JP6776171B2 - Radiation imaging device, image processing device and image processing program - Google Patents

Description

The present invention relates to a technique for processing data obtained by detecting radiation that has passed through a subject, and more particularly to a technique for correcting fluctuations caused by radiation scattering.

In the technique of irradiating a subject such as a human body with radiation such as X-rays, detecting the intensity distribution of the radiation transmitted through the subject with a detector, and capturing a transmitted image, the radiation transmitted linearly through the subject (primary). Since the scattered line image obtained from the radiation (scattered line) scattered inside the subject is added to the primary line image obtained from the line), the contrast of the acquired transmitted image is lowered and the sharpness is lowered. It is generally known that various image quality fluctuations occur.

In order to suppress this fluctuation in image quality, a grid, which is a thin alternating layer of substances with high radiation absorption and low radiation absorption, is installed between the subject and the detector, and is incident on the detector. An imaging method that keeps the scattered dose low is generally used. However, when the grid is installed, the primary dose incident on the detector is also attenuated by the grid, so that it is necessary to irradiate the subject with stronger radiation than when the grid is not used, and the exposure dose of the subject increases.

Therefore, many technologies have been proposed so far to obtain the same image quality as the transparent image (grid image) acquired by using the grid by performing signal processing on the transparent image (gridless image) acquired without using the grid. Has been done.

For example, in the technique described in Patent Document 1, a transparent image is analyzed to estimate the body thickness distribution of the subject to obtain a virtual model of the subject, and an estimated primary line image and estimated scattered radiation estimated from this virtual model. An estimated transparent image is generated by combining the images, and the body thickness distribution of the virtual model is modified so that the difference between the estimated transparent image and the actually acquired transparent image becomes small. As a result, a transparent image in which image quality fluctuation due to scattered rays is suppressed is obtained. At this time, if the difference between the estimated transparent image and the actually acquired transparent image remains even if the corrected body thickness distribution is used, the body thickness distribution of the virtual model is repeatedly corrected so that this difference becomes smaller. Perform processing.

JP-A-2015-43959

In the technique described in Patent Document 1, as described above, the body thickness distribution of the virtual model is modified by using iterative processing so that the difference between the estimated transparent image and the actually acquired transparent image becomes small.

However, when the iterative processing as in Patent Document 1 is performed, a considerable processing time is required until the final image is obtained, and as a result, the number of images obtained per unit time is reduced. Therefore, when it is desired to display a transmitted image as a moving image as in fluoroscopic imaging of an X-ray imaging device, the technique of Patent Document 1 may result in an unnatural moving image in which the movement of the subject is jerky. It is also possible to increase the number of images obtained per unit time by using a special calculation resource capable of executing high-speed processing, but in that case, the device becomes expensive.

The present invention has been made in view of such a situation, and it is possible to obtain an image in a short time in which image quality fluctuation due to scattered rays is suppressed while not performing iterative processing or greatly reducing the number of times of processing is repeated. It is in.

A brief outline of the typical inventions disclosed in the present application is as follows. That is, a typical radiation imaging device includes a radiation source that irradiates a subject with radiation, a radiation detector that detects the intensity distribution of radiation that has passed through the subject, and a radiation intensity distribution in the spatial axis direction and the time axis direction. It has an extraction unit that extracts at least one high-frequency component, and a thickness distribution calculation unit that obtains the distribution of the thickness of the subject based on the high-frequency component extracted by the extraction unit.

Further features relating to the present invention will become apparent from the description herein and the accompanying drawings. Moreover, the aspect of the present invention is achieved and realized by the combination of elements and various elements and the following detailed description and the aspect of the appended claims.

According to the present invention, it is possible to obtain a radiation image in a short time while suppressing fluctuations in image quality due to scattered rays.

It is a block diagram which shows the structure of the radiation imaging apparatus of embodiment of this invention. It is a block diagram which shows an example of the structure of the radiation imaging apparatus in a specific Embodiment 1. (a) and (b) are explanatory views explaining the primary line and the scattered line of the radiation transmitted through a subject. It is a block diagram which shows an example of the structure of the image processing part of the radiation imaging apparatus of FIG. (A) to (d) are block diagrams showing an example of the configuration of the high frequency component extraction unit of the image processing unit of FIG. 4, respectively. It is a block diagram which shows an example of the structure of the body thickness distribution calculation part of the image processing part of FIG. (A) to (c) are block diagrams showing an example of the configuration of the scattered ray image estimation unit of the image processing unit of FIG. 4, respectively. (A) and (b) are block diagrams showing an example of the configuration of the scattered ray image removing section of the image processing section of FIG. It is a flowchart which shows an example of the processing operation of the image processing part of FIG. Each of (a) and (b) is a block diagram showing an example of the configuration of an image processing unit included in the radiation imaging apparatus according to the second embodiment. It is a block diagram which shows an example of the structure of the image processing part which the radiation image pickup apparatus has in Embodiment 3. It is a block diagram which shows an example of the structure of the radiation imaging apparatus in Embodiment 4.

The present invention provides a technique for obtaining a radiation image in a short time while suppressing fluctuations in image quality due to scattered radiation.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The accompanying drawings show specific embodiments based on the principles of the present invention, but these are for the purpose of understanding the present invention and are never used for a limited interpretation of the present invention. is not.

In the present embodiment, the description is given in sufficient detail for those skilled in the art to carry out the present invention, but other implementations and embodiments are also possible, without departing from the scope and spirit of the technical idea of the present invention. It is necessary to understand that it is possible to change the structure and structure and replace various elements. Therefore, the following description should not be construed as limited to this.

Further, in the embodiment of the present invention, all the functions may be implemented by hardware, or some or all of the functions may be implemented by software running on a general-purpose computer.

Further, in all the drawings for explaining the embodiment, the same members are, in principle, given the same reference numerals, and the repeated description thereof will be omitted.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a block diagram showing a radiation imaging device according to an embodiment of the present invention. As shown in FIG. 1, the radiation imaging apparatus of the present embodiment includes a radiation source 102 that irradiates the subject 108 with radiation, a radiation detector 111 that detects the intensity distribution of radiation that has passed through the subject 108, and a radiation detector 111. With respect to the radiation intensity distribution detected by, the thickness distribution of the subject 108 is obtained based on the extraction unit 301 that extracts at least one high-frequency component in the spatial axis direction and the time axis direction and the high-frequency component extracted by the extraction unit 301. It has a thickness distribution calculation unit 302. Hereinafter, considering the case where the subject 108 is a human body as an example, the thickness distribution is referred to as a body thickness distribution, and the thickness distribution calculation unit 302 is referred to as a body thickness distribution calculation unit 302. The radiation imaging apparatus of the present embodiment. Is not limited to those whose imaging target is the human body.

The radiation detector 111 includes a plurality of detecting elements arranged one-dimensionally or two-dimensionally, and detects a spatial intensity distribution of radiation in the arrangement direction of the plurality of detecting elements, that is, a radiation image. The high-frequency component of the radiation intensity distribution detected by the radiation detector 111 refers to at least one high-frequency component of the radiation intensity distribution (radiation image) in the spatial axis direction and the time axis direction. The high-frequency component is a frequency component in a band in which the intensity of the frequency component constituting the radiation (scattered rays) scattered inside the subject 108 is relatively attenuated in the band of the frequency component constituting the intensity distribution of the radiation. It should be.

The radiation intensity distribution detected by the radiation detector 111 is represented by the sum of the intensity distribution of the primary line transmitted linearly through the subject 108 and the intensity distribution of the radiation (scattered line) scattered inside the subject 108. .. The intensity distribution of the primary line corresponds to the thickness distribution of the subject. At this time, some of the temporal and spatial high-frequency components contained in the radiation emitted from the radiation source 102 to the subject 108 linearly pass through the subject 108, and the others are scattered inside the subject 108. Since the scattered high-frequency components are greatly attenuated in the subject 108, the high-frequency components included in the radiation intensity distribution detected by the radiation detector 111 are almost the same as the high-frequency components of the primary line linearly transmitted through the subject 108. It is due. Therefore, the extraction unit 301 extracts at least one of the high frequency components in the spatial axis direction and the time axis direction included in the radiation intensity distribution detected by the radiation detector 111, so that the intensity distribution of the primary line (intensity of the high frequency component). Distribution) can be obtained. The body thickness distribution calculation unit 302 can calculate the body thickness distribution of the subject 108 from the intensity distribution of the extracted high-frequency component.

As described above, since the radiation imaging apparatus of the present embodiment can calculate the body thickness distribution of the subject 108 from the intensity distribution of the high frequency component, the intensity distribution of the scattered rays is obtained based on the body thickness distribution of the subject 108. The influence of scattered radiation can be removed from the radiation intensity distribution detected by the radiation detector. Therefore, it is possible to obtain an image in a short time in which image quality fluctuation due to scattered rays is suppressed without performing iterative processing.

The body thickness distribution calculation unit 302 can be configured to obtain the thickness of the subject 108 corresponding to the intensity of the high frequency component, for example, from the relationship between the body thickness obtained in advance and the intensity of the high frequency component.

Further, as shown in FIG. 1, the radiation imaging device is a scattered radiation distribution estimation unit that obtains the distribution of scattered radiation generated by the passage of radiation through the subject 108 from the body thickness distribution of the subject 108 obtained by the body thickness distribution calculation unit 302. 303 may be provided. Further, the radiation imaging device 101 may further include a scattered radiation distribution removing unit 304 that removes the scattered radiation distribution obtained by the scattered radiation distribution estimation unit 303 from the radiation intensity distribution detected by the radiation detector 111.

The scattered radiation distribution removing unit 304 generates a scattered radiation distribution equivalent to the scattered radiation distribution generated when the grid is arranged between the subject 108 and the radiation detector 111, based on the body thickness distribution of the subject. The scattered radiation distribution obtained by the scattered radiation distribution estimation unit 303 may be added to the removed radiation distribution. As a result, it is possible to display to the user (doctor, radiologist, etc.) the same radiation distribution as when the grid is arranged and imaged.

Hereinafter, more specific embodiments of the present invention will be described. In the following description, X-rays are used as radiation, and the radiation detector 111 uses two-dimensionally arranged X-ray detection elements. As a result, the radiation detector 111 detects the two-dimensional distribution of X-rays and obtains an X-ray image of the subject. However, the radiation imaging device of the present embodiment is not limited to the X-ray imaging device that acquires a two-dimensional X-ray image, and uses an X-ray detector in which X-ray detection elements are arranged in at least one dimension. It is possible to apply this embodiment to an X-ray CT apparatus. Further, in the following description, the scattered radiation distribution estimation unit 303 obtains a scattered radiation image of the subject as the scattered radiation distribution.

(Embodiment 1)
The radiation imaging apparatus according to the first embodiment of the present invention will be described.

<Configuration example of radiation imaging device>
FIG. 2 is a block diagram showing an example of a configuration in the radiation imaging apparatus according to the first embodiment of the present invention.

As shown in FIG. 2, the radiation imaging device (101) is electrically connected to an X-ray tube (radiation source) (102) that generates X-rays and irradiates the subject, and an X-ray tube (102). It is provided with a high voltage generating unit (103) to be generated, and an X-ray control unit (104) electrically connected to the high voltage generating unit (103). A diaphragm (105), an X-ray compensation filter (106), and a table (109) are arranged in this order in the X-ray irradiation direction of the X-ray tube (102). A mechanism control unit (110) is connected to the table (109). A diaphragm / filter control unit (107) is connected to the diaphragm (105) and the X-ray compensation filter (106). An X-ray detector (111) is arranged on the X-ray tube (102) at positions facing each other across the diaphragm (105), the X-ray compensation filter (106), and the table (109). A detector control unit (112) is connected to the X-ray detector (111), and an image processing unit (115) is connected to the detector control unit (112). A central processing unit (114) is connected to the X-ray control unit (104), aperture / filter control unit (107), mechanism control unit (110), and detector control unit (112), and the central processing unit (114) A storage unit (113), an input unit (116), and a display unit (117) are connected to.

The high voltage generator (103) generates a high voltage applied to the X-ray tube (102). The X-ray tube (102) irradiates the subject (108) placed on the table (109) with X-rays. The X-ray control unit (104) controls the high voltage generation unit (103) and controls the dose and quality of X-rays emitted from the X-ray tube (102). The diaphragm (105) controls the area irradiated with X-rays generated by the X-ray tube (102) by opening and closing a metal having a high X-ray absorption rate. The X-ray compensation filter (106) is composed of a substance having a high X-ray absorption rate, and reduces halation by attenuating X-rays reaching a portion of the subject (108) having a low X-ray absorption rate. The table (109) is a sleeper on which the subject (108) is placed. The mechanism control unit (110) moves the table (109) and controls the subject (108) to move to a position suitable for shooting. At this time, the X-ray control unit (111) may also have a structure that moves integrally with the table (109).

The X-ray detection unit (111) has a configuration in which X-ray detection elements are arranged two-dimensionally, and functions as an image generation unit. That is, the X-ray detector (111) detects the X-rays emitted from the X-ray tube (102) and transmitted through the subject (108) by the X-ray detection element, so that the image corresponds to the intensity distribution of the X-rays. Outputs data (radiation image, hereinafter referred to as transmission image). The X-rays that have passed through the subject (108) here are the X-rays that have passed through the subject (108) linearly and reached the X-ray detector (11), and the X-rays scattered within the subject (108). Includes X-rays that have reached the line detector (111). Therefore, the transmitted image is the sum of the image of the primary line transmitted linearly through the subject (108) and the image of the scattered lines scattered inside the subject (108). The detector control unit (112) controls the X-ray detection unit (111) to acquire transparent image data and inputs the data to the image processing unit (115). By controlling the X-ray detector (111) by the detector control unit (112), the X-ray detector (111) can also generate a transparent image as a still image. It is also possible to generate a plurality of transparent images taken at different timings in time and generate them as moving images. At this time, in general, the images are often taken at a fixed time interval such as 30 frames per second or 15 frames per second, but the time interval is not limited to this. The image processing unit (115) receives the transmission image (input image) output by the X-ray detector (111) via the detector control unit (112), and performs image processing such as extracting high-frequency components. .. The display unit (117) displays an image (output image) after processing by the image processing unit (115). The storage unit (113) is provided with a recording medium such as a semiconductor memory or a magnetic disk, and can store images, image acquisition conditions, various characteristics and parameters described later as data, and software programs described later. it can. The type of recording medium is not limited to this. The input unit (116) is a user interface for the user to set image acquisition conditions and the like. The input unit (116) may be provided with a keyboard, a mouse, control buttons, or the like, or may be provided with a sensor or the like for performing voice input, gesture input, or the like. The central processing unit (114) controls each electrically connected unit.

A general computer configuration typified by a personal computer (PC) usually includes a storage unit (113), an input unit (116), and a display unit (117) in addition to a central processing unit (114) called a CPU. In addition to being provided, the X-ray control unit (104), the aperture / filter control unit (107), the mechanism control unit (110), the detector control unit (112), and the image processing unit (115) can be realized by a software program. .. Therefore, the central processing unit (114), the storage unit (113), the input unit (116), the display unit (117), the X-ray control unit (104), the aperture / filter control unit (107), and the mechanism control unit (110). , The detector control unit (112) and the image processing unit (115) may be configured by a computer. Further, the function of the image processing unit (115) may be realized by using dedicated hardware, an image processing processor, or the like. The details of the image processing unit (115) will be described in detail later.

<Primary and scattered radiation of radiation imaging equipment>
FIG. 3 is an explanatory diagram illustrating a primary line and a scattered line of radiation transmitted through a subject. Note that FIG. 3 is a diagram used only for explaining the primary line and the scattered line in the radiation imaging apparatus, and is not a diagram for explaining the operation in a normal use state.

Here, first, the intensity (intensity distribution) Im (x, y) of each pixel of the transmitted image obtained by detecting the X-rays transmitted through the subject, the intensity distribution Ip (x, y) of the primary line image, and the scattered rays. The generally known characteristics of the image intensity distribution Is (x, y) will be described. Note that (x, y) in the following equation indicates the pixel position.

Equation (1) shows that the transmitted image Im (x, y) is represented by the sum of the primary line image Ip (x, y) and the scattered line image Is (x, y). Equation (2) shows that the intensity of the primary line image Ip (x, y) is exponentially attenuated according to the thickness T (x, y) of the subject. Here, Io (x, y) indicates the incident dose at the position (x, y), and μ indicates the X-ray attenuation rate (line attenuation coefficient) per unit thickness. Equation (3) is expressed by the convolution operation (*) of the intensity of the scattered ray image Is (x, y) and the intensity of the linear image Ip (x, y) and the point diffusion function Sσ (T (x, y)). It is shown that this point diffusion function Sσ (T (x, y)) changes according to the thickness T (x, y) of the subject. It should be noted that these equations (1), (2) and (3) are mathematical expressions based on the contents described in the above-mentioned Patent Document 1.

In FIG. 3A, an experiment was conducted in which the irradiation area of X-rays emitted from the X-ray tube (102) was controlled by an aperture (201 (a)) and the subject (202) placed on the table (109) was irradiated. It shows the situation when I went. At this time, the aperture (201 (a)) may be the same as the aperture (105) shown in FIG. 2, but it is different from the aperture (105) shown in FIG. 2 for the purpose of explaining the operating principle. It is assumed that the metal has a high X-ray absorption rate. Further, the subject (202) is an object having a thickness T (x, y) of a constant value (T) regardless of the position (x, y), such as an acrylic plate, for the purpose of explaining the operating principle.

When the intensity distribution of X-rays transmitted through the subject (202) and the table (109) is detected by the X-ray detector (111 (a)), as shown in FIG. 3 (a1), the central portion has a raised shape. The intensity distribution Im (x, y) is obtained. This is also because the X-ray detector (111 (a)) has a slightly longer path for X-rays to pass through the subject (202) at the edges (left and right) than at the center. It is one, but more than that, the influence of the difference in the intensity distribution Is (x, y) of the scattered radiation between the central part and the end part of the X-ray irradiation region is large. That is, in the central part of the X-ray irradiation region, scattered rays on both sides (left side and right side) are incident on the X-ray detector (111 (a)), whereas in the end part (left end and right end), one side (left end). Then, only the scattered rays on the right side and on the left side at the right end will be incident on the X-ray detector (111 (a)), so the intensity of the incident X-rays will be stronger at the center than at the ends. caused by.

This phenomenon can be confirmed experimentally by moving the position of the aperture (201 (b)) to a position different from that of the aperture (201 (a)) as shown in FIG. 3 (b). In the example shown in FIG. 3 (b), the metal plate on one side (left side when facing) of the diaphragm (201 (b)) is moved to shield the X-rays emitted to the left side of the X-ray tube (102). ing. Then, although the positional relationship between the X-ray tube (102), the subject (202), and the X-ray detector (111 (b)) and the thickness of the subject (202) are not changed from those in FIG. 3 (a), As shown in FIG. 3 (b1), the intensity distribution Im (x, y) of the transmitted image changes, and the value becomes smaller as a whole than the intensity distribution Im (x, y) shown in FIG. 3 (a1). This phenomenon is caused by the fact that the X-rays emitted from the left side of the subject (202) are blocked, so that the X-rays scattered from the left side to the right side of the subject (202) are eliminated.

In this way, even if the thickness of the subject (202) is a constant value, the intensity distribution Im (x, y) of the transmitted image changes when the position or area of the region irradiated with X-rays changes. In the case of a subject having locally different thicknesses such as the human body, the intensity distribution Im (x, y) of the transmitted image changes more complicatedly. Therefore, with the conventional technique, it is difficult to calculate the thickness T (x, y) of a certain position (x, y) from only the intensity distribution Im (x, y) of the transmitted image at that position. Ip (x, y) shown in (2) and Is (x, y) shown in Eq. (3) cannot be calculated easily. Therefore, until now, the thickness T (x, y) of the subject (202) had to be calculated by using an iterative process or the like as described in Patent Document 1.

On the other hand, in the radiation imaging apparatus according to the first embodiment of the present invention, attention is paid to the noise shown in FIGS. 3 (a1) and 3 (b1). This noise is included in the transmitted image, and in the X-ray tube (102), when an electron beam is made to collide with a target metal (anode) (not shown) in a vacuum to generate X-rays, the position where the electrons collide and It is generated by the probability that the time interval changes every time, and it is essentially difficult to eliminate this noise. That is, such noise is normally generated. In addition, this noise often has an impulse-like waveform and contains a large amount of high-frequency components spatially and temporally.

When X-rays containing such noise are emitted from the X-ray tube (102) to the subject (202), a part of the noise is scattered while passing through the subject (202). According to Eq. (3), the intensity of the scattered ray image is expressed as the intensity of the linear image Ip (x, y) and the convolution operation of the point diffusion function Sσ (T (x, y)), that is, the low-pass filter operation. Therefore, the high frequency component contained in the noise is greatly attenuated. Conversely, the noise (high frequency component) remaining in the transmitted images shown in FIGS. 3 (a1) and 3 (b1) is not caused by scattered rays, but most of them are caused by primary lines. It can be said that.

Here, when the transmitted image shown in FIG. 3 (a1) is separated into a spatial high-frequency component and a low-frequency component, the high-frequency component becomes as shown in FIG. 3 (a2), and the low-frequency component becomes as shown in FIG. 3 (a3). become. Similarly, when the transmitted image shown in FIG. 3 (b1) is separated into a high frequency component and a low frequency component, the high frequency component becomes as shown in FIG. 3 (b2), and the low frequency component becomes as shown in FIG. 3 (b3). At this time, as described above, most of the high frequency components are caused by the primary line. Therefore, from the above equation (2), the high frequency components shown in FIGS. 3 (a 2) and 3 (b2) are , Shows almost the same intensity distribution according to the thickness of the subject. By setting each intensity distribution in Fig. 3 (a2) and Fig. 3 (b2) as Ip (x, y), equation (4) can be derived from equation (2), and the incident dose Io (x, y) can be determined in advance. If it is measured, the thickness T (x, y) of the subject can be calculated in a short time without using the iterative process. Although the spatial high frequency components are shown in FIGS. 3 (a2) and 3 (b2), the same applies to the high frequency components in the time axis direction.

In other words, focusing on the intensity Im (x, y) of the transmitted image at a certain position (x, y), the intensity Ip (x, y) of the primary line is the position (x +) in the vicinity. The intensity of the primary line of dx, y + dy may be significantly different from that of the primary line Ip (x + dx, y + dy), but the intensity of the scattered radiation Is (x, y) is the intensity of the scattered radiation Is (x, y) in the vicinity. It uses the property that it is almost equal to x + dx, y + dy). That is, as shown in Eq. (5), the difference in intensity between the transmitted image Im and the neighboring pixels (Im (x + dx, y + dy) -Im (x, y), that is, the high frequency component) is obtained. The intensity Is of the scattered radiation can be canceled (Is (x + dx, y + dy) -Is (x, y) ≒ 0), and the difference in intensity from the neighboring pixels in the primary line image Ip (Ip (x + dx, y) + dy) -Ip (x, y)) is obtained. Utilizing this, the thickness T (x, y) of the subject from Eq. (2) or Eq. (4) without being affected by the scattered radiation Is (x, y) in Eqs. (1) and (3). Can be calculated in a short time.

<Structure example of image processing unit>
FIG. 4 is a block diagram showing an example of the configuration in the image processing unit (115) included in the radiation imaging apparatus of FIG.

As shown in FIG. 4, the image processing unit (115) includes a high-frequency component extraction unit (301), a body thickness distribution calculation unit (302), a scattered radiation image estimation unit (303), and a scattered radiation image removal unit (303). It is composed of 304).

The high frequency component extraction unit (301) extracts at least one high frequency component in the spatial axis direction and the time axis direction from the transmission image (input image) output by the X-ray detector (111), and extracts the extraction result as the high frequency component. It is input to the body thickness distribution calculation unit (302) as information. This detail will be described in detail later with reference to FIG.

The body thickness distribution calculation unit (302) calculates body thickness information based on the high frequency component information extracted by the high frequency component extraction unit (301), and scatter line image estimation unit (scattered line distribution estimation unit) (303). ). This detail will be described in detail later with reference to FIG.

The scattered radiation image estimation unit (303) creates a scattered radiation image (estimated scattered radiation image) estimated to be included in the input image based on the input image and the body thickness information from the body thickness distribution calculation unit (302). Calculate and input to the scattered radiation image removal unit (304). This detail will be described in detail later with reference to FIG.

The scattered radiation image removing unit (304) removes the estimated scattered radiation image obtained by the scattered radiation image estimation unit (303) from the input image, and calculates an output image. This detail will be described in detail later with reference to FIG.
The image acquisition conditions set in the image processing unit (115) will be described in detail later.

<Structure example of high frequency component extraction unit>
FIG. 5 is a block diagram showing an example of the configuration of the high frequency component extraction unit (301) included in the image processing unit (115) of FIG. The high frequency component extraction unit (301) extracts at least one high frequency component in the spatial axis direction and the time axis direction from the transmission image (input image) output by the X-ray detector (111), and extracts the extraction result as the high frequency component. It is input to the body thickness distribution calculation unit (302) as information.

As shown in FIGS. 5 (a) to 5 (d), various modifications can be considered for the high frequency component extraction unit (301). Hereinafter, these configurations and operations will be described one by one.

FIG. 5A shows an example (301 (a)) in which the high-frequency component extraction unit (301) is configured by the in-frame high-pass filter (401). Here, the in-frame high-pass filter (401) is a filter that extracts high-frequency components of the intensity distribution in the spatial axis direction of each pixel value constituting the input image by using only one (1 frame) input image. , A general one-dimensional or two-dimensional high-pass filter can be used as it is. A high-pass filter is a filter having a frequency characteristic in which the amount of attenuation of low-frequency components including direct current is larger than the amount of attenuation of high-frequency components. For example, a general horizontal high-pass filter or vertical high-pass filter (both are one-dimensional high-pass filters) can be used as they are as the in-frame high-pass filter (401). Further, a general horizontal high-pass filter and a vertical high-pass filter may be connected in series or in parallel to form a two-dimensional high-pass filter to form an in-frame high-pass filter (401). The in-frame high-pass filter (401) is not limited to the configuration described here, and has a large scattered ray image (low frequency component including direct current) as described earlier with reference to FIG. It suffices to have a frequency characteristic that attenuates.

FIG. 5 (b) shows another configuration example (301 (b)) of the high-frequency component extraction unit (301). The high frequency component extraction unit (301 (b)) is composed of an expansion processing unit (402), a contraction processing unit (403), and a subtractor (404). Here, the expansion process in the expansion processing unit (402) is generally known as a dilate process, and is 9 pixels in the vicinity of the attention position (pixel) (x, y) (for example, 9 pixels centered on the pixel at the attention position). ) Is a process in which the maximum value of the input signal (image value) is set as the output signal (pixel value) at the position of interest. Further, the shrinkage processing in the shrinkage processing unit (403) is generally known as erode processing, and the minimum value of the input signal (pixel value) in the vicinity of the attention position (x, y) is the output signal of the attention position. This is a process of setting (pixel value).

Therefore, when the difference between the output signals from the expansion processing unit (402) and the contraction processing unit (403) is taken by the subtractor (404), the maximum and minimum values of the input signals near the attention position (x, y) are taken. As shown in Eq. (5), the difference in intensity (Ip (x + dx, y + dy) -Ip (x, y)) with the neighboring pixels in the primary line image Ip is extracted. Therefore, it is possible to attenuate the scattered ray image having a small difference in intensity from the neighboring pixels.

The number of pixels in which the above "nearby" is set is arbitrary, and when an X-ray tube (102) having a small half-value width of noise contained in X-rays is used, the "nearby" is set to a small number of pixels (for example). When an X-ray tube (102) having a large half-value width of noise is used, the number of pixels in the “nearby” may be large (for example, 7 horizontal pixels × 7 vertical pixels).

FIG. 5 (c) shows yet another configuration example (301 (c)) of the high frequency component extraction unit (301). This high-frequency component extractor (301 (c)) is composed of a frame memory (405) and a subtractor (406), and is the difference between the current input image and the input image one frame before (that is, in the time direction). It is configured to output high frequency components). With this configuration, when the subject is stationary, a noise component can be extracted. The configuration for extracting the high frequency component in the time direction is not limited to the configuration described here, and the number of frame memories (405) may be increased to obtain a difference between a plurality of frames. When the subject is stationary, the intensity of the primary line may change significantly between frames due to noise, whereas the intensity of scattered lines is averaged between the neighborhoods within one frame, resulting in ergodicity. The high-frequency component extraction unit (301 (c)) may have a frequency characteristic that greatly attenuates low-frequency components including DC in the time frequency by utilizing the property of not changing so much between frames. The ergodicity is a property in which the time average and the set average are statistically consistent. Here, the average value between frames of scattered rays (time average) and the average value within one frame (set average) Represents the property of statistically matching.

FIG. 5D shows yet another configuration example (301 (d)) of the high frequency component extraction unit (301). The high frequency component extraction unit (301 (d)) is shown in FIG. 5 (a) and the high frequency component extraction unit (301 (a)) for extracting the high frequency component in the spatial axis direction shown in FIG. 5 (a). It is composed of a high-frequency component extractor (301 (c)) that extracts high-frequency components in the time axis direction, a motion detector (407), and a mixer (408).

The configuration and operation of the high-frequency component extraction unit (301 (a)) are as described above, and the high-frequency components in the spatial axis direction in the frame are extracted from the input image and output. The configuration and operation of the high-frequency component extraction unit (301 (c)) are as described above, and the high-frequency components between frames (time axis direction) are extracted from the input image and output. Here, the high-frequency component extraction unit (301 (a)) that extracts the high-frequency components in the spatial axis direction extracts not only the noise components (high-frequency components) but also the contour components of the subject included in the input image. In the contour portion, an error is included in the thickness T (x, y) of the subject calculated by using Eq. (2) or Eq. (4). On the other hand, the high-frequency component extraction unit (301 (c)), which extracts high-frequency components in the time axis direction, extracts only the noise component (high-frequency component) in the region where the subject is stationary, regardless of the presence or absence of the contour of the subject. On the other hand, in the region where the subject is moving, not only the noise component but also the component that changes according to the difference in the thickness T (x, y) of the subject for each position (x, y) is extracted. Will end up. Therefore, in the region where the subject moves, an error is included in the thickness T (x, y) of the subject calculated by using Eq. (2) or Eq. (4).

ここで、動き情報k(x,y)は、位置(x,y)ごとのフレーム差の大小を表す情報であり、0(静止)<=k(x,y)<=1(動き)となるように正規化しておく。 Therefore, the motion information k (x, y) of the subject is detected by using the motion detector (407), and as shown in Eq. (6), the high frequency component extraction unit (301 (a)) is used in the region where the subject moves significantly. ) Is the high frequency component information Y (x, y), and the result of the high frequency component extractor (301 (c)) (B (x, y)) in the region where the movement of the subject is small. The mixer (408) is controlled so that is the high frequency component information Y (x, y). As a result, it is possible to extract a high frequency component that reduces the error of the thickness T (x, y).

Here, the motion information k (x, y) is information indicating the magnitude of the frame difference for each position (x, y), and is 0 (rest) <= k (x, y) <= 1 (movement). Normalize so that

The motion detector (407) is a known technique using, for example, an operation of taking an absolute value of a frame difference for each position (x, y) and a divider for normalization (division by a constant). Since it can be realized by, the illustration is omitted.

<Structure example of body thickness distribution calculation unit>
FIG. 6 is a block diagram showing an example of the configuration of the body thickness distribution calculation unit (302) included in the image processing unit (115) of FIG. The body thickness distribution calculation unit (302) calculates the body thickness information based on the high frequency component information extracted by the high frequency component extraction unit (301) and inputs it to the scattered radiation image estimation unit (303).

As shown in FIG. 6, the body thickness distribution calculation unit (302) includes an absolute value calculation unit (501), a smoothing processing unit (502), and a look-up table (503). In the look-up table (503), the relationship between the average value of the noise component (high frequency component) intensity and the body thickness (conversion characteristic (504)), which was obtained in advance, is the image acquisition condition (tube voltage value, tube current). And the combination of aperture values, etc.).

The high-frequency component information input from the high-frequency component extraction unit (301) to the body thickness distribution calculation unit (302) has both positive and negative polarities and has an impulse waveform as shown in FIG. There are many. Therefore, the absolute value calculation unit (501) takes the absolute value of the high frequency component information received from the high frequency component extraction unit (301), and the smoothing processing unit (502) performs low-pass filter processing to obtain the attention position ( Pixel) Calculate the average value of the noise component intensity in the vicinity of (x, y). After that, the body thickness distribution calculation unit (302) uses the image acquisition conditions (tube voltage value, tube current value, etc.) set in the X-ray control unit (104) and the aperture / filter control unit (107) shown in FIG. The smoothing processing unit (502) calculates by reading the aperture value, etc.) and referring to the relationship between the average value of the noise component intensity and the body thickness under the image acquisition conditions stored in the lookup table (503). The average value of the noise component intensity in the vicinity of the attention position (x, y) is converted into the body thickness information of that position (x, y) and output.

A method of obtaining the relationship (conversion characteristic (504)) between the average value of the noise component intensity and the body thickness stored in this lookup table (503) will be described. For example, using the configuration shown in FIG. 3 (a), the transparent image shown in FIG. 3 (a1) is acquired while variously changing the image acquisition conditions and the thickness of the subject (202) having a constant thickness. After that, the high-frequency component information is extracted by the function of the high-frequency component extraction unit (301) shown in FIG. 4, and the attention position (attention position (502) by the functions of the absolute value calculation unit (501) and the smoothing processing unit (502) shown in FIG. Calculate the average value of the noise component intensity near x, y). Specifically, while changing the thickness of the subject (202) to T = 0 cm, 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, etc., the tube voltage value for each thickness is 60 kV, 70 KV, 80 KV, 90 KV, 100 KV, etc. By changing the tube current value to 1mA, 2mA, 4mA, 8mA, etc. for each tube voltage value, the X-ray detector (111 (11)) under the conditions of a total of 140 types (= 7 × 5 × 4). By obtaining the average value of the noise component intensity at the position corresponding to the central portion of a)), the conversion characteristic (504) from the average value of the noise component intensity to the thickness can be obtained. Create a lookup table (503) that stores this conversion characteristic (504).

At this time, if the subject (202) is an acrylic plate or the like having characteristics similar to those of the human body in terms of line attenuation coefficient and scattering characteristics, the above-mentioned thickness can be directly read as body thickness. It should be noted that each value shown here is an example for explanation, and is not limited thereto. Further, the value not set in advance (for example, the tube voltage value = 63KV) may be interpolated by using the average value of the noise component intensities in the value in the vicinity thereof. For example, the average value of the noise component intensity at the tube voltage value = 63 KV is obtained by dividing the average value of the noise component intensity at the tube voltage value = 60 KV and the average value of the noise component intensity at the tube voltage value = 70 KV into 7: 3. Just ask. In addition, using a generally known technique such as curve fitting, a conversion function that approximately represents the conversion characteristic (504) is obtained, and the parameters (coefficients, etc.) of the conversion function are stored in the lookup table (503). It may be stored.

<Structure example of scattered radiation image estimation unit>
FIG. 7 is a block diagram showing an example of the configuration of the scattered radiation image estimation unit (303) included in the image processing unit (115) of FIG. The scattered radiation image estimation unit (303) creates a scattered radiation image (estimated scattered radiation image) estimated to be included in the input image based on the input image and the body thickness information from the body thickness distribution calculation unit (302). calculate.

Here, first, the principle of calculating the estimated scattered radiation image from the body thickness in the scattered radiation image estimation unit (303) included in the image processing unit (115) of FIG. 4 will be described below.

Eq. (7) can be obtained by convolving the point diffusion function Sσ (T (x, y)) on both sides of the above equation (1).

By substituting the first term on the right-hand side of Eq. (7) with Is (x, y) using Eq. (3) and rearranging it, Eq. (7) can be converted as Eq. (8).

Focusing on the second term of Eq. (8), the point diffusion function Sσ (T (x, y)) is further convoluted with respect to the scattered radiation image (Is (x, y)). Compared with the primary line image Ip (x, y), it can be considered that the high frequency component is significantly attenuated, and the second term of Eq. (8) is a constant value regardless of the position (x, y) ( It may be approximated by a DC image). Further, the intensity of this constant value (DC image) may be regarded as extremely small, and the second term of the equation (8) may be set to 0 for simplification. By this simplification, an approximate expression of Eq. (8) to Eq. (9) can be obtained.

Therefore, the scattered radiation image estimation unit (303) is configured to calculate the right side of the equation (9) and output it as an estimated scattered radiation image.

As shown in FIGS. 7 (a) to 7 (c), various modifications can be considered for the scattered radiation image estimation unit (303). Hereinafter, these configurations and operations will be described one by one.

FIG. 7A shows an example (303 (a)) in which the scattered radiation image estimation unit (303) is configured as a two-dimensional low-pass filter (601). Here, the two-dimensional low-pass filter (601) convolves the point diffusion function Sσ (T (x, y)) (602) of the scattered radiation shown in Eq. (3) into the input image to obtain an estimated scattered radiation image. What you get.

The characteristics of this two-dimensional low-pass filter (601) are the same as when the characteristics of the look-up table (503) described above are obtained, using the configuration shown in FIG. 3 (a) and the thickness of the subject (202). The transparent image shown in FIG. 3 (a1) was acquired and obtained while changing the image acquisition conditions in various ways. At this time, outside the end (left end or right end) of the X-ray detector (111 (a)) (the part where the X-ray is shielded by the aperture (201 (a))), scattered rays that do not include the primary line. Since only the image can be obtained, the point diffusion function Sσ (T (x, y)) (602) of the scattered rays can be obtained using this intensity distribution. Specifically, when the X-ray radiated to the subject (202) is a step input in which the dose on the outside of the end is 0 and the dose on the inside of the end is 1, the response due to scattering in the subject ( Since the step response) is obtained as the intensity distribution of the transmitted image, the impulse response (that is, the point diffusion function Sσ (T (x, y)) (602) can be obtained by differentiating this step response.

In the configuration shown in FIG. 7 (a), the point diffusion function Sσ (T (x, y)) (602) is also located (x) in the case of a subject whose body thickness changes according to the position (x, y). It is necessary to change according to, y), which complicates the process. Therefore, it is approximately replaced by the configuration shown in FIG. 7B described below.

FIG. 7 (b) shows an example (303 (b)) in which the scattered radiation image estimation unit (303) is composed of a multiplier (603), a look-up table (604), and a two-dimensional low-pass filter (605). Shown. Here, the point diffusion function Sσ (606) of the two-dimensional low-pass filter (605) has a characteristic that is invariant with respect to the thickness T (x, y), but the two-dimensional low-pass filter (a) shown in FIG. Different from 601).

As a general feature of the scattered rays, the intensity of the scattered rays is weak in the place where the body thickness is thin, and the intensity of the scattered rays becomes stronger as the body thickness is increased. On the other hand, when the body thickness becomes thicker than a certain level, the primary line passing through the subject becomes weak, so that the scattered rays generated from the primary line also become weak. This characteristic is obtained in advance in the same manner as when the characteristic of the two-dimensional low-pass filter (601) described above is obtained.

That is, using the configuration shown in FIG. 3A, the transparent image shown in FIG. 3A1 is acquired while variously changing the thickness of the subject (202) and the image acquisition conditions, and FIG. 7B ) Shows the lookup table (604). At this time, the thickness when the point diffusion function Sσ (T (x, y)) (602) is most widened is obtained by the configuration shown in FIG. y)) (602) is fixed as the point diffusion function Sσ (606) of the two-dimensional low-pass filter (605). Then, the output of the two-dimensional low-pass filter (601) shown in FIG. 7 (a) and the result of the two-dimensional low-pass filter (605) shown in FIG. 7 (b) are input to the multiplier (603) so as to match as much as possible. Determine the strength factor to be used. While appropriately changing the body thickness (thickness), the relationship between the body thickness (thickness) and the strength coefficient is obtained, and stored in the lookup table (604) as a conversion characteristic (607) for converting the body thickness (thickness) into the strength coefficient. To do.

In addition, a conversion function that approximates the conversion characteristic (607) is obtained by using a generally known technique such as curve fitting, and the parameters (coefficients, etc.) of the conversion function are stored in the lookup table (604). It may be stored. Note that each value shown in the conversion characteristic (607) is an example for explanation, and is not limited thereto.

As described above, even if the characteristics of the two-dimensional low-pass filter (605) in the scattered radiation image estimation unit (303 (b)) shown in FIG. 7 (b) are invariant with respect to the thickness T (x, y), FIG. An estimated scattered radiation image similar to the output of the scattered radiation image estimation unit (303 (a)) shown in (a) can be obtained approximately.

FIG. 7 (c) shows the scattered radiation image estimation unit (303), the multipliers (608) (609), the mask information generation unit (612), and the scattered radiation image estimation unit (303 (b) -1) ( An example (303 (c)) composed of 303 (b) -2) and an adder (613) is shown.

When the radiation imaging apparatus of FIG. 2 is actually used, a transmitted image of a subject (108) smaller than the X-ray detector (111) may be acquired. In this case, on the outside of the subject, the X-rays emitted from the X-ray tube (102) directly enter the X-ray detector through only the air layer. X-rays are also scattered in the air layer, but the degree of scattering is smaller than that inside the subject (108).

Therefore, as shown in FIG. 7 (c), the scattered radiation image estimation unit (303 (b) -1) that estimates the scattering inside the subject and the scattered radiation that estimates the scattering outside the subject (air layer). The image estimation unit (303 (b) -2) is provided separately, and the mask information (610) generated by the mask information generation unit (612) indicating the inner region of the subject and the mask information generation unit (612) are generated. After dividing the input image into each region using the mask information (611) indicating the outer region of the subject and the multipliers (608) (609), the scattered radiation image estimation unit (303 (b) -1) (303 (b) -2) is used to obtain each estimated scattered radiation image, and finally the adder (613) is used to add both estimated scattered radiation images to output the final estimated scattered radiation image. ..

Here, the mask information (610) indicating the inner region of the subject has a value of 1 at the position (x, y) of the inner region of the subject and 0 at the position (x, y) of the outer region of the subject. Information. In the mask information generation unit (612), the area where the luminance value of the input image is smaller than the predetermined threshold value is defined as the inner region of the subject, and the region where the luminance value of the input image is larger than the predetermined threshold value is defined as the outer region of the subject. Generate information (610).

The mask information (610) generated by binarization in this way is low-pass filtered so that the value at the position (x, y) of the inner and outer boundary regions is an intermediate value between 0 and 1. May be good.

Further, the mask information (611) indicating the outer region of the subject may be a value complementary to the mask information (610) indicating the inner region of the subject, and each value of the mask information (610) and the mask information (611). May be set to 1 when added for each position (x, y).

The configuration of the scattered radiation image estimation unit (303 (b) -1) (303 (b) -2) is the same as that of the scattered radiation image estimation unit (303 (b)) shown in FIG. 7 (b). However, the two-dimensional low-pass filters (605-1) and (605-2) have different characteristics. That is, the two-dimensional low-pass filter (605-1) performs a convolution operation of the point diffusion function Sσ (606-1) that simulates scattering in the inner region of the subject, and the two-dimensional low-pass filter (605-2) performs the convolution calculation on the outside of the subject. Convolution of the point diffusion function Sσ (606-2) that simulates scattering in the region is performed.

The point diffusion function Sσ (606-1) and the look-up table (604-1) are the same as the point diffusion function Sσ (606) and the look-up table (604) shown in FIG. 7 (b) described above. It may be a characteristic. On the other hand, for the point diffusion function Sσ (606-2) and the lookup table (604-2), in the configuration of FIG. 3 (a), after the subject (202) is not installed, the procedure is the same as described above. Then, each characteristic of the point diffusion function Sσ (606-2) and the lookup table (604-2) can be obtained.

Although not shown, the scattered radiation image estimation unit (303 (b) -1) in the configuration of FIG. 7 (c) may be subdivided. At this time, for example, a scattered ray image estimation unit for a region with a thin body thickness (for a region with a large amount of X-ray transmission) such as the lung, and a scattered radiation image estimation unit for a region with a small amount of X-ray transmission such as bone. It may be subdivided into a part, a scattered ray image estimation part for other areas (for internal organs and muscles), and the like. In that case, for example, in the configuration of FIG. 3A, the subject (202) is replaced with a subject simulating the characteristics of each region, and the point diffusion function Sσ (606) and the look-up table (604) are performed in the same procedure as described above. ) Can be obtained. Further, the mask information generation unit (612) may be configured to generate mask information for each region according to the brightness value of the input image.

The contents of the above-mentioned lookup tables (503) and (604) and the characteristics (602) and (606) of the point diffusion function are obtained in advance and recorded in the storage unit (113) shown in FIG. The central processing unit (114) shown in FIG. 2 may control to read each content from the storage unit (113) and set it in each unit when the device is used.

<Structure example of scattered radiation image removal unit>
FIG. 8 is a block diagram showing an example of the configuration of the scattered ray image removing unit (304) included in the image processing unit (115) of FIG. The scattered radiation image removing unit (304) removes the estimated scattered radiation image obtained by the scattered radiation image estimation unit (303) from the input image, and calculates an output image.

As shown in FIGS. 8 (a) and 8 (b), various modifications can be considered for the scattered radiation image removing unit (304). Hereinafter, these configurations and operations will be described one by one.

As shown in FIG. 8 (a), an example (scattered radiation image removing unit (304 (a))) in which the scattered radiation image removing unit (304) is composed of only the subtractor (701) is shown.

Here, by solving the above-mentioned equation (1) for Ip (x, y), the equation (10) is obtained.

Estimated primary line by approximating the second term (Is (x, y)) of equation (10) with the output (that is, the estimated scattered radiation image) of the scattered radiation image estimation unit (303) shown in FIG. An image (Ip (x, y)) can be obtained.

According to this equation (10), in the configuration of the scattered radiation image removing unit (304 (a)) shown in FIG. 8 (a), the estimated scattered radiation image is subtracted from the input image by the subtractor (701), and the estimated primary line image is obtained. Is output as an output image. As a result, it is possible to obtain an output image (estimated primary line image) in which image quality fluctuation due to scattered rays is suppressed.

Since the estimated primary line image obtained in this way does not include the scattered line image, the user may have an impression that the image quality is significantly different from that of the grid image described as the background technique. The reason is that even if the grid is used, the scattered radiation cannot be completely suppressed, so that the user is accustomed to the grid image in which a part of the scattered radiation remains, and may not be accustomed to the estimated primary line image. is there.

Therefore, in the configuration of FIG. 8B, an equivalent scattered ray image is generated when the grid is arranged, and is added to the estimated primary line image. As a result, an output image equivalent to that when the grid is used is obtained. That is, in the configuration of FIG. 8 (b), the configuration of FIG. 8 (a) and the second scattered radiation image estimation unit (304 (a)) are inside the scattered radiation image removing unit (304 (b)). It is equipped with a 303), a multiplier (702), and an adder (703). Then, the estimated primary line image output by the scattered line image removing unit (304 (a)) is input to the second scattered line image estimating unit (303), and the output (estimated scattered line image) is multiplied. Multiply the grid loss factor using a device (702) to generate a scattered radiation image equivalent to that when the grid is placed.

This scattered ray image is added to the output (estimated primary line image) of the scattered ray image removing unit (304 (a)) using an adder (703) to obtain an output image (an image simulating a grid image). .. Here, the grid loss coefficient is a coefficient indicating the rate at which scattered rays are attenuated by the grid, and may be a constant value regardless of the position (x, y) of the image. This grid loss coefficient is the end (left end) when the grid is inserted between the table (109) and the X-ray detector (111 (a)) and when it is not inserted in the configuration shown in FIG. 3 (a). Alternatively, the ratio of the scattered radiation intensities outside the right end) may be measured and obtained.

<Operation example of image processing unit>
FIG. 9 is a flowchart showing an example of processing operations in each of the image processing units (115) (301) to (304).

The image processing unit (115) described above is composed of a computer including a calculation unit such as a CPU and a storage unit in which a program is stored in advance, and the calculation unit reads and executes a program in the storage unit. The functions of the respective parts (301) to (304) may be realized by software processing, or a part or all of the functions of the respective parts (301) to (304) of the image processing unit (115) may be ASICly used. The configuration may be realized by hardware such as Application Specific Integrated Circuit) and FPGA (Field-Programmable Gate Array).

Hereinafter, the processing operation of the image processing unit (115) will be described with reference to the flowchart of FIG. Here, a case where the functions of the respective parts (301) to (304) of the image processing unit (115) are realized by software processing will be described as an example.

First, the central processing unit 114 receives an X-ray control unit (104), a filter / filter control unit (107), a mechanism control unit (110), according to the image acquisition condition received from the user via the input unit (116). By controlling the detector control unit (112), X-rays are emitted from the X-ray tube (102) to the subject (108), and the X-rays that have passed through the subject (108) are emitted from the X-ray detector (111). A transparent image is generated by the detection of.

In step (1001) of FIG. 9, the image processing unit (115) operates the functions of each unit (301) to (304) by the arithmetic unit reading and executing the program in the storage unit, and starts the following processing. In step (1002), the image processing unit (115) acquires a transparent image (hereinafter, also referred to as an input image) generated by the X-ray detector (111) via the detector control unit (112).

In step (1003), the high frequency component extraction unit (301) of the image processing unit (115) extracts at least one high frequency component in the spatial axis direction and the time axis direction from the input image. In step (1004), the body thickness distribution calculation unit (302) calculates the body thickness distribution from the high frequency component. In step (1005), the scattered radiation image estimation unit (303) estimates the scattered radiation image from the body thickness distribution calculated in step (1004). In step (1006), the scattered radiation image removing unit (304) generates an output image by subtracting the scattered radiation image estimated in step (1005) from the input image. In step (1007), the image processing unit (115) outputs the output image generated in step (1006), and ends the process in step (1008).

Since the content of the processing in each of these steps is the same as the processing operation of each part (301) to (304) described with reference to FIGS. 2 to 8, detailed description thereof will be omitted. Further, even for the processes not specifically shown in FIG. 9, the operations of the respective parts (301) to (304) in the configurations shown in FIGS. 2 to 8 can be realized by software.

In this way, a software program that operates on a general computer configuration typified by a personal computer (PC) makes it possible to obtain an image in which image quality fluctuation due to scattered radiation is suppressed in a short time.

<Summary of Embodiment 1>
As described above, in the radiation imaging apparatus of the first embodiment, by using the configuration and operation of each part shown in FIGS. 2 to 9, the body thickness distribution of the subject can be obtained in a short time without performing any iterative processing. In addition to being able to obtain it, it is possible to obtain an image in which image quality fluctuation due to scattered radiation is suppressed by using this body thickness distribution.

(Embodiment 2)
The radiation imaging apparatus according to the second embodiment of the present invention will be described.

<Other configuration examples of the image processing unit>
The radiation imaging apparatus according to the second embodiment has a configuration in which the image processing unit (115) in the radiation imaging apparatus according to the first embodiment shown in FIG. 2 is replaced with the image processing unit (801) shown in FIG. The description of the block common to that of FIG. 2 will be omitted, and the image processing unit (801) after replacement will be described below.

FIG. 10 is a block diagram showing an example of the configuration of the image processing unit (801) included in the radiation imaging apparatus according to the second embodiment. The image processing unit (801) of the second embodiment suppresses the influence of halation (blown out) caused by the saturation of the X-ray detector (111) in the transparent image, and the body thickness. Find the distribution. That is, the detection unit that determines whether the X-ray detector that detects the transmitted image is saturated with X-rays, and if the X-ray detector (111) is saturated, the body thickness distribution for the saturated position. It has a replacement unit that replaces the body thickness calculated by the calculation unit (302) with a different value.

As described with reference to FIG. 3, the radiation imaging apparatus according to the first embodiment of the present invention pays attention to X-ray noise (high frequency component) as shown in FIGS. 3 (a1) and 3 (b1). , The transmitted image was separated into a high frequency component and a low frequency component, and the body thickness distribution was obtained from the intensity of the high frequency component. However, if the intensity of the X-rays emitted from the X-ray tube (102) is too strong, the X-ray detector (111) will be saturated, and halation (overexposure) will occur in the brightness of the transmitted image, resulting in high-frequency components. May seem to disappear. In this case, the average value of the noise component intensity becomes 0, and the body thickness distribution calculation unit (302) shown in FIG. 6 refers to the conversion characteristic (504) of the lookup table (503) and is different from the actual body. The thickness is calculated. That is, even though the X-ray intensity is strong (that is, the body thickness is thin), the average value of the noise component intensity is 0, so that the body thickness distribution calculation unit (302) has noise. Calculate an extremely thick body thickness that does not allow permeation. Therefore, the image processing unit (115) shown in FIG. 4 may result in an erroneous output image.

Therefore, in the image processing unit (801) shown in FIG. 10A, the high-frequency component extraction unit (301), the body thickness distribution calculation unit (302), and the scattered radiation that constitute the image processing unit (115) shown in FIG. 4 Based on the image estimation unit (303) and the scattered radiation image removal unit (304), a new body thickness distribution calculation unit (802), comparator (detection unit) (803), and switch (replacement unit) ( 804) is added. The operation of each part will be described below.

First, the body thickness distribution calculation unit (802) calculates the body thickness distribution for each position (x, y) using the brightness value of the input image instead of the high frequency component. Specifically, the relationship (conversion characteristic) between the thickness of the subject under each image acquisition condition and the average value of the brightness values of the input image, which has been obtained in advance, is stored in a look-up table (not shown), and the body thickness is obtained. The distribution calculation unit (802) obtains the body thickness from the brightness value of the input image for each position (x, y) with reference to the conversion characteristics of this lookup table, and outputs the obtained body thickness distribution as body thickness information. To do. The relationship between the thickness of the subject and the average value of the brightness values of the input image is shown in FIG. 3 (a) for each image acquisition condition while appropriately changing the thickness of the subject (202) using the configuration shown in FIG. 3 (a). After acquiring the transparent image shown in a1), the relationship between the thickness under each image acquisition condition and the average value of the brightness values of the input image may be obtained.

Subsequently, the comparator (803) compares the body thickness information calculated by the body thickness distribution calculation unit (802) with a predetermined threshold value for each position (xy), and the body thickness at each position is greater than the threshold value. When it is small (thin), it is determined that the transparent image at that position (x, y) may be overexposed. Using this determination result, the switch (804) uses the body thickness information output from the body thickness estimation unit (302) for the position (x, y) where the transparent image may be overexposed. Instead, the body thickness information output from the body thickness estimation unit (802) is input to the scattered ray image estimation unit (303).

As a result, even if the X-ray detector (111) is saturated and halation (overexposure) occurs in the brightness of the transmitted image, the scattered ray image estimation unit (303) can check the position where the overexposure occurs. Since the body thickness information obtained from the brightness value of the transparent image can be used, the scattered ray image can be estimated based on the body thickness without being affected by overexposure.

On the other hand, the image processing unit (805) shown in FIG. 10 (b) is a configuration example in which the configuration of the image processing unit (804) shown in FIG. 10 (a) is simplified. The image processing unit (805) includes a high-frequency component extraction unit (301), a body thickness distribution calculation unit (302), a scattered radiation image estimation unit (303), and a scattered beam image estimation unit (303) that constitute the image processing unit (115) shown in FIG. A comparator (806) and a switch (807) are newly added based on the scattered radiation image removing unit (304). The operation of each added part will be described below.

The comparator (806) compares the luminance value of the input image with a predetermined threshold value for each position (x, y), and when the luminance value at each position is larger than the threshold value, the position (x, y). It is determined that the transparent image of the above may be overexposed. Using this determination result, at the position (x, y) where the transparent image may be overexposed, the body thickness information output from the body thickness estimation unit (302) is replaced by the switch (807). , The body thickness setting value is input to the scattered ray image estimation unit (303). At this time, the body thickness set value may be a set value representing, for example, body thickness = 0 cm by using a predetermined constant.

As a result, the scattered ray image estimation unit (303) can use a predetermined body thickness setting value for the position where the whiteout occurs even if the brightness of the transmitted image has halation (whiteout). Therefore, it is possible to estimate a scattered ray image in which the influence of overexposure is reduced.

<Summary of Embodiment 2>
If the image processing unit (801) or the image processing unit (805) is configured as described above and used in place of the image processing unit (115), the image processing unit (801) may be caused by overexposure of the transparent image. ) (805) can be prevented from outputting an erroneous image.

(Embodiment 3)
The radiation imaging apparatus of the third embodiment will be described.
<Another configuration example of the image processing unit>
The radiation imaging apparatus according to the third embodiment has a configuration in which the image processing unit (115) in the radiation imaging apparatus according to the first embodiment shown in FIG. 2 is replaced with the image processing unit (901) shown in FIG. The description of the block common to that of FIG. 2 will be omitted, and the image processing unit (901) after the replacement will be described below.

FIG. 11 is a block diagram showing an example of the configuration in the image processing unit (901) of the third embodiment.

In the configurations and operations of the first and second embodiments described above, since the body thickness distribution is calculated by incorporating some approximations, an error due to the approximation may be mixed in the output image. For applications where the user observes moving images (X-ray fluoroscopy), it is sufficient to allow this error and give priority to high-speed processing. On the other hand, in applications where the user observes a still image (X-ray photography), it may be better to reduce the error at the expense of processing speed.

Therefore, in the image processing unit (901) shown in FIG. 11, the body thickness distribution correction unit (902) and the correction unit (902) that correct the body thickness value calculated by the body thickness distribution calculation unit (302) are output. Estimated transmission line image (estimated input image) generator (904) that generates an estimated transmission line image based on the corrected body thickness, and transmission image (input image, that is, radiation) output by the X-ray detector (111). It has a comparison unit (905) that compares the intensity distribution) with the estimated transmission line image. The correction unit (902) adjusts the correction amount based on the output of the comparison unit (905).

Specifically, the high-frequency component extraction unit (301), the body thickness distribution calculation unit (302), the scattered radiation image estimation unit (303), and the scattered radiation image removal unit that constitute the image processing unit (115) shown in FIG. Based on the unit (304), the image processing unit (901) newly adds a body thickness distribution correction unit (902), a switch (903), an estimated input image generation unit (904), and a comparator (905). to add. Hereinafter, before explaining the operation of each part, a method of acquiring parameters prepared in advance will be described.

First, using the configuration shown in FIG. 3 (a), the brightness value of the transmitted image detected by the X-ray detector (111 (a)) while appropriately changing the image acquisition conditions and the thickness of the subject (202). Is obtained, and the line attenuation coefficient μ is obtained in advance based on Eq. (2). Subsequently, the point diffusion function Sσ (T (x, y)) (602) or the point diffusion function Sσ (606) when X-rays are scattered in the subject (202) is obtained by using the method described above. deep.

Next, the operation of each part when the radiation imaging device is actually used will be described.

The image processing unit (901) obtains body thickness information (T (x, y)) from the input image via the high-frequency component extraction unit (301) and the body thickness distribution calculation unit (302). The operation (initial operation) up to this point is the same as the operation of each unit in the image processing unit (115) shown in FIG.

Next, in the initial operation, the body thickness information (x, y) is input to the estimation input image generation unit (904) via the switch (903) switched to the upper path in FIG. The estimated input image generation unit (904) generates an estimated input image based on the body thickness information (T (x, y)) using the above equations (1), (2), and (3).

Specifically, the linear attenuation coefficient μ obtained in advance, body thickness information (T (x, y)), and dose Io (x, y) are used to estimate the primary line image Ip (x) from Eq. (2). , y) is calculated. In addition, using this estimated primary line image Ip (x, y) and the point diffusion function Sσ (T (x, y)) or the point diffusion function Sσ obtained in advance, the estimated scattered line image from Eq. (3). Find Is (x, y). Subsequently, the estimated input image Im (x, y) is obtained from Eq. (1) using the obtained estimated primary line image Ip (x, y) and the estimated scattered line image Is (x, y).

The luminance value of the estimated input image Im (x, y) obtained in this way and the luminance value of the actual input image are compared for each position (x, y) by the comparator (905), and the difference between the two images. δ (x, y) is obtained, and this difference δ (x, y) is input to the body thickness distribution correction unit (902).

The body thickness distribution correction unit (902) corrects the body thickness information T (x, y) based on the sign (positive or negative) of the value of the difference δ (x, y). When the difference δ (x, y) is positive (that is, when the luminance value of the estimated input image is larger than the luminance value of the actual input image (x, y)), that position (x, y) ), The value of the body thickness information T (x, y) is corrected to a slightly larger value (T (x, y) + Δ, where Δ is a positive value). Conversely, if the difference δ (x, y) is negative (that is, if the luminance value of the estimated input image is smaller than the luminance value of the actual input image (x, y)), then that position (that is, The value of the body thickness information T (x, y) of x, y) is corrected to a slightly smaller value (T (x, y) -Δ, where Δ is a positive value). The corrected body thickness information (T (x, y) ± Δ) is output as new body thickness information T (x, y) from the body thickness distribution correction unit (902).

Here, the switch (903) is switched to the lower path in FIG. 11, and the estimated input image (904), the comparator (905), and the body thickness distribution correction unit (as in the case of the upper path described above). When each operation of 902) is repeated, the absolute value of the difference δ (x, y) between the luminance value of the estimated input image and the luminance value of the actual input image gradually decreases. When the absolute value of this difference δ (x, y) becomes smaller than the predetermined threshold value at all positions (x, y), or when the predetermined number of iterations is reached, the corrected body. The iterative processing is completed with the thickness information T (x, y) as the final body thickness information T (x, y).

Using this final body thickness information T (x, y) and the input image, the scattered radiation image estimation unit (303) obtains the estimated scattered radiation image, and the scattered radiation image removal unit (304) estimates the scattering from the input image. The line image is reduced to obtain the output image of the image processing unit (901).

Before processing the new input image, the switch (903) is switched to the upper path in FIG. 11 to return to the initial operation.

As described above, the image processing unit (901) of the third embodiment can reduce the error included in the body thickness calculated by the body thickness distribution calculation unit (302) by performing the iterative processing.

In the configuration example of the image processing unit (901) shown in FIG. 11, each unit of the body thickness distribution correction unit (902), the estimated input image generation unit (904), and the comparator (905) is controlled so as not to function. If the switch (903) is left switched to the upper path in FIG. 11, the output of the body thickness distribution calculation unit (302) will be input to the scattered line image estimation unit (303). The image processing unit (901) shown in 11 has the same function as the image processing unit (115) shown in FIG. By configuring the path of body thickness information to be switched in this way, the function can be switched between the purpose of observing a moving image by the user (X-ray fluoroscopy) and the purpose of observing a still image by the user (X-ray photography). Will be available.

In the device using the iterative processing as described above, the initial value of the body thickness information T (x, y) (that is, the body thickness information T (x, y) output from the body thickness distribution calculation unit (302)) The number of iterations varies greatly depending on the accuracy. In the radiation imaging apparatus according to the third embodiment, since the body thickness information is estimated from the noise (high frequency component) contained in the transmitted image as described above, the body thickness is estimated from the intensity distribution Im (x, y) of the transmitted image. Since the influence of scattered radiation can be suppressed and the accuracy of body thickness information can be kept high compared to estimating information, the number of repetitions can be greatly reduced, and an image in which image quality fluctuation due to scattered radiation is suppressed can be obtained in a short time. It becomes possible.

<Summary of Embodiment 3>
As described above, in the radiation imaging apparatus according to the third embodiment, it is possible to reduce the error mixed in the output image due to the error included in the calculated body thickness. Further, as compared with the conventional technique, the number of times of processing repetition can be greatly reduced, and an image in which image quality fluctuation due to scattered rays is suppressed can be obtained in a short time.

(Embodiment 4)
The radiation imaging apparatus of the fourth embodiment will be described.
<Other configuration examples of the radiation imaging device>
FIG. 12 is a block diagram showing an example of the configuration of the radiation imaging apparatus according to the fourth embodiment.

In the configuration example of the radiation imaging device according to the first embodiment shown in FIG. 2, it is assumed that each part constituting this device is incorporated in the same device or a plurality of devices arranged in close proximity to each other. Therefore, it is necessary to incorporate an image processing unit for each device.

Therefore, in the fourth embodiment, as shown in FIG. 12, the radiation imaging device (1101) is separated into a client unit (1102) that acquires and displays a transmitted image and a server unit (1105) that performs image processing. , Both are connected by a communication network (1104).

The client unit (1102) removes the image processing unit (115) from the configuration example of the radiation imaging apparatus according to the first embodiment shown in FIG. 2, and provides a network interface (I / F) unit (1103) in its place. It is a configuration. Since each part other than the network I / F part (1103) has the same configuration and operation as each part shown in FIG. 2, description thereof will be omitted.

The network I / F section (1103) included in the client section (1102) includes a network transmission I / F section (not shown) for transmitting image data to the communication network (1104), and includes HTTP (HyperText Transfer Protocol) and FTP (HyperText Transfer Protocol). A transparent image (input image) detected by the X-ray detection unit (111) is transmitted to the server unit (1105) via the communication network (1104) using a general network protocol such as File Transfer Protocol). .. Further, the network I / F section (1103) includes a network reception I / F section (not shown) for receiving image data from the communication network (1104), and an image (output image) processed by the server section (1105). Is received via the communication network (1104) and sent to the display unit (117).

The network I / F unit (1103) may be configured to be connected to and controlled by the central processing unit (114). Since the network I / F section (1103) can be realized by a general technique, detailed description thereof will be omitted.

The communication network (1104) may be a general Internet or an intranet, a private network closed in a facility, a public network such as a fixed telephone line or a wireless telephone line, a wireless LAN or BlueTooth (registration). It may be a wireless network such as a trademark).

The server unit (1105) is composed of a network I / F unit (1106), an image processing unit (1107), a central processing unit (1108), and a storage unit (1109).

The network I / F section (1106) included in the server section (1105) includes a network reception I / F section (not shown) for receiving image data from the communication network (1104), and includes HTTP (HyperText Transfer Protocol) and FTP (HyperText Transfer Protocol). The input image transmitted from the client unit is received via the communication network (1104) using a general network protocol represented by File Transfer Protocol). In addition, a network transmission I / F unit (not shown) for transmitting image data to the communication network (1104) is provided, and the image processed by the image processing unit (1107) can be sent to the client unit (1102) via the communication network (1104). ). The network I / F unit (1106) may be configured to be connected to and controlled by the central processing unit (1108). Since the network I / F section (1106) can be realized by a general technique, detailed description thereof will be omitted.

The image processing unit (1107) receives an input image received from the client (1102) via the network I / F unit (1106) (that is, a radiation intensity distribution obtained by detecting the radiation passing through the subject (108)). Thickness distribution calculation to obtain the distribution of the thickness of the subject based on the high-frequency components extracted by the extraction unit (301) and the extraction unit (301) that extract at least one of the high-frequency components in the spatial axis direction and the time axis direction. Scattered ray distribution that obtains the distribution of scattered rays generated by the passage of radiation through the subject based on the thickness distribution of the subject calculated by the part (body thickness distribution calculation unit) (302) and the thickness distribution calculation unit (302). It includes an estimation unit (303) and a scattered radiation distribution removing unit (304) that removes the scattered radiation distribution obtained by the scattered radiation distribution estimation unit (303) from the input image. The image processing unit (1107) is the image processing unit (115) shown in FIGS. 2 and 4, the image processing unit (801) (805) shown in FIG. 10, and the image processing unit (901) shown in FIG. Of these, it can be realized with the same configuration as either one. Further, as a configuration in which the computer functions as an extraction unit (extraction means) (301), a body thickness distribution calculation unit (body thickness distribution calculation means) (302), etc. by using the program shown in the flowchart shown in FIG. May be good. The image processing unit (1107) may be configured to be connected to and controlled by the central processing unit (1108).

The storage unit (1109) is connected to the central processing unit (1109), and the contents of the above-mentioned lookup tables (503) and (604) and the characteristics of the point diffusion function (602) necessary for the operation of the image processing unit (1107) are required. ) (606) is stored.

As described above, the radiation imaging device (1101) is separated into a client unit (1102) that acquires and displays a transmitted image and a server unit (1105) that performs image processing, and both are connected by a communication network (1104). The following effects can be obtained by configuring the connection.

First, since it is sufficient to install one server unit (1105) for a plurality of client units (1102), a large-scale radiation imaging device can be economically constructed.

Further, by using the Internet or the like as the communication network (1104), the client unit (1102) and the server unit (1105) can be installed at remote locations from each other.

Further, if a login control unit (not shown) is provided in the client unit (1102) and a user authentication / management unit and a billing processing unit (not shown) are provided in the server unit (1105), the client unit (1102) can be operated. It becomes possible to carry out a billing business using the server unit (1105) for the user.

The login control unit is software program processing executed by the central processing unit (114) of the client unit (1102), and the user authentication / management unit and billing processing unit are executed by the central processing unit (1108) of the server unit (1105). In the case of software program processing, each part can be easily realized by using a generally known technique, and therefore detailed description of each part will be omitted.

<Summary of Embodiment 4>
As described above, if the radiation imaging device according to the fourth embodiment is used, it becomes possible to obtain an image in which image quality fluctuation due to scattered rays is suppressed via a network, and a large-scale radiation imaging device is economical. It will be possible to build it in a remote location, to install it in a remote location, and to carry out a billing business.

<Overall summary>
(I) According to the embodiment of the present invention described above, the radiation source for irradiating the subject, the radiation detector for detecting the intensity distribution of the radiation passing through the subject, and the radiation intensity distribution in the spatial axis direction. Image quality due to scattered radiation is provided by having an extraction unit that extracts at least one high-frequency component in the time axis direction and a body thickness distribution calculation unit that obtains the distribution of the thickness of the subject based on the high-frequency component extracted by the extraction unit. A radiation transmission image with suppressed fluctuation can be obtained in a short time.
(Ii) The present invention can be realized by a program code of hardware and software that realizes the functions of the embodiment.

For the functions realized by the software program code, a storage medium in which the program code is recorded is provided to the device or the device, and the device or the computer (or CPU or MPU) of the device provides the program code stored in the storage medium. read out. In this case, the program code itself read from the storage medium realizes the function of the above-described embodiment, and the program code itself and the storage medium storing the program code itself constitute the present invention. Storage media for supplying such program code include, for example, flexible disks, CD-ROMs, DVD-ROMs, hard disks, optical disks, magneto-optical disks, CD-Rs, magnetic tapes, non-volatile memory cards, and ROMs. Etc. are used.

Further, based on the instruction of the program code, the OS (operating device) or the like running on the computer performs a part or all of the actual processing, and the processing enables the functions of the above-described embodiment to be realized. You may. Further, after the program code read from the storage medium is written in the memory on the computer, the CPU of the computer or the like performs a part or all of the actual processing based on the instruction of the program code, and the processing is performed. May realize the functions of the above-described embodiment.

Further, by distributing the program code of the software that realizes the functions of the embodiment via the network, the device or a storage means such as a hard disk or a memory of the device or a storage medium such as a CD-RW or a CD-R can be distributed. The device or the computer (or CPU or MPU) of the device may read and execute the program code stored in the storage means or the storage medium at the time of use.

Finally, it should be understood that the processing content and techniques described here are not essentially related to any particular device and can be implemented in any suitable combination of components. In addition, various types of devices for general purpose can be used according to the teachings described herein. You may find it useful to build a dedicated device to carry out the steps of the method described here. In addition, various inventions can be formed by appropriately combining the plurality of components disclosed in the embodiments. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate. The present invention has been described in the context of specific examples, but these are for illustration, not limitation, in all respects.

Those skilled in the art will find that there are numerous combinations of hardware, software, and firmware suitable for implementing the present invention. For example, the described hardware may be implemented by ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), etc., and the described software may be assembler, C / C ++, perl, Shell, PHP, Python. , Java®, etc., may be implemented in a wide range of programs or scripting languages.

Further, in the above-described embodiment, the control lines and information lines are shown as necessary for explanation, and not all control lines and information lines are necessarily shown in the product. All configurations may be interconnected.

In addition, to those with ordinary knowledge of the art, other implementations of the invention will become apparent from the discussion of the specification and embodiments of the invention disclosed herein. The various aspects and / or components of the described embodiments can be used alone or in any combination in a computerized storage device having the ability to manage data.

101, 1101 ... Radiation imaging device 108, 202 ... Subject 115, 801,805,901,1106 ... Image processing unit 301 ... High frequency component extraction unit 302 ... Body thickness distribution calculation unit 303.・ ・ Scattered ray image estimation unit 304 ・ ・ ・ Scattered ray image removing unit 503, 604 ・ ・ ・ Lookup table 602,606 ・ ・ ・ Scattered ray point diffusion function 610, 611 ・ ・ ・ Mask information 1102 ・ ・ ・ Client Part 1104 ... Communication network 1105 ... Server part

Claims (15)

A radiation source that irradiates a subject, a radiation detector that detects the intensity distribution of radiation that has passed through the subject, and at least one high-frequency component in the spatial axis direction and the time axis direction of the radiation intensity distribution is extracted. A radiation imaging apparatus comprising: an extraction unit and a thickness distribution calculation unit for obtaining a thickness distribution of the subject based on a high-frequency component extracted by the extraction unit. The radiation imaging apparatus according to claim 1, wherein the thickness distribution calculation unit of the subject corresponds to the intensity of the high-frequency component from the relationship between the thickness of the subject and the intensity of the high-frequency component obtained in advance. A radiation imaging device characterized by determining the thickness. The scattered radiation according to claim 1, wherein the distribution of scattered radiation generated by the radiation passing through the subject is obtained from the thickness distribution of the subject obtained by the thickness distribution calculation unit. A radiation imaging device characterized by further having a distribution estimation unit. The radiation imaging apparatus according to claim 3, further comprising a scattered radiation distribution removing unit that removes the scattered radiation distribution obtained by the scattered radiation distribution estimation unit from the intensity distribution of the radiation detected by the radiation detector. A radiation imaging device characterized by this. The radiation imaging apparatus according to claim 3, wherein the scattered radiation distribution estimation unit includes a filter for obtaining the degree of radiation spread according to the thickness of the subject at each position of the subject. Radiation imaging device. In the radiation imaging apparatus according to claim 4, the scattered radiation distribution removing unit obtains a scattered radiation distribution equivalent to that generated when a grid is arranged between the subject and the radiation detector. A radiation imaging apparatus characterized in that it is generated based on the distribution of the thickness of the subject and the scattered radiation distribution obtained by the scattered radiation distribution estimation unit is added to the removed radiation intensity distribution. The radiation imaging apparatus according to claim 4, wherein the radiation intensity distribution is a radiation image of the subject, the scattered radiation distribution is an image of scattered radiation generated by the subject, and the scattered radiation distribution is removed. The unit is a radiation imaging device characterized by removing an image of the scattered radiation from the radiation image. The radiation imaging apparatus according to claim 1, wherein the radiation detector that detects the intensity distribution of the radiation determines whether or not the radiation detector is saturated with the radiation.
When the radiation detector is saturated, the radiation imaging apparatus is characterized by having a replacement unit that replaces the thickness calculated by the thickness distribution calculation unit with a different value at the saturated position. The radiation imaging apparatus according to claim 8, wherein the replacement unit replaces the thickness of the saturated position with a thickness obtained from the radiation intensity detected by the radiation detector. Radiation imaging device. The radiation imaging device according to claim 8, wherein the replacement unit replaces the thickness of the saturated position with a predetermined value. The radiation imaging device according to claim 1.
A correction unit that corrects the thickness value calculated by the thickness distribution calculation unit,
An estimated transmission line image generation unit that generates an estimated transmission line image based on the corrected thickness output by the correction unit,
It further has a comparison unit for comparing the intensity distribution of the radiation with the estimated transmission line image.
The radiation imaging device is characterized in that the correction unit repeats an operation of adjusting a correction amount with respect to a value of the thickness of the correction unit one or more times based on the output of the comparison unit. The radiation imaging device according to claim 1.
The extraction unit is characterized by including at least one of a high-pass filter that extracts high-frequency components in the radiation intensity distribution and a high-pass filter that extracts high-frequency components between a plurality of the radiation intensity distributions detected at different times. Radiation imaging device. An extraction unit that receives the radiation intensity distribution obtained by detecting the radiation that has passed through the subject from the outside and extracts at least one high-frequency component in the spatial axis direction and the time axis direction with respect to the radiation intensity distribution, and the extraction unit. An image processing apparatus including a thickness distribution calculation unit that obtains a thickness distribution of the subject based on an extracted high-frequency component. The image processing apparatus according to claim 13.
A network reception interface unit that receives and acquires the radiation intensity distribution via a communication network,
Image processing unit and
It has a network transmission interface unit that transmits and outputs an image generated by the image processing unit via the communication network.
The image processing unit is a scattered radiation generated by the radiation passing through the subject based on the thickness distribution of the subject calculated by the extraction unit, the thickness distribution calculation unit, and the thickness distribution calculation unit. It is provided with a scattered radiation distribution estimation unit for obtaining a distribution and a scattered radiation distribution removing unit for removing the scattered radiation distribution obtained by the scattered radiation distribution estimation unit from the radiation intensity distribution, and the scattered radiation distribution removing unit is the scattered radiation radiation. An image processing apparatus characterized in that an image is generated from the radiation intensity distribution from which the distribution has been removed. An extraction means that receives a radiation intensity distribution obtained by detecting radiation passing through a subject by a computer from the outside and extracts at least one high frequency component in the spatial axis direction and the time axis direction with respect to the radiation intensity distribution.
An image processing program for functioning as a thickness distribution calculation means for obtaining a thickness distribution of the subject based on high-frequency components extracted by the extraction means.

Images