Information processing device, information processing method, and information processing program

Abstract

According to the present invention, this information processing device: uses three-dimensional point group data obtained by imaging a reference surface that has a portion overlapping a subject and a radiation detector along an irradiation direction of radiation emitted from a radiation source, to derive information representing the reference surface; and uses the derived information representing the reference surface to derive at least one among the distance between the radiation source and the radiation detector and the incident angle on the reference surface of the radiation emitted from the radiation source.

Description

Information processing device, information processing method, and information processing program

[0001] This disclosure relates to an information processing device, an information processing method, and an information processing program.

[0002] Japanese Patent Publication No. 2011-092612 discloses a technique for calculating the distance between a radiation source and a radiation detector based on the distance between markers captured in an image taken by a camera.

[0003] Incidentally, a technique is known in which the distance between a radiation source and a radiation detector is measured using a distance measuring sensor placed near the radiation source. However, with this technique, it can be difficult to accurately derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation, for example, when an object is present between the radiation source and the radiation detector.

[0004] This disclosure is made in view of the above circumstances and aims to provide an information processing device, an information processing method, and an information processing program that can accurately derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation.

[0005] The information processing device in the first embodiment includes a processor, which uses three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the direction of irradiation of radiation emitted from a radiation source to derive information representing the reference plane, and uses the derived information representing the reference plane to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation emitted from the radiation source with respect to the reference plane.

[0006] In the second embodiment of the information processing apparatus, the processor derives the distance by deriving the intersection point of a straight line along the direction of irradiation and a reference plane in three-dimensional space, compared with the information processing apparatus of the first embodiment.

[0007] In the third embodiment of the information processing apparatus, the processor derives the angle of incidence using the normal vector of the reference plane and inverse trigonometric functions, in the information processing apparatus of the first or second embodiment.

[0008] The fourth embodiment of the information processing device is an information processing device according to any one of the first to third embodiments, in which the processor derives information representing a candidate reference plane using three-dimensional point cloud data, and if the incident angle derived for a candidate reference plane exceeds a threshold, the candidate reference plane is excluded from processing.

[0009] The fifth embodiment of the information processing device is an information processing device according to any one of the first to fourth embodiments, in which the processor derives information representing a reference plane by iterative processing using three-dimensional point cloud data and a regression algorithm.

[0010] The sixth embodiment of the information processing device is an information processing device of any one of the first to fifth embodiments, in which the processor derives the distance between the radiation source and the body surface of the subject by searching for three-dimensional point cloud data along the irradiation direction, and derives information representing a reference plane by excluding data within a range set from the derived distance in the irradiation direction from the three-dimensional point cloud data.

[0011] The information processing method of the seventh embodiment involves an information processing device equipped with a processor, in which the processor derives information representing a reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source, and using the derived information representing the reference plane, performs a process to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane.

[0012] The information processing program of the eighth embodiment causes the processor of an information processing device equipped with a processor to derive information representing a reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the direction of irradiation of radiation emitted from a radiation source, and to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation emitted from the radiation source with respect to the reference plane using the derived information representing the reference plane.

[0013] According to this disclosure, at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation can be accurately derived.

[0014] This is a front view showing an example of a radiography system. This is a side view showing an example of a radiography system. This is a diagram illustrating the positional relationship between the radiation source and the ToF camera. This is a front view showing an example of a radiography system. This is a block diagram illustrating an example of the console's hardware configuration. This is a block diagram illustrating an example of the console's functional configuration. This is a diagram illustrating the SSD derivation process. This is a diagram illustrating the SSD derivation process. This is a diagram illustrating the reference plane derivation process. This is a diagram illustrating the effect of re-deriving the plane. This is a diagram illustrating the incident angle derivation process. This is a diagram illustrating the incident angle derivation process. This is a flowchart illustrating an example of the SID and incident angle derivation process.

[0015] Hereinafter, with reference to the drawings, examples of embodiments for carrying out the technology of this disclosure will be described in detail.

[0016] First, the configuration of the radiography system 1 will be described with reference to Figures 1 and 2. As shown in Figures 1 and 2, the radiography system 1 is a system that takes a radiographic image of a subject H by irradiating the subject H with radiation R such as X-rays, and is operated by a user such as a radiologic technologist. The radiography system 1 includes a radiation source 10, an imaging device 13, a radiation detector 14, a patient table 15, and a console 16. Figure 1 is a front view when looking from the head side to the foot side of the subject H, and Figure 2 is a side view when looking from the right side to the left side of Figure 1. The console 16 is an example of an information processing device relating to the disclosed technology.

[0017] The radiation source 10 includes a radiation tube 11 that emits radiation R and a field limiter (also called a collimator) 12 that limits the irradiation field of radiation R. The radiation tube 11 is provided with, for example, a filament, a target, and a grid electrode. A voltage is applied from a voltage generator between the filament, which is the cathode, and the target, which is the anode. This voltage applied between the filament and the target is called the tube voltage. The filament emits thermionic electrons toward the target in accordance with the applied tube voltage. The target emits radiation R through collisions with thermionic electrons emitted from the filament. The grid electrode is placed between the filament and the target. The grid electrode changes the flow rate of thermionic electrons from the filament toward the target in accordance with the voltage applied from the voltage generator. This flow rate of thermionic electrons from the filament toward the target is called the tube current.

[0018] The irradiation field limiter 12 has an entrance aperture through which radiation R from the radiation tube 11 enters, and an exit aperture through which radiation R exits. Four shielding plates are provided near the exit aperture. The shielding plates are made of a material that shields radiation R, such as lead. The shielding plates are arranged on each side of a rectangle, in other words, in a checkered pattern, forming a rectangular irradiation aperture that allows radiation R to pass through. The irradiation field limiter 12 changes the size of the irradiation aperture by changing the position of each shielding plate, thereby changing the irradiation field of radiation R.

[0019] The imaging device 13 is mounted on the outside of the irradiation field limiter 12. The imaging device 13 includes an optical camera 17 and a ToF (Time of Flight) camera 18 (see Figure 3). The optical camera 17 is a camera capable of capturing R (Red), G (Green), and B (Blue) color images by detecting reflected light from the subject H. The optical camera 17 includes an optical system and an image sensor such as a CCD (Charge Coupled Device) image sensor. The optical camera 17 outputs the image obtained by capturing the subject H (hereinafter referred to as the "optical image") to the console 16. In the example in Figure 1, the imaging device 13 is shown mounted on the outside of the irradiation field limiter 12, but the imaging device 13 may also be mounted on the ceiling or the like. In this case, it is sufficient to be able to obtain the positional relationship between the imaging device 13 and the radiation source 10.

[0020] The ToF camera 18 is a camera capable of capturing a distance image representing the distance between itself and the object being photographed using a ToF sensor. The ToF camera 18 outputs the distance image obtained by photographing the reference plane P to the console 16. Details of the reference plane P will be described later. In this embodiment, the distance in the distance image represents the distance between the focal point of the ToF camera 18 and the object being photographed.

[0021] The radiation detector 14 is portable and acquires a radiation image of the subject H by detecting radiation R that has passed through the subject H. The radiation detector 14 outputs the radiation image of the subject H to the console 16. The radiation detector 14 is used in a position corresponding to the imaging area between the surface of the examination table 15 on which the subject H lies and the subject H. In the example in Figure 1, the examination table 15 is shown as a bed in a hospital room in a supine position, but it may also be in a semi-sitting position, or the examination table 15 may be a supine examination table in an imaging room that houses the radiation detector 14.

[0022] The console 16 has functions for the user to confirm and input radiation irradiation conditions R, and functions for image processing on radiation images obtained by the radiation detector 14. Examples of the console 16 include personal computers or server computers.

[0023] In this embodiment, the reference plane P is a plane that serves as a reference when measuring the thickness of the subject H, and is a plane that has a portion that overlaps with the subject H and the radiation detector 14 along the irradiation direction D of the radiation R irradiated from the radiation source 10. That is, the reference plane P is a plane located in the path along which the radiation R is irradiated. The reference plane P is also the surface of the bed 15 to which at least a part of the subject H is in contact, and is a surface parallel to the radiation detection surface of the radiation detector 14. Here, parallel means parallel within a range that includes tolerance. In the example in Figure 1, the reference plane P is the surface of the bed 15 to which the subject H is in contact. The reference plane P may also be a part of the surface of the bed 15. If the bed 15 is a bed, the reference plane P is the surface of the bed to which the subject H is in contact, and if the bed 15 is a supine imaging table to which the radiation detector 14 is housed, the reference plane P is the surface of the supine imaging table to which the subject H is in contact. The aforementioned distance image also includes distances to objects other than the reference plane P, such as pillows, floors, and subject H.

[0024] In Figure 1, the case where the subject H is in a supine position is illustrated, but the subject H may also be in an upright position. In this case, an upright imaging table is used instead of the bed 15. In this case, the reference plane P is the surface of the upright imaging table, which houses the radiation detector 14 installed in the imaging room, that the subject H is in contact with. Also, in this case, the radiation detector 14 does not have to be portable.

[0025] In Figure 1, arrow Y1 represents the distance between the focal point of the ToF camera 18 and the surface of the bed 15. Arrow Y2 represents the distance between the radiation source 10 and the surface of the bed 15. Hereafter, the distance between the radiation source 10 and the surface of the bed 15 will also be referred to as "SID (Source to Image receptor Distance)". In this embodiment, since the height difference between the surface of the bed 15 and the detection surface of the radiation detector 14 is relatively small, the distance between the radiation source 10 and the surface of the bed 15 will be treated as the distance between the radiation source 10 and the radiation detector 14. In this embodiment, the case where the distance between the focal point of the radiation source 10 and a preset position such as the center of the detection surface of the radiation detector 14 is applied as the SID will be explained as an example. In Figure 1, arrow Y3 represents the distance between the radiation source 10 and the body surface of the subject H. Hereafter, the distance between the radiation source 10 and the body surface of the subject H will also be referred to as "SSD (Source to Surface Distance)".

[0026] Next, with reference to Figure 3, the positional relationship between the focal point of the radiation source 10 and the focal point of the ToF camera 18 will be explained. In this embodiment, a three-dimensional Cartesian coordinate system using the X, Y, and Z axes is used. Below, the direction of the first side of the field of view of the ToF camera 18 (the direction of the long side in this embodiment) will be described as the X-axis direction. The direction of the second side that intersects (orthogonal in this embodiment) the first side of the field of view of the ToF camera 18 (the direction of the short side in this embodiment) will be described as the Y-axis direction. The irradiation direction D of the radiation R will be described as the Z-axis direction. The irradiation direction D of the radiation R means the axis direction of the radiation R that is irradiated in a cone-beam shape. The axis of the radiation R means the axis connecting the focal point of the radiation source 10 and a predetermined position such as the center of the radiation detector 14. The X-axis direction and the Y-axis direction correspond to the width direction and body axis direction of the subject H when the ToF camera 18 and the subject H are facing each other.

[0027] As shown in Figure 3, the distance between the focus of the radiation source 10 and the focus of the ToF camera 18 along the X-axis is represented as Δx. The distance between the focus of the radiation source 10 and the focus of the ToF camera 18 along the Y-axis is represented as Δy. The distance between the focus of the radiation source 10 and the focus of the ToF camera 18 along the Z-axis is represented as Δz. In this embodiment, the focus of the ToF camera 18 is set as the origin in the three-dimensional Cartesian coordinate system. That is, in the example in Figure 3, the coordinates of the focus of the radiation source 10 are represented as (-Δx, Δy, -Δz).

[0028] In such a three-dimensional space, the reference plane P can be expressed by equation (1), which is the equation of a plane. Note that while Figure 1 shows an example where the direction of radiation R D is perpendicular to the reference plane P, as shown in Figure 4, the reference plane P can also be expressed by equation (1) when radiation R is incident obliquely on the reference plane P. ax + by + cz + d = 0 ... (1)

[0029] Referring to Figure 5, the hardware configuration of the console 16 according to this embodiment will be described. As shown in Figure 5, the console 16 includes a CPU (Central Processing Unit) 31, a memory 32 as a temporary storage area, and a non-volatile storage unit 33. The console 16 also includes a display 34 such as a liquid crystal display, input devices 35 such as a keyboard and mouse, and a network interface 36. The CPU 31, memory 32, storage unit 33, display 34, input devices 35, and network interface 36 are connected to a bus 37. The CPU 31 is an example of a processor. The console 16 transmits and receives data to and from the radiation source 10, radiation detector 14, optical camera 17, and ToF camera 18 via the network interface 36.

[0030] The storage unit 33 is implemented by an HDD (Hard Disk Drive), SSD (Solid State Drive), or flash memory, etc. The storage unit 33, as a storage medium, stores the information processing program 40. The CPU 31 reads the information processing program 40 from the storage unit 33, expands it into the memory 32, and executes the expanded information processing program 40.

[0031] Next, referring to FIG. 6, the functional configuration of the console 16 will be described. As shown in FIG. 6, the console 16 includes an acquisition unit 50, a conversion unit 52, a first derivation unit 54, a second derivation unit 56, a third derivation unit 58, and a display control unit 60. When the CPU 31 executes the information processing program 40, it functions as the acquisition unit 50, the conversion unit 52, the first derivation unit 54, the second derivation unit 56, the third derivation unit 58, and the display control unit 60.

[0032] The acquisition unit 50 acquires the distance image obtained by photographing the reference plane P with the ToF camera 18 via the network I / F 36. The conversion unit 52 converts the distance image acquired by the acquisition unit 50 into three-dimensional point cloud data by a known conversion algorithm. At this time, the conversion unit 52 sets the focal point of the ToF camera 18 at the origin and sets the irradiation direction D of the radiation R in the Z-axis direction. The three-dimensional point cloud data obtained by the conversion unit 52 is an example of the three-dimensional point cloud data obtained by photographing the reference plane according to the disclosed technology.

[0033] The first derivation unit 54 derives the SSD by searching the three-dimensional point cloud data obtained by the conversion unit 52 along the irradiation direction D. Specifically, as shown in FIG. 7, the coordinates (X

[0034] , ｘｒａｙ , Y <00……(2)

[0034] ​​​​​​​​​​​​​​​​​For example, as shown in Figure 8, the first derivation unit 54 detects point B2 by searching within a set range of the X-Y plane along the irradiation direction D from point B1, which is the focal point of the radiation source 10. In Figure 8, the set range of the X-Y plane is defined as having a side length in the X-axis direction of X. ｒａｎｇｅ And the length of the side in the Y-axis direction is Y ｒａｎｇｅ This shows an example of a rectangular area. In this case, the set area may also be a circular area. Furthermore, the first derivation unit 54 sequentially searches for multiple points, such as the second and third closest points, not just the point closest to the focal point of the radiation source 10, and calculates the average of the Z coordinates of the multiple points that were searched. Ｓｕｒｆａｃｅ This is also acceptable. This helps to suppress variations in search results due to noise contained in the distance image.

[0035] The second derivation unit 56 derives information representing the reference plane P using the three-dimensional point cloud data obtained by the transformation unit 52. In this embodiment, the second derivation unit 56 derives equation (1) above as information representing the reference plane P. In addition, in this embodiment, the second derivation unit 56 derives information representing the reference plane P by iterative processing using the three-dimensional point cloud data and a regression algorithm. A specific example of the derivation process performed by the second derivation unit 56 will be described below.

[0036] The second derivation unit 56 uses RANSAC (RANDOM SAmple Consensus), a robust algorithm, as the regression algorithm. As an example, as shown in Figure 9, the second derivation unit 56 first randomly selects three points from the 3D point cloud data and derives information representing a plane passing through the three selected points. In the example in Figure 9, point C represents the three points. The second derivation unit 56 derives equation (1), which represents the plane passing through the three points, as information representing the plane.

[0037] Next, as shown in Figure 10, the second derivation unit 56 derives the number of points in the 3D point cloud data whose distance from the derived plane is within a threshold δ. For each of several different sets of three points, the second derivation unit 56 derives information representing the plane and the number of points whose distance from that plane is within a threshold δ. Then, the second derivation unit 56 selects the plane with the largest number of derived points.

[0038] Further, the second derivation unit 56 uses points within a distance of threshold δ from the selected plane to re-derive the plane according to an optimization algorithm such as the least squares method, and uses the information representing the derived plane as the information representing the reference plane P. As shown in FIG. 11 as an example, by re-deriving the plane, the second derivation unit 56 can use, as the reference plane P, a plane closer to the target plane than the plane selected based on the number of points within the distance of threshold δ.

[0039] The third derivation unit 58 uses the information representing the reference plane P derived by the second derivation unit 56 to derive the incident angle of the radiation R irradiated from the radiation source 10 with respect to the reference plane P of the SID. In the present embodiment, the case where the third derivation unit 58 derives both the SID and the incident angle will be described as an example, but the third derivation unit 58 may derive only one of the SID and the incident angle.

[0040] Specifically, the third derivation unit 58 derives the SID by deriving the intersection point A (see FIG. 1) of the straight line along the irradiation direction D and the reference plane P in the three-dimensional space. As described above, the coordinates of the focal point of the radiation source 10 are known coordinates (−Δx, Δy, −Δz), and the second derivation unit 56 derives the equation (1) as the information representing the reference plane P. Therefore, the third derivation unit 58 can derive the SID from the three-dimensional positional relationship between the focal point of the radiation source 10 and the intersection point A.

[0041] Further, the third derivation unit 58 derives the incident angle using the normal vector of the reference plane P and the inverse trigonometric function. Referring to FIGS. 12 and 13, a specific example of the incident angle derivation process executed by the third derivation unit 58 will be described. As shown in FIGS. 12 and 13, the normal vector n, which is the unit normal vector of the reference plane P represented by the equation (1), is (a, b, c), and the unit vector x in the irradiation direction D of the radiation is (0, 0, 1). The relationship between the normal vector n and the unit vector x and the angle θ formed by the normal vector n and the unit vector x is represented by the following equation (3). θ corresponds to the incident angle in the three-dimensional space. x · n = c = cos θ... (3)

[0042] As shown in Figure 13, if ψ is the angle between the vector obtained by projecting the normal vector n onto the Y-Z plane and the direction of illumination D, then tanψ is expressed by equation (4) below. Therefore, ψ is expressed by equation (5) below. ψ corresponds to the angle of incidence in the Y-Z plane. tanψ = b / c ... (4) ψ = atan(b / c) ... (5)

[0043] Similarly, if φ is the angle between the vector obtained by projecting the normal vector n onto the Z-X plane and the direction of illumination D, then tanφ is expressed by equation (6) below. Therefore, φ is expressed by equation (7) below. φ corresponds to the angle of incidence in the Z-X plane. tanφ = a / c ... (6) φ = atan(a / c) ... (7)

[0044] In this embodiment, the third derivation unit 58 derives ψ and φ as the angle of incidence of radiation R with respect to the reference plane P, using the normal vector n(a, b, c) and atan as an example of an inverse trigonometric function, according to equations (5) and (7).

[0045] Furthermore, the third derivation unit 58 may derive θ as the angle of incidence of radiation R with respect to the reference plane P, using the normal vector n(a, b, c) and acos as an example of an inverse trigonometric function, according to equation (8) below: θ = acos(c) ... (8)

[0046] The display control unit 60 controls the display of the SID and incident angle derived by the third derivation unit 58. For example, the display control unit 60 controls the display of the SID and incident angle derived by the third derivation unit 58 on a display provided on the outer surface of the irradiation field limiter 12. As a result, the user can grasp the SID and incident angle, thereby supporting the positioning work of the radiation source 10 and subject H performed by the user. The display control unit 60 may also control the display of the SID and incident angle on the display 34, on a display installed on a display cart with casters, or on multiple displays.

[0047] Next, the operation of the console 16 will be explained with reference to Figure 14. The CPU 31 executes the information processing program 40, which performs the SID and incidence angle derivation process shown in Figure 14. The SID and incidence angle derivation process is performed, for example, when the user inputs an instruction to start execution, or when the position of the radiation source 10 is changed.

[0048] In step S10 of Figure 14, the acquisition unit 50 acquires a distance image obtained by photographing the reference plane P with the ToF camera 18 via the network I / F 36. In step S12, the conversion unit 52 converts the distance image acquired in step S10 into 3D point cloud data. In step S14, the first derivation unit 54 derives the SSD by searching the 3D point cloud data obtained by the processing in step S12 along the irradiation direction D.

[0049] In step S16, the second derivation unit 56 derives information representing the reference plane P using the three-dimensional point cloud data obtained in step S12. In step S18, the third derivation unit 58 derives the SID and the incident angle of the radiation R irradiated from the radiation source 10 with respect to the reference plane P using the information representing the reference plane P derived in step S16. In step S20, the display control unit 60 controls the display of the SID and incident angle derived in step S18. When the processing in step S20 is completed, the derivation process of the SID and incident angle is completed.

[0050] As described above, according to this embodiment, the SID and the incident angle of radiation can be derived with high accuracy.

[0051] In the above embodiment, the case in which a distance image is captured by a ToF camera 18 has been described, but the disclosed technology is not limited to this embodiment. For example, the distance image may be captured by a stereo camera.

[0052] Furthermore, in the above embodiment, the second derivation unit 56 may derive a plane passing through the three selected points as a candidate reference plane P, and if the angle of incidence of radiation R with respect to the candidate reference plane P exceeds a threshold, the candidate reference plane P may be excluded from processing. Specifically, in this case, the second derivation unit 56 may omit the process of deriving the number of points whose distance is within the threshold δ for the candidate reference plane P. This reduces the computation cost. The second derivation unit 56 can derive the angle of incidence in this case in the same way as the third derivation unit 58.

[0053] Furthermore, in the above embodiment, the second derivation unit 56 may derive information representing the reference plane P after excluding data within a range set from the SSD derived by the first derivation unit 54 in the irradiation direction D from the 3D point cloud data. For example, the second derivation unit 56 may exclude data within a set range from the 3D point cloud data, or it may exclude data outside a set range from the 3D point cloud data. As a result, the second derivation unit 56 can derive information representing the reference plane P after removing data near the body surface of the subject H that is presumed not to be in contact with the surface of the bed 15 from the 3D point cloud data. This can reduce computation costs. Note that the second derivation unit 56 may set a range that is not excluded from the 3D point cloud data.

[0054] Furthermore, in the above embodiment, if the reference plane P and the detection surface of the radiation detector 14 are separated along the Z-axis direction and their positional relationship is known, the third derivation unit 58 may derive SID by adding the distance between the reference plane P and the detection surface of the radiation detector 14 along the Z-axis direction to the distance between the focal point of the radiation source 10 and the intersection point A.

[0055] Furthermore, at least one of the functional units of the console 16 in the above embodiment may be provided by other devices such as the control unit of the radiation source 10, the control unit of the imaging device 13, and the control unit of the radiation detector 14.

[0056] Furthermore, in the above embodiments, each process is executed on any computer. The computer may execute these processes using a processor as hardware, a program as software, or a combination thereof. In this case, the processor is configured to work in cooperation with the program to execute the various processes in the above embodiments, and can function as a unit or means in the above embodiments. The execution order of the processes by the processor is not limited to the order described and may be changed as appropriate. The computer may be a general-purpose computer, a computer designed for a specific purpose, a workstation, or any other system capable of executing each process.

[0057] A processor may consist of one or more hardware components, and the type of hardware is not limited. For example, a processor may consist of programmable logic devices such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), FPGA (Field Programmable Gate Array), dedicated circuits for performing specific processing such as an ASIC (Application Specific Integrated Circuit), a GPU (Graphic Processing Unit), or an NPU (Neural Processing Unit). Furthermore, the type of hardware may be a combination of different types of hardware. When multiple hardware components are configured to execute one or more processes of a processor, these components may reside in physically separate devices or in the same device. Furthermore, in any embodiment, the order of the processes performed by the processor is not limited to the order described above and may be changed as appropriate. The hardware components are composed of electrical circuits (circuits) and the like, which are combinations of circuit elements such as semiconductor elements.

[0058] Furthermore, the program may be firmware or software such as microcode. Alternatively, the program may be, for example, a set of program modules, each function of which may be implemented by a processor configured to perform its respective function. The program may be program code or multiple code segments stored on one or more non-temporary computer-readable media (e.g., storage media or other storage). The program may be divided and stored on multiple non-temporary computer-readable media located on physically separate devices. Program code or code segments may represent any combination of procedures, functions, subprograms, routines, subroutines, modules, software packages, classes, or instructions, data structures, or program statements. Program code or code segments may be connected to other code segments or hardware circuits by sending and receiving information, data, arguments, parameters, or memory contents.

[0059] Furthermore, although the above embodiment describes an embodiment in which the information processing program 40 is pre-stored (installed) in the storage unit 33, the invention is not limited to this. The information processing program 40 may be provided in the form of being recorded on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), and USB (Universal Serial Bus) memory. The information processing program 40 may also be provided in the form of being downloaded from an external device via a network. The information processing program 40 can also be provided as a program product. A program product includes any form of product for providing a program. For example, a program product includes a program provided via a network such as the Internet, and a non-temporary computer-readable recording medium such as a CD-ROM or DVD on which the program is stored.

[0060] The following further notes are disclosed regarding the above embodiments. (Note 1) An information processing device comprising a processor, wherein the processor derives information representing the reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source, and uses the derived information representing the reference plane to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane.

[0061] (Note 2) The information processing apparatus according to Note 1, wherein the processor derives the distance by deriving the intersection point of a straight line along the irradiation direction and the reference plane in three-dimensional space.

[0062] (Note 3) The information processing apparatus according to Note 1 or Note 2, wherein the processor derives the incident angle using the normal vector of the reference plane and an inverse trigonometric function.

[0063] (Note 4) The information processing apparatus according to any one of Notes 1 to 3, wherein the processor derives information representing a candidate reference surface using the three-dimensional point cloud data, and if the incident angle derived for the candidate reference surface exceeds a threshold, the candidate reference surface is excluded from processing.

[0064] (Note 5) The information processing device according to any one of Notes 1 to 4, wherein the processor derives information representing the reference plane by iterative processing using the three-dimensional point cloud data and a regression algorithm.

[0065] (Note 6) The information processing device according to any one of Notes 1 to 5, wherein the processor derives the distance between the radiation source and the body surface of the subject by searching the three-dimensional point cloud data along the irradiation direction, and derives information representing the reference plane after excluding data within a range set from the derived distance in the irradiation direction from the three-dimensional point cloud data.

[0066] (Note 7) An information processing method comprising an information processing device equipped with a processor, wherein the processor derives information representing the reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source, and uses the derived information representing the reference plane to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane.

[0067] (Note 8) An information processing program for causing the processor of an information processing device equipped with a processor to perform the following processes: using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source, to derive information representing the reference plane; and using the derived information representing the reference plane, to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane.

[0068] The disclosure of Japanese Patent Application No. 2025-017421, filed on 5 February 2025, is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated as being incorporated by reference.

Claims

1. An information processing device comprising a processor, wherein the processor derives information representing the reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source, and uses the derived information representing the reference plane to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane.

2. The information processing apparatus according to claim 1, wherein the processor derives the distance by deriving the intersection point of a straight line along the irradiation direction and the reference plane in three-dimensional space.

3. The information processing apparatus according to claim 1 or 2, wherein the processor derives the incident angle using the normal vector of the reference plane and an inverse trigonometric function.

4. The information processing apparatus according to claim 1 or 2, wherein the processor derives information representing a candidate reference surface using the three-dimensional point cloud data, and excludes the candidate reference surface from processing if the incident angle derived for the candidate reference surface exceeds a threshold.

5. The information processing apparatus according to claim 1 or 2, wherein the processor derives information representing the reference plane by iterative processing using the three-dimensional point cloud data and a regression algorithm.

6. The information processing apparatus according to claim 1 or 2, wherein the processor derives the distance between the radiation source and the body surface of the subject by searching the three-dimensional point cloud data along the irradiation direction, and derives information representing the reference plane after excluding data within a range set from the derived distance in the irradiation direction from the three-dimensional point cloud data.

7. An information processing method comprising an information processing device having a processor, wherein the processor derives information representing the reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source, and uses the derived information representing the reference plane to derive at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane.

8. An information processing program for causing the processor of an information processing device equipped with a processor to perform the following processes: deriving information representing a reference plane using three-dimensional point cloud data obtained by photographing a reference plane having a portion that overlaps with the subject and the radiation detector along the irradiation direction of the radiation irradiated from the radiation source; and deriving at least one of the distance between the radiation source and the radiation detector and the angle of incidence of the radiation irradiated from the radiation source with respect to the reference plane using the derived information representing the reference plane.

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