JPS63181746A - 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] [Object of the Invention] (Industrial Field of Application) The present invention relates to an apparatus for diagnosing tissues within a subject using ultrasound, and in particular to the ultrasonic propagation velocity (hereinafter referred to as sound velocity) of tissues. The present invention relates to an ultrasonic diagnostic device that diagnoses tissue by measuring.

(Prior Art) As a device for diagnosing living tissue, there is an ultrasonic diagnostic device that diagnoses living tissue by measuring the sound velocity of the living tissue. The basic principle of the ultrasonic diagnostic apparatus will be explained below with reference to FIG.

That is, an ultrasonic probe for linear electronic scanning (hereinafter referred to as
Using a probe (referred to as a probe) 1, ultrasonic pulses are emitted into the body in the θ direction from one end A of an ultrasonic wave 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, for example, and the ultrasound reflected at point P passes through the reception path 5 and is received by the ultrasonic transducer on the right @B (hereinafter referred to as the transducer). Ru. Since the distance y between A and 8 is known, by measuring the propagation time t for propagating through paths 4 and 5, the sound speed C in the liver tissue is C = y/ (t - sin θ') - (1)
It can be found as

Furthermore, when the sound speed of standard biological tissue is Co = 1530 m/s, in order to radiate the ultrasound beam in the θ0 direction, the delay time difference τ0 between adjacent transducers of the probe 1 is expressed as 'l:o = (d/Co) −sinθ・(
2).

If the sound speed of the living tissue is Go, the ultrasound beam is θ0
However, in general, the value C is not limited to Go but is different from Go. At this time, the direction of propagation of the ultrasonic wave is determined by Snell's law as sinθ/C=sinθo/Co −(3
) is the value shown.

By the way, the sound speed C calculated using the above equation (1) is the fifth
This is the average speed of sound over the propagation path A-P-B in the figure, but apart from this, there is also a strong clinical demand to understand, for example, the sound speed of the entire liver from a macroscopic perspective. This is because in digestible liver diseases, the entire liver changes macroscopically and its spread is three-dimensional.

(Problems to be Solved by the Invention) However, according to the conventional device, the sound velocity information obtained is one-dimensional information, so the influence of non-uniform substances such as blood vessels that enter the ultrasound propagation path is strongly affected. Therefore, it is not possible to obtain sound velocity information that reflects macroscopic changes in the liver as a whole.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks, and its purpose is to provide an ultrasonic diagnostic apparatus that can accurately obtain sound velocity information that reflects macroscopic changes in a desired part of a subject. .

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a set of ultrasonic waves that transmit ultrasonic waves to a subject and receive reflected components of the transmitted ultrasonic waves from the subject. The ultrasound propagation time in each ultrasound propagation path is obtained from the received echoes collected by multiple sets of ultrasound transmissions, each with a different intersection point between the ultrasound transmission directivity and ultrasound reception directionality. It is equipped with a calculation circuit that calculates the average ultrasonic propagation velocity in the internal tissue of the subject based on the propagation time and propagation path length obtained from the above and using an evaluation function that minimizes the propagation time error. be.

(Function) The ultrasonic propagation time in each ultrasonic propagation path is determined, and based on the obtained propagation time and propagation path length, an evaluation function that minimizes the propagation time error is used to calculate the average in the internal tissue of the subject. By determining the sound speed, sound speed information that reflects macroscopic changes in the desired region of the subject can be obtained with high accuracy.

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

FIG. 1 is a block diagram of an 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 (T1-T12B) has a transducer width a of 0.
．． 67# later is 128 with element center spacing d=0.72M
The elements are lined up in a straight line. Electric signals are sent and received to and from each of these vibrators through lead wires 12 within the cable 3.

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 transmitted to the transducer array 1 via the multiplexer 13.
The voltage is applied to a predetermined vibrator in 1. 1
6 is a reception delay circuit that synthesizes and outputs the received echoes of ultrasonic waves received by predetermined transducers in the transducer array 11 after a predetermined time delay; 19 is the output of this reception delay circuit 16; This is a receiving circuit that amplifies and detects the waves. 2
2 is a memory for storing the output data of this receiving circuit 19, and 23 is an averaging process based on the relationship between the stored contents of this memory 22 and the data newly taken in via the receiving circuit 19. This is a processing circuit that performs 24 is a waveform analysis circuit that analyzes the waveform of the result of the averaging process, and 25 measures the peak value or the time (address) of the center of gravity of the waveform from the output of this waveform analysis circuit 24 to obtain the ultrasonic propagation time t. At the same time, the spatial average sound speed of the internal tissue of the subject is determined based on the obtained propagation time t and the ultrasound propagation path length. Also, in this average sound speed calculation, an evaluation function that minimizes the propagation time error is taken into consideration. Note that this calculation will be explained in detail later. 26
is a display that displays the calculation results of this calculation circuit 25. 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 and the transmission delay circuit 15 according to a predetermined program.
It also controls the setting of the delay time of the reception delay circuit 16, the write/read control of the memory 22, and the operation control of the calculation circuit 25.

Next, the operation of the embodiment device having the above configuration will be explained.

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 set so that the delay time difference τ0 between adjacent vibrators satisfies the relationship expressed by equation (1) above. Then, by the switching operation of the multiplexer 13, the transducer group T belonging to the point A of the probe 1 is
1 to T32 are connected to the output end of the pulser 14, and 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 receiving delay circuit 16 is set under the control of the system control means 27, and the transducer group T97 to T12 belonging to the point B of the probe 1 is set by the switching operation of the multiplexer 13.
8 and the input terminal of the reception delay circuit 16 are connected.

As a result, the reflected component of the ultrasonic waves transmitted toward the subject from the transducer group belonging to point A of the probe 1 at point Poo is received by the transducer group belonging to point B of the probe 1,
The reception 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 sent to the memory 22.
will be written to. 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 1, the processing circuit 23 performs averaging processing of the received echoes. The received echo read out from the memory 22 is sent to the calculation circuit 2 via the waveform analysis circuit 24.
5, and is used to measure the time t1 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 T belonging to the zero point of the probe 1 is
96～ding! 27 and the input end of the reception delay circuit 16 are connected, and the reflected component at point P11 of the ultrasound transmitted from the transducer group belonging to point A of probe 1 is the transducer group belonging to point 0 of probe 1. The waves are received by Then, the reception 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 amplified and detected by the receiving circuit 19 in the same way as in the above case, and then stored in the memory 22. The signal is input to the calculation circuit 25 via the waveform analysis circuit 24, and is 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 T belonging to the point D of the probe 1 is activated.
2 to T33 and the output end of the pulser 14 are connected, and
The transducer groups T97 to T9m belonging to point B of the probe 1 are connected to the input end of the receiving delay circuit 16. Then, the reflected component at point P12 of the ultrasonic wave transmitted from the transducer group belonging to point D of probe 1 is received by the transducer group belonging to point B of probe 1, and the received echo is as described above. Similarly, 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 transducer group T belonging to point A
The movement distance of the center position of each of the transducer groups T2 to T33 belonging to points 1 to T32 and point D in the transducer arrangement direction is Δy, which corresponds to one transducer element in this embodiment. The same relationship as above exists between the transducer groups T96 to Ti27 belonging to point 0 and the transducer groups T97 to T128 belonging to point B. In addition, the deflection angle of the ultrasound beam is always θ°
and are equal.

Therefore, point Pn and point P12 are in a line-symmetrical positional relationship with respect to a line that passes through point Poo and is perpendicular to the ultrasound transmission/reception wave surface of probe 1, and the distance between them is △
It becomes y.

Here, point Poo, point P112, and point P12 are ultrasound reflection points in the internal tissue of the subject. It means the intersection of transmitting and receiving directivity.

By the above procedure, the propagation times ti, t2', and t3 for the intersection of Poo, Pn, and PI3 are obtained.

Similarly, as shown in Fig. 3, a large number of intersections P21゜P
22. Pn, P3t, P32. P33. P34
．． Propagation time t4 for P41°°°. t5. t6.
t7. Ti.

Obtain ts, tlo, and tll. Here, the data collection area 28 is a triangle Poo-P71-P78, and this triangle is displayed superimposed on the B-mode image on the display 26 to inform the operator of the data collection area. At this time, if necessary, the data collection area can be moved, enlarged, or reduced using a trackball or the like.

Next, calculation of the average sound speed using the obtained propagation time data ti will be explained.

First, as shown in Figure 4, the propagation time ti in a two-layer medium with different sound velocities is expressed as, where yi is the distance between the transmitting and receiving elements, θ is the deflection angle, and C is the sound velocity in the medium to be measured, and is proportional to yi. It is expressed by a term to and a constant term to. Here, to also includes the delay time of the circuit related to transmission and reception of ultrasonic waves. Furthermore, from the set of (2) and (3) 12, ti is expressed as follows. Here, α=(d/τo C”).

Therefore, the propagation time error εi is defined as follows from the propagation time ti obtained as described above and the distance yi between the transmitting and receiving elements at that time.

ε1=ti−αyi−to (6) Here, ε: is caused by the nonuniformity of the propagation medium and scattering characteristics. This mean squared error f(α.

to ) is , and if this is the minimum α, and to are α, to, then C... (8) From α=jNΣyiti−Σy1Σtj]/INXyi2−
(Σyi)2]...(9) is obtained.

Since 6=d/τo '6''' - (to), the estimated sound speed @C is: c=ra/τo6/2 (111) The calculation of equation (II) is performed by the calculation circuit 25, The calculation output is displayed on the display 26.

In this way, in the device of this embodiment, the average sound speed is determined by executing the calculation of the previous equation (II), and according to this, the evaluation function that minimizes the error (ε:) in the ultrasonic propagation time is calculated. Since this is taken into account, it is possible to reduce the influence of non-uniformity of the propagation medium and scatterer, and accurately obtain sound velocity information that reflects macroscopic changes in the desired part of the subject, such as the entire liver. be able to. This information is considered particularly useful in the diagnosis of digestible liver diseases.

Here, for example, another method for obtaining the average sound velocity at a desired part of the subject is to measure the sound velocity at multiple locations and simply average them. Since the influence of the non-uniformity of the scatterer cannot be accurately removed, the sound speed information according to this embodiment is more accurate.

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, ultrasonic waves are transmitted from the transducer group belonging to point A or point D of probe 1, and
Although a case has been described in which ultrasonic waves are received by a group of transducers belonging to a point or a point 0, the same effect can be obtained even if the groups of transducers used for transmitting and receiving ultrasonic waves are reversed to the above case.

Furthermore, in the above embodiment, when switching the transducers by the multiplexer 13, the distance Δy between the center positions of the transducer group was explained as one transducer element, but the distance is not limited to this, and it is two or more transducers. It's good as well.

Furthermore, in the above embodiment, the delay times of the transmitting delay circuit 15 and the receiving delay circuit 16 were set so that the delay time difference τ0 between adjacent transducers satisfies the relationship expressed by the above equation (1). The delay time τ(X) expressed by the following equation may be set by taking into account the focal path @F of the beam.

τ(X)=(F/Co H1+(X/F)2 +2(X
/F) sin θ-1) (12) 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 match, 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 accurately detected.

Further, in the above embodiment, the area to be measured is triangular (see FIG. 3, 28), but various modifications such as rectangular, bicircular, etc. are possible.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to obtain sound velocity information that reflects microscopic changes in a desired part of a subject with high accuracy, and it is possible to obtain clinically extremely useful information. An ultrasonic diagnostic device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, FIGS. 2 to 4 are diagrams illustrating the operation of this embodiment, and FIG. 5 is a diagram illustrating the principle of measurement of ultrasonic propagation velocity. 11... Vibrator array, 25... Calculation circuit, 26.
··display.

Claims (1)

[Claims] A transducer array consisting of a plurality of ultrasonic transducers arranged, the plurality of ultrasonic transducers constituting this transducer array,
Each adjacent ultrasound transducer group is used for ultrasound transmission and ultrasound reception, and the ultrasound transducer is used for ultrasound transmission and ultrasound reception, and the ultrasound transducer is used for ultrasound transmission and ultrasound reception. In an ultrasonic diagnostic device that obtains ultrasound propagation velocity information in internal tissues and uses it for diagnosis, a set of ultrasound waves is transmitted to the subject and a reflected component of the transmitted ultrasound is received from the subject. The ultrasonic propagation time in each ultrasonic propagation path is determined from the received echoes collected by multiple sets of ultrasonic transmitters with different intersection points between the ultrasonic transmitting directivity and the ultrasonic receiving directivity. and a calculation circuit that calculates the average ultrasonic propagation velocity in the internal tissue of the subject based on the obtained propagation time and propagation path length and using an evaluation function that minimizes the propagation time error. An ultrasonic cutting device featuring: