Tissue Discrimination and Applications in Medical Procedures

Abstract

A system and method for discriminating tissue types, controlling the level of therapy to tissue, and determining the health of a known tissue by measuring the characteristics of an electrical signal applied to a conductive element located within or by the tissue. Additionally, the system and method may be used for determining whether the conductive tip of a pedicle probe or pedicle screw is located in one of cortical bone, cancellous bone, and cortical bone near a boundary with soft tissue, whether the conductive tip of a cannula is located adjacent to one of nerve tissue and annulus tissue, and whether the conductive tip of a cathode is located adjacent to one of nerve tissue and prostate gland tissue.

1 . A method of determining whether a conductive element of a probe is located within body tissue of at least one of cancellous bone, cortical bone, and cortical bone near a boundary with soft tissue, comprising the steps of:
 (a) applying an electrical signal to a bi-polar electrode comprising the conductive element;   (b) determining at least one of the capacitance and impedance characteristics of the body tissue by assessing the response to the applied electrical signal; and   (c) determining whether the conductive element of the probe is located within the body tissue of at least one cancellous bone, cortical bone, and cortical bone near a boundary with soft tissue based on at least one of the capacitance and impedance characteristics of the body tissue.   
     
     
         2 . The method of  claim 1 , wherein the determined characteristics of the body tissue include a phase angle relationship between a voltage and current of the applied electrical signal and the response to the applied electrical signal. 
     
     
         3 . The method of  claim 1 , wherein the probe is a pedicle probe. 
     
     
         4 . The method of  claim 1 , wherein the applied electrical signal has a range of predetermined frequencies. 
     
     
         5 . The method of  claim 4 , wherein the range of predetermined frequencies is from 400 KHz to 100 MHz. 
     
     
         6 . The method of  claim 1 , wherein the probe is a pedicle screw. 
     
     
         7 . The method of  claim 1 , wherein the applied electrical signal has a sliding frequency. 
     
     
         8 . An article of manufacture for use in determining whether a conductive element of a probe is located within body tissue of at least one cancellous bone, cortical bone, and cortical bone near a boundary with soft tissue, the article of manufacture comprising computer readable storage media including program logic embedded therein that causes control circuitry to perform the steps:
 (a) applying an electrical signal to a bi-polar electrode comprising the conductive element;   (b) determining at least one of the capacitance and impedance characteristics of the body tissue by assessing the response to the applied electrical signal; and   (c) determining whether the conductive element of the probe is located within the body tissue of at least one of cancellous bone, cortical bone, and cortical bone near a boundary with soft tissue based on at least one of the capacitance and impedance characteristics of the body tissue.   
     
     
         9 . The article of manufacture of  claim 8 , wherein the determined characteristics of the body tissue further include a phase angle relationship between a voltage and current of the applied electrical signal and the response to the applied electrical signal. 
     
     
         10 . The article of manufacture of  claim 8 , wherein the probe is a pedicle probe. 
     
     
         11 . The article of manufacture of  claim 8 , wherein the applied electrical signal has a range of predetermined frequencies. 
     
     
         12 . The article of manufacture of  claim 11 , wherein the range of predetermined frequencies is from 400 KHz to 100 MHz. 
     
     
         13 . The article of manufacture of  claim 8 , wherein the probe is a pedicle screw. 
     
     
         14 . The article of manufacture of  claim 8 , wherein the applied electrical signal has a sliding frequency. 
     
     
         15 . An apparatus for use in determining whether a conductive element of a probe is located within body tissue of at least one cancellous bone, cortical bone, and cortical bone near a boundary with soft tissue, the apparatus including:
 (a) means for applying an electrical signal to a bi-polar electrode comprising the conductive element;   (b) means for determining least one of the capacitance and impedance characteristics of the body tissue by assessing the response to the applied electrical signal; and   (c) means for determining whether the conductive element of the probe is located within the body tissue of at least one of the cancellous bone, cortical bone, and cortical bone near a boundary with soft tissue based on at least one of the capacitance and impedance characteristics of the body tissue.   
     
     
         16 . The apparatus of  claim 15 , wherein the determined characteristics of the body tissue include a phase angle relationship between a voltage and current of the applied electrical signal and the response to the applied electrical signal. 
     
     
         17 . The apparatus of  claim 15 , wherein means for applying an electrical signal includes means for applying an electrical signal having a range of predetermined frequencies. 
     
     
         18 . The apparatus of  claim 17 , wherein the range of predetermined frequencies is from 400 KHz to 100 MHz. 
     
     
         19 . The apparatus of  claim 15 , wherein the probe is a pedicle screw. 
     
     
         20 . The apparatus of  claim 15 , wherein the applied electrical signal has a sliding frequency. 
     
     
         21 . The apparatus of  claim 15 , wherein the probe is a pedicle probe.