JP5202138B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus using a continuous wave.

  A continuous wave Doppler is known as a technique using a continuous wave of an ultrasonic diagnostic apparatus. In continuous wave Doppler, for example, a transmission wave that is a sine wave of several MHz is continuously emitted into the living body, and a reflected wave from the living body is continuously received. The reflected wave includes Doppler shift information by a moving body (for example, blood flow) in the living body. Therefore, by extracting the Doppler shift information and performing frequency analysis, a Doppler waveform reflecting the velocity information of the moving body can be formed.

  In an ultrasonic diagnostic apparatus using a continuous wave, leakage of a signal from the transmission system to the reception system cannot be ignored. For example, if a signal or the like leaks from the transmission system to the reception system due to acoustic or electrical influences, a relatively large unnecessary signal component is included in the reception signal, which is not preferable in extracting a weak Doppler signal.

  Therefore, it is desirable to reduce unnecessary signal components included in the received signal. However, it is not preferable that the circuit scale and design cost of the transmission / reception system increase due to the reduction.

  Incidentally, Patent Document 1 describes a technique for performing phasing addition of received signals with a small circuit scale without using a delay line in continuous wave Doppler mode.

JP 2007-14456 A

  The present invention has been made in view of the above-described background art, and an object thereof is to provide a technique for reducing unnecessary signal components with a relatively simple configuration in an ultrasonic diagnostic apparatus using a continuous wave. is there.

  In order to achieve the above object, an ultrasonic diagnostic apparatus according to a preferred aspect of the present invention includes a transmission signal processing unit that outputs a continuous wave transmission signal, and an ultrasonic wave corresponding to the transmission signal transmitted to a living body. A transmission / reception unit that obtains a reception signal by receiving a reflected wave from a living body, and a correction signal obtained by subjecting the transmission signal to phase adjustment processing and amplitude adjustment processing are added to the reception signal. A correction processing unit that obtains a corrected received signal in which unnecessary signal components included are reduced, and reception that obtains a demodulated signal by performing demodulation processing on the corrected received signal using a reference signal having a waveform substantially equal to the transmitted signal A signal processing unit and an in-vivo information extraction unit that extracts in-vivo information from the demodulated signal are provided.

  In a desirable aspect, the transmission / reception unit includes a transmission vibrator for transmitting an ultrasonic wave corresponding to a transmission signal to a living body, a receiving vibrator for obtaining a reception signal by receiving a reflected wave from the living body, The correction processing unit adjusts the amplitude of the transmission signal and inverts the phase of the transmission signal so that the acoustic leakage component of the ultrasonic wave from the transmission transducer to the reception transducer is reduced. The correction signal is generated.

  In a preferred aspect, the correction processing unit adjusts the amplitude of the transmission signal so as to reduce an electrical leakage component from the transmission signal to the reception signal, and inverts the phase of the transmission signal to generate the correction signal. It is characterized by that.

  In a preferred aspect, the correction processing unit generates the correction signal by adjusting the amplitude of the transmission signal so as to reduce the reflected wave component from the body surface of the living body and inverting the phase of the transmission signal. And

  According to the present invention, it is possible to reduce unnecessary signal components with a relatively simple configuration in an ultrasonic diagnostic apparatus using a continuous wave.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 shows a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a functional block diagram showing the overall configuration thereof. The transmitting vibrator 10 continuously transmits a transmission wave into the living body, and the receiving vibrator 12 continuously receives a reflected wave from the living body. In this way, transmission and reception are performed by different vibrators, and transmission / reception is performed by a so-called continuous wave Doppler method.

  For example, the RF wave oscillator 20 outputs an RF wave that is a sine wave having a constant frequency. In the present embodiment, this RF wave becomes a continuous wave transmission signal.

  Note that the RF wave may be modulated based on a periodic signal to form a continuous wave transmission signal. For example, even if a continuous wave transmission signal is formed by performing modulation processing on an RF wave supplied from the RF wave oscillator 20 based on a periodic signal supplied from a modulation signal generator (not shown). Good. As the modulation processing, analog modulation processing such as frequency modulation (FM) and phase modulation (PM) and digital modulation processing such as frequency shift keying (FSK) and phase shift keying (PSK) are suitable.

  The power amplifier 14 amplifies the power of the continuous wave transmission signal and supplies it to the transmission vibrator 10. In this way, the transmission wave corresponding to the continuous wave transmission signal is transmitted from the transmission vibrator 10, and the reflected wave from the living body is continuously received by the reception vibrator 12.

  The correction signal generation unit 22 performs a phase adjustment process and an amplitude adjustment process on the continuous wave transmission signal output from the RF wave oscillator 20 to generate the correction signal Vc. In an ultrasonic diagnostic apparatus using a continuous wave, leakage of a signal from the transmission system to the reception system cannot be ignored. For example, if a signal or the like leaks from the transmission system to the reception system due to acoustic or electrical influences, a relatively large unnecessary signal component is included in the reception signal, which is not preferable for extracting a weak Doppler signal.

  The correction signal generation unit 22 generates a correction signal Vc for reducing an unnecessary signal component accompanying leakage of a signal or the like from the transmission system to the reception system. Then, the correction signal Vc is added to the reception signal obtained in the reception transducer 12 by the adding unit 24, and unnecessary signal components included in the reception signal are reduced. Therefore, the correction signal generation unit 22 performs the phase adjustment and the amplitude adjustment so as to cancel the unnecessary signal component included in the reception signal, and generates the correction signal Vc.

  The correction signal generation unit 22 includes an acoustic leakage component of ultrasonic waves from the transmission transducer 10 to the reception transducer 12, an electrical leakage component from the transmission signal to the reception signal in the transmission / reception circuit, The amplitude of the transmission signal is adjusted so that the reflected wave component from the body surface is reduced. For example, the amplitude of the transmission signal is set to be equal to that of the unnecessary signal component consisting of the sum of the three components of the acoustic leakage component, the electrical leakage component, and the reflected wave component from the body surface. Adjust the amplitude. Of course, one of these three components or the sum of the two components is used as an unnecessary signal component, and the amplitude of the transmission signal is adjusted so that the amplitude is equal to that of the unnecessary signal component. May be.

  Regarding the acoustic leakage component of the ultrasonic wave from the transmission transducer 10 to the reception transducer 12 and the electrical leakage component from the transmission signal to the reception signal in the transmission / reception circuit, the configuration of this ultrasonic diagnostic apparatus Therefore, the amplitude of the transmission signal having the same magnitude as these leakage components may be determined on the basis of, for example, theoretical design predictions and experimental results. For the reflected wave component from the body surface of the living body, the amplitude of the transmission signal having the same magnitude as the reflected wave component may be determined based on, for example, an experimental result using a standard phantom or the like.

  Furthermore, the correction signal generation unit 22 generates the correction signal Vc by inverting the phase of the transmission signal whose amplitude is adjusted as described above. That is, the correction signal Vc is generated by shifting the phase of the transmission signal by 180 °. Then, the correction signal Vc is added by the adder 24 to the reception signal obtained in the reception transducer 12, so that the unnecessary signal component and the correction signal Vc included in the reception signal are canceled out, and the unnecessary signal component. Is reduced. Desirably, unnecessary signal components are completely removed.

  When a modulation process is performed on the RF wave supplied from the RF wave oscillator 20 to form a continuous wave transmission signal, the correction signal generation unit 22 applies the modulation process to the continuous wave transmission signal. The correction signal Vc is generated by performing the phase adjustment process and the amplitude adjustment process.

  The preamplifier 16 performs reception processing such as low noise amplification on the reception signal whose unnecessary signal component has been reduced in the adder 24, forms a reception RF signal, and outputs the reception RF signal to the reception mixer 30. The reception mixer 30 is a circuit that performs quadrature detection on the received RF signal to generate a complex baseband signal, and is composed of two mixers 32 and 34. Each mixer is a circuit that mixes the received RF signal with a predetermined reference signal.

  The reference signal supplied to each mixer of the reception mixer 30 is generated based on the transmission signal. That is, the RF wave supplied from the RF wave oscillator 20 is supplied to the mixer 32, and the RF wave supplied from the RF wave oscillator 20 is supplied to the mixer 34 via the π / 2 shift circuit 26. The π / 2 shift circuit 26 is a circuit that delays the phase of the RF wave by π / 2.

  In this way, the in-phase signal component (I signal component) is output from the mixer 32, and the quadrature signal component (Q signal component) is output from the mixer 34. The high-frequency components of the in-phase signal component and the quadrature signal component are cut by LPFs (low-pass filters) 36 and 38 provided at the subsequent stage of the receiving mixer 30 and the demodulated signal only in the necessary band after detection is extracted. Is done.

  When a continuous wave transmission signal is formed by performing modulation processing on the RF wave supplied from the RF wave oscillator 20, the reference signal supplied to each mixer of the reception mixer 30 is modulated. It is generated based on the transmission signal. In this case, a reference signal is formed by subjecting the modulated continuous wave transmission signal to delay processing corresponding to the depth of the target position in the living body. As a result, as a result of the mixing process of the reception RF signal and the reference signal executed by each mixer of the reception mixer 30, it is possible to obtain a signal including a large amount of reception signal components from the target position.

  FFT circuits (fast Fourier transform circuits) 40 and 42 perform an FFT operation on each demodulated signal (in-phase signal component and quadrature signal component). As a result, the demodulated signal is converted into a frequency spectrum in the FFT circuits 40 and 42. The frequency spectrum output from the FFT circuits 40 and 42 is output as frequency spectrum data with a frequency resolution δf depending on circuit setting conditions and the like.

  The Doppler information analysis unit 44 extracts Doppler information from the demodulated signal converted into a frequency spectrum. For example, the Doppler information analysis unit 44 calculates the speed of a moving body such as a blood flow in a living body. Note that in the case where a continuous wave transmission signal is formed by performing modulation processing on the RF wave, Doppler information from the target position is selectively extracted. In this case, the Doppler information analysis unit 44 extracts Doppler information for each depth (each position) in the living body, for example, the velocity of the tissue in the living body for each depth on the ultrasonic beam (sound ray). Is calculated. Note that the speed of each position of the in-vivo tissue may be calculated two-dimensionally or three-dimensionally by scanning an ultrasonic beam.

  The display processing unit 46 forms, for example, a Doppler waveform or a graph including speed information based on the Doppler information obtained by the Doppler information analysis unit 44, and the formed Doppler waveform or graph is displayed on the display unit 48 in real time. To display. Each unit in the ultrasonic diagnostic apparatus shown in FIG. 1 is controlled by the system control unit 50.

  According to the present embodiment, unnecessary signal components included in the reception signal are reduced, and a reception signal having a relatively small amplitude is appropriately extracted. For this reason, a circuit with a small dynamic range can be used in the present embodiment, compared with a case where a received signal containing a relatively large unnecessary signal component is processed. For example, an increase in circuit scale, design cost, etc. Can be suppressed as much as possible.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

1 is a functional block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention.

Explanation of symbols

  20 RF wave oscillator, 22 correction signal generator, 24 adder, 40, 42 FFT circuit, 44 Doppler information analyzer.

Claims (5)

A transmission signal processing unit for outputting a continuous wave transmission signal;
A transmission / reception unit for obtaining a reception signal by transmitting an ultrasonic wave corresponding to the transmission signal to the living body and receiving a reflected wave from the living body;
A correction processing unit that obtains a corrected reception signal in which unnecessary signal components included in the reception signal are reduced by adding a correction signal obtained by performing phase adjustment processing and amplitude adjustment processing to the transmission signal to the reception signal;
A received signal processing unit that obtains a demodulated signal by performing demodulation processing on the corrected received signal using a reference signal having a waveform substantially equal to the transmitted signal;
An in-vivo information extracting unit for extracting in-vivo information from the demodulated signal;
I have a,
The correction processing unit adjusts the amplitude of the transmission signal so as to reduce the reflected wave component from the body surface of the living body and inverts the phase of the transmission signal to generate the correction signal.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The correction processing unit adjusts the amplitude of the transmission signal so as to be the same size as the reflected wave component determined based on an experimental result using a phantom.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1 or 2 ,
The transmission / reception unit includes a transmission vibrator for transmitting an ultrasonic wave corresponding to a transmission signal to a living body, and a reception vibrator for obtaining a reception signal by receiving a reflected wave from the living body,
The correction processing unit adjusts the amplitude of the transmission signal and inverts the phase of the transmission signal so as to reduce the acoustic leakage component of the ultrasonic wave from the transmission transducer to the reception transducer, thereby correcting the correction signal. Generate
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3 ,
The correction processing unit adjusts the amplitude of the transmission signal so as to reduce an electrical leakage component from the transmission signal to the reception signal and inverts the phase of the transmission signal to generate the correction signal.
An ultrasonic diagnostic apparatus. In the ultrasonic diagnostic apparatus according to any one of claims 1 to 4,
The transmission signal processing unit outputs a continuous wave transmission signal modulated based on a periodic signal,
The reception signal processing unit uses a reference signal obtained by performing a delay process on the modulated continuous wave transmission signal by a delay amount corresponding to the depth of the target position in the living body, and a corrected reception signal. A demodulated signal from the target position is obtained by performing demodulation processing on
An ultrasonic diagnostic apparatus.

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