U.S. patent application number 13/280130 was filed with the patent office on 2012-02-23 for implantable pulse generator having current steering means.
This patent application is currently assigned to BOSTON SCIENTIFIC NEUROMODULATION CORPORATION. Invention is credited to Gerald E. Loeb, Paul M. Meadows, David K.L. Peterson, Carla Mann Woods.
Application Number | 20120046712 13/280130 |
Document ID | / |
Family ID | 31721388 |
Filed Date | 2012-02-23 |
United States Patent
Application |
20120046712 |
Kind Code |
A1 |
Woods; Carla Mann ; et
al. |
February 23, 2012 |
IMPLANTABLE PULSE GENERATOR HAVING CURRENT STEERING MEANS
Abstract
An implantable pulse generator includes a current steering
capability that allows a clinician or patient to quickly determine
a desired electrode stimulation pattern, including which electrodes
of a group of electrodes within an electrode array should receive a
stimulation current, including the amplitude, width and pulse
repetition rate of such current. Movement of the selected group of
electrodes is facilitated through the use of remotely generated
directional signals, generated by a pointing device, such as a
joystick. As movement of the selected group of electrodes occurs,
current redistribution amongst the various electrode contacts takes
place. The redistribution of stimulus amplitudes utilizes
re-normalization of amplitudes so that the perceptual level remains
fairly constant. This prevents the resulting paresthesia from
falling below the perceptual threshold or above the comfort
threshold.
Inventors: |
Woods; Carla Mann; (Los
Angeles, CA) ; Peterson; David K.L.; (Saugus, CA)
; Meadows; Paul M.; (Glendale, CA) ; Loeb; Gerald
E.; (South Pasadena, US) |
Assignee: |
BOSTON SCIENTIFIC NEUROMODULATION
CORPORATION
Valencia
CA
|
Family ID: |
31721388 |
Appl. No.: |
13/280130 |
Filed: |
October 24, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12948336 |
Nov 17, 2010 |
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13280130 |
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12120162 |
May 13, 2008 |
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12948336 |
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11158670 |
Jun 21, 2005 |
7555346 |
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12120162 |
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10641905 |
Aug 15, 2003 |
6909917 |
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11158670 |
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10150679 |
May 17, 2002 |
6609032 |
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10641905 |
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09550217 |
Apr 17, 2000 |
6393325 |
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10150679 |
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09226849 |
Jan 7, 1999 |
6052624 |
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09550217 |
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Current U.S.
Class: |
607/46 |
Current CPC
Class: |
A61N 1/37247 20130101;
A61N 1/0551 20130101; A61N 1/36185 20130101; A61N 1/36071 20130101;
A61N 1/37235 20130101; A61N 1/0553 20130101 |
Class at
Publication: |
607/46 |
International
Class: |
A61N 1/36 20060101
A61N001/36 |
Claims
1-17. (canceled)
18. A method comprising: storing an electrode combination map that
maps an output of a control device to a predetermined subset of
electrode combinations available from a set of electrodes implanted
within a patient, wherein the electrode combinations specify
polarities of electrodes of the set of electrodes; receiving the
output from the control device, wherein the output reflects
manipulation of a directional controller of the control device by a
user; selecting one of the predetermined subset of electrode
combinations based on the received output and the electrode
combination map; and controlling a stimulation device coupled to
the set of electrodes to apply electrical stimulation to the
patient via the selected electrode combination.
19. The method of claim 18, wherein the output of the control
device comprises directional information that reflects a direction
of a manipulation of the directional controller, and selecting the
electrode combination comprises selecting the electrode combination
such that a direction of movement of paresthesia resulting from
application of electrical stimulation via the selected electrode
combination reflects the direction of the manipulation of the
directional controller.
20. The method of claim 18, further comprising: storing a plurality
of electrode combination maps, each of the electrode combination
maps mapping the output of the control device to a respective
predetermined subset of electrode combinations available from one
of a plurality of electrode set configurations; receiving
information that describes a configuration of the set of electrodes
coupled to the stimulation device; and selecting the electrode
combination map based on the configuration information.
21. The method of claim 18, wherein the user manipulates the
directional controller to test a plurality of electrode
combinations by application of electrical stimulation from the
stimulation device to the patient via the plurality of electrode
combinations.
22. The method of claim 21, wherein the map comprises amplitude
scale factors associated with at least some of the electrode
combinations, the method further comprising determining the
amplitude scale factors based on paresthesia information received
from the user during the testing.
23. The method of claim 21, further comprising: identifying one of
the tested electrode combinations based on input received from the
user via the control device; and storing the identified electrode
combination for reapplication by the stimulation device at a later
time.
24. The method of claim 18, wherein the set of electrodes are
implanted proximate to the spinal cord of the patient, and the
electrical stimulation comprises spinal cord stimulation.
25. The method of claim 18, wherein each of the predetermined
subset of electrode combinations corresponds to a respective
stimulation location.
26. The method of claim 25, wherein each of the predetermined
subset of electrode combinations corresponds to a respective
paresthesia location.
27. The method of claim 25, wherein the set of electrodes comprises
a two dimensional array of electrodes, and the mapping of the
subset of electrode combinations to the output of the control
device enables the user to move the stimulation longitudinally and
laterally.
28. A mapping system comprising: an input circuit to receive an
output from a control device, the output reflecting manipulation of
a directional controller of the control device by a user; an
electrode combination map that maps the output of the control
device to a predetermined subset of electrode combinations
available from a set of electrodes implanted within a patient,
wherein the electrode combinations specify polarities of electrodes
of the set of electrodes; a telemetry circuit; and a processor to
select one of the subset of electrode combinations based on the
received output and the map, and provide the selected electrode
combination to a stimulation device coupled to the set of
electrodes via the telemetry circuit for application of electrical
stimulation to the patient via the selected electrode
combination.
29. The system of claim 28, wherein the output of the control
device comprises directional information that reflects a direction
of a manipulation of the directional controller, and the processor
selects the electrode combination such that a direction of movement
of paresthesia resulting from application of electrical stimulation
via the selected electrode combination reflects the direction of
the manipulation of the directional controller.
30. The system of claim 28, wherein the memory stores a plurality
of electrode combination maps, each of the electrode combination
maps mapping the output of the control device to a respective
predetermined subset of electrode combinations available from one
of a plurality of electrode set configurations, and wherein the
processor receives information that describes a configuration of
the set of electrodes coupled to the stimulation device, and
selects the electrode combination map based on the configuration
information.
31. The system of claim 12, wherein the processor is configured to
select a plurality of electrode combinations and provide the
selected electrode combinations to the stimulation device in
response to the user manipulating the directional controller to
test the plurality of electrode combinations by application of
electrical stimulation from the stimulation device to the patient
via the plurality of electrode combinations.
32. The system of claim 31, wherein the map comprises amplitude
scale factors associated with at least some of the electrode
combinations, and the processor determines the amplitude scale
factors based on paresthesia information received from the user
during the testing via the input circuit.
33. The system of claim 31, wherein the processor is further
configured to identify one of the tested electrode combinations
based on input received from the user via the control device, and
store the identified electrode combination within the memory for
reapplication by the stimulation device at a later time.
34. The system of claim 31, wherein each of the predetermined
subset of electrode combinations corresponds to a respective
stimulation location.
35. The system of claim 34, wherein each of the predetermined
subset of electrode combinations corresponds to a respective
paresthesia location.
36. The system of claim 34, wherein the set of electrodes comprises
a two dimensional array of electrodes, and the mapping of the
subset of electrode combinations to the output of the control
device in the electrode combination map enables the user move the
stimulation longitudinally and laterally.
37. A computer readable storage medium comprising instructions that
cause a programmable processor to: receive an output from the
control device that reflects manipulation of a directional
controller of the control device by a user; select one of a
predetermined subset of electrode combinations based on the
received output and an electrode combination map, wherein the
electrode combination map maps the output of the control device to
the predetermined subset of electrode combinations available from a
set of electrodes implanted within a patient, wherein the electrode
combinations specify polarities of electrodes of the set of
electrodes; and provide the selected electrode combination to a
stimulation device coupled to the set of electrodes for application
of electrical stimulation to the patient via the selected electrode
combination.
38. A mapping system comprising: an input circuit to receive an
output from a control device, the output reflecting manipulation of
a directional controller of the control device by a user; an
electrode combination map that maps the output of the control
device to a predetermined subset of electrode combinations
available from a set of electrodes implanted within a patient,
wherein the electrode combinations specify polarities of electrodes
of the set of electrodes; and a processor to select one of the
subset of electrode combinations based on the received output and
the map, and control a stimulation device coupled to the set of
electrodes to apply electrical stimulation to the patient via the
selected electrode combination.
Description
[0001] This application is a continuation of U.S. application Ser.
No. 10/641,905, filed Aug. 15, 2003, now U.S. Pat. No. 6,909,917;
which is a continuation of U.S. application Ser. No. 10/150,679,
filed May 17, 2002, now U.S. Pat. No. 6,609,032; which is a
continuation of U.S. patent application Ser. No. 09/550,217, filed
Apr. 17, 2000, now U.S. Pat. No. 6,393,325; which is a
continuation-in-part of U.S. patent application Ser. No.
09/226,849, filed Jan. 7, 1999, now U.S. Pat. No. 6,052,624; which
application claims the benefit of the following U.S. Provisional
Applications: Ser. No. 60/145,829, filed Jul. 27, 1999, and Ser.
No. 60/172,167, filed Dec. 17, 1999; which applications and patents
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a device for programming an
implantable electrode array used with an implantable stimulator.
More particularly, one embodiment of the invention relates to a
device used to provide directional programming for the implantable
electrode array associated with an implantable stimulator that
electrically stimulates the spinal cord for the purposes of
controlling and reducing pain.
[0003] Within the past several years, rapid advances have been made
in medical devices and apparatus for controlling chronic
intractable pain. One such apparatus involves the implantation of
an electrode array within the body to electrically stimulate the
area of the spinal cord that conducts electrochemical signals to
and from the pain site. The stimulation creates the sensation known
as paresthesia, which can be characterized as an alternative
sensation that replaces the pain signals sensed by the patient. One
theory of the mechanism of action of electrical stimulation of the
spinal cord for pain relief is the "gate control theory". This
theory suggests that by simulating cells wherein the cell activity
counters the conduction of the pain signal along the path to the
brain, the pain signal can be blocked from passage.
[0004] Spinal cord stimulator and other implantable tissue
stimulator systems come in two general types: "RF" controlled and
fully implanted. The type commonly referred to as an "RF" system
includes an external transmitter inductively coupled via an
electromagnetic link to an implanted receiver that is connected to
a lead with one or more electrodes for stimulating the tissue. The
power source, e.g., a battery, for powering the implanted
receiver-stimulator as well as the control circuitry to command the
implant is maintained in the external unit, a hand-held sized
device that is typically worn on the patient's belt or carried in a
pocket. The data/power signals are transcutaneously coupled from a
cable-connected transmission coil placed over the implanted
receiver-stimulator device. The implanted receiver-stimulator
device receives the signal and generates the stimulation. The
external device usually has some patient control over selected
stimulating parameters, and can be programmed from a physician
programming system. An example of an RF system is described, e.g.,
in U.S. Pat. No. 4,793,353, incorporated herein by reference.
[0005] The fully implanted type of stimulating system contains the
programmable stimulation information in memory, as well as a power
supply, e.g., a battery, all within the implanted pulse generator,
or "implant", so that once programmed and turned on, the implant
can operate independently of external hardware. The implant is
turned on and off and programmed to generate the desired
stimulation pulses from an external programming device using
transcutaneous electromagnetic, or RF links. Such stimulation
parameters include, e.g., the pulse width, pulse amplitude,
repetition rate, and burst rates. An example of such a
commercially-available implantable device is the Medtronic Wel II,
Model 7424. Such device is substantially described in U.S. Pat. No.
4,520,825, also incorporated herein by reference.
[0006] The '825 patent describes a circuit implementation of a
cyclic gradual turn on, or ramping of the output amplitude, of a
programmable tissue stimulator. The implementation contains
separate memory cells for programming the output amplitude and
number of pulses at each increasing output level or "step". In
devices of the type described in the referenced '825 patent, it is
desirable to provide some means of control over the amplitude
(intensity), the frequency, and the width of the stimulating
pulses. Such control affords the patient using the device the
ability to adjust the device for maximum effectiveness. For
example, if the pulse amplitude is set too low, there may be
insufficient pain relief for the user; yet, if the pulse amplitude
is set too high, there may be an unpleasant or uncomfortable
stinging or tingling sensation felt by the user. Moreover, the
optimum stimulation parameters may change over time. That is,
numerous and varied factors may influence the optimum stimulation
parameters, such as the length of time the stimulation has been ON,
user (patient) postural changes, user activity, medicines or drugs
taken by the user, or the like.
[0007] In more complex stimulation systems, one or more leads can
be attached to the pulse generator, with each lead usually having
multiple electrode contacts, Each electrode contact can be
programmed to assume a positive (anode), negative (cathode), or OFF
polarity to create a particular stimulation field when current is
applied. Thus, different combinations of programmed anode and
cathode electrode contacts can be used to deliver a variety of
current waveforms to stimulate the tissue surrounding the electrode
contacts.
[0008] Within such complex systems, once one or more electrode
arrays are implanted in the spinal cord, the ability to create
paresthesia over the painful site is firstly dependent upon the
ability to accurately locate the stimulation site. This may more
readily be accomplished by programming the selection of electrode
contacts within the array(s) than by physically maneuvering the
lead (and hence physically relocating the electrode contacts).
Thus, the electrode arrays may be implanted in the vicinity of the
target site, and then the individual electrode contacts within the
array(s) are selected to identify an electrode contact combination
that best addresses the painful site. In other words, electrode
programming may be used to pinpoint the stimulation area
correlating to the pain. Such electrode programming ability is
particularly advantageous after implant should the lead contacts
gradually or unexpectedly move, thereby relocating the paresthesia
away from the pain site. With electrode programmability, the
stimulation area can often be moved back to the effective site
without having to re-operate on the patient in order to reposition
the lead and its electrode array.
[0009] Electrode programming has provided different clinical
results using different combinations of electrode contacts and
stimulation parameters, such as pulse width, amplitude and
frequency. Hence, an effective spinal cord stimulation system
should provide flexible programming to allow customization of the
stimulation profile for the patient, and thereby allow for easy
changes to such stimulation profile over time, as needed.
[0010] The physician generally programs the implant, external
controller, and/or external patient programmer through a
computerized programming station or programming system. This
programming system can be a self-contained hardware/software
system, or can be defined predominately by software running on a
standard personal computer (PC). The PC or custom hardware can have
a transmitting coil attachment to allow for the programming of
implants, or other attachments to program external units. Patients
are generally provided hand-held programmers that are more limited
in scope than are the physician-programming systems, with such
hand-held programmers still providing the patient with some control
over selected parameters.
[0011] Programming of the pulse generators, or implants, can be
divided into two main programming categories: (1) programming of
stimulation pulse variables, and (2) programming electrode
configurations. Programmable stimulation pulse variables, as
previously indicated, typically include pulse amplitude, pulse
duration, pulse repetition rate, burst rate, and the like.
Programmable electrode configuration includes the selection of
electrodes for simulation from the available electrode contacts
within the array as well as electrode polarity (+/-) assignments.
Factors to consider when programming an electrode configuration
include the number of electrode contacts to be selected, the
polarity assigned to each selected electrode contact, and the
location of each selected electrode contact within the array
relative to the spinal cord, and the distance between selected
electrodes (anodes and cathodes), all of which factors combine to
define a stimulation field. The clinician's electrode selection
results in a simulating "group" containing at least one anode and
at least one cathode that can be used to pass stimulating currents
defined by the programmed pulse variables. For an electrode array
having eight electrode contacts, this can result in an unreasonable
large number of possible combinations, or stimulation groups, to
chose from.
[0012] Moreover, within each stimulation group, there are a large
number of pulse stimulation parameters that may be selected. Thus,
through the programmer, the clinician must select each electrode,
including polarity, for stimulation to create each combination of
electrode contacts for patient testing. Then, for each combination,
the clinician adjusts the stimulation parameters for patient
feedback until the optimal pain relief is found for the patient.
Disadvantageously, it is difficult to test many stimulation
variables with hundreds or even thousands of possible electrode and
stimulus parameter combinations. To test all such combinations,
which is typically necessary in order to find the optimum
stimulation settings, is a very lengthy and tedious process.
Because an all-combination test is lengthy and tedious, some
clinicians may not bother to test many different electrode
combinations, including many that may be considered far more
optimal than what is ultimately programmed for the patient. It is
thus evident that there is a need in the art for a more manageable
programming technique for testing and handling a large number of
possible electrode and pulse parameter combinations.
[0013] One method that has recently been developed for simplifying
the programming process is described in U.S. Pat. No. 5,370,672,
incorporated herein by reference. The '672 patent describes a
programming system where the patient interacts with the clinician's
programmer. More specifically, the '672 patent teaches a system
wherein the patient identifies the pain site by "drawing" the pain
site on a touch screen that displays an illustration of the human
body. After entering the patient's stimulation thresholds and
associated tolerances into the system, the computer generates a
recommended electrode configuration for that patient using
algorithms based on spinal cord stimulation research. The patient
responds to the resulting stimulation by drawing the amount of
paresthesia coverage over the body illustration. If the drawing
paresthesia site does not fully match the pain site, the system
adjusts the recommendation, and the patient responds again to the
new sense of paresthesia. This process is repeated until the
best-tested settings are reached.
[0014] Advantageously, the process described in the '672 patent
effectively eliminates the manual selection of electrode
combinations, and reduces the selection process to a reasonable
testing of electrode/parameter combinations based on an extensive
pre-organized set of rules for programming optimization and patient
input. Moreover, the physician/clinician is not directly
controlling the programming session; rather, the patient provides
the system with the feedback without the need for the physician or
clinician to interpret the patient's sensations or empirically
estimate changes required in stimulation parameters.
[0015] Disadvantageously, using the method described in the '672
patent, the patient must still test and respond to each of the
chosen combinations and must depend upon the system
recommendations, which system recommendations might exclude a
possible optimal setting for that patient. Further, the patient
must be able to accurately translate subtle sensations and
differences to a drawing on a screen, and then wait for device
programming before having to react and redraw the paresthesia from
the new settings. Such process can still be time consuming.
Furthermore, subtle sensation differences felt by the patient
between combinations cannot necessarily be translated in a drawing
of paresthesia that only address "coverage area." In summary, by
reducing the combinations to a computer-generated recommendation,
many electrode combinations might be omitted that could provide a
more effective paresthesia. Hence, the process of
computer-recommended combinations, although superior to manual
arbitrary selection, can still be viewed as an undesirable
"discrete" method of patient feedback evaluation: i.e., electrodes
are programmed and patient feedback is entered for each
combination, one iteration at a time.
[0016] In view of the above, it is evident that profound
improvements are still needed in the way multiple implanted
electrode combinations are programmed. In particular, it is seen
that improvements in programming techniques and methods are needed
that do not compromise the patient's ability to feel the subtle
effects of many different combinations, and that provide a more
immediately responsive programming-to-feedback loop.
SUMMARY OF THE INVENTION
[0017] The present invention advantageously addresses the needs
above, as well as other needs, by providing improved programming
methods for electrode arrays having a multiplicity of electrodes.
The present invention advantageously simplifies the programming of
multiple electrode contact configurations by using a directional
input device in conjunction with a programmer/controller to
automatically combine and reconfigure electrodes with alternating
current paths as determined by the directional input device. The
directional input device used with the invention may take many
forms, e.g., a joystick, a button pad, a group of keyboard arrow
keys, a touch screen, a mouse, or equivalent directional input
mechanisms. Advantageously, the use of a directional input device
to automatically adjust electrode configurations in order to
"steer" the stimulation current allows the patient to immediately
feel the effect of electrode configuration changes. Then, without
having to translate the subtle differences of sensation to a
drawing for discrete computer-generated recommendations, or
manually and arbitrarily selecting different combinations, the
patient responds continuously to the sensation by steering
directional or equivalent controls. Hence, the patient more
directly controls the programming without being cognizant of actual
electrode combinations and variables. The patient is also more
immediately responsive, since there is no need to translate the
perceived sensations to specific locations on a displayed drawing.
This process is thus analogous to continuous feedback as opposed to
discrete feedback and system manipulation.
[0018] While the directional programming device provided by the
invention is primarily intended to program implanted stimulator
devices having at least two electrode contacts, it should also be
noted that it can also be used to program the electrodes used with
external stimulators.
[0019] The invention described herein thus relates, inter alia, to
a method of programming utilizing directional input signals to
"steer" and define current fields through responsive automated
electrode configuring. Hence, in accordance with one aspect of the
invention, programming equipment is utilized including a computer
and/or custom transmitter, coil and programming software to achieve
the desired current field steering effect. Additional control
mechanisms (software and/or hardware) are used to respond to
directional control signals generated, e.g., with a joystick or
other directional means, so as to configure and combine the
electrodes as directed by the joystick or other directional-setting
device so as to redistribute the current/voltage field in a way
that prevents the paresthesia felt by the patient from either
falling below a perceptual threshold or rising above a comfort
threshold. As needed, one or more other input devices can be used
to control different aspects of the electrode configuration.
[0020] In accordance with another aspect of the invention, a
representation of the changing current fields resulting from
movement of the directional device is visually provided on a
display screen associated with the programming equipment, thereby
providing visual feedback to the user as to the electrode
configurations and/or resulting stimulation fields that are
achieved through manipulation of the directional input
mechanism.
[0021] In use, a spinal cord stimulator is implanted with one or
more leads attached to the spinal cord. The implanted spinal cord
stimulator is coupled through an RF or other suitable link to the
external spinal cord stimulation system, which system is used to
program and/or control the implanted stimulator. The style and
number of leads are entered into the system software. The clinician
then maneuvers the joystick, or other directional instructor, to
redirect current to different groups of implanted electrodes. The
software then automatically reconfigures electrodes according to
directional responsive rules in the software and/or electronics.
Automatic configuring of the electrodes to steer current includes,
e.g., the number of electrodes, the selection of electrodes, the
polarity designation of individual electrodes, and the distribution
of stimulation intensities among the selected electrodes.
[0022] The advantage achieved with the programming system provided
by the invention is that the clinician never has to actually select
and test a multitude of electrode combinations with the patient,
which otherwise takes time for each configuration. Instead, the
patient immediately responds to maneuvers conducted by
himself/herself or the clinician, which causes the user to move
toward or away from certain directions. The directional programming
feature may also be made available directly to the patient through
a small portable programming device. Advantageously, all
reconfiguring of the electrodes is done automatically as a function
of the directional signals generated by the joystick or other
directional device(s), and is done in a way that prevents the
paresthesia felt by the patient from falling below the perceptual
threshold or rising above the comfort threshold.
[0023] One embodiment of the invention may be viewed as a
programming system for use with a neural stimulation system. Such
neural stimulation system includes: (1) a multiplicity of
implantable electrodes adapted to contact body tissue to be
stimulated; (2) an implantable pulse generator connected to each of
the multiplicity of electrodes, the implantable pulse generator
having electrical circuitry responsive to programming signals that
selectively activates a plurality of the implantable electrodes,
wherein at least one electrode in the plurality of activated
implantable electrodes functions as a cathode, and wherein at least
one electrode in the plurality of activated implantable electrodes
functions as an anode, whereby stimulus current flows from the at
least one activated anodic electrode to the at least one activated
cathodic electrode; (3) a programming device coupled with the
implantable pulse generator, the programming device having control
circuitry that generates programming signals adapted to control the
implantable pulse generator; (4) an input device coupled with the
programming device, wherein the input device generates directional
signals as a function of user control; and (5) control logic within
the programming device that continuously activates selected ones of
the multiplicity of implantable electrodes in response to the
directional signals received from the user controlled input device,
whereby stimulus current is selectively redistributed among
cathodic and anodic electrodes as directed by the user controlled
input device. The electrical circuitry within the implantable pulse
generator may activate the selected electrodes by forcing a
prescribed current to flow into (a current sink) a cathodic
electrode, by forcing a prescribed current to flow from (a current
source) an anodic electrode, by causing a prescribed positive
voltage to be applied to an anodic electrode, by causing a
prescribed negative voltage to be applied to a cathodic electrode,
or by combinations of the above.
[0024] It is thus a feature of the present invention to provide a
system and a method for programming that allows a clinician or
patient to quickly determine a desired electrode stimulation
pattern, including which electrodes of a multiplicity of electrodes
in an electrode array should receive a stimulation current, the
polarity, distance between anodes and cathodes, and distribution of
stimulation intensity or amplitude.
[0025] It is another feature of the invention to provide an
electrode selection system that allows the user (the person
operating the programmer) to readily select and visualize a
particular group of electrodes of an electrode array for receipt of
a stimulation pulse current, and when selected to allow different
combinations of pulse amplitude, pulse width, pulse repetition
rate, or other pulse-defining parameters to be applied to the
selected group.
[0026] It is yet an additional feature of the invention to allow an
implantable tissue stimulator, having an array of stimulation
electrodes attached thereto, to be readily and quickly programmed
so that only those electrodes which prove most effective for a
desired purpose, e.g., pain relief, are selected and configured to
receive a pulsed current having an amplitude, width, repetition
frequency, or burst parameters that best meets the needs of a
particular patient.
[0027] It is still another feature of the invention to provide a
system and a method of steering or programming the perceived
paresthesia so that any needed redistribution of the stimulus
current occurs in small step sizes, thereby making neural
recruitment more effective. In accordance with this feature of the
invention, the small step size in current or voltage amplitude
settings that is used amongst the electrode contacts is selected to
effectively correspond to the spatial resolution to which neural
elements can be activated. That is, this spatial resolution is
meaningful to the extent that the micro-anatomy of the neural
structures being activated gives rise to different clinical
effects. Advantageously, by using such a system that automatically
redistributes current or voltage amplitudes amongst electrodes in
suitable small step sizes, desired neural activation patterns may
be found more easily.
[0028] It is another feature of the invention to provide a system
for redistributing current and/or voltage amplitudes amongst
selected electrodes using a user interface that is simple and
intuitive.
[0029] It is an object of the invention to eliminate the need for
either a clinician to manually select electrode combinations, or
even for a computer to select electrode combinations that must be
discretely tested for patient feedback. That is, based on the
feedback as to the amount of coverage, an educated guess for
another combination must be made (by clinician or computer) and the
patient must then discretely respond to that combination before
another combination is set up and turned on. Such discrete testing
with patient feedback is very tedious and time consuming.
Advantageously, by practicing the present invention, discrete
selection and patient feedback of location and amount of
paresthesia coverage (either to the clinician or to a computer) is
avoided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The above and other aspects, features and advantages of the
present invention will be more apparent from the following more
particular description thereof, presented in conjunction with the
following drawings wherein:
[0031] FIG. 1A is a perspective view of one embodiment of a
directional programmer device with a visual display in accordance
with the present invention;
[0032] FIG. 1B is a perspective view of another embodiment of a
directional programmer device in accordance with the present
invention;
[0033] FIG. 2 is a functional block diagram of a directional
programmer system in accordance with the present invention;
[0034] FIG. 3 is a schematic view of a patient with an implanted
stimulator, coupled to a directional programmer system;
[0035] FIG. 4 is a view of the directional programmer display
screen of FIG. 1A;
[0036] FIG. 5A schematically illustrates the various functions
provided by the directional-programmer device;
[0037] FIG. 5B illustrates one type of electrode grouping that may
be achieved with the invention;
[0038] FIG. 6A illustrates a representative electrode array usable
with the invention having eight electrode contacts;
[0039] FIG. 6B illustrates an alternative electrode array usable
with the invention;
[0040] FIG. 6C illustrates yet another representative electrode
array usable with the invention;
[0041] FIG. 7 shows a table-based current shifting algorithm for
horizontal shifting;
[0042] FIGS. 8 and 8A-8Q (note, there is no FIG. 8I or FIG. 8O)
show a table-based current shifting algorithm for vertical
shifting, with FIG. 8 providing a map to FIGS. 8A-8Q;
[0043] FIG. 9 is a block diagram of the software architecture used
in an SCS system, or other neural stimulation system, in accordance
with the present invention;
[0044] FIG. 10 depicts a representative patent information screen
that may be used with the software architecture of FIG. 9;
[0045] FIG. 11 is a flow chart that depicts the steps utilized by a
software wizard in order to guide a user through the fitting
process associated with an SCS, or other neural stimulation
system;
[0046] FIGS. 12A through 12J (note, there is no FIG. 12I)
illustrate various screens that may be used by the software wizard
as it carries out the steps depicted in FIG. 11;
[0047] FIG. 13 illustrates a representative measurement screen used
as a part of the fitting process which graphically shows the
measured and calculated threshold settings;
[0048] FIG. 14 illustrates a representative programming screen used
as part of the fitting process carried out by the software wizard
of FIG. 11;
[0049] FIG. 15 similarly illustrates a representative programming
screen used as part of the fitting process; and
[0050] FIG. 16 shows an illustrative navigator map that may be used
with the fitting system of the present invention in order to teach
and guide the patient through the complete fitting process.
[0051] Like reference numerals are used to refer to like elements
or components throughout the several drawing figures.
DETAILED DESCRIPTION OF THE INVENTION
[0052] The following description is of the best mode presently
contemplated for carrying out the invention. This description is
not to be taken in a limiting sense, but is made merely for the
purpose of describing the general principles of the invention. The
scope of the invention should be determined with reference to the
claims.
[0053] At the outset, it is to be noted that a preferred
implementation for a directional programming device in accordance
with the present invention is through the use of a joystick-type
device or equivalent. Hence, in the description that follows, a
joystick device is described. It is to be understood, however, that
other directional-programming devices may also be used in lieu of a
joystick, e.g., a roller ball tracking device, horizontal and
vertical rocker-type arm switches, selected keys (e.g.,
directional-arrow keys) on a computer keyboard, touch-sensitive
surfaces on which a thumb or finger may be placed, recognized voice
commands (e.g., "up", "down", "diagonal", etc.), recognized
movement of body parts (e.g., detecting eye blinks, finger taping,
muscle contraction, etc.), and the like. Any type of hardware or
software that allows directional signals to be generated through
motion or movement of a body part, or through the movement of keys,
levers, or the like, or through recognition of voice or visual
commands, may be used as the directional programming device used
with the invention.
[0054] Thus, it is seen that any input device capable of driving
software, electrical hardware, as well as mechanical systems that
configure stimulation electrodes, may be used with the present
invention as a directional programming device. Additional input
devices include voice activated and mechanical dials that can cause
the switching of electrodes and output distributions. The shifting
of electrodes occurs in response to input signals derived from the
user controlled input device.
[0055] While the embodiment described below relates to a spinal
cord stimulator for the treatment of pain, it is to be understood
that the principles of the invention also apply to other types of
tissue stimulator systems. Likewise, although the preferred
embodiment includes software for use in conjunction with a PC, it
is to be understood that the invention can also be implemented
through custom programming devices for either the clinician or the
patient, with or without visual displays.
[0056] Turning first to FIG. 1A, there is shown a representative
view of a directional programmer system 10 implemented in
accordance with one embodiment of the invention. Such system 10
comprises a joystick 12 (or other type of directional programming
device), a keyboard 14, and a programming display screen 16, housed
in a case 18. As seen in FIG. 1A, the overall appearance of the
system 10 is that of a laptop personal computer (PC) and, in fact,
the system 10 may be implemented using a PC that has been
appropriately configured to include a directional-programming
device and programmed to perform the functions described herein. As
indicated previously, it is to be understood that in addition to,
or in lieu of, the joystick 12, other directional programming
devices may be used, such as a mouse 13, or directional keys 15
included as part of the keys associated with the keyboard 14.
[0057] FIG. 1B depicts a custom directional programmer system 10'
that may also be used with the invention. The programmer system 10'
is built within a case 18' designed to fit within the hand of the
user, and includes an array 12' of directional keys which allow
directional signals to be generated, equivalent to those generated
by a joystick. The hand-held unit 10' further includes a functional
display 16', typically realized using light emitting diodes (LEDs),
as is known in the art. Various programmable features or functions
associated with the programmer system 10' may be selected using the
keys 17'. Once selected, a "store" button 19' is provided to allow
a desired electrode configuration, including other selected
parameters, or a desired function, to be selected and saved in
memory so that it can be recalled as desired to define the
electrode configuration to be used at a later date.
[0058] The joystick programmer system 10 of FIG. 1A, or the
alternate hand-held programmer 10' of FIG. 1B, is intended to be
used with an implanted tissue stimulator, e.g., an implantable
spinal cord tissue stimulator 20 (see FIG. 3). A spinal cord tissue
stimulator, as shown in FIG. 3, is typically implanted in the
abdomen of a patient 22. An electrode array 23, electrically
connected to the simulator 20, has individual electrode contacts,
or electrodes 24, arranged in a desired pattern and positioned near
the spinal column 26. The spinal stimulator 20, when appropriately
programmed, is used by the patient for the control of pain. A more
thorough description of a spinal cord stimulator may be found in
the previously referenced '829 provisional patent application,
which application has been incorporated herein by reference.
[0059] Advantageously, the directional programmer systems 10 or 10'
greatly simplify the programming of multiple implanted electrode
contact configurations. As previously indicated, programming
systems currently require the physician or clinician to
specifically select and manually input the electrode combinations
that are to used for stimulation--a time-consuming and frustrating
process. In contrast, the present invention allows the physician or
clinician to readily determine a desired combination of electrodes,
i.e., a selected "group" of electrodes, using the joystick 12 (or
other directional programming device) that affects which electrodes
are selected, the polarity of individual electrodes, and the
stimulation intensity distribution, all of which parameters can
contribute to "steer" and/or "focus" the stimulation current. In
other words, through use of the present invention, the operator can
adjust the stimulation field location, concentration and spread by
maneuvering the joystick 12 that automatically configures
electrodes for stimulation. Advantageously, as the stimulating
group of electrodes is being configured and positioned using the
directional signals generated by the joystick 12, the programmed
stimulation is automatically directed to the electrodes for
immediate and continuous patient response. A preferred technique
for generating the directional signals that are automatically
directed to electrodes in accordance with the invention,
particularly in relation to moving the directional signals from one
stimulation site to another in small steps, is described
hereinafter.
[0060] FIG. 2 shows a functional block diagram of a directional
programming system 10 made in accordance with the present
invention, and further includes a functional block diagram of the
implantable tissue stimulator 20 that is programmed and controlled
using such system. It is to be emphasized that the block diagram
shown in FIG. 2 is a functional block diagram, i.e., a diagram that
illustrates the functions performed by the programming system 10
and stimulator 20. Those of skill in the art, given the
descriptions of the invention presented herein, can readily
configure various hardware and/or software components that may be
used to carry out the functions of the invention.
[0061] The implantable tissue stimulator 20 will be described
first. It should be noted that the implantable tissue stimulator
20, per se, is not the subject of the present invention. Rather,
the invention relates to a device or system for programming and/or
controlling the stimulator 20 so that a desired pattern of tissue
stimulation currents are applied to a selected group of electrodes
that form part of the tissue stimulator 20. Nonetheless, in order
to better understand and appreciate how the programming system 10
of the invention interacts with the stimulator 20, it will also be
helpful to have at least a functional understanding of how the
stimulator 20 operates.
[0062] Thus, as seen in FIG. 2, the implantable tissue stimulator
20 includes a coil 62 for receiving RF or other control signals and
power from an external source, e.g., from the programmer 10. The
signals thus received are passed through a receiver circuit 64. A
rectifier/filter circuit 68 extracts power from the received
signals and presents such extracted power to a voltage regulator
circuit 74, which regulator circuit 74 generates the operating
voltages needed within the implantable stimulator device 20. A
preferred implantable tissue stimulator 20 includes a rechargeable
or replenishable energy source 78, e.g., a rechargeable battery
and/or large capacitor. If so, a suitable recharging circuit 76
derives power from the voltage regulator 74 and/or rectifier/filter
circuit 68 for recharging or replenishing such power source 78. The
power source 78, in turn, provides its stored energy to the voltage
regulator circuit 74.
[0063] The signals received by the implant receiver circuit 64 are
also directed to a data demodulator 66, which demodulator
demodulates the control information (data) that is included in the
signals received from the programmer 10. Typically, such control
data are arranged in a sequence of frames, with certain bits of
data in each frame signifying different commands or other
information needed by the tissue stimulator 20 in order for it to
carry out its intended function. Such control data, once recovered
by the data demodulator 66, is presented to a controller 70. e.g.,
a microprocessor (.mu.P) controller. The .mu.P controller 70, upon
receipt of the data, acts upon it in order to carry out whatever
commands have been received.
[0064] The .mu.P controller 70 may be programmed to operate in
numerous modes. Typically, an operating program, stored in a
suitable memory device 67 included within the implantable
stimulator 20, directs or controls the .mu.P controller 70 to carry
out a sequence of operations. In some implementations, the
operating program itself may be received and programmed into the
memory 67 through receipt of the data commands received from the
programmer 10. In other implementations, a basic operating program
is permanently stored in the memory 67, e.g, in a read only memory
(ROM) portion of memory 67, and various parameters associated with
carrying out such basic operating program may be modified and
stored in a random access memory (RAM) portion of the memory 67
through the data commands received from the programmer 10.
[0065] Regardless of how the operating program is received and
stored within the tissue stimulator 20, it generally causes an
electrical stimulation current, e.g., a biphasic stimulation
current, to be applied to one or more selected pairs of a
multiplicity of electrodes, E1, E2, E3, . . . . En, associated with
the stimulator. That is, as controlled by the control signals
received from the programmer 10, which signals may be acted on
immediately, or stored in memory 67 for subsequent action, a given
electrode of the multiplicity of electrodes E1, E2, E3, . . . En
included within an array 23 of electrodes, is either turned ON or
turned OFF, and if turned ON, it receives a biphasic or other
current pulse having a selected amplitude, pulse width, and
repetition frequency. In this manner, then, as controlled by the
control signals received from the programmer 10, the tissue
stimulator 20 thus applies a selected stimulation current to
selected pairs of the electrodes included within the electrode
array 23.
[0066] In some programming modes, an indifferent or return
electrode, Eg, which may in fact form part of the case or housing
of the implantable stimulator 20, may be paired with individual
ones of the electrodes E1, E2, E3, . . . En so as to provide
"monopolar" stimulation. When two of the electrodes E1, E2, E3, . .
. En are paired together, such stimulation is generally referred to
as "bipolar" stimulation. Stimulation currents must always be
applied through two or more electrodes, with at least one electrode
functioning as an anode and with at least one electrode functioning
as a cathode, so that the stimulation current may flow into the
tissue to be stimulated through one path and return therefrom
through another path.
[0067] Still with reference to FIG. 2, the functions performed by
the directional programmer system 10 will next be described. As
seen in FIG. 2, a key element of such system 10 is the directional
control device 12, which may comprise, e.g., a joystick device.
Coupled with the directional control device 12 is a plurality of
up/down buttons or selector buttons 42. The control device 12 and
selector buttons 42 provide signals to an electrode group
location/size map generator circuit 50 that defines a group 45 of
electrodes 24 (see FIG. 4) within the array 23 of electrodes,
which, depending upon the selected polarity of individual
electrodes 24 within the group 45 of electrodes, further defines an
electric field 33 between the selected electrodes that effectively
defines a stimulation area 36 that receives the stimulation
current. The definition of the group of electrodes 45 is provided
to a stimulator processor circuit 52 and/or to a memory circuit
54.
[0068] Also provided to the stimulator processor circuit 52 are
data that define a desired pulse amplitude, pulse width, and pulse
repetition rate, and any other stimulation parameters (e.g., burst
repetition rate, etc.) that characterize the stimulation pulses
that are to be applied to the selected group of electrodes. Such
characterization data may be preprogrammed into the processor 52,
or it may be set through use of manual selection input/output (I/O)
devices 35, 37 and 39, which devices may be implemented in hardware
(e.g., slide switches) or software (e.g., simulated slide switches
that appear on the display screen 16 of the programmer 10).
Further, amplitude programming (also referred to as "magnitude
programming"), as explained in more detail below, and as further
described in the '167 provisional patent application previously
referenced and incorporated herein by reference, is preferably
implemented to facilitate the programming of the stimulator system.
Other I/O devices may also be used, e.g., the keyboard 14, as
required, in order to enter needed characterization data.
[0069] The stimulator processor 52 takes the pulse characterization
data, as well as the electrode group data, and processes such data
so that the appropriate commands can be sent to the implantable
receiver 20. A suitable data frame format generator circuit 56 may
be used to form the data into suitable data frames that will be
recognized and acted upon by the implant stimulator 20, as is known
in the art. In practice, the function of the data frame format
generator circuit 56 may be carried out as part of the processing
functions performed by the stimulator processor 52. Once properly
framed, such data commands are sent to a coil driver circuit 58,
which drives the external coil 28, causing such signals to be
inductively or otherwise coupled into the implant coil 62 and
implant receiver circuit 64 of the implantable stimulator 20. The
implantable stimulator 20 then acts on the data received so as to
provide the programmed stimulation currents to the group of
electrodes selected by the directional device 12 and selectors 42,
using the polarity defined by the received data.
[0070] Also included as part of the programming system 10 is a
display screen 16, and associated screen driver circuit 15. The
display screen provides a display as controlled by the stimulator
processor 52 of data, or other information, in conventional manner.
For purposes of the present invention, as explained in more detail
below in connection with FIGS. 4 and 5A, the display screen 16
displays a simulated picture of the implanted electrodes, as well
as the selected group of electrodes. The moving, expanding, or
contracting stimulation field 33 is then displayed in response to
the directional controller 12 and selection controls 42.
[0071] It is noted that the implantable stimulator 20 may also
include back telemetry capability which allows it to send data to
the external programmer 20. Such back telemetry data may include
status signals, e.g., voltage levels within the stimulator 20,
and/or sensed data, e.g., sensed through one or more of the
electrodes 24. In such instances, the programmer 10 includes
appropriate circuitry for sensing and acting upon such received
back telemetry data. For simplicity, such back telemetry features
are not included in the functional block diagram of FIG. 2, but it
is to be understood that such features may be used with the
invention.
[0072] The following issued United States patents, each of which is
incorporated herein by reference, provide additional detail
associated with implantable tissue stimulators, programming such
stimulators, and the use of biphasic stimulation pulses in a
bipolar, monopolar or other stimulation mode: U.S. Pat. Nos.
5,776,172; 5,649,970; 5,626,629; and 5,601,617.
[0073] Turning next to FIG. 3, a typical implanted programmable
spinal cord stimulator 20 is schematically illustrated. Such
stimulator is typically implanted in the abdomen of a patient 22
for control of pain by electrical stimulation of the spinal cord.
The stimulator 20 is connected to an array 23 of electrodes 24
implanted near the spinal column 26 of the patient 22. The
preferred placement of the electrodes 24 is adjacent, i.e., resting
upon, the spinal cord area to be stimulated. The stimulator 20
includes a programmable memory located inside of it which is used
to direct electrical current to the lead electrodes 24. Modifying
the parameters in the programmable memory of the stimulator 20
after implantation is performed by a physician or clinician using
the directional programmer system 10. For example, control signals,
e.g., modulated RF signals, are transmitted to a receiving coil
inside the stimulator 20 by a transmission coil 28 connected to the
programmer 10 via a cable 30.
[0074] In accordance with the teachings of the present invention,
the directional programmer system 10 is used by the physician to
modify operating parameters of the implanted electrodes 24 near the
spinal cord 26. As it does so, the modification of operating
parameters in carried out in an optimum manner such that changes in
stimulus current occur gradually, in small steps, as the stimulus
field moves from one group of electrodes to another. That is, in a
preferred implementation, the inclusion or exclusion of a given
electrode within a selected group of electrodes is gradually phased
in or out, as directed by the directional controls received from
the directional programmer system 10. The programmer system 10, as
indicated above in connection with the description of FIG. 2, may
selectively turn the stimulator 200N or OFF, or adjust other
parameters such as pulse rate, pulse width and/or pulse amplitude,
as desired.
[0075] FIG. 4 illustrates a representative programming display
screen 16 used with the directional programmer system 10. The
programming screen 16 visually provides all of the information
required to program the stimulator 20 and electrodes 24. Various
types of programming information may be provided depending on the
complexity desired from the system.
[0076] For the programmer system 10 to carry out its intended
function, it must know the style, number, and location of the
electrodes 24 that have been implanted near the spinal cord 26,
along with information characterizing the implanted spinal cord
stimulator 20 (i.e., the model number which determines performance
capabilities of the implanted stimulator). Information regarding
the type of electrode array 23, including the number and relative
position of the individual electrodes 24 included within the array
23, as well as information characterizing the stimulator 20, may be
entered and stored in the system 10 using the keyboard 14, or other
suitable data-entry input/output (I/O) device. Alternatively, the
electrode array and electrode information may be preprogrammed into
the system 10. The electrode array position data may be determined
using any suitable procedure, such as X-ray, xerography,
fluoroscopy, or other imaging techniques, which position data is
then entered into the programming system.
[0077] The programming screen shown in FIG. 4 includes an "Implant
Selection" button 38. By clicking on the Implant Selection button
38 (or pressing on the button when a touch-sensitive screen is
employed) displayed on the display screen 16, a drop-down list
appears containing data that characterizes the available
stimulators 20 and electrode array designs. Using the joystick 12
or keyboard 14 or other I/O device, the information for the
implanted unit may be chosen from the list and input into the
system. If the information for a particular unit is not on the
list, the information can be entered. Pressing the "Advanced"
button 40 provides access, through an appropriate menu selection,
to advanced programming features such as manual electrode
selection, burst programming, stimulation ramping, and other
features commonly used in the art. The information is provided to
the programmable memory 67 (FIG. 2) of the stimulator 20 in order
to control the delivery of electrical pulses to the desired
electrodes 24.
[0078] Once information characterizing the electrodes 24 and
stimulator 20 are input into the system, a simulated display
appears on one portion (e.g., the right portion as shown in FIG. 4)
of the programming display screen 16 that illustrates the placement
and relative position of each of the electrodes 24 included within
the array 23 of electrodes relative to the patient's spinal column
26. A simulated display 32 of the electrode array pattern 23 thus
appears on the display screen 16 just as though the programmer
could view inside the patient to see the electrode placement on or
near the spinal column. For the representative electrode array 23
shown in FIG. 4, two columns of electrodes 24 are used, each having
six electrodes. Thus, the particular electrode array 23 shown in
FIG. 4 has a total of twelve (12) electrodes. Each electrode in
each column is spaced apart from adjacent electrodes along the same
column. It is to be emphasized that the type of array shown in FIG.
4 is exemplary of only one type of many different types of arrays
that may be used. Often, two or more leads are implanted, each
having its own array. In such instance, the information (two or
more leads with respective arrays) is entered into the system and
accounted for in the programming and visual displays. What is
relevant to the programmer is which lead(s) is (are) being used (to
determine the electrode array layout, how the lead(s) is (are)
oriented with respect to one another and the spinal cord, and which
pulse generator within the implant is driving the stimulation
electrode contacts.
[0079] The basic functions addressed by directional programming in
accordance with the present invention include moving,
concentrating, and focusing the stimulation field. While these
functions could be separately controlled by several input devices,
a preferred embodiment of the present invention advantageously
minimizes hardware and software buttons by combining all these
functions into one device, e.g., a single joystick device 12,
thereby providing simplification in both design and use. The manner
in which the preferred joystick device addresses each of these
functions is depicted in FIG. 5A.
[0080] Any number of electrodes 24, out of the total available, may
be formed into an electrode group 45 which can be displayed as a
stimulation field 36. Through use of an additional data input
device, e.g., selector button 42, the number of electrodes within
the electrode group 45 can be increased or decreased. Such action
(increasing or decreasing the number of electrodes in the group)
redistributes, or concentrates, the stimulation current over a
greater of smaller area.
[0081] The selector 42, for the embodiment shown in FIG. 3,
comprises a pair of arrow buttons (up/down) that are located on top
of the joystick 12. Of course, such selector 42 could also be
separate, i.e., accessed from keyboard buttons. In a preferred
implementation, the number of electrodes in a stimulation group 45,
from 2 to n, where n is an integer greater than or equal to three,
is initially determined by increase/decrease input from the
selector, rather than by manually selecting electrodes.
[0082] Once the starting number of electrodes (concentration of
stimulation) is determined, it is then focused and/or moved by the
directional input of joystick 12. Selection software algorithms,
stored in memory 54, work in conjunction with the position defined
by the joystick 12, and/or other directional instructional means,
to configure and combine the electrodes 24 into the electrode group
creating the stimulation field 36. As the physician or patient
maneuvers the joystick 12, the resulting stimulation field 36
and/or the selected electrodes can be visualized on display 32
(e.g., by a different color, by shading, by a dashed line
encircling the selected electrodes, or the like.) The preferred
manner in which the current stimuli is applied through the
electrodes in the stimulation group 45, and more particularly the
manner in which the current stimuli increases or decreases as the
stimulation field is increased or decreased, is described more
fully below.
[0083] In FIG. 5B, for example, an illustration is given of two
columns of five electrodes 24. The selected group 45 of electrodes
comprises two electrodes in the left column (second and third from
the bottom), which are set to a "+" polarity, and one electrode in
the right column (second from the bottom) which is set to a "-"
polarity. This polarity and grouping creates an electric field
which will cause electrical current to flow from both of the "+"
electrodes to the single "-" electrode, which in turn defines a
stimulation area 36 that is nearer to the right column than the
left column, and that tends to be more concentrated nearer the "-"
electrode.
[0084] Next, as illustrated in FIG. 5A, it is seen that the
joystick 12 (or other directional programming device) can move a
group selection of electrodes up and down within the array, which
thus moves the field 36 up or down the spinal cord respectively. As
the joystick 12, or other directional input device, is maneuvered
forward, for example, the current field is steered up the spinal
cord. This occurs, in one embodiment, by moving the selected group
of electrodes up one level along the array. Because stimulation is
generally associated with the cathode, or negative polarity
electrodes, the stimulation can also be distributed among a group
of electrodes by changing positive polarities to negative, and
negative to positive, in the path of the direction programming
within the group.
[0085] For even finer control of current steering, the amplitude of
a group 45 of electrodes which includes more than a single anode
and cathode is assigned a "group amplitude". The group amplitude
is, in effect, a cumulative amplitude and might be, e.g., 5 mA,
which is the absolute value total for all of the cathodes (-
electrodes) in a single stimulating group. Thus, if a group of
electrodes consists of four electrodes, including 2 anodes and 2
cathodes, the default value for such group might be -2.5 mA on each
negative electrode, and +2.5 mA on each positive electrode. As the
joystick 12 moves the stimulation area in an upward direction, the
amplitude distribution is graduated to the higher anodes and
cathodes until the lower anodes and cathodes are eventually turned
off, after which the next higher electrodes start increasing in
amplitude as the joystick 12 is held in the forward portion. This
process is explained more fully below.
[0086] By way of illustration, reference is made to FIG. 6A, which
shows a four electrode group 45. Electrodes A and F each have -2.5
mA flowing to the electrode, totaling -5 mA, and electrodes B and E
each have +2.5 MA flowing from the electrode. Hence, each polarity
totals an absolute value of 5 mA. As the joystick 12 is moved
forward, causing the electrodes C and G to be included in the group
45, and the electrodes A and E to be excluded from the group 45,
the current flowing through electrode B and F each increases toward
an absolute value of 5 mA, while electrodes A and E decrease toward
0 mA. As soon as electrodes A and E reach zero, electrodes C and G
begins to increase toward an absolute value of 5 mA, while the
electrodes B and F decrease toward zero. In this manner, the
joystick 12 is able to steer the current up or down to a desired
stimulation area 36. Note that current may also be steered in this
manner left or right, although this is only possible when there are
at least two rows of electrodes. The objective of directional
programming is simply to steer current in the direction desired
within the constraints of the electrode array(s) and pulse
generator(s) by automatically configuring electrodes by defining or
controlling the state (positive, negative, or off) of each
electrode and by distributing current, including amplitudes, among
the ON electrodes.
[0087] Another function available with directional programming,
which could be linked to a separate direction input mechanism, is
illustrated in FIG. 5 as field "spread" on the off-axis directions
of a combined joystick 12. This directional input of the "spread"
feature increases or decreases the current path, or the distance
between selected electrodes. This affects the stimulating field by
having a broader expanded field or a more focused field. To spread
the field in a particular direction, for example, certain
electrodes are locked in position, while others are moved in the
direction of the spread desired. Referring to the four electrode
group identified in FIG. 6A, including electrodes A, B, F and E,
the following process is used: to move the spread up, electrodes A
and E are held, while F and E are switched to C and G. In this
manner, the positive to negative current path is lengthened, and
the spread is increased. It is to be understood that there are many
ways to organize the effect of directions to electrode
configuration changes, all of which are included within the spirit
of the invention. It is the use of a directional input device, or
directional signals however generated, to automatically reconfigure
electrodes for directing or steering current, whether to move a
field, spread/focus a field, or concentrate a field for
stimulation, that comprises the essence of the invention.
[0088] The constraints of the directional programming for the
selection of electrodes depends on the lead style being used as
well as the pulse generator. For example, a single in-line lead,
such as is shown in FIG. 6C, would not have any left-to-right
steering mobility. On the other hand, if two in-line leads are
placed with electrodes in parallel, which would be input to the
system, there would be left-to-right current steering
possibilities. Likewise, use of existing pulse generators, such as
the Itrel II pulse generator manufactured by Medtronic, would not
be able to include more than four electrodes in a group.
[0089] The electrical current information for the electrode group
45 is transmitted by the RF signals to a receiving coil inside the
stimulator 20 by a transmission coil 28 connected to the programmer
10 via a cable 30 (as shown in FIG. 3). As has been indicated, the
advantage of using the joystick 12 (or other directional
programming device) is that the clinician never has to manually
select each possible combination of electrodes 24, or manually
select each possible combination of electrodes 24, or manually
input the desired stimulation parameters associated with each
electrode selection. The initial parameters associated with the
stimulation can be set, and then, by using the joystick 12,
different electrode combinations can be selected while the
clinician observes an immediate response from the patient, or
alternatively the patient can directly operate the system. This
allows the operator to move toward or away from certain joystick 12
maneuvers, with the electrical current for each of the electrodes
24 being reconfigured automatically with the joystick (directional
programming) software.
[0090] In one embodiment, the operator adjusts the pulse amplitude
(in milliamps, "mA"), the pulse width (in microseconds, ".mu.S"),
or pulse repetition rate (in pulses per second, "pps") of the
pulses that are delivered to the group of electrodes selected by
the joystick 12 using the simulated "slide switches" 35, 37 and 39
displayed on the screen 16. The amplitude is set for a
"stimulation" channel, a single but alterable stimulation field.
The channel amplitude is distributed among electrodes (+/-) as they
are added or subtracted into the channel's electrode group with
respective polarities. In this manner, the operator may simply
maneuver the selected group 45 of electrodes to a desired area
using the joystick (or other directional device), and make
adjustments in the pulse width, pulse amplitude, and pulse
repetition rate, and observe whether favorable or unfavorable
results are achieved.
[0091] For some embodiments, the configuration software
automatically makes configuration adjustments as a function of the
stimulation parameters selected. For example, if the amplitude of
the current stimulation pulses is set to a high value, then the
size of the group 45 of electrodes included within the selected
group may swell or increase, e.g., to four or five or more
electrodes (from a nominal group size of, e.g., three electrodes);
whereas if the amplitude of the current stimulation pulses is set
to a low value, the size of the group 45 of electrodes included
within the selected group may decrease, e.g., to one or two
electrodes.
[0092] In one embodiment, the configuration software selects the
size of the group 45 of electrodes in the manner illustrated in
FIG. 5A. As seen in FIG. 5A, the electrodes are configured to move
the stimulation field up by moving the joystick arm up, to move it
down by moving the joystick arm down, to move it right by moving
the joystick arm right, and to move it left by moving the joystick
arm left. The relative size (number of electrodes within the group)
of the group of electrodes is set by depressing one of two selector
buttons 42 (increasing or decreasing) on top of the joystick arm
(or otherwise positioned near the directional-programming device).
The selected size may then be spread up and left by moving the
joystick arm up and to the left; may be spread down and left by
moving the joystick arm down and left; may be spread down and right
by moving the joystick arm down and right; or may be spread up and
right by moving the joystick arm up and right.
[0093] FIG. 6B illustrates an alternative embodiment of one type of
electrode array 23' that may be used with the invention. In FIG.
66, the individual electrodes A, B, C and D included in the left
column of electrodes are offset from the individual electrodes E,
F, G and H included in the right column of electrodes.
[0094] FIG. 6C depicts yet another embodiment of an electrode array
23'' that may be used with the invention. In FIG. 6C, electrodes
E1, E2, E3, E4, E5, E6, E7, and E8 are arranged in a single column
to form an in-line electrode array. The in-line array shown in FIG.
6C is electrically connected with a pulse generator 20'. The case
of the pulse generator 20', or at least a portion of the case of
the pulse generator 20', may be electrically connected as a
reference electrode, Eg (see FIG. 2). By way of example, a group
45' of electrodes may include electrodes E4, E5 and E6, with
electrodes E4 and E6 being positive electrodes, and electrode E5
being a negative electrode. The group 45' could "swell" to a larger
group by including electrodes E3 and E7 in the group.
Alternatively, the electrode group 45' could decrease to a smaller
group by removing electrode E3 or electrode E7 from the group. The
electrode group 45' could move up the electrode array by gradually
deleting electrode E6 from the group while at the same time
gradually including electrode E3 in the group, until such time as
the group includes electrodes E3, E4 and E5. Continued movement of
the electrode group up the array could continue by gradually
deleting electrode E5 from the group while at the same time
gradually including electrode E2 in the group. The inclusion and
deletion of electrodes within the group is preferably accomplished
in small steps, while maintaining current balance and perceived
stimulation levels, as explained more fully below.
[0095] The present invention is preferably practiced using a
stimulating system, e.g., an SCS system, that includes individually
programmable electrodes. That is, it is preferred to have a current
generator wherein individual current-regulated amplitudes from
independent current sources for each electrode may be selectively
generated. Although this system is optimal to take advantage of the
invention, other stimulators that may be used with the invention
include stimulators having voltage regulated outputs. While
individually programmable electrode amplitudes are optimal to
achieve fine control, a single output source switched across
electrodes may also be used, although with less fine control in
programming. Mixed current and voltage regulated devices may also
be used with the invention. With a single output source, the finest
shifting of amplitude between electrodes is a total shift of the
field from one or more selected electrodes to the next
configuration. With two output sources, finer control can be
achieved by gradually reducing output on one or more electrodes to
be deleted from the group, and proportionately increasing the
outputs on the electrodes to be included within the group. When as
many output sources as electrodes are available, even finer
shifting (smaller steps) may be achieved on each of the electrodes
included in the shifting process.
[0096] In accordance with one aspect of the invention, a method of
programming is provided wherein current (via current or voltage
regulation) is shifted between two or more electrodes. The method
begins with setting an amplitude level, in addition to other
parameters such as pulse width and rate, as is currently done in
practice. Advantageously, the amplitude level may be set in one of
two ways: (1) using a fixed output value (standard method), or (2)
using normalized output values (a new method).
[0097] As indicated, the amplitude level may be set using a fixed
output value, such as 3 mA, or 3 Volts. Although it is possible to
use a fixed amplitude value with the programming method described
herein, there are disadvantages that will be apparent as the
programming method is further described.
[0098] The amplitude level is preferably set using normalized
output values, as described, e.g., in the '167 provisional
application, previously referenced. This approach provides a
normalized amplitude across electrodes with respect to patient
thresholds. To better understand the normalized amplitude approach,
it will be helpful to review how programming is currently
performed. Currently, a patient or clinician adjusts the actual
amplitude value, e.g. in voltage units within the range of the
system capability. For example, the output on electrode E1 may be
set to 3 volts, the output on electrode E2 may be set to 4 volts,
and the like. However, an electrode array with n electrodes in a
row (E1-En) on the spinal cord will likely have a variety of
perception thresholds and maximum comfortable thresholds for each
possible electrode at a given location in each possible
combination. In a system that has an output range of 1-10 mA, for
example, a patient might first perceive stimulation at 1 mA on E1
and might begin to feel uncomfortable stimulation at 5 mA.
Likewise, electrode En might have a perception threshold (PT) of 2
mA and a maximum threshold (MT) of 4 mA. Thus, the first perception
level of stimulation, or the lowest perceptible stimulation, may be
different for electrode E1 than it is for electrode En; and the
highest comfortable level of stimulation may also be different for
electrode E1 than it is for electrode En. If a fixed value were to
be set, e.g., 3 mA, and switched between electrodes, not only would
the location of sensation change, but so would the intensity of the
perceived stimulation.
[0099] The present invention, through use of normalized output
levels, advantageously normalizes stimulation levels to perception.
That is, a programmable amplitude range is utilized having an
arbitrary scale, e.g., 0-10 (or min-max), with n steps. This
arbitrary scale is then correlated to an actual current or voltage
value. A zero level is equal to zero mA; a level one (or minimum
level) is set to be equal to the perception level; a level 10 (or
maximum level) is set to be equal to a maximum threshold level
(i.e., the threshold level at which the patient begins to
experience discomfort or pain). Thus, for example, setting the
output of a given electrode to level 5 would place the output
current stimulus (or voltage) so as to proportionately fall in the
middle of the comfort zone for each electrode. Thus, using
normalized intensity levels based on thresholds to control
stimulation output comprises an important part of the present
invention. In order to use normalized intensity levels based on
threshold, a brief recording of the thresholds to be used in the
programming equipment must initially be made.
[0100] In addition, electrode thresholds vary with the anodic and
cathodic combinations. Typical electrode configurations are
monopolar (one electrode paired with the implantable pulse
generator, IPG, case ground), bipolar (a relatively close +- pair
of electrodes), and multipolar (e.g. +-+). It is generally
impractical to collect and record each threshold of each electrode
in every possible combination to use in the programming of a
stimulator. However, it has been found in the spinal cord that the
bipolar thresholds, monopolar thresholds, and tripolar thresholds
follow a similar trend. Thus, it is possible to record a minimal
subset of thresholds, and then interpolate or estimate the
remaining thresholds for each possible combination.
[0101] Normalizing amplitude for programming a stimulation system,
such as an SCS system, is thus an additional feature of the present
invention, although it is not required to practice the invention.
Normalized amplitude programming offers an advantage because in
order to recombine electrodes without manually resetting the
amplitude to ensure a comfortable stimulation level, the normalized
amplitude will aid in automatically calculating actual current or
voltage amplitudes for recombined electrodes. Stimulation
perception is also a product of pulse width, however, and pulse
width should also be included in any threshold estimations or
adjustments. Also, it should be noted that the same normalizing
method may be used for motor thresholds instead of perception
thresholds in applications where motor function is being achieved
(FES).
[0102] Thus, it is seen that the present invention includes, inter
alia, the setting of amplitudes and/or pulse widths during
programming on selected electrodes based on normalization to
perception values, with the ability to discriminate between various
configuration types to adjust the threshold ranges. That is, the
invention includes a means to increase the amplitude and/or pulse
width, a means to record the thresholds for selected electrodes,
and a means to estimate and/or interpolate thresholds for
unrecorded electrodes in any given combination.
[0103] A preferred means to accomplish the above functions includes
a software program that steps the patient or clinician through a
process that records a minimum set of threshold values required to
estimate the remaining thresholds to be used in the programming of
the stimulator (i.e. a software wizard or a threshold user
interface screen). Another means comprises use of a hardware device
that has a location to identify the minimum and maximum thresholds
for a given set of electrodes.
[0104] Currently, to Applicants' knowledge, threshold data is not
recorded nor used to drive the programming of multiple electrode
combinations. Instead, an electrode combination is selected, the
amplitude is turned up from zero to a comfortable level, the
patient responds to where the stimulation is felt, and the process
is repeated for as many combinations as can or would be tried. This
is true for manual selection or computer generated electrode
selections.
[0105] An example of an equation that may be programmed into a
processor and used by the invention to normalize amplitude levels
is as follows:
[0106] X=Amplitude Level (0-10), 0 level=0 mA
[0107] I.sub.i=Current Amplitude, mA for electrode I of n
[0108] P.sub.i=Perception Threshold, mA for electrode I of n
[0109] M.sub.i=Maximum Threshold, mA for electrode I of n
[0110] F.sub.i=Fractional stimulation (.+-.100%), % on electrode I
of n
[0111] For all cathodes (i.e. F, <0):
I.sub.i=F.sub.i.times.P.sub.i.times.X for 0.ltoreq.X.ltoreq.1
and
I.sub.i=F.sub.i.times.[{(M.sub.i-P.sub.1)/9}.times.(X-1)+P.sub.i]
for X>1.
[0112] Note that:
If X=0, I.sub.i=0
If X=1, I.sub.i=P.sub.i.times.F.sub.i
If X=10, I.sub.i=M.sub.i.times.F.sub.i
[0113] The total current for all cathodes is then:
I cathode = I = 1 , F i < 0 n I i ##EQU00001##
[0114] The current for anodes (i.e. F.sub.1>0) is:
I.sub.i=-F.sub.i.times.I.sub.cathode
[0115] An example of output currents for different values of X
using simple monopolar stimulation is as illustrated below in Table
1:
TABLE-US-00001 TABLE 1 Electrode E1 E2 E3 E4 E5 E6 E7 E8 CASE
P.sub.i (mA) 2 3 3.3 2 2.2 2 3 4 NA M.sub.i (mA) 10 12 12.7 11 10 9
11 12.7 NA F.sub.i (%) -100% 100% I.sub.i (mA) X = 0 0.00 0.00 X =
0.5 -1.50 1.50 X = 1 -3.00 3.00 X = 5 -7.00 7.00 X = 10 -12.00
12.00
[0116] An example of output currents for multi-cathode stimulation
is as depicted in Table 2, presented below:
TABLE-US-00002 TABLE 2 Electrode E1 E2 E3 E4 E5 E6 E7 E8 CASE
P.sub.i (mA) 2 3 3.3 2 2.2 2 3 4 NA M.sub.i (mA) 10 12 12.7 11 10 9
11 12.7 NA F.sub.i (%) -90% -10% 100% I.sub.i (mA) X = 0 0.00 0.00
0.00 X = 0.5 -1.35 -0.17 1.52 X = 1 -2.70 -0.33 3.03 X = 5 -6.30
-0.75 7.05 X = 10 -10.80 -1.27 12.07
[0117] A more complex example, involving multipolar stimulation, is
shown in Table 3:
TABLE-US-00003 TABLE 3 Electrode E1 E2 E3 E4 E5 E6 E7 E8 CASE
P.sub.i (mA) 2 3 3.3 2 2.2 2 3 4 NA M.sub.i (mA) 10 12 12.7 11 10 9
11 12.7 NA F.sub.i (%) 10% -90% -10% 90% I.sub.i (mA) X = 0 0.00
0.00 0.00 0.00 X = 0.5 0.10 -0.90 -0.11 0.91 X = 1 0.20 -1.80 -0.22
1.82 X = 5 0.60 -5.40 -0.57 5.37 X = 10 1.09 -9.90 -1.00 9.81
[0118] Another example of this implementation is:
E1: P=1 mA, M=4 mA
E2: P=2 mA, M=4 mA
[0119] If X=5, then:
E1=2.5 mA or E2=3 mA
[0120] If X=5 then: If stimulation is 100% on E1, then E1=2.5 mA If
stimulation is 90% on E1 and 10% on E2, then E1=90%*2.5 mA and
E2=10%*3 mA. Thus, if the level is set to X=5, and a shifting
process moves the current field from E1 at 100% stimulation to 90%
E1 and 10% E2 then the normalized values are proportionately
shifted. The maximum shift would be from 100%*E1 to 100%*E2.
[0121] If normalized values are not used and X is set to 3 mA
Then:
[0122] E1*100%=3 mA
Or,
[0123] E1 (90%) and E2 (10%): E1=2.7 mA and E2=0.3 mA.
[0124] A key part of the invention includes using a programming
scheme to automatically switch electrode combinations, current
distributions, etc. A suitable input mechanism, such as a joystick,
or other input device, such as voice or sensor activation, may be
used as the control input. Automatic preset shifting may also be
used. In accordance with the invention, a suitable control
mechanism (driven in software, hardware, and/or mechanical) is used
to direct or steer stimulation (a current field) by combining
anodic and cathodic electrodes in whole or in part of a given
output. This requires independently programmable electrode outputs
for at least two electrodes, and optimally n outputs for n
electrodes. To illustrate, assume electrode E1 is selected as a
cathode and electrode E3 is selected as an anode, either by default
or manual selection. After the amplitude level is set (normalized
or constant), current can be steered by automatically combining
electrodes with various current distributions (depending on the
stimulators capability). In a single row electrode, such as is
illustrated in FIG. 6C, steering can only occur in the same axis.
In a dual row (or more) electrode array, such as is shown in FIGS.
6A and 6B, an x-y axis can be steered. Additionally, a z axis can
be included (depth of penetration by modulating intensity).
[0125] To shift current, the amplitude on a particular electrode is
reduced proportionately to another electrode's increase. If, for
example, a cathode electrode E1 has an amplitude of 3 mA (or 3V),
the output can be reduced to 90%, 80%, etc., down to zero while
another electrode E3 is increased to 3 mA starting from zero and
increasing to 100%. The current summation in this case is always 3
mA.
[0126] The same shifting of current may also be accomplished with a
normalized amplitude distribution among electrodes. Instead of
applying a proportional increase or decrease on electrodes based on
a constant total amplitude, however, the increase is proportional
to the normalized level. This enables the shifting of current to
stay at a relatively consistent perceptual intensity as the current
field is directed to new locations. If, for example, a normalized
"Level 5" (out of 10) is set, as cathodic current flow, and is
shifted from the location of electrode E1 to the location of
electrode E2, the intensity applied to electrode E1 beginning at
100% would have a value in the middle of the comfortable range
(e.g., half way between the perception threshold and the maximum
threshold). Should the threshold range for electrode E1 be 1 mA to
3 mA, then level 5 for electrode E1 would be 2 mA. Likewise, if the
threshold range for electrode E2 is 3 mA to 5 mA, then level 5 for
electrode E2 would be 4 mA. Thus, as current is shifted from
electrode E1 to electrode E2 in a gradual manner, electrode E1
would be reduced by percentages of 2 mA (at level 5) as E2 is
proportionately increased to its level 5, or 4 mA. Such can result
in differing current summations as the current field is shifted,
but there should be little or no perceptual change in intensity
felt or sensed by the patient. If a constant current value of 4 mA
were to be used instead of a normalized value, then as the current
is shifted back from E2 to E1, the maximum threshold for the
patient would be exceeded and could prove very uncomfortable for
the patient. Thus, it is seen that by using a single current value,
the current shifting could result in fluctuation intensity
perceptions that can drop below the perception threshold or exceed
the maximum tolerable threshold. To avoid this undesirable result,
frequent adjustments in amplitude would have to be made during the
shifting process. That is why use of the normalized value is
preferred for the present invention: total amplitude adjustments
may be automated while maintaining a comfortable stimulation
perception.
[0127] It is noted that non proportional shifts could also be made,
but such would be less optimal and would defeat the purpose or ease
of calculation. However, if the shifting differences are minimal,
such differences would not likely be perceived. An example of a non
proportional shift is as follows: reducing E1 by 10% while
increasing E2 by 20%, then reducing E1 by 20% while increasing E2
by 10%. Each shift is not proportional, but the shift ultimately
results in a shift from electrode E1 to electrode E2, as is the
case with proportional shifts.
[0128] Furthermore, it is noted that stimulation is typically
driven by cathodic current. However, the positive and negative
settings must equal zero. Any shifting of anodic electrode values
must total the current on all of the cathodic electrodes, not
perception thresholds. When shifting current fields using
normalized levels, the combined current will fluctuate. Thus,
proportional shifting of anodic values would not be based on the
perception level, but on the total cathodic current. If driven by
anodic current, then the opposite is true.
[0129] To move current from one location to another without having
to set up each combination in a discretely tested process comprises
a key element of the invention. Such is accomplished through use of
a continuous current shifting process where stimulation is not
interrupted. Several implementations of the continuous shifting
process may be used. For example, the shifting process may include
an algorithm that responds to an input signal indicating a
directional move to calculate the next configuration to move
current. The steering input device is used to indicate the next
location of data to be used to calculate the electrode
configuration. The data may be extracted from a "solve for"
formula, or by locations on one or more tables advanced by the
input device, or a combination of formulas and tables. In any case,
the next configuration is predicated on, or calculated from, the
previous configuration. Each input move configures the electrodes
and distributes the current.
[0130] An example of a current shifting table-based algorithm used
to shift current horizontally across an electrode array is
illustrated in FIG. 7. In FIG. 7, as well as in FIGS. 8 and 8A-8Q
(which show a table-based algorithm used to shift current
vertically), explained below, the gray or shaded portion of the
table represents that portion of cathodic amplitude value that is
based on the normalized constant value set, whereas the white
(non-shaded) portion of the table represents that portion of anodic
current that is based on the sum of all the cathodic currents. The
sequence of numbers arranged in a column along the left side of the
table represent the discrete steps that are utilized in the
shifting process, which steps are controlled by the user through an
appropriate input mechanism, e.g., a joystick or equivalent device.
Thus, in FIG. 7, at step number 1, the stimulus current (normalized
to "1.0" in the table) flows from the anode (+) to the cathode (-)
on the left side of the array. At step number 2, the anodic current
(+) on the left is decreased 10%, the anodic current (+) on the
right side of the array is increased the same amount, while the
cathodic current (-) remains the same. Following this pattern, the
anodic current (+) is gradually shifted from the left side to the
right side while the cathodic current (-) is held at a constant
value. Thus, at step number 11, all of the anodic current (+) has
shifted to the right, while all of the cathodic current (-) remains
on the left. Then, beginning at step 12, the cathodic current
begins to shift in discrete steps of 10% from the left side to the
right side, while the anodic current shifts in similar amounts from
the right side back to the left side. This continues until at step
21 all of the cathodic current (-) has been shifted to the right
side and all of the anodic current (+) is back to the left side.
Then, while holding the cathodic current (-) constant on the right
side, the anodic current (+) is shifted back to the right side in
discrete steps of 10%, until at step 31 all of the anodic current
(+) has been shifted back to the right side, resulting in a
complete shift of the stimulus current from the left side of the
array to the right side.
[0131] It should be noted that in the shifting algorithm shown in
FIG. 7, as well as that shown in FIGS. 8 and 8A-8Q below, that the
illustrated discrete step size of 10% is only exemplary. In
practice, the step size could be smaller or larger than this
amount, as desired.
[0132] In a similar manner, FIGS. 8 and 8A-8Q illustrate an
exemplary table-based algorithm that may be used to shift current
vertically within an electrode array, e.g., up or down an in-line
array of the type shown in FIG. 6C. For purposes of the example
shown in FIGS. 8 and 8A-8Q, it is assumed that monopolar
stimulation is present at electrode E1 (paired with the case
electrode), and that it is desired to shift the stimulation
vertically so that eventually monopolar stimulation is achieved at
electrode E8 (paired with the case electrode). Starting at step
number 1 in FIG. 8A, all of the anodic current (+) flows from the
case electrode, and all of the cathodic current (-) flows to
electrode E1. The anodic current (+) flowing from the case
electrode is gradually decreased in small discrete steps of, e.g.,
10%, while the anodic current (+) flowing from electrode E3
gradually increases in the same step sizes, until at step 11, all
of the anodic current (+) has been shifted to electrode E3. Then,
beginning at step 12, the anodic current (+) flowing from electrode
E3 is gradually decreased in discrete steps of 10%, while the
anodic current (+) flowing from electrode E4 gradually increases in
the same step sizes, until at step 21 (FIG. 88), all of the anodic
current (+) has been shifted to electrode E4. Beginning at step 22
the cathodic current (-) flowing to electrode E1 is gradually
decreased in discrete steps of 10%, while the cathodic current (-)
flowing to electrode E2 is gradually increased in discrete steps of
the same value, while at the same time the anodic current (+)
flowing from electrode E4 is gradually decreased in discrete steps
of 10%, while the anodic current (+) flowing from the case
electrode increased in discrete steps of the same value. Following
this process, at step number 31, all of the cathodic current (-)
has been shifted to electrode E2, while all of the anodic current
(+) has been shifted back to the case electrode. Then, beginning at
step 32, the anodic current (+) is gradually shifted to a second
case electrode, until at step 41 all of the anodic current (+) has
been shifted to the second case electrode.
[0133] Following a process similar to that described above, the
cathodic current (-), which is generally considered as the current
responsible for achieving a desired stimulation, is gradually
shifted in small discrete step sizes, as shown in the balance of
FIG. 8B, and continuing through FIGS. 8C-8Q, until at step number
291 of FIG. 8Q, the cathodic current (-) has been shifted
vertically all the way to electrode E8 and the anodic current (+)
is all flowing from the case electrode (monopolar simulation).
[0134] It is to be emphasized that the equivalent of using formulas
and/or tables to configure electrodes and distribute current may be
achieved through other means, such as the use of a mechanical
switching matrix mechanically controlled by an input steering
device, such as a joystick. It is submitted that those of skill in
the art could readily fashion such a switching matrix, given the
teachings provided herein.
[0135] Turning next to FIG. 9, there is shown a block diagram of
the software architecture used in a preferred embodiment of the
present invention. As seen in FIG. 9, a core program 100 invokes
other programs, e.g., subroutines and/or databases, as required to
assist it as the stimulation system carries out its intended
function. The core program 100 includes two sections: a main
section 102' that invokes a main program 102 where the underlying
programs that control the operation of the SCS system reside, and a
navigator section 104' that invokes a Navigator Wizard program 104
where set up programs reside that aid the user as he or she
initially sets up, i.e, programs, the system. That is, the
Navigator Wizard program 104 facilitates programming the main
program 102 so that the main program 102 has all the data and
parameter settings it needs to carry out its intended function.
[0136] When invoked, the main program 102 provides stimulation
pulses to the patient at selected electrode locations with
stimulation pulses having a selected amplitude, pulse width, pulse
repetition rate, and other control parameters. Being able to
readily determine the optimum location where the stimulation pulses
should be applied, and the parameters associated with the applied
stimulation pulses (amplitude, width, rate) is the primary focus of
the present invention.
[0137] Data files 106 and 108 track the patient's history, and
patient file 110 provides patient data information. The information
contained in patient file 110, e.g., patient name, address, type of
stimulator, serial number of stimulator, etc., is generally entered
by the physician or other medical personnel at the time the patient
is first fitted with the SCS system. The data in the history file
108 keeps a chronology of when the patient visited the SCS
physician and for what purpose, while the data in the selected
visit file 106 provides detail data regarding what occurred during
a given visit.
[0138] An exemplary patient information screen display that is
generated on the display screen 16 of a suitable programming device
10 (FIGS. 1A, 2 and 3) when patient information is entered or
reviewed is shown in FIG. 10. Such patient information display
allows information such as the patient name, birthday, purpose of
visit, diagnosis resulting from the visit, lead (electrode) type,
area of pain, and the like, to be displayed and/or entered into the
system. Included on the particular screen shown in FIG. 10 is a
drop down menu 126 that allows the user to specify the type of
electrode array that the patient has, e.g., a single in-line lead,
two in-line leads positioned end to end, two in-line leads
positioned side by side, and the like.
[0139] Referring back to FIG. 9, a pain map file 112 contains the
needed data for allowing the main programs 100, 102 to display a
map of the patient's body. Using this map, the patient, or other
programming personnel, may select those areas of the body where
pain and/or paresthesia is felt.
[0140] An electrode file 114 stores data that defines the types of
electrodes and electrode arrays that may be used with the SCS.
Using the data in the electrode file 114, the physician or other
programming personnel, can define the electrodes available through
which stimulation pulses may be applied to the patient. Further,
diagnostic testing of the available electrodes may be performed to
verify that an electrode which should be available for use is in
fact available for use.
[0141] A measurement file 116 stores and tracks the perception
threshold and maximum comfort threshold that are either measured
using the navigator wizard program 104, or calculated based on an
interpolation of measured data by the main program 100.
[0142] An advanced program file 118 provides various programs and
data needed to perform advanced functions associated with operation
of the SCS system. In general such advanced functions are not that
relevant to the present invention, and are thus not described in
detail. The advanced program file 118 further provides a location
where future enhancements for the SCS system operation may be
stored and updated. For example, should an improved interpolation
technique be devised to calculate threshold data stored in the
measurement file 116, then such improved interpolation technique
could be stored in the advanced program file 118.
[0143] A key feature of the present invention is the use of a
navigator wizard program 104. The wizard program(s) 104 provides a
software interface that advantageously walks the user step by step
through the measurement and programming process. Additionally, to
make the process even easier, and enjoyable, the wizard may use a
map, akin to a treasure map, which is animated (akin to a video
game) and incorporated into the fitting software. Alternatively,
the treasure map, or other type of map, may be published as a
printed document. The purpose of the animated treasure map, or
printed document, or other software interface, as the case may be,
is to detail the fitting procedure, and more particularly to
graphically assist the clinician and patient as they search for the
optimum program settings that can be used by the system to best
treat the pain (or other neural condition) felt or experienced by
the patient.
[0144] By way of illustration, the main steps carried out by a
preferred measurement/programming wizard are illustrated in the
flow diagram of FIG. 11. In a first step (block 130), the user is
directed to select a stimulation channel. In some instances, there
may be only one stimulation channel that is being used. In other
instances, more than one stimulation channel may be used. Once the
channel has been selected, the user is prompted to click on the
areas where pain is felt (block 132). In one embodiment, this
prompt is accomplished by displaying a screen similar to that shown
in FIG. 12A. As seen in FIG. 12A, a patient body 158 is displayed
having various stimulation areas 160 depicted. By clicking on one
of the areas 160, it is shaded, or colored, in an appropriate
manner to indicate that it has been selected. This selection
activates electrodes which are, as a first try, believed to be the
electrode(s) which can treat the pain area selected.
[0145] Referring back to FIG. 11, after the user has selected the
areas where pain is felt, the user is prompted to increase the
stimulation level until it is first felt (block 134). This step, in
effect, measures the stimulation perception threshold. The user is
prompted to measure this threshold, in one embodiment, by
displaying a screen as shown in FIG. 12B. Such threshold
measurement screen provides instructions to the user in the upper
left hand corner. It also displays three buttons, an OFF button
162, a decrease button 163, and an increase button 164. By pressing
(i.e., clicking) the OFF button 162, the user is able to
selectively turn the stimulus current On of Off. Once on, the user
can increase or decrease the amplitude of the stimulation current
using the buttons 163 and 164. As he or she does so, a vertical bar
graph 166, within a vertical window 165, increases or decreases in
height, thereby providing a visual indication of the relative level
of the stimulus current. Once the user has determined the level at
which stimulation is first felt, the NEXT button 167 is pressed in
order to advance to the next step in the process.
[0146] Returning again to FIG. 11, the user next increases the
stimulation level until the maximum comfortable level is determined
(block 136). This step thus measures the maximum comfortable
stimulation threshold for the patient on the selected channel. To
aid in this process, in one embodiment of the invention, a prompt
screen as shown in FIG. 12C is displayed. The screen shown in FIG.
12C is essentially the same as the one shown in FIG. 12B except
that different instructions are provided in the upper left hand
corner. As the user increases the stimulation level to the maximum
comfortable level, the bar graph 166 increases in height. Once the
user has determined the maximum comfortable stimulation level, the
NEXT button 167 is pressed in order to advance to the next step of
the fitting process.
[0147] As seen in FIG. 11, the next step in the fitting process is
to determine if more threshold measurements need to be taken (block
138). Typically, more than one electrode, or more than one grouping
of electrodes, will be associated with the selected pain site.
Hence, the first threshold measurements are taken for a first group
of electrodes associated with the site, and second threshold
measurements are taken for a second group of electrodes, and
perhaps third threshold measurements are taken for a third group of
electrodes. Typically, no more than about two or three groups of
electrodes are used to determine thresholds, although more
combinations than three could be measured for thresholds if
desired. If every possible electrode combination were measured, the
fitting process would take too long. Hence, in accordance with the
teachings of the present invention, after two or three threshold
measurements have been made, the threshold values for other
possible electrode combinations associated with the selected pain
site are calculated using interpolation or other suitable
estimation techniques.
[0148] Once an adequate number of threshold measurements have been
made (FIG. 11, blocks 134, 136, 138), the user is instructed to
manipulate the location arrow buttons to determine an optimal pain
coverage. This step is done, in one embodiment, by displaying a
locator screen as shown in FIG. 12D. The locator screen includes,
on its right side, controls for the stimulation level, including an
ON/OFF button 162, increase button 164, decrease button 163, and
stimulation level bar graph indicator 166, much the same as, or
similar to, those shown in FIGS. 12B and 12C. Also included within
the locator screen seen in FIG. 12D, in addition to specific
instructions in the upper left hand corner, is an up arrow button
169, a down arrow button 168, a left horizontal arrow button 171
and a right horizontal button 171. The screen shown in FIG. 12D
assumes that only an in-line electrode is used, hence only the up
button 169 and the down button 168 are activated. (For electrode
arrays that allow horizontal movement, the right and left buttons
170 and 171 would also be activated.) As these locator buttons are
pressed, the effective stimulation site, schematically illustrated
at area 172 in the center of the locator buttons, shifts up or down
the electrode. Hence, through use of the locator buttons 168, 169,
170 and/or 171, the user is able to zero in on an optimal pain
coverage location.
[0149] Once the user has located the optimal pain coverage location
for the selected channel, the pulse duration is selected (FIG. 11,
block 142). To assist the user in selecting the pulse duration, in
one embodiment, a pulse duration screen is displayed as shown in
FIG. 12E. Such pulse duration screen includes instructions in the
upper left hand corner of the screen, and stimulation level
controls 162, 163, and 164 on the right side of the screen, similar
to the previously-described wizard screen of FIG. 12D. The pulse
duration screen further includes arrow buttons 173 and 174 which,
when clicked, allow the user to decrease or increase the
stimulation pulse width. As adjustments to the stimulation pulse
width are made, an analog knob 176, having a pointer 175, rotates
to the location indicative of the selected pulse width. For the
selection shown in FIG. 12E, the pulse width is approximately 390
microseconds. As an alternative to increasing and decreasing the
pulse width using the arrow buttons 173 and 174, the user may also
simply click and hold the mouse cursor on the knob 76, and then by
moving the cursor, cause the knob to rotate to a desired pulse
width selection.
[0150] Once the pulse duration, or pulse width, has been set, the
next step is to select the pulse rate (FIG. 11, block 144). In one
embodiment of the invention, this step is prompted by displaying a
rate screen as shown in FIG. 12F. Such pulse rate screen includes
instructions in the upper left hand corner of the screen, and
stimulation level controls 162, 163, and 164 on the right side of
the screen, similar to the previously-described wizard screens of
FIGS. 12D and 12E. The pulse rate screen further includes arrow
buttons 177 and 178 which, when clicked, allow the user to decrease
or increase the stimulation pulse rate. The rate selected is
displayed as a number in the area 179. For the rate screen shown in
FIG. 12F, the rate has been set to 40 pulses per second (pps). Once
the rate has been set to a most comfortable level, the NEXT button
167 is clicked in order to advance to the next step of the fitting
process.
[0151] The next step of the fitting process, as shown in the flow
diagram of FIG. 11, comprises defining where the stimulation is
felt (block 146). This process is facilitated by displaying a
patient FIG. 180 as illustrated in FIG. 12G. Once the FIG. 180 has
been displayed, one area 181 of the patient FIG. 180 is selected as
the area where the patient feels stimulation. While the area 181 is
shown in FIG. 12G as cross-hatched, such is shown only for purposes
of illustration in a black and white drawing. Typically, the area
181 changes to a different color, e.g., red, yellow, blue or green,
when selected.
[0152] As part of step of selecting where stimulation is felt, some
embodiments of the invention further allow the user to select one
of up to three different stimulation settings as the best setting
for that channel. Such selection is facilitated by displaying a
navigation results screen as depicted in FIG. 12H. The navigation
results screen shown in FIG. 12H includes instructions in the upper
left hand corner of the screen, and stimulation level controls 162,
163, and 164 on the right side of the screen, similar to the
previously-described wizard screens of FIGS. 12D, 12E and 12F. Also
included are three selection buttons 182, 183 and 184, labeled "A",
"B" and "C" in FIG. 12H. Selection button "A" (button 182) selects
a first set of stimulation parameters; selection button "B" (button
183) selects a second set of stimulation parameters; and selection
button "C" (button 184) selects a third set of stimulation
parameters. These different sets of stimulation parameters may be
derived from the threshold measurements (FIG. 11. blocks 134, 136),
the location manipulator adjustments (FIG. 11, block 140), and/or
the pulse duration (FIG. 11, block 142) and pulse rate selections
(FIG. 11, block 144) previously made, or previously selected by the
user. The ability to select a "best" set of stimulation parameters
in this manner offers the user the chance to "feel" and "compare"
stimulations based on differing sets of stimulation parameters in
close proximity in time. In this regard, the selection offered in
the navigation results screen of FIG. 12H is similar to the choice
an optometrist or ophthalmologist offers a patient while testing
vision when he/she asks the patient "which looks better, A, B or
C?" as different lenses are switched in and out of the viewer
through which the patient views an eye chart.
[0153] After the user has selected the "best" selection of
stimulation parameters for the given channel (FIG. 11, block 148),
he or she is offered the choice to program additional channels
(FIG. 11, block 150). In one embodiment, such choice is presented
by way of a prompt screen such as the screen depicted in FIG. 12J.
Such prompt screen asks the user whether he or she wants to program
another channel, e.g., channel 2 (see upper left hand corner),
while presenting a display of the patient's body 180' wherein the
other channel to be programmed is defined. For the situation
represented in FIG. 12J, channel 1 comprises stimulation pulses
applied to, or felt in, the right leg; while channel 2 comprises
stimulation pulses applied to, or felt in, the left leg. If the
user does want to program another channel, e.g., channel 2, then he
or she clicks on a YES button 185. If the user does not want to
program another channel, then he or she clicks on the FINISH button
186.
[0154] Should the user indicate that he or she is finished, by
clicking the FINISH button 186, then the user is provided the
opportunity to review and/or verify the program settings that have
been made (FIG. 11, block 152). Such verification and review, in
one embodiment, allows the user to select, inter alia, a chart, as
shown in FIG. 13, that graphically displays the normalized settings
as a function of each electrode position. As seen in FIG. 13, for
example, the minimum perceived threshold (level 1) is illustrated
for all 8 electrodes. The minimum perceived threshold was measured
only for electrodes E1, E4 and E8, and from these measurements the
minimum perceived threshold was calculated using interpolation for
the remaining electrodes E2, E3, E5, E6 and E7. Similarly, the
maximum comfortable threshold was measured only for electrodes E1,
E4 and E8, and from these measurements the maximum comfortable
threshold was calculated using interpolation for the remaining
electrodes E2, E3, E5, E6 and E7. The program settings screen shown
in FIG. 13 further shows that electrode E2 is selected as the
cathodic (-) electrode, with electrode E3 selected as the anodic
(+) electrode, and with the stimulation current level being
represented as a vertical bar 166'. Such vertical bar 166' shows
that for the settings represented in FIG. 13, the stimulation level
on electrode E2 is approximately half way (level 5 or 6) between
the minimum (level 1) and maximum (level 10) amplitude settings.
The chart in FIG. 13 also shows that a level 1 stimulation level on
electrode E2 corresponds to a stimulation current amplitude of
about 5 ma, while a level 10 stimulation level on electrode E2
corresponds to a stimulation current having an amplitude of about
8.5 ma. Other buttons include in FIG. 13 allow other settings to be
verified, adjusted, or saved, in conventional manner.
[0155] Other of the data that may be reviewed and adjusted or
modified, as desired (FIG. 11, block 152), includes the parameter
settings as summarized, e.g., on the screen shown in FIG. 14.
Included in such parameter setting display is a schematic
representation 190 of the channels on the left side of the screen.
In the preferred embodiment, up to four independent channels may be
provided by the SCS system. For the condition represented by the
parameter settings in FIG. 14, only one channel is active (the one
at the top of the channel windows, and it is programmed to provide
a biphasic pulse). One of the channels is paused, and two of the
channels have no electrodes selected, which means these channels
are inoperable for this setting.
[0156] The parameter settings represented in FIG. 14 also include a
schematic representation of the electrode array. For the conditions
represented by FIG. 14, two side-by-side in-line electrode arrays
191 and 192 are used, with staggered electrodes. The stimulation
site selected is near the bottom of the arrays, as oriented in FIG.
14. The parameter settings associate with the active channel are
also represented in FIG. 14, and may readily be adjusted, if
needed. As seen in FIG. 14, the stimulation level is set to "7",
the pulse width (or duration) is set to 350 .mu.sec, and the
stimulation rate is set to 50 pps. Any of these values may be
readily adjusted by simply clicking on to the respective slide bars
194, 195 or 196 and moving the bar in one direction or the other.
Before such values can be adjusted, they must be unlocked, by
clicking on the respective locked icon 197 at the bottom of the
slide bar. Unlocking these values for adjustment may, in some
embodiments, require a password.
[0157] FIG. 15 illustrates another type of screen that may be
displayed as the channel settings are reviewed and/or modified. For
the most part, the screen shown in FIG. 15 contains much of the
same information as is included in FIG. 14. However, FIG. 15
further includes a patient display 197 that allows selected areas
on the patient, e.g., areas 198 and/or 199, to be selected for
receiving stimulus pulses.
[0158] Next, with respect to FIG. 16, a representation of a
treasure map is displayed, which map may be used, in some
embodiments of the invention, to aid the clinician and patient as
the fitting process is carried out. The treasure map depicted in
FIG. 16 highlights the path the patient must follow to achieve a
successful fitting of his or her SCS system, represented by a
treasure chest, the ultimate goal of following the map. The
treasure map shown in FIG. 16 may be displayed on the screen 16 of
the programming device 10 (see FIG. 1A) and/or printed as a
fold-out map. Eye-catching illustrations may be positioned at
various locations on the map, such as a sail boat carrying a
trained, faithful and talented crew of clinicians and other medical
personnel to assure that the patient stays on course on route to
the treasure. Other fun and interesting information (not shown in
FIG. 16) may also be included on the map. When shown on a display
screen, each of the main blocks, or steps, included on the path to
the treasure chest, may flash or be lighted or change color as
these steps are traversed by the patient. Sound bites may also be
interspersed at key locations along the path to the treasure to
educate and entertain.
[0159] As is evident from FIG. 16, the fitting process involves
much more than a single visit from the patient with the clinician.
Rather, numerous steps must be traversed, in a prescribed sequence,
in order for the fitting to be successful. These steps are
described more fully in the previously referenced '829 provisional
patent application. As seen in FIG. 16, at least the following
steps lie along the path to reach the treasure--a successful
fitting and a happy patient--: (1) a patient interview office
visit; (2) surgical planning; (3) percutaneous electrode
Implantation; (4) operating room (OR) fitting procedure; (5) First
Post-surgical office visit; (6) trial stimulation parameters
fitting; (7) trial stimulation period; (8) second post-surgical
office visit; (9) assessment of trial stimulation; (10) surgical
planning; (11) IPG (implantable pulse generator) procedure; (12)
First Post-IPG-Surgical Office Visit; and (13) final fitting.
[0160] As described above, it is thus seen that the present
invention provides numerous functions and meets various needs.
These functions and needs include the following: [0161] 1. A
programming system using an input device and control logic (by
software, hardware, or electrical design) to continuously configure
electrodes and current distributions in response to the user
controlled input device. [0162] 2. A method of stimulating where
current shifting and electrode configurations are determined in
response to an input mechanism controlled by the user, that
interprets the shifting based on a table, formula, or mathematical
model. [0163] 3. A programming method where reconfiguring
electrodes is achieved without stopping stimulation to select the
next configuration to be tested. [0164] 4. A programming method
where reconfiguring electrodes (or current shifting) is achieved
without stopping stimulation to select the next configuration to be
tested: [0165] A. Using a table based approach (preset list of
possible sequences). [0166] B. Using a "solve for" equation (or a
mathematical model). [0167] 5. A neural stimulating system where
electrodes can have current split to unequal and independently
determined levels on a single channel. [0168] 6. A neural
stimulating system wherein a threshold/maximal range is used to
normalize amplitude levels in a current summation process to
determine the amount of current that should be applied on a given
electrode in a group based on a given "level". [0169] 7. A method
for changing electrode configurations and current levels on
selected electrodes of a neural stimulating system while
maintaining a relative intensity perception of the stimulation.
[0170] 8. A patient useable take-home programmer that interprets
normalized levels to proportionately increase or decrease amplitude
on the programmed group of electrodes, thereby ensuring that the
patient cannot exceed the maximum tolerable level. [0171] 9. A
method of programming where any change in distribution can be
implemented in the smallest obtainable change in stimulation
parameters on adjacent electrodes. [0172] 10. A method of
programming where a transition from one distribution of current or
voltage amplitudes X={x.sub.1, x.sub.2, . . . , x.sub.n} on n
electrodes to a second distribution of current or voltage
amplitudes Y={y.sub.1, y.sub.2, . . . y.sub.n} such that
[0172] i = 1 n ( x i - y i ) 2 < Maximum of [ i = 1 n ( x i - y
i ) 2 ] ##EQU00002## [0173] 11. A system that must use the maximal
resolution available to the system at all points of its operation
parameters, i.e. a 16 bit DAC system must use 16 bit resolution.
[0174] 12. A user interface useable in a neural stimulation system
that visually represents the changing current field. [0175] 13. A
user interface useable in a neural stimulation system that uses
consecutive windows in a "wizard" process to step the user through
each step in the fitting process. [0176] 14. A system that allows a
clinician and the patient to quickly determine the desired
electrode stimulation pattern, including which electrodes of a
multiplicity of electrodes in an electrode array should receive a
stimulation current, including the amplitude, width and pulse
repetition rate of such current, so that the tissue stimulator can
be programmed with such information. [0177] 15. An electrode
selection/programming system that allows the clinician to readily
select and visualize a particular group of electrodes of an
electrode array for receipt of a stimulation pulse current, and/or
to allow different combinations of pulse amplitude, pulse width,
and pulse repetition rates to be applied to the selected group.
[0178] 16. A system that facilitates the programming of an
implantable tissue stimulator, having an array of stimulation
electrodes attached thereto, so that only those electrodes which
prove most effective for a desired purpose, e.g., pain relief, are
selected to receive a pulsed current having an amplitude, width and
repetition frequency that best meets the needs of a particular
patient.
[0179] While the invention herein disclosed has been described by
means of specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in the art without departing from the scope of the invention set
forth in the claims.
* * * * *