# US 2014/0194869 A1 · Method and apparatus for controlling lesion size in catheter-based ablation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0194869 A1 - Document ID: US20140194869A1 - Status: Published application - Kind: A1 - Application number: 14/160,108 - Filed: 2014-01-21 - Published: 2014-07-10 - Earliest claimed: 2009-05-08 - Assignees: St. Jude Medical Luxembourg Holding S.À.R.L. - Applicants: Endosense SA - Inventors: Giovanni Leo; Dipen Shah; Hendrik Lambert - Web page: https://patentgrep.com/patent/US20140194869A1 ## CPC - A61B 5/103: Measuring devices for testing the shape, pattern, {colour,} size or movement of the body or parts thereof, for diagnostic purposes (measuring instruments specially adapted for dentistry A61C19/04) - A61B 5/6885: {Monitoring or controlling sensor contact pressure} - A61B 18/082: {Probes or electrodes therefor} - A61B 18/1492: {having a flexible, catheter-like structure, e.g. for heart ablation (A61B18/1477 takes precedence)} - A61B 34/30: Surgical robots - A61B 2018/00351: {Heart} - A61B 2018/00577: {Ablation} - A61B 2018/00648: {using more than one sensed parameter} - A61B 2018/00678: {upper} - A61B 2018/00708: {switching the power on or off} - A61B 2018/00779: {Power or energy} - A61B 2018/00839: {Bioelectrical parameters, e.g. ECG, EEG} - A61B 2034/104: {Modelling the effect of the tool, e.g. the effect of an implanted prosthesis or for predicting the effect of ablation or burring} - A61B 2090/064: {for measuring force, pressure or mechanical tension} - A61B 2090/065: {for measuring contact or contact pressure} - A61B 2218/002: Irrigation - A61B 2562/0261: Strain gauges - A61B 2562/0266: Optical strain gauges - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A method and apparatus that utilizes a force-time integral for real time estimation of lesion size in catheter-based ablation systems. The apparatus measures the force exerted by a contact ablation probe on a target tissue and integrates the force over an energization time of the ablation probe. The force-time integral can be calculated and utilized to provide an estimated lesion size (depth, volume and/or area) in real time. The force-time integral may also account for variations in the power delivered to the target tissue in real time to provide an improved estimation of the lesion size. In one embodiment, the force metric can be used as feedback to establish a desired power level delivered to the probe to prevent steam popping. ## Claims ### Claim 1 A system for ablating a target tissue during a medical procedure, the system comprising: an elongate flexible catheter adapted to be introduced into a patient during said medical procedure, said catheter including a distal portion; an ablation head disposed at said distal portion of said catheter, said ablation head adapted to contact with said target tissue during said medical procedure; a force sensor operatively coupled with said ablation head for measurement of a contact force exerted on said ablation head, said force sensor configured to output a signal in response to said contact force; a power source operatively coupled with said ablation head for energization of said ablation head; and a control system configured to receive said signal from said force sensor and to produce a sequence of contact force values acquired over a time period of energization based on said signal output by said force sensor for calculation of a force-time integral that is utilized by said control system to control ablation of said target tissue. ### Claim 2 (depends on 1) The system of claim 1 wherein said force-time integral is one of a force over time integral, a force-energization over time integral and a force time product. ### Claim 3 (depends on 1) The system of claim 1 wherein said control system is adapted to determine a magnitude of an energization parameter delivered to said ablation head and to predict a size parameter of a lesion on said target tissue created by said energization parameter, said prediction being based on said force-time integral and said magnitude of said energization parameter, said energization parameter being one of power and electrical current. ### Claim 4 (depends on 3) The system of claim 3, wherein said size parameter is one of lesion volume and lesion depth. ### Claim 5 (depends on 1) The system of claim 1 wherein said control system is adapted to control said time period of energization of said ablation head. ### Claim 6 (depends on 1) The system of claim 1 wherein said control system is adapted to control a magnitude of an energization parameter delivered to said ablation head with said power source. ### Claim 7 (depends on 1) The system of claim 1 wherein said control system is adapted to control a magnitude of an energization parameter delivered to said ablation head with said power source, said magnitude of said energization parameter being based on the magnitude of said contact force. ### Claim 8 (depends on 1) The system of claim 1 further comprising a robotic manipulator for movement of said distal portion of said catheter. ### Claim 9 (depends on 8) The system of claim 8 wherein said robotic manipulator is controlled by said control system. ### Claim 10 (depends on 1) The system of claim 1 wherein said force-time integral is calculated in real time. ### Claim 11 (depends on 10) The system of claim 10 wherein said control system is adapted to substantially disable energization of said ablation head with said power source when said force-time integral reaches a predetermined value. ### Claim 12 (depends on 3) The system of claim 3 wherein said energization parameter is said electrical current and said control system further comprises a current sensor adapted detect said electrical current to said ablation head. ### Claim 13 (depends on 12) The system of claim 12 wherein said control system is adapted to determine the magnitude of said electrical current delivered to said ablation head, said control system being further adapted to predict a size parameter of a lesion on said target tissue created by the magnitude of current, said prediction being based on said force-time integral and said magnitude of current. ### Claim 14 (depends on 1) The system of claim 1 wherein said control system includes a central processor that computes said force-time integral. ### Claim 15 (depends on 14) The system of claim 14 wherein said central processor is adapted for said production of said sequence of contact force values. ### Claim 16 (depends on 14) The system of claim 14 wherein said force sensor includes a fiber optic strain gauge and said force signal conditioning system includes a fiber optic interrogator operatively coupled with said fiber optic strain gauge and said central processor. ### Claim 17 (depends on 14) The system of claim 14 wherein said control system includes a force signal conditioning system adapted to digitize said signal received from said force sensor and to provide the digitized signal to said central processor. ### Claim 18 (depends on 17) The system of claim 17 wherein said force signal conditioning system is adapted for said production of said sequence of contact force values. ### Claim 19 (depends on 17) The system of claim 17 wherein said force-time integral is based on one of a pressure and a strain measurement. ### Claim 20 A system for delivering energy to a target tissue during a medical procedure, the system comprising: an elongate flexible catheter adapted to be introduced into a patient during said medical procedure, said catheter including a distal portion; an ablation head disposed at said distal portion of said catheter and arranged to contact said target tissue during said medical procedure; a force sensor operatively coupled with said ablation head for detection of a contact force exerted on said ablation head, said force sensor adapted produce an output that correlates with said contact force; a power source operatively coupled with said ablation head for energization of said ablation head; and a control system including a central processor and being operatively coupled to said force sensor and said power source, said central processor having access to a storage medium that contains programming instructions to be carried out by the central processor, said programming instructions comprising: measuring a sequence of contact forces with said force sensor while said ablation head is in contact with said target tissue, said sequence of contact forces being in reaction to said contact; energizing said ablation head for a period of time while said sequence of contact forces is being measured; and determining a force-time integral based on said sequence of contact forces that were measured with said force sensor over said period of time of energizing said ablation head. ### Claim 21 (depends on 20) The system of claim 20 wherein said programming instructions further comprise estimating a size parameter of said lesion based on said force-time integral. ### Claim 22 (depends on 20) The system of claim 20 wherein said programming instructions include: determining a magnitude of an energization parameter delivered to said ablation head during said energizing of said ablation head; and determining a size parameter of a lesion based on said force-time integral and said magnitude of said energization parameter. ### Claim 23 (depends on 22) The system of claim 22 wherein: said energization parameter is electrical current; said control system includes a current sensor adapted to determine said magnitude of said energization parameter; and said programming instructions further comprise measuring said electrical current delivered to said ablation head during said energizing of said ablation head. ### Claim 24 (depends on 20) The system of claim 20 wherein said control system further comprises a current sensor adapted to detect energization of said ablation head. ### Claim 25 (depends on 20) The system of claim 20 wherein said force-time integral is determined in real time. ### Claim 26 (depends on 25) The system of claim 25 wherein said programming instructions further comprise terminating energization of said ablation head when said force-time integral reaches a predetermined value. ### Claim 27 (depends on 20) The system of claim 20 wherein said control system includes a force signal conditioning system adapted to digitize said signal received from said force sensor and to provide the digitized signal to said central processor. ### Claim 28 (depends on 27) The system of claim 27 wherein said force sensor includes a fiber optic strain gauge and said force signal conditioning system includes a fiber optic interrogator operatively coupled with said fiber optic strain gauge and said central processor. ### Claim 29 (depends on 28) The system of claim 28 wherein said force signal conditioning system is configured for said measuring of said sequence of contact forces and providing said sequence of forces to said central processor. ### Claim 30 (depends on 22) The system of claim 22 wherein said programming instructions include controlling said magnitude of said energization parameter during said energizing of said ablation head. ### Claim 31 (depends on 30) The system of claim 30 wherein the magnitude of said energization parameter is selected based on the contact forces of said sequence of contact forces to prevent or reduce the incidence of steam pop. ### Claim 32 A system for delivering energy to a target tissue during a medical procedure, the system comprising: an elongate flexible catheter adapted to be introduced into a patient during said medical procedure, said catheter including a distal portion; an ablation head disposed at said distal portion of said catheter and arranged to contact said target tissue during said medical procedure; a force sensor operatively coupled with said ablation head for detection of a contact force exerted on said ablation head, said force sensor adapted produce an output that correlates with said contact force; a power source operatively coupled with said ablation head for energization of said ablation head; means for controlling energization of said ablation head; means for measuring a sequence of contact forces from said force sensor; and means for determining a force-time integral, wherein said force-time integral is based on said sequence of contact forces acquired while said ablation head is energized. ### Claim 33 (depends on 32) The system of claim 32 wherein said force sensor includes a fiber optic strain gauge and said force signal conditioning system includes a fiber optic interrogator operatively coupled with said fiber optic strain gauge and said central processor.