JP2002010062A - Image constructor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct an emphasis image for highlighting a 'frosted glassy shadow' which is particularly for a lung cancer examination using a CT image. SOLUTION: In order to highlight a 'frosted glassy shadow' having a small difference in adjacent pixel values, the shadows having a large difference in the adjacent pixel values are overshadowed. Then, a limitation value C is introduced, and the sum V (=|Vi-Vi-1|+|Vi+1-Vi|) of absolute values of differences in pixel values Vi-1, Vi, Vi+1 between the pixels at the same position of the adjacent CT images is acquired (step 4), and it is judged whether or not the sum V of these absolute values is larger than the limitation value C (step 6), and when being larger, a value obtained by increasing constant-fold the limitation value C is stored in a memory (step 8), and when being smaller, a value obtained by increasing contact-fold the sum V of the absolute values is stored in a memory (step 7), thereby constructing an emphasis image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus for processing a volume image formed by stacking a plurality of tomographic images to form an enhanced image of a tomographic image which is particularly useful in a lung cancer screening. Related to the device.

[0002]

2. Description of the Related Art In a lung cancer screening using a tomographic image (for example, a CT image), an indistinct shadow called a "ground glass shadow" may be observed. on the other hand,
Since the cross section of the blood vessel can be observed clearly and roundly, an unclear "ground glass-like shadow" may be overlooked.

For this reason, images are generally emphasized and displayed. One of the image emphasizing methods is a method of taking a difference between each CT image. For example, two adjacent images of 512 × 512
C of the pixel at the same address (x, y) between the CT images
The difference between the T values is calculated, and the difference between the CT values is stored at the address (x, y) of the memory.
To obtain an enhanced image.

[0004]

However, as shown at 31 in FIG. 5, the "frosted glass shadow" has a small difference between adjacent pixel values since the shadow is thin, and another shadow having a large difference between adjacent pixel values. There is a problem that it is easily overlooked.

The present invention has been made in view of such circumstances, and a shadow having a small difference between adjacent pixel values such as a "frosted glass shadow" cannot be buried in another shadow having a large difference between adjacent pixel values. It is an object of the present invention to provide an image forming apparatus that can be made to stand out as described above.

[0006]

According to the first aspect of the present invention, there is provided an image forming apparatus for processing a volume image formed by stacking a plurality of tomographic images to form an enhanced image. An enhanced image creating means for creating one enhanced image based on three adjacent tomographic images of the plurality of tomographic images, wherein the enhanced image creating means Pixel value V between pixels
The sum V of the absolute values of the differences between _i−1 , V _i and V _{i + 1} (= | V _i −V
_i-1 | + | V _{i + 1} −V _i |), and sums the absolute values V
Is greater than or equal to a predetermined limit value C, a value obtained by multiplying the limit value C by a constant number (including 1) is stored in a memory, and when the sum V of the absolute values is smaller than the limit value Storing a value obtained by multiplying the sum V of the absolute values by a constant number (including 1) in the memory, and storing the emphasized image in the memory by performing the above-described processing for pixels at all positions of the tomographic image. Features.

Further, the invention according to claim 2 of the present application provides a
Process volume images that are stacked
An image composing device for composing an enhanced image by
1 based on three adjacent tomographic images among the tomographic images
Comprising an enhanced image creating means for creating one enhanced image,
The emphasized image creating means includes a pixel at the same position of an adjacent tomographic image.
Pixel value V between_i-1, V_i, V_{i + 1}The absolute value of the difference
V_i-V_i-1|, | V _{i + 1}-V_iThe larger of |)
Is obtained, and the obtained absolute value V is a predetermined limit value.
In the case of C or more, the limit value C is multiplied by a constant number (including 1)
The absolute value V is stored in the memory so that the absolute value V becomes smaller than the limit value C.
Is smaller than the absolute value V by a constant number (including 1 time).
The stored values are stored in the memory, and all of the tomographic images are stored.
The above processing is performed for the pixel at the position
It is characterized in that the emphasis image is stored in the moly.

That is, in order to make the “ground glass-like shadow” having a small difference between adjacent pixel values noticeable, a shadow having a large difference between adjacent pixel values should be made less noticeable. Therefore,
If the limit value C is newly introduced, and the sum V of the two absolute values or the larger absolute value V of the two absolute values is larger than the limit value C, the limit value C is multiplied by a constant number (1 time). including)
The stored value is stored in the memory. As a result, a value of a shadow having a large difference between adjacent pixel values such that the sum V of the absolute values or the like exceeds the limit value C is limited by the limit value C, so that the value of the shadow does not become more conspicuous than necessary. The difference between adjacent pixel values such as “frosted glass shadow” makes small shadows stand out.

[0009]

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

First, the present invention will be described in principle with reference to FIGS.

As shown in FIG. 1, a tomographic image (CT
, I-1, i, i + 1,... Are sequentially reconstructed from measurement data measured by the X-ray CT apparatus. In addition, CT
The pixel data of the image is a CT value calculated based on the X-ray absorption value of the part of the human body corresponding to the pixel.

Conventionally, the difference between images is based on using two images, but in the present invention, one enhanced image is created from three CT images based on using three CT images. I do.

That is, as shown in FIG. 1, the pixel value (CT value) of the pixel at the same position (x, y) of three adjacent CT images i-1, i, i + 1 is V _i-1. , V _i , V _{i + 1} ,
The sum V of the absolute value of the difference between these CT values V _i−1 , V _i , V _{i + 1} is represented by the following equation:

[0014]

## EQU1 ## It is obtained by the following equation: V = | V _i −V _i−1 | + | V _i −V _{i + 1} |

As is clear from the CT values V _i−1 , V _i , and V _{i + 1} shown in FIGS. 2A and 2B and the absolute values between these CT values, the CT values are large. Also, when the difference between the CT values is small, the sum V has a small value. Therefore, the CT values V _i−1 , V _i ,
In the example of V _{i + 1} , the sum V of the absolute values in FIG. 2A is larger, and is emphasized more than in FIG. 2B. Also, relatively continuous shadows between adjacent CT images, such as the cross sections 30a and 30b of the blood vessel shown in FIG. 5, are suppressed and become inconspicuous.

In the present invention, a predetermined limit value C is provided for the sum V of the absolute values shown in the above equation (1), and the sum V of the absolute values does not exceed the limit value C (the limit value C). To saturate). That is, when V ≧ C, C is stored in the memory, and when V <C, V is stored in the memory.

The limit value C maintains the sum V of the absolute values corresponding to the "ground glass-like shadow" (not saturated), and has a value V larger than the sum V of the absolute values corresponding to the "ground glass-like shadow". Is an optimal value that saturates as much as possible.

FIG. 3 is a flowchart showing a processing procedure of the image forming apparatus according to the present invention. In addition, in FIG.
The case where one emphasized image is formed from T images i-1, i, i + 1 is shown. [Step 1] The above-described limit value (constant value) C, a constant value k (including 1) used as a constant, and a target C
Threshold values t1 and t2 for selecting the T value are set. [Step 2] To process the first point of the CT image i,
(X, y) = (0, 0). [Step 3] C of pixel at position (x, y) of CT image i
The T value Vi is determined by the conditions of the threshold values t1 and t2 (that is, t1 ≦
Vi ≦ t2) is determined. If the condition of the threshold value is satisfied, the process jumps to step 4; otherwise, the process jumps to step 5. [Step 4] As shown in equation (1), three CT images i-
The CT value V _i−1 of the pixel at the position (x, y) at 1, i, i + ₁ ,
Based on V _i , V _{i + 1} , these CT values V _i−1 , V _i ,
The sum V of the absolute value of the difference of V _{i + 1} is obtained. [Step 5] Since the CT value Vi does not satisfy the condition of the threshold value, zero is stored in the memory corresponding to the position (x, y) and displayed on the CRT display. Thereby, the CT value Vi that does not satisfy the threshold condition is not displayed. [Step 6] It is determined whether the sum V of the absolute values is larger than the limit value C (V> C). If it is smaller, it jumps to step 7; if it is larger, it jumps to step 8. [Step 7] The sum V of the absolute values is multiplied by a constant value k, and the product k · V is stored in the memory corresponding to the position (x, y).
Display on CRT display. [Step 8] The limit value C is multiplied by a constant value k, and the product k
・ Store C in the memory corresponding to the position (x, y),
Display on the T display. [Step 9] 1 is added to x. [Step 10] It is determined whether or not x is the maximum value. When the image size of the CT image is 512 × 512, the maximum value of x is
512. If x is the maximum value, the process jumps to step 11; [Step 11] Return x = 0 and add 1 to y. [Step 12] Determine whether or not y is the maximum value. If the image size of the CT image is 512 × 512, the maximum value of y is
512. If y is the maximum value, the process ends. If y is not the maximum value, the process jumps to step 3 and returns to steps S3 to
Step S11 is repeated.

In the above-described embodiment, the processed image constituted by the values stored in the memory is displayed on the CRT display as it is. However, the present invention is not limited to this. As shown in FIG. -1, i, i + 1 may be processed to form the processed image, and the sum of the processed images may be displayed as the emphasized image, or the image formed by ORing each bit may be displayed. It may be displayed as an emphasized image.

In the above embodiment, the sum V of the two absolute values is obtained as shown in the equation (1), and the sum V is compared with the limit value C. However, the present invention is not limited to this. As shown in the equation, the larger one of the two absolute values may be adopted as V, and this V may be compared with the limit value C.

[0021]

In the case of | V _i −V _i−1 | ≧ | V _i −V _{i + 1} |, V = | V _i −V _i−1 | | V _i −V _i−1 | <| V _i In the case of −V _{i + 1} |, V = | V _i −V _{i + 1} | (2) FIG. 4 is a block diagram showing a hardware configuration of the image forming apparatus according to the present invention.

This image construction apparatus is for constructing and displaying an enhanced image or the like from a plurality of tomographic images collected for a target part of a subject by, for example, an X-ray CT apparatus, and stores the tomographic images and the like. A magnetic disk 20 to be executed, a main memory 22 storing software necessary for arithmetic processing,
Central processing unit (hereinafter referred to as CPU) 2 for performing arithmetic processing
4 and a display memory 26 for recording display data of the processing result
And a CRT display 28 for displaying the display data
, A mouse 30 for operating a soft switch on the screen and its controller 32, a keyboard 34, and a common bus 36 for connecting the above components.

[0023]

As described above, according to the present invention, a shadow having a large difference between adjacent pixel values and exceeding a predetermined limit value is replaced with a limit value, whereby the difference between adjacent pixel values is reduced. Since a large shadow is made less noticeable, a shadow having a small difference between adjacent pixel values, such as a “frosted glass shadow”, can be relatively noticeable.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an original CT image and a processed image.

FIG. 2 is a diagram used to explain the magnitude of the CT value of a pixel at the same position in three CT images and the magnitude of the absolute value of the difference between these CT values;

FIG. 3 is a flowchart showing a processing procedure of the image forming apparatus according to the present invention.

FIG. 4 is a block diagram showing the overall configuration of an image forming apparatus according to the present invention.

FIG. 5 is a diagram showing a “ground glass-like shadow” and other shadows and the like on a CT image;

[Explanation of symbols]

20 ... magnetic disk, 22 ... main memory, 24 ... central processing unit (CPU), 26 ... display memory, 28 ... CRT _{display, V i-1, V i} , V i + 1 ... pixel value, C ... limit

Continued on the front page F term (reference) 4C093 AA21 AA26 CA18 DA03 FF07 FF17 FF33 5B057 AA09 BA03 CA02 CA08 CA13 CA16 CB02 CB08 CB12 CB16 CE03 CE11 DA04 DC32 5C076 AA19 AA40 BA03 5C077 LL01 PP03 PP09 PP47 P20

Claims (2)

[Claims] An image forming apparatus configured to process a volume image formed by stacking a plurality of tomographic images to form an enhanced image, based on three adjacent tomographic images among the plurality of tomographic images. with an emphasis image creation means for creating a single enhanced image, the enhanced image generating means, pixel values of each other pixels at the same position of the tomographic images adjacent to V _i-1, V _i, of the difference between V i _{+ 1} Sum of absolute values V (= | V _i −
V _i-1 | + | V _{i + 1} −V _i |), and when the sum V of the absolute values is equal to or greater than a predetermined limit value C, the limit value C is multiplied by a constant number (including one) When the sum V of the absolute values is smaller than the limit value C, a value obtained by multiplying the sum V of the absolute values by a constant number (including 1) is stored in the memory. An image forming apparatus characterized in that an enhanced image is stored in the memory by performing the above processing for pixels at all positions of a tomographic image. 2. An image forming apparatus for processing a volume image formed by stacking a plurality of tomographic images to form an enhanced image, wherein the image forming apparatus performs processing based on three adjacent tomographic images among the plurality of tomographic images. with an emphasis image creation means for creating a single enhanced image, the enhanced image generating means, pixel values of each other pixels at the same position of the tomographic images adjacent to V _i-1, V _i, of the difference between V i _{+ 1} the absolute value (| V _i -V
_i-1 |, | V _{i + 1} −V _i |), and when the determined absolute value V is equal to or greater than a predetermined limit value C,
A value obtained by multiplying the limit value C by a constant number (including 1) is stored in a memory, and when the absolute value V is smaller than the limit value C,
A value obtained by multiplying the absolute value V by a constant number (including 1) is stored in the memory, and the above processing is performed on pixels at all positions of the tomographic image to store an emphasized image in the memory. Image forming device.