Dual Frequency Band Ultrasound Transducer Arrays

• US 20090182237A1
• Filed: 01/09/2009
• Published: 07/16/2009
• Est. Priority Date: 07/26/2005
• Status: Active Grant

• Current Assignee: Surf Technology AS
• Original Assignee: Surf Technology AS
• Inventors: Nasholm, Sven Peter, Angelsen, Bjorn A.J., Masoy, Svein-Erik, Johansen, Tonni F., Hansen, Rune
• Granted Patent: US 8,182,428 B2
• Time in Patent Office: Days
• US Class Current: 600/459
• CPC Class Codes: A61B 8/4488 the transducer being a phased array
• CPC Class Codes: B06B 1/064 with multiple active layers
• CPC Class Codes: G01S 15/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S15/46
• CPC Class Codes: G01S 15/89 for mapping or imaging
• CPC Class Codes: G01S 15/8918 the array being linear
• CPC Class Codes: G01S 15/8922 the array being concentric or annular
• CPC Class Codes: G01S 15/8927 using simultaneously or sequentially two or more subarrays or subapertures
• CPC Class Codes: G01S 15/8952 using discrete, multiple frequencies
• CPC Class Codes: G01S 7/52003 Techniques for enhancing spatial resolution of targets G01S7/52046 takes precedence

Abstract

An acoustic probe transmits/receives acoustic pulses with frequencies both in a high frequency (HF), and a selectable amount of lower frequency (LF1, LF2, . . . , LFn, . . . ) bands. The radiation surfaces of at least two of the multiple frequency bands have a common region. The arrays and elements can be of a general type such as annular arrays, phased or switched arrays, linear arrays with division in both azimuth and elevation direction, like a 1.5D, a 1.75D and a full 2D array, or curved arrays. The element division, array type, and array aperture sizes for the different bands can also be different.

Claims

1. An acoustic transducer array probe for transmission from a front face of said probe of acoustic waves in separate high frequency (HF) and at least a 1^st lower frequency (LF1) bands and reception of acoustic waves at least in the HF band, the transducer comprising:

different arrays of transducer elements configured for respective HF and the LF1 electro-acoustic transduction, the array for the HF electro-acoustic transduction having HF array elements and the array for the LF1 electro-acoustic transduction having LF1 array elements, and

radiation surfaces for the HF band and the LF1 band, wherein at least a portion of said radiation surfaces for the HF and LF1 bands is common in a common radiation surface, wherein the LF1 array elements within the common radiation surface have larger radiation surfaces with larger distance between neighboring element centers, than do the HF array elements within the common radiation surface, and

wherein the radiation surfaces include at least an LF1 transmit surface for LF1 band transmission and an HF transmit surface for HF band transmission, the outer boundaries of said LF1 transmit surface extends at least in a region outside the outer boundaries of said HF transmit surface.

4. An acoustic transducer array probe according to claim 1, wherein said array for HF electro-acoustic transduction and said array for LF1 electro-acoustic transduction are independently arranged as one of

a single element array, and

an annular array of transducer elements, and

a linear array of transducer elements, and

a curved array of transducer elements, and

a two dimensional array of transducer elements, and

a composition of transducer elements of any form.

7. An instrument utilizing an acoustic probe according to claim 1, wherein

a thickness of the structure of the different arrays is the same throughout the entire radiation surface, and sizes of LF1 and HF transmit and receive apertures are selectable electrically by the electrical connection to the transducer elements, and wherein active HF and LF1 transmit apertures are selected one of

a) automatically by the instrument depending on an image range, an acoustic imaging modality and an application, and

b) directly by the instrument operator through instrument controls.

9. An acoustic transducer array probe according to claim 1, wherein the radiation surfaces also include an HF receive surface for HF band reception, and the transducer elements are selectively activable so that the HF receive surface is larger than the LF1 transmit surface.

11. An acoustic array probe according to claim 1, wherein

said radiation surfaces include an HF transmit surface, an LF1 transmit surface, and at least one of an HF receive surface and an LF1 receive surface, wherein at least one of said radiation surfaces is made as a sparse array of said transducer elements, and wherein

said sparse arrays are designed so that potential grating lobes of said sparse HF transmit array are directed relative to the LF beam so that the LF pulse pressure at the HF pulse in said HF grating lobes is so low that the nonlinear manipulation of the object elasticity by the LF pulse at the HF pulse is negligible along said HF grating lobes compared to along the HF main lobe.

12. An acoustic transducer array probe according to claim 1, wherein

said acoustic transducer array probe further comprising at least one electronic substrate layer with integrated electronics connecting to array elements, the at least one electronic substrate layer is at least one of:

stacked within said different physical structures of said HF and LF1 array elements, and

mounted behind said different physical structures of said HF and LF1 array elements.

13. An acoustic transducer array probe according to claim 1, wherein the thickness structure of the array is the same throughout an entire array surface including the radiation surfaces for the HF band and the LF1 band, and wherein each of the different arrays of transducer elements comprise array element electrodes defining a size of HF and LF1 transmit and receive apertures.

14. An acoustic transducer array probe according to claim 1, further comprising a further array of transducer elements for electro-acoustic transduction in at least one lower frequency band LF2 through at least said common radiation surface, the electro-acoustic transduction for said at least one lower frequency band being obtained with electro-acoustic transduction structures for each of said at least one lower frequency band, at least parts of a radiation surface of said at least one lower frequency band are common with the radiation surface of the HF and LF1 bands.

15. An acoustic transducer array probe according to claim 14, where the electro-acoustic transduction for each of said at least one lower frequency band is obtained with a piezoelectric layer placed behind the transduction structures for HF, LF1 and any other higher frequency bands.

16. An acoustic transducer array probe according to claim 15, where an acoustic isolation section is placed to the front of each piezoelectric layer, where said isolation section provides backwards acoustic attenuation for vibrations in the resonant band of the transduction structure to the front of said each piezoelectric layer.

46. An instrument utilizing an acoustic probe according to claim 13, where an electrical connection to the array element electrodes is electronically selectable, and the size of HF and LF1 transmit and receive apertures are selected electronically by the electrical connection to array element electrodes.

47. An instrument utilizing an acoustic probe according to claim 14, where the one of the HF, LF1, and LF2 arrays for imaging is determined by one of i) automatically by the application situation and ii) manually by the operator.

48. An instrument utilizing an acoustic probe according to claim 46, where the active HF and LF1 transmit apertures are selected through one of

a) automatic selection by the instrument depending on the image range and the acoustic imaging modality and application, and

b) directly by the instrument operator through instrument controls.

49. An acoustic transducer array probe according to claim 12, wherein said at least one electronic substrate layer with electronic circuits include one or more of

a) receiver pre-amplifiers connected to array elements,

b) transmitter amplifiers connected to array elements,

c) electronic switches that connect selectable groups of array elements to single wires that further connects to an instrument,

d) sub-aperture circuits connecting to a group of elements and adding delays to the individual sub-aperture signals before summing to sub-aperture signals where each sub-aperture signal connects to a single wire that further connects to an instrument,

e) time multiplex circuits that time multiplexes samples of signals from groups of elements or groups of sub-apertures of elements on single wires that further connect to an instrument.

2. An acoustic transducer array probe for transmission from a front face of said probe of acoustic waves in separate high frequency (HF) and at least a 1^st lower frequency (LF1) bands and reception of acoustic waves in at least the HF band, the transducer comprising:

different arrays of transducer elements configured for respective HF and the LF1 electro-acoustic transduction, the array for the HF electro-acoustic transduction having HF array elements and the array for the LF1 electro-acoustic transduction having LF1 array elements, and

radiation surfaces for the HF band and the LF1 band, wherein at least a portion of said radiation surfaces for the HF and LF1 bands is common in a common radiation surface, wherein LF1 the array elements within the common radiation surface have larger radiation surfaces with larger distance between neighboring element centers, than do the HF array elements within the common radiation surface, and

wherein the radiation surfaces include at least an LF1 transmit surface for LF1 band transmission and an HF transmit surface for HF band transmission, said LF1 transmit surface being not common with the HF transmit surface in a region around the center of said LF1 transmit surface.

5. An acoustic transducer array probe according to claim 2, wherein said array for HF electro-acoustic transduction and said array for LF1 electro-acoustic transduction are independently arranged as one of

a single element array, and

an annular array of transducer elements, and

a linear array of transducer elements, and

a curved array of transducer elements, and

a two dimensional array of transducer elements, and

a composition of transducer elements of any form.

8. An instrument utilizing an acoustic probe according to claim 2, wherein

a thickness of the structure of the different arrays is the same throughout the entire radiation surface, and sizes of LF1 and HF transmit and receive apertures are selectable electrically by the electrical connection to the transducer elements, and wherein active HF and LF1 transmit apertures are selected one of

a) automatically by the instrument depending on an image range, an acoustic imaging modality and an application, and

b) directly by the instrument operator through instrument controls.

10. An acoustic transducer array probe according to claim 2, wherein the radiation surfaces also include an HF receive surface for HF band reception, and the transducer elements are selectively activable so that the HF receive surface is larger than the LF1 transmit surface.

45. An acoustic transducer array probe according to claim 2, where the HF and LF1 array elements have different shapes.

50. An acoustic transducer array probe according to claim 2, wherein the thickness structure of the array is the same throughout an entire array surface including the radiation surfaces for the HF band and the LF1 band, and wherein each of the different arrays of transducer elements comprise array element electrodes defining a size of HF and LF1 transmit and receive apertures.

3. An acoustic transducer array probe for transmission from a front face of said probe of acoustic waves in separate high frequency (HF) and a at least a 1^st lower frequency (LF1) bands and reception of acoustic waves in at least the HF band, the transducer comprising:

radiation surfaces for the HF band and the LF1 band including at least an HF transmit surface for HF band transmission and an LF1 transmit surface for LF1 band transmission, wherein at least a portion of said radiation surfaces for the HF and LF1 bands are common in a common radiation surface, and

HF array elements and LF1 array elements, at least said LF1 array elements being selectively activable so that the size of the LF1 transmit surface can selectively be varied to be one of

a) the outer boundary of the LF1 surface is equal to the outer boundary of the HF transmit surface,

b) the outer boundary of the LF1 surface is at least in a region outside the outer boundary of the HF transmit surface,

c) there is no active LF1 transmit surface in a central region of said LF1 transmit surface, and

d) a combination of a) and c, and

e) a combination of b) and c)

and wherein the LF1 array elements within the common radiation surface have larger radiation surfaces with a larger distance between neighboring element centers, than do the HF array elements within the common radiation surface.

6. An instrument utilizing an acoustic probe according to claim 3, wherein an active LF1 transmit aperture is selected one of

a) automatically by the instrument depending on an image range, an acoustic imaging modality and an application, and

b) directly by the instrument operator through instrument controls.

17. An acoustic transducer array probe for transmission from a front face of said probe of acoustic waves in separate high frequency (HF) and a at least a 1^st lower frequency (LF1) bands and reception of acoustic waves in at least the HF band, the transducer comprising:

radiation surfaces for the HF band and the LF1 band, wherein at least a portion of said radiation surfaces for the HF and LF1 bands are common in a common radiation surface, and

at least in a region of the common radiation surface, a stack of layers stacked in a thickness direction substantially normal to the common radiation surface, said stack including separate HF and LF1 piezoelectric layers configured for respective HF and LF1 electro-acoustic transductions, wherein said HF piezoelectric layer is disposed closer to the common radiation surface than is said LF1 piezoelectric layer, and

an acoustic isolation section composed of at least two acoustic layers stacked in the thickness direction and disposed between said HF and LF1 piezoelectric layers.

18. An acoustic transducer array probe according to claim 17, wherein said isolation section includes a back layer with characteristic acoustic impedance greater than 17 MRayl and at least one layer with characteristic impedance less than 5 MRayl.

19. An acoustic transducer array probe according to claim 18, wherein said back layer is made of one of the materials Cu, Ag, Au, Pd, Pt, W, or alloys of these materials, or powders of the one of the materials Cu, Ag, Au, Pd, Pt, W, or alloys of these materials, the powders being sintered or glued together.

20. An acoustic transducer array probe according to claim 17, wherein a back layer of said isolation section comprises a ceramic layer.

21. An acoustic transducer array probe according to claim 20, wherein said LF1 piezoelectric layer is made from material comprising a ceramic/polymer composite wherein the ceramic/polymer composite is diced from the back and not fully through said LF1 piezoelectric layer, so that a front portion of said ceramic piezoelectric layer forms a laterally continuous layer that forms said back layer of said isolation section.

22. An acoustic transducer array probe according to claim 21, wherein a 2^nd layer from the back of said isolation section is made of one of the materials Cu, Ag, Au, Pd, Pt, W, or alloys of these materials, or powders of the one of the materials Cu, Ag, Au, Pd, Pt, W, or alloys of these materials, the powders being sintered or glued together.

23. An acoustic array probe according to claim 17, wherein said radiation surfaces include an HF transmit surface, an LF1 transmit surface, and at least one of an HF receive surface and an LF1 receive surface, wherein at least one of said radiation surfaces is made as a sparse array of said transducer elements, and where said sparse arrays are designed so that potential grating lobes of said sparse HF transmit array are directed relative to the LF beam so that the LF pulse pressure at the HF pulse in said HF grating lobes is so low that the nonlinear manipulation of the object elasticity by the LF pulse at the HF pulse is negligible along said HF grating lobes compared to along the HF main lobe.

24. An instrument utilizing an acoustic probe according to claim 17, wherein the radiation surfaces also include an HF receive surface for HF band reception, and the transducer elements are selectively activable so that the HF receive surface is larger than the LF1 transmit surface.

25. An instrument utilizing an ultrasound probe according to claim 17, wherein the thickness structure of the stack is the same throughout the entire common radiation surface, and sizes of HF and LF1 transmit and receive apertures are selectable electrically by the electrical connection to array elements in the stack.

26. An acoustic transducer array probe according to claim 17, where at least one electronic substrate layer with integrated electronics connecting to array elements is stacked in the stack of layers and being one of:

part of said acoustic isolation section, and

mounted to the back of said HF piezo-layer, and

mounted to the front of said HF piezo-layer, and

mounted to the back of said LF1 piezo-layer, and

electronic substrate layers are mounted to the back of a backing material.

27. An acoustic transducer array probe according to claim 17, wherein acoustic waves in at least one further lower frequency band (LF2) can be transmitted and received through at least said common radiation surface,

the electro-acoustic transduction for each of said at least one further lower frequency band is obtained with an additional electro-acoustic transduction structure composed of a piezoelectric layer with an acoustic isolation section to the front,

said isolation section is placed in acoustic contact with a back-side of the transduction section for a next higher frequency band, and wherein

said isolation section provides backwards isolation of vibrations in the next higher frequency band of the neighbor transduction section to the front.

51. An acoustic transducer array probe according to claim 26, wherein said at least one electronic substrate layer with electronic circuits include one or more of

a) receiver pre-amplifiers connected to array elements,

b) transmitter amplifiers connected to array elements,

c) electronic switches that connect selectable groups of array elements to single wires that further connects to an instrument,

d) sub-aperture circuits connecting to a group of elements and adding delays to the individual sub-aperture signals before summing to sub-aperture signals where each sub-aperture signal connects to a single wire that further connects to an instrument,

e) time multiplex circuits that time multiplexes samples of signals from groups of elements or groups of sub-apertures of elements on single wires that further connect to an instrument.

52. An acoustic transducer array probe according to claim 26, wherein said at least one electronic substrate layer with electronic circuits include one or more of

a) receiver pre-amplifiers connected to array elements,

b) transmitter amplifiers connected to array elements,

c) electronic switches that connect selectable groups of array elements to single wires that further connects to an instrument,

d) sub-aperture circuits connecting to a group of elements and adding delays to the individual sub-aperture signals before summing to sub-aperture signals where each sub-aperture signal connects to a single wire that further connects to an instrument,

e) time multiplex circuits that time multiplexes samples of signals from groups of elements or groups of sub-apertures of elements on single wires that further connect to an instrument.

28. An acoustic transducer array probe for transmission from a front face of said probe of acoustic waves in separate high frequency (HF) and a at least a 1^st lower frequency (LF1) bands and reception of acoustic waves in at least the HF band, the transducer comprising:

radiation surfaces for the HF band and the LF1 band, wherein at least a portion of said radiation surfaces for the HF and LF1 bands are common in a common radiation surface, and

at least in a region of the common radiation surface, a stack of layers stacked in a thickness direction substantially normal to the common radiation surface portion, wherein said stack includes a piezoelectric layer configured for one of HF and LF1 electro acoustic transduction, and a substrate layer with cmut/pmut based transduction membranes on a front face configured for the other of HF and LF1 electro acoustic transduction, wherein

the stack of layers includes HF array elements and LF1 array elements respectively in the region of the radiation surfaces for the HF band and the LF1 band, the LF1 array elements within the common radiation surface having larger radiation surfaces with larger distance between neighboring element centers, than do the HF array elements within the common radiation surface, and wherein

said substrate layer based on cmut/pmut transduction membranes is placed to the front of said piezoelectric layer.

29. An acoustic transducer array probe according to claim 28, wherein said LF1 electro acoustic transduction is obtained by said piezoelectric layer.

30. An acoustic transducer array probe according to claim 28, wherein said HF electro acoustic transduction is obtained by said piezoelectric layer.

31. An acoustic array probe according to claim 28, wherein said radiation surfaces include an HF transmit surface, an LF1 transmit surface, and at least one of an HF receive surface and an LF1 receive surface, wherein at least one of said radiation surfaces is made as a sparse array of said transducer elements, and where said sparse arrays are designed so that potential grating lobes of said sparse HF transmit array are directed relative to the LF beam so that the LF pulse pressure at the HF pulse in said HF grating lobes is so low that the nonlinear manipulation of the object elasticity by the LF pulse at the HF pulse is negligible along said HF grating lobes compared to along the HF main lobe.

32. An instrument utilizing an acoustic probe according to claim 28, wherein the radiation surfaces also include an HF receive surface for HF band reception, and the transducer elements are selectively activable so that the HF receive surface is larger than the LF1 transmit surface.

33. An instrument utilizing an acoustic probe according to claim 28, wherein at least one electronic substrate layer with integrated electronics connecting to array elements is arranged at least at one of:

a back of said substrate layer with cmut/pmut membranes,

a back of said piezoelectric layer, and

a back of a backing material.

34. An acoustic transducer array probe according to claim 28, wherein acoustic waves in at least one further lower frequency bands (LF2) can be transmitted and received through at least said common radiation surface,

the electro-acoustic transduction for each of said at least one further lower frequency bands is obtained with an additional electro-acoustic transduction structure composed of a piezoelectric layer with an acoustic isolation section to the front,

said isolation section is placed in acoustic contact with a back-side of the transduction section for a next higher frequency band, and

said isolation section provides backwards isolation of vibrations in the next higher frequency band of the neighbor transduction section to the front.

53. An acoustic transducer array probe according to claim 33, wherein said at least one electronic substrate layer with electronic circuits include one or more of

a) receiver pre-amplifiers connected to array elements,

b) transmitter amplifiers connected to array elements,

c) electronic switches that connect selectable groups of array elements to single wires that further connects to an instrument,

d) sub-aperture circuits connecting to a group of elements and adding delays to the individual sub-aperture signals before summing to sub-aperture signals where each sub-aperture signal connects to a single wire that further connects to an instrument,

e) time multiplex circuits that time multiplexes samples of signals from groups of elements or groups of sub-apertures of elements on single wires that further connect to an instrument.

35. An acoustic transducer array probe for transmission from a front face of said probe of acoustic waves in separate high frequency (HF) and a at least a 1^st lower frequency (LF1) bands and reception of acoustic waves in at least the HF band, the transducer comprising:

radiation surfaces for the HF band and the LF1 band, wherein at least a portion of said radiation surfaces for the HF and LF1 bands are common in a common radiation surface, and

a substrate wherein at least in a region of the common radiation surface, separate cmut/pmut based HF and LF1 transduction membranes are arranged on said substrate and configured for respective HF and LF1 electro acoustic transductions, and wherein

said HF and LF1 transduction membranes form HF array elements and LF1 array elements within the common radiation surface, the LF1 array elements within the common radiation surface having larger radiation surfaces with larger distance between neighboring element centers, than do the HF array elements within the common radiation surface.

36. An acoustic transducer array probe according to claim 35, wherein within said common radiation surface the HF transduction membranes are placed in front of the LF1 transduction membranes.

37. An acoustic transducer array probe according to claim 35, wherein within said common radiation surface the HF transduction membranes are placed side by side of the LF1 transduction membranes, at a distance from each other such that HF and LF1 beams appear to originate from overlapping elements.

38. An acoustic array probe according to claim 35, wherein said radiation surfaces include an HF transmit surface, an LF1 transmit surface, and at least one of an HF receive surface and an LF1 receive surface, wherein at least one of said radiation surfaces is made as a sparse array of said transducer elements, and where said sparse arrays are designed so that potential grating lobes of said sparse HF transmit array are directed relative to the LF beam so that the LF pulse pressure at the HF pulse in said HF grating lobes is so low that the nonlinear manipulation of the object elasticity by the LF pulse at the HF pulse is negligible along said HF grating lobes compared to along the HF main lobe.

39. An instrument utilizing an acoustic probe according to claim 35, wherein the radiation surfaces also include an HF receive surface for HF band reception, and the transducer elements are selectively activable so that the HF receive surface is larger than the LF1 transmit surface.

40. An instrument utilizing an acoustic probe according to claim 35, wherein at least one electronic substrate layer with integrated electronics connecting to array elements is disposed in back of said substrate layer with cmut/pmut membranes.

41. An instrument utilizing an acoustic probe according to claim 35, wherein additional acoustic pulses in a 2 lower frequency (LF2) band can be transmitted and received through the common radiation surface, the LF1 cmut/pmut membranes also having resonances in the LF2 band.

42. An instrument utilizing an acoustic probe according to claim 35, wherein additional acoustic pulses in a 2 lower frequency (LF2) band can be transmitted and received through the common radiation surface, the electro-acoustic transduction for said LF2 band being obtained with cmut/pmut membranes on the same substrate as said HF and LF1 transduction membranes, wherein one of:

the HF and LF1 membrane are placed on top of the LF2 membranes, and

the LF2 membranes are placed by the side of the HF and LF1 membranes.

43. An instrument utilizing an acoustic probe according to claim 35, wherein additional acoustic pulses in a 2 lower frequency (LF2) band can be transmitted and received through the common radiation surface, the electro-acoustic transduction for said LF2 band is obtained with a LF2 piezoelectric layer placed behind said HF/LF1 common substrate, such that at least part of a LF2 radiation surface is common in the common radiation surface of said HF and LF2 array.

44. An instrument utilizing an acoustic probe according to claim 43, wherein acoustic waves in at least one further lower frequency band (LF3) can be transmitted and received through at least said common radiation surface,

the electro-acoustic transduction for each of said at least one further lower frequency band is obtained with an added electro-acoustic transduction structure composed of a piezoelectric layer with an acoustic isolation section to the front,

said isolation section disposed in acoustic contact with a back-side of the transduction section for the next higher frequency band, and where

said isolation section providing backwards isolation of vibrations in the next higher frequency band of the neighbor transduction section to the front.

54. An acoustic transducer array probe according to claim 40, wherein said at least one electronic substrate layer with electronic circuits include one or more of

a) receiver pre-amplifiers connected to array elements,

b) transmitter amplifiers connected to array elements,

c) electronic switches that connect selectable groups of array elements to single wires that further connects to an instrument,

d) sub-aperture circuits connecting to a group of elements and adding delays to the individual sub-aperture signals before summing to sub-aperture signals where each sub-aperture signal connects to a single wire that further connects to an instrument,

e) time multiplex circuits that time multiplexes samples of signals from groups of elements or groups of sub-apertures of elements on single wires that further connect to an instrument.