Three-dimensional ultrasonic image processing apparatus

Abstract

To suppress artifacts generated when a pixel value waves in a depth direction of an ultrasonic image.SOLUTION: An information processing unit 10 constituting a three-dimensional ultrasonic image processing device executes processing for acquiring spatial frequency distribution data in a depth direction, and processing for subjecting each two-dimensional ultrasonic image data to filter processing based on filter characteristics determined according to the spatial frequency distribution data and the characteristics of the transmission ultrasonic wave when each two-dimensional ultrasonic image data is acquired for one frame of two dimensional ultrasonic image data of a plurality of frames constituting three-dimensional ultrasonic image data. The information processing unit 10 searches for a spatial frequency corresponding to the maximum value in the distribution shown by the spatial frequency distribution data in a search range determined according to the pulse width of the transmission ultrasonic wave, and obtains the characteristics for suppressing the level of the spatial frequency distribution in the spatial frequency band including the spatial frequency that has been searched for as filter characteristics.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a three-dimensional ultrasonic image processing device, and more particularly to a device that performs filtering on two-dimensional ultrasonic image data that constitutes three-dimensional ultrasonic image data. [Background technology]

[0002] There are ultrasound diagnostic devices that acquire three-dimensional ultrasound image data by acquiring multiple frames of B-mode image data at different positions on a subject. Some of these ultrasound diagnostic devices have a two-dimensional array probe as an ultrasound probe, and repeatedly acquire B-mode image data while performing electronic scanning not only in the long axis direction but also in the short axis direction (depth direction). Each B-mode image data is acquired, for example, by scanning a transmission beam on a plane. One frame of B-mode image data is generated by receiving reflected ultrasound arriving from each direction toward which the transmission beam scanned on one plane is directed. Multiple frames of B-mode images arranged in the short axis scanning direction constitute a three-dimensional ultrasound image.

[0003] In an ultrasound diagnostic device, the next ultrasound is transmitted after the previously transmitted ultrasound has traveled back and forth. Therefore, there is an upper limit to the number of transmissions and receptions per unit time, and also to the frame rate (sometimes called volume rate in three-dimensional imaging). In order to increase the frame rate and shorten the time to acquire three-dimensional ultrasound image data, the interval at which the transmission beam is scanned is made larger than when B-mode image data is acquired on one plane. The number of transmission beams per frame when acquiring three-dimensional ultrasound image data is made smaller than when only B-mode image data is generated on one plane. Furthermore, the spatial resolution of the B-mode image is improved by forming multiple reception beams for one transmission beam and generating B-mode image data based on multiple reception signals obtained from the multiple reception beams, i.e., signals obtained by parallel reception phasing.

[0004] The following Patent Document 1 describes parallel receive phasing. Patent Document 2 describes, as a technology related to the present invention, filtering of spatial frequency distribution in two axes, the depth direction and the azimuth direction, of an ultrasound image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-87302 A [Patent Document 2] JP 2020-69304 A Summary of the Invention [Problem to be solved by the invention]

[0006] In ultrasound images such as B-mode images and Doppler images generated by parallel receive phasing, pixel values ​​may ripple not only in the scanning direction of the transmission beam (the azimuth direction in sector scanning) but also in the depth direction in which the ultrasound is transmitted and received, resulting in spot-like speckles extending in the scanning direction. This may result in stripe patterns extending in the scanning direction appearing as artifacts. These stripe patterns tend to become more noticeable as the scanning interval of the transmission beam becomes larger.

[0007] An object of the present invention is to suppress artifacts caused by rippling of pixel values ​​in the depth direction of an ultrasound image in a plurality of ultrasound images constituting a three-dimensional ultrasound image. [Means for solving the problem]

[0008] The three-dimensional ultrasound image processing device according to the present invention is characterized in that it includes an information processing unit that executes a process of acquiring spatial frequency distribution data in the depth direction for one frame of multiple frames of two-dimensional ultrasound image data that constitute three-dimensional ultrasound image data, and a process of applying a filter process to each of the two-dimensional ultrasound image data based on filter characteristics determined according to the spatial frequency distribution data and characteristics of transmitted ultrasound when each of the two-dimensional ultrasound image data is acquired.

[0009] Preferably, the information processing unit searches for a spatial frequency corresponding to a maximum value in the distribution indicated by the spatial frequency distribution data within a search range determined according to the pulse width of the transmitted ultrasound, and determines, as the filter characteristic, a characteristic that suppresses the level of the distribution indicated by the spatial frequency distribution data in a spatial frequency band including the searched spatial frequency.

[0010] Preferably, the information processing unit changes the filter characteristics when a maximum value of the distribution indicated by the spatial frequency distribution data acquired from the two-dimensional ultrasound image data subjected to the filtering process does not satisfy a predetermined condition.

[0011] Desirably, the information processing unit sequentially generates the two-dimensional ultrasound image data over time, and applies the same filtering process to a frame of the two-dimensional ultrasound image data generated later, as the filtering process applied to a frame of the two-dimensional ultrasound image data generated earlier.

[0012] Preferably, when the artifact condition is not satisfied for a frame of the two-dimensional ultrasound image data generated later, the information processing unit applies the filtering process with the changed filter characteristics to a frame of the two-dimensional ultrasound image data generated later.

[0013] Desirably, the two-dimensional ultrasound image data is obtained by transmitting and receiving ultrasound while scanning an ultrasound transmission beam at a predetermined scanning interval, and the information processing unit applies the filter processing to the two-dimensional ultrasound image data when the scanning interval exceeds a predetermined scanning interval threshold.

[0014] Preferably, the scanning interval threshold is determined based on characteristics of the transmitted ultrasonic waves.

[0015] Preferably, the filter characteristic is a characteristic that makes the amount of attenuation in a spatial frequency band corresponding to a predetermined structure equal to or less than an attenuation limit value.

[0016] Preferably, the two-dimensional ultrasound image data is data representing a B-mode image on which a blood flow image is superimposed. Effect of the Invention

[0017] According to the present invention, it is possible to suppress artifacts caused by pixel values ​​rippling in the depth direction of an ultrasound image. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing the configuration of an ultrasound diagnostic apparatus according to an embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating an example of the positional relationship between a transmission beam and multiple reception beams when linear scanning is performed. [Diagram 3] 1A and 1B are diagrams showing an example of the positional relationship between a transmission beam and multiple reception beams when sector scanning is performed; [Figure 4] FIG. 2 is a diagram showing a schematic diagram of a B-mode image and speckles appearing in the B-mode image. [Diagram 5] FIG. 1 is a diagram showing an outline of a spatial frequency distribution. [Figure 6] FIG. 2 is a diagram showing the outline of a transmission pulse transmitted from an ultrasonic probe. [Figure 7] FIG. 2 is a diagram showing a spatial frequency distribution in which a lower limit spatial frequency and an upper limit spatial frequency are indicated. [Figure 8] FIG. 13 is a diagram illustrating a low-pass filter characteristic. [Figure 9] FIG. 13 is a diagram showing band-stop filter characteristics. [Figure 10] FIG. 4 is a diagram showing notch filter characteristics. [Figure 11] 13 is a flowchart of a process for determining unnecessary component suppression filter characteristics and performing a filter process on B-mode image data. [Figure 12] FIG. 13 is a diagram showing a plurality of spatial frequency distributions. [Figure 13] FIG. 1 is a diagram showing the outline of the spatial frequency distribution when an image of a structure appears in a B-mode image, and the characteristics of a filter for suppressing unnecessary components. [Figure 14] 13 is a flowchart of a process for determining unnecessary component suppression filter characteristics and performing a filter process on B-mode image data. [Figure 15] FIG. 13 is a diagram showing the outline of a spatial frequency distribution obtained for one sample line data in one frame of B-mode image data. [Figure 16] 13 is a flowchart of a process in which unnecessary component suppression filter characteristics are determined by adaptive filtering and filtering is performed on B-mode image data. [Figure 17] FIG. 13 is a diagram showing an example of an image showing a spatial frequency distribution and unnecessary component suppression filter characteristics together with a B-mode image. [Figure 18] 13 is a flowchart of a process for determining unnecessary component suppression filter characteristics and performing a filter process on B-mode image data. [Figure 19] FIG. 1 is a diagram showing the configuration of a color Doppler ultrasound diagnostic device according to an application embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An embodiment of the present invention will be described with reference to the drawings. The same components shown in multiple drawings are given the same reference numerals and their description will be omitted. In this specification, when the term "P image data" is used to specify certain image data, the image indicated by the P image data is called a P image.

[0020] 1 shows the configuration of an ultrasound diagnostic device 100 according to an embodiment of the present invention. The ultrasound diagnostic device 100 includes an information processing unit 10, a transmitting unit 12, an ultrasound probe 14, a receiving unit 16, a display unit 18, and an operation unit 20. The information processing unit 10 includes a control unit 40, a memory 44, a B-mode image generating unit 46, an image processing unit 50, and a filter processing unit 52, and constitutes a three-dimensional ultrasound image processing device that executes processing related to ultrasound images.

[0021] The information processing unit 10 may be configured with one or more processors that execute a program to realize the functions of the control unit 40, the B-mode image generating unit 46, the image processing unit 50, and the filter processing unit 52. The program may be stored in the memory 44.

[0022] The control unit 40 performs overall control over the ultrasound diagnostic apparatus 100. The operation unit 20 includes a keyboard, a mouse, a lever, buttons, etc., and outputs information related to user operations to the control unit 40. When a touch panel is configured on the display screen of the display unit 18, the operation unit 20 may include the touch panel. The control unit 40 may control the ultrasound diagnostic apparatus 100 in response to operations on the operation unit 20.

[0023] The operation of the ultrasonic diagnostic device 100 will be described. The ultrasonic probe 14 is in contact with the surface of the subject 54. The ultrasonic probe 14 includes a plurality of transducer elements 22. The transmitting unit 12 outputs a transmission signal to each transducer element 22 of the ultrasonic probe 14 under the control of a beam control unit 42 included in the control unit 40. This causes ultrasonic waves to be transmitted from the ultrasonic probe 14. The beam control unit 42 controls the transmitting unit 12 to form a transmission beam in the ultrasonic probe 14, and the subject 54 is scanned with the transmission beam. That is, the transmitting unit 12 adjusts the delay time or level of each transmission signal under the control of the beam control unit 42, forms a transmission beam in the ultrasonic probe 14, and scans the subject 54 with the transmission beam.

[0024] When the ultrasonic waves reflected in the subject 54 are received by each transducer element 22 of the ultrasonic probe 14, each transducer element 22 outputs an electric signal corresponding to the received ultrasonic waves to the receiving unit 16. The receiving unit 16 performs processing such as amplification, detection, and frequency band limitation on the received signals output from each transducer element 22 according to the control of the beam control unit 42. The receiving unit 16 further performs phasing and addition of the received signals output from each transducer element 22 to generate a phased received signal. As a result, a phased received signal is generated in which the phases of the received signals based on the ultrasonic waves received from a specific direction are adjusted and added so that they are reinforced with each other, and a receiving beam is formed in that specific direction. The receiving unit 16 outputs the phased received signal to the B-mode image generating unit 46.

[0025] The B-mode image generator 46 generates B-mode image data based on the phased receive signals obtained for each receive beam direction, and outputs the data to the image processor 50. The B-mode image data based on one scan of the transmit beam and receive beam is one frame of image data, and corresponds to one B-mode image.

[0026] The ultrasonic probe 14 has a two-dimensional array structure, and oscillates the scanning plane in a direction intersecting the scanning plane on which the transmission beam and the reception beam are scanned, for example, in the azimuth direction in the depth direction. For example, the ultrasonic probe 14 oscillates the scanning plane in the azimuth direction in the depth direction by a predetermined interval each time B-mode image data of one scanning plane is generated. The B-mode image generating unit 46 generates B-mode image data as two-dimensional ultrasonic image data of one scanning plane each time the ultrasonic probe 14 oscillates the scanning plane by the interval, and outputs it to the image processing unit 50. The image processing unit 50 generates three-dimensional ultrasonic image data composed of multiple frames of B-mode image data (two-dimensional ultrasonic image data) acquired at different positions in the subject 54. This three-dimensional ultrasonic image data is data representing each pixel value of multiple voxels (pixels) arranged in three axial directions.

[0027] The image processing unit 50, for example, selects one frame of B-mode image data from among multiple frames of B-mode image data based on an operation on the operation unit 20, generates a video signal displaying an image represented by the selected B-mode image data, and outputs the video signal to the display unit 18. The display unit 18 displays the B-mode image based on the video signal. The image processing unit 50 may also generate volume rendering image data that stereoscopically represents a three-dimensional ultrasound image as a two-dimensional image. The image processing unit 50 generates a video signal displaying the volume rendering image, and outputs the video signal to the display unit 18. The display unit 18 displays the volume rendering image based on the video signal.

[0028] In the ultrasonic diagnostic device 100 according to this embodiment, three-dimensional ultrasonic image data representing a plurality of voxels arranged in three axial directions is acquired by oscillating the scanning plane of the ultrasonic probe 14. In addition to this process, a process of acquiring three-dimensional ultrasonic image data by conveying the ultrasonic probe 14 in a straight line or a curved line may be executed.

[0029] For example, a plurality of transducer elements 22 are two-dimensionally arranged along the long axis and short axis directions of a substantially rectangular surface where the ultrasonic probe 14 contacts the subject 54. In this case, a surface including a virtual long axis extending in the long axis direction may be used as a scanning surface, and the ultrasonic probe 14 may be linearly transported in the short axis direction. The ultrasonic probe 14 is transported in the short axis direction by a predetermined interval each time one frame of B-mode image data is generated. The B-mode image generating unit 46 generates B-mode image data as one frame of two-dimensional ultrasonic image data each time the ultrasonic probe 14 is transported by the interval, and outputs the B-mode image data to the image processing unit 50. The image processing unit 50 generates three-dimensional ultrasonic image data composed of a plurality of frames of B-mode image data (two-dimensional ultrasonic image data) acquired at different positions in the subject 54.

[0030] Incidentally, in order to maintain a certain frame rate of the B-mode image data generated by the ultrasound diagnostic device 100, it is necessary to shorten the time for scanning a transmission beam on one scanning plane. Therefore, the number of transmission beams per frame when acquiring three-dimensional ultrasound image data is made smaller than the case of generating B-mode image data only on one scanning plane. In addition, multiple reception beams are formed for one transmission beam, and B-mode image data is generated based on multiple reception signals obtained from the multiple reception beams, i.e., signals obtained by parallel reception phasing.

[0031] The parallel reception phasing will now be described. The receiving unit 16 forms multiple M reception beams for one transmission of an ultrasonic pulse. That is, the receiving unit 16 performs parallel reception phasing on multiple reception signals output from multiple transducer elements 22 to form M reception beams. When the transmission beam is linearly scanned, the receiving unit 16 forms M reception beams that have the same direction as the transmission beam and are arranged in parallel. When the transmission beam is sector scanned, the receiving unit 16 forms M reception beams that are arranged at equal azimuth intervals. Here, the azimuth angle refers to the angle that defines the direction as seen from the center of the sector scan.

[0032] Figure 2 shows an example of the positional relationship between the transmission beam T0 and the reception beams R0 to R7 when linear scanning is performed. As shown in Figure 2, the transmission beam T0 is formed in the depth direction (positive direction of the r-axis). In this example, eight reception beams R0 to R7 (M=8) are formed at equal intervals, oriented in the negative direction of the r-axis, with the transmission beam T0 at the center at a depth of r=r0.

[0033] Figure 3 shows an example of the positional relationship between the transmit beam T0 and the receive beams R0 to R7 when sector scanning is performed. In Figure 3, the positive r-axis direction is defined as the depth direction, and the θ-axis is defined as the angular direction in which the transmit beam oscillates. Figure 3 shows eight receive beams (M=8) R0 to R7 that are aligned at equal angular intervals and point in the negative r-axis direction, with the transmit beam T0 at the center at a depth of r=r0.

[0034] The receiving unit 16 generates a phased receive signal for each of the M receive beams, and outputs the phased receive signal generated for each of the M receive beams to the B-mode image generating unit 46. The B-mode image generating unit 46 generates B-mode image data of an area where the M receive beams are arranged in each direction of the scanned transmit beam.

[0035] In a B-mode image represented by B-mode image data generated by parallel receive beamforming, pixel values ​​may ripple not only in the scanning direction of the transmission beam but also in the depth direction, resulting in spot-like speckles extending in the scanning direction. Here, the scanning direction is the direction perpendicular to the transmission beam in linear scanning, and the azimuth direction in sector scanning. The occurrence of such speckles may result in stripe patterns extending in the scanning direction appearing as artifacts. These stripe-like artifacts tend to become more noticeable as the scanning interval becomes larger.

[0036] 4 shows a schematic diagram of a B-mode image 30 obtained by sector scanning and speckles 56 appearing in the B-mode image 30. As shown in FIG. 4, gaps 58 between a plurality of speckles 56 extending in the scanning direction (azimuth direction) cause a stripe pattern extending in the scanning direction to appear as an artifact. The larger the scanning interval, the more obvious the shape of one speckle 56 extending in the scanning direction becomes, and the more prominent the stripe pattern becomes.

[0037] Therefore, in the ultrasound diagnostic apparatus 100 according to this embodiment, the filter processing unit 52 determines filter characteristics for suppressing stripe artifacts based on the B-mode image data. The filter processing unit 52 performs filter processing based on the filter characteristics on the B-mode image data to generate filtered B-mode image data. The image processing unit 50 causes the display unit 18 to display the filtered B-mode image and a volume rendering image based on multiple frames of filtered B-mode images. Specific processing will be described below.

[0038] The image processing unit 50 outputs the B-mode image data to a filter processing unit 52. The filter processing unit 52 extracts depth direction line data representing each pixel value of a plurality of pixels arranged in the depth direction for each of a plurality of azimuth angle directions from the B-mode image data. In Fig. 4, one set of depth direction line data 32 and pixels 34 arranged in the depth direction are conceptually shown on the B-mode image 30.

[0039] The filter processing unit 52 selects one set of the depth direction line data 32 generated for each of the azimuth directions as sample line data. One set of sample line data corresponds to one set of depth direction line data 32 corresponding to one azimuth direction. The filter processing unit 52 performs a spatial Fourier transform on the sample line data to obtain spatial frequency distribution data.

[0040] Fig. 5 shows the outline of the distribution (spatial frequency distribution) indicated by the spatial frequency distribution data obtained for the sample line data. The horizontal axis indicates the spatial frequency, and the vertical axis indicates the level of the spatial frequency component (spatial frequency component level). The speckle spatial frequency fs shown in Fig. 5 corresponds to the maximum value that appears based on the speckle. Also, the speckle spatial frequency band Bs is the spatial frequency band occupied by the speckle.

[0041] The filter processing unit 52 searches for a speckle spatial frequency fs corresponding to a maximum value in the spatial frequency distribution of the sample line data, and defines a speckle spatial frequency band Bs including the speckle spatial frequency fs. The filter processing unit 52 further applies a filter process to the B-mode image data to suppress the spatial frequency components of the speckle spatial frequency band Bs. In detail, the filter processing unit 52 applies a filter process to suppress the spatial frequency components of the speckle spatial frequency band Bs to a plurality of sets of depth direction line data 32 corresponding to a plurality of azimuth directions over the entire region of the B-mode image. As a result, the filter processing unit 52 generates filtered B-mode image data and outputs it to the image processing unit 50. The filtered B-mode image data is composed of a plurality of sets of filtered depth direction line data obtained by applying a filter process to a plurality of sets of depth direction line data 32 corresponding to a plurality of azimuth directions over the entire region of the B-mode image.

[0042] A process of searching for the speckle spatial frequency fs, defining the speckle spatial frequency band Bs, and obtaining the filter characteristics will be described. FIG. 6 shows a schematic diagram of a transmission pulse 60 transmitted from the transducer 22 to generate B-mode image data. The horizontal axis shows time, and the vertical axis shows sound pressure. FIG. 6 shows a pulse width σ as one feature value indicating the characteristics of the transmitted ultrasound. The pulse width σ is defined as, for example, the time length during which the sound pressure becomes half the maximum value for the envelope 62 of the transmission pulse 60. The average value Sr [mm] of the depth direction width of the speckle 56 shown in FIG. 4 is approximately expressed as (Equation 1) using the pulse width σ [sec] of the transmission pulse and the sound speed c [mm / sec] in the subject 54.

[0043] (Equation 1) Sr=2.51×σ×c

[0044] It is known that the speckle spatial frequency fs is close to a reference spatial frequency fs0 obtained by multiplying the inverse of Sr by the sound speed c, as shown in (Equation 2).

[0045] (Equation 2) fs0=c×1 / Sr=1 / (2.51σ)

[0046] The filter processing unit 52 acquires a spatial frequency component level corresponding to a spatial frequency while sequentially increasing the spatial frequency from the reference spatial frequency fs0 by an increment width δ within a search range including the reference spatial frequency fs0 (within a spatial frequency band determined according to the pulse width of the transmitted ultrasonic wave). The filter processing unit 52 also acquires a spatial frequency component level corresponding to a spatial frequency while sequentially decreasing the spatial frequency from the reference spatial frequency fs0 by an increment width δ. The filter processing unit 52 determines the spatial frequency at which the spatial frequency component level is maximum as the speckle spatial frequency fs.

[0047] 7, the filter processing unit 52 determines a spatial frequency that is higher than the speckle spatial frequency fs by a predetermined upper frequency width Δb as an upper limit spatial frequency fb of the speckle spatial frequency band Bs. Also, the filter processing unit 52 determines a spatial frequency that is lower than the speckle spatial frequency fs by a predetermined lower limit frequency width Δa as a lower limit spatial frequency fa of the speckle spatial frequency band Bs.

[0048] The filter processing unit 52 configures a band suppression filter having a suppression bandwidth of a speckle spatial frequency band Bs that is equal to or greater than a lower limit spatial frequency fa and equal to or less than an upper limit spatial frequency fb. The band suppression filter has, for example, an unnecessary component suppression filter characteristic that suppresses the level by 6 dB or more in a frequency band that is equal to or greater than a lower limit spatial frequency fa and equal to or less than an upper limit spatial frequency fb. The unnecessary component suppression filter characteristic may be a characteristic that attenuates the level at the speckle spatial frequency fs by 6 dB or more, preferably by 20 dB or more.

[0049] Fig. 8 shows low-pass filter characteristics as an example of unnecessary component suppression filter characteristics. With the attenuation amount at a spatial frequency of 0 being 0 dB, an attenuation amount of 6 dB or more is realized in the frequency band equal to or higher than the cutoff spatial frequency fc. The cutoff spatial frequency fc is set to a spatial frequency lower than the lower limit spatial frequency fa. Note that the attenuation amount is a decibel scale value that increases in the positive direction as the attenuation increases.

[0050] 9 shows band-stop filter characteristics as an example of unnecessary component suppression filter characteristics. When the spatial frequency is 0 and when it is infinity, the attenuation is 0 dB, and an attenuation of 6 dB or more is realized in the spatial frequency band from the low cutoff spatial frequency fc1 to the high cutoff spatial frequency fc2. For example, the low cutoff spatial frequency fc1 is set to the lower limit spatial frequency fa, and the high cutoff spatial frequency fc2 is set to the upper limit spatial frequency fb.

[0051] FIG. 10 shows a notch filter characteristic as an example of an unnecessary component suppression filter characteristic. The notch filter characteristic is a special type of band-stop filter characteristic. In the notch filter characteristic, a notch in which the amount of attenuation is theoretically infinite appears in the attenuation band. For example, the low cutoff spatial frequency fc1 is set to the lower limit spatial frequency fa, and the high cutoff spatial frequency fc2 is set to the upper limit spatial frequency fb.

[0052] The filter processing unit 52 performs filtering based on the unnecessary component suppression filter characteristics on each of the multiple sets of depth direction line data 32 corresponding to multiple azimuth directions over the entire area of ​​the B-mode image, and generates multiple sets of filtered depth direction line data corresponding to multiple azimuth directions over the entire area of ​​the B-mode image. The filter processing unit 52 configures filtered B-mode image data based on the multiple sets of filtered depth direction line data, and outputs the filtered B-mode image data to the image processing unit 50. The image processing unit 50 generates a video signal for displaying the filtered B-mode image, and outputs the video signal to the display unit 18. The display unit 18 displays the filtered B-mode image based on the video signal. The image processing unit 50 may also generate a video signal for displaying a volume rendering image based on multiple frames of filtered B-mode images, and output the video signal to the display unit 18. In this case, the display unit 18 displays the volume rendering image based on the video signal.

[0053] FIG. 11 shows a flowchart of a process of determining the unnecessary component suppression filter characteristic and performing a filter process on the B-mode image data. In FIG. 11, the term "unnecessary component suppression filter characteristic" is simplified to "filter characteristic". The B-mode image generating unit 46 generates B-mode image data (S101). The filter processing unit 52 extracts sample line data from the B-mode image data (S102), and performs a spatial Fourier transform on the sample line data to obtain a spatial frequency distribution (S103). The filter processing unit 52 calculates a reference spatial frequency fs0 based on the pulse width σ of the transmission pulse according to (Equation 2) (S104). The filter processing unit 52 searches for a speckle spatial frequency fs using the reference spatial frequency fs0 to determine the unnecessary component suppression filter characteristic (S105). The filter processing unit 52 performs a filter process on the B-mode image data based on the determined unnecessary component suppression filter characteristic, and generates filtered B-mode image data (S106).

[0054] According to this process, a reference spatial frequency fs0 is obtained as a characteristic of the transmitted ultrasonic wave based on the pulse width σ of the transmitted pulse according to (Equation 2). Then, a speckle spatial frequency fs at which the level in the spatial frequency distribution is maximized is searched for on the high-frequency side and the low-frequency side of the reference spatial frequency fs0. Furthermore, a spatial frequency higher than the speckle spatial frequency fs by a predetermined upper frequency width Δb is determined as an upper spatial frequency fb, and a spatial frequency lower than the speckle spatial frequency fs by a predetermined lower frequency width Δa is determined as a lower spatial frequency fa, and the unnecessary component suppression filter characteristics in the filter processing unit 52 are determined. This allows the process of determining the unnecessary component suppression filter characteristics for suppressing stripe artifacts to be performed quickly.

[0055] In the above process, the filter processing unit 52 determines a spatial frequency higher than the speckle spatial frequency fs by a predetermined upper frequency width Δb as the upper limit spatial frequency fb, and determines a spatial frequency lower than the speckle spatial frequency fs by a predetermined lower limit frequency width Δa as the lower limit spatial frequency fa. Instead of the process of determining spatial frequencies that are a certain value away from the speckle spatial frequency fs as the upper limit spatial frequency fb and the lower limit spatial frequency fa in this manner, the following process may be executed.

[0056] That is, the filter processing unit 52 may determine, as the lower limit spatial frequency fa, a spatial frequency on the low side at which the level of the spatial frequency distribution drops by a predetermined ratio, based on the maximum value in the speckle spatial frequency fs of the spatial frequency distribution. The filter processing unit 52 may also determine, as the upper limit spatial frequency fb, a spatial frequency on the high side at which the level of the spatial frequency distribution drops by a predetermined ratio. The filter processing unit 52 may execute a process of adaptively determining the lower limit spatial frequency fa and the upper limit spatial frequency fb, as described next.

[0057] The filter processing unit 52 selects multiple K sets of the depth direction line data 32 generated for multiple azimuth angle directions as K sets of sample line data. The filter processing unit 52 performs spatial Fourier transform on each of the K sets of sample line data to obtain K spatial frequency distributions. The filter processing unit 52 searches for a speckle spatial frequency fs for each of the K spatial frequency distributions by a process similar to the process based on one set of sample line data. The filter processing unit 52 obtains the minimum of the K speckle spatial frequencies fs obtained from the K spatial frequency distributions as a lower limit spatial frequency fa and the maximum of the K speckle spatial frequencies fs as an upper limit spatial frequency fb.

[0058] 12 shows a spatial frequency distribution 70 in which the minimum speckle spatial frequency fs1 is obtained, a spatial frequency distribution 72 in which the maximum speckle spatial frequency fs2 is obtained, and a spatial frequency distribution 74 in which a speckle spatial frequency fs3 between the speckle spatial frequencies fs1 and fs2 is obtained. Filter processing unit 52 sets the unnecessary component suppression filter characteristics in filter processing unit 52 by setting the minimum speckle spatial frequency fs1 as the lower limit spatial frequency fa and the maximum speckle spatial frequency fs2 as the upper limit spatial frequency fb.

[0059] The filter processing unit 52 may obtain one spatial frequency distribution by obtaining statistics such as the average, median, maximum, and minimum values ​​of K spatial frequency component levels at each spatial frequency from K spatial frequency distributions obtained from K sets of sample line data. The filter processing unit 52 may execute the same processing as the processing based on the one set of sample line data for one spatial frequency distribution obtained from the K spatial frequency distributions. That is, the filter processing unit 52 may search for a speckle spatial frequency fs for one spatial frequency distribution obtained from the K spatial frequency distributions, and obtain a lower limit spatial frequency fa and an upper limit spatial frequency fb.

[0060] Images of biological tissue structures such as blood vessels, heart walls, and heart valves may appear in a B-mode image. In this case, the structures may be difficult to see in a filtered B-mode image in which stripe artifacts are suppressed. The spatial frequency components included in the sample line data due to the structures may be lower than the speckle spatial frequency. Therefore, the filter processing unit 52 may execute a process of limiting the amount of attenuation in the spatial frequency band corresponding to the structures.

[0061] The upper part of Fig. 13 shows an outline of the spatial frequency distribution when an image of a structure appears in a B-mode image. In this spatial frequency distribution, a maximum value appears not only at the speckle spatial frequency fs but also at the structure spatial frequency fsT corresponding to the structure. The control unit 40 reads the structure spatial frequency fsT and the spatial frequency band STR including the structure spatial frequency fsT by the user's operation of the operation unit 20. The structure spatial frequency fsT and the spatial frequency band STR may be stored in the memory 44 in advance and read by the control unit 40. The filter processing unit 52 determines the unnecessary component suppression filter characteristics in the spatial frequency band STR including the structure spatial frequency fsT so that the attenuation is equal to or less than a predetermined attenuation limit value Lim based on the control of the control unit 40.

[0062] 13 shows an example of an unnecessary component suppression filter characteristic 66 in which the amount of attenuation is not limited in the spatial frequency band STR, and an example of an unnecessary component suppression filter characteristic 68 in which the amount of attenuation is limited in the spatial frequency band STR. When the filter processing unit 52 applies filtering to the B-mode image data using the unnecessary component suppression filter characteristic 68, stripe artifacts that appear in the B-mode image after filtering are suppressed, and structures are clearly displayed.

[0063] FIG. 14 shows a flowchart of a process of determining the unnecessary component suppression filter characteristic and performing a filter process on the B-mode image data. This flowchart is different from the flowchart shown in FIG. 11 in that step S201 is added between steps S105 and S106. In this figure, the term "unnecessary component suppression filter characteristic" is changed to "filter characteristic" for simplification. The filter processing unit 52 searches for the speckle spatial frequency fs using the reference spatial frequency fs0 to determine the unnecessary component suppression filter characteristic (S105), and then changes the unnecessary component suppression filter characteristic so that the attenuation in the spatial frequency band STR is equal to or less than the attenuation limit value Lim (S201). The filter processing unit 52 performs a filter process on the B-mode image data based on the unnecessary component suppression filter characteristic changed in step S201, and generates filtered B-mode image data (S106).

[0064] The B-mode image generating unit 46 sequentially outputs B-mode image data to the image processing unit 50 over time. The image processing unit 50 sequentially generates B-mode image data over time and outputs it to the filter processing unit 52. The filter processing unit 52 performs filter processing on each of the B-mode image data sequentially outputted over time from the image processing unit 50, and sequentially outputs the post-filter processing B-mode image data to the image processing unit 50 over time.

[0065] The filter processing unit 52 may perform filter processing (hereinafter referred to as adaptive filter processing) in which filter characteristics change adaptively according to previously generated post-filter-processed B-mode image data, on the B-mode image data sequentially output from the image processing unit 50. The filter processing unit 52 may further sequentially output the post-filter-processed B-mode image data to the image processing unit 50 over time.

[0066] Here, the adaptive filter processing will be described. The adaptive filter processing repeats the process of changing the filter characteristics when the maximum value of the distribution indicated by the spatial frequency distribution data obtained from the B-mode image data after the filter processing does not satisfy a predetermined condition. Here, the predetermined condition is a condition for suppressing stripe artifacts.

[0067] FIG. 15 shows a schematic of the spatial frequency distribution obtained for one sample line data in the B-mode image data after the filter processing of a certain frame. The level of the component with a spatial frequency of 0 is normalized to 1, and the maximum value at the speckle spatial frequency fs is A. When the target value of the level at the speckle spatial frequency fs is R and R < A holds, the filter processing unit 52 adjusts and changes the unnecessary component suppression filter characteristics so that the attenuation amount at the speckle spatial frequency fs is 20 log(A / R) [dB] or more. Here, log is a logarithmic function with base 10, and the attenuation amount is a value that increases in the positive direction as the attenuation becomes larger.

[0068] The filter processing unit 52 performs filter processing based on the unnecessary component suppression filter characteristics changed based on the previous B-mode image data on the B-mode image data of the next frame output from the image processing unit 50, and outputs the B-mode image data after the filter processing to the image processing unit 50. When R < A holds again in the spatial frequency distribution obtained for one sample line data in the B-mode image data after the filter processing of one frame output to the image processing unit 50, the filter processing unit 52 changes the unnecessary component suppression filter characteristics so that the attenuation amount at the speckle spatial frequency fs is 20 log(A / R) or more.

[0069] In this way, the filter processing unit 52 sets the unnecessary component suppression filter characteristics based on the previous data among the post-filter processing B-mode image data that is sequentially generated over time, and performs filter processing based on the determined filter characteristics on the B-mode image data of the next frame. By the filter processing unit 52 sequentially executing such processing on the B-mode image data that is sequentially generated over time, the unnecessary component suppression filter characteristics converge to ideal characteristics.

[0070] From another viewpoint, the filter processing unit 52 executes the following process. That is, the filter processing unit 52 performs the same filter processing as that performed on one frame of B-mode image data generated earlier, on one frame of B-mode image data generated later. When the condition regarding artifacts is not satisfied for the one frame of B-mode image data generated later, the filter processing unit 52 performs filter processing with changed filter characteristics on the B-mode image data of the frame generated later. The condition regarding artifacts is, for example, a condition that A≦R is satisfied for the maximum value A and the target value R at the speckle spatial frequency fs for the spatial frequency distribution obtained for one sample line data.

[0071] Fig. 16 shows a flowchart of a process for determining unnecessary component suppression filter characteristics by adaptive filtering and performing filtering on B-mode image data. This flowchart differs from the flowchart shown in Fig. 11 in that steps S301 and S302 are added after step S106. In this figure, the term "unnecessary component suppression filter characteristics" is simplified to "filter characteristics".

[0072] The filter processing unit 52 searches for the speckle spatial frequency fs using the reference spatial frequency fs0 and determines the unnecessary component suppression filter characteristics (S105). The filter processing unit 52 performs filtering on the B-mode image data based on the determined unnecessary component suppression filter characteristics to generate filtered B-mode image data (S106).

[0073] The filter processing unit 52 extracts sample line data from the filtered B-mode image data, and determines whether the spatial frequency distribution obtained for the sample line data satisfies a condition related to artifacts (S301). If the condition related to artifacts is satisfied, the filter processing unit 52 maintains the unnecessary component suppression filter characteristics and ends the process.

[0074] On the other hand, if the condition regarding the artifact is not satisfied, the filter processing unit 52 changes the unnecessary component suppression filter characteristics (S302) and returns to the process of step S107. In the second or subsequent steps of step S107, the filter processing unit 52 performs filtering based on the changed unnecessary component suppression filter characteristics on the previously generated filtered B-mode image data (S106).

[0075] According to such a process, the unnecessary component suppression filter characteristics are repeatedly changed until the artifact-related conditions are satisfied for the filtered B-mode image data sequentially generated over time by steps S301 and S302. As a result, the unnecessary component suppression filter characteristics converge to characteristics that satisfy the artifact-related conditions for the filtered B-mode image data.

[0076] Whether or not to perform filtering on the B-mode image data may be determined according to the scanning interval. For example, filtering may be performed when the scanning interval in the azimuth angle direction exceeds a predetermined threshold. When the scanning interval exceeds a predetermined scanning interval threshold, the control unit 40 causes the image processing unit 50 and the filter processing unit 52 to perform filtering. On the other hand, when the scanning interval is equal to or less than the scanning interval threshold, the control unit 40 does not cause the image processing unit 50 and the filter processing unit 52 to perform filtering on the B-mode image data, and causes the display unit 18 to display a B-mode image or a volume rendering image based on the B-mode image data that has not been subjected to filtering.

[0077] The scanning interval threshold may be determined based on the theoretical value of the size of the speckle 56 in the scanning direction. The average width Sθ [mm] of the speckle 56 in the scanning direction is approximately expressed as (Equation 3). Here, λ is the wavelength [mm] of the ultrasonic wave, z is the measurement depth [mm], and D is the aperture width [mm]. The aperture width D is the length over which the multiple transducer elements 22 of the ultrasonic probe 14 are arranged on the surface scanned by the ultrasonic beam.

[0078] (Equation 3) Sθ=0.9λz / D

[0079] When the width of the speckle 56 in the scanning direction is expressed by an azimuth angle, the scanning interval threshold θt [rad] may be obtained according to Equation 4.

[0080] (Math. 4) θt≒arctan(Sθ / z)=arctan(0.9λ / D)

[0081] In the ultrasonic diagnostic device 100, a man-machine interface may be configured that changes the unnecessary component suppression filter characteristics in response to a user's operation. The man-machine interface may be configured by the image processing unit 50, the display unit 18, and the operation unit 20. That is, the unnecessary component suppression filter characteristics may be set based on the operation of the operation unit 20 by the user referring to the display unit 18. For example, the control unit 40 may read the speckle spatial frequency fs, the lower limit spatial frequency fa, the upper limit spatial frequency fb, the attenuation in the speckle spatial frequency band, the structure spatial frequency fsT, the attenuation in the spatial frequency band STR including the structure spatial frequency fsT, and the like in response to the operation of the operation unit 20. In this case, the image processing unit 50 may display at least one of the spatial frequency distribution and the unnecessary component suppression filter characteristics obtained for the sample line data on the display unit 18 and present it to the user. The unnecessary component suppression filter characteristics may be represented by a graph with the horizontal axis representing the spatial frequency and the vertical axis representing the attenuation, the phase rotation, and the like.

[0082] 17 shows an example of an image indicating a spatial frequency distribution 80 and an unnecessary component suppression filter characteristic 82 together with a B-mode image. Note that the image processing unit 50 may display the actually applied unnecessary band suppression filter characteristic, the type of filter (low-pass filter, band-stop filter, notch filter, etc.) and the like on the display unit 18 using text information or the like.

[0083] The graphical user interface displayed on the display unit 18 when the unnecessary component suppression filter characteristics are set may include, for example, buttons or icons displaying "none," "weak," "medium," "strong," etc. Also, the image processing unit 50 may display on the display unit 18 a graphical user interface for setting the unnecessary component suppression filter characteristics via the operation unit 20.

[0084] FIG. 18 shows a flowchart of a process of determining the unnecessary component suppression filter characteristics and performing a filter process on the B-mode image data. This flowchart is different from the flowchart shown in FIG. 11 in that steps S301 and S302 are added between steps S105 and S106. In addition, the term "unnecessary component suppression filter characteristics" is changed to "filter characteristics" for simplified expression. The filter processing unit 52 searches for the speckle spatial frequency fs using the reference spatial frequency fs0 to determine the unnecessary component suppression filter characteristics (S105), and then reads information for setting the unnecessary component suppression filter characteristics from the operation unit 20 (S301). The filter processing unit 52 changes the unnecessary component suppression filter characteristics based on the information read from the operation unit 20 (S302). The filter processing unit 52 performs a filter process based on the unnecessary component suppression filter characteristics changed in step S302 on the B-mode image data, and generates filtered B-mode image data (S106).

[0085] FIG. 19 shows a color Doppler ultrasound diagnostic device 102 according to an application embodiment of the present invention. The color Doppler ultrasound diagnostic device 102 is obtained by adding a blood flow image generating unit 48 to the ultrasound diagnostic device 100 shown in FIG. 1. The color Doppler ultrasound diagnostic device 102 performs each measurement in B mode and Doppler mode. In the B mode operation, the color Doppler ultrasound diagnostic device 102 generates B mode image data based on ultrasound reflected by the subject 54, and in the Doppler mode operation, generates Doppler image data of the subject 54 based on the Doppler shift frequency of the ultrasound received from the subject 54. Here, the Doppler image data refers to data showing a Doppler image in which colors indicating the speed and direction of blood flow are added to the B mode image. The operation in the B mode is similar to the operation of the ultrasound diagnostic device 100 shown in FIG. 1 generating B mode image data.

[0086] The operation in the Doppler mode will be described. In the Doppler mode, the transmitter 12 outputs a transmission signal to each transducer element 22 of the ultrasonic probe 14 N times so that ultrasonic pulses are transmitted N times with a repetition time interval T for one transmission beam direction. The receiver 16 generates N types of phased reception signals corresponding to the N ultrasonic pulses reflected in the subject 54 and received by the ultrasonic probe 14.

[0087] The receiving unit 16 forms multiple M receiving beams in response to one transmission of an ultrasonic pulse. That is, the receiving unit 16 performs parallel reception phasing on multiple receiving signals output from multiple transducer elements 22 to form M receiving beams. When the transmitting beam is linearly scanned, the receiving unit 16 forms M receiving beams that have the same direction as the transmitting beam and are arranged in parallel. When the transmitting beam is sector scanned, the receiving unit 16 forms M receiving beams that are arranged at equal azimuth intervals.

[0088] The receiving unit 16 generates N types of phased receive signals for each of the M receive beams, corresponding to the ultrasonic pulses transmitted N times for one transmit beam, and outputs the N types of phased receive signals for each of the M receive beams to the blood flow image generating unit 48.

[0089] The blood flow image generating unit 48 calculates the blood flow velocity v(r) in the depth direction at each depth r of each of the M receiving beams based on the N types of phased receiving signals generated for each of the M receiving beams, for example, according to the autocorrelation processing shown in Reference 1.

[0090] The blood flow image generating unit 48 generates blood flow image data based on the blood flow velocity v(r) in the depth direction at each depth r of each of the M receiving beams. The blood flow image represented by the blood flow image data is an image that shows a color according to the blood flow velocity v(r) at the position of each depth r on each receiving beam. That is, the blood flow image shows the distribution of the blood flow velocity v(r) in the area where the M receiving beams are arranged by color. In the blood flow image, for example, blue is added to the area where blood flows in the direction away from the ultrasonic probe 14, and red is added to the area where blood flows in the direction toward the ultrasonic probe 14, and the brightness is increased as the blood flow velocity increases. The blood flow image generating unit 48 outputs the blood flow image data to the image processing unit 50.

[0091] The color Doppler ultrasound diagnostic device 102 performs, for example, B-mode and Doppler mode measurements in a time period corresponding to one frame in a time-division manner, and generates color Doppler image data as data showing a color Doppler image in which one frame of a B-mode image and one frame of a blood flow image are superimposed.

[0092] The B-mode image generating unit 46 generates B-mode image data for one scanning plane, for example, each time the ultrasonic probe 14 oscillates the scanning plane by the increment width, and outputs the data to the image processing unit 50. The blood flow image generating unit 48 generates blood flow image data for one scanning plane, for example, each time the ultrasonic probe 14 oscillates the scanning plane by the increment width, and outputs the data to the image processing unit 50.

[0093] The image processor 50 generates Doppler image data acquired at different positions at intervals of the increment based on the B-mode image data and blood flow image data generated each time the ultrasonic probe 14 oscillates the scanning plane by the increment. The image processor 50 generates three-dimensional ultrasonic image data composed of multiple frames of Doppler image data acquired at different positions in the subject 54.

[0094] The image processing unit 50, for example, selects one frame of Doppler image data from among a plurality of frames of Doppler image data based on an operation on the operation unit 20, generates a video signal for displaying an image represented by the selected Doppler image data, and outputs the video signal to the display unit 18. The display unit 18 displays the Doppler image based on the video signal. The image processing unit 50 may also generate volume rendering image data that stereoscopically represents a three-dimensional ultrasound image as a two-dimensional image. The image processing unit 50 generates a video signal for displaying the volume rendering image, and outputs the video signal to the display unit 18. The display unit 18 displays the volume rendering image based on the video signal.

[0095] In the B-mode image represented by the B-mode image data generated by the parallel receive beamforming as described above, stripe patterns extending in the scanning direction may appear as artifacts. These stripe artifacts tend to become more noticeable as the scanning interval becomes larger.

[0096] Furthermore, in order to maintain a certain level of frame rate of the B-mode image data generated by the color Doppler ultrasound diagnostic device 102, it is necessary to shorten the time to scan one scanning plane. Therefore, in the color Doppler ultrasound diagnostic device 102, the scanning interval of the transmission beam when performing the B-mode and Doppler mode measurements in a time-division manner is set to be longer than the scanning interval when operating only in B mode. This causes stripe artifacts to appear in the image displayed on the display unit 18 to become more noticeable.

[0097] Therefore, in the color Doppler ultrasound diagnostic device 102, the image processing unit 50 outputs the B-mode image data to the filter processing unit 52. The filter processing unit 52 performs filter processing on the B-mode image data based on the unnecessary component suppression filter characteristics to generate filtered B-mode image data and output it to the image processing unit 50. The filter processing performed by the filter processing unit 52 is similar to the filter processing performed by the filter processing unit 52 of the ultrasound diagnostic device 100.

[0098] The image processor 50 generates Doppler image data acquired at different positions at intervals of the step size based on the filtered B-mode image data and the blood flow image data. The image processor 50 generates three-dimensional ultrasound image data composed of multiple frames of Doppler image data acquired at different positions in the subject 54.

[0099] In this way, by applying filtering based on the unnecessary component suppression filter characteristics to the B-mode image data from which the Doppler image data is generated, stripe artifacts that appear in the image displayed on the display unit 18 based on the 3D ultrasound image data are suppressed.

[0100] [Configuration of the present invention] Configuration 1: A process of acquiring spatial frequency distribution data in a depth direction for one frame of two-dimensional ultrasound image data of a plurality of frames constituting the three-dimensional ultrasound image data; and performing, on each of the two-dimensional ultrasound image data, a filter process based on a filter characteristic determined according to the spatial frequency distribution data and characteristics of the transmitted ultrasound when each of the two-dimensional ultrasound image data is acquired. Configuration 2: The three-dimensional ultrasound imaging device according to configuration 1, The information processing unit includes: A three-dimensional ultrasound image processing device characterized in that a spatial frequency corresponding to a maximum value in a distribution indicated by the spatial frequency distribution data is searched for within a search range determined according to a pulse width of the transmitted ultrasound, and a characteristic that suppresses a level of the distribution indicated by the spatial frequency distribution data in a spatial frequency band including the searched spatial frequency is obtained as the filter characteristic. Configuration 3: The three-dimensional ultrasound image processing device according to configuration 2, The information processing unit includes: a filter characteristic change step for changing a filter characteristic when a maximum value of a distribution indicated by the spatial frequency distribution data obtained from the two-dimensional ultrasound image data on which the filtering process has been performed does not satisfy a predetermined condition. Configuration 4: The three-dimensional ultrasound image processing device according to any one of configurations 1 to 3, The information processing unit includes: generating the two-dimensional ultrasound image data sequentially over time; A three-dimensional ultrasound image processing device, characterized in that the same filtering process as that performed on a previously generated frame of two-dimensional ultrasound image data is performed on a subsequently generated frame of two-dimensional ultrasound image data. Configuration 5: 5. The three-dimensional ultrasound image processing device according to claim 4, The information processing unit includes: and performing the filtering process with the changed filter characteristics on the 2D ultrasound image data of one frame generated later, when the artifact condition is not satisfied for the 2D ultrasound image data of one frame generated later. Configuration 6: 6. The three-dimensional ultrasound image processing method according to any one of configurations 1 to 5, The two-dimensional ultrasound image data is The ultrasonic wave is transmitted and received while scanning a transmission beam of the ultrasonic wave at a predetermined scanning interval, The information processing unit includes: 2. A three-dimensional ultrasonic image processing apparatus comprising: a filter processing unit for filtering the two-dimensional ultrasonic image data when the scanning interval exceeds a predetermined scanning interval threshold value. Configuration 7: 7. The three-dimensional ultrasound imaging device according to claim 6, The three-dimensional ultrasound image processing device is characterized in that the scanning interval threshold is determined based on characteristics of the transmitted ultrasound. Configuration 8: The three-dimensional ultrasound image processing device according to any one of configurations 1 to 7, The filter characteristics are A three-dimensional ultrasonic image processing device characterized in that it has a characteristic of making an attenuation amount in a spatial frequency band corresponding to a predetermined structure equal to or less than an attenuation amount limit value. Configuration 9: The three-dimensional ultrasound image processing device according to any one of configurations 1 to 8, The two-dimensional ultrasound image data is A three-dimensional ultrasonic image processing device characterized in that the data represents a B-mode image on which a blood flow image is superimposed. [Explanation of symbols]

[0101] 10 information processing unit (three-dimensional ultrasound image processing device), 12 transmission unit, 14 ultrasound probe, 16 reception unit, 18 display unit, 20 operation unit, 22 vibration element, 30 Doppler image, 32 sample line data, 34 pixel, 40 control unit, 42 beam control unit, 44 memory, 46 B-mode image generation unit, 48 blood flow image generation unit, 50 image processing unit, 52 filter processing unit, 54 subject, 56 speckle, 58 gap, 60 transmission pulse, 62 envelope, 70, 72, 74, 80 spatial frequency distribution, 82 unnecessary component suppression filter characteristics, 100 ultrasound diagnostic device, 102 color Doppler ultrasound diagnostic device.

Claims

1. A process of acquiring spatial frequency distribution data in a depth direction for one frame of two-dimensional ultrasound image data of a plurality of frames constituting the three-dimensional ultrasound image data; a filter processing based on a filter characteristic determined according to the spatial frequency distribution data and the characteristic of the transmitted ultrasound when each of the two-dimensional ultrasound image data is acquired, for each of the two-dimensional ultrasound image data.

2. 2. The three-dimensional ultrasound imaging device according to claim 1, The information processing unit includes: A three-dimensional ultrasound image processing apparatus characterized in that a spatial frequency corresponding to a maximum value in the distribution indicated by the spatial frequency distribution data is searched for within a search range determined according to a pulse width of the transmitted ultrasound, and a characteristic that suppresses the level of the distribution indicated by the spatial frequency distribution data in a spatial frequency band including the searched spatial frequency is obtained as the filter characteristic.

3. 3. The three-dimensional ultrasound imaging device according to claim 2, The information processing unit includes: a filter characteristic change step for changing a filter characteristic when a maximum value of a distribution indicated by the spatial frequency distribution data obtained from the two-dimensional ultrasound image data on which the filtering process has been performed does not satisfy a predetermined condition.

4. 2. The three-dimensional ultrasound imaging device according to claim 1, The information processing unit includes: generating the two-dimensional ultrasound image data sequentially over time; 2. A three-dimensional ultrasonic image processing apparatus comprising: a first filter processing section for filtering a first frame of two-dimensional ultrasonic image data;

5. 5. The three-dimensional ultrasound imaging device according to claim 4, The information processing unit includes: a filter processing device for filtering out the two-dimensional ultrasound image data of one frame generated later, the filter processing having the changed filter characteristics being applied to the two-dimensional ultrasound image data of one frame generated later, when the artifact condition is not satisfied for the two-dimensional ultrasound image data of one frame generated later.

6. 2. The three-dimensional ultrasound imaging method of claim 1, The two-dimensional ultrasound image data is The ultrasonic wave is transmitted and received while scanning a transmission beam of the ultrasonic wave at a predetermined scanning interval, The information processing unit includes:

2. A three-dimensional ultrasonic image processing apparatus comprising: a first section for filtering the two-dimensional ultrasonic image data when the scanning interval exceeds a predetermined scanning interval threshold value;

7. 7. The three-dimensional ultrasound imaging device according to claim 6, The three-dimensional ultrasound image processing apparatus according to claim 1, wherein the scanning interval threshold is determined based on characteristics of the transmitted ultrasound.

8. 2. The three-dimensional ultrasound imaging device according to claim 1, The filter characteristics are A three-dimensional ultrasonic image processing apparatus having a characteristic that an attenuation amount in a spatial frequency band corresponding to a predetermined structure is equal to or less than an attenuation amount limit value.

9. 2. The three-dimensional ultrasound imaging device according to claim 1, The two-dimensional ultrasound image data is A three-dimensional ultrasonic image processing apparatus, characterized in that the data represents a B-mode image on which a blood flow image is superimposed.

Images