JP2005202791A - Method, device, and program for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method, a device and a program whereby a user who is not skilled in image processing can execute image processing for a desired purpose easily and in a way that secures reproducibility. <P>SOLUTION: The method generates an image suitable for a desired purpose using a volume rendering technique on a computer 20. This method comprises a step (401) in which the computer 20 obtains a plurality of voxels each having a CT value, a step (402) in which the computer 20 assigns an opacity and an RGB combination ratio corresponding to a CT value of the voxel to each of the plurality of voxels by referring to a template selected by a user from at least one template, and a step (403) in which the computer 20 generates a two dimensional color image by executing predetermined processing to the plurality of voxels. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method, an apparatus, and a program for generating an image suitable for a desired purpose.

  In recent years, image processing using a volume rendering method has become mainstream in the field of three-dimensional image processing. The volume rendering method assigns opacity and RGB color information to each voxel constituting a three-dimensional object, and performs ray tracing (ray casting) from an arbitrary viewpoint. It is also known as a method for visualizing internal information of a three-dimensional object.

  However, there is no clear guideline on how to assign opacity and RGB color information to each voxel, and it relies solely on the intuition and experience of image processing experts, so users who are not image processing experts However, it has been very difficult to perform image processing according to a desired purpose.

  One of the objects of the present invention is a method, apparatus, and program that enables a user who is not an expert in image processing to easily perform image processing according to a desired object in a form that ensures reproducibility. Is to provide.

  The method of the present invention is a method of generating an image suitable for a desired purpose using a volume rendering method on a computer, and at least one template is stored in the memory of the computer, Each of the two templates defines at least the relationship between the CT value and the opacity and the relationship between the CT value and the RGB blend ratio so as to be suitable for the desired purpose. Obtaining a plurality of voxels each having a CT value, and the computer refers to a template selected by a user among the at least one template, whereby a CT value of the voxel is assigned to each of the plurality of voxels. Assigning opacity and RGB blending ratio according to But by performing predetermined processing on voxel plurality of, it includes the step of generating a two-dimensional color image, the objects can be achieved.

  The at least one template may be designed in advance for each organ, each body part, each disease, or each surgery type.

  The method further includes the computer generating a two-dimensional image of at least one color between the two-dimensional images of the plurality of colors by linearly interpolating the two-dimensional images of the plurality of colors. Also good.

  An apparatus of the present invention is an apparatus that generates an image suitable for a desired purpose using a volume rendering method, and at least one template is stored in a memory of the apparatus, and the at least one template is stored in the apparatus. Each defines at least the relationship between the CT value and the opacity and the relationship between the CT value and the RGB blending ratio so as to suit the desired purpose, and the apparatus includes a plurality of CT values each having a CT value. , And by referring to a template selected by the user among the at least one template, each of the plurality of voxels has an opacity and an RGB blending ratio according to the CT value of the voxel. A color two-dimensional image is generated by assigning and performing predetermined processing on the plurality of voxels. And a stage, the object is achieved.

  The program of the present invention is a program for causing a computer to execute an image generation process for generating an image suitable for a desired purpose using a volume rendering method, and at least one template is stored in the memory of the computer. Each of the at least one template defines at least a relationship between a CT value and an opacity and a relationship between a CT value and an RGB blend ratio so as to be suitable for the desired purpose, The generation processing includes a step of acquiring a plurality of voxels each having a CT value and referring to a template selected by the user from among the at least one template, whereby the CT value of the voxel is set to each of the plurality of voxels. Assigning a corresponding opacity and RGB blending ratio, and the plurality By performing predetermined processing on voxel encompasses and generating a two-dimensional color image, the objects can be achieved.

  According to the present invention, by referring to a template selected by a user among at least one template stored in a memory, each of the plurality of voxels has an opacity and an RGB mixture ratio according to the CT value of the voxel. And are assigned. As a result, it is possible to reflect the contents of the template selected by the user (that is, the relationship between the CT value and the opacity and the relationship between the CT value and the RGB blend ratio) in a plurality of voxels. As a result, even a user who is not skilled in image processing can easily perform image processing according to a desired purpose while ensuring reproducibility.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of the configuration of an image processing system 1 according to an embodiment of the present invention. The image processing system 1 is suitable as a system for processing medical images.

  The image processing system 1 includes a CT apparatus 10, a computer 20 connected to the CT apparatus 10, and a display device 30 connected to the computer 20.

  The CT apparatus 10 stacks slice images of a three-dimensional object (for example, a human body), and divides the stacked slice images into a plurality of voxels, thereby generating a plurality of voxels arranged in three dimensions. The plurality of voxels generated by the CT apparatus 10 are output to the computer 20.

In FIG. 1, reference numeral 12 schematically indicates a set of a plurality of voxels V _{(i, j, k)} generated by the CT apparatus 10 and arranged three-dimensionally. Here, i = 1, 2,... L; j = 1, 2,... M; k = 1, 2,... N, and L, M, and N are each one or more. It is an arbitrary integer. Each voxel V _{(i, j, k)} has a CT value. The CT value is a value measured in units of voxels by the CT apparatus 10, and is represented by an integer, for example. As the CT apparatus 10, any type of CT apparatus capable of outputting the set 12 of voxels shown in FIG. 1 can be used.

  Based on the set 12 of voxels, the computer 20 generates a two-dimensional image of a color suitable for a desired purpose using a volume rendering method. The color two-dimensional image generated by the computer 20 is output to the display device 30. As the computer 20, any type of computer including a CPU that executes various programs and a memory that stores various data can be used.

  The display device 30 displays a color two-dimensional image. As the display device 30, any type of display device capable of displaying a color two-dimensional image can be used. For example, the display device 30 may be a liquid crystal display device or a CRT display device.

  FIG. 2 shows an exemplary configuration of the computer 20.

  The computer 20 includes a CPU 21, a memory 22, an input interface unit 23, an output interface unit 24, a user interface unit 25, and a bus 26.

  The CPU 21 executes a program. For example, the program is a program that causes the computer 20 to execute an image generation process for generating an image suitable for a desired purpose using the volume rendering method. The program and data necessary for executing the program are stored in the memory 22, for example. It does not matter how the program is stored in the memory 22. For example, when the memory 22 is a rewritable memory, the program may be stored in the memory 22 by loading the program from the outside of the computer 20. Alternatively, when the memory 22 is a non-rewritable memory (read-only memory), the program may be stored in the memory 22 in a form fixed (burned) in the memory 22.

  Further, at least one template is stored in the memory 22. Each of the at least one template defines at least the relationship between the CT value and the opacity and the relationship between the CT value and the RGB blend ratio so as to suit the desired purpose. It does not matter how the relationship between the CT value and the opacity is defined. It does not matter how the relationship between the CT value and the RGB blending ratio is defined. As long as the template defines at least the relationship between CT value and opacity and the relationship between CT value and RGB blending ratio, the template can have any data structure. For example, the template can be represented by tabular data indicating the relationship between CT values and opacity, and tabular data indicating the relationship between CT values and RGB blending ratios. Further, the tabular data indicating the relationship between the CT value and the RGB blending ratio includes the tabular data indicating the relationship between the CT value and the R blending ratio and the tabular data indicating the relationship between the CT value and the G blending ratio. And tabular data indicating the relationship between the CT value and the B blending ratio.

  The input interface unit 23 functions as an input interface for receiving a plurality of voxels from the CT apparatus 10.

  The output interface unit 24 functions as an output interface for outputting a color two-dimensional image to the display device 30.

  The user interface unit 25 functions as an interface with the user. For example, input devices such as a mouse 25a and a keyboard 25b are connected to the user interface unit 25.

  The bus 26 is used to connect the components 21 to 25 in the computer 20 to each other.

  FIG. 3A shows an example of the relationship between the CT value and opacity defined in the “lung” template, and the relationship between the CT value and the RGB blend ratio. The template for “lung” is designed in advance so as to be suitable for displaying the organ “lung” so that the original sense of the organ is expressed. Such a template can be designed in advance by a person skilled in image processing.

  In FIG. 3A, the horizontal axis indicates the CT value, and the vertical axis indicates the RGB blend ratio and opacity. The solid line R indicates the blending ratio of R (red) according to the CT value, the solid line G indicates the blending ratio of G (green) according to the CT value, and the solid line B indicates B (blue) according to the CT value. ). For the same CT value, the sum of the blending ratio of R (red), the blending ratio of G (green), and the blending ratio of B (blue) is equal to 1. The solid line “opacity” indicates the opacity corresponding to the CT value. The opacity is pre-designed to change continuously over a range of CT values.

  Such a template can be pre-designed to suit the desired purpose. For example, if the purpose is to display the organs so that the actual sensation of the organ is expressed, a template suitable for the purpose of each organ (for example, a template for “lung”, a “heart” Template). For example, when it is intended to display the body part so that the actual feeling of each part is expressed, a template suitable for the purpose of each part (for example, a template for “chest”, “abdomen” ”Template etc.) should be designed. For example, if the purpose is to clearly display the focus of each disease, design a template suitable for that purpose for each disease (for example, a template for “lung cancer”, a template for “breast cancer”, etc.) You just have to do it. For example, when the purpose is to simulate the progress of surgery for a specific disease (for example, breast cancer), a template suitable for that purpose for each type of surgery (for example, a template for “lung cancer” surgery). , “Breast cancer” surgery template, etc.) may be designed.

  Such various templates can be displayed on the display device 30 in the form of an icon, for example. The user operates an input device such as a mouse 25a or a keyboard 25b connected to the user interface unit 25, and selects one of at least one icon displayed on the display device 30. The computer 20 can be instructed to use the template corresponding to the icon selected by.

  FIG. 3B is an extraction of the solid line R shown in FIG. 3A, and shows an example of the relationship between the CT value and the blending ratio of R (red).

  FIG. 3C is an extraction of the solid line G shown in FIG. 3A and shows an example of the relationship between the CT value and the blending ratio of G (green).

  FIG. 3D is an extraction of the solid line B shown in FIG. 3A and shows an example of the relationship between the CT value and the blending ratio of B (blue).

  FIG. 3E is an extraction of the solid line opacities shown in FIG. 3A, and shows an example of the relationship between CT values and opacity.

  FIG. 3F reflects the contents of the “lung” template shown in FIG. 3A (ie, the relationship between the CT value and opacity and the relationship between the CT value and the RGB blend ratio shown in FIG. 3A) in a plurality of voxels. An example of a color two-dimensional image obtained by performing the processing is shown. From FIG. 3F, it can be seen that the actual appearance of the organ “lung” is expressed realistically. As described above, the template for “lung” provides standardized opacity and standardized coloring (RGB blending ratio) for realistically expressing the actual feeling of the organ “lung”.

  FIG. 4 shows an example of an image generation processing procedure for generating an image suitable for a desired purpose using the volume rendering method. Such image generation processing can be realized in the form of a program, for example. Such a program is executed by the CPU 21, for example.

  Step 401: The computer 20 acquires a plurality of voxels. Each of the plurality of voxels has a CT value. Such acquisition of a plurality of voxels is achieved, for example, when the CPU 21 receives a plurality of voxels output from the CT apparatus 10 via the input interface unit 23. However, the aspect of acquiring a plurality of voxels is not limited to this. The computer 20 may obtain a plurality of voxels in any manner. For example, the computer 20 may acquire a plurality of voxels by reading a plurality of voxels recorded on a recording medium such as a magnetic disk, or a part of the plurality of voxels received from the CT apparatus 10 (for example, , One selected by the user among the plurality of voxels received from the CT apparatus 10) may be acquired.

  Step 402: The computer 20 refers to the template selected by the user among the at least one template stored in the memory 22 to respond to each of the plurality of voxels acquired in Step 401 according to the CT value of the voxel. Assign opacity and RGB blending ratio. For example, the voxel has a CT value = 100, and the opacity corresponding to the CT value = 100 is set to 0.2 in the template selected by the user, and is selected by the user. Assume that the RGB blending ratio corresponding to CT value = 100 in the template is set to (R, G, B) = (0.1, 0.3, 0.6). In this case, in step 402, the computer 20 refers to the relationship between the CT value and the opacity defined in the template selected by the user, and the relationship between the CT value and the RGB blend ratio. As a result, the computer 20 has the opacity (0.2) corresponding to the CT value = 100 and the RGB blending ratio ((R, G, B) = (0.1, 0.3) corresponding to the CT value = 100. , 0.6)) is assigned to the voxel.

  In this way, the contents of the template selected by the user (that is, the relationship between the CT value and the opacity and the relationship between the CT value and the RGB blend ratio) can be reflected in a plurality of voxels. As a result, even a user who is not skilled in image processing can easily perform image processing according to a desired purpose while ensuring reproducibility. This is because it is sufficient for the user to select an appropriate template according to the desired purpose (for example, when the user desires to display “lung” in color with a sense of reality, the user selects a template for “lung”. This is because the user does not need to know or understand the contents of the template.

  Step 403: The computer 20 performs a predetermined process on the plurality of voxels to which the opacity and the RGB blending ratio are assigned in Step 402, thereby generating a color two-dimensional image. The predetermined process includes, for example, projecting a plurality of voxels onto a projection plane (two-dimensional plane) by performing voxel tracking (ray tracing) from an arbitrary viewpoint. Since such ray tracing is a well-known process, the detailed description thereof is omitted.

  The computer 20 outputs the color two-dimensional image generated in step 403 to the display device 30. Such output is achieved, for example, when the CPU 21 outputs a color two-dimensional image to the display device 30 via the output interface unit 24.

  As described above, when the CPU 21 executes the program for realizing the above-described image generation processing, the computer 20 acquires a plurality of voxels each having a CT value, and at least one template stored in the memory 22. By referring to the template selected by the user, a means for assigning opacity and RGB blending ratio according to the CT value of the voxel to each of the plurality of voxels, and predetermined processing for the plurality of voxels To function as an apparatus (an apparatus that generates an image suitable for a desired purpose using a volume rendering method).

  Note that the function of each step shown in FIG. 4 is not limited to being realized by software (for example, a program). The function of each step shown in FIG. 4 may be realized by hardware (for example, a circuit, a board, a semiconductor chip), or may be realized by a combination of software and hardware. For example, a device that generates an image suitable for a desired purpose using the volume rendering method may be a volume rendering board.

  FIG. 5 shows an example of a user interface for realizing the function of step 402 shown in FIG.

  In the example shown in FIG. 5, at least one template is displayed on the display device 30 in the form of an icon list 500, and a plurality of voxels are displayed on the display device 30 in the form of a file list 510. In this case, the operation to be performed by the user is, for example, selecting one of at least one template displayed on the display device 30 (for example, the template 501 for “lung”) and performing the operation on the display device 30. Selecting at least a part of the displayed file list 510 (for example, a range indicated by reference numeral 512 in FIG. 5). By such a user operation, “the user selects the template” and “the contents of the template selected by the user (that is, the relationship between the CT value and the opacity and the relationship between the CT value and the RGB blending ratio). It is possible to realize “assignment to a plurality of voxels”. For example, when the mouse 25a is connected to the user interface unit 25, when the user clicks the button of the mouse 25a, the CPU 21 recognizes that the user has selected the one at the position pointed to by the mouse 25a. can do.

  The file list 510 includes, for example, a number (image number) for identifying a voxel, a bed position, an X coordinate, a Y coordinate, and a Z coordinate. Here, the X coordinate, Y coordinate, and Z coordinate are used to specify the position of the voxel in the three-dimensional space.

  For example, a patient list 520 can be used to identify the file list 510. This is because the file list 510 may exist for each patient. The patient list 520 includes, for example, a patient name, patient ID, sex, date / time, modality, examination ID, and age. A patient list 520 may also be displayed on the display device 30.

  A plurality of color two-dimensional images generated according to the image generation process shown in FIG. 4 can be displayed as an animation. Such a display mode is particularly suitable for simulating the progress of surgery for a specific disease (for example, breast cancer).

  FIG. 6A shows an example of four types of transfer functions required to perform animation display. In the example shown in FIG. 6A, the transfer function “Skin” defines the relationship between the CT value and the opacity and the relationship between the CT value and the RGB distribution ratio so as to be suitable for displaying “skin”. . The transfer function “Tumor” defines the relationship between the CT value and the opacity and the relationship between the CT value and the RGB distribution ratio so as to be suitable for displaying “tumor tissue”. The transfer function “Lymph node” defines the relationship between the CT value and the opacity and the relationship between the CT value and the RGB distribution ratio so as to be suitable for displaying the “lymph node”. The transfer function “Vessel” defines the relationship between the CT value and the opacity and the relationship between the CT value and the RGB distribution ratio so as to be suitable for displaying “blood vessels”.

  At least one transfer function is generated between these transfer functions by linearly interpolating the transfer function “Skin” and the transfer function “Tumor”, and the transfer function “Tumor” and the transfer function “Lymph node” are linearly interpolated. To generate at least one transfer function between these transfer functions, and at least one transfer function between these transfer functions by linearly interpolating between the transfer function “Lymph node” and the transfer function “Vessel”. By generating the above, it is possible to obtain four or more types of transfer functions required for performing animation display. Here, the linear interpolation between the transfer function X and the transfer function Y is to linearly interpolate the R (red) mixture ratio in the transfer function X and the R (red) mixture ratio in the transfer function Y, The G (green) blending ratio and the G (green) blending ratio in the transfer function Y are linearly interpolated, and the B (blue) blending ratio in the transition function X and the B (blue) blending ratio in the transition function Y are obtained. Linear interpolation is performed, and the opacity in the transfer function X and the opacity in the transfer function Y are linearly interpolated. By performing such linear interpolation continuously, it is possible to realize an animation display without unnatural color change. In addition to continuously performing linear interpolation of the transfer function, continuous linear interpolation of movement, enlargement / reduction, rotation, and parallel movement of the viewpoint enables animation display with no unnatural motion. Can be realized.

  FIG. 6B shows an example of an animation display using the transfer function shown in FIG. 6A. From FIG. 6B, those skilled in the art can understand that “skin” → “tumor tissue” → “lymph node” → “blood vessel” is sequentially displayed in the order of (1) to (5). Such a display mode is particularly suitable for simulating the progress of surgery for a specific disease (for example, breast cancer).

  As mentioned above, although this invention has been illustrated using preferable embodiment of this invention, this invention should not be limited and limited to this embodiment. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments of the present invention.

  The present invention is useful as a method, apparatus, program, and the like for generating an image suitable for a desired purpose using a volume rendering method.

The figure which shows an example of a structure of the image processing system 1 of embodiment of this invention The figure which shows an example of a structure of the computer 20 The figure which shows an example of the relationship between CT value and opacity defined in the template for “lung”, and the relationship between CT value and RGB blending ratio The solid line R shown in FIG. 3A is extracted, and shows an example of the relationship between the CT value and the blending ratio of R (red) The solid line G shown in FIG. 3A is extracted, and shows an example of the relationship between the CT value and the blending ratio of G (green) FIG. 3B is a diagram showing an example of the relationship between the CT value and the blending ratio of B (blue), extracted from the solid line B shown in FIG. FIG. 3B is a diagram showing an example of the relationship between CT value and opacity, extracted from the solid line opacity shown in FIG. 3A. The figure which shows an example of the color two-dimensional image obtained by reflecting the content of the template for "lung" shown in FIG. 3A on a plurality of voxels The flowchart which shows an example of the procedure of the image generation process which produces | generates the image suitable for the desired objective using a volume rendering method The figure which shows an example of the user interface for implement | achieving the function of step 402 shown by FIG. The figure which shows an example of four types of transfer functions (Transfer function) required in order to perform an animation display The figure which shows an example of the animation display using the transfer function shown by FIG. 6A

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image processing system 10 CT apparatus 12 Set of voxels 20 Computer 30 Display apparatus

Claims (5)

A method for generating an image suitable for a desired purpose using a volume rendering method on a computer,
At least one template is stored in the memory of the computer;
Each of the at least one template defines at least a relationship between the CT value and the opacity and a relationship between the CT value and the RGB blend ratio so as to suit the desired purpose.
The method
The computer obtaining a plurality of voxels each having a CT value;
The computer assigning an opacity and an RGB blending ratio to each of the plurality of voxels by referring to a template selected by the user among the at least one template;
The computer generating a color two-dimensional image by performing predetermined processing on the plurality of voxels.   The method according to claim 1, wherein the at least one template is designed in advance for each organ, for each body part, for each disease, or for each type of surgery. The method
The computer further includes generating at least one color two-dimensional image between the plurality of color two-dimensional images by linearly interpolating the plurality of color two-dimensional images. The method described. An apparatus for generating an image suitable for a desired purpose using a volume rendering method,
At least one template is stored in the memory of the device;
Each of the at least one template defines at least a relationship between the CT value and the opacity and a relationship between the CT value and the RGB blend ratio so as to suit the desired purpose.
The device
Means for obtaining a plurality of voxels each having a CT value;
Means for allocating opacity and RGB blending ratio according to the CT value of the voxel to each of the plurality of voxels by referring to the template selected by the user among the at least one template;
Means for generating a color two-dimensional image by performing predetermined processing on the plurality of voxels. A program for causing a computer to execute image generation processing for generating an image suitable for a desired purpose using a volume rendering method,
At least one template is stored in the memory of the computer;
Each of the at least one template defines at least a relationship between the CT value and the opacity and a relationship between the CT value and the RGB blend ratio so as to suit the desired purpose.
The image generation process includes:
Obtaining a plurality of voxels each having a CT value;
Assigning an opacity and an RGB blending ratio according to the CT value of the voxel to each of the plurality of voxels by referring to a template selected by the user among the at least one template;
Generating a color two-dimensional image by performing predetermined processing on the plurality of voxels.