Electrical discharge devices and techniques for medical procedures

Abstract

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 medical device for delivering energy to targeted tissue, comprising: 
 an elongated member having a distal working end;    an interior flow channel having a first cross-section, the flow channel transitioning to at least one channel portion having a second smaller cross-section and terminating in at least one outlet in the distal working end;    at least one electrode element carried in said working end; and    a conductive flow media source for providing a flow through the interior flow channel, and wherein the electrical energy delivery to the flow proximate the at last one outlet creates a plasma for ablation of tissue.    
   
   
       2 . The medical device of  claim 1  further comprising a vibration source coupled to the elongated member.  
   
   
       3 . The medical device of  claim 1  further comprising a vibration source coupled to the working end.  
   
   
       4 . The medical device of  claim 1  wherein the at least one channel portion comprises one substantially linear channel.  
   
   
       5 . The medical device of  claim 1  wherein the at least one channel portion comprises a plurality of substantially linear channels.  
   
   
       6 . The medical device of  claim 1  wherein the at least one channel portion comprises a microporous structure.  
   
   
       7 . The medical device of  claim 1  wherein the working end is a ceramic.  
   
   
       8 . The medical device of  claim 1  wherein the at least one channel portion has a mean cross section across a principal axis of less than about 1000 microns.  
   
   
       9 . The medical device of  claim 1  wherein the at least one channel portion has a mean cross section across a principal axis of less than about 500 microns.  
   
   
       10 . The medical device of  claim 1  wherein the at least one channel portion has a mean cross section across a principal axis of less than about 250 microns.  
   
   
       11 . The medical device of  claim 1  wherein the flow media comprises saline solution.  
   
   
       12 . The medical device of  claim 1  wherein the flow media comprises hypertonic saline solution.  
   
   
       13 . The medical device of  claim 1  further including first and second polarity electrical terminals for coupled electrical energy to the flow media.  
   
   
       14 . The medical device of  claim 13  wherein the first polarity electrical terminal is within the interior channel.  
   
   
       15 . The medical device of  claim 13  wherein the first polarity electrical terminal is within the on an exterior of the working end.