Information processing apparatus and method, storage medium, and radiographic system

Abstract

The information processing device performs the following processes: distance image acquisition processing, acquiring a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device; detection surface region search processing, searching for a detection surface region containing a portion of the detection surface from the distance image; first distance acquisition processing, acquiring the distance of the searched detection surface region based on the distance image as a first distance from the distance image imaging device to the detection surface; second distance acquisition processing, acquiring the distance from the distance image imaging device to the subject based on the distance image as a second distance; and thickness derivation processing, deriving the difference between the first distance and the second distance as the thickness of the subject.

Description

Technical Field

[0001] The present invention relates to an information processing device, an information processing method, a storage medium, and a radiographic system. Background Technology

[0002] In radiography, it is preferable to set the radiography conditions appropriately according to the body thickness of the patient or other subject. Radiography conditions include the tube voltage and the product of tube current and time of the radiation source. Whether from the perspective of obtaining sufficient image quality clinically or from the perspective of suppressing overexposure of the subject, it is preferable to set the radiography conditions to an appropriate radiation dose corresponding to the body thickness of the subject.

[0003] The thickness of a subject varies depending on the subject being radiographed. Therefore, in order to properly set the radiography conditions, it is necessary to measure the thickness of the subject with high accuracy. Japanese Patent Application Publication Nos. 2017-136300 and 2018-196791 disclose a method for measuring the thickness of a subject.

[0004] Japanese Patent Application Publication No. 2017-136300 discloses a method for calculating the thickness of a subject based on distance image information obtained by optical photography of the subject. More specifically, Japanese Patent Application Publication No. 2017-136300 describes a technique for calculating the thickness of a subject based on distance image information obtained by an optical sensor, and based on a first distance from the optical sensor to the irradiated side of the subject and a second distance from the optical sensor to the photographic platform.

[0005] Japanese Patent Application Publication No. 2018-196791 discloses the following technology: measuring the distance SID (Source Image receptor Distance) between the radiation irradiation device (i.e., radiation source) and the surface of the radiation detector, and the distance SOD (Source Object Distance) between the radiation irradiation device and the surface of the subject using a distance sensor, and calculating the thickness of the subject by subtracting SOD from SID. Summary of the Invention

[0006] The technical problem to be solved by the invention

[0007] The technologies described in Japanese Patent Application Publication Nos. 2017-136300 and 2018-196791 are both techniques for calculating the thickness of a subject by finding the difference between a first distance from a sensor used to measure distance to the detection surface of a radiation detector and a second distance from the sensor to the subject.

[0008] However, during radiography, the subject is positioned on the detection surface, thus becoming an obstruction and making it difficult to determine the first distance based on the distance information obtained from the sensor. Although it is possible to measure the first distance beforehand, the first distance can vary each time a radiography is performed. In particular, in radiography setups where the radiation source and detector are separate, the first distance deviates each time the photographer prepares for radiography, making it impossible to determine the first distance in advance.

[0009] Japanese Patent Application Publication Nos. 2017-136300 and 2018-196791 do not disclose a specific method for determining the first distance. Therefore, the techniques described in these publications cannot accurately determine the thickness of the subject.

[0010] The purpose of this invention is to provide an information processing device, information processing method, program, and radiographic system capable of accurately determining the thickness of a subject.

[0011] means for solving technical problems

[0012] To achieve the above objectives, the information processing apparatus of the present invention is used in a radiographic system to derive the thickness of a subject. The radiographic system includes a radiation source and a radiation image detector. The radiation image detector has a detection surface that is irradiated by radiation from the radiation source and positions the subject.

[0013] The information processing device includes a processor.

[0014] The processor performs the following processing:

[0015] Distance image acquisition processing acquires a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device;

[0016] The detection surface region search process searches for a portion of the detection surface region from the distance image.

[0017] The first distance acquisition process obtains the distance of the searched detection surface region based on the distance image, and uses it as the first distance from the distance image capturing device to the detection surface;

[0018] The second distance acquisition process obtains the distance from the distance image capturing device to the subject as the second distance based on the distance image; and

[0019] The thickness is exported by processing the difference between the first distance and the second distance.

[0020] In the second distance acquisition process, the preferred processor obtains the distance as the second distance based on the distance image, corresponding to the coordinates of the center of the radiation beam irradiating the subject from the radiation source.

[0021] In the second distance acquisition process, the preferred processor derives the coordinates of the radiation center based on the relative positional relationship between the distance image imaging device and the radiation source.

[0022] In the detection surface region search process, the preferred processor sets a region of interest that is presumed to exist as a detection surface region based on a temporary setting value that corresponds to the first distance and the size of the detection surface, and uses the set region of interest as the search range to search for the detection surface region.

[0023] In the detection surface region search processing, the preferred processor excludes abnormal pixels with abnormal pixel values ​​from the region of interest, and derives the region with the largest distance from the region after excluding abnormal pixels from the region of interest as the detection surface region.

[0024] The region of interest is preferably the area that includes the end of the radiation image detector and the background outside the radiation image detector.

[0025] In the detection area search process, the preferred processor excludes pixels that are at a distance of a certain value or higher and correspond to the background, as well as flying pixels that appear at the boundary between the end and the background, from the area of ​​interest as abnormal pixels.

[0026] In the detection area search processing, the preferred processor sets the position of the area of ​​interest according to the photographic part of the subject.

[0027] The distance image imaging device is preferably a TOF (Time-of-Flight) distance image camera.

[0028] The radiography system of the present invention is a radiography system equipped with any of the above-described information processing devices, which determines the radiography conditions based on the body thickness derived from the body thickness derivation processing.

[0029] Preferably, the determined radiographic conditions can be changed through user operation.

[0030] The information processing method of the present invention is used in a radiography system, including a step of deriving the thickness of a subject. The radiography system includes a radiation source and a radiation image detector, wherein the radiation image detector has a detection surface that is irradiated by radiation from the radiation source and positions the subject.

[0031] The information processing method includes the following steps:

[0032] Acquire a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device;

[0033] The detection surface region is located within a portion of the detection surface from the distance image;

[0034] The distance to the detected surface region is obtained from the distance image and used as the first distance from the distance image capturing device to the detection surface;

[0035] The distance from the distance image capturing device to the subject is obtained as the second distance based on the distance image; and

[0036] The difference between the first distance and the second distance is derived as the thickness of the subject.

[0037] A program for a radiographic system, used to cause a computer to perform processing including deriving the thickness of a subject, the radiographic system comprising a radiation source and a radiation image detector, the radiation image detector having a detection surface irradiated by radiation from the radiation source and locating the subject.

[0038] The procedure includes the following steps:

[0039] Acquire a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device;

[0040] The detection surface region is located within a portion of the detection surface from the distance image;

[0041] The distance to the detected surface region is obtained from the distance image and used as the first distance from the distance image capturing device to the detection surface;

[0042] The distance from the distance image capturing device to the subject is obtained as the second distance based on the distance image; and

[0043] The difference between the first distance and the second distance is derived as the thickness of the subject.

[0044] Invention Effects

[0045] According to the technology of the present invention, an information processing device, information processing method, program, and radiographic system capable of accurately determining the thickness of a subject can be provided. Attached Figure Description

[0046] Figure 1 This is a diagram illustrating an example of the structure of an X-ray imaging system.

[0047] Figure 2 This is a block diagram illustrating an example of the hardware structure of an X-ray imaging system.

[0048] Figure 3 This is a block diagram illustrating an example of the functional structure of the X-ray imaging condition determination unit.

[0049] Figure 4 This is a diagram representing an example of a distance image generated by a distance image camera.

[0050] Figure 5 This is a diagram illustrating an example of surface region search processing.

[0051] Figure 6 This is a diagram illustrating an example of the detection surface region search process and the first distance acquisition process.

[0052] Figure 7 This is a diagram illustrating an example of the first distance acquisition process.

[0053] Figure 8 This is a diagram illustrating in detail an example of the setting and processing of the region of interest based on the detection surface region search unit.

[0054] Figure 9 This is a diagram illustrating an example of volume thickness export processing.

[0055] Figure 10 This is an example diagram representing a photographic conditions table.

[0056] Figure 11 This is a diagram illustrating an example of the processing flow based on an X-ray imaging system.

[0057] Figure 12 This is a diagram representing an example of information about a region of interest.

[0058] Figure 13 A diagram showing a variation of the photographic conditions table.

[0059] Figure 14 This is a diagram illustrating a variation of the processing flow based on an X-ray imaging system. Detailed Implementation

[0060] Figure 1 This illustrates an example of the structure of an X-ray imaging system 2 that uses X-rays as radiation. The X-ray imaging system 2 includes an X-ray source 10, an X-ray image detector 20, a control console 30, and a repeater 50. A distance imaging camera 40 is mounted on the X-ray source 10. The control console 30 communicates with the X-ray source 10, the X-ray image detector 20, and the distance imaging camera 40 via the repeater 50. The repeater 50 functions, for example, as an access point.

[0061] X-ray source 10 is an example of a radiation source that generates radiation. X-ray image detector 20 is an example of a "radiation image detector" that detects radiation and generates radiation images.

[0062] The X-ray source 10, X-ray image detector 20, and control console 30 in this embodiment are all small and portable devices. The X-ray imaging system 2 of this embodiment can be taken to the scene of an accident, disaster, or other emergency medical response, or to the home of a patient receiving home medical care, to perform X-ray imaging.

[0063] In the X-ray imaging system 2, the X-ray image detector 20 is positioned opposite the X-ray source 10 on its detection surface 20A. By positioning the subject H between the X-ray source 10 and the X-ray image detector 20, X-ray imaging of the imaging portion of the subject H can be performed. Figure 1 In the example shown, the subject H is photographed in the abdomen.

[0064] The X-ray source 10 is held, for example, by a holding device 60. The holding device 60 is, for example, a four-legged structure with 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 three-strand connectors 63, thereby assembling the holding device 60. A clamp 64 for mechanically mounting the X-ray source 10 is provided on the crossbar 62. The X-ray source 10 is suspended by the clamp 64 with the X-ray 4 irradiation direction facing downwards.

[0065] The irradiation switch 11 is connected to the X-ray source 10 via cable 11A. Users such as radiology engineers or physicians 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.

[0066] The X-ray image detector 20 has an automatic X-ray detection function that detects radiation starting from the X-ray 4 emitted by the X-ray source 10. Therefore, the X-ray image detector 20 does not need to be connected to the X-ray source 10. Furthermore, since the X-ray image detector 20 has a built-in battery and wireless communication capabilities, it does not need to be connected to a power source or control console 30 via a cable. The X-ray image detector 20 is wirelessly connected to the repeater 50 and communicates with the control console 30 via the repeater 50.

[0067] The console 30 is, for example, a personal computer, and includes a display unit 31 and an input operation unit 32. The console 30 is connected to a repeater 50, for example, via a communication cable 51. The display unit 31 is a display device such as a liquid crystal display or an organic EL (Flectroluminescent) 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" according to the technology of this invention.

[0068] Users can input patient information, imaging sites, and imaging conditions through the input unit 32. The X-ray images received by the console 30 from the X-ray image detector 20 are displayed on the display unit 31.

[0069] The distance imaging camera 40 is, for example, positioned near the collimator 17 included in the X-ray source 10. For instance, the distance imaging camera 40 is a TOF (Time of Flight) type distance imaging camera. Specifically, the distance imaging camera 40 emits illumination light, such as infrared light, toward the object being photographed, and measures the time from the emission of the illumination light to the receipt of the reflected light, thereby measuring the distance between the distance imaging camera 40 and the object. Alternatively, the distance imaging camera 40 may emit amplitude-modulated illumination light, such as infrared light, toward the object and determine the distance between the distance imaging camera 40 and the object based on the phase delay of the reflected light relative to the illumination light. Furthermore, the distance imaging camera 40 may also be a laser scanning type TOF camera that measures distance by scanning a laser onto the object.

[0070] The distance image captured by the distance image camera 40 has distance information for each pixel, representing the distance between the distance image camera 40 and the photographed object. Furthermore, a distance image refers to an image having distance information capable of deriving the distance to the photographed object. The distance image camera 40 is an example of a "distance image photographing device" according to the technology of this invention.

[0071] In this embodiment, such as Figure 1 As shown, the distance image camera 40 captures a distance image by using the area including the photographed part of the subject H and the detection surface 20A of the X-ray image detector 20 as the photographing range 41. For example, the photographing range 41 is a rectangular area larger than the detection surface 20A.

[0072] X-ray source 10 and range image camera 40 are wirelessly connected to repeater 50, and communicate with console 30 via repeater 50. The range image DP generated by range image camera 40 (reference) Figure 2 The image is transmitted to the control console 30 via repeater 50. In this embodiment, the control console 30 derives the body thickness (hereinafter referred to as the body thickness of the subject H) in the photographic portion of the subject H based on the distance image DP received from the distance image camera 40.

[0073] Furthermore, the console 30 determines the X-ray imaging conditions SC based on the derived volume thickness and sends 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 product of tube voltage and tube current time, etc. The X-ray source 10 generates X-rays 4 according to 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.

[0074] Figure 2This illustrates an example of the hardware structure of the X-ray imaging system 2. The X-ray source 10 includes a processor 12, an input operation unit 13, a communication I / F (interface) 14, a high-voltage generator 15, an X-ray tube 16, and a collimator 17. The processor 12 functions as a control unit that controls the operation of the high-voltage generator 15 and the collimator 17. The processor 12 is connected to the aforementioned irradiation switch 11. Furthermore, the input operation unit 13 is connected. The input operation unit 13 includes an imaging condition adjustment button 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 collimator 17, and a power button.

[0075] The processor 12 controls the high-voltage generator 15 and the collimator 17 according to the setting conditions set by the input operation unit 13. The processor 12 causes the high-voltage generator 15 to generate a high voltage in response to the operation of the illumination switch 11. The communication I / F 14 is wirelessly connected to the repeater 50.

[0076] X-ray tube 16 is, for example, a fixed anode type X-ray tube without a target rotation mechanism. X-ray tube 16 consists of a cold cathode electron source that emits electrons, an electron accelerator, a target that generates X-rays 4 through electron collisions, and an outer tube housing them. In the case of a hot cathode, the cold cathode electron source does not require a filament or a heater to heat the filament. Since X-ray tube 16 lacks a target rotation mechanism, a filament, and a heater, it is small and lightweight. Furthermore, since X-ray tube 16 does not require residual heat from the filament, it can generate X-rays 4 in response to the irradiation start command.

[0077] Collimator 17 defines the irradiation field of X-rays 4 generated by X-ray tube 16. The X-rays 4 generated by X-ray tube 16 are irradiated onto the imaging portion of the subject H by the collimator 17 defining the irradiation field. The X-rays 4 that penetrate the imaging portion of the subject H are incident on the X-ray image detector 20.

[0078] The distance imaging camera 40 is connected, for example, to the communication I / F14 of the X-ray source 10. The distance imaging camera 40 will capture images within a photographic range 41 (reference). Figure 1 The generated distance image DP is transmitted to the control console 30 via communication I / F14 and repeater 50. Alternatively, the X-ray source 10 and the distance image camera 40 can be wired to the repeater 50 via communication cable.

[0079] The X-ray image detector 20 includes a processor 21, an X-ray detection panel 22, a memory 23, and a communication I / F 24. The processor 21 functions as a control unit that controls the various parts within the X-ray image detector 20. The X-ray detection panel 22 is, for example, a flat panel detector with a matrix substrate on which multiple pixels composed of thin film transistors (TFTs) and X-ray detection elements are arranged in two dimensions.

[0080] The X-ray detection panel 22 stores X-rays incident upon a charge accumulation state (TFT-off) by converting them into electrical charge using an X-ray detection element. Then, in a charge readout state (TFT-on), the X-ray detection panel 22 reads the charge stored in the X-ray detection element to a signal processing circuit. In the signal processing circuit, the readout charge is converted into a voltage signal by an integrating amplifier, and the converted voltage signal is then converted to digital image data by an A / D converter. This image data will be referred to as the X-ray image XP.

[0081] The memory 23 is a non-volatile memory such as flash memory, storing the X-ray image XP generated by the X-ray detection panel 22. The communication I / F 24 is wirelessly connected to the repeater 50. The processor 21 transmits the X-ray image XP stored in the memory 23 to the console 30 via the repeater 50. Alternatively, the X-ray image detector 20 can also be wired to the repeater 50 via a communication cable.

[0082] The console 30 includes a display unit 31, an input operation unit 32, a processor 33, RAM (Random Access Memory) 34, non-volatile memory (NVM) 35, and communication I / F 36. The processor 33 is, for example, a CPU (Central Processing Unit). The RAM 34 is working memory used for processing performed by the processor 33. The NVM 35 is a storage device such as flash memory that stores programs 37. The console 30 is an example of a "computer" according to the technology of this invention.

[0083] The processor 33 functions as a console control unit 38 and an X-ray imaging condition determination unit 39 that centrally control the various parts of the console 30 by loading the program 37 stored in the NVM 35 into the RAM 34 and executing the processing according to the program 37.

[0084] The console control unit 38 can input patient information and imaging sites using the input operation unit 32 by displaying a GUI (Graphical User Interface) screen on the display unit 31. Furthermore, the console control unit 38 causes the display unit 31 to display the X-ray image XP received from the X-ray image detector 20.

[0085] The X-ray imaging condition determination unit 39 derives the thickness of the subject H from the distance image DP sent from the distance image camera 40 and determines the X-ray imaging condition SC based on the derived thickness.

[0086] Figure 3 This illustrates an example of the functional structure of the X-ray imaging condition determination unit 39. The X-ray imaging condition determination unit 39 comprises 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 thickness derivation unit 74, and a selection unit 75. The X-ray imaging condition determination unit 39 derives the thickness and determines the X-ray imaging conditions based on information stored in the NVM 35, such as temporary setting value D1T, panel size L, relative position information RT, imaging part information SP, and imaging condition table ST.

[0087] The distance image acquisition unit 70 performs distance image acquisition processing to acquire the distance image DP sent from the distance image camera 40. The distance image acquisition unit 70 supplies the acquired distance image DP to the detection surface region search unit 71, the first distance acquisition unit 72, and the second distance acquisition unit 73.

[0088] Figure 4 This represents an example of a distance image DP generated by a distance image camera 40. For example... Figure 4 As shown, the distance image camera 40 generates a distance image DP by capturing an image range 41 including the subject H and the detection surface 20A. In the distance image DP, distance is represented by density. In the distance image DP, areas with higher density represent areas farther away from the distance image camera 40.

[0089] The distance image camera 40 defines a distance range that can be measured, and sets a first pixel region 80, which includes pixels whose distance from the distance image camera 40 is a predetermined value or greater, as having the maximum density (e.g., black). For example, the distance image camera 40 determines a pixel region 80 that represents a distance greater than a predetermined value that is longer than the distance from the distance image camera 40 to the detection surface 20A.

[0090] Furthermore, the distance imaging camera 40 sets the second pixel region 81, including the flying pixels generated at the end of the object, to a 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, from Japanese Patent No. 6143747. Figure 4 In the example shown, the second pixel region 81 is generated at the boundary between the end of the X-ray image detector 20 and the background, and at the boundary between the subject H and the background.

[0091] Furthermore, the specific and density changes of the first pixel region 80 and the second pixel region 81 of the distance image DP are not limited to the distance image camera 40, but can be performed inside the console 30.

[0092] The detection surface region search unit 71 performs a search from the distance image DP for a detection surface region DA (reference) containing a portion of the detection surface 20A. Figure 5 ) detection surface region search processing.

[0093] Figure 5 and Figure 6 An example of surface region search processing is illustrated below. For example... Figure 5 As shown, the detection surface region search unit 71 sets a region of interest (ROI) in the area where it is presumed that a detection surface region DA exists within a distance from the image DP, and searches for the detection surface region DA using the set ROI as the search range. For example, the ROI is rectangular. Furthermore, the ROI is smaller than the area corresponding to the detection surface 20A. The ROI includes the end of the X-ray image detector 20 and the background outside the X-ray image detector 20.

[0094] exist Figure 5 In the example shown, the detection surface region search unit 71 sets the region of interest (ROI) to include the corner of the detection surface 20A. Furthermore, in Figure 5 In the example shown, the subject H is photographed at its abdomen, with a portion of the detection surface 20A exposed on both sides of the subject H's waist. Therefore, the detection surface region search unit 71 sets a pair of regions of interest (ROIs) on both sides of the subject H's waist, corresponding to the corners of the detection surface 20A. Furthermore, the detection surface region search unit 71 only needs to set at least one ROI within a distance of the image DP.

[0095] like Figure 6As shown, the detection area search unit 71 excludes abnormal pixels with anomalous pixel values ​​from the region of interest (ROI). Specifically, the detection 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 ROI. Next, the detection area search unit 71 derives the region with the largest distance among the regions in the ROI from which abnormal pixels have been excluded as the detection area DA. Sometimes, the region from which abnormal pixels have been excluded includes a part of the subject H, but the subject H is located further away from the image camera 40 than the detection area 20A, and therefore the distance is shorter than that of the detection area 20A. Therefore, the detection area DA corresponds to the detection area 20A.

[0096] In addition, when a region of interest (ROI) of 2 or more is set within the image DP, the detection surface region search unit 71 searches for a detection surface region DA from the respective ROI.

[0097] The first distance acquisition unit 72 performs a first distance acquisition process, which obtains the distance of the detection surface region DA searched by the detection surface region search unit 71 based on the distance image DP, as the first distance D1 from the distance image camera 40 to the detection surface 20A. Furthermore, when the detection surface region search unit 71 extracts multiple detection surface regions DA and the distance to each detection surface region DA is different, the first distance acquisition unit 72 acquires the maximum distance as the first distance D1.

[0098] Figure 7 The details of the region of interest (ROI) setting process based on the detection surface region search unit 71 will be explained. It is presumed that the region containing the detection surface region DA at a distance from the image DP depends on the distance from the image camera 40 to the detection surface 20A and the size of the detection surface 20A. Therefore, in this embodiment, the detection surface region search unit 71 sets the ROI based on the temporary setting value D1T stored in the NVM 35 and the panel size L. The temporary setting value D1T is a value temporarily 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, for example, representing the length of the detection surface 20A in the X direction.

[0099] For example, the temporary setting value D1T is set according to the size of the holding device 60 and the X-ray source 10. The temporary setting value D1T and the panel size L can be set by the user using the input operation unit 32.

[0100] The distance imaging camera 40 includes a light source 42 that emits illumination light 42A, such as infrared light, toward the imaging range 41, and an image sensor 43 that receives reflected light 43A from the imaging range 41. The imaging range 41 corresponds to the viewing angle 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 geometric relationships based on a temporary setting value D1T and the panel size L, and sets the region of interest (ROI) to include the corner of the detection surface 20A.

[0101] The second distance acquisition unit 73 performs a second distance acquisition process, which acquires the distance from the distance image camera 40 to the subject H based on the distance image DP as the second distance D2. Specifically, as follows... Figure 8 As shown, the second distance acquisition unit 73 acquires the distance D2 as the distance to the center coordinate C of the X-ray beam 4 irradiated from the X-ray source 10 toward the subject H. More specifically, the second distance acquisition unit 73 acquires the distance D2 based on the relative positional relationship between the distance image camera 40 and the X-ray source 10 (see reference). Figure 7 The relative position information RT (reference) Figure 3 The first distance acquisition unit 72 obtains a first distance D1, from which the X-ray center coordinates C are derived, and the distance of the derived X-ray center coordinates C is obtained as a second distance D2. Alternatively, the second distance acquisition unit 73 can use a temporary setting value D1T instead of the first distance D1 to derive the X-ray center coordinates C. Furthermore, the X-ray center coordinates C is an example of the "radiation center coordinates" involved in the technology of this invention.

[0102] The thickness exporting unit 74 exports 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 as the thickness BT (reference). Figure 9 The volume thickness is exported. Specifically, such as... Figure 9 As shown, the thickness derivation unit 74 derives the thickness BT by subtracting the second distance D2 from the first distance D1.

[0103] The selection unit 75 determines the X-ray imaging condition SC based on the volume thickness BT exported by the volume thickness export unit 74. Specifically, the selection unit 75 selects the X-ray imaging condition SC corresponding to the imaging location represented by the volume thickness BT and the imaging location information SP from the imaging condition table ST stored in the NVM 35, and outputs the selected X-ray imaging condition SC to the X-ray source 10. The imaging location information SP can be set by the user using the input operation unit 32. Furthermore, the X-ray imaging condition SC is an example of the "radiographic imaging condition" involved in the technology of this invention.

[0104] Figure 10This represents an example of a radiographic condition table ST. Each radiographic location and thickness BT in the radiographic condition table ST is associated with a corresponding X-ray radiographic condition SC. The selection unit 75 selects from the radiographic condition table ST the X-ray radiographic condition SC most suitable for the radiographic location represented by the thickness BT and radiographic location information SP derived by the thickness derivation unit 74. The X-ray radiographic condition SC is, for example, defined by the product of the tube voltage and tube current time of the X-ray tube 16.

[0105] Then, while referring to Figure 11 The process shown Figure 1 The function of the X-ray imaging system 2 with the above structure will be explained.

[0106] Before taking the image, the physician or other user inputs patient information and imaging site information SP into the X-ray source 10 and console 30. The imaging site of the subject H is then positioned relative to the detection surface 20A of the X-ray image detector 20. When the user initiates the image preparation operation on the console 30 (step S10: Yes), a distance image DP is captured by the distance image camera 40 (step S11). The distance image DP is sent from the distance image camera 40 to the console 30.

[0107] Within the console 30, the distance image acquisition unit 70 performs distance image acquisition processing to acquire the distance image DP sent from the distance image camera 40 (step S12). While acquiring the distance image DP through the distance image acquisition unit 70, the detection surface region search unit 71 performs detection surface region search processing to search for a portion of the detection surface 20A located in the detection surface region DA from the distance image DP (step S13).

[0108] Next, the first distance acquisition unit 72 performs a first distance acquisition process (step S14) to acquire the distance from the detection surface region DA searched by the detection surface region search unit 71 as the first distance D1 from the distance image camera 40 to the detection surface 20A. The second distance acquisition unit 73 performs a second distance acquisition process (step S15) 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.

[0109] Next, the thickness exporting unit 74 performs a thickness exporting process, exporting the difference between the first distance D1 and the second distance D2 as the thickness BT (step S16). Furthermore, the selection unit 75 performs a photography condition selection process, selecting the X-ray photography condition SC from the photography condition table ST based on the thickness BT exported by the thickness exporting unit 74 (step S17). The X-ray photography condition SC selected by the selection unit 75 is then sent to the X-ray source 10.

[0110] Subsequently, when a photographic command to start irradiating X-ray source 10 with X-ray 4 is issued by the user through the irradiation switch (step S18: Yes), X-ray source 10 irradiates X-ray 4 using the X-ray photographic conditions SC received from the control console 30 (step S19). That is, X-ray photography is performed. During the period up to the time the user issues the photographic command, steps S11 to S18 are repeated. That is, when the body thickness BT is changed by changing the state of the subject H, etc., the X-ray photographic conditions SC are changed.

[0111] As described above, in the technique of the present invention, the detection surface region DA is searched from the distance image DP, and the distance of the searched detection surface region DA is obtained as the first distance D1. The body thickness BT is derived based on the first distance D1 and the second distance D2. Therefore, the body thickness of the subject can be determined with good accuracy. Therefore, according to the technique of the present invention, even users unfamiliar with X-ray photography can easily perform X-ray photography with an appropriate linear modulus.

[0112] Conversely, when the distance from the X-ray source 10 to the detection surface 20A (i.e., SID) is preset in the X-ray imaging system 2, the thickness of the subject H can be determined by measuring the distance from the X-ray source 10 to the subject H (i.e., SOD). However, in mobile radiographic systems such as the X-ray imaging system 2 described above, SID information is mostly not stored, and even if SID information is stored, the actual SID sometimes differs from the SID information. If the actual SID differs from the SID information, the measurement accuracy of the subject's thickness decreases. In contrast, in the technology of the present invention, the thickness is derived from the first distance D1 and the second distance D2 without relying on SID information, thus enabling the thickness to be determined with good accuracy.

[0113] In the above embodiment, the detection surface region DA is detected from a region of interest (ROI) set at a position corresponding to the end of the detection surface 20A. It is also considered to set the ROI to include the entire detection surface 20A. However, when viewed from a distance of 40 from the image camera, the portion of the subject H that protrudes outward from the detection surface 20A ( Figure 8 The portion representing the hand is sometimes located further inward (on the +Z direction side) than the detection surface 20A. In this case, if the region of interest (ROI) is set to include the entire detection surface 20A, there is a possibility of falsely detecting the distance from the portion protruding outward from the detection surface 20A as a first distance D1. To suppress such false detections, in the above embodiment, a region of interest (ROI) smaller than the area corresponding to the detection surface 20A is set at a position corresponding to the end of the detection surface 20A.

[0114] [Variation Example]

[0115] Next, various modifications of the X-ray imaging system 2 according to the above embodiments will be described.

[0116] In the above embodiment, the detection area search unit 71 sets a region of interest (ROI) at a position corresponding to the corner of the lower side (-Y direction side) of the detection surface 20A, based on the premise that the imaging part of the subject H is the abdomen. Figure 5 The detection area search unit 71 can change the position of the region of interest (ROI) based on the photographic part of the subject H.

[0117] In this case, for example, such as Figure 12 As shown, the region of interest (ROI) information RS, which pre-associates the positions of the photographed parts with those of the ROIs, can be stored in the NVM35. The detection surface region search unit 71 selects the position of the ROI corresponding to the photographed part based on the photographed part information SP. Figure 12 In the example shown, the Region of Interest (ROI) information RS includes information indicating the location of the ROI corresponding to the case where the imaging site is the abdomen, and information indicating the location of the ROI corresponding to the case where the imaging site is the front of the chest. When the imaging site is the front of the chest, the upper corner (+Y direction side) of the detection surface 20A is not covered by the subject H and is exposed. Therefore, the ROI is associated with the position corresponding to the upper corner of the detection surface 20A.

[0118] Region of interest (RS) information is not limited to the abdomen and front of the chest; it can include information indicating the location of the region of interest (ROI) relative to other imaging areas such as the side of the chest and the buttocks.

[0119] Furthermore, in the above embodiments, such as Figure 10 As shown, each imaging region in the imaging conditions table ST is associated with body thickness BT and X-ray imaging conditions SC. However, body thickness BT and X-ray imaging conditions SC can also be associated with the body information representing the subject H. For example, as... Figure 13 As shown, the size of the subject H is classified into three categories: "large," "medium," and "small." Each category corresponds to a range of body thickness BT and X-ray imaging conditions SC. In this case, information about the subject corresponding to the X-ray imaging conditions SC selected by the selection unit 75 can be displayed on the display unit 31 of the control panel 30. Furthermore, by using the input operation unit 32 to select a subject, the X-ray imaging conditions SC corresponding to the selected subject can be set.

[0120] Furthermore, in the above embodiment, the selection unit 75 outputs the X-ray imaging condition SC selected from the imaging condition table ST to the X-ray source 10. However, based on displaying the selected X-ray imaging condition SC on the display unit 31 of the control console 30, the X-ray imaging condition SC selected by the user using the input operation unit 32 can be output to the X-ray source 10.

[0121] Figure 14 The diagram shows an example of the processing flow of the X-ray imaging system 2 at this time. Figure 14 The flowchart shown is in Figure 11 The flowchart shown includes steps S20 to S22, which are appended between steps S17 and S18. In step S20, the selection unit 75 causes the display unit 31 of the control console 30 to display the X-ray imaging condition SC selected from the imaging condition table ST. At this time, for example, the selection unit 75 causes the display unit 31 to display... Figure 10 or Figure 13 The imaging conditions table ST is shown. The user can select the X-ray imaging conditions SC to be used in X-ray imaging based on the imaging conditions table ST while referring to the X-ray imaging conditions SC selected via the selection unit 75. That is, the user can change to X-ray imaging conditions SC different from those selected via the selection unit 75.

[0122] The selection unit 75 determines whether the user has used the input operation unit 32 to select X-ray imaging condition SC (step S21). When the user selects 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). When the user does not select X-ray imaging condition SC (step S21: No), the process proceeds to step S18. Other processes are the same as in the above embodiment.

[0123] In addition, in the above embodiment, the distance image camera 40 is set to TOF mode. However, the distance image camera 40 can be any camera capable of acquiring distance images, and can be a distance image camera with a pattern illumination mode other than TOF mode.

[0124] Furthermore, in the above embodiment, the X-ray imaging system 2 is configured as a mobile radiography system; however, the technology of the present invention is not limited to mobile radiography systems and can be applied to various radiography systems. The technology of the present invention is particularly suitable for radiography systems that do not store SID information. For example, a mobile medical vehicle can be used for the X-ray imaging system 2. Furthermore, the X-ray imaging system 2 can be a ground-based, general-purpose X-ray imaging system. The posture of the subject H is not limited to a supine position and can also be a standing position. Furthermore, the X-ray imaging system 2 can be a mammography device for imaging the breast of the subject H.

[0125] Furthermore, the technology of the present invention is not limited to X-rays, but can also be applied to systems that use other types of radiation, such as gamma rays, to photograph subjects.

[0126] In the above embodiments, the hardware structure of the processing unit that performs various processes, such as the distance image acquisition unit 70, the detection surface region search unit 71, the first distance acquisition unit 72, the second distance acquisition unit 73, the volume thickness export unit 74, and the selection unit 75, is as shown below.

[0127] Processors include CPUs, programmable logic devices (PLDs), and application-specific circuits (ASICs). A CPU is a general-purpose processor that functions as a processing unit to execute well-known software (programs). A PLD is a processor such as a field-programmable gate array (FPGA) whose circuit structure can be modified after manufacturing. An application-specific circuit (ASIC) is a processor with a circuit structure specifically designed to perform a particular process.

[0128] A processing unit can consist of one of these various processors, or it can consist of a combination of two or more processors of the same or different types (e.g., multiple FPGAs, a combination of CPU and FPGA). Furthermore, multiple processing units can also be composed of a single processor.

[0129] As examples of a single processor comprising multiple processing units, firstly, there are processors that consist of a combination of one or more CPUs and software, and that processor functions as multiple processing units. Secondly, as exemplified by System-on-Chip (SoC), there is a method where a single IC chip is used to implement the overall system functionality including multiple processing units. Thus, various processing units are constructed as hardware structures using one or more of the aforementioned processors.

[0130] Furthermore, the hardware architecture of these various processors is more specifically a circuit composed of combined semiconductor elements and other circuitry.

[0131] This invention is not limited to the embodiments described above; various structures can be adopted as long as they do not depart from the spirit of the invention. Furthermore, this invention also relates to a computer-readable storage medium that is not a temporary storage medium for programs other than the program itself.

Claims

1. An information processing apparatus for use in a radiographic system to derive the thickness of a subject, the radiographic system comprising a radiation source and a radiation image detector, the radiation image detector having a detection surface irradiated by radiation from the radiation source and positioned to locate the subject. The information processing device includes a processor. The processor performs the following processing: Distance image acquisition processing: acquiring a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device; The detection surface region search process searches for a portion of the detection surface region from the distance image. The first distance acquisition process obtains the distance of the searched detection surface region based on the distance image, and uses it as the first distance from the distance image imaging device to the detection surface; The second distance acquisition process involves obtaining the distance from the distance image capturing device to the subject as the second distance based on the distance image; and The thickness is derived by processing the difference between the first distance and the second distance, which is then used as the thickness of the subject. In the detection surface region search process, based on the temporary setting value corresponding to the first distance and the size of the detection surface, a region of interest is set as if the detection surface region exists, and the set region of interest is used as the search range to search the detection surface region.

2. The information processing apparatus according to claim 1, wherein, In the second distance acquisition process, the processor acquires, based on the distance image, the distance corresponding to the center coordinates of the radiation center of the beam of radiation irradiating the subject from the radiation source as the second distance.

3. The information processing apparatus according to claim 2, wherein, In the second distance acquisition process, the processor derives the coordinates of the radiation center based on the relative positional relationship between the distance image imaging device and the radiation source.

4. The information processing apparatus according to claim 1, wherein, In the detection surface region search process, the processor excludes abnormal pixels with abnormal pixel values ​​from the region of interest, and derives the region with the largest distance from the region after excluding the abnormal pixels from the region of interest as the detection surface region.

5. The information processing apparatus according to claim 4, wherein, The region of interest is the area including the end of the radiation image detector and the background outside the radiation image detector.

6. The information processing apparatus according to claim 5, wherein, In the detection surface region search process, the processor excludes pixels that are at a distance of a certain value or more and correspond to the background, as well as flying pixels that appear at the boundary between the end and the background, from the region of interest as abnormal pixels.

7. The information processing apparatus according to claim 1, wherein, In the detection area search process, the processor sets the position of the region of interest according to the photographic part of the subject.

8. The information processing apparatus according to claim 1, wherein, The distance image imaging device is a TOF (Time-of-Flight) distance image camera.

9. A radiography system comprising the information processing apparatus of any one of claims 1 to 3, wherein the radiography system determines radiography conditions based on the body thickness derived from the body thickness derivation processing.

10. The radiographic system according to claim 9, wherein, The determined radiographic conditions can be changed through user operation.

11. An information processing method for a radiographic system, comprising a step of deriving the thickness of a subject, the radiographic system comprising a radiation source and a radiation image detector, the radiation image detector having a detection surface irradiated by radiation from the radiation source and locating the subject. The information processing method includes the following steps: Acquire a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device; The detection surface region is searched from the distance image. Based on the temporary setting value corresponding to the first distance and the size of the detection surface, a region of interest is set as the inferred location of the detection surface region. The set region of interest is used as the search range to search the detection surface region. The distance to the detected surface region is obtained from the distance image and used as the first distance from the distance image imaging device to the detected surface; The distance from the distance image capturing device to the subject is obtained as a second distance based on the distance image; and The difference between the first distance and the second distance is derived as the body thickness of the subject.

12. A computer-readable storage medium storing a program for a radiographic system and for causing a computer to perform a process including deriving the thickness of a subject, the radiographic system comprising a radiation source and a radiation image detector, the radiation image detector having a detection surface irradiated by radiation from the radiation source and locating the subject. The program is used to cause the computer to perform a process that includes the following steps: Acquire a distance image generated by capturing a photographic range including the subject and the detection surface using a distance image imaging device; The detection surface region is searched from the distance image. Based on the temporary setting value corresponding to the first distance and the size of the detection surface, a region of interest is set as the inferred location of the detection surface region. The set region of interest is used as the search range to search the detection surface region. The distance to the detected surface region is obtained from the distance image and used as the first distance from the distance image imaging device to the detected surface; The distance from the distance image capturing device to the subject is obtained as a second distance based on the distance image; and The difference between the first distance and the second distance is derived as the body thickness of the subject.

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