Method and device for performing ultrasonic imaging with row-column addressing

Abstract

The present invention relates to a method for acquiring an image of a body by means of a row-column addressing matrix ultrasound imaging device (100), the device (100) comprising a matrix of M rows (R i) by N columns (C j) of elementary ultrasonic transducers (101), each row (R i) being divided into n portions of lines, and each line portion comprising several transducers.

Description

DESCRIPTION TITLE: Method and device for line-column addressing ultrasound imaging This application is based on, and claims priority from, French patent application FR2305309 filed on May 29, 2023 and entitled "Method and device for line-column addressing ultrasound imaging" which is considered to be an integral part of this description within the limits provided by law. Technical field

[0001] The present description relates to the field of ultrasound imaging, and more particularly relates to a device comprising a matrix of ultrasonic transducers with row-column addressing, and a method for acquiring an image of a body by means of such a device. Prior art

[0002] An ultrasound imaging device conventionally comprises a plurality of ultrasonic transducers, and an electronic control circuit connected to the transducers. In operation, all of the transducers are arranged facing a 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 ultrasonic waves by the transducers, in the direction of the body or object to be analyzed. The ultrasonic 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] The ultrasonic transducers can be arranged in a bar in the case of a two-dimensional image acquisition device, or in a matrix in the case of a three-dimensional image acquisition device. In the case of a two-dimensional image acquisition device, the acquired image is representative of a section of the body studied in a plane defined by the alignment axis of the transducers of the bar on the one hand, and by the emission direction of the transducers on the other hand. In the case of a three-dimensional image acquisition device, the acquired image is representative of a volume defined by the two alignment directions of the transducers of the matrix and by the emission direction of the transducers.

[0004] Among the three-dimensional image acquisition devices, we can distinguish between so-called fully populated devices, in which each transducer in the matrix is ​​individually addressable, and so-called row-column addressing or RCA devices, in which the transducers in the matrix are addressable by row and by column.

[0005] Fully populated devices offer greater flexibility in shaping the transmit and receive ultrasonic beams. However, the matrix control electronics are complex, with the required number of transmit / receive channels being M*N in the case of an M-row by N-column matrix. In addition, the signal-to-noise ratio is generally relatively low since each transducer has a small surface area exposed to ultrasonic waves.

[0006] RCA-type devices use different ultrasonic beam shaping algorithms. The beam shaping capabilities may be reduced compared to fully populated devices. However, the matrix control electronics are considerably simplified, with the required number of transmit / receive channels being reduced to M+N in the case of an M-row by N-column matrix. In addition, the signal-to-noise ratio is improved due to the interconnection of the transducers in rows or columns during the transmit and receive phases.

[0007] We are particularly interested here in devices and methods for acquiring three-dimensional images with row-column addressing (RCA).

[0008] International patent application WO2022 / 268512, previously filed by the applicant, describes a method for acquiring an image of a body using a row-column addressing matrix ultrasound imaging device, this method making it possible to trace the individual contributions of the elementary transducers of the matrix, so as to benefit from the advantages of both fully populated devices in terms of imaging resolution, and row-column addressing devices in terms of electronic complexity.

[0009] It would be desirable to improve at least in part certain aspects of the devices and methods for acquiring three-dimensional ultrasound images with row-column addressing described in international patent application WO2022 / 268512, and, more generally, known devices and methods for acquiring three-dimensional ultrasound images with row-column addressing. Summary of the invention

[0010] For this, one embodiment provides a method for acquiring an image of a body by means of a matrix ultrasound imaging device with row-column addressing, the device comprising a matrix of M rows by N columns of elementary ultrasound transducers, each row being divided into n row portions, each row portion comprising several elementary ultrasound transducers, with n integer greater than or equal to two, in which: - the elementary transducers of the same line portion are connected to the same line portion electrode; the elementary transducers of distinct line portions are connected to distinct line portion electrodes; and the elementary transducers of the same column are connected to the same column electrode, the method comprising: - carry out p successive shots of the same ultrasonic wave towards the body, where p is an integer designating the number of elementary ultrasonic transducers of the largest portion of lines; - after each shot, implementing a reception phase, by means of the device, of a return ultrasonic wave, reflected by the body, in which, during each of the reception phases, a variable electrical quantity representative of the received wave is read on each line portion electrode of the device, and in which, between any two reception phases among the p reception phases, the sign of the individual contribution of at least one elementary ultrasonic transducer of the matrix is ​​modified, the method further comprising a calculation step, by means of an electronic processing device, by linear combinations of the variable electrical quantities read on the electrodes of line portions of the device during the p reception phases, of an individual contribution from each of the elementary transducers of the matrix.

[0011] According to one embodiment, the line portions all comprise the same integer number N / n of elementary ultrasonic transducers.

[0012] According to one embodiment, the number M of rows of the matrix is ​​equal to the number N of columns of the matrix.

[0013] According to one embodiment, the calculation of the individual contributions of the elementary transducers of the matrix comprises a multiplication of the variable electrical quantities read on the line portion electrodes of the device during the p reception phases by coefficients of a matrix, determined beforehand during a characterization or simulation phase and stored in a memory of the electronic processing device.

[0014] According to one embodiment, during each of the p reception phases, each column electrode of the matrix is ​​maintained at a DC bias voltage, and in which, between any two reception phases among the p reception phases, the sign of the DC bias voltage applied to at least one of the column electrodes of the device is modified.

[0015] According to one embodiment, the signs of the bias voltages applied respectively to the column electrodes of the device during the p reception phases are coded by vectors of an orthogonal matrix, for example a Hadamard matrix.

[0016] According to one embodiment, the successive shots are carried out using the ultrasound imaging device row-column addressing matrix, and wherein, during each of the p shots, each column electrode of the matrix is ​​maintained at a DC bias voltage, and an AC excitation voltage superimposed on the DC bias voltage is applied to said column electrode, and wherein, during each shot, the signs of the DC bias voltages applied respectively to the column electrodes of the matrix are the same as the signs of the DC bias voltages applied respectively to the column electrodes during the subsequent reception phase.

[0017] According to one embodiment, at each shot, the same emission circuit simultaneously applies the same direct bias voltage and the same alternating excitation voltage to the column electrodes of n columns of the matrix.

[0018] According to one embodiment, the ultrasonic transducers are CMUT or PMUT transducers.

[0019] According to one embodiment, n is equal to two.

[0020] According to one embodiment, the variable electrical quantity read on each line portion electrode of the device is a voltage.

[0021] Another embodiment provides a row-column addressing matrix ultrasound imaging device, the device comprising a matrix of M rows by N columns of elementary ultrasound transducers, each row being divided into n row portions, each row portion comprising several elementary ultrasound transducers, with n being an integer greater than or equal to two, in which: - the elementary transducers of the same line portion are connected to the same line portion electrode; the elementary transducers of distinct line portions are connected to distinct line portion electrodes; and the elementary transducers of the same column are connected to the same column electrode, the device further comprising a control circuit configured to implement a method as defined above.

[0022] According to one embodiment, the device comprises M*n reception circuits connected respectively to the M*n line portion electrodes of the matrix of elementary ultrasonic transducers.

[0023] According to one embodiment, the device comprises an integer number s strictly less than N of transmission circuits, the same transmission circuit being able to be connected simultaneously to column electrodes of elementary transducers belonging to distinct row portions of the same row of the matrix.

[0024] According to one embodiment, the line portions all comprise the same integer number N / n of elementary ultrasonic transducers, and in which the number s of transmission circuits is equal to N / n. Brief description of the drawings

[0025] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which:

[0026] Figure 1 is a top view schematically and partially illustrating an example of a row-column addressing matrix ultrasound imaging device;

[0027] Figure 2 includes a sectional view along a plane AA of figure 1, and a sectional view along a plane BB of Figure 1, illustrating in more detail an exemplary embodiment of the device of Figure 1;

[0028] Figure 3 is an equivalent electrical diagram of a 2x2 row-column addressing matrix ultrasound imaging device operating in reception mode;

[0029] Figure 4 is an equivalent electrical diagram of a matrix ultrasound imaging device with row-column addressing of dimensions NxN operating in reception;

[0030] Figure 5 schematically illustrates a TX transmission step and an RX reception step of an embodiment of a method for acquiring an image of a body by means of a matrix ultrasound imaging device with row-column addressing of dimensions NxN according to one embodiment;

[0031] Figure 6 schematically illustrates steps of a method for acquiring an image of a body using a 2x2 row-column addressing matrix ultrasound imaging device according to one embodiment;

[0032] Figure 7 schematically illustrates steps of a method for acquiring an image of a body using a 4x4 row-column addressing matrix ultrasound imaging device according to one embodiment; and

[0033] Figure 8 is a cross-sectional view of an example of a row-column addressing matrix ultrasound imaging device according to one embodiment. Description of the embodiments

[0034] 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.

[0035] 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 various applications that the described imaging devices and methods may have have have not been detailed, the described embodiments being compatible with the usual applications of ultrasound imaging solutions. In particular, the properties (frequencies, shapes, amplitudes, etc.) of the electrical excitation signals applied to the ultrasound transducers have not been detailed, the described embodiments being compatible with the excitation signals usually used in ultrasound imaging systems, which can be chosen according to the application considered and in particular the nature of the body to be analyzed and the type of information that one seeks to acquire.Similarly, the various processing operations applied to the electrical signals provided by the ultrasonic transducers to extract useful information about the body to be analyzed have not been detailed, the embodiments described being compatible with the processing operations usually implemented in ultrasound imaging systems. In addition, the control circuits for the ultrasonic transducers of the imaging devices described have not been detailed, the embodiments being compatible with all or most of the known control circuits for ultrasonic transducers of row-column addressing matrix ultrasound imaging devices, or the production of these circuits being within the scope of the person skilled in the art upon reading this description. In addition, the production of the ultrasonic transducers of the imaging devices described has not been detailed, the embodiments described being compatible. with all or most of the known ultrasonic transducer structures.

[0036] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

[0037] 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.

[0038] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0039] Figure 1 is a top view schematically and partially illustrating an example of a row-column addressed matrix ultrasound imaging device 100.

[0040] Figure 2 includes two sectional views (A) and (B) of the device 100 of Figure 1 according to planes AA and BB of Figure 1 respectively.

[0041] The device 100 comprises a plurality of ultrasonic transducers 101 arranged in a matrix according to M rows Ri and N columns Cj, with M and N integers greater than or equal to 2, i integer ranging from 1 to M, and j integer ranging from 1 to N.

[0042] In Figure 1, four rows Ri, R2, R3, R4 and four columns Ci, C2, C3, C4 have been shown. In practice, the numbers M of rows and N of columns of the device 100 may be different from 4.

[0043] Each transducer 101 of the device 100 comprises a lower electrode E1 and an upper electrode E2 (Figures 2A and 2B). When an appropriate excitation voltage is applied between its electrodes E1 and E2, the transducer emits an ultrasonic acoustic wave. When the transducer receives an ultrasonic acoustic wave in a certain frequency range, it provides between its electrodes E1 and E2 a voltage representative of the received wave.

[0044] In this example, the transducers 101 are capacitive membrane transducers, also called CMUT transducers (from the English "Capacitive Micromachined Ultrasonic Transducer" - micro-machined capacitive ultrasonic transducer).

[0045] In each column Cj of the transducer matrix, the transducers 101 of the column have their respective lower electrodes El connected to each other. The lower electrodes El of transducers 101 of separate columns are not connected to each other. In addition, in each row R± of the transducer matrix, the transducers 101 of the row have their respective upper electrodes E2 connected to each other. The upper electrodes E2 of transducers 101 of separate rows are not connected to each other.

[0046] In each column Cj of the device 100, the lower electrodes El of the transducers 101 of the column form a continuous conductive or semiconductive strip 103, extending over substantially the entire length of the column. As a variant, each strip 103 of electrodes El comprises a vertical stack of a semiconductive strip and a conductive strip each extending over substantially the entire length of the column. In addition, in each row R± of the device 100, the upper electrodes E2 of the transducers 101 of the row form a continuous conductive or semiconductive strip 105, extending over substantially the entire length of the row. As a variant, each strip 105 of electrodes E2 comprises a vertical stack of a semiconductive strip and a conductive strip each extending over substantially the entire length of the row. For the sake of simplification, only the lower 103 and upper 105 electrode strips are shown in FIG. 1.

[0047] In the example shown, the strips 103 forming the column electrodes are made of a doped semiconductor material, for example doped silicon. In addition, in this example, the strips 105 forming the row electrodes are made of metal. For example, in top view, the lower strips 103 are parallel to each other, and the upper strips 105 are parallel to each other and perpendicular to the strips 103.

[0048] In the example of Figure 1, the device 100 comprises a support substrate 110, for example made of a semiconductor material, for example silicon. The matrix of ultrasonic transducers 101 is arranged on the upper face of the substrate 110. More particularly, in this example, a dielectric layer 112, for example a layer of silicon oxide, forms an interface between the substrate 110 and the matrix of ultrasonic transducers 101. The dielectric layer 112 extends for example continuously over the entire upper surface of the support substrate 110. By way of example, the layer 112 is in contact, by its lower face, with the upper face of the substrate 110, over substantially the entire upper surface of the substrate 110.

[0049] The lower electrode strips 103 are arranged on the upper face of the dielectric layer 112, for example in contact with the upper face of the dielectric layer 112. The strips 103 may be separated laterally from each other by dielectric strips 121, for example made of silicon oxide, extending parallel to the strips 103 and having a thickness substantially identical to that of the strips 103.

[0050] Each transducer 101 comprises a cavity 125 formed in a rigid support layer 127, and a flexible membrane 123 suspended above the cavity 125. The layer 127 is for example a layer of silicon oxide. The layer 127 is arranged on the upper surface, for example substantially flat, of the assembly formed by the alternating strips 103 and 121. In each transducer 101, the cavity 125 is located opposite the lower electrode E1 of the transducer.

[0051] In the example shown, each transducer 101 comprises a single cavity 125 opposite its lower electrode E1. As a variant, in each transducer 101, the cavity 125 can be divided into a plurality of elementary cavities, for example arranged, in top view, in a matrix according to rows and columns, separated laterally from each other by side walls formed by portions of the layer 127.

[0052] In the example shown, at the bottom of each cavity 125, a dielectric layer 129, for example made of silicon oxide, coats the lower electrode E1 of the transducer, so as to prevent any electrical contact between the flexible membrane 123 and the lower electrode E1 of the transducer. As a variant, to ensure this electrical insulation function, a dielectric layer (not shown) can coat the lower face of the membrane 123. In this case, the layer 129 can be omitted.

[0053] In each transducer 101, the flexible membrane 123, covering the cavity 125 of the transducer, is for example made of a doped or undoped semiconductor material, for example silicon.

[0054] In each transducer 101, the upper electrode E2 of the transducer is arranged on and in contact with the upper face of the flexible membrane 123 of the transducer, directly above the cavity 125 and the lower electrode E1 of the transducer. Alternatively, in the case of a semiconductor membrane, the upper electrode E2 of each transducer 101 may be formed by the membrane itself, in which case the layer 105 may be omitted.

[0055] For example, in each R± line of the device 100, the flexible membranes 123 of the transducers 101 of the line form a continuous membrane strip extending over substantially the entire length of the line, separated laterally from the membrane strips of the neighboring lines by a dielectric region. In each line R±, the membrane strip 123 of the line coincides, for example, in top view, with the upper electrode strip 105 of the line.

[0056] For each line R± of the transducer matrix 101, the device 100 may comprise a transmission circuit, a reception circuit, and a controllable switch for, in a first configuration, connecting the electrodes E2 of the transducers of the line to an output terminal of the transmission circuit of the line, and, in a second configuration, connecting the electrodes E2 of the transducers of the line to an input terminal of the reception circuit of the line.

[0057] In addition, for each column Cj of the transducer matrix 101, the device 100 may comprise a transmission circuit, a reception circuit, and a controllable switch for, in a first configuration, connecting the electrodes El of the transducers of the column to a terminal output terminal of the column transmitting circuit, and, in a second configuration, connect the electrodes El of the column transducers to an input terminal of the column receiving circuit.

[0058] For the sake of simplification, the transmission and reception circuits and the switches of the device 100 have not been shown in the figures. In addition, the embodiment of these elements has not been detailed, the embodiments described being compatible with the usual embodiments of transmission / reception circuits of matrix ultrasound imaging devices with row-column addressing. By way of non-limiting example, the transmission / reception circuits may be identical or similar to those described in French patent application No. 19 / 06515 filed by the applicant on June 18, 2019.

[0059] The acquisition of an ultrasound image of a body by means of a row-column addressing matrix ultrasound imaging device, for example of the type described in relation to figures 1 and 2, may comprise a phase of transmitting an ultrasound wave, followed by a phase of receiving a return ultrasound wave, reflected by the body.

[0060] For example, during the transmission phase, the row electrodes of the transducer matrix (corresponding to electrodes 105 in the example of Figures 1 and 2) are maintained at a fixed reference potential, for example ground, and a continuous bias potential Vbi as is applied to each of the column electrodes of the matrix (corresponding to electrodes 103 in the example of figures 1 and 2). An alternating excitation voltage V exc is further applied to each of the column electrodes of the matrix. Thus, each transducer 101 of the matrix sees, between its electrodes E1 and E2, the excitation voltage alternative V exc superimposed on a DC bias voltage V bias This causes the transducer membrane to vibrate, leading to the emission of an ultrasonic acoustic wave.

[0061] During the receiving phase, the column electrodes can be maintained at the DC bias potential V bias . An alternating voltage superimposed on the direct bias voltage V bias then appears between the electrodes E1 and E2 of each transducer 101 under the effect of the return acoustic wave. The alternating voltages produced individually by the elementary transducers of the matrix, also called individual contributions of the elementary transducers, combine on the row and column electrodes of the matrix and resulting voltages can be read on said row and column electrodes.

[0062] The aforementioned international patent application WO2022 / 268512, the content of which is considered to be an integral part of the present description, describes a method for acquiring an ultrasound image by means of a matrix ultrasound imaging device with row-column addressing, making it possible to trace the individual contributions of the elementary transducers of the matrix, so as to benefit from the advantages of both fully populated devices in terms of imaging resolution, and row-column addressing devices in terms of electronic complexity.

[0063] Figure 3 is an equivalent electrical diagram of a 2-row, 2-column row-column addressing matrix ultrasound imaging device, during a reception phase of an ultrasonic wave.

[0064] Each elementary transducer can be modeled by a voltage generator e±j in series with an impedance Z th between a row electrode R± (corresponding to an electrode 105 in the implementation example of Figures 1 and 2) and a column electrode Cj (corresponding to an electrode 103 in the implementation example of Figures 1 and 2). Each voltage value e±j is representative of the vibration of the elementary transducer of coordinates i, j in the matrix under the effect of the received ultrasonic wave, and corresponds to the individual contribution of the elementary transducer to the voltages measured on the row and / or column electrodes of the device. In addition, for each row of the matrix, a load impedance Z has been shown. R between the row electrode R± and ground, and, for each column of the matrix, a load impedance Z c between the column electrode Cj and ground. The impedances Z th of the different elementary transducers of the matrix are for example all identical or substantially identical. The load impedances Z R connected to the different row electrodes R± of the matrix are for example all identical or substantially identical. The load impedances Z c connected to the different column electrodes Cj of the matrix are for example all identical or substantially identical. Here we denote by V Ri the alternating voltage appearing on the R± line during a reception phase of an ultrasonic wave, and by V C j the alternating voltage appearing on column Cj during a reception phase of an ultrasonic wave.

[0065] By applying the principle of superposition, we can write the following system of equations: [Math 1] where each coefficient a±j Rk is representative of the weight of the contribution of the generator e±j to the voltage V R k of the line Rk, with k being an integer ranging from 1 to N, and where each coefficient a±jck is representative of the weight of the contribution of the generator eij to the voltage V C k of column C k .

[0066] Figure 4 is an equivalent electrical schematic of a row-column addressing matrix ultrasound imaging device with N rows and N columns. The equivalent electrical schematic in Figure 4 is similar to that in Figure 2. For simplicity, the load impedances Z R connected on the lines and load impedances Z c connected on the columns have not been shown in Figure 4.

[0067] Using the previous notations, the aforementioned system of equations [Math 1] can be rewritten in matrix form as follows: [A]* [e] = [V]

[0068] With : [Math 2]

[0069] And : [Math 3]

[0070] And : [Math 4]

[0071] The 2N* (N*N) coefficients of the matrix [A] can be determined beforehand during a characterization or simulation phase of the device, and stored in a memory of an electronic processing device. The 2N* (N*N) coefficients of the matrix [A] are for example non-nuisance and non-unitary (in absolute value).

[0072] The 2N vector voltages [V] can be read on the row and column electrodes of the matrix.

[0073] We thus obtain a system with 2N equations and N*N unknowns (the N*N voltage values ​​e±j).

[0074] As it stands, this system cannot be solved, the number of independent equations being less than the number of unknowns.

[0075] In the aforementioned international patent application WO2022 / 268512, it is proposed to increase the number of discriminant equations of the system, by carrying out several successive firings of the same ultrasonic wave (i.e. a beam with the same characteristics) in the direction of the body to be analyzed, and by modifying each time, during the reception phase of the return wave, the sign of at least one generator e±j.

[0076] More particularly, it is provided, at each shot, to modify the sign of the polarization voltage applied to at least one of the column electrodes of the matrix during the reception phase of the return wave, so as to invert the sign of all the generators e±j of said at least one column. This takes advantage of the symmetrical voltage behavior of the CMUT transducers, explained in relation to the Figures 5 and 6 of international patent application WO2022 / 268512.

[0077] By carrying out several successive shots of the same ultrasonic wave, by modifying each time the sign of the polarization voltages applied to certain columns in the reception phase, and by carrying out linear combinations of the voltages measured on the line electrodes Ri, it is possible to go back to the individual contributions e±j of each of the elementary transducers of the matrix.

[0078] A limitation of the solution proposed in the aforementioned international patent application WO2022 / 268512 lies in the relatively high number of successive shots of the same ultrasonic wave to be implemented to trace the individual contributions e±j of each of the elementary transducers of the matrix.

[0079] More particularly, for a matrix of N rows by N columns of elementary ultrasonic transducers, the solution proposed in the aforementioned international patent application WO2022 / 268512 requires implementing at least N successive shots of the same ultrasonic wave by modifying each time the sign of the polarization voltage applied to at least one of the column electrodes of the matrix during the reception phase of the return wave, to go back to the individual contributions e±j of each of the N*N elementary transducers of the matrix.

[0080] Figure 5 schematically illustrates a TX transmission step and an RX reception step of a method for acquiring an image of a body by means of a matrix ultrasound imaging device with row-column addressing of dimensions NxN, according to one embodiment.

[0081] The acquisition device of Figure 5 differs from the devices previously described in relation to the figures 1 to 4 in that, in the example of Figure 5, each line R± is divided into two portions of lines R L I and R R ±, corresponding respectively to a left portion and a right portion of the line. The portions of line R L I and R R I include for example each N / 2 elementary transducers. In this example, N is an even integer.

[0082] Figure 8 is a schematic and partial sectional view illustrating in more detail an exemplary embodiment of the row-column addressing matrix ultrasound imaging device of Figure 5. Figure 8 is a sectional view of the device in the same plane as view (B) of Figure 2.

[0083] As in the examples described previously in relation to Figures 1 and 2, in each column Cj of the transducer matrix, the transducers 101 of the column have their respective lower electrodes El connected to each other. The lower electrodes El of transducers 101 of separate columns are not, however, connected to each other.

[0084] In addition, in each portion of line R L I, respectively R R ±, of the transducer matrix, the transducers 101 of the line portion considered have their respective upper electrodes E2 connected to each other. The upper electrodes E2 of transducers 101 of distinct line portions are not, however, connected to each other.

[0085] As in the example described previously in relation to figures 1 and 2, in each column Cj of the device, the lower electrodes El of the transducers 101 of the column form a continuous conductive and / or semiconductive strip 103, extending over substantially the entire length of the column.

[0086] In addition, in each portion of line R L I, respectively RRI, of the device, the upper electrodes E2 of the transducers 101 of the line portion form a continuous conductive and / or semiconductive strip 105L, respectively 105R, extending over substantially the entire length of the line portion.

[0087] For example, the device of Figure 8 differs from the device 100 described in connection with Figures 1 and 2 essentially in that, in the device of Figure 8, in each row of the ultrasonic transducer array, the upper electrode strip 105 is interrupted substantially in its center, and thus divided into two disjoint (not electrically connected to each other) strips 105L and 105R.

[0088] Similarly, in the case where the membranes 123 of the transducers of the same row form a continuous strip of a conductive or semiconductive material, in each row of the matrix of ultrasonic transducers, the membrane strip 123 can be interrupted substantially in its center, and thus divided into two separate strips 123L and 123R. The membrane strips 123L and 123R of each row coincide, for example, respectively, in top view, with the upper electrode strips 105L and 105R of the row.

[0089] For example, for each portion of line R L I, respectively RRI, of the transducer matrix 101, the device may comprise a receiving circuit having an input terminal connected or linked, for example via a switch, to the electrodes E2 of the transducers of the line portion.

[0090] In addition, for each column Cj of the transducer matrix 101, the device may comprise a transmission circuit, for example a pulse generator, having an output terminal connected or linked, for example by via a switch, to the electrodes El of the column transducers.

[0091] Thus, in this example, compared to a configuration of the type described in relation to figures 1 to 4, the number of row reception circuits is doubled (two reception circuits per row of the matrix instead of just one in the examples of figures 1 to 4). The number of column transmission circuits remains unchanged (one transmission circuit per column of the matrix).

[0092] For the sake of simplification, the transmitting and receiving circuits have not been shown in the figures.

[0093] In the example of Figure 5, during the transmission phase TX, a continuous bias voltage V bias and an alternating excitation voltage V exc are applied to the column electrodes Cj of odd rank, and an opposite DC bias voltage -V bias and an opposite alternating excitation voltage -V excare applied to the column electrodes Cj of even rank. For example, during the emission phase, the electrodes of the row portions R L I, RRI of the transducer matrix (corresponding to the electrodes 105L, 105R in the example of Figure 8) are maintained at a fixed reference potential, for example ground. In Figure 5, each elementary transducer is represented by an impedance Z t h during the TX transmission phase.

[0094] During the RX reception phase, the continuous bias voltages V bias and -V bias applied respectively to the odd-rank column electrodes Cj and to the even-rank column electrodes Cj remain unchanged.

[0095] As explained in relation to Figures 5 and 6 of the aforementioned patent application WO2022 / 268512, the inversion of the sign of the voltages V bias and V exc on the row columns pair has no impact on the acoustic wave emitted by the column transducers. In other words, the emitted ultrasonic wave is the same as if the signs of the voltages Vbias and V exc were the same on all columns.

[0096] In reception, the inversion of the sign of the DC polarization voltage in the even-rank columns leads, on the other hand, to inverting the signs of the contributions e±j of the elementary transducers of said columns.

[0097] By carrying out several successive shots of the same ultrasonic wave, by modifying each time the sign of the polarization voltages applied to certain columns in the reception phase, and by carrying out linear combinations of the voltages measured on the line electrodes R L I, RRI, it is possible to go back to the individual contributions e±j of each of the elementary transducers of the matrix.

[0098] The division of each row of the matrix into two portions of rows R L ±, RRI advantageously allows to divide by two the number of shots necessary to go back to the individual contributions e±j of each of the elementary transducers of the matrix.

[0099] Thus, in the example of figure 5, N / 2 successive shots of the same ultrasonic wave make it possible to trace the individual contributions e±j of all the elementary transducers in the matrix.

[0100] More generally, the embodiments described make it possible to trace the individual contributions e±j of each of the elementary transducers of the matrix with a number of shots strictly less than N.

[0101] Figure 6 schematically illustrates an example of an embodiment of a method for acquiring an image of a body using an ultrasound imaging device. 2x2 row-column addressing matrix, of the type described in relation to Figure 5.

[0102] The method of Figure 6 involves a single shot of an ultrasonic wave toward the body to be analyzed.

[0103] More particularly, the method comprises a first step TX1 of transmitting the ultrasonic wave, followed by a first step RX1 of receiving a return wave reflected by the body to be analyzed.

[0104] During the emission step TX1, the column electrodes Ci and C2 are polarized at the same direct voltage Vbias, and receive the same alternating excitation voltage V exc superimposed on the voltage V bi has S .

[0105] During the reception phase RX1, the column electrodes Ci and C2 remain polarized at voltage V bi has S , and alternating voltages V RL1 and V RR1are read respectively on the electrodes of the portions of line R L I and RRI, and alternating voltages V RL2 and V RR2 are read respectively on the electrodes of the portions of line R L2 and R R2 .

[0106] The following systems of equations can thus be written: [Math 5] [Math 6]

[0107] We thus obtain a system with four equations and four unknowns which can be solved directly, which makes it possible to determine the respective contributions in, in, e 2i and e22 of the elementary transducers.

[0108] Figure 7 schematically illustrates, by way of illustrative example, an embodiment of a method for acquiring an image of a body by means of a 4x4 row-column addressing matrix ultrasound imaging device, of the type described in relation to Figure 5.

[0109] Figure 7 represents more particularly the signs of the bias voltages applied to the column electrodes Cj of the matrix during two successive reception phases RX1, RX2 of the process. In this figure, a + sign is represented at the head of the column when the bias voltage applied to the column is equal to Vbias, and a - sign at the head of the column when the bias voltage applied to the column is equal to -V bias •

[0110] In the RX1 reception phase following the first shot, the column electrodes Ci, C2, C3 and C4 are all positively polarized (++++). In the RX2 reception phase following the second shot, the column electrodes Ci, C2, C3 and C4 are positively, negatively, positively and negatively polarized ( + - + -) respectively.

[0111] For each of the reception phases RX1 and RX2 two systems of equations of the same type as the systems [Math 5] and [Math 6] described above can be written, with, each time, 4 equations per system and 8 terms aij RL i*eij or aijRRi*eij by equation.

[0112] We thus obtain, for each ultrasonic shot, a set of 8 equations and 16 unknowns.

[0113] With 2 ultrasonic shots, we therefore obtain 16 equations for 16 unknowns, which makes it possible to go back to the individual contributions eij of all the elementary transducers

[0114] More particularly, in the example shown, we obtain, for the reception phase RX1, the following systems: [Math 5]

[0115] And, for the RX2 reception phase, the following systems: [Math 5]

[0116] It should be noted that as set out in the aforementioned patent application WO2022 / 268512, the inversion of the sign of the bias voltages V bias and excitation V exc during the emission phase has no effect on the emitted ultrasonic wave. Thus, one could plan to carry out the two shots with the same polarization and excitation voltages, and modify the sign of the polarization voltage of the columns C2 and C4 only during the RX2 reception phase. In practice, however, it can be difficult to reverse the sign of the polarization voltage of a column between the emission phase and the reception phase of the same ultrasonic wave. It is therefore preferable to modify the sign of the polarization voltage of the electrode of columns C2 and C4 from the emission phase.

[0117] The person skilled in the art will be able to adapt the method described regardless of the number N of lines and columns of the device.

[0118] For a matrix of dimensions NxN, it will be sufficient to carry out N / 2 successive shots TX1, ... TXN / 2, each time modifying the sign of the polarization voltage applied to at least one of the column electrodes of the matrix during the respective subsequent reception phase RX1, ... RXN / 2.

[0119] For each of the reception phases RX1 and RXN / 2, two systems of equations of the same type as the systems [Math 5] and [Math 6] described above can be written, with, each time, N equations per system and N* (N / 2) terms aijRLi*eij or aijRRi*eij per equation.

[0120] We thus obtain, for each ultrasonic shot, a set of 2N equations and N*N unknowns.

[0121] With N / 2 ultrasonic shots, we therefore obtain N*N equations for N*N unknowns, which allows us to go back to the individual contributions e±j of all the elementary transducers.

[0122] For example, the signs of the polarization voltages applied respectively to the N column electrodes Ci, . . . C N during the N / 2 reception phases RX1, . . . RXN / 2 are coded by vectors of an orthogonal matrix, for example a Hadamard matrix, for example the first N / 2 vectors of a Hadamard matrix of dimension N. By using N / 2 linear combinations of the voltage measurements carried out on the line electrodes RLi, RRi of the matrix, we can go back to the individual contributions e±j of the N*N elementary transducers of the device.

[0123] According to a preferred embodiment, at each shot of the ultrasonic wave, the polarization voltage applied to each of the column electrodes Cj, with j ranging from 1 to N / 2, is equal to the bias voltage applied to the column electrode of one of the columns C( N / 2>+i, C N , for example column Cj +(N / 2) .

[0124] In this case, the same transmission circuit, for example the same pulse generator, can be used to simultaneously control the electrodes of two columns.

[0125] This advantageously makes it possible to halve the number of transmission circuits of the device. Thus, compared to a configuration of the type described in relation to figures 1 to 4, the number of row reception circuits is doubled (two reception circuits per row of the matrix instead of just one in the examples of figures 1 to 4), and the number of column transmission circuits is halved (one transmission circuit for two columns of the matrix).

[0126] An advantage of the proposed embodiments is that they allow one to benefit from the advantages of both fully populated devices in terms of imaging resolution, and row-column addressing devices in terms of electronic complexity.

[0127] Furthermore, compared to the solution described in the aforementioned patent application WO2022 / 268512, the number of shots of the same ultrasonic wave required to reconstruct a fully resolved image is reduced.

[0128] It will be noted that the described embodiments are not limited to the example described above in which each row of ultrasonic transducers of the array is divided into two portions of rows R L I, RRI. More generally, the person skilled in the art will know how to adapt the operation described to a device in which each line of the matrix of ultrasonic transducers is divided into n portions of lines of the same dimensions, with n an integer greater than or equal to 2, N a multiple of n, and N / n an integer greater than or equal to 2.

[0129] In this case, the number of ultrasonic shots required to reconstruct the individual contributions e±j of all the elementary transducers of the matrix will be reduced to N / n, at the cost of an increase by a factor n of the number of reception circuits (equal to n*N) connected respectively to the electrodes of the n*N row portions of the device. Advantageously, the same transmission circuit can be used to simultaneously control n columns of the matrix, reducing the number of transmission circuits of the device to N / n.

[0130] Furthermore, the person skilled in the art will know how to adapt the embodiments described in the case where the line portions do not all comprise the same number of ultrasonic transducers.

[0131] Furthermore, the person skilled in the art will know how to adapt the described embodiments to the case where the line portions are made up of transducers that are not necessarily adjacent. For example, for a given line of ultrasonic transducers, the transducers of the even-rank columns may be connected to a first line electrode defining a first line portion, and the transducers of the odd-rank columns may be connected to a second line electrode distinct from the first electrode (i.e. not connected to the first electrode), defining a second line portion.

[0132] 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 example particular embodiment of the matrix of elementary transducers described in relation to figure 8.

[0133] Furthermore, the embodiments described are not limited to devices based on CMUT type ultrasonic transducers, but apply more generally to any type of transducer exhibiting symmetrical behavior, in particular in reception, for example PMUT transducers (from the English "Piezoelectric Micromachined Ultrasonic Transducers"). By symmetrical behavior in reception, it is meant here that the sign of the alternating voltage produced by the transducer during a reception phase of an ultrasonic wave is reversed when the sign of the direct bias voltage applied to the transducer during this same reception phase is reversed.

[0134] Furthermore, although in the examples described above the DC bias voltages V bias and -V bias applied to the different column electrodes Cj of the device are all of the same amplitude in absolute value, the embodiments described are not limited to this particular case. As a variant, the amplitude levels of the DC bias voltages applied to the different column electrodes Cj, in transmission and / or in reception, can be differentiated. Similarly, the AC excitation voltages V exc applied to the column electrodes Cj in emission can be differentiated by column.

[0135] Furthermore, the described embodiments are not limited to the examples detailed above in which the inversion of the sign of the contribution e±j of the elementary transducers of a column is obtained by inverting the sign of the DC bias voltage Vbias applied to this column. More generally, any other means allowing to reverse the sign of the contribution e±j of one or more elementary transducers between two successive shots of the same ultrasonic wave can be provided. For example, each elementary transducer of position (i,j) in the matrix is ​​associated with a system of switches, for example electromechanical switches, making it possible to reverse the direction of connection of the electrodes of the transducer between the row electrodes Ri and column electrodes Cj of the matrix. In other words, in a first configuration of the system of switches, the transducer has a first electrode connected to the electrode R± and a second electrode connected to the electrode Cj, and, in a second configuration of the system of switches, the transducer has its first electrode connected to the electrode Cj and its second electrode connected to the electrode R±.Thus, by changing, between two successive shots of the same ultrasonic wave, the configuration of the switch system associated with an elementary transducer of position (i, j), the sign of the contribution e±j of this transducer is reversed. This makes it possible to increase the number of discriminant equations of the system and thus to go back to the individual contributions e±j of all the elementary transducers of the matrix. In this embodiment, the switch systems associated with the individual transducers can be controlled individually, transducer by transducer, or simultaneously by column. It will be noted that this embodiment is compatible with any type of ultrasonic transducers, including transducers not exhibiting symmetrical voltage behavior. In particular, this embodiment is not limited to CMUT and PMUT transducers.

[0136] Furthermore, although exemplary implementations based on voltage measurements on the electrodes of the device have been described above, the embodiments described are not limited to this particular case. Alternatively, the described embodiments may be adapted to trace the individual contributions of the elementary transducers from measurements of another variable electrical quantity, for example a current, charges or an impedance, on the electrodes of the device.

[0137] Furthermore, although the above detailed examples of the proposed acquisition method have been given for square transducer matrices of N lines by N columns, the described embodiments are not limited to this particular case. Upon reading this description, the person skilled in the art will know how to adapt the proposed method to matrix devices having a number of lines different from the number of columns.

[0138] Furthermore, in the embodiments described above, at each firing of the ultrasonic wave, the wave is generated by the same matrix device as that used for receiving the return wave. The embodiments described are not, however, limited to this particular case. As a variant, the transducer matrix is ​​used solely as a receiving device, to receive the ultrasonic wave returned by the body to be analyzed, and a separate transmitting device (not detailed) is used to transmit the ultrasonic wave towards the body to be analyzed. The transmitting device and the receiving device are then synchronized to implement the N / n alternating TX transmission phases and the N / n alternating RX reception phases.

[0139] Furthermore, the practical implementation of the described embodiments and variants is within the reach of the person skilled in the art from the functional indications given above. In particular, the production of the electronic circuits for controlling the transmitter and receiver devices to implement the proposed method does not have been detailed, the production of these circuits being within the reach of the person skilled in the art upon reading this description. In addition, the production of the electronic processing devices making it possible to trace the individual contributions of the elementary transducers from the quantities measured on the electrodes of the device have not been detailed, the production of such devices being within the reach of the person skilled in the art from the teachings of this description.

[0140] Furthermore, it should be noted that in the examples described above, the row and column names are arbitrary and can of course be reversed.

Claims

CLAIMS 1. Method for acquiring an image of a body by means of a row-column addressing matrix ultrasound imaging device (100), the device (100) comprising a matrix of M rows (Ri) by N columns (Cj) of elementary ultrasound transducers (101), each row (Ri) being divided into n row portions, each row portion comprising several elementary ultrasound transducers, with n integer greater than or equal to two, in which: - the elementary transducers of the same line portion are connected to the same line portion electrode; the elementary transducers of distinct line portions are connected to distinct line portion electrodes; and - the elementary transducers of the same column are connected to the same column electrode, the method comprising: - carry out p successive shots (TX1, ...TXp) of the same ultrasonic wave towards the body, where p is an integer designating the number of elementary ultrasonic transducers of the largest portion of lines; - after each shot, implement a reception phase (RX1, ...RXp), by means of the device, of a return ultrasonic wave, reflected by the body, in which, during each of the reception phases (RX1, ...RXp), a variable electrical quantity representative of the received wave is read on each line portion electrode (Ri) of the device, and in which, between any two reception phases among the p reception phases (RX1, ...RXp), the sign of the individual contribution (e±j) of at least one elementary ultrasonic transducer (101) of the matrix is ​​modified, the method further comprising a calculation step, at by means of an electronic processing device, by linear combinations of variable electrical quantities (V RLi , V RRi ) read on the electrodes of line portions (R Ri , R Li ) of the device during the p reception phases (RX1, ...RXp), of an individual contribution (eij) of each of the elementary transducers (101) of the matrix.

2. Method according to claim 1, in which the line portions all comprise the same integer number N / n of elementary ultrasonic transducers.

3. Method according to claim 1 or 2, in which the number M of rows (R±) of the matrix is ​​equal to the number N of columns (Cj) of the matrix.

4. Method according to claim 1 or 2, in which the calculation of the individual contributions (e±j) of the elementary transducers (101) of the matrix comprises a multiplication of the variable electrical quantities (V RL i, V RRi) read on the line portion electrodes (R L I, RRI) of the device during the p reception phases (RX1, ...RXp) by coefficients of a matrix, determined beforehand during a characterization or simulation phase and stored in a memory of the electronic processing device.

5. Method according to any one of claims 1 to 4, in which, during each of the p reception phases (RX1, ...RXp), each column electrode (Cj) of the matrix is ​​maintained at a DC bias voltage (Vbias, -Vbias), and in which, between any two reception phases among the p reception phases (RX1, ...RXp), the sign of the DC bias voltage (Vbias, -Vbias) applied to at least one of the column electrodes (Cj) of the device is modified.

6. Method according to claim 5, in which the signs of the bias voltages (Vbias, -Vbias) applied respectively to the column electrodes (Cj) of the device during the p reception phases (RX1, ...RXN) are coded by vectors of an orthogonal matrix, for example a Hadamard matrix.

7. Method according to claim 5 or 6, wherein the p successive shots (TX1, ... TXp) are carried out by means of the row-column addressing matrix ultrasound imaging device (100), and wherein, during each of the p shots (TX1, ... TXp), each column electrode (Cj) of the matrix is ​​maintained at a DC bias voltage (Vbias, -Vbias), and an AC excitation voltage (Vexe) superimposed on the DC bias voltage is applied to said column electrode (Cj), and wherein, during each shot, the signs of the DC bias voltages respectively applied to the column electrodes (Cj) of the matrix are the same as the signs of the DC bias voltages respectively applied to the column electrodes (Cj) during the subsequent reception phase.

8. Method according to claim 7, in which, at each shot, the same emission circuit simultaneously applies the same continuous bias voltage (Vbias, -Vbias), and the same alternating excitation voltage (Vexe) to the column electrodes of n columns of the matrix.

9. Method according to any one of claims 1 to 8, wherein the ultrasonic transducers (101) are CMUT or PMUT transducers.

10. Method according to any one of claims 1 to 9, in which n is equal to two.

11. Method according to any one of claims 1 to 10, in which the variable electrical quantity (V RLi , V RRi ) read on each line portion electrode (R L I, RRI) of the device is a voltage.

12. Line-column addressing matrix ultrasound imaging device (100), the device (100) comprising a matrix of M lines (R±) by N columns (Cj) of elementary ultrasound transducers (101), each line (Ri) being divided into n line portions (R L I, RRI), each portion of line comprising several elementary ultrasonic transducers, with n an integer greater than or equal to two, in which: - the elementary transducers of the same line portion are connected to the same line portion electrode; the elementary transducers of distinct line portions are connected to distinct line portion electrodes; and - the elementary transducers of the same column are connected to the same column electrode, the device further comprising a control circuit configured to implement a method according to any one of claims 1 to 11.

13. Device according to claim 12, comprising M*n reception circuits connected respectively to the M*n line portion electrodes (R L I, RRI) of the matrix of elementary ultrasonic transducers.

14. Device according to claim 12 or 13, comprising an integer number s strictly less than N of transmission circuits, the same transmission circuit being able to be connected simultaneously to column electrodes of elementary transducers belonging to distinct row portions of the same row of the matrix.

15. Device according to claim 14, in which the line portions all comprise the same integer number N / n of elementary ultrasonic transducers, and in which the number s of transmission circuits is equal to N / n.

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