Scaling impedance location measurements of a balloon catheter

1 . A system, comprising:

a balloon catheter comprising a shaft, an inflatable balloon fitted at a distal end of the shaft, multiple large-area ablation electrodes disposed on the inflatable balloon, first and second small-area sensing electrodes fitted on the shaft, the first small-area sensing electrode proximal of the inflatable balloon and the second small-area sensing electrode distal of the inflatable balloon, and a magnetic sensor fitted on the shaft proximal of the first small-area sensing electrode; and

a processor, which is configured to:

receive position signals (i) generated as coarse position-signals by the multiple large-area ablation electrodes disposed on the inflatable balloon and (ii) from the first and second small-area sensing electrodes fitted on the shaft;

receive from the magnetic sensor one or more direction signals indicative of a direction of the distal end, and

calculate positions of the multiple large-area ablation electrodes disposed on the balloon based on the received signals of positions of (i) the multiple large-area ablation electrodes, and (ii) the first and second small-area sensing electrodes, on the one or more direction signals, and on a known distance between the first and second small-area sensing electrodes, by estimating positions of the first and second small-area sensing electrodes based on the position signals;

estimating a direction of the catheter distal end based on the one or more direction signals;

based on the known distance between the first and second small-area sensing electrodes, calculating displacements of the first and second small-area sensing electrodes such that the first and second small-area sensing electrodes are brought into correct positions along the direction of the catheter distal end; and

scaling the positions of the multiple large-area ablation electrodes based on the calculated displacements.

2 . A method, comprising:

generating electrical excitation energy around a patient's organ;

generating a magnetic field around a patient's organ; and in a processor,

receiving position signals generated by multiple large-area ablation electrodes in response to the electrical excitation energy, the multiple large-area ablation electrodes disposed on an inflated balloon fitted at a distal end of a catheter;

receiving additional position signals generated by first and second small-area sensing electrodes in response to the electrical excitation energy, the first and second small-area sensing electrodes fitted on a shaft of the catheter, the first small-area sensing electrode being proximal of the balloon, the second small-area sensing electrode being distal of the balloon;

based on the position signals and the additional position signals, determining positions of the multiple large-area ablation electrodes in a coordinate system that includes the patient's organ, by;

receiving a direction signal generated by a magnetic sensor in response to the magnetic field, the magnetic sensor fitted on the shaft and proximal of the first small-area sensing electrode, the direction signal representative of a direction to which a distal end of the shaft points; and

applying corrective displacements, including adjusting the direction of the distal end of the shaft in the coordinate system based on the direction signal and adjusting the positions of the multiple large-area ablation electrodes in the coordinate system based on a scaling factor.

3 . The method of claim 2 , wherein the positions of the multiple large-area ablation electrodes include positions of the multiple large-area ablation electrodes on an equator in the coordinate system, the equator defined by a radius representative of the inflated balloon, and the adjusting the positions of the multiple large-area ablation electrodes includes adjusting the positions of the multiple large-area ablation electrodes on the equator.

4 . The method of claim 3 , wherein the adjusting the positions of the multiple large-area ablation electrodes on the equator includes adjusting the radius of the equator in the coordinate system.

5 . The method of claim 3 , wherein the adjusting the radius of the equator includes:

determining a mean location based on the additional position signals of the first and second small-area sensing electrodes; and

projecting the mean location onto the direction of the distal end of the shaft to determine an estimated center of the balloon.

6 . The method of claim 2 , wherein the determining the positions of the multiple large-area ablation electrodes is based on previously acquired magnetic location-calibrated position signals.

7 . The method of claim 2 , wherein the scaling factor is based on position signals of the first and second small-area sensing electrodes acquired by current distribution proportions.

8 . The method of claim 2 , wherein the scaling factor is based on a known distance between the first and second small-area sensing electrodes.

9 . The method of claim 2 , further including adjusting the scaling factor by using coarse position-signals generated by the multiple large-area ablation electrodes in response to the electrical excitation energy.

10 . The method of claim 2 , wherein the determining the positions of the multiple large-area ablation electrodes includes determining in parallel positions of the first and second small-area sensing electrodes, the direction of the distal end of the shaft, and the corrective displacements.

11 . A system, comprising:

a balloon catheter comprising:

a shaft,

an inflatable balloon fitted at a distal end of the shaft,

multiple large-area ablation electrodes disposed on the inflatable balloon,

first and second small-area sensing electrodes fitted on the shaft, the first small-area sensing electrode proximal of the inflatable balloon, the second small-area sensing electrode distal of the inflatable balloon, and

a magnetic sensor fitted on the shaft, proximal of the first small-area sensing electrode;

a processor configured to:

receive position signals generated by the multiple large-area ablation electrodes in response to electrical excitation energy;

receive additional position signals generated by the first and second small-area sensing electrodes in response to the electrical excitation energy;

based on the position signals and the additional position signals, determine positions of the multiple large-area ablation electrodes within a coordinate system that includes a patient's organ, by;

receiving a direction signal generated by the magnetic sensor, the direction signal representative of a direction to which a distal end of the shaft points; and

applying corrective displacements, including adjusting the direction of the distal end of the shaft in the coordinate system based on the direction signal and adjusting the positions of the multiple large-area ablation electrodes in the coordinate system based on a scaling factor.

12 . The system of claim 11 , wherein the positions of the multiple large-area ablation electrodes include positions of the multiple large-area ablation electrodes on an equator in the coordinate system, the equator defined by a radius representative of the inflated balloon, and the processor is configured to adjust the positions of the multiple large-area ablation electrodes by adjusting the positions of the multiple large-area ablation electrodes on the equator.

13 . The system of claim 12 , wherein the processor is configured to adjust the positions of the multiple large-area ablation electrodes on the equator by adjusting the radius of the equator in the coordinate system.

14 . The system of claim 12 , wherein the processor is configured to adjust the radius of the equator by:

determining a mean location based on the additional position signals of the first and second small-area sensing electrodes; and

projecting the mean location onto the direction of the distal end of the shaft to determine an estimated center of the balloon.

15 . The system of claim 11 , wherein the processor is configured to determine the positions of the multiple large-area ablation electrodes based on previously acquired magnetic location-calibrated position signals.

16 . The system of claim 11 , wherein the processor is configured to determine the positions of the first and second small-area sensing electrodes based on current distribution proportions.

17 . The system method of claim 11 , wherein the processor is configured to determine the scaling factor based on a known distance between the first and second small-area sensing electrodes.

18 . The system of claim 11 , wherein the processor is configured to adjust the scaling factor by using coarse position-signals generated by the multiple large-area ablation electrodes in response to the electrical excitation energy.

19 . The method of claim 11 , wherein the processor is configured to determine the positions of the multiple large-area ablation electrodes by determining in parallel positions of the first and second small-area sensing electrodes, the direction of the distal end of the shaft, and the corrective displacements.