Techniques for minimizing radiofrequency-induced tissue heating

#1. Field of the Invention

#This invention relates to remotely powering wireless devices. More particularly, this invention relates to minimizing heating of body tissues during exposure to an electromagnetic field while powering a wireless medical device.

#2. Description of the Related Art

#For a better understanding of the present invention, reference is made to the detailed description of the invention, by way of example, which is to be read in conjunction with the following drawings, wherein like elements are given like reference numerals, and wherein:

#FIG. 1 is a pictorial illustration of a system for wirelessly energizing a medical device in accordance with a disclosed embodiment of the invention;

#FIG. 2 shows exemplary field strength curves produced by the system shown in FIG. 1, in accordance with a disclosed embodiment of the invention;

#In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent to one skilled in the art, however, that the present invention may be practiced without these specific details. In other instances, well-known circuits, and control logic have not been shown in detail in order not to obscure the present invention unnecessarily.

#Turning now to the drawings, reference is initially made to FIG. 1, which is a pictorial illustration of a system 10 for wirelessly energizing a medical device in accordance with a disclosed embodiment of the invention. The system 10 comprises a power-driving unit 12 disposed external to a subject 14 and an implantable or insertable wireless medical device 16. The medical device 16 is typically incorporated in a catheter (not shown) or implanted in the subject 14. The medical device 16 comprises at least one power coil 18, for receiving energy transmitted by the power-driving unit 12. For applications in which the medical device 16 functions as a wireless location transponder, the system 10 typically further comprises one or more position signal generators 20, which generate position signals received by at least one position sensing coil 22 incorporated in the medical device 16. A control unit 24 controls and energizes the position signal generators 20 and the power driving unit 12.

#A transponder, which is suitable for use as the medical device 16, and which transmits digital high-frequency signals is described in U.S. Patent Application Publication No. 2005/0099290 entitled, “Digital Wireless Position Sensor,” whose disclosure is herein incorporated by reference.