Systems for radiofrequency ablation with phase sensitive power detection and control

• US 5,722,975 A
• Filed: 06/07/1995
• Issued: 03/03/1998
• Est. Priority Date: 11/08/1991
• Status: Expired due to Term

• Current Assignee: EP Technologies Incorporated (Boston Scientific Corporation)
• Original Assignee: EP Technologies Incorporated (Boston Scientific Corporation)
• Inventors: Edwards, Stuart D., Stern, Roger A.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US08/480,146
• Time in Patent Office: 1,000 Days
• Field of Search: 606/34, 606/38, 606/39, 606/41, 607/99, 607/113, 607/122, 128/642
• US Class Current: 606/34
• CPC Class Codes: A61B 18/12 by passing a current through the tissue to be heated, e.g. high-frequency current
• CPC Class Codes: A61B 18/1206 Generators 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 2017/00101 using an array of thermosensors
• CPC Class Codes: A61B 2017/00292 mounted on or guided by flexible, e.g. catheter-like, means
• CPC Class Codes: A61B 2018/0066 without feedback, i.e. open loop control
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00755 Resistance or impedance
• CPC Class Codes: A61B 2018/00767 Voltage
• CPC Class Codes: A61B 2018/00779 Power or energy
• CPC Class Codes: A61B 2018/00791 Temperature
• CPC Class Codes: A61B 2018/00797 measured by multiple temperature sensors
• CPC Class Codes: A61B 2018/00815 measured by a thermistor
• CPC Class Codes: A61B 2018/00827 Current
• CPC Class Codes: A61B 2018/00869 Phase
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/00892 Voltage
• CPC Class Codes: A61B 2018/1253 monopolar
• CPC Class Codes: A61B 2018/1467 using more than two electrodes on a single probe

Abstract

Systems for ablating tissue control radiofrequency power to an ablation electrode by relying upon actual phase sensitive power measurements, unaffected by phase shifts between radiofrequency voltage and current. The systems also detect these phase differences, if they develop, and integrate this factor in making their control decisions.

Claims

1. A system for ablating tissue at an ablation site using radiofrequency energy comprising

an electrode,

a source of radiofrequency energy coupled to the electrode for transmitting radiofrequency energy at the ablation site resulting in measurable voltage and current waveforms,

a monitoring element coupled to the electrode to monitor the current and voltage waveforms,

a sensing element coupled to the monitoring element to derive a phase shift between the monitored current and voltage waveforms, and

a controller coupled to the sensing element and responsive to the derived phase shift and operable to interrupt conduction of radio frequency energy when the derived phase shift exceeds a predetermined value.

2. A system according to claim 1

and further including an element coupled to the sensing element and that computes real power.

3. A system according to claim 2

and further including a device coupled to the element that computes real power to display the computed real power.

4. A system according to claim 1

and further including an element coupled to the sensing element and that computes apparent power.