JPS61203950A - 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 an apparatus for diagnosing the tissue of a subject using ultrasound, and particularly to a non-invasive (i.e.
illi? The present invention relates to an ultrasonic diagnostic device that can perform measurements without placing an equal burden on the specimen.

[Technical background of the invention]

With conventional ultrasonic diagnostic equipment that displays B-mode images, diagnosing convoluted pinched lesions (e.g., fatty liver, cirrhosis, etc.) relies heavily on the skills of two doctors and technicians. If non-invasive measurement of the sound velocity within a specimen can be achieved, it will have extremely great clinical significance.

As a device for non-invasively measuring the speed of sound, the fourth
As shown in the figure, the ultrasound probe transmits and receives ultrasound beam B5. It has been proposed that the speed of sound is measured by crossing the BRs, detecting the peak of the scattered waves from the intersection C8, and measuring the propagation time from the time of transmission of the ultrasonic pulse to the time of reception ( Patent application 1986-1046
(See No. 94).

[Problems with background technology]

The above-mentioned conventional device will be further described in detail with reference to FIGS. 5(al to (f+) and FIG. 6.

Figure 5(a) shows the rate signal during transmission and reception of ultrasonic waves in this device. Figure 6(d) shows an enlarged time axis of the detection signal from point C1 other than the intersection C8. The average of a plurality of detection signals from the point C1 is shown in the figure (f+ indicates the average of a plurality of detection signals from the point C2, respectively).

As is clear from Fig. 5(c) and (dl), the above-mentioned scattered waves are generated as a result of the interference of each scattered wave from the minute scatterers in the object medium, so the waveform is not smooth, and the sound within the beam intersection region is not smooth. In addition to information on the absolute value of the field, it includes information on the different phases of each scatterer, and if peak detection is performed directly from such scattered waves, a large amount of error will occur.

In addition, even if you average the scattered waves and smooth the waveform as shown in Figure 5 (e), if the number of averaging is not sufficient, fluctuations will remain, and the peak time of these scattered waves will change. t,
, t, and b have different values, resulting in a large measurement error.

Furthermore, the generally performed curve fitting of scattered waves requires a long calculation time, and the real-time nature of the measurement is also compromised.

As described above, when measuring the speed of sound by detecting the peak of scattered waves, the speed of sound fluctuates each time the measurement is performed, resulting in a large error. For this reason, spatial averaging may be considered for the purpose of removing speckles, but even in this case, speckles cannot be completely removed near the peak point of the scattered waves unless the number of averaging is sufficient.

To completely remove speckles, a large amount of data is required, and there is a problem in terms of real-time performance.

In addition, in the beam crossing method, the speckle pattern of the scattered waves itself does not contain useful information.

The propagation time of the ultrasound signal through the center of the beam intersection contains useful information.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned situation C.

It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of non-invasively measuring the speed of sound by determining the time of the center of gravity of the scattered wave pattern using the amplitude of the entire scattered wave pattern or a predetermined region.

[Summary of the invention]

The outline of the present invention for achieving the above object is to provide an ultrasonic wave having two or several transducers arranged so that the directivity patterns of ultrasonic wave transmission and reception can intersect at least. a probe, an ultrasonic transmitting/receiving means that switches and controls the timing of excitation and reception of the ultrasonic probe, transmits ultrasonic pulses to a subject, and obtains scattered waves based on echo signals from the subject; A center of gravity calculation means for calculating a center of gravity using the amplitude of a temporal or spatial pattern of a wave, and a sound speed of an ultrasound propagating within a subject based on the center of gravity and the angle of the directional pattern. The invention is characterized in that it has a calculation means.

[Embodiments of the invention]

The ultrasonic pulse is emitted into the body in the θ direction from one end A of the ultrasonic transmitting/receiving surface 2 that is in contact with the body surface (not shown), and the ultrasonic pulse travels along a transmission path 4 in, for example, liver tissue and reaches a point P. The repulsed ultrasonic waves pass through the Uesaka path 5 and are received by the Ishigami B transducer. The distance y between A and B is 13: knowledge, so if we measure the propagation time + time 1, the speed of sound C in the liver tissue is C=y/(t-8inθ)・・・・・・・
...(1) is determined.

The above is the method for measuring sound velocity according to the present invention) A': Feed material j
It is jII. Since the speed of sound is unknown, θ is unknown to the enemy, and since there is no reflector at point P inside the living body, in order to find the speed of sound from equation (1), we actually use (
Second, it requires a lot of effort. An embodiment of the present invention in which the speed is 6 [1: constant] will be described below.

The block diagram in FIG. 2 shows the configuration of this embodiment. k
Ultra-i of ultrasonic probe 1 of %r array array 111 diagram
They are arranged on the wave velocity receiving surface 2, and when a heavy pressure pulse is applied, they emit an ultrasonic pulse from the A end, and when the ultrasonic wave enters, they generate suppression and emit ultrasonic waves.

The transducer array 11 (Tl-T128) has a transducer element width a
0.45 mm has 128 elements lined up in a straight line with an element center spacing of d-0.5 mm. Electric signals are sent and received to and from each of these transducer elements using the lead wire 1 in the cable 3.
Do this through step 2.

The clock oscillator 21 has a reference clock of, for example, 10 MHz, frequency-divides it, generates a rate pulse of, for example, 4 KH,z, and transmits the clock signal through 32 transmission delay circuits 15 to 32 pulses.
Drive Ke's Parsa 14! 1III''.The output of the pulser 14 is connected to T1 to T32 (2) at the A end of the transducer array 11 by the multiplayer 13.The transducer array 11 contacts the body surface through the coating material of the probe, and vibrates. The ultrasonic waves generated from the element are radiated into the living body.The sound speed in standard living tissue is Co = 1530 m/
s, the delay time τ0 between each adjacent lattice to radiate the ultrasonic beam in the 00 direction is τ o-(d/CO)・Sinθo −・−−−−−−−
(21), and the transmission delay circuit 15 is set so that each element is driven with such a delay time difference.

That is, PD1=O1PD2-ro, PD3=2τ
0. . . . gives a delay time of PD32=31τ0.

If the sound speed of living tissue is CO, the ultrasound beam will be θ0
In general, (= is a value C different from CO, which is not limited to CO.) At this time, the direction θ in which the ultrasonic wave propagates is sinθ/C=stnθo/Co −····························
-(The value is shown as 31.

After emitting the ultrasonic pulse, the multiplexer 13
It is switched to connect the reception delay circuit 16 with the 32 transducer elements T97 to T128.

The ultrasonic reflected wave signals received by the transducer elements T97 to T128 are delayed in the same way as in the case of transmission, are synthesized, and are input to the receiving circuit 19. That is, the delay time of the reception delay circuit 16 is RD1=31τ0°RD2-30 to, -
-...=, RD31-ro-RD32*0. In this way, the transducer element group T97 to T12
8 is in the θ0 (θ) direction (
It has bidirectionality and receives reflected waves from the θ0 (θ) direction. The received signal is amplified and detected by a receiving circuit 19, and a threshold circuit 28, which can be manually set, is used in a centroid calculation means 30, and an A/D.
1 sent from the converter 20 and the clock oscillator 21
A memory 22 that counts and transmits a 0 MHz reference clock and stores the received signal converted into a digital signal from the A/D converter 20 in response to the lock at a predetermined address, and the output of the memory 22. and an arithmetic circuit 24 that inputs a large number of received signals from the memory 22 and calculates their centroid times tg, and has an address of a sample value of the received signal stored in the memory 22. is 100n in time from the time of ultrasonic pulse emission
It is designed to match with an accuracy of s.

Further, the arithmetic circuit 24 calculates the center of gravity time tg by calculating the following equation (4) from the time t of the received signal stored in the memory 22 and the amplitude 1 (1) at this time t. ing.

On the other hand, from fi+, (3) above, the sound velocity C in the subject can be expressed by the following equation (5).

”” y O(tgSinθo) −−°(5
1 Calculation circuit 25 calculates the sound speed C by calculating the speed of sound C from the center of gravity time tg obtained by the calculation circuit 24 and the known value 7, Co, θ0 by equation (5) (2), and displays this result on the display 26. and display it.

In the process of processing the above-mentioned series of received signals.

When the distance y between the micro-oscillators that make up the ultrasound probe 1 is large, the side lobes and grating lobes also become large, and as shown in Figure 3 (bl), many scattered waves from other than the two-beam intersection are included. Since the leak corresponds to the scattered waves from the points C1 and C2 shown in FIG. 6 as described above, there is a risk that the measurement error of the center of gravity time tg will increase.

Therefore, using the gate signal from the counter circuit 27, a time gate is applied so that the received 4M signal has a constant time width as shown in FIG. 3 (C1), and a threshold value circuit is applied as shown in FIG. By setting a constant threshold level TH at 28 and using only the received signals above the threshold level TH as shown in FIG. 3 (dl), it is possible to reduce measurement errors and measurement deviations.

In this way, according to the device of this embodiment, in the peak detection by the conventional device, there was a difference in the peak times tpa and tpb as shown in FIG. , (center of gravity time tg as shown in fl
It is possible to match IIL and tgb, and it is possible to calculate the sound speed with less measurement error.In addition, in B-Kui Mide, the resolution of propagation time is limited by the clock cycle during A/I) & conversion. However, in the apparatus of this embodiment, the center of gravity measuring means performs statistical processing, so that resolution greater than the clock cycle can be obtained.

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made within the scope of the gist thereof.

For example, in the above-described embodiment, a case has been described in which scattered waves are obtained by intersecting the directivity pattern of the ultrasonic beam at point co. get a pattern,
Various delay times are set for each of the transmission delay circuit 15 and the reception delay circuit 16j, the intersection points of the ultrasound beams are scanned to obtain spatially different scattered wave patterns, and the center of gravity is calculated for these scattered wave patterns. The means 30 may obtain the average time centroid point of the scattered wave pattern or the average centroid point of each scattered wave pattern.

〔Effect of the invention〕

According to the present invention described in detail above, it is possible to provide an ultrasonic diagnostic device that is non-invasive and is capable of determining an accurate sound velocity with few errors even from a scattered wave pattern in which fluctuations due to speckle remain. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an overview of the measurement principle of ultrasonic propagation velocity in the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 (at indicates the rate signal of the embodiment device). Waveform diagram, Figure 3 (bl ~ (di is a waveform diagram % showing the scattered wave pattern obtained by the same device, respectively) Figure 4 is an explanatory diagram showing the crossed state of ultrasound beams in the conventional equipment, Figure 5 (al is the waveform diagram of the ultrasonic rate signal - Figure 5 (b
l is the waveform diagram of the transmission pulse, Fig. 5 ((!l, (dl
are waveform diagrams of detection signals from points other than the intersection points of the ultrasonic beams, respectively, and FIG.
, (A waveform diagram of the detection signal obtained by taking the average of the detection signals shown in dl. FIG. 6 is a side lobe corresponding to the crossing state of the ultrasonic beam shown in FIG. 4. It is an explanatory diagram showing the state of the grating lobe. 1... Ultrasonic probe, 2... Ultrasonic wave transmission/reception wave surface, 3
...cable, 11... vibrator array, 12...
Lead wire, 13...Multiplephenar, 14...Pulser, 15...Transmission delay circuit %16...Reception delay circuit, 19...Reception circuit, 20...A/D converter, 21
...Clock oscillator, 22...Memory, 23...
Addition circuit, 24... Arithmetic circuit, 25... Calculation circuit,
26... Display, 27... Counter circuit, 2
8... Threshold circuit, 30... Center of gravity calculation means. Representative Patent Attorney Masayoshi Misawa ^ “3 Diagram Condolences No. 4 - Diagram C.

Claims (5)

[Claims] (1) An ultrasonic probe having two or more transducers arranged so that the directivity patterns of ultrasonic transmission and reception can intersect, and an ultrasonic probe that has excitation and reception an ultrasonic transmitting/receiving means that switches and controls the timing of the waves and transmits the ultrasonic pulses to the subject to obtain scattered waves based on echo signals from the subject; and a calculation means for calculating the sound speed of the ultrasound propagating inside the subject based on the center of gravity and the angle of the directional pattern. Sonic diagnostic equipment. (2) The ultrasonic transmitting/receiving means includes means for repeatedly generating ultrasonic pulses and means for giving a predetermined delay time to an excitation signal to the vibrator and a received signal from the vibrator, and The ultrasonic diagnostic apparatus according to claim 1, wherein different scattered wave patterns are obtained. (3) The ultrasound diagnostic apparatus according to claim 1, wherein the center of gravity calculation means includes means for applying a time gate to the scattered wave pattern, and calculates the center of gravity of the scattered wave pattern within the time gate. . (4) The ultrasonic diagnostic apparatus according to claim 1, wherein the center of gravity calculation means includes means for setting a threshold value on the scattered wave pattern, and calculates the center of gravity point of a signal that is greater than or equal to the threshold value. (5) The ultrasonic diagnostic apparatus according to claim 1, wherein the center of gravity calculation means includes means for applying a time gate to the scattered wave pattern and means for setting a threshold value.