System for excitation leadless miniature marker

• US 6,838,990 B2
• Filed: 01/11/2002
• Issued: 01/04/2005
• Est. Priority Date: 12/20/2001
• Status: Expired due to Term

• Current Assignee: Varian Medical Systems Incorporated (Siemens AG)
• Original Assignee: Calypso Medical Technologies, Inc. (Siemens AG)
• Inventors: Dimmer, Steven C.
• Primary Examiner(s): Mullen, Thomas J
• Application Number:
  US10/044,056
• Publication Number:
  US 20030117269A1
• Time in Patent Office: 1,089 Days
• Field of Search: 340/572.1, 340/572.4, 340/572.5, 340/573.1
• US Class Current: 340/572.4
• CPC Class Codes: A61B 2017/00411 actuated by application of energy from an energy source outside the body
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/3958 emitting a signal
• CPC Class Codes: A61B 2090/3975 active
• 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 90/36 Image-producing devices or illumination devices not otherwise provided for
• CPC Class Codes: A61N 2005/1051 using an active marker
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam

Abstract

A system for generating an excitation field for excitation of a leadless marker assembly. One aspect of the system comprises a source generator assembly having a power supply, an energy storage device, a switching network and a source coil interconnected and configured to deliver a magnetic excitation signal waveform. The power supply is configured to deliver power to energize the energy storage device. The switching network is configured to: direct electrical current through the source coil; alternately switch between a first on position and a second on position; alternately transfer stored energy from the energy storage device to the source coil and to transfer stored energy from the source coil back to the energy storage device; and the source coil being coupled to the switching network to generate an excitation signal.

Claims

1. A system for generating an excitation field for excitation of a leadless marker assembly in or on a body, comprising:

an energy storage device;

a source coil configured to deliver a magnetic excitation signal waveform to the leadless marker assembly; and

a switching network coupled to the energy storage device and the source coil, wherein the switching network is configured to;

(a) direct electrical current through the source coil;

(b) switch between a first on position and a second on position; and

(c) transfer stored energy from the energy storage device to the source coil and transfer energy from the source coil back to the energy storage device.

2. The system of claim 1 wherein the magnetic excitation signal is a generally triangular-shaped bipolar waveform having both a positive and negative polarity.

3. The system of claim 1 wherein the magnetic excitation signal has a non-sinusoidal waveform having both a positive and negative polarity.

4. The system of claim 1 wherein the switching network includes at least two switches configured to switch the source coil voltage between a positive voltage polarity and a negative voltage polarity.

5. The system of claim 1 wherein the switching network includes a first H-bridge configured to switch the source coil voltage between a positive voltage polarity and a negative voltage polarity.

6. The system of claim 1, further comprising a power supply that delivers electrical current to energize the energy storage device, and the switching network is configured so the electrical current cycles between having a positive polarity and having a negative polarity, and the electrical current has the positive polarity and the negative polarity for substantially the same period of time.

7. The system of claim 1 wherein the magnetic excitation signal is a continuous wave excitation signal, and further comprising a plurality of sensors to measure signals from the leadless marker assembly during excitation by the continuous wave excitation signal.

8. The system of claim 1 further comprising a marker signal location system.

9. The system of claim 1 wherein the magnetic excitation signal is a programmable frequency continuous wave magnetic excitation signal.

10. The system of claim 1 wherein the switching network and the source coil are a first switch network and first source coil, respectively, that generate a first source signal in a first spatial orientation, and further comprising a second switch network and a second source coil that generate a second source signal in a second spatial orientation different than the first spatial orientation.

11. A marker system, comprising:

a plurality of leadless resonating marker assemblies implantable in or attachable on a body and configured to generate marker resonant signals at one or more selected resonant frequencies;

a plurality of location sensors external to the body and configured to receive the marker signals; and

a source generator assembly having an energy storage device, first and second switching networks coupled to the energy storage device, and first and second source coils, the first switching network and first source coil being interconnected, and the second switching network and the second source coil being interconnected.

12. The system of claim 11 wherein the first switching network is configured to:

direct electrical current through the first source coil to generate a first magnetic field;

alternately switch between a first on, and a second on position to generate a first magnetic field; and

alternately transfer stored energy from the energy storage device to the first source coil and from the first source coil back to the energy storage device by switching between the first and second on positions.

13. The system of claim 12 wherein the second switching network is configured to:

direct electrical current through the second source coil to generate a second magnetic field;

alternately switch between a first on position, and a second on position to generate a second magnetic field; and

alternately transfer stored energy from the energy storage device to the second source coil and from the second source coil back to the energy storage device by switching between the first and second on positions.

14. The system of claim 11 wherein the source coils are configured to generate excitation signals having spatial orientations different from each other.

15. A marker locating system, comprising:

a resonating, leadless marker assembly being excitable by an excitation source signal to generate a marker signal distinguishable from the excitation source signal;

a source signal generating system having an energy storage device, a switching network and a source coil coupled together;

the switching network being configured to;

alternately switch between a first on position and a second on position to generate a magnetic field;

alternately transfer stored energy from the energy storage device to the source coil and from the source coil back to the energy storage device; and

direct electrical current through the source coil to generate a pulsed excitation source signal; and

a plurality of location sensors remote from the marker assembly and being configured to receive the marker signal.

16. The system of claim 15 wherein the pulsed excitation source signal is a non-sinusoidal waveform having both a positive and negative polarity.

17. A method of exciting a leadless marker assembly in or on a body, comprising:

creating a pulsed excitation source signal by directing a current through a source coil, the current being alternated between a first current flow having a continuously increasing electrical current ramp with time, and a second current flow having a continuously decreasing electrical current ramp with time;

exciting a leadless resonating marker assembly with the pulsed excitation source signal;

generating a marker signal from a resonating marker assembly;

detecting the marker signal; and

communicating a location of the leadless marker assembly in three-dimensional space.

18. The method of claim 17 wherein generating the excitation source signal includes generating a non-sinusoidal waveform having both a positive and negative polarity.

19. The method of claim 17, further including receiving the source signal by a plurality of sensors during detection of the marker signal.

20. A method of energizing a leadless marker assembly in or on a body, comprising:

(a) storing electrical energy in an energy storage device;

(b) directing the energy from the energy storage device through a switching mechanism to alternately transfer stored energy from the energy storage device to a source coil, and discharge energy from the source coil back to the energy storage device, thereby creating a magnetic field; and

(c) energizing the leadless resonating marker assembly with the magnetic field.

21. The method of claim 20 wherein the magnetic field is a non-sinusoidal waveform having both a positive and negative polarity.

22. The method of claim 20 wherein the waveform frequencies of the magnetic field are adjusted to excite multiple markers of unique resonant frequencies.

23. The method of claim 20 wherein the waveform frequencies of the magnetic field are adjusted to excite a first marker substantially at the first marker resonant frequency.

24. A marker locating system, comprising:

a resonating, leadless marker being excitable by an excitation source signal to generate a marker signal distinguishable from the source signal, wherein the marker is enclosed and sealed in a discrete encapsulation member and configured to be permanently implantable in a patient;

a source signal generating system having an energy storage device, a switching network coupled to the energy storage device, and a source coil coupled to the switching network, wherein the switching network is configured to direct electrical current through the source coil to generate the excitation source signal; and

a plurality of location sensors remote from the marker, the sensors being configured to receive the marker signal.