CN102525568A - Subtraction elastography method - Google Patents

Abstract

The invention relates to a subtraction elastography method, and belongs to the technical field of ultrasonic subtraction elastography. The method comprises the following steps of: carrying out certain compression on a tissue before injury is introduced, and collecting ultrasonic radio frequency data before and after compression; carrying out certain compression to the tissue after injury is introduced, and collecting ultrasonic radio frequency data before and after compression; calculating a displacement field of the tissue before injury is introduced according to the collected ultrasonic radio frequency data; calculating a displacement field of the tissue after injury is introduced according to the collected ultrasonic radio frequency data; and calculating a subtraction elastography image according to the results obtained in the two steps. The subtraction elastography method combines an elastography technology and a subtraction angiography technology, and can highlight differences in an elastography image, and inhibit the same background structure at the same time. Meanwhile, the invention provides an embodiment of strain field-based subtraction elastography and an embodiment of regular displacement field-based subtraction elastography. The method provided by the invention can be used in other elastography methods.

Description

A kind of elasticity subtraction imaging method

Technical field

The invention belongs to the ultrasonic elastograph imaging technical field of medical imaging, particularly a kind of elasticity subtraction imaging method.

Background technology

Elastogram can be provided as the hardness information of picture tissue as a kind of imaging pattern.In more than ten years, elastogram has obtained research in some Wicresoft's ablation monitoring are used in the past.In these ablations, through some physics or chemical method, produce local tissue necrosis, this process is accompanied by the variation of organizing hardness usually.For reaching therapeutic effect, require to extract fully lesion tissue on the one hand, want the least possible infringement surrounding health tissue on the other hand, therefore accurately assessing, the zone of coagulation necrosis is even more important.Elastogram develops so far, and the feasibility of its monitoring imaging in HIFU treatment, RF ablation, anhydrous alcohol injection for curing is verified.Other imaging mode; Also can be used in the monitoring of these treatments such as nuclear magnetic resonance (MRI), enhancement mode CT; But they are relatively more expensive; Mobility is not enough, is not simultaneously to be applicable to all patients (patient of the inapplicable band cardiac pacemaker of MRI, enhancement mode CT is not suitable for the patient who contrast agent is had severe allergic reaction).Ultra sonic imaging is also attempted being used for the monitoring of above-mentioned ablation, but because the sound characteristics of tissue is active and uncorrelated with tissue, so effect is unsatisfactory.Compare said method, elastogram can directly provide hardness information, and has real-time, low-cost, safe characteristics, therefore is expected to become a kind of Perfected process of ablation monitoring.

Tradition realizes that the elastograph imaging method step is following:

1) gathers the preceding ultrasonic rf data of tissue compression;

2) apply certain decrement from outer bound pair tissue, and obtain the ultrasonic rf data after the tissue compression;

3) according to step 2), the method for utilizing this professional to know to the data that obtain before and after the compression calculates strain field, thereby obtains the elastic image of response organization's Hardness Distribution.

But present elastogram has certain limitation.Possibly influence the final result of elastogram like the pseudo-shadow in some elastograms (the pseudo-shadow that mechanical pseudo-shadow, the pseudo-shadow of acoustics and signal processing method cause).And for some focuses, like inocarcinoma, hardness own is just big, though damage the variation that can cause hardness in the treatment, because background hardness is very big, contrast will diminish, thereby is difficult for detecting the firmness change that treatment causes.

In the medical imaging field, deshadowing technology is widely used.Cover plate image (mask image) through from trap image (live image), deducting, make that the difference in two width of cloth images is highlighted, identical background structure can be inhibited simultaneously.The application of deshadowing technology can suppress pseudo-shadow greatly, improves the signal noise ratio and the contrast noise ratio of imaging results.Now; The application that is widely known by the people most in the deshadowing technology is digital blood vessel substraction imaging (digital subtraction angiography; DSA), in the DSA flow process, at interested blood vessel bolus injection contrast agent; And obtain the digital X-ray projected image before and after the injection, afterwards two image subtractions are obtained not have the blood vessel substraction imaging of background information.

Though, widely people's research of elastogram, deshadowing technology is widely used in medical imaging, deshadowing technology is not used for the systematic study of elastogram and elastogram and these two kinds of technology of deshadowing technology are carried out bonded relevant report.

Summary of the invention

The objective of the invention is to overcome the weak point of existing elastogram technology; A kind of elasticity subtraction imaging method is proposed; This method combines elastogram technology and subtraction imaging technology, and image quality is improved, and can in the damage monitoring, obtain better effect than traditional elastogram.

The combination elastogram technology that the present invention proposes and the elasticity subtraction imaging method of subtraction imaging technology may further comprise the steps:

1) preceding tissue is introduced in damage and applied certain compression, and gather the ultrasonic rf data before and after the compression;

2) tissue after the damage introducing is applied certain compression, and gather the ultrasonic rf data before and after the compression;

3) the ultrasonic rf data of gathering according to step 1) calculates the displacement field (computational methods can adopt cross-correlation method, absolute and method, Doppler method, the displacement estimation method that these professionals such as correlation method knew) of the tissue before damage is introduced;

4) according to step 2) the ultrasonic rf data of being gathered calculates the displacement field (computational methods can adopt cross-correlation method, absolute and method, Doppler method, the displacement estimation method that these professionals such as correlation method knew) of the tissue after damage is introduced;

5) according to step 3), 4) result that obtains, the calculating elastic subtraction image.

Principle of the present invention:

Elastic image can be provided as the hardness information of picture tissue, and deshadowing technology covers plate image (mask image) through from trap image (live image), deducting, and can trap image and the difference of covering in the plate image be highlighted, and suppresses identical background structure simultaneously.The present invention just is being based on the These characteristics of elastic image and subtraction imaging technology; Thereby the elastic image that deducts before damage is introduced through the elastic image that will damage after introducing obtains the elasticity subtraction image, thus the better detection of the damage that obtains to introduce for treatment than the ordinary elasticity imaging.

Characteristics of the present invention:

1) the elastogram technology is combined with deshadowing technology.

2) can the difference in the image be highlighted, suppress identical background structure simultaneously, the pseudo-shadow that the stress concentration of introducing like the hard thing of background causes can be effectively suppressed.

3) can obtain higher signal noise ratio and contrast noise ratio, image quality is improved, and the power of test of damage in the tissue is got a promotion.

4) be not easy to receive the influence of sclerous tissues's background, and can provide and damage boundary information more reliably.

5) can adopt image fusion technology, elasticity subtraction imaging result is merged demonstration with other images, not only can highlight the nonhomogeneous hardness between two width of cloth elastic graph, and image background information can be provided.

Description of drawings

Fig. 1 is the elasticity subtraction imaging flow processs of embodiments of the invention 1 based on strain field;

Fig. 2 is the elasticity subtraction imaging flow processs of embodiments of the invention 2 based on regularization displacement field;

Fig. 3 is embodiment 1 and traditional method comparison diagram as a result;

Fig. 4 is embodiment 2 design sketch as a result.

The specific embodiment

A kind of elasticity subtraction imaging method that the present invention proposes combines specific embodiment and accompanying drawing to specify as follows:

Embodiment 1 is based on the embodiment of the elasticity subtraction imaging of strain field, and this embodiment comprises following several steps:

1) preceding tissue is introduced in damage and applied certain compression; And the ultrasonic rf data before and after the collection compression; Concrete steps are following: earlier according to shown in Fig. 1 (a); The preceding compression that longitudinally applies total length 1% of organizing is introduced in damage, and according to the ultrasonic rf data of gathering shown in Fig. 1 (b) before and after compressing.Suppose that the ultrasonic rf data of gathering comprises N bar scanning line, every scanning line comprises the L point data, and the corresponding actual range of adjacent two point data is Δ z.

2) tissue after the damage introducing is applied certain compression; And the ultrasonic rf data before and after the collection compression; Concrete steps are following: shown in Fig. 1 (d), the tissue after damage introduced vertically applies the compression of total length 1%, and according to the ultrasonic rf data of gathering shown in Fig. 1 (d) before and after the compression.Suppose that the ultrasonic rf data of gathering comprises N bar scanning line, every scanning line comprises the L point data, and the corresponding actual range of adjacent two point data is Δ z.

3) the ultrasonic rf data of gathering according to step 1) calculates the displacement field of the tissue before damage is introduced, and concrete steps are following:

3-1) scanning line before and after every in the step 1) compression being divided into length is that 2M+1, Center Gap are the L-2M segment data of 1 data points.The center of this L-2M segment data be respectively M+1 on the scanning line, M+2 ..., the L-M point.Be that data segment and the compression at center is the correlation coefficient C of the data segment at center with the q point on the k bar scanning line afterwards with the p point on preceding the k bar scanning line of compression then _{P, q}For:

$C_{p,q}=\frac{\underset{i=-M}{\overset{M}{\mathrm{\Σ}}}{r}_k(p+i)R_k(q+i)}{\sqrt{\underset{i=-M}{\overset{M}{\mathrm{\Σ}}}{\left(r_k(p+i)\right)}^2\underset{i=-M}{\overset{M}{\mathrm{\Σ}}}{\left(R_k(q+i)\right)}^2}}$

R wherein _k, R _kPreceding k bar scan-line data and compression back k bar scan-line data are compressed in representative respectively;

Be the correlation coefficient of all data segments on data segment and the compression back k bar scanning line at center 3-2), and search for and obtain correlation coefficient maximum

as follows through calculating on preceding the k bar scanning line of compression with p:

$C_{p,q_{\max }}=\max \{C_{p,q},q=M+1,M+2,...,L-M\}$

q _MaxFor

Q value when getting maximum, the center of just can arriving thus is in p ● the Δ z degree of depth, length are (2M+1) ● the displacement of the tissue fragment of Δ z before and after compression is following:

d ₁(z，k)| _{z＝p●Δz，k}＝(q _max-p)●Δz

Wherein, z representes the residing degree of depth in tissue fragment center;

3-3) each segment data on the k bar scanning line is repeated said process, just can obtain the displacement of the tissue fragment compression front and back of all data segments correspondences on the k bar scanning line, a sequence d is formed in these displacements ₁(z, k) | _{Z=(M+1) ● Δ z, (M+2) ● Δ z ..., (L-M) ● Δ z, k}

3-4) all scanning lines are repeated said process, before just can obtaining to damage introducing, the displacement field { d of tissue before and after the compression ₁(z, k) } | _{Z=(M+1) ● Δ z, (M+2) ● Δ z ..., (L-M) ● Δ z, k=1,2 ..., N}

4) according to step 2) the ultrasonic rf data of being gathered calculates the displacement field (the same step 3) of calculation procedure) of the tissue after damage is introduced, and obtains damaging the displacement field of the tissue after the introducing:

{d ₂(z，k)}| _{z＝(M+1)●Δz、(M+2)●Δz、…、(L-M)●Δz，k＝1、2、...、N}；

D wherein ₂(z is that central depths is the displacement of the corresponding tissue of data segment of z on the tissue k bar scanning line that damages after introducing k);

5) according to step 3), 4) the result, the calculating elastic subtraction image, concrete steps are following:

5-1), the displacement of the tissue before the damage introducing calculates the strain stress 1 of i the corresponding tissue of data segment on the k bar scanning line through being differentiated at depth direction _{I, k}, as follows:

${\mathrm{\ϵ}1}_{i,k}=\mathrm{\ϵ}1(z,k){|}_{z=(M+i)\·\mathrm{\Δz},k}=\frac{\∂d_1(z,k)}{\∂z}{|}_{z=(M+i)\·\mathrm{\Δz},k}$

Wherein ε 1 (z, k), d ₁(z; K) be respectively that central depths is the strain and the displacement of the corresponding tissue of data segment of z on the preceding tissue k bar scanning line of damage introducing; Δ z is the corresponding actual ranges of adjacent two point data, M for scanning line on the relevant constant (2M+1 is a data segment, length) of data segment, length;

With this can and obtain the corresponding tissue of each data segment on every scanning line before damage is introduced strain was constituted organizes stress distribution S1:

S ₁＝{ε1 _i，k}| _{i＝1、2、...、(L-2M)，k＝1、2、...、N}

Wherein L is the number of data points that every scanning line comprises, the number of scanning lines that N comprises for the ultrasonic rf data of gathering;

5-2) use above-mentioned steps 5-1) calculate strained method, calculate the corresponding tissue of each data segment on every scanning line after damage is introduced strain constituted organizes stress distribution S2:

S ₂＝{ε2 _i，k}| _{i＝1、2、...、(L-2M)，k＝1、2、...、N}

Wherein ε 2 _{I, k}It is the strain of i the corresponding tissue of data segment on the tissue k bar scanning line after damage is introduced;

5-3) according to step 5-1) and result 5-2), after damage introduced organize stress distribution S2 to deduct damage to introduce before the stress distribution S1 that organizes promptly obtain elasticity outline imaging S _Sub, that is:

S _sub＝S ₂-S ₁＝{ε2 _i，k-ε1 _i，k}| _{i＝1、2、...、(L-2M)，k＝1、2、...、N}。

Embodiment 1 is based on the method for strain field, and it is in full accord that this method requires that the decrement of being applied for tissue in front and back is introduced in damage, otherwise the difference of decrement will be introduced bigger noise and make the subtraction imaging poor in subtracting the shadow result.

Embodiment 2 is based on the embodiment of the elasticity subtraction imaging of regularization displacement field, can handle the damage front and back based on the elasticity subtraction imaging of regularization displacement field and organize the inconsistent situation of suffered decrement.Through regularization processing to displacement field, even the decrement difference of front and back to tissue introduced in damage, also can obtain elasticity subtraction imaging result preferably, this embodiment comprises following several steps:

1) preceding tissue is introduced in damage and applied certain compression; And gather the ultrasonic rf data before and after the compression, concrete steps are following: shown in Fig. 2 (a), it is 1% compression that organizing before damage introduced longitudinally applies total length; And the ultrasonic rf data before and after collection is compressed shown in Fig. 2 (b); Suppose that the ultrasonic rf data of gathering comprises N bar scanning line, every scanning line comprises the L point data, and the corresponding actual range of adjacent two point data is Δ z.

2) tissue after the damage introducing is applied certain compression; And gather the ultrasonic rf data before and after the compression, concrete steps are following: shown in Fig. 2 (d), it is 2% compression that organizing after damage introduced longitudinally applies total length; And the ultrasonic rf data before and after collection is compressed shown in Fig. 2 (e); Suppose that the ultrasonic rf data of gathering comprises N bar scanning line, every scanning line comprises the L point data, and the corresponding actual range of adjacent two point data is Δ z.

3) the ultrasonic rf data of gathering according to step 1) calculates the displacement field of the tissue before damage is introduced, and concrete steps are following:

3-1) scanning line before and after every in the step 1) compression being divided into length is that 2M+1, Center Gap are the L-2M segment data of 1 data points.The center of this L-2M segment data be respectively M+1 on the scanning line, M+2 ..., the L-M point.Be that data segment and the compression at center is the correlation coefficient C of the data segment at center with the q point on the k bar scanning line afterwards with the p point on preceding the k bar scanning line of compression then _{P, q}For:

$C_{p,q}=\frac{\underset{i=-M}{\overset{M}{\mathrm{\Σ}}}{r}_k(p+i)R_k(q+i)}{\sqrt{\underset{i=-M}{\overset{M}{\mathrm{\Σ}}}{\left(r_k(p+i)\right)}^2\underset{i=-M}{\overset{M}{\mathrm{\Σ}}}{\left(R_k(q+i)\right)}^2}}$

R wherein _k, R _kPreceding k bar scan-line data and compression back k bar scan-line data are compressed in representative respectively;

Be the correlation coefficient of all data segments on data segment and the compression back k bar scanning line at center 3-2), and search for and obtain correlation coefficient maximum

as follows through calculating on preceding the k bar scanning line of compression with p:

$C_{p,q_{\max }}=\max \{C_{p,q},q=M+1,M+2,...,L-M\}$

q _MaxFor

Pairing q value, the center of just can arriving thus is in p ● the Δ z degree of depth, length are (2M+1) ● the displacement of the tissue fragment of Δ z before and after compression is following:

d ₁(z，k)| _{z＝p●Δz，k}＝(q _max-p)●Δz

Wherein, z representes the residing degree of depth in tissue fragment center;

3-3) each segment data on the k bar scanning line is repeated said process, just can obtain the displacement of the tissue fragment compression front and back of all data segments correspondences on the k bar scanning line, a sequence d is formed in these displacements ₁(z, k) | _{Z=(M+1) ● Δ z, (M+2) ● Δ z ..., (L-M) ● Δ z, k}

3-4) all scanning lines are repeated said process, before just can obtaining to damage introducing, the displacement field { d of tissue before and after the compression ₁(z, k) } | _{Z=(M+1) ● Δ z, (M+2) ● Δ z ..., (L-M) ● Δ z, k=1,2 ..., N}

4) according to step 2) the ultrasonic rf data of being gathered calculates the displacement field (the same step 3) of calculation procedure) of the tissue after damage is introduced

{d ₂(z，k)}| _{z＝(M+1)●Δz、(M+2)●Δz、…、(L?M)●Δz，k＝1、2、...、N}

D wherein ₂(z is that central depths is the displacement of the corresponding tissue of data segment of z on the tissue k bar scanning line that damages after introducing k);

5) according to step 3), 4) the result, the calculating elastic subtraction image, concrete steps are following:

The displacement field of the tissue after the damage of 5-1) step 4) being calculated is introduced carries out following regularization processing:

${\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA0000131720480000021.png"\; state="\{\{state\}\}">d</figure-callout>}}_2^{\&prime;}(z,k)=d_2(z,k)\&CenterDot;\frac{d_1((L-M)\&CenterDot;\mathrm{\&Delta;z},k)}{d_2((L-M)\&CenterDot;\mathrm{\&Delta;z},k)}{|}_{z=(M+1)\&CenterDot;\mathrm{\&Delta;z},(M+2)\&CenterDot;\mathrm{\&Delta;z},\&CenterDot;\&CenterDot;\&CenterDot;,(L-M)\&CenterDot;\mathrm{\&Delta;z},k=\mathrm{1,2},...,N}$

D wherein ₂(z, k), d ' ₂(z, k) be respectively on the tissue k bar scanning line after damage is introduced central depths be z the corresponding tissue of data segment displacement and to the displacement after this regularization of displacement processing, d ₁((L-M) Δ z, k), d ₂((L-M) Δ z; K) be respectively the displacement that the many corresponding tissues of last data segment on the k bar scanning line of front and back are introduced in damage; L is the number of data points that every scanning line comprises; Δ z is the corresponding actual ranges of adjacent two point data, M for scanning line on the relevant constant (2M+1 is a data segment, length) of data segment, length, the number of scanning lines that N comprises for the ultrasonic rf data of collection;

Thereby obtain the displacement field after new regularization:

{d′ ₂(z，k)}| _{z＝(M+1)●Δz、(M+2)●Δz、…、(L?M)●Δz，k＝1、2、...、N}；

Displacement field before the damage that 5-2) utilizes displacement field and step 3) after regularization to calculate is introduced subtracts the shadow operation, obtains subtracting shadow displacement field D _Sub:

D _sub＝{d′ ₂(z，k)-d ₁(z，k)}| _{z＝(M+1)●Δz、(M+2)●Δz、…、(L?M)●Δz，k＝1、2、...、N}

D wherein ₁(z is that central depths is the displacement of the corresponding tissue of data segment of z on the preceding tissue k bar scanning line of damage introducing k);

5-3) subtract shadow displacement field D to what obtain _SubObtain elasticity subtraction imaging S along tissue depth direction differential _Sub:

$S_{\mathrm{sub}}=\frac{{\&PartialD;D}_{\mathrm{sub}}}{\&PartialD;z}$

$=\left\{\frac{\&PartialD;({\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA0000131720480000021.png"\; state="\{\{state\}\}">d</figure-callout>}}_2^{\&prime;}(z,k)-d_1(z,k))}{\&PartialD;z}\right\}{|}_{z=(M+1)\&CenterDot;\mathrm{\&Delta;z},(M+2)\&CenterDot;\mathrm{\&Delta;z},\&CenterDot;\&CenterDot;\&CenterDot;,(L-M)\&CenterDot;\mathrm{\&Delta;z},k=\mathrm{1,2},...,N}.$

The present invention is to introducing the imaging effect of damage in the uniform formation.

Embodiment 1 is following with prior elastic formation method effect:

Among Fig. 3, Fig. 3 (a) is the modulus scattergram of damage model, and model is in the B1 of uniform formation of a 5cm*5cm, introduces the circle damage E1 of a diameter 1cm, and the elastic modelling quantity of damage is 5 times of background uniform formation; Fig. 3 (b) is the desirable diagram of strains of model under 1% vertical compression among Fig. 3 (a), can see that damage is rendered as the dark partially low strain zone of color; Fig. 3 (c) and Fig. 3 (d) are the elastic graph after introducing with damage before the damage of adopting traditional elastograph imaging method to calculate is introduced; Can see common elastic graph from Fig. 3 (d); The damage of introducing is rendered as the dark partially low strain zone of color; But because effect of noise, Fig. 3 (d) also has the homogeneous background part among Fig. 3 (c) not present a homogeneous area, thereby makes the prior elastic imaging receive effect of noise for the imaging results on especially its border of damage; Fig. 3 (e) is elasticity subtraction imaging result of the present invention, can see background noise by good restraining, damages better must having obtained and highlights, and the result is in close proximity to the desirable diagram of strains shown in Fig. 3 (b).Fig. 3 (e) and Fig. 3 (d) relatively can see in the elastic graph of damage before and after introducing, and similar background parts subtracts among the shadow figure in elasticity and is cancelled, and correspondence position damage border is also very clear; In addition, the noise in the elastic graph subtracts in elasticity and has also arrived better inhibited among the shadow figure.Therefore elasticity subtraction imaging method has better effect than traditional elastograph imaging method aspect the damage monitoring.

Among the embodiment 2 based on the elasticity subtraction imaging method effect of regularization displacement field:

Among Fig. 4, Fig. 4 (a) is in uniform formation's model of a 5cm*5cm, applies vertical compression of 1%, and gathers the ultrasonic rf data in compression front and back; Fig. 4 (b) after in this uniform formation's model, introducing the sclerosis damage of diameter 1cm, applies vertical compression of 2%, and gathers the ultrasonic rf data in compression front and back; Fig. 4 (c) utilizes damage to introduce the displacement of tissue field under 1% compression of preceding ultrasonic rf data calculating; Fig. 4 (d) is the displacement of tissue field that utilizes under 2% compression that damages the ultrasonic rf data calculating after introducing; The advanced professional etiquette integralization in displacement of tissue field after Fig. 4 (e) will damage and introduce is handled, and the displacement of tissue field before introducing with damage then subtracts the shadow operation, and what obtain subtracts the shadow displacement field; Fig. 4 (f) is that the elasticity that the shadow displacement field obtains along the depth direction differential that subtracts shown in Fig. 4 (e) subtracts shadow figure, and in the figure, the damage of the circle of introducing is rendered as the darker zone of color, and edge clear, and background noise seldom.Therefore, based on the elasticity subtraction imaging method of regularization displacement field, introduce front and back tissue compression amount condition of different among the employing embodiment 2 for damage, also can obtain effect preferably.

Claims (3)

1. elasticity subtraction imaging method is characterized in that this method may further comprise the steps:

1) preceding tissue is introduced in damage and applied certain compression, and gather the ultrasonic rf data before and after the compression;

2) tissue after the damage introducing is applied certain compression, and gather the ultrasonic rf data before and after the compression;

3) the ultrasonic rf data of gathering based on step 1) calculates the displacement field of the tissue before damage is introduced;

4) according to step 2) the ultrasonic rf data of being gathered calculates the displacement field of the tissue after damage is introduced;

5) according to step 3), 4) result that obtains, the calculating elastic subtraction image.

2. method according to claim 1 is characterized in that, said step 5) calculating elastic subtraction image, and concrete steps are following:

5-1), the displacement of the tissue before the damage introducing calculates the strain stress 1 of i the corresponding tissue of data segment on the k bar scanning line through being differentiated at depth direction _{I, k}, as follows:

${\mathrm{\&epsiv;}1}_{i,k}=\mathrm{\&epsiv;}1(z,k){|}_{z=(M+i)\&CenterDot;\mathrm{\&Delta;z},k}=\frac{\&PartialD;d_1(z,k)}{\&PartialD;z}{|}_{z=(M+i)\&CenterDot;\mathrm{\&Delta;z},k}$

Wherein ε 1 (z, k), d ₁(z; K) be respectively that central depths is the strain and the displacement of the corresponding tissue of data segment of z on the preceding tissue k bar scanning line of damage introducing; Δ z is the corresponding actual ranges of adjacent two point data, M for scanning line on the relevant constant (2M+1 is a data segment, length) of data segment, length;

With this obtain to damage the corresponding tissue of each data segment on every scanning line before introducing strain was constituted organizes stress distribution S1:

S ₁＝{ε1 _i，k}| _{i＝1、2、...、(L-2M)，k＝1、2、...、N}

Wherein L is the number of data points that every scanning line comprises, the number of scanning lines that N comprises for the ultrasonic rf data of gathering;

5-2) use above-mentioned steps 5-1) calculate strained method, calculate the corresponding tissue of each data segment on every scanning line after damage is introduced strain constituted organizes stress distribution S2:

S ₂＝{ε2 _i，k}| _{i＝1、2、...、(L-2M)，k＝1、2、...、N}

Wherein ε 2 _{I, k}It is the strain of i the corresponding tissue of data segment on the tissue k bar scanning line after damage is introduced;

5-3) according to step 5-1) and result 5-2), after damage introduced organize stress distribution S2 to deduct damage to introduce before the stress distribution S1 that organizes promptly obtain elasticity outline imaging S _Sub, that is:

S _sub＝S ₂-S ₁＝{ε2 _i，k-ε1 _i，k}| _{i＝1、2、...、(L-2M)，k＝1、2、...、N}。

3. method according to claim 1; It is characterized in that, said step 5) calculating elastic subtraction image, concrete steps are following:

The displacement field of the tissue after the damage of 5-1) step 4) being calculated is introduced carries out following regularization processing:

$d_2^{\&prime;}(z,k)=d_2(z,k)\&CenterDot;\frac{d_1((L-M)\&CenterDot;\mathrm{\&Delta;z},k)}{d_2((L-M)\&CenterDot;\mathrm{\&Delta;z},k)}{|}_{z=(M+1)\&CenterDot;\mathrm{\&Delta;z},(M+2)\&CenterDot;\mathrm{\&Delta;z},\&CenterDot;\&CenterDot;\&CenterDot;,(L-M)\&CenterDot;\mathrm{\&Delta;z},k=\mathrm{1,2},...,N}$

D wherein ₂(z, k), d ' ₂(z, k) be respectively on the tissue k bar scanning line after damage is introduced central depths be z the corresponding tissue of data segment displacement and to the displacement after this regularization of displacement processing, d ₁((L-M) ● Δ z, k), d ₂((L-M) ● Δ z; K) be respectively the displacement that the corresponding tissue of last data segment on the k bar scanning line of front and back is introduced in damage; L is the number of data points that every scanning line comprises; Δ z is the corresponding actual ranges of adjacent two point data, M for scanning line on the relevant constant (2M+1 is a data segment, length) of data segment, length, the number of scanning lines that N comprises for the ultrasonic rf data of collection; Thereby obtain the displacement field after new regularization:

{d′ ₂(z，k)}| _{z＝(M+1)●Δz、(M+2)●Δz、…、(L?M)●Δz，k＝1、2、...、N}；

Displacement field before the damage that 5-2) utilizes displacement field and step 3) after regularization to calculate is introduced subtracts the shadow operation, obtains subtracting shadow displacement field D _Sub:

D _Sub=d ' ₂(z, k)-d ₁(z, k) } | _{Z=(M+1) ● Δ z, (M+2) ● Δ z ..., (L M) ● Δ z, k=1,2 ..., N}D wherein ₁(z is that central depths is the displacement of the corresponding tissue of data segment of z on the preceding tissue k bar scanning line of damage introducing k);

5-3) subtract shadow displacement field D to what obtain _SubDirection differential along tissue depth obtains elasticity subtraction imaging S _Sub:

$S_{\mathrm{sub}}=\frac{{\&PartialD;D}_{\mathrm{sub}}}{\&PartialD;z}$

$=\left\{\frac{\&PartialD;(d_2^{\&prime;}(z,k)-d_1(z,k))}{\&PartialD;z}\right\}{|}_{z=(M+1)\&CenterDot;\mathrm{\&Delta;z},(M+2)\&CenterDot;\mathrm{\&Delta;z},\&CenterDot;\&CenterDot;\&CenterDot;,(L-M)\&CenterDot;\mathrm{\&Delta;z},k=\mathrm{1,2},...,N}.$

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