Current control methods and systems

Abstract

Apparatus, systems, and methods of controlling energy delivered to electrodes used in electrically and/or thermally induced neuromodulation are provided to improve neuromodulation. In particular, a catheter treatment device having a control algorithm that regulates current or current density delivered to an electrode is provided. The electrode may maintain a known and consistent electrode contact surface area with the vessel. The control algorithm controls energy delivery to provide consistent current or current density to the treatment site, even though the tissue impedance Z may vary from patient to patient and vessel to vessel, and despite changes in impedance of the treatment site during the course of the treatment. The controlled delivery of energy can be used to control and maintain placement of the zone of thermal treatment and reduce undesirable energy delivery to unwanted locations near the treatment site.

1 - 20 . (canceled) 
     
     
         21 : A system comprising:
 at least one electrode;   a signal generator; and   processing circuitry configured to control the signal generator to increase energy delivered to the at least one electrode to a target energy value by at least:
 causing the signal generator to deliver the energy to the at least one electrode at a first rate until the energy reaches a predetermined energy threshold, the predetermined threshold being less than the target energy value; and 
 after the energy reaches the predetermined energy threshold, causing the signal generator to adjust the delivery of the energy to the at least one electrode at a second rate. 
   
     
     
         22 : The system of  claim 21 , wherein the processing circuitry is further configured to:
 determine one or more treatment metrics or parameters;   determine that the one or more treatment metrics or parameters is greater than or equal to a parameter threshold; and   based on a determination that the one or more treatment metrics or parameters is greater than or equal to the parameter threshold, cause the signal generator to adjust one or more of the predetermined energy threshold or the target energy value.   
     
     
         23 : The system of  claim 22 , wherein the one or more treatment metrics or parameters comprises one or more of a temperature, a time, a current, a voltage, an impedance, a contact area, a blood flow, a flow velocity, a volumetric flow rate, a blood pressure, or a heart rate. 
     
     
         24 : The system of  claim 22 , wherein to determine the one or more treatment metrics or parameters, the processing circuitry is configured to determine a temperature of tissue proximate the at least one electrode, and wherein to determine that the one or more treatment metrics or parameters is greater than or equal to the parameter threshold, the processing circuitry is configured to determine that the temperature is greater than or equal to a threshold temperature value. 
     
     
         25 : The system of  claim 22 , wherein to determine the one or more treatment metrics or parameters, the processing circuitry is configured to determine the power delivered to tissue proximate the at least one electrode, and wherein to determine that the one or more treatment metrics or parameters is greater than or equal to the parameter threshold, the processing circuitry is configured to determine that the power is greater than or equal to a threshold power value. 
     
     
         26 : The system of  claim 21 , wherein to cause the signal generator to deliver the energy to the at least one electrode at the first rate, the processing circuitry is configured to cause the signal generator to increase a current delivered to the at least one electrode at the first rate to begin treatment. 
     
     
         27 : The system of  claim 26 , wherein to cause the signal generator to adjust the delivery of the energy to the at least one electrode at the second rate, the processing circuitry is configured to cause the signal generator to increase the current delivered to the at least one electrode at the second rate until the target energy value is reached, wherein the second rate is lower than the first rate. 
     
     
         28 : The system of  claim 26 , wherein the processing circuitry is further configured to:
 cause the signal generator to maintain the current delivered to the at least one electrode at the target energy value for a first period;   cause the signal generator to decrease the current delivered to the at least one electrode for a second period; and   cause the signal generator to cease delivery of the current to the at least one electrode at an end of the second period.   
     
     
         29 : The system of  claim 28 , wherein to cause the signal generator to decrease the current delivered to the at least one electrode, the processing circuitry is configured to cause the signal generator to decrease the current delivered to the at least one electrode at a third rate. 
     
     
         30 : A system comprising:
 at least one electrode; and   a signal generator; and   processing circuitry configured to:
 cause the signal generator to deliver current to the at least one electrode at a first rate until the current reaches a predetermined current threshold, the predetermined current threshold being less than a target current; 
 determine one or more treatment metrics or parameters; and 
 cause the signal generator to deliver the current to the at least one electrode at a second rate to the target current when the one or more treatment metrics or parameters is greater than or equal to a parameter threshold. 
   
     
     
         31 : The system of  claim 30 , wherein the one or more treatment metrics or parameters comprises one or more of a temperature, a time, a current, a voltage, an impedance, a contact area, a blood flow, a flow velocity, a volumetric flow rate, a blood pressure, or a heart rate. 
     
     
         32 : The system of  claim 30 , wherein the processing circuitry is further configured to:
 cause the signal generator to maintain the current at the target current for a first period;   cause the signal generator to decrease the current delivered to the at least one electrode at a third rate for a second period; and   cause the signal generator to cease delivery of the current to the at least one electrode at an end of the second period.   
     
     
         33 : The system of  claim 30 , wherein the processing circuitry is configured to determine a temperature of tissue proximate the at least one electrode, wherein the parameter threshold comprises a threshold temperature value, and wherein to cause the signal generator to deliver the current to the at least one electrode at the second rate to the target current, the processing circuitry is configured to:
 cause the signal generator to change delivery of the current to the at least one electrode from delivery at the first rate to delivery at the second rate based on a determination that the temperature is greater than or equal to the threshold temperature value.   
     
     
         34 : The system of  claim 30 , wherein the processing circuitry is configured to determine an amount of current delivered to tissue proximate the at least one electrode, wherein the parameter threshold comprises a predetermined current value, and wherein to cause the signal generator to deliver the current to the at least one electrode at the second rate to the target current value, the processing circuitry is configured to:
 cause the signal generator to change delivery of the current to the at least one electrode from delivery at the first rate to delivery at the second rate based on a determination that the amount of current delivered to tissue proximate the at least one electrode is greater than or equal to the predetermined current value.   
     
     
         35 : A system comprising:
 a therapeutic assembly comprising at least one electrode having a total surface area (TSA), a portion of the TSA being configured to be in contact with a vessel wall of a patient and defining an electrode active surface area (ASA); and   a signal generator; and   processing circuitry configured to:
 determine a desired current density for ablating target tissue; 
 determine a surface area size of the ASA; 
 cause the signal generator to deliver an amount of energy to the at least one electrode to achieve the desired current density throughout the ASA; 
 determine one or more treatment metrics or parameters; and 
 based the one or more treatment metrics or parameters, cause the signal generator to adjust the amount of energy delivered to the at least one electrode to achieve or maintain the desired current density throughout the ASA. 
   
     
     
         36 : The system of  claim 35 , wherein the one or more treatment metrics or parameters comprises a temperature, a time, a current, a voltage, an impedance, a contact area, a blood flow, a flow velocity, a volumetric flow rate, a blood pressure, or a heart rate. 
     
     
         37 : The system of  claim 35 , wherein to cause the signal generator to adjust the amount of energy delivered to the at least one electrode to achieve or maintain the desired current density through the ASA, the processing circuitry is configured to:
 determine a current level based on one or more of a change in temperature of the electrode, a change in impedance of the at least one electrode, or a calculated power of the at least one electrode; and   cause the signal generator to increase or decrease the amount of energy delivered to the electrode to achieve the determined current level throughout the at least one electrode.   
     
     
         38 : The system of  claim 37 , wherein the processing circuitry is further configured to:
 determine a maximum increase in current throughout the at least one electrode based on one or more of a maximum current level, a maximum temperature, a maximum power, or a maximum change in impedance of the target tissue, and   wherein to cause the signal generator to adjust the amount of energy delivered to the at least one electrode, the processing circuitry is configured to cause the signal generator to override the maximum increase in current throughout the at least one electrode based on at least one of a measured temperature, a measured power, or a measured impedance of the one or more treatment metrics or parameters.   
     
     
         39 : The system of  claim 35 , wherein to adjust the amount of energy delivered to the at least one electrode, the processing circuitry is configured to:
 monitor a rate of change in temperature of tissue proximate the at least one electrode; and   cause the signal generator to decrease the amount of energy delivered to the at least one electrode based on a determination that the rate of change in temperature is greater than a predetermined rate.   
     
     
         40 : The system of  claim 35 , wherein to adjust the amount of energy delivered to the at least one electrode, the processing circuitry is configured to:
 monitor a rate of change in tissue impedance through a return path of the delivered energy; and   cause the signal generator to decrease the amount of energy delivered to the at least one electrode based on a determination that the rate of change in impedance is greater than a predetermined rate.