Methods and Systems for Measuring Tissue Impedance and Monitoring PVD Treatment Using Neuro-Implants with Improved Ultrasound Powering

Abstract

Methods and systems for measuring tissue impedance and monitoring PVD treatment using neuro-implants with improved wireless powering are disclosed. In some embodiments, an implanted device including a wireless energy receiver, a demodulation circuit, and electrodes may be configured to received modulated energy from an energy transmitter. The implanted device may convert the energy to an electrical voltage to be applied to tissue to adjust the tissue's impedance. The tissue impedance may be measured with a computing system by receiving and processing an energy signal emitted/produced in response to the electrical voltage applied by the implanted device. In some embodiments, improved microwave powering schemes may be utilized to power the implanted device. In some embodiments, improved ultrasound powering schemes may be utilized to power the implanted device. For example, energy transfer efficiency from different transmitters may be evaluated to select for energy transmission the transmitter that yields optimal energy transfer efficiency.

What is claimed is: 
     
         1 . A method for adjusting tissue impedance using an implantable device, comprising:
 receiving, by a wireless device implanted in a body, a modulated energy signal comprising a carrier signal and an input signal;   converting, by the implanted device, the received modulated energy signal to an electrical voltage corresponding to the input signal; and   adjusting, by the implanted device, the impedance of tissue in contact with the implanted device by applying the electrical voltage to the tissue in contact with the implanted device.   
     
     
         2 . The method of  claim 1 , wherein the modulated energy signal comprises one of:
 a microwave energy signal; and   an ultrasound energy signal.   
     
     
         3 . The method of  claim 1 , wherein converting comprises demodulating the received modulated energy signal with an envelope detector. 
     
     
         4 . The method of  claim 1 , wherein the input signal is varied to identify a response sensitivity of the tissue to the input signal. 
     
     
         5 . An apparatus for adjusting tissue impedance, comprising:
 a receiver configured to receive a modulated energy signal comprising a carrier signal and an input signal;   a demodulation circuit configured to convert the received modulated energy signal to an electrical voltage corresponding to the input signal; and   at least two electrodes, coupled to the demodulation circuit, configured to apply the electrical voltage to the tissue in contact with the implanted device.   
     
     
         6 . The apparatus of  claim 5 , wherein the receiver comprises one of:
 a wire dipole antenna configured to detect microwave energy; and   a piezoelectric material configured to detect ultrasound energy.   
     
     
         7 . The apparatus of  claim 5 , further comprising:
 a voltage limiter configured to limit the voltage available across the at least two electrodes; and   wherein the demodulation circuit comprises an envelope detector.   
     
     
         8 . A method for measuring and monitoring tissue impedance using an implantable device, comprising:
 transmitting, by a wireless impedance measurement system, a modulated energy signal comprising a carrier signal and an input signal to a wireless device implanted in a body;   receiving, by the wireless impedance measurement system, an energy signal produced by tissue in response to application of a voltage to the tissue by the implanted device, wherein the voltage corresponds to the input signal and the implanted device is in contact with the tissue; and   processing, by the wireless impedance measurement system, the received energy signal to determine an impedance characteristic of the tissue.   
     
     
         9 . The method of  claim 8 , wherein transmitting comprises one of:
 transmitting a modulated microwave energy signal; and   transmitting a modulated ultrasound energy signal.   
     
     
         10 . The method of  claim 8 , wherein receiving comprises at least one of:
 detecting a backscattered microwave energy signal with a microwave receiver; and   detecting current in the tissue with at least one of a biopotential electrode and body surface antenna.   
     
     
         11 . The method of  claim 8 , wherein processing comprises determining a relationship between a change in the input signal and a change in the tissue impedance. 
     
     
         12 . An apparatus for measuring and monitoring tissue impedance, comprising:
 a signal generator configured to transmitting a modulated energy signal comprising a carrier signal and an input signal to a wireless device implanted in a body;   a receiver configured to receive an energy signal produced by tissue in response to application of a voltage to the tissue by the implanted device, wherein the voltage corresponds to the input signal and the implanted device is in contact with the tissue; and   a signal processor configured to process the received energy signal to determine an impedance characteristic of the tissue.   
     
     
         13 . The apparatus of  claim 12 , wherein the signal generator comprises at least one of:
 a microwave signal generator; and   an ultrasound signal generator.   
     
     
         14 . The apparatus of  claim 12 , wherein the receiver comprises at least one of an antenna to detect a backscattered microwave energy signal and at least one of a biopotential electrode and a body surface antenna to detect current in the tissue, and wherein the signal processor is configured to determine a relationship between a change in the input signal and a change in the tissue impedance. 
     
     
         15 . A method for improved ultrasound powering of an implanted device, comprising:
 sequentially, by a processor, actuating each group of ultrasound energy transmitters in an array of groups of ultrasound transmitters, wherein each group of ultrasound transmitters comprises one or more ultrasound transmitters;   monitoring, by the processor, a return signal returned from an implanted device that detected ultrasound energy from an actuated group of ultrasound transmitters;   identifying, by the processor, the return signal with the largest amplitude;   determining, by the processor, which group of ultrasound transmitters of the array of groups of ultrasound transmitters transmitted the ultrasound energy that produced the identified return signal with the largest amplitude; and   selecting, by the processor, the determined group of ultrasound transmitters for emission of ultrasound energy.   
     
     
         16 . The method of  claim 15 , wherein the array of groups of ultrasound transmitters are placed on a body surface over the implant. 
     
     
         17 . The method of  claim 15 , wherein one or more steps of  claim 15  are performed periodically in time. 
     
     
         18 . A system employing improved ultrasound powering of an implanted device, comprising:
 an array of groups of ultrasound energy transmitters, wherein each group of ultrasound energy transmitters comprises one or more ultrasound transmitters;   an implantable device configured to detect ultrasound energy; and   a processor, wherein the processor is configured to execute the steps of:
 sequentially actuating each group of ultrasound energy transmitters in an array of groups of ultrasound transmitters, wherein each group of ultrasound transmitters comprises one or more ultrasound transmitters; 
 monitoring a return signal returned from an implanted device that detected ultrasound energy from an actuated group of ultrasound transmitters; 
 identifying the return signal with the largest amplitude; 
 determining which group of ultrasound transmitters of the array of groups of ultrasound transmitters transmitted the ultrasound energy that produced the identified return signal with the largest amplitude; and 
 selecting the determined group of ultrasound transmitters for emission of ultrasound energy. 
   
     
     
         19 . The system of  claim 18 , wherein the implantable device comprises a piezoelectric material configured to detect ultrasound energy, and wherein the array of groups of ultrasound transmitters are placed on a body surface over the implant. 
     
     
         20 . The system of  claim 18 , wherein the processor is configured to perform one or more of the steps comprising sequentially actuating, monitoring, identifying, determining, and selecting periodically in time.