Patent Publication Number: US-2019192857-A1

Title: Techniques for current steering directional programming in a neurostimulation system

Description:
RELATED APPLICATIONS DATA 
     The present application is a continuation of U.S. application Ser. No. 14/200,702, filed Mar. 7, 2014, which claims the benefit under 35 U.S.C. § 119 to U.S. Provisional Application Ser. No. 61/801,561, filed Mar. 15, 2013 and U.S. Provisional Application Ser. No. 61/923,137, filed Jan. 2, 2014, all of which applications are all incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present inventions relate to tissue stimulation systems, and more particularly, to user interface for automated programming of leads of neurostimulation systems. 
     BACKGROUND OF THE INVENTION 
     Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. Pacemakers and Implantable Cardiac Defibrillators (ICDs) have proven highly effective in the treatment of a number of cardiac conditions (e.g., arrhythmias). Spinal Cord Stimulation (SCS) systems have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of tissue stimulation has begun to expand to additional applications, such as angina pectoralis and incontinence. Deep Brain Stimulation (DBS) has also been applied therapeutically for well over a decade for the treatment of refractory chronic pain syndromes, and DBS has also recently been applied in additional areas, such as movement disorders and epilepsy. Further, in recent investigations, Peripheral Nerve Stimulation (PNS) systems have demonstrated efficacy in the treatment of chronic pain syndromes and incontinence, and a number of additional applications are currently under investigation. Furthermore, Functional Electrical Stimulation (FES) systems, such as the Freehand system by NeuroControl Corporation, Cleveland, Ohio, have been applied to restore some functionality to paralyzed extremities in spinal cord injury patients. 
     These implantable neurostimulation systems typically include one or more electrode carrying stimulation leads, which are implanted at the desired stimulation site, and a neurostimulator (e.g., an implantable pulse generator (IPG)) implanted remotely from the stimulation site, but coupled either directly to the stimulation lead(s) or indirectly to the stimulationleads) via a lead extension. The neurostimulation system may further include an external control device in the form of a remote control to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters, 
     Electrical stimulation energy may be delivered from the neurostimulator to the electrodes in the form of an electrical pulsed waveform. Thus, stimulation energy may be controllably delivered to the electrodes to stimulate neural tissue. The combination of electrodes used to deliver electrical pulses to the targeted tissue constitutes an electrode combination, with the electrodes capable of being selectively programmed to act as anodes (positive), cathodes (negative), or left off (zero). In other words, an electrode combination represents the polarity being positive, negative, or zero. Other parameters that may be controlled or varied include the amplitude, width, and rate of the electrical pulses provided through the electrode array. Each electrode combination, along with the electrical pulse parameters, can be referred to as a “stimulation parameter set.” 
     With some related art neurostimulation systems, and in particular, those with independently controlled current or voltage sources, the distribution of the current to the electrodes (including the case where the neurostimulator acts as an electrode) may be varied, such that the current is supplied via numerous different electrode configurations. However, the electrodes of different configurations may provide current or voltage in different relative percentages of positive and negative current or voltage to create different electrical current distributions (i.e., fractionalized electrode combinations) 
     As briefly discussed above, a remote control can be used to instruct the neurostimulator to generate electrical stimulation pulses in accordance with the selected stimulation parameters. Typically, the stimulation parameters programmed into the neurostimulator can be adjusted by manipulating controls on the remote control to modify the electrical stimulation provided by the neurostimulator system to the patient. Thus, in accordance with the stimulation parameters programmed by the remote control, electrical pulses can be delivered from the neurostimulator to the stimulation electrode(s) to stimulate or activate a volume of tissue in accordance with a set of stimulation parameters, and provide the desired efficacious therapy to the patient. The best stimulus parameter set will typically be one that delivers stimulation energy to the volume of tissue that must be stimulated in order to provide the therapeutic benefit (e.g., treatment of pain), while minimizing the volume of non-target tissue that is stimulated. 
     However, the number of electrodes that are available, combined with the ability to generate a variety of complex stimulation pulses, presents a huge selection of stimulation parameter sets to the clinician or patient. For example, if the neurostimulation system to be programmed has an array of sixteen electrodes, millions of stimulation parameter sets may be available for programming into the neurostimulation system. Today, neurostimulation systems may include up to thirty-two electrodes, thereby exponentially increasing the number of stimulation parameter sets available for programming. 
     To facilitate selection among the large number of potential stimulation parameter sets, clinicians generally program the neurostimulator through a computerized programming system. The programming system can be a self-contained hardware/software system, or can be defined predominantly by software running on a standard personal computer (PC). The PC or custom hardware may actively control the characteristics of the electrical stimulation generated by the neurostimulator to allow the optimum stimulation parameters to be determined based on patient feedback (or other data), and to subsequently program the neurostimulator and optionally the remote control, with the optimum stimulation parameter set(s). 
     The Bionic Navigator®, available from Boston Scientific Neuromodulation Corporation, Valencia, Calif., is a related art computerized programming system for SCS. The Bionic Navigator® is a software package that operates on a suitable PC, and allows clinicians to program stimulation parameters into an external handheld programmer (referred to as a remote control). Each set of stimulation parameters, including fractionalized current distribution to the electrodes (as percentage cathodic current, percentage anodic current, or off), may be stored in both the Bionic Navigator® and the remote control, and combined into a stimulation program that can then be used to stimulate multiple regions within the patient. 
     Prior to creating the stimulation programs, the Bionic Navigator® may be operated by a clinician in a “manual mode” to manually select the percentage cathodic current and percentage anodic current flowing through the electrodes, or may be operated by the clinician in an “automated mode” to electrically “steer” the current along the implanted leads in real-time using a directional input device as an integral part of the user interface (e.g., joystick, button pad, group of keyboard arrow keys, and/or similar or equivalent controls), thereby facilitating the clinician&#39;s attempts to determine preferable or e most efficacious stimulation parameter sets that can then be stored and eventually combined into stimulation programs. The steering depends on the type of leads, the number of leads, and the arrangement of the electrodes implanted. Once a polarity and the amplitude (either as an absolute or a percentage) for the current or voltage on an active electrode is selected in a typical computerized programming system, the polarity and amplitude value associated with the electrodes may be presented on a display screen so as to be viewable by the user. 
     Despite the fact that computerized programming systems have been used to speed up the programming process, programming electrical stimulation systems using present-day computerized programming systems are relatively time-consuming. In the automated or current steering mode, the clinician manipulates the directional input device in pre-defined increments to adjust a current stimulation field generated due to the realignment of the stimulation parameters, such as amplitude of the current associated with the electrodes, from one preset value to the next preset value. If the difference between the desired preset value and the existing preset value is large, then the number of manipulations of the input directional device may be high, which delays the process of selecting optimized stimulation parameter settings. 
     Also for the automated or current steering mode, the inherent limitation of directional input device restricts the user&#39;s ability to maneuver the device minutely or with complete freedom, and thus the user may fail to benefit from preferable or optimal stimulation settings. 
     There, thus, remains a need to provide a simplified and efficient directional current steering programming of the electrodes of neurostimulation system. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present inventions, an external control device for use with a two-dimensional array of electrodes implanted within tissue and a neurostimulator capable of delivering electrical stimulation energy to the electrodes to create a volume of activation is provided. The external control device comprises a user interface including a current steering initiation control element and a current steering direction control element (e.g., a knob or wheel) capable of being rotated about an axis, in an optional embodiment, the user interface includes a display screen configured for displaying the direction control element as a graphical element configured for being rotated by a pointing element. 
     The external control device further comprises a controller/processor configured for, in response to actuation of the initiation control element, generating a series of different combinations of the electrodes (e.g., fractionalized electrode combinations) in a manner that the volume of activation gradually translates in a specific direction when the electrical stimulation energy is delivered to the different electrode combinations. In one embodiment, the controller/processor is configured for translating an ideal multipole relative to the electrode array in response actuation of the initiation control element, in which case, the different electrode combinations emulate the translation of the ideal multipole. In an optional embodiment, the user interface includes a display screen configured for displaying the volume of activation relative to the electrode array, in which case, the controller/processor will be configured for estimating the volume of activation based on the different electrode combinations. 
     The controller/processor is further configured for, in response to rotation of the direction control element about the axis, defining the specific direction in which the volume of activation is translated. In one embodiment, the controller/processor is configured for defining the specific direction in response to the actuation of the direction control element prior to the generation of the series of different electrode combinations. In another embodiment, the controller/processor is configured for defining the specific direction in response to the actuation of the direction control element while the series of different electrode combinations are being generated. 
     The direction control element may include an arrow that indicates the specific direction in which the volume of activation is translated. The direction control element may be capable of being selectively rotated about the axis in a clockwise direction and a counterclockwise direction, in which case, the controller/processor will be configured for, in response to rotation of the direction control element about the axis in the clockwise direction, adjusting the direction in which the volume of activation is translated in a first direction, and in response to rotation of the direction control element about the axis in the counterclockwise direction, adjusting the direction in which the volume of activation is translated in a second direction opposite to the first direction. 
     The external control device further comprises output circuitry (e.g., telemetry circuitry) configured for transmitting the different electrode combinations to the neurostimulator. The external control device may comprise a housing containing the user interface, controller/processor, and output circuitry. 
     In an optional embodiment, the user interface further includes a current steering speed. control element, in which case, the controller/processor is configured for, in response to actuation of the speed control element, modifying the manner in which the electrode combinations are generated to adjust the speed at which the volume of activation translates. The speed control element may have an acceleration sub-element and a deceleration sub-element, in which case, the controller/processor may be configured for, in response to actuation of the acceleration sub-element, modifying the manner in which the electrode combinations are generated to increase the speed at which the volume of activation translates, and in response to actuation of the deceleration sub-element, modifying the manner in which the electrode combinations are generated to decrease the speed at which the volume of activation translates. In another optional embodiment, the user interface further includes a current steering time control element, in which case, the controller/processor is configured for, in response to actuation of the time control element, generating the series of different combinations of the electrodes for a specified time period, such that the translation of the volume of activation ceases when the time period has elapsed, 
     In accordance with a second aspect of the present inventions, a neurostimulation system is provided. The neurostimulation system comprises at least one neurostimulation lead configured for being implanted within tissue. The neurostimulationleads) carries a plurality of electrodes capable of being arranged in a two-dimensional pattern. The neurostimulation system further comprises a neurostimulator configured for delivering electrical stimulation energy to the electrodes to create a volume of activation. 
     The neurostimulation system further comprises an external control device including a current steering direction control element (e.g., a knob or wheel) capable of being rotated about an axis. In an optional embodiment, the user interface includes a display screen configured for displaying the direction control element as a graphical element configured for being rotated by a pointing element. The external control device is configured for prompting the neurostimulator to deliver the electrical stimulation energy to the electrodes in a manner that gradually translates the volume of activation in a specific direction, and for defining the specific direction in which the volume of activation is translated in response to rotation of the direction control element about the axis. In one embodiment, the external control device is configured for defining the specific direction in response to the actuation of the direction control element prior to the generation of the series of different electrode combinations. In another embodiment, the external control device is configured for defining the specific direction in response to the actuation of the direction control element while the series of different electrode combinations are being generated. 
     The direction control element may include an arrow that indicates the specific direction in which the volume of activation is translated. The direction control element may be capable of being selectively rotated about the axis in a clockwise direction and a counterclockwise direction, in which case, the external control device will be configured for, in response to rotation of the direction control element about the axis in the clockwise direction, adjusting the direction in which the volume of activation is translated in a first direction, and in response to rotation of the direction control element about the axis in the counterclockwise direction, adjusting the direction in which the volume of activation is translated in a second direction opposite to the first direction. In an optional embodiment, the external control device is configured for adjusting the speed at which the volume of activation translates. In another optional embodiment, the external control device is configured for defining a time period and automatically ceasing translation of the volume of activation when the time period has elapsed. 
     In accordance with a third aspect of the present invention, another external control device for use with a two-dimensional array of electrodes implanted within tissue and a neurostimulator capable of delivering electrical stimulation energy to the electrodes to create a volume of activation is provided. The external control device comprises a user interface including a current steering speed control element. In an optional embodiment, the user interface includes a display screen configured for displaying the current steering speed control element as a graphical element configured for being rotated by a pointing element. 
     The external control device further comprises a controller/processor configured for generating a series of different combinations (e.g., fractionalized electrode combinations) of the electrodes in a manner that the volume of activation gradually translates in a specific direction when the electrical stimulation energy is delivered to the different electrode combinations, and in response to actuation of the speed control element, modifying the manner in which the electrode combinations are generated to adjust the speed at which the volume of activation translates. 
     The external control device further comprises an output circuitry (e.g., telemetry circuitry) configured for transmitting the different electrode combinations to the neurostimulator. The external control device may comprise a housing containing the user interface, controller/processor, and output circuitry. 
     In an optional embodiment, the user interface further includes a current steering initiation control element and a current steeling direction control element, in which case, the controller/processor will be configured for, in response to actuation of the initiation control element, generating the series of different electrode combinations in a manner that the volume of activation gradually translates in a specific direction when the electrical stimulation energy is delivered to the different electrode combinations, and in response to actuation of the direction control element, defining the specific direction in which the volume of activation is translated. 
     In one embodiment, the controller/processor is configured for translating an ideal multipole relative to the electrode array in response actuation of the initiation control element, in which case, the different electrode combinations emulate the translation of the ideal multipole. In an optional embodiment, the user interface includes a display screen configured for displaying the volume of activation relative to the electrode array, in which case, the controller/processor will be configured for estimating the volume of activation based on the different electrode combinations. 
     The speed control element may have an acceleration sub-element and a deceleration sub-element, in which case, the controller/processor may be configured for, in response to actuation of the acceleration sub-element, modifying the manner in which the electrode combinations are generated to increase the speed at which the volume of activation translates, and in response to actuation of the deceleration sub-element, modifying the manner in which the electrode combinations are generated to decrease the speed at which the volume of activation translates. In another optional embodiment, the user interface further includes a current steering time control element, in which case, the controller/processor is configured for, in response to actuation of the time control element, generating the series of different combinations of the electrodes for a specified time period, such that the translation of the volume of activation ceases when the time period has elapsed. 
     In accordance with a fourth aspect of the present inventions, another neurostimulation system is provided. The neurostimulation system comprises at least one neurostimulation lead configured for being implanted within tissue. The neurostimulation lead(s) carries a plurality of electrodes capable of being arranged in a two-dimensional pattern. The neurostimulation system further comprises a neurostimulator configured for delivering electrical stimulation energy to the electrodes to create a volume of activation. 
     The neurostimulation system further comprises an external control device configured for prompting the neurostimulator to deliver the electrical stimulation energy to the electrodes in a manner that gradually translates the volume of activation in a specific direction, and for adjusting the speed at which the volume of activation translates, which may be performed in response to a user input. In an optional embodiment, the external control device is further configured for defining the specific direction in which the volume of activation is translated in response to a use input. In another optional embodiment, the external control device is further configured for defining a time period and automatically ceasing translation of the volume of activation when the ti me period has elapsed. 
     Other and further aspects and features of the disclosed embodiments will be evident from reading the following detailed description of the embodiments, which are intended to illustrate, not limit, the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate the design and utility of various embodiments of the present invention, in which similar elements are referred to by common reference numerals. In order to better appreciate how the above-disclosed and other advantages and objects of the various embodiments are obtained; a more particular explanation is provided below with reference to specific embodiments thereof, which are illustrated in the accompanying drawings. However, these drawings depict only some embodiments of the invention, and are not therefore to be considered limiting of its scope. A brief description of the drawings is provided below: 
         FIG. 1  is a plan view of a Spinal Cord Stimulation (SCS) system constructed in accordance with one embodiment of the present disclosure; 
         FIG. 2  is a perspective view of the arrangement of the SCS system of  FIG. 1  with respect to a patient; 
         FIG. 3  is a profile view of an implantable pulse generator (IPG) and percutaneous leads used in the SCS system of  FIG. 1 ; 
         FIG. 4  is front view of a remote control (RC) used in the SCS system of  FIG. 1 ; 
         FIG. 5  is a block diagram of the internal components of the RC of  FIG. 4 ; 
         FIG. 6  is a block diagram of the internal components of a clinician&#39;s programmer (CP) used in the SCS system of FIG,  1 ; 
         FIG. 7  is a plan view of an exemplary user interface of the CP of  FIG. 6 , for automated current steering programming of the IPG of  FIG. 3 , in accordance with a first embodiment of the present disclosure; and 
         FIG. 8  is the user interface of  FIG. 7 , in accordance with a second embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is provided in the context of Spinal Cord Stimul anon (SCS) systems. However, it is to be understood that, while the invention lends itself well to applications in SCS, the invention, in its broadest aspects, may not be so limited. Rather, the invention may be used with any type of implantable electrical circuitry used to stimulate tissue. For example, the present invention may be used as part of a pacemaker, a defibrillator, a cochlear stimulator, a retinal stimulator, a stimulator configured to produce coordinated :limb movement, a cortical stimulator, a deep brain stimulator, peripheral nerve stimulator, micro-stimulator, and/or in any other neural stimulator configured to treat urinary incontinence, sleep apnea, shoulder sublaxation, headache, etc. 
       FIG. 1  shows an exemplary SCS system  10  that generally includes multiple (in this case, two) implantable neurostimulation leads  12 , an Implantable Pulse Generator (IPG)  14 , an external Remote Controller (RC)  16 , a clinician&#39;s programmer (CP)  18 , an external trial stimulator (ETS)  20 , and an external charger  22 . 
     The IPG  14  is physically connected via one or more percutaneous lead extensions  24  to the neurostimulation leads  12 , which carry multiple electrodes  26  arranged in an array. In the illustrated embodiment, the neurostimulation leads  12  are percutaneous leads, and to this end, the electrodes  26  are arranged in-line along the neurostimulation leads  12 . Depending upon the desired therapy, the electrodes  26  may be implanted within the tissue in more than one dimension. Alternatively, a surgical paddle lead can be used in place of, or in addition to, the percutaneous leads. As will be described in further detail below, the IPG  14  includes pulse generation circuitry that delivers electrical stimulation energy in the form of a pulsed electrical waveform (i.e., a temporal series of electrical pulses) to the electrodes  26  in an electrode array in accordance with a set of stimulation parameters. 
     The ETS  20  may also be physically connected via the percutaneous lead extensions  28  and external cable  30  to the neurostimulation leads  12 . The ETS  20 , which has similar pulse generation circuitry as the IPG  14 , also delivers electrical stimulation energy in the form of a pulse electrical waveform to the electrodes  26 , in accordance with a set of stimulation parameters. A significant difference between the ETS  20  and the IPG  14  is that the ETS  20  is a non-implantable device that is used on a trial basis, after the neurostimulation leads  12  have been implanted and prior to implantation of the IPG  14 , to test the responsiveness of the stimulation that is to be provided. Thus, any functions described herein with respect to the IPG  14  can likewise be performed with respect to the ETS  20 . 
     The RC  16  may be used to telemetrically control the ETS  20  via a bi-directional RF communications link  32 . Once the IPG  14  and the neurostimulation leads  12  are implanted, the RC  16  may be used to telemetrically control the IPG  14  via a bi-directional RF communications link  34 . Such control allows the IPG  14  to be turned on or off and to be programmed with different stimulation parameter sets. The IPG  14  may also be operated to modify the programmed stimulation parameters to actively control the characteristics of the electrical stimulation energy output by the IPG  14 . As will be described in further detail below, the CP  18  provides clinician detailed stimulation parameters for programming the IPG  14  and the ETS  20  in the operating room and in follow-up sessions. 
     The CP  18  may perform this function by indirectly communicating with the IPG  14  or the ETS  20 , through the RC  16 , via an IR communications link  36 . Alternatively, the CP  18  may directly communicate with the IPG  14  or the ETS  20  via an RF communications link (not shown). The clinician detailed stimulation parameters provided by the CP  18  are also used to program the RC  16 , so that the stimulation parameters can be subsequently modified by operation of the RC  16  in a stand-alone mode (i.e., without the assistance of the CP  18 ). In an embodiment, the CP  18  may include a user interface, which has a current steering initiation control element and a current steering direction control element, which is capable of being rotated about an axis. 
     The external charger  22  is a portable device used to transcutaneously charge the IPG  14  via an inductive link  38 . For purposes of brevity, the details of the external charger  22  will not be described herein. Once the IPG  14  has been programmed, and its power source has been charged by the external charger  22  or otherwise replenished, the IPG  14  may function as programmed without the RC  16  or the CP  18  being present. 
     For purposes of brevity, the details of the IPG  14 , the ETS  20 , and the external charger  22  will not be described herein. Details of exemplary embodiments of these devices are disclosed in U.S. Pat. No. 6,895,280, which is expressly incorporated herein by reference in its entirety. 
     As shown in  FIG. 2 ., the neurostimulation leads  12  are implanted within the spinal column  42  of a patient  40 . A beneficial or even preferred placement of the neurostimulation leads  12  is adjacent, i.e., resting over, the spinal cord area to he stimulated. Due to the lack of space near the location where the neurostimulation leads  12  exit the spinal column  42 , the IPG  14  is generally implanted in a surgically made pocket, either in the abdomen or above the buttocks of the patient. The IPG  14  may also be implanted in other locations of the patient&#39;s body. The lead extensions  24  facilitate locating the IPG  14  away from the exit point of the neurostimulation leads  12 . As shown in the  FIG. 2 , the CP  18  communicates with the IPG  14  via the RC  16 . 
     Features of the neurostimulation leads  12  and the  11 PG  14  are briefly described below with reference to  FIG. 3 . One of the neurostimulation leads  12 ( 1 ) has eight electrodes  26  (labeled E 1 -E 8 ), and the other neurostimulation lead  12 ( 2 ) has eight electrodes  26  (labeled E 9 -E 16 ). The actual number and shape of leads and arrangement of electrodes may vary according to the intended application. The IPG  14  comprises an outer case  44  for housing the electronic and other components (described in further detail below). The outer case  44  is composed of an electrically conductive, biocompatible material, such as titanium, and forms a hermetically sealed compartment in which the internal electronics are protected from the body tissue and fluids. In some cases, the outer case  44  may serve as an electrode. The IPG  14  further comprises a connector  46  to which the proximal ends of the neurostimulation leads  12  mate in a manner that electrically couples the electrodes  26  to the internal electronics (described in further detail below) within the outer case  44 . To this end, the connector  46  includes one or more ports (two ports  48  for two percutaneous leads) for receiving the proximal end(s) of the neurostimulation leads  12 . In the case where the lead extensions  24  are used, the ports  48  may instead receive the proximal ends of such lead extensions  24 . 
     The IPG  14  includes a battery and pulse generation circuitry that delivers the electrical stimulation energy in the form of a pulsed electrical waveform to the electrodes  26  in accordance with a set of stimulation parameters programmed into the IPG  14 . Such stimulation parameters may comprise electrode combinations, which define the electrodes that are activated as anodes (positive), cathodes (negative), and turned off (zero), percentage of stimulation energy assigned to each electrode (fractionalized electrode configurations), and electrical pulse parameters, which define the pulse amplitude (measured in milliamps or volts depending on whether the IPG  14  supplies constant current or constant voltage to the electrodes  26 ), pulse width (measured in microseconds), and pulse rate (measured in pulses per second). 
     Electrical stimulation will occur between two (or more) activated electrodes, one of which may be the IPG outer case  44 . Stimulation energy may be transmitted to the tissue in a monopolar or multipolar (e.g., bipolar, tripolar, etc.) fashion. Monopolar stimulation occurs if a selected one of the lead electrodes  26  is activated along with the outer case  44  of the IPG  14 , so that stimulation energy is transmitted between the selected electrode  26  and the outer case  44 . Bipolar stimulation occurs if two of the lead electrodes  26  are activated as anode and cathode, so that stimulation energy is transmitted between the selected electrodes  26 . For example, electrode E 3  on the first lead  12 ( 1 ) may be activated as an anode, at the same time that electrode E  11  on the second lead  12 ( 2 ) is activated as a cathode. Tripolar stimulation occurs if three of the lead electrodes  26  are activated, two as anodes and the remaining one as a cathode, or two as cathodes and the remaining one as an anode. For example, electrodes E 4  and E 5  on the first lead  12 ( 1 ) may be activated as anodes at the same time that electrode E 12  on the second lead  12 ( 2 ) is activated as a cathode. 
     The IPG  14  can individually control the magnitude of electrical current flowing through each of the electrodes. In this case, it is beneficial or even preferred to have a current generator, wherein individual current-regulated outputs from independent current sources for each electrode  26  may be selectively generated. Although this system may be beneficial or even optimal for reasons discussed above, other stimulators may be used with the invention, such as stimulators having voltage-regulated outputs. While individually programmable electrode  26  are beneficial or even optimal to achieve fine control, a single output source switched across electrodes  26  may also be used, although with less fine control in programming. Mixed current and voltage-regulated devices may also be used with the various embodiments. Further details of the structure and function of PPGs are provided more fully in U.S. Pat. Nos. 6,516,227 and 6,993,384, which are expressly incorporated herein by reference in their entireties. 
     Rather than an IPG, the SCS system  10  may alternatively utilize an implantable receiver-stimulator (not shown) connected to the neurostimulation leads  12 . In this case, the power source, e.g., a battery, for powering the implanted receiver, as well as control circuitry to command the receiver-stimulator, is contained in an external controller inductively coupled to the receiver-stimulator via an electromagnetic link. Data/power signals are transcutaneously coupled from a cable-connected transmission coil placed over the implanted receiver-stimulator. The implanted receiver-stimulator receives the signal and generates the stimulation in accordance with the control signals. 
       FIG. 4  shows one exemplary embodiment of an RC  16 . As previously discussed, the RC  16  is capable of communicating with the IPG  14 , the CP  18 , or the ETS  20 . The RC  16  comprises a casing  50 , which houses internal components (including a printed circuit board (PCB)), as well as a lighted display screen  52  and a button pad  54  provided at the exterior of the casing  50 . The display screen  52  is a lighted flat panel display screen, and the button pad  54  comprises a membrane switch with metal domes positioned over a flex circuit, and a keypad connector connected directly to a PCB. However, embodiments are intended to cover any other applicable structures. For example, in another embodiment, the display screen  52  has touch screen capabilities. 
     The button pad  54  can include multiple buttons  56 ,  58 ,  60 , and  62 , which allow the IPG  14  to be turned ON and OFF, provide for the adjustment or setting of stimulation parameters within the IPG  14 , and provide for selection between screens. The button  56  serves as an ON/OFF button that can be actuated to turn the IPG  14  ON and OFF. The button  58  serves as a select button that allows the RC  16  to switch between screen displays and/or parameters. The buttons  60  and  62  serve as up/down buttons that can be actuated to increment or decrement any of stimulation parameters of the pulse generated by the IPG  14 , including pulse amplitude, pulse width, and pulse rate. For example, the selection button  58  can be actuated to place the RC  16  in a “Pulse Amplitude Adjustment Mode,” during which the pulse amplitude can be adjusted via the up/down buttons  60 ,  62 , a “Pulse Width Adjustment Mode,” during which the pulse width can be adjusted via the up/down buttons  60 ,  62 , and a “Pulse Rate Adjustment Mode,” during which the pulse rate can be adjusted via the up/down buttons  60 ,  62 . Alternatively, the dedicated up/down buttons  60 ,  62  can be provided for each stimulation parameter. The buttons  56 ,  58 ,  60  and  62  are used for the manual adjustment mode but may be customized to operate in automatic current steering mode. Rather than using up/down buttons  60 , any other type of actuator, such as a dial, slider bar, or keypad, can be used to increment or decrement the stimulation parameters in the manual mode of programming the IPG  14 , where the stimulation parameters like electrode selection are adjusted to deliver beneficial or even optimal therapy through the selected electrodes. Further details of the functionality and internal components of the RC  16  are disclosed in U.S. Pat. No. 6,895,280, which has previously been incorporated herein by reference. 
     The internal components of an exemplary RC  16  are described below with reference to  FIG. 5 . The RC  16  generally includes a processor  64  (e.g., a microcontroller), a programmable memory  66  that stores an operating program for execution by the processor  64 , as well as stimulation parameter sets in a navigation table (described below), a telemetry circuitry  68  for outputting stimulation parameters to the IPG  14  and receiving status information from the IPG  14 , and an input/output circuitry  70  for receiving stimulation control signals from the button pad  54  and transmitting status information to the display screen  52  (shown in  FIG. 4 ). As well as controlling other functions of the RC  16 , which will not be described herein for purposes of brevity, the processor  64  generates new stimulation parameter sets in response to the user operation of the button pad  54 . These new stimulation parameter sets are then transmitted to the IPG  14  via the telemetry circuitry  68 . Further details of the functionality and internal components of the RC  16  are disclosed in U.S. Pat. No. 6,895,280, which has previously been incorporated herein by reference. 
     As briefly discussed above, the CP  18  greatly simplifies the programming of multiple electrode combinations, allowing the user (e.g., the physician or clinician) to readily determine the desired stimulation parameters to be programmed into the IPG  14 , as well as the RC  16 . Thus, modification of the stimulation parameters in the programmable memory  66  of the RC  16  as well in the IPG  14  after implantation is performed by a user using the CP  18 , which can directly communicate with the IPG  14  or indirectly communicate with the IPG  14  via the RC  16 . 
     As shown in  FIG. 2 , the overall appearance of the CP  18  can be that of a laptop personal computer (PC), and in fact, may be implanted using a PC that has been appropriately configured to include a directional programming device and programmed to perform the functions described herein. Thus, the programming methodologies can be performed by executing software instructions contained within the CP  18 . Alternatively, such programming methodologies can be performed using firmware or hardware. In any event, the CP  18  may actively control the characteristics of the electrical stimulation generated by the IPG  14  to allow the optimum stimulation parameters to be determined based on patient feedback, and for subsequently programming the IPG  14  with the optimum stimulation parameters. 
     The CP  18  includes a mouse  72 , a keyboard  74 , and a display screen  76  housed in a case  78 , to enable the user to perform the above operations. The display screen  76  is shown as a conventional screen in  FIG. 2 . However, embodiments can include other or additional elements to perform the above operations. For example, in addition to, or in lieu of, the mouse  72 , other directional programming devices may be used, such as a trackball, touchpad, or joystick. Alternatively, instead of being conventional, the display screen  76  may be a digitizer screen, such as a touchscreen (not shown), and may be used in conjunction with an active or passive digitizer stylus/finger touch. Further details discussing the use of a digitizer screen for programming are set forth in U.S. Provisional Patent Application Ser. No. 61/561,760, entitled “Technique for Linking Electrodes Together during Programming of Neurostimulation System,” which is expressly incorporated herein by reference in its entirety. 
     As shown in FIG,  6 , the CP  18  generally includes a controller/processor  80  (e.g., a central processor unit (CPU)) and a memory  82  that stores a stimulation programming package  84 , which can be executed by the controller/processor  80  to allow the user to program the IPG  14  and the RC  16 . The CP  18  further includes output circuitry  86  (e.g., via the telemetry circuitry of the RC  16 ) for downloading stimulation parameters to the IPG  14  and the RC  16 , and for uploading stimulation parameters already stored in the memory  66  of the RC  16 , via the telemetry circuitry  68  of the RC  16 . In addition, a user input device  88 , such as the mouse  72  or the keyboard  74 , is attached to provide user commands. Although the controller/processor  80  is shown in  FIG. 6  as a single device, the processing functions and controlling functions can be performed by a separate controller and a processor. 
     Execution of the programming package  84  by the controller/processor  80  provides a multitude of display screens  90  that can be navigated through. These display screens  90  allow the clinician, among other functions, to select or enter patient profile information (e.g., name, birth date, patient identification, physician, diagnosis, and address), enter procedure information (e.g., programming/follow-up, implant trial system, implant IPG, implant IPG and lead(s), replace IPG, replace IPG and leads, replace or revise leads, explant, etc.), generate a pain map of the patient, define the configuration and orientation of the leads, initiate and control the electrical stimulation energy output by the neurostimulation leads  12 , and select and program the IPG  14  with stimulation parameters in both a surgical setting and a clinical setting. Further details discussing the above-described CP functions are disclosed in U.S. patent application Ser. No. 12/501,282, entitled “System and Method for Converting Tissue Stimulation Programs in a Format Usable by an Electrical Current Steering Navigator,” and U.S. patent application Ser. No. 12/614,942, entitled “System and Method for Determining Appropriate Steering Tables for Distributing Stimulation Energy Among Multiple Neurostimulation Electrodes,” which are expressly incorporated herein by reference. 
     As one example, and with reference to  FIG. 7 , an exemplary programming screen  100  generated by the CP  18  to allow a user to program the IPG  14  will now be described. The programming screen  100  includes various control elements described below that can be actuated to perform various control functions. 
     A pointing element may be used to graphically touch the control elements to perform the actuation event. Therefore, in the case of the digitizer touch screen, the pointing element will be a physical pointing element (e.g., a finger or active or passive stylus) that can be used to tap the screen on a respective graphical control element, or otherwise brought into proximity with respect to the graphical control element. In case of a conventional screen, the pointing element will be a virtual pointing element (e.g., a cursor) that can be used to graphically click on the respective control element. 
     The programming screen  100  includes stimulation on/off control  104  that can be alternately actuated to initiate or cease the delivery of electrical stimulation energy from the IPG  14  via the electrodes  26 . The programming screen  100  further includes various stimulation parameter controls that can be operated by the user to manually adjust stimulation parameters for a selected electrode combination. In particular, the programming screen  100  includes a pulse width adjustment control  106  (expressed in microseconds (μs)), a pulse rate adjustment control  108  (expressed in Hertz (Hz)), and a pulse amplitude adjustment control  110  (expressed in milli-amperes (mA)). Each of the controls  106 ,  108 ,  110  includes a first arrow that may be actuated to decrease the value of the respective stimulation parameter, and a second arrow that may be actuated to increase the value of the respective stimulation parameter. Further, each of the controls  106 ,  108 ,  110  may include a display to indicate the present value of the respective parameter. For example, the present value of the pulse width adjustment control is “80 μs”, the present value of the pulse rate adjustment control is “50 Hz” and the present value of pulse amplitude adjustment control is “15 mA”. 
     To enable a user to select individual electrodes, the programming screen  100  displays graphical representations of the neurostimulation leads  12 ′ including the electrodes  26 ′. Each electrode representation  26 ′ can take the form of a closed geometric figure, such as a rectangle, circle, ellipse, trapezoid etc. The electrode representations  26 ′ can be actuated with a physical pointing device, or otherwise clicked with a virtual pointing device, multiple times to switch the corresponding active electrodes  26  between an on-state, which includes either positive polarity (anode) or a negative polarity (cathode), and an off-state. In essence, the electrode representations  26 ′ operate as the graphical control elements, the actuations of which prompt the controller/processor  80  to assign the polarities to the selected electrodes  26 . In alternative embodiments, control elements separate from the electrode representations  26 ′ may be used to change the polarity of the selected electrodes  26 . 
     To enable selection between a multipolar configuration and a monopolar configuration, the programming screen  100  also includes a multipoladmonopolar stimulation selection control  112 , which includes check boxes that can be alternately actuated by the user to selectively provide multipolar or monopolar stimulation. If a multipolar electrode arrangement is desired, at least one of the electrodes E 1 -E 16  will be selected as an anode (+), and at least one other of the electrodes E 1 -E 16  will be selected as a cathode (−). If a monopolar electrode arrangement is desired, none of the electrodes E 1 -E 16  will be selected as an anode (+), and thus the electrode representations  26 ′ can only be actuated to toggle the corresponding electrode  26  between a cathode (−) and off (0). 
     The programming screen  100  further includes an electrode-specific current adjustment control  114  that can be manipulated to independently vary stimulation amplitude values for the electrodes E 1 -E 16 . In particular, for each electrode selected to be activated as either a cathode or anode, the clinician can actuate the upper arrow of the control  114  to incrementally increase the absolute value of the stimulation amplitude of the selected electrode, and the clinician can actuate the lower arrow of the control  114  to incrementally decrease the absolute value of the stimulation amplitude of the selected electrode. The control  114  also includes an indicator that provides an alphanumeric indication of the stimulation amplitude currently assigned to the selected electrode. In an alternative embodiment, non-alphanumeric indicators, such as different colors, different color luminance, different patterns, different textures, different graphical objects, etc., can be used to indicate the stimulation amplitude presently assigned to the selected electrodes, as discussed in U.S. patent application Ser. No. 13/200,629, entitled ‘Neurostimulation System and Method for Graphically Displaying Electrode Stimulation Values,” which is expressly incorporated herein by reference in its entirety. 
     In addition, the stimulation amplitude values may be fractionalized electrical current values (i.e., percentage of electric current), such that the summation of values for each polarization is  100 . However, in alternative embodiments, the stimulation amplitude values may be normalized current or voltage values (e.g., 1-10), absolute current or voltage values (e.g., mA or V), etc. Furthermore, the stimulation amplitude values may be parameters that are a function of current or voltage, such as charge (current amplitude×pulse width) or charge injected per second (current amplitude×pulse width×rate (or period)). 
     In alternative embodiments, a stimulation amplitude adjustment control (not shown) may appear next to the electrode representations  26 ′ that has been actuated, as described in U.S. patent application Ser. No. 13/200,629, which has been previously incorporated herein by reference, or may be superimposed over the electrode representations  26 ′ that has been actuated, as described in U.S. Provisional Patent Application Ser. No. 61/486,141, entitled “Neurostimulation System with On-Effector Programmer Control,” which is expressly incorporated herein by reference in its entirety. In another embodiment, the stimulation amplitude values may be typed or written into a graphical data entry symbol associated with an electrode (e.g., adjacent, next to and/or superimposed over the electrode representations  26 ′). 
     The programming screen  100  facilitates automated current steering; for example, by allowing the user to switch between a manual mode using the electrode selection and current adjustment techniques described above and an automated current steering mode. The automated current steering mode can be implemented through techniques, such as, (1) an electronic trolling (“e-troll”) mode that quickly sweeps the electrode array using a limited number of electrode configurations to gradually move a cathode in bipolar stimulation, and (2) a Navigation programming mode that finely tunes and optimizes stimulation coverage for patient comfort using a wide number of electrode configurations, as described in U.S. Provisional Patent Application Ser. No. 61/576,924, entitled “Seamless Integration of Different Programming Modes for a Neurostimulator Programming System,” which is expressly incorporated herein by reference in its entirety. 
     These current steering techniques may be performed, e.g., using virtual target poles to steer the current within the electrode array, as described in U.S. Provisional Patent Application Ser. No. 61/452,965, entitled “Neurostimulation System for Defining a Generalized Virtual Multipole,” which is expressly incorporated herein by reference. Alternatively, steering tables may be utilized to execute these techniques and steer the current within the electrode array, as described in U.S. patent application Ser. No. 12/614,942, entitled “System and Method for Determining Appropriate Steering Tables for Distributing Stimulation Energy Among Multiple Neurostimulation Electrodes,” which is also expressly incorporated herein by reference. More pertinent to the present disclosure, the current steering programming is enabled through a current steering initiation control element “start” button  118  and a current steering direction control element “knob”  120  capable of being rotated about an axis. 
     The knob  120  includes a bi-directional arrow  122  positioned within the circumferential periphery of the knob  120 . The bi-directional arrow  122  representation enables exact visual indication of the direction, specified at that instant, in which the electric stimulation current is being steered, with respect to the axis of the leads  12  and the electrodes  26 . In an alternative embodiment, the exact direction of the steeling is visually highlighted by a higher luminance of the arrow head of the bi-directional arrow  122  that is aligned towards the direction in which the steering is specified by the user, as compared to the lumen intensity of the opposite arrow head of the bi-directional arrow  122 . 
     The programming screen  100  also includes graphical representations of a pair of single directional arrows  124 ,  126 , positioned and aligned along the outer circumferential periphery of the knob  120 . Alternatively, the arrows  124 ,  126  may be positioned inside the knob  120 . The arrows  124  and  126  are represented to be curved in opposite directions to each other, to indicate counter-clockwise and clockwise directions respectively. The arrows  124  and  126 , when actuated, emulate the functionality provided by rotating the knob  120 , in small increments. For example, when the arrow  124  is actuated, the knob  120  rotates in counter-clockwise direction and when the arrow  126  is actuated, the knob  120  rotates in clockwise direction, proportionate to the amount of actuation applied to the respective arrows. The arrows  124 ,  126  can be actuated in a single continuous or multiple discreet times to impart the knob  120 , with the desired degree of rotation. 
     Further, the programming screen  100  displays a two-dimensional graphical rendering of the leads  12 ″ relative to a graphical representation of the anatomical structure  200  that is preferably the stimulation target. The leads  12 ″ include the electrodes  26 ″. Each electrode representation  26 ′ may take the form of a closed geometric figure, such as a rectangle, circle, ellipse, trapezoid, etc. Based on the current stimulation parameter set, the controller/processor  80  computes an estimate of a resulting Volume of Activation (VOA)  202 , and generates display signals that prompt the display screen  76  to display a graphical representation of the VOA  202  with the graphical electrode array  26 ″ and graphical anatomical structure  200 . In the preferred embodiment, the graphical VOA  202  is superimposed over the graphical anatomical structure  200 . In response to actuation of the start button  118 , the controller/processor  80  is configured to steer current by generating a series of different combinations of the electrodes in a manner that the VOA  202  gradually translates in a specific direction when the electrical stimulation energy is delivered to the different electrode combinations. Further, the controller/processor  80  is configured for defining the specific direction of current steering in which the VOA  202  is translated, in response to rotation of the knob  120  about the axis, prior to the generation of the series of different electrode combinations. In an exemplary embodiment, the controller/processor  80  translates an ideal multipole relative to the electrodes  26  in response to actuation of the initiation control element  118  and the knob  120 , such that the different electrode combinations emulate the translation of the ideal multipole. 
     The programming screen  100  further includes a speed control button  144  with a positive sign (+&#39; and a speed control button  146  with a negative sign (−) to provide the user with visual options to accelerate or decelerate the rate at which the VOA can be displaced relative to the leads  12  or the electrodes  26 . Actuating the speed control button  144  increases the speed of steering in comparison to the speed at that instant. Similarly actuating the speed control button  146  decreases the steering speed in comparison to the speed of steering at that instant. Alternatively, the user can release the speed control buttons  144  and  146  to set the speed of steering at a rate at which the speed was being varied, at that instant. Such speed variations generate new stimulation parameters that will proportionately change the rate at which the locus of the VOA will be displaced. 
     The current steering through directional input controls  120 ,  124 ,  126  and the speed variation of the current steering through speed control buttons  144 ,  146  may be conducted by the user simultaneously. 
     The programming screen  100  further provides a termination control “stop” button  140 , which when actuated instantly terminates the speed variation of the current steering. The button  140  may use different luminance intensity to visually indicate the on/off stage of speed variation. If the speed is being varied, the representation of the control button  140  may have more luminance, and if actuated to turn off speed variation, the button  140  may visually decrease the lower luminance to indicate the speed variation has been ceased. 
     The programming screen  100  further provides a timing control element  142  set the duration for which the current steeling may be enabled or disabled. The controller/processor  80  is configured for, in response to actuation of the timing control element  142 , generating the series of different combinations of the electrodes for a specified time period, such that the translation of the VOA ceases when the time period has elapsed. 
     As one example, and with reference to  FIG. 7 , an exemplary programming screen  100  ( FIG. 8 ) generated by the CP  18  to allow a user to program the IPG  14  will now be described. The programming screen  200  includes similar elements as provided by programming screen  100 , except that the knob  120  is replaced by a wheel  134  that acts as a current steering direction control element. The wheel  134  further includes a single directional arrow  130  placed at the center of the wheel  134 . The arrow  130  may act as the visual pivot for the wheel  134  about which it is rotated and provides visual indication of the direction in which the user intends to steer the locus of VOA with respect to the axis of the leads  12  and electrodes  26 . The arrow  130  may have a large width and may employ varying color composition and luminance to visually highlight the direction in which the wheel  134  may be rotated at any instant. 
     The programming screen  200  further provides a pair of single directional arrows  128 ,  132 , positioned and aligned along the outer circumferential periphery of the wheel  134 . Alternatively, the arrows  128 ,  132  may be positioned inside the wheel  134 . The arrows  128  and  132  are curved in opposite directions to each other, to indicate counter-clockwise and clockwise directions respectively. As described above in conjunction with  FIG. 7 , the arrows  128  and  132 , when actuated, emulate the functionality provided by rotating the wheel  134 , in small increments. For example, when the arrow  128  is actuated the wheel  134  rotates in the counter-clock direction and when the arrow  132  is actuated, the wheel  134  rotates in the clockwise direction. The arrows  128 ,  132  can be actuated in a single continuous or multiple discreet times to impart the wheel  134  with the desired degree of rotation. The wheel  134 , when rotated, provides the directional input control to displace locus of the electrical stimulation field (and thus, the VOA), relative to the axis of the leads  12  or the electrode  26 , in the direction in which the wheel  134  has been rotated. 
     Although the techniques have been described as being implemented by the CP  18 , these techniques may be alternatively or additionally implemented by the RC  16 . Furthermore, although particular embodiments of the present inventions have been shown and described, it will be understood that it is not intended to limit the present inventions to the disclosed embodiments, and it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present inventions. Thus, the present embodiments are intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the invention as defined by the claims.