System and method for assessing coupling between an electrode and tissue

Abstract

A system and method for assessing a degree of coupling between an electrode and tissue in a body is provided. Values for first and second components of a complex impedance (e.g., resistance and reactance or impedance magnitude and phase angle) between the electrode and the tissue are obtained. These values are used together with a standardization value indicative of a deviation from a reference standard by a parameter associated with at least one of the body, the electrode and another component of the system to calculate a coupling index that is indicative of a degree of coupling between the electrode and the tissue. The coupling index may be displayed to a clinician in a variety of ways to indicate the degree of coupling to the clinician. The system and method find particular application in ablation of tissue by permitting a clinician to create lesions in the tissue more effectively and safely.

1 - 21 . (canceled) 
     
     
         22 . A method for assessing a degree of coupling between an electrode and tissue of a body, comprising:
 acquiring a phase angle value of a complex impedance between the electrode and the tissue responsive to an output of a complex impedance sensor;   calculating an electrical coupling index responsive to at least the phase angle value and indicative of a degree of electrical coupling between the electrode and the tissue;   acquiring a force value indicative of a degree of force exerted between the electrode and the tissue; and   determining a coupling condition between the electrode and the tissue based on the electrical coupling index and the force value.   
     
     
         23 . The method of  claim 22 , wherein calculating an electrical coupling index comprises calculating the electrical coupling index in response to at least the phase angle value and a variable parameter. 
     
     
         24 . The method of  claim 23 , wherein the variable parameter comprises one or more of a temperature of the body, an electrolyte concentration in the body, and a size of the electrode. 
     
     
         25 . The method of  claim 23 , further comprising acquiring an impedance magnitude of the complex impedance between the electrode and the tissue, wherein calculating an electrical coupling index comprises calculating the electrical coupling index in response to at least the phase angle value and the impedance magnitude. 
     
     
         26 . The method of  claim 22 , wherein determining a coupling condition between the electrode and the tissue comprises determining both when the electrode moves from a position of no contact to contact with tissue, and the degree of force between the electrode and the tissue. 
     
     
         27 . The method of  claim 22 , wherein determining a coupling condition between the electrode and the tissue comprises determining an ablation efficacy of the tissue. 
     
     
         28 . The method of  claim 22 , further comprising further comprising displaying a representation of the coupling condition. 
     
     
         29 . The method of  claim 22 , further comprising displaying a representation of the electrical coupling index. 
     
     
         30 . The method of  claim 29 , wherein displaying a representation of the electrical coupling index comprises displaying at least the representation of the electrical coupling index relative to a threshold value. 
     
     
         31 . The method of  claim 22 , further comprising displaying a representation of the electrode that is dependent on the coupling condition. 
     
     
         32 . The method of  claim 22 , further comprising one or more of identifying a type of the tissue, determining a proximity of the electrode to the tissue, and determining an orientation of the electrode relative to the tissue in response to the coupling condition. 
     
     
         33 . A system for assessing the degree of coupling between a first electrode and a tissue in a body, comprising:
 a complex impedance sensor;   a force sensor; and   an electronic control unit configured to:
 acquire a phase angle value of a complex impedance between the electrode and the tissue responsive to an output of a complex impedance sensor; 
 calculate an electrical coupling index responsive to at least the phase angle value and indicative of a degree of electrical coupling between the electrode and the tissue; 
 acquire a force value indicative of a degree of force exerted between the electrode and the tissue; and 
 determine a coupling condition between the electrode and the tissue based on the electrical coupling index and the force value. 
   
     
     
         34 . The system of  claim 33 , wherein calculating an electrical coupling index comprises calculating the electrical coupling index in response to at least the phase angle value and a variable parameter. 
     
     
         35 . The system of  claim 34 , wherein the variable parameter comprises one or more of a temperature of the body, an electrolyte concentration in the body, and a size of the electrode. 
     
     
         36 . The system of  claim 34 , further comprising acquiring an impedance magnitude of the complex impedance between the electrode and the tissue, wherein calculating an electrical coupling index comprises calculating the electrical coupling index in response to at least the phase angle value and the impedance magnitude. 
     
     
         37 . The system of  claim 33 , wherein determining a coupling condition between the electrode and the tissue comprises determining both when the electrode moves from a position of no contact to contact with tissue, and the degree of force between the electrode and the tissue. 
     
     
         38 . The system of  claim 33 , wherein determining a coupling condition between the electrode and the tissue comprises determining an ablation efficacy of the tissue. 
     
     
         39 . The system of  claim 33 , further comprising further comprising displaying a representation of the coupling condition. 
     
     
         40 . The system of  claim 33 , further comprising displaying a representation of the electrical coupling index. 
     
     
         41 . The system of  claim 40 , wherein displaying a representation of the electrical coupling index comprises displaying at least the representation of the electrical coupling index relative to a threshold value. 
     
     
         42 . The system of  claim 33 , further comprising displaying a representation of the electrode that is dependent on the coupling condition. 
     
     
         43 . The system of  claim 33 , further comprising one or more of identifying a type of the tissue, determining a proximity of the electrode to the tissue, and determining an orientation of the electrode relative to the tissue in response to the coupling condition.