JPS61159944A - 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 is an ultrasonic diagnostic method that uses ultrasound to obtain a tomographic image of a living body and quantitatively observes the velocity of particularly slow blood flow. It is related to the device.

[Technical background of the invention and its problems]

Observing the state of blood flow within a living organ is an extremely effective means for obtaining information regarding the function of a living organ. In particular, the ultrasound Doppler method, which allows percutaneous non-invasive measurement of blood flow, enables accurate positioning of the area to be measured when used in conjunction with real-time ultrasound tomographic images, and has reached the stage of practical application in the cardiac field. .

In recent years, attempts have been made to observe blood flow velocity in blood vessels using similar methods in the abdominal and obstetric fields, and for example, research has been reported on diagnosing liver cirrhosis from the state of hepatic venous blood flow.

As shown in FIG. 4, an ultrasonic diagnostic method that has been attempted in the abdominal region in the past involves emitting pulse-modulated ultrasonic waves into the area to be inspected using a linear electronic scanning array probe 21 and reflecting them from a reflective surface. The probe 22 for blood flow observation attached to the end of the array probe 21 emits ultrasonic waves toward the blood flow observation point A, and the reflected waves are transmitted and amplified to display a tomographic image. There is an ultrasonic diagnostic device that calculates blood flow velocity from the amount of Doppler frequency deviation of waves.

In this way, when ultrasonic waves are emitted into a blood vessel from the blood flow observation probe 22, the reflected waves from blood cells flowing through the blood vessel undergo a frequency shift due to the Doppler effect.

The Doppler frequency fd at this time is the angle θ between the ultrasound beam and the blood flow direction, the propagation speed of the ultrasound C2, the ultrasound frequency f
When o is the blood flow velocity, it is expressed by the following equation.

However, as is clear from equation (1), the Doppler frequency fd depends on the angle θ, and as θ increases, it becomes difficult to obtain a Doppler signal.

Therefore, in order to obtain a proper Doppler frequency fd, it is important to determine the direction of the ultrasound incident beam so that the angle θ is as small as possible. However,
The beam direction of the linear scanning array probe 21 is always perpendicular to the scanning plane of the probe 21, and moreover, it is often incident almost perpendicularly (90° in θ) to the abdominal blood vessels, so the linear scanning array probe 21 21 could not be used also for blood flow measurement. Therefore, conventionally, as shown in FIG. 4, a probe 22 for blood flow observation is provided separately from the array probe 21 for linear scanning.

However, this device had extremely poor operability and was difficult to use because the radiation direction of the blood flow observation beam was fixed.

In addition, since blood flow is measured using the Doppler effect of continuous ultrasound waves, it is possible to confirm whether or not the blood flow observation beam actually reaches the observation area set on the fault. It becomes difficult. Moreover, when continuous ultrasonic waves hit a moving object, the frequency changes due to the Doppler effect due to the movement of the object, which may lead to incorrect diagnosis. Furthermore, when the blood flow velocity V decreases, the Doppler frequency decreases as is clear from equation (1), so there is a drawback that the Doppler signal becomes difficult to obtain for low-velocity blood flow such as in liver cirrhosis.

Furthermore, in order to quantify the flow velocity, it is necessary to determine the angle 0 between the blood flow observation beam and the direction of blood flow, which has the disadvantage that determining the angle θ is troublesome and requires time for inspection.

[Purpose of the invention]

This invention was made to eliminate the above-mentioned drawbacks, and provides an ultrasonic diagnostic device that enables observation of tomographic images of a living body and low-velocity blood flow in blood vessels that are approximately parallel to the body surface. The purpose is to

[Summary of the invention]

This invention correlates the reflected waves from blood cells that are scattered in multiple areas within the blood vessel at the lower right side of the tomographic view, and measures the distances between the multiple areas to determine the flow velocity. It is characterized in that tomographic display and blood flow observation are performed using the same electroacoustic transducer element.

The principle of this invention will be explained below with reference to FIG.

Here, as shown in FIG.
A case will be described in which blood flow in a blood vessel approximately parallel to the scanning plane is measured using -1 to 2-N. Normally, several adjacent electroacoustic transducers 2-1 to 2-N are selected to transmit and receive ultrasonic waves, but for the sake of explanation, one electroacoustic transducer is used to transmit and receive ultrasonic waves. think.

Now, suppose that a blood cell group above the beam B moves at a speed V and reaches the beam S' after 10 seconds.The reflected wave S from the person R is t) and S< t) and S□′(t)
Between 8A'(t)-8A(t-' -・・−・−・(2)
The relationship holds true. However, it is assumed that vwlvl, /-person A'.

The reflected wave Sm(1) is 8A1t)=4t)Cos *@t +y(t) s
in (kl@ txRe(载, ja+, t) ・-
. . . It is shown as (3). However, person t) proverb x (t) + j y (t), and IA (
t) 1 indicates the envelope of received No. 4.

Also, the reflected wave 8A'(t) is 8A'(t) xRe (A'(t) e jabt]
-------------(4).

Here 8A law)-xtt ejo. '8A/Alt
) = = (t) ej (a) oi and find the following degree of correlation r.

At this time, since τ=ma, the correlation degree r has a peak value of 1. (
The red stamp indicates complex conjugation. ) and scan Ss' h et al. scan 5. / τX
Then, the following relationship holds between τ and τ: τX τ+−(7m−7x)・−1・・−(6). Here, C indicates the speed of sound, and yl and yt indicate the distances from the scanning plane to the sample points A and A'.

Therefore, sample point A on the fault.

Determine the position of The calculation is rxmax-7+H(yt)'1) ・== ・
” (It will be 71.

At this time, if the sample points A and A are specified on the fault, scanning 3. The distance between / and SI' is xd,
Furthermore, the distance from the scanning plane to each sample point A, A' can be measured as 3'l p Y2, and the distance l between sample points A, A' can be measured as 3'l p Y2.
M! = "d + 0't yt)".

That is, the flow velocity V of blood flowing in a blood vessel can be easily calculated from equation (7).

On the other hand, when calculating the correlation degree r, the reception number S person (t) is used.

It is necessary to obtain A(t) and A'(t) from S*'(t), but this can be easily obtained using the phase detection method.

That is, the ultrasonic frequency fo = ω of the receiving No. 4 8A(t)
Two reference signals approximately equal to o/2π and 90° out of phase with each other (e.g. sin G) @j, C01al@i
By multiplying by 8 people (t) and further removing the component of ω〉ω0 by a low-pass filter, we get (SAit)Cosω,t)−(x(t)Cos”ω6
t+%t)sina4tcosa)t)(however []
indicates the output of the filter. ), and the real and imaginary parts of A(t) are obtained.

Note that A'(t) can be found in the same manner.

〔Effect of the invention〕

According to the present invention, since tomographic image display and blood flow observation can be performed using the same electroacoustic transducer, operability is excellent and examination time can be shortened. Moreover, since the blood flow velocity can be determined without depending on the angle between the beam and the blood flow direction as in the Doppler method, it is possible to determine the blood flow velocity even for blood vessels parallel to the body surface such as abdominal blood vessels. It has features such as being able to effectively observe blood flow and accurately determining the speed of low-speed blood flow.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 2, the linear electronic scanning method used in the principle of the present invention is applied, and for convenience of explanation, the same parts as in FIG. 1 are denoted by the same reference numerals. In the figure, 1 is an array type ultrasonic probe in which a plurality of electroacoustic transducers 2-4-2-N are arranged in a straight line, and the same number of electroacoustic transducers 2-□ to 2-N are arranged in a straight line. Electronic switches 3-1 to 3-N are provided. The electronic switches 3-1 to 3-N are controlled by a control signal from the scan control circuit 4, and one of the electroacoustic transducers 2-1 to 2-N is selected to be used for scanning. However, multiple scans for blood flow observation (for example, S and ' in FIG. 1).

88') can be designated by the examiner from the panel.

These electronic switches 5-3-N are equipped with a transmitting pulser 5-
A variable frequency divider 6 is connected to the pulsers 5-1 to 5-N selected by the electronic switches 3-1 to 3-N.
The output of a high frequency oscillator 8 is supplied via a branching unit 7 and a branching unit 7 . At this time, as shown in FIG.
-1-8-, a tomographic image observation pulse P for performing lJ near electron scanning is generated.

Here, the order of scanning will be established using the time chart shown in FIG. In scanning for blood flow observation, after the electroacoustic transducer 2-1 is driven by the drive pulse P1 for blood flow observation, τ
The electroacoustic transducer 2-8 is driven with a delay of -τ0. In the next scan, the electroacoustic transducer 2-8 is driven with a delay of T-τ0+Δt with respect to the transducer 2-5. In this way, during blood flow observation, scans S-j and S-8' always form a pair, and even for small scans, the delay time increases by Δτ and is repeated.

On the other hand, in scanning for tomographic image observation, the tomographic image observation pulse P,
The electroacoustic transducers 2-8 to 2-N are sequentially driven. At this time, the tomographic image observation drive pulse Pt is generated outside the refractory period before and after the blood flow observation drive pulse P is generated.

In scans S-8 to S-8 for tomographic image observation, pulsar 5-□~
The drive pulse made by 5-N is transmitted to electroacoustic transducer 2.
-1 to 2-N, and ultrasonic waves are emitted from the elements 2-1 to 2-N toward the subject. Then, the reflected waves from the subject are received by the electroacoustic transducers 2-1 to 2-Nζζ, amplified by amplifiers 9-1 to 9-N as in the conventional method, and then passed through the envelope detection circuit 10. CRTII top 2
Displayed as a dimensional image.

In the scans am' and f%' for blood flow observation, the electroacoustic transducer elements 2-, . 2-, each signal received at a booster 9-. ．． 9
-8, and then multiplier circuits 12-, . 12-m.

The ultrasonic frequency (ω・/2
Reference signals which are approximately equal to π) and whose phases differ by 90 degrees from each other are sent and multiplied with the outputs of the amplifiers 9-□ and 9-1. Further, multiplication circuits 12-, . 1
The outputs of 2- and 14- are low-pass filters 14-1 and 14-.

After components of ωo/2x or more are removed, the signal is converted into a digital signal by N converters IL1.15-8.

These signals are sent to the memories 16-, , IL, and the correlation processing circuit 17, for example, for scanning 3. / signal is memory IL,
, 16-, l are once stored, and correlation processing is performed between the signals of scanning B and t obtained after τ8. The degree of correlation r obtained by the correlation processing circuit 17 is expressed by r-τX coordinates and displayed on the CRT 18.

Therefore, while looking at the tomographic image displayed on the CRT II, we can point the sample point on the blood vessel that is almost parallel to the body surface.
' Specify the position of sample point A.

Find the distance t between A'. For example, sample poly.

By indicating the position of sample points A and A' with a marker, the distance l between sample points A and A' can be automatically measured. Next, the interval τ of scanning S, /, 8·′ is approximately 18
τX (τXmaX) when the correlation degree r takes the maximum value is determined while looking at the r-τ8 coordinates mapped in .

In this way, by finding the distance j and τ8, (
7) Blood flow velocity can be determined from equation 〇 According to this configuration, sample point A.

By determining the correlation of the reflected waves from A', it is possible to determine the blood flow velocity without depending on the angle between the beam and the blood flow direction as in the Dugra blood flow device. It is excellent for measuring the flow rate of blood cells flowing in blood vessels parallel to the body surface, and can also accurately determine the flow velocity of low-speed blood flow, so it can be applied to diagnose diseases such as liver cirrhosis. can. Furthermore, unlike the Doppler method blood flow apparatus, there is no need for the troublesome work of determining the angle 0 between the beam and the blood flow direction, so the examination time can be significantly shortened.

In addition, by using the tomographic observation probe as a blood flow observation probe and displaying tomographic and blood flow observations at the same time, it is possible to check whether the blood flow observation beam actually reaches the observation area while looking at the tomographic image. This makes it possible to prevent misdiagnosis, as well as to easily specify the observation area and shorten the examination time.

Furthermore, since τxmix can be automatically determined, the blood flow velocity V can be automatically measured, and information inside the living body can be observed in an extremely short period of time.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without changing the gist.

[Brief explanation of drawings]

! Fig. 1 is an explanatory diagram showing the measurement principle of this invention, Fig. 2 is a block diagram showing an embodiment of this invention, Fig. 3 is a time chart of the driving pulse of the blue tatami conversion element in the same embodiment, and Fig. 4 is a conventional diagram. FIG. 2 is an explanatory diagram showing the principle of the Doppler blood flow rate determination method. 1...Array type ultrasonic probe 2-□~2-N...Electroacoustic transducer element 3-1~3-N
++・Electronic switch 4...Scanning control circuit 7-・Frequency divider 5-□～
5-N... Pulsar for transmission 6... Variable frequency divider 8.
...High frequency oscillator 9-8~9-N...Amplifier l
O...Envelope detection circuit Engineering 1...C 几T111.
12-,... Multiplier circuit 13... Phase shifter 1jL,
, 14-, -...Low pass filter 11, . 15-,-
A/D converter 16-0.16-,--memory 17
...Correlation processing circuit 18...CRT21...
Linear scanning array probe 22...probe for blood flow observation Fig. 4

Claims (1)

[Claims] an electro-acoustic transducer; a transmitting means for driving the electro-acoustic transducing element to emit ultrasonic waves; and a receiving means for receiving and processing reflected signals by the electro-acoustic transducing element and displaying the reflected signals two-dimensionally. , a display means for displaying the output of the receiving means, a correlation means for correlating reflected signals from a plurality of arbitrary points on the two-dimensional image obtained by the display means, and a distance between the plurality of points is measured. An ultrasonic diagnostic apparatus characterized by comprising means.