Wireless Magnetic Tracking

• US 20130166002A1
• Filed: 12/12/2012
• Published: 06/27/2013
• Est. Priority Date: 12/12/2011
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Ziaie, Babak, Jung, Byunghoo
• Granted Patent: US 9,474,909 B2
• Time in Patent Office: Days
• US Class Current: 607/100
• CPC Class Codes: A61B 2090/3958 emitting a signal
• CPC Class Codes: A61N 2005/1051 using an active marker markers in general A61B90/39
• CPC Class Codes: A61N 5/00 Radiation therapy ultrasound therapy A61N7/00; devices or apparatus applicable to both therapy and diagnosis A61B6/00
• CPC Class Codes: A61N 5/1049 for verifying the position of the patient with respect to the radiation beam

Abstract

Illustrative embodiments of systems and methods for wireless magnetic tracking are disclosed. In one illustrative embodiment, a wireless magnetic tracking system may include a plurality of transmitting coils each configured to generate a magnetic field when energized, an active transponder configured to simultaneously (i) obtain measurements of the magnetic field when one of the plurality of transmitting coils is energized and (ii) transmit a wireless signal containing data concerning the measurements, and a computing device configured to (i) cause each of the plurality of transmitting coils to be sequentially energized, (ii) receive the data concerning the measurements, and (iii) determine a position and an orientation of the active transponder relative to the plurality of transmitting coils in response to the data concerning the measurements.

Claims

1. A wireless magnetic tracking system comprising:

a plurality of transmitting coils each configured to generate a magnetic field when energized;

an active transponder configured to simultaneously (i) obtain measurements of the magnetic field when one of the plurality of transmitting coils is energized and (ii) transmit a wireless signal containing data concerning the measurements; and

a computing device configured to (i) cause each of the plurality of transmitting coils to be sequentially energized, (ii) receive the data concerning the measurements, and (iii) determine a position and an orientation of the active transponder relative to the plurality of transmitting coils in response to the data concerning the measurements.

2. The wireless magnetic tracking system of claim 1, wherein the active transponder is adapted to be implantable in a patient'"'"'s tissue.

3. The wireless magnetic tracking system of claim 1, wherein the active transponder comprises at least two magneto-resistive sensors, each of the at least two magneto-resistive sensors being configured to measure a different component of the magnetic field.

4. The wireless magnetic tracking system of claim 3, wherein the at least two magneto-resistive sensors comprise three magneto-resistive sensors, the three magneto-resistive sensors being configured to measure components of the magnetic field that are normal to one another.

5. The wireless magnetic tracking system of claim 1, further comprising a coil driver circuit configured to selectively supply an excitation signal to each of the plurality of transmitting coils, wherein the computing device is configured to control the coil driver circuit.

6. The wireless magnetic tracking system of claim 5, wherein the computing device is configured to control the coil driver circuit such that each of the plurality of transmitting coils is energized over an integer multiple of a period of the excitation signal.

7. The wireless magnetic tracking system of claim 5, wherein the computing device is configured to control the coil driver circuit such that each of the plurality of transmitting coils is grounded when not being energized.

8. The wireless magnetic tracking system of claim 5, wherein the active transponder comprises a wireless transmitter with a carrier radio frequency that is greater than a frequency of the excitation signal.

9. The wireless magnetic tracking system of claim 5, wherein the excitation signal is a pulsed direct-current excitation signal.

10. The wireless magnetic tracking system of claim 5, further comprising a receiver configured to (i) receive the wireless signal from the active transponder and (ii) provide the data concerning the measurements to the computing device.

11. The wireless magnetic tracking system of claim 10, wherein the receiver comprises a plurality of antennas configured to simultaneously receive the wireless signal from the active transponder and a combiner configured to sum the wireless signals received by the plurality of antennas.

12. The wireless magnetic tracking system of claim 10, wherein the receiver is configured to integrate a multiplication product of the wireless signal received from the active transponder and the excitation signal supplied by the coil driver circuit.

13. The wireless magnetic tracking system of claim 1, further comprising an additional active transponder, the additional active transponder being configured to simultaneously (i) obtain additional measurements of the magnetic field when one of the plurality of transmitting coils is energized and (ii) transmit an additional wireless signal containing data concerning the additional measurements, wherein the wireless signal and the additional wireless signal have different carrier radio frequencies.

14. The wireless magnetic tracking system of claim 1, wherein the computing device is configured to determine the position and the orientation of the active transponder relative to the plurality of transmitting coils in six degrees of freedom.

15. The wireless magnetic tracking system of claim 1, wherein the computing device is configured to determine the position and the orientation of the active transponder relative to the plurality of transmitting coils using an iterative method with a previously determined position and orientation of the active transponder as an initial guess.

16. The wireless magnetic tracking system of claim 1, wherein the computing device is further configured to re-determine the position and the orientation of the active transponder relative to the plurality of transmitting coils each time another one of the plurality of transmitting coils is energized.

17. The wireless magnetic tracking system of claim 1, wherein the computing device is configured to determine the position and the orientation of the active transponder relative to the plurality of transmitting coils with an error of less than 5 millimeters.

18. The wireless magnetic tracking system according to any of the preceding claims, wherein the plurality of transmitting coils consists of two transmitting coils.

19. An active transponder for wireless magnetic tracking comprising:

a plurality of magneto-resistive sensors, each of the plurality of magneto-resistive sensors being configured to measure a different component of a magnetic field;

an analog-to-digital converter (ADC) configured to convert an analog voltage signal output by one of the plurality of magneto-resistive sensors into a digital signal;

a transmitter configured to generate an output signal by modulating a carrier signal with the digital signal; and

an antenna configured to broadcast the output signal.

20. The active transponder of claim 19, wherein the plurality of magneto-resistive sensors comprises three magneto-resistive sensors, the three magneto-resistive sensors being configured to measure components of the magnetic field that are normal to one another.

21. The active transponder of claim 19, wherein each of the plurality of magneto-resistive sensors comprises an enable switch configured to selectively connect the magneto-resistive sensor to a supply voltage.

22. The active transponder of claim 21, further comprising a controller configured to sequentially activate the enable switch of each of the plurality of magneto-resistive sensors.

23. The active transponder of claim 22, further comprising a sensor front-end circuit configured to amplify the analog voltage signal output by one of the plurality of magneto-resistive sensors before the analog voltage signal is supplied to the ADC.

24. The active transponder of claim 23, wherein the transmitter, the ADC, the controller, and the sensor front-end circuit are implemented on an integrated circuit chip and have a combined chip area of less than four square millimeters.

25. The active transponder of claim 23, wherein the analog voltage signal supplied to the ADC is linearly related to the magnetic field when the magnetic field is between 0 gauss and 1.5 gauss.

26. The active transponder of claim 19, wherein the ADC is a successive approximation register ADC.

27. The active transponder of claim 19, wherein the transmitter comprises an integer-N phase-locked loop (PLL) configured to generate the carrier signal.

28. The active transponder of claim 27, wherein the integer-N PLL comprises a phase frequency detector, a charge pump, a voltage-controlled oscillator, and a frequency divider.

29. The active transponder of claim 28, wherein the charge pump comprises dynamic threshold transistors, a body and a gate of each of the dynamic threshold transistors being electrically coupled to one another.

30. The active transponder of claim 28, wherein the frequency divider comprises a pulse-swallow counter with a dual-modulus prescaler.

31. The active transponder of claim 19, further comprising a dosimeter configured to measure an amount of radiation delivered to the active transponder and supply a measurement signal indicating the amount of radiation to the ADC.

32. The active transponder of claim 19, further comprising a power supply configured to wirelessly receive energy at a frequency between 1 MHz and 10 MHz.

33. The active transponder of claim 19, wherein the transmitter, the ADC, and the plurality of magneto-resistive sensors each use a supply voltage of about 500 millivolts.

34. The active transponder according to any one of claims 19-33, wherein the active transponder has a total power consumption that is less than 1 milliwatt.