JPS60232136A - 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 [Field of Application of the Invention] The present invention relates to an ultrasonic diagnostic device capable of measuring the speed of sound using a reflection method.

[Background of the invention]

In recent years, tissue identification ('l'1Hue Characteri
zation) is being actively pursued at home and abroad, but the sound velocity meter side is an important issue. The conventional sound velocity measurement method is Sing Around.
) method and ultrasonic computer tomography (compute
erTomograp)l)') However, since it is a transmission method, there is a limit to the ability to measure the sound velocity inside the body of a subject.

On the other hand, as a sound velocity measurement method using a reflection method, there is a method in which an ultrasonic beam is irradiated to the same target from two directions, and refraction at the interface between a living body and an acoustic coupling liquid is utilized.

However, this method has problems such as the positional accuracy of the two probes and the complexity of calculation processing.

[Purpose of the invention]

An object of the present invention is to provide a method and a device for easily measuring biological sound velocity using a high-resolution ultrasonic diagnostic device using a reflection method.

[Summary of the invention]

The present invention provides a reflection-type ultrasound diagnostic apparatus that converges an ultrasound beam by controlling the amplitude and phase of the transmitted and received signals of each element of a multiple ring transducer or an array transducer.
a received signal delay means having a variable delay time; a control means for sequentially changing the delay time; a means for automatically detecting convergence of the received signal from the reflector phased by the delay; The present invention is characterized by a configuration that includes calculation means for calculating the speed of sound from the delay time of time, and display means for displaying the calculated speed of sound.

[Embodiments of the invention]

A detailed explanation will be given below with reference to the drawings. FIG. 1 is an explanatory diagram of a conventional linear ultrasonic diagnostic apparatus, in which 1 to N are all array elements of a probe, and 1 to n are array elements within the transmitting and receiving aperture. The transmitting and receiving aperture position is alb.

By moving C sequentially, the ultrasonic beam becomes a', b
', C'. In this conventional device, the transmitting and receiving apertures are the same, and a relatively small aperture is adopted from the viewpoint of cost performance.

FIG. 2 shows an embodiment of the present invention, in which the transmitting aperture Dl and the receiving aperture are different in diameter, and the receiving aperture D2 is larger than that of the conventional device. Therefore, the wave transmitting and receiving directivity characteristics are determined by the wave diameter D2, and the resolution R1 and depth of focus are given by the following equations.

R=λ/Dg (1) where λ: wavelength, X: depth. For example, depth X = 100■, wavelength λ
= 0.4311111% When receiving wave diameter Ih = 64m, resolution R = O1007 (rad) = 0.4 (deg
), the depth of focus L=4■.

In this way, when the resolution is high and the depth of focus becomes shallow, the influence of the sound velocity in the medium becomes large. In other words, if the sound speed set at the time of device design differs greatly from the sound speed in the medium of the object, high resolution cannot be obtained.

As shown in Fig. 2, the depth is X1, the array element is Y (the origin is the center of the aperture), and the initial values of the convergence delay time and the sound velocity in the medium are To (Y) and vo, respectively, then vo・To (Y
) = 7";E"";"'j'
becomes. Here, the right side is a value determined only by the geometric shape.

When the exact speed of sound in the medium is set to ■, the delay time τ is set so that the image of the reflector at depth X is focused. (Y) is changed to delay time τ(Y). At this time, (4) .tau.(Y)=547-X (4).

Formula +31. (From 41, the exact speed of sound in the medium is ■=■
o・To(y)/τ(Y)・・・・・・・・・(5), and since Vol To(Y) is known, τ(Y
), the speed of sound ■ can be measured.

FIG. 3 shows an embodiment of a one-channel reception delay circuit. 1
0 is a delay circuit, 11 is an AD converter, 12 is a line memory, 13 is a timing generator, and 14 is a clock generator. 15 is an input terminal, and 16 is an output terminal. Now, when the clock frequency of the clock generator 14 is f, and if the delay time of the delay circuit 10 is To (Y), then the clock frequency becomes. Therefore 151. From +61.

In this way, the change in the clock frequency f of the variable delay means,
p/f, and the initial sound speed Vo, determine the exact sound speed in the medium ■
will be measured. At the same time, the depth X is also determined.

A conceivable method for determining whether or not the reflector P is focused is based on observation by the operator of the device, but this method has the drawback that subjectivity is likely to be involved.

FIG. 4 is an explanatory diagram of automatic focus according to the present invention. Fourth
Figure (a) is a schematic diagram of a point reflector image displayed on the display of an ultrasound imaging device, and its position is (xo + )'0
). Here, X is the depth direction and y is the array direction. In FIG. 4(b) (2), the A mode waveform at y=y is shown by a solid line, and the detected waveform is shown by a dotted line. Let A be the peak value of this detected waveform. FIG. 4(b) (■) shows the Z signal of the display when X = X o.

This is the azimuthal beam pattern of the device, and the beam width at the first zero point is B. Figure 4 (C) is Figure 4 (b) ■
The relationship between the detected waveform A and the frequency f of the clock generator 14 in FIG. 3 is shown. In FIG. 4(e), the peak value A becomes maximum at a value fat of the clock frequency different from the initial value f0, and the point target image is focused.

It is clear that the clock frequency f may be similarly varied so that the azimuth resolution B is minimized.

In FIG. 4(a), the position of the point reflector image is Xo + Y.

To determine , set the cursors 41 and 42 according to the υ method.

FIG. 5 shows an embodiment of the automatic focus explained in FIG. 4, where 20 is an array transducer, 21 is a switch for selecting the transmitting and receiving aperture from all array elements, 22 is a preamplifier, and 23 is an adder. , 24 is a compression circuit, 25 is a detection circuit, 26 is an image memory, 27 is an image display, and 28 is an automatic focus detection circuit, which detects a focus point using, for example, the "Yamatoshi method". 29 calculates the sound speed from the change in AJ clock frequency using equation (7).

30 is a sound velocity display, 31 is an operation knob, and inputs the point target position XO+y6.

According to this configuration, the cursor position yo is input to the switch 21, and the transmitting/receiving aperture is selected. The received signal is transmitted through a preamplifier 22, delay means 10. After passing through the adder 23, the phase is matched, and the signal passes through the compression circuit 24 and the detection circuit 25, as shown in FIG. 4(b).
The detected waveform is obtained.

This detected waveform is input to the automatic focus detection circuit 28.

In the automatic focus circuit 28, the scan direction)'=)
Depth x = x from the detected waveform for one line at 'o
A signal near o is cut out and sent to the clock signal generator 14.
The clock frequency f is gradually increased from the initial value f as shown in FIG. 4(C), and the clock frequency fopk at which the peak value A of the detected waveform is maximum is automatically detected.

When fop is determined in this way, calculation according to equation (7) is executed in the arithmetic circuit 29, and the sound speed ■ is displayed on the sound speed display 30.

In the above explanation, explanation of the operation of the image memory 26 has been omitted. However, if the beam width of the beam no. (turn) shown in FIG. It is necessary to change the clock frequency.

In the above embodiment, the average sound speed between the vibrator and the reflector is measured.

However, in the case of a living body, the sound speed of the medium is generally non-uniform, so it is necessary to measure the sound speed of each part.

FIG. 6 illustrates the present invention in the case of forming a layered structure in the depth direction as a model of an unrestricted-sound associated medium.

Reflector P11 P* + ・・'+ Depth of P4 by X1
+X2+...+X4, each layer 1. II, ...,■
Let the sound speeds within be Vl, Vl, . . . +V4.

Since the inside of the first layer is a homogeneous medium, by focusing the reflector Ps at the boundary between the first layer and the second layer,
The speed of sound v1 and the depth XI are determined.

Next, the sound velocity (3) of the (2) layer is determined so that the reflector P3 at the boundary between the first layer and the (2) layer is focused.

Depth X at the same time! is determined. Thereafter, the sound velocity and depth Vs, V4:X31X4 of each layer can be measured sequentially in the same manner.

According to this method, even when a foreign substance such as a spherical medium (II) is present in the uniform medium (I) as shown in FIG. 6(C), the reflector P1. By setting Pg as shown in the figure, it is possible to measure the speed of sound in a foreign material.

In the embodiment of the sequential measurement of the speed of sound shown in FIG. 6, the clock frequency of the clock generator shown in FIG. 5 changes with depth, that is, with time.

In the embodiment shown in FIG. 5, the delay means of all channels are controlled at the same clock frequency, so the switching time is based on the switching time of the channel at the center of the receiving aperture.

However, the scattered wave from the reflector P2 in Fig. 6(a) is P2
It is a spherical wave centered on It needs to be set dynamically each time.

In the case of FIG. 6(a), it is assumed that each layer of the non-uniform medium is uniform, but when a living body is targeted, there may be non-uniformity within each layer.

FIG. 7 shows an embodiment of the present invention regarding the method of measuring the sound velocity at each part in this case, where d1 to d4 are the partial apertures, and P1 to Pro are the respective reflectors.

First, for the reflectors P1 to P4 at depth x1, the partial aperture d
1 to d4 to measure the speed of sound between depth x=0 and x=xt. Next, for the reflectors P5 to P7 at depth x2, the partial apertures are d1 + d21 d2 + d3', respectively.
, d3+d4, depth X=xl and x=x*
Measure the speed of sound between. In the same way, reflector P8
This is a method of measuring ~P1o.

As described above, according to the present invention, the average sound velocity in a medium can be automatically measured by the reflection method.

Further, even in the case of a medium that is non-uniform in the depth direction, it is possible to successively measure the sound speed in each part from the short distance side.

The sound velocity data of living tissues obtained in this way is useful for tissue differentiation, and can contribute medically to dogs.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional device, Fig. 2 is an explanatory diagram showing the principle of the present invention, Fig. 3 is a block diagram showing the main part of an embodiment of the present invention, and Fig. 4 is an explanatory diagram of an embodiment of the present invention. FIG. 5 is a block diagram showing the overall configuration of an embodiment of the present invention, and FIGS. 6 and 7 are diagrams showing applied examples of the present invention. 10... Variable delay means, 11... A/D converter, 1
4... Clock generator, 28... Automatic focus detection recovery 1st vJ z Figure vJ4 (a-) Figure 4 (b) 'jlJ4 Figure (C) A b 30

Claims (1)

[Claims] 1. In a reflection-type ultrasound diagnostic device that converges an ultrasound beam by controlling the amplitude and phase of the transmitted and received signals of each element of a multi-ring transducer or an array transducer, means for making the delay time of the signal delay means variable; means for automatically detecting the convergence of the received signal from the reflector; arithmetic means for calculating the speed of sound from the variable delay time; and means for displaying the speed of sound. An ultrasonic diagnostic device characterized by automatically measuring and displaying the speed of sound in a transparent medium. 2. An ultrasonic diagnostic apparatus according to claim 1, in which reflectors are set at different depths and the speed of sound between each reflector is sequentially measured from the short distance side.