Ultrasound imaging device

Abstract

Ultrasound imaging device The present description relates to an ultrasound imaging device (100) comprising a set (101) of ultrasonic transducers, an acoustic coupling layer (140) coating said set (101) of ultrasonic transducers, and a heating device (150) adapted to heat an object to be imaged placed on the acoustic coupling layer (140) during a phase of acquisition of an ultrasound image. Figure for abstract: Fig. 1

Description

Title of the invention: Ultrasound imaging device Technical field

[0001] The present description relates to the field of ultrasound imaging devices, and more particularly relates to skin print acquisition devices and / or microvascular imaging devices based on ultrasound transducers. Prior art

[0002] An ultrasound imaging device conventionally comprises a plurality of ultrasound transducers, and an electronic control circuit connected to the transducers. In operation, all of the transducers are arranged facing an object or body of which an image is to be acquired. The electronic control circuit is configured to apply electrical excitation signals to the transducers, so as to cause the emission of ultrasound waves by the transducers, in the direction of the body to be analyzed. The ultrasound waves emitted by the transducers are reflected by the body to be analyzed (by its internal and / or superficial structure), then return to the transducers which convert them again into electrical signals. These electrical response signals are read by the electronic control circuit, and can be stored and analyzed to deduce information about the body studied.

[0003] It would be desirable to improve at least in part certain aspects of known ultrasound imaging devices. Summary of the invention

[0004] For this, one embodiment provides an ultrasound imaging device comprising a set of ultrasound transducers, an acoustic coupling layer coating said set of ultrasound transducers, and a heating device adapted to heat an object to be imaged placed on the acoustic coupling layer during a phase of acquisition of an ultrasound image.

[0005] According to one embodiment, the device further comprises an electronic power supply and control circuit.

[0006] According to one embodiment, the heating device is adapted to recover heat generated by the electronic power supply and control circuit and to dissipate all or part of this heat in the acoustic coupling layer, above the set of ultrasonic transducers.

[0007] According to one embodiment, the heating device comprises one or more metal sheets arranged to conduct the heat generated by the electronic power supply and control circuit and dissipate all or part of this heat in the acoustic coupling layer, above the set of ultrasonic transducers.

[0008] According to one embodiment, the heating device further comprises one or more switches configured to interrupt the transfer of heat to the acoustic coupling layer if an internal temperature of the device exceeds a predetermined threshold.

[0009] According to one embodiment, the heating device comprises a flexible Peletier module, a cold face of which is turned towards the electronic power supply and control circuit and a hot face of which is turned towards the object to be imaged.

[0010] According to one embodiment, the heating device comprises a heating mat comprising a serpentine metal resistor, arranged between the set of ultrasonic transducers and the object to be imaged.

[0011] According to one embodiment, the heating mat is embedded in the acoustic coupling layer.

[0012] According to one embodiment, the heating mat covers the acoustic coupling layer.

[0013] According to one embodiment, the heating device comprises a heating layer made of a thermoelectric polymer material, integrated into the acoustic coupling layer.

[0014] According to one embodiment, the heating layer is electrically connected to the electronic power supply and control circuit by connection elements.

[0015] According to one embodiment, the ultrasonic transducers of the set of ultrasonic transducers are CMUT or PMUT transducers, piezoelectric or piezocomposite transducers, or single crystal transducers.

[0016] According to one embodiment, the acoustic coupling layer comprises at least one layer of an activatable polymer material configured to have a first Young's modulus during an ultrasound image acquisition phase and a second Young's modulus greater than the first Young's modulus outside of said acquisition phase.

[0017] Another embodiment provides an ultrasound imaging device comprising a set of ultrasound transducers and an acoustic coupling layer coating said set of ultrasound transducers, in which the acoustic coupling layer is made of an activatable polymer material configured to have a first Young's modulus during a phase of acquisition of an ultrasound image and a second Young's modulus greater than the first Young's modulus outside of said acquisition phase.

[0018] According to one embodiment, the acoustic coupling layer is made of a thermo-active, photo-active, electro-active polymer, or a polymer that can be activated under the effect of a chemical or mechanical stimulus.

[0019] According to one embodiment, the acoustic coupling layer is made of a polymer thermo-active, the imaging device comprising a heating device configured to heat the acoustic coupling layer during an acquisition phase of an ultrasound image, and interrupt the heating outside of said acquisition phase.

[0020] According to one embodiment, the acoustic coupling layer is made of a thermo-active polymer that can be activated directly under the effect of heat generated by an object to be imaged, for example a user's finger.

[0021] According to one embodiment, the acoustic coupling layer is made of a thermo-active polymer which can be activated to exhibit the first Young's modulus when its temperature exceeds a threshold between 25°C and 40°C.

[0022] According to one embodiment, the acoustic coupling layer is made of a photoactive material whose Young's modulus takes the first value under the effect of light irradiation at a first wavelength A, and takes the second value under the effect of light irradiation at a second wavelength B, different from A, or when the irradiation at the first wavelength A is interrupted, or under the effect of another stimulus.

[0023] According to one embodiment, the device comprises one or more first light sources adapted to emit radiation at wavelength A through the acoustic coupling layer, and one or more second light sources adapted to emit radiation at wavelength B through the acoustic coupling layer.

[0024] According to one embodiment, the device further comprises an electronic circuit for supplying and controlling the set of ultrasonic transducers, said one or more first and one or more second light sources being controlled by the electronic supply and control circuit.

[0025] According to one embodiment, the acoustic coupling layer is made of an electroactive material whose Young's modulus takes the first value under the effect of an electrical polarization, and takes the second value in the absence of said electrical polarization.

[0026] According to one embodiment, the device further comprises an electronic circuit for supplying and controlling the set of ultrasonic transducers, the device comprising first and second electrodes in contact with the acoustic coupling layer and connected to the electronic supply and control circuit for the application of said electrical polarization.

[0027] According to one embodiment, the ultrasonic transducers of the set of ultrasonic transducers are CMUT or PMUT transducers, piezoelectric or piezocomposite transducers, or single crystal transducers.

[0028] According to one embodiment, the device is adapted to heat an object to be imaged placed on the acoustic coupling layer during an acquisition phase of a ultrasound image. Brief description of the drawings

[0029] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0030] [Fig.l] schematically represents an example of an ultrasound imaging device according to one embodiment;

[0031] [Fig.2] schematically represents another example of an ultrasound imaging device according to one embodiment;

[0032] [Fig.3] schematically represents another example of an ultrasound imaging device according to one embodiment;

[0033] [Fig.4] schematically represents another example of an ultrasound imaging device according to one embodiment;

[0034] [Fig.5] schematically represents another example of an ultrasound imaging device according to one embodiment;

[0035] [Fig.6] schematically represents another example of an ultrasound imaging device according to one embodiment;

[0036] [Fig.7] schematically represents another example of an ultrasound imaging device according to one embodiment; and

[0037] [Fig.8] schematically represents another example of an ultrasound imaging device according to one embodiment. Description of the embodiments

[0038] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0039] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the production of the ultrasonic transducers and the electronic control circuits of the described devices has not been detailed, the described embodiments being compatible with the usual productions of these elements. In addition, the various applications that the described devices may have have not been detailed, the described embodiments being compatible with all or most of the usual applications of ultrasonic imaging devices, and in particular applications for imaging parts of the human or animal body.

[0040] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when we refer to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0041] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0042] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0043] [Fig.l] is a sectional view schematically showing an example of an ultrasound imaging device 100 according to one embodiment.

[0044] The device 100 of [Fig. 1] comprises a set 101 of ultrasonic transducers (US), for example arranged in a matrix, in a bar, or in any other arrangement. The transducers of the set 101 are for example CMUT type transducers (capacitive ultrasonic membrane transducers), PMUT type transducers (piezoelectric membrane transducers), crystal transducers, or any other type of ultrasonic transducers, for example piezoelectric or piezocomposite transducers, or single crystal transducers.

[0045] The transducers of the assembly 101 are for example integrated into a monolithic chip, for example formed in and on a semiconductor substrate, for example a silicon substrate, or even in and on an insulating substrate, for example a glass substrate (not detailed in the figure).

[0046] In the example shown, the set of transducers 101 is mounted on a printed circuit board 103. The printed circuit board 103 comprises, for example, a support made of an electrically insulating material, for example plastic, and a set of metal interconnection pads and tracks (not detailed in the figure) formed on at least one face of the support. In this example, the set 101 of ultrasonic transducers is fixed and electrically connected to the upper face of the printed circuit board 103.

[0047] The device 100 of [Fig.l] further comprises an electronic power supply and control circuit 110.

[0048] The circuit 110 comprises a transmission circuit 111 (PULS) adapted to provide electrical excitation signals to the ultrasonic transducers of the assembly 101 so as to cause the emission of ultrasonic waves by the transducers.

[0049] The circuit 110 further comprises a receiving circuit 113 (REC) adapted to read electrical response signals generated by the ultrasonic transducers of the assembly 101 under the effect of an ultrasonic wave received from the object to be imaged.

[0050] The circuit 110 further comprises a circuit 115 (PROC) for processing the electrical signals emitted by the transmission circuit 111 and / or received by the reception circuit 113.

[0051] The circuit 110 further comprises an electrical power supply circuit 117 (SUPP). The circuit 117 is in particular adapted to electrically supply the transmission 111, reception 113 and / or processing 115 circuits.

[0052] The circuits 111, 113, 115 and 117 are for example integrated in one or more integrated circuit chips. For example, the circuits 111, 113, 115 and 117 are respectively integrated in four separate integrated circuit chips. The embodiments described are however not limited to this particular case.

[0053] The circuits 111, 113, 115 and 117 are for example mounted on one or more printed circuit boards. In the example shown, the transmission 111 and reception 113 circuits are mounted on a printed circuit board 121, and the processing 115 and power supply 117 circuits are mounted on another printed circuit board 123. More particularly, in this example, the transmission 111 and reception 113 circuits are fixed and electrically connected to the upper face of the printed circuit board 121, and the processing 115 and power supply 123 circuits are fixed and electrically connected to the upper face of the printed circuit board 123.

[0054] In the example of [Fig.l], the set of ultrasonic transducers 101 and the electronic power supply and control circuit 110 are integrated monolithically, for example in the same housing (not visible in the figure) so as to form a monolithic ultrasonic imaging module.

[0055] In this example, the assembly 101 of ultrasonic transducers is arranged above the electronic power supply and control circuit 110. More particularly, in the example shown, the printed circuit board 103 is arranged above the assembly comprising the printed circuit board 121 and the circuits 111 and 113, which is itself arranged above the assembly comprising the printed circuit board 123 and the circuits 115 and 117. In other words, the printed circuit boards 123, 121 and 103 are stacked vertically. Mechanical fastening elements, not shown, may be provided to mechanically fasten the printed circuit boards to each other. In addition, electrical connection elements, not shown, may be provided to electrically connect the printed circuit boards to each other.

[0056] A protective dielectric material 131, for example a protective resin, may be disposed between the printed circuit boards 123 and 121 and between the printed circuit boards 121 and 103. For example, the material 131 completely fills the free spaces between the printed circuit board 123 and the printed circuit board 121 and between the printed circuit board 121 and the printed circuit board 103. The protective material 131 may further cover the underside of the printed circuit board 123, and the upper side of the printed circuit board 103 around the set 101 of ultrasonic transducers.

[0057] The device 100 of [Fig. 1] further comprises a coupling layer 140, for example made of a polymer material, for example electrically insulating, coating the upper face of the set 101 of ultrasonic transducers. By way of example, the layer 140 is arranged on and in contact with the upper face of the set 101 of ultrasonic transducers. As a variant, the layer 140 is fixed to the upper face of the set 101 of transducers by means of an adhesive layer, not shown.

[0058] In the example shown, the layer 140 also covers the upper face of the printed circuit board 103 around the set 101 of ultrasonic transducers. More particularly, in this example, the layer 140 extends continuously over the entire surface of the printed circuit board 103.

[0059] The thickness of the coupling layer 140 is for example between 100 μm and 5 mm, for example between 500 μm and 1 mm.

[0060] The upper face of the layer 140 defines a contact surface on which an object to be imaged is placed, for example one or more fingers of a user, the palm of a user, or any other part of the human or animal body that it is desired to image.

[0061] The layer 140 has an ultrasonic coupling function between the transducers of the assembly 101 and the object to be imaged. In particular, the layer 140 is preferably relatively flexible and deformable to avoid the presence of air gaps between the transducers of the assembly 101 and the object to be imaged. In addition, the layer 140 preferably has an acoustic impedance adapted to that of the object to be imaged, for example an acoustic impedance substantially equal to the acoustic impedance of the skin. Thus, the layer 140 makes it possible to maximize the transfer of acoustic energy between the ultrasonic transducers and the object to be analyzed.

[0062] The layer 140 may also have a function of protecting the device and in particular the ultrasonic transducers of the assembly 101. In particular, the layer 140 preferably has relatively high mechanical strength so as not to deteriorate over time and in contact with the objects to be imaged.

[0063] Experiments carried out by the inventors have shown that, for certain applications, for example for microvascular imaging applications, the quality of the acquired images depends strongly on the temperature of the imaged object. For example, imaging of low blood flows and microscopic vessels located at the ex The tip of the fingers and toes is difficult to perform because these vessels are located at the coldest extremities and can undergo vasoconstriction and therefore a reduction in blood flow.

[0064] According to one aspect of a first embodiment, provision is made to integrate into the imaging device a heating device adapted to heat the object to be imaged during an ultrasound image acquisition phase. This makes it possible to increase the temperature of the object during acquisition, and thus to increase the quality of the acquired images, in particular for microvascular imaging applications.

[0065] In the example of [Fig.l], the heating device 150 is a heat sink configured to collect heat generated by the electronic control and power supply circuit 110, and conduct it to the upper face of the device, above the set 101 of ultrasonic transducers.

[0066] More particularly, in this example, the heating device 150 comprises a first metal sheet or layer 151 covering the upper face of the transmission circuit 111, a second metal sheet or layer 153 covering the upper face of the reception circuit 113, a third metal sheet or layer 155 covering the upper face of the processing circuit 115, and a fourth metal sheet or layer 157 covering the upper face of the power supply circuit 117. Each of the metal sheets 151, 153, 155 and 157 extends for example continuously over the entire surface of the underlying electronic circuit 111, respectively 113, respectively 115, respectively 117.

[0067] The heating device 150 of [Fig. 1] further comprises a metal foil or layer 159 covering the upper face of the assembly 101 of ultrasonic transducers. The metal foil 159 extends, for example, continuously over the entire upper surface of the assembly 101 of ultrasonic transducers. For example, the metal foil 159 is embedded in the coupling layer 140, between the upper face of the assembly 101 of ultrasonic transducers and the upper face of the layer 140. In other words, the metal foil 159 covers a lower portion of the layer 140 and is covered by an upper portion of the layer 140. Alternatively, the metal foil 159 is located on and in contact with the upper face of the coupling layer.

[0068] The heating device 150 of [Fig.l] further comprises metal regions 160 thermally connecting the metal sheets 151, 153, 155 and 157 to the upper metal sheet 159.

[0069] In the example of [Fig.l], the heating device 150 further comprises four thermal switches 161, 163, 165, 167 thermally connecting respectively the metal sheets 151, respectively 153, respectively 155, respectively 157, to the upper metal sheet 159. Each of the switches 161, 163, 165, 167 is adapted to, in a first configuration, thermally connect the metal sheet 161, respectively 163, respectively 165, respectively 167, to the upper metal sheet 159, and, in a second configuration, thermally insulate the metal sheet 161, respectively 163, respectively 165, respectively 167, to the upper metal sheet 159.

[0070] The switches 161, 163, 165 and 167 are for example mechanical switches, for example metal bimetallic strips, adapted to automatically switch from the first configuration to the second configuration when their temperature exceeds a first predefined threshold, and from the second configuration to the first configuration when their temperature falls below a second predefined threshold, equal to the first threshold or lower than the first threshold (hysteresis). As a variant, the switches 161, 163, 165, 167 are switches electrically controlled as a function of temperature measurements carried out by means of one or more temperature sensors of the device, not detailed in the figure. As a variant, the switches 161, 163, 165 and 167 can be omitted, the heat-collecting metal sheets 151, 153, 155 and 157 being for example directly thermally connected to the upper metal sheet 159.

[0071] In operation, the heat produced by the electronic control and power supply circuit 110 is collected by the metal collection sheets 151, 153, 155 and 157, and conducted to the upper face of the device where it is dissipated by the metal dissipation sheet 159.

[0072] This makes it possible to heat the object to be imaged during an ultrasound image acquisition phase.

[0073] The switches 161, 163, 165, 167 make it possible, if necessary, to stop all or part of the heat flow transmitted to the upper metal sheet 159 if the heat generated by the electronic control and power supply circuit 110 is too high, so as to prevent risks of burning the user and / or degradation of the coupling layer 140 or the ultrasonic transducers. In this case, the heat flow can possibly be redirected to an auxiliary heat sink, not shown, arranged, for example, on the lower face of the device.

[0074] An advantage of the device 100 of [Fig.l] is that the heating device 150 recovers the heat generated by the electronic control and power supply circuit 110 to heat the object to be imaged and thus improve the quality of the acquired images. Another advantage is that the metal layers also provide a shielding function for the ultrasonic transducers, protecting them against possible electromagnetic disturbances.

[0075] [Fig.2] is a sectional view schematically showing another example of an ultrasound imaging device 200 according to one embodiment.

[0076] The device 200 of [Fig.2] differs from the device 100 of [Fig.l] essentially in that, in the device 200, the heating device 150 of [Fig.l] is replaced by a heating device 250.

[0077] The heating device 250 of [Fig. 2] is a flexible Peletier module. The Peletier module 250 has the shape of a flexible ribbon or sheet and has a first face 250a, called the cold face, intended to be placed against a heat-generating device, and a second face 250b, called the hot face, intended to be turned towards a heat evacuation zone.

[0078] In this example, the Peletier module covers the upper surface of the set 101 of ultrasonic transducers, the edges of the Peletier module being folded under a part of the electronic control and power supply circuit 110.

[0079] More particularly, in the example of [Fig.2], the transmitting 111 and receiving 113 circuits are fixed and electrically connected to the underside of the printed circuit board 103, and the edges of the Peletier module are folded under the underside of the circuits 111 and 113 and above the circuits 115 and 117. In this example, the printed circuit board 121 can be omitted.

[0080] By way of example, the upper part of the Peletier module, covering the set 101 of ultrasonic transducers, is embedded in the coupling layer 140, between the upper face of the set 101 of ultrasonic transducers and the upper face of the layer 140.

[0081] In this example, at the upper part of the Peletier module 250, the hot face 250b of the Peletier module is turned towards the upper face of the imaging device, that is to say towards the object to be imaged. At the folded edges of the Peletier module 250, the cold face 250a of the Peletier module is in contact with the lower face of the electronic circuits 111 and 113.

[0082] In operation, the Peletier module 250 cools the electronic circuits 111 and 113 and evacuates the heat generated on the side of its hot face and in particular on the side of the upper face of the imaging device, on which the object to be imaged is placed.

[0083] An advantage of the device 200 of [Fig.2] is that the heating device 250 recovers the heat generated by the electronic control and power supply circuit 110 to heat the object to be imaged, and also makes it possible to cool the electronic control and power supply circuit 110.

[0084] [Fig. 3] is a sectional view schematically showing another example of an ultrasound imaging device 300 according to one embodiment.

[0085] The device 300 of [Fig. 3] differs from the device 100 of [Fig. 1] essentially in that, in the device 300, the heating device 150 of [Fig. 1] is replaced by a heating device 350.

[0086] The heating device 350 of [Fig.3] is a resistive heating mat comprising a metal coil resistor, for example arranged between two sheets of an electrically insulating material, for example a polyimide.

[0087] The heating mat 350 covers, for example, the entire upper surface of the set 101 of ultrasonic transducers. The heating mat 350 is, for example, connected to the power supply circuit 117 for its electrical power supply.

[0088] In the example of [Fig. 3], the heating mat 350 is embedded in the coupling layer 140, between the upper face of the set 101 of ultrasonic transducers and the upper face of the layer 140.

[0089] An advantage of the device 350 of [Fig. 3] is that the heating device 350 can be precisely controlled to obtain the desired temperature at the upper face of the coupling layer 140.

[0090] [Fig.4] is a sectional view schematically representing an alternative embodiment of the ultrasound imaging device 300 of [Fig.3].

[0091] In this variant, the heating mat 350 is flush with the upper face of the coupling layer 140. This variant is less favorable for the acquisition of skin prints because the image plane to be acquired (the surface of the skin) is very close to the metal coils of the heating mat. Thus, the print of the metal coils is superimposed on the image of the finger, which degrades the quality of the acquisition. This variant is, however, suitable for the acquisition of an image in a plane further from the contact surface of the device, for example a microvascular image, the heating mat then no longer being visible on the acquired image.

[0092] [Fig.5] is a sectional view schematically showing another example of an ultrasound imaging device 500 according to one embodiment.

[0093] The device 500 of [Fig. 5] differs from the device 100 of [Fig. 1] essentially in that, in the device 500, the heating device 150 of [Fig. 1] is replaced by a heating device 550.

[0094] The heating device 550 comprises a heating layer 551 made of a thermoelectric polymer material, i.e. a polymer material suitable for generating heat under the effect of an electrical polarization.

[0095] The layer 551 is for example made of a material based on poly(3,4-ethylenedioxythiophene) (PEDOT), or of a polymer material in which conductive nanoparticles are added, for example silver nanowires, making it possible to obtain a level of conductivity generating heating during electrical stress. As a variant, the layer 551 is made of a transparent conductive oxide, for example indium tin oxide (ITO), fluorine-doped indium tin oxide (FTO), or aluminum-doped zinc oxide (AZO). As a variant, the layer 551 is made of a material based on carbon nanotubes or graphene.

[0096] In this example, the heating layer 551 is integrated into the coupling layer 140. More particularly, in this example, the layer 551 covers a lower portion of the coupling layer 140 and is covered by an upper portion of the coupling layer 140.

[0097] In this example, the thickness of the heating layer 551 is relatively thin compared to the total thickness of the coupling layer 140.

[0098] By way of example, the thickness of the heating layer 551 is between 50 and 200 nm, for example of the order of 100 nm.

[0099] The heating device 550 of [Fig. 5] further comprises electrical connection elements 553 electrically connecting the heating layer 551 to the electronic power supply circuit 117 of the device.

[0100] [Fig.6] is a sectional view schematically showing an alternative embodiment of the ultrasound imaging device 500 of [Fig.5].

[0101] In this variant, the heating layer 551 has a relatively large thickness, and constitutes the majority of the thickness of the coupling layer 140. The coupling layer 140 may further comprise a relatively thin electrically insulating layer 552 covering the layer 551, to prevent any risk of electrocution of the user.

[0102] More generally, the heating devices 150, 250, 350 and 550 of the imaging devices described in relation to FIGS. 1, 2, 3, 4, 5 and 6 can be replaced by any other heating device suitable for heating the object to be imaged during a phase of acquisition of an ultrasound image of the object, for example a device based on infrared LEDs.

[0103] According to one aspect of a second embodiment, the coupling layer 140 of the imaging device is made of a polymer material having mechanical properties and in particular a Young's modulus that can be modified under the effect of a stimulus, for example a thermal (heating or cooling), light, electrical, chemical (water, pH, etc.) or mechanical (pressure or impact) stimulus. The coupling layer 140 is configured to have a first Young's modulus during an ultrasound image acquisition phase, and a second Young's modulus greater than the first Young's modulus outside of said acquisition phase. In other words, it is planned to control the mechanical properties of the coupling layer 140 so as to improve the acoustic coupling properties of the layer 140 during acquisition.More particularly, it is planned to make the coupling layer 140 more conformable, for example softer or more flexible during acquisition, so as to improve the acoustic coupling between the transducers and the object to be analyzed, and less conformable, for example harder or more rigid outside of acquisition, to reinforce. the mechanical protection properties provided by the layer 140. For example, the Young's modulus of the coupling layer 140 during the acquisition of an ultrasound image is at least 10% lower, preferably at least 20% lower, and preferably at least 50% lower, than outside of the acquisition, for example when the imaging device is switched off. For example, the Young's modulus of the coupling layer 140 is less than 1.7 MPa and preferably less than 0.7 MPa during the acquisition, and greater than 2.5 MPa and preferably greater than 5.5 MPa outside of the acquisition.

[0104] According to a first exemplary embodiment, the coupling layer 140 is made of a thermo-active polymer material, that is to say a polymer material whose mechanical properties and in particular Young's modulus are modified under the effect of heat.

[0105] In this case, the coupling device may comprise a heating device adapted to heat the coupling layer 140 to a temperature above ambient temperature, for example to a temperature above 25°C, preferably above 30°C, preferably above 35°C, preferably above 40°C, during a phase of acquisition of an ultrasound image, so as to reduce the Young's modulus of the layer 140. Outside of the acquisition phases, the heating device may be interrupted so as to bring the coupling layer 140 back to ambient temperature and thus increase its Young's modulus.

[0106] The heating device may be identical or similar to the devices described previously in relation to Figures 1 to 6. In other words, the first embodiment (heating of the object to be imaged during acquisition) and the first example of the second embodiment (modification of the mechanical properties of the coupling layer by heating during acquisition) may be combined.

[0107] As a variant, the heat used to reduce the Young's modulus of the coupling layer during acquisition is only the heat emitted by the object to be imaged itself, for example a user's finger, when the latter is placed on the upper face of the coupling layer. In this case, the imaging device may not comprise a specific heating device.

[0108] For example, the coupling layer 140 is made of a thermo-active polymer based on PTFE (polytetrafluoroethylene), PL A (polylactide), EVA (ethylene-vinyl acetate), PCL (poly(e-caprolactone), tBA / PEGDMA (tert-butyl acrylate / poly(ethylene glycol) dimethacrylate), PU (polyurethane), PMMA (poly(methyl methacrylate), polystyrene (PS), or silicone.

[0109] Alternatively, a similar operation can be obtained with a polymer whose mechanical properties are modified under the effect of cooling. In this case, the heating device can be replaced by a cooling device.

[0110] [Fig.7] is a sectional view schematically showing a second example of an ultrasound imaging device 700 according to the second embodiment.

[0111] In this example, the coupling layer 140 is made of a photoactive polymer material, that is to say a polymer material whose mechanical properties and in particular Young's modulus are modified under the effect of light radiation.

[0112] The device 700 of [Fig.7] comprises substantially the same elements as the device 100 of [Fig.l], with the exception of the heating device 150.

[0113] In this example, the coupling layer 140 is made of a photoactive polymer whose Young's modulus takes a first relatively low value under the effect of light irradiation at a first wavelength A, and takes a second relatively high value under the effect of light irradiation at a second wavelength B, different from A.

[0114] Wavelengths A and B are, for example, visible or infrared wavelengths. The described embodiments are, however, not limited to this particular case.

[0115] The device 700 comprises one or more light sources 710 adapted to emit radiation at wavelength A through the coupling layer 140, and one or more light sources 712 adapted to emit radiation at wavelength B through the coupling layer 140. The light sources 710 and 712 are for example fixed and connected to the printed circuit board 103, at the periphery of the set 101 of ultrasonic transducers. The light sources 710 and 712 are for example light-emitting diodes (LEDs) adapted to emit respectively at wavelength A and wavelength B.

[0116] The electronic control and power supply circuit 110 is configured to, before a phase of acquisition of an ultrasonic image, for example when an object to be imaged is detected opposite the set 101 of ultrasonic transducers, activate the light source(s) 710, so as to make the coupling layer 140 relatively soft and improve its acoustic coupling properties, then, after the acquisition, activate the light source(s) 712 so as to make the coupling layer 140 relatively hard and improve its mechanical protection properties.

[0117] For example, when the user places a finger on the upper face of the layer 140 for the purpose of capturing a fingerprint, the circuit 110 activates the emission at wavelength A, which allows the stress to be released and allows the layer 140 to adapt to the morphology of the finger. At the end of the capture, the polymer returns to its smooth shape (in other words, the upper face of the layer 140 becomes substantially flat again) and the emission at wavelength B is activated, which allows the polymer to be stiffened and the layer 140 to be maintained in this state.

[0118] Advantageously, the embodiment of [Fig.7] can be adapted to a photoacoustic imaging device, i.e. a device in which, during the acquisition of an ultrasound image, modulated light is emitted towards the object to be imaged. In this case, the same light source can be used to emit the modulated light during acquisition and soften the coupling polymer of layer 140 (wavelength A).

[0119] Alternatively, the return to the initial state (relatively high Young's modulus) can be achieved simply by interrupting the irradiation at wavelength A, by heating or cooling, or under the effect of another stimulus. In this case, the light sources emitting at wavelength B can be omitted.

[0120] For example, the coupling layer 140 is made of a photoactive polymer comprising diazo-type groups, acrylate derivatives, cinamic derivatives, furan derivatives or other groups known for their photosensitive properties. A person skilled in the art will be able to choose the appropriate group depending on its chemical compatibility with the coupling polymer of the layer 140 and the desired photoactivation properties.

[0121] [Fig.8] is a sectional view schematically showing a third example of an ultrasound imaging device 800 according to the second embodiment.

[0122] In this example, the coupling layer 140 is made of an electroactive polymer material, that is to say a polymer material whose mechanical properties and in particular Young's modulus are modified under the effect of an electrical polarization, for example under the effect of an electrical voltage.

[0123] The device 800 of [Fig.8] comprises substantially the same elements as the device 100 of [Fig.l], with the exception of the heating device 150.

[0124] In this example, the coupling layer 140 is made of an electroactive polymer whose Young's modulus takes a first relatively low value under the effect of an electrical polarization, for example an electrical voltage, applied between electrodes E and F in contact with the polymer, and a second relatively high value in the absence of said electrical polarization.

[0125] The electrodes E and F are for example in contact with the polymer of the coupling layer 140 in the vicinity of two opposite lateral edges of the layer 140 respectively.

[0126] The electrodes E and F are for example connected to the electronic power supply circuit 117 of the device for the application of the electrical polarization.

[0127] The electronic control and power supply circuit 110 is configured to, before a phase of acquisition of an ultrasonic image, for example when an object to be imaged is detected opposite the set 101 of ultrasonic transducers, apply the electrical polarization so as to make the coupling layer 140 relatively soft and improve its acoustic coupling properties, then, after the acquisition, deactivate electrical polarization so as to make the coupling layer 140 relatively hard and improve its mechanical protection properties.

[0128] For example, when the user places a finger on the upper face of the layer 140 for the purpose of capturing a fingerprint, the circuit 110 activates the electrical polarization of the layer 140, which allows the stress to be released and allows the layer 140 to adapt to the morphology of the finger. At the end of the capture, the polymer returns to its smooth shape (in other words, the upper face of the layer 140 becomes substantially flat again) and the electrical polarization is deactivated, which allows the polymer to be stiffened to maintain the layer 140 in this state.

[0129] By way of example, the coupling layer 140 is made of an electroactive polymer from the family of polyacrylates, polyurethanes, latexes, natural rubbers, silicones, butadiene-acrylonitrile copolymers, piezoelectric polymers for example PVDF type (polyvinylidene fluoride), or its copolymer P(VDF-TrFE) (vinylidene fluoride and trifluoroethylene).

[0130] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the described embodiments are not limited to the examples of materials and dimensions mentioned in this description.

[0131] Furthermore, the person skilled in the art will be able to combine the different embodiments described above according to the needs of the intended application. In particular, the person skilled in the art will be able to combine the first and second embodiments described above to benefit from both the advantage linked to the heating of the object to be imaged during acquisition and the adaptation of the mechanical properties of the coupling layer under the effect of a stimulus. In particular, the embodiments of Figures 7 and 8 can be combined with the embodiments of Figures 1, 2, 3, 4, 5 or 6.

[0132] Furthermore, although only examples of application to ultrasound imaging devices have been described above, the person skilled in the art will know, from the indications of the present description, how to adapt the embodiments described to other devices for transmitting and / or receiving ultrasound, for example devices for treating the human or animal body by transmitting ultrasound, or even non-destructive testing devices using ultrasound not necessarily applied to the human or animal body.

[0133] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. Ultrasound imaging device (100; 200; 300; 500) comprising a set (101) of ultrasonic transducers, an acoustic coupling layer (140) coating said set (101) of ultrasonic transducers, and a heating device (150; 250; 350; 550) adapted to heat an object to be imaged placed on the acoustic coupling layer (140) during a phase of acquisition of an ultrasonic image.

2. Device (100; 200; 300; 500) according to claim 1, further comprising an electronic power supply and control circuit (110).

3. Device (100; 200) according to claim 2, in which the heating device (150; 250) is adapted to recover heat generated by the electronic power supply and control circuit (110) and to dissipate all or part of this heat in the acoustic coupling layer (140), above the set (101) of ultrasonic transducers.

4. Device (100) according to claim 3, wherein the heating device (150) comprises one or more metal sheets (151, 153, 155, 157, 159) arranged to conduct the heat generated by the electronic power supply and control circuit (110) and dissipate all or part of this heat in the acoustic coupling layer (140), above the assembly (101) of ultrasonic transducers.

5. The device (100) of claim 4, wherein the heating device (150) further comprises one or more switches (161, 163, 165, 167) configured to interrupt heat transfer to the acoustic coupling layer (140) if an internal temperature of the device exceeds a predetermined threshold.

6. Device (200) according to claim 3, in which the heating device (250) comprises a flexible Peletier module of which a cold face (250a) is turned towards the electronic power supply and control circuit (110) and of which a hot face (250b) is turned towards the object to be imaged.

7. Device (300) according to claim 1 or 2, wherein the heating device (350) comprises a heating mat comprising a serpentine metal resistor, disposed between the set (101) of ultrasonic transducers and the object to be imaged.

8. The device (300) of claim 7, wherein the heating mat is embedded in the acoustic coupling layer (140).

9. Device (300) according to claim 7, wherein the heating mat covers the acoustic coupling layer (140).

10. Device (500) according to claim 1 or 2, wherein the heating device (550) comprises a heating layer (551) of a thermoelectric polymer material, integrated with the acoustic coupling layer (140).

11. Device (500) according to claim 10 in its attachment to claim 2, in which the heating layer (551) is electrically connected to the electronic power supply and control circuit (110) by connection elements (553).

12. Device (100; 200; 300; 500) according to any one of claims 1 to 11, wherein the ultrasonic transducers of the set (101) of ultrasonic transducers are CMUT or PMUT transducers, piezoelectric or piezocomposite transducers, or single crystal transducers.

13. Device according to any one of claims 1 to 12, in which the acoustic coupling layer (140) comprises at least one layer of an activatable polymer material configured to have a first Young's modulus during an acquisition phase of an ultrasound image and a second Young's modulus greater than the first Young's modulus outside of said acquisition phase.

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