System and method for measuring force and torque applied to a catheter electrode tip

Abstract

A contact sensing assembly including a catheter including an electrode having a base portion mounted adjacent a head portion of the catheter body. A sensor is disposed adjacent the base portion for measuring compression or tensile forces applied to an electrode tip portion, and includes a predetermined sensitivity. The base and head portions include predetermined rigidity so that forces applied to the electrode tip portion are determinable as a function of the sensitivity and a sensor output. A contact sensing assembly also includes an electrode pipe operatively connected to the catheter body for movement and bending with the catheter body, and an electrode wire disposed in the electrode pipe and including isolation. A change in capacitance resulting from movement of the electrode wire toward the electrode pipe or contact of the electrode wire with the electrode pipe during bending of the catheter correlates to a force applied to the catheter.

What is claimed is: 
     
         1 - 39 . (canceled) 
     
     
         40 . A contact sensing assembly comprising:
 a catheter comprising a body having a proximal end, a distal end, and a head portion;   an electrode comprising a tip portion and a base portion, wherein the base portion is adjacent to the head portion of the catheter body;   a gap separating the base portion of the electrode and the head portion of the catheter body; and   three individual sensors, each individual sensor being attached in the gap between the base portion of the electrode and the head portion of the catheter so that each of the sensors is configured to experience the following forces:
 (i) a compressive force when a part of the base portion adjacent the particular individual sensor is forced toward a part of the head portion adjacent the particular individual sensor, and 
 (ii) a tensile force when the part of the base portion adjacent the particular sensor is forced away from the part of the head portion adjacent the particular sensor; 
   wherein each of the three sensors is adapted to provide an output signal corresponding to a compressive or tensile force across the gap experienced by each respective sensor; and   wherein a contact force applied to the electrode is a function of an aggregation of the output signals from the three sensors.   
     
     
         41 . The contact sensing assembly of  claim 40 , wherein the output signals are voltage output signals. 
     
     
         42 . The contact sensing assembly of  claim 40 , wherein each of the three sensors has a predetermined sensitivity; and wherein the base and head portions of the electrode include a predetermined rigidity so that an axial component of the contact force applied to the electrode is determinable as a sum of the output signals from the three sensors divided by the predetermined sensitivity of each of the three sensors, respectively. 
     
     
         43 . The contact sensing assembly of  claim 42 , wherein torque applied to the electrode is determinable as a function of the output signals from the three sensors divided by the predetermined sensitivity of each of the three sensors, respectively, and a distance of the three sensors from a central axis of the electrode. 
     
     
         44 . The contact sensing assembly of  claim 43 , wherein for an electrode having a central axis disposed along a z-direction, torque applied to the electrode is determinable as follows: T_y=¾*D*(V_c/α —c−V _a/α_a−V_b/α_b), where T_y is the torque applied to the electrode in a y-direction, D is a diameter of a circle passing through the center of each of the three sensors, V is a voltage output of each respective individual sensor, and α is the predetermined sensitivity of each respective individual sensor. 
     
     
         45 . The contact sensing assembly of  claim 43 , wherein for an electrode having a central axis disposed along a z-direction, torque applied to the electrode is determinable as follows: T_x=sqrt(3)/2*D*(V_a/α_a−V_b/α_b), where T_x is the torque applied to the electrode in a x-direction, D is a diameter of a circle passing through the center of each of the three sensors, V is a voltage output of each respective individual sensor, and α is the predetermined sensitivity of each respective individual sensor. 
     
     
         46 . The contact sensing assembly of  claim 40 , further comprising a coupling member connecting the electrode to the catheter body. 
     
     
         47 . The contact sensing assembly of  claim 46 , wherein the coupling member comprises an elastic material. 
     
     
         48 . The contact sensing assembly of  claim 40 , wherein the individual sensors are emplaced in the gap between at least two annular or circular rings. 
     
     
         49 . The contact sensing assembly of  claim 40 , wherein the tip portion of the electrode comprises a temperature sensor. 
     
     
         50 . The contact sensing assembly of  claim 49 , wherein the tip portion of the electrode comprises an irrigation port. 
     
     
         51 . The contact sensing assembly of  claim 40 , wherein the electrode comprises one of an RF ablation electrode, a HIFU ablation transducer, a laser ablation assembly, a cryogenic ablation assembly, an ultrasonic imaging apparatus, an electrical cardiac pacing electrode, and an electrical cardiac sensing electrode. 
     
     
         52 . The contact sensing assembly of  claim 40 , wherein the three sensors are fabricated using at least one of flex circuit technology, lithographic technology, thin-film technology, and thick film technology. 
     
     
         53 . The contact sensing assembly of  claim 40 , wherein the contact force applied to the electrode is utilized for at least one of:
 a) automatically limiting a maximum force;   b) warning of a high or unacceptable force;   c) giving visual or audible feedback to a practitioner regarding a tissue contact force;   d) warning of a loss of contact force or contact; and   e) warning of a contact force which is too low.   
     
     
         54 . A contact sensing assembly comprising:
 a catheter comprising a body having a proximal end, a distal end, and a head portion;   an electrode comprising a tip portion and a base portion, wherein the base portion is adjacent to the head portion of the catheter body;   a gap separating the base portion of the electrode and the head portion of the catheter body; and   three individual sensors, each individual sensor being attached in the gap between the base portion of the electrode and the head portion of the catheter, each of the three individual sensors including the following:
 A) a first sensor located at a first position between the base portion of the electrode and the head portion of the catheter body, wherein said first sensor is configured for outputting a first signal related to a first compressive or tensile force applied to the first sensor by movement of the electrode relative to the catheter, and 
 (B) a second sensor located at a second position between the base portion of the electrode and the head portion of the catheter body, wherein the second position is different from the first position, and wherein said second sensor is configured for outputting a second signal related to a second compressive or tensile force applied to the second sensor by movement of the electrode relative to the catheter; 
   wherein the base and head portions at the first and second positions include predetermined rigidities so that an axial component of a contact force applied to the electrode is determinable as a function of the predetermined sensitivities of the first and second sensors and the first and second output signals from the first and second sensors, respectively.   
     
     
         55 . The contact sensing assembly of  claim 54 , wherein a torque applied to the electrode is determinable as a function of a sum of the first and second output signals of each of the three individual sensors divided by, respectively, the predetermined sensitivity of each individual sensor, and a distance of the individual sensors from a central axis of the electrode. 
     
     
         56 . The contact sensing assembly of  claim 55 , wherein for an electrode having a central axis disposed along a z-direction, a torque applied to the electrode is determinable as follows: T_y=¾*D*(V_c/α_c−V_a/α_a−V_/α_b), where T_y is the torque applied to the electrode in a y-direction, D is a diameter of a circle passing through the center of each individual sensor, V is a voltage output of each respective individual sensor, and a is the predetermined sensitivity of each respective individual sensor. 
     
     
         57 . The contact sensing assembly of  claim 55 , wherein for an electrode having a central axis disposed along a z-direction, a torque applied to the electrode is determinable as follows: T_x=sqrt(3)/2*D*(V_a/α_a−V_b/α_b), where T_x is the torque applied to the electrode in a x-direction, D is a diameter of a circle passing through the center of each individual sensor, V is a voltage output of each respective individual sensor, and α is the predetermined sensitivity of each respective individual sensor. 
     
     
         58 . The contact sensing assembly of  claim 54 , further comprising a coupling member connecting the electrode to the catheter body. 
     
     
         59 . The contact sensing assembly of  claim 58 , wherein the coupling member comprises an elastic material. 
     
     
         60 . The contact sensing assembly of  claim 54 , wherein the individual sensors are emplaced in the gap between at least two annular or circular rings. 
     
     
         61 . The contact sensing assembly of  claim 54 , wherein the tip portion of the electrode comprises a temperature sensor. 
     
     
         62 . The contact sensing assembly of  claim 54 , wherein the tip portion of the electrode comprises an irrigation port. 
     
     
         63 . The contact sensing assembly of  claim 54 , wherein the electrode comprises one of an RF ablation electrode, a HIFU ablation transducer, a laser ablation apparatus, a cryogenic ablation assembly, an ultrasonic imaging transducer, a cardiac pacing electrode, and a cardiac sensing electrode. 
     
     
         64 . The contact sensing assembly of  claim 54 , wherein the individual sensors are fabricated using at least one of flex circuit technology, lithographic technology, thin-film technology, and thick film technology. 
     
     
         65 . The contact sensing assembly of  claim 54 , wherein the determined contact force applied to the electrode is utilized for at least one of:
 a) automatically limiting a maximum force;   b) warning of a high or unacceptable force;   c) giving visual or audible feedback to a practitioner regarding a tissue contact force;   d) warning of a loss of contact force or contact; and   e) warning of a contact force which is too low.   
     
     
         66 . The contact sensing assembly of  claim 54 , wherein each sensor of the individual sensors is one of a resistive force sensor and a capacitive force sensor.