JP7348361B2 - Image processing device - Google Patents

Description

The present invention relates to an image processing device.

In the medical field, diagnosis based on radiation images detected by radiation image detection devices is actively performed. The radiation image detection device has a sensor panel. A photographing area is provided on the sensor panel. A plurality of pixels are arranged two-dimensionally in the imaging area. The pixels accumulate electric charge in response to radiation emitted from a radiation source and transmitted through a subject (patient). A radiation image detection device converts charges accumulated in pixels into a digital signal and outputs this as a radiation image.

There are two types of radiation image detection devices: a stationary type that is fixed to an imaging stand installed in an imaging room, and a portable type that has a sensor panel and the like housed in a portable housing. A portable radiation image detection device is called an electronic cassette. Electronic cassettes include wired types that are powered from a commercial power source via cables, and wireless types that are powered from a battery attached to the casing.

Due to its mobility, electronic cassettes can be taken out and used outside the shooting room. For example, it is used for round imaging, in which patients who are unable to go to the imaging room are visited and imaged in hospital rooms. Furthermore, electronic cassettes are sometimes used outside medical facilities to photograph elderly people receiving home treatment or people who become suddenly ill due to an accident, disaster, or the like. Hereinafter, shooting without using a shooting stand will be referred to as free shooting.

By the way, the radiation source is provided with an irradiation field limiter (also called a collimator). The irradiation field limiter has an irradiation aperture that sets an irradiation field. Here, the irradiation field is a region to which radiation is irradiated. An operator such as a radiologic technologist changes the size of the irradiation aperture of this irradiation field limiter to set an irradiation field according to an imaging order instructed by an imaging requester such as a doctor.

Depending on the contents of the imaging order, the entire imaging area of the sensor panel may not be the irradiation field, and there may be a region (hereinafter referred to as a non-irradiation field) in which the imaging area is not irradiated with radiation. In this case, the part of the radiation image that corresponds to the non-irradiation field (hereinafter referred to as the "non-irradiation field applicable part") is displayed white as it is, and the part that corresponds to the irradiation field (hereinafter referred to as the irradiation field applicable part) is displayed blackishly. The contrast is too strong and obstructs observation.

Therefore, conventionally, as described in Patent Document 1, for example, when displaying a radiation image, the position of the irradiation field is detected, and the area other than the irradiation field corresponding to the detected irradiation field, that is, the non-irradiation field Radiation images were subjected to blackening processing, which fills out the area with black, and trimming processing, which removes non-irradiated areas.

In Patent Document 1, the position of the irradiation field is detected by image analysis of a radiation image. For example, a portion of a radiation image where the pixel value (density) changes rapidly is extracted as the boundary (edge) between the irradiated field and the non-irradiated field, and the rectangular area formed by the extracted boundary is detected as the irradiated field. ing. Alternatively, a dynamic contour extraction algorithm such as the Snake method is applied to radiation images to extract the contour of the irradiation field and detect it as the irradiation field.

JP 2015-100592 Publication

However, the irradiation field is not limited to a rectangular shape but is set to various shapes, the pixel values of the radiation image vary depending on the radiation irradiation conditions, and radiation has characteristics such as scattering and diffraction. For this reason, the outline of the irradiation field in the radiation image may not be clear. Therefore, in the method disclosed in Patent Document 1, in which the position of the irradiation field is detected by analyzing a radiation image, the reliability of the detected position of the irradiation field is not very high.

An object of the present invention is to provide an image processing device that can accurately detect the position of an irradiation field and perform appropriate image processing on a radiation image.

The image processing device of the present invention includes a camera image acquisition section that is attached to a radiation source and that acquires a camera image output from at least a camera that photographs a subject; a detection unit that detects an irradiation field applicable portion and a non-irradiation field applicable portion in a radiation image based on the radiation obtained; and a detection unit that performs image processing on the radiation image based on the irradiation field applicable portion and the non-irradiation field applicable portion. an image processing unit; a first acquisition unit that acquires a reference size LIM0 of an irradiation field in a camera image at a preset reference distance SID0 with the focal position of the radiation tube of the radiation source as an end point; It is equipped with a second acquisition unit that acquires the focal position and the distance SID1 from the imaging area for detecting the radiation image provided in the electronic cassette for detecting the radiation image, and the irradiation field corresponding portion is the area to which radiation is irradiated. The part of the radiation image that corresponds to the irradiation field is the part of the radiation image that corresponds to the irradiation field, and the non-irradiation field part is the part of the radiation image that corresponds to the non-irradiation field that is the area that is not irradiated with radiation other than the irradiation field. Recognizing a marker showing the position of the electronic cassette shown in the image, detecting the position coordinates of the marker in the camera image as the position of the electronic cassette, and a reference size LIM0 acquired by the first acquisition unit; From the reference distance SID0 and the distance SID1 acquired by the second acquisition unit, the size LIM1 of the irradiation field in the camera image at the time of radiography is calculated, and the size LIM1 of the irradiation field is calculated as the size LIM1 of the irradiation field in the camera image. The image processing unit outputs the position of the irradiation field by converting it into the position coordinates of Identify the part.

The radiation source is provided with an irradiation field limiter having an irradiation aperture for setting an irradiation field, and the first acquisition unit acquires the size of the irradiation aperture during radiography and calculates the size of the irradiation aperture obtained. It is preferable to obtain a reference size LIM0 corresponding to . It is preferable that the reference size LIM0 is obtained using an arithmetic expression that is a function using the size of the irradiation aperture as a variable.

It is preferable that the distance measurement sensor includes a distance measurement sensor, and that the second acquisition unit receives the distance SID1 from the distance measurement sensor. It is preferable that the second acquisition unit calculates the distance SID1 by using the size of the electronic cassette that appears in the camera image at the reference distance SID0, which is stored in advance.

The image processing section includes a first image processing section that performs first image processing as image processing on the portion corresponding to the irradiation field, and/or a second image processing section that performs second image processing as image processing on the portion corresponding to the non-irradiation field. It is preferable to include parts.

The first image processing unit preferably performs multi-frequency processing and dynamic range compression processing on the corresponding portion of the irradiation field as the first image processing. As the second image processing, the second image processing unit may perform blackening processing that fills the non-irradiation field applicable portion with black, or trimming processing that removes the non-irradiation field applicable portion and leaves only the irradiation field applicable portion. preferable. It is preferable to include an association processing unit that associates information of either the irradiation field applicable portion or the non-irradiation field applicable portion with the radiation image as supplementary information of the radiation image.

According to the present invention, it is possible to provide an image processing device that can accurately detect the position of an irradiation field and perform appropriate image processing on a radiation image.

FIG. 1 is a diagram showing an X-ray imaging system. FIG. 3 is a diagram showing an image file. FIG. 2 is a perspective view of the electronic cassette. It is a figure showing an X-ray image. FIG. 3 is a diagram showing the flow of operations performed by the electronic cassette. It is a figure showing a camera image. FIG. 2 is a block diagram of a computer that constitutes a console. FIG. 2 is a block diagram of a CPU of the console. FIG. 2 is a block diagram of an image processing section. 3 is a flowchart showing the processing procedure of the CPU of the console. 3 is a flowchart showing a processing procedure of an image processing section. FIG. 12A shows free imaging when the irradiation field is set obliquely to the imaging area and the arm is the imaging site, and FIG. 12B shows an X-ray image. FIG. 7 is a block diagram of another example of an image processing unit. It is a block diagram of CPU of the console of 2nd embodiment. It is a reference diagram of a 2nd embodiment. FIG. 3 is a block diagram of a CPU of a console according to a third embodiment.

[First embodiment]
In FIG. 1, an X-ray imaging system 10 that uses X-rays as radiation includes an X-ray generator 11 and an X-ray imaging device 12. The X-ray generator 11 includes an X-ray source 13, which corresponds to a radiation source, and a radiation source control device 14. The X-ray imaging device 12 includes an electronic cassette 15 and a console 16 corresponding to an image processing device.

In FIG. 1, in an imaging room where an X-ray imaging system 10 is installed, an electronic cassette 15 is placed on a table 17 facing an X-ray source 13, and the imaging region of a subject H (in this example, a hand ) is placed to perform X-ray photography. That is, the X-ray imaging shown in FIG. 1 is free imaging performed without using an imaging table.

The X-ray source 13 includes an X-ray tube 20 that generates X-rays, an irradiation field limiter 21 that limits an irradiation field IF (see FIG. 3, etc.) which is an area where X-rays are irradiated, and an irradiation field limiter 21 that defines an irradiation field IF. It has a built-in irradiation field display light source 22 that emits a field display light LIF (see also FIG. 3, etc.).

The X-ray tube 20 includes a filament that emits thermoelectrons and a target that emits X-rays when the thermoelectrons emitted from the filament collide with each other. The irradiation field limiter 21 has, for example, four lead plates that shield X-rays arranged on each side of a rectangle, and a rectangular irradiation opening that transmits the X-rays formed in the center. In this case, the irradiation field limiter 21 changes the size of the irradiation aperture by moving the position of the lead plate, and sets the irradiation field IF. The irradiation field display light source 22 irradiates the irradiation field display light LIF through the irradiation aperture of the irradiation field limiter 21 . Therefore, the irradiation field display light LIF literally has the same shape and size as the irradiation field IF. The irradiation field display light source 22 emits irradiation field display light LIF of a special color (for example, yellow) so that the operator can see it even in a dimly lit imaging room.

An optical camera 23 is attached to the X-ray source 13. After the operator has positioned the X-ray source 13, electronic cassette 15, and subject H relative to each other for X-ray photography, the camera 23 is positioned within its field of view (hereinafter referred to as FOV). The electronic cassette 15 and the subject H are captured. The camera 23 takes a camera image 63 (see FIG. 6), which is an optical image including the electronic cassette 15 and the subject H. The camera image 63 is, for example, a color image and a still image.

Here, the "camera attached to the radiation source" as used in the claims refers not only to the case where it is attached directly to the outer periphery of the X-ray source 13 as shown in FIG. This also includes the case where it is built into the radiation source 13. Even if an objective lens is disposed on the outer periphery of the X-ray source 13 and an image pickup device is built into a part other than the X-ray source 13 (for example, in an arm that hangs the X-ray source 13 from the ceiling), it is considered a "radiation source" in the claims. Included in "Cameras attached to"

The camera 23 has a wireless communication unit and a battery, and operates wirelessly. The camera 23 wirelessly receives a photographing instruction signal from the console 16 and photographs a camera image 63 in accordance with the photographing instruction signal. The camera 23 wirelessly transmits a captured camera image 63 to the console 16.

The radiation source control device 14 includes a touch panel 25, a voltage generation section 26, a control section 27, and an irradiation switch 28. The touch panel 25 is operated when setting the X-ray irradiation conditions consisting of the tube voltage, tube current, and X-ray irradiation time applied to the X-ray tube 20, as well as the size of the irradiation aperture of the irradiation field limiter 21. Ru. Here, the tube current is a parameter that determines the flow rate of thermoelectrons from the filament of the X-ray tube 20 toward the target.

The voltage generator 26 generates a tube voltage to be applied to the X-ray tube 20. The control section 27 controls the operation of the voltage generation section 26 to control the tube voltage, tube current, and X-ray irradiation time. The control unit 27 has a timer that starts measuring when X-rays are generated from the X-ray tube 20, and when the time measured by the timer reaches the irradiation time set in the irradiation conditions, the control unit 27 starts the operation of the X-ray tube 20. Stop the operation. Further, the control unit 27 operates the irradiation field limiter 21 to set the size of the irradiation aperture to the size set on the touch panel 25 .

The irradiation switch 28 is operated by the operator when starting X-ray irradiation. The irradiation switch 28 is of a two-stage push type. When the irradiation switch 28 is pressed to the first step (half-pressed), the control unit 27 causes the X-ray tube 20 to start a preparatory operation before generating X-rays. When the irradiation switch 28 is pressed to the second stage (fully pressed), the control unit 27 causes the X-ray tube 20 to generate X-rays. As a result, X-rays are irradiated toward the hand of the subject H, which is the part to be imaged.

The electronic cassette 15 detects an X-ray image 40 (see FIG. 2) based on X-rays emitted from the X-ray source 13 and transmitted through the subject H. Like the camera 23, the electronic cassette 15 has a wireless communication unit and a battery, and operates wirelessly. Electronic cassette 15 wirelessly transmits X-ray image 40 to console 16 .

The console 16 is configured by installing a control program such as an operating system and various application programs on a computer such as a notebook personal computer. The console 16 has a display 30 and an input device 31 such as a touch pad or a keyboard. The console 16 displays various operation screens equipped with GUI (Graphical User Interface) operation functions on the display 30, and accepts input of various operation instructions from the input device 31 by the operator through the various operation screens.

Various operation instructions input via the input device 31 include a shooting menu and condition setting instructions including corresponding irradiation conditions and the like. The imaging menu defines, for example, an imaging technique that includes a set of imaging site, posture, and orientation. In addition to the hand illustrated in FIG. 1, the photographed parts include the head, cervical vertebrae, chest, abdomen, fingers, elbows, arms, knees, and the like. The posture is the posture of the subject H such as standing, lying, sitting, etc., and the orientation is the orientation of the subject H with respect to the X-ray source 13 such as front, side, and back. The condition setting instruction is an instruction for setting the imaging menu and irradiation conditions according to the imaging order, and is input by the operator. An imaging order is issued by an imaging requester, such as a doctor in a medical department, to instruct an operator to perform X-ray imaging. When a condition setting instruction is input via the input device 31, the console 16 wirelessly transmits a condition setting signal including the set imaging menu and irradiation conditions to the electronic cassette 15.

The various operation instructions include an instruction to take a camera image 63. When an instruction to capture the camera image 63 is input via the input device 31, the console 16 wirelessly transmits a capture instruction signal to the camera 23.

The console 16 converts the X-ray image 40 from the electronic cassette 15 into an image file 41 in a format compliant with the DICOM (Digital Imaging and Communication in Medicine) standard, as shown in FIG. 2, for example. This is then transmitted to a medical picture archiving and communication system (PACS, not shown).

The image file 41 is an X-ray image 40 and supplementary information 42 associated with each other using one image ID. The supplementary information 42 includes subject information such as the name and gender of the subject H, order ID, shooting menu, irradiation conditions, and the like. The order ID is a symbol or number that identifies the imaging order.

In FIG. 3, the electronic cassette 15 includes a sensor panel 50, a circuit section 51, and a rectangular parallelepiped-shaped portable housing 52 that houses these components. The housing 52 has a size that complies with the international standard ISO (International Organization for Standardization) 4090:2001, which is approximately the same as, for example, a film cassette, an IP (Imaging Plate) cassette, or a CR (Computed Radiography) cassette.

A rectangular opening is formed in the front surface 52A of the housing 52, and a transmission plate 53 having X-ray transparency is attached to the opening. The electronic cassette 15 is positioned with the front surface 52A facing the X-ray source 13, and the front surface 52A is irradiated with X-rays. Although not shown, the housing 52 also includes a switch for turning the main power on/off, and an indicator that indicates the operating status of the electronic cassette 15, such as the remaining battery usage time and the ready status for shooting. is provided.

The sensor panel 50 includes a scintillator 55 and a photodetection board 56. The scintillator 55 and the photodetection substrate 56 are stacked in this order when viewed from the front surface 52A side. The scintillator 55 has a phosphor such as CsI:Tl (thallium-activated cesium iodide) or GOS (Gd ₂ O ₂ S:Tb, terbium-activated gadolinium oxysulfide), and transmits the X-rays incident through the transmission plate 53. Converts into visible light and emits it. Note that a sensor panel may be used in which the photodetection substrate 56 and the scintillator 55 are stacked in this order when viewed from the front surface 52A side that is irradiated with X-rays. Alternatively, a direct conversion sensor panel may be used that directly converts X-rays into signal charges using a photoconductive film such as amorphous selenium.

The photodetection substrate 56 detects visible light emitted from the scintillator 55 and converts it into an electric charge. The circuit unit 51 controls the driving of the photodetection board 56 and generates the X-ray image 40 based on the charge output from the photodetection board 56.

The photodetection board 56 is provided with a photographing area RX. The photographing region RX has approximately the same size as the transmission plate 53, and a plurality of pixels are arranged in a two-dimensional matrix of N rows and M columns. The pixels accumulate charges in response to visible light from the scintillator 55. The X-ray image 40 is detected by converting the charges accumulated in the pixels into digital signals in the circuit section 51.

N and M are integers of 2 or more, for example, N and M≈2000. Note that the number of pixels in rows and columns is not limited to this. Further, the pixels may be arranged in a square arrangement, or the pixels may be tilted at 45 degrees and arranged in a staggered manner.

L-shaped markers 57A are arranged at the four corners of the photographing region RX. Further, a rod-shaped marker 57B is arranged at the center of one short side of the photographing region RX. The side where this rod-shaped marker 57B is placed is on the upper side in the X-ray image 40. Further, a cross-shaped marker 57C is arranged at the center of the photographing region RX. The long side of the marker 57A is longer than the short side. From these markers 57A to 57C, the position and direction of the photographing region RX can be determined.

FIG. 3 shows a state in which the hand of the subject H is placed on the electronic cassette 15, as in FIG. The irradiation field display light LIF (indicated by dashed hatching) is emitted from the irradiation field display light source 22, and the irradiation field IF shown by the dashed line is irradiated with the irradiation field display light LIF.

In this example, in the irradiation field IF, the side corresponding to the wrist of the subject H is the same as the photographing region RX, and the other three sides are parallel to the three opposing sides of the photographing region RX. Furthermore, the irradiation field IF is set to be one size smaller than the imaging region RX. Therefore, in the imaging region RX, a region other than the irradiation field IF where X-rays are not irradiated, that is, a non-irradiation field NIF occurs.

In this case, as shown in FIG. 4, the X-ray image 40 output from the electronic cassette 15 includes an irradiation field corresponding portion 60 (indicated by dashed hatching) corresponding to the irradiation field IF and a non-irradiation field NIF. It is divided into a non-irradiation field corresponding portion 61 (indicated by solid hatching). In the X-ray image 40, the portion where the amount of X-rays reaching the portion is larger is displayed blacker. For this reason, the irradiation field corresponding portion 60 is displayed blackish because it is the portion that is irradiated with X-rays. On the other hand, since the non-irradiation field corresponding portion 61 is a portion that is not irradiated with X-rays, it has the maximum brightness and is displayed pure white.

The electronic cassette 15 is equipped with a function of detecting the start of X-ray irradiation. This irradiation start detection function is, for example, provided with an irradiation start detection sensor in the photographing region RX of the photodetection board 56. Then, a dose signal corresponding to the reached dose of X-rays output from the irradiation start detection sensor at a predetermined sampling period is compared with a preset irradiation start detection threshold, and the dose signal exceeds the irradiation start detection threshold. In this case, it is determined that X-ray irradiation has started. For example, a part of the pixel serves as the irradiation start detection sensor.

Further, the electronic cassette 15, like the control unit 27 of the radiation source control device 14, has a timer that starts measuring when the start of X-ray irradiation is detected. The electronic cassette 15 determines that the X-ray irradiation has ended when the time measured by the timer reaches the irradiation time of the irradiation conditions set on the console 16.

As shown in FIG. 5, when the electronic cassette 15 receives the condition setting signal from the console 16, it starts a pixel reset operation in which dark charges are read out from the pixels and reset (discarded). Note that the electronic cassette 15 is in a standby operation before receiving the condition setting signal. The standby operation is a state in which power is supplied only to the minimum necessary parts, such as the wireless communication unit that plays the role of receiving the condition setting signal.

Next, when the electronic cassette 15 detects the start of X-ray irradiation using the irradiation start detection function, it completes the pixel reset operation and starts a pixel charge accumulation operation that accumulates charges in the pixels according to the amount of X-rays reached. do. Thereby, the timing of starting X-ray irradiation from the X-ray source 13 and the timing of starting the pixel charge accumulation operation can be synchronized.

Thereafter, when the timer detects the end of X-ray irradiation, the electronic cassette 15 finishes the pixel charge accumulation operation and starts an image readout operation for reading out the X-ray image 40 for diagnosis. This completes one X-ray photographing session in which one screen worth of X-ray images 40 is obtained. After the image reading operation is completed, the electronic cassette 15 returns to the standby operation again.

FIG. 6 is a camera image 63 showing the X-ray photography shown in FIGS. 1 and 3. The camera image 63 includes the table 17, the electronic cassette 15 placed on the table 17, the hand of the subject H placed on the electronic cassette 15, and the irradiation field display light LIF from the irradiation field display light source 22. It's reflected.

Since the camera 23 is attached to the X-ray source 13, the positional relationship between the X-ray source 13 and the camera 23 does not change. Therefore, in the camera image 63, the center of the irradiation field display light LIF and, by extension, the irradiation field IF is always located at the same position.

In FIG. 7, the console 16 includes a storage device 65, a memory 66, a CPU (Central Processing Unit) 67, and a communication section 68 in addition to the display 30 and input device 31 described above. These are interconnected via a data bus 69.

The storage device 65 is a hard disk drive built into the console 16 or connected through a cable or a network, or a disk array in which a plurality of hard disk drives are connected in series. The storage device 65 stores control programs such as an operating system, various application programs, and various data accompanying these programs.

The memory 66 is a work memory for the CPU 67 to execute processing. The CPU 67 loads a program stored in the storage device 65 into the memory 66 and performs processing according to the program, thereby controlling each part of the console 16 in an integrated manner. The communication unit 68 is responsible for communicating various data such as the X-ray image 40 and camera image 63 between the electronic cassette 15 and the camera 23.

In FIG. 8, an operating program 75 is stored in the storage device 65. The operating program 75 is an application program for causing the computer constituting the console 16 to function as an image processing device. When the operating program 75 is started, the CPU 67 functions as a camera image acquisition section 80, an X-ray image acquisition section 81, a detection section 82, an image processing section 83, and a display control section 84 in cooperation with the memory 66 and the like. do.

The camera image acquisition unit 80 has a camera image acquisition function of acquiring a camera image 63 from the camera 23. The camera image acquisition section 80 outputs the acquired camera image 63 to the detection section 82 . The X-ray image acquisition unit 81 corresponds to a radiation image acquisition unit and has an X-ray image acquisition function of acquiring the X-ray image 40 from the electronic cassette 15. The X-ray image acquisition unit 81 outputs the acquired X-ray image 40 to the image processing unit 83.

The detection unit 82 has a detection function of detecting the position of the electronic cassette 15 based on the camera image 63. More specifically, the detection unit 82 applies a known image recognition technique such as pattern matching to the camera image 63 and recognizes the markers 57A to 57C on the front surface 52A of the casing 52 of the electronic cassette 15. Then, the position coordinates of the recognized markers 57A to 57C in the camera image 63 are detected as the position of the electronic cassette 15. Since the markers 57A and 57B are arranged along the photographing region RX, the position of the electronic cassette 15 detected by the detection unit 82 is the position of the photographing region RX. The detection unit 82 outputs information on the detected position of the electronic cassette 15 (hereinafter referred to as cassette position information) to the image processing unit 83.

If the marker 57C in this example is covered by the subject H and does not appear in the camera image 63, it will not be recognized by the detection unit 82, as a matter of course. However, if at least one of the four markers 57A can be recognized, the position of the electronic cassette 15 can be detected. Note that instead of or in addition to the markers 57A to 57C, the outline of the outer periphery of the front surface 52A may be image recognized.

The detection unit 82 also has a detection function of detecting the position of the irradiation field IF based on the camera image 63. In this embodiment, the irradiation field display light LIF is emitted from the irradiation field display light source 22, and this irradiation field display light LIF is reflected in the camera image 63 as shown in FIG. Therefore, in this embodiment, the detection unit 82 detects the position of the irradiation field IF based on the irradiation field display light LIF. In this case, as in the case of the position of the electronic cassette 15, the detection unit 82 recognizes the contour of the outer periphery of the irradiation field display light LIF using well-known image recognition technology, and determines the position coordinates of the recognized contour in the camera image 63. , is detected as the position of the irradiation field IF. At this time, since the irradiation field display light LIF emits light in a special color, the detection unit 82 recognizes the outline of the outer periphery of the irradiation field display light LIF with reference to the color information. The detection unit 82 outputs information on the detected position of the irradiation field IF (hereinafter referred to as irradiation field position information) to the image processing unit 83.

The image processing section 83 has an image processing function of performing image processing on the X-ray image 40 from the X-ray image acquisition section 81 based on the cassette position information and the irradiation field position information from the detection section 82 . The image processing section 83 outputs the image-processed X-ray image to the display control section 84.

The display control unit 84 controls displaying the image-processed X-ray image 40 from the image processing unit 83 on the display 30.

As shown in FIG. 9, the image processing section 83 includes a first image processing section 83A and a second image processing section 83B. The first image processing unit 83A specifies the irradiation field corresponding portion 60 of the X-ray image 40 based on the cassette position information and the irradiation field position information from the detection unit 82. Then, first image processing is performed on the irradiation field corresponding portion 60 as image processing. On the other hand, the second image processing unit 83B identifies the non-irradiation field applicable portion 61 of the X-ray image 40, and performs second image processing as image processing on the non-irradiation field applicable portion 61.

More specifically, the first image processing unit 83A performs multi-frequency processing and dynamic range compression processing on the irradiation field corresponding portion 60 as the first image processing. Further, the second image processing unit 83B performs blackening processing on the non-irradiation field corresponding portion 61 as second image processing.

In the multi-frequency processing, first, a plurality of smoothed images are created for the X-ray image 40 before image processing. Then, a difference image between the respective smoothed images is obtained, and a nonlinear transformation process is performed on the difference image. Next, frequency emphasis is performed using the sum of the difference images that have been subjected to the nonlinear transformation process, and edges of structures such as bones are emphasized. Dynamic range compression processing is part of the multi-frequency processing functionality. Dynamic range compression processing uses the sum of each differential image that has been subjected to nonlinear conversion processing using multi-frequency processing to brighten the dark parts of the X-ray image 40 to make it easier to see, or conversely, to make the bright parts of the X-ray image 40 easier to see. This process darkens the image to make it easier to see. The blackening process is a process of filling the non-irradiation field corresponding portion 61 with black.

Next, the operation of the above configuration will be explained with reference to the flowcharts of FIGS. 10 and 11. First, the operator sets a desired shooting menu via the input device 31 of the console 16. As a result, a condition setting signal including the set imaging menu and the corresponding irradiation conditions is transmitted from the console 16 to the electronic cassette 15. After setting the imaging menu, the operator sets the same irradiation conditions as the irradiation conditions corresponding to the set imaging menu on the radiation source control device 14 via the touch panel 25. Thereafter, relative positioning of the X-ray source 13, electronic cassette 15, and subject H is started.

For example, in the case of photographing a hand, the operator places the electronic cassette 15 on the table 17, places the hand of the subject H on the electronic cassette 15, and then moves the X-ray source 13 to the subject, as shown in FIG. Place it directly above H's hand. Also, at this time, the operator sets the size of the irradiation aperture of the irradiation field limiter 21, that is, the irradiation field IF, in the radiation source control device 14 via the touch panel 25.

The operator operates the irradiation field display light source 22 to irradiate the irradiation field display light LIF toward the electronic cassette 15 . Using the irradiation field display light LIF as a clue, the operator finely adjusts the positions of the X-ray source 13, electronic cassette 15, and subject H so that the positional relationship between them becomes a desired one.

After positioning is completed, the operator inputs an instruction to shoot the camera image 63 via the input device 31 of the console 16. As a result, a photographing instruction signal for the camera image 63 is wirelessly transmitted from the console 16 to the camera 23.

The camera 23 shoots a camera image 63 in response to a shooting instruction signal from the console 16. Camera image 63 is wirelessly transmitted from camera 23 to console 16 .

As shown in step ST100 in FIG. 10, the camera image 63 from the camera 23 is acquired by the camera image acquisition unit 80 (camera image acquisition step). The camera image 63 is output from the camera image acquisition section 80 to the detection section 82 .

The operator operates the irradiation switch 28 to cause the X-ray source 13 to generate X-rays. The X-rays emitted from the X-ray source 13 and transmitted through the subject H are emitted onto the front surface 52A of the electronic cassette 15. As a result, the X-ray image 40 is detected by the electronic cassette 15. The X-ray image 40 is wirelessly transmitted from the electronic cassette 15 to the console 16.

As shown in step ST110, the X-ray image 40 from the electronic cassette 15 is acquired by the X-ray image acquisition section 81 (corresponding to an X-ray image acquisition step or a radiation image acquisition step). The X-ray image 40 is output from the X-ray image acquisition section 81 to the image processing section 83.

As shown in step ST120, the detection unit 82 detects the position of the electronic cassette 15 and the position of the irradiation field IF based on the camera image 63 from the camera image acquisition unit 80 (detection step). Cassette position information, which is information on the detected position of the electronic cassette 15, and irradiation field position information, which is position information on the irradiation field IF, are output to the image processing unit 83.

As shown in step ST130, the image processing unit 83 performs image processing on the X-ray image 40 from the X-ray image acquisition unit 81 based on the cassette position information and the irradiation field position information from the detection unit 82. (image processing step).

FIG. 11 shows a series of image processing steps performed by the image processing section 83. As shown in FIG. 9, the first image processing unit 83A performs multi-frequency processing and dynamic range compression processing on the irradiation field corresponding portion 60 as first image processing (step ST1301). Next, the second image processing unit 83B performs blackening processing on the non-irradiation field corresponding portion 61 as second image processing (step ST1302). The image-processed X-ray image 40 that has been subjected to such image processing is output from the image processing section 83 to the display control section 84. Note that the order of the first image processing in step ST1301 and the second image processing in step ST1302 may be reversed.

In step ST140 in FIG. 10, the image-processed X-ray image 40 is displayed on the display 30 by the display control unit 84. The X-ray image 40 is further converted into an image file 41 by the console 16 and transmitted to the PACS for viewing by the imaging client.

The console 16 detects the position of the irradiation field IF based on the camera image 63 output from the camera 23, instead of detecting the position of the irradiation field IF by image analysis of the X-ray image 40 as in the conventional case. do. Therefore, it is possible to detect the position of the irradiation field IF more accurately than detection based on the X-ray image 40 in which the outline of the irradiation field IF may not be clear. Then, appropriate image processing can be performed on the X-ray image 40 based on the information on the position of the irradiation field IF detected in this way.

The effects of the present invention will be further explained in comparison with a conventional example in which an X-ray image 40 is analyzed. As shown in FIG. 12A, the irradiation field IF is set obliquely with respect to the imaging area RX so that each side of the irradiation field IF and each side of the imaging area RX are not parallel, and the relatively straight line component of the arm etc. Consider the case where the imaged area contains a large amount of .

In conventional image analysis of the X-ray image 40, for example, a portion where pixel values change rapidly is extracted as a boundary between the irradiation field IF and the non-irradiation field NIF. Then, a rectangular area formed by the extracted boundaries is detected as an irradiation field. Therefore, if the irradiation field IF is not rectangular as shown in FIG. 12A, it becomes difficult to detect the position of the irradiation field IF.

Further, as shown in FIG. 12B, when the imaging site is an arm, there are many linear components such as the arm outline 90 and the bones (ulna and radius) outlines 91. Since these contours 90 and 91 are also portions where pixel values change rapidly, they are likely to be mistakenly extracted as boundaries between the irradiation field IF and the non-irradiation field NIF. Moreover, since these contours 90 and 91 are straight lines, there is an increased possibility that they will be mistakenly extracted as the boundary between the irradiation field IF and the non-irradiation field NIF, which are also straight lines.

On the other hand, in the present invention in which the position of the irradiation field IF is detected based on the camera image 63 output from the camera 23, the position of the irradiation field IF can be detected independently of the X-ray image 40. As shown in 12, even when the irradiation field IF is set obliquely to the imaging region RX and the imaging region contains relatively many linear components, it is possible to accurately detect the position of the irradiation field IF. be.

That is, since the detection unit 82 detects the position of the irradiation field IF based on the irradiation field display light LIF from the irradiation field display light source 22 reflected in the camera image 63, the irradiation field can be easily determined by using well-known image recognition technology. The position of the IF can be detected. Since the irradiation field display light source 22 is standard equipment in many X-ray sources, existing equipment can be effectively utilized.

The first image processing unit 83A performs multi-frequency processing and dynamic range compression processing on the irradiation field corresponding portion 60 of the X-ray image 40, so edges of structures such as bones are emphasized and the overall contrast is uniform. , it is possible to obtain an X-ray image 40 with image quality suitable for diagnosis. Furthermore, since these first image processes need only be performed on the irradiation field corresponding portion 60, the processing load on the first image processing unit 83A can be reduced.

Further, since the second image processing unit 83B performs the blackening process on the non-irradiation field applicable portion 61, the non-irradiation field applicable portion 61 is not displayed in white and does not interfere with observation.

The second image processing performed on the non-irradiation field corresponding portion 61 is not limited to the blackening processing described above. As in the second image processing section 95B of the image processing section 95 shown in FIG. 13, a trimming process may be performed in which the non-irradiation field applicable portion 61 is removed and only the irradiation field applicable portion 60 is left. In this case, as in the blackening process, the non-irradiation field applicable portion 61 itself is removed, so the non-irradiation field applicable portion 61 is not displayed in white and does not interfere with observation.

Although the first image processing section 95A has a different code for convenience, its functions are the same as the first image processing section 83A.

[Second embodiment]
In the second embodiment shown in FIGS. 14 and 15, the size of the irradiation field IF in the camera image 63 at the time of X-ray imaging (hereinafter referred to as the "intra-image size") is calculated.

In FIG. 14, the CPU 67 of the console 16 of this embodiment includes a first acquisition unit 100 in addition to the units 80, 81, 83, 84 (not shown in FIG. 14) shown in FIG. 8 of the first embodiment. and a second acquisition unit 101 are provided. Further, a detection unit 102 is provided instead of the detection unit 82. Hereinafter, the functions of the first acquisition section 100, the second acquisition section 101, and the detection section 102 will be explained with reference to FIG. 15 as well.

The first acquisition unit 100 acquires an irradiation field IF0 in the camera image 63 at a preset reference distance SID (Source to Image receptor Distance) 0 with the focal position FP of the X-ray tube 20 of the X-ray source 13 as an end point. A reference size (hereinafter referred to as reference image size) LIM0 is obtained.

More specifically, the first acquisition unit 100 first acquires the size (vertical and horizontal length of the irradiation aperture) x and y of the irradiation aperture of the irradiation field limiter 21 during X-ray imaging. Then, based on the arithmetic expression 103 (LIM0=F(x,y)) stored in the storage device 65, a reference image size LIM0 corresponding to the obtained irradiation aperture sizes x and y is obtained. Arithmetic expression 103 is a function of the standard image size LIM0 with the sizes x and y of the irradiation aperture as variables. The first acquisition unit 100 acquires the standard image size LIM0 by substituting the acquired sizes x and y of the irradiation aperture into the arithmetic expression 103. The first acquisition unit 100 outputs the acquired reference intra-image size LIM0 and reference distance SID0 to the detection unit 102.

Here, the reference image size LIM0 is the vertical and horizontal length X0 of the irradiation field IF0 projected on a plane whose normal is a line connecting the focal position FP and a point CP0 located at a reference distance SID0 from the focal position FP. , Y0.

The second acquisition unit 101 acquires the distance SID1 between the focal position FP and the imaging region RX during X-ray imaging. The distance SID1 is the length of a perpendicular line drawn from the focal position FP to the imaging area RX.The second acquisition unit 101 outputs the acquired distance SID1 to the detection unit 102.

The detection unit 102 determines the size within the image of the irradiation field IF1 in the camera image 63 during X-ray photography based on the reference image size LIM0 and reference distance SID0 from the first acquisition unit 100 and the distance SID1 from the second acquisition unit 101. Calculate the size LIM1. That is, the intra-image size LIM1 is determined by calculation using the similarity ratio SID1/SID0 shown in equation (1) below.
LIM1=(SID1/SID0)・LIM0...(1)

Similarly to the standard image size LIM0, the intra-image size LIM1 is also determined by the length and width of the irradiation field IF1 projected onto a plane whose normal is a line connecting the focal position FP and a point CP1 located a distance SID1 from the focal position FP. The lengths are X1 and Y1. Therefore, the above equation (1) can be rewritten into the following equations (2) and (3).
X1=(SID1/SID0)・X0...(2)
Y1=(SID1/SID0)・Y0...(3)

For example, if the reference distance SID0=5m, X0=1m, Y0=50cm, and the distance SID1=2.5m, the similarity ratio SID1/SID0=2.5/5=0.5, so X1=50cm , Y1=25cm.

The detection unit 102 converts the calculated intra-image size LIM1 into position coordinates of the outline of the irradiation field IF1 within the camera image 63. The converted position coordinates are then output to the image processing unit 83 as irradiation field position information. The subsequent processing is the same as that in the first embodiment, so the explanation will be omitted.

In this way, at the reference distance SID0, the reference image size LIM0 of the irradiation field IF0 in the camera image 63 and the distance SID1 between the focal position FP and the imaging area RX at the time of X-ray photography are acquired, and the reference image size is determined. Since the image size LIM1 of the irradiation field IF1 in the camera image 63 at the time of X-ray photography is calculated from LIM0, the reference distance SID0, and the distance SID1, the irradiation field display light source 22 may fail and the irradiation field display light LIF Even if the X-ray source cannot irradiate the radiation field or the X-ray source does not include the radiation field display light source 22 itself, the position of the radiation field IF1 can be detected without any problem.

Note that the sizes x and y of the irradiation aperture during X-ray imaging are input directly to the console 16 by the operator via the input device 31, for example. Alternatively, the sizes x and y of the irradiation aperture during X-ray imaging may be transmitted from the radiation source control device 14 to the console 16.

Similarly, the operator inputs the distance SID1 between the focal position FP and the imaging region RX during X-ray imaging directly into the console 16 via the input device 31. Alternatively, a distance measurement sensor for measuring the distance SID1 may be attached to the X-ray source 13, and the measured distance SID1 may be transmitted from the distance measurement sensor to the console 16. As the distance measurement sensor, a time of flight camera, an ultrasonic sensor, a radar sensor, etc. can be used.

Alternatively, the distance SID1 may be determined based on the size of the electronic cassette 15 reflected in the camera image 63. In this case, the size of the electronic cassette 15 that appears in the camera image 63 at the reference distance SID0 is stored in the storage device 65 in advance. Then, in the same way as the intra-image size LIM1 of the irradiation field IF1 in the camera image 63 at the time of X-ray photography, SID1 is determined by calculation using the similarity ratio.

Although the reference image size LIM0 corresponding to the sizes x and y of the irradiation aperture is calculated using equation 103, the present invention is not limited to this. The reference image size LIM0 corresponding to the sizes x and y of the irradiation aperture may be stored in the storage device 65 in the form of a data table. In this case, the first acquisition unit 100 reads the reference image size LIM0 corresponding to the acquired irradiation aperture sizes x and y from the data table of the storage device 65.

[Third embodiment]
In the third embodiment shown in FIG. 16, information on the corresponding portion of the irradiation field is associated with the X-ray image 40 as supplementary information 42 of the X-ray image 40.

In FIG. 16, the CPU 67 of the console 16 of this embodiment is provided with an association processing section 110 in addition to the sections 80 to 84 (only the detection section 82 is shown) shown in FIG. 8 of the first embodiment.

The detection unit 82 outputs the cassette position information and the irradiation field position information to the association processing unit 110. The association processing unit 110 specifies the irradiation field applicable portion 60 of the X-ray image 40 based on the cassette position information and the irradiation field position information from the detection unit 82 . The association processing unit 110 includes information on the identified irradiation field applicable portion 60 (hereinafter referred to as irradiation field applicable portion information) in the supplementary information 42 of the image file 41. Specifically, the irradiation field applicable portion information is the positional coordinates of the irradiation field applicable portion 60 within the X-ray image 40 .

In this way, since the irradiation field applicable portion information is associated with the X-ray image 40 as the supplementary information 42, image processing for the irradiation field applicable portion 60 can be performed on other equipment other than the console 16, such as a client terminal of the imaging client. When administering, you can refer to the irradiation field applicable part information.

Note that instead of the irradiation field applicable portion information, non-irradiation field applicable portion information, which is information on the non-irradiation field applicable portion 61, may be associated with the X-ray image 40 as the supplementary information 42. Further, although FIG. 16 illustrates the detection unit 82 of the first embodiment, the detection unit 102 of the second embodiment may also be used.

The image processing section may include at least one of the first image processing section and the second image processing section.

The camera image 63 may be captured as a moving image, and the position of the electronic cassette 15 and the position of the irradiation field IF may be detected based on the camera image 63 captured immediately before the start of X-ray irradiation.

In each of the above embodiments, the camera image 63 is used only to detect the position of the electronic cassette 15 and the position of the irradiation field IF. While relative positioning of the electronic cassette 15 and the subject H is being performed, the camera image 63 may be displayed on the display 30 to assist in positioning.

In each of the above embodiments, for example, the camera image acquisition section 80, the X-ray image acquisition section 81, the detection sections 82, 102, the image processing sections 83, 95 (first image processing sections 83A, 95A, second image processing section 83B, 95B), the display control unit 84, the first acquisition unit 100, the second acquisition unit 101, and the association processing unit 110, the hardware structure of the processing unit that executes various processes is as shown below. There are various types of processors.

Various types of processors include CPUs, programmable logic devices (PLDs), dedicated electric circuits, and the like. As is well known, a CPU is a general-purpose processor that executes software (programs) and functions as various processing units. A PLD is a processor such as an FPGA (Field Programmable Gate Array) whose circuit configuration can be changed after manufacturing. The dedicated electric circuit is a processor such as an ASIC (Application Specific Integrated Circuit) that has a circuit configuration specifically designed to execute a specific process.

One processing unit may be composed of one of these various types of processors, or may be composed of a combination of two or more processors of the same type or different types (for example, multiple FPGAs or a combination of a CPU and an FPGA). may be done. Further, the plurality of processing units may be configured with one processor. First, as an example of configuring multiple processing units with one processor, there is a configuration in which one processor is configured by a combination of one or more CPUs and software, and this processor functions as multiple processing units. . Second, there is a form that uses a processor that implements the functions of an entire system including a plurality of processing units with a single IC chip, as typified by a system on chip (SoC). In this way, various processing units are configured using one or more of the various processors described above as a hardware structure.

Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit (circuitry) that is a combination of circuit elements such as semiconductor elements.

From the above description, it is possible to understand the image processing apparatus described in Additional Note 1 below.

[Additional note 1]
a radiation image acquisition processor that acquires a radiation image based on radiation emitted from a radiation source and transmitted through a subject and detected by an electronic cassette;
a camera image acquisition processor that is attached to the radiation source and that acquires a camera image output from a camera that photographs at least the electronic cassette;
a detection processor that detects the position of the electronic cassette and the position of an irradiation field, which is an area to which the radiation is irradiated, based on the camera image;
An image processing apparatus comprising: an image processing processor that performs image processing on the radiation image based on information on the position of the electronic cassette and information on the position of the irradiation field.

In each of the above embodiments, the case where free imaging is performed using the X-ray imaging system 10 installed in the imaging room is illustrated, but a mobile X-ray generating device, which is a mobile X-ray generating device, is used to perform free imaging. The present invention is also applicable when free photography is performed in a hospital room.

The present invention is applicable not only to X-rays but also to cases where other radiations such as γ-rays are used.

It goes without saying that the present invention is not limited to the embodiments described above, and that various configurations can be adopted as long as they do not depart from the gist of the present invention. Furthermore, the present invention extends not only to the program but also to a storage medium that stores the program.

10 X-ray imaging system 11 X-ray generator 12 X-ray imaging device 13 X-ray source (radiation source)
14 Radiation source control device 15 Electronic cassette 16 Console (image processing device)
20 X-ray tube 21 Irradiation field limiter 22 Irradiation field display light source 23 Camera 25 Touch panel 26 Voltage generation section 27 Control section 28 Irradiation switch 30 Display 31 Input device 40 X-ray image (radiation image)
41 Image file 42 Additional information 50 Sensor panel 51 Circuit section 52 Housing 52A Front side 53 Transmissive plate 55 Scintillator 56 Photodetection board 57A to 57C Marker 60 Irradiation field applicable portion 61 Non-irradiation field applicable portion 63 Camera image 65 Storage device 66 Memory 67 CPU
68 Communication Department 69 Data Bus 75 Operating Program 80 Camera Image Acquisition Unit 81 X-ray Image Acquisition Unit (Radiation Image Acquisition Unit)
82, 102 Detection unit 83, 95 Image processing unit 83A, 95A First image processing unit 83B, 95B Second image processing unit 84 Display control unit 90 Arm outline 91 Bone outline 100 First acquisition unit 101 Second acquisition unit 103 Arithmetic formula 110 Association processing unit H Subject LIF Irradiation field display light FOV Camera field of view IF, IF0, IF1 Irradiation field NIF Non-irradiation field RX Imaging area ST100 to ST140, ST1301, ST1302 Step FP X-ray tube focal position x, y Size of irradiation aperture during X-ray imaging SID0 Reference distance SID1 Distance between focal position and imaging area during X-ray imaging LIM0 Standard size within image LIM1 Intra-image size of irradiation field within camera image during X-ray imaging CP0, CP1 Points X0, Y0, X1, Y1 Length and width of irradiation field

Claims (9)

a camera image acquisition unit that acquires a camera image output from an optical camera that is attached to the radiation source and that photographs at least a subject;
a detection unit that detects an irradiation field applicable portion and a non-irradiation field applicable portion of a radiation image based on radiation irradiated from the radiation source and transmitted through the subject;
an image processing unit that performs image processing on the radiation image based on the irradiation field applicable portion and the non-irradiation field applicable portion;
a first acquisition unit that acquires a reference size LIM0 of the irradiation field in the camera image at a preset reference distance SID0 with the focal position of the radiation tube of the radiation source as an end point;
comprising a second acquisition unit that acquires the focal position during radiography and a distance SID1 between the focal position and the imaging area for detecting the radiation image provided in the electronic cassette for detecting the radiation image;
The irradiation field applicable portion is a portion of the radiation image that corresponds to an irradiation field that is an area to which the radiation is irradiated,
The non-irradiation field corresponding portion is a portion of the radiation image that corresponds to a non-irradiation field that is an area other than the irradiation field that is not irradiated with the radiation,
The detection unit recognizes a marker showing the position of the electronic cassette shown in the camera image, and detects the position coordinates of the marker in the camera image as the position of the electronic cassette, and the first acquisition unit Calculate the size LIM1 of the irradiation field in the camera image at the time of radiography from the reference size LIM0 acquired by the reference distance SID0 and the distance SID1 acquired by the second acquisition unit. , and outputting the position of the irradiation field by converting the size LIM1 of the irradiation field into position coordinates of the irradiation field within the camera image;
The image processing unit is an image processing device that identifies a portion corresponding to the irradiation field and a portion corresponding to the non-irradiation field in the radiation image based on the position of the irradiation field and the position of the electronic cassette. The radiation source is provided with an irradiation field limiter having an irradiation aperture that sets the irradiation field,
The image processing device according to claim 1, wherein the first acquisition unit acquires the size of the irradiation aperture during radiography, and acquires the reference size LIM0 corresponding to the acquired size of the irradiation aperture. . The image processing apparatus according to claim 2 , wherein the reference size LIM0 is obtained using an arithmetic expression that is a function using the size of the irradiation aperture as a variable.
Equipped with a distance measurement sensor,
The image processing device according to any one of claims 1 to 3, wherein the second acquisition unit receives the distance SID1 from the distance measurement sensor. 4. The second acquisition unit calculates the distance SID1 by using a size of the electronic cassette that appears in a camera image at a reference distance SID0, which is stored in advance. Image processing device. The image processing unit is a first image processing unit that performs first image processing as the image processing on the portion corresponding to the irradiation field, and/or a first image processing portion that performs second image processing as the image processing on the portion corresponding to the non-irradiation field. The image processing apparatus according to any one of claims 1 to 5, further comprising a second image processing section that performs image processing. The image processing apparatus according to claim 6, wherein the first image processing section performs multi-frequency processing and dynamic range compression processing on the corresponding portion of the irradiation field as the first image processing. The second image processing unit performs, as the second image processing, blackening processing that fills the non-irradiation field applicable portion with black, or trimming that removes the non-irradiation field applicable portion and leaves only the irradiation field applicable portion. The image processing apparatus according to claim 6 or 7, wherein the image processing apparatus performs processing. 9. The apparatus according to claim 1, further comprising an association processing unit that associates information of either the irradiation field applicable portion or the non-irradiation field applicable portion with the radiation image as supplementary information of the radiation image. Image processing device.

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