Method and apparatus for radiofrequency ablation with increased depth and/or decreased volume of ablated tissue

Abstract

A method of ablating a tissue site includes at least two stages. A first stage involves conducting bipolar ablation between a first pair of electrodes situated in an opposing arrangement on opposing sides of the tissue site to form a pair of opposing first stage ablation regions extending from respective sides of the tissue towards the center. A second stage involves conducting bipolar ablation between a second pair of electrodes situated in a diametrical arrangement with respect to the first stage ablation regions, which forms a second stage ablation region intermediate the pair of first stage ablation regions. The second stage completes the ablation through the entire depth of the tissue site. Since the overall process can accommodate incomplete ablation during the first stage, lower power, reduced ablation times or both may be used during the first stage, avoiding overheating and with a decrease in ablated tissue volume.

1 .- 21 . (canceled) 
     
     
         22 . An apparatus, comprising:
 means for conducting bipolar ablation between a first pair of electrodes in an opposing arrangement on opposing sides of the tissue site so as to form a pair of opposing first stage ablation regions in the site during a first stage; and   means for conducting bipolar ablation between a second pair of electrodes in a diametrical arrangement with respect to the first stage ablation regions to form a second stage ablation region intermediate said first stage ablation regions during a second stage.   
     
     
         23 . An apparatus according to  claim 22 , wherein the diametrical arrangement comprises a first diametrical arrangement, and further comprising:
 means for conducting bipolar ablation during the second stage between a third pair of electrodes in a second diametrical arrangement with respect to the first stage ablation regions.   
     
     
         24 . An apparatus according to  claim 22 , wherein the second pair of electrodes comprises a different pair from the third pair of electrodes. 
     
     
         25 . An apparatus according to  claim 22 , wherein the second stage comprises a first interval and a second interval and wherein said means for conducting bipolar ablation during the second stage further comprises:
 means for conducting bipolar ablation during the first interval using the second pair of electrodes in the diametrical arrangement;   means for moving the second pair of electrodes to a second diametrical arrangement; and   means for conducting bipolar ablation during the second interval using the second pair of electrodes in the second diametrical arrangement.   
     
     
         26 . The apparatus of  claim 22  wherein said pair of opposing first stage ablation regions in the site extend from respective sides of said tissue site towards a center of said tissue site, said first stage being conducted in accordance with at least one of a selected power and time duration parameter such that upon termination of said first stage ablation, said pair of opposing first stage ablation regions together extend less than said depth of said tissue site; and
 wherein said second stage ablation region is in the center of said tissue site and is different than said first stage ablation regions wherein said second stage ablation regions completes the ablation through the entire depth of said tissue site. 
 
     
     
         27 . The apparatus of  claim 26  wherein said second stage occurs after termination of said first stage. 
     
     
         28 . The apparatus of  claim 26  wherein said means for conducting bipolar ablation between said first pair of electrodes and said means for conducting bipolar ablation between said second pair of electrodes, comprises a radio frequency (RF) ablation generator including a main controller and an RF power source selectively coupled to said first and second pairs of electrodes, said main controller being configured to control the operation of said RF power source. 
     
     
         29 . The apparatus of  claim 28  wherein said main controller is configured to control operation of said RF power source in accordance with a plurality of inputs received from a user thereof through a user interface. 
     
     
         30 . The apparatus of  claim 28  wherein said main controller is configured to interact with an impedance detection circuit to obtain data indicative of an impedance value measured through or using one or more of the electrodes. 
     
     
         31 . The apparatus of  claim 28  wherein said main controller is further configured to control a switching function block to make connections between said RF power source and said first and second pair of electrodes. 
     
     
         32 . The apparatus of  claim 28  wherein said main controller is configured to control said RF power source so as to provide power in counter-phase to the electrodes of at least one of said first and second pairs of electrodes. 
     
     
         33 . The apparatus of  claim 32  wherein said main controller is further configured to control said RF power source so as to apply a first signal to one of the electrodes of said at least one first and second electrode pairs and to apply a second signal to the other one of the electrodes of said at least one first and second electrode pairs, wherein said first and second signals are offset in phase by 180 electrical degrees. 
     
     
         34 . The apparatus of  claim 33  wherein said first and second signals are alternating current (AC) signals having a predetermined frequency. 
     
     
         35 . The apparatus of  claim 34  wherein said predetermined frequency is in the radio frequency (RF) range between about 50 kHz and 500 kHz. 
     
     
         36 . The apparatus of  claim 28  wherein said RF ablation generator is configured to power said first pair of electrodes at a substantially constant power. 
     
     
         37 . The apparatus of  claim 28  wherein said main controller is configured to monitor an impedance of said tissue site as detected by an impedance detection circuit and discontinue bipolar ablation during said first stage when said monitored impedance satisfies predetermined criteria. 
     
     
         38 . The apparatus of  claim 37  wherein said predetermined criteria includes a saturation condition. 
     
     
         39 . An apparatus, comprising:
 a main controller; and   an RF power source configured to be coupled to a first pair of electrodes and to a second pair of electrodes;   wherein said main controller is configured to control the operation of said RF power source for conducting bipolar ablation between said first pair of electrodes in an opposing arrangement on opposing sides of a tissue site so as to form a pair of opposing first stage ablation regions in said site during a first stage and for conducting bipolar ablation between said second pair of electrodes in a diametrical arrangement with respect to said first stage ablation regions to form a second stage ablation region intermediate said first stage ablation regions during a second stage.   
     
     
         40 . The apparatus of  claim 39  wherein said pair of opposing first stage ablation regions in said site extend from respective sides of said tissue site towards a center of said tissue site, said main controller being configured to conduct said first stage in accordance with at least one of a selected power and time duration parameter such that upon termination of said first stage ablation, said pair of opposing first stage ablation regions together extend less than said depth of said tissue site; and
 wherein said second stage ablation region is in the center of said tissue site and is different than said first stage ablation regions wherein said second stage ablation region completes the ablation through the entire depth of said tissue site. 
 
     
     
         41 . The apparatus of  claim 40  wherein said main controller is further configured to control a switching function block to make connections between said RF power source and said first and said second pair of electrodes, said main controller is further configured to control operation of said RF power source in accordance with a plurality of inputs received from a user thereof through a user interface, and wherein said main controller is further configured to monitor an impedance of said tissue site as detected by an impedance detection circuit and discontinue bipolar ablation during said first stage when said monitored impedance satisfies predetermined criteria comprising saturation.