JP6789130B2 - X-ray equipment - Google Patents

Description

In the present invention, an irradiation area of X-rays emitted from an X-ray source is set by an X-ray aperture, and X-rays transmitted through the area corresponding to the set irradiation area are detected by using a detector to image the image. X-ray imaging equipment.

Conventionally, an X-ray diaphragm that narrows the irradiation range of X-rays emitted from an X-ray tube has been used for the purpose of improving image quality by reducing the scattered rays of X-rays in addition to reducing the exposure of areas that do not require radiography. An X-ray imaging device provided is known. In such an X-ray imaging apparatus, the position information of the X-ray diaphragm is acquired by using a position detector or the like, and the region corresponding to the opening portion of the X-ray diaphragm is imaged.
For example, Patent Document 1 discloses an X-ray image diagnostic apparatus that identifies an X-ray aperture region in an image based on position information, X-ray tube angle information, and the like by an X-ray aperture position detector.

Japanese Unexamined Patent Publication No. 2008-200075

However, since the X-ray diagnostic imaging apparatus of Patent Document 1 does not consider the heel effect, it is mentioned that there is a difference in the sharpness of the aperture side located on the anode side and the cathode side of the X-ray tube. This may not be the case, and the detection accuracy of the X-ray aperture region may decrease.

In an X-ray tube, a high voltage of several tens of kV to several hundreds of kV is applied between the cathode (filament) and the anode (target), and thermions emitted from the cathode are accelerated toward the anode to become the anode. By colliding, X-rays are generated. At this time, in the cathode-anode direction, the X-rays emitted to the anode side travel through the anode and then are emitted, so that more low-energy X-rays are absorbed by the metal inside the anode and high-energy X-rays are emitted. More released. On the other hand, the X-rays emitted to the cathode side are not so affected by the absorption by the metal in the anode. Therefore, among the X-rays emitted from the X-ray tube, the energy distribution of the X-rays emitted to the anode side in the cathode-anode shifts to a side higher than the energy distribution of the X-rays emitted to the cathode side. (See FIG. 11).

Therefore, in the X-ray image after the aperture transmission, the sharpness of the image near the side located on the cathode side is gentler than the image near the side located on the anode side among the four sides of the rectangular X-ray irradiation region. Will be.
For this reason, the X-ray irradiation region may not be detected accurately unless it is accurately grasped whether the side of the X-ray irradiation region is located on the anode side or the cathode side.

The present invention has been made in view of the above circumstances, and of the four sides of the X-ray irradiation region after transmission through the X-ray aperture, the side located on the cathode side is also accurately detected, and the X-ray irradiation region is accurately detected. The purpose is to do.

In order to solve the above problems, the present invention provides the following means.
One aspect of the present invention is an X-ray source having an X-ray tube that irradiates a subject with X-rays, an X-ray diaphragm that limits an X-ray irradiation region that irradiates the subject with the X-ray source, and the like. An X-ray detector that detects X-rays that are irradiated through an X-ray diaphragm and have passed through the subject, and an image processing unit that generates an X-ray image based on an electrical signal output from the X-ray detector. Of the four sides of the X-ray irradiation region in the X-ray image generated by the image processing unit, the cathode detection unit that detects the cathode position information indicating the side located on the cathode side of the X-ray tube, and the cathode. Provided is an X-ray imaging apparatus including an irradiation area detection unit that detects an X-ray irradiation region in the X-ray image based on the cathode position information obtained from the detection unit.

According to the present invention, it is possible to accurately detect the side located on the cathode side among the four sides of the X-ray irradiation region, and accurately detect the X-ray irradiation region.

It is a block diagram which shows the schematic structure of the X-ray imaging apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the flow of the process which stores the installation information in the X-ray photographing apparatus which concerns on 1st Embodiment of this invention. In the X-ray imaging apparatus according to the first embodiment of the present invention, (A) is a diagram for explaining a reading area for profiling an captured image, and (B) is a graph showing a profile result. is there. It is a flowchart which shows the flow of the X-ray irradiation area detection processing in the X-ray imaging apparatus which concerns on 1st Embodiment of this invention. It is a flowchart which shows the flow of the cathode position information generation processing in the X-ray imaging apparatus which concerns on 1st Embodiment of this invention. It is a figure which compares (A) the graph obtained by plotting the pixel value of a read area, and (B) the graph which performed the thinning process. It is a flowchart which shows the flow of the cathode position information generation processing in the X-ray imaging apparatus which concerns on 2nd Embodiment of this invention. It is a graph which shows the relationship between the thinning number and the pixel position at the time of the thinning process in the X-ray imaging apparatus which concerns on the 1st Embodiment and 2nd Embodiment of this invention. It is a graph which shows the relationship between the thinning number and the tube voltage at the time of thinning processing in the X-ray apparatus which concerns on the 1st Embodiment and 2nd Embodiment of this invention. It is a graph which shows the relationship between the coefficient of the differential filter and the pixel position at the time of generating a frequency image in the X-ray apparatus which concerns on the 1st Embodiment and 2nd Embodiment of this invention. (A) is a diagram for explaining the state of X-rays generated from an X-ray tube, and (B) is a graph for comparing the energy distribution of X-rays emitted to the anode side and the cathode side.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The X-ray imaging apparatus according to the embodiment of the present invention has an X-ray source 11 having an X-ray tube for irradiating the subject with X-rays, and an X-ray irradiation region irradiated from the X-ray source 11 to the subject P. An X-ray filter 12 for limiting, an X-ray detector 13 for detecting X-rays irradiated through the X-ray filter 3 and transmitted through the subject P, a rotating mechanism 14 for rotating the X-ray detector 13, and X-rays. An image processing unit 20 that generates an X-ray image based on an electric signal output from the detector 13 and an image storage unit 21 that temporarily stores the X-ray image generated by the image processing unit 20. The cathode position information 22 that detects the cathode position information indicating the side of the X-ray tube located on the cathode side of the four sides of the X-ray irradiation region in the X-ray image, and the cathode position information obtained from the cathode detection unit 22. An irradiation area detection unit 23 for detecting an X-ray irradiation area in an image based on the image is provided.

<First Embodiment>
Specifically, as shown in FIG. 1, the X-ray imaging apparatus according to the first embodiment of the present invention includes an X-ray source 11, an X-ray aperture 12, an X-ray detector 13, and a rotation mechanism 14. , An image processing unit 1, a system control unit 2, and a display 3. The X-ray imaging device may capture an X-ray fluoroscopic image or may capture an X-ray captured image (still image).

The X-ray source 11 includes an X-ray tube that generates X-rays, and irradiates the subject with X-rays generated in the X-ray tube. The X-ray tube is rotationally driven by the X-ray tube rotation mechanism 10 as needed. The X-ray diaphragm 12 limits the X-ray irradiation region irradiated from the X-ray source 11 to the subject P. The X-ray detector 13 detects the X-rays irradiated through the X-ray diaphragm 3 and transmitted through the subject P, and outputs an electric signal corresponding to the transmitted X-ray dose to the image processing unit 1. The X-ray detector 13 is rotationally driven by the detector rotation mechanism 14.

The image processing unit 1 includes an image processing unit 20, an image storage unit 21, a cathode detection unit 22, and an irradiation area detection unit 23.
The image processing unit 20 generates an X-ray image based on the electric signal output from the X-ray detector 13, and performs necessary image processing such as gradation processing. The image storage unit 21 is generated by the image processing unit 20. The X-ray image is temporarily stored.

The cathode detection unit 22 detects the cathode position information indicating the side located on the cathode side of the X-ray tube among the four sides of the X-ray irradiation region in the generated X-ray image.
More specifically, for example, the cathode detection unit 22 acquires the installation information of the X-ray tube in the X-ray source 11 stored in the system information storage unit 28, which is a storage area of the system control unit 2 described later. , The cathode position on the X-ray image generated by the image processing unit 20 is specified based on the installation information, and the cathode position information is generated. At this time, when the X-ray tube or the X-ray detector 13 is rotating, the relative position of the cathode on the generated X-ray image is different, so that the X-ray tube by the X-ray tube rotation mechanism 10 is used. The rotation information of is also acquired.

Here, the installation information of the X-ray tube is information stored in the system control unit 2 by, for example, the installer when installing the X-ray imaging apparatus, and is acquired according to the procedure shown in the flowchart of FIG. 2, for example. Information.
Hereinafter, a procedure for storing the installation information in the storage area of the system control unit will be described according to the flowchart of FIG.

In step S11, when the X-ray imaging apparatus is installed, the X-ray imaging apparatus acquires an image according to the operation by the installer in the absence of a subject. In the next step S12, in the X-ray image acquired in step S11, as shown in FIG. 3A, the boundary is crossed with respect to each of the four sides of the X-ray irradiation region 31 on the X-ray image 30. A pixel value profile is created by reading out the pixels of the line-shaped reading area 32 composed of a plurality of pixels predetermined in.

In step S13, the side located on the cathode side is detected based on the profile result of the pixel values of the four sides of the X-ray irradiation region. For example, it is determined whether or not the inclination of the profile exceeds a predetermined threshold value. Of the four sides of the X-ray irradiation region, the sharpness of the image differs between the vicinity of the side located on the cathode side and the vicinity of the side located on the anode side. Therefore, as shown in FIG. 3B, the reading region 32 When plotting the pixel values with respect to the pixel positions of, the inclinations of the reading region on the cathode side and the region on the anode side are significantly different. Similarly, the inclination differs greatly between the reading area on the cathode side and the reading area other than the cathode side.

Therefore, by comparing the profile result of each read region (for example, the slope of the graph in FIG. 3B) with a predetermined threshold value, the sides located on the cathode side from the four sides of the X-ray irradiation region can be specified. Can be done. Therefore, in step S13, it is determined whether or not the profile results of the four sides of the X-ray irradiation region each exceed a predetermined threshold value, and if it exceeds the threshold value, it is assumed that the sides are not located on the cathode side. Proceeding to S14, a flag indicating that it is not on the cathode side is stored in the system information storage unit 28. In the determination of step S13, if the profile result is smaller than the threshold value, it is assumed that the side is located on the cathode side, and the process proceeds to step S15, and a flag indicating that it is on the cathode side is stored in the system information storage unit 28. In this way, the position information of the cathode and the anode of the X-ray source is stored in the system information storage unit 28 as the installation information, and the above processing is completed. The above processing may be performed once when the X-ray imaging apparatus is installed.

The irradiation region detection unit 23 detects the X-ray irradiation region in the image based on the cathode position information obtained from the cathode detection unit 22. That is, the position of the boundary line of the X-ray irradiation region is detected. That is, the irradiation region detection unit 23 identifies the side located on the cathode side among the four sides of the X-ray irradiation region from the cathode position information which is the output of the cathode detection unit 22, and the side on the cathode side and the other three sides. By making the X-ray irradiation area detection process different according to each characteristic, the X-ray irradiation area is accurately detected.

The system control unit 2 includes a system information storage unit 28 that stores various information including the above-mentioned installation information of the X-ray source, controls the image processing unit 1 and each of the above units, and an image generated by the image processing unit 1. Is displayed on the display 3.
The display 3 displays an X-ray image generated by the image processing unit 1 and subjected to predetermined image processing according to the instructions of the system control unit 2.

The image processing unit 1 and the system control unit 2 can be constructed in part or in whole as a system including a CPU (central processing unit), a memory, and the like, and constitute the image processing unit 1 and the system control unit 2. The functions of each unit can be realized by the CPU loading the program stored in the storage unit in advance into the memory and executing the program. In addition, some or all of the functions can be configured by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The X-ray irradiation region detection process in the X-ray imaging apparatus configured as described above and in which the position information of the cathode and the anode is stored in the system information storage unit 28 as installation information will be described with reference to the flowchart of FIG.

In step S41, the irradiation area detection unit 23 takes in the X-ray image generated by the image processing unit 20 and stored in the image storage unit 21, and proceeds to step S42. In step S42, the cathode position information obtained from the cathode detection unit 22 whether or not the irradiation region detection unit 23 is the side on the cathode side for each of the vicinity of the four sides of the boundary of the X-ray irradiation region in the captured X-ray image. Judgment is based on. In step S42, if it is determined that the side is on the cathode side, the process proceeds to step S43, and if it is determined that the side is not on the cathode side, the process proceeds to step S44.

Here, the irradiation region detection unit 23 determines whether or not the side is on the cathode side based on the cathode position information acquired from the cathode detection unit 22. The cathode position information in the cathode detection unit 22 is generated according to the cathode position information generation process. FIG. 5 shows an example of a flowchart related to the cathode position information generation process.
In step S51 of FIG. 5, the cathode detection unit 22 acquires installation information from the system information storage unit 28. In the next step S52, the rotation information of the X-ray source 11 and the X-ray detector 2 is acquired. In step S53, the cathode position information on the X-ray image is generated based on the installation information and the rotation information, and is output to the irradiation area detection unit 23.

Returning to FIG. 4, in step S43, a first thinned image is generated in order to detect the boundary line of the side located on the cathode side. In step S44, a second thinned image is generated in order to detect the boundary line of the side other than the side located on the cathode side.

As shown in FIG. 6, referring to the graph obtained by plotting the read area near each side, the result for the read area near the side on the cathode side and the result for the read area near the other side are , The slope on the graph is different. For example, when the difference in inclination is three times, the thinning number of the first thinned image is set to three times the thinning number of the second thinned image in order to apparently match the accuracy of the sides other than the cathode.

In the flowchart of FIG. 4, the thinning number of the first thinned image is 30, and the thinning number of the second thinned image is 10. By performing the thinning process in this way, it is possible to proceed with the process by apparently matching the inclinations of the two as shown in the right figure of FIG.

In step S45, a high frequency image is generated for each of the first thinned image and the second thinned image. This is because the boundary of the X-ray irradiation region is detected by extracting the edge by generating a high-frequency image in which the low-frequency component is removed by using a differential filter or the like. In step S46, straight line detection is performed on each of the two high-frequency images by Hough transform, the length of the straight line and the density difference of the boundary value are detected, and it is determined whether or not the two high-frequency images are the boundary line of the X-ray irradiation region. Specify the coordinates of the X-ray irradiation area. In the next step S47, the coordinates of the specified X-ray irradiation region are converted into the coordinates for the X-ray image before the thinned-out image is generated, the X-ray irradiation region is finally detected, and the above process is completed.

As described above, according to the present embodiment, when the X-ray irradiation region is specified in the image acquired based on the X-rays generated in the X-ray tube, irradiated through the X-ray diaphragm, and transmitted through the subject. After determining whether each side of the X-ray irradiation region is located on the cathode side of the X-ray tube, the X-ray irradiation region is detected by different processing between the side located on the cathode side and the other side. .. Therefore, it is possible to detect the boundary line of the X-ray irradiation region with high accuracy by performing image processing according to the characteristics of the side on the cathode side having a lower sharpness than the other side. On the other hand, the edges other than the cathode side have a higher sharpness than the edges on the cathode side, so the boundaries of the X-ray irradiation region should be detected with high accuracy by processing according to the characteristics of the edges other than the cathode side. Can be done. As a result, the X-ray irradiation region on the X-ray image can be accurately detected.

By accurately detecting the X-ray irradiation region, the X-ray irradiation region can be used in the subsequent image processing such as gradation processing and frequency processing, so that the image quality can be improved.
Even when the X-ray aperture is inserted diagonally or when the X-ray tube is injected and the X-ray irradiation area on the X-ray image is trapezoidal, the position on the cathode side can be specified to determine the cathode. By making the detection process different between the side side and the other side, it is possible to improve the detection accuracy of the X-ray irradiation region.

<Second embodiment>
In the X-ray imaging apparatus according to the first embodiment described above, the cathode position on the X-ray image is determined based on the information possessed by the system information storage unit such as installation information and rotation information. In the present embodiment, the cathode position is determined each time a picture is taken based on the acquired X-ray image. Since the processing other than the configuration of the X-ray imaging apparatus and the determination of the cathode position is the same as that of the first embodiment, the description thereof will be omitted. Hereinafter, the cathode position determination processing for determining the cathode position by image processing will be described in FIG. This will be described according to the flowchart.

In step S71, the irradiation area detection unit 23 takes in the X-ray image generated by the image processing unit 20 and stored in the image storage unit 21, and proceeds to step S72. In the next step S72, in the image acquired in step S71, as shown in FIG. 3A, the boundaries are predetermined for each of the four sides of the X-ray irradiation region 31 on the image 30. A profile is created by reading out the pixels of the line-shaped reading area 32 composed of a plurality of pixels.

In step S73, it is determined whether or not the profile results of the four sides of the X-ray irradiation region each exceed a predetermined threshold value. Of the four sides of the X-ray irradiation region, the sharpness of the image differs between the vicinity of the side located on the cathode side and the vicinity of the side located on the anode side. Therefore, as shown in FIG. 3B, the reading region 32 When plotting the pixel values with respect to the pixel positions of, the inclinations of the reading region on the cathode side and the region on the anode side are significantly different. Similarly, the inclination differs greatly between the reading area on the cathode side and the reading area other than the cathode side. Further, when the X-ray diaphragm is not applied at the time of shooting, that is, when the X-ray irradiation area is not limited by the X-ray diaphragm, the inclination becomes substantially 0 when the pixel value with respect to the pixel position is plotted in the read area 32. ..

Therefore, it can be determined whether or not the X-ray diaphragm is used by comparing the profile result of each read area (for example, the slope of the graph in FIG. 3B) with the predetermined threshold value A. In step S72, it is determined whether or not the profile results of the four sides of the X-ray irradiation region each exceed a predetermined threshold value A, and if it exceeds the threshold value A, the process proceeds to step S74 assuming that there is an X-ray diaphragm. If the profile results of the four sides of the X-ray irradiation region are below the predetermined threshold values A, the process proceeds to step S77 with no X-ray diaphragm.

In step S74, the sides located on the cathode side from the four sides of the X-ray irradiation region are specified based on the profile result of each read region. That is, in step S74, it is determined whether or not the profile results of the four sides of the X-ray irradiation region each exceed a predetermined threshold value B, and if it exceeds the threshold value B, it is assumed that the sides are not located on the cathode side. , Step S75, and a flag indicating that it is not on the cathode side is stored in the storage area of the cathode detection unit 22.

In the determination in step S74, if the profile result is smaller than the threshold value B, it is assumed that the side is located on the cathode side, and the process proceeds to step S76, and a flag indicating that it is on the cathode side is stored in the storage area of the cathode detection unit 22. In this way, the cathode position information indicating the position of the cathode of the X-ray source is stored in the storage area of the cathode detection unit 22. In step S77, it is determined whether or not the processing of all four sides is completed, and if not, the process returns to step S73 and the above processing is repeated. When the processing of all four sides is completed, the above processing is completed.

(Modification example)
In the X-ray imaging apparatus according to the first embodiment and the second embodiment described above, an example in which the number of thinning out is set to a fixed value at the time of thinning out processing has been described. As shown in the graph of FIG. 8, when the X-ray tube is located at the center of the X-ray detector, it is more accurate to change the thinning number from the center of the X-ray detector according to the position of the X-ray filter. Good detection is possible.
Also, when the X-ray tube is not in the center of the X-ray detection device (for example, when the X-ray tube has a swing angle and shoots shots), the thinning number is set variably from the geometric position. You can also do it.

Further, the profile result changes depending on the tube voltage applied to the X-ray tube during X-ray photography. That is, the higher the tube voltage, the gentler the inclination of the profile due to the influence of the X-ray transmittance and the scattered rays. Therefore, in this case, as shown in FIG. 9, according to the proportional relationship between the thinning number and the tube voltage, it depends on the tube voltage in addition to the geometric position, and the thinning number can be changed to enable accurate detection.

Furthermore, in the above example, an example in which the number of thinnings is different between the side where the cathode is located and the other side based on the cathode position information has been described, but it is not always necessary to generate a thinning image, and a high-frequency image is used. The coefficient K of the differential filter at the time of generating the above may be different between the side on the cathode side and the other side. FIG. 10 shows an example in which the coefficient of the differential filter is increased from the center of the X-ray detector to the peripheral portion. By increasing the coefficient of the differential filter used when generating high-frequency images toward the cathode side (Yn direction side), it is corrected that the slope of the profile at the boundary line of the X-ray irradiation region located on the cathode side is gentle. You may.

The present invention is not limited to the above-mentioned examples, and includes various modifications. For example, the above-mentioned examples have been described in detail for a better understanding of the present invention, and are not necessarily limited to those having all the configurations of the description. For example, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

1 ... Image processing unit, 2 ... System control unit, 3 ... Display, 10 ... X-ray tube rotation mechanism, 11 ... X-ray source, 12 ... X-ray aperture, 13 ... X-ray detector, 14 ... detector rotation mechanism, 20 ... image processing unit, 21 ... image storage unit, 22 ... cathode detection unit, 23 ... irradiation area detection unit, 28 ... System information storage unit, 30 ... X-ray image, 31 ... X-ray irradiation area, 32 ... Read area, P ... Subject

Claims (6)

An X-ray source having an X-ray tube that irradiates the subject with X-rays,
An X-ray diaphragm that limits the X-ray irradiation area that irradiates the subject from the X-ray source,
An X-ray detector that detects X-rays that are irradiated through the X-ray diaphragm and have passed through the subject.
An image processing unit that generates an X-ray image based on an electrical signal output from the X-ray detector,
A cathode detection unit that generates cathode position information indicating a side located on the cathode side of the X-ray tube among the four sides of the X-ray irradiation region in the X-ray image generated by the image processing unit.
An irradiation region detection unit that detects an X-ray irradiation region in the X-ray image based on the cathode position information obtained from the cathode detection unit is provided.
The irradiation region detection unit performs a thinning process on the X-ray image, so that the first thinning for detecting the boundary line of the side located on the cathode side of the X-ray tube in the X-ray image. An image and a second thinned image for detecting a boundary line of a side other than the side located on the cathode side in the X-ray image are generated, and X is generated from the first thinned image and the second thinned image. Detects the irradiation area of the line and
The irradiation area detection unit plots the pixel values of the line-shaped reading area set so as to straddle the boundary of the side located on the cathode side of the first thinned image, and the slope of the graph is obtained. The slope of the graph obtained by plotting the pixel values of the line-shaped read region set so as to straddle the boundary of the side other than the side located on the cathode side of the second thinned image is apparently matched. The X-ray imaging apparatus according to claim 1 , wherein the number of thinning lines is set . The X-ray imaging apparatus according to claim 1, wherein the cathode detection unit detects cathode position information on the X-ray image based on the installation information of the X-ray tube. The X-ray imaging apparatus according to claim 1, wherein the cathode detection unit detects cathode position information on the image based on the installation information of the X-ray tube and the rotation information of the X-ray detector. The irradiation region detection unit extracts edges for each of the first thinned image and the second thinned image, so that the coordinates of the boundary of the side located on the cathode side from the first thinned image. Is specified, the coordinates of the boundary of the side other than the side located on the cathode side are specified from the second thinned image, and the specified coordinates are determined based on the thinned number of the first and second thinned images. The X-ray imaging apparatus according to claim 1, wherein the X-ray irradiation region is detected by converting the coordinates with respect to the X-ray image before thinning out. The cathode detecting unit, by processing the X-ray image generated by the image processing unit, the X-ray imaging apparatus according to claim 1, wherein generating the cathode position information. The cathode detection unit obtains by plotting the pixel values of a line-shaped reading region set so as to straddle the boundary with respect to each of the four sides of the X-ray irradiation region of the X-ray image generated by the image processing unit. The X-ray imaging apparatus according to claim 5, wherein a side whose slope is smaller than a predetermined threshold value is a side located on the cathode side.

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