METHOD AND APPARATUS FOR CONTROLLING LESION SIZE IN CATHETER-BASED ABLATION TREATMENT

• US 20100298826A1
• Filed: 05/10/2010
• Published: 11/25/2010
• Est. Priority Date: 05/08/2009
• Status: Active Grant

• Current Assignee: ST JUDE MEDICAL INTERNATIONAL HOLDING S. R.L.
• Original Assignee: St. Jude Medical Luxembourg Holding SARL (Abbott Laboratories Incorporated)
• Inventors: Leo, Giovanni, Aeby, Nicolas
• Granted Patent: US 8,641,705 B2
• Time in Patent Office: Days
• US Class Current: 606/41
• CPC Class Codes: A61B 18/082 Probes or electrodes therefor
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00648 using more than one sensed parameter
• CPC Class Codes: A61B 2018/00678 upper
• CPC Class Codes: A61B 2018/00708 switching the power on or off
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00839 Bioelectrical parameters, e.g. ECG, EEG
• CPC Class Codes: 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
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61B 2218/002 Irrigation
• CPC Class Codes: A61B 2562/0261 Strain gauges
• CPC Class Codes: A61B 2562/0266 Optical strain gauges
• CPC Class Codes: A61B 34/30 Surgical robots
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure

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

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.

2. 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.

3. 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.

4. The system of claim 3, wherein said size parameter is one of lesion volume and lesion depth.

5. The system of claim 1 wherein said control system is adapted to control said time period of energization of said ablation head.

6. 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.

7. 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.

8. The system of claim 1 further comprising a robotic manipulator for movement of said distal portion of said catheter.

9. The system of claim 8 wherein said robotic manipulator is controlled by said control system.

10. The system of claim 1 wherein said force-time integral is calculated in real time.

11. 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.

12. The system of claim 1 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.

13. 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.

14. The system of claim 1 wherein said control system includes a central processor that computes said force-time integral.

15. The system of claim 14 wherein said central processor is adapted for said production of said sequence of contact force values.

16. 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.

17. 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.

18. The system of claim 17 wherein said force signal conditioning system is adapted for said production of said sequence of contact force values.

19. The system of claim 17 wherein said force-time integral is based on one of a pressure and a strain measurement.

20. A method for ablating a target tissue, comprising:

providing an elongate flexible catheter adapted to be introduced into a patient during said medical procedure, said catheter including a distal portion having an ablation head operatively coupled with a force sensor;

exerting said ablation head of said catheter against said target tissue;

measuring a sequence of contact forces with said force sensor while said ablation head is exerted against said target tissue, said contact forces being in reaction to said exerting of said ablation head against said target tissue;

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.

21. The method of claim 20 further comprising estimating a size parameter of said lesion based on said force-time integral.

22. The method of claim 21, wherein said size parameter of said lesion is one of volume and depth of said lesion.

23. The method of claim 20 further comprising:

determining a magnitude of an energization parameter delivered to said ablation head during said energizing of said ablation head; and

estimating a size parameter of said lesion using said magnitude of said energization parameter.

24. The method of claim 20 further comprising:

measuring a sequence of magnitudes of an energization parameter delivered to said ablation head during said energizing of said ablation head.

25. The method of claim 24 wherein said force-time integral is one of a force-energization-time integral, a force-energization-time product and a normalized force-time integral.

26. The method of claim 20 wherein said force-time integral is a force over time integral.

27. The method of claim 20 wherein said energization parameter is one of a power and an electrical current.

28. The method of claim 20 further comprising controlling said magnitude of said energization parameter during said energizing of said ablation head.

29. The method of claim 28 wherein said 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.

30. The method of claim 20 wherein said force-time integral is calculated in real time.

31. The method of claim 30 further comprising terminating energization of said ablation head when said force-time integral reaches a predetermined value.

54. The method of claim 30 wherein said central processor provided in the step of providing said central processor is configured for termination of said energization of said ablation head when said force-time integral reaches a predetermined value.

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; 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.

33. The system of claim 32 wherein said programming instructions further comprise estimating a size parameter of said lesion based on said force-time integral.

34. The system of claim 32 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.

35. The system of claim 34 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.

36. The system of claim 32 wherein said control system further comprises a current sensor adapted to detect energization of said ablation head.

37. The system of claim 32 wherein said force-time integral is determined in real time.

38. The system of claim 37 wherein said programming instructions further comprise terminating energization of said ablation head when said force-time integral reaches a predetermined value.

39. The system of claim 32 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.

40. The system of claim 39 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.

41. The system of claim 40 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.

42. The system of claim 32 wherein said programming instructions include controlling said magnitude of said energization parameter during said energizing of said ablation head.

43. The system of claim 42 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.

44. 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.

45. The system of claim 44 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.

46. A method for ablating a target tissue, comprising:

providing an elongate flexible catheter adapted to be introduced into a patient during said medical procedure, said catheter including an ablation head operatively coupled with a force sensor;

providing a power source for energization of said ablation head;

providing a force signal conditioning system adapted to source said force sensor and to monitor an output of said force sensor;

providing a central processor that receives said output of said force sensor, said central processor being configured to determine a force-time integral that is utilized to characterize ablation of said target tissue; and

providing a set of instructions on a tangible medium for operation of said elongate flexible catheter, said instructions including;

exerting said ablation head of said catheter against said target tissue; and

monitoring a sequence of contact forces with said force sensor while said ablation head is exerted against said target tissue, said contact forces being in reaction to said exerting of said ablation head against said target tissue.

47. The method of claim 46 wherein said instructions provided in the step of providing said set of instructions further include energizing said ablation head for a period of time while said sequence of contact forces is being measured

48. The method of claim 47 wherein said central processor provided in the step of providing said central processor is configured to determine a magnitude of an energization parameter delivered to said ablation head during said step of energizing said ablation head and to estimate a size parameter of said lesion using said magnitude of said energization parameter.

49. The method of claim 47 wherein said central processor provided in the step of providing said central processor is configured to monitor a sequence of magnitudes of an energization parameter delivered to said ablation head during said step of energizing said ablation head.

50. The method of claim 47 wherein said central processor provided in the step of providing said central processor is configured for control of a magnitude of an energization parameter during said step of energizing said ablation head.

51. The method of claim 46 wherein said central processor provided in the step of providing said central processor is adapted to estimate a size parameter of a lesion formed on said target tissue by energization of said power source.

52. The method of claim 46 further comprising providing a current sensor for detection of electrical current that flows between said power source and said ablation head, and wherein said energization parameter electrical current.

53. The method of claim 52 wherein said 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.