Electrosurgical generator with adaptive power control
First Claim
1. An electrosurgical generator for applying output power to tissue to desiccate tissue, the electrosurgical generator comprising:
- a controller for cycling the output power to cause a cycling of the tissue impedance; and
a tissue impedance measurement circuit coupled to said controller for measuring impedance of the tissue;
wherein the controller cycles the output power by applying a predetermined amount of output power to said tissue, lowering the output power upon an output voltage reaching a predetermined maximum, re-applying the predetermined amount of output power to said tissue of a measured tissue impedance does not indicate desiccation of the tissue, and terminating output power when the measured tissue impedance exceeds a predetermined value, the predetermined value corresponding to a desiccated condition of tissue.
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Accused Products
Abstract
An electrosurgical generator has an output power control system that causes the impedance of tissue to rise and fall in a cyclic pattern until the tissue is desiccated. The advantage of the power control system is that thermal spread and charring are reduced. In addition, the power control system offers improved performance for electrosurgical vessel sealing and tissue welding. The output power is applied cyclically by a control system with tissue impedance feedback. The impedance of the tissue follows the cyclic pattern of the output power several times, depending on the state of the tissue, until the tissue becomes fully desiccated. High power is applied to cause the tissue to reach a high impedance, and then the power is reduced to allow the impedance to fall. Thermal energy is allowed to dissipate during the low power cycle. The control system is adaptive to tissue in the sense that output power is modulated in response to the impedance of the tissue.
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Citations
24 Claims
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1. An electrosurgical generator for applying output power to tissue to desiccate tissue, the electrosurgical generator comprising:
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a controller for cycling the output power to cause a cycling of the tissue impedance; and
a tissue impedance measurement circuit coupled to said controller for measuring impedance of the tissue;
wherein the controller cycles the output power by applying a predetermined amount of output power to said tissue, lowering the output power upon an output voltage reaching a predetermined maximum, re-applying the predetermined amount of output power to said tissue of a measured tissue impedance does not indicate desiccation of the tissue, and terminating output power when the measured tissue impedance exceeds a predetermined value, the predetermined value corresponding to a desiccated condition of tissue. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An electrosurgical generator for treating tissue by applying energy comprising:
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a desiccation detector for measuring a degree of desiccation of tissue; and
a controller for minimizing the burning of tissue comprising power control circuitry for repeatedly increasing and decreasing output power to the tissue to be treated, the power control circuitry coupled to the desiccation detector and operating to adjust the output power in response to the degree of desiccation of the tissue by applying a predetermined amount of output power to said tissue, lowering the output power upon an output voltage reaching a predetermined maximum, and re-applying the predetermined amount of output power to said tissue if said desiccation detector does not indicate desiccation of the tissue. - View Dependent Claims (12, 13, 14, 15)
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16. A method for applying energy to tissue to treat tissue, the method including supplying a generator having a power control system to produce an adaptive oscillatory power curve to minimize the heating effect on tissue, the method comprising:
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a) applying a high current into a low impedance load until a maximum power is reached;
b) adjusting the output voltage to maintain constant output power as impedance increases as tissue begins to desiccate;
c) dropping the output power in response to a rapid rise in tissue impedance indicating the boiling of tissue;
d) allowing the tissue impedance to fall to a predetermined minimum value and then raising the output power to cause an increase in tissue impedance;
e) repeating steps b and c until impedance reaches a maximum value.
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17. A method for applying energy to tissue to treat tissue, the method including supplying a generator having a power control system to produce an adaptive oscillatory power curve to minimize the heating effect on tissue, the method comprising:
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a) applying a high current into a low impedance load until a maximum power is reached;
b) adjusting the output voltage to maintain constant output power as impedance increases as tissue begins to desiccate;
c) dropping the output power if the output voltage exceeds a maximum value;
d) raising the output power after a predetermined period of time to cause an increase in tissue impedance; and
e) repeating steps b and c until impedance reaches a maximum value.
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18. A method for applying energy to tissue to treat the tissue, comprising steps of:
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providing an electrosurgical generator;
coupling an output of the generator to tissue to be treated; and
coupling electrosurgical energy from the generator into the tissue in an oscillatory manner until an impedance of the tissue rises to a value that indicates that the tissue is desiccated, wherein the electrosurgical energy is coupled into the tissue with an oscillatory frequency that lies within a thermal bandwidth of the tissue. - View Dependent Claims (19)
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20. A method of applying energy to tissue to treat the tissue, the method including supplying a generator having a power control system to produce an adaptive oscillatory power curve to minimize the heating effect on tissue, the method comprising the steps of:
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applying a high current into a low impedance load until a maximum power is reached;
adjusting the output voltage to maintain constant output power as impedance increases as tissue begins to desiccate;
dropping the output power in response to a rapid rise in tissue impedance indicating the boiling of tissue;
allowing the tissue to cool until the tissue impedance reaches a predetermined minimum value and then raising the output power to cause an increase in tissue impedance; and
repeating the adjusting and dropping steps until the tissue impedance reaches a maximum value.
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21. A method of applying energy to tissue to treat tissue, the method comprising the steps of:
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supplying a generator having a power control system to produce an adaptive oscillatory power curve to minimize the heating effect on tissue;
coupling electrosurgical energy from the generator into the tissue in an oscillatory manner until an impedance of the tissue rises to a value that indicates that the tissue is desiccated;
adjusting an output voltage to apply output power to the tissue in a cyclical fashion such that there are periods of increased power application and periods of reduced power application; and
allowing thermal energy to dissipate during the periods of reduced power application. - View Dependent Claims (22, 23, 24)
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Specification