JPH0324855B2 - - Google Patents

Description

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

[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 ultrasonic beams in order to display accurate information.

This electronic focus control includes methods such as fixed focus, dynamic focus, and reception dynamic focus. The fixed focus uses vibrators arranged in an array as shown in FIG. 4a. Adjust the fixed focal point F ₀ to the intermediate point where the image is to be displayed under electronic control. and,
By sequentially moving and scanning this fixed focal point F ₀ in the direction of the transducer rows at the same depth, an image of the inside of the subject is displayed.

Furthermore, as shown in FIG. 4b, the dynamic focus defines a plurality of focal points, for example, three focal points F ₁ , F ₂ , F ₃ on the same radiation axis 100 that emits the ultrasonic beam, 3 for this focal position
Transmit and receive ultrasonic waves twice. 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, the receiving dynamic focus, as _shown in _FIG . For reception at focus _F3 . Therefore, since receiving dynamic focus does not require multiple ultrasonic wave transmissions, image quality can be improved without reducing the frame rate (number of scanning lines per unit time). Can be applied well to fast-moving areas.

[Problems to be Solved by the Invention] However, with the fixed focus, parts other than the focus point are blurred and good image quality cannot be obtained, and with dynamic focus, although good image quality can be obtained, Ultrasonic waves must be transmitted and received three times on the same radiation axis, that is, to obtain one scanning line on the screen, and generally 128 scanning lines are required to obtain one tomographic image screen. Therefore, in this case, 128x3=
There is a problem in that the wave must be transmitted and received 384 times, and it takes a long time to obtain one screen.

As a solution to these problems with fixed focus and dynamic focus, the above-mentioned receiving dynamic focus is attracting attention because it can obtain high-quality images without reducing the frame rate, and this book describes this method. The invention also focuses on this. However, in the reception dynamics focus,
There is 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 ₀ of the received signal, the local frequency f _L
Then, it can be converted to an intermediate frequency of f ₀ + f _L or f ₀ - f _L , and one of these signals will be extracted, 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 becomes a signal with a large phase difference in the order of figure a → figure b → figure c, and by multiplying this local oscillator signal with the received signals from near to far distances in the above order, the reception dynamics at multiple focal points can be adjusted. Can perform Mitsuku Focus. According to this, it is possible to significantly reduce noise during signal conversion and obtain a high-quality image without reducing the 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.

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 outside the receiving focus cannot be accurately received, and the dynamic image that is transmitted and received multiple times as described above is Compared to dregs, improvements in resolution are still insufficient.

OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide an electronic focus control that can continuously move the reception focus in the reception dynamic focus and obtain an image with good resolution. The purpose of the present invention is to provide ultrasonic diagnostic equipment.

[Means for Solving the Problems] In order to achieve the above object, the present invention transmits an ultrasonic beam into a living body by exciting a plurality of arrayed transducers, and transmits an ultrasound beam into a living body to transmit an ultrasound beam that is reflected from the living body. In an electronic focus-controlled ultrasonic diagnostic device that receives the reflected waves as information from multiple reception focuses on the radiation axis at a receiving dynamic focus, a variable frequency signal is generated by smoothly sweeping the changing frequency signal. A multi-phase signal generator that generates a multi-phase signal whose phase changes over time, and a delay line that provides a predetermined amount of delay to the output of the variable frequency signal generator circuit. The ultrasonic beam is received by continuously changing the receiving focus of the ultrasonic 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. It is characterized by

[Operation] According to the above configuration, the multiple phase signal generation circuit continuously outputs multiple identical signals with different phases with a predetermined amount of delay, and these outputs become signals consisting of multiple phases. The phase signal is mixed with the received signal 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 is formed by one ultrasonic wave transmission. It becomes possible to obtain a received signal that can be used.

[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 receiving dynamic focus, a signal is obtained that is continuously focused at each point on the radiation axis, and this is achieved by obtaining a signal that is continuously focused at each point on the radiation axis. This is done by multiplying the signal as a local oscillator signal with the received signal.

In FIG. 1, variable frequency signal generation circuit 16
and a multiphase signal generation circuit 20 by the delay line 18.
is configured. This variable frequency signal generation circuit 16
generates a sweep signal whose frequency changes continuously, but first generates a signal with a different frequency, in this embodiment, a signal from a high frequency to a low frequency, and by continuously sweeping this frequency signal, the signal shown in FIG.
A signal as shown at 0 is formed.

Further, the delay line 18 delays the variable frequency signal by a predetermined time Δt to form a multiphase signal. Therefore, the signal output from the multi-phase signal generation circuit 20 becomes a multi-phase signal whose phase changes over time, for example, signal 201 and signal 2.
Comparing with 03, there is a phase difference of θ ₁ = 360° at the time of 2Δt at the leading edge of the signal, while there is only a phase difference of θ ₂ = 180° at the time of 2Δt at the trailing edge of the signal, and the phase difference is continuous. It is understood that a phase change has occurred.

In this way, the phase difference between the multiple phase signals is determined by the multiple frequencies of the variable frequency signal and the amount of delay of the delay line 18. In particular, when increasing the phase difference, it is necessary to increase the frequency difference between the variable frequency signals. Bye.
By multiplying this multiphase signal as a local oscillation signal by the received signal, it is possible to obtain information at consecutive reception focal points on the same radiation axis.

FIG. 2 shows an ultrasonic diagnostic apparatus according to an embodiment, and in the figure, an amplifier 12 is connected to a transducer 10 that transmits and receives ultrasonic waves.
A multiplier 14 is connected to. In addition to the characteristic configuration of the multiphase signal generation circuit 20 described above, a local oscillator signal selection circuit 22 and a multiplier 22 are provided, and a fixed delay line 24 that provides a fixed delay amount for signal synthesis; An adder 26 that adds the signals of each vibrator, and a filter 2 that removes redundant signals.
8. Image signal processing circuit 30 that performs processing for image display and display circuit 3 for displaying images
2 is provided.

The embodiment has the above configuration, and the output of the multiphase signal generation circuit 20 is supplied to the local signal selection circuit 22, where it is multiplied by the received signal received by each transducer (multiplier 14). Select the local oscillator signal.

Then, the multipliers 14-1 to 14-n receive the signals received by the transducers 10-1 to 10-n and the gain-controlled amplifiers 12-1 to 12-n.
The received signal obtained through the multiplier 12-n is supplied, and the multiphase local oscillator signal is mixed with the received signal by the multiplier 14.

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, considering the foci of F ₁ , F ₂ , and F ₃ ,
Ultrasonic surfaces 301, 302, 303 as shown in the order
is formed, and it can be seen that the delay time in the vibrator 10 becomes smaller as the focus moves from this wavefront in the order of F ₁ →F ₂ →F ₃ .

In other words, the farther the distance is, the smaller the delay time required to receive the reflected wave means that the farther the distance is, the smaller the phase difference between the local oscillator signal and the reception dynamics focus. means. Therefore, in the present invention, the multi-phase signal output from the multi-phase signal generating 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, so that it can be used from a short distance to a long distance. A continuously focused received signal can be obtained over a wide range of areas.

The output of the multiplier 14 obtained in this way is
The signal 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 by each transducer 10 are added together, and the output of this adder 26 is added on the same radiation axis, that is, on the radiation axis 1 in FIG.
00 is the received dynamic focus signal.

The output of this adder 26 is sent to an image signal processing circuit 30 after the noise signal is removed by a filter 28.
is supplied to The image signal processing circuit 30 performs predetermined signal processing for tomographic image display or speed display, and the processed signals are sent to the display circuit 3.
2 and the image is displayed.

Further, according to the present invention, by variable aperture control of the vibrator, it is possible to obtain signals with good resolution over a wide range. In other words, by increasing the number of transducers that dynamically focus on the receiving object with the reception time, the execution width of the focusing transducer can be made variable. It is possible to receive reflected echoes of successive reception focal points over a wide range within the center.

[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 dynamics at consecutive reception focuses on the same radiation axis is A received signal is obtained. Therefore, it is possible to obtain a signal with good resolution without reducing the frame rate by transmitting ultrasonic waves once, and it is possible to obtain a clear diagnostic image.

In addition, the reception dynamic focus of the present invention does not require switching the local oscillator signal for each reception focus as in the past, and uses a delay line in the multiplex signal phase signal generation circuit, so it can be done using a simple circuit. The present invention has the advantage that the invention can be constructed and image quality can be improved at low cost.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1. An ultrasonic beam is transmitted into a living body by exciting a plurality of arranged transducers, and the reflected waves reflected from the living body are received by a dynamic focus on the radiation axis. A variable frequency signal generation circuit that generates a variable frequency signal by smoothly sweeping a changing frequency signal in an electronic focus control ultrasonic diagnostic device that receives information from multiple reception focuses, and this variable frequency signal generation circuit. a delay line that provides a predetermined amount of delay to the output of the circuit, and a multi-phase signal generating circuit that generates a multi-phase signal whose phase changes over time, the multi-phase signal being used as a local oscillation signal. 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 received signals obtained by each transducer. 2. In the device according to claim 1, the electronically focused transducers perform variable aperture control that increases the number of electronically focused transducers with the reception time to vary the effective width of the focus transducers, so that the receiving focus is continuously maintained over a wide range. An ultrasonic diagnostic device with electronic focus control.