Ultrasound transducers on predetermined radii of balloon catheter

1. An apparatus comprising:

a probe having a distal portion and a lumen;

an inflatable balloon having a surface wall, a longitudinal axis and latitudes between an_equator and a distal pole on the surface wall;

a plurality of ablation electrodes arranged circumferentially on the balloon about the longitudinal axis; and

a first plurality of ultrasound transducers circumferentially distributed on the balloon along a first one of the latitudes and superimposed on a first set of ablation electrodes of the plurality of ablation electrodes such that a sole ultrasound transducer of the first plurality of ultrasound transducers is superimposed on each ablation electrode of the first set of ablation electrodes, each of the first set of ablation electrodes spanning the first one of the latitudes and a second one of the latitudes;

a second plurality of ultrasound transducers circumferentially distributed on the balloon along the second one of the latitudes and superimposed on a second set of ablation electrodes of the plurality of ablation electrodes such that a sole ultrasound transducer of the second plurality of ultrasound transducers is superimposed on each ablation electrode of the second set of ablation electrodes, each of the second set of ablation electrodes spanning the first one of the latitudes and the second one of the latitudes, wherein the first plurality of ultrasound transducers are staggered with the second plurality of ultrasound transducers on respective first and second sets of longitudes.

2. The apparatus according to claim 1 , further comprising a substrate configured as a plurality of longitudinal strips circumferentially distributed on the balloon wherein the plurality of ablation electrodes are disposed on the strips.

3. The apparatus according to claim 2 , wherein the strips and the first and second plurality of ultrasound transducers are superimposed.

4. The apparatus according to claim 1 , wherein the first plurality of ultrasound transducers and the second plurality of ultrasound transducers each comprise five ultrasound transducers.

5. The apparatus according to claim 1 , wherein the first one of the latitudes is at least 30° above the equator and the second one of the latitudes is at least 60° above the equator toward the distal pole.

6. The apparatus according to claim 1 , wherein the first one of the latitudes is from 20°-40° and the second one of the latitudes is at least 60° above the equator toward the distal pole.

7. The apparatus according to claim 1 , wherein the first and second plurality of ultrasound transducers are configured for A-mode operation.

8. A method comprising:

providing a probe having a distal portion and a lumen;

deploying an inflatable balloon through the lumen beyond the distal portion, the balloon having a surface wall, a longitudinal axis and latitudes between an equator and a distal pole on the surface wall;

arranging a plurality of ablation electrodes circumferentially on the balloon about the longitudinal axis;

arranging a first set of ultrasound transducers circumferentially on the balloon along a first latitude and superimposed on a first set of ablation electrodes of the plurality of ablation electrodes such that a sole ultrasound transducer of the first set of ultrasound transducers is superimposed on each ablation electrode of the first set of ablation electrodes, each of the first set of ablation electrodes spanning the first latitude and a second latitude and distributing a second set of ultrasound transducers circumferentially on the balloon along the second latitude and superimposed on a second set of ablation electrodes of the plurality of ablation electrodes such that a sole ultrasound transducer of the second set of ultrasound transducers is superimposed on each ablation electrode of the second set of ablation electrodes, each of the second set of ablation electrodes spanning the first latitude and the second latitude,

wherein the first set of ultrasound transducers are staggered with the second set of ultrasound transducers on respective first and second sets of longitudes;

processing signals from the first set of ultrasound transducers and the second set of ultrasound transducers;

determining that the inflatable balloon is at an ablation position based on the signals from both of the first set of ultrasound transducers and the second set of ultrasound transducers; and

powering the plurality of ablation electrodes based on the determination.

9. The method according to claim 8 , further comprising:

circumferentially distributing a substrate configured as a plurality of longitudinal strips on the balloon; and

disposing the plurality of ablation electrodes on the strips.

10. The method according to claim 9 , further comprising superimposing the strips and the first and second set of ultrasound transducers.

11. The method according to claim 8 , further comprising superimposing the plurality of ablation electrodes and the first and second set of ultrasound transducers.

12. The method according to claim 8 , wherein the plurality of ablation electrodes comprise ten ablation electrodes, and the first set of ultrasound transducers and the second set of ultrasound transducers each comprise five ultrasound transducers.

13. The method according to claim 8 , wherein the first latitude is at least 30° above the equator and the second latitude is at least 60° above the equator toward the distal pole.

14. The method according to claim 8 , wherein the first latitude is from 20°-40° and the second latitude is from 50°-70° above the equator toward the distal pole.

15. The method according to claim 8 , further comprising operating the first set of ultrasound transducers in A-mode.

16. A system comprising:

a probe having a distal portion and a lumen;

an inflatable balloon having a surface wall, a longitudinal axis and latitudes between equator and a distal pole on the surface wall;

a plurality of ablation electrodes arranged circumferentially on the balloon about the longitudinal axis;

a first plurality of ultrasound transducers circumferentially distributed on the balloon along a first one of the latitudes and superimposed on a first set of ablation electrodes of the plurality of ablation electrodes, such that a sole ultrasound transducer of the first plurality of ultrasound transducers is superimposed on each ablation electrode of the first set of ablation electrodes, each of the first set of ablation electrodes spanning the first one of the latitudes and a second one of the latitudes;

a second plurality of ultrasound transducers circumferentially distributed on the balloon along the second one of the latitudes and superimposed on a second set of ablation electrodes of the plurality of ablation electrodes, such that a sole ultrasound transducer of the second plurality of ultrasound transducers is superimposed on each ablation electrode of the second set of ablation electrodes, each of the second set of ablation electrodes spanning the first one of the latitudes and the second one of the latitudes; and

a processor configured to receive first signals from the first plurality of ultrasound transducers and determine that a distance between the inflatable balloon and a tissue is approximately zero based on the first signals.

17. The system of claim 16 , wherein the processor is further configured to receive second signals from the second plurality of ultrasounds transducers and determine that the distance between the inflatable balloon and a tissue is approximately zero based on the first signals and the second signals.