WO2017182344A1 - Ultrasound transducer positioning - Google Patents

Ultrasound transducer positioning Download PDF

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Publication number
WO2017182344A1
WO2017182344A1 PCT/EP2017/058724 EP2017058724W WO2017182344A1 WO 2017182344 A1 WO2017182344 A1 WO 2017182344A1 EP 2017058724 W EP2017058724 W EP 2017058724W WO 2017182344 A1 WO2017182344 A1 WO 2017182344A1
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WO
WIPO (PCT)
Prior art keywords
ultrasound transducer
ultrasound
transducer element
respective
tiles
Prior art date
Application number
PCT/EP2017/058724
Other languages
French (fr)
Inventor
David Andrew Fish
Mark Thomas Johnson
Original Assignee
Koninklijke Philips N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to EP16166044 priority Critical
Priority to EP16166044.4 priority
Application filed by Koninklijke Philips N.V. filed Critical Koninklijke Philips N.V.
Publication of WO2017182344A1 publication Critical patent/WO2017182344A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0292Electrostatic transducers, e.g. electret-type
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/44Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
    • A61B8/4483Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/44Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
    • A61B8/4483Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer
    • A61B8/4488Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer the transducer being a phased array
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/54Control of the diagnostic device
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88Sonar systems specially adapted for specific applications
    • G01S15/89Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8909Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration
    • G01S15/8915Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration using a transducer array
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/18Methods or devices for transmitting, conducting, or directing sound
    • G10K11/26Sound-focusing or directing, e.g. scanning
    • G10K11/32Sound-focusing or directing, e.g. scanning characterised by the shape of the source
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06Measuring instruments not otherwise provided for
    • A61B2090/067Measuring instruments not otherwise provided for for measuring angles
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/42Details of probe positioning or probe attachment to the patient
    • A61B8/4245Details of probe positioning or probe attachment to the patient involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient
    • A61B8/4254Details of probe positioning or probe attachment to the patient involving determining the position of the probe, e.g. with respect to an external reference frame or to the patient using sensors mounted on the probe
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00Ultrasound therapy
    • A61N2007/0086Beam steering
    • A61N2007/0095Beam steering by modifying an excitation signal
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N7/00Ultrasound therapy
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88Sonar systems specially adapted for specific applications
    • G01S15/89Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8909Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88Sonar systems specially adapted for specific applications
    • G01S15/89Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/899Combination of imaging systems with ancillary equipment

Abstract

Disclosed is an ultrasound transducer probe (10) comprising a plurality of ultrasound transducer element tiles (100) each flexibly mounted on a rigid carrier (50) common to said ultrasound transducer element tiles, each tile comprising at least one ultrasound transducer element; and a plurality of capacitive sensors (70), each sensor comprising a first sensing electrode (71) on a surface (101) of one of the ultrasound transducer element tiles facing a surface portion of the rigid carrier; and a second sensing electrode (73) spatially separated from the first sensing electrode on said surface portion, wherein each ultrasound transducer element tile comprises at least one first sensing electrode. Also disclosed is an ultrasound system (1) including such an ultrasound transducer probe (10) and a method (200) of controlling such an ultrasound transducer probe (10).

Description

Ultrasound transducer positioning

FIELD OF THE INVENTION

The present invention relates to a transducer probe comprising a plurality of transducer element tiles flexibly mounted on a rigid carrier.

The present invention further relates to an ultrasound system comprising such a transducer probe.

The present invention yet further relates to a method of controlling such a transducer probe.

BACKGROUND OF THE INVENTION

Ultrasound waves find several applications in medicine. One such application is ultrasound imaging, wherein ultrasound waves are emitted by an array of ultrasound transducers into the body of a patient and echoes of the ultrasound waves are collected by the ultrasound transducers or by dedicated ultrasound receivers and processed to generate an ultrasound image, e.g. a ID, 2D or 3D ultrasound image. Another application is ultrasound therapy such as high intensity focused ultrasound (HIFU) therapy in which ultrasound beams are generated by ultrasound transducer element tiles and are focused on diseased tissue. The significant energy deposition at the focus creates local temperatures in the range of about 65°C to 85°C, which destroys the deceased tissue by coagulative necrosis.

Such applications face several challenges. For instance, in imaging applications it is far from trivial to achieve a good contact between the ultrasound transducer array and the part of the body to be imaged. This is typically achieved by using special gels that improve the contact between the ultrasound transducer array and the body part.

However, a drawback of this approach is that usually large amounts of gel have to be used, which may contain air bubbles that interfere with the transmission or reception of the ultrasound signals. Moreover, the ultrasound transducer array, e.g. in the form of the probe, is typically hand-held during an imaging procedure, which makes the procedure prone to errors.

Similar challenges exist in therapeutic applications, where the focused beam requires periodic readjustment to treat multiple regions of the diseased tissue. This may be done manually by adjusting a focusing element tile or by beam steering by adjustment of the relative phases of the signals generated by the respective ultrasound transducer elements. The manual adjustment is prone to inaccuracies and the range of phase controlled beam steering may not be sufficient to reach all diseased tissue without array displacement.

These challenges may be at least partially overcome by providing a probe on which the ultrasound transducer elements are flexibly mounted on a carrier, such that the probe surface conforms better to the body of a subject to be subjected to the ultrasound waves. However, this improved conformality of the probe surface to the body causes new challenges. For example, in applications where beam forming, e.g. beam steering, of the ultrasound beam is required, it is imperative that the relative orientation of the individual ultrasound transducer elements is well-defined such that the desired beam forming can be achieved by selection of targeted ultrasound transducer elements. If such ultrasound transducer elements are flexibly mounted on a carrier their relative orientation can change, e.g. through out of plane bending. In such a scenario, the relative orientation of the ultrasound transducer elements is no longer known, such that the desired beam forming becomes cumbersome or even impossible.

SUMMARY OF THE INVENTION

The present invention seeks to provide an ultrasound transducer probe that can generate information regarding the relative orientation of the ultrasound transducer elements of such a probe.

The present invention further seeks to provide an ultrasound system

comprising such an ultrasound transducer probe.

Of the present invention yet further seeks to provide a method of controlling such an ultrasound transducer probe.

According to an aspect, there is provided an ultrasound transducer probe comprising a plurality of ultrasound transducer element tiles each flexibly mounted on a rigid carrier common to said ultrasound transducer element tiles, each tile comprising at least one ultrasound transducer element; and a plurality of capacitive sensors, each sensor comprising a first sensing electrode on a surface of one of the ultrasound transducer element tiles facing a surface portion of the rigid carrier; and a second sensing electrode spatially separated from the first sensing electrode on said surface portion.

The provision of such capacitive sensors facilitates the determination of the relative orientation of the ultrasound transducer element tiles due to the fact that the distance between the first and second sensing electrodes of the respective capacitive sensors typically changes upon the relative orientation of the associated ultrasound transducer element tiles changing, such that this change in distance can be determined by measuring the change in the capacitance of the capacitive sensors.

In an embodiment, each ultrasound transducer element tiles comprises at least one of said first sensing electrodes to maximize the accuracy of the relative orientation determination. However, it is not necessary that each ultrasound transducer element tiles comprises such a sensing electrode. In alternative embodiments, only selected ultrasound transducer element tiles comprise such a sensing electrode, in which case the selected ultrasound transducer element tiles act as reference points, with the relative orientation of the ultrasound transducer element tiles not been fitted with capacitive sensing capability being extrapolated from the relative orientations of one or more of such reference points in the vicinity of the ultrasound transducer element tiles without capacitive sensing capability.

Preferably, the surface of each ultrasound transducer element tile carries the respective first sensing electrodes of a further plurality of capacitive sensors distributed across said surface, the further plurality forming a subset of the plurality of capacitive sensors. The inclusion of multiple first sensing electrodes on the surface of the ultrasound transducer element tiles facing the rigid carrier facilitates a particularly fine-grained determination of the relative orientation of the ultrasound transducer element tiles in respect of the rigid carrier. For example, the respective first sensing electrodes of the further plurality of capacitive sensors may be located along respective edges or in respective corners of said surface.

In an embodiment, the rigid carrier may comprise an integrated circuit die for generating control signals for the ultrasound transducer element tiles. A control circuit for controlling the capacitive sensors may form part of this integrated circuit die.

The surface of the rigid carrier comprising the respective surface portions may have any suitable shape. For example, the surface of the rigid carrier may be flat, concavely curved or convexly curved.

In an embodiment, the plurality of ultrasound transducer element tiles is mounted on a flexible layer on the rigid carrier in order to facilitate the movement of the ultrasound transducer element tiles relative to the rigid carrier.

The ultrasound transducer element tiles may comprise any suitable type and number of ultrasound transducer elements; for example, the ultrasound transducer elements may be capacitive micromachined ultrasound transducer elements (CMUTs). Each tile may comprise a plurality of CMUTs, e.g. organized as sub-arrays. Such tiles may have any suitable dimensions, e.g. the tiles may be square tiles having an area of several cm squared, e.g. may have dimensions of 2x2 cm, by way of non-limiting example. Such sizes allow for the simplification of beamforming processing because a regular active aperture of the ultrasound beam fits onto one tile and only one orientation position (of said tile) needs to be taking into account during the image reconstruction. Further, the aperture can either change its active size or "slide" to another tile during an anatomy scan.

According to another aspect, there is provided an ultrasound system comprising the ultrasound transducer probe of any of the embodiments described in the present application and a processor adapted to process the respective sensor signals of the plurality of capacitive sensors and to extract orientation information of the respective ultrasound transducer element tiles from the processed sensor signals. Such an ultrasound system benefits from being able to generate more accurate control signals for the ultrasound transducer element tiles by using the orientation information extracted for the respective ultrasound transducer element tiles.

Consequently, the system may be further adapted to control the respective ultrasound transducer elements in response to the extracted orientation information of the respective transducer element tiles. For example, the system may be adapted to control at least a subset of the ultrasound transducer elements in response to the extracted orientation information of the respective transducer element tiles in order to shape an ultrasound beam produced with the ultrasound transducer elements in response to the extracted orientation information of the respective transducer element tiles. In this manner, an accurately shaped ultrasound beam may be formed regardless of the relative orientation of the respective ultrasound transducer element tiles in respect of the rigid carrier.

The processor may be integrated in the integrated circuit die, e.g. may form part of control circuitry for controlling the capacitive sensors. Alternatively, the processor may form part of a control unit communicatively coupled to the transducer probe.

The ultrasound system may be an imaging system or a therapeutic system. According to yet another aspect, there is provided a method of controlling the transducer probe of any of the embodiments described in the present application, the method comprising obtaining a capacitive sensor reading from each of the capacitive sensors;

determining the respective orientations of the ultrasound transducer element tiles from the obtained capacitive sensor readings; and generating respective control signals for the respective ultrasound transducer elements of the ultrasound transducer element tiles in response to the determined respective orientations of the transducer element tiles.

Generating the respective control signals for the ultrasound transducer elements in response to the determined respective orientations of the ultrasound transducer element tiles may comprise configuring an ultrasound beam having a predetermined form in response to the determined respective orientations of the transducer element tiles.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail and by way of non- limiting examples with reference to the accompanying drawings, wherein:

FIG. 1 schematically depicts a cross-section of an ultrasound transducer probe;

FIG. 2 schematically depicts a cross-section of an ultrasound transducer element tile of such an ultrasound transducer probe;

FIG. 3 is a schematic block diagram of an ultrasound system according to an embodiment;

FIG. 4 schematically depicts a cross-section of a part of an ultrasound transducer probe according to an embodiment;

FIG. 5 schematically depicts an aspect of an ultrasound transducer probe according to an embodiment in more detail;

FIG. 6 schematically depicts an aspect of an ultrasound transducer probe according to another embodiment in more detail;

FIG. 7 schematically depicts a cross-section of part of an ultrasound transducer probe according to an embodiment explaining a principle of the present invention; and

FIG. 8 is a flowchart of a method of controlling an ultrasound transducer probe according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

FIG. 1 shows an ultrasound probe 10 having a transducer array 110

comprising ultrasound transducer element tiles 100 comprising one or more ultrasound transducer elements (not shown). The tile 100 for example may be a diced chip or the like onto which the one or more ultrasound transducer elements have been formed or mounted. In the present invention, the ultrasound transducer elements may be implemented in any suitable manner. For example, the ultrasound transducer elements may be implemented by a piezoelectric ceramic material such as a lead zirconate titanate (PZT)-based material, a piezoelectric single crystal or composite material, a capacitive micromachined ultrasound transducer (CMUT) and so on. The ultrasound transducer element tiles 100 may have any suitable shape, e.g. a circular shape or polygonal shape. A polygonal shape such as a rectangular, e.g. square, shape is particularly mentioned as such a shape facilitates a close packing of the ultrasound transducer element tiles 100 within the transducer array 110, wherein the gap between adjacent ultrasound transducer element tiles 100 is minimized. The avoidance of relatively large gaps between adjacent ultrasound transducer element tiles 100 ensures that a substantially continuous image may be generated with the ultrasound probe 10 and may at least reduce the formation of ultrasound artifacts such as grating lobes. The transducer array 110 may have any suitable shape, e.g. may be a 1 -dimensional or 2- dimensional transducer array.

The ultrasound transducer element tiles 100 may comprise any suitable type and number of ultrasound transducer elements; for example, the ultrasound transducer elements may be capacitive micromachined ultrasound transducer elements (CMUTs). Each tile may comprise a plurality of CMUTs, e.g. organized as sub-arrays. Such tiles may have any suitable dimensions, e.g. the tiles may be square tiles having an area of several cm squared, e.g. may have dimensions of 2x2 cm, by way of non-limiting example. Such sizes allow for the simplification of beamforming processing because a regular active aperture of the ultrasound beam fits onto one tile and only one orientation position (of said tile) needs to be taking into account during the image reconstruction. Further, the aperture can either change its active size or "slide" to another tile during an anatomy scan.

An example embodiment of a CMUT element forming part of an ultrasound transducer element tile 100 is schematically depicted in FIG. 2. The tile 100 may comprise any suitable number of such CMUT elements as previously explained. The CMUT element typically comprises a flexible membrane or diaphragm 114 suspended above a silicon substrate 112 with a gap or cavity 118 there between. A top electrode 120 is located on the diaphragm 114 and moves with the diaphragm. A bottom electrode is located on the floor of the cell on the upper surface of the substrate 112 in this example. Other realizations of the electrode 120 design can be considered, such as electrode 120 may be embedded in the membrane 114 or it may be deposited on the membrane 114 as an additional layer. In this example, the bottom electrode 122 is circularly configured and embedded in the substrate layer 112 by way of non-limiting example. Other suitable arrangements, e.g. other electrode shapes and other locations of the bottom electrode 122, e.g. on the substrate layer 112 such that the bottom electrode 112 is directly exposed to the gap 118 or separated from the gap 118 by an electrically insulating layer or film to prevent a short-circuit between the top electrode 120 and the bottom electrode 122. In addition, the membrane layer 114 is fixed relative to the top face of the substrate layer 112 and configured and dimensioned so as to define a spherical or cylindrical cavity 118 between the membrane layer 114 and the substrate layer 112. It is noted for the avoidance of doubt that in FIG. 2 the bottom electrode 122 is grounded by way of non-limiting example. Other arrangements, e.g. a grounded top electrode 120 or both top electrode 120 and bottom electrode 122 floating are of course equally feasible.

The CMUT element and its cavity 118 may exhibit alternative geometries. For example, cavity 118 could exhibit a rectangular or square cross-section, a hexagonal cross- section, an elliptical cross-section, or an irregular cross-section. Herein, reference to the diameter of the CMUT element shall be understood as the biggest lateral dimension of the cell.

The bottom electrode 122 may be insulated on its cavity-facing surface with an additional layer (not pictured). A preferred electrically insulating layer is an oxide-nitride- oxide (ONO) dielectric layer formed above the substrate electrode 122 and below the membrane electrode 120 although it should be understood any electrically insulating material may be contemplated for this layer. The ONO-dielectric layer advantageously reduces charge accumulation on the electrodes which leads to device instability and drift and reduction in acoustic output pressure.

An example fabrication of ONO-dielectric layers on a CMUT is discussed in detail in European patent application EP 2,326,432 A2 by Klootwijk et al., filed September 16, 2008 and entitled "Capacitive micromachined ultrasound transducer." Use of the ONO- dielectric layer is desirable with pre-collapsed CMUTs, which are more susceptible to charge retention than CMUTs operated with suspended membranes. The disclosed components may be fabricated from CMOS compatible materials, e.g., Al, Ti, nitrides (e.g., silicon nitride), oxides (various grades), tetraethyloxysilane (TEOS), poly-silicon and the like. In a CMOS fabrication, for example, the oxide and nitride layers may be formed by chemical vapor deposition and the metallization (electrode) layer put down by a sputtering process. Suitable CMOS processes are LPCVD and PECVD, the latter having a relatively low operating temperature of less than 400°C. Exemplary techniques for producing the disclosed cavity 118 involve defining the cavity in an initial portion of the membrane layer 114 before adding a top face of the membrane layer 114. Other fabrication details may be found in US Pat. 6,328,697 (Fraser).

In FIG. 2, the diameter of the cylindrical cavity 118 is larger than the diameter of the circularly configured electrode plate 122. Electrode 120 may have the same outer diameter as the circularly configured electrode plate 122, although such conformance is not required. Thus, the membrane electrode 120 may be fixed relative to the top face of the membrane layer 114 so as to align with the electrode plate 122 below. The electrodes of the CMUT element provide the capacitive plates of the device and the gap 118 is the dielectric between the plates of the capacitor. When the diaphragm vibrates, the changing dimension of the dielectric gap between the plates provides a changing capacitance which is sensed as the response of the CMUT element to a received acoustic echo.

The spacing between the electrodes is controlled by applying a static voltage, e.g. a DC bias voltage, to the electrodes with a voltage supply 45. The voltage supply 45 may optionally comprise separate stages 102, 104 for providing the DC and AC or stimulus components respectively of the drive voltage of the CMUT cells 100, e.g. in transmission mode. The first stage 102 may be adapted to generate the static (DC) voltage component and the second stage 104 may be adapted to generate an alternating variable voltage component or stimulus having a set alternating frequency, which signal typically is the difference between the overall drive voltage and the aforementioned static component thereof. The static or bias component of the applied drive voltage preferably meets or exceeds the threshold voltage when forcing the CMUT elements into their collapsed states, i.e. when operating the CMUT elements in collapsed mode. This has the advantage that the first stage 102 may include relatively large capacitors, e.g. smoothing capacitors, in order to generate a particularly low-noise static component of the overall voltage, which static component typically dominates the overall voltage such that the noise characteristics of the overall voltage signal will be dominated by the noise characteristics of this static component.

Other suitable embodiments of the voltage source supply 45 should be apparent, such as for instance an embodiment in which the voltage source supply 45 contains three discrete stages including a first stage for generating the static DC component of the CMUT drive voltage, a second stage for generating the variable DC component of the drive voltage and a third stage for generating the frequency modulation or stimulus component of the signal, e.g. a pulse circuit or the like. It is summarized that the voltage source supply 45 may be implemented in any suitable manner.

FIG. 3 schematically depicts an ultrasonic diagnostic imaging system with an ultrasound transducer probe 10 including a transducer array 110, i.e. an array of ultrasound transducer element tiles 100, in block diagram form. In FIG. 10 a transducer array 110 is provided in an ultrasound probe 10 for transmitting ultrasonic waves and receiving echo information. As previously explained, the transducer array 110 may be a one- or a two-dimensional array of ultrasound transducer element tiles 100 capable of scanning in a 2D plane or in three dimensions for 3D imaging.

The transducer array 110 may be coupled to a microbeam former 12 in the probe 10 which controls transmission and reception of signals by the ultrasound transducer cells 100. Microbeam formers are capable of at least partial beam forming of the signals received by groups or "patches" of transducer element tiles for instance as described in US patents US 5,997,479 (Savord et al), US 6,013,032 (Savord), and US 6,623,432 (Powers et al.)

The microbeam former 12 may be coupled by a probe cable, e.g. coaxial wire, to a terminal, e.g. a user console device or the like, comprising a transmit/receive (T/R) switch 16 which switches between transmission and reception modes and protects the main beam former 20 from high energy transmit signals when a microbeam former is not present or used and the transducer array 110 is operated directly by the main system beam former 20. The transmission of ultrasonic beams from the transducer array 110 under control of the microbeam former 12 may be directed by a transducer controller 18 coupled to the microbeam former by the T/R switch 16 and the main system beam former 20, which receives input from the user's operation of the user interface or control panel 38. One of the functions controlled by the transducer controller 18 is the direction in which beams are steered and focused. Beams may be steered straight ahead from (orthogonal to) the transducer array 110, or at different angles for a wider field of view. The transducer controller 18 may be coupled to control the aforementioned voltage source 45 for the ultrasound transducer array 110. For instance, the voltage source 45 sets the DC and AC bias voltage(s) that are applied to CMUT elements of a CMUT array 110, e.g. to operate the CMUT elements in collapse mode, as is well-known per se.

The partially beam- formed signals produced by the microbeam former 12 may be forwarded to the main beam former 20 where partially beam-formed signals from individual patches of transducer elements are combined into a fully beam-formed signal. For example, the main beam former 20 may have 128 channels, each of which receives a partially beam- formed signal from a patch of dozens or hundreds of ultrasound transducer cells 100. In this way the signals received by thousands of transducer elements of a transducer array 110 can contribute efficiently to a single beam-formed signal.

The beam- formed signals are coupled to a signal processor 22. The signal processor 22 can process the received echo signals in various ways, such as bandpass filtering, decimation, I and Q component separation, and harmonic signal separation which acts to separate linear and nonlinear signals so as to enable the identification of nonlinear (higher harmonics of the fundamental frequency) echo signals returned from tissue and microbubbles.

The signal processor 22 optionally may perform additional signal enhancement such as speckle reduction, signal compounding, and noise elimination. The bandpass filter in the signal processor 22 may be a tracking filter, with its passband sliding from a higher frequency band to a lower frequency band as echo signals are received from increasing depths, thereby rejecting the noise at higher frequencies from greater depths where these frequencies are devoid of anatomical information.

The processed signals may be forwarded to a B-mode processor 26 and optionally to a Doppler processor 28. The B-mode processor 26 employs detection of an amplitude of the received ultrasound signal for the imaging of structures in the body such as the tissue of organs and vessels in the body. B-mode images of structure of the body may be formed in either the harmonic image mode or the fundamental image mode or a combination of both for instance as described in US Patents US 6,283,919 (Roundhill et al.) and US 6,458,083 (Jago et al.)

The Doppler processor 28, if present, processes temporally distinct signals from tissue movement and blood flow for the detection of the motion of substances, such as the flow of blood cells in the image field. The Doppler processor typically includes a wall filter with parameters which may be set to pass and/or reject echoes returned from selected types of materials in the body. For instance, the wall filter can be set to have a passband characteristic which passes signal of relatively low amplitude from higher velocity materials while rejecting relatively strong signals from lower or zero velocity material.

This passband characteristic will pass signals from flowing blood while rejecting signals from nearby stationary or slowing moving objects such as the wall of the heart. An inverse characteristic would pass signals from moving tissue of the heart while rejecting blood flow signals for what is referred to as tissue Doppler imaging, detecting and depicting the motion of tissue. The Doppler processor may receive and process a sequence of temporally discrete echo signals from different points in an image field, the sequence of echoes from a particular point referred to as an ensemble. An ensemble of echoes received in rapid succession over a relatively short interval can be used to estimate the Doppler shift frequency of flowing blood, with the correspondence of the Doppler frequency to velocity indicating the blood flow velocity. An ensemble of echoes received over a longer period of time is used to estimate the velocity of slower flowing blood or slowly moving tissue.

The structural and motion signals produced by the B-mode (and Doppler) processor(s) are coupled to a scan converter 32 and a multiplanar reformatter 44. The scan converter 32 arranges the echo signals in the spatial relationship from which they were received in a desired image format. For instance, the scan converter may arrange the echo signal into a two dimensional (2D) sector-shaped format, or a pyramidal three dimensional (3D) image.

The scan converter can overlay a B-mode structural image with colors corresponding to motion at points in the image field with their Doppler-estimated velocities to produce a color Doppler image which depicts the motion of tissue and blood flow in the image field. The multiplanar reformatter 44 will convert echoes which are received from points in a common plane in a volumetric region of the body into an ultrasonic image of that plane, for instance as described in US Patent US 6,443,896 (Detmer). A volume renderer 42 converts the echo signals of a 3D data set into a projected 3D image as viewed from a given reference point as described in US Pat. 6,530,885 (Entrekin et al.)

The 2D or 3D images are coupled from the scan converter 32, multiplanar reformatter 44, and volume renderer 42 to an image processor 30 for further enhancement, buffering and temporary storage for display on an image display 40. In addition to being used for imaging, the blood flow values produced by the Doppler processor 28 and tissue structure information produced by the B-mode processor 26 are coupled to a quantification processor 34. The quantification processor produces measures of different flow conditions such as the volume rate of blood flow as well as structural measurements such as the sizes of organs and gestational age. The quantification processor may receive input from the user control panel 38, such as the point in the anatomy of an image where a measurement is to be made.

Output data from the quantification processor is coupled to a graphics processor 36 for the reproduction of measurement graphics and values with the image on the display 40. The graphics processor 36 can also generate graphic overlays for display with the ultrasound images. These graphic overlays can contain standard identifying information such as patient name, date and time of the image, imaging parameters, and the like. For these purposes the graphics processor receives input from the user interface 38, such as patient name.

The user interface is also coupled to the transmit controller 18 to control the generation of ultrasound signals from the transducer array 110 and hence the images produced by the transducer array and the ultrasound system. The user interface is also coupled to the multiplanar reformatter 44 for selection and control of the planes of multiple multiplanar reformatted (MPR) images which may be used to perform quantified measures in the image field of the MPR images.

As will be understood by the skilled person, the above embodiment of an ultrasonic diagnostic imaging system 1 is intended to give a non-limiting example of such an ultrasonic diagnostic imaging system. The skilled person will immediately realize that several variations in the architecture of the ultrasonic diagnostic imaging system are feasible without departing from the teachings of the present invention. For instance, as also indicated in the above embodiment, the microbeam former 12 and/or the Doppler processor 28 may be omitted, the ultrasound probe 10 may not have 3D imaging capabilities and so on. Other variations will be apparent to the skilled person.

Moreover, it will be understood that the present invention is not limited to an ultrasonic diagnostic imaging system 1. The teachings of the present invention are equally applicable to ultrasonic therapeutic systems in which the ultrasound transducer elements of the probe 10 may be operable in transmission mode only as there is no need to receive pulse echoes. As will be immediately apparent to the skilled person, in such therapeutic systems the system components described with the aid of FIG. 10 and required to receive, process and display pulse echoes may be omitted without departing from the teachings of the present application.

Upon returning to FIG. 1, the ultrasound probe 10 comprises a rigid carrier 50, which may comprise a backing material to absorb reflected or otherwise strayed ultrasound waves. The rigid carrier 50 may include an isolating substrate that electrically and/or acoustically isolates the ultrasound transducer element tiles 100 from circuitry (not shown) on the ultrasound probe 10. The rigid carrier 50 may comprise an integrated circuit die, e.g. an ASIC, containing circuitry for controlling the ultrasound transducer element tiles 100 and/or circuitry for processing ultrasound echoes collected by the ultrasound transducer element tiles 100, as is well-known per se. The ultrasound transducer element tiles 100 are typically flexibly mounted on the rigid carrier 50, e.g. on a flexible layer 60, i.e. a compressible layer, such as a polymer or foam layer to allow the probe surface formed by the ultrasound transducer element tiles 100 to conform to a surface, e.g. a body part, against which the ultrasound probe 10 is pressed. This is schematically depicted by the lower image in FIG. 1, in which this probe surface has adopted a concave shape after being pressed against a convex body (not shown) due to the compression of the flexible layer 60. In this manner, the probe surface can obtain a good degree of conformance with the body surface against which the ultrasound probe 10 is pressed. However, as can be seen in the lower image in FIG. 1, the different localized compressions of the flexible layer 60 causes the ultrasound transducer element tiles 100 to exhibit different out of plane orientations relative to the rigid carrier 50, with the different relative orientations being a function of the localized compression of the flexible layer 60.

Because these relative out of plane orientations of the respective ultrasound transducer element tiles 100 are unknown, this complicates or prohibits beam forming or beam shaping of the ultrasound beam produced by the ultrasound transducer element tiles

100. In such beam forming, a transmit beam former, e.g. the main beam former 20 and/or the microbeam former 12, typically generates timed electrical pulses and applies them to selected individual ultrasound transducer elements in a predetermined timing sequence, causing the selected ultrasound transducer elements to remit corresponding pressure waves that are phased to form a transmit beam that propagates in a predetermined direction from the transducer probe 10.

In order for the shaped ultrasound beam to propagate in the predetermined direction, the relative orientation of the ultrasound transducer element tiles 100 in the transducer array 110 must be known, such that the appropriate ultrasound transducer elements can be selected and their control signals appropriately timed to facilitate the generation of the desired ultrasound beam. In the absence of such relative orientation information, it can be understood that it is not possible to accurately control the shape of the ultrasound beam because it is unknown how the ultrasound transducer elements should be controlled in order to create an ultrasound beam having the desired beam shape.

The rigid carrier 50, flexible layer 60 and ultrasound transducer element tiles

100 may be combined in any suitable manner, e.g. through adhesion or the like.

FIG. 4 schematically depicts an embodiment of an ultrasound probe 10 in which a plurality of capacitive sensors 70 is incorporated in the ultrasound probe 10 for determining the relative orientation of each ultrasound transducer element tile 100 of the probe. Each capacitive sensor 70 comprises a first sensing electrode 71 on a surface 101 of one of the transducer element tiles 100 facing a surface portion 51 of the rigid carrier 50 and a second sensing electrode 73 spatially separated from the first sensing electrode 71 on the surface portion 51 by the flexible layer 60. The first sensing electrode 71 and the second sensing electrode 73 preferably perfectly oppose each other when the first sensing electrode 71 is oriented parallel to the second sensing electrode 73 although other configurations, e.g. in which the first sensing electrode 71 is laterally displaced to the second sensing electrode 73 when the first sensing electrode 71 is oriented parallel to the second sensing electrode 73 may also be contemplated.

The first sensing electrode 71 and the second sensing electrode 73 may be individually made of any suitable material that is electrically conductive, such as for example a metal or metal alloy, a conductive polymer, a conductive composite material such as a material comprising conductive nanoparticles or other nanostructures, graphene, graphite, and so on. The first sensing electrode 71 and the second sensing electrode 73 may have any suitable shape, e.g. may be plate electrodes, patterned electrodes, and so on.

The capacitance C of a capacitive sensor 70 having a plate-shaped first sensing electrode 71 parallel to a plate-shaped second sensing electrode 73 may be expressed by equation (1):

In equation (1), A is the area of overlap of the first sensing electrode 71 and the second sensing electrode 73 (in m ); εΓ is the relative static permittivity (sometimes called the dielectric constant) of the flexible layer 60; ε0 is the electric constant (εθ ~ 8.854x 10-12 F-m-1); and d is the separation between the first sensing electrode 71 and the second sensing electrode 73 (in m). From equation (1), it can be seen that the capacitance C is a function of the distance d between the first sensing electrode 71 and the second sensing electrode 73. It should be understood that one of the sensing electrodes, e.g. the second sensing electrode 73 may be a common electrode such as an electrode implemented as a continuous ground plane.

Therefore, by storing a unit charge q on the first sensing electrode 71 and the second sensing electrode 73, the distance d may be determined by measuring the capacitance of the capacitive sensor 70 by determining the voltage across the capacitive sensor 70, as expressed in equation (2): c - Vq

A time-varying voltage V(t) may be measured across the capacitive sensor 70 using a time-varying (e.g. alternating) current I(t), from which its capacitance may be derived using equation (3):

dt

Equations (l)-(3) are applicable for a capacitive sensor 70 having parallel plates. It will be immediately understood that for a capacitive sensor 70 in which the first sensing electrode 71 and the second sensing electrode 73 are not embodied by parallel plates, other equations may be applicable. As such equations are well-known per se, this is not explained in further detail for the sake of brevity only.

The capacitive sensors 70 are conductively coupled to control circuit 80. The control circuit 80 may be adapted to store the defined amount of charge on the respective capacitive sensors 70 and to measure the respective voltages across the capacitive sensors 70 as explained above in order to derive the respective distances between the first sensing electrode 71 and the second sensing electrode 73 of the capacitive sensors 70. To this end, the control circuit 80 may include a processor for processing the sensor signals from the respective capacitive sensors 70 and to derive the distance d between the respective first sensing electrodes 71 and the second sensing electrodes 73 from these processed sensor signals.

The determined distance may be indicative of the amount of compression experienced by the flexible layer 60 and thus may provide an indication of the relative orientation of the ultrasound transducer element tile 100 associated with the capacitive sensor 70 for which this distance is determined. This is particularly the case if the first sensing electrode 71 is positioned off-center on the surface 101, e.g. along an edge of the surface 101 or in a corner of the surface 101, such that a tilt of the ultrasound transducer element tile 100 can be determined as a function of the determined distance d between the first sensing electrode 71 and the second sensing electrode 73 of the capacitive sensor 70 associated with the ultrasound transducer element tile 100. In order to further refine the accuracy of the determination of the relative orientation of a particular ultrasound transducer element tile 100, the surface 101 of the ultrasound transducer element tile 100 facing the rigid carrier 50 may comprise a plurality of first sensing electrodes that are spatially distributed across the surface 101 to define a further plurality of capacitive sensors 70 on the surface 101 that form part of the overall plurality of capacitive sensors 70 across the ultrasound probe 10.

FIG. 5 schematically depicts an example embodiment in which the surface 101 of each ultrasound transducer element tile 100 comprises first sensing electrodes 71a-d along the respective edges of the surface 101 and FIG. 6 schematically depicts an example embodiment in which the surface 101 of each ultrasound transducer element tile 100 comprises first sensing electrodes 71a-d in the respective corners of the surface 101.

Although not explicitly shown, the rigid carrier 50 may comprise a separate counter electrode (i.e. second sensing electrode) for each of the first sensing electrodes 71a-d or may comprise a common counter electrode for at least some of the first sensing electrodes 71a-d, e.g. a common counter electrode for each of the ultrasound transducer element tiles 100 or a single common counter electrode for the respective first sensing electrodes 71a-d of the ultrasound transducer element tiles 100.

This is explained in more detail with the aid of FIG. 7, in which a single ultrasound transducer element tile 100 of the ultrasound probe 10 is depicted. The single ultrasound transducer element tile 100 is associated with a plurality of capacitive sensors including a first capacitive sensor 70a having a first sensing electrode 71a in a first corner of the surface 101 of the ultrasound transducer element tile 100 and a second capacitive sensor 70b having a first sensing electrode 71b in a second corner of the surface 101 of the ultrasound transducer element tile 100. In this manner, all corners of the surface 101 may comprise a first sensing electrode of a respective capacitive sensor.

In FIG. 7, the first capacitive sensor 70a further comprises a second sensing electrode 73 a and the second capacitive sensor 70b further comprises a second sensing electrode 73b on the rigid carrier 50 by way of non-limiting example only; the respective second sensing electrodes 73 a, 73b may be replaced by a common counter electrode as previously explained. Similarly, the common electrode may be located on the surface 101, with the respective capacitive sensors having discrete sensing electrodes 73 on the rigid carrier 50.

Upon compression of the flexible layer 60 such that the orientation of the ultrasound transducer element tile 100 relative to the rigid carrier 50 is changed, the capacitance of at least some of the capacitive sensors 70a,b will change. For example, as shown in FIG.7, upon compression of the flexible layer 60 such that the left edge or left corner of the ultrasound transducer element tile 100 is brought closer to the rigid carrier 50, the distance between the first sensing electrode 71a and the second sensing electrode 73 a (or common counter electrode) of the first capacitive sensor 70a is reduced, which leads to an increase in the capacitance of this capacitive sensor as can be understood from equation (1). In this manner, by quantifying the change in capacitance for each of the capacitive sensors 70 on the ultrasound transducer element tile 100, the orientation of the ultrasound transducer element tile 100 relative to the rigid carrier 50 may be accurately determined by the controller 80.

Now upon returning to FIG. 4, the controller 80 may pass the determined relative orientations of the respective ultrasound transducer element tiles 100 of the ultrasound probe 10 onto the beamforming circuitry of the ultrasound system 1, such as the main beam former 20 or the micro-beam former 12. The beam forming circuitry may use the determined relative orientations of the respective ultrasound transducer element tiles 100 to determine which ultrasound transducer element tiles 100, or individual ultrasound transducer elements on such tiles, are to be selected for forming the desired ultrasound beam and to determine the timing sequence of the electrical pulses for controlling the selected ultrasound transducer elements or tiles 100 in order to cause the selected ultrasound transducer elements or tiles 100 to remit corresponding pressure waves that are phased to form a transmit beam that propagates in a predetermined direction from the transducer probe 10 when these electrical pulses are applied to the selected ultrasound transducer elements or tiles 100 in accordance with the determined timing sequence.

For example, in transmit or receive beamforming event, beam forming is performed across tiles 100 for which the relative displacement and orientations of each tile is known from the capacitive sensor measurements. Such beam forming may comprise choosing a focus point in the body of a subject to be images or treated. For each tile 100, the time delays to and from the tile to the selected focus point can be calculated. As is well- known per se, in beamforming the delays relative a central reference element within the tile are subtracted and then summed the result to give the reflection from the focus point upon which the ultrasound beam was focused. When beam forming across tiles 100, it may be assumed that a particular tile 100 is the reference such that from the displacement and orientation of the second tile with respect to the reference tile the delays or advances that the elements in the displaced second tile may be calculated. The calculated delays (or advances) may then be applied to the signals from the second tile before summation of signals across both tiles to give the ultrasound beam reflection from the focus point.

The respective first sensing electrodes 71 may be connected to the control circuit 80 in any suitable manner. For example, as shown in FIG.4, each first sensing electrode 71 may be contacted by a contact on the further surface 103 of the ultrasound transducer element tile 100, with a via 75, e.g. a through-silicon via in case of the ultrasound transducer element tile 100 being implemented as a CMUT cell, extending from the contact on the further surface 103 to the first sensing electrode 71. Similarly, the respective second sensing electrodes 73 (or one or more common counter electrodes) may be contacted through further contacts on the further surface 53 of the rigid carrier 50 through further vias 77 extending from the further contact to the second sensing electrodes 73. The provision of such vias is well-known per se and is therefore not explained in further detail for the sake of brevity. It is noted that such vias 75, 77 may be made of any suitable material or combination of materials as will be immediately apparent to the person skilled in the art.

Conductive tracks, e.g. conductive copper tracks embedded in an electrically insulating flexible foil such as a polyimide foil may be used to connect the first sensing electrodes to the control circuit 80. The control circuit 80 may be located on the rigid carrier 50, in which case the rigid carrier 50 may comprise conductive tracks, e.g. copper tracks, extending from the further contacts on the further surface 53 to the control circuit 80. For example, the rigid carrier 50 may include a printed circuit board comprising the conductive tracks, with the printed circuit board being connected to the further contacts in any suitable manner, e.g. through a ball grid array. For example, the control circuit 80 may form part of an application specific integrated circuit (ASIC) die mounted on the printed circuit board, which ASIC may further comprise the micro-beam former 12 for example.

However, it should be understood that the above embodiment of the interconnections between the respective sensing electrodes 71, 73 of the capacitive sensors 70 to the control circuit is by way of non-limiting example only and that any suitable interconnection arrangement may be contemplated. Moreover, the control circuit 80 is not necessarily located within the ultrasound probe 10 but instead may be located in the aforementioned terminal, e.g. user console device, or the like.

At this point, it is noted that although in the above embodiments of the ultrasound transducer probe 10 the ultrasound transducer element tiles 100 are flexibly mounted on the rigid carrier 50 through the flexible layer 60, embodiments of the present invention are not limited to this particular arrangement. For example, it is equally feasible that the ultrasound transducer element tiles 100 are mounted on a controllable flexible material, i.e. a material that can adopt different conformations in response to a stimulus such as electromagnetic radiation or heat. Examples of such materials include one-way and two- way shape memory materials, electro-actuated polymer materials, and so on. Such materials for example may be controlled by an electrode arrangement, for example the electrode arrangement comprising a first electrode on the rigid carrier 50 and a second electrode on the surface 101 of an ultrasound transducer element tile 100. Alternatively, the controllable flexible materials may carry such an electrode arrangement.

In the above embodiments, each ultrasound transducer element tile 100 is fitted with a capacitive sensor 70. However, it should be understood that alternative embodiments are equally feasible in which only some of the ultrasound transducer element tiles 100 are fitted with such a capacitive sensor 70. In such embodiments, the relative orientations of the ultrasound transducer element tiles 100 without such capacitive sensing capability may be extrapolated from the relative orientations of ultrasound transducer element tiles 100 with such capacitive sensing capability in the direct vicinity of one or more ultrasound transducer element tiles 100 without such capacitive sensing capability. This is because the ultrasound transducer probe 10 is typically conformed to a continuous surface, e.g. a body surface, for which a (complex) curvature may be extrapolated from reference points provided by the ultrasound transducer element tiles 100 with such capacitive sensing capability. Based on this extrapolation, the relative orientation of an ultrasound transducer element tile 100 without such capacitive sensing capability can be approximated from its position along this continuous surface.

FIG. 8 is a flowchart of a method 200 for controlling the ultrasound transducer probe 10 according to embodiments of the present invention. The method 200 starts in 201 in which the ultrasound transducer probe 10 is positioned on a body to be imaged or treated with ultrasound beams. This positioning may cause deformation of the flexible layer 60 (or alternatively a controllable flexible material may be controlled accordingly), which may in turn causes at least some of the ultrasound transducer element tiles 100 to change their orientation relative to the rigid carrier 50 as explained in more detail above.

In 203, the capacitive sensors 70 associated with the respective ultrasound transducer element tiles 100 are interrogated in order to determine the actual capacitance C of these capacitive sensors as explained above. This for instance may include storing a charge on each capacitive sensor and determining the voltage across the first sensing electrode 71 and the second sensing electrode 73 to determine the actual capacitance C in 205. Other suitable ways of determining the actual capacitance C may be contemplated and will be immediately apparent to the skilled person.

Upon determination of actual capacitance of the respective capacitive sensors 70, the method 200 may proceed to 207 in which the relative orientation of the respective ultrasound transducer element tiles 100 is determined based on the distance(s) between the first sensing electrode 71 and the second sensing electrode 73 as derived from the actual capacitance of the respective capacitive sensors 70, and through extrapolation for ultrasound transducer element tiles 100 without capacitive sensing capability as previously explained. The thus obtained relative orientations of the respective ultrasound transducer element tiles 100 may be used in 209 to generate control signals for the respective ultrasound transducer element tiles 100 based on their relative orientations. For example, the relative orientations may be utilized to select ultrasound transducer element tiles 100, or individual ultrasound transducer elements on such tiles, and generate timing sequences for the control signals to be applied to the selected ultrasound transducer elements or tiles 100 in order to produce an ultrasound beam having a predetermined form. Such an ultrasound beam for example may be used to generate an ultrasound image of a particular area within the body being imaged with an ultrasound imaging system 1 or alternatively may be used to target a tissue anomaly in a particular location within a body being treated with ultrasound therapy system 1.

In an embodiment, the orientation data is extracted at the ultrasound transmission rate of the ultrasound transducer probe, e.g. about every 200 μβ. In this manner, changes in the orientation of the tiles, e.g. through breathing or other noise sources, may be tracked and compensated for in real-time.

It is subsequently checked in 211 if the method 200 may be terminated. If this is not the case, the method 200 may revert back to previously described operation 203;

otherwise, the method 200 may terminate in 213.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of element tiles or steps other than those listed in a claim. The word "a" or "an" preceding an element tile does not exclude the presence of a plurality of such element tiles. The invention can be implemented by means of hardware comprising several distinct element tiles. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:
1. An ultrasound transducer probe (10) comprising :
a plurality of ultrasound transducer element tiles (100), each flexibly mounted on a rigid carrier (50) common to said ultrasound transducer element tiles, each ultrasound transducer element tile comprising at least one ultrasound transducer element; and
a plurality of capacitive sensors (70), each sensor comprising:
a first sensing electrode (71) on a surface (101) of one of the ultrasound transducer element tiles facing a surface portion of the rigid carrier; and
a second sensing electrode (73) spatially separated from the first sensing electrode on said surface portion.
2. The ultrasound transducer probe (10) of claim 1, wherein each ultrasound transducer element tile comprises at least one first sensing electrode.
3. The ultrasound transducer probe (10) of claim 1 or 2, wherein the surface (101) of each ultrasound transducer element tile (100) carries the respective first sensing electrodes (71a-d) of a further plurality of capacitive sensors (70a, 70b) distributed across said surface (101), the further plurality forming a subset of the plurality of capacitive sensors.
4. The ultrasound transducer probe (10) of claim 3, wherein the respective first sensing electrodes (71a-d) of the capacitive sensors (70a, 70b) of said further plurality are located along respective edges or in respective corners of said surface (101).
5. The ultrasound transducer probe (10) of any of claims 1-4, wherein the rigid carrier (50) comprises an integrated circuit die.
6. The ultrasound transducer probe (10) of any of claims 1-5, wherein a surface (51) of the rigid carrier (50) comprising the respective surface portions is flat, concavely curved or convexly curved.
7. The ultrasound transducer probe (10) of any of claims 1-6, wherein the plurality of ultrasound transducer element tiles (100) is mounted on a flexible layer (60) on the rigid carrier (50).
8. An ultrasound system ( 1 ) comprising the ultrasound transducer probe ( 10) of any of claims 1-7 and a processor (80) adapted to process the respective sensor signals of the plurality of capacitive sensors (70) and to extract orientation information of the respective ultrasound transducer element tiles (100) from the processed sensor signals.
9. The ultrasound system (1) of claim 8, wherein the system is further adapted to control the respective ultrasound transducer elements of the plurality of ultrasound transducer element tiles (100) in response to the extracted orientation information of the respective ultrasound transducer element tiles.
10. The ultrasound system (1) of claim 9, wherein the system is adapted to shape an ultrasound beam produced with at least a subset of the respective ultrasound transducer elements of the plurality of ultrasound transducer element tiles (100) in response to the extracted orientation information of the respective transducer element tiles.
11. The ultrasound system (1) of any of claims 8-10, wherein the processor (80) is integrated in the integrated circuit die.
12. The ultrasound system (1) of any of claims 8-10, wherein the processor (80) forms part of a control unit communicatively coupled to the ultrasound transducer probe (10).
13. The ultrasound system (1) of any of claims 8-12, wherein the system is an imaging system or a therapeutic system.
14. A method (200) of controlling the transducer probe of any of claims 1-7, comprising:
obtaining a capacitive sensor reading from each of the capacitive sensors; determining the respective orientations of the ultrasound transducer element tiles from the obtained capacitive sensor readings; and generating respective control signals for the ultrasound transducer elements of the ultrasound transducer element tiles in response to the determined respective orientations of the ultrasound transducer element tiles.
15. The method of claim 14, wherein generating respective control signals for the ultrasound transducer elements of the ultrasound transducer element tiles in response to the determined respective orientations of the transducer element tiles comprises configuring an ultrasound beam having a predetermined form in response to the determined respective orientations of the transducer element tiles.
PCT/EP2017/058724 2016-04-19 2017-04-12 Ultrasound transducer positioning WO2017182344A1 (en)

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