U.S. patent application number 16/518412 was filed with the patent office on 2020-01-09 for devices and methods for connecting implantable devices to wireless energy.
The applicant listed for this patent is Stimwave Technologies Incorporated. Invention is credited to Chad Andresen, Laura Tyler Perryman.
Application Number | 20200009392 16/518412 |
Document ID | / |
Family ID | 49887256 |
Filed Date | 2020-01-09 |
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United States Patent
Application |
20200009392 |
Kind Code |
A1 |
Perryman; Laura Tyler ; et
al. |
January 9, 2020 |
DEVICES AND METHODS FOR CONNECTING IMPLANTABLE DEVICES TO WIRELESS
ENERGY
Abstract
A device for providing an implantable lead with wireless energy,
the device including: a housing configured for implantation in a
patient's body; one or more non-inductive antennas substantially
enclosed within the housing and configured to receive
electromagnetic energy radiated from a source located outside of
the patient's body; electronic circuitry coupled to each of the one
or more non-inductive antennas and configured to extract electric
power and excitation waveforms from the radiated electromagnetic
energy as received by the one or more non-inductive antennas; and
one or more connection pads substantially enclosed within the
housing, wherein the connection pads are configured to couple with
one or more electrodes in the implantable lead and form an electric
connection over which the connection pads provide the extracted
excitation waveforms from the electronic circuit to the electrodes
in the implantable lead, the implantable lead being separate from
the device.
Inventors: |
Perryman; Laura Tyler;
(Pompano Beach, FL) ; Andresen; Chad; (Miami
Beach, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Stimwave Technologies Incorporated |
Pompano Beach |
FL |
US |
|
|
Family ID: |
49887256 |
Appl. No.: |
16/518412 |
Filed: |
July 22, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14648604 |
May 29, 2015 |
10369369 |
|
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PCT/US2013/073326 |
Dec 5, 2013 |
|
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16518412 |
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61733867 |
Dec 5, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61N 1/37229 20130101;
A61N 1/3752 20130101; A61N 1/37223 20130101; A61N 1/0553 20130101;
A61N 1/3787 20130101; A61N 1/36071 20130101; A61N 1/36125 20130101;
A61N 1/37205 20130101; A61N 1/3756 20130101; A61N 1/0551
20130101 |
International
Class: |
A61N 1/372 20060101
A61N001/372; A61N 1/375 20060101 A61N001/375; A61N 1/378 20060101
A61N001/378; A61N 1/05 20060101 A61N001/05; A61N 1/36 20060101
A61N001/36 |
Claims
1. A device for providing an implantable lead with wireless energy,
the device comprising: a housing configured for implantation in a
patient's body; one or more non-inductive antennas substantially
enclosed within the housing and configured to receive
electromagnetic energy radiated from a source located outside of
the patient's body; electronic circuitry coupled to each of the one
or more non-inductive antennas and configured to extract electric
power and excitation waveforms from the radiated electromagnetic
energy as received by the one or more non-inductive antennas; and
one or more connection pads substantially enclosed within the
housing, wherein the connection pads are configured to couple with
one or more electrodes in the implantable lead and form an electric
connection over which the connection pads provide the extracted
excitation waveforms from the electronic circuit to the electrodes
in the implantable lead, the implantable lead being separate from
the device.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/648,604, filed May 29, 2015, now allowed, which claims
priority to International Application No. PCT/US2013/073326, filed
Dec. 5, 2013, which claims the benefit of U.S. Provisional
Application Ser. No. 61/733,867, filed Dec. 5, 2012. The complete
disclosures of all of the above patent applications are hereby
incorporated by reference in their entirety for all purposes.
TECHNICAL FIELD
[0002] This document relates generally to the delivery of energy
impulses (and/or fields) to bodily tissues for therapeutic purposes
and more specifically to devices and methods for the selective
modulation (and/or recording activity) of excitable tissue of a
patient.
BACKGROUND
[0003] 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,
arthritis, sleep apnea, seizures, incontinence, pain associated
with cancer, incontinence, problems of movement initiation and
control, involuntary movements, vascular insufficiency, heart
arrhythmias, obesity, diabetes, craniofacial pain, such as
migraines and more. A variety of therapeutic intra-body electrical
stimulation techniques and devices can be used to treat these
conditions. Typically, such devices include an implantable lead
with two or more electrodes attached by a wired connector to a
subcutaneous battery operated implantable pulse generator (IPG) or
other charge storage to provide power and create the electrical
impulses carried by hard wire to the lead body containing the
electrodes.
SUMMARY
[0004] In one aspect, a device for providing an implantable lead
with wireless energy includes: a housing configured for
implantation in a patient's body; one or more non-inductive
antennas substantially enclosed within the housing and configured
to receive electromagnetic energy radiated from a source located
outside of the patient's body; electronic circuitry coupled to each
of the one or more non-inductive antennas and configured to extract
electric power and excitation waveforms from the radiated
electromagnetic energy as received by the one or more non-inductive
antennas; and one or more connection pads substantially enclosed
within the housing, wherein the connection pads are configured to
couple with one or more electrodes in the implantable lead and form
an electric connection over which the connection pads provide the
extracted excitation waveforms from the electronic circuit to the
electrodes in the implantable lead, the implantable lead being
separate from the device.
[0005] Implementations may include the following features. The
connection pads may be configured to mate with at least one
connector of the electrode of the implantable lead by a form fit
between the connection pads and the at least one connector. The
device may further include at least one set screw to tighten the
mated connection pads and the at least one connector in forming the
electric connection from the connection pads to the at least one
connector of the electrode of the implantable lead.
[0006] The electronic circuitry may include one or more diodes and
one or more charge balancing components, wherein the one or more
diodes are configured to extract the electric power and excitation
waveforms, and wherein the one or more charge balancing components
are configured to facilitate distributing the excitation waveforms
to the connection pads.
[0007] The non-inductive antennas may include two to ten
non-inductive antennas, each having a length from about 0.25 cm to
12 cm. The connection pads may include two to eight connection pads
spaced apart from each other and each having a length of 1 cm or
less.
[0008] The housing may include a hollow biocompatible tube having a
distal opening configured for receiving at least a portion of the
implantable lead. The connection pads are circumferential
connection pads spaced from each other around an inside surface of
the hollow tube and configured to mate with electrode contacts on
the implantable lead. The implantable lead may include a paddle
lead comprising a plurality of electrode contacts and wherein the
connection pads are longitudinally spaced from each other on an
inside surface of the hollow tube and configured for mating to the
electrode contacts of the paddle lead. The hollow tube comprises a
Y-shaped proximal end having first and second tubes, wherein the
connection pads are arranged on an inside surface of the first tube
and an inside surface of the second tube, wherein the connection
pads on the inside surface of the first tube are configured to mate
to at least one connector of an electrode of a first implantable
lead, and wherein the connection pads on the inside surface of the
second tube are configured to mate to at least one connector of an
electrode of a second implantable lead.
[0009] The housing may be from about ten to fifty centimeter in
length. The connection pads may be separated from each other by a
distance of about 0.1 to 1.0 cm. The housing may include a hollow
tube having a diameter small enough to pass through a 12 to
22-gauge tube.
[0010] In one embodiment, the housing of the connector receiver
device preferably comprises of a hollow tube having a distal
opening for receiving the male connector portion of an implantable
lead and an overall length of between about 6 cm to 50 cm. The
hollow tube may be sized to pass through a standard 12 to 22 gauge
introducer tube, such as a cannula or needle. The internal
connection pads preferably have a length of less than 1 cm and are
arranged on the inside surface of the distal portion of the tube,
preferably spaced from each other so as to mate with the male
connector contacts on an implantable lead. In certain embodiments,
the connection pads have a substantially circumferential shape and
are wrapped around the inside surface of the tube. In other
embodiments, the pads may have other shapes that conform to the
shape of the male connector contacts on the implantable lead.
[0011] The antennas may comprise non-inductive antennas, such as
dipoles, each having a length of between about 0.25 cm to 12 cm and
configured to receive an input signal containing energy and
waveform parameters through radiative coupling from a remote source
outside of the patient's body (up to 3 feet away from the patient).
The connector receiver device may include a plurality of such
antennas, from one to 20, preferably between one to four,
preferably arranged on the proximal end portion of the device.
[0012] The electronic circuitry within the connector receiver
device preferably comprises of components configured for receiving
energy from the input signal to power the device. In the preferred
embodiment, all of the power requirements are supplied by energy
transmitted from the remote source. Thus, the connector receiver
device does not require a battery or other energy storage
component, such as a high voltage capacitor. The circuitry within
the connector receiver device may comprise of flexible circuits
configured to generate one or more electrical impulses from the
waveform parameters in the input signal and then route the impulses
through the connection pads to an implantable lead. The electrical
impulses are sufficient to modulate a nerve or nerve ganglion at
the target site.
[0013] In another embodiment, the connector receiver device
comprises of a Y-shaped tube having a proximal end with first and
second hollow tubes. The connection pads are arranged on an inside
surface of the first hollow tube and second hollow tube, mated to
another tubing segment containing the electronic circuitry.
[0014] In another aspect, a system for modulating excitable tissue
in a body of a patient includes: a connector receiver device for
connecting to an implantable lead in the patient's body, the
connector device including; one or more receiving antennas; one or
more connection pads; and an electronic circuit coupled to the
non-inductive antennas and the connection pads; a control device
having a transmitter located outside of the patient's body and
configured to transmit an input signal containing electrical energy
and waveform parameters to the receiving antennas through radiative
coupling; and wherein the electronic circuit is configured to
convert the waveform parameters into one or more electrical
impulses sufficient to modulate excitable tissue; and wherein the
connection pads are configured to couple with one or more
electrodes in the implantable lead and form an electric connection
over which the connection pads provide the one or more pulses from
the electronic circuit to the electrodes in the implantable lead,
the implantable lead being separate from the connector receiver
device.
[0015] Implementations may include the following features. The
connector receiver device may include an enclosure for housing the
receiving antennas, connection pads and electronic circuitry, the
enclosure comprising a substantially hollow tube with a distal end
configured for receiving at least a portion of the implantable
lead.
[0016] The electronic circuit may include: one or more diodes and
one or more charge balancing components. The control device may
include a transmitting antenna configured to transmit the input
signal through a carrier signal having a frequency between about
300 MHz and 8 GHz. The control device may include a pulse generator
configured to generate an electrical impulse with a frequency of
about 10 to 500 Hz. The control device may be configured to
transmit the input signal at least 10 cm from an outer skin surface
of the patient through tissue to the target site.
[0017] The connector receiver device may be coated with a
biocompatible material, such as polyurethane or silicon and the
internal connection pads preferably comprise MP35N, platinum,
platinum/iridium or other biocompatible alloy.
[0018] In another embodiment, the implantable lead may further
comprise recording or sensing electrodes configured to sense data
or information related to the stimulation parameters. In this
embodiment, the connector receiver device will contain telemetry
circuitry configured to transmit wirelessly the recorded sensing
information to a controller located outside of the patient's body.
This facilitates a close looped therapy wherein the stimulation
parameters may be adjusted to optimize the waveform and the therapy
applied to the patient.
[0019] In another aspect, a method for modulating excitable tissue
in a body of a patient includes: coupling one or more connection
pads on a connector receiver device to one or more electrodes in an
implantable stimulation device; advancing the connector receiver
device and the implantable stimulation device to a target site in
the patient's body adjacent to or near an excitable tissue;
radiating an input signal containing energy and waveform parameters
from a location outside of the patient's body to one or more
antennas in the connector device such that the waveform parameters
are converted to one or more electrical impulses and the electrical
impulses are applied to the electrodes in the implantable
stimulation device.
[0020] Implementations may include the following features. Coupling
may include mating a distal end of a hollow tube of the connector
receiver device to a proximal end of the implantable stimulation
device. Coupling may occur within the patient's body at the target
site. Radiating the input signal may include radiating the input
signal on a carrier signal having a frequency between about 300 MHz
and 8 GHz.
[0021] In certain embodiments, the connector receiver device is
coupled to the implantable lead outside of the patient's body and
both devices are then advanced together to a target site within the
body. In other embodiments, the connector receiver device is mated
to the implantable lead within the patient's body at the target
site. In these embodiments, the lead may already be implanted and
directly wired to an implanted pulse generator. The lead is
disconnected from the implanted pulse generator and mated with the
connector receiver device such that the lead can be powered
wirelessly through the connector receiver device. This allows the
operator to, for example, replace a wired implanted pulse generator
that has expended its battery life with wireless energy to avoid
recharging and/or replacing the implantable pulse generator.
[0022] The systems, devices and methods for modulating excitable
tissue of the exiting spinal nerves are more completely described
in the following detailed description of some implementations, with
reference to the drawings provided herewith, and in claims appended
hereto. Other aspects, features, advantages, etc. will become
apparent to one skilled in the art when the description of some
implementations herein is taken in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 depicts a high-level diagram of an example of a
connector receiver device.
[0024] FIG. 2 depicts a detailed diagram of an example of the
connector receiver device.
[0025] FIG. 3 is a flowchart showing an example of the operation of
the connector receiver device.
[0026] FIG. 4 is a circuit diagram showing an example of a
connector receiver device.
[0027] FIG. 5 is a circuit diagram of another example of a
connector receiver device.
[0028] FIG. 6 is a block diagram showing an example of control and
feedback functions of a wireless stimulation device.
[0029] FIG. 7 is a schematic showing an example of a connector
receiver device with components to implement control and feedback
functions.
[0030] FIG. 8 is a schematic of an example of a polarity routing
switch network.
[0031] FIG. 9A is a diagram of an example microwave field
stimulator (MFS) operating along with a connector receiver
device.
[0032] FIG. 9B is a diagram of another example MFS operating along
with a wireless stimulation device.
[0033] FIG. 10 is a detailed diagram of an example MFS.
[0034] FIG. 11 is a flowchart showing an example process in which
the MFS transmits polarity setting information to the connector
receiver device.
[0035] FIG. 12 is another flow chart showing an example process in
which the MFS receives and processes the telemetry feedback signal
to make adjustments to subsequent transmissions.
[0036] FIG. 13 is a schematic of an example implementation of
power, signal and control flow on the connector receiver
device.
[0037] FIG. 14A to FIG. 14D illustrate a connector receiver device
1400 according to some implementations.
[0038] FIG. 15 illustrates a connector receiver device being mated
with an implantable lead.
[0039] FIG. 16 illustrates a Y-shaped connector receiver
device.
DETAILED DESCRIPTION
[0040] In various implementations, systems and methods are
disclosed for applying one or more electrical impulses to targeted
excitable tissue, such as nerves, for treating chronic pain,
inflammation, arthritis, sleep apnea, seizures, incontinence, pain
associated with cancer, incontinence, problems of movement
initiation and control, involuntary movements, vascular
insufficiency, heart arrhythmias, obesity, diabetes, craniofacial
pain, such as migraines or cluster headaches, and other disorders.
In certain embodiments, a wireless stimulation device may be used
to send electrical energy to targeted nerve tissue by using remote
radio frequency (RF) energy with neither cables nor inductive
coupling to power the passive implanted wireless stimulation
device. The targeted nerves can include, but are not limited to,
the spinal cord and surrounding areas, including the dorsal horn,
dorsal root ganglion, the exiting nerve roots, nerve ganglions, the
dorsal column fibers and the peripheral nerve bundles leaving the
dorsal column and brain, such as the vagus, occipital, trigeminal,
hypoglossal, sacral, coccygeal nerves and the like.
[0041] A wireless stimulation system can include an implantable
lead body with one or more electrodes and a connector receiver
device comprising of an enclosure that houses one or more
conductive antennas (for example, dipole or patch antennas),
internal circuitry for frequency waveform and electrical energy
rectification, and one or more connection pads for coupling to the
implantable lead. The connector receiver device may further
comprise an external controller and antenna for sending radio
frequency or microwave energy from an external source to the
connector receiver device with neither cables nor inductive
coupling to provide power.
[0042] In various embodiments, the connector receiver device is
powered wirelessly (and therefore does not require a wired
connection) and contains the circuitry necessary to receive the
pulse instructions from a source external to the body. For example,
various embodiments 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. 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 have been previously incorporated by
reference.
[0043] FIG. 1 depicts a high-level diagram of an example of a
connector receiver device. The connector receiver device may
include four major components, namely, a programmer module 102, a
RF pulse generator module 106, a transmit (TX) antenna 110 (for
example, a patch antenna, slot antenna, or a dipole antenna), and
an implanted wireless stimulation device 114. Note that FIGS. 1-13
do not separately describe the connector receiver device and
implantable lead, but rather describe them as one element that is
already connected together and operating as a single unit (a
wireless stimulation device). In these figures, it can be assumed
that the wireless stimulation device 114 incorporates both a
connector receiver device 1400, such as the one shown in FIG. 14A
and an implantable lead 1602, such as the one shown in FIG. 16. The
separate connector receiver device and implantable lead are more
fully described in FIGS. 14-18. The programmer module 102 may be a
computer device, such as a smart phone, running a software
application that supports a wireless connection 114, such as
Bluetooth.RTM.. The application can enable the user to view the
system status and diagnostics, change various parameters,
increase/decrease the desired stimulus amplitude of the electrode
pulses, and adjust feedback sensitivity of the RF pulse generator
module 106, among other functions.
[0044] The RF pulse generator module 106 may include communication
electronics that support the wireless connection 104, the
stimulation circuitry, and the battery to power the generator
electronics. In some implementations, the RF pulse generator module
106 includes the TX antenna embedded into its packaging form factor
while, in other implementations, the TX antenna is connected to the
RF pulse generator module 106 through a wired connection 108 or a
wireless connection (not shown). The TX antenna 110 may be coupled
directly to tissue to create an electric field that powers the
implanted neural stimulator module 114. The TX antenna 110
communicates with the implanted neural stimulator module 114
through an RF interface. For instance, the TX antenna 110 radiates
an RF transmission signal that is modulated and encoded by the RE
pulse generator module 110. The implanted wireless stimulation
device of module 114 contains one or more antennas, such as dipole
antenna(s), to receive and transmit through RE interface 112. In
particular, the coupling mechanism between antenna 110 and the one
or more antennas on the implanted wireless stimulation device of
module 114 utilizes electrical radiative coupling and not inductive
coupling. In other words, the coupling is through an electric field
rather than a magnetic field.
[0045] Through this electrical radiative coupling, the TX antenna
110 can provide an input signal to the implanted stimulation module
114. This input signal contains energy and may contain information
encoding stimulus waveforms to be applied at the electrodes of the
implanted stimulation module 114. In some implementations, the
power level of this input signal directly determines an applied
amplitude (for example, power, current, or voltage) of the one or
more electrical pulses created using the electrical energy
contained in the input signal. Within the implanted wireless
stimulation device 114 are components for demodulating the RF
transmission signal, and electrodes to deliver the stimulation to
surrounding neuronal tissue.
[0046] The RF pulse generator module 106 can be implanted
subcutaneously, or it can be worn external to the body. When
external to the body, the RF generator module 106 can be
incorporated into a belt or harness design to allow for electric
radiative coupling through the skin and underlying tissue to
transfer power and/or control parameters to the implanted wireless
stimulation device module 114. In either event, receiver circuit(s)
internal to the wireless stimulation device 114 (or connector
device 1400 shown in FIG. 14A) can capture the energy radiated by
the TX antenna 110 and convert this energy to an electrical
waveform. The receiver circuit(s) may further modify the waveform
to create an electrical pulse suitable for the stimulation of
neural tissue.
[0047] In some implementations, the RF pulse generator module 106
can remotely control the stimulus parameters (that is, the
parameters of the electrical pulses applied to the neural tissue)
and monitor feedback from the wireless stimulation device 114 based
on RF signals received from the implanted wireless stimulation
device module 114. A feedback detection algorithm implemented by
the RF pulse generator module 106 can monitor data sent wirelessly
from the implanted wireless stimulation device module 114,
including information about the energy that the implanted wireless
stimulation device 114 is receiving from the RF pulse generator and
information about the stimulus waveform being delivered to the
electrode pads. In order to provide an effective therapy for a
given medical condition, the system can be tuned to provide the
optimal amount of excitation or inhibition to the nerve fibers by
electrical stimulation. A closed loop feedback control method can
be used in which the output signals from the implanted wireless
stimulation device 114 are monitored and used to determine the
appropriate level of neural stimulation current for maintaining
effective neuronal activation, or, in some cases, the patient can
manually adjust the output signals in an open loop control
method.
[0048] FIG. 2 depicts a detailed diagram of an example of the
wireless stimulation device. As depicted, the programming module
102 may comprise user input system 202 and communication subsystem
208. The user input system 221 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 208
may transmit these instruction sets (and other information) via the
wireless connection 104, such as Bluetooth or Wi-Fi, to the RF
pulse generator module 106, as well as receive data from module
106.
[0049] For instance, the programmer module 102, 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 106. 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 TABLE 1 Stimulation Parameter Pulse Amplitude: 0 to
20 mA Pulse Frequency: 0 to 10000 Hz Pulse Width: 0 to 2 ms
[0050] The RF pulse generator module 114 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.
[0051] The programmer module 102 may be functionally a smart device
and associated application. The smart device hardware may include a
CPU 206 and be used as a vehicle to handle touchscreen input on a
graphical user interface (GUI) 204, for processing and storing
data.
[0052] The RF pulse generator module 106 may be connected via wired
connection 108 to an external TX antenna 110. Alternatively, both
the antenna and the RF pulse generator are located subcutaneously
(not shown).
[0053] The signals sent by RE pulse generator module 106 to the
implanted wireless stimulation device 114 may include both power
and parameter-setting attributes in regards to stimulus waveform,
amplitude, pulse width, and frequency. The RF pulse generator
module 106 can also function as a wireless receiving unit that
receives feedback signals from the implanted wireless stimulation
device 114. To that end, the RF pulse generator module 106 may
contain microelectronics or other circuitry to handle the
generation of the signals transmitted to the device 114 as well as
handle feedback signals, such as those from the device 114. For
example, the RF pulse generator module 106 may comprise controller
subsystem 214, high-frequency oscillator 218, RE amplifier 216, a
RF switch, and a feedback subsystem 212.
[0054] The controller subsystem 214 may include a CPU 230 to handle
data processing, a memory subsystem 228 such as a local memory,
communication subsystem 234 to communicate with programmer module
102 (including receiving stimulation parameters from programmer
module), pulse generator circuitry 236, and digital/analog (D/A)
converters 232.
[0055] The controller subsystem 214 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 106 to the device 114). 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 102, 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 238, typically a dipole antenna
(although other types may be used), in the implanted wireless
stimulation device 214. 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.
[0056] The controller subsystem 214 may store received parameter
settings in the local memory subsystem 228, until the parameter
settings are modified by new input data received from the
programming module 102. The CPU 206 may use the parameters stored
in the local memory to control the pulse generator circuitry 236 to
generate a stimulus waveform that is modulated by a high frequency
oscillator 218 in the range from 300 MHz to 8 GHz (preferably
between about 700 MHz and 5.8 GHz and more preferably between about
800 MHz and 1.3 GHz). The resulting RF signal may then be amplified
by RF amplifier 226 and then sent through an RF switch 223 to the
TX antenna 110 to reach through depths of tissue to the RX antenna
238.
[0057] In some implementations, the RF signal sent by TX antenna
110 may simply be a power transmission signal used by the wireless
stimulation device module 114 to generate electric pulses. In other
implementations, a telemetry signal may also be transmitted to the
wireless stimulation device module 114 to send instructions about
the various operations of the wireless stimulation device module
114. 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 106 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) 238 and does not interfere with the input
received on the same lead to power the wireless stimulation device.
In one embodiment the telemetry signal and powering signal are
combined into one signal, where the RF telemetry signal is used to
modulate the RE powering signal, and thus the wireless stimulation
device is powered directly by the received telemetry signal;
separate subsystems in the wireless stimulation device harness the
power contained in the signal and interpret the data content of the
signal.
[0058] The RF switch 223 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 110
with minimal insertion loss while simultaneously providing two
low-level outputs to feedback subsystem 212; one output delivers a
forward power signal to the feedback subsystem 212, where the
forward power signal is an attenuated version of the RF pulse sent
to the TX antenna 110, and the other output delivers a reverse
power signal to a different port of the feedback subsystem 212,
where reverse power is an attenuated version of the reflected RF
energy from the TX Antenna 110.
[0059] During the on-cycle time (when an RF signal is being
transmitted to wireless stimulation device 114), the RF switch 223
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 wireless stimulation device module 114), the RF
switch 223 can change to a receiving mode in which the reflected RE
energy and/or RF signals from the wireless stimulation device
module 114 are received to be analyzed in the feedback subsystem
212.
[0060] The feedback subsystem 212 of the RF pulse generator module
106 may include reception circuitry to receive and extract
telemetry or other feedback signals from the wireless stimulation
device 114 and/or reflected RF energy from the signal sent by TX
antenna 110. The feedback subsystem may include an amplifier 226, a
filter 224, a demodulator 222, and an A/D converter 220.
[0061] The feedback subsystem 212 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 214. In this way
the characteristics of the generated RF pulse can be compared to a
reference signal within the controller subsystem 214. If a
disparity (error) exists in any parameter, the controller subsystem
214 can adjust the output to the RF pulse generator 106. The nature
of the adjustment can be, for example, proportional to the computed
error. The controller subsystem 214 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.
[0062] The reverse power signal can be used to detect fault
conditions in the RE-power delivery system. In an ideal condition,
when TX antenna 110 has perfectly matched impedance to the tissue
that it contacts, the electromagnetic waves generated from the RE
pulse generator 106 pass unimpeded from the TX antenna 110 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 110 relative to the body
surface. Since the impedance of the antenna 110 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 110 with the
body surface. When such a mismatch occurs, the electromagnetic
waves sent from the RE pulse generator 106 are partially reflected
at this interface, and this reflected energy propagates backward
through the antenna feed.
[0063] The dual directional coupler RF switch 223 may prevent the
reflected RF energy propagating back into the amplifier 226, and
may attenuate this reflected RF signal and send the attenuated
signal as the reverse power signal to the feedback subsystem 212.
The feedback subsystem 212 can convert this high-frequency AC
signal to a DC level that can be sampled and sent to the controller
subsystem 214. The controller subsystem 214 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.
[0064] In order to sense impedance mismatch conditions, the
controller subsystem 214 can measure the reflected-power ratio in
real time, and according to preset thresholds for this measurement,
the controller subsystem 214 can modify the level of RF power
generated by the RF pulse generator 106. For example, for a
moderate degree of reflected power the course of action can be for
the controller subsystem 214 to increase the amplitude of RF power
sent to the TX antenna 110, 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 RE pulse generator 106 and set a
fault code to indicate that the TX antenna 110 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 lead to unwanted
heating of internal components, and this fault condition means the
system cannot deliver sufficient power to the implanted wireless
stimulation device and thus cannot deliver therapy to the user.
[0065] The controller 242 of the wireless stimulation device 114
may transmit informational signals, such as a telemetry signal,
through the antenna 238 to communicate with the RF pulse generator
module 106 during its receive cycle. For example, the telemetry
signal from the wireless stimulation device 114 may be coupled to
the modulated signal on the dipole antenna(s) 238, 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 106. The antenna(s) 238 may be connected to electrodes 254
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) 238 of the
wireless stimulation device 114.
[0066] A telemetry signal from the implanted wireless stimulation
device module 114 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 116 to indicate the strength of the
stimulus at the nerve bundle by means of coupling the signal to the
implanted RX antenna 238, which radiates the telemetry signal to
the external (or remotely implanted) RF pulse generator module 106.
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 stimulation device 114, and sent on the
telemetry signal. The frequency of the carrier signal may be in the
range of at 300 MHz to 8 GHz (preferably between about 700 MHz and
5.8 GHz and more preferably between about 800 MHz and 1.3 GHz).
[0067] In the feedback subsystem 212, the telemetry signal can be
down modulated using demodulator 222 and digitized by being
processed through an analog to digital (ND) converter 220. The
digital telemetry signal may then be routed to a CPU 230 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 230 of the
controller subsystem 214 can compare the reported stimulus
parameters to those held in local memory 228 to verify the wireless
stimulation device 114 delivered the specified stimuli to tissue.
For example, if the wireless stimulation device reports a lower
current than was specified, the power level from the RF pulse
generator module 106 can be increased so that the implanted
wireless stimulation device 114 will have more available power for
stimulation. The implanted wireless stimulation device 114 can
generate telemetry data in real time, for example, at a rate of 8
Kbits per second. All feedback data received from the implanted
lead module 114 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.
[0068] The sequence of remotely programmable RF signals received by
the internal antenna(s) 238 may be conditioned into waveforms that
are controlled within the implantable wireless stimulation device
114 by the control subsystem 242 and routed to the appropriate
electrodes 254 that are placed in proximity to the tissue to be
stimulated. For instance, the RE signal transmitted from the RE
pulse generator module 106 may be received by RX antenna 238 and
processed by circuitry, such as waveform conditioning circuitry
240, within the implanted wireless stimulation device module 114 to
be converted into electrical pulses applied to the electrodes 254
through electrode interface 252. In some implementations, the
implanted wireless stimulation device 114 contains between two to
sixteen electrodes 254.
[0069] The waveform conditioning circuitry 240 may include a
rectifier 244, which rectifies the signal received by the RX
antenna 238. The rectified signal may be fed to the controller 242
for receiving encoded instructions from the RF pulse generator
module 106. The rectifier signal may also be fed to a charge
balance component 246 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 248
to the electrode interface 252, which applies the pulses to the
electrodes 254 as appropriate.
[0070] The current limiter 248 insures the current level of the
pulses applied to the electrodes 254 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
248 to prevent excessive current or charge being delivered through
the electrodes, although current limiter 248 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 248 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).
[0071] In the event the implanted wireless stimulation device 114
receives a "strong" pulse of RF power sufficient to generate a
stimulus that would exceed the predetermined safe-charge limit, the
current limiter 248 can automatically limit or "clip" the stimulus
phase to maintain the total charge of the phase within the safety
limit. The current limiter 248 may be a passive current limiting
component that cuts the signal to the electrodes 254 once the safe
current limit (the threshold current level) is reached.
Alternatively, or additionally, the current limiter 248 may
communicate with the electrode interface 252 to turn off all
electrodes 254 to prevent tissue damaging current levels.
[0072] 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 106. The
feedback subsystem 212 detects the threshold power signal and
demodulates the signal into data that is communicated to the
controller subsystem 214. The controller subsystem 214 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 106 can reduce
the RF power delivered to the body if the implanted wireless
stimulation device 114 reports it is receiving excess RF power.
[0073] The controller 250 of the stimulator 205 may communicate
with the electrode interface 252 to control various aspects of the
electrode setup and pulses applied to the electrodes 254. The
electrode interface 252 may act as a multiplex and control the
polarity and switching of each of the electrodes 254. For instance,
in some implementations, the wireless stimulator 106 has multiple
electrodes 254 in contact with tissue, and for a given stimulus the
RF pulse generator module 106 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
250 uses to set electrode interface 252 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.
[0074] Also, in some implementations, for a given stimulus pulse,
the controller 250 may control the electrode interface 252 to
divide the current arbitrarily (or according to instructions from
pulse generator module 106) among the designated stimulating
electrodes. This control over electrode assignment and current
control can be advantageous because in practice the electrodes 254
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.
[0075] 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 250, on its own or in response to instructions from
pulse generator 106, can control electrode interface 252 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.
[0076] 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 250 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 250 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 250 was configured to match the repetition rate for
set B to that of set A, for such a case the controller 250 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.
[0077] In some implementations, the controller 250 can arbitrarily
shape the stimulus waveform amplitude, and may do so in response to
instructions from pulse generator 106. 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 250 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 250 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 a leading anodic pulse
(prior to the stimulus phase) may also be amplitude-shaped.
[0078] As described above, the wireless stimulation device 114 may
include a charge-balancing component 246. 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/cm.sup.2. 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/cm.sup.2. 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. The wireless stimulation device 114 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.
[0079] 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.
[0080] In some implementations, the charge balance component 246
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 as disclosed herein, 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.
[0081] 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.
[0082] In some implementations, the wireless stimulation device
module 114 may create a drive-waveform envelope that follows the
envelope of the RF pulse received by the receiving dipole
antenna(s) 238. In this case, the RF pulse generator module 106 can
directly control the envelope of the drive waveform within the
wireless stimulation device 114, 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.
[0083] In some implementations, the implanted wireless stimulation
device 114 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.
[0084] 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.
[0085] 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 106, and
in others this control may be administered internally by circuitry
onboard the wireless stimulation device 114, such as controller
250. In the case of onboard control, the amplitude and timing may
be specified or modified by data commands delivered from the pulse
generator module 106.
[0086] FIG. 3 is a flowchart showing an example of an operation of
the neural stimulator system. In block 302, the wireless
stimulation device 114 is implanted in proximity to nerve bundles
and is coupled to the electric field produced by the TX antenna
110. That is, the pulse generator module 106 and the TX antenna 110
are positioned in such a way (for example, in proximity to the
patient) that the TX antenna 110 is electrically radiatively
coupled with the implanted RX antenna 238 of the wireless
stimulation device 114. In certain implementations, both the
antenna 110 and the RF pulse generator 106 are located
subcutaneously. In other implementations, the antenna 110 and the
RF pulse generator 106 are located external to the patient's body.
In this case, the TX antenna 110 may be coupled directly to the
patient's skin.
[0087] Energy from the RF pulse generator is radiated to the
implanted wireless stimulation device 114 from the antenna 110
through tissue, as shown in block 304. The energy radiated may be
controlled by the Patient/Clinician Parameter inputs in block 301.
In some instances, the parameter settings can be adjusted in an
open loop fashion by the patient or clinician, who would adjust the
parameter inputs in block 301 to the system.
[0088] The implanted wireless stimulation device 114 uses the
received energy to generate electrical pulses to be applied to the
neural tissue through the electrodes 238. For instance, the
wireless stimulation device 114 may contain circuitry that
rectifies the received RF energy and conditions the waveform to
charge balance the energy delivered to the electrodes to stimulate
the targeted nerves or tissues, as shown in block 306. The
implanted wireless stimulation device 114 communicates with the
pulse generator 106 by using antenna 238 to send a telemetry
signal, as shown in block 308. The telemetry signal may contain
information about parameters of the electrical pulses applied to
the electrodes, such as the impedance of the electrodes, whether
the safe current limit has been reached, or the amplitude of the
current that is presented to the tissue from the electrodes.
[0089] In block 310, the RF pulse generator 106 detects amplifies,
filters and modulates the received telemetry signal using amplifier
226, filter 224, and demodulator 222, respectively. The A/D
converter 230 then digitizes the resulting analog signal, as shown
in 312. The digital telemetry signal is routed to CPU 230, which
determines whether the parameters of the signal sent to the
wireless stimulation device 114 need to be adjusted based on the
digital telemetry signal. For instance, in block 314, the CPU 230
compares the information of the digital signal to a look-up table,
which may indicate an appropriate change in stimulation parameters.
The indicated change may be, for example, a change in the current
level of the pulses applied to the electrodes. As a result, the CPU
may change the output power of the signal sent to wireless
stimulation device 114 so as to adjust the current applied by the
electrodes 254, as shown in block 316.
[0090] Thus, for instance, the CPU 230 may adjust parameters of the
signal sent to the wireless stimulation device 114 every cycle to
match the desired current amplitude setting programmed by the
patient, as shown in block 318. The status of the stimulator system
may be sampled in real time at a rate of 8 Kbits per second of
telemetry data. All feedback data received from the wireless
stimulation device 114 can be maintained against time and sampled
per minute to be stored for download or upload to a remote
monitoring system accessible by the health care professional for
trending and statistical correlations in block 318. If operated in
an open loop fashion, the stimulator system operation may be
reduced to just the functional elements shown in blocks 302, 304,
306, and 308, and the patient uses their judgment to adjust
parameter settings rather than the closed looped feedback from the
implanted device.
[0091] FIG. 4 is a circuit diagram showing an example of a wireless
neural stimulator, such as wireless stimulation device 114. This
example contains paired electrodes, comprising cathode electrode(s)
408 and anode electrode(s) 410, as shown. When energized, the
charged electrodes create a volume conduction field of current
density within the tissue. In this implementation, the wireless
energy is received through a dipole antenna(s) 238. At least four
diodes are connected together to form a full wave bridge rectifier
402 attached to the dipole antenna(s) 238. Each diode, up to 100
micrometers in length, uses a junction potential to prevent the
flow of negative electrical current, from cathode to anode, from
passing through the device when said current does not exceed the
reverse threshold. For neural stimulation via wireless power,
transmitted through tissue, the natural inefficiency of the lossy
material may lead to a low threshold voltage. In this
implementation, a zero biased diode rectifier results in a low
output impedance for the device. A resistor 404 and a smoothing
capacitor 406 are placed across the output nodes of the bridge
rectifier to discharge the electrodes to the ground of the bridge
anode. The rectification bridge 402 includes two branches of diode
pairs connecting an anode-to-anode and then cathode to cathode. The
electrodes 408 and 410 are connected to the output of the charge
balancing circuit 246.
[0092] FIG. 5 is a circuit diagram of another example of a wireless
stimulation device 114. The example shown in FIG. 5 includes
multiple electrode control and may employ full closed loop control.
The wireless stimulation device includes an electrode array 254 in
which the polarity of the electrodes can be assigned as cathodic or
anodic, and for which the electrodes can be alternatively not
powered with any energy. When energized, the charged electrodes
create a volume conduction field of current density within the
tissue. In this implementation, the wireless energy is received by
the device through the dipole antenna(s) 238. The electrode array
254 is controlled through an on-board controller circuit 242 that
sends the appropriate bit information to the electrode interface
252 in order to set the polarity of each electrode in the array, as
well as power to each individual electrode. The lack of power to a
specific electrode would set that electrode in a functional OFF
position. In another implementation (not shown), the amount of
current sent to each electrode is also controlled through the
controller 242. The controller current, polarity and power state
parameter data, shown as the controller output, is be sent back to
the antenna(s) 238 for telemetry transmission back to the pulse
generator module 106. The controller 242 also includes the
functionality of current monitoring and sets a bit register counter
so that the status of total current drawn can be sent back to the
pulse generator module 106.
[0093] At least four diodes can be connected together to form a
full wave bridge rectifier 302 attached to the dipole antenna(s)
238. Each diode, up to 100 micrometers in length, uses a junction
potential to prevent the flow of negative electrical current, from
cathode to anode, from passing through the device when said current
does not exceed the reverse threshold. For neural stimulation via
wireless power, transmitted through tissue, the natural
inefficiency of the lossy material may lead to a low threshold
voltage. In this implementation, a zero biased diode rectifier
results in a low output impedance for the device. A resistor 404
and a smoothing capacitor 406 are placed across the output nodes of
the bridge rectifier to discharge the electrodes to the ground of
the bridge anode. The rectification bridge 402 may include two
branches of diode pairs connecting an anode-to-anode and then
cathode to cathode. The electrode polarity outputs, both cathode
408 and anode 410 are connected to the outputs formed by the bridge
connection. Charge balancing circuitry 246 and current limiting
circuitry 248 are placed in series with the outputs.
[0094] FIG. 6 is a block diagram showing an example of control
functions 605 and feedback functions 630 of a implantable wireless
stimulation device 600, such as the ones described above or further
below. An example implementation may be a wireless stimulation
device module 114, as discussed above in association with FIG. 2.
Control functions 605 include functions 610 for polarity switching
of the electrodes and functions 620 for power-on reset.
[0095] Polarity switching functions 610 may employ, for example, a
polarity routing switch network to assign polarities to electrodes
254. The assignment of polarity to an electrode may, for instance,
be one of: a cathode (negative polarity), an anode (positive
polarity), or a neutral (off) polarity. The polarity assignment
information for each of the electrodes 254 may be contained in the
input signal received by implantable wireless stimulation device
600 through Rx antenna 238 from RF pulse generator module 106.
Because a programmer module 102 may control RF pulse generator
module 106, the polarity of electrodes 254 may be controlled
remotely by a programmer through programmer module 102, as shown in
FIG. 2.
[0096] Power-on reset functions 620 may reset the polarity
assignment of each electrode immediately on each power-on event. As
will be described in further detail below, this reset operation may
cause RF pulse generator module 106 to transmit the polarity
assignment information to the implantable wireless stimulation
device 600. Once the polarity assignment information is received by
the implantable wireless stimulation device 600, the polarity
assignment information may be stored in a register file, or other
short-term memory component. Thereafter the polarity assignment
information may be used to configure the polarity assignment of
each electrode. If the polarity assignment information transmitted
in response to the reset encodes the same polarity state as before
the power-on event, then the polarity state of each electrode can
be maintained before and after each power-on event.
[0097] Feedback functions 630 include functions 640 for monitoring
delivered power to electrodes 254 and functions 650 for making
impedance diagnosis of electrodes 254. For example, delivered power
functions 640 may provide data encoding the amount of power being
delivered from electrodes 254 to the excitable tissue and tissue
impedance diagnostic functions 650 may provide data encoding the
diagnostic information of tissue impedance. The tissue impedance is
the electrical impedance of the tissue as seen between negative and
positive electrodes when a stimulation current is being released
between negative and positive electrodes.
[0098] Feedback functions 630 may additionally include tissue depth
estimate functions 660 to provide data indicating the overall
tissue depth that the input radio frequency (RF) signal from the
pulse generator module, such as, for example, RF pulse generator
module 106, has penetrated before reaching the implanted antenna,
such as, for example, RX antenna 238, within the wireless
implantable neural stimulator 600, such as, for example, implanted
wireless stimulation device 114. For instance, the tissue depth
estimate may be provided by comparing the power of the received
input signal to the power of the RF pulse transmitted by the RF
pulse generator 106. The ratio of the power of the received input
signal to the power of the RF pulse transmitted by the RF pulse
generator 106 may indicate an attenuation caused by wave
propagation through the tissue. For example, the second harmonic
described below may be received by the RF pulse generator 106 and
used with the power of the input signal sent by the RF pulse
generator to determine the tissue depth. The attenuation may be
used to infer the overall depth of implantable wireless stimulation
device 600 underneath the skin.
[0099] The data from blocks 640, 650, and 660 may be transmitted,
for example, through Tx antenna 110 to an implantable RF pulse
generator 106, as illustrated in FIGS. 1 and 2.
[0100] As discussed above in association with FIGS. 1, 2, 4, and 5,
a implantable wireless stimulation device 600 may utilize
rectification circuitry to convert the input signal (e.g., having a
carrier frequency within a range from about 300 MHz to about 8 GHz)
to a direct current (DC) power to drive the electrodes 254. Some
implementations may provide the capability to regulate the DC power
remotely. Some implementations may further provide different
amounts of power to different electrodes, as discussed in further
detail below.
[0101] FIG. 7 is a schematic showing an example of a implantable
wireless stimulation device 700 with components to implement
control and feedback functions as discussed above in association
with FIG. 6. An RX antenna 705 receives the input signal. The RX
antenna 705 may be embedded as a dipole, microstrip, folded dipole
or other antenna configuration other than a coiled configuration,
as described above. The input signal has a carrier frequency in the
GHz range and contains electrical energy for powering the wireless
implantable neural stimulator 700 and for providing stimulation
pulses to electrodes 254. Once received by the antenna 705, the
input signal is routed to power management circuitry 710. Power
management circuitry 710 is configured to rectify the input signal
and convert it to a DC power source. For example, the power
management circuitry 710 may include a diode rectification bridge
such as the diode rectification bridge 402 illustrated in FIG. 4.
The DC power source provides power to stimulation circuitry 711 and
logic power circuitry 713. The rectification may utilize one or
more full wave diode bridge rectifiers within the power management
circuitry 710. In one implementation, a resistor can be placed
across the output nodes of the bridge rectifier to discharge the
electrodes to the ground of the bridge anode, as illustrated by the
shunt register 404 in FIG. 7.
[0102] Turning momentarily to FIG. 8, a schematic of an example of
a polarity routing switch network 800 is shown. As discussed above,
the cathodic (-) energy and the anodic energy are received at input
1 (block 722) and input 2 (block 723), respectively. Polarity
routing switch network 800 has one of its outputs coupled to an
electrode of electrodes 254 which can include as few as two
electrodes, or as many as sixteen electrodes. Eight electrodes are
shown in this implementation as an example.
[0103] Polarity routing switch network 800 is configured to either
individually connect each output to one of input 1 or input 2, or
disconnect the output from either of the inputs. This selects the
polarity for each individual electrode of electrodes 254 as one of:
neutral (off), cathode (negative), or anode (positive). Each output
is coupled to a corresponding three-state switch 830 for setting
the connection state of the output. Each three-state switch is
controlled by one or more of the bits from the selection input 850.
In some implementations, selection input 850 may allocate more than
one bits to each three-state switch. For example, two bits may
encode the three-state information. Thus, the state of each output
of polarity routing switch device 800 can be controlled by
information encoding the bits stored in the register 732, which may
be set by polarity assignment information received from the remote
RE pulse generator module 106, as described further below.
[0104] Returning to FIG. 7, power and impedance sensing circuitry
may be used to determine the power delivered to the tissue and the
impedance of the tissue. For example, a sensing resistor 718 may be
placed in serial connection with the anodic branch 714. Current
sensing circuit 719 senses the current across the resistor 718 and
voltage sensing circuit 720 senses the voltage across the resistor.
The measured current and voltage may correspond to the actual
current and voltage applied by the electrodes to the tissue.
[0105] As described below, the measured current and voltage may be
provided as feedback information to RE pulse generator module 106.
The power delivered to the tissue may be determined by integrating
the product of the measured current and voltage over the duration
of the waveform being delivered to electrodes 254. Similarly, the
impedance of the tissue may be determined based on the measured
voltage being applied to the electrodes and the current being
applied to the tissue. Alternative circuitry (not shown) may also
be used in lieu of the sensing resistor 718, depending on
implementation of the feature and whether both impedance and power
feedback are measured individually, or combined.
[0106] The measurements from the current sensing circuitry 719 and
the voltage sensing circuitry 720 may be routed to a voltage
controlled oscillator (VCO) 733 or equivalent circuitry capable of
converting from an analog signal source to a carrier signal for
modulation. VCO 733 can generate a digital signal with a carrier
frequency. The carrier frequency may vary based on analog
measurements such as, for example, a voltage, a differential of a
voltage and a power, etc. VCO 733 may also use amplitude modulation
or phase shift keying to modulate the feedback information at the
carrier frequency. The VCO or the equivalent circuit may be
generally referred to as an analog controlled carrier modulator.
The modulator may transmit information encoding the sensed current
or voltage back to RF pulse generator 106.
[0107] Antenna 725 may transmit the modulated signal, for example,
in the GHz frequency range, back to the RF pulse generator module
106. In some embodiments, antennas 705 and 725 may be the same
physical antenna. In other embodiments, antennas 705 and 725 may be
separate physical antennas. In the embodiments of separate
antennas, antenna 725 may operate at a resonance frequency that is
higher than the resonance frequency of antenna 705 to send
stimulation feedback to RF pulse generator module 106. In some
embodiments antenna 725 may also operate at the higher resonance
frequency to receive data encoding the polarity assignment
information from RF pulse generator module 106.
[0108] Antenna 725 may be a telemetry antenna 725 which may route
received data, such as polarity assignment information, to the
stimulation feedback circuit 730. The encoded polarity assignment
information may be on a band in the GHz range. The received data
may be demodulated by demodulation circuitry 731 and then stored in
the register file 732. The register file 732 may be a volatile
memory. Register file 732 may be an 8-channel memory bank that can
store, for example, several bits of data for each channel to be
assigned a polarity. Some embodiments may have no register file,
while some embodiments may have a register file up to 64 bits in
size. The information encoded by these bits may be sent as the
polarity selection signal to polarity routing switch network 721,
as indicated by arrow 734. The bits may encode the polarity
assignment for each output of the polarity routing switch network
as one of: + (positive), - (negative), or 0 (neutral). Each output
connects to one electrode and the channel setting determines
whether the electrode will be set as an anode (positive), cathode
(negative), or off (neutral).
[0109] Returning to power management circuitry 710, in some
embodiments, approximately 90% of the energy received is routed to
the stimulation circuitry 711 and less than 10% of the energy
received is routed to the logic power circuitry 713. Logic power
circuitry 713 may power the control components for polarity and
telemetry. In some implementations, the power circuitry 713,
however, does not provide the actual power to the electrodes for
stimulating the tissues. In certain embodiments, the energy leaving
the logic power circuitry 713 is sent to a capacitor circuit 716 to
store a certain amount of readily available energy. The voltage of
the stored charge in the capacitor circuit 716 may be denoted as
Vdc. Subsequently, this stored energy is used to power a power-on
reset circuit 716 configured to send a reset signal on a power-on
event. If the wireless implantable neural stimulator 700 loses
power for a certain period of time, for example, in the range from
about 1 millisecond to over 10 milliseconds, the contents in the
register file 732 and polarity setting on polarity routing switch
network 721 may be zeroed. The implantable wireless stimulation
device 700 may lose power, for example, when it becomes less
aligned with RF pulse generator module 106. Using this stored
energy, power-on reset circuit 740 may provide a reset signal as
indicated by arrow 717. This reset signal may cause stimulation
feedback circuit 730 to notify RF pulse generator module 106 of the
loss of power. For example, stimulation feedback circuit 730 may
transmit a telemetry feedback signal to RF pulse generator module
106 as a status notification of the power outage. This telemetry
feedback signal may be transmitted in response to the reset signal
and immediately after power is back on wireless stimulation device
700. RF pulse generator module 106 may then transmit one or more
telemetry packets to implantable wireless stimulation device. The
telemetry packets contain polarity assignment information, which
may be saved to register file 732 and may be sent to polarity
routing switch network 721. Thus, polarity assignment information
in register file 732 may be recovered from telemetry packets
transmitted by RF pulse generator module 106 and the polarity
assignment for each output of polarity routing switch network 721
may be updated accordingly based on the polarity assignment
information.
[0110] The telemetry antenna 725 may transmit the telemetry
feedback signal back to RF pulse generator module 106 at a
frequency higher than the characteristic frequency of an RX antenna
705. In one implementation, the telemetry antenna 725 can have a
heightened resonance frequency that is the second harmonic of the
characteristic frequency of RX antenna 705. For example, the second
harmonic may be utilized to transmit power feedback information
regarding an estimate of the amount of power being received by the
electrodes. The feedback information may then be used by the RF
pulse generator in determining any adjustment of the power level to
be transmitted by the RF pulse generator 106. In a similar manner,
the second harmonic energy can be used to detect the tissue depth.
The second harmonic transmission can be detected by an external
antenna, for example, on RF pulse generator module 106 that is
tuned to the second harmonic. As a general matter, power management
circuitry 710 may contain rectifying circuits that are non-linear
device capable of generating harmonic energies from input signal.
Harvesting such harmonic energy for transmitting telemetry feedback
signal could improve the efficiency of implantable wireless
stimulation device 700.
[0111] FIG. 9A is a diagram of an example implementation of a
microwave field stimulator (MFS) 902 as part of a stimulation
system utilizing an implantable wireless stimulation device 922. In
this example, the MFS 902 is external to a patient's body and may
be placed within in close proximity, for example, within 3 feet, to
an implantable wireless stimulation device 922. The RF pulse
generator module 106 may be one example implementation of MFS 902.
MFS 902 may be generally known as a controller module. The
implantable wireless stimulation device 922 is a passive device.
The implantable wireless stimulation device 922 does not have its
own independent power source, rather it receives power for its
operation from transmission signals emitted from a TX antenna
powered by the MFS 902, as discussed above.
[0112] In certain embodiments, the MFS 902 may communicate with a
programmer 912. The programmer 912 may be a mobile computing
device, such as, for example, a laptop, a smart phone, a tablet,
etc. The communication may be wired, using for example, a USB or
firewire cable. The communication may also be wireless, utilizing
for example, a bluetooth protocol implemented by a transmitting
blue tooth module 904, which communicates with the host bluetooth
module 914 within the programmer 912.
[0113] The MFS 902 may additionally communicate with wireless
stimulation device 922 by transmitting a transmission signal
through a Tx antenna 907 coupled to an amplifier 906. The
transmission signal may propagate through skin and underlying
tissues to arrive at the Rx antenna 923 of the wireless stimulation
device 922. In some implementations, the wireless stimulation
device 922 may transmit a telemetry feedback signal back to
microwave field stimulator 902.
[0114] The microwave field stimulator 902 may include a
microcontroller 908 configured to manage the communication with a
programmer 912 and generate an output signal. The output signal may
be used by the modulator 909 to modulate a RE carrier signal. The
frequency of the carrier signal may be in the microwave range, for
example, from about 300 MHz to about 8 GHz, preferably from about
800 MHz to 1.3 GHz. The modulated RE carrier signal may be
amplified by an amplifier 906 to provide the transmission signal
for transmission to the wireless stimulation device 922 through a
TX antenna 907.
[0115] FIG. 9B is a diagram of another example of an implementation
of a microwave field stimulator 902 as part of a stimulation system
utilizing a wireless stimulation device 922. In this example, the
microwave field stimulator 902 may be embedded in the body of the
patient, for example, subcutaneously. The embedded microwave field
stimulator 902 may receive power from a detached, remote wireless
battery charger 932.
[0116] The power from the wireless battery charger 932 to the
embedded microwave field stimulator 902 may be transmitted at a
frequency in the MHz or GHz range. The microwave field stimulator
902 shall be embedded subcutaneously at a very shallow depth (e.g.,
less than 1 cm), and alternative coupling methods may be used to
transfer energy from wireless battery charger 932 to the embedded
MFS 902 in the most efficient manner as is well known in the
art.
[0117] In some embodiments, the microwave field stimulator 902 may
be adapted for placement at the epidural layer of a spinal column,
near or on the dura of the spinal column, in tissue in close
proximity to the spinal column, in tissue located near a dorsal
horn, in dorsal root ganglia, in one or more of the dorsal roots,
in dorsal column fibers, or in peripheral nerve bundles leaving the
dorsal column of the spine.
[0118] In this embodiment, the microwave field stimulator 902 shall
transmit power and parameter signals to a passive Tx antenna also
embedded subcutaneously, which shall be coupled to the RX antenna
within the wireless stimulation device 922. The power required in
this embodiment is substantially lower since the TX antenna and the
RX antenna are already in body tissue and there is no requirement
to transmit the signal through the skin.
[0119] FIG. 10 is a detailed diagram of an example microwave field
stimulator 902. A microwave field stimulator 902 may include a
microcontroller 908, a telemetry feedback module 1002, and a power
management module 1004. The microwave field stimulator 902 has a
two-way communication schema with a programmer 912, as well as with
a communication or telemetry antenna 1006. The microwave field
stimulator 902 sends output power and data signals through a TX
antenna 1008.
[0120] The microcontroller 908 may include a storage device 1014, a
bluetooth interface 1013, a USB interface 1012, a power interface
1011, an analog-to-digital converter (ADC) 1016, and a digital to
analog converter (DAC) 1015. Implementations of a storage device
1014 may include non-volatile memory, such as, for example, static
electrically erasable programmable read-only memory (SEEPROM) or
NAND flash memory. A storage device 1014 may store waveform
parameter information for the microcontroller 908 to synthesize the
output signal used by modulator 909. The stimulation waveform may
include multiple pulses. The waveform parameter information may
include the shape, duration, amplitude of each pulse, as well as
pulse repetition frequency. A storage device 1014 may additionally
store polarity assignment information for each electrode of the
wireless stimulation device 922. The Bluetooth interface 1013 and
USB interface 1012 respectively interact with either the bluetooth
module 1004 or the USB module to communicate with the programmer
912.
[0121] The communication antenna 1006 and a TX antenna 1008 may,
for example, be configured in a variety of sizes and form factors,
including, but not limited to a patch antenna, a slot antenna, or a
dipole antenna. The TX antenna 1008 may be adapted to transmit a
transmission signal, in addition to power, to the implantable,
passive neural stimulator 922. As discussed above, an output signal
generated by the microcontroller 908 may be used by the modulator
909 to provide the instructions for creation of a modulated RF
carrier signal. The RF carrier signal may be amplified by amplifier
906 to generate the transmission signal. A directional coupler 1009
may be utilized to provide two-way coupling so that both the
forward power of the transmission signal flow transmitted by the TX
antenna 1008 and the reverse power of the reflected transmission
may be picked up by power detector 1022 of telemetry feedback
module 1002. In some implementations, a separate communication
antenna 1006 may function as the receive antenna for receiving
telemetry feedback signal from the wireless stimulation device 922.
In some configurations, the communication antenna may operate at a
higher frequency band than the TX antenna 1008. For example, the
communication antenna 1006 may have a characteristic frequency that
is a second harmonic of the characteristic frequency of TX antenna
1008, as discussed above.
[0122] In some embodiments, the microwave field stimulator 902 may
additionally include a telemetry feedback module 902. In some
implementations, the telemetry feedback module 1002 may be coupled
directly to communication antenna 1006 to receive telemetry
feedback signals. The power detector 1022 may provide a reading of
both the forward power of the transmission signal and a reverse
power of a portion of the transmission signal that is reflected
during transmission. The telemetry signal, forward power reading,
and reverse power reading may be amplified by low noise amplifier
(LNA) 1024 for further processing. For example, the telemetry
module 902 may be configured to process the telemetry feedback
signal by demodulating the telemetry feedback signal to extract the
encoded information. Such encoded information may include, for
example, a status of the wireless stimulation device 922 and one or
more electrical parameters associated with a particular channel
(electrode) of the wireless stimulation device 922. Based on the
decoded information, the telemetry feedback module 1002 may be used
to calculate a desired operational characteristic for the wireless
stimulation device 922.
[0123] Some embodiments of the MFS 902 may further include a power
management module 1004. A power management module 1004 may manage
various power sources for the MFS 902. Example power sources
include, but are not limited to, lithium-ion or lithium polymer
batteries. The power management module 1004 may provide several
operational modes to save battery power. Example operation modes
may include, but are not limited to, a regular mode, a low power
mode, a sleep mode, a deep sleep/hibernate mode, and an off mode.
The regular mode provides regulation of the transmission of
transmission signals and stimulus to the wireless stimulation
device 922. In regular mode, the telemetry feedback signal is
received and processed to monitor the stimuli as normal. Low-power
mode also provides regulation of the transmission of transmission
signals and stimulus to the electrodes of the wireless stimulation
device. However, under this mode, the telemetry feedback signal may
be ignored. More specifically, the telemetry feedback signal
encoding the stimulus power may be ignored, thereby saving MFS 902
overall power consumption. Under sleep mode, the transceiver and
amplifier 906 are turned off, while the microcontroller is kept on
with the last saved state in its memory. Under the deep
sleep/hibernate mode, the transceiver and amplifier 906 are turned
off, while the microcontroller is in power down mode, but power
regulators are on. Under the off mode, all transceiver,
microcontroller and regulators are turned off achieving zero
quiescent power.
[0124] FIG. 11 is a flowchart showing an example process in which
the microwave field stimulator 902 transmits polarity setting
information to the wireless stimulation device 922. Polarity
assignment information is stored in a non-volatile memory 1102
within the microcontroller 908 of the MFS 902. The polarity
assignment information may be representative-specific and may be
chosen to meet the specific need of a particular patient. Based on
the polarity assignment information chosen for a particular
patient, the microcontroller 908 executes a specific routine for
assigning polarity to each electrode of the electrode array. The
particular patient has an wireless stimulation device as described
above.
[0125] In some implementations, the polarity assignment procedure
includes sending a signal to the wireless stimulation device with
an initial power-on portion followed by a configuration portion
that encodes the polarity assignments. The power-on portion may,
for example, simply include the RF carrier signal. The initial
power-on portion has a duration that is sufficient to power-on the
wireless stimulation device and allow the device to reset into a
configuration mode. Once in the configuration mode, the device
reads the encoded information in the configuration portion and sets
the polarity of the electrodes as indicated by the encoded
information.
[0126] Thus, in some implementations, the microcontroller 908 turns
on the modulator 909 so that the unmodulated RF carrier is sent to
the wireless stimulation device 1104. After a set duration, the
microcontroller 908 automatically initiates transmitting
information encoding the polarity assignment. In this scenario, the
microcontroller 908 transmits the polarity settings in the absence
of handshake signals from the wireless stimulation device. Because
the microwave field stimulator 902 is operating in close proximity
to wireless stimulation device 922, signal degradation may not be
severe enough to warrant the use of handshake signals to improve
quality of communication.
[0127] To transmit the polarity information, the microcontroller
908 reads the polarity assignment information from the non-volatile
memory and generates a digital signal encoding the polarity
information 1106. The digital signal encoding the polarity
information may be converted to an analog signal, for example, by a
digital-to-analog (DAC) converter 1112. The analog signal encoding
the waveform may modulate a carrier signal at modulator 909 to
generate a configuration portion of the transmission signal (1114).
This configuration portion of the transmission signal may be
amplified by the power amplifier 906 to generate the signal to be
transmitted by antenna 907 (1116). Thereafter, the configuration
portion of the transmission signal is transmitted to the wireless
stimulation device 922 (1118).
[0128] Once the configuration portion is transmitted to the
wireless stimulation device, the microcontroller 908 initiates the
stimulation portion of the transmission signal. Similar to the
configuration portion, the microcontroller 908 generates a digital
signal that encodes the stimulation waveform. The digital signal is
converted to an analog signal using the DAC. The analog signal is
then used to modulate a carrier signal at modulator 909 to generate
a stimulation portion of the transmission signal.
[0129] In other implementations, the microcontroller 908 initiates
the polarity assignment protocol after the microcontroller 908 has
recognized a power-on reset signal transmitted by the neural
stimulator. The power-on reset signal may be extracted from a
feedback signal received by microcontroller 908 from the wireless
stimulation device 922. The feedback signal may also be known as a
handshake signal in that it alerts the microwave field stimulator
902 of the ready status of the wireless stimulation device 922. In
an example, the feedback signal may be demodulated and sampled to
digital domain before the power-on reset signal is extracted in the
digital domain.
[0130] FIG. 12 is a flow chart showing an example of the process in
which the microwave field stimulator 902 receives and processes the
telemetry feedback signal to make adjustments to subsequent
transmissions.
[0131] In some implementations, the microcontroller 908 polls the
telemetry feedback module 1002 (1212). The polling is to determine
whether a telemetry feedback signal has been received (1214). The
telemetry feedback signal may include information based on which
the MFS 902 may ascertain the power consumption being utilized by
the electrodes of the wireless stimulation device 922. This
information may also be used to determine the operational
characteristics of the combination system of the MFS 902 and the
wireless stimulation device 922, as will be discussed in further
detail in association with FIG. 13. The information may also be
logged by the microwave field stimulator 902 so that the response
of the patient may be correlated with past treatments received over
time. The correlation may reveal the patient's individual response
to the treatments the patient has received up to date.
[0132] If the microcontroller 908 determines that telemetry
feedback module 1002 has not yet received telemetry feedback
signal, microcontroller 908 may continue polling (1212). If the
microcontroller 908 determines that telemetry feedback module 1002
has received telemetry feedback signal, the microcontroller 908 may
extract the information contained in the telemetry feedback signal
to perform calculations (1216). The extraction may be performed by
demodulating the telemetry feedback signal and sampling the
demodulated signal in the digital domain. The calculations may
reveal operational characteristics of the wireless stimulation
device 922, including, for example, voltage or current levels
associated with a particular electrode, power consumption of a
particular electrode, and/or impedance of the tissue being
stimulated through the electrodes.
[0133] Thereafter, in certain embodiments, the microcontroller 908
may store information extracted from the telemetry signals as well
as the calculation results (1218). The stored data may be provided
to a user through the programmer upon request (1220). The user may
be the patient, the doctor, or representatives from the
manufacturer. The data may be stored in a non-volatile memory, such
as, for example, NAND flash memory or EEPROM.
[0134] In other embodiments, a power management schema may be
triggered 1222 by the microcontroller (908). Under the power
management schema, the microcontroller 908 may determine whether to
adjust a parameter of subsequent transmissions (1224). The
parameter may be amplitude or the stimulation waveform shape. In
one implementation, the amplitude level may be adjusted based on a
lookup table showing a relationship between the amplitude level and
a corresponding power applied to the tissue through the electrodes.
In one implementation, the waveform shape may be pre-distorted to
compensate for a frequency response of the microwave field
stimulator 902 and the wireless stimulation device 922. The
parameter may also be the carrier frequency of the transmission
signal. For example, the carrier frequency of the transmission
signal may be modified to provide fine-tuning that improves
transmission efficiency.
[0135] If an adjustment is made, the subsequently transmitted
transmission signals are adjusted accordingly. If no adjustment is
made, the microcontroller 908 may proceed back to polling the
telemetry feedback module 1002 for telemetry feedback signal
(1212).
[0136] In other implementations, instead of polling the telemetry
feedback module 1002, the microcontroller 908 may wait for an
interrupt request from telemetry feedback module 1002. The
interrupt may be a software interrupt, for example, through an
exception handler of the application program. The interrupt may
also be a hardware interrupt, for example, a hardware event and
handled by an exception handler of the underlying operating
system.
[0137] FIG. 13 is a schematic of an example implementation of the
power, signal and control flow for the wireless stimulation device
922. A DC source 1302 obtains energy from the transmission signal
received at the wireless stimulation device 922 during the initial
power-on portion of the transmission signal while the RF power is
ramping up. In one implementation, a rectifier may rectify the
received power-on portion to generate the DC source 1302 and a
capacitor 1304 may store a charge from the rectified signal during
the initial portion. When the stored charge reaches a certain
voltage (for example, one sufficient or close to sufficient to
power operations of the wireless stimulation device 922), the
power-on reset circuit 1306 may be triggered to send a power-on
reset signal to reset components of the neural stimulator. The
power-on set signal may be sent to circuit 1308 to reset, for
example, digital registers, digital switches, digital logic, or
other digital components, such as transmit and receive logic 1310.
The digital components may also be associated with a control module
1312. For example, a control module 1312 may include electrode
control 252, register file 732, etc. The power-on reset may reset
the digital logic so that the circuit 1308 begins operating from a
known, initial state.
[0138] In some implementations, the power-on reset signal may
subsequently cause the FPGA circuit 1308 to transmit a power-on
reset telemetry signal back to MFS 902 to indicate that the
implantable wireless stimulation device 922 is ready to receive the
configuration portion of the transmission signal that contains the
polarity assignment information. For example, the control module
1312 may signal the RX/TX module 1310 to send the power-on reset
telemetry signal to the telemetry antenna 1332 for transmission to
MFS 902.
[0139] In other implementations, the power-on reset telemetry
signal may not be provided. As discussed above, due to the
proximity between MFS 902 and implantable, passive neural
stimulator 922, signal degradation due to propagation loss may not
be severe enough to warrant implementations of handshake signals
from the implantable, passive stimulator 922 in response to the
transmission signal. In addition, the operational efficiency of
implantable, passive neural stimulator 922 may be another factor
that weighs against implementing handshake signals.
[0140] Once the FPGA circuit 1308 has been reset to an initial
state, the FPGA circuit 1308 transitions to a configuration mode
configured to read polarity assignments encoded on the received
transmission signal during the configuration state. In some
implementations, the configuration portion of the transmission
signal may arrive at the wireless stimulation device through the RX
antenna 1334. The transmission signal received may provide an AC
source 1314. The AC source 1314 may be at the carrier frequency of
the transmission signal, for example, from about 300 MHz to about
8.
[0141] Thereafter, the control module 1312 may read the polarity
assignment information and set the polarity for each electrode
through the analog mux control 1316 according to the polarity
assignment information in the configuration portion of the received
transmission signal. The electrode interface 252 may be one example
of analog mux control 1316, which may provide a channel to a
respective electrode of the implantable wireless stimulation device
922.
[0142] Once the polarity for each electrode is set through the
analog mux control 1316, the implantable wireless stimulation
device 922 is ready to receive the stimulation waveforms. Some
implementations may not employ a handshake signal to indicate the
wireless stimulation device 922 is ready to receive the stimulation
waveforms. Rather, the transmission signal may automatically
transition from the configuration portion to the stimulation
portion. In other implementations, the implantable wireless
stimulation device 922 may provide a handshake signal to inform the
MFS 902 that implantable wireless stimulation device 922 is ready
to receive the stimulation portion of the transmission signal. The
handshake signal, if implemented, may be provided by RX/TX module
1310 and transmitted by telemetry antenna 1332.
[0143] In some implementations, the stimulation portion of the
transmission signal may also arrive at implantable wireless
stimulation device through the RX antenna 1334. The transmission
signal received may provide an AC source 1314. The AC source 1314
may be at the carrier frequency of the transmission signal, for
example, from about 300 MHz to about 8 GHz. The stimulation portion
may be rectified and conditioned in accordance with discussions
above to provide an extracted stimulation waveform. The extracted
stimulation waveform may be applied to each electrode of the
implantable wireless stimulation device 922. In some embodiments,
the application of the stimulation waveform may be concurrent,
i.e., applied to the electrodes all at once. As discussed above,
the polarity of each electrode has already been set and the
stimulation waveform has been applied to the electrodes in
accordance with the polarity settings for the corresponding
channel.
[0144] In some implementations, each channel of analog mux control
1316 is connected to a corresponding electrode and may have a
reference resistor placed serially. For example, FIG. 13 shows
reference resistors 1322, 1324, 1326, and 1328 in a serial
connection with a matching channel. Analog mux control 1316 may
additionally include a calibration resistor 1320 placed in a
separate and grounded channel. The calibration resistor 1320 is in
parallel with a given electrode on a particular channel. The
reference resistors 1322, 1324, 1326, and 1328 as well as the
calibration resistor 1320 may also be known as sensing resistors
718. These resistors may sense an electrical parameter in a given
channel, as discussed below.
[0145] In some configurations, an analog controlled carrier
modulator may receive a differential voltage that is used to
determine the carrier frequency that should be generated. The
generated carrier frequency may be proportional to the differential
voltage. An example analog controlled carrier modulator is VCO
733.
[0146] In one configuration, the carrier frequency may indicate an
absolute voltage, measured in terms of the relative difference from
a pre-determined and known voltage. For example, the differential
voltage may be the difference between a voltage across a reference
resistor connected to a channel under measurement and a standard
voltage. The differential voltage may be the difference between a
voltage across calibration resistor 1320 and the standard voltage.
One example standard voltage may be the ground.
[0147] In another configuration, the carrier frequency may reveal
an impedance characteristic of a given channel. For example, the
differential voltage may be the difference between the voltage at
the electrode connected to the channel under measurement and a
voltage across the reference resistor in series. Because of the
serial connection, a comparison of the voltage across the reference
resistor and the voltage at the electrode would indicate the
impedance of the underlying tissue being stimulated relative to the
impedance of the reference resistor. As the reference resistor's
impedance is known, the impedance of the underlying tissue being
stimulated may be inferred based on the resulting carrier
frequency.
[0148] For example, the differential voltage may be the difference
between a voltage at the calibration resistor and a voltage across
the reference resistor. Because the calibration resistor is placed
in parallel to a given channel, the voltage at the calibration is
substantially the same as the voltage at the given channel. Because
the reference resistor is in a serial connection with the given
channel, the voltage at the reference resistor is a part of the
voltage across the given channel. Thus, the difference between the
voltage at the calibration resistor and the voltage across the
reference resistor correspond to the voltage drop at the electrode.
Hence, the voltage at the electrode may be inferred based on the
voltage difference.
[0149] In yet another configuration, the carrier frequency may
provide a reading of a current. For example, if the voltage over
reference resistor 1322 has been measured, as discussed above, the
current going through reference resistor and the corresponding
channel may be inferred by dividing the measured voltage by the
impedance of reference resistor 1322.
[0150] Many variations may exist in accordance with the
specifically disclosed examples above. The examples and their
variations may sense one or more electrical parameters concurrently
and may use the concurrently sensed electrical parameters to drive
an analog controlled modulator device. The resulting carrier
frequency varies with the differential of the concurrent
measurements. The telemetry feedback signal may include a signal at
the resulting carrier frequency.
[0151] The MFS 902 may determine the carrier frequency variation by
demodulating at a fixed frequency and measure phase shift
accumulation caused by the carrier frequency variation. Generally,
a few cycles of RF waves at the resulting carrier frequency may be
sufficient to resolve the underlying carrier frequency variation.
The determined variation may indicate an operation characteristic
of the implantable wireless stimulation device 922. The operation
characteristics may include an impedance, a power, a voltage, a
current, etc. The operation characteristics may be associated with
an individual channel. Therefore, the sensing and carrier frequency
modulation may be channel specific and applied to one channel at a
given time. Consequently, the telemetry feedback signal may be time
shared by the various channels of the implantable wireless
stimulation device 922.
[0152] In one configuration, the analog MUX 1318 may be used by the
controller module 1312 to select a particular channel in a
time-sharing scheme. The sensed information for the particular
channel, for example, in the form of a carrier frequency
modulation, may be routed to RX/TX module 1310. Thereafter, RX/TX
module 1310 transmits, through the telemetry antenna 1332, to the
MFS 902, the telemetry feedback encoding the sensed information for
the particular channel.
[0153] Referring now to FIGS. 14A to 14D, a connector device 1400
includes a housing 1401 having a distal end 1402 for mating or
coupling with an implantable device, such as an implantable
stimulation lead (not shown) or other implantable electrical
devices, such as a pacemaker or the like. As discussed above, a
implantable stimulation lead may include one or more electrodes,
for example, arranged in pairs. Each electrode may couple to a
connector configured to be driven by an excitation waveform. The
excitation waveforms may cause electric charges to be released at
an implantation site to excite an excitable tissue. As illustrated
in FIGS. 14A and 14B, housing 1401 includes a hollow tube with an
opening 1403 at the distal end 1402 of housing 1401. Opening 1403
is configured to receive the proximal end of the implantable
device. The distal end 1402 also includes a set screw 1404 for
tightening the distal end 1402 of housing 1401 around the proximal
end of an implantable device. Housing 1401 may have a small profile
to fit in an introducer, such as the inner space of a cannula or a
syringe. In one configuration, housing 1401 may be small enough to
pass through a 22 gauge tube. In other configurations, housing 1401
may be small enough to pass through a 12, 14, or 18 gauge tube.
Housing 1401 may include a biocompatible coating material, such as
polyurethane, silicon or the like and may have a length of 2-20 cm,
preferably about 2-10 cm. The overall length of housing 1401 may be
from about ten to fifty centimeters. Generally, housing 1401 may be
flexible, and capable of being bent during a deployment procedure.
Housing 1401 may also include a bio-compatible coating to reduce
tissue coagulation. The bio-compatible coating may also be
electrically insulating.
[0154] As shown in FIG. 14B, connector device 1400 includes one or
more connection pads 1406 spaced apart from one another along the
inside surface of the distal end of device 1400. The shape of the
metallic connection pads may be circumferential or circular. In
particular, connection pads 1406 are circumferentially shaped and
include conductive, corrosion resistant, biocompatible material,
such as platinum, platinum-iridium, gallium-nitride,
titanium-nitride, iridium-oxide or the like. As shown, each of the
connection pads 1406 is a circular ring that extends
circumferentially around the inner surface of the housing 1401 such
that a central axis of the connection pads 1406 is coaxial with a
central axis of the housing 1401. The connection pads 1406 may be
separated, for example, by anywhere between about 1 mm to 10 mm.
The connection pads include two to eight individual connection
pads. Connection pads 1406 may be configured to mate with
connectors of electrodes of an implantable lead. The mating may be
achieved by form fit in which the shape of a connection pad
compliments the shape of a corresponding connector such that the
connection pad and the complimentary connect snap into each other.
The connectors of electrodes of an implantable lead may also be
known as electrode contacts. In some implementations, housing 1401
may be in the shape of a hollow tube and the connection pads may
form one or more rings along the inner surface of housing 1401. In
particular, the rings may be spaced along a direction coaxial to
the central axis of the hallow tube. In other words, the connector
pads 1406 may be spaced longitudinally within housing 1401.
[0155] The Connector receiver device 1400 further includes one or
more antennas 1408 and flexible microelectronic circuitry 1410
coupling the antennas 1408 to the connection pads 1406. Antennas
1408 receive an input signal through radiative coupling from a
remote source exterior to connector receiver device 1400. As
described in detail above, the source may be located outside a
patient's body. The source may also be known as a pulse generator.
The input signal transmitted through radiative coupling and
received by antennas 1408 may include wireless energy and waveform
parameters. Based on the input signal, microelectronic circuitry
1410 may harvest the electric energy and excitation waveforms for
driving an implantable lead through connection pads 1406.
Specifically, circuitry 1410 converts waveform parameters from the
input signal into electrical impulses and distributes the
electrical impulses through wires in housing 1401 to connection
pads 1406. The material of the metallic connection pads 1406 may
include a conductive, corrosion resistant, biocompatible material
like platinum, platinum-iridium, gallium-nitride, titanium-nitride,
or iridium-oxide. The non-inductive antennas may include two to ten
non-inductive antennas, each having a length from about 0.25 cm to
12 cm. The non-inductive antennas may include patch antennas.
[0156] During a deployment procedure, the connection pads are
affixed to at least one connector of an electrode of an implantable
lead, as discussed above, to form an electric connection from the
connection pads to the at least one connector of an implantable
lead. In some implementations, the electric connection may be
formed in-situ, i.e., during the procedure and inside the patient's
body. As noted above, housing 1401 can be as small as the inner
diameter of a 22-gauge tube. Set screw 1401 may have a commensurate
size. During the deployment procedure, when, for example, the
patient has an existing stimulation lead already implanted, housing
1401 may be surgically introduced into the patient body. The
proximal end of the implanted stimulation lead may be inserted into
housing 1402 through opening 1403. Set screw 1404 may be tightened
to couple connection pads 1406 inside housing 1401 with connections
of electrodes on the implanted stimulation lead. In some
implementations, set screw 1404 may be manipulated by a screw
driver. Thereafter, the incision entry point may be sutured.
Because of the small size of housing 1401 and set screw 1404, the
incision can made of a commensurate size to reduce trauma and
improve healing. Once connector device 1400 has been embedded,
non-inductive antenna 1408 may receive an input signal from a
source exterior to the patient's body. Microelectronic circuitry
1410 may harvest electric energy and waveform parameters from the
input signal to generate one or more electric impulses. Connection
pads 1406 may distribute the electric impulses to connectors of the
implantable lead so that the electrodes of the implantable lead may
release charges to at the implantation site to excite the excitable
tissue.
[0157] As noted herein, the electric connection may be formed
in-situ. In contrast, some devices may form such electric
connections before the device has been implanted inside the body of
a subject patient, as noted above.
[0158] The input signal may include wireless power and modulation
instructions for generating one or more electrical impulses at the
electrodes of the implantable lead. The electrical impulse(s) may
have a frequency of 10,000 Hz or less and a pulse width of 1 ms or
less. The duty cycle may be less than 10%. In certain embodiments,
the frequency may be between about 1-500 Hz. The receiving
antenna(s) may include dipole antennas or the like that receive the
input signal through electrical radiative coupling, as discussed in
detail above.
[0159] Microelectronic circuitry 1410 may include flexible circuits
between about 15 mm to 90 mm long, 0.7 mm to 2.0 mm wide and about
0.2 mm to 0.4 mm high. The flexible circuits, when placed inside
the circumferential housing 1401, undergo a bend radius of about
0.0 mm to 0.5 mm. The flexible circuits may include diodes and
charge balancing components (not shown) to condition the wireless
power and produce a suitable stimulation waveform that is routed to
the connection pads 1406, as discussed above. In certain
implementations, circuitry 1410 may include a conductive trace
feature (not shown) that functions as an antenna. In other
embodiments, non-inductive antennas 1406 are fabricated with
conductive wires connected to circuitry 1410.
[0160] FIG. 14C illustrates connector receiver device 1400
comprising a housing 1401 with a distal connector terminal 1403
designed for receiving an implantable lead, such as a paddle lead.
As in the previous embodiment, housing 1401 comprises connection
pads 1406, circuitry 1410, and antennas 1408 to receive the input
signal and transmitting electrical impulses to the implantable lead
(not shown) being mated through distal connector terminal 1403.
Housing 1401 also includes a set screw 1404 for attaching the
distal connector terminal 1403 to the proximal end of the
implantable lead. Stopper 1412 may prevent the proximal end from
advancing too far into the connector terminal to cause damage to
microelectronic circuit 1410. As noted herein, set screw may be
used to affix connectors on an implantable lead to connection pads
houses in the distal connector terminal 1403 of housing 1401. The
connectors on the implantable lead may be coupled to the electrodes
on the implantable lead (not shown). Housing 1401 may include a
height profile of between 1.0 mm and 1.3 mm, which allows for
multiple implantable leads (for example, paddle connector
stimulators) to be mated with housing 1501 concurrently (at one
time) and sequentially (at different times). In configuration, the
mating may occur before the mated connector-leads assembly are
placed inside the patient. The mated connection device 1400 and
implanted leads may be introduced into a patient's body through an
introducer (not shown). In another configuration, the mating may
occur during the placement procedure. Through an incision on the
patient's body, a screw driver may tighten set screw 1404 to affix
the connection pads 1406 to at least one connection on the
implantable lead.
[0161] FIG. 14D illustrates connector receiver device 1400
including a hollow tube enclosure 1401 that houses circumferential
connection pads 1406, non-inductive antennas 1408 and a flexible
electronic circuit 1410 that couples pads 1804 to antennas 1806.
Connector receiver device 1400 may include between 1-4 flexible
circuits 1410, typically between 15 mm and 90 mm long, and 0.7 mm
and 2.0 mm wide.
[0162] FIG. 15 illustrates an exemplary method of mating a
connector device 1400 with an implanted lead 1500. In some
implementations, a patient may have a lead 1500 already implanted.
Connection receiver device 1500 is advanced into the patient body.
The advancement may be through an incision entry on the patient's
body. Thereafter, connection receiver device 1400 may mate with
implanted lead 1500 by moving the connection receiver device 1400
and lead 1500 relative to each other such that the lead 1500 passes
through distal opening 1403 in connector receiver device 1400 until
the connectors 1502 on implanted lead 1500 are mated with
connection pads 1406 on the inside of connector device 1400.
Connectors 1502 are the ring structures as shown in FIG. 15 and are
connected to electrodes on the distal end (not shown) of the
implanted lead 1500. The implanted lead 1500 may include a standard
commercial percutaneous or paddle lead. A set screw 1404 on
connector receiver device 1400 is then tightened down to insure
that connectors 1502 remain fixed to connection pads 1406 on
connector receiver device 1400. The antenna(s) are connected via
conducting wires within connector receiver device 1400 to the
microelectronic circuit 1410 (e.g., waveform conditioning
circuitry) within the proximal end of connection receiver device
1400. Thereafter, introducer devices may be withdrawn and the
incision point may be sutured. After both the connector receiver
device 1400 and lead 1500 have been implanted at the target site
within the patient, a subcutaneous anchor (not shown) may be used
to mitigate vertical and horizontal migration of the combined
device. As noted above, the small size of housing 1401 and set
screw 1404 may give rise to smaller incision points and the use of
smaller incision devices and screw tightening devices. The smaller
sizes can lead to reduced trauma during the deployment procedure
and improved healing after the deployment procedure.
[0163] A method for modulating a target nerve in a patient can now
be described. As discussed above, connector receiver device 1400 is
coupled to an implantable lead 1500 by mating the male end of lead
1500 with the female distal end of device 1400. Set screw 1404 may
then be tightened down and the combined device is implanted at a
target site within the patient. In some embodiments, an introducer,
such as a cannula or the like, is advanced to a target site within
the patient adjacent to excitable tissue, such as a target nerve.
The introducer may be advanced through a percutaneous penetration
in the patient, through an endoscopic opening in the patient, or
directly in an open surgical procedure.
[0164] Once connector receiver device 1400 and lead 1500 are
suitably positioned at the target site, an input signal is
delivered to one or more receiving antenna(s) (not shown) in
connector receiver device 1400 from an external transmitting
antenna and controller located outside of the patient's body. As
discussed in detail above, the input signal preferably contains
energy and waveform parameters. Circuitry within connector receiver
device 1400 converts the waveform parameters into one or more
electrical impulses that are delivered through connection pads 1406
to electrodes within lead and on to the nerve sufficient to
modulate the nerve. For example, the electrical impulses may be
sufficient to generate an action potential in the nerve to treat
chronic pain or a disorder in the patient.
[0165] In some implementations, the connector receiver device may
be implanted into a person to stimulate the spinal cord to treat
pain after mating with the existing commercially available systems.
The small incision at the skin is stitched with a suture or sterile
strip after placement of the anchoring mechanism.
[0166] FIG. 16 illustrates an embodiment of a Y-shaped connector
device 1600 comprising a hollow tube housing 1602 with a distal
connection terminal 1604 having first and second internal tubes
1606, 1608. In one embodiment, first tube 1606 is configured to
receive an implantable lead (not shown) for mating connection pads
within device 1600 with the connectors of electrodes of the lead.
Second tube 1608 includes flexible circuitry for coupling the
connection pads with antennas in the proximal end of device 1600.
In another embodiment, first tube 1606 includes connection pads
coupled to an electronic circuit in housing 1602. First tube 1606
is configured to couple with a first implantable lead (not shown)
such that connection pads with the first tube are mated with
connectors of the electrodes of the first implantable lead.
Likewise, second tube 1608 also includes connection pads coupled to
an electronic circuit in housing 1602. Second tube 1608 is
configured to couple with a second implantable lead (not shown)
such that connection pads with the second tube are mated with
connectors of the electrodes of the second implantable lead.
[0167] In certain embodiments, the connecting device further
comprises recording electrodes and electronics for recording
sensing information and parameters regarding the electrical
impulses that are applied to the targeted nerve. The
recording/sensing electrodes may be separate from the stimulation
electrodes or they may be the same electrodes that used for the
stimulation. These parameters are transmitted wirelessly
(preferably through electrical radiative coupling as discussed
above) to receiving antennas (not shown) outside of the patient's
body. A controller (not shown), such as the microwave field
stimulator discussed above, receives the parameters from the
connector device and adjusts the input signal based on those
parameters. The adjusted input signal is then sent back to the
receiving antennas within the connector device such that the
electrical impulses may be adjusted in a closed-loop fashion.
[0168] Some or all of the implementations described in this may
have advantages compared to devices that include an implantable
lead with two or more electrodes attached by a wired connector to a
subcutaneous battery-operated implantable pulse generator (IPG) or
other charge storage to provide power and create the electrical
impulses carried by hard wire to the lead body containing the
electrodes.
[0169] In particular, some implementations may avoid the
disadvantages of IPG based systems with have several disadvantages,
such as: a large surgical pocket to house the implantable pulse
generator with a battery or charge storage component; extensions
and connectors between the IPG and the proximal end of the lead
that are housed under the skin, and a need to recharge or explant
the IPG. Having the IPG tethered to the implant within the
patient's body may be a disadvantage because this connection can
cause lead migration and the possibility for loss of therapy from a
disconnection from the IPG. Placement of an IPG also requires an
invasive surgical procedure, as the physician must create a pocket
of a substantial size of 18 to 75 cc within the body of the
patient, typically around the abdomen or buttocks area. Tunneling
may also be required to connect the IPG to the proximal end of the
lead located at the targeted nerves. The lead or extension wires
must be routed under the skin to reach the wired implantable lead.
However, devices that utilize a battery-powered or charge-storage
component are no longer functional once the battery cannot be
recharged or charge cannot be stored. Consequently, for an
implanted device, a patient would need to undergo a subsequent
surgical procedure to obtain a functional replacement device.
[0170] IPG based systems are also associated with numerous failure
modes, including, for example, mechanical dislodgement due to
motion, acceleration and impingement of the lead electrode
assembly, infection and uncomfortable irritation. In addition,
wires leads have severe limitations with respect to the ability to
precisely position the leads close to the targeted nerve fibers,
weakening the signal and/or requiring greater power to reach the
targeted nerves. Increased power consumption can decrease battery
life, which may require more frequency surgical replacement of the
implanted battery. Failure to place the leads in the proper
position can also lead to sub-optimal clinical outcomes and/or
potential undesired stimulation of non-targeted tissues within the
body, such as activation of muscle responses.
[0171] 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.
* * * * *