SENSOR CARRIER

Abstract

The invention relates to an auxiliary instrument for insertion into vessels or lumens with small inner diameters. The auxiliary instrument has a proximal end and a distal end and has at least one localization element whose position and orientation can be determined with an electromagnetic position detection system. The localization element is located directly adjacent to or at least close to the distal end of the auxiliary instrument and is configured to capture an alternating electromagnetic field. A distal end region of the auxiliary instrument extends from the distal end of the auxiliary instrument to a proximal end of the localization element such that the localization element is located within the distal end region. In that part of the distal end region in which the localization element is located, the auxiliary instrument has a low bending stiffness of less than 10 Nmm.sup.2, at least in sections. At least two lines are led from the localization element to the proximal end of the auxiliary instrument and are electrically conductively connected at least to the localization element. The localization element has a length with an amount that is at least ten times the amount of an outer diameter of the localization element.

Claims

1-21. (canceled)

22. An auxiliary instrument for determining the position of a device, the auxiliary instrument having a proximal end, a distal end region, and a first localization element and a second localization element whose positions and orientations can be determined with an electromagnetic position detection system, wherein the first localization element is arranged within the distal end region and comprises a first coil, and the second localization element is arranged within the distal end region and comprises a second coil.

23. The auxiliary instrument of claim 22, wherein the distal end region comprises a bending stiffness of less than about 10 Nmm.sup.2.

24. The auxiliary instrument of claim 22, wherein the first localization element is configured to have a total inductance between about 2 mH and about 4 mH.

25. The auxiliary instrument of claim 22, wherein the first localization element is configured to have an electrical resistance between about 70 ohms and about 100 ohms.

26. The auxiliary instrument of claim 22, wherein the first coil has two coil ends and an outer diameter of 0.5 millimeters or less.

27. The auxiliary instrument of claim 22, wherein the first and second coils are electrically independent and each of the coils is electrically conductively connected to at least two electrical lines, the electrical lines being led from the respective coil to the proximal end of the auxiliary instrument.

28. The auxiliary instrument of claim 22, wherein the first coil is wound around a coil core being formed of a single piece extending at least from a distal end of the first coil to a proximal end of the first coil, or around the coil core being formed of several pieces movably stringed together, the coil core extending at least from a distal end of the first coil to a proximal end of the first coil.

29. The auxiliary instrument of claim 28, wherein the first coil end of the first coil is electrically conductively connected to the first of the at least two electrical lines, and the second coil end of the first coil is electrically conductively connected to a distal end of the coil core, and a proximal end of the coil core is electrically conductively connected to the second of the at least two electrical lines so that the coil core establishes an electrically conductive connection between the second coil end and the second electrical line.

30. The auxiliary instrument of claim 28, wherein the first coil end of the first coil is electrically conductively connected to the first of the at least two electrical lines, and the second coil end of the first coil is electrically conductively connected to a distal end of the coil core, and wherein the coil core extends from the distal end of the first coil to the proximal end of the auxiliary instrument and is one of the at least two electrical lines of the auxiliary instrument.

31. The auxiliary instrument of claim 22, wherein the first coil comprises a bending section that is less rigid than the remaining part of the coil.

32. The auxiliary instrument of claim 22, wherein the first localization element comprises a coil arrangement comprising a number of coils connected in series, the coil arrangement having at least one bending section which is located between two of the coils of the coil arrangement.

33. The auxiliary instrument of claim 32, wherein each coil of the coil arrangement is wound around a respective coil core extending from a proximal end of a respective coil to a distal end of that coil such that no coil core is arranged in a bending section between two of the coils.

34. The auxiliary instrument of claim 22, wherein the localization element is surrounded by a tube.

35. The auxiliary instrument of claim 34, wherein the tube is coated with a biocompatible material.

36. The auxiliary instrument of claim 22, wherein a connection for an electrical contact is arranged at the proximal end of the auxiliary instrument.

37. The auxiliary instrument of claim 22, wherein the distance between the proximal end and the distal end of the auxiliary instrument is between about 10 cm and about 150 cm.

38. The auxiliary instrument of claim 22, further comprising a proximal localization element at the proximal end of the auxiliary instrument.

39. The auxiliary instrument of claim 22, wherein the proximal end comprises a bending stiffness of less than 10 Nmm.sup.2.

40. The auxiliary instrument of claim 38, wherein the proximal localization element is configured to have a total inductance between about 2 mH and about 4 mH.

41. The auxiliary instrument of claim 22, wherein the device comprises a catheter.

42. The auxiliary instrument of claim 41, wherein the catheter comprises a balloon catheter.

43. The auxiliary instrument of claim 41, wherein the catheter comprises an angioplasty catheter, a urinary catheter, a gastrointestinal catheter, or a dialysis catheter.

44. The auxiliary instrument of claim 22, wherein the device comprises a bone screw, a pedicle screw, or a Jamshidi needle.

45. A surgical instrument comprising an externally accessible lumen and an auxiliary instrument removably arranged within the lumen, wherein the auxiliary instrument comprises a proximal end, a distal end region, and a first localization element and a second localization element whose positions and orientations can be determined with an electromagnetic position detection system, wherein the first and second localization elements are arranged within the distal end region.

46. The surgical instrument of claim 45, wherein the first localization element comprises a first coil, and the second localization element comprises a second coil.

47. The surgical instrument of claim 45, wherein the distal end region of the auxiliary instrument has a bending stiffness of less than about 10 Nmm.sup.2.

48. The surgical instrument of claim 45, wherein the proximal end comprises a bending stiffness of less than 10 Nmm.sup.2.

49. The surgical instrument of claim 45, wherein the surgical instrument comprises a balloon catheter, an angioplasty catheter, a urinary catheter, a gastrointestinal catheter, a dialysis catheter, a bone screw, a pedicle screw, or a Jamshidi needle.

50. A method for calculating a bend of a distal end region of an auxiliary instrument comprising: generating an alternating electromagnetic field; outputting a voltage signal with a localization element arranged in the distal end region, the voltage signal representing a voltage induced in the localization element; outputting a voltage signal with a proximal localization element which, starting from the distal end region in the direction of a proximal end of the auxiliary instrument, is arranged at a distance from the distal end region, the voltage signal representing a voltage induced in the proximal localization element; determining a position and an orientation of the localization element arranged in the distal end region by evaluating the voltage signal output from the localization element; determining a position and an orientation of the proximal localization element that is arranged at a distance from the distal end region by evaluating the voltage signal output from the proximal localization element; and calculating a bend of the distal end region of the auxiliary instrument based on the determined position and orientation of the localization element arranged in the distal end region and the determined position and orientation of the proximal localization element arranged at a distance from the distal end region.

51. The method of claim 50, further comprising reconstructing an outer shape of a surgical instrument with a lumen in which the auxiliary instrument is arranged based on the determined position and orientation of the localization element arranged in the distal end region and the determined position and orientation of the proximal localization element arranged at a distance from the distal end region.

Description

[0077] In the following, embodiments of the invention are described with reference to the figures. In the figures:

[0078] FIG. 1: shows a schematic and simplified illustration of an auxiliary instrument with a localization element and electrical lines, which are enveloped in a tube;

[0079] FIG. 2: shows a schematic and simplified illustration of a localization element which is formed by a coil that at each of its coil ends is electrically conductively connected to a respective electrical line;

[0080] FIG. 3: shows a schematic and simplified illustration of a localization element which is formed by a coil wound around a coil core;

[0081] FIG. 4: shows a schematic and simplified illustration of a coil core which is formed by several pieces that are movably stringed together;

[0082] FIG. 5: shows a schematic and simplified illustration of a single piece of a coil core, that can be formed by several of such pieces stringed together;

[0083] FIG. 6: shows a schematic and simplified illustration of a localization element formed by a coil wound around a coil core, wherein a first coil end of the coil being electrically conductively connected to a first electrical line, and a second coil end of the coil being electrically conductively connected to a distal end of the coil core and the proximal end of the coil core being electrically conductively connected to a second electrical line;

[0084] FIG. 7: shows a schematic and simplified illustration of a localization element formed by a coil wound around a coil core, wherein a first coil end of the coil being electrically conductively connected to a first electrical line, a second coil end of the coil being electrically conductively connected to the distal end of the coil core, and the coil core being a second electrical line;

[0085] FIG. 8: shows a schematic and simplified illustration of a localization element formed by a coil wound around a coil core, said coil having a bending section;

[0086] FIG. 9: shows a schematic and simplified illustration of a localization element formed by a coil arrangement comprising two coils connected in series, wherein a bending section being located between the coils, the coil arrangement being electrically conductively connected to a third electrical line in the bending section;

[0087] FIG. 10: shows a schematic and simplified illustration of a localization element formed by a coil arrangement, wherein the coil arrangement is formed by coils connected in series;

[0088] FIG. 11: shows a schematic and simplified illustration of a localization element formed by a coil arrangement, wherein the coil arrangement being formed by coils connected in series and each of the coils being wound around a respective coil core;

[0089] FIG. 12: shows a schematic illustration of a Jamshidi needle with an auxiliary instrument.

[0090] FIG. 1 shows a schematically depicted auxiliary instrument 100 with a localization element 102. The localization element 102 is electrically conductively connected to two electrical lines 104,106. The wires 104,106, are led from the localization element 102 to a proximal end 108 of the auxiliary instrument 100.

[0091] The localization element 102 and the lines 104,106 are surrounded by a tube 110, the tube extending from the proximal end 108 to a distal end 112 of the auxiliary instrument. The tube 110 is made of a biocompatible material so that the auxiliary instrument 100 is particularly suitable for use in a surgical procedure inside a human body. The tube 110 has an external diameter 114 of 0.5 mm and a tube wall of the tube has a thickness of 0.1 mm. The tube 110 extends beyond a distal end of the localization element 102 so that the distal end of the tube 110 forms the distal end 112 of the auxiliary instrument 100. Thus, the localization element 102 is arranged close to the distal end 112 of the auxiliary instrument 100 so that a distal end region 116 extends from the proximal end of the localization element 102 to the distal end of the tube 110. The localization element 102 is thus arranged within the distal end region 116 near the distal end 112 of the auxiliary instrument 100.

[0092] The localization element 102 has an outer diameter of 118, which is 0.4 mm and an inductance that is between 2 and 4 mH. The localization element 102 can, e.g., be formed by a coil as described with reference to FIG. 2, 3, 6, 7 or 8 or by a coil arrangement as described with reference to FIG. 9, 10 or 11. In particular then, if the localization element 102 is formed by a coil or a coil arrangement, the auxiliary instrument 100 in that part of the distal end region 116 in which the localization element 102 is arranged has at least in sections a low bending stiffness of less than 10 Nmm.sup.2. A tube made of PEEK having the dimensions given herein typically has a bending stiffness of between 5 Nmm.sup.2 and 10 Nmm.sup.2 such that the bending stiffness of the auxiliary instrument 100 in that part of the distal end region 116 in which the localization element 102 is arranged, preferably, at least sectionwise corresponds substantially to the bending stiffness of the tube 110. Between the sections or outside the sections with a bending stiffness of less than 10 Nmm.sup.2, the auxiliary instrument 100 can also have a bending stiffness of more than 10 Nmm.sup.2, in particular, in that part of the distal end region 116 in which the localization element 102 is arranged. However, in a localization element 102 having a coil with an outer diameter of less than 0.5 mm and a length of more than 5 mm, preferably, more than 10 mm, it is possible that the bending stiffness of a used tube 110 is greater than the bending stiffness of the localization element 102. This can be particularly the case if a tube wall of the tube has a thickness that is in the order of the thickness of the outer diameter of a localization element or even significantly larger.

[0093] Due to the small outer diameter 118 of the localization element 102 and the small outer diameter 114 of the tube 110, the auxiliary instrument 100 itself is comparatively thin and particularly suitable for insertion into vessels or for insertion into lumens with small inner diameters, even if these are comparatively difficult to access. Here, it is advantageous that the auxiliary instrument 100, in particular in that part of the distal end region 116 in which the localization element 102 is arranged, is at least sectionwise flexible. The auxiliary instrument 100 thus has a comparatively small outer diameter and is nevertheless comparatively flexible, at least in sections, especially in the distal end region. The auxiliary instrument 100 can therefore be arranged in or inserted into vessels or lumens with small inner diameters and adapt flexibly to a shape given by the vessel or lumen. If, for example, a vessel of a human body has different branches, a branch can be selected by bending the auxiliary instrument in the distal end region and the remaining part of the auxiliary instrument can then follow the distal end of the auxiliary instrument into this branch.

[0094] The auxiliary instrument 100 with the localization element 102, whose position and orientation can be determined with an electromagnetic position detection system, can advantageously be connected to such a position detection system. With a position detection system position and orientation of the localization element 102 can then be determined while inserting the auxiliary instrument into a vessel. The information about position and orientation of the localization element 102 and, derived therefrom, position and orientation of the auxiliary instrument 100 can be made available to a user of the auxiliary instrument 100 during insertion into a vessel so that he can change or adapt a handling of the auxiliary instrument 100 on the basis of the information made available to him. For example, the position of the auxiliary instrument or of a surgical instrument with an arranged auxiliary instrument can be displayed in tomographically obtained sectional images of an object under examination during insertion into the human body on a monitor to a user. Thereby, advantageously, errors can be avoided and/or mechanical stress of human tissue can be reduced while inserting the auxiliary instrument into a vessel or while inserting the surgical instrument with auxiliary instrument into the human body. Because of determining position and orientation of the localization element a user can thus use an auxiliary instrument or a surgical instrument with auxiliary instrument in a more targeted and controlled manner. This is particularly important if a vessel has only a small inner diameter, is difficult to access and/or has a sensitive condition, e.g., has a sensitive outer wall and/or a surgical instrument has to be positioned precisely and/or penetration of a surgical instrument into sensitive tissue, e.g. bone tissue, shall be performed with improved control.

[0095] To use an auxiliary instrument 100 together with a position detection system, the auxiliary instrument 100 is typically connected via a cable (not shown) to a data processing device (not shown) of a position detection system so that a tapped voltage signal can be transmitted from the localization element 102 to a data processing device via the electrical lines 104, 106 and evaluated by the data processing device. The auxiliary instrument 100 can, for example, be connected via a plug connection (not shown) with a respective cable. For example, the auxiliary instrument 100 can have a connection (not shown) electrically conductively connected to electrical lines 104, 106 and located at the proximal end 108 of the auxiliary instrument 100.

[0096] The length of the auxiliary instrument 100 shown can be adapted to a planned use of the auxiliary instrument 100. Preferably, however, the auxiliary instrument 100 has a length of between 10 cm and 150 cm.

[0097] The auxiliary instrument 100 is also suitable to be inserted into a lumen of a surgical instrument (not shown). Since the auxiliary instrument 100 has a localization element 102 whose position and orientation can be determined with an electromagnetic position detection system, the auxiliary instrument 100 can be used to connect a surgical instrument to a position detection system. Preferably, such a surgical instrument has a lumen with a small inner diameter in which the auxiliary instrument 100 can be arranged. The lumen can have a small inner diameter that is just dimensioned to allow the auxiliary instrument to be immovably arranged in the lumen. Accordingly, the surgical instrument with a lumen itself can also be comparatively thin.

[0098] Since the auxiliary instrument 100 has a comparatively small outer diameter and, at the same time, despite the localization element, is comparatively flexible at least sectionwise, in particular in the distal end region, the auxiliary instrument can adapt to a given shape or course of a lumen of a surgical instrument and be immovably arranged in the lumen.

[0099] FIG. 2 shows a localization element formed by a coil 200. At each of the two coil ends 202, 204, the coil 200 is electrically conductively connected to a respective one of the electrical lines 206, 208 of an auxiliary instrument (not shown). The coil 200 is configured to capture an alternating electromagnetic field generated, e.g., by a field generator (not shown) of a position detection system. By changing the magnetic flux density, an electric field is generated in the coil 200 according to the principle of electromagnetic induction. Thereby, the current induced in the coil 200 depends on the orientation of the coil to the alternating electromagnetic field. Via the electrical lines 206, 208, a characteristic voltage signal can be tapped which represents an induced voltage applied between the coil ends 202, 204. The voltage signal can then be transmitted to and evaluated by a data processing device (not shown) of a position detection system. With the position detection system, position and orientation of the coil to the alternating electromagnetic field can be determined.

[0100] To ensure that a tapped voltage signal has a sufficiently good signal-to-noise ratio, the coil 200 is configured to have an inductance of between 2 mH and 4 mH. With a given outer diameter, the coil 200 must therefore have a corresponding number of windings and a length, such that an inductance in this range is achieved. An outer diameter of less than 0.5 mm typically results in a coil 200 having a length of more than 10 mm.

[0101] An auxiliary instrument can also have several localization elements, each formed by coils 200 as shown in FIG. 2. Preferably, each of the coils is then electrically conductively connected to at least two electrical lines, respectively. It is preferred that the several coils are not electrically connected to each other, so that an individual and, in particular, independent voltage signal can be tapped from each of the coils.

[0102] FIG. 3 shows a localization element formed by a coil 300 wound around a coil core 302. The coil 300 is preferably configured as described with reference to FIG. 2. Due to the comparatively small outer diameter of the coil 300 of less than 0.5 mm, the coil core 302 typically has a bending stiffness of significantly less than 10 Nmm.sup.2 due to the low geometrical moment of inertia. Thus, if a localization element is formed by a coil 300 with coil core 302 as described herein and is surrounded by a tube (not shown) of an auxiliary instrument, it is possible that the relevant bending stiffness of the auxiliary instrument is determined by the bending stiffness of the tube.

[0103] If the coil core 302 is made of a material with high permeability, the inductance of the coil 300 can be significantly increased so that an inductance between 2 mH and 4 mH, for example, can already be achieved with a lower number of windings. When keeping the coil wire diameter constant, a lower number of windings results in a shorter length of coil 300. For example, coil core 302 can be made of soft iron which can have a permeability of up to 10,000. The coil core 302 shown is formed from a single piece and extends from a proximal end 304 of coil 300 to a distal end 306 of coil 300.

[0104] However, it can also be advantageous if a coil core is formed by several pieces that are movably stringed together. Such a coil core 400 is shown in FIG. 4. If such a coil core 400 is wound with a coil, this results in the synergetic effect of an increase in the inductance of the coil with simultaneously increased mobility of the pieces of the coil core 400 movably stringed together. The base area of the cylindrical pieces of the coil core 400 can be configured as a smooth surface as shown in FIG. 4. However, in order to avoid the forming of larger cavities during bending of such a coil core 400 formed by several pieces, it can be advantageous if a piece of such a coil core 400 has a base area with a different shape.

[0105] FIG. 5 shows a piece 500, which is one piece of a coil core formed by several pieces (not shown). This cylindrical piece of 500 does not have smooth base areas. Instead, one base area 502 has a concave curvature and the opposite base area 504 has a convex curvature. A coil core formed by such pieces of 500 can then be assembled in such a way that a respective concave curvature of one piece adjoins a convex curvature of an adjacent piece and these preferably fit exactly into one another. The two pieces can then move relative to each other similar to a joint. It is also possible that a piece (not shown) has two concave curved base areas and a coil core is formed from several of such pieces stringed together. The individual pieces can then roll against each other at their concave curved base areas in order to ensure comparatively good mobility of the coil core.

[0106] FIG. 6 shows a localization element formed by a coil 600 wound around a coil core 602. A first coil end 604 is electrically connected to a first line 606. A second coil end 608 is electrically connected to the distal end 610 of the coil core 602. The proximal end 612 of the coil core 602 is electrically conductively connected to a second line 614. The coil core 602 thus establishes an electrically conductive connection between the second coil end 608 of coil 600 and the second electrical line 614. The coil 600 has an outer diameter of less than 0.5 mm and a length preferably greater than 10 mm and, in particular, has a number of windings and a length chosen such that the coil 600 has an inductance of between 2 mH and 4 mH. Advantageously, the inductance of the coil 600 can be increased by a coil core formed by a material with high permeability, so that in turn a comparatively lower number of windings can be chosen in order to achieve an inductance of between 2 mH and 4 mH. In that the coil core 602 establishes an electrically conductive connection between the second coil end 608 and the second line 614, it is not necessary to guide the second line 614 past the coil 600 toward the distal end of the coil 600 to electrically connect the second line 614 to the second coil end 608 of the coil 600. An outer diameter of a localization element is then advantageously not increased by a line passing the coil 600.

[0107] FIG. 7 shows a localization element formed by a coil 700 wound around a coil core 702. At a first coil end 704, the coil 700 is electrically conductively connected to a first line 706. With a second coil end 708, the coil 700 is electrically conductively connected to the distal end 710 of the coil core 702. At its proximal end 712, the coil core extends beyond the proximal end of the coil and, in particular, to a proximal end of an auxiliary instrument (not shown). In contrast to the embodiment described with reference to FIG. 6, in which a coil core is electrically conductively connected at its proximal end to a second line, no further line is provided in the embodiment shown here. Instead, the coil core itself forms a second line that extends to a proximal end of an auxiliary instrument (not shown) and can be electrically conductively connected to a connection (not shown), particularly to connection contacts of a connection. It is possible that an auxiliary instrument can be given additional mechanical stability by a coil core extending to a proximal end of the auxiliary instrument.

[0108] FIG. 8 shows a coil 800 being wound around a coil core 802 and having a bending section 804. In the bending section 804 the coil 800 is comparatively flexible compared to the rest of the coil 800. The bending section 804 of coil 800 is configured in such a way that in this section a number of windings per unit length of coil 800 is smaller than in the rest of coil 800. Merely exemplary, in the embodiment shown, only two windings are provided in the bending section. This is intended to provide a better understanding of the bend section 804 of coil 800 de-scribed here, which, in a more realistic embodiment of a coil with a bend section can typically have several 100 windings in such a bend section, whereas the adjacent remaining parts of the coils can also have several 1000 windings. In contrast to a coil with a constant number of windings per unit length, the bending section 804 of the coil 800 shown here defines a section which, due to the lower number of windings per unit length, bends preferentially when force is exerted on the coil. The remaining parts of such a coil are therefore exposed to comparatively less mechanical stress. A single coil can also have several bending sections in which a number of windings per unit length of the coil is smaller than in the rest of the coil. Under the exertion of a force, a coil formed in this way then bends preferably at the several bending sections.

[0109] The coil 800 with bending section 804 shown in FIG. 8 is electrically conductively connected at a first coil end 806 with a first line 808 and at a second coil end 810 with a second line 812. However, it is also possible that at its second coil end 810 the coil 800 is electrically conductively connected to a proximal end of the coil core 802 as described with reference to FIG. 6. The distal end of the coil core 802 can then be electrically conductively connected to the second line 812 or can extend to a proximal end of an auxiliary instrument as described with reference to FIG. 7 to form the second electrical line itself. The coil core 802 in the embodiment shown is formed from a single piece, but can also be formed by several pieces movably stringed together as described with reference to FIG. 4 or 5.

[0110] FIG. 9 shows a coil arrangement 900 formed by two coils 902, 904 connected in series. The coil arrangement 900 has a bending section 906 located between the coils 902 and 904. Due to the simple wire connection of the two coils 902, 904, in this bending section 906 the coil arrangement 900 is comparatively flexible. The bending section 906 thus defines a section in which the coil arrangement 900 bends preferentially under the exertion of a force, so that the coils themselves change their shape comparatively minor under the exertion of a force.

[0111] The coils 902, 904 have a length, an outer diameter and a number of windings which are chosen in such a way that the respective inductances of the individual coils 902, 904 add up to a total inductance that is between 2 mH and 4 mH.

[0112] The coil 902 arranged at the proximal end 908 is electrically conductively connected at its proximal coil end to a first line 910. At its distal coil end 904, the coil 904 arranged at the distal end 912 of the coil arrangement 900 is electrically conductively connected to a second line 914. Via the first line 910 and the second line 914 a voltage signal can be tapped representing a voltage applied between the proximal end of coil 902 and the distal end of coil 904. The coil arrangement 900 is also electrically conductively connected to a third line 916. In the embodiment shown, the third electrical line 916 is electrically conductively connected to the coil arrangement 900 in the bending section 906. Thus, a further voltage signal can be tapped via the first line 910 and the third line 916, representing a voltage applied between the distal end of coil 902 and the proximal end of coil 902. Furthermore, a third voltage signal can be tapped via the third line 916 and the second line 914, representing a voltage applied between the distal end of coil 904 and the proximal end of coil 904.

[0113] Via the electrical lines 910, 914, 916 electrically conductively connected to the coil arrangement shown here, voltage signals assigned to the individual coils 902, 904 and a voltage signal assigned to the coil arrangement 900 can be tapped. All voltage signals can be transmitted to and evaluated by a data processing device (not shown). From the individual voltage signals or from the combination of the transmitted voltage signals position and orientation of the coil arrangement 900 of a localization element can then be determined. If no reliable determination of position and orientation is possible from a single voltage signal alone, e.g., due to a signal-to-noise ratio close to or less than one, by comparing the voltage signals it can nevertheless be possible to draw conclusions about position and orientation of the coil arrangement in an alternating electromagnetic field.

[0114] Only exemplary, the coil arrangement 900 is formed of only two coils 902, 904. However, for a coil arrangement to have a total inductance between 2 mH and 4 mH, it can be necessary, depending on the inductances of the individual coils, if a coil arrangement has more than two coils. Preferably, between these several coils there are bending sections. In the bending sections, a coil arrangement can be electrically conductively connected to a further line, respectively, so that voltage signals assigned to respective ones of the coils can be tapped via two of the respective lines. For example, a voltage signal can be tapped via a fourth and a fifth line, the fourth line being electrically conductively connected to the coil arrangement in a bend section adjacent to a proximal end of a respective coil, and the fifth line being electrically conductively connected to the coil arrangement in a bend section adjacent to a distal end of said respective coil. It is also possible, that further lines are electrically conductively connected to a coil arrangement in such a way that a voltage signal can be tapped which represents a voltage applied between the proximal end of a first coil and a distal end of an adjacent coil and can thus be assigned to these several coils.

[0115] FIG. 10 shows a coil arrangement 1000 formed by three coils 1002, 1004, 1006 connected in series. Between each two of the coils 1002, 1004, 1006 there is a bending section 1008, 1010. Due to the simple wire connections, in this bending section 1008, 1010 the coil arrangement 1000 is comparatively flexible compared to areas where coils 1002, 1004, 1006 are arranged. Only exemplarily, here, the number of coils 1002, 1004, 1006 is chosen to be three. In embodiments not shown here, a coil arrangement can also be formed by two coils connected in series or by more than three coils connected in series. Since the inductances of the individual coils 1002, 1004, 1006 add up to a total inductance of between 2 mH and 4 mH of the coil arrangement 1000, it is advantageous to increase the number of coils 1002, 1004, 1006 to such an extent that the coil arrangement 1000 has a total inductance in this range. In particular, if the coils 1002, 1004, 1006 have a comparatively small number of windings and, accordingly, a comparatively small inductance, a comparatively large number of such coils 1002, 1004, 1006 can be necessary for a coil arrangement to have a total inductance of between 2 mH and 4 mH.

[0116] At its proximal coil end, the coil 1002 arranged at a proximal end 1012 of the coil arrangement 1000 is electrically conductively connected to a first line 1014. The coil 1006 arranged at the distal end 1016 of the coil arrangement 1000 is electrically conductively connected with its distal coil end to a second line 1018, so that via the first line 1014 and the second line 1018 a voltage signal can be tapped which represents a voltage applied between the proximal coil end 1012 and the distal coil end 1016 of the coil arrangement 1000. The coil arrangement 1000 shown here can be electrically conductively connected to other lines, in particular, in the bending sections 1008, 1010, as described with reference to FIG. 9. If the coil arrangement 1000 in the bending sections 1008, 1010 is electrically conductively connected to a further electrical line, respectively, respective further voltage signals can be tapped. These additional voltage signals can, e.g., be assigned to a respective coil 1002, 1004, 1006 of coil arrangement 1000.

[0117] FIG. 11 shows a coil arrangement 1100 formed by three coils 1102, 1104, 1106 connected in series. Between two of the coils 1102, 1104, 1106, respectively, there is a bending section 1103, 1105 in which the coil arrangement is comparatively flexible. Each of the coils 1102, 1104, 1106 is wound around a respective coil core 1108, 1110, 1112. Each of the coil cores 1108, 1110, 1112 extends from a proximal end of a respective coil 1102, 1104, 1106 to a distal end of said respective coil 1102, 1104, 1106. Because each of the coil cores 1108, 1110, 1112 extends from a proximal end to a distal end of a respective coil 1102, 1104, 1106, only, in particular, no coil cores 1108, 1110, 1112 are arranged in the bending sections 1103, 1105. The bending stiffness of a bending section 1103, 1105 is therefore not influenced by a coil core 1108, 1110, 1112, but solely defined by the wire connection between the coils 1102, 1104, 1106.

[0118] Coil 1102 that is arranged at a proximal end of coil arrangement 1114, is electrically conductively connected at its proximal coil end to a first line 1116. Coil 1106, arranged at the distal end 1118 of coil arrangement 1000, is electrically conductively connected at its distal coil end to a second line 1120. As described with reference to FIG. 9, the coil arrangement 1100 can be electrically conductively connected, especially in the bending sections 1103, 1105, with a further line (not shown), respectively. Via the first line 1116 and the second line 1118 a voltage signal assigned to the coil arrangement 1100 can be tapped and via optional further electrical lines further voltage signals, e.g., assigned to the individual coils 1102, 1104, 1106 can be tapped.

[0119] Coils 1102, 1104, 1106 each can also have a further bending section that is realized in that in this section the number of windings per unit length is smaller than in the rest of a corresponding coil 1102, 1104, 1106, as described with reference to FIG. 8. Thereby, in addition to the bending sections 1103, 1105 already provided between two of the coils 1102, 1104, 1106, further bending sections that are configured as described with reference to FIG. 8 can be implemented, in which the coil arrangement 1100 bends preferentially under the exertion of a force.

[0120] FIG. 12 shows a schematically illustrated Jamshidi needle 1200 as an example of a surgical instrument with auxiliary instrument. In a 1202 lumen of the Jamshidi needle 1200 an auxiliary instrument 1204 is arranged. The auxiliary instrument 1204 comprises a localization element 1206 which can be formed by a coil as described with reference to FIG. 2, 3, 6, 7 or 8 or by a coil arrangement as described with reference to FIG. 9, 10 or 11. The localization element 1206 is connected to two lines 1208, 1210, which are led from the localization element 1206 to a connection 1212 of the auxiliary instrument 1204 for electrical contacting with a complementary connection, e.g. of a cable (not shown). The cable can be connected at its other end to a position detection system which is also not shown.

[0121] Localization element 1206 and lines 1208, 1210 are surrounded by a tube 1214, which gives the auxiliary instrument 1204 additional stability. Via the lines 1208, 1210 and the cable, a voltage signal representing a voltage induced in the localization element 1206 can then be transmitted to and evaluated by the position detection system for determining position and orientation of the localization element 1206. From the determined position and orientation of the localization element 1206, position and orientation of the Jamshidi needle 1200 can then be calculated. For example, the localization element 1206 can be calibrated to the tip of the Jamshidi needle 1200 prior to surgery with the Jamshidi needle 1200.