CN1313056C - Two dimension complex interrelative biological tissue displacement evaluating method - Google Patents
Two dimension complex interrelative biological tissue displacement evaluating method Download PDFInfo
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Abstract
The present invention relates to a two-dimension complex crosscorrelation biological tissue displacement evaluating method which belongs to the technical field of ultrasound elastic imaging. The method comprises the following procedures: the data of scanning line No. (m+1) is respectively taken from two-dimension radio frequency signals of a tissue before compressed and the tissue after compressed, wherein m is a two-dimension complex crosscorrelation coefficient of colligation; a plurality of small segments of data with the length of T is taken from scanning line data which is not compressed, crosscorrelation functions of the small segments of data and scanning line data after compressed are respectively calculated, weight average is carried out to each crosscorrelation function to obtain a two-dimension complex crosscorrelation function, and a position to which the maximum value of each crosscorrelation function corresponds is displacement to which each segment of data corresponds; the displacement evaluation of a tissue to which each scanning line data corresponds is obtained in the same way. The present invention reduces errors introduced by tissue lateral displacement by comprehensively considering the information of the data of a plurality of adjacent scanning lines and preferably inhibits a tissue longitudinal displacement evaluation error and a strain evaluation error which are introduced by tissue lateral displacement to improve the precision of tissue longitudinal displacement evaluation.
Description
Technical field
The invention belongs to the ultrasonic elastograph imaging technical field, particularly the biological tissue displacement method of estimation.
Background technology
The variation of biological tissue elasticity modulus is relevant with its pathological phenomenon usually.For example, virulent pathological lesion, for example breast inocarcinoma, carcinoma of prostate, thyroid carcinoma and hepatic metastases etc. are usually expressed as hard brief summary.The breast inocarcinoma is the most common form of breast carcinoma, accounts for 3/4ths of breast carcinoma sum greatly, shows as fine and close lump owing to its density of matrix increases.The breast carcinoma of other types such as intraductal carcinoma and papilloma then show as softish tissue, and benign fibrocystic disease of breast also seldom shows as lump.
The elastic modelling quantity information of biological tissue has important value for the diagnostic procedure of disease.Yet the traditional medicine image mode that comprises x-ray imaging, ultra sonic imaging, computer tomography (CT) and nuclear magnetic resonance (MRI) etc. all can not directly provide the information about the basic mechanical attribute of this tissue of elastic modelling quantity.1991, J.Ophir proposed the method for ultrasonic elastograph imaging (ultrasound elastography), the elastic modelling quantity of tissue is distributed quantitatively estimate, imaging.At present, ultrasonic elastic modulus has become one of medical ultrasound image research focus, is widely used in the detection and the assessment of the infringement (lesion) that breast, prostate, atherosclerotic plaque, myocardium kinetics and high intensity focused ultrasound and radio-frequency (RF) ablation cause.
The ultimate principle of ultrasonic elastograph imaging is: ultrasonic probe is embedded in the extruding flat board, along vertical compress tissue of probe, gathers the forward and backward radiofrequency signal of tissue compression respectively; Tissue will produce a strain along compression direction in the tissue when being compressed, if organization internal elastic modelling quantity skewness, in-house stress distribution is difference to some extent also; The zone that elastic modelling quantity is bigger, the strain ratio that causes is less; Otherwise, the zone that elastic modelling quantity is less, corresponding strain ratio is bigger.Estimate the displacement of organization internal diverse location by certain methods, thereby calculate the stress distribution situation of organization internal, be used for the elastic modelling quantity of intermediate description organization internal to distribute, thereby describe physiology, the pathological state of tissue.
For the two-dimensional ultrasound elastogram, the general Type B ultrasonic probe that adopts linear array, gather the radiofrequency signal of forward and backward each the bar scanning line of probe of tissue compression, carry out above-described Displacement Estimation respectively, thereby the uniaxial train that calculates the corresponding tissue of each bar scanning line distributes.At last the uniaxial train of all scanning line correspondences is distributed and press the scanning line order and form a two-dimentional stress distribution, represent, be used for the elastic modelling quantity distribution of intermediate description organization internal with the form of gray-scale map or pcolor.
General ultrasonic elastograph imaging method may further comprise the steps:
1. utilize commercial B-mode ultrasonic apparatus device (generally adopting linear array probe) to obtain biological tissue to be measured and (be generally tissue, also can be animal tissue, hereinafter to be referred as tissue) a digitized two-dimentional radiofrequency signal before the compression (can adopt analog radio-frequency signal output termination signal amplifier, connect high-speed data acquisition card again, obtain digitized two-dimentional radiofrequency signal; Also can on digitized B-mode ultrasonic apparatus device, directly obtain digitized two-dimentional radiofrequency signal);
2. the probe of hand-held this B-mode ultrasonic apparatus device or utilize motor or screw drives this probe, along probe vertically this tissue is applied a small extruding (it is 1% the order of magnitude that the decrement of tissue generally is controlled at), obtain a digitized two-dimentional radiofrequency signal after the tissue compression;
3. the data of taking out article one scanning line respectively from the forward and backward two-dimentional radiofrequency signal of the tissue compression that obtains of step 1 and 2 are made as s
1(n) and s
2(n), n represents the data sequence number on these two scanning lines, 1≤n≤n
Max, the maximum n of n
MaxProbing depth, the spread speed of ultrasonic waves transmitted in tissue and the sample frequency decision of radiofrequency signal by this B-mode ultrasonic apparatus device;
4. from this scan-line data s
1(n) get the data d that a bit of length is T in
1, its data number is U, U=round (T * U
1), wherein, the unit of T is mm, U
1Represent the data number of the tissue correspondence of 1mm, by spread speed and the sample frequency of the radiofrequency signal decision of ultrasonic waves transmitted in tissue, round () representative rounds up rounds operation, these data d
1Sequence number from n
1To n
1+ U-1, n
1Can be at 1≤n
1Select in the scope of≤U; At τ
1To τ
2Ask this little segment data and scan-line data s in the hunting zone of determining
2(n) cross-correlation function R (τ), computing formula is as follows
Wherein i is the cyclic variable of computational process invading the exterior registration according to sequence number, τ
1Be 0, τ
2Be the decrement that tissue is applied, represent with the number of sampled data; (, generally also needing to carry out interpolation) as parabola interpolation to calculating cross-correlation function in order to improve the precision of Displacement Estimation;
5. the position t of the maximum correspondence of the cross-correlation function R (τ) that obtains of determining step 4
1, t
1Be exactly data d
1Displacement after tissue compression (is s
1(n) sequence number in is from n
1To n
1The segment data d of+U-1
1After tissue compression, move to s
2(n) sequence number in is from n
1-t
1To n
1+ U-1-t
1The position);
6. successively from scan-line data s
1(n) getting a bit of length in is that T is that the data number is the data d of U
2, d
3..., d
N, the sequence number of every segment data staggers V sampled data successively (as V=round (0.4 * T * U
0), V=round (0.5 * T * U
0) etc.), V sampled data will exceed s up to staggering again
1(n) scope, 4,5 identical methods obtain the displacement t of each segment data correspondence successively set by step
2, t
3..., t
N, wherein N is the sum of little segment data; Then displacement sequence t
1, t
2..., t
NBe article one scan-line data s
1(n) Displacement Estimation of Dui Ying tissue;
7. utilize the method identical with step 3-6, obtain the 2nd, 3 successively ..., M bar scan-line data correspondence the Displacement Estimation of tissue, wherein M is the scanning line sum of expression probe, by the probe decision;
8. to article one scan-line data s
1(n) the Displacement Estimation sequence t of Dui Ying tissue
1, t
2..., t
NAsk difference, obtain organizing article one scanning line s
1(n) stress distribution of corresponding tissue, computing formula is as follows,
Wherein, ε
1, ε
2..., ε
N-1Be respectively d
1, d
2..., d
N-1Corresponding organize strain;
9. utilize the method identical with step 8, obtain organizing the 2nd, 3 successively ..., M bar scan-line data correspondence the stress distribution of tissue;
10. the stress distribution of the M bar scan-line data correspondence that step 9 is obtained is synthesized a 2-D data according to the der group of scanning line, and is showed with the form of gray-scale map or pcolor, just obtains the two-dimentional diagram of strains of organizing.
In ultrasonic elastograph imaging, crucial problem is the Displacements Distribution of tissue is estimated, just the step 3-7 of above-described method.The value of cross-correlation function is big more, illustrate that the forward and backward little segment data of compression is identical well more, the maximum value position of cross-correlation function has been represented the position of the correspondence after compression of the little segment data before the compression, thereby can obtain the displacement of this little segment data, just the displacement of the tissue of this segment data correspondence.
In the ultrasonic elastograph imaging, tissue is applied a little decrement, the displacement of tissue that utilizes cross-correlation analysis to estimate is length travel, promptly along the displacement of compression direction.But when tissue was applied a little decrement, the motion of tissue was very complicated, was subjected to the influence of factors such as the organization internal elastic modelling quantity distributes, the geometry of tissue, boundary condition.Organizing not only along compression direction (be linear array probe vertically) has a compression, along also expanding perpendicular to the direction of compression direction (comprise linear array probe laterally and perpendicular to the planar direction of scanning probe).Studies show that, cause that along displacement meeting the amplitude of the cross-correlation function of the forward and backward signal of compression reduces, that is to say that the similarity that compresses forward and backward signal reduces perpendicular to compression direction.And ultrasonic elastograph imaging utilizes the similarity of the forward and backward signal of compression to follow the tracks of displacement of tissue just, so the precision that makes displacement of tissue estimate along displacement meeting perpendicular to compression direction reduces.And, littler perpendicular to the influence of the displacement of scanning probe in-plane than the influence of lateral displacement, so, reduce along influence perpendicular to the displacement of compression direction, mainly be the Influence of Displacement that reduces perpendicular to the planar direction of scanning probe.
Be that signal to each bar scanning line carries out cross-correlation analysis in the above-mentioned displacement estimation method, the Displacement Estimation that obtains organizing, the influence of organizing lateral displacement to introduce is bigger, and the precision of organizing length travel to estimate is relatively poor, and the signal to noise ratio that stress distribution is estimated is lower.
Summary of the invention
The objective of the invention is for overcoming the weak point of prior art, a kind of displacement of tissue method of estimation of two-dimension integrated cross-correlation has been proposed, can make full use of the two-dimensional signal of the radiofrequency signal that obtains from commercial B-mode ultrasonic apparatus device, by taking all factors into consideration the information of adjacent multi-strip scanning line data, reduce to organize the error of lateral displacement introducing, realize to suppress preferably to organize length travel estimation and strain estimation difference, thereby improve the precision of organizing length travel to estimate by what organize that lateral displacement introduces.
The displacement of tissue method of estimation of a kind of two-dimension integrated cross-correlation that the present invention proposes may further comprise the steps:
1. the data of taking out m+1 bar scanning line respectively from the forward and backward two-dimentional radiofrequency signal of tissue compression are made as s
1, m+1(n) and s
2, m+1(n), n represents the data sequence number on these two scanning lines, 1≤n≤n
Max, the maximum n of n
MaxBy probing depth, the spread speed of ultrasonic waves transmitted in tissue and the sample frequency decision of radiofrequency signal of this B-mode ultrasonic apparatus device, m is the coefficient of colligation of two-dimension integrated cross-correlation, and m is integer (its span is preferably 1≤m≤5);
2. from this scan-line data s
1, m+1(n) get the data d that a bit of length is T in
1, m+1, its data number is U, U=round (T * U
1), wherein, the unit of T is mm, U
1Represent the data number of the tissue correspondence of 1mm, by spread speed and the sample frequency of the radiofrequency signal decision of ultrasonic waves transmitted in tissue, round () representative rounds up rounds operation, these data d
1, m+1Sequence number from n
1To n
1+ U-1, n
1Can be at 1≤n
1Select in the scope of≤U; At τ
1To τ
2Ask this little segment data and scan-line data s in the hunting zone of determining
2, m+1(n) cross-correlation function R
M+1(τ), computing formula is as follows
Wherein i is the cyclic variable of computational process invading the exterior registration according to sequence number, τ
1Be 0, τ
2For tissue is applied decrement, represent with the number of sampled data;
3. from the forward and backward two-dimentional radiofrequency signal of tissue compression, take out the data of the preceding m bar and the back m bar scanning line of m+1 bar scanning line successively, promptly the 1st to m bar scanning line and m+2 to the data of 2m+1 bar scanning line, compress forward and backward scan-line data and be made as s respectively
1,1(n), s
1,2(n) ... s
1, m(n), s
1, m+2(n), s
1, m+3(n) ..., s
1,2m+1(n) and s
2,1(n), s
2,2(n) ..., s
2, m(n), s
2, m+2(n), s
2, m+3(n) ..., s
2,2m+1(n), get successively and d
1, m+1(sequence number is from n for same length (T) and same sequence number
1To n
1+ U-1) a bit of data d
1,1(n), d
1,2(n) ..., d
1, m(n), d
1, m+2(n), d
1, m+3(n) ..., d
1,2m+1(n), utilize the computational methods identical, at τ with step 2
1To τ
2Ask segment data d respectively in the hunting zone of determining
1,1(n), d
1,2(n) ..., d
1, m(n), d
1, m+2(n), d
1, m+3(n) ... d
1,2m+1(n) with corresponding compression after the cross-correlation function of scan-line data, promptly ask d
1,1(n) and s
2,1(n) cross-correlation function R
1(τ), ask d
1,2(n) and s
2,2(n) cross-correlation function R
2(τ) ..., ask d
1, m(n) and s
2, m(n) cross-correlation function R
m(τ), ask d
1, m+2(n) and s
2, m+2(n) cross-correlation function R
M+2(τ), ask d
1, m+3(n) and s
2, m+3(n) cross-correlation function R
M+3(τ) ..., ask d
1,2m+1(n) and s
2,2m+1(n) cross-correlation function R
2m+1(τ);
4. the cross-correlation function R that step 2-3 is obtained
1(τ), R
2(τ) ..., R
m(τ), R
M+1(τ), R
M+2(τ) ..., R
2m+1(τ) be weighted on average, obtained comprising the compound cross-correlation function of radiofrequency signal two-dimensional signal, promptly two-dimension integrated cross-correlation function R
M+1' (τ), computing formula is as follows
Wherein, α
kRepresent the weight of the corresponding cross-correlation function of each scan-line data, α
k＞0 (m≤k≤m), and the weight sum of the corresponding cross-correlation functions of all scan-line datas is 1, promptly
(, generally also need this two-dimension integrated cross-correlation function R in order to improve the precision of Displacement Estimation
M+1' (τ) carry out interpolation, as parabola interpolation);
5. determine this cross-correlation function R
M+1' (τ) the position t of maximum correspondence
1, t
1Be exactly data d
1, m+1Displacement after tissue compression, i.e. s
1, m+1(n) sequence number is from n in
1To n
1The segment data d of+U-1
1, m+1After tissue compression, move to s
2, m+1(n) sequence number in is from n
1-t
1To n
1+ U-1-t
1The position;
6. successively from this scan-line data s
1, m+1(n) getting a bit of length in is that T is that the data number is the data d of U
2, m+1, d
3, m+1..., d
N, m+1, the sequence number of every segment data staggers V sampled data successively (as V=round (0.4 * T (1) * U
0), V=round (0.5 * T (1) * U
0) etc.), V sampled data will exceed s up to staggering again
1, m+1(n) scope, the method that 2-5 is identical obtains the displacement t of each segment data correspondence successively set by step
2, t
3..., t
N, wherein N is the sum of little segment data; Then displacement sequence t
1, t
2..., t
NBe m+1 bar scan-line data s
1, m+1(n) Displacement Estimation of Dui Ying tissue;
7. utilize the method identical with step 1-4, obtain successively m+2, m+3 ..., M-m bar scan-line data correspondence the Displacement Estimation of tissue, wherein M is the scanning line sum of expression probe, by the probe decision.
Principle of the present invention:
The inventive method is to calculate j (during the displacement of certain the tracking wave band before the compression of the bar scanning line of m+1≤j≤M-m) in the data, not only calculate the cross-correlation function of data after the compression of this tracking wave band and j scanning line, also calculate the equal length in the preceding data of compression of the 2m bar scanning line adjacent with j bar scanning line, the cross-correlation function of data after the compression of the tracking wave band of same position and correspondence, promptly calculated the equal length the data before the compression of 2m+1 bar scanning line from j-m to j+m, the cross-correlation function of data after the compression of the tracking wave band of same position and correspondence, 2m+1 the cross-correlation function that calculates is weighted on average, obtained comprising the compound cross-correlation function of radiofrequency signal two-dimensional signal, promptly two-dimension integrated cross-correlation function.
As shown in Figure 1, calculating j (during the displacement of certain the tracking wave band before the compression of the bar scanning line of m+1≤j≤M-m) in the data, the 2m+1 bar scanning line 11 of employing from j-m to j+m, calculate the cross-correlation function 13 between the data 12 after the tracking wave band of the equal length in the data, same position before the compression of every scanning line and the corresponding compression, and 2m+1 the cross-correlation function 13 that calculates be weighted average 14, obtain two-dimension integrated cross-correlation function 15, utilize two-dimension integrated cross-correlation function 15 to organize the estimation of length travel.
Owing to be subjected to the influence of various factors, compress forward and backward signal and must include signal component and noise contribution.Like this, the cross-correlation function that compresses between the forward and backward radiofrequency signal has also comprised signal component and noise contribution.
The basic ideas of the method for the two-dimension integrated cross-correlation that the present invention proposes are exactly that the cross-correlation function between the forward and backward radiofrequency signal of compression of multi-strip scanning line correspondence is weighted on average, obtained comprising the compound cross-correlation function of radiofrequency signal two-dimensional signal, thereby the signal component in the outstanding cross-correlation function, and offset a part by the noise contribution of organizing the lateral displacement influence to introduce in the cross-correlation function.Like this, the noise of organizing lateral displacement to introduce reduces, and utilizes cross-correlation function to estimate that the displacement accuracy of organizing is higher after the weighted average.Simultaneously, other noises also obtain counteracting to a certain degree, thereby have further improved the precision of organizing length travel to estimate.
If the displacement of the equal length before the compression of adjacent 2m+1 bar scanning line in the data, the tracking wave band of same position is identical, there be not noise ideally, they are identical with the maximum value position of cross-correlation function of data after the corresponding compression, and for example organize under the situation of the noise that lateral displacement introduces containing noise, there is certain deviation in the maximum value position of these cross-correlation functions.The displacement of tissue method of estimation of the two-dimension integrated cross-correlation that the present invention proposes, exactly these cross-correlation functions are weighted on average, thereby reduce because the deviation that the noise jamming that noise for example organizes lateral displacement to introduce causes, thereby improve the precision of organizing length travel to estimate.
If the equal length before the compression of adjacent 2m+1 bar scanning line in the data, there are some differences in the displacement of the tracking wave band of same position, then the comprehensive cross-correlation function that obtains of the displacement of tissue method of estimation of the two-dimension integrated cross-correlation that proposes of the present invention is the equal length in the data before the compression of adjacent 2m+1 bar scanning line, the smoothing result of the cross-correlation function after the tracking wave band of same position and the corresponding compression between the data, estimate also to get certain smoothing effect to organizing length travel, thereby the elimination interference of noise improves the precision of organizing length travel to estimate.Simultaneously, this method also causes the reducing of lateral resolution of ultrasonic elastograph imaging.Generally speaking, adopt spacing less (as the order of magnitude of 0.1mm) between the scanning line of probe (being generally linear array probe) of commercial B-mode ultrasonic apparatus device, after the cross-correlation function between the data is weighted on average after the tracking wave band of the equal length in the data before the compression of adopting some not many scanning lines (m≤5 expression number of scanning lines are no more than 11), same position and the corresponding compression, to the influence of the lateral resolution of imaging and not obvious, and can improve the precision of organizing the length travel estimation.
The parameter that influences two-dimension integrated cross-correlation method comprises the weight of coefficient of colligation m and each scanning-line signal cross-correlation
k(m≤k≤m).In the application of reality,, will reduce the lateral resolution of ultrasonic elastograph imaging if the value of m is excessive; Value is too small, then the DeGrain of two-dimension integrated cross-correlation method.The value of general m is 1, or 2.Weight
k(value of m≤k≤m) has several different methods, and is simple, can make the weight of the cross-correlation function of each scan-line data correspondence equate, is 1/ (2m+1), also can be other the α that satisfies
k＞0 (m≤k≤m) and
Weighting scheme.
If m=0, perhaps α
-m=α
-m+1=...=α
-1=α
1=α
2=...=α
m=0, α
0=1, then
R
j+1′(τ)＝R
j+1(τ)
Expression two-dimension integrated cross-correlation function is at this time degenerated and is become the cross-correlation function that conventional method adopts, because this method does not make full use of the two-dimensional signal of radiofrequency signal, be subjected to organizing the influence of lateral displacement easily, thus the precision that influence organizes length travel to estimate.
Therefore, the displacement of tissue method of estimation of the two-dimension integrated cross-correlation that the present invention proposes requires to satisfy m 〉=1 and α
k＞0 (m≤k≤m).
The displacement of tissue method of estimation of the two-dimension integrated cross-correlation that the present invention proposes has improved the precision that the m+1 bar is estimated to the displacement of tissue of M-m bar scanning line correspondence.For the 1st to m bar scanning line and M-m+1 to M bar scanning line, can not carry out displacement of tissue estimates, this will reduce the lateral extent (being number of scanning lines) of ultrasonic elastograph imaging, but because number less (m≤5 expression number of scanning lines are no more than 11) is also not obvious on last two-dimentional diagram of strains; Also can adopt general method to carry out the displacement of tissue estimation, thereby not reduce the lateral extent of ultrasonic elastograph imaging; Though these scanning lines are positioned at the edge of probe, organize the influence of lateral displacement bigger, because it is number is less, also not obvious on last two-dimentional diagram of strains.
Characteristics of the present invention:
1) before the compression of comprehensive adjacent multi-strip scanning line after the tracking wave band of the equal length in the data, same position and the corresponding compression a plurality of cross-correlation functions between the data organize the length travel estimation;
2) above-mentioned a plurality of cross-correlation functions are weighted on average, have obtained comprising the compound cross-correlation function of radiofrequency signal two-dimensional signal, promptly two-dimension integrated cross-correlation function;
3) utilize above-mentioned two-dimension integrated cross-correlation function to organize length travel to estimate, thereby reduce to organize the influence of lateral displacement.
Description of drawings
The displacement of tissue of the two-dimension integrated cross-correlation that Fig. 1 proposes for the present invention estimate sketch map.
Fig. 2 is the organize models of the Computer Simulation of present embodiment;
Fig. 3 is a desired result of organizing stress distribution of utilizing finite element analysis computation to obtain;
The computer artificial result of organizing stress distribution that Fig. 4 obtains for general displacement of tissue method of estimation;
Fig. 5 is the computer artificial result of organizing stress distribution that the displacement of tissue method of estimation of the two-dimension integrated cross-correlation of coefficient of colligation m=1 obtains;
Fig. 6 is the computer artificial result of organizing stress distribution that the displacement of tissue method of estimation of the two-dimension integrated cross-correlation of coefficient of colligation m=2 obtains.
The specific embodiment
The displacement of tissue method of estimation of the two-dimension integrated cross-correlation that the present invention proposes reaches accompanying drawing in conjunction with specific embodiments and is described in detail as follows:
Embodiment 1 utilize computer program and general ultrasonic scattering model emulation obtain one mimic be organized in the compression before and the compression after two-dimentional radiofrequency signal.Mimic organizational structure is organized 21 sizes, 60 * 60mm as shown in Figure 2
2, being distributed with 3 circular foreign bodies 22,23,24 that elastic modelling quantity is bigger in the tissue, their elastic modelling quantity is 2 times of tissue 1, their diameter is 5mm; The tissue compression ratio is 1%, and promptly decrement is 0.6mm; The center probe frequency is 3.5MHz,-three dB bandwidth is 2.0MHz, scanning probe line width and interval are respectively 2mm and 0.4mm, the probe width is with to organize width consistent, also be 60mm, therefore always have 151 scanning lines, i.e. central part and organization edge position are organized in M=151, and probe central part and probe edge correspondence respectively; The sample frequency of radiofrequency signal is 20MHz, supposes that ultrasound wave is 1540m/s in in-house spread speed, thus 1mm organize the corresponding 1mm/ (1540 * 10 of length
3Mm/s * 1/20 * 10
6/ 2) 26 data of Hz ≈, because tissue depth is 60mm, so the data of each bar scanning line are 60 * 26=1560, the decrement that tissue is applied is expressed as 16 sampled datas of 60 * 1% * 26 ≈ with the number of sampled data.
Fig. 3 represents to utilize the MARC software of U.S. MSC company to carry out finite element analysis, the ideal stress distribution of the organize models that this embodiment that calculates adopts.The lateral attitude and the lengthwise position (being tissue depth) of the horizontal and vertical tissue of expression respectively, gray scale is represented the desirable strained size calculated, gray value big more (being that color is bright more or white more), the expression strain is big more, gray value more little (being that color is dark more or black more), the expression strain is more little, and 31 is the contrast relationship of gray value and strain size.Among Fig. 3, darker zone (being 32-34) organized layer (be 22-24 in Fig. 2) bigger with elastic modelling quantity is corresponding, illustrates that the bigger areal strain of elastic modelling quantity is less.
In the present embodiment, the value of m is 1, makes the weight of the cross-correlation function of each scan-line data correspondence
k(m≤k≤m) equate is 1/ (2m+1), is 1/3; Follow the tracks of the length T of wave band and get 3mm, the data number of promptly following the tracks of wave band is 26 * 3=78, adjacent tracking wave band stagger 26 sampled datas, i.e. V=26.
Utilize the displacement of tissue method of estimation of the two-dimension integrated cross-correlation that the present invention proposes, estimate the displacement of tissue of m+1 bar, thereby obtain corresponding stress distribution to M-m bar scanning line correspondence; And for the 1st to m bar scanning line and M-m+1 to M bar scanning line, not carrying out displacement of tissue estimates, reduce the lateral extent (being number of scanning lines) of ultrasonic elastograph imaging, but because number less (m≤5 expression number of scanning lines are no more than 11), influence is little.
The concrete steps of present embodiment are as follows:
1. the data of taking out article one scanning line respectively from the forward and backward two-dimentional radiofrequency signal (Computer Simulation obtains) of tissue compression are made as s
1, m+1(n) and s
2, m+1(n), 1≤n≤1560, m is the coefficient of colligation of two-dimension integrated cross-correlation method, m=1;
2. from this scan-line data s
1, m+1(n) get the data d that a bit of length is T in
1, m+1, T=3mm, its data number is U, U=78, the sequence number of these data from 13 to 90; In 0 to 16 hunting zone, ask this little segment data and scan-line data s
2, m+1(n) cross-correlation function R
M+1(τ), computing formula is as follows
Wherein i is the cyclic variable of computational process invading the exterior registration according to sequence number;
3. from the forward and backward two-dimentional radiofrequency signal of tissue compression, take out the data of the preceding m bar and the back m bar scanning line of m+1 bar scanning line successively, promptly the 1st to m bar scanning line and m+2 to the data of 2m+1 bar scanning line, compress forward and backward scan-line data and be made as s respectively
1,1(n), s
1,2(n) ... s
1, m(n), s
1, m+2(n), s
1, m+3(n) ..., s
1,2m+1(n) and s
2,1(n), s
2,2(n) ..., s
2, m(n), s
2, m+2(n), s
2, m+3(n) ..., s
2,2m+1(n), get successively and d
1, m+1The a bit of data d of same length (3mm) and same sequence number (sequence number from 13 to 90)
1,1(n), d
1,2(n) ..., d
1, m(n), d
1, m+2(n), d
1, m+3(n) ..., d
1,2m+1(n), utilize the computational methods identical with step 2,0 to 16 the hunting zone in ask segment data d respectively
1,1(n), d
1,2(n) ..., d
1, m(n), d
1, m+2(n), d
1, m+3(n) ... d
1,2m+1(n) with corresponding compression after the cross-correlation function of scan-line data, promptly ask d
1,1(n) and s
2,1(n) cross-correlation function R
1(τ), ask d
1,2(n) and s
2,2(n) cross-correlation function R
2(τ) ..., ask d
1, m(n) and s
2, m(n) cross-correlation function R
m(τ), ask d
1, m+2(n) and s
2, m+2(n) cross-correlation function R
M+2(τ), ask d
1, m+3(n) and s
2, m+3(n) cross-correlation function R
M+3(τ) ..., ask d
1,2m+1(n) and s
2,2m+1(n) cross-correlation function R
2m+1(τ);
4. the cross-correlation function R that step 2-3 is obtained
1(τ), R
2(τ) ..., R
m(τ), R
M+1(τ), R
M+2(τ) ..., R
2m+1(τ) be weighted on average, obtained comprising the compound cross-correlation function of radiofrequency signal two-dimensional signal, promptly two-dimension integrated cross-correlation function R
M+1' (τ), computing formula is as follows
Wherein, α
iRepresent the weight of the corresponding cross-correlation function of each scan-line data, α
k=1/ (2m+1) (m≤k≤m); (, generally also need this two-dimension integrated cross-correlation function R in order to improve the precision of Displacement Estimation
M+1' (τ) carry out interpolation, as parabola interpolation);
5. determine this cross-correlation function R
M+1' (τ) the position t of maximum correspondence
1, t
1Be exactly data d
1, m+1Displacement after tissue compression (is s
1, m+1(n) the segment data d of sequence number from 13 to 90 in
1, m+1After tissue compression, move to s
2, m+1(n) sequence number in is from 13-t
1To 90-t
1The position);
6. successively from this scan-line data s
1, m+1(n) getting a bit of length in is that 3mm is that the data number is 78 data d
2, m+1, d
3, m+1..., d
N, m+1, the sequence number of every segment data 26 sampled datas (being V=26) that stagger successively, 26 sampled datas will exceed s up to staggering again
1, m+1(n) scope, the method that 2-5 is identical obtains the displacement t of each segment data correspondence successively set by step
2, t
3..., t
N, wherein N is the sum of little segment data, N=60; Then displacement sequence t
1, t
2..., t
NBe m+1 bar scan-line data s
1, m+1(n) Displacement Estimation of Dui Ying tissue;
7. utilize the method identical with step 1-4, obtain successively m+2, m+3 ..., M-m bar scan-line data correspondence the Displacement Estimation of tissue, wherein M is the scanning line sum of expression probe, M=151;
Calculating j (during the displacement of certain the tracking wave band before the compression of the bar scanning line of m+1≤j≤M-m) in the data, calculated the cross-correlation function of data after the tracking wave band of the equal length the data, same position before the compression of 2m+1 bar scanning line and the corresponding compression from j-m to j+m, 2m+1 the cross-correlation function that calculates is weighted on average, obtain two-dimension integrated cross-correlation function, utilize two-dimension integrated cross-correlation function to organize the estimation of length travel.
The organize models of embodiment 2 is identical with embodiment 1 with parameter designing, and just the value of m is 2, the weight of the cross-correlation function of each scan-line data correspondence
k(m≤k≤m) be 1/5, concrete steps are also identical with embodiment 1, just at m and α
kThe value difference.
Displacement Estimation effect and the conventional method of embodiment 1 and embodiment 2 are compared as follows:
The computer artificial result of organizing stress distribution that Fig. 4 obtains for general displacement of tissue method of estimation, promptly coefficient of colligation m is 0 o'clock result; Fig. 5 is the computer artificial result of organizing stress distribution that obtains of embodiment 1, and promptly adopting coefficient of colligation m is the result that the displacement of tissue method of estimation of 1 two-dimension integrated cross-correlation obtains; Fig. 6 is the computer artificial result of organizing stress distribution that obtains of embodiment 2, and promptly adopting coefficient of colligation m is the result that the displacement of tissue method of estimation of 2 two-dimension integrated cross-correlation obtains; Among Fig. 4-6, the lateral attitude and the lengthwise position (being tissue depth) of the horizontal and vertical tissue of expression respectively, gray scale is represented the strain size that estimates, gray value big more (being that color is bright more or white more), the expression strain is big more, gray value more little (being that color is dark more or black more), the expression strain is more little, and 41,51 and 61 are respectively the gray value of Fig. 4, Fig. 5 and Fig. 6 and the contrast relationship of strain size.
Organization edge position 42,43,52,53,62,63 among the comparison diagram 4-6, as seen, when adopting general displacement of tissue method of estimation, the influence of organizing lateral displacement to introduce is bigger, the precision of organizing length travel to estimate is relatively poor, and the signal to noise ratio that stress distribution is estimated is lower.And the displacement of tissue method of estimation of the two-dimension integrated cross-correlation of employing m=1 and m=2 can reduce because the influence of organizing lateral displacement to introduce improves the precision that length travel is estimated, the signal to noise ratio that the raising stress distribution is estimated.And m is big more, and the effect of the method for two-dimension integrated cross-correlation is obvious more.
Claims (1)
1, a kind of displacement of tissue method of estimation of two-dimension integrated cross-correlation may further comprise the steps:
1) data of taking out m+1 bar scanning line respectively from the forward and backward two-dimentional radiofrequency signal of tissue compression are made as S
1, m+1(n) and S
2, m+1(n), n represents the data sequence number on these two scanning lines, 1≤n≤n
Max, the maximum n of n
MaxBy probing depth, the spread speed of ultrasonic waves transmitted in tissue and the sample frequency decision of radiofrequency signal of B-mode ultrasonic apparatus device, m is the coefficient of colligation of two-dimension integrated cross-correlation, and m is an integer;
2) from this scan-line data s
1, m+1(n) get the data d that a bit of length is T in
1, m+1, its data number is U, U=round (T * U
1), wherein, the unit of T is mm, U
1Represent the data number of the tissue correspondence of 1mm, by spread speed and the sample frequency of the radiofrequency signal decision of ultrasonic waves transmitted in tissue, round () representative rounds up rounds operation, these data d
1, m+1Sequence number from n
1To n
1+ U-1, n
1At 1≤n
1Select in the scope of≤U; At τ
1To τ
2Ask this little segment data and scan-line data s in the hunting zone of determining
2, m+1(n) cross-correlation function R
M+1(τ), computing formula is as follows
Wherein i is the cyclic variable of computational process invading the exterior registration according to sequence number, τ
1Be 0, τ
2Be the decrement that tissue is applied, represent with the number of sampled data;
3) from the forward and backward two-dimentional radiofrequency signal of tissue compression, take out the data of the preceding m bar and the back m bar scanning line of m+1 bar scanning line successively, promptly the 1st to m bar scanning line and m+2 to the data of 2m+1 bar scanning line, compress forward and backward scan-line data and be made as s respectively
1,1(n), s
1,2(n) ... s
1, m(n), s
1, m+2(n), s
1, m+3(n) ..., s
1,2m+1(n) and s
2,1(n), s
2,2(n) ..., s
2, m(n), s
2, m+2(n), s
2, m+3(n) ..., s
2,2m+1(n), get successively and d
1, m+1The a bit of data d of same length and same sequence number
1,1(n), d
1,2(n) ..., d
1, m(n), d
1, m+2(n), d
1, m+3(n) ..., d
1,2m+1(n), utilize and step 2) identical computational methods, at τ
1To τ
2Ask segment data d respectively in the hunting zone of determining
1,1(n), d
1,2(n) ..., d
1, m(n), d
1, m+2(n), d
1, m+3(n) ... d
1,2m+1(n) with corresponding compression after the cross-correlation function of scan-line data, promptly ask d
1,1(n) and s
2,1(n) cross-correlation function R
1(τ), ask d
1,2(n) and s
2,2(n) cross-correlation function R
2(τ) ..., ask d
1, m(n) and d
2, m(n) cross-correlation function R
m(τ), ask d
1, m+2(n) and s
2, m+2(n) cross-correlation function R
M+2(τ), ask d
1, m+3(n) and s
2, m+3(n) cross-correlation function R
M+3(τ) ..., ask d
1,2m+1(n) and s
2,2m+1(n) cross-correlation function R
2m+1(τ);
4) to step 2)-3) the cross-correlation function R that obtains
1(τ), R
2(τ) ..., R
m(τ), R
M+1(τ), R
M+2(τ) ..., R
2m+1(τ) be weighted on average, obtained comprising the compound cross-correlation function of radiofrequency signal two-dimensional signal, promptly two-dimension integrated cross-correlation function R
M+1' (τ), computing formula is as follows
Wherein, α
kRepresent the weight of the corresponding cross-correlation function of each scan-line data, its value is 1/ (2m+1) ,-m≤k≤m;
5) determine this cross-correlation function R
M+1' (τ) the position t of maximum correspondence
1, t
1Be exactly data d
1, m+1Displacement after tissue compression, i.e. s
1, m+1(n) sequence number is from n in
1To n
1The segment data d of+U-1
1, m+1After tissue compression, move to s
2, m+1(n) sequence number in is from n
1-t
1To n
1+ U-1-t
1The position;
6) successively from this scan-line data s
1, m+1(n) getting a bit of length in is that T is that the data number is the data d of U
2, m+1, d
3, m+1..., d
N, m+1, the sequence number of every segment data V the sampled data that stagger successively, V sampled data will exceed s up to staggering again
1, m+1(n) scope, set by step 2)-5) identical method obtains the displacement t of each segment data correspondence successively
2, t
3..., t
N, wherein N is the sum of little segment data; Then displacement sequence t
1, t
2..., t
NBe m+1 bar scan-line data s
1, m+1(n) Displacement Estimation of Dui Ying tissue;
7) utilize and step 1)-6) identical method, obtain successively m+2, m+3 ..., M-m bar scan-line data correspondence the Displacement Estimation of tissue, wherein M is the scanning line sum of expression probe, by the probe decision; Coefficient of colligation 1≤m≤5 of described two-dimension integrated cross-correlation.
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| CN102525568A (en) * | 2012-01-17 | 2012-07-04 | 北京索瑞特医学技术有限公司 | Subtraction elastography method |
| CN102764141B (en) * | 2012-07-20 | 2014-05-21 | 中国科学院深圳先进技术研究院 | Elastography method, elastography system, and biological tissue displacement estimation method and biological tissue displacement estimation system in elastography |
| CN102920485A (en) * | 2012-10-30 | 2013-02-13 | 浙江大学 | Estimation method for biological tissue two-dimensional displacement field in ultrasonic elastography |
| CN102973296A (en) * | 2012-11-16 | 2013-03-20 | 清华大学 | Vascular tissue displacement estimation method |
| CN103040488B (en) * | 2012-12-21 | 2014-06-04 | 深圳大学 | System and method for real-time ultrasonic elastography displacement estimation |
| CN103211625B (en) * | 2013-01-11 | 2015-08-19 | 深圳市恩普电子技术有限公司 | Based on the biological displacement computational methods of elastogram |
| CN103735287B (en) * | 2013-12-05 | 2015-11-18 | 中国科学院苏州生物医学工程技术研究所 | A kind of intravascular ultrasound elastogram two-dimensional multistage mixing displacement estimation method |
| CN104799816A (en) * | 2015-04-17 | 2015-07-29 | 上海交通大学 | Evaluation device for implant damage and fretting damage of neural electrode |
| CN107095692B (en) * | 2016-02-19 | 2024-02-09 | 乐普（北京）医疗器械股份有限公司 | Ultrasonic imaging system, ultrasonic imaging method and one-dimensional displacement scanning method |
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