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

Abstract

This information processing device performs: a distance image acquisition process for acquiring a distance image generated through a distance image capturing device capturing an image of an imaging range including a subject and a detection surface; a detection surface area search process for searching the distance image for a detection surface area in which a portion of the detection surface is present; a first distance acquisition process for acquiring, on the basis of the distance image, the distance of the thus found detection surface area as a first distance from the distance image capturing device to the detection surface; a second distance acquisition process for acquiring, on the basis of the distance image, the distance from the distance image capturing device to the subject as a second distance; and a body thickness derivation process for deriving, as the subject's body thickness, the difference between the first distance and the second distance.

Description

Technical Field

[0001] The technology of the present disclosure relates to an information processing apparatus, an information processing method, a program, and a radiation imaging system.

Background Art

[0002] In radiation imaging, it is desirable to appropriately set radiation imaging conditions according to the thickness of a subject such as a patient. Radiation imaging conditions include the tube voltage of a radiation source and the tube current-time product. Setting the radiation imaging conditions so that radiation imaging is performed with an appropriate radiation dose according to the thickness of the subject is desirable both for obtaining clinically sufficient image quality and for suppressing excessive exposure to the subject.

[0003] The thickness of the subject varies depending on the subject to be imaged by radiation. Therefore, in order to appropriately set the radiation imaging conditions, it is necessary to accurately measure the thickness of the subject. JP-A-2017-136300 and JP-A-2018-196791 disclose methods for measuring the thickness of a subject.

[0004] JP-A-2017-136300 discloses calculating the thickness of a subject based on distance image information obtained by performing optical imaging of the subject. More specifically, JP-A-2017-136300 describes calculating the thickness of a subject based on the first distance from an optical sensor to the irradiation side of the subject and the second distance from the optical sensor to the imaging table based on the distance image information obtained by the optical sensor.

[0005] JP-A-2018-196791 describes measuring the SID (Source Image receptor Distance), which is the distance between a radiation irradiation device (i.e., a radiation source) and the surface of a radiation detector, and the SOD (Source Object Distance), which is the distance between the radiation irradiation device and the surface of the subject, by a distance sensor, and obtaining the thickness of the subject by subtracting the SOD from the SID. [Overview of the project] [Problems that the invention aims to solve]

[0006] The techniques described in Japanese Patent Publication No. 2017-136300 and Japanese Patent Publication No. 2018-196791 are both techniques for calculating the thickness of an object by determining the difference between a first distance from a distance measuring sensor to the detection surface of a radiation detector and a second distance from the sensor to the object.

[0007] However, during radiography, the subject is positioned on the detection surface, and the subject obstructs the view, making it difficult to determine the first distance from the distance information obtained by the sensor. While it is conceivable to measure the first distance in advance, the first distance may vary each time radiography is performed. In particular, in radiography systems where the radiation source and radiation detector are independent, variations occur in the first distance each time the radiographer prepares for radiography, making it impossible to measure the first distance in advance.

[0008] Japanese Patent Publication No. 2017-136300 and Japanese Patent Publication No. 2018-196791 do not describe specific methods for determining the first distance. Therefore, the techniques described in Japanese Patent Publication No. 2017-136300 and Japanese Patent Publication No. 2018-196791 cannot accurately determine the thickness of the subject.

[0009] The technology disclosed herein aims to provide an information processing device, an information processing method, a program, and a radiography system that enable accurate determination of the thickness of a subject. [Means for solving the problem]

[0010] To achieve the above objective, the information processing device of the present disclosure is used in a radiography system comprising a radiation source and a radiation image detector having a detection surface to which radiation from the radiation source is irradiated and to which an object is positioned, and is an information processing device that performs processing to derive the thickness of an object, comprising a processor, the processor performing: a distance image acquisition process to acquire a distance image generated by capturing an imaging range including the object and the detection surface with a distance image capture device; a detection surface area search process to search for a detection surface area in which a part of the detection surface exists from the distance image; a first distance acquisition process to acquire the distance of the searched detection surface area as a first distance from the distance image capture device to the detection surface based on the distance image; a second distance acquisition process to acquire the distance from the distance image capture device to the object as a second distance based on the distance image; and a thickness derivation process to derive the difference between the first distance and the second distance as the thickness of the object.

[0011] In the second distance acquisition process, the processor preferably acquires the distance to the radiation center coordinates corresponding to the center of the radiation beam irradiated from the radiation source toward the subject, based on the distance image, as the second distance.

[0012] In the second distance acquisition process, the processor preferably derives the radiation center coordinates based on the relative positional relationship between the distance image acquisition device and the radiation source.

[0013] In the detection surface area search process, the processor preferably sets a region of interest where the detection surface area is estimated to exist, based on a provisional setting value that is provisionally set as a value corresponding to the first distance and the size of the detection surface, and searches for the detection surface area using the set region of interest as the search range.

[0014] In the detection surface area search process, the processor preferably excludes abnormal pixels with abnormal pixel values ​​from the area of ​​interest, and derives the area with the maximum distance among the areas from which abnormal pixels have been excluded as the detection surface area.

[0015] The region of interest is preferably the region that includes the edge of the radiation image detector and the background outside the radiation image detector.

[0016] In the detection area search process, the processor preferably excludes pixels that are at a certain distance or greater and correspond to the background, as well as flying pixels that appear at the boundary between the edge and the background, from the area of ​​interest as abnormal pixels.

[0017] In the detection surface area search process, the processor preferably sets the position of the area of ​​interest according to the area of ​​the subject being photographed.

[0018] The distance imaging device is preferably a TOF (Time-of-Flight) type distance imaging camera.

[0019] The radiography system of this disclosure is a radiography system equipped with any of the above-described information processing devices, wherein radiography conditions are determined based on the body thickness derived by the body thickness derivation process.

[0020] It is preferable that the determined radiography conditions can be changed by the user.

[0021] The information processing method disclosed herein is used in a radiography system comprising a radiation source and a radiation image detector having a detection surface to which radiation from the radiation source is irradiated and to which an object is positioned, and includes deriving the thickness of an object, comprising: acquiring a depth image generated by photographing a shooting range including the object and the detection surface with a depth image capture device; searching for a detection surface region in which a part of the detection surface exists from the depth image; acquiring the distance of the searched detection surface region based on the depth image as a first distance from the depth image capture device to the detection surface; acquiring the distance from the depth image capture device to the object as a second distance based on the depth image; and deriving the difference between the first distance and the second distance as the thickness of the object.

[0022] The program of the present disclosure is a program for causing a computer to execute a process including deriving the body thickness of a subject, and is used in a radiographic imaging system including a radiation source and a radiation image detector having a detection surface irradiated with radiation from the radiation source and on which the subject is positioned. The program includes: acquiring a distance image generated by imaging a imaging range including the subject and the detection surface with a distance image imaging device; searching for a detection surface region where a part of the detection surface exists from the distance image; acquiring, based on the distance image, the distance of the searched detection surface region as a first distance from the distance image imaging device to the detection surface; acquiring, based on the distance image, the distance from the distance image imaging device to the subject as a second distance; and deriving the difference between the first distance and the second distance as the body thickness of the subject.

Effect of the Invention

[0023] According to the technology of the present disclosure, it is possible to provide an information processing device, an information processing method, a program, and a radiographic imaging system that can accurately obtain the body thickness of a subject.

Brief Description of the Drawings

[0024] [Figure 1] It is a diagram showing an example of the configuration of an X-ray imaging system. [Figure 2] It is a block diagram showing an example of the hardware configuration of an X-ray imaging system. [Figure 3] It is a block diagram showing an example of the functional configuration of an X-ray imaging condition determination unit. [Figure 4] It is a diagram showing an example of a distance image generated by a distance image camera. [Figure 5] It is a diagram for explaining an example of a detection surface region search process. [Figure 6] It is a diagram for explaining an example of a detection surface region search process and a first distance acquisition process. [Figure 7] It is a diagram for explaining an example of a first distance acquisition process. [Figure 8] It is a diagram for explaining in detail an example of a setting process of a target region by a detection surface region search unit. [Figure 9]This diagram illustrates an example of the process for deriving body thickness. [Figure 10] This figure shows an example of a shooting conditions table. [Figure 11] This figure shows an example of the processing flow using an X-ray imaging system. [Figure 12] This figure shows an example of area of ​​interest information. [Figure 13] This is a diagram showing a modified version of the shooting conditions table. [Figure 14] This diagram shows a modified example of the processing flow using an X-ray imaging system. [Modes for carrying out the invention]

[0025] Figure 1 shows an example of the configuration of an X-ray imaging system 2 that uses X-rays as radiation. The X-ray imaging system 2, which uses X-rays as radiation, comprises an X-ray source 10, an X-ray image detector 20, a console 30, and a repeater 50. A depth image camera 40 is attached to the X-ray source 10. The console 30 communicates with the X-ray source 10, the X-ray image detector 20, and the depth image camera 40 via the repeater 50. The repeater 50 functions, for example, as an access point.

[0026] The X-ray source 10 is an example of a radiation source that generates radiation. The X-ray image detector 20 is an example of a "radiation image detector" that detects radiation and generates a radiation image.

[0027] The X-ray source 10, X-ray image detector 20, and console 30 of this embodiment are all small, portable devices. The X-ray imaging system 2 of this embodiment can be carried to sites requiring emergency medical response, such as accidents and disasters, or to the homes of patients receiving home medical care, for X-ray imaging.

[0028] In the X-ray imaging system 2, the X-ray image detector 20 is positioned so that its detection surface 20A faces the X-ray source 10. By placing the subject H between the X-ray source 10 and the X-ray image detector 20, the area of ​​subject H can be X-rayed. In the example shown in Figure 1, the area of ​​subject H is the abdomen.

[0029] The X-ray source 10 is held by, for example, a holding device 60. The holding device 60 is, for example, a quadruped having four support legs 61 and a crossbar 62. The upper ends of the support legs 61 and both ends of the crossbar 62 are connected to a three-pronged joint 63, thereby assembling the holding device 60. The crossbar 62 is provided with a mounting fixture 64 for mechanically attaching the X-ray source 10. The X-ray source 10 is suspended by the mounting fixture 64 such that the direction of X-ray irradiation 4 is directed downwards.

[0030] An irradiation switch 11 is connected to the X-ray source 10 via cable 11A. A user such as a radiologist or physician using the X-ray imaging system 2 can start irradiating the X-ray source 10 with X-rays 4 by operating the irradiation switch 11.

[0031] The X-ray image detector 20 has an automatic X-ray detection function that detects the start of irradiation of X-rays 4 emitted from the X-ray source 10. Therefore, the X-ray image detector 20 does not need to be connected to the X-ray source 10. In addition, since the X-ray image detector 20 has a built-in battery and wireless communication function, it does not need to be connected to a power supply or console 30 via a cable. The X-ray image detector 20 is wirelessly connected to the repeater 50 and communicates with the console 30 via the repeater 50.

[0032] The console 30 is, for example, composed of a personal computer and has a display unit 31 and an input operation unit 32. The console 30 is connected to a repeater 50 via, for example, a communication cable 51. The display unit 31 is a display device such as a liquid crystal display or an organic EL (Electro-Luminescence) display. The input operation unit 32 is an input device including a keyboard, mouse, or touchpad. The console 30 is an example of an "information processing device" related to the technology of this disclosure.

[0033] The user can input patient information, imaging site, and imaging conditions by operating the input operation unit 32. The display unit 31 shows the X-ray image received by the console 30 from the X-ray image detector 20.

[0034] The distance imaging camera 40 is positioned, for example, near the irradiation field limiter 17 included in the X-ray source 10. For example, the distance imaging camera 40 is a Time of Flight (TOF) type distance imaging camera. Specifically, the distance imaging camera 40 emits illumination light, such as infrared light, toward the object to be photographed, and measures the time from the emission of the illumination light to the reception of the reflected light to measure the distance between the distance imaging camera 40 and the object to be photographed. Alternatively, the distance imaging camera 40 may emit amplitude-modulated illumination light, such as infrared light, toward the object to be photographed, and measure the distance between the distance imaging camera 40 and the object to be photographed based on the phase delay amount of the reflected light relative to the illumination light. Furthermore, the distance imaging camera 40 may be a laser scanning type TOF camera that measures distance by scanning the object to be photographed with laser light.

[0035] The depth image captured by the depth image camera 40 has distance information for each pixel that represents the distance between the depth image camera 40 and the object being photographed. A depth image is an image that has distance information that makes it possible to derive the distance to the object being photographed. The depth image camera 40 is an example of a "distance image capturing device" related to the technology of this disclosure.

[0036] In this embodiment, as shown in Figure 1, the depth image camera 40 captures a depth image with a shooting range 41 that includes the area to be photographed of the subject H and the detection surface 20A of the X-ray image detector 20. For example, the shooting range 41 is a rectangular area larger than the detection surface 20A.

[0037] The X-ray source 10 and the depth image camera 40 are wirelessly connected to a repeater 50 and communicate with the console 30 via the repeater 50. The depth image DP (see Figure 2) generated by the depth image camera 40 is transmitted to the console 30 via the repeater 50. In this embodiment, the console 30 derives the body thickness of the subject H at the imaging site (hereinafter simply referred to as the body thickness of the subject H) based on the depth image DP received from the depth image camera 40.

[0038] Furthermore, the console 30 determines the X-ray imaging conditions SC based on the derived body thickness and transmits the determined X-ray imaging conditions SC to the X-ray source 10 via the repeater 50. The X-ray imaging conditions SC include the tube voltage and the tube current-time product. The X-ray source 10 generates X-rays 4 based on the X-ray imaging conditions SC received from the console 30 and emits the generated X-rays 4 toward the X-ray image detector 20.

[0039] Figure 2 shows an example of the hardware configuration of the X-ray imaging system 2. The X-ray source 10 includes a processor 12, an input control unit 13, a communication interface 14, a high-voltage generator 15, an X-ray tube 16, and an irradiation field limiter 17. The processor 12 functions as a control unit that controls the operation of the high-voltage generator 15 and the irradiation field limiter 17. The irradiation switch 11 described above is connected to the processor 12. The input control unit 13 is also connected to the processor 12. The input control unit 13 includes buttons for manually setting the tube voltage and tube current-time product of the X-ray tube 16, an irradiation field button for adjusting the size of the irradiation field of the irradiation field limiter 17, and a power button, etc.

[0040] The processor 12 controls the high-voltage generator 15 and the irradiation field limiter 17 based on the setting conditions set by the input operation unit 13. The processor 12 generates a high voltage in the high-voltage generator 15 in response to the operation of the irradiation switch 11. The communication I / F 14 is wirelessly connected to the repeater 50.

[0041] The X-ray tube 16 is, for example, a fixed anode type X-ray tube without a target rotation mechanism. The X-ray tube 16 consists of a cold cathode electron source that emits electrons, an electron accelerator, a target that generates X-rays 4 by electron collisions, and an outer tube that houses these components. The cold cathode electron source does not require a filament and a heater to heat it, as in the case of a hot cathode. The X-ray tube 16 is small and lightweight because it does not have a target rotation mechanism, a filament, or a heater. Furthermore, since the X-ray tube 16 does not require preheating of the filament, it is possible to generate X-rays 4 immediately in response to the irradiation start command.

[0042] The irradiation field limiter 17 limits the irradiation field of the X-rays 4 generated by the X-ray tube 16. The X-rays 4 generated by the X-ray tube 16 are irradiated onto the imaging area of ​​the subject H with the irradiation field limited by the irradiation field limiter 17. The X-rays 4 that have passed through the imaging area of ​​the subject H are incident on the X-ray image detector 20.

[0043] The depth image camera 40 is connected, for example, to the communication interface 14 of the X-ray source 10. The depth image camera 40 transmits the depth image DP generated by capturing the imaging range 41 (see Figure 1) to the console 30 via the communication interface 14 and the repeater 50. It is also possible to connect the X-ray source 10 and the depth image camera 40 to the repeater 50 via a wired connection using a communication cable.

[0044] The X-ray image detector 20 includes a processor 21, an X-ray detection panel 22, a memory 23, and a communication interface 24. The processor 21 functions as a control unit that controls various parts within the X-ray image detector 20. The X-ray detection panel 22 is, for example, a flat panel detector having a matrix substrate in which multiple pixels, each consisting of thin-film transistors (TFTs) and X-ray detection elements, are arranged in two dimensions.

[0045] The X-ray detection panel 22 converts incident X-rays into charge using an X-ray detection element and stores it in the charge storage state when the TFT is turned off. Then, in the charge readout state when the TFT is turned on, the charge stored in the X-ray detection element is read out to the signal processing circuit. In the signal processing circuit, the readout charge is converted into a voltage signal using an integrating amplifier, and the converted voltage signal is converted to digital by an A / D converter to generate digital image data. Hereinafter, this image data will be referred to as the X-ray image XP.

[0046] Memory 23 is a non-volatile memory such as flash memory, and stores the X-ray image XP generated by the X-ray detection panel 22. The communication interface 24 is wirelessly connected to the repeater 50. The processor 21 transmits the X-ray image XP stored in memory 23 to the console 30 via the repeater 50. It is also possible to connect the X-ray image detector 20 to the repeater 50 via a communication cable.

[0047] The console 30 comprises a display unit 31, an input operation unit 32, a processor 33, RAM (Random Access Memory) 34, non-volatile memory (NVM) 35, and a communication interface 36. The processor 33 is, for example, a CPU (Central Processing Unit). The RAM 34 is work memory for the processor 33 to execute processing. The NVM 35 is a storage device such as flash memory and stores the program 37. The console 30 is an example of a "computer" related to the technology of this disclosure.

[0048] The processor 33 loads the program 37 stored in the NVM 35 into the RAM 34 and executes processing according to the program 37, thereby functioning as a console control unit 38 that comprehensively controls each part of the console 30, and an X-ray imaging condition determination unit 39.

[0049] The console control unit 38 enables input of patient information and imaging area, etc., using the input operation unit 32 by displaying a GUI (Graphical User Interface) screen on the display unit 31. The console control unit 38 also displays the X-ray image XP received from the X-ray image detector 20 on the display unit 31.

[0050] The X-ray imaging condition determination unit 39 derives the body thickness of the subject H based on the distance image DP transmitted from the distance image camera 40, and determines the X-ray imaging condition SC based on the derived body thickness.

[0051] Figure 3 shows an example of the functional configuration of the X-ray imaging condition determination unit 39. The X-ray imaging condition determination unit 39 consists of a distance image acquisition unit 70, a detection surface area search unit 71, a first distance acquisition unit 72, a second distance acquisition unit 73, a body thickness derivation unit 74, and a selection unit 75. The X-ray imaging condition determination unit 39 derives the body thickness and determines the X-ray imaging conditions based on information such as the provisional setting value D1T, panel size L, relative position information RT, imaging area information SP, and imaging condition table ST stored in the NVM 35.

[0052] The distance image acquisition unit 70 performs distance image acquisition processing to acquire the distance image DP transmitted from the distance image camera 40. The distance image acquisition unit 70 supplies the acquired distance image DP to the detection surface area search unit 71, the first distance acquisition unit 72, and the second distance acquisition unit 73.

[0053] Figure 4 shows an example of a depth image DP generated by the depth image camera 40. As shown in Figure 4, the depth image camera 40 generates a depth image DP by capturing the shooting range 41 which includes the subject H and the detection surface 20A. In the depth image DP, distance is represented by density. In the depth image DP, areas with higher density indicate a greater distance from the depth image camera 40.

[0054] The depth image camera 40 has a defined distance range in which distance measurement is possible, and the first pixel region 80 containing pixels whose distance from the depth image camera 40 is greater than or equal to a certain value is set to maximum density (for example, black). For example, the depth image camera 40 identifies the pixel region that shows a distance greater than or equal to a certain value that is longer than the distance from the depth image camera 40 to the detection surface 20A as the first pixel region 80.

[0055] Furthermore, the depth image camera 40 sets the second pixel region 81, which includes flying pixels occurring at the edges of the object, to the minimum density (e.g., white). Flying pixels are "blurred" pixels that appear at the boundary between the object and the background. Flying pixels are known, for example, by Japanese Patent No. 6143747. In the example shown in Figure 4, the second pixel region 81 occurs at the boundary between the edge of the X-ray image detector 20 and the background, and at the boundary between the subject H and the background.

[0056] Furthermore, the identification and density modification of the first pixel region 80 and the second pixel region 81 from the depth image DP are not limited to the depth image camera 40, but may also be performed inside the console 30.

[0057] The detection surface area search unit 71 performs a detection surface area search process to search for a detection surface area DA (see Figure 5) in which a part of the detection surface 20A exists, using the distance image DP.

[0058] Figures 5 and 6 illustrate an example of the detection surface area search process. As shown in Figure 5, the detection surface area search unit 71 sets a region of interest (ROI) in the area where the detection surface area DA is estimated to exist within the distance image DP, and searches for the detection surface area DA using the set region of interest ROI as the search range. For example, the region of interest ROI is rectangular. Also, the region of interest ROI is smaller than the area corresponding to the detection surface 20A. The region of interest ROI is an area that includes the edge of the X-ray image detector 20 and the background outside the X-ray image detector 20.

[0059] In the example shown in Figure 5, the detection surface area search unit 71 sets the region of interest (ROI) to include the corners of the detection surface 20A. Also, in the example shown in Figure 5, the area of ​​the subject H being photographed is the abdomen, and a portion of the detection surface 20A is exposed on both sides of the subject H's waist. Therefore, the detection surface area search unit 71 sets a pair of region of interest (ROIs) on both sides of the subject H's waist, corresponding to the corners of the detection surface 20A. Note that the detection surface area search unit 71 only needs to set at least one region of interest (ROI) within the depth image DP.

[0060] As shown in Figure 6, the detection surface area search unit 71 excludes abnormal pixels with abnormal pixel values ​​from the region of interest (ROI). Specifically, the detection surface area search unit 71 excludes the first pixel region 80 with the highest density and the second pixel region 81 with the lowest density from the region of interest (ROI). Next, the detection surface area search unit 71 derives the region with the greatest distance from the region of interest (ROI) from which the abnormal pixels have been excluded as the detection surface area DA. The region from which the abnormal pixels have been excluded may include a part of the subject H, but since the subject H is located on the distance image camera 40 side of the detection surface 20A, the distance is shorter than that of the detection surface 20A. Therefore, the detection surface area DA corresponds to the detection surface 20A.

[0061] Furthermore, if two or more ROIs of interest are set within the distance image DP, the detection surface area search unit 71 searches for a detection surface area DA from each of the ROIs of interest.

[0062] The first distance acquisition unit 72 performs a first distance acquisition process based on the distance image DP, acquiring the distance of the detection surface area DA searched by the detection surface area search unit 71 as the first distance D1 from the distance image camera 40 to the detection surface 20A. If the detection surface area search unit 71 extracts multiple detection surface areas DA and the distances differ for each detection surface area DA, the first distance acquisition unit 72 acquires the maximum distance as the first distance D1.

[0063] Figure 7 illustrates the details of the process by which the detection surface area search unit 71 sets the region of interest (ROI). The region in the depth image DP in which the detection surface area DA is estimated to exist depends on the distance from the depth image camera 40 to the detection surface 20A and the size of the detection surface 20A. Therefore, in this embodiment, the detection surface area search unit 71 sets the region of interest (ROI) based on the provisional setting value D1T and the panel size L stored in the NVM 35. The provisional setting value D1T is a value that has been provisionally set in advance as a value corresponding to the first distance D1. The panel size L corresponds to the size of the detection surface 20A and represents, for example, the length of the detection surface 20A in the X direction.

[0064] For example, the provisional setting value D1T is set based on the size of the holding device 60 and the X-ray source 10. The provisional setting value D1T and the panel size L may be set by the user using the input operation unit 32.

[0065] The distance image camera 40 includes a light source 42 that emits illumination light 42A, such as infrared light, toward the shooting range 41, and an image sensor 43 that receives reflected light 43A from the shooting range 41. The shooting range 41 corresponds to the field of view θ of the image sensor 43. The detection surface area search unit 71 determines the position corresponding to the corner of the detection surface 20A from a geometric relationship based on the provisional setting value D1T and the panel size L, and sets the region of interest (ROI) to include the corner of the detection surface 20A.

[0066] The second distance acquisition unit 73 performs a second distance acquisition process to acquire the distance from the distance image camera 40 to the subject H as the second distance D2, based on the distance image DP. Specifically, as shown in Figure 8, the second distance acquisition unit 73 acquires the distance of the X-ray center coordinate C, which corresponds to the center of the beam of X-rays 4 irradiated from the X-ray source 10 toward the subject H, as the second distance D2. More specifically, the second distance acquisition unit 73 derives the X-ray center coordinate C based on relative position information RT (see Figure 3), which represents the relative positional relationship between the distance image camera 40 and the X-ray source 10 (see Figure 7), and the first distance D1 acquired by the first distance acquisition unit 72, and acquires the distance of the derived X-ray center coordinate C as the second distance D2. The second distance acquisition unit 73 may also derive the X-ray center coordinate C using a provisional setting value D1T instead of the first distance D1. The X-ray center coordinate C is an example of a "radiation center coordinate" related to the technology of this disclosure.

[0067] The body thickness derivation unit 74 performs a body thickness derivation process in which the difference between the first distance D1 obtained by the first distance acquisition unit 72 and the second distance D2 obtained by the second distance acquisition unit 73 is derived as the body thickness BT (see Figure 9). Specifically, as shown in Figure 9, the body thickness derivation unit 74 derives the body thickness BT by subtracting the second distance D2 from the first distance D1.

[0068] The selection unit 75 determines the X-ray imaging conditions SC based on the body thickness BT derived by the body thickness derivation unit 74. Specifically, the selection unit 75 selects the X-ray imaging conditions SC corresponding to the body thickness BT and the imaging area information SP from the imaging conditions table ST stored in the NVM 35, and outputs the selected X-ray imaging conditions SC to the X-ray source 10. The imaging area information SP may be set by the user using the input operation unit 32. Note that the X-ray imaging conditions SC is an example of "radiography conditions" related to the technology of this disclosure.

[0069] Figure 10 shows an example of an imaging conditions table ST. The imaging conditions table ST associates body thickness BT and X-ray imaging conditions SC for each imaging area. The selection unit 75 selects from the imaging conditions table ST the X-ray imaging conditions SC that are most suitable for the imaging area represented by the body thickness BT derived by the body thickness derivation unit 74 and the imaging area information SP. The X-ray imaging conditions SC are defined, for example, by the tube voltage and tube current-time product of the X-ray tube 16.

[0070] Next, the operation of the X-ray imaging system 2 with the above configuration will be explained with reference to the flowchart shown in Figure 11.

[0071] Prior to imaging, the user, such as a physician, inputs patient information and imaging area information SP to the X-ray source 10 and console 30, and then positions the imaging area of ​​the subject H relative to the detection surface 20A of the X-ray image detector 20. When the user initiates the imaging preparation operation to the console 30 (step S10: YES), the depth image camera 40 takes a depth image DP (step S11). The depth image DP is transmitted from the depth image camera 40 to the console 30.

[0072] Within the console 30, the distance image acquisition unit 70 performs a distance image acquisition process to acquire the distance image DP transmitted from the distance image camera 40 (step S12). Once the distance image DP is acquired by the distance image acquisition unit 70, the detection surface area search unit 71 performs a detection surface area search process to search for the detection surface area DA in which a part of the detection surface 20A exists from the distance image DP (step S13).

[0073] Next, the first distance acquisition unit 72 performs a first distance acquisition process to acquire the distance of the detection surface area DA searched by the detection surface area search unit 71 as the first distance D1 from the distance image camera 40 to the detection surface 20A (step S14). The second distance acquisition unit 73 performs a second distance acquisition process to acquire the distance from the distance image camera 40 to the subject H as the second distance D2 based on the distance image DP (step S15).

[0074] Next, the body thickness derivation unit 74 performs a body thickness derivation process to derive the difference between the first distance D1 and the second distance D2 as the body thickness BT (step S16). Then, the selection unit 75 performs an imaging condition selection process to select the X-ray imaging condition SC from the imaging condition table ST based on the body thickness BT derived by the body thickness derivation unit 74 (step S17). The X-ray imaging condition SC selected by the selection unit 75 is transmitted to the X-ray source 10.

[0075] Subsequently, when the user operates the irradiation switch 11 to give an imaging instruction to the X-ray source 10 to start irradiating with X-rays 4 (step S18: YES), the X-ray source 10 irradiates with X-rays 4 using the X-ray imaging conditions SC received from the console 30 (step S19). In other words, X-ray imaging is performed. Steps S11 to S18 are repeatedly executed until the user gives an imaging instruction. That is, when the body thickness BT changes due to a change in the state of the subject H, the X-ray imaging conditions SC are changed.

[0076] As described above, the technology of this disclosure searches for a detection surface area DA from a depth image DP, obtains the distance of the searched detection surface area DA as a first distance D1, and derives the body thickness BT based on the first distance D1 and the second distance D2. Therefore, the body thickness of the subject can be determined with high accuracy. Accordingly, according to the technology of this disclosure, even users unfamiliar with X-ray imaging can easily perform X-ray imaging with an appropriate dose.

[0077] Furthermore, if the distance from the X-ray source 10 to the detection surface 20A (i.e., SID) is pre-set in the X-ray imaging system 2, it is possible to measure the thickness of the subject H by measuring the distance from the X-ray source 10 to the subject H (i.e., SOD). However, portable radiography systems such as the X-ray imaging system 2 of the above embodiment often do not retain SID information, and even if they do, the actual SID may differ from the SID information. If the actual SID differs from the SID information, the accuracy of measuring the thickness of the subject decreases. In contrast, the technology of this disclosure derives the thickness based on the first distance D1 and the second distance D2 described above, without relying on SID information, so the thickness can be determined with high accuracy.

[0078] In the above embodiment, the detection surface region DA is detected from a region of interest (ROI) set at a position corresponding to the edge of the detection surface 20A. It is also conceivable to set the region of interest (ROI) to include the entire detection surface 20A. However, a part of the subject H that extends outward from the detection surface 20A (the hand in Figure 8) may be located behind the detection surface 20A (+Z direction) when viewed from the distance image camera 40. In such cases, if the region of interest (ROI) is set to include the entire detection surface 20A, there is a possibility that the distance of the part extending outward from the detection surface 20A may be erroneously detected as the first distance D1. To suppress such erroneous detection, in the above embodiment, a region of interest (ROI) smaller than the region corresponding to the detection surface 20A is set at a position corresponding to the edge of the detection surface 20A.

[0079] [Differentiation] Next, various modified examples of the X-ray imaging system 2 according to the above embodiment will be described.

[0080] In the above embodiment, the detection surface area search unit 71 assumes that the area of ​​the subject H being photographed is the abdomen and sets the region of interest (ROI) at a position corresponding to the lower corner (-Y direction side) of the detection surface 20A (see Figure 5). The detection surface area search unit 71 may change the position of the region of interest (ROI) according to the area of ​​the subject H being photographed.

[0081] In this case, for example, as shown in Figure 12, the NVM35 can be pre-stored with region information RS, which associates the imaging area with the location of the region of interest (ROI). The detection surface area search unit 71 can then select the location of the region of interest corresponding to the imaging area based on the imaging area information SP described above. In the example shown in Figure 12, the region of interest information RS includes information representing the location of the region of interest when the imaging area is the abdomen, and information representing the location of the region of interest when the imaging area is the front of the chest. When the imaging area is the front of the chest, the upper corner (+Y direction side) of the detection surface 20A is exposed without being covered by the subject H, so the region of interest ROI is associated with the position corresponding to the upper corner of the detection surface 20A.

[0082] The region of interest information RS is not limited to the abdomen and frontal chest, but may also include information indicating the location of the region of interest (ROI) for other imaging areas such as the lateral chest and buttocks.

[0083] Furthermore, in the above embodiment, as shown in Figure 10, the imaging conditions table ST associates body thickness BT and X-ray imaging conditions SC for each imaging area. However, the body thickness BT and X-ray imaging conditions SC may also be associated with information representing the physique of the subject H. For example, as shown in Figure 13, the physique of the subject H may be classified into three categories: "large," "medium," and "small," and the range of body thickness BT and X-ray imaging conditions SC may be associated for each category. In this case, the information representing the physique corresponding to the X-ray imaging conditions SC selected by the selection unit 75 may be displayed on the display unit 31 of the console 30. Alternatively, the user may select the physique using the input operation unit 32 to set the X-ray imaging conditions SC corresponding to the selected physique.

[0084] Furthermore, in the above embodiment, the selection unit 75 outputs the X-ray imaging conditions SC selected from the imaging conditions table ST to the X-ray source 10. However, the selected X-ray imaging conditions SC may be displayed on the display unit 31 of the console 30, and then the X-ray imaging conditions SC selected by the user using the input operation unit 32 may be output to the X-ray source 10.

[0085] Figure 14 shows an example of the processing flow of the X-ray imaging system 2 in this case. The flowchart shown in Figure 14 is the flowchart shown in Figure 11 with steps S20 to S22 added between steps S17 and S18. In step S20, the selection unit 75 displays the X-ray imaging conditions SC selected from the imaging conditions table ST on the display unit 31 of the console 30. At this time, for example, the selection unit 75 displays the imaging conditions table ST shown in Figure 10 or Figure 13 on the display unit 31. The user can select the X-ray imaging conditions SC to be used for X-ray imaging based on the imaging conditions table ST, while referring to the X-ray imaging conditions SC selected by the selection unit 75. In other words, the user can change to X-ray imaging conditions SC that are different from the X-ray imaging conditions SC selected by the selection unit 75.

[0086] The selection unit 75 determines whether the user has selected the X-ray imaging condition SC using the input operation unit 32 (step S21). If the user has selected the X-ray imaging condition SC (step S21: YES), the selection unit 75 outputs the selected X-ray imaging condition SC to the X-ray source 10 (step S22). If the user has not selected the X-ray imaging condition SC (step S21: NO), the process proceeds to step S18. Other processes are the same as in the above embodiment.

[0087] In the above embodiment, the distance image camera 40 is a TOF type, but the distance image camera 40 can be any camera capable of acquiring distance images, and may be a distance image camera other than a TOF type, such as a pattern illumination type.

[0088] Furthermore, although the X-ray imaging system 2 is a portable radiography system in the above embodiment, the technology of this disclosure is not limited to portable radiography systems and is applicable to various radiography systems. The technology of this disclosure is particularly suitable for radiography systems that do not retain SID information. The X-ray imaging system 2 may, for example, use a mobile mobile medical unit. Alternatively, the X-ray imaging system 2 may be a floor-mounted general X-ray imaging system. The posture of the subject H is not limited to lying down, but may also be standing. The X-ray imaging system 2 may also be a mammography device that images the breast as the subject H.

[0089] Furthermore, the technology disclosed herein can be applied not only to X-rays but also to systems that use other types of radiation, such as gamma rays, to image subjects.

[0090] In the above embodiment, the hardware structure of the processing unit that performs various processes such as the distance image acquisition unit 70, the detection surface area search unit 71, the first distance acquisition unit 72, the second distance acquisition unit 73, the body thickness derivation unit 74, and the selection unit 75 is the following type of processor.

[0091] Various types of processors include CPUs, programmable logic devices (PLDs), and dedicated electrical circuits. A CPU, as is well known, is a general-purpose processor that executes software (programs) and functions as various processing units. A PLD, such as an FPGA (Field Programmable Gate Array), is a processor whose circuit configuration can be changed after manufacturing. Dedicated electrical circuits are processors with circuit configurations specifically designed to perform particular processing, such as an ASIC (Application Specific Integrated Circuit).

[0092] A single processing unit may be composed of one of these various processors, or it may be composed of a combination of two or more processors of the same or different types (for example, multiple FPGAs, or a combination of a CPU and an FPGA). Alternatively, multiple processing units may be composed of a single processor. This is also possible. Examples of configuring multiple processing units with a single processor include, firstly, a configuration in which one or more CPUs and software are combined to form a single processor, and this processor functions as multiple processing units. Secondly, a configuration using a processor that realizes the functions of the entire system, including multiple processing units, on a single IC chip, as exemplified by System-on-a-Chip (SoC). Thus, various processing units are configured as hardware structures using one or more of the above-mentioned processors.

[0093] Furthermore, the hardware structure of these various processors is, more specifically, an electrical circuit composed of circuit elements such as semiconductor devices.

[0094] The present invention is not limited to the embodiments described above, and various configurations can be adopted without departing from the spirit of the invention. Furthermore, the present invention extends not only to programs but also to computer-readable storage media for non-temporarily storing programs.

Claims

1. An information processing device used in a radiography system comprising a radiation source and a radiation image detector having a detection surface to which radiation from the radiation source is irradiated and to which an object is positioned, for processing the thickness of the object, A distance image acquisition process that acquires a distance image generated by capturing the shooting range including the subject and the detection surface with a distance image capture device, A detection surface region search process that searches for a detection surface region in which a part of the detection surface exists from the distance image, A first distance acquisition process is performed to acquire the distance of the searched detection surface region based on the distance image as the first distance from the distance image acquisition device to the detection surface. A second distance acquisition process is performed to acquire the distance from the distance image acquisition device to the subject as a second distance based on the distance image, A body thickness derivation process that derives the difference between the first distance and the second distance as the body thickness of the subject, Equipped with a processor that runs, The aforementioned processor, In the detection surface area search process, a provisional setting value, which is provisionally set as a value corresponding to the first distance, and the size of the detection surface are used to set a region of interest where the detection surface area is estimated to exist, and the detection surface area is searched using the set region of interest as the search range. In the second distance acquisition process, based on the distance image, the distance to the radiation center coordinates corresponding to the center of the beam of radiation irradiated from the radiation source toward the subject is acquired as the second distance. Information processing device.

2. The aforementioned processor, In the second distance acquisition process, the radiation center coordinates are derived based on the relative positional relationship between the distance image acquisition device and the radiation source. The information processing apparatus according to claim 1.

3. The aforementioned processor, In the detection surface region search process, Abnormal pixels with abnormal pixel values ​​are excluded from the aforementioned region of interest. Of the regions from which the abnormal pixels have been excluded from the aforementioned region of interest, The region where the distance is maximized is derived as the detection surface region. The information processing apparatus according to claim 1 or claim 2.

4. The region of interest is a region that includes the edge of the radiation image detector and the background outside the radiation image detector. The information processing apparatus according to claim 3.

5. The aforementioned processor, In the detection surface region search process, Pixels that are at a certain distance or greater and that correspond to the background, and flying pixels that appear at the boundary between the edge and the background, are excluded from the area of ​​interest as abnormal pixels. The information processing apparatus according to claim 4.

6. The aforementioned processor, In the detection surface region search process, The position of the area of ​​interest is set according to the part of the subject being photographed. An information processing apparatus according to any one of claims 1 to 5.

7. The aforementioned distance image acquisition device is a TOF (Time of Flight) type distance image camera. An information processing apparatus according to any one of claims 1 to 6.

8. A radiography system comprising an information processing device according to any one of claims 1 to 7, Based on the body thickness derived by the body thickness derivation process, the radiography conditions are determined. Radiography system.

9. The determined radiography conditions can be changed by the user. The radiography system according to claim 8.

10. An information processing method used in a radiography system comprising a radiation source and a radiation image detector having a detection surface to which radiation from the radiation source is irradiated and to which an object is positioned, the method including deriving the thickness of the object, A distance image acquisition process that acquires a distance image generated by capturing the shooting range including the subject and the detection surface with a distance image capture device, A detection surface region search process that searches for a detection surface region in which a part of the detection surface exists from the distance image, A first distance acquisition process is performed to acquire the distance of the searched detection surface region based on the distance image as the first distance from the distance image acquisition device to the detection surface. A second distance acquisition process is performed to acquire the distance from the distance image acquisition device to the subject as a second distance based on the distance image, A body thickness derivation process that derives the difference between the first distance and the second distance as the body thickness of the subject, Includes, In the detection surface area search process, a provisional setting value, which is provisionally set as a value corresponding to the first distance, and the size of the detection surface are used to set a region of interest where the detection surface area is estimated to exist, and the detection surface area is searched using the set region of interest as the search range. In the second distance acquisition process, based on the distance image, the distance to the radiation center coordinates corresponding to the center of the beam of radiation irradiated from the radiation source toward the subject is acquired as the second distance. Information processing methods.

11. A program for use in a radiography system comprising a radiation source and a radiation image detector having a detection surface to which radiation from the radiation source is irradiated and to which an object is positioned, which causes a computer to perform a process including deriving the thickness of the object, A distance image acquisition process that acquires a distance image generated by capturing the shooting range including the subject and the detection surface with a distance image capture device, A detection surface region search process that searches for a detection surface region in which a part of the detection surface exists from the distance image, A first distance acquisition process is performed to acquire the distance of the searched detection surface region based on the distance image as the first distance from the distance image acquisition device to the detection surface. A second distance acquisition process is performed to acquire the distance from the distance image acquisition device to the subject as a second distance based on the distance image, A body thickness derivation process that derives the difference between the first distance and the second distance as the body thickness of the subject, Includes, In the detection surface area search process, a provisional setting value, which is provisionally set as a value corresponding to the first distance, and the size of the detection surface are used to set a region of interest where the detection surface area is estimated to exist, and the detection surface area is searched using the set region of interest as the search range. In the second distance acquisition process, based on the distance image, the distance to the radiation center coordinates corresponding to the center of the beam of radiation irradiated from the radiation source toward the subject is acquired as the second distance. A program that causes a computer to perform a process.

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