Information processing apparatus and method

Abstract

To provide an information processing apparatus which acquires a phantom image and a gain correction image in a proper arrangement state of a phantom and reduces a risk of erroneous photographing.SOLUTION: The information processing apparatus includes: an image acquisition unit that acquires two types of radiation images captured under two types of imaging conditions with different amounts of radiation energy; a determination unit that determines whether a phantom placement situation satisfies a predetermined condition using information about an area where the phantom is placed; at least one of the two types of radiation images in which it is determined that the phantom is placed so as to satisfy a predetermined condition; and a bone density acquisition unit that acquires a first bone density of the phantom using at least one of two types of radiological images that is different from the at least one of the two types of radiological images and that is determined to be one in which the phantom is not placed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an information processing device and method. [Background technology]

[0002] Conventionally, a measurement method called BMD (Bone Mineral Density) has been used for diagnosing osteoporosis. BMD measurement requires measuring the quantity of bone mineral in the bone. DXA (Dual-energy X-ray Absorptiometry) is used as a method for measuring bone mineral quantity.

[0003] DXA is a technique that uses two types of X-rays with different energy distributions to measure bone density based on the difference in X-ray absorption coefficients between soft tissue and bone tissue. Devices specifically designed for bone density measurement using DXA include those equipped with a line sensor that alternately irradiates high-energy X-rays and low-energy X-rays at regular intervals. There are also filter-type devices that use a filter placed in front of the X-ray tube to change the irradiation energy.

[0004] In recent years, digital imaging diagnosis using X-ray images taken with general imaging equipment has become widespread, and attempts to apply it to bone density measurement have begun. When bone density imaging is performed using a flat panel detector (hereinafter referred to as FPDe), a radiation detector used for general imaging, X-rays are irradiated onto the entire surface of the sensor to obtain an image (cone beam imaging). This has the advantage of shortening the time required for each imaging session and reducing the burden on the patient.

[0005] Furthermore, a bone density calibration value is required to calculate bone density. The bone density calibration value is a conversion coefficient required to convert bone density calculated from the sensor output value into actual bone density. The bone density calibration value can be obtained by capturing an image (hereinafter referred to as a phantom image) taken with a phantom whose bone density is known in advance, and an image (hereinafter referred to as a gain correction image) showing the incident dose distribution of X-rays taken without the phantom. The operation of calculating the bone density calibration value by capturing the phantom image and the gain correction image is periodically performed by the operator.

[0006] A method of performing calibration by placing a phantom is described in Patent Document 1. In Patent Document 1, in the calibration of BMD measurement using cone beam imaging, calibration is performed based on an image captured with a phantom placed and an image captured without a subject placed and without a phantom placed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-166157 Summary of the Invention [Problem to be solved by the invention]

[0008] When bone density measurement is performed using an imaging device that uses an FPDe and is also used for general imaging, the operator must manually attach and detach the phantom during bone density calibration. That is, the operator must manually place the phantom in the appropriate location, capture a phantom image, then remove the phantom and capture a gain correction image. As a result, for example, there is a possibility that the phantom may not be positioned at the time when it should be positioned appropriately for imaging, or even if it is positioned, it may be positioned in a location other than the appropriate location and imaged, resulting in a problem of bone density calibration not being performed properly.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an information processing device that, when performing bone density calibration, acquires a phantom image and a gain correction image in an appropriate phantom positioning situation, thereby reducing the risk of erroneous imaging. [Means for solving the problem]

[0010] The information processing device of the present disclosure includes an image acquisition unit that acquires two types of radiological images captured under two types of imaging conditions with different amounts of energy of irradiated radiation, a determination unit that determines whether the placement of the phantom satisfies a predetermined condition using information related to an area where a phantom is placed, and a bone density acquisition unit that acquires a first bone density of the phantom using at least one of the two types of radiological images that has been determined to have the phantom placed in a manner that satisfies the predetermined condition, and at least one of the two types of radiological images that is different from the at least one of the two types of radiological image and has been determined to have the phantom not placed. [Effects of the Invention]

[0011] According to the present disclosure, an information processing device is realized that, when performing bone density calibration, acquires a phantom image and a gain correction image in an appropriate phantom positioning situation, thereby reducing the risk of erroneous imaging. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a schematic configuration of a radiation imaging system according to a first embodiment. [Figure 2] 1 is a system configuration diagram of an information device according to a first embodiment. [Figure 3] FIG. 2 is a functional configuration diagram of an information device according to the first embodiment. [Figure 4] FIG. 1 is a flow diagram illustrating an information processing method for obtaining bone mineral density calibration values. [Figure 5] FIG. 10 is a flowchart showing a determination operation in an image type determination unit. [Figure 6]FIG. 1 is a cross-sectional view showing one bone region in a calibration phantom. [Figure 7] FIG. 1 is a flow diagram for performing bone density calibration. [Figure 8] FIG. 10 is a schematic diagram for explaining a bone mineral density calibration process. [Figure 9] FIG. 10 is a schematic diagram showing an example of a display screen during imaging for bone density calibration. [Figure 10] FIG. 1 is a flow diagram illustrating an information processing method for obtaining bone mineral density calibration values. [Figure 11] FIG. 10 is a functional configuration diagram of an information device according to a second embodiment. [Figure 12] FIG. 10 is a schematic diagram illustrating an example of a display screen after a radiation image is acquired. [Figure 13] FIG. 10 is a schematic diagram illustrating an example of a warning dialog box. [Figure 14] FIG. 10 is a system configuration diagram of an information device 106 according to a third embodiment. [Figure 15] FIG. 10 is a functional configuration diagram of an information device according to a third embodiment. [Figure 16] 1A-1C are schematic diagrams illustrating aspects of the geometry of a calibration phantom. [Figure 17] FIG. 11 is a flowchart showing a geometric arrangement determination operation according to the third embodiment. [Figure 18] FIG. 10 is a schematic diagram illustrating an example of a warning dialog display. [Figure 19] FIG. 10 is a schematic diagram illustrating an example of a determination method. [Figure 20] FIG. 10 is a schematic diagram showing the general configuration of a radiation imaging system according to a fourth embodiment. [Figure 21] FIG. 10 is a system configuration diagram of an information device according to a fourth embodiment. [Figure 22] FIG. 10 is a functional configuration diagram of an information device according to a fourth embodiment. [Figure 23] FIG. 10 is a flow diagram showing the determination operation and bone density calibration. [Figure 24] FIG. 10 is a schematic diagram illustrating an example of a warning dialog box. [Figure 25] FIG. 10 is a schematic diagram showing the general configuration of a radiation imaging system according to a fifth embodiment. [Figure 26] FIG. 11 is a functional configuration diagram of an information device according to a fifth embodiment. [Figure 27] FIG. 1 is a plan view showing an example of a calibration phantom and an electrode configuration in its arrangement area. [Figure 28] FIG. 1 is a plan view showing the arrangement of a calibration phantom. [Figure 29] FIG. 10 is a flow diagram showing the determination operation and bone density calibration. [Figure 30] FIG. 10 is a schematic diagram illustrating an example of a warning dialog box. DETAILED DESCRIPTION OF THE INVENTION

[0013] -Basic configuration of information processing device in various embodiments- Before specifically disclosing the embodiments, the basic configuration of an information processing device in each embodiment will be described.

[0014] The information processing device according to the present disclosure is an information processing device that acquires bone density of a subject using a radiation image in a radiation imaging system that irradiates the subject with radiation, detects the radiation that has passed through the subject, and acquires a radiation image.

[0015] This information processing device includes an image acquisition unit, a determination unit, and a bone density acquisition unit. The image acquisition unit acquires two types of radiographic images captured under two imaging conditions with different amounts of radiation energy. The determination unit uses information about the area where the phantom is disposed to determine whether the phantom placement satisfies a predetermined condition. Examples of the information about the phantom placement area include radiographic image information, optical image information, and electrical signal information. The radiographic image information is information about two types of radiographic images capturing the placement of the phantom in the phantom placement area. The optical image information is information about an optical image captured by a predetermined camera. The electrical signal information is information from the phantom and electrodes and the like appropriately provided in the phantom placement area. The use of radiographic image information will be described in detail in the first to third embodiments, the use of optical image information in the fourth embodiment, and the use of electrical signal information in the fifth embodiment.

[0016] The "predetermined conditions" are various criteria for determining the placement status of a phantom. The contents of the placement status determination include, first, whether or not a phantom is placed in the phantom placement area (presence or absence of phantom placement). Other conditions include whether or not anything other than the phantom is placed, and even if a phantom is placed in the phantom placement area, whether or not the geometric placement state of the phantom (for example, the relative position and relative angle of the phantom with respect to the placement area) is appropriate.

[0017] The bone density acquisition unit acquires a first bone density of the phantom using at least one of the two types of radiation images, which is determined to have a phantom arranged in a manner satisfying predetermined conditions, and at least one of the two types of radiation images which is different from the at least one of the two types of radiation images and is determined to have no phantom arranged therein. Here, the first bone density is a measurement value of the bone density of the phantom. The former two types of radiation images are so-called phantom images, and the latter two types of radiation images are so-called gain correction images. "The phantom is arranged in a manner satisfying predetermined conditions" means that the phantom is arranged in the phantom arrangement area and that the geometric arrangement of the phantom is appropriate for obtaining a phantom image.

[0018] The information processing device further has a calibration value acquisition unit, which compares the first bone density acquired by the bone density acquisition unit with a second bone density, which is a true bone density value known from the phantom, to acquire a bone density calibration value that calibrates the first bone density to the second bone density.

[0019] In the information processing device according to the present disclosure, the determination unit determines whether the phantom placement satisfies a predetermined condition and distinguishes between the obtained phantom image and the gain correction image based on the determination result. This reduces the risk of human error in capturing images related to the phantom placement. The bone density acquisition unit then performs appropriate arithmetic processing using the distinguished phantom image and the gain correction image to acquire an accurate bone density calibration value. The calibration value acquisition unit uses this bone density calibration value to accurately determine the bone density of a patient, etc.

[0020] Preferred embodiments to which the present disclosure can be applied will be described in detail below with reference to the drawings. In the following description, common components across multiple drawings are assigned common reference numerals. Therefore, the common components will be described with mutual reference to multiple drawings, and descriptions of the components assigned common reference numerals will be omitted as appropriate. The radiation in the various embodiments may include α-rays, β-rays, γ-rays, and the like, which are beams formed by particles (including photons) emitted by radioactive decay, as well as beams having the same or higher energy levels, such as X-rays, particle beams, and cosmic rays.

[0021] -First embodiment- In this embodiment, an example of an information processing apparatus and a radiation imaging system to which the present disclosure is applied will be described.

[0022] <Radiation imaging system configuration> FIG. 1 is a schematic diagram showing the general configuration of a radiation imaging system according to the first embodiment. As shown in FIG. 1, a radiation imaging system 101 includes a radiation generating device 102 that generates radiation such as X-rays to be irradiated onto a subject P such as a patient, and a radiation detector 103 that detects radiation generated by the radiation generating device 102 and transmitted through the subject P to obtain a radiological image. The radiation detector 103 is a so-called FPDe for general radiography. As an example, in this embodiment, a general radiography system is considered in which the radiation generating device 102 is fixed by a gantry 105 or the like, and the radiation detector 103 is fixed inside a bed 104. The subject P or a calibration phantom 108 for bone density calibration is placed on the bed 104, and an operator G operates an exposure switch 107 to irradiate radiation.

[0023] Information equipment 106 is an information processing device of this embodiment, and is connected to a user input device 200A such as a mouse or keyboard, and a UI display device 200B such as a display. User input device 200A receives user input from an operator, and UI display device 200B displays radiation images acquired from radiation detector 103. Calibration phantom 108 is made of a material such as acrylic to simulate soft tissue of the human body, and has a structure simulating bones with known bone densities inside. In this embodiment, as an example, phantom 108 is used in which bones with three levels of known bone densities are arranged.

[0024] <Configuration of Information Device 106> The following describes the information device 106. Fig. 2 is a system configuration diagram of the information device 106, and Fig. 3 is a functional configuration diagram of the information device 106. For the sake of convenience, Fig. 3 omits the illustration of a central processing unit (CPU) 231 and a main memory 232. The same applies to Figs. 11, 15, 22, and 26, which will be described later.

[0025] The information device 106 is provided with a user input control unit 201, a display control unit 202, an imaging mode setting unit 203, an imaging condition setting unit 204, a radiation image acquisition unit 205, an image type determination unit 206, a bone density calibration unit 207, and a bone density examination unit 208. The information device 106 is also provided with a CPU 231, a main memory 232, and a storage unit 233. The storage unit 233 is provided with a test image storage unit 234, a gain correction image storage unit 235, and a calibration phantom image storage unit 236. The various units of the information device 106 are connected via a CPU bus 230, and are capable of exchanging data with one another.

[0026] The CPU 231 is an example of a processor that controls the operation of the information device 106. The CPU 231 uses the main memory 232 to control the operation of the entire information device 106. The processor in the information device 106 is not limited to a CPU, and may include, for example, an MPU (Micro Processing Unit) and a GPU (Graphic Processing Unit). The storage unit 233 can store various image data processed by the information device 106.

[0027] The display control unit 202 controls the display of the radiation image and the like acquired from the radiation detector 103 on the UI display device 200B such as a display.

[0028] The imaging mode setting unit 203 sets the imaging mode via the user input control unit 201 based on a user operation input from the user input device 200A such as a mouse or a keyboard. In this embodiment, the imaging mode can be set to a mode for performing bone density calibration (hereinafter referred to as bone density calibration mode) or a mode for measuring the bone density of a patient (hereinafter referred to as examination mode). In the bone density calibration mode, calibration phantom images and gain correction images required for bone density calibration are captured, and in the examination mode, images of the patient whose bone density is to be measured (hereinafter referred to as examination images) are captured.

[0029] The imaging condition setting unit 204 sets imaging conditions. Here, imaging conditions refer to conditions necessary for executing radiation irradiation, including at least tube voltage, tube current, and irradiation time. The imaging conditions set by the imaging condition setting unit 204 are used to control the irradiation conditions of the radiation generator 102 via generator communication. In the information device 106 using the DXA method, two different imaging conditions are set: a first imaging condition in which the radiation is low-energy and a second imaging condition in which the radiation is high-energy, and two types of radiation images can be captured: an image under the second imaging condition and an image under the first imaging condition.

[0030] The two types of radiation images may be obtained sequentially in two imaging sessions, or simultaneously in a single imaging session. In the latter case, the radiation detector 103 is configured with two layers of radiation X-ray sensors, and one of the two layers of radiation sensors obtains a low-energy image, and the other obtains a high-energy image. This allows two types of radiation images to be obtained simultaneously in a single imaging session.

[0031] The radiation image acquisition unit 205 acquires, via communication with the radiation detector 103, a first radiation image captured under the first imaging condition and a second radiation image captured under the second imaging condition.

[0032] In this embodiment, the determination unit in the present disclosure includes an image type determination unit 206. The image type determination unit 206 determines the image type of the radiographic image acquired by the radiographic image acquisition unit 205. Image types include a test image, a calibration phantom image which is the first radiographic image and the second radiographic image, and a gain correction image which is the first radiographic image and the second radiographic image. The image type determination unit 206 determines the image type, and based on the determination result, adds information about the image type to the tag of the captured image and stores it in the storage unit 233. As a result, images corresponding to each image type are appropriately stored in each image storage unit (test image storage unit 234, calibration phantom image storage unit 236, gain correction image storage unit 235) corresponding to each image type.

[0033] The bone density calibration unit 207 performs bone density calibration based on the calibration phantom images captured under the first and second imaging conditions stored in the calibration phantom image storage unit 236 and the gain correction images captured under the first and second imaging conditions stored in the gain correction image storage unit 235. Specifically, the bone density calibration unit 207 performs arithmetic processing using the calibration phantom images and the gain correction images to obtain a first bone density of the calibration phantom, and compares it with a second bone density (true bone density) that is known for the calibration phantom 108. Then, it obtains a bone density calibration value for calibrating the first bone density to the second bone density.

[0034] When examining the bone density of a patient, the bone density examination unit 208 reads out the examination images captured under the first and second imaging conditions stored in the examination image storage unit 234, and uses these to obtain a bone density measurement value of the patient. Then, the bone density measurement value is corrected using the bone density calibration value obtained by the bone density calibration unit 207, thereby obtaining the bone density of the patient.

[0035] <Information processing method for obtaining bone density calibration value> The operation of the radiation system and the operation by the operator when capturing a calibration phantom image and a gain correction image in the bone mineral density calibration mode will be described below. Fig. 4 is a flowchart showing an information processing method for acquiring a bone mineral density calibration value according to this embodiment.

[0036] In imaging in the bone density calibration mode, either the calibration phantom image or the gain correction image may be captured first, but as an example, a flow in which the calibration phantom image is captured first will be described here.

[0037] First, in S401, the operator G places the calibration phantom 108 in the placement area (area to be irradiated with radiation) of the bed 104. In this embodiment, it is assumed that when placing the calibration phantom 108, the operator G places the calibration phantom 108 in an appropriate geometric position in the placement area of ​​the bed 104.

[0038] In S402, the operator G presses the irradiation switch 107 to irradiate radiation under the first and second imaging conditions from the radiation generation device 102. The radiation image acquisition unit 205 acquires a first radiation image captured under the first imaging condition and a second radiation image captured under the second imaging condition.

[0039] Here, the placement of the calibration phantom 108 in S401 is a manual operation by the operator G. Therefore, in this embodiment, the information device 106 determines whether the operator G is taking an image of the calibration phantom with the calibration phantom 108 placed, or whether the operator G is taking an image of the gain correction without placing the calibration phantom 108.

[0040] In S403, the image type determination unit 206 analyzes the first and second radiographic images acquired in S402 to determine whether the acquired images are calibration phantom images or gain correction images. If the determination result is that the images are calibration phantom images, the image type determination unit 206 stores the first and second radiographic images in the calibration phantom image storage unit 236 (S404). If the determination result is that the images are gain correction images, the image type determination unit 206 stores the first and second radiographic images in the gain correction image storage unit 235 (S605).

[0041] In S406, the image type determination unit 206 determines whether or not to end imaging. The condition for ending imaging is that imaging is ended when all of the calibration phantom images and gain correction images for the first and second imaging conditions required for bone density calibration have been stored in the image storage unit. In this embodiment, since the gain correction images have not yet been captured, imaging does not end and the radiation imaging system accepts the next radiation irradiation.

[0042] In S401, the operator G removes the calibration phantom 108 from the placement area of ​​the bed 104 in order to capture a gain correction image.

[0043] In S402, the operator G presses the exposure switch 107 to perform imaging again under the first imaging condition and the second imaging condition, and the radiation image acquisition unit 205 acquires the first radiation image and the second radiation image.

[0044] In S403, the image type determination unit 206 analyzes the acquired first and second radiographic images and determines whether they are calibration phantom images or gain correction images. Based on the determination result, the image type determination unit 206 stores the first and second radiographic images in the calibration phantom image storage unit 236 or the gain correction image storage unit 235 (S404, S405).

[0045] In 406, the image type determination unit 206 determines again whether the shooting end condition is met, and if the condition is met, ends shooting.

[0046] In S407, the bone mineral density calibration unit 207 calculates a bone mineral density calibration value. Specifically, the bone mineral density calibration value is calculated according to the flow of Fig. 7, which will be described later, using the calibration phantom image stored in the calibration phantom image storage unit 236 in S404 and the gain correction image stored in the gain correction image storage unit 235 in S405.

[0047] As described above, the image type determination unit 206 determines whether or not a calibration phantom has been placed by user operation, and stores the radiation image in the correct image storage unit, thereby enabling bone density calibration to be performed using the correct radiation image.

[0048] <Determination operation of the image type determination unit> The following describes the determination operation of the image type determination unit 206 in S403 of Fig. 4. Fig. 5 is a flow chart showing the determination operation of the image type determination unit 206.

[0049] First, in S501, the image type determination unit 206 calculates the irradiation field area of ​​the first radiographic image and the second radiographic image. Methods for recognizing the irradiation field area include rule-based and machine learning methods. An example of a rule-based method is a method using a Hough transform. The Hough transform is capable of extracting straight line components. The irradiation field can be recognized by narrowing down the straight line components while also incorporating pixel values ​​and geometric arrangements as conditions. An example of a machine learning method is semantic segmentation. By creating the irradiation field area as ground truth data and training it using a learning model such as U-NET, training data for recognizing the irradiation field can be generated. Alternatively, a combination of rule-based and machine learning methods may be used.

[0050] Next, in S502, the image type determination unit 206 analyzes the statistics of the pixel values ​​in the calculated irradiation field region to obtain a score indicating the likelihood of the image being a calibration phantom image. For example, the score can be calculated by calculating the difference between the maximum and minimum pixel values ​​in the irradiation field region and dividing the difference by the average value to remove dose dependency.

[0051] Here, a method for deriving a score from the first radiographic image and the second radiographic image will be described. In this embodiment, the average value of the scores calculated from the first radiographic image and the second radiographic image is used as the final score, thereby improving the accuracy of the determination. As a reason for using the average value, a method for changing the first and second radiographic conditions will be described. Generally, the first and second radiographic conditions are changed in the following manner. For example, the radiographic conditions may be changed by operating the information device 106. Also, when the operator G presses the irradiation switch once, the first and second radiographic conditions may be sequentially switched to irradiate radiation, thereby acquiring the first radiographic image and the second radiographic image.

[0052] As described above, the possibility that the presence or absence of the calibration phantom 108 changes between imaging under the first imaging condition and imaging under the second imaging condition is extremely low, and the average value of the scores calculated from the first radiographic image and the second radiographic image may be used as the final score.

[0053] In this embodiment, the final score Score is calculated by calculating a first score Score_Low from the first radiographic image and a second score Score_High from the second captured image. Each calculated value is weighted and averaged to obtain the final score [Score = A·Score_Low+(1−A)×Score_High]. The first radiographic image, which has lower radiation energy, has the property of having greater image contrast than the second radiographic image, which is advantageous for determining whether the image is a calibration phantom image or a gain correction image. Therefore, Score may be calculated by weighting Score_Low. Alternatively, image type determination may be performed by calculating Score from either the first or second radiographic image, with A=0 or A=1.

[0054] Next, in S503, the image type determination unit 206 determines that the image is a calibration phantom image if the calculated score is equal to or greater than a predetermined threshold (S504), and determines that the image is a gain correction image if the calculated score is less than the threshold (S505). Here, the threshold is determined in advance based on the difference in pixel values ​​between the soft tissue region and the bone region when the calibration phantom is imaged, and it is necessary to set the threshold depending on the calibration phantom to be used.

[0055] In this embodiment, the method of calculating the score has been described as using the maximum, minimum, and average pixel values, but a method of analyzing a histogram of pixel values ​​or a method of analyzing a profile of pixel values ​​may also be used. There is no limitation on the type of feature amount used to calculate the score.

[0056] <Bone density calibration method> A method of calibrating bone density in bone density calibration unit 207 of Fig. 4 will be described below. Bone density calibration unit 207 has, for example, a bone density acquisition unit and a calibration value acquisition unit. Note that bone density calibration unit 207 may have the bone density acquisition function and the calibration value acquisition function as a single component.

[0057] The bone density calibration unit 207 first acquires a calibration phantom image and a gain correction image captured under the first and second imaging conditions, respectively, from the calibration phantom storage unit 236 and the gain correction image storage unit 235, and generates a bone image. A bone image is an image that represents the thickness of bone.

[0058] The method for calculating the bone image will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing one bone region in the calibration phantom 108, and illustrates the manner in which radiation passes through. The calibration phantom is composed of soft tissue 601 and bone 602. The dose of incident radiation 603 under the first imaging condition is IL, and the dose of incident radiation 603 under the second imaging condition is IH. If the dose of penetrating radiation 604 under the first imaging condition is IOL, and the dose of penetrating radiation 604 under the second imaging condition is IOH, the bone image dImg is expressed as in equation (1). dImg=β[ln(IH / IOH)-αln(IL / IOL)] ···(1)

[0059] Here, the transmitted radiation dose IOL corresponds to the calibration phantom image captured under the first imaging condition, and the transmitted radiation dose IOH corresponds to the calibration phantom image captured under the second imaging condition. The incident radiation dose IL corresponds to the gain correction image under the first imaging condition, and the incident radiation dose IH corresponds to the gain correction image under the second imaging condition. The bone image is calculated using equation (1). The coefficients α and β are values ​​expressed by the attenuation coefficients of radiation attenuation in the soft tissue 301 and bone 302.

[0060] Next, the bone density calibration unit 207 calculates a bone density calibration value. The bone density calibration value is a conversion coefficient that converts the bone density calculated from the bone image into a correct bone density. Fig. 7 is a flow diagram of bone density calibration, and Fig. 8 is a schematic diagram for explaining the bone density calibration process.

[0061] First, in S701, the bone density calibration unit 207 classifies bone regions from a calibration phantom image 801, as shown in FIGS. 8(a) and 8(b). In this embodiment, there are three bones, and bone regions 802, 803, and 804 are extracted. The bone region extraction method may be, for example, a rule-based method using Otsu's binarization. Since Otsu's binarization maximizes inter-class variance, it is possible to separate bone regions from other regions. Then, bone regions 802, 803, and 804 can be extracted from geometric information.

[0062] The extraction result of the bone region is output as a bone region mask in which the bone region is set to 1 and the rest is set to 0. Once the bone region is recognized, in S702, the bone density calibration unit 207 calculates the average value boVal of the bone region. The average value boVal of the bone region is calculated from the bone image dImg as shown in Equation (2). boVal(i)=(1 / nbo(i))·Σ x Σ y dImg(x,y)·BoMaSk(i,x,y)···(2)

[0063] Here, BoMaSk is the bone region mask, nbo is the number of pixels where the bone region mask is 1, and i exists for the number of extracted bone regions. In this embodiment, there are three bone regions, so three average values ​​are calculated.

[0064] Next, in S703, the bone density calibration unit 207 extracts base areas 805, 806, and 807 for each of bone regions 802, 803, and 804 classified from the bone image 801. A base area is a region of soft tissue. One method for extracting the base area is to provide a fixed-size region at a certain distance from the extracted bone region.

[0065] Once the base area has been recognized, in S704, the bone density calibration unit 207 calculates the average value baVal of the base area from the bone image dImg using the following equation (3). baVal(i)=(1 / nbg(i))·Σ x Σ y dImg(x,y) · BgMaSk(i,x,y) ···(3)

[0066] Here, BgMaSk is the base area mask, nbg is the number of pixels where the base area mask is 1, and i exists for the number of extracted bone regions. In this embodiment, there are three base areas, so three average values ​​are calculated.

[0067] Once the average values ​​of the bone region and the base area have been calculated, in S705, the bone density calibration unit 207 removes the influence of soft tissue by taking the difference as shown in Equation (4) using the bone density acquisition unit, and calculates the bone density densF obtained from the FPDe output value. In this embodiment, since there are three bone regions, three bone densities are calculated. There are as many i as there are extracted bone regions. densF= boVal(i)- baVal(i) ···(4)

[0068] Then, in S706, the bone mineral density calibration unit 207 uses the calibration value acquisition unit to compare the bone mineral density obtained from the FPDe output value with the true bone mineral density defined in the calibration phantom 108, and calculates a bone mineral density calibration value for conversion to the true bone mineral density. The calibration phantom 108 has known bone mineral density for each bone portion, which is used as the true bone mineral density. As shown in FIG. 8(c), the calibration value acquisition unit performs least-squares approximation from the bone mineral density obtained from the FPDe output value and the true bone mineral density to calculate an approximation formula 508, and uses the regression coefficient k0 and intercept k1 as the bone mineral density calibration value.

[0069] As described above, in the information device 106 according to this embodiment, when capturing an image in bone mineral density calibration mode, the image type determination unit 206 determines whether the radiological image was captured with or without the calibration phantom 108. This prevents the mistake of capturing a phantom image instead of a gain correction image, thereby reducing the risk of erroneous capture. Then, the bone mineral density calibration unit 207 can perform accurate bone mineral density calibration using a radiological image of the correct image type.

[0070] -Second embodiment- In the first embodiment, an example of a configuration was described in which, when the operator G selects the bone density calibration imaging mode, the determination of whether to capture a calibration phantom image or a gain correction image is performed fully automatically by only the image type determination unit. In the second embodiment, an example of a configuration is disclosed in which, taking into consideration the case in which the image type determination unit makes an erroneous determination, the calibration phantom image and the gain correction image are more reliably stored in the corresponding storage units.

[0071] In this embodiment, the selection unit is provided to enable selection of an imaging protocol for capturing a calibration phantom image and an imaging protocol for capturing a gain correction image. By selecting an imaging protocol from the user input device, the operator G can start capturing a calibration phantom image and a gain correction image. When capturing an image, if the selection result of the imaging protocol for that image does not match the determination result of the image type determination unit, a warning is displayed on the UI display unit to prompt the user to check the captured image, thereby preventing erroneous capture of a calibration phantom image and a gain correction image. In other words, in this embodiment, the determination of the image type determination unit is treated as part of a fail-safe function.

[0072] FIG. 9 is a schematic diagram showing an example of a display screen during imaging for bone density calibration in this embodiment. The bone mineral density calibration screen 901 has a calibration phantom imaging protocol button 902, a gain correction image imaging protocol button 903, and a preview image display area 904. The calibration phantom imaging protocol button 902 is for starting imaging of a calibration phantom image. The gain correction image imaging protocol button 903 is for starting imaging of a gain correction image. The preview image display area 904 has a preview image display area 904 that displays a preview of a radiographic image acquired from the radiographic image acquisition unit 205. The operator G presses the calibration phantom imaging protocol button 802 or the gain correction image imaging protocol button 803 from the user input device 200A. This notifies the image type determination unit 206 via the user input control unit 201 of which image type of radiographic image the operator G is capturing, and the capturing can be started.

[0073] <Method of judgment and bone density calibration> The operation of the information device 106 and the operation of the operator G in bone mineral density calibration according to this embodiment will be described below. Fig. 10 is a flow chart showing an information processing method for acquiring a bone mineral density calibration value according to this embodiment, and Fig. 11 is a functional configuration diagram of the information device 106 according to this embodiment. It should be noted that either the calibration phantom image or the gain correction image may be captured first, but as an example, a case where the calibration phantom image is captured first will be described here.

[0074] First, in S1001, the operator G places the calibration phantom 108 in the placement area (area to be irradiated with radiation) of the bed 104. In this embodiment, similar to the first embodiment, it is assumed that the operator G places the calibration phantom 108 at an appropriate geometric position in the placement area of ​​the bed 104 when placing the calibration phantom 108.

[0075] In S1002, the operator G uses the user input device 200A to press the calibration phantom imaging protocol button 802 to start imaging. In S1003, the operator G presses the irradiation switch 107 to irradiate radiation under the first and second imaging conditions from the radiation generation device 102. The radiation image acquisition unit 205 acquires a first radiation image captured under the first imaging condition and a second radiation image captured under the second imaging condition.

[0076] FIG. 12 is a schematic diagram showing an example of a display screen after a radiation image is acquired. When imaging is completed, a preview of the image acquired during imaging is displayed in the preview display area 904. Furthermore, the calibration phantom imaging protocol button 902 and the gain correction image imaging protocol button 903 each have thumbnail image display areas 905, 906. A thumbnail image of the first radiographic image is displayed in the thumbnail image display area 905, and a thumbnail image of the second radiographic image is displayed in the thumbnail image display area 906. The preview image displayed in the preview image display area 904 may be switched by an operation by the operator G.

[0077] In S1004, the image type determination unit 206 analyzes the first and second radiographic images acquired in S1002 to determine whether the acquired images are calibration phantom images or gain-corrected images.

[0078] In S1005, if the image type determination unit 206 determines that the determination result by the image type determination unit 206 does not match the shooting protocol selected by the operator G, the process proceeds to S1006. In S1006, the image type determination unit 206 displays a warning dialog on the UI display device 200B via the display control unit 202 (S1006).

[0079] FIG. 13 is a schematic diagram showing an example of the warning dialog. If the selected imaging protocol is the calibration phantom imaging protocol and the determination result of the image type determination unit 206 is that the image is for gain correction, a warning dialog 1301 shown in Fig. 13(a) is displayed. On the other hand, if the selected imaging protocol is the gain correction image imaging protocol and the determination result of the image type determination unit 206 is that the image is for calibration phantom, a warning dialog 1302 shown in Fig. 13(b) is displayed.

[0080] In S1007, operator G, who has seen the warning dialog, checks the preview image displayed on the UI display device 200B and confirms whether the selected imaging protocol matches the presence or absence of the placement of the calibration phantom 108. If operator G has placed the calibration phantom 108 incorrectly and the selected imaging protocol does not match the presence or absence of the placement of the calibration phantom 108, operator G presses button 1303 to close the warning dialog. Then, operator G selects the correct imaging protocol and performs radiation imaging again, or places or removes the phantom and performs imaging again (repeated radiation imaging) in a state where the imaging protocol matches the presence or absence of the phantom placement.

[0081] On the other hand, if the image type determination unit 206 has made an erroneous determination, the operator G presses the button 1304 to close the warning dialogue, thereby notifying the image type determination unit 206 of the erroneous determination.

[0082] In S1005, if the image type determination unit 206 determines that the determination result by the image type determination unit 206 matches the imaging protocol selected by the operator G, the process proceeds to S1008. The image type determination unit 206 stores the captured radiographic image in the calibration phantom image storage unit 236 or the gain correction image storage unit 235 corresponding to the determination result. However, if the operator G has been notified by operation in S1007 that the image type determination unit 206 made an incorrect determination, the image type determination unit 206 stores the image based on the selected imaging protocol.

[0083] The subsequent steps S1009 to S1010 are the same as S406 to S407 in FIG. 4 in the first embodiment.

[0084] As described above, in the information device 106 according to this embodiment, if the determination result made by the image type determination unit 206 does not match the imaging protocol selected by the operator G, a warning is issued to the operator G to prompt him or her to perform radiation imaging again. This prevents erroneous imaging of calibration phantom images and gain correction images, and enables accurate bone density calibration to be performed using radiation images of the correct image type.

[0085] -Third embodiment- In the first and second embodiments, configuration examples were described that assume that when placing a calibration phantom, the operator places the calibration phantom in an appropriate geometric position in the placement area of ​​the bed. In the third embodiment, when the calibration phantom is placed in the placement area, the geometric placement of the calibration phantom is also taken into consideration. In this embodiment, a configuration example is disclosed in which a calibration phantom image is analyzed, and if it is determined that the geometric placement of the calibration phantom is inappropriate, a warning is issued to the operator G to urge him or her to perform radiation imaging again.

[0086] <Configuration of Information Device 106> FIG. 14 is a system configuration diagram of the information device 106 in this embodiment, and FIG. 15 is a functional configuration diagram of the information device 106. In this embodiment, only the differences from the first and second embodiments will be described. The information device 106 has a determination unit 240. The determination unit 240 has an image type determination unit 206 similar to those in the first and second embodiments, and a calibration phantom geometric arrangement determination unit 209. Note that the determination unit 240 may be configured to have both an image type determination function and a geometric arrangement determination function.

[0087] In this embodiment, when the determination result by the image type determination unit 206 is a calibration phantom image, the geometric arrangement determination unit 209 analyzes the radiographic image acquired by the radiographic image acquisition unit 205 to detect the geometric arrangement of the calibration phantom 108. Then, it determines whether or not the geometric arrangement is appropriate. If the determination result is appropriate, the captured image is stored in the calibration phantom image storage unit 236, and if it is not appropriate, a warning is displayed on the UI display device 200B via the display control unit 202 to prompt the user to perform radiography again.

[0088] The following describes the criteria for determining whether the geometric arrangement of the calibration phantom is appropriate or not, in the geometric arrangement determining unit 209. Fig. 16 is a schematic diagram showing various aspects of the geometric arrangement of the calibration phantom.

[0089] 16(a) shows an appropriate geometric arrangement of the calibration phantom. 1607 is the image area, 1608 is the radiation irradiation field area, and 1601 is the calibration phantom. The bones of the calibration phantom 1601 are designated 1609, 1610, and 1611 in order of decreasing bone density.

[0090] The first criterion is whether or not all of the bones in the calibration phantom 1601, which is the region to be referenced during bone density calibration, are reflected in the irradiation field region 1608. In this embodiment, the bones 1609, 1610, and 1611 must be positioned so that they are within the irradiation field region 1608.

[0091] A counterexample is shown in Figure 16(b). Figure 16(b) shows a state in which all bones 1609, 1610, and 1611 are not located within the irradiation field region 1608, and the bone 1609 is located outside the range of the irradiation field region 1608. In this case, it is impossible to calculate the bone density of the bone 1609, and therefore it is determined that the geometric arrangement of the calibration phantom 1601 is inappropriate. In addition, a case in which the bones to be referenced during bone density calibration are not captured also corresponds to a case in which an image of a subject other than the calibration phantom is captured.

[0092] The second criterion is the relative position of the calibration phantom 1601 with respect to at least one of the image region 1607 and the irradiation field region 1608, here both. In this embodiment, the calibration phantom 108 needs to be placed approximately at the center of the radiation detector 103, and needs to be imaged approximately at the center with respect to the image region 1307. In addition, it is desirable that the positions of the bones 1609, 1610, and 1611 are placed sufficiently inside the position of the irradiation field region 1608.

[0093] A counterexample is shown in Figure 16(c), which shows a state in which the imaging position of the calibration phantom 1601 is away from the center of the image area 1607. In this case, there is a possibility that the accuracy of bone density calibration will be reduced due to the influence of in-plane characteristic unevenness in the radiation detector.

[0094] 16(d) shows that a sufficient distance cannot be secured between the positions of the bones 1609, 1610, and 1611 and the edge positions of the irradiation field region 1608. In this case, it is not possible to calculate the base area (S703 in FIG. 7), which is the soft tissue region necessary for calculating the bone density calibration value, and calibration is not performed correctly, so it is determined that the geometric arrangement of the calibration phantom 1601 is not appropriate.

[0095] The third criterion is the orientation of the calibration phantom 1601 relative to the image area. In this embodiment, the three bones 1609, 1610, and 1611 must be positioned approximately parallel to the radiation detector 103, and it is desirable that they are imaged approximately parallel to the height direction of the image area. Furthermore, the calibration phantom 1601 is oriented so that the bone densities of the bones 1609, 1610, and 1611 are in ascending order from highest to lowest in the height direction of the image area.

[0096] A counterexample is shown in Figure 16(e), which shows a state in which the orientation of the calibration phantom 1601 is rotated relative to the orientation of the image. In this case, the calibration accuracy may be reduced, and it is determined that the geometric arrangement of the calibration phantom 1601 is inappropriate.

[0097] 16(f) shows a state in which the calibration phantom 1601 is imaged inverted with respect to the height direction of the image. In this case, too, a correct bone mineral density value cannot be obtained, and bone mineral density calibration cannot be performed normally. Therefore, it is necessary to determine that the geometric arrangement of the calibration phantom 1601 is inappropriate.

[0098] As described above, the geometric arrangement determination unit 209 determines whether all bone regions referenced during bone density calibration are captured, whether the relative position of the calibration phantom with respect to the image region and irradiation field region, and whether the orientation of the calibration phantom with respect to the radiation image are in an appropriate geometric arrangement.

[0099] <Determination operation of the geometric arrangement determination unit> The following describes the determination operation in the geometric arrangement determination unit 209. Fig. 17 is a flowchart showing the geometric arrangement determination operation according to this embodiment.

[0100] In S1701, the radiographic image acquisition unit 205 acquires a first radiographic image captured under the first radiographic condition and a second radiographic image captured under the second radiographic condition.

[0101] In S1702, the geometric arrangement determination unit 209 analyzes the acquired radiographic image and detects the geometric arrangement of the calibration phantom 108. In this embodiment, the positions of the bones 1609, 1610, and 1611 are detected. Methods for position detection include, for example, a method of detecting the coordinates of each bone using YOLO (You Only Look Once), which is an object detection algorithm, and a method using semantic segmentation. By using such methods, the region of each bone can be obtained. Next, the center of gravity coordinates are calculated for each region of each calculated bone, and the center of gravity coordinates are defined as the position of each bone.

[0102] In S1703, the geometric arrangement determination unit 209 determines whether all bones in the calibration phantom 1601 referenced during bone density calibration are captured in the irradiation field region 1608. The number of centroid coordinates of each bone detected in S1702 is counted. In this embodiment, the calibration phantom 1601 has three bones, so this determination is made based on whether the count of the number of centroid coordinates is three. This determination makes it possible to determine whether all bones are captured in the irradiation field region 1608 and whether an object other than the calibration phantom 108 has been imaged. If the count of the number of centroid coordinates is three, the process proceeds to the determination in S1704. If the count of the number of centroid coordinates is not three, in S1706 the geometric arrangement determination unit 209 displays a warning dialog on the UI display device 200B via the display control unit 202 to prompt the operator G to perform radiation imaging again. An example of a warning dialog display is shown in 1801 in FIG.

[0103] In S1704, the geometric arrangement determination unit 209 determines whether the relative positions of the calibration phantom with respect to the image region and the irradiation field region are appropriate. FIG. 19 is a schematic diagram showing an example of the determination method. In FIG. 19, the barycentric coordinates of the three detected bones are respectively designated as 1901, 1902, and 1903, and the distance L between the barycentric coordinate 1902 of the center of the three bones and the center coordinate 1904 of the image region is calculated. If the calculated distance L is equal to or less than a predetermined threshold, the process proceeds to the determination in S1705. If the calculated distance L is greater than the predetermined threshold, in S1706, the geometric arrangement determination unit 209 displays a warning dialog on the UI display device 200B via the display control unit 202.

[0104] An example of the dialog display is shown in 1802 in FIG. 18. The dialog display 1802 prompts the operator G to perform radiography again and displays the amount of shift of the position of the calibration phantom 108 from the center of the radiation detector 103 to inform the operator G. The geometric arrangement determination unit 209 also calculates the distances between the centroid coordinates 1901, 1902, and 1903 of each bone and each side 1905, 1906, 1907, and 1908 of the irradiation field area, and calculates the minimum distance l among the distances. A warning dialog is also displayed if the calculated minimum distance l is smaller than a predetermined threshold. Note that instead of calculating the minimum distance, the maximum distance among the distances between the centroid coordinates 1901, 1902, and 1903 of each bone and each side 1905, 1906, 1907, and 1908 of the irradiation field area may be calculated. An example of the dialog display is shown in 1803 in FIG. 18. If the above cases do not apply, the determination in S1705 is made.

[0105] In S1705, the geometric arrangement determination unit 209 determines whether the orientation of the calibration phantom 108 with respect to the radiation image is appropriate. First, a straight line 1909 is obtained by fitting three points, namely, bone center coordinates 1901, 1902, and 1903, with a linear function. The rotation angle θ of the calibration phantom with respect to the height direction of the image area is calculated from the slope of the straight line 1909. If the calculated rotation angle θ is greater than a predetermined threshold, a warning dialog is displayed, and the operator G is prompted to perform radiation imaging again and is notified of the rotation angle. An example of the displayed dialog is shown in 1804 in Figure 18.

[0106] Furthermore, the coordinates of the centers of gravity of the three bones are 1901, 1902, and 1903, in descending order of height, and average pixel values ​​AVE1, AVE2, and AVE3 within a certain range are calculated, centered on the coordinates of the centers of gravity 1901, 1902, and 1903. If AVE1>AVE2>AVE3, it is determined that the bone densities are arranged in ascending order, descending from the highest point on the image. If this is not the case, the geometric arrangement determination unit 209 determines that the arrangement of the calibration phantom 108 is upside down, and displays a warning dialog in S1706. An example of the displayed dialog is shown at 1805 in FIG. 18.

[0107] If it is determined in steps S1703 to S1705 that the geometric arrangement of the calibration phantom 108 is appropriate, the geometric arrangement determining unit 209 stores the radiation image in the calibration phantom image storage unit 236.

[0108] The conditions for satisfying the criteria for determining whether the geometric arrangement of this calibration phantom is appropriate depend on the structure of the calibration phantom used in this embodiment, and vary depending on the structure of the calibration phantom used, and the conditions for determination are not limited.

[0109] Furthermore, in this embodiment, the method of calculating the center of gravity of each bone portion has been described as a method of detecting the geometric arrangement of the calibration phantom, but the present invention is not limited to this. For example, a method of detecting the edges of bone portions using a technique such as edge detection and calculating the coordinates of the vertices of the bone portions may be used, and any method may be used as long as it can detect the geometric arrangement of the calibration phantom.

[0110] As described above, the information device 106 according to this embodiment detects whether the geometric arrangement of the calibration phantom 108 is appropriate for performing bone mineral density calibration. This improves the accuracy of bone mineral density calibration, enabling accurate bone mineral density calibration. Furthermore, if the geometric arrangement of the calibration phantom 108 is not appropriate, a warning is displayed to the operator G, thereby preventing inaccurate bone mineral density calibration. Furthermore, by notifying the operator G of the reason for this determination, radiation imaging can be easily performed again.

[0111] In this embodiment, first, the image type determination unit 206 determines whether the captured radiographic image is a calibration phantom image captured with a calibration phantom placed, or a gain correction image captured without a calibration phantom placed. Second, when the radiographic image is determined to be a calibration phantom image, the geometric arrangement determination unit 209 analyzes the radiographic image acquired by the radiographic image acquisition unit 205 to determine the geometric arrangement of the calibration phantom. However, this embodiment is not limited to the above example. For example, instead of performing the determination in two stages as described above, the determination unit may determine, as a series of determinations, whether the arrangement of the calibration phantom in the radiographic image satisfies predetermined conditions. The predetermined conditions are various criteria for determining whether a calibration phantom is placed, and, even if a calibration phantom is placed, whether the geometric arrangement of the calibration phantom is appropriate. If it is determined as a result of this series of determinations that the calibration phantom is arranged so as to satisfy predetermined conditions, the determination unit 240 stores the radiographic image as a calibration phantom image in the calibration phantom image storage unit 236. If it is determined that the calibration phantom is not arranged, the determination unit 240 stores the radiographic image as a gain correction image in the gain correction image storage unit 235.

[0112] -Fourth embodiment- In the first to third embodiments, the determination unit determines the placement status of the calibration phantom using the radiation image acquired by the radiation image acquisition unit. In the fourth embodiment, before acquiring the radiation image (before irradiating radiation), the image determination unit determines whether or not the calibration phantom is placed using the optical image. Furthermore, in this embodiment, a warning is notified to the operator before irradiating radiation in predetermined cases.

[0113] <Radiation imaging system configuration> 20 is a schematic diagram showing the general configuration of a radiation imaging system according to this embodiment. Here, only the differences from FIG. 1 of the first embodiment will be described. As shown in Fig. 20, the radiation imaging system 101 includes a predetermined camera, for example, an optical camera 110, in addition to the radiation imaging system 101 according to the first embodiment, and is appropriately attached so as to be able to image the bed 104. The optical camera 110 is connected to the information device 106 and captures optical images under the control of the information device 106. The optical camera 110 transmits the optical images obtained by the capture to the information device 106. Note that the optical camera 110 may be configured as a camera capable of capturing moving images, such as a video camera, or may be configured as a camera that only captures still images.

[0114] <Configuration of Information Device 106> FIG. 21 is a system configuration diagram of the information device 106 in this embodiment, and FIG. 22 is a functional configuration diagram of the information device 106. As shown in FIG.

[0115] In this embodiment, only the differences from the first and second embodiments will be described. The information device 106 has an optical image acquisition unit 251 and an optical image determination unit 250 instead of the image type determination unit 206 in Figures 3 and 11. The optical image acquisition unit 251 acquires an optical image of the arrangement area of ​​the calibration phantom 108, photographed by the optical camera 110, before radiation is irradiated. The optical image determination unit 250 uses the optical image acquired by the optical image acquisition unit 251 to determine whether the calibration phantom 108 is arranged.

[0116] <Method of judgment and bone density calibration> The following describes the determination operation and bone density calibration method in the optical image determination unit 250 of this embodiment. Fig. 23 is a flowchart showing the determination operation and bone density calibration according to this embodiment. It should be noted that either the calibration phantom image or the gain correction image may be captured first, but as an example, a case where the calibration phantom image is captured first will be described here.

[0117] First, in S2301, the operator G places the calibration phantom 108 in the placement area (area to be irradiated with radiation) of the bed 104. In this embodiment, similar to the first embodiment, it is assumed that when placing the calibration phantom 108, the operator G places the calibration phantom 108 at an appropriate geometric position in the placement area of ​​the bed 104.

[0118] In S2302, the operator G presses the calibration phantom imaging protocol button using the user input device 200A.

[0119] In S2303, the optical image acquisition unit 251 acquires an optical image of the arrangement area of ​​the calibration phantom 108 photographed by the optical camera 110.

[0120] In S2304, the optical image determination unit 250 analyzes the optical image acquired by the optical image acquisition unit 251, and determines whether or not the calibration phantom 108 is placed in the placement area on the bed 104. As a method of determination, an optical image onto which the calibration phantom is projected is learned using YOLO (You Only Look Once), which is an object detection algorithm. In this way, the optical image determination unit 250 detects the calibration phantom in the optical image and determines whether or not the calibration phantom 108 is placed.

[0121] In S2305, the optical image determination unit 250 determines whether the imaging protocol selected by the operator G matches the presence or absence of phantom placement determined in S2304. If they match, the phantom placement status is appropriate, and the process proceeds to S2307. If they do not match, the process proceeds to S2306, and the optical image determination unit 250 displays a warning dialog on the UI display device 200B via the display control unit 202.

[0122] FIG. 24 is a schematic diagram showing an example of the warning dialog. Numeral 2401 is an example of a warning dialog displayed when the optical image determination unit 250 determines that a calibration phantom is not placed even though the calibration phantom imaging mode is selected as the imaging protocol. Numeral 2402 is an example of a warning dialog displayed when the optical image determination unit 250 determines that a calibration phantom is placed even though the gain correction imaging mode is selected as the imaging protocol.

[0123] Upon seeing the warning dialog, operator G can correct the placement of the calibration phantom 108 or reselect the imaging protocol from the user input device 200A to resolve the discrepancy between the placement of the calibration phantom 108 and the imaging protocol.

[0124] In S2307, radiation is irradiated by the operator G pressing the irradiation switch 107. The radiation image acquisition unit 205 acquires a first radiation image captured under the first imaging condition and a second radiation image captured under the second imaging condition.

[0125] The subsequent steps S2308 to S2310 are the same as S1008 to S1010 in FIG. 11 of the second embodiment.

[0126] As described above, in the information device 106 according to this embodiment, the optical image determination unit 250 determines whether or not a calibration phantom is positioned using an optical image before irradiating radiation. This prevents the phantom image from being mistakenly captured instead of a gain correction image, reducing the risk of erroneous imaging. Furthermore, if the determination result by the optical image determination unit 250 does not match the imaging protocol selected by the operator G, a warning is issued to the operator G, urging him or her to perform radiation imaging again. This allows accurate bone density calibration to be performed using a radiation image of the correct image type.

[0127] -Variations- In the fourth embodiment, a case has been described in which the optical image determination section 250 determines whether or not a calibration phantom is arranged using an optical image. It is also conceivable that the optical image determination section 250 may use an optical image to determine not only whether or not a calibration phantom is arranged, but also the geometric arrangement of the calibration phantom.

[0128] As a determination method, for example, the placement status of the calibration phantom in the optical image is detected by learning an optical image onto which the calibration phantom is projected using YOLO (You Only Look Once), an object detection algorithm. Then, not only is the presence or absence of the calibration phantom determined, but also its geometrical arrangement, if present. The geometrical arrangement of the calibration phantom is detected by detecting the position and angle of the calibration phantom relative to the calibration phantom placement area and the position and angle of the calibration phantom relative to the irradiation field position. The irradiation field position can be detected from a marker of visible light irradiated from a radiation generating device.

[0129] As described above, the information device 106 according to this modification not only determines whether the calibration phantom 108 is disposed, but also determines whether the geometric arrangement of the calibration phantom 108 is appropriate for performing bone mineral density calibration. This improves the accuracy of bone mineral density calibration, enabling accurate bone mineral density calibration to be performed. Furthermore, if the geometric arrangement of the calibration phantom 108 is not appropriate, a warning is displayed to the operator G, thereby preventing inaccurate bone mineral density calibration. Furthermore, by notifying the operator G of the reason for the determination, accurate bone mineral density calibration can be easily performed.

[0130] -Fifth embodiment- In the fourth embodiment, an image determination unit determines whether a calibration phantom is placed using an optical image before radiation is irradiated. In the fifth embodiment, a contact determination unit determines the contact state of the electrodes between the calibration phantom and its placement area before radiation is irradiated. Furthermore, in this embodiment, as in the fourth embodiment, a warning is notified to the operator before radiation is irradiated in predetermined cases.

[0131] <Configuration of Information Device 106> FIG. 25 is a system configuration diagram of the information device 106 in this embodiment, and FIG. 26 is a functional configuration diagram of the information device 106. In this embodiment, only the differences from the first and second embodiments will be described. The information device 106 has a contact determination unit 260 instead of the image type determination unit 206 in Fig. 3. The radiation imaging system is provided with an electric sensor 120. Before radiation is irradiated, the contact determination unit 260 determines whether or not the calibration phantom 108 is placed, using an electric signal transmitted from the electric sensor 120.

[0132] <Calibration phantom and electrode configuration in its placement area> FIG. 27 is a plan view showing an example of a calibration phantom and an electrode configuration in its arrangement area, and FIG. 28 is a plan view showing the arrangement of the calibration phantom.

[0133] In this embodiment, electrodes are provided in the calibration phantom and its placement area. As shown in Fig. 27(a), electrodes 111a and 111b are provided on the back surface of calibration phantom 108 at at least two locations asymmetrical with respect to the center point of the back surface, here at two locations in the upper part of the back surface. By providing electrodes at least at two locations asymmetrical with respect to the center point of the back surface, it is possible to detect differences even when calibration phantom 108 is placed upside down.

[0134] 27(b), electrodes 112a and 112b corresponding to the electrodes 111a and 111b are provided in the placement area 130 of the bed 104 for the calibration phantom 108. Furthermore, an electrode 113 is provided in the placement area 130, covering the entire surface of the placement area 130, with a slight gap 114 (approximately the diameter of the electrodes 111a and 111b) between the electrodes 112a and 112b. Note that the gap 114 is extremely narrow, and the probability that both the electrodes 111a and 111b are positioned exactly within the gap 114 and become non-conductive when the calibration phantom 108 is placed in the placement area 130 is negligibly small, and therefore, this case is not taken into consideration in this embodiment. The electrodes 111a, 111b, 112a, 112b, and 113 used in this embodiment are, for example, electrodes made of a conductive material having radiotransparency.

[0135] The electrodes 111a, 111b and the electrodes 112a, 112b, and 113 are connected to respective wirings (not shown), and are connected to the electric sensor 120 through the respective wirings. When the calibration phantom 108 is placed in the placement area 130 and the electrodes 111a, 111b come into contact with the electrodes 112a, 112b, and 113, electrical conduction occurs and a current flows, which is detected by the electric sensor 120.

[0136] The electrodes 111a and 111b are point electrodes of extremely small size. The electrodes 112a and 112b are larger than the electrodes 111a and 111b and have a predetermined shape so that the electrodes 111a and 111b can contact each other within a predetermined tolerance. In other words, as long as an appropriate radiographic image can be acquired, there is no problem even if the geometric arrangement of the calibration phantom 108 in the arrangement area 130 is slightly misaligned, and therefore the size and shape of the electrodes 112a and 112b are specified to correspond to the allowable misalignment.

[0137] 28(a) shows an example in which the calibration phantom 108 is appropriately placed in the placement area 130. At this time, the electrode 111a of the calibration phantom 108 is in contact with the electrode 112a in the placement area 130, and the electrode 111b is in contact with the electrode 112b, both of which are encompassed by each other in a planar view. The electrodes 111a and 111b are not in contact with the electrode 113. In this case, the electric sensor 120 detects both the current flowing due to the former contact and the current flowing due to the latter contact, and transmits a first electric signal to the contact determination unit 260, which indicates that the placement of the calibration phantom 108 is appropriate.

[0138] When only one of electrodes 111a and 111b is in contact with electrode 112a or 112b, and the other of electrodes 111a and 111b is in contact with electrode 113, electric sensor 120 detects two types of currents flowing due to the two types of contact. An example of the arrangement of calibration phantom 108 in this case is shown in FIG. 28(b). When electric sensor 120 detects the two types of currents, this means that calibration phantom 108 is arranged, but its geometric arrangement is inappropriate. In this case, electric sensor 120 transmits a second electric signal to contact determination unit 260, indicating that calibration phantom 108 has an inappropriate geometric arrangement.

[0139] When electrodes 111a and 112a are not in contact with electrodes 111b and 112b, and both electrodes 111b and 112b are in contact with electrode 113, electric sensor 120 detects a current flowing due to the contact. Thus, when electric sensor 120 detects the current, it means that the calibration phantom 108 is positioned, but its geometric arrangement is inappropriate. In this case, electric sensor 120 also transmits a second electric signal to contact determination unit 260, indicating that the calibration phantom 108 has an inappropriate geometric arrangement.

[0140] If the calibration phantom 108 is not placed in the placement area 130, no current flows through the electric sensor 120. For example, if no current flows through the electric sensor 120 even after a certain period of time has elapsed, this means that the calibration phantom 108 is not placed in the placement area 130. In such a case, the electric sensor 120 transmits a third electric signal to the contact determination unit 260, which indicates that the calibration phantom 108 is not placed. In this embodiment, it is assumed that nothing other than the calibration phantom 108 will be placed in the placement area 130.

[0141] <Method of judgment and bone density calibration> The following describes the determination operation and bone density calibration method in the optical image determination unit 250 of this embodiment. Fig. 29 is a flowchart showing the determination operation and bone density calibration according to this embodiment. Although either the calibration phantom image or the gain correction image may be captured first, the case where the calibration phantom image is captured first will be described as an example here. In addition, in this embodiment, when performing bone density calibration, it is first necessary to appropriately adjust the irradiation state (irradiation position) of the radiation emitted from the radiation generating device to the calibration phantom placement position.

[0142] First, in S2901, the operator G places the calibration phantom 108 in the placement area 130 of the bed 104.

[0143] In S2902, the operator G presses the calibration phantom imaging protocol button using the user input device 200A.

[0144] In S2903, the electric sensor 120 detects the current from the electrodes 111a, 111b, 112a, and 112b.

[0145] In S2904, the contact determination section 260 receives the first electric signal, the second electric signal, or the third electric signal transmitted from the electric sensor 120, and determines the placement status of the calibration phantom .

[0146] In S2905, the contact determination unit 260 determines whether the imaging protocol selected by the operator G matches the arrangement status determined in S2904. If it is determined that they match, the phantom arrangement status is appropriate, and the process proceeds to S2907. Here, a case in which it is determined that they match is when the imaging protocol selected by the operator G is the calibration phantom imaging mode, and the contact determination unit 260 has received a first electrical signal from the electrical sensor 120. Furthermore, when the operator G selected the gain correction imaging mode in S2902, a case in which it is determined that they match is when the imaging protocol selected by the operator G is the gain correction imaging mode, and the contact determination unit 260 has received a third electrical signal from the electrical sensor 120.

[0147] On the other hand, if it is determined in S2905 that the photographing protocol does not match the arrangement state determined in S2904, the process proceeds to S2906, and the contact determination unit 260 displays a warning dialog on the UI display device 200B via the display control unit 202. Here, the following situations (1) to (4) are possible as cases where it is determined that they do not match.

[0148] (1) Although the calibration phantom imaging mode is selected as the imaging protocol, the electrical signal received by the contact determination unit 260 is the third electrical signal, which means that the calibration phantom is not placed. (2) When the gain correction imaging mode is selected as the imaging protocol, but the electrical signal received by the contact determination unit 260 is the first electrical signal which means that the calibration phantom is properly positioned. (3) The calibration phantom imaging mode is selected as the imaging protocol, and the electrical signal received by the contact determination unit 260 is a second electrical signal that indicates that the geometric arrangement of the calibration phantom is inappropriate. (4) The gain correction imaging mode is selected as the imaging protocol, and the electrical signal received by the contact determination unit 260 is a second electrical signal that means that the geometric arrangement of the calibration phantom is inappropriate.

[0149] FIG. 30 is a schematic diagram showing an example of the warning dialog. 3001 is an example of a warning dialog that is displayed when it is determined that the above-mentioned (1) or (3) applies, and 3002 is an example of a warning dialog that is displayed when it is determined that the above-mentioned (2) or (4) applies.

[0150] Upon seeing the warning dialog, operator G can correct the placement of the calibration phantom 108 or reselect the imaging protocol from the user input device 200A to resolve the discrepancy between the placement of the calibration phantom 108 and the imaging protocol.

[0151] In S2907, radiation is irradiated by the operator G pressing the irradiation switch 107. The radiation image acquisition unit 205 acquires a first radiation image captured under the first imaging condition and a second radiation image captured under the second imaging condition.

[0152] The subsequent steps S2908 to S2910 are the same as S2308 to S2310 in FIG. 23 of the fourth embodiment.

[0153] As described above, the information device 106 according to this embodiment determines whether the geometric arrangement is appropriate for performing bone mineral density calibration, in addition to determining whether the calibration phantom 108 is arranged. If the geometric arrangement is not appropriate, a warning is displayed to the operator G, thereby preventing inaccurate bone mineral density calibration. Furthermore, by notifying the operator G of the reason for the determination, accurate bone mineral density calibration can be easily performed.

[0154] -Other embodiments- In the first to fifth embodiments described above, the main memory 232 or a storage medium stores a computer program for controlling the information device 106, which is an information processing device. This computer program is a program for implementing the functions of each component of the information device 106, such as a program corresponding to steps S401 to S407 in FIG. 4, S501 to S505 in FIG. 5, S701 to S706 in FIG. 7, S1001 to S1010 in FIG. 10, S1701 to S1706 in FIG. 17, S2301 to S2310 in FIG. 23, and S2901 to S2910 in FIG. 29. The CPU 231 then reads out the computer program from the main memory 232 or the storage medium and executes it. In this way, the CPU 231 controls the information device 106.

[0155] The disclosure of the various embodiments and modifications includes the following configurations and methods. (Configuration 1) an image acquisition unit that acquires two types of radiation images captured under two imaging conditions with different amounts of radiation energy; a determination unit that determines whether the placement of the phantom satisfies a predetermined condition using information about the area where the phantom is placed; a bone density acquisition unit that acquires a first bone density of the phantom using at least one of two types of radiographic images, which is determined to have the phantom arranged so as to satisfy the predetermined condition, and at least one of two types of radiographic images that is different from the at least one of two types of radiographic image and is determined to have no phantom arranged therein, among the plurality of two types of radiographic images; An information processing device having the above. (Configuration 2) a calibration value acquisition unit that compares the first bone density acquired by the bone density acquisition unit with a second bone density that is known in the phantom, and acquires a bone density calibration value that calibrates the first bone density to the second bone density; Further comprising: 2. The information processing device according to configuration 1. (Configuration 3) The information is information on the two types of radiation images capturing the placement status of the phantom in the region. 2. The information processing device according to configuration 1. (Configuration 4) The determination unit determining whether the two types of radiation images are a first image captured with the phantom placed or a second image captured without the phantom placed; 4. The information processing device according to any one of configurations 1 to 3. (Configuration 5) The determination unit determining the first image and the second image based on a score calculated from pixel values ​​of the two types of radiographic images as the predetermined condition; 5. The information processing device according to configuration 4. (Configuration 6) The determination unit determining the first image and the second image using, as the predetermined condition, a score calculated by weighting and averaging a first score calculated from pixel values ​​of one of the two types of radiographic images and a second score calculated from pixel values ​​of the other of the two types of radiographic images; 5. The information processing device according to configuration 4. (Configuration 7) a selection unit that allows an operator to select whether to capture the first image or the second image, The determination unit issuing a warning when the selection result by the selection unit and the determination result by the determination unit do not match; 7. The information processing device according to any one of configurations 4 to 6. (Configuration 8) The determination unit issuing the warning to prompt the operator to retake the two types of radiation images; 8. The information processing device according to configuration 7. (Configuration 9) a display control unit that controls the display of the warning issued by the determination unit; 9. The information processing device according to configuration 7 or 8. (Configuration 10) The determination unit determining the geometry of the phantom using the first image; 5. The information processing device according to configuration 4. (Configuration 11) The determination unit issuing a warning if the geometry of the phantom does not satisfy the predetermined condition; 11. The information processing device according to configuration 10. (Configuration 12) a display control unit that displays the warning issued by the determination unit; 12. The information processing device according to claim 11. (Configuration 13) The determination unit As the predetermined condition, it is determined whether or not all of the parts of the phantom referred to by the bone density acquisition unit are included in the irradiation field area in the first image. 11. The information processing device according to configuration 10. (Configuration 14) The determination unit The predetermined condition is determined based on the relative position of the phantom with respect to at least one of the central coordinates of the irradiation field area in the first image and the central coordinates of the image area in the first image. 11. The information processing device according to configuration 10. (Configuration 15) The determination unit As the predetermined condition, a determination is made regarding the orientation of the phantom in the image area in the first image based on a relative angle of the phantom with respect to the image area. 11. The information processing device according to configuration 10. (Configuration 16) The determination unit determining whether the two types of radiation images are a first image captured in such a manner that the geometric arrangement of the phantom placed in the region satisfies the predetermined condition, or a second image captured without placing the phantom in the region; 4. The information processing device according to configuration 3. (Configuration 17) The information is information on an optical image obtained by capturing the arrangement of the phantom in the region. 2. The information processing device according to configuration 1. (Configuration 18) The determination unit determining whether the optical image was taken with the phantom placed in the region or without the phantom placed in the region; 18. The information processing device according to configuration 17. (Configuration 19) a selection unit that allows an operator to select whether to perform radiation imaging with the phantom placed or without the phantom placed, The determination unit issuing a warning when the selection result by the selection unit and the determination result by the determination unit do not match; 19. The information processing device according to configuration 18. (Configuration 20) the determination unit issues the warning to prompt an operator to make the arrangement of the phantom appropriate. 20. The information processing device according to claim 19. (Configuration 21) a display control unit that controls the display of the warning issued by the determination unit; 21. The information processing device according to configuration 19 or 20. (Configuration 22) The determination unit determining whether the optical image was captured with the geometric arrangement of the phantom placed in the region satisfying the predetermined condition, or whether the optical image was captured without the phantom placed in the region; 18. The information processing device according to configuration 17. (Configuration 23) the information is information on electrical signals from the phantom and the region corresponding to the arrangement of the phantom in the region; 2. The information processing device according to configuration 1. (Configuration 24) The phantom is provided with a first electrode, In the region, a second electrode is provided at a position corresponding to the first electrode, and a third electrode is provided at a position not corresponding to the first electrode, The determination unit using the electric signals emitted by contact between the first electrode and the second electrode, contact between the first electrode and the third electrode, or no contact between the first electrode and the second electrode and the third electrode, determining whether the geometric arrangement of the phantom placed in the region satisfies the predetermined condition or whether the phantom is not placed in the region; 24. The information processing device according to configuration 23. (Configuration 25) a selection unit that allows an operator to select whether to perform radiation imaging with the phantom placed or without the phantom placed, The determination unit issuing a warning when the selection result by the selection unit and the determination result by the determination unit do not match; 25. The information processing device according to configuration 23 or 24. (Configuration 26) the determination unit issues the warning to prompt an operator to make the arrangement of the phantom appropriate. 26. The information processing device according to configuration 25. (Configuration 27) a display control unit that controls the display of the warning issued by the determination unit; 27. The information processing device according to configuration 25 or 26. (Configuration 28) a radiation generating device that irradiates radiation onto an object to be examined; a radiation detector that detects radiation that has been irradiated from the radiation generating device and transmitted through the subject, and acquires a radiological image; An information processing device according to any one of configurations 1 to 27; A radiation imaging system comprising: (Method 1) a first step of acquiring two types of radiation images captured under two imaging conditions with different amounts of radiation energy; a second step of determining whether the placement of the phantom satisfies a predetermined condition using information about the area where the phantom is placed; a third step of acquiring a first bone mineral density of the phantom using at least one of the two types of radiographic images, which is determined to have the phantom arranged so as to satisfy the predetermined condition, and at least one of the two types of radiographic images, which is different from the at least one of the two types of radiographic image and is determined to have no phantom arranged therein; An information processing method comprising: (Configuration 29) A program for causing a computer to execute each step of method 1. [Explanation of symbols]

[0156] 101: Radiography system 102: Radiation generator 103: Radiation detector 104:Bed 106: Information equipment 110: Optical camera 200A: User Input Device 200B:UI display device 201: User input control unit 202: Display control unit 203: Shooting mode setting section 204: Shooting condition setting section 205: Radiation image acquisition unit 206: Image type determination unit 207: Bone density calibration section 208: Bone Density Testing Department 209: Geometric placement determination section 233: Storage section 234: Inspection image storage unit 235: Image storage unit for gain correction 236: Calibration phantom image storage section 240: Judgment section 250: Optical image judgment unit 251: Optical image acquisition unit 260: Contact determination section

Claims

1. an image acquisition unit that acquires two types of radiation images captured under two imaging conditions with different amounts of radiation energy; a determination unit that determines whether the placement of the phantom satisfies a predetermined condition using information about the area where the phantom is placed; a bone density acquisition unit that acquires a first bone density of the phantom using at least one of two types of radiographic images, among the plurality of two types of radiographic images, which is determined to have the phantom arranged so as to satisfy the predetermined condition, and at least one of two types of radiographic images that is different from the at least one of two types of radiographic image and is determined to have no phantom arranged therein; An information processing device having the above.

2. a calibration value acquisition unit that compares the first bone density acquired by the bone density acquisition unit with a second bone density that is known in the phantom, and acquires a bone density calibration value that calibrates the first bone density to the second bone density; Further comprising: The information processing device according to claim 1 .

3. The information is information on the two types of radiation images capturing the arrangement of the phantom in the region. The information processing device according to claim 1 .

4. The determination unit determining whether the two types of radiation images are a first image captured with the phantom placed or a second image captured without the phantom placed; The information processing device according to claim 3 .

5. The determination unit determining the first image and the second image based on a score calculated from pixel values ​​of the two types of radiographic images as the predetermined condition; The information processing device according to claim 4 .

6. The determination unit determining the first image and the second image using, as the predetermined condition, a score calculated by weighting and averaging a first score calculated from pixel values ​​of one of the two types of radiographic images and a second score calculated from pixel values ​​of the other of the two types of radiographic images; The information processing device according to claim 4 .

7. a selection unit that allows an operator to select whether to capture the first image or the second image, The determination unit issuing a warning when the selection result by the selection unit and the determination result by the determination unit do not match; The information processing device according to claim 4 .

8. The determination unit issuing the warning to prompt the operator to retake the two types of radiation images; The information processing device according to claim 7 .

9. a display control unit that displays the warning issued by the determination unit; The information processing device according to claim 7 .

10. The determination unit determining the geometry of the phantom using the first image; The information processing device according to claim 4 .

11. The determination unit issuing a warning if the geometry of the phantom does not satisfy the predetermined condition; The information processing device according to claim 10.

12. a display control unit that controls the display of the warning issued by the determination unit; The information processing device according to claim 11.

13. The determination unit As the predetermined condition, it is determined whether or not all of the parts of the phantom referred to by the bone density acquisition unit are included in the irradiation field region in the first image. The information processing device according to claim 10.

14. The determination unit The predetermined condition is determined based on a relative position of the phantom with respect to at least one of a radiation field area in the first image and a center coordinate of an image area in the first image. The information processing device according to claim 10.

15. The determination unit As the predetermined condition, a determination is made regarding the orientation of the phantom in the image area in the first image based on a relative angle of the phantom with respect to the image area. The information processing device according to claim 10.

16. The determination unit determining whether the two types of radiation images are a first image captured in such a manner that the geometric arrangement of the phantom placed in the region satisfies the predetermined condition, or a second image captured without placing the phantom in the region; The information processing device according to claim 3 .

17. The information is information on an optical image obtained by capturing the arrangement of the phantom in the region. The information processing device according to claim 1 .

18. The determination unit determining whether the optical image was taken with the phantom placed in the region or without the phantom placed in the region; The information processing device according to claim 17.

19. a selection unit that allows an operator to select whether to perform radiation imaging with the phantom placed or without the phantom placed, The determination unit issuing a warning when the selection result by the selection unit and the determination result by the determination unit do not match; The information processing device according to claim 18.

20. the determination unit issues the warning to prompt an operator to make the arrangement of the phantom appropriate. The information processing device according to claim 19.

21. a display control unit that controls the display of the warning issued by the determination unit; The information processing device according to claim 19.

22. The determination unit determining whether the optical image was captured with the geometric arrangement of the phantom placed in the region satisfying the predetermined condition, or whether the optical image was captured without the phantom being placed in the region; The information processing device according to claim 17.

23. the information is information on electrical signals from the phantom and the region corresponding to the arrangement of the phantom in the region; The information processing device according to claim 1 .

24. The phantom is provided with a first electrode, In the region, a second electrode is provided at a position corresponding to the first electrode, and a third electrode is provided at a position not corresponding to the first electrode, The determination unit using the electrical signals generated by contact between the first electrode and the second electrode, contact between the first electrode and the third electrode, or no contact between the first electrode and the second electrode and the third electrode, determining whether the geometric arrangement of the phantom placed in the region satisfies the predetermined condition or whether the phantom is not placed in the region; The information processing device according to claim 23.

25. a selection unit that allows an operator to select whether to perform radiation imaging with the phantom placed or without the phantom placed, The determination unit issuing a warning when the selection result by the selection unit and the determination result by the determination unit do not match; The information processing device according to claim 23.

26. the determination unit issues the warning to prompt an operator to make the arrangement of the phantom appropriate. The information processing device according to claim 25.

27. a display control unit that controls the display of the warning issued by the determination unit; The information processing device according to claim 25.

28. a radiation generating device that irradiates radiation onto an object to be examined; a radiation detector that detects radiation that has been irradiated from the radiation generating device and transmitted through the subject, and acquires a radiological image; An information processing device according to any one of claims 1 to 27; A radiation imaging system comprising:

29. a first step of acquiring two types of radiation images captured under two imaging conditions with different amounts of radiation energy; a second step of determining whether the placement of the phantom satisfies a predetermined condition using information about the area where the phantom is placed; a third step of acquiring a first bone mineral density of the phantom using at least one of the two types of radiographic images, which is determined to include the phantom arranged so as to satisfy the predetermined condition, and at least one of the two types of radiographic images, which is different from the at least one of the two types of radiographic image and is determined to include no phantom; An information processing method comprising:

30. A program for causing a computer to execute the steps recited in claim 29.

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