JPS6368141A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to an ultrasonic diagnostic device that uses ultrasound to obtain information inside a living body, and particularly relates to an ultrasound diagnostic device that uses ultrasound to obtain information inside a living body. It relates to a telescopic ultrasound diagnostic device "lVc" which has a function of measuring the speed of sound.

(Conventional technology) Diagnostic methods using ultrasound have the advantage of being able to diagnose soft tissue without placing any burden on the patient, and are non-invasive! 7. It has rapidly become popular due to recent advances in high-speed scanning devices. Since this ultrasonic diagnostic method is a pulse reflection method, it has a superior operating method compared to a transmission method, and the diagnostic sites to which it can be applied are not very limited, which is another reason for its widespread use.

Recently, there has been an increasing demand for quantification of images in such ultrasonic diagnostic methods.

It is considered to be particularly effective in the differential diagnosis of benign and malignant organ diseases. However, in the conventional pulse reflection method, the reflected wave intensity is determined not only by the difference in acoustic impedance (product of density and sound speed) between tissues in the living body, but also by the shape of the reflecting surface, the incident angle of the ultrasound beam with respect to the reflecting surface, ultrasonic absorption fl
kv? However, it is difficult to separate and release this information, making it extremely difficult to quantify a single port.

On the other hand, the conventional method of measuring only sound waves is the transmission type! e
It has been carried out in T (Reference; Greenleaf
, J, F, et, al, Acoustical Ho
Logography.

Vol. 81975), but the transmission method cannot be applied to areas where there is bone or gas in the ultrasound propagation path.

It has a major drawback in that it can only be used in very limited areas such as milk spraying.

On the other hand, a method has been devised in recent years to measure the speed of sound inside an organ using the pulse reflection method. Figure 5 shows the fast creation method reported by Akamatsu et al.

This uses two ffl sound wave deacers 51.52 with strong directivity for transmission and reception, respectively, and the @sonic waves transmitted from the transmission Mi sound wave transducer 51 are transmitted to each transducer 51.52. Center of @PP1
, reflected near the intersection 0 of QQl.

The time it takes to reach the receiving ultrasonic transducer 52 and the reception is measured, and from this time and the expected propagation distance calculated from the distance X and angle θ between the transducers 51 and 52, the liver This is a method to find the average sound speed within.

This method is thought to be effective in diagnosing chronic diseases such as liver cirrhosis, in which the entire liver has uniform acoustic characteristics;
? 8 The speed of sound is the average speed of sweat within the propagation path, so 5
It cannot be applied to localized diseases because ultrasound waves also propagate through the epidermis or fat layer, where the sound speed is different from the inside of the liver. There is a possibility that the error in measuring the speed of sound is large.

In response to such problems, the present inventor previously proposed a local sound velocity law using a pulse reflection method.

Fig. 2 shows the principle diagram of the transmission 11 transducer 41144 and the receiving transducer 42, 43.
is placed on the body surface as shown in the figure, and the sound velocity CO is estimated in the area Al3CD surrounded by the transmitted and received ultrasound beams.
The sound waves transmitted from the transducer 41 are A and B.
K is scattered by a certain scatterer and the transducers 42 and 43
The time t1**iH until reception is "11"tGA+'l: A tu-toA+tyc+(λ]1+1°C-)/C.

It is indicated by. Similarly, the sound velocity transmitted from the transducer 44 is disrupted at D and C, and the transducer 42
and the propagation time when received at 43
ist @@-! HC+ t E A + (A D+
CD) / C01, -1, C+1. Letting the incident angle of the transmission beam be θoEF-do, the propagation time Δt, that is, the speed of sound Co in the region of interest, can be determined from the following equation by determining the propagation time difference Δt.

(Problems to be Solved by the Invention) When transmitting and receiving @sonic beams intersect within the body and measure the reception time of the reflected wave from the intersection, each ultrasonic beam has a finite width. The reflected waves from many reflectors near the intersection are combined to form the received waveform. That is, the received waveform differs from the transmitted waveform and interferes with each other, so it presents a complicated pattern and becomes a major cause of deterioration in accuracy in one-hour measurement.

The present invention was made with the aim of improving the above-mentioned problem, that is, the deterioration of time measurement accuracy due to wave interference, and provides an @sonic diagnostic device that can accurately measure the ultra-f wave propagation velocity in the living body. It is about providing.

[Invention■Composition]

(Means for Solving the Problems) The present invention measures the local sound speed at the same site multiple times while varying the transmitting beam angle when performing local sound speed measurements by intersecting the transmit beam and the receive beam inside the body. However, the estimated value is calculated from the average value of the values obtained at this time.

(Function) Ultrasonic reflectors in living bodies are often approximated by a model in which point reflections are randomly arranged.Reflected waves from such densely arranged reflectors cause interference as described above. −
However, if the beam position or beam direction is slightly changed, the way of interference changes significantly. Therefore, by obtaining reflected waves from the same location while changing the direction (angle) of the transmitted beam, and applying statistical processing (for example, averaging) to these waves, it is possible to significantly reduce the effects of interference, and to accurately determine the propagation time. Measurement becomes possible.

<5 Examples) Fig. 1 shows the configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, which is capable of measuring the local speed of sound inside a human body. Ducer 2-1.2-
2. Hemorrhoid 1 transmission transducer group 2 consisting of 2-3
Same as three transducers 3-1.3-213-
A second transmitting transducer group 3 and a first receiving transducer group 4 and 5 are placed on the body surface.

In each transmitting transducer group, one of the three transducers is selectively used by the switch circuit 6.7.
For example, the transducers 2-2, 3-2 are driven by drive pulses supplied from the pulsers 8-1 and 8-2 via the switch circuits 6 and 7, and transmit ultrasonic pulses into the living body 1. This ultrasonic pulse is scattered by the tissues in the living body, but the ultrasonic pulses scattered at points A and D in the figure are received by the receiving transducer 4, and the JIJ pulses scattered at points B, a, and 0 are
f is received by the receiving transducer 5. This i
The easy transmission transducers 2-2t3-2 may be driven simultaneously, but if the region of interest ABCD is not sufficiently large relative to the beam width, it is desirable to drive them sequentially.

The signal received by the reception transducer 4.5 is amplified by an intensifier 10 and then subjected to envelope detection by a transverse wave circuit 11. Furthermore, this signal is converted into a digital quantity by the A/D converter 12 and is once stored in the memory in the arithmetic unit 13.

The propagation time g is calculated 1. For example, the more a sound wave pulse is emitted from the transmitting transducer 2-2, the more the sound wave pulse is scattered near point A, and the envelope waveform of the signal received by the receiving transducer 4. The result will be as shown in Figure 3. Since the propagation time cannot be accurately determined by the method of ejecting the flot edge or peak position [1] of such a waveform, the centroid calculation method is adopted here. In other words, if the receiving 1 waveform is P(ri), the center of gravity ty can be calculated from 2-
Calculate the propagation time of the valley from other combinations using 2゜3-2s4*5 transmitting and receiving transducers,
The region of interest ACBDo, speed Co, is determined, and its value e is temporarily stored in the memory within the computing unit 13. Next, transmitting transducers 2-1 and 3-1, and further 2-3 and 3-3
is selected by the switch circuit 6.7 to transmit the I wave, and the shape of the region of interest (l & dense) depends on the transmitting beam angle, but if the range of angle change is small h, the shape of the region of interest is almost the same. The sound velocity C can be the region of interest.
Calculate Oc *CO1. Next, the sound speed C in the area of interest (ACBD) is determined from the average of the three calculated sound speed estimates f[Co HI Co HI CO,.

In this embodiment, the transmitting transducer group is composed of three transducers, but it is not limited to this.

FIG. 4 shows another embodiment of the present invention, in which a part of an array-type ultrasonic transducer used to obtain a tomographic image of a living body 1 by electronic scanning is shown. This is an example of use for measuring the speed of sound. That is, play fWJ
Of the nine transducer elements arranged in the f-wave transducer 30, during transmission, 31-
1.31-2, 31-3, 34-1, 34-2, 34-
Area 3 is used, and during reception, area 3 shown in the shaded area is also used.
Areas 2 and 33 are used.

When transmitting ultrasonic waves from the area 31 of the array-type ultrasonic transducer 30, the ultrasonic beam is deflected by shifting the drive timing of a plurality of adjacent transducers in the area 31 by a predetermined time using a delay means. can be done. The same applies to 34. As a specific driving method for performing such electronic deflection, for example, the method described in Japanese Patent Publication No. 56-10058 can be used.

This embodiment has excellent scanning performance because it is possible to measure the local ultrasonic sound velocity using a single 7-ray ultrasonic transducer, and can also display the B-mode image D1 in real time. Since this can be done at the same time, there is an advantage that it is easy to accurately set the region of interest in which the supercosonic sound velocity is to be measured.

In addition, the position of the super sweat wave transducer (area 31
34) and the deflection angle of the transmitted ultrasound beam by electronic means, the cross-reception between the transmitter region and the receiver region can be changed. It is possible to measure the local ultrasonic travel velocity in the entire region, and it is also possible to display a two-dimensional sound velocity distribution. In other words, it is possible to determine the "velocity distribution of implanted waves in living organisms" using the pulse reflection method, which was previously impossible.

〔Effect of the invention〕

According to the present invention, since the influence of interference of scattered waves from within the body can be reduced, the accuracy of measurement of propagation time is greatly improved, and it is possible to accurately measure the local speed of sound inside the body, and also to obtain a two-dimensional sound speed distribution.

[Brief explanation of drawings]

FIG. 1 is a diagram of an ultrasonic diagnostic device according to an embodiment of the present invention, and FIG. 2 is a diagram of the principle of local sound velocity measurement. FIG. 3 is a diagram showing a received waveform according to the present invention, FIG. 4 is a diagram showing another embodiment of the present invention, and FIG. 5 is a diagram showing the principle of a conventional average sound velocity measurement method. 1... Living body, 2.3... Transmission transducer. 4.5...Receiving transducer・6g7゛°8
Itchi circuit, 8...pulsar, 9... oscillator, lO・
...Amplifier, 11...Detection circuit, 12...A/D converter, 13...Arithmetic unit, 14...CRT, 15...
・Switching controller, 41*44...transmission transducer+, 42143...reception transducer, 51...transmission transducer, 52...
- Receiving transducer. Agent Patent Attorney Nori Chika Kikuo Takehana Figure 2 111 To 1 Figure 8 Figure 4 Figure 5

Claims (1)

[Claims] one or more transmitting transducers that transmit ultrasonic waves into a medium, and arranged such that a receiving area intersects a transmitting area of the transmitting transducer in the medium,
one or more reception transducers that receive reflected waves of ultrasound from within the medium, and ultrasonic pulses emitted from the transmission transducer are received by the reception transducer after being scattered in the transmission/reception intersection region. In an ultrasonic diagnostic apparatus equipped with a means for measuring the time until the propagation time and a means for calculating the local sound velocity in the medium from this propagation time and the positional relationship of the transmitting and receiving transducers, An ultrasonic diagnostic device characterized by measuring a plurality of times while changing the speed of sound, and determining a local sound speed value from the average value of the measured values obtained at the time.