Electrosurgical generator

• US 7,195,627 B2
• Filed: 01/11/2005
• Issued: 03/27/2007
• Est. Priority Date: 01/09/2003
• Status: Active Grant

• Current Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Original Assignee: Gyrus Medical Incorporated (Olympus Corporation)
• Inventors: Amoah, Francis, Goble, Colin C. O.
• Primary Examiner(s): Dvorak; Linda C. M.
• Assistant Examiner(s): Toy; Alex
• Application Number:
  US11/032,141
• Publication Number:
  US 20050177150A1
• Time in Patent Office: 805 Days
• Field of Search: 606 32- 35, 606/41, 607102-105
• US Class Current: 606/34
• CPC Class Codes: A61B 18/1206 Generators therefor
• CPC Class Codes: A61B 2018/00666 using a threshold value
• CPC Class Codes: A61B 2018/00684 using lookup tables
• CPC Class Codes: A61B 2018/00702 Power or energy
• 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 2018/1213 creating an arc

Abstract

An electrosurgical generator for supplying RF power to an electrosurgical instrument for cutting or vaporising tissue has an RF output stage with RF output devices, a series-resonant output network and an RF output. The generator offers improved cutting and vaporising performance, especially in relation to the reliability with which an arc can be struck when presented with an initial load impedance load. This is achieved by virtue of the output stage being capable of maintaining output pulses of at least 1 kW peak by supplying the RF output devices from a large reservoir capacitor. An appropriate combination of cutting performance and haemostasis is provided by allowing for pulsed or continuous wave operation once an arc has been established, according to whether or not a surplus energy condition exists, as indicated by the voltage across the reservoir capacitor.

Claims

1. An electrosurgical generator for supplying radio frequency (RF) power to an electrosurgical instrument for cutting or vaporising tissue, wherein the generator comprises:

an RF output stage having at least one RF power device, at least one pair of output lines for delivering RF power to the instrument, and

a series-resonant output network coupled between the RF power device and the said pair of output lines;

a power supply stage coupled to the RF output stage to supply power thereto and having a sensing element for sensing energy levels in the power supply stage; and

a control circuit coupled to the sensing element for interrupting the delivery of RF power by the RF output stage, the control circuit being configured to interrupt the power delivery whilst the energy level in the power supply stage exceeds an interruption energy threshold and to cause continuous wave operation of the RF output stage when the energy level is below the threshold, both the interrupted delivery of RF power and the continuous wave operation being capable of cutting or vaporizing tissue.

2. A generator according to claim 1, wherein the output impedance of the output stage at the output lines is less than 200/√

P ohms, where P is the maximum continuous RF output power of the generator in watts.

3. A generator according to claim 1, wherein the control circuit is a pulsing circuit configured to apply the said interruptions repeatedly in the form of pulse modulation of the RF output stage with a mark-to-space ratio of between 2:

1 and 1;

10.

4. A generator according to claim 1, wherein the control circuit is configured such that the RF power ON periods between successive interruptions have a duration in the range of from 0.2 ms to 5 ms.

5. A generator according to claim 1, wherein the control circuit is configured such that the interruptions in the delivery of RF power have a duration of less than 10 ms.

6. A generator according to claim 5, wherein the control circuit is configured such that the interruptions have a duration of less than 1.5 ms.

7. A generator according to claim 5, wherein the control circuit is configured such that the interruptions have a duration of at least 0.5 ms.

8. A generator according to claim 1, wherein the said energy level threshold is set at a value which is between 2 and 20 percent below a predetermined maximum power supply energy level.

9. A generator according to claim 1, wherein the control circuit is configured such that delivery of RF power by the RF output stage is substantially terminated when the power supply energy level falls below a minimum energy threshold which is lower than the interruption energy threshold.

10. A generator according to claim 9, wherein the control circuit is configured such that the delivery of RF power is resumed after the said termination only when the power supply energy level reaches a maximum power supply energy threshold which is higher than the interruption energy threshold.

11. A generator according to claim 10, wherein the minimum energy threshold is set at a value which is between 5 and 50 percent lower than the maximum energy threshold.

12. A generator according to claim 1, wherein the power supply stage includes a charge-storing element for supplying power to the RF output stage and wherein the sensing element comprises a voltage sensing circuit arranged to sense the voltage supplied to the RF output stage by the charge-storing element, the or each said energy level threshold being defined as a respective threshold value of the sensed voltage.

13. A generator according to claim 1, wherein the control circuit is a pulsing circuit configured to apply pulse modulation with a predetermined mark-to-space ratio and pulse repetition rate.

14. An electrosurgical generator for supplying radio frequency (RF) power to an electrosurgical instrument for cutting or vaporizing tissue, wherein the generator comprises an RF output stage having at least one RF power device, and at least one pair of output lines for delivering RF power to the instrument, and a power supply stage which is coupled to the RF output stage to supply power thereto and which has a sensing element for dynamically sensing energy levels in the power supply stage, the generator being capable of delivering RF power at the output lines with a peak current of at least 1 A and a simultaneous peak voltage of at least 300V, and wherein the generator further comprises a control circuit coupled to the sensing element to receive an energy level sensing signal from the sensing element and to cause interruptions in the delivery of RF power when the energy level sensing signal is indicative of the power supply energy level being in an upper energy region and to cause continuous wave supply of RF power when the energy level sensing signal is indicative of the power supply energy level being in a lower energy region, both the interrupted delivery of RF power and the continuous wave operation being capable of cutting or vaporizing tissue.

15. A generator according to claim 14, wherein the circuit is a pulsing circuit configured to apply the said interruptions repeatedly in the form of pulse modulation of the RF power.

16. A generator according to claim 15, wherein, during pulsed operation, RF power is delivered with a peak voltage of at least 300V during the entire pulse length.

17. A generator according to claim 15, wherein the pulsing circuit includes a timer operable to define a pulsed operation mark-to-space ratio in the region of from 2:

1 to 1;

10.

18. A generator according to claim 17, wherein the timer is configured such that the mark-to-space ratio lies between 1:

1 and 1;

5.

19. A generator according to claim 17, including a control for adjusting the said mark-to-space ratio.

20. A generator according to claim 14, wherein the output impedance of the output stage at the output lines is less than 10 ohms.

21. A generator according to claim 14, arranged such that RF power delivery to the output lines is cut off when the power supply energy level falls below a predetermined minimum value.