Electrical discharge devices and techniques for medical procedures
A medical instrument coupled to first and second energy means and a computer controller for the controlled volumetric removal of thin tissue layers. The system provides a source for introducing a gas to controllably form and capture transient gas volumes in a microchannel structure at the working surface of the instrument that interfaces with a targeted tissue site. Each of the microchannel features of the working surface carries an electrode element coupled to the electrical source. The energy may be applied to the targeted site in either of two modes of operation, depending in part on voltage and repetition rate of energy delivery. In one mode of energy application, electrical potential is selected to cause an intense electrical arc across the transient ionized gas volumes to cause an energy-tissue interaction characterized by tissue vaporization. In another preferred mode of energy delivery, the system applies selected levels of energy to the targeted site by means of an energetic plasma at the instrument working surface to cause molecular volatilization of surface macromolecules thus resulting in material removal. Both modes of operation limit collateral thermal damage to tissue volumes adjacent to the targeted site. Another preferred embodiment provides and an ultrasound source or other vibrational source coupled to the working end to cause cavitation in fluid about the working end.
1. A method for modifying tissue, comprising the steps of:
positioning an instrument working end in a fluid immersed site proximate to targeted tissue wherein the working end includes at least one electrode;
applying vibrational energy to the working end thereby creating at least one bubble in the fluid; and
applying electrical energy from said at least one electrode across said at least one bubble to thereby modify the targeted tissue.
2. The method of claim 1 , wherein said vibrational energy comprises ultrasonic vibration.
3. The method of claim 1 , further including introducing a gas through at least one outlet in the working end.
4. A medical device for delivering energy to targeted tissue, comprising:
a member defining a distal working surface;
at least one electrode element carried in said working surface; and
a vibration source coupled to said working surface wherein the working surface is configured to generate a cavitation bubble in a fluid contacting the working surface when the member is energized by the vibration source to create a standing wave in the member.
5. The medical device of claim 4 , wherein the vibration source is an ultrasonic source.
6. The medical device of claim 4 , wherein the member includes a tuned acoustic transmission assembly.
7. The medical device of claim 4 , further comprising at least one channel with an open distal termination in said working surface.
8. The medical device of claim 7 , further comprising a gas source coupled to the at least one channel.
9. The medical device of claim 4 , further comprising a light energy channel with a distal termination in the working surface.
10. The medical device of claim 7 , wherein said at least one channel has an open distal termination with a cross-sectional dimension less than 1 μm.
11. The medical device of claim 7 , wherein said at least one channel has an open distal termination with a cross-sectional dimension less than 0.5 μm.
12. The medical device of claim 7 , wherein said at least one channel defines a cross-sectional dimension that prevents fluid flows therethrough.
13. The medical device of claim 12 , wherein said at least one channel defines a cross-sectional dimension that allows gas flows therethrough.
14. The medical device of claim 4 , wherein the working surface includes at least one concavity.
15. The medical device of claim 4 , wherein the working surface includes an electrode coupled to a first pole of an electrical source.
16. The medical device of claim 4 , wherein the working surface includes first and second electrodes coupled to first and second opposing poles of an electrical source.
17. The medical device of claim 4 , wherein the member has a length configured to produce an anti-node characteristic at the working surface.