JP4909137B2 - Volume data processing apparatus and method - Google Patents

Description

  The present invention relates to volume data processing, and more particularly, to processing for forming a three-dimensional ultrasonic image based on volume data obtained by transmission and reception of ultrasonic waves.

  Volume data as a three-dimensional ultrasonic data set can be acquired by transmitting and receiving ultrasonic waves to and from a three-dimensional region in the living body. A three-dimensional ultrasonic image can be formed by rendering processing for volume data (for example, Patent Document 1 discloses a technique for volume rendering). In the volume rendering method, voxel operations using opacity are sequentially executed along the ray (line of sight). Here, opacity is opacity. Transparency, which is the opposite of opacity, can also be used for voxel operations, which is essentially the use of opacity.

  By using the volume rendering method, it becomes possible to stereoscopically observe organs such as the heart and fetuses. For example, in the case of observing an organ or the like, a technique is known in which the boundary between organs is detected in volume data, voxels corresponding to the organ are identified, and voxel computation is performed only on voxels that substantially correspond to the organ. It has been.

  Using the volume rendering method has an advantage that the internal structure of the organ can be reflected in the image. On the other hand, since the internal structure of the organ is reflected, the surface shape of the organ may be difficult to understand.

  Incidentally, Patent Document 2 describes an image processing technique for a CT image, and for an extracted organ, an image that can clearly distinguish an organ by fusing a shadow obtained by depth shading and an actual CT value. The forming technique is described.

JP-A-10-33538 JP-A-6-20065

  Against such a background, the inventors of the present application have conducted research and development on a process for forming a three-dimensional image in which the contour of a target part such as an organ (or the inside thereof) and the shape of the surface are easily expressed.

  The present invention has been made in the course of research and development, and an object thereof is to form a three-dimensional image with a clear outline and surface of a target part and a three-dimensional effect.

  In order to achieve the above object, a volume data processing apparatus according to a preferred aspect of the present invention is a volume data processing that processes volume data obtained by transmitting and receiving ultrasonic waves to and from a three-dimensional region in a living body. In the apparatus, internal processing means for performing homogenization processing on the inside of the target part in the volume data, boundary processing means for performing gradation processing on the boundary between the target part and other part in the volume data, and homogenization processing and gradation processing An image that forms image data of a three-dimensional image that three-dimensionally represents a target portion by performing volume rendering processing along each of a plurality of virtually set rays for the volume data subjected to Forming means.

  In the above aspect, the target site is a part in the living body, and includes not only an organ or a fetus but also the inside (cavity part) of the organ. In other words, the heart chamber inside the heart is also included in the target region. According to the above aspect, since the homogenization process is performed inside the target part, the internal structure of the target part is not strongly reflected on the three-dimensional image. In addition, since gradation processing is performed on the boundary between the target part and the other part, the stereoscopic effect of the target part in the three-dimensional image is emphasized.

  In a desirable mode, the internal processing means, as the equalization processing, among the plurality of voxel data constituting the volume data, a plurality of internal voxel data corresponding to the inside of the target portion is converted into a substantially uniform voxel value. The process which performs is performed. In a preferred aspect, the boundary processing means uses the voxel values of the plurality of boundary voxel data corresponding to the boundary between the target part and the other part among the plurality of voxel data constituting the volume data as the gradation process. It is characterized in that processing that changes stepwise toward the outside is executed.

  In a preferred aspect, the boundary processing unit is configured to receive the target voxel data when a plurality of voxel data existing in the vicinity of the target voxel data includes both voxel data corresponding to the target part and voxel data corresponding to another part. Is determined to be the boundary voxel data. In a preferred aspect, the boundary processing means calculates the voxel value after the gradation processing of the target voxel data based on the target voxel data determined to be the boundary voxel data and a plurality of voxel data existing around the target voxel data. It is characterized by determining.

  In order to achieve the above object, a volume data processing method according to a preferred aspect of the present invention is a volume data processing volume data obtained by transmitting and receiving ultrasonic waves to a three-dimensional region in a living body. In the processing method, an internal processing step for applying homogenization processing to the inside of the target portion in the volume data, a boundary processing step for applying gradation processing to the boundary between the target portion and other portion in the volume data, and the homogenization processing and gradation The volume data subjected to the processing is subjected to volume rendering processing along each of a plurality of virtually set rays, thereby forming image data of a three-dimensional image that three-dimensionally represents the target portion. And an image forming step.

  The volume data processing method of the above aspect is executed by, for example, an ultrasonic diagnostic apparatus or a computer. When executed by a computer, for example, a program for causing the computer to execute each step of the volume data processing method is used. For example, when the computer reads the program, the computer executes the volume data processing method.

  According to the present invention, it is possible to form a three-dimensional image with a clear three-dimensional effect with a clear outline and surface of a target part.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a preferred embodiment according to the present invention, and FIG. 1 is a block diagram showing the entire configuration of an ultrasonic diagnostic apparatus having a volume data processing function according to the present invention.

  The 3D probe 20 has a 2D array transducer in this embodiment. The 2D array transducer is constituted by a plurality of vibration elements arranged two-dimensionally. An ultrasonic beam is formed by the 2D array transducer, and the ultrasonic beam is two-dimensionally scanned. As a result, a three-dimensional space (three-dimensional echo data capturing space) is formed in the living body. Here, the space is a space defined by r coordinate, θ coordinate, and φ coordinate. Various shapes can be raised as the shape of the three-dimensional space, such as a cubic shape and a pyramid shape. Instead of providing the 2D array transducer in the 3D probe 20, a 1D array transducer and a mechanism for mechanically scanning the 1D array transducer may be provided.

  The transmission / reception unit 22 functions as a transmission beam former and a reception beam former. The transmission / reception unit 22 supplies a plurality of transmission signals to the 2D array transducer during transmission. As a result, a transmission beam is formed. Reflected waves from within the living body are received by a plurality of vibration elements, whereby a plurality of received signals are output from the 2D array transducer to the transmitting / receiving unit 22. The transmission / reception unit 22 performs phasing addition processing on a plurality of reception signals, thereby forming a reception beam electronically and outputting the reception signal after phasing addition.

  The received signal, that is, beam data is output to the coordinate conversion unit 24. The coordinate conversion unit 24 is a module that configures a three-dimensional data space by data reconstruction, and executes, for example, processing for converting an rθφ coordinate system to an xyz coordinate system. If necessary, the coordinate conversion unit 24 is provided with a 3D memory. Incidentally, it is also possible to execute the voxel calculation in real time along the beam data with the transducer side as a fixed viewpoint without performing coordinate conversion.

  The tomographic image forming unit 28 is a module that forms a tomographic image of an arbitrary cross section set for a three-dimensional space or a predetermined cross section. In that case, data output from the coordinate conversion unit 24 is used. The image data representing the tomographic image is sent to the display unit 32 via the display processing unit 30, and the tomographic image is displayed on the display unit 32 as necessary. The position of the cross section corresponding to the tomographic image can be variably set by the user in the three-dimensional space, and such an operation is performed by input to the operation panel 36 described later.

  The 3D image forming unit 26 is a module that applies volume rendering processing to the volume data based on the volume data after coordinate conversion, and forms a three-dimensional image as a result. The image data of the formed three-dimensional image is sent to the display unit 32 via the display processing unit 30, and the three-dimensional image is displayed on the display unit 32. Specifically, the 3D image forming unit 26 sets a plurality of rays extending from the viewpoint set by the user, and sequentially executes voxel calculation along each ray in the region of interest set by the user. To do.

  The image processing function in the 3D image forming unit 26 can be described by being divided into an internal processing unit 262, a boundary processing unit 264, and a voxel computing unit 266. The internal processing unit 262 performs equalization processing on the inside of the target part in the volume data, and the boundary processing unit 264 performs gradation processing on the boundary between the target part and other part in the volume data. Then, the voxel computing unit 266 performs volume rendering processing on the volume data that has been subjected to equalization processing and gradation processing, thereby forming image data of a three-dimensional image that three-dimensionally represents the target portion.

  Incidentally, the 3D image forming unit 26 can be realized as a function of a program executed on the CPU, and a control unit 34 described later can also be realized as a function of a control program executed on the CPU.

  The control unit 34 controls the operation of each component (each unit) shown in FIG. 1, and an operation panel 36 is connected to the control unit 34. The operation panel 36 includes a keyboard and a trackball, and the user can use the operation panel 36 to set a position of a cross section for forming a tomographic image, set a region of interest, select an opacity curve (opacity determination function), and the like. .

  FIG. 2 is a flowchart for explaining the operation of the ultrasonic diagnostic apparatus in FIG. 1, and particularly shows the operation of the 3D image forming unit 26. The processing shown in FIG. 2 is executed for each ray.

  In S101, it is determined whether or not the target voxel existing on the ray to be calculated exists inside the target part. The target part is a part in the living body, and includes not only an organ or a fetus but also the inside of the organ. In the present embodiment, a heart cavity inside the heart will be described as a target site.

  FIG. 3 is a diagram for explaining the volume data 10 including the heart chamber 12. In FIG. 3, the volume data 10 is filled with a plurality of voxels 18 arranged in a three-dimensional lattice pattern. In general, the heart chamber 12 has a lower echo level (voxel value or echo value of the voxel 18) than the surrounding myocardium 14 or the like. Therefore, the voxel 18 corresponding to the heart chamber 12 can be extracted by performing binarization processing or the like on each voxel 18 in the volume data 10. For example, by setting a threshold value smaller than the level corresponding to the myocardium 14 and larger than the level corresponding to the heart chamber 12, the myocardium 14 and the heart chamber 12 can be roughly classified based on the threshold value.

  In addition to simple binarization processing, for example, a window composed of nine 3 × 3 voxels 18 is provided, and each voxel 18 constituting the window is binarized to a voxel 18 that is equal to or greater than a threshold and less than the threshold. Based on the result of the classification of the nine voxels 18 in the window, it may be determined whether the target voxel positioned at the center of the window corresponds to the myocardium or the heart chamber.

  Returning to FIG. 2, when it is determined that the target voxel is inside the target region, that is, the heart chamber (reference numeral 12 in FIG. 3), in S102, the internal processing unit (reference numeral 262 in FIG. 1) The echo value (voxel value) is set to a predetermined value. In this case, the predetermined value is 127, for example. If it is determined that the target voxel is not inside the target region, that is, the myocardium (reference numeral 14 in FIG. 3), the echo value (voxel value) of the target voxel is set to 0 (zero) in S105. The

  Thus, when the equalization processing is performed by the internal processing unit, in S103, the boundary processing unit (reference numeral 264 in FIG. 1) determines whether or not the target voxel is near the boundary between the heart chamber and the myocardium. Further, the boundary processing unit executes the light / dark process for the voxels determined to be near the boundary in S104.

  FIG. 4 is a diagram for explaining recognition processing in the vicinity of the boundary by the boundary processing unit. FIG. 4 shows the vicinity of the target voxel in the volume data (reference numeral 10 in FIG. 3). In FIG. 4, the target voxel exists at the coordinates (x, y, z). The boundary processing unit determines that the target voxel is in the vicinity of the boundary when both the voxel corresponding to the heart chamber and the voxel corresponding to the myocardium are included in the plurality of voxels existing in the vicinity of the target voxel.

  The boundary processing unit is, for example, four voxels existing in the vicinity of the target voxel (x, y, z), that is, coordinates (x-1, y-1, z-1), (x + 2, y-1, Reference is made to four voxels existing in (z + 2), (x + 2, y + 2, z-1), (x-1, y + 2, z + 2). When all four points correspond to the myocardium, the target voxel is determined to be the myocardium, and when one to three of the four points correspond to the heart chamber, the target voxel is determined to be near the boundary. If all four points correspond to the heart chamber, the target voxel is determined to be the heart chamber.

  5 and 6 are diagrams for explaining the density processing by the boundary processing unit. FIG. 5 and FIG. 6 respectively show the vicinity of the target voxel in the volume data (reference numeral 10 in FIG. 3) as in FIG. The boundary processing unit determines a voxel value after gradation processing (gradation processing) of the target voxel based on the target voxel determined to be near the boundary and a plurality of voxels existing around the target voxel.

  First, as shown in FIG. 5, the boundary processing unit, the target voxel existing at the coordinates (x, y, z) and the surrounding coordinates (x + 1, y−1, z−1) to (x−1, A total of 9 voxels comprising 8 voxels of y + 1, z + 1) are used. When the voxel at each point used is a voxel corresponding to the heart chamber by the internal processing unit (reference numeral 262 in FIG. 1), the echo value is set to 127, and the voxel corresponding to the myocardium is used. The echo value is set to 0 (zero). In this state, the boundary processing unit calculates an average value of the echo values related to the nine voxels, and executes an averaging process using the calculated average value as the echo value of the target voxel.

  Further, the boundary processing unit uses the attention described with reference to FIG. 5 for each of the voxels existing at the other seven coordinates shown in FIG. 6 in addition to the attention voxel existing at the coordinates (x, y, z). The same averaging process as in the case of voxels is performed. Thus, a total of eight voxel echo values (averaged) existing in the eight coordinates (x, y, z), (x + 1, y, z), (x + 1, y, z + 1),. Echo value after processing) is calculated. Then, the boundary processing unit executes an interpolation process based on the echo values of these eight voxels, and obtains the echo value of the target voxel existing at the coordinates (x, y, z) (echo value after the density process). decide. For example, the average value of the eight voxels shown in FIG. 6 (the echo value after the averaging process) is calculated, and the average value for the eight voxels is calculated as the echo value of the target voxel (the echo value after the density process). ).

  In the shading processing of the boundary processing unit in FIG. 6 described above, the shading processing is performed on the target voxel that performs the interpolation processing based on the echo values of the eight voxels around the target voxel. Sample points on the ray may be used instead of the target voxel.

  In the volume rendering process, it is generally assumed that the ray can be set in an arbitrary direction, and the coordinates of the sample points set on the ray do not always match the coordinates of the voxel. For this reason, the echo value of the sample point is set by an interpolation process based on the echo values of voxels around the sample point.

  This is a specific method of shading processing on sample points. In the recognition processing near the boundary shown in FIG. 4, it is determined whether or not the target voxel is positioned in the vicinity of the boundary. By examining the coordinates of the sample point, it is determined whether the sample point is included in the target voxel near the boundary and a plurality of voxels existing in the vicinity, that is, whether the sample point is a sample point near the boundary. .

  Next, after performing the averaging process using the eight voxels existing in the vicinity of the target voxel in the vicinity by the first gradation process shown in FIG. 5, as the second gradation process, Interpolation processing (averaging processing) is performed on the sample points based on the echo values of the eight neighboring voxels, and the echo values at the sample points are determined. In the interpolation process, an averaging process is performed in which the echo value of each voxel is weighted according to the distance between the sample point and each voxel.

  According to this method, since the shading process can be executed based on the ray direction, a highly reliable three-dimensional image of the target part can be obtained.

  The shading process described with reference to FIGS. 5 and 6 is performed while the attention voxel is advanced along the ray on each ray by repeatedly executing the flowchart of FIG. 2. As a result, shading processing is performed so that the echo values of a plurality of voxels determined to be near the boundary change stepwise toward the outside of the heart chamber. In place of the shading process described with reference to FIGS. 5 and 6, for example, a table for determining an echo value according to the distance from the surface of the heart chamber is set in advance, and the table is used. The shading process may be performed so that the echo value of the voxel changes stepwise toward the outside of the heart chamber.

  Returning to FIG. 2, if it is determined in S103 that the target voxel is in the vicinity of the boundary by the boundary vicinity recognition process (see FIG. 4), in S104, the density process (FIGS. Is executed. On the other hand, if it is determined in S103 that the target voxel is not near the boundary, the shading process is not executed. When the density process is not executed, the echo value remains 127 if the target voxel is the heart chamber, and the echo value remains 0 if the target voxel is the myocardium.

  Next, in S106 and S107, the voxel calculation unit (reference numeral 266 in FIG. 1) executes the voxel calculation. In the voxel calculation, the opacity (opacity) is determined for each voxel. In this case, the opacity is determined for each voxel based on the echo value. For example, the opacity corresponding to the echo value of the target voxel is determined by referring to an opacity table prepared in advance.

  In S106, the opacity integrated value is calculated by multiplying the opacity corresponding to the target voxel by the value obtained by subtracting the previous opacity integrated value from 1. In S107, the luminance integrated value is obtained by executing the calculation as shown in the drawing using the opacity and echo value corresponding to the target voxel. Note that the arithmetic expressions shown in S106 and S107 in FIG. 2 are merely examples, and voxel arithmetic may be executed using expressions other than these expressions.

  In S108, it is determined whether or not the final step has been reached. If the final step has not been reached, the target voxel is advanced by one step along the ray in S109, and each step from S101 is repeated. If it has been reached, this process ends. The integrated luminance value at the end of the process corresponds to a pixel value, which is mapped to a pixel associated with the ray. By executing the processing for each ray shown in FIG. 2 for all the rays, the pixel values obtained for each ray are mapped on a virtual screen, and a three-dimensional image is formed on the screen.

  FIG. 7 is a diagram illustrating an image example and a comparative image example according to the present embodiment. FIG. 7A is an example of a comparative image, which is an example of an image when the equalization processing and gradation processing according to the present embodiment are not performed. In FIG. 7A, the image indicated by reference numeral 50A is a three-dimensional image that reflects the heart chamber. Further, three orthogonal cross sections regarding the heart cavity are images indicated by reference numerals 52A, 54A, and 56A.

  On the other hand, FIG. 7B is an image example of the present embodiment, and is an image example when the equalization processing and gradation processing according to the present embodiment are performed. In FIG. 7B, the image indicated by reference numeral 50B is a three-dimensional image that reflects the heart chamber. Further, three orthogonal cross sections regarding the heart cavity are images indicated by reference numerals 52B, 54B, and 56B. The three-dimensional image 50B is formed by the 3D image forming unit (reference numeral 26 in FIG. 1), and the orthogonal three cross sections 52B, 54B, and 56B are formed by the tomographic image forming unit 28.

  The internal structure of the heart chamber is reflected on the surface of the image of the heart chamber displayed in the three-dimensional image 50A in FIG. 7A, and the surface shape (boundary shape) of the heart chamber is difficult to understand. On the other hand, since the image of the heart chamber displayed in the three-dimensional image 50B in FIG. 7B is subjected to a homogenization process, the internal structure of the heart chamber is not strongly reflected on the image. In addition, since gradation processing (gradation processing) is performed on the boundary between the heart chamber and the myocardium, the three-dimensional feeling of the heart chamber in the three-dimensional image is emphasized. Thus, according to the present embodiment, it is possible to form a three-dimensional image having a clear three-dimensional effect with a clear outline and surface of the target part.

  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.

1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus having a volume data processing function according to the present invention. 3 is a flowchart for explaining the operation of the ultrasonic diagnostic apparatus in FIG. 1. It is a figure for demonstrating the volume data containing a heart chamber. It is a figure for demonstrating the recognition process of the boundary vicinity by a boundary process part. It is a figure for demonstrating the shading process by a boundary process part. It is a figure for demonstrating the shading process by a boundary process part. It is a figure which shows the example of an image by this embodiment, and a comparative image example.

Explanation of symbols

  20 3D probe, 22 transmitting / receiving unit, 26 3D image forming unit, 262 internal processing unit, 264 boundary processing unit, 266 voxel computing unit.

Claims (6)

In a volume data processing apparatus that processes volume data obtained by transmitting and receiving ultrasonic waves to and from a three-dimensional region in a living body,
Internal processing means for performing equalization processing on the inside of the target portion in the volume data;
Boundary processing means for performing gradation processing on the boundary between the target part and other part in the volume data;
A volume rendering process is performed along each of a plurality of virtually set rays for the volume data that has been subjected to the homogenization process and the gradation process, thereby generating a three-dimensional image representing the target part in a three-dimensional manner. Image forming means for forming image data;
Having
A volume data processing apparatus. The volume data processing device according to claim 1,
The internal processing means executes, as the equalization process, a process of making a plurality of internal voxel data corresponding to the inside of the target part out of a plurality of voxel data constituting volume data substantially uniform voxel values. To
A volume data processing apparatus. The volume data processing device according to claim 1,
The boundary processing means, as the gradation process, sets the voxel values of a plurality of boundary voxel data corresponding to the boundary between the target part and the other part among the plurality of voxel data constituting the volume data toward the outside of the target part. Execute a process that changes in stages,
A volume data processing apparatus. In the volume data processing device according to claim 3,
The boundary processing means, when the voxel data corresponding to the target part and the voxel data corresponding to another part are included in the plurality of voxel data existing in the vicinity of the target voxel data, It is determined to be data,
A volume data processing apparatus. The volume data processing device according to claim 4,
The boundary processing means determines the voxel value after the gradation processing of the target voxel data based on the target voxel data determined to be the boundary voxel data and a plurality of voxel data existing therearound.
A volume data processing apparatus. In a volume data processing method for processing volume data obtained by transmitting and receiving ultrasonic waves to a three-dimensional region in a living body,
An internal processing step for performing a homogenization process on the inside of the target part in the volume data;
A boundary processing step for performing gradation processing on the boundary between the target part and the other part in the volume data;
A volume rendering process is performed along each of a plurality of virtually set rays for the volume data that has been subjected to the homogenization process and the gradation process, thereby generating a three-dimensional image representing the target part in a three-dimensional manner. An image forming process for forming image data;
including,
And a volume data processing method.