A three-dimensional ultrasonic interferometric imaging method employing multiple linear array acoustic sensors

Abstract

The application relates to a three-dimensional ultrasonic interference imaging method using multiple linear array ultrasonic sensors, comprising the following steps: step 1, arranging two-dimensional transmitters and receiving ultrasonic sensors composed of multiple one-dimensional linear array ultrasonic sensor groups; step 2, transmitting multiple groups of wide-beam ultrasonic waves with different directions to an imaging target by a one-dimensional linear array ultrasonic sensor transmitter, and simultaneously performing AD conversion on reflected signal channel data received by a two-dimensional receiver; step 3, performing Fourier transformation on the converted channel data by a processor to obtain various frequency components of the data, forming coherent data and closed-loop coherent data; step 4, obtaining a reconstructed image I of scattering intensity by using a least square solution of an optimized solution target function J(I); and step 5, converting the reconstructed image I to obtain an image pixel value with a length-width ratio, and finally sending the image pixel value to a display device for display.

Description

TECHNICAL FIELD

[0001] The present application relates to a three-dimensional ultrasonic interferometric imaging system and method using multiple linear array acoustic sensors. BACKGROUND

[0002] At present, the ultrasonic imaging system is mostly two-dimensional imaging system using one-dimensional linear array probe, and the so-called three-dimensional imaging system is a false three-dimensional image obtained by splicing two-dimensional images obtained at different times.

[0003] In addition, there are also some real three-dimensional ultrasonic imaging systems, and these systems are true three-dimensional images obtained by two-dimensional surface array probes transmitting two-dimensional surface waves for three-dimensional imaging. However, the manufacture of two-dimensional surface array probes is extremely expensive due to the complexity of manufacturing technology and process. In addition, there are also some 2.5-dimensional imaging systems using three linear array probes. However, in the vertical direction of the linear array probe, there are only two fixed focus points of the 2.5-dimensional imaging system obtained by the mechanical mirror probe.

[0004] Regarding the coherent interferometric imaging method, in the ultrasonic imaging industry, a typical one is US patent (US21500342567A1). The method of this patent is two-dimensional ultrasonic imaging, and of course, the patent also mentions that it can be applied to three-dimensional, but the method of this patent is to measure the covariance between the frame amplitude images of the transmission channels obtained by more than twice transmission of wide beams, and then calculate the interference to obtain the interferometric image from the measured covariance.

[0005] In addition, in the observation of astrophysics, coherent imaging has also been extensively studied (https: / / people.csail.mit.edu / klbouman / pw / papers_and_presentations / cvpr2016bouman.pdf). Their theoretical basis is the Van Cittert-Zernike theory, first, the theory is based on the far-field approximation, second, the imaging radiation source is a natural celestial object, and third, the received signal is electromagnetic or optical. SUMMARY

[0006] The present application designs a three-dimensional ultrasonic interferometric imaging method using multiple linear array acoustic sensors, which solves the technical problem that the existing ultrasonic imaging system is a false three-dimensional image obtained by splicing two-dimensional images obtained at different times, not a true three-dimensional image.

[0007] In order to solve the above-mentioned technical problems, the present application adopts the following scheme:

[0008] A three-dimensional ultrasonic interferometric imaging method employing multiple linear array acoustic sensors includes the following steps: Step 1, setting up multiple columns of one-dimensional linear array ultrasonic sensors to form a two-dimensional surface array ultrasonic sensor; Step 2, using one-dimensional linear array ultrasonic sensor to emit multiple sets of wide-beam acoustic waves in different directions towards the imaging target, while simultaneously performing AD conversion on the reflected signal channel data received by the two-dimensional array receiver set in Step 1; Step 3, the processor performs Fourier transform on the converted channel data to obtain the various frequency components of the data, forming coherent data. and closed-loop coherent data Step 4: Use the least squares solution of the objective function J(I) to obtain the reconstructed image I of the scattering intensity; Step 5: Perform a scanning aspect ratio conversion on the reconstructed image I to obtain the image pixel values ​​for display, and finally send it to the display device for display.

[0009] This invention utilizes a linear acoustic probe to emit a wide-beam acoustic wave from its main plane. The signal is received by a sensor element on a two-dimensional surface composed of multiple linear array probes. A mathematical-physical integral equation is established to determine the relationship between the scattering intensity of the imaging surface and the coherence values ​​of the frequency signals from two different channels. This equation is directly solved discretely to obtain the reconstructed value of the scattering intensity at each display pixel. These reconstructed values ​​are then scanned and converted to the desired display format and size before being sent to the display. This only completes the image reconstruction of a two-dimensional imaging surface for three-dimensional imaging reconstruction. To obtain a three-dimensional reconstructed image, a two-dimensional array probe composed of multiple linear array probes is moved at a constant speed in one direction while the aforementioned image reconstruction method is continuously applied. This allows for the reconstruction of one image and the entire three-dimensional reconstructed image of the scanned target.

[0010] Preferably, in step 1, the two-dimensional surface array ultrasonic sensor moves at a constant speed in an arbitrary direction to complete the scanning of the imaging target.

[0011] Preferably, in step 2, the two-dimensional transmitter emits a wide beam onto the imaging plane of the imaging target and emits an ultrasonic wave with a focused beam generated by the geometric lens of the probe itself in the direction perpendicular to the imaging plane.

[0012] Preferably, the coherent data in step 3 is:

[0013] V ij =V(ω) l r i r j )=<U(r i ω l )U * (r j ωl )>=U(r i ω l )U * (r j ω l );

[0014] Preferably, the closed-loop coherent data mentioned in step 3 The calculation formula is as follows:

[0015] To address the phase deviation caused by non-uniformity, a phase correction value is introduced for the i-th and j-th receivers in these linear array receivers, respectively. and The actual measurements obtained for:

[0016]

[0017] The coherence values ​​V obtained by three different receivers ij V jk and V ki Multiplying these yields an expression invariant to non-homogeneous media. Since the unknown phase bias is eliminated, we get:

[0018]

[0019] Preferably, the least squares solution calculation method in step 4 is as follows:

[0020] J = ||GI-d|| 2 →Min

[0021]

[0022] Where β is a weighting factor (0≤β≤1), or the equation can be solved using the back projection method, as follows:

[0023]

[0024] or

[0025]

[0026] Where z n It is a non-zero number of gkn (1≤k≤K), and β is a weighting factor (0≤β≤1).

[0027] Preferably, the method for calculating the reconstructed image I of the scattering intensity in step 4 is as follows:

[0028] V(ω,r i r j )=∫I(R,ω)G(R,r i ,rj ,ω)ds

[0029] Where V(ω, r) i r j )=<U(r i ,ω)U * (r j ,ω)>=U(r i ,ω)U * (r j ,ω),V ij =V(ω, r) i r j ),

[0030] I(R, ω)=<P(R,ω)P*(R,ω)>

[0031] By discretizing the above equation, we obtain:

[0032] (g kn ) KN (I n ) N =(d k ) K ;

[0033] GI = d

[0034] Where N is the number of pixels in the imaging plane, and n is the nth pixel; K is the total number of data pairs, i.e., the number of combinations of (i, j); if there are L receivers for each transmitted beam, then... I n It is the value of I(R, ω) at the nth pixel, g kn It corresponds to G(R, r) of the k(i,j)th pair of coherent data. i r j The value of ω in the nth pixel, d k It is the k(i,j)th pair of coherent data V(ω,r) i r j The measured value of ).

[0035] A three-dimensional ultrasonic interferometric imaging system employing multiple linear array acoustic sensors is characterized by comprising a two-dimensional transmitter and receiver array, an analog-to-digital converter (ADC), a central processor, and a display. The two-dimensional transmitter and receiver array consists of multiple rows of linear array ultrasonic sensors. A one-dimensional transmitter emits multiple sets of wide-beam acoustic waves in different directions towards the imaging target; the two-dimensional receiver receives the reflected signal channel data. The ADC performs an analog-to-digital converter (AD / AD) conversion on the reflected signal channel data. The central processor performs a Fourier transform on the AD-converted data to obtain the various frequency components of the data, forming coherent data pairs and closed-loop data. By iteratively solving the least-squares solution of the objective function using an optimization method, a reconstructed true three-dimensional image of the scattering intensity can be obtained. The display shows the reconstructed true three-dimensional image.

[0036] Preferably, multiple linear array ultrasonic sensors are arranged in parallel to each other, and the spacing between them can be adjusted.

[0037] Preferably, the central processor can be one of a GPU, DSP, FPGA, CPU, and various data processing chips.

[0038] Compared with existing technologies, the three-dimensional ultrasonic interferometric imaging system and method employing multiple linear array acoustic sensors have the following advantages:

[0039] (1) The two-dimensional array ultrasonic probe of the three-dimensional ultrasonic imaging system of the present invention is composed of multiple one-dimensional linear ultrasonic array ultrasonic probes. Compared with the two-dimensional dense element area array ultrasonic probe, the manufacturing cost and process are greatly reduced.

[0040] (2) In terms of coherent imaging, this invention overcomes the errors caused by the far-field approximation of previous methods. In addition, by using the closed-loop coherent data obtained by this imaging system, the phase error caused by the non-uniformity of the medium along the path of the scattered signal of the imaging target to the receiver can be corrected, thereby improving the imaging resolution and accuracy. Attached Figure Description

[0041] Figure 1 This is a block diagram illustrating the structure of the three-dimensional ultrasonic interferometric imaging system employing multiple linear array acoustic sensors according to the present invention.

[0042] Figure 2 This is a schematic diagram of the combined array of transmitter and receiver for three-dimensional coherent imaging using multiple linear probes according to the present invention.

[0043] Figure 3 yes Figure 2 Side view;

[0044] Figure 4 This is a block diagram illustrating the implementation steps of coherent imaging according to the present invention;

[0045] Figure 5 This is a schematic diagram of the combined transmitter and receiver array A of multiple linear probes for three-dimensional coherent imaging according to the present invention;

[0046] Figure 6 This is a schematic diagram of the combined transmitter and receiver array B of the present invention, which uses multiple linear probes to perform three-dimensional coherent imaging;

[0047] Figure 7 This is a schematic diagram of the combined transmitter and receiver array C of the present invention, which uses multiple linear probes to perform three-dimensional coherent imaging;

[0048] Figure 8 This is a schematic diagram of the combined transmitter and receiver array D for three-dimensional coherent imaging using multiple linear probes of the present invention;

[0049] Figure 9 This is a schematic diagram of the combined transmitter and receiver array E of the present invention, which uses multiple linear probes to perform three-dimensional coherent imaging. Detailed Implementation

[0050] The following is combined with Figures 1 to 9 The present invention will be further described as follows:

[0051] This invention employs a two-dimensional planar array ultrasonic sensor probe composed of multiple linear array probes to scan and image a three-dimensional target, replacing the traditional one-dimensional linear ultrasonic probe method for two-dimensional imaging. The received data is channel data received by the two-dimensional planar array ultrasonic sensor probe, containing spatial three-dimensional information of the imaging target. By repeatedly transmitting wide-beam ultrasonic signals to the imaging target and statically or dynamically adjusting the spacing between the receivers, the data obtained from these receivers are used to obtain coherent data and closed-loop coherent data between different receivers according to the method described in this invention. The three-dimensional imaging inversion method of this invention is then used to reconstruct a three-dimensional image of the target based on its scattering intensity. Finally, by uniformly moving the two-dimensional planar array ultrasonic sensor probe (comprising multiple linear array probes) along a certain direction to scan and image the target, a true three-dimensional image reconstruction and display of the imaging target can be obtained. Furthermore, the closed-loop coherent data reconstruction inversion method used in this invention can eliminate the difference between the actual and theoretical phases of the coherent data caused by the non-uniform speed of the ultrasonic wave propagation path, thereby improving the spatial resolution of the three-dimensional image reconstruction.

[0052] In this invention, a two-dimensional surface array ultrasonic sensor probe composed of multiple linear array probes is moved at a constant speed in one direction to acquire channel data. The coherent scattering integral equation that establishes the relationship between coherent data and scattering intensity is directly discretized. By solving the least squares solution of the discretized equation, a certain image of the three-dimensional reconstructed image of the scattering intensity is obtained. The scanning of the three-dimensional imaging target is completed by the two-dimensional surface array ultrasonic sensor probe composed of multiple linear array probes moving at a constant speed in one direction, and the three-dimensional reconstructed image of the entire imaging target can be obtained.

[0053] The scattering intensity of the imaging surface is obtained by having one of the probes in a two-dimensional acoustic wave receiving sensor array composed of multiple linear array probes emit a wide-beam ultrasonic wave to the target on the imaging surface. The scattering intensity is formed by the reflection of the target. The reflected signals from various directions of the target are received by the two-dimensional acoustic wave receiving sensor array. The frequency domain signals received by two, three or more different sensing elements form coherent data and closed-loop data. The imaging scattering intensity is then retrieved from these data.

[0054] like Figure 1 and Figure 4 As shown, a three-dimensional ultrasonic interferometric imaging system employing multiple linear array acoustic sensors includes a two-dimensional transmitter and receiver array, an analog-to-digital converter (ADC), a central processor, and a display. The two-dimensional transmitter and receiver array consists of multiple rows of linear array ultrasonic sensors. A one-dimensional transmitter emits multiple sets of wide-beam acoustic waves in different directions towards the imaging target. The two-dimensional receiver receives the reflected signal channel data. The ADC is used to perform AD conversion on the reflected signal channel data. The central processor performs Fourier transform on the AD-converted data to obtain the various frequency components of the data, forming coherent data pairs and closed-loop data. By iteratively solving the least-squares solution of the objective function using an optimization method, a reconstructed true three-dimensional image of the scattering intensity can be obtained. The display is used to display the reconstructed true three-dimensional image.

[0055] like Figure 2 and Figure 3 As shown, a linear array A emits multiple wide-beam ultrasonic waves with different directions. The emitted incident pressure wave field at any point R within the imaging area it covers is u. in (R,ω), the pressure wave field received at any point r in three-dimensional space is as shown in equation (1):

[0056] U(r, ω)=∫[O(R)u in (R, ω)]e -iω(|R-r| / c) / |Rr|dS (1)

[0057] U(r,ω)=∫[P(R,ω)]e -iω(|R-r| / c) / |Rr|dS (2)

[0058] Where P(R, ω) = O(R)u in (R, ω).

[0059] Assume there are two different receivers located at r i and r j The received signals are as follows:

[0060]

[0061]

[0062] The complex cross-correlation of the pressure fields at points r1 and r2 caused by point R is as follows:

[0063]

[0064] The superscript asterisk indicates complex conjugation. Note that it is assumed that the source is spatially incoherent, which means that when R and R' are not equal, <P(R,ω)P * (R′,ω)> is zero.

[0065]

[0066] V(ω,r i r j )=∫I(R,ω)G(R,r i r j ,ω)dS (7)

[0067] Among them, V ij =V(ω, r) i r j )= <U(r i ,ω)U * (r j ,ω)>=U(r i ,ω)U * (r j ,ω),

[0068] I(R, ω)= <P(R,ω)P * (R, ω)>

[0069] By discretizing equation (6) above, we can obtain:

[0070] (g kn ) KN (I n ) N =(d k ) K (8)

[0071] GI = d (9)

[0072] Where N is the number of pixels in the imaging plane, and n is the nth pixel; K is the total number of data pairs, i.e., the number of combinations of (i, j); if there are L receivers for each transmitted beam, then... i n It is the value of I(R,ω) at the nth pixel, g kn It corresponds to G(R,r) of the k(i,j)th pair of coherent data. i r j The value of ω in the nth pixel, d k It is the k(i,j)th pair of coherent data V(ω,r) i r j The measured value of ).

[0073] I can be obtained by the following method:

[0074] 1. Least squares solution:

[0075] J = ||GI-d|| 2 →Min (10)

[0076]

[0077] Where β is a weighting factor (0 ≤ β ≤ 1). The equation can also be solved using the back projection method, as follows:

[0078]

[0079] or

[0080]

[0081] Among them, z n It is g kn The non-zero number of (1≤k≤K), β is the weighting factor (0≤β≤1).

[0082] 2. Closed-loop coherent data method:

[0083] Up to this point, all equations have assumed that sound waves propagate from the scattering source to the receiver through a homogeneous medium. However, the inhomogeneities in the imaging medium cause sound waves to propagate at different speeds to each receiver. These delays significantly affect the measurement results. Although absolute phase measurements cannot be used, employing a closed-loop coherent data method will allow us to recover some of the distorted information from the phase.

[0084] To address the phase deviation caused by non-uniformity, a phase correction value is introduced for the i-th and j-th receivers in these linear array receivers, respectively. and The actual measurements obtained for:

[0085]

[0086] The coherence values ​​V obtained by three different receivers ij V jk and V ki Multiplying these yields an expression invariant to non-homogeneous media. Since the unknown phase bias is eliminated, we can obtain...

[0087]

[0088] As can be seen from the above equation, the coherent imaging data obtained by the closed-loop coherent data method is time-invariant to non-uniform media; however, the trade-off is that it reduces the number of constraints available for image reconstruction. Although N r The number of three pairs in each receiver is The number of independent values ​​is only

[0089] L observation data can be obtained. Corresponding calculated values ​​of closed-loop coherent data

[0090] definition:

[0091]

[0092] These are the amplitudes of the observed and calculated values ​​of the closed-loop coherent data, respectively. These are the phases of the observed and calculated values ​​of the closed-loop coherent data, respectively.

[0093] definition:

[0094] J1(I)=||V ob -V cal || 2 →Min(16)

[0095] J2(I)=||amp ob -amp cal || 2 →Min(17)

[0096]

[0097] By employing various optimization methods, the image reconstruction values ​​I = [I1, I2, ..., I] can be obtained. N ], I n This is the image value of the nth pixel.

[0098] like Figure 5As shown, array A is a combination of transmitters and receivers for three-dimensional coherent imaging using multiple linear array probes, wherein B-series ultrasonic probes are arranged perpendicularly to A-series ultrasonic probes.

[0099] like Figure 6 As shown, a combined array B of transmitters and receivers for three-dimensional coherent imaging using multiple linear probes is used. The B-series ultrasonic probes are arranged perpendicularly to the A-series ultrasonic probes. There can be more than or equal to 2 B-series ultrasonic probes, and the spacing between them can be varied and adjusted.

[0100] like Figure 7 As shown, a combined array C of transmitters and receivers for three-dimensional coherent imaging using multiple linear probes is provided. The A-series ultrasonic probes are arranged in parallel, and there can be more than or equal to 2 A-series ultrasonic probes. The spacing between them can be varied and adjusted.

[0101] like Figure 8 As shown, a combined array D of transmitters and receivers for three-dimensional coherent imaging using multiple linear probes is used. The A-series ultrasonic probes are arranged in parallel, and there can be more than or equal to 2 A-series ultrasonic probes. The spacing between them can be varied and adjusted. The B-series ultrasonic probes are arranged perpendicularly to the A-series ultrasonic probes.

[0102] like Figure 9 As shown, an array E of transmitters and receivers for three-dimensional coherent imaging using multiple linear probes is provided. The A-series ultrasonic probes are arranged in parallel, and there can be more than or equal to 2 A-series ultrasonic probes. The spacing between them can be varied and adjusted. The B-series ultrasonic probes are arranged perpendicularly to the A-series ultrasonic probes, and there can be more than or equal to 2 B-series ultrasonic probes. The spacing between them can be varied and adjusted.

[0103] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A three-dimensional ultrasonic interferometric imaging method employing multiple linear array acoustic sensors, comprising the following steps: Step 1: Set up a two-dimensional transmitter and receiver transducer composed of multiple columns of one-dimensional linear array ultrasonic sensors; the multiple columns of one-dimensional linear array ultrasonic sensors form a two-dimensional surface array ultrasonic sensor. Step 2: A one-dimensional transmitter emits multiple sets of wide-beam sound waves in different directions toward the imaging target, while the reflected signal channel data received by the two-dimensional receiver is converted by A / D conversion, and the spacing between the receivers is adjusted statically or dynamically. Step 3: The processor performs a Fourier transform on the converted channel data to obtain the various frequency components U(r) of the data. i , ω), forming coherent data and closed-loop coherent data as follows: Where, ω l r i r j Let represent the l-th angular frequency, and the position vectors of the i-th and j-th receivers, respectively; To address the phase deviation caused by non-uniformity, a phase correction value is introduced for the i-th and j-th receivers in these linear array receivers, respectively. and The actual coherent data can be obtained. in This represents the measured coherent data formed by the i-th and j-th receivers due to the non-homogeneity of the medium. At that time, relative to coherent data in an ideal homogeneous medium background Introduced phase deviation; The coherence values ​​V obtained by three different receivers ij V jk and V ki Multiplying these yields an expression invariant to non-homogeneous media. Since the unknown phase bias is eliminated, we get: Step 4: Use optimization to solve the least squares solution of the objective function J(I) to obtain the reconstructed image I of the scattering intensity; Step 5: Scan the reconstructed image I to convert its display size to obtain the pixel values ​​of the display image, and finally send it to the display device for display.

2. The three-dimensional ultrasonic interferometric imaging method using multiple linear array acoustic sensors according to claim 1, characterized in that: In step 1, the two-dimensional surface array ultrasonic sensor, moving at a constant speed in an arbitrary direction, completes the scanning of the imaging target.

3. The three-dimensional ultrasonic interferometric imaging method using multiple linear array acoustic sensors according to claim 1 or 2, characterized in that: In step 2, a certain one-dimensional transmitter emits a wide beam onto the imaging plane of the imaging target and emits ultrasonic waves with focused beams generated by lenses on a plane perpendicular to the imaging plane.

4. The three-dimensional ultrasonic interferometric imaging method using multiple linear array acoustic sensors according to any one of claims 1-3, characterized in that: The least squares solution calculation method in step 4 is as follows: J = ||GI-d|| 2 →Min formula a Where β is a weighting factor, 0 ≤ β ≤ 1; or the equation can be solved using the back projection method, as follows: or Where z n It is g kn The non-zero number of , 1≤k≤K, and β is the weighting factor, 0≤β≤1.

5. The three-dimensional ultrasonic interferometric imaging method using multiple linear array acoustic sensors according to claim 1, characterized in that: The method for calculating the reconstructed image I of the scattering intensity in step 4 is as follows: V ij =V(ω,r i ,r j )=<U(r i ,ω)U * (r j ,ω)>=U(r i ,ω)U * (r j ,ω), By discretizing the above equation, we obtain: (g kn ) KN (I n ) N =(d k ) K ; GI = d Where N is the number of pixels in the imaging plane, and n is the nth pixel; K is the total number of data pairs, i.e., the number of combinations of (i, j); if there are L receivers for each transmitted beam, then... I n It is the value of I(R, ω) at the nth pixel, g kn It corresponds to G(R, r) of the k(i,j)th pair of coherent data. i r j The value of ω in the nth pixel, d k It is the k(i,j)th pair of coherent data V(ω,r) i r j The measured value of ).

6. A three-dimensional ultrasonic interferometric imaging system employing multiple linear array acoustic sensors, the system being used to implement the imaging method of claim 1, characterized in that: Includes a two-dimensional transmitter and receiver array, an analog-to-digital converter, a central processor, and a display; The two-dimensional transmitter and receiver array consists of multiple linear array ultrasonic sensors. The two-dimensional transmitter emits multiple sets of wide-beam sound waves in different directions to the imaging target. The two-dimensional receiver receives the reflected signal channel data and adjusts the spacing between the receivers statically or dynamically. The analog-to-digital converter is used to perform AD conversion on the reflected signal channel data; The central processor obtains the frequency components of the data by performing Fourier transform on the data after AD conversion, and forms coherent data pairs and closed-loop coherent data. By iteratively solving the least squares solution of the objective function through optimization methods, a reconstructed true three-dimensional image of scattering intensity can be obtained. The display is used to show a reconstructed true 3D image.

7. The three-dimensional ultrasonic interferometric imaging system employing multiple linear array acoustic sensors according to claim 6, characterized in that: Multiple linear array ultrasonic sensors are arranged in parallel to each other, and the spacing between them can be adjusted.

8. The three-dimensional ultrasonic interferometric imaging system employing multiple linear array acoustic sensors according to claim 7, characterized in that: The central processor can be one of a GPU, DSP, FPGA, CPU, or various data processing chips.

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