The present invention relates to the technical field of ultrasonic shear wave elasticity imaging, and more particularly relates to a first-order estimation method of shear wave velocity.
Medical ultrasound equipment evaluates tissue hardness by measuring the movement speed of shear wave in human tissue. This technology is used in various diagnostic applications, such as evaluating liver diseases. Shear wave velocity can characterize tissue hardness characteristics to allow detection of tumors or other parts.
The conventional method of calculating shear wave velocity is:
The above method needs to calculate the instantaneous velocity vl(t) of the particle at first, then calculate the displacement ∫0Tvl(t)dt, and finally calculate the shear wave velocity vs(t). The calculation process is complicated, and the calculated displacement curve is susceptible to the signal-to-noise ratio of the ultrasonic signal and the human motion, resulting in inaccurate and poor stable shear wave velocity.
The present invention provides a first-order estimation method that can efficiently and accurately estimate the shear wave velocity.
According to the present invention, the first-order estimation of shear wave velocity includes the following steps.
Entry data is demodulated. During an ultrasonic inspection process, an ultrasonic echo signal is converted into an electrical signal by an ultrasonic probe, and the electrical signal is converted into digital echo data by an ultrasonic equipment. In this step, a data matrix is formed with different echo data obtained at different scanning positions and different scanning times during the ultrasonic inspection process. And the data matrix is formed to an entry matrix I1 based on IQ data in complex form by a quadrature modulation.
Angle value of the complex IQ data is calculated. The angle value of the complex IQ data of each data point of the matrix I1 demodulated by the entry data is calculated, and a real number of the corresponding data point is obtained to form an angle value matrix I2.
An average evaluation of the angle value matrix is obtained. In this step, the real average value of all data at the same scanning position of the angle value matrix I2 is calculated to obtain a single-column mean value matrix I3.
An offset matrix is obtained. In this step, a matching matrix I4 is introduced. The matching matrix I4 is a single-row matrix which has the same columns as the angle value matrix I2 and its data point values are all real numbers “1”. The mean matrix I3 is multiplied by the matching matrix I4 to obtain the offset matrix I5.
A displacement matrix is obtained. In this step, by the mutual operations of the angle value matrix I2 and the offset matrix I5, the displacement matrix I6 is obtained. The displacement matrix I6 is the displacement value of the particle that changes with time in the propagation of the shear wave.
The shear wave velocity is calculated. In this step, the data of the displacement matrix I6 is formed into multiple sets of displacement curves on the coordinate axis, and the highest point of each displacement curve is taken to calculate the shear wave velocity Vs(t).
In the step of entry data demodulation, the matrix rows of the data matrix are echo information of different scanning positions; and the matrix columns are echo information at the same position at different scanning times.
In the coordinate system where the displacement curve is located, the ordinate is distance, and the abscissa is time.
The expression of the data points of the entry matrix I1 is Zn=an+bn*j, and the solution formula of the data points of the angle value matrix I2 is An=sin−1(bn/an).
In the formula of the shear wave velocity, Vs(t)=sn/tn, sn is the distance difference between the highest point of each displacement curve in each set of displacement curves, and tn is the corresponding time difference between the highest point of each displacement curve in each set of displacement curves.
The method further includes the following steps.
The displacement curve is decomposed and reconstructed. After the singular value decomposition of the displacement matrix I6, a construction matrix I7 is obtained based on the singular value matrix obtained by the decomposition.
Specifically, the formula for solving the reconstruction matrix I7 is I7=U*S*V. In this formula, U is a left singular matrix, V is a right singularity Matrix and S is a diagonal matrix containing singular values.
According to the present invention, the first-order estimation of the shear wave velocity extracts the main contour of the displacement curve by the orthogonal decomposition of matrix, thereby improving the signal quality of the shear wave estimation. And unlike conventional method, which needs estimating twice, the present invention can estimate the shear wave's displacement curve directly to reduce estimation errors and improve estimation efficiency.
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The invention will be described in detail with embodiments.
A first-order estimation method of shear wave velocity in an embodiment of the invention takes a complex matrix of a 4 by 9 array as the entry matrix I1 as an example. The specific operation process is as follows.
First is the entry data demodulation. A data matrix is formed with different echo data obtained at different scanning positions and different scanning times during the ultrasonic inspection process. And then the data matrix is formed to an entry matrix I1 by a quadrature modulation. The entry matrix I1 takes IQ data in complex form as data points. Specifically, in demodulation, the matrix rows of the data matrix are echo information of different scanning positions; and the matrix columns are echo information at the same position at different scanning times. The obtained entry matrix I1 is shown in
Then the angle value of the entry matrix I1 is calculated. The angle value of the complex IQ data of each data point of the matrix I1 demodulated by the entry data is calculated, and the real number of the corresponding data point is obtained to form an angle value matrix I2. The expression of the data points of the entry matrix I1 is Zn=an+bn*j, and the solution formula of the data points of the angle value matrix I2 is
The obtained angle value matrix I2 of the 4 by 9 array in this embodiment is shown in
The average of the matrix based on the angle value matrix I2 is obtained. In this step, the average value of all data at the same scanning position of the angle value matrix I2 is calculated to obtain a single-column mean value matrix I3. The average calculation method is conventional, which is to calculate the average value of all data in the same column. For this embodiment, for the above column contains 9 data, the formula of average value of the column is m=(i1+i2+ . . . i9)/9 Specifically, the mean matrix I3 of the 1 by 4 array in this embodiment is obtained as shown in
An offset matrix on the base of mean matrix I3 is obtained. In this step, a matching matrix I4 is introduced. The matching matrix I4 is a single-row matrix which has the same columns as the angle value matrix I2 and its data point values are all real numbers “1”. The mean matrix I3 is multiplied by the matching matrix I4 to obtain the offset matrix I5.
That is, the offset matrix I5 is the product of the mean matrix I3 and the matching matrix I4. The specific offset matrix I5 in this embodiment is shown in
By mutual operations of the angle value matrix I2 and the offset matrix I5, a displacement matrix I6 is obtained. The displacement matrix I6 is the displacement value of the particle that changes with time in the propagation of the shear wave. Actual displacement matrix I6 is the difference between the angle value matrix I2 and the offset matrix I5. That is, the corresponding data points of the matrix are performed operation to obtained the displacement matrix I6. The displacement matrix I6 of the present embodiment is as shown in
The shear wave velocity is calculated by the displacement matrix I6. In this step, the data of the displacement matrix I6 is formed into multiple sets of displacement curves on the coordinate axis, and the highest point of each displacement curve is taken to calculate the shear wave velocity Vs(t). In the coordinate system where the displacement curve is located, the ordinate is distance, and the abscissa is time. In the formula of the shear wave velocity,
sn is the distance difference between the highest point of each displacement curve in each set of displacement curves, tn is the corresponding time difference between the highest point of each displacement curve in each set of displacement curves.
After the shear wave velocity is obtained, an orthogonal decomposition and reconstruction of the displacement curve can be performed to further remove the noise of the displacement curve, and keep the most critical message of the displacement curve, so as to make displacement curve more precise and the final estimation more accurate. Specifically, it includes the following steps.
The displacement curve is decomposed and reconstructed. After the singular value decomposition of the displacement matrix I6, a construction matrix I7 is obtained based on the singular value matrix obtained by the decomposition.
After performing singular value decomposition on the displacement matrix I6, a left singular matrix U, a diagonal matrix S containing the singular values and a right singular matrix V can be obtained.
The left singular matrix U in the present embodiment is a 4 by 4 array matrix, as shown in
The diagonal matrix S of the singular values in the present embodiment is a 4 by 9 matrix, as shown in
The right singular matrix Vin the present embodiment is a 9 by 9 matrix, as shown in
Specifically, the solution formula of the reconstruction matrix I7 is I7=U*S0*VT, in which S0 is the diagonal matrix based on the first two singular values, and VT is the right singular matrix based on the first 4 columns, as shown in
The reconstruction matrix I7 after reconstruction in the present embodiment is as shown in
Compared with the unreconstructed displacement matrix I6, the reconstructed reconstruction matrix I7 can obtain a smoother and more consistent displacement curve, which can in turn obtain a more accurate shear wave velocity Vs(t). The method of directly estimating the particle displacement curve based on the complex matrix constructed from the original data and improving the estimation accuracy of velocity by matrix reconstruction is called first-order estimation.
The above content is a further detailed description of the invention with specific preferred embodiments. It cannot be considered that the specific embodiment of this invention is limited to these descriptions. For those skilled in the art, simple deductions or substitutions which can be made without departing from the concept of the invention, should be regarded that it is within the protection scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
201911051147.2 | Oct 2019 | CN | national |
The present application is a continuation of International Application No. PCT/CN2019/116431, filed on Nov. 8, 2019, which claims priority from Chinese Patent Application No. 201911051147.2 filed on Oct. 31, 2019, all of which are hereby incorporated herein by reference.
Number | Date | Country |
---|---|---|
103431874 | Dec 2013 | CN |
103519848 | Jan 2014 | CN |
104546014 | Apr 2015 | CN |
104739451 | Jul 2015 | CN |
105212961 | Jan 2016 | CN |
107616814 | Jan 2018 | CN |
109589138 | Apr 2019 | CN |
2013102959 | May 2013 | JP |
WO-2019179758 | Sep 2019 | WO |
Number | Date | Country | |
---|---|---|---|
20210378636 A1 | Dec 2021 | US |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/CN2019/116431 | Nov 2019 | US |
Child | 17411751 | US |