JPS58146338A - 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 ultrasonic diagnostic apparatus that obtains a single tomographic image of a living body using ultrasonic waves. The present invention relates to an ultrasonic diagnostic device that improves azimuth resolution by mechanically moving the device.

[Technical background of the invention and its problems]

Ultrasonic diagnostic methods are used to diagnose living organisms, and this method emits ultrasonic pulses within the living body and reflects them from the boundaries of tissues with different acoustic characteristics (acoustic impedance). Information inside the body is obtained by signals. Since such ultrasonic examinations can be performed non-invasively, they do not cause any pain to the examinee, and are not only less likely to cause damage due to exposure to radiation than in the case of X-ray examinations.

It has become rapidly popular recently because it allows to easily obtain tomographic images of soft tissues.

A specific example of a device for implementing this is an ultrasonic diagnostic device.In conventional electronic scanning type ultrasonic diagnostic devices, in order to improve azimuth resolution, transducers are A relative delay time is given to the drive signal and the wave is transmitted and received.

A so-called electron focusing method is being used. Furthermore, a moving focusing method is also known in which the focusing position is sequentially moved in the ultrasound transmission direction to uniformly improve the resolution at any depth.

Also, the direction perpendicular to the array direction (hereinafter referred to as the lens direction)
In this case, a focusing method using an acoustic lens is used. but,
In the focusing method using such a lens, since the focusing point is fixed, there is a drawback that it is not possible to obtain good resolution at a location far from the focusing point.

[Purpose of the invention]

σ) The invention eliminates the drawbacks of the ultrasound beam, makes it easy to adjust the focal point of the ultrasonic beam, and allows the area to be diagnosed to be accurately positioned near the focal point at all times, thus producing high-quality tomographic images. The purpose of the present invention is to provide an ultrasonic diagnostic device that can be obtained.

[Summary of the invention]

The ultrasonic diagnostic apparatus of the present invention includes means for mechanically moving an array type ultrasonic probe in a direction perpendicular to the arrangement direction of a plurality of transducer elements, and a predetermined means for correcting signals received by the transducer elements. The ultrasonic beam is provided with a means for giving a delay time of 1 and aligning and synthesizing the reflected waves in phase, and focuses the ultrasonic beam in the direction in which the plurality of vibrating elements are arranged and in the direction perpendicular thereto by electronic means.

The array type ultrasonic probe 10 used in this invention has omnidirectional or weak directivity in the direction (lens direction) perpendicular to the transducer arrangement direction, and one side transducer arrangement as shown in Figure 1 fal to fcl. In the direction (array direction) Y, strong beam focusing is performed over a relatively wide range by the electron focusing method as described above. In the figure, numerals 1, 2, 3, . . . indicate arranged vibrators. Further, arrow E indicates electronic scanning in that direction, and arrow M indicates mechanical scanning in that direction.

FIG. 2 shows the principle of operation of the lens in the direction X of the present invention. The probe 10 emits ultrasonic pulses while
It moves on the axis in the order of A→B, C, D, and E, and receives the reflected wave from the reflecting object P placed directly below the 0 point. In this case, it is assumed that one reflecting object P is included within the beam width of the probe 10 at any position of points A to E.

In FIG. 2, the probe 10 is located at point A or point E.
An ultrasonic pulse is emitted from and reflected by a reflecting object P,
By the time you return to the probe 10 again, t□-1 = Niru Taishi Sekiji 009101. ．． (1) takes time.

Similarly, at point 8 or point D, 2 □ tB=tn= -/a'+L・2 ・・・・・・・・・
... (2). Also, at 0 points, jo=-L ・・・・・・・・・・・・・・・・・・
......(3). However, (1) to (
In equation 3), d is the moving pitch of the probe 10, L is the distance from the 0 point to the reflecting object P, and V is the ultrasonic velocity in the medium.

Therefore, a correction delay time corresponding to the above-mentioned time is given to the signal obtained at points A-E, so that the phases of the reflected waves from the reflecting object P in the signals obtained at each point match. For example, only these reflected waves are combined in the same phase. In other words, only the signal from the reflecting object P is received stronger than other signals, and can be clearly detected.

This correction delay time is based on the received signals at points A and E, and is 8. Relative delay time τ3 to be given to the received signal at point D or point 0. τ9. τ. are respectively.

Figure 3 shows the received signal at points A-E when there is another reflective object P' alongside the reflective object P at the depth L, fal is before time correction, and (b) is the received signal before time correction. The signal after correction by giving a delay time, and (cl shows the signal synthesized from fbl. Looking at the signal after synthesis in Fig. 3 rc+, the signal from one reflecting object P is emphasized. , it can be seen that it can be distinguished from other things.

〔Effect of the invention〕

In this invention, when an array type ultrasonic probe is mechanically moved in a direction perpendicular to the arrangement direction, the ultrasonic beams are focused in the transducer arrangement direction and in a direction perpendicular to this by electronic means. It is. Therefore, the focal point of the ultrasound beam can be adjusted easily and relatively quickly in any direction, so the area to be diagnosed can always be accurately positioned near the focal point, and high-quality tomographic images can be obtained. It has its features.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of an array-type ultrasonic probe 21 and an ultrasonic transceiver circuit 22 that transmits and receives ultrasonic waves through the probe 21, and FIG. 5 is a diagram showing such an ultrasonic probe 21 and the ultrasonic transceiver circuit 22 is a circuit configuration diagram of the entire embodiment.

As shown in FIG. 4, the ultrasonic probe 21 has a plurality of transducers 211 to 219...21M arranged in a straight line, and the same number of electronic switches corresponding to these transducers. 231-239...23M are provided. Each of the vibrators 211 to 215 is an electronic switch 23
1 to 235 to one end of the delay lines 241 to 245, and the other ends of the delay lines 241 to 245 are connected to the pulsers 2 at once.
5 and the input end of limiter 26, respectively.

The vibrators 216 to 219...21M and the electronic switches 236 to 239...23M are each 5
One by one! Vibrators 211 to 215 respectively are soaked in water
Similarly to the circuit and electronic switches 231-235, they are connected to the pulser 25 and limiter 26 via delay lines 241-245, respectively. 27 in the figure is a preamplifier,
28 indicates a scanning control circuit.

In the case of tf transmission, the drive pulses generated by the pulser 25 are supplied to the vibrators 211 to 215 via the delay lines 241 to 245, respectively, by turning on the electronic switches 231 to 235.
5 generates ultrasonic waves.

As a result, the ultrasonic waves reflected in the medium (for example, the reflective object P in FIG. 2) are received by the imagers 211 to 215, respectively, and are received by the electronic switches 231 to 235. Delay lines 241-245
After passing through, the signals are added and sent to the preamplifier 27 via the limiter circuit 26. The limiter circuit 26
Excessive amplitude signals such as the high voltage pulse output of
7 is blocked by +hl.

At this time, the delay lines 241 and 245 are short-circuited between terminals on both sides (that is, delay time is zero), and the delay lines 242, 244, and 24
For example, the delay times in Eq. 3 are set as shown in Equation (4) and Equation (5), respectively. In this way, electron focusing of the ultrasonic beam is performed.

The output of the preamplifier 27 is as shown in FIG.

After being sent to the sample and hold circuit 29 and converted into a digital signal by the MD converter 3°, it is stored in a RAM (random access memory) 311.

Next, in FIG. 4, the same operation as before is performed with the electronic switch 241 turned off and the terminal switch 246 turned on, but at this time the delay lines 242 and 246 are short-circuited between both terminals (that is, the delay is zero). , the delay line 243245, and the delay line 244 are set as shown in equations (4) and (5), respectively, and the transducers 212 to 2J6 are used to transmit and receive ultrasonic waves. The received signal at this time is also converted into a digital signal and then stored in the R, AM 311.

In this way, the vibrators 211 to 219...21
These operations are repeated (M-4) times while shifting M one by one in the direction shown by arrow Y until camera elements 21 (M-4) to 21M are finally used. The signals are stored in R and AM 311, respectively. That is, the R, AM 311 stores all received signals when the ultrasonic probe 21 is electronically scanned in the array direction at the initial position.

Next, the ultrasonic probe 21 takes one step (for example, 11113) in the direction of the lens using a signal from the probe drive circuit 32.
Moving. Similarly to the first position, electronic scanning in the array direction is performed at this position number, and the signals obtained by (M-4) ultrasonic transmission and reception are converted to FO as digital signals.
AM 312.

Thereafter, these operations are continued until the position of the ultrasound probe 21 is moved by (N-1) steps in the direction of the lens indicated by arrow X.

FIG. 6 is an explanatory diagram schematically showing a memory circuit in the case of RAM 311. As shown in the figure, the width of the section is represented by -■ bits, the depth direction is \, and the array direction is represented by M-4 pieces of three-dimensional information.

The depth direction area to be stored here is ΔL, and the sample must satisfy the sampling theorem for the received signal. That is, if the highest frequency component of the received signal is fh and the sampling frequency is f5, then f, and 2fh ・・・・・・・・・・・・・・・・・・
(6), and fs=□ ・・・・・・・・・・・・・・・・・・(
The force is 2ΔX.

Next, we will discuss how to combine the signals stored in R and AM 311 to 31M and focus the beam in the lens direction.

Since the stored signals have already been beam focused in the array direction, the signal synthesis here is mainly done by using the same transducer group (for example, 211 to 215) and moving the ultrasound probe 21 in the lens direction. The beam is focused in the lens direction by correcting the delay time between signals obtained while moving the lens.

First, the case of the first signal in the array direction in the RAMs 311 to 31N (R and AM 311 in FIG. 6 are indicated by diagonal lines) will be described.

This principle has already been shown in FIGS. 2 and 3, but here the delay time can be corrected by specifying the addresses of the FOAMs 311 to 31N. This address is designated by the delay time designation circuit 33 for the RAMs 311-31N.

The correction accuracy at this time depends on the sampling period Ts in the sample and hold circuit 29, and the allowable error △
τ, that is, the sampling frequency is determined by the above (in addition to the force equation).

As described above, in the present invention, since the beam focusing in both the lens direction and the array direction of the array type ultrasonic probe is performed electronically, the focusing point can be changed arbitrarily. Therefore, the region to be diagnosed can always be accurately located near the focal point, which has the advantage of providing high-quality tomographic images.

In FIG. 5, signal synthesis is performed by a digital adder 34, and an envelope signal of the output signal is extracted by a detection circuit 35 and stored in a frame memory 36. One or more images displayed on a display 38 such as CR or T are stored as they are in the frame memory 36. The output of the frame memory 36 is converted into an analog signal by a D/A converter 37 and displayed on a display 38. If the output of the frame memory 36 is adjusted to the TV format, it becomes possible to display it on a general TV monitor. In FIG. 5, numeral 39 indicates a main control circuit for controlling the entire system, and numeral 40 indicates a probe position signal generator.

In this invention, since the focal point of the beam can be changed freely in both the array direction and the lens direction ζ and at relatively high speed, B
Needless to say, the rL mode method is more effective when applied to the C mode method, that is, when obtaining a tomographic image in a plane with a constant depth.

In the case of the C-mode method, the amount of data t in the depth direction to be stored is extremely small compared to the case of the B-mode method, and the image quality in this case is mainly determined by the azimuth resolution in the array and lens directions. Therefore, the effects of applying this invention are significant.

In addition, this invention e can be applied to a so-called water immersion test in which the array probe is immersed in water in order to move it, and this can be applied to a breast cancer actual examination device as already reported by the present inventor. is also possible.

Although the embodiments of the present invention have been described using electronic scanning type probes, a configuration in which the sector probes are mechanically moved may also be adopted.

The focusing method in the lens direction in this invention is similar to the aperture synthesis method in the radar field, but its distinctive feature is that real-time electronic focusing is used in the array direction, so the aperture synthesis method is This method has the advantage that the image configuration time is relatively short. Regarding the synthesizing means in the lens direction, as an example, a method that processes on the time axis has been described, but it can also be performed by converting to one frequency axis using an F'F'T (fast Fourier transform circuit).

In addition, in the aperture synthesis method, in order to obtain high resolution, it is preferable that the transmitting and receiving sensitivity of the probe in the lens direction is as non-directional as possible, and for this purpose, the aperture must be made small.

That is, let D be the aperture of the probe in the lens direction.

Under the condition that the medium is homogeneous and ignoring ultrasonic attenuation, the lateral resolution at any depth is given by XΔΔX:D/2.

However, if the aperture in the lens direction of the array type probe is made smaller.

1) Transmission and reception sensitivity decreases.

2) The transverse vibration mode in the lens direction affects the thickness vibration mode.

3) Difficult to manufacture.

There are other problems. Therefore, as an improvement on this, a configuration for obtaining an isometric omnidirectional beam while increasing the aperture will be described with reference to FIG. 7 (al to tel).

@ In Figure 7, fa) indicates the beam width when the aperture of the probe in the lens direction is made smaller. In the figure, 41 is a vibrator. In (b) and (c), a single beam is focused on a relatively shallow portion by a lens 42 or a concave vibrator 43, and a diffused region behind it is used to produce a beam similar to that in the case of fal.

(dl (e) similarly shows a configuration in which a diffused beam is obtained using a lens 44 or a concave vibrator 45.

In signal processing, it is necessary to perform calculations on the assumption that a small-diameter probe is placed at the virtual point Q, [the focal point in the case of fb)tel].

[Brief explanation of the drawing]

Figures 1 (al~(C)) are explanatory diagrams of an example of an array-type ultrasonic probe used in the present invention and the ultrasonic beams generated thereby, and Figures 2 and 3 (al~(cl)
4 is an explanatory diagram showing the operating principle in the lens direction of this invention, FIG. 4 is a configuration diagram extracting an array type ultrasonic probe and an ultrasonic wave transmitting/receiving circuit according to an embodiment of this invention, and FIG.
The figure is a circuit configuration diagram of the entire embodiment, and FIG. 6 is an explanatory diagram schematically showing an example of a memory circuit used in this embodiment.
FIGS. 7(a) to 7(e) are explanatory diagrams of a configuration for obtaining an omnidirectional beam in the lens direction while keeping the aperture large. 1.2, 3: Transducer 10 Near-array type ultrasonic probe 21 Near-array type ultrasonic probe 211-219...21M: Vibrator 22: Ultrasonic wave transmitting/receiving circuit 231-239...23M: Naruko switch 241-2
45: Delay line 25: Pulser 26: Limiter 27: Preamplifier 28: Scan control circuit 29: Sample hold circuit 30: A/D converter 311-3
13...31N: RAM 32 Nibrobe drive circuit 33: Delay time control circuit 34: Digital adder 3-5: Detection circuit 36: Frame memory 37: D/A converter 39: Main control circuit 40 Nibrobe position signal generation vessel

Claims (4)

[Claims] (1) An array-type ultrasonic probe consisting of a plurality of transducers arranged in one dimension, and a means for mechanically vertically moving the probe in a direction perpendicular to the arrangement direction of the transducers. , means for giving a delay time for correction to the signal received by the vibrator and aligning and synthesizing the reflected waves in phase, the arrangement direction of the plurality of vibrators and the direction perpendicular thereto An ultrasonic diagnostic apparatus characterized in that an ultrasonic beam is focused by electronic means. (2) Focusing of the ultrasonic beam in the direction in which the plurality of image sensors are arranged is performed by giving a delay time to the received signal using a delay element, and focusing the ultrasound beam in the direction perpendicular to the direction in which the image sensors are arranged. The ultrasonic diagnostic apparatus according to claim 1, wherein the receiving signals of each step are stored in a plurality of storage circuits, and then the addresses of these storage circuits are designated and read out. . (3) Claims 1 or 2, characterized in that only received signals at a certain depth with respect to the moving plane of the array type ultrasound probe are peeked out and displayed as a C-mode tomographic image. The ultrasonic diagnosis and analysis device described above. (4) Claims 1 to 4 are characterized in that a curved UIrI camera element or an acoustic lens is used to diffuse the dark acoustic beam in the direction perpendicular to the direction in which the plurality of transducers are arranged. The ultrasonic diagnostic apparatus according to any one of 3.