JPS6399848A - Electronic focus controlled ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ultrasonic diagnostic apparatus with electronic focus control, and particularly an electronic focus control system that performs so-called reception dynamic focusing, which receives intra-subject information from multiple focal points on the same radiation axis. The present invention relates to a focus-controlled ultrasonic diagnostic device.

[Prior Art] Ultrasonic diagnostic equipment that displays in-vivo information, such as abdominal tomograms and movement states such as intracardiac blood flow, is well-known. Electronic focus control is used to improve the directivity of the ultrasonic beam in order to accurately display the information.

This electronic focus control has fixed focus.

There are methods such as dynamic focus or reception dynamic focus, and the fixed focus method is as shown in Fig. 4 (
As shown in a), a fixed focal point F is placed at the intermediate point where the transducers arranged in an array are electronically controlled to display an image.
. Match. And this fixed focus F. By sequentially moving and scanning in the direction of the transducer rows at the same depth, an image of the inside of the subject is displayed.

In addition, dynamic focusing is performed by focusing on a point on the same radiation axis that emits the ultrasonic beam, as shown in FIG. 4(b).
00, a plurality of, for example three, focal points F1. F2. F
3 is determined, and ultrasonic wave transmission and reception is performed three times with respect to this focal position. Therefore, with dynamic focus, it is possible to obtain images with good resolution over the entire range from short distances to long distances without losing real-time performance.

Furthermore, as shown in FIG. 4(c), the receiving dynamic focus transmits an ultrasonic beam to, for example, a focal point F2, and receives the ultrasonic beam only at the focal point Fl for a short distance region, while for a long distance region. Reception at focal point F3. Therefore, since reception dynamic focus does not require multiple ultrasound transmissions, it is possible to improve image quality without reducing the frame rate (number of scanning lines per unit time), especially for fast-moving areas. It can be applied well to

[Problems to be Solved by the Invention] However, with the fixed focus, parts other than the focus point become blurred, making it impossible to obtain good image quality.
In addition, although it is possible to obtain good image quality with dynamic focus, it is necessary to transmit and receive ultrasonic waves three times on the same radiation axis, that is, to obtain one scanning line on the screen. Since 128 scanning lines are required to obtain a tomographic image screen, in this case, 128x
3-3F There is a problem in that wave transmission and reception must be performed four times, and it takes time to obtain one screen.

As a solution to these problems with fixed focus and dynamic focus, the above-mentioned dynamic reception focus is attracting attention because it can obtain high-quality images without reducing the frame rate, and the present invention also addresses this problem. This is something to focus on.

However, reception dynamic focus has a problem in that spike noise occurs when switching signals.

Therefore, conventional devices have adopted a heterodyne method to reduce the spike noise.

In other words, this heterodyne system shifts the frequency of the received signal, and as shown in FIG. , to drop the received signal to an intermediate frequency.

That is, the frequency f of the received signal. If one local oscillation frequency is f, it can be converted to an intermediate frequency of fo+fL or fo-fL, and one of these signals will be taken out, but it can be converted to an intermediate frequency signal by multiplying different local oscillation signals. By doing so, a signal corresponding to the amount of delay can be obtained.

For example, three local oscillator signals as shown in FIG. 6 are used for three reception focal points. This local oscillator signal is shown in Figure (a)-
The signals have larger phase differences in the order of figure (b) - figure (c),
By sequentially multiplying this local oscillator signal with received signals from short distances to long distances in the above order, reception dynamic focusing at multiple focal points can be performed. According to this,
It significantly reduces noise during signal conversion, allowing you to obtain high-quality images without reducing frame rate.

However, even with such a heterodyne system, there remains the problem that the circuit scale becomes large, and a device with a simple structure is desired.

Furthermore, there are still unresolved problems with conventional reception dynamic focus. In other words, the image quality for the receiving focus is improved to some extent, but since the receiving focus is switched in stages, information from areas other than the receiving focus cannot be received accurately, and this is compared to the dynamic focus that transmits and receives multiple times. In comparison, improvements in resolution are still insufficient.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems.
The purpose is to provide an electronic focus-controlled ultrasonic diagnostic apparatus that can continuously move the reception focus in the reception dynamic focus and obtain a high-resolution image.

Means for Solving Problem E] In order to achieve the above object, the present invention transmits an ultrasonic beam into a living body by exciting a plurality of arranged transducers, and transmits an ultrasound beam into a living body, In ultrasonic diagnostic equipment with electronic focus control, which receives reflected waves as information from multiple reception focuses on the radiation axis using a receiving dynamic focus, a variable frequency signal is generated by smoothly sweeping signals with changing frequencies. The multiphase signal generation circuit is composed of a frequency signal generation circuit and a delay line that provides a predetermined amount of delay to the output of the variable frequency signal generation circuit, and has a multiphase signal generation circuit that generates a multiphase signal whose phase changes over time. ,
The ultrasound beam is received by continuously changing the receiving focus of the ultrasound beam in the depth direction of the diagnostic site by multiplying the received signal obtained by each transducer by the multiphase signal as a local oscillation signal. .

[Operation] According to the above configuration, the multiphase signal generation circuit continuously outputs a plurality of identical signals with different phases with a predetermined delay amount, and these outputs become signals consisting of multiphase,
This multiphase signal is mixed into the received signals received by the individual transducers. Therefore, the mixed signal is not a reception signal of stepped focal points as in the past, but a signal from continuous reception focal points on the same radiation axis, and a high-resolution image can be formed by one ultrasound transmission. It becomes possible to obtain a received signal.

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

FIG. 1 shows a circuit configuration for forming a multiphase signal and its waveform, and FIG. 2 shows a schematic configuration of an ultrasonic diagnostic apparatus according to the present invention.

The characteristic feature of the present invention is that in the reception dynamic focus, a signal is obtained that is continuously focused at each point on the radiation axis, which means that multiple phase signals with different phases are continuously obtained. This is done by multiplying the received signal as a local signal.

In FIG. 1, a multiphase signal generation circuit 20 is configured by a variable frequency signal generation circuit 16 and a delay line 18.

This variable frequency signal generation circuit 16 generates a sweep signal whose frequency changes continuously. First, it generates signals of different frequencies, in this embodiment, signals from a high frequency to a low frequency, and then continuously sweeps this frequency signal. By doing so,
A signal as shown in diagram 200 is formed.

Further, the delay line 18 transmits the variable frequency signal for a predetermined time Δ
A multiphase signal is formed by delaying by t. Therefore, the signal output from the multi-phase signal generation circuit 20 becomes a multi-phase signal whose phase changes over time. For example, when comparing the signal 201 and the signal 203, at the signal tip, θl-380' changes at the time of 2Δt. It is understood that while there is a phase difference, at the trailing end of the signal there is only a phase difference of θ2-isoo in a time period of 2Δt, and that phase changes occur continuously.

In this way, the phase difference between the multiple phase signals is determined by the multiple frequencies of the variable frequency signal and the delay amount of the delay line 18,
In particular, when increasing the phase difference, the frequency difference between the variable frequency signals may be increased.

By multiplying this multiphase signal as a local signal by the received signal, it is possible to obtain information at continuous reception focal points on the same radiation axis.

FIG. 2 shows an ultrasonic diagnostic apparatus in an embodiment,
In the figure, an amplifier 12 is connected to a transducer 10 that transmits and receives ultrasonic waves, and a multiplier 14 is connected to this amplifier 2''&12.
In addition to the characteristic configuration of 0, a local oscillator signal selection circuit 222 and a multiplier 22 are provided, and a fixed delay line 24 . Adder 26 that adds the signals of each vibrator. A filter 282 for removing unnecessary signals, an image signal processing circuit 30 for processing for image display, and a display circuit 32 for displaying the image are provided.

The embodiment has the above configuration, and includes a multiphase signal generation circuit 2
The output of 0 is supplied to the local oscillator signal selection circuit 22, which selects a multiphase local oscillator signal to be multiplied by the received signal received by each vibrator (multiplier 14).

The multipliers 14-1 to 14-n include each vibrator 10.
-1 to 10-n, and the received signals obtained through gain-controlled amplifiers 12-1 to 12-n are supplied, and this multiplier 14 outputs multiple phase signals. The local signal is mixed with the received signal.

Here, the output signal of the multiplier 14 will be explained based on FIG.

As shown in the figure, when one ultrasonic beam is formed using eight transducers 10, the emitted ultrasonic waves are focused on the radiation axis 100. For example, Fl, F2
．． Considering the focus of F3, ultrasonic waves 301, 302, 303 are formed in order as shown in the figure, and as the focus moves from this wavefront to F, → F2 → F3, the delay time at the transducer 10 becomes smaller. I understand that.

In other words, the farther the distance is, the smaller the delay time needed to receive the reflected wave means that the farther the distance is, the more it is necessary to perform reception dynamic focusing using a local signal with a smaller phase difference. . Therefore, in the present invention, the multiphase signal output from the multiphase signal generation circuit 22 is made to correspond to a signal with a large phase difference for a short distance and a signal with a small phase difference to a long distance. Continuously focused received signals can be obtained over a wide range.

The output of the multiplier 14 thus obtained is supplied to a fixed delay line 24, where the signal processing time is adjusted. The output of the fixed delay line 24 is supplied to an adder 26, where all the received signals obtained from each transducer 10 are added together.
This results in a received dynamic focus signal on the radiation axis 100 in the figure.

The output of this adder 26 is supplied to an image signal processing circuit 30 after noise signals are removed by a filter 28 .

The image signal processing circuit 30 performs predetermined signal processing for tomographic image display or speed display, and the processed signal is supplied to the display circuit 32 for image display.

In addition, the present invention provides variable aperture control of the vibrator.
It is also possible to obtain signals with good resolution over a wide range. In other words, by increasing the number of transducers for reception dynamic focusing with the reception time, the execution range of the focusing transducers can be made variable. It is possible to receive reflected echoes of continuous reception focal points over a wide range.

[Effects of the Invention] As explained above, according to the present invention, reception dynamic focusing is performed by multiplying the received signal by a local oscillation signal of multiple phases, so that the reception signal at consecutive reception focuses on the same radiation axis is is obtained.

Therefore, it is possible to obtain a signal with good resolution without reducing the frame rate by transmitting ultrasonic waves twice, and it is possible to obtain a clear diagnostic image.

In addition, the reception dynamic focus of the present invention eliminates the need to switch the local oscillator signal for each reception focus, unlike conventional methods.
Further, since a delay line is used in the multiple signal phase signal generation circuit, the present invention can be constructed with a simple circuit, and has the advantage that image quality can be improved at low cost.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the circuit configuration for forming a multiphase signal and its waveform. Figure 2 is a circuit block diagram showing the overall configuration of the ultrasonic diagnostic device. Figure 3 is reception of reception focal points on the same radiation. Figure 4 is an explanatory diagram showing the ultrasonic plane, Figure 4 is an explanatory diagram showing various methods of electronic focusing, Figure 5 is an explanatory diagram showing a conventional device that performs reception dynamic focusing using the heterodyne method, and Figure 6 is Figure 5. FIG. 3 is a waveform diagram showing a local oscillator signal obtained by the device of FIG. 10... Vibrator 14... Multiplier 16... Variable frequency signal generation circuit 18...
Delay line 20...Multi-phase signal generation circuit 22...Local signal selection circuit 24...Fixed delay line 26...Adder.

Claims (2)

[Claims] (1) Transmit an ultrasound beam into the living body by exciting multiple arrayed transducers, and receive the reflected waves from the living body using dynamic focus to receive information on multiple receiving focal points on the radiation axis In an electronic focus-controlled ultrasonic diagnostic device that receives signals as and a multiphase signal generation circuit that generates a multiphase signal whose phase changes over time, and receives the multiphase signal as a local oscillation signal by each transducer. An electronic focus control ultrasonic diagnostic apparatus characterized by continuously changing the receiving focus of an ultrasonic beam in the depth direction of a diagnostic site by multiplying signals. (2) In the device according to claim (1), the electronically focused vibrator performs variable aperture control in which the number of electronically focused vibrators increases with the reception time to vary the effective width of the focus vibrator, and An electronic focus control ultrasonic diagnostic device characterized by continuously changing the reception focus.