JP2017185085A - Ultrasound imaging apparatus and ultrasound transmission/reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of synthetic grating lobes in an ultrasound transmission/reception technique in which images are generated by inter-transmission aperture synthesis of focal point data obtained by phasing using a virtual sound source method.SOLUTION: A plurality of ultrasound beams are sequentially transmitted from an ultrasound probe having a plurality of transducers arranged two-dimensionally into a three-dimensional imaging region within a subject. With each transmission, ultrasound returning from the subject is received by the plurality of transducers in the ultrasound probe, and the resulting reception signals are each delayed by a delay time set for each of a plurality of predetermined reception focal points and are then added together to generate focal point data at each of the reception focal points. The focal point data generated by a receiving unit for the same reception focal points in different transmissions are added together. At this time, transmission focal points of the plurality of ultrasound beams are set to be randomly positioned such that synthetic grating lobes are suppressed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an ultrasonic imaging apparatus and an ultrasonic transmission / reception method.

  The ultrasonic imaging apparatus scans an ultrasonic beam from an ultrasonic element over an imaging region, and receives an echo generated in the imaging region by each transmission. The echo received in each transmission is received by a plurality of ultrasonic elements and converted into a plurality of received signals. The plurality of received signals are added after being delayed (phased) by a delay time set for each ultrasonic element according to the reception focus, and converted into focus data in a target imaging region. As described in Patent Document 1, the delay time is determined by assuming that the focal position of the ultrasonic beam is a virtual sound source and that a spherical wavefront is propagating from the virtual sound source. A virtual sound source method is known. Furthermore, an inter-transmission aperture synthesis technique for synthesizing focus data respectively obtained by ultrasonic beams directed in different directions for reception focal points at the same position is also known (Patent Document 2). Since a plurality of wavefronts from the virtual sound source can be synthesized by aperture synthesis between transmissions, an effect of improving image quality can be obtained.

JP-A-11-212214 Japanese Patent Laid-Open No. 10-277042

  For the transmission of different ultrasonic beams, when the respective focus data obtained by the virtual sound source method described in Patent Document 1 are combined by the transmission aperture synthesis described in Patent Document 2, a plurality of wavefronts from different virtual sound sources are combined. Although the effect of improving the image quality can be obtained by this action, the wavefront synthesis action may occur in an unintended direction, and an image (false image) that does not originally exist may be generated. The wavefront synthesis action in the unintended direction is called a synthesis grating lobe, and degrades the image quality.

  An object of the present invention is to suppress generation of a synthetic grating lobe in an ultrasonic transmission / reception technique in which an image is generated by synthesizing an aperture between transmissions of focus data phased by a virtual sound source method.

  The ultrasonic imaging apparatus of the present invention includes an ultrasonic probe in which a plurality of transducers are two-dimensionally arranged to transmit and receive ultrasonic waves, and a plurality of ultrasonic transducers from the ultrasonic probe to a three-dimensional imaging region in a subject. A transmission unit that sequentially transmits the ultrasonic beam, and a reception signal output by a plurality of transducers of the ultrasonic probe that has received the ultrasonic wave returning from the subject for each transmission. After adding a delay time set for each reception, the addition is performed, and the reception unit that generates focus data for each reception focus and the focus data for the same reception focus generated by the reception unit in different transmissions are added. And a transmission focus setting unit that sets positions of transmission focal points of the plurality of ultrasonic beams in the transmission unit. The arrangement of the transmission focal points of the plurality of ultrasonic beams set by the transmission focal point setting unit is random.

  According to the present invention, generation of a synthetic grating lobe is suppressed, and generation of a false image can be suppressed.

It is a block diagram which shows the structure of the ultrasonic imaging device of 1st embodiment. (A) is explanatory drawing which shows the ultrasonic beam transmitted to a three-dimensional imaging area | region from an ultrasonic imaging device, (b) is a figure which shows the beam shape of an ultrasonic beam, (c) and ( d) is an explanatory view showing a distribution of positions of transmission focal points. (A)-(d) is a figure explaining aperture composition between transmissions. It is a figure which shows the position of the transmission focus arrange | positioned at random. (A) is explanatory drawing which shows the ultrasonic beam of another shape transmitted to a three-dimensional imaging area | region from an ultrasonic imaging device, (b) is a figure which shows the beam shape of a transmission ultrasonic beam. (A) is explanatory drawing which shows another example of the ultrasonic beam transmitted to a three-dimensional imaging area from an ultrasonic imaging device, (b) and (c) are the depth (z) of a transmission focus. It is a figure which shows the space | interval of the transmission focus at the time of changing. (A) is explanatory drawing which shows another example of the ultrasonic beam transmitted to a three-dimensional imaging area from an ultrasonic imaging device, (b) And (c) is the depth (z) of a transmission focus. It is a figure which shows the space | interval of the transmission focus at the time of changing. It is explanatory drawing which shows arrange | positioning a transmission focus at random three-dimensionally in the depth range set by the user. It is a block diagram which shows the whole structure of the ultrasonic imaging device of 2nd embodiment. It is an example of the screen which the reception part of 2nd embodiment displays on a display part. It is explanatory drawing which shows setting the phasing range in the predetermined range from the center of the opening (vibrator) which transmitted the ultrasonic beam. It is explanatory drawing which shows the calculation method of the delay time by a virtual sound source method. It is a flowchart which shows operation | movement of the ultrasonic imaging device of 2nd embodiment. It is a flowchart which shows operation | movement of the ultrasonic imaging device of 2nd embodiment. It is an example of the screen which the transmission focus setting part of 2nd embodiment displays on a display part. (A) is a figure which shows the position of the transmission focus arrange | positioned regularly, (b) is a figure which shows the position of the transmission focus arrange | positioned at random.

  An ultrasonic imaging apparatus according to an embodiment of the present invention will be described.

<< First Embodiment >>
The ultrasonic imaging apparatus (ultrasonic transmitting / receiving apparatus) of the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the ultrasonic imaging apparatus of the present embodiment. 2A shows an ultrasonic beam transmitted from the ultrasonic imaging apparatus to the three-dimensional imaging region, FIG. 2B shows a beam shape of the ultrasonic beam, and FIGS. ) Is an explanatory diagram showing a distribution of positions of transmission focal points. FIGS. 3A to 3D are views for explaining transmission aperture synthesis. FIG. 4 is a diagram showing the positions of transmission focal points arranged randomly. FIG. 16A is a diagram illustrating the positions of transmission focal points that are regularly arranged, and FIG. 16B is a diagram illustrating the positions of transmission focal points that are randomly arranged.

As shown in FIG. 1, the ultrasonic imaging apparatus 100 according to the first embodiment includes an ultrasonic probe 108, a transmission unit 102, a reception unit 105, a synthesis unit 25, and a transmission focus setting unit 103. Yes. In the ultrasonic probe 108, a plurality of ultrasonic transducers (hereinafter referred to as “vibrators”) 109 are arranged one-dimensionally or two-dimensionally, and each transducer 109 converts an electrical signal into an ultrasonic wave. A transducer that transmits and receives ultrasonic waves by converting ultrasonic waves into electrical signals. The transmitter 102 transmits a plurality of ultrasonic beams 3-1 to 3-N from the ultrasonic probe 108 to the three-dimensional imaging region 120a in the subject 120 as shown in FIGS. 2 (a) and 3 (a). Are sent sequentially. For example, the transmission unit 102 sequentially transmits ultrasonic beams 3-1 to 3-N having a transmission focal point at a predetermined position by delivering a transmission signal delayed by a predetermined amount to each of the plurality of transducers 109. be able to. The plurality of transducers 109 of the ultrasonic probe 108 receive the ultrasonic waves returning from the subject 120 every time they are transmitted. The receiving unit 105 includes a delay adding unit 21. The delay adding unit 21 presets reception signals output from the plurality of transducers 109 of the ultrasound probe 108 on a reception scanning line 241 that is a line in which a plurality of points for constructing an ultrasound image are collected. Each of the received focal points 52 (see FIGS. 3B and 3C), which are each point for constructing an ultrasonic image, is added after being delayed by a set delay time. Focus data of the phasing range 35 is generated every 52. The synthesizer 25 performs aperture combination between transmissions by adding the focus data for the same reception focus 52 generated by the receiver 105 in different transmissions (see FIG. 3D). For example, the delay adding unit 21 includes a phasing range 35- (N-1) corresponding to the ultrasonic beam 3- (N-1) and a phasing range 35-N corresponding to the ultrasonic beam 3-N. The focus data is generated, and the synthesizer 25 adjusts the phasing range 35- (N-1) and the phasing range 35- (N-1) in the range 135-N where the phasing range 35-N overlaps. The focus data of the phase range 35-N are added to each other to perform aperture synthesis between transmissions.
The synthesizing unit 25 transmits post-combination data, which is focus data synthesized by inter-transmission aperture synthesis, to another device (not shown) or a subsequent functional unit in the ultrasonic imaging apparatus 100.

  The transmission focus setting unit 103 sets the positions of the transmission focal points 30-1 to 30-N of the plurality of ultrasonic beams 3-1 to 3-N in the transmission unit 102. At this time, the arrangement of the transmission focal points 30-1 to 30-N of the plurality of ultrasonic beams 3-1 to 3-N set by the transmission focal point setting unit 103 is random.

  The term “random” as used herein refers to an arrangement in which the intervals between the plurality of transmission focal points 30-N to 30- (N−1) in the three-dimensional space have no regularity or an aperiodic arrangement. For example, it means that the distances of the transmission focal points transmitted continuously are unequal intervals. If the distance is not regular, the transmission focal points 30-1 to 30-N may be arranged in any plane or direction in the three-dimensional space. For example, the arrangement of the transmission focal points 30-1 to 30-N viewed from the xy plane is random as shown in FIG. 2C, but the transmission focal point 30- viewed from the zx plane as shown in FIG. 1 to 30-N may be arranged at a predetermined z depth.

  The transmission focus setting unit 103 can set the delay time determined by the virtual sound source method in the reception unit 105 according to the set random transmission focus position.

  As described above, by randomly arranging the transmission focal points 30-1 to 30N, even if the focal point data obtained by different transmissions are synthesized by the aperture synthesis between transmissions, a wavefront synthesis action occurs in an unintended direction (synthesis) (Grating lobes) can be suppressed, and generation of false images can be prevented in the combined data. Therefore, the effect of improving the image quality can be obtained by the action of synthesizing a plurality of wavefronts from a plurality of virtual sound sources, which is the original action of aperture synthesis, while preventing the generation of false images.

  The transmission focal point setting unit 103 is configured such that the transmission focal points 30-1 to 30-N of the plurality of ultrasonic beams 3-1 to 3-N all have the ultrasonic beam 3-1 having a distance from the nearest transmission focal point. It is desirable to be smaller than the wavelength of ˜3-N. Thereby, a synthetic grating lobe can be suppressed more effectively. Note that the wavelength is the time of a sound wave waveform consisting of frequency components that affect the image in the frequency band of the ultrasonic pulse transmitted from each element and the frequency band obtained by convolution of the sensitivity frequency band of the transducer. Point to the length.

  More specifically, it is desirable that the average distance obtained as follows for the transmission focal points 30-1 to 30-N arranged at random is smaller than the wavelength of the ultrasonic beams 3-1 to 3-N. That is, as shown in FIG. 4, the transmission focal points 30-1 to 30 -N randomly arranged, a straight line 41 connecting a certain transmission focal point 30-1 and the transmission focal point 30-5 closest to the transmission focal point 30-1. The transmission focal point 30-7 closest to the straight line 41 is selected from the other one or more transmission focal points 30-2 and 30-7 positioned in the direction orthogonal to the straight line 41. A perpendicular line 42 is dropped from the transmission focal point 30-7 to a straight line 41, and the straight line 41 is divided by the intersection point O between the perpendicular line 42 and the straight line 41 to set two line segments AO and BO. The lengths of the two line segments AO and BO are obtained respectively. This operation is performed for all the transmission focal points 30-1 to 30-N, and the average length of all the obtained line segments is calculated. By setting the arrangement of the transmission focal points 30-1 to 30-N so that the obtained average value is smaller than the wavelength of the ultrasonic beams 3-1 to 3-N, the combined grating lobe is more effectively suppressed. can do.

  Moreover, the average value of the distance calculated | required as follows may be smaller than the wavelength of ultrasonic beam 3-1 to 3-N. The distance to the transmission focal point 30-2 arranged at the closest distance to a certain transmission focal point 30-1 is obtained. This operation is performed for all the transmission focal points 30-1 to 30-N, and the transmission focal point 30- is such that the average value of all the obtained distances is smaller than the wavelength of the ultrasonic beams 3-1 to 3-N. By setting the arrangement of 1 to 30-N, the synthetic grating lobe can be more effectively suppressed.

  By arranging the transmission focal points 30-1 to 30-N at random in this way, the transmission focal point distance dx as shown in FIG. Arrangement like 16 (b) is possible. As a result, transmission aperture synthesis in which the composite grating lobe is suppressed with a small number of transmission focal points can be performed, leading to a reduction in imaging time and an improvement in frame rate.

  FIG. 5A shows an ultrasonic beam having another shape transmitted from the ultrasonic imaging apparatus to the three-dimensional imaging region, and FIG. 5B shows a beam shape of the transmission ultrasonic beam. 6A shows another example of an ultrasonic beam transmitted from the ultrasonic imaging apparatus to the three-dimensional imaging region, and FIGS. 6B and 6C show the depth (z) of the transmission focal point. The interval of the transmission focus when changing is shown. FIG. 7A shows still another example of the ultrasonic beam transmitted from the ultrasonic imaging apparatus to the three-dimensional imaging region, and FIGS. 7B and 7C show the depth of transmission focus (z). The transmission focus interval when the value is changed is shown. FIG. 8 is an explanatory diagram showing that transmission focal points are randomly arranged in a three-dimensional range within the depth range set by the user.

  The transmission focal points 30-1 to 30-N set by the transmission focal point setting unit 103 are not limited to the case where the transmission focal points 30-1 to 30-N are located in the three-dimensional imaging region 120a in the subject 120 as shown in FIG. For example, as illustrated in FIGS. 5A and 5B, the transmission focus setting unit 103 generates ultrasonic beams 3-1 to 3 -N whose beam shape expands from the ultrasonic probe 108 within the subject 120. In the case of transmission, the transmission focal points 30-1 to 30-N are virtually set in a space in the negative Z direction with respect to the subject 120.

  The transmission directions of the ultrasonic beams 3-1 to 3-N may be parallel as shown in FIGS. 2 (a) and 5 (a), or FIG. 6 (a) and FIG. 7 (a). ), The transmission directions of the ultrasonic beams 3-1 to 3-N may be arranged at a predetermined angle. When the transmission directions of the ultrasonic beams 3-1 to 3-N are arranged at a predetermined angle, the depth (z) of the transmission focal point is changed to change the transmission focus depth (z) as shown in FIGS. As shown in b) and (c), the distance between the transmission focal points changes. Therefore, it is desirable that the distance of the transmission focal point after the depth change is smaller than the wavelength of the ultrasonic beams 3-1 to 3-N.

  Note that the ultrasonic imaging apparatus of the present embodiment may further include a reception unit 121 that receives a setting of the depth range 81 of the transmission focal points 30-1 to 30-N from the user (operator). In this case, every time the transmission focus setting unit 103 receives the transmission focus depth range 81 received by the reception unit 121, the transmission focus 30− is three-dimensionally within the set depth range 81 as shown in FIG. 1-30-N may be arranged at random and the position may be determined. Further, the storage unit 103a (not shown) that stores a predetermined random pattern of the transmission focal points 30-1 to 30-N for each transmission focal depth (z) that can be accepted by the reception unit 121 is exceeded. It is good also as a structure with which a sound wave imaging device is provided. In that case, the transmission focal point setting unit 103 reads out the random arrangement of the transmission focal points 30-1 to 30-N corresponding to the depth (z) of the transmission focal point received by the reception unit 121 from the storage unit 103a. You may set to 102.

  As described above, the ultrasonic imaging apparatus according to the present embodiment transmits ultrasonic beams by randomly arranging the transmission focal points 30-1 to 30-N of the plurality of ultrasonic beams 3-1 to 3-N. Thus, the generation of the synthetic grating lobe due to the wavefront synthesis action can be suppressed, and the generation of the false image on the ultrasonic image can be suppressed. Further, since the transmission focal interval can be increased appropriately, transmission aperture synthesis can be performed with a small number of transmission focal points. As a result, the imaging time is shortened and the frame rate can be improved.

<< Second Embodiment >>
A specific configuration example of the ultrasonic imaging apparatus of the present invention will be described according to the second embodiment.

<Overall configuration of device>
The overall configuration of the ultrasonic imaging apparatus 100 according to the second embodiment will be described with reference to FIG. FIG. 9 is a block diagram showing the overall configuration of the ultrasonic imaging apparatus according to the second embodiment. In FIG. 9, the same components as those of the first embodiment shown in FIG. As in the first embodiment, the ultrasonic imaging apparatus 100 includes an ultrasonic probe 108, a transmission unit 102, a reception unit 105, a synthesis unit 25, a transmission focus setting unit 103, and a reception unit (user interface: UI) 121. In addition, in addition to these, the second embodiment includes a control unit 106, a transmission / reception switching unit 101, an image processing unit 107, and a display unit 122. In addition to the delay addition unit 21, the reception unit 105 includes a virtual sound source method delay time setting unit 104 and a memory 40.

  The control unit 106 controls the overall operation. The accepting unit 121 is an interface that accepts an instruction from a user, input of various parameters, and the like. The virtual sound source method delay time setting unit 104 takes the positions of the transmission focal points 30-1 to 30-N from the transmission focal point setting unit 103, sets the position as the position of the virtual sound source, and sets the delay time for each reception focal point 52 as the delay time. Set in the adder 21. The transmission / reception switching unit 101 connects the ultrasonic probe 108 to the transmission unit 102 at the time of ultrasonic transmission and switches the selection of the transmission unit 102 or the reception unit 105 to be connected to the reception unit 105 at the time of ultrasonic reception. Under the control of The image processing unit 107 generates image data of an ultrasonic image using the focus data (post-synthesis data) after the synthesis unit 25 has synthesized the transmission aperture, and transmits the image data to the display unit 122. The display unit 122 displays an ultrasonic image based on the transmitted image data. The display unit 122 displays various screens under the control of the reception unit 121 via the control unit 106.

  The ultrasonic probe 108 includes a plurality of transducers 109 that are arranged in a one-dimensional or two-dimensional manner in a predetermined arrangement. The plurality of arranged transducers 109 are virtually or physically divided into transmission openings that are regions of the transducers 109 that transmit (irradiate) ultrasonic waves in a plurality of predetermined directions. The ultrasonic probe 108 is tailored to have an outer shape suitable for use by bringing the surface (ultrasonic transmission / reception surface) on which the transducer 109 is disposed into contact with the imaging target 120.

<Reception unit 121>
FIG. 10 is an example of the screen 10 that the reception unit 121 displays on the display unit 122. As shown in FIG. 10, the reception unit 121 includes the depths of the transmission focal points 30-1 to 30 -N, the angle of view, the frequencies of the ultrasonic beams 3-1 to 3 -N, the frame rate, and the directions of the ultrasonic beams. The screen 10 including the areas 10a to 10e, which are objects that receive information from the user, is displayed. The user sets one or more set values by inputting one or more values or directions in the areas 10a to 10e. The screen 10 is also provided with a region 10f for displaying an ultrasonic image generated for the three-dimensional imaging region 120a.

<Transmission focus setting unit 103>
The transmission focus setting unit 103 is capable of receiving the transmission focus depth (z), the angle of view (the three-dimensional imaging region 102a), the frequency of the ultrasonic beam, and the direction of the ultrasonic beam that can be received by the ultrasonic imaging apparatus. A storage unit 103a that stores a predetermined or determined random pattern of the transmission focal points 30-1 to 30-N for each combination is incorporated. Whenever the setting of the transmission focus depth range 81 is received via the reception unit 121 or when the setting is not received, the transmission focus setting unit 103 corresponds to the default transmission focus depth (z). The random arrangement pattern of the transmission focal points 30-1 to 30-N to be read is read from the storage unit 103a and set in the transmission unit 102. In addition, when the transmission focus depth (z) for which the transmission focal point random arrangement pattern is not stored in the storage unit 103a is received from the user via the reception unit 121, the transmission focus setting unit 103 sets the set depth. A random point is generated in the three-dimensional space of (z), and each point is set as the transmission focal point 30-1 to 30-N in the transmission unit 102. Further, the transmission focus setting unit 103 may transmit the position of the transmission focus corresponding to the set random pattern of the transmission focus to the virtual sound source method delay time setting unit 104.

<Transmitter 102>
The transmission unit 102 selects the transmission aperture of the ultrasonic probe 108 for each transmission of the ultrasonic beam in accordance with an instruction from the control unit 106. The transmission unit 102 determines the waveform type, delay time, amplitude modulation, weighting, and the like of the transmission signal, and generates a transmission signal according to the determined type. At this time, the transducer 109 is set so that the ultrasonic beam (for example, 3-1) transmitted from the transmission aperture has the transmission focus at the position of the transmission focus (for example, 30-1) set by the transmission focus setting unit 103. Set the delay time of each transmission signal. The transmission unit 102 outputs (transmits) the generated transmission signal to the plurality of transducers 109 in the transmission opening via the transmission / reception switching unit 101. Thereby, for example, as shown in FIG. 2A, the ultrasonic beam 3-1 having the transmission focal point 30-1 is transmitted into the three-dimensional imaging region 120a. The transmission unit 102 repeats this operation at a predetermined transmission interval set by the control unit 106, and sequentially transmits ultrasonic beams 3-1 to 3-N having transmission focal points 30-1 to 30-N.

<Receiving unit 105>
Every time the ultrasonic beams 3-1 to 3-N are transmitted to the three-dimensional imaging region 120a, an echo or the like is generated in the three-dimensional imaging region 120a. Each transducer 109 of the ultrasonic probe 108 receives an echo or the like returned to the ultrasonic probe 108, converts it into an electrical signal, and outputs it as a received signal to the receiving unit 105 via the transmission / reception switching unit 101 ( Send. The reception unit 105 that has received the reception signal every time the ultrasonic beam is transmitted temporarily stores the obtained reception signal in the memory 40 in the reception unit 105. The delay adder 21 reads the received signal from the memory 40, and for each reception focus 52 on the reception scanning line 241 set by the control unit 106, the delay 109 set by the virtual sound source method delay time setting unit 104 is added to the transducer 109. The received signal is delayed and then added. Thereby, focus data focused on a predetermined reception focus 52 is generated (reception beam forming). The receiving unit 105 passes the generated focus data to the synthesizing unit 25. For reception beam forming, the reception signals of all the transducers 109 of the ultrasonic probe 108 may be used, or only the reception signals of channels within a predetermined reception opening (active channel) may be used.

  The virtual sound source method delay time setting unit 104 fetches the positions of the transmission focal points 30-1 to 30-N from the transmission focal point setting unit 10 from the transmission focal point setting unit 103, and sets the position as the virtual sound source position for each reception focal point. The delay time is obtained and set in the delay time adding unit 21. Since the calculation method of the delay time by the virtual sound source method is a widely known method, it will be briefly described with reference to FIG. FIG. 12 is an explanatory diagram showing a delay time calculation method by the virtual sound source method. The transmitted sound wave propagates from the vibrator 109 to the scatterer, is reflected by the scatterer, and propagates to the vibrator 109 again. The time required for propagation is defined as the forward propagation time and the backward propagation time, respectively. The virtual sound source method delay time setting unit 104 calculates the forward propagation time from the transmission start trigger of the ultrasonic beam 3-1 and the like to the reception focus 52 and the return propagation time from the reception focus 52 and the like to each transducer 109. The delay time is calculated by obtaining and summing both. When the reception focal point 52 is closer to the ultrasonic probe 108 than the transmission focal point 30-1 (for example, in the case of the reception focal point 52-1 in FIG. 12), the forward propagation time is the transducer 109 at the center of the transmission aperture. -1 to the transmission focal point 30-1 is calculated by subtracting the propagation time from the transmission focal point 30-1 to the reception focal point 52-1. When the reception focal point 52 is located farther from the ultrasonic probe 108 than the transmission focal point 30-1 (for example, in the case of the reception focal point 52-2), the transmission focal point 30 is transmitted from the transducer 109-1 at the center of the transmission aperture. The forward propagation time is calculated by adding the propagation time from the transmission focal point 30-1 to the reception focal point 52-2 to the propagation time up to -1. In this way, in the virtual sound source method, the forward propagation time is determined according to the distance from the transmission focal point 30-1 to the reception focal point 52, and concentric arcs 204 and 205 centering on the transmission focal point 30-1 are in phase with the wave front. Become. The forward propagation times of the reception focal points 52 on the same wavefront all have the same value.

  Each time the virtual sound source method delay time setting unit 104 fetches the positions of the transmission focal points 30-1 to 30-N from the transmission focal point setting unit 10 from the transmission focal point setting unit 103, all of the reception focal points 52 on the reception scanning line 241 are obtained. The delay time is calculated and set in the delay adder 21. Alternatively, a delay time obtained in advance for each combination of the positions of the transmission focal point 30 and the reception focal point 52 is stored in a built-in memory, and the positions of the transmission focal points 30-1 to 30-N from the transmission focal point setting unit 10 are stored. May be read from the memory and set in the delay time adding unit 21 each time the image is captured from the transmission focus setting unit 103.

  FIG. 11 is an explanatory diagram showing setting the phasing range within a predetermined range from the center of the aperture (vibrator) that transmits the ultrasonic beam. The control unit 106 sets the phasing ranges 35-1 to 35 -N within a predetermined range from the center of the opening (vibrator 109) through which the ultrasonic beams 3-1 to 3 -N are transmitted, as shown in FIGS. A plurality of reception scanning lines 241 are set in the phasing range 35, and the focus adder 21 generates focus data for all reception focal points 52 on the reception scanning line 241. Thereby, at least in the range 135 (shown in FIG. 3) where the phasing ranges 35-1 to 35-N of the adjacent ultrasonic beams 3-1 to 3-N overlap, the reception scanning line 241 and the reception focal point 52 are Since they overlap, the combining unit 25 can add the focus data.

<Synthesis unit 25>
As illustrated in FIG. 3D, the combining unit 25 combines the plurality of focus data of the reception focus 52 having the same coordinates in the range 135. After the combined focus data of all the reception scanning lines 241 in the imaging region 102a are gathered, the combined data is transferred to the image processing unit 107. The image processing unit 107 processes the data for display and generates ultrasonic waves. Image data of the image is generated and transmitted to the display unit 122 to display an ultrasonic image.

  Next, the operation of the ultrasonic imaging apparatus according to the present embodiment will be described with reference to FIGS. FIG. 13 is a flowchart showing operations of the control unit 106, the transmission focus setting unit 103, the transmission unit 102, the reception unit 105, the synthesis unit 105, and the image processing unit 107. FIG. 14 is a flowchart showing the operation of the transmission focus setting unit 103. Each of these is constituted by a CPU (Central Processing Unit) and a memory, and when the CPU reads and executes a program stored in the memory in advance, the operation of FIG. 13 can be realized by software. Also, it is of course possible to realize a part or all of it by hardware such as a custom IC such as ASIC (application specific integrated circuit) or a programmable IC such as FPGA (field-programmable gate array).

  The reception unit 121 displays the reception screen 10 as illustrated in FIG. 10 on the display unit 122. In the areas 10 a to 10 e in the screen 10, the reception unit 121 uses, as parameters from the user, the depth of transmission focus, the angle of view (three-dimensional imaging area 102 a), the frequency of the ultrasonic beam, the frame rate, and the ultrasonic beam One or more settings of the direction are accepted, and parameters are determined from the UI (step 131). The depth of the transmission focus accepts a setting of a specific z value or a predetermined range of z values. As for the direction of the ultrasonic beam, by inputting an angle, the ultrasonic beams 3-1 to 3-N are parallel to the z direction (0 degree) as shown in FIG. 2A and FIG. 5A. In some cases, as shown in FIG. 6A and FIG. 7A, an arrangement in which the adjacent ultrasonic beams 3-1 to 3-N form a predetermined angle can be set. Further, the receiving unit 121 may select the direction of the ultrasonic beam according to the type of the ultrasonic probe 108 to be used. In addition, the reception unit 121 treats parameters that have not been accepted as being set with predetermined default values.

The transmission focus setting unit 103 receives the setting of the depth of transmission focus, the angle of view (three-dimensional imaging region 102a), the frequency of the ultrasonic beam, the frame rate, and the direction of the ultrasonic beam from the reception unit 121, and the frame rate. A search is made as to whether or not a random arrangement pattern of the transmission focal points 30-1 to 30-N satisfying some parameters other than (matching the parameters) exists in the storage unit 103a (step 132).

  In step 132, when there are one or more matching patterns, the transmission focus setting unit 103 reads the one or more patterns. The transmission focus setting unit 103 then reads the ultrasonic beam 3 at a predetermined time interval toward the N transmission focal points 30-1 to 30-N of the one or more random arrangement patterns that have been read out. The frame rate when the image (one frame) of the angle of view (three-dimensional imaging region 120a) is generated is calculated by sequentially transmitting -1 to 3-N. When the frame rate calculated from each of the two or more read random arrangement patterns is equal to or higher than the frame rate received from the user, the transmission focus setting unit 103 selects and selects one of the random arrangement patterns. The number N of transmission focal points of the random arrangement pattern and the frame rate achieved by the random arrangement pattern are displayed on the display unit 122 (step 133). The transmission focal point setting unit 103 may select the random arrangement pattern by comparing the number N of transmission focal points of the read random arrangement patterns. For example, the transmission focal point setting unit 103 compares the number N of transmission focal points of the read patterns of each random arrangement, and in order to improve the frame rate, the random arrangement pattern having the smallest number of Ns, that is, the transmission focal point 30- You may select the pattern of the random arrangement | positioning with the fewest numbers of 1-30-N.

  When the read random arrangement pattern is 1, the transmission focal point setting unit 103 calculates the frame rate for the read random arrangement pattern, and when it is equal to or higher than the frame rate received from the user, the random arrangement The number N of the transmission focal points of the selected random arrangement pattern and the frame rate achieved by the random arrangement pattern are displayed on the display unit 122 (step 133).

  In step 132, the transmission focal points 30-1 to 30-30 that match the depth of the transmission focal point, the angle of view (three-dimensional imaging region 102 a), the frequency of the ultrasonic beam, and the direction of the ultrasonic beam received from the reception unit 121. When the pattern of -N random arrangement is not in the storage unit 103a, the transmission focus setting unit 103 generates and displays a pattern of random arrangement of the transmission focal points 30-1 to 30-N that satisfies these random arrangement parameters. It is displayed on the part 122 (step 134).

  Step 134 will be described in detail with reference to the flow of FIG. 14 to generate a pattern of random arrangement of the transmission focal points 30-1 to 30-N by the transmission focal point setting unit 103. First, the transmission focal point setting unit 103 calculates the number N of transmission focal points 30-1 to 30-N so as to satisfy the frame rate set in the reception unit 121 (step 1141). For example, the transmission focus setting unit 103 obtains the maximum value of N. The transmission focal point setting unit 103 generates a pattern of random arrangement of N transmission focal points in a predetermined depth range, and sets the transmission focal points 30-1 to 30-N (step 1142). For example, as shown in FIG. 8, the transmission focus setting unit 103 generates the transmission focus depth (or depth range) and angle of view (three-dimensional imaging region 102a) received from the reception unit 121 by random numbers or the like. N random transmission focal points 30-1 to 30-N are set (step 1142). Then, the transmission focal point setting unit 103 calculates the average distance for the transmission focal points 30-1 to 30-N arranged at random as follows (step 1143).

  That is, as shown in FIG. 4, the transmission focal point setting unit 103 sets a straight line 41 that connects a certain transmission focal point 30-1 and the transmission focal point 30-5 that is closest to the transmission focal point 30-1. The transmission focal point 30-7 closest to the straight line 41 is selected from the other one or more transmission focal points 30-2 and 30-7 positioned in the orthogonal direction. A perpendicular line 42 is dropped from the transmission focal point 30-7 to a straight line 41, and the straight line 41 is divided by the intersection point O between the perpendicular line 42 and the straight line 41 to set two line segments AO and BO. The lengths of the two line segments AO and BO are obtained respectively. The transmission focal point setting unit 103 performs this operation for all the transmission focal points 30-1 to 30-N, and calculates the average length (average distance) of all the obtained line segments.

  The transmission focus setting unit 103 compares the average value of the calculated distances with the wavelength λ obtained from the frequencies of the ultrasonic beams 3-1 to 3-N received by the receiving unit 121 (step 1144). If the average value of the distances is smaller than the wavelength λ, a pattern of random arrangement of the transmission focal points 30-1 to 30-N that satisfies the parameters received from the user has been generated. The number N and the frame rate are displayed on the display unit 122 (step 1145), and the process proceeds to step 135.

  On the other hand, in step 1144, if the average value of the calculated line segment length (average distance value) is equal to or greater than the wavelength λ, the parameter received from the user is not satisfied. Accepting settings from the user, such as whether the angle of view may be reduced, the frame rate may be reduced, or if the ultrasound beams are angled, the depth of focus may be moved in a shallower direction The screen 15 is displayed on the display unit 122 (step 1146). FIG. 15 is an example of the screen 15 that the transmission focus setting unit 103 displays on the display unit 122 in step 1146. Each setting 15a to 15c on the screen 15 is shown to the user, and the transmission focus setting unit 103 receives a setting from the user through a radio box 15d which is an object that receives an input.

  For example, if the user sets that the angle of view may be narrowed, the transmission focus setting unit 103 sets the parameter angle of view by a predetermined amount and reduces the frame rate. If the frame rate is reduced by a predetermined amount and the depth of focus is set to move in a shallower direction, the focal depth of the parameter is moved in a shallower direction by a predetermined amount. Then, the transmission focus setting unit 103 returns to Steps 1141 to 1144 and generates a random pattern again using the parameters after the change in Step 1146. As a result, it is possible to change the value of the parameter acceptable by the user and generate the patterns of the transmission focal points 30-1 to 30-N that satisfy the parameter. In the case where the ultrasonic beams are arranged at an angle, the depth of focus is moved in a shallower direction as shown in FIGS. 6B, 6C, and 7B. This is because the distance between the transmission focal points 30-1 to 30-N can be reduced.

  The transmission focus setting unit 103 sets the position of the transmission focus 30-m (m = 1) among the transmission focal points 30-1 to 30-N in the transmission unit 102, and the control unit 106 sets the transmission aperture to the transmission unit 102. The transmission unit 102 starts scanning (step 135). The transmission unit 102 transmits the ultrasonic beam 3-m to the ultrasonic probe 109 (step 136). Specifically, the transmission unit 102 transmits the transmission focal point 30-m from the plurality of transducers 109 in the transmission aperture. In order to transmit the ultrasonic beam 3-m focused on (m = 1), a transmission signal given a predetermined delay time is generated for each transducer 109. The transmission signal is transferred to two or more transducers 109 in the selected transmission aperture of the ultrasonic probe 109 via the transmission / reception switching unit 101. Thereby, the ultrasonic beam 3-m focused from the ultrasonic probe 108 to the transmission focal point 30-m (m = 1) is transmitted toward the three-dimensional imaging region 120a as shown in FIG. 2A, for example. (Step 136).

  An echo or the like generated in the three-dimensional imaging region 120a reaches the transducer 109 of the ultrasonic probe 108 and is received and converted into a received signal (step 137). The virtual sound source method delay time setting unit 104 receives the position of the transmission focal point 30-m (m = 1) from the transmission focal point setting unit 103, and each of the reception focal points 52 and the like on the reception scanning line 241 set by the control unit 106. In addition, the delay time by the virtual sound source method using the transmission focal point 30-m (m = 1) as a virtual sound source is calculated or read from a built-in memory and set in the delay adding unit 21. The receiving unit 105 stores the received signal of each transducer 109 in the memory 40. The delay adder 21 uses the set delay time to delay and add the received signals for each transducer 109 (received beam forming) (step 138). As a result, the delay adding unit 21 obtains focus data for each reception focus 52 and stores (stores) the focus data in the memory 40 (step 139). The transmission focus setting unit 103 compares m and N (step 140). When m and N are not equal, the transmission focus setting unit 103 sets m = m + 1 = 2 (step 141), returns to step 136, and performs steps 136 to 140 for the next transmission focus 30-m (m = 2). To repeat transmission / reception of an ultrasonic beam for all N transmission focal points 30-N (step 140).

  If m and N are equal in step 140, the synthesizer 25 reads all the focus data obtained by transmitting the ultrasonic beams 3-1 to 3-N from the memory 40, and focuses on the same reception focus 52 and the like. The data is added and aperture synthesis is performed (step 142). Using the focus data after the aperture synthesis, the image processing unit 107 generates image data of an ultrasonic image and displays the ultrasonic image on the display unit 122 (step 143). Thereby, an image (one frame) of the entire three-dimensional imaging region 120a is displayed.

  Next, a parameter change is received from the user (step 144), and if there is no change, the transmission focus setting unit 103 returns to step 135 to step with the same pattern of transmission focus 30-1 to 30-N as the previous time. 135 to 143 are repeated, an ultrasonic image of the entire three-dimensional imaging region 120a of the next frame is acquired, and the image is updated.

  On the other hand, if there is a parameter change in step 144, the process returns to steps 131 to 134, the reception unit 121 determines the parameter from the UI (step 131), and the transmission focus setting unit 103 sets the changed parameter. A pattern of randomly arranged transmission focal points 30-1 to 30-N satisfying the above is selected (Step 133) or generated (Step 134), and Steps 135 and thereafter are repeated to capture an image of the next frame. Thereby, the pattern of the random arrangement | positioning of the transmission focal points 30-1 to 30-N can be changed for every frame.

  In this way, by changing the pattern of the random arrangement of the transmission focal points 30-1 to 30-N for each frame, even if there is some bias in the pattern of the transmission focal points 30-1 to 30-N, every time By changing the pattern of the random arrangement every time the ultrasonic beam is transmitted, there is an effect that the bias of the pattern of the random arrangement hardly affects the displayed ultrasonic image (several tens of frames per second).

  In addition, when changing the pattern of random arrangement every time in step 144, it is not limited to a method of accepting different parameter settings every time from the user, but two or more types of values are accepted in advance for each parameter set. Alternatively, a pattern of random arrangement of the transmission focal points 30-1 to 30-N may be generated, and these random arrangement patterns may be alternately used. Thereby, the effect which suppresses affecting the ultrasonic image which the bias | inclination of the pattern of random arrangement | positioning displays without bothering a user's hand can be acquired.

  In this embodiment, since the transmission focus setting unit 103 sets random transmission focal points 30-1 to 30-N, it is possible to suppress the synthetic grating lobe while performing the inter-transmission aperture synthesis. The influence of the bias on the ultrasonic image (several tens of frames per second) can be reduced.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. In addition, each of the above-described configurations, functions, processing units, processing means, and the like are realized by hardware by designing a part or all of them with an integrated circuit such as a field-programmable gate array (FPGA). Also good. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function is stored in memory, a hard disk, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, SD card, or DVD. be able to.

  Although it has been described that each information is recorded in the storage unit using the expressions “store” and “store”, it may be expressed as “register” or “set”.

  In addition, control lines, information lines, and connection lines are those that are considered necessary for the explanation, and not all control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

3-1-3 -N Ultrasonic beams 30-1 to 30 -N Transmission focal point 100 Ultrasonic imaging device 108 Ultrasonic probe 109 Transducer 102 Transmission unit 103 Transmission focal point setting unit 104 Virtual sound source method delay time setting unit 105 Receiving unit 21 Delay adding unit 25 Combining unit 120 Subject 241 Reception scanning line

Claims (11)

An ultrasonic probe in which a plurality of transducers are two-dimensionally arranged to transmit and receive ultrasonic waves;
A transmitter that sequentially transmits a plurality of ultrasonic beams from the ultrasonic probe to a three-dimensional imaging region in the subject;
A delay time set for each of a plurality of preset reception focal points, for each of the transmission signals, the reception signals output from the plurality of transducers of the ultrasonic probe that have received the ultrasonic waves returning from the subject. A reception unit that generates the focus data for each reception focus;
A combining unit that adds the focus data for the same reception focus generated by the reception unit in different transmissions;
A transmission focal point setting unit that sets transmission focal point positions of the plurality of ultrasonic beams in the transmission unit;
2. The ultrasonic imaging apparatus according to claim 1, wherein the transmission focal points of the plurality of ultrasonic beams set by the transmission focal point setting unit are random.   2. The ultrasonic imaging apparatus according to claim 1, wherein the random is an arrangement having no regularity in a distance between the plurality of transmission focal points in a three-dimensional space.   The ultrasonic imaging apparatus according to claim 1, wherein the transmission focus setting unit sets the delay time determined by a virtual sound source method in the reception unit according to the set transmission focus position. Ultrasonic imaging device.   2. The ultrasonic imaging apparatus according to claim 1, wherein each of the transmission focal points of the plurality of ultrasonic beams has a smaller distance from the nearest transmission focal point than a wavelength of the ultrasonic beam. An ultrasonic imaging apparatus.   2. The ultrasonic imaging apparatus according to claim 1, wherein the transmission focal points of the plurality of ultrasonic beams are orthogonal to a straight line connecting one transmission focal point and the transmission focal point located closest thereto. 3. The length of two line segments obtained by dividing the straight line by the perpendicular line when the perpendicular line is dropped from the transmission focal point closest to the straight line to the straight line. An ultrasonic imaging apparatus, wherein an average of lengths of all line segments obtained by performing the operations for determining the lengths of all the transmission focal points is smaller than a wavelength of the ultrasonic beam.   2. The ultrasonic imaging apparatus according to claim 1, wherein the transmission focus set by the transmission focus setting unit is a transmission focus located in a three-dimensional imaging region in the subject, and the ultrasonic probe is An ultrasonic imaging apparatus comprising: a transmission focal point that is virtually set outside the subject when transmitting an ultrasonic beam that expands within the subject. The ultrasonic imaging apparatus according to claim 1, further comprising a reception unit that receives a setting of a depth range of a transmission focus from an operator,
The ultrasonic imaging apparatus, wherein the transmission focal point setting unit randomly arranges the transmission focal points in three dimensions in a depth range of the transmission focal point received by the reception unit. The ultrasound imaging apparatus according to claim 1, wherein a reception unit that receives a setting of a transmission focus depth from an operator, and the transmission focus that is predetermined for each transmission focus depth that can be received by the reception unit. A storage unit for storing the random arrangement of
The transmission focal point setting unit reads out a random arrangement of the transmission focal points corresponding to the depth of the transmission focal point received by the reception unit from the storage unit, and sets the transmission focal point in the transmission unit. Imaging device.   The ultrasound imaging apparatus according to claim 7, wherein the transmission focus setting unit calculates an average distance between the transmission focal points for the plurality of transmission focal points arranged in the depth range of the transmission focal point received by the reception unit. An ultrasonic imaging apparatus characterized in that when the average of the distances is larger than the wavelength of the ultrasonic beam, the depth range of the transmission focal point is changed to be shallow.   2. The ultrasonic imaging apparatus according to claim 1, wherein the transmission focus setting unit sets an arrangement of transmission focal points of the plurality of ultrasonic beams every time transmission of all the ultrasonic beams to the three-dimensional imaging region is completed. An ultrasonic imaging apparatus characterized by being changed. Sequentially transmitting a plurality of ultrasonic beams from an ultrasonic probe in which a plurality of transducers are arranged two-dimensionally to a three-dimensional imaging region in a subject;
For each transmission, ultrasonic waves returning from the subject are received by the plurality of transducers of the ultrasonic probe, and the obtained reception signals are respectively set for a plurality of preset reception focal points. Adding after delaying by a delay time, and generating focus data for each reception focus;
Adding the focus data for the same reception focus generated by the receiver in different transmissions, and
An ultrasonic transmission / reception method, wherein the arrangement of transmission focal positions of the plurality of ultrasonic beams is random.

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