JPH0981786A - Three-dimensional image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display the three-dimensional position relation of a point of attention and its peripheral areas of interest to other areas from an arbitrary direction when a three-dimensional image is displayed by projecting three-dimensional data on a plane. SOLUTION: This three-dimensional image processing method has a step 103 wherein a point of attention is specified in the three-dimensional image, a step 104 wherein three-dimensional coordinates of the sets point of attention are found, a step 105 wherein areas of interest are set around the point of attention, and steps 111-117 wherein a rendering means having rendering parameters for the areas of interest and other areas renders the areas respectively with inputted parameters when the parameters are inputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional image processing method, and in particular, it calculates an image obtained by projecting a three-dimensional shape onto a two-dimensional plane from three-dimensional data composed of voxel data obtained from an X-ray CT apparatus or the like. The present invention relates to a three-dimensional image processing method for displaying the same.

[0002]

2. Description of the Related Art As a method for generating a three-dimensional image projected on a two-dimensional plane from three-dimensional data composed of voxels, a volume rendering method capable of obtaining a high quality image is widely used in the medical field and the like. Further, there is known a technique of displaying such a three-dimensional image and performing special image processing on a local area in addition to simply displaying the three-dimensional image for use in medical treatment and data analysis. For example, in “Preoperative simulation of cerebellopontine angle tumor by helical scan CT (HES-CT)” (The 2nd Computer Surgery Research Society Proceedings, pp.49-50 (1993)), preoperative treatment plan For this reason, a method called synthesized oblique display is described in which a cross-sectional image at a specified depth position is displayed for a specified area on a three-dimensional image. Also,
Japanese Unexamined Patent Publication No. 3-219377 discloses a method of displaying the measured three-dimensional voxel data by cutting out the three-dimensional data of a designated area by the three-dimensional mask and combining and displaying. Further, when displaying three-dimensional data segmented in advance, there is known a method of displaying an internal state by displaying a specific tissue in a specific region.
dering ", IEEE CG & A, vol.10, pp.41-53 (March,
1990) shows a display example. Also, "Clinical
Planning Support System-CliPSS ", IEEE
CG & A, vol.13, No.6, pp.76-84 (Nov., 1993),
An example in which a three-dimensional image in which a state when a guide tube is inserted into a head tumor is synthesized is displayed is described. In this, the surface data obtained by extracting the tumor and the skull in advance is processed, and the insertion direction of the guide tube is determined by the numerical input of parameters.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Each had the following problems. First, in the above-described synthesized oblique method, it is difficult to grasp the three-dimensional shape because only the cross-sectional display can be performed. Also,
In the method of cutting out data by masking a certain area as described above, by rotating the display target, if the depth direction in which the area is cut out and the hole does not match the line-of-sight direction, the bottom of the hole It becomes impossible to display the area in. In this case, the purpose cannot be achieved even if the data is removed and the attention area in the back is observed. Therefore, a basic object of the present invention is to provide a three-dimensional image processing method capable of grasping the three-dimensional shape of the attention area and the positional relationship between the entire three-dimensional data and the attention area from all angles. Is to provide.

Another object of the present invention is 3 for internal display.
The method of segmenting and displaying dimensional data takes a very long time to perform segmentation. Therefore, it is possible to display the attention area inside without segmentation or by performing segmentation quickly and easily. A three-dimensional image processing method is provided. In this case, how to specify the attention area is important. Yet another object of the present invention is a method of displaying the above tumor approach, comprising:
It is an object of the present invention to provide a three-dimensional image processing method capable of solving this problem in view of the necessity of defining surface data and the time required for preprocessing. It is another object of the present invention to provide a three-dimensional image processing method capable of solving the problem that the image quality becomes a problem in measurement data where the surface definition is difficult and the method of designating the approach direction is not intuitive.

[0005]

The above objects of the present invention can be achieved by the following constitutions. That is, first, a three-dimensional shape can be grasped by means of displaying by volume rendering. In addition, the attention point is set in the three-dimensional space, the position of the attention point after rotation is calculated, and the region of interest R centering on the attention point on the projection plane is set.
A means for automatically calculating and setting the OI (Region of Interest) is realized, and further, for the ROI along the line-of-sight direction, the parameters for the volume rendering calculation are set separately from the other areas, and the calculation is displayed. By implementing the means, the line-of-sight direction and the depth direction of the ROI are matched. Further, regarding the rendering in the ROI, the number of samplings is set to be larger than that of the other areas, and a means for displaying the attention area with high definition is realized. Further, a means for specifying the depth of the starting point of the rendering in the ROI is implemented so as to delete the region having the desired depth. Also, a means for designating the size and shape of the ROI is realized. Further, it realizes a means for displaying the position of the attention point on the three-dimensional image in a superimposed manner when there is no display target between the attention point and the projection surface.
As a method of designating the position of this point of interest, after the temporary point of interest is designated, a means for displaying a cross-sectional image that passes through the temporary point of interest and is parallel to the projection surface and the cutting position of the cross section are moved in parallel. Means and means for designating a true point of interest on the cross-sectional image are realized. Further, it realizes a means for setting an approach direction parallel to the line-of-sight direction passing through the attention point and a means for displaying the three-dimensional image and the attention point and the approach direction in an overlapping manner.

[0006]

With the above-mentioned means, the ROI always surrounds the point of interest.
In addition, since the depth of the ROI matches the line-of-sight direction, it is possible to observe the attention area from any angle even if the rotation center and the attention point are different. Further, the following operation can be provided by realizing the means for displaying only the ROI portion with parameters different from those of the other areas. First, in many cases, a simple segmentation can be performed by using a threshold value, and a target of interest can be displayed only by changing a threshold value that is a parameter without performing extraction. If the number of samplings is further increased, a detailed image can be obtained. However, the amount of calculation basically increases on the order of the third power, so that the conventional technique has a problem in calculating the entire image with high precision. By the means, it is possible to display a high-definition display only for the ROI portion, and since the calculation area is small, it is possible to observe in detail the area of interest in a short calculation time.

Further, by implementing the means for designating the ROI rendering start point, a low opacity voxel region inside a voxel region with high opacity can be displayed, and the depth specified for the ROI can be displayed. You can perform operations such as drilling holes. Also, RO
By realizing the means for inputting the size and shape of I, the field of view of the ROI that matches the size and shape of the region of interest can be secured. Further, by realizing the means for displaying the attention point on the three-dimensional image when there is no display object in front of the attention point, the effect that the attention point is written in the three-dimensional data is obtained. The 3D position can be confirmed with the same feeling as the 3D data. In addition, it is possible to set the attention point not only on the surface of an object but also at the center thereof by means for designating the position of the attention point using the provisional attention point and the cross-sectional image. As a result, the object of interest can always be rotated and displayed at the center of the ROI. Furthermore, the approach direction can be intuitively designated by setting the approach direction so as to match the line-of-sight direction.

[0008]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a flow chart showing a three-dimensional image processing method according to the first embodiment of the present invention, and FIG. 2 is a diagram explaining a volume rendering method of the present embodiment. In FIG. 2, 1 is three-dimensional data, 2 is a projection plane, 3 is a pixel for which a value is currently projected on the projection plane 2,
4 is a set of resampled voxels existing on the line 7 perpendicular to the projection plane from the pixel 3, 5 is a coordinate system A of three-dimensional data, and coordinate values are represented by (x, y, z) ,
Further, 6 is a coordinate system V for projection, and coordinate values are (X, Y,
Z). FIG. 3 is an example of re-sampling voxels of the three-dimensional data 1 in the three-dimensional image processing method according to this embodiment, and the right diagram is an enlarged view of a part of the left diagram. In FIG. 3, 11 is the center point of the voxel of the three-dimensional data 1, 12 is the center position of the voxel to be resampled, and 13 is the voxel 1 to be resampled.
It is a cell that consists of eight voxel centers that surround 2.

FIG. 4 is a diagram showing the correspondence between voxel values and opacity in this embodiment. Reference numeral 21 is a threshold value at which opacity is 0, and 22 is a proportional constant. FIG. 5 is an example of a three-dimensional image of the head displayed according to this embodiment. In FIG.
31 is the surface of the head that is the display target, 32 is the point of interest, 33 is the ROI centered at the point of interest 32, and 34 is the surface of the brain that is the display target based on the display parameters. The operation of the three-dimensional image processing method according to this embodiment will be described below with reference to FIGS. First, 3 by volume rendering
Display a three-dimensional image of the entire dimensional data (step 10
1). This volume rendering method will be described with reference to FIG. The projection plane 2 is arranged with respect to the three-dimensional data 1 as shown, and the line-of-sight direction is assumed to be perpendicular to the projection plane.

Each voxel of the voxel 4 resampled to the projected coordinate system V system has an opacity α and a shaded color C. Resampling will be described later. The opacity α has a value of “0” if the voxel is completely transparent and allows light to pass therethrough, and takes a value of “1” if the voxel is completely opaque and does not allow light to pass therethrough. Color is the color emitted by a voxel. For the color that the voxel itself has, the reflection of light on the virtual surface at the voxel position is the voxel data value.
The tilt vector (hereinafter referred to as “voxel value”) is considered by considering it as the direction of the virtual surface, and the shadow is cast by the direction of the light source, the direction of the projection surface, and the like. At this time, the voxels of the voxel set 4 are numbered in order from the projection plane, and the opacity and color of each voxel are α (1), C (1), ..., α (n ), C (n).

Here, for simplification, light is assumed to be parallel light, and light rays are incident on the three-dimensional data in the direction perpendicular to the projection surface from the projection surface side. In the above cases, light is transmitted from the closest voxel to the farthest voxel from the projection surface,
The value P projected on the pixel 3 is calculated by the equation (1) by a method of adding the reflection amount at each voxel. In this embodiment, only diffuse reflection is handled in consideration of simplification of description and the nature of data to be handled, and light is assumed to be parallel light and perpendicular to the projection surface.

[Equation 1] It should be noted that A (i) in the equation (1) represents the transmittance of light incident on the i-th voxel.

Here, resampling will be described with reference to FIG. As shown in the diagram on the left side of FIG. 3, when trying to resample a certain voxel, among the cells surrounded by the eight voxel centers of the coordinate system A as shown in the diagram on the right side, the resampling with those voxel centers is performed. As shown in the figure, the ratio of the distance to the voxel center 12 is s: (1--
s), t: (1-t), u: (1-u). At this time, values such as opacity and color of the resampled voxels are obtained by the trilinear method of the following equation (2). Here, Q is used as a representative of values such as opacity and color.

[Equation 2]

As a method of performing resampling, another method such as a nearest neighbor method using a value of an original voxel closest to a voxel to be resampled may be used. When the calculation is performed by the above method, the parameters in the volume rendering calculation are defined. First, the opacity α is defined from the voxel value, but various displays can be made by changing this association. Therefore, in this embodiment, the opacity is determined in proportion to the voxel value. As shown in FIG. 4, the voxel value f and the opacity α are associated with each other, and the threshold value fth of the voxel value where the opacity is 0 is set.
And the proportional constant k is used as a parameter. This is to make it easy to set the opacity
This is because when displaying three-dimensional data such as a human body measured by the line CT or the like, if the higher the voxel value is, the higher the opacity is, so that the natural display can be performed.

According to the above embodiment, the display object can be changed by changing the threshold value fth which is a rendering parameter and the proportional constant k. Further, by changing the positional relationship between the three-dimensional data and the projection surface, it becomes possible to display a three-dimensional image from various directions. Therefore, a matrix for performing coordinate conversion between the coordinate system A in the three-dimensional data space and the coordinate system V in the projection space, particularly in the present embodiment, only rotation is considered and the rotation matrix is used as a parameter. In this embodiment, for simplification, only the above elements are used as parameters, the voxel color is monochrome, and the direction of the light source and the like are fixed. Of course, these may be added to the parameters and may be variable. Needless to say. Now, using the method described above, step 10
When performing volume rendering with 1, the distance from the projection surface of the voxel closest to the projection surface that exceeds the threshold fth among voxels on the line when the projection value of each pixel is obtained is stored as the Z buffer ( Step 10
2).

Next, the 3 calculated and displayed as above.
Specify the point of interest on the 3D image with the mouse and display it
(Step 103). Referring to the Z buffer of the specified point of interest, the coordinate value of the point of interest in the rotated coordinate system V is obtained.
(Step 104). In step 105, as the ROI on the three-dimensional image, a circle centered on the point of interest and having a predetermined initial radius is set, and the ROI on the three-dimensional image is set.
Display the range of. The coordinates of the point of interest in the coordinate system V are converted, and the coordinates of the point of interest in the original coordinate system A are obtained and stored (step 106). As described above, the setting of the point of interest and the setting of the ROI are completed, and the display parameter changing / input waiting state is set. The three-dimensional image displayed at this time is as shown in FIG.

Next, a case where the display direction is changed by performing rotation will be described. Here, it is assumed that the parameter given to the rendering processing unit when instructing rotation is a rotation matrix for converting the coordinate values of the coordinate system A and the coordinate system V. A parameter is input (step 107), and it is checked in step 108 whether it is a rotation parameter. Here, since the rotation parameter is input, step 10
Go to 9. In step 109, the input rotation matrix is used to obtain the coordinate value in the coordinate system V from the stored coordinates of the point of interest in the coordinate system A. A circular ROI centered on the coordinates of the point of interest in the obtained coordinate system V on the projection plane is set and displayed (step 110). After that, in step 111, volume rendering is performed on the entire projection surface. At this time, it is determined whether the pixel position under calculation is within the set ROI region (step 112),
The ROI is used as display parameters for ROI, and the other areas are displayed by performing volume rendering with normal display parameters (steps 113 and 114).
The image displayed at this time is as shown in FIG. 5B, and the ROI 33 centering on the point of interest 32 rotates with the point of interest.

Next, when the display parameter other than rotation is changed, it is determined in step 114 whether the display parameter for ROI is changed. In the case of the ROI parameter, volume rendering is performed with the ROI parameter only for pixels within the ROI, and only the ROI portion is displayed again (step 116). The image displayed at this time is as shown in FIG. 5C, and another region can be displayed only for the ROI. When the normal parameter is changed, volume rendering is performed with the normal parameter only for pixels other than the ROI, and only the portion other than the ROI is displayed again (step 117). As for the image displayed at this time, as shown in FIG. 5D, the display portion can be changed for the portion other than the ROI. When the display is completed, the next input is awaited. When the rendering parameters are input, the process returns to step 107. According to the above-described embodiment, the ROI can be set around the point of interest, and the point of interest can be displayed with a special display parameter even when the ROI is rotated. Furthermore, since the depth direction of the ROI matches the line-of-sight direction, the ROI can be displayed without being hidden.

As an application of the present embodiment, for example, the body surface can be displayed as a whole and the internal organs can be displayed for the region of interest, and the internal state and the external positional relationship can be grasped. It can be displayed easily. Further, in the above embodiment, the volume rendering method is used as the projection image calculation method, but other methods may be used. For example, considering that there is a surface at a voxel position that exceeds a threshold value, the inclination of the surface is obtained from the position of the surface voxel, the reflection on the surface is calculated, and a projection image is generated, a method called the voxel method, etc. But good. Furthermore, although the mouse is used to set the attention point in the above-mentioned embodiment, a keyboard,
Other coordinate pointing devices such as a pen input device may be used.
Further, when the position of the Z buffer is determined, the position of the voxel that exceeds the threshold value closest to the projection plane is taken, but the position of the voxel on the line of sight that has the largest amount of reflected light may be taken. This is how to define a virtual surface, and neither is a problem because the actual surface is ambiguous in such data.

Further, after once setting the point of interest, the process may return to step 103 to reset the point of interest, or the setting of the point of interest may be canceled and normal three-dimensional display may be performed. Further, in the above embodiment, high-definition rendering can be performed by increasing the number of ROI samplings as a display parameter. FIG. 6 shows this embodiment. For simplification, it is assumed that the three-dimensional data 1 is parallel to the projection plane 2. 41 is an object on a line existing in the three-dimensional data, 42 is a ROI on the projection plane, 43
Is an area on the three-dimensional data corresponding to ROI, and 44 is RO
An ROI image when displayed at the same sampling interval as the region other than I, 45 an ROI image when displayed at a sampling interval half the region other than the ROI, and 46
Is an area where the object 41 is projected. A finer and more accurate image can be obtained when the sampling interval is made smaller as shown in FIG. Although the number of samplings increases, the calculation time increases, but since the calculation is performed only for the limited ROI of interest, the amount of calculation is overwhelmingly smaller than the detailed calculation.

According to the above embodiment, for example, when the inspection of the package is performed by the three-dimensional image using the high-energy X-ray CT, the entire display considers the processing time and the sampling interval is set to some extent. If you find an abnormal object, for example, something that looks like a handgun, mark that area, sample only the ROI around that area for precise observation, and rotate it further. It is possible to grasp the three-dimensional shape by displaying it. Here, an example in which the depth of the ROI is designated as a rendering parameter for the data shown in FIG. 7 will be described. In FIG. 7, in order to simplify the explanation, rendering of one cross section in the three-dimensional data will be considered. In the figure, 51 is one cross section of the three-dimensional data of interest, 52 is an object existing in the three-dimensional data, and has a round shape 53, a square shape 54, and a triangular shape 55 inside. The voxel values of the area are 10, 50, 100, and 30 indicated by circled numbers.

Reference numeral 56 denotes a region where the cross-section 51 is projected on the projection surface, and 57 denotes a region corresponding to the ROI out of 53 regions. Reference numerals 58, 59 and 60 indicate the positions of the start points of the ROI area rendering calculation. First, when calculation is performed from the normal rendering calculation start position 58, if the threshold value is smaller than 10, the surface of a square object is displayed and
A round object is displayed at 0 to 50, and a rod-shaped object is displayed at 50 to 100. In this way, the inside of the object in the ROI can be displayed by changing the threshold value. Next, when the calculation is performed from the rendering calculation start position 59, the threshold value becomes 30.
If it is smaller, the surface of the triangular object and the inside of the round object are displayed. At 30 to 50, the inside of the round object is 50 to 10
At 0, a rod-shaped object is displayed. Furthermore, when the calculation is performed from the rendering calculation start position 60, if the threshold value is smaller than 50, the inside of a round object is displayed, and at 50 to 100, a rod-shaped object is displayed.

As in the above-mentioned embodiment, the inside of the object can be displayed by making a hole in the object by making the rendering start position deep. Further, it becomes possible to display a triangular object having a low voxel value in an object having a high voxel value, which could not be displayed from the normal rendering position. In the above embodiments, the rendering start position is set by the distance from the projection surface, but other setting methods may be used, for example, the depth from the surface of the object having a voxel value of 10 may be set. Next, an example of changing the shape and size of the ROI will be described with reference to FIG. In the figure, 35 is the ROI after the change. First, ROI
Assume, for example, that the initial state is a square centered on the point of interest 32 and one side has a length of 20. At this time, the size of the ROI is changed by dragging the vertices of the square ROI with the mouse. It is assumed that the ROI changes around the point of interest, and the changed ROI 35 has 30 on one side.
Here, for example, if the ROI shape is selected from the pop-up menu and changed to a circle, the ROI has a diameter of 3
It becomes a circle of 0. The size of the ROI can be changed by dragging this circumference with the mouse.

In the above embodiment, the mouse is used to intuitively change the size, but numerical values such as the length of one side, the diameter and the radius may be input from the keyboard. The shape of the ROI may be a rectangle or a triangle, or may be a free shape traced with a mouse (however, the point of interest is included inside the ROI). Further, the ROI shape may be designated without switching from the menu, for example, the shape may be switched each time the middle button of the mouse is pressed. Next, FIG. 9 shows an example in which the position of the point of interest is displayed. In the figure, 61 is a display object. First, the attention point 32 is set when the image is displayed at the angle (a). These are rotated and displayed from different angles are (b), (c), and (d). (b) shows the case where the display object 61 exists in front of the point of interest in the coordinate system V after rotation, that is, between the point of interest and the projection surface. In such a case, the position of the point of interest is Is not displayed. By doing so, it is possible to obtain the effect of writing the attention point in the three-dimensional data, and display can be performed in a natural context.

However, in the method of (b), the position of the point of interest in the shadow of the object is unknown, so in (c), the position of the point of interest is displayed in any case. However,
In this method, the sense of depth at the point of interest may not be known. Further, in (d), when an object exists between the point of interest and the projection surface, the color of the point of interest and the color of the object are displayed in an averaged color, and are displayed semitransparently. This is (b), (c)
Has both strengths and weaknesses. Therefore, the above (b), (c),
Use the method of (d) properly depending on the case. The display of the position of the attention point is performed in step 111 or 1 in FIG.
After the end of 16, the above method is performed using the coordinates of the point of interest in the V system obtained in step 109 and the Z buffer of the three-dimensional image. In the above embodiments, the attention point can be set only on the surface of the object, so an embodiment in which it can be set inside the object will be described with reference to FIGS. 10 and 11.

FIG. 10 shows a flow chart of this embodiment, and FIG. 11 shows an example of operations and images corresponding to the flow chart shown in FIG. Reference numeral 65 is an object to be displayed, 66 is a temporary attention point on the surface of the object, 67 is a three-dimensional image on which the object 65 is projected, 68 is a position of the attention point on the three-dimensional image, and 69 is a temporary attention point. The ROI cross-sectional image set around is designated by 70, which is a true point of interest specified on the cross-section. At this time, it is assumed that the display target in the three-dimensional data 1 is a solid object having a spherical content like 65 shown in FIG. Hereinafter, a method of setting a point of interest will be described using a flowchart. First, in step 201, a temporary attention point 68 is designated on the three-dimensional image 67 on which the object 65 is projected. Then, the surface position 6 of the object in the three-dimensional space
An attention point is set at 6 (see FIG. 11A). At the next step 202, the temporary attention point 6 set at step 201 is set.
An image 69 of a cross section passing through 6 and parallel to the projection plane 2 is calculated,
Display in step 203. At this stage, the cross section is in contact with the surface of the object, and thus is displayed as a dot as shown in FIG.

Then, in step 205, the position of the cross section is moved in parallel to find the cross section position to be designated as the true point of interest, and the display as shown in FIG. When the position to set the point of interest is decided while performing the parallel movement, step 2
In step 04, the process proceeds to step 206 for setting a point of interest, and FIG.
The position of the true point of interest is designated as in (d). The three-dimensional position of the point of interest specified on the cross-sectional image is obtained and stored, and
It can be used for the processing after step 107 of the embodiment shown in FIG. With the above embodiment, the point of interest can be specified inside the object. Thereby, for example, it is possible to always display the center of the tumor as the center of the region of interest, and rotate the tumor so that it does not extend beyond the region of interest. Now, next, set the approach direction to the point of interest,
An example for displaying will be described with reference to the flowchart of FIG. 12 and FIG. The present embodiment can be used, for example, in the case of designating a tumor as a point of interest for three-dimensional data obtained by imaging a patient with a tumor and examining the approach for surgery in advance.

This embodiment can be used in combination with the above-described embodiment such as the method of setting the ROI centering on the point of interest shown in FIG. 1, but here, for the sake of simplification of description, the approach is set independently. The following shows an example of displaying. The approach passes through the specified point of interest and is set in the direction perpendicular to the projection plane.
In FIG. 13, 71 is an approach direction, 72 is an approach direction unit vector, 73 is a projected image of the object 65, 74 is a projected point, and 75 is an approach projected. First, the setting of the point of interest is the same as in the embodiment shown in FIG. 1 (steps 101 and 10).
2, 103, 104, 106). After setting the point of interest,
Rotate, observe the display target from various angles,
The optimum direction for approaching the point of interest is searched for and the approach direction is determined (step 301). In the post-rotation coordinate system V system, the value of the unit vector in the Z-axis direction (perpendicular to the projection plane) in the original coordinate system A system is obtained,
It is stored as an approach direction unit vector (step 302).

The approach direction can be set by the above steps. Next, the set approach is displayed.
When the approach is set, the approach direction is perpendicular to the projection plane, so that it is displayed as a point on the projection plane at a position overlapping with the target point (FIG. 13A). When the rotation is performed and the approach direction and the line-of-sight direction do not match, the approach is displayed as a straight line. At this time, if an object exists between the straight line indicating the approach and the projection plane, the approach is not displayed. (FIG. 13B). In addition, the approach is displayed only a certain length from the point of interest in the direction of the approach direction unit vector. It is assumed that this length is initially set. The approach was set,
Or if parameters such as rotation are entered
In step 311 and step 312, the coordinates of the point of interest in the V system after rotation are obtained.

Next, the approach direction unit vector in the V system is obtained (step 313). Further, the end point which is not the target point when displaying the approach is obtained from the already specified approach length, the approach direction unit vector and the coordinates of the target point (step 314). Therefore, a straight line connecting the target point and the end point is projected on the projection surface, and the Z buffer in the V system at that time is stored (step 315).
Volume rendering is performed to obtain a three-dimensional image (step 316), the Z buffer of the image obtained at that time (step 317) is compared with the Z buffer of the approach, and when the Z buffer of the image is closer to the projection plane. Displays a 3D image, otherwise displays the approach. (Step 318). After that, the point of interest is displayed as in the embodiment of FIG. 9, for example. According to the present embodiment, natural composite display can be performed in consideration of the context, but other methods may be used as long as the approach and the three-dimensional image are composite displayed. Further, the length and thickness of the approach may be changeable.

According to the above-described embodiment, after determining the approach direction, it is possible to examine the approach by rotating and observing from various angles. Here, by displaying the set approach direction and the line-of-sight direction in the same direction, it is possible to simulate a state of observing from the approaching direction during the operation. Therefore, FIG. 14 shows an embodiment for displaying the approach view. The following processing is added to the flowchart in FIG. After the approach direction is determined in step 302, the rotation matrix from the coordinate system A to the coordinate system V at the current display angle is stored (step 401). Thereby, the approach view direction is stored. When an instruction to display the approach view is input (step 411), the rotation matrix stored in step 401 is input as a parameter (step 412). Then, the process proceeds to step 311 in FIG. 12, and the approach view in which the approach direction and the line-of-sight direction match is displayed according to the embodiment of FIG. 12 described above.

Although the above-described embodiment can plan a surgical approach, the surgical planning can be further assisted by determining from which surface of the body the approach should be taken. FIG. 15 shows an embodiment for obtaining the approach surface position. First, before setting the attention point and the approach, volume rendering is performed, and parameters for displaying the body surface are set and stored (step 50).
1). In this embodiment, the threshold value is stored. Here, FIG.
After the approach direction is set in steps 301 and 302 of the second embodiment, the parameter (threshold value) stored in step 501 is called and the rendering parameter is input (step 511). Then, according to the embodiment shown in FIG. 12 (steps 311 to 318), the three-dimensional image of the body surface, the approach, and the point of interest are combined and displayed. At this time, the approach becomes a point because it is perpendicular to the projection plane, and the approach and the point of interest overlap each other, as shown in FIG.

Then, the position where the body surface and the approach direction intersect is determined by the Z buffer obtained in step 317 (step 512). Since the obtained approach surface position is the coordinate of the V system, it is converted into the coordinate of the A system and stored.
(Step 513). After that, the stored approach surface position is the coordinate system A that was stored when the target point was displayed.
Is converted to the coordinate system V and displayed as in the embodiment of FIG. According to the above example, the approach direction before surgery,
A study of approach surface position can be made. In addition,
Needless to say, each of the above-mentioned embodiments shows an example of the present invention, and the present invention should not be limited thereto.

[0033]

As described above, according to the present invention, the region of interest is always set centering on the portion of interest regardless of the viewing direction, and the relationship between the region of interest and other regions is
By interactively changing the display parameter, it becomes possible to grasp in three dimensions. In addition, by rendering only the region of interest, high-speed processing becomes possible and a high-definition image can be obtained. Furthermore, a display that makes a hole in the display target,
By displaying the approach direction, it becomes possible to plan an operation.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method of setting a region of interest around a point of interest and a rendering method according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of volume rendering.

FIG. 3 is a diagram illustrating an example of resampling.

FIG. 4 is a diagram showing an example of correspondence between opacity and voxel value.

FIG. 5 is a diagram illustrating an example of a rendering result when an attention point and a region of interest are set.

FIG. 6 is a diagram showing an example when high-definition display is performed.

FIG. 7 is a diagram illustrating an example of changing a rendering calculation start position.

FIG. 8 is a diagram showing an example of changing the size and shape of a region of interest.

FIG. 9 is a diagram showing an example of displaying an attention point.

FIG. 10 is a diagram showing an example of designating a target point inside an object.

FIG. 11 is a diagram showing an example of designating a target point inside an object.

FIG. 12 is a flowchart showing an example of approach direction setting and rendering.

FIG. 13 is a diagram showing a display example of an approach direction.

FIG. 14 is a flowchart showing an example of returning to the approach view.

FIG. 15 is a flowchart showing an example of obtaining a surface position on an approach.

[Explanation of symbols]

 1 3D data 2 Projection plane 5 3D data original coordinate system 6 Projected coordinate system after rotation 21 Threshold 22 Proportional constant defining opacity 32 Attention point 33 ROI 66 Temporary attention point 70 True attention point 71 Approach direction

Claims (8)

[Claims] 1. A three-dimensional array of voxel data
A three-dimensional image processing method for generating and displaying an image in which a display target object in the three-dimensional data is projected on a two-dimensional plane using three-dimensional data, which is at least a three-dimensional image that is the projected image. In the above, the step of designating the attention point, the step of obtaining the depth coordinate value of the attention point on the designated three-dimensional image, the step of storing the three-dimensional coordinate value of the attention point, and the interior of the attention point on the projection surface In the three-dimensional image processing method, there is a step of setting a region of interest included in the step of setting a region of interest in the region of interest and a step of setting a parameter for projection image generation calculation for the region of interest separately from other regions. And the step of moving the region of interest by following the point of interest that moves on the projection surface due to the change in the display direction when the positional relationship with A three-dimensional image processing method, characterized in that it includes a step of performing projection image generation calculation for both areas by using respective parameters of the area and other areas, and displaying them. 2. In addition to the above steps, the step of performing projection image generation calculation for the region of interest is performed by making the sampling interval of the parameters of the projection image generation calculation finer than the other regions. Item 3. The three-dimensional image processing method according to item 1. 3. The method according to claim 1, further comprising the step of designating the position of the start point of the projection image generation calculation of the parameters of the projection image generation calculation for the region of interest, in addition to the above steps. Three-dimensional image processing method. 4. The three-dimensional image processing method according to claim 1, further comprising a step of inputting a size of the region of interest and a step of inputting a shape of the region of interest, in addition to the respective steps. 5. The step of designating the point of interest includes the step of designating a temporary point of interest, the step of displaying a cross-sectional image of three-dimensional data by a plane passing through the temporary point of interest and perpendicular to the projection plane, 2. The three-dimensional image processing method according to claim 1, further comprising a step of moving and displaying the position of the cross section in parallel and a step of designating a true point of interest on the cross sectional image. 6. A three-dimensional array of voxel data
A three-dimensional image processing method for generating and displaying a two-dimensionally projected image of a display target object in the three-dimensional data using three-dimensional data, which is at least a three-dimensional image which is the projected image. Then, the step of designating the attention point, the step of obtaining the depth coordinate value of the attention point on the designated three-dimensional image, the step of storing the three-dimensional coordinate value of the attention point, and passing through the attention point in the current line-of-sight direction And a step of setting an approach to the point of interest, which is a line, and each time a parameter of the projection image generation calculation is changed / input, a three-dimensional image based on the parameter is combined with the point of interest and the approach to the point of interest. A three-dimensional image processing method having a step of displaying. 7. In addition to the above steps, in one operation,
7. The three-dimensional image processing method according to claim 6, further comprising the step of matching the approach direction and the line-of-sight direction. 8. In addition to the above steps, a step of storing parameters for projection image generation calculation when displaying a surface of an object, and a step of setting an approach to a point of interest,
Changing the parameters to display the object surface,
The step of obtaining the position of a point on the surface of the object on the approach, and whenever the parameters of the projection image generation calculation are changed / input, the three-dimensional image, the point of interest, the approach to the point of interest, and the object on the approach 7. The method according to claim 6, further comprising a step of combining and displaying points on the surface.
The described three-dimensional image processing method.