JPH0216142B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is an ultrasonic diagnostic device, in particular, a plurality of echo signals received by a plurality of transducer elements are added by both linear addition and nonlinear addition, and after the addition, The present invention relates to an ultrasonic diagnostic apparatus that displays an image based on a signal.

BACKGROUND ART Ultrasonic diagnostic devices that transmit and receive ultrasound beams from a probe into a subject and display images of desired biological tissues based on echo signals reflected from the subject are well known; The probe has a plurality of arrayed vibrating elements, and each vibrating element within the probe is sequentially excited to transmit and receive ultrasound beams.
Ultrasonic diagnostic equipment is equipped with a transmitting focus system and a receiving focus system in order to improve the directivity of the ultrasound beam. By delaying the trigger little by little, the wavefronts of the transmitted ultrasound beams can be matched at the focal point, and a focus system at the time of reception ensures that the phases of the echo signals reflected from the focal point to each vibrating element are aligned. It can be delayed as follows. The echo signals having the same phase are used for displaying a predetermined image after being appropriately added, and FIG. 1 shows a conventional ultrasonic diagnostic apparatus that performs linear addition.

In FIG. 1, the probe 10 has N arranged vibrating elements 12-1 to 12-N, and an echo signal 100 from the vibrating elements 12-1 to 12-N.
-1 to 100-N are linearly added in the linear addition circuit 14 and then used for displaying a predetermined image. However, when echo signals are linearly added,
There has been a problem in that side lobes occur due to the element spacing of the arrayed vibrating elements, and these side lobes generate virtual images in diagnostic images.

Therefore, in order to reduce sidelobes, an apparatus has been proposed that performs nonlinear addition of echo signals, and FIG. 2 shows a conventional ultrasonic diagnostic apparatus that performs nonlinear addition.

In FIG. 2, a probe 10 and a linear addition circuit 1
4, nonlinear conversion circuits 16-1 to 16-N are provided corresponding to the vibration elements 12-1 to 12-N. And the vibration elements 12-1 to 12-
The echo signals 100-1 to 100-N from N are
After being non-linearly converted by the non-linear converting circuits 16-1 to 16-N, they are supplied to the linear adding circuit 14 and linearly added.
6-N and the linear addition circuit 14, the vibration element 1
Echo signals 100-1~ from 2-1~12-N
100-N will be non-linearly added.

Therefore, according to the device of FIG.
Echo signals 100-1 to 1 from -1 to 12-N
Since 00-N is added nonlinearly, the influence of side lobes is suppressed, and the signal for image display is generated in the same way as when transmitting and receiving ultrasound by narrowing the ultrasound beam (main beam). Obtainable. However, this method requires the same number of nonlinear conversion circuits as the number of vibrating elements that transmit data simultaneously, which has the drawback of increasing the size and cost of the device. Furthermore, since there are many nonlinear conversion circuits,
The non-linear conversion circuit has the drawback of increasing noise.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.The purpose of the present invention is to perform addition by appropriately combining linear addition and non-linear addition, and to use the added signal for image display. It is possible to suppress the influence of lobes and obtain reception information similar to that obtained by transmitting and receiving ultrasonic waves by narrowing the main beam. To provide an ultrasonic diagnostic device that can thereby improve directivity and improve azimuth resolution, further reduce the number of nonlinear conversion circuits, and achieve miniaturization and cost reduction of the device. It is in.

Structure of the Invention In order to achieve the above object, the present invention includes a probe having a plurality of arranged vibrating elements, and a plurality of echo signals received by the plurality of vibrating elements, which are collected into a predetermined number of echo signal bundles. an integrating circuit which further collects a predetermined number of the plurality of echo signal bundles into an echo signal group, further organizes and integrates the plurality of echo signal groups in a predetermined order and outputs them as a predetermined number of echo signal groups; Group linear addition circuits of the same number as the number of echo signal groups linearly add the echo signals of each echo signal group connected to the integrated circuit, and addition signals from the group linear addition circuits connected to each of these group linear addition circuits. a nonlinear conversion circuit consisting of the same number of logarithmic amplifier circuits as the number of group linear addition circuits that perform nonlinear conversion, respectively, and a comprehensive linear addition circuit that linearly adds the nonlinear signals from these nonlinear conversion circuits, and performs nonlinear addition of echo signals. It is characterized by

Embodiments Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

First, the relationship between each vibrating element of the probe and a point sound source will be explained.

FIG. 3 shows the relationship between each vibrating element and a point sound source.
2-N are arranged at intervals d.

In FIG. 3, in order to take into account directivity during reception, a point sound source 18 inside the subject is first placed at the probe 10.
is at the initial point P ₀ , distance F from the front of
After that, let us consider the case of moving in an arc shape with radius F. The point after this movement is Pθ, and the echo signal reflected from the point sound source 18 at the point Pθ is transmitted to the vibration element 12.
-1 to 12-N, a time difference _tip is given to each echo signal of the vibrating elements 12-1 to 12-N. Here, the time difference t _ip is such that the point sound source 18 is the point P ₀
It is set so that the phases of the echo signals received by the vibration elements 12-1 to 12-N are all the same when the vibration elements 12-1 to 12-N are present. Also, ₀ ===F θ=r _i , θ ₀ =r _i , o = (2i-N-1)d/2. The signal waveform including the time difference of the echo signal 100-i received by the vibrating element 12-i is defined as giθ(t), which is defined as the following equation. Furthermore, in Fig. 4, this echo signal giθ
(t) waveform is shown.

However, T=i/f, _i 〓=t _ip −r _i 〓/c+F/c, n _c
Let be the number of cycles in the RF pulse and c be the speed of sound.

In addition, γ _i 〓 is calculated from Fig. 3, assuming the oscillator spacing as d. It can be expressed as

Next, FIG. 5 shows a block circuit of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

In FIG. 5, the probe 10 has a plurality of arrayed vibrating elements 12-1 to 12-N, and echo signals 100- from the vibrating elements 12-1 to 12-N.
1 to 100-N are organized and integrated in a predetermined order by an integration circuit (not shown) to form N echo signal groups, and these N echo signal groups are each processed by a group linear addition circuit 20-N.
1 to 20-M and are linearly added. The effect of sorting and integrating echo signals by the integrating circuit will be explained below.

The integrated circuit collects Ne echo signals (three in the embodiment) into an echo signal bundle, and further
Ng echo signal bundles (four in the example) are combined into an echo signal group, and multiple echo signal groups are further consolidated in a predetermined order, that is, the echo signal groups are consolidated with a period M to form an echo signal group. Let the echo signal group be Therefore, for example, the first stage group linear addition circuit 20-1 receives the echo signal 100-1.
1 to 100-(Ne×Ng) is input, then the echo signal 100-(Ne×Ng×M+1) to 100
((Ne×Ng)×(M+1)) is input, and will be input in the same manner thereafter.

That is, group linear addition circuits 20-1 to 20-2
0-M, (Ne×Ng) echo signals are sequentially inputted with a period M, and therefore, each group linear addition circuit 20-1 to 20-M receives N/M echo signals, respectively.
echo signals will be input.

The addition signals 102-1 to 102-M from the group linear addition circuits 20-1 to 20-M are respectively supplied to normalization circuits 22-1 to 22-M and normalized, and then, the nonlinear conversion circuits 24- 1-24
- supplied to M. Nonlinear conversion circuits 24-1 to 24-2
In the embodiment, 4-M is a logarithmic amplifier circuit, which divides the normalized signals 104-1 to 104-M from the normalization circuits 22-1 to 22-M into positive and negative signals and logarithmically transforms them separately. , positive, and negative, respectively, and supply them to the overall linear addition circuit 26. The comprehensive linear addition circuit 26 is a nonlinear conversion circuit 2
Nonlinear signals 106-1~ from 4-1~24-M
106-M is linearly added to output a sum signal 108, which is normalized by a normalization circuit 28 and then used as a predetermined image display signal.

Therefore, the nonlinear conversion circuits 24-1 to 24-M and the total linear addition circuit 26
0 is configured, and the nonlinear addition circuit 30 can nonlinearly add the echo signals 100-1 to 100-N to generate a multiplication effect in input terms, suppressing the influence of side lobes and converting the main beam. It is possible to obtain a received signal similar to that obtained by transmitting and receiving ultrasonic waves by making the beam thinner, and it is possible to improve directivity and improve azimuth resolution. Further, the echo signals 100-1 to 100-N are combined into M summed signals 1 by group linear addition circuits 20-1 to 20-M.
02-1 to 102-M and then supplied to the nonlinear addition circuit 30, the nonlinear conversion circuit 24-1 is ~24-
The number of M can be reduced, thereby
The device can be made smaller and cheaper, and noise caused by the nonlinear conversion circuit can be reduced.

Next, the above-mentioned nonlinear addition of echo signals can be expressed mathematically as follows.

If the normalized signal 104-k before nonlinear transformation is h _k 〓, h _k 〓 becomes as shown in equation (3).

h _k 〓=1/(N/M)N/(Nc・Ng・M)Ne・Ng Σ _l=1 Σ _j=1 g _{NeNg(Ml-M+k-1)+j} , θ ^(t) … ...(3) Then, if the nonlinear signal 106-k from the nonlinear conversion circuit 24-k is Y(h _k 〓), then Y(h _k 〓) is
It can be expressed as equation (4). Note that FIG. 6 shows the conversion action of the nonlinear conversion circuit, that is, the relationship between h and Y(h).

Y(h _k 〓)＝Alog(h _k 〓／α) for h _k 〓α 0 for −α＜h _k 〓＜α −Alog(h _k 〓／−α)for h _k 〓−α ………( 4) The addition signal 108 from the nonlinear addition circuit 30 is
It is normalized by the normalization circuit 28, and this normalization circuit 2
If the output signal from 8 is Vθ(t), then Vθ(t)
becomes as shown in equation (5).

Vθ(t)=1/M _M 〓 ^k=1 Y(h _k 〓) ………(5) Therefore, since the directivity coefficient R(θ) has already been logarithmically compressed, it can be expressed as in equation (6). Define.

However, it is assumed that the input condition satisfies N=k・M (k: natural number) N/MNe.

In the above equation, when M=1, the output signal of the linear addition circuit is logarithmically compressed, which is the same as the conventional system. Then, the number of nonlinear additions is assumed to be two. That is, when M=2, there is a dip in the directivity at the angle θ _do in the directivity during linear addition, and by using this dip, it is possible to improve the directivity.

Next, FIG. 7 shows a specific configuration of an ultrasonic diagnostic apparatus according to an embodiment. In the block circuit of FIG. 7, there are four nonlinear circuits, that is, M=4.

In FIG. 7, the oscillator circuit 32 supplies a trigger signal to the electron focusing phase control circuit 34,
The electronic focusing phase control circuit 34 performs phase control based on the trigger signal so that the phases of the transmission pulses are in the same phase, and supplies the trigger pulse to the scanner circuit 36 . The scanner circuit 36 supplies a transmission trigger to the probe 10 based on the trigger pulse from the electronic focusing phase control circuit 34, and as a result, each vibrating element in the probe 10 is excited, so that the probe An ultrasound beam will be transmitted from the child 10 to a subject (not shown).

The echo signal reflected from the object is transmitted to the probe 1
0 and is supplied to the electronic focusing phase control circuit 34 via the scanner circuit 36. Since the electron focusing phase control circuit 34 performs phase control similar to that during transmission, the echo signals reflected from the focus within the subject all have the same phase.

The echo signal group 100 from the electron focusing phase control circuit 34 is supplied to the integration circuit 38, and the echo signal group 100, that is, the echo signals 100-1 to 100-N, are processed in the above-described predetermined order by the integration circuit 38. The signals are organized and integrated into four echo signal groups. Then, each of the four echo signal groups is connected to a group linear addition circuit 20-1.
~20-4 is linearly added, and the normalization circuit 22-1
~22-4, and then supplied to the nonlinear addition circuit 30 for nonlinear addition. That is, the nonlinear addition circuit 30 is the nonlinear conversion circuit 24
-1 to 24-4 and the general linear addition circuit 26, and the normalized signals 104-1 to 104-4 from the normalization circuits 22-1 to 22-4 are transmitted to the nonlinear conversion circuits 24-1 to 24-4, respectively. After being non-linearly converted in step 4, the signal is supplied to a total linear addition circuit 26 for linear addition, and the total linear addition circuit 26 receives the addition signal 10.
Outputs 8.

The sum signal 108 is normalized by the normalization circuit 28 , amplified and detected by the amplification/detection circuit 40 , and then supplied to the scan converter 42 . Then, the scan converter 42 stores the signal from the amplification/detection circuit 40 as image data to form an image, so that a desired diagnostic image is displayed on the CRT 44.

Therefore, in the block circuit of FIG. 7, the echo signals 100-1 to 100-N are nonlinearly added by the nonlinear addition circuit 30 (nonlinear conversion circuits 24-1 to 24-4 and the total linear addition circuit 26). As a result, it is possible to suppress the influence of side lobes and obtain a received echo signal similar to that obtained when transmitting and receiving ultrasonic waves by narrowing the main beam, improving directivity and improving azimuth resolution. , This makes it possible to obtain good ultrasound diagnostic images. Further, a group linear addition circuit group 20 is provided before the nonlinear addition circuit 30, and the echo signals 100-1 to 100-N are linearly added in the group linear addition circuits 20-1 to 20-4, and then added to the nonlinear addition circuit group 20. Since it is supplied to the adder circuit 30, the number of nonlinear conversion circuits can be reduced to four in the embodiment, thereby achieving miniaturization and cost reduction of the device. be able to.

Note that FIG. 8 shows the relationship between the angle from the central axis and the directivity coefficient, and in the figure, lines l ₁ , l ₂ ,
l ₃ and l ₄ are, respectively, in the case of total linear addition, in the case of a concave single oscillator, in the case of total linear addition (transmission) + logarithmic addition (M = 4, Ng = 4) (reception), and logarithmic addition ( M=4, Ng=4). It is understood that in the case of logarithmic addition (M = 4, Ng = 4), the directivity coefficient is significantly lower than in other cases, and in the normal case, when transmitting (or receiving) Since the image is composed of echo signals of −30 dB or more in Directional resolution can be improved.

Effects of the Invention As explained above, according to the present invention, by adding an appropriate combination of linear addition and nonlinear addition, received echoes due to side lobes are suppressed, and the main beam is narrowed to transmit and receive ultrasonic waves. A received echo signal similar to that obtained by transmitting waves can be obtained. As a result, the directional resolution can be improved by improving the directivity, and it is therefore possible to obtain a good ultrasonic diagnostic image. Furthermore, in the present invention, high resolution can be maintained and the number of nonlinear conversion circuits can be reduced, so that the device can be made smaller and lower in price.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram of a conventional ultrasonic diagnostic device that performs linear addition, Fig. 2 is a block circuit diagram of a conventional ultrasonic diagnostic device that performs nonlinear addition, and Fig. 3 shows the relationship between each vibrating element and a point sound source. Explanatory diagram showing the relationship, 4th
Figure 5 is an explanatory diagram showing the waveform of an echo signal, Figure 5 is a block circuit diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, Figure 6 is a graph diagram showing the conversion action of the nonlinear conversion circuit, and Figure 7 is an implementation example. FIG. 8 is a block circuit diagram showing a specific configuration of the ultrasonic diagnostic apparatus according to an example, and a graph diagram showing the relationship between the angle from the central axis and the directivity coefficient. 10... Probe, 12-1 to 12-N... Vibration element, 20... Group linear addition circuit group, 20-1 to
20-M...Group linear addition circuit, 24-1 to 2
4-N...Nonlinear conversion circuit, 26...Comprehensive linear addition circuit, 38...Integration circuit, 100-1 to 100-N...
Echo signal, 102-1 to 102-M... addition signal, 106-1 to 106-M... nonlinear signal.

Claims (1)

[Claims] 1. A probe having a plurality of arranged vibrating elements; a predetermined number of echo signals received by the plurality of vibrating elements; an integration circuit that collects a predetermined number of signal bundles into an echo signal group, and further integrates the plurality of echo signal groups in a predetermined order and outputs them as a predetermined number of echo signal groups; Group linear addition circuits of the same number as the number of echo signal groups that linearly add the echo signals of each signal group, and group linear addition circuits that are connected to each of these group linear addition circuits and perform nonlinear conversion on the added signals from the group linear addition circuits. A nonlinear conversion circuit consisting of logarithmic amplifier circuits of the same number as the number of addition circuits, and a general linear addition circuit that linearly adds nonlinear signals from each of these nonlinear conversion circuits, and performs nonlinear addition of echo signals. Sonic diagnostic equipment.