Resonator with adjustable capacitance for medical device

• US 7,423,496 B2
• Filed: 11/09/2005
• Issued: 09/09/2008
• Est. Priority Date: 11/09/2005
• Status: Expired due to Fees

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Inventors: Scheuermann, Torsten
• Primary Examiner(s): Pascal; Robert J.
• Assistant Examiner(s): JOHNSON, RYAN
• Application Number:
  US11/270,417
• Publication Number:
  US 20070106151A1
• Time in Patent Office: 1,035 Days
• Field of Search: 128/897, 128/898, 128/899, 600/410, 600/420, 600/421, 600/422, 600/423, 600/424, 600/429, 600/431, 600/435, 324/307, 324/309, 324/318, 324/322, 331/167, 331/177.V, 331/187, 331/18
• US Class Current: 331/177.00V
• CPC Class Codes: G01R 33/286 involving passive visualization of interventional instruments, i.e. making the instrument visible as part of the normal MR process
• CPC Class Codes: G01R 33/3628 Tuning/matching of the transmit/receive coil

Abstract

Systems and methods for a resonator with an adjustable capacitance for a medical device. In one embodiment, a resonator system includes a resonator device with an LC resonator circuit that has an adjustable capacitance, an inductor coil in series with the adjustable capacitance, and an adjustable capacitance control that can control the adjustable capacitance to obtain different particular capacitance values. This embodiment also includes a medical device, positioned with the resonator device, so that at least a portion of the inductor coil surrounds a space that is surrounded by at least a portion of the medical device.

Claims

1. A resonator system for detecting a deliverable device in a body, comprising:

a resonator device with an LC resonator circuit, including;

an inductor coil

a plurality of individually switched parallel capacitors in series with the inductor coil;

a varactor in parallel with the plurality of individually switched parallel capacitors;

a processor coupled to the plurality of individually switched parallel capacitors;

a magnetic flux sensor coupled to the processor, where the magnetic flux sensor can sense a flux of a magnetic field and transmit a signal that represents the flux to the processor that changes the capacitance of the LC resonator circuit by switching a number of the plurality of individually switched parallel capacitors based on the signal;

a power source electrically connected to the processor; and

a deliverable device, positioned with the resonator device, so that at least a portion of the inductor coil surrounds a space that is surrounded by at least a portion of the deliverable device.

2. The resonator system of claim 1, where:

the deliverable device is an implantable medical device; and

the power source can generate electrical power from a field for use by the processor, where the field is selected from the group including;

an electro-magnetic field; and

an alternating magnetic field.

3. The resonator system of claim 2, wherein the resonator device includes a current sensor that can sense an electrical current flow through a path of the LC resonator circuit.

4. The resonator system of claim 2, where the resonator device includes a voltage sensor that can sense an electrical voltage differential across the plurality of individually switched parallel capacitors.

5. The resonator system of claim 2, wherein:

at least a portion of the inductor coil has an adjustable radius; and

at least a portion of the inductor coil surrounds at least a portion of a passageway of the implantable medical device.

6. The resonator system of claim 5, wherein the implantable medical device is a permanently implantable medical device selected from the group including:

a balloon expandable stent;

a self-expandable stent;

a graft;

a shunt; and

a vena cava filter.

7. The resonator system of claim 5, wherein the implantable medical device is a temporarily implantable medical device selected from the group including:

a guiding catheter;

a guiding wire;

a catheter for stent delivery; and

a catheter for dilation without a stent.

8. The resonator system of claim 1, wherein:

the implantable medical device is a temporarily implantable medical device; and

the resonator device is inside the temporarily implantable medical device.

9. A resonator system, comprising:

a resonator circuit that includes an inductor coil in series with a plurality of individually switched parallel capacitors;

a varactor that is;

parallel to the plurality of individually switched parallel capacitors; and

connectable to the resonator circuit

a processor coupled to the resonator circuit,

a power source electrically connected to the processor;

a magnetic flux sensor coupled to the processor, where the magnetic flux sensor can sense a flux from a magnetic field and transmit a signal based on the flux to the processor that automatically adjusts the capacitance to a resonant capacitance by switching a number of the plurality of individually switched parallel capacitors; and

an implantable medical device, wherein at least a portion of the implantable medical device is surrounded by the inductor coil.

10. The resonator system of claim 9, including a selector that manually adjusts the capacitance, at least in part, by changing a number of the plurality of individually switched parallel capacitors that are connected to the resonator circuit.

11. The resonator system of claim 9, where:

the resonator circuit includes capacitors that are;

in parallel; and

connectable to the resonator circuit; and

the processor automatically adjusts the capacitance, at least in part, by changing a number of the plurality of individually switched parallel capacitors that are connected to the resonator circuit.

12. The resonator system of claim 11, where:

the processor automatically adjusts the capacitance, at least in part, by adjusting a capacitance of the varactor.

13. The resonator system of claim 9, including a sensor:

connected to a the processor; and

selected from the group including;

a voltage sensor connected across the plurality of individually switched parallel capacitors; and

a current sensor connected in line with a path of the resonator circuit.

14. The resonator system of claim 9, wherein the power source is selected from the group including:

the inductor coil;

a coil;

a battery;

a capacitor; and

a secondary resonator circuit.

15. A method comprising:

providing a resonator circuit with;

an inductor coil in series with a plurality of individually switched parallel capacitors;

a processor which is coupled to the resonator circuit to change a capacitance of the resonator circuit;

a power source connected to the processor; and

a magnetic flux sensor coupled to the processor, where the magnetic flux sensor can sense a flux of a magnetic field and transmit a signal that represents the flux to the processor that changes the capacitance of the LC resonator circuit by switching a number of the plurality of individually switched parallel capacitors based on the signal, to a deliverable device, deliverable in a lumen of a body, so that at least a portion of the inductor coil surrounds at least a portion of the deliverable device;

determining a resonant capacitance at which the resonator circuit will resonate in a particular magnetic field by;

sensing a flux of the particular magnetic field; and

calculating the resonant capacitance of the resonator circuit, based on the sensed flux and a known inductance of the resonator circuit; and

adjusting the capacitance of the resonator circuit to the resonant capacitance in the lumen.

16. A method comprising:

fabricating a resonator device that includes;

a resonator circuit with an inductor coil in series with a plurality of individually switched parallel capacitors;

a varactor that is;

parallel to the plurality of individually switched parallel capacitors; and

connectable to the resonator circuit;

a processor that can automatically adjust a capacitance to a resonant capacitance in response to magnetic fields of different strength;

a power source connected to the processor;

a magnetic flux sensor coupled to the processor, where the magnetic flux sensor can sense a flux of a magnetic field and transmit a signal that represents the flux to the processor that changes the capacitance of the LC resonator circuit by switching a number of the plurality of individually switched parallel capacitors based on the signal; and

connecting the resonator device to a medical device so that at least a portion of the inductor coil surrounds at least a portion of the medical device.

17. The method of claim 16 wherein:

fabricating the resonator device includes fabricating an inductor coil out of a flexible conductive material so that the coil has an adjustable radius; and

connecting the resonator includes securing the inductor coil around a stent so that the adjustable radius can increase as the stent expands.

18. The method of claim 16, wherein connecting the resonator includes securing the resonator device in a distal end of a catheter.

19. The method of claim 16, wherein the processor automatically adjusts the capacitance to a resonant capacitance by:

adjusting the capacitance to a known capacitance;

calculating an inductance of the resonator circuit, based on the known capacitance and the sensed flux of the magnetic field; and

calculating the resonant capacitance of the resonator circuit, based on the sensed flux and the calculated inductance of the resonator circuit.

20. The method of claim 16, wherein the processor automatically adjusts the capacitance to a resonant capacitance by:

adjusting the capacitance to a particular capacitance;

sensing a voltage across the capacitance; and

repeating the adjusting and the sensing to determine a particular capacitance at which the voltage across the capacitance is a maximum voltage that can be obtained by the capacitance in the particular magnetic field.

21. The method of claim 16, wherein the processor automatically adjusts the capacitance to a resonant capacitance by:

adjusting the capacitance to a particular capacitance;

sensing a current through the resonator circuit at the particular capacitance; and

repeating the adjusting and the sensing to determine a particular capacitance at which the current through the resonator circuit is a maximum current that can be obtained by the capacitance in the particular magnetic field.