JP2002237948A - Image processing unit, image processing system, image processing method, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing unit that can provide satisfactory image, after processing with a configuration of properly suppressing overshoots and of not losing even the information of a very small structure of an area where the overshoot is suppressed. SOLUTION: A 1st high-frequency component acquisition means 112 acquires a 1st high-frequency component from an object image. An area detection means 113 detects an overshoot area of the object image, on the basis of the 1st high- frequency component. A 2nd high-frequency component acquisition means 114 acquires a 2nd high-frequency component from the object image, on the basis of the overshoot area. A frequency component replacement means 115 replaces the 1st high-frequency component with the 2nd high-frequency component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation conversion process for an image taken by radiation such as X-rays.
An image processing apparatus, an image processing system, an image processing method, a program for realizing the functions of the apparatus or the system, and a program for implementing the functions of the apparatus or the system, which are used in an apparatus or a system that performs image processing such as a dynamic range changing process and a sharpening process A program for executing the processing steps,
And a computer-readable storage medium storing the programs.

[0002]

2. Description of the Related Art In recent years, with the advance of digital technology, an image (radiation image) obtained by radiography is digitized and obtained as a digital image, and the digital image is subjected to image processing. Display and output of the processed digital image on a CRT or the like or film output have been performed.

[0003] In the case of a radiation image, in order to convert the digital image into an image suitable for display output or film output, a gradation conversion process or a dynamic range change process may be performed as the above image processing.

However, even if the above-described image processing is performed, for example, an image (X-ray chest image) obtained by imaging a chest with X-rays is an image of a lung field through which X-rays are easily transmitted, Since the image is composed of an image of a mediastinum part where X-rays are very difficult to transmit, the range in which the pixel values (the values of the pixels constituting the digital image) exist is very wide. For this reason,
It has been very difficult to obtain an X-ray chest image that allows simultaneous observation of both the lung field and the mediastinum.

Therefore, as a method for avoiding the above problem, for example, “SPIE Vol.626 Medic”
ine XIV / PACS (1986) "(hereinafter referred to as" first method ").

In the first method, a pixel value S _D after processing, an original pixel value (input pixel value) S _org , a pixel value S _US of a low-frequency image of the original image (input image), and a constant A,
With B and C (for example, A = 3, B = 0.7),

[0007]

(Equation 1)

This is represented by the following equation (1).

In the first method, a high frequency component (the first term of the above equation (1)) and a low frequency component (the second term of the above equation (2)) are used.
By changing the weighting of the term, specifically, for example, A
By setting = 3 and B = 0.7, the effect of enhancing the high-frequency components of the target image and compressing the dynamic range of the entire target image can be obtained.

Incidentally, for the first method, five radiologists have evaluated that it is more effective for diagnosis than an image without processing.

For example, Japanese Patent No. 2509503 and the like disclose a pixel value S _D after processing, an original pixel value (input pixel value) S _org , and a Y value of an original image (input image).
I more than the average profile P _x of the average profile Py and the X-direction profile of direction profile,

[0012]

(Equation 2)

The method represented by the following equation (2)
"The second method" is described.

In the above equation (2), the function F (x) is
When “x> D _th ”, F (x) becomes “0” and “0 ≦ x
≦ D _th ”, F (x) indicates that the intercept is“ E ”and the slope is“ E /
D _th ”monotonically decreases,

[0015]

(Equation 3)

Equations (3) to (5) are used.

In the above equations (4) and (5), i = 1 to n. “P _yi ” and “P _xi ” indicate profiles in the Y and X directions. G (P _x , P _y ) is, for example,

[0018]

(Equation 4)

Equation (6) is given.

The second method is to compress the density range equal to or less than " _Dth " with the pixel value of the low frequency portion of the target image.

As a method similar to the second method,
There is a method described in "Journal of the Japanese Society of Radiological Technology, Vol. 45, No. 8, August 1989, page 1030, Anan et al.", And a patent publication No. 2663189 (hereinafter, referred to as "third method"). .

The third method is an average when a moving average of the processed pixel value S _D , the original pixel value (input pixel value) S _org , and the original image (input image) is obtained with a mask size of M × M pixels. With the pixel value S _US and the monotone decreasing function f (X),

[0023]

(Equation 5)

This is expressed by the following equations (7) and (8).

The third method is different from the second method represented by the above equation (2) in the method of creating a low-frequency image. That is, in the above equation (2), a low-frequency image is created by one-dimensional data, whereas in the above equations (7) and (8), a low-frequency image is created by two-dimensional data.

In the third method, as in the second method,
The pixel value of the low-frequency portion of the image, "D _thThe following concentration ren
Is compressed.

The dynamic range compression according to the first to third methods as described above uses the function f1 for converting a low-frequency image.
() And the constant AX,

[0028]

(Equation 6)

Expression (9) is obtained.

In Japanese Patent Application Laid-Open No. Hei 10-272283, the following method (hereinafter, referred to as a "fourth method") is described.

The fourth method is that a gradation conversion function F1 (), a gradation conversion rate c (x, y), a pixel value fd of a processed image
(X, y), first image f0 (x, y), pixel value f1 (x, y) of second image, smoothing of second image (low frequency)
The pixel value fus (x, y) of the image and the coordinates (x,
y)

[0032]

(Equation 7)

Has a relationship represented by the following formula:

[0034]

(Equation 8)

Is represented by the following equation (10).

The image processing by the fourth method has an effect that it can be easily combined with the gradation conversion processing and the like, and has an effect that it can be performed simultaneously with the gradation conversion processing, and that the adjustment of the high frequency component can be performed at the same time. Have.

In addition to the image processing by the first to fourth methods as described above, there is a so-called sharpening processing for facilitating observation of the fine structure of the image. For example, as the sharpening processing, the original image f (x, y), the processed image fp
(X, y), the low-frequency image S _US 2 (x, y) of the original image, and a constant C I than,

[0038]

(Equation 9)

There is a process represented by the following equation (11).

[0040] However, in the processing represented by the formula (11), from the original image f (x, y), the low-frequency image S _US 2 (x, y) of the original image is subtracted to produce a high-frequency image Processing is performed. At this time, a high-frequency component that causes overshoot or undershoot may occur in a portion of the high-frequency image corresponding to the edge portion of the original image f (x, y). In this case, the high-frequency component is added to the original image, the original image after gradation conversion, or the low-frequency image in the above processing, and as a result, after the processing in which overshoot or undershoot occurs. Will be obtained.

[0041] Here, the overshoot and undershoot original image f (x, y) low-frequency image S _US 2 (x, y) of the original image from the absolute value in the high-frequency component obtained by subtracting the A component whose absolute value is positive is overshoot, and a component whose absolute value is negative is undershoot. Hereinafter, when simply referred to as overshoot,
In principle, overshoot and undershoot are generically referred to.

Therefore, as a method for suppressing the above-mentioned overshoot, for example, in Japanese Patent Application Laid-Open No. H11-124747, the high-frequency component of the target image is further subjected to gradation conversion so that the component having a large absolute value of the high-frequency component is obtained. There has been proposed a method of suppressing a portion corresponding to an overshoot. In addition, a method of suppressing the above-described overshoot by creating a low-frequency component using an intermediate value filter or a morphological filter has been proposed.

[0043]

However, in the conventional image processing method for suppressing the overshoot described above, for example, in the image processing method described in Japanese Patent Application Laid-Open No. Although the shoot can be appropriately suppressed, the information amount of the high frequency component itself is lost when the overshoot having a large amplitude is suppressed. For this reason, although the overshoot is suppressed, there is a problem that the fine structure of the image in the region where the overshoot is suppressed is difficult to see.

In an image processing method using an intermediate value filter or a morphological filter, a low frequency component is created by the filter, so that overshoot is less likely to occur, but much processing time (calculation time) is required. In addition, there is a problem that the restorability of the fine structure is deteriorated depending on the region where the low frequency component is created.

Therefore, the present invention has been made to eliminate the above-mentioned disadvantages, and it is intended to appropriately suppress the overshoot and not lose the information of the fine structure in the region where the overshoot is suppressed. An image processing apparatus, an image processing system, an image processing method, a program for realizing functions of the apparatus or the system, and a program for executing processing steps of the method, which can provide a good processed image by a configuration to be realized. And a storage medium in which the program is stored in a computer-readable manner.

[0046]

For such a purpose,
According to a first aspect, a first high-frequency component acquisition unit that acquires a first high-frequency component from a target image, and a first high-frequency component obtained by the first high-frequency component acquisition unit, the first high-frequency component acquisition unit acquires Area detecting means for detecting an overshoot area, second high frequency component obtaining means for obtaining a second high frequency component based on the overshoot area obtained by the area detecting means, and obtaining the first high frequency component Frequency component replacement means for replacing the first high frequency component obtained by the means with the second high frequency component obtained by the second high frequency component acquisition means.

According to a second aspect of the present invention, there is provided a first high-frequency component obtaining means for obtaining a first high-frequency component from a target image;
Area detecting means for detecting an overshoot area of the target image based on the first high-frequency component obtained by the high-frequency component obtaining means, and a second area detecting means for detecting an overshoot area obtained by the area detecting means. A second high-frequency component obtaining means for obtaining a high-frequency component, and a second high-frequency component obtained by the second high-frequency component obtaining means, the first high-frequency component obtained by the first high-frequency component obtaining means. And a post-processing image acquisition unit that acquires a target image for output based on the high-frequency component replaced by the frequency component replacement unit.

According to a third aspect, in the second aspect,
The post-processing image obtaining means obtains, as the output target image, a result obtained by subjecting the high-frequency component replaced by the frequency component replacing means to predetermined conversion and adding the result to a target image.

According to a fourth aspect, in the third aspect,
The target image includes at least one of an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and an image after gradation conversion of the low-frequency image. I do.

In a fifth aspect based on the first or second aspect, the second high frequency component acquiring means converts the high frequency component deviated to a higher frequency range than the first high frequency component into the second high frequency component. It is characterized by being acquired as.

In a sixth aspect based on the first or second aspect, the second high frequency component acquiring means compresses at least a predetermined low frequency component contained in the first high frequency component to thereby form the second high frequency component. 2 is obtained as the high frequency component.

According to a seventh aspect, in the sixth aspect,
The second high frequency component acquisition means performs dynamic range compression on the first high frequency component.

In an eighth aspect based on the first or second aspect, the second high-frequency component obtaining means includes a smoothed image obtained by using at least one of an intermediate value filter and a morphological filter. Is used to acquire the second high frequency component.

In a ninth aspect based on the first or second aspect, the second high frequency component obtaining means obtains the second high frequency component only for the overshoot area obtained by the area detecting means. The frequency component replacing means converts the first high frequency component obtained by the first high frequency component obtaining means corresponding to the overshoot region into a second high frequency component obtained by the second high frequency component obtaining means. It is characterized by replacement with a high frequency component.

According to a tenth aspect, at least a first high-frequency component obtaining means for obtaining a first high-frequency component from a target image and at least a first high-frequency component obtained by the first high-frequency component obtaining means are provided. And a second high-frequency component obtaining unit that obtains a second high-frequency component by performing a predetermined process including a process of reducing the predetermined low-frequency component.

According to an eleventh aspect of the present invention, at least a first high-frequency component obtaining means for obtaining a first high-frequency component from a target image and at least a first high-frequency component obtained by the first high-frequency component obtaining means are provided. A second high-frequency component obtaining unit that obtains a second high-frequency component by performing a predetermined process including a process of reducing the predetermined low-frequency component; and a high-frequency component obtained by the second high-frequency component obtaining unit. And a post-processing image acquisition means for acquiring a target image for output based on the image data.

In a twelfth aspect based on the eleventh aspect, the processed image acquiring means performs a predetermined conversion on the high-frequency component replaced by the second high-frequency component acquiring means and adds the converted high-frequency component to the target image. A result is obtained as the output target image.

In a thirteenth aspect based on the twelfth aspect, the target image is an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and a low-frequency image of the low-frequency image. It is characterized by including at least one of the images after gradation conversion.

According to a fourteenth aspect, in the tenth or eleventh aspect, the second high frequency component obtaining means is configured to at least apply the first high frequency component obtained by the first high frequency component obtaining means to the first high frequency component. A second high-frequency component is obtained by performing a predetermined process including a process of reducing a low-frequency component exceeding a predetermined threshold among the predetermined low-frequency components.

In a fifteenth aspect based on the tenth aspect or the eleventh aspect, the second high frequency component obtaining means includes at least a signal corresponding to the first high frequency component obtained by the first high frequency component obtaining means. A second high-frequency component is obtained by performing a predetermined process including a process of reducing a low-frequency component exceeding a predetermined threshold among predetermined low-frequency components and a process of adjusting the predetermined high-frequency component. .

A sixteenth invention is an image processing system in which a plurality of devices are communicably connected to each other, wherein at least one of the plurality of devices is the first to the fifth invention.
15. It has the function of the image processing device according to any one of 15.

According to a seventeenth aspect, a first high-frequency component obtaining step of obtaining a first high-frequency component from a target image, and a first high-frequency component obtained by the first high-frequency component obtaining step are performed based on the first high-frequency component obtaining step. An area detecting step of detecting an overshoot area of the target image; a second high-frequency component obtaining step of obtaining a second high-frequency component based on the overshoot area obtained in the area detecting step; A frequency component replacing step of replacing the first high frequency component obtained in the high frequency component obtaining step with the second high frequency component obtained in the second high frequency component obtaining step.

An eighteenth invention is characterized in that, in the seventeenth invention, a post-processing image acquisition step of acquiring an output target image based on the high-frequency component replaced in the frequency component replacement step is provided. I do.

According to a nineteenth aspect, a first high-frequency component generating step for generating a first high-frequency component of a target image, and a high-frequency component generated by the first high-frequency component generating step are analyzed to analyze the target image. An area detection step of detecting an overshoot area, a second high-frequency component creation step of creating a second high-frequency component of the target image, and the first high frequency corresponding to the overshoot area detected by the area detection step A frequency component replacing step of replacing the first high frequency component created by the component creating step with the second high frequency component created by the second high frequency component creating step.

According to a twentieth aspect, a first high-frequency component creating step for creating a first high-frequency component of a target image, and a high-frequency component created by the first high-frequency component creating step are analyzed to analyze the target image. An area detection step of detecting an overshoot area, a second high-frequency component creation step of creating a second high-frequency component of the target image, and the first high frequency corresponding to the overshoot area detected by the area detection step A frequency component replacing step of replacing the first high frequency component created by the component creating step with the second high frequency component created by the second high frequency component creating step; and a high frequency replaced by the frequency component replacing step. A post-processing image obtaining step of performing predetermined conversion on the component, adding the result to the target image, and obtaining a post-processing image. And wherein the Mukoto.

In a twenty-first aspect based on the nineteenth or twentieth aspect, the target image is an input image, an image obtained by converting the gradation of the input image, a low-frequency image obtained from the input image, and the low-frequency image. It is characterized by including at least one of the images after gradation conversion of the image.

In a twenty-second aspect based on the nineteenth or twentieth aspect, the second high-frequency component creating step includes the step of converting the second high-frequency component into the first high-frequency component created by the first high-frequency component creating step. And a step of converting the high-frequency component into a high-frequency component that is more deviated from the high-frequency region.

According to a twenty-third aspect, in the nineteenth or twentieth aspect, the second high frequency component creating step includes the step of converting the second high frequency component into the first high frequency component created by the first high frequency component creating step. And converting the high-frequency component into a high-frequency component subjected to dynamic range compression.

In a twenty-fourth aspect based on the twenty-third aspect, the second high-frequency component generation step includes the step of converting the smoothed image used for performing the dynamic range compression by using an intermediate value filter or a morphological filter. The method includes the step of creating.

In a twenty-fifth aspect based on the nineteenth or twentieth aspect, the second high-frequency component creating step includes the step of converting the second high-frequency component to a smoothness obtained by an intermediate value filter or a morphological filter. Characterized in that the method includes a step of creating from a converted image.

The twenty-sixth invention is directed to the nineteenth, twentieth and twenty-fourth embodiments.
Alternatively, in the invention according to the twenty-fifth aspect, the second high-frequency component generation step includes a step of generating the second high-frequency component only for the overshoot region detected by the region detection step.

According to a twenty-seventh aspect, at least a first high-frequency component obtaining step of obtaining a first high-frequency component from a target image and at least a first high-frequency component obtained by the first high-frequency component obtaining step are performed. By performing a predetermined process including a process of reducing the predetermined low frequency component, the second
And a second high frequency component obtaining step of obtaining the high frequency component.

According to a twenty-eighth aspect, at least a first high-frequency component obtaining step for obtaining a first high-frequency component from a target image and at least a first high-frequency component obtained by the first high-frequency component obtaining step are performed. By performing a predetermined process including a process of reducing the predetermined low frequency component, the second
A second high frequency component obtaining step of obtaining a high frequency component of
A post-processing image acquisition step of acquiring an output target image based on the high-frequency component obtained in the second high-frequency component acquisition step.

In a twenty-ninth aspect based on the twenty-eighth aspect, in the post-processing image obtaining step, the high-frequency component obtained in the second high-frequency component obtaining step is subjected to a predetermined conversion and added to a target image. A result is obtained as the output target image.

In a thirtieth aspect based on the twenty-ninth aspect, the target image is an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and an image of the low-frequency image. It is characterized by including at least one of the images after gradation conversion.

According to a thirty-first aspect, in the twenty-seventh aspect or the twenty-eighth aspect, the second high frequency component obtaining step includes at least the first high frequency component obtained in the first high frequency component obtaining step. A second high-frequency component is obtained by performing a predetermined process including a process of reducing a low-frequency component exceeding a predetermined threshold among the predetermined low-frequency components.

According to a thirty-second aspect, in the twenty-seventh aspect or the twenty-eighth aspect, the second high frequency component obtaining step includes at least the first high frequency component obtained in the first high frequency component obtaining step. A second high-frequency component is obtained by performing a predetermined process including a process of reducing a low-frequency component exceeding a predetermined threshold among predetermined low-frequency components and a process of adjusting the predetermined high-frequency component. .

According to a thirty-third aspect, a program for causing a computer to realize the functions of the image processing apparatus according to any one of claims 1 to 15 or the functions of the image processing system according to claim 16 is computer-readable. It is characterized by being recorded on a storage medium.

According to a thirty-fourth aspect, a program for causing a computer to execute the processing steps of the image processing method according to any one of claims 17 to 32 is recorded on a computer-readable storage medium. .

A thirty-fifth aspect of the present invention is a program for causing a computer to realize the functions of the image processing apparatus according to any one of claims 1 to 15 or the functions of the image processing system according to claim 16. And

According to a thirty-sixth aspect, the present invention is a program for causing a computer to execute the processing steps of the image processing method according to any one of claims 17 to 32.

[0082]

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

[First Embodiment] The present invention is applied to, for example, an X-ray imaging apparatus 100 as shown in FIG. The X-ray imaging apparatus 100 of the present embodiment is configured to appropriately prevent high-frequency components of a target image from being overshot or the like by changing the high-frequency component of the target image by the configuration and operation described below.

<Structure of X-ray imaging apparatus 100> As shown in FIG. 1, the X-ray imaging apparatus 100
A line generating circuit (in the drawing, a section) 101 and a two-dimensional X-ray sensor 104 on which X-ray light transmitted through the subject 103 is formed.
, A data collection circuit (in the drawing,...) 105 for collecting captured images output from the two-dimensional X-ray sensor 104, and a preprocessing circuit (the drawing) for performing preprocessing on the captured images collected by the data collection circuit 105. And...) 106 and a main memory 1 for storing various information such as a captured image after pre-processing by the pre-processing circuit 106 and a processing program for executing various processes.
09, an operation panel 110 for giving instructions such as execution of X-ray imaging and various settings to the apparatus, and a preprocessing circuit 106
An image processing circuit 111 that performs image processing on the captured image after the pre-processing in the above, and an output circuit 118 that displays or outputs the image or the like after the processing in the image processing circuit 111
A data collection circuit 105, a preprocessing circuit 106, an image processing circuit 111, an output circuit 118, a CPU 108,
The main memory 109 and the operation panel 110 are each connected to the CPU bus 107 and are configured to be able to exchange data with each other.

The image processing circuit 111 includes a pre-processing circuit 106
A first high-frequency component generation circuit 112 that generates a first high-frequency component from the image that has been subjected to the pre-processing in step (1) An area detection circuit 113 for detecting a generated area, a second high-frequency component generation circuit 114 for generating a second high-frequency component corresponding to the detection area obtained by the area detection circuit 113, and a first high-frequency component generation Circuit 112
Region detection circuit 113 of the first high-frequency components obtained in
A frequency component replacement circuit 115 for replacing the high frequency component corresponding to the detection region obtained by the above with the second high frequency component obtained by the second high frequency component creation circuit 114;
And a post-processing image circuit 116 that adds the replaced high-frequency component obtained in step 15 to the original image, low-frequency image, or image after gradation conversion to obtain a processed image.

<Operation of X-Ray Imaging Apparatus 100> The main memory 109 stores in advance data and processing programs required for the CPU 108 to execute various control processes, and includes a work memory for the CPU 108 to work. It is a thing. As a processing program stored in the main memory 109, particularly, a processing program for image processing, for example, a processing program according to the flowchart in FIG. 2 is used here. Therefore, the CPU 108
The processing program and the like shown in FIG.
09 to be read and executed, the operation panel 110
This device 10 as described below according to the operation from
0 overall operation control.

Step S200: First, the X-ray generation circuit 1
Numeral 01 radiates an X-ray beam 102 to a subject (test object) 103. The X-ray beam 102 emitted from the X-ray generation circuit 101 passes through the subject 103 while attenuating, reaches the two-dimensional X-ray sensor 104, and is output as an X-ray image by the two-dimensional X-ray sensor 104. Is done. 2
Examples of the X-ray image output from the dimensional X-ray sensor 104 include a human body image such as a chest image.

Next, the data collection circuit 105 performs two-dimensional X
The X-ray image output from the line sensor 104 is converted into an electric signal and supplied to the pre-processing circuit 106. The preprocessing circuit 106 performs preprocessing such as offset correction processing and gain correction processing on the signal (X-ray image signal) from the data collection circuit 105. The X-ray image signal pre-processed by the pre-processing circuit 106 is used as input image information by the CPU 1.
Under the control of 08, the data is transferred to the main memory 109 and the image processing circuit 111 via the CPU bus 115.

Step S 201: In the image processing circuit 111, the gradation conversion circuit (not shown) applies a gradation conversion function F to the image f (x, y) processed by the pre-processing circuit 106.
1 ()

[0090]

(Equation 10)

A gradation conversion process is performed according to the following equation (12) to obtain an original image (original image) f0 (x, y). still,
In the above equation (12), “x” and “y” represent an X coordinate and a Y coordinate, respectively.

Step S202: The first high frequency component generation circuit 112

[0093]

[Equation 11]

As shown in equations (13) and (14), the original image f (x, y) obtained in step S201
By subtracting the low frequency image f _us (x, y) from
The first high frequency component h1 (x, y) is obtained.

The low frequency image f in the above equation (13)
_us (x, y) is created by moving average of the original image f (x, y) as shown in the above equation (14), and “d1” in the above equation (14) is Hereinafter, it is simply referred to as a mask size.

Step S203: area detection circuit 113
Detects a region where the absolute value of the high-frequency component h1 (x, y) obtained by the first high-frequency component generation circuit 112 is equal to or greater than a predetermined threshold Th, and detects the detected region (a region where overshoot is likely to occur; Hereinafter, the coordinates (x, y) of the “overshoot area” are simply stored in the main memory 1.
09. Thus, the high-frequency component h1 (x,
The region where the absolute value of y) is equal to or greater than the fixed threshold Th is detected as the overshoot region because the high-frequency component causing overshoot has a larger absolute value than the normal high-frequency component.

Step S204: The second high-frequency component generation circuit 114 generates the high-frequency component based on the coordinates of the overshoot area stored in the main memory 109.

[0098]

(Equation 12)

According to equations (15) and (16), the second
To obtain the high-frequency component h2 (x, y).

Here, “d2” in the above equation (16)
Is simply referred to as a mask size hereinafter. Mask size d2
Has a relationship of d2 <d1 with the mask size d1 in the above equation (14). Thereby, the second high frequency component h2
(X, y) has a higher frequency component than the first high frequency component h1 (x, y). Further, due to this relationship, the second high-frequency component h2 (x, y) reduces a component that causes an overshoot than the first high-frequency component h1 (x, y).

If the mask size d2 is set to an excessively small value, the resilience of the fine structure in the target image may be reduced. It is desirable to determine d2. In this case, the resilience of the medium frequency is deteriorated as compared with the case of using the mask size d1 of the normal size, but the resilience of the fine structure does not decrease.
Overshoot can be suppressed.

Further, “f _us 2 (x,
y) ”is a low-frequency image (smoothed image) represented by the above equation (16), and this low-frequency image f _us 2 (x,
As another acquisition method of y), for example, the following methods (1) and (2) can be mentioned.

Method (1): Method Using Morphological Filter (Morphological Operation) In this method (1), a morphological filter (morphological operation) represented by the following equations (17) to (20) is used. ), A low-frequency image f _us 2 (x, y) is generated.

[0104]

(Equation 13)

In the above equations (17) to (20), “D
(X, y) "is a disc-shaped filter represented by the following equation (21), and is selected according to the target image, with" r1 "being an arbitrary constant.

[0106]

[Equation 14]

Method (2): Method Using Intermediate Filter In this method (2), a low-frequency image f _us 2 (x, y) is generated using an intermediate filter. Specifically, the coordinates (x,
y), the original image f within a certain distance d2
(X, y) is sorted, and the pixel value in the middle is f _us 2
(X, y).

Method (1) or method (2) as described above
The low-frequency image f _us 2 (x, y) obtained by using is for preserving the edge structure. Then, the above equation (15)
As indicated, the low-frequency image f _us 2 (x, y) a second high frequency component h2 (x, y) obtained with the ones that hardly de component underlying the overshoot is there.
Also, by generating a low-frequency image f _us 2 (x, y) obtained using a morphological filter or an intermediate value filter only for an area in which overshoot is likely to occur, the entire target image is generated. Processing time can be reduced as compared with a case where a morphological filter or an intermediate value filter is applied.

Step S205: Frequency component replacement circuit 1
Reference numeral 15 denotes the first high-frequency component h1 obtained by the first high-frequency component generation circuit 112 in step S202.
(X, y)

[0110]

(Equation 15)

Based on the relational expression (22), the second high-frequency component h2 (x, y) is replaced. The above relational expression (2)
2), the first high-frequency component h1 (x,
In y), the component whose absolute value is equal to or greater than the fixed threshold Th is replaced with the second high-frequency component h2 (x, y).

Step S206: Image processing circuit 1 after processing
16 is

[0113]

(Equation 16)

According to the following equation (23), the first high-frequency component h1 after replacement obtained by the frequency component replacement circuit 115 is obtained.
By adding (x, y) to, for example, the original image f0 (x, y), the processed image fd (x, y) is obtained.

In step S206, the replaced first high-frequency component h obtained by the frequency component replacement circuit 115 is output.
The image to which 1 (x, y) is added includes the original image f
The present invention is not limited to 0 (x, y). For example, a pre-processed image, a low-frequency image, or an image obtained by performing gradation conversion on a low-frequency image may be used.

Step S207: The processed image fd (x, x, y) obtained by the image processing circuit 111 as described above.
y) is output by the output circuit 118 for display output or film output.

As described above, in the present embodiment, an overshoot region is detected by analyzing the first high-frequency component obtained from the original image, and the first high-frequency component in the overshoot region is over-detected. Since the configuration is such that high-frequency components (second high-frequency components) that do not easily cause a shoot are replaced, a good processed image in which overshoot is suppressed can be provided.

Further, only in the overshoot region, the first high-frequency component is replaced with a high-frequency component (a second high-frequency component having a smaller mask size d2) depending on the higher-frequency region. Thus, overshoot can be suppressed without reducing the resilience of the fine structure.

Further, as a method of generating the second high-frequency component, a method using a morphological filter or an intermediate value filter is used, and the processing is performed only on the overshoot region. It is possible to expect further suppression of overshoot, as compared with a case where a morphological filter or an intermediate value filter is applied to the entire target image.
Processing time can be reduced.

[Second Embodiment] In this embodiment, the operation of the X-ray imaging apparatus 100 shown in FIG.
The operation is performed according to the flowchart of FIG.

In the flowchart shown in FIG.
Steps that execute the same processes as those in the flowchart of FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

Steps S200 to S203: Similarly to the first embodiment, the image obtained by the X-ray photography is processed by the preprocessing circuit 106, and the image f (x, y) after the processing is processed. Is transferred to the image processing circuit 111 (step S200). The image processing circuit 111 outputs the image f
An original image (original image) f0 (x, y) is obtained by performing a gradation conversion process on (x, y) (step S20).
1) The first high-frequency component generation circuit 112 obtains the first high-frequency component h1 (x, y) from the original image f (x, y) (step S202). An overshoot region is detected from the high frequency component h1 (x, y) (step S203).

Note that step S203 is not essential, and is necessary when a low-frequency image is created only in an area corresponding to the overshoot area as described later, but is not always necessary in other cases.

Step S301: The second high-frequency component generation circuit 114 converts the result of the dynamic range compression of the first high-frequency component h1 (x, y) into the second high-frequency component h2.
(X, y).

As the processing method of the dynamic range compression, any method can be applied. In the present embodiment, as an example, the method described in Japanese Patent Laid-Open No.
The method described in No. 72283 or the like is used. Therefore, here, the absolute value of the first high-frequency component h1 (x, y) is
The dynamic range compression processing is performed so that the dynamic range of the fixed threshold Th or more, that is, only the overshoot region, is compressed. The compression ratio at this time is arbitrary, but in the present embodiment, as an example, the maximum compression ratio is set. Thereby, the first threshold value equal to or greater than the fixed threshold value Th
Is compressed as much as possible. For example, the dynamic range of the first high-frequency component h1 (x, y) is compressed such that a predetermined low-frequency component in the first high-frequency component h1 (x, y) is clipped to be equal to or less than a substantially constant threshold Th.

Here, for a low-frequency image (smoothed image) f _us 3 (x, y) used for dynamic range compression,
As the acquisition method, for example, the following method (1)
-Method (3).

Method (1): Method Based on Coordinates of Overshoot Area In this method (1), based on the coordinates of the overshoot area stored in the main memory 109,

[0128]

[Equation 17]

According to the following equation (24), the low-frequency image f _us 3
(X, y) is obtained. “D” in the above equation (24)
2 ″ is a mask size, and has a relationship of d2 <d1 with the mask size d1 in the above equation (14).

Method (2): Method Using Morphological Filter In this method (2), a low-frequency image f _{us is obtained} by a morphological filter represented by the following equations (25) to (28). 3 (x, y) is generated.

[0131]

(Equation 18)

In the above formulas (25) to (28), “D
(X, y) "is a disc-shaped filter represented by the following equation (29), and is selected according to the target image, with" r1 "being an arbitrary constant.

[0133]

[Equation 19]

Method (3): Method Using Intermediate Filter In this method (3), a low-frequency image f _us 3 (x, y) is generated using an intermediate filter. Specifically, the coordinates (x,
y), the original image f within a certain distance d2
Sort (x, y) and find the middle pixel value fus3
(X, y).

Method (2) or method (3) as described above
Low-frequency image f _us 3 (x, y) obtained with is to store the edge structure, the low-frequency image f _us 3
The second high frequency component h2 obtained using (x, y)
(X, y) is a component in which a component that causes overshoot is hardly generated. In addition, a low-frequency image f _us 3 acquired using a morphological filter or an intermediate value filter only for an area where overshoot is likely to occur.
By generating (x, y), the processing time can be reduced as compared with a case where a morphological filter or an intermediate value filter is applied to the entire target image.

Step S302: Image processing circuit 1 after processing
16 is

[0137]

(Equation 20)

The processed image fd (x, y) is obtained by the following equations (30) to (32).

In the above formulas (30) to (32),
“H1 (x, y)” is the second high-frequency component generation circuit 11
4 shows the first high-frequency component (second high-frequency component) after the dynamic range compression. In addition, the above equation (3)
0) and (31) indicate the sharpening process, and the above equation (3)
2) shows a dynamic range compression process. Also,
In the above equation (32), “F2 ()” indicates a function for performing gradation conversion of a low-frequency image.

Step S207: The processed image fd (x, x, x) obtained by the image processing circuit 111 as described above.
y) is output by the output circuit 118 for display output or film output.

As described above, in the present embodiment, as the second high frequency component, a component obtained by performing a dynamic range compression on the first high frequency component is used. In other words, since the predetermined low-frequency component in the first high-frequency component corresponding to the region where overshoot is likely to occur is compressed, the overshoot can be suppressed without impairing the resilience of the fine structure. Further, as the first high frequency component compression method, a predetermined low frequency component is compressed and a dynamic range compression method capable of adjusting the predetermined high frequency component is employed, so that the first high frequency component can be freely changed. Thus, it is possible to obtain the second high-frequency component capable of suppressing the overshoot without impairing the resilience of the fine structure. Furthermore, if a low-frequency image used for dynamic range compression is created using a morphological filter or an intermediate value filter only in an area where overshoot is likely to occur, overshoot can be effectively suppressed. And the processing time can be reduced as compared with the case where a morphological filter or an intermediate value filter is used for the entire first high-frequency component image.

Further, by configuring the mask size d2 of the low-frequency image used for the dynamic range compression to be smaller than d1, the overshoot can be suppressed.

Further, the first high-frequency component is replaced by a high-frequency component (a second high-frequency component with a smaller mask size d2) in a higher-frequency region in a region where overshoot is likely to occur. In addition, overshoot can be suppressed without lowering the resilience of the fine structure.

An object of the present invention is to supply a storage medium storing program codes of software for realizing the functions of the host and the terminal according to the first and second embodiments to a system or an apparatus, and to provide the system or apparatus with the storage medium. By reading and executing the program code stored in the storage medium by the computer (or CPU or MPU) of the device,
It goes without saying that this is achieved. In this case, the program code itself read from the storage medium is the first and second program codes.
The functions of the embodiment are realized, and the program code and a storage medium storing the program code constitute the present invention. As a storage medium for supplying the program code, a ROM, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, or the like can be used. it can. The functions of the first and second embodiments are realized by executing the program code read by the computer, and the OS running on the computer based on the instruction of the program code. Perform part or all of the actual processing, and
Needless to say, a case where the functions of the second embodiment are realized is also included. Further, after the program code read from the storage medium is written to a memory provided in an extension function board inserted into the computer or a function extension unit connected to the computer, the function extension is performed based on the instruction of the program code. It goes without saying that the CPU included in the board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the first and second embodiments.

[0145]

As described above, according to the present invention, in the target image (such as an image obtained by radiography), the first
Is replaced with the second high-frequency component obtained based on the overshoot region. Specifically, for example, a second high-frequency component is acquired as a high-frequency component in which overshoot is unlikely to occur based on the overshoot region, and the first high-frequency component corresponding to the overshoot region is obtained using the second high-frequency component. Replace Thereby, it is possible to provide a good processed image of the target image (an image for display output or film output, etc.) in which overshoot is suppressed.

Further, for only the overshoot region, the second high-frequency component is transformed into a high-frequency component (a high-frequency component obtained by reducing a predetermined low-frequency component from the first high-frequency component). And so on), it is possible to suppress the overshoot without deteriorating the resilience of the fine structure in the target image.

When the second high frequency component is configured to be a component obtained by compressing the first high frequency component into a dynamic range, overshoot is suppressed while restoring the fine structure in the target image is maintained. be able to. Further, when the first high-frequency component is compressed by using a predetermined low-frequency component in the first high-frequency component and dynamic range compression capable of adjusting the predetermined high-frequency component is used, overshoot is suppressed. And a good post-processing image can be obtained.

The acquisition of the second high frequency component and the first
If the processing for replacement of the high frequency component is performed only for the overshoot region, an excessive increase in processing time can be avoided.

Further, the smoothed image used for obtaining the second high-frequency component is obtained using a filter which does not easily cause overshoot, such as an intermediate value filter (intermediate value operation) or a morphological filter (morphological operation). With such a configuration, it is possible to acquire a good processed image in which overshoot is suppressed.

The acquisition of the second high frequency component and the first
And a smoothing image used for obtaining the second high-frequency component is converted to an intermediate value filter (intermediate value operation) or a morphological filter. When the acquisition is performed using a filter that does not easily cause overshoot such as (morphological operation), it is possible to acquire a good processed image in which overshoot is suppressed without excessively increasing the processing time. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an X-ray imaging apparatus to which the present invention is applied in a first embodiment.

FIG. 2 is a flowchart illustrating an operation of the X-ray imaging apparatus.

FIG. 3 is a flowchart illustrating an operation of the X-ray imaging apparatus according to the second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 X-ray imaging apparatus 101 X-ray generation circuit 102 X-ray beam 103 subject 104 two-dimensional X-ray sensor 105 data collection circuit 106 preprocessing circuit 107 CPU bus 108 CPU 109 main memory 110 operation panel 111 image processing circuit 112 first high frequency Component creation circuit 113 Area detection circuit 114 Second high frequency component creation circuit 115 Frequency component replacement circuit 116 Image processing circuit after processing 118 Output circuit

Continued on the front page F term (reference) 5B057 AA08 BA03 CA02 CA08 CA12 CA16 CB02 CB08 CB12 CB16 CC01 CE03 CE06 CE08 DA08 DA17 5C077 LL19 MP01 NN02 PP03 PP10 TT10

Claims (36)

[Claims] A first high-frequency component acquisition unit for acquiring a first high-frequency component from the target image; and an over-range of the target image based on the first high-frequency component obtained by the first high-frequency component acquisition unit. Area detecting means for detecting a shot area; second high frequency component obtaining means for obtaining a second high frequency component based on the overshoot area obtained by the area detecting means; and first high frequency component obtaining means Is converted to the second high-frequency component obtained by the second high-frequency component obtaining means.
An image processing apparatus comprising: a frequency component replacing unit that replaces a high frequency component with a high frequency component. A first high-frequency component acquisition unit that acquires a first high-frequency component from the target image; and an over-range of the target image based on the first high-frequency component obtained by the first high-frequency component acquisition unit. Area detecting means for detecting a shoot area; second high frequency component obtaining means for obtaining a second high frequency component based on the overshoot area obtained by the area detecting means; and the first high frequency component obtaining means Is converted to the second high-frequency component obtained by the second high-frequency component obtaining means.
Image processing, comprising: a frequency component replacing unit that replaces the high frequency component; and a post-processing image acquiring unit that acquires a target image for output based on the high frequency component replaced by the frequency component replacing unit. apparatus. 3. The post-processing image obtaining means obtains, as the output target image, a result obtained by subjecting the high-frequency component replaced by the frequency component replacing means to predetermined conversion and adding the result to a target image. 3. The image processing apparatus according to claim 2, wherein: 4. The target image is at least one of an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and an image after gradation conversion of the low-frequency image. The image processing apparatus according to claim 3, wherein the image processing apparatus includes: 5. The apparatus according to claim 1, wherein said second high frequency component acquiring means acquires a high frequency component deviated by a higher frequency range than said first high frequency component as said second high frequency component. An image processing apparatus as described in the above. 6. The apparatus according to claim 1, wherein said second high-frequency component obtaining means compresses at least a predetermined low-frequency component included in said first high-frequency component and obtains said second high-frequency component as said second high-frequency component. Item 3. The image processing device according to item 1 or 2. 7. The image processing apparatus according to claim 6, wherein said second high frequency component acquiring means performs dynamic range compression on said first high frequency component. 8. The second high-frequency component obtaining means obtains the second high-frequency component using a smoothed image obtained by using at least one of an intermediate value filter and a morphological filter. 3. The image processing apparatus according to claim 1, wherein: 9. The second high-frequency component acquiring means acquires the second high-frequency component only for the overshoot area obtained by the area detecting means, and the frequency component replacing means comprises: 2. The method according to claim 1, wherein the first high-frequency component obtained by the first high-frequency component obtaining means corresponding to the first high-frequency component obtaining means is replaced with a second high-frequency component obtained by the second high-frequency component obtaining means. Or the image processing apparatus according to 2. 10. A first high-frequency component obtaining means for obtaining a first high-frequency component from a target image, and at least a predetermined low-frequency component of the first high-frequency component obtained by the first high-frequency component obtaining means. An image processing apparatus comprising: a second high-frequency component acquisition unit that obtains a second high-frequency component by performing a predetermined process including a process of reducing a frequency component. 11. A first high-frequency component obtaining means for obtaining a first high-frequency component from a target image, and at least a predetermined low-frequency component with respect to the first high-frequency component obtained by the first high-frequency component obtaining means. A second high-frequency component obtaining unit that obtains a second high-frequency component by performing a predetermined process including a process of reducing the frequency component; and an output based on the high-frequency component obtained by the second high-frequency component obtaining unit. An image processing apparatus comprising: a post-processing image acquisition unit that acquires a target image for use. 12. The image processing device according to claim 1, wherein
2. A result obtained by subjecting the high-frequency component replaced by the high-frequency component obtaining means to predetermined conversion and adding the result to a target image is obtained as the target image for output.
2. The image processing device according to 1. 13. The target image includes at least one of an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and an image after gradation conversion of the low-frequency image. The image processing apparatus according to claim 12, wherein the image processing apparatus includes: 14. The second high-frequency component obtaining means, for the first high-frequency component obtained by the first high-frequency component obtaining means, includes a low-frequency component that exceeds a predetermined threshold of at least the predetermined low-frequency component. The image processing apparatus according to claim 10, wherein a second high-frequency component is obtained by performing a predetermined process including a process of reducing a component. 15. The second high-frequency component obtaining means, for the first high-frequency component obtained by the first high-frequency component obtaining means, includes a low-frequency component that exceeds a predetermined threshold among at least the predetermined low-frequency components. The image processing apparatus according to claim 10, wherein a second high-frequency component is obtained by performing a predetermined process including a process of reducing the component and a process of adjusting the predetermined high-frequency component. 16. An image processing system in which a plurality of devices are communicably connected to each other, wherein at least one of the plurality of devices is the image processing apparatus according to any one of claims 1 to 15. An image processing system having the following functions. 17. A first high-frequency component obtaining step of obtaining a first high-frequency component from a target image, and a first high-frequency component obtaining step obtained by the first high-frequency component obtaining step.
Detecting an overshoot area of the target image based on the high-frequency component of the above, and obtaining a second high-frequency component based on the overshoot area obtained by the area detecting step And a first high-frequency component obtaining step.
A frequency component replacing step of replacing the high frequency component of the above with the second high frequency component obtained in the second high frequency component obtaining step. 18. The image processing method according to claim 17, further comprising a post-processing image obtaining step of obtaining a target image for output based on the high-frequency component replaced by the frequency component replacing step. 19. A first high-frequency component creating step for creating a first high-frequency component of a target image; and analyzing the high-frequency component created by the first high-frequency component creating step to determine an overshoot region of the target image. An area detection step to be detected, a second high frequency component creation step for creating a second high frequency component of the target image, and a first high frequency component creation step corresponding to the overshoot area detected by the area detection step. A frequency component replacement step of replacing the created first high frequency component with the second high frequency component created in the second high frequency component creation step. 20. A first high-frequency component creation step for creating a first high-frequency component of the target image, and analyzing the high-frequency component created by the first high-frequency component creation step to determine an overshoot region of the target image. An area detecting step to be detected, a second high-frequency component creating step for creating a second high-frequency component of the target image, and the first high-frequency component creating step corresponding to the overshoot area detected by the area detecting step. A frequency component replacement step of replacing the created first high frequency component with the second high frequency component created by the second high frequency component creation step; and a predetermined high frequency component replaced by the high frequency component replaced by the frequency component replacement step. A post-processing image obtaining step of performing conversion, adding to the target image, and obtaining a processed image. Image processing method 21. The target image may be at least one of an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and an image after gradation conversion of the low-frequency image. 21. The method according to claim 19, wherein
The image processing method described in the above. 22. The second high-frequency component creation step, wherein the second high-frequency component is a high-frequency component that is shifted to a higher-frequency region than the first high-frequency component created by the first high-frequency component creation step. 21. The image processing method according to claim 19, further comprising a step. 23. The step of creating the second high-frequency component, wherein the second high-frequency component is converted into a high-frequency component obtained by performing a dynamic range compression on the first high-frequency component created by the first high-frequency component creation step. The image processing method according to claim 19, further comprising: 24. The method according to claim 24, wherein the second high-frequency component creating step includes a step of creating a smoothed image used for performing the dynamic range compression using an intermediate value filter or a morphological filter. Item 24. The image processing method according to Item 23. 25. The method according to claim 25, wherein the step of creating the second high-frequency component includes a step of creating the second high-frequency component from a smoothed image obtained by an intermediate value filter or a morphological filter. The image processing method according to claim 19. 26. The method according to claim 19, wherein the step of creating the second high-frequency component includes the step of creating the second high-frequency component only for the overshoot region detected by the region detection step. 2
26. The image processing method according to 0, 24 or 25. 27. A first high-frequency component obtaining step for obtaining a first high-frequency component from a target image, and a first high-frequency component obtaining step obtained by the first high-frequency component obtaining step.
A high-frequency component obtaining step of obtaining a second high-frequency component by performing a predetermined process including a process of reducing at least the predetermined low-frequency component with respect to the high-frequency component. Method. 28. A first high-frequency component obtaining step of obtaining a first high-frequency component from a target image, and a first high-frequency component obtaining step obtained by the first high-frequency component obtaining step.
A second high-frequency component obtaining step of obtaining a second high-frequency component by performing a predetermined process including a process of reducing at least the predetermined low-frequency component with respect to the high-frequency component, and the second high-frequency component obtaining step A post-processing image acquisition step of acquiring a target image for output based on the high-frequency component obtained by the method. 29. The post-processing image obtaining step includes performing a predetermined conversion on the high-frequency component obtained in the second high-frequency component obtaining step and adding the result to a target image.
29. The image processing method according to claim 28, wherein the image is acquired as the output target image. 30. The target image may be at least one of an input image, an image after gradation conversion of the input image, a low-frequency image obtained from the input image, and an image after gradation conversion of the low-frequency image. 30. The image processing method according to claim 29, comprising: 31. The second high frequency component obtaining step, wherein the first high frequency component obtaining step obtains the first high frequency component obtained in the first high frequency component obtaining step.
28. A second high frequency component is obtained by performing a predetermined process including a process of reducing at least a low frequency component exceeding a predetermined threshold among the predetermined low frequency components with respect to the high frequency component. Or the image processing method according to 28. 32. The second high frequency component obtaining step, wherein the first high frequency component obtaining step includes the first high frequency component obtaining step.
The second high frequency component is subjected to a predetermined process including a process of reducing a low frequency component exceeding a predetermined threshold among at least the predetermined low frequency component and a process of adjusting the predetermined high frequency component. 29. The image processing method according to claim 27, wherein a component is obtained. 33. A computer-readable storage medium storing a program for causing a computer to realize the functions of the image processing apparatus according to claim 1 or the functions of the image processing system according to claim 16. . 34. A computer-readable storage medium storing a program for causing a computer to execute the processing steps of the image processing method according to claim 17. 35. A program for causing a computer to realize the function of the image processing apparatus according to claim 1 or the function of the image processing system according to claim 16. A program for causing a computer to execute the processing steps of the image processing method according to any one of claims 17 to 32.