Ultrasound diagnostic device and beam forming method

Abstract

To acquire good sound pressure distribution in a region of interest while avoiding excessive concentration of acoustic energy in a living body when forming a transmission beam.SOLUTION: A region of interest 54 is set in a living body. A plurality of transmission beams 62 and 64 are formed along a transmission center axis simultaneously so that a plurality of transmission focal points F1 and F2 are formed at a plurality of positions shallower than the region of interest 54 on the transmission center axis. A composite transmission beam 66 is generated in the living body. A reception beam set 69 is formed after the composite transmission beam 66 is formed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an ultrasound diagnostic apparatus and a beamforming method, and in particular to transmission beamforming. [Background technology]

[0002] Observing blood flow is useful for diagnosing and treating cardiovascular diseases, and for this reason, ultrasound diagnostic devices are widely used in the medical field.

[0003] Color Doppler is a well-known method for observing blood flow using an ultrasound diagnostic device. Color Doppler measures the movement of moving acoustic scatterers (mainly red blood cells) by utilizing the Doppler effect that occurs when ultrasound waves are reflected by these objects. Typically, color Doppler calculates velocity distribution based on frame data obtained from a two-dimensional data acquisition region within a living body. Recently, three-dimensional color Doppler, which applies color Doppler to volume data obtained from a three-dimensional data acquisition region within a living body, has become popular.

[0004] When performing color Doppler imaging, it is necessary to ensure a data acquisition rate (frame rate or volume rate) above a certain value. For example, in three-dimensional color Doppler imaging, if the volume rate is low, such as 5 to 6 Hz, it becomes impossible to accurately observe temporal changes in blood flow. Reducing the number of transmission beams formed when acquiring one frame of data or one volume of data, i.e., reducing the transmission beam density, can improve the frame rate or volume rate, but this will result in a deterioration in the image quality of the color Doppler image.

[0005] The parallel reception method is a method of simultaneously forming multiple spatially aligned receive beams for one transmit beam. In other words, it is a method of acquiring a receive beam set with one transmit / receive operation. By using the parallel reception method, it is possible to increase the receive beam density even in situations where the transmit beam density cannot be increased due to frame rate or volume rate constraints.

[0006] When forming ultrasound images such as color Doppler images using the parallel reception method, block artifacts are likely to occur. Because sound pressure decreases depending on the distance in the beam scanning direction from the central axis of the transmit beam (transmission central axis), sound pressure differences tend to occur between receive beams within each receive beam set, and sound pressure differences tend to occur between two adjacent receive beam sets. These factors cause the block artifacts. Block artifacts are particularly noticeable when the transmit beam density is reduced and the spread (half-width) of the transmit beam in the beam scanning direction is narrow, resulting in low sound pressure areas (e.g., areas located outside the half-width) in the receive beam set.

[0007] One method for suppressing block artifacts is to form a transmit beam with a focal point (single focus) shallower than the user-specified region of interest (ROI). Such a transmit beam can be called a near-focus wide beam. The near-focus wide beam has a diffuse portion located deeper than the focal point. This diffuse portion passes through the ROI. Because the diffuse portion has a relatively large half-width, block artifacts are less likely to occur when parallel reception is performed.

[0008] On the other hand, when forming a transmit beam, it is necessary to satisfy the mechanical index (MI) and thermal index (TI) conditions from the viewpoint of biological safety. That is, it is necessary to limit the transmit power sent into the living body so that the MI and TI conditions are satisfied. When forming a near-focal wide beam, the acoustic pressure in its diffused portion is likely to be insufficient. To increase the acoustic pressure in the diffused portion, it is necessary to increase the transmit power, but doing so increases the acoustic energy concentrated at the focal point, and the MI and TI conditions are no longer satisfied. When using a near-focal wide beam with a single focal point, it is difficult to increase the acoustic pressure in its diffused portion.

[0009] Patent Document 1 discloses a technique for forming a transmission beam. In this technique, two delay time curves are weighted and added. Patent Document 1 does not disclose a technique for synthesizing multiple transmission beams in a living body.

[0010] 6 of Patent Document 2 shows that two transmit apertures are set on the transducer array, and two transmit focal points are set at the proximal and distal ends of the focus area (FA), and two transmit beams are simultaneously formed. Patent Document 2 does not describe setting a transmit focal point at a position shallower than the region of interest, or utilizing the divergent portion of the transmit beam. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-175038 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-192709 Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present disclosure is to form a transmit beam with an appropriate spread within a region of interest, or to obtain a good sound pressure distribution within a region of interest while avoiding excessive acoustic energy concentration within a living body. [Means for solving the problem]

[0013] The ultrasound diagnostic apparatus according to the present disclosure includes a transducer array and a control unit that controls the operation of the transducer array, and controls the operation of the transducer array to generate a signal on a central transmission axis. , a two-dimensional or three-dimensional blood flow observation region having a diverging shape. a plurality of transmit beams are simultaneously formed along the transmit central axis so that a plurality of transmit foci are formed at a plurality of positions shallower than the region of interest, and a composite transmit beam is generated in the living body by the simultaneous formation of the plurality of transmit beams; After generating the composite transmit beam, a receive beam set consisting of a plurality of receive beams is formed according to a parallel receive method, and transmission and reception consisting of generating the composite transmit beam and forming the receive beam set is repeated n times for each azimuth (where n is an integer of 2 or more), and a blood flow image representing blood flow within the region of interest is formed based on the n receive beam data sets for each azimuth obtained thereby.It is characterized by:

[0014] The beam forming method according to the present disclosure is , a two-dimensional or three-dimensional blood flow observation region having a diverging shape. A step of setting a region of interest, a step of setting transmission conditions for forming the plurality of transmission beams along the transmission central axis so that a plurality of transmission focal points are formed at a plurality of positions shallower than the region of interest on the transmission central axis, a step of simultaneously forming the plurality of transmission beams according to the transmission conditions, thereby generating a composite transmission beam in a living body, and Generate later According to the parallel reception method Multiple receive beams A receive beam set consisting of forming a and repeating the transmission and reception consisting of generating the composite transmission beam and forming the reception beam set n times for each direction (where n is an integer of 2 or more), and forming a blood flow image representing blood flow within the region of interest based on the n reception beam data sets for each direction obtained thereby. It is characterized by: [Effects of the Invention]

[0015] According to the present disclosure, a transmit beam with an appropriate spread can be formed within a region of interest, or a good sound pressure distribution can be obtained within a region of interest while avoiding excessive acoustic energy concentration within a living body. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram showing an ultrasound diagnostic apparatus according to an embodiment. [Figure 2] 10A and 10B are diagrams illustrating transmission and reception operations in a CFM mode. [Figure 3] FIG. 1 is a diagram showing a single-focus transmission beam and its sound pressure distribution. [Figure 4] FIG. 2 is a diagram illustrating a first example of a composite transmission beam according to the embodiment. [Figure 5] FIG. 1 is a diagram illustrating a first comparative example. [Figure 6] FIG. 10 is a diagram illustrating a second comparative example. [Figure 7] FIG. 10 is a diagram illustrating a third comparative example. [Figure 8] FIG. 10 is a diagram illustrating a second example of a composite transmit beam according to the embodiment. [Figure 9] FIG. 10 illustrates multiple focal depth combinations. [Figure 10]FIG. 10 is a diagram showing a first display example. [Figure 11] FIG. 10 is a diagram showing a second display example. [Figure 12] 10 is a flowchart showing an example of operation. [Figure 13] FIG. 10 is a diagram illustrating a third example of a composite transmission beam according to an embodiment. [Figure 14] FIG. 1 illustrates two-dimensional scanning of a composite transmit beam. [Figure 15] FIG. 2 is a diagram showing a first example of a transmit aperture pattern. [Figure 16] FIG. 10 is a diagram showing a second example of a transmit aperture pattern. [Figure 17] FIG. 10 is a diagram showing a third example of a transmit aperture pattern. [Figure 18] 1 is a flowchart illustrating a composite transmit beam design method. [Figure 19] FIG. 10 is a diagram illustrating a target condition. [Figure 20] FIG. 10 is a diagram illustrating a plurality of transmission conditions. [Figure 21] FIG. 10 is a diagram showing evaluation results of a plurality of transmission conditions. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment will be described with reference to the drawings.

[0018] (1) Overview of the embodiment An ultrasound diagnostic apparatus according to an embodiment includes a transducer array and a controller that controls the operation of the transducer array. By controlling the operation of the transducer array, multiple transmit beams are simultaneously formed along a central transmit axis such that multiple transmit focal points are formed at multiple positions shallower than a region of interest on the central transmit axis. The simultaneous formation of multiple transmit beams generates a composite transmit beam within a living body.

[0019] According to the above configuration, multiple transmit focal points are formed in a single transmission, preventing acoustic energy from concentrating at one location within the living body. This allows for increased transmit power, resulting in increased sound pressure within the diffusion area. Furthermore, the beam width of the composite transmit beam can be widened within the region of interest, while at the same time achieving a favorable sound pressure distribution within the region of interest. Therefore, block artifacts are less likely to occur when performing parallel reception. The above configuration also offers the advantage of being able to relatively easily change the shape of the composite transmit beam by individually changing the conditions for forming multiple transmit beams.

[0020] The depths of the multiple transmission foci may be fixedly determined, or the depths of the multiple foci may be adaptively determined based on the depth of the region of interest (particularly the depth of its upper side or upper surface).

[0021] In embodiments, the portion of the composite transmit beam deeper than the multiple focal points is a diffuse portion. The diffuse portion passes through the region of interest. The diffuse portion has a two-dimensional or three-dimensional divergent form.

[0022] In an embodiment, the control unit sets a plurality of transmit apertures on the transducer element array. A plurality of transmit beams are simultaneously formed by the plurality of transmit apertures. In an embodiment, the plurality of transmit apertures includes an inner transmit aperture and an outer transmit aperture set outside the inner transmit aperture.

[0023] In an embodiment, the multiple transmit beams include a first transmit beam formed by the inner transmit aperture and a second transmit beam formed by the outer transmit aperture. The multiple transmit foci include a first transmit focus of the first transmit beam and a second transmit focus of the second transmit beam. The first transmit focus is a near focus, and the second transmit focus is a far focus that occurs at a position deeper than the near focus. Alternatively, the first transmit focus is a far focus, and the second transmit focus is a near focus that occurs at a position shallower than the far focus.

[0024] A diffused portion with a moderate spread can be formed by setting the first transmission focus formed by the inner transmission aperture as a near focus and the second transmission focus formed by the outer transmission aperture as a far focus.On the other hand, a diffused portion with a large spread can be formed by setting the first transmission focus formed by the inner transmission aperture as a far focus and the second transmission focus formed by the outer transmission aperture as a near focus.

[0025] By adjusting the conditions for forming the first and second transmission beams, particularly by adjusting the positions of the first and second transmission foci, the sound pressure distribution in the diffused area and the beam width can be freely controlled. In order to suppress phase disturbance of the transmission waves reaching each observation point, it is best not to make the distance between the first and second transmission foci excessively large.

[0026] In embodiments, the region of interest is a three-dimensional region of interest. The transducer element array is a two-dimensional transducer element array. The inner transmit aperture is a two-dimensional transmit aperture. The outer transmit aperture is a two-dimensional transmit aperture surrounding the inner transmit aperture. Each transmit beam is a three-dimensional transmit beam. The composite transmit beam is a three-dimensional composite transmit beam.

[0027] According to the above configuration, the beam width of the diffused portion of the composite transmit beam (specifically, the half-width in the first electronic scanning direction and the half-width in the second electronic scanning direction) can be increased, so that the block-shaped artifacts described above are less likely to occur when parallel reception is performed. The three-dimensional transmit beam is a transmit beam formed by applying electronic focusing technology in both the first electronic scanning direction and the second electronic scanning direction. The half-width is usually defined as the width between two points that are -6 dB down from the peak on either side of the peak in the sound pressure distribution.

[0028] In an embodiment, the control unit controls the formation of multiple transmit beams according to a specific composite transmit beamforming condition selected from multiple composite transmit beamforming conditions. Switching between the specific composite transmit beamforming conditions changes the sound pressure distribution in the composite transmit beam in the region of interest. The change in sound pressure distribution includes a change in the beamwidth of the composite transmit beam. For example, the specific composite beamforming condition is selected automatically or manually depending on the depth of the region of interest, the transmit beam density, etc.

[0029] In an embodiment, each composite transmit beamforming condition has a depth combination of a plurality of transmit focal depths, and the depth combinations of the plurality of transmit beamforming conditions are different from each other.

[0030] In an embodiment, the transducer array non-simultaneously forms a single-focus transmit beam and a composite transmit beam. The single-focus transmit beam is a transmit beam for acquiring tissue structure information. The composite transmit beam is a transmit beam for acquiring tissue motion information. After the composite transmit beam is formed, multiple receive beams are simultaneously formed to acquire tissue motion information. This configuration allows the acquisition of tissue structure information and tissue motion information while selectively using two types of transmit beams.

[0031] In an embodiment, the control unit individually sets the transmit focal depth of the monofocal transmit beam and the multiple transmit focal depths of the composite transmit beam. The ultrasound diagnostic apparatus according to the embodiment includes a generation unit that generates an image for a user to set the transmit focal depth of the monofocal transmit beam and the multiple transmit focal depths of the composite transmit beam. The display processing unit, which will be described later, corresponds to the generation unit.

[0032] A beam forming method according to an embodiment includes a region of interest setting step, a transmission condition setting step, a transmission step, and a reception step. In the region of interest setting step, a region of interest is set within a living body. In the transmission condition setting step, transmission conditions are set for forming multiple transmission beams along the transmission central axis so that multiple transmission focal points are formed at multiple positions shallower than the region of interest on the transmission central axis. In the transmission step, multiple transmission beams are formed simultaneously in accordance with the transmission conditions. This results in a composite transmission beam within the living body. In the reception step, multiple reception beams are formed simultaneously after the composite transmission beam is formed.

[0033] According to the above method, it is possible to generate a good sound pressure distribution within a region of interest while avoiding concentration of acoustic energy at one point within a living body, thereby improving the quality of an image representing the region of interest.

[0034] (2) Details of the embodiment An ultrasonic diagnostic apparatus according to an embodiment is shown in Figure 1. This ultrasonic diagnostic apparatus is a medical apparatus for performing ultrasonic examinations in medical institutions.

[0035] The probe 10 has a transducer array 12 consisting of a plurality of transducer elements arranged in a linear or curved line. The transmitting and receiving surface of the probe 10 is placed in contact with the surface of a living body 14, and in this state, ultrasonic waves are transmitted into the living body 14, and reflected waves generated within the living body 14 are received.

[0036] Specifically, an ultrasonic beam is formed by the transducer array 12, and a scanning plane is formed by electronically scanning the ultrasonic beam. In Fig. 1, the r direction is the depth direction, and the θ direction is the electronic scanning direction. Known electronic scanning methods include electronic sector scanning and electronic linear scanning.

[0037] The ultrasound diagnostic apparatus according to the embodiment has a color flow mapping (CFM) mode. The CFM mode is also called a color Doppler mode. In the CFM mode, a first beam scanning plane for observing tissue structures and a second beam scanning plane for observing blood flow information are formed. In FIG. 1, reference numeral 16 indicates the second beam scanning plane. For example, multiple transmissions and receptions for forming the first beam scanning plane and multiple transmissions and receptions for forming the second beam scanning plane are performed according to a predetermined time-division sequence.

[0038] When forming the first beam scanning plane, a transmit beam and a receive beam are formed sequentially for each azimuth. In practice, multiple receive beams (receive beam sets) are simultaneously formed for each transmit beam according to the parallel reception method. The transmit beam has a single transmit focus, as in the conventional method.

[0039] On the other hand, when forming the second scan plane 16, a composite transmit beam 22 is formed for each azimuth, and then a receive beam set is formed according to the parallel receive method. In practice, by simultaneously forming a transmit beam having a near focus Fa and a transmit beam having a far focus Fb, the first transmit beam and the second transmit beam are acoustically combined within the living body 14, thereby generating the composite transmit beam 22.

[0040] As will be described in detail later, both the near focus Fa and the far focus Fb are set on the transmission central axis 20 on the near side (probe 10 side) of a region of interest (ROI) 18. A diffused portion of the composite transmission beam 22 passes through the region of interest 18. The region of interest 18 is a blood flow observation region set by a user (doctor, medical technician, etc.) who is an examiner.

[0041] In the illustrated example, the region of interest 18 is a two-dimensional region having a fan or trapezoidal shape. Typically, a transmit beam for observing blood flow information, i.e., a composite transmit beam 22, is electronically scanned within the width of the region of interest 18 in the electronic scanning direction, and a receive beam array for observing blood flow information is also formed within that width.

[0042] When performing three-dimensional color Doppler, a probe having a two-dimensional transducer element array is used. The two-dimensional transducer element array is composed of a plurality of transducer elements arranged in a first direction and a second direction. As described above, two transmit beams are simultaneously formed by the two-dimensional transducer element array, resulting in a composite transmit beam in the living body. The composite transmit beam is scanned in a first electronic scanning direction and a second electronic scanning direction. An electronic circuit for sub-beam forming may be provided in the probe together with the two-dimensional transducer element array. In this case, the electronic circuit may function as the transmitter 24 described below.

[0043] The transmitter 24 is an electronic circuit that supplies multiple transmission signals in parallel to the transducer array 12 during transmission and functions as a transmission beamformer. The receiver 26 is an electronic circuit that forms a reception beam by applying phasing and summation to multiple reception signals output in parallel from the transducer array 12 during reception and functions as a reception beamformer. The receiver 26 generates multiple reception beam data in parallel according to the parallel reception method. The receiver 26 includes multiple amplifiers, multiple A / D converters, a memory, an adder, etc.

[0044] The plurality of receive beam data obtained by forming the first scan plane is sent to the tissue image forming unit 28. The plurality of receive beam data obtained by forming the second scan plane 16 is sent to the blood flow image forming unit 30.

[0045] The tissue image forming unit 28 forms a tomographic image (B-mode tomographic image) representing a tissue structure based on the plurality of receive beam data obtained by forming the first scanning plane. The tissue image forming unit 28 includes a beam data processing unit, a digital scan converter (DSC), and the like. A three-dimensional tissue image may be generated in the tissue image forming unit 28. In this case, the tissue image forming unit 28 is supplied with the plurality of receive beam data (first volume data) acquired from a three-dimensional data acquisition region within the living body.

[0046] The blood flow image forming unit 30 forms a blood flow image (color Doppler image) that represents the movement of blood flow based on the multiple received beam data obtained by forming the second scanning plane 16. The blood flow image is, for example, an image that represents velocity distribution or an image that represents power distribution. An image that represents velocity distribution and velocity variance distribution may also be formed. An image that represents soft tissue movement may also be formed instead of a blood flow image.

[0047] The blood flow image forming unit 30 includes a clutter filter, an autocorrelator, a velocity calculator, a DSC, etc. A three-dimensional blood flow image may be generated in the blood flow image forming unit 30. In this case, a plurality of receive beam data (second volume data) acquired from a three-dimensional data acquisition region in a living body is supplied to the blood flow image forming unit 30.

[0048] The display processing unit 32 has an image generation function, a color calculation function, an image synthesis function, etc. In CFM mode, the display processing unit 32 synthesizes a tissue image and a blood flow image to generate a CFM image. Generally, the tissue image is a black and white image, and the blood flow image is a color image. The display processing unit 32 functions as a generation unit that generates an image for selecting composite beam forming conditions, and as a generation unit that generates graphics, which will be described later.

[0049] An ultrasound image is displayed on the display 33. In the CFM mode, a CFM image is displayed on the display 33. The display 33 is configured with an organic EL display device, an LCD, or the like. A three-dimensional CFM image generated based on the three-dimensional tissue image and the three-dimensional blood flow image may be displayed on the display 33.

[0050] The control unit 34 controls the operation of each element shown in Fig. 1. The control unit 34 has a transmission / reception control function. In Fig. 1, this function is represented as a transmission / reception control unit 36. The transmission / reception control unit 36 ​​controls the formation of transmission beams and reception beams through control of the transmitter 24 and receiver 26, that is, through control of the operation of the transducer element array 12.

[0051] In the embodiment, in the CFM mode, when blood flow information is acquired, two independent transmit apertures are set for the transducer element array 12 under the control of the transmission / reception control unit 36, and a first transmit beam and a second transmit beam are simultaneously formed using these apertures. This generates a composite transmit beam within the living body 14. A composite transmit beam may also be formed when forming a tissue image.

[0052] The control unit 34 is configured by a processor that executes a program. The processor is configured by, for example, a CPU (Central Processing Unit). The information processing unit 40 including the control unit 34 and the like may be configured by a single processor or multiple processors. Known processors include an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), and a GPU (Graphics Processing Unit).

[0053] An operation panel 38 is connected to the control unit 34. The operation panel 38 has a plurality of switches, a plurality of knobs, a trackball, a keyboard, etc. In the embodiment, a user uses the operation panel 38 to set a region of interest and to set or select composite beam forming conditions.

[0054] 2 shows the transmission and reception operation in CFM mode. A first scanning plane 42 is formed by repeating transmission and reception for each direction. Specifically, a transmission beam 44 is formed for each direction, followed by parallel reception. A tissue image (B-mode tomographic image) 42A is formed based on the frame data obtained from the first scanning plane 42.

[0055] The second scanning plane 46 is also formed by repeating transmission and reception for each direction. However, transmission and reception are repeated n times for each direction. n is an integer equal to or greater than 2, for example, 4 to 16. All numerical values ​​described in this specification are examples. In the embodiment, a composite transmission beam 47 is formed in each transmission and reception for acquiring blood flow information, followed by parallel reception.

[0056] In practice, transmission and reception are repeated for each direction within the width of a region of interest 48 set by the user. The region of interest 48 is a sector-shaped or trapezoidal region, with the upper side of the region of interest 48 at a depth r1 and the lower side at a depth r2. In the electronic scanning direction, the region of interest 48 has a width from θ1 to θ2. The region of interest 48 corresponds to a blood flow observation area or a blood flow image display area. A blood flow image 46A is formed based on frame data (specifically, Doppler information) obtained from the second scanning plane 46.

[0057] A CFM image 50 is generated by superimposing the blood flow image 46A on the tissue image 42A. Reference numeral 48A denotes a region of interest. The CFM image 50 is a real-time moving image that represents, for example, the movement of the heart and the movement of blood flow inside the heart.

[0058] 3 shows a transmit beam 53 for tissue imaging. The x-direction is the element array direction. In the illustrated example, a transmit / receive aperture 51 is set across the transducer element array 12. The transmit / receive aperture 51 is used to form the transmit beam 53 and a receive beam set 56.

[0059] The transmit beam 53 has a single focal point F, which in the illustrated example is located within the region of interest 54. The upper end of the region of interest 54 is located at depth za, and the lower end of the region of interest 54 is located at depth zb, with a depth range D between them.

[0060] In Fig. 3, the transmission beam 53 is depicted schematically and exaggeratedly. This also applies to Figs. 4, 8, and 13, which will be described later. In Fig. 3, the region of interest 54 is depicted schematically and for reference only, and its width, in particular, is not accurately depicted. This also applies to Figs. 4, 8, and 13, which will be described later.

[0061] 3 shows sound pressure distributions A1 to A4 at multiple depth positions z1 to z4 in the transmission beam 53. In each of the sound pressure distributions A1 to A4, the horizontal axis is the x-axis as the spatial axis, and the vertical axis is the sound pressure axis (power axis). In each of the sound pressure distributions A1 to A4, multiple half-widths B1 to B4 are shown. The half-width is the distance between two points that are -6 dB down from the peak on either side of the peak in the sound pressure distribution.

[0062] After the transmission beam 53 is formed, a reception beam set 56 consisting of multiple reception beams 56-1 to 56-4 is formed according to the parallel reception method. For example, the reception beam set 56 is composed of 10 or more reception beams, but in Figure 3, the reception beam set 56 is simply represented by a small number of reception beams 56-1 to 56-4. This also applies to Figures 4 and 8, which will be described later.

[0063] When imaging tissue, high image quality is required throughout the entire depth direction, and block artifacts are less of a problem. For this reason, a transmit beam 53 with a single transmit focus F is utilized.

[0064] 4 shows a first example of a composite beam according to the embodiment. An inner transmit aperture 58 is set for the transducer element array 12, and outer transmit apertures 60A and 60B are also set. In the example shown, the inner transmit aperture 58 is set in the center of the transducer element array 12, and the outer transmit apertures 60A and 60B are set on both sides of it. During reception, a receive aperture 52 is set for the entire transducer element array 12.

[0065] A first transmit beam 62 is formed using the inner transmit aperture 58, and simultaneously, a second transmit beam 64 is formed using the outer transmit apertures 60A and 60B. The first transmit beam 62 has a first transmit focus F1 located on the near side (the transducer element array 12 side) of the region of interest 54 on the transmit central axis. The second transmit beam 64 has a second transmit focus F2 located on the near side of the region of interest 54 on the transmit central axis. The first transmit focus F1 is a near focus, and the second transmit focus F2 is a far focus located deeper than the first transmit focus F1.

[0066] In order to suppress phase shifts between the multiple transmission wavefronts reaching each observation point within the scanning plane, a relatively small distance is set between the first transmission focal point Fa and the second transmission focal point Fb. For example, the distance is within a range of 3 to 10 mm. The lower limit of the range is determined in order to avoid acoustic energy concentration.

[0067] The first transmit beam 62 has a focused portion 62A located in front of the first transmit focal point F1 and a divergent portion 62B located behind the first transmit focal point F1. Similarly, the second transmit beam 64 has a focused portion 64A located in front of the second transmit focal point F2 and a divergent portion 64B located behind the second transmit focal point F2.

[0068] The simultaneous formation of the first transmit beam 62 and the second transmit beam 64 generates a composite transmit beam 66 in the living body. The composite transmit beam 66 has a constricted portion near the two transmit foci F1 and F2. The composite transmit beam 66 has a focused portion 66A located in front of the two transmit foci F1 and F2 and a divergent portion 66B located behind the two transmit foci F1 and F2. The divergent portion 66B expands in the electronic scanning direction at each depth. In other words, the half-width is appropriately increased at each depth. This divergent portion 66B passes through the region of interest 54.

[0069] After forming the composite transmit beam 66, a receive beam set 69 is formed according to the parallel receive method. According to an embodiment, electronic scanning of the diffuse portion 82B relative to the region of interest 54 is achieved.

[0070] When the transmit beam density is low, the transmit beam spacing increases, making it necessary to increase the width of the receive beam set in the electronic scanning direction. In contrast, according to the embodiment, the diffused portion 66B passes through the region of interest 54, so the acoustic pressure distribution is somewhat uniform over a wide range within the region of interest 54. This prevents low acoustic pressure areas from occurring within the receive beam set 69 within the region of interest 54. This effectively suppresses the block-like artifacts described above in blood flow images.

[0071] The shape of the diffused portion 66B and its sound pressure distribution can be freely manipulated by adjusting the aperture pattern, adjusting the depth of the two transmit focal points F1 and F2, etc. Depending on the depth and range of the region of interest, the composite transmit beamforming conditions are optimized or selected so that an appropriate diffused portion 66B is formed.

[0072] FIG. 5 shows a first comparative example. The first comparative example uses a single-focus wide beam 68. In the first comparative example, if the acoustic power is increased to increase the sound pressure in the diffusing portion, the acoustic energy will be excessively concentrated at the transmission focal point F. FIG. 6 shows a second comparative example. The second comparative example transmits a plane wave 70. FIG. 7 shows a third comparative example. The third comparative example transmits a diverging wave 72 with the virtual transmission focal point F as the base point. In the second and third comparative examples, the half-width becomes too wide, which can be pointed out as a problem in that the blood flow image becomes blurred.

[0073] The composite transmit beam according to the embodiment can increase the acoustic power injected into the living body while avoiding energy concentration at one point, that is, increase the average sound pressure in the diffused part, and also appropriately widen the half-width in the diffused part.

[0074] 8 shows a second example of a composite transmit beam according to the embodiment. An inner transmit aperture 74 is set for the transducer element array 12, and outer transmit apertures 76A and 76B are set on both sides of the inner transmit aperture 74. During reception, a receive aperture 52 is set for the entire transducer element array 12.

[0075] A first transmit beam 78 is formed using the inner transmit aperture 74, and simultaneously, a second transmit beam 80 is formed using the outer transmit apertures 76A and 76B. The first transmit beam 78 has a first transmit focus F1 located on the transmit central axis and closer to the region of interest 54. The second transmit beam 80 has a second transmit focus F2 located on the transmit central axis and closer to the region of interest 54. Unlike the first example, the first transmit focus F1 is a far focus, and the second transmit focus F2 is a near focus located shallower than the first transmit focus F1.

[0076] The first transmit beam 78 has a focused portion 78A located in front of the first transmit focal point F1 and a divergent portion 78B located behind the first transmit focal point F1. Similarly, the second transmit beam 80 has a focused portion 80A located in front of the second transmit focal point F2 and a divergent portion 80B located behind the second transmit focal point F2.

[0077] The simultaneous formation of the first transmit beam 78 and the second transmit beam 80 generates a composite transmit beam 82 in vivo. The composite transmit beam 82 has a focused portion 82A located in front of the two transmit foci F1 and F2 and a divergent portion 82B located behind the two transmit foci F1 and F2. The focused portion 82A corresponds to a combination of the two focused portions 78A and 80A. The divergent portion 82B corresponds to a combination of the two divergent portions 78B and 80B. The divergent portion 82B expands in the electronic scanning direction at each depth. In other words, the half-width increases at each depth. This divergent portion 82B passes through the region of interest 54. After the composite transmit beam 82 is formed, a receive beam set 69 is formed according to the parallel receive method.

[0078] In the second example as well, the occurrence of low acoustic pressure areas within the receive beam set 69 within the region of interest 54 is prevented. This effectively prevents or reduces the occurrence of the block-like artifacts described above. In this second example as well, the shape of the diffused portion 66B and its acoustic pressure distribution can be manipulated by adjusting the aperture pattern, adjusting the depths of the two transmit focal points F1 and F2, etc.

[0079] FIG. 9 shows a table 84 for managing multiple focal depth combinations. Each focal depth combination is defined by a near focal depth and a far focal depth, and also by an aperture condition. For example, the contents of table 84 or a list showing multiple focal depth combinations is presented to the user. A specific focal depth combination is selected by the user. The control unit sets composite transmit beamforming conditions for the transmitter that are compatible with the selected focal depth combination. The composite beamforming conditions include transmit aperture conditions, delay conditions, transmit voltage conditions, weighting conditions, etc. If the composite transmit beamforming conditions are changed during CFM mode execution, particularly if the focal depth combination is changed, the sound pressure distribution of the divergent portion of the composite transmit beam changes, particularly the half-width. The composite transmit beamforming conditions are selected depending on the examination purpose, the subject, etc.

[0080] 10 shows a first display example. A display image 86 includes a CFM image 88. The CFM image 88 is composed of a tissue image 90 and a blood flow image 92. Reference numeral 94 denotes a region of interest marker. A graphic 96 displayed together with the CFM image 88 includes a depth axis 98 and a plurality of figures 100-104.

[0081] Graphics 100 and 102 are two markers indicating the depths of the near and far foci of a composite transmit beam for restricting blood flow imaging. Graphic 104 is a marker indicating the depth of a transmit beam for forming a tissue image. Graphic 96 allows intuitive understanding of the depth relationship between multiple transmit foci. The positions of graphics 100-104 may be slidable, allowing the user to change the depth of each transmit focus. Each of graphics 100-104 is a triangle, but other shapes may also be used for each of graphics 100-104.

[0082] A second display example is shown in Figure 11. In Figure 11, elements similar to those shown in Figure 10 are given the same reference numerals, and their description will be omitted. Graphic 106 has a depth axis 108, figure 110, and figure 104. An upper end 110a of figure 110 indicates the depth of the near focus. A lower end 110b of figure 110 indicates the depth of the far focus. Although figure 110 is rectangular, other shapes may be adopted for figure 110.

[0083] 12 shows a flowchart of an example of operation in the CFM mode. In S10, for example, a region of interest is set by the user on a tissue image. In S11, a list showing multiple composite transmit beamforming conditions is displayed, and a specific composite transmit beamforming condition selected by the user from the list is accepted.

[0084] In S14, actual transmission conditions are set in the transmitter according to specific composite transmit beamforming conditions, and actual reception conditions are set in the receiver. In S16, transmission and reception according to the CFM mode is started. In S18, if it is determined based on user input or automatic determination that the composite transmit beamforming conditions should be changed, the steps from S11 onwards are executed again. The composite transmit beamforming conditions may be switched until the desired image quality is obtained, that is, until the desired half-width and sound pressure distribution are obtained. In S20, it is determined whether to continue executing the CFM mode.

[0085] 13 shows a third example of a composite transmit beam according to the embodiment. The two-dimensional transducer element array 112 is composed of a plurality of transducer elements arranged in the x and y directions. An inner transmit aperture 114 and an outer transmit aperture 116 are set on the two-dimensional transducer element array 112. Specifically, the inner transmit aperture 114 is set in the center of the two-dimensional transducer element array 112, and the outer transmit aperture 116 is set to surround it. During reception, a receive aperture is set for the entire two-dimensional transducer element array 112.

[0086] A first transmit beam 118 is formed using the inner transmit aperture 114, and simultaneously, a second transmit beam 120 is formed using the outer transmit aperture 116. The first transmit beam 118 has a first transmit focus F1 located on the transmit central axis, closer to the region of interest 122. The second transmit beam 120 has a second transmit focus F2 located on the transmit central axis, closer to the region of interest 122. The first transmit focus F1 is the near focus, and the second transmit focus F2 is the far focus. The relationship between these may be reversed.

[0087] The first transmit beam 78 is a three-dimensional transmit beam formed by applying electronic focusing techniques in the θ direction (first electronic scanning direction) and the φ direction (second electronic scanning direction). Similarly, the second transmit beam 80 is a three-dimensional transmit beam formed by applying electronic focusing techniques in the θ direction and the φ direction. The region of interest 122 is a three-dimensional region of interest extending in the depth direction, the θ direction, and the φ direction. It has a conical or pyramidal shape. Alternatively, a cylindrical or prismatic shape may be adopted.

[0088] The first transmit beam 118 has a focused portion in front of the first transmit focal point F1 and a divergent portion behind the first transmit focal point F1. Similarly, the second transmit beam 120 has a focused portion in front of the second transmit focal point F2 and a divergent portion behind the second transmit focal point F2.

[0089] The simultaneous formation of the first transmit beam 118 and the second transmit beam 120 generates a composite transmit beam 124 in vivo. The composite transmit beam 124 is a three-dimensional transmit beam. The composite transmit beam 124 has a focused portion located in front of the two transmit foci F1 and F2 and a divergent portion located behind the two transmit foci F1 and F2. The divergent portion extends in the θ and φ directions at each depth. Such a divergent portion passes through the region of interest 122. After the composite transmit beam 124 is formed, a receive beam set is formed using the parallel receive method, consisting of multiple receive beams aligned in the θ and φ directions.

[0090] In the third example as well, the sound pressure distribution is made uniform to some extent over a wide range within the region of interest 122. This effectively prevents low sound pressure areas from occurring within the receive beam set.

[0091] Figure 14 shows an example of a transmission sequence when performing three-dimensional color Doppler. The horizontal axis indicates the θ direction, and the vertical axis indicates the φ direction. Each figure indicates the transmit beam address, that is, the direction of the transmit central axis. T1 to T36 indicate the transmission order. In blood flow observation, the volume rate should be, for example, 15 to 20 Hz or higher. To achieve this, the number of transmit beams aligned in the θ and φ directions must be reduced, for example, to just a few. When performing three-dimensional color Doppler, the transmit beam density inevitably becomes quite small. For this reason, it is necessary to increase the number of receive beams obtained per transmission and reception using the parallel reception method.

[0092] According to the third example, the diffused portion extends in two electronic scanning directions, and a good sound pressure distribution can be generated in the diffused portion, so that even if the receive beam set is spatially expanded, low sound pressure areas can be prevented or reduced from occurring within the receive beam set, making it difficult for block-shaped artifacts to occur.

[0093] 15 shows a first example of a transmit aperture pattern set for the two-dimensional transducer element array 112. The inner transmit aperture 114A is nearly circular, and the outer transmit aperture 116A is set around the inner transmit aperture 114A.

[0094] A second example of a transmit aperture pattern is shown in Figure 16. The inner transmit aperture 114B is nearly elliptical, and the outer transmit aperture 116B is set around the inner transmit aperture 114B.

[0095] 17 shows a third example of a transmit aperture pattern. The inner transmit aperture 114C is rectangular, and the outer transmit aperture 116C is set around the inner transmit aperture 114C. In the first to third examples, the outer edge of the outer transmit aperture may be circular or elliptical. Three or more transmit apertures may be set, and three or more transmit beams may be formed simultaneously.

[0096] Next, a method for designing a composite transmission beam to achieve a desired half-width and a desired sound pressure distribution in the diffusion portion will be described.

[0097] FIG. 18 shows a flowchart of an example of a composite transmit beam design method. In S30, preconditions and target conditions are specified. The preconditions include the position and size of the region of interest, or the range of their variation. The preconditions further include the transmit frequency, transmit beam density, the number of waves constituting the transmit pulse, parallel receive conditions, probe type (type of transducer array), MI conditions, TI conditions, etc. The target conditions include the target half-width and target sound pressure distribution for the diffuse portion.

[0098] In S32, the conditions for forming the second transmit beam formed by the outer transmit aperture are provisionally set under the above preconditions. The outer shape of the divergent portion of the composite transmit beam is generally determined by the outer shape of the divergent portion of the second transmit beam. Therefore, it is reasonable to design the second transmit beam first.

[0099] In S34, a second transmission beam is tentatively formed according to the provisionally set formation conditions. The second transmission beam may be formed by computer simulation. In S36, S32 and S34 are repeatedly executed while changing the formation conditions of the second transmission beam until it is determined that a diffused portion pattern that satisfies certain conditions is obtained.

[0100] If it is determined in S36 that the diffusion portion pattern satisfies certain conditions, the second transmission beam forming conditions that produced the favorable results are provisionally determined as the forming conditions to be actually used in S38. Note that the certain conditions are determined in accordance with the target conditions.

[0101] In S40, conditions for forming a first transmission beam by the inner transmit aperture are provisionally set under the above prerequisites and the above second transmission beam forming conditions. In S42, the first transmission beam is tentatively formed according to the provisionally set forming conditions. The first transmission beam may be formed by computer simulation. In S44, S40 and S42 are repeatedly executed while changing the conditions for forming the first transmission beam until it is determined that the state of the diffused portion of the composite transmission beam satisfies the above target conditions.

[0102] If it is determined in S44 that the state of the divergent portion of the composite transmit beam satisfies the target condition, the first transmit beam forming conditions that produced the favorable result are provisionally determined as the forming conditions to be actually used in S46. The evaluation in S44 particularly evaluates the degree of cancellation of the side lobes of the first transmit beam and the second transmit beam within the region of interest.

[0103] In S46, the first transmission beam forming conditions and the second transmission beam forming conditions are finely adjusted as necessary. In S48, the finally determined first transmission beam forming conditions and the second transmission beam forming conditions are registered. Each forming condition includes an aperture condition, a transmission focal depth, etc.

[0104] For reference, several formulas that can be used when determining the transmit beamforming conditions are explained below. The target half-width condition is expressed, for example, by the following formula (1).

number

[0105] Here, He is the half-width of the transmission beam, d is the pitch between the transmission beams, and α is a predetermined coefficient. As the half-width, a representative value (average value, maximum value, minimum value, etc.) of the half-width within the region of interest can be used.

[0106] The sound pressure condition may be that a representative sound pressure in the region of interest exceeds a predetermined threshold. Examples of representative sound pressures include the average sound pressure, which is the left side of the following equation (2), and the deepest sound pressure, which is the left side of the following equation (3).

number

number

[0107] where P represents the sound pressure distribution, V represents the volume, ROI represents the region of interest, and V ROI represents the volume of the region of interest, Pz represents the sound pressure at the deepest position of the region of interest, and Ps1 and Ps2 are thresholds.

[0108] Alternatively, the condition may be that the sound pressure at the maximum depth at which the ultrasonic pulse travels back and forth exceeds a predetermined threshold. Optimal conditional expressions and optimal thresholds may be found by previously performing numerical simulations or actual imaging to evaluate the occurrence of block-shaped artifacts.

[0109] The relationship between the volume rate and the pitch between the transmitted beams is expressed by, for example, the following equation (4).

number

[0110] where VR represents the volume rate, PRF represents the pulse repetition frequency, and t B represents the time required to capture a B-mode image, N represents the number of repeated transmissions in color Doppler imaging (n shown in Figure 2), and θ represents the angle of view. Equation (4) is based on the premise that the number of transmission beams aligned in the first electronic scanning direction is equal to the number of transmission beams aligned in the second electronic scanning direction.

[0111] In three-dimensional color Doppler, the transmitted beam scans two-dimensionally, so when the volume rate is doubled, the pitch between transmitted beams increases roughly according to the square root of the volume rate. Based on this relationship and equation (1), the following conditional equation (5) can be derived.

number

[0112] On the other hand, when two-dimensional color Doppler is performed, the transmission beam is scanned one-dimensionally, so the pitch between the transmission beams is roughly proportional to the frame rate. In this case, the following equation (6) can be used as a conditional equation.

number

[0113] Here, FR is the frame rate.

[0114] The transmission delay time given to each transmitting element can be calculated by the following equation (7).

number

[0115] where x i and y i represents the x and y coordinates of the i-th transmitting element. f , y f and z frepresents the coordinates of the transmission focal point allocated to the transmitting element. τ is the transmission delay time, and c is the speed of sound in the living body. A smoothing filter may be applied to multiple transmission delay times allocated to multiple transmitting elements according to equation (7).

[0116] An example of target conditions is shown in Figure 19. The target conditions 126 shown include a half-width condition and a sound pressure condition. A composite transmit beam is designed so that the target conditions 126 are satisfied.

[0117] 20 shows a list 128 of multiple transmit conditions (multiple composite transmit beamforming conditions) generated by performing the composite transmit beam design method. Each transmit condition includes a near focal depth, a far focal depth, a first size of the inner transmit aperture (size in the first electronic scanning direction), and a second size of the inner transmit aperture (size in the second electronic scanning direction).

[0118] Prior to the execution of the CFM mode, the list shown in Fig. 20 may be presented to the user, and a specific transmission condition (specific composite transmit beamforming) may be selected from the list. The transmission condition may be switched while the CFM mode is being executed.

[0119] An evaluation result table 130 shown in Fig. 21 may be presented to the user. The evaluation result table 130 may be displayed together with the above list or separately from the above list. The evaluation result table 130 shows the results of evaluation for each transmission condition.

[0120] Specifically, the evaluation result table 130 includes the half width (representative half width), sound pressure (representative sound pressure), and whether the target condition is satisfied for each transmission condition. The evaluation result table 130 shown in Fig. 21 also includes transmission condition 4, which did not satisfy the target condition. When displaying the list shown in Fig. 20, transmission condition 4 may be excluded from the list.

[0121] As described above, according to the embodiment, it is possible to obtain a good sound pressure distribution in a region of interest while avoiding excessive acoustic energy concentration in a living body. Therefore, it is possible to effectively suppress the occurrence of block-shaped artifacts when performing CFM mode, particularly when performing 3D CFM mode, and improve the image quality of two-dimensional or three-dimensional blood flow images. [Explanation of symbols]

[0122] 10 probe, 12 transducer array, 18,54,122 region of interest, 22,66,82,124 composite transmit beam, 28 tissue imaging unit, 30 blood flow imaging unit, 36 transmit / receive control unit.

Claims

1. a vibration element array; a control unit that controls the operation of the transducer array; Including, By controlling the operation of the transducer array, a plurality of transmission beams are simultaneously formed along the transmission central axis so that a plurality of transmission focal points are formed on the transmission central axis at a plurality of positions shallower than a region of interest, which is a two-dimensional or three-dimensional blood flow observation region having a diverging shape; the simultaneous formation of the plurality of transmit beams results in a composite transmit beam in vivo; a receive beam set consisting of a plurality of receive beams is formed according to a parallel receive method after generating the composite transmit beam; The transmission and reception consisting of the generation of the composite transmission beam and the formation of the reception beam set is repeated n times for each azimuth (where n is an integer of 2 or more), A blood flow image representing the blood flow in the region of interest is formed based on the n receive beam data sets for each orientation obtained by this. An ultrasonic diagnostic device characterized by:

2. 2. The ultrasonic diagnostic apparatus according to claim 1, a diffuse portion of the composite transmit beam that is deeper than the plurality of focal points; the diffused portion passing through the region of interest; An ultrasonic diagnostic device characterized by:

3. 2. The ultrasonic diagnostic apparatus according to claim 1, the control unit sets a plurality of transmit apertures on the transducer element array; the plurality of transmit beams are simultaneously formed by the plurality of transmit apertures; An ultrasonic diagnostic device characterized by:

4. 4. The ultrasonic diagnostic apparatus according to claim 3, The plurality of transmit apertures include: an inner transmit aperture; an outer transmission aperture set outside the inner transmission aperture; Including, An ultrasonic diagnostic device characterized by:

5. 5. The ultrasonic diagnostic apparatus according to claim 4, The plurality of transmit beams are: a first transmit beam formed by the inner transmit aperture; a second transmit beam formed by the outer transmit aperture; and Including, The plurality of transmit focal points are a first transmit focal point of the first transmit beam; a second transmit focal point of the second transmit beam; Including, the first transmit focus is a near focus; the second transmission focus is a far focus that occurs at a position deeper than the near focus; An ultrasonic diagnostic device characterized by:

6. 5. The ultrasonic diagnostic apparatus according to claim 4, The plurality of transmit beams are: a first transmit beam formed by the inner transmit aperture; a second transmit beam formed by the outer transmit aperture; and Including, The plurality of transmit focal points are a first transmit focal point of the first transmit beam; a second transmit focal point of the second transmit beam; Including, the first transmit focus is a far focus; the second transmission focus is a near focus that occurs at a position shallower than the far focus; An ultrasonic diagnostic device characterized by:

7. 5. The ultrasonic diagnostic apparatus according to claim 4, the region of interest is a three-dimensional region of interest; the transducer element array is a two-dimensional transducer element array; the inner transmit aperture is a two-dimensional transmit aperture; the outer transmit aperture is a two-dimensional transmit aperture surrounding the inner transmit aperture, each of the transmit beams is a three-dimensional transmit beam; the composite transmit beam is a three-dimensional composite transmit beam. An ultrasonic diagnostic device characterized by:

8. 2. The ultrasonic diagnostic apparatus according to claim 1, the control unit controls formation of the plurality of transmit beams in accordance with a specific composite transmit beam forming condition selected from a plurality of composite transmit beam forming conditions; a sound pressure distribution in the composite transmit beam in the region of interest is changed by switching the specific composite transmit beam forming condition; the change in the sound pressure distribution includes a change in the beamwidth of the composite transmit beam. An ultrasonic diagnostic device characterized by:

9. 9. The ultrasonic diagnostic apparatus according to claim 8, each of the composite transmit beamforming conditions has a depth combination of a plurality of transmit focal depths; a plurality of depth combinations of the plurality of transmit beamforming conditions that are different from each other; An ultrasonic diagnostic device characterized by:

10. 2. The ultrasonic diagnostic apparatus according to claim 1, the transducer element array forms a single-focus transmit beam and the composite transmit beam non-simultaneously; the monofocal transmit beam is a transmit beam for acquiring tissue structure information; the composite transmit beam is a transmit beam for acquiring tissue motion information; and forming a plurality of receive beams simultaneously to acquire the tissue motion information after forming the composite transmit beam. An ultrasonic diagnostic device characterized by:

11. The ultrasonic diagnostic apparatus according to claim 10, the control unit individually sets a depth of a transmission focus of the single-focus transmission beam and a depth of the plurality of transmission focuses of the composite transmission beam. An ultrasonic diagnostic device characterized by:

12. The ultrasonic diagnostic apparatus according to claim 11, a generating unit that generates an image for a user to set a transmit focal depth of the single-focus transmit beam and a transmit focal depth of the multiple transmit focal points of the composite transmit beam; An ultrasonic diagnostic device characterized by:

13. A step of setting a region of interest, which is a two-dimensional or three-dimensional blood flow observation region having a diverging shape, in a living body; setting transmission conditions for forming the plurality of transmission beams along the transmission central axis so that a plurality of transmission focal points are formed at a plurality of positions shallower than the region of interest on the transmission central axis; generating a composite transmit beam in vivo by simultaneously forming the plurality of transmit beams in accordance with the transmit conditions; forming a receive beam set of a plurality of receive beams according to a parallel receive technique after generating the composite transmit beam; Including, The transmission and reception consisting of the generation of the composite transmission beam and the formation of the reception beam set is repeated n times for each azimuth (where n is an integer of 2 or more), A blood flow image representing the blood flow in the region of interest is formed based on the n receive beam data sets for each orientation obtained by this. A beam forming method comprising:

14. In the ultrasound diagnostic device according to claim 1, the plurality of transmit beams are composed of a first transmit beam and a second transmit beam; The plurality of transmit focal points are a first transmit focal point of the first transmit beam; a second transmit focal point of the second transmit beam; Including, the first transmit focus is a near focus; the second transmission focus is a far focus that occurs at a position deeper than the near focus, The distance between the first transmission focus and the second transmission focus is within a range of 3 to 10 mm. An ultrasonic diagnostic device characterized by:

Images