JP4010034B2 - Image creation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image creation apparatus that creates an image based on volume data (three-dimensional array data) including image information of a region of interest having a three-dimensional surface, and more particularly to create an image of a three-dimensional surface of a region of interest. Regarding technology.
[0002]
[Prior art]
Volume data obtained by X-ray tomography (X-ray CT imaging) and magnetic resonance tomography (MRI) image reconstruction processing includes image information of a region of interest having a three-dimensional surface such as a human skeleton, internal organs, or blood vessels. Yes. In the case of these tomographic images, a tomographic image is usually created and displayed based on the volume data obtained by the image reconstruction process. In recent years, the appearance of a shaded region of interest is created and displayed. A three-dimensional image (stereoscopic image) is also created by rendering such as a so-called volume rendering method. In the case of creating an image by this rendering, the region of interest may be displayed in a partially cut state.
[0003]
In conventional image creation by volume rendering, a parallel projection method as shown in FIG. 9A or a perspective projection method as shown in FIG. 9B is used. As a result, a three-dimensional image can be obtained, which is very useful for an observer (such as a doctor) to accurately grasp the situation of the region of interest.
[0004]
[Problems to be solved by the invention]
However, in the case of a three-dimensional image obtained by conventional rendering, there is a problem that it is difficult to grasp at a glance the entire surface of the three-dimensional surface of the region of interest. In order to grasp the entire surface of the 3D surface of the region of interest, you can create several 3D images at the same time from different viewpoints (for example, from the front, from the back, from the left and right sides). This is because they are displayed and observed.
[0005]
This invention makes it a subject to provide the image creation apparatus which can produce the image which can grasp | ascertain the whole figure of the solid surface of the region of interest which is an image preparation object at a glance in view of said situation.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an image creating apparatus according to the present invention includes volume data storage means for storing volume data (three-dimensional array data) including image information of a region of interest having a three-dimensional surface, and image creation based on the volume data. A three-dimensional surface extracting means for extracting a three-dimensional surface of a target region of interest; a line-of-sight reference setting means for setting a reference for determining a line-of-sight direction of a virtual line of sight when observing the three-dimensional surface of the target portion; A light source setting means for setting a virtual light source to illuminate, a line-of-sight scanning means for running the three-dimensional surface of the region of interest so that the virtual line of sight is in the line-of-sight direction determined by the line-of-sight reference setting unit, A shadow obtaining means for obtaining a virtual shadow attached to the three-dimensional surface of the region of interest based on the surface shape; Image developing means for developing a developed image by developing a single flat image according to a coordinate system set corresponding to the mode and adding a change corresponding to the virtual shadow obtained by the shadow obtaining means to the image. And an image output means for outputting a developed image created by the image creating means, and the line-of-sight reference setting means, when creating an image of the outer surface of the region of interest, as a reference for the line-of-sight direction of the virtual line of sight, The center point, which is one point inside the region of interest, is set to look from all directions outside the region of interest. On the other hand, when creating an image of the inner surface of the region of interest, It is set so that the line of sight looks in all directions from a central point which is one point inside the region of interest.
[0007]
[Action]
Next, the operation when image creation is executed by the image creation apparatus of the present invention will be described.
In creating an image, first, volume data including image information of a region of interest having a three-dimensional surface is stored in the volume data storage means. Next, the three-dimensional surface extraction means extracts the three-dimensional surface of the region of interest as the image creation target based on the volume data. Then, the line-of-sight reference setting means sets a reference for determining the line-of-sight direction of the virtual line of sight when observing the three-dimensional surface of the region of interest, and the light source setting means uses a virtual light source that illuminates the three-dimensional surface of the region of interest of the image creation target. Set. Specifically, when creating an image of the outer surface of the region of interest, the line-of-sight reference setting means uses a central point that is one point inside the region of interest as a reference for the line-of-sight direction of the virtual line of sight. On the other hand, when creating an image of the inner surface of the region of interest, the line of sight is omnidirectional from the central point that is one point inside the region of interest. Set to watch.
[0008]
Then, the visual line scanning unit causes the virtual line of sight to move from the line-of-sight direction determined by the line-of-sight reference setting unit while moving the three-dimensional surface of the region of interest of the image creation target in a scanning manner according to the development method. Thus, after obtaining a virtual shadow attached to the three-dimensional surface of the region of interest based on the illumination by the virtual light source and the surface shape of the region of interest, the three-dimensional surface of the region of interest corresponds to the scanning mode of the line-of-sight scanning by the image development means. In accordance with the coordinate system set in the above, the image is developed as a single planar image, and a developed image is created so that a change corresponding to the virtual shadow obtained by the shadow finding means is given to the image. The created developed image is output by the image output means.
That is, in the image creating apparatus of the present invention, the three-dimensional surface of the region of interest that is the object of image creation is created and output as a single flat developed image with an appropriate shadow and a three-dimensional effect.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating an overall configuration of an image creating apparatus according to an embodiment. FIG. 2 is a schematic diagram illustrating a specific example of image creation by the image creating apparatus according to the embodiment. Hereinafter, in order to facilitate understanding, description will be made with reference to the specific example of FIG. 2 as needed.
[0010]
The image creating apparatus of FIG. 1 includes a volume data memory unit 1 that stores volume data obtained and transmitted by image reconstruction processing in X-ray CT imaging, for example. The volume data includes image information of a region of interest having a three-dimensional surface such as a skull / blood vessel or an organ such as the heart or kidney as tomographic image information of the patient. The three-dimensional surface of the region of interest here refers not only to the outer surface of the region of interest (the outer surface of the skull and the outer wall surface of the blood vessel), but also to the inner surface of the region of interest (the inner surface of the skull and blood vessels). May also refer to the inner wall surface.
In the case of FIG. 2, the region of interest is a spherical body such as the skull M, for example, and is used when an image of the outer surface (three-dimensional surface) MS of the skull M is created.
[0011]
The apparatus according to this embodiment includes a three-dimensional surface extraction unit that extracts a three-dimensional surface of a region of interest as an image creation target based on volume data. That is, with the three-dimensional surface extraction means, the outer surface MS of the skull M shown in FIG. 2 is extracted as an image creation target, but the extraction of the outer surface MS is performed on the skull M and the soft tissue such as the scalp surrounding it. Since the boundary surface is extracted, boundary surface extraction in a so-called surface rendering method can be used. Since there is a certain difference between the CT value of the skull and the CT value of the soft tissue, an appropriate CT value between the two CT values is set as a threshold value, so that the boundary surface between the bone and the soft tissue, that is, the outer surface MS of the skull M Can be extracted.
[0012]
A CT value serving as a threshold value for extracting the outer surface MS is input from the keyboard 2 or the mouse 3 and stored in the setting data memory unit 4.
In the case of the present invention, in addition to the surface rendering method that clearly extracts the boundary surface, for example, boundary surface extraction of a volume rendering method that can extract the boundary surface with a certain degree of ambiguity can be used.
[0013]
Further, as in the present invention, in order to observe (visualize or image) the three-dimensional surface of the region of interest inherent in the volume data, a virtual line of sight and virtual illumination are required. A line-of-sight reference setting unit that sets a reference for determining the line-of-sight direction of the virtual line of sight when observing the surface, and a light source setting unit that sets a virtual light source that illuminates the three-dimensional surface of the region of interest to be image-created.
If the line-of-sight direction is random, the stereoscopic surface of the region of interest cannot be correctly viewed. Therefore, it is necessary to determine the line-of-sight direction along a certain standard.
[0014]
In the case of FIG. 2, the reference of the line-of-sight direction of the virtual line of sight E is set so as to always look at the center point ma inside the skull M from the outside of the skull M, and all line-of-sight directions are center points ma inside the skull M. Will point to.
Further, the direction of the virtual light source is set so that the illumination light irradiation direction always coincides with the virtual line of sight. Of course, in the case of the present invention, it is not essential that the virtual light source always sets the illumination light irradiation direction to coincide with the virtual line of sight.
The center point ma for setting the line-of-sight direction is obtained by displaying a tomographic image of a cross section horizontally crossing the vertical center of the skull M on the screen of the monitor 5 and specifying the corresponding position with the keyboard 2 or the mouse 3. The position of the center point ma is stored in the setting data memory unit 4.
The type and position of the virtual light source are also set by the keyboard 2 and the mouse 3 and stored in the setting data memory unit 4.
[0015]
In addition, the embodiment apparatus includes line-of-sight scanning means for causing the virtual line of sight to run on the three-dimensional surface of the region of interest. Of course, the line-of-sight direction of the virtual line of sight during scanning is determined by the reference determined by the line-of-sight reference setting means.
In the case of FIG. 2, the virtual line of sight E always looks at the center point ma and performs a round scan (360 °) around the outer surface MS of the skull M along the θ direction, with a slight angle φ corresponding to the latitude. The whole area of the outer surface MS is scanned by repeating the process step by step repeatedly.
[0016]
Furthermore, in order to accurately grasp the state of the three-dimensional surface of the region of interest, shading (shading) is necessary, and the embodiment apparatus uses the three-dimensional image of the region of interest based on the illumination by the virtual light source and the line-of-sight direction of the virtual line of sight. A shadow finding means for finding a virtual shadow attached to the surface is provided.
In the case of the image creation shown in FIG. 2, the visual direction of the virtual visual line and the irradiation direction of the illumination light always coincide with each other, and shading by a gray level gradient method or the like can be used.
[0017]
In the case of the shaving of the Gravel gradient method in the embodiment, as shown in FIG. 3, the inclination of the outer surface MS at the intersection PS of the line-of-sight direction E and the outer surface MS, specifically, the normal N is represented in three dimensions of CT data. While calculating | requiring according to an intensity | strength gradient, the shade degree according to the direction (angle) of the normal line N is given with respect to each intersection PS.
The direction of the normal N indicates the inclination of the outer surface MS at the intersection PS, and a shadow is produced according to the product of the cosine of the angle formed by the normal N and the light source (illumination light direction) and the intensity of the light source. If attached, an appropriate stereoscopic effect is added to the image. In order to obtain a three-dimensional intensity gradient of CT data, for example, a 3 × 3 × 3 data matrix centered on the intersection PS is extracted, and intensity gradients in the X, Y, and Z directions in this data matrix are extracted. After obtaining by data processing, these intensity gradients may be vector-synthesized.
Of course, it goes without saying that the shading may be performed by a method other than the gray level gradient method.
[0018]
The image creating apparatus according to the embodiment develops a three-dimensional surface of a region of interest as an image creation target as a single planar image according to a coordinate system set corresponding to the scanning mode of the line-of-sight scanning, and uses a shadow finding unit. Image development means for creating a developed image so as to give a change corresponding to the determined virtual shadow to the image, and image output means for outputting the created developed image are provided. That is, in the case of FIG. 2, the outer surface MS of the skull M is developed and displayed with an appropriate shadow on a single plan view by the image expanding means so that it can be seen at a glance.
[0019]
More specifically, each intersection PS of each virtual line of sight and outer surface MS associated with line-of-sight scanning is plotted at a corresponding position according to a coordinate system with the scanning direction θ as the horizontal axis and the scanning direction φ as the vertical axis. At the same time, the intensity (pixel value) of each pixel corresponding to each intersection PS is the direction of the normal N at each intersection PS and the illumination light as described above. Calculation is made based on the direction and intensity, and is stored in the developed image memory unit 7.
The developed image stored in the developed image memory unit 7 is read out at any time and displayed on the screen of the monitor (image output means) 5.
[0020]
Each unit of the above-described embodiment apparatus is constituted by a control program stored in a CPU (microprocessor) 8 and a program memory unit 9, and a timing required for creating and displaying a final developed image. Thus, necessary data processing and arithmetic control are executed.
[0021]
Subsequently, some specific examples other than FIG. 2 of image creation by the image creation apparatus of the embodiment will be given.
In the specific example of the image creation shown in FIG. 4, the reference of the line-of-sight direction is set so that the line of sight looks in all directions from the center point ma inside the skull M, and the virtual line of sight E is always around the center point ma. Except for going, it is the same as the specific example of FIG. Therefore, the developed image Mp2 obtained is an image in which the entire surface of the inner surface MT of the skull M is developed and displayed with an appropriate shadow on a single plan view so that it can be seen at a glance.
[0022]
In the case of the reference example of image creation shown in FIG. 5, the region of interest for image creation is a pipe-like blood vessel B, for example. The reference of the line-of-sight direction is set so that the outer side is viewed horizontally from the inner center line na of the blood vessel B, and the line of sight is moved slightly along the center line na every time it makes one turn. Specifically, two tomographic images corresponding to the positions of the cross-sections Ba and Bb of the blood vessel B are displayed, a center point of each tomographic image is designated, and a command to connect both center points is input. Thus, the center line na is input and stored in the setting data memory unit 4. Therefore, the inner wall surface BT of the blood vessel B is created as a developed image Mp3 in a coordinate system with the scanning direction θ as the horizontal axis and the scanning direction Z as the vertical axis.
Other than this, it is the same as the case of FIG. 2, and the developed image Mp3 obtained is the one in which the entire image of the inner wall surface BT of the blood vessel B is unfolded and displayed on a single plan view with an appropriate shade. It becomes.
[0023]
In the case of the reference example of image creation shown in FIG. 6, the setting of the reference of the line-of-sight direction is the same as the reference example of FIG. 5 except that the virtual line-of-sight E is always set to look at the center line na from the outside of the blood vessel B. It is. Therefore, the developed image Mp4 obtained is the one in which the entire appearance of the outer wall surface BS of the blood vessel B is developed and displayed with appropriate shading on one plan view and can be seen at a glance.
[0024]
In the case of FIG. 5, as shown in FIG. 7, the blood vessel B may be bent without extending straight, but the tomographic image corresponding to the cross section Bc in addition to the cross sections Ba and Bb of the blood vessel B. The reference center line na can be set by performing a process of smoothing the line after creating a line connecting the center points in order. The same applies to the case where the blood vessel B does not extend straight and is bent in the case of FIG.
[0025]
Next, the operation of the apparatus when creating and displaying a developed image by the image creating apparatus of the embodiment having the above-described configuration will be described with reference to the flowchart of FIG. Here, the case of creating an image of the outer surface MS of the skull M shown in FIG. 2 is taken as an example.
[0026]
[Step S1] Volume data obtained by image reconstruction processing such as X-ray CT imaging is stored in the volume data memory unit 1.
[0027]
[Step S2] A CT value serving as a threshold for extracting the outer surface MS of the skull M is input from the keyboard 2 and the mouse 3, and stored in the setting data memory unit 4.
[0028]
[Step S3] A reference for determining the viewing direction of the virtual viewing line E is input from the keyboard 2 and the mouse 3, and the center point ma and the like are stored in the setting data memory unit 4.
[0029]
[Step S4] A virtual light source for illuminating the outer surface MS of the skull M is input and set from the keyboard 2 and the mouse 3 so that the irradiation direction always matches the line-of-sight direction.
[0030]
[Step S5] While performing a line-of-sight scan that runs the virtual line of sight E over the outer surface MS of the skull M, the normal direction of the intersection PS of the line-of-sight direction E and the outer surface MS is obtained, and this normal N and illumination The product of the cosine of the angle formed by the light direction and the intensity of the light source is obtained to determine the shade of each intersection PS.
[0031]
[Step S6] Each intersection PS of the virtual line of sight E and the outer surface MS accompanying the line-of-sight scan is plotted at a corresponding position according to a coordinate system with the scanning direction θ as the horizontal axis and the scanning direction φ as the vertical axis. At the same time as the developed image Mp1 in the figure, the intensity (pixel value) of each pixel corresponding to each intersection PS is stored in the developed image memory unit 7 as a value corresponding to the shade degree obtained in step S5.
[0032]
[Step S7] The developed developed image Mp1 is displayed on the screen of the monitor 5. In the developed image Mp1, the outer surface MS of the skull M is shown with appropriate shading in one plan view.
[0033]
[Step S8] If a developed image having a different line-of-sight reference is obtained, the process returns to step S2, and if not, image creation is terminated.
[0034]
The present invention is not limited to the above embodiment, and can be modified as follows.
[0035]
(1) In the image creating apparatus according to the embodiment, the volume data is obtained by the image reconstruction process of the X-ray CT apparatus, but the volume data is the image reconstruction process of the MRI apparatus (magnetic resonance tomography apparatus). The volume data targeted for image formation by the present invention is not limited to a specific type.
[0036]
(2) In the apparatus according to the embodiment, the shade density generated on the three-dimensional surface of the region of interest is expressed as high or low brightness on the developed image, but the shade density is a color on the developed image. A configuration that appears as a difference is given as a modification.
[0037]
(3) The image creating apparatus of the present invention may be configured to be integrally incorporated in another apparatus such as an X-ray CT apparatus, or may be an independent separate configuration that is not incorporated at all in another apparatus. But you can.
[0038]
(4) In the image creating apparatus of the embodiment, the monitor 5 is provided as the image output means. However, a film recorder that prints a developed image on a film and outputs it can also be used as the image output means.
[0039]
【The invention's effect】
According to the image creating apparatus of the present invention, based on the volume data of the region of interest, the three-dimensional surface of the region of interest to be image-created is displayed as a single flat developed image with an appropriate shadow and a three-dimensional appearance. As a result, it is possible to grasp at a glance the entire surface of the three-dimensional surface of the region of interest.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating an overall configuration of an image creating apparatus according to an embodiment.
FIG. 2 is a schematic diagram showing a specific example of image creation by the embodiment apparatus.
FIG. 3 is a schematic diagram for explaining shading of a three-dimensional surface to be image created in the embodiment apparatus.
FIG. 4 is a schematic diagram illustrating another specific example of image creation by the embodiment apparatus.
FIG. 5 is a schematic diagram illustrating a reference example of image creation by the embodiment device.
FIG. 6 is a schematic diagram illustrating a reference example of image creation by the embodiment device.
FIG. 7 is a schematic diagram illustrating a reference example of image creation by the example device.
FIG. 8 is a flowchart showing a series of flow of creating a developed image by the embodiment apparatus.
FIG. 9 is a schematic diagram illustrating a conventional method for creating a three-dimensional image.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Volume data memory part 2 ... Keyboard 3 ... Mouse 5 ... Monitor 7 ... Expanded image memory part 8 ... CPU
9: Program memory M: Skull MS ... Outer surface MT ... Inner surface ma ... Center point na ... Center line B ... Blood vessel BS ... Outer wall surface BT ... Inner wall surface Mp1-Mp4 ... Expanded image

Claims (1)

  Volume data storage means for storing volume data (three-dimensional array data) including image information of a part of interest having a three-dimensional surface, and three-dimensional surface extraction means for extracting a three-dimensional surface of the part of interest to be imaged based on the volume data , Line-of-sight reference setting means for setting a reference for determining the line-of-sight direction of the virtual line of sight when observing the three-dimensional surface of the region of interest, light source setting means for setting a virtual light source that illuminates the three-dimensional surface of the region of interest, and line of sight of the virtual line of sight A line-of-sight scanning means for running the three-dimensional surface of the site of interest so as to be in the direction of the line of sight determined by the reference setting means, and a virtual shadow attached to the three-dimensional surface of the site of interest based on the illumination by the virtual light source and the surface shape of the site of interest And a shadow finding means for finding a solid surface according to a coordinate system in which the three-dimensional surface of the region of interest is set corresponding to the scanning mode of the line-of-sight scanning. An image development means for creating a developed image so as to give the image a change corresponding to the virtual shadow obtained by the shadow finding means while developing the image, and an image for outputting the developed image created by the image creation means Output means, and when the visual line reference setting means creates an image of the outer surface of the region of interest, a central point that is one point inside the region of interest is used as a reference of the visual line direction of the virtual line of sight. When the image of the inner surface of the region of interest is created, the line of sight from the center point, which is one point inside the region of interest, is used as the reference for the direction of the line of sight of the virtual line of sight. An image creating apparatus, characterized in that it is set so as to see a direction.

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