Implantable marker with wireless signal transmitter

• US 20050154293A1
• Filed: 12/24/2003
• Published: 07/14/2005
• Est. Priority Date: 12/24/2003
• Status: Active Grant

• Current Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Original Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Inventors: Dimmer, Steven C., Seiler, Keith, Gisselberg, Margo
• Granted Patent: US 8,196,589 B2
• Time in Patent Office: Days
• US Class Current: 600/420
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/3954 magnetic, e.g. NMR or MRI
• CPC Class Codes: A61B 2090/3958 emitting a signal
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/06 Devices, other than using radiation, for detecting or locating foreign bodies for removing same A61B17/50 ; determining position of probes within or on the body of the patient
• CPC Class Codes: A61B 5/061 Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body A61B1/00158 takes precedence
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: A61B 5/064 using markers A61B5/062 takes precedence
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 90/39 Markers, e.g. radio-opaque or breast lesions markers
• CPC Class Codes: A61N 2005/1051 using an active marker markers in general A61B90/39

Abstract

A wireless marker for localizing a target of a patient comprises a casing and a magnetic transponder at least partially received in the casing. The magnetic transponder produces a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation energy. The magnetic transponder also has a magnetic centroid. The marker also comprises an imaging element carried by the casing and/or the magnetic transponder. The imaging element has a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

Claims

1. A wireless marker for localizing a target of a patient, comprising:

a casing;

a magnetic transponder at least partially encased in the casing, the magnetic transponder producing a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation energy and having a magnetic centroid; and

an imaging element carried by the casing and/or the magnetic transponder, the imaging element having a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

2. The marker of claim 1 wherein the magnetic transponder comprises a ferrite core, a plurality of windings around the core, and a capacitor electrically coupled to the windings.

3. The marker of claim 1 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element and a second contrast element, the first and second contrast elements being configured symmetrically with respect to the magnetic transponder.

4. The marker of claim 1 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element at the first end of the magnetic transponder and a second contrast element at the second end of the magnetic transponder.

5. The marker of claim 4 wherein the first contrast element comprises a first ring and the second contrast element comprises a second ring.

6. The marker of claim 4 wherein the first and second rings are continuous.

7. The marker of claim 4 wherein the first and second rings are discontinuous annular members having a gap.

8. The marker of claim 4 wherein the first contrast element is a first sphere and the second contrast element is a second sphere.

9. The marker of claim 4 wherein the first and second contrast elements comprise Au, W and/or Pt.

10. The marker of claim 1 wherein the imaging element has a density of at least approximately 19 g/cm³.

11. The marker of claim 1 wherein the imaging element is sufficiently absorbent of incident photon fluence of a megavolt photon therapy beam to be visible in a radiographic image generated using such a therapy beam.

12. The marker of claim 1 wherein the imaging element is a ring around a medial region of the magnetic transponder.

13. The marker of claim 12 wherein the ring is within the casing.

14. The marker of claim 12 wherein the ring is exterior of the casing.

15. The marker of claim 1 wherein:

the magnetic transponder comprises a ferrite core having a first end and a second end, a plurality of windings around the core, and a capacitor electrically coupled to the windings and located at the first end of the core, wherein the capacitor has a radiographic profile in a radiographic image; and

the marker further comprises a module at the second end of the core, the module having a radiographic profile similar to the radiographic profile of the capacitor.

16. The marker of claim 15 wherein the capacitor and the module are arranged to be approximately symmetrical with respect to the core and the windings.

17. The marker of claim 15 wherein:

the capacitor and the module are arranged to be approximately symmetrical with respect to the core and the windings; and

the imaging element comprises a first contrast element at least proximate to the first end of the core and a second contrast element at least proximate to the second end of the core.

18. The marker of claim 17 wherein the first contrast element comprises a first ring around the first end of the core and the second contrast element comprises a second ring around the second end of the core.

19. The marker of claim 17 wherein the first contrast element comprises a first sphere at least proximate to the first end of the core and the second contrast element comprises a second sphere at least proximate to the second end of the core.

20. A wireless marker for localizing a target of a patient, comprising:

a casing;

a magnetic transponder in the casing, the magnetic transponder producing a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation field, and the magnetic transponder having a first density; and

an imaging element carried by the casing and/or the magnetic transponder, the imaging element having a second density greater than the first density of the magnetic transponder.

21. The marker of claim 20 wherein:

the magnetic transponder has a magnetic centroid; and

the imaging element has a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

22. The marker of claim 21 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element and a second contrast element, the first and second contrast elements being configured symmetrically with respect to the magnetic transponder.

23. The marker of claim 21 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element at the first end of the magnetic transponder and a second contrast element at the second end of the magnetic transponder.

24. The marker of claim 21 wherein the first density is less than 19 g/cm³ and the second density is not less than 19 g/cm³.

25. The marker of claim 20 wherein the first density is less than 19 g/cm³ and the second density is not less than 19 g/cm³.

26. A wireless marker for localizing a target of a patient, comprising:

a casing;

a magnetic transponder at least partially encased in the casing, the magnetic transponder producing a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation field; and

an imaging element carried by the casing and/or the magnetic transponder, the imaging element being sufficiently absorbent of incident photon fluence of a megavolt photon therapy beam to be visible in a radiographic image generated using such a therapy beam.

27. The marker of claim 26 wherein:

the magnetic transponder has a magnetic centroid; and

the imaging element has a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

28. The marker of claim 27 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element and a second contrast element, the first and second contrast elements being configured symmetrically with respect to the magnetic transponder.

29. The marker of claim 27 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element at the first end of the magnetic transponder and a second contrast element at the second end of the magnetic transponder.

30. The marker of claim 27 wherein the magnetic transponder has a first density less than 19 g/cm³ and the imaging element has a second density not less than 19 g/cm³.

31. The marker of claim 26 wherein the magnetic transponder has a first density less than 19 g/cm³ and the imaging element has a second density not less than 19 g/cm³.

32. A wireless marker for localizing a target of a patient, comprising:

a casing;

a magnetic transponder at least partially encased in the casing, the magnetic transponder producing a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation field; and

an imaging element carried by the casing and/or the magnetic transponder, the imaging element having a density of at least 19 g/cm³.

33. The marker of claim 32 wherein:

the magnetic transponder has a magnetic centroid; and

the imaging element has a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

34. The marker of claim 33 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element and a second contrast element, the first and second contrast elements being configured symmetrically with respect to the magnetic transponder.

35. The marker of claim 33 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element at the first end of the magnetic transponder and a second contrast element at the second end of the magnetic transponder.

36. A wireless marker for localizing a target of a patient, comprising:

a casing;

a magnetic transponder at least partially encased in the casing, the magnetic transponder producing a wirelessly transmitted magnetic field in response to a wirelessly transmitted excitation field; and

an imaging element incorporated with the casing and/or the magnetic transponder, the imaging element producing a radiographic profile in a radiographic image such that the marker has a radiographic centroid at least approximately coincident with the magnetic centroid.

37. The marker of claim 36 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element and a second contrast element, the first and second contrast elements being configured symmetrically with respect to the magnetic transponder.

38. The marker of claim 36 wherein:

the magnetic transponder has a first end and a second end; and

the imaging element comprises a first contrast element at the first end of the magnetic transponder and a second contrast element at the second end of the magnetic transponder.

39. The marker of claim 36 wherein the magnetic transponder comprises a ferrite core, a plurality of windings around the core, and a capacitor electrically coupled to the windings.

40. The wireless marker of claim 39 wherein the imaging element comprises a high density material integrated into the ferrite core.

41. The wireless marker of claim 36 wherein the imaging element comprises a high density material integrated into the casing.

42. The wireless marker of claim 36 wherein the casing is sealed by a sealant and the imaging element comprises a high density material integrated with an adhesive in the casing.

43. A method of tracking a target of a patient, comprising:

imaging a marker attached to the patient using a first energy to obtain an image of the marker, the marker having a magnetic transponder that produces a wirelessly transmitted signal in response to a wirelessly transmitted excitation energy; and

locating the marker by transmitting the excitation energy to the marker.

44. The method of claim 43 wherein the first energy is radiation.

45. The method of claim 43 wherein the marker further comprises an imaging element that is opaque to the radiation such that the marker has a radiographic centroid at least approximately coincident with a magnetic centroid of the magnetic transponder, and the imaging procedure comprises irradiating the marker.