JP7020052B2 - Ultrasound signal processing device, ultrasonic diagnostic device, ultrasonic signal processing method, and ultrasonic image display method - Google Patents

Description

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

The ultrasonic diagnostic apparatus transmits ultrasonic waves to the inside of a subject by an ultrasonic probe (hereinafter referred to as “probe”), and receives an ultrasonic reflected wave (echo) generated by a difference in acoustic impedance of the subject tissue. Further, based on the received signal obtained from this 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”). Ultrasound diagnostic equipment is widely used for morphological diagnosis of living organisms because it does not invade the subject and can observe the state of internal tissues in real time using a tomographic image or the like.

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

On the other hand, a received beamforming method has been devised by the Synthetic Aperture Method to obtain a high-quality image with high spatial resolution even in a region other than the vicinity of the transmission focus point (for example, non-patent documents). 2). According to this method, the delay control is performed in consideration of both the propagation path of the ultrasonic transmission wave and the arrival time of the reflected wave by the propagation path to the vibrator, so that the ultrasonic wave located outside the vicinity of the transmission focus point is controlled. Received beam forming that also reflects the reflected ultrasonic waves from the main irradiation area can be performed. As a result, it is possible to generate an acoustic line signal for the entire ultrasonic main irradiation region from one ultrasonic transmission event. The ultrasonic main irradiation region refers to a region in which ultrasonic waves transmitted from each oscillator constituting the transmission oscillator train propagate at all points in the region. Further, in the synthetic aperture method, the transmission focus is virtually set 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 becomes possible to obtain an ultrasonic image having a high spatial resolution and an S / N ratio.

Japanese Unexamined Patent Publication No. 4-60653

Masayasu Ito and Takeshi Mochizuki, "Ultrasonic Diagnostic Device", published by Corona Publishing Co., Ltd., 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 is being studied to expand the target region for generating an ultrasonic image (hereinafter referred to as "imaging region") in the direction in which the oscillators are arranged in the probe (hereinafter referred to as "element train direction"). As a method of expanding the imaging region in the element train 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 radially. There is a method of expanding the passing area of the ultrasonic beam by transmitting, and 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. .. However, in the method (1), the spatial resolution in the element row direction is lowered and the S / N ratio is lowered at the cost of expanding the passing region of the ultrasonic beam in the element row direction. Further, the method (2) involves an increase in the number of transmission events required to generate one ultrasonic image, which causes a decrease in the frame rate.

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

The ultrasonic signal processing apparatus according to one aspect of the present invention selectively drives a plurality of vibrators arranged in a row on an ultrasonic probe to transmit ultrasonic waves to a subject by repeating a transmission event a plurality of times, and each transmission is performed. It is an ultrasonic signal processing device that receives reflected ultrasonic waves 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 waves. Then, in one transmission event, a transmission oscillator row is selected from the plurality of oscillators, and ultrasonic waves are transmitted from the transmission oscillator row so as to be focused in the subject, and synchronized with each transmission event. The transmitter section that selects the transmitter sequence that transmits ultrasonic waves to move sequentially in the column direction, and the receiver oscillator sequence that selects the receiver oscillator sequence from the plurality of oscillators in synchronization with each transmission event, and the receiver oscillator sequence A receiving unit that generates a received signal sequence for each oscillator of the receiver oscillator sequence based on the reflected ultrasonic waves received from the subject, and a region in the subject in which the corresponding frame acoustic line signal should be formed. The imaging area setting unit that sets the imaging main area and the additional area adjacent to the imaging main area in the column direction, and each transmission event and each transmission event are obtained from each observation point. Based on the phasing addition unit that generates the subframe acoustic line signal by pacing and adding the received signal sequence based on the reflected reflected ultrasonic waves, and the plurality of subframe acoustic line signals generated by the phasing addition unit. A synthesizing unit that synthesizes the frame acoustic line signal, and the phasing addition unit includes a main target area including a region included in an area where ultrasonic waves are focused in the subject, and a column in the main target area. When a part or all of the area adjacent to the direction is present in the additional area, the sub-target area which is a part existing in the additional area among the areas adjacent to the main target area in the column direction is defined as the sub-target area. The ultrasonic waves transmitted between the observation points in the imaging main region and the main target region and the observation points included in the sub-target region reach the observation points, which are set as the region including the observation point. It is characterized in that the calculation method of the transmission time to be performed is different.

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 embodiment of the present invention, the frame rate is not lowered and the spatial resolution and S / are. The imaging region can be expanded by the area of the additional region without lowering the N ratio.

It is a block diagram which shows the structure of the ultrasonic diagnostic apparatus 100 which concerns on 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 received beam former part 104 which concerns on embodiment. It is a functional block diagram which shows the structure of the phase adjustment addition part 1041 which concerns on embodiment. It is a figure which shows the main area Bx and the sub area Cx which concerns on embodiment. It is a schematic diagram which shows the relationship between the virtual reception opening Rv, the reception opening Rx and the virtual transmission opening Tv, and the transmission opening Tx according to the embodiment. It is a schematic diagram which shows the propagation path of the ultrasonic wave which reaches the receiving oscillator Rk from the transmission opening Tx via the observation point Pij, which concerns on embodiment. It is a schematic diagram which shows the propagation path of the ultrasonic wave which reaches the observation point Qmn from the virtual transmission opening Tv which concerns on embodiment. It is a functional block diagram which shows the structure of the synthesis part 1140 which concerns on embodiment. It is a figure which shows the main area Bx and the sub area Cx in each transmission event which concerns on embodiment. It is a figure which shows the main area Bx and the sub area Cx in each transmission event which concerns on embodiment. It is a schematic diagram which shows the process of synthesizing the synthetic acoustic line signal in the addition processing part 11401 which concerns on embodiment. It is a schematic diagram which shows the maximum superposition number in the synthetic acoustic line signal which concerns on embodiment, and the outline of the amplification processing in the amplification processing unit 11402. It is a flowchart which shows the beamforming processing operation of the received beamformer part 104 which concerns on embodiment. It is a flowchart which shows the acoustic line signal generation operation about observation points Pij, Qmn in the reception beam former part 104 which concerns on embodiment. It is a schematic diagram for demonstrating the acoustic line signal generation operation about observation points Pij, Qmn in the reception beam former part 104 which concerns on embodiment. It is a schematic diagram which shows the relationship between the virtual reception opening Rv, the reception opening Rx, and the virtual transmission opening Tv, and the transmission opening Tx set by the reception opening setting unit according to the first modification. It is a flowchart which shows the beamforming processing operation of the received beamformer part which concerns on modification 1. FIG. It is a schematic diagram for demonstrating the acoustic line signal generation operation about observation points Pij, Qmn in the reception beam former part which concerns on modification 1. FIG. It is a figure which shows the main region Bx and the sub region Cx which concerns on modification 2. FIG. It is a figure which shows the imaging area in the conventional synthetic opening method.

<< Background to the form for implementing the invention >>
The inventor has conducted various studies in order to expand the imaging region in an ultrasonic diagnostic apparatus using a synthetic aperture method.

In an ultrasonic diagnostic apparatus, generally, when ultrasonic transmission to a subject is performed by a plurality of oscillators, a transmission beam that focuses the wavefront so that the ultrasonic beam is focused at a certain depth of the subject. Forming is performed (hereinafter, the depth at which focus is formed is referred to as "focus depth"). Therefore, by transmitting ultrasonic waves once (transmission event), ultrasonic waves mainly irradiate the ultrasonic main irradiation area from a plurality of oscillators used for ultrasonic transmission (hereinafter referred to as "transmission oscillator series"). Will be done. Here, the "ultrasonic main irradiation region" is a region in which ultrasonic waves transmitted from each oscillator constituting the transmission oscillator train propagate. When the transmission focus point is one point, the ultrasonic main irradiation region is an hourglass-shaped region surrounded by two straight lines passing through the transmission focus point from both ends of the base, with the transmission oscillator row as the base. The wavefront has an arc shape centered on the transmission focus point. It should be noted that the ultrasonic beam does not always focus at one point, and for example, it may only focus on a region focused from 1.5 elements to several elements (hereinafter referred to as "focus area"). However, in this case, the width of the ultrasonic main irradiation region in the column direction narrows at the focus depth, becomes the width of the focus region in the column direction at the focus depth, and the column direction expands again in the region deeper than the focus depth. .. That is, the ultrasonic main irradiation region has a shape in which the width in the column direction is the narrowest in the focus depth, and the width in the column direction is widened in the other depths according to the distance to the focus depth.

In the synthetic aperture method, since the observation point can be set for any point in the ultrasonic main irradiation region in one transmission event, the entire ultrasonic main irradiation region is the region where the acoustic wave signal is generated (hereinafter referred to as the region). , "Target area"). Since the entire area for generating an ultrasonic image cannot be set as a target area in one transmission event, a plurality of transmission events having different target areas are performed in order to generate a one-frame ultrasonic image. From the viewpoint of the utilization efficiency of ultrasonic waves, it is preferable that the target area is large, and it is preferable that the overlapping area of the target areas of two consecutive transmission events is large in order to improve the spatial resolution and the signal S / N ratio.

Therefore, a transmission event is performed with the entire area of the ultrasonic main irradiation region in the shape of an hourglass as the target region, and in synchronization with the transmission event, the ultrasonic main irradiation region and the target region are moved by one element to generate an acoustic line signal. (Hereinafter, the acoustic line signal generated by one transmission event is referred to as a "subframe acoustic line signal"), and a plurality of subframe acoustic line signals can be combined to generate a one-frame ultrasonic image. It has been done conventionally.

On the other hand, if a part of the set transmission oscillator sequence (hereinafter referred to as "virtual transmission oscillator sequence") protrudes from the oscillator sequence, the portion where the oscillator does not physically exist is the transmission oscillator sequence. Cannot be. Therefore, the configurable range of the center of the virtual transmission oscillator sequence (hereinafter referred to as “transmission aperture center”) in the element array direction cannot exceed the width of the oscillator array of the ultrasonic probe. Further, since the width of the target region in the element row direction is the minimum in the focus depth, the width of the imaging region in the element row direction is also the minimum in the focus depth. For the above reasons, for example, in the case of a linear probe, the range of a rectangle, a fan shape, and a trapezoidal shape having the oscillator row of the ultrasonic probe as the base is the maximum range of the imaging region. Further, for example, in the case of a convex probe, the central angle of the arc formed by the oscillator train of the ultrasonic probe is the maximum value of the central angle of the imaged region in the imaged region which is substantially fan-shaped.

On the other hand, as a method of expanding the imaging region in the element train direction, as described above, one is to change the transmission direction of the ultrasonic beam for each transmission event and transmit the ultrasonic beam radially. Thereby, there is a method of expanding the passing region of the ultrasonic beam. As shown in FIG. 21 (b), this is a method of steering so that the traveling direction of the ultrasonic beam is separated from the center of the oscillator row as the transmission aperture center is separated from the center of the oscillator train of the ultrasonic probe. Is. Specifically, the more the center of the transmission opening is in the positive direction of x (right side in the figure), the more the traveling direction of the ultrasonic beam is tilted in the positive direction of x (upper right side in the figure), and similarly, the center of the transmission opening. The more the is in the negative direction of x (left side in the figure), the more the traveling direction of the ultrasonic beam is tilted in the negative direction of x (upper left side in the figure). As a result, in the case of a linear probe, the imaging region has a trapezoidal shape with the width of the oscillator row as the upper base, and the imaging region is expanded in the element row direction by the difference in length between the lower base and the upper base. Can be done. However, in this method, since the target area expands radially, the overlapping area of the target areas of two consecutive transmission events becomes smaller as the depth becomes larger, the composite number becomes smaller, and the spatial resolution and the signal-to-noise ratio become smaller. It will decrease.

Further, as another method of expanding the imaging region, 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 in FIG. 21 (a) is generated by a normal transmission event, and an additional region is provided outside in the element train direction of the normal imaging region to provide an additional region. Is a method of steering with the traveling direction of the ultrasonic beam directed to an additional region, as in FIG. 21 (b). As a result, the imaged region can be expanded in the element row direction without affecting the spatial resolution and the signal-to-noise ratio for the normal imaged region. However, in this method, since a transmission event for imaging an additional area must be performed separately, the number of transmission events required to generate one ultrasonic image increases, and it is difficult to improve the frame rate. It becomes.

Therefore, in view of the above problems, the inventor has set the imaging region in the element row direction without adversely affecting the spatial resolution, the signal-to-noise ratio, and the frame rate in the combination of the transmission beamforming that focuses the wave surface and the synthetic aperture method. After studying the technology to be expanded to the above, we came up with the ultrasonic signal processing device, the ultrasonic diagnostic device, and the ultrasonic signal processing method according to the embodiment.

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

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

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

<Structure of ultrasonic diagnostic apparatus 100>
The ultrasonic diagnostic apparatus 100 selects an oscillator to be used for transmission or reception from among the plurality of oscillators 101a of the probe 101, and secures input / output to the selected oscillator. Obtained by a plurality of oscillators 101a based on the transmission beam former unit 103 that controls the timing of high voltage application to each oscillator 101a of the probe 101 and the reflected wave of ultrasonic waves received by the probe 101. It has a reception beam former unit 104 that amplifies the electric signal, performs A / D conversion, and performs reception beam forming to generate an acoustic line signal. Further, an ultrasonic image generation unit 105 that generates an ultrasonic image (B mode image) based on an output signal from the reception beam former unit 104, an acoustic line signal output by the reception beam former unit 104, and an ultrasonic image generation unit 105. A data storage unit 107 for storing an ultrasonic image output by the camera and a control unit 108 for controlling each component are provided.

Of these, the multiplexer section 102, the transmit beam former section 103, the receive beam former section 104, and the ultrasonic image generation section 105 constitute an ultrasonic signal processing device 150.

Each element constituting the ultrasonic diagnostic apparatus 100, for example, a multiplexer unit 102, a transmission beam former unit 103, a reception beam former unit 104, an ultrasonic image generation unit 105, and a control unit 108, respectively, is, for example, an FPGA (Field Programmable Gate). It is realized by a hardware circuit such as an array) and an ASIC (Application Specific Integrated Circuit). Alternatively, the configuration may be realized by a programmable device such as a processor and software. A CPU (Central Processing Unit) or GPGPU can be used as the processor, and a configuration using the GPU is called a GPGPU (General-Purpose computing on Graphics Processing Unit). These components can be a single circuit component or an aggregate of a plurality of circuit components. Further, a plurality of components can be combined into one circuit component, or an aggregate of a plurality of circuit components can be formed.

The data storage unit 107 is a computer-readable recording medium, and for example, a flexible disk, a hard disk, MO, DVD, DVD-RAM, BD, a semiconductor memory, or the like can be used. Further, the data storage unit 107 may be a storage device connected to the ultrasonic diagnostic device 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, there may be no multiplexer section 102, and the transmission beam former section 103 and the reception beam former section 104 may be directly connected to each oscillator 101a of the probe 101. Further, the probe 101 may be configured to include a transmission beam former unit 103, a reception beam former unit 104, and a part thereof. This is not limited to the ultrasonic diagnostic apparatus 100 according to the present embodiment, and the same applies to the ultrasonic diagnostic apparatus according to other embodiments and modifications described later.

<Structure of the main part of the ultrasonic diagnostic apparatus 100>
The ultrasonic diagnostic apparatus 100 according to the first embodiment receives an electric signal obtained from a transmission beam former unit 103 that transmits ultrasonic waves from each vibrator 101a of the probe 101 and reception of ultrasonic reflected waves by the probe 101. It is characterized by a receiving beam former unit 104 that generates an acoustic line signal for calculating and generating an ultrasonic image. Therefore, in the present specification, the configuration and function of the transmission beam former unit 103 and the reception beam former unit 104 will be mainly described. Regarding the configurations other than the transmission beam former unit 103 and the reception beam former unit 104, the same configurations as those used in the known ultrasonic diagnostic equipment can be applied, and this is applied to the beam former unit of the known ultrasonic diagnostic equipment. It is possible to replace and use the beam former unit according to the embodiment.

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

1. 1. Transmission beam former unit 103
The transmission beam former unit 103 is connected to the probe 101 via the multiplexer unit 102, and is from a transmission oscillator train that hits all or part of a plurality of oscillators 101a existing in the probe 101 in order to transmit ultrasonic waves from the probe 101. The timing of applying a high voltage to each of the plurality of oscillators included in the transmission opening Tx is controlled. The transmission beam former unit 103 is composed of a transmission unit 1031.

The transmission unit 1031 is a pulse-shaped transmission signal for transmitting an ultrasonic beam to each of the oscillators included in the transmission opening Tx among the plurality of oscillators 101a existing in the probe 101 based on the transmission control signal from the control unit 108. Performs 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 that drives each oscillator. The delay circuit is a circuit for setting the delay time for 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 transmission unit 1031 repeats ultrasonic transmission while moving the virtual transmission opening Tv in the column direction by a predetermined movement pitch Mp for each ultrasonic transmission, and performs ultrasonic transmission from all the vibrators 101a existing in the probe 101. Here, the virtual transmission aperture Tv is a setting transmission aperture that is set regardless of the presence or absence of the oscillator, and its column length (hereinafter referred to as “transmission aperture length”) is constant regardless of the transmission event. Is. When the oscillator exists in the entire range of the virtual transmission opening Tv, the virtual transmission opening Tv and the transmission opening Tx match. On the other hand, when there is a place where the oscillator does not exist within the range of the virtual transmission opening Tv, the portion of the virtual transmission opening Tv where the oscillator exists becomes the transmission opening Tx. In the present embodiment, the moving pitch Mp is set to one oscillator, and the virtual transmission opening Tv moves by one oscillator for each ultrasonic wave transmission. The moving pitch Mp is not limited to one oscillator, and may be, for example, 0.5 oscillators. The information indicating the position of the virtual transmission opening Tv and the information indicating the position of the oscillator 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 oscillators 101a existing in the probe 101 is 192, for example, 20 to 100 may be selected as the number of oscillator trains constituting the transmission opening Tx, and the movement pitch Mp may be selected for each ultrasonic transmission. It may be configured to make it. Hereinafter, the ultrasonic transmission performed by the transmission unit 1031 from the same transmission opening Tx is referred to as a “transmission event”.

FIG. 2 is a schematic diagram showing a propagation path of an ultrasonic wave transmitted by the transmission beam former unit 103. In a certain transmission event, a row of oscillators 101a (transmission oscillator row) arranged in an array that contributes to ultrasonic transmission is illustrated as a transmission opening Tx.

In the transmission beam former unit 103, the transmission timing of each oscillator is controlled so that the oscillator located at the center of the virtual transmission opening Tv delays the transmission timing. As a result, the ultrasonic transmission wave transmitted from the oscillator sequence in the transmission opening Tx has a focus at one point having a wavefront, that is, a transmission focus point F (Focal point) at a certain depth (Focal depth) of the subject. It will be in a state of meeting (focusing). The depth of the transmission focus point F (hereinafter referred to as “focus depth”) can be arbitrarily set. The wavefront focused at the transmission focus point F diffuses again, and the ultrasonic transmission wave propagates in the hourglass-shaped space separated by two intersecting straight lines with the transmission aperture Tx as the bottom and the transmission focus point F as the node. do. That is, the ultrasonic waves radiated at the transmission opening Tx gradually reduce the width in the space (horizontal axis direction in the figure), minimize the width at the transmission focus point F, and deeper than that (in the figure). Then, as it progresses to the upper part), it spreads and propagates again while increasing its width. This hourglass-shaped region is the ultrasonic main irradiation region Ax. As described above, the ultrasonic main irradiation region Ax may not be focused on one transmission focus point F, but may be focused on the focus region.

As described above, the ultrasonic main irradiation region Ax is a region in which the phases of the ultrasonic waves transmitted from each oscillator in the transmission oscillator row are aligned, and is also outside the ultrasonic main irradiation region Ax. The ultrasonic transmitted wave is propagating. However, since the phases of the sound waves transmitted from each oscillator in the transmission oscillator row are not aligned outside the ultrasonic main irradiation region Ax, the ultrasonic transmitted wave is compared with the inside of the ultrasonic main irradiation region Ax. Is deteriorated, and in particular, the deterioration becomes more remarkable as the distance from the ultrasonic main irradiation region Ax increases.

2. 2. Configuration of the reception beam former unit 104 The reception beam former unit 104 generates an acoustic line signal from the electric signals obtained by the plurality of oscillators 101a based on the reflected wave of the ultrasonic wave received by the probe 101. The "acoustic wire signal" is a signal after phasing addition processing has been 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 the reception beam former unit 104. As shown in FIG. 3, the receiving beam former unit 104 includes a receiving unit 1040, a phasing addition unit 1041, and a synthesizing unit 1140.

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

(1) Receiver 1040
The receiving unit 1040 is connected to the probe 101 via the multiplexer unit 102, and the received signal (RF signal) that is AD-converted after amplifying the electric signal obtained from the reception of the ultrasonic reflected wave by the probe 101 in synchronization with the transmission event. ) Is a circuit that generates. Received signals are generated in chronological order in the order of transmission events, output to the data storage unit 107, and the received 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 oscillator, and is an ultrasonic wave received by each oscillator. A sequence of signals connected in the transmission direction (depth direction of the subject) is formed.

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

The transmission unit 1031 repeats ultrasonic transmission while moving the transmission opening Tx in the column direction by the movement pitch Mp in synchronization with the transmission event, and performs ultrasonic transmission from the entire plurality of oscillators 101a existing in the probe 101. The receiving unit 1040 generates a sequence of received signals for each wave receiving oscillator in synchronization with the transmission event, and the generated received signals are stored in the data storage unit 107.

(2) Phase adjustment addition unit 1041
The phasing addition unit 1041 sets the main region Bx and the sub region Cx, which are the target regions for generating the subframe acoustic line signal in the subject, in synchronization with the transmission event. Next, for each of the plurality of observation points Pij existing in the main region Bx and the plurality of observation points Qmn existing in the sub-region Cx, the received signal strings received by each receiving oscillator Rk from the observation points are phase-adjusted and added. do. Then, it is a circuit that generates a subframe 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. 4, the phase adjustment addition unit 1041 includes a target area setting unit 1042, a reception opening 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, and a weight. It includes a calculation unit 1048 and an addition unit 1049.

Hereinafter, the configuration of each unit constituting the phasing addition unit 1041 will be described.

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

Here, the "subframe acoustic line signal" is a set of acoustic line signals for all the observation points existing in the target region generated from one transmission event. The subframe acoustic line signal is a "main region acoustic line signal" which is a set of acoustic line signals for all observation points Pij existing in the main region Bx, and an acoustic for all observation points Qmn existing in the subregion Cx. It consists of a "subregion acoustic line signal" which is a set of line signals. The "subframe" refers to a unit obtained by one transmission event and forming a cohesive signal corresponding to all observation points existing in the target area. A frame is a combination of multiple subframes with different acquisition times.

The target area setting unit 1042 first sets an imaged area including an imaged main area Hx and 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 unit 103.

FIG. 5 is a schematic diagram showing an imaging region and a target region. As shown in FIG. 5A, the imaging main region Hx is set as a rectangular region having the oscillator row 101a as a base. Then, the additional region Ha and the additional region Hb are set so as to be adjacent to the imaging main region Hx in the element train direction, respectively. In the present embodiment, the width in the column direction at the depth y of the additional region Ha and the additional region Hb is 0 (the interface between the subject and the probe) is 1 / of the transmission aperture width Tx when the transmission aperture width is Tx. The depth y is 2 and the widths in the row direction at the deepest portions of the additional regions Ha and Hb are Wa and Wb, respectively, and the width in the element row 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 far from the end of the imaging main region Hx, as shown in FIG. 5A, the entire area where the ultrasonic main irradiation region Ax and the imaging region Hx overlap is mainly covered. Set as 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 region Hx, the main region Bx and the sub region Cx are set. Specifically, as shown in FIG. 5 (b), the virtual transmission aperture Tv is regarded as a transmission aperture, and the entire area where the ultrasonic main irradiation region Ax and the imaging region Hx or the additional regions Ha and Hb overlap. Is set as the main area Bx. That is, the virtual transmission opening Tv is set as the base, and the hourglass-shaped region surrounded by two straight lines passing through the transmission focus points from both ends of the base is set as the main area Bx. Further, the sub-region Cx is determined by the following method. First, the region excluding the main region Bx from the region in which the additional region Ha is translated to the right along the element row direction so that the transmission aperture central axis Txo, which is the central axis of the virtual transmission aperture Tv, and the right end of the additional region Ha coincide with each other. Is the first region Ja. That is, a point separated by Tx / 2 to the left from the center of the transmitting aperture and a point Ja separated by Wa to the left from the point C on the center axis Txo of the transmitting aperture and having a depth at the deepest part of the imaging main region Hx. Of the regions sandwiched between the straight line connecting the two and the transmission aperture center axis Txo, the region that does not overlap with the main region Bx is defined as the first region Ja. Similarly, the region excluding the main region Bx from the region in which the additional region Hb is translated to the left along the element train direction so that the transmission aperture central axis Txo and the left end of the additional region Hb coincide with each other is defined as the second region Jb. That is, of the region sandwiched between the straight line connecting the point separated by Tx / 2 to the right from the center of the transmission opening and the point Jb separated by Wb to the right from the point C and the transmission opening center axis Txo, the main region Bx. The region that does not overlap with the second region Jb is defined as the second region Jb. Then, the overlapping region between the first region Ja and the additional region Ha and the overlapping region between the second region Jb and the additional region Hb are referred to as a sub-region Cx. If the first region Ja and the additional region Ha do not overlap, or if the second region Jb and the additional region Hb do not overlap, the sub-region Cx is not set.

10 and 11 are schematic views showing the main region Bx and the sub region Cx in each transmission event in more detail. When the virtual transmission opening Tv is the left end, that is, the center of the transmission opening is the left end oscillator of the oscillator row 101a, the virtual transmission opening Tv is the base and both ends of the bottom are each as shown in FIG. 10 (a). The hourglass-shaped region surrounded by two straight lines passing through the transmission focus point is defined as the main region Bx. At this time, since the transmission aperture central axis Txo and the right end of the additional region Ha coincide with each other, the region excluding the main region Bx from the additional region Ha becomes the first region Ja. Therefore, the sub-region Cx, which is the overlapping region of the first region Ja and the additional region Ha, is inevitably the entire area of the first region Ja, that is, the region excluding the main region Bx from the additional region Ha. On the other hand, when the virtual transmission opening Tv has moved to the right but the left end is outside the oscillator row 101a, the virtual transmission opening Tv is the base and both ends of the bottom are as shown in FIG. The hourglass-shaped region surrounded by two straight lines passing through the transmission focus point from each is defined as the main region Bx. At this time, since the transmission aperture central axis Txo is on the right side of the right end of the additional region Ha, the region excluding the main region Bx from the region where the additional region Ha is shifted to the right is the first region Ja. Therefore, the sub-region Cx, which is the overlapping region of the first region Ja and the additional region Ha, is shifted to the right as compared with the case shown in FIG. 10 (a), and the overlapping portion with the imaging main region Hx is eliminated. It becomes a shape. On the other hand, when the center of the transmission opening is substantially at the center of the oscillator row 101a, the transmission opening Tx coincides with the virtual transmission opening Tv, the transmission opening Tx is the base, and both ends of the bottom are shown in FIG. 10 (c). The hourglass-shaped region surrounded by two straight lines passing through the transmission focus point from each of the above is defined as the main region Bx. At this time, since the entire area of both the first region Ja and the second region Jb exists in the imaging main region Hx, the sub-region Cx does not exist. Further, when the virtual transmission opening Tv moves to the right and the right end is outside the oscillator row 101a, as shown in FIG. 11A, the virtual transmission opening Tv is set as the base, and transmission is performed from both ends of the bottom. The hourglass-shaped region surrounded by two straight lines passing through the focus point is defined as the main region Bx. At this time, since the transmission aperture central axis Txo is on the left side of the left end of the additional region Hb, the region excluding the main region Bx from the region where the additional region Hb is shifted to the left becomes the first region 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 inverted as compared with the case shown in FIG. 10 (b). Further, when the virtual transmission opening Tv is the right end, that is, the center of the transmission opening is the right end oscillator of the oscillator row 101a, as shown in FIG. 11B, the virtual transmission opening Tv is the base and both ends of the base. The hourglass-shaped region surrounded by two straight lines passing through the transmission focus point from each of the above is defined as the main region Bx. At this time, since the transmission aperture central axis Txo and the left end of the additional region Hb coincide with each other, the region excluding the main region Bx from the additional region Hb becomes the second region Jb. Therefore, the sub-region Cx, which is an overlapping region of the second region Jb and the additional region Hb, is inevitably the entire area of the second region Jb, that is, the region excluding the main region Bx from the additional region Hb.

Since the range of the first region Ja and the second region Jb is uniquely determined by the shape of each of the additional regions Ha and Hb and the position of the center of the transmission aperture, the positions of the imaging main region Hx and the additional regions Ha and Hb are respectively. And if the size is known, it can be determined whether or not the sub-region Cx exists based on the position of the center of the transmission aperture. For example, when the additional areas Ha and Hb are defined as described above, 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, the sub-region Cx exists, and in other cases, the sub-region Cx does not exist. Therefore, the target area setting unit 1042 may hold the range of the position of the transmission aperture center where the sub-region Cx exists with respect to the positions and sizes of the imaging main region Hx and the additional regions Ha and Hb, respectively. .. By doing so, it is possible to determine 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, only the main area Bx needs to be set, which is effective in reducing the amount of calculation. In addition, the target area setting unit 1042 replaces the range of the position of the center of the transmission opening where the sub-region Cx exists, the range of the position of the virtual transmission opening Tv where the sub-region Cx exists, or the transmission where the sub-region Cx exists. The range of the position of the focus point F may be maintained.

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
The reception aperture setting unit 1043 hits a part of a plurality of oscillators existing in the probe 101 based on the control signal from the control unit 108 and the information indicating the position of the transmission aperture Tx from the transmission beam former unit 103, and is centered on the column. Is a circuit that selects a oscillator sequence (receiver oscillator array) that matches the oscillator that is most spatially close to the observation point as the receiver oscillator and sets the receive aperture Rx.

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

Further, in order to receive the reflected wave from the entire ultrasonic main irradiation region, the number of oscillators included in the reception aperture Rx should be set to be equal to or larger than the number of oscillators included in the transmission aperture Tx in the corresponding transmission event. Is preferable. The number of oscillator trains constituting the reception opening Rx may be, for example, 32, 64, 96, 128, 192 or the like.

The virtual reception opening Rv and the reception opening Rx are set at least as many times as the maximum number of observation points Pij and Qmn in the column direction. Further, the virtual reception opening Rv and the reception opening Rx may be set sequentially in synchronization with the transmission event, or the virtual reception opening corresponding to each transmission event after all the transmission events are completed. Rv and reception opening Rx may be set collectively for the number of transmission events.

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

The data storage unit 107 outputs information indicating the position of the reception opening Rx and the reception signal corresponding to the reception oscillator 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 for calculating the transmission time at which the transmitted ultrasonic wave reaches the observation point P in the subject. The target area is based on the information indicating the position of the oscillator included in the transmission opening Tx 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 in response to the transmission event. For any observation points Pij and Qmn existing in the subject, the transmission time for the transmitted ultrasonic waves to reach the observation points Pij and Qmn in the subject is calculated.

FIG. 7 is for explaining the propagation path of ultrasonic waves emitted from the transmission opening Tx, reflected at the observation point Pij at an arbitrary position in the main region Bx, and reaching the reception oscillator Rk located in the reception opening Rx. It is a schematic diagram. Note that FIG. 7A shows a case where the observation point Pij is deeper than the focus depth, and FIG. 7B shows a case where the observation point Pij is deeper than the focus depth.

The wavefront of the transmitted wave radiated from the transmission opening Tx is focused at the transmission focus point F through the path 401 and diffused again. The transmitted wave reaches the observation point Pij in the middle of focusing or diffusion, and if there is a change in the acoustic impedance at the observation point Pij, a reflected wave is generated, and the reflected wave is sent to the receiving oscillator Rk in the receiving opening Rx in the probe 101. I will go back. Since the transmission focus point F is defined as a design value of the transmission beam former unit 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. 7 (a). When the observation point Pij is deeper than the focus depth, the transmission wave radiated from the transmission opening 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. It is calculated as if it was done. Therefore, the total value of the time for the transmitted wave to pass through the path 401 and the time for passing through the path 402 is the transmission time. As a specific calculation method, for example, the total path length obtained by adding the length of the path 401 and the length of the path 402 is divided by the propagation speed of the ultrasonic wave in the subject.

On the other hand, a case where the depth of the observation point Pij is equal to or less than the focus depth will be described with reference to FIG. 7 (b). When the depth of the observation point Pij is less than or equal to the focus depth, the time when the transmitted wave radiated from the transmission opening Tx reaches the transmission focus point F through the path 401 and the observation point Pij through the path 404. Is calculated on the assumption that the time when the observation point Pij reaches the transmission focus point F through the path 402 is the same. That is, the value obtained by subtracting the time for the transmitted wave to pass through the path 402 from the time for the transmitted wave to pass through the path 401 is the transmission time. As a specific calculation method, for example, it is 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 the ultrasonic wave in the subject.

FIG. 8A describes the propagation path of ultrasonic waves emitted from the transmission opening Tx, reflected at the observation point Qmn at an arbitrary position in the sub-region Cx, and reaching the reception oscillator Rk located in the reception opening Rx. It is a schematic diagram for doing. Note that FIG. 8A describes a case where the observation point Qmn is deeper than the focus depth. There are the following three calculation methods for the transmission time at which the transmitted ultrasonic wave reaches the observation point Qmn in the subject. One is that, as described above, the transmitted wave radiated from the transmission opening Tx reaches the transmission focus point F through the path 401, and reaches the observation point Qmn through the path 402 from the transmission focus point F. It is a method of calculating as. That is, the total value of the time for the transmitted wave to pass through the path 401 and the time for passing through the path 402 is the transmission time. As a specific calculation method, for example, the total path length obtained by adding the length of the path 401 and the length of the path 402 is divided by the propagation speed of the ultrasonic wave in the subject. This transmission time is hereinafter referred to as transmission time T ₂ . The other is a method of calculating that the transmitted wave radiated from the transmission opening Tx reaches the observation point Qmn directly through the path 411 without passing through the transmission focus point F. That is, the time that the transmitted wave passes through the path 411 is the transmission time. As a specific calculation method, for example, it is obtained by dividing the length of the path 411 by the propagation speed of the ultrasonic wave in the subject. This transmission time is hereinafter referred to as transmission time T ₁ . The last one is a method of calculating by assuming that the transmitted wave radiated from the transmission opening Tx also reaches the observation point Qmn at the same time as the time when the transmission wave reaches the reference point R at the same depth as the observation point Qmn. Is. That is, the time that the transmitted wave passes through the path 412 is the transmission time. As a specific calculation method, for example, it is obtained by dividing the length of the path 412 by the propagation speed of the ultrasonic wave in the subject. This transmission time is hereinafter referred to as transmission time T ₃ .

FIG. 8B is a diagram showing the depth of the observation point Qmn on the horizontal axis and the transmission time on the vertical axis for each of the above-mentioned three transmission times T ₁ , T ₂ , and T ₃ . In FIG. 8B, system 501 indicates transmission time T ₂ , system 502 indicates transmission time T ₁ , and system 503 indicates transmission time T ₃ . The transmission time T ₂ is discontinuous at the focus depth. This is because the minimum value of the length of the path 402 is not zero but the distance between the observation point Qmn and the transmission focus point F in the element train direction. Therefore, assuming that the distance is d and the ultrasonic velocity in the subject is cs. This is because the transmission time difference between two observation points Q adjacent to each other across the focus depth is 2 d / cs. Therefore, it is preferable to adopt the transmission time T ₁ or T ₃ in the vicinity of the focus depth. Further, when the depth of the observation point Qmn is shallow, it is considered that ultrasonic waves are directly propagated from each oscillator in the transmission opening 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 region Bx and the sub region Cx, inconsistency is conspicuous if the calculation method of the transmission time is changed between the main region Bx and the sub region Cx, so it is preferable to adopt the transmission time T ₂ . Summarizing the above, (1) transmission time T ₁ or T ₃ near the focus depth, (2) transmission time T ₁ in the region shallower than the focus depth, and (3) near the interface between the region Bx and the sub-region Cx. , The transmission time T ₂ is preferable. Therefore, as a method of calculating the transmission time _TM , for example, it can be calculated as follows.
TM = _{αT 1} + (1-α) βT ₂ + (1-α) (1-β) T ₃
Here, α and β are 0 <α ≦ 1 and 0 ≦ β ≦ 1, respectively, and it is preferable that both α and β are functions with respect to the depth of the observation point Qmn. Specifically, α is preferably 1 in the vicinity of the focus depth, and is preferably small in the vicinity of the interface with the main region Bx. Further, β is preferably a value that increases as the depth of the observation point Qmn increases. For example, α and β can be defined so as to be the system 511 in FIG. 8 (b). The transmission time _TM is not limited to the case illustrated here as long as it satisfies the above-mentioned conditions and monotonically increases with an increase in depth.

The transmission time calculation unit 1044 calculates 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 for one transmission event. And output to the delay amount calculation unit 1046.

iv) Reception time calculation unit 1045
The reception time calculation unit 1045 is a circuit for calculating the reception time for the reflected waves from the observation points P and Q to reach each of the reception oscillators Rk included in the reception aperture Rx. Arbitrary existing in the target area based on the information indicating the position of the receiving oscillator 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 in response to the transmission event. For the observation points Pij and Qmn of the above, the reception time at which the transmitted ultrasonic wave is reflected by the observation points Pij and Qmn in the subject and reaches each reception oscillator Rk of the reception opening Rx is calculated.

As described above, the transmitted wave that has reached the observation points Pij and Qmn generates a reflected wave if there is a change in the acoustic impedance at the observation points Pij and Qmn, and the reflected wave is each received vibration in the reception opening Rx in the probe 101. Return to child Rk. Since the position information of each receiving oscillator Rk in the receiving opening Rx is acquired from the data storage unit 107, the length of the path 403 from arbitrary observation points Pij and Qmn to each receiving oscillator Rk is geometrically calculated. can do.

In the reception time calculation unit 1045, for one transmission event, the transmitted ultrasonic waves are reflected at the observation points Pij and Qmn for all the observation points Pij and Qmn existing in the target area, and each reception oscillator Rk. The reception time to reach is calculated and output to the delay amount calculation unit 1046.

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

vi) Delay processing unit 1047
The delay processing unit 1047 selects a reception signal corresponding to the delay amount for each reception oscillator Rk from the sequence of reception signals for the reception oscillator Rk in the reception opening Rx, based on the reflected ultrasonic waves from the observation points Pij and Qmn. This is a circuit for identifying as a received signal corresponding to the receiving oscillator Rk.

In response to the transmission event, the delay processing unit 1047 has information indicating the position of the reception oscillator Rk from the reception opening setting unit 1043, the reception signal corresponding to the reception oscillator Rk from the data storage unit 107, and the target area setting unit 1042. Information indicating the position of the acquired target area and the delay amount applied to the sequence of the received signal for each receiving oscillator Rk from the delay amount calculation unit 1046 are acquired as inputs. Then, the received signal corresponding to the time obtained by subtracting the delay amount for each receiving oscillator Rk from the sequence of the received signals corresponding to each receiving oscillator Rk is identified as the received signal based on the reflected wave from the observation points Pij and Qmn. , Is 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 oscillator Rk so that the weight for the oscillator 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 received signal corresponding to each oscillator in the reception opening Rx. The weight sequence has a symmetrical distribution centered on the transmission focus point F. As the shape of the distribution of the weight sequence, a humming window, a hanning window, a rectangular window, or the like can be used, and the shape of the distribution is not particularly limited. The weight sequence is set so that the weight for the oscillator located at the center of the reception opening Rx in the column direction is maximized, and the central axis of the weight distribution coincides with the reception opening central axis Rxo. The weight calculation unit 1048 receives information indicating the position of the reception oscillator Rk output from the reception opening setting unit 1043 as input, calculates a weight sequence for each reception oscillator Rk, and outputs the weight sequence to the addition unit 1049.

viii) Addition unit 1049
The addition unit 1049 takes the reception signal identified corresponding to each reception oscillator Rk output from the delay processing unit 1047 as an input, adds them, and adds phasing to the observation points Pij and Qmn. It is a circuit that generates a signal. Alternatively, further, the weight sequence for each receiving oscillator Rk output from the weight calculation unit 1048 is used as an input, and the receiving signal identified corresponding to each receiving oscillator Rk is multiplied by the weight for each receiving oscillator Rk. It may be configured to generate an acoustic line signal for the observation points Pij and Qmn by adding them. By adjusting the phase of the received signal detected by each receiving oscillator Rk located in the reception opening Rx in the delay processing unit 1047 and performing the addition processing in the addition unit 1049, it is based on the reflected wave from the observation points Pij and Qmn. The received signals received by each receiving oscillator Rk can be superposed to increase the signal-to-noise ratio, and the received 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 FIGS. 10 and 11, ultrasonic transmission is repeated while moving the transmission aperture Tx in the column direction by the movement pitch Mp in synchronization with the transmission event, and ultrasonic waves are emitted from all the vibrators 101a existing in the probe 101. By performing transmission, 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 “synthetic acoustic line signal”.

The addition unit 1049 generates subframe acoustic line signals for all observation points Pij and Qmn existing in the target region 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 will be referred to as a “subframe acoustic line signal”. The generated subframe acoustic line signal is output to the data storage unit 107 and stored.

(3) Synthesis unit 1140
The synthesizing 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 the configuration of the synthesis unit 1140. As shown in FIG. 9, the synthesis unit 1140 includes addition processing units 11401-1 and 11401-2, amplification processing units 1142-1 and 11402-2, and coupling unit 11403. The addition processing units 11401-1 and 11401-2, respectively, have a plurality of subframes held in the data storage unit 107 after the generation of a series of subframe acoustic line signals for synthesizing the frame acoustic line signals is completed. Read the acoustic line signal. Then, a plurality of subframe acoustic line signals are added using the positions of the observation points Pij and Qmn from which the acoustic line signals included in each subframe acoustic line signal are acquired as indexes. In the present embodiment, the addition processing unit 11401-1 synthesizes the main synthetic acoustic line signal with a plurality of main region acoustic line signals as addition targets, and the addition processing unit 11401-2 combines a plurality of sub-region acoustic line signals. The sub-synthesis acoustic line signal is synthesized as an addition target. That is, the synthetic acoustic line signal is composed of a main synthetic acoustic line signal and a sub-synthetic acoustic line signal. Even when the main region acoustic line signal and the sub-region acoustic line signal exist for the observation points Pij and Qmn, the addition between the main region acoustic line signal and the sub-region acoustic line signal is not performed.

Hereinafter, the configuration of each unit constituting the synthesis unit 1140 will be described.

i) Addition processing units 11401-1, 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 synthesizing the frame acoustic line signals is completed. Then, a composite acoustic wire signal for each observation point is generated by adding a plurality of subframe acoustic wire signals using the position of the observation point Pij from which the acoustic wire signal included in each main region acoustic wire signal is acquired as an index. Synthesize the main partial acoustic line signal. Similarly, the addition processing unit 11401-2 adds 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 subregion acoustic line signal is acquired as an index. Synthesize the acoustic wire signal for the point is generated and the sub-partial acoustic wire signal is synthesized. Therefore, the acoustic line signals for the 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, the addition processing unit 11401 is referred to as the addition processing unit 11401.

FIG. 12 is a schematic diagram showing a process of synthesizing a synthetic acoustic line signal in the addition processing unit 11401. As described above, ultrasonic transmission is sequentially performed by differentiating the oscillators used for the transmission oscillator train (transmission aperture Tx) by one oscillator in the oscillator train direction in synchronization with the transmission event. Therefore, the positions of the target areas Bx and Cx based on different transmission events are different for each transmission event by one oscillator in the same direction. By adding a plurality of subframe acoustic wire signals using the positions of the observation points Pij and Qmn from which the acoustic wire signals included in each subframe acoustic wire signal are acquired as indexes, the frame acoustic wire covering all the target areas is covered. The signal is synthesized.

Further, for the observation points Pij and Qmn that exist over a plurality of target regions having different positions, the values of the acoustic line signals in each subframe acoustic line signal are added, so that the synthetic acoustic line signal can be straddled. It shows a large value accordingly. Hereinafter, the number of times that the observation points Pij and Qmn are included in different target regions is referred to as "superimposition number", and the maximum value of the superimposition number in the oscillator train direction is referred to as "maximum superimposition number".

Further, in the present embodiment, the main region Bx exists in the hourglass-shaped region. Therefore, as shown in FIG. 13A, the number of superpositions and the maximum number of superpositions change in the depth direction of the subject, so that the value of the synthetic acoustic line signal also changes in the depth direction. Although not shown, the number of superimpositions and the maximum number of superimpositions also change in the depth direction of the subject even in the sub-region Cx.

When adding the positions of the observation points Pij and Qmn from which the acoustic line signals included in each subframe acoustic line signal are acquired as an index, the addition is performed while weighting the positions of the observation points Pij and Qmn as an index. May be good.

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

ii) Amplification processing unit 1142-1, 11402-2
As described above, the value of the synthetic acoustic line signal changes in the depth direction of the subject. To compensate for this, the amplification processing unit 11402 multiplies each synthetic acoustic line signal by an 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 diagram showing an outline of the amplification processing in the amplification processing unit 11402. As shown in FIG. 13 (b), the maximum number of superpositions changes in the depth direction of the subject. Therefore, in order to compensate for this change, the amplification changes in the depth direction of the subject determined according to the maximum number of superpositions. The rate is multiplied by the synthetic acoustic line signal. As a result, the fluctuation factor of the synthetic acoustic line signal due to the change in the number of superimpositions in the depth direction is eliminated, and the value of the synthetic acoustic line signal after the amplification process is made uniform in the depth direction.

Further, a process of multiplying the synthetic acoustic line signal by the amplification factor that changes in the direction of the oscillator train determined according to the number of superpositions may be performed. When the number of superimpositions changes in the oscillator train direction, the fluctuation factor is eliminated, and the value of the synthetic acoustic line signal after the amplification process is made uniform in the oscillator train direction.

It should be noted that a signal obtained by subjecting the synthesized acoustic wire signal for each generated observation point to amplification processing may be used as a frame acoustic wire signal.

iii) Joint 11403
The coupling portion 11403 combines the main partial acoustic line signal and the sub partial acoustic line signal for synthesizing the frame acoustic line signal to generate the frame acoustic line signal.

The coupling portion 11403 uses 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 region Hx. On the other hand, for the observation points Q in the additional regions Ha and Hb, the frame acoustic wire signal is created as follows. When the corresponding main partial acoustic line signal does not exist for the observation point Q, the value of the sub partial acoustic line signal is set as the value of the frame acoustic line signal at the observation point Q. On the other hand, when both the corresponding main partial acoustic line signal and the sub partial acoustic line signal are present, the frame at the observation point Q is performed by using either or both of the main partial acoustic line signal and the sub partial acoustic line signal. Calculate the value of the acoustic wire signal. In the present embodiment, the value of the main partial acoustic wire signal is taken as the value of the frame acoustic wire signal at the observation point Q. By doing so, 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 region Bx, and the spatial resolution and the signal S / N ratio can be obtained. 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, an arithmetic mean, a geometric mean, or a first-order coupling. By doing so, it is possible to avoid that the value of the frame acoustic line signal changes abruptly and the image quality is not sufficiently improved at the interface of the region.

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 received beamformer unit 104.

First, in step S101, the transmission unit 1031 supplies a transmission signal for transmitting an ultrasonic beam to each of the vibrators included in the transmission openings Tx in the plurality of vibrators 101a existing in the probe 101 (transmission event). I do.

Next, in step S102, the receiving unit 1040 generates a received signal based on the electric signal obtained from the reception of the ultrasonic reflected wave by the probe 101, outputs the received signal to the data storage unit 107, and outputs the received signal to the data storage unit 107. save. It is determined whether or not the ultrasonic transmission is completed from all the oscillators 101a existing in the probe 101 (step S103). Then, if it is not completed, the process returns to step S101, a transmission event is performed while moving the transmission opening Tx by the movement pitch Mp in the column direction, and if it is 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 region Bx and the sub region Cx obtained from the virtual transmission opening Tv in the first transmission event are set.

Next, the process proceeds to the observation point synchronous beamforming process (steps S220 (S221 to S228)). In step S220, first, the coordinates ij and mn indicating the positions of the observation points Pij and Qmn are initialized to the minimum values in the main region Bx and the sub region Cx (steps S221 and S222), and the reception opening setting unit 1043 is centered on the column. Selects the reception aperture Rx oscillator sequence so that it matches the oscillator Xk closest spatially to the observation points Pij and Qmn (step S223).

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

Here, the 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 acoustic line signal generation operation for the observation points Pij and Qmn in the reception beam former unit 104. FIG. 16 is a schematic diagram for explaining the acoustic line signal generation operation for the observation points Pij and Qmn in the reception beam former unit 104.

First, in step S2241, the transmission time calculation unit 1044 has transmitted ultrasonic waves in the subject for any observation point Pij existing in the main region Bx and any observation point Qmn existing in the sub-region Cx. The transmission time to reach the observation point Pij or Qmn is calculated. As described above, the transmission time is observed for the observation point Pij from the center of the geometrically determined virtual transmission opening Tv via the transmission focus point F when the observation point Pij is deeper than the focus depth. By dividing the length of the path (401 + 402) leading to the point Pij by the sound velocity cs of the ultrasonic wave, (2) when the observation point Pij is shallower than the focus depth, it is geometrically determined or geometrically determined. It can be calculated by dividing the length of the difference (401-402) between the path from the center of the transmission opening Tv to the transmission focus point F and the path from the observation point Pij to the focus point by the sound velocity cs of the ultrasonic wave. For the observation point Qmn, (a) the time calculated by dividing the length of the path (411) from the center of the geometrically determined virtual transmission opening Tv to the observation point Qmn by the sound velocity cs of ultrasonic waves, (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 opening Tv to the reference point R at the same depth as the observation point Qmn. It can be calculated by the linear coupling using at least one of (a), (b) and (c) among the time calculated by dividing the above by the sound velocity cs of the ultrasonic wave.

Next, the coordinate k indicating the position of the receiving oscillator Rk in the receiving opening Rx obtained from the receiving opening Rx is initialized to the minimum value in the receiving opening Rx (step S2242), and the transmitted ultrasonic wave is observed in the subject. The reception time reflected at the point Pij and reaching the reception oscillator 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 oscillator Rk by the sound wave cs of the ultrasonic wave. Further, from the total of the transmission time and the reception time, the total propagation time until the ultrasonic waves transmitted from the transmission opening Tx are reflected at the observation points Pij and Qmn and reach the reception oscillator Rk is calculated (step S2244). The delay amount for each receiving oscillator Rk is calculated from the difference in the total propagation time for each receiving oscillator Rk in the receiving opening Rx (step S2245).

It is determined whether or not the calculation of the delay amount is completed for all the receiving oscillators Rk existing in the receiving opening Rx (step S2246), and if not, the coordinate k is incremented (step S2247). Further, the delay amount is calculated for the receiving oscillator Rk (step S2243), and if it is completed, the process proceeds to step S2248. At this stage, the delay amount of arrival of the reflected wave from the observation points Pij and Qmn is calculated for all the receiving oscillators Rk existing in the receiving opening Rx.

In step S2248, the delay processing unit 1047 obtains a received signal corresponding to the time obtained by subtracting the delay amount for each receiving oscillator Rk from the sequence of the received signals corresponding to the receiving oscillator Rk in the receiving opening Rx. It is identified as a received signal based on the reflected wave from Qmn.

Next, the weight calculation unit 1048 calculates a weight sequence for each receiving oscillator Rk so that the weight for the oscillator located at the center of the receiving aperture Rx in the column direction is maximized (step S2249). The addition unit 1049 multiplies the received signal identified corresponding to each receiving oscillator Rk by a weight for each receiving oscillator Rk and adds them to generate an acoustic line signal for the observation points Pij and Qmn (step S2250). ), The acoustic line signal for the generated observation points Pij and Qmn is 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 region Bx,. Acoustic line signals are generated for all observation points Qmn located at coordinates mn in the subregion Cx. It is determined whether or not the generation of the acoustic line signal is completed for all the observation points existing in the target area (steps S225 and S227), and if not, the coordinates ij and mn are incremented (steps S226 and S228). ), An acoustic line signal is generated for the observation points Pij and Qmn (step S224), and when completed, the process proceeds to step S230. At this stage, subframe acoustic line signals for all observation points Pij and Qmn existing in the target area associated with one transmission event are generated, output to the data storage unit 107, and stored.

Next, for all transmission events, it is determined whether or not the generation of the acoustic line signal of the subframe is completed (step S230), and if not, the process returns to step S210 and the observation points Pij and Qmn are returned to. Initialize the position coordinates ij and mn to the minimum values in the target area obtained from the virtual transmission opening Tv in the next transmission event (steps S221 and S222), set the reception opening Rx (step S223), and set the acoustic line. The signal is created (step S224), and if it is completed, the process proceeds to step S301.

Next, in step S301, the addition processing unit 11401 reads out a plurality of subframe acoustic line signals held in the data storage unit 107, and uses the positions of the observation points Pij and Qmn as indexes to generate a plurality of subframe acoustic line signals. By adding, a synthetic acoustic line signal for each observation point Pij and Qmn is generated, and a main partial acoustic line signal and a sub 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 each synthetic acoustic line signal 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 coupling portion 11403. Next, the coupling unit 11403 combines the main partial acoustic wire signal and the sub partial acoustic wire signal to generate a frame acoustic wire signal (step S303), and outputs the frame acoustic wire signal to the ultrasonic image generation unit 105 and the data storage unit 107. (Step S304), the process is terminated.

<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 of the observation points at the same position generated by different transmission events. .. As a result, even at an observation point at a depth other than the transmission focus point F for a plurality of transmission events, the effect of virtually performing transmission focus can be obtained, and the spatial resolution and the signal-to-noise ratio can be improved. ..

Further, in the ultrasonic diagnostic apparatus 100, in the additional region, at least the length of the path (411) from the center of the geometrically determined virtual transmission opening Tv to the observation point Qmn is divided by the sound wave 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 an observation point distant from the imaging main region Hx in the element train direction. .. On the other hand, at the observation point close to the main region Bx, the boundary between the main region Bx and the sub region Cx becomes apparent by calculating the transmission time based on the transmission time calculated by the same method as the main region Bx. You can avoid that. Therefore, as compared with the case where only the imaging main region Hx is imaged, the number of transmission events is not added, and the boundary between the imaging main region Hx and the additional regions Ha and Hb, and within the additional regions Ha and Hb. The imaging region can be expanded in the element train direction while suppressing abrupt changes in image quality.

Further, in the ultrasonic diagnostic apparatus 100, the reception opening setting unit 1043 selects the reception opening Rx oscillator row so that the center of the row matches the vibrator closest to the observation point in space, and does not depend on the transmission event. Based on the position of the observation point, receive beamforming is performed using a reception aperture that is symmetrical around the observation point. Therefore, the position of the reception aperture becomes constant without synchronizing with the transmission event that changes (moves) the transmission focus point F in the horizontal axis direction, and even in different transmission events, the same reception opening is adjusted for the same observation point. Phase addition can be performed. At the same time, the reflected wave from the observation point can be applied with a larger weight sequence as the oscillator has a smaller distance from the observation point. Therefore, even considering that the ultrasonic wave is attenuated depending on the propagation distance, it is observed. The reflected wave can be received with the highest sensitivity to the point. As a result, high spatial resolution and signal-to-noise ratio can be locally realized.

<< Modification 1 >>
In the ultrasonic diagnostic apparatus 100 according to the first embodiment, the reception aperture setting unit 1043 has a configuration in which the reception aperture Rx is selected so that the center of the column matches the oscillator closest to the observation point in space. However, the configuration of the reception opening Rx is the total until the ultrasonic wave transmitted from the transmission opening Tx is reflected at the observation point in the target region via the transmission focus point F and reaches the reception oscillator Rk of the reception opening Rx. It suffices as long as it generates acoustic line signals for all observation points in the target area 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 be done.

In the first modification, the first embodiment is provided with a transmission synchronous type reception aperture setting unit (hereinafter, “Tx reception aperture setting unit”) for selecting a reception aperture Rx oscillator column whose column center matches the transmission aperture center. Is different from. The configuration other than the Tx reception opening setting portion is the same as each element shown in the first embodiment, and the description of the same portion will be omitted.

FIG. 17 is a schematic diagram showing the relationship between the virtual reception opening Rv and the reception opening Rx set by the Tx reception opening setting unit and the virtual transmission opening Tv and the transmission opening Tx. In the first modification, the virtual reception opening Rv is selected so that the column center of the virtual reception opening Rv coincides with the transmission opening center. 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 virtual reception opening Rv is an opening symmetrical with respect to 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 that moves in the column direction for each transmission event. Of the virtual transmission aperture Rv, the range in which the oscillator on the oscillator row 101a exists is the reception aperture Rx.

Further, the weight sequence (reception apodization) for each of the receiving oscillators Rk of the receiving opening Rx is calculated so that the weights for the oscillators located on the central axis Rxo of the virtual receiving opening Rv and the central axis Txo of the virtual transmitting opening Tv are maximized. Will be done. The weight sequence has a symmetrical distribution centered on the center of the transmission aperture. As the shape of the distribution of the weight sequence, a humming window, a hanning window, a rectangular window, or the like can be used, and the shape of the distribution is not particularly limited.

<Operation>
FIG. 18 is a flowchart showing a beamforming processing operation of the receiving beamformer unit of the ultrasonic diagnostic apparatus according to the first modification. This flowchart differs in that the transmission synchronous beamforming process (steps S420 (S421 to S428)) is performed instead of the observation point synchronous beamforming process (steps S220 (S221 to S228)) in FIG. The processing other than step S420 is the same as in FIG. 14, and the description of the same portion will be omitted.

In the process of step S420, first, in step S421, the Tx reception aperture setting unit selects a oscillator sequence whose column center matches the column center of the transmission aperture center as the virtual reception oscillator Rv 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 values in the target area (steps S422 and S423), and the acoustic lines are obtained for the observation points Pij and Qmn. Generate a signal (step S424). FIG. 18 is a schematic diagram for explaining the acoustic line signal generation operation for the observation points Pij and Qmn in the reception beam former unit according to the first modification. The positional relationship between the transmission opening Tx and the reception opening Rx is different from that of FIG. 16 according to 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 or not the generation of the acoustic line signal is completed for all the observation points Pij and Qmn existing in the target area (steps S425 and S427), and if not, the coordinates ij and mn are incremented (step). S426, S428) to generate an acoustic line signal for the observation points Pij and Qmn (step S424), and if completed, the process proceeds to step S230. At this stage, the acoustic line signals of the subframes of all the observation points Pij and Qmn existing in the target area associated with one transmission event are generated, output to the data storage unit 107, and stored.

<Effect>
The ultrasonic diagnostic apparatus according to the first modification described above exhibits the following effects in place of the effects shown in the first embodiment excluding the portion related to the reception opening of the observation point synchronization type. That is, in the first modification, the Tx reception aperture setting unit selects the oscillator sequence whose column center matches the transmission aperture center as the virtual reception aperture Rv and sets the reception aperture Rx in response to the transmission event. 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 reception is performed in synchronization with the position change of the transmission opening center that moves 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 openings in synchronization with the transmission event, and although the reception time is different over a plurality of transmission events, as a result, the effect of reception processing using a wider reception aperture can be obtained. Therefore, the spatial resolution can be made uniform over a wide observation area. Further, for the observation point Qmn, since the position of the central axis Rxo of the virtual reception opening Rv exists on the oscillator sequence 101a, the oscillator to which the largest weight sequence is applied always exists, and reception is performed. The sensitivity can be improved.

<< Modification 2 >>
In the embodiment and the modified example, 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 kind of probe.

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

In the ultrasonic diagnostic apparatus according to the second modification, as shown in FIG. 20, the imaging main region Hx has an arc that is the surface of the sector, a straight line that passes through one end of the sector and is orthogonal to the arc, and a sector. It is a region of the shape excluding a small fan shape having the same center from the fan shape, which is surrounded in three directions by a straight line passing through the other end of the row and orthogonal to the arc. Further, the additional regions Ha and Hb are regions having a virtual arc as one side, which is an extension of the arc on the surface of the oscillator. The main area Bx and the sub area Cx for each transmission event can be set by the same method as in the embodiment.

As a result, even when the convex probe is used, the imaging region can be expanded in the element train direction.

<< Other variants of the embodiment >>
(1) In the embodiment and each modification, for the observation point P in the main region 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. By dividing the length of the path to the observation point Pij by the speed of sound cs of the ultrasonic wave, (b) when the observation point Pij is shallower than the focus depth, the center of the virtual transmission opening Tv becomes the transmission focus point F. It was calculated by dividing the length of the difference between the path to the path and the path from the observation point Pij to the focus point by the sound velocity cs of the ultrasonic wave. However, for example, among the observation points P in the main region Bx, the observation points existing in the additional region Ha or the additional region Hb and shallower than the focus depth are the same as the observation points Q in the subregion Cx. It may be calculated by a method. Further, in this case, for the region shallower than the focus depth of the boundary between the sub-region Cx and the main region Bx, the weighting coefficient (1-α) of the transmission time T ₂ may remain small even in the vicinity of the boundary. 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, the accuracy of delay processing can be improved particularly in a region far from the focus point and a region having a shallow depth.

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

(3) In the embodiment and each modification, an ultrasonic image is generated for a region consisting of an imaging main region and an additional region, but the present invention is not limited to this case. For example, (steering) imaging may be performed by changing the emission direction of the ultrasonic beam to the outside in a region further outside the additional region in the element train direction. Even in this case, since the number of transmission events can be reduced as compared with the case where the additional area is imaged by steering, the number of transmission events per frame can be reduced as compared with the conventional technique. It is effective in improving the frame rate.

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

For example, the present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor may operate according to the computer program. For example, it may be a computer system having a computer program of the ultrasonic signal processing method of the present invention and operating according to this program (or instructing each connected part to operate).

Further, all or part of the ultrasonic diagnostic apparatus, and all or part of the ultrasonic signal processing apparatus, are configured by a computer system composed of a microprocessor, a recording medium such as ROM, RAM, a hard disk unit, and the like. Cases are also included in the present invention. The RAM or the hard disk unit stores a computer program that achieves the same operation as each of the above devices. When the microprocessor operates according to the computer program, each device achieves its function.

Further, a part or all of the components constituting each of the above-mentioned devices may be composed of one system LSI (Large Scale Integration (large-scale integrated circuit)). A system LSI is a super-multifunctional LSI manufactured by integrating a plurality of components on one chip, and specifically, is a computer system including a microprocessor, ROM, RAM, and the like. .. These may be individually integrated into one chip, or may be integrated into one chip so as to include a part or all of them. The LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. A computer program that achieves the same operation as each of the above devices is stored in the RAM. When the microprocessor operates according to the computer program, the system LSI achieves its function. For example, the present invention also includes a case where the beamforming method of the present invention is stored as an LSI program, and the LSI is inserted into a computer to carry out a predetermined program (beamforming method).

The method of making an integrated circuit is not limited to the LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection and settings of circuit cells inside the LSI may be used.

Furthermore, if an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology or another technology derived from it, it is naturally possible to integrate functional blocks using that technology.

Further, a part or all of the functions of the ultrasonic diagnostic apparatus according to each embodiment may be realized by executing a program by a processor such as a CPU. It may be a non-temporary computer-readable recording medium on which a diagnostic method of the ultrasonic diagnostic apparatus or a program for carrying out a beamforming method is recorded. By recording a program or signal on a recording medium and transferring it, the program may be executed by another independent computer system, and the above program can be distributed via a transmission medium such as the Internet. Needless to say.

The ultrasonic diagnostic apparatus according to the above embodiment has a configuration in which a data storage unit, which is a storage device, is included in the ultrasonic diagnostic apparatus, but the storage device is not limited to this, and a semiconductor memory, a hard disk drive, an optical disk drive, and a magnetic device are used. The storage device, etc. may be configured to be connected to the ultrasonic diagnostic device from the outside.

In addition, the division of functional blocks in the block diagram is an example, and multiple functional blocks can be realized as one functional block, one functional block can be divided into multiple, and some functions can be transferred to other functional blocks. You may. Further, the functions of a plurality of functional blocks having similar functions may be processed by a single hardware or software in parallel or in a time division manner.

Further, the order in which the above steps are executed is for exemplifying the present invention in detail, and may be an order other than the above. Further, a part of the above steps may be executed simultaneously with other steps (parallel).

Further, the ultrasonic diagnostic apparatus is configured such that the probe and the display unit are connected from the outside, but these may be configured to be integrally provided in the ultrasonic diagnostic apparatus.

Further, in the above embodiment, the probe shows 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, and for example, a two-dimensional array oscillator in which a plurality of piezoelectric conversion elements are arranged in a two-dimensional direction or a plurality of oscillators arranged in a one-dimensional direction is machined. A oscillating probe that oscillates to acquire a three-dimensional tomographic image may be used, and can be appropriately used depending on the measurement. For example, when a probe arranged in two dimensions is used, the irradiation position and direction of the ultrasonic beam to be transmitted can be controlled by individually changing the timing and voltage value of applying a voltage to the piezoelectric conversion element. ..

Further, the probe may include a part of the function of the transmission / reception unit in the probe. For example, based on the control signal for generating the 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 ultrasonic waves. At the same time, it is possible to adopt a configuration in which the received reflected ultrasonic wave is converted into a received electric signal and a received signal is generated based on the received electric signal in the probe.

Further, at least a part of the functions of the ultrasonic diagnostic apparatus according to each embodiment and the modified examples thereof may be combined. Further, the numbers used above are all exemplified for the purpose of specifically explaining the present invention, and the present invention is not limited to the exemplified numbers.

Further, the present invention also includes various modifications in which modifications within the range conceivable by those skilled in the art are made to the present embodiment.

≪Summary≫
(1) The ultrasonic signal processing apparatus according to the embodiment repeats a transmission event for selectively driving a plurality of vibrators arranged in a row on an ultrasonic probe and transmitting ultrasonic waves to a subject a plurality of times, and each of them. An ultrasonic signal processing device that receives reflected ultrasonic waves from a subject in synchronization with a transmission event and synthesizes a frame acoustic line signal from multiple subframe acoustic line signals generated based on the received reflected ultrasonic waves. Therefore, in one transmission event, a transmission oscillator row is selected from the plurality of oscillators, and ultrasonic waves are transmitted from the transmission oscillator row so as to be focused in the subject, in synchronization with each transmission event. , A transmitter that selects the transmitter row that transmits ultrasonic waves to move sequentially in the column direction, and a receiver oscillator row that selects a receiver oscillator row from the plurality of oscillators in synchronization with each transmission event. In the subject where the receiving unit that generates the received signal sequence for each oscillator of the receiver oscillator sequence and the corresponding frame acoustic line signal should be formed based on the reflected ultrasonic wave received from the subject. An imaging region setting unit that sets an imaging main region as a region and an additional region adjacent to the imaging main region in the column direction, and a reflected ultrasonic wave obtained from each observation point for each transmission event. Based on the phasing addition unit that generates the subframe acoustic line signal by pacing and adding the received signal sequence based on the above, and the plurality of subframe acoustic line signals generated by the phasing addition unit, the frame acoustic line. The phase adjustment addition unit includes a synthesis unit for synthesizing signals, and the phase adjustment addition unit includes a main target region including a region included in an area where ultrasonic waves are focused in the subject, and a region adjacent to the main target region in the column direction. When a part or all of the above is present in the additional region, the sub-target region which is the portion in the additional region is set as a region including the observation point, and the imaging main region and the main target are set. It is characterized in that the method of calculating the transmission time at which the transmitted ultrasonic wave reaches the observation point differs between the observation point in the region and the observation point included in the sub-target region.

Further, in the ultrasonic signal processing method according to the embodiment, a transmission event of selectively driving a plurality of vibrators arranged in an ultrasonic probe to transmit ultrasonic waves to a subject is repeated a plurality of times, and each transmission is performed. It is an ultrasonic signal processing method that receives reflected ultrasonic waves 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 waves. Then, in one transmission event, a transmission oscillator row is selected from the plurality of oscillators, and ultrasonic waves are transmitted from the transmission oscillator row so as to be focused in the subject, and synchronized with each transmission event. The transmitter row that transmits ultrasonic waves is selected to move sequentially in the column direction, the receiver oscillator train is selected from the plurality of oscillators in synchronization with each transmission event, and the receiver oscillator train is in the subject. A received signal sequence is generated for each oscillator of the received oscillator row based on the reflected ultrasonic waves received from the receiver, and the received signal train based on the reflected ultrasonic waves obtained from each observation point is generated for each transmission event. Is an ultrasonic signal processing method that generates the subframe acoustic line signal by phasing and adding, and synthesizes the frame acoustic line signal based on the plurality of subframe acoustic line signals generated by the phasing addition unit. Further, when the subframe acoustic line signal is generated, a main target region including a region included in the area where ultrasonic waves are focused in the subject and a part of a region adjacent to the main target region in the column direction. Alternatively, when all of them exist in the additional region, the sub-target region which is the portion in the additional region is set as a region including the observation point, and the imaging main region and the main target region are set. It is characterized in that the method of calculating the transmission time at which the transmitted ultrasonic wave reaches the observation point differs between the observation point and the observation point included in the sub-target area.

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

(2) Further, in the ultrasonic signal processing apparatus of the above (1), when the phase adjustment addition unit is at 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 region. Is the first time until the transmitted ultrasonic wave reaches the reference point in the main target region and at the focus depth, and the ultrasonic wave reaches the observation point from the reference point. The arrival time calculated by adding 2 hours is calculated by subtracting the 2nd time from the 1st time when the depth of the observation point is less than the focus depth. It may be the transmission time of the above.

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 for the observation points in the main target region.

(3) Further, in the ultrasonic signal processing device of the above (1) or (2), in the phasing addition unit, the transmitted ultrasonic wave has recently been transferred to the focus point for the observation point included in the sub-target region. The time from a point on the contacting transmitter row to reach the observation point may be defined as the transmission time for the observation point.

According to the above configuration, it is possible to improve the S / N ratio of the acoustic line signal by performing delay processing with a small error for the observation points in the sub-target region, particularly in the region far from the focus point.

(4) Further, in the ultrasonic signal processing device of the above (1) or (2), in the phasing addition unit, the transmitted ultrasonic wave has recently reached the focus point for the observation point included in the sub-target region. The time from the point on the contacting oscillator train to reach the observation point is T ₁ , and when the depth of the observation point is deeper than the focus depth, the transmitted sound wave is the main target. The observation, which is the time calculated by adding the fourth time from the reference point to the observation point of the ultrasonic wave to the third time until the reference point in the focus depth is included in the region. When the depth of the point is less than the focus depth, the transmission time TM is calculated by the formula _TM = _{αT 1} when the time calculated by subtracting the fourth time from the third time is T ₂ . Calculated using + (1-α) T ₂ , the value of α may be greater than 0 and less than or equal to 1.

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

(5) Further, in the ultrasonic signal processing device of the above (1) or (2), in the phasing addition unit, the transmitted ultrasonic wave has recently reached the focus point for the observation point included in the sub-target region. The time from a point on the contacting oscillator train to reach the observation point is T ₁ , and when the depth of the observation point is deeper than the focus depth, the transmitted sound wave is the main target. The observation, which is the time calculated by adding the fourth time from the reference point to the observation point of the ultrasonic wave to the third time until the reference point in the focus depth is included in the region. When the depth of the point is less than the focus depth, the time calculated by subtracting the fourth time from the third time is defined as T ₂ , and the transmitted sound wave is the center of the row of the ultrasonic oscillator row. When the time from to reach the second reference point closest to the center of the row of the ultrasonic oscillator train at the same depth as the observation point and T3 _, the transmission time _TM is calculated by the equation _TM =. Calculated using αT ₁ + (1-α) βT ₂ + (1-α) (1-β) T ₃ , the value of α is greater than 0 and less than or equal to 1, and the value of β is greater than or equal to 0 and 1 It may be as follows.

According to the above configuration, the S / N ratio of the acoustic line signal can be improved and the focus depth can be improved by performing delay processing with a small error for the observation points in the sub-target region, especially in the region far from the focus point. It is possible to suppress a large change in the transmission time in the vicinity and at the boundary between the main target area and the sub target area, and to prevent insufficient image quality improvement.

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

With the above configuration, it is possible to prevent the transmission time from changing significantly in the vicinity of the focus depth and to prevent the image quality from being insufficiently improved.

(7) Further, in the ultrasonic signal processing apparatus of (5) or (6), the value of α may be reduced as the difference between the depth of the corresponding observation point and the focus depth becomes larger.

With the above configuration, it is possible to prevent a large change in the transmission time at the boundary between the main target area and the sub target area, and to prevent insufficient image quality improvement.

(8) Further, in the ultrasonic signal processing apparatus of (1) to (7), the main target area is a straight line connecting a point on the transmission oscillator train that is in close contact with the focus point and the focus point. It may have a shape that is line-symmetrical with respect to the relative.

With the above configuration, since the number of synthesiss in the synthesis unit is substantially equal in the element row direction, it is possible to suppress variations in the S / N ratio and spatial resolution of the acoustic line signal.

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

With the above configuration, it is possible to improve the S / N ratio and the spatial resolution of the acoustic line signal by improving the utilization efficiency of ultrasonic waves in the main target region and maximizing the number of synthesis in the synthesis unit.

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

With the above configuration, the S / N ratio and spatial resolution of the acoustic line signal 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. Can be improved.

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

With 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, the ultrasonic signal processing devices (1) to (11) connect the boundary line between the additional region and the imaging main region, the focus point, and one end of the transmission oscillator row. Assuming that the distance from the straight line in the column direction is m, the first region is a region obtained by shifting the additional region by m along the column direction and excluding the overlapping region with the main target region. May be good.

With the above configuration, the effect of improving the S / N ratio and the spatial resolution of the acoustic line signal by the synthetic aperture method can be enjoyed to the maximum even in the additional region.

(13) Further, in the ultrasonic signal processing apparatus of the above (1) to (12), the phasing addition unit is based on the respective ranges of the imaging main region and the additional region and the position of the focus point. Information for determining whether or not the sub-target region is an empty region is held based on the determined range of the first region, and it is determined that the sub-target region is an empty region 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 becomes an empty area, it is not necessary to assume the first area, which is effective in reducing the amount of calculation.

(14) Further, in the ultrasonic signal processing apparatus of (1) to (13), the synthesis unit has the subframe acoustic line corresponding to the main target region for the observation point included in the imaging main region. The frame acoustic line signal may be generated by synthesizing the signals based on the positions of the observation points.

With the above configuration, a frame acoustic line signal can be generated in the main target region based on the acoustic line signal related to the main target region having a high S / N ratio.

(15) The ultrasonic image display method according to the embodiment is an ultrasonic image display method in an ultrasonic signal processing device that can connect to a display unit and executes the ultrasonic signal processing method of (1) above. Then, the frame acoustic line signal is converted into an ultrasonic image and displayed on the display unit.

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

The ultrasonic signal processing device, ultrasonic diagnostic device, ultrasonic signal processing method, program, and computer-readable non-temporary recording medium according to the present disclosure are used by expanding the imaging area of the conventional ultrasonic diagnostic device. Useful for expanding the upper field of view.

1000 Ultrasonic diagnostic system 100 Ultrasonic diagnostic device 150 Ultrasonic signal processing device 101 Probe 102 multiplexer section 103 Transmit beam former section 1031 Transmitter section 104 Receive beam former section 1040 Receiver section 1041 Phase adjustment addition section 1042 Target area setting section 1043 Reception opening 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 Synthesis unit 11401 Addition processing unit 11402 Amplification processing unit 11403 Coupling unit 105 Ultrasound image generation unit 106 Display Unit 107 Data storage unit 108 Control unit

Claims (17)

A transmission event that selectively drives multiple oscillators arranged in a row on the ultrasonic probe to transmit ultrasonic waves to the subject is repeated multiple times, and reflected ultrasonic waves are received from the subject in synchronization with each transmission event. It is an ultrasonic signal processing device that synthesizes a frame acoustic wave signal from a plurality of subframe acoustic wave signals generated based on the received reflected ultrasonic wave.
In one transmission event, a transmission oscillator row is selected from the plurality of oscillators, ultrasonic waves are transmitted from the transmission oscillator rows so as to be focused in the subject, and ultrasonic waves are synchronized with each transmission event. A transmitter that selects the transmitter row to move sequentially in the column direction,
A receiving oscillator sequence is selected from the plurality of oscillators in synchronization with each transmission event, and each oscillator in the receiving oscillator sequence is based on the reflected ultrasonic waves received by the receiving oscillator row from within the subject. And the receiver that generates the receive signal sequence for
An imaging region setting unit that sets an imaging main region as an region in the subject in which the corresponding frame acoustic line signal should be formed and an additional region adjacent to the imaging main region in the column direction.
For each transmission event, a phasing addition unit that generates the subframe acoustic line signal by pacing and adding the received signal sequence based on the reflected ultrasonic waves obtained from each observation point.
A synthesis unit for synthesizing the frame acoustic line signal based on the plurality of subframe acoustic line signals generated by the phase adjustment addition unit is provided.
The phasing addition unit includes a main target region including a region included in an area where ultrasonic waves are focused in the subject, and a part or all of a region adjacent to the main target region in the column direction is in the additional region. When present in, the sub-target region, which is a portion existing in the additional region among the regions adjacent to the main target region in the column direction, is set as the region including the observation point, and the imaging main region is set. The method of calculating the transmission time for the transmitted ultrasonic waves to reach the observation point is different between the observation points in the main target area and the observation points included in the sub-target area. Ultrasonic signal processing device. In the phasing addition unit, when the depth of the observation point is deeper than the focus depth of the observation point included in the main target area, the transmitted ultrasonic wave is in the main target area. The arrival time calculated by adding the second time until the ultrasonic wave reaches the observation point from the reference point to the first time until the reference point at the focus depth is reached is the arrival time of the observation point. The first aspect of claim 1, wherein when the depth is less than the focus depth, the arrival time calculated by subtracting the second time from the first time is set as the transmission time for the observation point. The ultrasonic signal processing device described. The phasing addition unit sets the time required for the transmitted ultrasonic wave to reach the observation point from the point on the transmission oscillator train closest to the focus point for the observation point included in the sub-target region. The ultrasonic signal processing apparatus according to claim 1 or 2, wherein the transmission time is set for the observation point. The phasing addition unit sets the time until the transmitted ultrasonic wave reaches the observation point from the point on the transmission oscillator train that is in close contact with the focus point for the observation point included in the sub-target region. When the depth of the observation _point is deeper than the focus depth, the transmitted ultrasonic wave is included in the main target region and reaches the reference point at the focus depth in the third time. , The time calculated by adding the fourth time from the reference point to the observation point, and when the depth of the observation point is less than the focus depth, the third time to the third time. _Assuming that the time calculated by subtracting 4 hours is T ₂ , the transmission time TM is calculated by the formula TM = _{αT 1} + (1-α) T ₂
The ultrasonic signal processing apparatus according to claim 1 or 2, wherein the value of α is larger than 0 and 1 or less. The phasing addition unit sets the time from the point on the transmission oscillator train in which the transmitted ultrasonic wave is in close contact with the focus point to the observation point for the observation point included in the sub-target region. When the depth of the observation _point is deeper than the focus depth, the transmitted ultrasonic wave is included in the main target region and reaches the reference point at the focus depth in the third time. , The time calculated by adding the fourth time from the reference point to the observation point, and when the depth of the observation point is less than the focus depth, the third time to the third time. Let T ₂ be the time calculated by subtracting 4 hours, and the transmitted ultrasonic wave is at the same depth as the observation point from the row center of the ultrasonic transducer row and recently to the row center of the ultrasonic transducer row. _Assuming that the time required to reach the second reference point in contact with T ₃ and T 3, the transmission time TM is the formula TM = _{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 larger than 0 and 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 becomes smaller as the difference between the depth of the corresponding observation point and the focus depth becomes larger. Any of claims 1 to 7, wherein the main target region has a shape that is line-symmetrical with respect to a straight line connecting a point on the transmitter row that is in close contact with the focus point and the focus point. The ultrasonic signal processing apparatus according to item 1. In a transmission event in which the transmission oscillator row does not include the oscillator at the end of the ultrasonic probe, the main target area includes a straight line connecting the focus point and one end of the transmission oscillator train, and the focus point. The ultrasonic signal processing apparatus according to claim 8, wherein the region is located between the straight line connecting the other end of the transmission oscillator train and the straight line. In a transmission event in which the transmission oscillator train includes a vibrator at the end of the ultrasonic probe, the transmission oscillator train is different from the end of the ultrasonic probe in the transmission oscillator train on a virtual line extending the oscillator train. Assuming a virtual transmission oscillator train having an end as one end and a point on the transmission oscillator train that is in close contact with the focus point as a middle point, the main target area is the focus point and the virtual transmission. 8. The region according to claim 8 or 9, wherein the region is located between a straight line connecting one end of the oscillator train and a straight line connecting the focus point and the other end of the virtual transmission oscillator train. Ultrasonic signal processing device. The additional region is a region whose base is a portion of the virtual transmission oscillator row that is not included in the transmission oscillator row 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. When the distance in the column direction between the boundary line between the additional region and the imaging main region and the straight line connecting the focus point and one end of the transmission oscillator row is m, the first region is the additional region. The ultrasonic signal processing apparatus according to any one of claims 1 to 11, wherein the region is a region obtained by removing an overlapping region with the main target region from a region shifted by m along the column direction. In the phasing addition unit, whether the sub-target region is an empty region based on the respective ranges of the imaging main region and the additional region and the range of the first region determined by the position of the focus point. In the transmission event that retains the information for determining whether or not the sub-target area is used and determines that the sub-target area is an empty area, the sub-target area is not set and only the main target area is set. The ultrasonic signal processing apparatus according to any one of claims 1 to 12. The synthesizing unit generates a frame acoustic line signal by synthesizing the subframe acoustic line signal corresponding to the main target region based on the position of the observation point for the observation point included in the imaging main area. The ultrasonic signal processing apparatus according to any one of claims 1 to 13. With an ultrasonic probe,
The ultrasonic signal processing apparatus according to any one of claims 1 to 14.
An ultrasonic diagnostic apparatus characterized by being provided with. A transmission event that selectively drives multiple oscillators arranged in a row on the ultrasonic probe to transmit ultrasonic waves to the subject is repeated multiple times, and reflected ultrasonic waves are received from the subject in synchronization with each transmission event. It is an ultrasonic signal processing method that synthesizes a frame acoustic wave signal from a plurality of subframe acoustic wave signals generated based on the received reflected ultrasonic wave.
In one transmission event, a transmission oscillator row is selected from the plurality of oscillators, ultrasonic waves are transmitted from the transmission oscillator rows so as to be focused in the subject, and ultrasonic waves are synchronized with each transmission event. Select the transmitter row to move sequentially in the column direction,
A receiving oscillator sequence is selected from the plurality of oscillators in synchronization with each transmission event, and each oscillator in the receiving oscillator sequence is based on the reflected ultrasonic waves received by the receiving oscillator row from within the subject. Generates a received signal sequence for
An imaging main region and an additional region adjacent to the imaging main region in the column direction are set as regions in the subject in which the corresponding frame acoustic line signal should be formed.
For each transmission event, the received signal sequence based on the reflected ultrasonic waves obtained from each observation point is phase-adjusted and added to generate the subframe acoustic line signal.
An ultrasonic signal processing method for synthesizing the frame acoustic line signal based on the plurality of subframe acoustic line signals generated by the phase adjustment addition unit.
When generating the subframe acoustic line signal, a main target region including a region included in an area where ultrasonic waves are focused in the subject, and a part or all of a region adjacent to the main target region in the column direction. When is present in the additional region, the sub-target region, which is a portion of the region adjacent to the main target region in the column direction and existing in the additional region, is set as the region including the observation point. The method of calculating the transmission time for the transmitted ultrasonic waves to reach the observation point differs between the observation points in the imaging main region and the main target region and the observation points included in the sub-target region. An ultrasonic signal processing method characterized by. A method for displaying an ultrasonic image in an ultrasonic signal processing apparatus in which a display unit can be connected and the ultrasonic signal processing method according to claim 16 is executed.
An ultrasonic image display method for converting a frame acoustic line signal into an ultrasonic image and displaying it on the display unit.

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