U.S. patent application number 14/190920 was filed with the patent office on 2014-06-26 for system and method for estimating lead configuration from neighboring relationship between electrodes.
This patent application is currently assigned to BOSTON SCIENTIFIC NEUROMODULATION CORPORATION. The applicant listed for this patent is BOSTON SCIENTIFIC NEUROMODULATION CORPORATION. Invention is credited to David K.L. Peterson, Changfang Zhu.
Application Number | 20140180363 14/190920 |
Document ID | / |
Family ID | 45467549 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140180363 |
Kind Code |
A1 |
Zhu; Changfang ; et
al. |
June 26, 2014 |
SYSTEM AND METHOD FOR ESTIMATING LEAD CONFIGURATION FROM
NEIGHBORING RELATIONSHIP BETWEEN ELECTRODES
Abstract
A method and neurostimulation control system for programming
electrodes disposed adjacent tissue of a patient. A fixed spatial
grid of electrode positions is generated. One of the electrodes is
designated as a reference electrode to be currently examined, and
assigned to one of the electrode grid positions. One or more
previously unassigned ones of the electrodes neighboring the
reference electrode are assigned respectively to one or more of the
electrode grid positions immediately surrounding the electrode grid
position to which the reference electrode is assigned. The
electrodes are programmed based on the assignment of the electrodes
to the electrode grid positions.
Inventors: |
Zhu; Changfang; (Valencia,
CA) ; Peterson; David K.L.; (Valencia, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOSTON SCIENTIFIC NEUROMODULATION CORPORATION |
Valencia |
CA |
US |
|
|
Assignee: |
BOSTON SCIENTIFIC NEUROMODULATION
CORPORATION
Valencia
CA
|
Family ID: |
45467549 |
Appl. No.: |
14/190920 |
Filed: |
February 26, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13184454 |
Jul 15, 2011 |
8700165 |
|
|
14190920 |
|
|
|
|
61365287 |
Jul 16, 2010 |
|
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Current U.S.
Class: |
607/59 |
Current CPC
Class: |
A61N 1/36071 20130101;
A61N 1/0553 20130101; A61N 1/36185 20130101; A61N 1/37247
20130101 |
Class at
Publication: |
607/59 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/372 20060101 A61N001/372 |
Claims
1. A neurostimulation control system for use with a plurality of
electrodes implanted in a patient in a respective plurality of
actual electrode positions, comprising: a user interface configured
for receiving an input from a user; at least one processor
configured for, in response to the input from the user, (a)
generating a fixed spatial grid of electrode positions that is
misaligned with the plurality of actual electrode positions, (b)
designating one of the electrodes as a reference electrode to be
currently examined, (c) assigning the reference electrode to one of
the electrode grid positions, and (d) assigning one or more
previously unassigned ones of the electrodes neighboring the
reference electrode respectively to one or more of the electrode
grid positions immediately surrounding the electrode grid position
to which the reference electrode is assigned; and a controller
configured for programming the electrodes based on the assignment
of the electrodes to the electrode grid positions.
2. The neurostimulation control system of claim 1, wherein the
electrode grid positions are spatially arranged in columns
respectively representing linear arrays of electrodes, and the at
least one processor is further configured for assigning different
numbers respectively to the electrodes.
3. The neurostimulation control system of claim 2, wherein the at
least one processor is configured for assigning the one or more
neighboring electrodes to the electrode grid positions in
accordance with a set of rules comprising determining at least one
in-line electrode of the one or more neighboring electrodes having
a number sequential to the number of the reference electrode, and
assigning the at least one in-line electrode to an electrode grid
position within the same column having the electrode grid position
to which the reference electrode is assigned.
4. The neurostimulation control system of claim 3, wherein the set
of rules further comprises determining at least one off-line
electrode of the one or more neighboring electrodes having a number
non-sequential to the number of the reference electrode, and
assigning the at least one off-line electrode to an electrode grid
position within a column different from the column having the
electrode grid position to which the reference electrode is
assigned.
5. The neurostimulation control system of claim 4, wherein the set
of rules further comprises determining if the at least one off-line
electrode has a number sequential to the number of a neighboring
electrode previously assigned to the electrode grid position, and
assigning the at least one off-line electrode to an electrode grid
position within the same column having the electrode grid position
to which the previously assigned neighboring electrode is
assigned.
6. The neurostimulation control system of claim 1, wherein only six
electrode grid positions immediately surround the electrode grid
position with which the reference electrode is assigned.
7. The neurostimulation control system of claim 1, wherein the
electrode grid positions are uniformly spaced from each other.
8. The neurostimulation control system of claim 1, wherein the at
least one processor is further configured for (f) designating one
of the previously assigned neighboring electrodes as the reference
electrode to be currently examined, and (g) again assigning one or
more previously unassigned ones of the electrodes neighboring the
reference electrode respectively to one or more of the electrode
grid positions immediately surrounding the electrode grid position
to which the reference electrode is assigned.
9. The neurostimulation control system of claim 8, wherein the at
least one processor is further configured for repeating steps (f)
and (g) until all the electrodes have been assigned to the
electrode grid positions.
10. The neurostimulation control system of claim 9, wherein the at
least one processor is further configured for determining, for each
electrode, neighboring ones of the remaining electrodes, wherein,
for the each electrode designated as the reference electrode to be
currently examined, the one or more previously unassigned
electrodes assigned to the one or more of the electrode grid
positions immediately surrounding the electrode grid position to
which the reference electrode is assigned are selected from the
determined ones of the remaining electrodes that neighbor the each
electrode.
11. The neurostimulation control system of claim 9, wherein the at
least one processor is further configured for iteratively merging
each electrode into a single electrode subset in an order dictated
by merging the electrode closest in proximity to the single
electrode for each iteration, wherein the electrodes are designated
as the reference electrode in the order in which they are merged
into the single electrode subset.
12. The neurostimulation control system of claim 1, wherein the
controller is configured for programming the electrodes by
selecting at least one of the electrodes as a cathode and selecting
at least another of the electrodes as an anode based on the
assignment of the electrodes to the electrode grid positions.
13. The neurostimulation control system of claim 1, wherein the
controller is configured for programming the electrodes by
selecting a plurality of groups of the electrodes to create a
respective plurality of stimulation regions based on the assignment
of the electrodes to the electrode grid positions.
14. The neurostimulation control system of claim 1, wherein the at
least one processor and the controller are contained within an
external control device.
15. The neurostimulation control system of claim 1, wherein the
electrodes are carried by a plurality of stimulation leads
implanted within a patient.
16. The neurostimulation control system of claim 15, wherein at
least two of the plurality of stimulation leads have different
electrode spacings.
17. The neurostimulation control system of claim 1, further
comprising assigning unique numbers to the electrodes corresponding
to connector port terminals to which the electrodes are
respectively coupled, wherein the at least one processor is
configured for assigning the one or more neighboring electrodes to
the electrode grid positions at least partially based on the one or
more unique numbers respectively assigned to the one or more
neighboring electrodes relative to the unique number assigned to
the reference electrode.
18. The neurostimulation control system of claim 1, wherein the
relative position of the reference electrode and the one or more
previously unassigned ones of the electrodes are unknown prior to
the input from the user, the neurostimulation control system
further comprises monitoring circuitry configured for measuring one
or more electrical parameters in response to the conveyance of one
or more electrical signals between the reference electrode and the
one or more previously unassigned ones of the electrodes, and the
at least one processor is configured for determining that the one
or more previously unassigned ones of the electrodes neighbor the
reference electrode based on the one or more measured electrical
parameters.
19. The neurostimulation control system of claim 9, wherein the at
least one processor is further configured for generating an
electrode configuration map of relative positions of the electrodes
at the resolution of the electrode grid based on the assignment of
all the electrodes to the electrode grid positions, and the
controller is configured for programming the electrodes based on
the electrode configuration map.
Description
RELATED APPLICATION DATA
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/184,454, filed Jul. 15, 2011, now issued as
U.S. Pat. No. ______ which claims the benefit under 35 U.S.C.
.sctn.119 to U.S. provisional patent application Ser. No.
61/365,287, filed Jul. 16, 2010, which applications are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present inventions relate to tissue stimulation systems,
and more particularly, to neurostimulation systems for programming
neurostimulation leads.
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. Also,
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] Each of these implantable neurostimulation systems typically
includes one or more neurostimulation leads implanted at the
desired stimulation site and an implantable neurostimulator, such
as an implantable pulse generator (IPG), implanted remotely from
the stimulation site, but coupled either directly to the leads or
indirectly to the leads via one or more lead extensions in cases
where the length of the leads is insufficient to reach the IPG.
Thus, electrical pulses can be delivered from the neurostimulator
to the leads to stimulate the tissue and provide the desired
efficacious therapy to the patient.
[0005] In the context of an SCS procedure, one or more
neurostimulation leads are introduced through the patient's back
into the epidural space, such that the electrodes carried by the
leads are arranged in a desired pattern and spacing to create an
electrode array. One type of commercially available
neurostimulation lead is a percutaneous lead, which comprises a
cylindrical body with ring electrodes, and can be introduced into
contact with the affected spinal tissue through a Touhy-like
needle, which passes through the skin, between the desired
vertebrae, and into the epidural space above the dura layer. For
unilateral pain, a percutaneous lead is placed on the corresponding
lateral side of the spinal cord. For bilateral pain, a percutaneous
lead is placed down the midline of the spinal cord, or two or more
percutaneous leads are placed down the respective sides of the
midline of the spinal cord, and if a third lead is used, down the
midline of the special cord. After proper placement of the
neurostimulation leads at the target area of the spinal cord, the
leads are anchored in place at an exit site to prevent movement of
the leads. To facilitate the location of the neurostimulator away
from the exit point of the leads, lead extensions are sometimes
used.
[0006] Whether or not lead extensions are used, the proximal ends
of the neurostimulation leads exiting the spinal column are passed
through a tunnel subcutaneously formed along the torso of the
patient to a subcutaneous pocket (typically made in the patient's
abdominal or buttock area) where a neurostimulator is implanted.
The subcutaneous tunnel can be formed using a tunneling tool over
which a tunneling straw may be threaded. The tunneling tool can be
removed, the leads threaded through the tunneling straw, and then
the tunneling straw removed from the tunnel while maintaining the
leads in place within the tunnel.
[0007] The neurostimulation leads are then connected directly to
the neurostimulator by inserting the proximal ends of the
stimulation leads within one or more connector ports of the IPG or
connected to lead extensions, which are then inserted into the
connector ports of the IPG. The IPG can then be operated to
generate electrical pulses that are delivered, through the
electrodes, to the targeted tissue, and in particular, the dorsal
column and dorsal root fibers within the spinal cord.
[0008] 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. Intra-operatively
(i.e., during the surgical procedure), the neurostimulator may be
operated to test the effect of stimulation and adjust the
parameters of the stimulation (e.g., the electrodes that are acting
as anodes or cathodes, as well as the amplitude, duration, and rate
of the stimulation pulses). The patient may provide verbal feedback
regarding the presence of paresthesia over the pain area, and based
on this feedback, the lead positions may be adjusted and
re-anchored if necessary. A computerized programming system, such
as Bionic Navigator.RTM., available from Boston Scientific
Neuromodulation Corporation, can be used to facilitate selection of
the stimulation parameters. Any incisions are then closed to fully
implant the system. Post-operatively (i.e., after the surgical
procedure has been completed), a clinician can adjust the
stimulation parameters using the computerized programming system to
re-optimize the therapy.
[0009] The efficacy of SCS is related to the ability to stimulate
the spinal cord tissue corresponding to evoked paresthesia in the
region of the body where the patient experiences pain. Thus, the
working clinical paradigm is that achievement of an effective
result from SCS depends on the neurostimulation lead or leads being
placed in a location (both longitudinal and lateral) relative to
the spinal tissue such that the electrical stimulation will induce
paresthesia located in approximately the same place in the
patient's body as the pain (i.e., the target of treatment). If a
lead is not correctly positioned relative to the tissue or relative
to another lead, it is possible that the patient will receive
little or no benefit from an implanted SCS system. Thus, correct
lead placement can mean the difference between effective and
ineffective pain therapy.
[0010] Multi-lead configurations have been increasingly used in
electrical stimulation applications (e.g., neurostimulation,
cardiac resynchronization therapy, etc.). In the neurostimulation
application of SCS, the use of multiple leads that are grouped
together in close proximity to each other at one general region of
the patient (e.g., side-by-side parallel leads along the spinal
cord of the patient), increases the stimulation area and
penetration depth (therefore coverage), as well as enables more
combinations of anodic and cathodic electrodes for stimulation,
such as transverse multipolar (bipolar, tripolar, or quadra-polar)
stimulation, in addition to any longitudinal single lead
configuration. In more advanced applications, multiple leads may be
placed in different locations of the patient. For example, in an
SCS application, one lead may be placed along the cervical region
of the spinal cord, and another lead may be placed along the lumbar
region of the spinal cord. As another example, in a combined
SCS/PNS application, one lead may be placed along the spinal cord
of the patient, and another lead may be placed in a peripheral
location of a patient (e.g., an arm or a leg).
[0011] Whether the multiple leads are implanted in the patient in
close proximity to each other at a particular location or implanted
in the patient at separate locations, selection of cathodes/anodes
requires the identification of the electrodes that are positioned
close to each other and knowledge of the relative positions of the
electrodes that are to be activated as the cathodes or anodes.
Conventional electrical field-based techniques, such as those
described in U.S. Pat. No. 6,993,384, entitled "Apparatus and
Method for Determining the Relative Position and Orientation of
Neurostimulation Leads," and U.S. patent application Ser. No.
12/623,976, entitled "Method and Apparatus for Determining Relative
Positioning Between Neurostimulation Leads," which are expressly
incorporated herein by reference, have been developed to estimate
the positions of the electrodes relative to each other by
determining longitudinal offset and/or transverse separation
between the leads. These techniques usually assume that the
electrodes are arranged in-line along each lead and the arrangement
of the electrode array is known so that certain patterns of the
induced electrical field can be examined.
[0012] If not already taken into account by the programming system,
information related to the arrangement of electrode arrays may be
obtained through user input if it is available (e.g., a user can
enter the spatial orientation of the leads and/or electrodes
obtained from a recent radiographic image into the programming
system). However, radiographic imaging may not always be available,
and even when it is, the images do not allow for identification of
each electrode in the array unless certain prior information is
available, e.g., lead type, lead-port mapping and electrode
configuration. If such prior information is limited, identifying
the electrode arrays may be difficult. This problem may be more
complicated when, for example, different types of extensions (e.g.,
splitters) are used to connect the leads to the neurostimulator,
which may result in an electrode array configuration that is
different from the physical electrode array arrangement.
Furthermore, lead position determination software installed in
current neurostimulation systems oftentimes need to be updated to
accommodate new or unknown lead designs.
[0013] There, thus, remains an improved generic technique for
identifying electrodes that are in proximity to each other, the
relative positioning between the electrodes, and the configuration
of the electrodes.
SUMMARY OF THE INVENTION
[0014] In accordance with a first aspect of the present inventions,
a neurostimulation control system for use with a plurality of
electrodes is provided. The neurostimulation control system
comprises a user interface configured for receiving an input from a
user, and at least one processor configured for, in response to the
user input, (a) generating a fixed spatial grid of electrode
positions, which may be uniformly spaced from each other, (b)
designating one of the electrodes as a reference electrode to be
currently examined, and (c) assigning the reference electrode to
one of the electrode grid positions. In one embodiment, only six
electrode grid positions may immediately surround the electrode
grid position with which the reference electrode is assigned,
although the number of electrode grid positions immediately
surrounding the electrode grid position may differ depending on the
application.
[0015] The processor(s) is further configured for (d) assigning one
or more previously unassigned ones of the electrodes neighboring
the reference electrode respectively to one or more of the
electrode grid positions immediately surrounding the electrode grid
position to which the reference electrode is assigned.
[0016] In one embodiment, the electrode grid positions are
spatially arranged in columns respectively representing linear
arrays of electrodes, and the processor(s) is further configured
for assigning different numbers respectively to the electrodes. In
this case, the processor(s) may be configured for assigning the
neighboring electrodes to the electrode grid positions in
accordance with a set of rules comprising determining at least one
in-line electrode of the neighboring electrodes having a number
sequential to the number of the reference electrode, and assigning
the in-line electrode(s) to an electrode grid position within the
same column having the electrode grid position to which the
reference electrode is assigned. The set of rules may further
comprise determining at least one off-line electrode of the
neighboring electrodes having a number non-sequential to the number
of the reference electrode, and assigning the off-line electrode(s)
to an electrode grid position within a column different from the
column having the electrode grid position to which the reference
electrode is assigned. The set of rules may further comprise
determining if the off-line electrode(s) has a number sequential to
the number of a neighboring electrode previously assigned to the
electrode grid, and assigning the off-line electrode(s) to an
electrode grid position within the same column having the electrode
grid position to which the previously assigned neighboring
electrode is assigned.
[0017] In another embodiment, the processor(s) is further
configured for (f) designating one of the previously assigned
neighboring electrodes as the reference electrode to be currently
examined, and (g) again assigning one or more previously unassigned
ones of the electrodes neighboring the reference electrode
respectively to one or more of the electrode grid positions
immediately surrounding the electrode grid position to which the
reference electrode is assigned. In this case, the processor(s) may
be further configured for repeating steps (f) and (g) until all the
electrodes have been assigned to the electrode grid. The
processor(s) may be further configured for determining, for each
electrode, neighboring ones of the remaining electrodes, wherein,
for the each electrode designated as the reference electrode to be
currently examined, the previously unassigned electrodes to be
assigned to the electrode grid positions immediately surrounding
the electrode grid position to which the reference electrode is
assigned are selected from the determined ones of the remaining
electrodes that neighbor the respective electrode. The processor(s)
may be further configured for iteratively merging each electrode
into a single electrode subset in an order dictated by merging the
electrode closest in proximity to the single electrode subset for
each iteration, wherein the electrodes are designated as the
reference electrode in the order in which they are merged into the
single electrode subset.
[0018] The neurostimulation control system further comprises a
controller configured for programming the electrodes based on the
assignment of the electrodes to the electrode grid positions. For
example, the controller may select at least one of the electrodes
as a cathode and select at least another of the electrodes as an
anode based on the identified clustering relationship of the
electrodes. As another example, the controller may select a
plurality of groups of the electrodes to create a respective
plurality of stimulation regions based on the identified clustering
relationship of the electrodes. The processor(s) and controller may
be contained within an external control device.
[0019] In accordance with a second aspect of the present
inventions, a method of programming electrodes disposed adjacent
tissue of a patient is provided. The method comprises (a)
generating a fixed spatial grid of electrode positions, (b)
designating one of the electrodes as a reference electrode to be
currently examined, (c) assigning the reference electrode to one of
the electrode grid positions, (d) assigning one or more previously
unassigned ones of the electrodes neighboring the reference
electrode respectively to one or more of the electrode grid
positions immediately surrounding the electrode grid position to
which the reference electrode is assigned, and (e) programming the
electrodes based on the assignment of the electrodes to the
electrode grid positions. These steps and any optional steps may be
performed in the same manner at that in which the processor(s) and
controller performed the steps described above.
[0020] 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
[0021] 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. 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 plan view of one embodiment of a spinal cord
stimulation (SCS) system arranged in accordance with the present
inventions;
[0023] FIG. 2 is a plan view of an implantable pulse generator
(IPG) and two neurostimulation leads used in the SCS system of FIG.
1;
[0024] FIG. 3 is a plan view of the SCS system of FIG. 1 in use
with a patient;
[0025] FIG. 4 is a block diagram of the internal components of the
IPG of FIG. 1;
[0026] FIG. 5 is a plan view of a remote control that can be used
in the SCS system of FIG. 1;
[0027] FIG. 6 is a block diagram of the internal componentry of the
remote control of FIG. 5;
[0028] FIG. 7 is a block diagram of the components of a clinician's
programmer that can be used in the SCS system of FIG. 1;
[0029] FIG. 8a is a fluoroscopic image of a clinical case wherein
neurostimulation leads are implanted within a patient in a
side-by-side relationship;
[0030] FIG. 8b is a fluoroscopic image of a clinical case wherein
neurostimulation leads are implanted within a patient in
rostro-caudal relationship;
[0031] FIG. 9 is a flow diagram illustrated a generic method
implemented by the SCS system of FIG. 1 to perform an electrode
clustering analysis and program the electrodes;
[0032] FIG. 10a is a dendrogram of a clustering analysis performed
on the electrode arrangement of FIG. 8a using a first specific
technique implemented by the SCS system of FIG. 1;
[0033] FIG. 10b is a dendrogram of a clustering analysis performed
on the electrode arrangement of FIG. 8b using the first specific
technique implemented by the SCS system of FIG. 1;
[0034] FIG. 11a is a partitioned block diagram of a clustering
analysis performed on the electrode arrangement of FIG. 8a using
the first specific technique implemented by the SCS system of FIG.
1;
[0035] FIG. 11b is a partitioned block diagram of a clustering
analysis performed on the electrode arrangement of FIG. 8b using
the first specific technique implemented by the SCS system of FIG.
1;
[0036] FIG. 12a is a plot of a clustering analysis performed on the
electrode arrangement of FIG. 8a using a second specific technique
implemented by the SCS system of FIG. 1;
[0037] FIG. 12b is a plot of a clustering analysis performed on the
electrode arrangement of FIG. 8b using the second specific
technique implemented by the SCS system of FIG. 1;
[0038] FIG. 13a is an image of illustrating a first configuration
of three neurostimulation leads are implanted within a patient in a
side-by-side relationship;
[0039] FIG. 13b is an image of illustrating a second configuration
of three neurostimulation leads are implanted within a patient in a
side-by-side relationship;
[0040] FIG. 14 is a flow diagram illustrated a generic method
implemented by the SCS system of FIG. 1 to perform an electrode
configuration mapping technique and program the electrodes;
[0041] FIG. 15 is a plan view of a spatial grid of electrode
positions generated by the SCS system of FIG. 1 to which electrodes
will be assigned in accordance with the electrode configuration
mapping technique performed in FIG. 14;
[0042] FIG. 16a is a plan view of an electrode configuration map of
the neurostimulation lead configuration of FIG. 13a estimated by
the SCS system of FIG. 1 in accordance with the technique performed
in FIG. 14;
[0043] FIG. 16b is a plan view of an electrode configuration map of
the neurostimulation lead configuration of FIG. 13b estimated by
the SCS system of FIG. 1 in accordance with the technique performed
in FIG. 14;
[0044] FIGS. 17a-17h are plan views illustrating the iterative
assignment of electrodes from the neurostimulation lead
configuration of FIG. 13a to the electrode grid of FIG. 15 by the
SCS system of FIG. 1 in accordance with the technique performed in
FIG. 14; and
[0045] FIGS. 18a-18l are plan views illustrating the iterative
assignment of electrodes from the neurostimulation lead
configuration of FIG. 13b to the electrode grid of FIG. 15 by the
SCS system of FIG. 1 in accordance with the technique performed in
FIG. 14.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0046] The description that follows relates to a spinal cord
stimulation (SCS) system. However, it is to be understood that
while the invention lends itself well to applications in SCS, the
invention, in its broadest aspects, may not be so limited. Rather,
the invention may be used with any type of implantable electrical
circuitry used to stimulate tissue. For example, the present
invention may be used as part of a multi-lead system such as 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.
[0047] Turning first to FIG. 1, an exemplary SCS system 10
generally comprises a plurality of percutaneous neurostimulation
leads 12 (in this case, two percutaneous leads 12(1) and 12(2)), an
implantable pulse generator (IPG) 14, an external remote control
(RC) 16, a Clinician's Programmer (CP) 18, an External Trial
Stimulator (ETS) 20, and an external charger 22.
[0048] The IPG 14 is physically connected via two lead extensions
24 to the neurostimulation leads 12, which carry a plurality of
electrodes 26 arranged in an array. As will also 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. The IPG 14 and stimulation leads 12
can be provided as an implantable neurostimulation kit, along with,
e.g., a hollow needle, a stylet, a tunneling tool, and a tunneling
straw. Further details discussing implantable kits are disclosed in
U.S. Application Ser. No. 61/030,506, entitled "Temporary
Neurostimulation Lead Identification Device," which is expressly
incorporated herein by reference.
[0049] The ETS 20 may also be physically connected via percutaneous
lead extensions 28 or external cable 30 to the neurostimulation
lead 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 in
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
neurostimulation lead 12 has been implanted and prior to
implantation of the IPG 14, to test the responsiveness of the
stimulation that is to be provided. Further details of an exemplary
ETS are described in U.S. Pat. No. 6,895,280, which is expressly
incorporated herein by reference.
[0050] 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 lead 12 is 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 programs
after implantation. Once the IPG 14 has been programmed, and its
power source has been charged or otherwise replenished, the IPG 14
may function as programmed without the RC 16 being present.
[0051] 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. 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).
[0052] 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. Details of exemplary embodiments of
external chargers are disclosed in U.S. Pat. No. 6,895,280, which
has been previously incorporated herein by reference. 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.
[0053] Referring now to FIG. 2, the external features of the
neurostimulation leads 12 and the IPG 14 will be briefly described.
Each of the neurostimulation leads 12 has eight electrodes 26
(respectively labeled E1-E8 and E9-E16). The actual number and
shape of leads and electrodes will, of course, vary according to
the intended application. Further details describing the
construction and method of manufacturing percutaneous stimulation
leads are disclosed in U.S. patent application Ser. No. 11/689,918,
entitled "Lead Assembly and Method of Making Same," and U.S. patent
application Ser. No. 11/565,547, entitled "Cylindrical
Multi-Contact Electrode Lead for Neural Stimulation and Method of
Making Same," the disclosures of which are expressly incorporated
herein by reference.
[0054] The IPG 14 comprises an outer case 40 for housing the
electronic and other components (described in further detail
below). 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. The IPG 14 further
comprises a connector 42 to which the proximal ends of the
neurostimulation leads 12 mate in a manner that electrically
couples the electrodes 26 to the internal electronics (described in
further detail below) within the outer case 40. To this end, the
connector 42 includes two ports (not shown) for receiving the
proximal ends of the three percutaneous leads 12. In the case where
the lead extensions 24 are used, the ports may instead receive the
proximal ends of such lead extensions 24.
[0055] As will be described in further detail below, the IPG 14
includes pulse generation circuitry that provides electrical
stimulation energy to the electrodes 26 in accordance with a set of
parameters. Such parameters may comprise electrode combinations,
which define the electrodes that are activated as anodes
(positive), cathodes (negative), and turned off (zero), and
electrical pulse parameters, which define the pulse amplitude
(measured in milliamps or volts depending on whether the IPG 14
supplies constant current or constant voltage to the electrodes),
pulse duration (measured in microseconds), pulse rate (measured in
pulses per second), and pulse shape.
[0056] With respect to the pulse patterns provided during operation
of the SCS system 10, electrodes that are selected to transmit or
receive electrical energy are referred to herein as "activated,"
while electrodes that are not selected to transmit or receive
electrical energy are referred to herein as "non-activated."
Electrical energy delivery will occur between two (or more)
electrodes, one of which may be the IPG case 40, so that the
electrical current has a path from the energy source contained
within the IPG case 40 to the tissue and a sink path from the
tissue to the energy source contained within the case. Electrical
energy may be transmitted to the tissue in a monopolar or
multipolar (e.g., bipolar, tripolar, etc.) fashion.
[0057] Monopolar delivery occurs when a selected one or more of the
lead electrodes 26 is activated along with the case 40 of the IPG
14, so that electrical energy is transmitted between the selected
electrode 26 and case 40. Monopolar delivery may also occur when
one or more of the lead electrodes 26 are activated along with a
large group of lead electrodes located remotely from the one or
more lead electrodes 26 so as to create a monopolar effect; that
is, electrical energy is conveyed from the one or more lead
electrodes 26 in a relatively isotropic manner. Bipolar delivery
occurs when two of the lead electrodes 26 are activated as anode
and cathode, so that electrical energy is transmitted between the
selected electrodes 26. Tripolar delivery 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.
[0058] Referring to FIG. 3, the neurostimulation leads 12 are
implanted within the spinal column 46 of a patient 48. The
preferred placement of the neurostimulation leads 12 is adjacent,
i.e., resting near, or upon the dura, adjacent to the spinal cord
area to be stimulated. Due to the lack of space near the location
where the neurostimulation leads 12 exit the spinal column 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
extensions 24 facilitate locating the IPG 14 away from the exit
point of the neurostimulation leads 12. As there shown, the CP 18
communicates with the IPG 14 via the RC 16. While the
neurostimulation leads 12 are illustrated as being implanted near
the spinal cord area of a patient, the neurostimulation leads 12
may be implanted anywhere in the patient's body, including a
peripheral region, such as a limb, or the brain. After
implantation, the IPG 14 is used to provide the therapeutic
stimulation under control of the patient.
[0059] Turning next to FIG. 4, the main internal components of the
IPG 14 will now be described. The IPG 14 includes stimulation
output circuitry 60 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 62 over data
bus 64. Control of the pulse rate and pulse width of the electrical
waveform is facilitated by timer logic circuitry 66, which may have
a suitable resolution, e.g., 10 .mu.s. The stimulation energy
generated by the stimulation output circuitry 60 is output via
capacitors C1-C16 to electrical terminals 68 corresponding to the
electrodes 26.
[0060] The analog output circuitry 60 may either comprise
independently controlled current sources for providing stimulation
pulses of a specified and known amperage to or from the electrical
terminals 68, or independently controlled voltage sources for
providing stimulation pulses of a specified and known voltage at
the electrical terminals 68 or to multiplexed current or voltage
sources that are then connected to the electrical terminals 68. The
operation of this analog output circuitry, including alternative
embodiments of suitable output circuitry for performing the same
function of generating stimulation pulses of a prescribed amplitude
and width, is described more fully in U.S. Pat. Nos. 6,516,227 and
6,993,384, which are expressly incorporated herein by
reference.
[0061] The IPG 14 further comprises monitoring circuitry 70 for
monitoring the status of various nodes or other points 72
throughout the IPG 14, e.g., power supply voltages, temperature,
battery voltage, and the like. Notably, the electrodes 26 fit
snugly within the epidural space of the spinal column, and because
the tissue is conductive, electrical measurements can be taken from
the electrodes 26. Significantly, the monitoring circuitry 70 is
configured for taking such electrical measurements, so that, as
will be described in further detail below, the relative proximities
between pairs of electrodes may be determined.
[0062] Electrical signals can be transmitted between electrodes
carried by one of the neurostimulation lead 12 and one or more
other electrodes (e.g., electrodes on the same neurostimulation
lead 12, electrodes on the other neurostimulation lead 12, the case
40 of the IPG 12, or an electrode affixed to the tissue), and then
electrical parameters can be measured in response to the
transmission of the electrical signals. In the illustrated
embodiment, the electrical measurements taken by the monitoring
circuitry 70 for the purpose of determining the relative proximity
between electrode pairs are electrical field potentials, although
other suitable measurements, such as, e.g., an electrical impedance
or an evoked potential measurement, can be obtained.
[0063] Distances between electrodes can be determined based on the
measured electrical parameters in a conventional manner, such as,
e.g., any one or more of the manners disclosed in U.S. Pat. No.
6,993,384, entitled "Apparatus and Method for Determining the
Relative Position and Orientation of Neurostimulation Leads," U.S.
patent application Ser. No. 12/550,136, entitled "Method and
Apparatus for Determining Relative Positioning Between
Neurostimulation Leads," and U.S. patent application Ser. No.
12/623,976, entitled "Method and Apparatus for Determining Relative
Positioning Between Neurostimulation Leads," which are expressly
incorporated herein by reference.
[0064] The electrical parameter measurements can be made on a
sampled basis during a portion of the time while the electrical
stimulus pulse is being applied to the tissue, or immediately
subsequent to stimulation, as described in U.S. patent application
Ser. No. 10/364,436, which has previously been incorporated herein
by reference. Alternatively, the electrical data measurements can
be made independently of the electrical stimulation pulses, such as
described 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 processing circuitry in the
form of a microcontroller 74 that controls the control logic 62
over data bus 76, and obtains status data from the monitoring
circuitry 70 via data bus 78. The microcontroller 74 additionally
controls the timer logic 66. The IPG 14 further comprises memory 80
and an oscillator and clock circuit 82 coupled to the
microcontroller 74. The microcontroller 74, in combination with the
memory 80 and oscillator and clock circuit 82, thus comprise a
microprocessor system that carries out a program function in
accordance with a suitable program stored in the memory 80.
Alternatively, for some applications, the function provided by the
microprocessor system may be carried out by a suitable state
machine.
[0066] Thus, the microcontroller 74 generates the necessary control
and status signals, which allow the microcontroller 74 to control
the operation of the IPG 14 in accordance with a selected operating
program and parameters. In controlling the operation of the IPG 14,
the microcontroller 74 is able to individually generate electrical
pulses at the electrodes 26 using the analog output circuitry 60,
in combination with the control logic 62 and timer logic 66,
thereby allowing each electrode 26 to be paired or grouped with
other electrodes 26, including the monopolar case electrode, and to
control the polarity, amplitude, rate, and pulse width through
which the current stimulus pulses are provided.
[0067] The IPG 14 further comprises an alternating current (AC)
receiving coil 84 for receiving programming data (e.g., the
operating program and/or stimulation parameters) from the RC 16 in
an appropriate modulated carrier signal, and charging and forward
telemetry circuitry 86 for demodulating the carrier signal it
receives through the AC receiving coil 84 to recover the
programming data, which programming data is then stored within the
memory 80, or within other memory elements (not shown) distributed
throughout the IPG 14.
[0068] The IPG 14 further comprises back telemetry circuitry 88 and
an alternating current (AC) transmission coil 90 for sending
informational data (including the field potential and impedance
data) sensed through the monitoring circuitry 70 to the RC 16. The
back telemetry features of the IPG 14 also allow its status to be
checked. For example, any changes made to the stimulation
parameters are confirmed through back telemetry, thereby assuring
that such changes have been correctly received and implemented
within the IPG 14. Moreover, upon interrogation by the RC 16, all
programmable settings stored within the IPG 14 may be uploaded to
the RC 16.
[0069] The IPG 14 further comprises a rechargeable power source 92
and power circuits 94 for providing the operating power to the IPG
14. The rechargeable power source 92 may, e.g., comprise a
lithium-ion or lithium-ion polymer battery. The rechargeable
battery 92 provides an unregulated voltage to the power circuits
94. The power circuits 94, in turn, generate the various voltages
96, 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 92 is recharged using rectified AC power
(or DC power converted from AC power through other means, e.g.,
efficient AC-to-DC converter circuits) received by the AC receiving
coil 84. To recharge the power source 92, 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 84. The charging and forward
telemetry circuitry 86 rectifies the AC current to produce DC
current, which is used to charge the power source 92. While the AC
receiving coil 84 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 84 can be arranged as a dedicated
charging coil, while another coil, such as coil 90, can be used for
bi-directional telemetry.
[0070] It should be noted that the diagram of FIG. 4 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. It
should be noted that rather than an IPG for the neurostimulator,
the SCS system 10 may alternatively utilize an implantable
receiver-stimulator (not shown) connected to the neurostimulation
leads 12. In this case, the power source, e.g., a battery, for
powering the implanted receiver, as well as control circuitry to
command the receiver-stimulator, 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.
[0071] Referring now to FIG. 5, one exemplary embodiment of an RC
16 will now be described. As previously discussed, the RC 16 is
capable of communicating with the IPG 14, CP 18, or ETS 20. The RC
16 comprises a casing 100, which houses internal componentry
(including a printed circuit board (PCB)), and a lighted display
screen 102 and button pad 104 carried by the exterior of the casing
100. In the illustrated embodiment, the display screen 102 is a
lighted flat panel display screen, and the button pad 104 comprises
a membrane switch with metal domes positioned over a flex circuit,
and a keypad connector connected directly to a PCB. In an optional
embodiment, the display screen 102 has touchscreen capabilities.
The button pad 104 includes a multitude of buttons 106, 108, 110,
and 112, which allow the IPG 14 to be turned ON and OFF, provide
for the adjustment or setting of stimulation parameters within the
IPG 14, and provide for selection between screens.
[0072] In the illustrated embodiment, the button 106 serves as an
ON/OFF button that can be actuated to turn the IPG 14 ON and OFF.
The button 108 serves as a select button that allows the RC 106 to
switch between screen displays and/or parameters. The buttons 110
and 112 serve as up/down buttons that can be actuated to increase
or decrease any of stimulation parameters of the pulse generated by
the IPG 14, including pulse amplitude, pulse width, and pulse
rate.
[0073] Referring to FIG. 6, the internal components of an exemplary
RC 16 will now be described. The RC 16 generally includes a
processor 114 (e.g., a microcontroller), memory 116 that stores an
operating program for execution by the processor 114, and telemetry
circuitry 118 for transmitting control data (including stimulation
parameters and requests to provide status information) to the IPG
14 (or ETS 20) and receiving status information (including the
measured electrical data) from the IPG 14 (or ETS 20) via link 34
(or link 32) (shown in FIG. 1), as well as receiving the control
data from the CP 18 and transmitting the status data to the CP 18
via link 36 (shown in FIG. 1). The RC 16 further includes
input/output circuitry 120 for receiving stimulation control
signals from the button pad 104 and transmitting status information
to the display screen 102 (shown in FIG. 5). Further details of the
functionality and internal componentry of the RC 16 are disclosed
in U.S. Pat. No. 6,895,280, which has previously been incorporated
herein by reference.
[0074] As briefly discussed above, the CP 18 greatly simplifies the
programming of multiple electrode combinations, allowing the
physician or clinician to readily determine the desired stimulation
parameters to be programmed into the IPG 14, as well as the RC 16.
Thus, modification of the stimulation parameters in the
programmable memory of the IPG 14 after implantation is performed
by a clinician using the CP 18, which can directly communicate with
the IPG 14 or indirectly communicate with the IPG 14 via the RC 16.
That is, the CP 18 can be used by the physician or clinician to
modify operating parameters of the electrode array 26 near the
spinal cord.
[0075] As shown in FIG. 3, the overall appearance of the CP 18 is
that of a laptop personal computer (PC), and in fact, 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. Thus, the programming methodologies
can be performed by executing software instructions contained
within the CP 18. Alternatively, such programming methodologies can
be performed using firmware or hardware. In any event, the CP 18
may actively control the characteristics of the electrical
stimulation generated by the IPG 14 (or ETS 20) to allow the
optimum stimulation parameters to be determined based on patient
feedback and for subsequently programming the IPG 14 (or ETS 20)
with the optimum stimulation parameters.
[0076] To allow the clinician to perform these functions, the CP 18
includes a mouse 121, a keyboard 122, and a programming display
screen 124 housed in a case 126. It is to be understood that in
addition to, or in lieu of, the mouse 121, other directional
programming devices may be used, such as a joystick, or directional
keys included as part of the keys assigned to the keyboard 122. As
shown in FIG. 7, the CP 18 generally includes a processor 128
(e.g., a central processor unit (CPU)) and memory 130 that stores a
stimulation programming package 132, which can be executed by the
processor 128 to allow a clinician to program the IPG 14 (or ETS
20) and RC 16. The CP 18 further includes telemetry circuitry 134
for downloading stimulation parameters to the RC 16 and uploading
stimulation parameters already stored in the memory 116 of the RC
16 via link 36 (shown in FIG. 1). The telemetry circuitry 134 is
also configured for transmitting the control data (including
stimulation parameters and requests to provide status information)
to the IPG 14 (or ETS 20) and receiving status information
(including the measured electrical data) from the IPG 14 (or ETS
20) indirectly via the RC 16.
[0077] Significantly, the CP 18 is configured for identifying a
clustering relationship between the electrodes 26, such that the
electrodes 26 can be more efficiently programmed without having
prior knowledge of the type of lead or electrode array arrangement.
For example, knowing this clustering relationship provides
information related to which combination of electrodes should be
programmed with the same polarity (e.g., one cluster of neighboring
electrodes can be efficiently programmed as cathodes, and another
cluster of neighboring electrodes can be efficiently programmed as
anodes) and/or information related to the electrode combinations
that correlate to different anatomical regions of the patient
(e.g., one large cluster of neighboring electrodes may be
correlated to the cervical spinal region of a patient, and another
large cluster of neighboring electrodes may be correlated to the
lumbar spinal region of the patient), such that the electrodes can
be programmed to create multiple foci of stimulation respectively
over the multiple anatomical regions. As will be appreciated from
the following discussion, the electrode clustering techniques
described herein provide an effective search path (for any lead
configuration) to find a successively larger combination of a set
of closely positioned electrode for programming.
[0078] For example, if the neurostimulation leads 12 are arranged
in a parallel relationship with a staggered 3/4 electrode offset,
with the second neurostimulation lead 12(2) positioned below the
first neurostimulation lead 12(1), as shown in the fluoroscopic
image of one clinical case illustrated in FIG. 8a, the CP 18 may
identify a cluster of three electrodes (e.g., electrodes E1, E2,
and E9) and another cluster of two electrodes (e.g., electrodes E4
and E11). Knowing this, the cluster of three electrodes may, e.g.,
be programmed as cathodes, and the cluster of two electrodes may,
e.g., be programmed as anodes. Or, the CP 18 may identify a cluster
of four electrodes (e.g., electrodes E7, E8, E14, and E15) and
another cluster of four electrodes (e.g., electrodes E4, E5, E11,
and E12). Knowing this, the cluster of four electrodes may, e.g.,
be programmed as cathodes, and the other cluster of four electrodes
may, e.g., be programmed as anodes. Or, the CP 18 may successively
add or subtract electrodes to an electrode group over several
electrode testing iterations (e.g., adding electrode E3 to the
group of electrodes consisting of electrodes E9 and E10, testing
the new electrode group of electrodes E3, E9, and E10; adding
electrode E2 to the group of electrodes consisting of electrodes
E3, E9, and E10, testing the new electrode group of electrodes E2,
E3, E9, and E10, etc.)
[0079] As another example, if the neurostimulation leads 12 are
arranged in a rostro-caudal manner, with the first neurostimulation
lead 12(1) below the second neurostimulation lead 12(2), as shown
in the fluoroscopic image of another clinical case illustrated in
FIG. 8b, the CP 18 may identify a cluster of eight electrodes
(e.g., electrodes E1-E8) and another cluster of electrodes (e.g.,
electrodes E9-E16). Knowing this, the cluster of eight electrodes
may, e.g., be programmed to create one stimulation region, and the
other cluster of eight electrodes may be programmed to create
another stimulation region.
[0080] In identifying the clustering relationship between the
electrodes 26, the CP 18 performs a nearest neighbor analysis of
the electrodes 26. The problem of nearest neighbor analysis can be
characterized as given a set of points M in the data space S, and a
query point (or a set of query points) p in the same space S, find
a point in the set of points M that is closest to the query point
p. The analogue problem with respect to an electrode array can be
characterized as for any designated electrode (or a set of
electrodes), find the one (or a set) in the remaining electrode
sets that is closest to the designated electrode (or set of
electrodes). A single step of a nearest neighbor search will find
the neighboring relationship between two points (or in this
application, two electrodes), which search is repeated in order to
progressively find the neighboring relationship of the entire set
of points (i.e., electrodes).
[0081] To this end, and with reference to FIG. 9, the electrodes
are initially assigned to a plurality of electrode subsets to be
evaluated (step 200). In the illustrated embodiment, sixteen
electrodes (electrodes E1-E16) are respectively assigned to sixteen
electrode subsets (one electrode for each subset).
[0082] Next, a pair of immediately neighboring ones of the
electrode subsets is determined (step 202). By way of example, two
techniques can be used to determine the pair of immediately
neighboring electrodes subsets, as will be described in further
detail below. Each of these techniques can accomplish this step by
determining relative proximities between pairs of the electrode
subsets, and selecting the pair of electrode subsets that has the
minimum relative proximity therebetween as the determined pair of
immediately neighboring electrode subsets. As will be described in
further detail below, selection of the pair of electrode subsets
having the minimum relative proximity can be accomplished by
determining the minimum electrode proximity between the respective
pair of electrode subsets, the maximum electrode proximity between
the respective pair of electrode subsets, or the average electrode
proximity between the respective pair of electrode subsets.
[0083] As described above, determination of the relative proximity
between electrodes can be accomplished by generating an electrical
signal and measuring an electrical parameter (e.g., electrical
field potential) between the electrodes in response to the
electrical signal. Notably, because the electrodes are clustered
based on the relative proximity between electrode subsets, there is
no need to estimate the absolute proximity between electrodes. As
such, an indirect measure of the relative proximity between
electrodes would be sufficient. Monopolar electrical field
potentials can be measured between any pair of electrodes (one used
as a source of the electrical field potential that is returned to
the IPG case 40, and the other used to measure the electrical field
potential), with the value of the measured electrical field
potentials being inversely related to the distance between the two
electrodes. The field potential value can thus provide an indirect
measure of the relative proximity between electrodes.
[0084] Next the determined pair of immediately neighbored
electrodes subsets is merged into a new electrode subset that
includes all electrodes in the pair of immediately neighboring
electrode subsets (step 204), and then including the new electrode
subset within the plurality of electrode subsets to be evaluated,
while excluding the pair of immediately neighboring electrode
subsets from the plurality of electrode sets to be evaluated (step
206). For example, if a first electrode subset {E1} and a second
electrode subset {E2} are merged into a new electrode subset {E1,
E2}, the new electrode subset {E1, E2} will be included in
subsequent electrode evaluations, whereas the old electrode subsets
{E1} and {E2} will be eliminated from subsequent electrode
evaluations.
[0085] Next, steps 202-206 are repeated until all the electrode
subsets have been merged into a single electrode subset, and in
this case, until the sixteen electrode subsets {E1}-{E16} are
merged into a single electrode subset {E1-E16} (step 208). Next, a
clustering relationship of the electrodes is identified based at
least in part on the incremental merging of the electrode subsets
into the single electrode subset (step 210). As will be described
in further detail below, identification of the clustering
relationship of the electrodes will depend on the specific
technique used to merge the electrode subsets together.
[0086] Next, the electrodes are programmed based on the identified
clustering relationship of the electrodes (step 210). As examples,
at least one electrode can be selected as a cathode and at least
one other electrode can be selected as an anode based on the
identified clustering relationship of the electrodes, as discussed
above with respect to FIG. 8a, or groups of electrodes can be
selected to create a respective plurality of stimulation regions
based on the identified clustering relationship of the electrodes,
as discussed above with respect to FIG. 8b. The CP 18 may
automatically program the electrodes in response to the
identification of the clustering relationship between the
electrodes 26 and/or may display the clustering relationship
between the electrodes 26 to the user, after which, the CP 18 may
program the electrodes via user intervention (i.e., user
manipulation of the interface of the CP 18 or RC 16).
[0087] As briefly discussed above, two exemplary techniques may be
used to implement the generic electrode clustering method
illustrated in FIG. 9.
[0088] In the first electrode clustering technique, an
agglomerative algorithm is used in a hierarchical clustering
analysis. This technique involves determining, as the pair of
immediately neighboring electrode subsets determined in step 202, a
pair of electrode subsets closest in proximity to each other than
any other pair of electrode subsets is in proximity to each other,
which is reiterated via step 208, and identifying the clustering
relationship of the electrodes in step 210 by arranging the
electrodes in hierarchical clustering structures. As an example, if
there are N electrodes numbered as E.sub.1, E.sub.2, . . . E.sub.N,
the agglomerative algorithm processes the clustering as
follows.
[0089] Initially, each electrode is assigned to a single subset,
i.e., S.sub.1={E.sub.1}, S.sub.2={E.sub.2}, . . . ,
S.sub.N={E.sub.N}, all of which are included in the subsets to be
evaluated S.sub.EVAL; that is, subsets under evaluation
S.sub.EVAL={S.sub.1, S.sub.2, . . . , S.sub.N}.
[0090] Next, the pair-wise distance/proximities between all
possible combinations of two electrode subsets d.sub.i,j, i.noteq.j
(e.g., d.sub.1,2, d.sub.1,3, . . . , d.sub.1,N, d.sub.2,3, . . . ,
d.sub.N-1,N) is determined by implementing the minimum electrode
proximity, the maximum electrode proximity, or the average
electrode proximity techniques.
[0091] For the minimum electrode proximity technique, the following
equation can be used to determine the pair-wise distance/proximity
between given electrode subsets S.sub.i, S.sub.j:
d i , j = min E x .di-elect cons. S i , E y .di-elect cons. S j (
dist ( E x , E y ) ) ; ##EQU00001##
that is, the distance between a first given electrode subset
S.sub.i and a second given electrode subset S.sub.j is the minimum
pair-wise distance between all pair combinations of electrodes
E.sub.x, E.sub.y, where E.sub.x is a member of electrode subset
S.sub.i, and E.sub.y is a member of electrode subset S.sub.j.
[0092] For the maximum electrode proximity technique, the following
equation can be used to determine the pair-wise distance/proximity
between given electrode subsets S.sub.i, S.sub.j:
d i , j = max E x .di-elect cons. S i , E y .di-elect cons. S j (
dist ( E x , E y ) ) ; ##EQU00002##
that is, the distance between a first given electrode subset
S.sub.i and a second given electrode subset S.sub.j is the maximum
pair-wise distance between all pair combinations of electrodes
E.sub.x, E.sub.y, where E.sub.x is a member of electrode subset
S.sub.i, and E.sub.y is a member of electrode subset S.sub.j.
[0093] For the average electrode proximity technique, the following
equation can be used to determine the pair-wise distance/proximity
between given electrode subsets S.sub.i, S.sub.j:
d i , j = 1 K i .times. K j E x .di-elect cons. S i E y .di-elect
cons. S j ( dist ( E x , E y ) ) ; ##EQU00003##
that is, the distance between a first given electrode subset
S.sub.i and a second given electrode subset S.sub.j is the average
of the pair-wise distances between all possible pair combinations
of electrodes E.sub.x, E.sub.y, where E.sub.x is a member of
electrode subset S.sub.i, E.sub.y is a member of electrode subset
S.sub.j, K.sub.i is the number of members in the electrode subset
S.sub.i and K.sub.j is the number of members in the electrode
subset S.sub.j.
[0094] Next, the pair of electrode subsets S.sub.i, S.sub.j that
are closest to each other is identified; that is, find m,n such
that d.sub.m,n=min(d.sub.i,j,i.noteq.j). Then, the electrode
subsets S.sub.m, S.sub.n are merged into a new electrode subset
S.sub.NEW={S.sub.m, S.sub.n}, which includes all members of
electrode subsets S.sub.m and S.sub.n. Next, the electrode subsets
under evaluation S.sub.EVAL are updated to include the new
electrode subset S.sub.NEW, while excluding the merged electrode
subsets S.sub.m, S.sub.n from the electrode subsets under
evaluation S.sub.EVAL. The pair-wise distance/proximity
determination, closest electrode subset pair determination,
electrode subset merging, and electrode subset under evaluation
updating steps are then repeated until all the electrodes have been
merged into a single electrode subset.
[0095] As briefly discussed above, the agglomerative algorithm can
be used to identify the clustering relationship of the electrodes
by arranging the electrodes in hierarchical clustering structures.
For example, given the electrode arrangements illustrated in FIGS.
8a and 8b, dendrograms representing the clustering structures of
the electrodes can be generated, as respectively illustrated in
FIGS. 10a and 10b, or partitioned block diagrams representing the
clustering structures of the electrodes can be generated, as
respectively illustrated in FIGS. 11a and 11b. Each of the
dendrograms illustrated in FIGS. 10a and 10b starts from the root,
which consists of a single cluster containing all electrodes, and
is branched from top to bottom to illustrate the merging
relationship. Similarly, each of the partitioned block diagrams
illustrated in FIGS. 11a and 11b contains boxes that are
successively partitioned to illustrate the merging
relationship.
[0096] With respect to the electrode arrangement in FIG. 8a, a
review of these dendrograms and partitioned block diagrams reveals
that the electrode subsets {E2, E9}, {E3, E10}, {E4, E11}, {E5,
E12}, {E6, E13}, {E7, E14}, {E8, E15} can be identified as
two-electrode clusters; the electrode subset {E1, E2, E9} can be
identified as a three-electrode cluster; the electrode subsets {E4,
E5, E11, E12} and {E7, E8, E14, E15} can be identified as
four-electrode clusters; the electrode subset {E1-E3, E9, E10} can
be identified as a five-electrode cluster; the electrode subset
{E6-E8, E13-E15} can be identified as a six-electrode cluster; the
electrode subset {E6-E8, E13-E16} can be identified as a
seven-electrode cluster; and the electrode subset {E1-E5, E9-E12}
can be identified as a nine-electrode cluster. Thus, variously
sized electrode clusters, which are mapped to the electrodes, can
be easily programmed as anodes or cathodes.
[0097] With respect to the electrode arrangement in FIG. 8b, a
review of these dendrograms and partitioned block diagrams reveals
that the electrode subset {E1-E8} are located in one anatomical
region, and the electrode subset {E9-E16} are located in another
anatomical region. Thus, two electrode clusters, which are mapped
to the electrodes, can be easily respectively programmed to create
two stimulation regions.
[0098] In the second electrode clustering technique, an algorithm
is used in a cluster ordering analysis. This technique involves
including the new electrode subset and a single electrode closest
in proximity to the new electrode subset within the pair of
immediately neighboring electrode subsets subsequently determined
in step 202, which is reiterated via step 208, and identifying the
clustering relationship of the electrodes in step 210 by arranging
the single electrodes in an order in which they are included within
the pair of immediately neighboring electrode subsets. As an
example, if there are N electrodes numbered as E.sub.1, E.sub.2, .
. . , E.sub.N, this algorithm processes the clustering as
follows.
[0099] Initially, each electrode is assigned to a single subset,
i.e., S.sub.1={E.sub.1}, S.sub.2={E.sub.2}, . . . ,
S.sub.N={E.sub.N}, all of which are included in the subsets to be
evaluated S.sub.EVAL; that is, subsets under evaluation
S.sub.EVAL={S.sub.1, S.sub.2, . . . , S.sub.N}. Next, one of the
subsets is selected as the present subset S.sub.PRES into which all
subsequent single electrode subsets S.sub.j will eventually be
merged, as will be discussed in further detail below.
[0100] Then, the pair-wise distance/proximities between all
possible combinations of the present subset S.sub.PRES and the
remaining single-electrode subsets S.sub.j (i.e.,
S.sub.j.epsilon.S.sub.PRES) are determined by implementing the
minimum electrode proximity, the maximum electrode proximity, or
the average electrode proximity techniques.
[0101] For the minimum electrode proximity technique, the following
equation can be used to determine the pair-wise distance/proximity
between the present electrode subset S.sub.PRES and a remaining
single-electrode subset S.sub.j:
d j = min E x .di-elect cons. S PRES ( dist ( E x , E y ) ) ;
##EQU00004##
that is, the distance between the present subset S.sub.PRES and the
single-electrode subset S.sub.j is the minimum pair-wise distance
between all pair combinations of electrodes E.sub.x, E.sub.y, where
E.sub.x is a member of electrode subset S.sub.PRES, and E.sub.y is
the only member of electrode subset S.sub.j.
[0102] For the maximum electrode proximity technique, the following
equation can be used to determine the pair-wise distance/proximity
between the present electrode subset S.sub.PRES and a remaining
single-electrode subset S.sub.j:
d j = max E x .di-elect cons. S PRES ( dist ( E x , E y ) ) ;
##EQU00005##
that is, the distance between the present subset S.sub.PRES and the
single-electrode subset S.sub.j is the maximum pair-wise distance
between all pair combinations of electrodes E.sub.x, E.sub.y, where
E.sub.x is a member of electrode subset S.sub.PRES, and E.sub.y is
the only member of electrode subset S.sub.j.
[0103] For the average electrode proximity technique, the following
equation can be used to determine the pair-wise distance/proximity
between the present electrode subset S.sub.PRES and a remaining
single-electrode subset S.sub.j:
d j = 1 K E x .di-elect cons. S PRES dist ( E x , E y ) ;
##EQU00006##
that is, the distance between the present subset S.sub.PRES and the
single-electrode subset S.sub.j is the average of the pair-wise
distances between all possible pair combinations of electrodes
E.sub.x, E.sub.y, where E.sub.x is a member of present electrode
subset S.sub.PRES, E.sub.y is the only member of electrode subset
S.sub.j, and K is the number of members in the present electrode
subset S.sub.PRES.
[0104] Next, the single-electrode subset S.sub.i that is closest to
the present electrode subset S.sub.PRES is identified; that is,
find n such that d.sub.n=min(d.sub.j). Then, the present electrode
subset S.sub.PRES and the single-electrode subset S.sub.n are
merged into a new electrode subset S.sub.NEW={S.sub.PRES, S.sub.n},
which includes all members of the present electrode subset
S.sub.PRES and the single electrode subset S.sub.n. Optionally, the
pair-wise distance/proximity between the newly merged single
electrode subset S.sub.n and each of the existing electrodes in the
present electrode subset S.sub.PRES is assessed and sorted (i.e.,
dist(E.sub.n,E.sub.i) for E.sub.i.epsilon.S.sub.PRES. The two
electrodes in the present electrode subset S.sub.PRES that are
closest to the newly merged single electrode subset S.sub.n
provides an estimate of the direction in which the merged single
electrode subset S.sub.n is relative to the present electrode
subset S.sub.PRES.
[0105] Next, the electrode subsets under evaluation S.sub.EVAL are
updated to include the new electrode subset S.sub.NEW, while
excluding the merged electrode subsets S.sub.PRES, S.sub.n from the
electrode subsets under evaluation S.sub.EVAL. The new electrode
subset S.sub.NEW is then used as the next present electrode subset
S.sub.PRES. The pair-wise distance/proximity determination, closest
electrode subset pair determination, electrode subset merging, and
electrode subset under evaluation updating steps are then repeated
until all the electrodes have been merged into a single electrode
subset.
[0106] As briefly discussed above, this algorithm can be used to
identify the clustering relationship of the electrodes by arranging
the electrodes in an order in which they are included within the
pair of immediately neighboring electrode subsets.
[0107] For example, given the electrode arrangements illustrated in
FIGS. 8a and 8b, the clustering order of the electrodes can be
illustrated by successively plotting an electrode next to its
nearest neighbor in the order of merging, as respectively
illustrated in FIGS. 12a and 12b. The numbers in parentheses next
to the electrode numbers indicate the order of merging. It should
be noted that the plots of the electrode arrays may not faithfully
represent two linear leads, because the electrode position relative
to its nearest neighbor is determined solely by the relative
distances between the electrodes, and the algorithm does not assume
a linear electrode arrangement. The electrode array plot
illustrated in FIG. 12a looks more linear because the position of
each electrode in this case was determined from two immediately
adjacent neighbors (one in the longitudinal direction and one in
the lateral direction), while the electrode array plot illustrated
in FIG. 12b are carried by two separated leads and the position of
each electrode was determined from two in-line neighbors (one of
them not being immediately adjacent) without making a linear
electrode array assumption.
[0108] A review of the electrode arrangement in FIG. 12a reveals
that any electrode and its neighboring electrodes can be selected
to form any sized cluster. For example, electrode E4 and its
neighboring electrodes E3, E5, E11, and E12 can be selected to form
a five-electrode cluster; or electrode E1 and its neighboring
electrodes E2 and E9 can be selected to form a three-electrode
cluster, etc. Thus, variously sized electrode clusters, which are
mapped to the electrodes, can be easily programmed as anodes or
cathodes.
[0109] A review of the electrode arrangement in FIG. 12b reveals
that electrodes E1-E8 are located in one anatomical region, and the
electrodes E9-E16 are located in another anatomical region. Thus,
two electrode clusters, which are mapped to the electrodes, can be
easily respectively programmed to create two stimulation
regions.
[0110] While the foregoing electrode clustering techniques provide
a good estimate of the relative proximities between the electrodes,
it may be desirable to provide a more accurate representation of
the electrode array, so that, e.g., the electrodes can be mapped to
different linear electrode configurations that are closely spaced
from each other.
[0111] For example, each of FIGS. 13a and 13b illustrates three
neurostimulation leads 12(1)-12(3) arranged in a parallel
relationship, with each of the first two leads 12(1), 12(2) having
relatively large electrode spacings, and the third lead 12(3)
having relatively small electrode spacings. In FIG. 13a, the third
lead 12(3) is located between the leads 12(1), 12(2), whereas in
FIG. 13b, the third lead 12(3) is located on the left of the leads
12(1), 12(2). The numbers 1-16 illustrated on the left side of the
leads 12 spatially correspond to the active electrodes E1-E16
carried by the leads 12, whereas the X's correspond to inactive
electrodes carried by the leads.
[0112] In both cases, the leads 12(1), 12(2) are connected to one
connector port on the IPG 14 via a splitter (not shown), and the
lead 12(3) is connected to the other connector port on the IPG 14
without the use of a splitter, such that electrodes E1-E8 on lead
12(3) are coupled to one connector port, and electrodes E9-E12 at
the distal end of the lead 12(1) and electrodes E13-E16 at the
distal end of the lead 12(2) are coupled to the other connector
port. In effect, one 1.times.8 electrode array and two 1.times.4
electrode arrays have been created using the splitter, although the
IPG 14 has been designed to support two 1.times.8 electrode arrays.
Without prior knowledge of how the splitter is used to couple the
leads 12 to the IPG 14, the CP 18 is capable of identifying the
actual electrode positions relative to each other and mapping the
nominal electrodes E1-E16 to these actual electrode positions, as
will now be discussed.
[0113] Using electrode neighbor information obtained using a
suitable technique, such as, e.g., the second electrode clustering
technique described above, this method generates a map indicating
the positions of all electrodes in accordance with a set of rules
that presupposes that the electrodes are arranged in linear arrays.
This is accomplished by placing neighbor electrodes within a
spatial grid of electrode positions based on its relationship to a
designated reference electrode and other neighbor electrodes
surrounding the same reference electrode.
[0114] Placement of the electrodes in the grid is accomplished in
an iterative fashion to gradually expand the electrode map in that
once the first reference electrode and its neighbor electrodes are
placed in the grid, one of the neighbor electrodes of the first
reference electrode will be used as a second reference electrode to
position the neighbor electrodes of the second reference electrode
that have not already been positioned within the grid, then one of
the neighbor electrodes to the second reference electrode will be
used as the third reference electrode to position the neighbor
electrodes of the third reference electrode that have not already
been positioned within the grid, and so forth until all of the
electrodes are positioned in the grid.
[0115] To this end, and with reference to FIG. 14, a fixed spatial
grid of electrode positions (represented by circles) is generated
(step 300), as illustrated in FIG. 15. As there shown, the
electrode grid positions are arranged in columns representing
linear arrays of electrodes. Preferably, the number of columns and
number of grid positions in each column are at least equal to the
contemplated number of leads and number of active electrodes
carried by each lead that will be used in the neurostimulation
system 10. As illustrated in FIG. 15, the electrode grid can be
divided into hexagonal cells, with each cell having a reference
electrode grid position (labeled REF) and six electrode grid
positions (numbered 1-6) immediately surrounding the reference grid
position. Alternatively, the electrode grid can be divided into
other polygonal shapes, such as octagons, quadrangles, etc.
Although only one of the grid positions is shown as a reference
grid position, any of the grid positions can be designated as a
reference grid position, as will be described in further detail
below. Because this technique is only concerned with the relative
positions between the electrodes, the variation in distance among
the neighbor electrodes to the reference electrode, which may arise
from the variation in lead type, lead separation, noise level, etc.
can be ignored, and thus, the spacings between the grid positions
are fixed and uniformly spaced.
[0116] Next, different numbers are initially assigned to all of the
electrodes that are to be placed into the electrode grid (step
302). Preferably, the numbers are assigned to the electrodes based
on a conventional mapping between the connector port terminals and
the respective electrodes. For example, if there are two connector
ports that are conventionally coupled to two 1.times.8 electrode
arrays (as in the present case), connector terminals 1-8 correspond
to electrodes E1-E8, and connector terminals 9-16 correspond to
electrodes E9-E16. Thus, the electrodes will be designated E1-E16
in accordance to the connector terminals to which they are coupled.
In the illustrated embodiment, the numbers 1-16 are respectively
assigned to sixteen electrodes, as illustrated in FIGS. 13a and
13b. It should be noted that the CP 18 does not know, at this
point, the physical configuration of the electrodes E1-E16 shown in
FIGS. 13a and 13b. The CP 18 only knows the assigned number of the
electrode that is coupled to any particular connector
terminals.
[0117] As will be described in further detail below, each electrode
will be iteratively designated a reference electrode that will be
placed, along with its neighboring electrodes, in the electrode
grid in a specific order. In the illustrated embodiment, the
specific order in which each electrode is designated a reference
electrode is determined in accordance with the clustering order of
the electrodes determined using the second electrode clustering
technique described above. That is, each electrode is iteratively
merged into a single electrode subset in an order dictated by a
nearest neighbor analysis (i.e., by merging the electrode closest
in proximity to the single electrode subset) for each iteration
(step 304). This merging order will be the order in which each
electrode is designated a reference electrode with respect to the
electrode grid. Next, for each electrode, neighboring ones of the
remaining electrodes are determined (step 306), e.g., by analyzing
the pair-wise proximities between the electrodes acquired during
the electrode merging steps of the second electrode clustering
technique.
[0118] The electrode clustering analysis performed in steps 304 and
306 may yield a table-like data array that lists the electrodes in
the order of merging in one column (reference electrode column),
and up to six neighbor electrodes identified as the nearest
neighbors (Neighbor N1-N6 columns) to the respective reference
electrode.
[0119] Tables 1a and 1b below provide the list of the electrodes
(in their merging order) and their nearest neighbor electrodes for
the two example cases illustrated in FIGS. 13a and 13b,
respectively. Each table is generated by first populating the
reference electrode column with the electrodes in the order that
they are merged into the single subset of electrodes. For each
reference electrode, the two closest neighbors are determined from
the pair-wise proximity measurements obtained during the electrode
clustering technique, which are then filled into the locations in
the neighbor N1 and neighbor N2 columns corresponding to the
respective reference electrode.
[0120] To the extent that one of two nearest neighbors for a
currently identified reference electrode has previously been
identified as a reference electrode in the table, the currently
identified reference electrode is backfilled into the next
available neighbor electrode column (N3-N6) in the row of the table
corresponding to the previously identified reference electrode.
Notably, due to inherent noise in the proximity measurements, the
two nearest neighbors of the respective reference electrode may not
necessarily match the actual two nearest neighbors of the
respective reference electrode. It should also be noted that
electrode E12 is not listed in Table 1a, because there was an open
circuit in the electrode when taking the proximity measurements.
However, if it is known that electrode E12 is in use, due to the
redundancy built in the tables, electrode E12 can still be properly
placed within the electrode array, as evidenced below.
TABLE-US-00001 TABLE 1a (Electrodes in Order of Merging and Nearest
Neighbors for Case #1) Reference Neighbor Neighbor Neighbor
Neighbor Neighbor Neighbor Electrode N1 N2 N3 N4 N5 N6 7 8 6 16 --
-- -- 8 7 6 -- -- -- -- 6 7 8 16 5 4 -- 16 6 7 5 -- -- -- 5 6 16 4
3 -- -- 4 5 6 3 15 11 -- 3 4 5 15 11 2 1 15 3 4 -- -- -- -- 11 3 4
2 -- -- -- 2 3 11 1 10 14 -- 1 2 3 10 14 9 -- 10 1 2 9 -- -- -- 14
1 2 13 -- -- -- 9 10 1 13 -- -- -- 13 9 14 -- -- -- --
TABLE-US-00002 TABLE 1b (Electrodes in Order of Merging and Nearest
Neighbors for Case #2) Reference Neighbor Neighbor Neighbor
Neighbor Neighbor Neighbor Electrode N1 N2 N3 N4 N5 N6 8 7 6 -- --
-- -- 7 8 6 5 -- -- -- 6 7 8 5 4 -- -- 5 6 7 4 3 -- -- 4 5 6 3 12
-- -- 3 4 5 12 2 11 -- 12 3 4 16 2 -- -- 2 3 12 11 1 -- -- 11 2 3 1
16 15 10 1 11 2 -- -- -- -- 16 12 11 15 -- -- -- 15 16 11 10 14 --
-- 10 15 11 14 9 -- -- 14 10 15 9 13 -- -- 9 14 10 13 -- -- -- 13 9
14 -- -- -- --
[0121] After the electrode merging/neighbor table has been
generated, the first electrode in the table is designated as a
reference electrode to be currently examined (step 308), which is
then assigned to one of the electrode grid positions (step 310).
Next, one or more previously unassigned ones of the electrodes
neighboring the reference electrode are respectively assigned to
one or more of the electrode grid positions immediately surrounding
the current reference grid position (steps 312-344).
[0122] In the illustrated embodiment, the neighbor electrodes are
assigned to the neighbor grid positions surrounding the reference
grid position in accordance with a set of rules that distinguishes
between electrodes that are in-line with the reference electrode
and electrodes that are off-line with the reference electrode.
[0123] To this end, the next previously unassigned neighbor
electrode of the reference electrode is currently selected for
assignment within the electrode grid (step 312). In the illustrated
embodiment, the currently selected neighbor electrode will be the
next numbered neighbor electrode of the reference electrode, as
listed in the merging order/neighbor table. That is, if neighbor
electrode N1 has previously been assigned to the electrode grid,
and neighbor electrode N2 has not been previously been assigned to
the electrode grid, then neighbor electrode N2 will be currently
selected for assignment within the electrode grid. Of course, if no
neighbor electrodes relative to the currently reference electrode
have been assigned to the electrode grid, then the first neighbor
electrode N1 will be initially selected.
[0124] Next, one of the neighbor grid positions is ranked based on
the likelihood of the currently selected neighbor electrode being
in-line or off-line with the reference electrode (steps 314-340).
In particular, each of the six neighbor grid positions takes a
different priority when assigning each neighbor electrode within
the electrode grid.
[0125] Because the electrode grid positions are spatially arranged
in columns respectively representing linear arrays of electrodes,
the neighbor grid positions around the reference grid position can
be prioritized based on what column they are likely in relative to
the reference grid position. For example, grid positions #1 and #2
(same column in which the reference grid position is) will take
priority when assigning neighbor electrodes that are likely carried
by the same lead as the reference electrode; grid positions #3 and
#4 (column to the right of the column in which the reference grid
position is) will take priority when assigning neighbor electrodes
that are likely carried by a lead that is different from the lead
carrying the reference electrode; and grid positions #5 and #6
(column to the left of the column in which the reference grid
position is) will take priority when assigning neighbor electrodes
that are likely carried by a third lead that is different from the
leads carrying the reference electrode and the lead carrying
electrodes assigned to grid positions #3 and #4. The currently
selected neighbor electrode will be assigned to the open neighbor
position having the highest priority.
[0126] In particular, if the electrode number of the currently
selected neighbor electrode is sequential to the electrode number
of the reference electrode at a threshold (step 314), the neighbor
electrode is likely in-line with the reference electrode, and thus,
grid positions #1 and #2 relative to the reference grid position
take the highest rank (step 316). In the illustrated embodiment,
the threshold is one, such that electrode numbers are sequential
only if their difference is one (e.g., electrode E2 is sequential
to electrode E3, but not sequential to electrode E4). If the
threshold is increased to, e.g., two (which may be preferable if
the proximity measurements are anticipated to be noisy), the
electrodes numbers are sequential only if their difference is two
or less (e.g., electrode E2 is sequential to electrodes E3 or
E4).
[0127] The rank of grid position #1 versus grid position #2 depends
on the sign of the difference in the electrode numbers of the
neighbor electrode and reference electrode. In the illustrated
embodiment, if the number of the neighbor electrode is less than
the number of the reference electrode (step 318), grid position #1
is ranked over grid position #2, and thus, takes the highest rank
(step 320); otherwise, grid position #2 is ranked over grid
position #1, and thus, takes the highest rank (step 322).
Alternatively, if the number of the neighbor electrode is greater
than the number of the reference electrode, grid position #1 is
ranked over grid position #2; otherwise, grid position #2 is ranked
over grid position #1. Ultimately, it does not matter which of the
grid positions #1 or #2 ranks highest with respect to the sign of
difference between the electrode numbers, as long as all the
neighbor electrodes are assigned to the electrode grid positions in
accordance with the same rule.
[0128] If the number of the currently selected neighbor electrode
currently is not sequential with the number of the reference
electrode at the threshold (step 314), but rather is sequential to
the number of a neighbor electrode that has previously been
assigned to the electrode grid with respect to the reference
electrode at the threshold (step 324), the currently selected
neighbor electrode is likely in-line with the previously assigned
neighbor electrode, and thus, grid positions #1 and #2 relative to
the grid position corresponding to the previously assigned neighbor
electrode take the highest rank (step 326). Again, the rank of grid
position #1 versus grid position #2 depends on the sign of the
difference in the electrode numbers of the currently selected
neighbor electrode and previously assigned neighbor electrode. In
the illustrated embodiment, if the electrode number of the
currently selected neighbor electrode is less than the electrode
number of the previously assigned electrode (step 328), grid
position #1 is ranked over grid position #2, and thus, takes the
highest rank (step 330); otherwise, grid position #2 is ranked over
grid position #1, and thus, takes the highest rank (step 332).
[0129] If the number of the currently selected neighbor electrode
is not sequential with the number of the reference electrode or the
number of a neighbor electrode previously assigned to the electrode
grid with respect to the reference electrode (step 324), grid
positions #3-#6 relative to the reference grid position are ranked
the highest (step 334). If the number of the currently selected
neighbor electrode is not sequential with the number of any
electrode that has previously been assigned to grid positions in
the same column as grid positions #5 or #6 relative to the
reference grid position (step 336), grid positions #3 and #4
relative to the reference grid position ranks the highest (step
338), and positions #5 and #6 relative to the reference grid
position rank the highest otherwise (step 340). As a general rule,
position #3 ranks higher than position #4, and position #5 ranks
higher than position #6.
[0130] Once the grid positions are ranked (steps 320, 322, 338,
340), the currently selected neighbor electrode is assigned to the
highest ranking grid position (step 342). If the currently selected
neighbor electrode is not the last neighbor electrode of the
reference electrode currently under examination (step 344), the
next neighbor electrode of the reference electrode is selected and
assigned to the appropriate electrode grid position in accordance
with steps 312-342. If the currently selected neighbor electrode is
the last neighbor electrode of the reference electrode currently
under examination (step 344), and if not all of the electrodes have
been assigned to the electrode grid (step 346), the next electrode
in the table, which will have already been assigned to the
electrode grid, is designated as a reference electrode to be
currently examined (step 348), and previously unassigned ones of
the electrodes neighboring the reference electrode are respectively
assigned to the electrode grid positions immediately surrounding
the grid position to which the reference electrode is assigned
(steps 312-344).
[0131] After all of the electrodes have been assigned to the
electrode grid, a rough map of the electrodes can be obtained, and
the electrodes can be programmed (step 350). For example, the
electrode maps illustrated in FIGS. 16a and 16b, which show
electrode configurations along with the order in which the
electrodes are merged in parentheses, can be obtained by applying
the technique provided in FIG. 14 to Tables 1a and 1b, which were
obtained from the electrode configuration cases illustrated in
FIGS. 13a and 13b.
[0132] As one example, and with reference to FIG. 17a-17h, the
assignment of electrodes of the configuration illustrated in FIG.
13a to the electrode grid will now be discussed. For clarity, the
bolded circle in each iteration described with respect to FIGS.
17a-17h represents the reference electrode grid position.
[0133] Electrode E7, which is the first listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, and is then assigned to a reference grid
position (FIG. 17a). Electrode E8, as the first neighbor electrode
to electrode E7, is assigned to grid position #2 relative to the
current reference grid position, since electrode E8 is sequential
to, and has a higher number than, electrode E7. Electrode E6, as
the second neighbor electrode to electrode E7, is assigned to grid
position #1 relative to the current reference grid position, since
electrode E6 is sequential to, and has a lower number than,
electrode E7. Electrode E16, as the third neighbor electrode to
electrode E7, is assigned to grid position #3 relative to the
current reference grid position, since electrode E16 is not
sequential to electrode E7 or the other two previously assigned
neighbor electrodes E6 and E8, and no other electrode has been
previously assigned to a grid position in the same column in which
grid positions #5 or #6 relative to the current reference grid
position are located.
[0134] Electrode E8, which is the second listed reference electrode
in Table 1a, does not have any neighbor electrodes that have not
been previously assigned to the electrode grid, and therefore, is
not designated as a reference electrode for current
examination.
[0135] Electrode E6, which is the third listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E6 was
previously assigned to is designated as the current reference grid
position (FIG. 17b). Electrode E5, as the fourth and next
unassigned neighbor electrode to electrode E6, is assigned to
reference position #1 relative to the current reference grid
position, since electrode E5 is sequential to, and has a lower
number than, electrode E6. Electrode E4, as the fifth and next
unassigned neighbor electrode to electrode E6, is assigned to grid
position #1 relative to the grid position to which electrode E5 is
assigned, since electrode E4, while not sequential to electrode E6,
is sequential to, and a lesser number than, electrode E5, a
neighbor electrode previously assigned to the electrode grid
relative to the current reference grid position.
[0136] Electrode E16, which is the fourth listed reference
electrode in Table 1a, does not have any neighbor electrodes that
have not been previously assigned to the electrode grid, and
therefore, is not designated as a reference electrode for current
examination.
[0137] Electrode E5, which is the fifth listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E5 was
previously assigned to is designated as the current reference grid
position (FIG. 17c). Electrode E3, as the fourth and next
unassigned neighbor electrode to electrode E5, is assigned to grid
position #1 relative to the grid position to which electrode E4 is
assigned, since electrode E3, while not sequential to electrode E5,
is sequential to, and a lesser number than, electrode E4, a
neighbor electrode previously assigned to the electrode grid
relative to the current reference grid position.
[0138] Electrode E4, which is the sixth listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E4 was
previously assigned to is designated as the current reference grid
position (FIG. 17d). Electrode E15, as the fourth and next
unassigned neighbor electrode to electrode E4, is assigned to grid
position #3 relative to the current reference grid position, since
electrode E15 is not sequential to electrode E4 or any other
neighbor electrode previously assigned to a position relative to
the current reference grid position, but is sequential to electrode
E16, an electrode previously assigned to a grid position in the
same column in which grid position #3 relative to the current
reference grid position is located. Electrode E11, as the fifth and
next unassigned neighbor electrode to electrode E4, is assigned to
grid position #5 relative to the current reference grid position,
since electrode E11 is not sequential to electrode E4 or the other
previously assigned neighbor electrode E15, and is not sequential
to electrodes E15 and E16, two electrodes previously assigned to a
grid position in the same column in which grid positions #3 and #4
relative to the current reference grid position are located.
[0139] Electrode E3, which is the seventh listed reference
electrode in Table 1a, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E3 was
previously assigned to is designated as the current reference grid
position (FIG. 17e). Electrode E2, as the fifth neighbor electrode
to electrode E3, is assigned to grid position #1 relative to the
current reference grid position, since electrode E2 is sequential
to, and has a lower number than, electrode E3. Electrode E1, as the
sixth and next unassigned neighbor electrode to electrode E3, is
assigned to grid position #1 relative to the grid position to which
electrode E2 is assigned, since electrode E1, while not sequential
to electrode E3, is sequential to, and a lesser number than,
electrode E2, a neighbor electrode previously assigned to the
electrode grid relative to the current reference grid position.
[0140] Electrodes E15 and E11, which are the eighth and ninth
listed reference electrodes in Table 1a, do not have any neighbor
electrodes that have not been previously assigned to the electrode
grid, and therefore, are not designated as reference electrodes for
current examination.
[0141] Electrode E2, which is the tenth listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E2 was
previously assigned to is designated as the current reference grid
position (FIG. 17f). Electrode E10, as the fourth and next
unassigned neighbor electrode to electrode E2, is assigned to grid
position #5 relative to the current reference grid position, since
electrode E10 is not sequential to electrode E2, but is sequential
to electrode E11, an electrode previously assigned to a grid
position in the same column in which grid position #5 relative to
the current reference grid position is located. Electrode E14, as
the fifth and next unassigned neighbor electrode to electrode E2,
is assigned to grid position #3 relative to the current reference
grid position, since electrode E14 is not sequential to electrode
E2, but is sequential to electrode E15, an electrode previously
assigned to a grid position in the same column in which grid
position #3 relative to the current reference grid position is
located.
[0142] Electrode E1, which is the eleventh listed reference
electrode in Table 1a, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E1 was
previously assigned to is designated as the current reference grid
position (FIG. 17g). Electrode E9, as the fifth and next unassigned
neighbor electrode to electrode E1, is assigned to grid position #5
relative to the current reference grid position, since electrode E9
is not sequential to electrode E2, but is sequential to electrode
E10, an electrode previously assigned to a grid position in the
same column in which grid position #5 is located.
[0143] Electrode E10, which is the twelfth listed reference
electrode in Table 1a, does not have any neighbor electrodes that
have not been previously assigned to the electrode grid, and
therefore, is not designated as a reference electrode for current
examination.
[0144] Electrode E14, which is the thirteen listed reference
electrode in Table 1a, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E14 was
previously assigned to is designated as the current reference grid
position (FIG. 17h). Electrode E13, as the third and next
unassigned neighbor electrode to electrode E14, is assigned to grid
position #1 relative to the current reference grid position, since
electrode E14 is sequential to, and has a lower number than,
electrode E13.
[0145] Electrodes E9 and E13, which are the fourteen and fifteenth
listed reference electrodes in Table 1a, do not have any neighbor
electrodes that have not been previously assigned to the electrode
grid, and therefore, are not designated as reference electrodes for
current examination. As discussed above, electrode E12 could not be
used to take proximity measurements, and therefore, could not be
used in the method illustrated in FIG. 14. However, because it is
known that electrode E12 is sequential to, and a higher number
than, electrode E11, electrode E12 can be assigned to the electrode
grid somewhere below electrode E11.
[0146] Although the foregoing electrode cluster and programming
techniques have been described as being implemented in the CP 18,
it should be noted that these techniques are not computationally
intensive, such that they may be alternatively or additionally
implemented in the RC 16.
[0147] As another example, and with reference to FIG. 18a-18m, the
assignment of electrodes of the configuration illustrated in FIG.
13b to the electrode grid will now be discussed. For clarity, the
bolded circle in each iteration described with respect to FIGS.
18a-18m represents the reference electrode grid position.
[0148] Electrode E8, which is the first listed reference electrode
in Table 1b, is designated as the reference electrode to be
currently examined, and is then assigned to a reference grid
position (FIG. 18a). Electrode E7, as the first neighbor electrode
to electrode E8, is assigned to grid position #1 relative to the
current reference grid position, since electrode E7 is sequential
to, and has a lower number than, electrode E8. Electrode E6, as the
second and next unassigned neighbor electrode to electrode E8, is
assigned to grid position #1 relative to the grid position to which
electrode E7 is assigned, since electrode E6, while not sequential
to electrode E8, is sequential to, and a lesser number than,
electrode E7, a neighbor electrode previously assigned to the
electrode grid relative to the current reference grid position.
[0149] Electrode E7, which is the second listed reference electrode
in Table 1b, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E7 was
previously assigned to is designated as the current reference grid
position (FIG. 18b). Electrode E5, as the third and next unassigned
neighbor electrode to electrode E7, is assigned to grid position #1
relative to the grid position to which electrode E6 is assigned,
since electrode E5, while not sequential to electrode E7, is
sequential to, and a lesser number than, electrode E6, a neighbor
electrode previously assigned to the electrode grid relative to the
current reference grid position.
[0150] Electrode E6, which is the third listed reference electrode
in Table 1b, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E6 was
previously assigned to is designated as the current reference grid
position (FIG. 18c). Electrode E4, as the fourth and next
unassigned neighbor electrode to electrode E6, is assigned to grid
position #1 relative to the grid position to which electrode E5 is
assigned, since electrode E4, while not sequential to electrode E6,
is sequential to, and a lesser number than, electrode E5, a
neighbor electrode previously assigned to the electrode grid
relative to the current reference grid position.
[0151] Electrode E5, which is the fourth listed reference electrode
in Table 1b, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E5 was
previously assigned to is designated as the current reference grid
position (FIG. 18d). Electrode E3, as the fourth and next
unassigned neighbor electrode to electrode E5, is assigned to grid
position #1 relative to the grid position to which electrode E4 is
assigned, since electrode E3, while not sequential to electrode E5,
is sequential to, and a lesser number than, electrode E4, a
neighbor electrode previously assigned to the electrode grid
relative to the current reference grid position.
[0152] Electrode E4, which is the fifth listed reference electrode
in Table 1b, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E4 was
previously assigned to is designated as the current reference grid
position (FIG. 18e). Electrode E12, as the fourth neighbor
electrode to electrode E4, is assigned to grid position #3 relative
to the current reference grid position, since electrode E12 is not
sequential to electrode E4 or electrode E3, a neighbor electrode
previously assigned to the electrode grid relative to the current
reference grid position, and no other electrode has been previously
assigned to a grid position in the same columns in which grid
positions #5 or #6 relative to the current reference grid position
are located.
[0153] Electrode E3, which is the sixth listed reference electrode
in Table 1b, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E3 was
previously assigned to is designated as the current reference grid
position (FIG. 18f). Then, electrode E2, as the fourth neighbor
electrode to electrode E3, is assigned to grid position #1 relative
to the current reference grid position, since electrode E2 is
sequential to, and has a lower number than, electrode E3. Electrode
E11, as the fifth and next unassigned neighbor electrode to
electrode E3, is assigned to grid position #3 relative to the
current reference grid position, since electrode E11 is not
sequential to electrode E3 or any other neighbor electrode
previously assigned to a position relative to the current reference
grid position, but is sequential to electrode E12, an electrode
previously assigned to a grid position in the same column in which
grid position #3 relative to the current reference grid position is
located.
[0154] Electrode E12, which is the seventh listed reference
electrode in Table 1a, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E12 was
previously assigned to is designated as the current reference grid
position (FIG. 18g). Electrode E16, as the third and next
unassigned neighbor electrode to electrode E12, is assigned to grid
position #3 relative to the current reference grid position, since
electrode E16 is not sequential to electrode E12 or any other
neighbor electrode previously assigned to a position relative to
the current reference grid position, and is not sequential to
electrodes E2-E8, electrodes previously assigned to a grid position
in the same column in which grid positions #5 and #6 relative to
the current reference grid position are located.
[0155] Electrode E2, which is the eighth listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E2 was
previously assigned to is designated as the current reference grid
position (FIG. 18h). Electrode E1, as the fourth neighbor electrode
to electrode E2, is assigned to grid position #1 relative to the
current reference grid position, since electrode E1 is sequential
to, and has a lower number than, electrode E2.
[0156] Electrode E11, which is the ninth listed reference electrode
in Table 1a, is designated as the reference electrode to be
currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E11 was
previously assigned to is designated as the current reference grid
position (FIG. 18i). Electrode E15, as the fifth and next
unassigned neighbor electrode to electrode E11, is assigned to grid
position #3 relative to the current reference grid position, since
electrode E15 is not sequential to electrode E11 or any other
neighbor electrode previously assigned to a position relative to
the current reference grid position, but is sequential to electrode
E16, an electrode previously assigned to a grid position in the
same column in which grid position #3 relative to the current
reference grid position is located. Electrode E10, as the sixth and
next unassigned neighbor electrode to electrode E11, is assigned to
grid position #1 relative to the current reference grid position,
since electrode E10 is sequential to, and has a lower number than,
electrode E11.
[0157] Electrodes E1 and E16, which are the tenth and eleventh
listed reference electrodes in Table 1b, do not have any neighbor
electrodes that have not been previously assigned to the electrode
grid, and therefore, are not designated as reference electrodes for
current examination.
[0158] Electrode E15, which is the twelfth listed reference
electrode in Table 1b, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E15 was
previously assigned to is designated as the current reference grid
position (FIG. 18j). Electrode E14, as the fourth and next
unassigned neighbor electrode to electrode E15, is assigned to grid
position #1 relative to the current reference grid position, since
electrode E14 is sequential to, and has a lower number than,
electrode E15.
[0159] Electrode E10, which is the thirteen listed reference
electrode in Table 1b, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E10 was
previously assigned to is designated as the current reference grid
position (FIG. 18k). Electrode E9, as the fourth and next
unassigned neighbor electrode to electrode E10, is assigned to grid
position #1 relative to the current reference grid position, since
electrode E9 is sequential to, and has a lower number than,
electrode E10.
[0160] Electrode E14, which is the fourteen listed reference
electrode in Table 1b, is designated as the reference electrode to
be currently examined, since it does have at least one neighbor
electrode that has not been previously assigned to the electrode
grid, in which case, the grid position that electrode E14 was
previously assigned to is designated as the current reference grid
position (FIG. 18l). Electrode E13, as the fourth and next
unassigned neighbor electrode to electrode E14, is assigned to grid
position #1 relative to the current reference grid position, since
electrode E13 is sequential to, and has a lower number than,
electrode E14.
[0161] Electrodes E9 and E13, which are the fifteen and sixteenth
listed reference electrodes in Table 1b, do not have any neighbor
electrodes that have not been previously assigned to the electrode
grid, and therefore, are not designated as reference electrodes for
current examination.
[0162] It should be noted that the electrode configuration mapping
technique described above does not take into account the difference
in electrode-to-electrode spacing and lead separation, and thus,
the estimated map only reflects relative positions of the
electrodes, rather than faithfully replicating the actual electrode
positions. Conventional pattern recognition techniques (e.g.,
regression, template matching, maximal likelihood, optimal fitting,
etc.) can be applied to the electrode configuration map to further
identify the linear electrode arrays and correct possible errors or
deviations that arise in the estimate due to any limitations in the
rules used to assign neighbor electrodes to the electrode grid. The
pattern recognition techniques may also serve to identify the
linear electrode arrays consisting of non-sequential electrodes
(e.g., a 1.times.16 linear electrode array supported by two
connector ports). Once the linear electrode arrays are identified
in the electrode configuration map, this information can be input
to other electrode processing techniques to determine more details
concerning the lead configuration, such as, e.g., lead type,
stagger, separation, and/or medial-lateral order, etc.
[0163] Notably, the electrode assignment rules can be modified to
be more loose or more restrictive for particular applications. In
addition, pattern recognition techniques can be applied during
electrode configuration mapping to confine the configuration with
certain patterns. This can also serve as a real time correction to
any uncertainty that may arise in the assignment of the electrodes.
Furthermore, if the assumption that the electrode configuration is
arranged in linear arrays is removed, and an arbitrary electrode
arrangement is instead assumed, the use of nearest neighbors in the
electrode configuration mapping technique may still work. However,
different neighbor electrode assignment rules may have to be used
to estimate the position of each neighbor electrode relative to the
reference electrode. In this case, for example, if the hexagonal
electrode grid is still used to represent the neighbor electrode
positions, each grid position will have the same rank (i.e., the
chance that the grid position will be assigned an electrode will be
equal). Instead of assigning each neighbor electrode to a grid
position one-after-another, grid positions for all the neighbor
electrodes need to be assigned simultaneously.
[0164] In this case, the neighbor electrode assignment rules
described above will not apply. Instead, a pattern recognition
technique may be implemented here to estimate the most likely
electrode arrangement. By permutation and combination, a set of
grid position assignments for all possible neighbor electrode
arrangements can be obtained. For each set of grid position
assignments, one can compute the pair-wise electrode proximities
that are expected for this "assumed" electrode arrangement, and
then compare the measured pair-wise electrode proximities to check
for similarity. The grid position assignment that results in the
computed electrode proximity pattern that best matches the measured
electrode proximity pattern may be estimates as the most likely
electrode arrangement.
[0165] 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.
* * * * *