Abstract:
In a method and device for wireless energy transmission between a magnetic coil system, having multiple excitation coils located outside of a patient, to a working capsule located in the patient, the working capsule has at least one induction coil, and a positioning device determines the position and orientation of the working capsule relative to the magnetic coil system. Using the position and orientation information, the magnetic coil system generates a first magnetic field that exerts a force on the working capsule at a location of the working capsule in the patient. The magnetic system also uses at least one of the position or the orientation to generate a second magnetic field for energy transmission to the working capsule at the location within the patient.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention concerns a method and a device for wireless energy transmission from a magnetic coil system outside of a patient to a working capsule having at least one induction coil in the patient. If multiple induction coils are present, these are aligned parallel to one another. 
         [0003]    2. Description of the Prior Art 
         [0004]    In medicine it is frequently necessary to execute a medical procedure (which, for example, can be a diagnosis or a treatment) inside a (normally living) person or animal as a patient. The target area of such a medical procedure is often a hollow organ in the appertaining patient, in particular his gastrointestinal tract. For a long time the medical procedures have been conducted with the aid of catheter endoscopes which are inserted into the patient from the outside in a non-invasive or minimally-invasive manner. Conventional catheter endoscopes hereby exhibit various disadvantages; for example, they cause pain in the patient or can reach remote internal organs only with difficulty or not at all. 
         [0005]    Therefore, video capsules from the company Given Imaging which the patient swallows are known for catheter-free or wireless endoscopy, for example. The video capsule moves through the digestive tract of the patient due to peristalsis and hereby acquires a series of video images. These are transmitted to the outside and stored in a recorder. The patient can freely move during the multiple hours in which the capsule resides in the body since the patient takes corresponding reception antennas and a recorder with him or her on his or her body. The alignment of the capsule and therewith the viewing direction of the video images as well as the duration of residence in the body of the patient are random. The capsule has no active functionality except for the image acquisition. Diagnostic functions such as targeted observation, cleaning, biopsy are not possible, more are targeted treatments inside the patient, for example medicine administration. This is unacceptable or unsatisfactory for a complete diagnosis. 
         [0006]    Lately it has become known (for example from DE 103 40 925 B3) to move magnetic bodies through hollow organs of a patient by means of magnetic, contact-free force transfer with the use of a magnetic coil system. The force application ensues in a targeted manner, without contact and controlled from the outside. 
         [0007]    A magnetic body is, for example, a working capsule (also called an endocapsule or an endorobot) containing a permanent magnet. The working capsules exhibit functionalities of a conventional endoscope, for example video acquisition, biopsy or clips. A medical procedure can thus be implemented autarchically (i.e. wirelessly or without a catheter) with such a working capsule; no cable or mechanical connection from the working capsule to the exterior of the patient exists. 
         [0008]      FIG. 3  shows a magnetic coil system  100  (known from DE 103 40 925 B3) that is described briefly in the following. DE 103 40 925 B3 is referenced for a more comprehensive, detailed description of the magnetic coil system  100  and its mode of operation. The magnetic coil system  100  has fourteen excitation coils  102   a - n,  of which only the excitation coils  102   a - c,    102   d  and  102   g - n  are visible in  FIG. 3 . The six excitation coils  102   a - f  are thereby executed as rectangles and form the edges of a cuboid. 
         [0009]    The remaining eight excitation coils  102   g - n  together form the generated surface of a cylinder embedded in the cuboid just described. Every single one of the excitation coils  102   a - n  is connected to a power supply  106  via a supply line  104   a - n.  For clarity only the supply lines  104   a - c  and  104   e  are shown in  FIG. 3 . A specific current strength with specific time curve (naturally in the scope of the capacity of the power supply  106 ) is impressed on each of the excitation coils  102   a - n  independent of one another via the power supply  106 . Each of the excitation coils  102   a - n  thus generates its own magnetic field. A nearly arbitrary field distribution in terms of strength and direction can therewith be generated in the inner chamber  108  the magnetic coil system  100 . A patient (not shown) is located in this inner chamber  108 , and inside the body of this patient a working capsule  110  is located that contains a magnetic element (not shown), for example a permanent magnet. 
         [0010]    A positioning device  112  is associated with the magnetic coil system  1001  which positioning device  112  detecting the attitude and orientation of the working capsule  110  in a coordinate system  114  associated with the magnetic coil system  100 . The attitude of the working capsule  110  or the attitude of the geometric center of this is indicated by the dashed line  116  in  FIG. 3 . The orientation of the working capsule  110  is represented by the arrow  118  in  FIG. 3  and is detected by the positioning device  112  relative to the coordinate system  114 . The working capsule can exhibit an arbitrary (for example oblong or rotationally symmetrical) geometric shape. The orientation would then correspond to the direction of the unit vector in the longitudinal direction of the working capsule  1101  for example, The entire attitude of the working capsule  110  (thus in particular the center of gravity coordinates and the longitudinal axis direction) is thus completely described and known in the coordinate system  114 . 
         [0011]    The positioning device  112  transmits attitude and orientation information of the working capsule  110  to the power supply  106 . The power supply  106  thereupon feeds the excitation coils  102   a - n  with current such that a magnetic field  120  (represented by the field lines  120  in  FIG. 3 ) appears at the location of the working capsule  110 . The magnetic field is designed so that it interacts with the permanent magnets in the working capsule  110  such that a desired force  122  and/or a desired torque (not shown) acts upon the working capsule  110 . The working capsule  110  in the patient is moved, aligned and/or rotated in this manner. 
         [0012]    All of the entire energy that the working capsule itself requires during the implementation of the medical procedure is provided by batteries or capacitors inside the working capsule, for example. The energy quantity is in particular limited by the limited size of such a working capsule (of, for example, 20 mm length and 10 mm diameter) and the other internal components. The functional duration or functional capability of the working capsule is likewise limited by the available energy quantity. Particularly power-intensive medical procedures such as, for example, hollow organ illumination, taking biopsies, thermal coagulation or laser applications can be implemented only in a limited manner or not at all. 
         [0013]    In order to increase the available total energy for a working capsule it is known to wirelessly transmit energy from outside the patient to the working capsule inside the patient. A coil arrangement that can be worn like a jacket is known for this purpose from United States Patent Application Publication No. 2005/0065407 A1, which coil arrangement the patient wears on the body and from which energy is transmitted to the capsule inside the patient. The direction of the transmission field is constant; the reception coil must thus be correspondingly designed. A separate cooling of the transmission coils that is designed for this purpose is additionally provided in the wearable coil arrangement. 
         [0014]    To reduce the transmission losses of the energy from the outside of the patient to the working capsule inside the patient, WO 02/080753 A2 suggests to locate the capsule inside the patient and to shift an external energy source (which surrounds the patient approximately in the shape of circular sectors) in the longitudinal direction of the patient to the level of the position of the capsule. Since the orientation of the capsule is unknown, orthogonal coils for receiving the energy are provided in the capsule in order to be able to always receive as much energy as possible in the capsule in every capsule orientation. 
         [0015]    To improve the energy reception in the working capsule in a given external field, in DE 10 2004 034 444 A1 it is proposed to use for energy reception a number of reception elements that exhibit different directional dependencies with regard to the radiated fields. For example, ten differently oriented receiver coils are arranged inside the capsule in order to always ensure an optimal energy coupling in the capsule. 
         [0016]    The more receiver coils that are to be provided in the working capsule, the smaller these must be individually designed if the total size of the capsule is to remain unchanged, However, since the energy feed into a coil depends on the coil surface, this consequently entails a reduction of the maximum energy or power that can be transmitted into coil (and thus into the working capsule). 
       SUMMARY OF THE INVENTION 
       [0017]    An object of the present invention is to provide a method and a device for improved wireless energy transmission from a magnetic coil system to a working capsule. 
         [0018]    With regard to the method, the object is achieved by a method for wireless energy transmission from a magnetic coil system comprising multiple (in particular fourteen) excitation coils outside of a patient to a working capsule in the patient which has at least one induction coil of the same alignment as the excitation coils, wherein 
         [0019]    a positioning device determines the position and orientation of the working capsule relative to the magnetic coil system and 
         [0020]    using the position and orientation, the magnetic coil system generates a first magnetic field for force exertion on the working capsule at the location of the working capsule, in which: 
         [0021]    the magnetic coil system generates a second magnetic field for energy transmission to the working capsule at the location of the working capsule using the position and/or orientation. 
         [0022]    The magnetic coil system in accordance with the invention has a number of excitation coils that are able to generate the first magnetic field necessary for force exertion on the capsule, the exertion of a torque is also to be understood as force exertion. The first magnetic field can thus also be designated as a navigation magnetic field. The first inhomogeneity non-homogenous magnetic field is a gradient magnetic field of complicated geometry, which gradient magnetic field can be scaled in direction and strength. The coil system is therefore easily able to also generate the (normally homogeneous) second magnetic field for energy transmission, and in fact in any orientation relative to the magnetic coil system. The second magnetic field can also be designated as an induction magnetic field. Six Helmholtz coils arranged as a cylinder or cuboid are sufficient for such field generation. 
         [0023]    The position and orientation of the working capsule must be known for the navigation, thus force exertion on the working capsule. A corresponding positioning device is thus present which determines the position and orientation of the induction coil relative to the magnetic coil system. Naturally, the attitude of the induction coil in the capsule must be known. In this simplest case the induction coil is therefore rigidly installed in the capsule. The positioning device is independent of the inductive energy transmission. 
         [0024]    In particular the momentary orientation of the induction coil is therefore also known since its attitude in the working capsule is known. The direction in which the magnetic field for inductive energy transmission is to be generated is thus known to the magnetic coil system or its controller. Namely, the second magnetic field can always be generated so that it optimally crosses the induction coil, for example precisely along the coil axis. The power received in the induction coil is thus maximal at a given field strength. The excitation coils are therefore controlled so that a second magnetic field is generated which is optimally aligned relative to the induction coil. 
         [0025]    Since a corresponding positioning device is present anyway in the cited magnetic coil system for contact-less force execution on the working capsule and the excitation coils for generation of the first low-frequency magnetic field are likewise present anyway, the excitation coils need only to be suitably controlled (thus in an alternative manner, i.e. with alternative current patterns) in order to generate the second magnetic field and thus to enable an energy transmission to the working capsule. 
         [0026]    With regard to the energy feed into the working capsule, the excitation coils are likewise dimensioned for the generation of the first magnetic fields such that powers of a magnitude which cannot be generated by systems such as the jacket-like system from US 2005/0065407 can be generated easily. Corresponding power transmission stages and cooling devices are likewise present. A sufficiently large power can therewith be transmitted to the working capsule, which also enables power-intensive or energy-intensive medical procedures. 
         [0027]    Since only a single induction coil must be present in the working capsule, this can be designed as large as possible; for example, it can cover the maximum capsule projection surface. Due to the maximum possible surface, the energy feed into the induction coil is therefore likewise as large as is now possible for a given size of the working capsule. 
         [0028]    The magnetic coil system can generate first magnetic field and second magnetic field in first and second frequency ranges differing from one another. The frequency ranges can then in particular be executed so that they do not overlap, such that navigation and energy transmission are associated with separate frequency ranges. A mutual interference is thus precluded. Namely, the second magnetic field is not capable of setting the capsule into motion since this possesses no significant gradient portion at the capsule location and thus exerts no force on the capsule, and the moment of inertia of the capsule in connection with the relatively high frequency range of (for example) over 1000 Hz (1 kHz) ensures that the second magnetic field (which is on average immaterial over time) leads to a negligible jitter movements of the capsule due to the impressed torque. 
         [0029]    Magnetic fields in a first frequency range between 0 Hz and 50 Hz, for instance, are particularly advantageous for force exertion on the working capsule. A second, non-overlapping, higher frequency range from 500 Hz to 10 kHz can then be used for the magnetic fields for energy transmission without interfering with those for force exertion and those of the magnetic measurement system. The frequency range from 500 Hz to 10 kHz is particularly suitable for transmission of the energy through human body tissue to the capsule at the given distances of approximately 20 to 60 cm between magnetic coil system and working capsule. 
         [0030]    Due to the difference of the frequency ranges for the first and second magnetic fields for force exertion and for energy transmission, these mutually barely influence one another. For example, the second magnetic field for energy transmission can be selected to be high-frequency and the first for navigation can be selected to be low-frequency. 
         [0031]    First magnetic field and second magnetic field can therefore be superimposed, This leads to the situation that an energy transmission to the capsule occurs simultaneously during the navigation or force exertion and movement of the working capsule through the patient, An energy storage in the capsule can thereby be avoided, for example. The installation space of the components for energy supply in the capsule becomes smaller or can be used for other internals which, for example, serve for the implementation of the medical procedure. 
         [0032]    Alternatively, the second magnetic field can be generated temporally multiplexed with the first magnetic field. First and second fields are thus generated in temporal rotation and not simultaneously. The respective maximum power of the magnetic coil system is available both for the movement or, respectively, force exertion on the working capsule and for the energy transfer thereto. An excitation coil system that is sufficient for movement of the working capsule thus does not have to be dimensioned larger for energy transmission, but rather can be utilized in a temporally multiplexed manner. 
         [0033]    For example, during the energy transmission the capsule then rests without force exertion in the patient. Due to correspondingly short time intervals between two energy transmissions, the energy storage in the capsule can be dimensioned such that this must only bridge the intervening time of the force exertion, A capacitor with small capacity and thus a smaller structural size is then sufficient, for example. The working capsule can also be utilized so that this only implements an energy-intensive medical procedure in the rest state. 
         [0034]    The position and orientation of the induction coil relative to the magnetic coil system can be determined in various ways. One possibility is determination by an x-ray system, The patient is x-rayed during the implementation of the medical procedure, such that the capsule can be recognized in terms of its position and orientation on the x-ray image. Due to the high x-ray contrast of the capsule, the dose of the x-ray exposure for the patient can be kept very low. Naturally, a corresponding registration (thus knowledge of the positions relative to one another) of the coordinate systems of magnetic coil system and x-ray system is hereby necessary; corresponding solutions are known from the literature. 
         [0035]    Thus no additional positioning devices must be installed in the capsule. The entire internal space of the capsule is available for other internal components. 
         [0036]    A second alternative is the use of an electromagnetic measurement system. Only minimal internals (i.e. those with small space requirements) are necessary for this purpose, for example an electromagnetic transmission or reception device. These can be executed correspondingly small, such that they require only a small space in the working capsule. 
         [0037]    In particular three positioning coils aligned orthogonal to one another which are used to determine the orientation of the induction coil can be present in the working capsule. Since, for their functioning, the positioning coils must consume barely any energy from an external magnetic field in order to implement the position detection, these can be designed distinctly smaller than the induction coil and thus require barely any space in the capsule. 
         [0038]    The electromagnetic position measurement system can operate in a third frequency range (that is again different from the first frequency range and second frequency range) in order to interfere with none of the other systems. The electromagnetic position measurement system can in particular be operated with a frequency of at least 10 kHz. Alternatively, position measurement system and second magnetic field can be operated in alternation for inductive energy coupling. 
         [0039]    In order to be able to control the excitation coils particularly well for generation of the magnetic fields for force exertion and energy transmission, the excitation coils can exhibit a plurality of taps and be operated via various taps. Different coils thus do not need to be provided for generation of the various fields; rather, a coil can be operated in different operating modes. A corresponding mounting and a cooling for the excitation coils thus only needs to be provided once. 
         [0040]    With regard to the device, the object of the invention is achieved via a device for wireless energy transmission from a magnetic coil system possessing multiple (in particular fourteen) excitation coils outside of a patient to a working capsule possessing at least one induction coil in the patient. The device has a positioning device for determination of a position and orientation of the working capsule relative to the magnetic coil system. The device furthermore has a control unit controlling the magnetic coil system. The control unit thereby controls the magnetic coil system or, respectively, adjusts the currents flowing into the excitation coils such that the magnetic coil system generates a first magnetic field at the location of the working capsule for force exertion on the working capsule. For this purpose, the control unit uses the position and orientation of the working capsule that are determined by the positioning device. Moreover, for energy transmission to the working capsule the control unit controls the magnetic coil system such that this generates a second magnetic field at the location of the working capsule. The control unit also uses the determined position and orientation of the working capsule for this. 
         [0041]    The advantages resulting from the inventive device have already been explained in connection with the inventive method. 
         [0042]    The device can have an x-ray positioning system for determination of position and orientation of the working capsule as explained above. 
         [0043]    Alternatively, for this purpose the device can have an electromagnetic positioning system, the working capsule can have three positioning coils aligned orthogonally to one another. 
         [0044]    As described, the excitation coils also possess various taps via which they can be selectively operated, for example for generation of the first magnetic field and second magnetic field. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0045]      FIG. 1  illustrates a magnetic coil system for magnetic navigation and energy transmission in accordance with the invention. 
           [0046]      FIG. 2  illustrates coil currents in an excitation coil of  FIG. 1  for navigation and energy transmission (a) separately, (b) modulated on one another and (c) in a temporally multiplexed manner. 
           [0047]      FIG. 3  illustrates a magnetic coil system for movement of a magnetic body in a patient according to the prior art. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0048]      FIG. 1  shows the known magnetic coil system from  FIG. 3  according to the prior art, expanded by an evaluation and control unit  2 . The evaluation and control unit  2  receives from the positioning device  112  the current position data  4  of the working capsule  110  in the coordinate system  114  as well as target data for a new position and speed from an operator control device (not shown). The position data  4  are the attitude (lines  116 ) and orientation (arrow  118 ) of the working capsule  110  in the coordinate system  114 , as explained in detail in connection with  FIG. 3 . 
         [0049]    In contrast to  FIG. 3 , the working capsule  110  has an internal induction coil  6 . For a given capsule geometry of the working capsule, this induction coil  6 , together with the electrical consumer (not shown) connected to it, is designed such that it injects a greatest possible electrical power into the electrical consumer given a field distribution of the external magnetic field crossing it in the direction of its longitudinal axis. In the example from  FIG. 1 , the induction coil  6  is executed with the largest possible diameter, meaning that it abuts directly on the inner side of the outer casing of the working capsule  110 . Since the attitude of the induction coil  6  in the working capsule  110  is fixed and known, the position data  4  likewise deliver position and orientation of the induction coil  6  to the evaluation and control unit  2 . 
         [0050]    The evaluation and control unit  2  calculates the currents I A (t) through I N (t) in the excitation coils  102   a - n  from the position data  4 . Only I A (t) is exemplarily plotted in  FIG. 1 . How the evaluation and control unit  2  controls the power supply  106  is indicated by the arrow  10 , which power supply  106  then generates the actual currents I A (t) through I N (t) in the excitation coils  102   a - n.    
         [0051]    The currents I A (t) through I N (t) generate a magnetic field strength (indicated by the arrow  8 ) at the location of the induction coil  6  which induces the maximum possible electrical power in the induction coil  6 . For example, this is provided for a field distribution in which the magnetic field strength is aligned parallel to the center longitudinal axis in the cylinder coil indicated in  FIG. 1  as an induction coil  6 . 
         [0052]    Illustration a) in  FIG. 2  shows two temporal current curves I nav (t) and I ene (t) whose sum is the current strength I A (t) in the excitation coil  102   a  from  FIG. 1 . I nav (t) is an exemplary temporal current strength curve for navigation of the working capsule  110  according to the prior art. The frequency f 1  of I nav (t) lies in the range from 0-50 Hz. I ene (t) shows a temporal current curve for I A (t) for generation of electrical energy in the induction coil  6 . The working frequency f 2  of I ene (t) is 1-5 kHz. 
         [0053]    Two alternatives for the actual feeding of current to the excitation coils  102   a - n  in the example of the excitation coil  102   a  are shown in illustrations b) and c) in  FIG. 2 . Illustration b) in  FIG. 2  shows a current distribution I A (t) in which the currents I nav (t) and I ene (t) from  FIG. 2  are superimposed, indicated by the adding unit  12 . 
         [0054]    The current feed or wiring of the excitation coils  102   a - n  hereby ensues via the taps  18   a  and  18   b  of each individual excitation coil  102   a - n  that are arranged at the ends of these, meaning that the entire excitation coil  102   a - n  has the current I A (t) flowing through it. As described above, in  FIG. 1  the taps  18   a,b  and  c  for the excitation coil  102   a  are shown only as examples. 
         [0055]    The navigation (thus force exertion of the force  122  on the working capsule  110 ) as well as the energy feed of the capsule via injection of energy in the induction coil  6  ensue simultaneously with such a feed of current in  FIG. 1  since both current patterns I nav (t) and I ene (t) also flow simultaneously in the corresponding excitation coils  102   a - n.    
         [0056]    In contrast, illustration c) in  FIG. 2  shows a time curve of the current I A (t) in which the currents I nav (t) and I ene (t) from illustration a) in  FIG. 2  are switched in a temporal multiplex as a current I A (t) to the excitation coil  102   a.    
         [0057]    The current I nav (t) flows there from the point in time t 1  until t 2 , the current I ene (t) flows between t 2  and t 3 , I nav (t) flows again between t 3  and t 4  etc. Navigation or, respectively, exertion of the force  122  on the working capsule  110  thus occur only in the time periods t 1  through t 2 , t 3  through t 4  and after t 5 . By contrast, no force exertion on the working capsule  110  occurs in the time periods from t 2  to t 3  and t 4  to t 5 ; therefore injection of electrical energy into the induction coil  6  occurs, which just does not occur at the aforementioned time periods. 
         [0058]    As described above, the feeding of current to the conductors of the excitation coils  102   a - n  now ensues only for the current I nav (t) via the taps  18   a  and  19   b  of each individual excitation coil  102 - n.  The feeding of current I ene (t) ensues via the taps  18   a  and  18   c . The tap  18   c  is hereby arranged centrally in the excitation coils  102   a - n,  for instance. Current I ene (t) thus flows through only a portion of the windings of the excitation coil  102   a - n  (each has approximately 100 to 200 windings). The excitation coils  102   a - n  then exhibit a suitable inductance or, respectively, resistance for this current pattern. 
         [0059]    According to the previous description, the excitation coils  102   a - n  according to the prior art have been used both for direction of the navigation currents I nav (t) and for the energy transmission currents I ene (t). As an alternative to this, in  FIG. 1  the excitation coils  102   a - n  can also be used only in a more familiar manner for navigation (thus according to the prior art according to  FIG. 3 ), thus are exclusively fed with navigation currents I nav (t). Furthermore, these then serve solely for the exertion of force  122  on the working capsule  110 . 
         [0060]    For example, six cuboid or cylindrical induction transmission coils  14   a - f  (of which only  14   a,b  and  14   e  are visible in  FIG. 1 ) are then additionally provided in the magnetic coil system  100 . As an alternative to the manner described above, the induction transmission coils  14   a - f  are directly controlled by the evaluation and control unit  2  (thus not via the power supply  106 ), as indicated by the lines  16 . 
         [0061]    The induction transmission coils  14   a - f  serve exclusively for the inductive energy transmission to the working capsule  110  or, respectively, energy generation in the induction coil  6 ; currents I ene (t) thus flow through them. 
         [0062]    The magnetic field direction (represented by the arrow  8 ) required for energy generation can in particular be realized by the six cuboid or cylindrically arranged excitation coils  102   a - f  or induction transmission coils  14   a - f.  Navigation and energy transmission to the capsule  110  do not mutually influence one another due to the different frequency ranges of the currents I nav (t) and I ene (t). 
         [0063]    Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.