JP6907962B2 - Radiation image processing equipment, scattered radiation correction method and program - Google Patents

Description

The present invention relates to a radiographic image processing apparatus, a scattered radiation correction method and a program.

Conventionally, when a radiation image of a subject is taken by radiation transmitted through the subject, especially when the thickness of the subject is large, the radiation is scattered in the subject and scattered rays are generated, and the radiation image acquired by the scattered rays is generated. There is a problem that the contrast of the radiation is lowered. Therefore, when taking a radiation image, a scattered radiation removal grid (hereinafter simply referred to as a grid) is provided between the subject and the radiation detector so that the radiation detector for detecting the radiation and acquiring the radiation image is not irradiated with the scattered radiation. ) May be placed for shooting. When the image is taken using the grid, the radiation scattered by the subject is less likely to be applied to the radiation detector, so that the contrast of the radiation image can be improved. However, when a grid is used, the work load of grid placement and the burden on the patient during portable photography performed in a hospital room, etc. are heavy, moire corresponding to the grid pitch is recorded, and it is affected by the distance constraint of the grid. There is a problem. Therefore, in order to improve the contrast lowered by the scattered radiation component of radiation, image processing of scattered radiation correction is performed on the radiation image.

By the way, in the medical field, a relatively wide range of the entire spinal column and all lower limbs of the human body may be photographed in a long length. In long-length imaging, for example, a plurality of radiation detectors are arranged side by side in a holder of an imaging table for long-length imaging, and a radiation generator irradiates a plurality of radiation detectors via a subject. Then, one radiation image (long image) is acquired by combining the small radiation images read from each of the plurality of radiation detectors.

In the scattered radiation correction, the scattered dose is estimated for all pixels, and the pixel values (pixel signal values) of the surrounding pixels are used for estimating the scattered dose. Therefore, in each small radiation image constituting the long image, as shown in FIG. 11, the scattered rays can be estimated in the pixel A, but when they are combined as the long image, they are adjacent to the other small radiation images. At the boundary pixel B, the scattered dose cannot be correctly estimated from the pixels in the image region of the small radiation image.

Therefore, for example, in Patent Document 1, it is assumed that the scattered radiation component at the boundary portion of the small radiation image constituting the long image is affected by the scattered radiation component contained in the adjacent small radiation image, and the scattering dose of the boundary pixel is determined. It is stated that information from other small radiation images will be used for estimation.

JP-A-2016-32623

However, the radiation detection sensitivity of the radiation detector differs depending on the individual. Therefore, if the scattered dose is estimated using the information of another radiation detector as described in Patent Document 1, it cannot be estimated correctly, and there is a possibility that a density step may occur after the scattered radiation correction.

Further, even if the radiation image is obtained by photographing with only one radiation detector, the removal rate of the scattered dose is increased and scattered only in the region of the structure for the purpose of increasing the contrast of the structure. When line correction is performed, a density step occurs at the boundary between that region and another region.

An object of the present invention is to reduce the density difference caused by the scattered radiation correction.

In order to solve the above problems, the invention according to claim 1 is
Scattered ray estimating means for estimating the scattered dose contained in the pixel signal value of each pixel of the radiographic image obtained by radiographing the subject, and
A determination means for determining the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction based on the scattering dose estimated by the scattering ray estimating means.
A scattered radiation correction means that corrects the scattered radiation image by subtracting the scattered dose determined by the determining means from the pixel signal value of each pixel, and a scattered radiation correction means.
It is a radiographic image processing apparatus equipped with
A density step estimation means for estimating a density step that occurs when the scattering dose determined by the determination means is subtracted from the pixel signal value in the boundary pixels of a plurality of image regions constituting the radiation image.
An adjusting means for adjusting the scattering dose to be subtracted from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. When,
To be equipped.

The invention according to claim 2 is the invention according to claim 1.
The radiographic image is a long image obtained by combining a plurality of small radiographic images smaller than the radiographic image.
The scattered radiation estimation means estimates the scattered dose included in the pixel signal value of each pixel of the plurality of small radiation images.
The determination means determines the scattering dose to be subtracted from the pixel signal value of each pixel of the plurality of small radiation images in the scattering ray correction based on the scattering dose estimated by the scattering ray estimation means.
The density step estimation means obtains a density step that occurs when the scattering dose determined by the determination means is subtracted from the pixel signal value at the boundary pixels of a plurality of small radiation images adjacent to each other when combined as the radiation image. Estimate and
The adjusting means subtracts the scattered dose from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. Adjust and
The scattered radiation correction means performs scattered radiation correction by subtracting the determined scattering dose or the adjusted scattering dose from the pixel signal value of each pixel of the plurality of small radiation images.

The invention according to claim 3 is the invention according to claim 1.
A long coupling means that combines a plurality of small radiographic images smaller than the radiographic image to generate the radiological image,
A dividing means for generating a plurality of divided images by dividing the radiographic image coupled by the long coupling means into an arbitrary number of images.
With
The scattered radiation estimation means estimates the scattered dose included in the pixel signal value of each pixel for each of the plurality of divided images.
The determination means determines the scattering dose to be subtracted from the pixel signal value of each pixel in the scattering ray correction based on the scattering dose estimated by the scattering ray estimating means for each of the plurality of divided images.
The density step estimation means determines, for each of the plurality of divided images, the scattering dose determined by the determining means at the boundary pixels of the image region of the plurality of small radiation images included in the divided image from the pixel signal value. Estimate the density difference that occurs when subtracting,
The adjusting means is described in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means for each of the plurality of divided images. Adjust the scattering dose to be subtracted from the pixel signal value of the boundary pixel,
The scattered radiation correction means performs scattered radiation correction on each of the plurality of divided images by subtracting the determined scattering dose or the adjusted scattering dose from the pixel signal value of each pixel.
A recombination means for recombine the plurality of divided images that have been subjected to the scattered radiation correction by the scattered radiation correcting means is provided.

The invention according to claim 4 is the invention according to claim 2 or 3.
The plurality of small radiation images are images generated from a plurality of radiation detectors that detect radiation transmitted through the subject by radiography.
An acquisition means for acquiring the imaging conditions in the radiography, the imaging site, and the position information of the radiation detector that generated each of the plurality of small radiographic images is provided.
The scattered radiation estimation means determines the image signal value of each pixel of the radiation image based on the imaging conditions in the radiation imaging, the imaging site, and the position information of the radiation detector that generated each of the plurality of small radiation images. Estimate the scattered dose contained.

The invention according to claim 5 is the invention according to claim 1.
A region dividing means for dividing the radiation image into a plurality of image regions, and
A setting means for setting a scattered radiation removal rate in a plurality of image regions divided by the region dividing means is provided.
The determining means multiplies the scattered radiation dose estimated by the scattered radiation estimation means for each pixel of the divided image regions in the radiation image by the scattered radiation removal rate set by the setting means. To determine the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction.
The density step estimation means is a density generated when the scattering dose determined by the determination means is subtracted from the pixel signal value at the boundary pixels of a plurality of adjacent image regions divided by the region division means in the radiation image. Estimate the step and
The adjusting means subtracts the scattered dose from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. Adjust and
The scattered radiation correction means performs scattered radiation correction by subtracting the determined scattering dose or the adjusted scattering dose from the pixel signal value of each pixel of the radiation image.

The invention according to claim 6 is the invention according to claim 5.
A recognition means for recognizing a region of a specific structure from the radiographic image is provided.
The region dividing means divides the radiographic image into a plurality of regions based on the recognition result by the recognition means.

The invention according to claim 7
A scattering ray estimation process that estimates the scattering dose contained in the pixel signal value of each pixel of the radiation image obtained by radiographing the subject, and a scattered radiation estimation process.
A determination step of determining the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction based on the scattering dose estimated in the scattering ray estimation step.
A scattering ray correction step of performing scattering ray correction on the radiation image by subtracting the scattering dose determined in the determination step from the pixel signal value of each pixel, and
It is a scattered radiation correction method including
A density step estimation step for estimating a density step that occurs when the scattering dose determined in the determination step is subtracted from the pixel signal value at the boundary pixels of a plurality of image regions constituting the radiation image, and a density step estimation step.
An adjustment step of adjusting the scattering dose to be subtracted from the pixel signal value of the boundary pixel in the scattered ray correction step so that the density step after the scattered ray correction is reduced as compared with the density step estimated in the density step estimation step. When,
including.

The program of the invention according to claim 8 is
Scattered ray estimating means for estimating the scattered dose contained in the pixel signal value of each pixel of the radiographic image obtained by radiographing the subject, and
A determination means for determining the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction based on the scattering dose estimated by the scattering ray estimating means.
A scattered radiation correction means that corrects the scattered radiation image by subtracting the scattered dose determined by the determining means from the pixel signal value of each pixel, and a scattered radiation correction means.
A computer used in a radiographic image processing device equipped with
A density step estimation means for estimating a density step that occurs when the scattering dose determined by the determination means is subtracted from the pixel signal value in the boundary pixels of a plurality of image regions constituting the radiation image.
An adjusting means for adjusting the scattering dose to be subtracted from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. ,
To function as.

According to the present invention, it is possible to reduce the density difference caused by the scattered radiation correction.

It is a figure which shows the whole structure of the radiation imaging system in embodiment of this invention. It is a block diagram which shows the functional structure of the console of FIG. It is a figure which shows typically the flow of the long image generation processing A executed by the control part of FIG. 2 in 1st Embodiment. FIG. 5 is a flowchart showing a long image generation process A executed by the control unit of FIG. 2 in the first embodiment. It is a flowchart which shows the scattered ray correction process executed in step S1 of FIG. It is a figure which shows typically the density step adjustment. It is a figure which shows typically the flow of the long image generation processing B executed by the control part of FIG. 2 in the 2nd Embodiment. FIG. 5 is a flowchart showing a long image generation process B executed by the control unit of FIG. 2 in the second embodiment. It is a figure which shows an example of the radiographic image applied to the 3rd Embodiment. It is a flowchart which shows the scattering ray correction process for each area executed by the control part of FIG. 2 in 3rd Embodiment. It is a figure which shows the pixel which can estimate the scattered ray with high accuracy, and the pixel which cannot estimate a scattered ray.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

<First Embodiment>
[Structure of Radiation Imaging System 100]
First, the configuration of the first embodiment will be described.
FIG. 1 is a diagram showing an overall configuration example of the radiation imaging system 100 according to the present embodiment. As shown in FIG. 1, the radiographic image photographing system 100 is configured by connecting the photographing device 1 and the console 2 so as to be able to transmit and receive data.

The imaging device 1 includes a plurality of radiation detectors P1 to P3 for performing long imaging, an imaging table 11 for long imaging capable of loading the radiation detectors P1 to P3, and a radiation generator 12. It is configured. The photographing table 11 can be loaded with a plurality of radiation detectors P1 to P3 in the holder 11a so as to be partially overlapped in the vertical direction.

In the following, as shown in FIG. 1, a case where the holder 11a of the photographing table 11 is configured so that three radiation detectors can be loaded will be described. However, the present invention describes the case where the photographing table 11 can be loaded with three radiation detectors. The number of radiation detectors loaded in the device is not limited to three, and may be two or four or more.

The radiation detectors P1 to P3 are composed of a semiconductor image sensor such as an FPD (Flat Panel Detector), and are provided so as to face the radiation generator 12 with the subject H interposed therebetween. The radiation detectors P1 to P3 have, for example, a glass substrate or the like, and emit radiation (X-rays) emitted from the radiation generator 12 at a predetermined position on the substrate and transmitted at least through the subject H according to the intensity thereof. A plurality of detection elements (pixels) that are detected and the detected radiation is converted into an electric signal and stored are arranged in a matrix. Each pixel is configured to include a switching unit such as a TFT (Thin Film Transistor). The radiation detectors P1 to P3 control the switching unit of each pixel based on the image reading condition input from the console 2, and switch the reading of the electric signal accumulated in each pixel to each pixel. Image data is acquired by reading the accumulated electrical signal. Then, the radiation detectors P1 to P3 attach the position information (referred to as panel position information) of the radiation detector that acquired the image data to the acquired image data, and output the image data to the console 2. The panel position information includes the coordinate position information of the pixel of the part overlapping the adjacent radiation detector, and the coordinate position of the boundary pixel adjacent to the image data of the other radiation detector when combined with the image data of the other radiation detector. Information and position information of the radiation generator 12 with respect to the tube (for example, front, center, back; in FIG. 1, the radiation detector P1 is in the back, the radiation detector P2 is in the center, and the radiation detector P3 is in front).

The image data acquired from the radiation detectors P1 to P3 constitutes one long image (radiation image) by being combined, and is called a small radiation image.

The radiation generator 12 is arranged at a position facing the radiation detectors P1 to P3 with the subject H in between, and is loaded into the holder 11a via the patient who is the subject H based on the radiation irradiation conditions input from the console 2. A long-length image is taken by irradiating the plurality of radiation detectors P1 to P3 with radiation. The radiation irradiation conditions input from the console 2 are, for example, a tube current value, a tube voltage value, a radiation irradiation time, a mAs value, and a SID (the shortest distance between the radiation detectors P1 to P3 and the tube of the radiation generator 12). ) Etc.

The console 2 outputs radiation irradiation conditions and image reading conditions to the photographing device 1 to control the radiation photographing and the reading operation of the radiation image by the photographing device 1, and also performs image processing on the small radiation image acquired by the photographing device 1. It functions as a radiation image processing device to be applied.
As shown in FIG. 2, the console 2 includes a control unit 21, a storage unit 22, an operation unit 23, a display unit 24, and a communication unit 25, and each unit is connected by a bus 26.

The control unit 21 is composed of a CPU (Central Processing Unit), a RAM (Random Access Memory), and the like. The CPU of the control unit 21 reads out the system program and various processing programs stored in the storage unit 22 in response to the operation of the operation unit 23, expands them in the RAM, and operates each unit of the console 2 according to the expanded program. In addition, the irradiation operation and the reading operation of the photographing device 1 are centrally controlled. Further, the long image generation process A and the like, which will be described later, are executed using the small radiation images transmitted from the radiation detectors P1 to P3 of the photographing apparatus 1.
The control unit 21 functions as a scattered radiation estimation means, a determination means, a scattered radiation correction means, a concentration step estimation means, an adjustment means, and an acquisition means.

The storage unit 22 is composed of a non-volatile semiconductor memory, a hard disk, or the like. The storage unit 22 stores data such as parameters or processing results necessary for executing processing by various programs and programs executed by the control unit 21. Various programs are stored in the form of readable program code, and the control unit 21 sequentially executes operations according to the program code.
In addition, the storage unit 22 stores the irradiation conditions and the image reading conditions corresponding to the imaging site. Further, the storage unit 22 stores shooting order information transmitted from a RIS (Radiology Information System) or the like (not shown). The imaging order information includes patient information and examination information (examination ID, imaging site, examination date, etc.). The imaging region may be the imaging region of the entire long image, or may be the imaging region of individual images obtained by the radiation detectors P1 to P3.

Further, the storage unit 22 is obtained by an experiment in which the tube voltage is changed to photograph acrylic plates of various thicknesses (similar to the human body in X-ray attenuation rate) with a predetermined mAs value and SID, for each tube voltage. The relational expression (Equation 1) between the pixel value and the body thickness of the above, and the mAs value and the SID used in the experiment are stored. In addition, the storage unit 22 stores a table showing the relationship between the body thickness and the scattered radiation content for each imaging site, which has been obtained in advance by an experiment.

The operation unit 23 includes a keyboard equipped with cursor keys, number input keys, various function keys, and a pointing device such as a mouse, and controls an instruction signal input by key operation on the keyboard or mouse operation. Output to 21. Further, the operation unit 23 may include a touch panel on the display screen of the display unit 24, and in this case, the operation unit 23 outputs an instruction signal input via the touch panel to the control unit 21. Further, the operation unit 23 is provided with an exposure switch for instructing the radiation generator 12 to perform dynamic imaging.

The display unit 24 is composed of a monitor such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays input instructions, data, and the like from the operation unit 23 according to instructions of display signals input from the control unit 21. do.

The communication unit 25 has an interface for transmitting and receiving data with the radiation generator 12 and the radiation detectors P1 to P3. The communication between the console 2, the radiation generator 12, and the radiation detectors P1 to P3 may be wired communication or wireless communication.
Further, the communication unit 25 includes a LAN adapter, a modem, a TA (Terminal Adapter), etc., and controls data transmission / reception with a RIS or the like (not shown) connected to the communication network.

[Operation of Radiation Imaging System 100]
When the radiation detectors P1 to P3 are set in the holder 11a in the imaging device 1 and the imaging order information to be imaged is selected by the operation unit 23 on the console 2, the imaging conditions corresponding to the selected imaging order information are selected. (Radiation irradiation conditions and radiation image reading conditions) are transmitted to the photographing apparatus 1. When the subject H is positioned and the exposure switch is pressed, radiation is emitted by the radiation generator 12 in the photographing apparatus 1, and the image data of the radiation image is read by each of the radiation detectors P1 to P3. Panel position information is attached to the read image data (that is, a small radiation image) and transmitted to the console 2.

When a small radiation image is received from the radiation detectors P1 to P3, the control unit 21 executes the long image generation process A on the console 2. FIG. 3 is a diagram schematically showing the flow of the long image generation process A, and FIG. 4 is a flowchart showing the flow of the long image generation process A. The long image generation process A is executed in collaboration with the control unit 21 and the program stored in the storage unit 22.

First, the control unit 21 executes a scattered radiation correction process for each small radiation image received from the radiation detectors P1 to P3 (step S1).

FIG. 5 is a flowchart showing the flow of the scattered radiation correction process.
In the scattered radiation correction process, the control unit 21 first acquires information on the imaging conditions and the imaging region based on the imaging order information used for imaging, and also acquires panel position information attached to the small radiation image ( Step S101).

Next, the control unit 21 estimates the scattering dose for each pixel of the small area image based on the acquired imaging conditions, imaging site, and panel position information (step S102).
In step S102, the scattering dose for each pixel is estimated by the following processes (1) to (4).
Here, in order to carry out the estimation of the body thickness of (1), an acrylic plate of various thicknesses (similar to the human body in X-ray attenuation rate) with a predetermined mAs value and SID by changing the tube voltage by an experiment in advance. The relational expression between the pixel value obtained in the experiment and the acrylic thickness (the following (Equation 1)) was calculated, and the mAs value, SID, and tube voltage used in the experiment (Equation 1) were calculated. Is stored in the storage unit 22.
Acrylic thickness = Coefficient A x log (pixel value) + Coefficient B ... (Equation 1)
In addition, the storage unit 22 stores in advance a table showing the relationship between the body thickness and the scattered radiation content for each imaging site.

(1) Estimate the body thickness based on the shooting conditions and the panel position information First, the SID of the acquired shooting conditions is corrected based on the panel position information. For example, when the position information of the radiation generator 12 with respect to the tube included in the panel position information of the small radiation image is "center", the thickness of the radiation detectors 1P to 3P is stored in the SID stored in the storage unit 22. Add a certain α. When the panel position information of the image data is "back", 2α is added to the SID stored in the storage unit 22. As a result, an accurate SID can be obtained according to the position of the radiation detector, and the density step due to the scattered radiation correction error due to the difference in the photographing distance for each radiation detector can be reduced.
Next, the pixel value p_1 of the small radiation image acquired by photographing is converted into the pixel value p_0 when photographed under the imaging conditions of the above experiment by the following (Equation 2).
p_0 ＝ p_1 × (mAs_1 / mAs_0) × {(SID_0) ² / (SID_1) ² } ・ ・ ・ (Equation 2)
Here, mAs_0 is the mAs value used in the experiment, mAs_1 is the mAs value used in the actual shooting, SID_0 is the SID used in the experiment, and SID_1 is the SID (corrected SID) used in the actual shooting. (Equation 2) is based on the finding that the pixel value of the image data obtained by the radiation detector is proportional to the mAs value and inversely proportional to the SID.
Next, the converted pixel value p_0 is substituted into (Equation 1), and the obtained acrylic thickness is estimated as the body thickness.

(2) Estimating the scattered radiation content from the body thickness Calculated in (1) based on a table showing the relationship between the body thickness and the scattered radiation content according to the imaging site stored in the storage unit 22. Estimate the scattered radiation content from the body thickness.

(3) Extracting low-frequency components of a small-radiation image to generate a low-frequency component image For example, using a filter for extracting low-frequency components such as a Mean filter, a Gaussian filter, and a Bilateral filter, the low frequency of a small-radiation image is generated. Extract the ingredients. For example, suppose that each pixel of a small radiation image is affected by scattered rays generated from a region of n pixels × n pixels (n is a positive integer) around the pixel (pixel of interest). A low-frequency component image is generated by performing filter processing for each pixel using a filter of n pixels × n pixels centered on that pixel.
It should be noted that, in the case of a long image, with respect to the boundary pixels adjacent to other small radiation images and the pixels in the vicinity thereof, not all of the surrounding n pixels × n pixels may exist in the small radiation region. In this case, the pixel value of the corresponding pixel is estimated as the pixel value of the pixel closest to the position in the small radiation image.

(4) The scattering dose for each pixel is estimated from the pixel value of the low-frequency component image.
The scattered dose is estimated by multiplying the pixel value of the low frequency component image by the scattered radiation content.

Next, the control unit 21 determines the scattering dose to be removed from each pixel of the small radiation image (subtracted from the pixel value of each pixel) by the scattered radiation correction based on the estimated scattering dose (step S103).
For example, the scattering dose to be removed is determined by multiplying the estimated scattering dose for each pixel by a predetermined scattering ray removal rate.

Next, the control unit 21 estimates the density step after correction of the scattered radiation of the boundary pixel between the image and another small radiation image that is adjacent to the image when combined as a long image (step S104).
For example, the density is compared between the pixel value of the boundary pixel of the small radiation image minus the scattered dose to be removed and the pixel value of the boundary pixel of another adjacent small radiation image minus the scattered dose to be removed. Estimate the step.
For example, as shown in FIG. 6, the pixel value of pixel B1, which is the boundary pixel of the small radiation image acquired by the radiation detector P1, is 500, and the scattered dose to be removed is 200, which are acquired by the radiation detector P2. When the pixel value of the pixel B2 adjacent to the pixel B1 of the small radiation image is 600 and the scattered dose to be removed is 250, the pixel value (density value) after the scattered ray correction of the pixel B1 is 300, and the scattered ray correction of the pixel B2. The subsequent pixel value (density value) is 350, and the density step between the pixel B1 and the pixel B2 after the scattered ray correction is estimated to be 50.

Next, the control unit 21 determines the pixel value of the boundary pixel in the scattered radiation correction so that the density step between the boundary pixel of the small radiation image after the scattered radiation correction and the adjacent boundary pixel of the other small radiation image becomes zero. The scattering dose to be subtracted from is adjusted (step S105).
For example, in the case of the pixels B1 and B2 shown in FIG. 6, the scattered dose to be removed (subtracted) from the pixel B1 is 200 in order so that the pixel values of the pixels B1 and B2 after the scattered radiation correction are both 325. Adjust the scattering dose removed from pixel B2 to -25 = 175 and 250 + 25 = 275.

In step S105, the scattering dose to be subtracted from the boundary pixels so that the density near the boundary portion changes smoothly may be changed even for a plurality of pixels within a predetermined range.
Further, the processing time is shortened by performing irradiation field recognition and direct X-ray area recognition on the small radiation image in advance and removing these areas outside the subject from the processing target areas of the density step adjustment in steps S104 and S105. May be good.

Then, the control unit 21 subtracts the scattering dose determined from the pixel value of each pixel of the small radiation image (the scattering dose adjusted for the boundary pixel) to perform the scattered radiation correction (step S106), and the small radiation corrected. The radiation image is subjected to a grain suppression process (step S107), and the process proceeds to step S2 of FIG.

Here, in the present embodiment, the circuit board portion of the radiation detector P2 overlaps the coupling portion of the radiation detector P1 with the radiation detector P2. Therefore, the circuit board of the radiation detector P2 is reflected in a predetermined region of the small radiation image transmitted from the radiation detector P1. The area where this circuit board is reflected has poor graininess. Therefore, in the grain suppression process, it is preferable to change the grain suppression level between the circuit board portion and the other regions in the small radiation image based on the panel position information. Further, the noise magnitude may be estimated based on the dispersion of pixel values and the standard deviation, and the grain suppression level may be changed based on the estimated noise magnitude.

In step S2 of FIG. 4, the control unit 21 executes a long coupling process for combining a plurality of small radiation images (step S2).
In step S2, first, based on the panel position information, a plurality of small radiation images corrected for scattered radiation are combined to generate a long image. Next, the density difference between the combined small radiation images is corrected. For example, since the radiation detectors P1 to P3 have a sensitivity difference, the density difference between the small radiation images caused by the sensitivity difference or the like is corrected. In addition, the density difference caused by the positional relationship between the radiation detectors P1 to P3 is corrected. For example, since the radiation dose in front of the tube reduces the radiation dose reaching the radiation detector in the back, the concentration value corresponding to the reduced radiation dose in the radiation detector in the back is the pixel value. Add to. Also, if there is an reflection on the substrate of the radiation detector that overlaps in the foreground, correct it.
When the long combination process is completed, the control unit 21 ends the long image generation process A.

As described above, in the first embodiment, the control unit 21 estimates the scattering dose included in the pixel value of each pixel of the plurality of small radiation images, and subtracts the scattering dose from the pixel value based on the estimated scattering dose. Is determined, and the density step that occurs when the determined scattered dose is subtracted from the pixel value by scattered ray correction in the boundary pixels of a plurality of small radiation images adjacent to each other when combined as a long image is estimated and estimated. The scattered dose to be subtracted from the pixel value of the boundary pixel in the scattered ray correction is adjusted so that the resulting density step becomes 0. Then, after performing scattered radiation correction on a plurality of small radiation images using the determined or adjusted scattering dose, the plurality of small radiation images are combined to generate a long image. Therefore, in a long image, it is possible to reduce the density step at the boundary portion of a plurality of small radiation images caused by the scattered radiation correction.

<Second embodiment>
Next, a second embodiment of the present invention will be described.
In the first embodiment, as shown in FIG. 3, a plurality of small radiation images obtained by the radiation detectors P1 to P3 are subjected to a scattered radiation correction process and then a long coupling process to be coupled. However, in the second embodiment, as shown in FIG. 7, first, a plurality of small radiation images obtained by the radiation detectors P1 to P3 are combined by performing a long coupling process, and then the images are combined. A case will be described in which the combined long images are divided into images at an arbitrary number and locations, the scattered radiation correction process is executed, and then the divided images are recombined. In the second embodiment, when it is desired to divide the image in a place where the density difference is inconspicuous, or when the parallel calculation of the scattered radiation correction processing can be performed, the long image is divided into a number that can be calculated in parallel and the scattered radiation correction processing is performed in parallel. This is an example assuming a case where the processing speed is to be increased by performing the above.

Since the configuration and the shooting operation of the second embodiment are the same as those described in the first embodiment, the description will be incorporated, and the operation of the console 2 in the second embodiment will be described below.

When the image data is received from the radiation detectors P1 to P3, the control unit 21 executes the long image generation process B on the console 2. FIG. 8 is a flowchart showing the flow of the long image generation process B. The long image generation process B is executed in collaboration with the control unit 21 and the program stored in the storage unit 22.

First, the control unit 21 executes a long combination process to generate a long image (step S11).
In step S11, first, a plurality of small radiation images are combined to generate a long image based on the panel position information. Next, the density difference between the combined small radiation images is corrected. For example, since the radiation detectors P1 to P3 have a sensitivity difference, the density difference between the small radiation images caused by the sensitivity difference or the like is corrected. In addition, the density difference caused by the positional relationship between the radiation detectors P1 to P3 is corrected. For example, since the radiation dose in front of the tube reduces the radiation dose reaching the radiation detector in the back, the concentration value corresponding to the reduced radiation dose in the radiation detector in the back is the pixel value. Add to. Also, if there is an reflection on the substrate of the radiation detector that overlaps in the foreground, correct it.

Next, the long image generated in step S11 is divided to generate a plurality of divided images (step S12).
The division position and the number of divisions of the long image can be arbitrarily specified by the user by the operation unit 23.

Next, the control unit 21 executes the scattered radiation correction process for each of the plurality of divided images (step S13).
In step S13, the process described with reference to FIG. 5 in the first embodiment is executed for each of the plurality of divided images. However, in step S104, when the divided image includes the image areas of a plurality of small radiation images, the density step after the scattered radiation correction between the boundary pixels of the image areas of the plurality of small radiation images included in the divided image. To estimate. In step S105, the scattering dose to be subtracted from the pixel values of the boundary pixels in the scattered radiation correction is adjusted so that the density step between the boundary pixels of the plurality of small radiation images in the divided image after the scattered radiation correction becomes zero. ..

When the scattered radiation correction process is completed, the control unit 21 recombines the divided images after the scattered radiation correction (step S14), and ends the long image generation process B.

As described above, in the second embodiment, the control unit 21 combines a plurality of small radiation images and divides the combined long image at an arbitrary position to generate a plurality of divided images, and a plurality of divided images. For each of the images, the scattering dose contained in the pixel value of each pixel is estimated, the scattering dose to be subtracted from the pixel value is determined based on the estimated scattering dose, and a plurality of small radiation images included in the divided image. Estimate the density step that occurs when the scattered dose determined in the boundary pixel of is subtracted from the pixel value, and adjust the scattered dose to be subtracted from the pixel value of the boundary pixel in scattered ray correction so that the estimated density step becomes 0. do. Then, after performing scattering ray correction on the divided image using the determined or adjusted scattering dose, the plurality of divided images are recombined. Therefore, it is possible to reduce the density step at the boundary portion of a plurality of small radiation images caused by the scattered radiation correction in a long image. In addition, since it is possible to divide a long image into an arbitrary number and location and execute the scattered radiation correction processing, it is possible to divide the long image in a place where the density difference is inconspicuous or when parallel calculation of the scattered radiation correction processing can be performed in parallel. It is possible to increase the processing speed by dividing a long image into a calculable number.

<Third embodiment>
Next, a third embodiment of the present invention will be described.
If you want to increase the contrast of a certain part (for example, a specific structure) in one radiographic image, you can increase the contrast of that part by increasing the scattering ray removal rate than the other areas (Fig.). See inside the rectangle of 9). However, in this case, a density difference is formed between the portion where the scattered radiation removal rate is increased and the other region after the scattered radiation correction.
Therefore, in the third embodiment, an example of reducing the density difference caused by such a difference in the scattered radiation removal rate in one radiographic image will be described.

In the first embodiment, three small radiation images are acquired by using the three radiation detectors P1 to P3, but the holder 11a of the imaging table 11 of the third embodiment has one image. The radiation detector P can be attached. Since the other configurations are the same as those described in the first embodiment, the description will be incorporated, and the operation in the third embodiment will be described below.

When the shooting order information to be shot is selected by the operation unit 23 on the console 2 with the radiation detector P set in the holder 11a in the shooting device 1, the shooting conditions (radiation) according to the selected shooting order information are selected. Irradiation conditions and radiation image reading conditions) are transmitted to the photographing apparatus 1. When the subject H is positioned and the exposure switch is pressed, radiation is emitted by the radiation generator 12 in the imaging device 1, a radiation image is read by the radiation detector P, and the read radiation image is read by the console. It is sent to 2.

When the radiation image is received from the radiation detector P, the control unit 21 executes the area-specific scattered radiation correction process on the console 2. FIG. 10 is a flowchart showing the flow of the scattered radiation correction processing for each region. The area-specific scattered radiation correction process is executed in collaboration with the control unit 21 and the program stored in the storage unit 22.

First, the control unit 21 executes a region recognition process on the received radiation image (step S21). Here, the region of the specific structure set in advance is recognized. The area recognition may be performed automatically by, for example, image analysis, or the user may specify an area from the image displayed on the display unit 24 by the operation unit 23.

Next, the control unit 21 divides the received radiation image based on the result of the area recognition into a plurality of image areas (step S22).
For example, the received radiographic image is divided into a recognized specific structure area and other areas.

Next, the control unit 21 acquires information on the imaging conditions and the imaging region based on the imaging order information used for imaging, and estimates the scattered dose for each pixel of the radiation image based on the acquired imaging conditions and the imaging region. (Step S23). Since the process of step S23 is the same as the process performed on the small radiation region in step S102 of FIG. 5 in the first embodiment, the description is incorporated.

Next, the control unit 21 sets the scattered radiation removal rate for each divided image region, and removes the scattered radiation from each pixel of the radiation image based on the estimated scattering dose and the set scattered radiation removal rate for each pixel (). The scattering dose (subtracted from the pixel value of each pixel) is determined (step S24).
For example, for example, the input of the scattered radiation removal rate (0% to 100%) of the region of the specific structure recognized by the operation of the operation unit 23 by the user is accepted, and the input scattered radiation removal is performed for the region of the specific structure. The rate is set, and a predetermined scattered radiation removal rate is set for the other regions. Then, the scattered radiation dose to be removed is determined by multiplying the estimated scattering dose for each pixel by the set scattered radiation removal rate.

Next, the control unit 21 estimates the density step after the scattered radiation correction in the boundary pixels of a plurality of image regions adjacent to each other (step S25).
In step S25, the value obtained by subtracting the scattering dose to be removed from the pixel value of the boundary pixel in the image region of the specific structure and the value obtained by subtracting the scattering dose to be removed from the pixel value of the boundary pixel in another adjacent image region. Is compared to estimate the density difference (see FIG. 6).

Next, the control unit 21 adjusts the scattering dose to be subtracted by the scattered radiation correction so that the density step between the boundary pixels after the scattered radiation correction becomes 0 (step S26).

In the process of step S26, the scattering dose to be subtracted from the boundary pixels so that the density near the boundary portion changes smoothly may be changed even for a plurality of pixels within a predetermined range.
Further, the processing time may be shortened by performing irradiation field recognition and direct X-ray area recognition in advance and removing these areas outside the subject from the processing target areas for adjusting the density difference in steps S25 and S26.

Then, the scattering dose determined from the pixel value of each pixel of the radiation image (the scattering dose adjusted for the boundary pixel) is subtracted to perform the scattering ray correction (step S27), and the radiation image after the scattering ray correction is subjected to the grain suppression process. (Step S28), the area-specific scattered radiation correction process is completed.

As described above, in the third embodiment, the control unit 21 divides the radiation image into a plurality of image regions, sets the scattered radiation removal rate in each of the divided regions, and obtains the estimated scattering dose for each pixel. The scattering dose to be subtracted from the pixel value is determined by multiplying the set scattered radiation removal rate, and the density generated when the determined scattering dose is subtracted from the pixel value by scattered radiation correction at the boundary pixels of a plurality of image regions. The step is estimated, and the scattering dose to be subtracted from the pixel value of the boundary pixel in the scattered ray correction is adjusted so that the estimated density step becomes 0. Then, the radiation image is corrected for scattered radiation using the determined or adjusted scattering dose. Therefore, when the scattered radiation removal rate is changed depending on the image region in the radiation image, it is possible to reduce the density step caused by the difference in the scattered radiation removal rate in the radiation image.

As described above, the control unit 21 of the console 2 estimates the scattering dose included in the pixel value of each pixel of the radiation image obtained by radiographing the subject, and scatters based on the estimated scattering dose. In line correction, the scattering dose to be subtracted from the pixel values of the boundary pixels of multiple image regions in a radiation image is determined, and the density step that occurs when the determined scattering dose is subtracted from the pixel values of the boundary pixels of multiple image regions is estimated. Then, the scattered dose to be subtracted from the pixel value of the boundary pixel is adjusted so that the estimated density step becomes 0. Then, the radiation image is corrected for scattered radiation using the adjusted scattering dose. Therefore, it is possible to reduce the density difference caused by the scattered radiation correction in the radiation image.

The description in the above embodiment is a preferable example of the present invention, and is not limited thereto.

For example, in the above embodiment, the case where the present invention is applied to a radiographic image of the chest has been described as an example, but the present invention may be applied to a radiographic image obtained by photographing another part.

Further, in the above embodiment, the case where the console 2 that controls the photographing apparatus 1 has a function as a radiographic image processing apparatus has been described, but the radiographic image processing apparatus may be a separate body from the console.

Further, in the above embodiment, the concentration step is reduced to 0 as a preferable example, but the present invention is not limited to this.

Further, for example, in the above description, an example in which a hard disk, a non-volatile memory of a semiconductor, or the like is used as a computer-readable medium for the program according to the present invention has been disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. A carrier wave is also applied as a medium for providing data of the program according to the present invention via a communication line.

In addition, the detailed configuration and detailed operation of each device constituting the radiation imaging system can be appropriately changed without departing from the spirit of the present invention.

100 Radiation imaging system 1 Imaging device 11 Imaging table 11a Holder 12 Radiation generator P1 to P3 Radiation detector 2 Console 21 Control unit 22 Storage unit 23 Operation unit 24 Display unit 25 Communication unit 26 Bus

Claims (8)

Scattered ray estimating means for estimating the scattered dose contained in the pixel signal value of each pixel of the radiographic image obtained by radiographing the subject, and
A determination means for determining the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction based on the scattering dose estimated by the scattering ray estimating means.
A scattered radiation correction means that corrects the scattered radiation image by subtracting the scattered dose determined by the determining means from the pixel signal value of each pixel, and a scattered radiation correction means.
It is a radiographic image processing apparatus equipped with
A density step estimation means for estimating a density step that occurs when the scattering dose determined by the determination means is subtracted from the pixel signal value in the boundary pixels of a plurality of image regions constituting the radiation image.
An adjusting means for adjusting the scattering dose to be subtracted from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. When,
A radiographic image processing apparatus comprising. The radiographic image is a long image obtained by combining a plurality of small radiographic images smaller than the radiographic image.
The scattered radiation estimation means estimates the scattered dose included in the pixel signal value of each pixel of the plurality of small radiation images.
The determination means determines the scattering dose to be subtracted from the pixel signal value of each pixel of the plurality of small radiation images in the scattering ray correction based on the scattering dose estimated by the scattering ray estimation means.
The density step estimation means obtains a density step that occurs when the scattering dose determined by the determination means is subtracted from the pixel signal value at the boundary pixels of a plurality of small radiation images adjacent to each other when combined as the radiation image. Estimate and
The adjusting means subtracts the scattered dose from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. Adjust and
The scattered radiation correction means according to claim 1, wherein the scattered radiation correction means performs the scattered radiation correction by subtracting the determined scattering dose or the adjusted scattering dose from the pixel signal value of each pixel of the plurality of small radiation images. Radiation image processing equipment. A long coupling means that combines a plurality of small radiographic images smaller than the radiographic image to generate the radiological image,
A dividing means for generating a plurality of divided images by dividing the radiographic image coupled by the long coupling means into an arbitrary number of images.
With
The scattered radiation estimation means estimates the scattered dose included in the pixel signal value of each pixel for each of the plurality of divided images.
The determination means determines the scattering dose to be subtracted from the pixel signal value of each pixel in the scattering ray correction based on the scattering dose estimated by the scattering ray estimating means for each of the plurality of divided images.
The density step estimation means determines, for each of the plurality of divided images, the scattering dose determined by the determining means at the boundary pixels of the image region of the plurality of small radiation images included in the divided image from the pixel signal value. Estimate the density difference that occurs when subtracting,
The adjusting means is described in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means for each of the plurality of divided images. Adjust the scattering dose to be subtracted from the pixel signal value of the boundary pixel,
The scattered radiation correction means performs scattered radiation correction on each of the plurality of divided images by subtracting the determined scattering dose or the adjusted scattering dose from the pixel signal value of each pixel.
The radiation image processing apparatus according to claim 1, further comprising a recombination means for recombination of the plurality of divided images that have been subjected to scattered radiation correction by the scattered radiation correcting means. The plurality of small radiation images are images generated from a plurality of radiation detectors that detect radiation transmitted through the subject by radiography.
An acquisition means for acquiring the imaging conditions in the radiography, the imaging site, and the position information of the radiation detector that generated each of the plurality of small radiographic images is provided.
The scattered radiation estimation means determines the image signal value of each pixel of the radiation image based on the imaging conditions in the radiation imaging, the imaging site, and the position information of the radiation detector that generated each of the plurality of small radiation images. The radiographic image processing apparatus according to claim 2 or 3, wherein the included scattered dose is estimated. A region dividing means for dividing the radiation image into a plurality of image regions, and
A setting means for setting a scattered radiation removal rate in a plurality of image regions divided by the region dividing means is provided.
The determining means multiplies the scattered radiation dose estimated by the scattered radiation estimation means for each pixel of the divided image regions in the radiation image by the scattered radiation removal rate set by the setting means. To determine the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction.
The density step estimation means is a density generated when the scattering dose determined by the determination means is subtracted from the pixel signal value at the boundary pixels of a plurality of adjacent image regions divided by the region division means in the radiation image. Estimate the step and
The adjusting means subtracts the scattered dose from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. Adjust and
The radiation image processing according to claim 1, wherein the scattered radiation correction means performs scattered radiation correction by subtracting the determined scattering dose or the adjusted scattering dose from the pixel signal value of each pixel of the radiation image. Device. A recognition means for recognizing a region of a specific structure from the radiographic image is provided.
The radiographic image processing apparatus according to claim 5, wherein the region dividing means divides the radiographic image into a plurality of regions based on the recognition result by the recognition means. A scattering ray estimation process that estimates the scattering dose contained in the pixel signal value of each pixel of the radiation image obtained by radiographing the subject, and a scattered radiation estimation process.
A determination step of determining the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction based on the scattering dose estimated in the scattering ray estimation step.
A scattering ray correction step of performing scattering ray correction on the radiation image by subtracting the scattering dose determined in the determination step from the pixel signal value of each pixel, and
It is a scattered radiation correction method including
A density step estimation step for estimating a density step that occurs when the scattering dose determined in the determination step is subtracted from the pixel signal value at the boundary pixels of a plurality of image regions constituting the radiation image, and a density step estimation step.
An adjustment step of adjusting the scattering dose to be subtracted from the pixel signal value of the boundary pixel in the scattered ray correction step so that the density step after the scattered ray correction is reduced as compared with the density step estimated in the density step estimation step. When,
Scattered ray correction method including. Scattered ray estimating means for estimating the scattered dose contained in the pixel signal value of each pixel of the radiographic image obtained by radiographing the subject, and
A determination means for determining the scattering dose to be subtracted from the pixel signal value of each pixel of the radiation image in the scattering ray correction based on the scattering dose estimated by the scattering ray estimating means.
A scattered radiation correction means that corrects the scattered radiation image by subtracting the scattered dose determined by the determining means from the pixel signal value of each pixel, and a scattered radiation correction means.
A computer used in a radiographic image processing device equipped with
A density step estimation means for estimating a density step that occurs when the scattering dose determined by the determination means is subtracted from the pixel signal value in the boundary pixels of a plurality of image regions constituting the radiation image.
An adjusting means for adjusting the scattering dose to be subtracted from the pixel signal value of the boundary pixel in the scattered ray correcting means so that the density step after the scattered ray correction is reduced as compared with the density step estimated by the density step estimating means. ,
A program to function as.

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