ABLATION PERFORMANCE INDICATOR FOR ELECTROSURGICAL DEVICES

• US 20090209956A1
• Filed: 02/14/2008
• Published: 08/20/2009
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: ArthroCare Corporation (Smith & Nephew PLC)
• Original Assignee: ArthroCare Corporation (Smith & Nephew PLC)
• Inventors: Marion, Duane W.
• Granted Patent: US 9,358,063 B2
• Time in Patent Office: Days
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2017/00115 with audible or visual output with imaging means A61B90/37, A61B34/20
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00827 Current

Abstract

Ablation performance indicator for electrosurgical devices is described where ablation is typically characterized by the generation of a plasma discharge at the electrode assembly of an electrosurgical probe. When the electrode begins firing, the current waveform assumes a distinct appearance characterized by a spike at the leading edge of each half cycle followed by a lower level for the remaining period of the half cycle. A calculation of the waveform'"'"'s Crest Factor can be used to determine the state at the electrode, e.g., whether the ablative energy is causing a desirable ablative effect on the electrode. This provides real-time measurements of the RMS and peak current amplitudes along with the Crest Factor and may also be used as limits or inputs to control algorithms or as inputs to indicate whether the device is in its ablative or non-ablative state.

Claims

1. A method of determining a state of an electrosurgical instrument, comprising:

measuring a current waveform generated by the instrument;

determining a peak amplitude and a time-averaged amplitude of the current waveform;

calculating a peak-to-average ratio based upon the peak and time-averaged amplitudes; and

determining whether an electrode of the instrument is in an ablative mode or non-ablative mode based upon the calculated peak-to-average ratio.

2. The method of claim 1 further comprising activating an indicator disposed on the instrument when the instrument is determined to be operating in the ablative mode.

3. The method of claim 1 wherein measuring a current waveform comprises measuring the waveform via a current sensing transformer.

4. The method of claim 3 further comprising adding a DC bias to the measured waveform.

5. The method of claim 1 wherein calculating comprises calculating via a digital signal processor in electrical communication with the instrument.

6. The method of claim 1 wherein calculating further comprises removing a DC bias from the measured waveform.

7. The method of claim 1 further comprising sampling the measured waveform at some frequency slightly below the fundamental frequency of the waveform so that the sampling is performed over a multiple number of successive cycles of the waveform.

8. The method of claim 1 wherein calculating a peak-to-average ratio comprises calculating a Crest Factor of the current waveform whereby the waveform is characterized by a spike at a leading edge of a half cycle followed by a relatively lower level for a remainder of the half cycle.

9. The method of claim 7 wherein the Crest Factor of the waveform increases as an ablative load is applied by the instrument.

10. The method of claim 1 further comprising utilizing the peak-to-average ratio as an input for a control algorithm of the instrument.

11. A system for determining a state of an electrosurgical instrument, comprising:

an electrode circuit having a power supply in electrical communication with an electrode;

a current sensing circuit in communication with the electrode circuit via a current sensing transformer, and

wherein the current sensing circuit comprises a processor configured to calculate a peak-to-average ratio based upon a peak amplitude and a time-averaged amplitude of a current waveform detected from the electrode circuit via the transformer.

12. The system of claim 11 wherein the electrode comprises an RF electrode.

13. The system of claim 11 wherein the processor comprises an analog-to-digital converter in communication with the transformer.

14. The system of claim 11 wherein the peak-to-average ratio comprises a Crest Factor of the current waveform whereby the waveform is characterized by a spike at a leading edge of a half cycle followed by a relatively lower level for a remainder of the half cycle.

15. The system of claim 11 further comprising a controller for controlling the electrode based upon the calculated peak-to-average ratio.

16. The system of claim 11 further comprising an additional power supply in communication with the current sensing circuit.

17. The system of claim 11 further comprising an electrosurgical probe having a distal end, the electrode disposed on the distal end of the electrosurgical probe.

18. The system of claim 17 further comprising a indicator disposed on the electrosurgical probe, the indicator in communication with the current sensing circuit and operable to be activated when a desired state indicated by a defined peak-to-average ratio is detected.

19. The system of claim 17 further comprising a indicator disposed on the power supply, the indicator in communication with the current sensing circuit and operable to be activated when a desired state indicated by a defined peak-to-average ratio is detected.

20. The system of claim 19 wherein the indicator produces an audible tone when activated.