Title: Systems and methods for communicating with implantable devices
Abstract: Systems and methods for communicating with an implant within a patient's body using acoustic telemetry includes an external communications device attachable to the patient's skin. The device includes an acoustic transducer for transmitting acoustic signals into the patient's body and/or for receiving acoustic signals from the implant. The device includes a battery for providing electrical energy to operate the device, a processor for extracting data from acoustic signals received from the implant, and memory for storing the data. The device may include an interface for communicating with a recorder or computer, e.g., to transfer data from the implant and/or to receive instructions for controlling the implant. The device is secured to the patient's skin for controlling, monitoring, or otherwise communicating with the implant, while allowing the patient to remain mobile.
Patent Number: 7,024,248 Issued on 04/04/2006 to Penner, et al.
| Inventors:
|
Penner; Avl (Tel Aviv, IL);
Doron; Eyal (Kiryat Yam, IL)
|
| Assignee:
|
Remon Medical Technologies LTD (IL)
|
| Appl. No.:
|
989912 |
| Filed:
|
November 19, 2001 |
| Current U.S. Class: |
607/60; 607/30; 607/32; 128/903 |
| Current Intern'l Class: |
A61N 1/18 (20060101) |
| Field of Search: |
607/30-32,55-57,59-62
128/903
|
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| 4481950 | Nov., 1984 | Duggan.
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| 4651740 | Mar., 1987 | Schroeppel.
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| 4793825 | Dec., 1988 | Benjamin et al.
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| 5113859 | May., 1992 | Funke.
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| 5833603 | Nov., 1998 | Kovacs et al.
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| 6140740 | Oct., 2000 | Porat et al.
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| 6162238 | Dec., 2000 | Kaplan et al.
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| 6170488 | Jan., 2001 | Spillman et al.
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| 6200265 | Mar., 2001 | Walsh et al.
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| 6248080 | Jun., 2001 | Miesel et al.
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| 6764446 | Jul., 2004 | Wolinsky et al.
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| 2002/0045921 | Apr., 2002 | Lone et al.
| |
| Foreign Patent Documents |
| WO 99-3445/3 | Jul., 1999 | WO.
| |
| WO 00/4710/9 | Aug., 2000 | WO.
| |
| WO 01-2862/7 | Apr., 2001 | WO.
| |
| WO 01-7427/8 | Oct., 2001 | WO.
| |
| WO 02/0334/7 | Jan., 2002 | WO.
| |
Other References
Y. Porat, , et al., "Method for Transfer of Energy to an Electronic Circuit Implanted
in a Living Body and a Device for Such Method", PCT Publication No. WO 98/43338,
Oct. 1, 1998.
M. M. Friedman, "Piezoelectric Transducer", PCT Publication No. WO 99/34453,
Jul. 8, 1999.
|
Primary Examiner: Layno; Carl
Attorney, Agent or Firm: Bingham McCutchen LLP
Parent Case Text
This application is a Continuation-in-Part of application Ser. No. 09/690,615,
filed Oct. 16, 2000 now U.S. Pat. No. 6,628,989 granted Sep. 30, 2003 and entitled
"Acoustic Switch and Apparatus and Methods for Using Acoustic Switches Within a
Body," the disclosure of which is expressly incorporated herein by reference.
Claims
What is claimed is:
1. A system for activating an implant within a body, comprising:
an external controller for contacting an exterior surface of a patient's body,
the controller comprising a controller transducer for transmitting an acoustic
control signal into the patient's body, and an energy source for powering the controller
transducer; and
an implant for placement within the patient's body, the implant comprising an
electrical circuit configured for performing one or more commands when the implant
is activated, an energy storage device, a switch coupled between the electrical
circuit and the energy storage device, and an acoustic implant transducer coupled
to the switch, the implant transducer configured for receiving the control signal
from the controller transducer, the switch being closed in response to the control
signal to allow current flow from the energy storage device to the electrical circuit,
thereby activate the implant.
2. The system of claim 1, wherein the controller transducer is configured for
transmitting first and second a acoustic control signals separated by a predetermined
delay, and wherein the switch is configured to close only when the implant transducer
receives the first and second control signals separated by the predetermined delay.
3. The system of claim 1, the controller further comprising a processor for controlling
the controller transducer to transmit one of a first acoustic control signal and
a second acoustic control signal, wherein the switch is closed when the first control
signal is received by the implant transducer, and opened when the second control
signal is received by the implant transducer.
4. The system of claim 1, the implant further comprising a sensor coupled to
the electrical circuit, the one or more commands comprising measuring a physiological
parameter within the body using the sensor.
5. The system of claim 4, wherein the implant transducer is configured for transmitting
an acoustic data signal to the controller, the data signal comprising sensor data
indicative of the physiological parameter, and wherein the controller transducer
is configured for receiving the data signal from the implant.
6. The system of claim 5, wherein the controller further comprises memory for
storing the sensor data.
7. The system of claim 5, wherein the controller further comprises a processor
for extracting the sensor data from the data signal.
8. The system of claim 7, wherein the controller further comprises an interface
for transferring the extracted sensor data to an external electronic device separate
from the controller.
9. The system of claim 1, further comprising a therapeutic device coupled to
the electrical circuit, the electrical circuit being configured for controlling
the therapeutic device.
10. The system of claim 1, wherein the energy storage device comprises a rechargeable
device, and wherein the system further comprises an external charger configured
for placement against an exterior surface of the patient's body, the charger comprising
a source of electrical energy and a an energy exchange transducer the energy exchange
transducer configured for converting electrical energy from the source of electrical
energy into acoustic energy and transmitting an acoustic energy signal comprising
the acoustic energy into the patient's body.
11. The system of claim 10, wherein the implant transducer is further configured
for converting the acoustic energy signal into electrical energy for recharging
the energy storage device.
12. The system of claim 1, further comprising an adhesive for securing the controller
to the exterior surface of the patient's body.
13. The system of claim 1, wherein the controller is carried by a patch attachable
to the exterior surface of the patient's skin body.
14. The system of claim 1, the implant further comprising an actuator coupled
to the electrical circuit, the one or more commands comprising activating the actuator
to control a therapeutic device coupled to the actuator.
15. The system of claim 1, wherein the external controller is adapted to be coupled
to the exterior surface of the patient's body.
16. The system of claim 1, wherein the external controller is adapted to be secured
to the exterior surface of the patient's body.
17. A method for communicating with an implant located within a patient's body,
the implant comprising an acoustic implant transducer configured for communicating
using acoustic telemetry, the method comprising:
placing a portable communications device in contact with an exterior surface
of the patient's body, the communications device comprising one or more acoustic
transducers configured for communicating using acousitc telemetry, and an energy
source for providing electrical energy to operate the communications device; and
communicating with the implant using the one or more acoustic transducers to
transmit one or more acoustic signals from the communications device to the implant,
wherein upon receiving an acoustic signal, the acoustic implant transducer closes
a switch to allow electrical energy to flow from an energy storage device to power
the implant.
18. The method of claim 17, the one or more acoustic signals comprising a command
for controlling operation of the implant.
19. The method of claim 18, wherein the command comprises measuring a physiological
parameter within the body.
20. The method of claim 18, wherein the command comprises controlling a therapeutic
device coupled to the implant.
21. The method of claim 17, wherein communicating with the implant comprises
receiving one or more acoustic signals from the implant, the one or more acoustic
signals comprising data indicative of a physiological parameter measured by the implant.
22. The method of claim 21, further comprising extracting data from the one or
more acoustic signals received from the implant.
23. The method of claim 22, further comprising storing the extracted data in
a memory of the communications device.
24. The method of claim 22, further comprising transferring the extracted data
to an electronic device external to the patient's body.
25. The method of claim 21, further comprising charging the energy storage device
with an energy source located outside the patient's body.
26. The method of claim 24, wherein the energy source comprises a charger that
is separate from the communications device.
27. The method of claim 17, wherein the communications device comprises a patch
carrying the one or more acoustic transducers, and wherein placing the device in
contact with the patient's body comprises securing the patch to the exterior surface
of the patient's body.
28. The method of claim 27, wherein the one or more acoustic transducers are
acoustically coupled to the patient's body when the patch is secured to the exterior
surface of the patient's body.
29. The method of claim 17, wherein the portable communications device is coupled
to the exterior surface of the patient's body.
30. The method of claim 17, wherein the portable communications device is secured
to the exterior surface of the patient's body.
Description
FIELD OF THE INVENTION
The present invention relates generally to systems and methods for measuring
physiological conditions and/or performing therapeutic functions within a patient's
body, particularly to systems and methods for controlling and/or energizing devices
that may be implanted within a body, and more particularly to implants that may
be energized, activated, controlled, and/or otherwise communicate via acoustic energy.
BACKGROUND OF THE INVENTION
Devices are known that may be implanted within a patient's body for monitoring
one or more physiological conditions and/or to provide therapeutic functions. For
example, sensors or transducers may be located deep within the body for monitoring
a variety of properties, such as temperature, pressure, strain, fluid flow, chemical
properties, electrical properties, magnetic properties, and the like. In addition,
devices may be implanted that perform one or more therapeutic functions, such as
drug delivery, defibrillation, electrical stimulation, and the like.
Often it is desirable to communicate with such devices once they are implanted
within a patient by external command, for example, to obtain data, and/or to activate
or otherwise control the implant. An implant may include wire leads from the implant
to an exterior surface of the patient, thereby allowing an external controller
or other device to be directly coupled to the implant. Alternatively, the implant
may be remotely controlled, e.g., using an external induction device. For example,
an external radio frequency (RF) transmitter may be used to communicate with the
implant. RF energy, however, may only penetrate a few millimeters into a body,
because of the body's dielectric nature, and therefore may not be able to communicate
effectively with an implant that is located deep within the body. In addition,
although an RF transmitter may be able to induce a current within an implant, the
implant's receiving antenna, generally a low impedance coil, may generate a voltage
that is too low to provide a reliable switching mechanism.
In a further alternative, electromagnetic energy may be used to control an implant,
since a body generally does not attenuate magnetic fields. The presence of external
magnetic fields encountered by the patient during normal activity, however, may
expose the patient to the risk of false positives, i.e., accidental activation
or deactivation of the implant. Furthermore, external electromagnetic systems may
be cumbersome and may not be able to effectively transfer coded information to
an implant.
Accordingly, systems and methods for communicating with an implant that
may be implanted within a patient's body, such as a pressure sensor, a drug delivery
device, a pacemaker, or a nerve stimulator, would be considered useful.
SUMMARY OF THE INVENTION
The present invention is generally directed to systems and methods for communicating
with implants or other devices that are placed, e.g., using open surgical or minimally
invasive techniques, within a mammalian body. The implant may include one or more
sensors for monitoring pressure or other physiological parameters and/or may perform
one or more therapeutic functions. More particularly, the present invention is
directed to external systems for controlling, activating, energizing, and/or otherwise
communicating with such implants using acoustic telemetry, and to methods for using
such systems.
In accordance with one aspect of the present invention, a system is provided
for
communicating with an implant within a body that includes an external communications
device, e.g., a controller, securable to an exterior surface of a patient's body.
Preferably, the controller is sufficiently small and portable that it may remain
secured to the patient, possibly for extended time periods. For example, the device
may be attached to or within a patch that may be secured to a patient's skin.
In one embodiment, the device is an external controller that generally includes
one or more acoustic transducers, including a first acoustic transducer, for transmitting
one or more acoustic signals into the patient's body. The controller may also include
an energy source for powering the one or more acoustic transducers, and/or a processor
or other electrical circuit for controlling operation of the controller. In addition,
one or more of the acoustic transducers, such as the first acoustic transducer,
may be configured for receiving acoustic signals from an implant within the patient's
body. The controller may include memory for storing data, and the processor may
extract sensor data and/or other data from acoustic signals received from an implant,
e.g., for storage in the memory. In addition, the controller may include a connector,
lead, transmitter, receiver, or other interface for communicating with a recorder
or other electronic device, such as a computer, personal digital assistant, or
a wireless device, such as a cellular phone. The controller may be coupled to such
an electronic device for transferring sensor data or other data stored in the memory
of the controller and/or for receiving instructions or commands from the electronic device.
In addition, the system may include an implant for placement within the patient's
body. The implant may include an electrical circuit for performing one or more
commands when the implant is activated, an energy storage device, and/or one or
more acoustic transducers, e.g., a second acoustic transducer, coupled to the electrical
circuit and/or the energy storage device. Optionally, the electrical circuit may
include a switch coupled to the energy storage device and/or the second acoustic
transducer. The second acoustic transducer may receive one or more acoustic signals
from the first acoustic transducer of the external device. For example, the switch
may be closed and/or opened in response to a first acoustic signal to begin or
discontinue current flow from the energy storage device to the electrical circuit
or other components of the implant.
In a preferred embodiment, the external controller's processor controls the first
acoustic transducer to transmit a first acoustic signal/or and a second acoustic
signal. The switch of the implant may be closed when the first acoustic signal
is received by the second acoustic transducer, while the switch may be opened when
the second acoustic signal is received by the second acoustic transducer. In addition
or alternatively, the first acoustic transducer may transmit first and second acoustic
signals separated by a delay. The switch may be closed and/or opened only when
the second acoustic transducer receives the first and second acoustic signals separated
by a predetermined delay, thereby minimizing the risk of accidental activation
or deactivation of the implant.
In yet another alternative, the first acoustic transducer may transmit a first
acoustic signal, e.g., an activation signal, followed by a second acoustic signal,
e.g., including a set of commands. The second acoustic transducer may receive the
first and second acoustic signals, and the electrical circuit of the implant may
extract the set of commands from the second acoustic signal, and control operation
of the implant as instructed by the set of commands. In a further alternative,
the implant may run continuously or intermittently, and the external controller
may control, monitor, energize, and/or program the implant using acoustic telemetry
during operation of the implant.
In an exemplary embodiment, the implant may include a sensor coupled to the electrical
circuit, and the one or more commands may include measuring a physiological parameter
within the body using the sensor. The second acoustic transmitter may transmit
one or more acoustic signals including sensor data indicating the physiological
parameter to the controller. In an alternative embodiment, the implant may be coupled
to a therapeutic device or may include an internal therapeutic device coupled to
the electrical circuit. The electrical circuit may control the therapeutic device
in response to a physiological parameter measured by the sensor or in response
to acoustic signals received from the external controller. For example, the implant
may include a pacemaker that may be implanted via a minimally invasive catheter-based
procedure. Any programming and/or interrogation of the pacemaker may be accomplished
using acoustic telemetry from the external controller. In yet another alternative
embodiment, the implant may include an actuator coupled to the electrical circuit,
and the one or more commands may include activating the actuator to control a therapeutic
device coupled to the actuator, such as a nerve stimulator or a controlled delivery
drug release system.
In addition, the energy storage device of the implant may include a rechargeable
device, such as a capacitor or a battery. For this embodiment, the system may include
an external charger that may include a probe configured for placement against an
exterior of the patient's body. The charger may include a source of electrical
energy, such as a radio frequency (RF) generator, that is coupled to the probe.
The probe may include another acoustic transducer, e.g., a third acoustic transducer,
for converting electrical energy from the source of electrical energy into acoustic
energy. The third acoustic transducer may transmit acoustic signals including acoustic
energy into the patient's body. One or more acoustic transducers of the implant,
e.g., the second acoustic transducer, may be configured for converting these acoustic
signals into electrical energy for recharging the energy storage device and/or
powering the implant.
Thus, a system in accordance with the present invention may include an external
controller that has sufficient power to control its own operation and to communicate
with the implant. Because of its limited energy requirements, however, the controller
may be relatively small and portable, e.g., may be attached to the patient, while
still allowing the patient to engage in normal physical activity. The controller
may be used to communicate with an implant, e.g., periodically activating or deactivating
the implant, and/or recording data generated and transmitted by the implant. Because
it is located outside the patient's body, the controller may be more easily programmed
or reprogrammed than the implant, and/or may be repaired or replaced if necessary
without requiring an interventional procedure.
In addition, the system may include a separate external charger that includes
a substantially more powerful energy source, enabling it to recharge the energy
storage device of the implant. For this reason, unlike the external controller,
the charger may be a relatively bulky device that may include a portable probe
for contacting the patient's skin, and a large energy generator or converter that
is stationary or of limited mobility. In an alternative embodiment, the external
controller and charger may be provided as a single device, e.g., including one
or more acoustic transducers and/or one or more processors for performing the functions
of both devices, as described above. In this embodiment, however, portability of
the system and convenience to the patient may be compromised.
Other objects and features of the present invention will become apparent from
consideration of the following description taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is herein described, by way of example only, with reference to
the accompanying drawings, wherein:
FIGS. 1A-1C are schematic drawings, showing exemplary embodiments of an implant,
in accordance with the present invention.
FIG. 2 is a schematic of an exemplary circuit for use as an acoustic switch,
in accordance with the present invention.
FIG. 3 is a cross-sectional view of a patient's body, showing a system for communicating
with an implant, in accordance with the present invention.
FIG. 4 is a schematic of an external controller for communicating with an implant,
such as that shown in FIG. 3, in accordance with the present invention.
FIG. 5 is a schematic of another exemplary embodiment of an implant, in accordance
with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning to the drawings, FIGS. 1A-1C schematically show several exemplary
embodiments of an implant
110,
210,
310, in accordance with
the present invention. Generally, the implant
110,
210,
310
includes an electrical circuit
112,
212,
312 configured for
performing one or more functions or commands when the implant
110,
210,
310 is activated, as described furtherbelow. In addition, the implant
110,
210,
310 includes an energy storage device
114 and optionally
may include a switch
116 coupled to the electrical circuit
112,
212,
312 and the energy storage device
114. The switch
116 may
be activated upon acoustic excitation
100 from an external acoustic energy
source (not shown) to allow current flow from the energy storage device
114
to the electrical circuit
112,
212,
312.
In a preferred embodiment, the switch
116 includes an acoustic transducer
118, such as that disclosed in PCT Publication No. WO 99/34,453, published
Jul. 8, 1999, or in U.S. application Ser. No. 09/888,272, filed Jun. 21, 2001,
the disclosures of which are expressly incorporated herein by reference. In addition,
the switch
116 also includes a switch circuit
120, such as switch
circuit
400 shown in FIG. 2, although alternatively other switches, such
as a miniature electromechanical switch and the like (not shown) may be provided.
In a further alternative, the acoustic transducer
118 may be coupled to
the electrical circuit
112,
212,
312 and/or the energy storage
device
114, and the switch circuit
120 may be eliminated.
The energy storage device
114 may be any of a variety of known devices,
such as an energy exchanger, a battery and/or a capacitor (not shown). Preferably,
the energy storage device
114 is capable of storing electrical energy substantially
indefinitely for as long as the acoustic switch
116 remains open, i.e.,
when the implant
110,
210,
310 is in a "sleep" mode. In addition,
the energy storage device
114 may be capable of being charged from an external
source, e.g., inductively using acoustic telemetry, as will be appreciated by those
skilled in the art. In a preferred embodiment, the energy storage device
114
includes both a capacitor and a primary, non-rechargeable battery. Alternatively,
the energy storage device
114 may include a secondary, rechargeable battery
and/or capacitor that may be energized before activation or use of the implant
110,
210,
310.
The implant
110,
210,
310 may be surgically or minimally
invasively inserted within a human body in order to carry out a variety of monitoring
and/or therapeutic functions. For example, the electrical circuit
112,
212,
312 may include a control circuit
122,
222,
322, a
biosensor
124,
224, an actuator
226,
326, and/or a
transmitter
128, as explained in application Ser. No. 09/690,015, incorporated
by reference above. The implant
210,
310 may be configured for providing
one or more therapeutic functions, for example, to activate and/or control a therapeutic
device implanted within a patient's body, such as an atrial defibrillator or pacemaker,
a pain relief stimulator, a neuro-stimulator, a drug delivery device, and/or a
light source used for photodynamic therapy. Alternatively, the implant may be used
to monitor a radiation dose including ionizing, magnetic and/or acoustic radiation,
to monitor flow in a bypass graft, to produce cell oxygenation and membrane electroporation,
and the like. In addition or alternatively, the implant
110 may be used
to measure one or more physiological parameters within the patient's body, such
as pressure, temperature, electrical impedance, position, strain, pH, and the like.
The implant may operate in one of two modes, a "sleep" or "passive" mode when
the implant remains dormant and not in use, i.e., when the acoustic switch
116
is open, and an "active" mode, when the acoustic switch
116 is closed, and
electrical energy is delivered from the energy storage device
114 to the
electrical circuit
112,
212,
312. Alternatively, the implant
may operate continuously or intermittently. Because the acoustic switch
116
is open in the sleep mode, there is substantially no energy consumption from the
energy storage device
114, and consequently, the implant may remain in the
sleep mode virtually indefinitely, i.e., until activated. Thus, an implant in accordance
with the present invention may be more energy efficient and, therefore, may require
a relatively small energy storage device than implants that continuously draw at
least a small amount of current in their "passive" mode.
Turning to FIG. 1A, a first preferred embodiment of an implant
110
is shown in which the electrical circuit
112 includes a control circuit
122, a biosensor
124 coupled to the controller
122, and a
transmitter
128 coupled to the control circuit
122. The controller
122 may include circuitry for activating or controlling the biosensor
124,
for receiving signals from the biosensor
124, and/or for processing the
signals into data, for example, to be transmitted by the transmitter
128.
Optionally, the electrical circuit
112 may include memory (not shown) for
storing the data. The transmitter
128 may be any device capable of transmitting
data from the control circuit
122 to a remote location outside the body,
such as an acoustic transmitter, a radio frequency transmitter, and the like. Preferably,
the control circuit
122 is coupled to the acoustic transducer
118
such that the acoustic transducer
118 may be used as a transmitter
128,
as well as a receiver, instead of providing a separate transmitter.
The biosensor
124 may include one or more sensors capable of measuring
physiological parameters, such as pressure, temperature, electrical impedance,
position, strain, pH, fluid flow, electrochemical sensor, and the like. Thus, the
biosensor
124 may generate a signal proportional to a physiological parameter
that may be processed and/or relayed by the control circuit
122 to the transmitter
128, which, in turn, may generate a transmission signal to be received by
a device outside the patient's body. Data regarding the physiological parameter(s)
may be transmitted continuously or periodically until the acoustic switch
116
is deactivated, or for a fixed predetermined time, as will be appreciated by those
skilled in the art.
Turning to FIG. 1B, a second preferred embodiment of an implant
210
is shown in which the electrical circuit
212 includes a control circuit
222 and an actuator
226. The actuator
226 may be coupled to
a therapeutic device (not shown) provided in or otherwise coupled to the implant
210, such as a light source, a nerve stimulator, a defibrillator, an electrochemical
oxidation/reduction electrode, or a valve communicating with an implanted drug
reservoir (in the implant or otherwise implanted within the body in association
with the implant).
When the switch
120 is closed, the control circuit
222 may activate
the actuator
226 using a pre-programmed protocol, e.g., to complete a predetermined
therapeutic procedure, whereupon the switch
120 may automatically open,
or the controller
222 may follow a continuous or looped protocol until the
switch
120 is deactivated. Alternatively, the acoustic transducer
118
may be coupled to the control circuit
222 for communicating a new or unique
set of commands to the control circuit
222. For example, a particular course
of treatment for a patient having the implant
210 may be determined, such
as a flow rate and duration of drug delivery, drug activation, drug production,
or an energy level and duration of electrical stimulation. Acoustic signals including
commands specifying this course of treatment may be transmitted from an external
controller (not shown), as described below, to the acoustic switch
116,
e.g., along with or subsequent to the activation signal
100. The control
circuit
222 may interpret these commands and control the actuator
226
accordingly to complete the course of treatment.
Turning to FIG. 1C, yet another preferred embodiment of an implant
310
is shown in which the electrical circuit
312 includes a control circuit
322, a biosensor
324, and an actuator
326, all of which may
be coupled to one another. This embodiment may operate similarly to the embodiments
described above, e.g., to obtain data regarding one or more physiological parameters
and/or to control a therapeutic device. In addition, once activated, the control
circuit
322 may control the actuator
326 in response to data obtained
from the biosensor
324 to control or adjust automatically a course of treatment
being provided by a device connected to the actuator
326. For example, the
actuator
326 may be coupled to an insulin pump (not shown), and the biosensor
324 may measure glucose levels within the patient's body. The control circuit
322 may control the actuator to open or close a valve on the insulin pump
to adjust a rate of insulin delivery based upon glucose levels measured by the
biosensor
324 in order to maintain the patient's glucose within a desired range.
Turning to FIG. 2, a preferred embodiment of a switch
400 is shown
that may be incorporated into an implant in accordance with the present invention.
The switch
400 includes a piezoelectric transducer, or other acoustic transducer
(not shown, but generally connected to the switch
400 at locations piezo+and
piezo-), a plurality of MOSFET transistors (Q
1-Q
4) and resistors
(R
1-R
4), and switch S
1. A "load" may be coupled to the switch
400, such as one of the electrical circuits described above. In the switch's
"sleep" mode, all of the MOSFET transistors (Q
1-Q
4) are in an off
state. To maintain the off state, the gates of the transistors are biased by pull-up
and pull-down resistors. The gates of N-channel transistors (Q
1, Q
3
& Q
4) are biased to ground and the gate of P-channel transistor Q
2
is biased to +3V. During this quiescent stage, switch S
1 is closed and no
current flows through the circuit. Therefore, although an energy storage device
(not shown, but coupled between the hot post, labeled with an exemplary voltage
of +3V, and ground) is connected to the switch
400, no current is being
drawn therefrom since all of the transistors are quiescent.
When the acoustic transducer of the implant detects an external acoustic signal,
e.g., having a particular frequency, such as the transducer's resonant frequency,
the voltage on the transistor Q
1 will exceed the transistor threshold voltage
of about one half of a volt. Transistor Q
1 is thereby switched on and current
flows through transistor Q
1 and pull-up resistor R
2. As a result
of the current flow through transistor Q
1, the voltage on the drain of transistor
Q
1 and the gate of transistor Q
2 drops from +3V substantially to
zero (ground). This drop in voltage switches on the P-channel transistor Q
2,
which begins to conduct current through transistor Q
2 and pull-down resistor R
3.
As a result of the current flowing through transistor Q
2, the voltage
on
the drain of transistor Q
2 and the gates of transistors Q
3 and Q
4
increases from substantially zero to +3V. The increase in voltage switches on transistors
Q
3 and Q
4. As a result, transistor Q
3 begins to conduct current
through resistor R
4 and main switching transistor Q
4 begins to conduct
current through the "load," thereby switching on the electrical circuit.
As a result of the current flowing through transistor Q
3, the gate of
transistor
Q
2 is connected to ground through transistor Q
3, irrespective of
whether or not transistor Q
1 is conducting. At this stage, the transistors
(Q
2, Q
3 & Q
4) are latched to the conducting state, even if
the piezoelectric voltage on transistor Q
1 is subsequently reduced to zero
and transistor Q
1 ceases to conduct. Thus, main switching transistor Q
4
will remain on until switch S
1 is opened.
In order to deactivate or open the switch
400, switch S
1 must be
opened, for example, while there is no acoustic excitation of the piezoelectric
transducer. If this occurs, the gate of transistor Q
2 increases to +3V due
to pull-up resistor R
2. Transistor Q
2 then switches off, thereby,
in turn, switching off transistors Q
3 and Q
4. At this stage, the
switch
400 returns to its sleep mode, even if switch S
1 is again
closed. The switch
400 will only return to its active mode upon receiving
a new acoustic activation signal from the piezoelectric transducer.
It should be apparent to one of ordinary skill in the art that the above-mentioned
electrical circuit is not the only possible implementation of a switch for use
with the present invention. For example, the switching operation my be performed
using a CMOS circuit, which may draw less current when switched on, an electromechanical
switch, and the like.
Turning to FIGS. 3 and 4, a system
410 is shown for communicating
with an implant
412, such as one of those described above. Generally, the
system
410 includes an external communications device or controller
414,
and may include a charger
416, one or more implants
412 (only one
shown for simplicity), and an external recorder, computer, or other electronic
device
434.
With particular reference to FIG. 4, the external controller
414 may
include a processor or other electrical circuit
418 for controlling its
operation, and an energy source
420, e.g., a nonrechargeable or a rechargeable
battery, coupled to the processor
418 and/or other components of the controller
414, such as a power amplifier or an oscillator (not shown). In addition,
the controller
414 may include one or more acoustic transducers
422
that are configured for converting between electrical energy and acoustic energy,
similar to those described above. As shown, a single acoustic transducer
422
is provided that may communicate using acoustic telemetry, i.e., capable both of
converting electrical energy to acoustic energy to transmit acoustic signals, and
converting acoustic energy to electrical energy to receive acoustic signals, as
explained further below. Alternatively, separate and/or multiple acoustic transducers
may be provided for transmitting and receiving acoustic signals.
In a preferred embodiment, the controller
414 also includes memory
424
coupled to the processor
418, e.g., for storing data provided to the controller
414, as explained further below. The memory
424 may be a temporary
buffer that holds data before transfer to another device, or non-volatile memory
capable of storing the data substantially indefinitely, e.g., until extracted by
the processor
418 or other electronic device. For example, the memory
424
may be a memory card or an eprom (not shown) built into the controller
414
or otherwise coupled to the processor
418. The controller
414 may
also include an interface
426, such as a lead or connector, or a transmitter
and/or receiver, that may communicate with the external electronic device, as explained
further below.
Preferably, the controller
414 is carried by a patch
415
that may be secured to a patient, e.g., to the patient's skin
92. For example,
the patch
415 may include one or more layers of substantially flexible material
to which the controller
414 and/or its individual components are attached.
The patch
415 may include a single flexible membrane (not shown) to which
the controller
414 is bonded or otherwise attached, e.g., using a substantially
permanent adhesive, which may facilitate the patch
415 conforming to a patient's
anatomy. Alternatively, the controller
414 may be secured between layers
of material, e.g., within a pouch or other compartment (not shown) within the patch
415. For example, the patch
415 may include a pair of membranes (not
shown) defining the pouch or compartment. The space within which the controller
414 is disposed may be filled with material to acoustically couple the acoustic
transducer(s) (formed, for example, from PZT, composite PZT, Quartz, PVDF, and/or
other piezoelectric material) of the controller
414 to an outer surface
of the patch
415. Alternatively, the acoustic transducer(s) may be exposed,
e.g., in a window formed in a wall of the patch
415.
The patch
415 may be formed from a flexible piezoelectric material, such
as PVDF or a PVDF copolymer. Such polymers may allow the patch
415 to produce
ultrasonic waves, as well as allowing the controller
414 to be secured to
the patient's skin
92. Thus, the wall of the patch
415 itself may
provide an acoustic transducer for the controller
414, i.e., for transmitting
acoustic energy to and/or receiving acoustic energy from the implant
412.
The patch
415 may then be secured to the patient's skin
92 using
a material, such as a layer of adhesive (not shown), substantially permanently
affixed or otherwise provided on a surface of the patch. The adhesive may be hydrogel,
silicon, polyurethane, polyethylene, polypropylene, fluorocarbon polymer, and the
like. Alternatively, a separate adhesive may be applied to the patch
415
and/or to the patient's skin
92 before applying the patch
415 in
order to secure the controller
414 to the patient's skin
92. Such
an adhesive may enhance acoustically coupling of the acoustic transducer(s) of
the controller
414 to the patient's skin
92, and consequently to
the implant
412 within the patient's body
94. Optionally, additional
wetting material, including water, silicone oil, silicone gel, hydrogel, and the
like, and/or other acoustically conductive material may be provided between the
patch
415 or the acoustic transducer
422, and the patient's skin
92, e.g., to provide substantial continuity and minimize reflection or other
losses and/or to secure the patch
415 to the patient.
Alternatively, the controller
414 may be carried by a belt
(not shown) that may be secured around the patient, e.g., such that the acoustic
transducer
422 is secured against the patient's skin. The belt may carry
other components of the system
410, e.g., an external power supply for the
controller
414. For example, a battery pack (not shown) may be carried by
the belt that may be coupled to the controller
414 for providing electrical
energy for its operation.
The patch
415 may be relatively light and compact, for example, having
a maximum surface dimension (e.g., width or height) not more than about ten to
two hundred millimeters (10-200 mm), a thickness not more than about five to one
hundred millimeters (5-100 mm), and a weight not more than about twenty to four
hundred grams (20-400 g), such that the controller
414 may be inconspicuously
attached to the patient. Thus, the patient may be able to resume normal physical
activity, without substantial impairment from the controller. Yet, the internal
energy source of the controller
414 may be sufficiently large to communicate
with the implant
412 for an extended period of time, e.g., for hours or
days, without requiring recharging or continuous coupling to a separate energy source.
The system
410 may be used to control, energize, and/or otherwise communicate
with the implant
412. For example, the controller
414 may be used
to activate the implant
412. One or more external acoustic energy waves
or signals
430 may be transmitted from the controller
414 into the
patient's body
94, e.g., generally towards the location of the implant
412
until the signal is received by the acoustic transducer (not shown in FIGS. 3 and
4) of the implant
412. Upon excitation by the acoustic wave(s)
430,
the acoustic transducer produces an electrical output that is used to close, open,
or otherwise activate the switch (also not shown in FIGS. 3 and 4) of the implant
412. Preferably, in order to achieve reliable switching, the acoustic transducer
of the implant
412 is configured to generate a voltage of at least several
tenths of a volt upon excitation that may be used as an activation signal to close
the switch, as described above.
As a safety measure against false positives (e.g., erroneous activation or deactivation),
the controller
414 may be configured to direct its acoustic transducer
422
to transmit an initiation signal followed by a confirmation signal. When the acoustic
transducer of the implant
412 receives these signals, the electrical circuit
may monitor the signals for a proper sequence of signals, thereby ensuring that
the acoustic switch of the implant
412 only closes upon receiving the proper
initiation and confirmation signals. For example, the acoustic switch may only
acknowledge an activation signal that includes a first pulse followed by a second
pulse separated by a predetermined delay. Use of a confirmation signal may be particularly
important for certain applications, for example, to prevent unintentional release
of drugs by a drug delivery implant.
In addition to an activation signal, the controller
414 may transmit a
second acoustic signal that may be the same as or different than the acoustic wave(s)
used to activate the acoustic switch of the implant
412. Thus, the switch
may be opened when the acoustic transducer of the implant
412 receives this
second acoustic signal, e.g., by the acoustic transducer generating a termination
signal in response to the second acoustic signal, in order to return the implant
412 to its sleep mode.
For example, once activated, the switch may remain closed indefinitely, e.g.,
until the energy storage device (not shown in FIGS. 3 and 4) of the implant
412
is completely depleted, falls below a predetermined threshold, or until a termination
signal is received by the acoustic transducer of the implant
412 from the
controller
414. Alternatively, the acoustic switch of the implant
412
may include a timer (not shown), such that the switch remains closed only for a
predetermined time, whereupon the switch may automatically open, returning the
implant
412 to its sleep mode.
FIG. 5 shows an alternative embodiment of an implant
510 that does not
include an acoustic switch. Generally, the implant includes a sensor
512,
one or more energy transducers
514, one or more energy storage devices
516,
and a control circuit
518, similar to the embodiments described above. The
sensor
512 is preferably a pressure sensor for measuring intra-body pressure,
such as an absolute variable capacitance type pressure sensor. In alternative embodiments,
one or more other sensors may be provided instead of or in addition to a pressure
sensor
512. For example, the sensor
512 may include one or more biosensors
capable of measuring physiological parameters, such as temperature, electrical
impedance, position, strain, pH, fluid flow, and the like. An external controller
(not shown), such as that described above, may also be used to communicate with
this implant.
Returning to FIG. 3, an external controller
414 in accordance with
the present invention preferably has only sufficient power to control its own operation
and to communicate with the implant
412. Because of its limited energy requirements,
the controller
414 may be relatively small and portable, e.g., may be attached
to the patient, while still allowing the patient to engage in normal physical activity.
The controller
414 may be used to communicate with the implant
412,
e.g., periodically activating or deactivating the implant
412, and/or recording
data generated and transmitted by the implant
412. Because it is located
outside the patient's body, the controller
414 may be more easily programmed
or reprogrammed than the implant
412 itself, and/or may be repaired or replaced
if necessary or desired.
In addition to the external controller
414, the system
410 may
include
one or more electronic devices
434 that may be coupled to the controller
414 via the interface
426, such as a recorder, a computer, a personal
digital assistant, and/or a wireless device, such as a cellular telephone. The
electronic device
434 may be directly coupled to the controller
414,
by a connector or lead (not shown) extending from the patch
415 within which
the controller
414 is provided. Alternatively, the controller
414
and/or patch
415 may include a wireless transmitter and/or receiver (not
shown), e.g., a short-range RF transceiver, for communicating with the electronic
device
434.
The electronic device
434 may be used to extract data from the memory
424 of the controller
414, e.g., sensor data and the like, received
from the implant
412. This data may be included in a patient database maintained
by health care professionals monitoring the patient receiving the implant
412.
In addition, the electronic device
434 may be used to program the controller
414, e.g., to program commands, timing sequences, and the like.
The system
410 may also include an external charger
418. For example,
the implant
412 may include a rechargeable energy storage device (not shown
in FIG.
3), preferably one or more capacitors, that are coupled to the acoustic
transducer (also not shown in FIG.
3). The charger
416 may include
a probe
428, including an acoustic transducer
430 for contacting
a patient's skin
92. The charger
416 also includes a source of electrical
energy
432, such as a radio frequency (RF) generator, that is coupled to
the acoustic transducer
430. The charger
418 may also include electrical
circuits for controlling its operation and buttons or other controls (not shown)
for activating and/or deactivating the acoustic transducer
430.
The charger
418 may be used to charge or recharge the implant, e.g., periodically
or before each activation. Because the charger
418 includes a substantially
more powerful energy source than the controller
414, the charger
418
is generally a relatively bulky device compared to the controller
414, in
particular due to the energy generator, which may be stationary or of limited mobility.
In addition, the charger
418 may be used to recharge the controller
414
periodically, e.g., by a direct or wireless coupling. Alternatively, the controller
414 and patch
415 may be disposable, e.g., after its energy has been
depleted, and replaced with another.
For purposes of comparison, an exemplary charger
416 may need to generate
about ten kiloPascals (10 kPa) of acoustic energy for about twenty seconds (20
sec.) in order to fully charge the implant
412. In contrast, an exemplary
controller
414 may be limited to outputting relatively smaller bursts of
acoustic energy for communicating with, but not charging, the implant
412.
Such acoustic signals may have a duration of as little as about one millisecond
(1 ms), as opposed to the significantly longer charging signals generated by the
charger
416.
The transducer
422 of the controller
414 may consume about one
Watt (1 W) of power to produce a 1 kPa acoustic signal for about one millisecond.
If the controller
414 communicates with the implant
412 on an hourly
basis, the energy source
420 of the controller
418 may only need
sufficient capacity to provide 0.024 Watt seconds per day (0.024 W.sec./day). Because
of this low energy requirement, the energy source
420, and, consequently,
the controller
418, may be relatively compact and portable, as compared
to the charger
416. Thus, the energy source
420 may be self-contained
within the controller
418, i.e., carried by the patch
415. Alternatively,
a portable energy source, e.g., an external battery pack (not shown) may be provided
for supplying electrical energy to the controller
418 that may be carried
by the patient, e.g., on a belt (not shown).
In an alternative embodiment, the controller and charger may be provided as a
single device (not shown), e.g., including one or more acoustic transducers and/or
one or more processors for performing the functions of both devices, as described
above. In this embodiment, the implant
412 may operate in a "half-duplex"
mode, a quasi-continuous mode, or in a "full-duplex" mode, as described in the
applications incorporated above.
It will be appreciated that the above descriptions are intended only to serve
as examples, and that many other embodiments are possible within the spirit and
the scope of the present invention.
*
