FR3148711A1 - Lung tomography device and system and associated tomography method - Google Patents

Abstract

Title: Lung tomography device and system and associated tomography method The invention relates to a lung (20) tomography device and system (1), the device comprising a support (10), and at least five transceivers (11) fixed on the support (10) configured to transmit and receive an ultrasonic wave of variable frequency over a frequency range, the transceivers (11) being arranged according to at least two first sets (110) each facing a lung (20) of a human or animal body (2). The associated tomography method comprises the transmission and reception of the ultrasonic wave according to transmission and reception profiles, by the transceivers (11), and an analysis of the deformation between these profiles to obtain the speed of the wave as a function of the frequency and the direction of propagation of the wave, and to construct a tomography on the basis of data relating to this speed. Figure for abstract: Fig.2

Description

Lung tomography device and system and associated tomography method

The present invention relates to a device for lung tomography, a tomography system comprising it, and a method for lung tomography. It is more particularly applicable to lung tomography in the medical field, for example for monitoring pulmonary diseases whether in a hospital or in a medical office.

STATE OF THE ART

Imaging of human organs is a very common medical operation allowing diagnosis but also the study of the evolution of diseases. In pulmonary investigations, X-ray imaging is the most used imaging method.

X-rays are generated by specific tubes at very high frequencies (typically between 3 EHz and 30 EHz with 1 EHz = 10 ¹⁸ Hz) and very low wavelengths (typically between 1 nm and 10 pm), which explains both their penetration capacity and the very high resolution that allows very small anomalies to be visualized (of the order of μm). The principle of X-ray imaging is based on the absorption of X-rays as a function of tissue density, itself linked to the concentration of electrons. The regions of the body with a higher electron density absorb more X-rays and, on an imaging film, this will produce a brighter area. Conversely, regions with a lower electron density will absorb fewer X-rays and the corresponding areas will appear darker in the image.

Traditional X-ray imaging has some limitations. A first limitation is the two-dimensional nature of the representation of naturally three-dimensional structures. This does not allow for precise measurement of the size and position of regions of interest for diagnosis. A second limitation is the impossibility of quantifying the densities of the regions crossed by the rays.

To overcome these limitations, computer tomography (CT) is currently widely used. This technique provides high-resolution, three-dimensional images that allow for better diagnosis. By rotating the emission system and activating multiple receivers, both controlled by the computer, it is possible to image the object across multiple planes and thus provide a 3D image.

Although very effective for a precise diagnosis of lung diseases, CT remains a means of investigation using ionizing rays. This limits its use in terms of frequency of exposure. In addition, it is a relatively expensive means, due to the cost of the equipment and the cost of the medical procedure.

In order to reduce patient exposure to ionizing radiation, especially when the area to be explored is large and examinations must be carried out frequently, ultrasound imaging represents a promising solution.

With the COVID-19 pandemic, researchers have found correlations between lung ultrasound and CT scan data. In a conventional ultrasound scan, an ultrasound transducer is applied to the patient by a practitioner to obtain an image of a portion of the lungs.

Although less restrictive and less expensive than CT, ultrasound requires prolonged contact with patients with risks of contamination. The number of procedures that can be performed is also limited, since ultrasound requires the participation of a specialist practitioner, typically for 20 to 40 minutes.

An objective of the invention is therefore to provide an autonomous lung imaging solution, in particular to limit the need for the presence of the practitioner and/or offer the possibility of continuous monitoring.

SUMMARY

• un support, et
• au moins cinq émetteurs-récepteurs fixés sur le support et configurés pour émettre et recevoir une onde ultrasonore de fréquence variable sur une plage de fréquence comprise dans un domaine allant de 1 MHz à 20 MHz, les émetteurs-récepteurs étant agencés selon au moins deux premiers ensembles chacun en regard d’un poumon d’un corps humain ou animal.

To achieve this objective, according to a first aspect, a device for lung tomography is provided comprising

• a support, and
• at least five transceivers fixed on the support and configured to transmit and receive an ultrasonic wave of variable frequency over a frequency range in a domain extending from 1 MHz to 20 MHz, the transceivers being arranged in at least two first sets each facing a lung of a human or animal body.

The device thus allows the emission and reception of ultrasonic waves between the different transmitters-receivers, for their propagation in the human or animal body at the level of its lungs. The transmitters-receivers being fixed on the support, they form a network of determined geometry allowing the collection of information in the volume represented by the lungs by the propagation of ultrasonic waves in this organ. Thanks to this network of transmitters-receivers, the device can be placed on the human or animal body and then the measurements can be carried out autonomously without requiring the action of a practitioner. Since the measurements can be carried out autonomously, continuous monitoring of the state of the lungs is made possible, for example in the event of hospitalization. Compared to conventional CT techniques, the device remains less expensive and more easily usable, which makes this technique accessible both in hospital-type structures but also in smaller structures such as a city practice.

• le dispositif tel qu’introduit ci-dessus,
• des moyens de traitements aptes à :
  • envoyer, à un émetteur-récepteur, une consigne d’émission d’une onde ultrasonore de fréquence émise variant sur une plage de fréquence comprise dans un domaine allant de 1 MHz à 20 MHz, selon un profil déterminé de variation de fréquence en fonction de temps, dit « profil d’émission »,
  • recevoir, depuis au moins un autre émetteur-récepteur, un signal pour former un profil de variation de fréquence en fonction du temps), dit « profil de réception », de l’onde ultrasonore telle que reçue par l’au moins un autre émetteur récepteur,
  • analyser la déformation entre le profil d’émission et le profil de réception, de préférence entre le profil d’émission et chaque profil de réception, de façon à déterminer la vitesse de propagation de l’onde en fonction de la fréquence et selon au moins une direction de propagation correspondant au placement relatif de l’au moins un autre émetteur-récepteur, de préférence chaque autre émetteur-récepteur, par rapport à l’émetteur-récepteur émettant l’onde ultrasonore,
  • construire une tomographie des poumons selon une donnée relative à la vitesse de propagation de l’onde en fonction de la fréquence et de la direction de propagation.

A second aspect concerns a lung tomography system comprising:

• the device as introduced above,
• processing methods capable of:
  • sending, to a transceiver, an instruction to transmit an ultrasonic wave of transmitted frequency varying over a frequency range in a domain extending from 1 MHz to 20 MHz, according to a determined profile of frequency variation as a function of time, called "transmission profile",
  • receiving, from at least one other transceiver, a signal to form a frequency variation profile as a function of time), called a “reception profile”, of the ultrasonic wave as received by the at least one other transceiver,
  • analyzing the deformation between the emission profile and the reception profile, preferably between the emission profile and each reception profile, so as to determine the propagation speed of the wave as a function of the frequency and according to at least one propagation direction corresponding to the relative placement of the at least one other transceiver, preferably each other transceiver, with respect to the transceiver emitting the ultrasonic wave,
  • construct a tomography of the lungs based on data relating to the speed of propagation of the wave as a function of the frequency and direction of propagation.

The system has the same effects and advantages as the device according to the first aspect and, like the device, allows the implementation of the method according to the following aspect.

• une application d’un dispositif selon le premier aspect sur le tronc du corps humain ou animal, de façon à mettre chacun des deux premiers ensembles en regard d’un des deux poumons du corps humain ou animal,
• une pluralité de mesures, chaque mesure comprenant :
  • une émission, par un émetteur-récepteur, d’une onde ultrasonore de fréquence émise variant sur une plage de fréquence comprise dans un domaine allant de 1 MHz à 20 MHz, selon un profil déterminé de variation de fréquence en fonction du temps, dit « profil d’émission »,
  • une réception, par au moins un autre émetteur-récepteur, de l’onde ultrasonore émise pour former un profil de variation de fréquence en fonction du temps de l’onde ultrasonore émise, dit « profil de réception »,

l’émetteur-récepteur émettant l’onde ultrasonore étant distinct entre au moins deux mesures successives,

• pour chaque mesure, une analyse de la déformation entre le profil d’émission et le profil de réception, de façon à déterminer la vitesse de propagation de l’onde en fonction de la fréquence et selon au moins une direction de propagation correspondant au placement relatif de l’autre émetteur-récepteur par rapport à l’émetteur-récepteur émettant l’onde ultrasonore,
• une construction d’une tomographie des poumons selon une donnée relative à la vitesse de l’onde en fonction de la fréquence et de la direction de propagation.

A third aspect relates to a method of tomography of the lungs of a human or animal body, comprising:

• an application of a device according to the first aspect on the trunk of the human or animal body, so as to place each of the first two sets opposite one of the two lungs of the human or animal body,
• a plurality of measures, each measure comprising:
  • an emission, by a transmitter-receiver, of an ultrasonic wave of emitted frequency varying over a frequency range in a domain extending from 1 MHz to 20 MHz, according to a determined profile of frequency variation as a function of time, called "emission profile",
  • a reception, by at least one other transmitter-receiver, of the emitted ultrasonic wave to form a frequency variation profile as a function of time of the emitted ultrasonic wave, called a “reception profile”,

the transmitter-receiver emitting the ultrasonic wave being distinct between at least two successive measurements,

• for each measurement, an analysis of the deformation between the emission profile and the reception profile, so as to determine the propagation speed of the wave as a function of the frequency and according to at least one propagation direction corresponding to the relative placement of the other transmitter-receiver with respect to the transmitter-receiver emitting the ultrasonic wave,
• a construction of a lung tomography according to data relating to the speed of the wave as a function of the frequency and direction of propagation.

The plurality of measurements, with sequential changes of the transmitter-receiver emitting the ultrasonic wave between at least two successive measurements, makes it possible to have distinct points of origin for the different ultrasonic waves emitted, and therefore several emission-reception directions. The propagation of each ultrasonic wave in the human or animal body makes it possible to obtain a reception profile which will depend on the local state of the patient's lung, along these wave propagation paths. In particular, the propagation speed of the wave changes according to the frequency according to the state of the lung, in the area crossed by the ultrasonic wave. The method makes it possible, from the reception profile and the emission profile, to obtain the propagation speed of the wave in a considered area of the lung according to the frequency of the wave, according to the relative placement of the transmitter-receiver emitting the wave and the transmitter(s)-receiver(s) receiving the wave. A tomography of the lung can thus be reconstructed.

The device comprising a network of fixed transceivers, the method allows a tomography of the lungs without having to manually move a probe or the transceivers. The method can be performed autonomously without requiring the action of a practitioner during the measurements. Since the measurements can be made autonomously, continuous monitoring of the state of the lungs is made possible, for example in the event of hospitalization. As for the previous aspects, compared to conventional CT techniques, the method remains more easily usable and of reduced cost, which makes this technique accessible both in hospital-type structures but also in smaller structures such as a city practice. The method can implement the tomography system according to the previous aspect.

A fourth aspect relates to a computer program product comprising instructions, which when carried out by at least one processor, execute at least the steps of analyzing the deformation between the emission profile and the reception profile of the measurements, and of constructing the tomography of the lungs of the method according to the third aspect.

According to one example, the instructions further perform the step of analyzing the deformation between the calibration emission profile and the calibration reception profile.

A fifth aspect relates to a method of diagnosing and/or monitoring a pulmonary condition, for example a pulmonary disease, comprising the method according to the third aspect.

According to one example, the diagnostic and/or monitoring method comprises, following the construction of the tomography, a diagnosis of a pulmonary condition, for example an identification of an affected area of the lung.

According to one example, the diagnostic and/or monitoring method comprises constructing multiple tomograms at distinct times. The method may comprise comparing tomograms taken at distinct times to monitor the evolution of the pulmonary condition, and preferably of an affected area of the lung.

BRIEF DESCRIPTION OF THE FIGURES

The aims, objects, as well as the features and advantages of the invention will become more apparent from the detailed description of one embodiment thereof which is illustrated by the following accompanying drawings in which:

There represents a schematic diagram of ultrasound imaging.

There represents a diagram of the device placed on the patient, during a measurement of the tomography process, according to an exemplary embodiment.

There represents a diagram of the device placed on the patient, during a measurement of the tomography process other than that illustrated in , according to an example of realization.

There represents a diagram of the device placed on the patient, during another measurement of the tomography method, according to another exemplary embodiment in which each transmitter-receiver, other than the one emitting the ultrasound wave, receives a reception profile.

There represents a schematic diagram of the propagation of the ultrasonic wave in the tomography method according to an exemplary embodiment.

Figures 6A and 6B illustrate an example of frequency distribution versus time for an affected lung area and a healthy lung, respectively.

There is a graph of the propagation speed of the ultrasonic wave as a function of frequency, for different lung conditions and according to an exemplary embodiment.

There illustrates an example of tomography established from the propagation speed of the ultrasonic wave.

There is a diagram describing steps of the tomography method, according to an exemplary embodiment.

Figures 10A and 10B show the device for lung tomography, according to two exemplary embodiments.

The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. In particular, the relative dimensions of the transceivers and the device for lung tomography are not necessarily representative of reality.

DETAILED DESCRIPTION

Before commencing a detailed review of embodiments of the invention, optional features are set forth below which may optionally be used in combination or alternatively.

In one example, the transceivers are arranged such that the distance d between the first neighbor transceivers is less than or equal to 10 cm.

According to one example, the transceivers are arranged according to the at least two first sets, and furthermore a second set comprising at least one transceiver and arranged between said first sets. The first two sets are thus each facing a lung, and the transceiver(s) of the second set can be arranged facing other organs of the respiratory system, for example the larynx, the trachea and/or one or more bronchi. The acquired data are thus more complete.

According to one example, the number of said transceivers is greater than or equal to seven. According to one example, the number of said transceivers is less than or equal to twelve, preferably less than or equal to nine. The number of said transceivers may be between seven and twelve, and more preferably still between seven and nine. During the development of the invention, it was demonstrated that these numbers of transceivers were sufficient to construct a sufficiently detailed tomography of the lungs. The more the number of transceivers is increased, the more detailed the tomography obtained will be, at least until reaching the physical limit of setting up the transceiver network. In order to limit the complexity and cost of the device, it was demonstrated that for the construction of a tomography of the lungs, a number of transceivers less than or equal to twelve, and preferably less than or equal to nine, was sufficient.

In one example, the transceivers of the first two sets are arranged symmetrically relative to a median axis between the first two sets. A symmetrical transceiver array facing each lung is thus obtained. This thus facilitates the construction of a tomography of the lungs because this symmetrical arrangement is linked to the anatomy of the human respiratory system, which is substantially symmetrical .

In one example, the support forms a garment, for example a vest or an apron. The device can thus be put on by the patient himself, or by a person helping him, simplifying the placement and maintenance of the device on the patient and thus the autonomous execution of the tomography procedure.

In one example, the support comprises a sheet or fabric. The support is thus easily conformable to the human or animal body.

According to one example, the support comprises means of attachment external to the human or animal body. The device can thus be held in place despite possible movements of the body, which facilitates measurements and in particular the acquisition of measurements distributed over time, for example during continuous monitoring.

According to one example, an evolution of the propagation speed of the wave is determined, as a function of the frequency and according to at least one propagation direction corresponding to the relative placement of the at least one other transceiver, preferably each other transceiver, with respect to the transceiver emitting the ultrasonic wave. The constructed tomography can be a function of each determined speed evolution.

According to one example, during the emission of the ultrasonic wave, during the plurality of measurements and/or during the calibration step, the emission profile comprises a non-linear variation of the frequency as a function of time. This makes it possible to limit the influence of patient movements on the measurements.

According to one example, during the emission of the ultrasonic wave, during the plurality of measurements and/or during the calibration step, the emission profile includes a variation of the frequency as a function of time according to a cubic frequency modulation law. A cubic frequency modulation is in fact less sensitive to the Doppler effect. Cubic frequency modulation. The patient's movements therefore impact the measurements and/or the calibration even less with a cubic frequency modulation.

• une pluralité d’acquisitions, chaque acquisition comprenant :
  • une émission, par un émetteur-récepteur, d’une onde ultrasonore de fréquence variant sur une plage de fréquence comprise dans un domaine allant de 1 MHz à 20 MHz, selon un profil déterminé de variation de fréquence en fonction de temps, dit « profil d’émission de calibration »,
  • une réception, par au moins deux autres émetteurs-récepteurs, de l’onde ultrasonore émise pour former un profil de variation en fréquence en fonction du temps de l’onde ultrasonore émise, dit « profil de réception de calibration »,
• pour chaque acquisition, une analyse de la déformation entre le profil d’émission de calibration et le profil de réception de calibration, de façon à déterminer un profil d’émission optimal, et plus particulièrement augmentant, et de préférence maximisant, l’amplitude des profils de réception.

According to one example, the method comprises, prior to the plurality of measurements, a calibration of the device placed on the human or animal body, comprising:

• a plurality of acquisitions, each acquisition comprising:
  • an emission, by a transmitter-receiver, of an ultrasonic wave of frequency varying over a frequency range in a domain extending from 1 MHz to 20 MHz, according to a determined profile of frequency variation as a function of time, called a “calibration emission profile”,
  • a reception, by at least two other transceivers, of the emitted ultrasonic wave to form a frequency variation profile as a function of time of the emitted ultrasonic wave, called a “calibration reception profile”,
• for each acquisition, an analysis of the deformation between the calibration emission profile and the calibration reception profile, so as to determine an optimal emission profile, and more particularly increasing, and preferably maximizing, the amplitude of the reception profiles.

Calibration improves the resolution of the tomography, in particular by determining for each receiver the frequency domain and/or the relative phase shift in relation to the other receiver(s) which maximizes the level of signals measured.

• correspond à un profil de modulation en fréquence pour lequel une maximisation de la déformation entre le profil d’émission de calibration et le profil de réception de calibration est observée, et/ou
• correspond à un profil d’émission dont le déphasage maximise le signal reçu, et/ou
• présente une plage de variation de fréquence sur laquelle une maximisation de la déformation entre le profil d’émission de calibration et le profil de réception de calibration est observée.

For example, the optimal emission profile:

• corresponds to a frequency modulation profile for which a maximization of the distortion between the calibration emission profile and the calibration reception profile is observed, and/or
• corresponds to an emission profile whose phase shift maximizes the received signal, and/or
• presents a frequency variation range over which a maximization of the distortion between the calibration emission profile and the calibration reception profile is observed.

According to one example, between the different measurements of the plurality of measurements, each transceiver emits the ultrasonic wave at least once. Thus, this multiplies the origin points of the ultrasonic wave, and thus makes it possible to perform the tomography more precisely and more completely.

In one example, the reception of the reception profile is made by at least two, and preferably each, of the other transceivers, the propagation speed of the wave as a function of the frequency being determined for propagation directions corresponding to the relative placements of the at least two, and preferably each, of the other transceivers with respect to the transceiver emitting the ultrasonic wave. The reception profile is thus obtained for several and preferably for each of the transceivers. This multiplies the reception points of the ultrasonic wave and therefore the measured propagation paths of the ultrasonic wave in the lungs, to improve the information represented in the tomography.

According to a preferred example, the transmitted frequency is varied over a range between 1 MHz and 10 MHz. This range represents a better compromise between wave propagation performance and the resolution that can be obtained. According to another example, the transmitted frequency is varied over a range between 10 MHz and 20 MHz. The transceivers can thus be of smaller dimensions.

In one example, each of the plurality of measurements includes electronic channel shaping, and in particular for at least a portion and preferably for each reception profile. Electronic channel shaping improves spatial sensitivity and enables tomography of increased spatial resolution.

According to one example, the calibration comprises an electronic channel formation, and in particular for at least one part and preferably for each calibration reception profile. The electronic channel formation then makes it possible during the calibration to optimize the phase shift to maximize the received signal. The resolution of the tomography is therefore improved.

In the remainder of the description, the term “on” does not necessarily mean “directly on”. Thus, when it is indicated that a part or element A is supported “on” a part or element B, this does not mean that the parts or elements A and B are necessarily in direct contact with each other. These parts or elements A and B may either be in direct contact or be supported on each other by means of one or more other parts. The same applies to other expressions such as, for example, the expression “A acts on B” which may mean “A acts directly on B” or “A acts on B by means of one or more other parts”.

• positionnées à distance l’une de l’autre, et/ou
• mobiles l’une par rapport à l’autre et/ou
• solidaires l’une de l’autre en étant fixées par des éléments rapportés, cette fixation étant démontable ou non.

Une pièce unitaire monobloc ne peut donc pas être constituée de deux pièces distinctes.In this patent application, when two parts are indicated as distinct, this means that these parts are separate. They can be:

• positioned at a distance from each other, and/or
• mobile relative to each other and/or
• integral with each other by being fixed by added elements, this fixing being removable or not.

A single piece cannot therefore be made up of two separate pieces.

In the present patent application, the term "solidary" used to qualify the connection between two parts means that the two parts are connected/fixed relative to each other, according to all degrees of freedom, unless explicitly specified otherwise. For example, if it is indicated that two parts are solidary in translation in one direction, this means that the parts can be movable relative to each other, possibly according to several degrees of freedom, excluding freedom in translation according to the direction. In other words, if one part is moved in the direction, the other part performs the same movement.

Several embodiments of the invention implementing successive steps of the manufacturing method are described below. Unless explicitly stated, the adjective “successive” does not necessarily imply, even if this is generally preferred, that the steps follow one another immediately, intermediate steps being able to separate them.

Furthermore, the term “step” means the performance of a part of the process, and can designate a group of sub-steps.

Furthermore, the term "step" does not necessarily mean that the actions carried out during a step are simultaneous or immediately successive. Certain actions of a first step may in particular be followed by actions linked to a different step, and other actions of the first step may be repeated subsequently. Thus, the term step does not necessarily mean unitary and inseparable actions in time and in the sequence of the phases of the process.

A parameter that is “substantially equal to/greater than/less than” a given value means that the parameter is equal to/greater than/less than the given value, within plus or minus 10% of that value. A parameter that is “substantially between” two given values means that the parameter is at least equal to the smallest given value, within plus or minus 10% of that value, and at most equal to the largest given value, within plus or minus 10% of that value.

The term "ultrasonic wave" is used to describe an acoustic wave, i.e. a mechanical vibration propagating in a medium, in a frequency range between 1 MHz and 20 MHz.

The general principle of ultrasound imaging, and more particularly ultrasound, is first described with reference to the .

An ultrasound probe 60 is used, comprising several ultrasonic wave transmitters-receivers, typically in the band ranging from 1 MHz to 10 MHz generally used in ultrasound imaging. The ultrasound probe 60 is moved by a specialist practitioner on the skin of the body 2. During the measurement 61, the ultrasonic waves are emitted 610 and echo 611a, 611b on the internal structures of the body 2, in particular on an organ to be imaged 20'. Several two-dimensional scans are carried out and they each constitute an ultrasound image. The basic principle is that the organ of interest 20' and their constituent parts are generally characterized by echoes of stronger amplitudes than the reflections on other tissues that one does not seek to image.

The device for lung tomography 1 according to the first aspect of the invention makes it possible to dispense with the presence and manual operation carried out by the practitioner.

The device 1 comprises a support 10 on which are fixed, removably or not, transceivers 11, or equivalently “transducers”, as illustrated in FIGS. 2 to 4. These transceivers 11 form a network of transceivers 11 of determined geometry, integral with each other, superimposing at least in part on the lungs 20 of a human or animal body 2. For this, the transceivers 11 are divided into at least two first sets 110, each intended to be arranged facing a lung 20. Certain transceivers 11 may also be arranged in a second set 111 arranged between the first sets 110. These transceivers 11 of the second set 111 may for example be arranged so as to be facing other structures 21 of the respiratory system, for example the larynx, the trachea and/or one or more bronchi.

The operating principle of the invention is first described in general with reference to Figures 2 to 9, and particular embodiments are described. describes process steps, in which optional steps are indicated by dotted lines and parallel paths and branches indicate possible alternatives.

The device 1 is applied to the trunk 2a of a human or animal body 2, hereinafter referred to as body 2. The device 1 may preferably be applied to the chest, as illustrated in FIGS. 2 to 4. It may be provided, even if this is not preferred, that the device be applied to the back of the patient 2. The device 1 is placed so as to arrange each of the first sets 110 opposite a lung 20.

Following this placement, a transceiver 11a is configured to emit an ultrasonic wave 12 of a frequency varying over a frequency range comprised in a domain between 1 MHz and 20 MHz, as a function of time. The instantaneous frequency is therefore varied as a function of time to form a determined profile. Equivalently, we speak of modulation of the frequency of the ultrasonic wave 12. The transceiver 11a can emit a wave 12 of a frequency varying over a narrower frequency range than the domain between 1 MHz and 20 MHz. As explained in more detail later, the invention exploits a modification of frequency profile between the emission 410 of the wave 12 and its reception 411. For example, the wave varies over a range of 6 MHz, for example 5 MHz. This range is rather given by the processing capacity of the transceivers, for example between 1 MHz and 6 MHz, or between 5 MHz and 10 MHz.

According to one example, the range in which the frequency variation range is comprised is between 1 MHz and 15 MHz, and preferably between 1 MHz and 10 MHz, corresponding to the band generally used in ultrasound imaging. In these ranges, the higher the frequency, the greater the resolution will be. However, the propagation performance may decrease for high frequencies. The frequency ranges used further depend on the transceiver technology used, in a manner known to those skilled in the art.

As illustrated in , the ultrasonic wave emitted 410 by a transmitter-receiver 11a propagates in the body 2, and in particular in the volume of the lungs 20. Depending on the nature and state of the tissues encountered in the area crossed, noted Ω_m,n, by the ultrasonic wave 12, the properties of the ultrasonic wave are modified. The area Ω_m,nis also called volume Ω_{m,n ,} with m the transceiver 11a and n the transceiver 11b. Determining the modification of these properties allows the estimation of the information in order to construct the tomography 430 of the lungs 20.

More particularly, during a measurement 41, the transmitter-receiver 11a emits 410 the ultrasonic wave 12 of frequency varying over the frequency range, according to a determined profile of frequency variation as a function of time. The instantaneous frequency emitted varies over time to form this profile, called the “emission profile” 120. At least one other transmitter-receiver 11b, distinct from the transmitter-receiver 11a which emits the ultrasonic wave 12, captures the ultrasonic wave 12 after its propagation in the tissues. This transmitter-receiver 11b captures the signal of the wave to form a profile of frequency variation as a function of time, called the “reception profile” 121. The instantaneous frequency captured by the receiver 11b varies over time, which constitutes the reception profile 121.

For example, as illustrated by FIGS. 6A and 6B, the reception profile 121 can be deformed according to the nature of the tissues that the ultrasonic wave 12 passes through. Indeed, in a homogeneous medium, the speed of an ultrasonic wave does not depend on the frequencies. In a heterogeneous medium, composed of several types of materials as is the case for the lungs 20, the speed of the ultrasonic wave 12 depends on the acoustic impedances of the different layers passed through. These impedances influence the transmission coefficients of the waves in the medium. The transmission speed therefore varies, as does the frequency of the wave, according to the heterogeneous medium passed through. It is therefore understood that a deformation of the reception profile 121 relative to the emission profile 120 is obtained according to the nature of the tissues passed through.

Typically, in the presence of air, the propagation speed of an ultrasonic wave 12 is 330 m/sec while the propagation speed of an ultrasonic wave 12 in water is 1480 m/sec. Pulmonary damage generally results in congestion of the respiratory tract and obstruction of the passage of air. An increase in the propagation speed of the wave 12 will be observed, and an increase in the number of frequencies propagated, because ultrasonic waves propagate more easily in tissues containing water.

In an affected lung tissue 20b, the ultrasound wave 12 passes through the potentially damaged tissues and a volume of air partly occupied by secretions, mucus. illustrates as an example a deformation of the reception profile 121 relative to the emission profile 120, for an affected lung tissue 20b. In a healthy lung tissue 20a, the ultrasound wave 12 passes through the tissues and a larger volume of air. The illustrates as an example a slight deformation of the reception profile 121 compared to the emission profile 120, for healthy lung tissue 20a. The reception profile 121 will be less impacted than in the case of affected lung tissue 20b.

Knowing the location of the transceiver 11a emitting the ultrasonic wave 12, and that of the transceiver 11b receiving it, the analysis 42 of this deformation makes it possible to obtain the speed of the wave 12 as a function of the frequency and according to a propagation direction corresponding to the relative placement of the transceiver 11b with respect to the transceiver 11a. The propagation direction, or propagation volume denoted Ω _m,n , corresponds to the volume in which the ultrasonic wave propagates, with m the transceiver 11a and n the transceiver 11b. This volume can be at least partly inscribed in a plane including two transducers, one in transmission and the other in reception.

Several measurements 41 are carried out, the transmitter-receiver 11a emitting the ultrasonic wave being distinct between at least two successive measurements 41, as illustrated for example by FIGS. 2 and 3. The point of origin is therefore varied at least between two successive measurements. We therefore obtain by the analysis 42, for each measurement, the speed of the wave 12 as a function of the frequency and according to several directions of propagation in the zone Ω _m,n .

From the speed of the wave 12 as a function of the frequency and according to several directions of propagation in Ω _m,n , an image of the crossed area can be obtained. The image construction for the entire area covered by the transducer network can be continuous and makes it possible to have, for a series of measurements 41, a representation of the state of the patients' lungs. A tomography 430 can thus be obtained as shown in . This tomography represents the lung 20 according to data relating to the speed of the wave 12 as a function of the frequency and the direction of propagation. The person skilled in the art is able to identify and use any data relating to the speed of the wave for the construction 43 of the tomography. This data may be a color scale or a gray level. In the example illustrated in for example, parts with clutter 430a are indicated by darker colors than unaffected parts 430b.

Steps of method 4 are now described in more detail, according to exemplary embodiments.

During the plurality of measurements 41, the transceiver 11a emitting the ultrasonic wave 12 is distinct between at least two successive measurements 41 of the plurality of measurements 41. When the plurality of measurements comprises more than two measurements 41, the same transceiver 11a can emit 410 the ultrasonic wave 12 on several measurements 41, for example on two successive measurements 41.

At least one transceiver 11a of each first set 110 preferably emits 410 the ultrasonic wave 12 during the plurality of measurements 41. Some transceivers of one set 110 may be too far from the other set 110 to properly pick up the emitted ultrasonic wave 410. Thus, at least one point of origin of the wave is used for each first set 110. At least one transceiver 11a of the second set 111 can emit 410 the ultrasonic wave 12. Thus, a point of origin arranged between the first two sets 110 is used. This makes it possible in particular to perform tomography of central areas of the lungs such as the trachea or the larynx.

Preferably, each transceiver 11 emits the ultrasonic wave 12 at least once during the plurality of measurements 41. The method thus exploits the entire network of transceivers 11 to multiply the points of origin for the propagation of the ultrasonic wave 12, and thus obtain information for an increased number of propagation directions.

Preferably, a single transceiver 11a emits the ultrasonic wave 12 during a measurement, in order to avoid interference between the reception profiles 121 and facilitate the analysis 42 of the deformation.

At least one transceiver 11b captures the ultrasonic wave 12 to obtain the reception profile 121. Preferably, several transceivers 11b capture the ultrasonic wave 12 to each obtain a reception profile 121. Thus, the reception points 411 of the reception profiles 121 are multiplied. The same measurement 41 therefore makes it possible to obtain more information on the pulmonary tissues crossed. More preferably, all the transceivers 11b, other than that 11a which emits the ultrasonic wave 12, capture the ultrasonic wave 12 to each obtain a reception profile 121, as illustrated in .

It is therefore understood that the network of transmitters-receivers 11 of the device 1 allows, through the play of the different points of origin and reception of the ultrasonic wave 12, to improve the spatial acquisition of the information in the pulmonary volume to be imaged, and this in a rapid time.

According to one example, there are at least as many measurements 41 as there are transceivers 11. For a measurement, for a device comprising seven transceivers 11, six transceivers 11b can receive the ultrasonic wave 12 for each measurement 41. Six reception profiles 121 can be obtained per measurement 41, and seven measurements can be carried out, i.e. a total of 42 reception profiles for the seven measurements 41.

Synergistically between the number of measurements 41 with the number of distinct origin points for the emission 410 of the wave, and/or the number of reception points 411, both the number of reception profiles 121 and the number of associated propagation directions are increased. The spatial acquisition of information in the lung volume to be imaged is improved.

According to one example, the frequency modulation of the ultrasonic wave 12 follows a non-linear progression as a function of time, as for example illustrated by FIGS. 6A and 6B. The emission profile 120 can therefore be non-linear. This makes it possible to limit the influence of the patient's movements on the measurements. A non-linear modulation is in fact less sensitive to the Doppler effect because the polynomial coefficients associated with the non-linear modulation are small. The emitted wave 410 can be defined as a function of an amplitude and an instantaneous phase Φ(t) characterizing the non-linear modulation of the signal. More particularly, the frequency modulation of the ultrasonic wave 12 can follow a cubic progression.

For example, the emitted wave E _(t) can be defined by E _(t) = A.exp[j.Φ _(t) ], with where A is the signal amplitude and Φ(t) is a function of time, j being the imaginary number such that j² = -1.

On reception, after propagation in the lung tissues and therefore deformation of the wave modulation, the signal received R _k (t) by a receiver 11b can be a function of the amplitude A of the signal and of the instantaneous phase Φ(t) as a function of time, and in addition of a factor L _k /c ^m,n _k (f), for a direction k.

The received signal R(t) can notably have the following expression:

• Lk les distances de propagation des ondes entre un émetteur-récepteur 11a, noté m, émetteur de l’onde, et un récepteur-émetteur 11b, noté n, récepteur de l’onde, et définies dans le volume Ωm,n imagé par le couple d’émetteur-récepteur 11a, 11b ;
• cm,nk représente la vitesse de l’onde propagée dans la direction k entre l’émetteur m et le récepteur n, qui dépend de la fréquence f et du milieu de propagation, ces deux éléments étant intrinsèquement liés.

With :

• Lk the wave propagation distances between a transmitter-receiver 11a, denoted m, transmitter of the wave, and a receiver-transmitter 11b, denoted n, receiver of the wave, and defined in the volume Ωm,n imaged by the transmitter-receiver pair 11a, 11b;
• cm,nk represents the speed of the wave propagated in the direction k between the transmitter m and the receiver n, which depends on the frequency f and the propagation medium, these two elements being intrinsically linked.

The analysis 42 of the deformation can be made between a reception profile 121 and an emission profile 122, according to the modalities of which transmitter(s)-receiver(s) 11a emit(s) 410 the ultrasonic wave 12 and which transmitter(s)-receiver(s) receive(s) it 411. Preferably, the analysis 42 of the deformation can be made between each reception profile 121 and the emission profile 122.

This analysis step 42 may be at least partly simultaneous with the plurality of measurements 41, or separated in time, as shown by way of example by the arrows looping back to the emission 410 of the emission profile in .

According to one example, the analysis of the deformation between a reception profile 121 and a transmission profile 122 may comprise an estimation of the modulation law of the signal of the reception profile 121. For this, a time-frequency-phase concept may be used in order to automatically and accurately extract the non-linear modulation laws of a multi-component signal. The details of this time-frequency-phase concept are detailed in the document Cornel Ioana, et al . Localization in underwater dispersive channels using the time-frequency-phase continuity of signals . IEEE Transactions on Signal Processing, Institute of Electrical and Electronics Engineers, 2010, 58, pp.4093-4107.

As an example, a first step can be to adaptively build a local dictionary, using polynomial phase modeling, for example cubic modeling. This allows to establish a correspondence between the instantaneous frequency laws of the polynomial modulations and the instantaneous frequency laws of the analyzed signal, for different analysis windows. A second step can then include a fusion of the cubic modulations using the maximization of the local correlation between the signals extracted from the filters defined by the cubic modulations of the neighboring analysis windows. This second step allows to automate the tracking as well as to minimize the propagation of errors.

More particularly, the modulation law of the emission profile 120 being known, the estimation of the modulation laws of the signals received R _k (t) above makes it possible to estimate the deformations of the reception profile 122 with respect to the emitted modulation 120.

Analysis 42 may include a determination of the variation of the speed c according to the frequency, which depends on the presence of the volume of the different materials crossed, in the volume Ω_m,n for a direction k, the direction k being according to the relative placement of the transmitter-receiver 11b receiving the wave 12 and the transmitter-receiver 11a emitting it. This gives a frequency dispersion profile. For example, the estimation of the modulation laws of the signal of the reception profile 121 gives access for each frequency to the propagation speed in the directions k of the volume Ω_m,n. This dispersion profile indicates the variation of the speed c of each of the frequencies, which depends on the presence of the volume of the different materials crossed, in the volume Ω_m,n for direction k.

• Un profil de dispersion 130 pour des poumons sains,
• Un profil de dispersion 131 lors de l’installation initiale du système sur un patient, pour des poumons avec un début d’encombrement pulmonaire,
• Un profil de dispersion 132 à un temps qui correspond à un intervalle de surveillance, montrant une évolution de l’encombrement pulmonaire.

With this estimated dispersion profile, analysis 42 can include a quantification of the crowding rate in the volume Ω_m,n as illustrated for example by the . On the , speed 9 as a function of frequency 8 is represented for three cases:

• A 130 dispersion profile for healthy lungs,
• A 131 dispersion profile during initial installation of the system on a patient, for lungs with the onset of pulmonary congestion,
• A 132 dispersion profile at a time that corresponds to a monitoring interval, showing an evolution of pulmonary congestion.

We therefore understand that quantified data on the pulmonary state can, for example, be obtained by analyzing the speed of propagation of the wave according to the frequency and direction of propagation k.

An image 430 of the area Ω _m,n , as described above, can be obtained by integrating over all propagation directions k, the speed of the wave 12 as a function of the frequency. As an example, this integration can be expressed analytically by

With {L _k } belonging to Ω _m,n , and f1 the lower limit and f2 the upper limit of the variation range of the emitted wave (for example f1 = 1 MHz and f2 = 15 MHz).

• une émission 440, par un émetteur-récepteur 11a, et notamment celui qui va émettre l’onde ultrasonore lors des mesures 41, d’une onde ultrasonore 12 de fréquence variant sur la plage de fréquence prévue pour les mesures 41, selon un profil en fréquence et en fonction du temps dit « profil d’émission de calibration » 122,
• une réception 441, par au moins deux autres émetteurs-récepteurs 11b, de l’onde ultrasonore 12 émise, selon profil en fréquence et en fonction du temps de l’onde ultrasonore 12 émise, dit « profil de réception de calibration » 123.

Prior to the measurements 41, the method may further comprise a calibration step 44 of the emission profiles 120, which may also be referred to equivalently by the term “initialization”. This calibration aims to determine the emission profile 120 most suited to the acquisition of information on the state of the pulmonary tissues. For this, the calibration comprises a plurality of acquisitions 44a, each comprising:

• an emission 440, by a transmitter-receiver 11a, and in particular the one which will emit the ultrasonic wave during the measurements 41, of an ultrasonic wave 12 of frequency varying over the frequency range provided for the measurements 41, according to a frequency profile and as a function of time called “calibration emission profile” 122,
• a reception 441, by at least two other transmitters-receivers 11b, of the emitted ultrasonic wave 12, according to the frequency profile and as a function of the time of the emitted ultrasonic wave 12, called “calibration reception profile” 123.

An optimal reception configuration corresponds in fact to that which allows to obtain a signal of maximum amplitude at the level of the transmitter-receiver receiving the signal. To do this, it is for example possible to play on two parameters.

A first parameter is the band of the transmitted signal. Choosing a wide band (for example between 1 MHz and 15 MHz) allows to have a sufficiently wide range to guarantee that a maximum of frequencies arrive at the transceiver receiving the signal with a sufficient level. In addition, the larger the frequency range, the more effective the dispersion measurement will be.

A second parameter is the propagation direction. In the device, the transceivers are oriented towards the lungs and, between each one, the propagation medium is different from one patient to another. Since the transceivers are fixed, it is possible to play on the relative phase shifts between the receptions. This is the principle of electronic path formation which makes it possible to maximize the level of signals received by optimizing the relative phase shifts between the transceivers. The phase shift can therefore be optimized so as to maximize the level of signal received. During calibration, at least two other transceivers 11b can receive the emitted ultrasonic wave 12 to analyze these relative phase shifts.

According to one example, the calibration reception profile 123 is received 441 by the transceivers 11b intended to receive 411 the reception profile 122 during the measurements 41, and preferably by all the transceivers 11b of the device 1 other than the one which emits 440 the ultrasonic wave 12.

Between several acquisitions 44a, and preferably for the same transceiver 11a, the calibration emission profile 122 may be distinct between at least two successive acquisitions 44a. An analysis 44b of the deformation between the calibration emission profile 122 and the calibration reception profile 123 may be carried out. This deformation is for example represented by FIGS. 6A and 6B, in a manner similar to the deformations described for the measurement step 41. Between several acquisitions 44a, and preferably for the same transceiver 11a, an optimized emission profile may be determined.

This determination can be based on the calibration emission profile 121 for which the amplitude of the signals received will be maximum. The resolution of the tomography 430 will thus be improved. In particular, it is possible to seek to maximize the deformation by electronic channel formation, and/or the frequency variation range in the domain previously described.

The frequency modulation of the ultrasonic wave 12 emitted 440 during the calibration can have the same characteristics as those described with reference to the measurements 41.

This calibration 44 can be carried out for several and preferably for all the transceivers 11a intended to emit 410 the ultrasonic wave 12 during the measurements 41. As described for the measurements 41, preferably a single transceiver 11a emits the ultrasonic wave in an acquisition 44a. For example, the calibration 44 can be repeated for each of these transceivers 11a.

Here also, it can be provided that this analysis step 44b is at least partly simultaneous with the plurality of acquisitions 44a, or separated in time, as shown by way of example by the arrows looping back to the emission 440 of the calibration emission profile in .

During measurements 41 and/or during calibration 44, electronic channel formation 420, 442 (generally translated into English as adaptive beam forming ) can be carried out on the reception profile(s) 121, 123.

As is well known in the field, electronic channel formation methods are techniques that allow to play on a relative phase shift. This is the principle of electronic channel formation that allows to maximize the level of signals received by optimizing the relative phase shifts between the transmitters-receivers. This phase shift allows to virtually change the position of the transmitter of the ultrasonic wave. This therefore allows to obtain for a given position of a transmitter and a receiver, several configurations between which the measured signal levels can vary. During calibration, the phase shift can therefore be optimized in order to identify the phase shift configuration that maximizes the received signal level. During measurements, electronic channel formation allows to introduce phase shifts, which artificially increases the propagation directions. The resolution of the resulting tomography is therefore increased.

The device 1 is now described in more detail, according to several exemplary embodiments which can be illustrated by figures 10A and 10B.

The device 1 comprises at least five transceivers 11, and preferably between five and twelve. For example, the device 1 comprises seven transceivers 11. In the network of transceivers thus formed, the distance d between the first neighboring transceivers 11 can be chosen so as to distribute the transceivers above the lungs to be imaged. It is therefore understood that this distance d can be adapted according to the morphology of the human or animal body. The distance d can also be adapted according to the frequency of the ultrasound wave. The distance d is at least greater than or equal to the wavelength of the ultrasound wave. The distance d can be between a few centimeters and several tens of centimeters, for example substantially greater than or equal to 5 cm and/or substantially less than or equal to 30 cm. For example, the distance d is substantially greater than or equal to 7 cm. The distance d can be substantially less than or equal to 20 cm, preferably 15 cm. For example, the distance d can be substantially equal to 10 cm. These distances with the number of receivers allow a good distribution of the transceivers 11 over the area of the lungs 20 to be imaged. Note that this distance d can vary in this range between the transceivers 11. It is for example possible that the distance d is reduced between certain transceivers, in order to increase the resolution of a given area and obtain a more precise tomography.

The transceivers 11 are preferably all placed in the same plane parallel to or coincident with the plane of the support 10. Note that the plane of the support 10 may be curved to conform to the human or animal body. The distance between the transceivers 11 furthest apart may be less than or equal to 50 cm, preferably 30 cm, in a lateral direction parallel to direction B. This distance may be greater than or equal to 15 cm, preferably 20 cm. The distance between the transceivers 11 furthest apart may be less than or equal to 50 cm, preferably 30 cm, in a longitudinal direction parallel to direction A. This distance may be greater than or equal to 15 cm, preferably 20 cm. Within each first set 110, the distance between the transceivers 11 furthest apart may be less than or equal to 25 cm, preferably 15 cm. This distance may be greater than or equal to 5 cm, in a lateral direction parallel to direction A and/or a longitudinal direction parallel to direction A. Here again, we understand that these distances can be adapted according to the morphology of the human or animal body.

The first two sets 110 may be separated from each other, i.e. placed at a distance from each other in the plane of the support 10. They are for example separated by a distance greater than or equal to 5 cm, preferably 10 cm. The first sets 110 are preferably arranged symmetrically relative to a median axis A ₁₁₀ between the first two sets 110. In this case, preferably the first two sets comprise an equal number of transceivers 11. The transceiver(s) 11 in the second set 11 may also be arranged symmetrically relative to this axis A _110. At least one transceiver 11 of this set 111 may be arranged on this axis for example.

According to one example, the support 10 forms a garment suitable for being put on by a patient, as illustrated in . This garment may be an apron or a vest for example. According to another example, the support 10 may be configured to simply rest on the trunk 2a of the body 2, as illustrated by the .

The support 10 may comprise attachment means 101 external to the human or animal body 2, i.e. non-invasive. For example, these attachment means 101 may be straps, elastic belts or any other means conceivable by those skilled in the art.

The support 10 may be flexible, i.e. manually deformable without tools, to conform to the body 2. The support 10 may be made of a sheet (for example paper or plastic) or of a fabric 100. Those skilled in the art are able to identify and implement a support capable of receiving the transceivers 11 in the device 1.

The tomography system 3, for example illustrated by FIGS. 2 to 4, comprises the device 1 as well as processing means 30 configured to send instructions or commands to the transceivers 11, and to receive the profiles received from the transceivers 11, in particular for implementing the steps of the method 4. Note that it can be provided that the reception means receive data by data the signal received by the transceivers 11b, and that the processing means 30 constitutes the reception profile 121, 123. These means 30 can also carry out the analysis steps 42, 44b and construction 43 of the tomography described above.

The system 3 may further comprise a display means (not shown in the drawings) on which the tomography 430 may be displayed 45. The processing means 30 may further comprise a memory in which the acquired and calculated data is recorded, for example the reception profiles 121, 123 during the measurements 41 and/or acquisition 44a.

Communication between the device 1 and the processing means 30 and/or display means can be done wired or wirelessly. The processing means 30 can be integrated into the device 1 or remote from the device 1.

These processing means 30 may for example comprise a computer program product comprising instructions allowing the implementation of the steps of the method 4, and in particular the steps of analysis 42, 44b of the deformation between the emission profile 120, 122 and the reception profile 121, 123 during the measurements and/or the calibration 44, and of construction 43 of the tomography 430. The computer program product may further comprise instructions for coordinating the emissions 410, 440 of ultrasonic waves, and their reception 411, 441.

The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention. In particular, the device, the tomography system and/or the computer program product may comprise any feature configured to allow the implementation of a step of the method, and conversely the method may comprise any step resulting from the implementation of a feature of the device, the tomography system and/or the computer program product.

Claims (17)

Device for tomography (1) of the lungs (20) characterized in that it comprises:

• a support (10), and
• at least five transceivers (11) fixed on the support (10), and configured to transmit and receive an ultrasonic wave (12) of variable frequency over a frequency range in a domain extending from 1 MHz to 20 MHz, the transceivers (11) being arranged in at least two first sets (110) each facing a lung (20) of a human or animal body (2).

Device (1) according to the preceding claim, wherein the transceivers (11) are arranged according to the at least two first sets (110), and a second set (111) comprising at least one transceiver (11) and arranged between said first sets (110). Device (1) according to any one of the preceding claims, the number of said transceivers (11) is between seven and twelve. Device (1) according to any one of the preceding claims, wherein the transceivers (11) of the first two sets (110) are further arranged symmetrically relative to a median axis (A ₁₁₀ ) between the first two sets (110). Device (1) according to any one of the preceding claims, in which the support (10) forms a garment. Device (1) according to any one of the preceding claims, in which the support (10) comprises a sheet or fabric (100) and attachment means (101) external to the human or animal body (2). System (3) for tomography of the lungs (20) comprising:

• The device (1) according to any one of the preceding claims,
• Treatment means (30) capable of:
  • Send, to a transmitter-receiver (11a), an emission instruction (410) of an ultrasonic wave (12) of emitted frequency varying over a frequency range included in a domain extending from 1 MHz to 20 MHz, according to a determined profile of frequency variation as a function of time, called “emission profile” (120),
  • receiving, from at least one other transceiver, a signal to form a frequency variation profile as a function of time, called a “reception profile” (121), of the ultrasonic wave as received by the at least one other transceiver (11b),
  • analyzing (42) the deformation between the emission profile (120) and the reception profile (121), so as to determine the propagation speed of the wave (12) as a function of the frequency and according to at least one propagation direction corresponding to the relative placement of the at least one other transmitter-receiver (11b) with respect to the transmitter-receiver (11a) emitting the ultrasonic wave (12),
  • construct (43) a tomography (430) of the lungs (20) according to data relating to the speed of the wave (12) as a function of the frequency and direction of propagation.

Method (4) for tomography of the lungs (20) of a human or animal body (2), comprising:

• an application (40) of a device (1) according to any one of claims 1 to 6 on the trunk (2a) of the human or animal body (2), so as to place each of the first two assemblies (110) opposite one of the two lungs (20) of the human or animal body (2),
• a plurality of measures (41), each measure (41) comprising:
  • an emission (410), by a transmitter-receiver (11a), of an ultrasonic wave (12) of emitted frequency varying over a frequency range comprised in a domain extending from 1 MHz to 20 MHz, according to a determined profile of frequency variation as a function of time, called “emission profile” (120),
  • a reception (411), by at least one other transmitter-receiver (11b), of the emitted ultrasonic wave to form a frequency variation profile as a function of the time of the emitted ultrasonic wave, called “reception profile” (121),

the transmitter-receiver (11a) emitting the ultrasonic wave being distinct between at least two successive measurements (41),

• for each measurement (41), an analysis (42) of the deformation between the emission profile (120) and the reception profile (121), so as to determine (421) the propagation speed of the wave (12) as a function of the frequency and according to at least one propagation direction corresponding to the relative placement of the other transmitter-receiver (11b) with respect to the transmitter-receiver (11a) emitting the ultrasonic wave (12),
• a construction (43) of a tomography (430) of the lungs according to data relating to the speed of propagation of the wave (12) as a function of the frequency and the direction of propagation.

Method (4) according to the preceding claim, in which, during the emission (410) of the ultrasonic wave (12), the emission profile (120) comprises a non-linear variation of the frequency as a function of time. Method (4) according to the preceding claim, in which, during the emission (410) of the ultrasonic wave (12), the emission profile (120) comprises a variation of the frequency as a function of time according to a cubic frequency modulation law. Method (4) according to any one of the three preceding claims, comprising, prior to the plurality of measurements (41), a calibration (44) of the device (1) placed on the human or animal body (2), comprising:

• a plurality of acquisitions (44a), each acquisition (44a) comprising:
  • an emission (440), by a transmitter-receiver (11a), of an ultrasonic wave (12) of frequency varying over a frequency range comprised in a domain extending from 1 MHz to 20 MHz, according to a determined profile of frequency variation as a function of time, called “calibration emission profile” (122),
  • a reception (441), by at least two other transceivers (11b), of the emitted ultrasonic wave (12), to form a frequency variation profile as a function of the time of the emitted ultrasonic wave (12), called a “calibration reception profile” (123),
• for each acquisition (44a), an analysis (44b) of the deformation between the calibration emission profile (122) and the calibration reception profile (123), so as to determine (443) an emission profile (120) increasing the amplitude of the reception profiles (121).

Method (4) according to any one of the four preceding claims, in which, between the different measurements (41) of the plurality of measurements (41), each transceiver (11) emits at least once the ultrasonic wave (12). Method (4) according to any one of the five preceding claims, in which the reception (411) of the reception profile (121) is made by at least two, and preferably each, of the other transceivers (11b), the propagation speed of the wave (12) as a function of the frequency being determined for propagation directions corresponding to the relative placements of the at least two, and preferably each, of the other transceivers (11b) with respect to the transceiver (11a) emitting the ultrasonic wave (12). Method (4) according to any one of the six preceding claims, in which the transmitted frequency is varied over a range between 1 MHz and 10 MHz. A method (4) according to any one of the preceding seven claims, wherein each measurement (41) of the plurality of measurements (41) comprises an electronic channel formation (420) and/or the calibration (44) comprises an electronic channel formation (442). Computer program product comprising instructions, which when carried out by at least one processor, execute at least the steps of analysis (42) of the deformation between the emission profile (120) and the reception profile (121) of the measurements and construction (43) of the tomography (430) of the lungs (20) of the method (4) according to any one of the eight preceding claims. Computer program product according to the preceding claim, in which the instructions further execute the step of analyzing (44b) the deformation between the calibration emission profile (122) and the calibration reception profile (123).