Electromagnetic system and method

Abstract

Differences of electromagnetic (EM) properties between healthy and cancerous tissues allow detection of abnormal conditions occurring in a tissue of an animal, for example, intra-operative cancer detection. By using a time-varying EM field, electrical eddy currents are generated in the tissue sample, and assessed using phase-sensitive detection. In some aspects, a change in phase shift between the voltage in a receiver coil and the voltage in a driver coil provide a direct and immediate indication of differences in EM properties of specimens.

What is claimed is: 
     
         1 . A system for detecting differences in tissue property in a tissue of an animal or human, the system adapted to connect to an alternating current or power supply, the system comprising:
 a probe comprising a driver coil and a receiver coil and wherein the driver coil is adapted to receive a non-sinusoidal, asymmetric signal from the alternating current or power supply for inducing eddy currents in the tissue when the probe is placed adjacent to the tissue;   a measurement circuit, operably connected to the receiver coil and configured to measure a phase shift between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil when the driver and receiver coils are positioned adjacent to the tissue and wherein the voltage or current produced in the probe has at least a first and second duty cycle each comprised of multiple peaks and wherein the driver coil and receiver coil has inductances and capacitances so the last peak of the voltage or current produced in the first duty cycle coincides on a sloping side of the first peak of the second duty cycle; and   a hardware processing system operably connected to the measurement circuit, the hardware processing system programmed with one or more software routines executing on the hardware processing system to compare the phase shift between the voltage or current on the driver coil and the voltage or current on the receiver coil to detect differences in tissue property.   
     
     
         2 . A system according to  claim 1  wherein the measurement circuit is a lock-in amplifier configured to provide a DC output voltage indicative of the detected phase shift between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil. 
     
     
         3 . A system according to  claim 1 , further comprising:
 a means for raster scanning the probe at various positions across the tissue; and   wherein the measurement circuit provides the measured phase shift between the input voltage or current imposed on the driver coil and the alternating voltage or current induced in the receiver coil at positions across the tissue in order to create an image.   
     
     
         4 . A system according to  claim 1 , wherein the measurement circuit is configured to measure a change in amplitude between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil, and
 wherein the hardware processing system is programmed with one or more software routines executing on the hardware processing system to compare differences in amplitude between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil to detect differences in tissue property.   
     
     
         5 . A system according to  claim 1 , further comprising a capacitor electrically connected to the receiver coil and wherein the system is configured to produce a periodic detector coil voltage trace comprising several peaks. 
     
     
         6 . A system according to  claim 1 , wherein the alternating current or power supply connected to the driver coil is configured to provide a sawtooth signal to the driver coil; and wherein the system is further comprised of a capacitor added in parallel to the receiver coil. 
     
     
         7 . A system according to  claim 1 , wherein the non-sinusoidal, asymmetric signal has a frequency between 1 Hz and 1 MHz. 
     
     
         8 . A system for detecting differences in tissue property in a tissue of an animal or human, the system adapted to connect to an alternating current or power supply, the system comprising:
 a probe comprising a driver coil and a receiver coil and wherein the driver coil is adapted to receive a non-sinusoidal, asymmetric signal from the alternating current or power supply for inducing eddy currents in the tissue when the probe is placed adjacent to the tissue;   a measurement circuit, operably connected to the receiver coil and configured to measure a phase shift between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil when the driver and receiver coils are positioned adjacent to the tissue; and   a hardware processing system operably connected to the measurement circuit, the hardware processing system programmed with one or more software routines executing on the hardware processing system to compare the phase shift between the voltage or current on the driver coil and the voltage or current on the receiver coil to detect differences in tissue property.   
     
     
         9 . A system according to  claim 8 , wherein the measurement circuit is a lock-in amplifier configured to provide a DC output voltage indicative of the detected phase shift between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil. 
     
     
         10 . A system according to  claim 8 , further comprising:
 a means for raster scanning the probe at various positions across the tissue; and   wherein the measurement circuit provides the measured phase shift between the input voltage or current imposed on the driver coil and the alternating voltage or current induced in the receiver coil at positions across the tissue in order to create an image.   
     
     
         11 . A system according to  claim 8 , wherein the voltage or current produced in the probe has at least a first and second duty cycle each comprised of multiple peaks and wherein the driver coil and receiver coil has inductances and capacitances so the last peak of the voltage or current produced in the first duty cycle coincides on a sloping side of the first peak of the second duty cycle. 
     
     
         12 . A system according to  claim 8 , further comprising:
 a capacitor electrically connected to the probe and wherein the system is configured to produce a periodic receiver coil voltage trace comprising several peaks.   
     
     
         13 . A system according to  claim 8 , wherein the alternating current or power supply connected to the driver coil is configured to provide a sawtooth signal to the driver coil; and wherein the system is further comprised of a capacitor added in parallel to the receiver coil. 
     
     
         14 . A system according to  claim 8 , wherein the non-sinusoidal, asymmetric signal has a frequency between 1 Hz and 1 MHz. 
     
     
         15 . A system according to  claim 8 , wherein the measurement circuit is configured to measure a change in amplitude between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil, and
 wherein the hardware processing system is programmed with one or more software routines executing on the hardware processing system to compare differences in amplitude between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil to detect differences in tissue property.   
     
     
         16 . A system according to  claim 8 , further comprising
 a capacitor electrically connected to the probe for increasing the sensitivity of the probe.   
     
     
         17 . A system for detecting differences in tissue property in a tissue of an animal or human, the system adapted to connect to an alternating current or power supply, the system comprising:
 a probe comprising a driver coil and a receiver coil and wherein the driver coil is adapted to receive a non-sinusoidal, asymmetric signal from the alternating current or power supply for inducing eddy currents in the tissue when the probe is placed adjacent to the tissue;   a measurement circuit, operably connected to the receiver coil and configured to measure a change in amplitude between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil when the driver and receiver coils are positioned adjacent to the tissue; and   a hardware processing system operably connected to the measurement circuit, the hardware processing system programmed with one or more software routines executing on the hardware processing system to compare differences in amplitude between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil to detect differences in tissue property.   
     
     
         18 . A system according to  claim 17 , wherein the voltage or current produced in the probe has at least a first and second duty cycle each comprised of multiple peaks and wherein the driver coil and receiver coil has inductances and capacitances so the last peak of the voltage or current produced in the first duty cycle coincides on a sloping side of the first peak of the second duty cycle. 
     
     
         19 . A system according to  claim 17 , further comprising:
 a capacitor electrically connected to the probe and wherein the system is configured to produce a periodic receiver coil voltage trace comprising several peaks.   
     
     
         20 . A system according to  claim 17 , wherein the system is further comprised of a capacitor electrically connected to the probe to optimize an output signal from the measurement circuit. 
     
     
         21 . A system according to  claim 17 , wherein the non-sinusoidal, asymmetric signal has a frequency between 1 Hz and 1 MHz. 
     
     
         22 . A system according to  claim 17 , wherein the measurement circuit is configured to
 measure a phase shift between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil when the driver and receiver coils are positioned adjacent to the tissue; and   wherein the hardware processing system is programmed with one or more software routines executing on the hardware processing system to compare the phase shift between the voltage or current on the driver coil and the voltage or current on the receiver coil to detect differences in tissue property.   
     
     
         23 . A system according to  claim 17 , further comprising
 a capacitor electrically connected to the probe for increasing the sensitivity of the probe.   
     
     
         24 . A system according to  claim 22 , wherein the measurement circuit is a lock-in amplifier configured to provide a DC output voltage indicative of the detected phase shift between the voltage or current on the driver coil and the voltage or current produced thereby in the receiver coil. 
     
     
         25 . A system according to  claim 22 , further comprising:
 a means for raster scanning the probe at various positions across the tissue; and   wherein the measurement circuit provides the measured phase shift between the input voltage or current imposed on the driver coil and the alternating voltage or current induced in the receiver coil at positions across the tissue in order to create an image.