US20170007840A1 - System and method for resetting an implantable medical device - Google Patents

Abstract

In one embodiment, a method, of operating an implantable medical device, comprises: (i) operating reset logic within the implantable medical device that is independently operable from a processor of the implantable medical device after the implantable medical device is implanted within a patient, wherein the processor is adapted for central control of the implantable medical device; (ii) operating a magnetic field sensor in the implantable medical device; (iii) generating digital data using, at least, the magnetic field sensor; (iv) detecting, by the reset logic, a digital key in the digital data; (v) in response to (iv), asserting a reset signal on a pin of the processor by the reset logic; and (vi) conducting reset operations in the processor in response to the reset signal.

Description

RELATED APPLICATIONS
• This application is a divisional application of U.S. patent application Ser. No. 13/593,233, filed Aug. 23, 2012 which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/548,614, filed Oct. 18, 2011, which are incorporated herein by reference.
BACKGROUND
• The medical device industry produces a wide variety of electronic and mechanical devices for addressing patient medical conditions. Clinicians use medical devices alone or in combination with drug therapies and surgery to address numerous patient medical conditions. Medical devices may provide the best and sometimes the only therapy for selected medical conditions and disorders. Common implantable medical devices include neurostirnulation systems, pacemakers, defibrillators, drug delivery pumps, and diagnostic recorders.
• For example, neurostimulation systems are devices that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is the most common type of neurostimulation. In SCS, electrical pulses are delivered to nerve tissue in the spine typically for the purpose of chronic pain control, While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of an electrical field to spinal nervous tissue can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated nerve tissue. Specifically, applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions. Thereby, paresthesia can effectively mask the transmission of non-acute pain sensations to the brain.
• SCS systems generally include a pulse generator and one or more leads, A stimulation lead includes a lead body of insulative material that encloses wire conductors. The distal end of the stimulation lead includes multiple electrodes that are electrically coupled to the wire conductors. The proximal end of the lead body includes multiple terminals, which are also electrically coupled to the wire conductors, that are adapted to receive electrical pulses. The distal end of a respective stimulation lead is implanted within the epidural space to deliver the electrical pulses to the appropriate nerve tissue within the spinal cord that corresponds to the dermatome(s) in which the patient experiences chronic pain. The stimulation leads are then tunneled to another location within the patient's body to be electrically connected with a pulse generator or, alternatively, to an “extension.”
• The pulse generator is typically implanted within a subcutaneous pocket created during the implantation procedure. In SCS, the subcutaneous pocket is typically disposed in a lower back region, although subclavicular implantations and lower abdominal implantations are commonly employed for other types of neuromodulation therapies,
• The pulse generator is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses, control circuitry, communication circuitry, a rechargeable battery, etc. The pulse generating circuitry is coupled to one or more stimulation leads through electrical connections provided in a “header” of the pulse generator. Specifically, feedthrough wires typically exit the metallic housing and enter into a header structure of a moldable material. Within the header structure, the feedthrough wires are electrically coupled to annular electrical connectors. The header structure holds the annular connectors in a fixed arrangement that corresponds to the arrangement of terminals on a stimulation lead.
SUMMARY
• In one embodiment, a method, of operating an implantable medical device, comprises: (i) operating reset logic within the implantable medical device that is independently operable from a processor of the implantable medical device after the implantable medical device is implanted within a patient, wherein the processor is adapted for central control of the implantable medical device; (ii) operating a magnetic field sensor in the implantable medical device; (iii) generating digital data using, at least, the magnetic field sensor; (iv) detecting, by the reset logic, a digital key in the digital data; (v) in response to (iv), asserting a reset signal on a pin of the processor by the reset logic; and (vi) conducting reset operations in the processor in response to the reset signal.
• The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures, it is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 depicts a stimulation system according to some representative embodiments.
• FIG. 2A depicts one electrode configuration at the distal end of a lead that may be employed in stimulator systems according to some representative embodiments,
• FIG. 2B depicts another electrode configuration at the distal end of a lead that may be employed in stimulator systems according to some representative embodiments.
• FIG. 2C depicts another electrode configuration at the distal end of a lead that may be employed in stimulator systems according to some representative embodiments.
• FIG. 3 depicts circuitry involved in a reset operation of an implanted medical device according to some representative embodiments.
• FIG. 4 depicts a flowchart of operations involved in resetting an implanted medical device according to some representative embodiments.
DETAILED DESCRIPTION
• FIG. 1 depictsstimulation system100 that generates electrical pulses for application to tissue of a patient according to some representative embodiments. For example,system100 may be adapted to stimulate spinal cord tissue, peripheral nerve tissue, deep brain tissue, cortical tissue, cardiac tissue, digestive tissue, pelvic floor tissue, or any other suitable tissue within a patient's body. Although a stimulation system is described according to some embodiments, any implantable medical device may be reset according to other embodiments.
• The stimulation system includesimplantable pulse generator150 that is adapted to generate electrical pulses for application to tissue of a patient,implantable pulse generator150 typically comprises a metallic housing that enclosescontroller151,pulse generating circuitry152,charging component153,battery154, far-field and/or nearfield communication circuitry155,battery charging circuitry156,switching circuitry157, etc, of the device,Controller151 typically includes a microcontroller or other suitable processor for controlling the various other components of the device. Software code is typically stored in memory of thepulse generator150 for execution by the microcontroller or processor to control the various components of the device.
• Although not required, in this specific embodiment,pulse generator150 comprises attachedextension component170. That is, in lieu of providing a separate extension lead that is physically placed within a header of an IPG by the surgeon during Implant,extension component170 is directly attached to and is non-removable frompulse generator150 according to some representative embodiments. Other embodiments may employ aseparate extension component170 for connectingstimulation lead110 with thegenerator150. Alternatively,stimulation lead110 may be directly coupled within the header of thegenerator150. Withinpulse generator150, electrical pulses are generated bypulse generating circuitry152 and are provided to switchingcircuitry157. The switching circuit connects to output wires, traces, lines, or the like (not shown inFIG. 1) which are, in turn, electrically coupled to internal conductive wires (not shown inFIG. 1) oflead body172 ofextension component170. The conductive wires, in turn, are electrically coupled to electrical connectors (e.g., “Bal-Seal” connectors) withinconnector portion171 ofextension component170.
• The terminals of one or more stimulation leads110 are inserted withinport175 ofconnector portion171 for electrical connection with respective electrical connectors (not shown) withinconnector portion171.Connector portion171 may include one or more set-screw mechanisms (not shown) to secure the lead(s)110 withinconnector portion171. The pulses originating frompulse generator150 and conducted through the conductors oflead body172 are provided tostimulation lead110. The pulses are then conducted through the conductors oflead110 and applied to tissue of a patient viaelectrodes111. Any suitable known or later developed design may be employed forconnector portion171. Also,connector portion171 may includemultiple ports175 for receipt of a suitable number of stimulation leads110.
• Although not required,extension component170 is arranged to placeport175 in a specific arrangement relative to the housing of pulse generator150 (as shown inFIG. 1). Specifically, whenlead body172 is disposed in a linear configuration and extends away substantially perpendicularly from the housing ofpulse generator150,port175 preferably faces the housing ofpulse generator150. That is, at least oneport175 is on the side ofextension component170 that is proximal to housing ofpulse generator150, i.e. the side on whichlead body172 meetsconnector portion171. Also, when the terminals oflead110 are placed withinconnector portion171, lead110 initially extends back toward the housing ofpulse generator150. In other embodiments, any suitable form factor may be employed forgenerator150 according to other embodiments. Also,extension component170 may be implemented as a separate discrete component fromgenerator150 as is known in the art.
• Also, at any suitable time, the clinician may input data into controller device160 (see below) indicating theports175 in which leads110 are placed, thereby permittingcontroller device160 to properly correlate the various electrodes and terminals oflead110 to the corresponding electrical connectors ofconnector portion171.
• For implementation of the components withinpuke generator150, a processor and associated charge control circuitry for an implantable pulse generator is described in U.S. Patent Publication No. 20060259098, entitled “SYSTEMS AND METHODS FOR USE IN PULSE GENERATION,” which is incorporated herein by reference. Circuitry for recharging a rechargeable battery of an implantable pulse generator using inductive coupling and external charging circuits are described in U.S. patent Ser. No. 11/109,114, entitled “IMPLANTABLE DEVICE AND SYSTEM FOR WIRELESS COMMUNICATION,” which is incorporated herein by reference.
• An example and discussion of “constant current” pulse generating circuitry is provided in U.S. Patent Publication No. 20060170486 entitled “PULSE GENERATOR HAVING AN EFFICIENT FRACTIONAL VOLTAGE CONVERTER AND METHOD OF USE,” which is incorporated herein by reference. One or multiple sets of such circuitry may be provided withinpulse generator150. Different pulses on different electrodes may be generated using a single set of pulse generating circuitry using consecutively generated pulses according to a “multi-stimset program” as is known in the art. Alternatively, multiple sets of such circuitry may be employed to provide pulse patterns that include simultaneously generated and delivered stimulation pulses through various electrodes of one or more stimulation leads as is also known in the art. Various sets of parameters may define the pulse characteristics and pulse timing for the pulses applied to various electrodes as is known in the art. Although constant current pulse generating circuitry is contemplated for some embodiments, any other suitable type of pulse generating circuitry may be employed such as constant voltage pulse generating circuitry.
• Stimulation lead(s)110 may comprise a lead body of insulative material about a plurality of conductors within the material that extend from a proximal end oflead110 to its distal end. The conductors electrically couple a plurality ofelectrodes111 to a plurality of terminals (not shown) oflead110. The terminals are adapted to receive electrical pulses and theelectrodes111 are adapted to apply stimulation pulses to tissue of the patient, Also, sensing of physiological signals may occur throughelectrodes111, the conductors, and the terminals. Additionally or alternatively, various sensors (not shown) may be located near the distal end ofstimulation lead110 and electrically coupled to terminals through conductors within thelead body172.Stimulation lead110 may include any suitable number ofelectrodes111, terminals, and internal conductors. Likewise,connector portion171 may comprise any suitable number of electrical connectors andlead body172 may comprise any suitable number of conductors.
• FIGS. 2A-2C respectively depictstimulation portions200,225, and250 for inclusion at the distal end oflead110.Stimulation portion200 depicts a conventional stimulation portion of a “percutaneous” lead with multiple ring electrodes.Stimulation portion225 depicts a stimulation portion including several “segmented electrodes.” The term “segmented electrode is distinguishable from the term ring electrode.” As used herein, the term “segmented electrode” refers to an electrode of a group of electrodes that are positioned at the same longitudinal location along the longitudinal axis of a lead and that are angularly positioned about the longitudinal axis so they do not overlap and are electrically isolated from one another. Example fabrication processes are disclosed in U.S. Provisional Patent Application Ser. No. 61/247,360, entitled, “METHOD OF FABRICATING STIMULATION LEAD FOR APPLYING ELECTRICAL STIMULATION TO TISSUE OF A PATIENT,” which is incorporated herein by reference,Stimulation portion250 includes multiple planar electrodes on a paddle structure. Any suitable stimulation portion design may be employed forlead110.
• Although not required for all embodiments, the lead bodies of lead(s)110 andextension component170 may be fabricated to flex and elongate in response to patient movements upon implantation within the patient. By fabricating lead bodies according to some embodiments manner, a lead body or a portion thereof is capable of elastic elongation under relatively low stretching forces. Also, after removal of the stretching force, the lead body is capable of resuming its original length and profile. For example, the lead body may stretch 10%, 20%, 25%, 35%, or even up or above to 50% at forces of about 0.5, 1.0, and/or 2.0 pounds of stretching force.
• The ability to elongate at relatively low forces may present one or more advantages for implantation in a patient, For example, as a patient changes posture (e.g., “bends” the patient's back), the distance from the implanted pulse generator to the stimulation target location changes. The lead body may elongate in response to such changes in posture without damaging the conductors of the lead body or disconnecting from pulse generator. Also, deep brain stimulation implants, cortical stimulation implants, and occipital subcutaneous stimulation implants usually involve tunneling of the lead body through tissue of the patient's neck to a location below the clavicle. Movement of the patient's neck subjects a stimulation lead to significant flexing and twisting which may damage the conductors of the lead body. Due to the ability to elastically elongate responsive to movement of the patient's neck, certain lead bodies according to some embodiments are better adapted for such implants than some other known lead body designs. Fabrication techniques and material characteristics for “body compliant” leads are disclosed in greater detail in U.S. Provisional Patent Application Ser. No. 60/788,518, entitled “Lead Body Manufacturing,” filed Mar. 31, 2006, which is incorporated herein by reference.
• Controller device160 may be implemented to rechargebattery154 of pulse generator150 (although a separate recharging device could alternatively be employed). A “wand”165 may be electrically connected to controller device through suitable electrical connectors (not shown). The electrical connectors are electrically connected to coil166 (the “primary” coil) at the distal end ofwand165 through respective wires (not shown). Typically,coil166 is connected to the wires through capacitors (not shown). Also, in some embodiments,wand165 may comprise one or more temperature sensors for use during charging operations.
• The patient then places theprimary coil166 against the patients body immediately above the secondary coil (not shown), i.e., the coil of the implantable medical device. Preferably, theprimary coil166 and the secondary coil are aligned in a coaxial manner by the patient for efficiency of the coupling between the primary and secondary coils.Controller160 generates an AC signal to drive current throughcoil166 ofwand165. Assuming thatprimary coil166 and secondary coil are suitably positioned relative to each other, the secondary coil is disposed within the field generated by the current driven throughprimary coil166. Current is then induced in secondary coil, The current induced in the coil of the implantable pulse generator is rectified and regulated to rechargebattery154 by chargingcircuitry156.Charging circuitry156 may also communicate status messages tocontroller160 during charging operations using pulse-loading or any other suitable technique. For example,controller160 may communicate the coupling status, charging status, charge completion status, etc.
• External controller device160 is also a device that permits the operations ofpulse generator150 to be controlled by user afterpulse generator150 is implanted within a patient, although in alternative embodiments separate devices are employed for charging and programming. Also, multiple controller devices may be provided for different types of users (e.g., the patient or a clinician).Controller device160 can be implemented by utilizing a suitable handheld processor-based system that possesses wireless communication capabilities, Software is typically stored in memory ofcontroller device160 to control the various operations ofcontroller device160. Also, the wireless communication functionality ofcontroller device160 can be integrated within the handheld device package or provided as a separate attachable device. The interface functionality ofcontroller device160 is implemented using suitable software code for interacting with the user and using the wireless communication capabilities to conduct communications withIPG150.
• Controller device160 preferably provides one or more user interfaces to allow the user to operatepulse generator150 according to one or more stimulation programs to treat the patient's disorder(s). Each stimulation program may include one or more sets of stimulation parameters including pulse amplitude, pulse width, pulse frequency or inter-pulse period, pulse repetition parameter (e.g., number of times for a given pulse to be repeated for respective stimset during execution of program), etc.IPG150 modifies its internal parameters in response to the control signals fromcontroller device160 to vary the stimulation characteristics of stimulation pulses transmitted throughstimulation lead110 to the tissue of the patient. Neurostimulation systems, stir sets, and multi-stirnset programs are discussed in PCT Publication No. WO 01/93953, entitled “NEUROMODULATION THERAPY SYSTEM,” and U.S. Pat. No. 7,228,179, entitled “METHOD AND APPARATUS FOR PROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” which are incorporated herein by reference.
• As previously discussed, implantable pulse generators (and typically many active implantable medical devices) include a processor, microcontroller, or similar circuitry to control the operations of the device. The electronics of such devices are subject to faults. Many of the faults are mitigated by known fault handling mechanisms implemented within software of the device. However, there are number of faults that are not subject to mitigation through conventional fault handling mechanisms. For example, if a critical bit in flash memory becomes flipped, the implanted device may become inoperable or may operate in an unintended, unacceptable manner. The communication capabilities of the device may also be lost thereby making device diagnostics impossible. In such conventional circumstances, the implanted device is simply explanted from the patient and replaced with another device.
• Some representative embodiments provide a mechanism for resetting an implantable medical device into a safe mode or a boot mode (using a modulated magnetic). From the safe mode or boot mode, it may be possible to diagnose device faults and repair the faults (if necessary). For example, from the safe mode or boot mode, any memory corruption of the device may be corrected by rewriting the device code through wireless communications supported by the safe mode or boot mode. As used herein, the term “reset” is intended to take its ordinary meaning as applied to a reset of a processor. As known in the art, a reset typically involves placing related logic elements or peripherals (that are controlled by the processor) into a known state. Also, the reset typically involves “vectoring” to a known location to begin execution of binary code at that location, where the binary code invokes certain initialization operations.
• FIG. 3 depictscontroller160 and a portion ofpulse generator150 during reset operations according to one representative embodiment.Controller160 may include suitable code for initiating a reset operation whenpulse generator150 becomes non-functional. The reset operation may be employed to attempt to diagnose any potential issues and to reestablish operation of pulse generator150 (if possible). By attempting such operations, some amount of otherwise unnecessary explant surgeries may be avoided.
• In operation,controller160 may drive current throughcoil166 to generate a modulated magnetic field. In some embodiments,controller160 initially drives a RF signal throughcoil166. Whencoil166 is placed adjacent tomagnetic receiver component153 of pulse generator150 (across the tissue barrier350), the magnetic field causescomponent153 to generate a signal related to the modulated magnetic field. The generated signal is than optionally processed by circuitry301 (if deemed necessary).
• In one embodiment,component153 may be implemented using a giant magnetoresistive (GMR) device or sensor. GMR sensors typically employ thin film structures composed of ferromagnetic alloys sandwiched around an ultrathin nonmagnetic conducting middle layer. The thin film structures exhibit a large change in resistance (typically 10 to 20%) when the sensors are subjected to a magnetic field, compared with a maximum sensitivity of a few percent for other types of magnetic sensors. That is, ferromagnetic layers transition between anti-parallel and parallel magnetic moments depending upon whether an external magnetic field is applied. In turn, the anti-parallel and parallel orientations of the ferromagnetic layers changes the resistance of the conductive layer via electron spin states in the ferromagnetic layers adjacent to the conductive layer, Digital GMR sensors are commercially available (such as from NVE Corporation, Eden Prairie, Minn.) which may be employed forcomponent153.
• Circuitry301 may be optionally employed to process (e.g., filter, demodulate, etc.) the time-varying signal fromcomponent153 and communicates a bit stream generated by the processing operations to resetlogic303.Reset logic303 stores a window of the bit stream inmemory reset logic303.Reset logic303 monitors the bit stream to identify one or more predefined sequence of bits. The predefined sequence of bits may define a key to causereset logic303 to resetcontroller151 or to causecontroller151 to executecode311 that defines a safe mode of operations ofpulse generator150.Reset logic303 may be implemented using any suitable electronic logic circuitry according to, for example, conventional digital logic design techniques. If desired, a limited set of Instructions may be stored in electronic memory for implementation ofreset logic303.
• In some embodiments, resetlogic303 is connected to the reset pin ofcontroller151 throughreset line304. In the event that resetlogic303 detects the appropriate reset key in the bit stream generated from the modulated magnetic field, resetlogic303 asserts a suitable logic signal online304. The signal online304 causescontroller151 to conduct a reset (which is known in the art). That is,controller151 begins to execute code programmed into itsnon-volatile memory310 such as a bootstrap loader program. The bootstrap loader program may initiate certain system operations and, in turn, load the fullyfunctional application code312 to controlpulse generator150. After communicating the defined key for a system reset,external controller160 may then attempt to conduct conventional communications (e.g., through near field or far field telemetry) withpulse generator150 to determine whether thepulse generator150 has returned to a properly functioning state, if no response is obtained through telemetry attempts after communicating the reset key, it may be assumed that the reset attempt was unsuccessful in resolving the system fault.
• In one embodiment, the bootstrap loader program (executed after reset) may perform a verification of or an integrity check of software or firmware code stored in memory310 (e.g., using a checksum operation or CRC operations, etc.). if a memory error is detected, the bootstrap loader program may automatically default to a safe mode of operation (e.g., as defined by code311).
• In some embodiments, resetlogic303 may communicate other logic signals tocontroller151 in an attempt to resolve a fault inpulse generator150. As shown in the specific embodiment ofFIG. 3, resetlogic303 includespolling line305 andlogic signal line306.Rest logic303 may set a flag viapolling line305 after a reset operation ofcontroller151 has occurred. Whencontroller151 detects the flag as set vialogic signal line306,controller151 may then execute code stored inmemory310 ofcontroller151. The executed code may be adapted to permit recovery and/or repair of pulse generator150 (e.g., to permit a re-write of system code inmemory310 or elsewhere in pulse generator150). For example,code311 may be adapted to implement a “safe mode” mode of operation ofpulse generator150 in which a minimum number of system operations are performed to permit software to be reloaded intopulse generator150. The software/firmware update may be performed bycode311 using conventional operations which are known in the art.
• In some embodiments, resetlogic303 may communicate different logic states onlogic signal line306. For example, resetlogic303 may communicate a vector to identify code for execution (e.g., safe mode code311) after polling operations. Also, depending upon the data communicated in this manner, the executed code may perform different functions. For example, different data values may be employed for diagnostic, operations, external communications withcontroller160, software reload operations, etc.
• Although it is not a critical requirement of the invention, resetlogic303 is preferably provided withinpulse generator150 to operate independently ofmicrocontroller151. By providing independent operation, ifmicrocontroller151 enters a non-recoverable state due to a hardware or software fault, it is possible to reestablish proper operation of the implant device without physically accessing the device. Further, in some embodiments, the reset operations are implemented in such a manner that extraneous signals will not inadvertently cause a device reset. A specific sequence of operations (e.g., communication of one or more digital keys) may be required as a condition before the reset signal is provided to the microcontroller or processor.
• FIG. 4 depicts a flowchart for attempting to recover proper functioning of a medical device implanted within a patient. In401, the patient initially reports that the patient's implant device is non-responsive. The patient may have previously noticed that the therapy provided by the implant device is no longer being delivered. Additionally or alternatively, the patient may have previously noticed that the implant device is not responsive to communication attempts by the patient's external controller device.
• In402, conventional wireless communications (near field or far field) are attempted using clinician device. In403, it is determined whether the communication attempt was successful. If so, implant device faults (if any) are resolved using conventional communications (404).
• In405, if the conventional wireless communications are unsuccessful, a modulated magnetic field is provided. The reset functionality may require the modulated magnetic field to be provided at or near a defined frequency to permit the reset functionality to be activated (e.g., using band-pass filtering of the resulting signal in the pulse generator).
• In406, a digital key is communicated for the reset logic of the pulse generator via the modulated magnetic field. Although a digital key is mentioned according to some embodiments, any suitable message sequence, format, or protocol may be employed according to other embodiments. Upon receipt, the reset logic of the device (assuming some level of operability still exists in the implanted device) causes the microcontroller or processor to be reset by asserting a suitable logic signal on the reset pin of the microcontroller or processor. A safe mode of operation may be employed upon reset. The safe mode may be initiated using further operations of the reset logic (e.g., according to a parameter value communicated with or after the reset key). Alternatively, the safe mode of operation may be a default state after reset
• After attempting reset operations by communication of the digital key, in407, an attempt to establish communications with the implanted medical device is performed (e.g., using near field or far field communications). In408, it is determined whether the communication attempt was successful. If successful, software is reloaded into implant device (409) and further diagnostic operations may be optionally performed (410), if desired. The software/firmware update may be performed using conventional protocols, which are known in the art, or any subsequently developed protocol. If the communications attempt is not successful, it is concluded that an explant procedure to remove the implanted device from the patient's body may be necessary (411).
• Although certain representative embodiments and advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate when reading the present application, other processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the described embodiments may be utilized. Accordingly, the appended claims are intended to include within theft scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims (9)

1. An implantable medical device, comprising:

a therapy module adapted to provide a therapy to a patient after implantation in the body of the patient;

a processor adapted for central control of the implantable medical device

a magnetic sensor for sensing an external magnetic field: and

reset logic that is independently operable from a processor of the implantable medical device and that is adapted to (i) detect a digital key in digital data generated from a modulated magnetic field detected by the magnetic sensor; (ii) in response to detecting the digital key in the digital data, asserting a reset signal on a pin of the processor by the reset logic; wherein the processor is adapted to conduct reset operations in response to assertion of the reset signal on the reset pin of the processor.

2. The implantable medical device ofclaim 1 wherein the implantable medical device comprises memory storing a first set of software instructions of a safe mode of operations that are different from a second set of software instructions of an application mode of operations wherein the application mode of operations controls provision of a therapy by the implantable medical device to the patient.

3. The implantable medical device ofclaim 2 wherein the reset logic is operable to cause the processor to execute the first set of software instructions after the processor is reset.

4. The implantable medical device ofclaim 2 wherein the first set of software instructions comprises code for performing a software or firmware update.

5. The implantable medical device ofclaim 2 wherein the first set of software instructions comprises code for performing an integrity check of software or firmware of the implantable medical device.

6. The implantable medical device ofclaim 2 wherein the reset logic is connected to the processor by a polling line.

7. The implantable medical device ofclaim 6 wherein the reset logic is operable to cause the processor to execute the first set of software instructions by communicating a signal on the polling line after reset operations.

8. The implantable medical device ofclaim 2 wherein the magnetic field sensor is a giant magnetoresistive (GMR) sensor.

9. The implantable medical device ofclaim 8 wherein the GMR sensor is a digital sensor.

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