Radiation image processing device, radiation image processing system, radiation image processing method, and program

Abstract

To provide a radiation image processing device capable of acquiring a composite image easy to interpret, a radiation image processing system, a radiation image processing method, and a program.SOLUTION: A console 30 functioning as a radiation image processing device comprises: a control unit 31 which functions as an image acquisition unit for acquiring a plurality of radiation images captured under respectively different imaging conditions, of a subject; a pixel value correction part which corrects a pixel value of at least one of the plurality of radiation images; and an image processing unit 36 which functions as an image composing unit for acquiring one composite image by composing the plurality of radiation images. Each of the plurality of radiation images has an image overlapping area with at least one or more other radiation images. The pixel value correction part corrects the pixel value in such a manner where the maximum value of the pixel value of the at least one radiation image is equal to or less than the maximum value of gradation of the image.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a radiation image processing apparatus, a radiation image processing system, a radiation image processing method, and a program. [Background technology]

[0002] Conventionally, a method for creating a composite image by combining a plurality of images obtained by changing the irradiation direction of a radiation source in the body axis direction (so-called swivel length) has been known.

[0003] This method requires the subject to be exposed to radiation multiple times, which may have adverse health effects on the subject. Therefore, for example, Patent Documents 1 and 2 describe methods for reducing the effects of radiation by changing the imaging conditions each time an image is captured, and automatically correcting the pixel values ​​of each image when combining images. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5759405 [Patent Document 2] Patent No. 4754812 Summary of the Invention [Problem to be solved by the invention]

[0005] However, no specific method for correcting pixel values ​​is described in Patent Documents 1 and 2. As a result, the pixel values ​​of the composite image may exceed the maximum value of the gradation (so-called density saturation), causing crushed blacks and making interpretation difficult.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radiation image processing device, a radiation image processing system, a radiation image processing method, and a program that are capable of obtaining a composite image that can be easily interpreted. [Means for solving the problem]

[0007] In order to solve the above problems, the invention described in claim 1 is a radiation image processing device, an image acquisition unit that acquires a plurality of radiographic images of a subject, each image being captured under different imaging conditions; a pixel value correcting unit that corrects pixel values ​​of at least one of the plurality of radiographic images; an image synthesis unit that synthesizes the plurality of radiographic images to obtain a single synthesized image, each of the plurality of radiographic images has an image overlapping area with at least one other radiographic image; The pixel value correcting unit corrects pixel values ​​of the at least one radiographic image so that the maximum pixel value is equal to or less than the maximum gradation value of the image.

[0008] The invention described in claim 2 is the radiation image processing apparatus described in claim 1, an imaging condition acquisition unit that acquires mAs values ​​from a plurality of said imaging conditions; The pixel value correcting unit corrects pixel values ​​of the at least one radiographic image based on the mAs value.

[0009] The invention described in claim 3 is the radiation image processing apparatus described in claim 2, The pixel value correcting unit corrects pixel values ​​of the other radiographic images using pixel values ​​of the radiographic image with the lowest mAs value among the plurality of radiographic images as a reference.

[0010] The invention described in claim 4 is the radiation image processing apparatus described in claim 1, When the pixel values ​​of the at least one radiographic image after correction become decimals, the pixel value correction unit multiplies the pixel values ​​of all the radiographic images by a predetermined coefficient to make the pixel values ​​of all the radiographic images integers.

[0011] The invention described in claim 5 is the radiation image processing apparatus described in claim 1, a display control unit that displays the composite image and the plurality of radiation images on a display unit; The display control unit causes the display unit to distinguishably display, from among the plurality of radiographic images, a radiographic image that is used as a reference for correction of pixel values ​​of the at least one radiographic image by the pixel value correction unit.

[0012] The invention described in claim 6 is a radiation image processing system, The radiation image processing device according to any one of claims 1 to 5, a radiation generating device that generates radiation; and a radiographic imaging device that receives the radiation generated by the radiation generating device and generates a radiographic image.

[0013] The invention described in claim 7 is a radiation image processing method, an image acquisition step of acquiring a plurality of radiographic images of a subject, each image being captured under different imaging conditions; a pixel value correcting step of correcting pixel values ​​of at least one of the plurality of radiographic images; an image synthesis step of synthesizing the plurality of radiographic images to obtain a single synthetic image, each of the plurality of radiographic images has an image overlapping area with at least one other radiographic image; The pixel value correcting step corrects pixel values ​​so that the maximum pixel value of the at least one radiographic image is equal to or less than the maximum gradation value of the image.

[0014] The invention described in claim 8 is Computer, an image acquisition unit that acquires a plurality of radiographic images of a subject, each image being captured under different imaging conditions; a pixel value correcting unit that corrects pixel values ​​of at least one of the plurality of radiographic images; a program that functions as an image synthesis unit that synthesizes the plurality of radiographic images to obtain a single synthetic image, each of the plurality of radiographic images has an image overlapping area with at least one other radiographic image; The pixel value correcting unit corrects pixel values ​​of the at least one radiographic image so that the maximum pixel value is equal to or less than the maximum gradation value of the image. [Effects of the Invention]

[0015] According to the present invention, a composite image that can be easily interpreted can be obtained. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a radiation image processing system. [Figure 2] FIG. 2 is a block diagram of a console. [Figure 3] 10 is a flowchart of a composite image acquisition process. [Figure 4] FIG. 2 is a diagram showing an example of a plurality of radiation images. [Figure 5] FIG. 10 is a diagram illustrating an example of one composite image. [Figure 6] FIG. 10 is a diagram illustrating an example of a display unit on which a composite image is displayed. [Figure 7] FIG. 10 is a diagram showing an example of a composite image according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the following embodiments and those described in the drawings.

[0018] [Radiation image processing system] First, a radiation image processing system 100 according to this embodiment will be described.

[0019] 1, the radiation image processing system 100 includes a radiation generating device 10, a radiation imaging device 20, and a console 30 which is a radiation image processing device. The devices constituting the radiation image processing system 100 are connected to each other so as to be able to communicate with each other via, for example, a communication network (such as a LAN (Local Area Network), a WAN (Wide Area Network), or the Internet).

[0020] The radiation image processing system 100 may be communicably connected to a system (not shown), such as a Hospital Information System (HIS), a Radiology Information System (RIS), or a Picture Archiving and Communication System (PACS).

[0021] (Radiation Generator) The radiation generating device 10 generates radiation in a manner corresponding to the type of radiographic image. The radiation generating device 10 includes a generator 11, an exposure switch 12, and a radiation source 13.

[0022] {Generator, exposure switch} In response to the operation of the exposure switch 12, the generator 11 applies a voltage to the radiation source 13 according to preset imaging conditions.

[0023] {radiation source} The radiation source 13 includes a tube, a filament, and the like (not shown). The radiation source 13 is disposed opposite the radiographic imaging device 20 with the subject sandwiched between them. When a voltage is applied from the generator 11, the filament irradiates the rotating anode with an electron beam corresponding to the voltage. The rotating anode irradiates the subject with radiation (X-rays) at a dose corresponding to the intensity of the electron beam. The radiation source 13 can also change the orientation of the radiation outlet by rotating around rotation axes parallel to the X-axis direction, the Y-axis direction perpendicular to the X-axis, and the Z-axis direction perpendicular to the X-axis and Y-axis.

[0024] 1 illustrates an example in which the generator 11, exposure switch 12, and radiation source 13 are separate and independent, but the present invention is not limited to this. The generator 11, exposure switch 12, and radiation source 13 may be integrated. The exposure switch 12 may be connected to an operation console (not shown) instead of the generator 11. The radiation generating device 10 may be installed in an imaging room, or may be a portable type that can be moved by being incorporated into, for example, a medical cart.

[0025] (Radiation imaging device) The radiation imaging device 20 detects radiation emitted from the radiation source 13 and transmitted through the subject to capture a radiation image. The radiation imaging device 20 is configured with an FPD (Flat Panel Detector) or the like. The radiation imaging device 20 has, for example, a glass substrate. The radiation imaging device 20 detects radiation (X-rays) emitted from the radiation generating device 10 at a predetermined position on the substrate and transmitted at least through the subject, according to the intensity of the radiation. The radiation imaging device 20 has a plurality of detection elements (pixels) arranged in a matrix, which convert the detected radiation into an electrical signal and store the signal. Each pixel is configured with a switching unit, such as a TFT (Thin Film Transistor). The radiation imaging device 20 controls the switching unit of each pixel based on image reading conditions input from the console 30 to switch the reading of the electrical signal stored in each pixel, thereby reading the electrical signal stored in each pixel. Through this control, the radiation imaging device 20 acquires image data (frame image). The radiation imaging device 20 then outputs the acquired image data to the console 30.

[0026] (console) The console 30 accepts input of imaging conditions to be set for at least one of the radiation generation device 10 and the radiation imaging device 20. The console 30 is a dedicated device such as a PC. There is no particular limitation on the method of inputting imaging conditions to the console 30. For example, the imaging conditions may be input by a user, obtained from another system (such as an HIS or RIS), or input by another user (such as a technician). The detailed configuration of the console 30 will be described later.

[0027] In the radiation image processing system 100 configured as described above, when a user operates the irradiation instruction switch 111, the radiation source 13 irradiates the subject with radiation under imaging conditions in accordance with the imaging order information (described later). Then, the radiation imaging device 20 located behind the subject receives the radiation that has passed through the subject, reads out image data, and transmits the image data to the console 30.

[0028] (Detailed console configuration) The detailed configuration of the console 30 will be described. Fig. 2 is a block diagram of the console 30. The console 30 includes a control unit 31, a communication unit 32, a storage unit 33, a display unit 34, an operation unit 35, and an image processing unit 36. The various units of the console 30 are electrically connected via a bus or the like. The console 30 functions as a radiological image processing device that receives various inputs related to the composite image acquisition process described below and executes various processes.

[0029] {Control Unit} The control unit 31 is composed of a CPU (Central Processing Unit), RAM (Random Access Memory), etc. The CPU reads out various programs stored in the storage unit 33 and loads them into the RAM. The CPU executes various processes in accordance with the loaded programs. With this configuration, the control unit 31 centrally controls the operation of each unit of the console 30.

[0030] {Communications Department} The communication unit 32 is configured with a communication module, etc. The communication unit 32 transmits and receives various signals and various data to and from other devices such as the radiation generation device 10 and the radiation imaging device 20 connected via a communication network.

[0031] {Storage section} The storage unit 33 is configured with a non-volatile semi-dynamic memory, a hard disk, etc. The storage unit 33 stores various programs executed by the control unit 31, parameters required for executing the programs, etc. The storage unit 33 may also be capable of storing image data of radiographic images. The storage unit 33 also stores imaging order information transmitted from the RIS, etc.

[0032] The radiography order information includes information on the subject (patient), examination information, and radiography conditions. The examination information includes an examination ID, an imaging region, an examination date, etc. The radiography conditions include various conditions related to the radiation dose irradiated by the radiation generating device 10. For example, the angle of the radiation source 13 (i.e., an imaging region), positioning (PA, LAT, etc.), tube voltage (kV), tube current (mA), irradiation time (ms), current-time product (mAs value), and focal spot-radiography device distance (SID).

[0033] {Display section} The display unit 34 displays various screens. The display unit 34 is configured, for example, with an LCD (Liquid Crystal Display), an ELD (Electronic Luminescent Display), a CRT (Cathode Ray Tube), etc. The display unit 34 displays lists, radiological images, etc. in accordance with image signals received from the control unit 31.

[0034] {Operation section} The operation unit 35 is an operation means configured to be operable by the user. The operation unit 35 is a keyboard equipped with cursor keys, numeric input keys, various function keys, etc., a pointing device (such as a mouse), or a touch panel laminated on the surface of the display unit 34. The operation unit 35 outputs a control signal to the control unit 31 in accordance with an operation performed by the user.

[0035] {Image processing section} The image processing unit 36 ​​performs image processing on the radiographic image acquired from the radiographic imaging device 20. Examples of image processing include dynamic range compression processing, contrast conversion processing, LUT (Look Up Table) processing, frequency emphasis processing, scattered radiation correction processing, noise suppression processing, image trimming, image masking, image rotation, and image inversion.

[0036] In particular, the image processing unit 36 ​​functions as a pixel value correcting unit that performs pixel value correction processing to correct the pixel values ​​of multiple radiographic images acquired from the radiography apparatus 20 so as not to cause density saturation. The image processing unit 36 ​​also functions as an image combining unit that performs image combining processing to combine multiple radiographic images after the pixel value correction processing to generate a single combined image. The pixel value correction processing and the image combining processing will be described in detail below.

[0037] [Composite image acquisition process] The composite image acquisition process performed by the radiation image processing system 100 described above will be described with reference to the flowchart of FIG.

[0038] The user selects radiography order information for the subject to be radiographed using the operation unit 35 of the console 30. The communication unit 32 transmits the selected radiography order information to the radiation generation device 10. After positioning the subject, the user presses the exposure switch 12. This causes radiation to be irradiated from the radiation source 13. The radiation imaging device 20 that has received the radiation reads the radiographic image and transmits it to the console 30 (step S101).

[0039] After acquiring the radiographic image, the user uses the operation unit 35 to select radiography order information with different radiography conditions from the previous radiography order information (here, step S101). These radiography order information have different radiography conditions, at least the angle of the radiation source 13. The communication unit 32 transmits the selected radiography order information to the radiation generation device 10. After positioning the subject, the user presses the exposure switch 12. Then, radiation is irradiated from the radiation generation device 10. The radiation imaging device 20 that has been irradiated with radiation reads the radiographic image and transmits it to the console 30 (step S102).

[0040] After acquiring the second or subsequent radiographic images, the control unit 31 displays a confirmation screen on the display unit 34 to ask whether radiography has been completed, and accepts instructions from the user (step S103). If radiography has not been completed (step S103; No), the user proceeds to step S102 and acquires further radiographic images based on radiography order information whose radiography conditions are different from those of the previous radiography order information.

[0041] When radiography is completed (step S103; Yes), the user instructs the control unit 31 to execute pixel value correction processing and image synthesis processing via the operation unit 35. Upon receiving the instruction to execute pixel value correction processing, the image processing unit 36 ​​corrects pixel values ​​based on the actual mAs values ​​in each piece of radiography order information (step S104). During pixel value correction processing, the image processing unit 36 ​​corrects the pixel values ​​of each image so that the pixel values ​​are equal to or less than the maximum value of the gradation (i.e., so as not to cause density saturation).

[0042] As described above, in this step, the image processing unit 36 ​​uses the actual mAs value, not the set value. Therefore, even if the dose changes based on the imaging order information, for example, by providing an AEC (Automatic Exposure Control), processing can be performed in accordance with the change. The actual mAs value can be obtained from the radiation generating device 10.

[0043] In the following description, it is assumed that two radiographic images, a first radiographic image with an mAs value of 3 and a second radiographic image with an mAs value of 6, are acquired from the radiographic apparatus 20, as shown in FIG. 4 . The first radiographic image and the second radiographic image are both 16-bit images. Therefore, the maximum gradation value of the first radiographic image and the second radiographic image is 65,535. As described above, the pixel values ​​of the first radiographic image are between 1,000 and 40,000. The pixel values ​​of the second radiographic image are between 2,000 and 50,000.

[0044] In this case, if pixel value correction processing is performed to match the pixel values ​​of the first radiographic image to the pixel values ​​of the second radiographic image based on the mAs value, the pixel values ​​of the first radiographic image will be between 2000 and 80000, which may result in density saturation. Therefore, in this embodiment, the image processing unit 36 ​​performs pixel value correction processing to match the pixel values ​​of the second radiographic image to the pixel values ​​of the first radiographic image with the lowest mAs value. As a result, the pixel values ​​of the second radiographic image will be between 1000 and 25000, so density saturation will not occur.

[0045] If the pixel values ​​of a radiographic image become decimal as a result of correcting the pixel values, the pixel values ​​may be multiplied by a predetermined coefficient so that all pixel values ​​of the radiographic image become integers. This control can suppress the occurrence of rounding errors and the occurrence of density deviations.

[0046] After the pixel value correction process, the image processing unit 36 ​​executes image synthesis process (step S105) to synthesize the multiple radiographic images to generate one synthesized image, as shown in Fig. 5. As shown in Fig. 4 and Fig. 5, in steps S101 and S102, the user captures radiographic images so that there is an image overlap area. Therefore, the image processing unit 36 ​​synthesizes the multiple radiographic images so that the image overlap areas overlap.

[0047] After generating the composite image, image processing unit 36 ​​performs gradation processing to adjust the contrast of the composite image (step S106). Control unit 31 causes display unit 34 to display the composite image generated by image processing unit 36 ​​as shown in Fig. 6 (step S107). The user adjusts the pixel values ​​and composition position of the displayed composite image using operation unit 35 as appropriate (step S108).

[0048] [Effects of the embodiment] As described above, the console 30 according to this embodiment includes a control unit 31 that functions as an image acquisition unit that acquires multiple radiographic images of a subject, each captured under different imaging conditions. The console 30 also includes a pixel value correction unit that corrects the pixel values ​​of at least one of the multiple radiographic images, and an image processing unit 36 ​​that functions as an image synthesis unit that synthesizes the multiple radiographic images to acquire a single synthetic image. The pixel value correction unit corrects the pixel values ​​so that the maximum pixel value of the at least one radiographic image is equal to or less than the maximum gradation of the image. Therefore, the console 30 according to this embodiment can acquire a synthetic image that can be easily interpreted and that suppresses density saturation while suppressing the effects of multiple exposures on the subject.

[0049] [Other configurations] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments and can be modified in various ways within the scope of the invention as defined in the claims and their equivalents.

[0050] For example, in the above example, the image processing unit 36 ​​corrects the pixel values ​​of the second radiographic image to match the pixel values ​​of the first radiographic image having the lowest mAs value, but this is not limiting. The pixel value correction process by the image processing unit 36 ​​is not particularly limited to a specific method, as long as the final composite image does not cause density saturation. Therefore, the image processing unit 36 ​​may correct the pixel values ​​of the first radiographic image having a relatively low mAs value to match the pixel values ​​of another radiographic image having a relatively high mAs value, for example.

[0051] In the above example, the image processing unit 36 ​​uniformly corrects the pixel values ​​of the second radiographic image to match those of the first radiographic image, but the present invention is not limited to this. As shown in Fig. 7, the image processing unit 36 ​​may sequentially change the suitability of image processing for the other radiographic images in the body axis direction.

[0052] In the above example, step S105 of image synthesis processing is executed after step S104 of pixel value correction processing, but this is not limiting. That is, pixel value correction processing may be executed after image synthesis processing. With this configuration, the user can check the synthesized image first, and can more quickly determine whether re-imaging is required due to body movement.

[0053] 6, the control unit 31 may perform highlighting so as to indicate which radiographic image was used as a reference for pixel value correction processing in step S107. Note that in FIG. 6, an identification mark M is added as an example of highlighting, but this is not limiting. For example, a configuration may be adopted in which only the reference radiographic image is overlaid and displayed.

[0054] Furthermore, step S108 is not limited to manual adjustment of the composite image using the operation unit 35. That is, after selecting a radiographic image that serves as a reference for pixel values, the process may proceed to step S104, causing the image processing unit 36 ​​to execute the pixel value correction process and image composition process again. At this time, the configuration may be such that the user can select a pixel value processing method to be executed by the image processing unit 36 ​​from among the above-mentioned types. Furthermore, the configuration may be such that the user can select a pixel value processing method at the timing of issuing an instruction to execute the pixel value correction process and image composition process immediately before step S104.

[0055] In the above example, the photographing order information acquired from the RIS is stored in the storage unit 33, but the present invention is not limited to this. The photographer may input the photographing order information by operating the operation unit 35.

[0056] In the above description, the image processing unit 36 ​​performs pixel value correction processing because multiple radiographic images have density differences, but this is not limited to this. That is, radiographic images having pixel values ​​that are approximately the same as those of a reference radiographic image may be combined without undergoing pixel value correction processing.

[0057] Although the above example illustrates a configuration in which multiple radiographic images are acquired by changing the angle of the radiation source 13, this is not limiting. A configuration may be adopted in which multiple radiation sources 13 with different irradiation angles are provided, and multiple radiation sources 13 are caused to irradiate radiation based on different imaging order information, thereby acquiring multiple radiographic images at one time. This configuration can reduce misalignment of the radiographic images due to movement of the subject between radiation irradiations.

[0058] Furthermore, although the above describes examples in which a hard disk or a semiconductor nonvolatile memory is used as a computer-readable medium for the program according to the present invention, the present invention is not limited to this. Portable recording media such as CD-ROMs can also be used as other computer-readable media. Furthermore, carrier waves can also be used as a medium for providing the program data according to the present invention via a communication line. [Explanation of symbols]

[0059] 100 Radiation image processing system 10 Radiation Generator 20 Radiography equipment 30 Console (Radiological Image Processing Device) 31 control unit (image acquisition unit, shooting condition acquisition unit, display control unit) 36 Image processing unit (pixel value correction unit, image synthesis unit)

Claims

1. an image acquisition unit that acquires a plurality of radiographic images of a subject, each image being captured under different imaging conditions; a pixel value correcting unit that corrects pixel values ​​of at least one of the plurality of radiographic images; an image synthesis unit that synthesizes the plurality of radiographic images to obtain a single synthesized image, each of the plurality of radiographic images has an image overlapping area with at least one other radiographic image; The pixel value correcting unit corrects pixel values ​​of the at least one radiographic image so that the maximum pixel value is equal to or less than the maximum gradation value of the image.

2. an imaging condition acquisition unit that acquires mAs values ​​from a plurality of said imaging conditions; The radiation image processing apparatus according to claim 1 , wherein the pixel value correcting section corrects pixel values ​​of the at least one radiation image based on the mAs value.

3. The radiation image processing apparatus according to claim 2 , wherein the pixel value correcting section corrects pixel values ​​of the other radiation images based on pixel values ​​of the radiation image with the lowest mAs value among the plurality of radiation images.

4. 2. The radiographic image processing device according to claim 1, wherein, when a pixel value of the at least one radiographic image after correction becomes a decimal, the pixel value correction unit multiplies the pixel values ​​of all of the radiographic images by a predetermined coefficient to convert the pixel values ​​of all of the radiographic images to integers.

5. a display control unit that displays the composite image and the plurality of radiation images on a display unit; 2. The radiographic image processing apparatus according to claim 1, wherein the display control unit causes the display unit to distinguishably display, from among the plurality of radiographic images, a radiographic image that is used as a reference for correction of pixel values ​​of the at least one radiographic image by the pixel value correction unit.

6. The radiation image processing device according to claim 1 , a radiation generating device that generates radiation; a radiation imaging device that generates a radiation image by receiving radiation generated by the radiation generating device.

7. an image acquisition step of acquiring a plurality of radiographic images of a subject, each image being captured under different imaging conditions; a pixel value correcting step of correcting pixel values ​​of at least one of the plurality of radiographic images; an image synthesis step of synthesizing the plurality of radiographic images to obtain a single synthetic image, each of the plurality of radiographic images has an image overlapping area with at least one other radiographic image; The pixel value correcting step corrects pixel values ​​of the at least one radiographic image so that the maximum pixel value of the at least one radiographic image is equal to or less than the maximum gradation value of the image.

8. Computer, an image acquisition unit that acquires a plurality of radiographic images of a subject, each image being captured under different imaging conditions; a pixel value correcting unit that corrects pixel values ​​of at least one of the plurality of radiographic images; a program that functions as an image synthesis unit that synthesizes the plurality of radiographic images to obtain a single synthetic image, each of the plurality of radiographic images has an image overlapping area with at least one other radiographic image; The pixel value correction unit is a program that corrects pixel values ​​of the at least one radiographic image so that the maximum pixel value is equal to or less than the maximum gradation value of the image.

Images