Systems and methods to locate an implantable stimulator device inside a subject
Implementations provide a method that includes: placing a controller device over a surface region of the patient where the implantable wireless stimulation device has been implanted; configuring the controller device to (i) monitor a return loss representing electrical power reflected from the implantable wireless stimulation device to the controller device; (ii) compute a first path loss metric based on a first monitored return loss when the controller device is place over a first location within the surface region; (iii) compute a second path loss metric based on a second monitored return loss when the controller device is over a second location within the surface region; and (iv) generate a feedback to an operator to indicate whether the second path loss is smaller than the first path loss such that the controller device is placed at a location with more electrical energy non-inductively transferred to the implantable wireless stimulation device.
1. A method comprising:
directing, from a detection device, a radio-frequency signal to a wireless implantable medical device that is coupled to the detection device via non-inductive electrical radiative coupling, the radio-frequency signal being directed to the wireless implantable medical device while an impedance of an antenna of the wireless implantable medical device is actively modified between at least two different levels;
monitoring, at the detection device, a plurality of shifts in power of a plurality of reflections of the radio-frequency signal caused by the modification of the impedance of the antenna of the wireless implantable medical device; and
generating feedback regarding a location of the detection device in relation to a location of the wireless implantable medical device based on the monitored shifts in power.
2. The method of claim 1 , further comprising determining a magnitude of two or more of the plurality of shifts in power, wherein the feedback is generated based on the magnitude.
3. The method of claim 1 , further comprising after generating the feedback, directing a second radio-frequency signal to the wireless implantable medical device for powering the wireless implantable medical device.
4. The method of claim 1 , wherein the active modification of the impedance of the antenna results in the power of the plurality of reflections of the radio-frequency signal periodically varying.
5. The method of claim 1 , wherein the impedance of the antenna is modified by coupling or decoupling a load to the antenna.
6. The method of claim 1 , wherein the feedback is provided by the detection device via audio feedback, visual feedback, or haptic feedback.
7. The method of claim 1 , wherein monitoring the plurality of shifts in power of the plurality of reflections of the radio-frequency signal comprises:
obtaining a plurality of power measurements, and
determining a weighted sum of the plurality of power measurements.
8. A detection device comprising:
an antenna configured to:
transmit a radio-frequency signal to a wireless implantable medical device that is coupled to the detection device via non-inductive electrical radiative coupling, the radio-frequency signal being directed to the wireless implantable medical device while an impedance of an antenna of the wireless implantable medical device is actively modified between at least two different levels, and
obtain a plurality of reflections of the radio-frequency signal;
a sensor coupled to the antenna and configured to measure power of each of the plurality of reflections, the reflections have varying power caused by the modification of the impedance of the antenna of the wireless implantable medical device; and
a processor coupled to the sensor and configured to generate feedback regarding a location of the detection device in relation to a location of the wireless implantable medical device based on the measured varying power of the plurality of reflections.
9. The detection device of claim 8 , wherein the processor is further configured to determine a magnitude between reflections, wherein the feedback is generated based on the magnitude.
10. The detection device of claim 8 , wherein the antenna is further configured to direct a second radio-frequency signal to the wireless implantable medical device for powering the wireless implantable medical device after the feedback is generated.
11. The detection device of claim 8 , wherein the active modification of the impedance of the antenna of the wireless implantable medical device results in the power of the plurality of reflections of the radio-frequency signal periodically varying.
12. The detection device of claim 8 , wherein the impedance of the antenna of the wireless implantable medical device is modified by coupling or decoupling a load to the antenna of the wireless implantable medical device.
13. The detection device of claim 8 , wherein the feedback is provided by the detection device via audio feedback, visual feedback, or haptic feedback.
14. The detection device of claim 8 , wherein the processor is further configured to:
determine a weighted sum of the plurality of power measurements, wherein the feedback is generated based on the weighted sum.
15. A system comprising:
a wireless implantable medical device that includes a first antenna, the wireless implantable medical device configured to actively modify an impedance of the first antenna between at least two different levels;
a detection device comprising:
a second antenna configured to:
transmit a radio-frequency signal to the wireless implantable medical device that is coupled to the detection device via non-inductive electrical radiative coupling, the radio-frequency signal being directed to the wireless implantable medical device while the impedance of the first antenna is actively modified and obtain a plurality of reflections of the radio-frequency signal;
a sensor coupled to the second antenna and configured to measure power of each of the plurality of reflections, the reflections have varying power caused by the modification of the impedance of the first antenna of the wireless implantable medical device; and
a processor coupled to the sensor and configured to generate feedback regarding a location of the detection device in relation to a location of the wireless implantable medical device based on the measured power of the plurality of reflections.
16. The system of claim 15 , wherein the processor is further configured to determine a magnitude between reflections, wherein the feedback is generated based on the magnitude.
17. The system of claim 15 , wherein the second antenna is further configured to direct a second radio-frequency signal to the wireless implantable medical device for powering the wireless implantable medical device after the feedback is generated.
18. The system of claim 15 , wherein the active modification of the impedance of the first antenna results in the power of the plurality of reflections of the radio-frequency signal periodically varying.
19. The system of claim 15 , wherein the impedance of the first antenna is modified by coupling or decoupling a load to the first antenna.
20. The system of claim 15 , wherein the processor is further configured to:
determine a weighted sum of the plurality of power measurements, wherein the feedback is generated based on the weighted sum.