JPS6244228A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a device for diagnosing tissue within a subject using ultrasound, and in particular, to a device for diagnosing tissue within a subject using ultrasound, and in particular, for diagnosing tissue within a subject by measuring the ultrasonic propagation velocity (hereinafter referred to as sound velocity) of the tissue. The present invention relates to an ultrasonic diagnostic device for diagnosing.

[Technical background of the invention]

2. Description of the Related Art As a device for diagnosing living tissue, there is an ultrasonic diagnostic device that diagnoses living tissue by measuring the speed of sound in living tissue. The basic principle of the ultrasonic diagnostic apparatus will be explained below with reference to FIG.

That is, using an ultrasonic probe for linear electronic scanning (hereinafter referred to as probe) 1, ultrasonic pulses are emitted into the body in the θ direction from one end A of an ultrasonic transmitting/receiving surface 2 that is in contact with a body surface (not shown). Then, the ultrasonic pulse goes straight along the transmission path 4 in the liver tissue, and the ultrasound reflected at point P goes straight through the transmission path 5.
and is received by the ultrasonic transducer (hereinafter referred to as the transducer) at the right end B. Since the distance y between A and B is known, route 4
．． By measuring the propagation time t for propagating through 5, the sound speed C in the liver tissue' can be determined as C=y/(t-8inθ)·(1).

In addition, the sound speed in standard living tissues is Co ”” 1530
m/s, the ultrasonic beam is θ. To radiate in the direction, the delay time difference τ0 between adjacent oscillators of probe l
, To = (d/Co) ・sinθ ・・
・It is sufficient to set it so that (2) is obtained.

If the sound speed of the living tissue is 00, the ultrasound beam is θ.

A value C that is different from C0, but is generally not limited to C0.
It is. At this time, the propagation direction θ of the ultrasonic wave is sin θ/C=sin θo/G o from Snell's law.
−(3).

By the way, the sound speed C calculated using the above equation (1) is the third
Since it is the average sound speed over the propagation path A-P-B in the figure, it is actually affected by the body surface layers (fat layer, muscle layer), causing errors in the sound speed measurements. Therefore, the applicant company of the present application has developed the wave transmitting directivity of the wave transmitting transducer group A and the receiving wave transducer group B, as shown in FIG.

Collect the received waveforms from the intersections P, , P, with B′, and
Attempts have been made to remove the influence of the body surface layer from the difference in the times at which the peaks or centers of gravity appear in the two waveforms. This method is referred to as a two-beam method for convenience.

However, if the liver surface is not parallel to the ultrasonic wave transmitting/receiving plane, there is a risk that a non-negligible error will occur even in the two-beam method. The reason is that the
As is clear from the figure, if the inclination angle of the body surface layer is 10'' or more, an error of 1% or more will occur.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to achieve high accuracy even when the surface of the sound velocity measurement site within the subject is not parallel to the ultrasonic wave transmission/reception plane. An object of the present invention is to provide an ultrasonic diagnostic device capable of measuring the speed of sound.

[Summary of the invention]

The outline of the present invention for achieving the above object is as follows. Third. The ultrasonic diagnostic apparatus includes a fourth transducer group and obtains ultrasound propagation velocity information in the tissue of a subject based on reflected components of ultrasound transmitted toward the subject for diagnosis. The second transducer group receives an ultrasonic reflection component from a first intersection where the ultrasonic wave transmitting directivity of the transducer group intersects with the ultrasonic receiving directivity of the second transducer group. a second wave on the ultrasonic wave transmission directivity of the first transducer group, where this ultrasonic wave transmission directivity and the ultrasonic reception directivity of the third transducer group intersect. The ultrasonic reflected component from the intersection is received by the third transducer group, and the ultrasonic receiving directivity of the second transducer group is on the ultrasonic receiving directivity and the fourth ultrasonic receiving directivity is The second transducer group receives the ultrasonic reflection component from the third intersection where it intersects the ultrasonic transmission directivity of the transducer group, and captures the received echoes. The device is characterized in that it includes a calculation circuit that calculates the ultrasonic propagation velocity from the echo.

[Embodiments of the invention]

Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. The transducer array 11 is arranged on the ultrasonic wave transmitting/receiving surface 2 of the probe shown in FIG. To detect.

The transducer array 11 (T+~'I'+zs) has a transducer width a
0.6711, 128 elements are lined up on a straight line with an element center spacing d=0.72n. Electric signals are sent and received to and from each of these transducer elements using the lead wire 12 in the cable 3.
It is done through.

A clock oscillator 21 generates a reference clock of, for example, 10 MHz, divides the frequency thereof, and outputs a rate pulse of, for example, 4 kHz.

15 is a transmission delay circuit that delays the rate pulse; 14 is a pulser that outputs an excitation pulse in response to input of the delayed rate pulse. The excitation pulse output from this pulser 14 is passed through the multiplexer 13 to the transducer array 11.
The voltage is applied to a predetermined vibrator inside. 16
19 is a reception delay circuit that synthesizes and outputs received echoes of ultrasonic waves received by predetermined transducers in the transducer array 11 after a predetermined time delay; 19 amplifies the output of this reception delay circuit 16; This is a receiving circuit that detects waves. 22 is a memory for storing output data of this receiving circuit 19;
A processing circuit 23 performs averaging processing based on the relationship between the contents stored in the memory 22 and data newly taken in via the receiving circuit 19. 24 is a waveform analysis circuit that performs waveform analysis of the result of the averaging process; 25 is a waveform analysis circuit that measures the time of the peak value of the waveform from the output of this waveform analysis circuit 24 to obtain the propagation time of the ultrasonic wave; This is a calculation circuit that calculates the speed of sound based on time. 26 is this calculation circuit 25
This is a display that displays the calculation results. 27 is a system control means, which is mainly composed of a CPU (central processing unit).

This system control means 27 controls the operation of the multiplexer 13 according to a predetermined program, sets the delay times of the transmission delay circuit 15 and the reception delay circuit 16,
It controls writing and reading of the memory 22 and controls the operation of the calculation circuit 25.

Next, the operation of the embodiment apparatus having the above configuration will be explained with reference to FIG. 2 as well.

FIG. 2 is an explanatory diagram of ultrasonic wave transmission and reception in this embodiment.

The delay time of the transmission delay circuit 15 is set under the control of the system control means 27. This delay time is the delay time difference τ between adjacent oscillators. is set so that it has the relationship shown in equation 11. Then, by the switching operation of the multiplexer 13, the transducer group (first transducer group) belonging to point A of the probe is connected to the output terminal of the pulser 14. Excitation pulses output from the pulser 14 with a predetermined time difference are applied to the vibrator group belonging to the point A. On the other hand, the delay time of the reception delay circuit 16 is set under the control of the system control means 27. , the vibration belonging to point B of the probe is determined by the switching operation of the multiplexer 13.

The transducer group (second transducer group) and the input terminal of the reception delay circuit 16 are connected. As a result, the reflected component at point po (first intersection) of the ultrasonic wave transmitted toward the subject from the transducer group belonging to point A of the probe is reflected at point B of the probe.
The waves are received by the transducer group belonging to the point, and the received echoes are given the same time difference as in the case of transmission by the reception delay circuit 16, and then synthesized and output. The combined output of the reception echoes from the reception delay circuit 16 is amplified and detected by the reception circuit 19, and then written into the memory 22. When the above-described ultrasonic wave transmission and reception is performed multiple times via the transducer groups belonging to points A and B of the probe, the processing circuit 23 performs averaging processing of the received echoes. The received echoes read out from the memory 22 are input to the calculation circuit 25 via the waveform analysis circuit 24, and are used to measure the time t from the transmission of the ultrasonic wave to the reception of the ultrasonic wave. This measurement can be easily performed by detecting the peak of the received waveform.

Next, the multiplexer 13 is operated under the control of the system control means 27, and the transducer group (third transducer group) belonging to point D of the probe is connected to the input terminal of the receiving delay circuit 16, and the input terminal of the receiving delay circuit 16 is connected to the probe A. The reflected component at point p+ (second intersection) of the ultrasound transmitted by the transducer group belonging to the point is received by the transducer group belonging to point D of the probe. The received echoes are given a time difference similar to that in the case of transmission by the reception delay circuit 16, and then synthesized and output.

The combined output of the received echoes is output from the receiving circuit 1 as in the above case.
After being amplified and detected by the waveform analysis circuit 24 in the memory 22 and the waveform analysis circuit 24, the signal is input to the calculation circuit 25 and used to measure the time t2 from the transmission of the ultrasonic wave to the reception of the ultrasonic wave.

Next, the multiplexer 13 is operated under the control of the system control means 27, and the transducer group (fourth transducer group) belonging to the point E of the probe is connected to the output end of the pulser 14, and the output terminal of the pulser 14 is connected to the point B of the probe. Transducer group and reception delay circuit 1 belonging to
It is connected to the input terminal of No. 6. And now probe E
Point P2 of the ultrasonic wave transmitted from the transducer group belonging to the point
The reflected component at the (third intersection) is received by the transducer group belonging to point B of the probe, and the received echo is sent to the reception delay circuit 16. Receiving circuit 19゜Memory 2
2. The signal is input to the calculation circuit 25 via the waveform analysis circuit 24, and is used to measure the time t3 from the transmission of the ultrasonic wave to the reception of the ultrasonic wave.

In the above ultrasonic wave transmission and reception, the distance between point A and point B is yl, the distance between point A and point D, and the distance between point B and point E is y2. Also, points P1 and P2 are
They have a symmetrical positional relationship with respect to the line connecting the center O on the line connecting points A and B and point P0 as an axis.

Here, points P09, P11, and P2 are the ultrasound reflection points in the liver parenchyma within the subject, but at the same time, the ultrasound waves generated by the transducer groups belonging to the probe's points A, D, E, and B, respectively. It means the intersection of transmitting and receiving directivity.

Here, the time 1. obtained by the above-mentioned ultrasonic wave transmission and reception.
．． 1. By using 1-t2-ΔL and executing the calculation of the following equation, the ultrasonic propagation paths P, -P are obtained.

−P, can be determined using the average sound speed over P (corresponding to the two-beam method).

However, Δy (y)'l-'It.

However, since the boundary surface (liver surface) indicated by diagonal lines in FIG. 2 is not parallel to the ultrasound transmission and reception plane, in the two sets of ultrasound propagation paths A-P, -B and A-P, -D, The time to propagate along path 1-K at the speed of sound C2 and the path J-
The time it takes for C to propagate at the speed of sound C, is different, and this time difference becomes an error.

That is, Δ1=1. The two items when expressed as −12 Ct CI are error terms. However, IK
= JG, and t (PI popz ) can be expressed as the propagation time in the ultrasonic propagation path PI Po-Pz, and if α=0, the error is 0, and the larger α is, the larger the error is.

Therefore, in the apparatus of this embodiment, the time jl+tff is used and the time difference between them is also calculated. If the time difference is Δt', then Δt'=t, -t.

As in the previous equation (5), the two items become error terms. However, NQ=ML. Further, NQ is expressed as. Then, the arithmetic average Δt of the obtained Δt, Δt′
is calculated by executing the following formula.

-Δt+Δt' Δ 1= □ (9) Since the calculated Δt represents the average propagation time, Δt is used instead of Δt in the previous equation (4) to calculate the estimated sound speed. . That is, the arithmetic expression is expressed as.

Calculation of Δt and Δt' as described above, Δt.

The arithmetic mean processing of Δt' (formula (9) above) and the calculation using the estimated sound speed (formula (10) above) are all performed by the calculation circuit 25, and the final estimated sound speed value is displayed on the display 26.
will be displayed. As is clear from the simulation results below, the displayed sound speed estimation value has an extremely small sound speed measurement error due to the inclination angle of the body surface layer, and is a highly reliable value.

Next, the results of a simulation conducted by the inventor of the present application will be explained.

First, let 1>(tanα) (tanθ) and evaluate the two items in each of the previous equations (5) l(7L f9). Let the error in the previous equation (5) be ε(,), and let the previous equation (6
) is substituted into the previous equation (5), it becomes. Similarly, the error ε(,) in the previous equation (7) is
C+ Ct 1-(tanα) (tanθ)
The error of cosθε(,) is canceled out, and ε(,) 0 ...(
13).

In the above discussion, we ignored the refraction of sound waves at the interface, but even in simulation results that take this into account, its influence is extremely small. For example, y, = 57.6 cranes, )'z = 17
．． 281m, C+ = 1430m/s.

In the case of θ = 12.5° and α = 20', according to the two-beam method using the intersection point P in Figure 2, the error ε1 in the sound speed value obtained from the previous equation (4) is as follows, Similarly, the error ε2 in the sound velocity value when using the intersection P2 is as follows. On the other hand, in the device of this embodiment, the error ε of the sound velocity value
3 is as follows, and even if refraction is taken into account, in the case of the apparatus of this embodiment, the error is sufficiently small. This value does not pose any problem in practice.

As is clear from the above simulation results, in this example device, the sound velocity measurement error caused by the inclination angle of the subject's body surface layer is extremely small, and therefore, the liver surface, which is the sound velocity measurement site, is exposed to ultrasonic waves. Even when the beam is not parallel to the transmitting/receiving wave surface, it is possible to measure the sound velocity with high accuracy, unlike the two-beam method described above.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist of the present invention.

For example, in the above embodiment, the propagation time Δt.

We have explained how to perform arithmetic averaging processing of Δt' (formula (9) above) and calculate the estimated sound speed based on the processing result. The average sound speed may be calculated using a formula, and the calculation results may be arithmetic averaged.

In this case, the arithmetic mean value is equal to the average sound speed obtained by the αω equation, and as in the above embodiment, the sound speed measurement error is small and reliability is high.

In addition, a new pair of intersections that are at the same depth as the intersections P and P in Figure 2 and in a symmetrical positional relationship are added, and the speed of sound is estimated from the arithmetic average of all of them. Also good.

In the above embodiment, for example, it was explained that ultrasonic waves are transmitted from a group of transducers belonging to point A, and the reflected wave from the intersection P0 is received by a transducer belonging to point B. The ultrasonic wave transmission/reception relationship is completely symmetrical, and the wave may be transmitted from the transducer group belonging to point B and received by the transducer group belonging to point A.

Furthermore, in the above embodiment, the delay time difference τ between adjacent vibrators. The delay times of the transmission delay circuit 15 and the reception delay circuit 16 were set so that ) may be set.

(6) Here, X is the position (coordinate) of each transducer in the transducer group of the probe 1 in the arrangement direction. When the delay time is set in this way, the directional intersection area and the focal point coincide with each other, and the area of the directional intersection area becomes smaller, so that the peak of the received waveform becomes steeper. Therefore, the peak value of the received waveform can be detected accurately, and the local speed of sound can be measured with high precision.

〔Effect of the invention〕

As detailed above, according to the present invention, ultrasonic diagnostics allows highly accurate sound speed measurement even when the surface of the sound speed measurement site within the subject is not parallel to the ultrasonic wave transmission/reception plane. equipment can be provided.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the device of the present invention, Fig. 2 is an explanatory diagram of ultrasonic wave transmission and reception in this embodiment, Fig. 3 is an explanatory diagram of the measurement principle of ultrasonic propagation velocity, and Figs. FIG. 5 is an explanatory diagram and a characteristic diagram for explaining conventional ultrasonic propagation velocity measurement, respectively. 11... Vibrator array, 25... Calculation circuit, 26.
...Display, A...Point indicating the position of the first transducer group, B...Second
Point indicating the position of the transducer group, D... Point indicating the position of the third transducer group, E... Point indicating the position of the fourth transducer group, Po... Point indicating the position of the third transducer group, Po... Point indicating the position of the third transducer group, Intersection, P+...second intersection, P2...third intersection.

Claims (4)

[Claims] (1) The first waveform is formed by arranging a plurality of ultrasonic transducers, respectively.
, a second, third, and fourth transducer group, and an ultrasound system that obtains information on the ultrasound propagation velocity in the tissue of a subject based on the reflected components of the ultrasound waves transmitted toward the subject and provides the information for diagnosis. In the diagnostic apparatus, a first transducer is provided at which the ultrasound transmission directivity of the first transducer group and the ultrasound reception directivity of the second transducer group intersect.
The second group of transducers receives an ultrasonic reflected component from the intersection of The third transducer group receives an ultrasonic reflection component from a second intersection where it intersects the ultrasonic receiving directivity of the transducer group, and the ultrasonic wave is received by the second transducer group. The ultrasonic reflection component from a third intersection point on the directivity where this ultrasonic receiving directivity intersects with the ultrasonic transmitting directivity of the fourth transducer group is transmitted to the second transducer group. What is claimed is: 1. An ultrasonic diagnostic apparatus comprising: a calculation circuit that captures received echoes collected by receiving waves and calculates an ultrasonic propagation velocity from the captured received echoes. (2) The second and third intersections are in a positional relationship that is symmetrical with respect to a line that passes through the first intersection and is perpendicular to the array plane of the ultrasonic transducers. The ultrasonic diagnostic device according to item 1. (3) The calculation circuit calculates the ultrasonic propagation time difference between the received echoes from the first and second intersections, and also calculates the ultrasonic propagation time difference from the received echoes from the first and third intersections. The ultrasonic diagnostic apparatus according to claim 1 or 2, which calculates a time difference and calculates and outputs an ultrasonic propagation velocity from the arithmetic mean of the calculation results. (4) The calculation circuit calculates the ultrasonic propagation time difference between the received echoes from the first and second intersections, and also calculates the ultrasonic propagation time difference from the received echoes from the first and third intersections. Claim 1: Calculates the time difference, calculates the ultrasonic propagation velocity for each ultrasonic propagation time difference, and outputs the arithmetic average of the calculated ultrasonic propagation velocities.
3. The ultrasonic diagnostic apparatus according to item 1 or 2.