JP2002236910A - Three-dimensional image creating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To confirm an intended region of interest in various directions and observe the peripheral region of the region of interest in creating a three- dimensional image. SOLUTION: A region of interest ROI is set in an intended lesion in an obtained three-dimensional image (step 12). Subsequently, a weighting factor and a raising value for raising a CT value in the ROI are set (step 14). According to the raising value, the CT value of the three-dimensional original image is corrected (step 18), and a three-dimensional image is created by MIP method (step 20).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for creating a three-dimensional image, and more particularly to a method for creating a desired three-dimensional image from image data acquired by an X-ray CT apparatus, an MRI apparatus or the like. About.

[0002]

2. Description of the Related Art Conventionally, there is an RI test method in which a radioisotope (RI) is administered to an affected area, and the affected area inside a human body can be observed by an RI image obtained by imaging the distribution.

[0003] In the RI inspection method, when creating an RI image,
When the MIP (Max Intensity Projection) method is used, a target affected part inside the human body can be displayed from various directions. The reason for this is that only a specific diseased part often has a large pixel value in an RI image. However, since the MIP method projects the maximum pixel value on a projection line onto a projection surface and attaches a density according to the size of the pixel value to create an RI image,
An RI image without depth information without depth information is created.

On the other hand, 3 measured by an X-ray CT system
A three-dimensional original image (an image formed by stacking a plurality of tomographic images in a direction orthogonal to the body axis direction of the human body) on a projection plane by the MIP method to create a three-dimensional CT image including an affected part Image creation methods are known.

[0005]

By the way, in the RI image, only the target diseased part is displayed, whereas in the CT image, all organs, bones and tissues in the human body are displayed. When observing, a three-dimensional image is often created by directing the line of sight to each tomographic image in the vertical direction. This is because the CT image viewed from the side of the human body (the direction parallel to the tomographic image) and other directions is the C
Other organs and bones with a CT value greater than the T value are in the way,
This is because the target affected area is hidden.

On the other hand, a target region of interest (ROI: Region Of Interest) is extracted from the three-dimensional original image, and this ROI is extracted.
There is a method of creating only a three-dimensional image, but in this case, there is a problem that a region around the ROI cannot be observed.

The present invention has been made in view of such circumstances, and when creating a three-dimensional image, it is possible to confirm a target region of interest from various directions, and also to determine a peripheral region of the region of interest. It is an object of the present invention to provide a method for creating a three-dimensional image that can be observed.

[0008]

According to the present invention, in order to achieve the above object, a region of interest is set from a three-dimensional original image, and the region of interest is set such that the set region of interest is relatively emphasized. A difference is made between each pixel value in the region and each pixel value in the other region, and a three-dimensional original image of the region of interest and the other region in which the pixel values are different is projected on the projection surface. To create a three-dimensional image.

According to the present invention, a target region of interest is set from a three-dimensional original image. Then, in order to relatively highlight the image set as the region of interest, the pixel value in the region of interest is raised by a certain value or the like so as to be different from the pixel values of other regions. Thus, when a three-dimensional image is created by the MIP method or the like, a target region of interest can be raised.

As set forth in claim 2 of the present application, for each pixel value of the three-dimensional original image before or after making a difference between the pixel values,
It is characterized in that weighting corresponding to the distance from the projection plane is performed. That is, since each pixel value of the three-dimensional original image is weighted according to the distance from the projection plane, M
By projecting the three-dimensional original image on the projection surface by the IP method or the like, a three-dimensional image having a perspective can be created.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a three-dimensional image forming method according to the present invention will be described below in detail with reference to the accompanying drawings.

First, the principle of the three-dimensional image creation method according to the present invention will be described.

FIG. 1 is a conceptual diagram when a three-dimensional image is created by projecting a three-dimensional original image obtained by an X-ray CT apparatus onto a projection plane based on a predetermined algorithm. In FIG. 1, the three-dimensional original image is shown as one tomographic image 10 in a direction orthogonal to the body axis direction of the human body, but a plurality of the three-dimensional original images are stacked in a direction orthogonal to the paper surface (body axis direction). It is configured. Also, in this embodiment, the maximum pixel value (C
The MIP method of creating a three-dimensional image by retrieving (T value) and projecting it on the projection plane 12 is used.

When the MIP method is used, when the CT value of the target affected area 16 on the projection line 14 is smaller than the CT value of a part other than the affected area 16, it is not projected on the projection surface 12, and especially the projection line When the direction of 14 is parallel to the tomographic image 10 as shown in FIG. 1, a bone 18 having a high CT value exists on the projection line 14, and the entire target diseased part 16 is not projected.

Therefore, in the present invention, the target affected area 16
ROI is set so as to surround, and the CT value inside the ROI is raised to be larger than the CT value of the part outside the ROI. In this embodiment, the CT value is multiplied by a weight coefficient corresponding to the position on the projection line 14 in order to create a three-dimensional image with a more perspective.

That is, the CT value of the pixel i on a certain projection line 14 is corrected as follows according to whether it is inside the ROI or outside the ROI.

[0017]

(1) When pixel i is within ROI Cf (i) = {C (i) × w (i)} + Cup (2) When pixel i is outside ROI Cf (i) = C (i) ) × w (i) i: pixel on projection line (i = 1,2 ...) Cf (i): CT value after weighting and raising C (i): CT value at pixel i w (i) : Weight coefficient Cup: Raised value Next, the three-dimensional image creation method according to the present invention will be described with reference to the flowchart shown in FIG.

First, from a plurality of tomographic images acquired by the X-ray CT apparatus, a tomographic image 10 including a target diseased part 16 is obtained.
Is selected and displayed on the display device (step 1).
0).

Subsequently, on the tomographic image 10 displayed on the display device, an ROI is set to a target affected area 16 by an input device such as a mouse or a keyboard (step 1).
2). Further, ROIs are respectively enclosed on several sheets of the tomographic image 10 in which the target affected part 16 is displayed. RO
The setting of I may be performed by sequentially expanding a region from a certain point of the target affected area to a connected region considered to belong to the same region, and applying a region growing method of extracting an ROI. The ROI extracted by the glowing method may be further manually corrected.

Next, a weighting factor is set as shown in FIG. 1 in order to create a three-dimensional image having a perspective, and weighting is performed in order to make the target affected area 16 stand out. A lift value to be added to the CT value in the weighted ROI is set (step 14).

Next, the angle α to be projected is set to the front of the human body (α =
0) (step 16), followed by step 1
Based on the weighting factor and the inflation value set in step 4, the CT value is corrected according to equation (1) (step 18). Next, a three-dimensional image is created by the MIP method based on the projection angle α set in step 16 and the CT value obtained in step 18, and this three-dimensional image is output to a display device and displayed (steps 20, 22). ).

The method of projecting the maximum pixel value on a projection line on a projection plane using the MIP method in the present embodiment is performed as follows.

The tomographic image 1 from a certain direction along the projection line 14
When seeing 0, first, the CT value of a certain pixel is stored. Then, move to the next pixel on the projection line 14,
The CT value at that pixel is calculated. Next, the newly calculated CT value is compared with the stored CT value, and if the calculated CT value is larger, the CT value is stored. The above process is repeated on one projection line 14.

When the calculated CT value is smaller than the stored CT value, the stored CT value is determined as the CT value of the projection line 14. In this way, the maximum pixel value on the projection line is determined and projected on the projection plane 12.

Subsequently, it is determined whether or not the displayed three-dimensional image is appropriate (step 24). If not, a weighting factor and a raising value are set again so that the image becomes appropriate (step 24). Step 14). Subsequently, a three-dimensional image is created and displayed by the above-described MIP method using the set weight coefficient and the raised value (steps 16 to 22).

If the three-dimensional image is properly displayed (step 24), the projection angle α is set by rotating the projection angle α by a small angle Δ from the front of the human body (step 26), and based on the projection angle α A weighting calculation of the CT value is performed (step 28). The MIP based on the projection angle α changed in step 26 and the CT value obtained in step 28
A three-dimensional image is created by the method (step 30).

Until the projection angle α from the front of the human body becomes 360 ° (step 32), the image is further rotated to change the projection angle α, and a three-dimensional image is created by the above method (steps 26 to 30). ). When the projection angle α becomes 360 ° (step 30), the process of creating a three-dimensional image ends.

When a plurality of three-dimensional images for 360 ° created as described above are sequentially displayed (Cine display),
The target affected part 16 can be rotated and displayed, and the depth from the surface of the human body can be read.

FIG. 3 is a block diagram showing an example of a hardware configuration of a three-dimensional image forming apparatus to which the three-dimensional image forming method according to the present invention is applied. As shown in FIG. 3, the three-dimensional image creating apparatus 20 according to the present invention mainly includes an X-ray CT apparatus,
A recording medium 22 such as a magnetic disk or a hard disk for storing a three-dimensional original image acquired by an image diagnostic apparatus such as an MRI apparatus; an interface (I / F) 24 for inputting the stored three-dimensional original image; A memory 26 for temporarily storing a three-dimensional original image; a central processing unit (CPU) 28 for controlling the operation of each component; a display device 30 for displaying an image based on image data; Hard disk 32 in which programs and programs are stored
And input devices such as a mouse 34 and a keyboard 36 for performing input / output processing and processing operations, and a common bus 38 for connecting the above-described components.

The effective means for implementing the three-dimensional image creation method according to the present invention is not only the MIP method but also a method of integrating on a projection line (DRR (Digitally Recons)).
tructed Radiograph), sum value projection display, etc., and volume rendering method are also effective.

In this embodiment, C in the ROI
The T value was raised, but not limited to this, CT outside the ROI
Subtract a predetermined value from the value, or add a constant a to the CT value outside the ROI.
(0 <a <1) may be applied to lower the CT value outside the ROI to relatively emphasize the ROI.

[0032]

As described above, according to the three-dimensional image forming method according to the present invention, the pixel value in the set region of interest is raised, for example, to make a difference from the pixel values in other regions. Accordingly, a three-dimensional image in which the region of interest is raised can be created. Thereby, the shape and position of the region of interest and its surrounding region can be easily recognized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment using a three-dimensional image creation method according to the present invention.

FIG. 2 is a flowchart showing an embodiment of a three-dimensional image creation operation by the three-dimensional image creation method according to the present invention.

FIG. 3 is a block diagram showing an example of a hardware configuration of a three-dimensional image creating apparatus to which the three-dimensional image creating method according to the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Tomographic image, 12 ... Projection plane, 14 ... Projection line, 16 ... Affected part, 18 ... Bone, 20 ... Three-dimensional image creation apparatus, 22 ... Recording medium, 24 ... Interface (I / F), 26 ... Memory, 28 ... Central processing unit (CPU), 30 ... Display device,
32: Hard disk, 34: Mouse, 36: Keyboard, 38: Common bus

Claims (2)

[Claims] 1. A region of interest is set from a three-dimensional original image, and each pixel value in the region of interest and each pixel in other regions are set so that the set region of interest is relatively emphasized. A three-dimensional image is created by projecting a three-dimensional original image of the region of interest and the other region with the difference in pixel value onto a projection plane. Dimensional image creation method. 2. The three-dimensional image according to claim 1, wherein each pixel value of the three-dimensional original image before or after the difference between the pixel values is weighted in accordance with a distance from the projection plane. Image creation method.