Implanted sensor processing system and method for processing implanted sensor output

Abstract

A quantitative measurement system includes an external unit and an internal unit and is provided for obtaining quantitative analyte measurements, such as within the body. In one example application, the internal unit would be implanted either subcutaneously or otherwise within the body of a subject. The internal unit contains optoelectronics circuitry, a component of which may be comprised of a fluorescence sensing device. The optoelectronics circuitry obtains quantitative measurement information and modifies a load as a function of the obtained information. The load in turn varies the amount of current through coil, which is coupled to a coil of the external unit. A demodulator detects the current variations induced in the external coil by the internal coil coupled thereto, and applies the detected signal to processing circuitry, such as a pulse counter and computer interface, for processing the signal into computer-readable format for inputting to a computer.

What is claimed is: 
     
         1 . A system comprising:
 (a) an internal unit including (a 1 ) a first coil, (a 2 ) a load, and (a 3 ) sensor circuitry configured to obtain quantitative measurement information and modify the load as a function of the obtained quantitative measurement information; and   (b) an external unit including (b 1 ) a second coil configured to inductively couple with the first coil, (b 2 ) an oscillator configured to provide an RF signal to the second coil such that the second coil provides electromagnetic energy to the first coil, (b 3 ) a demodulator configured to detect current variations induced in the second coil by the first coil as a result of the modifications to the load, and (b 4 ) processing circuitry configured to process the detected current variations into a computer-readable format;   wherein the electromagnetic energy provides operating power for the sensor circuitry of the internal unit, and the sensor circuitry is configured to determine whether the operating power is greater than a threshold and, if the operating power is greater than the threshold, obtain the quantitative measurement information and modify the load as a function of the obtained quantitative measurement information.   
     
     
         2 . The system of  claim 1 , wherein the sensor circuitry comprises a light emitting diode (LED). 
     
     
         3 . The system of  claim 2 , wherein the threshold is a threshold voltage of the LED plus a feedback voltage. 
     
     
         4 . The system of  claim 1 , wherein the sensor circuitry further comprises a radiation source and a photosensitive element, and the internal unit further comprises a sensor body, a matrix layer on the exterior surface of the sensor body, and indicator molecules distributed throughout the matrix layer. 
     
     
         5 . The system of  claim 1 , wherein the external unit further comprises a computer, and the processed current variations are input into the computer. 
     
     
         6 . An internal unit comprising:
 a coil configured to inductively couple with a coil of an external unit and to receive electromagnetic energy from the coil of the external unit;   a load; and   sensor circuitry configured to obtain quantitative measurement information and modify the load as a function of the obtained quantitative measurement information;   wherein the electromagnetic energy provides operating power for the sensor circuitry, and the sensor circuitry is configured to determine whether the operating power is greater than a threshold and, if the operating power is greater than the threshold, obtain the quantitative measurement information and modify the load as a function of the obtained quantitative measurement information.   
     
     
         7 . The internal unit of  claim 6 , wherein the sensor circuitry comprises a light emitting diode (LED). 
     
     
         8 . The internal unit of  claim 7 , wherein the threshold is a threshold voltage of the LED plus a feedback voltage. 
     
     
         9 . The internal unit of  claim 6 , wherein the sensor circuitry further comprises a radiation source and a photosensitive element, and the internal unit further comprises a sensor body, a matrix layer on the exterior surface of the sensor body, and indicator molecules distributed throughout the matrix layer. 
     
     
         10 . A method comprising:
 using a coil of an internal unit to receive electromagnetic energy from a coil of an external unit, wherein the coils of the internal and external units are inductively coupled, and the electromagnetic energy provides operating power for the sensor circuitry of the internal unit;   using sensor circuitry determine whether the operating power is greater than a threshold; and   if the sensor circuitry determines the operating power to be greater than the threshold, using the sensor circuitry to obtain the quantitative measurement information and modify the load as a function of the obtained quantitative measurement information.   
     
     
         11 . The method of  claim 10 , further comprising:
 using an oscillator of the external unit to provide an RF signal to the coil external unit such that the coil of the external unit provides the electromagnetic energy to the coil of the internal unit;   using a demodulator to detect current variations induced in the coil of the external unit by the coil of the internal unit as a result of the modifications to the load.   
     
     
         12 . The method of  claim 10 , wherein the threshold is a threshold voltage of a light emitting diode (LED) plus a feedback voltage. 
     
     
         13 . The method of  claim 10 , wherein obtaining the quantitative measurement information comprises:
 using radiation source to emit radiation to indicator molecules distributed throughout a matrix layer on an exterior surface of a sensor housing; and   using a photosensitive element to generate a signal indicative of a level of fluorescence of the indicator molecules.