U.S. patent application number 15/667891 was filed with the patent office on 2017-11-16 for methods to avoid frequency locking in a multi-channel neurostimulation system using pulse shifting.
The applicant listed for this patent is Boston Scientific Neuromodulation Corporation. Invention is credited to Kerry Bradley, Rafael Carbunaru, Andrew DiGiore, Courtney C. Lane, Michael A. Moffitt, David K.L. Peterson.
Application Number | 20170326365 15/667891 |
Document ID | / |
Family ID | 43625993 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170326365 |
Kind Code |
A1 |
Lane; Courtney C. ; et
al. |
November 16, 2017 |
METHODS TO AVOID FREQUENCY LOCKING IN A MULTI-CHANNEL
NEUROSTIMULATION SYSTEM USING PULSE SHIFTING
Abstract
A method and neurostimulation system for treating a patient are
provided. A plurality of pulsed electrical waveforms are
respectively delivered within a plurality of timing channels of the
neurostimulation system, thereby treating the patient. Sets of
stimulation pulses within the pulsed electrical waveforms that will
potentially overlap temporally are predicted. Stimulation pulses in
the respective pulsed electrical waveforms are temporally shifted
in a manner that prevents overlap of the potentially overlapping
pulse sets while preventing frequency locking between the timing
channels.
Inventors: |
Lane; Courtney C.; (Ventura,
CA) ; Carbunaru; Rafael; (Valley Village, CA)
; Bradley; Kerry; (Glendale, CA) ; Peterson; David
K.L.; (Valencia, CA) ; DiGiore; Andrew; (San
Fransisco, CA) ; Moffitt; Michael A.; (Saugus,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Boston Scientific Neuromodulation Corporation |
Valencia |
CA |
US |
|
|
Family ID: |
43625993 |
Appl. No.: |
15/667891 |
Filed: |
August 3, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12550213 |
Aug 28, 2009 |
9724513 |
|
|
15667891 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/36103 20130101;
A61B 5/04004 20130101; A61N 1/0529 20130101; A61N 1/36062 20170801;
A61N 1/36031 20170801; A61B 5/02405 20130101; A61B 5/1118 20130101;
A61N 1/36082 20130101; A61B 5/024 20130101; A61N 1/306 20130101;
A61B 5/021 20130101; A61B 5/4836 20130101; A61N 1/3605 20130101;
A61N 1/36171 20130101; A61B 5/0488 20130101; A61B 5/4812 20130101;
A61M 5/1723 20130101; A61N 1/36021 20130101; A61B 5/112 20130101;
A61N 1/36025 20130101; A61N 1/36071 20130101; A61N 1/36178
20130101; A61N 1/36034 20170801 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/36 20060101 A61N001/36; A61N 1/36 20060101
A61N001/36; A61N 1/36 20060101 A61N001/36; A61N 1/36 20060101
A61N001/36; A61N 1/30 20060101 A61N001/30; A61N 1/05 20060101
A61N001/05; A61M 5/172 20060101 A61M005/172; A61B 5/00 20060101
A61B005/00; A61B 5/00 20060101 A61B005/00; A61B 5/11 20060101
A61B005/11; A61B 5/11 20060101 A61B005/11; A61B 5/0488 20060101
A61B005/0488; A61B 5/04 20060101 A61B005/04; A61B 5/024 20060101
A61B005/024; A61B 5/024 20060101 A61B005/024; A61B 5/021 20060101
A61B005/021; A61N 1/36 20060101 A61N001/36; A61N 1/36 20060101
A61N001/36; A61N 1/36 20060101 A61N001/36; A61N 1/36 20060101
A61N001/36 |
Claims
1. (canceled)
2. A method, comprising: receiving at least two programs for
respectively delivering at least two pulsed electrical waveforms
using at least two timing channels; and processing the at least two
programs to prevent the at least two timing channels from having
overlapping pulses, wherein the processing includes temporally
adjusting at least one pulse in at least one of the at least two
pulsed electrical waveforms.
3. The method of claim 2, wherein the temporally adjusting includes
alternately adjusting the at least two pulsed electrical
waveforms.
4. The method of claim 2, wherein the temporally adjusting
includes: temporally adjusting one of the stimulation pulses in one
of the at least two pulsed electrical waveforms forward; and
temporally adjusting another of the stimulation pulses in another
one of the at least two pulsed electrical waveforms backward.
5. The method of claim 2, wherein the temporally adjusting
includes: determining which pulse of the at least two pulsed
electrical waveforms need to be shifted to prevent overlapping
pulses; and temporally shifting the determined pulse.
6. The method of claim 2, wherein the temporally adjusting
includes: determining non-overlapping stimulation pulse sets within
the at least two pulsed electrical waveforms that are indicated for
adjustment based on temporal proximity; and temporally shifting at
least one pulse in each of the determined non-overlapping pulse
sets.
7. The method of claim 2, wherein the temporally adjusting
includes: temporally shifting at least one pulse in each the at
least two pulsed electrical waveforms a random amount.
8. The method of claim 2, wherein the at least two pulsed
electrical waveforms have different pulse frequencies.
9. The method of claim 2, further comprising defining the at least
two pulsed electrical waveforms in response to a user input.
10. A system, comprising: a plurality of electrical terminals
configured to be respectively coupled to a plurality of electrodes;
output circuitry configured to deliver to the electrical terminals
at least two pulsed electrical waveforms using at least two timing
channels; and control circuitry configured to: receive at least two
programs for respectively delivering at least two pulsed electrical
waveforms using at least two timing channels; and process the at
least two programs to prevent the at least two timing channels from
having overlapping pulses by temporally adjusting at least one
pulse in at least one of the at least two pulsed electrical
waveforms.
11. The system of claim 10, wherein the control circuitry is
configured to alternately adjust the at least two pulsed electrical
waveforms.
12. The system of claim 10, wherein the control circuitry is
configured to temporally adjust one of the stimulation pulses in
one of the at least two pulsed electrical waveforms forward, and
temporally adjust another of the stimulation pulses in one of the
at least two pulsed electrical waveforms backward.
13. The system of claim 10, wherein the control circuitry is
configured to determine which pulse of the at least two pulsed
electrical waveforms need to be shifted to prevent overlapping
pulses, and temporally shift the determined pulse.
14. A non-transitory machine-readable medium including
instructions, which when executed by a machine, cause the machine
to: receive at least two programs for respectively delivering at
least two pulsed electrical waveforms using at least two timing
channels; and process the at least two programs to prevent the at
least two timing channels from having overlapping pulses by
temporally adjusting at least one in at least one of the at least
two pulsed electrical waveforms.
15. The non-transitory machine-readable medium of claim 14, wherein
the temporally adjusting includes alternately adjusting the at
least two pulsed electrical waveforms.
16. The non-transitory machine-readable medium of claim 14, wherein
the temporally adjusting includes: temporally adjusting one of the
stimulation pulses in one of the at least two pulsed electrical
waveforms forward; and temporally adjusting another of the
stimulation pulses in another one of the at least two pulsed
electrical waveforms backward.
17. The non-transitory machine-readable medium of claim 14, wherein
the temporally adjusting includes: determining which pulse of the
at least two pulsed electrical waveforms need to be shifted to
prevent overlapping pulses; and temporally shifting the determined
pulse.
18. The non-transitory machine-readable medium of claim 14, wherein
the temporally adjusting includes: determining non-overlapping
stimulation pulse sets of the at least two pulsed electrical
waveforms that are indicated for adjustment based on temporal
proximity; and temporally shifting at least one pulse in each of
the determined non-overlapping pulse sets.
19. The non-transitory machine-readable medium of claim 14, wherein
the temporally adjusting includes temporally shifting at least one
pulse in each the at least two pulsed electrical waveforms a random
amount.
20. The non-transitory machine-readable medium of claim 14, wherein
the at least two pulsed electrical waveforms have different pulse
frequencies.
21. The non-transitory machine-readable medium of claim 14, further
comprising instructions, which when executed by the machine, cause
the machine to define the at least two pulsed electrical waveforms
in response to a user input.
Description
CLAIM OF PRIORITY
[0001] The application is a continuation of U.S. application Ser.
No. 12/550,213, filed Aug. 28, 2009, which is hereby incorporated
by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to tissue stimulation systems,
and more particularly, to a system and method for eliminating or
reducing frequency locking in multi-channel neurostimulation
systems.
BACKGROUND OF THE INVENTION
[0003] Implantable neurostimulation systems have proven therapeutic
in a wide variety of diseases and disorders. Pacemakers and
Implantable Cardiac Defibrillators (ICDs) have proven highly
effective in the treatment of a number of cardiac conditions (e.g.,
arrhythmias). Spinal Cord Stimulation (SCS) systems have long been
accepted as a therapeutic modality for the treatment of chronic
pain syndromes, and the application of tissue stimulation has begun
to expand to additional applications such as angina pectoralis and
incontinence. Deep Brain Stimulation (DBS) has also been applied
therapeutically for well over a decade for the treatment of
refractory chronic pain syndromes, and DBS has also recently been
applied in additional areas such as movement disorders and
epilepsy. Further, in recent investigations, Peripheral Nerve
Stimulation (PNS) systems have demonstrated efficacy in the
treatment of chronic pain syndromes and incontinence, and a number
of additional applications are currently under investigation.
Furthermore, Functional Electrical Stimulation (FES) systems, such
as the Freehand system by NeuroControl (Cleveland, Ohio), have been
applied to restore some functionality to paralyzed extremities in
spinal cord injury patients.
[0004] These implantable neurostimulation systems typically include
one or more electrode carrying stimulation leads, which are
implanted at the desired stimulation site, and a neurostimulator
(e.g., an implantable pulse generator (IPG)) implanted remotely
from the stimulation site, but coupled either directly to the
stimulation lead(s) or indirectly to the stimulation lead(s) via a
lead extension. The neurostimulation system may further comprise an
external control device to remotely instruct the neurostimulator to
generate electrical stimulation pulses in accordance with selected
stimulation parameters.
[0005] Electrical stimulation energy may be delivered from the
neurostimulator to the electrodes in the form of a pulsed
electrical waveform. Thus, stimulation energy may be controllably
delivered to the electrodes to stimulate neural tissue. The
combination of electrodes used to deliver electrical pulses to the
targeted tissue constitutes an electrode combination, with the
electrodes capable of being selectively programmed to act as anodes
(positive), cathodes (negative), or left off (zero). In other
words, an electrode combination represents the polarity being
positive, negative, or zero. Other parameters that may be
controlled or varied include the amplitude, duration, and rate of
the electrical pulses provided through the electrode array. Each
electrode combination, along with the electrical pulse parameters,
can be referred to as a "stimulation parameter set."
[0006] With some neurostimulation systems, and in particular, those
with independently controlled current or voltage sources, the
distribution of the current to the electrodes (including the case
of the neurostimulator, which may act as an electrode) may be
varied such that the current is supplied via numerous different
electrode configurations. In different configurations, the
electrodes may provide current or voltage in different relative
percentages of positive and negative current or voltage to create
different electrical current distributions (i.e., fractionalized
electrode configurations).
[0007] As briefly discussed above, an external control device can
be used to instruct the neurostimulator to generate electrical
stimulation pulses in accordance with the selected stimulation
parameters. Typically, the stimulation parameters programmed into
the neurostimulator can be adjusted by manipulating controls on the
external control device to modify the electrical stimulation
provided by the neurostimulator system to the patient. However, the
number of electrodes available combined with the ability to
generate a variety of complex stimulation pulses, presents a vast
selection of stimulation parameter sets to the clinician or
patient.
[0008] To facilitate such selection, the clinician generally
programs the neurostimulator through a computerized programming
system. This programming system can be a self-contained
hardware/software system, or can be defined predominantly by
software running on a standard personal computer (PC). The PC or
custom hardware may actively control the characteristics of the
electrical stimulation generated by the neurostimulator to allow
the optimum stimulation parameters to be determined based on
patient feedback or other means and to subsequently program the
neurostimulator with the optimum stimulation parameter set or sets,
which will typically be those that stimulate all of the target
tissue in order to provide the therapeutic benefit, yet minimizes
the volume of non-target tissue that is stimulated. The
computerized programming system may be operated by a clinician
attending the patient in several scenarios.
[0009] Often, multiple timing channels are used when applying
electrical stimulation to target different tissue regions in a
patient. For example, in the context of SCS, the patient may
simultaneously experience pain in different regions (such as the
lower back, left arm, and right leg) that would require the
electrical stimulation of different spinal cord tissue regions. In
the context of DBS, a multitude of brain structures may need to be
electrically stimulated in order to simultaneously treat ailments
associated with these brain structures. Each timing channel
identifies the combination of electrodes used to deliver electrical
pulses to the targeted tissue, as well as the characteristics of
the current (pulse amplitude, pulse duration, pulse frequency,
etc.) flowing through the electrodes.
[0010] The use of multiple timing channels can often lead to
problems with the electrical stimulation systems due to the
potential of an overlap in pulses between two or more timing
channels. Overlapping of pulses using a common electrode can make
neurostimulation systems ineffective or even harmful. Current
neurostimulation systems employing multiple timing channels use a
method known as the "token" method to prevent overlap of pulses.
This method allows an electrical pulse to be transmitted in the
timing channel with the "token," while the other timing channels
wait their turn. Then, the "token" is passed to the next timing
channel. However, if the frequencies of the channels overlap, such
that they need the "token" at the same time, transmission of an
electrical pulse within the second channel must wait until the end
of the transmission of the electrical pulse in the first timing
channel. One possible result is that the frequency of the
electrical pulses transmitted in the second timing channel gets
"locked" to (i.e. matches) the frequency of the electrical pulses
transmitted in the first timing channel; alternatively, one can get
galloping or clumping of electrical pulses. Therefore, when the
occurrence of stimulation pulses is pushed out in time, stimulation
therapy becomes ineffective or even harmful for tissue regions,
such as brain structures to be stimulated in DBS applications, that
require stimulation at specific, regular frequencies.
[0011] The "token" method may best be understood with reference to
FIG. 1. As there shown, a first pulsed electrical waveform 5a
having a first frequency is transmitted within timing channel A,
and a second pulsed electrical waveform 5b having a second
frequency is desired to be transmitted within timing channel B.
Because timing channel A has the "token," the pulses of the second
pulsed electrical waveform 5b that are to be transmitted in timing
channel B must be "bumped" each time they overlap with the pulses
of the first pulsed electrical waveform 5a. As can be seen in the
bumped pulsed electrical waveform 5c, when a pulse is bumped (shown
by the horizontal arrows), the next pulse relies on the new
(bumped) pulse for timing. Thus, the next pulse is "double bumped":
once when the previous pulse is bumped and a second time when it
overlaps a pulse of the pulsed electrical waveform 5a transmitted
in the timing channel A. As a result, the frequency of the pulses
in the second pulsed electrical waveform 5b is forced (i.e.,
locked) into the frequency for the first pulsed electrical waveform
5a, resulting in a pulsed electrical waveform 5d that has a
frequency twice as small as the desired frequency.
[0012] There, thus, remains a need to provide an improved method
for preventing or minimizing frequency locking within multi-channel
neurostimulation systems.
SUMMARY OF THE INVENTION
[0013] In accordance with a first aspect of the present inventions,
a method for treating a patient using a multi-channel
neurostimulation system is provided. The method comprises
delivering a plurality of pulsed electrical waveforms respectively
within a plurality of timing channels of the neurostimulation
system, thereby treating the patient.
[0014] The method comprises delivering a plurality of pulsed
electrical waveforms respectively within a plurality of timing
channels of the neurostimulation system, thereby treating the
patient. In one method, the pulsed electrical waveforms are
delivered via a common electrode and have different pulse
frequencies. The pulsed electrical waveforms may, e.g., be defined
in response to a user input. The method further comprises
predicting sets of stimulation pulses within the electrical
waveforms that will potentially overlap temporally. In one method,
the stimulation pulses of each of the potentially overlapping pulse
sets have the same polarity. The method further comprises
temporally shifting stimulation pulses in the respective pulsed
electrical waveforms in a manner that prevents overlap of the
potentially overlapping pulse sets while preventing frequency
locking between the timing channels. An optional method further
comprises predicting a charge recovery pulse and a stimulation
pulse within the electrical waveforms that will potentially overlap
temporally, and dropping or temporally shifting at least a portion
of the charge recovery pulse, thereby preventing temporal overlap
between the charge recovery pulse and the stimulation pulse of the
respective electrical waveforms. In one embodiment, each
replacement stimulation pulse is delivered within all of the
respective timing channels.
[0015] In one method, the temporal shifting of the stimulation
pulses in the respective pulsed electrical waveforms comprises
alternately shifting one of the stimulation pulses of each
potentially overlapping pulse set between the timing channels. In
another method, the temporal shifting of stimulation pulses in the
respective pulsed electrical waveforms comprises temporally
shifting one of the stimulation pulses of each potentially
overlapping pulse set forward, and temporally shifting another of
the stimulation pulses of each potentially overlapping pulse set
backward. In still another method, the temporal shifting of the
stimulation pulses in the respective pulsed electrical waveforms
comprises determining which pulse of each potentially overlapping
pulse set would need to be shifted the least to prevent overlapping
of the stimulation pulses within the respective potentially
overlapping pulse set, and temporally shifting the determined pulse
of each potentially overlapping pulse set. In yet another method,
the temporal shifting of the stimulation pulses in the respective
pulsed electrical waveforms comprises determining sets of
stimulation pulses within the pulsed electrical waveforms that will
not potentially overlap temporally, and temporally shifting at
least one pulse in each of the non-overlapping pulse sets. In yet
another method, the temporal shifting of the stimulation pulses in
the respective pulsed electrical waveforms comprises temporally
shifting at least one pulse in each potentially overlapping pulse
set a random amount. In this case, the method may further comprise
determining the random amount by multiplying a nominal pulse shift
by a randomization variable. This method may further comprise
limiting the random amount that differs from the nominal pulse
shift.
[0016] In accordance with a second aspect of the present
inventions, a multi-channel neurostimulation system is provided.
The neurostimulation system comprises a plurality of electrical
terminals configured for being respectively coupled to a plurality
of electrodes, and analog output circuitry configured for
delivering a plurality of pulsed electrical waveforms respectively
within a plurality of timing channels to the electrical terminals.
In one embodiment, the stimulation pulses of each of the
potentially overlapping pulse sets have the same polarity. In
another embodiment, the analog output circuitry is configured for
delivering the pulsed electrical waveforms via a common electrode.
In another embodiment, the pulsed electrical waveforms have
different pulse frequencies.
[0017] The neurostimulation system comprises control circuitry
configured for predicting sets of stimulation pulses within the
pulsed electrical waveforms that will potentially overlap
temporally, and temporally shifting stimulation pulses in the
respective pulsed electrical waveforms in a manner that prevents
overlap of the potentially overlapping pulse sets while preventing
frequency locking between the timing channels. In an optional
embodiment, the control circuitry is further configured for
predicting a charge recovery pulse and a stimulation pulse within
the electrical waveforms that will potentially overlap temporally,
and dropping or temporally shifting at least a portion of the
charge recovery pulse, thereby preventing temporal overlap between
the charge recovery pulse and the stimulation pulse of the
respective electrical waveforms.
[0018] In one embodiment, the control circuitry is configured for
shifting stimulation pulses in the respective pulsed electrical
waveforms by alternately shifting one of the stimulation pulses of
each potentially overlapping pulse set between the timing channels.
In another embodiment, the control circuitry is configured for
temporally shifting stimulation pulses in the respective pulsed
electrical by temporally shifting one of the stimulation pulses of
each potentially overlapping pulse set forward, and temporally
shifting another of the stimulation pulses of each potentially
overlapping pulse set backward. In still another embodiment, the
control circuitry is configured for temporally shifting stimulation
pulses in the respective pulsed electrical waveforms by determining
which pulse of each potentially overlapping pulse set would need to
be shifted the least to prevent overlapping of the stimulation
pulses within the respective potentially overlapping pulse set, and
temporally shifting the determined pulse of each potentially
overlapping pulse set. In yet another embodiment, the control
circuitry is configured for temporally shifting stimulation pulses
in the respective pulsed electrical waveforms by determining sets
of stimulation pulses within the pulsed electrical waveforms that
will not potentially overlap temporally, and temporally shifting at
least one pulse in each of the non-overlapping pulse sets. In yet
another embodiment, the control circuitry is configured for
temporally shifting stimulation pulses in the respective pulsed
electrical waveforms by temporally shifting at least one pulse in
each potentially overlapping pulse set a random amount. In this
case, the control circuitry may be configured for determining the
random amount by multiplying a nominal pulse shift by a
randomization variable. The control circuitry may also be further
configured for limiting the random amount that differs from the
nominal pulse shift.
[0019] Other and further aspects and features of the invention will
be evident from reading the following detailed description of the
preferred embodiments, which are intended to illustrate, not limit,
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The drawings illustrate the design and utility of preferred
embodiments of the present invention, in which similar elements are
referred to by common reference numerals. In order to better
appreciate how the above-recited and other advantages and objects
of the present inventions are obtained, a more particular
description of the present inventions briefly described above will
be rendered by reference to specific embodiments thereof, which are
illustrated in the accompanying drawings.
[0021] Understanding that these drawings depict only typical
embodiments of the invention and are not therefore to be considered
limiting of its scope, the invention will be described and
explained with additional specificity and detail through the use of
the accompanying drawings in which:
[0022] FIG. 1 is timing diagram illustrating a prior art technique
for preventing the overlap between pulses of pulsed electrical
waveforms programmed in multiple timing channels;
[0023] FIG. 2 is a plan view of an embodiment of a deep brain
stimulation (DBS) system arranged in accordance with the present
inventions;
[0024] FIG. 3 is a profile view of an implantable pulse generator
(IPG) and percutaneous leads used in the DBS system of FIG. 2;
[0025] FIG. 4 is a plot of monophasic cathodic electrical
stimulation energy;
[0026] FIG. 5a is a plot of biphasic electrical stimulation energy
having a cathodic stimulation pulse and an active charge recovery
pulse;
[0027] FIG. 5b is a plot of biphasic electrical stimulation energy
having a cathodic stimulation pulse and a passive charge recovery
pulse;
[0028] FIG. 6 is a plan view of the DBS system of FIG. 2 in use
with a patient;
[0029] FIG. 7 is a block diagram of the internal components of the
IPG of FIG. 3;
[0030] FIG. 8 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein pulses of the respective electrical
waveforms temporally overlap with each other;
[0031] FIG. 9 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a first technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0032] FIG. 10 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a second technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0033] FIG. 11 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a third technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0034] FIG. 12 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a fourth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0035] FIG. 13 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a fifth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0036] FIG. 14 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a sixth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0037] FIG. 15 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a seventh technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0038] FIG. 16 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein pulses of the respective electrical
waveforms temporally overlap with each other;
[0039] FIG. 17 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein an eighth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0040] FIG. 18 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a ninth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0041] FIG. 19 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a tenth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0042] FIG. 20 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein an eleventh technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms;
[0043] FIG. 21 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a twelfth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms; and
[0044] FIG. 22 is a timing diagram of two pulsed electrical
waveforms delivered within two respective timing channels of the
IPG of FIG. 3, wherein a thirteenth technique is used to prevent
temporal overlap between the pulses of the respective electrical
waveforms.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0045] The description that follows relates to a deep brain
stimulation (DBS) system. However, it is to be understood that the
while the invention lends itself well to applications in DBS, the
invention, in its broadest aspects, may not be so limited. Rather,
the invention may be used with any type of implantable electrical
circuitry used to stimulate tissue. For example, the present
invention may be used as part of a pacemaker, a defibrillator, a
cochlear stimulator, a retinal stimulator, a stimulator configured
to produce coordinated limb movement, a cortical stimulator, a deep
brain stimulator, peripheral nerve stimulator, microstimulator, or
in any other neural stimulator configured to treat urinary
incontinence, sleep apnea, shoulder sublaxation, headache, etc.
[0046] Turning first to FIG. 2, an exemplary DBS neurostimulation
system 10 generally includes one or more (in this case, two)
implantable stimulation leads 12, an implantable pulse generator
(IPG) 14, an external remote controller RC 16, a clinician's
programmer (CP) 18, an External Trial Stimulator (ETS) 20, and an
external charger 22.
[0047] The IPG 14 is physically connected via one or more
percutaneous lead extensions 24 to the stimulation leads 12, which
carry a plurality of electrodes 26 arranged in an array. In the
illustrated embodiment, the stimulation leads 12 are percutaneous
leads, and to this end, the electrodes 26 may be arranged in-line
along the stimulation leads 12. In alternative embodiments, the
electrodes 26 may be arranged in a two-dimensional pattern on a
single paddle lead. As will be described in further detail below,
the IPG 14 includes pulse generation circuitry that delivers
electrical stimulation energy in the form of a pulsed electrical
waveform (i.e., a temporal series of electrical pulses) to the
electrode array 26 in accordance with a set of stimulation
parameters.
[0048] The ETS 20 may also be physically connected via the
percutaneous lead extensions 28 and external cable 30 to the
stimulation leads 12. The ETS 20, which has similar pulse
generation circuitry as the IPG 14, also delivers electrical
stimulation energy in the form of a pulse electrical waveform to
the electrode array 26 accordance with a set of stimulation
parameters. The major difference between the ETS 20 and the IPG 14
is that the ETS 20 is a non-implantable device that is used on a
trial basis after the stimulation leads 12 have been implanted and
prior to implantation of the IPG 14, to test the responsiveness of
the stimulation that is to be provided.
[0049] The RC 16 may be used to telemetrically control the ETS 20
via a bi-directional RF communications link 32. Once the IPG 14 and
stimulation leads 12 are implanted, the RC 16 may be used to
telemetrically control the IPG 14 via a bi-directional RF
communications link 34. Such control allows the IPG 14 to be turned
on or off and to be programmed with different stimulation parameter
sets. The IPG 14 may also be operated to modify the programmed
stimulation parameters to actively control the characteristics of
the electrical stimulation energy output by the IPG 14. As will be
described in further detail below, the CP 18 provides clinician
detailed stimulation parameters for programming the IPG 14 and ETS
20 in the operating room and in follow-up sessions.
[0050] The CP 18 may perform this function by indirectly
communicating with the IPG 14 or ETS 20, through the RC 16, via an
IR communications link 36. Alternatively, the CP 18 may directly
communicate with the IPG 14 or ETS 20 via an RF communications link
(not shown). The clinician detailed stimulation parameters provided
by the CP 18 are also used to program the RC 16, so that the
stimulation parameters can be subsequently modified by operation of
the RC 16 in a stand-alone mode (i.e., without the assistance of
the CP 18).
[0051] The external charger 22 is a portable device used to
transcutaneously charge the IPG 14 via an inductive link 38. For
purposes of brevity, the details of the external charger 22 will
not be described herein. Once the IPG 14 has been programmed, and
its power source has been charged by the external charger 22 or
otherwise replenished, the IPG 14 may function as programmed
without the RC 16 or CP 18 being present.
[0052] For purposes of brevity, the details of the RC 16, CP 18,
ETS 20, and external charger 22 will not be described herein.
Details of exemplary embodiments of these devices are disclosed in
U.S. Pat. No. 6,895,280, which is expressly incorporated herein by
reference.
[0053] Referring now to FIG. 3, the features of the stimulation
leads 12 and the IPG 14 will be briefly described. One of the
stimulation leads 12(1) has eight electrodes 26 (labeled E1-E8),
and the other stimulation lead 12(2) has eight electrodes 26
(labeled E9-E16). The actual number and shape of leads and
electrodes will, of course, vary according to the intended
application. The IPG 14 comprises an outer case 40 for housing the
electronic and other components (described in further detail
below), and a connector 42 to which the proximal ends of the
stimulation leads 12 mates in a manner that electrically couples
the electrodes 26 to the electronics within the outer case 40. The
outer case 40 is composed of an electrically conductive,
biocompatible material, such as titanium, and forms a hermetically
sealed compartment wherein the internal electronics are protected
from the body tissue and fluids. In some cases, the outer case 40
may serve as an electrode.
[0054] As will be described in further detail below, the IPG 14
includes a battery and pulse generation circuitry that delivers the
electrical stimulation energy in the form of a pulsed electrical
waveform to the electrode array 26 in accordance with a set of
stimulation parameters programmed into the IPG 14. Such stimulation
parameters may comprise electrode combinations, which define the
electrodes that are activated as anodes (positive), cathodes
(negative), and turned off (zero), percentage of stimulation energy
assigned to each electrode (fractionalized electrode
configurations), and electrical pulse parameters, which define the
pulse amplitude (measured in milliamps or volts depending on
whether the IPG 14 supplies constant current or constant voltage to
the electrode array 26), pulse duration (measured in microseconds),
pulse rate (measured in pulses per second), and burst rate
(measured as the stimulation on duration X and stimulation off
duration Y).
[0055] Electrical stimulation will occur between two (or more)
activated electrodes, one of which may be the IPG case. Simulation
energy may be transmitted to the tissue in a monopolar or
multipolar (e.g., bipolar, tripolar, etc.) fashion. Monopolar
stimulation occurs when a selected one of the lead electrodes 26 is
activated along with the case of the IPG 14, so that stimulation
energy is transmitted between the selected electrode 26 and case.
Bipolar stimulation occurs when two of the lead electrodes 26 are
activated as anode and cathode, so that stimulation energy is
transmitted between the selected electrodes 26. For example,
electrode E3 on the first lead 12(1) may be activated as an anode
at the same time that electrode E11 on the second lead 12(1) is
activated as a cathode. Tripolar stimulation occurs when three of
the lead electrodes 26 are activated, two as anodes and the
remaining one as a cathode, or two as cathodes and the remaining
one as an anode. For example, electrodes E4 and E5 on the first
lead 12 may be activated as anodes at the same time that electrode
E12 on the second lead 12 is activated as a cathode
[0056] The stimulation energy may be delivered between a specified
group of electrodes as monophasic electrical energy or multiphasic
electrical energy. As illustrated in FIG. 4, monophasic electrical
energy includes a series of pulses that are either all negative
(cathodic), or alternatively all positive (anodic). Multiphasic
electrical energy includes a series of pulses that alternate
between positive and negative.
[0057] For example, as illustrated in FIGS. 5a and 5b, multiphasic
electrical energy may include a series of biphasic pulses, with
each biphasic pulse including a cathodic (negative) stimulation
pulse (during a first phase) and an anodic (positive) charge
recovery pulse (during a second phase) that is generated after the
stimulation pulse to prevent direct current charge transfer through
the tissue, thereby avoiding electrode degradation and cell trauma.
That is, charge is conveyed through the electrode-tissue interface
via current at an electrode during a stimulation period (the length
of the stimulation pulse), and then pulled back off the
electrode-tissue interface via an oppositely polarized current at
the same electrode during a recharge period (the length of the
charge recovery pulse).
[0058] The second phase may have an active charge recovery pulse
(FIG. 5a), wherein electrical current is actively conveyed through
the electrode via current or voltage sources, and a passive charge
recovery pulse, or the second phase may have a passive charge
recovery pulse (FIG. 5b), wherein electrical current is passively
conveyed through the electrode via redistribution of the charge
flowing from coupling capacitances present in the circuit. Using
active recharge, as opposed to passive recharge, allows faster
recharge, while avoiding the charge imbalance that could otherwise
occur. Another electrical pulse parameter in the form of an
interphase can define the time period between the pulses of the
biphasic pulse (measured in microseconds).
[0059] As shown in FIG. 6, the stimulation leads 12 are introduced
through a burr hole 46 formed in the cranium 48 of a patient 44,
and introduced into the parenchyma of the brain 49 of the patient
44 in a conventional manner, such that the electrodes 26 are
adjacent a target tissue region whose electrical activity is the
source of the dysfunction (e.g., the ventrolateral thalamus,
internal segment of globus pallidus, substantia nigra pars
reticulate, subthalamic nucleus, or external segment of globus
pallidus). Thus, stimulation energy can be conveyed from the
electrodes 26 to the target tissue region to change the status of
the dysfunction. Due to the lack of space near the location where
the stimulation leads 12 exit the burr hole 46, the IPG 14 is
generally implanted in a surgically-made pocket either in the
abdomen or above the buttocks. The IPG 14 may, of course, also be
implanted in other locations of the patient's body. The lead
extension(s) 24 facilitates locating the IPG 14 away from the exit
point of the electrode leads 12.
[0060] Turning next to FIG. 7, the main internal components of the
IPG 14 will now be described. The IPG 14 includes stimulation
output circuitry 50 configured for generating electrical
stimulation energy in accordance with a defined pulsed waveform
having a specified pulse amplitude, pulse rate, pulse width, pulse
shape, and burst rate under control of control logic 52 over data
bus 54. Control of the pulse rate and pulse width of the electrical
waveform is facilitated by timer logic circuitry 56, which may have
a suitable resolution, e.g., 10 .mu.s. The stimulation energy
generated by the stimulation output circuitry 50 is output via
capacitors C1-C16 to electrical terminals 55 corresponding to the
electrodes 26. The analog output circuitry 50 may either comprise
independently controlled current sources for providing stimulation
pulses of a specified and known amperage to or from the electrodes
26, or independently controlled voltage sources for providing
stimulation pulses of a specified and known voltage at the
electrodes 26.
[0061] Any of the N electrodes may be assigned to up to k possible
groups or "channels." In one embodiment, k may equal four. The
channel identifies which electrodes are selected to synchronously
source or sink current to create an electric field in the tissue to
be stimulated. Amplitudes and polarities of electrodes on a channel
may vary, e.g., as controlled by the RC 16. External programming
software in the CP 18 is typically used to set stimulation
parameters including electrode polarity, amplitude, pulse rate and
pulse duration for the electrodes of a given channel, among other
possible programmable features.
[0062] The N programmable electrodes can be programmed to have a
positive (sourcing current), negative (sinking current), or off (no
current) polarity in any of the k channels. Moreover, each of the N
electrodes can operate in a multipolar (e.g., bipolar) mode, e.g.,
where two or more electrode contacts are grouped to source/sink
current at the same time. Alternatively, each of the N electrodes
can operate in a monopolar mode where, e.g., the electrode contacts
associated with a channel are configured as cathodes (negative),
and the case electrode (i.e., the IPG case) is configured as an
anode (positive).
[0063] Further, the amplitude of the current pulse being sourced or
sunk to or from a given electrode may be programmed to one of
several discrete current levels, e.g., between 0 to 10 mA in steps
of 0.1 mA. Also, the pulse duration of the current pulses is
preferably adjustable in convenient increments, e.g., from 0 to 1
milliseconds (ms) in increments of 10 microseconds (.mu.s).
Similarly, the pulse rate is preferably adjustable within
acceptable limits, e.g., from 0 to 1000 pulses per second (pps).
Other programmable features can include slow start/end ramping,
burst stimulation cycling (on for X time, off for Y time),
interphase, and open or closed loop sensing modes.
[0064] The operation of this analog output circuitry 50, including
alternative embodiments of suitable output circuitry for performing
the same function of generating stimulation pulses of a prescribed
amplitude and duration, is described more fully in U.S. Pat. Nos.
6,516,227 and 6,993,384, which are expressly incorporated herein by
reference.
[0065] The IPG 14 further comprises monitoring circuitry 58 for
monitoring the status of various nodes or other points 60
throughout the IPG 14, e.g., power supply voltages, temperature,
battery voltage, and the like. The IPG 14 further comprises
processing circuitry in the form of a microcontroller (.mu.C) 62
that controls the control logic over data bus 64, and obtains
status data from the monitoring circuitry 58 via data bus 66. The
IPG 14 additionally controls the timer logic 56. The IPG 14 further
comprises memory 68 and oscillator and clock circuitry 70 coupled
to the microcontroller 62. The microcontroller 62, in combination
with the memory 68 and oscillator and clock circuit 70, thus
comprise a microprocessor system that carries out a program
function in accordance with a suitable program stored in the memory
68. Alternatively, for some applications, the function provided by
the microprocessor system may be carried out by a suitable state
machine.
[0066] Thus, the microcontroller 62 generates the necessary control
and status signals, which allow the microcontroller 62 to control
the operation of the IPG 14 in accordance with a selected operating
program and stimulation parameters. In controlling the operation of
the IPG 14, the microcontroller 62 is able to individually generate
a train of stimulus pulses at the electrodes 26 using the analog
output circuitry 60, in combination with the control logic 52 and
timer logic 56, thereby allowing each electrode 26 to be paired or
grouped with other electrodes 26, including the monopolar case
electrode. In accordance with stimulation parameters stored within
the memory 68, the microcontroller 62 may control the polarity,
amplitude, rate, pulse duration and channel through which the
current stimulus pulses are provided. The microcontroller 62 also
facilitates the storage of electrical parameter data (or other
parameter data) measured by the monitoring circuitry 58 within
memory 68, and also provides any computational capability needed to
analyze the raw electrical parameter data obtained from the
monitoring circuitry 58 and compute numerical values from such raw
electrical parameter data.
[0067] Significantly, as will be described in further detail below,
the microcontroller 62 uses a set of rules to prevent overlap of
pulses between multiple timing channels. Alternatively, functions
such as the management of stimulation pulses and timing information
may be performed in a digital state machine, with the
microcontroller 62 having a supervisory role to manage information
flow, e.g., sending stimulation parameters to the analog circuitry
and/or converting sampled analog data into a digital form, and then
post-processing the digital data for storage or transmission to the
RC 16.
[0068] The IPG 14 further comprises an alternating current (AC)
receiving coil 72 for receiving programming data (e.g., the
operating program and/or stimulation parameters) from the RC 16
(shown in FIG. 2) in an appropriate modulated carrier signal, and
charging and forward telemetry circuitry 74 for demodulating the
carrier signal it receives through the AC receiving coil 72 to
recover the programming data, which programming data is then stored
within the memory 68, or within other memory elements (not shown)
distributed throughout the IPG 14.
[0069] The IPG 14 further comprises back telemetry circuitry 76 and
an alternating current (AC) transmission coil 78 for sending
informational data sensed through the monitoring circuitry 58 to
the RC 16. The back telemetry features of the IPG 14 also allow its
status to be checked. For example, when the RC 16 initiates a
programming session with the IPG 14, the capacity of the battery is
telemetered, so that the external programmer can calculate the
estimated time to recharge. Any changes made to the current
stimulus parameters are confirmed through back telemetry, thereby
assuring that such changes have been correctly received and
implemented within the implant system. Moreover, upon interrogation
by the RC 16, all programmable settings stored within the IPG 14
may be uploaded to the RC 16. Significantly, the back telemetry
features allow raw or processed electrical parameter data (or other
parameter data) previously stored in the memory 68 to be downloaded
from the IPG 14 to the RC 16, which information can be used to
track the physical activity of the patient.
[0070] The IPG 14 further comprises a rechargeable power source 80
and power circuits 82 for providing the operating power to the IPG
14. The rechargeable power source 80 may, e.g., comprise a
lithium-ion or lithium-ion polymer battery. The rechargeable
battery 80 provides an unregulated voltage to the power circuits
82. The power circuits 82, in turn, generate the various voltages
84, some of which are regulated and some of which are not, as
needed by the various circuits located within the IPG 14. The
rechargeable power source 80 is recharged using rectified AC power
(or DC power converted from AC power through other means, e.g.,
efficient AC-to-DC converter circuits, also known as "inverter
circuits") received by the AC receiving coil 72. To recharge the
power source 80, an external charger (not shown), which generates
the AC magnetic field, is placed against, or otherwise adjacent, to
the patient's skin over the implanted IPG 14. The AC magnetic field
emitted by the external charger induces AC currents in the AC
receiving coil 72. The charging and forward telemetry circuitry 74
rectifies the AC current to produce DC current, which is used to
charge the power source 80. While the AC receiving coil 72 is
described as being used for both wirelessly receiving
communications (e.g., programming and control data) and charging
energy from the external device, it should be appreciated that the
AC receiving coil 72 can be arranged as a dedicated charging coil,
while another coil, such as coil 78, can be used for bi-directional
telemetry.
[0071] It should be noted that the diagram of FIG. 7 is functional
only, and is not intended to be limiting. Those of skill in the
art, given the descriptions presented herein, should be able to
readily fashion numerous types of IPG circuits, or equivalent
circuits, that carry out the functions indicated and described,
which functions include not only producing a stimulus current or
voltage on selected groups of electrodes, but also the ability to
measure electrical parameter data at an activated or non-activated
electrode.
[0072] Additional details concerning the above-described and other
IPGs may be found in U.S. Pat. No. 6,516,227, U.S. Patent
Publication No. 2003/0139781, and U.S. patent application Ser. No.
11/138,632, entitled "Low Power Loss Current Digital-to-Analog
Converter Used in an Implantable Pulse Generator," which are
expressly incorporated herein by reference. It should be noted that
rather than an IPG, the DBS system 10 may alternatively utilize an
implantable receiver-stimulator (not shown) connected to leads 12.
In this case, the power source, e.g., a battery, for powering the
implanted receiver, as well as control circuitry to command the
receiver-stimulator, will be contained in an external controller
inductively coupled to the receiver-stimulator via an
electromagnetic link. Data/power signals are transcutaneously
coupled from a cable-connected transmission coil placed over the
implanted receiver-stimulator. The implanted receiver-stimulator
receives the signal and generates the stimulation in accordance
with the control signals.
[0073] As briefly discussed above, the IPG 14 may be programmed by
the CP 18 (or alternatively the RC 16) to operate over multiple
timing channels. The IPG 14 may prevent overlap between the
electrical pulses generated in the respective timing channels, and
to do so without frequency locking occurring between the timing
channels. While the techniques described herein for preventing
overlapping of electrical pulses and frequency locking between
timing channels lend themselves well when the electrode
combinations assigned to the respective timing channels have one or
more common electrodes, these techniques may be useful even if the
electrode combinations assigned to the respective timing channels
are completely different from each other. These techniques will now
be described.
[0074] Referring first to FIG. 8, two timing channels (Channel A
and Channel B) of the IPG 14 may be programmed by the CP 18 (or
alternatively, the RC 16) with two pulsed electrical waveforms
100a, 100b, respectively, which when delivered by the analog output
circuitry 50 of the IPG 14, will provide treatment to the patient
in which the IPG 14 has been implanted. The electrode combinations
assigned to the respective timing channels will typically be those
that result in the treatment of two different regions. As briefly
discussed above, each timing channel identifies the electrodes that
are selected to synchronously source or sink current to create an
electrical field in the tissue to be stimulated, and that the
amplitude and polarities of electrodes assigned to each timing
channel may vary. Notably, more than one pulsed electrical waveform
can be delivered within any particular timing channel, such as
those exemplified in U.S. Pat. No. 6,895,280, which has been
previously incorporated herein by reference. For purposes of
brevity and clarity, however, only one pulsed electrical waveform
is shown for each timing channel. Furthermore, although the pulsed
electrical waveforms illustrated in FIG. 8 are monophasic in
nature, the pulsed electrical waveforms delivered during a timing
channel can be multiphasic in nature, as described in further
detail below.
[0075] As seen in FIG. 8, without modification, certain sets of
respective stimulation pulses of the electrical waveforms 100a,
100b will temporally overlap each other (either partially or
completely). However, the microcontroller 62 of the IPG 14 may
predict the sets of stimulation pulses that will potentially
overlap each other temporally prior to their delivery within the
respective timing channels, and replace each of these potentially
overlapping pulse sets with a stimulation pulse, such that each
replacement stimulation pulse is delivered within at least one of
the respective timing channels (and thus, delivered to the both
electrode combinations assigned to the timing channels in the case
where the electrode combinations are the same for both timing
channels), thereby preventing temporal overlap between the
stimulation pulses of the respective pulsed electrical waveforms
100a, 100b while preventing frequency locking between the timing
channels. If delivered in both timing channels, the replacement
stimulation pulse will preferably be simultaneously delivered
within the timing channels. If the potentially overlapping
stimulation pulses that are replaced are displaced from each other
in time, then the replacement stimulation pulse may be slightly
displaced or offset in time from the potentially overlapping pulses
that they replace.
[0076] In one embodiment, the IPG 14 may determine the relative
amplitude and/or duration (width) of the pulses within each
potentially overlapping pulse set, and select the single
replacement stimulation pulse for each potentially overlapping
pulse set based on the determined relative amplitude and/or pulse
duration, with each replacement stimulation pulse being delivered
within both timing channels. For example, as shown in FIG. 9, for
each potentially overlapping pulse set, the IPG 14 selects the
stimulation pulse having the largest amplitude as the replacement
stimulation pulse. In this manner, any difference between the
amount current delivered to the electrode combinations by a set of
non-overlapping stimulation pulses of the respective pulsed
electrical waveforms 100a, 100b and the amount of current delivered
to the electrode combinations by the replacement stimulation pulse
(which will have to be distributed amongst two combinations of
electrodes) is minimized. Alternatively, the pulse with the largest
duration may be selected as the replacement stimulation pulse, as
shown in FIG. 10.
[0077] In another embodiment, the IPG 14 may define each of the
replacement stimulation pulses as a function of the stimulation
pulses within the respective potentially overlapping pulse set that
is replaced, with each replacement stimulation pulse being
delivered within both timing channels. For example, as shown in
FIG. 11, for each potentially overlapping pulse set, the IPG 14
averages the amplitudes and the pulse widths of the respective
stimulation pulses within the pulse set and uses this average as
the amplitude and pulsewidth of the replacement stimulation pulse.
Alternatively, the IPG 14 may average only the amplitudes or only
the durations of the respective pulses within the pulse set and use
this average as the respective amplitude or duration of the
replacement stimulation pulse.
[0078] As another example shown in FIG. 12, for each potentially
overlapping pulse set, the IPG 14 sums the amplitudes of the
respective stimulation pulses within the pulse set and uses this
sum as the amplitude of the replacement stimulation pulse. By
summing the pulses in each potentially overlapping pulse set, a
sufficient amount of electrical current delivered in each timing
channel will be ensured, so that the respective tissue regions of
the patient will be adequately stimulated. The IPG 14 may limit the
amplitude of each replacement stimulation pulse (e.g., 20 mA) to
prevent over-stimulation of either tissue regions, and in
particular, the tissue region associated with the timing channel
having the lower amplitude pulses.
[0079] In still another embodiment, the IPG 14 may alternately
select the stimulation pulse of the respective pulsed electrical
waveforms 100a, 100b as the replacement stimulation pulse for each
of the potentially overlapping pulse sets. Each replacement
stimulation pulse is delivered within both timing channels. For
example, as shown in FIG. 13, the IPG 14 selects the stimulation
pulse in the pulsed electrical waveform 100a to replace the first
potentially overlapping pulse set, then selects the stimulation
pulse in the pulsed electrical waveform 100b to replace the second
potentially overlapping pulse set, then selects the stimulation
pulse in the pulsed electrical waveform 100a to replace the third
potentially overlapping pulse set, etc. As shown in FIG. 14, each
replacement stimulation pulse can be delivered within only the
timing channel from which it was selected. Essentially, the
stimulation pulse of the respective potentially overlapping pulse
set that is not selected is suppressed, such that no stimulation
pulse is delivered in the timing channel when the selected
stimulation pulse is delivered in the other timing channel.
[0080] In yet another embodiment, the IPG 14 assigns one of the
timing channels as a high priority timing channel, and selects the
stimulation pulse associated with the high priority timing channel
as the replacement stimulation pulse for a series of potentially
overlapping pulse sets. If the timing channels are respectively
associated with different tissue regions, the timing channel
associated with the tissue region that would be more adversely
affected by dropping a stimulation pulse within the timing channel
can be assigned as the high priority timing channel (e.g., in
response to a user input via the CP 18 or RC 16). Each replacement
stimulation pulse is delivered within the high priority timing
channel. Essentially, the stimulation pulse of the lower priority
timing channel is suppressed. For example, as shown in FIG. 15, the
IPG 14 assigns Timing Channel B as the high-priority channel, and
selects the stimulation pulse of the pulsed electrical waveform
100b as the replacement stimulation pulse for all of the
potentially overlapping pulse sets. As shown in FIG. 15, each
replacement stimulation pulse is delivered only in Timing Channel
B. Alternatively, each replacement stimulation pulse can be
delivered in both Timing Channels A and B.
[0081] This embodiment may be especially useful when stimulating a
key structure in the brain that requires highly regular pulsed
frequencies, with the timing channel associated with the key
structure having a high priority. Also, although this embodiment is
discussed in the context of DBS, in occipital nerve stimulation,
lesser occipital nerve stimulation may be a lower priority than
greater occipital nerve stimulation. In this case, the timing
channel associated with the greater occipital nerve stimulation
will be given high priority, such that the stimulation pulse within
the potentially overlapping pulse associated with greater occipital
nerve stimulation will be selected as the replacement stimulation
pulse.
[0082] Although the stimulation pulses in the potentially
overlapping pulse sets have been described as being cathodic, it
should be noted that the overlapping pulse sets can be anodic, in
which case, the same techniques can be applied. If one pulse in a
potentially overlapping pulse set is anodic and another pulse in
the same potentially overlapping pulse set is cathodic, other
techniques can be utilized to resolve this conflict. For example,
as illustrated in FIG. 16, two timing channels (Channel A and
Channel B) of the IPG 14 may be programmed by the CP 18 (or
alternatively, the RC 16) with two pulsed electrical waveforms
100c, 100d, respectively, which when delivered by the IPG 14, will
provide treatment to the patient in which the IPG 14 has been
implanted.
[0083] As with the pulsed electrical waveforms 100a, 100b
illustrated in FIG. 8, without modification, certain sets of
respective pulses of the electrical waveforms 100c, 100d will
temporally overlap each other (either partially or completely).
Again, the IPG 14 may determine the sets of pulses that will
potentially overlap each other temporally prior to their delivery
within the respective timing channels, and replace each of these
potentially overlapping pulse sets with a pulse, such that each
pulse is delivered within at least one of the respective timing
channels (and thus, delivered to the both electrode combinations
assigned to the timing channels), thereby preventing temporal
overlap between the pulses of the respective pulsed electrical
waveforms 100c, 100d.
[0084] In this embodiment, however, the cathodic pulse in each
potentially overlapping pulse set of the electrical waveforms 100c,
100d is selected as the replacement stimulation pulse, as
illustrated in FIG. 17. Significantly, cathodic pulses are often
the stimulating pulses, and are therefore, more important than
anodic pulses, which are generally not stimulating. As such,
retaining the cathodic pulse as the replacement stimulation pulse,
while discarding or suppressing the anodic pulse, may not adversely
affect therapy. In applications where the anodic pulses are used as
the stimulating pulses, the anodic pulse may be retained as the
replacement stimulation pulse, while the cathodic pulse is
discarded or suppressed.
[0085] Instead of replacing each of the potentially overlapping
pulse sets with a pulse in the manner discussed above with respect
to FIGS. 9-17, the microcontroller 62 of the IPG 14 may temporally
shift pulses in the respective pulsed electrical waveforms in a
manner that prevents overlap of the determined pulse sets while
preventing frequency locking between the timing channels.
[0086] In one embodiment, the IPG 14 alternately shifts stimulation
pulses within the potentially overlapping pulse sets. For example,
as shown in FIG. 18, the IPG 14 temporally shifts the stimulation
pulse of the pulsed electrical waveform 100a for the first
potentially overlapping pulse set, temporally shifts the
stimulation pulse of the pulsed electrical waveform 100b for the
second potentially overlapping pulse set, temporally shifts the
stimulation pulse of the pulsed electrical waveform 100a for the
third potentially overlapping pulse set, etc. Notably, the IPG 14
shifts each of the stimulation pulses in the direction that would
minimize the amount that the stimulation pulses are shifted from
their original position. For example, in FIG. 18, the stimulation
pulse in the pulsed electrical waveform 100a is shifted forward in
time for the first potentially overlapping pulse set, the
stimulation pulse in the pulsed electrical waveform 100b is shifted
backward in time for the second potentially overlapping pulse set,
and the stimulation pulse in the pulsed electrical waveform 100a is
shifted forward time for the third potentially overlapping pulse
set.
[0087] In another embodiment, the IPG 14 temporally shifts one of
the stimulation pulses of each potentially overlapping pulse set
forward, and temporally shifts the other of the stimulation pulses
of the each potentially overlapping pulse set backward. Notably,
the IPG 14 shifts each of the stimulation pulses in the direction
that would minimize the amount that the stimulation pulses are
shifted from their original position. For example, as shown in FIG.
19, the stimulation pulse in the electrical waveform 100a is
shifted backward in time, and the stimulation pulse in the
electrical waveform 100b is shifted forward in time for the first
potentially overlapping pulse set, the stimulation pulse in the
electrical waveform 100a is shifted forward in time, and the
stimulation pulse in the electrical waveform 100b is shifted
backward in time for the second potentially overlapping pulse set,
and the stimulation pulse in the electrical waveform 100a is
shifted forward in time, and the stimulation pulse in the
electrical waveform 100b is shifted backward in time for the third
potentially overlapping pulse set
[0088] In still another embodiment, the IPG 14 determines which
stimulation pulse of each of the potentially overlapping pulse sets
would need to be shifted the least to prevent overlapping of the
stimulation pulses within the respective potentially overlapping
pulse set, and temporally shifts that stimulation pulse within the
timing channel.
[0089] For example, as shown in FIG. 20, for the second and third
overlapping pulse sets, the stimulation pulses in the electrical
waveform 100a would need to be shifted forward the least as
compared to the stimulation pulses in the electrical waveform 100b,
and thus, the stimulation pulses in the electrical waveform 100a
are temporally shifted forward within the Timing Channel A. With
respect to the first overlapping pulse set, the respective
stimulation pulses of the electrical waveforms 100a, 100b would
need to be shifted forward an equal amount to prevent the
overlapping of the stimulation pulses. In this case, selection of
the stimulation pulse that is to be temporally shifted can be
performed arbitrarily or based on other criteria.
[0090] In the example illustrated in FIG. 20, the pulses in the
electrical waveforms 100a and 100b are temporally shifted forward
within the respective Timing Channels A and B. It should be
appreciated that the pulses may be temporally shifted backward to
avoid overlapping of the pulses. Selection of whether the pulses
are to be shifted forward or backward may be determined based on
any one of a variety of criteria. For example, the user or the
system 10 may select the direction (either forward or backward) in
which the pulses are to be shifted, or the direction in which the
pulses are to be shifted may alternate or be randomly or
pseudo-randomly selected. In these examples, the pulse that needs
to be shifted the least in the selected direction would be shifted
to prevent overlap.
[0091] In yet another embodiment, the IPG 14 predicts sets of
stimulation pulses within the pulsed electrical waveforms that will
not temporally overlap prior to their delivery within the
respective timing channels, and temporally shifts at least one
stimulation pulse in each of the potentially non-overlapping pulse
sets. Thus, when the stimulation pulses are getting closer to the
potentially overlapping pulse set (e.g., 4 pulses away), the IPG 14
may slightly shift one or both stimulation pulses of the pulsed
electrical waveforms before they overlap. The advantage of this
technique is that the stimulation pulses will only need to slightly
be shifted in time from their original position, so that the
frequency of the original pulsed electrical waveform is closer to
the frequency of the modified pulsed electrical waveform.
[0092] For example, as shown in FIG. 21, two timing channels
(Channel A and Channel B) of the IPG 14 may be programmed by the CP
18 (or alternatively, the RC 16) with two pulsed electrical
waveforms 100e, 100f, respectively, which when delivered by the IPG
14, will provide treatment to the patient in which the IPG 14 has
been implanted. As with the pulsed electrical waveforms 100a, 100b
illustrated in FIG. 8, without modification, certain sets of
respective stimulation pulses of the electrical waveforms 100e,
100f will temporally overlap each other (either partially or
completely).
[0093] However, rather than shifting only one or both of the
stimulation pulses in the potentially overlapping pulse set, the
stimulation pulses of the potentially non-overlapping pulse sets
previous to the potentially overlapping pulse set are temporally
shifted to prevent the stimulation pulses from bunching up. In this
case, the stimulation pulses of the potentially non-overlapping
pulse sets are shifted slightly backward, so that when the
stimulation pulse of the subsequent potentially overlapping pulse
set is shifted backward to prevent overlap, the deviation of the
spacings between the resulting stimulation pulses and the spacings
between the original unshifted stimulation pulses will be slight.
Essentially, the frequency of the resulting pulsed electrical
waveforms will vary only slightly from the original frequency of
the original pulsed electrical waveforms.
[0094] Although the stimulation pulses in the potentially
non-overlapping pulse sets and potentially overlapping pulse sets
are illustrated as being shifted forward time (essentially,
decreasing the frequency of the electrical waveform), it should be
appreciated that the stimulation pulses may be shifted backward in
time (essentially, increasing the frequency of the electrical
waveform).
[0095] In yet another embodiment, the IPG 14 temporally shifts one
or both of the stimulation pulses in the potentially overlapping
pulse set by a randomized amount. For the purposes of this
specification, a random value includes a pseudo-random value (i.e.,
a process that appears random, but is not, and exhibits statistical
randomness while being generated by an entirely deterministic
causal process). The value of the random amount can be computed
using a conventional pseudo-random generator. The IPG 14 may
determine the randomized amount of time that the stimulation pulse
or pulses are shifted by multiplying a nominal pulse shift (e.g.,
the time shift used to prevent pulse overlap) with a randomization
variable. In order to prevent ineffective treatment, the IPG 14 may
limit the difference between the randomized amount and normal time
shift (e.g., 16 msec). For example, as shown in FIG. 22, the
stimulation pulses in the electrical waveform 100a are shifted
forward a randomized amount of time. As shown by the dashed lines
in each of the potentially overlapping pulse sets, the difference
between the randomized shift and the nominal shift needed to
prevent overlap between the respective pulses is different for each
of the potentially overlapping pulse sets, indicating that that the
pulses shifts are randomized.
[0096] It should be noted that the embodiments illustrated in FIGS.
18-22 do not shift the stimulation pulses of a particular
electrical waveform that are subsequently delivered after a
stimulation pulse that has been shifted within the same electrical
waveform if the subsequent stimulation pulses do not temporally
overlap the pulses of the other electrical waveform. That is, the
stimulation pulses in each pulsed electrical waveform that do not
overlap the stimulation pulses in the other pulsed electrical
waveform or waveforms remain in their original position regardless
of any shifting of other stimulation pulses. In this manner, the
frequency ratio between the respective pulsed electrical waveforms
remains substantially the same. Alternatively, however, stimulation
pulses of a particular electrical waveform, even though they would
not temporally overlap with any stimulation pulse of the other
electrical waveform or waveforms, may be shifted in order to
maintain a uniform spacing between the pulses of the electrical
waveform as much as possible. For example, if a stimulation pulse
of a particular electrical waveform is shifted forward in time, the
next stimulation pulse may be shifted forward in time the same
amount in order to maintain the nominal spacing between the
respective stimulation pulses. In this manner, the frequency of
each pulsed electrical waveform is maintained as uniformly as
possible.
[0097] In the previous embodiments, the pulsed electrical waveforms
are illustrated and describes as being monophasic in nature. It
should be appreciated that the pulsed electrical waveforms may be
multiphasic (e.g., biphasic) in nature. In this case, a charge
recovery pulse (either passive or active) will accompany each
stimulation pulse, as illustrated in FIGS. 5a and 5b. In this case,
the IPG 14 attempts to prevent the overlap between a charge
recovery pulse delivered within one timing channel and a
stimulation pulse delivered within another timing channel. For
example, the IPG 14 may predict a charge recovery pulse and a
stimulation pulse within the pulsed electrical waveforms that will
potentially overlap temporally, and dropping or temporally shifting
at least a portion of the charge recovery pulse, thereby preventing
temporal overlap between the charge recovery pulse and the
stimulation pulse of the respective electrical waveforms. In
another embodiment, the IPG 14 drops or temporally shifts any
charge recovery pulse associated with a stimulation pulse that is
averaged or summed within another stimulation pulse (e.g., shown in
FIGS. 11 and 12).
[0098] If a charge recovery phase is dropped or temporally shifted,
the IPG 14 may employ an interlock algorithm to make sure that
there is charge recovery after a certain number of drops or delays
of the charge recovery pulse, a certain number of stimulation
pulses, the next stimulation pulse, a set amount of time, an amount
of time determined by a certain number of stimulation pulses,
and/or a specified amount of charge is injected into the tissue (or
before a specified amount is injected). If a charge recovery pulse
is interrupted, a countdown time may be used to manage the length
of the interrupted charge recovery pulse and make sure the
remainder of the charge recovery pulse is completed.
[0099] The limit on the time between passive charge recovery pulses
may also be determined by the amplitude, pulse width, and frequency
of the pulses. For example, pulsed electrical waveforms with a high
amplitude and short pulse width may require passive charge recovery
pulses less often. Alternatively, coupling capacity may be measured
at the end of each stimulation pulse to determine how much charge
is injected into the tissue, and trigger the recharge pulse at the
appropriate time and with the appropriate duration. Measurement of
the coupling capacity may be accomplished by measuring the output
bias on the output capacitors.
[0100] If a passive charge recovery pulse delivered in one timing
channel temporally overlaps an active charge recovery pulse in
another timing channel, the first charge recovery pulse in time may
be interrupted to prevent overlap with the second charge recovery
pulse in time.
[0101] Although particular embodiments of the present inventions
have been shown and described, it will be understood that it is not
intended to limit the present inventions to the preferred
embodiments, and it will be obvious to those skilled in the art
that various changes and modifications may be made without
departing from the spirit and scope of the present inventions.
Thus, the present inventions are intended to cover alternatives,
modifications, and equivalents, which may be included within the
spirit and scope of the present inventions as defined by the
claims.
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