Abstract:
In supplying energy to a medical device implanted in a mammal patient a first coil system ( 20 ) external to the patient&#39;s body for wirelessly transferring energy can be used that inductively cooperates with a second coil system ( 12 ) that, when implanted in the patient&#39;s body, receives wirelessly transferred energy for supplying energy or control signals to the medical device, when implanted in the patient&#39;s body. The first and second coil systems comprise each at least two individual coils ( 50, 51; 60, 61 ) which are not directly electrically connected to each other and operate basically independently of each other. This may give a very efficient and versatile transfer of energy or control signals. The coils in each of the coil systems can be operating at different frequencies by being connected to respective electric circuits, where each of these respective electric circuits operate basically independently of each other generating e.g. alternating electric current of different frequencies.

Description:
This application is the U.S. national phase of International Application No. PCT/SE2010/050857 filed 19 Jul. 2010 which designated the U.S. and claims the benefit of U.S. Provisional No. 61/213,804, filed 17 Jul. 2009; and which claims priority to Swedish Application No. 0901004-2 filed 17 Jul. 2009, the entire contents of each of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to medical implants, and, more particularly, to coil systems for supplying energy or control signals to, or information from, a medical device implanted in a human or animal patient&#39;s body. 
     BACKGROUND 
     Medical devices are implanted in humans or animals for many reasons. Some of these devices are used to monitor one or more bodily functions. Other devices are used to stimulate or out rightly control bodily functions. Often, the medical devices will include some kind of communications circuit for receiving signals used to power and/or control the devices, or for sending outside a patient&#39;s body information about the medical device or bodily functions monitored or controlled by the device. Typically, medical devices are powered by an electric power supply, such as a battery, that provides the voltage and current needed for their operation. 
     Medical devices are often intended to be implanted in a patient&#39;s body for many years, and in some instances, for the rest of a patient&#39;s life. As such, the power supplies used to power these long-term medical devices are implanted in a patient at a location that permit easy access from outside the patient&#39;s body for recharging or replacement of the power supply. Typically, these power supplies are recharged by energy drawn from an alternating magnetic field generated outside of a patient&#39;s body and extending into inside of the patient&#39;s body using a pair of coils. The pair of coils includes a first or primary coil that generates the alternating magnetic field when an electric current is flowing therein and a second or secondary coil that is implanted in a patient&#39;s body. Alternatively, the second coil implanted in a patient&#39;s body may be connected directly to a power supply or to a medical device implanted in the patient. There can exist a problem that it is difficult to transfer sufficient amounts of energy for driving such a medical device. Thus, it would be desirable to provide a coil system including primary and secondary coils allowing a relatively high rate of energy transfer. 
     SUMMARY 
     The present invention is directed to coil arrangements or coil systems for supplying energy or control signals to, or providing information from, a medical device implanted in a human or animal patient where the medical device is used to monitor one or more bodily functions or to stimulate or out rightly control one or more bodily functions. 
     Thus generally, apparatus for supplying energy to a medical device implanted in a mammal patient comprises a coil arrangement including: 
     a first coil system external to the patient&#39;s body for wirelessly transmitting energy, and 
     a second coil system that when implanted in the patient&#39;s body, receives wirelessly transferred energy for supplying energy or control signals to the medical device, when implanted in the patient&#39;s body, 
     At least one of the first and second coil systems comprises a plurality of, i.e. at least two, individual coils. These coils are not directly electrically connected to each other. They operate basically independently of each other. Thus, each of the plurality of individual coils can be connected to a respective electric circuit and then each of these respective electric circuits operate basically independently of each other. 
     Each of the respective electric circuits can then generate an alternating electric current so that the currents generated for and supplied to different coils having different frequencies. 
     Each of the respective electric circuits can then be arranged for receiving on different frequencies. 
     In an alternative embodiment the apparatus for supplying energy to a medical device implanted in a mammal patient, the apparatus comprising: 
     a first coil system external to the patient&#39;s body for wirelessly transmitting energy for powering the medical device, 
     a second coil system that when implanted in the patient&#39;s body, receives wirelessly transferred energy for supplying energy or control signals to the medical device, when implanted in the patient&#39;s body, 
     wherein at least one of the first and second coil systems comprise a plurality of individual coils which in terms of frequency tuned energy supply operate basically independently of each other, for improving energy transmitting capacity, when implanted. 
     In an alternative and preferred embodiment the coil systems are working independently, but both at least two coil systems are connected to the same electronic circuit. The coil systems are preferable tuned with a capacitor so to have the sending outer coil tuned with the same frequency as the receiving coil, but the different integrated coil systems tuned with different frequencies. Thus, reducing the amount of energy field the patient have to tolerate at each frequency span, thus allowing higher energy transmission. The electric circuit may comprise a separate rectifier system for each coil system. They may be integrated in one common energy supply to an implant. Two or more different batteries connected in series may be used. 
     The apparatus may have each of said plurality of individual coils connected to one common electric circuit, handling the different tuned frequency supplies of energy. The apparatus may have each of said plurality of individual coils connected the electric circuit generating an alternating electric current, the currents generated for different coils having different frequencies. The apparatus may have each of said plurality of individual coils connected to the electric circuit for receiving on different frequencies. 
     The apparatus preferable have each of said plurality of individual coils connected to different rectifiers of the electric circuit for receiving on different frequencies. The different rectifiers may supply energy to two or more different batteries supplying energy to an implant and connected in series after each other. The different rectifiers are preferable integrated in one electronic circuit solution for one energy supply. A switched coil may be used in such integration. Each of said plurality of individual coils are preferable tuned with a capacitor connected in parallel over the coil, wherein each coil system comprising said sending outer coil and receiving inner coil are tuned at a different frequency. 
     In the case where the second coil system is implanted in a patient to supply energy to an energy-consuming implanted medical device, the second coil system can be connected to an implanted control device which, in turn, is connected to an implanted power supply connected to an implanted medical device, or directly to the implanted medical device. Alternatively, the second coil system can be connected to the implanted power supply connected to the medical device, or directly to the implanted medical device. 
     In the case where the second coil system is implanted in a patient to receive control signals for controlling the operation of an implanted medical device, the implanted second coil system is preferably connected to an implanted control device that is a receiver which, in turn, is connected to the implanted medical device. In the case where the implanted coil also transmit information from the implanted medical device, the second coil system can be connected to an implanted control device that is a transceiver which, in turn, is connected to the implanted medical device. The transceiver functions to receive control signals received by the second coil system and to provide informational signals to the second coil for transfer outside the patient&#39;s body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of apparatus for supplying energy or control signals to, or information from, a medical device implanted in a human or animal patient&#39;s body. 
         FIG. 2A  is a schematic of the configuration and location of coils included in a coil arrangement used in the apparatus of  FIG. 1  illustrating transfer of energy and information. 
         FIG. 2B  is similar to  FIG. 2A  but illustrating only transfer of energy. 
         FIGS. 2C-2F  are similar to  FIG. 2B  of coils having various alternative configurations and locations. 
         FIG. 3  is a schematic diagram showing the coil arrangement of any of  FIGS. 2A-2F  and the apparatus of  FIG. 1  implanted in the body of a human patient. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic diagram of an apparatus  10  using a coil arrangement  11  to supply energy and/or control signals to and/or information from a medical device  14  implanted in a human or animal patient&#39;s body.  FIG. 1  shows the basic park of the apparatus  10 . All park placed to the left of the patient&#39;s skin  16  are located outside the patient&#39;s body and all park placed to the right of the skin  16  are implanted in the patient&#39;s body. 
     The coil arrangement  11  includes a first or primary coil system  20  and a second or secondary coil system  12 , the first and second coils systems functioning as electrical conductors inductively coupled to each other, forming a transformer like circuit or transformer like circuit for the purpose of transferring alternating electrical energy signals into and out of a patient&#39;s body that supply energy or control signals to, or information from, the medical device  14  implanted in the patient&#39;s body  36 . 
     The coil arrangement  11  has many similarities with an electrical transformer. An electrical transformer is an electrical device that transfers electrical energy from one circuit to another circuit through inductively coupled electrical conductors that may be formed into coils. An alternating current in a first winding or circuit of the transformer, often called the primary circuit, creates an alternating magnetic field, which induces an alternating voltage in a second winding or circuit of the transformer, often called the secondary circuit. An electric current, derived from induced alternating voltage, can then flow in the secondary winding or circuit to a load circuit connected to the secondary circuit, so as to transfer energy from the primary circuit through the secondary circuit to the load circuit connected to secondary circuit. 
     The apparatus  10  includes an external control unit  18  located outside of the patient&#39;s body. The external control unit  18  typically comprises a generator for generating an alternating electromagnetic signal, a modulator circuit and a power amplifier. The external control unit  18  may include a microprocessor for generating control signals to be sent to the implanted medical device  14 . The microprocessor is capable of switching the generator on and off and of controlling the modulator circuit to modulate signals generated by the generator to send control information to the implanted medical device  14  via the power amplifier and a transmitting coil system  20  connected to the power amplifier in the external control unit  18 . In the case where the external control unit  18  is a transceiver that functions to both transmit control signals to the implanted medical device  14  and receive information signals from the implanted medical device  14 , the external control unit  18  also includes a demodulator that is connected to the first coil system  20 , which receives the information sent from the implanted medical device  14 . The demodulator demodulates information signals received by the first coil system  20  so as to strip out the information sent from the implanted medical device  14 . Typically, such information will relate to bodily functions being monitored by the implanted medical device or the results of bodily functions controlled by the implanted medical device. 
     Implanted in the patient&#39;s body is an implanted control unit  22 , which is connected to the implanted coil system  12 . In the case where the second, implanted coil  12  is used to supply energy to the implanted medical device  14 , the implanted control unit  22  may e.g. include a rectifier circuit for converting alternating signals received by the second coil system  12  into a direct current signal that is suitable for either powering the operation of the implanted medical device  14  or for charging an implanted rechargeable energizer unit  24  that powers the operation of the implanted medical device  14 . 
     In the case where the second coil system  12  is used to receive control signals from the external control unit  18  and to transmit information signals from the implanted medical device  14  to the external control unit  18 , the implanted control unit  24  will further comprise a demodulator and a microprocessor. The demodulator demodulates signals sent from the external control unit  18 . The microprocessor receives the demodulated signal and sends control signals via a control line  26  to the implanted medical device to control its operation. 
     In the case where the implanted control unit  22  is a transceiver that functions to both receive control signals from the external control unit  18  and transmit information from the implanted medical device  14 , the implanted control unit  22  will also include a generator for generating an alternating electromagnetic signal, a modulator circuit for modulating the generated alternating electromagnetic signal and a power amplifier connected to the implanted coil  12 . The microprocessor is capable of switching the generator on and off and of controlling the modulation circuit to modulate the signals generated by the generator to send information from the implanted medical device  14  via the power amplifier and the second, implanted coil system  12  connected to the power amplifier to the external control unit  18 . 
       FIG. 2A  is a schematic of a coil arrangement  11  comprising a first coil system  20  comprising generally two or more individual coils  50 ,  51  and a second, implanted coil system  2  generally comprising two or more individual, implanted coils  60 ,  61 . The wireless energy transfer from the first coil system  20  to the second coil system  12  is indicated by the arrows  70  and the transfer of signals between the two coil systems is indicated by the dashed lines  71 . 
     Each of the individual coils  50 ,  51  of the first coil system  20  can be connected to an own generator for generating an alternating electromagnetic signal and also, an own modulator circuit when required and an own power amplifier when required. The individual generators can then generate alternating electromagnetic signals of frequencies that are different from each other so that one coil  50  is supplied with an alternating electromagnetic signal of a first frequency and another coil  51  is supplied with an alternating electromagnetic signal of a second frequency different from the first frequency. 
     The microprocessor in the external control unit  18  can then be capable of switching each of the generators on and off and of controlling the respective modulator circuit to modulate signals generated by the generators to send control information to the implanted medical device  14  via respective power amplifiers if required and the coils of the transmitting, first coil system  20 . 
     In the case where the external control unit  18  is a transceiver that functions to both transmit control signals and receive information signals, the external control unit  18  also includes individual, respective demodulators connected to the individual coils of the first coil system  20 , which receive the information sent from the implanted medical device  14 . The demodulators demodulate information signals received by coils of the first coil system  20  to extract the information sent from the implanted medical device  14 . 
     In the case where the second, implanted coil system  12  is used to supply energy to the implanted medical device  14 , each of the individual coils  60 ,  61  of the second coil system  12  can be connected to respective, individual rectifier circuits for converting alternating signals received by the respective coil of the second coil system  12  into a direct current signal that is suitable for either powering the operation of the implanted medical device  14  or for charging an implanted rechargeable energizer unit  24  that powers the operation of the implanted medical device  14 . 
     In the case where the second coil system  12  is used to receive control signals from the external control unit  18 , the implanted control unit  24  comprises individual demodulators connected to the coils  60 ,  61  of the second coil system, one demodulator arranged for and connected to each of the coils. The demodulators demodulate signals sent from the external control unit  18  and forwards them to the microprocessor included in the implanted control unit. 
     In the case where the implanted control unit  22  is a transceiver that functions to both receive control signals from the external control unit  18  and transmit information from the implanted medical device  14 , the implanted control unit  22  also includes for each of the coils  60 ,  61  in the second coil system  12  an individual generator for generating alternating electromagnetic signals, the signals generated by one of such generators having wavelengths that are different from those generated by the other of such generators. For each of the coils also an individual modulator circuit for modulating the generated alternating electromagnetic signal is arranged and a power amplifier connected to the respective implanted coil  60 ,  61  can be provided when required. The microprocessor in implanted control unit  22  is capable of switching the generators on and off and of controlling the individual modulation circuits to modulate the signals generated by the respective generator to send information from the implanted medical device  14  via the power amplifier and the second, implanted coil system  12  to the external control unit  18 . 
     Obvious alternatives to the above described total system for transferring energy and information include 
     that only one of the individual coils  50 ,  51  of the first coil system  20  and only one of the individual coils  60 ,  61  of the second coil system are used to transfer information, or 
     that only one of the individual coils  50 ,  51  of the first coil system  20  is used to transfer information to one of the individual coils  60 ,  61  of the second coil system  12  and another of the individual coils  60 ,  61  of the second coil system is used to transfer information in the opposite direction to another of the individual coils  50 ,  51  of the first coil system  20 . 
     Then, obviously, modulators and demodulators are only provided where required. 
     Thus, the individual coils of the first coil system  20  and the individual coils of the second coil system can be arranged in pairs, so that each pair comprises one coil in the first coil system and one coil in the second system, each coil only included in one pair. The transfer of energy and/or information between the coils in one pair is made using frequencies that are different from the frequencies used by the other pair or the other pairs. 
     The individual coils of the first and second coil systems  20 ,  12  can have different geometric configurations as illustrated in the schematics of  FIGS. 2A-2F . Each of the coils is as conventional formed from an electrically conducting wire. As seen in  FIGS. 2A and 2B  the coils  50 ,  51 ;  60 ,  61 , also called windings, can have a generally toroidal shape. Such a coil is formed from a wire that is helically wound around a toroidal axis that has the shape of a closed curve. The toroidal axis can be substantially flat. It can e.g. as illustrated be a circle. The toroidal axes of the coils included in each of the first and second coils systems  20 ,  12  can be located in the same plane. As illustrated, the toroidal axes of the coils included in each of the first and second coils systems  20 ,  12  can also be concentric so that an inner coil  51 ;  61  has a toroidal axis of a size or diameter that is smaller than that of an outer coil  50 ;  51 . The inner coil can then be located completely separated from the outer coil, such as inside the outer coil as illustrated. 
     The individual coils seen in  FIGS. 2C and 2D  included in one of the first and second coil systems  20 ,  12  are also located completely separated from each other. They are also located in the same plane but in these cases at the sides of each other and can then both have the same basic shape and size. The coils  50 ′,  51 ′;  60 ′,  61 ′ of  FIG. 2C  have toroidal axes that include a substantially straight segment whereas the rest of the respective axis is curved, such as having a substantially part-circular or part-elliptic shape. The straight segments of the two coils in one of the first and second coil systems can then be parallel to each other and located adjacent to or facing each other. 
     As seen in  FIG. 2D  the coils included in the first coil system  20  can have a configuration that is different from, even quite different from, the configuration of the coils included in the second coil system  12 . 
     The coils included in one of the first and second coil systems  20 ,  12  can also, as seen in  FIG. 2F , be located so that the electrically conducting wire of one of the coils is intermeshed with or entangled with the wire of another of the coils. Thus, the two coils can have the same toroidal axis but e.g. different diameters of the helical winding. Also, the pitch of the helical windings can be different. 
       FIG. 3  is a schematic diagram showing a coil arrangement  11  according to any of  FIGS. 2A-2F  and the apparatus  10  of  FIG. 1  implanted in the body  34  of a human patient  36 . As shown in  FIG. 3 , the second coil system  12  is implanted in the body  34  of patient  36  at a location  38  that may permit easy access to the second coil system from outside the patient&#39;s body  34 . For example, the coil  12  can be implanted subcutaneously in the skin  16  of the patient  36  at a location for such easy access. Then, the implanted control unit  22  and the rechargeable energizer unit  24  can also be located at an easy access location within the body  34  of the patient  36  and then connected by one or more wires to the implanted medical device  14 . 
     It should be noted that  FIGS. 1 ,  2 A- 2 F and  3  are not intended to depict a particular orientation of the external coil system  20  and/or the implanted coil system  12  with respect to the body of a patient with whom these devices are used. Rather, it should be noted that either or both of these devices can be oriented horizontally, vertically or otherwise with respect to the body of a patient to accommodate the needs of a particular application in which these devices are used. Furthermore, the coil system . . . itself could be done any one of many different ways. Preferably, the coil winding is compact with the windings concentrated in a small transversal area. A core could also be used with the coil, but it is not required. If such a coil were to be implanted in a patient with a substantially horizontal orientation vis-à-vis the substantially vertical orientation of the patient, when standing, the coil would preferably be very low in subcutaneous height, thereby avoiding protruding material under the skin. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangement included within the spirit and scope of the appended claims.