Impedance controlled tissue ablation apparatus and method

• US 20030130711A1
• Filed: 09/28/2002
• Published: 07/10/2003
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: AngioDynamics, Inc.
• Original Assignee: AngioDynamics, Inc.
• Inventors: Yassinzadeh, Zia, Balbierz, Daniel J., Daniel, Steven A., Pearson, Robert M., Johnson, Theodore C.
• Granted Patent: US 7,344,533 B2
• Time in Patent Office: Days
• US Class Current: 607/101
• CPC Class Codes: A61B 18/1477 Needle-like probes
• CPC Class Codes: A61B 2018/00011 with fluids
• CPC Class Codes: A61B 2018/00083 low, i.e. electrically insulating
• CPC Class Codes: A61B 2018/00196 reciprocating lengthwise
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00726 Duty cycle
• CPC Class Codes: A61B 2018/00738 Depth, e.g. depth of ablation
• CPC Class Codes: A61B 2018/00744 Fluid flow
• CPC Class Codes: A61B 2018/0075 Phase
• CPC Class Codes: A61B 2018/00755 Resistance or impedance
• CPC Class Codes: A61B 2018/00761 Duration
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00869 Phase
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/124 switching the output to different electrodes, e.g. sequentially
• CPC Class Codes: A61B 2018/1253 monopolar
• CPC Class Codes: A61B 2018/1425 Needle
• CPC Class Codes: A61B 2018/143 multiple needles
• CPC Class Codes: A61B 2018/1432 curved
• CPC Class Codes: A61B 2218/002 : Irrigation

Abstract

A method and apparatus for carrying our thermal ablation of target tissue is disclosed. The apparatus includes an RF ablation device having a multi-electrode electrode assembly designed to be deployed in target tissue, defining a selected-volume tissue region to be ablated, and having infusion channels for infusing a liquid into the target tissue during the ablation process. A control unit in the apparatus is operably connected to an RF energy source, for controlling the RF power level supplied to the electrodes, and to an infusion device, for controlling the rate of infusion of a liquid through the device into the tissue. During both electrode deployment and tissue ablation, impedance and or temperature measurements made within the tissue are used to control the RF source and infusion device, for optimizing the time and extent of tissue ablation.

Claims

1. A cell necrosis apparatus for use in ablating target tissue, comprising, in operative condition:

an elongated delivery device including a lumen;

an energy delivery device including a plurality of electrodes, each electrode having a tissue piercing distal portion and being positionable in the elongated delivery device in a compacted state and preformed to assume a curved shape when deployed, the plurality of electrodes exhibiting a changing direction of travel when advanced from the elongated delivery device to a selected tissue site and defining an ablation volume when in said deployed state;

at least one of (i) the elongated delivery device or (ii) at least one of the plurality of electrodes being adapted for fluid delivery therethrough to at least one infusion port disposed on at least one of (i) the elongated delivery device or (ii) at least one of the plurality of electrodes;

a source of RF energy connected to said energy delivery device;

a fluid delivery device operably connected to at least one of the elongated delivery device or the energy delivery device for delivering fluid therethrough to said at least one infusion port, into the target tissue;

a control unit operably connected to (I) the source of RF energy, for controlling RF energy delivery to said energy delivery device, and to (ii) the energy delivery device for use in detecting impedance; and

a control for the fluid delivery device by which the amount of fluid infused from the device into the target tissue can be controlled in response to said detected impedance.

2. The apparatus according to claim 1, wherein said control unit is operably connected to at least one of the plurality of electrodes to determine tissue impedance.

3. The apparatus of claim 2, wherein local impedance is determined directly by determining the impedance along conductive pathways between one or more sites on at least one of the plurality of electrodes.

4. The apparatus of claim 3, wherein said one or more sites is at least two sites on the same electrode for determining local impedance across a fixed distance.

5. The apparatus according to claim 2, wherein at least one of said plurality of electrodes is a passive electrode, and the control unit is operably connected to said passive electrode(s).

6. The apparatus according to claim 1, further comprising:

a temperature sensor positioned on at least one of the plurality of electrodes and operably connected to the control unit.

7. The apparatus according to claim 1, where said control unit is operably connected to said fluid delivery device for regulating the amount of fluid infused from the fluid delivery device in response to said detected impedance.

8. The apparatus according to claim 1, where the control unit is manually adjustable for regulating the amount of energy delivered to said at least one electrode in response to said detected impedance.

9. The apparatus according to claim 1, where the control is manually adjustable for regulating the amount of fluid infused from the fluid delivery device in response to said detected impedance.

10. The apparatus of claim 1, wherein each of at least two of the plurality of electrodes includes a separate infusion lumen for delivering fluid therethrough.

11. The apparatus of claim 10, wherein said control for the fluid delivery device is operable to provide independent control of infusion through the separate infusion lumens.

12. A method for use in ablating target tissue in a patient comprising:

positioning an RF delivery device having (a) an elongated delivery device that includes a lumen, (b) a plurality of RF electrodes, with a tissue piercing distal end, that are positionable in the introducer in a compacted state and preformed to assume a curved shape when deployed, the plurality of RF electrodes exhibiting a changing direction of travel when advanced from the introducer to a selected tissue site, at least one of the plurality of electrodes being adapted for fluid delivery therethrough to at least one infusion port, (c) a fluid delivery device operably connected to at least one of the elongated delivery device or the plurality of electrodes for delivering fluid therethrough to said at least one infusion port, (d) a control unit operably connected to at least one of the plurality of electrodes for use in detecting impedance, and (e) a control for the fluid delivery device; and

wherein said positioning is effective to place the distal tip of the catheter in or adjacent a target tissue;

deploying said electrodes to define an ablation volume that includes at least a portion of the target tissue,

infusing a fluid through said electrodes into the defined ablation volume;

applying an ablating RF current to the electrodes,

by said applying, ablating target tissue contained within the defined volume, determining impedance; and

regulating the impedance by controlling the amount of fluid infused from the RF delivery device.

13. The method of claim 12, where said infusing step is performed at one or more of prior to, during, and after said ablating step.

14. The method of claim 12, wherein said regulating step includes varying the fluid flow at different electrodes of the plurality of electrodes.

15. The method of claim 12, wherein said ablating step is additionally performed during said deploying step.

16. The method of claim 12, wherein the fluid infused is an infused electrolytic solution and the method further comprises varying the conductivity of the infused solution, by controlling the concentration of an electrolyte in the infused electrolytic solution.

17. The method of claim 16, wherein said infused electrolytic solution is a saline solution and the conductivity of the infused electrolytic solution is controlled by varying the salinity of the solution.

18. The method of claim 16, wherein said infusing step is effective to control a zone of infusion around individual electrodes of the plurality of electrodes.

19. The method of claim 12, wherein said impedance is system or local impedance determined from the impedance between one or more electrodes and an exterior of the patient for system impedance, and between electrodes or between two or more sites on the same electrode for local impedance.

20. The method of claim 19 further comprising:

maximizing a power dissipation efficiency by controlling system and/or local impedance to an optimal value.

21. The method of claim 19, wherein said controlling impedance is controlling impedance between a minimum value and maximum value.

22. The method of claim 19, wherein said infusing step is performed at a preprogrammed flow rate profile to produce a time variable impedance profile.

23. The method of claim 19, wherein determining said impedance is performed with a frequency selected from the group consisting of the same frequency as the energy source, a different frequency from the energy source and a range of frequencies.