Ultrasound diagnostic device, control method and program for ultrasound diagnostic device

Abstract

The accuracy of blood flow images is improved by using more precise information on blood flow velocity and direction. [Solution] The ultrasound diagnostic apparatus according to the present disclosure includes an ultrasound transmitting and receiving unit that transmits and receives ultrasound to a subject; a data acquisition unit that acquires data of reflected waves in the subject due to the transmission and reception of ultrasound over a plurality of frames; a first image generation unit that generates a first blood flow image showing the blood flow of the subject using the data from the plurality of frames; a second image generation unit that generates a second blood flow image including components with lower spatial frequencies than the first blood flow image using the data from the plurality of frames; a detection unit that detects the maximum value of the blood flow signal within a predetermined range of the second blood flow image; a calculation unit that calculates the blood flow velocity and blood flow direction of the subject based on the position information of the detected maximum value; and a third image generation unit that generates a third blood flow image based on the first blood flow image, the blood flow velocity and the blood flow direction.

Description

Technical Field

[0005] ,

[0004] , , ,

[0001] The present invention relates to an ultrasonic diagnostic apparatus, a control method thereof, and a program.

Background Art

[0002] Ultrasonic diagnostic apparatuses are widely used for observing and diagnosing the blood flow of a living body. An ultrasonic diagnostic apparatus generates blood flow information of a living body using a reflected wave of ultrasonic waves from the living body by a Doppler method based on the Doppler effect. Examples of the blood flow information generated by the ultrasonic diagnostic apparatus include a color Doppler image and a Doppler waveform (Doppler spectrum).

[0003] A color Doppler image is an ultrasonic image obtained by imaging using a color flow mapping (CFM) method. In the CFM method, transmission and reception of ultrasonic waves are performed a plurality of times on a plurality of scanning lines. In the CFM method, by applying an MTI (Moving Target Indicator) filter to a data series at the same position of the living body, a signal (clutter signal) derived from a stationary tissue or a tissue with slow movement is suppressed, and a signal derived from blood flow is extracted. Then, in the CFM method, blood flow information such as the velocity of blood flow, the dispersion of blood flow, and the power of blood flow is estimated from the extracted blood flow signal, and a distribution of the estimation result is generated as a Doppler image.

[0004] In a B-mode image or a Doppler image, it is known that the resolution decreases due to a point spread function (PSF) determined by the wavelength of transmitted ultrasonic waves, the transmission / reception aperture width, and the like. As a solution to this problem, a method of increasing the frequency of transmitted ultrasonic waves can be mentioned, but since there is also a limit to the ultrasonic frequency band that can be realized in a probe, there is also a limit to the resolution of the image that can be generated.

[0005] Non-Patent Document 1 describes a super-resolution technique for blood flow images that achieves a resolution of about 1 / 5 of the wavelength of ultrasound transmitted from a probe. Non-Patent Document 1 improves the resolution of the generated blood flow image by acquiring a large number of Doppler images and integrating the peak image values ​​of the acquired Doppler images. Furthermore, Non-Patent Document 1 proposes a technique for displaying blood flow velocity and direction by tracking peaks between consecutive frames. [Prior art documents] [Patent Documents]

[0006] [Non-Patent Document 1] Super Resolution Ultrasound using Recursive Imaging of Highly Dense Scatterers, Mostafa Amin-Naji, Jorgen Arendt Jensen, Proceedings 2022 IEEE International Ultrasonics Symposium (IUS) [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In peak tracking for calculating blood flow velocity in blood flow images, accurate blood flow velocity calculation may not be possible due to factors such as the density of peak points.

[0008] The technology disclosed herein has been made in view of the above, and aims to provide an ultrasound diagnostic device that improves the accuracy of blood flow images using more accurate information on blood flow velocity and blood flow direction. [Means for solving the problem]

[0009] The ultrasound diagnostic apparatus relating to this disclosure includes an ultrasound transmitting and receiving unit that transmits and receives ultrasound to and from a subject, and The system includes: a data acquisition unit that acquires data of reflected waves from the subject by transmitting and receiving ultrasound over multiple frames; a first image generation unit that generates a first blood flow image showing the blood flow of the subject using the data from the multiple frames acquired by the data acquisition unit; a second image generation unit that generates a second blood flow image including components with lower spatial frequencies than the first blood flow image using the data from the multiple frames acquired by the data acquisition unit; a detection unit that detects the maximum value of the blood flow signal within a predetermined range of the second blood flow image; a calculation unit that calculates the blood flow velocity and blood flow direction of the subject based on the position information of the maximum value detected by the detection unit; and a third image generation unit that generates a third blood flow image based on the first blood flow image, the blood flow velocity, and the blood flow direction.

[0010] Furthermore, the control method for an ultrasound diagnostic apparatus according to this disclosure includes: an ultrasound transmission / reception step of transmitting and receiving ultrasound waves to and from a subject; a data acquisition step of acquiring data of reflected waves at the subject due to the transmission and reception of ultrasound waves over a plurality of frames; a first image generation step of generating a first blood flow image showing the blood flow of the subject using the data of the plurality of frames acquired by the data acquisition step; a second image generation step of generating a second blood flow image including components with lower spatial frequencies than the first blood flow image using the data of the plurality of frames acquired by the data acquisition step; a detection step of detecting the maximum value of the blood flow signal within a predetermined range of the second blood flow image; a calculation step of calculating the blood flow velocity and blood flow direction of the subject based on the position information of the maximum value detected by the detection step; and a third image generation step of generating a third blood flow image based on the first blood flow image, the blood flow velocity, and the blood flow direction. [Effects of the Invention]

[0011] The technology disclosed herein can improve the accuracy of blood flow images. [Brief explanation of the drawing]

[0012] [Figure 1] Block diagram showing an example of the configuration of an ultrasound diagnostic device. [Figure 2] Block diagram showing an example of the configuration of the received signal processing unit. [Figure 3] Flowchart of the process performed by the ultrasound diagnostic device according to the first embodiment [Figure 4] A diagram showing an example of a blood flow image in the first embodiment. [Figure 5] Figure showing an example of an image illustrating the local maximum value in the first embodiment. [Figure 6] A diagram showing an example of the movement of the local maximum value between frames in the first embodiment. [Figure 7] Figure showing an example of a blood flow image in the second embodiment. [Figure 8] Flowchart of the process performed by the ultrasound diagnostic device according to the third embodiment [Figure 9] A diagram showing an example of the frequency band used by the ultrasound diagnostic device according to the third embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the image processing apparatus of the present invention will be described in detail with reference to the attached drawings. However, the components described in the following embodiments are merely illustrative, and the technical scope of the present invention is determined by the claims and is not limited to the following individual embodiments.

[0014] <First Embodiment> The ultrasound diagnostic apparatus according to the first embodiment will now be described. In the ultrasound diagnostic apparatus according to this embodiment, ultrasound is transmitted and received to a subject using an ultrasound probe. The ultrasound diagnostic apparatus then extracts low-frequency components from the received signal based on the reflected wave from the subject to generate a low-frequency blood flow image, and calculates blood flow velocity and blood flow direction by tracking local maximum values ​​such as power values ​​in the low-frequency blood flow image between frames. The ultrasound diagnostic apparatus also generates a super-resolution blood flow image in which the calculated blood flow velocity and blood flow direction are color-coded.

[0015] FIG. 1 is a block diagram showing an example of the hardware configuration of an ultrasonic diagnostic apparatus according to the present embodiment. The ultrasonic diagnostic apparatus 1 includes an ultrasonic probe (ultrasonic transducer) 102, a probe connection unit 103, a transmission electric circuit 104, a reception electric circuit 105, a reception signal processing unit 106, an image processing unit 107, a display unit 108, and a system control unit 109. The ultrasonic diagnostic apparatus 1 transmits an ultrasonic pulse from the ultrasonic probe 102 to the subject 100, receives the reflected ultrasonic wave reflected from the subject 100 by the ultrasonic probe 102, and generates image information (ultrasonic image) inside the subject 100. The ultrasonic image generated by the ultrasonic diagnostic apparatus 1 is used for various clinical examinations.

[0016] The ultrasonic probe 102 is a probe using an electronic scanning method and has a plurality of vibrators 101 arranged one-dimensionally or two-dimensionally at the tip. The vibrator 101 is an electromechanical conversion element that performs mutual conversion between an electric signal (voltage pulse signal) and an ultrasonic wave (acoustic wave). The ultrasonic probe 102 is an ultrasonic transmission / reception unit that transmits ultrasonic waves from a plurality of vibrators 101 to the subject 100 and receives the reflected ultrasonic wave from the subject 100 by the plurality of vibrators 101. The reflected acoustic wave from the subject 100 reflects the difference in acoustic impedance within the subject 100. When the ultrasonic pulse transmitted from the ultrasonic probe 102 is reflected on the surface of a moving blood flow or the heart wall in the subject 100, the reflected wave signal undergoes a frequency shift depending on the velocity component in the ultrasonic transmission direction of the moving object due to the Doppler effect.

[0017] The transmission electric circuit 104 outputs a pulse signal (drive signal) to the vibrator 101 of the ultrasonic probe 102 via the probe connection part 103. The transmission electric circuit 104 applies the pulse signal to the plurality of vibrators 101 with a time difference. As a result, ultrasonic waves with different delay times are transmitted from the plurality of vibrators 101, and a transmitted ultrasonic beam is formed. Further, the transmission electric circuit 104 can control the direction and focus of the transmitted ultrasonic beam by selectively changing the vibrator 101 to which the pulse signal is applied (i.e., the vibrator 101 to be driven) or by changing the delay time (application timing) of the pulse signal. By sequentially changing the direction and focus of the transmitted ultrasonic beam, the observation region inside the subject 100 is scanned.

[0018] Also, the transmission electric circuit 104 can form a transmitted ultrasonic beam that is a plane wave (focus is at infinity) or a divergent wave (focus points are in the opposite direction of the ultrasonic transmission direction with respect to the plurality of vibrators 101) by changing the delay time of the pulse signal. Similarly, the transmission electric circuit 104 can also form a transmitted ultrasonic beam using one vibrator or a part of the plurality of vibrators 101 by changing the delay time of the pulse signal. The transmission electric circuit 104 can generate transmitted ultrasonic waves having a predetermined transmission waveform at the vibrator 101 by transmitting a pulse signal with a predetermined drive waveform to the vibrator 101.

[0019] The reception electric circuit 105 receives the electric signal output from the vibrator 101 that has received the reflected ultrasonic wave from the subject. The reception electric circuit 105 inputs the received signal to the reception signal processing unit 106. The operations of the transmission electric circuit 104 and the reception electric circuit 105, that is, the transmission and reception of ultrasonic waves, are controlled by the system control unit 109. The system control unit 109 changes, for example, the voltage signal and the timing for forming the transmitted ultrasonic wave according to each of the generation processes of the B-mode image and the blood flow image described later.

[0020] When generating a B-mode image, the ultrasound diagnostic device 1 acquires the received signal of reflected ultrasound obtained by scanning the observation area of ​​the subject, and generates a B-mode image using the acquired received signal. Furthermore, when generating a blood flow image, the ultrasound diagnostic device 1 performs multiple transmissions and receptions of ultrasound on one or more scan lines within the observation area of ​​the subject, acquires the received signals of reflected ultrasound for multiple frames, and extracts blood flow information using the acquired signals. In the ultrasound diagnostic device 1, the scanning performed for generating a blood flow image involves multiple transmissions and receptions on a single scan line. The method may involve transmitting and receiving on the next scan line after the previous scan line, or it may involve transmitting and receiving once on each scan line and repeating this multiple times. Furthermore, the ultrasound diagnostic device 1 can reduce the number of scan lines in the generation of B-mode images and blood flow images, that is, it can transmit ultrasound over a wide observation area by transmitting plane waves or diffuse waves. In addition, the ultrasound diagnostic device 1 can change the transmission angle of the plane waves or diffuse waves and the range of the observation area to which they are transmitted, perform multiple transmissions and receptions over a wide observation area, add the received signals, and use the added signal to generate the image.

[0021] In this specification, both the analog signal output from the oscillator 101 and the digital data obtained by sampling (digital conversion) the output analog signal are referred to as the received signal without any particular distinction. However, depending on the context, the received signal may also be referred to as the received data to explicitly indicate that it is digital data.

[0022] The receiving signal processing unit 106 is an image generation unit that generates image data based on the received signal obtained from the ultrasonic probe 102. The image processing unit 107 performs image processing such as brightness adjustment, interpolation, and filtering on the image data generated by the receiving signal processing unit 106. The display unit 108 is a display unit that displays image data and various information related to the image, and is composed of, for example, a liquid crystal display or an organic EL display. The system control unit 109 is a control unit that comprehensively controls the transmitting electrical circuit 104, the receiving electrical circuit 105, the receiving signal processing unit 106, the image processing unit 107, the display unit 108, and the like.

[0023] (Configuration of the received signal processing unit) Figure 2 is a block diagram showing an example of the functions of the received signal processing unit 106. As shown in Figure 2, the received signal processing unit 106 includes a received signal storage unit 200, a phase-correcting and adding processing unit 201, a signal storage unit 202, a B-mode processing unit 203, a correction unit 204, a Doppler processing unit 205, and a super-resolution processing unit 206.

[0024] The received signal storage unit 200 temporarily stores the received signal received by the receiving electrical circuit 105. Depending on the configuration of the ultrasound diagnostic device 1 and the type of received signal, the received signal storage unit 200 may not store the received signal, but rather store it in a signal storage unit 202 located after the phase aligning and adding processing unit 201, which will be described later. Alternatively, the received signal storage unit 200 may consist of a common block with the signal storage unit 202, which will be described later, and may store the received signal from the receiving electrical circuit 105 and the received signal after the phase aligning and adding processing unit 201.

[0025] The phase-alignment and addition processing unit 201 performs phase-alignment and quadrature detection processing on the received signal obtained from the receiving electrical circuit 105, and stores the processed received signal in the signal storage unit 202. Here, phase-alignment and addition processing is a process in which the received signals of multiple transducers 101 are added together by changing the delay time and signal addition weight for each transducer 101 to form a received ultrasonic beam. This is also called Sum(DAS) beamforming. Furthermore, quadrature detection is a process that converts the received signal into a common-mode signal (I signal) and a quadrature signal (Q signal) in the baseband. Phase-alignment and quadrature detection are performed based on various conditions (aperture control, signal filtering) for element arrangement and image generation input from the system control unit 109. The received signal after phase-alignment and quadrature detection is stored in the signal storage unit 202. While a typical example of DAS beamforming is assumed here, any other process for forming the received ultrasonic beam, such as adaptive beamforming, model-based processing, or machine learning-based processing, may be employed.

[0026] The B-mode processing unit 203 performs envelope detection processing, logarithmic compression processing, etc., on the received signal for B-mode image generation stored in the signal storage unit 202, and generates image data in which the signal intensity at each point within the observation area is represented by brightness intensity. In addition, the B-mode processing unit 203 performs the following auxiliary processing B-mode processing may be performed on the received signal after alignment by the standard unit 204.

[0027] The correction unit 204 calculates the amount of tissue displacement between frames due to body movement, etc., for received signals from multiple frames. The correction unit 204 calculates the amount of tissue displacement between frames using a block matching operation called the speckle tracking method. Specifically, the correction unit 204 sets a region of interest within a frame and calculates the amount of displacement of the region of interest in multiple frames by tracking the correlation between the regions of interest between frames. In addition, the correction unit 204 calculates the total displacement of the frame by setting multiple regions of interest within a frame. Here, an example of a method that utilizes correlation between frames is shown, but other methods can be used instead as long as the amount of displacement of the region of interest can be determined.

[0028] In the speckle tracking method, speckles, which are scattered images of ultrasound reflected from scatterers within the subject's tissue, are tracked against the ultrasound signal. In this embodiment, the correlation calculation of regions of interest between frames may be performed on the received signal after any of the following processing methods: phase-aligned summation, quadrature detection, or envelope detection. Furthermore, the correlation calculation of regions of interest between frames may be performed on the time waveform of the received signal, or on the frequency space data obtained by the discrete Fourier transform of the received signal. The correction unit 204 aligns the subject's tissue between frames by moving the received signal relative to the reference frame using the calculated displacement amount. The amount of movement of the received signal based on the displacement amount may be a uniform amount across the entire frame, such as using the average value of the displacement amounts of each region of interest, or it may be a different amount of movement for each region of interest within a frame. Furthermore, the displacement amounts calculated for each region of interest across the entire frame may be interpolated in the time direction of the data sequence within a frame and across multiple frames using linear interpolation or spline interpolation. Also, similar to this interpolation, the received signal to be aligned may be interpolated before moving the received signal.

[0029] The Doppler processing unit 205 extracts blood flow information (Doppler information) from the received signal for blood flow image generation stored in the signal storage unit 202 and generates a blood flow image by imaging the blood flow information. The Doppler processing unit 205 performs Doppler processing on the received signal after movement by the correction unit 204. The correction unit 204 may also calculate the displacement amount between frames based on the blood flow image output by the Doppler processing unit 205 and perform alignment processing. In this embodiment, the correction unit 204 may perform alignment on the blood flow image output from the Doppler processing unit 205 and output the corrected signal to the B-mode processing unit 203. Alternatively, the correction unit 204 may correct the received signal for blood flow image generation stored in the signal storage unit 202, and then the Doppler processing unit 205 may perform Doppler processing on the signal again to output the blood flow image to the B-mode processing unit 203.

[0030] Here, the processing of the Doppler processing unit 205 will be described in detail. The Doppler processing unit 205 extracts blood flow information based on the Doppler effect of the subject object (i.e., blood in this case) within the scanning range by performing frequency analysis on the received signal for Doppler image generation stored in the signal storage unit 202. In this embodiment, it is assumed that the object is blood, but the object may be internal tissue or an object such as a contrast agent. Furthermore, examples of blood flow information include at least one of the following: blood flow velocity, dispersion value, and power value. Here, the power value is a value that represents the strength of the blood flow signal shown by the received signal, and as a specific example, it is a value obtained by squaring the absolute value of the received signal derived from blood flow after reducing components derived from stationary tissue or tissue with little movement. Note that in the processing performed by the ultrasound diagnostic device 1 described below, it is assumed that the power value is the power value obtained by this specific example. Furthermore, here, components derived from stationary tissue or tissue with little movement are clutter components related to the subject's blood flow, and are unwanted components other than the signal from the blood flow.

[0031] Furthermore, the Doppler processing unit 205 may generate blood flow information at one point (one location) within the subject, or it may generate blood flow information at multiple locations in the depth direction of the subject. The Doppler processing unit 205 may generate blood flow information at multiple points in time in a time series. This allows the ultrasound diagnostic device 1 to display the time-dependent changes in blood flow information.

[0032] In the generation of blood flow images using the Doppler method in this embodiment, a series of received data frames in the time direction is acquired at locations including the same position within the subject. The Doppler processing unit 205 applies an MTI (Moving Target Indicator) filter to the received data series. As a result, the Doppler processing unit 205 reduces clutter components between frames and extracts components derived from blood flow. The Doppler processing unit 205 then calculates blood flow information such as blood flow velocity, blood flow dispersion, and blood flow power from the extracted blood flow-derived components.

[0033] Furthermore, a Butterworth-type IIR (Infinite Impulse Response) filter may be used as the MTI filter in the Doppler processing unit 205. Alternatively, a polynomial regression filter may be used as the MTI filter. Filters with fixed filter coefficients can be used as MTI filters. Alternatively, the MTI filter may be an adaptive filter that changes its coefficients according to the input signal using eigenvalue decomposition or singular value decomposition. The Doppler processing unit 205 can also decompose the received signal data into basis elements using eigenvalue decomposition or singular value decomposition, and remove clutter components by extracting only specific basis elements.

[0034] The super-resolution processing unit 206 generates a super-resolution blood flow image, which is a blood flow image with improved resolution, from the blood flow image data generated by the Doppler processing unit 205. Details of the process for generating the super-resolution blood flow image in this embodiment will be explained along with the following processing flow.

[0035] The image data output from the B-mode processing unit 203, the Doppler processing unit 205, and the super-resolution processing unit 206 is processed by the image processing unit 107 and then finally displayed on the display unit 108. The respective image data may be displayed superimposed, displayed in parallel, or only a portion of the image data may be displayed.

[0036] The received signal processing unit 106 may consist of one or more processors and memory. In this case, the functions of each part of the received signal processing unit 106 shown in Figure 2 are realized by a computer program. For example, the CPU can provide the functions of each part of the received signal processing unit 106 by reading and executing a program stored in memory. In addition to the CPU, the received signal processing unit 106 may also include processors (such as a GPU or FPGA) that are responsible for the calculations of the B-mode processing unit 203, the correction unit 204, the Doppler processing unit 205, and the super-resolution processing unit 206. Furthermore, the memory may include memory for non-temporarily storing programs, memory for temporarily storing data such as received signals, and working memory used by the CPU.

[0037] (Processing flow for generating blood flow images) The configuration of the ultrasound diagnostic device 1 according to the first embodiment has been described above. Next, the processing flow for generating blood flow images in this embodiment will be described. Figure 3 shows a flowchart of the process for generating super-resolution blood flow images according to this embodiment. As an example, when the system control unit 109 starts transmitting and receiving ultrasound to and from a subject 100 using the ultrasound probe 102 in response to user operation of the ultrasound diagnostic device 1, it executes the processing shown in this flowchart.

[0038] In step S310, the system control unit 109 repeatedly transmits and receives ultrasound signals to the same location within the target area for acquiring blood flow information using the ultrasound probe 102 over multiple frames. The system control unit 109 then controls the receiving electrical circuit 105. Then, a received signal is generated that includes a data sequence of multiple frames that are continuous in the time direction. Generally, the number of frames in the data sequence used to generate super-resolution blood flow images is greater than the number of frames in the data sequence used to generate normal Doppler images. For example, while the number of frames in the data sequence used to generate normal Doppler images is around 5 to 20, the number of frames in the data sequence used to generate super-resolution blood flow images is around several hundred to tens of thousands. Here, the system control unit 109 is a data acquisition unit that acquires data of reflected waves from the subject by transmitting and receiving ultrasound over multiple frames.

[0039] Then, the phase-alignment and addition processing unit 201 of the received signal processing unit 106 performs phase-alignment and addition processing and quadrature detection processing on the received signal which includes the data sequence of multiple generated frames, and stores the processed data in the signal storage unit 202. In this embodiment, the data sequence for one frame may be a received signal obtained by performing one ultrasonic transmission and reception in the target area, or it may be a signal obtained by adding up received signals obtained by performing multiple ultrasonic transmission and reception in the target area. For example, plane wave or spread wave ultrasonic waves can be transmitted to a range including the target area, and multiple received signals received by changing the transmission angle can be added together to obtain the data for one frame.

[0040] Next, in step S320, the correction unit 204 calculates the amount of tissue displacement between frames due to body movement or the like from the received signal, which includes a data sequence of multiple frames. Then, the correction unit 204 uses the calculated displacement amount to move the received signal relative to a reference frame, thereby aligning the subject's tissue between frames. At this time, the reference frame used to calculate the displacement amount may be a single frame for the entire data sequence, or it may be a series of reference frames that are changed according to the position in the time direction, or it may be a frame calculated based on adjacent frames.

[0041] Next, in step S330, the Doppler processing unit 205 generates a blood flow image from the received signal, which includes a data sequence of multiple frames after alignment. Specifically, the Doppler processing unit 205 applies an MTI filter to the received signal after alignment to reduce clutter components and extracts components derived from blood flow from the filtered signal. Then, the Doppler processing unit 205 generates a multi-frame blood flow image based on the extracted blood flow components. In this step, the MTI filter may be applied to a portion of the data sequence after alignment or to the entire data sequence after alignment. The blood flow image generated in this step is a fourth blood flow image showing the subject's blood flow, generated using data with reduced clutter components.

[0042] Next, in step S331, the super-resolution processing unit 206 extracts the local maximum power value in each frame. Note that the super-resolution processing unit 206 may extract not only the local maximum value, but also the maximum pixel value within each image, or it may extract the pixel value that exceeds a predetermined threshold among the maximum pixel values ​​of each frame. Furthermore, the super-resolution processing unit 206 may extract pixel values ​​that fall within a predetermined range from among multiple peaks of pixel values ​​within the local region of each frame.

[0043] Next, in step S332, the super-resolution processing unit 206 generates a super-resolution blood flow image by integrating the local maximum values ​​of multiple frames extracted in step S331. Because the position of the local maximum value moves between frames, the super-resolution processing unit 206 can generate a super-resolution blood flow image with improved resolution compared to a normal Doppler image by integrating multiple blood flow images. In this step, the super-resolution processing unit 206 is a first image generation unit that generates a first blood flow image showing the blood flow of the subject using data from multiple frames.

[0044] Furthermore, in step S340, the Doppler processing unit 205 extracts low-frequency components from the received signal, which includes the data sequence of multiple frames after alignment, in order to calculate blood flow velocity and blood flow direction from the received signal of multiple frames. Here, the Doppler processing unit 205 extracts the low-frequency signal If a low-frequency blood flow image can be generated from the data, a filter with arbitrary frequency characteristics, such as a low-pass filter, can be used to extract the low-frequency component from the data sequence. Furthermore, the frequency band to be extracted by the Doppler processing unit 205 may be pre-set according to the sensitivity characteristics of the ultrasound probe 102, or an arbitrary frequency band may be specified by the user. For example, the display unit 108 may be a touch panel and be configured as a reception unit that accepts the user's specification of the blood flow velocity of the subject. In this step, the Doppler processing unit 205 is a second image generation unit that generates a second blood flow image containing components with lower spatial frequencies than the first blood flow image using data from multiple frames.

[0045] As described later, the frequency of the received signal suitable for calculating blood flow velocity and blood flow direction depends on the blood flow velocity to be calculated and the frame rate of the blood flow image. Therefore, in this embodiment, the user may operate the ultrasound diagnostic device 1 to specify the blood flow velocity of the blood vessel to be observed, and the Doppler processing unit 205 may determine the frame rate and the bandwidth to be used according to the specified blood flow velocity. In this case, it is preferable that the distance the blood travels between frames is half or less of the transmission wavelength of the transmitted ultrasound. For example, under imaging conditions where the center frequency of the transmitted ultrasound is 10 MHz and the frame rate is 500 Hz, a blood vessel with a blood flow velocity of 100 m / s is the target of blood flow image generation. Let's consider the following scenario. In this case, the distance the blood travels between frames is 200 μm, and the center frequency of the low-frequency region to be extracted should be set to 3 MHz or less. Furthermore, if the blood flow to be observed has a slower velocity than in this example, the frame rate needs to be higher and the frequency band used needs to be set lower. In this case, the system control unit 109 controls the transmission frame rate of the transmitting electrical circuit 104 to a higher frame rate. Also, the Doppler processing unit 205 changes the filter settings to extract lower frequencies.

[0046] Next, in step S341, the Doppler processing unit 205 applies an MTI filter to the received signal of the low-frequency component extracted in step S340 to reduce the clutter component and extract the component derived from blood flow. Then, the Doppler processing unit 205 generates low-frequency blood flow images of multiple frames using the extracted blood flow component. Then, in step S342, the Doppler processing unit 205 extracts the local maximum value of the power value in each frame, similar to step S331. In this step, the Doppler processing unit 205 is a detection unit that detects the maximum value of the blood flow signal within a predetermined range of the second blood flow image.

[0047] Next, in step S343, the Doppler processing unit 205 calculates blood flow velocity and blood flow direction by tracking the local maximum values ​​extracted in step S342 between frames. A general particle tracking algorithm can be used to track the local maximum values ​​in this step. For example, the Doppler processing unit 205 performs a nearest neighbor search using the coordinates in the plane of the blood flow image for each local maximum value between adjacent frames, and calculates the distance and direction of movement of the local maximum value before and after movement. Then, the Doppler processing unit 205 calculates the blood flow velocity based on the calculated distance of movement and the time interval between frames. In this step, the Doppler processing unit 205 is a calculation unit that calculates the blood flow velocity and blood flow direction of the subject based on the positional information of the detected maximum values.

[0048] In this case, the range of the nearest neighbor search may be a pre-set range or may be determined according to the target blood flow velocity. Furthermore, the tracking target may not be limited to adjacent frames, but may be three or more frames. In addition, tracking may be performed using methods such as pattern matching based on cross-correlation calculations using multiple particles, rather than tracking a single particle in the image. When tracking particles, a mask may be applied to limit the search range to the blood flow region based on the power values ​​of the blood flow image.

[0049] The Doppler processing unit 205 performs the above tracking process on multiple frames of received signals, and tracks blood flow. The blood flow velocity and direction are calculated for each coordinate in the image. Here, the blood flow velocity and direction calculated for each local maximum value vary from position to position and from frame to frame in the image due to the influence of the blood flow velocity distribution within the blood vessel, peak tracking error, reconstruction pixel pitch, etc. Therefore, the blood flow velocity and direction may be calculated for each pixel containing the local maximum value, or values ​​based on statistical indicators such as the mean, mode, and median of pixels containing the local maximum value within a predetermined region may be calculated as the blood flow velocity and direction for that region. Alternatively, values ​​based on statistical indicators such as the mean, mode, and median across frames may be calculated as the blood flow velocity and direction for that region.

[0050] Here, we will explain why blood flow velocity and direction are calculated from low-frequency blood flow images. Figures 4A and 4B show examples of blood flow images generated in step S330 and low-frequency blood flow images generated in step S341. Compared to the blood flow image containing high-frequency components shown in Figure 4A, the low-frequency blood flow image shown in Figure 4B has lower spatial resolution and a coarser speckle pattern. Figures 5A and 5B also show examples of images in which local maximum values ​​are extracted from the blood flow image containing high-frequency components generated in step S332 and from the low-frequency blood flow image generated in step S342. In the images of Figure 5A and Figure 5B, it can be seen that the density of local maximum values ​​differs depending on the spatial resolution of the blood flow images and low-frequency blood flow images in Figures 4A and 4B, respectively. Furthermore, as shown in Figures 5A and 5B, it can be seen that the density of local maximum values ​​in the blood flow image containing high-frequency components is higher than that of the low-frequency blood flow image.

[0051] Figures 6A and 6B show an example of the movement of local maximum values ​​between adjacent frames. In Figures 6A and 6B, the local maximum value of the nth frame is shown as a white dot, and the local maximum value of the (n+1)th frame is shown as a black dot. It is also assumed that the frame rates in Figures 6A and 6B are the same. In this case, blood flow images containing high-frequency components have a higher density of local maximum values ​​than low-frequency blood flow images, and the distance between the local maximum value of interest and the local maximum values ​​surrounding it may be shorter than the distance moved between frames. As a result, the local maximum value detected by nearest neighbor search for the local maximum value of interest may be another local maximum value surrounding the local maximum value of interest, rather than the local maximum value of the local maximum value of interest after the movement. For this reason, blood flow velocity and blood flow direction may not be calculated correctly in blood flow images containing high-frequency components. On the other hand, in the low-frequency blood flow image shown in Figure 6B, the density of local maximum values ​​is low, so the local maximum value of interest can be correctly tracked without being confused with local maximum values ​​in its vicinity, and there is a higher probability that the blood flow velocity and blood flow direction for each pixel can be correctly calculated.

[0052] Furthermore, the accuracy of tracking local maximum values ​​using blood flow images depends on the density of local maximum values ​​within the blood flow image and the distance traveled between frames. Therefore, in this embodiment, it is desirable that the distance between adjacent local maximum values ​​within the same blood flow image is longer than the distance traveled between frames. The density of local maximum values ​​depends on the spatial frequency of the speckle pattern in the blood flow image. The distance traveled between frames of local maximum values ​​is determined by the blood flow velocity of the target blood flow and the frame rate of the blood flow image. In other words, in order to appropriately calculate the blood flow velocity and direction, it is desirable to increase the frame rate of the blood flow image or decrease the frequency of the received signal.

[0053] Here, the blood flow velocity v(x,y) at position (x,y) in the xy-plane, which consists of mutually orthogonal x and y axes in the blood flow image, can be calculated by the following equation (1). Here, dx is the distance the local maximum value moves in the x-axis direction between frames, dy is the distance the local maximum value moves in the y-axis direction between frames, and dt is the time interval between frames.

number

[0054] Furthermore, when the positive x-axis is defined as 0 degrees, the blood flow direction (blood flow angle) θ(x,y) can be calculated using the following equation (2).

number

[0055] Then, in step S350, the image processing unit 107 generates a super-resolution blood flow image showing blood flow velocity and direction using the super-resolution blood flow image generated in step S332 and the blood flow velocity and direction for each pixel calculated in step S343. In this step, the image processing unit 107 is a third image generation unit that generates a first blood flow image and a third blood flow image based on blood flow velocity and direction. In this step, the image processing unit 107 also colors the blood flow velocity and direction in the generated super-resolution blood flow image. For example, the image processing unit 107 selects pixels with power values ​​above a certain threshold from the super-resolution blood flow image and assigns hues to the selected pixels according to the blood flow velocity and direction calculated in step S343. The super-resolution blood flow image generated by the image processing unit 107 is displayed on the display unit 108. Furthermore, the display unit 108 may display the super-resolution blood flow image in any combination of B-mode image, super-resolution blood flow image, blood flow velocity, and blood flow direction in parallel, or switch between them. The image processing unit 107 may also generate a histogram showing the variation in blood flow velocity and blood flow direction, and the generated histogram may be displayed on the display unit 108. The image processing unit 107 may also generate the super-resolution blood flow image, blood flow velocity, and blood flow direction (vectors indicating the blood flow direction) as the third blood flow image, and the generated blood flow image may be displayed in parallel and / or superimposed on the display unit 108.

[0056] Furthermore, the image processing unit 107 can also generate a converted image converted to RGB using a two-dimensional color map of blood flow velocity in the super-resolution image and power values ​​in the super-resolution blood flow image. For example, the image processing unit 107 can generate a converted image using a two-dimensional color map in which blood flow velocity is assigned to hue and power values ​​in the super-resolution blood flow image are assigned to brightness. The image processing unit 107 can also determine the hue of the blood flow direction based on a circular gradient map that changes in the direction of rotation in the xy plane. Alternatively, the image processing unit 107 may determine the hue of the blood flow direction using a color map that changes one-dimensionally for any direction in the xy plane. For example, the image processing unit 107 can represent the direction to the right of the screen (positive x-axis direction) with reddish colors and the direction to the left (negative x-axis direction) with blued colors to indicate the difference in blood flow direction by hue. The image processing unit 107 may also determine the hue based on a two-dimensional color map corresponding to the flow velocity vector determined by the blood flow velocity and blood flow direction. For example, the image processing unit 107 can use a two-dimensional color map in which the blood flow direction is assigned to hue and the blood flow velocity is assigned to brightness.

[0057] Based on the above, the ultrasound diagnostic device 1 according to this embodiment can generate a super-resolution blood flow image that represents blood flow velocity and blood flow direction, calculated with greater accuracy than conventional technology, using the low-frequency component of the received signal obtained by transmitting and receiving ultrasound to and from the subject.

[0058] In this embodiment, the ultrasound diagnostic device 1 executes the processes in steps S330 to S332 and steps S340 to S343 in parallel, but the processes in steps S330 to S332 and steps S340 to S343 may be executed individually.

[0059] <Second Embodiment> Next, an ultrasound diagnostic apparatus according to the second embodiment will be described. In the following description, components and processes similar to those in the ultrasound diagnostic apparatus 1 according to the first embodiment will be denoted by the same reference numerals, and detailed explanations will be omitted.

[0060] The ultrasound diagnostic device 1 according to the first embodiment generates a super-resolution blood flow image by coloring the blood flow velocity and blood flow direction at each location of the local maximum value calculated from the low-frequency blood flow image. On the other hand, the ultrasound diagnostic device 1 according to the second embodiment displays the blood flow velocity and blood flow direction by integrating and plotting the trajectory of the local maximum value between frames.

[0061] The ultrasound diagnostic device 1 according to this embodiment performs the processing shown in the flowchart in Figure 3. However, in step S343 of this embodiment, the blood flow velocity and blood flow direction are calculated by a different process than in the first embodiment. In the first embodiment, the Doppler processing unit 205 calculates the blood flow velocity and blood flow direction using the coordinates of the local maximum value for each frame. On the other hand, in this embodiment, the Doppler processing unit 205 calculates the blood flow velocity and blood flow direction by accumulating the trajectory, which is formed by connecting the coordinates of the local maximum value before and after movement between frames with a straight line, over multiple frames. By calculating the blood flow velocity and blood flow direction by accumulating the trajectory in this way, the ultrasound diagnostic device 1 according to this embodiment can calculate the blood flow velocity and blood flow direction of blood vessels with fewer frames than when the coordinates are accumulated as in the first embodiment.

[0062] However, as shown in Figures 4A and 4B, low-frequency blood flow images have low spatial resolution, so in this embodiment, the spatial resolution of the image showing blood flow velocity, generated by integrating the trajectories of local maximum values ​​in the low-frequency blood flow images, is also low. Figure 7A shows the low-frequency blood flow image generated by the ultrasound diagnostic device 1 in this embodiment. Because low-frequency blood flow images have low spatial resolution, local maximum values ​​may occur outside the blood vessels. Therefore, as shown in Figure 7A, when the trajectories 721, 722, and 723 of local maximum values ​​outside the blood vessels are integrated, the blood vessel 720 in the low-frequency blood flow image is drawn thicker than the actual blood vessel diameter 710.

[0063] Figure 7B shows the super-resolution blood flow image 730 generated in step S332 in this embodiment. As shown in Figure 7B, the super-resolution blood flow image generated from a received signal containing high-frequency components has higher spatial resolution than the low-frequency blood flow image, and the blood vessel diameter depicted in the super-resolution blood flow image is theoretically the same as the actual blood vessel diameter 710. In the ultrasound diagnostic device 1 according to this embodiment, the super-resolution blood flow image in Figure 7B is used as a mask image for the low-frequency blood flow image in Figure 7A to generate the super-resolution blood flow image shown in Figure 7C.

[0064] As a specific example, the image processing unit 107 performs thresholding based on the power values ​​of the super-resolution blood flow image to generate a binary image in which each pixel is assigned a value of either "0" or "1". For example, the image processing unit 107 sets the pixel value to "0" for pixels with a power value less than the threshold, and the pixel value to "1" for pixels with a power value equal to or greater than the threshold. The image processing unit 107 applies the generated binary image to the low-frequency blood flow image to use it as a mask image for extracting vascular structures by excluding blood flow velocity and direction outside the vascular region. The image processing unit 107 assigns transparency corresponding to the pixel values ​​of "0" or "1" in the mask image and superimposes it with the low-frequency blood flow image to generate the super-resolution blood flow image 740 shown in Figure 7C. Note that the mask image used in this step does not have to be a binary image; for example, the power values ​​of the super-resolution blood flow image may be used as pixel values. Alternatively, the image processing unit 107 can assign transparency to the pixel values ​​of the mask image and increase the transparency of pixels with higher power values ​​to generate a blood flow image in which the vascular structure is more emphasized.

[0065] Based on the above, the ultrasound diagnostic device 1 according to this embodiment generates blood flow images in which the blood vessels of the subject are depicted with greater accuracy, allowing the user to more accurately understand the blood flow velocity and direction of the blood vessels.

[0066] <Third Embodiment> Next, an ultrasound diagnostic apparatus according to the third embodiment will be described. In the following description, components and processes similar to those in the ultrasound diagnostic apparatus 1 according to the first or second embodiment will be denoted by the same reference numerals, and detailed explanations will be omitted.

[0067] In the ultrasound diagnostic apparatus 1 according to the first embodiment, a blood flow image is generated by extracting low-frequency components from a received signal containing a data sequence of multiple frames in the time direction using a bandpass filter in order to calculate blood flow velocity and blood flow direction (steps S340, S341). On the other hand, the ultrasound diagnostic apparatus 1 according to this embodiment generates a low-frequency blood flow image using data acquired by ultrasound transmission and reception that is different from the ultrasound transmission and reception used to acquire data used to generate a high-frequency blood flow image. In this way, received signals acquired by different ultrasound transmission and reception are used to generate each blood flow image. As a result, the difference between the low-frequency blood flow image and the high-frequency blood flow image can be made larger compared to the case where low-frequency components are extracted from the same received signal as the received signal used to generate the high-frequency blood flow image.

[0068] Figure 8 shows an example of a flowchart of the process performed by the ultrasound diagnostic apparatus 1 according to this embodiment. In step S810, the system control unit 109 uses the ultrasound probe 102 to repeatedly transmit and receive ultrasound signals for generating low-frequency blood flow images and high-frequency blood flow images at the same position within the target area for which blood flow information is to be acquired, over multiple frames. As a result, the system control unit 109 acquires low-frequency received signals and high-frequency received signals containing data sequences of multiple frames in the time direction. In this step, the system control unit 109 may alternately transmit low-frequency signals and high-frequency signals one wave at a time or multiple waves at a time using the ultrasound probe 102. Furthermore, if the subject's body movement is large and positional displacement may occur in a short time, the system control unit 109 may alternately transmit low-frequency signals and high-frequency signals using the ultrasound probe 102 with as few waves as possible.

[0069] Next, in step S820, the correction unit 204 calculates the amount of tissue displacement between frames due to body movement, etc., from the received signal, which includes a data sequence of multiple frames, similar to step S320. Then, using the calculated displacement amount, the correction unit 204 moves the received signal relative to the reference frame to align the subject's tissue between frames. In this step, the correction unit 204 may perform independent alignment processing for the low-frequency image and the high-frequency image, or it may perform alignment in the low-frequency image based on the alignment result in the high-frequency image, which has higher spatial resolution.

[0070] Next, in step S830, the super-resolution processing unit 206 generates a high-frequency blood flow image from the high-frequency received signal, which includes a data sequence of multiple frames after alignment. Also, in step S840, the Doppler processing unit 205 generates a low-frequency blood flow image from the low-frequency received signal, which includes a data sequence of multiple frames after alignment. Steps S831, S832, S841, S842, and S850 are the same processes as steps S331, S332, S342, S343, and S350, respectively, so a detailed explanation is omitted here.

[0071] Figure 9 is a graph showing an example of the frequency band of the received signal acquired by transmitting and receiving ultrasound in this embodiment. In Figure 9, the horizontal axis is the frequency of the received signal, and the vertical axis is the power value of the received signal. The ultrasound diagnostic device 1 according to this embodiment acquires received signals in the low frequency band 920 and the high frequency band 930 within the frequency band of ultrasound that the ultrasound probe 102 can transmit and receive (dashed line: 910) by separate transmission / reception and band filtering processing. Furthermore, the ultrasound diagnostic device 1 prevents the generation of unwanted artifacts in the generated blood flow image. Therefore, it is preferable to make the ratio bandwidth of the high-frequency bandwidth 930 and the low-frequency bandwidth 920 approximately the same in the figure.

[0072] In this embodiment, the ultrasound diagnostic device 1 executes the processes in steps S830 to S832 and steps S840 to S842 in parallel, but the processes in steps S830 to S832 and steps S840 to S842 may be executed individually.

[0073] <Fourth Embodiment> Next, an ultrasound diagnostic apparatus according to the fourth embodiment will be described. In the following description, the same reference numerals are used for components and processes as in the ultrasound diagnostic apparatus 1 according to the first to third embodiments, and detailed explanations are omitted.

[0074] In the first to third embodiments, we assume the generation of super-resolution blood flow images showing blood flow velocity and direction in a two-dimensional image. On the other hand, the ultrasound diagnostic device 1 according to this embodiment generates super-resolution blood flow images showing blood flow velocity and direction in three dimensions.

[0075] In this embodiment, an ultrasonic probe 102, which is a two-dimensional probe, is used to repeatedly transmit and receive ultrasound signals at the same location so as to include the target area for which blood flow information is to be acquired. In this embodiment, the ultrasonic diagnostic device 1 executes the process shown in the flowchart in Figure 3 or Figure 8. A detailed explanation of the process for each step is omitted here.

[0076] The received signal processing unit 106 generates a received signal containing a data sequence of multiple frames in the time direction. The Doppler processing unit 205 then generates three-dimensional blood flow data using the acquired received signal and extracts three-dimensional local maximum values ​​across multiple frames. The super-resolution processing unit 206 then generates three-dimensional super-resolution blood flow data by integrating the three-dimensional local maximum values. The Doppler processing unit 205 also generates three-dimensional low-frequency blood flow data using the low-frequency component of the received signal and generates three-dimensional low-frequency local maximum value data. The Doppler processing unit 205 then calculates three-dimensional blood flow velocity and blood flow direction by tracking the low-frequency local maximum values ​​using three-dimensional coordinates between frames. The image processing unit 107 then performs rendering processing on the three-dimensional super-resolution blood flow data and the three-dimensional blood flow velocity and blood flow direction data to generate various two-dimensional image data for display on the display unit 108.

[0077] Therefore, the ultrasound diagnostic device 1 according to this embodiment can generate a super-resolution blood flow image showing three-dimensional blood flow velocity and blood flow direction by applying the above process to the flowchart shown in Figure 3 or Figure 8.

[0078] <Other Embodiments> Furthermore, the disclosed technology can take the form of, for example, a system, apparatus, method, program, or recording medium (storage medium). Specifically, it may be applied to a system consisting of multiple devices (for example, a host computer, interface devices, imaging devices, web applications, etc.), or to an apparatus consisting of a single device.

[0079] Furthermore, it goes without saying that the object of the present invention is achieved as follows: a recording medium (or storage medium) containing program code (computer program) of software that realizes the functions of the embodiments described above is supplied to a system or device. Such a recording medium is, needless to say, a computer-readable recording medium. The computer (or CPU or MPU) of the system or device then reads and executes the program code stored on the recording medium. In this case, the recording medium containing the program code read from the recording medium constitutes the present invention.

[0080] In the above embodiment, the various controls described as being performed by the system control unit 109 may be performed by one piece of hardware (e.g., a processor or circuit), or not. Multiple pieces of hardware (e.g., multiple processors, multiple circuits, or a combination of one or more processors and one or more circuits) may share the processing to control the entire device.

[0081] Furthermore, the above-mentioned processors are processors in a broad sense, and include general-purpose processors and dedicated processors. General-purpose processors include, for example, CPUs (Central Processing Units) and MP3s. These include U (Micro Processing Unit) and DSP (Digital Signal Processor). Examples of such processors include GPUs (Graphics Processing Units). Also, dedicated processors include ASICs (Application Specific Integrated Circuits) and P Examples include LDs (Programmable Logic Devices). Programmable logic devices are, for example... Examples include FPGAs (Field Programmable Gate Arrays) and CPLDs (Complex Programmable Logic Devices).

[0082] Furthermore, while embodiments and modifications of the present invention have been described in detail, the present invention is not limited to these specific embodiments, and various forms that do not depart from the spirit of the invention are also included in the present invention. Moreover, the above embodiments and modifications merely illustrate one embodiment of the present invention, and it is possible to combine the above embodiments and modifications as appropriate.

[0083] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit that implements one or more functions.

[0084] This embodiment includes the following configurations, methods, and programs. (Composition 1) An ultrasonic transmitting and receiving unit that transmits and receives ultrasound to and from a subject, A data acquisition unit that acquires data of the reflected waves from the subject due to the transmission and reception of the aforementioned ultrasound over multiple frames, A first image generation unit generates a first blood flow image showing the blood flow of the subject using the data of the multiple frames acquired by the data acquisition unit, A second image generation unit generates a second blood flow image that includes components with lower spatial frequencies than the first blood flow image, using the data of the multiple frames acquired by the data acquisition unit. A detection unit for detecting the maximum value of the blood flow signal within a predetermined range of the second blood flow image, A calculation unit calculates the blood flow velocity and blood flow direction of the subject based on the position information of the maximum value detected by the detection unit, A third image generation unit generates a third blood flow image based on the first blood flow image, the blood flow velocity, and the blood flow direction, An ultrasound diagnostic device characterized by having the following features. (Configuration 2) The first image generation unit is, The data acquisition unit reduces the clutter component related to the blood flow of the subject, which is included in the data of the multiple frames acquired by the data acquisition unit. Using the data with reduced clutter components, a fourth blood flow image showing the blood flow of the subject is generated. The maximum value of the blood flow signal within a predetermined range of the fourth blood flow image is detected. The first blood flow image is generated by integrating the detected maximum values. The ultrasound diagnostic apparatus according to configuration 1, characterized by the features described above. (Composition 3) The ultrasound diagnostic apparatus according to configuration 1 or 2, characterized in that the second image generation unit generates the second blood flow image using the low-frequency components of the data of the plurality of frames acquired by the data acquisition unit. (Composition 4) The ultrasound diagnostic apparatus according to any one of configurations 1 to 3, characterized in that the second image generation unit generates a second blood flow image using data acquired by the data acquisition unit through ultrasound transmission and reception different from that used to acquire the data used to generate the first blood flow image. (Composition 5) The ultrasound diagnostic apparatus according to any one of configurations 1 to 4, characterized in that the data acquisition unit calculates the amount of displacement of the subject's tissue included in the reflected wave data, and acquires the data obtained by aligning the tissue with the reflected wave data using the calculated amount of displacement as the data for the multiple frames. (Composition 6) The system further includes a reception unit that accepts the user's specification of the blood flow velocity of the subject, The ultrasound diagnostic apparatus according to any one of configurations 1 to 5, characterized in that the second image generation unit generates the second blood flow image based on the frame rate and bandwidth determined according to the flow velocity received by the reception unit. (Composition 7) The ultrasound diagnostic apparatus according to configuration 6, characterized in that the second image generation unit determines the frame rate such that the distance the blood travels between frames, as indicated by the flow velocity, is less than or equal to half the transmission wavelength of the ultrasound. (Composition 8) The ultrasound diagnostic apparatus according to any one of configurations 1 to 7, characterized in that the third image generation unit generates a third blood flow image by coloring the blood flow velocity and the blood flow direction according to the position of the maximum value detected by the detection unit. (Composition 9) The ultrasound diagnostic apparatus according to any one of configurations 1 to 8, characterized in that the third image generation unit generates the third blood flow image by integrating the trajectories connecting the maximum values ​​detected by the detection unit over the multiple frames. (Composition 10) The ultrasound diagnostic apparatus according to any one of configurations 1 to 9, characterized in that the third image generation unit generates the third blood flow image by excluding the blood flow velocity and blood flow direction outside the vascular region shown in the first blood flow image. (Method 1) An ultrasonic transmission and reception step in which ultrasound is transmitted and received to a subject, A data acquisition step of acquiring data of the reflected waves from the subject due to the transmission and reception of the ultrasound over multiple frames, A first image generation step involves generating a first blood flow image showing the blood flow of the subject using the data of the multiple frames acquired in the data acquisition step, A second image generation step involves generating a second blood flow image that includes components with lower spatial frequencies than the first blood flow image, using the data of the multiple frames acquired in the data acquisition step. A detection step of detecting the maximum value of the blood flow signal within a predetermined range of the second blood flow image, A calculation step which calculates the blood flow velocity and blood flow direction of the subject based on the position information of the maximum value detected in the detection step, A third blood flow image is generated based on the first blood flow image, the blood flow velocity, and the blood flow direction. The third image generation step, A control method for an ultrasound diagnostic apparatus, characterized by including the following: (program) A program for causing a computer to perform each step of the control method for an ultrasound diagnostic apparatus described in Method 1. [Explanation of symbols]

[0085] 1 Ultrasound diagnostic device, 102 Ultrasound probe, 106 Received signal processing unit, 107 Image processing unit, 205 Doppler processing unit, 206 Super-resolution processing unit

Claims

1. An ultrasonic transmitting and receiving unit that transmits and receives ultrasound to and from a subject, A data acquisition unit that acquires data of the reflected waves from the subject due to the transmission and reception of the aforementioned ultrasound over multiple frames, A first image generation unit generates a first blood flow image showing the blood flow of the subject using the data of the multiple frames acquired by the data acquisition unit, A second image generation unit generates a second blood flow image that includes components with lower spatial frequencies than the first blood flow image, using the data of the multiple frames acquired by the data acquisition unit. A detection unit for detecting the maximum value of the blood flow signal within a predetermined range of the second blood flow image, A calculation unit calculates the blood flow velocity and blood flow direction of the subject based on the position information of the maximum value detected by the detection unit, A third image generation unit generates a third blood flow image based on the first blood flow image, the blood flow velocity, and the blood flow direction, An ultrasound diagnostic device characterized by having the following features.

2. The first image generation unit is, The data acquisition unit reduces the clutter component related to the blood flow of the subject, which is included in the data of the multiple frames acquired by the data acquisition unit. Using the data with reduced clutter components, a fourth blood flow image showing the blood flow of the subject is generated. The maximum value of the blood flow signal within a predetermined range of the fourth blood flow image is detected. The first blood flow image is generated by integrating the detected maximum values. The ultrasound diagnostic apparatus according to feature 1.

3. The ultrasound diagnostic apparatus according to claim 1, characterized in that the second image generation unit generates the second blood flow image using the low-frequency components of the data of the plurality of frames acquired by the data acquisition unit.

4. The ultrasound diagnostic apparatus according to claim 1, characterized in that the second image generation unit generates a second blood flow image using data acquired by the data acquisition unit through ultrasound transmission and reception that is different from the ultrasound transmission and reception used to acquire the data used to generate the first blood flow image.

5. The ultrasound diagnostic apparatus according to claim 1, characterized in that the data acquisition unit calculates the amount of displacement of the subject's tissue included in the reflected wave data, and acquires the data obtained by aligning the tissue with the reflected wave data using the calculated amount of displacement as the data for the multiple frames.

6. The system further includes a reception unit that accepts the user's specification of the blood flow velocity of the subject, The ultrasound diagnostic apparatus according to claim 1, characterized in that the second image generation unit generates the second blood flow image based on the frame rate and bandwidth determined according to the flow velocity received by the reception unit.

7. The ultrasound diagnostic apparatus according to claim 6, characterized in that the second image generation unit determines the frame rate such that the distance the blood travels between frames, as indicated by the flow velocity, is less than or equal to half the transmission wavelength of the ultrasound.

8. The third image generation unit, according to the position of the maximum value detected by the detection unit, The ultrasound diagnostic apparatus according to claim 1, characterized in that it generates a third blood flow image by coloring the recorded blood flow velocity and the blood flow direction.

9. The ultrasound diagnostic apparatus according to claim 1, characterized in that the third image generation unit generates the third blood flow image by integrating the trajectories connecting the maximum values ​​detected by the detection unit over the multiple frames.

10. The ultrasound diagnostic apparatus according to claim 1, characterized in that the third image generation unit generates the third blood flow image by excluding the blood flow velocity and blood flow direction outside the vascular region shown in the first blood flow image.

11. An ultrasonic transmission and reception step in which ultrasound is transmitted and received to a subject, A data acquisition step of acquiring data of the reflected waves from the subject due to the transmission and reception of the ultrasound over multiple frames, A first image generation step involves generating a first blood flow image showing the blood flow of the subject using the data of the multiple frames acquired in the data acquisition step, A second image generation step involves generating a second blood flow image that includes components with lower spatial frequencies than the first blood flow image, using the data of the multiple frames acquired in the data acquisition step. A detection step of detecting the maximum value of the blood flow signal within a predetermined range of the second blood flow image, A calculation step which calculates the blood flow velocity and blood flow direction of the subject based on the position information of the maximum value detected in the detection step, A third image generation step that generates a third blood flow image based on the first blood flow image, the blood flow velocity, and the blood flow direction, A control method for an ultrasound diagnostic apparatus, characterized by including the following:

12. A program for causing a computer to perform each step of the control method for an ultrasound diagnostic apparatus described in claim 11.

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