JP6373952B2 - Radiation image analysis apparatus and method, and program - Google Patents

Description

  The present invention relates to an image analysis apparatus, method, and program for analyzing a radiographic image obtained by imaging a subject.

  Conventionally, when taking a radiographic image of a subject with radiation that has passed through the subject, the greater the thickness of the subject, the greater the effects of scattering of radiation inside the subject, the reduction in radiation transmittance, etc. There is a problem that the image quality of the radiation image varies.

  In order to deal with the above problems, the thickness of the subject is roughly determined by various information such as imaging conditions, radiographic signal value, histogram width of the radiographic signal value, and length of the subject in the predetermined direction in the subject image. A technique has been proposed in which image processing conditions such as scattered radiation removal processing for a captured radiographic image and imaging conditions applied to radiographic image capturing are changed according to the estimated thickness of the subject. Yes.

  For example, Patent Document 1 proposes a technique for creating a simulation image for determining an appropriate imaging condition according to body thickness data of a human body. From a CT image (Computed Tomography Image) as a body thickness of a subject. It is disclosed to use a representative thickness of the measured imaging region.

International Publication No. 2007/114470

  Here, in order to further enhance the effect of improving the image quality by determining the image processing condition or the imaging condition based on the body thickness of the subject as described above, it is preferable to obtain the body thickness of the subject more accurately. However, when the body thickness of the subject is represented by one representative value as in the method described in Patent Document 1, the image quality of the subject having different body thickness varies depending on each position of the subject. It is difficult to change image processing conditions and imaging conditions so that they can be sufficiently suppressed.

  The present invention has been made in view of the above circumstances, and performs an image analysis process that analyzes a radiographic image taken by irradiating a subject with radiation and accurately estimates a body thickness distribution of the subject. The purpose is to be able to.

  A radiological image analysis apparatus according to the present invention is a radiological image analysis apparatus that analyzes a subject image captured by irradiating a subject with radiation and estimates a body thickness distribution of the subject. Acquires model information obtained by irradiating a model with radiation and a model thickness associated with the model thickness distribution of the model for a plurality of models different from the image acquisition unit to be acquired and the subject. A model information acquisition unit that acquires feature information that represents the feature of the subject image, and obtains feature information that represents the feature of the plurality of model images based on the plurality of model information, A body thickness distribution determining unit that identifies model images having similar feature information and determines the body thickness distribution associated with the identified model image as the body thickness distribution of the subject image And wherein the door.

  A radiological image analysis method according to the present invention is executed in a radiological image analysis apparatus, and analyzes a subject image taken by irradiating a subject with radiation to estimate a body thickness distribution of the subject. A radiological image analyzer for analyzing a subject image taken by irradiating a subject with radiation and estimating a body thickness distribution of the subject, wherein the image acquisition step acquires the subject image And a model information acquisition step of acquiring, for a plurality of models different from the subject, model information obtained by associating a model image captured by irradiating the model with radiation and a model thickness distribution of the model image, respectively And obtaining feature information representing the characteristics of the subject image, obtaining feature information representing the features of the plurality of model images based on the plurality of model information, and obtaining the subject image. A body thickness distribution step for identifying a model image having feature information similar to the feature information and determining a body thickness distribution associated with the identified model image as a body thickness distribution of the subject image; .

  The radiographic image processing method according to the present invention may be provided as a program for causing a computer to execute the method.

  The “body thickness” means the total thickness of the subject area excluding the air area on the path of the irradiated radiation. The body thickness distribution indicates the distribution of the subject thickness at each position on the two-dimensional radiation image.

  The “characteristic information” may be information defined from an arbitrary viewpoint as long as it represents the characteristics of the radiation image. For example, the feature information can be one or more pieces of information selected from information related to an imaging target, information related to imaging conditions at the time of imaging, grid information related to the presence / absence and type of a scattered radiation removal grid, or any combination thereof. . The feature information may be information representing one feature of the radiation image, or may be information representing a plurality of features. The feature information may define each feature by an arbitrary method. For example, each feature may be defined by one parameter or a plurality of parameters.

  In the radiological image analysis apparatus according to the present invention, it is preferable that the feature information is imaging target information representing a physical feature of the imaging target.

  Note that the “photographing target information” is specified by any method as long as it represents the physique characteristics of the subject to be photographed, such as the skeleton shape, skeleton size, muscle mass, and fat mass. It's okay. For example, the histogram width of the signal value of the radiographic image (difference between the maximum value and the minimum value of the histogram of the signal value), the representative length of the predetermined part of the subject in the radiographic image (for example, the width of the abdomen), the height of the subject, the weight, Gender, age (adult, child), etc. may be used. Further, the shooting target information may be one or plural.

  In the above-described case, the apparatus further includes an alignment unit that aligns the subject image and the model image so that the corresponding positions of the subject image and the model image match, and the body thickness distribution determination unit is aligned. More preferably, feature information is acquired from each of the subject image and the model image, and a model image having feature information similar to the feature information of the subject image is specified.

  In the above case, the image acquisition unit determines whether or not the scattered radiation removal grid is used during imaging of the subject image, and the type of scattered radiation removal grid when the scattered radiation removal grid is used during imaging. The model information acquisition unit further acquires the grid information of the model image, and the body thickness distribution determination unit includes the subject image and the model having grid information that matches the grid information of the subject image. More preferably, the feature information is acquired from the model image included in the information, and the model image having the feature information similar to the feature information of the subject image is specified.

  The “information indicating the type of grid” includes at least one of grid ratio, grid density, focusing type or parallel type, focusing distance in the case of the focusing type, and interspace material (aluminum, fiber, bakelite, etc.). be able to.

  In the radiological image analysis apparatus according to the present invention, the radiographic image can be an image taken without using the scattered radiation removal grid. In this case, the model image is preferably an image taken without using the scattered radiation removal grid.

  In the present invention, the body thickness distribution of the model image is acquired on a straight line corresponding to the radiation path of the model image at each position of the acquired three-dimensional image by acquiring a three-dimensional image obtained by photographing the model three-dimensionally. It is preferable that it is created by measuring body thickness.

  The image acquisition unit further acquires part information representing a part to be imaged of the subject image, the model information acquisition unit further acquires part information of the model image, and the body thickness distribution determination unit includes the subject image. And acquiring feature information from the model image included in the model information having the part information that matches the part information of the subject image, and specifying the model image having the feature information similar to the feature information of the subject image Is preferred.

  According to the present invention, a subject image is acquired, and for a plurality of models different from the subject, the model image photographed by irradiating the model with radiation is associated with the model thickness distribution of the model image The model information is acquired, the feature information representing the feature of the subject image is obtained, the feature information representing the feature of the plurality of model images is obtained based on the plurality of model information, and the feature information of the subject image is obtained. A model image having feature information similar to the above is specified, and the body thickness distribution associated with the specified model image is determined as the body thickness distribution of the subject image. Therefore, the body thickness distribution of the model image having characteristics similar to the subject image among the body thickness distributions for a plurality of models can be set as the body thickness distribution of the subject image. Body thickness distribution can be determined.

1 is a schematic block diagram showing the configuration of a radiographic image capturing system to which a radiographic image analyzer according to a first embodiment of the present invention is applied. Diagram for explaining the measurement method of the body thickness distribution of the model image and the correspondence between the model image and the body thickness distribution of the subject image The flowchart which shows the process performed in 1st Embodiment. The flowchart which shows the process performed in 2nd Embodiment. The flowchart which shows the process performed in 3rd Embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a configuration of a radiographic image capturing system to which a radiographic image analyzing apparatus according to a first embodiment of the present invention is applied. As shown in FIG. 1, the radiographic image capturing system according to the present embodiment includes an image capturing device 10, a control device 20 that controls the system, and an image analysis device 30 (radiation image analysis device).

  The imaging apparatus 10 includes an X-ray source 12 that irradiates the subject K with X-rays, and a radiation detector 14 that detects X-rays transmitted through the subject K and acquires a radiation image of the subject K. In the present embodiment, between the subject K and the radiation detector 14, a scattered radiation removal grid for removing scattered radiation scattered by the subject K out of X-rays transmitted through the subject K. (Grid) is not placed.

  The control device 20 controls the radiation source drive control unit 22 that controls driving of the X-ray source 12 according to the set imaging conditions and the radiation detector 14 to acquire and store a radiation image (subject image) of the subject. And a detector control unit 24 stored in the unit 42.

  The image analysis device 30 includes an image acquisition unit 31 that acquires a subject image Ik obtained by imaging the subject K from the detector control unit 24 or a storage unit 42 described later, and a plurality of different subjects K. For the model Mi (1 <i <n: n is an integer greater than 1), the model image Imi taken by irradiating the model Mi with radiation, and the body thickness distribution Tmi (x, y) of the model Mi of the model image Imi ), The model information acquisition unit 32 that acquires the model information Cmi, the registration unit 33 that aligns the corresponding positions of the subject image Ik and the model image Imi, and the characteristics of the subject image Ik. Feature information is obtained, feature information representing features of the plurality of model images Imi is obtained based on the plurality of model information, and feature information similar to the feature information of the subject image Ik is obtained. Body thickness distribution determining unit that identifies the model image Imi to be determined and determines the body thickness distribution Tmi (x, y) associated with the identified model image Imi as the body thickness distribution Tk (x, y) of the subject image 34, a scattered ray information acquisition unit 35 for acquiring scattered component information representing the scattered component of X-rays included in the subject image Ik based on the determined body thickness distribution Tk (x, y), and a scattered ray information acquisition unit Based on the scattered component information acquired by the radiation detector 35, a scattered radiation removing unit 36 that performs scattered radiation removal processing of the radiation image acquired by the radiation detector 14, an input unit 38, a display unit 40, a memory, a hard disk, and the like And a storage unit 42 configured from a storage medium and storing various types of information. The input unit 38 accepts various inputs from the operator to the image analysis device 30. Specifically, the input unit 38 includes a keyboard, a mouse, a touch panel, and the like. The display unit 40 includes a CRT, a liquid crystal display, and the like, and assists various inputs necessary for a radiation image acquired by the imaging apparatus 10 and a scattered radiation removal process described later.

  The image acquisition unit 31, the model information acquisition unit 32, the alignment unit 33, the body thickness distribution determination unit 34, the scattered radiation information acquisition unit 35, the scattered radiation removal unit 36, the input unit 38, and the display unit 40 described above. The storage unit 42 can be configured by a computer system such as a general personal computer.

  The image analysis apparatus 30 analyzes a subject image Ik photographed by irradiating the thoracoabdominal part of the subject K who is the subject to be examined, and estimates the body thickness distribution Tk of the subject K. .

  The storage unit 42 of the image analysis device 30 stores the subject image Ik acquired by the detector control unit 24. In addition, the storage unit 42 includes a plurality of model images Imi (1) which are radiographic images obtained by radiographing the chest and abdomen for a model Mi (1 <i <n) which is a human body different from the subject K. <I <n) and model information Cmi (1 <i <n) in which the body thickness distribution Tmi (1 <i <n) of the model Mi that is the subject of the model image Imi (1 <i <n) is associated. Are created and stored in advance. Furthermore, the storage unit 42 also stores a three-dimensional CT image Vmi having the model Mi as a subject, and other various information necessary for the scattered radiation removal process. The plurality of models Mi (1 <i <n) includes people having various physiques, genders, and ages. In this embodiment, it is assumed that the model image Imi (1 <i <n) included in the subject image Ik and each model information Cmi (1 <i <n) is an image taken without using a grid. .

  Further, the above-described body thickness distribution Tmi (x, y) (1 <i <n) is created in advance based on the three-dimensional CT image Vmi (1 <i <n) of the model Mi that is the subject of the model image Imi. Has been. The body thickness in this specification means the total thickness of the subject area excluding the air area on the path of the irradiated radiation.

  FIG. 2 is a diagram for explaining the measurement method of the body thickness distribution of the model image Imi and the correspondence relationship between the body thickness distributions of the model image Imi and the subject image Ik. A method of measuring the body thickness of the coordinates P and Q on the model image Imi will be described as an example with reference to FIG. 2 shows an example of a model image Imi that is a two-dimensional radiation image of the model Mi, and the left side of FIG. 2 shows an example of a tomographic image S generated from the three-dimensional image Vmi of the model Mi. On the right, an example of the subject image Ik is shown. In FIG. 2, the tomographic image S indicates a tomographic image including a path of radiation passing through the coordinates Ps and Qs in the three-dimensional image Vmi corresponding to the coordinates P and Q on the model image Imi. A line A in FIG. 4 indicates a projection plane corresponding to the model image Imi in the tomographic image S. As shown in FIG. 2, the body thicknesses corresponding to the coordinates P and Q on the model image Imi are the body thicknesses Tp and Tq on the radiation path passing through the coordinates Ps and Qs on the tomogram S, respectively. It is obtained by measuring with. Note that, for example, the body thickness Tp in FIG. 2 includes many air portions in the lung field on the path, so the distance of the air region is not converted into the body thickness, and the total body thickness is 72 mm. Further, the body thickness Tq corresponding to the coordinate Q has a small air region on the path, so the total body thickness is 221 mm.

  A method of creating the body thickness distribution Tmi (x, y) (1 <i <n) will be described. First, the image analysis apparatus 30 acquires from the storage unit 42 a model image Imi and a three-dimensional CT image Vmi having the model Mi as a subject. Then, the coordinate system of the model image Imi and the three-dimensional CT image Vmi is relatively enlarged and moved to align with corresponding positions. Further, a projection plane in the three-dimensional CT image Vmi corresponding to the model image Imi and a straight line (virtual radiation path) in the three-dimensional CT image Vmi corresponding to the radiation passage path with respect to the model image Imi are calculated. Then, on the projection plane, the coordinates (x1, y1, z1) in the three-dimensional CT image Vmi corresponding to the coordinates (x1, y1) of one pixel of the model image Imi are specified, and the coordinates (x1, y1, The thickness (body thickness) of the subject located on the virtual radiation path passing through z1) is measured. And the measured body thickness is registered as body thickness Tmi (x1, y1) of coordinates (x1, y1). Similarly, with respect to the coordinates of all other pixels on the model image Imi, the body thickness corresponding to each coordinate is measured, and the process of registering the measured body thickness as the body thickness corresponding to each coordinate is repeated. Thus, the body thickness distribution Tmi (x, y) of the model image Imi is created.

  Hereinafter, the flow of the radiation image analysis process performed by the image analysis apparatus 30 according to the present embodiment will be described using the flowchart shown in FIG. Hereinafter, the body thickness distribution Tmi (x, y) may be referred to as a body thickness distribution Tmi, and the body thickness distribution Tk (x, y) may be referred to as a body thickness distribution Tk. In addition, the model image Imi (1 <i <n), the model information Cmi (1 <i <n), and the model Mi (1 <i <n) are referred to as a model image Imi, model information Cmi, and model Mi, respectively.

  First, the image acquisition unit 31 acquires from the storage unit 42 a subject image Ik obtained by radiographing the chest and abdomen of a patient who is the subject K (S01).

  Next, the model information acquisition unit 32 acquires a plurality of model information Cmi (S02). Note that the object image Ik acquisition process (S01) and the model information Cmi acquisition process (S02) may be interchanged, or may be performed simultaneously.

  Subsequently, the alignment unit 33 appropriately scales and moves the plurality of model images Imi so that the corresponding positions of the subject image Ik and the plurality of model images Imi coincide with each other. The model image Imi is aligned (S03).

  Any known method may be used to align the subject image Ik and the plurality of model images Imi. For example, it is preferable to perform alignment using an image obtained by extracting a low frequency component from the subject image Ik and an image obtained by extracting the low frequency component of the model image Imi. By aligning low-frequency components from which high-frequency components including detailed information such as blood vessels have been removed, it is possible to align with rough targets such as bones and organs, so positioning is more accurate. This is because they can be combined.

  Next, the body thickness distribution determination unit 34 acquires feature information from the aligned subject image Ik (S04), and similarly acquires feature information from a plurality of model images Imi (S05). Note that the processing of acquiring feature information from the subject image Ik (S04) and the processing of acquiring feature information from the model image Imi (S05) may be interchanged or performed simultaneously.

  Note that the feature information may be information defined from an arbitrary viewpoint as long as it represents the feature of the radiation image. For example, the characteristic information may be one or more information selected from information related to an imaging target, information related to imaging conditions at the time of imaging, information related to the presence / absence and type of a scattered radiation removal grid, or any combination thereof. The feature information may be information representing one feature of the radiation image, or may be information representing a plurality of features. The feature information may define each feature by an arbitrary method. For example, each feature may be defined by one parameter or a plurality of parameters.

  In the present embodiment, the body thickness distribution determination unit 34 uses the subject image Ik and the plurality of model images Imi to determine the maximum value of the signal value of the radiographic image that is imaging target information representing the physical characteristics of the imaging target (subject). And the minimum value difference (histogram width) is extracted and acquired as feature information.

  Note that the imaging target information may be specified by any method as long as it represents a physique characteristic of the imaging target such as the skeleton shape, the size of the skeleton, the muscle mass, and the fat mass. . For example, the histogram width of the signal value of the radiographic image (difference between the maximum value and the minimum value of the histogram of the signal value), the representative length of the predetermined part of the subject in the radiographic image (for example, the width of the abdomen), the height of the subject, the weight, Gender, age (adult, child), etc. may be used. Further, the shooting target information may be one or plural. Further, the photographing target information may be acquired by an arbitrary method, for example, may be acquired by extracting from the supplementary information of the image, may be acquired by extracting from the image by a known image recognition process, and may be acquired by the user. You may receive and acquire an input.

  Then, the body thickness distribution determination unit 34 compares the histogram widths of the signal values of the subject image Ik and the plurality of model images Imi, and specifies the model image Imo having the closest histogram width to the histogram width of the subject image Ik. (S06). In a radiographic image, as the subject's physique increases, the spread of the signal value tends to increase. Therefore, by using the histogram width of the signal value as the imaging target information, the subject K and the physique of the subject image Ik are used. It is possible to specify a model image Imo having a model Mo having a similar subject as the subject.

  Then, the body thickness distribution determination unit 34 determines the body thickness distribution Tmo associated with the identified model image Imo as the body thickness distribution Tk of the subject image Ik, and ends the radiation image analysis processing of the first embodiment. (S07). As a result, for example, the body thicknesses Tp and Tq at the coordinates P and Q in the model image Imi shown at the center of FIG. 2 are respectively the body thicknesses at the corresponding coordinates Pk and Qk of the subject image Ik shown at the right of FIG. It is determined.

In the present embodiment, after the body thickness distribution determination process (S07) shown in FIG. 3 is performed, when an instruction input for the scattered radiation removal process for the subject image Ik is received, the image analysis apparatus 30. Scattered ray information acquisition processing and scattered ray removal processing are implemented as optional functions. First, the scattered radiation information acquisition unit 35 acquires the subject image Ik and its body thickness distribution Tk (x, y), and the primary line image Ip (x, y) according to the following equations (1) and (2). And the scattered radiation image Is (x, y) is calculated.
Ip (x, y) = Ik (x, y) × exp (−μ × Tk (x, y)) (1)
Is (x, y) = Ik (x, y) * P (Tk (x, y)) (2)
Here, (x, y) is the coordinates of the pixel position of the subject image Ik, Ip (x, y) is the primary line image at the pixel position (x, y), and Is (x, y) is the pixel position (x, y). The scattered radiation image at y), Ik (x, y) is the incident dose at the pixel position (x, y), μ is the linear attenuation coefficient of the subject, and P (Tk (x, y)) is the pixel position (x, y). This is a convolution kernel representing a point diffusion function corresponding to the subject thickness at. Expression (1) is an expression based on a known exponential attenuation law. In the storage unit 42, it is assumed that scattered ray information obtained by acquiring a point spread function of scattered rays for each of a plurality of body thicknesses and associated is created and stored in advance. For details of the point spread function, reference can be made to, for example, the description of JP-A-10-57361.

  Then, the scattered radiation removal unit 36 generates a processed image in which the influence of the scattered radiation is removed by subtracting the scattered radiation image Is (x, y) from the subject image Ik (x, y), and the storage unit 42. To remember. The processed image is appropriately displayed on the display unit 40 in accordance with a user instruction.

  According to the present embodiment, among the body thickness distributions for a plurality of models, the body thickness distribution of the model image Imo having characteristics similar to the subject image Ik can be set as the body thickness distribution of the subject image Ik. The body thickness distribution of the subject image Ik can be accurately determined. For this reason, by using the body thickness distribution Tk for removing scattered rays, it is possible to accurately remove scattered rays from the subject image Ik and improve image quality such as contrast in the processed image.

  Further, as shown in the present embodiment, when the imaging target information indicating the physique of the subject is used as the feature information, the body thickness distribution of the model Mi that approximates the physique is represented by the body thickness of the subject image Ik. Since it can be determined as the distribution Tk, the body thickness distribution Tk can be calculated more accurately.

  Further, as in the above-described embodiment, the image analysis device 30 includes the alignment unit 33, and after the object image Ik and the plurality of model images Imi are aligned, the feature information is acquired from the object image Ik. When acquiring feature information from the plurality of model images Imi, the influence of the positional deviation of the subject between the subject image Ik and the plurality of model images Imi is reduced, and the feature information and the plurality of models of the subject image Ik are reduced. The feature information of the image Imi can be compared, and the model image Imo whose feature information is similar to the subject image Ik can be more accurately determined. When the determined model image Imo and the subject image Ik are aligned, the body thickness distribution of the model image Imo can be appropriately reflected on the body thickness distribution at each position of the subject image Ik.

  Further, when one of the subject image Ik and the model image Imi is photographed using a grid and the other is photographed without using a grid, generation of scattered rays of the subject image Ik and the plurality of model images Imi is generated. Since the amounts are different, it may be difficult to accurately compare the feature information of the subject image Ik and the model image Imi. For this reason, as in the above-described embodiment, both the subject image Ik and the plurality of model images Imi are taken without using a grid, thereby approximating the scattered dose contained in both images. Thus, it is possible to more accurately determine the similarity between the feature information of the subject image Ik and the feature information of the model image Imi.

  Further, as in the above embodiment, each body thickness distribution of the plurality of model images Imi acquires a three-dimensional image Vmi obtained by three-dimensionally photographing the model Mi, and at each position of the acquired three-dimensional image Vmi. When it is created by measuring the body thickness on a straight line corresponding to the radiation path of the model image Imi, the body thickness distribution Tmi corresponding to each model image Imi can be made more accurate. Various three-dimensional images can be applied as the three-dimensional image, but it is most preferable to use a three-dimensional CT image because the thickness of the subject can be determined based on the signal value obtained by imaging with radiation. .

  Hereinafter, the second embodiment will be described. FIG. 4 is a flowchart illustrating a flow of processing according to the second embodiment. In the second embodiment, the image acquisition unit 31 further acquires the grid information of the subject image Ik, the model information acquisition unit 32 further acquires the grid information of the plurality of model images Imi, and the body thickness distribution determination unit 34 The feature information is acquired from the model image Imi included in the model information Cmi having the grid information that matches the grid information of the subject image Ik, and the image acquisition unit 31 represents the region to be imaged of the subject image Ik. Part information is further acquired, the model information acquisition unit 32 further acquires part information of the model image Imi, and the body thickness distribution determination unit 34 is included in the model information Cmi having part information that matches the part information of the subject image Ik. This is different from the first embodiment in that feature information is acquired from each model image Imi. In the second embodiment, the functions and processes of the other units are the same, and therefore, different parts from the first embodiment will be mainly described, and description of the common parts will be omitted as appropriate.

  Further, in the second embodiment, it is assumed that the supplementary information of the subject image Ik and the plurality of model images Imi includes part information and grid information, respectively. In the storage unit 42, the model image Imi included in the plurality of model information Cmi includes a plurality of model images photographed without a grid and a plurality of model images photographed using a plurality of types of grids. . In addition, it is assumed that the model image Imi included in the plurality of model information Cmi includes model images in which the imaging region is any one of the head, chest, and abdomen.

  Note that the grid information includes at least whether or not the grid is used at the time of shooting. If the grid is used, the grid information includes information indicating the type of the grid. The information indicating the type of grid shall include at least one of grid ratio, grid density, focusing type or parallel type, focusing distance in the case of the focusing type, and interspace material (aluminum, fiber, bakelite, etc.). Can do. The grid information may be obtained by any method. For example, it is conceivable to extract grid information from user input or image supplementary information. Here, the grid information includes information indicating whether or not the grid is used at the time of shooting, and information indicating the type of the grid when the grid is used at the time of shooting.

  The site information includes information on the imaging target site such as the head, chest, and abdomen. The site information may be indirectly specified by an organ included in the site. Further, the part information may include information on the imaging direction of each part or the posture of the subject. Further, the part information may be obtained by any method. For example, it may be acquired from the header information of the image, user input information, or the like, or may be acquired by performing organ recognition processing on the image and determining a part from the organ included in the image.

  First, in the second embodiment, the image acquisition unit 31 acquires the subject image Ik (S11), and the model information acquisition unit 32 acquires a plurality of model information Cmi (S12). S11 and S12 are processes corresponding to S01 and S02, respectively.

  Next, the image acquisition unit 31 acquires the part information of the subject image Ik from the incidental information of the subject image Ik (S13). Moreover, the model information acquisition part 32 acquires site | part information from each incidental information of the some model image Imi, respectively (S14). In addition, the part information acquisition process (S13) of the subject image Ik and the part information acquisition process (S14) of the plurality of model images Imi may be reversed in order or performed simultaneously.

  Next, the body thickness distribution determination unit 34 specifies only the model image Imi included in the model information Cmi having the part information that matches the part information of the subject image Ik among the plurality of model images Imi (S15).

  Subsequently, the image acquisition unit 31 acquires the grid information of the subject image Ik from the incidental information of the subject image Ik (S16). Further, the model information acquisition unit 32 acquires grid information from the incidental information of each of the plurality of model images Imi (S17). Note that the grid information acquisition process (S16) of the subject image Ik and the grid information acquisition process (S17) of the plurality of model images Imi may be reversed in order or performed simultaneously.

  Next, the body thickness distribution determining unit 34 further selects a model image Imi included in the model information Cmi having grid information that matches the grid information of the subject image Ik among the plurality of model images Imi specified in S15. Specify (S18).

  Next, the alignment unit 33 aligns the model image Imi identified in S18, that is, the one or more model images Imi whose grid information and part information match the subject image Ik and the subject image Ik. (S19).

  Then, similarly to the first embodiment, the body thickness distribution determination unit 34 acquires feature information for the aligned subject image Ik (S20), acquires feature information for the model image Imi (S21), and The model image Imo most similar to the feature information of the subject image is identified (S22), and the body thickness distribution Tmo corresponding to the identified model image Imo is determined as the body thickness distribution Tk of the subject image Ik. The radiation image analysis process of the embodiment is terminated (S23). S20 to S23 are processes corresponding to S04 to S07 in the first embodiment, respectively.

  As in the second embodiment, a feature corresponding to the model image Imi having grid information that matches the grid information of the subject image Ik is acquired, and the model image having feature information similar to the feature information of the subject image Ik When Imo is specified and the body thickness distribution Tmo corresponding to the specified model image is determined as the body thickness distribution Tk of the subject image Ik, the grid information of the subject image Ik and the plurality of model images Imi match. Therefore, the influence of the amount of scattered radiation generated due to the difference in grid information can be reduced, and the features of both images can be accurately extracted. For this reason, the model image Imo having a feature similar to the subject image Ik can be accurately extracted, and the body thickness distribution can be determined more accurately.

  Further, as in the second embodiment, the model information Imi having the part information that matches the part information of the subject image Ik is compared with the feature information, and has the feature information similar to the feature information of the subject image Ik. When the model image Imo is specified and the body thickness distribution Tmo corresponding to the specified model image Imo is determined as the body thickness distribution Tk of the subject image Ik, the part information of the subject image Ik and the plurality of model images Imi Therefore, it is possible to accurately extract the features of both images by reducing the influence of the difference in the amount of scattered radiation generated due to the difference in the parts. For this reason, the model image Imo having a feature similar to the subject image Ik can be accurately extracted, and the body thickness distribution can be determined more accurately.

  In the second embodiment described above, the series of processes shown in S13 to S15 and the series of processes shown in S16 to S18 can be performed even if S13 to S15 are performed first by performing the processes shown in S16 to S18. Good. One of the series of processes shown in S13 to S15 and the series of processes shown in S16 to S18 may be omitted.

  In each of the above-described embodiments, the image analysis device 30 may have a configuration in which the alignment unit is omitted, and the alignment process may not be performed. Further, the image analysis apparatus 30 may be configured such that the scattered radiation information acquisition unit 35 and the scattered radiation removal unit 36 are omitted, and the scattered radiation information acquisition process and the scattered radiation removal process are not performed. In this case, it is conceivable that the determined body thickness distribution is output to another device, and various image processing and imaging conditions are determined using the body thickness distribution in the other device. In addition, the image analysis device 30 may not acquire the body thickness distribution Tmi of the model image Mi, and the image analysis device 30 may acquire and use the body thickness distribution Tmi created by another device.

  The body thickness distribution of the model image is not limited to the above embodiments, and may be obtained by any method as long as it represents the body thickness distribution of the model.

  In addition, after obtaining the subject image, the process of determining the body thickness distribution of the subject image according to the present invention (for example, see S02 to S07 in FIG. 3 and S12 to S23 in FIG. 4 in the above embodiments). From the subject image acquisition to the post-processing image display, when the post-processing image is generated and displayed by performing other desired image processing such as scattered radiation removal processing using the determined body thickness distribution of the subject image Required time (after obtaining the subject image, processing to determine the body thickness distribution of the subject image, and other desired image processing such as scattered radiation removal processing on the subject image, and the obtained processing It is preferable to shorten the time until the subsequent image is displayed as much as possible.

  For this purpose, in the image analysis device according to the present invention, the image acquisition unit 31 generates and acquires a reduced image obtained by reducing the subject image to a predetermined size, and the model information acquisition unit 32 has a size corresponding to the reduced image. The model information including the model image is acquired, the body thickness distribution determination unit 34 specifies a model image having feature information similar to the feature information of the reduced image, and the body thickness distribution associated with the specified model image is obtained. The body thickness distribution of the reduced image may be determined, and the determined body thickness distribution of the reduced image may be enlarged to the size of the desired subject image and used as the body thickness distribution of the subject image. In this case, one of the process of determining the body thickness distribution of the subject image (particularly the process of acquiring the feature information of the reduced image and the process of specifying the model image having feature information similar to the feature information of the reduced image or Both) processing load and processing time are likely to be reduced, and the time required from the subject image acquisition to the post-processing image display is reduced, thereby reducing the waiting time of the user and improving the efficiency of the user's observation work. Can help. Further, in a medical institution or the like, a plurality of subject images obtained by radiographing a plurality of subjects are acquired, and the body of the subject image as shown in each of the above embodiments for the radiation images of the plurality of subjects is provided. The above effect is very useful in a situation where desired image processing such as thickness distribution determination processing and scattered radiation removal processing is sequentially performed, and a user displays the obtained processed images in order. The working time can be significantly reduced. It should be noted that the reduced image preferably has a resolution as small as possible within a range that maintains the resolution with which the similarity can be suitably determined using the feature information acquired from the reduced image and the feature information of the model image. A method in which an optimal size is set in advance based on the size of the organ to be interpreted is considered.

  Further, in a medical institution or the like, a plurality of subject images obtained by radiographing a plurality of subjects are acquired, and the body thickness distribution of the subject images in the present invention is determined for each of the plurality of subject radiographic images. Processing (for example, see S02 to S07 in FIG. 3 and S12 to S23 in FIG. 4 in each of the above embodiments) and desired image processing such as scattered radiation removal processing are sequentially performed. In the case of observing images in order, it is preferable to effectively use the time required from acquisition of the subject image to display of the processed image. As an example, it may be possible to display information to be a reference for image observation prior to the display of the processed image during the time required from the subject image acquisition to the processed image display according to the above embodiments.

  For example, as a third embodiment, which is a modification of the image analysis apparatus of the first embodiment, a series of processes (in FIG. 3) for determining the body thickness distribution Tk of the subject image Ik after acquiring the subject image. During the processing period of S02 to S07), the scattered radiation information acquisition unit 35 acquires the scattered radiation information of the subject image using the preset temporary body thickness distribution, and the scattered radiation removal unit 36 acquires the temporary body thickness distribution. A process for generating a post-provisional image by performing a scattered-radiation removal process on the subject image Ik based on the scattered-radius information acquired by using the process, and causing the display unit 40 to display the post-provisional image (generation of the post-provisional image) Part or all of the display process may be performed.

  FIG. 5 shows a flowchart of the third embodiment. In the image analysis apparatus according to the third embodiment, the scattered radiation information acquisition unit 35 is set in advance during a processing period of a series of processes (S02 to S07 in FIG. 3) for determining the body thickness distribution Tk of the subject image Ik. Based on the scattered radiation information acquired by the scattered radiation removal unit 36 based on the temporary body thickness distribution, the scattered radiation information representing the X-ray scattered radiation included in the subject image Ik is acquired based on the temporary body thickness distribution. This is different from the first embodiment in that scattered image removal processing of the subject image is performed to generate a post-provisional image, and the display unit 40 displays the post-provisional image. As for the other portions, the image analysis apparatus according to the third embodiment includes the same components as those of the image analysis device 30 shown in FIG. 1, and the functions and processes of the respective components are generally the same. The description will focus on parts different from those of the first embodiment, and description of common parts will be omitted as appropriate.

  In the third embodiment, as shown in FIG. 5, the image acquisition unit 31 acquires the subject image Ik in the same manner as S01 of the first embodiment (S31), and the first embodiment (FIG. 3). The processing (S32) for determining the body thickness distribution Tk of the subject image Ik is performed in the same manner as S02 to S07), and the conditional expressions (1) and (2) are performed in the same manner as in the optional example of the first embodiment. Is obtained using the determined body thickness distribution Tk (primary line image Ip and scattered radiation image Is) (S33), and acquired in the same manner as the option example of the first embodiment. The scattered radiation image Is is subtracted from the subject image Ik, and the scattered radiation removal process (S34) is performed.

  In the third embodiment, when the image acquisition unit 31 acquires a subject image (S31), in parallel with the processing of S32, the scattered radiation information acquisition unit 35 acquires a preset provisional body thickness distribution. Then, similarly to the example of the option of the first embodiment, based on the conditional expressions (1) and (2), the acquired temporary body thickness distribution is used to obtain scattered ray information (primary line image Ip and scattered ray image). Is) is acquired (S37), and the scattered radiation image Is ′ is obtained from the subject image Ik based on the scattered radiation image Is ′ acquired using the temporary body thickness distribution in the same manner as the optional example of the first embodiment. By performing subtraction, an image after provisional processing in which the influence of scattered radiation is removed is generated and stored in the storage unit 42 (S38). Subsequently, the image analysis device 30 determines whether or not a post-processing image obtained by the processing shown in S34 has been generated. If a post-processing image has not been generated (S39, No), the post-processing image Until the image is generated (S39, Yes), the temporarily processed image is displayed on the display unit 40 (S40). On the other hand, when the processed image obtained by the process shown in S34 is generated (S39, Yes), the image analysis apparatus displays the processed image on the display unit 40 (S35).

  According to the third embodiment, after obtaining the subject image Ik and performing the process of determining the body thickness distribution Tk of the subject image Ik, the desired image processing such as the scattered radiation removal process is performed and obtained. In the radiological image analysis apparatus that displays the processed image thus obtained, during the processing period of a series of processes for determining the body thickness distribution Tk of the subject image Ik, a preliminarily set temporary body thickness distribution is used for the subject image. A process of performing desired image processing such as scattered radiation removal processing, generating a post-processing image obtained using the temporary body thickness distribution as a post-processing image, and displaying the post-processing image on the display unit 40. Part of the subject image should be noted by observing the post-processed image using the temporary body thickness distribution by effectively using the time until the display of the processed image by the user. Or radiography applied to the subject image Matter of Compliance and may be able to get a sense, it is possible to provide information that can help the user of the observation while efficient observation user.

  In the third embodiment, as the “preset body thickness distribution”, any body thickness distribution that substantially corresponds to the subject K can be used. Of the body thickness distributions obtained by performing the process of determining the body thickness shown in the embodiment, the latest body thickness distribution can be used, and the body thickness distribution of a standard subject can also be used. In addition, a series of processing (S32) for determining the body thickness distribution of the subject image Ik in the third embodiment is performed by irradiating the model with radiation for at least a plurality of models different from the subject. A model information acquisition process for acquiring model information in which an image is associated with a model thickness distribution of a model of the model image, and feature information representing the characteristics of the subject image is acquired, and a plurality of models are obtained based on the plurality of model information Feature information representing the features of each model image is obtained, a model image having feature information similar to the feature information of the subject image is identified, and a body thickness distribution associated with the identified model image is determined. As long as it includes at least the body thickness distribution determining process (the body thickness distribution determining process of the present invention) for determining the body thickness distribution of the subject, any body thickness distribution Tk for the subject K is determined. It may be used as the physical. For example, a series of processing (S32) for determining the body thickness distribution may be processing corresponding to the second embodiment (processing corresponding to S12 to S23 in FIG. 4), and the alignment processing may be omitted. . In the third embodiment, the example in which the scattered radiation removal process (S33, S34, S37, S38) is performed from the subject image Ik has been described. However, the present invention is not limited to this, and the subject image is replaced with the scattered radiation removal process. Other image processing may be performed on Ik, and other image processing may be further performed on the subject image Ik in accordance with the scattered radiation removal processing. Further, the processing of S36 to S38 can be performed in an arbitrary period in which a part or all of the processing of S32 overlaps, and the information after the provisional processing is displayed earlier and the information for reference of the user can be displayed earlier. In order to provide it, it is preferable to perform the processing of S36 to S38 after acquisition of the subject image Ik at an early timing.

  It should be noted that the body thickness distribution obtained by the present invention is not limited to each of the embodiments, and is used for all processes for determining image processing conditions according to the body thickness of the subject with respect to the subject image. Can do. For example, it may be used for gradation processing such as density and contrast, noise suppression processing, dynamic range adjustment processing, frequency enhancement processing, and the like for a subject image that is a still image or a moving image. Further, the body thickness distribution obtained by the present invention can be used for any processing for determining imaging conditions corresponding to the body thickness for the subject image. When each image processing condition or imaging condition is determined using the body thickness distribution obtained by the present invention, the determined image processing condition or imaging is performed by applying an accurate body thickness distribution for the subject image. The effect of improving image quality depending on conditions can be enhanced.

  In addition, for example, in the energy subtraction technique for acquiring a radiographic image based on a difference between two radiographic images acquired by imaging high energy and low energy radiation with different tube voltages, the subject obtained by the present invention Depending on the body thickness distribution, when the low energy image is subtracted from the high energy image, the weight coefficient may be determined so as to increase the weight of the high energy image at the position where the body thickness is large. In this case, by applying an accurate body thickness distribution to the subject image, the influence of the occurrence of the beam hardening phenomenon in which the radiation quality varies depending on the thickness of the subject is reduced. The image quality of the post-image can be preferably improved.

  In the technical field of acquiring multiple radiographic images by capturing multiple images of the same subject, such as radioscopy image application technology, tomosynthesis and video imaging technology, Preferably, the body thickness distribution of the subject is acquired by the method of the invention, and the imaging conditions of the subject to be subsequently imaged are determined based on the acquired body thickness distribution. Since a subject image that is subsequently captured can be captured under appropriate imaging conditions according to the body thickness, the subsequently captured subject image can be an image with an image quality suitable for diagnosis.

  Moreover, it is preferable to store the dose management information in which the body thickness distribution of the subject obtained by the present invention is associated with the imaging conditions for each subject. Imaging conditions can include set values and exposure times set for radiation sources, etc., and include actual values and exposure times measured by detectors etc. You can also. For each subject, a plurality of dose management information of the subject is acquired as dose history information, and based on this dose history information, the cumulative exposure dose at each position during a predetermined period of the subject is calculated. Thus, it is possible to provide useful information that serves as an index for dose management for each region, such as whether or not the cumulative exposure dose exceeds a predetermined threshold that is not acceptable for a predetermined region such as a predetermined organ. In addition, by acquiring dose management information for a plurality of different subjects and performing statistical analysis, it is possible to identify what imaging conditions were used according to the tendency of the body thickness distribution. Information that is helpful for determining imaging conditions for the subject or estimating imaging conditions for past subjects can be provided.

  Further, when selecting two subject images constituting a stereoscopic image from a plurality of subject images photographed by the tomosynthesis photographing apparatus, the body thickness distribution of the subject obtained by the present invention is obtained and obtained. It is preferable to select the two subject images so as to have an appropriate amount of parallax or convergence angle (an angle formed by each photographing direction of the two subject images constituting the stereoscopic image) according to the distribution of body thickness. . For example, the index value indicating the characteristics of the body thickness distribution such as the maximum value, average value, and median value is extracted from the body thickness distribution of the subject, and the larger the body thickness of the subject for each range of index values, Index value extracted from the body thickness distribution of the subject based on the parallax determination information, which is generated in advance and acquired parallax determination information associated with an appropriate amount of parallax (or convergence angle) so that the angle) increases. Is determined as a parallax amount (or convergence angle) of a stereoscopic image, and two subject images having such a parallax amount (or convergence angle) are configured as a stereoscopic image. The subject image can be selected. As an example, an index value indicating characteristics of the body thickness distribution is calculated according to the body thickness distribution of the subject, and the subject is divided into a plurality of physiques such as a narrow type, a standard type, and a thick type based on the index value. Dividing into classifications, determining the amount of parallax (or convergence angle) corresponding to the classified classification as the amount of parallax of the stereo image of the subject, and constructing a stereoscopic image with two subject images that have such a parallax amount The subject image can be selected. Thus, when selecting two subject images constituting a stereoscopic image from a plurality of subject images, the body thickness distribution of the subject obtained by the present invention is obtained, and the obtained body thickness distribution is obtained. If the two subject images are appropriately selected so that the larger the body thickness is, the larger the parallax amount or the convergence angle is, a stereoscopic image with a quality suitable for observation is generated according to the body thickness distribution. can do. For the amount of parallax and the angle of convergence, reference can be made to past applications of the present application (for example, JP 2013-198736, JP 2013-198508, JP 2013-154165, etc.).

  Each of the above embodiments is merely an example, and all of the above description should not be used to limit the technical scope of the present invention. The aspect of the present invention is not limited to the above-described individual examples (first to third embodiments, other modifications and application examples), and any combination of elements of the individual examples is not limited to the present invention. In addition, various modifications that can be conceived by those skilled in the art are also included. That is, various additions, modifications, and partial deletions can be made without departing from the concept and spirit of the present invention derived from the contents defined in the claims and equivalents thereof.

  In addition, the system configuration, the hardware configuration, the processing flow, the module configuration, the user interface, the specific processing content, etc. in the above embodiment have been variously modified without departing from the spirit of the present invention. It is included in the technical scope of the present invention. For example, some or all of the components of the image analysis apparatus may be configured by a single workstation, and may be configured by one or more workstations, servers, and storage devices connected via a network. It may be configured.

  In the above-described embodiment, the scattered radiation removal process is performed using the radiographic image acquired by the imaging apparatus 10 that captures a radiographic image of the subject using the radiation detector 14, but JP-A-8-266529 is disclosed. Radiation images acquired by accumulating and recording radiographic image information of a subject on a stimulable phosphor sheet as a radiation detector shown in Japanese Patent Laid-Open No. 9-24039 and the like, and photoelectrically reading from the stimulable phosphor sheet Of course, the present invention can also be applied when using.

DESCRIPTION OF SYMBOLS 10 Imaging device 20 Control apparatus 30 Image analyzer (radiation image analyzer)
Reference Signs List 31 Image acquisition unit 32 Model information acquisition unit 33 Positioning unit 34 Body thickness distribution determination unit 35 Scattered ray information acquisition unit 36 Scattered ray removal unit 38 Input unit 40 Display unit 42 Storage unit Cmi model information Ik Subject image Imi model image Tk Body thickness distribution of subject image Body thickness distribution of Tmi model image Three-dimensional image corresponding to Vmi model image

Claims (9)

A radiological image analyzer that analyzes a subject image photographed by irradiating a subject with radiation and estimates a body thickness distribution of the subject,
An image acquisition unit for acquiring the subject image;
Model information for acquiring model information obtained by associating a model image photographed by irradiating the model with radiation and a body thickness distribution of the model image for a plurality of models different from the subject An acquisition unit;
Feature information representing features of the subject image is obtained, feature information representing the features of the plurality of model images is obtained based on the plurality of model information, respectively, and similar to the feature information of the subject image A body thickness distribution determining unit that identifies the model image having the feature information, and determines the body thickness distribution associated with the identified model image as a body thickness distribution of the subject image;
And scatter information acquisition unit that determined above using the body thickness distribution of the test object to obtain the scattered radiation information estimated scattered radiation of the test object image,
The acquired scatter information and on the basis of the subject image, and a scattered ray removal unit for removing processing of scattered radiation the to the subject body image,
The feature information is shooting target information representing a physical feature of the shooting target;
The body thickness distribution determination unit obtains a histogram width that is a difference between a maximum value and a minimum value of a signal value of the subject image as the photographing target information of the subject image, and the photographing target of each model image A radiological image analysis apparatus characterized by acquiring a histogram width which is a difference between a maximum value and a minimum value of signal values of the model image as information . An alignment unit that aligns the subject image and the model image so that the corresponding positions of the subject image and the model image match;
The body thickness distribution determination unit acquires the feature information from the aligned subject image and the model image, and identifies the model image having the feature information similar to the feature information of the subject image The radiological image analysis apparatus according to claim 1, wherein: The image acquisition unit includes grid information including presence / absence of use of a scattered radiation removal grid at the time of imaging of the subject image and a type of the scattered radiation removal grid when the scattered radiation removal grid is used at the time of imaging. Get more and
The model information acquisition unit further acquires the grid information of the model image,
The body thickness distribution determining unit obtains the feature information from the model image included in the model information including the subject image and grid information that matches grid information of the subject image, and the subject imaging radiation image analyzer according to claim 1 or 2, wherein the identifying the model image with the feature information similar to the feature information of. The radiation image analysis apparatus according to claim 3, wherein the subject image is an image taken without using a scattered radiation removal grid, and the model image is an image taken without using a scattered radiation removal grid. The object image is an image photographed using a scattered radiation removal grid, and the model image is an image photographed using a scattered radiation removal grid used for the subject image. Item 4. The radiological image analysis apparatus according to item 3 . The body thickness distribution of the model image is acquired on a straight line corresponding to the radiation path of the model image at each position of the acquired 3D image by acquiring a 3D image obtained by 3D imaging of the model. body thickness radiographic image analyzing apparatus according to any one of claims 1 to 5, characterized in that it is prepared by measuring. The image acquisition unit further acquires site information representing a site to be imaged of the subject image, the model information acquisition unit further acquires the site information of the model image, and the body thickness distribution determination unit The feature information is obtained from the model image included in the model information including the subject image and the model information having the part information that matches the part information of the subject image, and the feature information of the subject image radiation image analyzing apparatus according to any one of claims 1 to 6, characterized in that identifying the model image with the feature information similar. A radiological image analysis method for analyzing a subject image taken by irradiating a subject with radiation and estimating a body thickness distribution of the subject, which is executed in a radiation image analysis device,
An image acquisition step of acquiring the subject image;
Model information for acquiring model information obtained by associating a model image photographed by irradiating the model with radiation and a body thickness distribution of the model image for a plurality of models different from the subject An acquisition step;
Feature information representing features of the subject image is obtained, feature information representing the features of the plurality of model images is obtained based on the plurality of model information, respectively, and similar to the feature information of the subject image A body thickness distribution determining step for identifying the model image having the feature information and determining the body thickness distribution associated with the identified model image as a body thickness distribution of the subject image;
And scatter information acquisition step of acquiring scattered radiation information estimated scattered radiation of the test object image determined above using the body thickness distribution of the test body,
The acquired scatter information and on the basis of the subject image, and a scattered ray removal step for removing processing of scattered radiation the to the subject body image,
The feature information is shooting target information representing a physical feature of the shooting target;
The body thickness distribution determining step acquires a histogram width that is a difference between the maximum value and the minimum value of the signal value of the subject image as the photographing target information of the subject image, and the photographing target of each of the model images A radiological image analysis method characterized by acquiring a histogram width which is a difference between a maximum value and a minimum value of signal values of the model image as information . A radiological image analysis program for analyzing a subject image taken by irradiating a subject with radiation and estimating a body thickness distribution of the subject,
On the computer,
An image acquisition step of acquiring the subject image;
Model information for acquiring model information obtained by associating a model image photographed by irradiating the model with radiation and a body thickness distribution of the model image for a plurality of models different from the subject An acquisition step;
Feature information representing features of the subject image is obtained, feature information representing the features of the plurality of model images is obtained based on the plurality of model information, respectively, and similar to the feature information of the subject image A body thickness distribution determining step for identifying the model image having the feature information and determining the body thickness distribution associated with the identified model image as a body thickness distribution of the subject image;
And scatter information acquisition step of acquiring scattered radiation information estimated scattered radiation of the test object image determined above using the body thickness distribution of the test body,
Obtained on the basis of the scattered radiation information and the subject image, wherein to execute the scattered ray removing step for removing processing of scattered radiation to the subject body image,
The feature information is shooting target information representing a physical feature of the shooting target;
The body thickness distribution determining step acquires a histogram width that is a difference between the maximum value and the minimum value of the signal value of the subject image as the photographing target information of the subject image, and the photographing target of each of the model images A radiological image analysis program characterized by acquiring a histogram width which is a difference between a maximum value and a minimum value of signal values of the model image as information .