JP2012239576A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve image processing for projecting the surface of an object tissue by comparatively simple processing and comparatively clearly.SOLUTION: A boundary determining part 50 compares a reference vector V with each normal vector N, specifies the normal vector N decided to point to the same side as the reference vector V, and a polygon corresponding to the normal vector N is determined to be a non-display boundary. A display image forming part 60 forms a display image projecting the surface of the object tissue according to a plurality of polygons except polygon of the non-display boundary in volume data. Thus, as shown in (B), even when a fetus is observed from the placental site, a surface T3 corresponding to the face of the fetus is clearly projected.

Description

  The present invention relates to an ultrasound diagnostic apparatus, and more particularly to a technique for forming a display image that reflects the surface of a target tissue.

  A technique for forming a three-dimensional ultrasonic image that three-dimensionally displays a target tissue based on volume data obtained by transmitting and receiving ultrasonic waves to and from a three-dimensional space including the target tissue is known. For example, Patent Document 1 discloses a technique for forming a three-dimensional ultrasonic image by a volume rendering method. According to the volume rendering method, it is possible to form a display image that reflects the target tissue or the like so as to penetrate from the surface to the inside.

  On the other hand, a surface rendering method is also known in which a surface of a target tissue or the like is extracted from volume data and only the surface is three-dimensionally projected. According to the surface rendering method, for example, the face of a fetus can be projected.

  However, a placenta or the like is also present in the vicinity of the fetus in the mother's body, and when the surface of the tissue is extracted by the surface rendering method, the surface of the placenta is also extracted together with the surface of the fetus. Therefore, for example, when a line of sight (ray) for image processing is set from the placenta side to the fetus side, the surface of the placenta is formed in front of the fetus, and the face of the fetus being observed is placed on the placenta. May be hidden.

  In order to display only the observation target, for example, a technique for setting a region of interest (ROI) in the fetus while avoiding the placenta, or a starting point of image processing on the line of sight (ray) so as not to include the placenta. Technology is also conceivable. However, if the device sets the region of interest and the starting point, complicated processing to accurately set these settings is required. On the other hand, if these settings are left to the user, a large amount of operation is required for the user. Will be forced to burden.

JP 2008-259697 A

  In the above-described situation, the inventors of the present application have conducted research and development on a technique for projecting the surface of a target tissue such as a fetus.

  The present invention has been made in the course of research and development, and an object thereof is to realize image processing for relatively clearly processing and relatively clearly displaying the surface of a target tissue.

  An ultrasonic diagnostic apparatus suitable for the above-described object includes a probe that transmits and receives ultrasonic waves to and from a three-dimensional space including a target tissue, a transmission and reception unit that obtains a reception signal from the three-dimensional space by controlling the probe, and a reception In the volume data of the three-dimensional space formed based on the signal, a boundary setting unit that sets a plurality of minute surfaces corresponding to the boundary of the tissue, and the target based on the orientation of each minute surface in the volume data A boundary determination unit that determines a micro surface of a non-display boundary that hinders the projection of the surface of the tissue, and a surface of the target tissue based on a plurality of micro surfaces excluding the micro surface of the non-display boundary in volume data And a display image forming unit that forms image data of the displayed display image.

  In the above configuration, the volume data is composed of, for example, a plurality of echo data (voxel data) arranged in a three-dimensional coordinate system, and binarization processing is performed on the plurality of echo data, for example, in the volume data. The tissue boundaries are extracted at. Of course, the process for extracting the boundary is not limited to the binarization process, and the boundary may be extracted using other known processes.

  The boundary setting unit sets a plurality of minute surfaces corresponding to the tissue boundary. The size (area) of each minute surface only needs to be minute in comparison with the entire boundary. For example, each minute surface is set to include several adjacent voxel data. More specifically, triangular polygons having apexes of three voxel data adjacent to each other in the volume data are suitable as each minute surface. The plurality of minute surfaces are set so as to fill the entire boundary, for example.

  The boundary determination unit determines whether or not the minute surface belongs to the non-display boundary based on the direction of each minute surface, that is, whether or not the minute surface should be displayed. For example, it is determined that a minute surface having a direction greatly different from the direction of each minute surface belonging to the surface of the target tissue is a non-display boundary. Of course, the criterion for determining whether or not the surface is a non-display boundary minute surface may be appropriately changed, or the criterion may be adjusted by the user.

  In this way, the surface of the target tissue is clearly displayed as compared with a case where all of a plurality of minute surfaces are displayed while being a simple process compared to a complicated process such as setting of a region of interest.

  In a desirable specific example, the boundary determination unit determines a micro surface of the non-display boundary by comparing a reference direction with a direction of each micro surface.

  In a preferred embodiment, a reference vector for setting the reference direction is set for the volume data, and a normal vector for setting the direction is set for each of a plurality of minute surfaces set by the boundary setting unit. The boundary determination unit determines the minute surface of the non-display boundary based on an angle between a normal vector of each minute surface and a reference vector.

  In a preferred embodiment, the reference vector is set along a straight line passing through the placenta, amniotic fluid, and the fetus that is the target tissue in the volume data, and a plurality of micro planes corresponding to the boundary between the placenta and the amniotic fluid and the boundary between the amniotic fluid and the fetus The normal vector of the direction based on the amniotic fluid is set for each of the above, and the boundary determination unit is the non-display boundary based on the inner product value of the normal vector of each minute surface and the reference vector It is characterized in that a minute surface corresponding to the boundary between the placenta and the amniotic fluid is determined.

  In a preferred embodiment, the reference vector is set in the volume data from the placenta side to the fetal side direction through the amniotic fluid, and is applied to each of a plurality of minute planes corresponding to the boundary between the placenta and the amniotic fluid and the boundary between the amniotic fluid and the fetus. On the other hand, a normal vector is set in the direction of the amniotic fluid side, and the boundary determination unit determines each micro surface where the inner product value of the normal vector and the reference vector exceeds a threshold value as a micro surface corresponding to the placenta and amniotic fluid boundary. It is characterized by determining.

  According to the present invention, it is possible to realize image processing that displays the surface of a target tissue relatively clearly and relatively clearly.

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 the binarization process in a binarization process part. It is a figure for demonstrating the polygon set by the boundary setting part. It is a figure for demonstrating the normal vector set by the boundary setting part. It is a figure for demonstrating the determination of the boundary by a boundary determination part.

  FIG. 1 is a diagram showing an overall configuration of an ultrasonic diagnostic apparatus suitable for implementing the present invention. The probe 10 is an ultrasonic probe that transmits / receives ultrasonic waves to / from a region including a target tissue. The probe 10 includes a plurality of vibration elements that transmit and receive ultrasonic waves, and transmission of the plurality of vibration elements is controlled by the transmission / reception unit 12 to form a transmission beam. In addition, a plurality of vibration elements receive ultrasonic waves obtained from the region including the target tissue, and a signal obtained thereby is output to the transmission / reception unit 12, and the transmission / reception unit 12 forms a reception beam to form a reception beam. Echo data is collected along.

  The probe 10 is preferably a three-dimensional probe that three-dimensionally collects echo data by scanning an ultrasonic beam (transmission beam and reception beam) in a three-dimensional space. For example, the ultrasonic beam is three-dimensionally scanned by mechanically moving a scanning surface electronically formed 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 two-dimensionally arranged vibration elements (2D array transducers).

  When echo data is collected by scanning an ultrasonic beam in the three-dimensional space, the echo data (voxel data) for a plurality of voxels constituting the three-dimensional data space corresponding to the three-dimensional space is not shown. Is remembered. A three-dimensional data space composed of a plurality of voxel data is called volume data. Then, various processes are executed on the volume data in each unit after the binarization processing unit 20.

  A suitable target tissue in the present invention is a fetus, and in this embodiment, a display image in which the face of the fetus is projected is formed using surface rendering. Therefore, various processes until a display image is formed will be described. In addition, about the part (structure) shown in FIG. 1, the code | symbol of FIG. 1 is utilized in the following description.

  FIG. 2 is a diagram for explaining the binarization processing in the binarization processing unit 20. The binarization processing unit 20 binarizes a plurality of voxel data constituting the volume data with a threshold value. In the mother's body, a fetus is present in the amniotic fluid, and a placenta is also present in the vicinity of the fetus. A relatively large echo value (voxel value) is obtained from the fetus or placenta, and an echo value (voxel value) obtained from amniotic fluid is relatively small. Therefore, the binarization processing unit 20 binarizes a plurality of voxel data using a threshold value appropriately set between the voxel value of the fetus or placenta and the voxel value of amniotic fluid.

  FIG. 2A shows an example of an image obtained by binarization processing. Since the binarization processing is executed over the entire area of the three-dimensional volume data, the binarized image (binarized data) obtained thereby is also three-dimensional. FIG. 2A shows a cross section in the binarized image obtained three-dimensionally.

  As a result of the binarization processing, the volume data is discriminated into regions T1 to T3 corresponding to fetuses and placenta where voxel values above the threshold are obtained, and region F corresponding to amniotic fluid where voxel values smaller than the threshold are obtained. The After the discrimination, for example, a voxel value “1” is associated with a voxel that is equal to or greater than the threshold, and a voxel value “0” is associated with a voxel that is smaller than the threshold.

  Thus, amniotic fluid and other tissues are discriminated by the binarization process, and the boundary between them can be specified. Therefore, when surface rendering is performed on the binarized volume data from the direction of the line-of-sight vector V, a display image as shown in FIG. 2B is obtained.

  FIG. 2B shows a conventional display image obtained from the volume data after binarization processing. For example, when surface rendering is performed by setting a plurality of lines of sight (rays) from the direction of the line-of-sight vector V shown in FIG. 2A, the placenta is placed before the region T3 of the voxel data relating to the fetus to be diagnosed. Since the voxel data region T1 exists, the surface T3 of the fetus is hidden by the surface T1 of the placenta as shown in FIG. The surface T2 is, for example, a fetal hand.

  As described above, when the surface rendering is simply performed on the volume data after the binarization processing, the fetal face or the like to be diagnosed may be hidden in the placenta. Therefore, in the present embodiment, various processes described below are executed on the volume data after the binarization process.

  The boundary setting unit 30 in FIG. 1 sets a plurality of minute surfaces corresponding to the tissue boundaries in the volume data after binarization processing. A specific example of the minute surface is a triangular polygon.

  FIG. 3 is a diagram for explaining a polygon set by the boundary setting unit 30. A cube indicated by a broken line in FIG. 3 is an example of the arrangement of voxel data regarded as a tissue boundary. Eight voxel data are arranged at the vertices of each cube, and each voxel data is binarized into data F corresponding to amniotic fluid or data T corresponding to fetus or placenta.

  In each arrangement example of sample 1 and sample 2, a triangular polygon P having three data T as vertices is defined. In FIG. 3, only sample 1 and sample 2 are shown, but about 28 samples are defined so as to cover all patterns that can be regarded as boundaries.

  The boundary setting unit 30 confirms the arrangement state of the eight voxel data in the binarized volume data, and when the same arrangement state as the boundary sample is confirmed, the polygon P defined by the sample is determined. Set. As a result, a small triangular polygon P is set across the entire boundary between the area of data F corresponding to amniotic fluid and the area of data T corresponding to the fetus and placenta.

  The boundary setting unit 30 further sets, for each polygon P, a normal vector indicating the orientation of the polygon P. The normal vector is set so as to go from the fetus or placenta side toward the amniotic fluid side. Of course, a normal vector corresponding to the polygon P may be defined in advance for each sample shown in FIG.

  FIG. 4 is a diagram for explaining a normal vector set by the boundary setting unit 30. FIG. 4 shows an example in which a normal vector N is set for the binarized image of FIG. As shown in FIG. 4, a plurality of polygons are set and a plurality of normal vectors N are set at the boundaries between the regions T1 to T3 corresponding to the fetus and placenta and the region F corresponding to the amniotic fluid. Each normal vector N indicates the direction of the corresponding polygon, and is set so as to go from the fetus or placenta side toward the amniotic fluid side. The magnitudes of the plurality of normal vectors N are constant, and for example, it is desirable that they are unit vectors having a magnitude of 1. In this embodiment, the boundary determination unit 50 determines a non-display boundary that hinders the display of the fetal surface based on the normal vector N indicating the orientation of each polygon.

  FIG. 5 is a diagram for explaining boundary determination by the boundary determination unit 50. The boundary determination unit 50 determines the non-display boundary based on the normal vector N indicating the direction of each polygon. In this determination, the reference vector V set for the volume data is referred to. For example, the reference vector V is preferably set along a straight line passing through the placenta, the amniotic fluid, and the fetus that is the target tissue in the volume data. In this case, the reference vector V is set in the direction from the placenta to the fetus. It is desirable that the unit vector is set and has a magnitude of 1.

  The reference vector V may be provided along a line of sight (ray) in surface rendering. The line of sight (ray) is set from the viewpoint set by the viewpoint setting unit 40 according to the user operation toward the fetus that is the target tissue. In surface rendering, a plurality of rays are set and a rendering operation is performed for each ray. A plurality of rays may be set in parallel with one ray starting from the viewpoint, or a plurality of rays may be extended from one viewpoint.

  The boundary determination unit 50 compares the reference vector V set in the direction from the placenta side to the fetus side and the normal vector N indicating the orientation of each polygon, and based on the angle between these vectors, the reference vector V A normal vector N determined to face the same side is specified, and a polygon corresponding to the normal vector N is determined as a non-display boundary. For example, when the inner product value of the reference vector V and each normal vector N is calculated and the inner product value is larger than the threshold value Vth, the boundary determination unit 50 determines the polygon corresponding to the normal vector N as a non-display boundary. . Note that the threshold value Vth may be a fixed value, or may be a value that can be adjusted by the user, for example.

  FIG. 5A shows a determination result by the boundary determination unit 50, that is, among the plurality of normal vectors N shown in FIG. 5A, a normal vector N indicated by a dashed arrow. Corresponds to the polygon of the non-display boundary. In the example of FIG. 5A, the entire surface of the region T1 corresponding to the placenta is a non-display boundary, and a part of the region T2 corresponding to the fetal hand is a non-display boundary. On the other hand, the surface of the region T3 corresponding to the fetal face is not a non-display boundary.

  Thus, when the non-display boundary is determined by the boundary determination unit 50, the display image forming unit 60 displays the surface of the target tissue based on a plurality of polygons excluding the non-display boundary polygons in the volume data. Image data is formed. That is, the surface rendering process is executed along each of a plurality of lines of sight (rays). The plurality of rays may be set in parallel with the reference vector V, or may be set according to a viewpoint set regardless of the reference vector V.

  FIG. 5B shows an example of a display image formed by the display image forming unit 60 and displayed on the display unit 70. Since the polygon of the non-display boundary determined by the boundary determination unit 50, that is, the polygon corresponding to the surface of the placenta is excluded, even when the fetus is observed from the placenta side, the surface T3 corresponding to the face of the fetus is clearly displayed. The surface T2 corresponding to the hand of the fetus is also projected.

  As shown in FIG. 5A, a part of the surface of the region T2 corresponding to the fetal hand is a non-display boundary. Therefore, the depth for determining the non-display boundary (distance from the end on the placenta side of the volume data) may be adjusted so that the surface of the region T2 is displayed over the entire area.

  In FIG. 4, each normal vector N is set so as to go from the fetus or placenta side to the amniotic fluid side. Conversely, each normal vector N goes from the amniotic fluid side to the fetus or placenta side. May be set. In that case, a normal vector N determined to face the opposite side to the reference vector V shown in FIG. 5A is specified, and the polygon corresponding to the normal vector N is set as a non-display boundary. What is necessary is just to judge. In the determination, it goes without saying that the angle between the reference vector V and each normal vector N and the inner product value of the reference vector V and each normal vector N can be used.

  Furthermore, the reference vector V may be set from the fetus side toward the placenta side. Even in that case, there is a standard for determining the non-display boundary according to the setting state of each normal vector N (from the fetus or placenta to the amniotic fluid side or from the amniotic fluid side to the fetus or placenta). It is changed appropriately.

  In the example shown in FIG. 5A, the entire surface of the region T1 corresponding to the placenta is a non-display boundary, but a part of the surface is not a non-display boundary due to the shape of the placenta or the like. Is also possible. Therefore, for one boundary composed of a plurality of polygons adjacent to each other, for example, when the ratio of the number of polygons set as non-display boundaries is larger than a reference value, the entire boundary may be set as a non-display boundary.

  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.

  10 probe, 30 boundary setting unit, 50 boundary determination unit, 60 display image forming unit.

Claims (5)

A probe for transmitting and receiving ultrasonic waves to and from a three-dimensional space including the target tissue;
A transmission / reception unit for obtaining a reception signal from the three-dimensional space by controlling a probe;
In the volume data of the three-dimensional space formed based on the received signal, a boundary setting unit that sets a plurality of minute surfaces corresponding to the boundary of the tissue,
A boundary determination unit that determines a micro surface of a non-display boundary that hinders the projection of the surface of the target tissue based on the orientation of each micro surface in the volume data;
A display image forming unit that forms image data of a display image that reflects the surface of the target tissue based on a plurality of minute surfaces excluding the minute surfaces of the non-display boundary in volume data;
Having
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The boundary determination unit determines a micro surface of the non-display boundary by comparing a reference direction and a direction of each micro surface,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
A reference vector for setting the reference direction for the volume data is set,
A normal vector that determines the orientation of each of the plurality of micro-surfaces set in the boundary setting unit is set,
The boundary determination unit determines the minute surface of the non-display boundary based on an angle between a normal vector of each minute surface and a reference vector;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
The reference vector is set along a straight line passing through the placenta, the amniotic fluid, and the fetus that is the target tissue in the volume data,
For each of a plurality of microfacets corresponding to the placenta and amniotic fluid boundary and the amniotic fluid and fetal boundary, a normal vector of the direction relative to the amniotic fluid is set,
The boundary determination unit determines a microsurface corresponding to the boundary between the placenta and the amniotic fluid, which is the non-display boundary, based on the inner product value of the normal vector and the reference vector of each microsurface,
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 4,
The reference vector is set in the volume data from the placenta side to the fetal side direction through the amniotic fluid,
A normal vector is set in the direction of the amniotic fluid side for each of a plurality of microfacets corresponding to the placenta / amniotic fluid boundary and the amniotic fluid / fetal boundary,
The boundary determination unit determines each minute surface whose inner product value of the normal vector and the reference vector exceeds a threshold value as a minute surface corresponding to the boundary between the placenta and the amniotic fluid,
An ultrasonic diagnostic apparatus.

Images