Ultrasound transducer array

A transducer array for an ultrasound imaging system includes a substrate and a single array comprising individual sub-sets of transducer elements disposed on the substrate, wherein the individual sub-sets are physically separate from each other and spatially arranged contiguous to each other. An apparatus includes a transducer array with a substrate and a single array comprising individual sub-sets of transducer elements disposed on the substrate, wherein the individual sub-sets are not in physical contact with each other and are serially arranged with respect to each other. The apparatus further includes transmit circuitry that conveys an excitation pulse to the transducer array, receive circuitry that receives a signal indicative of an ultrasound echo from the transducer array, and a beamformer that processes the received signal, generating ultrasound image data.

TECHNICAL FIELD

The following generally relates to ultrasound imaging and more particularly to an ultrasound imaging transducer array with individual elements and/or sub-groups of elements on a substrate rather than a fabricated entire array of physically connected elements mounted on the substrate.

BACKGROUND

Micromachined ultrasonic transducers (MUT), such as capacitive (CMUT) or piezoelectric (PMUT) types, have demonstrated performance benefits relative to traditional piezoelectric-based transducers. These benefits include increased bandwidth, which enables a wider range of imaging options such as more harmonic frequencies and improved contrast agent imaging. However, very few MUT based probes have been marketed commercially. One challenge in the production of commercial MUT probes is a performance implication of the silicon backbone. The literature has explored the inter-element acoustic crosstalk that can be supported by the rigid, continuous backbone. Some have used diced or etched grooves on the backbone or between elements to reduce crosstalk, which has been fairly effective. In another approach, a compliant substrate was fabricated in the wafer processing to decouple adjacent CMUT cells. The ideal crosstalk configuration, though, would provide complete backbone separation between elements.

Another challenge in the production of commercial MUT probes is the finite number of arrays that can be produced on each wafer. For instance, while it may be possible to fit twenty-three high-frequency linear arrays on a standard6″ wafer (FIG. 1) or eight abdominal arrays in the same circular area (FIG. 2), the fabrication cost for any one wafer is roughly the same, regardless of the number of arrays produced on the wafer. Consequently, the cost per array scales with the area of the array. Some area of the wafer remains unused because of the limit to the number of rectangles/arrays that can be fit into the circular wafer (i.e. the empty spaces inFIGS. 1 and 2). Furthermore, the yield of any individual element has consequences on the yield of the whole array. For instance, if one element has a poor etching characteristic, or if some contamination inhibits the sputtering adhesion on that element, then the entire array must be scrapped. InFIGS. 1 and 2, each rectangle is a fabricated monolithic array and include a plurality of physically connected elements, and the individual elements of an array are not physically separate and distinct components.

Another challenge in commercial production is the fabrication of curved arrays. MUT designs use a solid backbone of silicon, which prohibits curving the array in azimuth. The silicon backbone could be thinned with chemical-mechanical polishing after the top-side processing is complete, but this puts the individual elements at risk, introduces additional variability, and does not eliminate the risk that the thinned silicon backbone could still break during bending. Another approach involves etching grooves into the backbone and optionally filling them with a flexible polymer, but this approach requires complex etching and alignment between the top and bottom surfaces of the wafer, complicates handling in the pre-polymer state, and requires a non-standard polymer groove-filling application to the silicon. A reverse fabrication process has been implemented in which the silicon backbone is completely removed late in the process, which could possibly facilitate curvature after the backbone removal. However, this technique makes it impossible to test elements at the wafer-level, thereby increasing the cost of any wafer-level failures that could not be discovered until the probe assembly is nearly complete. Unfortunately, all of these approaches add wafer-level complexity and the potential for increased cost.

SUMMARY

Aspects of the application address the above matters, and others.

In one aspect, a transducer array for an ultrasound imaging system includes a substrate and a single array comprising individual sub-sets of transducer elements disposed on the substrate, wherein the individual sub-sets are physically separate from each other and spatially arranged contiguous to each other.

In another aspect, an apparatus includes a transducer array with a substrate and a single array comprising individual sub-sets of transducer elements disposed on the substrate, wherein the individual sub-sets are not in physical contact with each other and are serially arranged with respect to each other. The apparatus further includes transmit circuitry that conveys an excitation pulse to the transducer array, receive circuitry that receives a signal indicative of an ultrasound echo from the transducer array, and a beamformer that processes the received signal, generating ultrasound image data.

In another aspect, a method includes transmitting an ultrasound signal with a transducer array having a plurality of individual and physically separate elements and/or sub-groups of elements, receiving an echo signal with the transducer array, beamforming the echo signal to create an image, and displaying the image.

Those skilled in the art will recognize still other aspects of the present application upon reading and understanding the attached description.

DETAILED DESCRIPTION

In the illustrated embodiment, the transducer elements304are only individual elements, only sub-groups of elements (each with two or more, but not all), or a combination of at least one individual element and at least one sub-group of elements, and are not all part of a fabricated monolithic array, such as those fabricated on wafers such as those shown inFIGS. 1 and 2. In one non-limiting instance, radiating surfaces of the elements304are planar on the order of ±0.015 millimeters (mm), lateral spacing of the elements304with respect to each other and along an array direction (azimuth) is on the order of ±0.015 mm, and/or consistency along element direction (elevation) is on the order of ±0.05 mm. Other surfaces, lateral spacing and/or consistency are contemplated herein.

Non-limiting examples of the transducer array302are described in connection withFIGS. 4 and 5for linear arrays andFIGS. 6 and 7for curved arrays. Other array configurations are contemplated herein.

FIG. 4depicts an example in which element4021,4022,4023, . . . ,402N(where N is a positive integer), collectively referred to herein as elements402, are disposed on a (rigid or flexible) substrate404, which includes pairs of electrical traces4061,4062,4063, . . . ,406N, one pair for each element. Each element402is electrically coupled to a corresponding pair of traces via a wire, etc. The substrate404is configured to include predetermined acoustic properties, e.g., to mitigate any reflections and/or suppress any vibrational modes (e.g., Lamb waves) that could couple into it from the element vibration. Alternately, the substrate404consists of integrated circuits (e.g., for signal conditioning and/or processing) that could have exposed attachment pads.

An electro-mechanical machine408(or alternatively, tweezers) is shown placing the element402Non the substrate404. For example, after the elements406are cut out of a wafer, each element402is individually and independently (with respect to the other element(s)) picked up and placed on the substrate404(i.e. into the array302) using known technology. In this instance, each of the elements402is not physically connected to another element(s)402or fabricated on a same wafer with another element(s)402. For example, each of the elements402is only physically connected to the substrate404, with the exception of wires, active and/or passive components, etc., if any. The elements402are attached to the substrate404using an adhesive, solder, and/or other bonding mechanism.

In the illustrated example, the elements4021,4022, and4023are individual elements disposed on the substrate404(e.g., similar to the element402N) and with a separation there between on the order of ±0.015 mm. In a variation, the sub-group of elements4021and4022or the sub-group of elements4021,4022, and4023are fabricated on and as part of a single unity sub-array and the sub-array (and not individual elements) is disposed on the substrate404. For example, the sub-group of elements4021and4022or the sub-group of elements4021,4022, and4023could be individual sub-arrays formed on a wafer. With this configuration, the sub-group of elements4021and4022or the sub-group of elements4021,4022, and4023are physically connected to each other, and neither the elements4021and4022nor the elements4021,4022, and4023are physically connected to the element402N.

FIG. 5depicts an example in which elements5021,5022,5023, . . . ,502N(collectively referred to herein as elements502) are disposed on a substrate504. The substrate504includes a plurality of electrical interconnects506embedded in the substrate504. Each of the elements5021,5022,5023, . . . ,502Nincludes one or more electrical connections508through a thickness dimension of the element instead of from a top surface of the element (e.g., a through-silicon vias (TSV's) where the material is silicon, etc.) through which electrical signals are transferred from a respective one of the elements5021,5022,5023, . . . ,502Nto the substrate504. Similar to the configuration described inFIG. 4, a machine, etc. can place the individual elements502on the substrate504, and the elements5021,5022, and5023are individually and independently disposed on the substrate504, or the elements5021and5022or the elements5021,5022, and5023are part of a single unity piece disposed on the substrate504.

FIG. 6depicts an example in which a flexible substrate602with elements604is disposed on a backing606having a rigid curved surface608. In one instance, the elements604are disposed individually on the flexible substrate602while the flexible substrate602is flat, e.g., similar to the element402NofFIG. 4. In another instance, the elements604are disposed on the flexible substrate602while the flexible substrate602is flexed. For example, the flexible substrate602can first be flexed around and/or disposed on the rigid curved surface608, and then the elements604can be disposed on the flexible substrate602. Likewise, a machine, etc. can place the elements604, and the elements604are individually and/or group-wise placed on the flexible substrate602.

FIG. 7depicts the array inFIG. 6except that the flexible substrate602is omitted, and the elements604are individually disposed directly on the curved backing606. In this instance, the curved backing606serves as a substrate. Likewise, a machine, etc. can place the elements604, and the elements604are individually and/or group-wise placed on the backing606.

For the approached described herein, the individual and/or sub-groups of elements (and not the entire array302) are first fabricated in a wafer, then individually separated (e.g., etched, diced, etc.) from the wafer, and subsequently assembled individually into the transducer array302. Relative to a configuration (e.g.,FIGS. 1 and 2) in which entire arrays are fabricated on a wafer, the approach described herein enables increased wafer area utilization optimizing cost per element, increased array geometry flexibility (e.g., elements can be assembled into curved transducers without additional wafer-level complexity), and/or a reduction of acoustic cross-talk, e.g., by the elimination of a common backbone.FIG. 8depicts an example wafer800with a plurality of rows802of individual and/or groups of fabricated transducer elements804, and not complete arrays.

Returning toFIG. 3, transmit circuitry306generates pulses that excite a predetermined set of the elements to transmit the ultrasound signals. Receive circuitry308receives the electrical signals. In one instance, the receive circuitry308is configured to pre-process the received signals, e.g., by amplifying, digitizing, etc. the signals. A switch310switches between the transmit and receive circuitry306and308, depending on whether the transducer array302is in transmit or receive mode. A beamformer312processes the received signals, for example, by applying time delays and weights, summing, and/or otherwise processing the received signal. Other processing is also contemplated herein.

A scan converter314scan converts the beamformed data, converting the beamformed data into the coordinate system of a display316, which visually displays the images. The data can be visually displayed in a graphical user interface (GUI), which allows the user to selectively rotate, scale, and/or manipulate the displayed data through a mouse, a keyboard, touch-screen controls, etc. A controller318controls one or more of the components of the system300, e.g., based on a mode of operation (e.g., B-mode, etc.). A user interface320includes an input device (e.g., a physical control, a touch-sensitive surface, etc.) and/or an output device (e.g., a display screen, etc.). A mode, scanning, and/or other function can be activated by a signal indicative of input from the user interface320.

In one instance, the transducer array302is part of a probe and the transmit circuitry306, the receive circuitry308, the switch310, the beamformer312, the scan converter314, the controller318, the user interface320, and the display316are part of a console. Communication there between can be through a wired (e.g., a cable and electro-mechanical interfaces) and/or wireless communication channel. In this instance, the console can be a portable computer such as a laptop, a notebook, etc., with additional hardware and/or software for ultrasound imaging. The console can be docked to a docketing station and used.

Alternatively, the console can be part (fixed or removable) of a mobile or portable cart system with wheels, casters, rollers, or the like, which can be moved around. In this instance, the display316may be separate from the console and connected thereto through a wired and/or wireless communication channel. Where the cart includes a docking interface, the console can be interfaced with the cart and used. An example of such a system is described in US publication 2011/0118562 A1, entitled “Portable ultrasound scanner,” and filed on Nov. 17, 2009, which is incorporated herein in its entirety by reference.

Alternatively, the transducer array302, the transmit circuitry306, the receive circuitry308, the switch310, the beamformer312, the scan converter314, the controller318, the user interface320, and the display316are all housed by and enclosed within a hand-held ultrasound apparatus, with a housing that mechanically supports and/or shields the components within. An example of a hand-held device is described in U.S. Pat. No. 7,699,776, entitled “Intuitive Ultrasonic Imaging System and Related Method Thereof,” and filed on Mar. 6, 2003, which is incorporated herein in its entirety by reference.

The transducer array302described herein can have alternating high- and low-frequency elements (e.g., odd elements are low frequency, even elements are high frequency). Such a design could enhance tissue harmonic imaging (transmit primarily on low-frequency elements, receive primarily on high-frequency elements) and/or improve image quality through the entire depth (use smaller-elevation high-frequency elements for shallow imaging and large-elevation low-frequency elements for deep imaging).

Furthermore, the surface profile of the elements can be varied across elevation by depositing multiple rows of varying thicknesses. This allows for elevation focusing, which is difficult to do on a basically planar piece of silicon. Furthermore, elements from varying sizes, shapes, and/or compositions can be assembled. For instance, the array302can have alternating CMUT and PZT elements, e.g., where the PZT elements are used for transmit and the CMUT elements for receive. This arrangement would be very difficult without the fine-scale assembly approach described herein.

The element and/or group-wise construction described herein is compatible with a wide variety of cell designs (e.g., square, hexagonal, circular, extra membrane mass, non-flat surfaces, etc.), element designs (e.g., multi-frequency, apodization, patterned electrodes, etc.), wafer processing techniques (e.g., sacrificial release, wafer bonding, etc.), and/or interconnect configurations (e.g., top surface only for wire bonding or other attachment, through-silicon vias, trench connections, etc.). Generally, the element and/or group-wise construction described herein is independent of the specific design of the transducer element304.

FIG. 9illustrates an example method. At902, an ultrasound signal is transmitted via a transducer array that includes a plurality of individual elements (i.e., elements not part of a common substrate) and/or a plurality of sub-groups of elements (i.e., each sub-group is part of a common substrate, and the different sub-groups are part of different substrates). At904, an echo signal is received via the transducer array. At906, the echo signal is processed to produce an image.

The application has been described with reference to various embodiments. Modifications and alterations will occur to others upon reading the application. It is intended that the invention be construed as including all such modifications and alterations, including insofar as they come within the scope of the appended claims and the equivalents thereof.