JP2004160251A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute the contrast echo method for accurately performing display and measurement of velocity information of a contrast agent by the Doppler method by intravenous infusion even for a site (cardiac muscle, organ parenchyma, etc.) significantly affected by a tissue echo from circumference. <P>SOLUTION: This ultrasonic diagnostic system is equipped with means (341-345) to extract the Doppler shift frequency of the nonlinear component of a reflection signal of an ultrasonic beam signal reflecting nonlinear vibration of an ultrasonic contrast agent generated by responding to the irradiation when the ultrasonic beam signal is irradiated against the ultrasonic contrast agent infused in blood vessel of a subject, means (346, 347) to convert the extracted Doppler shift frequency fd to a velocity component according to the converting formula. and means (35, 36) to associate the converted velocity component v with a velocity scale for the nonlinear component to code it in color to display it in color as velocity information of the ultrasonic contrast agent in the subject. <P>COPYRIGHT: (C)2004,JPO

Description

  According to the present invention, a contrast image is obtained by injecting an ultrasonic contrast agent into a subject, and a contrast image is obtained by utilizing the property that echo is enhanced by the strong scattering characteristic of the contrast agent with respect to ultrasonic waves. The present invention relates to an ultrasonic diagnostic apparatus capable of measuring the speed of an agent.

About.

  In recent years, a contrast echo method using an ultrasonic contrast agent has been attracting attention in the field of myocardial image analysis.

  As one of the contrast echo methods, a myocardial contrast echo method by arterial infusion in which an ultrasonic contrast agent is injected from an artery has been studied, and is used for evaluation of a perfusion area of myocardial blood flow using a myocardial distribution image (perfusion). ing. In this myocardial contrast echo method, an ultrasonic contrast agent (for example, 5% human albumin in which bubbles are generated manually or by a sonicator) is injected from a catheter placed in the aorta. The perfusion area of the blood flow in the myocardium by the contrast agent is displayed as a brightness enhancement area on the B mode. Similarly, in order to evaluate the perfusion area of blood flow or the vasculature dominating the tumor, a contrast echo method by arterial infusion in the abdominal region has been studied. An ultrasonic diagnostic apparatus for general inspection or a workstation is used as a diagnostic apparatus for performing these contrast echo methods. Thus, the luminance enhancement of the B-mode image is visually evaluated, or the image data stored in the memory is appropriately processed on a workstation, and then the change in the luminance level is quantitatively evaluated.

  In recent years, the development of an ultrasonic contrast agent itself has also been actively developed, and an ultrasonic contrast agent capable of injecting from a vein to evaluate the left heart system has been developed, and an ultrasonic contrast echo method using this agent has been attempted. .

  As the ultrasonic contrast agent, for example, “the average particle size of air containing air enclosed in an albumin film formed when sonicating 5% human serum albumin”, which is imported and sold by Shionogi & Co., Ltd., is used. 4 μm air microspheres ”(brand name: Albunex Note 5 ml).

  This contrast echo method by vein injection is currently in the testing and research stages, and its usefulness in the diagnosis of the head, heart cavity, abdomen, etc. is expected to increase in the future.

  However, among the above-mentioned conventional contrast echo methods, the contrast echo method using arterial injection requires that the catheter be placed in the aorta, so that the facility (operating room) where the catheter can be performed is limited to a relatively large hospital, In addition, it is assumed that it will not be easily spread to general clinical practice in the future due to the fact that the burden on the patient is large due to the diagnosis accompanied by invasiveness.

  In addition, since the air bubbles of the contrast agent due to the arterial injection are relatively large, the air bubbles tend to be clogged in the myocardium and the peripheral portion, and the staining may be continued for several minutes. Therefore, even if Doppler measurement is performed at those blood vessel sites, the moving speed of the bubble does not accurately reflect the blood flow velocity.

  On the other hand, the contrast echo method by venous injection is extremely invasive and requires a small burden on the patient, but the contrast agent reaches the myocardium and other target sites through the lungs, so the contrast by arterial injection can be used. Compared with the echo method, the contrast agent concentration is lower and the brightness enhancement is lower. For this reason, it is extremely difficult to observe the enhancement of the brightness by the contrast agent in a region where the influence of the tissue echo is large, such as the myocardium and the peripheral region of the abdomen, and it is extremely difficult to observe the perfusion area of the blood flow in the myocardium by the myocardial distribution image. It cannot be applied to evaluation or detection of blood flow in the parenchyma of the liver.

  In addition, when a color Doppler image is obtained, especially in the abdomen and the like, there is a large effect of motion artifacts caused by movement of surrounding tissues due to respiration and the movement of a blood vessel wall, and there is a problem that the image is not used as a color Doppler image.

  The present invention has been made in view of the current state of such a contrast echo method using a conventional ultrasonic contrast agent, and is applicable to a part (myocardium, organ substance, etc.) where the influence of a tissue echo from the surroundings is large. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of performing a contrast echo method by venous injection, and accurately displaying and measuring velocity information of a contrast agent by a Doppler method.

In order to achieve the above object, an ultrasonic diagnostic apparatus according to one aspect of the present invention includes a transmission driving unit that drives an ultrasonic probe to transmit an ultrasonic beam signal to a subject, and the ultrasonic probe includes: Receiving processing means for phasing and adding the echo signal of the electric quantity to be output, and the ultrasonic beam signal emitted to the ultrasonic contrast agent injected into the blood vessel of the subject, which is generated in response to the irradiation. Doppler extraction means for extracting from the echo signal a Doppler shift frequency of a non-linear component of a reflected signal of the ultrasonic beam signal reflecting the non-linear vibration of the ultrasonic contrast agent, and the Doppler shift extracted by the Doppler extraction means. The transfer frequency fd

Frequency / speed conversion means for converting the velocity component v converted by the frequency / speed conversion means in accordance with the conversion formula of Display means for performing color display as velocity information of the ultrasonic contrast agent.

Further, according to an ultrasonic diagnostic apparatus according to another aspect of the present invention, a transmission driving unit that transmits an ultrasonic beam signal to a subject by driving an ultrasonic probe, and an amount of electricity output by the ultrasonic probe Receiving processing means for phasing and adding the echo signal, and the ultrasonic contrast agent generated in response to the irradiation when the ultrasonic beam signal is irradiated to the ultrasonic contrast agent injected into the blood vessel of the subject Doppler extraction means for extracting the Doppler shift frequency of the nonlinear component of the reflected signal of the ultrasonic beam signal reflecting the nonlinear vibration from the echo signal, and the Doppler shift frequency fd extracted by the Doppler extractor,

Frequency / speed conversion means for converting the velocity component v converted by the frequency / speed conversion means into a velocity component v according to the conversion formula, and the ultrasonic contrast agent in the subject on the speed scale for the non-linear component Display means for performing FFT display as the speed information.

According to an ultrasonic diagnostic apparatus according to still another aspect, transmission driving means for driving an ultrasonic probe to transmit an ultrasonic beam signal to a subject, and adjusting an echo signal of an electric quantity output by the ultrasonic probe. Reception processing means for performing phase addition, and when the ultrasonic beam signal is irradiated on the ultrasonic contrast agent injected into the blood vessel of the subject, nonlinear vibration of the ultrasonic contrast agent generated in response to the irradiation is performed. Doppler extraction means for extracting the Doppler shift frequency of the nonlinear component of the reflected signal of the reflected ultrasonic beam signal from the echo signal, and the Doppler shift frequency fd extracted by the Doppler extraction means,

Frequency / speed conversion means for converting the velocity component v into a velocity component v in accordance with the following conversion formula; and converting the velocity component v converted by the frequency / velocity conversion means into a color code in association with a velocity scale for the non-linear component. Means for displaying color as velocity information of the ultrasonic contrast agent, or means for displaying the velocity component v by FFT as velocity information of the ultrasonic contrast agent in the subject on a velocity scale for the non-linear component And a measuring means capable of measuring the speed information of a desired area designated on the image displayed by the displaying means.

The various configurations according to the present invention described above are based on the following principle. In the present invention, the contrast echo method based on the non-linear scattering characteristics of the bubbles forming the ultrasonic contrast agent injected into the subject is particularly called a “harmonic echo method”, and the Doppler method is applied to the harmonic echo method. is there. Conventionally, it has not been known at all how the Doppler effect of the nonlinear wave component of the echo signal when transmitting the ultrasonic beam signal of the frequency f ₀ is qualitatively and quantitatively expressed. The present inventor paid attention to the second harmonic component as a component representing the non-linear component and tried experiments on the evaluation of the Doppler effect of the second harmonic component. It was confirmed that the frequency was equivalent to the Doppler shift frequency when transmitting and receiving by the ultrasonic wave having the frequency of the component itself. The present invention has been made based on such knowledge.

  The ultrasonic contrast agent is composed of minute bubbles, and the echo is enhanced by its strong scattering characteristics. It is known that bubble scattering has a strong nonlinear characteristic, and by using this, it is possible to distinguish echoes other than bubbles from echoes from a contrast medium (bubbles). Specifically, the operation is performed as follows.

  (1) A harmonic component is generated by nonlinear scattering. By utilizing this, only the harmonic component of the transmitted fundamental wave is received. Considering the biological attenuation and the band of the transmission / reception system, the use of the second harmonic is particularly excellent.

(2) A subharmonic component or its superharmonic component is generated by nonlinear scattering. Using this, the subharmonic component and f ₀ with respect to the transmitted fundamental wave, harmonic components, subharmonic components, when the super-harmonic component is expressed as alpha · f _0, one aspect of the present invention Then

Conversion formula or approximation conversion formula based on the fact that the moving speed of the target is lower than the sound speed

Thus, the moving speed of the contrast agent is detected. Here, the transmission frequency basically refers to the carrier frequency of the pulsar or the center frequency (center of the bandwidth) / peak frequency of the transmission sound pressure waveform spectrum.

In this mode, it is extremely important that the nonlinear component α · f ₀ does not exist in the transmission frequency band.

Therefore, according to the ultrasonic diagnostic apparatus of the present invention, the ultrasonic probe is driven to transmit the ultrasonic beam signal to the subject, and the echo signal of the electric quantity output from the ultrasonic probe is phased and added. Is done. The Doppler shift frequency of the nonlinear component of the echo signal due to the reflection of the ultrasound beam signal of the ultrasound contrast agent injected into the subject is extracted from the echo signal, and the Doppler shift frequency fd is

Is converted into the velocity component v according to the conversion formula Thereafter, the speed information of the ultrasonic contrast agent in the subject is displayed and / or measured based on the speed component v.

  ADVANTAGE OF THE INVENTION According to the ultrasonic diagnostic apparatus which concerns on this invention, the contrast agent by a vein injection performs a contrast echo method by a vein injection even in the site | part (myocardium, an organ parenchyma, etc.) where the influence of the tissue echo from the periphery is large. The display and measurement of the speed information can be accurately performed.

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  An embodiment of the present invention will be described with reference to FIGS. The ultrasonic diagnostic apparatus according to this embodiment efficiently detects second harmonic components generated by nonlinear scattering of bubbles contained in an ultrasonic contrast agent, displays a two-dimensional distribution image thereof, and performs Doppler measurement. This is an apparatus to which the contrast echo method can be applied.

  As shown in FIG. 1, the ultrasonic diagnostic apparatus includes an ultrasonic probe 10 that transmits and receives an ultrasonic signal to and from a subject, drives the ultrasonic probe 10, and converts a received signal of the ultrasonic probe 10 into a signal. It consists of an apparatus body 11 for processing.

  The ultrasonic probe (hereinafter, referred to as “probe”) 10 is configured as a phased array type in which a plurality of transducers are arranged in a scanning direction. The receiving characteristics of each vibrator are formed identically, and have a sufficiently wide signal pass band capable of detecting a fundamental wave component for driving the vibrator and a second harmonic component generated in a living body.

  The apparatus main body 11 has a transmission system for driving the probe 10, a reception / processing system for receiving and processing a signal from the probe 10, a display system for displaying a processed image, and an input system. In addition to this, there are biosignal detection systems such as ECG, etc., which are omitted in the drawings.

  The transmission system includes a clock generation circuit 20, a transmission delay circuit 21, a pulser circuit 22, and a transmission resonance circuit 23. The clock generation circuit 20 is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of an ultrasonic signal, and the transmission delay circuit 21 is a circuit that delays transmission and performs transmission focus. The pulsar circuit 22 incorporates pulsars corresponding to the number of individual paths (hereinafter, referred to as “channels”) corresponding to the respective vibrators, generates a drive pulse at a delayed transmission timing, and supplies the driving pulses to the respective vibrators of the probe 10. Supply.

  The transmission resonance circuit 23 is one of the features of the present apparatus, and is provided for efficiently detecting, for example, a second harmonic component of an echo signal generated by an ultrasonic contrast agent injected into a living body. That is, unless the pulsar is driven completely by sine waves at the time of transmission, the pulsar has a function of removing generated harmonic components without fail. Specifically, as shown in FIG. 2, the transmission resonance circuit 23 includes a limiter 24 composed of a diode anti-parallel circuit and a coil unit that resonates with a capacitive impedance such as a probe or a cable and has a pass band only near a fundamental wave. 25. Since the limiter 24 is turned on when the applied signal value exceeds a certain level, the transmission resonance circuit 23 is in a resonance state only when transmitting with a high signal level, and remains in a non-resonance state when receiving. The series circuit of the limiter 24 and the coil unit 25 is actually provided for each channel.

  Further, the reception / processing system includes, on the output side of the probe 10, a preamplifier circuit 30, a reception delay / addition circuit 31, band-pass filters (BPF) 32a and 32b, receiver circuits 33a and 33b, and a speed calculator 34, for example. Prepared in order. The preamplifier circuit 30 amplifies the power of the reception echo for each reception channel and sends the amplified power to the reception delay / addition circuit 31. The reception delay / addition circuit 31 has a delay unit for each reception channel and an addition unit for adding these delay results, and performs reception focusing on the reception echo signal. On the output side of the reception delay / addition circuit 31, bandpass filters 32a and 32b for the fundamental wave and the non-linear wave are connected in parallel. The passband of the bandpass filter 32a for the fundamental wave matches the fundamental wave component of the echo signal, while that of the bandpass filter 32b for the nonlinear wave matches the second harmonic component of the echo signal. The output side of the fundamental wave band-pass filter 32a is connected to a DSC 35 to be described later via a fundamental wave receiver circuit 33a, and that of the nonlinear wave band-pass filter 32b is passed through a nonlinear wave receiver circuit 33b. It is connected to DSC35. The two receiver circuits 33a and 33b are reception processing circuits that perform processing such as envelope detection and log compression for each of the fundamental wave component and the second harmonic component to obtain a B-mode image signal.

  Further, the receiving / processing system has a DSC (Digital Scan Converter) 35 and a monitor 36. The DSC 35 includes an A / D converter for receiver output, a multiplexer, a frame memory, a write / read circuit, a D / A converter, and the like, and forms an image signal of one frame corresponding to a commanded display mode. The image signal can be read by a standard TV system. The image signal read from the DSC 35 is output to the monitor 36 via the panel interface 37 and displayed.

  Further, a CPU 39 is connected to the DSC 35 via a DSC memory unit 38.

  The input system of the diagnostic device includes the panel interface 37 and a panel 40 operated by an operator.

  In the speed calculation unit 34, the speed of the ultrasonic contrast agent injected into the subject is detected. FIG. 3 shows an example of the configuration of the speed calculator 34.

The speed calculator 34 shown in the figure includes a reference oscillator 341, a 90 ° phase shifter 342, a phase detector 343, an FFT calculator 344, an MTI calculator 345, and first and second frequency / speed converters 346 and 347. Have. The reference oscillator 341 outputs a reference signal (reference frequency fr) for phase (orthogonal) detection of the phase-added echo signal. The 90 ° phase shifter 342 changes the phase of the input signal by exactly 90 ° and outputs it. Phase detector 343 has a series circuit of two channels of the mixer 3431a (3431b) and a low-pass filter 3432a (3432b) (is set to the cut-off frequency fc = reference frequency _{f r),} on one of the mixer 3431a directly The other mixer 3431b receives the reference signal via the phase shifter 342. Thus, the echo signal that has passed through the non-linear waveform bandpass filter 32b is subjected to quadrature detection by the phase detector 343, and is supplied to the FFT operation unit 344 and the MTI operation unit 345.

  The FFT operation unit 344 includes a two-channel processing circuit including a sample-and-hold circuit 3441a (3442b), a bandpass filter 3442a (3442b), and an A / D converter 3443a (3443b). A frequency analyzer 3444 that performs Fourier transform) is provided. As a result, from the phase-detected echo signal, only a Doppler signal of an arbitrary depth is extracted by the sample and hold, and unnecessary components are removed by the bandpass filters 3442a and 3442b. This Doppler signal is directly frequency-analyzed by the frequency analyzer 3444 in real time.

On the other hand, the MTI calculator 345 includes a two-channel circuit including an A / D converter 3451a (3451b) and an MTI filter 3452a (3452b), an autocorrelator 3453, an average speed calculator 3454, a dispersion calculator 3455, and a power An arithmetic unit 3456 is provided. As a result, the phase-detected echo signal is subjected to A / D conversion, and then unnecessary fixed reflection signals such as a heart wall are removed by the MTI filters 3452a and 3452b. After that, the echo data is subjected to frequency analysis (Doppler analysis) of each point on the two-dimensional tomographic plane in real time by the autocorrelator 3453. Using the Doppler shift frequency f _d that is generated by this analysis, the average speed calculator 3454 with the average Doppler frequency of the fault plane each point is calculated, similarly variance (Spectrum lands), the power (intensity A) value is calculated by each calculator 3455 (3456).

  That is, the FFT operation unit 344 and the MTI operation unit 345 detect the Doppler shift frequency caused by the contrast agent moving in the blood vessel. In the spectrum Doppler mode, the FFT operation unit 344 operates, and in the color Doppler mode, the MTI operation unit 345 operates.

  The analysis data of the FFT operation unit 344 is supplied to the DSC 35 via the first frequency / speed converter 346, and the operation data of the average speed operation unit 3454 of the MTI operation unit 345 is supplied via the second frequency / speed converter 347. Is supplied to the DSC 35.

The first and second frequency / velocity converters 346 and 347 embody the features of the present invention, and determine the dimension of the Doppler shift frequency f _d based on the following conversion equation, corresponding to the velocity v, It is converted into the dimension of the moving speed of the contrast agent (bubble).

In this embodiment, the reference frequency _{f r} for the mixers 3431a and 3431b of the phase detector 343 are matched to the second harmonic component of the transmission frequency _{f 0} "2 · _{f 0".} The reference frequency _fr and the second harmonic frequency 2 · f ₀ form a set frequency f _set for speed conversion according to the present invention.

Doppler shift frequency f _d by the following equation is converted to the ultrasound beam direction component v of the moving speed.

Here, α = 2, C: sound speed, V: moving speed of the object, θ: angle between the moving direction of the object and the ultrasonic beam, f ₀ : transmission frequency, f _d : Doppler shift frequency.

Alternatively, an approximate expression based on the fact that the moving speed of the target (bubble) is lower than the sound speed

Is converted by

A transmission frequency f ₀ is basically a peak frequency (the center of the bandwidth) the center frequency of the carrier frequency or transmission sound pressure waveform spectrum pulser.

  The conversion coefficient α is a value in the range of α = 1.5 to 2.0 in consideration of a width in consideration of biological attenuation when the second harmonic is used as a target nonlinear wave component. Desirably. Also, when a subharmonic wave is employed, a value of α = 0.7 or less is desirable in consideration of the width in the same manner. When considering all harmonics, α may be a natural number other than 1.

In the present invention, it is essentially important that the reference frequency _fr is not in the transmission frequency band. The transmission frequency band refers to a band near the peak frequency component of the ultrasonic signal transmitted from the ultrasonic probe 10 as shown in FIG. 4B, and the level of “−20” dB or more is smaller than the peak frequency component. It is a guide. In this method, even if the reference frequency _fr is the second harmonic frequency (= 2f ₀ ), it is meaningless if the above condition is not satisfied. That is, in the received signal, it becomes impossible to discriminate the second harmonic component caused by the contrast agent from the echo component by the surrounding organs of the second harmonic component included in the transmission, and the effect expected by this method is obtained. Because it cannot be obtained.

As shown in FIG. 5, in a conventional Doppler device, a so-called transmission frequency and a reference frequency are sometimes set to be shifted from each other. In this method, a reference frequency is set on the lower frequency side than a peak frequency component of transmission in consideration of biological attenuation. In this case, it is essentially important that the reference frequency be within a transmission frequency band. Set frequency f _{The set} for speed conversion of the present invention, as described above, may be defined using any of the transmission frequency f ₀ and the reference frequency f _r.

In addition, in the case where non-linear scattered echo of a contrast agent, which is a premise of the present method, is not targeted, the reference frequency is set outside the transmission frequency band, and the observed Doppler shift frequency is converted into the above-mentioned conversion formula (1) or (2). It does not make sense to convert to speed by). The Doppler effect differs depending on the transmission frequency, and the transmission frequency f ₀ before the shift and the Doppler shift frequency f _d have the following simple relationship.

Therefore, the conversion is meaningless unless the frequency f ₀ before the shift is used. That is,

  Basically, in the conventional pulse Doppler method, the Doppler effect for all the frequency components in the transmission signal band is convoluted. Therefore, it is best to use the peak frequency component as the reference frequency in terms of speed accuracy. In the method, one of the bands of nonlinear components (harmonics, subharmonics, superharmonics) outside the transmission signal band is selected, and the reference frequency is set to the peak frequency component of the received signal in that band. Best for speed accuracy.

  The data thus converted into the speed dimension by the first and second frequency / speed converters 346 and 347 are sent to the DSC 35 together with other necessary data, and converted into frame image data in the commanded display mode. Is done. The panel interface 37 has a built-in color processing circuit and D / A converter. The image data of the DSC 35 is subjected to a coloring process as necessary, and sent to the monitor 36 as an analog signal. Note that an external device such as a recorder or a memory may be connected instead of the monitor 36 or in parallel with the monitor 36.

  The CPU 39 reads a command from an operator who has operated the panel 40 via the panel interface 37, outputs a marker for superimposition display, character data, and the like from the DSC memory unit 38 to the DSC 35, and performs speed measurement.

  Subsequently, the operation and effect of this embodiment will be described.

  At the time of transmission, a driving voltage signal is supplied to each transducer of the probe 10 from the pulsar circuit 22 via the transmission resonance circuit 23 for each channel in a state where transmission focus is applied by the transmission delay circuit 21. At this time, the limiter 24 of the transmission resonance circuit 23 is kicked on because the drive voltage signal is higher than the predetermined level, and the resonance unit 24 resonates. Due to this resonance, only the fundamental wave component of the drive voltage signal passes through the transmission resonance circuit 23 and is supplied to each transducer of the probe 10.

  Complete sine wave driving of the pulsar circuit 22 is practically difficult, and usually includes a harmonic component in the generated driving voltage signal. However, such a harmonic component is intentionally removed by the transmission resonance circuit 23 described above. And each vibrator is excited by the drive voltage signal of only the fundamental wave component.

  When each transducer of the probe 10 is excited in this way, the probe 10 transmits an ultrasonic beam signal with transmission focus applied to a diagnosis site such as a myocardium of the subject. This ultrasonic beam signal becomes an ultrasonic echo signal reflected and scattered by an ultrasonic contrast agent (for example, the above-mentioned “Albunex Injection 5 ml”: trade name) injected into each tissue of a diagnostic site from a vein. . In particular, the ultrasonic contrast agent is composed of minute bubbles, and the echo signal is enhanced by strong scattering characteristics of the bubbles. This scattering has a nonlinear characteristic, and a harmonic component is also generated by the scattering of the nonlinear characteristic. As a result, the ultrasonic echo signal contains an echo component (fundamental wave component) from a living tissue other than the contrast agent (bubble) and an echo component (fundamental wave component and its harmonic components) from the contrast agent.

This ultrasonic echo signal is received by each transducer of the probe 10 and is converted into a corresponding electric signal. Since the power of the echo signal of this electric quantity is weak, each limiter 24 of the transmission resonance circuit 23 is not kicked on, and the transmission resonance circuit 23 remains in a non-resonance state. As a result, the echo signal containing the fundamental wave component and the harmonic wave component reaches the preamplifier circuit 30 without being involved in the transmission resonance circuit 23 and is power-amplified. Then, the reception delay / addition circuit 31 delays the reception for each channel. Are added. Thereby, the reception focus is set. The received echo signal is sent in parallel to the fundamental wave BPF 32a and the nonlinear wave BPF 32b. In the fundamental wave for BPF32a, fundamental component _{S f} of the echo signal is extracted are directed to the subsequent stage of the receiver circuit 33a, only the second harmonic wave component _{S 2f} of the echo signals in the non-linear wave for BPF32a extraction The data is similarly sent to the receiver 33b and the speed calculator 34.

Echo signal of one receiver circuit 33a to sent fundamental component S _f is subjected to processing such as envelope detection or logarithmic compression, image data of the B-mode image of the fundamental wave component (luminance modulation image amplitude) generated Is done. The echo signal of the second harmonic component _S2f sent to the other receiver circuit 33b is also subjected to the same processing, and the image data of the B-mode image of the second harmonic component is generated.

The image data of each of the B-mode images of the fundamental wave component and the second harmonic component is then converted by the DSC 35 into image data of a designated display mode. The display modes of the B-mode image IM _f based on the fundamental wave component (hereinafter, simply referred to as “fundamental wave image”) and the B-mode image IM _2f based on the second harmonic component (hereinafter, simply referred to as “second harmonic image”) are as follows. There are a variety, a command display mode to superimpose the second harmonic image IM _2f in contrast echo Law when, for example, on the fundamental wave image IM _f is made. DSC35 be synthesized both image data in response to this, the supply to the monitor 36, the monitor 36 as shown in FIG. 6, the image in the fundamental wave image IM _f is second harmonic image IM _2f superimposed " IM _{f + 2f} "is displayed, and the morphology of the living tissue and the distribution of the ultrasonic contrast agent therein can be observed.

  As described above, in the present embodiment, the transmission resonance circuit 23 intentionally (actively) cuts harmonic components other than the fundamental wave component and transmits the ultrasonic beam in a state of only the fundamental wave component. Therefore, most of the second-order harmonic components included in the echo signal are caused only by the nonlinear scattering characteristics of the ultrasonic contrast agent. In other words, it is possible to selectively process only the second harmonic component due to the scattering of the contrast agent from the transmitted ultrasonic signal of the fundamental wave component to form an image. Considering this, an excellent use of the second harmonic component is obtained.

  Further, in the present embodiment, when the spectrum Doppler mode is instructed, the FFT operation unit 344 of the speed operation unit 34 performs the FFT operation as described above, and the analysis data is converted by the first frequency / speed converter 346 into the speed data. is converted to v. The speed data v is displayed on the monitor 36 via the DSC 35 as a grayscale spectrum Doppler image in which the speed information is luminance-modulated as shown in FIG. On the other hand, when the color Doppler mode is instructed, the MTI calculator 345 of the speed calculator 34 performs frequency analysis as described above, and the analysis data is converted into speed data v by the second frequency / speed converter 347. . The data v is displayed on the monitor 36 via the DSC 35 and the panel interface 37 as, for example, a color Doppler image in which speed information is color-modulated as shown in FIG.

  In the spectrum Doppler image shown in FIG. 7, the vertical axis is a speed axis (frequency axis; speed scale), and the horizontal axis is a time axis. The speed axis is based on the speed conversion formula, for example, the maximum detected speed is displayed on a scale. When the measurement function is used, as shown in the figure, a peak speed and the like are obtained and displayed based on the speed conversion formula. At this time, as shown in FIG. 1, an instruction from the operation panel 40 is sent to the CPU 39 via the panel interface 37, and the measurement data is displayed on the monitor 36 by the DSC 37 and the DSC memory unit 38 under the control of the CPU. . Memory information and the like are also displayed on the monitor 36 by the DSC 37 and the DSC memory unit 38.

  On the other hand, the color Doppler image shown in FIG. 8 is colored by a color map based on the conversion formula, and the speed value based on the speed conversion formula is displayed on a scale or a desired value when the measurement function is used together with a color bar or a color palette. Is displayed for the ROI.

As described above, the contrast echo method using the contrast agent has been developed into a harmonic echo method based on the non-linear scattering characteristics of bubbles forming the contrast agent. Furthermore, the Doppler method by the harmonic echo method, the experimental confirmation of the group to be equivalent to the Doppler shift frequency when the Doppler shift frequency is transmitted and received by the second harmonic component, the Doppler shift frequency f _d Since the set frequency f _set used for the conversion to the velocity v is _set with confidence that f _set = reference frequency _fr = 2f ₀ , the second harmonic component 2f ₀ from the bubble can be reliably measured. . As a result, a blood flow having a low speed and a minute flow, such as a tissue blood flow or a blood flow in a myocardium, can be detected at a high S / N ratio, and the speed can be measured with high accuracy. Particularly in color Doppler imaging (CDI) in the abdomen, motion artifacts are reduced and a high-quality CDI image is obtained.

By the way, in the embodiment shown in FIG. 1, since the transmission frequency component is relatively strongly reflected by the surrounding tissue, the non-linear scattered echo component due to the contrast agent in the blood vessel in the tissue becomes the received echo component as shown in FIG. Is assumed to be outside the fundamental frequency band on the spectrum. In this sense, it can be said that the reference frequency is set outside the fundamental frequency band of the reception signal received by the ultrasonic probe. However, this does not apply to the case where the frequency characteristics of the transducer to be received have relatively low sensitivity to the fundamental wave component at the time of transmission as in the ultrasonic diagnostic apparatus shown in FIGS. The probe 10 of the phased array type of the ultrasonic diagnostic apparatus shown in FIG. 10 is divided into transducer groups A and B. Each of the vibrators 10 ₁ , 10 ₃ ,..., 10 _n-1 of the vibrator group A has its frequency band set so as to substantially respond to only the fundamental wave component f (see FIG. a)). Each of the vibrators 10 ₂ , 10 ₄ ,... 10 _n of the vibrator group B has its frequency band set so as to substantially respond to only the second harmonic component “2 · f”. (See FIG. 11B). These frequency bands are set, for example, by changing the resonance frequency of the vibrator for each group.

By forming the probe 10 in this manner, transmission / reception of the ultrasonic signal of only the fundamental wave component is performed via the transducer group A, and the preamplifier circuit 30a and the reception delay / addition circuit connected to the transducer group A directly from 31a, the echo signal of only the fundamental wave component _{S f} is obtained. Similarly, an echo signal of only the second harmonic component _S2f among the nonlinear wave components generated by the nonlinear scattering of the ultrasonic contrast agent is received via the transducer group B, and connected to the transducer group B. An echo signal of the second harmonic component _S2f is directly obtained from the preamplifier circuit 30b and the reception delay / addition circuit 31b.

  In the configuration of FIG. 10, the transmission resonance circuit 23 and the BPFs 32a and 32b can be omitted. Other configurations and functions are the same as or the same as those in FIG.

  As described above, in the Doppler method based on the above-described harmonic echo method, it was experimentally confirmed that the Doppler shift frequency is equivalent to the Doppler shift frequency when transmitting and receiving the second harmonic component as a representative of the nonlinear wave component. Based on this, it is possible to optimize the set frequency used when converting the Doppler shift frequency into speed data.

As a result, in an ultrasonic diagnostic apparatus using the nonlinear scattering characteristics of the contrast agent, it becomes possible to measure the velocity of the contrast agent based on the Doppler principle for an echo signal generated under the nonlinear scattering of the contrast agent,
(1) Peripheral blood flow, such as blood flow in the myocardium and blood flow in the parenchyma of the liver, which was impossible with the conventional arterial administration type contrast echo method because the moving speed of the contrast agent did not reflect the blood flow velocity Speed can be evaluated,
(2) Peripheral blood flow velocities such as myocardium and parenchyma of the liver, which could not be achieved by the conventional intravenous contrast echo method because the contrast agent concentration was lower than that of arterial injection, can be evaluated.
(3) Conventionally, in the abdomen and the like, motion artifacts caused by movement of surrounding tissues due to respiration and the movement of blood vessel walls have been an error factor of blood flow velocity detection accuracy in blood vessels, but this can be greatly reduced. Excellent effect is obtained.

  In the above embodiment, the case where the nonlinear wave component to be extracted is the second harmonic component is illustrated, but the present invention is not necessarily limited thereto. For example, as other nonlinear wave components, an Nth harmonic component (N × f: f is a fundamental frequency, N is a positive integer), an Nth subharmonic component (f / N: f is a fundamental frequency, N is a positive integer) ) And superharmonics (M × f / N: f is the fundamental frequency, M and N are positive integers other than 1), and those frequency components are selectively selected by the non-linear wave BPF as described above. May be extracted. In addition, in order to simultaneously target a plurality of harmonic components, a plurality of signal extraction / processing systems are individually provided for each of the plurality of harmonic components, or a plurality of nonlinear wave components are passed through one system without being separated. It may be configured.

  In the above embodiment, the signal processing of the fundamental wave component and the signal processing of the non-linear wave component are respectively performed by separate systems. However, after the signal is received by the preamplifier circuit, it is digitized. And signal processing of the fundamental wave component and the nonlinear wave component may be performed in a time-division manner. Further, a memory can be provided to perform signal processing on a desired component.

  Further, in the above-described embodiment, two BPFs for extracting the fundamental wave component and the non-linear wave component are inserted after the reception delay / addition circuit. It may be provided at a position. However, when the BPF is provided on the output side of the reception delay / addition circuit as in the above embodiment, the number of filters can be reduced, which is advantageous for avoiding an increase in the size of the device and an increase in manufacturing cost. It is.

  Further, the probe according to the ultrasonic diagnostic apparatus is not limited to the electronic array probe, but may be a mechanical scanning probe.

  Furthermore, in the above embodiment, beamforming (phasing addition) is performed with an RF (high frequency) signal, but beamforming may be performed after shifting the signal band to an intermediate frequency.

  In the above-described embodiment, as the suppression means for intentionally and positively suppressing the non-fundamental wave component, a transmission filter that passes only the fundamental wave component, and a transmission resonance circuit based on series resonance may be used.

  Further, the frequency / velocity conversion means in the present invention is not limited to the frequency / velocity converters 346 and 347 described above. A mechanism may be provided, or the same memory mechanism may be provided inside the DSC 35.

FIG. 1 is a block diagram of an ultrasonic diagnostic apparatus according to one embodiment of the present invention. FIG. 4 is a circuit diagram illustrating an example of a transmission resonance circuit. FIG. 3 is a block diagram of a speed calculation unit. (A), (b) is a figure which illustrates an ultrasonic probe and a transmission spectrum. The figure which illustrates the relationship between a transmission spectrum and a reference frequency. FIG. 3 is a diagram showing an example of a tomographic image obtained in the embodiment. The figure which shows an example of a Doppler spectrum. FIG. 3 is a diagram illustrating an example of a color Doppler image. The figure which illustrates the relationship between a transmission spectrum and a nonlinear scattering component. FIG. 9 is a block diagram of an ultrasonic diagnostic apparatus according to a modification. (A), (b) is a frequency characteristic figure for every group of the vibrator concerning the modification.

Explanation of reference numerals

10 Probe 11 Device body 20 Clock generation circuit (transmission drive means)
21 Transmission delay circuit (transmission drive means)
22 Pulser circuit (transmission drive means)
23 transmission resonance circuit 30, 30a, 30b preamplifier circuit (reception processing means)
31, 31a, 31b Reception delay / addition circuit (reception processing means)
32a, 32b BPF (reception processing means)
33a, 33b Receiver circuit 34 Speed calculation unit 35 DSC (display means)
36 monitor (display means)
341 Reference oscillator (Doppler extraction means)
342 90 ° phase shifter (Doppler extraction means)
343 phase detector (Doppler extraction means)
344 FFT operation unit (Doppler extraction means)
345 MTI operation unit (Doppler extraction means)
346, 347 First and second frequency / speed converters (frequency / speed conversion means)

Claims (3)

Transmission driving means for driving an ultrasonic probe to transmit an ultrasonic beam signal to a subject,
Reception processing means for phasing and adding the echo signal of the electric quantity output by the ultrasonic probe,
When the ultrasonic beam signal is applied to the ultrasonic contrast agent injected into the blood vessel of the subject, the ultrasonic beam signal reflects the nonlinear vibration of the ultrasonic contrast agent generated in response to the irradiation. Doppler extraction means for extracting the Doppler shift frequency of the nonlinear component of the reflected signal from the echo signal,
The Doppler shift frequency fd extracted by the Doppler extraction means is:

Frequency / speed conversion means for converting to a speed component v according to the conversion formula
Display means for color-coding the velocity component v converted by the frequency / velocity conversion means in association with a velocity scale for the non-linear component and color-displaying the velocity information of the ultrasonic contrast agent in the subject in color. An ultrasonic diagnostic apparatus characterized in that: Transmission driving means for driving an ultrasonic probe to transmit an ultrasonic beam signal to a subject,
Reception processing means for phasing and adding the echo signal of the electric quantity output by the ultrasonic probe,
When the ultrasonic beam signal is applied to the ultrasonic contrast agent injected into the blood vessel of the subject, the ultrasonic beam signal reflects the nonlinear vibration of the ultrasonic contrast agent generated in response to the irradiation. Doppler extraction means for extracting the Doppler shift frequency of the nonlinear component of the reflected signal from the echo signal,
The Doppler shift frequency fd extracted by the Doppler extraction means is:

Frequency / speed conversion means for converting to a speed component v according to the conversion formula
Display means for displaying an FFT of the velocity component v converted by the frequency / velocity conversion means as velocity information of the ultrasonic contrast agent in the subject on a velocity scale for the non-linear component. Ultrasound diagnostic device. Transmission driving means for driving an ultrasonic probe to transmit an ultrasonic beam signal to a subject,
Reception processing means for phasing and adding the echo signal of the electric quantity output by the ultrasonic probe,
When the ultrasonic beam signal is applied to the ultrasonic contrast agent injected into the blood vessel of the subject, the ultrasonic beam signal reflects the nonlinear vibration of the ultrasonic contrast agent generated in response to the irradiation. Doppler extraction means for extracting the Doppler shift frequency of the nonlinear component of the reflected signal from the echo signal,
The Doppler shift frequency fd extracted by the Doppler extraction means is:

Frequency / speed conversion means for converting to a speed component v according to the conversion formula
Means for converting the velocity component v converted by the frequency / velocity conversion means into a color code in association with a velocity scale for the non-linear component and color-displaying the velocity information of the ultrasonic contrast agent in the subject in color, or Display means having any one of means for performing FFT display as velocity information of the ultrasonic contrast agent in the subject on a velocity scale for the velocity component v on the non-linear component,
An ultrasonic diagnostic apparatus, comprising: a measuring unit capable of measuring the speed information of a desired area designated on the image displayed by the display unit.

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