JP5880850B2 - Radiography equipment - Google Patents

Description

  The present invention relates to a radiation imaging apparatus that acquires an image by irradiating a subject with radiation, and more particularly to a radiation imaging apparatus in which a radiation source moves with respect to the subject during imaging.

  The medical institution is provided with a radiation tomography apparatus 51 that acquires a tomographic image of a subject. In such a radiation tomography apparatus 51, a series of fluoroscopic images are continuously shot while a radiation source 53 for irradiating radiation and an FPD 54 for detecting radiation move synchronously, and the series of fluoroscopic images are superimposed. Some are configured to acquire a tomographic image (see FIG. 24). In such a radiation tomography apparatus 51, during a series of fluoroscopic imaging, the radiation source 53 and the FPD 54 move so as to approach each other in the body axis direction of the subject, and the body axis direction of the radiation source 53 and the FPD 54 After the positions at the positions coincide with each other, the radiation source 53 and the FPD 54 are moved away from each other in the body axis direction.

  An operation when the radiation tomography apparatus 51 captures the tomographic image as described above will be described. First, the radiation source 53 emits radiation intermittently while moving. That is, every time one irradiation is completed, the radiation source 53 moves in the direction of the body axis of the subject and irradiates the radiation again. In this way, 74 perspective images are acquired, and these are reconstructed into tomographic images by the filter back projection method. The completed tomographic image is an image in which a tomographic image obtained by cutting the subject with a certain cut surface is reflected.

  Such a radiation tomography apparatus 51 can acquire a subtraction image in which a soft tissue or a bone part of a subject is emphasized by acquiring a difference between two images obtained by performing two types of imaging. . An operation when a subtraction image is captured in the conventional radiation tomography apparatus 51 will be described.

  In the conventional radiation tomography apparatus, as shown in FIG. 25, the radiation source 53 and the FPD 54 move relative to the subject while alternately performing imaging with the radiation source 53 at a high voltage and imaging at a low voltage. Is done. As a result, the perspective image of the high voltage condition and the perspective image of the low voltage image are alternately photographed. If a tomographic image is reconstructed only from a fluoroscopic image acquired by high-voltage imaging after imaging, a high-voltage condition tomographic image can be acquired. Further, if a tomographic image is reconstructed only from a fluoroscopic image acquired by low-voltage imaging, a tomographic image under a low-voltage condition is acquired. At this time, the radiation source 53 always moves in the same direction during imaging.

  When comparing tomographic images with different imaging conditions, the state of the captured subject image is different. Specifically, the difference in contrast between the soft tissue and the bone portion of the subject reflected in the tomographic image under the high voltage condition is different from the difference in contrast between the soft tissue and the bone portion in the tomographic image under the low voltage condition. Therefore, when a high voltage condition tomographic image is subtracted from a low voltage condition tomographic image, both images are not simply canceled out, but the soft tissue of the subject is more emphasized or the bone is emphasized. The conventional radiation tomography apparatus 51 uses this to acquire a subtraction image in which the soft tissue or bone of the subject is emphasized.

  The conventional radiation tomography apparatus 51 includes a filter 53f that changes the radiation quality of the radiation source 53 (see FIG. 24). This filter 53f includes a gadolinium filter for high voltage irradiation and a copper filter for low voltage irradiation. The gadolinium filter and the copper filter can be switched by controlling the drive unit of the filter 53f (see, for example, Patent Document 1).

JP-A-4-141156

However, the conventional radiation tomography apparatus has the following problems.
That is, the conventional radiation tomography apparatus has a problem that the imaging method cannot be changed flexibly. That is, a subtraction tomography function cannot be easily added to a general-purpose radiation imaging apparatus.

  The filter 53f must be provided adjacent to the radiation source 53. The reason for this will be described. The radiation beam emitted from the radiation source 53 reaches the subject M while spreading radially. Therefore, the width of the radiation beam immediately after being emitted from the radiation source 53 is narrow. Then, as the radiation beam moves away from the radiation source 53, the width of the beam increases. In order to ensure that the radiation beam irradiated from the radiation source 53 passes through the filter 53f, the beam must pass through the filter 53f while the beam is narrow. That is, the filter 53f must be provided adjacent to the radiation source 53.

  Therefore, the filter 53f needs to be provided at a position between the radiation source 53 and the collimator. The collimator is a movable slit that adjusts the spread of the radiation beam emitted from the radiation source 53. That is, the radiation beam passes through the filter 53f and then passes through the collimator. On the contrary, if the collimator and the filter 53f are set to transmit the radiation beam in this order, a considerably large filter 53f is required. This is because the radiation beam transmitted through the filter 53f is considerably wide. Such a setting is not realistic.

  The restriction on the installation position of the filter 53f as described above causes the following problems. That is, if a general-purpose radiation imaging apparatus is to be able to capture a subtraction tomographic image, a major modification is required.

  In order to be able to capture a subtraction tomographic image, the filter 53f is required. The filter 53f needs to be inserted between the radiation source 53 and the collimator as described above. However, a general-purpose radiation imaging apparatus is already in a state where a collimator is installed in the radiation source 53. Therefore, in order to be able to take a subtraction tomographic image, a modification is required in which the collimator is removed from the radiation source 53, the filter 53f is attached, and the collimator is further attached.

  Once the filter 53f is attached, the radiation imaging apparatus is dedicated to subtraction image acquisition. In order to perform general shooting such as spot shooting in this state, the filter 53f must be removed from the apparatus. However, if general imaging is performed with the filter 53f provided, the radiation passes through the filter 53f and the radiation quality changes, and imaging as prescribed cannot be performed.

  There are various imaging methods for radiography. There are cases where you want to switch the shooting method flexibly as you continue shooting. In such a case, a conventional apparatus that requires a large-scale modification cannot be said to have an optimum configuration for use.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a radiation imaging apparatus capable of flexibly switching an imaging method in a radiation imaging apparatus capable of capturing a subtraction tomographic image. is there.

The present invention has the following configuration in order to solve the above-described problems.
That is, a radiation imaging apparatus according to the present invention includes a radiation source that irradiates radiation toward a subject, and a collimator that generates a fan-shaped radiation beam related to slot imaging by limiting the spread of radiation irradiated from the radiation source. When a radiation source control means for controlling the voltage of the radiation source, the radiation source and the radiation source moving means for moving relative to the object, a radiation source moving control means for controlling the radiation source moving means, the radiation source is a high voltage A subtraction image capturing filter having a high-voltage region that transmits radiation irradiated when the radiation source is low, and a low-voltage region that transmits radiation irradiated when the radiation source is at a low voltage, and movement of the radiation source with moves following a holder filter for subtraction imaging is held in one of a plurality provided holes, the holder times to A holder rotating means for, after the radiation one of areas where the filter has by reversing the direction of rotation of the holder has moved to a position to pass through, so as to move the other area in a position where the radiation passes A holder rotation control means for controlling the holder rotation means, a radiation detection means for detecting radiation that has passed through the filter and the subject, an image generation means for generating an image based on the output of the radiation detection means, and a radiation source at a high voltage An image subtracting unit that generates a subtraction image by obtaining a difference between an image continuously shot under conditions and an image continuously shot under a low voltage condition of the radiation source, and an image that generates a composite image by combining the subtraction images It comprises a synthesizing means .

[Operation / Effect] The present invention has a configuration in which a subtraction image is generated by taking a difference between high-voltage imaging and low-voltage imaging in a radiation imaging apparatus configured to move the radiation source relative to the subject. ing. According to the configuration of the present invention, by rotating the holder, it is possible to switch whether or not to transmit the subtraction image capturing filter to the radiation emitted from the radiation source. In other words, after taking an image in a state where the radiation passes through the filter for capturing the subtraction image, if you want to take an image in a state that does not pass through this filter, you can continue the image immediately by rotating the holder. it can. This is because according to the apparatus of the present invention, it is possible to cope with a change in the photographing method by simply rotating the holder between photographing. The apparatus according to the present invention is capable of capturing a subtraction image, but can immediately perform shooting other than subtraction image shooting. Therefore, according to the present invention, a radiation imaging apparatus capable of performing imaging flexibly can be provided.
Also, as described above, after moving one of the regions of the filter to a position where the radiation passes, when moving the other region to a position where the radiation passes, the rotation direction of the holder is changed. If it is reversed, the subtraction image can be taken with a slight movement of the filter.
Further, the above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. If a collimator for limiting the irradiation range of the radiation that has passed through the holder is provided, the holder is necessarily in a position sandwiched between the radiation source and the collimator. By doing in this way, the filter with which the holder was equipped, and a radiation source can be made adjacent. Then, the size of the filter can be reduced. This is because the width of the radiation emitted from the radiation source is the smallest immediately after emission.

  Further, in the above-described radiation imaging apparatus, the holder rotating means switches whether the radiation emitted from the radiation source is transmitted through the filter, and when capturing the image, when the radiation source is at a high voltage, the high voltage of the filter. When the radiation area is moved to a position where the radiation passes and the radiation source has a low voltage, it is more desirable to move the low voltage area of the filter to a position where the radiation passes.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. If the holder rotating means changes the radiation passing position in the filter in accordance with the voltage of the radiation source, it is possible to surely take an image with appropriate exposure.

  Further, in the above-described radiation imaging apparatus, when performing imaging other than subtraction image imaging, the holder rotating means moves the holder so that the radiation passes through holes other than the holes provided with the filter for subtraction image imaging. It is more desirable to rotate.

  In the above-described radiation imaging apparatus, the holder also holds a filter used for purposes other than subtraction image capturing, and the type of filter through which radiation is transmitted is changed by rotating the holder by the holder rotating means. More desirable.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. In other words, the filter can be changed according to the purpose of imaging by allowing the holder to rotate to change the type of filter through which the radiation passes. For example, when performing spot photography, it is possible to perform photography by selecting a filter suitable for this photography method.

  Further, in the above-described radiation imaging apparatus, when the radiation source is moved, the detector includes a detector moving unit that moves the radiation detecting unit relative to the subject, and a detector movement control unit that controls the detector moving unit. It is more desirable if the radiation detection means is moved relative to the subject.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. That is, according to the above configuration, the radiation detection means can be moved relative to the subject. By doing in this way, the radiography apparatus which can respond to a more various imaging | photography mode can be provided.

  In the above-described radiation imaging apparatus, it is more preferable that the image synthesizing unit generates a tomographic image when the subject is cut on a virtual plane as a synthesized image.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. That is, according to the above configuration, a tomographic image can be generated. At this time, the movement modes of the radiation source and the radiation detection means are opposite to each other.

  In the above-described radiographic apparatus, the image synthesizing unit may generate a synthesized image by arranging and joining the elongated subtraction images extending in the direction orthogonal to the moving direction of the radiation source in the moving direction of the radiation source. desirable.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. That is, according to the above-described configuration, an intermediate image acquired by slot imaging is captured, and a tomographic image is captured from these images. By performing such imaging, it is possible to provide a radiation imaging apparatus that can acquire tomographic images captured over a wide range.

  In the above radiographic apparatus, the image synthesizing unit divides the subtraction image into strip-like strip images extending in a direction perpendicular to the moving direction of the radiation source, and joins strip-like images having the same radiation irradiation direction. It is more desirable if a combined intermediate image is generated, and a tomographic image obtained by cutting the subject on the virtual plane from the intermediate image is generated as a composite image.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. That is, according to the above-described configuration, an intermediate image acquired by slot imaging is captured, and a tomographic image is captured from these images. By performing such imaging, it is possible to provide a radiation imaging apparatus that can acquire tomographic images captured over a wide range.

  In the above radiographic apparatus, the synthesized image generated by the image synthesizing means is an elongated subtraction image extending in a direction orthogonal to the moving direction of the radiation source arranged in the moving direction of the radiation source and connected. Yes, it is more desirable if the radiation detection means does not move relative to the subject during image capture.

  [Operation / Effect] The above-described configuration shows a specific configuration of the radiation imaging apparatus of the present invention. That is, according to the above-described configuration, a configuration is shown in which the radiation detection means does not move during imaging. By doing so, it is possible to provide a radiation imaging apparatus with simpler control.

  According to the configuration of the present invention, by rotating the holder, it is possible to switch whether or not to transmit the subtraction image capturing filter to the radiation emitted from the radiation source. In other words, after taking an image in a state where the radiation passes through the filter for capturing the subtraction image, if you want to take an image in a state that does not pass through this filter, you can continue the image immediately by rotating the holder. it can. Therefore, according to the present invention, a radiation imaging apparatus capable of performing imaging flexibly can be provided.

1 is a functional block diagram illustrating an overall configuration of a radiation imaging apparatus according to Embodiment 1. FIG. FIG. 3 is a schematic diagram illustrating the imaging principle of the radiation imaging apparatus according to the first embodiment. 3 is a functional block diagram illustrating a collimator according to Embodiment 1. FIG. FIG. 3 is a plan view illustrating the configuration of a holder according to the first embodiment. 3 is a plan view illustrating the configuration of a filter according to Embodiment 1. FIG. 3 is a cross-sectional view illustrating a configuration of a filter according to Embodiment 1. FIG. It is a top view explaining rotation of the holder concerning Example 1. It is a top view explaining rotation of the holder concerning Example 1. FIG. 3 is a schematic diagram illustrating functions of a filter according to the first embodiment. FIG. 3 is a schematic diagram illustrating functions of a filter according to the first embodiment. 6 is a flowchart for explaining the operation of the radiation imaging apparatus according to the first embodiment. FIG. 6 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the first embodiment. FIG. 6 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the first embodiment. FIG. 6 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the second embodiment. FIG. 6 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the second embodiment. FIG. 10 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the third embodiment. FIG. 10 is a schematic diagram illustrating the imaging principle of the radiation imaging apparatus according to the third embodiment. FIG. 10 is a schematic diagram illustrating the imaging principle of the radiation imaging apparatus according to the third embodiment. FIG. 10 is a schematic diagram illustrating the imaging principle of the radiation imaging apparatus according to the third embodiment. FIG. 10 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the third embodiment. FIG. 10 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the third embodiment. FIG. 10 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the fourth embodiment. FIG. 10 is a schematic diagram for explaining the operation of the radiation imaging apparatus according to the fourth embodiment. It is a schematic diagram explaining the structure of the conventional radiography apparatus. It is a schematic diagram explaining the structure of the conventional radiography apparatus.

  Next, an embodiment of a radiation tomography apparatus according to the present invention will be described with reference to the drawings. In addition, the X-ray in an Example is corresponded to the radiation of the structure of this invention. Note that FPD is an abbreviation for flat panel X-ray detector (flat panel detector).

  FIG. 1 is a functional block diagram illustrating the configuration of the radiation imaging apparatus according to the first embodiment. As shown in FIG. 1, the X-ray imaging apparatus 1 according to the first embodiment includes a top plate 2 on which a subject M that is a target of X-ray tomography is placed, and an upper portion of the top plate 2 An X-ray tube 3 that irradiates the subject M with a cone-shaped X-ray beam toward the subject M, and a lower portion of the top 2 (the other side of the top). The FPD 4 that detects the transmitted X-ray image of the subject M, and the X-ray tube 3 and the FPD 4 are connected to the subject M in a state where the central axis of the cone-shaped X-ray beam and the center point of the FPD 4 always coincide with each other. A synchronous movement mechanism 7 that moves synchronously in opposite directions across the region of interest, a synchronous movement control unit 8 that controls the synchronous movement mechanism 7, and scattered X-rays provided so as to cover the X-ray detection surface that detects the X-rays of the FPD 4 And an X-ray grid 5 that absorbs. In this way, the top plate 2 is disposed at a position sandwiched between the X-ray tube 3 and the FPD 4. The FPD 4 detects X-rays that have passed through the filter 25f and the subject M described later. The X-ray tube 3 corresponds to the radiation source of the present invention, and the FPD 4 corresponds to the radiation detection means of the present invention.

  The synchronous movement mechanism 7 includes an X-ray tube movement mechanism 7a that moves the X-ray tube 3 in the body axis direction A with respect to the subject M, and an FPD movement mechanism that moves the FPD 4 in the body axis direction A with respect to the subject M. 7b. The synchronous movement control unit 8 includes an X-ray tube movement control unit 8a that controls the X-ray tube movement mechanism 7a and an FPD movement control unit 8b that controls the FPD movement mechanism 7b. The X-ray tube movement mechanism 7a corresponds to the radiation source movement means of the present invention, and the X-ray tube movement control unit 8a corresponds to the radiation source movement control means of the present invention. The FPD movement mechanism 7b corresponds to the detector movement means of the present invention, and the FPD movement control unit 8b corresponds to the detector movement control means of the present invention.

  The X-ray tube 3 is configured to repeatedly irradiate the subject M with a cone-shaped and pulsed X-ray beam according to the control of the X-ray tube control unit 6. The X-ray tube 3 is provided with a collimator 3a for collimating the X-ray beam into a cone shape that is a pyramid. The X-ray tube 3 and the FPD 4 generate imaging systems 3 and 4 that capture X-ray fluoroscopic images. The X-ray tube control unit 6 can control the voltage of the X-ray tube 3 to apply a high voltage to the X-ray tube 3 to irradiate X-rays, or apply a low voltage to the X-ray tube 3. X-rays can also be irradiated. The X-ray tube control unit 6 corresponds to the radiation source control means of the present invention.

  The synchronous movement mechanism 7 is configured to move the X-ray tube 3 and the FPD 4 in synchronization with the subject M. The synchronous movement mechanism 7 linearly moves the X-ray tube 3 along a linear trajectory (longitudinal direction of the top 2) parallel to the body axis direction A of the subject M according to the control of the synchronous movement control unit 8. The moving direction of the X-ray tube 3 and the FPD 4 coincides with the longitudinal direction of the top 2. Moreover, during the examination, the cone-shaped X-ray beam irradiated by the X-ray tube 3 is always irradiated toward the region of interest of the subject M. The X-ray irradiation angle is determined by the X-ray tube 3. Is changed from, for example, an initial angle of −20 ° to a final angle of 20 °. Such an X-ray irradiation angle change is performed by the X-ray tube tilting mechanism 9. The X-ray tube tilt control unit 10 is provided for the purpose of controlling the X-ray tube tilt mechanism 9.

  Further, the X-ray imaging apparatus 1 according to the first embodiment further includes a main control unit 30 that comprehensively controls the control units 6, 8, 10, 18b, and 22 and a display unit 27 that displays the tomographic image D. I have. The main control unit 30 is constituted by a CPU, and realizes the control units 6, 8, 10, 18b, and 22 and later-described units 11, 12, and 13 by executing various programs. The storage unit 23 stores all data related to control of the X-ray imaging apparatus 1 such as parameters related to control of the X-ray tube 3. The console 26 allows the operator to input each operation on the X-ray imaging apparatus 1.

  Further, the synchronous movement mechanism 7 synchronizes with the linear movement of the X-ray tube 3 described above, and causes the FPD 4 provided at the lower part of the top 2 to move in the body axis direction A (the longitudinal direction of the top 2) of the subject M. Move straight ahead. The moving direction is opposite to the moving direction of the X-ray tube 3. In other words, a cone-shaped X-ray beam whose focal position and irradiation direction change as the X-ray tube 3 moves is always received by the entire surface of the X-ray detection surface of the FPD 4. Yes. As described above, in one inspection, the FPD 4 acquires, for example, 74 fluoroscopic images while moving in synchronization with the X-ray tube 3 in opposite directions. Specifically, the imaging systems 3 and 4 are opposed to the position indicated by the alternate long and short dash line illustrated in FIG. 1 through the position indicated by the broken line with the position of the solid line as the initial position. That is, a plurality of fluoroscopic images are taken while changing the positions of the X-ray tube 3 and the FPD 4. By the way, since the cone-shaped X-ray beam is always received by the entire surface of the X-ray detection surface of the FPD 4, the central axis of the cone-shaped X-ray beam during imaging always coincides with the center point of the FPD 4. During imaging, the center of the FPD 4 moves straight, but this movement is in the direction opposite to the movement of the X-ray tube 3. That is, the X-ray tube 3 and the FPD 4 are moved in the body axis direction A synchronously and in directions opposite to each other.

  Further, an image generation unit 11 that generates a fluoroscopic image based on a detection signal output from the FPD 4 is provided (see FIG. 1). An image subtracting unit 12 that generates a subtraction image s by obtaining a difference between a fluoroscopic image P1 continuously shot under a high voltage condition and a fluoroscopic image P2 continuously shot under a low voltage condition. And an image reconstruction unit 13 that generates a tomographic image D by synthesizing the subtraction images s. The image generation unit 11 corresponds to an image generation unit of the present invention. The image subtraction unit 12 corresponds to the image subtraction unit of the present invention, and the image reconstruction unit 13 corresponds to the image synthesis unit of the present invention.

  Next, the principle of obtaining a tomographic image of the X-ray imaging apparatus 1 according to the first embodiment will be described. FIG. 2 is a diagram illustrating a tomographic image acquisition method of the X-ray imaging apparatus according to the first embodiment. For example, a virtual plane (reference cut section MA) parallel to the top plate 2 (horizontal with respect to the vertical direction) will be described. As shown in FIG. The FPD 4 is synchronized with the opposite direction of the X-ray tube 3 in accordance with the irradiation direction of the cone-shaped X-ray beam B by the X-ray tube 3 so as to be projected onto the fixed points p and q of the X-ray detection surface of the FPD 4. A series of fluoroscopic images P are generated by the image generator 11 while being moved. The projected images of the subject M are reflected in the series of fluoroscopic images P1 and P2 while changing the position. Then, when the series of fluoroscopic images P1 and P2 are reconstructed by the image reconstruction unit 13, images (for example, fixed points p and q) positioned on the reference cut surface MA are accumulated and imaged as an X-ray tomographic image. Will be. On the other hand, the point I that is not located on the reference cut surface MA is reflected as a point i in a series of subject images while changing the projection position on the FPD 4. Unlike the fixed points p and q, such a point i is blurred without forming an image when the image reconstruction unit 13 superimposes the fluoroscopic images. In this way, by superimposing a series of fluoroscopic images, an X-ray tomographic image in which only an image located on the reference cut surface MA of the subject M is reflected is obtained. Thus, when the fluoroscopic images are simply superimposed, a tomographic image D at the reference cut surface MA is obtained.

  Furthermore, by changing the setting of the image reconstruction unit 13, a similar tomographic image can be obtained even at an arbitrary cut surface that is horizontal to the reference cut surface MA. During shooting, the projection position of the point i moves in the FPD 4, but this moving speed increases as the separation distance between the point I before projection and the reference cut surface MA increases. If this is used to reconstruct a series of acquired subject images while shifting the body image in the body axis direction A at a predetermined pitch, a tomographic image D at a cutting plane parallel to the reference cutting plane MA is obtained. It is done. Such a series of subject image reconstruction is performed by the image reconstruction unit 13.

  The collimator 3a will be specifically described. The collimator 3a is a member that limits the irradiation range of X-rays that have passed through a holder 25 described later. FIG. 3 is a diagram illustrating the configuration of the collimator 3a. As shown in FIG. 3, the collimator 3a has a pair of leaves 3b that move mirror-symmetrically with respect to the central axis C, and another pair of leaves 3b that similarly move mirror-symmetrically with respect to the central axis C. I have. The collimator 3a can move the leaf 3b to irradiate the entire detection surface of the FPD 4 with the cone-shaped X-ray beam B. For example, only the central portion of the FPD 4 has a fan-shaped X-ray beam B. Can also be irradiated. The central axis C is also an axis indicating the center of the X-ray beam B. One of the pairs of leaves 3b is for adjusting the spread in the body axis direction A of the X-ray beam having a quadrangular pyramid shape, and the other pair of leaves 3b is the body side direction S of the X-ray beam. It is to adjust the spread of. The collimator moving mechanism 18a changes the opening of the collimator 3a. The collimator control unit 18b controls the collimator moving mechanism 18a and is controlled by the main control unit 30. Moreover, it is good also as a structure which a pair of leaf 3b moves independently, without setting it as the structure which moves the collimator 3a mirror-image symmetrically. The positional relationship between the collimator 3a and the X-ray tube 3 is not changed by the movement / tilting of the X-ray tube 3, and the collimator 3a follows the movement / tilting of the X-ray tube 3.

  FIG. 4 illustrates the configuration of the holder 25 according to the configuration of the first embodiment. The holder 25 holds a filter that transmits X-rays. The holder 25 is a disk-shaped member that spreads on a plane orthogonal to the direction in which the X-ray beam B is emitted. As shown in FIG. 1, the holder 25 is disposed at a position between the X-ray tube 3 and the collimator 3a. Therefore, the X-ray beam emitted from the X-ray tube 3 passes through the holder 25 and reaches the collimator 3a. Since the holder 25 is held by the X-ray tube 3, the positional relationship between the holder 25 and the X-ray tube 3 is not changed by the movement / tilting of the X-ray tube 3, and the holder 25 moves / tilts the X-ray tube 3. Follow.

  The holder 25 can rotate with respect to the X-ray tube 3. That is, a center axis 25a extending in the X-ray beam emission direction is provided at the center of the holder 25, and the holder 25 is rotatable about the center axis 25a. The holder 25 is rotated by the holder rotating mechanism 21. The holder rotation control unit 22 is provided for the purpose of controlling the holder rotation mechanism 21. The holder rotation control unit 22 corresponds to the holder rotation control means of the present invention. The holder rotation mechanism 21 corresponds to the holder rotation means of the present invention.

  The holder 25 is provided with a plurality of rectangular holes 25b. The hole 25b penetrates the holder 25 in the X-ray beam emission direction. Therefore, the hole 25b penetrates the holder 25 in the central axis C direction. The hole 25b is provided so as to surround the central axis 25a of the holder. In FIG. 4, four holes 25b are provided, but the number of holes 25b can be freely changed. The hole 25b is a through hole provided in the holder 25 through which the X-ray beam passes.

  The manner in which the holder 25 holds the filter 25f will be described. The filter 25f is fixed to the holder 25 so as to close the hole 25b. FIG. 4 shows a state where the filter 25f fixed to the holder 25 is removed. The filter 25f is a thin plate-like member in the X-ray beam emission direction.

  The filter 25f provided in the holder 25 will be described. This filter 25f is used for taking a subtraction image. That is, the filter 25f is a dual-purpose filter when performing high-dose imaging and low-dose imaging. As shown in FIG. 4, the filter 25 f is a plate-like member that is larger than the hole 25 b of the holder 25.

  FIG. 5 illustrates a specific configuration of the filter 25f. The filter 25f has a configuration in which a copper plate indicated by diagonal lines and a gadolinium plate indicated by hatching are attached to an aluminum plate 25f1. The copper plate is provided at a position where X-rays pass when performing high-dose imaging, and the gadolinium plate is provided at a position where X-rays pass when performing low-dose imaging. The portion of the filter 25f where the copper plate is attached is a high voltage region RH that transmits X-rays irradiated when the X-ray tube 3 is in a high voltage state. And the part where the gadolinium plate is affixed in the filter 25f is a low voltage region RL that transmits X-rays irradiated when the X-ray tube 3 is in a low voltage state.

  The arrangement of the high voltage region RH and the low voltage region RL in the filter 25f will be described. The high voltage region RH and the low voltage region RL are provided adjacent to each other without a gap, and are arranged in a direction indicated by an arrow in FIG. The direction of the arrow is the direction in which the filter 25f moves by the rotation of the holder 25 when the filter 25f is fixed to the holder 25. Therefore, when the holder 25 is slightly rotated in a state where the high voltage region RH is set in the X-ray tube 3, the low voltage region RL is set in the X-ray tube 3 this time.

  FIG. 6 shows a cross section of the filter 25f. As shown in FIG. 6, the filter 25f has a configuration in which a copper plate 25f2 and a gadolinium plate 25f3 are attached to an aluminum plate 25f1. Therefore, when the X-ray beam passes through the copper plate 25f2, the aluminum plate 25f1 also passes through. This situation is the same for the gadolinium plate 25f3.

  FIG. 7 shows a state where the high voltage region RH of the filter 25 f is set in the X-ray tube 3. A region P represents a passage through which X-rays emitted from the X-ray tube 3 pass. In the configuration of FIG. 7, X-rays emitted from the X-ray tube 3 pass through the aluminum plate 25f1 and the copper plate 25f2 of the filter 25f, and travel toward the collimator 3a. At this time, since the hole 25 b is provided in the holder 25, X-rays do not enter the members constituting the holder 25.

  In FIG. 7, the filter 25f is screwed to the holder 25 at the same time. The screw is fastened to the holder 25 in a state of being engaged with a screw passage recess (see FIG. 5) provided in the filter 25f.

  FIG. 8 shows a state where the low voltage region RL of the filter 25 f is set in the X-ray tube 3. A region P represents a passage through which X-rays emitted from the X-ray tube 3 pass. In the configuration of FIG. 8, X-rays emitted from the X-ray tube 3 pass through the aluminum plate 25f1 and the gadolinium plate 25f3 of the filter 25f and travel toward the collimator 3a. At this time, since the hole 25 b is provided in the holder 25, X-rays do not enter the members constituting the holder 25.

  The change of the area set in the X-ray tube 3 will be described. In order to change from the state where the high voltage region RH is set to the X-ray tube 3 to the state where the low voltage region RL is set, the holder 25 in the state of FIG. 7 is changed from the low voltage region RL to the high voltage region. Rotate in the direction toward RH to obtain the state shown in FIG. On the contrary, in order to change from the state where the low voltage region RL is set to the X-ray tube 3 to the state where the high voltage region RH is set, the holder 25 in the state of FIG. 8 is lowered from the high voltage region RH. It is rotated in the direction toward the voltage region RL to obtain a state as shown in FIG. The positional relationship between the central axis 25 a and the region P does not change with the rotation of the holder 25.

  Thus, when the holder rotating mechanism 21 rotates the holder 25 to capture a subtraction image and the X-ray tube 3 is at a high voltage, the position where the X-ray passes through the high voltage region of the filter 25f. When the X-ray tube 3 has a low voltage, the low voltage region of the filter 25f is moved to a position where the X-rays pass. Specifically, the holder rotating mechanism 21 moves the high voltage region RH included in the filter 25f to a position where the X-ray passes, and then moves the low voltage region RL to a position where the X-ray passes. The direction of rotation of the holder 25 is reversed. Then, after moving the low voltage region RL to the position where the X-ray passes, the holder rotating mechanism 21 changes the rotation direction of the holder 25 when moving the high voltage region RH to the position where the X-ray passes. Invert again. Thus, the holder rotation mechanism 21 has a role of switching the region.

  The holder rotating mechanism 21 has another role. That is, it is a function for switching whether or not to transmit the filter 25f to the X-rays emitted from the X-ray tube 3. The X-ray imaging apparatus 1 is not a dedicated machine for subtraction image capturing. Shooting other than subtraction image shooting may be performed. The holder rotating mechanism 21 rotates the holder 25 and moves the filter 25f to a position away from the X-ray tube 3 when the subtraction image is not taken. By doing so, X-rays emitted from the X-ray tube 3 do not pass through the filter 25f. At this time, the holes 25a other than the hole 25a in which the filter 25f is inserted are rotated to a position adjacent to the region P (see FIG. 7). Since the X-rays irradiated from the X-ray tube 3 pass through the hole 25a, the X-rays do not enter the members constituting the holder 25.

  The reason why the X-ray imaging apparatus 1 of the present invention includes the filter 25f will be described. The filter 25f is provided for the purpose of acquiring the subtraction image s using two images having different outputs from the X-ray tube 3. The subtraction image s is generated by subtracting an image acquired by controlling the X-ray tube 3 at a low voltage from an image acquired by controlling the X-ray tube 3 at a high voltage. Comparing two images that are the basis of the subtraction image s, the image density in the soft tissue of the subject M is different from the image density in the bone portion of the subject M.

  If two images having the same soft tissue image density with respect to the bone image density are subjected to subtraction processing, the subject images appearing in the image are simply canceled and erased. However, when two images having different soft tissue image densities relative to the density of the bone part image of the subject M are subtracted, for example, in the portion where the soft tissue in the image is reflected, the images do not cancel each other much. In the part where the bone part is reflected in the image, a phenomenon occurs in which the cancellation of the images strongly occurs. In this example, a subtraction image in which the soft tissue of the subject M is emphasized more than the bone is obtained by subtracting two images. The bone part of the subject M can also be emphasized by changing the coefficient for performing the subtraction process.

  In order to acquire the highly visible subtraction image s, the image density in the soft tissue of the subject M must be surely different between the two images to be acquired with respect to the image density in the bone portion of the subject M. I must. Such a difference in image density is derived from the difference in the properties of X-rays emitted when two images are taken. If two images are shot by irradiating X-rays with the same radiation quality, the density of the soft tissue image is similar to the density of the bone image between the two images. Even if such a difference between the two images is taken, the subject images appearing in the images are simply canceled out, and the soft tissue of the subject M is not emphasized.

  FIG. 9 shows an X-ray spectrum when the subtraction image s is acquired without the filter 25f. In the figure, the spectrum of X-rays irradiated when the X-ray tube 3 is at a high voltage is represented by H, and the spectrum of X-rays irradiated when the X-ray tube 3 is at a low voltage is represented by L. Referring to FIG. 9, it can be seen that although each spectrum has a different frequency distribution, there is a common part a where the spectra partially overlap. This common part a means that X-rays of the same quality were included over two X-ray irradiations. In order to ensure that the X-ray properties are different between when the X-ray tube 3 is at a high voltage and when it is at a low voltage, it is desirable to reduce the common portion a as much as possible.

  Therefore, the filter 25f is used to acquire the subtraction image s. That is, when the X-ray tube 3 is at a high voltage, the X-rays pass through the high voltage region RH that the filter 25f has. The high voltage region RH cuts a component having a low X-ray frequency under a high voltage condition. Further, when the X-ray tube 3 is at a low voltage, the X-rays pass through the low voltage region RL of the filter 25f. The low voltage region RL cuts a component having a high X-ray frequency under a low voltage condition.

  By the action of the filter 25f, the spectrum of the X-ray irradiated toward the subject M changes as shown in FIG. As can be seen from FIG. 10, it can be seen that the common part a of the spectra H and L is reduced as compared with the case of FIG. 9 due to the action of the filter 25f. In this way, the filter 25f is provided for the purpose of ensuring that the properties of the X-rays irradiated when two images are taken are different.

<Operation of X-ray tomography apparatus>
Next, the operation of the X-ray imaging apparatus 1 according to the first embodiment will be described with reference to FIG. In order to acquire a tomographic subtraction image using the X-ray imaging apparatus 1 according to the first embodiment, the subject M is first placed on the top 2 (subject placement step S1), and imaging is started. Subsequently, a subtraction image s is generated from the fluoroscopic image P1 captured under high voltage conditions and the fluoroscopic image P2 captured under low voltage conditions, and (image subtraction). Step S3) Finally, the subtraction image s is reconstructed to obtain a tomographic image D (image reconstruction step S4). Hereinafter, each step will be described in order.

  The configuration of the first embodiment employs a configuration in which shooting under high voltage conditions and shooting under low voltage conditions are alternately repeated.

<Subject placement step S1, imaging start step S2>
After placing the subject M on the top 2, when the operator gives an instruction to start imaging through the console 26 to the X-ray imaging apparatus 1, the X-ray tube control unit 6 is stored in the storage unit 23. Setting values relating to control of the X-ray tube 3 such as tube voltage, tube current, and pulse width are read out. The X-ray tube control unit 6 controls the X-ray tube 3 according to the set value, and causes the X-ray tube 3 to generate X-rays. X-rays transmitted through the subject M are detected by the FPD 4, and the detection signal at this time is sent to the image generation unit 11. The image generation unit 11 generates a fluoroscopic image in which a fluoroscopic image of the subject M is reflected based on the detection signal.

  At this time, the set values read out to the X-ray tube control unit 6 are both those relating to high voltage imaging and those relating to low voltage imaging. An X-ray fluoroscopic image taken under a high voltage condition is denoted by reference symbol P1, and an X-ray fluoroscopic image photographed under a low voltage condition is denoted by reference symbol P2.

  The X-ray tube control unit 6 sends a message to that effect to the holder rotation control unit 22 before performing imaging under high pressure conditions. Then, the holder rotation control unit 22 rotates the holder 25 through the holder rotation mechanism 21, and the high voltage region RH of the filter 25 f is set in the X-ray tube 3. Similarly, the X-ray tube control unit 6 sends a message to that effect to the holder rotation control unit 22 before performing imaging under low pressure conditions. Then, the holder rotation control unit 22 rotates the holder 25 through the holder rotation mechanism 21, and the low voltage region RL of the filter 25 f is set in the X-ray tube 3.

  FIG. 12 shows a state immediately before shooting is started. When imaging is started, the X-ray tube 3 in the state of FIG. 12 emits X-rays continuously while being moved in one direction from the head of the subject M to the toes. At this time, the X-ray tube 3 continuously fires X-ray irradiation at a high voltage and X-ray irradiation at a low voltage. Further, the FPD 4 detects X-rays while being moved in the opposite direction from the toes of the subject M toward the head with respect to the subject M. A filter used in capturing a series of fluoroscopic images P1 is for subtraction imaging and is constant. The holder 25 is rotated so as to swing even during photographing. By doing so, the high voltage region RH of the filter 25f is used for photographing during high voltage photographing, and the low voltage region RL of the filter 25f is used for photographing during low voltage photographing. 74 pieces of fluoroscopic images P1 and fluoroscopic images P2 are acquired. FIG. 13 shows a state immediately after the shooting is finished.

<Image Subtraction Step S3>
The fluoroscopic image P1 and the fluoroscopic image P2 are sent to the image subtracting unit 12. The image subtracting unit 12 acquires a difference between the fluoroscopic image P1 and the fluoroscopic image P2 and generates a subtraction image s.

  The relationship between the perspective image P1 and the perspective image P2 will be described. The fluoroscopic image P1 and the fluoroscopic image P2 are obtained by imaging the subject M under almost the same conditions except that the voltage condition of the X-ray tube 3 is different. More specifically, a fluoroscopic image P2 is taken before and after each of the 74 fluoroscopic images P1 is taken. That is, the fluoroscopic image P2 is photographed with substantially the same positional relationship as the positional relationship between the subject, the X-ray tube 3 and the FPD 4 when a certain fluoroscopic image P1 is photographed.

  The image subtracting unit 12 acquires the subtraction image s by acquiring a difference between the perspective image P1 and the corresponding perspective image P2. Since 74 fluoroscopic images P1 and 74 fluoroscopic images P2 are taken, 74 subtraction images s are also acquired. In each of the subtraction images s, an image in which the soft tissue or the bone portion of the subject M is emphasized is reflected. The image subtraction unit 12 can adjust the state of image enhancement in the subtraction image s by changing the coefficient used for the difference calculation.

<Image reconstruction step S4>
The 74 subtraction images s are sent to the image reconstruction unit 13. The image reconstruction unit 13 reconstructs a series of subtraction images s in which subject images having different projection directions are captured to generate a tomographic image D. As described above, the image reconstruction unit 13 generates a tomographic image when the subject M is cut on the virtual plane as a composite image. The tomographic image D is displayed on the display unit 27, and the operation of the X-ray imaging apparatus 1 ends.

  As described above, the present invention generates a subtraction image by taking the difference between high-voltage imaging and low-voltage imaging in an X-ray imaging apparatus configured to move the X-ray tube 3 relative to the subject M. It is the composition to do. According to the configuration of the present invention, by rotating the holder 25, it is possible to switch whether the X-ray emitted from the X-ray tube 3 is transmitted through the filter 25f for subtraction image capturing. That is, after taking an image in a state where X-rays pass through the filter 25f for taking a subtraction image, and wanting to take an image without passing through the filter 25f, the image is immediately taken by rotating the holder. can do. This is because according to the apparatus of the present invention, it is possible to cope with the change of the photographing method only by rotating the holder 25 between photographing. The apparatus according to the present invention is capable of capturing a subtraction image, but can immediately perform shooting other than subtraction image shooting. Therefore, according to the present invention, an X-ray imaging apparatus capable of performing imaging flexibly can be provided.

  Further, after moving one of the regions of the filter 25f to a position where the X-ray passes, the rotation direction of the holder 25 can be reversed when the other region is moved to a position where the X-ray passes. For example, a subtraction image can be captured by moving the filter 25f slightly.

  If a collimator that limits the irradiation range of the X-rays that have passed through the holder 25 is provided, the holder 25 is necessarily positioned between the X-ray tube 3 and the collimator. By doing in this way, the filter 25f with which the holder 25 was equipped, and the X-ray tube 3 can be made adjacent. Then, the size of the filter 25f can be reduced. This is because the width of X-rays emitted from the X-ray tube 3 is the smallest immediately after emission.

  Subsequently, an X-ray imaging apparatus according to Embodiment 2 will be described. In the second embodiment, the X-ray tube 3 is moved, and imaging is performed in a moving manner in which the FPD 4 is not moved. The configuration of the X-ray imaging apparatus according to the second embodiment is the same as the functional block diagram in FIG. 1 differs from the first embodiment in that the FPD 4 does not move, the X-ray tube 3 does not tilt, and a tomographic image is not generated. Therefore, in the second embodiment, the synchronous movement mechanism 7, the FPD movement mechanism 7b, the synchronous movement control unit 8, the FPD movement control unit 8b, the X-ray tube tilting mechanism 9, the X-ray tube tilt control unit 10, and the image reconstruction unit in FIG. The component 13 is not necessarily required.

  The configuration of the second embodiment employs a configuration in which shooting under high voltage conditions and shooting under low voltage conditions are alternately repeated.

  In the X-ray imaging apparatus according to the second embodiment, X-rays emitted from the X-ray tube 3 are limited by the collimator 3a. Since the collimator 3a limits the spread of the X-ray in the body axis direction A, the fan-shaped X-ray beam elongated in the body side direction S reaches the FPD 4. That is, the X-ray imaging apparatus according to the second embodiment acquires an elongated X-ray fluoroscopic image extending in the body side direction S of the subject M by one X-ray irradiation. This elongated image is taken a plurality of times and arranged in the body side direction to form a single composite image. In this way, X-ray imaging is divided into a plurality of times and the subject M is imaged little by little, so that the amount of scattered radiation reflected in the image can be reduced, so that bone mineral is quantified with high quantitativeness. Will be. Such X-ray imaging with limited spread is called slot imaging.

  The image reconstruction unit 13 according to the second embodiment does not perform the operation of generating the tomographic image D as described in the first embodiment. The image reconstruction unit 13 joins the subtraction images s taken while changing the position of the X-ray tube 3 with respect to the subject M, and generates a single composite image. That is, the image reconstruction unit 13 generates a composite image by arranging and joining the subtraction images s that are elongated in the body-side direction S of the subject M in the body axis direction A of the subject M.

<Operation of X-ray imaging apparatus>
The operation of the X-ray imaging apparatus according to the second embodiment is the same as the operation of the apparatus according to the first embodiment described with reference to FIG. FIG. 14 shows a state immediately before the X-ray imaging is started in the imaging start step S2. As shown in FIG. 14, the X-ray tube 3 is located at one end on the head side of the subject M among both ends of the FPD 4, and moves in one direction while continuously projecting the X-ray beam B, so that the legs of the subject M Head ahead. At this time, the FPD 4 does not move. Imaging ends when the X-ray tube 3 reaches the toe side of the subject M. FIG. 15 shows a state immediately after the photographing is finished. Since the control of the X-ray tube 3 and the holder 25 in this imaging is the same as in the first embodiment, the description thereof is omitted.

  As described above, the configuration of Example 2 is a radiographic apparatus for bone mineral quantification. When bone mineral content is determined, slot imaging is performed in such a manner that the X-ray tube 3 is moved relative to the subject M and the FPD 4 is not moved relative to the subject M. The present invention can also be employed in such a configuration.

  Subsequently, an X-ray tomography apparatus according to Embodiment 3 will be described. In the configuration of the third embodiment, as shown in FIG. 14, a tomographic image can be taken while the X-ray tube 3 and the FPD 4 are moved in the body axis direction A of the subject M while maintaining the mutual positional relationship. It is a possible configuration. At this time, the imaging method is not slot imaging as in the second embodiment, but imaging is performed by irradiating the entire surface of the FPD 4 with X-rays.

  The configuration of the third embodiment employs a configuration in which imaging under high voltage conditions and imaging under low voltage conditions are alternately repeated.

  The configuration of the X-ray imaging apparatus according to Embodiment 3 is the same as the functional block diagram in FIG. 1 differs from the first embodiment in that the FPD 4 moves following the X-ray tube 3 (see FIG. 16) and the X-ray tube 3 does not tilt. Therefore, in the third embodiment, the X-ray tube tilt mechanism 9 and the X-ray tube tilt control unit 10 in FIG. 1 are not necessarily required.

  The principle of capturing a tomographic image according to the third embodiment will be described. First, as shown in FIG. 16, X-rays are intermittently emitted while moving with respect to the subject M in a state where the imaging systems 3 and 4 maintain the relative positions. That is, every time one irradiation is completed, the X-ray tube 3 moves in the body axis direction A of the subject M and again performs X-ray irradiation. In this way, a plurality of fluoroscopic images are acquired, and a processed image (a long fluoroscopic image described later) of the fluoroscopic image is reconstructed into a tomographic image by the filter back projection method. The completed tomographic image is an image in which a tomographic image obtained by cutting the subject M with a certain cut surface is reflected.

  In order to generate a tomographic image, an image when the subject M is seen through from different directions is required. The X-ray tomography apparatus according to Embodiment 3 generates the image by dividing and connecting the obtained fluoroscopic images. This operation will be described. FIG. 17 shows the position of the FPD 4 when the focal point of the X-ray tube 3 that irradiates the X-rays is at the position d1. In this imaging, a fluoroscopic image is captured every time the X-ray tube 3 and the FPD 4 move in this direction with respect to the top 2 by a width of 1/5 of the FPD 4 in the body axis direction A of the subject M. To do.

  Since the X-ray spreads radially from the X-ray tube 3 and reaches the FPD 4, when the generated fluoroscopic image is divided into five in the body axis direction A of the subject M, the incident angle of the X-ray with respect to the FPD 4 is as shown by an arrow. The divisions are different from each other. Pay attention to one of the directions k. Since the X-rays traveling in the direction k pass through the hatched portion of the subject M and are reflected in the FPD 4, the diagonal lines of the subject M are included in the FPD 4 in which the X-rays in the direction k are incident. The part is reflected. In the fluoroscopic image, a portion corresponding to this division is referred to as a fragment R1.

  FIG. 18 shows the position of the FPD 4 when the focal point for irradiating the X-ray of the X-ray tube 3 is at the position of d2 moved from the distance d1 by 1/5 of the width of the FPD4. Since the positional relationship between the X-ray tube 3 and the FPD 4 does not change, the FPD 4 should also have a division in which the X-rays traveling in the direction k are reflected in the imaging at this time, and the X-rays in the direction k The hatched portion of the subject M is reflected in the divisional area of the FPD 4 on which is incident. In the fluoroscopic image, a portion corresponding to this division is defined as a fragment R2.

  When the fragment R1 and the fragment R2 are compared, since the position of the subject M with respect to the imaging systems 3 and 4 is different, the portions of the subject M reflected in both the fragments R1 and R2 are different from each other. By shifting the X-ray tube 3 by 1/5 the width of the FPD 4, assuming that nine times of imaging were performed at the focal points d 1 to d 9, Each fragment R1 to R9 includes a different position of the subject M. Accordingly, as shown in FIG. 19, if the pieces R1 to R9 of the fluoroscopic image are connected in this order to the body axis direction A of the subject M, the X-ray is taken when the whole body of the subject M is irradiated in a certain direction k. Images can be obtained. This image will be referred to as a long perspective image. The long image corresponds to the intermediate image of the present invention.

  The X-ray tomography apparatus according to the third embodiment generates a long fluoroscopic image in directions other than the direction k in the image reconstruction unit 13. Then, the image reconstruction unit 13 generates a tomographic image when the subject M is cut at a predetermined cutting position on the basis of a plurality of long fluoroscopic images having different directions in which the subject M is projected.

<Operation of X-ray tomography apparatus>
The operation of the X-ray imaging apparatus according to the third embodiment is the same as the operation of the apparatus according to the first embodiment described with reference to FIG. FIG. 20 shows a state immediately before the X-ray imaging is started in the imaging start step S2. As shown in FIG. 20, the X-ray tube 3 and the FPD 4 are located on the head side of the subject M, move in one direction while continuously capturing fluoroscopic images, and move toward the toe side of the subject M. When the X-ray tube 3 and the FPD 4 reach the toe side of the subject M, the imaging is finished. Since the control of the X-ray tube 3 and the holder 25 in this imaging is the same as in the first embodiment, the description thereof is omitted. FIG. 21 shows a state immediately after the shooting is finished.

  The image subtracting unit 12 acquires the subtraction image s by acquiring the difference between the perspective image P1 and the corresponding perspective image P2 in the image subtraction step S3. The fluoroscopic image P2 corresponding to the fluoroscopic image P1 is a fluoroscopic image P2 captured before and after the fluoroscopic image P1 is captured. At this time, the same number of subtraction images s as the fluoroscopic images P1 are acquired.

  In the image reconstruction step S4, the image reconstruction unit 13 acquires a plurality of subtraction images s. The image reconstruction unit 13 divides each of the subtraction images s into strip-shaped images extending in the body side direction S of the subject M. Thereafter, the image reconstruction unit 13 generates a plurality of long images by stitching together strip-shaped images having the same X-ray irradiation direction. These long images include a whole body image of the subject M having different projection directions.

  The image reconstruction unit 13 generates a tomographic image D by superimposing a plurality of long images. The principle of generating the tomographic image D is the same as that described with reference to FIG. That is, if a plurality of long images are simply superimposed, a tomographic image of the entire body of the subject at the reference cut surface MA is acquired. Further, if a plurality of long images are overlapped while being shifted, a tomographic image of the entire body of the subject at an arbitrary cut surface parallel to the reference cut surface MA is acquired. As described above, the image reconstruction unit 13 generates a tomographic image when the subject M is cut on the virtual plane as a composite image.

  As described above, according to the configuration of the third embodiment, a long image acquired by slot imaging is captured and a tomographic image D is captured therefrom. By performing such imaging, it is possible to provide a radiation imaging apparatus that can acquire tomographic images captured over a wide range.

  Subsequently, an X-ray imaging apparatus according to Embodiment 4 will be described. In the configuration of the fourth embodiment, as shown in FIG. 22, a fluoroscopic image can be taken while being moved in the body axis direction A of the subject M in a state where the X-ray tube 3 and the FPD 4 maintain the mutual positional relationship. It is a possible configuration. At this time, the imaging method is slot imaging as in the second embodiment, and imaging is performed while the collimator 3a limits the width of the X-ray in the body axis direction A. In this way, a clear image can be taken over a wide range without being affected by scattered radiation.

  The configuration of the fourth embodiment employs a configuration in which shooting under high voltage conditions and shooting under low voltage conditions are alternately repeated.

  The configuration of the X-ray imaging apparatus according to Embodiment 4 is the same as the functional block diagram in FIG. The configuration of the fourth embodiment with respect to FIG. 1 is different from that of the first embodiment in that the FPD 4 moves following the X-ray tube 3 while maintaining the positional relationship (see FIG. 22). It is not inclined and does not generate a tomographic image. Therefore, in the fourth embodiment, the X-ray tube tilt mechanism 9, the X-ray tube tilt control unit 10, and the image reconstruction unit 13 in FIG. 1 are not necessarily required.

<Operation of X-ray imaging apparatus>
The operation of the X-ray imaging apparatus according to the fourth embodiment is the same as the operation of the apparatus according to the first embodiment described with reference to FIG. FIG. 22 shows a state immediately before the X-ray imaging is started under the high voltage condition in the imaging start step S2. As shown in FIG. 22, the X-ray tube 3 and the FPD 4 are located on the head side of the subject M, move in one direction while continuously capturing fluoroscopic images, and move toward the toe side of the subject M. When the X-ray tube 3 and the FPD 4 reach the toe side of the subject M, the imaging is finished. Since the control of the X-ray tube 3 and the holder 25 in this imaging is the same as in the first embodiment, the description thereof is omitted. FIG. 23 shows a state immediately after the shooting is finished.

  The image subtracting unit 12 acquires the subtraction image s by acquiring the difference between the perspective image P1 and the corresponding perspective image P2 in the image subtraction step S3. The fluoroscopic image P2 corresponding to the fluoroscopic image P1 is a fluoroscopic image P2 captured before and after the fluoroscopic image P1 is captured. At this time, the same number of subtraction images s as the fluoroscopic images P1 are acquired. The subtraction image s has an elongated shape extending in the body side direction S of the subject M.

  In the image reconstruction step S4, the image reconstruction unit 13 arranges a plurality of subtraction images s in the body axis direction A of the subject M and connects them to generate a composite image.

  As described above, according to the configuration of the fourth embodiment, the subtraction image s is shot in the slot shooting mode. By performing the subtraction image s by slot imaging, it is possible to provide a radiation imaging apparatus that can acquire a clear subtraction image s without being affected by scattered radiation.

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

  (1) In FIG. 4 of the above-described embodiment, the holder 25 is provided with only the filter 25f for subtraction imaging, but the present invention is not limited to this configuration. That is, among the plurality of holes 25b provided in the holder 25, a filter used for purposes other than subtraction imaging may be held in the hole 25b in which the filter 25f is not provided. Thus, if the holder rotating mechanism 21 can change the type of the filter 25f that transmits X-rays by rotating the holder 25, the filter 25f can be changed in accordance with the purpose of imaging. For example, when spot photographing is performed, it is possible to perform photographing by selecting a filter 25f suitable for this photographing method.

  (2) In each of the embodiments described above, the tomographic image D is generated after the subtraction image s is generated, but the present invention is not limited to such a configuration. After generating the tomographic image D related to the high voltage imaging and the tomographic image D related to the low voltage, the subtraction image s may be acquired by taking the difference between them. In the functional block diagram of such a configuration, the positions of the image subtraction unit 12 and the image reconstruction unit 13 in FIG. 1 are interchanged.

  (3) Although the embodiment described above is a medical device, the present invention can also be applied to industrial and nuclear devices.

  (4) X-rays referred to in the above-described embodiments are an example of radiation in the present invention. Therefore, the present invention can be applied to radiation other than X-rays.

3 X-ray tube (radiation source)
4 FPD (radiation detection means)
6 X-ray tube control unit (radiation source control means)
7a X-ray tube moving mechanism (radiation source moving means)
7b FPD moving mechanism (detector moving means)
8a X-ray tube movement control unit (radiation source movement control means)
8b FPD movement control unit (detector movement control means)
11 Image generation unit (image generation means)
12 Image subtraction unit (image subtraction means)
13 Image reconstruction unit (image composition means)
21 Holder rotation mechanism (holder rotation means)
22 Holder rotation control unit (holder rotation control means)
25 Holder 25f Filter

Claims (9)

A radiation source for irradiating the subject with radiation;
A collimator that generates a fan-shaped radiation beam for slot imaging by limiting the spread of radiation emitted from the radiation source;
Radiation source control means for controlling the voltage of the radiation source;
Radiation source moving means for moving the radiation source relative to the subject;
Radiation source movement control means for controlling the radiation source movement means;
A high voltage region for transmitting radiation irradiated when the radiation source is at a high voltage, and a low voltage region for transmitting radiation irradiated when the radiation source is at a low voltage . Filters,
With moves following the movement of the radiation source, the Holder that the filter for subtraction imaging is held in one of a plurality provided holes,
Holder rotating means for rotating the holder;
The holder rotating means is configured to move one of the regions of the filter to a position where the radiation passes by reversing the rotation direction of the holder and then move the other region to a position where the radiation passes. Holder rotation control means for controlling
Radiation detecting means for detecting radiation that has passed through the filter and the subject;
Image generating means for generating an image based on the output of the radiation detecting means ;
An image subtracting means for obtaining a subtraction image by obtaining a difference between an image continuously shot on the radiation source under a high voltage condition and an image continuously shot on the radiation source under a low voltage condition;
A radiation imaging apparatus comprising: an image synthesizing unit that synthesizes the subtraction images to generate a synthesized image . The radiographic apparatus according to claim 1,
The holder rotating means switches whether to allow the radiation emitted from the radiation source to pass through the filter, and when taking an image, when the radiation source is at a high voltage, the high-voltage region of the filter is irradiated with radiation. The radiation imaging apparatus is characterized in that when the radiation source is at a low voltage, the low voltage region of the filter is moved to a position where the radiation passes. The radiographic apparatus according to claim 1 or 2 ,
The holder also holds a filter used for purposes other than subtraction image capturing,
The radiation imaging apparatus according to claim 1, wherein the holder rotating means rotates the holder to change a type of the filter through which radiation is transmitted. The radiographic apparatus according to any one of claims 1 to 3 ,
When performing imaging other than subtraction image capturing, the holder rotating means rotates the holder so that the radiation passes through holes other than the hole provided with the filter for capturing the subtraction image. apparatus. The radiation imaging apparatus according to any one of claims 1 to 6,
Detector moving means for moving the radiation detecting means relative to the subject;
Detector movement control means for controlling the detector movement means,
The radiation imaging apparatus according to claim 1, wherein when the radiation source is moved, the radiation detection means is moved relative to the subject. The radiographic apparatus according to claim 5 ,
The radiographic apparatus according to claim 1, wherein the image synthesizing unit generates a tomographic image when the subject is cut on a virtual plane as the synthesized image. The radiographic apparatus according to claim 6 ,
The image synthesizer generates the synthesized image by arranging and joining elongated subtraction images extending in a direction orthogonal to the moving direction of the radiation source in the moving direction of the radiation source. apparatus. The radiographic apparatus according to claim 1 ,
The image synthesizing unit divides the subtraction image into strip-like strip images extending in a direction orthogonal to the moving direction of the radiation source, and generates an intermediate image by joining the strip-like images having the same radiation irradiation direction. And a tomographic image obtained by cutting the subject from the intermediate image on a virtual plane as the synthesized image. The radiographic apparatus according to claim 1 ,
The synthesized image generated by the image synthesizing means is an elongated subtraction image extending in a direction orthogonal to the moving direction of the radiation source, arranged in the moving direction of the radiation source and connected,
A radiation imaging apparatus, wherein the radiation detection means does not move relative to a subject during imaging.

Images