JP2017189240A - X-ray detector and X-ray diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray detector and an X-ray diagnostic apparatus capable of improving efficiency of an examination using a portable X-ray detector.SOLUTION: An X-ray detector includes a detection part and a generation part. The detection part detects an X-ray irradiated from an X-ray tube. The generation part averages out each signal based on the respective X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube, and based on the averaged signal, generates a correction coefficient used for the correction of an X-ray image.SELECTED DRAWING: Figure 4

Description

  Embodiments described herein relate generally to an X-ray detector and an X-ray diagnostic apparatus.

  The X-ray diagnostic apparatus emits X-rays to a subject and detects X-rays transmitted through the subject with an X-ray detector (for example, an X-ray flat panel detector (FPD)). Thus, an X-ray image is generated. In recent years, along with the wireless and lightweight X-ray detectors, portable X-ray detectors that can be moved as a single unit without being incorporated into an X-ray diagnostic apparatus have come to be used. .

  The portable X-ray detector can be shared by a plurality of X-ray diagnostic apparatuses, and the operator can freely combine the X-ray diagnostic apparatus and the portable X-ray detector. . For example, when there are a plurality of X-ray diagnostic apparatuses and a plurality of X-ray detectors in a hospital, the operator installs an X-ray detector that can be used for the examination and an X-ray diagnostic apparatus suitable for the examination. In combination, X-ray images can be taken. Hereinafter, the use of a portable X-ray detector shared by a plurality of X-ray diagnostic apparatuses is also referred to as FPD sharing.

JP 2005-111054 A JP 2011-102702 A JP2012-120200A

  The problem to be solved by the present invention is to provide an X-ray detector and an X-ray diagnostic apparatus capable of improving the efficiency of inspection using a portable X-ray detector.

  The X-ray detector according to the embodiment includes a detection unit and a generation unit. The detection unit detects X-rays emitted from the X-ray tube. The generation unit averages each signal based on the X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube, and uses the correction for correcting the X-ray image based on the averaged signal Generate coefficients.

FIG. 1 is a diagram illustrating an example of an X-ray diagnostic apparatus according to the first embodiment. FIG. 2 is a block diagram showing an example of the configuration of the X-ray diagnostic apparatus according to the first embodiment. FIG. 3 is a diagram illustrating an example of the FPD according to the first embodiment. FIG. 4 is a block diagram illustrating an example of the configuration of the FPD according to the first embodiment. FIG. 5 is a diagram for explaining correction of an X-ray image. FIG. 6A is a diagram for describing gain correction of an X-ray image. FIG. 6B is a diagram for explaining the X-ray image gain correction. FIG. 7 is a diagram for explaining gain calibration according to the first embodiment. FIG. 8 is a diagram for explaining gain calibration according to the first embodiment. FIG. 9 is a diagram for explaining gain calibration according to the first embodiment. FIG. 10 is a diagram for explaining photographing according to the first embodiment. FIG. 11 is a diagram for explaining gain correction according to the first embodiment. FIG. 12 is a flowchart for explaining a series of processes of FPD processing according to the first embodiment. FIG. 13 is a flowchart for explaining a series of gain calibration processes according to the first embodiment.

  Hereinafter, an X-ray detector and an X-ray diagnostic apparatus according to embodiments will be described with reference to the drawings. In the following, an X-ray diagnostic apparatus provided with a portable X-ray detector will be described. In the following, a portable X-ray flat panel detector (FPD) in which X-ray detection elements are two-dimensionally arranged on a plane will be described as an example of the X-ray detector.

(First embodiment)
First, an example of the X-ray diagnostic apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating an example of an X-ray diagnostic apparatus according to the first embodiment. As shown in FIG. 1, the X-ray diagnostic apparatus according to the first embodiment includes an X-ray high voltage apparatus, an X-ray tube, an X-ray movable diaphragm, an X-ray tube holding device, an X-ray flat panel detector (FPD), Equipped with a standing shooting stand, a supine shooting stand, an image processing device, and the like. The X-ray diagnostic apparatus shown in FIG. 1 is connected to an imager, an image server, etc. (not shown) through a network.

  The X-ray high voltage apparatus shown in FIG. 1 supplies a high voltage to the X-ray tube, and the X-ray tube emits X-rays using the supplied high voltage. The X-ray movable diaphragm controls the X-ray irradiation field for the purpose of reducing the exposure dose to the subject and improving the image quality of the image data. The X-ray tube holding device holds the X-ray tube and the X-ray movable diaphragm with an arm, and drives the arm to move the positions of the X-ray tube and the X-ray movable diaphragm to an imaging position, a retracted position, and the like. Here, the X-ray tube holding device is a ceiling traveling type, and the position of the X-ray tube and the X-ray movable diaphragm can be moved by traveling on a rail laid on the ceiling surface. The portable FPD is an X-ray detector that is used by being incorporated in each position shown in FIG. 1. The X-ray information transmitted through the subject is converted into image data and sent to the image processing apparatus.

  Moreover, as shown in FIG. 1, portable FPD is installed in a standing position stand or a standing position stand. The standing position photographing stand can hold the FPD by an arm having one end connected to the rail, and slide the FPD up and down by moving the arm on the rail. In addition, the supine imaging stand includes a top plate on which the subject is placed, and the FPD is placed under or on the top plate. Here, in the X-ray diagnostic apparatus according to the first embodiment, X-ray images are collected using a portable FPD. For example, an FPD is placed on the top plate of the supine imaging stand shown in FIG. 1, and image data based on X-rays transmitted through the subject is sent to the image processing apparatus.

  The image processing apparatus shown in FIG. 1 collects image data transmitted from the FPD, and executes preset image processing on the collected image data. The image processing apparatus performs image processing change and workflow operation by operations from a mouse, a keyboard, and the like. Further, the image processing device displays an image on a display. The image processing apparatus temporarily stores and transfers images.

  For example, the X-ray diagnostic apparatus shown in FIG. 1 emits X-rays from an X-ray tube to a subject standing in front of a standing imaging table, and transmits X-rays transmitted through the subject to a standing position. By detecting with the FPD installed on the photographing stand, photographing in a standing position is executed. Further, for example, the X-ray diagnostic apparatus shown in FIG. 1 emits X-rays from an X-ray tube to a subject placed on a top plate included in a supine imaging stand and transmits the subject. The X-rays are detected by the FPD installed on the supine imaging stand, and imaging in the supine position is executed. In addition, for example, the X-ray diagnostic apparatus shown in FIG. 1 performs imaging by detecting X-rays with an FPD placed on a top plate included in a supine imaging platform.

  Next, an example of the configuration of the X-ray diagnostic apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing an example of the configuration of the X-ray diagnostic apparatus 1 according to the first embodiment. As shown in FIG. 2, the X-ray diagnostic apparatus 1 according to the first embodiment includes an X-ray high voltage apparatus 110, an X-ray tube 120, an X-ray movable diaphragm 130, a quality filter 140, and an FPD 150. A display 160, an input circuit 170, a storage circuit 180, and a processing circuit 190. Note that the input circuit 170, the storage circuit 180, and the processing circuit 190 are included in, for example, the image processing apparatus shown in FIG.

  The X-ray high voltage apparatus 110 supplies a high voltage to the X-ray tube 120, and the X-ray tube 120 exposes the X-rays using the supplied high voltage. The X-ray movable diaphragm 130 controls an X-ray irradiation area irradiated from the X-ray tube 120. Here, the X-ray tube 120 and the X-ray movable diaphragm 130 are supported by a support unit such as an arm, for example, and are driven by a driving device (not shown). The drive device moves the positions of the X-ray tube 120 and the X-ray movable diaphragm 130 under the control of the processing circuit 190. In addition, the drive device controls the irradiation range of the X-rays emitted from the X-ray tube 120 by adjusting the opening degree of the diaphragm blades of the X-ray movable diaphragm 130 under the control of the control function 190a. The X-ray filter 140 is arranged on an X-ray path (for example, an X-ray movable diaphragm) so that X-rays having a predetermined X-ray quality and dose are incident on the FPD 150 under predetermined SID (Source Image Distance) and X-ray conditions. 130 is a filter installed in front of 130. For example, the wire quality filter 140 is a metal plate having a predetermined material and thickness.

  Here, the FPD 150 will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of the FPD 150 according to the first embodiment. As shown in FIG. 3, the FPD 150 according to the first embodiment includes a detection film, a pixel capacitor, a TFT (Thin Film Transistor), and the like. The detection film shown in FIG. 3 converts the energy of the irradiated X-rays into electric charges. The pixel capacitor unit is a capacitor for accumulating charges converted by the detection film, and includes a pixel electrode for receiving charge input from the detection film, a metal sandwiched between insulating films, and a ground electrode for discharging leakage current Etc. The TFT is a semiconductor switch that extracts charges from each pixel capacitor section, and is connected to a gate line that inputs a drive signal from a drive circuit (not shown) and a signal line that flows charges extracted from the pixel capacitor section.

  Next, an example of the configuration of the FPD 150 according to the first embodiment will be described with reference to FIG. FIG. 4 is a block diagram illustrating an example of the configuration of the FPD 150 according to the first embodiment. As illustrated in FIG. 4, the FPD 150 according to the first embodiment includes a processing circuit 151 and a storage circuit 152.

  The processing circuit 151 executes a collection function 151a, a generation function 151b, and a transmission function 151c. In the embodiment in FIG. 1, each processing function performed by the component collection function 151a, the generation function 151b, and the transmission function 151c is recorded in the storage circuit 152 in the form of a program executable by a computer. The processing circuit 151 is a processor that implements a function corresponding to each program by reading the program from the storage circuit 152 and executing the program. In other words, the processing circuit 151 in a state where each program is read has each function shown in the processing circuit 151 of FIG. In FIG. 4, it has been described that the processing functions performed by the collection function 151a, the generation function 151b, and the transmission function 151c are realized by a single processing circuit. However, the processing circuit is formed by combining a plurality of independent processors. And each processor may implement a function by executing a program.

  The processing circuit 151 controls the entire processing by the FPD 150. The processing by the FPD 150 is a series of processing related to collection of image data and generation and transmission of data used for correction of an X-ray image. For example, the processing circuit 151 includes a detection film, a pixel capacitor, a TFT, an amplifier, an AD converter (Analog to Digital Converter), and the like, and the two-dimensional intensity of the X-rays emitted from the X-ray tube 120. Distribution data (two-dimensional intensity distribution data) is collected. Specifically, the processing circuit 151 converts the X-ray photons incident on the detection film into electric charges, sequentially reads out each pixel composed of the pixel capacitor unit and the TFT, amplifies it with an amplifier, and then performs digital conversion with an AD converter. Image data is collected by converting it into a signal (pixel value).

  For example, the processing circuit 151 calculates data used for correcting the X-ray image. For example, the processing circuit 151 calculates a correction coefficient for correcting the nonuniformity of the gain (Adjustable gain) caused by the spatial nonuniformity of the detection film and the manufacturing variation of each amplifier. Further, for example, the processing circuit 151 transmits data used for X-ray image correction to a predetermined storage device (for example, the storage circuit 180) in order to back up data used for X-ray image correction. Data used for correcting the X-ray image will be described later.

  The storage circuit 152 stores data used when the processing circuit 151 controls the entire processing by the FPD 150. For example, the storage circuit 152 stores each program executed by the processing circuit 151. The storage circuit 152 stores data used for correcting the X-ray image. Data used for correcting the X-ray image will be described later.

  Returning to FIG. 2, the display 160 is a monitor referred to by the operator, and displays a photographed X-ray image or the like under the control of the processing circuit 190. The input circuit 170 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, and the like used for inputting various instructions and various settings, and receives instructions and settings from an operator. The storage circuit 180 stores data used when the processing circuit 190 controls the entire processing performed by the X-ray diagnostic apparatus 1, image data, and the like. For example, the storage circuit 180 stores each program executed by the processing circuit 190. The storage circuit 180 also stores backup data for data used for X-ray image correction. Data used for correcting the X-ray image will be described later.

  The processing circuit 190 executes a control function 190a and an image generation function 190b. In the embodiment in FIG. 2, each processing function performed by the component control function 190a and the image generation function 190b is recorded in the storage circuit 180 in the form of a program executable by a computer. The processing circuit 190 is a processor that realizes a function corresponding to each program by reading the program from the storage circuit 180 and executing the program. In other words, the processing circuit 190 in the state where each program is read has the functions shown in the processing circuit 190 of FIG. In FIG. 2, the processing function performed by the control function 190a and the image generation function 190b is realized by a single processing circuit. However, a processing circuit is configured by combining a plurality of independent processors. Each processor may implement a function by executing a program.

  The term “processor” used in the above description is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), a programmable logic device (for example, It means circuits such as a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA). The processor implements a function by reading and executing a program stored in the storage circuit 152 or the storage circuit 180. Instead of storing the program in the storage circuit 152 or the storage circuit 180, the program may be directly incorporated in the circuit of the processor. In this case, the processor realizes the function by reading and executing the program incorporated in the circuit. Note that each processor of the present embodiment is not limited to being configured as a single circuit for each processor, but may be configured as a single processor by combining a plurality of independent circuits to realize the function. Good. Furthermore, a plurality of components shown in FIGS. 2 and 4 may be integrated into one processor to realize the function.

  The collection function 151a in the first embodiment is an example of a detection unit in the claims. The generation function 151b in the first embodiment is an example of a generation unit in the claims.

  The processing circuit 190 controls the entire processing by the X-ray diagnostic apparatus 1. The process performed by the X-ray diagnostic apparatus 1 is a series of processes related to imaging for acquiring data used for X-ray image correction and X-ray image imaging for diagnosis. Specifically, the processing circuit 190 controls generation of a high voltage by the X-ray high voltage apparatus 101, X-ray exposure by the X-ray tube, collection of X-rays by the FPD 150, and the like.

  The overall configuration of the X-ray diagnostic apparatus 1 according to the first embodiment has been described above. With this configuration, the X-ray diagnostic apparatus 1 according to the first embodiment averages signals based on X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube 120. Then, the inspection efficiency is improved by generating a correction coefficient used for correcting the X-ray image based on the averaged signal. Specifically, in the X-ray diagnostic apparatus 1, the inspection efficiency is improved by making the correction for the image data collected by the FPD 150 constant regardless of the X-ray diagnostic apparatus.

  First, correction for image data will be described. The X-ray image generated from the X-ray detected by the FPD 150 by the X-ray diagnostic apparatus 1 has non-uniformity based on various factors. For example, an X-ray image collected using the FPD 150 has an offset component caused by a leak charge from a detection film or TFT, a non-uniformity of gain caused by a spatial non-uniformity of the detection film or manufacturing variations of individual amplifiers. And defect points due to defects in the detection film and TFT.

  Therefore, in imaging using the FPD 150, the X-ray diagnostic apparatus 1 corrects the X-ray image in order to reduce the influence of the above-described non-uniformity and generate a uniform X-ray image that can be used for diagnosis. Here, correction of the X-ray image will be described with reference to FIG. FIG. 5 is a diagram for explaining correction of an X-ray image. First, the X-ray diagnostic apparatus 1 generates an X-ray image by exposing X-rays to the subject from the X-ray tube 120 and collecting the X-rays transmitted through the subject with the FPD 150.

  Next, as shown in FIG. 5, the X-ray diagnostic apparatus 1 removes an offset component by subtracting a predetermined offset image from the captured X-ray image. Further, as shown in FIG. 5, the X-ray diagnostic apparatus 1 corrects the gain non-uniformity by multiplying the X-ray image by a predetermined correction coefficient (hereinafter also referred to as a gain correction coefficient). Further, for example, as shown in FIG. 5, the X-ray diagnostic apparatus 1 interpolates defect points using pixel values of normal pixels around the defect points along a predetermined defect point map. Hereinafter, the process of removing the offset component, the process of correcting the non-uniformity of the gain, and the process of interpolating the defect point are referred to as offset correction, gain correction, and defect point correction, respectively. Hereinafter, a series of processes for creating a correction coefficient used for gain correction is also referred to as gain calibration.

  Here, gain correction will be described with reference to FIG. 6A. FIG. 6A is a diagram for describing gain correction of an X-ray image. First, as shown in FIG. 6A, prior to the execution of gain correction, gain calibration is executed to create a correction coefficient used for gain correction. Here, only the X-ray image output from the FPD 150 irradiated with X-rays can collect all of the gain non-uniformity caused by the spatial non-uniformity of the detection film and the manufacturing variation of each amplifier. Therefore, in gain calibration, as shown in FIG. 6A, X-rays are emitted from the X-ray tube 120 to the FPD 150 to collect pixel value distributions, and correction coefficients are created based on the collected pixel value distributions. The Next, gain correction is performed by multiplying the captured X-ray image by a correction coefficient. For example, when gain correction is performed on an X-ray image captured at the time of gain calibration, the pixel value distribution becomes uniform as shown in FIG. 6A.

  Here, the pixel value of the X-ray image collected by the FPD 150 is proportional to the X-ray dose to be irradiated. Therefore, the correction coefficient obtained by the above-described gain calibration includes X-ray dose non-uniformity in addition to spatial non-uniformity and gain non-uniformity that are originally corrected by gain correction. Ideally, it is possible to collect correction coefficients for correcting only the spatial non-uniformity and the non-uniformity of gain, which are the original correction targets, after eliminating the influence of non-uniformity of the X-ray dose. preferable. However, since the X-ray dose decreases in inverse proportion to the square of the distance from the X-ray tube 120, as shown in the pixel value distribution on the center line ab of the FPD 150 in FIG. 6A, compared to the center of the X-ray irradiation field, The peripheral X-ray dose and pixel values decrease. Further, due to the influence of the heel effect (tilting effect), as shown in the pixel value distribution on the center line ab of the FPD 150 in FIG. 6A, the X-ray dose and the pixel value on the X-ray tube anode side compared to the X-ray tube cathode side. Will decline. In the following, a description will be given of a pixel value distribution that omits spatial non-uniformity and gain non-uniformity and shows only X-ray dose non-uniformity.

  Accordingly, the pixel value distribution obtained by gain calibration has an asymmetric shape in the anode-cathode direction (X direction) of the X-ray tube 120 as shown in FIG. 6A. In addition, the correction coefficient created based on the pixel value distribution also has an asymmetric shape in the X direction, as shown in FIG. 6A. Note that the degree of reduction or asymmetry in the periphery of the FPD 150 in the pixel value distribution obtained by gain calibration increases as the field of view size of the FPD 150 increases and as the SID decreases.

  When the FPD 150 is incorporated in the X-ray diagnostic apparatus 1 and the combination of the FPD 150 and the X-ray diagnostic apparatus 1 is fixed, as shown in FIG. 6A, gain correction is executed using a correction coefficient having an asymmetric shape. However, the asymmetry of the pixel value distribution can be eliminated, and the pixel value distribution of the corrected image can be corrected flatly. This is because the influence of non-uniformity of the X-ray dose is the same for imaging for gain calibration and imaging for diagnostic X-ray images. That is, in the system in which the FPD 150 is incorporated in the X-ray diagnostic apparatus 1, although the imaging conditions are different between imaging of the diagnostic X-ray image and gain calibration, the tendency of the pixel value distribution is the same. Even if gain correction is performed using a correction coefficient having an asymmetric shape, the flatness of the corrected image is not greatly impaired, and the X-ray image after gain correction can be used for inspection.

  On the other hand, when the portable FPD 150 is shared by a plurality of X-ray diagnostic apparatuses, gain correction may be performed inappropriately by using a correction coefficient having an asymmetric shape. Here, with reference to FIG. 6B, a description will be given of a case where the X-ray diagnostic apparatus 1 that performs gain calibration differs from the X-ray diagnostic apparatus that performs X-ray image capturing for the FPD 150. Note that FIG. 6B is a diagram for explaining X-ray image gain correction.

  First, as shown in the upper diagram of FIG. 6B, gain calibration is executed. Here, in the gain calibration, as shown in the upper diagram of FIG. 6B, the cathode side of the X-ray tube is on the “a” side on the center line ab of the FPD 150 and the anode side of the X-ray tube is on the “b” side. It corresponds. Therefore, the pixel value distribution collected at the time of gain calibration has a tendency that the pixel value increases on the “a” side on the center line ab as shown in the upper diagram of FIG. 6B. The correction coefficient is created so as to cancel the tendency of the pixel value distribution.

  Next, the FPD 150 that has been subjected to gain calibration shown in the upper diagram of FIG. 6B is installed in another X-ray diagnostic apparatus (another system) different from the X-ray diagnostic apparatus 1 that has performed gain calibration, and an X-ray image is captured. I do. 6B, in the inspection by another system shown in the lower part of FIG. 6B, the anode side of the X-ray tube 120 is on the “a” side on the center line ab of the FPD 150, and the cathode of the X-ray tube 120 is on the “b” side. The side corresponds. Therefore, the pixel value distribution on the center line ab collected in the inspection by another system has a tendency that the pixel value increases on the “b” side as shown in the lower diagram of FIG. 6B. Here, when the gain correction is executed using the correction coefficient shown in the upper diagram of FIG. 6B, the shape of the pixel value distribution becomes an asymmetric shape by the gain correction, as shown in the lower diagram of FIG. 6B.

  That is, the correction coefficient created by gain calibration depends on the X-ray diagnostic apparatus performing gain calibration and the direction of the X-ray tube (the direction of the anode / cathode). Therefore, if the portable FPD 150 is shared between a plurality of systems and the FPD 150 is used in a state where the orientation with respect to the X-ray tube is different between gain calibration and X-ray imaging, the X-ray dose distribution is Since they are different, the pixel values are unnaturally corrected. In particular, as shown in FIG. 6B, when the orientation of the FPD 150 with respect to the anode / cathode of the X-ray tube is reversed, the region that was the anode side during gain calibration (for example, the center line of the X-ray detector shown in the upper diagram of FIG. 6B). The “a” side on ab) is excessively corrected, and the pixel value distribution of the corrected image becomes larger than the non-uniformity of the X-ray dose. In addition, the generation of a non-uniform X-ray image hinders diagnosis using the X-ray image, and may reduce the inspection efficiency.

  In addition, inappropriate gain correction as shown in FIG. 6B may lead to an automatic window malfunction. Here, the automatic window malfunction is an erroneous determination when determining a peak corresponding to an X-ray (direct line) that does not pass through the subject or a skin line from a histogram of a captured X-ray image. Say. For example, since the direct line is not attenuated by passing through the subject, the direct line usually corresponds to a peak having the largest pixel value among a plurality of peaks on the histogram. The skin line corresponds to the peak with the largest pixel value next to the peak of the direct line. These correspondences are used in various image processing. For example, the area (background) corresponding to the direct line is black, and the area corresponding to the subject in the skin line is detailed using many gradations. An X-ray image is generated to be represented.

  Here, when the pixel value distribution of the X-ray image becomes non-uniform due to inappropriate gain correction as shown in FIG. 6B, the pixel value of the direct line changes depending on the position on the X-ray image. For example, as shown in the pixel value distribution of the corrected image in the lower diagram of FIG. 6B, the pixel value of the direct line in the region on the cathode side of the X-ray tube at the time of imaging and the pixel value of the direct line in the region on the anode side Different values. That is, a plurality of peaks corresponding to the direct line are generated on the histogram, and in actuality, the peak corresponding to the direct line may be erroneously determined as the peak corresponding to the skin line. Therefore, an auto window malfunction causes, for example, an X-ray image in which the background portion is expressed in detail but the area corresponding to the subject in the skin line is not sufficiently expressed, and the examination efficiency is improved. There was a case of decline.

  The inappropriate gain correction described above is performed by executing gain calibration for each FPD in the hospital in combination with each X-ray diagnostic apparatus, and for all combinations of the anode / cathode direction of the X-ray tube. This can be avoided by creating a coefficient. However, as FPD sharing progresses and the number of portable X-ray detectors and X-ray diagnostic apparatuses increases, the number of gain calibrations required increases, and the effort and burden of creating correction coefficients increases. Become. In addition, since a plurality of correction coefficients are created for each FPD, the complexity of managing correction coefficient data also increases.

  Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment simply creates a correction coefficient that does not result in inappropriate gain correction even if the FPD 150 is used in a different direction in another system by FPD sharing. Improve inspection efficiency. Specifically, the X-ray diagnostic apparatus 1 according to the first embodiment averages each signal based on X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube 120. The inspection efficiency is improved by generating a correction coefficient used for correcting the X-ray image based on the averaged signal. Hereinafter, processing performed by the X-ray diagnostic apparatus 1 according to the first embodiment will be described in detail.

  First, the X-ray diagnostic apparatus 1 according to the first embodiment performs gain calibration and creates a correction coefficient. Here, gain calibration according to the first embodiment will be described with reference to FIG. FIG. 7 is a diagram for explaining gain calibration according to the first embodiment. First, as shown in FIG. 7, the collection function 151a is in a state where no subject, grid, AEC (Automatic Exposure Control) detector, etc. are placed between the X-ray tube 120 and the FPD 150 (X-ray path). X-rays are detected. Here, the collection function 151a detects X-rays using a predetermined quality filter 140 under predetermined SID and X-ray conditions.

  More specifically, first, the collection function 151a converts the X-rays incident on the FPD 150 into charges in the detection film, and sequentially reads out each pixel composed of the pixel capacitor unit and the TFT, thereby irradiating from the X-ray tube 120. X-rays collected. Next, as shown in FIG. 7, the collection function 151a amplifies the collected X-ray information with an amplifier, and then performs AD conversion to convert it into a digital signal (pixel value). Generate. Further, the collection function 151a generates image data (average image data) obtained by averaging a predetermined number of collected image data. Further, as shown in FIG. 7, the collection function 151a performs offset correction on the generated average image data.

  Here, the collection function 151a collects X-rays emitted from the X-ray tube 120 in a plurality of arrangement states arranged in different directions with respect to the X-ray tube 120, respectively. For example, the X-ray diagnostic apparatus 1 executes imaging for gain calibration once, collects image data (average image data) subjected to offset correction shown in FIG. 7, and then makes the FPD 150 orthogonal to the detection surface. The image is rotated by 180 ° about the direction, and photographing for gain calibration is executed again to collect average image data. In the following description, the FPD 150 rotates with respect to the X-ray tube 120 around the direction orthogonal to the detection surface for detecting the X-rays irradiated by the X-ray tube 120 during the second imaging for gain calibration. This angle is referred to as a rotation angle.

  For example, the rotation angle of the FPD 150 at the time of the first shooting is “0 °”, and the FPD 150 is rotated by “90 °” at the time of the second shooting based on the state of the FPD 150 at the time of the first shooting. In this case, the rotation angle in the second shooting is “90 °”. For example, when the FPD 150 rotates “90 °” based on the state of the FPD 150 at the time of the second shooting at the time of the third shooting, the rotation angle at the third shooting is “180 °”. is there. The rotation angle when the FPD 150 makes one rotation is “0 °”, and the rotation angle is described in the range of “0 °” to “360 °”. The direction in which the FPD 150 rotates with respect to the X-ray tube 120 is arbitrary.

  Hereinafter, creation of a gain correction coefficient using a plurality of image data collected in a plurality of arrangement states having different directions with respect to the X-ray tube 120 will be specifically described with reference to FIG. Here, FIG. 8 is a diagram for explaining the gain calibration according to the first embodiment. First, the collection function 151a collects pixel value distributions by detecting X-rays emitted from the X-ray tube 120 and generating average image data in the first imaging shown in the upper left diagram of FIG. Here, in the first imaging shown in the upper left diagram of FIG. 8, the cathode side of the X-ray tube 120 corresponds to the “a” side of the center line ab of the FPD 150 and the X-ray tube 120 of the “b” side corresponds to the “b” side. Since the anode side corresponds, the pixel value distribution on the center line ab of the FPD 150 is as shown in the upper left diagram of FIG.

  Next, for example, as shown in the upper right diagram of FIG. 8, the collection function 151 a performs the second time in a state where the rotation is “180 °” about the direction (Z direction) orthogonal to the detection surface for detecting X-rays. In imaging, pixel value distribution is collected by detecting X-rays emitted from the X-ray tube 120 and generating average image data. Here, in the second imaging shown in the upper right diagram of FIG. 8, the anode side of the X-ray tube 120 corresponds to the “a” side of the center line ab of the FPD 150 and the X-ray tube 120 of the “b” side corresponds to the “a” side. Since the cathode side corresponds, the pixel value distribution on the center line ab of the FPD 150 is as shown in the upper right diagram of FIG. Therefore, the collection function 151a collects a set of pixel value distributions in which the cathode side and the anode side of the X-ray tube are opposite by the two imaging operations shown in FIG.

  Here, as shown in the upper left diagram and the upper right diagram in FIG. 8, the pixel value distribution by the first imaging and the pixel value distribution by the second imaging collected by the acquisition function 151 a are the same as the cathode of the X-ray tube 120. The distribution is inverted in the anode direction (X direction). Accordingly, the generation function 151b generates a pixel value distribution symmetrical in the X direction as shown in the lower diagram of FIG. 8 by averaging the two pixel value distributions shown in the upper left diagram and the upper right diagram of FIG. Can do. That is, each of the image data collected in the first and second imaging has an asymmetric pixel value distribution in the cathode-anode direction (X direction) of the X-ray tube 120, but the generation function 151b is shown in the lower diagram of FIG. As shown in FIG. 5, the asymmetric pixel value distribution is canceled by averaging the image data in these two directions, and a bilaterally symmetric pixel value distribution is calculated.

  Note that the pixel value distribution in the direction orthogonal to the cathode-anode direction of the X-ray tube 120 (the Y direction in FIG. 8) is substantially bilaterally symmetric, and the decrease in the pixel value in the peripheral portion with respect to the central portion of the FPD 150 is small. Further, when the X-ray tube 120 and the FPD 150 do not face each other due to insufficient installation accuracy, the pixel value distribution in the Y direction shown in FIG. 8 can be asymmetrical, but the generation function 151b is 1 shown in FIG. By averaging the pixel value distribution by the second shooting and the pixel value distribution by the second shooting, the left-right asymmetry of the pixel value distribution in the Y direction can be offset. That is, the generation function 151b is bilaterally symmetric with respect to the X direction and the Y direction by averaging the two pixel value distributions shown in the upper left diagram and the upper right diagram of FIG. 8, and gradually decreases from the center of the FPD 150 toward the periphery. Pixel value distribution can be calculated.

  Next, as shown in the lower diagram of FIG. 8, the generation function 151b generates a gain correction coefficient on the center line ab from the pixel value distribution calculated by averaging the pixel value distributions obtained by the first and second imaging. . Specifically, first, the generation function 151b averages the pixel value distributions of the image data collected in the plurality of arrangement states shown in the upper diagram of FIG. 8, and as shown in the lower diagram of FIG. Generate a distribution. Next, the generation function 151b calculates the average value of the pixel values in the symmetrical pixel value distribution shown in the lower diagram of FIG. 8, and calculates the ratio of the pixel value to the calculated average value for each pixel as a correction coefficient. To do.

  Returning to FIG. 7, the generation function 151 b can store the calculated gain correction coefficient in the storage circuit 152. Note that the storage circuit 152 can store an offset image and a defect point map in addition to the correction coefficient. In addition, the transmission function 151c can transmit the correction coefficient, the offset image, and the defect point map to a predetermined storage device via the access point and save it as backup data. The predetermined storage device is a server external to the FPD 150, such as the storage circuit 180. When the data such as the offset image, the gain correction coefficient, and the defect point map held by the storage circuit 152 is damaged, the FPD 150 can recover the damaged data using the backup data.

  In FIG. 8, the FPD 150 according to the first embodiment creates a correction coefficient by averaging the image data collected for two orientations whose rotation angles are “0 °” and “180 °”. Although described, the embodiment is not limited to this. For example, as shown in FIG. 9, the FPD 150 creates correction coefficients by averaging image data collected for four directions of rotation angles “0 °”, “90 °”, “180 °”, and “270 °”. It may be the case. FIG. 9 is a diagram for explaining gain calibration according to the first embodiment.

  For example, the collection function 151a collects image data in each of four arrangement states having different directions with respect to the X-ray tube 120 as shown in the upper diagram of FIG. Next, the generation function 151b calculates the pixel value distribution by averaging the pixel value distributions obtained by the first, second, third, and fourth shootings as shown in the lower diagram of FIG. To calculate the gain correction coefficient. Here, the generation function 151b generates a correction coefficient by, for example, averaging X-ray images taken in four directions of rotation angles “0 °”, “90 °”, “180 °”, and “270 °”. Thus, a correction coefficient that is symmetric with respect to the top, bottom, left and right (X direction and Y direction) of the FPD 150 can be created.

  The gain calibration according to the first embodiment has been described above. As described above, the FPD 150 according to the first embodiment averages image data collected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube 120, and calculates a correction coefficient. Hereinafter, a case where the FPD 150 is installed in another X-ray diagnostic apparatus (separate system) different from the X-ray diagnostic apparatus 1 and imaging of the subject P will be described with reference to FIG. FIG. 10 is a diagram for explaining photographing according to the first embodiment.

  First, as shown in FIG. 10, the collection function 151a is in a state where a subject P, a grid, an AEC (Automatic Exposure Control) detector, etc. are installed between the X-ray tube 120 and the FPD 150 (X-ray path). Collect X-ray information. Next, as shown in FIG. 10, the collection function 151a amplifies the collected X-ray information with an amplifier, and then performs AD conversion to convert it into a digital signal (pixel value) to generate image data.

  The collection function 151a executes various corrections on the generated image data. Specifically, as illustrated in FIG. 10, the collection function 151 a first reads an offset image from the storage circuit 152 and executes offset correction. Next, the collection function 151 a reads the gain correction coefficient from the storage circuit 152 and executes gain correction. In addition, the collection function 151a reads a defect point map from the storage circuit 152 and executes defect point correction.

  Here, the type, the SID, the direction of the X-ray tube, and the like used for collecting the image data shown in FIG. 10 may be different from those of the X-ray diagnostic apparatus 1 that has executed calibration. Therefore, the pixel value distribution due to the non-uniformity of the X-ray dose may have a different shape from the pixel value distribution at the time of gain calibration. However, the gain correction coefficient created by the gain calibration according to the first embodiment is generated based on an averaged image of two directions, as shown in the upper diagram of FIG. It is symmetrical. Therefore, the use of such a correction coefficient does not cause a phenomenon that the range of the pixel value distribution of the corrected image becomes larger than the non-uniformity of the X-ray dose. FIG. 11 is a diagram for explaining gain correction according to the first embodiment.

  That is, the acquisition function 151a has a symmetrical gain correction coefficient shown in the upper diagram of FIG. 11 even when the FPD 150 is installed in another system other than the X-ray diagnostic apparatus 1 that has performed gain calibration. By executing the gain correction using, it is possible to avoid the excessive correction as shown in FIG. 6B. Then, the collection function 151a can perform gain correction gently and symmetrically toward the periphery of the irradiation field, and generate a natural correction image.

  Returning to FIG. 10, after the collection function 151a collects image data and executes various corrections, the transmission function 151c transmits the image data to the image processing apparatus via an access point, for example. The image processing apparatus executes preset image processing on the image data collected from the FPD 150, and displays the X-ray image on which the image processing has been performed on the monitor.

  Next, an example of a processing procedure performed by the FPD 150 will be described with reference to FIG. FIG. 12 is a flowchart for explaining a series of processing steps of the FPD 150 according to the first embodiment. Step S1300, Step S1400, Step S1500, Step S1600, Step S1700, and Step S1900 are steps corresponding to the collection function 151a. Step S1800 is a step corresponding to the transmission function 151c.

  First, the processing circuit 151 executes gain calibration (step S1100) and creates a gain correction coefficient. Next, after installing the FPD 150 in the same system as the system that executed the gain calibration or another system (step S1200), the processing circuit 151 determines whether or not an inspection start request has been received from the operator (step S1200). S1300). When the inspection start request is not accepted (No at Step S1300), the processing circuit 151 enters a standby state. On the other hand, when an examination start request is received (Yes at Step S1300), the processing circuit 151 detects X-rays that have passed through the subject P and collects image data (Step S1400). In addition, the processing circuit 151 performs offset correction on the collected image data (step S1500).

  Next, the processing circuit 151 performs gain correction on the image data subjected to offset correction using the gain correction coefficient created by the gain calibration in step S1100 (step S1600). Further, the processing circuit 151 performs defect point correction on the image data that has been subjected to gain correction (step S1700), and transmits the image data to the image processing apparatus (step S1800). Then, the processing circuit 151 determines whether or not an inspection end request has been received from the operator (step S1900). If the inspection end request is not accepted (No at step S1900), the processing circuit 151 enters a standby state. On the other hand, when the inspection end request is received (Yes at step S1900), the processing circuit 151 ends the processing.

  Heretofore, a series of processing flow of the FPD 150 according to the first embodiment has been described. Next, gain calibration according to the first embodiment will be described with reference to FIG. FIG. 13 is a flowchart for explaining a series of gain calibration processes according to the first embodiment. Here, FIG. 13 shows processing corresponding to step S1100 of FIG. In FIG. 13, step S1101, step S1102, step S1103, and step S1106 are steps corresponding to the collection function 151a. Step S1104 is a step corresponding to the generation function 151b. Step S1105 is a step corresponding to the transmission function 151c.

  First, the processing circuit 151 determines whether or not a gain calibration start request has been received from the operator (step S1101). When the gain calibration start request is not accepted (No in step S1101), the processing circuit 151 enters a standby state. On the other hand, when a gain calibration start request is received (Yes at step S1101), the processing circuit 151 detects X-rays emitted from the X-ray tube 120 and image data in a plurality of arrangement states with respect to the X-ray tube 120. Are collected (step S1102). In addition, the processing circuit 151 performs offset correction on the collected image data (step S1103).

  Next, the processing circuit 151 averages each signal based on the X-rays detected in the plurality of arrangement states, creates a gain correction coefficient based on the averaged signal (step S1104), and stores it in the storage circuit 152. . In addition, the processing circuit 151 transmits the created gain correction coefficient to a predetermined storage device and uses it as backup data (step S1105). Then, the processing circuit 151 determines whether a gain calibration end request has been received from the operator (step S1106). When the gain calibration end request is not accepted (No at Step S1106), the processing circuit 151 enters a standby state. On the other hand, if a gain calibration end request is received (Yes at step S1106), the processing circuit 151 ends the process.

  As described above, according to the first embodiment, the collection function 151 a detects X-rays emitted from the X-ray tube 120. The generation function 151b averages each signal based on X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube 120, and corrects the X-ray image based on the averaged signal. A correction coefficient used in the above is generated. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment avoids excessive correction and auto window malfunction even when performing FPD sharing, and can obtain a natural corrected image. A correction count can be created to improve inspection efficiency.

  In addition, the X-ray diagnostic apparatus 1 according to the first embodiment creates a gain correction coefficient that can obtain a natural correction image by gain calibration in one system. Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment can perform comparison without increasing the labor of gain calibration even when a plurality of X-ray diagnostic apparatuses and a plurality of FPDs are used in combination. A gain correction coefficient can be created easily and conveniently.

  Further, according to the first embodiment, the generation function 151b creates a gain correction coefficient using the pixel value distribution in the image data in two directions in which the anode side and the cathode side of the X-ray tube 120 are opposite to each other. . Therefore, in the X-ray diagnostic apparatus 1 according to the first embodiment, the orientation of the FPD 150 with respect to the anode side and the cathode side of the X-ray tube is reversed during gain calibration and when imaging a diagnostic X-ray image. Even so, it is possible to create a gain correction coefficient that is not excessively corrected and improve the efficiency of the inspection.

  Further, according to the first embodiment, the generation function 151b uses the pixel value distribution in the image data in the four directions rotated by “90 °” with respect to the X-ray tube 120, and the gain correction coefficient that is symmetrical vertically and horizontally. Create Therefore, the X-ray diagnostic apparatus 1 according to the first embodiment further improves the degree of freedom in installing the FPD 150 when taking a diagnostic X-ray image, creates a more versatile gain correction coefficient, and performs inspection. Efficiency can be improved.

  In addition, according to the first embodiment, the generation function 151b is not limited to the case where the FPD 150 is installed in the X-ray diagnostic apparatus 1 that performs gain calibration, and the FPD 150 is installed in another X-ray diagnostic apparatus for diagnosis. A gain correction coefficient capable of generating a natural X-ray image is also created when the X-ray image is taken. Therefore, the FPD 150 according to the first embodiment can create a gain correction coefficient as unique to the FPD 150, and can eliminate the complexity of managing data used for correcting an X-ray image.

  Further, according to the first embodiment, the storage circuit 152 stores the gain correction coefficient, the offset image, and the defect point map created by the generation function 151 b in the storage circuit 152. Therefore, the FPD 150 according to the first embodiment can eliminate the complicated management of data used for correction of X-ray images when performing FPD sharing by holding correction data indicating the feature itself. it can.

  Further, according to the first embodiment, the transmission function 151c can transmit the gain correction coefficient, the offset image, and the defect point map created by the generation function 151b to a predetermined storage device, and can be used as a backup. Therefore, the FPD 150 according to the first embodiment can receive and recover the backup data even when the data held in the storage circuit 152 is damaged.

  In the first embodiment described above, the generation function 151b included in the FPD 150 has been described for calculating a correction coefficient used for X-ray image correction. However, the embodiment is not limited to this. For example, the processing circuit 190 of the X-ray diagnostic apparatus 1 may calculate the correction coefficient. For example, the FPD 150 detects X-rays emitted from the X-ray tube 120. The processing circuit 190 averages each signal based on the X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube 120, and uses it for correcting the X-ray image based on the averaged signal. A correction coefficient is generated. Further, for example, the X-ray diagnostic apparatus generates correction coefficients for a plurality of different FPDs and stores them in the storage circuit. Here, the X-ray diagnostic apparatus may execute a gain correction coefficient on the image data received from the FPD using a correction coefficient corresponding to the FPD. In addition, for example, the X-ray diagnostic apparatus may generate correction coefficients for a plurality of different FPDs and store the generated correction coefficients in a storage circuit included in each FPD.

  Each component of each device according to the first embodiment described above is functionally conceptual and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or a part of the distribution / integration may be functionally or physically distributed in arbitrary units according to various loads or usage conditions. Can be integrated and configured. Further, all or a part of each processing function performed in each device may be realized by a CPU and a program that is analyzed and executed by the CPU, or may be realized as hardware by wired logic.

  Further, the control method described in the first embodiment can be realized by executing a control program prepared in advance on a computer such as a personal computer or a workstation. This control program can be distributed via a network such as the Internet. The control program can also be executed by being recorded on a computer-readable recording medium such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, and a DVD and being read from the recording medium by the computer.

  According to at least one embodiment described above, the efficiency of inspection using a portable X-ray detector can be improved.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

1 X-ray diagnostic equipment 150 FPD
151 Processing Circuit 151a Collection Function 151b Generation Function 151c Transmission Function 152 Storage Circuit 190 Processing Circuit 190a Control Function 190b Image Generation Function

Claims (8)

A detection unit for detecting X-rays emitted from the X-ray tube;
Each signal based on X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube is averaged, and a correction coefficient used for correcting the X-ray image is generated based on the averaged signal. A generator,
An X-ray detector comprising:   2. The X-ray detector according to claim 1, wherein the different orientations are two orientations rotated by 180 ° about a direction orthogonal to a detection surface for detecting X-rays irradiated by the X-ray tube.   2. The X-ray detector according to claim 1, wherein the different directions are four directions that are rotated by 90 ° about a direction orthogonal to a detection surface that detects X-rays emitted by the X-ray tube.   The X-ray detector as described in any one of Claims 1-3 further provided with the memory | storage part which memorize | stores the said correction coefficient.   The X-ray detector according to claim 4, wherein the storage unit further stores data used for removing an offset component in the X-ray image and data used for correcting a defect point in the X-ray image.   The X-ray detector according to claim 4, further comprising a transmission unit that transmits the correction coefficient to a predetermined storage device.   The X-ray detector according to claim 5, further comprising a transmission unit that transmits the correction coefficient, data used for removing the offset component, and data used for correcting the defect point to a predetermined storage device. An X-ray tube that emits X-rays;
A detection unit for detecting X-rays irradiated from the X-ray tube;
Each signal based on X-rays detected in a plurality of arrangement states arranged in different directions with respect to the X-ray tube is averaged, and a correction coefficient used for correcting the X-ray image is generated based on the averaged signal. A generator,
An X-ray diagnostic apparatus comprising:

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