JPH0390137A - Reception aperture control circuit - Google Patents

Abstract

PURPOSE:To improve picture quality with a step difference of a picture image and unevenness of resolution in the same picture image eliminated by performing a reception aperture control with an amplifier gain continuously changed for the lapse of time. CONSTITUTION:A gain control amplifier 7a is provided before an adder 8, and a received analog signal Z2, which passes through a reception focusing delay 5a and a delay amount selecting circuit 5b, is reception aperture-controlled. A reception aperture control here is performed by a reception amplifier gain which is an output signal of an aperture gain control circuit 9a, synchronized with a trigger signal Y and changed with the lapse of time. As described in the above, a gain control signal is generated with the lapse of time in every trigger pulse and input to the reception gain control amplifier with amplitude of a reception signal of a vibrator block continuously controlled in a depth direction, and by eliminating a rapid change of reception amplitude in the close- open point of a reception aperture and a rapid change or the like of reception beam width, a clear picture image is obtained by eliminating a step difference of the picture image and unevenness of resolution.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a medical ultrasonic diagnostic apparatus, and more specifically, when receiving ultrasonic echoes from a specimen, the aperture control is performed to adjust the receiving focus point as well as the receiving focus point. This invention relates to an improvement of an aperture control circuit for narrowing the receiving beam other than the receiving focus point and improving azimuth resolution.

[Conventional technology]

Medical ultrasound diagnostic equipment irradiates the human body with ultrasound beams,
A device that receives ultrasonic waves reflected from the interface of the RCA in the body, that is, the interface of the human body Q, U, and Tri with different acoustic impedances, and diagnoses the internal state of the body by converting these received images into images. It is.

FIG. 5 is a block diagram showing an outline of such an ultrasonic diagnostic apparatus.

In the figure, reference numeral 1 is a probe, inside which there are many microscopic ultrasonic transducer blocks (hereinafter simply referred to as transducer blocks). Emit sound waves and receive ultrasound echoes. A matrix switch 2 selects which transducer block is used for transmission or reception among the transducer blocks in the probe, and selectively switches the order in which the transducer blocks are scanned pitch by pitch. 3 is a transmission circuit that generates a high voltage transmission pulse to energize the transducer block within the probe, and 4 is a reception circuit that receives and amplifies ultrasonic echoes from within the body. Reference numeral 5 denotes a delay circuit which secures a delay time for focusing the ultrasonic waves by phase synthesis in both transmission and reception. A transmission trigger 6 generates a timing pulse for energizing the transducer block within the probe. 7 is an aperture control circuit which uses aperture control to narrow the reception beam width not only at the reception focus point but also at areas other than the reception focus point to improve azimuth resolution. 9 is an aperture control signal generation circuit that generates a control signal for aperture control. Reference numeral 8 denotes an adder that adds the received signals of each transducer block after aperture control by the circuit 7. The reason for performing this addition is to convert the ultrasound beam corresponding to the video signal of each scanning line of the image into one time-series signal (also called RF video signal). In order to effectively operate the dynamic band pass filter (DBPF), the received signal is amplified. 11 is the DBPF
Then, the frequency spectrum that changes in the direction of depth inside the body (corresponding to time) is filtered by the filter characteristic that changes in the direction of time, and is corrected by 111i.In other words,
Since the frequency of the received signal decreases depending on the depth within the body, it is provided to correct this and extract only the desired signal. Note that filters with such characteristics are publicly known. Reference numeral 12 is a detection/smoothing circuit.
The F video signal is detected from a ± signal to a child signal, and harmonic components are smoothed. 13 is a time gain control circuit (also abbreviated as TCC), which amplifies the RF video signal on a LOG (logarithmic) scale in consideration of the brightness of the image on the TV monitor and the human visual sensitivity. An RF video signal that is attenuated with depth is determined to have a constant amplitude regardless of the depth inside the body.

Here, a series of operations will be explained.

First, a transmission trigger pulse is generated from the transmission trigger 6,
In order to focus, the transmission trigger pulse is delayed through the delay circuit 5, and the transmission circuit 3 applies a high voltage energizing transmission pulse to the matrix switch 2, and selects the scanning line from which transducer block assembly in the probe is to be transmitted. After selecting the scanning order of the transducer block assembly using the signal generation circuit 15, the ultrasonic waves are emitted through the probe 1.9 At the same time as the ultrasonic waves are emitted into the human body, ultrasonic echoes from within the human body are emitted. Reception is started, and the received signal is passed through the matrix switch 2, which transducer block assembly in the probe is to receive the signal, and the received signal is amplified by the receiving circuit 4. After that, it is delayed by a delay circuit 5, and after aperture control is performed by a circuit 7, one ultrasonic beam corresponding to the video signal for each scanning line of the image is converted into a time-series RF video signal by an adder 8. . This signal passes through the amplifier IO, the DBPF II, the detection/smoothing circuit 12. The signal is passed through the TGC 13, A/D converted by the digital circuit 16, and processed as a video signal for each scanning line of the image on the television monitor.

By the way, as is well known, aperture control is the aperture diameter (number of transducers) that captures echo signals depending on the depth of the sample, that is, the aperture's diameter when the ultrasonic echo from the sample is received by the transducer block. It changes size. For example, as shown in Figure 6, at the shallow depth of the specimen Pl, the aperture is narrow as shown in A1.
At the deep point P3, the aperture is widened like A3. Note that the dotted lines in the figure virtually indicate the positions of the received signals received at the same time, and it is therefore understood that it is necessary to delay the reception (ε signal) depending on the position of the vibrator.

FIG. 7 is a partially enlarged view of FIG. 5 related to aperture control, and FIG. 8 is an explanatory diagram for explaining a conventional example of an aperture control circuit.

That is, in FIG. 7, the receiving circuit 4 of FIG. 5 is replaced with the receiving amplifier 4.
The circuit is exactly the same as FIG. 5, except that the delay circuit 5 is shown as a representative by 5a and the delay circuit 5 is divided into a delay 5a and a delay selection circuit 5b. However, Zl in Fig. 7 is an RF analog signal,
Z2. Z3 indicates an analog signal, and Z4 indicates an RF video signal.

That is, conventionally, as shown in FIG. 8(a), an analog switch 71 is provided inside the aperture control circuit, and each of the analog switches 71 is connected to the outputs S1 to S6 from the aperture control signal generation circuit 9 (here, the number of oscillators is 12). Since each vibrator is symmetrical with respect to the axis indicated by symbol C in Fig. 6,
For example, as shown in FIGS. 8(C) to 8(H), on/off control is performed by using two pairs of switches (two each are used in pairs). At this time, as is clear from Fig. 6, the central oscillator starts receiving at the same time as transmitting, so (
In contrast to (c) and (d), which are used all the time, the outer transducers are used only at deep depths, and therefore their opening time is later than that of the central transducer, and their opening time is also shorter. I can see that Incidentally, FIG. 8(b) shows a trigger signal, and in response to the fall of signal No. 13, transmission and reception δ of ultrasonic waves are started.

[Problem to be solved by the invention]

As mentioned above, conventionally the receiving aperture is controlled by operating the analog switch connected to the transducer block from closed to open depending on the depth. As shown by ta, the amplitude of the received signal changes rapidly when the receiving aperture opens and opens, resulting in uneven image quality.Also, as shown by the symbol BWI in Fig. 10, when the receiving aperture opens and opens, Since the receiving beam width suddenly changes at time ta, there is a problem that a step appears in the image and uneven resolution occurs within the same image.
The figure shows the beam width characteristics.

[Means to solve the problem]

When applying ultrasonic waves to a sample and receiving the ultrasonic waves reflected from the sample via a transducer block, the receiver aperture control circuit adjusts the opening diameter (aperture) for capturing the received signal of the transducer block. a signal generating means that generates a plurality of signals that sequentially increase with the passage of time and whose increases differ from each other; and an amplifier whose gain is individually adjusted in response to each output signal from the signal generating means. The receiving aperture control is performed continuously by applying weights to individual received signals that change over time.

[Effect]

A gain control signal is generated as time passes for each trigger pulse, and this signal is input to the reception gain control amplifier to continuously control the amplitude of the reception signal of the transducer block in the depth direction (corresponding to time). This eliminates sudden changes in the reception amplitude at the opening/opening point of the receiving aperture and sudden changes in the receiving beam width at the opening/opening point of the receiving aperture, which are caused by conventional aperture control with open/close operation. Eliminates image differences and uneven resolution within the same image.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is an explanatory diagram for explaining the present invention in detail.

In the embodiment shown in FIG. 1, a gain control amplifier 7a is installed before the adder 8, and the reception aperture of the reception analog signal Z2 after passing through the reception focus delay 5a and the delay group selection circuit 5b is controlled. So, the fifth
Conventional aperture control signal generation circuit 9 shown in the figure
It can be said that the output signal is changed from an aperture open/close binary signal to an analog signal, and the aperture control circuit 1 using an analog switch is replaced with the small circuit 7 by a gain control amplifier 7a.

Here, the RF analog signal Zl is amplified by the reception amplifier 4a, passed through the reception focus delay 5a, and received and focused by the delay group selection circuit 5b. This reception delay amount selection is performed by a binary switching signal from the delay m selection signal generation circuit 14. The received analog signal Z2 that has passed through the delay amount selection circuit 5b is input to a gain control amplifier 7a, where reception aperture control is performed. The reception aperture control here is performed by the reception amplifier gain that changes over time in synchronization with the trigger signal Y, which is the output signal of the aperture gain control circuit 9a. That is, the amplifier 7a is a variable gain amplifier, and each time the amplifier 7a receives a trigger signal Y as shown in FIG. 2(C), the gain changes from the circuit 9a as shown in FIGS. By applying a signal that changes the gain of each amplifier over time. At this time, as shown in Figure 2 (
By providing each of the amplifiers 7a shown in (b) with the characteristics shown in (a) of the same figure, it is possible to realize reception aperture control equivalent to that described in FIG. 8. Note that the vertical axis in Figure 2 (a) represents the receiving amplifier gain G,
The dotted line indicates the receiving amplifier gain at time t=O, and the solid arrow indicates the receiving amplifier gain that changes over time. This figure is expressed in a different way (
That's d)~(su).

FIG. 3 is a block diagram showing another embodiment of the present invention.

This is characterized by the fact that the gain control amplifier 7a shown in Fig. 1 is provided before the receiving focus delay 5a and also serves as the receiving amplifier, and the circuit configuration is simpler than the example shown in Fig. 1. There is. 4b is a gain control amplifier.

FIG. 4 is a block diagram showing still another embodiment of the present invention. This eliminates the adder 8 and the delay
This is further simplified by reducing the number of . Note that 5c is a delay amount selection switch circuit, and 5d is a buffer.

As described above, a gain control signal is generated as time passes for each trigger pulse, and this No. 18 is input to the reception gain control amplifier to adjust the amplitude of the reception signal of the transducer block in the depth direction, which corresponds to time. The rapid change in the receiving amplitude at the open/open point of the receiving aperture caused by the aperture control of the open/close binary operation shown in FIG. It is possible to eliminate sudden changes in the receiving beam width at the opening point. In other words, according to the present invention, the received waveform can be made smooth as shown in FIG. 9 (b), and the beam width can also be made smooth as shown by the dotted line BW2 in FIG. 10. That's why. As a result, steps in the image and unevenness in resolution within the same image, which are conventional, are eliminated, making it possible to obtain a clearer image.

〔Effect of the invention〕

According to the present invention, since the receiving aperture is controlled by continuously changing the amplifier gain over time, sudden changes in the receiving amplitude at the opening point of the receiving aperture and sudden changes in the receiving beam width can be avoided. As a result, steps in the image and unevenness in resolution within the same image, which are conventional, are eliminated, and the image quality can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
3 is a block diagram showing a second embodiment of the invention, FIG. 4 is a block diagram showing a third embodiment of the invention, and FIG. The figure is a block diagram showing an overview of an ultrasonic diagnostic device, Figure 6 is an explanatory diagram to explain the concept of conventional aperture control, Figure 7 is a partially enlarged view of Figure 5, and Figure 8 is an aperture control circuit. FIG. 9 is a waveform diagram for comparing and explaining the received signal waveform between the conventional example and the present invention. FIG. 1O is a diagram showing the beam width characteristics between the conventional example and the present invention It is a characteristic diagram for comparing and explaining. Code explanation 1...Probe, 2...Matrix switch, 3
... Transmission circuit, 4... Receiving circuit, 4a... Receiving amplifier, 4b, 7a... Gain control amplifier, 5
, 5a... Delay circuit, 5b... Delay amount selection circuit, 5C... Delay amount selection switch circuit, 5d
... Buffer, 6... Transmission trigger, 7... Aperture control circuit, 71... Analog switch,
8...Adder, 9...Averture control 13
No. 71 circuit, 9a...Aperture gain control circuit, 10...RF video amplifier, 11...Dynamic band pass filter (DBPF), 12...
・Detection/smoothing circuit, 13... Time gain control circuit (TCC), 14... Delay amount selection signal generation circuit, 15... Scanning line selection signal generation circuit, 16...
Digital circuit, 17...TV monitor.

Claims (1)

[Claims] 1) For adjusting the opening diameter (aperture) for capturing the received signal of the transducer block when applying ultrasonic waves to the sample and receiving the ultrasonic waves reflected from the sample via the transducer block. The receiving aperture control circuit includes a signal generating means that generates a plurality of signals that sequentially increase with the passage of time and whose increases differ from each other, and a signal generating means that individually generates a gain in response to each output signal from the signal generating means. What is claimed is: 1. A receiving aperture control circuit, comprising: an amplifier adjusted to 1;