Ultrasonic imaging method for the precise localization or sizing of an object
The method enhances ultrasonic imaging accuracy by iteratively adjusting aperture size and extrapolating flight times to optimize signal-to-noise ratio, addressing limitations in portable devices without energy or cost increases.
Patent Information
- Application Number
- FR2023014348
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-12-18
- Publication Date
- 2025-12-05
- Estimated Expiration
- 2043-12-18
AI Technical Summary
Existing ultrasonic imaging systems face limitations in accuracy due to compromises between frequency, energy consumption, and equipment resources, leading to delayed disease detection and limited understanding of phenomena like cardiovascular diseases, particularly in portable devices.
A method involving multiple iterations of ultrasonic field aperture size adjustments and flight time measurements, followed by mathematical extrapolation to enhance measurement accuracy without modifying the probe hardware, using a model to optimize signal-to-noise ratio.
Improves measurement accuracy by extrapolating flight times to minimize noise interference, enabling precise localization and sizing of objects without increasing energy consumption or cost, thus enhancing the usability of portable imaging devices.
Smart Images
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Abstract
Description
Title of the invention: Ultrasonic imaging method for the precise localization or sizing of an object
[0001] The invention relates to the field of ultrasound imaging, in particular medical imaging, and relates to a method of improving the accuracy of such measurements when carried out using an ultrasound probe having an emitted ultrasound field opening of a given size.
[0002] The invention applies in particular to the imaging of blood vessels, for example arteries, in order to determine precisely the diameter of such vessels, but it is not limited to this application and more generally aims at improving the measurement accuracy for ultrasonic imaging of all types of objects in the medical field or in the field of non-destructive testing by ultrasound.
[0003] In general, and particularly in the medical field, ultrasound imaging is a tool that allows for the precise monitoring, sometimes in real time, of certain anatomical structures such as blood vessels. Specifically, it allows for the localization and measurement of the dimensions of these vessels. However, the accuracy of ultrasound measurements varies depending on the type of equipment used.
[0004] The development of ultrasound-based technologies makes it possible to have compact monitoring systems offering a non-invasive solution. Fully automated, portable, real-time monitoring provides both relevant information on daily life and data over longer periods, in situations inaccessible in healthcare settings with fixed devices.
[0005] However, portable ultrasound imaging devices are limited in resources and energy consumption, which necessitates a compromise on accuracy and the frequencies used, thus limiting the usability of the collected data. These limitations in frequency and accuracy delay the early detection of diseases and limit the advancement and understanding of phenomena of interest, such as cardiovascular diseases in the medical field. Traditionally, existing solutions tend to prioritize accuracy at the expense of energy consumption, low cost, and algorithm simplicity.
[0006] There is therefore a general problem of improving the accuracy of ultrasonic imaging systems without increasing their energy consumption, their cost, and without needing to modify existing equipment.
[0007] In the field of medical imaging, several existing methods allow for the detection and characterization of arteries. References [1] and [2] and patent application WO2016057233 are particularly relevant.
[0008] All these methods have the disadvantage of limited measurement accuracy because they are most often based on an ultrasonic acquisition method that uses a set of elements to generate an ultrasonic field with an aperture whose size depends on the number of elements. The accuracy of the measurements depends on various parameters, in particular the frequency and bandwidth of the signal. But it also depends on the size of the probe's active window, that is, the total size of the set of active elements.
[0009] The smaller the active window, the higher the measurement accuracy in terms of resolution. However, an active window that is too small has the disadvantage of lowering the signal-to-noise ratio because the signal amplitude is weaker. It is for this second reason that ultrasonic probes are generally based on multi-element transducers that use several active elements to synthesize an ultrasonic beam in order to focus the beam by coherent summation of the amplitudes of the different elements.
[0010] The invention is based on an algorithmic solution that improves the resolution and accuracy of the measurement without modifying the acquisition equipment. The method is based on performing several successive measurements by varying the number of active elements or the aperture size of the generated ultrasonic field, and then extrapolating the measurement that would have been obtained with an aperture close to zero from the different measurement points.
[0011] The invention relates to a method for characterizing an object using an ultrasonic probe, the method comprising the steps of: - Perform several iterations of the steps of: i. To emit an ultrasonic field having an aperture of a given size, ii. To measure an echo of the ultrasonic field after reflection from an area of interest of an object to be imaged, iii. At each new iteration, modify the size of the ultrasonic field opening, - For at least one point of interest in the area of interest, record the associated flight time from the echo measurement. - Determine, from said flight time measurements, a model of variation of flight times as a function of the size of the ultrasonic field opening, - Extrapolate the flight time of the point of interest for an opening size tending towards 0 from said model.
[0012] According to a particular aspect of the invention, the ultrasonic probe comprises a plurality of elements and the variation in the size of the ultrasonic field opening is obtained by varying the number of active receiving elements.
[0013] According to a particular aspect of the invention, the number of active receiving elements is a multiple of two.
[0014] According to a particular aspect of the invention, the number of active transmitting elements is equal to the number of active receiving elements or to the maximum number of elements that the probe comprises.
[0015] According to a particular aspect of the invention, the object to be imaged is a blood vessel and the point of interest is a point on a wall of the blood vessel.
[0016] According to a particular aspect of the invention, the method is applied to two points of interest corresponding to a first point on the distal wall of the blood vessel and a second point on the proximal wall of the blood vessel, diametrically opposite to the first point, and the method further includes an estimation of the diameter of the blood vessel from the extrapolated times of flight of the two points.
[0017] The invention relates to an ultrasonic imaging device comprising an ultrasonic probe and a processing unit configured to perform the steps of the method according to the invention.
[0018] The invention thus makes it possible to optimize the accuracy of measurements without the need to modify the ultrasonic probe.
[0019] Other features and advantages of the present invention will become more apparent from the following description in relation to the following accompanying drawings.
[0020] [Fig. 1] represents a diagram of a multi-element ultrasonic probe capable of performing an ultrasonic signal acquisition sequence to image a blood vessel,
[0021] [Fig.2] represents a flowchart of the steps of a method for measuring a signal ultrasonic according to one embodiment of the invention,
[0022] [Fig. 3a] represents an example of an ultrasonic image obtained to characterize a blood vessel,
[0023] [Fig.3b] represents an ultrasonic signal extracted from a column of the image of the [Fig.3a]
[0024] [Fig.4a] represents a diagram of an ultrasonic probe according to a first configuration Active window size measurement in reception,
[0025] [Fig.4b] represents a diagram of an ultrasonic probe according to a second configuration Active window size measurement in reception,
[0026] [Fig.4c] represents a diagram of an ultrasonic probe according to a third configuration Active window size measurement in reception,
[0027] [Fig. 5] represents an example of an ultrasonic signal obtained according to a configuration specific size of active window,
[0028] [Fig.6a] represents a diagram showing the variation in flight time of a first point of interest of the ultrasonic signal as a function of the active window size,
[0029] [Fig.6b] represents a diagram showing the variation in the flight time of a second
[0030] [Fig. 6c] shows a diagram of a mathematical model of the variation in the estimated diameter of a blood vessel based on the time-of-flight of the two points of interest measured in Figures 6a and 6b.
[0031] The invention is now described in the context of a medical imaging application of a blood vessel, for example, an artery. Although the invention is advantageously applicable to this example, it is not limited to this particular case and applies more generally to any type of object to be imaged, particularly in the field of non-destructive testing and to any point of interest of an object that one seeks to locate precisely.
[0032] Figure 1 schematically illustrates an example of a multi-element ultrasound probe suitable for imaging an area of the human body using an ultrasound beam. In the example of Figure 1, the area corresponds to a transverse plane of a blood vessel that one wishes to locate precisely or whose diameter one wishes to determine precisely.
[0033] In the example of [Fig. 1], the probe 101 is positioned in contact with the skin 103 so that the row of elements 102 lies substantially in a transverse plane of an artery 104 to be imaged. The probe 101 is not necessarily centered on the artery 104; it is sufficient that the artery be covered in both transmission and reception by the ultrasound beam generated by the probe so as to obtain a transverse impression of the artery.
[0034] To perform an acquisition, the probe is positioned at a given point and a group of emitting elements is activated to generate an ultrasonic field in a given direction. The echoes of the field on the covered area are then measured by the same group of elements or a smaller group of elements. In the example of [Fig. 1], the ultrasonic field is emitted in a direction perpendicular to the axis of alignment of the elements 102, which also corresponds locally to the plane of the skin 103 on which the probe 101 is positioned.
[0035] Fig. 3a shows an example of a 2D image obtained by performing several successive acquisitions, each time shifting the emission center of the ultrasonic field relative to the covered area.
[0036] Fig. 3b shows a column of the 2D image of Fig. 3a which corresponds to a signal measured for an acquisition corresponding to a position of the probe located directly above the center of the vessel to be imaged.
[0037] Indeed, the 2D image of [Fig.3a] corresponds to a matrix in which each column is one of the ultrasonic signals acquired by the probe for a given position of the emitted field relative to the imaged area.
[0038] In [Fig. 3b], two triangles have been identified, two extrema which correspond to the echoes of the ultrasound field on the distal and proximal walls of the blood vessel (in (the occurrence of a radial artery).
[0039] These two points correspond to points of interest in the context of determining the vessel diameter. Indeed, from the measurement of the time-of-flights of these two extrema, it is possible to deduce the positions of the two points and then the diameter, assuming that the signal corresponds to a path passing through the center of the artery. The internal diameter of the vessel is equal to D = 0.5C(t² - ti), where t² and ti are the abscissas of the two extrema (times of flight) and C is the propagation speed of the ultrasonic wave in the medium, in this case, the blood.
[0040] However, the accuracy of the time-of-flight measurement of a point of interest depends on the size of the active window of the transmitting probe, as is now explained.
[0041] Figures 4a, 4b and 4c show three different acquisition configurations for the same ultrasound probe 401 positioned directly above a radial artery 402
[0042] For the first configuration shown in [Fig. 4a], the number of active elements 403 in transmitting and receiving is 16. In other words, the ultrasonic field is generated from the 16 central elements of the probe and also measured by these 16 elements. This acquisition makes it possible to obtain a first measurement of the signal shown in [Fig. 3b].
[0043] The second configuration shown schematically in [Fig.4b] shows a situation where the number of active elements 404 in reception is equal to 12. In this configuration, the number of active elements in transmission can also be taken as 12 or can be taken as 16, i.e. the maximum number of active elements in transmission predefined according to the intended application.
[0044] The third configuration shown in [Fig.4c] shows yet another situation where the number of active elements 405 in reception is equal to 8. The number of active elements in transmission is equal to 8 or 16.
[0045] In general, Figures 4a, 4b, and 4c show that it is possible to perform the same measurement using a variable active window size. The larger the window size, the higher the signal-to-noise ratio, but the lower the measurement accuracy of the echo at a given point. Conversely, a minimum active window size is required to obtain a measurement with a usable signal-to-noise ratio.
[0046] With reference to [Fig.2], the measurement method according to the invention begins with steps 201, 202, 203 which consist of carrying out several successive acquisitions of the same ultrasonic signal (for the same position of the probe relative to the object to be imaged) by varying the size of the active window at each iteration.
[0047] For example, in the case of a multi-element transducer, the number of active receiving elements can be reduced at each iteration compared to the maximum number of elements used to generate the ultrasonic beam. At each iteration, the number The number of active transmitting elements can be left constant, or the group of active transmitting elements can be taken to be equal to the group of active receiving elements.
[0048] For example, at each iteration, the number of active elements in reception can be reduced by a factor of 2.
[0049] According to another embodiment, if the ultrasonic probe is manufactured in a technology which allows the opening of the ultrasonic field to be varied with a single element, then the variation in the number of active elements in reception is replaced by a variation in the opening field at each iteration.
[0050] At the end of all the iterations of steps 201,202,203, we obtain N measurements of the same ultrasonic signal, with N being the number of acquisitions carried out.
[0051] One or more points of interest are then identified on the acquired ultrasound signal. For example, in the case of the signal in [Fig. 5], two points of interest 501, 502 are identified which correspond to echoes of the signal on the distal and proximal internal walls of the blood vessel.
[0052] We wish to determine precisely, for each of these two points, the time of flight or the associated depth (the two quantities being linked to each other by the speed of propagation of the ultrasonic wave in the medium located between the probe and the artery) which is represented on the abscissa of the diagram in [Fig.5].
[0053] For each point of interest considered, its abscissa (expressed in flight time or distance) is recorded, and the diagrams shown in Figures 6a and 6b are plotted (in step 204). These diagrams illustrate the evolution of these measurements as a function of the number of active receiving elements, also called the number of channels in Figures 6a and 6b. Figure 6a corresponds to the position of the signal echo on the proximal wall, and Figure 6b corresponds to the position of the signal echo on the distal wall. In the illustrated examples, the number of channels varies from 8 to 28, but this example is not limiting. The ordinate represents the flight time of each measurement.
[0054] In step 205, a numerical model of the evolution of the time-of-flight variation curves is then determined by mathematical optimization as a function of the number of channels for each point of interest.
[0055] This mathematical model is, for example, determined by a model in the form of a second-degree polynomial function or any other suitable numerical model. It can be defined by means of an interpolation of the measured points of the curve. This interpolation can be performed using a mixture of Gaussian functions or learned by a trained neural network model or any other suitable numerical optimization algorithm.
[0056] Figure 6c shows an example of such a numerical model determined for the difference between the two curves in Figures 6a and 6b which corresponds, in the intended application case, to the diameter of the blood vessel.
[0057] The mathematical model can be determined for each curve associated with each point of interest or for the final quantity that one wishes to determine from several points of interest, in this case the difference between the two flight times.
[0058] Finally, in step 206, the mathematical model obtained is extrapolated to determine an asymptotic value for a number of channels tending towards 0. Indeed, this value corresponds to the most precise measurement in terms of resolution and its determination via an extrapolation of a model makes it possible to avoid being subject to the problem of low signal-to-noise ratio inherent in a measurement carried out with a very small active window.
[0059] The diameter of the vessel is, for example, determined using the following relation:
[0060] D=0.5(tdistai(0)- tproximai(0)).C, where C denotes the propagation velocity of Fonde ul- trasonic in the traversed medium, tdistai(0) and tproximai(0) are the extrapolated values for a number of channels tending towards 0 of the evolution models of the times of flight associated with the points of interest corresponding to the echoes of the ultrasonic field respectively on the distal wall and the proximal wall of the vessel.
[0061] In general, the invention can be applied identically to improve the accuracy of a time-of-flight measurement of a point of interest corresponding to the echo of an ultrasonic field on the surface of an object to be imaged. References
[0062] [1] JH Gagan et al., “Automated Segmentation of Common Carotid Artery in Ul- trasound Images," in IEEE Access, vol. 10, pp. 58419-58430, 2022
[0063] [2] “System A feasibility study of a PMUT-based wearable sensor for the automatic monitoring of carotid artery parameters”, 2021 IEEE International Ultrasonics Symposium (IUS)
Claims
Demands
1. Method for characterizing an object using an ultrasonic probe, the method comprising the steps of: - Performing several iterations of the steps of: i. Emitting (201) an ultrasonic field having an aperture of a given size, ii. Measuring (202) an echo of the ultrasonic field after reflection on a region of interest of an object to be imaged, iii. At each new iteration, modify (203) the size of the ultrasonic field opening, - For at least one point of interest in the area of interest, record (204), on the echo measurement, the associated time of flight, - Determine (205), from said time of flight measurements, a model of variation of the times of flight as a function of the size of the ultrasonic field opening, - Extrapolate (206) the time of flight of the point of interest for an opening size tending towards 0 from said model.
2. Method of characterizing an object according to claim 1 wherein the ultrasonic probe (101) comprises a plurality of elements (102) and the variation in the size of the ultrasonic field opening is obtained by varying the number of active receiving elements.
3. Method of characterizing an object according to claim 2 wherein the number of active elements in reception is a multiple of two.
4. Method of characterizing an object according to any one of claims 2 or 3 wherein the number of active transmitting elements is equal to the number of active receiving elements or to the maximum number of elements that the probe comprises.
5. Method of characterizing an object according to any one of the preceding claims wherein the object to be imaged is a blood vessel and the point of interest is a point on a wall of the blood vessel.
6. A method for characterizing an object according to claim 5, wherein the method is applied to two points of interest corresponding to a first point on the distal wall of the blood vessel and
7. a second point on the proximal wall of the blood vessel, diametrically opposite the first point, and the method further comprises an estimation of the blood vessel diameter from the extrapolated times of flight of the two points. An ultrasound imaging device comprising an ultrasound probe and a processing unit configured to perform the steps of the method according to any one of the preceding claims.