Abstract:
A coil arrangement for contact-free guidance of a magnetic element such as an endoscopy capsule, has a number of individual coils arranged in pairs by which the components of a guidance field are generated. By arranging the individual coils to include coils corresponding to blades at an exterior of a cylindrical surface, the number of degrees of freedom required for guidance can be obtained with fewer individual coils and fewer power amplifiers to operate the coils.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention concerns a coil arrangement for contactless guidance of a magnetic element—in particular an endoscopy capsule—in a work space (cooperating space). 
         [0003]    2. Description of the Prior Art 
         [0004]    The use of endoscopes and catheters is increasingly widely applied in medicine for the diagnosis or the treatment of the inside of a patient. The instruments are introduced into the body via bodily orifices or cuts in the body and can be displaced in a longitudinal direction, directed from the outside, for which a mechanical connection to the instrument is necessary. However, given the forward movement of the instrument into the body, difficulties in the navigation normally occur at curves or branches, in the manner that the operator must direct the instrument in the desired direction, possibly via repeated testing, and a supporting force from the tissue on the instrument is required for the further navigation. This is linked with a large time cost for the operator and with pain for the patient. In the worst case, it is not to be precluded that the guidance in the planned direction is not achieved at all, or that the risk of tissue perforation arises. Furthermore, in the case of endoscopy it can be of interest to rotate the endoscopy head equipped with a camera in specific directions, for example in order to completely view the mucous membrane in a segment of the gastrointestinal tract. With current catheter endoscopes this is only conditionally possible because the catheter tip has only limited mobility. Moreover, typical catheter endoscopes have the disadvantage that remotely situated internal organs can only be reached with difficulty, or cannot be reached at all. 
         [0005]    The passive endoscopy capsule moved via the natural peristalsis of the gastrointestinal tract does not have the cited disadvantages, but also cannot be navigated, which means that the targeted viewing of specific points inside the gastrointestinal tract is not possible. Therefore, magnetic navigation or guidance systems have been proposed that enable a catheterless or wireless guidance of endoscopy capsules that contain a magnetic dipole moment. A catheterless or wireless guidance is also designated as “contactless” in the following. 
         [0006]    DE 103 40 925 B3 and WO 2006/092421 A1 respectively describe a magnetic coil arrangement consisting of 14 individual coils for navigation of an endoscopy capsule, a video capsule or another probe. The capsule is hereby equipped with a magnetic element, for example a permanent magnet or ferromagnet. The magnetic coil arrangement generates magnetic field components B x , B y , B z  along the axes x, y, z of a Cartesian coordinate system, as well as magnetic gradient fields that enable a contactless guidance of the endoscopy capsule. 
         [0007]    Use is made of the fact that the magnetic element—i.e. a body with a magnetic dipole moment {right arrow over (m)}—seeks to align parallel to the direction of the magnetic field {right arrow over (B)} consisting of the magnetic field components B x , B y , B z  in the direction of the axes of the Cartesian coordinate system. Since the magnetic element is firmly connected with the endoscopy capsule, the orientation of the capsule can thus be affected. A force {right arrow over (F)}= G ·{right arrow over (m)} with a gradient matrix  G  comprising the gradient fields, triggered by the magnetic gradient fields ∂B x /∂x etc., additionally acts on the magnetic dipole moment {right arrow over (m)} according to 
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         [0008]    The gradient matrix G is symmetrical and trace-free due to the Maxwell equations rot{right arrow over (B)}=0 and div{right arrow over (B)}=0, meaning that with ∂B x /∂y (=∂B y /∂x), ∂B x /∂z (=∂B z /∂x), ∂B y /∂z (=∂B z /∂y) and two of the three diagonal elements (for example ∂B x /∂x and ∂B y /∂y) it contains five independent gradient fields. 
         [0009]    The magnetic field {right arrow over (B)} and the gradient fields can be set arbitrarily via a targeted activation of the individual coils of the magnetic coil arrangement. It is therefore possible to rotate the magnetic element and thus to position it arbitrarily in a work space A within the magnetic coil arrangement. It is possible to exert a force {right arrow over (F)} on the magnetic element in order to shift it translationally in addition to the rotation. For this eight quasi-static magnetic degrees of freedom are realized, namely the magnetic field components B x , B y , B z  as well as two of the three entries of the diagonal elements (for example ∂B x /∂x and ∂B y /∂y) and three of the secondary diagonal elements (for example ∂B x /∂y ∂B z /∂x, ∂B z /∂y) of the gradient matrix  G . 
         [0010]    The systems described in DE 103 40 925 B3 and WO 2006/092421 A1 have the disadvantage that, because of the 14 individually activated coils that are required there, they are relatively cost-intensive in their manufacture and installation due to the high number of coils and power amplifiers. 
       SUMMARY OF THE INVENTION 
       [0011]    An object of the invention to provide a more cost-effective magnetic guidance system that includes a coil arrangement and multiple power amplifiers associated with the coils. 
         [0012]    The present invention assumes that only a limited number of maneuvers of an endoscopy capsule is required for the examination of a patient, thus that the design of a coil arrangement is to be optimized with regard to these maneuvers that are actually necessary. In particular, a markedly more cost-effective design is achieved via a detailed analysis of the requirements of the coil arrangement and a design of the individual coils such that only the field strengths and field gradients that are required in the consideration of the desired maneuvers of the endoscopy capsule must be able to be realized in a directionally selective manner. 
         [0013]    In the design of the coil arrangement it is assumed that a permanent magnet is firmly installed in the endoscopy capsule. The permanent magnet is thus firmly connected with the capsule so that movements of the permanent magnet that are triggered by the coil arrangement according to the invention are transferred to the endoscopy capsule. The magnetic moment {right arrow over (m)} of the permanent magnet is preferably oriented either in the direction of the longitudinal axis of the capsule or perpendicular to this. Depending on these two possibilities of the permanent magnet alignment, slight differences result in the magnetic guidance system according to the invention. 
         [0014]    The optimization with regard to the actual required maneuvers of the endoscopy capsule—which is described in the following in connection with Figures in the example of an examination of the esophagus, the stomach (gaster) and the duodenum (what is known as an “EGD” examination)—leads to a coil arrangement to guide the endoscopy capsule with only ten or twelve individual coils. A few of the ten or twelve individual coils are thereby operated in pairs, i.e. via the same power amplifier. This is advantageously reflected in that only six, seven or eight power amplifiers are required. 
         [0015]    The fundamental mode of operation of the coil arrangement according to the invention is analogous to the mode of operation of the arrangement described in DE 103 40 925 B3 or, respectively, in WO 2006/092421 A1. Therefore, reference is made to DE 103 40 925 B3 and WO 2006/092421 A1 with regard to this and with regard to theoretical foundations. 
         [0016]    The coil arrangement according to the invention advantageously allows that the same number of magnetic degrees of freedom (maximum of eight) relative to the arrangements described in DE 103 40 925 B3 or, respectively, in WO 2006/092421 A1 can be generated via an altered layout of the coil arrangement with fewer individual coils and fewer power amplifiers. If, due to a particular application or, respectively, examination, one or more of these degrees of freedom is not necessary, the coil arrangement can make do with fewer power amplifiers or possibly also with fewer coils as well. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  schematically illustrates an exemplary embodiment of a coil arrangement according to the present invention. 
           [0018]      FIG. 2  schematically illustrates different coil pairs of the coil arrangement in accordance with the present invention, with identification of current flow through the coil pairs. 
           [0019]      FIG. 3A  schematically illustrates a further exemplary embodiment of the coil arrangement according to the invention. 
           [0020]      FIG. 3B  is a perspective view of the exemplary embodiment of  FIG. 3A . 
           [0021]      FIG. 3C  shows an alternative arrangement for the exemplary embodiment of  FIG. 3A . 
           [0022]      FIG. 4A  illustrates a surface coil. 
           [0023]      FIG. 4B  illustrates a surface coil divided in sub-coils. 
           [0024]      FIG. 5A  is a cross-section through a coil arrangement according to the invention. 
           [0025]      FIG. 5B  illustrates a saddle coil in perspective view. 
           [0026]      FIG. 6  illustrates a ring coil in perspective view. 
           [0027]      FIG. 7  schematically illustrates a further exemplary embodiment of the coil arrangement according to the invention. 
           [0028]      FIGS. 8A through 8E  illustrate cylindrical cross-sections, in schematic form, of various embodiments of coils in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Exemplary Embodiment 
       [0029]      FIG. 1  shows a coil arrangement  100  according to the invention that is provided to guide or, respectively, navigate a magnetic element—in particular an endoscopy capsule  200 —inside a patient (not shown), which magnetic element contains a permanent magnet with a magnetic dipole moment {right arrow over (m)} in the direction of the longitudinal axis of the capsule (not shown). The permanent magnet is firmly connected with the endoscopy capsule  200  so that movements of the permanent magnet that are generated by the coil arrangement  100  are transferred directly to the endoscopy capsule  200 . In particular, the coil arrangement  100  can generate magnetic field components B x , B y , B z  as well as specific gradient fields (∂B x /∂x etc.) of the gradient matrix  G  that are defined in a Cartesian coordinate system x, y, z (as shown in  FIG. 1 ). The longitudinal axis of the coil arrangement  100  corresponds to the z-axis of the coordinate system. This definition of the coordinate system also applies in the same form to the further exemplary embodiments. 
         [0030]    In contrast to the coil arrangements described in DE 103 40 925 B3 and WO 2006/092421 A1 with fourteen individual coils, the coil arrangement  100  of the first exemplary embodiment contains only twelve individual coils  1 - 12 , comprising a first coil  1  through twelfth coil  12 . 
         [0031]    Four of the twelve individual coils  1 - 12  (in particular the first coil  1  through fourth coil  4 ) of the circuit arrangement  100  are fashioned as identically shaped saddle coils  1 - 4  and comprise a work space A in which the patient is positioned. The saddle coils  1 - 4  form an (imaginary) surface shell of a cylinder with circular cross section and extend along the periphery of the surface shell, respectively over the same solid angle α 1 =α 2  (see  FIG. 5A ). The center of the cylinder is located at the origin of the Cartesian coordinate system; the longitudinal axis or, respectively, axis of symmetry of the cylinder is oriented in the z-direction. The saddle coils  1 - 4  are advantageously arranged spaced apart from one another as viewed in the circumferential direction of the surface shell, meaning that an interstice that permits a thermal expansion of the saddle coils is respectively located between their facing side segments (and thus between their longitudinal sides running in the z-direction). The first saddle coils  1 ,  2  form a first coil pair  1 ,  2  and the second saddle coils  3 ,  4  form a second coil pair  3 ,  4 . 
         [0032]    The fifth coil  5  and the sixth coil  6  form the termination of the cylinder in the z-direction and are fashioned as ring coils, meaning that the individual coils  5 ,  6  are flat, circular coils and possess a rectangular cross section. The ring coils  5 ,  6  respectively lie in a plane parallel to the x-y plane and form a third coil pair  5 ,  6 . As viewed in the z-direction, the coil pairs  5 ,  6  are located at positions +z r  and −z r , for example with z r =400 mm. The center points of the ring coils  5 ,  6  lie on the z-axis; the inner diameters of the ring coils  5 ,  6  correspond to the inner diameter d M  of the surface shell formed by the saddle coils  1 - 4 , wherein d M =620 mm can apply, for example. The length of the surface shell in the z-direction is defined by the length of the saddle coils  1 - 4  in the z-direction. According to  FIG. 5B , a saddle coil can be 700 mm long, for example. 
         [0033]    The saddle coils  1 - 4  and/or the ring coils  5 ,  6  can alternatively be designed as surface coils. The position of the respective coils in the coordinate system that is described above can thereby remain unchanged. Surface coils are characterized in that they are fashioned as flat coils (for example in contrast to saddle coils) and advantageously exhibit a rectangular cross section. 
         [0034]    Six additional individual coils  7 - 12 , in particular the seventh coil  7  through twelfth coil  12  [sic], are arranged like blades and are fashioned as rectangular surface coils  7 - 12 , wherein the sides of the respective rectangle are aligned parallel to the corresponding axes of the coordinate system. The term “like blades” thereby designates that the respective individual coil is simultaneously arranged radially outside of the surface shell of the cylinder formed by the saddle coils  1 - 4  in the x-y-plane, in the x-z-plane or in they-z-plane, as is apparent in  FIG. 1 . 
         [0035]    In principle it applies that the individual coils  1 - 12  should be placed optimally close to the work space A. The surface coils  7 - 12  are specifically dimensioned such that they are markedly more flat than wide as viewed from the coordinate origin. 
         [0036]    The first surface coils  7 ,  8  are located in the x-z-plane, i.e. in the y-direction at positions y=0, and form a fourth coil pair  7 ,  8 . The radially inner conductive sections of the first surface coils  7 ,  8  are located at positions +r f  and −r f  in the x-direction, wherein 2r f =840 mm, for example. The first surface coils  7 ,  8  are positioned in the z-direction such that their geometric center points lie at z=0. 
         [0037]    The second surface coils  9 ,  10  are located in the x-y-plane, i.e. in the z-direction at positions z=0, and form a fifth coil pair  9 ,  10 . The radially inner conductive sections of the second surface coils  9 ,  10  are located at positions +r f  and −r f  in the y-direction. The second surface coils  9 ,  10  are positioned in the x-direction such that their geometric center points lie at x=0. 
         [0038]    Furthermore, third surface coils  11 ,  12  are provided that form a sixth coil pair  11 ,  12 . The surface coils  11 ,  12  are located in the x-y-plane, i.e. in the z-direction at positions z=0, and are crossed at the first surface coils  7 ,  8  and arranged within the first surface coils  7 ,  8 . The radially inner conductive sections of the additional surface coils  11 ,  12  are located at positions +r f  and −r f  in the x-direction. The additional surface coils  11 ,  12  are positioned in the y-direction such that their geometric center points lie at y=0. 
         [0039]    A coil pair, i.e. a saddle coil pair, a ring coil pair or, respectively, a surface coil pair, is characterized in that the two individual coils associated with the coil pair are point-symmetrical to one another relative to the origin of the Cartesian coordinate system (x, y, z). The line connecting the geometric center points of the coils of a coil pair passes through the origin of the coordinate system. It additionally applies—in particular for a saddle coil pair and a ring coil pair—that the respective line connecting the geometric center points of the coils of these coil pairs is perpendicular to the cross sectional surface of the coils. What is thereby to be understood by the cross sectional surface of a saddle coil is the surface that is defined by the two conductive segments running in the z-direction. For example, according to  FIG. 5   b  the cross sectional surface of the saddle coil  4  would accordingly lie in a plane parallel to the y-z-plane. The two individual coils associated with a coil pair can possibly be fed with current by a common power amplifier instead of respectively supplying the two individual coils with current via separate power amplifiers. 
         [0040]      FIGS. 2A-2C  show the current flow through the coil pairs  1  and  2  ( FIG. 2A ),  7  and  8  ( FIG. 2B) and 9  and  10  ( FIG. 2C ), wherein the direction of the current is symbolized by arrows. These three coil pairs are respectively operated by only one power amplifier. With this the coil pair  1 ,  2  generates the component B x  of the magnetic field {right arrow over (B)}. The coil pair  7 ,  8  is used to generate the gradient field ∂B y /∂x (=∂B x /∂y) and the coil pair  9 ,  10  generates the gradient field ∂B z /∂y. 
         [0041]    In contrast to the coil pairs described above in connection with  FIGS. 2A-2C , the coils  3  through  6  are operated individually by separate power amplifiers and on the one hand generate the component B y  (individual coils  3 ,  4 ) and B z  (individual coils  5 ,  6 ) of the magnetic field {right arrow over (B)}. On the other hand, the gradient fields ∂B y /∂y and ∂B z /∂z are generated in that the individual coils  3  and  4  are supplied with different currents to generate the gradient field ∂B y /∂y. The gradient field ∂B z /∂z is accordingly constructed via different currents in the individual coils  5  and  6 . 
         [0042]    The surface coils  11 ,  12  are operated by a common power amplifier and generate a gradient field ∂B z /∂x. 
         [0043]    With the coil arrangement  100  of the first exemplary embodiment it is accordingly possible to realize all eight magnetic degrees of freedom—i.e. the magnetic field components B x , B y , B z  and the five gradient fields ∂B y /∂y, ∂B z /∂z, ∂B x /∂y, ∂B z /∂x, ∂B z /∂y of the gradient matrix  G —with only twelve individual coils and eight power amplifiers. 
         [0044]    The coil arrangement  100  of the first exemplary embodiment is executed rigid, meaning that the individual coils  1 - 12  are mechanically immobile and no permanent magnets are provided. The same applies for the coil arrangements of the additional exemplary embodiments. 
         [0045]    Before the description of additional exemplary embodiments, in the following the further optimization with regard to the actual required maneuvers of the endoscopy capsule is described. 
         [0046]    A limited number of maneuvers M1-M5 of the endoscopy capsule  200  are necessary for a complete examination of the esophagus, the stomach (gaster) and the duodenum of the patient. The coil arrangement  100  can accordingly be designed for the specific application according to  FIGS. 3A ,  3 B,  8  and  9 . The patient is typically located inside the coil arrangement  100 , lying on his back or on his stomach with the longitudinal axis of the body in the z-direction. 
         [0047]    M1: To examine the esophagus, the endoscopy capsule  200  merely needs to be moved in the z-direction since the esophagus is also oriented in the z-direction to a good approximation. A force in the z-direction must accordingly be generated. The coil arrangement must accordingly construct a gradient field ∂B z /∂z. 
         [0048]    M2: For the navigation of the capsule  200  in the stomach it is required that it is partially filled with fluid. For this the patient must take water before and during the examination. In order to maneuver the endoscopy capsule (which is aligned in the y-direction) on the water&#39;s surface with permanent magnets magnetized in the longitudinal direction of the capsule, i.e. in the x-direction and/or z-direction, gradient fields ∂B y /∂x (=∂B x /∂y) and ∂B y /∂z (=∂B z /∂y) are necessary. The expressions placed in parentheses inevitably result due to the Maxwell Equation rot{right arrow over (B)}=0. 
         [0049]    M3: In order to hold the position of the endoscopy capsule  200  on the water&#39;s surface in the stomach, a magnetic force must be generated that counteracts the force of gravity. It is thereby again assumed that the magnetic moment {right arrow over (m)} of the endoscopy capsule  200  is oriented in the y-direction. A gradient field ∂B y /∂y must accordingly be generated. This can moreover by used in order to let the endoscopy capsule  200  submerge and surface again. 
         [0050]    M4: For the acquisition of images of the inner stomach wall, for example, it can be necessary to rotate the endoscopy capsule  200  in a specific, arbitrary direction {right arrow over (r)}. For this the coil arrangement  100  must construct a magnetic field {right arrow over (B)} parallel to the desired direction {right arrow over (r)}. It must accordingly be possible to generate all components B x , B y , B z  of the magnetic field {right arrow over (B)}. 
         [0051]    M5: In order to direct the endoscopy capsule  200  (which furthermore is essentially oriented in the y-direction) through the pyloric orifice, a gradient field ∂B y /∂y is necessary again. 
       Second Exemplary Embodiment 
       [0052]    In a second exemplary embodiment, the coil arrangement  100  shown in  FIGS. 3A-3B  is used to navigate the endoscopy capsule  200  in the stomach of the patient. For this it can be assumed that the endoscopy capsule  200  was conveyed into the stomach via the normal swallowing process. The maneuvers M2 through M4 listed above are necessary to maneuver the capsule  200  in the stomach. The coil arrangement  100  of the first exemplary embodiment must accordingly generate a magnetic field {right arrow over (B)} in an arbitrary direction as well as the gradient fields ∂B y /∂y, ∂B y /∂x and ∂B z /∂y. In comparison to the first exemplary embodiment, it is accordingly not necessary to generate a gradient field ∂B z /∂x. The third surface coils  11 ,  12  can therefore be omitted, such that in the second exemplary embodiment only ten individual coils  1 - 10 , i.e. the first coil  1  through tenth coil  10 , are necessary. 
         [0053]    Moreover, in a second exemplary embodiment only six power amplifiers are required to generate the cited magnetic field components and gradient fields: the four coil pairs consisting of the individual coils  1  and  2 ,  5  and  6 ,  7  and  8  and  9  and  10  are respectively supplied via a common power amplifier and generate the magnetic field components or gradient fields B x , B z , ∂B y /∂x and ∂B z /∂y. The individual coils  3  and  4  are operated with different currents (and therefore with two individual power amplifiers) to generate the magnetic field component B y  and the gradient field ∂B y /∂y. 
         [0054]    Since the gradient matrix  G  is symmetrical, as described above, ∂B y /∂x=∂B x /∂y applies. Instead of the positioning of the individual coils  7 ,  8  that is shown in  FIG. 3A  for the generation of the gradient field ∂B y /∂x, the individual coils  7 ,  8  can be arranged crossed with 9, 10 (as shown in  FIG. 3   c ) for the generation of a gradient field ∂B x /∂y. The coil pair  7 ,  8  is thereby furthermore supplied via a common power amplifier. The surface coils  7 ,  8  are now located in the y-z plane, i.e. in the x-direction at positions x=0. In the z-direction the first surface coils  7 ,  8  are positioned such that their geometric center points lie at z=0. 
       Third Exemplary Embodiment 
       [0055]    The coil arrangement  100  in the third exemplary embodiment is provided to guide the endoscopy capsule  200 —which is magnetized parallel to its longitudinal axis—through the esophagus, the stomach (gaster) an the duodenum of the patient, i.e. for a complete EGD examination. All of the maneuvers M1 through M5 that are listed above are accordingly to be realized in the third exemplary embodiment. 
         [0056]    The coil arrangement  100  must accordingly be fashioned such that a magnetic field {right arrow over (B)} in an arbitrary direction as well as gradient fields ∂B y /∂y, ∂B x /∂z, ∂B y /∂x and ∂B z /∂y can be generated. For this ten individual coils  1 - 10  are necessary, as in the second exemplary embodiment. However, in contrast to the second exemplary embodiment seven power amplifiers are required: the three coil pairs consisting of the first coil  1  and the second coil  2 , the seventh coil  7  and the eighth coil  8  and the ninth coil  9  and the tenth coil  10  are respectively operated via one power amplifier and generate the fields or, respectively, gradient fields B x , ∂B y /∂x and ∂B z /∂y. The third coil  3  and the fourth coil  4  are operated with different currents (and therefore with two individual power amplifiers) to generate the magnetic field component B y  and the gradient field ∂B y /∂y. The coils  5  and  6  are likewise operated with two individual power amplifiers to generate B z  and ∂B z /∂z. 
       Fourth Exemplary Embodiment 
       [0057]    In the fourth exemplary embodiment, the magnetic moment of the permanent magnet of the endoscopy capsule  200  is aligned perpendicular to the longitudinal axis of the endoscopy capsule  200 . 
         [0058]    In order to implement an examination of the stomach in the second exemplary embodiment, the maneuvers M2′ through M4′ (that are based on the maneuvers M2 through M4 that are described above) must be executable: 
         [0059]    M2′: In navigation of the capsule  200  aligned in the vertical direction on the water&#39;s surface in the stomach, the magnetic moment {right arrow over (m)} of the endoscopy capsule lies in the x-z-plane. In order to maneuver the endoscopy capsule in the x-direction and/or z-direction, gradient fields ∂B x /∂x and ∂B z /∂z are required. 
         [0060]    M3′: In order to hold the position of the endoscopy capsule  200  in the stomach at the water&#39;s surface, or in order to move the capsule  200  in the vertical direction, gradient fields ∂B y /∂x and ∂B z /∂y must be generated. 
         [0061]    M4′: To rotate the endoscopy capsule  200  in a specific, arbitrary direction {right arrow over (r)}, the coil arrangement  100  must construct a magnetic field {right arrow over (B)} parallel to the desired direction {right arrow over (r)}. 
         [0062]    In summary, the magnetic field components B x , B x , B x  and the gradient fields ∂B x /∂x, ∂B z/∂z, ∂B   y /∂x and ∂B z /∂y are accordingly required for stomach examination with a diametrally magnetized capsule  200 . 
         [0063]    To generate these fields, a coil arrangement with ten individual coils  1 - 10  (as shown in  FIGS. 3   a/b ) can again be used, wherein the three coil pairs (formed by the individual coils  3  and  4 ,  7  and  8  and  9  and  10 ) are respectively supplied via a common power amplifier in order to generate the fields or, respectively, gradient fields B y , ∂B y /∂x and ∂B z /∂y. The individual coils  1  and  2  are operated with different currents—and therefore with two individual power amplifiers—to generate the magnetic field component B x  and the gradient field ∂B x /∂x. The individual coils  5  and  6  are similarly operated with two individual power amplifiers to generate B z  and ∂B z /∂z. Seven power amplifiers are accordingly required. 
       Fifth Exemplary Embodiment 
       [0064]    The coil arrangement  100  of a fifth exemplary embodiment is identical to the coil arrangement  100  of the first exemplary embodiment and comprises twelve individual coils  1 - 12  ( FIG. 1 ) and eight power amplifiers. The first exemplary embodiment is referenced regarding the connection of the individual coils  1 - 12  and the power amplifiers. As is described in connection with the first exemplary embodiment, it is possible with the coil arrangement  100  according to  FIG. 1  (which comprises twelve individual coils  1 - 12 ) to generate all eight magnetic degrees of freedom. All maneuvers required in connection with the diametrally magnetized endoscopy capsule  200  can accordingly also be implemented. The coil arrangement  100  of the first exemplary embodiment and fifth exemplary embodiment is accordingly universally usable for endoscopy capsules  200  whose magnetic moment {right arrow over (m)} is aligned parallel or perpendicular to the longitudinal axis of the capsule. However, differences in the design of the coil arrangement  100  with regard to the current feed of the individual coils and the design of the individual coils (for example with regard to the linkage) result for a diametrally magnetized endoscopy capsule  200  relative to the first exemplary embodiment due to different forces and turning moments to be generated. 
       ADDITIONAL EMBODIMENTS 
       [0065]    The surface coils  7 - 12  can be dimensioned such that they are markedly flatter than they are wide as seen from the coordinate origin. The “flat” feature in the example of the surface coil  7  in  FIG. 4   a  thereby concerns the thickness d F  of the conductive segment, i.e. the extent of the inner (and outer) conductive segment as viewed in the x-direction. The “wide” feature describes the extent I F  of the conductive segment in the y-direction. For the surface coil  7  it can accordingly be designed so that d F &lt;I F  applies. The surface coil  8  can be dimensioned identically. The remaining surface coils  9  and  10  or, respectively,  11  and  12  can be fashioned identically. The dimensions d F , I F  that are selected for the different coil pairs  7  and  8 ,  9  and  10  and possibly  11  and  12  do not thereby need to coincide. 
         [0066]    The surface coils  7 - 12  can respectively be divided into multiple individual sub-coils. Again in the example of the surface coil  7  of  FIG. 4A , the surface coil  7  lying in the x-z-plane can be separated into sub-coils  7   a ,  7   b  and  7   c  lying atop one another in the y-direction (i.e. in the direction of the normal vector standing on the cross section surface of the coil  7 ), as is shown in  FIG. 4   b . The surface coil  8  would likewise accordingly be separated into sub-coils  8   a ,  8   b  and  8   c  (not shown). The dimensions of the sub-coils  7   a  and  8   a ,  7   b  and  8   b  and  7   c  and  8   c  advantageously coincide. A homogenization of the field gradients ∂B y /∂x that can be generated by the surface coils  7  and  8  is advantageously achieved. An interstice on the order of 1 cm can thereby lie between two coils situated one atop the other. The remaining surface coils  9 - 12  can accordingly also be divided into multiple sub-coils, with the corresponding homogenization of their gradient fields. The division into more or fewer sub-coils than shown in  FIG. 4B  is likewise conceivable. 
         [0067]    A further embodiment of the coil arrangement  100  according to  FIG. 5A  concerns only the saddle coils  1 - 4 . The special embodiment of the saddle coils  1 - 4  can replace the saddle coils  1 - 4  contained within the scope of the exemplary embodiments described previously. The saddle coils  1 - 4  can be fashioned differently with regard to the solid angle α along the periphery of the surface shell. The first coil  1  and the second coil  2  respectively extend over a first solid angle α 1  along the periphery of the surface shell while the third coil  3  and the fourth coil  4  respectively extend over a second solid angle α 2 . In order to amplify the magnetic field B y  in the z-direction as well as the gradient field ∂B y /∂y, the solid angles α 2  of the saddle coils  3  and  4  are increased to α 2 &gt;90°. However, the solid angles advantageously lie in a range of 90°&lt;α 2 &lt;110°. The first solid angle α 1  of the saddle coils  1  and  2  is then to be reduced accordingly. 
         [0068]    A preferred embodiment of the saddle coil  4  is shown in  FIG. 5   b . The remaining saddle coils can be dimensioned correspondingly. The saddle coil  4  is fashioned flat, meaning that the extent d S  of the conductive segment in the radial direction can be smaller than the lateral extent I S  of the conductive segment in, for example, the z-direction. 
         [0069]      FIG. 6  shows an embodiment of the ring coil  5  that is executed flat as viewed in the z-direction. This means that the extent I R  in the z-direction can be smaller than the width d R  of the ring, i.e. than the extent d R  of the ring coil  5  in the radial direction. The ring coil  6  can be fashioned identically. 
         [0070]    In a further embodiment that is drawn in  FIG. 7 , the surface coils  7 ,  8  and/or  9 ,  10  are brought spatially closer to the work space A. This has the advantage that the gradient fields corresponding to the secondary diagonal elements of the gradient matrix  G —in particular the gradient fields ∂B y /∂x and/or ∂B z /∂y in the present case—are amplified without more powerful electronics being required. For this the surface coils  7 ,  8  and/or  9 ,  10  are presently spatially integrated into the saddle coils so that at least the radially inner conductive segments of the surface coils  7 ,  8  and/or  9 ,  10  lie closer to the work space A. In contrast to the exemplary embodiments described above, the surface coils  7 ,  8  and/or  9 ,  10  are now no longer located completely radially outside of the surface shell of the cylinder formed by the saddle coils  1 - 3 . For this the surface coils  7 ,  8  and/or  9 ,  10  must be shortened in the z-direction corresponding to the dimensioning of the saddle coils, which can entail the additional advantage that the weight of the surface coils  7 ,  8  and/or  9 ,  10  is reduced. 
         [0071]    In addition to the number of individual coils to be used, the capsule magnetization direction and the operation of the individual coils as coil pairs or individually by power amplifiers, the exemplary embodiments described above also differ in that the concrete embodiments can vary with regard to the dimensions and the power requirement of the individual coils  1 - 10  or, respectively,  1 - 12 . 
         [0072]    In the exemplary embodiments with crossed coils that are shown in connection with  FIGS. 1 and 3C , one of the crossed coils can respectively lie within the other coil, meaning that the inner coil must be designed correspondingly smaller than the outer, surrounding coil. Alternatively, the conducting segments can intersect, meaning that the conductor traces of the two coils can alternate at the intersection point of the coils. 
         [0073]    It is noted that the above device of the coordinate system x, y, z is arbitrary, in particular concerning the alignment of the x-axis and the y-axis. A rotation of the coil arrangement  100  according to one of the exemplary embodiment described above by an arbitrary rotation angle around the longitudinal axis of the coil arrangement—i.e. around the z-axis of the coordinate system—is not additionally described but is likewise the subject matter of the present invention. This in particular pertains to the first exemplary embodiment and the fifth exemplary embodiment as well as their additional embodiments since all magnetic degrees of freedom can be generated with these. A rotation of the coil arrangement  100  by, for example, 90° around the z-axis produces a coil arrangement  100 ′ with which all magnetic degrees of freedom can likewise be generated. The coil arrangement  100 ′ accordingly works just like the coil arrangement  100 . 
         [0074]    All described exemplary embodiments of the coil arrangements  100  contain four saddle coils  1 - 4  and two ring coils  5 ,  6  that all lie on the surface shell of a cylinder with circular cross section (schematically shown in  FIG. 8A ) or, respectively, describe the surface shell of a circular cylinder. Alternatively, however, these 6-coil cylinders can also possess a quadratic or rectangular cross section ( FIGS. 8B ,  8 C). Instead of the four saddle coils and instead of the two ring coils, four flat coils and two rectangular coils are then used. Furthermore, the cross section of the cylinder can also be quadratic or rectangular with rounded corners, as indicated in  FIG. 8D . An elliptical cross section ( FIG. 8E ) or an asymmetrical cross section ( FIG. 8F ) are also conceivable, for example a flattened circle. The cross section of the cylinder is realized by the shape of the individual coils  1 - 6 . 
         [0075]    In the case that a water cooling of individual coils is required, a cooling system can be provided via a hollow conduit through which water—not current—flows. For the ring coils  5 ,  6 , the hollow conduit can lie as a winding layer on the outside of the winding package and can preferably be cast with the winding package. For the saddle coils  1 - 4 , the cooling conduit winding layer can lie on the outside of the current-carrying winding package. Given the flat coils  7 - 10  or  7 - 12 , a hollow conduit layer is advantageously first wound on the winding body and then the current-carrying rectangular conductor is wound on this. 
         [0076]    Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of his contribution to the art.