JP5034221B2 - Radiography equipment - Google Patents

Description

  The present invention relates to a radiation imaging apparatus that performs radiation imaging based on radiation detected by a radiation detection means, and more particularly to a technique for obtaining a current value of a radiation irradiation means as an imaging condition.

  An X-ray tomography apparatus will be described as an example of the radiation imaging apparatus. In the X-ray tomography apparatus, the incident X-ray dose to the detection surface of the X-ray detector continuously changes during tomography, or the X-ray transmission thickness of the subject changes for each detection data. Variation in S / N ratio occurs. As a result, the image quality of the tomographic image obtained by tomography deteriorates. In order to solve this problem, a technique for obtaining a high-quality tomographic image by controlling the X-ray tube current during tomography based on the incident angle and transmission data to the X-ray detector is disclosed. .

For example, an apparatus that performs imaging for the purpose of setting a tomographic plane in advance of tomographic imaging and sets the position, range, and shape of the tomographic plane is disclosed (see, for example, Patent Document 1). Further, for example, an optimal transmission X-ray reference value (pixel reference value) at a predetermined incident angle (here, the incident angle is 0 °) is set in advance in advance, and similarly based on the pixel reference value. An apparatus for setting and controlling the X-ray tube current according to the incident angle is disclosed (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 2004-350767 (pages 2, 4-8, FIGS. 1 and 2) Japanese Patent Laying-Open No. 2005-34436 (page 2-5, FIG. 1-3)

  However, in Patent Document 1 described above, the purpose of setting imaging prior to tomography is to set the position, range, and shape of the tomographic plane. It is also shown that tomographic conditions (X-ray aperture conditions, X-ray tube voltage, X-ray tube current, and X-ray tube scanning conditions) are set based on the set tomographic plane. It is not shown that the X-ray tube current is controlled according to the incident angle as in Reference 2, and the combination of the X-ray tube voltage and the X-ray tube current is obtained by analyzing the set tomographic plane. Is merely shown.

  On the other hand, the pixel reference value in Patent Document 2 is determined empirically (see Paragraph No. “0029” in Patent Document 2), and subject-specific information (for example, height, body thickness, bone density, and age) Etc.) and shooting settings are not taken into account. Therefore, it is difficult to stably obtain an X-ray tube current that is an optimum tomographic condition.

  This invention is made in view of such a situation, and it aims at providing the radiography apparatus which can obtain stably the electric current value of the radiation irradiation means at the time of radiography.

In order to achieve such an object, the present invention has the following configuration.
That is, the invention according to claim 1 includes a radiation irradiation unit that irradiates a subject with radiation, a radiation detection unit that detects radiation transmitted through the subject, the radiation irradiation unit, and the radiation detection unit. A drive control means for driving the radiation irradiating means and the radiation detecting means so as to control a change in the relative positional relationship, and the relative positional relation between the radiation irradiating means and the radiation detecting means is changed by the drive control means. A radiographic apparatus that performs radiography based on radiation detected by the radiation detection means, and performs setting imaging for setting a current value of the radiation irradiation means in advance of the radiography, and setting photographing means for performing for the analyte, a standard pixel value to the average value of each pixel value in the setting image obtained by the setting shooting The ratio of the difference, or the maximum value or values by a histogram analysis of pixel values of each obtained by the setting for photography, and pixel noise calculating means for determining a pixel noise, pixel noise and the obtained by pixel noise calculating means Based on the current value of the radiation irradiating means at the time of imaging for setting, the reference of the radiation irradiating means at the time of radiography based on the incident angle at which the radiation is incident on the radiation detecting means from the radiation irradiating means Reference current value calculation means for obtaining a current value is provided, and radiography is performed based on the reference current value of the radiation irradiation means obtained by the reference current value calculation means.

[Operation / Effect] According to the invention described in claim 1, the drive control means drives the radiation irradiation means and the radiation detection means so as to control the change in the relative positional relationship between the radiation irradiation means and the radiation detection means. Then, radiography is performed based on the radiation detected by the radiation detection means. Prior to this radiation imaging, the setting imaging means performs the setting imaging for setting the current value of the radiation irradiating means on the subject subject. Then, the ratio of the standard deviation of the pixel value to the average value of each pixel value in the setting image obtained by the setting shooting, or the maximum value of each pixel value obtained by the setting shooting or the value by histogram analysis Based on this, the pixel noise calculation means obtains the pixel noise. Further, based on the pixel noise obtained by the pixel noise calculating means and the current value of the radiation irradiating means at the time of setting photographing, the incident angle at which the radiation is incident on the radiation detecting means from the radiation irradiating means is a predetermined incident angle. The reference current value calculating means obtains the reference current value of the radiation irradiating means at the time of the radiation imaging as a reference. The above-described radiation imaging is performed based on the reference current value of the radiation irradiation means obtained by the reference current value calculation means. At this time, since imaging for setting is performed on the target subject, it is possible to obtain pixel noise that takes into account variations due to causes such as imaging settings depending on information specific to the subject. In addition, pixel noise can be obtained based on the statistic of each pixel value in the setting image (ratio of standard deviation with respect to the average value of pixel values, maximum value of pixel values, or value obtained by histogram analysis), and thus high reliability. Become. In this way, since it is based on the pixel noise and the current value of the radiation irradiating means at the time of setting photographing, the reference current value of the radiation irradiating means at the time of radiation photographing with reference to a predetermined incident angle can be stably obtained. be able to.

One example of the above-described invention includes a region-of-interest setting unit that sets a region of interest for the setting image obtained by the above-described setting shooting, and the pixel noise in the region of interest and the above-described predetermined incident angle are detected. based on the reference current value of the irradiation means in the setting for photography on the basis, the reference current value calculating means is to determine the reference current value of the radiation emitting means at the time of radiation imaging (claim 2) . By setting the region of interest, it is possible to stably obtain the reference current value of the radiation irradiating means at the time of radiography in the region of interest.

  In the invention provided with the region of interest setting means (the invention according to claim 2), the radiation region irradiated from the radiation irradiating means based on the information in which the imaging condition and the imaging position are associated includes a predetermined region of interest. It is preferable to provide an opening angle control means for controlling the opening angle of the radiation irradiating means so as to be in the region (the invention according to claim 3). By controlling the opening angle of the radiation irradiating means, the radiation region irradiated from the radiation irradiating means becomes a predetermined region including the region of interest by only one control. Therefore, it is possible to select from a predetermined area when setting the area of interest, and it is possible to prevent unnecessary radiation exposure to the subject.

In addition, a preferable example of these inventions described above includes an incident angle obtained by radiography before the predetermined radiography in the tomography including a series of radiography, and each pixel obtained by the previous radiography. The ratio of the standard deviation of the pixel value to the average value, or the pixel noise obtained based on the maximum value of each pixel value obtained by setting shooting or the value obtained by histogram analysis and the above-described predetermined incident angle An imaging current value calculation unit that obtains the current value of the radiation irradiation unit according to the incident angle at the time of the predetermined radiation imaging described above based on the reference current value of the radiation irradiation unit at the time of setting imaging based on (Invention of Claim 4) In the case of this example, the incident angle at the time of the predetermined radiography is obtained by using the incident angle and the pixel noise obtained in the radiography before the predetermined radiography in the tomography including a series of radiography. The current value of the radiation irradiating means can be obtained according to the angle. Therefore, it is possible to obtain a current value that is hardly affected by the incident angle.

In the invention provided with the imaging current value calculating means described above (the invention according to claim 4), based on the incident angle at the time of the predetermined radiation imaging described above and the incident angle performed at the previous radiation imaging described above , It is preferable to include imaging current value correcting means for correcting the current value of the radiation irradiating means in accordance with the incident angle obtained by the imaging current value calculating means (the invention according to claim 5). As described above, the current value of the radiation irradiating means corresponding to the incident angle at the time of predetermined radiation imaging is obtained using the incident angle obtained in the previous radiation imaging and the obtained pixel noise. In some cases, the current value may vary between the incident angles. Therefore, by correcting the current value of the radiation irradiating unit according to the incident angle by the imaging current value correcting unit, it is possible to reduce the deviation between the incident angles.

Furthermore, another preferable example of these inventions described above is based on the incident angle and the reference current value of the radiation irradiating means at the time of setting imaging based on the above-described predetermined incident angle. The imaging current value calculating means for obtaining the current value of the radiation irradiating means is provided (the invention according to claim 6). In the case of this example, based on the incident angle and the reference current value of the radiation irradiating means at the time of setting photographing, the current value of the radiation irradiating means can be obtained according to the incident angle. Therefore, it is possible to obtain a current value that is hardly affected by the incident angle.

According to the radiation imaging apparatus according to the present invention, since imaging for setting is performed on a subject subject, pixel noise that depends on subject-specific information and takes into account variations due to causes such as imaging settings is reduced. Since pixel noise is obtained based on the statistic of each pixel value in the setting image (the ratio of the standard deviation to the average value of the pixel values, the maximum value of the pixel values, or the value obtained by histogram analysis) , it is reliable. Increases the nature. Since it is based on the pixel noise and the current value of the radiation irradiating means at the time of setting imaging, the current value of the reference radiation irradiating means at the time of radiographic imaging based on the predetermined incident angle can be stably obtained.

Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of the X-ray tomography apparatus according to the first embodiment, and FIG. 2 is a side view schematically showing each imaging form using the X-ray tomography apparatus. In Example 1, including Example 2 to be described later, a flat panel X-ray detector (hereinafter referred to as “FPD” as appropriate) is taken as an example of radiation detection means, and an X-ray tomography apparatus is used as a radiation imaging apparatus. An example will be described.

  As shown in FIG. 1, the X-ray tomography apparatus according to the first embodiment includes a top plate 1 on which a subject M is placed, an X-ray tube 2 that emits X-rays toward the subject M, And an FPD 3 that detects X-rays transmitted through the subject M. The X-ray tube 2 corresponds to the radiation irradiating means in the present invention, and the FPD 3 corresponds to the radiation detecting means in the present invention.

  The X-ray tomography apparatus also includes a collimator 4 that controls the opening angle of the X-ray tube 2, an X-ray generator 5 that generates tube voltage and tube current of the X-ray tube 2, and a subject M. The X-ray tube 2 and the FPD 3 are opposed to each other so that the X-ray tube 2 and the FPD 3 change (see FIG. 2), and the X-ray detection signal detected from the drive controller 6 including the collimator 4 and driving the X-ray tube 2 and the FPD 3 In addition to storing various images calculated by the calculation unit 8 to be described later on the basis thereof and various data transmitted via the controller 15 to be described later, and reading from the memory unit 7 The region of interest ROI with respect to the calculation unit 8 that calculates various X-ray detection signals and acquires various images, the monitor 9 that displays the various images, and the setting image obtained by setting imaging described later. (See Figure 2 ), A pixel noise calculation unit 11 that calculates pixel noise in the region of interest ROI, a reference tube current value calculation unit 12 that calculates a reference tube current value, which will be described later, and a later-described tomography. An imaging tube current value calculation unit 13 that obtains a tube current value corresponding to the incident angle to be performed, a imaging tube current value correction unit 14 that corrects the tube current value, a controller 15 that controls and controls these, and an operator input setting The input unit 16 for performing is provided. In addition, you may provide the drive control part for the top plate which drives the top plate 1 so that the top plate 1 may be moved up and down, moved horizontally, or rotated between the standing posture and the horizontal posture.

The collimator 4 corresponds to the opening angle control unit in the present invention, the drive control unit 6 corresponds to the drive control unit in the present invention, the region of interest setting unit 10 corresponds to the region of interest setting unit in the present invention, and the pixel The noise calculator 11 corresponds to the pixel noise calculator in the present invention, the reference tube current value calculator 12 corresponds to the reference current value calculator in the present invention, and the photographing tube current value calculator 13 in the present invention. The imaging tube current value correction unit 14 corresponds to the imaging current value calculation unit, and corresponds to the imaging current value correction unit in the present invention. The tube current value corresponds to the current value of the radiation irradiation unit in the present invention.

  The collimator 4 is a diaphragm that controls the opening angle α (see FIG. 2) of the X-ray tube 2. By controlling the opening angle α, the width of the X-ray region formed by irradiating the subject M with X-rays at the opening angle α is controlled.

  In order to set a tube current value as one of imaging conditions for various types of imaging, the X-ray generation unit 5 includes a reference tube current value calculation unit 12, an imaging tube current value calculation unit 13, and an imaging tube current value correction unit. The tube current value obtained at 14 is obtained, and a tube current is generated with the tube current value.

  The drive control unit 6 controls changes in the relative positional relationship between the X-ray tube 2 and the FPD 3. In this embodiment, as shown in FIG. 2, the X-ray tube 2 and the FPD 3 are controlled to change while facing each other with the subject M interposed therebetween. More specifically, the drive control unit 6 controls the X-ray tube 2, the FPD 3, and the collimator 4 so that the above-described X-ray region becomes a region including the region of interest ROI.

  As for the X-ray tube 2 and the FPD 3, as shown in FIG. 2B, when the FPD 3 is horizontally moved from the left side to the right side in the drawing, the X-ray tube 2 is shown in the drawing so that the X-rays pass through the region of interest. Move the curve from the right side to the left side. Conversely, when the FPD 3 is horizontally moved from the right side to the left side in the figure, the X-ray tube 2 is moved in a curve from the left side to the right side in the figure so that the X-rays pass through the region of interest.

  For the collimator 4, the drive control unit 6 controls the collimator 4 so that the X-ray region always includes the region of interest ROI. Specifically, a data table in which imaging conditions and imaging positions are associated with each subject-specific information (height, body thickness, bone density, age, etc.) is written in the memory unit 7 in advance and stored. Based on the data table, the collimator 4 is controlled so that the X-ray region always includes the region of interest ROI. The imaging conditions include the X-ray aperture conditions (that is, the opening angle α), the tube voltage, the tube current, and the scanning conditions of the X-ray tube 2. The imaging positions include the position of the X-ray tube 2, the position of the FPD 3, There is a position of the subject M.

  The angle at which X-rays enter the FPD 3 from the X-ray tube 2 is defined as the incident angle θ. In this specification, the angle formed by the axis perpendicular to the detection surface of the FPD 3 and the incident central axis of the X-rays is defined as the incident angle θ. In Example 1, including Example 2 described later, since the detection surface of the FPD 3 is a horizontal surface, an axis perpendicular to the detection surface is a vertical axis. Therefore, as shown in FIG. 2A, when X-rays enter the FPD 3 in the vertical direction, the angle formed by the vertical axis and the X-ray incident center axis is 0 °, and the incident angle θ is 0 °. Become. Therefore, as shown by the solid line in FIG. 2B, when the X-ray is incident on the FPD 3 in an oblique direction, the angle formed by the vertical axis and the X-ray incident center axis is other than 0 °, and the incident angle θ is Other than 0 °.

  In this specification, “imaging for setting the tube current value of the X-ray tube 2 (that is, imaging not intended for tomographic imaging of the subject M) is performed prior to actual tomography. Shooting ”. FIG. 2A shows a configuration at the time of setting photographing, and FIG. 2B shows a configuration at the time of actual tomographic photographing. In addition, the tube current value set as one of the imaging conditions for tomographic imaging with the incident angle θ at the time of imaging for setting as a reference is referred to as “reference tube current value” in this specification. In Example 1, including Example 2 described later, since the incident angle θ at the time of setting photographing is 0 ° as shown in FIG. 2A, the case where the incident angle θ is 0 ° is used as a reference. . The reference incident angle θ is not limited to 0 ° as in the first embodiment, and may be other than 0 ° as long as it is a predetermined incident angle θ.

  The memory unit 7 includes a storage medium represented by ROM (Read-only Memory), RAM (Random-Access Memory), and the like. As described above, the memory unit 7 of the first embodiment stores the X-ray detection signal detected from the FPD 3 and stores various images calculated by the calculation unit 8 based on the X-ray detection signal. . In addition, the memory unit 7 stores various data sent via the controller 15.

  Examples of the various images stored in the memory unit 7 include a setting image obtained by the above-described setting photographing and a tomographic image obtained by actual tomography. Further, the memory unit 7 also stores pixel noise based on the statistic of each pixel value in the region of interest ROI obtained by various types of imaging.

  Various data stored in the memory unit 7 and sent via the controller 15 are respectively obtained by the reference tube current value calculation unit 12, the photographing tube current value calculation unit 13, and the photographing tube current value correction unit 14 described above. The obtained tube current value, the data table in which the above-described imaging conditions and the imaging position are associated, the incident angle θ at the time of each tomography, and the region of interest set by the region-of-interest setting unit 10 described above There are ROI, input data input and set by the input unit 16 described above, a data table in which an incident angle θ, pixel noise, and reference tube current value described later are associated with each other. Note that data transferred from an external device (for example, a radiation information system) via a network (not shown) can also be stored in the memory unit 7 via the controller 15.

  The calculation unit 8 is a central processing unit (a central processing unit) together with a region of interest setting unit 10, a pixel noise calculation unit 11, a reference tube current value calculation unit 12, a shooting tube current value calculation unit 13, a shooting tube current value correction unit 14, and a controller 15. CPU). As described above, the calculation unit 8 calculates various X-ray detection signals detected from the FPD 3 and acquires various images. For the X-ray detection signal detected from the FPD 3 in the setting imaging, the calculation unit 8 acquires a setting image, and for the X-ray detection signal detected from the FPD 3 in the tomography, the calculation unit 8 acquires a tomographic image. To do.

  The monitor 9 displays various images by the calculation unit 8. As described above, the region-of-interest setting unit 10 sets the region of interest ROI for the setting image obtained by setting photographing. Specifically, the operator may input and set the range of the region of interest ROI with the input unit 16 for the setting image displayed on the monitor 9, and may send it to the region of interest setting unit 10 via the controller 15. The region of interest setting unit 10 may automatically set the region of interest ROI for the setting image displayed on the monitor 9. When the automatic setting is performed, for example, the region of interest ROI may have a pixel value that is significantly different from other regions. Therefore, a threshold value of the pixel value is created in advance, and a group of pixel values that are larger or smaller than the threshold value. May be set as the region of interest ROI.

  The pixel noise calculation unit 11 obtains pixel noise based on the statistic of each pixel value in the setting image obtained by setting photographing, and in the first embodiment, each pixel image in the tomographic image obtained by tomographic imaging. Pixel noise is obtained based on the statistics of pixel values. The reference tube current value calculation unit 12 obtains the reference tube current value of the X-ray tube 2 at the time of tomography, using the incident angle θ as a reference at a predetermined incident angle θ (0 ° in the first embodiment). The imaging tube current value calculation unit 13 calculates the incident angle θ obtained in imaging (including setting imaging and previous tomography) before the target tomography, and each pixel value obtained in the imaging. Based on the pixel noise obtained based on the statistic and the reference tube current value of the X-ray tube 2 at the time of setting imaging, a tube current value corresponding to the incident angle θ at the time of tomographic imaging is obtained. The photographing tube current value correcting unit 14 is based on the incident angle θ at the time of the tomographic imaging as the target and the incident angle θ obtained at the photographing before the tomographic imaging as the target. 13 corrects the tube current value of the X-ray tube 2 in accordance with the incident angle θ obtained in step 13. These specific functions will be described later with reference to the flowchart of FIG.

  The input unit 16 includes a pointing device represented by a mouse, a keyboard, a joystick, a trackball, a touch panel, and the like. Further, the input unit 16 may be configured by a hand switch, a lever, a button, or the like.

  Next, a series of imaging including setting imaging and tomographic imaging according to the first embodiment will be described with reference to FIGS. FIGS. 3 and 4 are flowcharts showing a series of imaging processes including setting imaging and tomography according to the first embodiment, and FIG. 5 schematically shows the flow of each mode during tomography. It is a side view. Note that steps S1 to S6 in FIG. 3 are a series of processes related to setting imaging, and steps S7 to S16 in FIG. 4 are a series of processes related to tomographic imaging.

(Step S1) Setting of Shooting Conditions for Setting Shooting The shooting conditions for setting shooting are set. Specifically, an imaging condition is given from the controller 15 to the X-ray generation unit 5 and the drive control unit 6, and the X-ray generation unit 5 generates a tube voltage and a tube current of the X-ray tube 2 according to the imaging condition, and is driven. The control unit 6 includes the collimator 4 and drives the X-ray tube 2 and the FPD 3. Imaging conditions include X-ray aperture conditions (open angle α), tube voltage, tube current, scanning conditions for the X-ray tube 2, and the like. Among these, for setting the tube voltage and the tube current, a command is given from the controller 15 to the X-ray generator 5, and for setting the X-ray aperture condition (opening angle α) and the scanning condition of the X-ray tube 2, the controller 15 gives a command to the drive control unit 6. At the stage of step S1, these imaging conditions may be set to appropriate values for each imaging region of the subject M, and need not be set to exact values.

  As for these imaging conditions, input data related to imaging conditions input and set in the input unit 16 by the operator may be transferred to the X-ray generation unit 5 and the drive control unit 6 via the controller 15. Alternatively, the data may be transferred from an external device such as a radiation information system to the X-ray generation unit 5 and the drive control unit 6 via the network and further via the controller 15.

(Step S2) Setting of a Predetermined Region Including the Region of Interest When setting a predetermined region including the region of interest ROI, the predetermined incidence is set so as to be in the setting photographing mode as shown in FIG. The X-ray tube 2 and the FPD 3 are moved so that X-rays are incident at an angle θ (0 ° in the first embodiment). In this setting, when the operator moves the X-ray tube 2, the drive control unit 6 controls the FPD 3 so that the FPD 3 automatically moves to a position facing the X-ray tube 2 in conjunction with the movement. May be. Conversely, when the operator moves the FPD 3, the drive control unit 6 controls the X-ray tube 2 so that the X-ray tube 2 automatically moves to the position facing the FPD 3 in conjunction with the movement. Also good. Of course, the X-ray tube 2 and the FPD 3 may be automatically moved so that X-rays are incident at a predetermined incident angle θ, or the X-ray tube 2 and the FPD 3 may be moved manually by the operator. Good.

  In actual tomography to be described later, when the X-ray tube 2 and the FPD 3 are moved as shown in FIG. 2B while the opening angle α of the X-ray tube 2 is kept as it is without controlling the collimator 4. The X-ray region formed by irradiating the subject M with X-rays does not coincide with the region including the region of interest ROI. Therefore, even if the X-ray tube 2 and the FPD 3 are moved, the drive control unit 6 controls the X-ray tube 2, the FPD 3 and the collimator 4 so that the X-ray region always becomes a region including the region of interest ROI. As described above, based on the data table in which the imaging conditions and the imaging positions are associated with each piece of information unique to the subject M, the X-ray tube 2 position, the FPD3 position, and the subject M position imaging position are set. In addition, the size of the opening angle α is manipulated so that the X-ray region becomes a predetermined region including the region of interest ROI.

(Step S3) Setting Imaging Next, by pressing a hand switch (one of the input units 16) associated with the X-ray generation unit 5, setting imaging is started. Specifically, input data related to an imaging start command is given to the X-ray generation unit 5 via the controller 15 to the input unit 16 typified by a hand switch. 2A, the X-ray tube 2 emits X-rays toward the subject M, and the FPD 3 detects the X-rays transmitted through the subject M. Setting imaging is performed based on the detected X-rays.

More specifically, the X-ray detection signal detected from the FPD 3 is converted from an analog value to a digital value corresponding to the X-ray transmission amount, and is temporarily written and stored in the memory unit 7. Then, the arithmetic unit 8 performs various arithmetic processes on the X-ray detection signal converted into a digital value from the memory unit 7 and acquires an image. In the case of step S3, since the setting shooting is performed, the calculation unit 8 acquires a setting image . The acquired setting image is written and stored in the memory unit 7. Various calculation processes by the calculation unit 8 are representative of gain correction, loss correction, offset correction, etc., excluding pixel noise calculation, reference tube current value calculation, photographing tube current value calculation, and photographing tube current value correction, which will be described later. There is image processing to be performed. In step S3, the X-ray tube 2, the FPD 3, and the calculation unit 8 function as the setting imaging means in the present invention.

(Step S4) Region of Interest Setting A setting image obtained by setting photographing is displayed on the monitor 9. This setting image has a width corresponding to the X-ray region including the region of interest ROI. Specifically, the setting image is read from the memory unit 7 and sent to the region-of-interest setting unit 10 via the controller 15. On the other hand, the region-of-interest setting unit 10 sets the region of interest ROI for the setting image read from the memory unit 7 and displayed on the monitor 9. Specifically, as described above, the operator inputs and sets the range of the region of interest ROI with the input unit 16 with respect to the setting image displayed on the monitor 9, and enters the region of interest setting unit 10 via the controller 15. send. It is also possible for the region of interest setting unit 10 to automatically set the region of interest ROI for the setting image displayed on the monitor 9.

(Step S5) Pixel Noise Calculation The pixel noise calculation unit 11 calculates pixel noise based on the statistic of each pixel value in the region of interest ROI. Specifically, the region of interest ROI set by the region of interest setting unit 10 and the setting image read from the memory unit 7 are sent to the pixel noise calculation unit 11. In Example 1, including Example 2 described later, the ratio of the variation (standard deviation) of the pixel value to the average value of each pixel is adopted as the statistic of each pixel value in the region of interest ROI. Then, the ratio of the standard deviation of the pixel value to the average value is obtained as pixel noise. In the first embodiment, the ratio of the standard deviation of the pixel value to the average value is obtained as pixel noise. However, a maximum value or a value obtained by histogram analysis may be used. There is no particular limitation.

  This ratio represents the S / N ratio of the image. In general, when the imaging dose is small, pixel noise increases, the S / N ratio deteriorates, and the image quality deteriorates. Here, the imaging dose can be regarded as substantially equal to the tube current value of the X-ray tube 2. Therefore, when the pixel noise is large, the tube current value is decreased, and conversely, when the pixel noise is small, the tube current value is increased. Thus, the pixel noise and the tube current value have a predetermined correlation, for example, expressed by an inversely proportional correlation.

(Step S6) Calculation of Reference Tube Current Value Based on the pixel noise obtained by the pixel noise calculation unit 11 and the tube current value of the X-ray tube 2 at the time of setting imaging set in step S1, a predetermined incident angle The reference tube current value of the X-ray tube 2 at the time of tomography is obtained with θ as the reference (0 ° in the present embodiment 1). Specifically, the pixel noise obtained by the pixel noise calculation unit 11 is sent to the reference tube current value calculation unit 11. The reference tube current value calculation unit 11 obtains a reference tube current value based on the pixel noise and the tube current value.

  As described above, the reference tube current value is obtained using the fact that the pixel noise and the tube current value are inversely related to each other. Note that factors that increase or decrease the amount of pixel noise are: (1) change in path length of X-ray transmission amount due to incident angle θ (geometric amount), (2) tissue inside subject M along X-ray transmission path There are changes due to structural differences. If the tube current value is determined only by the pixel noise obtained in step S5, the above factors (1) and (2) cannot be separated, and an accurate tomographic image cannot be obtained. In particular, when considering the above-mentioned factor (1), the tube current value at the time of setting photographing is essential.

(Step S7) Setting of imaging conditions related to tomographic imaging at θ = θ ₀ Imaging conditions for performing tomographic imaging for each incident angle θ including a predetermined incident angle θ (0 ° in the first embodiment) Set. In step S7 subsequent tomography, the incident angle theta = theta ₀ as shown in FIG. _{5, θ 1, ..., θ} K, ..., θ N-1, is described as performing the order of theta _N. Further, when tomography is performed in accordance with the incident angle θ, the X-ray tube 2 and the FPD 3 are moved so as to match each incident angle θ. As the moving method, the same method as described in step S2 is used.

First, imaging conditions for tomography at an incident angle θ = θ ₀ are set. As described in step S1, the controller 15 gives imaging conditions to the X-ray generator 5 and the drive controller 6, and the X-ray generator 5 generates tube voltage and tube current of the X-ray tube 2 according to the imaging conditions. The drive control unit 6 includes the collimator 4 and drives the X-ray tube 2 and the FPD 3. Of the X-ray aperture conditions (open angle α), tube voltage, tube current, and X-ray tube 2 of the imaging conditions, the tube current is set as follows. When the reference tube current value obtained in step S6 is I _BASE and the tube current value to be set in step S7 is I ₀ , the following equation (1) is obtained.

I ₀ = I _BASE × (1 / cos θ ₀ ) (1)
I ₀ obtained by the above equation (1) is set as a tube current value for tomography at an incident angle θ = θ ₀ .

Regarding the opening angle α of the imaging condition, as described in step S2, the X-ray region includes the region of interest ROI even if the X-ray is irradiated in the form of the incident angle θ = θ ₀ shown in FIG. The opening angle α is set so that

(Step S8) Tomography at θ = θ _{0 As} with step S3, tomography at an incident angle θ = θ ₀ is started by pressing a hand switch or the like associated with the X-ray generator 5. Then, in the form of FIG. 5A (or FIG. 2B), X-rays are irradiated from the X-ray tube 2 toward the subject M of interest, and the X-rays transmitted through the subject M are converted into FPD3. Is detected, and based on this, tomography is performed at an incident angle θ = θ ₀ . Similar to step S3, storage in the memory unit 7 and calculation by the calculation unit 8 are performed. Then, a tomographic image at the incident angle θ = θ ₀ is acquired.

(Step S9) θ = θ ₀ pixel noise calculation incident angle theta = theta ₀ based on statistics of each pixel amounts in the region of interest ROI in a tomographic image obtained by the tomographic at pixel noise calculation unit 11 in Finds pixel noise at an incident angle θ = θ ₀ . As the pixel noise calculation method, the same method as described in step S5 is used. Let the pixel noise at the incident angle θ = θ ₀ be N ₀ .

(Step S10) Increase the value of K by 1 Here, K (K is a value from 0 to N) representing the subscript of the tube current value I and pixel noise N corresponding to the incident angle θ and the incident angle θ. (Increase value) is incremented by one and increased. When the process proceeds from step S9 to step S10, the value of K = 0 is incremented to K = 1. In addition to step S9, the process proceeds from step S16 described later to step S10. In step S10, the X-ray tube 2 and the FPD 3 are respectively moved so as to match the incremented incident angle θ _K at _K. As the moving method, the same method as described in step S2 is used.

As for the opening angle α of the imaging condition, as described in step S2, the X-ray region includes the region of interest ROI even if X-rays are emitted in the form of the incident angle θ = θ _K shown in FIG. The opening angle α is set so that

(Step S11) Calculation of Shooting Tube Current Value When θ = θ _K A case where K = 1 (that is, a case where the process proceeds from step S9 to step S10) will be described. Incident angle (in this case incident) performed in the previous tomography (in this case tomographic image at incident angle θ = θ ₀ ) prior to tomography (here tomographic image at incident angle θ = θ ₁ ) Angle θ = θ ₀ ), pixel noise obtained based on the statistic of each pixel value obtained by the tomography (here, pixel noise N ₀ obtained in step S9), and a reference at the time of setting photography based on the tube current value I _BASE, tomographic imaging tube current value corresponding to the incident angle at the (where the incident angle theta = theta ₁₎ (wherein tomography at the incident angle theta = theta ₁ is) to be the subject (I ₁ here) is obtained.

The description will be extended to the case of general K (K = 1 to N) including the case of shifting from step S16 to step S10. The incident angle (here, the tomography (here, the tomography at the incident angle θ = θ _K-1 ) before the tomography (here, the tomography at the incident angle θ = θ _K ) as the next target. , The incident angle θ = θ _K-1 ), the pixel noise obtained based on the statistics of each pixel value obtained by the tomography (here, the pixel noise N _K-1 obtained in step S9) and Based on the reference tube current value I _BASE at the time of setting imaging, the incident angle (here incident angle θ = θ _K ) at the target tomographic imaging (tomographic imaging at incident angle θ = θ _K here) A corresponding tube current value (I _{K in} this case) is obtained.

As described in step S6, the incident angle (here, incident angle θ = θ _K ) is utilized by utilizing the fact that the pixel noise (here, pixel noise N _K-1 ) and the tube current value have an inversely proportional correlation. The tube current value (I _{K in} this case) corresponding to is obtained. When the function representing the inverse proportion is F, the tube current value I _K corresponding to the incident angle θ = θ _K is expressed by the following equation (2).

I _K = F (I _BASE , cos θ _K−1 , N _K−1 ) (2)
I _K obtained by the above equation (2) is set as a tube current value for tomography at an incident angle θ = θ _K.

(Step S12) using the theta = theta _K shooting tube current value I _K corresponding to the incident angle theta = theta _K obtained in photographing tube current value correction step S11, the tomographic at the incident angle theta = theta _K Although the imaging condition setting (step S13) and tomographic imaging at the incident angle θ = θ _K (step S14) may be performed, it is preferable to perform correction as in step 12.

As is clear from the above equation (2), the left side of the equation is a parameter related to the tomographic imaging (tomographic imaging at the incident angle θ = θ _K in this case), and the right side of the equation is an earlier imaging ( Here, the parameters are related to tomography at an incident angle θ = θ _K−1 . Therefore, the incident angle made in any previous shooting from (tomography at the incident angle θ = θ _K-1 in this case) (tomography at the incident angle theta = theta _K in this case) tomography of interest (Here, incident angle θ = θ _K-1 ) and the obtained pixel noise (here, N _K-1 ), the target tomography (here, the tomographic image at incident angle θ = θ _K ) Since the tube current value (here, I _K ) corresponding to the incident angle (here, the incident angle θ = θ _K ) is obtained, the interval between the incident angles (here, the incident angles θ = θ _K−1 and θ _K The tube current value may be misaligned. Therefore, the tube current correction unit 14 corrects the tube current value (I _K here) corresponding to the incident angle (here, the incident angle θ = θ _K ).

Assuming that the corrected tube current value is I ′ _K , the tube current value I ′ _K is expressed by the following equation (3).

I ′ _K = I _K × (cos θ _K−1 / cos θ _K ) (3)
The corrected tube current value I ′ _K corrected by the above equation (3) is substituted into the uncorrected tube current value I _K. Hereinafter, for convenience of explanation, the corrected tube current value is set to I _K.

(Step S13) Setting of imaging conditions relating to tomography at θ = θ _{K The} imaging tube current value I _K corrected at step S12 is set as a tube current value for tomography at the incident angle θ = θ _K. To do.

(Step S14) Tomographic imaging at θ = θ _{K As} in step S8, tomographic imaging at an incident angle θ = θ _K is started, and a tomographic image at an incident angle θ = θ _K is acquired by the tomographic imaging. .

(Step S15) theta = theta pixel noise calculation incident angle theta = theta pixel noise calculation unit 11 based on the statistics of each pixel amounts in the region of interest ROI in a tomographic image obtained by the tomographic at _K in _K Finds the pixel noise at the incident angle θ = θ _K. As the pixel noise calculation method, the same method as described in steps S5 and S9 is used. Let N _{K be} the pixel noise at an incident angle θ = θ _K.

(Step S16) K = N?
It is determined whether or not the incremented K has reached N. If K has not reached N, it is determined that tomography at the incident angle θ = θ _N , which is the last tomography, has not been completed, and the process returns to step S10, and in the incremented state, the same steps S10 to S10 are performed. Repeat S16. If K has reached N, it is determined that tomography (see FIG. 5C) at the incident angle θ = θ _N , which is the last tomography, is completed, and a series of imaging is completed.

  What is necessary is just to comprise so that the value calculated | required in each step S1-S16, the set value, etc. may be once memorize | stored in the memory part 7 via the controller 15 suitably. If there are a plurality of subjects M to be imaged, a series of imaging in steps S1 to S16 is repeated.

  According to the first embodiment configured as described above, the drive control unit 6 controls the X-ray tube 2 and the flat panel X-ray detector (FPD) 3 to change the relative positional relationship between them. The X-ray tomography is performed based on the X-rays detected from the FPD 3 by driving the tube 2 and the FPD 3. Prior to the tomography, setting imaging for setting the tube current value of the X-ray tube 2 is performed on the subject M as a target. Then, the pixel noise calculation unit 11 obtains pixel noise based on the statistic of each pixel value in the setting image obtained by setting shooting (in the first embodiment, the ratio of the standard deviation of the pixel value to the average value). . Further, based on the pixel noise obtained by the pixel noise calculation unit 11 and the tube current value at the time of imaging for setting, a predetermined incident angle θ (this embodiment) with respect to the incident angle θ at which X-rays enter the FPD 3 from the X-ray tube 2 The reference tube current value calculation unit 12 obtains the reference tube current value at the time of tomography based on 0 ° in Example 1. The above-described tomography is performed based on the reference tube current value obtained by the reference tube current value calculation unit 12.

  At this time, because the setting subject is imaged for the subject M, the fluctuation depends on the information specific to the subject M (height, body thickness, bone density, age, etc.), and the variation due to the cause of the imaging setting, etc. Can be obtained. Further, since the pixel noise is obtained based on the statistic of each pixel value in the setting image, the reliability is improved. As described above, since it is based on the pixel noise and the tube current value at the time of setting photographing, the reference tube current value at the time of tomographic photographing based on a predetermined incident angle θ (0 ° in the first embodiment) is obtained. It can be obtained stably.

  The first embodiment includes a region-of-interest setting unit 10 that sets a region of interest ROI with respect to a setting image obtained by setting photographing, pixel noise in the region of interest ROI, and reference tube current value at the time of photographing for setting. The reference tube current value calculation unit 12 obtains the reference tube current value at the time of tomography. By setting the region of interest ROI, it is possible to stably obtain the reference tube current value at the time of tomography in the region of interest ROI.

  Further, in the first embodiment, irradiation from the X-ray tube 2 is performed based on a data table in which imaging conditions and imaging positions are associated with information specific to the subject M (height, body thickness, bone density, age, etc.). The collimator 4 that controls the opening angle α of the X-ray tube 2 is provided so that the X-ray region to be processed becomes a predetermined region including the region of interest ROI. By controlling the opening angle α of the X-ray tube 2, the X-ray region irradiated from the X-ray tube 2 becomes a predetermined region including the region of interest ROI by only one control. Therefore, it becomes possible to select from a predetermined region when setting the region of interest ROI, and wasteful X-ray exposure to the subject M can be prevented.

The row in the first embodiment, the target tomography (tomography at the incident angle θ = θ _K-1 here) any previous shooting than (where tomography at the incident angle theta = theta _K is) Incident angle (here, incident angle θ = θ _K-1 ), pixel noise (N _K-1 here) obtained based on the statistic of each pixel value obtained by the imaging, and setting imaging Based on the reference tube current value at this time (here, I _BASE ), the incident angle (here, the incident angle θ = θ) at the time of the tomographic imaging (here, the tomographic image at the incident angle θ = θ _K ). imaging tube current value corresponding to _K) (here comprises an imaging tube current value calculating unit 13 for obtaining the I _K). When such a tube current value calculation unit 13 is provided, the target tomography is performed using the incident angle θ and the pixel noise obtained in the previous shooting before the target tomography. The tube current value can be obtained according to the incident angle θ at the time. Therefore, it is possible to obtain a tube current value that is not easily affected by the incident angle θ.

Further, in the first embodiment, the photographing tube current value calculation unit 13 is based on the incident angle θ at the time of the tomographic imaging to be performed and the incident angle θ performed at the imaging before the tomographic imaging of the target. An imaging current value correction unit 14 that corrects the imaging tube current value according to the determined incident angle θ is provided. As described above, tomography of interest incident made in any previous shooting from (tomography at the incident angle θ = θ _K-1 in this case) (where the incident angle theta = theta tomography _K is) Using the angle (here, the incident angle θ = θ _K-1 ) and the obtained pixel noise (here, N _K-1 ), the tomography of interest (here, the tomography at the incident angle θ = θ _K ) Since the tube current value (here, I _K ) corresponding to the incident angle (here, incident angle θ = θ _K ) is obtained, the incident angle θ (here, incident angles θ = θ _K−1 and θ _In some cases, the tube current value may vary. Therefore, the photographing tube current value correcting unit 14 corrects the photographing tube current value (here, I _K ) corresponding to the incident angle (here, the incident angle θ = θ _K ), thereby reducing the deviation between the incident angles θ. Can be made.

Next, Embodiment 2 of the present invention will be described with reference to the drawings.
The portions common to the above-described first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 6 is a block diagram of the X-ray tomography apparatus according to the second embodiment.

  In the second embodiment, the inter-shooting current value correction unit 14 as in the first embodiment is not provided, and other configurations are the same as those in the first embodiment as shown in FIG. Further, since the function of the tube current value calculation unit 13 is different from that of the first embodiment, the function will be described with reference to FIG. FIG. 7 is a flowchart illustrating a series of imaging processes in tomography according to the second embodiment. Note that a series of imaging processes for setting imaging is the same as steps S1 to S6 in FIG. 3 described in the first embodiment, and therefore a description thereof is omitted, and a series of processes relating to tomography (steps S7 to S16). ) Only.

(Step S7) Setting of Imaging Conditions Related to Tomography at θ = θ ₀ Since this is the same as Step S7 in Example 1 described above, description thereof is omitted. In order to obtain the tube current value I ₀ at the incident angle θ = θ ₀ , the above equation (1) is used as in step S7 in the first embodiment.

(Step S8) Tomographic imaging with θ = θ ₀ Since this is the same as Step S8 in Example 1 described above, description thereof is omitted.

For (pixel noise calculation at θ = θ ₀₎ step S9 in the first embodiment described above, since the time of calculation of the photographing tube current value by the photographing tube current value calculating unit 13 in this embodiment 2 is not essential, it performed always There is no need. Of course, step S9 in the first embodiment may be performed also in the second embodiment.

(Step S10) The value of K is increased by 1. Since this is the same as step S10 in the first embodiment described above, description thereof is omitted.

(Step S′11) Calculation of Shooting Tube Current Value at θ = θ _{K In the} second embodiment, the shooting tube current value calculation unit 13 determines the incident angle θ = θ _K and the reference tube current value I _BASE at the time of setting shooting. Based on the above, the tube current value I _K corresponding to the incident angle θ = θ _K is obtained. The tube current value I _K corresponding to the incident angle θ = θ _K is expressed by the following equation (4).

I _K = I _BASE × (1 / cos θ _K ) (4)
I _K obtained by the above equation (4) is set as a tube current value for tomography at an incident angle θ = θ _K. From the equation (4), when calculating the tube current value by the tube current value calculation unit 13 in the second embodiment, only the incident angle θ = θ _K and the reference tube current value I _BASE at the time of setting shooting are essential. Thus, it can be seen that the pixel noise obtained in the previous photographing as in the first embodiment is not essential. The expression (4) is an expression expanded from the case of K = 0 to the general case of K (K = 0 to N) with respect to the expression (1). That is, the equation (1) is obtained when K = 0 in the equation (4).

Step S12 (correction of the tube current value at θ = θ _K ) in the first embodiment described above is not performed because the inter-shooting current value correction unit 14 as in the first embodiment is not provided as described above.

(Step S13) Setting of Imaging Conditions for Tomography at θ = θ _K Since this is the same as Step S13 in Example 1 described above, the description thereof is omitted. However, in the first embodiment, the corrected tube current value I _K is set as a tube current value for tomography at an incident angle θ = θ _K , whereas in this embodiment, step S′11. the imaging tube current value I _K obtained in, is set as the tube current value for tomography at the incident angle θ = θ _K.

(Step S14) Tomographic imaging at θ = θ _K Since this is the same as Step S14 in Example 1 described above, description thereof is omitted.

For (pixel noise calculation at θ = θ _K) Step S15 in the first embodiment described above, since the time of calculation of the photographing tube current value by the photographing tube current value calculating unit 13 in this embodiment 2 is not essential, it performed always There is no need. Of course, step S15 in the first embodiment may be performed also in the second embodiment.

(Step S16) K = N?
Since this is the same as step S16 in the first embodiment described above, description thereof is omitted.

According to the second embodiment configured as described above, the tube current corresponding to the incident angle θ = θ _K based on the incident angle θ = θ _K and the reference tube current value I _BASE at the time of shooting for setting. A tube current value calculation unit 13 for obtaining the value I _K is provided. When the photographing tube current value calculation unit 13 is provided, the photographing tube current is determined according to the incident angle θ based on the incident angle θ = θ _K and the reference tube current value I _BASE at the time of setting photographing. Each value can be determined. Therefore, it is possible to obtain a tube current value that is not easily affected by the incident angle θ.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In each of the above-described embodiments, the X-ray tomography apparatus as shown in FIG. 1 has been described as an example. However, the present invention may be applied to an X-ray fluoroscopic apparatus.

  (2) In each of the above-described embodiments, the flat panel X-ray detector (FPD) 3 has been described as an example, but it is exemplified by a receiver including an image intensifier (II) and a TV camera. Thus, the present invention can be applied to any X-ray detection means that is normally used.

  (3) In each of the embodiments described above, X-rays have been described as examples. However, the present invention can be applied to radiation other than X-rays (for example, γ-rays).

  (4) In each embodiment described above, after obtaining a reference current value (reference tube current value in each embodiment) with a predetermined incident angle θ (θ = 0 ° in each embodiment) as a reference, While changing the angle θ in order, the current value corresponding to the incident angle (the tube current value in each embodiment) was obtained, and tomography was performed for each incident angle θ. After obtaining the reference current value, a certain incident angle was obtained. The fluoroscopic imaging at θ may be performed only once. The certain incident angle θ may be an angle different from the predetermined incident angle θ, or may be the same angle as the predetermined incident angle θ.

(5) In each embodiment described above, after obtaining a reference current value (reference tube current value in each embodiment) with a predetermined incident angle θ (θ = 0 ° in each embodiment) as a reference, While changing the angle θ in the order (incident angles θ = θ ₀ , θ ₁ ,..., Θ _K ,..., Θ _N−1 , θ _N in each embodiment), the current value according to the incident angle (imaging in each embodiment) Tube current value) and tomography at each incident angle θ, but after obtaining the reference current value, first tomography at a predetermined incident angle θ and further at every other incident angle θ You may perform tomography.

  (6) In each of the above-described embodiments, the pixel noise and the tube current value have a predetermined correlation represented by an inverse proportion, and the tube current value is obtained using such a correlation. A data table associated with the tube current value may be written and stored in the memory unit 7 in advance, and the tube current value may be obtained by referring to the table.

  (7) In each of the above-described embodiments, the region of interest ROI is set and pixel noise in the region of interest ROI is used. However, it is not always necessary to set the region of interest ROI. In particular, when the fluoroscopic imaging at a certain incident angle θ is performed only once as in the modification (4) described above, an image corresponding to the entire X-ray region irradiated from the X-ray tube 2 at a predetermined incident angle. Pixel noise may be obtained based on the statistic of each pixel value in.

  (8) In each of the above-described embodiments, in order to prevent unnecessary X-ray exposure to the subject M, the X-ray region irradiated from the X-ray tube 2 becomes a predetermined region including the region of interest ROI. Although the opening angle α of the X-ray tube 2 is controlled, an effective region that will always overlap when the opening angle α is fixed and the incident angle θ is sequentially changed may be used as the region of interest ROI. Further, the X-ray irradiation may be repeated twice or more at the same incident angle θ, and the opening angle α may be controlled so that an appropriate region is obtained by the later X-ray irradiation.

(9) In the first embodiment described above, imaging prior to the target tomography (here, the tomography at the incident angle θ = θ _K ) is taken as the tomography at the incident angle θ = θ _K−1 . The incident angle θ = θ _K-1 performed in the tomography, the pixel noise N _K-1 obtained based on the statistic of each pixel value obtained in the imaging, and the reference tube current at the time of setting imaging Based on the value I _BASE , the tube current value I _K corresponding to the incident angle θ = θ _K at the time of tomography as the target described above was obtained (I _K = F (I _BASE , cos θ _K−1 , N _K−1 )), but the imaging prior to the target tomographic imaging is set as the imaging for setting at the predetermined incident angle θ. Pixel noise N obtained based on the obtained statistics of each pixel value and reference tube current value I _BASE at the time of shooting for setting Based on the above, the tube current value I _K corresponding to the incident angle θ = θ _K at the time of the tomographic imaging as described above may be obtained. The formula is I _K = F (I _BASE , cos θ, N), which is obtained using this formula.

(10) In the first embodiment described above, in order to prevent displacement of tube current values between the incident angle, the incident angle imaging tube current value corresponding to (the incident angle theta = theta _K in this case) (I _K in this case) However, if the deviation does not affect the image quality, the correction is not necessarily required.

1 is a block diagram of an X-ray tomography apparatus according to Embodiment 1. FIG. It is the side view which represented typically each imaging | photography form using an X-ray tomography apparatus, (a) is the form at the time of setting imaging | photography, (b) is the form at the time of actual tomography. 3 is a flowchart illustrating a series of imaging processes including setting imaging and tomographic imaging according to Embodiment 1; 3 is a flowchart illustrating a series of imaging processes including setting imaging and tomographic imaging according to Embodiment 1; (A)-(c) is the side view which represented typically the flow of each form at the time of tomography. 6 is a block diagram of an X-ray tomography apparatus according to Embodiment 2. FIG. 12 is a flowchart illustrating a series of imaging processes in tomography according to the second embodiment.

Explanation of symbols

2 ... X-ray tube 3 ... Flat panel X-ray detector (FPD)
DESCRIPTION OF SYMBOLS 4 ... Collimator 6 ... Drive control part 10 ... Region of interest setting part 11 ... Pixel noise calculation part 12 ... Reference tube current value calculation part 13 ... Imaging tube current value calculation part 14 ... Imaging tube current value correction | amendment part ROI ... Region of interest θ ... Incident angle M ... subject

Claims (6)

A radiation irradiating means for irradiating the subject with radiation, a radiation detecting means for detecting the radiation transmitted through the subject, and a change in relative positional relationship between the radiation irradiating means and the radiation detecting means is controlled. And a drive control means for driving the radiation irradiation means and the radiation detection means, and the relative positional relationship between the radiation irradiation means and the radiation detection means is changed by the drive control means, based on the radiation detected from the radiation detection means. A radiographic apparatus that performs radiography, and setting imaging means for performing setting imaging for the current value setting of the radiation irradiating means on the same subject as the radiographic imaging in advance of the radiography, the ratio of the standard deviation of the pixel values to the average value of each pixel value in the setting image obtained by the setting for photography or photographic the setting The maximum value or values by a histogram analysis of pixel values obtained respectively, and the pixel noise calculating means for calculating a pixel noise, the current value of the radiation emitting device in the pixel noise and when the setting for photography obtained by pixel noise calculating means A reference current value calculating means for obtaining a reference current value of the radiation irradiating means at the time of radiography based on a predetermined incident angle with respect to an incident angle at which radiation is incident on the radiation detecting means from the radiation irradiating means. And a radiation imaging apparatus that performs radiation imaging based on the reference current value of the radiation irradiation means obtained by the reference current value calculation means.   The radiation imaging apparatus according to claim 1, further comprising a region of interest setting unit that sets a region of interest for a setting image obtained by the setting photographing, wherein the pixel noise and the predetermined incident angle in the region of interest are included. The reference current value calculating means obtains a reference current value of the radiation irradiating means at the time of radiography based on a reference current value of the radiation irradiating means at the time of setting imaging with reference to Shooting device.   The radiation imaging apparatus according to claim 2, wherein a radiation region irradiated from the radiation irradiation unit based on information in which an imaging condition and an imaging position are associated with each other is a predetermined region including the region of interest. A radiation imaging apparatus comprising: an opening angle control unit that controls an opening angle of the radiation irradiation unit. The radiation imaging apparatus according to any one of claims 1 to 3, wherein an incident angle and a previous radiation imaging performed in a radiography before the predetermined radiography in tomography including a series of radiography. The ratio of the standard deviation of the pixel value to the average value of each pixel value obtained in the above, or the pixel noise obtained based on the maximum value of each pixel value obtained by the setting shooting or the value by histogram analysis, and Imaging that obtains the current value of the radiation irradiating means according to the incident angle at the time of the predetermined radiation imaging based on the reference current value of the radiation irradiating means at the time of the setting imaging with respect to the predetermined incident angle. A radiation imaging apparatus comprising a current value calculation unit.   The radiation imaging apparatus according to claim 4, wherein the incident angle obtained by the imaging current value calculating unit is based on an incident angle at the time of the predetermined radiation imaging and an incident angle performed in the previous radiation imaging. A radiation imaging apparatus comprising imaging current value correcting means for correcting the current value of the corresponding radiation irradiating means.   In the radiation imaging apparatus according to any one of claims 1 to 3, based on a reference current value of radiation irradiating means at the time of the setting imaging with the incident angle and the predetermined incident angle as a reference, A radiation imaging apparatus comprising imaging current value calculation means for obtaining a current value of radiation irradiation means according to the incident angle.

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