JP5291952B2 - Ultrasonic diagnostic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new ultrasonic diagnostic apparatus utilizing continuous waves. <P>SOLUTION: A PM modulator 18 generates modulated continuous waves (PMCW waves) on the basis of RF waves supplied from an RF wave oscillator 22 and parabolic signals supplied from a parabolic signal generator 20. The parabolic signals are the signals in which the sharp change of an amplitude is made dull. In a reception mixer 28, detection using the modulated continuous waves for transmission as reference signals is performed to received RF signals, and frequency difference signals between transmission and reception signals are extracted by a band-pass filter 30. Then, a position computing part 32 computes the position of biological tissue on the basis of the frequency difference signals, and a speed computing part 34 computes the speed of the biological tissue on the basis of the frequency difference signals. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

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 configured as a sine wave of several MHz is continuously radiated into the living body, and a reflected wave from the living body is continuously received. The reflected wave includes Doppler shift information due to a moving body (for example, blood flow) in the living body. Therefore, the information is taken out and subjected to frequency analysis, and a Doppler waveform reflecting the velocity information of the moving body is formed.

  Continuous wave Doppler using a continuous wave is generally superior in terms of high-speed velocity measurement compared to pulse Doppler using a pulse wave. However, in continuous wave Doppler, position measurement is difficult due to the use of continuous waves. For example, position measurement cannot be performed with a conventional general continuous wave Doppler device.

  Under such circumstances, the inventor of the present application has proposed a technique of continuous wave Doppler that can measure the position of the in vivo tissue in addition to the speed of the in vivo tissue (see Patent Document 1).

JP 2006-14916 A

  The technique described in Patent Document 1 is an epoch-making technique that is capable of measuring a position in addition to a velocity of a tissue or the like while being a technique based on continuous wave Doppler.

  The inventor of the present application has further studied the innovative technique for improving the technique described in Patent Document 1.

  The present invention has been made in such a background, and an object thereof is to provide an improved technique related to an ultrasonic diagnostic apparatus that extracts at least one of velocity information and position information using a continuous wave. .

  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 transmission signal of a continuous wave that periodically changes a frequency, and an ultrasonic signal based on the transmission signal. A transmission / reception unit that obtains a reception signal by transmitting a sound wave to a living body and receiving a reflected wave from the living body, and a reference signal having a waveform substantially equal to the transmission signal, and demodulating the reception signal A reception signal processing unit that obtains a demodulated signal by performing processing, and a tissue information extraction unit that extracts at least one of position information and velocity information of the tissue in vivo based on the demodulated signal, and the transmission signal processing The unit is characterized in that the transmission signal is generated by performing phase modulation processing on the carrier wave signal using the modulation signal whose amplitude is sharply changed.

  In a preferred aspect, the transmission signal processing unit uses a modulation signal based on a parabolic signal that periodically repeats the waveform of a parabolic function.

  In a preferred aspect, the transmission signal processing unit uses a modulated signal of a parabolic signal in which a transient change in a connection portion between waveforms of parabola functions that are periodically repeated is blunted.

  In a preferred aspect, the tissue information extraction unit obtains position information of a living tissue based on a frequency difference between transmission / reception signals obtained from the demodulated signal.

  In a preferred aspect, the tissue information extraction unit calculates the position of the tissue corresponding to the frequency difference component based on at least one frequency difference component included in the frequency spectrum of the demodulated signal.

  In a preferred aspect, the tissue information extraction unit obtains velocity information of a tissue in a living body based on a time change of the frequency spectrum.

  In a preferred aspect, the tissue information extraction unit calculates a tissue velocity corresponding to the frequency difference component based on a temporal change of at least one frequency difference component included in the frequency spectrum.

  In a preferred aspect, the apparatus further includes a frequency characteristic compensation unit that controls the amplitude of the transmission signal so as to compensate the frequency characteristic of the transmission / reception unit.

  The present invention provides an improved technique related to an ultrasonic diagnostic apparatus that extracts at least one of velocity information and position information using a continuous wave.

  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 continuously executed by different vibrators. In FIG. 1, the transmission vibrator 10 and the reception vibrator 12 are each shown as one block, but the transmission vibrator 10 and the reception vibrator 12 are each formed of a plurality of vibration elements. May be.

  The transmitter 14 supplies a transmission signal to the transmission transducer 10 to transmit an ultrasonic wave. A continuous wave (modulated continuous wave) modulated so as to periodically change the frequency is input to the transmitter 14, and a transmission wave corresponding to the modulated continuous wave is transmitted from the transmitting transducer 10.

  The PM modulator 18 converts the RF wave (carrier wave signal) supplied from the RF wave oscillator 22 and the parabolic signal supplied from the parabolic signal generator 20 (the waveform in FIG. 3A described in detail later). Based on this, a modulated continuous wave (transmission waveform shown in FIG. 6A described in detail later) is generated. Then, the amplitude control unit 16 controls the amplitude of the modulated continuous wave generated by the PM modulator 18 so as to compensate the frequency characteristics of the transmitting transducer 10 and the receiving transducer 12.

  FIG. 2 is a diagram for explaining amplitude control in the amplitude control unit (reference numeral 16 in FIG. 1). In the following description, the parts shown in FIG.

  FIG. 2A shows the amplitude-frequency characteristics of a probe including the transmitting transducer 10 and the receiving transducer 12, and the amplitude of the probe varies depending on the frequency indicated on the horizontal axis. Therefore, the amplitude control unit 16 compensates the frequency characteristics of the probe by controlling the amplitude of the modulated continuous wave according to the frequency with the characteristics shown in FIG. In other words, the amplitude of the modulated continuous wave is controlled according to the frequency so as to be the inverse of the amplitude characteristic of the probe, and the amplitude of the ultrasonic wave transmitted from the probe is kept uniform within the frequency band. To compensate.

  Returning to FIG. 1, the preamplifier 24 and the main amplifier 26 perform amplification processing on the received signal supplied from the receiving transducer 12, forms a received RF signal, and outputs the received RF signal to the receiving mixer 28. The reception mixer 28 is a circuit that detects a received RF signal. The reference signal supplied to the reception mixer 28 is a modulated continuous wave generated by the PM modulator 18. Here, the modulated continuous wave whose amplitude is controlled by the amplification controller 16 may be supplied to the reception mixer 28 as a reference signal. In this way, the reception mixer 28 detects the reception RF signal with a modulated continuous wave for transmission to form a demodulated signal, and a band-pass filter (BPF) 30 extracts a frequency difference signal between the transmission and reception signals. . The frequency difference signal will be described in detail later using FIG. 5 and FIG.

  Note that the reception mixer 28 may perform quadrature detection on the received RF signal to generate a complex signal. In the case of quadrature detection, detection is performed using two continuous waves, which are a modulated continuous wave output from the PM modulator 18 and a continuous wave with the phase of the modulated continuous wave shifted by π / 2, as reference signals, and the in-phase component And two components of orthogonal components may be output.

  The frequency difference signal extracted by the BPF 30 is supplied to the position calculation unit 32 and further to the speed calculation unit 34 via the position calculation unit 32.

  The position calculation unit 32 calculates the position of the in vivo tissue based on the frequency difference signal, and the speed calculation unit 34 calculates the speed of the in vivo tissue based on the time change of each frequency spectrum corresponding to each frequency difference signal. To do. The position calculation unit 32 and the speed calculation unit 34 are configured by, for example, a calculator (such as a CPU or DSP) that performs an FFT calculation. The tissue position information and speed information obtained by the position calculation unit 32 and the speed calculation unit 34 are output to the display unit 36. For example, an in-vivo tomographic image based on the position information, a Doppler image based on the speed information, A color Doppler image or the like is displayed on the display unit 36.

  As described above, in the present embodiment, ultrasonic waves (PMCW waves) by continuous waves modulated (PM modulated) with a parabolic signal are transmitted and received to acquire tissue position information and velocity information. Then, the principle is explained in full detail next. In the following description, the parts shown in FIG.

  FIG. 3 is a diagram for explaining a transmission signal and a reception signal (transmission / reception signal) in the present embodiment. FIG. 3A shows a phase change of the transmission / reception signal. That is, FIG. 3A shows the phase change of the transmission signal (solid line) and the phase change of the reception signal (broken line) with the horizontal axis as the time axis and the vertical axis as the phase axis.

  The phase change of the transmission signal in the present embodiment is a parabolic signal that periodically repeats the waveform of the parabolic function. That is, in the PM modulator 18, a parabolic signal supplied from the parabolic signal generator 20 (solid line in FIG. 3A) with respect to an RF wave (carrier signal) having a constant frequency supplied from the RF wave oscillator 22. Phase modulation processing is performed using the same waveform), and a transmission signal (modulated continuous wave) is formed. As a result, the phase change of the transmission signal becomes a parabolic signal.

  Further, when an ultrasonic wave having a waveform corresponding to the transmission signal is transmitted and a reflected wave is received from one target tissue, a reception signal corresponding to the reflected wave is obtained. If attenuation in the tissue is ignored, a reception signal that is exactly the same shape as the transmission signal and is delayed by a round-trip propagation time in the tissue is obtained. The received signal thus obtained is shown in FIG. Therefore, as shown in FIG. 3A, the phase change (broken line) of the received signal is a waveform delayed in the same shape as the phase change (solid line) of the transmission signal.

  FIG. 3B shows a frequency change of the transmission / reception signal. That is, FIG. 3B shows the frequency change of the transmission signal (solid line) and the frequency change of the reception signal (broken line) with the horizontal axis as the time axis and the vertical axis as the frequency (instantaneous frequency) axis. When a transmission signal is formed by performing phase modulation processing on an RF wave having a constant frequency using the parabolic signal shown in FIG. 3A, as shown in FIG. The frequency change (solid line) is a sawtooth wave that repeats a change that increases linearly with time. The frequency change (broken line) of the received signal has a waveform that is exactly the same shape as the frequency change (solid line) of the transmission signal and is delayed by the round-trip propagation time τ in the tissue.

  FIG. 3C shows the phase difference between the transmission and reception signals. That is, in FIG. 3C, the horizontal axis is the time axis and the vertical axis is the phase difference axis, and the difference between the phase change of the transmission signal (solid line) and the phase change of the reception signal (broken line) in FIG. It is expressed.

  FIG. 3D shows the frequency difference between the transmission and reception signals. That is, in FIG. 3D, the horizontal axis is the time axis and the vertical axis is the frequency difference (instantaneous frequency difference) axis, and the frequency change of the transmission signal (solid line) and the frequency change of the reception signal in FIG. The difference of (broken line) is expressed. A frequency difference signal indicating a frequency difference between transmission and reception signals is output from a band pass filter (BPF) 30. In the present embodiment, tissue position information and velocity information are acquired based on the frequency difference signal.

  Note that the parabolic signal supplied from the parabolic signal generator 20 (the same waveform as the solid line in FIG. 3A) has a time during which the amplitude (voltage) changes abruptly with each repetition of the parabolic function waveform. To do. That is, the transitions similar to the solid line waveform in FIG. 3A are shown at times (k−1) Tm, kTm, and (k + 1) Tm in FIG. Due to such an instantaneous voltage change, the phase and frequency of the transmission signal (modulated continuous wave) also change abruptly. As a result, the frequency spectrum band increases. In order to transmit such a signal faithfully, a wide frequency band is required in the apparatus.

  Therefore, in the present embodiment, a modulation signal of a parabolic signal in which a transient change in the connection portion between the parabola function waveforms periodically repeated is used. That is, a signal in which a rapid voltage change of a parabolic signal (the same waveform as the solid line in FIG. 3A) is blunted by a low-pass filter or the like is used.

  FIG. 4 is a diagram showing a signal in which a sharp change in amplitude (voltage) is blunted. The waveforms shown in FIGS. 4A to 4D are the waveforms shown in FIGS. 3A to 3D. Is blunted.

  The parabolic signal supplied from the parabolic signal generator 20 (the same waveform as the solid line in FIG. 3A) is blunted by a low-pass filter or the like, and thereby the blunted parabolic signal (the solid line in FIG. 4A) The same waveform). FIG. 4A shows the phase change (solid line) of the transmission signal formed based on the blunted parabolic signal. Further, the phase change (broken line) of the reception signal obtained from the transmission signal is also dull.

  Further, as shown in FIGS. 4B to 4D, the frequency change of the transmission / reception signal, the phase difference of the transmission / reception signal, and the frequency difference of the transmission / reception signal are also changed to the waveforms of FIGS. 3B to 3D, respectively. It is dull compared. As a result, it is possible to narrow the bandwidth required for the transmission / reception system in the apparatus. In addition, since the length of time that changes abruptly is shorter than the period of the parabolic signal, the degradation of the position resolution accompanying the narrowing of the band is negligible.

  FIG. 5 is a diagram for explaining the principle of acquiring position information from the frequency difference signal. FIG. 5 shows an example in which a received signal is acquired from one target tissue. FIG. 5A shows how the transmission frequency 40 and the reception frequency 42 change with time, and FIG. 5B shows the change over time of the frequency difference (frequency difference signal 44) between the transmission and reception signals. Is shown. The transmission frequency 40 corresponds to the frequency change of the ultrasonic wave transmitted from the transmission transducer 10, and the reception frequency 42 corresponds to the frequency change of the reflected wave from the tissue received by the reception transducer 12. . The frequency difference signal 44 is a signal extracted by the BPF 30.

  As described above (see FIG. 3), when a transmission signal is formed by performing phase modulation processing on an RF wave having a constant frequency using a parabolic signal, the frequency change of the transmission signal is changed over time. At the same time, the transmission frequency 40 of the sawtooth wave repeats a linearly increasing change. That is, the transmission frequency 40 shows a sawtooth frequency change in which the frequency changes from −Δω to Δω during the time Tm and this is repeated. A transmission wave corresponding to the sawtooth transmission frequency 40 propagates in the living body and is reflected by the tissue. For this reason, the wave is received with a delay according to the round-trip propagation distance. This is shown by the reception frequency 42. That is, the reception frequency 42 is acquired by being shifted from the transmission frequency 40 by the delay time τ.

Time τ corresponds to the round-trip propagation time of the ultrasonic wave. Therefore, when the distance from the probe to the target tissue is L and the sound speed is c, the time τ is expressed by the following equation.

Further, since the frequency of the transmission frequency 40 changes from −Δω to Δω during the time Tm, the frequency change per unit time is expressed by the following equation.

Therefore, the frequency difference Δδ between the transmission and reception signals in the periods 1, 3, and 5 and the frequency difference Δδ between the transmission and reception signals in the periods 2, 4, and 6 shown in FIG.

となる。 Since time τ = 2L / c, considering the frequency difference Δδ between transmitted and received signals in periods 1, 3, and 5,

It becomes.

  Therefore, by knowing the frequency difference Δδ between the transmission and reception signals in the periods 1, 3, and 5, the distance L from the probe to the target tissue can be obtained from the known values Δω, Tm, c using Equation 4. Can be requested.

  FIG. 6 is a diagram for explaining the principle of acquiring position information from a frequency difference signal, and FIG. 6 shows an example in which received signals are acquired from a plurality of target tissues.

  FIG. 6A shows a transmission waveform (modulated continuous wave: PMCW wave) supplied to the transmission transducer 10. FIG. 6B shows how the transmission frequency 40 and the plurality of reception frequencies 42a to 42d change with time. The plurality of reception frequencies 42a to 42d respectively correspond to reception signals from target tissues existing at different depths. Each of the plurality of reception frequencies 42a to 42d is received with a delay with respect to the transmission frequency 40 in accordance with the depth of the corresponding tissue.

  FIG. 6C shows how the frequency difference signals 44a to 44d, which are differences from the transmission frequency 40, change with time for each of the plurality of reception frequencies 42a to 42d. The frequency difference signals 44a to 44d are signals that are collectively extracted by the BPF 30. That is, the BPF 30 outputs a signal in which the frequency difference signals 44a to 44d are superimposed.

  The position calculation unit 32 extracts a frequency difference signal for each depth from the superimposed signal. For this reason, the position calculation unit 32 sets a window in the signal processing time zone 48 shown in FIG. 6C, performs frequency analysis on the output signal from the BPF 30 using, for example, FFT in the set window, The frequency power spectrum shown in FIG. 6D is acquired.

  The frequency power spectrum shown in FIG. 6D corresponds to the frequency spectrum of a signal in which the frequency difference signals 44a to 44d are superimposed. Therefore, the waveform includes the spectrum components 50a to 50d at the frequency positions of the frequency difference signals 44a to 44d.

  Therefore, the position calculation unit 32 extracts a signal of a necessary frequency band, and then converts it into each spectrum component 50a to 50d of the frequency spectrum by FFT or the like, and performs signal processing of the frequency difference signals 44a to 44d from the frequency component. A frequency difference Δδ in the time zone 48 is obtained. Thus, for each depth, the distance L corresponding to the depth (position) of each tissue is obtained from the frequency difference Δδ and the known values Δω, Tm, c using Equation 4.

  FIG. 7 is a diagram for explaining the principle of acquiring speed information from the frequency difference signal, and shows the time change of the frequency spectrum of the frequency difference signal.

  FIG. 7 is a two-dimensional representation of the frequency spectrum described with reference to FIG. 6D using a frequency axis and a time axis. The frequency axis in FIG. 7 is the vertical axis in FIG. Corresponding to Therefore, also in FIG. 7, the spectrum at the predetermined frequency corresponds to the reflected wave from the depth corresponding to the frequency. In FIG. 7, the frequency spectrum is represented by a complex amplitude including an amplitude component and a phase component. The length of each spectrum bar represented in a bar shape in FIG. 7 corresponds to the amplitude, and the slope of the bar. Corresponds to the phase.

  If the target tissue is fixed, the frequency spectrum obtained from the target tissue is constant regardless of time. That is, in FIG. 7, the frequency spectrum corresponding to the fixed tissue has a constant rod length and inclination regardless of time. On the other hand, when the target tissue is moving, the frequency spectrum obtained from the target tissue changes with time. That is, in FIG. 7, in the spectrum of the frequency corresponding to the moving tissue, the length and inclination of the bar change with time. Therefore, by analyzing the time variation of the amplitude component and the phase component of the frequency spectrum, the velocity corresponding to the frequency component, that is, the tissue velocity corresponding to the frequency component can be obtained.

  FIG. 8 is a diagram for explaining the principle of acquiring speed information from a frequency difference signal, and is a complex representation of each frequency component (Δδ1 to Δδ4) of a frequency spectrum at a predetermined time. Each frequency component (Δδ1 to Δδ4) in FIG. 8 corresponds to a plurality of different frequency components arranged in the frequency axis direction in FIG.

  The speed calculator 34 analyzes the signal obtained by converting the output signal from the BPF 30 into the frequency amplitude spectrum by the position calculator 32, that is, the frequency difference signal shown in FIG. 6C using, for example, FFT. Then, as shown in FIG. 8, each frequency component (Δδ1 to Δδ4) is complex-represented by two components of an I channel signal component and a Q channel signal component. FIG. 8 shows the complex amplitude of each frequency component of the frequency spectrum at a predetermined time, but the speed calculation unit 34 obtains each frequency component in a complex expression at each time, and changes the time variation for each frequency component. To analyze.

  Since each frequency component (Δδ1 to Δδ4) corresponds to the received signal of the tissue at each depth, the tissue at each depth (position) is analyzed by analyzing the time change of each frequency component (Δδ1 to Δδ4). Can be determined.

  FIG. 9 shows a modification of the ultrasonic diagnostic apparatus shown in FIG. 1, and FIG. 9 is a functional block diagram showing the overall configuration.

  9, parts having the same reference numerals as those shown in FIG. 1 have the same configuration and operation as those in FIG. As described in FIG. 1, also in FIG. 9, the frequency difference signal between the transmission and reception signals is output from the BPF 30.

  The FFT 60 performs frequency analysis on the frequency difference signal (a signal corresponding to FIG. 6C) output from the BPF 30, and generates a complex signal of the frequency spectrum (a signal corresponding to FIG. 7) at each time.

  The multiplier 72 multiplies the complex signal of the current time frequency spectrum input from the FFT 60 by the complex signal of the frequency spectrum of a predetermined time before input via the delay line 70, and the low-pass filter 74 The difference between the complex signals at the two times is extracted. The speed calculation circuit 76 analyzes the time fluctuation for each frequency component of the frequency spectrum from the difference between the complex signals at two times extracted by the low-pass filter 74.

  Since each frequency component corresponds to the received signal of the tissue at each depth, the velocity of the tissue at each depth (position) can be obtained by analyzing the time change of each frequency component. The speed is displayed on the speed / speed dispersion display section 78.

  As shown in FIG. 9, a dispersion calculation circuit 80 is provided to calculate the speed dispersion from the complex signal of the frequency spectrum for each time output from the FFT 60 and display it on the speed / speed dispersion display section 78. You may let them.

  Further, the position calculation circuit 62 obtains the depth (distance L) of each tissue from the frequency difference Δδ and the known values Δω, Tm, c for each depth, using Equation 4. Then, information based on the obtained position (for example, a tomographic image or the like) is displayed on the position display unit 64.

  In the above description, the phase modulation process is performed using the parabolic signal supplied from the parabolic signal generator 20 (the same waveform as that of the solid line in FIG. 3A), and the transmission signal whose frequency changes in a sawtooth shape ( An example of forming a solid line in FIG. By reversing the polarity of the parabolic function included in the parabolic signal for each period, it is possible to form a transmission signal whose frequency changes in a symmetrical triangular wave shape.

  FIG. 10 is a diagram for explaining a symmetric triangular wave transmission signal and a reception signal. FIG. 10A shows a phase change of the transmission / reception signal. That is, FIG. 10A shows the phase change of the transmission signal (solid line) and the phase change of the reception signal (broken line) with the horizontal axis as the time axis and the vertical axis as the phase axis.

  The phase change of the transmission signal in FIG. 10A is obtained by inverting the polarity of the parabolic function included in the phase change (parabolic signal) of the transmission signal in FIG. The PM modulator 18 performs phase modulation processing using a parabolic signal having the same waveform as the solid line in FIG. 10A, whereby the transmission / reception signal in FIG. 10 is formed.

  FIG. 10B shows a frequency change of the transmission / reception signal. That is, FIG. 10B shows the frequency change of the transmission signal (solid line) and the frequency change of the reception signal (broken line) with the horizontal axis as the time axis and the vertical axis as the frequency (instantaneous frequency) axis. When a transmission signal is formed by performing phase modulation processing on an RF wave having a constant frequency using a parabolic signal in which the polarity shown in FIG. 10A is inverted every period, a transmission signal is formed in FIG. As shown, the frequency change (solid line) of the transmission signal is a symmetrical triangular wave that repeats a change that increases linearly with time and then decreases linearly. Note that the frequency change (broken line) of the received signal has the same shape as the frequency change (solid line) of the transmission signal, and has a waveform delayed by a round-trip propagation time τ in the tissue.

  FIG. 10C shows the phase difference between the transmitted and received signals. That is, in FIG. 10C, the horizontal axis is the time axis and the vertical axis is the phase difference axis, and the difference between the phase change of the transmission signal (solid line) and the phase change of the reception signal (broken line) in FIG. It is expressed.

  FIG. 10D shows the frequency difference between the transmission and reception signals. That is, in FIG. 10D, the horizontal axis is the time axis and the vertical axis is the frequency difference (instantaneous frequency difference) axis, and the frequency change of the transmission signal (solid line) and the frequency change of the reception signal in FIG. The difference of (broken line) is expressed. A frequency difference signal indicating a frequency difference between transmission and reception signals is output from a band pass filter (BPF) 30.

  Even in the case of a symmetrical triangular wave, the reception signal is delayed with respect to the transmission signal by a round-trip propagation time corresponding to the depth of the living body. Therefore, even in the case of a symmetric triangular wave, the tissue position can be calculated from the frequency difference between transmitted and received signals based on the same principle as that for a sawtooth wave.

  Regarding the tissue velocity, when the target is moving, the amplitude and phase components of the frequency spectrum change with time even in the case of a symmetric triangular wave as in the case of a sawtooth wave. Therefore, if the time variation of the amplitude and phase component of the frequency spectrum is known, the moving speed of the frequency component can be estimated.

  FIG. 11 is a diagram for explaining the principle of acquiring velocity information from a frequency difference signal in the case of a symmetric triangular wave, and shows a time change of the frequency spectrum of the frequency difference signal. As in the case of FIG. 7, also in FIG. 11, the frequency spectrum is expressed by a complex amplitude including an amplitude component and a phase component, and the length of each spectrum bar expressed in a bar shape in FIG. And the inclination of the bar corresponds to the phase.

  Also in the case of the symmetrical triangular wave shown in FIG. 11, as in the case of the sawtooth wave (FIG. 7), if the target tissue is fixed, the frequency spectrum obtained from the target tissue is constant regardless of time. That is, in FIG. 11, the frequency spectrum corresponding to the fixed tissue has a constant bar length and inclination regardless of time. On the other hand, when the target tissue is moving, the frequency spectrum obtained from the target tissue changes with time. That is, in FIG. 11, in the spectrum of the frequency corresponding to the moving tissue, the length and inclination of the bar change with time.

  However, the difference from the case of the sawtooth wave is that the complex vector of the moving target always appears in pairs, and the rotation direction is reverse. This is because the Doppler polarity is different between up-chirp and down-chirp. That is, the Doppler polarity is inverted every half cycle of the modulated wave. Therefore, if the difference in frequency spectrum between adjacent half cycles is calculated, the Doppler signal is doubled, while the reflected wave from the fixed target disappears. Further, if the sum of the frequency spectrums of the adjacent half cycles is calculated, the Doppler signal disappears, but the reflected wave from the fixed target is doubled. By these calculations, a Doppler or a fixed target can be selected, extracted and displayed.

  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. It is a figure for demonstrating the amplitude control in an amplitude control part. It is a figure for demonstrating a transmission signal and a received signal (transmission-and-reception signal). It is a figure which shows the signal which blunted the sharp change of the amplitude (voltage). It is a figure for demonstrating the principle which acquires positional information from a frequency difference signal. It is a figure for demonstrating the principle which acquires positional information from a frequency difference signal. It is a figure for demonstrating the principle which acquires speed information from a frequency difference signal. It is a figure for demonstrating the principle which acquires speed information from a frequency difference signal. It is a functional block diagram which shows the modification of the ultrasonic diagnosing device shown in FIG. It is a figure for demonstrating the transmission signal and reception signal of a symmetrical triangular wave. It is a figure for demonstrating the principle which acquires the speed information in the case of a symmetrical triangular wave.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Transmitting vibrator | oscillator, 12 Reception vibrator | oscillator, 16 Amplitude control part, 18 PM modulator, 20 Parabolic signal generator, 32 Position calculating part, 34 Speed calculating part.

Claims (7)

A transmission signal processing unit that outputs a continuous wave transmission signal that periodically changes the frequency;
A transmission / reception unit for obtaining a reception signal by transmitting an ultrasonic wave to a living body based on the transmission signal and receiving a reflected wave from the living body;
A received signal processing unit for obtaining a demodulated signal by performing a demodulation process on the received signal using a reference signal having a waveform substantially equal to the transmitted signal;
A tissue information extracting unit that extracts at least one of position information and velocity information of the tissue in the living body based on the demodulated signal;
Have
The transmission signal processing unit is a parabola that periodically repeats the waveform of a parabola function when generating the transmission signal by performing phase modulation processing on a carrier wave signal using a modulated signal with a sharp change in amplitude. Using a modulated signal based on the signal
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1 ,
The transmission signal processing unit uses a modulation signal of a parabolic signal in which a transient change in a connection part between waveforms of a parabola function that is periodically repeated is blunted.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1 or 2 ,
The tissue information extraction unit obtains in-vivo tissue position information based on a frequency difference between transmission and reception signals obtained from the demodulated signal;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3 .
The tissue information extraction unit calculates the position of the tissue corresponding to the frequency difference component based on at least one frequency difference component included in the frequency spectrum of the demodulated signal.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 4 ,
The tissue information extraction unit obtains velocity information of in vivo tissue based on the time change of the frequency spectrum.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 5 ,
The tissue information extraction unit calculates a tissue velocity corresponding to the frequency difference component based on a time change of at least one frequency difference component included in the frequency spectrum.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 1 to 6 ,
A frequency characteristic compensator that controls the amplitude of the transmission signal so as to compensate the frequency characteristic of the transmission / reception unit;
An ultrasonic diagnostic apparatus.

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