Method and apparatus to estimate location and orientation of objects during magnetic resonance imaging

• US 6,516,213 B1
• Filed: 02/15/2001
• Issued: 02/04/2003
• Est. Priority Date: 09/03/1999
• Status: Expired due to Fees

• Current Assignee: Robin Medical Inc.
• Original Assignee: Robin Medical Inc.
• Inventors: Nevo, Erez
• Primary Examiner(s): Walberg, Teresa
• Assistant Examiner(s): VAN, QUANG T
• Application Number:
  US09/762,953
• Time in Patent Office: 719 Days
• Field of Search: 600/424, 600/410, 600/407, 600/411, 128/899, 324/207.13, 324/207.22, 324/260, 324/207.17, 324/326
• US Class Current: 600/424
• 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

Abstract

Method and apparatus for determining the instantaneous location, the orientation of an object moving through a three-dimensional space by applying to the object a coil assembly including a plurality of sensor coils (20) having axes of known orientation with respect to each other including components in the three orthogonal planes; generating a time-varying, three-dimensional magnetic field gradient having known instantaneous values of magnitude and direction; applying the magnetic field gradient to the space, and object moving therethrough to induce electrical potentials in the sensor coils; measuring the instantaneous values of the induced electrical potentials generated in the sensor coils; processing the measured instantaneous values generated in the sensor coils together with the known magnitude, direction of the generated magnetic field gradient, the known relative orientation of the sensor coils in the coil assembly to compute the instantaneous location, orientation of the object within the space.

Claims

1. A method of determining the instantaneous location and orientation of an object moving through a three-dimensional space within the imaging space of magnetic resonance imaging apparatus during operation of said magnetic resonance imaging apparatus, comprising:

applying to said object a sensor that measure instantaneous magnetic field within said imaging space of magnetic resonance imaging apparatus;

measuring the instantaneous values of the magnetic fields which are generated by the activation of the gradient coils of said magnetic resonance imaging apparatus during operation of said magnetic resonance imaging apparatus; and

processing said measured instantaneous values of the magnetic fields, together with the known magnitude and direction of said magnetic fields of said gradient coils, to compute the instantaneous location and orientation of said object within said space.

2. The method according to claim 1, wherein said sensor comprises a coil assembly including a plurality of sensor coils having axes of known orientation with respect to each other and including components in the three orthogonal planes.

3. The method of claim 2, wherein said step of measuring further includes the step of identifying a plurality of activations of the magnetic gradient fields of said magnetic resonance imaging apparatus, wherein said identification provides the timing and the amplitude of activations of a single gradient coil or combined activations of two or three gradient coils of said magnetic resonance imaging apparatus;

and

wherein said step of processing further comprises;

i. calculating voltage vectors by vectorial summation of induced electrical potentials in different sensor coils for each said activation of the gradient fields of the MRI scanner;

ii. calculating the magnitudes of all said voltage vectors and the angles between all possible pairs of said voltage vectors;

iii. storing in memory the reference magnetic field maps of each of the three gradient coils of said magnetic resonance imaging apparatus for the imaging space of said magnetic resonance imaging apparatus;

iv. estimating the location of the sensor by processing said calculated magnitudes and angles of said voltage vectors together with the known reference magnetic field maps and the known relative orientation of the sensor coils in said coils assembly; and

v. estimating the orientation of the sensor by processing said induced electrical potentials generated in said sensor coils together with the known reference magnetic field maps and the known relative orientation of the sensor coils in said coil assembly.

4. The method of claim 2, wherein said step of measuring further includes identifying a plurality of activations of the magnetic gradient fields of said magnetic resonance imaging apparatus, wherein said identification provides the timing and the amplitude of activations of a single gradient coil or combined activations of two or three gradient coils of said magnetic resonance imaging apparatus;

and

wherein said step of processing further comprises;

i. storing in memory the reference magnetic field maps of each of the three gradient coils of said magnetic resonance imaging apparatus for the imaging space of said magnetic resonance imaging apparatus; and

ii. simultaneously estimating the location and the orientation of the sensor by processing said induced electrical potentials generated in said sensor coils together with the known reference magnetic field maps and the known relative orientation of the sensor coils in said coil assembly.

5. The method according to claim 2, wherein said coil assembly includes at least three sensor coils oriented orthogonally with respect to each other.

6. The method according to claim 2, wherein said coil assembly includes three pairs of sensor coils, in which one sensor coil in each pair has the same orientation as the other sensor coil in the respective pair, and in which each pair of sensor coils has a different orientation from the other pairs of sensor coils.

7. The method according to claim 6, wherein each sensor coils in a pair is parallel to, but laterally spaced from, the other sensor coil of the pair.

8. The method according to claim 2, wherein said coil assembly includes a cylindrical sensor coil and two pairs of sensor coils positioned orthogonally with respect to the cylindrical sensor coil.

9. The method according to claim 8, wherein said two pairs of sensor coils are curved and in a saddle relation to said cylindrical sensor coil.

10. The method according to claim 8, wherein said two pairs of sensor coils are planar.

11. The method according to claim 1, wherein said processing is effected by an iterative optimization process.

12. The method according to claim 11, wherein said iterative optimization process is effected in real time to determine the instantaneous location and orientation of said object in real time.

13. The method according to claim 1, wherein said object is a medical instrument moving in the body of a person for medical diagnostic or treatment purposes.

14. The method according to claim 13, wherein said medical instrument is selected from the group consisting of:

a catheter for arteriogram, a catheter for venogram, a catheter for angioplasty, a catheter for stent placement, a catheter for percutaneous transmyocardial revascularization, a catheter for cardiac electrophysiology studies, and a catheter for gene therapy.

15. The method according to claim 13, wherein said medical instrument is a tool for minimal invasive surgery.

16. The method according to claim 13, wherein said medical instrument is selected from the group consisting of:

a biopsy gun, a biopsy needle, and an aspiration needle.

17. The method according to claim 13, wherein said medical instrument is selected from the group consisting of:

a rigid endoscope, a flexible endoscope, a ventriculoscope, a colonoscope, a duodenoscope, a gastroscope, a laryngoscope, a tracheoscope, a bronchoscope, a hysteroscope, an urethroscope, a cystoscope, an ureteroscope, and an arthroscope.

18. The method according to claim 1, wherein said object is a motion sensor.

19. Apparatus for determining the instantaneous location and orientation of an object moving through a three-dimensional space within the imaging space of magnetic resonance imaging apparatus during operation of said magnetic resonance imaging apparatus, comprising:

a sensor carried by said object that measures instantaneous magnetic field within said imaging space of magnetic resonance imaging apparatus;

means for measuring the instantaneous values of the magnetic fields which are generated by the activation of the gradient coils of said magnetic resonance imaging apparatus during operation of said magnetic resonance imaging apparatus; and

a processor for processing said measured instantaneous values of said magnetic fields, together with the known magnitude and direction of said magnetic fields of said gradient coils, to compute the instantaneous location and orientation of said object within said space.

20. The apparatus according to claim 19, wherein said sensor comprises a coil assembly including a plurality of sensor coils having axes of known orientation with respect to each other and including components in the three orthogonal planes.

21. The apparatus of claim 20, wherein said measuring means further includes the means for identifying a plurality of activations of the magnetic gradient fields of said magnetic resonance imaging apparatus, wherein said identification provides the timing and the amplitude of activations of a single gradient coil or combined activations of two or three gradient coils of said magnetic resonance imaging apparatus;

and

wherein said processor further comprises;

i. means for calculating voltage vectors by vectorial summation of induced electrical potentials in different sensor coils for each said activation of the gradient fields of the MRI scanner;

ii. means for calculating the magnitudes of all said voltages vectors and the angles between all possible pairs of said voltages vectors;

iii. memory for storing in reference magnetic field maps of each of the three gradient coils of said magnetic resonance imaging apparatus for the imaging space of said magnetic resonance imaging apparatus;

iv. means for estimating the location of the sensor by processing said calculated magnitudes and angles of said voltage vectors together with the known reference magnetic field maps and the known relative orientation of the sensor coils in said coil assembly; and

v. means for estimating the orientation of the sensor by processing said induced electrical potentials generated in said sensor coils together with the known reference magnetic field maps and the known relative orientation of the sensor coils in said coil assembly.

22. The apparatus of claim 20, wherein said measuring means further comprises means for identifying a plurality of activations of the magnetic gradient fields of said magnetic resonance imaging apparatus, wherein said identification provides the timing and the amplitude of activations of a single gradient coil or combined activations of two or three gradient coils of said magnetic resonance imaging apparatus;

and

wherein said processor further comprises;

i. memory for storing the reference magnetic field maps of each of the three gradient coils of said magnetic resonance imaging apparatus for the imaging space of said magnetic resonance imaging apparatus; and

ii. means for simultaneously estimating the location and the orientation of the sensor by processing said induced electrical potentials generated in said sensor coils together with the known reference magnetic field maps and the known relative orientation of the sensor coils in said coil assembly.

23. The apparatus according to claim 20, wherein said coil assembly includes at least three sensor coils oriented orthogonally with respect to each other.

24. The apparatus according to claim 20, wherein said coil assembly includes three pairs of sensor coils, in which one sensor coil in each pair has the same orientation as the other sensor coil in the respective pair, and in which each pair of sensor coils has a different orientation from the other pairs of sensor coils.

25. The apparatus according to claim 20, wherein each sensor coil in a pair is parallel to, but laterally spaced from, the other sensor coil of the pair.

26. The apparatus according to claim 20, wherein said coil assembly includes a cylindrical sensor coil and two pairs of sensor coils positioned orthogonally with respect to the cylindrical sensor coil.

27. The apparatus according to claim 26, wherein said two pairs of sensor coils are curved and in a saddle relation to said cylindrical sensor coil.

28. The apparatus according to claim 26, wherein said two pairs of sensor coils are planar.

29. The apparatus according to claim 19, wherein said processor effects an iterative optimization process.

30. The apparatus according to claim 29, wherein said iterative optimization process is effected in real time to determine the instantaneous location and orientation of said object in real time.

31. The apparatus according to claim 19, wherein said object is a medical instrument moving in the body of a person for medical diagnostic or treatment purposes, and wherein said sensor is adhered to, or integrated into, said medical instrument.

32. The apparatus according to claim 31, wherein said medical instrument is selected from the group consisting of:

a catheter for arteriogram, a catheter for venogram, a catheter for angioplasty, a catheter for stent placement, a catheter for percutaneous transmyocardial revascularization, a catheter for cardiac electrophysiology studies, and a catheter for gene therapy.

33. The apparatus according to claim 31, wherein said medical instrument is a tool for minimal invasive surgery.

34. The apparatus according to claim 31, wherein said medical instrument is selected from the group consisting of:

a biopsy gun, a biopsy needle, and an aspiration needle.

35. The apparatus according to claim 31, wherein said medical instrument is selected from the group consisting of:

a rigid endoscope, a flexible endoscope, a ventriculoscope, a colonoscope, a duodenoscope, a gastroscope, a laryngoscope, a tracheoscope, a bronchoscope, a hysteroscope, an urethroscope, a cystoscope, an ureteroscope, and an arthrocope.

36. The apparatus according to claim 19, wherein said object is a motion sensor.