Method for low temperature electrosugery and rf generator

Abstract

Method and apparatus for electrosurgery including tissue coagulation using very high voltage pulses of electrical energy applied to the electrosurgical probe. This minimizes heating of the surrounding tissue in the probe and is especially suitable for precise and limited coagulation and fulguration without excessive tissue charring or other damage. The power at rated load of the applied pulses to the probe is typically over 300 W and the duration of the on time is very short, so each group of pulse bursts is of relatively low duty cycle. An RF generator is also provided for delivering electrical energy to an electrosurgical probe with the proper characteristics, including fast switching times.

1 . A method of coagulating tissue, comprising the acts of:
 applying groups of bursts of pulsed electrical energy to a probe in contact with the tissue;   each group of bursts having a power of at least 300 W at a rated load during an on time and zero during an off time, the RF groups of bursts being of frequency in a range of 100 kHz to 5000 kHz and each group of bursts having a duty cycle in a range of 1% to 50%;   applying a plurality of the bursts in succession;   and providing an interval between successive pluralities of the bursts of at least 1 msec.   
     
     
         2 . The method of  claim 1 , wherein a temperature of the probe remains below 100° C. 
     
     
         3 . The method of  claim 1 , wherein a tip of the probe is of metal with an insulation layer thereover, the insulation defining on a side of the probe a plurality of openings to expose the metal. 
     
     
         4 . The method of  claim 3 , wherein each opening has a diameter in the range of 0.02 mm to 0.010 mm. 
     
     
         5 . The method of  claim 3 , wherein at an edge of the probe the insulation defines an opening to expose the metal. 
     
     
         6 . Electrosurgery apparatus, comprising:
 a probe adapted to be applied to tissue; and   a source of electrical energy electrically coupled to the probe, the source applying groups of bursts of pulsed electrical energy to the probe;   each group of bursts having a power of at least 300 W at rated load during an on time and zero during an off time, the RF groups of bursts being of frequency in a range of 100 kHz to 5000 kHz and each group of bursts having a duty cycle in a range of 1% to 50%;   the source applying a plurality of the bursts in succession;   and the source providing an interval between successive pluralities of the bursts of at least 1 msec.   
     
     
         7 . A circuit to generate high frequency signals, comprising:
 a first channel and a second channel, each including a switching transistor, an output terminal of each transistor being coupled to a common output node;   a control terminal of each transistor being coupled to an output terminal of a driver; and   an input terminal of each driver being coupled to a source of a negative voltage bias;   wherein the first channel provides positive going signals at the common output node and the second channel provides negative going signals at the common output node.   
     
     
         8 . The circuit of  claim 7 , further comprising coupling the input terminal of each driver to ground. 
     
     
         9 . The circuit of  claim 8 , further comprising:
 a current driver circuit having an output terminal coupled to the input terminal of each driver.   
     
     
         10 . The circuit of  claim 8 , further comprising a current protection circuit coupled to each channel.