JP2010029238A - X-ray diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray diagnostic apparatus which detects an obstacle located within an X-ray irradiation region when acquiring sensitivity information of an X-ray detector. <P>SOLUTION: When acquiring sensitivity information of the X-ray detector 5, a control section 61 performs Fourier transformation on X-ray detection data (p15) extracted from lines diagonal to grid stripes and having an amount of one column, among X-ray detection data acquired by air photography, and converts the data into frequency space. When a peak appears in frequency response (p17), the control section determines that an object is detected within the X-ray irradiation space. Because a frequency range where a peak may appear can be estimated in advance from a moire frequency characteristics generated by gaps between the grid space and the sampling pitch, the control section 61 detects presence or absence of a peak by searching the estimated region. When a peak is detected within the estimated region, the control section 61 determines that the grid 4 is inserted and issues an alarm showing detection of the grid 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an X-ray diagnostic apparatus. Specifically, it relates to sensitivity correction of an X-ray detector in the X-ray diagnostic apparatus.

  An X-ray diagnostic apparatus irradiates a subject with X-rays from an X-ray source, and X-ray flattening detector (FPD; Flat) is arranged so that X-ray attenuation amount data of X-rays transmitted through the subject are opposed to the X-ray source. Panel Detector (hereinafter, referred to as an X-ray detector), and an apparatus for generating a captured image or a fluoroscopic image of a subject using detected X-ray attenuation amount data.

  An X-ray detector of an X-ray diagnostic apparatus is generally composed of a scintillator, a photodiode, a capacitor, a TFT (thin film transistor), and the like. For this reason, dark current is generated even when X-rays are not irradiated, and charges are accumulated in the capacitor as noise. Therefore, if the detected data is used as image data as it is, the image quality deteriorates. Therefore, when the X-ray is not irradiated, the amount of charge (dark current amount) accumulated in the capacitor is read out, and the process of emptying (empty reading) is performed. Offset correction is performed to subtract this dark current amount from the output X-ray attenuation amount data (Patent Document 1).

  The X-ray detector has different sensitivities for each X-ray detector due to variations in characteristics of scintillators, photodiodes and the like constituting the detection element. Therefore, the X-ray detector is irradiated with X-rays having a certain characteristic intensity in a state where there is no subject or object (such as a grid for removing scattered rays or an X-ray aperture) in the X-ray irradiation space. Sensitivity information of the X-ray detector is obtained and stored from data output from the line detector, and X-ray attenuation amount data is corrected using the sensitivity information at the time of actual imaging (Patent Document 2). .

  When acquiring the sensitivity information, it is necessary to irradiate the X-ray with no subject or object in the X-ray irradiation space as described above. Therefore, in the conventional X-ray diagnostic apparatus, it is detected that a grid for removing scattered radiation is inserted using a sensor such as a micro switch, or the position information of the X-ray diaphragm is detected by the control unit. , To recognize the existence of the object. In addition, an average value and a standard deviation value are calculated from the output data of the X-ray detector to recognize that there is no subject or object.

JP 2002-159482 A WO2003 / 000136

  However, in the method using the above-described microswitch and position detection means, it is necessary to add hardware, and the cost is spent. Further, in the method of calculating the average value and the standard deviation value from the output data of the X-ray detector, it is difficult to specify what is inserted.

  In particular, if a grid for removing scattered radiation has been inserted when acquiring sensitivity information, sensitivity correction will be performed using sensitivity information obtained with the grid inserted in actual shooting. There is a problem that moire occurs in the output image due to interference of the grid stripes, the image quality is deteriorated, and the photographing itself is wasted.

  The present invention has been made in view of the above problems, and an X-ray diagnostic apparatus capable of detecting an obstacle present in an X-ray irradiation space when acquiring sensitivity information of an X-ray detector. The purpose is to provide.

  In order to achieve the above-described object, the present invention includes an X-ray source that irradiates a subject with X-rays, an X-ray detector that is disposed opposite to the X-ray source and detects X-ray data transmitted through the subject, Sensitivity information acquisition means for acquiring sensitivity information of the X-ray detector by detecting an X-ray dose irradiated from the X-ray source by the X-ray detector, and sensitivity acquired by the sensitivity information acquisition means Based on the information, a sensitivity correction unit that corrects the X-ray data detected by the X-ray detector, and an X-ray data corrected by the sensitivity correction unit is used to generate a captured image or a fluoroscopic image of the subject. An X-ray diagnostic apparatus comprising: an image processing unit configured to analyze the sensitivity information acquired by the sensitivity information acquiring unit, and insert the X-ray source between the X-ray source and the X-ray detector Detected objects And object detecting means, when detecting the object by said object detecting means is an X-ray diagnostic apparatus characterized by comprising an informing means for informing that it has detected an object, the.

  The object is a grid for removing scattered radiation.

  In addition, the X-ray detector includes a plurality of detection elements arranged in a two-dimensional matrix, and the object detection unit is configured to detect the grid from the sensitivity information of the X-ray detector acquired by the sensitivity information acquisition unit. The detection data is extracted from the detection element group arranged in the direction orthogonal to the direction, the extracted detection data is replaced with the frequency space data, and the appearance of the peak response in the frequency space data determines that the object has been detected. 1 determination means is provided.

  The first determination means calculates an estimated range in which a peak response is estimated to appear in advance in the frequency space data based on the sampling pitch of the X-ray detector and the grid density of the grid. It is determined whether there is a peak response in the frequency space data by comparing the maximum value of the response in the estimated range and the average value of the response outside the estimated range.

  Furthermore, it is desirable that the notification means clearly indicates on the display screen that the grid is inserted when the object detection means detects that the grid is inserted.

  The object is an X-ray stop.

  In addition, the X-ray detector includes a plurality of detection elements arranged in a two-dimensional matrix, and the object detection unit is configured to calculate the X-ray detector from the sensitivity information of the X-ray detector acquired by the sensitivity information acquisition unit. The detection data is extracted from at least one detection element group in the vertical direction or the horizontal direction of the line detector, the extracted detection data is replaced with frequency space data, and the appearance of a peak response in the frequency space data causes the object to 2nd determination means which determines that it was detected.

  Further, the second determination means calculates an estimation range in which a peak response is estimated to appear in advance in the frequency space data based on a sampling pitch of the X-ray detector and an edge position of the X-ray diaphragm, It is determined whether or not the frequency space data has a peak response by comparing the calculated maximum value of the response in the estimated range and the average value of the responses outside the estimated range.

  Furthermore, it is desirable that the notification means clearly indicates on the display screen that the X-ray diaphragm is inserted when the object detection means detects that the X-ray diaphragm is inserted.

  ADVANTAGE OF THE INVENTION According to this invention, when acquiring the sensitivity information of an X-ray detector, the X-ray diagnostic apparatus which can detect the obstruction which exists in X-ray irradiation space can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
First, the configuration of the X-ray diagnostic apparatus 1 will be described.
FIG. 1 is a block diagram showing the overall configuration of the X-ray diagnostic apparatus 1.
The X-ray diagnostic apparatus 1 of the present invention can be applied to any of a general imaging apparatus that images the chest, the head, and the like, and a fluoroscopic imaging apparatus that images the abdomen and the like.

  As shown in FIG. 1, an X-ray diagnostic apparatus 1 includes an X-ray generator (X-ray source) 2 connected to an X-ray high voltage apparatus 21 and an X-ray detector 5 provided on a bed for fixing a subject 3. , An operation console 6, a display device 7, and an operation device 8. The X-ray generator 2 is provided with an X-ray diaphragm 23 for adjusting the X-ray irradiation range. The X-ray detector 5 is provided with a grid 4 for removing scattered radiation so as to be freely inserted and removed. The X-ray diagnostic apparatus 1 irradiates the subject 3 fixed on the bed with X-rays from the X-ray generator 2, and acquires X-ray attenuation amount data transmitted through the subject 3 by the X-ray detector 5. . Further, a captured image and a fluoroscopic image of the subject 3 are generated by the image processing device 64 using the acquired X-ray attenuation amount data.

In addition, the X-ray diagnostic apparatus 1 irradiates the X-ray detector 5 with X-rays in the absence of the subject 3, and the X-ray detector 5 outputs data from the output data of the X-ray detector 5 at this time. Get sensitivity information. In the following description, irradiating the X-ray detector 5 with X-rays without the subject 3 is called air imaging. Data output from the X-ray detector 5 during air imaging is referred to as X-ray detection data or output data.
The acquisition of sensitivity information will be described later (see FIG. 4).

  The X-ray generator 2 includes an X-ray tube and an X-ray tube control device, and is controlled by the control unit 61 of the operation console 6 to irradiate X-rays continuously or intermittently. The X-ray high voltage device 21 is controlled by the control unit 61 and applies a predetermined X-ray tube voltage to the X-ray tube.

The X-ray diaphragm 23 is for adjusting the irradiation range of X-rays irradiated from the X-ray tube. The X-ray diaphragm 23 has blades covering the X-ray tube, and the blades are moved in a range from fully open to fully closed by the control of the control unit 61 to adjust the amount of diaphragm.
X-rays irradiated from the X-ray generator 2 pass through the subject 3 and enter the X-ray detector 5 through the grid 4.

  The X-ray detector 5 is disposed so as to face the X-ray generator 2 with the subject 3 interposed therebetween. The X-ray detector 5 detects the attenuation amount of X-rays emitted from the X-ray generator 2 and transmitted through the subject 3, and outputs the detected X-ray attenuation amount data to the image processing device 64.

  The X-ray detector 5 includes a scintillator that converts X-rays transmitted through the subject 3 into light, and a detection element that converts light emitted from the scintillator into an electric signal. A plurality of detection elements are arranged on a predetermined number of lines, respectively, and form a two-dimensional matrix as a whole. One detection element constitutes one pixel. Each detection element includes a photodiode that converts light output from the scintillator into electric charge, a capacitor that accumulates electric charge, and a switching element (for example, TFT) that reads out the accumulated electric charge. Instead of the combination of the scintillator and the photodiode, a direct conversion type detection element that directly converts X-rays into electric charges may be used.

The X-ray detector 5 of the present embodiment is assumed to have 256 detection elements per line as an example. The line direction of the X-ray detector 5 is defined as the X direction, and the direction orthogonal to the line is defined as the Y direction.
Detection signals detected by the detection elements of the X-ray detector 5 are collected by a data collection device (not shown) and output to the image processing device 64 as X-ray attenuation amount data (X-ray detection data at the time of air imaging). .

  The image processing device 64 acquires X-ray attenuation amount data detected by the X-ray detector 5 under the control of the control unit 61. Further, the sensitivity information of the X-ray detector 5 measured in advance is acquired from the storage device 65. The image processing device 64 performs sensitivity correction by subtracting sensitivity information from the acquired X-ray attenuation amount data. Further, preprocessing such as offset correction for subtracting the dark current amount of the X-ray detector 5 is performed. The image processing device 64 generates a captured image and a fluoroscopic image of the subject 3 using the X-ray attenuation amount data that has been subjected to preprocessing such as sensitivity correction, and outputs it to the storage device 65 or the display device 7.

  The operation console 6 includes a display device 7, an operation device 8, a control unit 61, an image processing device 64, and a storage device 65. The operation console 6 is connected to the X-ray generator 2, the X-ray high voltage device 21, the X-ray detector 5, and the bed.

  The display device 7 includes a display device such as a liquid crystal panel and a CRT monitor, and a logic circuit for executing display processing in cooperation with the display device, and is connected to the control unit 61. The display device 7 displays an image output from the image processing device 64 and various information handled by the control unit 61.

  The operation device 8 includes, for example, an input device such as a keyboard, a mouse, and a numeric keypad and various switch buttons, and outputs various instructions and information input by the operator to the control unit 61. The operator can interactively operate the X-ray diagnostic apparatus 1 using the display device 7 and the operation device 8.

  The control unit 61 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and includes the X-ray generator 2, the X-ray high voltage device 21, the bed, the X The line detector 5, the image processing device 64, the display device 7, the operation device 8, and the storage device 65 are controlled.

  In addition, when the sensitivity information of the X-ray detector 5 is acquired, the control unit 61 performs frequency analysis on the output data of the X-ray detector 5 to detect whether or not the grid 4 is inserted. Execute. Sensitivity information acquisition processing and grid detection processing will be described later (see FIGS. 4 and 5).

  The storage device 65 is configured by a hard disk or the like, and is connected to the control unit 61. The storage device 65 stores an X-ray image and an X-ray fluoroscopic image generated by the image processing device 64. The storage device 65 stores sensitivity information of the X-ray detector 5. The sensitivity information is referred to when the image processing device 64 generates an X-ray image and an X-ray fluoroscopic image, and is used for sensitivity correction. In addition to these various data, the storage device 65 stores a program and the like for realizing the function of the X-ray diagnostic apparatus 1.

  The grid 4 is for removing scattered X-rays of irradiated X-rays, and is made of a foil such as lead having a high X-ray absorption rate (grid lead) and an intermediate substance having a low X-ray absorption rate. It is arranged so as to be parallel to the longitudinal direction. The grid 4 is attached to the surface of the X-ray detector 5 on the X-ray irradiation space side so that the longitudinal direction of the foil coincides with the X direction or the Y direction of the pixels (detection elements) of the X-ray detector 5.

The grid 4 needs to be removed when the sensitivity information of the X-ray detector 5 is acquired, but air imaging may be started without being accidentally removed.
Therefore, the X-ray diagnostic apparatus 1 according to the present embodiment performs processing for detecting whether or not a grid is inserted when acquiring sensitivity information.

Here, the principle of grid detection when acquiring sensitivity information will be described with reference to FIGS.
FIG. 2 is a schematic diagram for explaining moire that appears in an output image when a grid is inserted.
FIG. 3 is a diagram showing moire appearing in the output image when the grid is inserted and its frequency characteristics.

  FIG. 2 shows a state in which the grid 4 is inserted between the X-ray generator 2 and the X-ray detector 5 of the X-ray diagnostic apparatus 1. As an example, the grid 4 in FIG. 2 has a grid density of 40 lines / cm (= 250 μm pitch). As shown in FIG. 2, the X-rays transmitted through the grid 4 generate the same X-ray intensity distribution p11 at intervals of 250 μm by grid lead arranged at intervals of 250 μm. If the sampling pitch of the X-ray detector 5 is 250 μm, which is the same as the X-ray intensity distribution p11, moire does not occur because the intensity distribution in the same phase can always be sampled. However, when the sampling pitch of the X-ray detector 5 is different from the X-ray intensity distribution p11, the phase is shifted, and moire appears in the output image.

  For example, when the grid interval is 250 μm and the sampling pitch of the X-ray detector 5 is 143 μm, the X-ray detector 5 samples data at a position indicated by a circle in the luminance distribution p13 in FIG. Therefore, moire is recognized by a dotted line connecting the sampling points.

  FIG. 3A shows a profile obtained by extracting data for one row (256 pixels) in the X direction from the X-ray detection data detected by the X-ray detector 5 when air imaging is performed with the grid 4 inserted. p15. In this profile p15, the vertical axis is a value obtained by standardizing the output data of the X-ray detector 5, and the horizontal axis indicates the pixel (X coordinate) in the X direction of the X-ray detector 5. In the profile p15, points represented by black squares are sampling points. The profile p15 is a simulation result obtained when the grid interval of the grid 4 is 40 lines / cm and the pixel size (sampling pitch) of the X-ray detector 5 is 143 μm. FIG. 3B is a frequency response p17 that represents the result of Fourier transform (FFT) of the profile p15 in FIG. In FIG. 3B, the horizontal axis represents the frequency band (lp / mm).

  As shown in FIG. 3, when the profile p15 (FIG. 3A) in which moire is generated due to a shift between the grid grating interval and the sampling pitch is replaced with a frequency space, a peak appears in a predetermined frequency region (FIG. 3). (B)). In the example of FIG. 3, the peak is a region near 3.2 lp / mm.

  In the X-ray diagnostic apparatus 1 of the present invention, paying attention to the peak that appears when the output data of the X-ray detector 5 is replaced with the frequency domain, the insertion of an object existing in the X-ray irradiation space (here, the grid 4) ) Is detected.

That is, the control unit 61 extracts one line line orthogonal to the grid 4 from the output data of the X-ray detector 5, and performs fast Fourier transform (FFT) on the extracted data (profile p15 in FIG. 3A). And replace with frequency space. And if a peak appears in a frequency response (frequency response p17 of FIG.3 (b)), it will determine with the object being inserted.
Further, the control unit 61 can also determine that the inserted object is the grid 4 when the position (frequency) where the frequency response peak exists can be identified as being caused by moire appearing by grid insertion. .

Here, a method for estimating the position of the peak appearing in the frequency response p17 will be described.
For simplicity, the X-ray intensity distribution (l) after passing through the grid 4 is a sine wave with the reciprocal of the grid density (N) as one cycle. At this time, the X-ray intensity (l (x)) after transmission through the grid 4 at a certain position (x) is expressed by the following equation (1).

    l (x) = sin (2πNx) (1)

  When the grid interval (grid density) of the grid 4 is 40 lines / cm and the pixel size (sampling pitch) of the X-ray detector is 143 μm, the moire appearing in the image is estimated as shown in FIG. In the frequency space, a peak exists in the vicinity of about 3.2 lp / mm. Including the tolerance range of the grid grating density, the frequency region where the peak appears is about 3.0 lp / mm to 3.4 lp / mm.

As described above, the range in which the peak is estimated to appear can be predicted in advance from the lattice interval of the grid 4 and the sampling pitch (pixel size) of the X-ray detector 5. When the grid interval of the grid 4 and the sampling pitch of the X-ray detector 5 are different, different estimation ranges are obtained.
The X-ray diagnostic apparatus 1 calculates and stores in advance the estimation ranges corresponding to the sampling pitches of the various grids 4 or X-ray detectors 5 in the storage device 65, and executes the process of acquiring sensitivity information. Reads out the estimation range corresponding to the X-ray detector 5 or grid 4 being used, and performs grid detection processing to be described later.

Next, the operation of the X-ray diagnostic apparatus 1 will be described with reference to FIGS.
FIG. 4 is a flowchart showing the flow of sensitivity information acquisition processing.
FIG. 5 is a flowchart showing the flow of the grid detection process.
FIG. 6 is a diagram illustrating data held in the RAM of the control unit 61 when the grid detection process is executed.
FIG. 7 is a diagram illustrating an example of a warning screen displayed when it is detected that the grid 4 is inserted.

  The control unit 61 reads a program and data for executing various processes from the storage device 65, and executes processes based on the program and data.

First, the overall flow of sensitivity information acquisition will be described.
As shown in FIG. 4, the control unit 61 of the X-ray diagnostic apparatus 1 first performs air imaging in which X-rays are irradiated to the X-ray detector 5 without the subject 3 (step S101). In air imaging, the control unit 61 controls the X-ray generator 2 to irradiate X-rays with a predetermined tube voltage and tube current. Further, the control unit 61 controls the X-ray detector 5 to collect X-ray detection data in air imaging.

  Next, the control part 61 performs a grid detection process based on the X-ray detection data output from the X-ray detector 5 (step S102). The grid detection process will be described later (see FIG. 5). When the grid 4 is detected in the grid detection process (step S103; Yes), the control unit 61 displays a warning that the grid 4 is inserted on the display device 7 (step S104; see FIG. 7). Thereafter, when the grid 4 is removed by an operator's manual operation or an operation instruction from the operation device 8 and an instruction to acquire sensitivity information is input from the operation device 8 again, the process returns to step S101 to perform air imaging. If the grid 4 is not detected in step S103, the X-ray detection data detected by air imaging in step S101 is stored as sensitivity information in the RAM of the control unit 61 or the storage device 65 (step S105).

  In order to obtain more accurate sensitivity information, after the control unit 61 enters a state where the grid 4 is not detected (step S103; No), the air shooting in step S101 is repeated a plurality of times, and is obtained by a plurality of air shootings. An average value of the obtained X-ray detection data may be calculated, and the calculated average value may be stored in the RAM or the storage device 65 as sensitivity information.

Next, the grid detection process in step S102 will be described with reference to FIGS.
In the grid detection process shown in FIG. 5, the control unit 61 first detects X-rays for one column (for example, 256 pixels) in the direction orthogonal to the grid stripes in the X-ray detection data output from the X-ray detector 5. Data is extracted (step S201), and the extracted X-ray detection data is stored as sensitivity information in the RAM of the control unit 61 (61a in FIG. 6).

Here, the direction orthogonal to the grid stripe will be described. When the direction in which the grid 4 is inserted is determined, the direction orthogonal to the grid stripe is specified. However, in the X-ray diagnostic apparatus having a structure in which the orientation in which the grid 4 is inserted is not determined, X-ray detection data of an arbitrary one column of pixels is acquired from both the X direction and the Y direction of the X-ray detector 5. The following processing (grid detection processing; step S202 to step S205) is performed on the X-ray detection data in these two directions. Then, it is determined that the grid 4 has been detected when a peak appears in the frequency characteristic described above in any one of the X direction and the Y direction.
In the following description, it is assumed that the direction orthogonal to the grid stripe is the X direction of the X-ray detector 5.

  The controller 61 performs one-dimensional Fourier transform (FFT) on the X-ray detection data for one column extracted from the X-ray detector 5 and replaces it with frequency space data (step S202). Hereinafter, the data replaced with the frequency space data is referred to as a frequency response (see FIG. 3B).

The control unit 61 searches for a pre-estimated frequency range (hereinafter referred to as an estimation range) of the frequency response obtained in step S202, acquires the maximum value (peak) of the response within the estimation range, and stores it in the RAM. (61b in FIG. 6).
Further, the control unit 61 calculates an average value of responses outside the estimation range and stores it in the RAM (61c in FIG. 6).

  The control unit 61 compares the maximum value (peak) of the response within the estimated range with the average value of responses outside the estimated range. As a result of the comparison, if the response of the peak is, for example, 10 times or more of the average response value outside the estimation range (step S203; Yes), it is determined that the grid 4 has been detected, and a flag with a grid is set (step S205). As a result of the comparison, when the peak response is less than 10 times the average value of the response outside the estimation range (step S203; No), it is determined that the grid 4 is not detected, and the no-grid flag is set (step S204).

Thus, since the control unit 61 preliminarily estimates the frequency range in which a peak appears in the frequency response and searches for the estimated range, the grid detection process can be performed at high speed.
Further, from the appearance position of the peak, the control unit 61 can also specify that the obstacle (object) in the X-ray irradiation space is the grid 4.

If the grid flag is set, the control unit 61 displays on the display device 7 that the grid 4 has been detected in step S104 of FIG.
FIG. 7 is an example of a warning screen 7a displayed when the grid 4 is detected. The control unit 61 causes the display device 7 to display a message such as “grid inserted”. When the operator confirms the message on the warning screen 7a, the operator temporarily stops photographing and removes the grid 4. When the insertion / removal of the grid 4 is performed by a mechanical operation, an instruction to remove the grid 4 is input from the operation device 8 to remove the grid 4.

In the above example, a warning screen is displayed when the grid 4 is inserted in the display device 7. However, when the grid 4 is not inserted, “the grid is not inserted”, “sensitivity information” is displayed. May be displayed. " Further, when the grid detection process is executed, specific data such as the profile p15 and the frequency response p17 shown in FIG. 3 may be displayed on the display device 7.
In addition to displaying a message, it may be notified that the grid 4 has been detected by a beep sound or the like.

  As described above, when acquiring the sensitivity information of the X-ray detector 5, the diagnostic imaging apparatus 1 according to the first embodiment performs frequency analysis on the X-ray detection data acquired by air imaging. The control unit 61 extracts one column of data in the direction orthogonal to the grid 4 from the output data of the X-ray detector 5, performs Fourier transform, and replaces it with the frequency space. If a peak appears in the frequency response, it is determined that an object exists in the X-ray irradiation space. Furthermore, when a peak appears in a frequency region (estimated range) estimated in advance from the grid interval of the grid 4 and the sampling pitch of the X-ray detector 5, it is determined that the grid 4 is inserted. When the grid 4 is inserted, a warning that the grid 4 is inserted is displayed.

  Accordingly, when the sensitivity information of the X-ray detector 5 is acquired, it is detected that the grid 4 is inserted by frequency analysis of the detection data of the X-ray detector 5 without using a device such as a microswitch. It becomes possible to do. Therefore, the apparatus configuration can be simplified and the cost can be suppressed.

(Second Embodiment)
Next, the configuration of the X-ray diagnostic apparatus 1 according to the second embodiment will be described.
Since the hardware configuration of the X-ray diagnostic apparatus 1 according to the second embodiment is the same as that of the X-ray diagnostic apparatus 1 shown in FIG. 1, the description thereof will be omitted. Will be attached.

  In the second embodiment, when acquiring the sensitivity information of the X-ray detector 5, the control unit 61 performs frequency analysis on the output data of the X-ray detector 5, so that the X-ray aperture 23 is placed in the X-ray irradiation space. Detect that there is.

The principle of detection of the X-ray diaphragm 23 will be described with reference to FIG.
FIG. 8 shows a profile p21 (X-ray detection data) obtained by air imaging and a frequency response p23 when a part of the X-ray irradiation space is shielded by the X-ray diaphragm 23.

FIG. 8A shows the profile p21 of the X-ray detector 5 for one column in the X direction (256 pixels). In this profile p <b> 21, the vertical axis is a value obtained by standardizing the output data of the X-ray detector 5, and the horizontal axis indicates the detection element (X coordinate) in the X direction of the X-ray detector 5.
In the profile p21 of FIG. 8A, the output value of the X-ray detector 5 changes greatly with the X coordinate in the range of 100 to 150 as a boundary. That is, it can be seen that the X-ray is shielded by the X-ray stop 23 in the range where the X coordinate is 0 to 100. Hereinafter, as shown in FIG. 8A, a position where the output value of the X-ray detector 5 greatly changes (here, X position) is referred to as an edge.

  FIG. 8B shows a frequency response p23 obtained by performing Fourier transform (FFT) on the profile p21 in FIG.

  As shown in FIG. 8, when the X-ray stop 23 exists in the X-ray irradiation space, if the X-ray detection data is replaced with frequency space data, a peak appears in a predetermined frequency region. In the example of FIG. 8B, a peak appears in a relatively low frequency region.

  In the second embodiment, as in the first embodiment, focusing on the peak that appears when the X-ray detection data is replaced with the frequency space data, the insertion of an object existing in the X-ray irradiation space (here Then, the insertion of the X-ray diaphragm 23) is detected.

That is, the control unit 61 extracts X-ray detection data for one line of lines orthogonal to the edge position from the output data of the X-ray diaphragm 23, and the extracted data (profile p21 in FIG. 8A) is fast Fourier transformed. Transform (FFT) and replace with frequency space data. If a peak appears in the frequency response (frequency response p23 in FIG. 8B), it can be determined that the object is inserted.
If the position where this peak exists is within the frequency region (estimated range) predicted in advance, it is determined that the X-ray diaphragm 23 is inserted.

  The control unit 61 also determines that the inserted object is the X-ray diaphragm 23 when the position where the peak of the frequency response exists can be identified as a peak that appears due to the insertion of the X-ray diaphragm 23. it can.

  It is assumed that the estimated range in which the peak appears in the frequency response is calculated in advance and stored in the storage device 65, and the control unit 61 reads the estimated range from the storage device 65 when executing the process of acquiring sensitivity information. , Use.

Next, the operation of the X-ray diagnostic apparatus 1 will be described with reference to FIGS.
FIG. 9 is a flowchart showing the flow of sensitivity information acquisition processing.
FIG. 10 is a flowchart showing the flow of X-ray aperture detection processing.
FIG. 11 is a diagram showing an example of a warning screen displayed when it is detected that the X-ray diaphragm 23 is inserted.

  The control unit 61 reads a program and data for executing various processes from the storage device 65, and executes processes based on the program and data.

First, acquisition of sensitivity information of the X-ray detector 5 in the X-ray diagnostic apparatus 1 will be described.
As shown in FIG. 9, the control unit 61 first irradiates the X-ray detector 5 with X-rays in the absence of the subject 3, and performs air imaging (step S301). In air imaging, the control unit 61 controls the X-ray generator 2 to irradiate X-rays with a predetermined tube voltage and tube current. In addition, the control unit 61 controls the X-ray detector 5 and acquires X-ray detection data in air imaging.

  Next, the controller 61 executes an X-ray aperture detection process based on the acquired X-ray detection data (step S302). The X-ray aperture detection process will be described later (see FIG. 10). When the X-ray diaphragm 23 is detected in the X-ray diaphragm detection process (step S303; Yes), the control unit 61 displays a warning that the X-ray diaphragm 23 is inserted on the display device 7 (step S304; FIG. 11). Thereafter, when the X-ray diaphragm 23 is fully opened and an instruction to acquire sensitivity information is input again from the controller device 8, the process returns to step S301 to perform air imaging. If the X-ray diaphragm 23 is not detected in step S303, the X-ray detection data detected by the air imaging in step S301 is used as sensitivity information and stored in the RAM of the control unit 61 or the storage device 65 (step S305).

  In order to obtain more accurate sensitivity information, after the control unit 61 enters a state where the X-ray diaphragm 23 is not detected (step S303; No), the air imaging in step S301 is repeated a plurality of times, thereby performing a plurality of air imagings. An average value of the X-ray detection data obtained in this way may be calculated, and the calculated average value may be stored in the RAM or the storage device 65 as sensitivity information.

  Next, the X-ray aperture detection process in step S302 will be described with reference to FIGS. In the X-ray aperture detection process shown in FIG. 10, the control unit 61 firstly, for the X-ray detection data output from the X-ray detector 5, one column (for example, 256) in the direction orthogonal to the edge of the X-ray aperture 23. Pixel detection data is extracted (step S401), and the extracted X-ray detection data is stored as sensitivity information in the RAM of the control unit 61 (61a in FIG. 6).

  Since the X-ray diaphragm 23 can shield both the X direction and the Y direction within an arbitrary range, the direction orthogonal to the edge of the X-ray diaphragm 23 cannot be specified. Therefore, the control unit 61 extracts the X-ray detection data for each column in the X direction and the Y direction of the X-ray detector 5, and each of the extracted X-ray detection data for one column will be described next. It is assumed that the processing from step S402 to S405 is performed. If the frequency response indicating the presence of the X-ray diaphragm 23 appears in at least one of the X-ray detection data in the X direction or the X-ray detection data in the Y direction, the control unit 61 determines that the X-ray diaphragm 23 has been detected. To do.

  In step S402, the control unit 61 performs one-dimensional Fourier transform (FFT) on the extracted X-ray detection data and replaces it with frequency space data.

And the control part 61 searches the frequency range (estimated range) estimated previously of the frequency response obtained by step S402, acquires the maximum value (peak) of the response in the estimated range, and preserve | saves it at RAM. (61b in FIG. 6).
Further, the control unit 61 acquires an average value of responses outside the estimation range and stores it in the RAM (61c in FIG. 6).

  The control unit 61 compares the maximum value (peak) of the response within the estimation range with the average value of the response outside the estimation range. As a result of the comparison, if the peak response is, for example, 10 times or more of the average value of the response outside the estimation range (step S403; Yes), the X-ray stop 23 flag is detected and the X-ray stop flag is set. (Step S405). As a result of the comparison, if the peak response is less than, for example, 10 times the average value of the response outside the estimation range (step S403; No), it is determined that the X-ray aperture is not detected, and the no X-ray aperture flag is set. (Step S404).

In this way, the control unit 61 estimates the frequency range in which a peak appears in the frequency response in advance and searches for the estimated range, so that the X-ray aperture detection process can be performed at high speed.
Further, from the peak appearance position, the control unit 61 can also specify that the obstacle (object) in the X-ray irradiation space is the X-ray stop 23.

If the X-ray aperture flag is set, in step S304 in FIG. 9, the control unit 61 displays on the display device 7 that the X-ray aperture has been detected.
FIG. 11 is an example of a warning screen 7b displayed when the X-ray diaphragm 23 is detected. The control unit 61 causes the display device 7 to display a message “X-ray diaphragm inserted”. When the operator confirms the message on the warning screen 7a, the operation is temporarily stopped and the X-ray diaphragm 23 is fully opened so as not to block the X-ray irradiation range.

The example of FIG. 11 shows an example in which a warning is displayed on the display device 7 when the X-ray diaphragm 23 is detected. However, when the X-ray diaphragm 23 is not detected, “the X-ray diaphragm is not inserted”. A message such as “No” or “Sensitivity information has been acquired” may be displayed. Further, when the X-ray aperture detection process is executed, specific X-ray detection data and frequency response may be displayed on the display device 7 as in the profile of FIG.
In addition to displaying a message, it may be notified that the X-ray diaphragm 23 is detected by a beep sound or the like.

  As described above, the diagnostic imaging apparatus 1 according to the second embodiment analyzes the frequency of X-ray detection data acquired by air imaging when acquiring sensitivity information of the X-ray detector 5. The control unit 61 extracts one column of data in each of the X direction and the Y direction from the output data of the X-ray detector 5, and performs Fourier transform on the extracted data to replace it with the frequency space. When a peak appears in the frequency response, the control unit 61 determines that an object exists in the X-ray irradiation space. Further, when a peak appears in a frequency region preliminarily estimated that the X-ray diaphragm 23 is inserted, it is determined that the X-ray diaphragm 23 is inserted. When the X-ray diaphragm 23 is inserted, a warning is displayed by displaying that the X-ray diaphragm 23 is inserted.

  Therefore, when acquiring the sensitivity information of the X-ray detector 5, the X-ray diaphragm 23 can be detected without using an apparatus such as an X-ray diaphragm position detector. Therefore, the apparatus configuration can be simplified and the cost can be suppressed.

  In the first and second embodiments described above, the X-ray diagnostic apparatus 1 is used for the timing of performing sensitivity information acquisition processing (including grid detection processing or X-ray aperture detection processing). It may be when a service person in charge goes to a hospital or the like to calibrate sensitivity information or defective pixels of the X-ray detector, or user calibration performed by the user himself / herself.

  Further, in the first and second embodiments, the appearance position of the peak of the frequency response is an example, and when the characteristics of the X-ray detector 5, the lattice density of the grid 4, and the like are different, the peak is present at a different position. May appear. Even in such a case, similarly to the above-described embodiment, the position where the peak appears can be estimated in advance, and the control unit 61 analyzes the output data of the X-ray detector 5 to analyze the grid 4 or The X-ray diaphragm 23 can be detected.

  The preferred embodiment of the X-ray diagnostic apparatus according to the present invention has been described above, but the present invention is not limited to the above-described embodiment. In addition, it is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. It is understood.

External view showing the overall configuration of the X-ray diagnostic apparatus 1 Schematic explaining the moire that appears when the grid is inserted (A) Output data of the X-ray detector 5 (X-ray detection data) (b) Frequency characteristics thereof Flow chart showing the flow of sensitivity information acquisition processing of the X-ray diagnostic apparatus 1 Flow chart showing the flow of grid detection processing The figure which shows the data hold | maintained at RAM of the control part 61 at the time of grid detection processing execution The figure which shows an example of the warning screen displayed when it detects that the grid is inserted (A) X-ray detection data obtained by aerial imaging when part of the X-ray irradiation space is shielded by the X-ray diaphragm 23 (b) Frequency characteristics thereof Flow chart showing the flow of sensitivity information acquisition processing of the X-ray diagnostic apparatus 1 Flow chart showing the flow of X-ray aperture detection processing The figure which shows an example of the warning screen displayed when detecting that the X-ray aperture is inserted

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... X-ray diagnostic apparatus 2 ... X-ray generator 21 ... X-ray high voltage apparatus 23 ... X-ray aperture 3 ... Test object 4 ... ..Grid for removing scattered radiation 5 X-ray detector (FPD)
6... Operation console 61... Control unit 64... Image processing device 65.

Claims (9)

An X-ray source that irradiates the subject with X-rays, an X-ray detector that is disposed opposite to the X-ray source and detects X-ray data transmitted through the subject;
Sensitivity information acquisition means for acquiring sensitivity information of the X-ray detector by detecting an X-ray dose irradiated from the X-ray source by the X-ray detector;
Sensitivity correction means for correcting X-ray data detected by the X-ray detector based on sensitivity information acquired by the sensitivity information acquisition means;
An X-ray diagnostic apparatus comprising: an image processing unit that generates a captured image or a fluoroscopic image of the subject using the X-ray data corrected by the sensitivity correction unit;
Object detection means for detecting an object inserted between the X-ray source and the X-ray detector by analyzing sensitivity information acquired by the sensitivity information acquisition means;
Informing means for informing that the object has been detected when the object is detected by the object detecting means;
An X-ray diagnostic apparatus comprising:   The X-ray diagnostic apparatus according to claim 1, wherein the object is a grid for removing scattered radiation. The X-ray detector includes a plurality of detection elements arranged in a two-dimensional matrix,
The object detection means includes
From the sensitivity information of the X-ray detector acquired by the sensitivity information acquisition means, detection data is extracted from detection element groups arranged in a direction orthogonal to the grid, and the extracted detection data is replaced with frequency space data. The X-ray diagnostic apparatus according to claim 2, further comprising: a first determination unit that determines that the object has been detected when a peak response appears in the frequency space data. The first determination means includes
Based on the sampling pitch of the X-ray detector and the grid density of the grid, an estimated range in which a peak response is estimated to appear in advance in the frequency space data is calculated, and the maximum value of the response in the calculated estimated range; 4. The X-ray diagnostic apparatus according to claim 3, wherein it is determined whether or not there is a peak response in the frequency space data by comparing with an average value of responses outside the estimation range.   3. The X according to claim 2, wherein when the object detection unit detects that the grid is inserted, the notification unit clearly indicates on the display screen that the grid is inserted. Line diagnostic equipment.   The X-ray diagnostic apparatus according to claim 1, wherein the object is an X-ray diaphragm. The X-ray detector includes a plurality of detection elements arranged in a two-dimensional matrix,
The object detection means includes
From the sensitivity information of the X-ray detector acquired by the sensitivity information acquisition means, detection data is extracted from at least one detection element group in the vertical direction or the horizontal direction of the X-ray detector, and extracted detection The X-ray diagnostic apparatus according to claim 6, further comprising second determination means that replaces data with frequency space data and determines that the object has been detected when a peak response appears in the frequency space data. The second determination means includes
Based on the sampling pitch of the X-ray detector and the edge position of the X-ray diaphragm, an estimated range in which a peak response is estimated to appear in the frequency space data in advance is calculated, and the maximum value of the response in the calculated estimated range The X-ray diagnostic apparatus according to claim 7, wherein it is determined whether or not there is a peak response in the frequency space data by comparing the average value of responses outside the estimated range.   7. The informing means clearly displays on the display screen that the X-ray diaphragm is inserted when the object detecting means detects that the X-ray diaphragm is inserted. X-ray diagnostic apparatus according to.

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