configured to recover the charge stored during the second single-phase pulse, The first single-phase pulse and the second single-phase pulse are charge balanced at the first electrode node.

2. A stimulator device according to claim 1, wherein the first passive charge recovery pulse is immediately followed by the first monophasic pulse in the first pulse at the first electrode node, and wherein the second passive charge recovery pulse is immediately followed by the second monophasic pulse in the second pulse at the first electrode node.

3. A stimulator device according to claim 1 or 2, wherein the first monophasic pulse has a first amplitude and a first pulse width, and wherein the second monophasic pulse has a second amplitude and a second pulse width.

4. A stimulator device according to claim 3, wherein the first amplitude and the second amplitude are equal, and wherein the first pulse width and the second pulse width are equal.

5. A stimulator device according to claim 1 or 2, wherein the stimulation circuit system includes one or more digital-to-analog converters (DACs), and the digital-to-analog converters are configured to actively drive the first monophasic pulse and the second monophasic pulse at the first electrode node.

6. A stimulator device according to claim 5, wherein the stimulation circuit system includes a plurality of passive recovery switches each coupled between one of the electrode nodes and a reference potential, wherein the first passive charge recovery pulse and the second passive charge recovery pulse are formed by closing the passive recovery switch coupled to the first electrode node, wherein the one or more DACs are not configured to actively drive the first passive charge recovery pulse and the second passive charge recovery pulse.

7. A stimulator device according to claim 5, wherein the one or more DACs include one or more positive DACs (PDACs) configured to source current and one or more negative DACs (NDACs) designed to sink current, wherein the first single-phase pulse is actively driven by at least one of the one or more PDACs at the first electrode node, and wherein the second single-phase pulse is actively driven by at least one of the one or more NDACs at the first electrode node.

8. A stimulator device according to claim 1 or 2, wherein the second pulse is centered in time relative to the first pulse at the first electrode node.

9. A stimulator device according to claim 1 or 2, in, at a second electrode node of the at least two electrode nodes, each first pulse comprises a third single-phase pulse of the second polarity and a third passive charge recovery pulse of the first polarity, the third passive charge recovery pulse being configured to recover charge stored during the third single-phase pulse, Wherein, at the second electrode node, each second pulse includes a fourth single-phase pulse of the first polarity and a fourth passive charge recovery pulse of the second polarity, and the fourth passive charge recovery pulse is configured to recover the charge stored during the fourth single-phase pulse.

10. A stimulator device according to claim 9, wherein the first monophasic pulse and the third monophasic pulse coincide in time, wherein the second monophasic pulse and the fourth monophasic pulse coincide in time, wherein the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time.

11. A stimulator device according to claim 9, further comprising a housing for housing the stimulation circuit system, wherein the housing is conductive and includes one electrode of the plurality of electrodes, wherein the second electrode node comprises an electrode node coupled to the conductive housing.

12. A stimulator device according to claim 1 or 2, wherein the interval period in which no stimulation current flows is between (i) the first monophasic pulse and the first passive charge recovery pulse in each first pulse, and (ii) the second monophasic pulse and the second passive charge recovery pulse in each second pulse.

13. A stimulator device according to claim 1 or 2, wherein the first pulse is emitted at the first electrode node at a first frequency, and wherein the second pulse is emitted at the first electrode node at the first frequency.

14. A stimulator device according to claim 1 or 2, wherein each electrode node is coupled to its associated electrode through a DC blocking capacitor.

15. A system comprising: a stimulator device including a plurality of electrode nodes, each electrode node configured to couple to one of a plurality of electrodes configured to contact tissue of a patient; as well as An external device for programming the stimulator device, comprising a non-transitory computer-readable medium containing a software program, wherein the software program, when executed on the external device, is configured to: presenting a graphical user interface (GUI) on the external device, receiving at the (GUI) stimulation parameters of pulses to be generated at at least two of the electrode nodes in the stimulator device, automatically deriving a waveform based on the stimulation parameters, wherein the waveform includes staggered first pulses and second pulses at the at least two electrode nodes, wherein in the automatically derived waveform, at a first electrode node of the at least two electrode nodes, each first pulse comprises a first monophasic pulse of a first polarity followed by a first passive charge recovery pulse configured to recover charge stored during the first monophasic pulse, and wherein in the automatically derived waveform, at the first electrode node, each second pulse comprises a second monophasic pulse of a second polarity opposite to the first polarity followed by a second passive charge recovery pulse configured to recover charge stored during the second monophasic pulse, The first single-phase pulse and the second single-phase pulse are charge balanced at the first electrode node.

16. The system of claim 15, wherein the stimulation parameters do not independently specify the interleaved first and second pulses.

17. The system according to claim 15 or 16, wherein in the automatically derived waveform, at a second electrode node of the at least two electrode nodes, each first pulse comprises a third monophasic pulse of the second polarity followed by a third passive charge recovery pulse configured to recover charge stored during the third monophasic pulse, Wherein in the automatically derived waveform, at the second electrode node, each second pulse comprises a fourth monophasic pulse of the first polarity followed by a fourth passive charge recovery pulse configured to recover charge stored during the second monophasic pulse.

18. The system of claim 17, wherein the first monophasic pulse and the third monophasic pulse coincide in time, and wherein the second monophasic pulse and the fourth monophasic pulse coincide in time.

19. The system of claim 18, wherein the first passive charge recovery pulse and the third passive charge recovery pulse coincide in time, and wherein the second passive charge recovery pulse and the fourth passive charge recovery pulse coincide in time.

20. The system of claim 15 or 16, wherein the software program, when executed on the external device, is further configured to transmit the derived waveform to the stimulator device to generate pulses at the at least two of the electrode nodes.

21. The system of claim 15 or 16, wherein the GUI includes a user selectable option to automatically derive the waveform based on the stimulation parameters.

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