JP2011139787A - Ultrasound diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for reconfiguring images so as to include a desired symptom. <P>SOLUTION: A pre-memory 14 stores a plurality of sets of tomographic image data in a time-series order. A base image searching unit 24 searches for a plurality of base images from the plurality of sets of tomographic image data using a virtual period. A division basis setting unit 25 sets a plurality of division bases at positions distant from respective base images by a specified interval within an image string constituted of the plurality of sets of tomographic image data. A reconfiguration processing unit 20 divides the image string into a plurality of image groups, with the respective division bases serving as the boundaries for the division. Then, a plurality of sets of tomographic image data which correspond to one another on a periodic basis are extracted from the respective image groups, and are stored in a post-memory 26 as one data block. A three-dimensional image forming unit 28 forms three-dimensional image data projecting the heart of a fetus three-dimensionally based on the plurality of sets of tomographic image data after the reconfiguration stored in the post-memory 26. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus that forms a display image of a target tissue that moves periodically.

  2. Description of the Related Art An ultrasonic diagnostic apparatus that forms a three-dimensional ultrasonic image of a tissue that accompanies motion such as the heart is known. For example, there is a technology that scans an ultrasonic beam in a three-dimensional space, collects echo data from the three-dimensional space, forms a three-dimensional ultrasonic image based on the collected echo data, and displays it in real time. It has been. However, in the case of real-time display, there is a principle restriction that the scan rate, the beam density, and the beam range are in a trade-off relationship with each other.

  Techniques for avoiding the fundamental limitations in real-time display of 3D ultrasound images have also been proposed. For example, Patent Document 1 collects a plurality of tomographic image data over a plurality of time phases at each position on the scanning plane while moving the scanning plane little by little in the three-dimensional space in synchronization with an electrocardiogram signal or the like. A technique (reconstruction process or reconstruction process) is described in which a plurality of collected tomographic image data is rearranged and reconstructed to form three-dimensional image data. This technique is difficult to apply to a fetus or the like for which it is difficult to directly obtain an electrocardiogram signal.

  Patent Document 2 describes a technique for scanning and reconstructing at certain time intervals instead of an electrocardiographic signal. However, this technique assumes that the period of the heart, etc. during data collection is constant, so that, for example, if the period of the heart is not constant, the shape of the heart in the reconstructed image is distorted from the actual one. Reliability may be reduced.

Japanese Patent No. 3537594 JP 2005-74225 A

  In view of the background art described above, the inventor of the present application has repeatedly researched and developed a technique for forming an ultrasonic image by reconstruction processing.

  The present invention has been made in the course of research and development, and an object thereof is to provide a technique for reconstructing an image so that a desired symptom is included.

  An ultrasonic diagnostic apparatus suitable for the above object includes a probe that transmits and receives ultrasonic waves in a three-dimensional space including a target tissue that periodically moves, and a plurality of motions related to the target tissue by controlling the probe. A transmission / reception control unit that forms a plurality of scanning planes in a three-dimensional space while moving the scanning planes over a period, and the target tissue from among a plurality of images corresponding to the plurality of scanning planes A reference image search unit for searching for a plurality of reference images at intervals corresponding to a virtual period of motion, and a division for setting a plurality of division references at a location separated from each of the plurality of reference images by a specified interval in the image sequence The image sequence is divided into a plurality of image groups by setting each of the plurality of division criteria as a division boundary, and a plurality of images periodically corresponding to each other from each of the plurality of image groups. An image reconstruction unit for output, and having a display image forming unit for forming a display image of the target tissue based on the plurality of images periodically correspond to one another.

  In the above configuration, since the image is reconstructed using a plurality of division criteria set apart from each of the plurality of reference images by a specified interval, a desired symptom is included by appropriately setting the specified interval. Thus, it becomes possible to reconstruct an image.

  In a preferred embodiment, the reference image search unit searches for a plurality of reference images based on a feature quantity related to periodicity obtained from a plurality of images constituting the image sequence, and the division reference setting unit includes a plurality of reference values. The specified interval is set based on the interval of images.

  In a desirable specific example, the reference image search unit sets one image corresponding to the maximum mutual difference value as a representative reference image based on the mutual difference value corresponding to each of the plurality of images calculated as the feature amount. From the representative reference image as a starting point, from among a plurality of images corresponding to the maximum mutual difference value, the image closest to the position separated by the virtual period is searched one after another as a plurality of reference images, and the division criterion The setting unit is characterized in that the specified interval is set based on a minimum interval among intervals between reference images adjacent to each other.

  In a preferred embodiment, the division criterion setting unit sets a plurality of division criteria at locations that are temporally retroactive from each of a plurality of reference images within the image sequence, and the image reconstruction unit includes: A plurality of images periodically corresponding to each other are extracted from each of a plurality of image groups to form one data block, and a plurality of data blocks each including a plurality of images corresponding to a plurality of division criteria are temporally headed. The data block is formed.

  In a desirable specific example, the ultrasonic diagnostic apparatus further includes a virtual period calculation unit that calculates the virtual period based on a feature amount related to periodicity obtained from a plurality of images constituting the image sequence. To do.

  According to the present invention, it is possible to reconstruct an image so that a desired symptom is included.

1 is a diagram illustrating an overall configuration of an ultrasonic diagnostic apparatus that is preferable in the practice of the present invention. It is a figure for demonstrating three-dimensional scanning. It is a figure which shows the change of a cross-sectional difference value. It is a figure which shows the change of a mutual difference value. It is a figure for demonstrating the search of a reference | standard image. It is a figure for demonstrating the setting of a division | segmentation reference | standard. It is a figure for demonstrating the process by the reconstruction process part.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a diagram showing an overall configuration of an ultrasonic diagnostic apparatus suitable for implementing the present invention. The probe 10 transmits and receives ultrasonic waves in a three-dimensional space including the target tissue. The probe 10 includes a plurality of vibration elements that transmit and receive ultrasonic waves. The plurality of vibration elements are transmission-controlled by the beam former 12 to form a transmission beam. Further, the plurality of vibration elements receive the ultrasonic waves reflected from the target tissue, and signals obtained thereby are output to the beam former 12, and the beam former 12 forms a reception beam.

  The probe 10 of the present embodiment is a 3D probe that collects echo data three-dimensionally by scanning an ultrasonic beam (a transmission beam and a reception beam) in a three-dimensional space. For example, the ultrasonic beam is scanned three-dimensionally by mechanically moving a scanning surface formed electronically by a plurality of vibration elements (1D array transducers) arranged one-dimensionally. Alternatively, the ultrasonic beam may be scanned three-dimensionally by electronically controlling a plurality of vibration elements (2D array transducers) arranged two-dimensionally.

  The beam former 12 forms an ultrasonic transmission beam by supplying a transmission signal corresponding to each of a plurality of vibration elements included in the probe 10. In addition, the beam former 12 forms an ultrasonic reception beam by performing a phasing addition process or the like on a reception signal obtained from each of a plurality of vibration elements included in the probe 10, and is obtained along the reception beam. Output echo data. In the present embodiment, the target tissue is a periodically moving tissue, such as a fetal heart.

  FIG. 2 is a diagram for explaining three-dimensional scanning in the present embodiment. In FIG. 2, the three-dimensional space including the target tissue is expressed in an XYZ orthogonal coordinate system. In the present embodiment, the scanning surface S is formed so as to be substantially parallel to the XY plane, and a plurality of scanning surfaces S are formed along the Z-axis direction while slowly moving the scanning surface S in the Z-axis direction. It is formed. The scanning plane S moves slowly in the Z-axis direction over a plurality of periods related to periodic movements such as the fetal heart, for example, over a period including about 20 heartbeats in about 8 seconds.

  Returning to FIG. 1, when a plurality of scanning planes are formed along the Z-axis direction over a plurality of periods of the fetal heartbeat, tomographic image data is collected for each scanning plane and corresponds to the plurality of scanning planes. A plurality of tomographic image data is sequentially stored in the previous memory 14.

  The error determination unit 16 determines whether or not the plurality of tomographic image data is good based on the difference amount between the images obtained from the plurality of tomographic image data stored in the previous memory 14. For example, the fetal heart may move greatly in the image due to the movement of the fetus, mother or probe, and a good image may not be obtained. Therefore, the error determination unit 16 determines whether a good image for diagnosis is obtained. In the determination, the error determination unit 16 uses a cross-sectional difference value defined by the following equation.

  X, y, and z in Equation 1 are coordinate values on each axis in the XYZ orthogonal coordinate system of FIG. 2, and p is a pixel value corresponding to each coordinate in the tomographic image data. The difference value between two pieces of tomographic image data adjacent in the Z-axis direction is calculated by Equation (1).

  FIG. 3 is a diagram showing changes in cross-sectional difference values, and the horizontal axis of FIG. 3 shows the position of each tomographic image data. That is, the horizontal axis in FIG. 3 corresponds to the position of each scanning plane and the time at which each scanning plane is obtained, and corresponds to the Z axis in FIG. 2 (the direction of change in position over time). .

  If the fetal heart does not move significantly, the adjacent tomographic image data will be similar to each other, and the difference value obtained from Equation 1 will be relatively small. On the other hand, for example, if there is a movement of the fetus itself, a breathing movement of the mother, a large displacement of the position of the probe 10, the fetal heart moves greatly in the tomographic image, and the difference value between adjacent tomographic image data is relatively large. growing. Therefore, the error determination unit 16 determines that the heart has greatly shifted in the image when the cross-sectional difference value exceeds a predetermined threshold value.

  Returning to FIG. 1, when the error determination unit 16 determines that the heart has greatly shifted, the control unit 40 controls, for example, the beamformer 12 to stop collecting tomographic image data. Note that the control unit 40 controls each unit in FIG. 1 in a concentrated manner. For example, when the error determination unit 16 determines that an error has occurred, a display or a warning indicating an error is displayed. You may display on the part 30. If the error determination unit 16 does not determine an error, a process to be described later is executed based on a plurality of tomographic image data stored in the previous memory 14.

  The virtual period calculation unit 22 calculates a virtual period that is a temporary period related to the fetal heart based on a plurality of tomographic image data stored in the previous memory 14. In calculating the virtual period, the virtual period calculation unit 22 uses a mutual difference value defined by the following equation.

  X, y, and z in Equation 2 are coordinate values on each axis in the XYZ orthogonal coordinate system of FIG. 2, and p is a pixel value corresponding to each coordinate in the tomographic image data. In Equation 2, one pixel value is multiplied by the difference between two pixel values between two tomographic image data adjacent in the Z-axis direction. As a result, the mutual difference value is relatively large when the heart expands compared to when the heart contracts, and it is possible to identify expansion and contraction that are difficult to identify with a simple difference value by the mutual difference value. .

  For example, in a certain tomographic image data z, it is assumed that the pixel p (x, y, z) is a myocardium in the vicinity of the inner wall of the heart, and the pixel value is set to p (x, y, z) = 100. When the heart expands and the heart chamber becomes larger, the pixel p (x, y, z + 1) becomes the heart chamber pixel in the tomographic image data z + 1 obtained following the tomographic image data z. Since the pixel value of the heart chamber is smaller than that of the myocardium, the pixel value is set to p (x, y, z + 1) = 10. In this example, the absolute value of the right side of Equation 2 is calculated to be 100 × (100−10) = 9000. When the heart expands, there are many pixels that change from the myocardium to the heart chamber around the inner wall of the heart, so that the mutual difference value of Equation 2 becomes relatively large.

  On the other hand, when the heart contracts, a phenomenon opposite to the above example occurs. That is, since the heart contracts and the heart chamber becomes smaller, the pixel p (x, y, z) = 10 corresponding to the heart chamber changes from the pixel p (x, y, z + 1) = 100 corresponding to the heart muscle. . In this example, when the absolute value of the right side of Equation 2 is calculated, | 10 × (10−100) | = 900, which is smaller than the value 9000 in the case of expansion. Therefore, expansion and contraction can be identified by the mutual difference value.

  FIG. 4 is a diagram illustrating changes in mutual difference values. The horizontal axis of FIG. 4 indicates the position of each tomographic image data (position and time of each scanning plane), and corresponds to the Z axis of FIG. 2 (change direction of position with time). When the mutual difference value is calculated at each position (z) on the Z-axis using Equation 2, the mutual difference value becomes a relatively large value when the heart expands. Therefore, the virtual cycle calculation unit 22 detects the peak value (maximum value) of the mutual difference value, and determines the interval between adjacent peak values as the heart cycle (heartbeat cycle).

  However, for example, in the fetal heart, the heartbeat period may fluctuate, and when the heartbeat period fluctuates, the interval between peak values also fluctuates. Therefore, for example, the virtual cycle calculation unit 22 sets the second largest interval among the peak value intervals as the virtual cycle. It should be noted that the most frequently used value or centroid value obtained from the peak value interval histogram may be used as the virtual period. Further, the user or device may select the virtual period from a plurality of preset values, or the user may input the value of the virtual period. As the virtual cycle, a value obtained based on a measurement result (for example, a result of M-mode measurement) of the ultrasonic diagnostic apparatus may be used, or a fixed value may be used constantly.

  Returning to FIG. 1, when the virtual period is set, the reference image search unit 24 searches for a plurality of reference images from the plurality of tomographic image data using the virtual period.

  FIG. 5 is a diagram for explaining the search for the reference image. Each of FIGS. 5A to 5C shows a change in the mutual difference value described with reference to FIG. First, the reference image search unit 24 searches for a representative reference image (representative reference image) from a plurality of tomographic images. As shown in FIG. 5A, the reference image search unit 24 sets tomographic image data corresponding to the position where the mutual difference value is maximum as a representative reference image (representative reference cross section). Then, the reference image search unit 24 sequentially searches for a tomographic image closest to a position separated by a virtual period from a plurality of tomographic images corresponding to the maximum mutual difference value with the representative reference image as a starting point.

  First, as shown in FIG. 5A, first, a tomographic image closest to a position separated from the representative reference image by a virtual period (VHR) in the positive and negative directions in the Z-axis direction is searched and used as a reference image. The Next, as shown in FIG. 5B, the reference image search unit 24 searches for a tomographic image closest to a position separated from the searched reference image by a virtual period (VHR) to be a new reference image. . In FIG. 5B, broken arrows indicate the positions of a plurality of reference images (reference cross sections).

  The reference image search unit 24 searches a plurality of reference images one after another using the representative reference image as a starting point. In this way, a plurality of reference images are searched from a plurality of tomographic images corresponding to the maximum mutual difference values as shown in FIG. In FIG. 5C, dashed arrows indicate the positions of a plurality of reference images (reference cross sections).

  Returning to FIG. 1, when a plurality of reference images are searched, the division reference setting unit 25 is separated from each of the plurality of reference images by a specified interval in an image sequence composed of a plurality of tomographic images (data). Set multiple division criteria at locations.

  FIG. 6 is a diagram for explaining the setting of the division criterion. Each of FIGS. 6A and 6B shows an image sequence composed of a plurality of tomographic images. That is, each horizontal axis indicates the position of the tomographic image (the position and time of the scanning plane), and a plurality of tomographic images are indicated by solid lines in a pulse shape along each horizontal axis.

  In FIG. 6A, a plurality of reference images F searched in the image sequence are clearly indicated by thick and long solid lines. The plurality of reference images F are searched based on the virtual period and the change of the mutual difference value (see FIG. 5). For this reason, the interval between adjacent reference images F changes according to the periodic fluctuation of the motion related to the target tissue.

  Therefore, the division reference setting unit 25 sets the designated interval based on the intervals between the plurality of reference images F. For example, the specified interval is set based on the minimum interval among the intervals between the reference images F adjacent to each other. In FIG. 6A, the minimum interval is the period Tmin, and the division reference setting unit 25 sets the period Tmin / 2 that is half of the minimum period as the specified interval.

  Then, the division reference setting unit 25 sets a plurality of division references DF at locations that are temporally backed by a specified interval from each of the plurality of reference images F in the image sequence. In FIG. 6B, a plurality of division references DF set in the same image sequence as in FIG. 6A are clearly indicated by thick and long solid lines.

  Thus, when a plurality of division references DF are set in an image sequence, the image sequence is divided into a plurality of image groups with each of the plurality of division references DF as a division boundary. In FIG. 6B, one image group is constituted by a plurality of tomographic images included in a period Tmin starting from each division reference DF. Then, as will be described in detail later, image reconstruction (reconstruction) is realized by extracting a plurality of tomographic images that periodically correspond to each other from each of a plurality of image groups.

  Note that in the reconstruction process by division described above, only a plurality of tomographic images belonging to the image group of the period Tmin shown in FIG. 6B is used for the reconstruction process. That is, a tomographic image existing between two adjacent image groups is not used for the reconstruction process.

  Returning to FIG. 1, when a plurality of division criteria are set, the reconstruction processing unit 20 divides the image sequence into a plurality of image groups using each of the plurality of division criteria as a division boundary. And the reconstruction process part 20 implement | achieves a reconstruction process by extracting the some tomographic image corresponding to each other periodically from each of several image groups. The reconstruction processing unit 20 reconstructs a plurality of tomographic image data stored in the previous memory 14 and stores it in the rear memory 26.

  FIG. 7 is a diagram for explaining the processing by the reconstruction processing unit 20, and FIG. 7 shows the correspondence between the data stored in the front memory 14 and the data stored in the rear memory 26. . In FIG. 7, “tomographic image Zn (n = 1, 2, 3,... 69,...)” Means tomographic image data at the position of the coordinate Zn on the Z axis (see FIG. 2). Yes.

  The previous memory 14 stores a plurality of tomographic image data corresponding to a plurality of scan planes formed one after another along the Z-axis direction. That is, the previous memory 14 stores a plurality of tomographic image data in the order of tomographic images Z1, tomographic images Z2,..., Tomographic images Z69,.

  The reconstruction processing unit 20 divides a plurality of tomographic images (data) stored in the previous memory 14 into a plurality of image groups by setting each of a plurality of division criteria as a division boundary. Then, a plurality of tomographic images periodically corresponding to each other are extracted from each of the plurality of image groups.

  In FIG. 7, the tomographic image Z5, the tomographic image Z35, and the tomographic image Z65 are a plurality of reference images searched by the reference image searching unit 24, and the tomographic image Z1, the tomographic image Z31, and the tomographic image Z61 are divided reference setting units. A plurality of division criteria set by 25.

  First, the reconstruction processing unit 20 extracts tomographic images Z1,..., Tomographic images Z31,. The tomographic images Z1,..., The tomographic images Z31,..., And the tomographic images Z61 are stored in the rear memory 26 as one data block.

  Next, the reconstruction processing unit 20 extracts and extracts a plurality of tomographic images adjacent in the positive direction in the Z-axis direction with respect to each of the plurality of division references as a plurality of tomographic images periodically corresponding to each other. A plurality of tomographic images are stored in the rear memory 26 as one data block. Furthermore, the reconstruction processing unit 20 sequentially forms data blocks based on a plurality of tomographic images that correspond periodically to each other and stores them in the rear memory 26.

  In the process of sequentially forming a plurality of data blocks, the tomographic images Z5,..., The tomographic images Z35,. Then, the tomographic image Z9,..., The tomographic image Z39,..., And the tomographic image Z69, which are the final images of each image group, are stored in the rear memory 26 as one data block, and a plurality of data Block formation is complete. That is, the reconstruction process is completed. In this reconstruction process, there is a tomographic image that is not used in the reconstruction process among a plurality of tomographic images, as described with reference to FIG.

  Returning to FIG. 1, the three-dimensional image forming unit 28 forms three-dimensional image data that three-dimensionally displays the fetal heart based on a plurality of reconstructed tomographic image data stored in the post-memory 26. The 3D image forming unit 28 forms 3D image data of each time phase based on one data block stored in the rear memory 26.

  The three-dimensional image forming unit 28 applies various methods such as a volume rendering method, an integration method, and a projection method to form three-dimensional image data over a plurality of time phases for each time phase. Thus, an image corresponding to the three-dimensional image data formed over a plurality of time phases is displayed on the display unit 30, and a pseudo real-time three-dimensional moving image is displayed. For example, an image corresponding to a plurality of time-phase three-dimensional image data may be repeatedly displayed and loop reproduction may be executed.

  According to the above-described embodiment, the first time-phase three-dimensional image data is formed based on the tomographic images Z1,..., The tomographic images Z31,. Based on the tomographic images Z5,..., The tomographic images Z35,. That is, it becomes possible to arrange the three-dimensional image data based on the reference image that is considered to have the most coincident temporal relationship with each other at the center of the temporal phase. In addition, since the plurality of reference images are, for example, time phase images corresponding to the end diastole of the heart, the time phases corresponding to the end diastole are arranged at the center of the plurality of time phases so as to be reliably observed. be able to.

  It should be noted that the data block corresponding to the reference image can be shifted from the center of all the data blocks by appropriately changing the designated interval used by the division reference setting unit 25 described with reference to FIG. Therefore, for example, the user may set a specified interval (for example, time, the number of frames, etc.) as appropriate so that the data block corresponding to the reference image can be shifted from the center.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention. The present invention includes various modifications without departing from the essence thereof.

  DESCRIPTION OF SYMBOLS 10 probe, 12 beam former, 16 error determination part, 20 reconstruction process part, 22 virtual period calculation part, 24 reference | standard image search part, 25 division | segmentation reference | standard setting part, 28 3D image formation part.

Claims (5)

A probe for transmitting and receiving ultrasonic waves in a three-dimensional space including a target tissue that moves periodically;
By controlling the probe, a transmission / reception control unit that forms a plurality of scanning planes in a three-dimensional space while moving the scanning planes over a plurality of periods of motion related to the target tissue;
A reference image search unit that searches a plurality of reference images at intervals corresponding to a virtual period of motion related to the target tissue from an image sequence composed of a plurality of images corresponding to the plurality of scanning planes;
A division reference setting unit for setting a plurality of division references at a location separated from each of a plurality of reference images by a specified interval in the image sequence;
An image reconstruction unit that divides the image sequence into a plurality of image groups by using each of the plurality of division criteria as a division boundary, and extracts a plurality of images periodically corresponding to each of the plurality of image groups. When,
A display image forming unit for forming a display image of the target tissue based on a plurality of images periodically corresponding to each other;
Having
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The reference image search unit searches for a plurality of reference images based on feature amounts related to periodicity obtained from a plurality of images constituting the image sequence,
The division reference setting unit sets the designated interval based on an interval between a plurality of reference images;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The reference image search unit sets one image corresponding to the maximum mutual difference value as a representative reference image based on the mutual difference value corresponding to each of the plurality of images calculated as the feature amount, and the representative reference image Starting from a plurality of images corresponding to the maximum mutual difference value, and sequentially searching for the image closest to the position separated by the virtual period as a plurality of reference images,
The division reference setting unit sets the specified interval based on a minimum interval among intervals between reference images adjacent to each other.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The division criterion setting unit sets a plurality of division criteria at a location that is temporally traced by the specified interval from each of a plurality of reference images in the image sequence,
The image reconstruction unit extracts a plurality of images periodically corresponding to each other from each of a plurality of image groups to form one data block, and temporally converts the data block including a plurality of images corresponding to a plurality of division criteria. To form a plurality of data blocks one after the other,
An ultrasonic diagnostic apparatus. In the ultrasonic diagnostic apparatus according to any one of claims 1 to 4,
A virtual period calculation unit that calculates the virtual period based on a feature amount related to periodicity obtained from a plurality of images constituting the image sequence;
An ultrasonic diagnostic apparatus.

Images