Method for image processing, system for image processing, program for image processing, and recording medium

Abstract

The present invention more accurately corrects blurring of a radiological image without actually measuring blurring for each imaging system.　This method for image processing comprises: an acquisition step (S01) for acquiring information indicating the shape of the focal point of a radiation source included in an imaging system that performs imaging using radiation; and a blurring information generation step (S02) for, on the basis of the information acquired in the acquisition step, generating focal point blurring information indicating a response to radiation corresponding to the focal point of the radiation source in a radiological image obtained by imaging by an imaging system 20.

Description

Image processing method, image processing system, image processing program, and recording medium

[0001] The present invention relates to an image processing method, an image processing system, an image processing program, and a recording medium for processing a radiation image.

[0002] Patent Document 1 discloses that the resolution of an X-ray image obtained by X-ray imaging is increased by using a blur function that indicates the blur of the focus in an X-ray imaging system. In Patent Document 1, the blur function that indicates the blur of the focus is an impulse response.

[0003] Japanese Patent Application Laid-Open No. 2016-224837

[0004] In Patent Document 1, the blur function is set by measuring the blur of the focal point of an X-ray imaging system. Usually, focal blur information indicating the response to X-rays corresponds to the imaging system (X-ray imaging system) that performs imaging using X-rays. Therefore, in order to correct the blur of an X-ray image using the method disclosed in Patent Document 1, it is necessary to actually measure the blur for each imaging system that performed the imaging. It is difficult to accurately correct the blur of an X-ray image obtained by imaging with an imaging system whose blur has not been actually measured. Furthermore, similar problems can occur with radiation images other than X-ray images.

[0005] An embodiment of the present invention has been made in view of the above, and aims to provide an image processing method, an image processing system, an image processing program, and a recording medium that can more accurately correct blur in a radiographic image without having to measure the blur for each imaging system.

[0006] In order to achieve the above object, an image processing method according to one embodiment of the present invention includes: an acquisition step of acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation step of generating, based on the information acquired in the acquisition step, focus blur information indicating a response to radiation in a radiation image obtained by imaging with the imaging system, depending on the focus of the radiation source.

[0007] In an image processing method according to an embodiment of the present invention, out-of-focus information for a radiological image obtained by imaging with an imaging system is generated based on information indicating the shape of the focus of a radiation source included in the imaging system. The generated out-of-focus information can be used to correct blur in the radiological image obtained by imaging with the imaging system. Therefore, the image processing method according to an embodiment of the present invention can more accurately correct blur in a radiological image without having to measure blur for each imaging system.

[0008] In the obtaining step, information identifying the radiation source may be obtained, and the focal shape of the radiation source may be identified based on the obtained information identifying the radiation source. According to this configuration, if the information identifying the radiation source can be obtained, it is possible to generate defocus information. As a result, it is possible to more easily correct blur in the radiographic image.

[0009] In the acquiring step, information indicating the size of the focal spot of the radiation source and the magnification ratio at the time of imaging may also be acquired. This configuration makes it possible to generate more appropriate defocus information, thereby enabling more appropriate correction of blur in the radiographic image.

[0010] The acquiring step may also acquire scintillator blur information indicating a response to radiation according to a scintillator included in the imaging system, and the blur information generating step may combine the generated focus blur information and the scintillator blur information acquired in the acquiring step to generate blur information indicating a response to radiation in the radiographic image. With this configuration, blur information can be generated that takes the scintillator blur information into consideration. As a result, blur in the radiographic image can be corrected more appropriately.

[0011] The image processing method may further include a correction step of acquiring a radiographic image to be corrected for blur, and correcting the blur of the acquired radiographic image based on the out-of-focus blur information generated in the blur information generating step. According to this configuration, the generated out-of-focus blur information can be used to actually correct the blur of the radiographic image.

[0012] In the correction step, an image of the resolution chart is acquired as the radiographic image to be corrected for blur, and the image processing method may further include a correction step of calculating a degree of blur correction from the radiographic image corrected in the correction step, and correcting the out-of-focus blur information generated in the blur information generation step based on the calculated degree of blur correction. This configuration makes it possible to make the out-of-focus blur information more appropriate. As a result, it is possible to more appropriately correct the blur in the radiographic image.

[0013] The image processing method may further include an image generation step of generating training images including blur, which are used for machine learning training, based on the focus blur information generated in the blur information generation step. According to this configuration, an inference model for correcting blur in a radiological image can be generated by machine learning training using the generated training images. As a result, blur in the radiological image can be corrected.

[0014] One embodiment of the present invention can be described not only as an invention of an image processing method as described above, but also as an invention of an image processing system, an image processing program, and a recording medium as described below. These are essentially the same invention, just in different categories, and have similar functions and effects.

[0015] That is, an image processing system according to one embodiment of the present invention includes an acquisition means for acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation, and a blur information generation means for generating, based on the information acquired by the acquisition means, focus blur information indicating a response to radiation in accordance with the focus of the radiation source in a radiation image obtained by imaging with the imaging system.

[0016] Furthermore, an image processing program according to one embodiment of the present invention causes a computer to function as an acquisition means for acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation, and a blur information generation means for generating, based on the information acquired by the acquisition means, focus blur information indicating a response to radiation in a radiation image obtained by imaging with the imaging system according to the focus of the radiation source.

[0017] A recording medium according to one embodiment of the present invention is a computer-readable recording medium on which the above-described image processing program is recorded.

[0018] According to one embodiment of the present invention, blur in a radiographic image can be corrected more accurately without actually measuring blur for each imaging system.

[0019] FIG. 1 is a diagram showing the configuration of an image processing system according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of the shape of the focal point of an X-ray source. FIG. 3 is a diagram for explaining the magnification ratio and penumbra during imaging in an imaging system. FIG. 4 is a diagram showing an example of a PSF which is out-of-focus information. FIG. 5 is a diagram showing an example of a PSF which is out-of-focus information. FIG. 6 is a flowchart showing an image processing method which is processing executed in an image processing system according to an embodiment of the present invention. FIG. 7 is an example of an image of a resolution chart. FIG. 8 is a diagram showing an example of a PSF which is out-of-focus information. FIG. 9 is a graph showing an example of CTF values ​​calculated from an image of a resolution chart. FIG. 10 is a flowchart showing processing executed when correcting out-of-focus information in an image processing system. FIG. 11 is a diagram showing the configuration of an image processing program according to an embodiment of the present invention, together with a recording medium.

[0020] Hereinafter, an embodiment of an image processing method, an image processing system, an image processing program, and a recording medium according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0021] FIG. 1 shows an image processing system 10 according to this embodiment. The image processing system 10 is a system (device) that performs information processing for processing images obtained by imaging using an imaging system 20. The imaging system 20 is a system (device) that captures images using radiation. In this embodiment, the imaging system 20 is an X-ray imaging system (X-ray camera) that captures images using X-rays. The radiation used for imaging by the imaging system 20 may be radiation other than X-rays. When radiation other than X-rays is used, X-rays can be read as radiation other than X-rays in the following description. The imaging system 20 may be the same as a conventional system.

[0022] The imaging system 20 obtains an X-ray image (radiation image) by irradiating an object to be imaged with X-rays and detecting the X-rays that have passed through the object. As shown in FIG. 1 , the imaging system 20 includes an X-ray source 21 and a detector (radiation detector) 22. An object 30 to be imaged is positioned and placed between the X-ray source 21 and the detector 22 before imaging. The X-ray source 21 generates X-rays to be irradiated onto the object 30. The X-rays are generated from an X-ray focus of the X-ray source 21. The detector 22 is a device that detects the X-rays that have been irradiated from the X-ray source 21 toward the object 30 and passed through the object 30 to generate an image. The detector 22 includes a scintillator and a photodetector, which detect the X-rays and generate an image.

[0023] An X-ray image (radiographic image) obtained by imaging with the imaging system 20 has blurring that corresponds to the X-ray focus of the X-ray source 21. Hereinafter, the blurring that corresponds to the X-ray focus will be referred to as "out-of-focus blur." The image processing system 10 corrects the out-of-focus blur that occurs in the X-ray image obtained by imaging with the imaging system 20, i.e., generates out-of-focus blur information that is used to reduce or remove the out-of-focus blur in the X-ray image.

[0024] Blurring of an X-ray image may also occur due to factors other than the X-ray focus. For example, blurring of an X-ray image may occur due to a scintillator included in the detector 22 of the imaging system 20. Hereinafter, blurring due to a scintillator will be referred to as scintillator blurring. The image processing system 10 may generate blur information used to correct blurring including focal blurring and blurring due to other factors. The image processing system 10 may correct blurring of an X-ray image based on the generated focal blurring information. That is, the image processing system 10 may perform automatic restoration correction of an X-ray image.

[0025] The image processing system 10 is configured to include a conventional computer including a processor such as a CPU (Central Processing Unit), a memory, a communication module, and other hardware. The functions of the image processing system 10, which will be described later, are realized by these components operating through programs or the like. The computer that constitutes the image processing system 10 may be a computer system including multiple computers. The computer may also be configured using cloud computing or edge computing.

[0026] Next, a description will be given of the functions of the image processing system 10 according to this embodiment. As shown in FIG.

[0027] The acquisition unit 11 is an acquisition means for acquiring information indicating the shape of the focal point of the X-ray source 21 included in the imaging system 20 that performs imaging using X-rays. The acquisition unit 11 may acquire information that identifies the X-ray source 21 and identify the focal point shape of the X-ray source 21 based on the acquired information that identifies the X-ray source 21. The acquisition unit 11 may also acquire information that indicates the size of the focal point of the X-ray source 21 and the magnification ratio at the time of imaging.

[0028] The acquisition unit 11 acquires information, for example, as follows: The acquisition of information by the acquisition unit 11 is performed, for example, by accepting an input operation from a user or by receiving information transmitted from the imaging system 20. The acquisition of information by the acquisition unit 11 may also be performed by other methods.

[0029] The acquisition unit 11 acquires the following information as information used to generate the defocus information: The acquisition unit 11 acquires information indicating the shape of the focal point of the X-ray source 21 included in the imaging system 20. The defocus occurring in the X-ray image corresponds to the shape of the focal point of the X-ray source 21. The shape of the focal point is, for example, the two-dimensional shape of the position where the X-rays are generated on a plane perpendicular to the X-rays generated from the X-ray source 21 and the intensity of the X-rays at each position.

[0030] The information indicating the shape of the focal spot is information indicating the type of the shape of the focal spot and information indicating the size of the focal spot. The type of the shape of the focal spot is, for example, a Gaussian shape or a rectangular shape. A Gaussian-shaped focal spot is a focal spot where the intensity distribution of the generated X-rays at each position is a Gaussian distribution. A rectangular-shaped focal spot is a focal spot where the intensity of the generated X-rays at each position is uniform and the focal spot is rectangular.

[0031] The focal spot size is, for example, the size (e.g., a value in μm units) of the focal spot of the X-ray source 21 when viewed from the imaging direction (the direction in which X-rays are generated). The focal spot size may be a value based on a standard set in advance depending on the type of focal spot shape. For a Gaussian-shaped focal spot, the focal spot size is the full width at half maximum of the Gaussian distribution. For a rectangular-shaped focal spot, the focal spot size is the rectangle width (the length of one side of the rectangle). The focal spot size may be specified from the focal spot size mode (e.g., small focus mode, medium focus mode, or large focus mode) set when the X-ray source 21 is used.

[0032] Furthermore, the information indicating the shape of the focal spot may be information indicating the intensity of the generated X-rays at each position. That is, the information indicating the shape of the focal spot may be a two-dimensional spatial intensity distribution of the X-ray source 21. The information indicating the shape of the focal spot of the X-ray source 21 can be obtained by a conventional measurement method (e.g., a pinhole camera method, a parallel pattern camera method, or a resolution method). Alternatively, the information indicating the shape of the focal spot of the X-ray source 21 can also be obtained by a conventional simulation method.

[0033] Figure 2 shows the two-dimensional spatial intensity distribution of the X-ray source 21, which is an example of information indicating the shape of the focal spot of the X-ray source 21. Figures 2(a), (b), 2(c), (d), and 2(e), (f) each show the shape of the focal spot of one X-ray source 21. Figures 2(a), (c), and (e) show two-dimensional intensity, with the vertical and horizontal axes corresponding to positions on a plane perpendicular to the X-ray. Figures 2(b), (d), and (f) are graphs in which the horizontal axis indicates the position on a horizontal line passing through the center of Figures 2(a), (c), and (e), and the vertical axis indicates the X-ray intensity at that position.

[0034] The focal shape of the X-ray source 21 shown in Figures 2(a) and 2(b) is a single-focus shape in which there is one peak (hump) of X-ray intensity. The focal shape of the X-ray source 21 shown in Figures 2(c) and 2(d) is a twin-focus shape in which there are two peaks of X-ray intensity. The focal shape of the X-ray source 21 shown in Figures 2(e) and 2(f) is a quaternary-focus shape in which there are four peaks of X-ray intensity.

[0035] The acquisition unit 11 may also acquire information indicating the magnification ratio at the time of imaging. The magnification ratio of the X-ray image corresponds to the position of the object 30 in the imaging direction. The defocusing that occurs in the X-ray image corresponds to the magnification ratio. For example, the acquisition unit 11 acquires the value of the magnification ratio of the X-ray image.

[0036] The magnification ratio M can be calculated, for example, by the following formula: The object 30 to be imaged is assumed to be located on a line connecting the X-ray focal point of the X-ray source 21 and the position at which X-rays are detected on the detector 22. M=1+b / a As shown in FIG. 3 , in the above formula, a is the distance (FOD: Focus Object Distance) between the X-ray focal point (position F) of the X-ray source 21 and the object 30 to be imaged (position S). b is the distance between the object 30 to be imaged (position S) and the position at which X-rays are detected on the detector 22. In FIG. 3 , the vertical direction is the imaging direction (the direction in which X-rays are generated). Furthermore, a+b is the distance (FDD: Focus Detector Distance) between the X-ray focal point of the X-ray source 21 and the position at which X-rays are detected on the detector 22.

[0037] The information related to the X-ray source 21 may be acquired based on information identifying the X-ray source 21. In this case, the acquisition unit 11 acquires the information identifying the X-ray source 21. The information identifying the X-ray source 21 is, for example, a model name of the X-ray source 21 that is set in advance for each type of X-ray source 21. The information identifying the X-ray source 21 is acquired by, for example, accepting an input operation from the user or receiving information transmitted from the imaging system 20. Alternatively, the information identifying the X-ray source 21 may be acquired by other methods.

[0038] The acquisition unit 11 stores in advance information indicating a correspondence relationship between information identifying the X-ray source 21 and the above-mentioned information related to the X-ray source 21. The acquisition unit 11 acquires information indicating the shape of the focal spot of the X-ray source 21, which is associated with the acquired information identifying the X-ray source 21 in the correspondence relationship. Furthermore, the acquisition unit 11 may acquire the above-mentioned information to be used in subsequent processing based on information at the time of imaging as information related to the X-ray source 21 (e.g., the above-mentioned focal spot size mode, tube voltage, or tube current related to the X-ray source 21). Furthermore, other than the above-mentioned information related to the X-ray source 21, the acquisition unit 11 may acquire the above-mentioned information to be used in subsequent processing based on information identifying an object related to the information (e.g., the detector 22).

[0039] The acquisition unit 11 may acquire information other than the above as information used to generate the focus blur information. The acquisition unit 11 outputs the acquired information to the blur information generation unit 12.

[0040] The blur information generation unit 12 is a blur information generation means that generates, based on the information acquired by the acquisition unit 11, focal blur information that indicates the response to X-rays in the X-ray image obtained by imaging with the imaging system 20 according to the focus of the X-ray source 21.

[0041] The out-of-focus information is, for example, a PSF (Point Spread Function). The PSF indicates how much a signal at a certain point (pixel) on an image spreads. The PSF is, for example, a two-dimensional spatial intensity distribution.

[0042] Examples of PSFs are shown in Figures 4 and 5. Figures 4(a)(b), 4(c)(d), 4(e)(f), 4(g)(h), 5(a)(b), 5(c)(d), 5(e)(f), and 5(g)(h) each show one PSF. Figures 4(a), (c), (e), (g) and 5(a), (c), (e), and (g) show two-dimensional intensity, with the vertical and horizontal axes corresponding to pixel positions in the image. Figures 4(b), (d), (f), and (h) and 5(b), (d), (f), and (h) are graphs in which the horizontal axis indicates the pixel position on a line passing through the center of the PSF, and the vertical axis indicates the intensity of the response at that pixel position. The center position of each image and graph in Figures 4 and 5 is the reference point for the signal spread (the "point (pixel) on the image" mentioned above).

[0043] Figures 4(a) and (b) show PSFs when the focal spot size is 100 μm, the pixel size is 100 μm, the magnification is 1.1 times, and the focal spot shape is rectangular. Figures 4(c) and (d) show PSFs when the focal spot size is 100 μm, the pixel size is 100 μm, the magnification is 1.1 times, and the focal spot shape is Gaussian. Figures 4(e) and (f) show PSFs when the focal spot size is 100 μm, the pixel size is 100 μm, the magnification is 4 times, and the focal spot shape is rectangular. Figures 4(g) and (h) show PSFs when the focal spot size is 100 μm, the pixel size is 100 μm, the magnification is 4 times, and the focal spot shape is Gaussian.

[0044] Figures 5(a) and (b) show PSFs when the focal spot size is 10 μm, the pixel size is 100 μm, the magnification is 2x, and the focal spot shape is rectangular. Figures 5(c) and (d) show PSFs when the focal spot size is 10 μm, the pixel size is 100 μm, the magnification is 2x, and the focal spot shape is Gaussian. Figures 5(e) and (f) show PSFs when the focal spot size is 10 μm, the pixel size is 100 μm, the magnification is 20x, and the focal spot shape is rectangular. Figures 5(g) and (h) show PSFs when the focal spot size is 10 μm, the pixel size is 100 μm, the magnification is 20x, and the focal spot shape is Gaussian.

[0045] However, the defocus information does not need to be a PSF, but may be anything that indicates a response to X-rays according to the focus of the X-ray source 21 and that can be used to correct blurring in an X-ray image. For example, the defocus information may be an OTF (optical transfer function) that expresses the PSF in frequency space, or an MTF (modulation transfer function) that is the absolute value of the OTF. The same applies to blurring information.

[0046] The blur information generation unit 12 generates the out-of-focus information, for example, as follows. The blur information generation unit 12 inputs information used to generate the out-of-focus information from the acquisition unit 11. The blur information generation unit 12 stores in advance generation rules for generating out-of-focus information from the information input from the acquisition unit 11, and generates the out-of-focus information in accordance with the generation rules. For example, the blur information generation unit 12 stores generation rules for each type of focus shape, and generates the out-of-focus information in accordance with the generation rule according to the type of focus shape indicated by the information input from the acquisition unit 11.

[0047] When the type of the shape of the focal point is Gaussian, the PSF also has a Gaussian shape. That is, the PSF is expressed by the following Gaussian distribution formula: f(x, y) = Aexp(-1 / 2σ{x - x ０} ２ + {y-y ０} ２ In the above equation, x and y are coordinates of the pixel position. ０ , y ０ are the coordinates of the point that is the reference for the spread of the signal (the central coordinates of the Gaussian). A is the amplitude (peak height) of the Gaussian shape. σ is the standard deviation of the Gaussian shape. Therefore, if A and σ of the Gaussian shape are obtained, the PSF can be obtained. The blur information generation unit 12 calculates A and σ from the information input from the acquisition unit 11.

[0048] The blur information generating unit 12 calculates the size H of the penumbra shown in FIG. 3 from the magnification ratio M and the size f of the focal point indicated by the information input from the acquiring unit 11 using the following formula: H=(M-1)×f

[0049] Here, it is assumed that the calculated PSF has a FWHV (full width at half maximum) = H. The relationship between FWHM and standard deviation σ is expressed by the following equation. The blur information generating unit 12 uses the calculated H as the FWHM to calculate σ of the PSF from the following equation: FWHM = 22ln(2)σ ≈ 2.35482σ

[0050] In the PSF, the sum of the intensity values ​​of all coordinates (two-dimensionally integrated value) is 1. The blur information generation unit 12 calculates A so as to satisfy the above using the calculated σ (i.e., performs normalization). The above is the calculation of the PSF, which is the focus blur information when the type of focus shape is a Gaussian shape.

[0051] When the shape of the focal point is rectangular, the PSF also has a rectangular shape. That is, the two-dimensional spatial intensity distribution of the PSF is a spatial intensity distribution in which the range in which blur occurs is rectangular and the intensity in that range is uniform. The blur information generation unit 12 calculates the rectangular range in which blur occurs from the information input from the acquisition unit 11.

[0052] The blur information generating unit 12 calculates the size H of the penumbra in the same manner as described above from the magnification ratio M and the size f of the focal point indicated by the information input from the acquiring unit 11. The blur information generating unit 12 generates a rectangular distribution in which the intensity in the rectangular range from the coordinates (center coordinates) of the point that is the reference for the spread of the signal to H is 1, and the intensity in the other ranges (outside) is 0.

[0053] The blur information generation unit 12 calculates the intensity of the rectangular range so that the sum of the intensity values ​​of all coordinates in the generated rectangular distribution (two-dimensionally integrated value) is 1 (i.e., normalizes). The blur information generation unit 12 sets the rectangular intensity distribution of the calculated intensities as the PSF. Note that since the PSF is a value in pixel units (pixel pitch), the calculated intensity distribution for the boundary portion of the rectangular distribution may be binned (averaged) according to the pixel size, and the intensity distribution after the binning process may be set as the PSF. This completes the calculation of the PSF, which is focus blur information when the focus shape type is rectangular.

[0054] The blur information generator 12 may generate the defocus information based on information other than the information acquired by the acquisition unit 11. The blur information generator 12 may generate the defocus information based on information acquired by the acquisition unit 11 using a method other than the above. For example, particle (electron, proton, neutron, photon, heavy ion) or radiation transport simulation software may be used to simulate the collision of electron beams with a target in the X-ray source and the generation of X-rays, thereby generating X-ray defocus information (shape and intensity distribution). When fitting, data may be modeled as a linear combination of multiple Gaussian distributions using a Gaussian mixture model (GMM). Similarly to the above (when the type of focal spot shape is Gaussian or rectangular), the blur information generator 12 may store rules for generating defocus information from information acquired by the acquisition unit 11 in advance for each type of focal spot shape, and generate the defocus information using the rules. Furthermore, when the shape of the focal spot is a combination of multiple basic shapes (e.g., the Gaussian shape or rectangular shape), the blur information generator 12 may calculate defocus information from each of the individual shapes before combination and combine them to generate final defocus information. Furthermore, when information indicating the intensity of the generated X-rays at each position is used as information indicating the shape of the focal spot, the blur information generator 12 may store rules for generating defocus information based on the intensity at each position (e.g., a model that inputs the intensity at each X-ray position and outputs defocus information) and generate the defocus information using the rules. Furthermore, conventional fitting techniques may be used to generate the defocus information. The blur information generator 12 outputs the generated defocus information to the correction unit 13.

[0055] In the image processing system 10, when blur information used to correct blur including focus blur and blur due to other factors is generated, the acquisition unit 11 acquires information used to generate the blur information. The acquisition unit 11 may also acquire, as the information, scintillator blur information indicating a response to radiation according to a scintillator included in the detector 22 of the imaging system 20. The acquisition of the scintillator blur information may be performed in the same manner as the acquisition of the above information by the acquisition unit 11. The acquisition unit 11 outputs the acquired scintillator blur information to the blur information generation unit 12.

[0056] The response of the scintillator to X-rays causes scintillator blur in the X-ray image. The scintillator blur information is, for example, a PSF.

[0057] The scintillator blur information may be estimated (specified) by performing imaging (actual measurement) for specifying the scintillator blur information, or by performing simulation calculations based on parameters related to the scintillator at the time of imaging. The estimation of the scintillator blur information may be performed by a conventional method.

[0058] For example, the actual measurement method is performed as follows. First, the MTF (Modulation Transfer Function) is measured by the edge method or the chart method. The edge method involves capturing an oblique image of a tungsten chart and calculating the MTF. The chart method involves capturing an image of a square wave chart and calculating the MTF. Next, the MTF is subjected to an inverse Fourier transform to calculate the PSF, which is scintillator blur information, as spatial information.

[0059] The simulation method is performed as follows. First, the tube voltage, filter conditions, and scintillator type and thickness during simulation imaging are set. A Monte Carlo simulation is performed under these conditions. For example, a scintillator model is created and a light scattering simulation is performed. The PSF is calculated from the simulation results.

[0060] The blur information generation unit 12 combines the generated focus blur information and the scintillator blur information acquired by the acquisition unit 11 to generate blur information indicating the response to X-rays in the X-ray image. The blur information generation unit 12 inputs the scintillator blur information from the acquisition unit 11. After generating the focus blur information, the blur information generation unit 12 combines the focus blur information and the scintillator blur information to generate blur information. Combining the focus blur information and the scintillator blur information, for example, combining PSFs, may be performed by a conventional method. For example, the blur information generation unit 12 convolves the PSF, which is the focus blur information, with the PSF, which is the scintillator blur information, to generate (calculate) a combined PSF, which is the blur information. After generating the blur information, the blur information generation unit 12 outputs the generated blur information to the correction unit 13.

[0061] The correction unit 13 is a correction means that acquires an X-ray image to be subjected to blur correction, and corrects the blur of the acquired X-ray image based on the out-of-focus blur information generated by the blur information generation unit 12 .

[0062] The correction unit 13 acquires an X-ray image and corrects blur in the acquired X-ray image, for example, as follows: The correction unit 13 inputs the out-of-focus information or blur information from the blur information generation unit 12 and stores it as information for correcting blur in the X-ray image acquired by imaging with the imaging system 20.

[0063] The correction unit 13 acquires an X-ray image, which is a radiographic image to be subjected to blur correction. The X-ray image is obtained by imaging using the imaging system 20, and is an image of a preset size. The X-ray image is acquired, for example, by receiving an X-ray image transmitted from the imaging system 20 or by accepting an input operation from a user. Alternatively, the X-ray image may be acquired by other methods.

[0064] The correction unit 13 corrects the blur of the X-ray image based on the stored out-of-focus blur information or blur information. The correction of the blur of the X-ray image based on the out-of-focus blur information or blur information may be performed by a conventional method. For example, the correction unit 13 may correct the blur of the X-ray image based on the PSF, which is the out-of-focus blur information or blur information, using a Wiener filter or the Richardson-Lucy method. The correction unit 13 outputs the generated blur-corrected X-ray image. The blur-corrected X-ray image may be output in the same manner as a conventional method depending on the purpose of use of the X-ray image. The functions of the image processing system 10 according to this embodiment have been described above.

[0065] Next, an image processing method, which is a process executed by the image processing system 10 according to this embodiment (an operating method performed by the image processing system 10), will be described using the flowchart of Fig. 6. In this process, the acquisition unit 11 acquires information used to generate defocus information related to an X-ray image obtained by imaging with the imaging system 20 (S01, acquisition step). The information includes information indicating the shape of the focal point of the X-ray source included in the imaging system 20.

[0066] Next, the blur information generating unit 12 generates defocus information related to the X-ray image obtained by imaging with the imaging system 20 based on the information acquired by the acquiring unit 11 (S02, blur information generating step). At this time, the generated defocus information may be used to generate blur information used to correct blur including defocus and blur due to other factors (for example, the above-mentioned scintillator blur).

[0067] The correction unit 13 acquires an X-ray image to be subjected to blur correction (S03, correction step). The acquisition of the X-ray image (S03) may be performed before the correction of blur of the X-ray image (S04), and is performed independently of the acquisition of information used to generate defocus information by the acquisition unit 11 (S01) and the generation of defocus information by the blur information generation unit 12 (S02).

[0068] Next, the correction unit 13 corrects the blur of the X-ray image to be corrected based on the focus blur information (S04, correction step). The blur-corrected X-ray image is output from the correction unit 13 to a predetermined output destination (S05). The image processing method, which is processing executed by the image processing system 10 according to this embodiment, has been described above.

[0069] In this embodiment, based on information indicating the shape of the focal point of the X-ray source 21 included in the imaging system 20, defocus information for an X-ray image obtained by imaging with the imaging system 20 is generated. By using the generated defocus information, it is possible to correct the blur of the X-ray image obtained by imaging with the imaging system 20. Therefore, according to this embodiment, it is possible to more accurately correct the blur of the X-ray image without actually measuring the blur for each imaging system 20.

[0070] As in the present embodiment, information identifying the X-ray source 21 may be acquired, and the focal shape of the X-ray source 21 may be identified based on the acquired information identifying the X-ray source 21. With this configuration, if information identifying the X-ray source 21 can be acquired, defocus information can be generated. As a result, blurring of the X-ray image can be corrected more easily. However, acquisition of information indicating the focal shape of the X-ray source 21 does not necessarily have to be performed as described above.

[0071] As in the present embodiment, information indicating the size of the focal spot of the X-ray source 21 and the magnification ratio at the time of imaging may also be acquired. With this configuration, more appropriate defocus information can be generated. As a result, the blur of the radiographic image can be corrected more appropriately. However, the above information does not necessarily have to be acquired as information for generating the defocus information.

[0072] As in the present embodiment, scintillator blur information indicating the response to X-rays according to the scintillator included in the imaging system 20 may also be acquired, and the focal point blur information and the scintillator blur information may be combined to generate blur information indicating the response to X-rays in the X-ray image. With this configuration, blur information can be generated that also takes the scintillator blur information into consideration. As a result, blur in the radiographic image can be corrected more appropriately. However, it is not necessarily necessary to generate blur information combined with scintillator blur information.

[0073] As in the present embodiment, the image processing system 10 may acquire an X-ray image to be corrected for blur, and correct the blur of the acquired X-ray image based on the out-of-focus blur information. With this configuration, the generated out-of-focus blur information can be used to actually correct the blur of the X-ray image. However, the image processing system 10 does not need to correct the blur of the X-ray image. In other words, the image processing system 10 does not need to include the correction unit 13. In this case, the image processing system 10 transmits or outputs the generated out-of-focus blur information or blur information to a system or module that corrects the blur of the X-ray image using the out-of-focus blur information or blur information.

[0074] Next, a modified example of this embodiment will be described. A modified example in which defocus information is corrected in the image processing system 10 will be described. The defocus information generated as described above may be corrected to perform more accurate blur correction. To correct the defocus information, an image in which a resolution chart is captured is used. The resolution chart is a chart for evaluating the resolution of an image obtained by capturing. The resolution chart is, for example, a chart with lines arranged at equal intervals (a square wave chart). FIG. 7 shows an example of an image in which a resolution chart is captured. Of the four example images of the resolution chart shown in FIG. 7, the top one is an image obtained by capturing (a blurred observed image). As shown in FIG. 7, the resolution chart used may include multiple resolution sections. In the example shown in FIG. 7, the resolution chart includes five resolution sections, from left to right: 0.01 (lp / mm), 1 (lp / mm), 2 (lp / mm), 3 (lp / mm), and 4 (lp / mm).

[0075] The configuration for correcting the focus blur information is as follows: The correction unit 13 acquires an image of a resolution chart as an X-ray image to be corrected for blur. In addition to the above configuration, the image processing system 10 further includes a correction unit. The correction unit is a correction means that calculates the degree of blur correction from the X-ray image of the resolution chart corrected by the correction unit 13, and corrects the focus blur information generated by the blur information generation unit 12 based on the calculated degree of blur correction. In other words, the correction unit provides feedback to the focus blur information based on the blur correction of the resolution chart.

[0076] The correction unit 13 and the correction unit have, for example, the following functions: The correction unit 13 acquires an image in which a resolution chart is captured by the imaging system 20 as an X-ray image to be corrected for blur. To acquire this image, a resolution chart is prepared, and the imaging system 20 captures the resolution chart. The acquisition of this image by the correction unit 13 may be performed in the same manner as the acquisition of the X-ray image to be corrected for blur described above.

[0077] The correction unit 13 corrects the blur of the acquired image based on the stored focus blur information or blur information. The correction of the blur of the image may be performed in the same manner as the correction of the blur of the X-ray image described above. The correction unit 13 outputs the image of the resolution chart before blur correction and the image of the resolution chart after blur correction to the correction unit.

[0078] The correction of the defocus blur information by the correction unit is performed when it is considered that the defocus blur information does not accurately correct the blur. Fig. 8 shows an example of a PSF, which is the defocus blur information. The PSF shown in Fig. 8(a) is the original (actual PSF). Therefore, when the blur of an X-ray image is corrected using the PSF shown in Fig. 8(a), the defocus blur is corrected accurately, and the X-ray image after the defocus correction is appropriate. Among the images in the resolution chart shown in Fig. 7, the second from the top is an image (restored image (actual PSF)) in which the blur of the image obtained by imaging (the top image) is corrected using the PSF shown in Fig. 8(a).

[0079] The PSF shown in Fig. 8(b) is a PSF with greater blur than the original PSF shown in Fig. 8(a). Therefore, if the blur of an X-ray image is corrected using the PSF shown in Fig. 8(b), excessive blur correction will be performed, and the X-ray image after blur correction will not be appropriate. Among the images in the resolution chart shown in Fig. 7, the third from the top is an image (restored image (PSF greater than the actual blur)) in which the blur of the image obtained by imaging (the top image) has been corrected using the PSF shown in Fig. 8(b).

[0080] The PSF shown in Fig. 8(c) has less blur than the original PSF shown in Fig. 8(a). Therefore, when the blur of an X-ray image is corrected using the PSF shown in Fig. 8(c), the blur is not corrected sufficiently, and the X-ray image after blur correction is not appropriate. Among the images in the resolution chart shown in Fig. 7, the fourth image from the top is an image (restored image (PSF with less blur than the actual blur)) in which the blur of the image obtained by imaging (the top image) is corrected using the PSF shown in Fig. 8(c).

[0081] The correction of the focus blur information by the correction unit is intended to bring the PSF closer to the original PSF shown in FIG. 8( a) when, for example, the blur information generated by the blur information generation unit 12 is the PSF shown in FIG. 8( b) or 8( c).

[0082] The correction unit inputs the images of the resolution chart before and after blur correction from the correction unit 13. The correction unit calculates the degree of blur correction for each of the images of the resolution chart before and after blur correction. For example, the correction unit calculates a CTF (Contrast Transfer Function) value as the degree of blur correction. The closer the CTF is to 1, the less blur the image has. Typically, the CTF is a value ranging from 0 to 1. As in the example shown in FIG. 7 , when the resolution chart includes multiple resolution sections, the correction unit calculates the CTF for each resolution section.

[0083] FIG. 9 shows examples of calculated CTF values. The graph shown in FIG. 9 is a graph of CTF values ​​calculated from the four resolution chart images shown in FIG. 7. In the graph of FIG. 9, the horizontal axis represents resolution (lp / mm) and the vertical axis represents CTF value. Graph G1 is a graph of CTF values ​​calculated from the top resolution chart image in FIG. 7. Graph G2 is a graph of CTF values ​​calculated from the second resolution chart image from the top in FIG. 7. Graph G3 is a graph of CTF values ​​calculated from the third resolution chart image from the top in FIG. 7. Graph G4 is a graph of CTF values ​​calculated from the fourth resolution chart image from the top in FIG. 7.

[0084] The correction unit determines whether or not to correct the out-of-focus information and the content of the correction based on the calculated CTF value, based on a pre-stored correction rule. For example, the correction unit makes the determination as follows: The correction unit compares the CTF value after blur correction with a pre-set threshold. A larger CTF value indicates a greater degree of blur correction. If the CTF value exceeds the threshold (condition 1), the correction unit determines that the edge emphasis is too strong and that the blur corrected by the out-of-focus information is overestimated, and therefore determines to correct the out-of-focus information. If the CTF value is calculated for each resolution, the correction unit compares the CTF value with the threshold for each resolution and makes the above determination. In this case, if the CTF value exceeds the threshold at any resolution, the correction unit determines to correct the out-of-focus information.

[0085] In this case, the threshold value is set in advance based on the above viewpoint. For example, the threshold value is set to 1. Alternatively, a different threshold value may be set for each resolution. For example, the threshold value may be set to 0.99 for 0.1 (lp / mm), 0.9 for 0.5 (lp / mm), and 0.8 for 1.5 (lp / mm). In this way, a smaller threshold value may be set as the resolution increases. Alternatively, the threshold value may be set based on the CTF value calculated from the image of the resolution chart before blur correction. For example, the threshold value may be set to a value that is two or three times the CTF value calculated from the image of the resolution chart before blur correction. For example, for CTF values ​​of each resolution (lp / mm) = [0.01, 1, 2, 3, 4] calculated from the image of the resolution chart before blur correction = [1, 0.9, 0.65, 0.45, 0.38], the threshold values ​​for each resolution may be set to twice the CTF values ​​[2, 1.8, 1.3, 0.9, 0.76].

[0086] In this case, the focus blur information is corrected in a direction that reduces the corrected blur. For example, the correction unit corrects the PSF by changing parameters from when the PSF was generated by the blur information generation unit 12 and regenerating the PSF. For example, the correction unit generates the PSF again using a value that is smaller than the size of the focal spot of the X-ray source 21 by a preset amount (for example, 10 μm). Furthermore, the correction unit may regenerate the PSF by changing other parameters, or may correct the PSF by a method other than changing the parameters.

[0087] The correction unit also compares the CTF value before blur correction with the CTF value after blur correction. Typically, the CTF value after blur correction is larger than the CTF value before blur correction. If the CTF value does not change significantly before and after blur correction, for example, if the corrected CTF value is within ±5% or ±3% of the pre-correction CTF value (condition 2), the correction unit determines that the blur is not sufficiently corrected and determines to correct the defocus information. If the CTF is calculated for each resolution, the correction unit compares the CTF with a threshold for each resolution to make the above determination. In this case, if the CTF values ​​before and after blur correction are approximately the same at any resolution, the correction unit determines to correct the defocus information. In this case (condition 2), the resolutions used for the determination do not need to be all resolutions related to the resolution chart, but may be a predetermined specific resolution among the resolutions. Typically, the CTF value at low resolution (low frequency) can be 1 or a value close to 1 both before and after blur correction, and is therefore not suitable for determining the correction of blur information. Therefore, when Condition 2 is used, the CTF value at low resolution (low frequency) may not be used. For example, when Condition 2 is used, the CTF value at a resolution of 0.1 (lp / mm) may not be used, and the CTF value at only the resolution (lp / mm) = [1, 2, 3, 4] may be used.

[0088] In this case, the focus blur information is corrected in a direction that increases the blur to be corrected. For example, the correction unit corrects the PSF by changing parameters from when the PSF was generated by the blur information generation unit 12 and regenerating the PSF. For example, the correction unit generates the PSF again using a value that is increased by a preset amount (for example, 10 μm) for the size of the focal spot of the X-ray source 21. Furthermore, the correction unit may regenerate the PSF by changing other parameters, or may correct the PSF by a method other than changing the parameters.

[0089] When the above two conditions, Condition 1 and Condition 2, are met, there is a contradiction in that the CTF value after blur correction is not significantly different from the CTF value before blur correction and exceeds the set threshold. Therefore, in this case, the correction unit may perform processing to prompt the user to change the condition setting without performing any further processing. For example, the correction unit may notify the user, by display or the like, that an error has occurred in the processing and prompt the user to change the setting.

[0090] For example, the condition settings may be changed as follows: When changing condition 1, the threshold is increased from its pre-change value. For example, the threshold is set to a value twice the CTF value calculated from the image before blur correction, so that condition 2 is not necessarily satisfied when condition 1 is satisfied. When changing condition 2, the range within ±5% of the pre-correction CTF value is narrowed. For example, the range within ±5% of the pre-correction CTF value is changed to within ±1% of the pre-correction CTF value.

[0091] The defocus blur information corrected by the correction unit is stored by the correction unit 13 and used to correct the blur of the X-ray image. When blur information obtained by combining the defocus blur information and the scintillator blur information is used to correct the blur of the X-ray image, the defocus blur information corrected by the correction unit is used, and blur information is generated and used in the same manner as described above.

[0092] Next, the processing according to this modification will be described with reference to the flowchart of Fig. 10. This processing may be performed, for example, in the processing in the image processing system 10 shown in Fig. 6 after the blur information generating unit 12 generates the defocus information (S02) and before the correcting unit 13 acquires the X-ray image to be corrected for blur (S03).

[0093] In this process, the correction unit 13 acquires an image of the resolution chart captured by the imaging system 20 as an X-ray image to be subjected to blur correction (S11, correction step). Subsequently, the correction unit 13 corrects the blur of the acquired image based on the stored focus blur information or blur information (S12, correction step).

[0094] Next, the correction unit calculates the degree of blur correction (e.g., the CTF value) from the X-ray images before and after correction (S13, correction step). Next, the correction unit corrects the defocus information based on the degree of blur correction (S14, correction step). The corrected defocus information is used by the correction unit 13 to correct the blur of the X-ray image. This completes the processing according to this modified example.

[0095] According to this configuration, the focus blur information generated by the blur information generating unit 12 can be made more appropriate through correction by the correction unit, thereby making it possible to more appropriately correct the blur of the X-ray image.

[0096] Although the CTF is used as the degree of blur correction in the above, any other factor than the CTF may be used as the degree of blur correction as long as it can be used to correct the out-of-focus information.Furthermore, the necessity of correcting the out-of-focus information and the content of the correction may also be other than the above as long as it is in line with the purpose of appropriately correcting the out-of-focus information.

[0097] Furthermore, the correction of the defocus information described above does not necessarily have to be premised on the generation of the defocus information based on information indicating the shape of the focus. The correction of the defocus information described above may be performed when the defocus information is generated by any method. The above is a modified example of correcting the defocus information in the image processing system 10.

[0098] Next, a modified example will be described in which the image processing system 10 generates learning images that are used for machine learning training and that include blur. In this modified example, an inference model generated by machine learning training is used to correct blur in X-ray images obtained by imaging with the imaging system 20. The out-of-focus blur information generated by the blur information generator 12 may be used to generate learning images that are used for machine learning training of the inference model. The image processing system 10 generates the learning images. Note that the generation of the inference model by machine learning training and the correction of blur in X-ray images using the inference model may be performed by the image processing system 10, or may be performed by a system or device other than the image processing system 10.

[0099] To generate training images, the image processing system 10 further includes an image generation unit in addition to the above configuration. The image generation unit is an image generation means that generates training images including blur, which are used for machine learning training, based on the focus blur information generated by the blur information generation unit 12.

[0100] The inference model may include, for example, a neural network. The neural network may be multi-layered. That is, the inference model may be generated by deep learning. The neural network may also be a convolutional neural network (CNN). The neural network may also be U-net, ResNet, or the like. The format of the inference model may be similar to that of an inference model generated by conventional machine learning training. For example, the inference model inputs an X-ray image and outputs an X-ray image after blur correction.

[0101] The image generation unit has, for example, the following functions: The image generation unit receives and stores focus blur information or blur information from the blur information generation unit 12. The image generation unit acquires an image that will be the basis for the learning image. The image that will be the basis for the learning image is an image that does not contain blur (a clear image). An X-ray image may be used as the image that does not contain blur. When an X-ray image is used as the image that does not contain blur, an image captured by the imaging system 20 may be used, or an image captured by another imaging system may be used.

[0102] Furthermore, the image without blur may be an image other than an X-ray image. For example, the image may be an image generated by simulation. Alternatively, the image may be an image such as a natural image captured by a camera that captures images using visible light.

[0103] The blur-free image may be obtained by, for example, receiving an image transmitted from another system or device or by accepting an input operation from a user. Alternatively, the blur-free image may be obtained by other methods.

[0104] The image generation unit generates blurred learning images from blur-free images based on the stored focus blur information or blur information. For example, the image generation unit convolves the PSF, which is the stored focus blur information or blur information, with the blur-free images to generate blurred learning images.

[0105] For example, a combination of an image without blur and a training image including the blur is used to train the inference model. The image generator may generate a number of these combinations sufficient to adequately train the inference model.

[0106] An inference model is trained from a combination of a blur-free image and a blur-free training image as follows. The inference model is trained for each combination. For example, a blur-free training image is input to the inference model, and a calculation is performed according to the inference model to obtain a corrected image. The corrected image obtained is compared with a blur-free image, and the parameters of the inference model are updated by backpropagation based on a loss resulting from the comparison. In this case, when a blur-free training image is input to the inference model, the inference model is trained so that the inference model outputs a blur-free image. Note that the inference model may be generated by a method other than the above.

[0107] The image generation unit outputs information necessary for generating an inference model including the generated learning information (e.g., a combination of the above-mentioned image without blur and the learning image including the blur). The output is provided, for example, to a system, device, or module that generates the inference model. Once an inference model is generated using the learning information generated by the image generation unit, the inference model is used to correct the blur in the X-ray image obtained by imaging with the imaging system 20.

[0108] The processing by the image generating section (image generating step) is performed after the blur information generating section 12 generates the focus blur information (S02) in the processing in the image processing system 10 shown in FIG. 6, for example.

[0109] According to this configuration, an inference model for correcting blur in X-ray images can be generated by machine learning training using the generated training images. As a result, blur in X-ray images can be corrected. The above is a modified example of the image processing system 10, in which training images for machine learning and blurred training images are generated.

[0110] Next, we will explain an image processing program for executing a series of processes by the above-mentioned image processing system 10. As shown in Fig. 11, the image processing program 100 is stored in a program storage area 111 formed on a computer-readable recording medium 110 that is inserted into a computer and accessed, or that is provided in the computer. The recording medium 110 may be a non-transitory recording medium.

[0111] The image processing program 100 is configured to include an acquisition module 101, a blur information generation module 102, and a correction module 103. Functions realized by executing the acquisition module 101, the blur information generation module 102, and the correction module 103 are similar to the functions of the acquisition unit 11, the blur information generation unit 12, and the correction unit 13, respectively, of the image processing system 10 described above. The image processing program 100 may also include a module that realizes at least one of the functions of the correction unit and the image generation unit of the image processing system 10 described above.

[0112] The image processing program 100 may be configured such that a part or all of it is transmitted via a transmission medium such as a communication line, and is received and recorded (including installed) by another device. Furthermore, each module of the image processing program 100 may be installed not only on one computer but on any of multiple computers. In this case, the above-described series of processes are performed by a computer system consisting of the multiple computers.

[0113] The image processing method, image processing system, image processing program, and recording medium disclosed herein have the following configurations: [1] An image processing method including: an acquisition step of acquiring information indicating the shape of a focal point of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation step of generating, based on the information acquired in the acquisition step, defocus information indicating a response to radiation in accordance with the focus of the radiation source in a radiation image obtained by imaging with the imaging system. [2] The image processing method according to [1], in which, in the acquisition step, information identifying the radiation source is acquired, and the focal shape of the radiation source is identified based on the acquired information identifying the radiation source. [3] The image processing method according to [1] or [2], in which, in the acquisition step, information indicating the size of the focal point of the radiation source and a magnification factor at the time of imaging is also acquired. [4] The image processing method according to any one of [1] to [3], wherein the acquiring step also acquires scintillator blur information indicating a response to radiation according to a scintillator included in the imaging system, and the blur information generating step combines the generated out-of-focus blur information and the scintillator blur information acquired in the acquiring step to generate blur information indicating a response to radiation in the radiographic image. [5] The image processing method according to any one of [1] to [4], further comprising a correction step of acquiring a radiographic image to be blur corrected and correcting the blur of the acquired radiographic image based on the out-of-focus blur information generated in the blur information generating step. [6] The image processing method according to [5], further comprising a correction step of acquiring an image of a resolution chart as the radiographic image to be blur corrected, calculating a degree of blur correction from the radiographic image corrected in the correction step, and correcting the out-of-focus blur information generated in the blur information generating step based on the calculated degree of blur correction. [7] The image processing method according to any one of [1] to [6], further comprising an image generation step of generating a learning image including blur, which is used for machine learning training, based on the focus blur information generated in the blur information generation step.[8] An image processing system comprising: an acquisition means for acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation means for generating, based on the information acquired by the acquisition means, defocus information indicating a response to radiation in accordance with the focus of the radiation source in a radiation image obtained by imaging with the imaging system. [9] An image processing program that causes a computer to function as: an acquisition means for acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation means for generating, based on the information acquired by the acquisition means, defocus information indicating a response to radiation in accordance with the focus of the radiation source in a radiation image obtained by imaging with the imaging system.

[10] A computer-readable recording medium having the image processing program according to [9] recorded thereon.

[0114] 10...image processing system, 11...acquisition unit, 12...blur information generation unit, 13...correction unit, 20...imaging system, 21...X-ray source, 22...detector, 100...image processing program, 101...acquisition module, 102...blur information generation module, 103...correction module, 110...recording medium, 111...program storage area

Claims

1. An image processing method comprising: an acquisition step of acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation step of generating, based on the information acquired in the acquisition step, focus blur information that indicates a response to radiation in a radiation image obtained by imaging with the imaging system, according to the focus of the radiation source.

2. The image processing method according to claim 1, wherein in the acquisition step, information identifying the radiation source is acquired, and the focal shape of the radiation source is identified based on the acquired information identifying the radiation source.

3. The image processing method according to claim 1 or 2, wherein the acquiring step also acquires information indicating the size of the focal spot of the radiation source and the magnification ratio at the time of imaging.

4. An image processing method according to claim 1 or 2, wherein in the acquisition step, scintillator blur information indicating a response to radiation according to a scintillator included in the imaging system is also acquired, and in the blur information generation step, the generated focus blur information and the scintillator blur information acquired in the acquisition step are combined to generate blur information indicating a response to radiation in the radiation image.

5. An image processing method according to claim 1 or 2, further comprising a correction step of acquiring a radiographic image to be corrected for blur, and correcting the blur of the acquired radiographic image based on the out-of-focus blur information generated in the blur information generation step.

6. The image processing method according to claim 5, further comprising a correction step of: acquiring an image of a resolution chart as a radiation image to be corrected for blur in the correction step; calculating a degree of blur correction from the radiation image after correction in the correction step; and correcting the out-of-focus blur information generated in the blur information generation step based on the calculated degree of blur correction.

7. The image processing method according to claim 1 or 2, further comprising an image generation step of generating learning images containing blur, which are used for machine learning training, based on the focus blur information generated in the blur information generation step.

8. An image processing system comprising: an acquisition means for acquiring information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation means for generating, based on the information acquired by the acquisition means, focus blur information indicating a response to radiation in accordance with the focus of the radiation source in a radiation image obtained by imaging with the imaging system.

9. An image processing program that causes a computer to function as: an acquisition means that acquires information indicating the shape of the focus of a radiation source included in an imaging system that performs imaging using radiation; and a blur information generation means that generates, based on the information acquired by the acquisition means, focus blur information that indicates the response to radiation in accordance with the focus of the radiation source in a radiation image obtained by imaging with the imaging system.

10. A computer-readable recording medium on which the image processing program according to claim 9 is recorded.

Images