U.S. patent application number 16/518432 was filed with the patent office on 2020-01-16 for controller interface for an implantable stimulator device.
The applicant listed for this patent is Stimwave Technologies Incorporated. Invention is credited to Chad David Andresen, Laura Tyler Perryman.
Application Number | 20200016408 16/518432 |
Document ID | / |
Family ID | 62488741 |
Filed Date | 2020-01-16 |
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United States Patent
Application |
20200016408 |
Kind Code |
A1 |
Perryman; Laura Tyler ; et
al. |
January 16, 2020 |
CONTROLLER INTERFACE FOR AN IMPLANTABLE STIMULATOR DEVICE
Abstract
Some computer-assisted methods include: presenting configuration
options to a user of the implanted stimulator device, the
configuration options comprising stimulation parameters for the
implanted stimulator; receiving a user specification of the
configuration options in response to the presented configuration
options; receiving user feedback when the user specified
configuration options are implemented at the implanted stimulator
device, the user feedback comprising a quantitative index of pain
resulting from implementing the user specified configuration
options on the implanted stimulator device; building a user profile
for the user based on the user specified configuration options and
the user feedback, the user profile including the user specified
configuration options as well as the corresponding quantitative
index of pain; and selecting at least one configuration option
based on the user profile when the configuration options are
subsequently presented to the user for a later treatment.
Inventors: |
Perryman; Laura Tyler;
(Pompano Beach, FL) ; Andresen; Chad David; (Miami
Beach, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stimwave Technologies Incorporated |
Pompano Beach |
FL |
US |
|
|
Family ID: |
62488741 |
Appl. No.: |
16/518432 |
Filed: |
July 22, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15661593 |
Jul 27, 2017 |
10369365 |
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16518432 |
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14952302 |
Nov 25, 2015 |
9731140 |
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15661593 |
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62084743 |
Nov 26, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/37247 20130101;
A61N 1/36142 20130101; A61N 1/36132 20130101; A61N 1/37217
20130101; A61N 1/37254 20170801; A61N 1/37241 20130101 |
International
Class: |
A61N 1/36 20060101
A61N001/36; A61N 1/372 20060101 A61N001/372 |
Claims
1. A computer-assisted method to configure settings on an implanted
stimulator device, the method comprising: presenting configuration
options to a user of the implanted stimulator device, the
configuration options comprising stimulation parameters for the
implanted stimulator; receiving a user specification of the
configuration options in response to the presented configuration
options; receiving user feedback when the user specified
configuration options are implemented at the implanted stimulator
device, the user feedback comprising a quantitative index of pain
resulting from implementing the user specified configuration
options on the implanted stimulator device; building a user profile
for the user based on the user specified configuration options and
the user feedback, the user profile including the user specified
configuration options as well as the corresponding quantitative
index of pain; and selecting at least one configuration option
based on the user profile when the configuration options are
subsequently presented to the user for a later treatment.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/661,593, filed Jul. 27, 2017, now allowed, which is a
continuation of U.S. application Ser. No. 14/952,302, filed Nov.
25, 2015, now U.S. Pat. No. 9,731,140, issued Aug. 15, 2017, which
claims the benefit of U.S. Provisional Patent Application No.
62/084,743, which was filed on Nov. 26, 2014. The contents of the
both of these foregoing applications are incorporated by reference
herein in their entireties.
TECHNICAL FIELD
[0002] This application relates generally to implantable stimulator
devices.
BACKGROUND
[0003] Active implanted stimulation devices have been utilized for
both subcutaneous treatments as well as deeper applications such as
pacing, defibrillation, spinal and gastric stimulation.
SUMMARY
[0004] In one aspect, some implementations provide a
computer-assisted method to configure settings on an implanted
stimulator device. The method includes: presenting configuration
options to a user of the implanted stimulator device, the
configuration options including stimulation parameters for the
implanted stimulator; receiving a user specification of the
configuration options in response to the presented configuration
options; receiving user feedback when the user specified
configuration options are implemented at the implanted stimulator
device, the user feedback including a quantitative index of pain
resulting from implementing the user specified configuration
options on the implanted stimulator device; building a user profile
for the user based on the user specified configuration options and
the user feedback, the user profile including the user specified
configuration options as well as the corresponding quantitative
index of pain; and selecting at least one configuration option
based on the user profile when the configuration options are
subsequently presented to the user for a later treatment.
[0005] Implementations may include one or more of the following
features.
[0006] The stimulation parameters may include polarity setting such
that presenting configuration options to the user of the implanted
stimulator device includes presenting configuration options that
include a polarity setting of each electrode of the implanted
stimulator device. Building a user profile for the user includes
building a user profile that includes the polarity setting of each
electrode that gives rise to the corresponding quantitative index
of pain. Selecting at least one configuration option may include
selecting a polarity setting for at least one of the electrodes of
the implanted stimulator device.
[0007] The stimulation parameters may include pulse rate, pulse
width, and pulse amplitude such that presenting configuration
options includes presenting configuration options that that include
pulse rate, pulse width, and pulse amplitude. The method may
further include, in response to determining that the quantitative
index of pain is above a threshold level, prompting the user to
change the configuration options. Prompting the user to change the
configuration options may include presenting at least one
configuration option based on the user profile. The method may
further include: increasing, by an amount that is proportional to
the quantitative index of pain, a pulse amplitude of stimulation
pulses for application at a particular electrode. The method may
further include: in response to determining that the quantitative
index of pain is below a threshold level, prompting the user to
reduce stimulation. Prompting the user to reduce stimulation may
include prompting the user to reduce stimulation by decreasing a
pulse amplitude of stimulation pulses for application at a
particular electrode. Presenting configuration options may further
include cycling through the each configuration option subject to
user adjustment, the configuration options including a polarity
setting of each electrode of the implanted stimulator device as
well as pulse parameters of stimulation pulses for application at a
particular electrode.
[0008] Building a user profile may further include recording an
adjustment in a configuration option made by the user that results
in an improved quantitative index of pain. Recording the adjustment
in the configuration option may include recording an adjustment in
a pulse parameter or a polarity setting.
[0009] Some implementations provide a controller device to
configure settings on an implanted stimulator device. The
controller device includes a processor configured to perform the
operations of: presenting configuration options to a user of the
implanted stimulator device, the configuration options including
stimulation parameters for the implanted stimulator; receiving a
user specification of the configuration options in response to the
presented configuration options; receiving user feedback when the
user specified configuration options are implemented at the
implanted stimulator device, the user feedback including a
quantitative index of pain resulting from implementing the user
specified configuration options on the implanted stimulator device;
building a user profile for the user based on the user specified
configuration options and the user feedback, the user profile
including the user specified configuration options as well as the
corresponding quantitative index of pain; and selecting at least
one configuration option based on the user profile when the
configuration options are subsequently presented to the user for a
later treatment.
[0010] Implementations may include one or more of the following
features.
[0011] The stimulation parameters may include polarity setting such
that presenting configuration options to the user of the implanted
stimulator device includes presenting configuration options that
include a polarity setting of each electrode of the implanted
stimulator device. Building a user profile for the user may include
building a user profile that includes the polarity setting of each
electrode that gives rise to the corresponding quantitative index
of pain. Selecting at least one configuration option may further
include selecting a polarity setting for at least one of the
electrodes of the implanted stimulator device.
[0012] The stimulation parameters include pulse rate, pulse width,
and pulse amplitude such that presenting configuration options
includes presenting configuration options that that include pulse
rate, pulse width, and pulse amplitude. The operations may further
include: in response to determining that the quantitative index of
pain is above a threshold level, prompting the user to change the
configuration options. The operations may further include: further
including in response to determining that the quantitative index of
pain is below a threshold level, prompting the user to reduce
stimulation.
[0013] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other
features, objects, and advantages will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a flow chart of an example of a process for
interacting with an implanted stimulator device.
[0015] FIG. 2A through 2F are illustrations of examples of user
interfaces.
[0016] FIG. 3 is a flow chart of a process to configure stimulation
settings of the implanted simulator device.
[0017] FIGS. 4A and 4B show example software decision trees to
auto-adjust therapy settings based on recorded pain.
[0018] FIGS. 5A and 5B are detailed diagrams of an example of a
wireless neural stimulation system.
[0019] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0020] In various implementations, systems and methods allow a user
to configure stimulation settings of an implanted stimulation
device wirelessly powered by an external controller device.
Notably, the implanted stimulator device does not include a battery
or inductive coupling. Instead, the implanted stimulator device
contains the circuitry necessary to receive the pulse instructions
from the external controller outside the body. For example, various
implementations employ internal dipole (or other) antenna
configuration(s) to receive RF power through electrical radiative
coupling. This allows such devices to produce electrical currents
capable of stimulating nerve bundles without a physical connection
to an implantable pulse generator (IPG) or use of an inductive
coil. Moreover, the implanted stimulator device includes one or
more electrodes and one or more conductive antennas (for example,
dipole or patch antennas), and internal circuitry for frequency
waveform and electrical energy rectification. In some
implementations, the polarity of the electrodes (or each electrode
pair) of the implanted stimulator device can be configured at a
controller device, along with other simulation parameters such as
waveform, duration, pulse width, and pulse repetition rate. Further
descriptions of exemplary wireless systems for providing neural
stimulation to a patient can be found in commonly-assigned,
co-pending published PCT applications PCT/US2012/23029 filed Jan.
28, 2011, PCT/US2012/32200 filed Apr. 11, 2011, PCT/US2012/48903,
filed Jan. 28, 2011, PCT/US2012/50633, filed Aug. 12, 2011 and
PCT/US2012/55746, filed Sep. 15, 2011, the complete disclosures of
which are incorporated by reference.
[0021] In these implementations, a user interface is provided for
the external controller device to register an implanted stimulator
device. The user interface also allows a patient to configure
stimulation settings to be effectuated on the implantable
stimulator device. The stimulation settings include polarity
settings at each electrode and pulse parameters for the stimulating
current. In particular, some implementations collect user feedback
reflecting pain relief resulting from various combination of
stimulation parameters. Such feedback may be assembled to build a
knowledge database, like an expert system. The knowledge database
may be subsequently leveraged to guide the patient, or other
patients, in configuring stimulation parameters including, for
example, the polarity settings at each electrode or electrode
pair.
[0022] In some cases, a software application may incorporate a
unique learning engine which uses the history of stimulation
parameter adjustments made by the patient and resulting patient
reported pain level scores to determine a combination of future
parameter settings that can be used to provide improved pain relief
for which the patient may prefer based on his/her historical usage
patterns and positions. In some instances, the stimulation
parameters include, for example, pulse current, pulse width, pulse
rate, dosage time, and electrode polarity patterns.
[0023] By way of illustration, the learning engine may determine
recommended stimulation parameter settings based on variables such
as patient age, patient gender, target nerve, depth of
implantation, type of implanted stimulator devices, anatomic
position, duration of therapy, time of day, prior stimulation
parameter settings (for example, prior pulse current, pulse
amplitude (or transmit power), pulse width, pulse rate, or
electrode polarity), and/or patient pain levels corresponding to
prior stimulation parameters. For example, each time after an
adjustment of parameters, the user can record his/her level of pain
using a numeric pain intensity scale presented by the software
application. Based on the recorded pain level and corresponding
parameter adjustments, as well as other variables such as those
described above, the learning engine may build a profile including
the combination of parameters that gives rise to improved
therapeutic pain relief. The learning engine may then be applied in
various approaches. In one implementation, after the user has built
up history for their profile, the software application may proceed
to offer an "Auto" mode on the front page of the Configure tab that
can enable the user to actively change the stimulation parameters.
In another implementation, after the user records his/her present
pain rating on the numeric pain intensity scale, the application
offers to automate setting a parameter or parameters which are
calculated by leveraging historical user input. In yet another
implementation, a "Build Your Stim Profile" section of the software
application may enable the user to rank the effectiveness of
therapy through visual analog scale, numeric pain intensity scale,
or binary (yes or no). While in the "Build Your Stim Profile" mode,
the software application may begin to cycle through calculated
settings and learn the user's preferences. In this cycling process,
the application can build a profile more quickly. The feature of
the learning engine and its automated parameter selection criteria
can offer the user a simplified form of interaction which can be
daunting when juggling the many variables involved with stimulation
parameters.
[0024] FIG. 1 is a flow chart 100 of an example of a process for a
user to interact with an implanted stimulator device. The process
may be implemented by software installed on an external controller
device in direct or indirect communication with an implantable
stimulator device. Example external controller devices can include
a portable computing device, such as a tablet, a handheld device,
or a laptop device. In some implementations, the external
controller device has its own power supply, for example, a battery
pack. The external controller device may be separate from or part
of a microwave field stimulator (MFS) that is in communication with
and providing power to the implantable stimulator device. If the
external controller is separate from the MFS, the external
controller may communicate with the MFS during operation such that
the MFS is programmed according to the instructions from the mobile
computing device. The communication may be in the form of a cabled
communication (e.g., USB connection) or a wireless communication
(e.g., based on Bluetooth and IEEE 801.11).
[0025] As shown in flow chart 100, a logo is displayed to identify
the application program invoked (102). An example logo display 202
is shown in FIG. 2A. The logo may be displayed along with a
background image 204. This example further shows a login window 206
as a mechanism to enforce access control.
[0026] Returning to FIG. 1, in one instance, a user enters a valid
user name and password before the user can login (104) to access
the controller and configure the stimulation parameters. In this
instance, the login attempt is first authenticated to determine
success (106). If the login attempt is not successful, the flow
will proceed back to display the login window. If the login attempt
is successful, the process will proceed to display a microwave
field stimulator (MFS) selection view (108) and grant access to
database 101. Database 101 may include encrypted data encoding past
stimulation parameters and patient feedback. In other words, only
registered user with a valid password entry may obtain access in
order to configure the stimulation parameters. Thus, such access
control enforces security features of configuring stimulation
parameters are tailored to a particular patient.
[0027] In some implementations, additional system level checks may
be performed before the user may configure stimulation parameters.
In one instance, a determination is made regarding whether a
microwave field stimulator (MFS) is connected to an implanted
stimulator device (112). The work flow may proceed when the MFS is
in communication with an implanted stimulator. In some cases, the
MFS is wirelessly connected to the implanted stimulator through
electrical radiative coupling (e.g., through the electromagnetic
midfield) and not inductive coupling. If the MFS is connected to an
implanted stimulator device, another determination is made
regarding whether the connected stimulator device is in the
database 101 containing recorded stimulation parameters (114). If
the connected stimulator device is not in the database 101, the
work flow may then proceed to capture patient/device information
and register the captured information in the database. In some
instances, a determination is made regarding whether the controller
is operating in a demo mode (110). For context, demo mode allows
the software to showcase the features and controls available to the
user without effectuating such features on the physical MFS unit
itself.
[0028] After successful login and verifications, a TabView may be
displayed in some implantations (118). The TabView may allow a user
to choose a view (120). Some implementations may provide five
views, namely, patient view 122, configure view 124, map view 126,
program view 128, and tools view 130. In one implementation, the
default mode is the patient view 122. In another implementation,
the chosen view is the configure view 124 by default.
[0029] Referring to FIG. 2B, an example user interface 210 is
displayed for patient view 122. Through search panel 212, a user
may look for a particular patient's profile in the database.
Generally, patient profile information 214 is only accessible to
authorized users such as the patient himself/herself, his/her
attending physician, his/her appointed nurse or caregiver. Such
profile information may also be anonymized to preserve patient
privacy information. For example, in some instances, only a patient
ID is displayed. In these instances, patient profile information
may include wearable antenna assembly (WAA) signal/noise (S/N),
link status, battery status, transmit power status, pulse rate,
pulse width, pulse pattern, duty cycle, current amplitude for each
channel of the each implanted stimulator. Such profile information
may correspond to the profile information as last accessed. In some
instances, the WAA can be an MFS device. In some instances, the WAA
may be a relay module that bridges signal transmission between an
MFS and an implanted stimulator device. When configured as a relay
module, the WAA may include a battery or other power source. The
WAA may also be a passive device without an on-board battery or
other power source. Generally, such profile information varies from
patient to patient. Tab 216 may allow an additional patient to be
added to the database. Tab 218 may allow the logged-in user to log
out.
[0030] FIG. 2C is an example user interface 220 for the configure
view 124, which allows a user to configure the stimulation
parameters for the implanted stimulator device. In this
illustration, the top panel of user interface 220 includes the same
logout tab 218 and patient profile information 214. The top panel
may also include connect button 221 to establish a wireless
connection with an implanted stimulator device.
[0031] As illustrated, the central panel enables a user to
configure the polarity and current for each electrode of the
implanted stimulator device. A user may tap an electrode icon on
electrode arrays 222A and 222B to initiate adjustment of a polarity
setting of corresponding electrode. The polarity setting on each
array 222A and 222B can be adjusted at the granularity of each
electrode. What is more, the central panel also allows the user to
configure stimulating current at each electrode pair of the
electrode array. For example, user interface 220 may include
control bars 223A and 223B, each representing an adjustable range
from 0.0 mA to 12.7 mA. In some instances, this adjustable range
can be a continuum. In other instances, the adjustable range can
include discrete levels. In some of these instances, the discretely
adjustable range can be turned up or down through bars 224A and
224B respectively for electrode arrays 222A and 222B.
[0032] In some implementations, other than allowing the user to
configure the polarity and current setting for each electrode or
electrode pair on electrode arrays 223A and 223B, user interface
220 allows the user to choose from pre-existing programs 225, which
may include program options I, II, and III, as well as polarity
settings options I, II, and III. Each program option may include
pre-set polarity settings for each electrode. Each program option
can also include pre-set pulse parameters such as transmit power,
pulse rate, and pulse width. Each polarity settings option may
include the polarity configuration for each electrode of the
multi-electrode stimulator device. Transmission buttons 226A and
226B allow information encoding a chosen setting to be sent to the
connected implantable device and effectuate the chosen setting.
[0033] The bottom panel of user interface 220 includes control bar
227 for configuring transmit power, control bar 228 for configuring
pulse rate, and control bar 229 for controlling pulse width. As
illustrated, the transmit power can be configured within an
adjustable range, for example, from level 1 to level 24. Each level
may represent a particular amount of transmit power with level 1
being the lowest and level 24 being the highest power. The levels
may be on a linear scale or a logarithmic scale. In some instances,
the levels may range from 1 W to 60 W. The transmit power may refer
to the electric power being transmitted over a wireless connection
from the controller device to the implanted stimulator device, and
may directly impact or result in the pulse amplitude applied at the
electrodes. The pulse rate may be configured within an adjustable
range from 0 Hz to 40 Hz. The pulse width may be configured within
an adjustable range from 0 to 180 .mu.s. As illustrated, the
adjustable ranges of transmit power, pulse rate, and pulse width
can be configured in discrete steps. In other cases, these
parameters may be implemented on a continuum range. Some
implementations may opt to have a configurable pulse amplitude
representing the actual pulse amplitude being applied at a
particular electrode. In such implementations, the pulse amplitude
configuration option may be provided in lieu of the transmit power
configuration option (e.g., shown in control bar 227).
[0034] FIG. 2D shows example user interface 230 for the map view
126, which can be used to capture user positioning information for
the implanted stimulator device as a media file element. In this
illustration, the top panel of user interface 230 includes the same
patient profile information 214. The captured user positioning
information may be placed in any of up to four quadrants. In some
implementations, the captured user positioning information may
include fluoroscopic image(s) of the implantation site, for
example, showing a radio-opaque implantable stimulator underneath
the skin. In these implementations, the fluoroscopic image(s) may
include a X-ray image that functions as a reference image being
presented in one of the four quadrants. In these implementations,
the fluoroscopic image(s) may be taken by a clinician (e.g., a
practicing nurse or caregiver) at a clinic. During an adjustment
session, the user may take photos from a camera on, for example, an
iPad device. The photos may be presented in other quadrants to
provide visual guidance during placement of a MFS device relative
to the implanted stimulator device underneath the skin. In some
implementations, the user or the clinician may take a photo of the
body area where the implantable stimulator was placed within the
body. The photo taken may be displayed at one of the quadrants, for
example, as a reference view. In these implementations, subsequent
photos taken from different angles may be displayed at the
remaining quadrants. In combination with the reference view, these
photos may allow the user to obtain a rather panoramic view of the
body area where stimulation parameters are being adjusted.
Similarly, subsequent photos may be compared to the reference view
to allow the user to replicate camera positioning or adjustment of
parameters. Thus, the four illustrated quadrants may allow the user
to take photos using, for example, an iPad, to quickly record
important information and store such information.
[0035] In some instances, the photos of the implantation site are
correlated with the fluoroscopic or other imaging technology image
showing the implanted stimulator device in the area of the
implantation site. In these instances, the photos may represent a
stereo view of the implantation site to guide the placement of the
controller device. Here, the correlation may provide navigational
guidance as to an improved positioning of the MFS device for better
coupling when establishing a wireless connection between an MFS
device and the implanted stimulator device.
[0036] FIG. 2E shows an example user interface 240 for the program
view 128, which may be used by a user to set up a stimulation
program on an implanted stimulator device. In this illustration,
the top panel of user interface 240 includes the same logout tab
218 and patient profile information 214. The top panel may also
include a disconnect button 241 to deactivate a wireless connection
with an implanted stimulator device. The main panel of user
interface 240 may include (i) pulse pattern panel 242 to determine
whether to set a pulse pattern for the stimulating currents, (ii)
dosage panel 244 to determine whether to use a timer to track
dosage, (iii) therapy panel 246 to set a lockout time in accordance
with configurable total therapy time, and (iv) program cycle
pattern 248 to set up a treatment sequence. For context, a
treatment sequence is a concatenation of one or more programs of
pulse patterns. A lockout time is a period above which the
controller device will be locked so that no more stimulation may be
accumulated.
[0037] FIG. 2F shows an example user interface 250 for the tools
view 130, which displays tools for a user to configure stimulation
parameters. In this illustration, the top panel of user interface
250 includes the same patient profile information 214. The main
tools panel includes a menu including menu option 252 for recording
pain, a menu option 253 for user reporting, a menu option 254 for
details of the wearable antenna assembly (WAA), a menu option 255
for Defaults, and a menu option 256 for transfer settings. Menu
option 252 allows a user to record pain levels during parameter
adjustment to help the user determining an improved parameter
setting. Menu option 253 allows a user to submit recorded pain
history as well as usage data showing how much and how often the
stimulator device has been used. Notably, menu option 252 may
record an adjustment in a configuration option made by the user
that results in an improved quantitative index of pain. When
recording the adjustment in the configuration option, adjustment in
a pulse parameter or a polarity setting may be recorded. In
particular, the recorded adjustment in the configuration option can
be leveraged when generating a recommended configuration setting.
In other words, the at least one recommended configuration option
may be generated faster than otherwise in the absence of the
recorded adjustment. The recorded adjustment may incorporate the
corresponding user-reported pain relief at this configuration
option. Menu option 255 allows a user to set default stimulation
parameter for a connected stimulator device. Menu option 256 allows
a user to copy patient settings to another WAA. The WAA is the
external transmitter unit that transmits power and instructions to
the implanted stimulators. In some implementations, the WAA is the
MFS device that the programming unit communicates with. If the user
interchanges a WAA for a different serialized WAA unit, the
application will facilitate the transfer of the configurations from
one WAA to the next on request. As explained above in association
with FIG. 1B, the WAA can be an MFS device or a relay module.
[0038] FIG. 3 is a flow chart 300 for a user interface module to
configure stimulation settings of the implanted simulator device.
Initially, through a user interface (UI) interaction (302), a user
announces an intent to change settings for a stimulation device
(304). In some instances, the announcement may be made by the
configure button to invoke a configuration user interface 220, as
illustrated in FIG. 2C. Subsequently, the control program may
impose safety limits (306). In some instances, the safety limits
may be a pre-determined threshold amount and documented in the
database 101. In some instances, the safety limits may be
determined based on a combination of polarity settings as well as
pulse parameters (including pulse rate, pulse width, and transmit
power). The safety limits may be determined by fuzzy logic or
neural network based weighting algorithms to factor in various
empirical data from past recorded data of patient experience. For
example, a user may be particularly sensitive to certain
combination of polarity settings and pulse parameters. Such
combinations, or combinations close to such combinations, may be
avoided as a pre-caution. In these instances, neural network based
weighting algorithm can provide judiciously chosen safety limits
(e.g., on pulse rates) based on a patient's diagnosis and past
experience.
[0039] If the parameter changes are deemed unsafe, the controller
program may display a warning message (310). In some instances, the
warning message may include a pop-up window. In some instances, the
warning message may include an audio component, such as an alarm
sound.
[0040] If the parameter changes are determined to be safe, the
controller program may proceed by transmitting changes to the MFS
(314), which may communicate with the implanted stimulator device
as appropriate. The transmitted data may be received by the MFS
and, in a handshake manner, the MFS may transmit a confirmation
message back to the external controller. The confirmation message
may be received and can serve as a success indication of the
parameter transmit (316). In some instances, the external
controller may ping the MFS for latest data encoding polarity
settings and pulse parameters (including pulse rate, pulse width,
and transmit power) (318). Thereafter, the controller program may
update a display (312), for example, by showing an updated user
profile 214 to reflect the latest parameters obtained. The
controller program may also update the selectable safety values
(320). In some implementations, the selectable safety values may
affect the choices for pulse pattern, dosage, and lockout time, as
illustrated in FIG. 2E.
[0041] Some implementations can allow users to navigate the wider
range of choices. As noted in FIG. 2C, the introduction of polarity
settings at the granularity of each electrode greatly expands the
possibility of the configuration space. For example, there are 16
possible polarity settings in addition to three continuum ranges
for RF power/pulse amplitude, pulse rate, and pulse width. To
navigate the user through this universe of configuration space,
software algorithms are incorporated in these implementations to
aid users in selecting configurations of the stimulation
parameters. In particular, some implementations record patient
feedback for each particular combination of polarity settings and
pulse parameters. The recorded patient feedback can form an expert
knowledge database to predict later configurations. The later
configurations may apply to the same patient, or patients in a
comparable group as classified by age, gender, target nerve or
tissue, depth of implantation, or type of implanted stimulator
devices. For example, a learning engine may be trained based on
training data from a group of users that includes, for example,
stimulation parameters and resulting pain indexes as well as other
variables such as patient age, patient gender, target nerve,
anatomic orientation, depth' of implantation, type of implanted
stimulator devices, duration of therapy, and/or time of day. The
trained learning engine may then suggest to a given patient one or
more initial stimulation parameters, such as pulse amplitude, pulse
width, pulse rate, and/or polarity based on, for instance, that
given patient's age, gender, target nerve, depth of implantation,
type of implanted stimulator devices, duration of therapy, time of
day, and/or non-suggested stimulation parameters. As that given
patient conducts therapy, the patient may provide feedback about
his or her pain and adjust the stimulation parameters, and the
learning engine may develop a profile specific that to that user
and provide suggested stimulation parameters for future
sessions.
[0042] FIGS. 4A and 4B show example software decision trees 400A
and 400B to auto-adjust therapy settings based on user recorded
pain. In 400A, initially, a user may select an interface to record
his/her current pain intensity (402). The selection may be through,
for example, menu option 252 at example user interface 250. When
the selection is made, the user may then record their pain level.
For the purpose of running through the two auto-configurations, the
state of `off` has no effect on the algorithm of auto-adjustment.
Thus recording can be made when the implanted stimulator device is
"on" or "off" (404). When the stimulator device is "on," a first
determination is made regarding whether the pain level is greater
than 5 or medium (406). In some instances, the determination is
based on user input.
[0043] If the pain level is greater than 5 or medium, a
determination is made regarding whether to improve therapy (414).
In one branch, the user may indicate whether the user may want to
improve therapy (414) by changing pulse parameters or polarity
settings. If the user does not wish to improve therapy, the process
may conclude (418). If the user's desire is to improve therapy,
then the process begins cycling through the parameters to be
adjusted (422A). In one branch, the process may adjust polarity
configurations in an effort to fine tune the effect of stimulation
(428). The adjustment may be initiated from a recommendation that
is derived based on a knowledge database/learning engine 427. For
example, the suggested polarity configuration can be determined by
the knowledge database/learning engine 427 based on parameters such
as patient's age, gender, target nerve, depth of implantation, type
of implanted stimulator device, duration of therapy, time of day,
non-suggested stimulation parameters, and/or historical stimulation
parameters and resulting pain.
[0044] In yet another branch, the process may proceed to set pulse
rate to a level (426). In still yet another branch, the process may
proceed to set pulse width to a level (420). In another branch, the
process may increase pulse amplitude by a particular amount (424).
The amount may scale with the reported pain level, for example, in
the amount of Pain Level.times.0.05. In these latter branches, the
pulse rate or pulse width may be randomly selected from a sub-range
of values from the full range of the values. The subrange may be
selected by the knowledge database/learning engine 427 based on
parameters such as patient's age, gender, target nerve, depth of
implantation, type of implanted stimulator device, duration of
therapy, time of day, non-suggested stimulation parameters, and/or
historical stimulation parameters and resulting pain. By randomly
selecting values for pulse width and pulse rate, the patient is
more likely to notice a difference in treatment than if values for
these parameters were sequentially changed.
[0045] After a given one of the stimulation parameters are
adjusted, a determination is made as to whether therapy was
improved (430). If the user indicates that the therapy has
improved, the process may loop back to ask the user to record pain
relief (404). If the user indicates that the therapy has not
improved, or no user feedback is received within 3 seconds, the
process may cycle to next parameter adjustment (434). For example,
the process may cycle from pulse width adjustment to pulse rate
adjustment (or vice versa). In this manner, the process 400A
adjusts one parameter sequentially at a time, asking the patient if
therapy has improved after each adjustment. If not, or after a
short period of time, the process updates the next parameter and
again asks the patient if therapy has improved.
[0046] The determination (430) also provides a third option for the
user to choose--the reset. If chosen, the program may enter the
reset branch in which stimulation parameters, including polarity
settings, are reset to original state before adjustments (432). The
reset branch reverts the stimulation configurations (including
pulse parameters and electrode polarity settings) back to the
original state prior to user adjustment.
[0047] When the user has already selected a therapy program and has
received pain relief from the therapy program, a pop-up window may
be displayed to ask the user if the user wants to decrease pulse
amplitude (408) if, for example, the pain level is not greater
than, for example, 5 or medium. In some cases, the user may receive
relief from the treatment, but the treatment may be uncomfortable
if the pulse amplitude is high. If the user does not want to
decrease the amplitude, the decision tree may conclude (410). If
the user indicates that the user wants to decrease the pulse
amplitude, the process 400A decreases pulse amplitude as executed
on the implanted stimulator device by a certain amount (e.g., by
0.3 mA) (416). A determination is then made regarding if therapy is
still providing sufficient pain relief even at the decreased pulse
amplitude such that the user may keep the adjusted pulse amplitude,
discard the adjusted pulse amplitude, or further adjust the pulse
amplitude (438). If the therapy is still providing sufficient pain
relief and the patient is no longer uncomfortable (or otherwise
decides that the current pulse amplitude is satisfactory), the user
may decide to keep the adjusted pulse amplitude and process 400A
may conclude (410). When the therapy is still providing sufficient
pain relief and the user still wishes to refine the pulse amplitude
(or the adjusted pulse amplitude remains an uncomfortable choice),
the decreased pulse amplitude may be further adjusted (416). If the
therapy is no longer providing sufficient pain relief, the user may
decide to revert the pulse amplitude to the previously set
amplitude and the process 400A may do so (440) before concluding
the adjustment (410).
[0048] Process 400B, as depicted in FIG. 4B, largely tracks process
400A from FIG. 4A. The main difference between process 400A and
400B is that when the user indicates that the user would like to
improve therapy, the user is asked which parameter to adjust and
then the process continues to adjust just that parameter.
Accordingly, if the user's desire is to improve therapy, then the
user is prompted to select a parameter to adjust (422B). For
example, the user can select the pulse width, pulse rate, pulse
amplitude, or polarity. The selected parameter is then adjusted
(420, 426, 428, or 424), for example, in the manner described with
respect to FIG. 4A and the user is asked if therapy is improved
(430). If not, then the selected parameter is adjusted until the
user decides therapy has improved (434). The other actions of
process 400B occur as described with respect to the corresponding
actions in process 400A.
[0049] FIG. 5 depicts a detailed diagram 500 of an example of a
neural stimulation system including programming module 560, RF
pulse generator module 570, and implantable neural stimulator
module 580. Programming module 560 and RF pulse generator module
570 may respectively correspond to the mobile computing device and
MFS discussed above in association with FIG. 1. Implantable neural
stimulator module 580 may correspond to the implanted stimulator
device discussed above in association with FIG. 1.
[0050] As depicted, the programming module 560 may comprise user
input system 502 and communication subsystem 508. The user input
system 521 may allow various parameter settings to be adjusted (in
some cases, in an open loop fashion) by the user in the form of
instruction sets. The communication subsystem 508 may transmit
these instruction sets (and other information) via the wireless
connection 564, such as Bluetooth or Wi-Fi, to the RF pulse
generator module 570, as well as receive data from module 570.
[0051] For instance, the programmer module 560, which can be
utilized for multiple users, such as a patient's control unit or
clinician's programmer unit, can be used to send stimulation
parameters to the RF pulse generator module 560. The stimulation
parameters that can be controlled may include pulse amplitude,
pulse frequency, and pulse width in the ranges shown in Table 1. In
this context the term pulse refers to the phase of the waveform
that directly produces stimulation of the tissue; the parameters of
the charge-balancing phase (described below) can similarly be
controlled. The patient and/or the clinician can also optionally
control overall duration and pattern of treatment.
TABLE-US-00001 Stimulation Parameter Table 1 Pulse Amplitude: 0 to
20 mA Pulse Frequency: 0 to 2000 Hz Pulse Width: 0 to 2 ms
[0052] The implantable neural stimulator module 580 or RF pulse
generator module 570 may be initially programmed to meet the
specific parameter settings for each individual patient during the
initial implantation procedure. Because medical conditions or the
body itself can change over time, the ability to re-adjust the
parameter settings may be beneficial to ensure ongoing efficacy of
the neural modulation therapy.
[0053] The programmer module 560 may be functionally a smart device
and associated application. The smart device hardware may include a
CPU 506 and be used as a vehicle to handle touchscreen input on a
graphical user interface (GUI) 504, for processing and storing
data.
[0054] The RF pulse generator module 506 may be connected via wired
connection 578 to an external TX antenna 510. Alternatively, both
the antenna and the RF pulse generator are located subcutaneously
(not shown).
[0055] The signals sent by RF pulse generator module 570 to the
implanted stimulator module 580 may include both power and
parameter-setting attributes in regards to stimulus waveform,
amplitude, pulse width, and frequency. The RF pulse generator
module 570 can also function as a wireless receiving unit that
receives feedback signals from the implanted stimulator module 580.
To that end, the RF pulse generator module 570 may contain
microelectronics or other circuitry to handle the generation of the
signals transmitted to the implanted stimulator module 580 as well
as handle feedback signals, such as those from the implanted
stimulator module 580. For example, the RF pulse generator module
570 may comprise controller subsystem 514, high-frequency
oscillator 518, RF amplifier 516, a RF switch, and a feedback sub
system 512.
[0056] The controller subsystem 514 may include a CPU 530 to handle
data processing, a memory subsystem 528 such as a local memory,
communication subsystem 534 to communicate with programmer module
560 (including receiving stimulation parameters from programmer
module), pulse generator circuitry 570, and digital/analog (D/A)
converters 532.
[0057] The controller subsystem 514 may be used by the patient
and/or the clinician to control the stimulation parameter settings
(for example, by controlling the parameters of the signal sent from
RF pulse generator module 570 to neural stimulator module 580).
These parameter settings can affect, for example, the power,
current level, or shape of the one or more electrical pulses. The
programming of the stimulation parameters can be performed using
the programming module 560, as described above, to set the
repetition rate, pulse width, amplitude, and waveform that will be
transmitted by RF energy to the receive (RX) antenna 538, typically
a dipole antenna (although other types may be used), in the
wireless implanted neural stimulator module 514. The clinician may
have the option of locking and/or hiding certain settings within
the programmer interface, thus limiting the patient's ability to
view or adjust certain parameters because adjustment of certain
parameters may require detailed medical knowledge of
neurophysiology, neuroanatomy, protocols for neural modulation, and
safety limits of electrical stimulation.
[0058] The controller subsystem 514 may store received parameter
settings in the local memory subsystem 528, until the parameter
settings are modified by new input data received from the
programming module 560. The CPU 506 may use the parameters stored
in the local memory to control the pulse generator circuitry 536 to
generate a stimulus waveform that is modulated by a high frequency
oscillator 518 in the range from 300 MHz to 8 GHz. The resulting RF
signal may then be amplified by RF amplifier 526 and then sent
through an RF switch 523 to the TX antenna 581 to reach through
depths of tissue to the RX antenna 538.
[0059] In some implementations, the RF signal sent by TX antenna
581 may simply be a power transmission signal used by stimulator
module 580 to generate electric pulses. In other implementations, a
telemetry signal may also be transmitted to the stimulator module
580 to send instructions about the various operations of the
stimulator module 580. The telemetry signal may be sent by the
modulation of the carrier signal (through the skin if external, or
through other body tissues if the pulse generator module 570 is
implanted subcutaneously). The telemetry signal is used to modulate
the carrier signal (a high frequency signal) that is coupled onto
the implanted antenna(s) 538 and does not interfere with the input
received on the same stimulator to power the implant. In one
embodiment the telemetry signal and powering signal are combined
into one signal, where the RF telemetry signal is used to modulate
the RF powering signal, and thus the implanted stimulator is
powered directly by the received telemetry signal; separate
subsystems in the stimulator harness the power contained in the
signal and interpret the data content of the signal.
[0060] The RF switch 523 may be a multipurpose device such as a
dual directional coupler, which passes the relatively high
amplitude, extremely short duration RF pulse to the TX antenna 581
with minimal insertion loss while simultaneously providing two
low-level outputs to feedback subsystem 512; one output delivers a
forward power signal to the feedback subsystem 512, where the
forward power signal is an attenuated version of the RF pulse sent
to the TX antenna 581, and the other output delivers a reverse
power signal to a different port of the feedback subsystem 512,
where reverse power is an attenuated version of the reflected RF
energy from the TX Antenna 581.
[0061] During the on-cycle time (when an RF signal is being
transmitted to stimulator 580), the RF switch 523 is set to send
the forward power signal to feedback subsystem. During the
off-cycle time (when an RF signal is not being transmitted to the
stimulator module 580), the RF switch 523 can change to a receiving
mode in which the reflected RF energy and/or RF signals from the
stimulator module 580 are received to be analyzed in the feedback
subsystem 512.
[0062] The feedback subsystem 512 of the RF pulse generator module
570 may include reception circuitry to receive and extract
telemetry or other feedback signals from the stimulator 580 and/or
reflected RF energy from the signal sent by TX antenna 581. The
feedback subsystem may include an amplifier 526, a filter 524, a
demodulator 522, and an A/D converter 520.
[0063] The feedback subsystem 512 receives the forward power signal
and converts this high-frequency AC signal to a DC level that can
be sampled and sent to the controller subsystem 514. In this way
the characteristics of the generated RF pulse can be compared to a
reference signal within the controller subsystem 514. If a
disparity (error) exists in any parameter, the controller subsystem
514 can adjust the output to the RF pulse generator 570. The nature
of the adjustment can be, for example, proportional to the computed
error. The controller subsystem 514 can incorporate additional
inputs and limits on its adjustment scheme such as the signal
amplitude of the reverse power and any predetermined maximum or
minimum values for various pulse parameters.
[0064] The reverse power signal can be used to detect fault
conditions in the RF-power delivery system. In an ideal condition,
when TX antenna 581 has perfectly matched impedance to the tissue
that it contacts, the electromagnetic waves generated from the RF
pulse generator 570 pass unimpeded from the TX antenna 581 into the
body tissue. However, in real-world applications a large degree of
variability may exist in the body types of users, types of clothing
worn, and positioning of the antenna 581 relative to the body
surface. Since the impedance of the antenna 581 depends on the
relative permittivity of the underlying tissue and any intervening
materials, and also depends on the overall separation distance of
the antenna from the skin, in any given application there can be an
impedance mismatch at the interface of the TX antenna 581 with the
body surface. When such a mismatch occurs, the electromagnetic
waves sent from the RF pulse generator 570 are partially reflected
at this interface, and this reflected energy propagates backward
through the antenna feed.
[0065] The dual directional coupler RF switch 523 may prevent the
reflected RF energy propagating back into the amplifier 526, and
may attenuate this reflected RF signal and send the attenuated
signal as the reverse power signal to the feedback subsystem 512.
The feedback subsystem 512 can convert this high-frequency AC
signal to a DC level that can be sampled and sent to the controller
subsystem 514. The controller subsystem 514 can then calculate the
ratio of the amplitude of the reverse power signal to the amplitude
of the forward power signal. The ratio of the amplitude of reverse
power signal to the amplitude level of forward power may indicate
severity of the impedance mismatch.
[0066] In order to sense impedance mismatch conditions, the
controller subsystem 514 can measure the reflected-power ratio in
real time, and according to preset thresholds for this measurement,
the controller subsystem 514 can modify the level of RF power
generated by the RF pulse generator 570. For example, for a
moderate degree of reflected power the course of action can be for
the controller subsystem 514 to increase the amplitude of RF power
sent to the TX antenna 581, as would be needed to compensate for
slightly non-optimum but acceptable TX antenna coupling to the
body. For higher ratios of reflected power, the course of action
can be to prevent operation of the RF pulse generator 570 and set a
fault code to indicate that the TX antenna 581 has little or no
coupling with the body. This type of reflected-power fault
condition can also be generated by a poor or broken connection to
the TX antenna. In either case, it may be desirable to stop RF
transmission when the reflected-power ratio is above a defined
threshold, because internally reflected power can result in
unwanted heating of internal components, and this fault condition
means the system cannot deliver sufficient power to the implanted
wireless neural stimulator and thus cannot deliver therapy to the
user.
[0067] The controller 542 of the stimulator 580 may transmit
informational signals, such as a telemetry signal, through the
antenna 538 to communicate with the RF pulse generator module 570
during its receive cycle. For example, the telemetry signal from
the stimulator 580 may be coupled to the modulated signal on the
dipole antenna(s) 538, during the on and off state of the
transistor circuit to enable or disable a waveform that produces
the corresponding RF bursts necessary to transmit to the external
(or remotely implanted) pulse generator module 570. The antenna(s)
538 may be connected to electrodes 554 in contact with tissue to
provide a return path for the transmitted signal. An A/D (not
shown) converter can be used to transfer stored data to a
serialized pattern that can be transmitted on the pulse modulated
signal from the internal antenna(s) 538 of the neural
stimulator.
[0068] A telemetry signal from the implanted wireless neural
stimulator module 580 may include stimulus parameters such as the
power or the amplitude of the current that is delivered to the
tissue from the electrodes. The feedback signal can be transmitted
to the RF pulse generator module 570 to indicate the strength of
the stimulus at the nerve bundle by means of coupling the signal to
the implanted RX antenna 538, which radiates the telemetry signal
to the external (or remotely implanted) RF pulse generator module
570. The feedback signal can include either or both an analog and
digital telemetry pulse modulated carrier signal. Data such as
stimulation pulse parameters and measured characteristics of
stimulator performance can be stored in an internal memory device
within the implanted neural stimulator 580, and sent on the
telemetry signal. The frequency of the carrier signal may be in the
range of at 300 MHz to 8 GHz.
[0069] In the feedback subsystem 512, the telemetry signal can be
down modulated using demodulator 522 and digitized by being
processed through an analog to digital (A/D) converter 520. The
digital telemetry signal may then be routed to a CPU 530 with
embedded code, with the option to reprogram, to translate the
signal into a corresponding current measurement in the tissue based
on the amplitude of the received signal. The CPU 530 of the
controller subsystem 514 can compare the reported stimulus
parameters to those held in local memory 528 to verify the
stimulator(s) 580 delivered the specified stimuli to tissue. For
example, if the stimulator reports a lower current than was
specified, the power level from the RF pulse generator module 570
can be increased so that the implanted neural stimulator 580 will
have more available power for stimulation. The implanted neural
stimulator 580 can generate telemetry data in real time, for
example, at a rate of 8 kbits per second. All feedback data
received from the implanted stimulator module 580 can be logged
against time and sampled to be stored for retrieval to a remote
monitoring system accessible by the health care professional for
trending and statistical correlations.
[0070] The sequence of remotely programmable RF signals received by
the internal antenna(s) 538 may be conditioned into waveforms that
are controlled within the implantable stimulator 580 by the control
subsystem 542 and routed to the appropriate electrodes 554 that are
placed in proximity to the tissue to be stimulated. For instance,
the RF signal transmitted from the RF pulse generator module 570
may be received by RX antenna 538 and processed by circuitry, such
as waveform conditioning circuitry 540, within the implanted
wireless neural stimulator module 580 to be converted into
electrical pulses applied to the electrodes 554 through electrode
interface 552. In some implementations, the implanted stimulator
580 contains between two to sixteen electrodes 554.
[0071] The waveform conditioning circuitry 540 may include a
rectifier 544, which rectifies the signal received by the RX
antenna 538. The rectified signal may be fed to the controller 542
for receiving encoded instructions from the RF pulse generator
module 570. The rectifier signal may also be fed to a charge
balance component 546 that is configured to create one or more
electrical pulses based such that the one or more electrical pulses
result in a substantially zero net charge at the one or more
electrodes (that is, the pulses are charge balanced). The
charge-balanced pulses are passed through the current limiter 548
to the electrode interface 552, which applies the pulses to the
electrodes 554 as appropriate.
[0072] The current limiter 548 insures the current level of the
pulses applied to the electrodes 554 is not above a threshold
current level. In some implementations, an amplitude (for example,
current level, voltage level, or power level) of the received RF
pulse directly determines the amplitude of the stimulus. In this
case, it may be particularly beneficial to include current limiter
548 to prevent excessive current or charge being delivered through
the electrodes, although current limiter 548 may be used in other
implementations where this is not the case. Generally, for a given
electrode having several square millimeters surface area, it is the
charge per phase that should be limited for safety (where the
charge delivered by a stimulus phase is the integral of the
current). But, in some cases, the limit can instead be placed on
the current, where the maximum current multiplied by the maximum
possible pulse duration is less than or equal to the maximum safe
charge. More generally, the limiter 548 acts as a charge limiter
that limits a characteristic (for example, current or duration) of
the electrical pulses so that the charge per phase remains below a
threshold level (typically, a safe-charge limit).
[0073] In the event the implanted wireless neural stimulator 580
receives a "strong" pulse of RF power sufficient to generate a
stimulus that would exceed the predetermined safe-charge limit, the
current limiter 548 can automatically limit or "clip" the stimulus
phase to maintain the total charge of the phase within the safety
limit. The current limiter 548 may be a passive current limiting
component that cuts the signal to the electrodes 554 once the safe
current limit (the threshold current level) is reached.
Alternatively, or additionally, the current limiter 548 may
communicate with the electrode interface 552 to turn off all
electrodes 554 to prevent tissue damaging current levels.
[0074] A clipping event may trigger a current limiter feedback
control mode. The action of clipping may cause the controller to
send a threshold power data signal to the pulse generator 570. The
feedback subsystem 512 detects the threshold power signal and
demodulates the signal into data that is communicated to the
controller subsystem 514. The controller subsystem 514 algorithms
may act on this current-limiting condition by specifically reducing
the RF power generated by the RF pulse generator, or cutting the
power completely. In this way, the pulse generator 570 can reduce
the RF power delivered to the body if the implanted wireless neural
stimulator 580 reports it is receiving excess RF power.
[0075] The controller 550 of the stimulator 580 may communicate
with the electrode interface 552 to control various aspects of the
electrode setup and pulses applied to the electrodes 554. The
electrode interface 552 may act as a multiplex and control the
polarity and switching of each of the electrodes 554. For instance,
in some implementations, the wireless stimulator 570 has multiple
electrodes 554 in contact with tissue, and for a given stimulus the
RF pulse generator module 570 can arbitrarily assign one or more
electrodes to 1) act as a stimulating electrode, 2) act as a return
electrode, or 3) be inactive by communication of assignment sent
wirelessly with the parameter instructions, which the controller
550 uses to set electrode interface 552 as appropriate. It may be
physiologically advantageous to assign, for example, one or two
electrodes as stimulating electrodes and to assign all remaining
electrodes as return electrodes.
[0076] Also, in some implementations, for a given stimulus pulse,
the controller 550 may control the electrode interface 552 to
divide the current arbitrarily (or according to instructions from
pulse generator module 570) among the designated stimulating
electrodes. This control over electrode assignment and current
control can be advantageous because in practice the electrodes 554
may be spatially distributed along various neural structures, and
through strategic selection of the stimulating electrode location
and the proportion of current specified for each location, the
aggregate current distribution in tissue can be modified to
selectively activate specific neural targets. This strategy of
current steering can improve the therapeutic effect for the
patient.
[0077] In another implementation, the time course of stimuli may be
arbitrarily manipulated. A given stimulus waveform may be initiated
at a time T_start and terminated at a time T_final, and this time
course may be synchronized across all stimulating and return
electrodes; further, the frequency of repetition of this stimulus
cycle may be synchronous for all the electrodes. However,
controller 550, on its own or in response to instructions from
pulse generator 570, can control electrode interface 552 to
designate one or more subsets of electrodes to deliver stimulus
waveforms with non-synchronous start and stop times, and the
frequency of repetition of each stimulus cycle can be arbitrarily
and independently specified.
[0078] For example, a stimulator having eight electrodes may be
configured to have a subset of five electrodes, called set A, and a
subset of three electrodes, called set B. Set A might be configured
to use two of its electrodes as stimulating electrodes, with the
remainder being return electrodes. Set B might be configured to
have just one stimulating electrode. The controller 550 could then
specify that set A deliver a stimulus phase with 3 mA current for a
duration of 200 us followed by a 400 us charge-balancing phase.
This stimulus cycle could be specified to repeat at a rate of 60
cycles per second. Then, for set B, the controller 550 could
specify a stimulus phase with 1 mA current for duration of 500 us
followed by a 800 us charge-balancing phase. The repetition rate
for the set-B stimulus cycle can be set independently of set A, say
for example it could be specified at 25 cycles per second. Or, if
the controller 550 was configured to match the repetition rate for
set B to that of set A, for such a case the controller 550 can
specify the relative start times of the stimulus cycles to be
coincident in time or to be arbitrarily offset from one another by
some delay interval.
[0079] In some implementations, the controller 550 can arbitrarily
shape the stimulus waveform amplitude, and may do so in response to
instructions from pulse generator 570. The stimulus phase may be
delivered by a constant-current source or a constant-voltage
source, and this type of control may generate characteristic
waveforms that are static, e.g. a constant-current source generates
a characteristic rectangular pulse in which the current waveform
has a very steep rise, a constant amplitude for the duration of the
stimulus, and then a very steep return to baseline. Alternatively,
or additionally, the controller 550 can increase or decrease the
level of current at any time during the stimulus phase and/or
during the charge-balancing phase. Thus, in some implementations,
the controller 550 can deliver arbitrarily shaped stimulus
waveforms such as a triangular pulse, sinusoidal pulse, or Gaussian
pulse for example. Similarly, the charge-balancing phase can be
arbitrarily amplitude-shaped, and similarly an anodic pulse (prior
to the stimulus phase) may also be amplitude-shaped.
[0080] As described above, the stimulator 580 may include a
charge-balancing component 546. Generally, for constant current
stimulation pulses, pulses should be charge balanced by having the
amount of cathodic current should equal the amount of anodic
current, which is typically called biphasic stimulation. Charge
density is the amount of current times the duration it is applied,
and is typically expressed in the units uC/cm2. In order to avoid
the irreversible electrochemical reactions such as pH change,
electrode dissolution as well as tissue destruction, no net charge
should appear at the electrode-electrolyte interface, and it is
generally acceptable to have a charge density less than 30 uC/cm2.
Biphasic stimulating current pulses ensure that no net charge
appears at the electrode after each stimulation cycle and the
electrochemical processes are balanced to prevent net dc currents.
Neural stimulator 580 may be designed to ensure that the resulting
stimulus waveform has a net zero charge. Charge balanced stimuli
are thought to have minimal damaging effects on tissue by reducing
or eliminating electrochemical reaction products created at the
electrode-tissue interface.
[0081] A stimulus pulse may have a negative-voltage or current,
called the cathodic phase of the waveform. Stimulating electrodes
may have both cathodic and anodic phases at different times during
the stimulus cycle. An electrode that delivers a negative current
with sufficient amplitude to stimulate adjacent neural tissue is
called a "stimulating electrode." During the stimulus phase the
stimulating electrode acts as a current sink. One or more
additional electrodes act as a current source and these electrodes
are called "return electrodes." Return electrodes are placed
elsewhere in the tissue at some distance from the stimulating
electrodes. When a typical negative stimulus phase is delivered to
tissue at the stimulating electrode, the return electrode has a
positive stimulus phase. During the subsequent charge-balancing
phase, the polarities of each electrode are reversed.
[0082] In some implementations, the charge balance component 546
uses a blocking capacitor(s) placed electrically in series with the
stimulating electrodes and body tissue, between the point of
stimulus generation within the stimulator circuitry and the point
of stimulus delivery to tissue. In this manner, a
resistor-capacitor (RC) network may be formed. In a multi-electrode
stimulator, one charge-balance capacitor(s) may be used for each
electrode or a centralized capacitor(s) may be used within the
stimulator circuitry prior to the point of electrode selection. The
RC network can block direct current (DC), however it can also
prevent low-frequency alternating current (AC) from passing to the
tissue. The frequency below which the series RC network essentially
blocks signals is commonly referred to as the cutoff frequency, and
in one embodiment the design of the stimulator system may ensure
the cutoff frequency is not above the fundamental frequency of the
stimulus waveform. In this embodiment, the wireless stimulator may
have a charge-balance capacitor with a value chosen according to
the measured series resistance of the electrodes and the tissue
environment in which the stimulator is implanted. By selecting a
specific capacitance value the cutoff frequency of the RC network
in this embodiment is at or below the fundamental frequency of the
stimulus pulse.
[0083] In other implementations, the cutoff frequency may be chosen
to be at or above the fundamental frequency of the stimulus, and in
this scenario the stimulus waveform created prior to the
charge-balance capacitor, called the drive waveform, may be
designed to be non-stationary, where the envelope of the drive
waveform is varied during the duration of the drive pulse. For
example, in one embodiment, the initial amplitude of the drive
waveform is set at an initial amplitude Vi, and the amplitude is
increased during the duration of the pulse until it reaches a final
value k*Vi. By changing the amplitude of the drive waveform over
time, the shape of the stimulus waveform passed through the
charge-balance capacitor is also modified. The shape of the
stimulus waveform may be modified in this fashion to create a
physiologically advantageous stimulus.
[0084] In some implementations, the wireless neural stimulator
module 580 may create a drive-waveform envelope that follows the
envelope of the RF pulse received by the receiving dipole
antenna(s) 538. In this case, the RF pulse generator module 570 can
directly control the envelope of the drive waveform within the
wireless neural stimulator 580, and thus no energy storage may be
required inside the stimulator itself. In this implementation, the
stimulator circuitry may modify the envelope of the drive waveform
or may pass it directly to the charge-balance capacitor and/or
electrode-selection stage.
[0085] In some implementations, the implanted neural stimulator 580
may deliver a single-phase drive waveform to the charge balance
capacitor or it may deliver multiphase drive waveforms. In the case
of a single-phase drive waveform, for example, a negative-going
rectangular pulse, this pulse comprises the physiological stimulus
phase, and the charge-balance capacitor is polarized (charged)
during this phase. After the drive pulse is completed, the charge
balancing function is performed solely by the passive discharge of
the charge-balance capacitor, where is dissipates its charge
through the tissue in an opposite polarity relative to the
preceding stimulus. In one implementation, a resistor within the
stimulator facilitates the discharge of the charge-balance
capacitor. In some implementations, using a passive discharge
phase, the capacitor may allow virtually complete discharge prior
to the onset of the subsequent stimulus pulse.
[0086] In the case of multiphase drive waveforms the wireless
stimulator may perform internal switching to pass negative-going or
positive-going pulses (phases) to the charge-balance capacitor.
These pulses may be delivered in any sequence and with varying
amplitudes and waveform shapes to achieve a desired physiological
effect. For example, the stimulus phase may be followed by an
actively driven charge-balancing phase, and/or the stimulus phase
may be preceded by an opposite phase. Preceding the stimulus with
an opposite-polarity phase, for example, can have the advantage of
reducing the amplitude of the stimulus phase required to excite
tissue.
[0087] In some implementations, the amplitude and timing of
stimulus and charge-balancing phases is controlled by the amplitude
and timing of RF pulses from the RF pulse generator module 570, and
in others this control may be administered internally by circuitry
onboard the wireless stimulator 580, such as controller 550. In the
case of onboard control, the amplitude and timing may be specified
or modified by data commands delivered from the pulse generator
module 570.
[0088] Modulation of excitable tissue in the body by electrical
stimulation has become an important type of therapy for patients
with chronic disabling conditions, including chronic pain, problems
of movement initiation and control, involuntary movements, vascular
insufficiency, heart arrhythmias and more. A variety of therapeutic
intra-body electrical stimulation techniques can treat these
conditions. For instance, devices may be used to deliver
stimulatory signals to excitable tissue, record vital signs,
perform pacing or defibrillation operations, record action
potential activity from targeted tissue, control drug release from
time-release capsules or drug pump units, or interface with the
auditory system to assist with hearing.
[0089] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made. Accordingly, other implementations are within the scope of
the following claims.
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