JP2002150311A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly acquire a clear rendering image hardly including low frequency components of an artifact or the like. SOLUTION: In making a pseudo three-dimensional display of an observation object included in a three-dimensional original image, using a volume rendering method or a surface rendering method, the difference (A-A') between an observation object region A and an observation object contraction region A' obtained by the contraction processing of the observation object region A, is obtained, and a region A" of the difference is made a rendering region, that is, the rendering region is determined by the set operation (such as the sum, product, difference and assembling) of the observation object region and a plurality of regions out of observation object expanded regions or observation object contracted regions obtained by expanding or contracting the observation object region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to a method for embedding a luminal organ inside an object to be observed such as a lung or a liver.
The present invention relates to an image processing device that displays a two-dimensional image.

[0002]

2. Description of the Related Art The following method is used as a method for forming a pseudo three-dimensional image by shading and projecting a three-dimensional original image obtained from an X-ray CT apparatus, an MRI apparatus or the like on a projection plane. ing.

[0003] The volume rendering method is a method of displaying the sum of the intensities of light sequentially transmitted while attenuating according to the opacity ratio when incident light goes to each voxel of an original image. For this reason, volume data having pixel values can be handled, but the projection image is greatly affected by which depth of light falls within the range of the sum. Also,
The surface rendering method is a method of displaying surface information when incident light reaches an observation target. Therefore, the projected image is greatly affected by how much light can reach only the observation target.

Conventionally, rendering by the volume rendering method or the surface rendering method is often performed on the entire observation area. When rendering is performed with the area limited, the distance that light travels with respect to the observation area is fixed. However, the region of interest is manually set by a circle or a cube without morphological information.

Next, a general method for expanding and contracting the observation area will be described. As shown in FIG. 8, a method of performing a hole filling process in an observation region and performing an expansion / contraction process on the region (actually, three-dimensional data, but simplified in FIG. 8 with two-dimensional data), or There is a method of expanding / shrinking the area by enlarging / reducing by the geometric transformation shown in (1). In this method, the outer wall information of the observation target is [x,
y, z], [X,
Y, Z].

[0006]

(Equation 1) Sx, Sy, Sz are scaling parameters. Here, the method of FIG. 8 performs data conversion of anisotropic voxels into isotropic voxels, and handles all three-dimensional data of the observation region. In the area expansion / contraction method based on enlargement / reduction by geometric transformation, the origin of the coordinate system is set at the center of the object.

[0007]

By the way, when regions such as lungs and liver are to be rendered, abnormal shadows in those regions often exist in a specific region, but only this specific region is rendered. As a result, it is difficult to extract a peripheral blood vessel having a small diameter and a low density value because the image contains a low-frequency component due to the influence of an artifact or the like. In addition, there is a problem that the rendering processing time is long.

The present invention has been made in view of such circumstances, and has as its object to provide an image processing apparatus capable of obtaining a clear rendered image at high speed.

[0009]

According to the present invention, in order to achieve the above object, a three-dimensional image is formed from a three-dimensional original image, the three-dimensional image is projected on a projection surface, and the projected image is formed. An image processing apparatus configured to form a pseudo three-dimensional image by shading, comprising: means for setting a plurality of observation target areas in the three-dimensional original image; and a logical sum and a logical product of these set observation target areas Means for performing a set operation;
Means for constructing the pseudo three-dimensional image from the set-observed observation target area.

According to the present invention, when a pseudo three-dimensional image is constructed and displayed by using a volume rendering method, a surface rendering method, or the like for an observation target included in a three-dimensional original image, an observation target region and an observation target Set operation (eg, union,
(Product, difference, assemble). As a result, it is possible to obtain a clear rendered image that is fast and does not include low-frequency components such as artifacts. There are various variations in the set operation, and the set can be considered not only for the observation target and the observation target expansion region, but also for the observation target regions.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the image processing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, for example, when a region of interest is a lung field, a lung field limited image (three-dimensional original image) is projected on a projection surface by shading by a volume rendering method, and a pseudo three-dimensional image is projected. Although an image is configured, in the present invention, an area to be rendered is limited as follows.

When rendering near the outer wall of the lung field is to be rendered, the difference between the observation target area A and the observation target contraction area A 'is calculated as shown in FIG.
By rendering only AA ′), a rendering image limited to the region near the outer wall can be obtained (the gray region is the region to be rendered).

When the bronchi are to be rendered, the sum of the observation region B including the bronchus and the observation expansion region B ′ (here, the observation expansion region) is shown in FIG. 2B. B 'only) to obtain a rendering image limited to the bronchial region (the gray region renders). Although the rendering area is three-dimensional, it is shown in two dimensions in FIG. 2 for simplicity.

In this image processing method, since an unnecessary area is not rendered, low-frequency components such as artifacts are hardly included, and clear and high-speed rendering can be performed.

Next, a description will be given of a method for obtaining the observation target area, the observation target contraction area, and the observation target expansion area.

FIG. 3A shows a wireframe model of a sphere represented by triangular elements as an example of a wireframe model. For example, if the region of interest is a lung field, the wire frame model can be configured by extracting a lung field region and obtaining edge information, and can also be configured by simply thresholding the region of interest. From the edge information.

The normal vector of the surface (triangle batch) composed of a plurality of pieces of edge information obtained in this manner is shown in FIG.
As shown in (b), it can be obtained from the cross product of three points. The edge information of the observed expansion / contraction area is located on a normal vector starting from the center of gravity of the triangular patch. The edge information of the observation target expansion region is set as a position moved by an arbitrary distance in the direction of the normal vector, and the edge information of the observation target contraction region is set in the direction opposite to the normal vector. The wireframe model that is further configured depends on the setting of the threshold,
A plurality of regions of interest can be simultaneously expressed, and the observation target expansion / contraction region can be set similarly.

The method for obtaining each area as described above is as follows.
When obtaining regions of interest such as lungs and liver, the small amount of data with only the outer wall information of the observation target is handled, the anisotropic voxel data does not need to be converted into isotropic data, and the processing depends on the observation target. The feature is that it is not restricted.

Assuming that an object is a set consisting of an infinite number of points in a three-dimensional space, a set operation between the objects, that is,
Sum, product, difference and assemble can be defined. Various shapes can be created by repeating the operation of applying and combining the set operations. In the case of taking the sum of objects, it is assumed that the value of the object is 1 when a point in the three-dimensional space is inside the object, and the value is 0 when the point is outside the object.

At this time, generally, the sum A of the object A and the object B
The object defined by ∪B is defined by a set of points such that the value defined in the operation table of FIG. When the product of the objects is taken, the object defined by the product A∩B of the object A and the object B is a set of points such that the value defined in the operation table of FIG. Defined. When taking the difference between the objects, the object defined by the difference AB between the object A and the object B is a set of points where the value defined in the calculation table of FIG. Defined. When assembling the objects together, the object defined by the assembly A + B of the object A and the object B is simply an arrangement of two objects A and B. The difference from the sum is that if the surfaces of the objects are exactly matched, the sum will be fused as one object, but the assembly will only be done and the boundary surface will remain.

The set operation can be easily performed if the line of sight is traced and executed as an operation between line segments on the line of sight (intersection lines with the object). That is, as shown in FIG. 5, (1) First, the intersection (line segment) between the line of sight and the basic solid is obtained, and (2) Next, the operation is performed on the line segment related to the basic solid on which the operation is to be performed. That should be done.

As described above, the observation target area and the observation target dilation / shrinkage area are regarded as a set, and a volume rendering display can be performed with a limited area of interest by performing a set operation. The observation target region and the observation target expansion / contraction region have the same shape and the same center of gravity of the object.

FIG. 2 illustrates the case where rendering is performed around the outer wall of the lung field and the case where bronchi are rendered. However, the bronchial region near the outer wall of the lung field is rendered. Can also.

In this case, the area A ″ near the outer wall of the lung field
(See FIG. 2 (a)) and the region of the bronchus B ′ (see FIG.
(B), the rendering area can be limited to the bronchial area C near the outer wall as shown in FIG. 6 (the gray area in FIG. 6). In this way, by performing the set operation, it is possible to limit the rendering region and reduce the time required for rendering.In addition, since rendering other than the region of interest is not performed, it is difficult to include low frequency components such as artifacts, A clear image is obtained.

FIG. 7 is a block diagram showing an example of a hardware configuration of the image processing apparatus according to the present invention. As shown in FIG. 1, the image processing apparatus includes a magnetic disk 20 storing a plurality of tomographic image data and programs, a main memory 22 storing an operation control program, and controlling the operation of each component. Central processing unit (CPU) 24, a display memory 26 for temporarily storing image data for display, and a C for displaying an image based on the image data from the display memory 26.
It comprises an RT 28, a mouse 30 for performing input / output processing and processing operations, a controller 32 thereof, a keyboard 34, and a common bus 36 for connecting the above components.

[0027]

As described above, according to the image processing apparatus of the present invention, when the observation target included in the three-dimensional original image is pseudo-three-dimensionally displayed by the volume rendering method or the surface rendering method, the observation target is displayed. Since the region to be rendered is limited by a set operation (for example, sum, product, difference, assemble) of the region and the region obtained by the expansion and contraction processing of the observation target region, it is clear that the region is high speed and hardly contains low frequency components such as artifacts. A rendered image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a lung field limited image (a three-dimensional original image) and a projection plane of an observation target area.

FIG. 2 is a view showing a method of limiting an area using a set operation of the image processing apparatus according to the present invention.

FIG. 3 is a diagram showing a wire frame model and an expansion / contraction processing method.

FIG. 4 is a diagram of a set operation.

FIG. 5 is a diagram showing that a set operation is performed on a line segment on the line of sight.

FIG. 6 is a view showing an example of obtaining a further limited area based on the limited area by the method shown in FIG. 2;

FIG. 7 is a block diagram illustrating a hardware configuration example of an image processing apparatus according to the present invention.

FIG. 8 is a diagram showing a conventional area expansion / contraction method.

[Explanation of symbols]

20 magnetic disk, 22 main memory, 24 CPU
26: display memory, 28: CRT, 30: mouse, 32
... controller, 34 ... keyboard, 36 ... common bus

Continued on the front page F-term (reference) 4C093 AA26 CA01 CA08 CA13 CA29 FD09 FF15 FF34 FF35 FF36 FF43 4C096 AA01 AB01 AB08 AB27 AC04 AC10 DC18 DC19 DC33 DC36 DD09 DE04 FC16 5B057 AA08 AA09 BA07 CA13 CB12 CE20 A080 CFA DA03 GA00 GA11

Claims (1)

[Claims] 1. An image processing apparatus for forming a three-dimensional image from a three-dimensional original image, projecting the three-dimensional image on a projection surface, shading the projected image to form a pseudo three-dimensional image, Means for setting a plurality of observation target areas in the three-dimensional original image, means for performing a set operation including a logical sum and a logical product for these set observation target areas,
Means for constructing the pseudo three-dimensional image from the set of observation target regions.