JPH0324854B2 - - 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 receiving dynamic focus system that receives intra-subject information from multiple focal points on one 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. 6a. 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. 6b, 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.

However, with the fixed focus, parts other than the focus point are blurred, making it impossible to obtain good image quality.Also, with dynamic focus, although good image quality can be obtained, it is possible to Ultrasonic waves must be transmitted and received three times to obtain the scanning line of a book, and generally 128 scanning lines are required to obtain one tomographic image screen, so in this case, There is a problem in that the wave must be transmitted and received 128x3 = 384 times, and it takes 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.
In other words, if the frequency of the received signal is f ₀ and the local frequency f _L , 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. , by multiplying different local oscillator signals and converting them into different intermediate frequency signals,
A signal corresponding to the amount of delay can be obtained.

For example, three local oscillator signals as shown in FIG. 8 are used for three reception focal points. This local oscillation signal has a large phase difference in the order of figure a → figure b → figure c, and by sequentially multiplying this local oscillation signal with the received signal from near to far distance in the above order, reception at multiple focal points is possible. Dynamic focus can be performed. According to this, it is possible to significantly reduce noise during signal conversion and obtain a high-quality image without reducing the frame rate.

[Problems to be solved by the invention] By the way, even in such a heterodyne system,
The problem of an increase in circuit scale remains, and a device with a simple configuration 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.

Therefore, the present inventors smoothly sweep a variable frequency signal and generate a multiphase signal as a local signal by giving a predetermined delay time to this sweep signal.
Then, by multiplying each received signal obtained by each transducer by this multiphase signal,
At the same time as the present invention, an apparatus for obtaining signals of continuous focal points on the same radiation axis has been proposed.

FIG. 2 is a diagram illustrating the multiphase signal, and a multiphase signal generation circuit 20 is constituted by the variable frequency signal generation circuit 16 and the delay line 18. This variable frequency signal generation circuit 16 generates a sweep signal whose frequency changes continuously.
First, by generating signals of different frequencies, in the example from a high frequency to a low frequency signal, and continuously sweeping this frequency signal, a signal as shown in FIG. 200 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.

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

This proposed invention has the advantage that a signal with good in-vivo resolution can be obtained by using a continuous focus signal instead of a stepwise reception focus signal.

However, as will be explained later, the multiple phase signals used to obtain continuous focus determine the positions of consecutive multiple focuses based on their phase differences, so as long as this phase difference does not exceed 360 degrees, Signals must be used. Therefore, reception at the continuous focal point has a certain limit in distance length (depth distance), and improvements are required to satisfactorily obtain a wide range of in-vivo information.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to obtain images with good resolution over a wide range within a living body when performing reception dynamic focusing with continuous focus. The purpose of the present invention is to provide an ultrasonic diagnostic device that can perform electronic focus control.

[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 reflected waves as information from multiple reception focuses on the radiation axis at a reception dynamic focus, a variable frequency signal is generated by smoothly sweeping the changing frequency signal. A multiphase signal is composed of a variable frequency signal generation circuit that generates a variable frequency signal, and a delay line that provides a predetermined amount of delay to the output of the variable frequency signal generation circuit, and generates a multiphase signal whose phase changes over time. The present invention is characterized in that it includes a generation circuit and multiplies the received signal obtained by each vibrator by the multiphase signal as a local oscillation signal to obtain a continuous focus signal.

[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 signals received by the individual transducers to form a continuous focus signal.

Then, this continuous focus signal is received by a delay controller installed in a divided region in which the ultrasonic transmission/reception region is divided into multiple stages, using the same operation as a conventional receiving dynamic focus signal. A continuous focus signal of Therefore, signals can be obtained from a wide range of continuous receiving focal points on the same radiation axis, and it is possible to form a high-resolution image by transmitting ultrasonic waves once.

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

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

In Figure 1, a transducer 1 that transmits and receives ultrasonic waves
0 is connected to an amplifier 12, and this amplifier 12 is connected to a multiplier 14. As described above, there are provided a multiphase signal generation circuit 20 that continuously generates signals with different phase differences, and a local oscillator signal circuit 22 that selects a multiphase signal to be multiplied by the received signal. As shown, multi-phase signal generation circuit 20 includes variable frequency signal generation circuit 16.
and a delay line 18. As described above, this variable frequency signal generation circuit 16 forms a signal as shown in FIG. 200 by continuously sweeping a signal from a high frequency to a low frequency, for example.

Further, since the delay line 18 delays the variable frequency signal by a predetermined time Δt to form a multiphase signal, each signal output from the multiphase signal generation circuit 20 is a multiphase signal whose phase changes over time. The signal is a multiphase signal in which the plurality of signals have mutually different phases.

The phase difference between the multiple phase signals is determined by the plurality of frequencies of the variable frequency signal and the delay amount of the delay line 18. In particular, when the phase difference is to be increased, the frequency difference between the variable frequency signals may be increased. and,
This multiphase signal is multiplied by the received signal as a local oscillation signal, thereby making it possible to obtain information at successive reception focal points on the same radiation axis.

Further, the ultrasonic diagnostic apparatus is provided with a filter 28 for removing unnecessary signals, an image signal processing circuit 30 for processing for displaying images, and a display circuit 32 for displaying images.

The characteristic feature of the present invention is that continuous focus signals are received in stepwise set distance areas to obtain continuous focus reception signals over a wide range, and this is achieved by adding a predetermined delay amount to the continuous focus signals. This is done by providing a plurality of step region delay controllers.

In an embodiment, two step-area delay controllers are provided, a first delay controller 34 for short range;
A second delay controller 36 is provided for long distances, and reception dynamic focusing is performed by dividing the diagnosis area into two stages, A and B, as shown in FIG. Therefore, as shown in the figure, it is possible to receive reception using two-step focus control over a wide range of areas where reception dynamic focus was conventionally performed for focal points _F1 to _F6 . 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 multiple phase 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 gain-controlled amplifiers 12-1 to 12-n
A received signal obtained through the multiplier 14 is supplied, and the multiphase local oscillator signal is mixed with the received signal in the multiplier 14 .

Here, the output signal of the multiplier 14, that is, the continuous focus signal, 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 the first and second stage delay controllers 34 and 36, and the continuous focus signal is received by the delay amount determined for each stage. This stepwise reception is performed in the same manner as in conventional reception dynamic focus control, and the signals given the delay amount are added and output from the stepwise delay controllers 34 and 36. Therefore, a received dynamic focus signal that is focused at successive points on the radiation axis 100 in FIG. 3 is obtained.

Figure 5 shows a beam profile showing the width of the received ultrasonic beam. It is seen that the focus range C has been expanded compared to the conventional one. In the embodiment, continuous dynamic focusing is performed over a wide range, and a beam profile can be drawn as shown in Fig. c when using a conventional device and as shown in Fig. d when using the embodiment.

According to this, it is possible to obtain a focused reception signal over a wider depth range than before, and unlike the conventional method, which requires switching the signal stepwise at depths d ₁ to _{d 5} . In contrast, the embodiment has the advantage that it is only necessary to switch stepwise at depth _d1 , and the number of signal switches can be significantly reduced.

The outputs of the delay controllers 34 and 36 are then supplied to an image signal processing circuit 30 after noise signals are removed by a filter 28. Therefore, the image signal processing circuit 30 performs predetermined signal processing for tomographic image display or velocity display, and this processed signal is supplied to the display circuit 32 for image display.

[Effects of the Invention] As explained above, according to the present invention, a multi-phase local signal is multiplied by a received signal to obtain a continuously focused signal, and this signal is received in stages with multiple delay controls. Since reception dynamic focusing is performed, reception signals can be obtained from continuous reception focuses over a wide range on the same radiation axis. Therefore, it is possible to obtain a high-resolution signal without reducing the frame rate by transmitting ultrasonic waves once, and it is possible to obtain clear images in a wide range of diagnostic areas.

In addition, the reception dynamic focus of the present invention can significantly reduce the conventional signal switching for each reception focus, and can also reduce the number of delay lines, reducing spike noise when switching signals. This has the advantage that image quality can be improved at low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing the overall configuration of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 2 is an explanatory diagram showing the circuit configuration for forming a multiphase signal and its waveform.
FIG. 3 is an explanatory diagram showing the receiving ultrasound plane of the receiving focus on the same radiation axis, FIG. 4 is an explanatory diagram showing the receiving ultrasound plane when receiving dynamic focusing is performed in the embodiment, and FIG. An explanatory diagram showing the ultrasonic beam profile in the case of reception focusing, Fig. 6 is an explanatory diagram showing various methods of electronic focusing, and Fig. 7 is an explanatory diagram showing a conventional device that performs reception dynamic focusing using the heterodyne method. , FIG. 8 is a waveform diagram showing the local oscillator signal obtained by the apparatus of FIG. 7. 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, 34... First delay controller for stage region,
36...Second delay controller for stage region.

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. In an electronic focus-controlled ultrasonic diagnostic device that receives information from multiple reception focuses, there is a variable frequency signal generation circuit that generates a variable frequency signal by smoothly sweeping a changing frequency signal, and a variable frequency signal generation circuit that generates a variable frequency signal. a delay line that provides a predetermined amount of delay to the output; a multiphase signal generation circuit that generates a multiphase signal whose phase changes over time; An electronic focus-controlled ultrasonic diagnostic device characterized in that a continuous focus signal is obtained by multiplying received signals obtained by each transducer.