RF ablation system and method having automatic temperature control

Abstract

A plurality of electrodes are positioned at the distal end of a catheter such that the electrodes may be positioned proximal biological tissue. A select number of the electrodes have a temperature sensing device associated with them for providing a temperature signal indicative of the temperature at the interface between the electrode and the tissue. A generator operates under the control of a processor to apply power to each of the electrodes. The power has an associated phase angle and, within a time duration, a plurality of alternating on periods and off periods, one set of adjacent on and off periods defining a duty cycle. The processor is programmed to determine the temperature at the electrode/tissue interface based on the temperature signals, compare the temperature to a target temperature and to adjust the power to the electrode accordingly. Such adjustments may comprise an increase or decrease in the duty cycle, a setting of the duty cycle to zero followed by an incremental increase in the duty cycle or a power interrupt.

What is claimed is:  
     
         1 . A system for delivering energy to biological tissue, said system comprising: 
 a plurality of electrodes adapted to be positioned at the biological tissue;    at least one temperature sensing device located on at least one of the electrodes for providing a temperature signal indicative of the temperature at the interface between the at least one electrode and the tissue; and    a power control system adapted to: 
 apply power to each of the electrodes such that a voltage potential is established between at least two of the electrodes, the power having a duty cycle;  
 in response to the temperature signal, determine the temperature at the at least one electrode/tissue interface;  
 compare the interface temperature to a target temperature; and  
 adjust the duty cycle of the power provided to the at least one electrode in response to the comparison.  
   
     
     
         2 . The system of  claim 1  wherein the power control system is adapted to increase the duty cycle of the power to the at least one electrode when the at least one electrode/tissue interface temperature is less than the target temperature.  
     
     
         3 . The system of  claim 1  wherein the power control system is adapted to decreases the duty cycle of the power to the at least one electrode when the at least one electrode/tissue interface temperature is greater than the target temperature.  
     
     
         4 . The system of  claim 1  wherein the power control system is adapted to: 
 set the power to the at least one electrode to zero when the at least one electrode/tissue interface temperature is a specified first number of degrees greater than the target temperature; and  
 incrementally increase the power level to the at least one electrode until the interface temperature is near the target temperature.  
 
     
     
         5 . The system of  claim 4  further comprising: 
 a power interruption device connected to the power control system;  
 wherein the power control system is further adapted to control the power interruption device to interrupt power to the at least one electrode when the at least one electrode/tissue interface temperature is a specified second number of degrees greater than the target temperature, the second number of degrees being greater than the first number of degrees.  
 
     
     
         6 . The system of  claim 1  wherein: 
 the system comprises a plurality of temperature sensing devices, at least one device associated with each of the electrodes, each device for providing a temperature signal to the power control system indicative of the temperature at the associated electrode; and  
 the power control system provides separate power to each of the plurality of electrodes with the power being individually controllable as to duty cycle and the duty cycle of each separate power is controlled in response to the temperature signal from the associated electrode.  
 
     
     
         7 . The system of  claim 7  wherein the power has an associated phase angle and the voltage potential is established between the at least two electrodes by providing power with different phase angles to the electrodes.  
     
     
         8 . A method of delivering energy to biological tissue, said method comprising: 
 positioning a plurality of electrodes adjacent the biological tissue, at least one of the electrodes carrying a temperature sensing device for providing a temperature signal indicative of the temperature at the interface between the electrode and the tissue;    establishing a voltage potential between at least two of the electrodes using duty cycled power;    determining the temperature at the at least one electrode/tissue interface in response to the temperature signal;    comparing the at least one electrode/tissue interface temperature to the target temperature; and    adjusting the duty cycle of the power provided to the at least one electrode in response to the comparison.    
     
     
         9 . The method of  claim 8  wherein positioning a plurality of electrodes comprises positioning a catheter carrying the electrodes proximal the tissue such that a select number of the plurality of electrodes are in contact with the tissue.  
     
     
         10 . The method of  claim 8  further comprising increasing the duty cycle of the power to the at least one electrode when the at least one electrode/tissue interface temperature is less than the target temperature.  
     
     
         11 . The method of  claim 8  further comprising decreasing the duty cycle of the power to the at least one electrode when the at least one electrode/tissue interface temperature is greater than the target temperature.  
     
     
         12 . The method of  claim 8  further comprising: 
 setting the power to the at least one electrode to zero when the at least one electrode/tissue interface temperature is a specified first number of degrees greater than the target temperature; and  
 incrementally increasing the power level to the at least one electrode until the interface temperature is near the target temperature.  
 
     
     
         13 . The method of  claim 12  further comprising interrupting the power to the at least one electrode when the at least one electrode/tissue interface temperature is a specified second number of degrees greater than the target temperature, the second number of degrees being greater than the first number of degrees.  
     
     
         14 . The method of  claim 8  wherein each of the electrodes carries a temperature sensing device and the method further comprises: 
 providing separate power to each of the plurality of electrodes; and  
 individually controlling the duty cycle of each separate power in response to the temperature signal from the electrode.  
 
     
     
         15 . The method of  claim 8  wherein the power has an associated phase angle and establishing the voltage potential between the at least two electrodes comprises providing power with different phase angles to the electrodes.  
     
     
         16 . A system for delivering energy to biological tissue, said system comprising: 
 a plurality of electrodes adapted to be positioned at the biological tissue;    at least one temperature sensing device located on at least one of the electrodes for providing a temperature signal indicative of the temperature at the interface between the at least one electrode and the tissue; and    a power control system adapted to: 
 apply power to each of the electrodes such that at least two of the electrodes are provided power with different phase angles;  
 in response to the temperature signal, determine the temperature at the at least one electrode/tissue interface;  
 compare the interface temperature to a target temperature; and  
 adjust the power provided to the at least one electrode in response to the comparison.  
   
     
     
         17 . The system of  claim 16  wherein the power control system is adapted to increase the power to the at least one electrode when the at least one electrode/tissue interface temperature is less than the target temperature.  
     
     
         18 . The system of  claim 16  wherein the power control system is adapted to decreases the power to the at least one electrode when the at least one electrode/tissue interface temperature is greater than the target temperature.  
     
     
         19 . The system of  claim 16  wherein the power control system is adapted to: 
 set the power to the at least one electrode to zero when the at least one electrode/tissue interface temperature is a specified first number of degrees greater than the target temperature; and  
 incrementally increase the power to the at least one electrode until the interface temperature is near the target temperature.  
 
     
     
         20 . The system of  claim 19  further comprising: 
 a power interruption device connected to the power control system;  
 wherein the power control system is further adapted to control the power interruption device to interrupt power to the at least one electrode when the at least one electrode/tissue interface temperature is a specified second number of degrees greater than the target temperature, the second number of degrees being greater than the first number of degrees.