Ultrasound data processing using first image based on sums of signal signs and second and third image based on first image

Abstract

Method of processing data representing ultrasound signals received from an object for imaging an interior material of the object, the method comprising obtaining a first image having first image pixel values at first image pixel coordinates and obtaining a second image having second image pixel values at second image pixel coordinates. The obtaining of the first image comprises, for at least some of the first image pixel coordinates, calculating a respective first image pixel value by summing of respective signal signs determined from respective signal values of the received ultrasound signals at predetermined respective signal receiving time and position combinations. The obtaining of the second image comprises applying a quadrature estimation operation to at least a portion of the first image to determine at least some of the second image pixel values, the quadrature estimation operation being configured to estimate a quadrature component from an in-phase component.

Description

[0001] P138547PC00

[0002] Title: Ultrasound data processing using first image based on sums of signal signs and second image based on first image

[0003] FIELD

[0004] The invention relates to a method of processing data representing ultrasound signals received from an object for imaging an interior material of the object. The invention further relates to: a method of examining an interior material of an object; a processing system; an examination system; and a computer readable storage medium.

[0005] BACKGROUND

[0006] Methods of examining an interior material of an object from outside the object using ultrasound are known as such, for example from W02005 / 068995, EP2565643, W02018 / 208151 and WO2023 / 063814A1. Such methods are used e.g. for inspection of welds and / or possible material flaws such as from corrosion, cracks and hydrogen damage. The methods typically use a so-called phased array or imaging approach involving an array of individually controlled ultrasound transceiver elements.

[0007] Meaningful examination generally requires data representing received ultrasound signals to be processed so as to obtain one or more images visualizing the interior material of the object, wherein in particular irregularities such as defects in the material are typically of interest to be visualized. Various approaches are known in this respect. A particular subclass of data processing approaches, considered as providing benefits over other sub-classes, relates to so-called ‘phase coherence’, see for example: Camacho et al., “Phase Coherence Imaging”, IEEE Trans. Ultrason.

[0008] Ferroelectr. Freq. Control, 56, 5, pp. 958-974, 2009; and Camacho and Fritsch, “Adaptive Beamforming by Phase Coherence Processing”, Ultrasound Imaging, 2011, ISBN: 978-953-307-239-5. Within the sub-class of phase coherence processing, different specific approaches andimplementation variants have been proposed. Examples thereof have been named in literature as ‘Phase Coherence F actor’ (PCF), ‘Sign Coherence Factor’ (SCF), ‘Circular Coherence Factor’ (CCF) and ‘Vector Coherence Factor’ (VCF).

[0009] For practical examination applications in the field, such as for inspection of welds in pipelines, the amount of data to be processed can pose a challenge, in particular in combination with a desired low latency of the processing as well as practical constraints on the hardware used for the processing. In view thereof, there is an ongoing desire to facilitate utilization of phase coherence processing for practical examination purposes in the field.

[0010] SUMMARY

[0011] An aim is to at least partly address the abovementioned desire, and / or to at least partly address the abovementioned challenge, and / or to at least provide an alternative to known variants of phase coherence processing, in particular in the context of examining an interior material of an object from outside the object using ultrasound, e.g. for inspection of welds.

[0012] Thereto, an aspect of the invention provides a method of processing data representing ultrasound signals received from an object for imaging an interior material of the object. The method of processing comprises obtaining a first image having first image pixel values at first image pixel coordinates, and obtaining a second image having second image pixel values at second image pixel coordinates. The set of second image pixel coordinates may be the same as the set of first image pixel coordinates, for example.

[0013] The obtaining of the first image comprises, for at least some of the first image pixel coordinates, calculating a respective first image pixel value by summing of respective signal signs determined from respective signalvalues of the received ultrasound signals at predetermined respective signal receiving time and position combinations.

[0014] The obtaining of the second image comprises applying a quadrature estimation operation to at least a portion of the first image to determine at least some of the second image pixel values. The quadrature estimation operation is configured to estimate a quadrature component from an in-phase component. An example of such an operation is a Hilbert transform operation.

[0015] The signal sign, i.e. an indication representing whether the signal value of a particular signal is positive or negative at a particular time, can be used as a surrogate indication for the in-phase component of that signal at that time. When summing or otherwise numerically combining signs, a negative sign may be represented numerically as -1 and a positive sign may be represented numerically as +1, for example. Since the sign will normally only take on two possible values, it may be represented digitally by a single bit, for example. Alternatively, the sign may be determined by applying a logical operation to the signal value. In that case, the sign of occasional signal values equal to zero (e.g. due to quantization) may be determined as either +1 or -1 or zero, e.g. depending on preference or convention. The very limited number of possible values of the signal sign then allows for very efficient calculation of the first image pixel values, in particular compared to when such pixel values would be based on more complex phase calculations. As the present first image is thus based on sums of signal signs, it may be referred to as a ‘sums-of-signs’ image.

[0016] Advantageously, the second image can serve as a surrogate for a quadrature component that can complement the abovementioned indication for the in-phase component. In known implementation variants of phase coherence processing (see for example: https: / / web.archive.org / web / 2024041415000 l / https: / / www. ndt.net / article / ndtnet / papers / Phase_Coherenc e_Imaging_for_Flaw_Detection.pdf), a relatively complex separate operationusing the individual signals is applied to derive corresponding indications of the quadrature components, generally leading to a high computational load. By contrast, the present invention allows to omit such an operation while still enabling use of a quadrature component indication as part of the phase coherence processing. In particular, the obtaining of the second image may be performed using the first image without access to the individual signals or even the individual signal signs, enabling a particularly efficient implementation.

[0017] It has been found that the obtaining of the first image and the second image enables a form of phase coherence processing that can provide high quality output in a scientifically meaningful manner while also respecting relevant hardware constraints and speed requirements for practical applications in the field, as explained further elsewhere herein.

[0018] Preferably, the method of processing comprises obtaining a third image having third image pixel values at third image pixel coordinates that correspond to at least some of the first image pixel coordinates as well as to at least some of the second image pixel coordinates. The set of third image pixel coordinates may be the same as the set of first image pixel coordinates and / or the set of second pixel coordinates, for example.

[0019] The obtaining of the third image comprises, for at least some of the third image pixel coordinates: calculating a respective first sign variability value from the respective first image pixel value and the number of the respective signal signs; and calculating a respective second sign variability value from the respective second image pixel value and the number of the respective signal signs. In the present context, the skilled person understands that a sign variability value may be defined as a value representing a variability of signal signs.

[0020] Advantageously, such first and second sign variability values can serve as respective coherence indications for the respective phase components, in particular in-phase and quadrature components,respectively. The first and second sign variability values can subsequently be combined, in particular by a calculation, to obtain an overall phase coherence indication that may then be represented as a pixel value in the third image, as explained further elsewhere herein.

[0021] A further aspect provides a method of examining an interior material of an object from outside the object using ultrasound. The method of examining comprises: transmitting ultrasound into the object from outside the object; receiving ultrasound signals from the object outside the object, the received ultrasound signals including reflections and / or diffractions of the ultrasound transmitted into the object; representing the received ultrasound signals as data to be processed; and processing the data as described herein to image the interior material.

[0022] In this way, the advantages of the data processing as described herein can be leveraged in the context of examining an interior material of an object, e.g. in the context of inspection of a weld. The transmitting of the ultrasound, the receiving of the ultrasound signals and the representing of the received ultrasound signals as data may be performed in a manner known as such. Preferably, one or more ultrasound transceiver arrays are used, in particular in accordance with a so-called full matrix capture (FMC) technique. Examples of techniques for processing data obtained using FMC are known as Inverse Wavefield Extrapolation (IWEX) and Total Focusing Method (TFM). Traditionally, these techniques deal with the amplitudes of received signals as opposed to their phase. For background information regarding IWEX, reference is made here to W02005 / 068995, EP2565643, WO2018 / 208151 and WO2023 / 063814A1.

[0023] The aforementioned signal receiving time and position combinations used for obtaining the first image of the present invention are preferably predefined in accordance with IWEX and / or another TFM technique. Thus, the same signal receiving time and position combinations that are used in known amplitude-related approaches can be used for thephase-related approach of the present invention. Typically, different signal receiving positions correspond to different ultrasound transceiver elements in the one or more arrays, wherein the time of receiving an ultrasound signal value at a particular position depends on a time and position of ultrasound emission, a path of ultrasound transmission that depends on reflections and diffractions, and a speed of sound propagation through the material. The speed of sound propagation through the material generally depends on mechanical properties of the material as well as on the type of sound wave (e.g. longitudinal or transverse) in a manner that is generally known as such. In view thereof, different signal receiving time and position combinations can be mapped to a grid of positions within the material that can be represented as a set of pixel coordinates. The resulting image or images can then be spatially interpreted essentially as a virtual cross section through the material.

[0024] A further aspect provides a processing system configured to perform the method of processing as described herein. The processing system preferably comprises at least one processing unit.

[0025] A further aspect provides an examination system for examining an interior material of an object from outside the object using ultrasound. The examination system comprises: at least one ultrasound transmitter configured to transmit ultrasound into the object from outside the object; at least one ultrasound receiver configured to receive ultrasound signals from the object outside the object and to represent the received ultrasound signals as data to be processed; and the processing system as described herein. In the examination system, the processing system is preferably operatively connected to the at least one ultrasound receiver for access to the data to be processed by the processing system.

[0026] A further aspect provides a computer readable storage medium or set of storage media storing data that, when executed by a computer or set of operatively interconnected computers, causes the computer or set ofcomputers to perform the method of processing as described herein. Such a computer readable storage medium or set of storage media may be comprised by the processing system, in particular in combination with one or more suitable computers.

[0027] The processing system, examination system and computer readable storage medium provide benefits corresponding to those as described herein for the method of processing and the method of examining.

[0028] DETAILED DESCRIPTION

[0029] In the following, the invention will be explained further using examples of embodiments and drawings. Although reference will be made to the drawings for illustration, it shall be appreciated that descriptions of embodiments herein can also be understood independent from the drawings. The drawings are schematic and merely show examples. In the drawings, corresponding elements are provided with corresponding reference signs. In the drawings:

[0030] Figs. 1A-1F illustrate different possible ultrasound travel path types in the context of one or two arrays of ultrasound transceiver elements interacting with an object;

[0031] Fig. 2 shows a diagram illustrating an embodiment of the method of processing as described herein;

[0032] Figs. 3A and 4A show examples of second images obtained using an embodiment of the method of processing as described herein;

[0033] Figs. 3B and 4B show respective comparative examples of images obtained using a less efficient method of processing not according to the invention;

[0034] Figs. 5A and 6A show examples of third images obtained using an embodiment of the method of processing as described herein;Figs. 5B and 6B show respective comparative examples of images obtained using a less efficient method of processing not according to the invention; and

[0035] Fig. 7 shows a diagram illustrating an embodiment of a processing system and an examination system as described herein.

[0036] In the following, merely to facilitate understanding of data objects and elements discussed herein, letter-based reference signs generally denote data, in particular digital data, wherein upper case letters generally denote multi-valued data such as a vector or matrix or set, whereas lower case letters generally denote single-valued data such as a scalar, and wherein preceding underscores generally denote index or subscript indications. So, for example, A_b may denote a vector or matrix A associated with (e.g. obtained for) a scalar index b, and A_B_cd may denote a vector or matrix A associated with a set of selection parameters B that in turn is associated with a scalar cd or a set of two scalars c and d. In some cases, letters or letter combinations used may serve as acronym or other form of short hand, as explained herein. It shall be appreciated that, as with reference signs in general, this form of notation for references to data merely serves to facilitate understanding of the associated text and any figures referred to, and should thus not be interpreted as limiting.

[0037] Fig. 2 illustrates a method of processing data representing ultrasound signals U received from an object 1 for imaging an interior material of the object 1.

[0038] The ultrasound signals U are in particular signals representing ultrasound amplitude variations over time, and are thus generally decomposable into in-phase and quadrature components that also vary over time. Different ones of the ultrasound signals U are in particular received at different positions p (e.g. pl, p2, p3) corresponding to different transducer elements of one or more arrays, in particular two arrays directed towards a same area around a target position k in the object 1, for example as shownin Figs. 1A to IF. Each individual transducer element may be operated as a transmitter at some times and as a receiver at other times. Hence, each of the two arrays of transducer elements is provided with both reference signs 21 and 22 in Figs. 1A to IF. The figures illustrate different possible types of transmission paths of an ultrasound signal u from an emitting transducer element to a receiving transducer element via a target position k in the material, wherein different types of paths are generally associated with different path lengths and thus different time delays between emission and reception. The different path types may be referred to as different modes. Possible details about such modes are describedin WO2023 / 063814A1, for example.

[0039] The method of processing comprises obtaining a first image Ml having first image pixel values SS_XY at first image pixel coordinates XY and obtaining a second image M2 having second image pixel values SSH_XY at second image pixel coordinates XY.

[0040] The second image pixel coordinates XY are preferably the same or substantially the same as the first image pixel coordinates XY. In view thereof, the same reference sign XY is used herein for both the first and second pixel coordinates. Alternatively, the set of second image pixel coordinates may form a subset of the set of first image pixel coordinates, and / or the set of second image pixel coordinates may comprise pixel coordinates not comprised by the set of first image pixel coordinates. For example, a second image pixel coordinate may be an intermediate coordinate or an adjacent coordinate compared to the set of first image pixel coordinates.

[0041] It shall be appreciated that an image generally has a respective pixel value at a respective pixel coordinate, in particular so that the image may be represented as a matrix of pixel values with the matrix coordinates representing pixel coordinates. It shall be appreciated that pixel coordinates for an image generally have at least two dimensions. Most commonly, thedimensions include an x-dimension and a y-dimension that are mutually orthogonal. Alternatively, other known coordinate systems such as polar coordinates may be used. In some cases, pixel coordinates for an image may have three dimensions, in which case respective pixels may be regarded as voxels. Although the present invention is explained herein mainly using two-dimensional images and pixel coordinates as examples, it shall be appreciated that generalizations to e.g. three dimensions are possible and not excluded. It shall also be appreciated that the term image as used herein does not as such require any visual representation such as on a display, but rather refers to a set of visually representable image data such as data representing a matrix of pixel values and / or a compressed version thereof.

[0042] The obtaining of the first image Ml (e.g. at block 101 in Fig. 2) comprises, for at least some, e.g. each, of the first image pixel coordinates XY, calculating a respective first image pixel value ss_xy by summing 101 of respective signal signs S_TP_xy determined from respective signal values of the received ultrasound signals U at predetermined respective signal receiving time and position combinations TP_xy.

[0043] As explained above, and also more generally, different ones of the ultrasound signal U may be received at different positions, in particular represented by different receivers of an array of receivers, wherein at each position or receiver the receiving may progress over time so as to obtain an amplitude variation over time for the respective position or receiver. A particular combination of signal receiving time and position may be predetermined to correspond to a particular reflection and / or diffraction position in the interior material of the object 1, wherein multiple such combinations are possible for a same target position k in view of different possible paths of the ultrasound signal u through the material. Accordingly, when the first image pixel coordinates XY correspond to a grid of positions in the interior material of the object 1, a look-up table or the-like may list one or more combinations TP_xy of a signal receiving time and a signalreceiving position (e.g. represented by a particular receiver) to be used for a particular first image pixel coordinate xy. Then, using the look-up table, for each pixel coordinate, relevant signal values may be selected. A respective signal sign s_tp_xy may be determined or retrieved for each selected signal value. For example, the signal sign may be represented by the first or last bit of the signal value. Then, signal signs S_TP_xy obtained for the particular pixel coordinate xy may be summed to obtain the associated first image pixel value ss_xy.

[0044] In reference signs in the present disclosure, merely to facilitate understanding, the reference ‘SS’ or ‘ss’ is used as short hand for ‘sum(s) of signs’. Accordingly, in embodiments, the resulting first image Ml, having first image pixel values SS_XY, may be referred to as a ‘sums-of-signs image’, for example.

[0045] The obtaining of the second image M2 (e.g. at block 102 in Fig. 2) comprises applying a quadrature estimation operation 102 to at least a portion, e.g. the entirety, of the first image Ml to determine at least some, e.g. all, of the second image pixel values SSH_XY. The quadrature estimation operation 102 is configured to estimate a quadrature component from an in-phase component. The quadrature estimation operation 102 may be a Hilbert transform operation, for example.

[0046] In reference signs in the present disclosure, merely to facilitate understanding, the reference ‘SSH’ or ‘ssh’ is used as a short hand for ‘Hilbert-transformed sum(s) of signs’. Accordingly, in embodiments, the resulting second image M2, having second image pixel values SSH_XY, may be referred to as a ‘Hilbert-transformed sums-of-signs image’, for example. Possible alternative quadrature estimation operations are known in the general art of signal processing.

[0047] Figs. 3A and 4A show examples of the second image M2 (‘SSH’). Figs. 3B and 4B show respective comparative examples of a quadrature image (‘Q’) obtained using a relatively inefficient traditional method thatrequires access to the individual signal values as opposed to merely requiring access to the sums-of-signs image Ml. Here, it can be seen that the examples of the second image M2 look highly similar to their respective comparative examples. Thus, the provided gain in efficiency does not appear to result in significant deterioration of data quality compared to the traditional approach. In Figs. 3A to 4B, pixel values are shown as shades of gray ranging from a darkest shade for the lowest negative value via an intermediate shade for values around zero to a brightest shade for the highest positive value.

[0048] In embodiments, the method comprises obtaining a third image M3 (e.g. at block 103, 104, 105) having third image pixel values CSCF_XY at third image pixel coordinates XY that correspond to at least some, e.g. all, of the first image pixel coordinates XY as well as to at least some, e.g. all, of the second image pixel coordinates XY.

[0049] The third image pixel coordinates XY are preferably the same or substantially the same as the first image pixel coordinates XY and / or the second image pixel coordinates XY.

[0050] The obtaining of the third image M3 comprises, for at least some, e.g. each, of the third image pixel coordinates XY: calculating 103 a respective first sign variability value vl_xy from the respective first image pixel value ss_xy and the number n of the respective signal signs S_TP_xy; and calculating 104 a respective second sign variability value v2_xy from the respective second image pixel value ssh_xy and the number n of the respective signal signs S_TP_xy.

[0051] As alluded to in the summary section, such a third image M3 may advantageously convey information interpretable as, e.g. approximating, phase coherence information. In this respect, the present invention advantageously provides an alternative and possible improvement to known approaches and implementation variants of phase coherence processing, of which examples have been indicated in the background section. Inparticular, it has been found that the method including the obtaining of the third image can provide a form of phase coherence processing that can provide high quality output in a scientifically meaningful manner while also respecting relevant hardware constraints and speed requirements for practical applications in the field.

[0052] In reference signs in the present disclosure, merely to facilitate understanding, the reference ‘CSCF’ or ‘cscf is used as a short hand for ‘circular sign coherence factor’, as explained further elsewhere herein.

[0053] Accordingly, in embodiments, the resulting third image M3, having third image pixel values CSCF_XY, may be referred to as a ‘circular sign coherence factor image’, or ‘CSCF image’, for example.

[0054] In embodiments, the number n of the signal signs S_TP_xy is the same number n for each of the third image pixel coordinates XY.

[0055] Alternatively, different pixel coordinates may be associated with different numbers n of signal signs, for example in case a signal value would be missing or discarded for one or more of the relevant signal receiving time and position combinations TP_xy.

[0056] In embodiments, the obtaining of the third image M3 comprises, for at least some, e.g. all, of the third image pixel coordinates XY, calculating 105 a combination of the respective first sign variability value vl_xy and the respective second sign variability value v2_xy.

[0057] In this way, an overall phase coherence indication can be obtained that relates to both in-phase and quadrature components.

[0058] In embodiments, the combination is or comprises a linear combination, in particular a weighted sum and / or weighted average, from the respective first sign variability value vl_xy and the respective second sign variability value v2_xy. In the weighted sum or weighted average, preferably substantially equal weights, for example of about 0.5, are applied to the first and second sign variability values.In this way, the combination can reflect a combined coherence, in particular in a relatively well balanced manner.

[0059] In embodiments, the obtaining of the third image M3 comprises, for at least some of the third image pixel coordinates XY, calculating a square root of the combination, in particular the calculated linear combination, of the respective first sign variability value vl_xy and the respective second sign variability value v2_xy.

[0060] In this way, an appropriate scaling can be applied to the calculated combination of the sign variability values, in particular so as to take a quadratic nature of the sign variability values into account.

[0061] In embodiments, the obtaining of the third image M3 comprises, for at least some of the third image pixel coordinates XY, calculating the respective third image pixel value cscf_xy as a linear function of the respective calculated square root of the combination of the respective first sign variability value vl_xy and the respective second sign variability value v2_xy.

[0062] In this way, further appropriate scaling can be applied, in particular so as to obtain higher values for higher coherence levels and / or to obtain values that are limited to a predefined range.

[0063] In embodiments, the third image pixel value cscf_xy is calculated in accordance with the following expression:

[0064] yl xy + v2 xy

[0065] cscf_xy = 1 —

[0066] In this way, the third image pixel values CSCF_XY can be valued higher for higher phase coherence levels while being limited to a range of from 0 to 1, thereby facilitating display and interpretation of the third image M3. It shall be appreciated that further or alternative scaling and / or mapping may be applied e.g. depending on a desired pixel value scale and / or discretization level.In embodiments, the first sign variability value vl_xy and / or the second sign variability value v2_xy is calculated in accordance with the following set of expressions:

[0067] p + n

[0068] a~ 2 ’

[0069]

[0070] a — b p

[0071] c = - = — ,

[0072] n n

[0073] a ■ (1 — c)2+ b ■ (—1 — c)2

[0074] v = - ,

[0075] n

[0076] wherein p is the first image pixel value ss_xy or the second image pixel value ssh_xy, n is the number n of the signal signs, and v is the first sign variability value vl_xy or the second sign variability value v2_xy, respectively.

[0077] Without wishing to be bound by theory, it is considered that, in this way, when the first and second sign variability values vl_xy and v2_xy are combined as described above, the result can be interpreted as an approximation of the so-called Circular Coherence Factor (CCF) that is known as such from literature, as may be understood in view of the following explanation. The values of a and b above are considered to represent the numbers of positive and negative signs, respectively, underlying the associated sum-of-signs p and number of signs n. The value of c is considered to represent an average of the underlying signs when represented as real numbers +1 and -1. Then, the value of v is considered to represent a variance of the underlying signs. Thus, it has been found that a variance v of signs can advantageously be derived from only the sum p and number n of those signs in an efficient and effective manner, without requiring access to the individual signs at the time of determining said variance. Thereby, relatively efficient calculations are enabled, thereby facilitating applications in the field.Figs. 5A and 6A show examples of the third image M3 (‘CSCF’). Figs. 5B and 6B show respective comparative examples of a ‘Circular Coherence Factor’ image (‘CCF’) obtained using a relatively inefficient traditional method that requires access to the individual signal values as opposed to merely requiring access to the sums-of-signs image Ml. Here, it can be seen that the examples of the third image M3 look highly similar to their respective comparative examples. Thus, the provided gain in efficiency does not appear to result in significant deterioration of data quality compared to the traditional approach. In Figs. 5A to 6B, pixel values are shown as shades of gray ranging from a brightest shade for the lowest value, e.g. about zero, to a darkest shade for the highest value, e.g. about one or a lower number such as about 0.3.

[0078] It shall be appreciated that in the images shown in Figs. 3A to 6B as examples and comparative examples, pixel values have been mapped to darkness levels, i.e. they are shown as shades of gray, in a manner aimed at conformity with formal requirements for drawings in patent applications. It shall be appreciated that different mappings of pixel values may be used in practice, e.g. a mapping to a color scale that may allow a more detailed differentiation of pixel values. Such mappings for visualization purposes are within the general competence of the skilled person.

[0079] In embodiments, the quadrature estimation operation comprises a convolution operation using a predefined kernel.

[0080] In this way, the quadrature estimation operation may be applied relatively efficiently and effectively to the first image Ml, wherein for example also appropriate windowing can be applied at the same time.

[0081] Suitable windowing schemes are known as such for use with quadrature estimation operations such as Hilbert transform operations. For example, a so-called Hamming window or a so-called Hanning window may be used.

[0082] In embodiments, the obtaining of the second image M2 and / or the obtaining of the third image M3 comprises applying a band-pass filteroperation to the at least portion of the first image Ml, in particular so as to cause the second image M2 and / or the third image M3 to be at least partly based on a band-pass filtered version of the first image Ml.

[0083] In this way, frequencies outside a predefined band of relevant frequencies can be suppressed, facilitating meaningful visualization and interpretation of the processing result. Appropriate filter parameters will generally depend on the specifics of the application such as a range of spatial dimensions of features to be examined. The band-pass filter operation may be applied as part of the obtaining of the first image Ml, but is preferably applied only after at least an initial version of the first image Ml has been obtained in order to limit required processing power for the obtaining of the fist image Ml.

[0084] In embodiments, the obtaining of the second image M2, and preferably the obtaining of the third image M3, is performed using the first image Ml without access to the individual signal signs S_TP_xy.

[0085] Advantageously, it has been found that continued access to the individual signs is not needed after the first image Ml has been obtained. For example, using the quadrature estimation operation, the second image M2 can be obtained without access to the individual signs. Also, as explained above, the first and second sign variability values vl_xy and v2_xy can be determined without access to the individual signs.

[0086] In embodiments, with particular reference to Fig. 7 as illustration, the obtaining of the first image Ml is performed at a first location 201, wherein the obtaining of the second image M2, and preferably the obtaining of the third image M3, is performed at a second location 202 that is spaced apart from the first location 201. In embodiments, the ultrasound signals U were received at the first location 201, e.g. in a hand held device that a user can position onto the object 1. Meanwhile, the second location 202 may be at or adjacent a location where the user and / or a further user can view the third image M3 and / or another result of the processing, for example on adisplay 13. Data transfer between such locations can thus remain relatively limited, facilitating speed and efficiency while respecting hardware constraints. Accordingly, in embodiments, a maximum data transfer rate of a data connection between the first location 201 and the second location 202 prevents data representing, or allowing to derive, the individual signal signs S_TP_xy from reaching the second location 202 via the data connection before the second image M2, and preferably the third image M3, is obtained.

[0087] Fig. 7 also illustrates a processing system 10 configured to perform the method of processing as described herein, the processing system 10 comprising at least one processing unit 11, 12. In embodiments, the at least one processing unit 11,12 comprises: a first processing unit 11 configured to perform the obtaining of the first image Ml; and a second processing unit 12 configured to perform the obtaining of the second image M2 and preferably the obtaining of the third image M3, wherein the second processing unit 12 is configured to be arranged spaced apart from the first processing unit 11 while being operatively connected to the first processing unit 11 for receiving the obtained first image Ml from the first processing unit 11 at the second processing unit 12.

[0088] The processing system 10 may comprise a computer readable storage medium or set of storage media 14, 15 storing data that, when executed by a computer or set of operatively interconnected computers, causes the computer or set of computers to perform the method of processing as described herein.

[0089] The first processing unit 11 may for example be or comprise or be part of a field programmable gate array (FPGA). The second processing unit 12 may for example be or comprise or be part of a personal computer, a tablet computer and / or a smart phone.

[0090] Fig. 7 also illustrates an examination system 20 for examining an interior material of an object 1 from outside the object 1 using ultrasound, comprising: at least one ultrasound transmitter 21 configured to transmitultrasound into the object 1 from outside the object 1; at least one ultrasound receiver 22 configured to receive ultrasound signals from the object 1 outside the object 1 and to represent the received ultrasound signals as data to be processed; and the processing system 10 as described herein, the processing system 10 being operatively connected to the at least one ultrasound receiver 22 for access to the data to be processed by the processing system 10.

[0091] Figs. 1, 2 and 7 together also illustrate a method of examining an interior material of an object 1 from outside the object 1 using ultrasound. The method of examining comprises: transmitting ultrasound into the object 1 from outside the object 1; receiving ultrasound signals U from the object 1 outside the object 1, the received ultrasound signals U including reflections and / or diffractions of the ultrasound transmitted into the object 1; representing the received ultrasound signals U as data to be processed; and processing the data as described herein to image the interior material.

[0092] Although the invention has been described herein using examples of embodiments and drawings, these do not limit the scope of the invention as defined by the claims. Within said scope, many variations are possible, as shall be appreciated by the skilled person having the benefit of the present disclosure.

[0093] LIST OF REFERENCE SIGNS

[0094] I. Object

[0095] 10. Processing system

[0096] II. First processing unit

[0097] 12. Second processing unit

[0098] 13. Display

[0099] 14. Storage medium of first processing unit

[0100] 15. Storage medium of second processing unit

[0101] 20. Examination system21. (Array of) Ultrasound transmitter(s)

[0102] 22. (Array of) Ultrasound receiver(s)

[0103] 101. Summing of signal signs

[0104] 102. Quadrature estimation operation

[0105] 103. Calculating first sign variability values

[0106] 104. Calculating second sign variability values

[0107] 105. Calculating combination of first and second sign variability values

[0108] 201. First location

[0109] 202. Second location

[0110] CSCF_XY. Third image pixel values (individually: cscf_xy) k. Target position in material

[0111] Ml. First image

[0112] M2. Second image

[0113] M3. Third image

[0114] n. Number of signal signs

[0115] pl. First position

[0116] p2. Second position

[0117] p3. Third position

[0118] Q. Quadrature image

[0119] S_TP_xy. Signal signs determined for coordinate xy SS_XY. First image pixel values (individually: ss_xy) SSH_XY. Second image pixel values (individually: ssh_xy) t. Time

[0120] TP_xy. Signal receiving time and position combinations for coordinate xy

[0121] U. Ultrasound signals (individually: u)

[0122] vl_xy. First sign variability value for coordinate xy v2_xy. Second sign variability value for coordinate xy x. x-dimensionXY. First, second and / or third image pixel coordinates (individually: xy)

[0123] y. y-dimension

Claims

22Claims1. A method of processing data representing ultrasound signals (U) received from an object (1) for imaging an interior material of the object (1), the method comprising obtaining a first image (Ml) having first image pixel values (SS_XY) at first image pixel coordinates (XY) and obtaining a second image (M2) having second image pixel values (SSH_XY) at second image pixel coordinates (XY),wherein the obtaining of the first image (Ml) comprises, for at least some of the first image pixel coordinates (XY), calculating a respective first image pixel value (ss_xy) by summing (101) of respective signal signs (S_TP_xy) determined from respective signal values of the received ultrasound signals (U) at predetermined respective signal receiving time and position combinations (TP_xy),wherein the obtaining of the second image (M2) comprises applying a quadrature estimation operation (102) to at least a portion of the first image (Ml) to determine at least some of the second image pixel values (SSH_XY), the quadrature estimation operation being configured to estimate a quadrature component from an in-phase component,wherein the method comprises obtaining a third image (M3) having third image pixel values (CSCF_XY) at third image pixel coordinates (XY) that correspond to at least some of the first image pixel coordinates (XY) as well as to at least some of the second image pixel coordinates (XY), wherein the obtaining of the third image (M3) comprises, for at least some of the third image pixel coordinates (XY):calculating (103) a respective first sign variability value (vl_xy) from the respective first image pixel value (ss_xy) and the number (n) of the respective signal signs (S_TP_xy); andcalculating (104) a respective second sign variability value (v2_xy) from the respective second image pixel value (ssh_xy) and the number (n) of the respective signal signs (S_TP_xy).

2. Method of processing according to claim 1, wherein a signal sign is defined as an indication representing whether the signal value of a particular signal is positive or negative at a particular time.

3. Method of processing according to claim 2, wherein a sign variability value is defined as a value representing a variability of signal signs.

4. Method of processing according to any of the preceding claims, wherein the obtaining of the third image (M3) comprises, for at least some of the third image pixel coordinates (XY), calculating (105) a combination of the respective first sign variability value (vl_xy) and the respective second sign variability value (v2_xy).

5. Method of processing according to claim 4, wherein the combination is or comprises a linear combination, in particular a weighted sum and / or weighted average, from the respective first sign variability value (vl_xy) and the respective second sign variability value (v2_xy).

6. Method of processing according to claim 4 or 5, wherein the obtaining of the third image (M3) comprises, for at least some of the third image pixel coordinates (XY), calculating a square root of the combination, in particular the calculated linear combination, of the respective first sign variability value (vl_xy) and the respective second sign variability value (v2_xy).

7. Method of processing according to claim 6, wherein the obtaining of the third image (M3) comprises, for at least some of the third image pixel coordinates (XY), calculating the respective third image pixel value (cscf_xy) as a linear function of the respective calculated square root of the combination of the respective first sign variability value (vl_xy) and the respective second sign variability value (v2_xy).

8. Method of processing according to claim 7, wherein the third image pixel value (cscf_xy) is calculated in accordance with the following expression:

9. Method of processing according to any of claims 1 - 8, wherein the first sign variability value (vl_xy) and / or the second sign variability value (v2_xy) is calculated in accordance with the following set of expressions:p + na =~ ’a — b pc = - = — ,n na ■ (1 — c)2+ b ■ (—1 — c)2v = - ,nwherein p is the first image pixel value (ss_xy) or the second image pixel value (ssh_xy), n is the number (n) of the signal signs, and v is the first sign variability value (vl_xy) or the second sign variability value (v2_xy), respectively.2510. Method according to any of claims 1 - 9, wherein the number (n) of the signal signs (S_TP_xy) is the same number (n) for each of the third image pixel coordinates (XY).

11. Method of processing according to any of the preceding claims, wherein the quadrature estimation operation comprises a convolution operation using a predefined kernel.

12. Method of processing according to any of the preceding claims, wherein the obtaining of the second image (M2), and preferably the obtaining of the third image (M3), is performed using the first image (Ml) without access to the individual signal signs (S_TP_xy).

13. Method of processing according to any of the preceding claims, wherein the obtaining of the first image (Ml) is performed at a first location (201), wherein the obtaining of the second image (M2), and preferably the obtaining of the third image (M3), is performed at a second location (202) that is spaced apart from the first location (201).

14. Method of processing according to claim 13, wherein the ultrasound signals (U) were received at the first location (201).

15. Method of processing according to any of the preceding claims, wherein the obtaining of the second image (M2) and / or the obtaining of the third image (M3) comprises applying a band-pass filter operation to the at least portion of the first image (Ml), in particular so as to cause the second image (M2) and / or the third image (M3) to be at least partly based on a band-pass filtered version of the first image (Ml).2616. A method of examining an interior material of an object (1) from outside the object (1) using ultrasound, wherein the method of examining comprises: transmitting ultrasound into the object (1) from outside the object (1); receiving ultrasound signals (U) from the object (1) outside the object (1), the received ultrasound signals (U) including reflections and / or diffractions of the ultrasound transmitted into the object (1); representing the received ultrasound signals (U) as data to be processed; and processing the data according to any of the preceding claims to image the interior material.

17. A processing system (10) configured to perform the method of processing according to any of claims 1 - 15, the processing system (10) comprising at least one processing unit (11, 12).

18. A processing system according to claim 17, wherein the at least one processing unit (11,12) comprises: a first processing unit (11) configured to perform the obtaining of the first image (Ml); and a second processing unit (12) configured to perform the obtaining of the second image (M2) and preferably the obtaining of the third image (M3), wherein the second processing unit (12) is configured to be arranged spaced apart from the first processing unit (11) while being operatively connected to the first processing unit (11) for receiving the obtained first image (Ml) from the first processing unit (11) at the second processing unit (12).

19. An examination system (20) for examining an interior material of an object (1) from outside the object (1) using ultrasound, comprising: at least one ultrasound transmitter (21) configured to transmit ultrasound into the object from outside the object (1); at least one ultrasound receiver (22) configured to receive ultrasound signals from the object (1) outside the object (1) and to represent the received ultrasound signals as data to be27processed; and the processing system (10) according to claim 17 or 18, the processing system (10) being operatively connected to the at least one ultrasound receiver (22) for access to the data to be processed by the processing system (10).

20. A computer readable storage medium or set of storage media (14, 15) storing data that, when executed by a computer or set of operatively interconnected computers (11, 12), causes the computer or set of computers (11, 12) to perform the method of processing according to any of claims 1 -

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