Patent Description:
Medical imaging is a life-saving tool in medical diagnostics and therapeutics, and yet it is not available to about <NUM>% of the global population. Over the past few decades, imagers using different modalities have reached the market. The most common are x-ray (XR), computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound. High cost and a steep learning curve have prevented imaging democratization.

<CIT> relates to a system for attaching the acoustic element of an ultrasonic transducer to an integrated circuit.

<CIT> relates to methods of generating enhanced flexure mode signals by piezoelectric transducers and ultrasound imaging probes using the same.

<CIT> relates to the design and construction of piezocomposite ultrasound arrays in conjunction with integrated circuits, and in particular to improvements in thermal and crosstalk performance in piezocomposite ultrasound array and integrated circuit assemblies.

<CIT> relates to ultrasound transducers, and more particularly to a system and method for assembling an ultrasound transducer array using electro-acoustic modules.

<CIT> relates to medical diagnostic ultrasound systems and, in particular, to backing materials for an ultrasonic transducer array.

<CIT> relates to ultrasound transducers, and more specifically ultrasound transducer assemblies configured for use with ultrasound imaging systems.

Aspects of the invention are as set out in the independent claims and optional features are set out in the dependent claims.

The World Health Organization (WHO) recommends addressing the lack of global medical imaging through the deployment of ultrasound imagers. The American Institute of Ultrasound in Medicine (AIUM) created the initiative "ultrasound first" that advocates the use of ultrasound as an effective imaging tool for patient diagnosis. The Gates Foundation estimates that <NUM>% of infant deaths (<NUM> million/year) in Africa could be prevented if ultrasound imagers were available (personal communication).

While each current imaging modality has different strengths, the advantages of ultrasound include:.

Advances in both ultrasound and complementary imaging technologies promise to dramatically enhance image quality and resolution, lower imager cost, and improve form factors (wearables), e.g., through transmissive ultrasound (tomography) and ultrasound fusion with light, thereby creating better and low-cost replacements for XR, MRI, and CT imagers in the near future. Coupling these hardware advances with artificial intelligence (AI) and machine learning (ML) leads to a transformative imaging revolution, making portable ultrasound easier to use and interpret.

Combining low cost with high quality imaging creates multiple challenges, including:.

The subject matter described herein addresses both challenges through multiple novel designs, with innovations included in the following areas:.

Customizable probe shape to reduce repetitive injury common for sonographers.

In one aspect, disclosed herein are ultrasound transducers for a handheld ultrasound imager device comprising a transducer element comprising an array of piezoelectric Micromachined Ultrasound Transducers (pMUTs). In some examples, the array comprises at least <NUM> transducer pixel. In further examples, the array comprises <NUM> or more transducer pixels. In some examples, the transducer element is integrated onto an application-specific integrated circuit (ASIC) forming a transducer tile. In further examples, a cavity is formed under the transducer element to provide acoustic isolation of the ultrasound transducer element from the ASIC. In still further examples, the cavity houses a gas, a vapor, a liquid, or a vacuum. In some embodiments, the integration between the transducer element and the ASIC is implemented by flip chip/direct bonding of transducer chip-to-ASIC Wafer (C2W), transducer chip-to-ASIC chip (C2C), or transducer wafer to ASIC wafer (W2W). In some embodiments, the ASIC module comprises connectors enabling connection to external signal processing electronics through wirebonds to dedicated pads on the ASIC or through silicon vias (TSV) directly to a high density printed circuit board (PCB). In some examples, the transducer tile is mounted on a transducer substrate. In further examples, the transducer tile is mounted on the transducer substrate through a high acoustic attenuation and high thermal conductivity acoustic absorber. In further examples, the transducer tile is mounted on the transducer substrate through a porous metal foam material. In still further examples, the porous metal foam is filled with a solid matrix, and wherein the solid matrix optionally contains a mixture of high acoustic impedance and low acoustic impedance powders to provide acoustic scattering. In some examples, the transducer substrate is mounted on a heatsink. In further examples, the heatsink comprises a multilayer heatsink structure with alternating electrically conductive and insulating layers that both remove heat from the transducer tile and provide multiple independent electrical power connections. In further examples, the heatsink provides flex retention to improve reliability during shock and vibration. In some embodiments, the transducer substrate is attached to one or more high density sub <NUM> micron pitch flex circuits enabling connection to external signal processing electronics. In some examples, the ultrasound transducer further comprises an overmolded multilayer lens, the multilayer lens comprising a plurality of layers comprising at least a first layer and a second layer, the first layer having an acoustic impedance higher than the transducer element and lower than the second layer, the second layer having an acoustic impedance higher than the first layer and lower than an imaging target; additionally, the overmolded multilayer lens may be configured to focus the imaging beams. In further examples, the plurality of layers have thicknesses of multiples of <NUM>/<NUM> of a targeted wavelength or set of wavelengths to maximize the acoustic transfer of the ultrasound energy and improve the efficiency of the low to high impedance materials. In further examples, the first layer comprises a silicone-based material. In still further examples, the second layer comprises the silicone-based material and a higher density material added to raise the acoustic impedance of the second layer. In a particular examples, the higher density material comprises an amorphous rare-earth doped aluminum oxide.

In another aspect, disclosed herein are handheld ultrasound imagers comprising: a case; an ultrasound transducer module disposed within the case and comprising an array of capacitive Micromachined Ultrasound Transducers (cMUT) or piezoelectric Micromachined Ultrasound Transducers (pMUT), the ultrasound transducer module in contact with a first heatsink and associated with a first heat zone; a plurality of receiver subsystems and transmitter subsystems disposed within the case and integrated into a multilayer stack, the multilayer stack in contact with a second heatsink and associated with a second heat zone; and an anisotropic thermally conductive material configured to move heat from the first heat zone to the second heat zone. In some examples, the anisotropic thermally conductive material comprises one or more heat pipes. In some examples, the anisotropic thermally conductive material comprises one or more pyrolytic graphite sheets (PGSs). In some examples, the handheld ultrasound imager is configured to generate one or more of a 2D, 3D, 4D, Doppler image with a power consumption under <NUM> W peak and under 7W average. In some examples, the handheld ultrasound imager further comprises an anisotropic thermally conductive material reducing the thermal coupling between the first heatsink and the second heat sink. In some examples, the first heatsink comprises a phase change material. In further examples, the phase change material comprises paraffin, a metal matrix, or a combination thereof. In some examples, the second heatsink comprises a phase change material. In further examples, the phase change material comprises paraffin, a metal matrix, or a combination thereof. In some examples, the second heatsink acts as primary structure providing internal rigid structure. In some examples, the case is a multimaterial case comprising a high thermal conductivity material and a low thermal conductivity material, wherein the multimaterial case facilitates heat transfer from the first heat zone to the second heat zone. In some examples, the handheld ultrasound imager further comprises logic to actively monitor an ultrasound procedure to manage ultrasound transducer module heating within transient heating limits by adjusting available user power to limit overheating. In some examples, the handheld ultrasound imager further comprises a bezel configured to secure the ultrasound transducer module disposed within the case. In further examples, the handheld ultrasound imager further comprises a bezel seal structure comprising spring structure to provide uniform force. In some examples, the handheld ultrasound imager further comprises a compliant joint between ultrasound transducer module and case to absorb force and improve drop resistance. In some examples, the multilayer stack provides structural support to improve drop resistance. In some examples, the case provides battery replacement access though a nondestructive case cut window which can be resealed with ultrasonic welding after battery replacement. In some examples, an internal surface of the case comprises thermal insulation material that selectively insulates internal heat sources from an external surface of the case at user grip points. In some examples, an interior surface of the case comprises thin film metalized shielding providing EMI shielding of electronics disposed within the case. In some examples, an exterior surface of the case comprises a hydrophobic material. In some examples, the handheld ultrasound imager further comprises a removable operator handle. In further examples, the operator handle is customized to fit the hand of an individual operator.

In another aspect, disclosed herein are ultrasound transducer assemblies comprising: an acoustic matching layer, a micromachined ultrasound transducer, and an intermediate layer. In some examples, the acoustic mathing layer has a first compliance. In some examples, the acoustic matching layer is configured to be placed against a subject's skin. In some examples, a micromachined ultrasound transducer has a second compliance. In some examples, the intermediate lens is between the acoustic matching layer and the micromachined ultrasound transducer. In some examples, the intermediate lens comprises a first material having a compliance greater than the first and second compliances. In further examples, the first material has a Young's modulus less than <NUM> Megapascals (MPa). In further examples, the first material includes a first plurality of micron-sized and a second plurality of nano-sized particles.

In further examples, the first material comprises an elastomeric material. In further examples, the first material comprises a PD MS-type silicone. In further examples, the first material comprises one or a combination of Sylgard <NUM>, RTV <NUM>, RTV <NUM>, Med-<NUM>, and/or Med-<NUM>. In further examples, the intermediate lens has an acoustical impedance different from an acoustical impedance of the first material.

In some examples, the micromachined ultrasound transducer is a capacitive micromachined ultrasound transducer (cMUT). In some examples, the micromachined ultrasound transducer is a piezoelectric micromachined ultrasound transducer (pMUT).

A better understanding of the features and advantages of the present subject matter will be obtained by reference to the following detailed description that sets forth illustrative examples and the accompanying drawings of which:.

Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Any reference to "or" herein is intended to encompass "and/or" unless otherwise stated.

In some examples, the handheld ultrasound imager comprises an ultrasound transducer module. In further examples, the ultrasound transducer module comprises a transducer element. In still further examples, the transducer element is integrated onto an electronic circuit to form a transducer tile by one of multiple suitable methodologies. In particular examples, the ultrasound transducer module comprises features to attenuate acoustic and/or thermal energy transfer, attenuate shock and/or vibration, and to provide flex retention.

Referring to <FIG>, in a particular examples, the ultrasound transducer module is a subset of the handheld ultrasound imager. In this embodiment, the ultrasound transducer module interfaces between the imaging probe module and the patient's body. The transducer element <NUM> suitably comprises a plurality of capacitive Micromachined Ultrasound Transducers (cMUTs) or piezoelectric Micromachined Ultrasound Transducers (pMUTs). Further, in this embodiment, the transducer tile is mounted on a transducer substrate through a high acoustic attenuation and high thermal conductivity acoustic absorber <NUM>.

Referring to <FIG>, in a particular examples, the transducer element <NUM> is integrated onto electronic circuit (ASIC) <NUM>, forming transducer tile. In this examples, the interconnection between the transducer and ASIC is implemented by one of multiple suitable means including, by way of non-limiting examples, flip chip/direct bonding of transducer chip-to-ASIC Wafer (C2W), transducer chip-to-ASIC chip (C2C), and transducer wafer to ASIC wafer (W2W). Further, in this examples , an air cavity <NUM> is formed under transducer <NUM> using a dispensed dam <NUM> around the perimeter of the transducer die to provide acoustic isolation of the transducer from the ASIC. The ASIC to transducer interconnect structure can be utilized to provide specific mechanical damping or tuning of the frequency of the transducer structure by adjusting the shape, dimensions, and materials of the interconnect structure.

Referring to <FIG>, in a particular examples, a multilayer heatsink structure <NUM> with electrical insulating layers (e.g., dielectric materials <NUM>, electrically and thermally conducting layer, including an electrical and thermal conductor <NUM> connected to a first voltage supply, an electrical and thermal conductor <NUM> connected to the ground or GND connection (the reference voltage and current return path for the first and second voltage supplies), and an electrical and thermal conductor <NUM> attached to a second voltage supply) provides heat removal from the tile and electrical power connections to the system. In this examples, the transducer substrate is mounted on a heatsink <NUM> which provides flex retention features to improve system reliability during shock and vibration, See <FIG>, <FIG>, and <FIG>.

Referring to <FIG>, in a particular examples, the ASIC connects with external electronics through wirebonds <NUM> to dedicated pads on the ASIC, or through silicon vias directly to a high density PCB. An advantage of the design and fabrication described herein is that the transducer tile can be fully tested prior to further assembly and prior to integration into the handheld ultrasound imager.

Referring to <FIG>, a non-limiting example of an ultrasound transducer module including a flex circuit <NUM> coupled to sensors and PCB <NUM> and a heat sink <NUM> with flex retention features, for example a clearance notch <NUM>, is shown. In a particular examples, the transducer substrate is attached to one or more high density flex circuits <NUM> enabling connection to signal processing electronics. In one examples, the multilayer flex <NUM> can include inductors and other components to improve localized power management. In another embodiment, the flex can include inductors and other components to improve transducer bandwidth.

Ultrasound transducers typically interface with organisms, for example the human body, which have a typical impedance of approximately <NUM> MRayl. cMUTs and pMUTs typically have an impedance less than the <NUM> MRayl. To efficiently couple power from the ultrasound transducers into the organisms, one or more acoustic impedance matching layers is beneficial. Additionally, the ultrasound transducer may need to focus its acoustic energy at a certain depth in the body. For multielement (e.g., array) ultrasound transducers, we may need to focus the beams of all the elements at a certain depth in the body. In some examples, of the handheld ultrasound imager and the ultrasound transducer described herein these functions, and others, are performed by lenses fabricated on the surface of the ultrasound transducers. An additional challenge in performing these functions is created by a need to operate over a broad frequency range, e.g., <NUM>- <NUM>, as opposed to a narrow frequency range, e.g., <NUM>-<NUM>.

Referring to <FIG>, in a particular examples, the transducer module is overmolded with a lens <NUM> comprising multiple layers (Layer <NUM> and Layer <NUM> in <FIG>) of chosen impedances and speeds of sound, forming acoustic matching to the imaging object and focusing the imaging beams. In this examples, Layer <NUM> forms the lens, while Layer <NUM> forms a matching layer and does not provide substantial lensing effects. The impedances of Layer <NUM> and Layer <NUM> are chosen to be between the transducer and organism impedances, gradually increasing or decreasing from one to the other. For example, in the typical case where the cMUT or pMUT is of low impedance compared to the organism, Layer <NUM> will have an impedance greater than the transudcer, Layer <NUM> will have an impedance larger than Layer <NUM> but less than that of the organism. Optionally, in this examples, Layer <NUM> may have a thickness of multiples of¼ the targeted wavelength to maximize the acoustic transfer of the ultrasound waves and improving the efficiency of the low to high impedance materials for a broadband transducer, particularly at the targeted wavelengths. Further, the transducer's imaging frequencies may be chosen to be an odd integer multiple of one frequency, such that Layer <NUM>'s ¼ wavelength thickness is appropriate for all imaging frequencies. For example, such a set of frequencies could be: <NUM>, <NUM>, <NUM>, <NUM>, and so on. Alternatively, the thickness could be chosen to be an odd multiple of¼ wavelengths (<NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, etc.) at all imaging frequencies.

In another examples, the transducer module could have a single layer lens (like <FIG>, with Layer <NUM> only, and without Layer <NUM>). This lens would act as both a lens and matching layer.

In the examples detailed in <FIG>, the compliances of the Layer <NUM> and Layer <NUM> are generally higher than the cMUTs and/or pMUTs on which they reside. Furthermore, Layer <NUM> is designed to resist wear and tear since it is exposed to the world, including frequent and prolonged contact with organisms, accidental shocks from dropping, and exposure to many chemicals including cleaning fluids. As a result, to protect against such wear and tear, the outside layer will frequently be of lower compliance than Layer <NUM>. In some examples, the Young's modulus of Layer <NUM> is between <NUM> and <NUM> MPa; Layer <NUM> is stiffer than Layer <NUM> and may have, for example, a Young's modulus between <NUM> to <NUM> MPa; and, additional layers over Layer <NUM> may be even stiffer, for example, having a Young's modulus between <NUM> to <NUM> MPa.

The basic example of <FIG> can be extended to a plurality of layers as shown in <FIG>, with Layers <NUM> to n-<NUM>, Layer n-<NUM>, and Layer n, for example. Each layer can act as a lens and matching layer if its thickness is variable across the surface to focus or de-focus the transducer acoustic output (e.g., having a spherical or cylindrical shape, as depicted by Layer <NUM> and Layer n-<NUM> in <FIG>). If the layer is substantially one thickness (such as Layer <NUM> and Layer n, then that layer provides primarily an impedance matching function (as opposed to a lensing function). Each layer can optionally contain nano-sized particles such as LCP (liquid crystal polymer), alumina beads, tungsten beads, vacuum nanobeads, etc..

In some examples, the overmolded multilayer lens is produced by a process wherein the first layer is formed by creating a dam around the pMUT and filling the dam with a silicone-based material. In further examples, the layer is formed as a flat layer which not only protects the wire bonds and pMUT but also has an impedance close to that of the low impedance pMUT (e.g., about <NUM> MRayl). The lens can also be fabricated using a prefabricated frame which provides structure stability to the transducer and enables lens materials to be dispenses into the frame structure. The frame dimensions are chosen to set the lens thickness and fill materials can be selected to provide shaping of the lens by using variations in surface tension between the lens and frame materials. This first lens structure can then be overmolded of cast to provide secondary lens structure and shapes.

In further examples, the additional layers are adhered to the flat layer and are chosen to have impedances increased stepwise toward that of the human body and are shaped to maximize transition over a broad range of frequencies and depths of focus. The overmolding methodology reduces costs and facilitates high volume manufacturing to address worldwide needs for medical imaging. To isolate adjacent transducers in an array from transmitting acoustic energy the lens molding process can be used to fill acoustic isolation channels between transducers which are formed during the transducer fabrication process.

Again referring to <FIG> and <FIG>, in a particular examples, the overmolded multilayer lens <NUM> has impedance stepping from the low impedance pMUT to the higher impedance of the human body. In further examples, the first layer comprises a silicone-based material whereas the second, third, etc. layers use second, third, etc. materials comprising the same silicone-based material with one or more higher density materials added to raise the impedance closer to that of the human body. In particular examples, the higher density materials comprise rare-earth doped aluminum oxide with an amorphous structure which results in less scattering due to the structures of the two materials being alike. Additionally, the geometrical structure of the material is spherical and glass-like which decreases agglomeration hence decreases attenuation losses resulting from scattering of the ultrasound energy.

Generally, an ultrasound transducer radiates energy in two directions: to the front towards the patient's body, and to the back towards the package. A patient image is formed from ultrasound reflections from the energy radiating towards the front. If strong back reflections are present, they distort the patient image. The handheld ultrasound imagers and ultrasound transducer modules described herein optionally include one or more of multiple features reducing back reflections.

Referring to <FIG>, in a one example, an air cavity acoustic mirror <NUM> or vacuum structure <NUM> is fabricated under the transducer tile <NUM> to provide uniform acoustic reflection, reducing back reflections that distort the patient image.

Continuing to refer to <FIG>, in a further examples, a high thermal conductivity substrate <NUM> with a central air cavity or a vacuum cavity within the substrate bond is located between the transducer tile <NUM> and the heat sink (not shown in <FIG>) such that the air or vacuum cavity transmits little to no acoustic energy while heat can be transmitted around the perimeter of the air or vacuum cavity through the top, bottom, and edges of the substrate <NUM>. In some examples, the high thermal conductivity substrate <NUM> may be sandwiched between die attached film(s) DAF.

In some examples, reduction of back reflections is achieved with etched pockets on the back surface of the ASIC. In further embodiments, the ASIC is located under the acoustic transducer, wherein the front surface of the ASIC mounts against the transducer and the back surface of the ASIC mounts against a heat sink, which may contain an acoustic absorbing material. In still further examples, the back surface of the ASIC comprises pockets etched into the surface to create an air cavity between the ASIC and the heat sink to reduce acoustic energy propagation from the ASIC to the heat sink. A coating on the PMUT back surface can also be fabricated to provide acoustic absorpsion made on multiple layers of differing density materials.

In some examples, reduction of back reflections is achieved with etched pockets on the back surface of the ASIC plus pockets in acoustic absorber. In further examples, the ASIC is located under the acoustic transducer and the front surface of the ASIC mounts against the transducer and the back surface of the ASIC mounts against a heat sink containing an acoustic absorbing material. In still further examples, the back surface of the ASIC has pockets etched into the surface to create an air cavity between the ASIC and the heat sink and the heat sink is constructed with pockets containing acoustic absorbing material. In such examples, the two structures are aligned so that the ribs between the pockets of acoustic absorbing material overlay with the cavities etched into the ASIC. The goal is to improve thermal transfer from the ASIC into the acoustic absorber backing while reducing the transmission of acoustic energy between these substrates.

Referring to <FIG>, in a particular examples, the transducer tile <NUM> is mounted on the PCB <NUM> through metal foam structure <NUM> that integrates low and high density materials functioning as an acoustic absorber, while exhibiting high heat conductivity. In this examples, a porous metal foam <NUM> placed behind an acoustic transducer to provide for a thermally conductive path allowing heat from the ASIC to pass into a heat sink located behind the ASIC. Further, in this example, the porous metal foam is filled with a solid matrix <NUM> such as epoxy or polyurethane or silicone and the matrix optionally contains a mixture of both high acoustic impedance and low acoustic impedance powders so as to provide for acoustic scattering.

Continuing to refer to <FIG>, in a further example, an acoustic absorber <NUM> reduces impact of CTE mismatch between transducer tile <NUM> and PCB <NUM>. In this example, CTE mismatch between an ASIC and the PCB is resolved by selection of an acoustic absorber with an intermediary CTE such that the acoustic absorber functions to not only reduce acoustic energy moving from the ASIC to the PCB but also serves to reduce thermal stresses at the interface. The absorber can also be formulated to provide a CTE to tune the stress to a specific level to manage curvature of the transducer to a specific target.

Referring to <FIG> and <FIG>, in a further example, a high acoustic impedance acoustic material <NUM> is placed between the ASIC <NUM> and the PCB <NUM> forming an acoustic reflector (<FIG>, <NUM>). In this example, acoustic energy passing through the ASIC is strongly reflected back towards the patient due to the impedance mismatch at the interface between the reflector and the ASIC. Candidate high impedance materials include, but are not limited to, tungsten and tungsten carbide. The acoustic reflector <NUM> may be used alone in place of the acoustic absorber (<FIG>, <NUM>, or may be used in conjunction with the acoustic absorber.

In some examples, the handheld ultrasound imagers described herein enable scanning a patient's body with a transducer module and the image reconstruction from the transducer signals in the probe, sending the image for display and post processing to a mobile computing device such as smartphone. To generate a high quality 2D/3D/4D/Doppler image, the transducer module must include a large number of transducer pixels (e.g., <NUM>) and transmit and receive channels (e.g., <NUM>). In such examples, the large number of channels increase power consumption, which in turn increase probe temperature. Furthermore, processing of 3D/4D/Doppler images further increases processing power demands. FDA limits surface temperature contacting patient's body to <NUM>, and contacting operator handle to <NUM>. Legacy handheld 2D imagers consume under 2W. Legacy 3D/4D/Doppler ultrasound imagers consume power on the order of IOOOW. To meet FDA temperature requirements, a 2D/3D/4D/Doppler handheld ultrasound imager described herein, in some examples, uses advanced electronics to lower average power consumption to under IOW and uses, in some examples, advanced heat management and packaging to keep the device temperature said temperature limits. In some examples, the handheld ultrasound imagers described herein have an average maximum power consumption of about 6W to about 7W. In some examples, the handheld ultrasound imagers described herein have a peak power consumption of about IOW.

Referring to <FIG>, in a particular example, a handheld ultrasound imager comprises a multimaterial case <NUM> having a case shape <NUM> and held together via single fastener accessed via USB-C port at rear. In this example, an internal heatsink structure <NUM> acts as primary structure for the probe to provide an internal rigid structure that enables thinner case design. In this example, multilayer stacks of receiver and transmitter sub-systems are integrated into a multilayer stack <NUM> which provides structural support to improve drop resistance. The case <NUM> design, in some example, selectively insulates internal heat sources from the case surface at user grip points with insulation inside the case between grip points and external case. The case <NUM> shape, in some example, reduces repetitive injury by minimizing case neck size and placement of grip points to limit wrist deflection from neutral position during application of force to patient by user.

Referring to <FIG>, in a particular example, a handheld ultrasound imager comprises a bezel seal structure <NUM> which provides uniform force with spring structure or retention springs <NUM>, which apply a spring force <NUM> to the bezel seal structure <NUM> which in response applies a normal force on the heat-sink/ sensor module assembly.

Referring to <FIG> and <FIG>, in a particular example, a handheld ultrasound imager comprises a compliant joint <NUM>, <NUM> design between a sensor module assembly <NUM> and a main probe <NUM> body to absorb force during drop test improving reliability.

In some examples, the case comprises a thin film metalized shielding structure on the inner case surface that provides EMI shielding of internal electronics. In some examples, the case comprises a hydrophobic surface. In some examples, the case provides battery replacement access though nondestructive case cut window which can be resealed with ultrasonic welding after battery replacement.

Handheld ultrasound imagers face maximum safe temperature limits, set by the U. FDA at <NUM> on a surface touching the patient, and <NUM> on the handle used by the operator. In simple terms, higher image quality requires increased power consumption of the electronics, which in turn increases probe temperatures. The handheld ultrasound imagers described herein, in various examples, deploy multiple new temperature reducing technologies to enable better image quality in a portable, handheld form factor.

Referring to <FIG>, in a particular example, a handheld ultrasound imager utilizes directed heat flow between discrete heat zones <NUM>.

Referring to <FIG> and <FIG>, in a particular example, a handheld ultrasound imager comprises two separate heat zones with separate heat sinks. In this example, Heat Zone <NUM><NUM> includes the transducer head circuit assembly. And, in this example, Heat Zone <NUM><NUM> includes system electronics. Heat Sink <NUM><NUM> is attached to components in Heat Zone <NUM><NUM> only. Heat Sink <NUM><NUM> is attached to components in Heat Zone <NUM><NUM> only. Heat Zones <NUM> and <NUM> are isolated by severing any high thermally conductive link from Heat Zone <NUM><NUM> to Heat Zone <NUM><NUM>. Mechanical support is made from low thermal conductivity materials in BODY <NUM><NUM>, while heat is directed away from Heat Zone <NUM> to the high thermal conductivity BODY <NUM><NUM> by means of high thermally conductive materials with anisotropic thermal conductivity <NUM>. Heat flow in one direction is enhanced, while heat flow in another direction is suppressed. This enables heat to be directed away from Heat Zone <NUM><NUM> in an efficient manner using widely available materials, while coupling to and from Heat Zone <NUM><NUM> is limited. Heat can be moved through the anisotropic materials in a specific direction, allowing discretization of the heat zones.

Referring to <FIG>, in a particular example, a handheld ultrasound imager comprises an anisotropic thermally conductive material <NUM> bonded between the chip <NUM> and the system board <NUM> (and coupled together with adhesive <NUM>) to spread heat away from the semiconductor chip, reducing thermal coupling between Heat Sink I <NUM> and Heat Sink <NUM><NUM>. In some examples, the anisotropic thermal conductive material <NUM> comprises a pyrolytic graphite sheet (PGS), heat pipes, or a combination thereof.

In some examples, a handheld ultrasound imager comprises phase change materials for transient heat control. In further examples, a handheld ultrasound imager comprises a heatsink with embedded phase change material that extends the transient thermal performance of the transducer head by the use of latent heat phenomenon. The heatsink provides a longer time constant than solid copper or aluminum due to a reservoir of unmolten material that has a melting temperature of -<NUM>. The volume of phase change material in the heat sink determines the transient behavior of the interface near the heat-sink base. In further examples, suitable phase change materials include paraffin (wax), which can be configured to various melting point temperatures and a metal matrix such as Bismuth, Indium, and other materials that have low melting temperatures.

In some examples, a handheld ultrasound imager comprises a combination acoustic absorber and thermal management solution. In further examples, a handheld ultrasound imager comprises a heat transfer device using latent heat phenomenon such as a vapor chamber or flat heat pipe. The apparatus optionally comprises a copper outer housing with "wick" structures on the walls to facilitate vapor/condensation at a specific temperature. The apparatus has a sealed inside volume to hold a small amount of liquid at some atmospheric pressure necessary to produce boiling at temperatures of interest. Intrinsic to the assembly is an internal air gap that may be used to reflect or attenuate impinging acoustic waves. The inclusion of an air gap is, in some cases, key to the acoustic properties of the assembly. In such examples, the benefit of the vapor chamber function is enhanced heat transfer while maintaining acoustic absorption or reflection. Heat transfer using a vapor chamber is much higher that a solid copper block. This optional feature allows use of high thermal conductive assembly while maintaining an air gap directly under the application device.

In some examples, a handheld ultrasound imager comprises a two-part probe body with an integrated heatsink. In further examples, a handheld ultrasound imager comprises a handheld probe body with mixed materials utilized to assist in segregating heat flow from two or more discreet heat sources. This example includes low thermal conductivity material bonded to high thermal conductivity material in a way that allows heat to be transferred to the high thermal conductivity part while insulating a separate heat source. This has the effect of splitting heat flow paths of two or more sources in the same enclosure. The high thermal conductivity material can add mechanical features such as fins or ribs to allow increased convection heat loss. This example is optionally used in conjunction with other thermal management options described herein to allow segregated and directed heat flow.

In some examples, temperature during ultrasound procedures is actively monitored and transient heating limits are applied to adjust available power to limit overheating.

In some examples, a heatsink comprises a ribbed section under the transducer substrate and an extension plate conducting heat away from transducer substrate. In some examples, a heatsink in contact with the ultrasound transducer module comprises ribs with pyramid shape to direct heat away from the transducer substrate.

Battery operation is challenging in a handheld ultrasound imager. A handheld ultrasound imager should be small and light enough to reduce and prevent operator injury, but must supply adequate power to generate medically useful images and even therapeutic effects. In some examples, the handheld ultrasound imagers described herein comprise a primary battery and a back-up battery, thus providing battery redundancy.

In some examples, one or more batteries comprise an external flat-pack/ conformal style that interfaces via a USB-C portal. In such examples, a battery becomes new outer-skin and increases external dimensions. In further examples, a battery provides mechanical shock absorption via molded in features in plastic case.

In some examples, one or more batteries includes fast recharge capability via built-in prongs for <NUM>/<NUM> volt outlet. In further examples, the handheld ultrasound imager uses internal circuitry to manage the charge. In various examples, the USB-C portal comprises a USB-C blade or a USB-C cord facilitating plugging into a power source for charging.

In some examples, a handheld ultrasound imager comprises an internal battery compartment, which is separate from the rest of interior, and sealed, with factory accessible exterior opening for battery service.

Traditional medical ultrasound imaging uses a variety of probes to interface with the patients' body. The shape of the probe is often optimized for the body parts being imaged and current systems use multiple probes. Despite optimization of the probes for imaging specific body organs, nearly <NUM>% of sonographers performing ultrasound imaging experience work-related pain; <NUM>% of them have experienced work-related pain for more than half their careers. One of every five sonographers sustains a career-ending work-related injury, and the average time in the profession before a sonographer experiences pain is five years, according to a landmark study by the SDMS in <NUM> based on responses from <NUM>,<NUM> participants in the U. and Canada.

A new type of a probe emerged in <NUM>, a universal ultrasound imager enabling imaging the <NUM> body organs. Newer probes target even more body organs with a single probe. However, this will increase problems for sonographers, as one probe shape can't be optimized for a broad range of applications, increasing strain on sonographers' hands. The handheld ultrasound imagers described herein, in some examples, reduce operator health problems resulting from using universal imagers.

Referring to <FIG>, in a particular example, a handheld ultrasound imager comprises an ultrasound transducer module <NUM> and a customizable operator handle <NUM> attachable to the imager case <NUM>, the part traditionally interfacing with sonographer/operator hand. Modifying imager case <NUM> to enable insertion of the customizable operator handle (e.g., sliding and snapping the operator handle <NUM> onto imager case <NUM>), provides an option for multiple operator handles, each optimized for specific applications and for a specific operator. Such examples, further enable optimization of the operator handle <NUM> to the operator's hand, by sending a 3D operator hand image to a 3D handle printing shop equipped with a suitable optimization software. Moreover, such examples enable personalization of the operator handle <NUM>.

In such examples, an additional benefit of the separate operator handle is an increase of allowed imager power dissipation, important to higher frame rate and 3D imaging. The operator handle is optionally made of thermally isolating and reflecting materials, allowing handle electronics enclosure temperature to be higher than the surface temperature touching operator hand.

Claim 1:
An ultrasound transducer (<NUM>) for a handheld ultrasound imager device comprising a transducer element (<NUM>) comprising an array of piezoelectric Micromachined Ultrasound Transducers (pMUTs),
wherein the transducer element (<NUM>) is integrated onto an application-specific integrated circuit (ASIC) (<NUM>) forming a transducer tile, and
characterized in that dam (<NUM>) around a perimeter of the transducer element (<NUM>) extends down to the ASIC (<NUM>) and forms a cavity (<NUM>) between the transducer element (<NUM>) and the ASIC (<NUM>) to provide acoustic isolation of the ultrasound transducer element (<NUM>) from the ASIC (<NUM>).