Ultrasonic diagnostic apparatus

Abstract

To provide high-definition image data obtained by reducing clutter components by movable body imaging.SOLUTION: An ultrasonic diagnostic apparatus according to embodiment comprises an extraction unit and a detection unit. The extraction unit extracts a nonlinear component of a reception signal obtained from an ultrasonic contrast injected into a blood vessel of a subject and moving as bubbles, out of the reception signal. The detection unit uses the nonlinear component and detects a projection component in a beam direction of the movement of an echo source, as a signal component having phase rotation between time series pulse echoes obtained at an identical depth.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to an ultrasound diagnostic device. [Background technology]

[0002] There are ultrasound diagnostic devices that perform moving object imaging (also called Doppler imaging) using color Doppler. In moving object imaging, clutter components can interfere with diagnosis. Therefore, it is desirable to obtain high-quality image data from which clutter components have been removed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-176997 [Patent Document 2] Japanese Patent Application Publication No. 11-178824 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-101165 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-147619 [Patent Document 5] Japanese Patent Application Laid-Open No. 2002-301068 [Patent Document 6] Japanese Patent Application Laid-Open No. 2005-312632 [Patent Document 7] Japanese Patent Publication No. 114244 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to obtain high-quality image data with reduced clutter components by imaging a moving object. However, the problem to be solved by the embodiments disclosed in this specification and the drawings is not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems.

Means for Solving the Problem

[0005] The ultrasonic diagnostic apparatus according to the embodiment includes an extraction unit and a detection unit. The extraction unit extracts a non-linear component of a received signal obtained from an ultrasonic contrast agent that moves as bubbles injected into a blood vessel of a subject from the received signal. The detection unit uses the non-linear component to detect a projection component of the movement of the echo source in the beam direction as a signal component having a phase rotation between time-series pulse echoes obtained at the same depth.

Brief Description of the Drawings

[0006]

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[0007] Hereinafter, each embodiment and each modification example of the ultrasonic diagnostic apparatus will be described in detail with reference to the drawings. Note that the ultrasonic diagnostic apparatus according to the present application is not limited to the embodiments and modification examples shown below. In addition, the content described in one embodiment is generally applicable to other embodiments and modification examples as well. Also, the content described in one modification example is generally applicable to the embodiment and other modification examples as well.

[0008] (First Embodiment) FIG. 1 is a diagram showing an example of the configuration of an ultrasonic diagnostic apparatus 10 according to a first embodiment. The ultrasonic diagnostic apparatus shown in FIG. 1 detects a harmonic component (also referred to as a non-linear component or a harmonic component) from a received signal, calculates the phase difference (phase rotation) of a time-series signal as moving body information using the harmonic component, generates speed information of the moving body using the phase rotation, and visualizes the speed information. The signal source of the harmonic signal is an ultrasonic contrast agent (more specifically, bubbles), blood (where blood cells are the scattering source), and the like.

[0009] As shown in FIG. 1, the ultrasonic diagnostic apparatus 10 according to the first embodiment includes an ultrasonic probe (hereinafter referred to as a "probe") 11 and an apparatus main body 12.

[0010] The probe 11 transmits and receives ultrasonic signals to and from the subject. Specifically, the probe 11 transmits ultrasonic waves to the subject and receives the ultrasonic waves (reflected waves) reflected by the subject. The probe 11 is configured in a phased array type in which a plurality of vibrators are arranged in the scanning direction. The reception characteristics of each vibrator are formed identically, and it has a sufficiently wide signal passband capable of detecting the fundamental wave component for driving the vibrator and the second harmonic component generated in the living body. For example, the vibrator receives the reflected wave and converts the received reflected wave into an electrical signal. Then, the vibrator transmits the electrical signal to the apparatus main body 12 as an echo signal (received signal).

[0011] The apparatus main body 12 drives the probe 11 and processes the echo signal from the probe 11. The apparatus main body 12 has circuits for a transmission system that drives the probe 11, a reception / processing system that receives and processes the echo signal from the probe 11, a display system that displays the processed image, and an input system. In addition to this, there is a detection system for biological signals such as an ECG, etc., but the illustration of the detection system is omitted in FIG. 1.

[0012] 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 the ultrasonic signal, and the transmission delay circuit 21 is a circuit that applies a delay during transmission to perform transmission focusing. The pulser circuit 22 has built-in pulsers equal to the number of individual paths (hereinafter referred to as "channels") corresponding to each transducer, and generates drive pulses at delayed transmission timings and supplies them to each transducer of the probe 11.

[0013] The transmitter resonant circuit 23 is also equipped to efficiently detect second-order harmonic components of echo signals generated by ultrasound contrast agents injected into the subject, blood, etc. In other words, the transmitter resonant circuit 23 functions to remove harmonic components that inevitably occur unless the pulser is driven with a perfect sine wave during transmission. For example, the transmitter resonant circuit 23 has a configuration similar to that of the transmitter resonant circuit described in Japanese Patent No. 3865800. Specifically, the transmitter resonant circuit 23 includes a limiter consisting of an anti-parallel diode circuit and a coil section that resonates with the capacitive impedance of the probe, cable, etc. and has a passband limited to the fundamental wave. The transmitter resonant circuit 23 includes a series circuit of a limiter and a coil section for each channel. Because the limiter turns on when the applied signal value is above a certain level, the transmitter resonant circuit 23 resonates only during transmission when the signal level is high, and remains non-resonant during reception.

[0014] The receiving and processing system includes, in this order, a preamplifier circuit 30, a receiving delay and addition circuit 31, a fundamental wave bandpass filter (fundamental wave BPF (Band Pass Filter)) 32a, a nonlinear wave bandpass filter (nonlinear wave BPF) 32b, receiver circuits 33a and 33b, and a velocity information calculation unit 34b on the output side of the probe 11. The preamplifier circuit 30 amplifies the power of the received echo signal for each receiving channel and transmits it to the receiving delay and addition circuit 31. The receiving delay and addition circuit 31 has a delay section for each receiving channel and an addition section that adds these delay results, and performs receiving focusing on the received echo signal. A fundamental wave BPF 32a and a nonlinear wave BPF 32b are connected in parallel to the output side of this receiving delay and addition circuit 31. The passband of the fundamental wave BPF 32a matches the fundamental wave component of the echo signal. On the other hand, the passband of the nonlinear wave BPF 32b matches the second harmonic component of the echo signal. The output side of the fundamental wave BPF 32a is connected to a DSC (Digital Scan Converter) 35 (described later) via a fundamental wave receiver circuit 33a. The output side of the nonlinear wave BPF 32b is connected to the DSC 35 via a nonlinear wave receiver circuit 33b. The receiver circuit 33a performs processes such as envelope detection and log compression on the fundamental wave component signal to obtain an image signal of a B-mode image (B-mode image data). The receiver circuit 33b performs processes such as envelope detection and log compression on the second harmonic component signal to obtain an image signal of a B-mode image.

[0015] The receiving and processing system further includes a DSC 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, etc., and forms one frame of an image signal corresponding to the commanded display mode, and is capable of reading out this image signal in the standard TV format. The image signal read out from the DSC 35 is output to the monitor 36 via a panel interface 37 and displayed on the monitor 36.

[0016] Furthermore, a CPU (Central Processing Unit) 39 is connected to the DSC 35 via a DSC memory unit 38.

[0017] The input system of the ultrasonic diagnostic apparatus 10 includes a panel interface 37 and a panel 40 operated by an operator.

[0018] The velocity information calculation unit 34b calculates velocity information indicating the velocity of an ultrasonic contrast agent, blood, etc. injected into the subject. FIG. 2 is a diagram showing an example of the configuration of the velocity information calculation unit 34b according to the first embodiment.

[0019] As shown in FIG. 2, the velocity information calculation unit 34b includes a reference oscillator 341, a 90° phase shifter 342, a phase detector 343, an MTI (Moving Target Indication) calculation unit 345, and a phase / velocity converter 347.

[0020] The reference oscillator 341 outputs a reference signal for phase detection (quadrature detection) of the echo signal that has been integrally added. The reference oscillator 341 outputs the reference signal to the 90° phase shifter 342 and a mixer 3431a described later. The frequency of the reference signal is “fr”, and this frequency is referred to as the reference frequency.

[0021] The 90° phase shifter 342 accurately changes the phase of the input signal by 90° and outputs it. For example, the 90° phase shifter 342 changes the phase of the input reference signal by 90° and outputs it to a mixer 3431b described later.

[0022] The phase detector 343 includes a two-channel series circuit of two mixers 3431a and 3431b and two low-pass filters 3432a and 3432b (set to cutoff frequency fc=reference frequency fr). As shown in Fig. 2, one mixer 3431a receives a reference signal directly from the reference oscillator 341, while the other mixer 3431b receives the reference signal from the reference oscillator 341 via a 90° phase shifter 342. As a result, the echo signal that has passed through the nonlinear wave BPF 32b is phase-detected by the phase detector 343 and supplied to the MTI calculation unit 345. The phase-detected echo signal is an analog echo signal.

[0023] The MTI calculation unit 345 includes a two-channel circuit including A / D converters 3451a and 3451b and MTI filters 3452a and 3452b, an autocorrelator 3453, a phase rotation calculator 3454, a variance calculator 3455, and a power calculator 3456. For example, in color Doppler mode, the MTI calculation unit 345 operates.

[0024] The A / D converters 3451a and 3451b convert the phase-detected echo signals into digital echo signals and output the digital echo signals to the MTI filters 3452a and 3452b. The MTI filters 3452a and 3452b remove clutter components (unnecessary fixed reflection signals) reflected by the heart wall and other components contained in the input echo signals from the echo signals, and output the echo signals from which the clutter components have been removed to the autocorrelator 3453. Note that, instead of the MTI filters 3452a and 3452b, known filters that estimate clutter by principal component analysis and remove the clutter from the echo signals may be used.

[0025] Here, the time-series signal (digital echo signal) R0(d) before being input to the MTI filters 3452a and 3452b is expressed by the following equation (1). R0(d)=Re0(d)+j*Im0(d) ···(1)

[0026] Here, the time-series signal R0(d) is the d-th complex signal in the time series of N data points, and consists of a real part (real number part) Re0(d) and an imaginary part (imaginary number part) j*Im0(d).

[0027] Also, the time-series signal (echo signal with clutter components removed) R(d) output by the MTI filter 3452a is represented by the following equation (2). R(d)=Re(d)+j*Im(d) ···(2)

[0028] Here, the time-series signal R(d) is the d-th complex signal in the time series of N data points, and consists of a real part Re(d) and an imaginary part j*Im(d).

[0029] The autocorrelator 3453 performs frequency analysis (Doppler analysis) of each point on the two-dimensional cross-sectional plane in real time. For example, the autocorrelator 3453 performs an autocorrelation operation on the echo signal. The result of the autocorrelation operation is used when the phase rotation of the time-series signal is calculated by the phase rotation calculator 3454. Also, the result of the autocorrelation operation is used when the variance value (spectrum randomness) is estimated by the variance calculator 3455 or when the power (strength) value is estimated by the power calculator 3456.

[0030] For example, the autocorrelator 3453 calculates the autocorrelation values at lag 0 and lag 1 from the time-series signal R(d). For example, if the autocorrelator 3453 sets lag 1 as "C1", it calculates lag 1 "C1" according to the following equation (3).

[0031]

Equation

[0032] However, R * (d) is the complex conjugate of R(d).

[0033] Also, for example, if the autocorrelator 3453 sets lag 0 as "C0", it calculates lag 0 "C0" according to the following equation (4).

[0034] [Number]

[0035] The phase rotation calculator 3454 calculates the phase rotation φ of the time series signal R(d) from lag 1 "C1" according to the following formula (5). φ = atan(Im_C1 / Re_C1) [rad] ···(5)

[0036] Here, "Im_C1" is the imaginary part of lag 1 "C1", and "Re_C1" is the real part of lag 1 "C1". "atan()" is the arctangent function. Then, the phase rotation calculator 3454 outputs the calculated phase rotation φ to the phase / velocity converter 347.

[0037] In this way, the autocorrelator 3453 and the phase rotation calculator 3454 use the second harmonic component S 2f (nonlinear component) to detect the projection component of the movement of the echo source (e.g., ultrasound contrast agent or blood) in the beam direction as a signal component having the phase rotation φ between the time series pulse echoes obtained at the same depth. Also, the autocorrelator 3453 and the phase rotation calculator 3454 detect the phase rotation φ associated with the movement of the echo source by autocorrelation operation. The autocorrelator 3453 and the phase rotation calculator 3454 are an example of a detection unit.

[0038] The variance calculator 3455 estimates the variance value using lag 0 "C0" and lag 1 "C1".

[0039] The power calculator 3456 estimates the power value using lag 0 "C0". In this way, the autocorrelator 3453 and the power calculator 3456 estimate the power information indicating the power of the signal component having the phase rotation φ associated with the movement of the echo source by autocorrelation operation. The autocorrelator 3453 and the power calculator 3456 are an example of an estimation unit.

[0040] The phase / velocity converter 347 estimates the velocity v [m / sec], that is, the moving speed of the ultrasound contrast agent (bubbles), blood, etc., based on the following equation (6). v=(C·PRF·φ) / (4π·cosθ·fr) (6)

[0041] where "C" is the speed of sound, "PRF" is the pulse repetition frequency, "θ" is the angle between the direction of movement of the object and the direction of the ultrasound beam, and "fr" is the reference frequency of the reference signal. In this way, the phase / velocity converter 347 converts the phase rotation φ into velocity information indicating the velocity v using the reference frequency fr, the speed of sound C, and the pulse repetition frequency PRF. The phase / velocity converter 347 is an example of a conversion unit.

[0042] Returning to the explanation of Figure 1, data indicating the velocity v obtained by the phase / velocity converter 347 is sent to the DSC 35 along with other necessary data (for example, data indicating dispersion values and data indicating power) and converted into frame image data in the commanded display mode. The panel interface 37 has a built-in color processing circuit and D / A converter, and the image data from the DSC 35 is colored as necessary and sent as an analog signal to the monitor 36. As a result, the velocity v, dispersion values, power, etc. are visualized and displayed on the monitor 36. Note that an external device such as a recorder or memory may be connected instead of or in parallel with the monitor 36.

[0043] The CPU 39 reads commands from the operator who operates the panel 40 via the panel interface 37, and outputs superimposed display markers, character data, etc. from the DSC memory unit 38 to the DSC 35, while also measuring the speed.

[0044] Next, the effects of the first embodiment will be described.

[0045] At the time of transmission, while a transmission focus is applied by the transmission delay circuit 21, a drive voltage signal is supplied from the pulsar circuit 22 to each vibrator of the probe 11 via the transmission resonance circuit 23 for each channel. At this time, the limiter of the transmission resonance circuit 23 is turned on because the drive voltage signal is higher than a predetermined level, and the coil portion 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 vibrator of the probe 11.

[0046] Full sine wave driving of the pulsar circuit 22 is actually difficult, and usually the generated drive voltage signal contains harmonic components. However, by the transmission resonance circuit 23, such harmonic components are blocked, and each vibrator is excited by a drive voltage signal of only the fundamental wave component.

[0047] When each vibrator of the probe 11 is excited in this way, an ultrasonic beam signal with a transmission focus applied thereto is sent out from the probe 11 toward a diagnostic site such as the myocardium of the subject. This ultrasonic beam signal becomes an ultrasonic echo signal reflected and scattered by an ultrasonic contrast agent injected from a vein into each tissue of the diagnostic site. In particular, the ultrasonic contrast agent is composed of minute bubbles, and the echo signal is enhanced due to the strong scattering characteristics of the bubbles. This scattering has non-linear characteristics, and harmonic components are also generated by the non-linear scattering. As a result, the ultrasonic echo signal contains an echo component (fundamental wave component) from a biological tissue other than the ultrasonic contrast agent (bubbles) and an echo component (fundamental wave component and its harmonic components) from the ultrasonic contrast agent. The same applies to blood (blood cells).

[0048] This ultrasonic echo signal is received by each of the vibrators of the probe 11 and converted into a corresponding electrical signal. Since the power of this electrical echo signal is weak, each limiter of the transmission resonance circuit 23 is not turned on, and the transmission resonance circuit 23 remains in a non-resonant state. As a result, the echo signal including the fundamental wave component and the harmonic component is not involved in the transmission resonance circuit 23 at all and reaches the preamplifier circuit 30, where it is power-amplified and then received and delayed by the reception delay / addition circuit 31 for each channel and added together. Thereby, a reception focus is applied to the echo signal. This echo signal is sent in parallel to the fundamental wave BPF 32a and the non-linear wave BPF 32b. In the fundamental wave BPF 32a, the fundamental wave component S f is extracted, and the echo signal of the fundamental wave component S f is sent to the subsequent receiver circuit 33a.

[0049] In the non-linear wave BPF 32b, only the second harmonic component S 2f of the echo signal is extracted, and the echo signal of the second harmonic component S 2f is sent to the receiver circuit 33b and the velocity information calculation unit 34b. That is, the non-linear wave BPF 32b extracts the second harmonic component S 2f (non-linear component) of the echo signal obtained from the ultrasonic contrast agent that moves as bubbles injected into the blood vessels of the subject. Also, the non-linear wave BPF 32b extracts the second harmonic component S 2f of the echo signal obtained from the blood cells of the moving blood of the subject. The non-linear wave BPF 32b is an example of an extraction unit.

[0050] The echo signal of the fundamental wave component S f sent to the receiver circuit 33a undergoes processes such as envelope detection and logarithmic compression, and image data of the B-mode image (amplitude luminance modulation image) of the fundamental wave component is generated. The echo signal of the second harmonic component S 2f sent to the other receiver circuit 33b also undergoes the same process, and image data of the B-mode image of the second harmonic component is generated.

[0051] The image data of each B-mode image of these fundamental wave components and second harmonic components is then converted in the DSC35 into image data of a commanded display mode. The B-mode image IM f (hereinafter simply referred to as the "fundamental wave image") and the B-mode image IM 2f (hereinafter simply referred to as the "second harmonic image") have various display modes. For example, when the contrast echo method is implemented, a command for a display mode in which the second harmonic image IM f is superimposed on the fundamental wave image IM 2f is given. In response to this, the DSC35 synthesizes both image data and supplies it to the monitor 36. Therefore, on the monitor 36, an image "IM f " in which the second harmonic image IM 2f is superimposed on the fundamental wave image IM f+2f is displayed. Thereby, the user can observe the form of the biological tissue and the distribution of ultrasonic contrast agents, blood, etc. therein.

[0052] Thus, in the present embodiment, since the transmission resonance circuit 23 cuts harmonic components other than the fundamental wave component and transmits the ultrasonic beam in a state of only the fundamental wave component, almost all of the second harmonic components included in the echo signal are only those resulting from the non-linear scattering characteristics of ultrasonic contrast agents, blood, etc. That is, for the ultrasonic signal of the transmitted fundamental wave component, only the second harmonic component due to the scattering of ultrasonic contrast agents, blood, etc. can be selectively signal-processed and imaged. Considering biological attenuation and the bandwidth of the transmission / reception system, it is an excellent use of the second harmonic component.

[0053] Furthermore, in the present embodiment, when the color Doppler mode is commanded, the MTI operation unit 345 of the velocity information operation unit 34b performs frequency analysis as described above, and the analysis data is converted into velocity information indicating the velocity v by the phase / velocity converter 347. This velocity information is displayed on the monitor 36 via the DSC3, panel interface 37 as a color Doppler image in which the velocity information is color-modulated. That is, in the present embodiment, the velocity information operation unit 34b and the DSC35 generate image data of the color Doppler image by performing the various processes described above on the echo signal.

[0054] In the color Doppler image, coloring is performed by a color map, and together with a color bar or a color palette, the speed value is displayed on the scale or for a desired ROI (Region Of Interest) when using the measurement function. In addition, in the color Doppler mode, in addition to the speed information, a color Doppler image including dispersion information indicating the dispersion value estimated by the dispersion calculator 3455 and power information indicating the power estimated by the power calculator 3456 may be displayed on the monitor 36.

[0055] FIG. 3 is a flowchart showing an example of the processing flow executed by the speed information calculation unit 34b according to the first embodiment in the color Doppler mode. As shown in FIG. 3, first, the phase detector 343 performs phase detection on the echo signal that has passed through the non-linear wave BPF 32b, and outputs the phase-detected echo signal to the A / D converters 3451a and 3451b of the MTI calculation unit 345 (step S101).

[0056] Then, the A / D converters 3451a and 3451b convert the phase-detected analog echo signal into a digital echo signal, and output the digital echo signal R0(d) to the MTI filters 3452a and 3452b (step S102).

[0057] The MTI filters 3452a and 3452b remove the clutter component (unwanted fixed reflection signal) reflected by the heart wall or the like included in the input echo signal R0(d) from the echo signal, and output the echo signal (time series signal) R(d) with the clutter component removed to the autocorrelator 3453 (step S103).

[0058] The autocorrelator 3453 calculates the lag 1 "C1" and the lag 0 "C0" from the time series signal R(d) according to the above-described equations (3) and (4) (step S104).

[0059] Then, the phase rotation calculator 3454 calculates the phase rotation φ of the time series signal R(d) from the lag 1 "C1" according to the above-described equation (5) (step S105).

[0060] Then, the distributed arithmetic unit 3455 estimates the distributed value using lag 0 "C0" and lag 1 "C1" (step S106).

[0061] Then, the power arithmetic unit 3456 estimates the power value using lag 0 "C0" (step S107).

[0062] Then, the phase / velocity converter 347 estimates the velocity v based on the above-described equation (6) (step S108), and ends the process shown in FIG. 3. The velocity information indicating the velocity v, the dispersion information indicating the dispersion value, and the power information indicating the power value estimated in steps S106 to S108 are displayed on the monitor 36 as a color Doppler image.

[0063] FIG. 4 is a diagram showing an example of a simulation result of a beam profile by the KZK (Khokhlov-Zabolotskaya-Kuznetsov) equation for a fundamental wave beam (1st) and a harmonic (second harmonic: 2nd) beam. In FIG. 4, the horizontal axis indicates the azimuth direction, and the vertical axis indicates the intensity.

[0064] From FIG. 4, it can be seen that the transmission side lobe is significantly reduced (-20 dB or more) compared to the fundamental wave signal by the application of the harmonic signal. As a result, the pulsatility and respiratory-related clutter components at a distant position that are superimposed on the received signal at the beam position by the transmission side lobe are large in the case of the fundamental wave, whereas they are sufficiently reduced when the harmonic component is used.

[0065] The above describes the ultrasonic diagnostic apparatus 10 according to the first embodiment. The ultrasonic diagnostic apparatus 10 extracts a harmonic component (harmonic signal) from an echo signal, and extracts the phase rotation φ of the time-series signal R(d) as moving body information from the harmonic component. Then, the ultrasonic diagnostic apparatus 10 estimates the velocity v using the phase rotation φ, and visualizes velocity information indicating the velocity v. In this way, the ultrasonic diagnostic apparatus 10 performs moving body imaging using the harmonic component. Here, as described above, when using the harmonic component, the clutter component is sufficiently reduced. Therefore, according to the first embodiment, high-quality image data with the clutter component reduced by moving body imaging can be obtained. Note that the ultrasonic diagnostic apparatus 10 is not limited to an ultrasonic contrast agent, and can also perform moving body imaging with reduced clutter having a low transmission side lobe due to a harmonic signal for body fluids such as blood.

[0066] (Second Embodiment) In the first embodiment, the case where the non-linear wave BPF 32b extracts the harmonic component from the echo signal (received signal) has been described. However, the ultrasonic diagnostic apparatus may extract the harmonic component from the echo signal by pulse inversion. Therefore, such an embodiment will be described as the second embodiment. In the description of the second embodiment, mainly, the points different from the first embodiment will be described, and the description of the configuration similar to the first embodiment may be omitted.

[0067] FIG. 5 is a diagram showing an example of the configuration of the ultrasonic diagnostic apparatus 10a according to the second embodiment. As shown in FIG. 5, the ultrasonic diagnostic apparatus 10a is different from the ultrasonic diagnostic apparatus 10 according to the first embodiment in that it includes a device main body 12a instead of the device main body 12. Further, the device main body 12a is different from the device main body 12 in that it includes a non-linear component extraction circuit 32c instead of the non-linear wave BPF 32b.

[0068] The non-linear component extraction circuit 32c extracts harmonic components from the echo signal by pulse inversion. A specific example of the operation of the non-linear component extraction circuit 32c will be described. For example, in the second embodiment, the probe 11 transmits two ultrasonic waves having phases different from each other by 180 degrees in the same direction toward the subject. That is, the probe 11 transmits two ultrasonic waves having different phases on the same scanning line (the same scan line). For example, the probe 11 transmits a positive-pole leading ultrasonic wave and then transmits a negative-pole leading ultrasonic wave. Then, the preamplifier circuit 30 and the reception delay / summation circuit 31 perform the above-described various processes on the two echo signals based on the two transmitted ultrasonic waves. In this way, the two echo signals subjected to the various processes are input to the non-linear component extraction circuit 32c.

[0069] The non-linear component extraction circuit 32c generates a harmonic signal that removes or suppresses the fundamental wave component and mainly corresponds to the second harmonic component by adding the two input echo signals. In this way, the non-linear component extraction circuit 32c extracts the second harmonic component (non-linear component) of the echo signal (received signal) from the echo signal using the pulse inversion scan sequence. Then, the non-linear component extraction circuit 32c outputs the generated harmonic signal to the velocity information calculation unit 34b and the receiver circuit 33b. The non-linear component extraction circuit 32c is an example of an extraction unit.

[0070] The velocity information calculation unit 34b and the receiver circuit 33b perform the same processes on the harmonic signal in the second embodiment as those performed on the second harmonic component S 2f in the first embodiment.

[0071] Here, a case will be described where, hypothetically, the non-linear component extraction circuit 32c performs a simple pulse inversion that shifts a pair of two echo signals (data) to be added (referred to as an addition pair) by two data units in the time series direction. FIG. 6 is a diagram for explaining an example of the process executed when the non-linear component extraction circuit 32c according to the second embodiment hypothetically performs a pulse inversion that shifts the addition pair by two data units in the time series direction. In FIG. 6, “+” indicates an echo signal (data) based on an ultrasonic wave with a positive pole leading, and “-” indicates an echo signal (data) based on an ultrasonic wave with a negative pole leading. As shown in FIG. 6, the non-linear component extraction circuit 32c generates four harmonic signals (data 1 to 4) from eight data. That is, the non-linear component extraction circuit 32c obtains (M / 2) addition pairs from M (M is an even number of 2 or more) time series data sets. However, in this case, the number of effective data is halved and significantly reduced.

[0072] Therefore, in the second embodiment, the non-linear component extraction circuit 32c performs a pulse inversion that shifts the addition pair by one data unit in the time series direction. FIG. 7 is a diagram for explaining an example of the process executed when the non-linear component extraction circuit 32c according to the second embodiment performs a pulse inversion that shifts the addition pair by one data unit in the time series direction. As shown in FIG. 7, the non-linear component extraction circuit 32c determines the addition pair while shifting by one data at a time. Thereby, the non-linear component extraction circuit 32c generates seven harmonic signals (data 1 to 7) from eight data. That is, the non-linear component extraction circuit 32c determines (M - 1) addition pairs from the time series data set of M data by determining the addition pairs of the pulse inversion while shifting by one data at a time in the time series direction. Thereby, a decrease in the number of effective data can be suppressed.

[0073] The physical meaning of adding two echo signals by pulse inversion is not only to remove or suppress the fundamental wave component by pulse inversion, but also to apply a low pass filter (LPF) by adding two data in the time series direction. Since the harmonic signal obtained by pulse inversion is subjected to an MTI filter in the velocity information calculation unit 34b, the processing is equivalent to applying a BPF in the time series direction. Therefore, this embodiment can also be realized as an MTI filter configuration having BPF characteristics.

[0074] However, the second embodiment has the limitation of blind speed characteristics, which removes aliasing speed components by filtering. On the other hand, the second embodiment has the effects obtained by maintaining a high number of data (the effect of being able to maintain the S / N ratio (signal-to-noise ratio) and the effect of being able to maintain the MTI filter characteristics) and the effects obtained by pulse inversion (the effect of being applicable to a wideband power mode, the effect of being able to improve the S / N ratio by 3 dB by addition, and the effect of being able to reduce the saturation frequency by reducing the signal dynamic range before applying it to the MTI filter), in addition to the effect of being able to reduce side lobes by utilizing harmonics in the first embodiment.

[0075] (Third embodiment) The nonlinear component extraction circuit 32c may perform D-THI (Differential-Tissue Harmonic Imaging) to extract nonlinear components. Therefore, such an embodiment will be described as the third embodiment. The description of the third embodiment will mainly focus on differences from the second embodiment, and descriptions of the same configuration as the second embodiment may be omitted.

[0076] FIGS. 8 to 11 are diagrams for explaining an example of a process executed when the ultrasonic diagnostic apparatus 10a according to the third embodiment performs D-THI for extracting a non-linear component. FIGS. 8 and 9 show an example of a process executed by the ultrasonic diagnostic apparatus 10a in the case of B-mode, and FIGS. 10 and 11 show an example of a process executed by the ultrasonic diagnostic apparatus 10a in the case of color Doppler (that is, when the ultrasonic diagnostic apparatus 10a performs blood flow imaging).

[0077] FIG. 8 shows an example of a transmission spectrum in the case of B-mode. The horizontal axis in FIG. 8 indicates frequency, and "transmission" indicates the transmission band of the probe 11. The same applies to other drawings. As shown in FIG. 8, in the case of B-mode, in order to improve the spatial resolution, the probe 11 transmits an ultrasonic wave (first ultrasonic wave) having peaks at the first harmonic 1f and the third harmonic 3f of the fundamental wave 1f toward the subject. That is, the probe 11 performs composite transmission of a plurality of frequencies. Subsequently, the probe 11 transmits an ultrasonic wave (second ultrasonic wave) having the phase of the first ultrasonic wave inverted on the same scanning line as the scanning line on which the first ultrasonic wave was transmitted. That is, the phase of the first ultrasonic wave and the phase of the second ultrasonic wave differ by 180 degrees.

[0078] Then, various processes described above are performed on the two echo signals based on the two transmitted ultrasonic waves (the first ultrasonic wave and the second ultrasonic wave) by the preamplifier circuit 30 and the reception delay / summation circuit 31. In this way, the two echo signals subjected to various processes are input to the non-linear component extraction circuit 32c.

[0079] FIG. 9 shows an example of a reception spectrum in the case of the B mode. "Reception" in FIG. 9 indicates the reception band of the probe 11. The same applies to other drawings. The non-linear component extraction circuit 32c adds the two input echo signals, thereby removing or suppressing the fundamental wave component and extracting harmonic components of both the second harmonic component 2f (1f × 2) and the difference tone component (3f - 1f) as shown in FIG. 9. As shown in FIG. 9, the non-linear component extraction circuit 32c may further apply a band-pass filter (BPF) having a pass band of the second harmonic component 2f and the difference tone component (3f - 1f) to the signal obtained by adding the two echo signals to extract the second harmonic component 2f and the difference tone component (3f - 1f). Then, the non-linear component extraction circuit 32c outputs the extracted second harmonic component 2f and difference tone component (3f - 1f) to the receiver circuit 33b.

[0080] The receiver circuit 33b performs processes such as envelope detection and log compression on the signals of the second harmonic component 2f and the difference tone component (3f - 1f) to generate image data of the B mode image of the second harmonic component 2f and the difference tone component (3f - 1f).

[0081] Next, the case of blood flow imaging will be described. FIG. 10 shows an example of a transmission spectrum in the case of blood flow imaging. As shown in FIG. 10, in the case of blood flow imaging, in order to emphasize sensitivity rather than spatial resolution, the probe 11 transmits an ultrasonic wave (third ultrasonic wave) having peaks at the first harmonic 1f and the second harmonic 2f of the fundamental wave 1f in a low frequency band with relatively little frequency-dependent attenuation toward the subject. That is, the probe 11 performs composite transmission of a plurality of frequencies. Subsequently, the probe 11 transmits an ultrasonic wave (fourth ultrasonic wave) with the phase of the third ultrasonic wave inverted on the same scanning line as the scanning line on which the third ultrasonic wave was transmitted. That is, the phase of the third ultrasonic wave and the phase of the fourth ultrasonic wave differ by 180 degrees.

[0082] Then, the two echo signals based on the two transmitted ultrasonic waves (the third ultrasonic wave and the fourth ultrasonic wave) are subjected to the various processes described above by the preamplifier circuit 30 and the reception delay and addition circuit 31. In this way, the two echo signals that have been subjected to the various processes are input to the nonlinear component extraction circuit 32c.

[0083] FIG. 11 shows an example of a reception spectrum in the case of blood flow imaging. The nonlinear component extraction circuit 32c adds two input echo signals, thereby removing or suppressing the fundamental component and extracting a harmonic component of the difference frequency component (2f-1f) as shown in FIG. 11. That is, the nonlinear component extraction circuit 32c extracts from the echo signals a nonlinear component due to the difference frequency of the fundamental frequency 1f and the double frequency 2f, which is obtained by synthesizing and transmitting the single frequency 1f and the double frequency 2f of the fundamental frequency 1f. The single frequency of the fundamental frequency 1f is an example of the fundamental frequency. The double frequency 2f is also an example of a frequency twice the fundamental frequency. Note that, as shown in FIG. 11, the nonlinear component extraction circuit 32c may further apply a bandpass filter (BPF) whose passband covers the difference frequency component (2f-1f) to the signal obtained by adding the two echo signals, thereby extracting the difference frequency component (2f-1f). Then, the nonlinear component extraction circuit 32c outputs the extracted difference frequency component (2f-1f) to the velocity information calculation section 34b.

[0084] The velocity information calculation unit 34b and the DSC 35 perform various processes on the signal of the difference frequency component (2f-1f) to generate image data of a color Doppler image of the difference frequency component (2f-1f).

[0085] Therefore, according to the ultrasonic diagnostic apparatus 10a according to the third embodiment, it is possible to reduce the frequency-dependent attenuation and improve the S / N ratio both in transmission and reception compared to the conventional D-THI. As a result, the ultrasonic diagnostic apparatus 10a can perform blood flow imaging with less clutter components using harmonic components to a deeper depth. Further, similar to the ultrasonic diagnostic apparatus 10 according to the first embodiment, the ultrasonic diagnostic apparatus 10a according to the third embodiment can obtain high-quality image data with reduced clutter components by moving body imaging.

[0086] In addition, the ultrasonic diagnostic apparatus 10a disperses (distributes) the energy included in the transmission waveform of the ultrasonic wave into a plurality of frequency components by performing synthetic transmission of a plurality of frequencies. For this reason, the ultrasonic diagnostic apparatus 10a can reduce the saturation frequency of the received signal.

[0087] In the case of blood flow imaging, the ultrasonic diagnostic apparatus 10a may perform processing based on D-THI for extracting non-linear components, which was described with reference to FIGS. 8 and 9. In this case, the non-linear component extraction circuit 32c extracts two non-linear components from the echo signal: the non-linear component due to the harmonic (2f) on the low-frequency side (frequency 1f) of a plurality of frequencies and the non-linear component due to the difference tone (3f - 1f) of a plurality of frequencies, which are obtained by performing synthetic transmission of a plurality of frequencies (frequency 1f and frequency 3f). Note that the non-linear component extraction circuit 32c may extract at least one non-linear component from the echo signal, which is the non-linear component due to the harmonic (2f) on the low-frequency side (frequency 1f) of a plurality of frequencies and the non-linear component due to the difference tone (3f - 1f) of a plurality of frequencies.

[0088] (Modification Example of the Third Embodiment) In the third embodiment, in D-THI, the case where the non-linear component extraction circuit 32c adds two echo signals has been described. However, the non-linear component extraction circuit 32c may extract the non-linear component by applying a band-pass filter to one echo signal without adding two echo signals. Therefore, such a modification will be described as a modification of the third embodiment. In the description of the modification of the third embodiment, mainly, the points different from the third embodiment will be described, and the description of the configuration similar to the third embodiment may be omitted.

[0089] In a modification of the third embodiment, in the case of the B mode, the probe 11 transmits the first ultrasonic wave described above toward the subject and does not transmit the second ultrasonic wave described above. The first ultrasonic wave is an ultrasonic wave having peaks at the first harmonic 1f and the third harmonic 3f of the fundamental wave 1f.

[0090] Then, various processes described above are performed on one echo signal based on the transmitted first ultrasonic wave by the preamplifier circuit 30 and the reception delay / summation circuit 31. In this way, one echo signal subjected to various processes is input to the non-linear component extraction circuit 32c.

[0091] Then, the non-linear component extraction circuit 32c applies a band-pass filter (BPF) having a pass band of the second harmonic component 2f and the difference tone component (3f - 1f) to the input one echo signal to extract the second harmonic component 2f and the difference tone component (3f - 1f). Then, the non-linear component extraction circuit 32c outputs the extracted second harmonic component 2f and difference tone component (3f - 1f) to the receiver circuit 33b.

[0092] In this modification, the receiver circuit 33b performs processes such as envelope detection and log compression on the signals of the second harmonic component 2f and the difference tone component (3f - 1f) in the same manner as in the third embodiment to generate image data of the B-mode images of the second harmonic component 2f and the difference tone component (3f - 1f).

[0093] Next, the case of blood flow imaging will be described. In the case of blood flow imaging, the probe 11 transmits the first ultrasonic wave described above toward the subject. The first ultrasonic wave is an ultrasonic wave having peaks at the first harmonic frequency 1f and the third harmonic frequency 3f of the fundamental wave 1f.

[0094] Then, various processes described above are performed on one echo signal based on one transmitted first ultrasonic wave by the preamplifier circuit 30 and the reception delay and addition circuit 31. In this way, one echo signal subjected to various processes is input to the non-linear component extraction circuit 32c.

[0095] Then, the non-linear component extraction circuit 32c applies a band-pass filter (BPF) whose passband is the difference tone component (3f - 1f) to the input one echo signal to extract the sum tone component (2 * 1f) in the same band as the difference tone component (3f - 1f). Note that "*" is an operator indicating multiplication, for example. Then, the non-linear component extraction circuit 32c outputs the extracted difference tone component and sum tone component to the velocity information calculation unit 34b.

[0096] In this modification, the velocity information calculation unit 34b and the DSC 35 perform various processes on the signals of the difference tone component and the sum tone component, similar to the third embodiment, to generate image data of the color Doppler image based on the difference tone component and the sum tone component.

[0097] In the ultrasonic diagnostic apparatus 10a according to a modification of the third embodiment, similar to the third embodiment, by performing composite transmission of a plurality of frequencies, the energy included in the transmission waveform of the ultrasonic wave is dispersed into a plurality of frequency components. Therefore, in the ultrasonic diagnostic apparatus 10a according to the modification of the third embodiment, the saturation frequency of the reception signal can be reduced. Further, in the ultrasonic diagnostic apparatus 10a according to the modification of the third embodiment, when extracting the non-linear component, instead of transmitting the ultrasonic wave twice as in the third embodiment, it can be done in one time, so that a decrease in the frame rate during imaging can be suppressed. Further, the ultrasonic diagnostic apparatus 10a according to the third embodiment can obtain high-quality image data with reduced clutter components by mobile imaging, similar to the ultrasonic diagnostic apparatus 10 according to the first embodiment.

[0098] (Fourth Embodiment) Here, there is known a mobile imaging technique capable of lengthening the time-series observation period and visualizing an extremely slow blood flow by analyzing the pulse echo signals obtained at the frame intervals. For example, in such a mobile imaging technique, the ultrasonic diagnostic apparatus acquires the time-series pulse echo signals at the frame intervals. Then, the ultrasonic diagnostic apparatus uses a matrix using the least squares method, singular value decomposition, or orthogonal expansion to obtain a mobile object-derived signal with the clutter component from the tissue suppressed from the time-series pulse echo signals. Then, the ultrasonic diagnostic apparatus estimates the mobile object information of the mobile object using the mobile object-derived signal. The mobile object here is, for example, a blood cell in the blood. Further, the mobile object information is, for example, blood flow information regarding the blood cell. The blood flow information includes information such as the velocity of the blood flow (blood cell), the dispersion of the blood flow, and the power of the blood flow.

[0099] For example, such mobile imaging technology is known and described in known documents such as Japanese Patent Application Laid-Open No. 2014-158698. Therefore, the ultrasonic diagnostic apparatus may perform imaging of extremely low-speed flow by using the above-described imaging technology with the non-linear component extracted at the frame interval as the pulse echo signal obtained at the above-described frame interval. Therefore, such an ultrasonic diagnostic apparatus will be described as the ultrasonic diagnostic apparatus according to the fourth embodiment. In the description of the fourth embodiment, mainly, the differences from the first embodiment will be described, and the description of the configuration similar to that of the first embodiment may be omitted.

[0100] FIG. 12 is a diagram showing an example of the configuration of an ultrasonic diagnostic apparatus 10b according to the fourth embodiment. The ultrasonic diagnostic apparatus 10b is different from the ultrasonic diagnostic apparatus 10 according to the first embodiment in that it includes a device main body 12b instead of the device main body 12. Further, the device main body 12b is different from the device main body 12 in that it includes a speed information calculation unit 34c instead of the speed information calculation unit 34b.

[0101] In the fourth embodiment, for example, the ultrasonic diagnostic apparatus 10b collects echo signals at the same position over a plurality of frames. For example, the ultrasonic diagnostic apparatus 10b according to the fourth embodiment collects echo signals at the same position over a plurality of frames by repeating a scanning mode in which ultrasonic transmission and reception in the scanning range is performed once for each scanning line. That is, the ultrasonic diagnostic apparatus 10b repeats a scanning mode in which ultrasonic transmission and reception in the scanning range is performed once for each scanning line in one frame.

[0102] FIG. 13 is a diagram showing an example of the configuration of the speed information calculation unit 34c according to the fourth embodiment. As shown in FIG. 13, the speed information calculation unit 34c includes a first acquisition function 51, a second acquisition function 52, and an estimation function 53. The first acquisition function 51 is an example of a first acquisition unit. The second acquisition function 52 is an example of a second acquisition unit. The estimation function 53 is an example of an estimation unit.

[0103] The speed information calculation unit 34c is realized by, for example, a processor. In this case, each of the above-described processing functions is stored in the memory included in the ultrasonic diagnostic apparatus 10b in the form of a program executable by a computer. Then, the speed information calculation unit 34c reads out each program stored in the memory and executes each read program, thereby realizing each processing function corresponding to each program. In other words, the speed information calculation unit 34c has each processing function shown in FIG. 13 in a state where each program is read out.

[0104] In the fourth embodiment, the non-linear wave BPF 32b extracts a harmonic component (non-linear component) from an echo signal (received signal) for each frame and outputs the extracted harmonic component to the first acquisition function 51. Such an echo signal is, for example, a signal obtained from blood cells of moving blood.

[0105] The first acquisition function 51 acquires the harmonic component output by the non-linear wave BPF 32b for each frame as a time-series pulse echo signal. That is, the first acquisition function 51 acquires a time-series pulse echo signal at frame intervals using the harmonic component of the echo signal obtained from blood cells of moving blood. Blood cells are an example of a moving body.

[0106] The second acquisition function 52 acquires a moving body-derived signal, which is a signal from which clutter components from tissues are suppressed, from the time-series pulse echo signal acquired by the first acquisition function 51 by using a matrix using the least squares method, singular value decomposition, or orthogonal expansion. Examples of such tissues include tissues with a slow moving speed or stationary tissues (fixed bodies). Examples of clutter components include signals derived from tissues with a slow moving speed or stationary tissues. A moving body-derived signal is, for example, a signal derived from blood cells, which are moving bodies.

[0107] The estimation function 53 estimates blood flow information regarding blood cells by using the moving body-derived signal acquired by the second acquisition function 52. The blood flow information includes information such as the velocity of the blood flow (blood cells), the dispersion of the blood flow, and the power of the blood flow.

[0108] As described above, the ultrasonic diagnostic apparatus 10b according to the fourth embodiment performs moving body imaging using harmonic components. When using harmonic components as described above, the clutter component is sufficiently reduced. Therefore, according to the fourth embodiment, high-quality image data with the clutter component reduced by moving body imaging can be obtained. Further, according to the fourth embodiment, moving body imaging capable of visualizing an extremely low-speed blood flow with a small clutter component can be performed.

[0109] (Modification of the Fourth Embodiment) In the fourth embodiment, the case where the non-linear wave BPF 32b extracts harmonic components from the echo signal every frame and outputs the extracted harmonic components to the first acquisition function 51 has been described. However, in the fourth embodiment, instead of the non-linear wave BPF 32b, a non-linear component extraction circuit 32c may be used. Therefore, such a modification will be described as a modification of the fourth embodiment. In the description of the modification of the fourth embodiment, mainly, the points different from the fourth embodiment will be described, and the description of the configuration similar to the fourth embodiment may be omitted.

[0110] The ultrasonic diagnostic apparatus 10b according to the modification of the fourth embodiment is different from the ultrasonic diagnostic apparatus 10b according to the fourth embodiment in that it includes a non-linear component extraction circuit 32c instead of the non-linear wave BPF 32b.

[0111] The non-linear component extraction circuit 32c according to the fourth embodiment extracts harmonic components from the echo signal by pulse inversion. A specific example of the operation of the non-linear component extraction circuit 32c according to the fourth embodiment will be described. For example, in the fourth embodiment, the probe 11 transmits two ultrasonic waves having phases different by 180 degrees from each other in the same direction toward the subject. That is, the probe 11 transmits two ultrasonic waves having phases different by 180 degrees from each other on the same scanning line (the same scan line). However, in the fourth embodiment, the probe 11 transmits, for example, an ultrasonic wave (the fifth ultrasonic wave) at the first rate of a certain frame, and then transmits an ultrasonic wave (the sixth ultrasonic wave) having a phase different by 180 degrees from the phase of the fifth ultrasonic wave at the next rate. Then, the preamplifier circuit 30 and the reception delay / summation circuit 31 perform the above-described various processes on the two echo signals based on the two transmitted ultrasonic waves. In this way, the two echo signals subjected to the various processes are input to the non-linear component extraction circuit 32c. However, the two echo signals are input to the non-linear component extraction circuit 32c at two rates instead of one rate.

[0112] The non-linear component extraction circuit 32c adds the two input echo signals for each two rates, thereby removing or suppressing the fundamental wave component and generating a harmonic signal mainly corresponding to the second harmonic component for each frame. Then, the non-linear component extraction circuit 32c outputs the generated harmonic signal to the velocity information calculation unit 34b and the receiver circuit 33b for each frame. Here, in the modification of the fourth embodiment, the velocity information calculation unit 34b performs the same processes as the various processes performed by the velocity information calculation unit 34b using the harmonic component in the previous fourth embodiment using the harmonic signal.

[0113] Therefore, in the modification of the fourth embodiment, the first acquisition function 51 of the speed information calculation unit 34b acquires, for each of the two rates, the harmonic signals output by the non-linear wave BPF 32b as time-series pulse echo signals. That is, the first acquisition function 51 acquires, for each of the two rates, the time-series pulse echo signals at intervals of one frame using the harmonic signals of the echo signals obtained from the blood cells of the moving blood.

[0114] Then, the second acquisition function 52 acquires, for each frame, the moving object-derived signal, which is a signal with the clutter component from the tissue suppressed, from the time-series pulse echo signals acquired for each frame by the first acquisition function 51 by using a matrix using the least squares method, singular value decomposition, or orthogonal expansion.

[0115] The estimation function 53 estimates, for each frame, the blood flow information regarding the blood cells by using the moving object-derived signal acquired for each frame by the second acquisition function 52.

[0116] Therefore, the display frame rate of the color Doppler image based on the blood flow information in the modification of the fourth embodiment is half of the display frame rate of the color Doppler image based on the blood flow information in the fourth embodiment.

[0117] Here, in the moving object imaging technology described as known above, the sampling frame rate required for the clutter component removal process or suppression process exceeds 100 Hz. On the other hand, the frame rate of general or general-purpose video is about 60 Hz. Therefore, since the color Doppler image based on the blood flow information cannot be displayed at an extremely high display frame rate, the frames are thinned out so that the display frame rate becomes about 60 Hz, and the color Doppler image based on the blood flow information is displayed.

[0118] According to a modification of the fourth embodiment, the sampling frame rate is halved compared to the fourth embodiment. For example, in the modification of the fourth embodiment, the sampling frame rate required for clutter component removal processing or suppression processing is about more than 50 Hz. Therefore, the sampling frame rate required for clutter component removal processing or suppression processing in the modification of the fourth embodiment is about the same as the display frame rate in the mobile imaging technology described as known. In the modification of the fourth embodiment, the display frame rate of the color Doppler image based on blood flow information does not extremely decrease, for example, to about 25 Hz, which is half of 50 Hz.

[0119] Therefore, according to the modification of the fourth embodiment, while maintaining the display frame rate of the color Doppler image based on blood flow information at a practically sufficient value, the effects obtained by pulse inversion (the effect that it can be applied to the broadband power mode, the effect that the S / N ratio can be improved by 3 dB by addition, the effect that the saturation frequency can be decreased by reducing the signal dynamic range before applying to the MTI filter), and the effect that the side lobe can be reduced by harmonic utilization are obtained.

[0120] (Fifth Embodiment) Next, an ultrasonic diagnostic apparatus according to the fifth embodiment will be described. In the description of the fifth embodiment, mainly, the differences from the first embodiment will be described, and the description of the same configuration as the first embodiment may be omitted.

[0121] FIG. 14 is a diagram showing an example of the configuration of an ultrasonic diagnostic apparatus 10c according to the fifth embodiment. The ultrasonic diagnostic apparatus 10c is different from the ultrasonic diagnostic apparatus 10 according to the first embodiment in that it includes a device main body 12c instead of the device main body 12. Further, the device main body 12c is different from the device main body 12 in that it includes a speed information calculation unit 34a connected in parallel to the receiver circuit 33a.

[0122] In the fifth embodiment, from the fundamental wave BPF 32a, the fundamental wave component Sf The echo signal is output to the subsequent receiver circuit 33a and the speed information calculation unit 34a. The speed information calculation unit 34a has the same configuration as the speed information calculation unit 34b. For example, the speed information calculation unit 34c is such that the speed information calculation unit 34b estimates moving body information regarding the moving body based on the second harmonic component S 2f In the same manner as estimating moving body information regarding the moving body based on the fundamental wave component S f estimates moving body information regarding the moving body. Here, the moving body is, for example, a bubble of an ultrasonic contrast agent or a blood cell in blood. The moving body information is, for example, at least one of the speed of the moving body, the dispersion value of the moving body, and the power value of the moving body.

[0123] Then, the DSC 35 performs weighted addition of the moving body information based on the fundamental wave component S f and the moving body information based on the second harmonic component S 2f . Specifically, the DSC 35 performs weighted addition in the distance direction of the moving body information obtained from the linear component of the echo signal and the moving body information obtained from the non-linear component of the echo signal. Note that the DSC 35 is an example of an addition unit. Then, the DSC 35 generates image data of a color Doppler image in which the moving body information obtained by weighted addition is color-modulated, and causes the monitor 36 to display the color Doppler image indicated by the generated image data.

[0124] There are two types of weighted addition methods. First, the first type of weighted addition method will be described. The harmonic component is generated with an accumulation effect along with the distance (depth). For this reason, the harmonic component may not obtain a sufficient S / N ratio in the shallow part. Therefore, the DSC 35 makes the moving body information based on the fundamental wave component S f relatively large in the shallow part up to a predetermined first depth, and makes the moving body information based on the second harmonic component S 2f relatively large in the part deeper than the predetermined first depth for weighting. For example, the DSC 35 increases the weight of the moving body information based on the fundamental wave component S f in the shallow part up to a predetermined first depth, and in the part deeper than the predetermined first depth, the second harmonic component S 2fIncrease the weight of the moving object information based on this. As a result, the ultrasonic diagnostic apparatus 10c can perform moving object imaging over all depths.

[0125] Next, a second type of weighted addition method will be described. Generally, the harmonic component has a smaller signal level than the fundamental wave component. Therefore, the harmonic component may not obtain a better S / N ratio than the fundamental wave component in the deep part due to frequency-dependent attenuation. Thus, in the shallow part up to a predetermined first depth, the DSC35 makes the moving object information based on the fundamental wave component S f relatively high, and in the portion from the predetermined first depth to the predetermined second depth, the moving object information based on the second harmonic component S 2f is relatively high, and in the part deeper than the predetermined second depth, the moving object information based on the fundamental wave component S f is weighted for the echo signal so that it becomes relatively high. Note that the predetermined second depth is deeper than the predetermined first depth. For example, in the shallow part up to the predetermined first depth, the DSC35 increases the weight of the moving object information based on the fundamental wave component S f , and in the portion from the predetermined first depth to the predetermined second depth, increases the weight of the moving object information based on the second harmonic component S 2f , and in the part deeper than the predetermined second depth, increases the weight of the moving object information based on the fundamental wave component S f . As a result, the ultrasonic diagnostic apparatus 10c can compensate for the attenuation of the harmonic component in the deep part deeper than the predetermined second depth with the fundamental wave component.

[0126] Note that the ultrasonic diagnostic apparatus 10c according to the fifth embodiment may include a non-linear component extraction circuit 32c instead of the non-linear wave BPF 32b.

[0127] (Other modification examples) In the fifth embodiment, the case where the ultrasonic diagnostic apparatus 10c performs weighted addition (compounding) on the outputs of the two velocity information calculation units 34a and 34b was described. However, a medical imaging diagnostic apparatus may provide an action similar to the action in the case of performing weighted addition on the outputs of the two velocity information calculation units 34a and 34b by weighting the fundamental wave component and the harmonic component included in the echo signal (received signal). Therefore, such a modification will be described as another modification example.

[0128] For example, in the first embodiment shown in FIG. 1, the characteristics of the non-linear wave BPF 32b may be set for each position in the depth direction according to the depth. Also, in the fifth embodiment shown in FIG. 14, the characteristics of the fundamental wave BPF 32a and the non-linear wave BPF 32b may be set for each position in the depth direction according to the depth. In particular, in the fifth embodiment, when setting the characteristics of the fundamental wave BPF 32a and the non-linear wave BPF 32b for each position in the depth direction, the weights of the fundamental wave component and the harmonic component change according to the bands passed by the fundamental wave BPF 32a and the non-linear wave BPF 32b. Therefore, the user sets the bands passed by the fundamental wave BPF 32a and the non-linear wave BPF 32b so as to obtain a desired weight.

[0129] For example, in the shallow part up to a predetermined first depth, the weight of the fundamental wave component S f included in the echo signal becomes relatively large, and in the portion from the predetermined first depth to the predetermined second depth, the weight of the second harmonic component S 2f included in the echo signal becomes relatively large, and in the part deeper than the predetermined second depth, the weight of the fundamental wave component S f included in the echo signal is set to be relatively large again. Note that the predetermined second depth is deeper than the predetermined first depth. Thereby, an effect similar to the effect obtained when performing the second type of weighted addition method described above is obtained.

[0130] By using the one-dimensional array probe as probe 11 and synthesizing tomographic images obtained by mechanically swinging, volume data can be obtained through mechanical 4D scanning. By combining this with the above-described embodiments or modified examples, it is possible to three-dimensionally transform the basic tomographic images.

[0131] Furthermore, it is also possible to combine real-time 3D scanning, which uses a two-dimensional array probe as probe 11 and obtains volume data by electronic scanning in probe 11, with the above-described embodiments or modified examples. Even in these cases, it will be understood that the basic concept of the above-described embodiments or modified examples can be extended, and the effect of clutter reduction according to the above-described embodiments or modified examples can be obtained during tomographic image acquisition or volume data acquisition.

[0132] Also, the term "processor" used in the above description means, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a circuit such as an application specific integrated circuit (ASIC), a programmable logic device (for example, a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). When the processor is, for example, a CPU, the processor realizes its function by reading and executing a program stored in a memory. On the other hand, when the processor is, for example, an ASIC, instead of storing a program in a memory, the function is directly incorporated as a logic circuit in the circuit of the processor. Note that each processor of the present embodiment is not limited to being configured as a single circuit for each processor, and a plurality of independent circuits may be combined to form one processor to realize its function.

[0133] Here, the program executed by the processor is provided by being pre - incorporated into a ROM (Read Only Memory), a storage circuit, etc. Note that this program may be provided by being recorded on a computer - readable non - transitory storage medium such as a CD (Compact Disk) - ROM, FD (Flexible Disk), CD - R (Recordable), DVD (Digital Versatile Disk) in a form installable or executable on these devices. Also, this program may be stored on a computer connected to a network such as the Internet and provided or distributed by being downloaded via the network. For example, this program is composed of modules including the above - described respective processing functions. As actual hardware, the CPU reads the program from a storage medium such as a ROM and executes it, whereby each module is loaded onto the main storage device and generated on the main storage device.

[0134] According to at least one of the embodiments or modifications described above, high - quality image data with reduced clutter components can be obtained by mobile imaging.

[0135] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0136] 32b BPF for non - linear wave 3453 Autocorrelator 3454 Phase rotation calculator 10 Ultrasonic diagnostic apparatus

Claims

1. An extraction unit that extracts a non-linear component of a received ultrasonic signal with respect to a contrast agent injected into a blood vessel of a subject from the received signal; A detection unit that detects, by autocorrelation calculation using the non-linear component, a signal component having a phase rotation of a time-series signal associated with the movement of the contrast agent as a projection component in the beam direction of the movement of the contrast agent; A conversion unit that converts the phase rotation of the time-series signal into speed information indicating the speed of the contrast agent based on information having a reference frequency, a sound speed, and a pulse repetition frequency of a signal for phase-detecting the received signal; An ultrasonic diagnostic apparatus comprising the above.

2. The ultrasonic diagnostic apparatus according to claim 1, further comprising an estimation unit that estimates power information indicating the power of the signal component having the phase rotation by autocorrelation calculation.

3. The ultrasonic diagnostic apparatus according to claim 1 or 2, wherein the extraction unit extracts the non-linear component of the received signal from the received signal using a pulse inversion scan sequence.

4. The ultrasonic diagnostic apparatus according to claim 3, wherein the extraction unit determines (M - 1) addition pairs from a time-series data set of M (M is an even number of 2 or more) data by shifting the addition pairs of the pulse inversion one data at a time in the time-series direction.

5. The ultrasonic diagnostic apparatus according to claim 1, wherein the extraction unit extracts, as the received signal, at least one non-linear component of a non-linear component due to a harmonic on the low-frequency side of the plurality of frequencies and a non-linear component due to an intermodulation product of the plurality of frequencies, which are obtained by performing composite transmission of a plurality of frequencies.

6. The ultrasonic diagnostic apparatus according to claim 5, wherein the extraction unit extracts, from the received signal, a non-linear component due to an intermodulation product of a fundamental frequency and a frequency twice the fundamental frequency, which are obtained by performing composite transmission of the fundamental frequency and the frequency twice the fundamental frequency as the plurality of frequencies.

Images