Electrosurgery system

Abstract

An electrosurgery system includes an electrosurgical generator ( 10 ) coupled to or part of an electrosurgical instrument, the generator being operable to generate electrosurgical power in low frequency (typically at 1 MHz) and high frequency bands (typically at 2.45 GHz) either simultaneously or individually. The generator includes a load-responsive control circuit which, in one mode, causes power to be generated predominantly at 1 MHz when the load impedance is high and predominantly at 2.45 MHz when it is low. This allows automatic switching between cutting and coagulation operation. In one embodiment, the instrument includes a gas plasma generator operating such that an ionisable gas is energised in a gas supply passage by the 2.45 GHz component to form a plasma stream which acts as a conductor for delivering the 1 MHz component to a tissue treatment outlet of the passage.

1 . An electrosurgery system comprising an electrosurgical generator, a feed structure and an electrode assembly, the electrode assembly having at least one active electrode and at least one adjacent return electrode, each of which is coupled to the generator via the feed structure, wherein the generator and feed structure are capable of delivering radio frequency (r.f.) power to the active and return electrodes in lower and upper frequency ranges, the upper range containing frequencies at least three times the frequencies of the lower frequency range.  
     
     
         2 . A system according to  claim 1 , wherein the lower frequency range is 100 kHz to 100 MHz and the upper frequency range is 300 MHz to 10 GHz.  
     
     
         3 . A system according to  claim 2 , wherein upper frequency range is above 1 GHz and the operating frequencies in the said upper and lower ranges have a frequency ratio of 5:1 or greater.  
     
     
         4 . A system according to  claim 2 , wherein the generator is arranged such that the r.f. power delivered in the upper frequency range is at a fixed frequency which is at least ten times the frequency of r.f. power delivered in the lower frequency range.  
     
     
         5 . A system according to  claim 4 , wherein the fixed frequency is fixed to the extent that it remains within 50 MHz of 2.45 GHz.  
     
     
         6 . A system according to  claim 1 , wherein the generator and feed structure are arranged to deliver r.f. power to the electrodes in the lower and upper frequency ranges simultaneously.  
     
     
         7 . A system according to  claim 1 , wherein the generator includes a control circuit responsive to electrical load and operable to cause the delivered power to have a predominant frequency component in the lower frequency range when the load impedance is in an upper impedance range and to have a predominant frequency component in the upper frequency range when the load impedance is in a lower impedance range.  
     
     
         8 . A system according to  claim 1 , comprising a supply unit, a handpiece, and a cable connecting the handpiece to the supply unit, wherein: 
 the electrode assembly is mounted in the handpiece,    the generator has first and second stages for generating power in the lower and upper frequency ranges respectively, both stages being contained in the supply unit, and    the supply unit and the cable are configured such that power is supplied to the handpiece in both the lower and the upper frequency range via the cable.    
     
     
         9 . A system according to  claim 1 , comprising a supply unit, a handpiece, and a cable connecting the handpeice supply unit, wherein 
 the electrode assembly is mounted in the handpiece, and    the generator has first and second stages for generating power in the lower and upper frequency ranges respectively, the fir stage being contained in the supply unit and the second stage being contained in the combination of the handpiece and the electrode assembly.    
     
     
         10 . A system according to  claim 1 , wherein the feed structure comprises: 
 a rigid or resilient coaxial feed supporting the electrodes at a distal end, the coaxial feed having an inner supply conductor and an outer supply conductor, and    an isolating choke element in the form of a conductive sleeve connected to the outer supply conductor in the region of the said distal end, and having an axial length which is an odd number multiple (1, 3, 5, . . . ) of a quarter wavelength at an operating frequency of the generator in the upper frequency band.    
     
     
         11 . A system according to  claim 1 , wherein the return electrode comprises a conductive sleeve.  
     
     
         12 . A system according to  claim 11 , wherein: 
 the active electrode comprises a rod projecting from the conductive sleeve;    the feed structure comprises a rigid or resilient coaxial feed; and    the active electrode and the return electrode are connected to the inner and outer conductors respectively of the feed at its distal end, and extend respectively distally and proximally with respect to the said connection to form a dipole at an operating frequency of the generator in the upper frequency range.    
     
     
         13 . A system according to  claim 1 , wherein the return electrode is covered with a electrically insulative layer.  
     
     
         14 . A system according to  claim 1 , wherein the electrode assembly includes a gas supply passage and the active electrode is located in the passage to act as a gas iodising electrode.  
     
     
         15 . A system according to  claim 6 , wherein the electrode assembly includes a gas supply passage and the active electrode is located in the passage to act as a gas ionising electrode, and wherein the active electrode is an elongate conductor having an electrical length in the region of a quarter wavelength at the operating frequency of the generator in the upper frequency range.  
     
     
         16 . A system according to  claim 14 , wherein the active electrode is capacitively coupled to the return electrode.  
     
     
         17 . A method of operating an electrosurgical instrument having an electrode assembly with an active electrode and a return electrode, comprising delivering to the electrodes radio frequency (r.f.) power at frequencies in both a lower frequency range and an upper frequency range, the upper frequency range containing frequencies which are at least three times the frequencies of the lower frequency range.  
     
     
         18 . A method according to  claim 17 , wherein the lower frequency range is 100 kHz to 100 MHz and the upper frequency range is 300 M to 10 GHz, power being delivered to the electrodes at upper and lower operating frequencies which have a frequency ratio of at least 5:1.  
     
     
         19 . A method according to  claim 18 , wherein the r.f. power delivered in the upper frequency range is at a fixed frequency which is at least ten times the frequency of power delivered in the lower frequency range.  
     
     
         20 . A method according to  claim 19 , wherein the fixed frequency is in the region of 2.45 GHz.  
     
     
         21 . A method according to  claim 17 , comprising delivering r.f. power to the electrodes in the lower and upper frequency ranges simultaneously.  
     
     
         22 . A method according to  claim 19 , wherein the r.f. power is delivered in the lower and upper frequency ranges via a common feed.  
     
     
         23 . A method according to  claim 17 , including automatically controlling the delivered power in response to electrical load impedance such that the delivered power has a predominant frequency component in the lower frequency range when the load impedance is in an upper impedance range and a predominant frequency component in the upper frequency range when the load impedance is in a lower impedance range.  
     
     
         24 . A method according to  claim 17 , in which an ionisible gas is passed through a passage containing the active electrode, the gas is ionised by delivering power to the electrodes in the said upper frequency range to form a gas plasma in the passage, and causing the gas plasma to emerge at a treatment outlet of the passage.  
     
     
         25 . A method according to  claim 24 , in which r.f. power is delivered to the electrodes simultaneously in both the upper and the lower frequency ranges, the emerging gas plasma generated by power in the upper frequency range acting as a conductor to the outside for treatment current in the lower frequency range.  
     
     
         26 . A method according to  claim 17 , wherein the return electrode acts as a capacitive non-tissue-contacting electrosurgical current return element.  
     
     
         27 . A method according to  claim 21 , in which the amplitudes of the delivered r.f. power in the lower and upper frequency ranges are varied with respect to each other.  
     
     
         28 . A dual frequency electrosurgical system for cutting living tissue, the system being arranged to operate normally in a low frequency cutting or vaporisation mode, but to operate in a UHF coagulation mode in response to detection of a lower than normal load impedance as would typically be encountered when a blood vessel is severed.  
     
     
         29 . A system according to  claim 28 , wherein the system comprises an electrosurgical generator, an electrode assembly and at least fist and second supply conductors coupling the electrode assembly to the generator, the electrode assembly comprising at least one active electrode and a capacitive return element adjacent the active electrode, and the active electrode and the return element being coupled to the generator by the first and second supply conductors respectively.  
     
     
         30 . A system according to  claim 28 , arranged to operate predominantly at a first frequency in the range of from 100 kHz to 40 MHz when in the low frequency cutting mode and predominantly at a second frequency above 300 MHz when in the UHF coagulation mode.  
     
     
         31 . A system according to  claim 30 , wherein the first frequency is less than 10 MHz and the second frequency is greater than 1 GHz.  
     
     
         32 . A method of electrosurgically treating tissue using an electrosurgical instrument having an electrode assembly with an active electrode and an adjacent return element set back from the active electrode, wherein electrosurgical cutting or vaporisation is performed by supplying electrosurgical energy to the assembly in a lower frequency range and electrosurgical coagulation is performed by supplying electrosurgical energy to the assembly in an upper frequency range, the upper frequency range containing frequencies which are at least three times the frequencies of the lower frequency range.  
     
     
         33 . A method of electrosurgically treating tissue using an electrosurgical instrument having a electrode assembly with an active electrode and an adjacent return element set back from the active electrode, wherein the active electrode is applied to the tissue to be treated and manipulated whilst r.f. electrosurgical energy is supplied to the assembly predominantly in a lower frequency range at a voltage level sufficient to cause cutting or vaporisation of the tissue until the load impedance drops to a predetermined degree at which time the energy is supplied predominantly in an upper frequency range to cause coagulation of the tissue, the supplied energy reverting predominantly to the lower frequency range when the load impedance rises again, and wherein the upper frequency range contains frequencies which are at least three times the frequencies of the lower frequency range.  
     
     
         34 . A method according to  claim 33 , wherein treatment in the lower and upper frequency ranges is performed respectively with and without arcing in a current path between the active electrode and the return element.  
     
     
         35 . A method according to  claim 33 , wherein the lower frequency range is from 100 kHz to 40 MHz and the upper frequency range is from 300 M to 10 GHz.  
     
     
         36 . A method according to  claim 33 , wherein the predominant frequency of the r.f. electrosurgical energy associated with said coagulation is at least ten times the predominant frequency of the r.f. electrosurgical energy associated with said cutting or vaporisation.  
     
     
         37 . A dual frequency electrosurgical system configured to perform electrosurgical cutting or vaporisation at a first frequency within a lower frequency range and electrosurgical coagulation at a second frequency within an upper frequency UHF range.  
     
     
         38 . A system according to  claim 37 , wherein the first frequency is within the range of from 100 kHz to 5 MHz and the second frequency is within the range of from 300 MHz to 10 GHz.  
     
     
         39 . An electrosurgical system comprising an electrode assembly with at least a pair of electrodes for receiving radio-frequency electrosurgical power, and a gas supply passage containing at least one of the said electrodes, the arrangement of the electrodes and the passage being such that when the electrodes are energised with sufficient radio frequency power at a frequency in the range of from 300 MHz to 10 GHz, and when an ionisable gas is passed through the passage, a gas plasma is formed in the passage.  
     
     
         40 . A system according to  claim 39 , wherein the passage terminates in a distal nozzle downstream of the said at least one electrode.  
     
     
         41 . A system according to  claim 39 , wherein the electrode assembly is part of a sterilised electrosurgical device.  
     
     
         42 . A system according to  claim 39 , including a generator coupled to the electrodes and operable to generate electrosurgical power at a frequency in the range of from 300 MHz to 10 GHz.  
     
     
         43 . A method of operating an electrosurgical instrument having at least a pair of electrodes, at least one of which is located in a gas supply passage, comprising delivering to the electrodes radio frequency power at a frequency in the range of from 300 GHz to 10 GHz and passing an ionisable gas through the passage to form a gas plasma in the passage.  
     
     
         44 . A method according to  claim 42 , fisher comprising causing the gas plasma to emerge at a treatment outlet of the passage.