CN113647978B - High-robustness symbol coherence coefficient ultrasonic imaging method with truncation factor - Google Patents
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Abstract
The invention relates to a high-robustness symbol coherence coefficient ultrasonic imaging method with a truncation factor, and belongs to the technical field of ultrasonic imaging. The method comprises the following steps: s1: preprocessing echo signals received by an ultrasonic array element; s2: extracting symbol values of echo data in each single-transmission total-reception mode; s3: sequentially obtaining a symbol correlation coefficient table in a synthetic aperture mode; s4: solving a symbol correlation coefficient table mean value under each transmitting aperture as a cut-off threshold value of a current symbol correlation coefficient table; s5: performing truncation processing on the echo symbol coherence coefficient by using the truncation threshold; s6: weighting the output of a delay superposition beam former formed by the echo, and sequentially obtaining a single-frame imaging subgraph in a single-shot total-receive mode; s7: carrying out space compounding on the imaging subgraphs in the multiple single-shot total-receiving mode to obtain a final imaging result; the invention can greatly improve the background imaging quality and solve the problem of background image distortion while almost not losing the resolution performance of the symbol coherence coefficient.
Description
Technical Field
The invention belongs to the technical field of ultrasonic imaging, and relates to a high-robustness symbol coherence coefficient ultrasonic imaging method with a truncation factor.
Background
The most widely applied ultrasonic imaging is the simplest beam forming technology, namely Delay And Sum (DAS), which is to calculate the Delay amount of the received echo signals according to the geometrical position relation of array element channels And then align And stack the delayed data. The traditional DAS algorithm has low complexity and high imaging speed, but the main lobe width is increased due to the fact that the fixed window function weighting is adopted, and the resolution ratio is low.
In recent years, adaptive algorithms have been increasingly studied in order to improve the contrast and resolution of beamforming algorithms. Among them, the Coherence Factor (CF) algorithm has been widely studied because of its advantages of high resolution and high contrast. It can be used to measure the focusing quality of ultrasonic sound beam and fully inhibit the formation of side lobe artifact. The symbol coherence factor (Sign Coherence Factor, SCF) is a relatively typical coherence factor type algorithm, and is widely focused because it uses only symbol values for calculation, and thus has great advantages in algorithm complexity. However, since it is similar to the conventional coherence coefficient algorithm, too severe suppression of incoherent signals is caused, thus causing image distortion problems and large-area black artifacts. When the signal-to-noise ratio is low, the coherence of the original desired signal will be completely destroyed by the strong interference noise and thus erroneously filtered out as noise by the symbol coherence factor beamformer, resulting in serious signal loss. The conventional solution reduces the influence of the coherence coefficient on the background quality by reducing the fluctuation degree of the symbol coherence coefficient value, but this also limits the performance of the algorithm in terms of resolution, so that it is difficult to achieve a good balance in the comprehensive imaging quality.
In view of the foregoing, there is a need for a beamforming algorithm that can not only maintain the original resolution performance of the symbol coherence coefficient, but also greatly improve the background quality of the strong speckle, and solve the problem of image distortion, so as to comprehensively improve the comprehensive imaging quality of the ultrasound algorithm.
Disclosure of Invention
In view of the above, the present invention aims to provide a high robustness symbol coherence coefficient ultrasonic imaging method with a truncation factor, which overcomes the problem that the conventional symbol coherence coefficient algorithm is difficult to simultaneously consider the image background quality and the imaging resolution, and performs the truncation threshold coefficient compensation on the weak coherence signal while maintaining the enhancement on the strong coherence signal, thereby ensuring the improvement of the image resolution, greatly improving the imaging background quality, and improving the comprehensive imaging effect of the ultrasonic algorithm.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a high robustness symbol coherence coefficient ultrasonic imaging method with a truncation factor specifically comprises the following steps:
s1: preprocessing echo signals received by an ultrasonic array element to obtain processed ultrasonic echo data, and storing the data obtained by each receiving and transmitting aperture into a table A;
s2: extracting symbol values of echo data in each single-transmission and total-reception mode, and sequentially storing in a table B sign In (a) and (b);
s3: under the synthetic aperture mode, calculating time domain symbol coherence coefficients corresponding to each transmitting array aperture under the single-shot total-receive mode according to the fluctuation characteristics of the ultrasonic echo symbol values, and sequentially obtaining a symbol coherence coefficient table;
s4: solving the average value of the symbol correlation coefficient table under each transmitting aperture as the cut-off threshold SATC of the current symbol correlation coefficient table sign ；
S5: the echo symbol coherence coefficient is truncated by utilizing the truncation threshold value, the symbol coherence coefficient of the strong coherence part is reserved, and the symbol coherence coefficient of the weak coherence part is compensated and optimized to obtain a truncated symbol coherence coefficient table TSCF;
s6: weighting the output of a delay superposition beam former formed by the echo, and sequentially obtaining a single-frame imaging subgraph in a single-shot total-receive mode;
s7: and performing space compounding on the imaging subgraphs in the multiple single-transmission total-reception modes to obtain a final ultrasonic imaging result of the high-robustness symbol coherence coefficient beam former with the truncation factors.
Optionally, in the step S1, processing the echo signal received by the ultrasonic array element includes: amplifying, AD conversion, noise filtering treatment, and storing data obtained by each receiving and transmitting aperture into a three-dimensional table A, wherein A is a three-dimensional table with dimension of D multiplied by M multiplied by N, D represents the total sampling time number of echo, N represents the number of transmitting apertures, and M represents the number of receiving apertures; the detection area is decomposed into Q multiplied by H pixel points, and the focusing delay of each receiving and transmitting aperture for each detection point of the detection area is calculated as follows:
wherein f s Represents the sampling frequency, t off Representing the time interval from the start of transmitting ultrasonic waves to the first time of receiving echoes, c representing the propagation speed of ultrasonic waves in a medium of a detection area, q representing the longitudinal sequence number of pixel points in the detection area, h representing the transverse sequence number of the pixel points in the detection area, m representing the receiving aperture sequence number, and n representing the transmitting aperture sequence number; x (q, h), x (0, m), x (0, n), y (q, h), y (0, m), y (0, n) represent the abscissa and ordinate of point (q, h) (0, m) (0, n), respectively; delta (q, h, m, n) represents the amount of delay required by the receive aperture m at the current sampling instant when the pixel point (q, h) is detected and the transmit aperture is n.
Optionally, in the step S2, symbol values of echo data in each single-transmission and total-reception mode are extracted and sequentially stored in the table B sign In (3), namely:
wherein a (Δ, m, n) represents delayed data obtained by the receiving aperture m when the target pixel point (q, h) is detected and when the transmitting aperture is n; b (B) sign (delta, m, n) represents the sign value of the delayed data obtained by the receiving aperture m when the target pixel (q, h) is detected and when the transmitting aperture is n.
Optionally, in the step S3, in the synthetic aperture mode, time domain symbol coherence coefficients corresponding to each transmitting array aperture in the single-shot total-receive mode are calculated according to the fluctuation characteristics of the ultrasonic echo symbol values, and a symbol coherence coefficient table is sequentially obtained:
SCF n and (q, h) represents the echo symbol coherence coefficient corresponding to the pixel point (q, h) of the detection area under the nth transmitting aperture, and the number N of the transmitting apertures and the number M of the receiving apertures are equal.
Optionally, in the step S4, a mean value of the symbol correlation coefficient table under each transmitting aperture is obtained as a cut-off threshold value SATC of the current symbol correlation coefficient table sign ：
Wherein SATC sign (n) represents a cutoff threshold of the symbol correlation coefficient table under the nth transmit aperture; Q×H represents the total number of pixel points in the detection rectangular region.
Optionally, in the step S5, the echo symbol coherence coefficient is truncated by using the truncation threshold, the symbol coherence coefficient of the strong coherence part is reserved, and the symbol coherence coefficient of the weak coherence part is compensated and optimized, so as to obtain a truncated symbol coherence coefficient table TSCF:
TSCF n (q,h)＝max(SATC sign (n)，SCF n (q,h))
TSCF n (q, h) denotes the symbol coherence coefficient, SCF, of the nth transmit aperture with a truncation factor at pixel point (q, h) n (q, h) represents the original symbol coherence coefficient of the nth transmit aperture at pixel point (q, h), SATC sign (n) represents a symbol coherence coefficient cutoff threshold at the nth transmit aperture; max (·) represents the maximum value calculation function.
Optionally, in the step S6, the output of the delay-superimposed beam former formed by the echo is weighted, so as to sequentially obtain a single-frame imaging sub-image in a single-shot total-receive mode:
wherein the method comprises the steps ofRepresenting the output gray value of the beam former at the pixel point (q, h) of the detection area based on the symbol coherence coefficient TSCF with a cut-off factor under the nth transmitting aperture, and G (q, h) represents the output gray value of the original beam former DAS at the pixel point (q, h) of the detection area; TSCF n (q, h) represents the symbol coherence coefficient of the nth transmit aperture with a truncation factor at pixel point (q, h).
Optionally, in S7, spatial compounding is performed on the imaging sub-image in the single-shot total-receive mode, so as to obtain a final ultrasound imaging chart:
wherein GZ TSCF (q, h) represents the final output gray value at the pixel point (q, h) of the beamformer based on the symbol coherence coefficient TSCF with the truncation factor in the synthetic aperture mode;representing the output gray values of the beamformer at the detection region pixel (q, h) based on the symbol coherence factor TSCF with a truncation factor at the nth transmit aperture.
The invention has the beneficial effects that: compared with the existing symbol coherence coefficient algorithm, the method has the advantages that the high-resolution performance of the method for the strong scattering target point is reserved, and meanwhile, the signal loss in the weak target strong interference environment can be effectively avoided. The invention can improve the resolution of the algorithm and avoid the generation of black region artifacts at the same time, thereby greatly improving the imaging quality of the image background, thus obtaining ideal comprehensive imaging effect and effectively solving the problem that the resolution, contrast and strong speckle background quality of the traditional coherence coefficient algorithm cannot be considered.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.
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For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:
FIG. 1 is a flow chart of an implementation of a beamformer of a symbol coherence coefficient TSCF with a truncation factor;
FIG. 2 is a graph comparing the multi-spot imaging results of 3 algorithms; FIG. 2 (a) is a multi-spot imaging result of a delay-and-accumulate algorithm DAS; FIG. 2 (b) is a multi-spot imaging result of a conventional symbol coherence coefficient algorithm SCF; FIG. 2 (c) is a multi-spot imaging result of the truncated symbol coherence coefficient algorithm TSCF;
FIG. 3 is a graph of the lateral resolution of a multi-spot imaged 50mm depth point target for 3 algorithms;
FIG. 4 is a geabr0 imaging map of 3 algorithms; FIG. 4 (a) is a geabr0 imaging result of a delay-and-add algorithm DAS; FIG. 4 (b) shows the result of the geabr0 imaging by the conventional symbol coherence coefficient algorithm SCF; FIG. 4 (c) is a geabr0 imaging result of the truncated symbol coherence coefficient algorithm TSCF;
FIG. 5 is a graph of lateral resolution at 77.5mm depth in a geabr0 imaging plot for 3 algorithms.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.
Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.
Referring to fig. 1 to 5, fig. 1 is a flowchart of the method of the present invention, and as shown in fig. 1, a preferred high robustness symbol coherence coefficient ultrasonic imaging method with a truncation factor of the present invention includes the following steps:
step S1: processing echo signals received by an ultrasonic array element mainly comprises the following steps: amplifying, AD conversion, noise filtering treatment, and storing data obtained by each receiving and transmitting aperture into a three-dimensional table A, wherein A is a three-dimensional table with dimension of D multiplied by M multiplied by N, D represents the total sampling time number of echo, N represents the number of transmitting apertures, and M represents the number of receiving apertures; the detection area is decomposed into Q multiplied by H pixel points, and the focusing delay of each receiving and transmitting aperture for each detection point of the detection area is calculated as follows:
wherein f s Represents the sampling frequency, t off Representing the time interval from the start of transmitting the ultrasonic wave to the first receipt of the echo, c representing the propagation velocity of the ultrasonic wave in the medium of the detection zone, q representing the detection zoneThe longitudinal serial numbers of the pixel points in the domain, h represents the transverse serial numbers of the pixel points in the detection region, m represents the receiving aperture serial numbers, and n represents the transmitting aperture serial numbers; x (q, h), x (0, m), x (0, n), y (q, h), y (0, m), y (0, n) represent the abscissa and ordinate of point (q, h) (0, m) (0, n), respectively; delta (q, h, m, n) represents the amount of delay required by the receive aperture m at the current sampling instant when the pixel point (q, h) is detected and the transmit aperture is n.
Step S2: extracting symbol values of echo data in each single-transmission and total-reception mode, and sequentially storing in a table B sign In (3), namely:
where a (Δ, m, n) represents delayed data obtained by the receiving aperture m when the target pixel point (q, h) is detected and when the transmitting aperture is n. B (B) sign (delta, m, n) represents the sign value of the delayed data obtained by the receiving aperture m when the target pixel (q, h) is detected and when the transmitting aperture is n.
Step S3: in the synthetic aperture mode, calculating time domain symbol coherence coefficients corresponding to each transmitting array aperture in the single-shot total-receive mode according to the fluctuation characteristics of ultrasonic echo symbol values, and sequentially obtaining a symbol coherence coefficient table:
SCF n and (q, h) represents the echo symbol coherence coefficient corresponding to the pixel point (q, h) of the detection area under the nth transmitting aperture, and the number N of the transmitting apertures and the number M of the receiving apertures are equal.
Step S4: solving the average value of the symbol correlation coefficient table under each transmitting aperture as the cut-off threshold SATC of the current symbol correlation coefficient table sign ：
Wherein SATC sign (n) represents a cutoff threshold of the symbol correlation coefficient table under the nth transmit aperture. Q×H represents the total number of pixel points in the detection rectangular region.
Step S5: the echo symbol coherence coefficient is truncated by utilizing the truncation threshold value, the symbol coherence coefficient of the strong coherence part is reserved, and the symbol coherence coefficient of the weak coherence part is compensated and optimized to obtain a truncated symbol coherence coefficient table TSCF:
TSCF n (q,h)＝max(SATC sign (n)，SCF n (q,h))
TSCF n (q, h) denotes the symbol coherence coefficient, SCF, of the nth transmit aperture with a truncation factor at pixel point (q, h) n (q, h) represents the original symbol coherence coefficient of the nth transmit aperture at pixel point (q, h), SATC sign (n) represents a symbol coherence coefficient cutoff threshold at the nth transmit aperture. max (·) represents the maximum value calculation function.
Step S6: weighting the output of the delay superposition beam former formed by the echo, and sequentially obtaining a single-frame imaging subgraph in a single-shot total-receive mode:
wherein the method comprises the steps ofRepresenting the output gray value of the beamformer at the detection region pixel (q, h) based on the symbol coherence coefficient TSCF with the truncation factor at the nth transmit aperture, G (q, h) represents the output gray value of the original beamformer DAS at the detection region pixel (q, h). TSCF n (q, h) represents the symbol coherence coefficient of the nth transmit aperture with a truncation factor at pixel point (q, h).
Step S7: performing space compounding on the imaging subgraph in the single-shot total-receive mode to obtain a final ultrasonic imaging chart:
wherein GZ TSCF (q, h) represents the final output gray value at the pixel point (q, h) of the beamformer based on the symbol coherence coefficient TSCF with the truncation factor in the synthetic aperture mode.Representing the output gray values of the beamformer at the detection region pixel (q, h) based on the symbol coherence factor TSCF with a truncation factor at the nth transmit aperture.
Verification experiment:
field II is an ultrasonic experimental simulation platform developed by the university of denmark based on acoustic principles, which has gained wide acceptance and use in theoretical research. To verify the effectiveness of the algorithm of the present invention, field II was used to image point scattering targets and acoustic plaques and strong speckles commonly used in ultrasound imaging, and imaging contrast experiments were performed using actual experimental data. In the multi-spot imaging simulation experiment, a row of 3 scattering point targets with the transverse positions at the center of 0mm and the longitudinal positions at the depths of 32.5mm,50mm and 67.5mm are arranged, and two scattering point targets are additionally arranged at the positions of 50mm in the longitudinal direction and the transverse + -5mm and are used for observing the transverse resolution of each algorithm, a synthetic aperture focusing mode is adopted, and the imaging dynamic range of an image is set to be 60dB. Meanwhile, in the speckle medium, two anechoic cysts with the radius of 3mm are arranged, the circle centers are respectively positioned at (-5 mm,40 mm), (5 mm,50 mm), and two strong speckles with the radius of 3mm, and the circle centers are positioned at (5 mm,40 mm) and (-5 mm,50 mm). The scattering point has an amplitude ratio of 10 times between the bulk cyst and the background and 40 times between the anechoic cyst and the background. The center frequency of array elements adopted by the Geabr0 data experiment is 3.33MHz, the number of array elements is 64, the distance is 0.2413mm, the sampling frequency is 17.76MHz, the sound velocity is 1500m/s, and the imaging dynamic range is set to be 60dB.
And adopting a time delay superposition algorithm (DAS), a symbol coherence coefficient (SCF), a symbol coherence coefficient with a truncated factor (TSCF) for the three experimental targets, and carrying out a contrast imaging experiment by the algorithm. FIG. 2 shows a comparison of the multi-spot imaging results of 3 algorithms, and FIG. 2 (a) shows the multi-spot imaging results of the DAS with the delay-and-add algorithm; FIG. 2 (b) is a multi-spot imaging result of a conventional symbol coherence coefficient algorithm SCF; fig. 2 (c) is a multi-spot imaging result of the truncated symbol coherence coefficient algorithm TSCF. As can be seen from fig. 2, the DAS algorithm has the worst imaging quality and the lowest resolution, compared with the other 2 algorithms, the transverse artifacts are the greatest, the SCF algorithm is obviously reduced compared with the sidelobe artifacts of the DAS algorithm, the resolution is obviously improved, but the background has obvious distortion. The TSCF algorithm gives consideration to the improvement of the contrast of the resolution ratio of the algorithm and the quality of the background of the algorithm, and effectively solves the problem of black area artifacts existing in the SCF algorithm. Compared to DAS algorithm, TSCF algorithm has clearer point target resolution capability and fewer in-shift artifacts. Compared with the CF algorithm, the TSCF algorithm effectively improves the background imaging effect under the condition of keeping the resolution ratio basically the same, and the comprehensive imaging performance is obviously improved.
FIG. 3 is a graph of the target lateral resolution of a multi-spot imaged 50mm depth point for 3 algorithms, measured at Full Width Half Maximum (FWHM) value data at-6 dB, as shown in Table 1. As can be seen from a combination of fig. 3 and table 1, DAS has the lowest of the 3 algorithms in lateral resolution at different depths. The SCF algorithm and TSCF algorithm have significantly higher resolution than the DAS algorithm. In addition, the TSCF algorithm is substantially the same as the SCF in resolution, so in terms of resolution, the TSCF algorithm can fully retain the resolution advantage of the SCF.
TABLE 1 FWHM contrast of 3 algorithms-6 dB at different depths in a multiple spot imaging simulation
Table 2 gives background imaging index contrast in the multi-spot imaging experiment. From the calculation, the true contrast of the dark spots should be 32.05, and it can be seen that the CR value of TSCF is much closer to the true value, and is significantly better than SCF in CNR. And both the background variance SD and the speckle signal-to-noise ratio of TSCF are significantly improved over SCF.
Table 2 comparison of imaging performance indicators for multiple spot imaging simulation of different imaging algorithms
FIG. 4 shows the geabr0 experimental imaging diagram of 3 algorithms, and FIG. 4 (a) shows the result of the geabr0 imaging of the DAS; FIG. 4 (b) shows the result of the geabr0 imaging by the conventional symbol coherence coefficient algorithm SCF; fig. 4 (c) shows the geabr0 imaging result of the truncated symbol coherence coefficient algorithm TSCF. As can be seen from fig. 4, the DAS algorithm has the worst imaging effect compared with other algorithms, and the inside of the spot is severely interfered by surrounding scattering points, so that a large amount of artifacts are generated, the outline of the circular spot is unclear, and the size is inaccurate. The SCF algorithm is greatly improved in side lobe suppression compared with the DAS, but the background is darkened, the image background distortion condition is clear, and the imaging robustness is poor. Compared with SCF, the TSCF has obviously improved background quality while retaining SCF sidelobe suppression capability, and has better dark spot background quality and better imaging effect. The resolution and contrast are also significantly improved over DAS. Table 3 gives a comparison of the imaging performance index of the different imaging algorithms geabr 0.
TABLE 3 comparison of imaging Performance indicators for different imaging algorithms geabr0
As can be seen from table 3, the DAS algorithm performs poorly overall, but the background robustness is stronger than the SCF algorithm. Whereas the defects of the SCF algorithm in the SD and sssnr indices are very pronounced. Compared with the traditional algorithm, the TSCF algorithm can keep good CR and CNR, and can greatly improve background imaging related indexes SD and sSNR. In conclusion, the TSCF algorithm can obtain better spot imaging effects compared with other traditional algorithms.
FIG. 5 shows a graph of lateral resolution at 77.5mm depth in a geabr0 imaging plot for 3 algorithms. It can be seen that the resolution of the DAS algorithm is obviously insufficient, the SCF greatly improves the resolution on the basis of the DAS, greatly reduces the main lobe width, and the TSCF algorithm completely retains the resolution advantage of the SCF algorithm, without sacrificing the imaging resolution due to the improvement of the background quality. Thus, TSCF is significantly better overall than conventional beamforming methods.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (8)
1. A high-robustness symbol coherence coefficient ultrasonic imaging method with a truncation factor is characterized by comprising the following steps of: the method specifically comprises the following steps:
s1: preprocessing echo signals received by an ultrasonic array element to obtain processed ultrasonic echo data, and storing the data obtained by each receiving and transmitting aperture into a table A;
s2: extracting symbol values of echo data in each single-transmission and total-reception mode, and sequentially storing in a table B sign In (a) and (b);
s3: under the synthetic aperture mode, calculating time domain symbol coherence coefficients corresponding to each transmitting array aperture under the single-shot total-receive mode according to the fluctuation characteristics of the ultrasonic echo symbol values, and sequentially obtaining a symbol coherence coefficient table;
s4: solving the average value of the symbol correlation coefficient table under each transmitting aperture as the cut-off threshold SATC of the current symbol correlation coefficient table sign ；
S5: the echo symbol coherence coefficient is truncated by utilizing the truncation threshold value, the symbol coherence coefficient of the strong coherence part is reserved, and the symbol coherence coefficient of the weak coherence part is compensated and optimized to obtain a truncated symbol coherence coefficient table TSCF;
s6: weighting the output of a delay superposition beam former formed by the echo, and sequentially obtaining a single-frame imaging subgraph in a single-shot total-receive mode;
s7: and performing space compounding on the imaging subgraphs in the multiple single-transmission total-reception modes to obtain a final ultrasonic imaging result of the high-robustness symbol coherence coefficient beam former with the truncation factors.
2. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in the step S1, processing the echo signal received by the ultrasonic array element includes: amplifying, AD converting, noise filtering, storing the data obtained by each receiving and transmitting aperture into a three-dimensional table A, wherein A is a three-dimensional table with dimension of D multiplied by M multiplied by N, D represents the total sampling time number of echo, N represents the number of transmitting apertures, and M represents the number of receiving apertures; the detection area is decomposed into Q multiplied by H pixel points, and the focusing delay of each receiving and transmitting aperture for each detection point of the detection area is calculated as follows:
wherein f s Represents the sampling frequency, t off Representing the time interval from the start of transmitting ultrasonic waves to the first time of receiving echoes, c representing the propagation speed of ultrasonic waves in a medium of a detection area, q representing the longitudinal sequence number of pixel points in the detection area, h representing the transverse sequence number of the pixel points in the detection area, m representing the receiving aperture sequence number, and n representing the transmitting aperture sequence number; x (q, h), x (0, m), x (0, n), y (q, h), y (0, m), y (0, n) represent the abscissa and ordinate of point (q, h) (0, m) (0, n), respectively; delta (q, h, m, n) represents the amount of delay required by the receive aperture m at the current sampling instant when the pixel point (q, h) is detected and the transmit aperture is n.
3. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in S2, extracting symbol values of echo data in each single-transmission and total-reception mode, and sequentially storing in the table B sign In (3), namely:
wherein a (Δ, m, n) represents delayed data obtained by the receiving aperture m when the target pixel point (q, h) is detected and when the transmitting aperture is n; b (B) sign (delta, m, n) represents the sign value of the delayed data obtained by the receiving aperture m when the target pixel (q, h) is detected and when the transmitting aperture is n.
4. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in the step S3, in the synthetic aperture mode, calculating time domain symbol coherence coefficients corresponding to each transmitting array aperture in the single-shot total-receive mode according to the fluctuation characteristics of the ultrasonic echo symbol values, and sequentially obtaining a symbol coherence coefficient table:
SCF n (q, h) represents the echo symbol coherence coefficient corresponding to the pixel point (q, h) of the detection area under the nth transmitting aperture, and the number N of the transmitting apertures and the number M of the receiving apertures are equal; b (B) sign (delta, m, n) represents the sign value of the delayed data obtained by the receiving aperture m when the target pixel (q, h) is detected and when the transmitting aperture is n.
5. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in the S4, the average value of the symbol correlation coefficient table under each transmitting aperture is obtained as the cut-off threshold SATC of the current symbol correlation coefficient table sign ：
Wherein SATC sign (n) represents a cutoff threshold of the symbol correlation coefficient table under the nth transmit aperture; Q×H represents the total number of pixel points in the detection rectangular region; SCF (SCF) n And (q, h) represents the echo symbol coherence coefficient corresponding to the pixel point (q, h) of the detection area under the nth transmitting aperture.
6. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in the step S5, the echo symbol coherence coefficient is truncated by using the truncation threshold, the symbol coherence coefficient of the strong coherence part is reserved, and the symbol coherence coefficient of the weak coherence part is compensated and optimized, so as to obtain a truncated symbol coherence coefficient table TSCF:
TSCF n (q,h)＝max(SATC sign (n)，SCF n (q,h))
TSCF n (q, h) denotes the symbol coherence coefficient, SCF, of the nth transmit aperture with a truncation factor at pixel point (q, h) n (q, h) represents the original symbol coherence coefficient of the nth transmit aperture at pixel point (q, h), SATC sign (n) represents a cutoff threshold of the symbol correlation coefficient table at the nth transmit aperture; max (·) represents the maximum value calculation function.
7. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in the step S6, the output of the delay-superimposed beam former formed by the echo is weighted, so as to sequentially obtain a single-frame imaging sub-image in the single-shot total-receive mode:
wherein the method comprises the steps ofRepresenting the output gray scale of a beamformer based on the symbol coherence factor TSCF with a truncation factor at the nth transmit aperture at a detection region pixel (q, h)The value G (q, h) represents the output gray value of the original beamformer DAS at the detection region pixel point (q, h); TSCF n (q, h) represents the symbol coherence coefficient of the nth transmit aperture with a truncation factor at the pixel point (q, h); a (Δ, m, n) represents delayed data obtained by the receiving aperture m when the target pixel (q, h) is detected and when the transmitting aperture is n.
8. The high robustness symbol coherence coefficient ultrasound imaging method with a truncation factor according to claim 1, wherein: in the step S7, the imaging subgraphs in the single-shot total-receive mode are subjected to space compounding to obtain a final ultrasonic imaging result:
wherein GZ TSCF (q, h) represents the final output gray value at the pixel point (q, h) of the beamformer based on the symbol coherence coefficient TSCF with the truncation factor in the synthetic aperture mode;representing the output gray values of the beamformer at the detection region pixel (q, h) based on the symbol coherence factor TSCF with a truncation factor at the nth transmit aperture.
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