Method and apparatus for localizing an ultrasound catheter

1. An imaging system, comprising:

an ultrasound catheter including a tubular body, comprising:

a localizer sensor adapted and configured to generate positional information for the ultrasound catheter, the localizer sensor comprising:

a first annular ultrasound sensor positioned on the tubular body; and

a second annular ultrasound sensor positioned on the tubular body displaced from the first annular sensor along a length of the tubular body; and

an imaging ultrasound sensor positioned on the tubular body so as to have a first restricted field of view; and

a controller coupled to the localizer sensor and the ultrasound catheter,

wherein the first restricted field of view spans less than 360 degrees about the tubular body, and

wherein the controller is configured to determine a position and direction of the ultrasound catheter in six dimensions with respect to a frame of reference defined by a recognizable heart structure imaged by the imaging ultrasound sensor, and to co-register ultrasound images from the imaging ultrasound sensor with the frame of reference.

2. The imaging system of claim 1 , wherein the localizer sensor further comprises:

a directional ultrasound sensor positioned on the tubular body so as to sense positional information along a second restricted field of view,

wherein the second field of view spans less than 360 degrees about the tubular body, and wherein the directional ultrasound sensor is circumferentially positioned relative to the imaging ultrasound sensor about the tubular body at a known angle.

3. The imaging system of claim 2 , wherein the known angle is within a range of about 90 degrees to about 180 degrees.

4. The imaging system of claim 3 , wherein the directional ultrasound sensor is positioned substantially opposite the imaging ultrasound sensor about the tubular body.

5. The imaging system of claim 1 , wherein at least one of the first annular ultrasound sensor and the second annular ultrasound sensor comprise a cylindrical array of ultrasound sensors.

6. The imaging system of claim 1 , wherein the first and second annular ultrasound sensors are ring shaped transducers.

7. The imaging system of claim 1 , wherein the controller is configured to determine position and direction of the ultrasound catheter in six dimensions by determining a distance based upon a measured time delay of a received ultrasound pulse and a known speed of sound in blood and applying spherical triangulation to the determined distance to determine a position.

8. The imaging system of claim 2 , wherein at least one of the first annular ultrasound sensor and the second annular ultrasound sensor are positioned within a flexible portion of the tubular body.

9. The imaging system of claim 2 , wherein the imaging ultrasound sensor is positioned between the first annular ultrasound sensor and the second annular ultrasound sensor along the length of the tubular body.

10. A method of displaying medical images from a catheter-based imaging ultrasound sensor having a first restricted field of view, the method comprising:

generating at least one image with the imaging ultrasound sensor;

receiving ultrasound signals at a first annular ultrasound sensor positioned on the catheter body and at a second annular ultrasound sensor positioned on the catheter body at a position displaced along a length of the catheter body from the first annular ultrasound sensor;

calculating a six dimensional position and direction of the imaging ultrasound sensor with respect to a frame of reference defined by a recognizable heart structure imaged by the imaging ultrasound sensor based on the ultrasound signals received at the first and second annular ultrasound sensors;

coregistering the calculated position with the at least one generated image within the frame of reference defined by the recognizable heart structure; and

displaying the at least one generated image based on the calculated positional and directional information,

wherein the first restricted field of view spans less than 360 degrees about a body of the catheter.

11. The method of claim 10 ,

wherein coregistering the position of the imaging ultrasound sensor with the at least one generated image comprises coregistering a section of a heart imaged in the at least one generated image, and

wherein displaying the at least one generated image based on the positional and directional information comprises:

displaying a three dimensional (3D) model of the heart; and

highlighting a section of the 3D model of the heart which corresponds to the coregistered section.

12. The method of claim 11 , wherein the 3D model of the heart is displayed in a first color, and wherein the highlighted section of the 3D model is displayed in a second color different from the first color.

13. The method of claim 10 , wherein the step of calculating a six dimensional position and direction of the imaging ultrasound sensor comprises:

measuring a time delay of a received ultrasound pulse received at one of the first and second annular ultrasound sensors;

determining a distance based upon the measured time delay and a known speed of sound in blood; and

applying spherical triangulation to the determined distance to determine a position of the one of the first and second annular ultrasound sensors.

14. The method of claim 11 , further comprising displaying the imaging ultrasound sensor in the 3D model of the heart based on the calculated positional information.

15. The method of claim 11 , wherein calculating the six dimensional position and direction of the imaging ultrasound sensor is further based on positional measurements by a directional ultrasound sensor having a second restricted field of view about the body of the catheter, the directional ultrasound sensor being positioned on the body of the catheter at a known angle to the imaging ultrasound sensor.

16. The method of claim 15 , further comprising:

sensing a first omni directional position information with the first annular ultrasound sensor; and

sensing a second omni directional position information with the second ultrasound annular sensor.

17. The method of claim 15 , wherein the first restricted field of view is substantially the same as the second restricted field of view, and the known angle is substantially zero.

18. The method of claim 17 , further comprising sensing a third position information with the imaging ultrasound sensor.

19. An imaging system, comprising:

an ultrasound catheter including a tubular body, comprising:

a localizer sensor adapted and configured to generate positional information for the ultrasound catheter, the localizer sensor comprising:

a first annular ultrasound sensor positioned on the tubular body;

a second annular ultrasound sensor positioned on the tubular body, the second annular sensor being displaced from the first annular sensor along a length of the tubular body; and

an imaging ultrasound sensor positioned relative to the tubular body so as to have a first restricted field of view;

a first positioning catheter comprising at least one ultrasound transducer; and

a controller coupled to the localizer sensor, the first positioning catheter and the ultrasound catheter,

wherein the first restricted field of view spans less than 360 degrees about the tubular body, and

wherein the controller is configured to determine position and direction of the ultrasound catheter in six dimensions with respect to a frame of reference defined by the first positioning catheter.

20. The imaging system of claim 19 , wherein the localizer sensor further comprises:

a directional ultrasound sensor positioned on the tubular body so as to receive ultrasound signals along a second restricted field of view,

wherein the second field of view spans less than 360degrees about the tubular body, and

wherein the directional ultrasound sensor is circumferentially positioned relative to the imaging ultrasound sensor about the tubular body at a known angle.

21. The imaging system of claim 19 , wherein the controller is configured to determine position and direction of the ultrasound catheter in six dimensions by determining a distance of one of the first and second annular ultrasound sensors to one ultrasound transducer on the first positioning catheter based upon a measured time delay of a received ultrasound pulse and a known speed of sound in blood and applying spherical triangulation to the determined distance to determine a position of the one of the first and second annular ultrasound sensors with respect to the first positioning catheter.

22. The imaging system of claim 19 , further comprising a second positioning catheter comprising at least one ultrasound transducer.

23. The imaging system of claim 19 , wherein the first positioning catheter comprises at least two annular ultrasound transducers.

24. The imaging system of claim 19 , further comprising a second positioning catheter

wherein the first and second positioning catheters each comprise at least two annular ultrasound transducers.

25. The imaging system of claim 24 , wherein the annular ultrasound transducers emit pulses at one of different sound frequencies and at different times.

26. The imaging system of claim 19 , wherein the first positioning catheter comprises at least three directional ultrasound transducers.

27. The imaging system of claim 19 , further comprising a second positioning catheter

wherein the first and second positioning catheters each comprise at least three directional ultrasound transducers.

28. The imaging system of claim 27 , wherein the directional ultrasound transducers emit pulses at one of different sound frequencies and at different times.

29. A medical imaging system, comprising:

a catheter including an imaging ultrasound sensor having a first restricted field of view spanning less than 360 degrees about a body of the catheter;

means for generating at least one image, with the imaging ultrasound sensor;

means for receiving ultrasound signals at a first annular ultrasound sensor positioned on the catheter body and a second annular ultrasound sensor positioned on the catheter body displaced along a length of the catheter body from the first annular ultrasound sensor;

means for calculating a six dimensional position and direction of the imaging ultrasound sensor with respect to a frame of reference defined by a recognizable heart structure imaged by the imaging ultrasound sensor based on the ultrasound signals received at the first and second annular ultrasound sensors;

means for coregistering the calculated position with the at least one generated image within the frame of reference defined by the recognizable heart structure; and

means for displaying the at least one generated image based on the calculated positional and directional information.

30. The medical imaging system of claim 29 ,

wherein means for coregistering the position of the imaging ultrasound sensor with the at least one generated image comprises means for coregistering a section of a heart imaged in the at least one generated image, and

wherein means for displaying the at least one generated image based on the positional and directional information comprises:

means for displaying a three dimensional (3D) model of the heart; and

means for highlighting a section of the 3D model of the heart which corresponds to the coregistered section.

31. The medical imaging system of claim 30 , wherein:

means for displaying a 3D model of the heart comprises means for displaying the 3D model of the heart in a first color; and

means for highlighting a section of the 3D model comprises means for highlighting the section of the 3D model in a second color different from the first color.

32. The medical imaging system of claim 29 , wherein means for calculating a six dimensional position and direction of the imaging ultrasound sensor comprises:

means for measuring a time delay of a received ultrasound pulse received at one of the first and second annular ultrasound sensors;

means for determining a distance based upon the measured time delay and a known speed of sound in blood; and

means for applying spherical triangulation to the determined distance to determine a position of the one of the first and second annular ultrasound sensors.

33. The medical imaging system of claim 30 , further comprising means for displaying the imaging ultrasound sensor in the 3D model of the heart based on the calculated positional information.

34. The medical imaging system of claim 30 , wherein means for calculating the six dimensional position and direction of the imaging ultrasound sensor comprises means for calculating the six dimensional position and direction of the imaging ultrasound sensor based on positional measurements by a directional ultrasound sensor having a second restricted field of view about the body of the catheter, the directional ultrasound sensor being positioned on the body of the catheter at a known angle to the imaging ultrasound sensor.

35. The medical imaging system of claim 34 , further comprising:

means for sensing a first omni-directional position information with the first annular ultrasound sensor; and

means for sensing a second omni-directional position information with the second ultrasound annular sensor.

36. The medical imaging system of claim 34 , further comprising means for sensing a third position information with the imaging ultrasound sensor,

wherein the first restricted field of view is substantially the same as the second restricted field of view, and the known angle is substantially zero.