Methods of determining catheter orientation
Systems, devices and methods of determining orientation of a distal end of a medical instrument (e.g., electrode-tissue orientation of an RF ablation catheter) are described herein. One or more processors may be configured to receive temperature measurements from each of a plurality of temperature-measurement devices distributed along a length of the distal end of the medical instrument and determine the orientation from a group of two or more possible orientation options based on whether temperature measurement values or characteristics of temperature response determined from the temperature measurement values satisfy one or more orientation criteria.
1. A method of determining an orientation of a distal end of an ablation catheter with respect to a target region, the method comprising:
receiving signals indicative of temperature from a plurality of temperature sensors distributed along the distal end of the ablation catheter at a first plurality of time points in a first period of time;
determining temperature measurement values at each of the first plurality of time points for each of the plurality of temperature sensors;
calculating an initial temperature value for each of the plurality of temperature sensors based on the determined temperature measurement values;
receiving signals indicative of temperature from the plurality of temperature sensors at a second plurality of time points in a second period of time after the first period of time;
determining temperature measurement values at each of the second plurality of time points for each of the plurality of temperature sensors;
calculating a rate of change between the determined temperature values at each of the second plurality of time points and the initial temperature value for each of the plurality of temperature sensors, the calculating including subtracting the initial temperature value from a moving average value and dividing by a time elapsed from the first period of time to the second period of time;
at each time point of the second plurality of time points, determining the orientation of the distal end of the ablation catheter relative to the target region based on a comparison of the calculated rate of change of at least two of the plurality of temperature sensors, which further includes determining whether the calculated rates of change satisfy one or more orientation criteria of a respective orientation, the orientation being determined from one of three orientation options including parallel, perpendicular, and oblique options, and the orientation criteria are different for each of the orientation options.
2. The method of claim 1 :
wherein the plurality of temperature sensors comprises a first plurality of temperature sensors positioned at a distal tip of the ablation catheter and a second plurality of temperature sensors positioned at a distance proximal to the first plurality of temperature sensors,
wherein the first plurality of temperature sensors consists of a first three thermocouples spaced apart circumferentially about a longitudinal axis of the ablation catheter,
wherein the second plurality of temperature sensors consists of a second three thermocouples spaced apart circumferentially about the longitudinal axis of the ablation catheter,
wherein the distal end of the ablation catheter further comprises at least one thermal shunt member in thermal communication with at least one energy delivery member and at least one fluid conduit extending at least partially through an interior of the ablation catheter, wherein the at least one thermal shunt member is in thermal communication with the at least one fluid conduit, and
wherein the step of determining the orientation of the distal end of the ablation catheter relative to the target region comprises determining an initial orientation in less than 5 seconds after application of ablative energy by an energy source coupled to the ablation catheter.
3. The method of claim 1 , wherein calculating the initial temperature value for each of the plurality of temperature sensors comprises averaging the temperature measurement values determined at each of the first plurality of time points.
4. The method of claim 1 , wherein the plurality of temperature sensors comprises a first plurality of temperature sensors positioned at a distal tip of the ablation catheter and a second plurality of temperature sensors positioned at a distance proximal to the first plurality of temperature sensors.
5. The method of claim 1 , wherein at least some of the orientation criteria are time-dependent.
6. The method of claim 1 , wherein the orientation criteria are empirically determined.
7. A method of determining an orientation of a distal end of an ablation catheter with respect to a target region, the method comprising:
receiving signals indicative of temperature from a plurality of temperature sensors distributed along a distal end of the ablation catheter at a plurality of time points over a period of time;
determining temperature measurement values at each of the plurality of time points for each of the plurality of temperature sensors;
calculating a rate of change between the determined temperature measurement values at each of the plurality of time points and a starting temperature value for each of the plurality of temperature sensors, the calculating including subtracting the starting temperature value from a moving average value and dividing by a time elapsed during the period of time;
at each time point of the plurality of time points, determining the orientation of the distal end of the ablation catheter relative to the target region based on a comparison of the calculated rate of change of at least two of the plurality of temperature sensors which includes determining whether the calculated rates of change satisfy one or more orientation criteria of a respective orientation, the orientation being determined from one of three orientation options including parallel, perpendicular, and oblique options, and the orientation criteria are different for each of the orientation options.
8. The method of claim 7 , wherein the plurality of time points each occur after delivery of ablative energy has been initiated by the ablation catheter.
9. The method of claim 7 , wherein the step of determining the orientation of the distal end of the ablation catheter comprises determining an initial orientation in less than 5 seconds after application of ablative energy by an energy source coupled to the ablation catheter.
10. The method of claim 7 , wherein the plurality of temperature sensors comprises a first plurality of temperature sensors positioned at a distal tip of the ablation catheter and a second plurality of temperature sensors positioned at a distance proximal to the first plurality of temperature sensors.
11. The method of claim 7 , wherein at least some of the orientation criteria are time-dependent.