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.

Description

FIELD OF THE INVENTION[0001]This invention relates to electrosurgery for biological tissue.BACKGROUND OF THE INVENTION[0002]The field of electrosurgery is well known, see for instance, Palanker U.S. Pat. No. 7,238,185 and Palanker, et al. U.S. Pat. No. 6,780,178 both incorporated herein in their entireties. Briefly, application of a voltage to an electrode is useful for cutting, ablating and fulgurating biological tissue. This is generally known as electrosurgery. Typically the voltage is applied as a train of high frequency pulses in the radio frequency (RF) range to a probe in contact with the tissue.[0003]A problem with electrosurgery is preventing excessive application of heat to the tissue being cut, fulgurated, dessicated, etc. since this tends to produce undesirable affects such as charring and collateral tissue damage. This is typically caused by high temperatures induced by the application of the electrical energy.[0004]Some highly localized high temperature is required dur...

AI Technical Summary

Benefits of technology

[0005]In accordance with this invention, a method and apparatus for pulsed applications of heat in electrosurgery provide sufficient peak temperature for tissue coagulation (and “blend” cutting) and allow for cooling of tissue between the application of electrical energy pulses, so avoiding excessive heating. Typically groups of pulse bursts are separated by a time interval sufficient for cooling both the probe and immediately neighboring tissue to close to ambient temperature.

[0006]In one embodiment this is achieved by using RF high power groups of pulse bursts, such as power levels of 300 W or higher during on time and zero during off time, the groups of bursts being of high frequency such as 100 kHz to 5000 kHz and each group of bursts having a duty cycle in the range of 1% to 50%. Duty cycle refers to the ratio of time when RF power is applied to the rated load to the full duration of the group of bursts. According to this definition a sine wave has a 100% duty cycle. For coagulation and blend cutting electrosurgery, the sine wave cycles (on time) occupy a short time in each burst, with a substantial part of each burst having no RF energy present (off time). A number of such bursts are grouped together, with an interval of at least 1 millisecond between each group of bursts, to allow for tissue cooling. Each burst of pulses has enough electrical power to rapidly heat the tissue to temperatures adequate for coagulation.

Problems solved by technology

A problem with electrosurgery is preventing excessive application of heat to the tissue being cut, fulgurated, dessicated, etc. since this tends to produce undesirable affects such as charring and collateral tissue damage.

This is typically caused by high temperatures induced by the application of the electrical energy.

Typically dessication occurs below or close to 100° C. and fulguration at higher temperatures above 100° C. A high temperature during fulguration outside the immediate area being treated results in undesirable tissue charring and buildup of debris on the electrosurgical probe, which decreases its efficiency of coagulation.

This may also result in adhesion of charred tissue to the probe and damage to the areas of the probe with low melting temperatures such as plastic components.

Also, high temperature may result in smoke obscuring the surgical field, especially for laparoscopic procedures.

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