ENGRAVED RETRO-REFLECTIVE TRACKING MARKER

Abstract

The present invention relates to a method of producing an optically detectable and retro-reflective medical tracking marker, wherein electromagnetic energy is applied to at least one section of a retro-reflective surface of a marker structure in an amount that is sufficient to alter the material properties of the retro-reflective surface, such that the capability of reflecting electromagnetic radiation of the at least one section is reduced to a second capability of reflecting electromagnetic radiation. The present invention further relates to a corresponding retro-reflective medical tracking marker and a corresponding use thereof.

Claims

1. A method of producing an optically detectable and retro-reflective medical tracking marker, comprising: providing a marker structure comprising a retro-reflective surface that comprises a plurality of elements of a transparent material, each of the plurality of elements having a substantially spherical shape and being retained by a matrix, and the retro-reflective surface having a first capability of reflecting electromagnetic radiation; and applying electromagnetic energy to at least one section of the retro-reflective surface in an amount that is sufficient to alter material properties of the retro-reflective surface such that a capability of reflecting electromagnetic radiation of the at least one section is reduced from the first capability of reflecting electromagnetic radiation to a second capability of reflecting electromagnetic radiation.

2. The method according to claim 1, wherein the second capability of reflecting electromagnetic radiation is a substantially eliminated capability of reflecting electromagnetic radiation.

3. The method according to claim 1, wherein the electromagnetic energy is applied via a laser-beam.

4. The method according to claim 1, wherein a location, orientation, size and/or shape of the at least one section of the retro-reflective surface is predefined with respect to a geometry of the marker structure.

5. The method according to claim 1, further comprising applying a transparent layer or coating to the marker structure, which covers the retro-reflective surface.

6. The method according to claim 1, wherein: the applying the electromagnetic energy to at least one section of the retro-reflective surface leaves at least one first retro-reflective section and at least one second retro-reflective section, the at least one first retro-reflective section and the at least one second retro-reflective section having the first capability of reflecting electromagnetic radiation, a location, orientation, size and/or shape of the at least one first retro-reflective section codifies a specific identity of the tracking marker, and a location, orientation, size and/or shape of the at least one second retro-reflective section enables a medical tracking system to detect a spatial location and/or orientation of the tracking marker.

7. The method according to claim 1, wherein the providing the marker structure comprising the retro-reflective surface involves: providing a two-dimensional retro-reflective film; and applying the two-dimensional retro-reflective film to the marker structure.

8. The method according to claim 7, wherein the two-dimensional retro-reflective film is glued to a flat surface of the marker structure.

9. The method according to claim 7, wherein the two-dimensional retro-reflective film is stretched over and glued to a three-dimensional spherical surface of the marker structure.

10. The method according to claim 7, wherein the two-dimensional retro-reflective film is applied to the marker structure before the electromagnetic energy is applied to at least one section of the retro-reflective surface.

11. The method according to claim 7, wherein the second capability of reflecting electromagnetic radiation results from at least one of: the substantially spherical shape of at least one of the plurality of elements being altered or destroyed responsive to the application of electromagnetic energy; the retention of at least one of the plurality of elements by the matrix being destroyed responsive to the application of electromagnetic energy; a color and/or a material property of the matrix being altered responsive to the application of electromagnetic energy.

12. The method according to claim 1, wherein the marker structure is positioned with respect to an electromagnetic energy application device, with at least one reference surface of the marker structure contacting at least one corresponding reference surface assigned to the electromagnetic energy application device.

13. (canceled)

14. (canceled)

15. (canceled)

16. The method according to claim 4, wherein the retro-reflective surface is predefined with respect to a mechanical interface of the marker structure, which is adapted to attach the optically detectable and retro-reflective medical tracking marker to a support structure.

17. The method according to claim 5, wherein the electromagnetic energy is applied to the retro-reflective surface through the transparent layer or the coating.

18. The method according to claim 12, wherein the electromagnetic energy application device is a laser.

19. A medical tracking marker comprising: a marker structure; and a retro-reflective surface, the retro-reflective surface comprising: a matrix; a plurality of elements of a transparent material, each of the plurality of elements having a substantially spherical shape and being retained by the matrix; a first retro-reflective section having a first capability of reflecting electromagnetic radiation; and an electromagnetic energy-treated second retro-reflective section having a second capability of reflecting electromagnetic radiation, the second capability of reflecting electromagnetic radiation being less than the first capability of reflecting electromagnetic radiation as a result of an electromagnetic energy treatment altering material properties of the matrix and/or the plurality of elements of the transparent material.

20. The medical tracking marker according to claim 19, wherein the retro-reflective surface comprises a two-dimensional retro-reflective film.

21. The medical tracking marker according to claim 20, wherein the two-dimensional retro-reflective film is stretched over a surface of the marker structure.

22. The medical tracking marker according to claim 19, wherein the altered material properties of the matrix and/or the plurality of elements of the transparent material comprises at least one of: an altered or destroyed substantially spherical shape of at least one of the plurality of elements; a destroyed retention of at least one of the plurality of elements by the matrix; an altered color and/or a material property of the matrix.

23. A system comprising: a laser; and a medical tracking marker comprising: a marker structure; and a retro-reflective surface, the retro-reflective surface comprising: a matrix; a plurality of elements of a transparent material, each of the plurality of elements having a substantially spherical shape and being retained by the matrix; a first retro-reflective section having a first capability of reflecting electromagnetic radiation; and an electromagnetic energy-treated second retro-reflective section having a second capability of reflecting electromagnetic radiation, the second capability of reflecting electromagnetic radiation being less than the first capability of reflecting electromagnetic radiation as a result of an electromagnetic energy treatment by the laser altering material properties of the matrix and/or the plurality of elements of the transparent material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the following, the invention is described with reference to the appended figures which give background explanations and represent specific embodiment of the invention.

[0038] The scope of the invention is however not limited to the specific features disclosed in the context of the figures, wherein

[0039] FIG. 1 illustrates the basic steps of the inventive method of producing a medical tracking marker;

[0040] FIG. 2 shows a tracking marker according to the present invention obtained by the method illustrated in FIG. 1;

[0041] FIG. 3 shows an example of a retro-reflective pattern of the medical tracking marker according to the present invention;

[0042] FIG. 4 shows a cross-section of a retro-reflective surface or layer;

[0043] FIG. 5 shows different appliances for the medical tracking marker according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0044] FIG. 1 illustrates the basic steps of the method according to a first aspect. Starting with the top left illustration, a retro-reflective film 3 is glued onto a flat surface 10 of a rigid marker structure 2 which from now on serves as a substrate for the retro-reflective film.

[0045] In a later step (top right in FIG. 1), the marker structure 2 is positioned with respect to a laser beam source 13 by bringing one of its outer reference surfaces 14 that frame the marker structure 2 into contact with a corresponding reference surface 15 that in turn takes a predefined position with respect to the laser beam source 13. Thus, the pattern engraved into the retro-reflective surface 3 by the laser beam 5 is calibrated with respect to the reference surface 14 of the marker structure 2.

[0046] In the specific example shown in FIG. 1, the laser-engraved pattern comprises sections 4 with a substantially eliminated capability of reflecting light, along with untreated sections 9 with an unamended capability of reflecting light (see bottom left illustration in FIG. 1).

[0047] In a later, final step, a protective transparent film 8 is glued, welded or otherwise attached to the substrate 2, such that it covers the retro-reflective film 3.

[0048] FIG. 2 shows a specific example of the inventive tracking marker 1, comprising a marker structure 2 with a specific pattern engraved into a retro-reflective film 3 underneath a transparent layer 8.

[0049] A plurality of sections 9A is provided in the edges of the substantially square-shaped film 3, such that a medical tracking system can determine from the location, orientation, size and/or shape of these sections 9A appearing in the camera image, how the tracking marker 1 is located and oriented in three-dimensional space.

[0050] On the other hand, the retro-reflective surface 3 comprises two concentric sections 9B which codify the specific identity of the tracking marker shown in FIG. 2.

[0051] In a further embodiment, instead of or in additional to such circles, sections are provided inside of circles or other forms that codify the specific identity of the tracking marker.

[0052] FIG. 3 again shows the specific marker pattern of FIG. 2 and further illustrates that the sections 9A and 9B are positioned at predefined distances (X1, X2) with respect to a spatial reference (REF). In particular, anyone of the reference surfaces 14 of the marker structure 2 can represent a spatial reference REF for positioning the sections 9A and 9B.

[0053] FIG. 4 illustrates the operating principle of retro-reflective surfaces. In contrast to a mere mirror, which reflects an incoming light-ray at an angle which is mirror-symmetrical to the angle direction of the incoming light-ray, a retro-reflective surface is adapted to reflect incoming light in substantially the opposite direction it came from. In the shown example, an incoming light-ray entering a glass-sphere 11 retained in a matrix 12 is reflected twice at the boundary interface of the glass-sphere 11, before it exits the glass sphere 11 in the opposite direction it initially came from. Of course, the glass spheres 11 may be substituted by any other element which is capable of retro-reflecting light, for example structures with orthogonal boundary interfaces such as glass cubes or pyramids.

[0054] FIG. 5 shows different appliances for the inventive medical tracking marker. In the illustration on the left, the support structure 6 of the tracking marker 1 is merely clamped onto a rod-shaped and rotationally symmetrical medical instrument, such that the tracking marker 1 which is fixed to the support structure 6 via the interface 7 can freely rotate around the longitudinal axis of the instrument 16. In this case, one single tracking marker 1 is sufficient to determine 5 degrees of freedom of the instrument's 16 spatial position in three-dimensional space.

[0055] The same applies to the appliances shown in the center and the right illustration, except for the fact that the marker 1 in the center illustration is freely rotatable around the longitudinal axis of the support structure 6, and that the tracking marker 1 in the right illustration is fixedly attached to the anatomical structure 17, such that it allows for determining 6 degrees of freedom of the anatomical structure 17 in three-dimensional space.