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SYSTEMS AND METHOD FOR
COMMUNICATING WITH IMPLANTABLE
CROSS-REFERENCE TO RELATED 5
This Application is a continuation of application Ser. No. 09/989,912, filed Nov. 19, 2001, now U.S. Pat. No. 7,024, 248, issued on Apr. 4,2006, which is a continuation-in-part of 10 application Ser. No. 09/690,015, filed Oct. 16, 2000, now U.S. Pat. No. 6,628,989, issued on Sep. 30, 2003, the disclosures of which are expressly incorporated herein by reference.
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, par- 20 ticularly 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. 25
BACKGROUND OF THE INVENTION
Devices are known that may be implanted within a patient's body formonitoring one ormore physiological con- 30 ditions 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, 35 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 com- 40 mand, 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 45 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 50 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 55 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, how- 60 ever, 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. 65
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 ormore 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 and/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 sepa- 5 rated 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 10 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 15 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 20 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 con- 25 trailer. 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 30 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 catheterbased procedure. Any programming and/or interrogation of the pacemaker may be accomplished using acoustic telemetry 35 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 con- 40 trolled 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 45 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 50 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 55 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 60 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 acti- 65 vating 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 forperforming 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
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 further below. 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