TECHNIQUES FOR MINIMIZING RADIOFREQUENCY-INDUCED TISSUE HEATING

• US 20080132975A1
• Filed: 11/30/2006
• Published: 06/05/2008
• Est. Priority Date: 11/30/2006
• Status: Active Grant

• Current Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Original Assignee: Biosense Webster Incorporated (Johnson & Johnson)
• Inventors: Aitmann, Andres Claudio, Govari, Assaf
• Granted Patent: US 8,078,286 B2
• Time in Patent Office: Days
• US Class Current: 607/61
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves

Abstract

Methods and systems are provided for wirelessly powering a medical device in a living subject using external radiofrequency energy. A radiofrequency driving unit outside the subject irradiates the medical device. A passive antenna is positioned outside the subject, generally opposing the driving unit to redirect the field generally toward the device. The reradiating element increases uniformity of the electromagnetic field produced by the driving unit, which reduces local tissue heating in the subject and in personnel attending the subject.

Claims

1. A method for wirelessly powering a medical device that is located in a living subject, comprising the steps of:

generating a radiofrequency energy field at a first position outside said subject, said field extending into said subject to energize said device; and

from a second position outside said subject passively reradiating said field generally toward said first position.

2. The method according to claim 1, wherein said second position generally opposes said first position across said subject.

3. The method according to claim 1, wherein said device is a transponder having position sensors that obtain power from said field.

4. The method according to claim 1, wherein said step of reradiating said field is performed by disposing exactly one passive antenna at said second position.

5. The method according to claim 4, wherein said passive antenna comprises a single coil of wire.

6. The method according to claim 4, wherein said field has a frequency of 13.6 MHz and said passive antenna has a capacitance of about 100 pF.

7. The method according to claim 1, wherein said step of reradiating is performed by resonating said field at said second position.

8. The method according to claim 1, further comprising the step of shielding a portion of said subject from said field, said portion excluding said device.

9. An apparatus for wirelessly powering a medical device that is located in a living subject that is energized by external radiofrequency energy, comprising:

a radiofrequency driving unit disposed at a first position outside said subject for generating a radiofrequency energy field, said field extending into said subject to irradiate said device; and

a reradiating element disposed in said field at a second position outside said subject to redirect said field generally toward said device.

10. The apparatus according to claim 9, wherein said second position generally opposes said first position across said subject.

11. The apparatus according to claim 9, wherein said device is a transponder having position sensors that derive power from said field.

12. The apparatus according to claim 9, wherein said reradiating element is exactly one passive antenna.

13. The apparatus according to claim 12, wherein said passive antenna comprises a single coil of wire.

14. The apparatus according to claim 12, wherein said field has a frequency of 13.6 MHz and said passive antenna has a capacitance of about 100 pF.

15. The apparatus according to claim 12, wherein said passive antenna is resonant at a frequency of said field.

16. The apparatus according to claim 9, further comprising a shield that reduces exposure of a portion of said subject from radiant energy of said field.

17. A method for wirelessly powering a medical device that is located in a living subject, comprising the steps of:

generating a radiofrequency energy field outside said subject, said field extending into said subject to energize said device; and

shielding a portion of said subject from said field, said portion excluding said device.

18. The method according to claim 17, wherein said device is a transponder having position sensors that obtain power from said field.

19. An apparatus for wirelessly powering a medical device that is located in a living subject that is energized by external radiofrequency energy, comprising:

a radiofrequency driving unit disposed at a first position outside said subject for generating a radiofrequency energy field, said field extending into said subject to irradiate said device; and

a shield that reduces exposure of a portion of said subject from radiant energy of said field.

20. The apparatus according to claim 19, wherein said device is a transponder having position sensors that obtain power from said field.