Ultrasound imaging apparatus and method employing continuous transmission and reception

Abstract

This invention relates to an ultrasound imaging apparatus and an associated method thereof, comprising: - at least one transmitter element configured to transmit a continuous excitation signal (S... em The excitation signal is emitted into a medium and encoded to form a series of N overlapping ultrasonic waves, each ultrasonic wave having its own signature (S). k ), k=[1,2,3,...,N], - at least one receiver element, which is different from the transmitter element, and is configured to receive the echo signal (S) simultaneously with the transmission of the excitation signal emitted by the transmitter element. echo The echo signal is generated by the excitation signal to the medium, and a filtering device is configured to determine the contribution of each wave in the echo signal by decoding each of the signatures in order to generate an image.

Description

[0001] The present invention relates to an ultrasonic imaging device and method, which combines two ultrasonic transducers, capable of simultaneously and continuously transmitting and receiving acoustic signals and recording echoes generated by a medium. Existing technology

[0002] Ultrasound is an imaging technique that uses ultrasound waves to visualize media, such as soft tissues, including tendons, muscles, joints, blood vessels, and internal organs. Unlike CT scanners, which use X-rays, and MRI scanners, which use radio waves, ultrasound scanners use ultrasound waves to create images.

[0003] One of the main components of an ultrasound scanner is the probe, which is called a "transducer". It typically produces short ultrasonic signals (called pulses) that travel at a presumably known speed of about 1540 m / s. Tissues and structures that encounter this wave absorb, reflect, or refract it.

[0004] When the wave returns to the transducer, the transducer converts the pressure field at its interface into an electrical signal. The signal is then processed and formatted to reconstruct an image of the medium during acquisition.

[0005] Soft tissues and organs are displayed in grayscale on the screen. Blood and other fluids are depicted in black, while the soft tissue / bone interface is shown in white.

[0006] High-frequency transducers enable the generation of highly detailed, high-resolution images of surface features, while low-frequency transducers are better suited for imaging deeper regions, but with less detail and lower resolution.

[0007] Ultrasonic scanners typically use a single transducer that includes a set of piezoelectric or other elements that operate alternately in a transmit mode, each emitting an ultrasonic pulse, and then in a receive mode to receive the echo from each pulse. All echoes are processed to reconstruct an image of the observed medium.

[0008] To improve image quality, it is necessary to optimize resolution and image contrast. Resolution is defined as the minimum distance that an instrument can distinguish.

[0009] When using ultrasound, the inherent resolution (which is directly related to the wavelength itself) is better at higher frequencies, but ultrasound attenuates more in the medium, resulting in lower penetration.

[0010] That's why we need to launch more energy.

[0011] Increasing the amplitude of the emitted wave can increase the energy emitted, but this is not without risk to the patient.

[0012] The transmitted energy can also be increased by extending the pulse duration, which inevitably leads to a so-called blind zone, corresponding to the shallowest depth of contact with the probe, and reduces resolution. In fact, current ultrasound imaging methods do not take into account the possibility of simultaneously transmitting and receiving ultrasound waves.

[0013] Furthermore, improving image quality and obtaining three-dimensional (3D) images requires shorter echo acquisition times, which is incompatible with the operation of current transducers, which operate continuously in transmit and receive modes, thus imposing an incompressible round-trip propagation time.

[0014] The prior art document US 2010 / 111217 A1 discloses a detection system and method configured to generate a set of N complementary Golay sequences. The encoder uses these sequences to encode a baseband signal. The Golay sequences exhibit ideal autocorrelation, and the sum of the cross-correlation values ​​of each set of Golay sequences is zero. The detection system and method also include a modulator for modulating each of the N coded Golay sequences at different frequencies, and a transducer for transmitting the N modulated sets of coded Golay sequences. The transmitting system (encoder, modulator, transducer) generates coded Golay sequences, which are simultaneously transmitted using modulation and frequency division multiplexing techniques. The receiving system (demodulator, filter) identifies the backscattered sequences as if they were transmitted continuously.

[0015] Document US 2016 / 213258 A1 relates to imaging systems and methods for generating and using mismatch-coded excitation signals. Using mismatch signals allows for spatial and / or temporal and / or functional coding of transmitted signals. In some embodiments, spatial and / or temporal coding is used for spatial and / or temporal coding, and high frame rate imaging can be achieved by using a subset of transducer elements as transmitters and another subset as receivers.

[0016] The coded excitation signal consists of a series of non-overlapping waves.

[0017] Document US 2002 / 049381 A1, identified as D4 in the written opinion, discloses an ultrasound imaging system for imaging an ultrasound scatterer, including a probe (208) for emitting ultrasound waves and detecting ultrasound echoes reflected by the ultrasound scatterer, wherein the probe includes: a first set of transducer elements, designated as the emitting group (T), for emitting ultrasound waves; and a different second set of transducer elements, designated as the receiving group (R), for detecting ultrasound echoes reflected by the ultrasound scatterer.

[0018] The system also includes a processing system (202) comprising transmitting and receiving devices coupled to the probe (208) for providing coded signals to the transmitting group (T) and receiving signals from the receiving group (R), respectively; a transmitting beamforming device (103) for focusing ultrasonic waves onto a focal line; a receiving beamforming device (105) for forming a summed received signal from the signals received from the focal line; and a processing device for processing these summed received signals to form a decoded signal; and a device for displaying an image (109) which is a function of these decoded signals.

[0019] The transmitted signal is not a continuous signal, but a simple sequence (pulse) that is continuous but with an extended duration.

[0020] To overcome some or all of these drawbacks, the present invention proposes a combination of two ultrasonic transducers, each capable of simultaneously and continuously transmitting and receiving acoustic signals.

[0021] This allows for the emission of more energy without sacrificing resolution and decouples the acquisition time from the round-trip propagation time of the ultrasound. Summary of the Invention

[0022] Therefore, the present invention proposes an ultrasound imaging device, which includes:

[0023] - At least one transmitter element configured to transmit a continuous excitation signal into a medium, the excitation signal being encoded to form a succession of N overlapping ultrasonic waves, each ultrasonic wave having its own signature.

[0024] - At least one receiver element, distinct from the transmitter element, is configured to receive an echo signal simultaneously with the transmitter element's transmission of the excitation signal, the echo signal being generated by the excitation signal exciting the medium.

[0025] - A filtering device configured to determine the contribution of each wave in the echo signal by decoding each of the signatures to generate an image.

[0026] Various embodiments of the invention are provided, incorporating different optional features set forth herein according to all possible combinations thereof.

[0027] To ensure good separability of spatially close components within the medium in terms of image resolution, as well as sufficient image contrast, decoding is preferably performed using mismatch filtering.

[0028] According to another preferred aspect, which enables the overcoming of heating phenomena affecting the at least one transmitter element and the at least one receiver element due to continuous emission and reception of ultrasonic waves, the ultrasonic imaging device includes means for cooling the at least one transmitter element and the at least one receiver element.

[0029] According to another preferred aspect enabling two-dimensional (2D) or three-dimensional (3D) imaging, the device includes:

[0030] - A plurality of transmitter elements, each configured to transmit an excitation signal into a medium, each excitation signal being encoded to form a series of N overlapping ultrasonic waves, each having its own signature.

[0031] - A second plurality of receiver elements, which are different from the transmitter elements, each is configured to receive an echo signal simultaneously with the transmission of the excitation signal by the associated transmitter, each echo signal being generated by the medium being excited by the associated excitation signal.

[0032] According to one aspect of the invention, the device is configured such that the N ultrasound frequencies are permissible from 1.5 to 50 MHz, for use in medical diagnostic methods.

[0033] According to another aspect of the invention, the device is configured such that the N permissible ultrasonic thermal and / or mechanical indices are at least about 1.5 times the maximum values ​​permissible for diagnostic applications, in the treatment of a therapeutic procedure.

[0034] The present invention also relates to a method for imaging a medium using ultrasound, comprising:

[0035] - The transmission step involves at least one transmitter element emitting a continuous excitation signal, which is encoded to form a series of N overlapping ultrasonic waves, each with its own signature.

[0036] - Simultaneous receiving step, wherein at least one receiver element, different from the transmitter element, receives the echo signal, the echo signal being generated by the excitation signal exciting the medium, and

[0037] - A filtering step for determining the contribution of each wave in the echo signal by decoding each of the signatures to generate an image.

[0038] Various embodiments of the invention are provided, incorporating different optional features set forth herein according to all possible combinations thereof.

[0039] According to a preferred aspect that enables the limitation of estimated noise in the medium within the echo signal, the filtering step (F) implements a mismatched filter.

[0040] According to another preferred aspect that enables rapid encoding and decoding of waves, the ultrasound waves are uncoordinated with each other, i.e., they each exhibit high autocorrelation and very low cross-correlation with each other.

[0041] According to yet another preferred aspect, the N signatures are spatiotemporal signatures, that is, these signatures are functions of the amplitude, frequency, and / or phase of the ultrasonic wave of the excitation signal. In other words, the amplitude, phase, and / or frequency depend on time and the position of the transmitter element.

[0042] According to another preferred aspect that enables high-speed imaging, the refresh rate of the one or more signals that generate the image is greater than the refresh rate based on the round-trip propagation time of the ultrasonic wave.

[0043] According to another preferred aspect that enables two-dimensional (2D) or three-dimensional (3D) imaging, the method is implemented as follows:

[0044] - The first plurality of transmitter elements forming the first transducer simultaneously perform the emission step.

[0045] - A second plurality of receiver elements, distinct from the transmitter element and forming a second transducer, perform the receiving step. Attached Figure Description

[0046] Other features and advantages will become apparent from the detailed description of the completely non-limiting embodiments and the accompanying drawings, wherein:

[0047] [ Figure 1 ] Figure 1 This is a schematic diagram of an ultrasound imaging device with continuous transmission and reception according to an embodiment of the present invention.

[0048] [ Figure 2 ] Figure 2 This is a comparison between an image obtained through continuous excitation (in this case, a line) and an image obtained through pulse excitation by two scattering elements (one stationary and the other moving).

[0049] [ Figure 3 ] Figure 3 This is a comparison between an image obtained through continuous excitation (in this case, a line) and an image obtained through pulse excitation of a scattering element moving at a constant speed.

[0050] [ Figure 4 ] Figure 4 This is a comparison between an image obtained through continuous excitation (in this case, a line) and an image obtained through pulse excitation of a scattering element that moves with acceleration and then deceleration.

[0051] [ Figure 5 ] Figure 5 This is a comparison between an image obtained by continuous excitation (in this case, a line) and an image obtained by pulse excitation of a scatterer element with a fast sinusoidal motion and a moderate amplitude motion.

[0052] [ Figure 6 ] Figure 6 This is a comparison between an image obtained by continuous excitation (in this case, a line) and an image obtained by pulse excitation based on a scatterer element with very fast sinusoidal motion and high amplitude motion. Detailed Implementation

[0053] According to the principles of the present invention and as follows Figure 1 As shown, the ultrasound imaging device includes:

[0054] - At least one transmitter element configured to transmit a continuous excitation signal S em The excitation signal, emitted into a medium, is encoded to form a series of N overlapping ultrasonic waves, each overlapping ultrasonic wave having its own signature k=[1,2,3,...,N].

[0055] - At least one receiver element, distinct from the transmitter element, is configured to receive the echo signal S simultaneously with the transmitter element's transmission of the excitation signal. echo The echo signal is generated by the excitation signal on the medium, and:

[0056] - Filtering devices, configured to determine the contribution of each wave in the echo signal by decoding each of the signatures, ultimately generate an image.

[0057] In the case of the present invention, in order to obtain a series of overlapping waves, the excitation signal is continuously emitted and then segmented into segments forming overlapping waves by a sliding sampling window method.

[0058] This division, and thus a series of overlapping waves, can be arbitrarily set by the user according to the desired refresh rate and the potential speed of ultrasound in the medium.

[0059] Using a series of overlapping signals allows for the transmission of a larger amount of signal, thereby improving the signal-to-noise ratio and thus the sensitivity of the imaging system.

[0060] Within this continuous signal, any segment of the excitation signal can be considered as a specific signature that can be retrieved / identified in the received signal.

[0061] It has become possible to reconstruct images of the probed medium at any time with a virtually infinite temporal resolution.

[0062] Both the at least one transmitter element and the at least one receiver element are elements capable of converting electrical energy into ultrasonic energy and vice versa. The operating mechanism of these elements may be based on a physical effect known as piezoelectricity.

[0063] Some crystals, known as piezoelectric crystals, such as quartz or tourmaline, naturally generate electrical charges on their surfaces when subjected to changes in mechanical pressure.

[0064] The effect is reciprocal; that is, if a potential change (and thus a charge change) is applied to the two opposing surfaces of such a crystal through electrodes, its thickness will vary (increase or decrease) in one direction or the other, depending on the polarity of the applied potential.

[0065] Conversely, this thickness variation acts on the medium like the vibration of a piston. The vibrational frequency of the crystal is controlled by the frequency of the alternating changes in the applied potential difference.

[0066] If the frequency is high (on the order of MHz), ultrasonic waves are generated. Conversely, when ultrasonic waves reflected by a medium are received by a receiver element, the sound pressure changes experienced by the piezoelectric crystal are converted into alternating changes in electrical potential, which can then be measured and recorded at electrodes. This is known as recording ultrasonic echoes.

[0067] Techniques other than piezoelectricity can be used, such as those employing CMUT-type transducers. Capacitive micromechanical ultrasonic transducers (CMUTs) can convert the mechanical energy provided by ultrasonic waves into electrical energy that can power very low-power electronic devices.

[0068] There are different modes for displaying ultrasound images.

[0069] The image representation can be generated by amplitude modulation of the echo (one-dimensional ultrasound examination or A mode) or by intensity (or brightness) modulation of the ultrasound spot (B mode or two-dimensional image).

[0070] TM mode (Time-Motion mode, which is in) Figures 2 to 6 The results shown use (in which) organ motion is tracked by adding a time scan to a one-dimensional B-mode (single scan line).

[0071] Therefore, the screen displays the motion of more or less intense points (representing echoes) in the organic tissue structure through which the ultrasound scan lines pass.

[0072] The electronic structure used to process echoes, then display and finally record images can be outlined through acquisition, signal processing and visualization steps.

[0073] When the probe records ultrasonic echoes, it transmits alternating signal pulses. After pre-amplification, the signal is first rectified, then demodulated, and finally amplified.

[0074] The purpose of rectification is to retain only the positive signal, while amplitude demodulation allows only the signal envelope to be preserved. The main function of the amplification stage is to amplify the signal without distortion, especially seeking to compensate for the effects of ultrasound attenuation in tissues.

[0075] The gain G of an amplifier is defined as the ratio of the input voltage to the output voltage.

[0076] The amplitude range of the received echoes is converted into grayscale.

[0077] However, in order to achieve better visualization of the echoes of interest, that is, those originating from the deep organs to be observed, the grayscale should be "compressed" to a greater or lesser extent in order to provide the widest possible range of levels for these echoes.

[0078] The function of an analog-to-digital converter is to convert an analog signal (i.e., a continuous change in voltage generated by an echo) into a series of discrete digital values. These discrete digital values ​​can then be subjected to mathematical processing (amplification, nonlinear filtering, etc.) that can modify these values ​​as needed.

[0079] Therefore, factors that may affect the quality of ultrasound images are crucial.

[0080] The so-called subjective factors involve the correct interpretation of the cross-sectional plane, the identification of normal and abnormal structures, the identification of induced motion (caused by breathing, coughing, changes in posture, etc.) and natural motion (heart, peristalsis, fetal movement, etc.) and the identification of artifacts.

[0081] The so-called objective factors involve the equipment used.

[0082] a) Spatial resolution: lateral and axial; as mentioned earlier, it is related to the ultrasound frequency, pulse duration, and focusing (fixed mechanical or electronic focusing). However, it is also necessary to consider the density of the ultrasound scan lines (parallel or divergent, depending on the type of mechanical or electronic linear probe). The number of scan lines is related to the image frame rate (number of images per second). The more lines, the better the lateral resolution.

[0083] b) Contrast quality, or contrast resolution, depends on the dynamic compression discussed earlier in this article. Grayscale can and should be adjusted according to clinical requirements.

[0084] c) Dynamic resolution is the ability to monitor moving organs, and it naturally depends on the image frame rate.

[0085] d) Noise corresponds to signals that do not contain any useful information for the image and degrade image quality. Noise depends partly on the electronic circuitry of the ultrasound scanner itself and partly on the scattering phenomena mentioned earlier. Overall, all noise can be considered random and can be reduced through image averaging.

[0086] e) Artifacts correspond to artificial images that do not represent the true anatomical structures. There are three main causes of artifacts: physical causes (e.g., multiple reflections), instrument-related factors (e.g., poor gain compensation), and operator-related factors (e.g., moving the probe too quickly).

[0087] Advantageously, the ultrasound imaging device includes means for cooling the at least one transmitter element and the at least one receiver element. These cooling means include, for example, a cooling circuit in which a refrigerant fluid circulates.

[0088] This circuit enables the limitation of heating of the transmitter and receiver components, which are continuously subjected to stress from the excitation signal.

[0089] In its basic version, which uses one transmitter element and one receiver element, and as... Figures 2 to 6 As shown, the device reconstructs only one line of the image.

[0090] To perform two-dimensional (2D) or three-dimensional (3D) imaging, it is advantageous to combine a first plurality of transmitter elements (thus forming a first transducer) with a second plurality of receiver elements (thus forming a second transducer), each transmitter element being configured to transmit a continuous excitation signal into a medium. The receiver elements are, of course, different from the transmitter elements, and each is configured to receive an echo signal simultaneously with the transmission of the set of excitation signals by the first plurality of transmitter elements.

[0091] The first and second transducers can be combined in a housing commonly referred to as a "probe".

[0092] Regarding the method, it includes at least:

[0093] - Transmission step E: At least one transmitter element E transmits a continuous excitation signal Sem, which is encoded to form a series of N overlapping ultrasonic waves, each overlapping ultrasonic wave having its own signature S. k k = [1, 2, 3, ..., N]

[0094] - Simultaneously, in the receiving step R, the echo signal S of the excitation signal is received by at least one receiver element different from the transmitter element. echo The echo signal is generated by the excitation signal exciting the medium, and

[0095] - Filtering step F, used to determine the contribution of each wave in the echo signal by decoding each of the signatures, to generate an image.

[0096] The method described above can be used to obtain two-dimensional (2D) or three-dimensional (3D) images, and the steps are as follows:

[0097] - Forming transducer T e The first plurality of transmitter elements simultaneously perform the transmission step E.

[0098] - A second transducer T, different from the transmitter element, is formed. r The second plurality of receiver elements perform the receiving step (R).

[0099] Excitation signal S for each transmitter element em It is continuous and modulated according to a series of N overlapping ultrasound waves, depending on the length of the code used.

[0100] The transmitted signal is modulated to allow for pulse compression during reception in order to improve resolution and signal-to-noise ratio along the measured ultrasonic axis.

[0101] Waves exhibit spatiotemporal coding, that is, a signature as a function of their amplitude, frequency, and / or phase. In other words, waves exhibit an acoustic signature, where amplitude, phase, and / or frequency depend on time and the location of the transmitting element.

[0102] The transmitted signal must indeed contain a time-variable and identifiable acoustic signature so that it can be retrieved in the received echo signal.

[0103] The wave can be encoded according to pseudo-random coding, such as Gray or Gold coding.

[0104] The encoding preferably uses Coded Division Multiplexing (CDM), a multiplexing technique used in spread spectrum communication. In spread spectrum communication, narrowband signals are spread across a wider frequency band or several channels by being divided. It does not limit the frequency of digital signals or bandwidth.

[0105] In order to recover the signal originating from the medium as if it were generated by the interaction of short pulses with the medium, a decoding operation is required.

[0106] It is recommended to use appropriate filtering or other techniques to perform decoding. The length of the sought acoustic signature and the refresh rate or overlap rate between the sought signatures are two adjustable parameters that allow setting the time resolution and refresh rate of the signal.

[0107] The filtering step (F) preferably uses a mismatched filter, enabling the received echo to be decoded relative to a portion of the transmitted signal. The transmitted signal is optimally identified in the echo relative to a given standard to subsequently reconstruct the image based on the propagation time. The aim is to achieve optimal noise gain relative to white noise in a least-squares sense. Therefore, the filter can be considered "mismatched" if the reference signal used for convolution is not a perfect copy.

[0108] The mismatch filter used, denoted by q, is based on minimizing the ISLR (integral sidelobe ratio) criterion for the transmitted signal (denoted by s):

[0109]

[0110] Introducing filter output signal γ:

[0111]

[0112] in:

[0113]

[0114] It is a matrix for all parts of all delayed and concatenated signals s. The optimization problem to be solved to obtain this filter for a given transmitted signal is:

[0115]

[0116] F and q are defined as follows:

[0117] - q corresponds to the mismatch filter used to obtain the image associated with the refresh signal (denoted as s in this paper). This filter q is optimal because the echo signal decoded by this filter (denoted as γ in this paper) must have an autocorrelation function that is as close as possible to the Dirac function.

[0118] - F is a diagonal matrix that allows the extraction of sidelobes from the autocorrelation function of γ. The energy of the sidelobes is optimized to obtain q.

[0119] The solution is obtained using Lagrange multipliers. Results show that the filter is effective relative to ISLR in high-noise environments.

[0120] Preferably, the ultrasound waves are uncoordinated, meaning they each exhibit high autocorrelation and very low cross-correlation.

[0121] This allows for obtaining an extended function of the imaging system that closely resembles the Dirac distribution. Mismatch filtering during reception also helps improve practical correlation characteristics.

[0122] Using the device and method according to the invention, a refresh rate at least 10 times higher than conventional methods that require waiting for the round-trip propagation time of sound waves is achieved, because it makes it possible to reconstruct the signal in a quasi-continuous manner. For example, a shift from 20 kHz to 200 kHz is entirely feasible.

[0123] like Figures 2 to 6 As shown, compared with conventional pulsed ultrasound scanners, improved spatiotemporal resolution can be observed using the ultrasound scanner according to the present invention, whether for static or dynamic media, including media moving at high speeds or over very short distances.

[0124] When the imaging device is used for medical diagnostic purposes, i.e. as a medical ultrasound scanner, the emitted signal is encoded according to N ultrasound waves with permissible frequencies of 1.5 to 50 MHz.

[0125] When the imaging device is used for therapeutic purposes, i.e. as a medical ultrasound scanner, the N permissible thermal and / or mechanical indices of ultrasound are at least about 1.5 times higher than the maximum values ​​permissible for diagnostic applications.

[0126] The thermal index (TI) is defined as the acoustic output power of the transducer divided by the estimated power required to raise the temperature of the detected medium by 1°C.

[0127] The mechanical index (MI) is defined as the maximum rarefaction pressure divided by the square root of the center frequency of the bandwidth of the excitation signal.

[0128] Ultrasound can actually be used to treat certain inflammatory conditions. The vibrations generated by ultrasound increase local blood circulation and help flush out inflammatory fluids. Such ultrasound can also aid in the uptake of nutrients and the removal of waste products from damaged tissues.

[0129] The full mechanisms of the biological effects of ultrasound absorption in human or animal tissues are beginning to be understood.

[0130] Ultrasound absorbed by tissues may produce three main effects:

[0131] 1) Thermal effect: Ultrasonic absorption generates a temperature rise in the absorbed medium. This temperature rise is due to the viscosity of the medium, which generates frictional forces at the molecular scale. These forces are dissipated, and the consumed energy is degraded into heat. Typically, the temperature rise increases steadily until it reaches a plateau, reflecting the thermal equilibrium corresponding to the dissipation of heat into the intracellular and extracellular media. For the ultrasound intensity used in the ultrasound procedure, if the examination time is estimated at 10 minutes, corresponding to a rise of 1°C to 2°C, this is negligible. The most important parameters involved in this process are: acoustic intensity, focus, tissue properties (viscosity, specific heat), and examination time.

[0132] 2) Cavitation: According to this effect, under certain conditions, an ultrasonic beam can generate cavities or bubbles within the medium it passes through. For this to occur, gas or vapor molecules must be present in the medium. Cavitation is a complex phenomenon that includes both cavity formation and implosion.

[0133] There are two different situations:

[0134] (i) Steady-state cavitation: A cavity forms under acoustic pressure (which is typically oscillating but of relatively low intensity), and microfluidics are observed around the cavity. This effect may reach 1 W / cm² in the 1–4 MHz range. 2 It occurs above the threshold.

[0135] (ii) Transient or implosion cavitation: This is a more intense effect that occurs only at high intensities (far exceeding those used in diagnostic ultrasound examinations). Implosion of gaseous cavities under ultrasonic fields can have secondary effects, such as shock waves that cause the degradation of certain macromolecules, significant temperature increases, alterations to existing chemical reactions or the initiation of new reactions (similar to ionizing radiation), or even sonoluminescence (light emission).

[0136] 3) Direct effects, which may lead to the breakage of macromolecules, even DNA, and the acceleration of enzyme-like chemical reactions. Changes in the charge on the surface of cells exposed to ultrasonic fields have also been observed in vitro.

[0137] In summary, the device and method according to the invention can be used in any context where the imaging frame rate is a limiting factor (high frame rate 3D ultrasound imaging, aortic blood flow jet mapping, potential compression wave velocity mapping, etc.).

[0138] The time accumulation of the collected signals also enables enhanced sensitivity and allows imaging in anatomical areas not currently covered by ultrasound (behind bones, such as the brain or lungs).

[0139] This type of sequence can also be used to perform ultrasound therapy and imaging simultaneously, with the therapeutic signal serving as support for the generated image.

[0140] The innovation lies in the fact of continuous transmission. The entire ultrasonic paradigm since its invention has been based on the use of short transmissions that ensure good temporal resolution and the use of the same transducer for reception.

[0141] Transmitting long codes results in blind spots in the image (it is impossible to transmit and receive simultaneously), and continuous transmission without an encoding-decoding stage hinders the acquisition of depth information from the received echoes.

[0142] This method is based on two separate transducers with continuous transmission and reception, departing from the ultrasonic method that uses pulse signals, which uses the same transducer for both transmission and reception.

[0143] Therefore, the method and apparatus according to the invention enable:

[0144] - Achieve a considerable gain in refresh rate.

[0145] - Achieve faster ultrasound imaging frame rates, thereby enabling ultrafast 3D imaging.

[0146] - Visualizing and representing the moving structures too fast for the current system is inadequate.

[0147] - Visualize and characterize very short physical phenomena.

[0148] - By transmitting a larger amount of signal, the signal-to-noise ratio is improved, and thus the sensitivity of the imaging system is increased, enabling imaging in areas that are currently impossible to image due to excessive attenuation.

[0149] Furthermore, the ultrasound imaging device and method according to the present invention offer a wide range of potential applications in the medical and other fields.

[0150] From a medical perspective, this technology can improve the quality of images subsequently used for diagnostic purposes.

[0151] In the fields of biology and biomedical research, this technology enables real-time cell imaging, that is, dynamic observation of cells and their movement. It can also achieve three-dimensional organ bioprinting, i.e., real-time monitoring of the bioprinting process to achieve optimal precision.

[0152] However, its applications are not limited to medicine. For example, in the field of the ocean floor, the device can be used for seabed exploration, facilitating detailed mapping of underwater structures.

[0153] Finally, in the field of nondestructive testing, this invention can be used in industry to inspect the quality of certain materials without altering their integrity.

[0154] Glossary

[0155] T e Transmitter transducer

[0156] T r Receiver transducer

[0157] S em Continuous transmission signal

[0158] S echo echo signal

[0159] S k Encoded transmission wave

Claims

1. An ultrasound imaging device, comprising: - At least one transmitter element configured to transmit a continuous excitation signal (S) em The excitation signal is emitted into a medium and encoded to form a series of N overlapping ultrasonic waves, each ultrasonic wave having its own signature (S). k ), k=[1, 2,3, ..., N], - At least one receiver element, distinct from the transmitter element, is configured to receive the echo signal (S) simultaneously with the transmission of the excitation signal emitted by the transmitter element. echo The echo signal is generated by the excitation signal exciting the medium, and - A filtering device configured to determine the contribution of each wave in the echo signal by decoding each of the signatures to generate an image.

2. The ultrasonic imaging device according to the preceding claim, characterized in that, The filtering device is configured to implement a so-called "mismatch" filter.

3. The ultrasonic imaging device according to claim 1 or 2, characterized in that, The device includes means for cooling the at least one transmitter element and the at least one receiver element.

4. The ultrasound imaging device according to any one of the preceding claims, characterized in that, The device includes: - A plurality of transmitter elements, each configured to transmit a continuous excitation signal into a medium, each excitation signal being encoded to form a series of overlapping ultrasonic waves, each ultrasonic wave having its own signature. - A second plurality of receiver elements, which are different from the transmitter elements, each receiver element is configured to receive an echo signal simultaneously with the transmission of the excitation signal emitted by the associated transmitter, each echo signal being generated by the medium excited by the associated excitation signal.

5. The ultrasound imaging device according to any one of the preceding claims, characterized in that, The device is configured such that the N ultrasound frequencies are permissible from 1.5 to 50 MHz, for use in medical diagnostic methods.

6. The ultrasound imaging device according to any one of the preceding claims, characterized in that, The device is configured such that the N permissible ultrasonic thermal and / or mechanical indices are at least about 1.5 times the maximum values ​​permissible for diagnostic applications, in therapeutic applications.

7. A method for ultrasound imaging of a medium, comprising: - Transmission step (E): A continuous excitation signal (S) is transmitted by at least one transmitter element. em The excitation signal is encoded to form a series of N overlapping ultrasound waves, each ultrasound wave having its own signature (S). k ), k=[1, 2, 3, ...,N], - Simultaneous receiving step (R), whereby at least one receiver element, different from the transmitter element, receives the echo signal (S) of the excitation signal. echo The echo signal is generated by the excitation signal exciting the medium, and - A filtering step (F) is used to determine the contribution of each wave in the echo signal by decoding each of the signatures to generate an image.

8. The method for ultrasonic imaging of a medium according to claim 7, wherein, The ultrasound waves are incoherent, meaning they each exhibit high autocorrelation and very low cross-correlation.

9. The method for ultrasonic imaging of a medium according to any one of claims 7 or 8, wherein, The N signatures are spatiotemporal signatures, i.e., acoustic signatures whose amplitude, phase, and / or frequency depend on time and the location of the transmitter element.

10. The method for ultrasonic imaging of a medium according to any one of claims 7 to 9, wherein, This ensures that the refresh rate of the signal capable of generating an image is greater than the refresh rate based on the round-trip propagation time of the ultrasonic wave.

11. The method for ultrasonic imaging of a medium according to any one of claims 7 to 10, wherein, The filtering step (F) implements a so-called "mismatch" filter.

12. The method for ultrasonic imaging of a medium according to any one of claims 7 to 11, wherein: - The first plurality of transmitter elements forming the first transducer (Te) perform the emission step (E). - A second plurality of receiver elements, distinct from the transmitter element and forming a second transducer (Tr), perform the receiving step (R) simultaneously with the transmitting step (E).

Images