JP2019072358A - Ultrasound signal processing device, ultrasound diagnosis device, ultrasound signal processing method, and ultrasound image display method - Google Patents

Abstract

To enlarge a region to be imaged in an element row direction while suppressing reduction in spatial resolution, S/N ratio, and frame rate, in a synthetic aperture method.SOLUTION: A synthetic aperture method includes: setting, as a region in a subject to which a frame acoustic line signal is to be formed correspondingly, a main region to be imaged and an additional region adjacent in a row direction to the main region to be imaged; for each transmission event, setting, as regions including an observation point, a main target region including a region included by an area in the subject on which ultrasound converges and a sub target region that when part or all of a region adjacent in the row direction to the main target region exists in the additional region, is the part or all in the additional region; and making a method for calculating a transmission time required for transmitted ultrasound arriving at an observation point that is in the main region to be imaged and in the main target region differ from a method for calculating a transmission time required for transmitted ultrasound arriving at an observation point included in the sub target region.SELECTED DRAWING: Figure 10

Description

  The present disclosure relates to an ultrasonic signal processing apparatus and an ultrasonic diagnostic apparatus including the same, and more particularly, to a reception beamforming processing method in an ultrasonic signal processing apparatus and an ultrasonic image display method.

  The ultrasonic diagnostic apparatus transmits ultrasonic waves to the inside of a subject by means of an ultrasonic probe (hereinafter referred to as a “probe”), and receives an ultrasonic reflected wave (echo) generated due to the difference in acoustic impedance of the subject tissue. Further, based on the reception signal obtained from the reception, an ultrasonic tomographic image showing the structure of the internal tissue of the subject is generated and displayed on a monitor (hereinafter, referred to as "display unit"). The ultrasonic diagnostic apparatus is widely used for the morphological diagnosis of a living body because the ultrasonic diagnostic apparatus is less intrusive to a subject and can observe the state of internal tissue in real time with a tomographic image or the like.

  In a conventional ultrasonic diagnostic apparatus, a method generally called a phasing addition method is used as a method for receiving beamforming of a signal based on the received reflected ultrasonic waves (for example, Non-Patent Document 1). In this method, when ultrasonic waves are transmitted to a subject by a plurality of transducers, transmission beam forming is performed so that the ultrasonic beam is focused at a certain depth of the subject. Moreover, in this method, an observation point is set on the central axis of the transmission ultrasonic beam. Therefore, only a small number of acoustic line signals in the vicinity of the central axis of the transmission ultrasonic beam can be generated in one ultrasonic transmission event, and the utilization efficiency of the ultrasonic waves is low. In addition, when the observation point is at a position away from the focus point, the spatial resolution of the acoustic line signal and the signal S / N ratio become low.

  On the other hand, a reception beamforming method for obtaining a high quality image with high spatial resolution even in a region other than the vicinity of the transmission focus point has been devised by the synthetic aperture method (for example, non-patent literature 2). According to this method, by performing delay control taking into consideration both the propagation path of the ultrasonic transmission wave and the arrival time of the reflected wave from the propagation path to the transducer, the ultrasonic wave located outside the vicinity of the transmission focus point Receive beamforming can also be performed that reflects the reflected ultrasound from the main irradiation area. As a result, it is possible to generate an acoustic line signal for the entire main ultrasound irradiation area from one ultrasound transmission event. The main ultrasound irradiation area refers to the area through which the ultrasound waves transmitted from the transducers constituting the transmission transducer array propagate at all points in the region. Further, in the synthetic aperture method, transmission focus is virtually adjusted based on a plurality of reception signals for the same observation point obtained from a plurality of transmission events, as compared with the reception beamforming method described in Non-Patent Document 1. It is possible to obtain an ultrasound image with high spatial resolution and S / N ratio.

Unexamined-Japanese-Patent No. 4-60653

Ito Masayasu and Takeshi Mochizuki, "Ultrasound diagnostic device" Corona company publication, August 26, 2002 (P42-P45) "Virtual ultrasound sources in high resolution ultrasound imaging", S. I. Nikolov and J. A. Jensen, in Proc, SPIE-Progress in biomedical optics and imaging, vol. 3, 2002, P. 395-405

  It has been considered to expand a region (hereinafter, referred to as “imaging region”) to be a target for generating an ultrasound image in a direction in which transducers in the probe are arranged (hereinafter, referred to as “element array direction”). As a method of expanding the imaging area in the element row direction, for example, as disclosed in Patent Document 1, (1) the transmission direction of the ultrasonic beam is changed for each transmission event, and the ultrasonic beam is made radially. There are a method of expanding the passing area of the ultrasonic beam by transmitting, and (2) a method of adding a transmitting event that directs the transmitting direction of the ultrasonic beam outward in addition to the normal transmitting event. . However, in the method (1), the compensation of the ultrasonic beam passage region in the element row direction is accompanied by a decrease in spatial resolution in the element row direction and a decrease in S / N ratio. In addition, in the method (2), the number of transmission events required to generate one ultrasound image is increased, which leads to a decrease in frame rate.

  The present invention has been made in view of the above problems, and in the synthetic aperture method using general transmission beam forming, an imaging area while suppressing a decrease in spatial resolution, S / N ratio, and frame rate. It is an object of the present invention to provide an ultrasonic signal processing apparatus, an ultrasonic diagnostic apparatus, an ultrasonic signal processing method, and an ultrasonic image display method capable of expanding the direction of the element in the element row direction.

  An ultrasonic signal processing apparatus according to an aspect of the present invention repeats a transmission event of ultrasonically transmitting to a subject a plurality of times by selectively driving a plurality of transducers arranged in a row in the ultrasonic probe, and performing each transmission An ultrasonic signal processing apparatus that receives a reflected ultrasonic wave from a subject in synchronization with an event and synthesizes a frame acoustic line signal from a plurality of subframe acoustic line signals generated based on the received reflected ultrasonic wave. The transmission transducer array is selected from the plurality of transducers in one transmission event, and ultrasonic waves are transmitted from the transmission transducer array so as to be focused in the subject, in synchronization with each transmission event, A transmission unit that selects a transmission transducer array that transmits ultrasonic waves to sequentially move in the column direction, and a reception transducer array selected from the plurality of transducers in synchronization with each transmission event, and the reception transducer array Receive waves from within the subject A reception unit that generates a reception signal sequence for each of the transducers of the reception transducer array based on the reflected ultrasound, and an imaging main region as a region within the subject in which a corresponding frame acoustic line signal is to be formed; An imaging area setting unit for setting an additional area adjacent to the imaging main area in the column direction, and for each transmission event, based on the reflected ultrasound obtained from each observation point for each transmission event The frame acoustic line signal is generated based on the plurality of subframe acoustic line signals generated by the phasing addition unit that generates the subframe acoustic line signal by performing phasing addition on the received signal sequence, and the plurality of subframe acoustic line signals generated by the phasing addition unit. And a synthesis target unit configured to perform synthesis, wherein the phasing addition unit includes a main target region including a region included in an area where ultrasonic waves converge in the object, and a region adjacent to the main target region in the column direction. Part or all The sub-target area, which is the portion in the additional area when it is in the additional area, is set as an area including the observation point, and an observation point in the main imaging area and in the main target area. The present invention is characterized in that the method of calculating the transmission time at which the transmitted ultrasonic waves reach the observation point is different from the observation point included in the sub-target area.

  According to the ultrasonic signal processing device, the ultrasonic diagnostic device, the ultrasonic signal processing method, and the ultrasonic image display method according to one aspect of the present invention, the spatial resolution and the S / are reduced without reducing the frame rate. The imaging area can be enlarged by the area of the additional area without reducing the N ratio.

FIG. 1 is a block diagram showing a configuration of an ultrasound diagnostic apparatus 100 according to an embodiment. It is a figure which shows the propagation path of the transmission ultrasonic beam by the transmission beam former part 103 which concerns on embodiment. It is a functional block diagram which shows the structure of the receiving beamformer part 104 which concerns on embodiment. It is a functional block diagram which shows the structure of the phasing addition part 1041 which concerns on embodiment. It is a figure which shows main area Bx and sub area Cx which concern on embodiment. It is a schematic diagram which shows the relationship between virtual reception opening Rv which concerns on embodiment, reception opening Rx, virtual transmission opening Tv, and transmission opening Tx. It is a schematic diagram which shows the propagation path of the ultrasonic wave which arrives at receiving vibrator Rk via observation point Pij from transmission aperture Tx based on embodiment. It is a schematic diagram which shows the propagation path of the ultrasonic wave which arrives at observation point Qmn from virtual transmission opening Tv based on embodiment. It is a functional block diagram which shows the structure of the synthetic | combination part 1140 which concerns on embodiment. It is a figure which shows main area | region Bx in each transmission event based on embodiment, and sub area | region Cx. It is a figure which shows main area | region Bx in each transmission event based on embodiment, and sub area | region Cx. It is a schematic diagram which shows the process which synthesize | combines the synthetic | combination acoustic line signal in the addition process part 11401 which concerns on embodiment. It is a schematic diagram which shows the outline | summary of the largest superimposition number in the synthetic | combination acoustic line signal based on embodiment, and the amplification process in the amplification process part 11402. It is a flowchart which shows the beam forming processing operation of the receiving beamformer part 104 which concerns on embodiment. FIG. 16 is a flowchart showing an acoustic line signal generation operation for observation points Pij and Qmn in the reception beam former unit 104 according to the embodiment. It is a schematic diagram for demonstrating the acoustic line signal production | generation operation | movement about observation point Pij and Qmn in the receiving beam former part 104 which concerns on embodiment. It is a schematic diagram which shows the relationship between virtual reception opening Rv set by the reception opening setting part which concerns on modification 1, reception opening Rx, virtual transmission opening Tv, and transmission opening Tx. 7 is a flowchart showing a beamforming processing operation of a reception beam former unit according to modification 1; FIG. 16 is a schematic diagram for explaining an operation of generating an acoustic line signal at observation points Pij and Qmn in the reception beam former according to the modification 1. It is a figure which shows the main area | region Bx which concerns on the modification 2, and the sub area | region Cx. It is a figure which shows the imaging area | region in the conventional synthetic aperture method.

<< Background to reach the form for carrying out the invention >>
The inventors conducted various studies to enlarge an imaging region in an ultrasonic diagnostic apparatus using a synthetic aperture method.

  In an ultrasound diagnostic apparatus, generally, when ultrasound transmission to a subject performed by a plurality of transducers is performed, a transmission beam for focusing a wavefront so that an ultrasound beam is focused at a certain depth of the subject Forming is performed (hereinafter, the depth at which focusing is established is referred to as “focus depth”). Therefore, ultrasonic waves are mainly irradiated to the main ultrasonic wave irradiation area from a plurality of transducers (hereinafter referred to as "transmission transducer array") used for ultrasonic wave transmission by transmission (transmission event) of ultrasonic waves once. Be done. Here, the “ultrasonic main irradiation area” is an area through which the ultrasonic waves transmitted from the respective transducers constituting the transmission transducer array propagate. When the transmission focus point is one point, the ultrasonic main irradiation area is an hourglass-shaped area surrounded by two straight lines passing the transmission focus point from the both ends of the base with the transmission transducer array as the base, The wavefront is in the form of an arc centered on the transmission focus point. The ultrasound beam is not always focused at one point, and, for example, in the case of focusing only on an area focused from 1.5 elements to several elements (hereinafter referred to as “focus area”). In this case, the main ultrasound irradiation area narrows the width in the column direction at the depth of focus, becomes the width in the column direction of the focus area at the depth of focus, and becomes wider again in the area deeper than the focus depth. . That is, the main ultrasound irradiation area has a shape in which the width in the column direction is the narrowest at the focus depth, and in the other depths, the width in the column direction is wider according to the distance to the focus depth.

  In the synthetic aperture method, since an observation point can be set for any point in the ultrasonic main irradiation area in one transmission event, an acoustic line signal is generated over the entire area of the ultrasonic main irradiation area (hereinafter referred to as , “Target region”) is preferable. Since one transmission event can not set the entire area for generating an ultrasound image as a target area, a plurality of transmission events having different target areas are performed to generate an ultrasound image of one frame. From the viewpoint of the utilization efficiency of ultrasonic waves, the target area is preferably large, and a larger overlapping area of target areas of two consecutive transmission events is preferable for improving the spatial resolution and the signal S / N ratio.

  Therefore, the transmission event is performed with the entire area of the hourglass-shaped ultrasonic main irradiation area as the target area, and the ultrasonic main irradiation area and the target area are moved by one element at a time in synchronization with the transmission event to generate an acoustic line signal. (Hereinafter, an acoustic line signal generated in one transmission event is referred to as “subframe acoustic line signal”), and a plurality of subframe acoustic line signals are synthesized to generate an ultrasonic image of one frame. It is conventionally performed.

  On the other hand, when a part of the transmission transducer array (hereinafter referred to as a “virtual transmission transducer array”) on the setting protrudes from the transducer array, a portion where no transducer physically exists is the transmission transducer array It can not be. Therefore, the settable range of the center of the virtual transmission transducer array in the element array direction (hereinafter referred to as “transmission aperture center”) can not exceed the width of the transducer array of the ultrasonic probe. Furthermore, since the width in the element row direction of the target area is minimized at the focus depth, the width in the element row direction of the imaging region is also minimized at the focus depth. For the above reasons, for example, in the case of a linear probe, the rectangular, sectoral, or trapezoidal range having the bottom of the transducer array of the ultrasonic probe is the maximum range of the imaging region. Further, for example, in the case of the convex probe, the central angle of the arc formed by the transducer array of the ultrasonic probe is the maximum value of the central angle of the imaging region in the imaging region which is substantially fan-shaped.

  On the other hand, as a method of expanding the imaging area in the element row direction, as described above, in one, the transmission direction of the ultrasonic beam is changed for each transmission event, and the ultrasonic beam is transmitted radially. Therefore, there is a method of enlarging the passing area of the ultrasonic beam. This is a method of steering the traveling direction of the ultrasonic beam away from the center of the transducer array as the transmission aperture center moves away from the center of the transducer array of the ultrasonic probe, as shown in FIG. It is. Specifically, as the transmission aperture center is in the positive direction of x (right side in the figure), the traveling direction of the ultrasonic beam is inclined in the positive direction of x (upper right side in the figure). The more the x is in the negative x direction (left in the figure), the more the ultrasonic beam travels in the negative x direction (upper left in the figure). As a result, in the case of a linear probe, the imaging area has a trapezoidal shape with the width of the transducer array as the upper base, and the imaging area is enlarged in the element array direction by the difference between the lower base and the upper base. Can. However, in this method, since the target area spreads radially, the overlapping area of the target areas of two consecutive transmission events becomes smaller as the depth becomes larger, and the number of composites becomes smaller, resulting in spatial resolution and signal S / N ratio. It will decrease.

  As another method of expanding the imaging area, as described above, there is a method of adding a transmission event in which the transmission direction of the ultrasonic beam is directed outward, in addition to the normal transmission event. That is, as shown in FIG. 21 (c), an image similar to that of FIG. 21 (a) is generated at a normal transmission event, and an additional area is provided outside the normal imaging area in the element row direction. As in the case of FIG. 21 (b), the method of steering with the traveling direction of the ultrasonic beam directed to the additional area is as in FIG. Thereby, the imaging area can be expanded in the element row direction without affecting the spatial resolution and the signal S / N ratio for a normal imaging area. However, in this method, since a transmission event for imaging the additional area has to be separately performed, the number of transmission events required to generate one ultrasound image increases, and it is difficult to improve the frame rate. It becomes.

  Therefore, in view of the above-mentioned problems, the inventor, in combination of the transmission beam forming for focusing the wavefront and the synthetic aperture method, does not adversely affect the spatial resolution, the signal S / N ratio, and the frame rate. The inventors have investigated the technology to be expanded, and have come to think of an ultrasonic signal processing apparatus, an ultrasonic diagnostic apparatus, and an ultrasonic signal processing method according to the embodiment.

  Hereinafter, an ultrasonic image processing method according to an embodiment and an ultrasonic diagnostic apparatus using the same will be described in detail with reference to the drawings.

<< Embodiment >>
<Overall configuration>
The ultrasonic diagnostic apparatus 100 according to the embodiment will be described below with reference to the drawings.

  FIG. 1 is a functional block diagram of an ultrasound diagnostic system 1000 according to the embodiment. As shown in FIG. 1, the ultrasound diagnostic system 1000 transmits and receives ultrasound to and from the probe 101 having a plurality of transducers 101 a that transmit ultrasound toward the subject and receive the reflected wave. The ultrasound diagnostic apparatus 100 generates an ultrasound image based on an output signal from the probe 101, and the display unit 106 displays an ultrasound image on a screen. The probe 101 and the display unit 106 are each configured to be connectable to the ultrasonic diagnostic apparatus 100. FIG. 1 shows a state in which a probe 101 and a display unit 106 are connected to an ultrasonic diagnostic apparatus 100. The probe 101 and the display unit 106 may be inside the ultrasonic diagnostic apparatus 100.

<Configuration of Ultrasonic Diagnostic Apparatus 100>
The ultrasonic diagnostic apparatus 100 selects, for each of a plurality of transducers 101a of the probe 101, transducers to be used for transmission or reception, and a multiplexer unit 102 for securing input / output to the selected transducers, and ultrasound The transmission beam former 103 controls the timing of high voltage application to each of the transducers 101 a of the probe 101 in order to perform transmission of It has a reception beam former unit 104 which amplifies the A / D signal, A / D converts it, and performs reception beam forming to generate an acoustic line signal. In addition, an ultrasonic image generation unit 105 that generates an ultrasonic image (B mode image) based on an output signal from the reception beam former 104, an acoustic line signal output from the reception beam former 104, and an ultrasonic image generation unit 105. And a control unit 108 for controlling each component.

  Among them, the multiplexer unit 102, the transmission beam former unit 103, the reception beam former unit 104, and the ultrasonic image generation unit 105 constitute an ultrasonic signal processing apparatus 150.

  Each component of the ultrasound diagnostic apparatus 100, for example, the multiplexer unit 102, the transmission beam former unit 103, the reception beam former unit 104, the ultrasound image generation unit 105, and the control unit 108, respectively, may be FPGA (Field Programmable Gate), for example. This is realized by a hardware circuit such as an array) or an application specific integrated circuit (ASIC). Alternatively, the configuration may be realized by programmable devices such as a processor and software. As a processor, a CPU (Central Processing Unit) or a GPGPU can be used, and a configuration using a GPU is called a GPGPU (General-Purpose Computing on Graphics Processing Unit). These components can be a single circuit component, or can be a collection of multiple circuit components. Also, a plurality of components can be combined into one circuit component, or can be a collection of a plurality of circuit components.

  The data storage unit 107 is a computer readable recording medium, and may be, for example, a flexible disk, a hard disk, an MO, a DVD, a DVD-RAM, a BD, a semiconductor memory, or the like. Further, the data storage unit 107 may be a storage device connected to the ultrasound diagnostic apparatus 100 from the outside.

  The ultrasonic diagnostic apparatus 100 according to the present embodiment is not limited to the ultrasonic diagnostic apparatus having the configuration shown in FIG. For example, the transmitting beam former 103 and the receiving beam former 104 may be directly connected to the transducers 101 a of the probe 101 without the multiplexer 102. Further, the probe 101 may be configured to have the transmission beam former 103, the reception beam former 104, a part thereof, and the like built therein. This is not limited to the ultrasonic diagnostic apparatus 100 according to the present embodiment, and the same applies to ultrasonic diagnostic apparatuses according to other embodiments and modifications described later.

<Configuration of Main Parts of Ultrasonic Diagnostic Apparatus 100>
The ultrasonic diagnostic apparatus 100 according to the first embodiment transmits an ultrasonic signal from each of the transducers 101 a of the probe 101, and an electrical signal obtained from the reception of the ultrasonic wave reflected by the probe 101. It has a feature in the reception beam former unit 104 which generates an acoustic line signal for calculating to generate an ultrasound image. Therefore, in the present specification, the configurations and functions of the transmission beam former 103 and the reception beam former 104 will be mainly described. The same configuration as that used in a known ultrasonic diagnostic apparatus can be applied to the configuration other than the transmission beam former 103 and the receive beam former 104, and the beam former of the known ultrasonic diagnostic apparatus can be used. It is possible to replace and use the beam former unit according to the embodiment.

  Hereinafter, configurations of the transmission beam former 103 and the reception beam former 104 will be described.

1. Transmission beam former 103
The transmission beam former unit 103 is connected to the probe 101 via the multiplexer unit 102, and a transmission transducer array corresponding to all or part of the plurality of transducers 101a present in the probe 101 for transmitting ultrasonic waves from the probe 101 The timing of high voltage application to each of the plurality of transducers included in the transmission aperture Tx is controlled. The transmission beam former 103 comprises a transmitter 1031.

  The transmitting unit 1031 transmits, based on the transmission control signal from the control unit 108, a pulse-shaped transmission signal for transmitting an ultrasonic beam to each of the transducers included in the transmission aperture Tx among the plurality of transducers 101a in the probe 101. Perform transmission processing to supply Specifically, the transmission unit 1031 includes, for example, a clock generation circuit, a pulse generation circuit, and a delay circuit. The clock generation circuit is a circuit that generates a clock signal that determines the transmission timing of the ultrasonic beam. The pulse generation circuit is a circuit for generating a pulse signal for driving each vibrator. The delay circuit is a circuit for setting the transmission timing of the ultrasonic beam for each vibrator and delaying the transmission of the ultrasonic beam by the delay time to perform focusing of the ultrasonic beam.

  The transmitting unit 1031 repeats ultrasonic transmission while moving the virtual transmission aperture Tv in the column direction by a predetermined moving pitch Mp every ultrasonic transmission, and performs ultrasonic transmission from all the transducers 101 a in the probe 101. Here, the virtual transmission aperture Tv is a transmission aperture on the setting which is set regardless of the presence or absence of the transducer, and the column length (hereinafter referred to as “transmission aperture length”) is constant regardless of the transmission event. It is. When a vibrator is present in the entire range of the virtual transmission aperture Tv, the virtual transmission aperture Tv and the transmission aperture Tx match. On the other hand, when there is a place where no transducer is present in the range of the virtual transmission aperture Tv, a portion where the transducer is present in the virtual transmission aperture Tv is the transmission aperture Tx. In the present embodiment, the movement pitch Mp is one vibrator, and the virtual transmission aperture Tv moves one vibrator at a time for each ultrasonic wave transmission. The movement pitch Mp is not limited to one vibrator, and may be, for example, 0.5 vibrator. Information indicating the position of the virtual transmission opening Tv and information indicating the position of the vibrator included in the transmission opening Tx are output to the data storage unit 107 via the control unit 108. For example, when the total number of transducers 101a existing in the probe 101 is 192, for example, 20 to 100 may be selected as the number of transducer rows constituting the transmission aperture Tx, and movement is performed by the movement pitch Mp for each ultrasound transmission. It may be configured to Hereinafter, ultrasound transmission performed from the same transmission opening Tx by the transmission unit 1031 is referred to as “transmission event”.

  FIG. 2 is a schematic view showing the propagation path of the ultrasonic wave transmitted by the transmission beam former 103. As shown in FIG. In a certain transmission event, a row (transmission transducer row) of the transducers 101a arranged in an array that contributes to ultrasonic transmission is illustrated as a transmission aperture Tx.

  The transmission beam former 103 controls the transmission timing of each transducer so that the transmission timing is delayed as the transducer located closer to the center of the virtual transmission aperture Tv. As a result, the ultrasound transmission wave transmitted from the transducer array in the transmission aperture Tx is focused at a point with a wave front at a certain depth (focal depth) of the object, that is, the transmission focus point F (focal point). It will be in a meeting (focusing) state. The depth of the transmission focus point F (Focal depth) (hereinafter referred to as "focus depth") can be set arbitrarily. The wavefront focused at the transmission focus point F diffuses again, and the ultrasonic transmission wave propagates in the space of an hourglass divided by two intersecting straight lines with the transmission aperture Tx as the base and the transmission focus point F as a node Do. That is, the ultrasonic wave emitted at the transmission aperture Tx gradually reduces its width in the space (horizontal axis direction in the figure), minimizes its width at the transmission focus point F, and is deeper than that (in the figure). Then, as it travels to the upper part, it spreads and propagates while increasing its width again. This hourglass-shaped area is the ultrasonic main irradiation area Ax. As described above, the main ultrasound irradiation area Ax may be focused on the focusing area without focusing on one transmission focus point F.

  As described above, the ultrasonic main irradiation area Ax is an area in which the phases of the ultrasonic waves transmitted from the transducers of the transmission transducer array are aligned, and also outside the ultrasonic main irradiation area Ax. The ultrasonic wave is propagating. However, since the phases of the ultrasonic waves transmitted from the transducers of the transmission transducer array are not aligned outside the main ultrasound irradiation area Ax, the ultrasound transmission wave is compared with the inside of the main ultrasound irradiation area Ax. In particular, the further the distance from the main ultrasonic irradiation area Ax, the more noticeable the deterioration.

2. Configuration of Reception Beam Former Unit 104 The reception beam former unit 104 generates an acoustic line signal from the electrical signals obtained by the plurality of transducers 101 a based on the reflected wave of the ultrasonic wave received by the probe 101. The "acoustic line signal" is a signal after phasing addition processing is performed on a certain observation point. The phasing addition process will be described later. FIG. 3 is a functional block diagram showing the configuration of reception beam former 104. As shown in FIG. As shown in FIG. 3, the reception beam former 104 includes a receiver 1040, a phasing adder 1041, and a combiner 1140.

  Hereinafter, the configuration of each part constituting the reception beam former 104 will be described.

(1) Receiver 1040
The receiving unit 1040 is connected to the probe 101 through the multiplexer unit 102, and amplifies the electrical signal obtained from the reception of the ultrasonic wave reflected by the probe 101 in synchronization with the transmission event and then AD converts it (RF signal ) Is generated. Reception signals are generated in time series in the order of transmission events and output to the data storage unit 107, and the reception signals are stored in the data storage unit 107.

  Here, the received signal (RF signal) is a digital signal obtained by A / D converting an electric signal converted from the reflected ultrasonic wave received by each transducer, and an ultrasonic wave received by each transducer A series of signals are formed in the transmission direction (the depth direction of the subject) of

  In the transmission event, as described above, the transmission unit 1031 causes the ultrasonic beam to be transmitted to each of the plurality of transducers included in the transmission aperture Tx among the plurality of transducers 101 a existing in the probe 101. On the other hand, the receiving unit 1040 receives a reception signal for each transducer based on the reflected ultrasonic waves obtained by each of the transducers corresponding to a part or all of the plurality of transducers 101a present in the probe 101 in synchronization with the transmission event. Generate a column of Here, a transducer that receives reflected ultrasonic waves is referred to as a "reception transducer". The number of wave receiving transducers is preferably greater than the number of transducers included in the transmission aperture Tx. Further, the number of wave receiving transducers may be the total number of transducers 101 a existing in the probe 101.

  The transmission unit 1031 repeats ultrasonic transmission while moving the transmission aperture Tx in the column direction by the moving pitch Mp in synchronization with the transmission event, and performs ultrasonic transmission from all of the plurality of transducers 101a in the probe 101. The receiving unit 1040 generates a train of reception signals for each of the wave receiving transducers in synchronization with the transmission event, and the generated reception signals are stored in the data storage unit 107.

(2) Phasing / adding unit 1041
The phasing addition unit 1041 sets a main area Bx and a sub area Cx which are target areas for generating a sub-frame acoustic line signal in the object in synchronization with the transmission event. Next, for each of a plurality of observation points Pij present in the main area Bx and a plurality of observation points Qmn existing in the sub area Cx, the reception signal train received by each receiving oscillator Rk from the observation points is phased and added Do. And it is a circuit which generates a sub-frame acoustic line signal by calculating a sequence of acoustic line signals at each observation point. FIG. 4 is a functional block diagram showing the configuration of the phasing addition unit 1041. As shown in FIG. As shown in FIG. 4, the phasing addition unit 1041 includes a target area setting unit 1042, a reception aperture setting unit 1043, a transmission time calculation unit 1044, a reception time calculation unit 1045, a delay amount calculation unit 1046, a delay processing unit 1047, weights. A calculation unit 1048 and an addition unit 1049 are provided.

  The configuration of each part of the phasing / adding unit 1041 will be described below.

i) Target area setting unit 1042
The target area setting unit 1042 sets a main area Bx and a sub area Cx, which are target areas for generating a sub-frame acoustic line signal in the subject. The “target area” is the area on the signal where the generation of the subframe acoustic line signal is to be performed in the subject in synchronization with the transmission event, and the observation point Pij in the main area Bx and the observation in the sub area Cx An acoustic line signal is generated for the point Qmn. The main area Bx and the sub area Cx are set for convenience of calculation in synchronization with one transmission event as a set of observation target points for which generation of acoustic line signals is performed.

  Here, the "subframe acoustic line signal" is a set of acoustic line signals for all observation points present in the target area generated from one transmission event. The subframe acoustic line signal is a "main area acoustic line signal" which is a set of acoustic line signals for all observation points Pij present in the main area Bx, and acoustics for all observation points Qmn present in the sub area Cx. It consists of a "sub-region acoustic line signal" which is a set of line signals. Note that “subframe” refers to a unit which is obtained in one transmission event and which forms a consolidated signal corresponding to all observation points present in the target area. A frame is obtained by combining a plurality of subframes having different acquisition times.

  The target area setting unit 1042 first sets an imaging area including the imaging main area Hx and the additional areas Ha and Hb. Then, in synchronization with the transmission event, the target area is set based on the information indicating the positions of the transmission aperture Tx and the virtual transmission aperture Tv acquired from the transmission beam former 103.

  FIG. 5 is a schematic view showing an imaging area and a target area. As shown in FIG. 5A, the imaging main area Hx is set as a rectangular area whose bottom is the transducer array 101a. The additional area Ha and the additional area Hb are each set to be adjacent to the imaging main area Hx in the element column direction. In the present embodiment, when the additional region Ha and the additional region Hb have a depth y of 0 (the interface between the object and the probe) and the width in the column direction is the transmission opening width Tx, 1/1 of the transmission opening width Tx The width in the column direction at the deepest portion of the additional regions Ha and Hb is 2, and the width in the element column direction increases as the depth y increases. In this embodiment, it is assumed that Wa = Wb> Tx / 2.

  Next, the target area will be described. When the transmission aperture Tx is sufficiently away from the end of the imaging main area Hx, as shown in FIG. 5A, the entire area where the ultrasonic main irradiation area Ax and the imaging area Hx overlap is the main Set as the area Bx. At this time, the sub area Cx is not set and becomes an empty area. On the other hand, when the transmission aperture Tx is close to the end of the imaging main area Hx, the main area Bx and the sub area Cx are set. Specifically, as shown in FIG. 5B, the virtual transmission aperture Tv is regarded as a transmission aperture, and the entire region of the ultrasonic main irradiation region Ax and the imaging region Hx or the additional regions Ha and Hb overlaps. Is set as the main area Bx. That is, the virtual transmission opening Tv is a base, and an hourglass-shaped area surrounded by two straight lines passing from the both ends of the base to the transmission focus point is a main area Bx. Furthermore, the subregion Cx is determined by the following method. First, an area excluding the main area Bx from the area parallel-shifted to the right along the element row direction such that the transmission opening central axis Txo, which is the central axis of the virtual transmission opening Tv, matches the right end of the additional area Ha As the first area Ja. That is, a point left on the left side of the transmission aperture center by Tx / 2, and a point Ja on the transmission aperture central axis Txo and a depth away from the point C on the deepest part of the imaging main region Hx by Wa on the left side Of the region sandwiched by the straight line connecting the two and the transmission opening central axis Txo, a region not overlapping the main region Bx is taken as a first region Ja. Similarly, the area excluding the main area Bx from the area parallel-shifted the additional area Hb to the left along the element row direction such that the transmission opening central axis Txo and the left end of the additional area Hb coincide with one another is a second area Jb. In other words, the main region Bx of the region between the transmission aperture center axis Txo and the straight line connecting the point separated by Tx / 2 to the right from the transmission aperture center and the point Jb separated by Wb to the right from the point C An area which does not overlap the area is referred to as a second area Jb. Then, an overlapping area of the first area Ja and the additional area Ha and an overlapping area of the second area Jb and the additional area Hb are referred to as a sub area Cx. If the first area Ja and the additional area Ha do not overlap, or if the second area Jb and the additional area Hb do not overlap, the sub area Cx is not set.

  10 and 11 are schematic diagrams showing the main area Bx and the sub area Cx in each transmission event in more detail. When the virtual transmission opening Tv is the left end, that is, when the transmission opening center is the transducer at the left end of the transducer array 101a, as shown in FIG. 10A, the virtual transmission opening Tv is the bottom and each end of the bottom is An hourglass-shaped area surrounded by two straight lines passing from the transmission focus point to the transmission focus point is a main area Bx. At this time, since the transmission opening central axis Txo and the right end of the additional area Ha coincide with each other, the area obtained by removing the main area Bx from the additional area Ha is the first area Ja. Therefore, the sub area Cx which is an overlapping area of the first area Ja and the additional area Ha is necessarily the entire area of the first area Ja, that is, the area obtained by removing the main area Bx from the additional area Ha. On the other hand, when the virtual transmission opening Tv moves to the right but the left end is outside the transducer array 101a, as shown in FIG. 10B, the virtual transmission opening Tv is the bottom and both ends of the bottom are An hourglass-shaped area surrounded by two straight lines passing from each of the transmission focus points is a main area Bx. At this time, since the transmission opening central axis Txo is on the right of the right end of the additional area Ha, the area obtained by shifting the additional area Ha to the right from the main area Bx is the first area Ja. Therefore, the sub-region Cx, which is the overlapping region of the first region Ja and the additional region Ha, shifts to the right compared with the case shown in FIG. 10A, and the overlapping portion with the imaging main region Hx disappears. It becomes a shape. On the other hand, when the transmission opening center is substantially at the center of the transducer array 101a, as shown in FIG. 10C, the transmission opening Tx matches the virtual transmission opening Tv, and the transmission opening Tx is the bottom and both ends of the bottom An hourglass-shaped area surrounded by two straight lines passing through the transmission focus point from each of the above is a main area Bx. At this time, since the entire area of both the first area Ja and the second area Jb exists in the imaging main area Hx, the sub area Cx does not exist. In addition, when the virtual transmission opening Tv moves to the right and the right end is outside the transducer array 101a, as shown in FIG. 11A, the virtual transmission opening Tv is the bottom and transmission is performed from each of both ends of the bottom. An hourglass-shaped area surrounded by two straight lines passing through the focus point is referred to as a main area Bx. At this time, since the transmission opening central axis Txo is on the left side of the left end of the additional area Hb, the area obtained by shifting the additional area Hb to the left from the main area Bx becomes the first area Ja. Therefore, the sub-region Cx, which is an overlapping region of the second region Jb and the additional region Hb, has a shape that is horizontally reversed as compared with the case shown in FIG. Further, when the virtual transmission opening Tv is the right end, that is, when the transmission opening center is the transducer at the right end of the transducer array 101a, as shown in FIG. 11B, the virtual transmission opening Tv is the bottom and both ends of the bottom are An hourglass-shaped area surrounded by two straight lines passing through the transmission focus point from each of the above is a main area Bx. At this time, since the transmission aperture central axis Txo and the left end of the additional area Hb coincide with each other, the area excluding the main area Bx from the additional area Hb is the second area Jb. Therefore, the sub-region Cx which is an overlapping region of the second region Jb and the additional region Hb is necessarily the entire region of the second region Jb, that is, the region excluding the main region Bx from the additional region Hb.

  The range of the first area Ja and the second area Jb is uniquely determined by the shapes of the additional areas Ha and Hb and the position of the transmission opening center, so the positions of the imaging main area Hx and the additional areas Ha and Hb And, if the size is known, it can be determined based on the position of the transmission aperture center whether the sub-region Cx is present. For example, when the additional areas Ha and Hb are determined as described above, if the distance between the point C and the left end of the imaging main area Hx is less than Wa, or the distance between the point C and the right end of the imaging main area Hx is If it is less than Wb, sub-region Cx is present, otherwise sub-region Cx is not present. Therefore, the target area setting unit 1042 may hold the range of the position of the transmission opening center at which the sub area Cx exists with respect to the position and size of each of the imaging main area Hx and the additional areas Ha and Hb. . By doing this, it can be determined whether or not the sub-region Cx is an empty region without calculating the positions of the first region Ja and the second region Jb, so that the sub-region Cx is an empty region. In some cases, it is sufficient to set only the main area Bx, which is successful in reducing the amount of computation. The target area setting unit 1042 changes the range of the position of the transmission opening center where the sub area Cx exists, and transmits the range of the position of the virtual transmission opening Tv where the sub area Cx exists or transmission where the sub area Cx exists. The range of the position of the focus point F may be held.

  The set target area is output to the transmission time calculation unit 1044, the reception time calculation unit 1045, and the delay processing unit 1047.

ii) Reception aperture setting unit 1043
Reception aperture setting unit 1043 hits part of a plurality of transducers present in probe 101 based on the control signal from control unit 108 and the information indicating the position of transmission aperture Tx from transmission beam former 103, and Is a circuit that sets a receiving aperture Rx by selecting a transducer row (receiving transducer row) that matches the transducer that is closest to the observation point in space as a receiving transducer.

  The reception aperture setting unit 1043 selects the virtual reception aperture Rv so that the column center coincides with the transducer Xk which is spatially closest to the observation point Pij or Qmn. Each transducer included in the virtual transmission aperture Rv constitutes a reception aperture Rx. As in the case of the transmission aperture, when the vibrator 101a is present in the entire range of the virtual reception aperture Rv, the reception aperture Rx matches the virtual reception aperture Rv. On the other hand, when there is a portion in which the vibrator 101a does not exist within the range of the virtual reception opening Rv, the range in which the vibrator 101a exists in the virtual reception opening Rv is the reception opening Rx. FIG. 6 is a schematic view showing the relationship among the virtual reception aperture Rv, the reception aperture Rx, the virtual transmission aperture Tv, and the transmission aperture Tx set by the reception aperture setting unit 1043. As shown in FIG. 6, the virtual reception aperture Rv is selected such that the center of the virtual reception aperture Rv coincides with the transducer Xk that is closest to the observation point Pij most spatially. Therefore, the positions of the virtual reception aperture Rv and the reception aperture Rx are determined by the positions of the observation points Pij and Qmn, and do not change based on the position of the transmission aperture Tx that fluctuates in synchronization with the transmission event. That is, even in the case of different transmission events, in the process of generating acoustic line signals for observation points Pij and Qmn at the same position, based on the reception signal acquired by the reception vibrator Rk in the same reception aperture Rx. A phasing addition is performed.

  In addition, in order to receive a reflected wave from the entire main ultrasound irradiation area, the number of transducers included in the reception aperture Rx should be set to be equal to or more than the number of transducers included in the transmission aperture Tx in the corresponding transmission event. Is preferred. The number of transducer rows constituting the receiving aperture Rx may be 32, 64, 96, 128, 192, etc., for example.

  The setting of the virtual reception aperture Rv and the reception aperture Rx is performed at least as many times as the maximum number of observation points Pij and Qmn in the column direction. In addition, the setting of the virtual reception aperture Rv and the reception aperture Rx may be configured to be gradually performed in synchronization with the transmission event, or after all transmission events have ended, virtual reception apertures corresponding to the respective transmission events The setting of Rv and the reception aperture Rx may be performed collectively for the number of transmission events.

  Information indicating the position of the selected reception aperture Rx is output to the data storage unit 107 via the control unit 108.

  The data storage unit 107 outputs the information indicating the position of the reception aperture Rx and the reception signal corresponding to the reception transducer to the transmission time calculation unit 1044, the reception time calculation unit 1045, the delay processing unit 1047, and the weight calculation unit 1048. .

iii) Transmission time calculation unit 1044
The transmission time calculation unit 1044 is a circuit that calculates the transmission time for the transmitted ultrasound to reach the observation point P in the subject. Based on the information indicating the position of the transducer included in the transmission aperture Tx acquired from the data storage unit 107 and the information indicating the position of the target region acquired from the target area setting unit 1042 corresponding to the transmission event, the target area The transmission time at which the transmitted ultrasonic waves reach the observation points Pij and Qmn in the subject is calculated for any observation points Pij and Qmn present inside.

  FIG. 7 is for explaining the propagation path of the ultrasonic wave emitted from the transmission aperture Tx and reflected at the observation point Pij at an arbitrary position in the main region Bx to reach the reception transducer Rk located in the reception aperture Rx. It is a schematic diagram. FIG. 7A shows the case where the observation point Pij is deeper than the focus depth, and FIG. 7B shows the case where the depth of the observation point Pij is equal to or less than the focus depth.

  The transmission wave emitted from the transmission aperture Tx converges at the transmission focus point F through the path 401 and diffuses again. The transmitted wave reaches the observation point Pij while it is focused or diffused, and if there is a change in acoustic impedance at the observation point Pij, a reflected wave is generated, and the reflected wave is received by the receiving vibrator Rk in the receiving aperture Rx of the probe 101. I will go back. Since the transmission focus point F is defined as a design value of the transmission beam former 103, the length of the path 402 between the transmission focus point F and an arbitrary observation point Pij can be geometrically calculated.

  The method of calculating the transmission time will be described in more detail below.

  First, the case where the observation point Pij is deeper than the focus depth will be described with reference to FIG. 7A. When the observation point Pij is deeper than the focus depth, the transmission wave emitted from the transmission aperture Tx reaches the transmission focus point F through the path 401 and reaches the observation point Pij from the transmission focus point F through the path 402. Calculated as Therefore, the value which added the time which a transmission wave passes path | route 401, and the time which passes path | route 402 becomes transmission time. As a specific calculation method, for example, it can be obtained by dividing the total path length obtained by adding the length of the path 401 and the length of the path 402 by the propagation speed of ultrasonic waves in the object.

  On the other hand, the case where the depth of the observation point Pij is less than or equal to the focus depth will be described using FIG. 7B. When the depth of the observation point Pij is less than or equal to the focus depth, the time when the transmission wave radiated from the transmission aperture Tx reaches the transmission focus point F through the path 401 and the observation point Pij through the path 404 , And the time to reach the transmission focus point F from the observation point Pij through the path 402 is calculated to be the same. That is, a value obtained by subtracting the time for passing the path 402 from the time for the transmission wave to pass the path 401 is the transmission time. As a specific calculation method, for example, it can be obtained by dividing the path length difference obtained by subtracting the length of the path 402 from the length of the path 401 by the propagation speed of ultrasonic waves in the object.

FIG. 8 (a) illustrates the propagation path of an ultrasonic wave emitted from the transmission aperture Tx and reflected at an observation point Qmn at an arbitrary position in the subregion Cx to reach the reception transducer Rk located in the reception aperture Rx. It is a schematic diagram for doing. FIG. 8A shows the case where the observation point Qmn is deeper than the focus depth. There are the following three calculation methods as the transmission time for the transmitted ultrasound to reach the observation point Qmn in the subject. One is that, as described above, the transmission wave radiated from the transmission aperture Tx reaches the transmission focus point F through the path 401 and reaches the observation point Qmn from the transmission focus point F through the path 402 It is a method to calculate as. That is, a value obtained by adding the time for the transmission wave to pass through the path 401 and the time for passing the path 402 is the transmission time. As a specific calculation method, for example, it can be obtained by dividing the total path length obtained by adding the length of the path 401 and the length of the path 402 by the propagation speed of ultrasonic waves in the object. The transmission time, hereinafter referred to as transmission time T _2. The other is a method of calculating that the transmission wave radiated from the transmission aperture Tx directly reaches the observation point Qmn through the path 411 without passing through the transmission focus point F. That is, the time for which the transmission wave passes through the path 411 is the transmission time. As a specific calculation method, for example, it can be obtained by dividing the length of the path 411 by the propagation velocity of ultrasonic waves in the subject. The transmission time, hereinafter referred to as transmission time T _1. The last one is a method of calculating by assuming that the observation point Qmn is reached at the same time as the time when the transmission wave radiated from the transmission aperture Tx reaches the reference point R at the same depth as the observation point Qmn It is. That is, the time for which the transmission wave passes through the path 412 is the transmission time. As a specific calculation method, for example, it can be obtained by dividing the length of the path 412 by the propagation velocity of ultrasonic waves in the subject. The transmission time, hereinafter referred to as transmission time T _3.

For each of the three transmission times T ₁ , T ₂ and T ₃ described above, FIG. 8B shows the depth of the observation point Qmn on the horizontal axis and the transmission time on the vertical axis. 8 (b), the line 501 represents the transmission time T _2, line 502 represents the transmission time T _1, line 503 represents the transmission time T _3. Transmission time T ₂ are discontinuous in the focus depth. This is because the minimum value of the length of the path 402 is not zero but the distance in the element row direction between the observation point Qmn and the transmission focus point F. Therefore, when the distance is d and the ultrasonic velocity in the object is cs This is because the transmission time difference between two adjacent observation points Q across the focus depth is 2d / cs. Therefore, it is preferable to adopt the transmission time T ₁ or T ₃ in the vicinity of the focus depth. In addition, when the depth of the observation point Qmn is shallow, it is considered that ultrasonic waves are directly propagated from the transducers in the transmission aperture Tx to the observation point Qmn, so it is preferable to adopt the transmission time T ₁ . On the other hand, in the vicinity of the interface between the main area Bx and subregions Cx, because noticeable inconsistencies and change the way of calculating the transmission time between the main region Bx and subregions Cx, it is preferable to employ a transmission time T _2. Taken together, (1) transmission time T ₁ or T ₃ in the vicinity of the focus depth, (2) transmission time T _{1 in} the region shallower than the focus depth, and (3) in the vicinity of the interface between the region Bx and the subregion Cx , the transmission time T _2, and thus preferred, respectively. Therefore, for example, the transmission time T _M can be calculated as follows.
T _M = αT ₁ + (1−α) βT ₂ + (1−α) (1−β) T ₃
Here, α and β are preferably 0 <α ≦ 1 and 0 ≦ β ≦ 1, respectively, and both α and β are preferably functions with respect to the depth of the observation point Qmn. Specifically, α is preferably 1 near the focus depth, and preferably small near the interface with the main region Bx. In addition, it is preferable that β be a value that increases as the depth of the observation point Qmn increases. For example, α and β can be determined so as to be the line 511 in FIG. 8 (b). The transmission time T _M is not limited to the case illustrated here as long as it satisfies the above-described conditions and monotonically increases with an increase in depth.

  The transmission time calculation unit 1044 calculates, for one transmission event, the transmission time at which the transmitted ultrasonic waves reach the observation points Pij and Qmn in the subject for all the observation points Pij and Qmn in the target area. Then, the delay amount calculation unit 1046 outputs the result.

iv) Reception time calculation unit 1045
The reception time calculation unit 1045 is a circuit that calculates the reception time at which the reflected waves from the observation points P and Q reach each of the reception transducers Rk included in the reception aperture Rx. In accordance with the transmission event, an arbitrary element existing in the target area based on the information indicating the position of the reception vibrator Rk acquired from the data storage unit 107 and the information indicating the position of the target area acquired from the target area setting unit 1042 For the observation points Pij and Qmn, the reception time at which the transmitted ultrasonic waves are reflected by the observation points Pij and Qmn in the subject and reaches the reception transducers Rk of the reception aperture Rx is calculated.

  As described above, when the acoustic impedance changes at the observation points Pij and Qmn, the transmission wave that has reached the observation points Pij and Qmn generates a reflected wave, and the reflected waves are received in the reception aperture Rx of the probe 101. Go back to the child Rk. Since the positional information of each receiving transducer Rk in the receiving aperture Rx is acquired from the data storage unit 107, the length of the path 403 from any observation point Pij, Qmn to each receiving transducer Rk is geometrically calculated can do.

  The reception time calculation unit 1045 reflects the transmitted ultrasonic waves at the observation points Pij and Qmn for all the observation points Pij and Qmn existing in the target area for one transmission event, and the reception vibrators Rk The reception time to arrive at is calculated and output to the delay amount calculation unit 1046.

v) Delay calculation unit 1046
The delay amount calculation unit 1046 calculates the total propagation time to each receiving transducer Rk in the receiving aperture Rx from the transmission time and the receiving time, and based on the total propagation time, the received signal for each receiving transducer Rk It is a circuit that calculates the amount of delay applied to a column. The delay amount calculation unit 1046 transmits the ultrasonic wave transmitted from the transmission time calculation unit 1044 to the observation points Pij and Qmn, and the reception time to be reflected by the observation points Pij and Qmn to reach each receiving transducer Rk. To get Then, the total propagation time until the transmitted ultrasonic waves reach each receiving transducer Rk is calculated, and the delay amount for each receiving transducer Rk is calculated from the difference in the total propagation time for each receiving transducer Rk. The delay amount calculation unit 1046 calculates, for all observation points Pij and Qmn present in the target area, the delay amount to be applied to the received signal sequence for each receiving transducer Rk, and outputs the calculated delay amount to the delay processing unit 1047.

vi) Delay processing unit 1047
The delay processing unit 1047 determines, based on the reflected ultrasonic waves from the observation points Pij and Qmn, the reception signals corresponding to the delay amounts for the reception transducers Rk from the train of reception signals for the reception transducers Rk in the reception aperture Rx. It is a circuit which identifies as a received signal corresponding to the receiving vibrator Rk.

  The delay processing unit 1047 receives information indicating the position of the reception transducer Rk from the reception aperture setting unit 1043 in response to the transmission event, a reception signal corresponding to the reception transducer Rk from the data storage unit 107, the target area setting unit 1042 The information indicating the position of the acquired target area, and the delay amount applied to the received signal sequence for each receiving transducer Rk from the delay amount calculating unit 1046 are acquired as an input. Then, the reception signal corresponding to the time obtained by subtracting the delay amount for each reception transducer Rk from the train of reception signals corresponding to each reception transducer Rk is identified as the reception signal based on the reflected waves from the observation points Pij and Qmn. , And output to the addition unit 1049.

vii) Weight calculation unit 1048
The weight calculation unit 1048 is a circuit that calculates a weight sequence (reception apodization) for each reception vibrator Rk such that the weight for the vibrator located at the center of the reception aperture Rx in the column direction is maximized.

  As shown in FIG. 6, the weight sequence is a sequence of weight coefficients applied to the reception signal corresponding to each transducer in the reception aperture Rx. The weight sequence has a symmetrical distribution about the transmission focus point F. The shape of the distribution of weight series can be a Hamming window, a Hanning window, a rectangular window or the like, and the shape of the distribution is not particularly limited. The weight sequence is set such that the weight for the vibrator located at the center of the receiving aperture Rx in the row direction is maximized, and the central axis of the weight distribution coincides with the receiving aperture central axis Rxo. The weight calculation unit 1048 receives the information indicating the position of the reception transducer Rk output from the reception aperture setting unit 1043, calculates a weight sequence for each reception transducer Rk, and outputs the weight sequence to the addition unit 1049.

viii) Addition unit 1049
The adding unit 1049 receives the reception signals identified corresponding to the receiving transducers Rk output from the delay processing unit 1047, adds them, and adds the phasing to the observation points Pij and Qmn. It is a circuit that generates a signal. Alternatively, the weight sequence for each receiving transducer Rk output from the weight calculating unit 1048 is input, and the received signal identified corresponding to each receiving transducer Rk is multiplied by the weight for each receiving transducer Rk. The acoustic line signals for the observation points Pij and Qmn may be generated by addition. Based on the reflected waves from the observation points Pij and Qmn, the delay processing unit 1047 adjusts the phases of the reception signals detected by the reception transducers Rk located in the reception aperture Rx and performs addition processing by the addition unit 1049. The reception signals received by the reception transducers Rk can be superimposed to increase the signal S / N ratio, and the reception signals from the observation points Pij and Qmn can be extracted.

  An acoustic line signal can be generated for all observation points Pij and Qmn in the target area from one transmission event and the processing associated therewith. Then, as shown in FIG. 10 and FIG. 11, the ultrasonic wave transmission is repeated while moving the transmission aperture Tx in the column direction by the moving pitch Mp in synchronization with the transmission event, and ultrasonic waves are transmitted from all the transducers 101a present in the probe 101. By transmitting, a frame acoustic line signal which is a synthesized acoustic line signal of one frame is generated.

  Further, the synthesized acoustic line signal for each observation point constituting the frame acoustic line signal is hereinafter referred to as a "synthesized acoustic line signal".

  The addition unit 1049 generates subframe acoustic line signals for all observation points Pij and Qmn present in the target area in synchronization with the transmission event. Hereinafter, the subframe acoustic line signal for the observation point Pij will be referred to as a "main region acoustic line signal", and the subframe acoustic line signal for the observation point Qmn as a "subregion acoustic line signal". The generated subframe acoustic line signal is output to the data storage unit 107 and stored.

(3) Combining unit 1140
The synthesis unit 1140 is a circuit that synthesizes a frame acoustic line signal from a subframe acoustic line signal generated in synchronization with a transmission event. FIG. 9 is a functional block diagram showing a configuration of the combining unit 1140. As illustrated in FIG. 9, the combining unit 1140 includes addition processing units 11401-1 and 11401-2, amplification processing units 11402-1 and 11402-2, and a combining unit 11403. The addition processing units 11401-1 and 11401-2 respectively complete the plurality of subframes held in the data storage unit 107 after the generation of a series of subframe acoustic line signals for combining frame acoustic line signals is completed. Read out the acoustic line signal. Then, a plurality of subframe acoustic line signals are added using the positions of the observation points Pij and Qmn at which the acoustic line signals included in each subframe acoustic line signal are acquired as an index. In the present embodiment, addition processing unit 11401-1 combines main synthesized acoustic line signals with a plurality of main area acoustic line signals as an addition target, and addition processing unit 11401-2 combines a plurality of sub-area acoustic line signals. The sub-synthesized acoustic line signal is synthesized as an addition target. That is, the synthetic acoustic line signal is composed of the main synthetic acoustic line signal and the sub synthetic acoustic line signal. Even when the main area acoustic line signal and the sub area acoustic line signal exist with respect to the observation points Pij and Qmn, the addition between the main area acoustic line signal and the sub area acoustic line signal is not performed.

  The configuration of each unit constituting the combining unit 1140 will be described below.

i) Addition processing units 11401-1 and 11401-2
The addition processing unit 11401-1 reads out a plurality of subframe acoustic line signals held in the data storage unit 107 after the generation of a series of subframe acoustic line signals for combining frame acoustic line signals is completed. Then, a plurality of subframe acoustic line signals are added using the position of the observation point Pij at which the acoustic line signal included in each main area acoustic line signal is acquired as an index, thereby generating a synthetic acoustic line signal for each observation point The main partial acoustic line signal is synthesized. Similarly, the addition processing unit 11401-2 performs each observation by adding a plurality of subframe acoustic line signals using the position of the observation point Qmn at which the acoustic line signal included in each sub-region acoustic line signal is acquired as an index. A synthetic acoustic line signal for the point is generated to synthesize the sub-partial acoustic line signal. Therefore, the acoustic line signals for observation points at the same position included in the plurality of subframe acoustic line signals are added to generate a synthetic acoustic line signal. Hereinafter, when the addition processing unit 11401-1 and the addition processing unit 11401-2 are not distinguished from one another, they are referred to as an addition processing unit 11401.

  FIG. 12 is a schematic view showing a process of combining the synthetic acoustic line signal in the addition processing unit 11401. As described above, ultrasonic wave transmission is sequentially performed by making the transducers used for the transmission transducer array (transmission aperture Tx) different by one transducer in the transducer array direction in synchronization with the transmission event. Therefore, the target areas Bx and Cx based on different transmission events also differ in position by one vibrator in the same direction for each transmission event. Frame acoustic lines covering all target areas by adding the positions of observation points Pij and Qmn at which acoustic line signals included in each subframe acoustic line signal are acquired as an index to a plurality of subframe acoustic line signals The signals are combined.

  In addition, for the observation points Pij and Qmn existing across a plurality of target areas at different positions, the value of the acoustic line signal in each subframe acoustic line signal is added, so the combined acoustic line signal has a degree of crossing. Shows a large value accordingly. Hereinafter, the number of times that the observation points Pij and Qmn are included in different target areas is referred to as “the number of superpositions”, and the maximum value of the number of superpositions in the transducer array direction is referred to as “the maximum number of superpositions”.

  Further, in the present embodiment, the main area Bx is present in an hourglass-shaped area. Therefore, as shown in FIG. 13A, since the number of superpositions and the number of maximum superpositions change in the depth direction of the object, the value of the synthetic acoustic line signal also changes in the depth direction. Although not shown, the number of overlaps and the maximum number of overlaps also change in the depth direction of the object in the sub-region Cx.

  When the positions of observation points Pij and Qmn at which the acoustic line signals included in each subframe acoustic line signal are acquired are added as an index, the positions of observation points Pij and Qmn are added while weighted as an index. It is also good.

  The synthesized frame acoustic line signal is output to the amplification processing unit 11402.

ii) amplification processing units 11402-1 and 11402-2
As described above, the value of the synthetic acoustic line signal changes in the depth direction of the subject. In order to compensate for this, the amplification processing unit 11402 performs an amplification process of multiplying each synthetic acoustic line signal by the amplification factor determined according to the number of times of addition in the synthesis of the synthetic acoustic line signal included in the frame acoustic line signal. I do.

  FIG. 13B is a schematic view showing an outline of amplification processing in the amplification processing unit 11402. As shown in FIG. 13B, since the maximum number of superpositions changes in the depth direction of the subject, amplification that changes in the depth direction of the subject determined according to the maximum number of superpositions is made to compensate for this change. The ratio is multiplied to the synthetic acoustic line signal. As a result, the variation factor of the synthetic acoustic line signal due to the change in the number of superpositions in the depth direction is eliminated, and the value of the synthetic acoustic line signal after amplification processing can be made uniform in the depth direction.

  Also, processing may be performed to multiply the synthetic acoustic line signal by an amplification factor that changes in the transducer array direction determined in accordance with the number of superpositions. When the number of superpositions changes in the transducer row direction, the variation factor is eliminated and equalization of the value of the synthetic acoustic line signal after amplification processing is achieved in the transducer row direction.

  A signal obtained by performing amplification processing on the synthesized acoustic line signal for each of the generated observation points may be used as a frame acoustic line signal.

iii) Coupling part 11403
The combining unit 11403 combines the main partial acoustic line signal and the sub partial acoustic line signal for synthesizing the frame acoustic line signal to generate a frame acoustic line signal.

  The combining unit 11403 sets the value of the main partial acoustic line signal as the value of the frame acoustic line signal at the observation point P for the observation point P in the imaging main area Hx. On the other hand, for the observation point Q in the additional area Ha, Hb, a frame acoustic line signal is created as follows. When there is no corresponding main partial acoustic line signal for the observation point Q, the value of the sub partial acoustic line signal is taken as the value of the frame acoustic line signal at the observation point Q. On the other hand, in the case where either the corresponding main partial acoustic line signal or sub-partial acoustic line signal is present, the frame at the observation point Q using either or both of the main partial acoustic line signal and the sub partial acoustic line signal Calculate the value of the acoustic line signal. In the present embodiment, the value of the main partial acoustic line signal is taken as the value of the frame acoustic line signal at the observation point Q. By doing this, the value of the frame acoustic line signal can be calculated based only on the main area acoustic line signal acquired as the observation point P in the main area Bx, and the spatial resolution and the signal S / N ratio can be calculated. It can be improved. However, the method of calculating the value of the frame acoustic line signal may be a value based on the main partial acoustic line signal and the sub partial acoustic line signal, for example, arithmetic mean, geometric mean, or linear combination. By doing this, it is possible to avoid that the value of the frame acoustic line signal changes rapidly and the improvement of the image quality is not sufficient at the interface of the area.

  The generated frame acoustic line signal is output to the data storage unit 107 and stored.

<Operation>
The operation of the ultrasonic diagnostic apparatus 100 having the above configuration will be described.

  FIG. 14 is a flowchart showing the beamforming processing operation of the reception beam former 104.

  First, in step S101, the transmission unit 1031 performs transmission processing (transmission event) for supplying a transmission signal for transmitting an ultrasonic beam to each transducer included in the transmission aperture Tx among the plurality of transducers 101a in the probe 101. I do.

  Next, in step S102, the receiving unit 1040 generates a reception signal based on the electrical signal obtained from the reception of the ultrasonic wave reflected by the probe 101 and outputs the reception signal to the data storage unit 107, and the reception signal to the data storage unit 107. save. It is determined whether ultrasonic wave transmission has been completed from all the transducers 101a present in the probe 101 (step S103). Then, if not completed, the process returns to step S101, a transmission event is performed while moving the transmission aperture Tx in the column direction by the movement pitch Mp, and if completed, the process proceeds to step S201.

  Next, in step S210, the target area setting unit 1042 sets the main area Bx and the sub area Cx based on the information indicating the position of the virtual transmission opening Tv in synchronization with the transmission event. In the first loop, as shown in FIG. 10A, the main area Bx and the sub area Cx obtained from the virtual transmission opening Tv in the first transmission event are set.

  Next, the process proceeds to observation point synchronous beamforming processing (steps S220 (S221 to S228)). In step S220, first, coordinates ij and mn indicating the positions of observation points Pij and Qmn are initialized to the minimum value in main area Bx and sub area Cx (steps S221 and S222), and reception aperture setting unit 1043 determines the column center The reception aperture Rx transducer array is selected so as to coincide with the transducer Xk which is spatially closest to the observation points Pij and Qmn (step S223).

  Next, an acoustic line signal is generated for the observation point Pij (step S224).

  Here, an operation of generating an acoustic line signal for the observation point Pij in step S224 will be described. FIG. 15 is a flowchart showing an operation of generating an acoustic line signal at observation points Pij and Qmn in the reception beam former 104. FIG. 16 is a schematic diagram for explaining an operation of generating an acoustic line signal at observation points Pij and Qmn in the reception beam former 104. As shown in FIG.

  First, in step S2241, the transmission time calculation unit 1044 transmits an ultrasonic wave transmitted from an object at an arbitrary observation point Pij present in the main area Bx and an arbitrary observation point Qmn existing in the sub area Cx. The transmission time to reach the observation point Pij or Qmn is calculated. As for the transmission time, as described above, for the observation point Pij, (1) when the observation point Pij is deeper than the focus depth, the observation is performed via the transmission focus point F from the center of the virtual transmission opening Tv geometrically determined. By dividing the length of the path (401 + 402) leading to the point P ij by the sound speed c s of the ultrasonic wave, (2) the geometrically determined virtual, determined geometrically, when the observation point P ij is shallower than the focus depth It can be calculated by dividing the length of the difference (401-402) between the path from the center of the transmission aperture Tv to the transmission focus point F and the path from the observation point Pij to the focus point by the ultrasonic velocity cs. For the observation point Qmn, (a) a time calculated by dividing the length of the path (411) from the center of the virtual transmission opening Tv geometrically determined to the observation point Qmn by the ultrasonic velocity cs (b ) The transmission time calculated in (1) or (2) above, (c) the length of the path (412) from the center of the geometrically determined virtual transmission aperture Tv to the reference point R at the same depth as the observation point Qmn The time can be calculated by primary combination using at least one of (a), (b) and (c) of the time calculated by dividing the length by the sound speed cs of the ultrasonic wave.

  Next, the coordinate k indicating the position of the receiving transducer Rk in the receiving aperture Rx, which is obtained from the receiving aperture Rx, is initialized to the minimum value in the receiving aperture Rx (step S2242), and the transmitted ultrasound is observed in the subject The reception time of the light reflected by the point Pij and arriving at the reception transducer Rk of the reception aperture Rx is calculated (step S2243). The reception time can be calculated by dividing the length of the path 403 from the geometrically determined observation points Pij and Qmn to the reception transducer Rk by the sound velocity cs of the ultrasonic wave. Further, from the sum of the transmission time and the reception time, the total propagation time until the ultrasonic wave transmitted from the transmission aperture Tx is reflected at the observation points Pij and Qmn and reaches the reception transducer Rk is calculated (step S2244) The amount of delay for each receiving transducer Rk is calculated based on the difference in total propagation time for each receiving transducer Rk in the receiving aperture Rx (step S2245).

  It is determined whether the calculation of the delay amount has been completed for all the receiving transducers Rk present in the receiving aperture Rx (step S2246), and if not completed, the coordinate k is incremented (step S2247), Furthermore, the delay amount of the reception vibrator Rk is calculated (step S2243), and if it is completed, the process proceeds to step S2248. At this stage, the delay amount of the reflected wave arrival from the observation points Pij and Qmn is calculated for all the receiving transducers Rk present in the receiving aperture Rx.

  In step S2248, the delay processing unit 1047 observes the reception signal corresponding to the time obtained by subtracting the delay amount for each reception vibrator Rk from the train of reception signals corresponding to the reception vibrator Rk in the reception aperture Rx as observation point Pij, It identifies as a received signal based on the reflected wave from Qmn.

  Next, the weight calculation unit 1048 calculates a weight number sequence for each reception vibrator Rk such that the weight for the vibrator located at the center of the reception aperture Rx in the column direction is maximized (step S2249). The adder 1049 multiplies the reception signal identified corresponding to each reception transducer Rk by the weight for each reception transducer Rk and adds them to generate an acoustic line signal for the observation points Pij and Qmn (step S2250). And the generated acoustic line signals for the observation points Pij and Qmn are output to the data storage unit 107 and stored (step S2251).

  Next, returning to FIG. 14, by incrementing the coordinates ij and mn and repeating steps S223 and S224, all the observation points Pij (“•” in FIG. 15) located at the coordinates ij in the main area Bx, Acoustic line signals are generated for all observation points Qmn located at coordinates mn in the subregion Cx. It is determined whether generation of acoustic line signals has been completed for all observation points present in the target area (steps S225 and S227), and if not completed, the coordinates ij and mn are incremented (steps S226 and S228). To generate an acoustic line signal for the observation points Pij and Qmn (step S224), and when it is completed, the process proceeds to step S230. At this stage, acoustic line signals of subframes for all the observation points Pij and Qmn existing in the target area associated with one transmission event are generated, and are output and stored in the data storage unit 107.

  Next, it is determined whether generation of the acoustic line signal of the sub-frame has been completed for all the transmission events (step S230), and if it has not been completed, the process returns to step S210 and the observation points Pij and Qmn are obtained. The coordinates ij and mn indicating the position are initialized to the minimum value in the target area obtained from the virtual transmission opening Tv at the next transmission event (steps S221 and S222), the reception opening Rx is set (step S223), and the acoustic line A signal is generated (step S224), and if completed, the process proceeds to step S301.

  Next, in step S301, the addition processing unit 11401 reads the plurality of subframe acoustic line signals stored in the data storage unit 107, and uses the positions of the observation points Pij and Qmn as an index to the plurality of subframe acoustic line signals. The signal is added to generate a synthetic acoustic line signal for each observation point Pij, Qmn, and the main partial acoustic line signal and the secondary partial acoustic line signal are synthesized. Next, the amplification processing unit 11402 multiplies each synthetic acoustic line signal by an amplification factor determined according to the number of additions of the synthetic acoustic line signals included in each of the main partial acoustic line signal and the sub partial acoustic line signal ( Step S302) The amplified main partial acoustic line signal and the sub partial acoustic line signal are output to the combining unit 11403. Next, the combining unit 11403 combines the main partial acoustic line signal and the sub partial acoustic line signal to generate a frame acoustic line signal (step S303), and outputs the frame acoustic line signal to the ultrasound image generation unit 105 and the data storage unit 107. Then (step S304), the process ends.

<Summary>
As described above, according to the ultrasonic diagnostic apparatus 100 according to the present embodiment, the synthetic aperture method superimposes and synthesizes the acoustic line signals for observation points at the same position generated by different transmission events. . As a result, the effect of virtually performing transmission focusing can be obtained even at observation points at depths other than the transmission focus point F with respect to a plurality of transmission events, and spatial resolution and signal S / N ratio can be improved. .

  Further, in the ultrasonic diagnostic apparatus 100, in the additional area, the length of the path (411) from the center of the virtual transmission aperture Tv determined at least geometrically to the observation point Qmn is divided by the acoustic velocity cs of the ultrasonic wave. The transmission time is calculated based on the calculated time. As a result, it is possible to obtain an acoustic line signal with an improved signal S / N ratio by reducing an error in delay processing at an observation point near the focus depth or at an observation point distant from the imaging main area Hx in the element row direction. . On the other hand, at the observation point close to the main area Bx, the boundary between the main area Bx and the sub area Cx becomes apparent by calculating the transmission time based on the transmission time calculated by the same method as the main area Bx. You can avoid that. Therefore, compared with imaging only the imaging main area Hx, without adding the number of transmission events, and at the boundary between the imaging main area Hx and the additional areas Ha, Hb and in the additional area Ha, Hb The imaging region can be expanded in the element row direction while suppressing a rapid change in image quality.

  Further, in the ultrasonic diagnostic apparatus 100, the reception aperture setting unit 1043 selects the reception aperture Rx transducer array so that the array center coincides with the transducer that is closest to the observation point most spatially, and does not depend on the transmission event. Based on the position of the observation point, reception beamforming is performed using reception apertures that are symmetrical about the observation point. Therefore, the position of the reception aperture is fixed, not synchronized with the transmission event that changes (moves) the transmission focus point F in the horizontal axis direction, and the same reception aperture is adjusted for the same observation point even in different transmission events. Phase addition can be performed. At the same time, as the reflected wave from the observation point can be applied to a larger weight sequence as the transducer whose distance is smaller from the observation point can be applied, the observation is performed even in view of the fact that the ultrasonic wave is attenuated depending on the propagation distance. The reflected wave can be received most sensitively to the point. As a result, high spatial resolution and signal S / N ratio can be realized locally.

«Modification 1»
In the ultrasound diagnostic apparatus 100 according to the first embodiment, the reception aperture setting unit 1043 selects the reception aperture Rx such that the column center coincides with the transducer that is spatially closest to the observation point. However, the configuration of the reception aperture Rx is the total of the ultrasonic waves transmitted from the transmission aperture Tx until they are reflected at the observation point in the target area via the transmission focus point F and reach the reception transducer Rk of the reception aperture Rx. It is sufficient that the acoustic line signals for all observation points in the target area be generated by calculating the propagation time and performing delay control based on the total propagation path, and the configuration of the reception aperture Rx should be changed as appropriate. Can.

  In the first modification, a transmission synchronization type reception aperture setting unit (hereinafter, “Tx reception aperture setting unit”) for selecting a reception aperture Rx transducer array in which the column center coincides with the transmission aperture center is provided. It is different from. The configuration other than the Tx reception aperture setting unit is the same as each element shown in the first embodiment, and the description of the same part will be omitted.

  FIG. 17 is a schematic view showing the relationship among the virtual reception aperture Rv, the reception aperture Rx, the virtual transmission aperture Tv, and the transmission aperture Tx set by the Tx reception aperture setting unit. In the first modification, the virtual reception aperture Rv is selected such that the column center of the virtual reception aperture Rv coincides with the transmission aperture center. The position of the central axis Rxo of the virtual reception aperture Rv is the same as the position of the central axis Txo of the virtual transmission aperture Tv, and the virtual reception aperture Rv is a symmetrical aperture around the transmission focus point F. Therefore, the position of the virtual reception opening Rv also moves in synchronization with the position change of the virtual transmission opening Tv moving in the column direction for each transmission event. Of the virtual transmission apertures Rv, the range in which the transducers on the transducer array 101a are present is the reception aperture Rx.

  In addition, the weight sequence (reception apodization) for each receiving transducer Rk of the receiving aperture Rx is calculated so that the weights for the transducers located on the central axis Rxo of the virtual receiving aperture Rv and the central axis Txo of the virtual transmitting aperture Tv become maximum. Be done. The weight sequence has a symmetrical distribution about the transmission aperture center. The shape of the distribution of weight series can be a Hamming window, a Hanning window, a rectangular window or the like, and the shape of the distribution is not particularly limited.

<Operation>
FIG. 18 is a flowchart showing the beamforming processing operation of the reception beam former of the ultrasonic diagnostic apparatus according to the first modification. This flowchart is different in that transmission synchronous beamforming processing (steps S420 (S421 to S428)) is performed instead of the observation point synchronous beamforming processing (steps S220 (S221 to S228)) in FIG. The processes other than step S420 are the same as those in FIG. 14, and the description of the same parts will be omitted.

  In the process of step S420, first, in step S421, the Tx reception aperture setting unit selects, as a virtual reception transducer Rv, a transducer array whose row center coincides with the row center of the transmission aperture center in response to the transmission event. Set the reception aperture Rx.

  Next, the coordinates ij and mn indicating the positions of the observation points Pij and Qmn in the target area calculated in step S210 are initialized to the minimum value in the target area (steps S422 and S423), and the acoustic lines for the observation points Pij and Qmn A signal is generated (step S424). FIG. 18 is a schematic diagram for explaining an operation of generating an acoustic line signal at observation points Pij and Qmn in the reception beam former according to the first modification. The positional relationship between the transmission aperture Tx and the reception aperture Rx is different from that in FIG. 16 regarding the first embodiment. The processing method in step S424 is the same as step S224 in FIG. 11 (steps S2241 to S2251 in FIG. 14).

  By incrementing the coordinates ij and mn and repeating step S424, acoustic line signals are generated for all the observation points Pij (“·” in FIG. 16) and Qmn located at the coordinates ij and mn in the target area. . It is determined whether generation of the acoustic line signal has been completed for all observation points Pij and Qmn present in the target area (steps S425 and S427), and if not completed, the coordinates ij and mn are incremented (step At steps S426 and S428, an acoustic line signal is generated for the observation points Pij and Qmn (step S424), and if it is completed, the process proceeds to step S230. At this stage, acoustic line signals of subframes of all the observation points Pij and Qmn existing in the target area accompanying one transmission event are generated and output to the data storage unit 107 and stored.

<Effect>
The ultrasonic diagnostic apparatus according to the first modification described above has the following effects, instead of the effects obtained by removing the part related to the observation point synchronous reception aperture from the effects shown in the first embodiment. That is, in the first modification, the Tx reception aperture setting unit selects the transducer array whose column center coincides with the transmission aperture center as the virtual reception aperture Rv in response to the transmission event, and sets the reception aperture Rx. Therefore, the position of the central axis Rxo of the virtual reception opening Rv is the same as the position of the central axis Txo of the virtual transmission opening Tv, and the reception is performed in synchronization with the position change of the transmission opening center moving in the column direction for each transmission event. The position of the opening Rx also changes (moves). Therefore, phasing addition can be performed at different reception apertures in synchronization with transmission events, and although reception times differ among a plurality of transmission events, the effect of reception processing using a wider reception aperture can be obtained as a result. The spatial resolution can be made uniform over a wide observation area. In addition, for the observation point Qmn, the position of the central axis Rxo of the virtual reception aperture Rv is present on the transducer array 101a, so that the transducer to which the largest weight sequence is applied is necessarily present. The sensitivity can be improved.

«Modification 2»
In the embodiment and the modification, the case where the ultrasonic probe is a linear probe has been described.

  However, the content of the present disclosure is not limited to the case where the ultrasonic probe is a linear probe, and may be any type of probe.

  The ultrasonic diagnostic apparatus according to the second modification is characterized in that a so-called convex probe in which a vibrator is disposed on a circular arc is used as an ultrasonic probe.

  In the ultrasonic diagnostic apparatus according to the second modification, as shown in FIG. 20, the imaging main area Hx has a circular arc which is the surface of the transducer array, a straight line passing through one end of the transducer array and orthogonal to the arc, and It is an area of a fan-shaped area excluding a small fan-shaped part having the same center, which is surrounded in three directions by straight lines orthogonal to the arc passing through the other end of the column. The additional areas Ha and Hb are areas having one side of a virtual arc obtained by extending the arc of the surface of the vibrator. The main area Bx and the sub area Cx for each transmission event can be set by the same method as in the embodiment.

  Thus, even in the case of using the convex probe, the imaging area can be expanded in the element row direction.

«Other Modifications of Embodiment»
(1) In the embodiment and each modification, for the observation point P in the main area Bx, (a) When the observation point Pij is deeper than the focus depth, the transmission focus point F is passed from the center of the virtual transmission opening Tv (B) When the observation point Pij is shallower than the focus depth by dividing the length of the path leading to the observation point Pij by the sound velocity cs of the ultrasonic wave, It was calculated by dividing the length of the difference between the leading route and the route from the observation point Pij to the focal point by the sound velocity cs of the ultrasonic wave. However, for example, among the observation points P in the main area Bx, the observation points existing in the additional area Ha or in the additional area Hb and shallower than the focus depth are similar to the observation point Q in the sub area Cx. It may be calculated by a method. Further, in this case, the region shallower than the focus depth of the boundary between the sub-region Cx and the main area Bx, hold even border neighboring small weighting coefficient transmission time T ₂ (1-α), as well Good.

Alternatively, for the observation point Q in the sub-region Cx, the reception time T ₁ may be applied as it is as the transmission time. As a result, it is possible to improve the accuracy of the delay processing particularly in an area far from the focus point and an area shallow in depth.

  (2) In the embodiment and each modification, the arrangement of the transducers of the ultrasonic probe is linear (linear probe) or arc (convex probe), but it is not limited to this and may be any arrangement. .

  (3) In the embodiment and each modification, an ultrasonic image is generated for the area including the imaging main area and the additional area, but the present invention is not limited to this case. For example, the imaging direction may be changed (steering) by changing the emission direction of the ultrasonic beam to the outside in a region further outside the additional region in the element row direction. Also in this case, the number of transmission events can be reduced compared to the case of imaging the additional area by steering, so the number of transmission events per frame can be reduced compared to the prior art I am successful in improving the frame rate.

  (4) Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment, and the following cases are also included in the present invention.

  For example, the present invention may be a computer system comprising a microprocessor and a memory, the memory storing the computer program, and the microprocessor operating according to the computer program. For example, it may be a computer system which has a computer program of the ultrasonic signal processing method of the present invention, and which operates (or instructs each connected part of the operation) according to this program.

  Further, all or part of the ultrasonic diagnostic apparatus, or all or part of the ultrasonic signal processing apparatus is constituted by a computer system including a recording medium such as a microprocessor, ROM, RAM, etc., a hard disk unit, etc. The case is also included in the present invention. The RAM or the hard disk unit stores a computer program that achieves the same operation as that of the above-described devices. Each device achieves its function by the microprocessor operating according to the computer program.

  In addition, some or all of the components constituting each of the above-described devices may be configured from one system LSI (Large Scale Integration (large scale integrated circuit)). The system LSI is a super-multifunctional LSI manufactured by integrating a plurality of components on one chip, and more specifically, a computer system including a microprocessor, a ROM, a RAM, and the like. . These may be individually made into one chip, or may be made into one chip so as to include some or all. The LSI may be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. The RAM stores a computer program that achieves the same operation as the above-described devices. The system LSI achieves its functions as the microprocessor operates in accordance with the computer program. For example, the beamforming method of the present invention is stored as a program of an LSI, and the present invention is included in the present invention when the LSI is inserted into a computer and a predetermined program (beamforming method) is performed.

  Note that the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. After the LSI is manufactured, an FPGA (field programmable gate array) that can be programmed or a reconfigurable processor that can reconfigure connection and settings of circuit cells in the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology.

  In addition, some or all of the functions of the ultrasonic diagnostic apparatus according to each embodiment may be realized by a processor such as a CPU executing a program. It may be a non-temporary computer-readable recording medium in which the diagnostic method of the ultrasonic diagnostic apparatus or the program for performing the beam forming method is recorded. The program may be implemented by another independent computer system by recording and transferring the program or signal on a recording medium, and the program can be distributed via a transmission medium such as the Internet. Needless to say.

  In the ultrasonic diagnostic apparatus according to the above embodiment, the data storage unit, which is a storage device, is configured to be included in the ultrasonic diagnostic device, but the storage device is not limited thereto. Semiconductor memory, hard disk drive, optical disk drive, magnetic The storage device or the like may be externally connected to the ultrasonic diagnostic apparatus.

  Also, division of functional blocks in the block diagram is an example, and a plurality of functional blocks may be realized as one functional block, one functional block may be divided into a plurality of parts, or some functions may be transferred to another function block. May be Also, a single piece of hardware or software may process the functions of a plurality of functional blocks having similar functions in parallel or in time division.

  In addition, the order in which the above-described steps are performed is for illustrating the present invention specifically, and may be an order other than the above. Also, some of the above steps may be performed simultaneously (in parallel) with other steps.

  Further, in the ultrasonic diagnostic apparatus, the probe and the display unit are connected from the outside. However, these may be integrally provided in the ultrasonic diagnostic apparatus.

  Further, in the above embodiment, the probe has a probe configuration in which a plurality of piezoelectric elements are arranged in a one-dimensional direction. However, the configuration of the probe is not limited to this. For example, a two-dimensional array transducer in which a plurality of piezoelectric conversion elements are arrayed in a two-dimensional direction, or a plurality of transducers arrayed in a one-dimensional direction Alternatively, a swinging probe that swings to obtain a three-dimensional tomographic image may be used, and it can be properly used according to the measurement. For example, in the case of using a two-dimensionally arranged probe, it is possible to control the irradiation position and direction of the ultrasonic beam to be transmitted by individually changing the timing of applying a voltage to the piezoelectric conversion element and the value of the voltage. .

  Also, the probe may include some functions of the transmitting and receiving unit in the probe. For example, based on a control signal for generating a transmission electric signal output from the transmission / reception unit, the transmission electric signal is generated in the probe, and the transmission electric signal is converted into an ultrasonic wave. In addition, it is possible to adopt a configuration in which the received reflected ultrasound is converted into a received electrical signal, and the probe generates a received signal based on the received electrical signal.

  In addition, at least a part of the functions of the ultrasonic diagnostic apparatus according to each embodiment and the modification thereof may be combined. Furthermore, all the numerals used above are illustrated to specifically explain the present invention, and the present invention is not limited to the illustrated numerals.

  Furthermore, the present invention also includes various modifications in which modifications within the scope of those skilled in the art can be made to the present embodiment.

«Summary»
(1) The ultrasonic signal processing apparatus according to the embodiment repeats a transmission event of selectively driving a plurality of transducers arrayed in an ultrasonic probe to transmit ultrasonic waves to a subject a plurality of times, and An ultrasonic signal processing apparatus that receives a reflected ultrasonic wave from an object in synchronization with a transmission event and synthesizes a frame acoustic line signal from a plurality of subframe acoustic line signals generated based on the received reflected ultrasonic wave. The transmitting transducer array is selected from the plurality of transducers in one transmission event, and ultrasonic waves are transmitted from the transmitting transducer array so as to be focused in the subject, in synchronization with each transmitting event. A transmitting unit that selects a transmission transducer array that transmits ultrasonic waves to move sequentially in the column direction; and a reception transducer array selected from the plurality of transducers in synchronization with each transmission event; Received from inside the subject A receiving unit that generates a reception signal sequence for each of the transducers of the receiving transducer array based on the reflected ultrasonic waves, and an imaging main region as a region within the subject in which a corresponding frame acoustic line signal is to be formed; An imaging area setting unit for setting an additional area adjacent to the imaging main area in the column direction; and the reception signal sequence based on the reflected ultrasound obtained from each observation point for each transmission event A phasing addition unit that generates the subframe acoustic line signal by phasing addition; and a combining unit that combines the frame acoustic line signals based on the plurality of subframe acoustic line signals generated by the phasing addition unit. The phasing and addition unit is configured to set a main target area including an area included in an area where ultrasonic waves are focused in the object, and a part or all of the areas adjacent to the main target area in the column direction. Exists in additional area In this case, the sub target area, which is the relevant part in the additional area, is set as the area including the observation point, and is included in the observation main point in the imaging main area and in the main target area and the sub target area. It is characterized in that the method of calculating the transmission time at which the transmitted ultrasonic waves reach the observation point is different from the observation point to be measured.

  Further, in the ultrasonic signal processing method according to the embodiment, a transmission event of selectively driving a plurality of transducers arrayed in the ultrasonic probe and transmitting ultrasonic waves to the object is repeated plural times, and each transmission is performed. An ultrasonic signal processing method of receiving a reflected ultrasonic wave from an object in synchronization with an event and synthesizing a frame acoustic line signal from a plurality of subframe acoustic line signals generated based on the received reflected ultrasonic wave. The transmission transducer array is selected from the plurality of transducers in one transmission event, and ultrasonic waves are transmitted from the transmission transducer array so as to be focused in the subject, in synchronization with each transmission event, The transmission transducer array for transmitting ultrasonic waves is selected to move sequentially in the column direction, and the reception transducer array is selected from the plurality of transducers in synchronization with each transmission event, and the reception transducer array is in the subject Reflected super received from Based on the waves, a reception signal sequence for each of the transducers of the reception transducer array is generated, and the reception signal sequence based on the reflected ultrasonic waves obtained from each observation point is phased and added for each of the transmission events. An ultrasonic signal processing method of generating the sub-frame acoustic line signal and combining the frame acoustic line signal based on the plurality of sub-frame acoustic line signals generated by the phasing addition unit, the sub-frame acoustic When generating a line signal, a main object area including an area included in an area where ultrasonic waves are focused in the object, and a part or all of the area adjacent to the main object area in the column direction may be the additional area The sub-target area, which is the relevant part in the additional area when it exists in the image, is set as the area including the observation point, and the observation point and the sub-target in the main imaging area and the main target area Include in area Between the observation points, and wherein varying the method of calculating the transmission time ultrasonic wave transmitted to reach the observation point.

  According to the above configuration or method, the imaging area can be enlarged by the area of the additional area without reducing the frame rate and without reducing the spatial resolution and the S / N ratio.

  (2) Further, in the ultrasonic signal processing device according to the above (1), the phasing / adding unit may be a position where the depth of the observation point is deeper than the focus depth with respect to the observation point included in the main target area. Is the first time from the reference point to the ultrasonic wave reaching the observation point at a first time until the transmitted ultrasonic wave reaches the reference point within the main target area and at the focus depth. For the arrival time calculated by adding 2 hours, if the depth of the observation point is less than the focus depth, the observation time calculated by subtracting the second time from the first time is the observation point And the transmission time for.

  According to the above configuration, the S / N ratio of the acoustic line signal can be improved by performing delay processing with a small error on the observation point in the main target area.

  (3) Further, in the ultrasonic signal processing device according to the above (1) or (2), the phasing / adding unit may transmit ultrasonic waves transmitted from the observation point included in the sub target area to the focus point recently. The time taken to reach the observation point from a point on the transmission transducer array in contact may be the transmission time for the observation point.

  According to the above configuration, the S / N ratio of the acoustic line signal can be improved by performing delay processing with a small error on the observation point in the sub target area, particularly in the area far from the focus point.

(4) Further, in the ultrasonic signal processing device according to the above (1) or (2), the phasing / adding unit may transmit ultrasonic waves transmitted recently to the focus point for an observation point included in the sub target area. Let T ₁ be the time from the point on the transmission transducer array in contact to reach the observation point, and if the depth of the observation point is deeper than the focus depth, the transmitted ultrasonic wave is the main target A time calculated by adding a fourth time until the observation point from the reference point to the observation point is added to the third time to reach the reference point included in the area and at the focus depth When the depth of a point is less than the focus depth, the transmission time T _M is expressed by the formula T _M = αT ₁ , where T ₂ is the time calculated by subtracting the fourth time from the third time. + calculated using (1-α) T _2, the value of alpha is larger than 0 Ku is 1 or less, may be.

  According to the above configuration, the S / N ratio of the acoustic line signal can be improved by performing delay processing with a small error particularly on the observation point in the sub target area, particularly in the area far from the focus point. It is possible to prevent the transmission time from largely changing at the boundary between the sub-target area and the sub-target area, and to prevent the improvement of the image quality from becoming insufficient.

(5) Further, in the ultrasonic signal processing device according to (1) or (2), the phasing / adding unit may transmit ultrasonic waves transmitted recently to the focus point with respect to the observation point included in the sub target area. Let T ₁ be the time from the point on the transmission transducer array in contact to reach the observation point, and if the depth of the observation point is deeper than the focus depth, the transmitted ultrasonic wave is the main target A time calculated by adding a fourth time until the observation point from the reference point to the observation point is added to the third time to reach the reference point included in the area and at the focus depth If the depth of the point is less than the focus depth, the third time calculated by subtracting the fourth hours hours and T _2, the column centers of the ultrasonic waves transmitted said ultrasonic vibrator column The ultrasonic transducer at the same depth as the observation point from _Assuming that the time to reach the second reference point closest to the center of the column and T ₃ , the transmission time T _M is expressed by the equation T _M = αT ₁ + (1−α) βT ₂ + (1−α) ) (1-beta) was calculated using T _3, the value of α is at greater than 1 than 0, the value of beta is 0 or more and 1 or less, may be.

  According to the above configuration, the S / N ratio of the acoustic line signal can be improved by performing delay processing with a small error in the observation point in the sub-target area, particularly in the area far from the focus point. A large change in transmission time can be suppressed in the vicinity and at the boundary between the main target area and the sub target area, and the improvement in the image quality can be suppressed.

  (6) Further, in the ultrasonic signal processing device of (5), the value of β may increase as the difference between the depth of the corresponding observation point and the focus depth increases.

  According to the above configuration, it is possible to suppress a large change in transmission time in the vicinity of the focus depth and to suppress the improvement of the image quality from being insufficient.

  (7) Further, in the ultrasonic signal processing device according to (5) or (6), the value of α may be smaller as the difference between the depth of the corresponding observation point and the focus depth is larger.

  According to the above configuration, it is possible to suppress a large change in transmission time at the boundary between the main target area and the sub target area, and to suppress the improvement of the image quality from being insufficient.

  (8) Further, in the ultrasonic signal processing device according to the above (1) to (7), the main target area is a straight line connecting a point on the transmission transducer array closest to the focus point and the focus point It may have a line symmetrical shape with respect to.

  According to the above configuration, since the number of times of synthesis in the synthesizing unit becomes approximately equal in the element row direction, it is possible to suppress the variation of the S / N ratio of the acoustic line signal and the spatial resolution.

  (9) Further, in the ultrasonic signal processing device according to the above (8), in the transmission event in which the transmission transducer array does not include the transducer at the end of the ultrasonic probe, the main target region is the focus point The region may be located between a straight line connecting one end of the transmission transducer array and a straight line connecting the focus point and the other end of the transmission transducer array.

  According to the above configuration, the S / N ratio of the acoustic line signal and the spatial resolution can be improved by improving the utilization efficiency of the ultrasonic waves in the main target area and maximizing the number of times of synthesis in the synthesis unit.

  (10) Further, in the ultrasonic signal processing device according to (8) or (9), in the transmission event in which the transmission transducer array includes a transducer at an end of the ultrasonic probe, the transducer array is extended A virtual transmission with an end different from the end of the ultrasonic probe in the transmission transducer array on an imaginary line as one end and a point on the transmission transducer array closest to the focus point as a middle point Assuming that a transducer row is assumed, the main target region is a straight line connecting the focus point and one end of the virtual transmission transducer row, and a straight line connecting the focus point and the other end of the virtual transmission transducer row It may be an area located between.

  With the above configuration, the S / N ratio of the acoustic line signal and the spatial resolution can be improved by improving the utilization efficiency of ultrasonic waves in the main target area set in the additional area and maximizing the number of times of synthesis in the synthesis unit. It can be improved.

  (11) Further, in the ultrasonic signal processing device according to (10), in the transmission event in which the position of the focus point in the column direction is closest to the additional area, the additional area is the transmission of the virtual transmission transducer array It may be a region whose base is a portion not included in the transducer array.

  According to the above configuration, not only the sub target area but also the main target area is set in the additional area, so that the S / N ratio and the spatial resolution of the acoustic line signal can be improved.

  (12) Further, in the ultrasonic signal processing device according to the above (1) to (11), a boundary line between the additional area and the imaging main area, and the focus point and one end of the transmission transducer array are connected. Assuming that the distance in the column direction from the straight line is m, the first area is an area obtained by shifting the additional area by m along the column direction, excluding the overlapping area with the main target area. It is also good.

  According to the above configuration, even in the additional area, the effect of improving the S / N ratio and the spatial resolution of the acoustic line signal by the synthetic aperture method can be maximally obtained.

  (13) Further, in the ultrasonic signal processing device according to any one of (1) to (12), the phasing / adding unit determines the range of each of the imaging main area and the additional area and the position of the focus point. Information for determining whether or not the sub target area is an empty area is held based on the range of the first area to be determined, and it is determined that the sub target area is an empty area using the information In the transmission event, only the main target area may be set without setting the sub target area.

  With the above configuration, when the sub target area is an empty area, it is not necessary to assume the first area, and the calculation amount can be reduced.

  (14) Further, in the ultrasonic signal processing device according to any one of (1) to (13), in the observation point included in the imaging main area, the synthesizing unit corresponds to the sub-frame acoustic line corresponding to the main target area. The signal may be synthesized based on the position of the observation point to generate a frame acoustic line signal.

  With the above configuration, it is possible to generate a frame acoustic line signal based on an acoustic line signal related to a main target area having a high S / N ratio in the main target area.

  (15) The ultrasonic image display method according to the embodiment is an ultrasonic image display method in an ultrasonic signal processing apparatus which is connectable to a display unit and executes the ultrasonic signal processing method of (1). The frame acoustic line signal is converted into an ultrasonic image and displayed on the display unit.

  According to the above method, it is possible to provide the user with an ultrasonic diagnostic apparatus having a wide viewing angle.

  An ultrasonic signal processing apparatus, an ultrasonic diagnostic apparatus, an ultrasonic signal processing method, a program, and a computer readable non-transitory recording medium according to the present disclosure are used by expanding an imaging area of a conventional ultrasonic diagnostic apparatus It is useful for the upper visual field expansion.

1000 ultrasonic diagnostic system 100 ultrasonic diagnostic apparatus 150 ultrasonic signal processor 101 probe 102 multiplexer unit 103 transmit beam former 1031 transmitter 104 receive beam former 1040 receiver 1041 phasing adder 1042 target area setting unit 1043 receiving aperture Setting unit 1044 Transmission time calculation unit 1045 Reception time calculation unit 1046 Delay amount calculation unit 1047 Delay processing unit 1048 Weight calculation unit 1049 Addition unit 1140 Combining unit 11401 Addition processing unit 11402 Amplification processing unit 11403 Coupling unit 105 Ultrasonic image generation unit 106 Display Unit 107 Data storage unit 108 Control unit

Claims (17)

A transmission event in which ultrasonic waves are transmitted to the subject by selectively driving a plurality of transducers arrayed in the ultrasonic probe is repeated a plurality of times, and reflected ultrasonic waves are received from the subject in synchronization with each transmission event. An ultrasonic signal processing apparatus that synthesizes a frame acoustic line signal from a plurality of sub-frame acoustic line signals generated based on the received reflected ultrasound;
A transmission transducer array is selected from the plurality of transducers in one transmission event, and ultrasonic waves are transmitted from the transmission transducer array so as to be focused in the subject, and synchronized with each transmission event, the ultrasound waves are transmitted. A transmitting unit that selects a transmitting transducer array that transmits a signal to sequentially move in the column direction;
The receiving transducer array is selected from the plurality of transducers in synchronization with each transmission event, and each transducer of the receiving transducer array is selected based on the reflected ultrasonic wave received by the receiving transducer array from within the object. A reception unit that generates a reception signal sequence for
An imaging area setting unit configured to set an imaging main area as an area in the subject in which a corresponding frame acoustic line signal is to be formed, and an additional area adjacent to the imaging main area in the column direction;
A phasing addition unit for phasing and adding the received signal sequence based on the reflected ultrasonic waves obtained from each observation point for each of the transmission events to generate the subframe acoustic line signal;
A synthesizing unit that synthesizes the frame acoustic line signal based on the plurality of subframe acoustic line signals generated by the phasing addition unit;
The phasing addition unit is configured to set a main target area including an area included in an area where ultrasonic waves converge in the object, and a part or all of areas adjacent to the main target area in the column direction in the additional area. The sub-target area, which is the relevant part in the additional area, is set as the area including the observation point, and the observation point and the sub-target area in the main imaging area and in the main target area An ultrasonic signal processing apparatus, which differs in the method of calculating the transmission time at which the transmitted ultrasonic waves reach the observation point with respect to the observation point included in. When the depth of the observation point is at a position deeper than the focus depth with respect to the observation point included in the first main target area, the phasing addition unit is in the main target area with the transmitted ultrasonic wave. An arrival time calculated by adding a second time for an ultrasonic wave to reach the observation point from the reference point to a first time until the reference point at the focus depth is reached, The arrival time calculated by subtracting the second time from the first time is taken as the transmission time for the observation point, when the depth of the object is less than the focus depth. The ultrasonic signal processing apparatus according to claim 1. The phasing addition unit is configured to, for an observation point included in the sub-target area, a time until the transmitted ultrasonic wave reaches the observation point from a point on the transmission transducer array closest to the focus point, It is set as the said transmission time about the said observation point. The ultrasonic signal processing apparatus of Claim 1 or 2 characterized by the above-mentioned. The phasing addition unit is configured to, for an observation point included in the sub target area, determine a time T from a point on the transmission transducer array closest to the focus point to a point at which the transmitted ultrasonic wave reaches the observation point. _1, and if the depth of the observation point is deeper than the focus depth, at a third time until the transmitted ultrasonic wave is included in the main target area and reaches the reference point at the focus depth. A time calculated by adding a fourth time until an ultrasonic wave reaches the observation point from the reference point, and when the depth of the observation point is less than the focus depth, the third time from the third time _Assuming that the time calculated by subtracting 4 hours is T ₂ , the transmission time T _M is expressed by the equation T _M = αT ₁ + (1−α) T ₂
The ultrasonic signal processing apparatus according to claim 1 or 2, wherein the value of α is calculated by using and is greater than 0 and less than or equal to 1. The phasing addition unit is configured to, for an observation point included in the sub target area, determine a time T from a point on the transmission transducer array closest to the focus point to a point at which the transmitted ultrasonic wave reaches the observation point. _1, and if the depth of the observation point is deeper than the focus depth, at a third time until the transmitted ultrasonic wave is included in the main target area and reaches the reference point at the focus depth. A time calculated by adding a fourth time until an ultrasonic wave reaches the observation point from the reference point, and when the depth of the observation point is less than the focus depth, the third time from the third time Let T ₂ be the time calculated by subtracting 4 hours, and the transmitted ultrasonic wave is at the same depth from the array center of the ultrasonic transducer array as the observation point and at the array center of the ultrasonic transducer array. time T ₃ until it reaches the second reference point contact When, the transmission time T _M, formula _{T M = αT 1 + (1} -α) βT 2 + (1-α) (1-β) T 3
The ultrasonic signal processing apparatus according to claim 1 or 2, wherein the value of α is greater than 0 and is 1 or less and the value of β is 0 or more and 1 or less. The ultrasonic signal processing apparatus according to claim 5, wherein the value of β increases as the difference between the depth of the corresponding observation point and the focus depth increases. The ultrasonic signal processing apparatus according to claim 5 or 6, wherein the value of α decreases as the difference between the depth of the corresponding observation point and the focus depth increases. The main object region has a shape of line symmetry with respect to a straight line connecting a point on the transmission transducer array closest to the focus point and the focus point. The ultrasonic signal processing apparatus according to any one of the preceding claims. In a transmission event in which the transmission transducer array does not include the transducer at the end of the ultrasonic probe, the main target area is a straight line connecting the focus point and one end of the transmission transducer array, and the focus point The ultrasound signal processing apparatus according to claim 8, wherein the ultrasound signal processing apparatus is an area located between the transmission transducer array and a straight line connecting the other end of the transmission transducer array. In a transmission event in which the transmission transducer array includes a transducer at the end of the ultrasonic probe, the end of the transmission transducer array is different from the end of the transmission transducer array on a virtual line extending the transducer array Assuming that a virtual transmission transducer array having an end as one end and a point on the transmission transducer array closest to the focus point as a middle point, the main target area is the focus point and the virtual transmission 10. A region located between a straight line connecting one end of the transducer array and a straight line connecting the focus point and the other end of the virtual transmission transducer array. Ultrasonic signal processor. The additional region is a region whose bottom is a portion of the virtual transmitting transducer array not included in the transmitting transducer array in the transmission event in which the position of the focus point in the column direction is closest to the additional region. The ultrasonic signal processing apparatus according to claim 10, characterized in that: When a distance in the column direction between a boundary line between the additional area and the imaging main area and a straight line connecting the focus point and one end of the transmission transducer array is m, the first area is the additional area The ultrasound signal processing apparatus according to any one of claims 1 to 11, wherein an area obtained by shifting the area by m along the column direction is an area excluding the overlapping area with the main target area. . The phasing addition unit determines whether the sub target area is an empty area based on the respective ranges of the imaging main area and the additional area and the range of the first area determined by the position of the focus point. Information to determine whether or not the sub-target area is not set in the transmission event in which the sub-target area is determined to be an empty area using the information, and only the main target area is set. The ultrasonic signal processing apparatus according to any one of claims 1 to 12, characterized in that The synthesizing unit generates a frame acoustic line signal by synthesizing the sub-frame acoustic line signal corresponding to the main target area based on the position of the observation point, with respect to the observation point included in the imaging main area. The ultrasonic signal processing device according to any one of claims 1 to 13, characterized in that An ultrasound probe,
The ultrasonic signal processing device according to any one of claims 1 to 14,
An ultrasonic diagnostic apparatus comprising: A transmission event in which ultrasonic waves are transmitted to the subject by selectively driving a plurality of transducers arrayed in the ultrasonic probe is repeated a plurality of times, and reflected ultrasonic waves are received from the subject in synchronization with each transmission event. An ultrasonic signal processing method for synthesizing a frame acoustic line signal from a plurality of subframe acoustic line signals generated based on the received reflected ultrasonic waves,
A transmission transducer array is selected from the plurality of transducers in one transmission event, and ultrasonic waves are transmitted from the transmission transducer array so as to be focused in the subject, and synchronized with each transmission event, the ultrasound waves are transmitted. Select to move the transmitting transducer array that transmits
The receiving transducer array is selected from the plurality of transducers in synchronization with each transmission event, and each transducer of the receiving transducer array is selected based on the reflected ultrasonic wave received by the receiving transducer array from within the object. Generate a received signal sequence for
An imaging main area and an additional area adjacent in the column direction with respect to the imaging main area are set as an area in the object in which a corresponding frame acoustic line signal is to be formed;
The sub-frame acoustic line signal is generated by phasing and adding the received signal sequence based on the reflected ultrasonic waves obtained from each observation point for each of the transmission events.
It is an ultrasonic signal processing method which synthesizes the frame acoustic line signal based on the plurality of subframe acoustic line signals generated by the phasing addition unit,
When generating the sub-frame acoustic line signal, part or all of a main target area including an area included in an area where ultrasonic waves are focused in the subject and a part adjacent to the main target area in the column direction The sub-target area, which is the relevant part within the additional area, is set as the area including the observation point when the area exists in the additional area, and the observation points within the main imaging area and the main target area And calculating the transmission time at which the transmitted ultrasonic waves reach the observation point between the observation point included in the sub-target area and the observation point. An ultrasonic image display method in an ultrasonic signal processing apparatus, which is connectable to a display unit and executes the ultrasonic signal processing method according to claim 16.
A method of displaying an ultrasonic image, comprising converting the frame acoustic line signal into an ultrasonic image and displaying the image on the display unit.

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