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 to locate an implantable wireless stimulation device implanted inside a patient and configured to receive electrical energy wirelessly from outside the patient via non-inductive coupling, the method comprising:
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 non-inductively couple to the implantable wireless stimulation device such that the controller device:
monitors, by modulating an impedance of a receiving non-inductive antenna in the implantable wireless stimulation device, a return loss representing electrical power reflected from the implantable wireless stimulation device to the controller device;
computes 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;
computes 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
generates 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.
2. The method of claim 1 , further comprising:
configuring the implantable wireless stimulation device in a location mode, wherein the location mode enables: (i) the impedance of the receiving non-inductive antenna to periodically change and (ii) the receiving non-inductive antenna to reflect the electrical power from the implantable wireless stimulation device to the controller device in response to the periodic changes of the impedance of the receiving non-inductive antenna.
3. The method of claim 2 , further comprising:
configuring the controller device to monitor the return loss by monitoring an impedance change at a non-inductive transmitting antenna of the controller device based on the reflected electrical power from the implantable wireless stimulation device.
4. The method of claim 3 , further comprising:
configuring the controller device to communicate with the implantable wireless stimulation device by transmitting the electrical power to the implantable wireless stimulation device using the non-inductive transmitting antenna.
5. The method of claim 4 , further comprising:
configuring the controller device to calculate a voltage standing wave ratio based on a magnitude of a shift between the impedance change at the non-inductive transmitting antenna during (i) the transmitting of the electrical power to the implantable wireless stimulation device and (ii) the monitoring of the reflected electrical power from the implantable wireless stimulation device.
6. The method of claim 5 , further comprising:
configuring the controller device to compute the first path loss metric at the first location or the second path loss metric at the second location based on the calculated voltage standing wave ratio.
7. The method of claim 5 , wherein the magnitude of the shift between the impedance change at the non-inductive transmitting antenna is at least based on a coupling between the non-inductive transmitting antenna of the controller device and the non-inductive receiving antenna of the implantable wireless stimulation device.
8. The method of claim 1 , wherein the second path loss being smaller than the first path loss reflects that the second location of the controller device is closer to the implantable wireless stimulation device than the first location of the controller device.
9. The method of claim 1 , further comprising:
configuring the controller device to generate the feedback by producing an audio signal to the operator indicating when more or less of the electrical energy is non-inductively transferred between the controller device and the implantable wireless stimulation device.
10. The method of claim 9 , wherein the audio signal is generated with increased pitch or amplitude when more of the electrical energy is non-inductively transferred at the second location than at the first location.
11. The method of claim 9 , wherein the audio signal is generated with decreased pitch or amplitude when less of the electrical energy is non-inductively transferred at the first location than at the second location.
12. The method of claim 1 , further comprising:
configuring the controller device to generate the feedback by producing a visual signal to the operator indicating when more or less of the electrical energy is non-inductively transferred between the controller device and the implantable wireless stimulation device.
13. The method of claim 12 , wherein the visual signal is generated with increased blinking frequency or amplitude when more of the electrical energy is non-inductively transferred at the second location than at the first location.
14. The method of claim 12 , wherein the visual signal is generated with decreased blinking frequency or amplitude when less of the electrical energy is non-inductively transferred at the first location than at the second location.
15. The method of claim 1 , further comprising:
configuring the controller device to generate a haptic feedback to the operator indicating when more or less of the electrical energy is non-inductively transferred.
16. The method of claim 15 , wherein the haptic feedback is generated with increased vibration frequency or amplitude when more of the electrical energy is non-inductively transferred at the second location than at the first location.
17. The method of claim 15 , wherein the haptic feedback is generated with decreased vibration frequency or amplitude when less of the electrical energy is non-inductively transferred at the first location than at the second location.
18. The method of claim 1 , further comprising:
configuring the controller device to obtain multiple instances of monitored return loss and perform a weighted sum of the multiple instances of the monitored return loss.
19. The method of claim 18 , further comprising:
configuring the controller device to obtain multiple instances of monitored return loss and implement a finite impulse response (FIR) filter to reduce noise contributions from the multiple instances of the monitored return loss.
20. The method of claim 1 , further comprising:
configuring the controller device to non-inductively couple to the implantable wireless stimulation device and a second implantable wireless simulation device, wherein the implantable wireless stimulation device and the second implantable wireless simulation device are both implanted in the patient.