Method and apparatus using shaped field of repositionable magnet to guide implant

• US 6,157,853 A
• Filed: 02/09/1998
• Issued: 12/05/2000
• Est. Priority Date: 11/12/1997
• Status: Expired due to Fees

• Current Assignee: Stereotaxis, Inc.
• Original Assignee: Stereotaxis, Inc.
• Inventors: Ritter, Rogers C., Blume, Walter M., Werp, Peter R., Hogg, Bevil J., Howard, Matthew A. III
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): MANTIS MERCADER, ELENI M
• Application Number:
  US09/020,934
• Time in Patent Office: 1,030 Days
• Field of Search: 600/407, 600/410, 600/426, 600/130, 378/20, 378/205, 324/309
• US Class Current: 600/426
• CPC Class Codes: A61B 2034/107 Visualisation of planned trajectories or target regions
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/732 arranged around the patient, e.g. in a gantry
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 34/70 Manipulators specially adapted for use in surgery
• CPC Class Codes: A61B 34/73 Manipulators for magnetic surgery

Abstract

Methods and apparatuses for displaying and using a shaped field of a repositionable magnet to move, guide, and/or steer a magnetic seed or catheter in living tissue for medicinal purposes. A moveable magnet assembly and a portion of a patient'"'"'s body undergoing magnetically-aided surgery are both provided with fiducial markers. The portion of the patient'"'"'s body is fixed in a location in which the fiducial markers are sensed and located by a set of localizers. The positions of the fiducial markers are determined by a processor, which operates on a stored representation of the magnetic field of a magnet in the magnet assembly to provide a display of the present magnetic field of the magnet. This display may be superimposed over an MRI, X-ray or CAT image during surgery. The repositionable magnet can be an electromagnet. In some embodiments, a computer calculates orientations and currents for an external electromagnet to move the implanted magnetic object in the patient'"'"'s body through a desired path. The display can provide real-time imaging of the implanted magnetic object in comparison to the desired path as the object is moved.

Claims

1. An apparatus for providing rapid interactive display of the aligning torque of a magnet, the apparatus comprising:

(a) a moveable magnet assembly having a plurality of fiducial marks thereon;

(b) a localizer comprising a plurality of imaging sensors configured to sense a position in three-dimensional space of the fiducial marks to thereby provide an indication of a location of the moveable magnet assembly; and

(c) a processor including memory having stored therein a representation of a magnetic field generated by the movable magnet assembly and a display configured to present a graphical representation of the magnetic field, the processor being configured to be responsive to the indication of the location of the moveable magnet assembly provided by the localizer so that the display provides an indication of the magnetic field within a selected volume of space resulting from the movable magnet assembly when the magnet is at a position indicated by the localizer.

2. The apparatus of claim 1 and further comprising a medical imaging device, and wherein an image sensed by the medical imaging device is superimposed upon the indication of the magnetic field within the selected volume of space.

3. The apparatus of claim 2 wherein the moveable magnet assembly is coupled to the processor and further comprising an operator input device coupled to the processor and operable to control a location and orientation of the movable magnet assembly.

4. The apparatus of claim 3 in which the operator input device is configured for non-tactile operator input.

5. The apparatus of claim 4 in which the non-tactile operator input device comprises a voice-recognition device.

6. The apparatus of claim 5 wherein the moveable magnet assembly comprises an electromagnet.

7. The apparatus of claim 6 wherein at least some of the fiducial marks on the moveable magnet assembly comprise light emitting diodes (LEDs).

8. The apparatus of claim 1 and further comprising a plurality of fiducial markers configured for positioning on a portion of a patient'"'"'s body.

9. A method for providing a rapid interactive display of the aligning torque of a magnet assembly, the method comprising:

(a) providing a plurality of fiducial marks on the magnet assembly;

(b) sensing a location and orientation of the fiducial marks;

(c) computing a magnetic field in a selected volume of space produced by the magnet assembly when the magnet assembly is in the location and orientation of the fiducial marks; and

(d) displaying a representation of the magnetic field in the selected volume of space.

10. The method of claim 9 and further comprising:

(a) placing a magnetic seed in a tissue of a living body;

(b) providing fiducial marks on an external surface of the living body proximate the tissue;

(c) sensing a location and orientation of the living body; and

(d) selecting the selected volume of space to include the tissue of the living body.

11. A method for providing a rapid interactive display of the aligning torque of a magnet assembly, the method comprising:

(a) positioning a body part of a patient in a fixed position in space relative to a plurality of localizers;

(b) displaying a view of the body part within a field of view of the localizers on a display;

(c) identifying landmarks on the body part;

(d) locating fiducial marks on a moveable magnet assembly;

(e) computing a position and orientation of the movable magnet assembly;

(f) determining relationships between a coordinate system of the display, the magnetic assembly, and a stored representation of a magnetic field produced by the movable magnet assembly;

(g) converting the representation of the magnetic field into display coordinates; and

(h) displaying a representation of the magnetic field in display coordinates on the display.

12. The method of claim 11 wherein the identification step comprises the touching of markers selected from the group consisting of anatomical landmarks and fiducial markers with a localizing device.

13. A device for navigating a surgical, diagnostic, or therapeutic object in a patient'"'"'s body, the device comprising:

a) an external magnet mounted on a gantry having an adjustable attitude;

b) a magnetic seed configured for implanting in a patient'"'"'s body; and

c) an imaging system configured to display a medical image of the magnetic seed implanted in a patient'"'"'s body and to superimpose thereon a representation of magnetic field lines of the external magnet, including those representing a near field, the superimposition being dependent upon an orientation and location of the external magnet.

14. The device of claim 13 and further comprising a servo-system mechanically coupled to the gantry.

15. The device of claim 14 wherein the servo-system is configured to provide exclusion zones into which movement of the external magnet and gantry are prevented.

16. The device of claim 13 wherein the imaging system is configured to display two orthogonal projections of the medical image.

17. The device of claim 13 wherein the imaging system is configured to display a rotatable three-dimensional representation of the medical image.

18. The device of claim 13 wherein the imaging system comprises a magnetic field-immune, fluoroscopic imaging system.

19. The device of claim 18 wherein the imaging system comprises a sensor selected from a group consisting of charge coupled device sensors, micro channel plate sensors, and amorphous silicon sensors.

20. A method of magnetic surgery using an external magnet comprising the steps of:

(a) implanting a magnetic seed in a patient'"'"'s body;

(b) imaging a region of the patient'"'"'s body including the implanted seed to thereby produce a medical image;

(c) superimposing on the medical image a representation of a set of magnetic field lines of the external magnet, including those representing a near field, the superimposition being dependent upon an orientation and location of the external magnet;

(d) aligning a portion of the superimposed representation along an intended path of the magnetic seed; and

(e) moving the external magnet into a position outside of the patient'"'"'s body to produce the magnetic field represented by the aligned superimposed representation to effect guidance or movement of the seed.

21. The method of claim 20 wherein the external magnet is a permanent magnet, and the aligning and moving steps occur simultaneously.

22. The method of claim 20 wherein the external magnet is an electromagnet, the alignment step occurs first, and the movement step is servo-controlled.

23. A method of computer-aided magnetic surgery comprising the steps of:

(a) implanting a magnetic seed in a patient'"'"'s body;

(b) imaging a region of the patient'"'"'s body including the implanted seed to thereby produce a medical image;

(c) storing information indicative of a path to be taken by the seed in a memory of a computer having a display;

(d) displaying a representation of the path and a current location of the seed on the display;

(e) calculating orientations and currents of an external electromagnet required to provide a magnetic field to the seed to move the seed along the path;

(f) activating a servo-controlled motor to move the external electromagnet to the calculated orientations;

(g) providing the calculated currents to the electromagnet; and

(h) updating the display to provide current locations of the seed relative to the path.

24. The method of claim 23 further comprising providing a non-tactile command to the computer.

25. The method of claim 24 wherein the step of providing a non-tactile command to the computer comprises speaking the command to a voice-recognition unit.

26. A device for navigating a surgical, diagnostic, or therapeutic object in a patient'"'"'s body, the device comprising:

a) an external magnet mounted on a gantry having an adjustable attitude;

b) a magnetic seed configured for implanting in a patient'"'"'s body; and

c) a magnetic locating device for determining and displaying a position and orientation of an implanted magnetic seed.