JPH0417842A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To obtain information on a position and a degree of hardness of a tissue by detecting a displacement rate of tissues at points using a pulse Doppler method to calculate a degree of change in the displacement rate depending on location. CONSTITUTION:A received signal 1 serves as an input of a rate detection means 2, a B-mode image generation means 8 and an M-mode image generation means 9. The rate detection means 2 composed of an orthogonal detection circuit or the like detects a depth-wise displacement rate of a tissue at an optional depth. A memory 3 is provided to store a depth-wise displacement rate of the tissue in a specified scan line or the displacement rate of the tissue in a plurality of scan lines within a certain interest area. A depth-wise differentiation means 4 differentiates the displacement rate calculated by the means 2 in depth-wise direction. An effective value detection means 5 calculates an effective value of a shift rate calculated by the means 4. A display means 6 is provided to display a two-dimensional function of time and depth of the shift rate in a scan line specified, a second dimensional distribution image of a spatial shift rate in a certain interest area which is obtained by scanning of the scan line or the effective value of the shift rate calculated by the means 5 in a combination of a B-mode image and an M-mode image.

Description

[Detailed Description of the Invention] [Summary] Regarding an ultrasonic diagnostic device equipped with a means for calculating and displaying the elastic properties of living tissue, the displacement velocity of the m weave at each depth obtained by the pulsed Doppler method is calculated in the depth direction. The purpose of this method is to calculate and display the "shear rate," which indicates the degree of tissue expansion and contraction, by differentiating the a velocity detecting means for detecting the displacement velocity of the tissue within the subject's body at each depth using a plurality of received signals; a depth direction differentiating means for differentiating the detected velocity in the depth direction; an effective value calculating means for calculating the effective value of the shear rate obtained by the depth direction differentiating means, and a two-dimensional function of time and depth, or a spatial As a two-dimensional distribution image,
Further, the present invention is configured to include display means for displaying the results obtained by the effective value calculation means as numerical values.

[Industrial Field of Application] The present invention is based on differentiating the displacement velocity of tissue at each depth obtained by the pulsed Doppler method in the depth direction, thereby calculating the elastic range, which indicates the degree of expansion and contraction of the tissue. The present invention relates to an ultrasonic diagnostic apparatus that calculates and displays diagnostic characteristics.

[Prior art and problems to be solved by the invention] Conventionally, as an ultrasonic diagnostic device that displays the elastic properties of tissue, the seventh
As shown in the figure, low-frequency vibration is applied from outside the living body and the amplitude and phase distribution of vibration waves propagating inside the living body are measured (Proceedings of the 52nd Japanese Society of Ultrasonics in Medicine 52-143).
P2S5-288 and Proceedings of the 53rd Japanese Society of Ultrasound in Medicine 53-83. P271-272), and the one that attempts to measure minute displacements of unrestricted Mi fabric using the spatial correlation function of the analytical signal as shown in Figure 8 (Proceedings of the 54th Japanese Society of Ultrasonics in Medicine, 54-116). P2S5-360) has been proposed.

FIG. 7 shows the positional relationship between the probe position and the mechanical vibrator for measuring the vibration amplitude and phase distribution of the vibration wave propagating inside the living body when low frequency vibration is applied.

The mechanical vibrator 2o applies vibration to the medium 19 through the flat plate 21 at a frequency of about 10 kHz to 1 kHz. Further, the ultrasonic pulses transmitted from the probe 11 are reflected inside the medium and are received by the probe 11. FIG. 7 shows an attempt to obtain the vibration amplitude and phase distribution of the vibration wave 22 using this received signal. 23 is a contact agent between the probe and the body surface, and 24 is a spring for absorbing vibrations of the mechanical vibrator 20.

FIG. 8 shows a method of measuring tissue displacement using a two-dimensional correlation function of analytical signals. In FIG. 8, reference numeral 11 denotes an ultrasonic probe for transmitting and receiving ultrasonic waves, and a transmitting/receiving circuit 10.
connected to. 1° is a transmitting/receiving circuit including a beamformer, etc., which generates a single word to drive the group of transducers that are the components of the processor 11, and focuses the signal received by each transducer in a specific direction. Generate received signal 1. The received signal I is sent to the next stage analysis signal generation means 12. 12, if the received signal is xr(t),
A signal xi(t) orthogonal to xr(t) is generated, and the complex signal Z(t)=xr(t)-1-j xi(t) is stored in the memory 13. 13 stores the received complex signals z(t) corresponding to all the scanning lines in multiple frames.

Here, in a certain frame, scanning line m and depth n! The two-dimensional complex signal data to the left is A (m, n)=Ar
(m, n) −= jAi (m, n) Expression (1) Expressed as follows. Also, in another frame, scanning line m,
Two-dimensional complex signal data at a depth n4 is expressed as B (m, n
) = Br (m, n) + jBi (m, n) Equation (2) The two-dimensional cross-correlation function C (τ, ρ1m, n) around (m, n) can be defined by the following equation .

C(τ, ρ1m, n) = <A(m, n)B” (m+r, n+ρ)>[<
l A(m,n) 12 >< l B(m+r
, n+ ρ ) l 2 > ko 1'' Equation (3) Here, <> in the above equation indicates an average operation in two-dimensional space.The maximum value of the above equation is calculated, and in the complex space, (1, 0), the displacement vector can be calculated.

14 is for calculating the two-dimensional cross-correlation function of equation (3), and 15 is a memory for storing the two-dimensional cross-correlation function calculated at an arbitrary position. The minute displacement detection means 16 calculates the displacement vector and displays the result on the display means 17.
send to The displacement vector calculated at each position is shown in Figure 8 (
As shown in b), the inclination of the vector is displayed as the direction of movement, and the length of the vector is displayed as the amount of movement.

However, the method shown in Figure 7 requires a mechanical system to apply external vibrations, which is impractical, and the method shown in Figure 8 is insufficient for calculating two-dimensional cross-correlation functions. Since it requires a wide area, it is difficult to obtain high spatial resolution, and there is a problem that calculation processing time is required.

By the way, in vivo tissues are displaced due to movements such as pulsation. The displacement speed of this tissue is not uniform but varies because the hardness differs depending on the location S. Variations in the speed of displacement depending on the location (This refers to the expansion and contraction of the tissue. For example, at a certain depth; pay attention to this. At a point closer to the probe than this depth, the speed of displacement toward the probe is 4 Fl- from that depth. If the displacement rate is faster than the displacement rate at that depth, it means that the tissue is being stretched.

If an abnormal tissue that is harder than the normal tissue exists within the normal tissue, it is considered that the variation in displacement speed within the hard abnormal tissue depending on the location is smaller than that of the normal tissue.

The present invention aims to display elastic properties by detecting the displacement speed of tissue at each location using the pulsed Doppler method and calculating the degree of change in the displacement speed depending on the location.

[Means for Solving the Problems] Specific means for solving the above problems will be explained using FIGS. 2 and 3.

Conventionally, a method of detecting blood flow velocity using the pulsed Doppler method is known. In the present invention, this technique is used to detect tissue displacement velocity. Reference numeral 2 in FIG. 3 is a bronch explaining this detection method.

In FIG. 3, 2-1 to 2-6 constitute quadrature detectors. Therefore, the output of the low-pass filter (LPF) 2-5 is the real part component of the orthogonal detection output of the received signal 1. Further, the output of the low-pass filter (LPF) 2-6 is the imaginary part component of the orthogonal detection output of the received signal 1.

The real part component of the orthogonal detection output of the received signal when ultrasonic pulses are transmitted eight times at intervals of period T in the same scanning line direction is calculated as the second
In the figure (a), it is indicated by R,, R2, ..., R9.

Similarly, the imaginary component is shown in II2. in FIG. 2(a).・・・・・・
...Denoted as 21N. These signal sequences are temporarily stored in the memory 2-9.2-10, respectively. Using the pulsed Doppler method, the displacement velocity in the depth direction at a certain depth can be calculated as follows.

As shown by the dotted arrow in FIG. 2(a), the complex signal sequence V, (Z) read in the time direction at depth Z is expressed as v, , (z ) −(R+(z), . . . ...RN
-, (z)) -J (11(z), ......,
Expressed as lN-1 (1)) 2 (4). Further, the complex signal sequence V is read out in the time direction at a depth Z with a period T shifted.

(z) to Vr, -1(z) -(R2(Z),...
R+(z))J(lz(z),=-,IN(z)
) is expressed as equation (5).

In FIG. 3, a complex autocorrelator 2-11 calculates a correlation coefficient between the two complex signal sequences. That is, the correlation coefficient Y, (z) is Yn (Z) = V, , (z) v, ” (
Z) = lYn (z) lexp (jΔθ, (2))
Formula (6) Mi YIIR (z) + J Ynr (
z) Equation (7) is obtained. Here, ° is the complex conjugate, Y-*(z) is the real component of the correlation coefficient, Ynl
(Z) is the imaginary component of the correlation coefficient, Δθ, and (z) is the phase difference caused by the Doppler effect.

From the above formula, the Doppler shift frequency fd, , (Z) is f
dn (z) = tan-' [Ynl(z)
/Yfi*(z) ]/T/(2π) =Δθ, (z)/T/(2π) Equation (8) is obtained.

Therefore, the displacement rate in the depth direction of the tissue is v, , (z)
-Lfi(z)C/ (2fo) Formula (9) is obtained. However, fo is the center frequency of the transmitted ultrasonic pulse, C
is the speed of sound.

In FIG. 3, the speed calculation unit 2-12 is for calculating equation (9). A conceptual diagram of the displacement speed in the depth direction of the tissue calculated for all depths is shown in FIG. 2(b).

Elastic tissue parameters that indicate the degree of tissue expansion and contraction:
Since it can be expressed by the degree of change of the displacement velocity depending on the location, it can be obtained by differentiating the displacement velocity shown in FIG. 2(b) twice in the depth direction. We define n as the "shear rate" 5 (z) representing the expansion and contraction of Mi as follows.

S,, (z)-dv, (z)/dz 2〇〇)
The shear velocity S, , (z) obtained by differentiating the displacement velocity v, (z) of the 21st m (b) in the depth direction as shown in (10) is conceptually shown in Figure 2 (C).

Increase the number of times the waves are transmitted in the same scanning line direction, that is, make N collection balls), and set the shear rate S, (z) to nn'-1, n÷2.
．． Iteratively calculates s, , (Z), S as a two-dimensional function of time and depth for a certain scanning line;
r+. , (z), = can be displayed. Furthermore, by scanning the scanning lines, it is possible to display a spatial two-dimensional distribution image of Sn (z) obtained for each scanning line.

Furthermore, by displaying the image in combination with the B-mode image and M-mode image of a conventional ultrasonic diagnostic apparatus, it becomes possible to accurately judge the state of expansion and contraction of the target region.

Also, in a certain scanning line, the depth z=jΔZj=0.1
,2.・・・・・・(ΔZ is the sample interval in the depth direction)
calculated for (Sn (J), S,.

j), ... ), the depth range CZI , Zz
If the time range [t+, tz] is specified, the effective value P of the shear rate can be defined by the following equation.

l nz Jz T(r+z-n,+1)ΔZ (jz-j+=1) n
=n+J" J+(Sn (j) a v)
2) ”” Equation (11) av is the depth range [z
+ , Zz ], the average value within the time range [t,, t2i, ■ nz J2 Σ ΣS, (j) T(nz-n++1)ΔZ (jz-J++1)n=n
+ J = L loading surface. Further, for simplicity, it may be calculated as a V=O. However, t+ =Tn+ Lx =Tnzz
I-JlΔZ% Z2-JzΔ2.

(11) The effective value of the shear rate, such as 2, is one parameter of the elastic properties of the tissue. Furthermore, it goes without saying that in equation (11), calculation may be performed only for a specific depth Z.

Two effects: According to the second aspect of the present invention, the shear rate, which is an elastic property of tissue, is a two-dimensional function of time and depth in a certain scanning line, and a spatial two-dimensional distribution image in a certain region of interest. , or
As an effective value, the B-mode image of a conventional ultrasound diagnostic device, M
It will now be displayed in combination with the mode image. This makes it possible to provide information on the position and degree of hardness of the Mi weave.

〔Example] Next, the present invention will be sequentially explained using FIGS. 1 to 6.

FIG. 1 shows the configuration of the present invention. Reference numeral 11 denotes an ultrasonic probe for transmitting and receiving ultrasonic waves to and from the medium 19, and is connected to the transmitting and receiving circuit 10.

Reference numeral 10 denotes a transmitting/receiving circuit including a beam former, etc., which generates signals for driving a group of transducers that are components of the probe 11, and generates a received signal 1 focused in a specific direction from a signal received by each transducer. generate. The received signal 1 becomes an input to the speed detection means 2, the B mode image generation means 8, and the M mode image generation means 9. 10.11.2.8 and 9 are provided in conventional ultrasonic diagnostic equipment. The velocity detection means 2 is for calculating equation (9), and is composed of an orthogonal detection circuit and the like, and detects the displacement velocity of the tissue in the depth direction at an arbitrary depth. Memo I73 indicates the displacement velocity of the tissue in the depth direction in the specified scanning line, or
It is for storing tissue displacement velocities in multiple scan lines within a certain region of interest. The depth direction differentiating means 4 is (
10) This is for calculating the equation, and the displacement velocity calculated by means 2 is differentiated in the depth direction. The effective value calculating means 5 is for calculating the equation (11), and calculates the effective value of the shear rate calculated by the means 4.

The display means 6 is a two-dimensional function of time and depth of the shear velocity in a specified scanning line, a two-dimensional distribution image of the spatial shear velocity in a certain region of interest obtained by scanning the scanning line, or the display means This is for displaying the effective value of the shear rate calculated by 5 in combination with the B-mode image and M-mode image of the conventional ultrasonic diagnostic apparatus. Scanning line or RO [The designating means 7 specifies the scanning line for calculating the shear rate, the Rot for specifying the region of interest, and the depth range and time interval for calculating the effective value of the shear rate. It is a means of FIG. 2 conceptually explains the invention of FIG. 1.

The received signal 1 is first subjected to orthogonal detection within the speed detection means 2. Here, the operation of means 2 will be explained using FIG.

FIG. 2(a) shows a complex signal sequence subjected to orthogonal detection when transmitted and received N times in the same direction. Here, among the complex signal sequences, the complex signal sequence V, , (Z
) (Equation (4)) is obtained. Next, the transmission period is shifted by T,
Signal complex signal sequence V, -1(z) at the same depth Z
(Equation (5)) is obtained. Next, the complex autocorrelation coefficient is calculated according to equation (6), and the tissue displacement velocity v7(z) at depth Z is calculated from equation (9). FIG. 2(b) shows the calculation of V and (z) for the total depth.

Next, the depth direction differentiating means 4 differentiates the tissue displacement velocity v, . FIG. 2(C) conceptually shows the shear rate at this time.

FIG. 3 illustrates the speed detecting means 2 and the depth direction differentiating means 4 in more detail. In FIG. 3, the speed detection means 2 includes orthogonal detectors 2-1 to 2-6, an ADC 2-7 for AD converting the real part component of the orthogonal detection signal, and an ADC 2-7 for AD converting the imaginary part component of the orthogonal detection signal. ADC2-8 for
, a memory 2-9 for storing real components, a memory IJ 2-10 for storing imaginary components, a complex autocorrelator 2-11, and a velocity calculation section 2-12. 2-1 is a mixer for multiplying the received signal 1 by a reference signal (cosωQ t,) 2'-3, and 2-5 is a low-pass for cutting the upper sideband component of the output of the mixer 2-1. It's a filter.

Similarly ↓, 2-2 refers to received signal 1 No. 13 1 needs
inω. L) Mixer for multiplying 2-4, 2 6B
11'lJ e; above the output of the mixer 2-2; is a low-pass filter for cutting band components. 2-
The outputs of 5 and 2-6 correspond to the real part and imaginary part of the quadrature detection signal. The real part and imaginary part of the quadrature detection signal are -d,
Stored in memory 2-9.2-10. 2-11 calculates the complex autocorrelation coefficient (
7) Calculate according to 2. Further, the tissue displacement velocity v, (z) is calculated from the complex autocorrelation coefficient calculated in 2-11 according to equation (9).

Here, when detecting blood flow velocity, complex self-phase opening 2-
Normally, an MTI filter is installed before the filter 11, but this is not necessary in the present invention.

The calculated tissue displacement speed is temporarily stored in the memory 3.

- The previously stored displacement velocity is read out as a time series in the depth direction, and differential processing in the depth direction is performed by the FIR filter 4-1. If the coefficient sequence of the FIR filter is set as shown in FIG. 3(b) as an example, an operation corresponding to equation (10) can be performed. This coefficient is F in Figure 3 (C).
IR filter coefficient sequence 4-1-2-0 to 4-1-2-m
shall be.

In FIG. 3(C), data shift register 4-11
is the signal sequence of displacement speed of human power v,, (i) (i=
0.1, 2. =...) is shifted one step at a time according to a system clock (not shown), and the shifted signal sequence (v, (i), Vfi (i-1)V, , (i-
2:+,...) and the coefficient (a.

The adder 4-13 adds the result of multiplying by ``l11-1+...1.The addition result is the displacement velocity V.(i
) in the depth direction, and the shear rate S, (
j). j indicating the data position in the depth direction is, for example, j
=i-m/2.

FIG. 4 shows an example of display of a two-dimensional function of time and depth of shear rate calculated for a certain scanning line.

FIG. 4(a) is a "B-mode" image obtained with a conventional ultrasonic diagnostic device.Here, in order to calculate the shear rate,
A line indicating the scanning line or the scanning line direction specified by the ROT specifying means 7 is displayed on the B-mode image by the display means 6. The data cents (Sn (Z), S, , (Z), ...) of the shear rate in this scanning line are
An example of direction and time displayed as a function of n direction is shown in Figure 4 (
b), and (C). (b) shows the shear velocity value as an amplitude, (C) shows the shear velocity as a grayscale or color image, and (d) shows the
The clay scale or color corresponding to the shear rate value in (C) is displayed. Further, as shown in FIG. 4(e), corresponding M mode images may be displayed simultaneously.

Here, as shown in FIG. 4(b), the scanning line or R
The OI specifying means 7 determines the depth range [z.

l21, Specify the time range [t+, tz] (11)
According to step 2, the effective value of the shear rate can be calculated by means 5.

FIG. 5 is an example in which the shear velocity of the liver is displayed as a two-dimensional function of time and depth, as in FIG. 4(b). Figure 5 (
A) is an example of a normal liver; FIG. 5) is a case where there is metastatic cancer (metastasized tumor) at a deep location. In the example (a) of a normal liver, it can be observed that the shear rate changes over time at each depth. Furthermore, in the case of metastatic cancer (b), the temporal change in shear rate at the depth A inside the tumor is extremely small. This is thought to indicate that the inside of the tumor is hard and expands and contracts little. Furthermore, it is shown that at depth B, which corresponds to the boundary between tumor and normal tissue, the velocity change is very large. As described above, by displaying the shear rate according to the present invention, it is possible to clearly determine the difference between normal tissue and tumor tissue. This is a superimposed display of spatial two-dimensional distribution images of velocity. The range for calculating the shear rate is indicated by the dotted line RCII in the figure. In the example of Figure 6, 2 is displayed superimposed on the B-mode image,
It goes without saying that the B-mode image and the spatial two-dimensional image of shear rate may be displayed separately.

[Effects of the Invention] As explained above, according to the present invention, the shear rate, which is an elastic property of tissue, can be calculated as a two-dimensional function of time and depth in a certain scanning line, or as a spatial function in a certain region of interest. It is displayed as a two-dimensional distribution image or an effective value in combination with a B-mode image and an M-mode image of a conventional ultrasonic diagnostic apparatus. This makes it possible to provide information on the position and degree of hardness of the 'Mi weave.

[Brief explanation of the drawing]

1 is an embodiment of the present invention, FIG. 2 is a diagram conceptually explaining an embodiment of the present invention, and FIG. 3 is a diagram illustrating the configuration of FIG. 1 in more detail. Figure 4 is a display example, Figure 5 is
Example of applying this method to normal liver and metastatic liver cancer, Part 6
The figure shows another example of the display, and FIGS. 7 and 8 show conventional embodiments. Received signal speed detection means Memory Depth direction differentiator Effective value calculation means Display means Rot designation means B mode image generation means M mode image generation means Ultrasonic probe Transmission/reception circuit Depth 2 Fig. 2 Fig. 1 Fig. 3 Figure 4 Figure 6 (b) Figure 5 Figure 7 Figure 8

Claims (6)

[Claims] (1) Ultrasonic pulses are transmitted multiple times in the same direction within the subject, and from multiple received signals received from the same direction,
a speed detection means (2) for detecting the displacement speed of the internal tissue of the subject at each depth; and a depth direction differentiator (4) for differentiating the detected speed in the depth direction to calculate the shear rate. and a display means (6) for displaying the shear rate obtained by the depth direction differentiating means (4) as a two-dimensional function of time and depth or as a spatial two-dimensional distribution image. Features of ultrasonic diagnostic equipment. (2) The spatial two-dimensional distribution image of the shear rate obtained by the depth direction differentiating means (4) is displayed simultaneously with the B-mode image on the same screen or superimposed on the B-mode image. An ultrasonic diagnostic apparatus according to claim 1. (3) Using the shear rate obtained by the depth direction differentiating means (4) as a two-dimensional function of time and depth, a B-mode image,
Alternatively, the ultrasonic diagnostic apparatus according to claim 1 is characterized in that it is displayed simultaneously with an M-mode image. (4) A scanning line is specified by the scanning line or ROI specifying means (7), and the depth direction differentiating means calculates the shear rate on the ultrasonic scanning line specified by the scanning line or ROI specifying means (7). The ultrasonic diagnostic apparatus according to claim 1, wherein the calculated shear rate is displayed as a two-dimensional function of time and depth. (5) A two-dimensional region of interest (ROI) is designated by the scanning line or the ROI designation means (7), and the shear rate calculated by the above-mentioned means (4) within the region of interest is distributed in a spatial two-dimensional distribution. The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic diagnostic apparatus displays the information as an image. (6) It has an effective value calculating means (5) for calculating an effective value at a shear rate in a specified time range and depth range among the shear rates obtained by the depth direction differentiating means (4). An ultrasonic diagnostic apparatus according to claim 1, characterized in that: