Radiation image processing apparatus, method, and program

Abstract

To suppress artifacts attributed to a difference in sharpness in a component image in which a specific component of a subject is highlighted in a radiation image processing apparatus, method, and program.SOLUTION: A processor acquires a first radiation image and a second radiation image obtained by imaging a subject on the basis of radiation rays in which energy distributions are different, executes sharpness conversion processing for at least one of the first radiation image and the second radiation image so that the sharpness of the first radiation image and the sharpness of the second radiation image are the same, and derives a component image in which a specific component in the subject is highlighted on the basis of the first radiation image and the second radiation image which have been subjected to the sharpness conversion processing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a radiation image processing device, method, and program. [Background technology]

[0002] Conventionally, energy subtraction processing has been known, which uses two radiation images obtained by irradiating a subject with two types of radiation with different energy distributions, utilizing the fact that the attenuation of transmitted radiation differs depending on the material that constitutes the subject. The energy subtraction processing is a method of obtaining an image in which a specific structure is extracted by matching the pixels of the two radiation images obtained as described above, multiplying the pixels by an appropriate weighting coefficient, and then performing subtraction. By performing such energy subtraction processing, for example, if a soft tissue image in which soft tissue is extracted is derived from a radiation image obtained by photographing the chest, shadows appearing in the soft tissue can be observed without being obstructed by bones. Conversely, if a bone image in which bone tissue is extracted is derived, shadows appearing in the bone can be observed without being obstructed by soft tissue.

[0003] Known techniques for imaging to perform energy subtraction processing (hereinafter referred to as energy subtraction imaging) include the one-shot method and the two-shot method. The one-shot method is a method in which two radiation detectors for detecting radiation and acquiring a radiation image are superimposed with a radiation energy conversion filter interposed therebetween, and radiation that has passed through the subject is simultaneously irradiated onto the two superimposed radiation detectors, thereby irradiating the two radiation detectors with radiation having different energy distributions. The two-shot method is a method in which imaging is performed twice using two types of radiation with different energy distributions.

[0004] Meanwhile, various methods have been proposed for improving the image quality of images acquired by energy subtraction processing. For example, Patent Document 1 proposes a method of performing energy subtraction processing after matching the contrasts of two radiation images acquired by energy subtraction imaging. Also, Patent Document 2 proposes a method of performing graininess suppression processing by deriving the processing content of graininess suppression processing for one of two radiation images acquired by energy subtraction imaging, which has a higher S / N ratio, based on the processing content of graininess suppression processing for the other radiation image.

[0005] In the one-shot method of energy subtraction imaging, radiation that has passed through a subject is simultaneously irradiated onto two radiation detectors that are stacked with a radiation energy conversion filter interposed therebetween. As a result, the radiation irradiated onto the radiation detector farther from the radiation source has relatively high energy because the low-energy components are attenuated more than the radiation irradiated onto the radiation detector closer to the radiation source. For this reason, when performing the one-shot method, radiation detectors with different radiation detection characteristics are used on the side closer to the radiation source and the side farther from the radiation source in order to improve the detection efficiency of radiation with different energies. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-359781 A [Patent Document 2] Patent Publication No. 2022-026929 Summary of the Invention [Problem to be solved by the invention]

[0007] However, if the radiation detection characteristics of the two radiation detectors differ, the sharpness of the two radiation images acquired by energy subtraction imaging may differ. If the sharpness of the two radiation images differs in this way, artifacts caused by the difference in sharpness will be superimposed on a component image in which a specific component of the subject is emphasized, such as a difference image acquired by energy subtraction processing.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an object to suppress artifacts caused by differences in sharpness in component images in which specific components of a subject are emphasized. [Means for solving the problem]

[0009] A radiation image processing device according to the present disclosure includes at least one processor, The processor acquires a first radiation image and a second radiation image acquired by photographing the subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize the sharpness of the first radiographic image and the second radiographic image; A component image in which a specific component within the subject is emphasized is derived based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion process.

[0010] In the radiological image processing device according to the present disclosure, the processor derives a sharpness conversion filter based on a difference between a sharpness characteristic of the first radiological image and a sharpness characteristic of the second radiological image; The sharpness conversion process may be performed using a sharpness conversion filter.

[0011] In the radiation image processing device according to the present disclosure, the processor may perform a sharpness conversion process so as to match the sharpness of one of the first radiation image and the second radiation image to the sharpness of the other radiation image.

[0012] In the radiation image processing device according to the present disclosure, the processor may perform a sharpness conversion process so as to match the sharpness of the first radiation image and the sharpness of the second radiation image to a specific sharpness.

[0013] In the radiation image processing device according to the present disclosure, the processor may derive a component image by performing weighted subtraction on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing.

[0014] Furthermore, in the radiation image processing device according to the present disclosure, the first radiation image and the second radiation image may be acquired by one-shot energy subtraction photography using two radiation detectors having characteristics that result in different sharpness in the acquired radiation images.

[0015] A radiation image processing method according to the present disclosure includes: acquiring a first radiation image and a second radiation image obtained by photographing a subject based on radiation having different energy distributions by a computer; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize the sharpness of the first radiographic image and the second radiographic image; A component image in which a specific component within the subject is emphasized is derived based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion process.

[0016] A radiological image processing program according to the present disclosure includes a step of acquiring a first radiological image and a second radiological image by photographing a subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize the sharpness of the first radiographic image and the second radiographic image; and deriving a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion process. Effect of the Invention

[0017] According to the present disclosure, artifacts caused by differences in sharpness can be suppressed in component images in which specific components within a subject are emphasized. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram of a radiation image capturing system to which a radiation image processing device according to an embodiment of the present disclosure is applied; [Diagram 2] FIG. 1 is a diagram showing a schematic configuration of a radiation image processing apparatus according to an embodiment of the present invention; [Diagram 3] FIG. 1 is a diagram showing a functional configuration of a radiation image processing apparatus according to an embodiment of the present invention. [Figure 4] FIG. 13 is a diagram for explaining the difference in sharpness between a first radiographic image G1 and a second radiographic image G2; [Diagram 5] FIG. 1 is a diagram showing MTF characteristics of a first and a second radiation detector; [Figure 6] A flowchart showing the processing performed in this embodiment. [Figure 7] Conceptual diagram of processing performed in this embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic block diagram showing the configuration of a radiographic image capturing system to which a radiographic image processing device according to an embodiment of the present disclosure is applied. As shown in Fig. 1, the radiographic image capturing system according to this embodiment includes a capturing device 1 and a radiographic image processing device 10 according to this embodiment.

[0020] The imaging device 1 is an imaging device for performing energy subtraction imaging by a so-called one-shot method in which radiation such as X-rays emitted from a radiation source 3 and transmitted through a subject H is irradiated to a first radiation detector 5 and a second radiation detector 6 with different energies. During imaging, as shown in Fig. 1, the first radiation detector 5, a radiation energy converting filter 7 made of a copper plate or the like, and the second radiation detector 6 are arranged in this order from the side closest to the radiation source 3, and the radiation source 3 is driven. The first and second radiation detectors 5 and 6 are in close contact with the radiation energy converting filter 7.

[0021] As a result, the first radiation detector 5 acquires a first radiation image G1 of the subject H using low-energy radiation including so-called soft rays. Meanwhile, the second radiation detector 6 acquires a second radiation image G2 of the subject H using high-energy radiation from which the soft rays have been removed. The first and second radiation images are input to the radiation image processing device 10. The first radiation image G1 and the second radiation image G2 are, for example, front images including the chest and abdomen of the subject H.

[0022] The first and second radiation detectors 5, 6 are capable of repeatedly recording and reading out radiation images, and may be so-called direct type radiation detectors that generate electric charges by directly receiving radiation, or so-called indirect type radiation detectors that convert radiation into visible light and then convert the visible light into an electric charge signal. As a method for reading out the radiation image signal, it is preferable to use a so-called TFT readout method in which the radiation image signal is read out by turning on and off a TFT (thin film transistor) switch, or a so-called optical readout method in which the radiation image signal is read out by irradiating the detector with readout light, but this is not limiting and other methods may also be used.

[0023] In this embodiment, in order to improve the detection efficiency of radiation of different energies, the first and second radiation detectors 5, 6 have different radiation detection characteristics. For example, the first radiation detector 5, which is closer to the radiation source 3, uses CsI (cesium iodide), which has good absorption of low energy components, as a scintillator. On the other hand, the second radiation detector 6, which is farther from the radiation source 3, uses GOS (Gd2O2S:Tb), which has good absorption of high energy components, as a scintillator.

[0024] Next, the radiation image processing device according to the present embodiment will be described. First, the hardware configuration of the radiation image processing device according to the present embodiment will be described with reference to FIG. 2. As shown in FIG. 2, the radiation image processing device 10 is a computer such as a workstation, a server computer, or a personal computer, and includes a CPU (Central Processing Unit) 11, a non-volatile storage 13, and a memory 16 as a temporary storage area. The radiation image processing device 10 also includes a display 14 such as a liquid crystal display, an input device 15 such as a keyboard and a mouse, and a network I / F (InterFace) 17 connected to a network. The CPU 11, the storage 13, the display 14, the input device 15, the memory 16, and the network I / F 17 are connected to a bus 18. The CPU 11 is an example of a processor in the present disclosure.

[0025] The storage 13 is realized by a hard disk drive (HDD), a solid state drive (SSD), a flash memory, etc. The storage 13 as a storage medium stores the radiation image processing program 12 installed in the radiation image processing device 10. The CPU 11 reads out the radiation image processing program 12 from the storage 13, expands it in the memory 16, and executes the expanded radiation image processing program 12.

[0026] The radiation image processing program 12 is stored in a storage device of a server computer connected to a network or in a network storage in an externally accessible state, and is downloaded and installed in the computer constituting the radiation image processing apparatus 10 upon request. Alternatively, the program is recorded on a recording medium such as a DVD (Digital Versatile Disc) or a CD-ROM (Compact Disc Read Only Memory) and distributed, and is installed in the computer constituting the radiation image processing apparatus 10 from the recording medium.

[0027] Next, the functional configuration of the radiation image processing device according to this embodiment will be described. Fig. 3 is a diagram showing the functional configuration of the radiation image processing device according to this embodiment. As shown in Fig. 3, the radiation image processing device 10 includes an image acquisition section 20, a filter derivation section 21, a sharpness conversion section 22, and an image derivation section 23. Then, the CPU 11 executes the radiation image processing program 12, whereby the CPU 11 functions as the image acquisition section 20, the filter derivation section 21, the sharpness conversion section 22, and the image derivation section 23.

[0028] The image acquisition unit 20 causes the imaging device 1 to capture an image of the subject H, thereby acquiring a first radiographic image G1 and a second radiographic image G2, which are front images of the subject H, from the first and second radiation detectors 5, 6. When acquiring the first radiographic image G1 and the second radiographic image G2, imaging conditions such as the radiation exposure dose, tube voltage, and SID (Source-to-Image receptor Distance: X-ray tube focus-to-image receptor distance) are set. The set imaging conditions are stored in the storage 13.

[0029] The first and second radiographic images G1, G2 may be acquired by a program separate from the radiographic image processing program of the present embodiment. In this case, the first and second radiographic images G1, G2 are stored in the storage 13, and the image acquisition section 20 reads out the first and second radiographic images G1, G2 stored in the storage 13 from the storage 13 for processing.

[0030] The filter derivation unit 21 derives a sharpness conversion filter used when the sharpness conversion unit 22 performs sharpness conversion processing on at least one of the first and second radiographic images G1, G2. As described above, in this embodiment, the first radiation detector 5 and the second radiation detector 6 have different radiation detection characteristics. When the first radiation detector 5 and the second radiation detector 6 have different radiation detection characteristics, the first radiation image G1 and the second radiation image G2 have different sharpness. The difference in radiation detection characteristics is caused by, for example, a difference in the film formation state of the scintillator. For example, CsI used as the scintillator of the first radiation detector 5 is made of independent thin columnar crystals in a fiber shape. On the other hand, GOS used as the scintillator of the second radiation detector 6 is not made of columnar crystals. As a result, CsI has higher MTF (Modulation Transfer Function) characteristics than GOS, and therefore the sharpness of the first radiation image G1 is higher than the sharpness of the second radiation image.

[0031] FIG. 4 is a diagram for explaining the difference between the sharpness of the first radiographic image G1 and the sharpness of the second radiographic image G2. FIG. 4 shows, from the top, a profile P1 of pixel values ​​at the edge portion of the subject in the first radiographic image G1, a profile P2 of pixel values ​​at the edge portion of the subject in the second radiographic image G2, and a profile Ps explaining the difference between the first and second radiographic images G1 and G2. In FIG. 4, the horizontal axis indicates the position, and the vertical axis indicates the pixel value. As shown in FIG. 4, in the profile P1 of the first radiographic image G1, the density change at the edge portion is steep. On the other hand, since the sharpness of the second radiographic image G2 is lower than that of the first radiographic image G1, in the profile P2 of the second radiographic image G2, the density change at the edge portion is gentler than that of the first radiographic image G1.

[0032] For this reason, when a difference image is derived by performing weighted subtraction between the first radiographic image G1 and the second radiographic image G2 as described below, the pixel values ​​of the shaded area are superimposed on the difference image as artifacts, as shown in the profile Ps of the difference image in FIG.

[0033] The filter derivation unit 21 derives a sharpness conversion filter for performing a sharpness conversion process so as to match the sharpness of the first radiographic image G1 with the sharpness of the second radiographic image G2. To this end, the filter derivation unit 21 acquires the MTF characteristics of the first radiation detector 5 and the second radiation detector 6. The MTF characteristics may be measured in advance by a known method, such as by photographing an MTF chart.

[0034] FIG. 5 is a diagram showing the MTF characteristics of the first and second radiation detectors 5 and 6. As shown in FIG. 5, the MTF characteristics M2 of the second radiation detector 6 have a lower response of high frequency components than the MTF characteristics M1 of the first radiation detector 5. The filter derivation unit 21 derives a conversion magnification B12 for converting the MTF characteristics M2 into the MTF characteristics M1 by dividing the MTF characteristics M1 by the MTF characteristics M2. The filter derivation unit 21 then derives a sharpness conversion filter for matching the sharpness of the second radiation image G2 with the sharpness of the first radiation image G1 based on the conversion magnification B12. The filter derivation unit 21 may derive the sharpness conversion filter F0 in advance and store it in the storage 13.

[0035] The derivation of the sharpness conversion filter F0 will be described below. The filter coefficients of the sharpness conversion filter F0 can be found by performing a Discrete Fourier Transform (DFT) on the desired frequency characteristics to derive an impulse response. First, the desired frequency characteristics, i.e., the frequency characteristics of the image after filtering by the sharpness conversion filter F0, are determined. The frequency characteristics are determined based on the amplitude characteristics and phase characteristics. In this embodiment, the frequency characteristics are those of the first radiographic image G1, and the amplitude characteristics are the above-mentioned conversion magnification B12. The phase characteristics are determined in advance.

[0036] When deriving the sharpness conversion filter F0, the conversion magnification is defined from 0 to the Nyquist frequency Fs / 2. Fs is the maximum frequency at which an image can be reproduced. For this reason, on the frequency axis in the frequency characteristics, the conversion magnification B12 is applied from 0 to the Nyquist frequency Fs / 2, and from the Nyquist frequency Fs / 2 to Fs, the characteristics from 0 to the Nyquist frequency Fs / 2 are applied with the left and right reversed.

[0037] Here, if the amplitude characteristic is G(f) and the phase characteristic is θ(f), then the desired frequency characteristic H(f) is derived by the following equation (1).

number

[0038] Next, equation (1) is discretized to derive the following equation (2).

number

[0039] The impulse response h[n] shown in the following equation (3) is derived by performing inverse DFT on equation (2), where n is the number of samples.

number

[0040] In formula (3), the impulse response h[k] for each k is the filter coefficient of the sharpness conversion filter F0. The larger the filter size, the more the image can be converted to have frequency characteristics closer to the desired ones, but the calculation time increases. For this reason, the filter size should be determined taking the calculation time into consideration. For example, the number of taps of the filter can be about 17 to 25. The sharpness conversion filter F0 is a one-dimensional filter, but may be a two-dimensional filter.

[0041] The sharpness conversion unit 22 performs a filtering process on the second radiographic image G2 using the sharpness conversion filter F0 derived by the filter derivation unit 21, and derives a second radiographic image G2' that has been subjected to the sharpness conversion process. Here, since the sharpness conversion filter F0 is a one-dimensional filter, the sharpness conversion unit 22 first performs a filtering process in one direction (e.g., the x direction) in the second radiographic image G2, and then performs a filtering process in a direction perpendicular to the one direction (e.g., the y direction).

[0042] The image derivation unit 23 derives a component image in which a specific component in the subject H is emphasized based on the first radiographic image G1 and the processed second radiographic image G2'. Specifically, as shown in the following formulas (4) and (5), weighted subtraction is performed between corresponding pixels of the first and second radiographic images G1 and G2 to derive a bone image Gb from which the bones of the subject H included in each of the radiographic images G1 and G2 are extracted and a soft tissue image Gs from which the soft tissues are extracted are extracted. The bone image Gb and the soft tissue image Gs are examples of component images. In formulas (4) and (5), α1 and α2 are weighting coefficients, which are set to values ​​that allow the bone tissues and soft tissues of the subject H included in each of the radiographic images G1 and G2 to be extracted by formulas (4) and (5) based on the radiation attenuation coefficients of the bone tissues and soft tissues.

[0043] Gb(x, y)=G1(x, y)-α1×G2′(x, y) (4) Gs(x, y)=G1(x, y)-α2×G2′(x, y) (5)

[0044] Next, the processing performed in this embodiment will be described. Fig. 6 is a flow chart showing the processing performed in this embodiment, and Fig. 7 is a conceptual diagram of the processing performed in this embodiment. It is assumed that the first and second radiographic images G1, G2 are acquired by imaging and stored in the storage 13. It is also assumed that the sharpness conversion filter F0 is derived by the filter derivation unit 21 and stored in the storage 13.

[0045] When an instruction to start processing is input from the input device 15, the image acquisition unit 20 acquires the first and second radiographic images G1, G2 from the storage 13 (step ST1). Next, the sharpness conversion unit 22 performs a sharpness conversion process on the second radiographic image G2 (step ST2). Then, the image derivation unit 23 performs a subtraction process on the first radiographic image G1 and the second radiographic image G2' that has been subjected to the sharpness conversion process, derives component images, i.e., a bone image Gb and a soft tissue image Gs (step ST3), and ends the processing. The bone image Gb and the soft tissue image Gs are displayed on the display 14 or stored in the storage 13.

[0046] In this manner, in the present embodiment, the second radiographic image G2 is subjected to a sharpness conversion process so as to make the sharpness of the first radiographic image G1 and the second radiographic image G2 uniform, and a component image in which a specific component of the subject H is emphasized is derived based on the second radiographic image G2' and the first radiographic image G1 that have been subjected to the sharpness conversion process. This makes it possible to prevent artifacts due to differences in sharpness between the first radiographic image G1 and the second radiographic image G2 from being superimposed on the component image, and as a result, it is possible to obtain a component image of high image quality.

[0047] Furthermore, a sharpness conversion filter F0 is derived based on the difference between the sharpness characteristics of the first radiographic image G1, i.e., the MTF characteristics M1, and the sharpness characteristics of the second radiographic image G2, i.e., the MTF characteristics M2, and a sharpness conversion process is performed using the sharpness conversion filter F0. Therefore, the difference in sharpness between the first radiographic image G1 and the second radiographic image G2 can be appropriately eliminated by the sharpness conversion process.

[0048] In the above embodiment, the sharpness conversion process is performed on the second radiographic image G2 using the sharpness conversion filter F0, but the present invention is not limited to this. The sharpness conversion process may be performed on the first radiographic image G1. In this case, the filter derivation unit 21 derives a conversion magnification (referred to as B21) for converting the MTF characteristics M1 into the MTF characteristics M2 by dividing the MTF characteristics M2 by the MTF characteristics M1, and derives a sharpness conversion filter for matching the sharpness of the first radiographic image G1 with the sharpness of the second radiographic image G2 based on the conversion magnification B21.

[0049] Furthermore, a sharpness conversion process may be performed to convert each of the first radiographic image G1 and the second radiographic image G2 to a predetermined specific sharpness. In this case, a sharpness conversion filter F1 for converting the sharpness of the first radiographic image G1 to the specific sharpness and a sharpness conversion filter F2 for converting the sharpness of the second radiographic image G2 to the specific sharpness are derived by the filter derivation unit 21. Then, the sharpness conversion process may be performed on the first radiographic image G1 by the sharpness conversion filter F1, and the sharpness conversion process may be performed on the second radiographic image G2 by the sharpness conversion filter F2.

[0050] In the above embodiment, the radiological image processing device 10 according to this embodiment includes the filter derivation unit 21, but this is not limited to this. The radiological image processing device 10 according to this embodiment may not include the filter derivation unit 21, and the sharpness conversion filter may be derived by a device different from the radiological image processing device 10 according to this embodiment.

[0051] In the above embodiment, the sharpness conversion process is performed by filtering, but the present invention is not limited to this. A function such as a mathematical formula for performing the sharpness conversion process may be derived, and the sharpness conversion process may be performed on at least one of the first and second radiographic images G1 and G2 using the derived function.

[0052] In the above embodiment, the component images are derived by subtraction processing, but the present invention is not limited to this. Any method other than subtraction processing may be used as long as it is possible to derive a component image in which the characteristic components of the subject are emphasized using the first and second radiation images G1 and G2.

[0053] In addition, in each of the above embodiments, the first and second radiation images G1, G2 are obtained by a one-shot method. However, the first and second radiation images G1, G2 may be obtained by a so-called two-shot method in which imaging is performed twice.

[0054] In the case of the two-shot method, the radiation dose is reduced in the second radiography compared to the first radiography in order to reduce the radiation exposure dose to the subject H. As a result, one of the first and second radiographic images G1, G2 (here, the second radiographic image G2) has a lower sharpness than the first radiographic image G1. Therefore, even when the first and second radiographic images G1, G2 are obtained by the two-shot method, the second radiographic image G2 may be subjected to a sharpness conversion process, and the processed second radiographic image G2′ and the first radiographic image G1 may be used for subtraction processing, as in the above embodiment.

[0055] In the above embodiment, the energy subtraction process is performed using a radiographic image acquired in a system that captures a radiographic image of the subject H using the first and second radiation detectors 5 and 6. However, the present disclosure can of course be applied to a case where the first and second radiographic images G1 and G2 are acquired using stimulable phosphor sheets instead of radiation detectors. In this case, two stimulable phosphor sheets are stacked and irradiated with radiation that has passed through the subject H, and the radiographic image information of the subject H is accumulatively recorded on each stimulable phosphor sheet, and the radiographic image information is photoelectrically read from each stimulable phosphor sheet to acquire the first and second radiographic images G1 and G2. The two-shot method may also be used when acquiring the first and second radiographic images G1 and G2 using stimulable phosphor sheets.

[0056] Moreover, the radiation in each of the above embodiments is not particularly limited, and in addition to X-rays, α-rays, γ-rays, etc. can be used.

[0057] In the above embodiment, the following various processors can be used as the hardware structure of the processing unit that executes various processes, such as the image acquisition unit 20, the filter derivation unit 21, the sharpness conversion unit 22, and the image derivation unit 23. As described above, the above various processors include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and a dedicated electric circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor having a circuit configuration designed specifically for executing specific processes.

[0058] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (e.g., a combination of multiple FPGAs or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor.

[0059] As an example of configuring multiple processing units with one processor, first, there is a form in which one processor is configured with a combination of one or more CPUs and software, as typified by computers such as client and server, and this processor functions as multiple processing units. Second, there is a form in which a processor is used that realizes the functions of the entire system including multiple processing units with one IC (Integrated Circuit) chip, as typified by System On Chip (SoC), etc. In this way, the various processing units are configured using one or more of the above various processors as a hardware structure.

[0060] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0061] The following are appended claims to this disclosure. (Additional note 1) at least one processor; The processor, acquiring a first radiation image and a second radiation image by photographing a subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize the sharpness of the first radiographic image and the second radiographic image; a radiation image processing device that derives a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing. (Additional note 2) the processor derives a sharpness conversion filter based on a difference between a sharpness characteristic of the first radiographic image and a sharpness characteristic of the second radiographic image; 2. The radiation image processing device according to claim 1, wherein the sharpness conversion process is performed by the sharpness conversion filter. (Additional note 3) 3. The radiological image processing device according to claim 1, wherein the processor performs the sharpness conversion process so as to match the sharpness of one of the first radiological image and the second radiological image to the sharpness of the other of the first radiological image and the second radiological image. (Additional note 4) 3. The radiological image processing device according to claim 1, wherein the processor performs the sharpness conversion process so as to match the sharpness of the first radiological image and the sharpness of the second radiological image to a specific sharpness. (Additional note 5) 5. The radiological image processing device according to claim 1, wherein the processor derives the component image by performing weighted subtraction on the first radiological image and the second radiological image that have been subjected to the sharpness conversion processing. (Additional note 6) 6. The radiation image processing device according to claim 5, wherein the first radiation image and the second radiation image are acquired by one-shot energy subtraction radiography using two radiation detectors having characteristics that result in acquired radiation images with different sharpness. (Additional note 7) a computer acquires a first radiation image and a second radiation image obtained by photographing an object based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize sharpness of the first radiographic image and the second radiographic image; A radiation image processing method for deriving a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing. (Additional note 8) obtaining a first radiographic image and a second radiographic image by imaging a subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize sharpness of the first radiographic image and the second radiographic image; and deriving a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing. [Explanation of symbols]

[0062] 1. Imaging device 3 Radiation source 5,6 Radiation detectors 7 Radiation Energy Conversion Filter 10 Radiation image processing device 11 CPU 12 Radiological image processing program 13. Storage 14 Display 15 Input Devices 16 Memory 17 Network Interface 18 Bus 20 Image acquisition section 21 Filter lead-out section 22 Sharpness conversion section 23 Image extraction section G1 First radiological image G2 Second radiographic image G2′ processed second radiographic image Gb bone image Gs Soft tissue image

Claims

1. At least one processor; The processor, acquiring a first radiographic image and a second radiographic image by capturing an image of a subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize sharpness of the first radiographic image and the second radiographic image; a radiation image processing device that derives a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing.

2. The processor derives a sharpness conversion filter based on a difference between a sharpness characteristic of the first radiographic image and a sharpness characteristic of the second radiographic image; 2. The radiation image processing apparatus according to claim 1, wherein the sharpness conversion process is performed by using the sharpness conversion filter.

3. The apparatus according to claim 1 , wherein the processor performs the sharpness conversion process so as to match the sharpness of one of the first radiographic image and the second radiographic image to the sharpness of the other of the first radiographic image and the second radiographic image.

4. The radiation image processing apparatus according to claim 1 , wherein the processor performs the sharpness conversion process so as to match the sharpness of the first radiation image and the sharpness of the second radiation image to a specific sharpness.

5. The radiation image processing apparatus according to claim 1 , wherein the processor derives the component images by performing weighted subtraction on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing.

6. 6. The radiation image processing device according to claim 5, wherein the first radiation image and the second radiation image are acquired by one-shot energy subtraction photography using two radiation detectors having characteristics that result in acquired radiation images with different sharpness.

7. a computer acquires a first radiation image and a second radiation image obtained by photographing a subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize sharpness of the first radiographic image and the second radiographic image; A radiation image processing method for deriving a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing.

8. obtaining a first radiographic image and a second radiographic image by imaging a subject based on radiation having different energy distributions; performing a sharpness conversion process on at least one of the first radiographic image and the second radiographic image so as to equalize sharpness of the first radiographic image and the second radiographic image; and deriving a component image in which a specific component within the subject is emphasized, based on the first radiation image and the second radiation image that have been subjected to the sharpness conversion processing.

Images