Implantable marker

Abstract

The invention relates to an implantable marker for marking animal or human body tissue regions, said marker comprising at least one strand made of a biocompatible material and having a three-dimensional shape that is pressurized during a molding process, said strand being forced to assume said three-dimensional shape by an external mechanical force and then assuming said three-dimensional shape when the mechanical force is removed, said pressurized three-dimensional shape of said strand comprising at least two fixed strand eyes, a first and a second strand eye each formed by at least one winding of said strand and having different relative spatial positions with respect to each other when the external mechanical force is removed. The invention is characterized in that a winding plane can be associated with at least two strand eyes, said winding planes of said at least two strand eyes forming an angle α not equal to 0°.

Description

[Technical Field]

[0001] The present invention relates to an implantable marker for marking an area of ​​tissue within an animal or human body, the marker comprising at least one strand made of a biocompatible material and having a three-dimensional shape that is pressurized during a molding process, wherein an external mechanical force forces the strand to assume the three-dimensional shape after which the strand assumes the three-dimensional shape when the mechanical force is removed, the three-dimensional shape pressurized into the strand comprising at least two fixed strand eyes, the first and second strand eyes each formed by at least one winding of the strand, and which have different spatial positions relative to each other when the mechanical force is removed. [Background technology]

[0002] Implantable markers are commonly used to identify tumors in soft tissues in humans and animals. For example, after a breast biopsy, the marker is often inserted into the tissue removal site using a cannula and then ejected from the distal end of the cannula using a stylet upon reaching the desired location. Once placed within the body, the marker remains stationary, providing the physician with the opportunity to locate and monitor the tissue area to be treated and / or diagnosed over time, preferably with the aid of imaging using ultrasound images.

[0003] A tissue marker for human tissue is described in U.S. Patent No. 6,053,925 and includes two stranded wires made of a shape memory metal, the distal end regions of which assume the shape of a ring or coil as an anchoring structure within the tissue. After the marker is located within the body, the stranded wires protrude proximally from the body region, defining a direct trajectory to the marked tissue site.

[0004] U.S. Patent Publication No. 2005 / 0059888A1 describes a marker for marking the location of a bioabsorber placed inside the body, the marker being made of a material detectable by mammography, x-ray, and ultrasound, such as a wire attached to the absorber.

[0005] US Patent Publication No. 2001 / 0023322A1 includes a cannula-like positioning unit for a marker that can be inserted into the body, the marker being made of a shape-memory metal wire, at least the tip of which deforms into a ring or coil after being positioned inside the body in order to provide a fixed position for the tissue area to be marked.

[0006] Finally, European Patent No. 1871266B1 describes a universal marker for human or animal tissue, made of a pre-programmable material, preferably a nickel-titanium alloy, that returns to a pre-programmed ring shape when forced longitudinal extension ceases.

[0007] All known common markers, particularly the ring marker described above, are representative of ultrasound reflectors due to their material properties, but known markers are visually recognizable to varying degrees in the ultrasound image they generate, depending on the direction of ultrasound interaction. For example, when ultrasound waves from a nearly two-dimensional, fan-shaped ultrasound field impinge on a ring marker whose ring plane is oriented perpendicular to the plane of the propagating ultrasound waves, a maximum of two point-like ultrasound reflection image signals appear, corresponding to the intersection of the fan plane and the ring marker. When the fan-shaped ultrasound field is dynamically swept over the ring marker in the above constellation, ideally, a point-like ultrasound reflection image signal first appears, then splits into two separate ultrasound reflection image signals whose mutual distance first increases, then decreases again until only a point-like ultrasound reflection image signal is again visible. On the other hand, when the fan-shaped ultrasound field is ideally oriented parallel to the plane of the ring and interacts with the ring marker, a complete ring shape appears in the ultrasound image, clearly visible to the diagnostician.

[0008] During ultrasound examinations, particularly in areas with a high proportion of dense tissue material, strong ultrasound reflections frequently occur, resulting in prominently perceptible reflection events in the ultrasound image that visually compete with the ultrasound reflection image signal emanating from the implanted marker. Only in the ideal case described above, where a tissue region marked with a ring parallel to the ring-shaped plane is sonicated, can the ring shape, clearly distinguishable from natural tissue structures due to its Euclidean three-dimensional shape, allow for clear visual identification of the marker's location and orientation.

[0009] Therefore, a great deal of experience is required to unambiguously recognize such markers, which are known per se and whose dimensions are in the range of a few millimeters, in a physically and spatially resolved manner within a biological tissue environment.

[0010] German Patent Publication No. 102019210963A1 describes an implantable marker in which at least two fixed strand eyes are provided along a strand made of biocompatible material, and these fixed strand eyes are integrally connected to each other via their respective strand portions. Summary of the Invention

[0011] The problem addressed by the present invention is to evolve an implantable marker for marking tissue regions in an animal or human body, the marker comprising at least one strand made of a biocompatible material and having a three-dimensional shape that is pressure molded during a molding process, whereby an external mechanical force forces the strand to assume the three-dimensional shape after which the strand assumes the three-dimensional shape upon removal of the mechanical force, thereby significantly improving the visibility and identifiability of the implanted marker for a physician during an ultrasound examination.

[0012] The solution to the problem addressed by the invention is set out in claims 1 and 7. Advantageously, further development features of the invention can be found in the dependent claims and in the description with reference to exemplary embodiments in conjunction with the drawings.

[0013] According to this solution, an implantable marker for marking tissue regions in the body of an animal or human is provided, the marker being made of a biocompatible material and comprising at least one strand having a three-dimensional shape that is pressurized during a molding process, the three-dimensional shape being forced onto the strand by an external mechanical force and then the strand assumes said three-dimensional shape when the mechanical force is removed, the three-dimensional shape pressurized onto the strand comprising at least two fixed strand eyes, a first and a second strand eye each being formed by at least one winding of the strand, each strand eye being associated with one winding plane, the at least two strand eyes being formed in a manner equivalent to an eye with a predetermined shape in the shape of a figure eight, the eyes being connected to each other via a common contact point in which the winding planes of the at least two strand eyes are oriented at an angle α to each other, the winding planes of the at least two strand eyes forming an angle α not equal to 0°.

[0014] The term "fixed strand eye" is borrowed from knot science and describes a simple geometric shape characterized by the formation of a loop along the strand. For this purpose, the strand is wound helically at least once, with a helical pitch such that the strand preferably touches itself in the overlapping region. In contrast to a closed ring shape, a fixed eye does not appear as a straight line with a constant line thickness when exposed to ultrasound from the side, but rather as a wedge or double wedge, with a maximum wedge width equal to twice the width of the strand in the case of a single helical winding. Therefore, when ultrasound is applied from the side to a fixed strand eye consisting of multiple helical windings, a clearer ultrasound signal is formed.

[0015] Alternatively, the term "fixed strand eye" should be understood to mean an annulus formed in the winding plane, with the ends of the strands located within the winding plane of the annulus.

[0016] The term "winding plane" is understood to mean a spatial plane in the sense of the present invention that can be associated with the fixed eye and that projects perpendicularly to said fixed eye, including the area spanning the latter.

[0017] The implantable marker according to this solution has at least two fixed strand eyes, each formed along the strand by a helical winding of said strand. Advantageously, but not necessarily, the at least two fixed strand eyes have the same shape and dimensions. Of course, eye shapes that deviate from a circular shape, such as elliptical or oval fixed eyes, are also conceivable. The strand eyes arranged along the strand may also differ in shape and dimensions from one another. Furthermore, the spatial location and relationship of the fixed strand eyes, as well as the winding direction orientation, may be selected uniformly or individually.

[0018] The marker designed according to this solution is based on the idea of ​​improving its detectability and identifiability by conventional ultrasound diagnostic techniques, in that at least two fixed eyes are tilted or aligned with respect to one another in such a way that when said marker is exposed to ultrasound perpendicular to the winding plane of one fixed strand eye, the other fixed strand eye is preferably exposed to ultrasound alternately along its winding plane so that it appears as at least a partial, preferably complete ring or annular contour in an ultrasound image by the ultrasound detection means.

[0019] What is particularly important to improve the detectability of a marker by ultrasound is that it has a three-dimensional shape that is as compact as possible, i.e. the ultrasound reflection signal emanating from the marker that is visualized on the monitor for the diagnostician should originate from a small spatial area; elongated marker shapes with reflective structures arranged next to each other in succession have proven to be rather difficult to detect.

[0020] The preferably direct connection of the two fixed eyes, which are integrally connected to each other through a contact point equivalent to the intersection of the figure-eight fixed eyes, and the preferably orthogonal orientation of both winding planes of the strand eyes, which are integrally connected to each other at said contact point, result in a dynamically changing reflection image or pattern on the observation monitor during ultrasound detection with the fan-shaped ultrasound field, which reflection image or pattern is characterized by a dynamically changing ring structure depending on the spatial orientation of the marker relative to the ultrasound field, and its technical shape can be interpreted as a clear indication of the marker's location, in contrast to reflection signal images based on internal biological tissue structures. Due to the compact spatial arrangement of the at least two strand eyes, the detectability of the marker is particularly obvious to the person performing the ultrasound examination due to the dynamic visibility resulting from the panning of the ultrasound field.

[0021] When a strand has one strand length and two strand ends, the at least two strand eyes are arranged as compactly as possible along the strand, with one of the two strand ends being located in the winding plane of the first strand eye and forming the first strand eye along half of the strand length, and the other of the two strand ends being located in the winding plane of the second strand eye and forming the second strand eye along the other half of the strand length. Preferably, in this case, the two strand ends are arranged laterally adjacent to and opposite the strand in the middle region of the strand length. In a particularly preferred embodiment, the winding planes of the two strand eyes are oriented orthogonal to each other. This constellation can be achieved by orienting the two strand eyes at 90° from a common plane at the junction. In this constellation, the two strand eyes are arranged without overlapping. Of course, other than the critical angle, any suitable angle between 0° and 180° deviating from 90° is also conceivable, but a three-dimensional shape in which at least two of the angle planes are perpendicular to each other or deviate from this by an angle of ±30° represents a particularly suitable three-dimensional shape for forming an implantable marker according to this solution.

[0022] In particular, good detection characteristics can be recorded on the marker when both strand eyes have an angle α of 60°≦α<120°. When 60°≦α<90°, both strand eyes overlap with each other and project perpendicular to the winding plane.

[0023] In a further embodiment, at least two strand eyes are designed and arranged such that one of the two strand eyes projects perpendicular to the other, with the other strand eye positioned midway between the first strand eye. This constellation can be realized by rotating both strand eyes by an additional 90° at the tangent point of the longitudinal axes of the strands, i.e., by torsionally rotating the strands by 90°, based on the constellation described above with α=90°.

[0024] An alternative embodiment of the implantable marker according to the present solution comprises at least two strand eyes connected to each other via curved strand sections having associated arc planes that form an angle β with each of the winding planes of the at least two strand eyes, the angle not equal to 0°, and the winding planes of the at least two strand eyes form an angle α not equal to 0°. The curved strand sections are preferably semicircular. Preferably, the at least two strand eyes have the same shape and dimensions. In this case, the curved strand sections have the same shape and dimensions as one half of the strand eyes.

[0025] In principle, an angle of β between 50° and β is appropriate. If the curved strand portion forms an angle of β = 60° with the winding plane of both strand eyes and, as described above, has the same shape and dimensions as half of two strand eyes, the two strand eyes together with the curved strand portions define an equilateral triangle. When a marker designed in this way is detected by dynamically panning through a fan-shaped ultrasonic field, the reflected signal, visually recognizable with a viewing device, appears as an unmistakably simple, dynamic, three-dimensional ring structure.

[0026] The marker, preferably comprised of a biocompatible metallic shape-memory material along the entire length of the strand, is inserted into a hollow cannula for implantation by applying a mechanical force to the shape-memory material, which transforms the marker from its pre-pressurized three-dimensional shape into a substantially straight strand. The cannula for the implantation procedure typically has a cannula diameter slightly larger than the diameter of the strand, and the substantially straight strand can be removed from the hollow cannula along its length at its distal end using a stylet. As the strand exits the hollow cannula, it transforms into its pre-pressurized three-dimensional shape, forming at least two fixed strand eyes integrally connected to one another.

[0027] In order to minimize the risk of damage to the tissue to be marked and at the same time optimize the detection and discrimination properties of the marker by ultrasound detection, the marker has a three-dimensional shape that is as compact as possible, i.e. the two strand ends that delimit the strand on either side are each located in a winding plane that can be associated with a strand eye, and in the case of two fixed strand eyes, form the fixed strand eye in each case with half the length of the strand.

[0028] When three or more strand eyes are formed along a strand, the ends of the strand are positioned within the winding plane of the fixed strand eyes formed at each end of the strand. In a particularly preferred embodiment for designing an implantable marker according to this solution, at least two fixed strand eyes along the strand are directly connected to each other or directly bonded to each other, i.e., in the absence of force, the implantable marker has exclusively curved strand portions that form the fixed strand eyes. Alternatively, the two strand eyes are integrally connected to each other via curved strand portions, the curved strand portions having approximately the same dimensions and shape as half of both strand eyes.

[0029] To increase the ultrasound reflectivity of strands made of biocompatible material, the surface of the strand is modified or treated in at least some areas to provide a structured surface that reflects ultrasound, for example by roughening the material.

[0030] Alternatively, or in combination with the above-mentioned measures for increasing ultrasonic reflectivity, the strand can be manufactured from a central wire and at least one additional single wire wound helically around the central wire, so that the strand surface appearing on the outside is provided by the helical winding structure of the at least one single wire, wherein at least the central wire or the at least one single wire is made here of a metallic shape memory material, preferably NiTi (nitinol), NiTiCu, CuZn, CuZnAl or CuAlNi.

[0031] Preferably, the cross section of the strand is 0.1 to 0.8 mm. If at least one solid wire is wound around the center wire, a wire cross section in the range of 0.1 mm to 0.5 mm is suitable.

[0032] Preferably, the ring-shaped strand eye typically has an inner ring diameter of 2 to 3 mm and an outer ring diameter of 3 to 5 mm.

[0033] Cannulae with a cannula size between 14G and 18G are particularly suitable for implanting markers according to the present solution.

[0034] The implantable marker according to the present solution is explained in more detail below on the basis of various exemplary embodiments and with reference to the following figures: [Brief explanation of the drawings]

[0035] The invention will now be described on the basis of exemplary embodiments with reference to the drawings, without limiting the general idea of ​​the invention, in which: [Figure 1] 1 is a schematic diagram illustrating the ultrasound detectability of an ultrasound marker formed according to the present solution; [Figure 2] (a) is a side view of the first exemplary embodiment; (b) is a perspective view of the first exemplary embodiment; [Figure 3] (a) is a plan view of the second exemplary embodiment; (b) is a perspective view of the second exemplary embodiment; [Figure 4] 2A and 2B are two side views of the third embodiment rotated by 90°; [Figure 5] FIG. 4 is a perspective view of a fourth exemplary embodiment; [Figure 6] 5 is a side view of a fifth exemplary embodiment; [Figure 7] FIG. 10 is a side view of a sixth exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0036] FIG. 1 shows a schematic representation of a marker 2 implanted within a tissue region 1, which assumes its press-formed three-dimensional shape upon removal of external mechanical forces and has at least two strand eyes 21, 22, each associated with a winding plane 3, 4 that together subtend an angle α≠0, preferably 90°.

[0037] In the case of ultrasound detection, a ring-shaped reflection pattern appears in the ultrasound image of the marker 2, shown diagrammatically in FIG. 1, interacting with the ultrasound waves 5 and 6, each of which has a direction of propagation perpendicular to one of the two winding planes 3 and 4. In the case of ultrasound wave 5, its direction of propagation is perpendicular to the winding plane 4, so it passes through the strand eye 21 in its longitudinal direction, which appears as a ring in the corresponding ultrasound image. In the case of ultrasound wave 6, on the other hand, the strand eye 22 appears as a ring in the corresponding ultrasound image. In both cases, Euclidean geometric shapes that do not exist in natural tissue regions appear in the ultrasound image, drawing the examiner's attention to the presence of the marker 2 placed inside the body.

[0038] In the implanted state, i.e., when the marker 2 assumes the three-dimensional shape inherent to the material due to pressure molding, the marker 2, which is made of a single strand of material, forms a substantially self-contained three-dimensional shape, i.e., the strand ends of the strands forming the marker 2 preferably lie along winding planes 3 and 4, respectively. Specific three-dimensional shapes according to this solution for forming the implantable marker 2 can be seen in the further figures. 2(a) and (b) show the marker 2 from two different perspectives, which is made from a strand 7 and includes two strand eyes 21, 22. The two strand ends 8, 9 of the strand 7 are arranged in the region of the strand midpoint 10, in each case on opposite sides of the strand 7, with the strand end 8 being associated with the strand eye 21, as shown in FIG. 2(a), and being arranged in a winding plane 3 corresponding to the drawing plane, and the strand end 9 being associated with the strand eye 22, and being arranged in a winding plane 4 oriented perpendicular to the drawing plane according to FIG. 2(a). The winding planes 3, 4 of the strand eyes 21, 22 form an angle α of 90°, as shown in FIG. 2(b).

[0039] The strands 7 of the marker 2 preferably have a single wire spirally wound around a center wire, although of course, two or more wires can be wound around the center wire.

[0040] Figures 3(a) and (b) respectively show, from different directions, a marker 2 formed according to the present solution and made from a strand 7, which forms two fixed strand eyes 21, 22. Figure 3(a) shows that the winding plane 3 associated with the first strand eye 21 corresponds to the sheet plane or drawing plane, while the winding plane 4 of the second strand eye 22 runs perpendicular to the winding plane 3, with the second strand eye 22 being positioned midway between the first strand eye 21 and projecting towards the latter.

[0041] Again, ultrasound waves interacting with a marker 2 parallel to the winding plane of one of the two strand eyes 21, 22 make it possible to display on the ultrasound image the complete eye shape of the strand eye oriented in the direction of transmission. Preferably, each of the strand eyes 21, 22 is ring-shaped or annular.

[0042] 4(a) and 4(b) are side views of the marker 2 rotated by 90 degrees relative to each other.

[0043] The strand 7 has a first fixed strand eye 21 with the winding plane 3 oriented perpendicular to the plane of the drawing. The strand end 8 shown in Figure 4(b) is located in the winding plane 3.

[0044] The second strand eye 22 extends three-dimensionally above the first strand eye 21 in a slightly spiraled manner to form the second strand eye 22 when viewed in the side view shown in Figure 4(b). The winding plane 4 that can be associated with the second strand eye 22 is oriented perpendicular to the sheet or drawing plane of Figure 4(a) or oriented corresponding to the sheet or drawing plane of Figure 4(b).

[0045] 5 shows an embodiment of a marker 2 formed according to the present solution, forming three strand eyes 21, 22, 23, the associated winding planes 3, 4, 11 in each case forming an angle α of 120°. In this case, strand end 8 is located in the first winding plane 3 and strand end 9 is located in the winding plane 11.

[0046] In contrast to the exemplary embodiments described above, the marker 2 illustrated in FIG. 5 allows a ring-shaped or annular image to be provided in the ultrasound image when sound waves are propagated in each of the winding planes 3, 4, 11, thus improving the spatial detectability and also the identifiability of the marker 2 compared to the markers described above, each having two strand eyes.

[0047] 6(a) and 6(b) show a further embodiment of the marker 2 from two different viewing directions. The strand 7 of the marker 2 includes three strand eyes 21, 22, and 23, one associated with each of the winding planes 3, 4, and 11. The winding planes 3 and 4 associated with the first and second strand eyes 21 and 22 are at an angle α, which in the illustrated exemplary embodiment is 120°. Three-dimensional shapes that deviate from this angle are also possible, for example, α = 90°. The winding plane 11 associated with the third strand eye 23 is tilted or oriented orthogonal to the second winding plane 4.

[0048] Again, a marker 2 designed according to this solution is able to generate a ring-shaped or annular ultrasound reflection image on the ultrasound image, with sound waves propagating in each case in three winding planes 3, 4, 11.

[0049] 7(a) and (b) each show the marker 2 in a side view rotated 90 degrees relative to one another, similar to the exemplary embodiment illustrated in FIGS. 4(a) and (b).

[0050] The first fixed strand eye 21 has a winding plane 3 oriented perpendicular to the plane of the drawing. The strand end 8 of the first strand eye 21 shown in FIG. 7(b) is located within the winding plane 3 and is directly adjacent to the bend point 12, where the first strand eye 21 is integrally joined to a curved strand portion 13 that is semicircular and ring-shaped and spans an arc plane 14. The arc plane 14 forms an angle β with the winding plane 3 of the first strand eye 21, preferably 60°. The upper end of the illustrated curved strand portion 13 is integrally connected to a second strand eye 22 at a bend point 15, whose associated winding plane 4 forms an angle β' with the arc plane 14, preferably corresponding to the angle β. The strand end 16 of the second strand eye 22 is located within the winding plane 4 and is directly adjacent to the second bend point 15.

[0051] The first and second strand eyes 21, 22 preferably have the same shape and approximately the same size. In this case, the curved portion 13 corresponds to half of the shape of one of the two strand eyes 21, 22. In this way, the marker 2 can be characterized by an equilateral triangle and is a three-dimensional object that can generate a very concise reflection pattern on an ultrasound echo image. When a fan-shaped ultrasound field is panned over the marker, the dynamic visibility of the pattern appears three-dimensionally on the monitor.

[0052] The first and second strand eyes 21, 22 do not necessarily have to have the same dimensions, rather the curved portion 13 should be appropriately adapted in shape and size to the second strand eye 22 shown in Figures 7(a) and (b) to form a self-contained three-dimensional triangular structure. [Explanation of symbols]

[0053] 1 Organizational area 2 Markers 3 Winding plane 4 Winding plane 5. Ultrasound 6. Ultrasound 7 strands 8 Strand Ends 9 Strand Ends 10 Mid-strand length 11 Winding plane 12 bending points 13 Curved section 14 Arc Plane 15 bending points 16 Strand End 21 Strand Eye 22 Strand Eye 23 Strand Eye α angle β, β' angles

Claims

1. An implantable marker for marking an area of ​​internal tissue in an animal or human, the marker being made of a biocompatible material and comprising at least one strand having a three-dimensional shape that is pressurized during a molding process, wherein an external mechanical force forces the strand to assume the three-dimensional shape after which the strand assumes the three-dimensional shape upon removal of the mechanical force, the three-dimensional shape pressurized into the strand comprising at least two strand eyes, each of a first and a second strand eye being formed by at least one winding of the strand, each strand eye being capable of being associated with a winding plane; the at least two strand eyes are formed in a manner equivalent to an eye having a predetermined shape in the shape of a figure of eight, and are connected to each other via a common contact point in which the winding planes of the at least two strand eyes are oriented at an angle α to each other; the winding planes of the at least two strand eyes form an angle α not equal to 0°; the strand has two strand ends; one of the two strand ends is disposed within the winding plane of the first strand eye and lies on the winding plane; An implantable marker, wherein the other of the two strand ends is disposed within the winding plane of the second strand eye and lies on the winding plane.

2. the strands have a single strand length; one of the two strand ends forms the first strand eye together with half of the strand length; 2. The implantable marker of claim 1, wherein the other of said two strand ends forms said second strand eye with the other half of said strand length.

3. 3. The implantable marker of claim 2, wherein the strand ends are positioned opposite each other laterally adjacent the strand in a region intermediate the length of the strand.

4. 4. The implantable marker of claim 1, wherein the at least two strand eyes are designed and arranged so that one of the two strand eyes projects perpendicular to the first strand eye, and the other strand eye does not overlap the first strand eye.

5. 4. The implantable marker of claim 1, wherein the angle α is 90°≦α<120°.

6. 3. The implantable marker of claim 1, wherein the at least two strand eyes are designed and arranged such that one of the two strand eyes projects perpendicular to the other strand eye, with the other strand eye positioned midway between the one strand eye.

7. An implantable marker for marking an area of ​​internal tissue in an animal or human, the marker comprising at least one strand made of a biocompatible material and having a three-dimensional shape that is pressurized during a molding process, wherein an external mechanical force forces the strand to assume the three-dimensional shape after which the strand assumes the three-dimensional shape upon removal of the mechanical force, the three-dimensional shape pressurized into the strand comprising at least two strand eyes, each of a first and a second strand eye being formed by at least one winding of the strand, each strand eye being capable of being associated with a winding plane; the at least two strand eyes are connected via curved strand portions associated with arc planes that form angles with respective winding planes of the at least two strand eyes, the angles not equal to 0°; the winding planes of the at least two strand eyes form an angle α not equal to 0°; the strand has two strand ends; one of the two strand ends is disposed within the winding plane of the first strand eye and lies on the winding plane; An implantable marker, wherein the other of the two strand ends is disposed within the winding plane of the second strand eye and lies on the winding plane.

8. 8. The implantable marker of claim 7, wherein the winding plane of at least one of said two strand eyes forms an angle β with said arc plane in the range of 50°≦β≦70°.

9. 9. An implantable marker as defined in claim 7 or 8, wherein said curved strand portion is semicircular.

10. the strands have a single strand length; 9. An implantable marker as claimed in claim 7 or 8, wherein the length of said strand corresponds to the sum of said curved strand portion and said two strand eyes.

11. 9. An implantable marker as claimed in any one of claims 1 to 3, 7 and 8, wherein the biocompatible material of the strand comprises a material that reflects ultrasound.

12. 9. An implantable marker according to any one of claims 1 to 3, 7 and 8, wherein the strand has a strand surface that is surface-structured to reflect ultrasound in at least some areas.

13. An implantable marker as described in any one of claims 1 to 3, 7, and 8, characterized in that the strand consists of a center wire and at least one solid wire wound around the center wire, the at least one solid wire being made of a metallic shape memory material.

14. An implantable marker as claimed in any one of claims 1 to 3, 7 and 8, characterized in that the strand of biocompatible material is at least one wire made of a metallic shape memory material from the group NiTi ("Nitinol"), NiTiCu, CuZn, CuZnAl or CuAlNi.

15. the strand is positionable within a hollow cannula that imparts an external mechanical force to the strand in a three-dimensional shape constrained by the external mechanical force, without the strand eye; An implantable marker as described in any one of claims 1 to 3, 7 and 8, characterized in that the at least two strand eyes are independently formed immediately after the strand is expelled from the hollow cannula and the associated external mechanical force is removed.

16. 16. The implantable marker of claim 15, wherein said hollow cannula is selected from hollow cannulas having a cannula size of 14G to 18G.

Images