Method and apparatus for pulsed plasma-mediated electrosurgery in liquid media

A method for electrosurgically cutting tissue surrounded by liquid using an electrosurgical probe, wherein the electrosurgical probe has a first electrode and a second electrode, and wherein the first electrode has an endface with area A in close proximity to the tissue, the method comprising the step of:

• a) applying to the first electrode an electrical pulse such that plasma streamers are formed from the electrode endface by an electrical discharge, wherein the electrical discharge starts in the tissue or the liquid, wherein the endface area A is less than 10000 microns.sup.2, and wherein the electrical pulse has a pulse power dissipation with a peak power dissipation, wherein the pulse power dissipation:
• i) is greater than 500 Watts for a nonzero duration less than 300 nanoseconds,
• ii) rises from 10% of the peak power dissipation to 90% of the peak power dissipation in less than 100 nanoseconds;
• iii) falls from 90% of the peak power dissipation to 10% of the peak power dissipation in less than 200 nanoseconds.

A method for electrosurgically cutting tissue surrounded by liquid using an electrosurgical probe, wherein the electrosurgical probe has a first electrode and a second electrode, and wherein the first electrode has a endface with area A in close proximity to the tissue, the method comprising the step of:

• a) applying to the first electrode an electrical pulse such that plasma streamers are formed from the endface by an electrical discharge, wherein the electrical discharge starts in the tissue or the liquid, wherein the endface area A is less than 10000 microns.sup.2, and wherein the electrical pulse has a pulse voltage which:
• i) is at least 1.5 kilovolts for a nonzero duration less than 300 nanoseconds;
• ii) rises from 100 Volts to 1.5 kV in less than 100 nanoseconds;
• iii) falls from 1.5 kV to 100 Volts in less than 300 nanoseconds.

An apparatus for electrosurgically cutting tissue, comprising:

• a) a high voltage source for providing a voltage of at least 2 kiloVolts;
• b) a probe having a first electrode for applying a high voltage pulse to the tissue, and a second electrode;
• c) a discharge switch connected between the high voltage source and the first electrode so that, when closed, the discharge switch applies high voltage to the first electrode;
• d) a shunt switch connected between the first electrode and the second electrode.

An apparatus for electrosurgically cutting tissue, comprising:

• a) a high voltage source for providing a voltage of at least 2 kiloVolts;
• b) a probe having a first electrode for applying a high voltage pulse to the tissue, and a second electrode;
• c) a discharge switch connected between the high voltage source and the first electrode so that the discharge switch applies high voltage to the first electrode when closed;
• d) a shunt resistor connected between the first electrode and the second electrode, wherein the shunt resistor has a resistance less than a normal state resistance between the first electrode and second electrode.