METHOD AND SYSTEM FOR DETERMINING A PHYSICAL CHARACTERISTIC OF A MEDIUM

Abstract

Examples of this disclosure include a method for determining a physical characteristic of a medium, the method including processing ultrasound signal data of the medium associated to at least three emitted ultrasound pulses for respectively providing at least three in-phase and quadrature phase data sets, the at least three emitted ultrasound pulses including a first emitted pulse having a first intensity and at least two supplementary emitted pulses having each a second intensity, wherein a sum of the second intensities corresponds to the first intensity, determining the physical characteristic as a function of a first phase lag between the first IQ data set and a sum of the at least two further IQ data sets, or a second phase lag between the at least two further IQ data sets.

Claims

1. A method for determining a physical characteristic of a medium, comprising: processing ultrasound signal data of the medium associated to at least three emitted ultrasound pulses for respectively providing at least three in-phase and quadrature phase (IQ) data sets I.sub.1(r), I.sub.2(r), I.sub.3(r), the at least three emitted ultrasound pulses comprising a first emitted pulse having a first intensity and at least two supplementary emitted pulses having each a second intensity, wherein a sum of the second intensities corresponds to the first intensity, determining the physical characteristic as a function of: a first phase lag between the first IQ data set I.sub.1(r) and a sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r), and/or a second phase lag between the at least two further IQ data sets I.sub.2(r), I.sub.3(r).

2. The method according to claim 1, wherein determining the physical characteristic further comprises: setting the first IQ data set I.sub.1(r) in-phase with the sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r) by introducing a compensation phase lag to the first IQ data set I.sub.1(r) and/or to the sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r).

3. The method according to claim 1, wherein determining the physical characteristic further comprises: setting the first IQ data set I.sub.1(r) in opposite phase to the sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r) by introducing pi minus the compensation phase lag.

4. The method according to claim 1, wherein the first phase lag .sub.1(r) between the first IQ data set I.sub.1(r) and a sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r) is measured by: a difference between the phase of I.sub.1(r) and the phase of the sum of I.sub.2(r), I.sub.3(r), or the phase of the scalar product between I.sub.1(r) and a sum of I.sub.2(r), I.sub.3(r), and/or by:
.sub.1(r)=arg[I.sub.1(r)conj(I.sub.2(r)+I.sub.3(r))](2), and/or the compensation phase lag is determined as a function of the first phase lag .sub.1(r).

5. The method according to claim 1, wherein the second phase lag .sub.2(r) between the at least two further IQ data sets I.sub.2(r) and I.sub.3(r) is measured by: a difference between the phase of I.sub.2(r) and the phase of I.sub.3(r), a phase of the scalar product between I.sub.2(r) and I.sub.3(r), and/or by:
.sub.2(r)=arg[I.sub.2(r)conj(I.sub.3(r))](4).

6. The method according to claim 1, wherein determining (e) the physical characteristic further comprises: determining a first segmentation map as a function of the first phase lag and/or a second segmentation map as a function of the second phase lag, wherein the physical characteristic is determined as a function of the first and/or the second segmentation map.

7. The method according to claim 6, wherein the physical characteristic is determined as a function of a third segmentation map generated by combining the first segmentation map and the second segmentation map, and/or by removing the content of the second segmentation map from the first segmentation map.

8. The method according to claim 6, wherein the first segmentation map is configured to segment an area of interest of the medium, and/or the second segmentation map is configured to detect and/or reduce noise in the IQ data sets I.sub.1(r), I.sub.2(r), I.sub.3(r).

9. The method according to claim 6, wherein the first segmentation map is determined by: $\begin{array}{cc}{}_1^{\mathrm{seg}}\left(r\right)=\left(\begin{array}{cc}1,& \mathrm{if}{}_1^{\min }<{}_1\left(r\right)<{}_1^{\max }\\ 0,& \mathrm{else}\end{array}\right),& \left(3\right)\end{array}$ wherein .sub.1.sup.min and .sub.1.sup.max are predefined values, and/or the second segmentation map is determined by: $\begin{array}{cc}{}_2^{\mathrm{seg}}\left(r\right)=\left(\begin{array}{cc}1,& \mathrm{if}.Math.{}_2\left(r\right).Math.>{}_2^{\max }\\ 0,& \mathrm{else}\end{array}\right),& \left(5\right)\end{array}$ wherein .sub.2.sup.max is a predefined value, and/or the third segmentation map is determined by: $\begin{array}{cc}{}_3^{\mathrm{seg}}\left(r\right)=\left(\begin{array}{cc}1,& \mathrm{if}{}_1^{\mathrm{seg}}\left(r\right)=1\mathrm{and}{}_2^{\mathrm{seg}}\left(r\right)=0\\ 0,& \mathrm{else}\end{array}\right).& \left(6\right)\end{array}$

10. The method according to claim 1, wherein the physical characteristic is determined based on at least one of: a predefined contrast-enhanced ultrasound method, a coherent summation of the IQ data sets I.sub.1(r), I.sub.2(r), I.sub.3(r),
I.sub.ceus.sup.+(r)=(I.sub.1(r)(I.sub.2(r)+I.sub.3(r))).sub.3.sup.seg(r)the equation (1b):
I.sub.ceus.sup.++(r)=I.sub.1(r)e.sup.i.sup.1.sup.(r).sup.3.sup.seg.sup.(r)(I.sub.2(r)+I.sub.3(r)),the equation (1c):
I.sub.ceus.sup.(r)=I.sub.1(r)e.sup.i(.sup.1.sup.(r)).sup.2.sup.seg.sup.(r)(I.sub.2(r)+I.sub.3(r)),the equation (1d):
I.sub.ceus.sup.(r)=I.sub.1(r)e.sup.i(.sup.1.sup.(r))(1.sup.3.sup.seg.sup.(r))(I.sub.2(r)+I.sub.3(r))the equation (1e):
I.sub.ceus.sup.++(r)=I.sub.1(r)e.sup.i.sup.1.sup.(r).sup.3.sup.seg.sup.(r)e.sup.i(.sup.1.sup.(r)).sup.2.sup.seg.sup.(r)(I.sub.2(r)+I.sub.3(r)),the equation (1f): $I_{\mathrm{ceus}}^{++--}\left(r\right)=I_1\left(r\right)e^{-i{}_1\left(r\right){}_3^{\mathrm{seg}}\left(r\right)}{e}^{-i\left(-{}_1\left(r\right)\right)\left(1-{}_3^{\mathrm{seg}}\left(r\right)\right)}-\left(I_2\left(r\right)+I_3\left(r\right)\right).$

11. The method according claim 1, further comprising before processing ultrasound signal data: transmitting an emitted sequence of ultrasound waves into the medium, the emitted sequence comprising the first emitted pulse and the at least two supplementary emitted pulses, and receiving a response sequence of ultrasound waves from the medium, wherein the ultrasound signal data are based on the response sequence of ultrasound waves, and/or the method comprising before sending the emitted sequence of ultrasound waves: introducing a contrast agent into the medium, wherein the first segmentation map is configured to segment the contrast agent in the medium.

12. The method according to claim 1, wherein the at least two supplementary emitted pulses are spatially offset from each other with respect to the medium, and/or the second and third pulse are emitted with different aperture modulations, and/or a set of transducer elements used for emitting the first pulse is split into at least two sub-sets which are respectively used to emit the at least two supplementary pulses, and/or a first sub-set corresponds to the odd numbers of the transducer elements used for emitting the first supplementary pulse, and a second sub-set corresponds to the even numbers of the transducer elements used for emitting the second supplementary pulse.

13. A method for determining physical characteristics of a plurality of regions of a medium, comprising: repeatedly performing the method according to any one of the preceding claims, wherein in each iteration ultrasound signal data of another region is processed.

14. The method according to claim 13, wherein at least one of: the first, second and third segmentation map are determined as a function of the plurality of regions, and/or an image is formed based on the determined physical characteristics of the plurality of regions.

15. A computer program comprising computer-readable instructions which when executed by a data processing system cause the data processing system to carry out the method according to claim 13.

16. A system for determining a physical characteristic of a medium, comprising a processing unit configured to: process ultrasound signal data of the medium associated to at least three emitted ultrasound pulses for respectively providing at least three in-phase and quadrature phase (IQ) data sets I.sub.1(r), I.sub.2(r), I.sub.3(r), the at least three emitted ultrasound pulses comprising a first emitted pulse having a first intensity and at least two supplementary emitted pulses having each a second intensity, wherein a sum of the second intensities corresponds to the first intensity, and determine the physical characteristic as a function of: a first phase lag between the first IQ data set I.sub.1(r) and a sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r), and/or a function of a second phase lag between the at least two further IQ data sets I.sub.2(r), I.sub.3(r).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] FIG. 1 shows an exemplary embodiment of the method according to embodiments of the present disclosure;

[0090] FIG. 2 shows a system carrying out a method according an exemplary embodiment of the present disclosure;

[0091] FIG. 3 shows a system carrying out a method according to another exemplary embodiment of the present disclosure;

[0092] FIG. 4 schematically shows different types of emitted pulses according to embodiments of the present disclosure;

[0093] FIG. 5 schematically shows the procedure of determining the first segmentation map according to the present disclosure; and

[0094] FIG. 6 schematically shows the procedure of determining the second segmentation map according to the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

[0095] Reference will now be made in detail to exemplary embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Moreover, the features explained in context of a specific embodiment, for example that one of FIG. 1, also apply to any one of the other embodiments, when appropriate, unless differently described.

[0096] FIG. 1 shows an exemplary embodiment of the method according to embodiments of the present disclosure. The method may be carried out by means of a system 1, more in particular by an ultrasound system 20. Examples are described in context of FIGS. 2 and 3.

[0097] The method may be an ultrasound method carried out by an ultrasound system. Possible ultrasound methods comprise B-mode imaging, shear wave elastography imaging (such as ShearWave mode developed by the applicant, Doppler imaging, M mode imaging, Ultrafast Doppler imaging or angio mode named under Angio P.L.U.S ultrasound imaging or any other ultrasound imaging mode, including a mode using bubbles and/or a mode using contrast agent(s) or the like. The method may be part of any of the above-mentioned methods or may be combined with any of these methods.

[0098] However, the method according to the present disclosure may also be applied to other technical fields than ultrasound examination. In particular, any technical field is possible which uses a plurality of transducer elements to acquire data/signals of an examined medium or environment and/or which may optionally use a beamforming technique based on the collected data/signals. Examples comprise methods using a radar system, sonar system, seismology system, wireless communications system, radio astronomy system, acoustics system, Non-Destructive Testing (NDT) system and biomedicine system. The principle of emitting pulses of different intensity by respectively selecting different numbers of transducer elements of an ensemble of transducer elements (e.g. all transducer elements, or only ODD/EVEN ones), what would conventionally lead to a corresponding number of channels, is always similar.

[0099] Accordingly, the method according to the present disclosure may in each of these cases achieve the same positive technical effects as described above, for example of enhanced quality of the determined physical characteristic. However, for mere illustration purposes of the present disclosure, in the following it is referred to the example of an ultrasound method.

[0100] The method may be for example a Contrast-enhanced ultrasound (CEUS) method. In the CEUS method, a contrast agent is provided in a region of interest of the medium (cf. operation (a)), which is then scanned (cf. operations (b), (c)).

[0101] In more detail, in an optional operation (a), a contrast agent is introduced (or injected) into the medium. Said contrast agent may comprise for example micro bubbles. The contrast agent may be configured to improve the contrast of physical properties of a region of interest of the medium. When insonified by ultrasound waves, such contrast agents generate non-linear echoes. Said operation (a) may be carried out by an injection device (not shown in the figures). The injection device may be configured to inject a fluid containing a predetermined quantity of contrast agents inside blood vessels of the medium.

[0102] In an optional operation (b) an emitted sequence of ultrasound waves is transmitted into the medium. The emitted sequence comprises a first emitted pulse and at least two supplementary emitted pulses. The first emitted pulse may have a first intensity and at least two supplementary emitted pulses may have each a second intensity, wherein a sum of the second intensities corresponds to the first intensity. For example, transmitting a pulse may comprise insonification of the medium with a cylindrical wave that focuses on a given point and/or plane waves of different angles. More in particular, transmitting a pulse may comprise transmitting a plurality of ultrasonic waves into an imaged region.

[0103] In an optional operation (c) a response sequence of ultrasound waves is received from the medium. Said response sequence may form the basis or may correspond to ultrasound signal data which will be processed in the next operation (d). For example, in the operation (c) backscattered echoes of the insonification of operation (b) may be used. More in particular, in the operation (c) a set of raw data may be acquired by a set of transducer elements in response to each emitted pulse.

[0104] It is noted that operations (a) to (c) are optional, as they may also be carried out by any other system than the system used for operations (d) and (e). Data may also be provided by other functionalities such as simulation devices, insonification on a phantom, etc. It is also possible that the ultrasound signal data processed in operation (d) are pre-stored, and for example provided by a data storage, a communication interface, etc.

[0105] In operation (d) ultrasound signal data of the medium associated to at least three emitted ultrasound pulses are processed for respectively providing (or obtaining) at least three in-phase and quadrature phase (IQ) data sets I.sub.1(r), I.sub.2(r), I.sub.3(r). The three emitted ultrasound pulses may comprise a first emitted pulse having a first intensity and at least two supplementary emitted pulses having each a second intensity, wherein a sum of the second intensities corresponds to the first intensity. However, it is also possible that more than three emitted ultrasound pulses are processed (e.g. 4) for respectively providing more than three IQ data sets (e.g. 4).

[0106] In operation (e) the physical characteristic as a function of a first phase lag between the first IQ data set I.sub.1(r) and a sum of the at least two further IQ data sets I.sub.2(r), I.sub.3(r), and/or a second phase lag between the at least two further IQ data sets I.sub.2(r), I.sub.3(r).

[0107] In an optional operation (f), an echographic image based on the physical characteristics, and/or carrying out a further method based on the determined physical characteristic is generated. For example, the determined physical characteristic may be used in a further algorithm (for example an AI-based algorithm) to determine or predict a diagnosis of the medium.

[0108] The operations (a) to (e) may be carried out successively, i.e. one after another. However, operations (b) to (e) and/or (d) to (e) may be carried out several times before thanks to optional loops L1 or L2. Hence, operation (f) may be carried out based on the respective plurality of determined characteristics. For example, in each iteration, another area in the medium may be insonified in operation (b), in order to determine respective plurality of determined characteristics associated to said different regions. Said determined characteristics may then serve to form a map, matrix or table of determined characteristics, and/or to form an image to be potentially displayed and/or analyzed, right after or in the future, locally or remotely.

[0109] The operations (b) and (c) may be carried out by a transducer device 12, for example mounted on an ultrasound probe. The transducer device is desirably a hand-held system. The output of the system 1 may be transmitted via an interface 10 to a central or main or external processing system having a processing unit 13 (cf. FIGS. 2 and 3).

[0110] The operations (d) and (e) may be carried out by a processing unit 13. Operation (f) may be carried out by a display or screen 4a associated with the processing system 4.

[0111] FIG. 2 shows a system carrying out a method according to an exemplary embodiment of the present disclosure.

[0112] The system 100 may for example be configured to determine a characteristic of a location inside a medium 11, or for instance for the purpose of imaging an area in a medium 11.

[0113] The medium 11 is for instance a living body and in particular human or animal bodies, or can be any other biological or physic-chemical medium (e.g. in vitro medium). The medium may comprise variations in its physical properties. For example, the medium may comprise tissues such as fat, muscles, bones, and blood vessels, each one having various physical properties.

[0114] For example, the tissue may comprise an area suffering from a disfunction and/or an illness (e.g. cancerous cells, muscular tearing, . . . ), or any other singular area, having various physical properties in comparison to other area of the medium. Some portions of the medium 11 may include some added contrast agent (e.g. micro bubbles) for improving the contrast of physical properties of these portions. When insonified by ultrasound waves, such contrast agents generate non-linear echoes. Therefore, a possible use of such contrast agents is the injection of a fluid containing a predetermined quantity of contrast agents inside blood vessels or dedicated part(s) of the body. The contrast agent may however also be introduced into the medium in another way. It may for example be injected into other parts or circulation systems of a body than a blood vessel. Moreover, it may also be inhaled or swallowed. Then, the physical characteristic of such blood vessels can be more easily detected in comparison to a physical characteristic of a tissue that does not comprise the contrast agent, as said contrast agent may only flows in the vessels.

[0115] The physical characteristics, that can be detected by the method that senses the medium via ultrasound waves, may be mechanical properties of the medium, like stiffness, or else. The method distinguishes values and/or variations of said physical properties. For example, the method may detect a mechanical interface between two materials in the medium. For example, it can detect bubble shells. Ultrasound contrast agents namely generally rely on the different ways in which sound waves are reflected from interfaces between substances. This may be the surface (i.e. the shell) of a small air bubble or a more complex structure.

[0116] The system 100 may include a probe 12 comprising a transducer device. Said transducer device may comprise one or a plurality of ultrasound transducer elements 20, for example in the form of a transducer array arranged along an x-axis. Each transducer element 20 may be adapted to transform a signal into an ultrasound wave (emit) and/or to transform an ultrasound wave into a signal (receive).

[0117] The system 100 may further include an electronic processing unit 13. Said unit may optionally control the transducers in the probe in both mode (receive and/or emit) in the case same probe is used for emission/reception. Different probes may also be used, either for emission/reception or for appropriate adaptation to scanned medium. Emit and receive transducers may be the same, different one located on one single probe or on different probes.

[0118] Furthermore, the unit 13 may process ultrasound signal data, and determine characteristics of the medium and/or images of said characteristics.

[0119] The probe 12 may comprise a curved transducer so as to perform an ultrasound focusing to a predetermined position in front of the probe into a direction of a z axis. The probe 12 may also comprise a linear array of transducer. Moreover, the probe 12 may comprise few tens of transducer elements (for instance 124, 258, or 64 to 300) juxtaposed along an x axis so as to perform ultrasound focusing into a bi-dimensional (2D) plane. The probe 12 may comprise a bi-dimensional array so as to perform ultrasound focusing into a tri-dimensional (3D) volume. Moreover, the probe may also comprise several transducer devices, for example at least one for emission and at least one for reception.

[0120] A first configuration of the method represented on FIG. 1 is for determining a physical characteristic of a location P0 inside the medium 11, said location P0 being substantially a punctual location or a small region inside the medium around said location P0 (near location P0).

[0121] The above processing unit 13 and the probe 12 may be configured to send an emitted sequence ES of ultrasound waves We into the medium 11 towards the location P0, the emitted sequence ES comprising at least three emitted pulses. Those three emitted ultrasound pulses may comprise a first emitted pulse having a first intensity and at least two supplementary emitted pulses having each a second intensity, wherein a sum of the second intensities corresponds to the first intensity. The above processing unit 13 and the probe 12 may further be configured to receive a received sequence RS of ultrasound waves 4 (i.e. ultrasound signal data) from the location P0 in response to the emitted pulses.

[0122] The ultrasound waves We, Wr toward and from the location may be a focused wave (beam) or a non-focused beam. In this context, a pre-defined beamforming method may be used, for example: The emitted ultrasound wave We may be generated by a plurality of transducers signals that are delayed and transmitted to each transducer of a transducer array. The received ultrasound wave Wr may be composed of a plurality of transducers signals that are combined by delay and summation to produce a received sequence RS.

[0123] The at least two different intensities or amplitudes of emitted pulses (i.e. the first pulse having a first intensity and the second and third pulse having each the same second intensity) may be produced by varying the transmit voltage or by varying the aperture size (i.e. by varying the number of transducers elements contributing to emit the emitted ultrasound wave, as further described in context of FIG. 4). The aperture may also be divided into two or more groups of elements.

[0124] FIG. 3 shows a system carrying out a method according to another exemplary embodiment of the present disclosure.

[0125] The second exemplary embodiment may generally correspond the first exemplary embodiment. In particular, the method may use identical or similar elements of the above disclosed system 100 of FIG. 2.

[0126] However, in the second exemplary embodiment of the method may determine physical characteristics of a plurality of regions of the medium 11. For example, the determined physical characteristics may be used for determining an image of a region R inside a medium 11.

[0127] The image produced by the method may be composed of a plurality of pixels (for example, a number K of pixels), each pixel corresponding to a different location (Pk) inside the region R, k being an index to identify each pixel in the image to be generated or each location in the region R. Optionally, the image may be composed of only one pixel. However, the image may comprise more than one ten thousand pixels (100100 pixels).

[0128] Moreover, it is noted that the determined physical characteristics may also be used for other purposes than forming an image. For example, the determined physical characteristics may be processed in another method to determine further characteristics and/or a diagnosis about the region R. The determined physical characteristics may also be transferred to an AI system or function, to train it, and/or to support diagnosis and/or to provide inputs to another system and/or display info to an end user.

[0129] The second embodiment (shown in FIG. 3) mainly differs from the previous first embodiment of the method by scanning a plurality of locations inside a region R so as to generate for example an image of said region.

[0130] At each location Pk inside the region R, the processing unit 13 and the probe 12 are configured to send an emitted sequence ES of ultrasound waves We towards the location, the emitted sequence ES comprising at least three emitted pulses, said pulses having different intensities, and receive a received sequence RS of ultrasound waves Wr from the location, said received pulses being responses (echoes) from said emitted pulses.

[0131] Similarly, as for the previous embodiment, the ultrasound waves We, can be focused or non-focused waves, according to known techniques. The emitted and received signals (representing the pulses) may also be similar or identical to those as represented on FIG. 4, and the corresponding above description also applies to the second configuration of the method.

[0132] FIG. 4 schematically shows different types of emitted pulses according to embodiments of the present disclosure. In particular, FIG. 4 shows three emitted ultrasound pulses P1, P2, P3. The first emitted pulse P1 has a first intensity and the two supplementary emitted pulses P2, P3 have each a second intensity, wherein a sum of the second intensities corresponds to the first intensity. The first intensity is hence double the second intensity in this example.

[0133] The different intensities in this example are due to the number of transducer elements 20 used to generate the pulse. Accordingly, the number of transducer elements used for emitting the first pulse may correspond to the total number of transducer elements for emitting all supplementary pulses. More in particular, the first pulse may be generated using a predefined number of adjacent transducer elements 20 (i.e. a full pulse). The second pulse may be generated using the EVEN numbered transducer elements 20 (i.e. an EVEN pulse) and the third pulse using the ODD numbered transducer elements 20 (i.e. an ODD pulse). ODD and EVEN pulses may also be vice versa.

[0134] It is also possible to use other configurations of transducer elements 20 for the second and the third pulse the EVEN and ODD pulses. For example, any configuration may be used, which equally distributes the number of transducer elements used for the first pulse between the further pulses (i.e. the second and third pulse and optionally any supplementary pulse). In other words, the set of transducer elements used for emitting the first pulse may be split into at least two (or more) equal sub-sets which are respectively used to emit the at least two (or more) supplementary pulses.

[0135] For example, a sub-set may also comprise at least one group of consecutive transducer elements (for example 2-10). The transducer elements of a group may hence be consecutively arranged in the transducer device (i.e. next to each other). In case the sub-set comprises more than one group, the groups of different sub-sets (i.e. associated with different supplementary pulses) may be alternating.

[0136] The pulses may be looped over time, i.e. first the pulse P1 may be emitted, then P2, then P3. This sequence may be repeated. In particular, the sequence may be repeated by looping over a set scanning lines. In other words, the scanning line or focus of the emitted pulses may be offset in an x-direction (cf. FIG. 2) at each iteration. Accordingly, after emission of P1, P2, P3, the method may continue with the emission of spatially offset P1, P2, P3. Apart from the mentioned offset, P1, P2, P3 may correspond to P1, P2, P3.

[0137] It is further possible that the focal point along the scanning line is offset in a depth direction of the medium in a further loop (i.e. along the z-axis in FIG. 2). In this way different regions of the medium can be scanned, wherein each region is insonified by the at least three pulses.

[0138] Accordingly, based on these pulses, a map (or matrix or table) of determined physical characteristics of the medium may be formed. Said map may serve to image the medium and/or to feed another method, e.g. an (AI-based) algorithm, for example comprising a machine learning algorithm, in particular one or several neural networks.

[0139] Said three pulses P1, P2, P3, in particular comprising a full pulse, an EVEN pulse and an ODD pulse may be used in a Contrast-enhanced ultrasound (CEUS) method.

[0140] Concerning the CEUS mode, contrast agent may be injected for example in the vascular system of a patient and corresponding region(s) of interest scanned during a contrast ultrasound scan. The goal of this technique is to analyze the contrast agent behavior, notably within and around suspicious tumors. To better observe the contrast agent, pulse amplitude and/or phase modulation techniques may be applied to advantageously distinguish between tissues and contrast agent, in particular when contrast agent micro bubbles observation is key for diagnosis for example. These techniques take advantages of the non-linearity of the contrast agent response compared to the linear response of the tissue.

[0141] Amplitude Modulation (AM) is one of those techniques that consists in exciting the medium with successive pulses characterized by various intensities. For instance, the pulses as described above in context of FIG. 4 may be used. One pulse called FULL is generated by all the probe transducers of a given aperture and the two other pulses called EVEN and ODD are generated by half of the selected transducers (with one transducer out of two as an example).

[0142] Amplitude Modulation may also be performed by modifying other characteristics of the transmit beam such as the amplitude of the emitted pulse (by varying the voltage of the exciting transducer element(s)), the duty cycle (percent of the transmit period of the ultrasound wave during which transducer element(s) are excited by an electrical signal).

[0143] For each pulse, a beamforming process may be performed in order to estimate the reflectivity of the insonified region. Complex IQ maps associated to each pulse are then obtained called I.sub.full(r) (i.e. I.sub.1(r)), I.sub.EVEN(r) (i.e. I.sub.2(r)) and I.sub.ODD(r) (i.e. I.sub.3(r)).

[0144] The CEUS complex image called I.sub.ceus(r) results from the coherent summation of the beamformed maps:

I.sub.ceus(r)=I.sub.1(r)(I.sub.2(r)+I.sub.3(r))(1a)

[0145] The modulus of this image may then be log-converted, potentially filtered and stored, sent to another device, and/or displayed on a screen or using any display technic (such as hologram, connected glasses, . . . ).

[0146] By using half of the selected transducers, the intensity levels of the second and third transmitting pulses are approximatively half of the first pulse. On the one hand, the medium generally may have a linear response. The coherent summation of equation (1a) then deeply cancels their associated responses in the CEUS map. To the other hand, the non-linear response of the contrast agent does not fully cancel their response when performing same summation.

[0147] The non-linearity of the contrast agent induces a phase lag between the FULL and the ODD or EVEN pulses. Their associated backscattered signals are then no longer in phase, which implies that the cancellation doesn't fully operate, that is to say, signals does not compensate.

[0148] The present disclosure deals with taking benefits of this phase lag to enhance the quality of the CEUS images. This enhancement in particular results from the potential combination of two different processes, one improves the signals coming from the contrast agent, while the other one reduces the signals level generated by tissues and electronic noise.

[0149] Prior to each of the above-mentioned process, the complex maps I.sub.1(r), I.sub.2(r) and I.sub.3(r) may be first computed, and the contrast agent may be segmented.

[0150] FIG. 5 schematically shows the procedure of determining the first segmentation map .sub.1.sup.seg(r) according to the present disclosure. In order to segment the contrast agent, a first operation may consist in measuring the phase lag between the full and the sum of the ODD and EVEN IQ data. This can be as example achieved by measuring the phase of the scalar product between I.sub.1(r) and the sum of I.sub.2(r) and I.sub.3(r):

.sub.1(r)=arg[I.sub.1(r)conj(I.sub.2(r)+I.sub.3(r))](2)

Linear scatterers such as soft tissues should generate a phase lag .sub.1 that is close to , meaning that I.sub.1 and (I.sub.2+I.sub.3) are then more in phased. On the contrary, contrast agents may induce a phase lag of for example around 2 rad. Based on this observation, a segmentation may be done to isolate the contrast agent that are associated with a given phase lag:

[00005]$\begin{array}{cc}{}_1^{\mathrm{seg}}\left(r\right)=\left(\begin{array}{cc}1,& \mathrm{if}{}_1^{\min }<{}_1\left(r\right)<{}_1^{\max }\\ 0,& \mathrm{else}\end{array}\right)& \left(3\right)\end{array}$

[0151] Exemplary values may comprise .sub.1.sup.min=2.5 rad and/or .sub.1.sup.max=0.5 rad. However, the values may also differ from on case to another and depending on medium, contrast agent(s), and other parameters. This segmentation may capture the contrast agent 20. As shown in FIG. 5, the contrast agent 20 is then shown as more obvious, i.e. has a better contrast in the first segmentation map .sub.1.sup.seg(r). In case an image is generated based on the map, it is thus advantageously more visible.

[0152] However, it is possible that on the edge (i.e. in peripheral areas of the insonified region of the medium) and at large depth, it also captures some electronic noise 21. Indeed, this noise is random and unpredictable. A part of it may thus fall within the selecting range [.sub.1.sup.min,.sub.1.sup.max].

[0153] FIG. 6 schematically shows the procedure of determining the second segmentation map .sub.2.sup.seg(r) according to the present disclosure. To separate electronic noise 21 from contrast agent(s), the phase difference between I.sub.ODD(r) and I.sub.EVEN(r) may then be investigated. This may be done by measuring the scalar product between I.sub.2 and I.sub.3:

.sub.2(r)=arg[I.sub.2(r)conj(I.sub.3(r))](2)

.sub.2 may as a result be close to 0 for points associated for example to a central area of the insonified region of the medium and for the contrast agent (i.e. the information of interest). Indeed, the intensity level received by each point is the same for the ODD and EVEN pulse. As a result, only electronic noise may produce a phase lag between those two pulses, while contrast agent and tissue signals may both be in phase. A second segmentation can then be done:

[00006]$\begin{array}{cc}{}_2^{\mathrm{seg}}\left(r\right)=\left(\begin{array}{cc}1,& \mathrm{if}.Math.{}_2\left(r\right).Math.>{}_2^{\max }\\ 0,& \mathrm{else}\end{array}\right)& \left(3\right)\end{array}$

An exemplary value may comprise .sub.2.sup.max=0.5 rad. However, the value may also differ.

[0154] By combining .sub.1.sup.seg(r) and .sub.2.sup.seg(r), a third segmentation map .sub.3.sup.seg(r) may be formed that can better segment the contrast agent:

[00007]$\begin{array}{cc}{}_3^{\mathrm{seg}}\left(r\right)=\left(\begin{array}{cc}1,& \mathrm{if}{}_1^{\mathrm{seg}}\left(r\right)=1\mathrm{and}{}_2^{\mathrm{seg}}\left(r\right)=0\\ 0,& \mathrm{else}\end{array}\right)& \left(4\right)\end{array}$

[0155] Accordingly, the physical characteristic may be determined by:

I.sub.ceus.sup.+(r)=(I.sub.1(r)(I.sub.2(r)+I.sub.3(r))).sub.3.sup.seg(r)(1b)

[0156] In case there remains still some noise in the considered signal, it may be removed using as example a spatial filter as it is more scattered than the contrast agent signal.

[0157] In one option the contrast of the IQ data sets may be further enhanced. For example, as already noted above, the contrast agent phase lag .sub.1 may be known based on current medium, contrast agent(s) and/or data considered, e.g. may have a value of around 2 rad. Moreover, as already noted above, the CEUS image results from the coherent summation of I.sub.1(r) with I.sub.2(r)+I.sub.3(r). Consequently, a phase lag of 2 may not produce an optimal coherent summation. To enhance it, an additional phase lag may be introduced during the construction of I.sub.ceus(r) such as an optimal coherent summation occurred. This phase lag is as example applied based on the segmentation map .sub.3

I.sub.ceus.sup.++(r)=I.sub.1(r)e.sup.i.sup.1.sup.(r).sup.3.sup.seg.sup.(r)(I.sub.2(r)+I.sub.3(r))(1c):

[0158] Thanks to the contrast agent segmentation .sub.3.sup.seg(r), the contrast agent signal may be enhanced without modifying the tissue signals within the resulting IQ data. For example, the average contrast agent signals may be enhanced by approximatively 3 dB and up to 10 dB.

[0159] In a further option, noise and/or medium cancelation may be optimized. For signals that have been detected as noise (e.g. .sub.2), a phase lag such as I.sub.1 may be inserted and as a consequence the sum of I.sub.2 and I.sub.3 is in opposite phase:

I.sub.ceus.sup.(r)=I.sub.1(r)e.sup.i(.sup.1.sup.(r)).sup.2.sup.seg.sup.(r)(I.sub.2(r)+I.sub.3(r))(1d)

and in a further enhancement. This process may be applied to any signal that is not considered as contrast agent (1.sub.3):

I.sub.ceus.sup.(r)=I.sub.1(r)e.sup.i(.sup.1.sup.(r))(1.sup.3.sup.seg.sup.(r))(I.sub.2(r)+I.sub.3(r))(1e).

[0160] For example, the cancellation may reduce the noise level by approximatively 1.5 dB.

[0161] Finally, both the filtering and enhancing process may be combined to further improve the data quality of the determined physical characteristic, i.e. by:

I.sub.ceus.sup.++(r)=I.sub.1(r)e.sup.i.sup.1.sup.(r).sup.3.sup.seg.sup.(r)e.sup.i(.sup.1.sup.(r)).sup.2.sup.seg.sup.(r)(I.sub.2(r)+I.sub.3(r))(1f)

and in a further enhancement by:

[00008]$\begin{array}{cc}{I}_{\mathrm{ceus}}^{++--}\left(r\right)=I_1\left(r\right)e^{-i{}_1\left(r\right){}_3^{\mathrm{seg}}\left(r\right)}{e}^{-i\left(-{}_1\left(r\right)\right)\left(1-{}_3^{\mathrm{seg}}\left(r\right)\right)}-\left(I_2\left(r\right)+I_3\left(r\right)\right).& \left(1g\right)\end{array}$

[0162] Throughout the description, including the claims, the term comprising a should be understood as being synonymous with comprising at least one unless otherwise stated. In addition, any range set forth in the description, including the claims should be understood as including its end value(s) unless otherwise stated. Specific values for described elements should be understood to be within accepted manufacturing or industry tolerances known to one of skill in the art, and any use of the terms substantially and/or approximately and/or generally should be understood to mean falling within such accepted tolerances.

[0163] Although the present disclosure herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure.

[0164] It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims.

[0165] A reference herein to a patent document or any other matter identified as prior art, is not to be taken as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.