Transponders and sensors for implantable medical devices and methods of use thereof

1. A method for broadcasting a signal using a portable reader, the method comprising:

broadcasting, in a range of an antenna of a medical device, radio frequency signals across a sweep of frequencies using the reader;

evaluating a signal strength of each return signal received by the reader from the medical device;

determining a frequency of a broadcasted radio frequency signal corresponding to the received return signal having the greatest signal strength; and

broadcasting a radio frequency signal at the determined frequency using the reader;

wherein the medical device does not include a ferromagnetic material.

2. The method of claim 1 , further comprising:

receiving, at a plurality of antennas of the reader, the return signals having a plurality of signal strengths.

3. The method of claim 1 , further comprising:

receiving a plurality of return signals from the medical device, the plurality of return signals having a plurality of signal strengths;

amplifying one or more received return signals having signal strengths below a threshold; and

converting each amplified signal to a digital value.

4. The method of claim 1 , wherein the step of evaluating the signal strength of each received return signal comprises converting the received return signal to a digital value.

5. The method of claim 1 , wherein the sweep of frequencies includes frequencies within a range of from about 80 kHz to about 400 kHz.

6. The method of claim 1 , wherein the range of the antenna of the medical device is from about one inch to about five feet.

7. A system for broadcasting a signal, the system comprising:

a reader comprising:

a microcontroller; and

at least one antenna;

wherein the microcontroller is programmed with instructions for performing steps of a method, the method comprising:

broadcasting, in the range of an antenna of a medical device, radio frequency signals across a sweep of frequencies, wherein the medical device does not include a ferromagnetic material;

evaluating a signal strength of each return signal received from the medical device;

determining a frequency of a broadcasted radio frequency signal corresponding to the received return signal having the greatest signal strength; and

broadcasting a radio frequency signal at the determined frequency.

8. The system of claim 7 , wherein the at least one antenna of the reader comprises a plurality of antennas, and the instructions further comprise:

receiving, at the plurality of antennas, a plurality of return signals having a plurality of signal strengths.

9. The system of claim 8 , wherein the reader further comprises:

a logarithmic amplifier; and

an analog-to-digital converter; and

wherein the instructions further comprise:

receiving, at the plurality of antennas, a plurality of return signals having a plurality of signal strengths;

amplifying, using the logarithmic amplifier, one or more received return signals having signal strengths below a threshold; and

converting each received and amplified signal signals to a digital value using the analog-to-digital converter.

10. The system of claim 7 , wherein the step of evaluating the signal strength of each return signal comprises converting the received return signal to a digital value.

11. The system of claim 7 , wherein the sweep of frequencies includes frequencies within a range of from about 80 kHz to about 400 kHz.

12. The system of claim 7 , further comprising the medical device, wherein the range of the antenna of the medical device is from about one inch to about five feet.

13. The system of claim 7 , wherein the reader further comprises a clock generator and a signal driver for performing the step of broadcasting the radio frequency signals across the sweep of frequencies.

14. The system of claim 7 , wherein the step of evaluating the strength of received return signals from the medical device comprises:

instructing at least one analog-to-digital converter to convert received return signals into digital values; and

comparing the digital values.

15. A method for broadcasting a signal using a portable reader, the method comprising:

broadcasting, in a range of an antenna of a medical device, radio frequency signals across a sweep of frequencies using a signal driver and an antenna of the reader;

receiving, using the antenna of the reader, return signals from the medical device;

amplifying, using a logarithmic amplifier of the reader, return signals from the medical device which are below a threshold;

converting, using an analog-to-digital converter of the reader, received return signals and amplified signals into digital values;

evaluating, using a microcontroller of the reader, the digital values to determine the strongest return signal or signals;

determining a frequency of a broadcasted radio frequency signal corresponding to the strongest received return signal or signals from the medical device; and

broadcasting, using the signal driver and antenna of the reader, a radio frequency signal at the determined frequency.

16. The method of claim 15 , further comprising receiving, at a pickup antenna of the reader, return signals from the medical device which are below the threshold.

17. The method of claim 15 , wherein the step of broadcasting, in the range of the antenna of the medical device, the radio frequency signals across the sweep of frequencies further comprises using a clock generator of the reader to determine a timing of the sweep of frequencies.

18. The method of claim 15 , further comprising displaying, on a light-emitting diode display of the reader, the determined frequency.

19. The method of claim 15 , wherein the sweep of frequencies includes frequencies within a range of from about 80 kHz to about 400 kHz.

20. The method of claim 15 , wherein the medical device does not include a ferromagnetic material, and the range of the antenna of the medical device is less than five feet.

21. The method of claim 15 , wherein the medical device is a tissue expander comprising a port, and the port includes the antenna of the tissue expander.

22. The method of claim 21 , further comprising displaying output from the microcontroller by illuminating lights of the reader, the output from the microcontroller including data indicating a location of the port.

23. The method of claim 21 , further comprising:

receiving, by the reader, information stored in an integrated circuit chip of the tissue expander, the information including a serial number of the tissue expander, a manufacturer of the tissue expander, a date of manufacture of the tissue expander, a lot number of the tissue expander, or a combination thereof; and

displaying, on a display of the reader, the information.

24. The method of claim 21 , wherein the tissue expander includes a sensor and the method further comprises:

receiving, by the reader, data measured by the sensor; and

displaying, on a display of the reader, the data.

25. A reader for locating a port of a tissue expander, the port including an antenna, wherein the reader comprises:

a microcontroller; and

at least one antenna;

wherein the microcontroller is programmed with instructions for performing steps of a method, the method comprising:

broadcasting, in the range of the antenna of the port, signals across a sweep of frequencies;

evaluating a signal strength of each return signal received from the port; and

determining a proximity of the reader to the port based on the signal strength of the return signals.

26. The reader of claim 25 , wherein the reader comprises a display configured to output data indicating the proximity of the reader to the port or a location of a center of the port.

27. The reader of claim 26 , wherein the display includes lights or a graphic display.

28. The reader of claim 25 , wherein the reader is wireless and portable.