Abstract:
An apparatus ( 10 ) for applying stimulation therapy to a patient includes an implantable medical device ( 20 ) and a remote controller ( 50   a ) for inductively powering the medical device and communicating with the medical device. The remote controller ( 50   a ) includes an improved coil configuration to improve communication performance between the remote controller ( 50   a ) and an implanted medical device ( 20 ).

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/649,535, filed on May 21, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to systems, devices, and methods for using an implantable medical device to deliver therapy to a patient. More specifically, this invention relates to improved coil configuration to improve communication performance between an external remote control device and an implanted medical device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Primary headaches are debilitating ailments that afflict millions of individuals worldwide. The specific pathophysiology of primary headaches is not known. Known causes of headache pain include trauma, vascular defects, autoimmune deficiencies, degenerative conditions, infections, drug and medication-induced causes, inflammation, neoplastic conditions, metabolicendocrine conditions, iatrogenic conditions, musculoskeletal conditions, and myofacial causes. In many situations, however, even though the underlying cause of the headache may be identified and treated, the headache pain itself may persist. 
         [0004]    Recent clinical studies in treatment of headaches have targeted the manipulation of sphenopalatine (pterygopalatine) ganglion (SPG), a large, extra-cranial parasympathetic ganglion. A ganglion is a mass of neural tissue found in some peripheral and autonomic nerves. Ganglia are located on the roots of the spinal nerves and on the roots of the trigeminal nerve. Ganglia are also located on the facial, glossopharyngeal, vagus and vestibulochoclear nerves. The SPG is a complex neural ganglion with multiple connections, including autonomic, sensory, and motor connections. The SPG includes parasympathetic neurons that innervate, in part, the middle cerebral and anterior cerebral blood vessels, the facial blood vessels, and the lacrimal glands. 
         [0005]    The maxillary branch of the trigeminal nerve and the nerve of the pterygoid canal (also known as the vidian nerve which is formed by the greater and deep petrosal nerves) send neural projections to the SPG. The fine branches from the maxillary nerve (pterygopalatine nerves) form the sensory component of the SPG. These nerve fibers pass through the SPG and do not synapse. The greater petrosal nerve carries the preganglionic parasympathetic axons from the superior salivary nucleus, located in the pons, to the SPG. These fibers synapse onto the postganglionic neurons within the SPG. The deep petrosal nerve connects the superior cervical sympathetic ganglion to the SPG and carries postganglionic sympathetic axons that again pass through the SPG without any synapsing in the SPG. 
         [0006]    The SPG is located within the pterygopalatine fossa. The pterygopalatine fossa is bounded anteriorly by the maxilla, posteriorly by the medial plate of the pterygoid process and greater wing of the sphenoid process, medially by the palatine bone, and superiorly by the body of the sphenoid process. The lateral border of the pterygopalatine fossa is the pterygomaxillary fissure, which opens to the infratemporal fossa. Various clinical approaches have been used to modulate the function of the SPG in order to treat headaches, such as cluster headaches or chronic migraines. These approaches vary from lesser or minimally invasive procedures (e.g., transnasal anesthetic blocks) to procedures or greater invasiveness (e.g., surgical ganglionectomy). Other procedures of varying invasiveness include those such as surgical anesthetic injections, ablations, gamma knife procedures, and cryogenic surgery. Although most of these procedures can exhibit some short term efficacy in the order of days to months, the results are usually temporary and the headache pain eventually reoccurs. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention relates to systems, devices, and methods for using an implantable medical device (“IMD”) to deliver therapy to a patient. According to one aspect, the invention relates to an IMD for delivering electrical stimulation to a peripheral, central or autonomic neural structure. In this aspect, the IMD may be a neurostimulator for treating primary headaches, such as migraines, cluster headaches, trigeminal autonomic cephalalgias and/or many other neurological disorders, such as atypical facial pain and/or trigeminal neuralgias. 
         [0008]    In one embodiment, an IMD and an associated handheld remote controller (“RC”) each may have an operating memory for storing a programmable operating instructions and data, both input and recorded, that govern the operation of each respective device. The IMD and RC each may also include processing hardware, associated with the operating memory, for executing the programmable operating instructions in accordance with the input and recorded data. According to one aspect, the IMD may receive, from the RC, operating instructions, data, or both operating instructions and data, that at least partially govern the therapies applied by the IMD. The IMD administers therapy in accordance with stimulation parameters stored on the IMD. The stimulation parameters may be programmed into the IMD in a variety of manners. For example, the stimulation parameters may be programmed via a programming system with the RC acting as an interface or wand. 
         [0009]    The ability of an inductively powered IMD to work at increasing implant depths depends on the ability to transmit greater amounts of power into the IMD from the external RC while still being able to detect the faint telemetry signals from the implanted device. In some RCs, a single coil of wire (also known as an inductive antenna, a loop antenna, a transmit/receiver coil or antenna, etc) is used for transmitting power and commands as well as for receiving telemetry from the IMD. The RC transmits power to the IMD while simultaneously receiving the telemetry signals from the IMD. As the IMD is planted physically further away from the RC, the power signal from the RC necessarily gets proportionally larger and the telemetry signal consequently gets proportionally smaller. 
         [0010]    Accordingly, the present invention relates to an apparatus for coupling a RC or similar external device to an IMD (or other device that needs to be powered at a distance, and has a telemetry link). The apparatus includes multiple coils in the RC to allow for sensitive detection of telemetry from the IMD while cancelling out the large power signal used for inductively powering the IMD. 
         [0011]    According to one aspect, the invention relates to an apparatus for applying stimulation therapy to a patient. The apparatus includes an implantable medical device and a remote controller for inductively powering the implantable medical device and communicating with the implantable medical device. The remote controller includes a transmit coil for transmitting a transmit signal to the implantable medical device and a receiver coil for receiving a telemetry signal from the implantable medical device. The receiver coil is configured to cancel out at least a portion of the transmit signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic illustration of the devices that form a portion of a system for delivering therapy using an IMD. 
           [0013]      FIG. 2  shows an implementation of a RC using a single coil to transmit and receive signals to an IMD. 
           [0014]      FIGS. 3  shows an implementation of the subject invention using a separate transmit coil and receiver coil, where the receiver coil is comprised of two coils. 
           [0015]      FIG. 4A  shows a possible geometric configuration of the coils. 
           [0016]      FIG. 4B  shows a cross section of  FIG. 4A . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]      FIG. 1  illustrates, by way of example, a medical device forming a portion of a system  10  that can be implemented in accordance with the invention. Referring to  FIG. 1 , according to one aspect of the invention, the system  10  includes an implantable medical device (“IMD”)  20  and a handheld remote controller (“RC”)  50 ,  50   a  for interfacing with the IMD  20  to provide power to and control operation of the IMD  20 . In this description, the term “implantable” is meant to describe that the medical device is configured for in vivo placement in the patient by surgical or other means. 
         [0018]    In the example embodiment illustrated in  FIG. 1 , the IMD  20  is an implantable neurostimulator. The IMD  20  may, for example, be a neurostimulator for delivering electrical stimulation to a peripheral, central, or autonomic neural structure. In this implementation, the IMD  20  may be a neurostimulator for treating primary headaches, such as migraines, cluster headaches, trigeminal autonomic cephalalgias and/or other neurological disorders, such as atypical facial pain and/or trigeminal neuralgias. Examples of these types of neurostimulators are shown and described in pending U.S. patent application Ser. Nos. 12/688,524 and 12/765,712, the disclosures of which are hereby incorporated by reference in their entireties. 
         [0019]    The RC  50 ,  50   a  illustrated in  FIG. 1  is for controlling and powering the IMD  20  which, in this example embodiment, is a neurostimulator. The RC  50 ,  50   a  of  FIG. 1  is therefore adapted to control and power a neurostimulator IMD  20 . The RC  50 ,  50   a  could, however, control and power alternative devices capable of receiving wireless control and power signals. The RC  50 ,  50   a  may, for example, have some or all of the features shown and described in U.S. Provisional Application Nos. 61/578,337 and 61/578,415, the disclosures of which are hereby incorporated by reference in their entireties. 
         [0020]      FIG. 2  illustrates schematically an example configuration of the system  10  of  FIG. 1 . In the example configuration of  FIG. 2 , the IMD  20  includes circuitry  100  that is adapted to perform the functions of that particular IMD. In the illustrated example, the IMD circuitry  100  is adapted to perform the neurostimulation functions of the IMD  20 . The circuitry  100  also includes a transmit/receive coil  110  that is operatively connected to the circuitry  100 . 
         [0021]    In the example configuration of  FIG. 2 , the RC  50  includes circuitry  200  that is configured to provide power and control signals to the IMD  20  and to receive feedback signals from the IMD. The circuitry  200  includes a single power/transmit/receive coil  210  that is connected to a driver circuit  230  and to a receiver circuit  250 . The driver circuit  230  is operatively connected to a power supply  220 , such as a rechargeable or replaceable battery power supply, and to a data source  240 , such as processing hardware and/or operating memory of the RC  50 . The receiver circuit  250  is configured and arranged to supply data  260  to components of the RC  50 , such as processing hardware and/or operating memory. 
         [0022]    In operation of the example configuration of the system  10  shown in  FIG. 2 , the driver circuit  230  utilizes electrical power from the power supply  220  to energize and drive the coil  210  to transmit a power signal to the IMD  20 . The driver circuit  230  transmits the power signal at a strength and frequency sufficient to power the IMD  20 , given the relative distance between the RC  50  and the implanted IMD. The power signal generated by the RC  50  excites coil  110  of the IMD  20  which induces electrical current in the coil  110 , thus powering the IMD  20  via induction. This induced electrical current supplies power to the IMD  20  which, in turn, utilizes the power to apply therapy (e.g., neuromodulation therapy) to the patient. 
         [0023]    The circuitry  200  of the RC  50  is also operable to provide commands to the IMD  20  for controlling its operation. In response to the received data  240 , the driver circuit  230  of the RC  50  is adapted to modulate a control signal that is transmitted to the IMD  20  via the coil  210 . The circuitry  100  of the IMD  20  receives the signal via the coil  110  acting as an antenna, and applies neurostimulation therapy according to the instructions/data contained therein. 
         [0024]    The IMD  20  also utilizes the induced power received from the RC  50  to transmit via the coil  110  any communication and/or feedback signals to the RC  50 . To do this, the IMD  20  circuitry  100  can selectively change the impedance of the coil  110  to create a telemetry signal that is transmitted to the RC  50 . 
         [0025]    The circuitry  200  of the RC  50 , while powering and controlling the IMD  20 , is further operable to simultaneously receive the communication and/or feedback signals from the IMD  20 . The telemetry signal is picked up by the coil  210  of the RC  50  and supplied to the receiver circuit  250 . The receiver circuit  250  filters and amplifies the telemetry signal and supplies the communication and/or feedback contained in the telemetry signal as the data  260  to the processing hardware and/or operating memory of the RC  50 . 
         [0026]    In the configuration  200  of  FIG. 2 , the driver circuit  230  generates a very large power signal that is transmitted via the coil  210  at the same time that the receiver circuit  250  is trying to detect a very faint telemetry signal received via the same coil  210 . This power/transmit/receive multiple functionality of the coil  210  is disadvantageous because the strong power signal can interfere with the detection of the comparatively weak telemetry signal. In the embodiment of  FIG. 3 , the system  10  has a configuration that is designed to help overcome these disadvantages and to help improve the transmit/receive performance of the system. 
         [0027]      FIG. 3  illustrates schematically a configuration of the RC  50   a  of the system  10  of  FIG. 1 . In the system  10  of  FIG. 3 , the IMD  20  can be identical to the IMD of the system shown in  FIG. 2 , thus including IMD circuitry  100  and IMD coil  110 . The IMD  20  therefore can be similar or identical in function and design to that which is described above in reference to the IMD of  FIG. 2 . 
         [0028]    According to the invention, the RC  50   a  of the system  10  illustrated in  FIG. 3  has circuitry  300  that differs from the circuitry  200  of the RC  50  illustrated in  FIG. 2 . The circuitry  300  is configured to provide power and control signals to the IMD  20  and to receive signals from the IMD. In the embodiment of  FIG. 3 , the RC circuitry  300  includes a power coil  310  and a separate receiver coil  315 . 
         [0029]    The power coil  310  is connected to a driver circuit  330 . The driver circuit  330  is operatively connected to a power supply  320 , such as a rechargeable or replaceable battery power supply. The driver circuit  330  is also operatively connected to a data source  340 , such as processing hardware and/or operating memory of the RC  50   a.    
         [0030]    The receiver coil  315  is operatively connected to the receiver circuit  350 . The receiver circuit  350  is configured and arranged to supply data  360  to components of the RC  50   a,  such as processing hardware and/or operating memory. In the system  50   a  of  FIG. 3 , the receiver coil  315  includes two sub-coils  317  and  319 . According to the invention, the sub-coils  317  and  319  are configured and geometrically aligned such that common signals received by both sub-coils cancel each other out and, therefore, the receiver  350  does not register the canceled signal. In this manner, the receiver coil  315  of RC  50   a  is configured to cancel the power signal from the transmit coil, which allows the receiver  350  to register and receive the telemetry signal from the IMD  20  with little or no interference from the power signal. 
         [0031]    The coils  310  and  315  of the RC  50   a  can have many alternative constructions. In one example construction of the RC  50   a,  the transmit coil  310  can be made of a comparatively heavy Litz wire and can carry peak currents of about 5 to 20 amps at a voltage of around 200 to 500 volts. The transmit coil  310  can have relatively few turns—for example in the range of 20 to 80 turns. The receiver coil  315  is made a fine single strand wire and does not carry high current. Since, however, the receiver coil  315  can have comparatively large numbers of turns—for example measured in the hundreds—it can produce voltages that can be in excess of 1000 volts. Thus, construction of the receiver coil  315  can require heavy build wire for its construction. 
         [0032]    Referring to  FIGS. 4A and 4B , the transmit coil  310  and receive coil  315  of the RC  50   a  are configured and arranged such that the receiver coil  315  cancels out the power signal generated by the transmit coil  310 . 
         [0033]    The transmit coil  310  and the receiver coil  315  are geometrically and spatially arranged relative to each other within the RC  50   a  so that the sub-coils  317  and  319  each receive the identical power signal from the transmit coil. More specifically, the receiver sub-coils  317  and  319  are arranged such that the wave of the power signal generated by the transmit coil  310  excites both sub-coils equally (e.g., in terms of frequency, amplitude, angle, etc.) and simultaneously to the greatest extent possible through their relative geometric and spatial configurations within the RC  50   a.    
         [0034]    Electrically, the receiver coil  315 , is configured such that the positive terminal  317   a  of sub-coil  317  is connected to the positive terminal  319   a  of sub-coil  319 , as shown in  FIG. 3 . The geometric and electrical configuration of the receiver sub-coils  317  and  319  are thus excited in an equal and opposite manner and thus cancel out the signal received from the transmit coil  310 . The other terminals of sub-coils  317  and  319  are connected to the receiver  350 . 
         [0035]    An example embodiment of one such suitable geometric relationship is illustrated schematically in  FIGS. 4A and 4B . In this embodiment, the transmit coil  310  has a circular coil configuration. The sub-coils  317  and  319  of the receiver coil  315  are have a “D” shaped configuration and are arranged symmetrically in a mirror-imaged fashion and nested centrally within the transmit coil  310 . The positive terminals  317   a  and  317   b  of the of sub-coils  317  and  319  are electrically connected by wire  515  and the other (negative) terminals  317   b  and  319   b  are connected to the receiver  350  via wires  525  and  526 , respectively. With this arrangement, the sub-coils  317  and  319  can be effectively wound in opposite directions. 
         [0036]    The degree of signal cancellation can be fine-tuned by adjusting the position of the receiver coil  315  relative to the transmit coil  310  and monitoring the signal received via the wires  525  and  526 . When the monitored signal strength reaches its lowest level, the position of the receiver coil  315  relative to the transmit coil  310  within the RC  50   a  is ideal. The receiver coil  315  can be fixed at this ideal position so that future signal detection performed by the RC  50   a  is done with optimal transmit signal cancellation. 
         [0037]    From the above, those skilled in the art will appreciate that the configuration of the receiver coil  315  in the RC  50   a  can effectively cancel reception of the power signal from the transmit coil  310 . Those skilled in the art will also appreciate that the configuration of the receiver coil  315  can have little or no effect on receiving the telemetry signal from the IMD  20  coil  110 . This is because, as discussed above, the effective cancellation of a signal (e.g., the power signal) by the receiver coil  315  relies on precise spatial and geometric positioning of the receiver sub-coils  317  and  319  relative to the transmitting coil. Since the IMD  20  is implanted according to patient&#39;s anatomy, the position of the IMD coil  110  relative to the receiver coil  315  is variable and constantly changing. Thus, cancelation of the IMD telemetry signal would be rare, sporadic, and coincidental, and would be alleviated simply by re-positioning the RC  50   a.    
         [0038]    The telemetry signal from the IMD  20  coil  110  is only cancelled out by the RC  50   a  receiver coil  315  if the IMD  20  coil  110  is perfectly aligned with the RC  50   a  receiver coil  315 . In an actual implant, it can be very difficult to get the IMD  20  coil  110  and the RC  50   a  receiver coil  315  to be perfectly aligned. And, if that should occur, it is easy for the user to move the RC  50   a  slightly to get the two coils to be slightly misaligned. 
         [0039]    To increase the sensitivity of the receiver coil  315  to faint telemetry signals from the IMD  20  coil  110 , the number of windings on both sub-coils  317  and  319  can be increased. However, the receiver coil  315  remains insensitive to the power signal on the transmit coil  310  since the power signal from the transmit coil  310  is cancelled out by the sub-coils  317  and  319 . This enables power to be sent to a more deeply implanted IMD  20  without adversely affecting the ability of the receiver  350  to detect a faint telemetry signal from the IMD coil  110 . 
         [0040]    The embodiment of  FIGS. 4A and 4B  illustrates a symmetrical configuration of the sub-coils  317  and  319 . The signal canceling features of the receiver coil  315  do not, however, necessarily rely on this symmetrical configuration. The RC  50   a  could, for example, have circuitry  300  configured such that the sub-coils of the receiver coil  315  have asymmetrical configurations. The sub-coils, while asymmetrical, can be configured to cancel the signal generated by transmit coil  310 . 
         [0041]    For example, the sub-coil  317  may be configured to be physically smaller than the sub-coil  319 . To compensate for this, the sub-coil  317  could be configured to have a greater number of turns/windings. Additionally or alternatively, the sub-coil  317  could be positioned relative to the sub-coil  319  and relative to the transmit coil  310  such that the power signal from the transmit coil  310  acts more directly or with a greater signal strength on the smaller sub-coil  317 . As a result, the excitation of the asymmetrical sub-coils  317  and  319  may nevertheless cancel the transmit signal, thus enabling a more effective reception of the telemetry signal from the IMD  110 . 
         [0042]    From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.