Patent EP0754437A2 successfully refreshed from Google Patents.
EP0754437A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
An electrosurgical generator and system
Assignee: Gyrus Medical Ltd
•
Filing: 1996-06-19
•
Granted: —
•
Expires: 2016-06-19
Abstract
Abstract An electrosurgical system including an electrode assembly having two electrodes for use immersed in an electrically conductive fluid has a generator with control circuitry for rapidly reducing the delivered radio frequency output power by at least 50% within approximately 100µs, corresponding to the time needed for a few cycles of the peak radio frequency output voltage to reach a pre determined threshold limit. In this way, tissue coagulation can be performed in, for example, saline without significant steam generation. The same peak voltage limitation technique is used in a tissue vaporization or cutting mode to limit the size of the steam pocket at the electrodes and to avoid electrode burning. The output power reduction is abtained by "on time control" (70) by producing a signal synchronous with the RF oscillator, thereby reducing progresseively the "conduction state" of the gate (80) which connects the power supply with the oscillator. Switch mode power supply (66) can itself vary its output voltage as a function of signal (66) from the controller (72), the speed of variation however will be much slower than the one produced by "ON" time control mechanism.
Inventors
- 👤 Nigel Mark Goble
- 👤 Colin Charles Owen Goble
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 16:43
CPC Classifications
A; A61; A61B; A61B18/00; A61B18/04; A61B18/12; A61B18/14; A61B18/1485; A61B18/08; A61B18/082; A61B18/1206; A61B18/148; A61B18/1482; A61B18/1402; A61B18/149; A61B18/1492; A61B17/00; A61B2017/00477; A61B2017/00482; A61B2018/00053; A61B2018/00172; A61B2018/00178; A61B2018/00315; A61B2018/00505; A61B2018/00571; A61B2018/00589; A61B2018/00625; A61B2018/00636; A61B2018/00666; A61B2018/00696; A61B2018/00755; A61B2018/00773; A61B2018/00875; A61B2018/00892; A61B2018/00988; A61B2018/1213; A61B2018/1246; A61B2018/126; A61B2018/1405; A61B2018/1425; A61B2018/143; A61B2018/1432; A61B2018/1435; A61B2018/1472; A61B18/16; A61B2018/162; A61B18/18; A61B18/1815; A61B2018/1861; A61M; A61M2205/00; A61M2205/60; A61M2205/6018; A61M2205/6027
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
121 words
An electrosurgical generator for supplying radio frequency power to an electrical instrument, the generator comprising a radio frequency output stage having at least a pair of electrosurgical output connections for the delivery of radio frequency power to the instrument, a power supply coupled to the output stage for supplying power to the output stage, and control circuitry including sensing means for deriving a sensing signal representative of the radio frequency peak output voltage developed across the output connections, wherein the output stage comprises a resonant output circuit coupled to the output connections and a switching device coupled to the resonant output circuit, and wherein the control circuitry is operable to actuate the switching device to reduce the delivered radio frequency power.
Claim 2
Dependent Claim
97 words
A generator according to claim 1, wherein the switching device is connected between the resonant output circuit and one of a pair of supply rails of the power supply means, and connected so as to switch current repeatedly through the resonant output circuit at its resonant frequency, and wherein the control circuitry is so arranged and coupled to the switching device as to reduce the "on" time of the switching device during individual radio frequency switching cycles sufficiently rapidly to cause a 50% reduction in delivered output power within 100µs of the predetermined threshold having been reached.
Claim 3
Dependent Claim
24 words
A generator according to claim 1 or claim 2, wherein the switching device is a power oscillator device coupled to an oscillator feedback loop.
Claim 4
Dependent Claim
41 words
A generator according to any of claims 1 to 3, wherein the control circuitry is arranged to reduce the delivered radio frequency power by at least 50% in less than 100µs in response to the output voltage reaching a predetermined threshold.
Claim 5
Dependent Claim
130 words
An electrosurgical generator for supplying power to an electrosurgical instrument, the generator comprising a radio frequency output stage including a radio frequency power device and having at least a pair of electrosurgical output connections for delivery of radio frequency power to the instrument, a power supply coupled to the output stage, and control circuitry including sensing means for deriving a sensing signal representative of the load impedance across the output connections, the control circuitry having a first output coupled to the power device to reduce the radio frequency duty cycle thereof and a second output coupled to the power supply to effect a reduction in the average power supply voltage supplied to the output stage, the said reductions occurring in response to the sensing signal reaching a predetermined threshold value.
Claim 6
Dependent Claim
131 words
A generator according to claim 5, wherein the control circuitry has means including a ramp generator operable to cause a first control signal applied via the first output to the power device initially to reduce the said duty cycle to cause at least a 50% reduction in the power delivered via the output connections and then progressively to increase the duty cycle at a less rapid rate until the sensing signal once again reaches the threshold value, and to cause a second control signal applied to the power supply via the second output to reduce the average power supply voltage for at least a minimum predetermined time interval the duration of which is several times greater than the duration of a single power device duty cycle reduction and progressive increase sequence.
Claim 7
Dependent Claim
136 words
An electrosurgical system including a generator for generating radio frequency power and an electrosurgical instrument having at least one electrode for use immersed in a conductive liquid, wherein the generator comprises an output stage including a radio frequency power device and at least a pair of output connections arranged to receive radio frequency power from the power device, one of the pair of connections being connected to the said electrode, and wherein the generator further comprises a control stage operable to reduce the conduction time of the power device during individual radio frequency cycles in response to a sensing signal representative of the peak output voltage across the output connections exceeding a predetermined sensing signal threshold value, whereby the radio frequency power delivered to the electrode structure is rapidly reduced when the conductive liquid is vaporised.
Claim 8
Dependent Claim
93 words
A system according to claim 7, wherein the electrode structure includes a projecting treatment electrode and a liquid contact electrode spaced from the treatment electrode, both electrodes being for use surrounded by the conductive liquid and each being connected to a respective one of the pair of output connections, the control stage being operable to reduce the conduction time of the power device when the conductive liquid at the treatment electrode is vaporised thereby to cause the collapse of vapour bubbles at the treatment electrode and a decrease in the electrical load impedance.
Claim 9
Dependent Claim
56 words
A system according to claim 8, wherein the electrosurgical instrument has an electrode structure having juxtaposed first and second electrodes for immersion in a conductive liquid, the first and second electrodes respectively forming a tissue contact electrode at an extreme distal end of the instrument and a return electrode proximally spaced from the tissue contact electrode.
Claim 10
Dependent Claim
41 words
A system according to claim 8 or claim 9, wherein the generator output stage includes a resonant circuit coupled between the power device and the output connections, and having a resonant frequency corresponding to the frequency of operation of the generator.
Claim 11
Dependent Claim
115 words
An electrosurgical system operable in at least a tissue desiccation mode and a tissue cutting or vaporisation mode comprising a generator for generating radio frequency power and an electrosurgical instrument coupled to the generator, the instrument having an electrode structure for operation immersed in a conductive liquid, wherein the generator includes a mode selection control and has power control circuitry for automatically adjusting the radio frequency power suppled to the electrode structure to limit the peak generator output voltage to a first value when the desiccation mode is selected and to at least one second value when the cutting or vaporisation mode is selected, the second value or values being higher than the first value.
Claim 12
Dependent Claim
32 words
A system according to claim 11, wherein the first and second values are in the ranges of from 150V to 200V and from 250V to 600V respectively, the voltages being peak voltages.
Claim 13
Independent Claim
120 words
A method of operating an electrosurgical system having at least a tissue desiccation mode and a tissue cutting or vaporisation mode, the system having a radio frequency power generator coupled to an electrode assembly having an electrode for operation in a conductive liquid, wherein the method comprises: selecting one of the said modes; when the desiccation mode is selected, automatically adjusting the radio frequency power supplied to the electrode assembly to maintain the conductive liquid adjacent the electrode at its boiling point for tissue desiccation without creating a vapour pocket surrounding the electrode; and when the cutting or vaporisation mode is selected, automatically adjusting the radio frequency power supplied to the electrode to maintain a vapour pocket surrounding the electrode.
Claim 14
Dependent Claim
31 words
A method according to claim 13, wherein , in the cutting or vaporisation mode, the radio frequency power supplied to the electrode is automatically limited to prevent overheating of the electrode.
Claim 15
Dependent Claim
65 words
A method according to claim 14, wherein the radio frequency power supplied to the electrode is automatically adjusted by limiting the output voltage applied to the electrode to predetermined first and second voltage values, the first voltage value being used in the desiccation mode, and the second voltage value, which is higher than the first voltage value, being used in the cutting or vaporisation mode.
Claim 16
Dependent Claim
33 words
A method according to claim 15, wherein the first and second voltage values are in the ranges of from 150V to 200V and from 250V to 600V respectively, the voltages being peak voltages.
Claim 17
Independent Claim
102 words
A method of operating an electrosurgical system which has a generator coupled to an electrode assembly having an electrode for operation in a conductive liquid, wherein the method comprises applying radio frequency power to the electrode, monitoring an electrical signal related to the load impedance presented to the generator, and reducing the applied power when the said signal reaches a predetermined threshold value associated with an increased load impedance, whereby only sufficient radio frequency power is applied to the electrode to maintain the liquid adjacent the electrode at its boiling point for tissue desiccation without creating a vapour pocket surrounding the electrode.
Claim 18
Dependent Claim
20 words
A method according to claim 17, wherein the monitored electrical signal is the peak output voltage applied to the electrode.
Claim 19
Dependent Claim
30 words
A method according to claim 17 or claim 18, wherein the applied power is reduced by at least 50% within 100µs of the peak output voltage exceeding the predetermined threshold.
Claim 20
Independent Claim
36 words
A method according to any of claims 17 to 19, wherein the applied power is reduced by reducing the conduction period of a radio frequency output power device of the generator during individual radio frequency cycles.
Claim 21
Dependent Claim
50 words
A method according to claim 20, further including reducing the supply voltage supplied to the output power device simultaneously with the said reduction in the conduction period, and then progressively increasing the conduction period at a rate which is less than the rate at which the conduction period is reduced.
Claim 22
Dependent Claim
69 words
A method according to claim 20, wherein the generator has a switched mode power supply and the supply voltage reduction is achieved by disabling the output of a supply current switching device of the power supply for a whole number n of the power supply switching cycles, where n is greater than or equal to 1, until the said monitored electrical signal no longer reaches the predetermined threshold value.
Claim 23
Dependent Claim
114 words
An electrosurgical generator for supplying radio frequency power to an electrosurgical instrument, the generator comprising a radio frequency output stage having at least a pair of electrosurgical output connections for the delivery of radio frequency power to the instrument, means coupled to the output stage for supplying power to the output stage, and control circuitry including sensing means for deriving a sensing signal representative of the radio frequency output voltage developed across the output connections and means responsive to the sensing signal for causing a reduction in delivered output power independently of supply voltage or in addition to supply voltage reduction when the sensing signal is indicative of a predetermined threshold having been reached.
Claim 24
Dependent Claim
55 words
A generator according to claim 23, wherein the means for causing a reduction in delivered output power is operable to cause at least a 50% reduction in delivered output power when the sensing signal is indicative of the said threshold having been reached, the said reduction being effected within a period of 20µs or less.
Claim 25
Dependent Claim
37 words
A generator according to claim 24, wherein the response time of the control circuitry and the means coupled to the output stage to the radio frequency output voltage reaching the predetermined threshold is 100 µs or less.
Claim 26
Dependent Claim
44 words
A generator according to any of claims 23 to 25, wherein the means for causing a reduction in output power include a first control line coupled to the radio frequency output stage for feeding a first power reduction control signal to the said stage.
Claim 27
Dependent Claim
64 words
A generator according to claim 25 and claim 26, wherein the output stage includes at least one radio frequency power device and wherein the control circuitry is arranged such that the at least 50% reduction in output power is effected by reducing the period of conduction of the device during individual cycles of radio frequency oscillation independently of the supply voltage to the device.
Claim 28
Dependent Claim
65 words
A generator according to claim 26 or claim 27, wherein the means for causing a reduction in output power further include a second control line coupled to the power supply means, the control circuitry being arranged such that a second power reduction signal is fed to the power supply means to effect a reduction in the average power supply voltage supplied to the output stage.
Claim 29
Dependent Claim
102 words
A generator according to claim 27, wherein the means for causing a reduction in output power further include a second control line coupled to the power supply means, the control circuitry being arranged such that a second power reduction signal is fed to the power supply means to effect a reduction in the average power supply voltage supplied to the output stage, and wherein the power supply means comprises a switched mode power supply circuit with output smoothing components, and wherein the supply circuit is arranged such that the second power reduction control signal has the effect of disabling the supply circuit.
Claim 30
Dependent Claim
85 words
A generator according to claim 27, wherein the control circuitry is operable repeatedly to effect a rapid reduction in the cycle by cycle conduction period of the power device from a peak level to a trough level followed by a less rapid progressive increase in the conduction period until the conduction period again reaches its peak level, the rapid reduction and progressive increase sequence being repeated until the said peak conduction period level can be reached without the output voltage exceeding the said predetermined threshold.
Claim 31
Dependent Claim
38 words
A generator according to claim 30, wherein the control circuitry and the power supply means are arranged such that the power supply circuit is enabled when the said peak conduction period has been maintained for a predetermined time.
Claim 32
Dependent Claim
53 words
A generator according to claim 31, wherein the control circuitry and the power supply means are arranged such that the power supply circuit is disabled until the end of a switched mode switching cycle in which the output voltage has not reached the said predetermined threshold for the whole of the switching cycle.
Claim 33
Dependent Claim
52 words
A generator according to any of claims 23 to 32, wherein the output stage has at least one radio frequency power switching device and frequency selective components which in combination with the switching device are operable to produce an output voltage waveform having a crest factor less than or equal to 1.7.
Claim 34
Dependent Claim
21 words
A generator according to any of claims 23 to 33, wherein the sensing signal is representative of a peak output voltage.
Claim 35
Dependent Claim
41 words
A generator according to any of claims 23 to 34, wherein, at least in a desiccation mode of the generator, the said predetermined threshold is in the range of 150V to 200V peak and is set independently of the supply voltage.
Claim 36
Dependent Claim
61 words
A generator according to any of claims 23 to 35, wherein the control circuitry is arranged such that in a coagulation mode of the generator the output voltage is limited to a first said predetermined voltage threshold, and in a cut or tissue vaporisation mode of the generator the output voltage is limited to a higher, second said predetermined voltage threshold.
Claim 37
Dependent Claim
41 words
A generator according to claim 36, wherein the output stage has a power/load impedance characteristic which, for a constant average supply voltage, has a peak lying on the low impedance side of a line representative of the second predetermined voltage threshold.
Claim 38
Dependent Claim
71 words
A generator according to claim 37, wherein, in the cut or tissue vaporisation mode, the said generator power/load impedance characteristic lies between the line representative of a the second predetermined voltage threshold and a line representative of the first predetermined voltage threshold, and wherein in the coagulation mode the said characteristic has a peak which lies on the low impedance side of the line representative of the said first voltage threshold.
Claim 39
Dependent Claim
21 words
A generator according to any of claims 23 to 38, wherein the sensing means are coupled between the said output connections.
Claim 40
Dependent Claim
31 words
A generator according to claim 39, wherein the sensing means include a transformer having a primary winding coupled across one element of a potential divider connected across the said output connections.
Claim 41
Dependent Claim
42 words
A generator according to any of claims 23 to 40, having an output stage operable continuously in open loop configuration, and having an output impedance in the range of from 50 ohms to 250 ohms, and preferably between 130 and 190 ohms.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.