Method and apparatus for delivering therapy in and association with an intravascular ultrasound device

• US 20030015037A1
• Filed: 09/13/2002
• Published: 01/23/2003
• Est. Priority Date: 02/09/2000
• Status: Active Grant

• Current Assignee: Volcano Corporation (Koninklijke Philips N.V.)
• Original Assignee: Jomed Inc.
• Inventors: Stephens, Douglas N., OʼDonnell, Matthew
• Granted Patent: US 7,736,317 B2
• Time in Patent Office: Days
• US Class Current: 73/626
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/445 Details of catheter construction
• CPC Class Codes: A61B 8/4488 the transducer being a phased array
• CPC Class Codes: B06B 1/0633 Cylindrical array
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

An ultrasound transducer array (408) includes at least one transducer element (412) having a first (604) and second (606) portions separated by an acoustical discontinuity (520). The first portion (604) has the desired length to form a half-wave k31 resonance, while the second portion (606) has a resonant length for an undesired very low frequency out-of-band k31 resonance. The thickness of the transducer element (412) is designed for k33 half-resonance. Given the design, the transducer element (412) can operate and provide for both forward-looking (514) and side looking (512) elevation apertures. A method is also disclosed for using the disclosed ultrasound transducer (412) in ultrasound imaging.

Claims

1. An ultrasound device, comprising:

a substrate; and

an ultrasound transducer element mounted on the substrate, the ultrasound transducer element having first and second portions separated by an acoustical discontinuity.

2. An ultrasound device as defined in claim 1, wherein the ultrasound transducer element is formed from piezoelectric material and the acoustical discontinuity comprises a notch.

3. An ultrasound device as defined in claim 2, wherein the notch is filled with a low acoustic impedance material.

4. An ultrasound device as defined in claim 1, wherein the substrate comprises a flexible substrate.

5. An ultrasound device as defined in claim 1, wherein the transducer element is piezoelectrically poled in one direction along the entire length of the transducer element.

6. An ultrasound device as defined in claim 5, wherein the transducer element is sized so that it is resonant in a thickness extensional mode and a length extensional mode.

7. An ultrasound device as defined in claim 6, wherein the thickness extensional mode is resonant at a frequency whose half wavelength in the transducer element is equal to the thickness of the transducer element.

8. An ultrasound device as defined in claim 6, wherein the length extensional mode is resonant at a frequency whose half wavelength in the transducer element is substantially equal to the distance of length of the first portion of the transducer element.

9. An ultrasonic imaging system, comprising:

a catheter having a distal end portion and a longitudinally extending axis;

a plurality of transducer elements arranged about the distal end portion of the catheter for transmitting and receiving ultrasonic energy; and

an ultrasound processing system for exciting the transducer elements and processing signals produced by the elements to selectively form images in a B-mode lateral plane which is perpendicular to the axis of the catheter and passes through the transducer elements, a B-mode forward plane which extends in a forward direction from the transducer at an arbitrary angle with respect to the axis of the catheter, and a C-mode plane which is perpendicular to the axis of the catheter and spaced in front of the transducer.

10. The ultrasonic imaging system of claim 9, wherein the transducer elements are arranged in a circular array.

11. The ultrasonic imaging system of claim 9, wherein the transducer elements are resonant in a thickness extensional mode for transmitting and receiving ultrasonic energy in a direction perpendicular to the axis of the catheter and in a length extensional mode for transmitting and receiving ultrasonic energy along the axis.

12. The ultrasonic imaging system of claim 11, wherein the ultrasound processing system includes a pulser for selectively exciting the elements at a first resonant frequency for the thickness extensional mode and at a second resonant frequency for the length extensional mode.

13. The ultrasonic imaging system of claim 12, wherein the resonant frequency for the thickness extensional mode is at least 1.5-2 times the resonant frequency for the length extensional mode.

15. The method of claim 14, wherein the transducer elements are operated in a thickness extensional mode for transmitting and receiving ultrasonic energy in a direction perpendicular to the axis of the catheter and in a length extensional mode for transmitting and receiving ultrasonic energy along the axis.

16. The method of claim 15, wherein the transducer elements are excited at a first resonant frequency for the thickness extensional mode and at a second resonant frequency for the length extensional mode.

17. The method of claim 16, wherein the resonant frequency for the thickness extensional mode is at least 1.5-2 times the resonant frequency for the length extensional mode.

19. The ultrasonic imaging device of claim 18, wherein the length dimension is on the order of twice the thickness dimension and the first resonant frequency is on the order of twice the second resonant frequency.

20. The ultrasonic imaging device of claim 18, wherein the body of each transducer element has a transversely extending notch toward one end thereof, with a wall of the notch being perpendicular to the axis, and the length dimension of the body being the distance between the one end and the wall.

21. The ultrasonic device of claim 20, wherein the notch has a generally triangular profile in cross-section.

14. A method for ultrasonic imaging utilizing a plurality of transducer elements arranged about the distal end portion of a catheter for transmitting and receiving ultrasonic energy, comprising the steps of:

exciting the transducer elements; and

processing signals produced by the elements to selectively form images in a B-mode lateral plane which is perpendicular to the axis of the catheter and passes through the transducer elements, a B-mode forward plane which extends in a forward direction from the transducer at an arbitrary angle with respect to the axis of the catheter, and a C-mode plane which is perpendicular to the axis of the catheter and spaced in front of the transducer.

18. An ultrasonic imaging device, comprising:

a plurality of transducer elements arranged in a circular array about an axis, each of the elements comprising a body of piezoelectric material having a thickness dimension perpendicular to the axis and a length dimension parallel to the axis; and

means for selectively exciting the transducer elements at a first resonant frequency having a half wavelength equal to the thickness dimension and at a second resonant frequency having a half wavelength equal to the length dimension.

22. A method of ultrasonic imaging, comprising the steps of:

arranging a plurality of transducer elements in a circular array about an axis, with each of the elements having a body of piezoelectric material with a thickness dimension perpendicular to the axis and a length dimension parallel to the axis, and

selectively exciting the transducer elements at a first resonant frequency having a half wavelength equal to the thickness dimension and at a second resonant frequency having a half wavelength equal to the length dimension.

23. The method of claim 22, wherein the length dimension is selected to be on the order twice the thickness dimension and the first resonant frequency is on the order of twice the second resonant frequency.

24. The method of claim 22, including the further step of:

forming a transversely extending notch toward one end of the body of each transducer element, with a wall of the notch being perpendicular to the axis, and the length dimension of the body being the distance between the one end and the wall.

25. The method of claim 24, wherein the notch is formed to have a generally triangular profile in cross-section.

27. The ultrasonic imaging device of claim 26, wherein the distance between the notch and the one end of the element is on the order of twice the thickness of the element, and the frequency at which the transducer elements resonate in the thickness extensional mode is on the order of twice the frequency at which the elements resonate in the length of the extensional mode.

28. The ultrasonic imaging device of claim 26, wherein the notch has a generally triangular profile in cross-section.

29. The ultrasonic imaging device of claim 26, further including an acoustic matching tube disposed coaxially within the cylindrical substrate, and a body of acoustic absorbing material between the transducer elements and the tube.

30. The ultrasonic imaging device of claim 29, further including a radiopaque marker disposed between the acoustic matching tube and the acoustic absorbing material.

26. An ultrasonic imaging device, comprising:

a cylindrical substrate, and

a plurality of longitudinally extending transducer elements of piezoelectric material spaced circumferentially apart on one side of the substrate, each of the elements having a transversely extending notch toward one end thereof and being resonant in a thickness extensional mode at a frequency corresponding to the thickness of the element and in a length extensional mode at a frequency corresponding to the distance between the notch and the one end of the element, and means carried by the substrate for applying signals and receiving signals from the transducer elements for selective operation in the thickness extensional mode and the length extensional mode.

31. A method of manufacturing an ultrasonic imaging device, comprising the steps of:

mounting a generally rectangular body of piezoelectric material on a flexible circuit substrate,

cutting a transversely extending notch in the body toward one end of the body, cutting the body lengthwise along transversally spaced apart lines to form a plurality of longitudinally extending transducer elements which are operable selectively in a thickness extensional mode and a length extensional mode at frequencies corresponding respectively to the thickness of the elements and to the length between the one end and the notch, and

forming the flexible circuit substrate into a substantially cylindrical shape with the transducer elements extending longitudinally thereof.

32. The method of claim 31, wherein the length between the one end and the notch is made equal to twice the thickness of the elements so that in the thickness extensional mode the transducers operate at twice the frequency of the length extensional mode.

33. The method of claim 31, including the further step of:

mounting integrated circuits on the substrate for interfacing with the transducer elements.

34. The method of claim 31, wherein the notch is formed to have a generally triangular profile in cross-section.

35. The method of claim 31, further including the steps of:

disposing an acoustic matching tube coaxially within the cylindrical substrate; and

filling a region between the transducer elements and the tube with an acoustic absorbing material.

36. The method of claim 35, further including the step of mounting a radiopaque marker between the acoustic matching tube and the acoustic absorbing material.