JP2007097754A - Radiographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of artifacts in image and to improve image quality. <P>SOLUTION: An image reconstitution part 303 reconstructs the slant surface image of a subject so that an axial surface where a column direction j is a perpendicular corresponds to inclined slant surfaces T1 and T2 within the range of an elevation angle θ of X-rays emitted in the column direction j by a scan gantry 2 inside an area where the X-rays are emitted by the scan gantry 2 in the subject. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation imaging apparatus, and more particularly, based on projection data obtained by performing a scan that radiates radiation to a subject so as to rotate around the subject and detects radiation that has passed through the subject. The present invention relates to a radiation imaging apparatus that reconstructs an image of a subject.

  A radiography apparatus such as an X-ray CT (Computed Tomography) apparatus irradiates a subject with radiation such as X-rays and performs a scan for detecting the radiation transmitted through the subject. Then, based on the projection data of the subject obtained by performing this scan, a slice image of the tomogram of the subject is reconstructed. Such radiation imaging apparatuses are used in a wide range of applications such as medical applications and industrial applications.

  The X-ray CT apparatus performs scanning by moving the X-ray tube and the multi-row X-ray detector so as to rotate around the subject around the body axis direction of the subject. Here, the X-ray tube emits cone-shaped X-rays that radiate in the channel direction along the rotation direction rotating around the subject and the column direction along the rotation axis of the rotation to the subject. The multi-row X-ray detector, in which a plurality of detection elements are arranged along the channel direction and the column direction, detects the X-rays that have passed through the subject, thereby performing a scan. This scan is performed by an axial scan method, a helical scan method, or the like. Based on the projection data obtained by this scan, a plurality of slice images of a plurality of axial planes continuously arranged in the body axis direction of the subject are reconstructed.

  Here, weighted addition processing is performed on projection data facing each other by an image reconstruction method based on the Feldkamp method, such as an image reconstruction method called a three-dimensional backprojection method or a cone beam backprojection method. The slice image is reconstructed so as to correspond to an axial plane that is a vertical plane with the body axis direction as a normal (see, for example, Patent Document 1).

  However, in the projection data facing each other, the path through which X-rays are radiated when each projection data is acquired may differ greatly, resulting in inconsistencies during image reconstruction and artifacts etc. In some cases, the image quality may deteriorate.

  In particular, when scanning is performed by the axial scan method and the slice image is reconstructed using the axial surface corresponding to the end of the multi-row X-ray detector in the column direction as the image reconstruction plane, the X-ray tube Since the elevation angle (elevation angle) of the cone-shaped X-ray from the focal point toward the end of the multi-row X-ray detector increases as the number of rows of the multi-row X-ray detector increases, In some cases, the above-mentioned problems may become apparent, such as a lack of data area called a missing cone that does not transmit X-rays on the construction surface, contradiction of opposing data, and cone beam artifacts appear in the image. This is because the X-rays radiated from the X-ray tube to the detection elements in each column of the multi-row X-ray detector are arranged on the surface whose vertical direction is the column direction even at the end of the multi-row X-ray detector in the column direction. This is mainly due to the fact that image reconstruction is being performed assuming that

  In order to improve such problems, the scan in the axial scan method is performed a plurality of times at a plurality of different positions in the body axis direction, and the data corresponding to the data shortage area in each scan is determined by the data of the other scan. Image reconstruction is performed by complementing each other with a boundary region (see, for example, Patent Document 2 and Patent Document 3).

JP 2005-58598 A JP 2004-313655 A JP 2004-313657 A

  However, even in such a method, there is a case where the path of the compensated projection data is greatly different and a contradiction may occur, so that the above-described problem may not be sufficiently improved.

  Further, even when scanning is performed by the helical scan method, the above-described problems may become apparent because the paths of projection data facing each other may be greatly different.

  Accordingly, an object of the present invention is to provide a radiation imaging apparatus that can prevent the occurrence of artifacts in an image and improve the image quality.

  In order to achieve the above object, the radiation imaging apparatus of the present invention emits radiation to the subject so as to rotate around the subject, and performs a scan for detecting the radiation that has passed through the subject. A scan unit that obtains projection data of the subject; and an image reconstruction unit that reconstructs an image of the subject based on the projection data obtained by the scan unit, and the image reconstruction unit The image of the subject is reconstructed so as to correspond to an oblique plane whose surface is perpendicular to the rotation axis direction in which the scanning unit rotates the radiation around the subject.

  In order to achieve the above object, the radiation imaging apparatus of the present invention emits radiation to the subject so as to rotate around the subject, and performs a scan for detecting the radiation that has passed through the subject. A scan unit that obtains projection data of the subject; and an image reconstruction unit that reconstructs an image of the subject based on the projection data obtained by the scan unit, and the scan unit includes: A first scan that scans a first subject region of the subject at a first position in a rotation axis direction that rotates the radiation around the subject is different from the first position in the rotation axis direction. A second scan that scans a second subject region of the subject at a second position, and the image reconstruction unit includes the first subject region and the second subject region. Then, after reconstructing a plurality of oblique plane images so as to correspond to a plurality of oblique planes whose surfaces perpendicular to the rotation axis direction are inclined, the direction of the rotation axis is based on the plurality of oblique plane images. An image of the subject corresponding to a surface having a perpendicular line is reconstructed.

  According to the present invention, it is possible to provide a radiation imaging apparatus capable of preventing the occurrence of artifacts in an image and improving the image quality.

  Embodiments according to the present invention will be described.

<Embodiment 1>
The first embodiment of the present invention will be described below.

  FIG. 1 is a block diagram showing an overall configuration of an X-ray CT apparatus 1 in an embodiment according to the present invention, and FIG. 2 is a perspective view showing an essential part of the X-ray CT apparatus 1 in this embodiment. .

  As shown in FIG. 1, the X-ray CT apparatus 1 includes a scanning gantry 2, an operation console 3, and a subject transport unit 4. The X-ray CT apparatus 1 reconstructs an image of a subject using projection data obtained by irradiating the subject with X-rays and performing a scan for detecting X-rays transmitted through the subject. To do.

  The scanning gantry 2 will be described.

  As shown in FIG. 1, the scanning gantry 2 includes an X-ray tube 20, an X-ray tube moving unit 21, a collimator 22, an X-ray detector 23, a data collecting unit 24, an X-ray controller 25, a collimator controller 26, and a rotating unit 27. And a gantry controller 28, based on a control signal CTL 30 a from the operation console 3, the subject moved to the imaging space 29 by the subject transport unit 4 is scanned with X-rays, and projection data of the subject Get. In the scanning gantry 2, as shown in FIG. 2, the X-ray tube 20 and the X-ray detector 23 are arranged facing each other so as to sandwich an imaging space 29 into which the subject is carried. A collimator 22 is disposed between the X-ray tube 20 and the X-ray detector 23 so as to shape X-rays irradiated from the X-ray tube 20 onto the subject in the imaging space 29. Then, the scanning gantry 2 rotates the X-ray tube 20, the collimator 22, and the X-ray detector 23 around the subject around the subject, and at each view angle v around the subject, the X-ray By performing a scan in which X-rays are emitted from the tube 20 to the subject and the X-rays transmitted through the subject are detected by the X-ray detector 23, projection data of the subject is obtained. Here, as shown in FIG. 1, the view angle v refers to an angle at which the X-ray tube 20 is rotated around the subject with the y direction as the vertical direction being 0 °. Although details will be described later, in the present embodiment, the scanning gantry 2 detects the subject at the first position in the column direction j based on the scanning conditions set by the scanning condition setting unit 302 of the operation console 3. A first scan that scans the first subject region using the axial scan method, and a second scan that scans the second subject region of the subject using the axial scan method at a second position different from the first position in the column direction j. Two scans are performed. Each part of the scanning gantry 2 will be described sequentially.

  The X-ray tube 20 is, for example, a rotary anode type, and emits X-rays to a subject. As shown in FIG. 2, the X-ray tube 20 irradiates X-rays having a predetermined intensity to the imaging region of the subject via the collimator 22 based on a control signal CTL 251 from the X-ray controller 25. The X-ray tube 20 is rotated around the subject by the rotating unit 27 around the body axis direction z along the direction in which the subject transport unit 4 moves the subject to the imaging space 29, X-rays are emitted from around. Here, the X-ray tube 20 emits X-rays so as to spread radially in a channel direction i that is a rotation direction rotated by the rotating unit 27 and a column direction j that is a rotation axis direction of the rotation. The X-rays emitted from the X-ray tube 20 are formed into a cone shape by the collimator 22 and emitted to the X-ray detector 23 side.

  As shown in FIG. 2, the X-ray tube moving unit 21 moves the radiation center of the X-ray tube 20 in the column direction j based on a control signal CTL 252 from the X-ray controller 25.

  As shown in FIG. 2, the collimator 22 is disposed between the X-ray tube 20 and the X-ray detector 23. The collimator 22 includes, for example, a shielding plate that shields X-rays without transmitting them, and two shielding plates are provided in each of the channel direction i and the column direction j. Based on the control signal CTL 261 from the collimator controller 26, the collimator 22 independently moves two shielding plates provided in the channel direction i and the column direction j, and the X-ray irradiated from the X-ray tube 20 The line is blocked in each direction, shaped into a cone, and the irradiation range of X-rays irradiated to the subject is adjusted. That is, the collimator 22 varies the size of the opening through which the X-rays irradiated from the X-ray tube 20 pass by moving the shielding plate in the channel direction i, so that the X-ray radiation angle becomes a predetermined fan angle. In addition, the size of the opening is varied by moving the shielding plate in the column direction j, and the X-ray radiation angle is adjusted to a predetermined cone angle.

  The X-ray detector 23 detects X-rays irradiated from the X-ray tube 20 and transmitted through the subject in the imaging space 29, and generates projection data of the subject. The X-ray detector 23 is rotated around the subject by the rotating unit 27 together with the X-ray tube 20. Then, X-rays irradiated from the periphery of the subject and transmitted through the subject are detected to generate projection data.

  As shown in FIG. 2, the X-ray detector 23 is a so-called multi-row X-ray detector. For example, the X-ray tube 20 is rotated along the direction in which the X-ray tube 20 rotates around the subject in the imaging space 29 by the rotating unit 27. The detection elements 23a are two-dimensionally arranged in an array in the channel direction i and in the column direction j along the rotation axis direction that becomes the central axis when the X-ray tube 20 is rotated by the rotation unit 27. . For example, in the X-ray detector 23, about 1000 detection elements 23a are arranged in the channel direction i and about 8 are arranged in the column direction j. The X-ray detector 23 has a detection surface curved in a concave shape by a plurality of detection elements 23a arranged two-dimensionally.

  The detection element 23a constituting the X-ray detector 23 is configured as, for example, a solid state detector, and includes a scintillator (not shown) that converts X-rays into light, and a photodiode that converts light converted by the scintillator into electric charge. (Not shown). The detection element 23a is not limited to this. For example, the detection element 23a is a semiconductor detection element using cadmium tellurium (CdTe) or the like, or an ionization chamber type detection element using xenon (Xe) gas. good.

  The data collection unit 24 is provided for collecting projection data from the X-ray detector 23. The data collection unit 24 collects X-ray projection data detected by each detection element 23 a of the X-ray detector 23 and outputs it to the operation console 3. As shown in FIG. 2, the data collection unit 24 includes a selection / addition switching circuit (MUX, ADD) 241 and an analog-digital converter (ADC) 242. The selection / addition switching circuit 241 selects projection data by the detection element 23a of the X-ray detector 23 in accordance with the control signal CTL303 from the central processing unit 30, or adds a combination thereof, and the result is analog- Output to the digital converter 242. The analog-digital converter 242 converts the projection data selected by the selection / addition switching circuit 241 or added in an arbitrary combination from an analog signal to a digital signal and outputs it to the central processing unit 30.

  As shown in FIG. 2, the X-ray controller 25 outputs a control signal CTL 251 to the X-ray tube 20 in accordance with a control signal CTL 301 from the central processing unit 30 to control X-ray irradiation. The X-ray controller 25 controls, for example, the tube current and irradiation time of the X-ray tube 20. Further, the X-ray controller 25 outputs a control signal CTL 252 to the X-ray tube moving unit 221 in response to the control signal CTL 301 from the central processing unit 30 so as to move the radiation center of the X-ray tube 20 in the column direction j. To control.

  As shown in FIG. 2, the collimator controller 26 outputs a control signal CTL 261 to the collimator 22 in response to the control signal CTL 302 from the central processing unit 30, and shapes X-rays irradiated from the X-ray tube 20 onto the subject. Thus, the collimator 22 is controlled.

  As shown in FIG. 1, the rotating unit 27 has a cylindrical shape, and a photographing space 29 is formed at the center. The rotation unit 27 drives, for example, a motor (not shown) according to the control signal CTL 28 from the gantry controller 28 and rotates around the body axis direction z of the subject in the imaging space 29. That is, the rotating unit 27 rotates in the channel direction i with the column direction j as the rotation axis. The rotating unit 27 includes an X-ray tube 20, an X-ray tube moving unit 21, a collimator 22, an X-ray detector 23, a data collection unit 24, an X-ray controller 25, and a collimator controller 26, and supports each unit. ing. And the rotation part 27 supplies electric power to each part via a slip ring (not shown). Further, the rotating unit 27 rotates each part around the subject, and relatively changes the positional relationship between the subject and each part carried into the imaging space 29 in the rotation direction.

  As shown in FIGS. 1 and 2, the gantry controller 28 outputs a control signal CTL28 to the rotating unit 27 based on the control signal CTL304 from the central processing unit 30 of the operation console 3, so that the rotating unit 27 rotates. Control.

  The operation console 3 will be described.

  As shown in FIG. 1, the operation console 3 includes a central processing device 30, an input device 41, a display device 51, and a storage device 61.

  The central processing unit 30 in the operation console 3 performs various processes based on a command input to the input device 41 by the operator. The central processing unit 30 includes a computer and a program that causes the computer to function as various means.

  FIG. 3 is a block diagram showing the configuration of the central processing unit 30.

  As illustrated in FIG. 3, the central processing unit 30 includes a control unit 301, a scan condition setting unit 302, and an image reconstruction unit 303. Each unit includes a program that causes a computer to function as various means.

  The control unit 301 is provided to control each unit of the X-ray CT apparatus 1. The control unit 301 controls each unit based on a command input to the input device 41 by the operator. For example, the control unit 301 performs scanning by controlling each unit so as to correspond to the scan condition set by the scan condition setting unit 302 based on a command input to the input device 41 by the operator. Specifically, the control unit 301 outputs a control signal CTL 30 b to the subject transport unit 4, causes the subject transport unit 4 to transport the subject to the imaging space 29 and move it. Then, the control unit 301 outputs a control signal CTL 304 to the gantry controller 28 to rotate the rotation unit 27 of the scanning gantry 2. Then, the control unit 301 outputs a control signal CTL 301 to the X-ray controller 25 so that X-rays are emitted from the X-ray tube 20. And the control part 301 outputs the control signal CTL302 to the collimator controller 26, controls the collimator 22, and shape | molds X-ray | X_line. In addition, the control unit 301 outputs a control signal CTL 303 to the data collection unit 24 and controls to collect projection data obtained by the detection element 23a of the X-ray detector 23.

  The scan condition setting unit 302 sets scan conditions for operating each unit in the execution of scanning based on the scan parameters input to the input device 41 by the operator. For example, the scan condition setting unit 302 sets scan conditions for operating each unit so as to correspond to slice thickness, scan start position, scan end position, scan pitch, X-ray beam width, tube current value, and the like. Then, the scan condition setting unit 302 outputs data on the set scan condition to the control unit 301 to control each unit.

  In the present embodiment, the scan condition setting unit 302 performs the first scan that scans the first subject region of the subject by the axial scan method at the first position in the column direction j, and the first scan in the column direction j. The scan condition is set so that the second scan of the subject is scanned by the axial scan method at a second position different from the position. Here, the scan conditions for the first scan and the second scan are set so as to scan the first subject region and the second subject region adjacent to each other in the column direction j.

  The image reconstruction unit 303 reconstructs the slice image of the slice of the subject as a digital image composed of a plurality of pixels based on the projection data collected by the data collection unit 24 by performing the scan. For example, the image reconstruction unit 303 reconstructs an image of a plurality of slices of the subject from the projection data obtained by the scan by using the cone beam backprojection method, using the CT values as pixel values. That is, the image reconstruction unit 303 reconstructs an image of a slice of the subject using projection data that matches the pixels on the image reconstruction plane. Here, first, the image reconstruction unit 303 performs preprocessing such as offset correction, logarithmic correction, X-ray dose correction, and sensitivity correction on the projection data collected by the data collection unit 24. Then, the image reconstruction unit 303 performs a filtering process on the preprocessed projection data. Here, a filtering process is performed in which the image reconstruction function is superimposed after the Fourier transform and the inverse Fourier transform is performed. Thereafter, a three-dimensional backprojection process is performed on the projection data subjected to the filtering process, and then post-processing is performed to generate image data.

  In the present embodiment, the image reconstruction unit 303 has an axial plane (xy plane) having a normal in the body axis direction z and the column direction j within a region where X-rays are emitted from the scanning gantry 2 in the subject. Then, an oblique plane image of the slice of the subject is image-reconstructed using an oblique plane inclined in the column direction j within the range of the elevation angle of the X-rays radiated in the column direction j as an image reconstruction plane. Specifically, the image reconstruction unit 303 is a first subject region of the subject on which the first scan is performed, and radiates in the column direction j by the X-ray tube 20 during the first scan. The first oblique plane image of the first oblique plane in which the axial plane with the column direction j perpendicular to the column direction j is tilted in the column direction j within the range of the elevation angle of the X-ray corresponding to the first oblique plane. Reconstruct an image from projection data. Further, the image reconstruction unit 303 is a second subject region of the subject on which the second scan has been performed, and X emitted from the X-ray tube 20 in the column direction j during the second scan. Within the range of the elevation angle of the line, a second oblique plane image of the second oblique plane whose axial plane is inclined in the column direction i is reconstructed from projection data corresponding to the second oblique plane. Here, the image reconstructing unit 303 has an X-ray path from the X-ray tube 20 to the detection elements 23a arranged in the column direction j in the X-ray detector 23 when the first scan and the second scan are performed. The oblique planes that are parallel to each other are defined as a first oblique plane and a second oblique plane, and the first oblique plane image and the second oblique plane correspond to the first oblique plane and the second oblique plane. Each of the oblique plane images is reconstructed. For example, the image reconstruction unit 303 performs the first scan to the center of the detection element 23a located on the side where the second scan is performed at the end in the column direction j of the X-ray detector 23. The oblique plane along the radiation direction of the X-rays emitted from the X-ray tube 20 is defined as the first oblique plane, and the first oblique plane image is reconstructed from the projection data obtained by the first scan and the second scan. Constitute. Then, the image reconstruction unit 303 performs the second scan to the center of the detection element 23a located on the side where the first scan is performed at the end in the column direction j of the X-ray detector 23. The oblique plane along the radiation direction of the X-ray emitted from the X-ray tube 20 is set as the second oblique plane, and the second oblique plane image is reconstructed from the projection data obtained by the first scan and the second scan. To do.

  The input device 41 of the operation console 3 is composed of, for example, a keyboard and a mouse. The input device 41 inputs various information and commands such as scan parameters and subject information to the central processing unit 30 based on an input operation by the operator. For example, when setting the main scan condition, the input device 41 receives, as scan parameters, data on the scan start position, scan end position, scan pitch, X-ray beam width, tube current value, and slice thickness from the operator. Input based on the command.

  The display device 51 of the operation console 3 includes, for example, a CRT, and displays an image on the display surface based on a command from the central processing unit 30. In the present embodiment, the display device 51 displays, for example, the slice image reconstructed by the image reconstruction unit 303 on the display surface.

  The storage device 61 of the operation console 3 includes a memory and stores various data. In the storage device 61, the stored data is accessed by the central processing unit 30 as necessary.

  The subject transport unit 4 will be described.

  The subject transport unit 4 transports the subject between the inside and outside of the imaging space 29.

  FIG. 4 is a perspective view showing the configuration of the subject transport unit 4.

  As shown in FIG. 4, the subject transport unit 4 includes a table unit 401 and a table moving unit 402.

  The table unit 401 of the subject transport unit 4 is formed such that the placement surface on which the subject is placed is along a horizontal plane, and supports the subject on the placement surface. For example, the subject is laid on the table so as to be on his back and supported by the table unit 401 of the subject transport unit 4.

  The table moving unit 402 of the subject transport unit 4 includes a horizontal moving unit 402a that moves the table unit 401 in the horizontal direction H along the body axis direction z of the subject, and a vertical direction V perpendicular to the horizontal direction H. The table unit 401 is moved so as to carry the subject into the imaging space 29 based on the control signal CTL 30 b from the central processing unit 30.

  An operation of the X-ray CT apparatus 1 of the present embodiment will be described.

  FIG. 5 is a flowchart showing the operation of the X-ray CT apparatus 1 in the present embodiment.

  First, as shown in FIG. 5, an axial scan is performed (S11).

  Here, based on the control signal CTL 30 a from the operation console 3, the scanning gantry 2 scans the subject moved to the imaging space 29 by the subject transport unit 4 with an X-ray by the axial scan method, and the subject's Obtain projection data.

  FIG. 6 is a side view showing the scanning gantry 2 when performing scanning in the present embodiment.

  As shown in FIG. 6, the first scan S1 that scans the first subject region of the subject at the first position J1 in the column direction j by the axial scan method is different from the first position J1 in the column direction j. The scanning gantry 2 sequentially performs the second scan S2 in which the second subject region of the subject is scanned by the axial scan method at the second position J2.

  Specifically, when performing the first scan S1, as shown in FIG. 6, the scanning gantry 2 moves the X-ray tube 20 and the X-ray detector 23 at the first position J1 in the column direction j. The subject is swung around the subject along an axial plane (xy plane) having the column direction j as a rotation axis and the column direction j and the body axis direction z as a perpendicular line. Then, while the X-ray tube 20 and the X-ray detector 23 are swung around the subject, the X-ray tube 20 irradiates the subject with X-rays having a predetermined cone angle α and transmits through the subject. The X-ray detector 23 detects the X-rays thus generated and generates projection data. The data collection unit 24 collects projection data from the X-ray detector 23.

  Then, the table moving unit 402 is configured so that the second scan S2 in which the second subject region of the subject is scanned by the axial scan method at the second position J2 different from the first position J1 in the column direction j. Moves along the body axis direction z and the column direction j. Here, as shown in FIG. 6, the table moving unit 402 moves the table unit 401 in the column direction so as to scan the first subject region and the second subject region that are adjacent to each other without any interval in the column direction j. Move along j.

  Thereafter, as shown in FIG. 6, at the second position J2 in the column direction j, the scanning gantry 2 uses the X-ray tube 20 and the X-ray detector 23 as the rotation axis in the column direction j and the axial plane (xy plane). ) Is swung around the subject so as to follow. Then, while the X-ray tube 20 and the X-ray detector 23 are swung around the subject, the X-ray tube 20 irradiates the subject with X-rays having a predetermined cone angle α and transmits through the subject. The X-ray detector 23 detects the X-rays thus generated and generates projection data. The data collection unit 24 collects projection data from the X-ray detector 23.

  Next, as shown in FIG. 5, image reconstruction of the oblique plane image is performed (S21).

  Here, the image reconstruction unit 303 reconstructs a slice image of the slice of the subject based on the projection data obtained by the above scan.

  FIG. 7 is a side view showing an oblique plane on which the image reconstruction unit 303 reconstructs an image in the present embodiment.

  As shown in FIG. 7, the X-ray emitted from the X-ray tube 20 in the column direction j is the first object region of the object on which the first scan S1 has been performed. Within the range of the elevation angle θ, the image reconstruction unit 303 obtains a first oblique plane image of the first oblique plane T1 whose axial plane is inclined in the column direction j from projection data corresponding to the first oblique plane T1. Reconstruct the image. Further, in the second subject region of the subject on which the second scan S2 has been performed, the elevation angle θ of the X-ray emitted in the column direction j by the X-ray tube 20 during the second scan S2 Within the range, the image reconstruction unit 303 reconstructs a second oblique plane image for the second oblique plane T2 with the inclined axial plane from projection data corresponding to the second oblique plane T2.

  Here, as shown in FIG. 7, when the first scan S <b> 1 and the second scan S <b> 2 are performed, X-rays traveling from the X-ray tube 20 toward the detection elements 23 a arranged in the column direction j in the X-ray detector 23 are detected. The oblique planes in which the paths are parallel to each other are defined as the first oblique plane T1 and the second oblique plane T2, and the first oblique plane T1 and the second oblique plane T2 correspond to the first oblique plane T1 and the second oblique plane T2. The image reconstruction unit 303 reconstructs the oblique plane image and the second oblique plane image, respectively.

  Specifically, as shown in FIG. 7, when the first oblique plane image is reconstructed, the column direction of the X-ray detector 23 when the view angle v is 0 degrees in the execution of the first scan S1. An oblique plane along the radiation direction of the X-rays radiated from the X-ray tube 20 to the center of the detection element 23a located on the side where the second scan S2 is performed at the end of j is an image reconstruction unit. Reference numeral 303 denotes a first oblique plane T1. When the second oblique plane image is reconstructed, as shown in FIG. 7, the end of the X-ray detector 23 in the column direction j when the view angle v is 180 degrees in the execution of the two scans S2. The image reconstruction unit 303 displays an oblique plane along the radiation direction of the X-rays emitted from the X-ray tube 20 toward the center of the detection element 23a located on the side where the first scan S2 is performed. The second oblique plane T2. That is, the first oblique plane image and the first oblique plane image T1 and the second oblique plane T2 in which the axial planes having the vertical direction in the column direction j and the body axis direction z are inclined with respect to the y direction are used as image reconstruction planes. The image reconstruction unit 303 reconstructs the second oblique plane image.

  FIG. 8 is a diagram illustrating a geometric relationship on the yz plane when performing image reconstruction.

  In the present embodiment, as shown in FIG. 8, when the oblique plane as described above is used as the image reconstruction plane R and the pixels P of the image reconstruction plane R are reconstructed, the following mathematical formula (1 The image reconstruction is performed using the projection data obtained by the detection element of the multi-row X-ray detector 23 corresponding to the row position (row_pos) as shown in FIG.

  row_pos = (zpos (x, y) * XL / L) / detector_configuration (1)

  In Equation (1), row_pos indicates the position of the column unit from the center of the multi-row X-ray detector 23. Further, as shown in FIG. 8, zpos (x, y) is a position connecting the focal point F of the X-ray tube 20 and the center in the body axis direction z (column direction j) of the multi-row X-ray detector 23 ( The distance from the xy plane) to the pixel P on the image reconstruction plane R in the body axis direction z (column direction j) is shown. 8, L indicates the distance that the pixel P on the image reconstruction plane R is away from the focal point F of the X-ray tube 20 in the y direction. Further, as shown in FIG. 8, XL indicates that the focal point of the X-ray tube 20 and the rotation axis C that becomes an axis when the focal point F of the X-ray tube 20 rotates around the subject are separated in the y direction. Shows the distance. Further, detector_configuration represents a conversion coefficient between coordinates in the z direction and coordinates in column units.

  Next, as shown in FIG. 5, an oblique plane image is displayed (S31).

  Here, as described above, the display device 51 displays the first oblique plane image and the second oblique plane image reconstructed by the image reconstruction unit 303 on the display surface.

  As described above, in the present embodiment, the X-ray tube 20 rotates around the subject around the column direction j as the rotation axis, and emits X-rays from the periphery of the subject to the subject. The scanning gantry 2 obtains the projection data of the subject by performing a scan for detecting the transmitted X-rays by the axial scan method. Then, based on the projection data obtained by the scanning gantry 2, the image reconstruction unit 303 reconstructs an image of the slice of the subject by the cone beam back projection method. Here, the image reconstruction unit 303 is in a region where X-rays are emitted from the scanning gantry 2 in the subject and within the range of the elevation angle θ of the X-rays emitted from the scanning gantry 2 in the column direction j. The oblique plane images of the subject are respectively reconstructed so that the plane with the column direction j as a perpendicular corresponds to the oblique planes T1 and T2 inclined in the column direction j. Specifically, the image reconstruction unit 303 reconstructs the oblique plane image so as to correspond to the oblique planes T1 and T2 along the radiation direction in which the scanning gantry 2 emits X-rays in the column direction j. . Therefore, since this embodiment suppresses the occurrence of contradiction in the opposing data, it is possible to prevent the occurrence of artifacts in the reconstructed oblique plane image and improve the image quality. Can do.

<Embodiment 2>
The second embodiment of the present invention will be described below.

  In the present embodiment, the operation of the image reconstruction unit 303 is different from that in the first embodiment. Except for this point, the present embodiment is the same as the first embodiment. For this reason, description is omitted about the overlapping part.

  FIG. 9 is a flowchart showing the operation of the X-ray CT apparatus 1 in this embodiment.

  First, as shown in FIG. 9, an axial scan is performed (S111).

  Here, as in the first embodiment, as shown in FIG. 6, the first scan S1 that scans the first subject region of the subject at the first position J1 in the column direction j by the axial scan method, and the column direction The scanning gantry 2 sequentially performs the second scan S2 in which the second subject region of the subject is scanned by the axial scan method at the second position J2 different from the first position J1 at j.

  Next, as shown in FIG. 9, image reconstruction of the oblique plane image is performed (S121).

  Here, as in the first embodiment, as shown in FIG. 7, when the view angle v is 0 ° in the first scan S1, the second scan is the end of the X-ray detector 23 in the column direction j. The image reconstruction unit 303 uses the first oblique plane T1 along the radiation direction of the X-rays emitted from the X-ray tube 20 to the center of the detection element 23a located on the side where S2 is performed as an image reconstruction surface. The first oblique plane image is reconstructed. Then, as shown in FIG. 7, when the view angle v is 180 ° in the second scan S2, it is located at the end of the X-ray detector 23 in the column direction j and on the side where the first scan S1 is performed. The second oblique plane T2 along the X-ray emission direction radiated from the X-ray tube 20 to the center of the detection element 23a to be used is an image reconstruction plane, and the image reconstruction unit 303 performs image reconstruction on the second oblique plane image. Constitute.

  In addition, in the present embodiment, image reconstruction of oblique plane images for other oblique planes is performed.

  FIG. 10 is a side view showing an oblique plane on which the image reconstruction unit 303 reconstructs an image in the present embodiment.

  As shown in FIG. 10, when the view angle v is 180 ° in the first scan S1, the detection is located at the end in the column direction j of the X-ray detector 23 on the side where the second scan S2 is performed. The image reconstruction unit 303 reconstructs the third oblique plane image using the third oblique plane T3 along the X-ray emission direction radiated from the X-ray tube 20 to the center of the element 23a as an image reconstruction plane. . As shown in FIG. 10, when the view angle v is 0 ° in the second scan S2, it is located at the end of the X-ray detector 23 in the column direction j and on the side where the first scan S1 is performed. The image reconstruction unit 303 converts the fourth oblique plane image into an image reconstruction plane using the fourth oblique plane T4 along the radiation direction of the X-rays emitted from the X-ray tube 20 to the center of the detection element 23a. Constitute. That is, the third oblique plane T3 and the fourth oblique plane T4 in which the axial plane is inclined in the direction opposite to the direction in which the first oblique plane T1 and the second oblique plane T2 are inclined with respect to the y direction are used as the image reconstruction plane. The image reconstruction unit 303 reconstructs the third oblique plane image and the fourth oblique plane image, respectively.

  In addition, although not particularly illustrated, in addition to this, when the view angle v is 90 ° in the first scan S1, it is the end of the X-ray detector 23 in the column direction j and the side on which the second scan S2 is performed. The image reconstruction unit 303 uses the fifth oblique plane T5 along the radiation direction of the X-rays radiated from the X-ray tube 20 to the center of the detection element 23a located at the image reconstruction plane as an image reconstruction plane. Reconstruct the image. When the view angle v is 270 ° in the second scan S2, the end of the X-ray detector 23 in the column direction j and to the center of the detection element 23a located on the side where the first scan S1 is performed. The image reconstruction unit 303 reconstructs the sixth oblique plane image using the sixth oblique plane T6 along the radiation direction of the X-rays emitted by the X-ray tube 20 as an image reconstruction plane. That is, the fifth oblique plane T5 and the sixth oblique plane T6 whose axial planes are inclined with respect to the x direction are used as image reconstruction planes, and the image reconstruction unit 303 obtains the fifth oblique plane image and the sixth oblique plane image. Reconstruct each image.

  Further, when the view angle v is 270 ° in the first scan S1, the end of the X-ray detector 23 in the column direction j and to the center of the detection element 23a located on the side where the second scan S2 is performed. The image reconstruction unit 303 reconstructs the seventh oblique plane image using the seventh oblique plane T7 along the radiation direction of the X-rays emitted by the X-ray tube 20 as an image reconstruction plane. When the view angle v is 90 ° in the second scan S2, the end of the X-ray detector 23 in the column direction j and to the center of the detection element 23a located on the side where the first scan S1 is performed. The image reconstruction unit 303 reconstructs an eighth oblique plane image using the eighth oblique plane T8 along the X-ray emission direction emitted by the X-ray tube 20 as an image reconstruction plane. That is, the seventh oblique plane T7 and the eighth oblique plane T8 in which the axial plane is inclined in a direction opposite to the direction in which the fifth oblique plane T5 and the sixth oblique plane T6 are inclined with respect to the y direction are used as image reconstruction planes. The image reconstruction unit 303 reconstructs the seventh oblique plane image and the eighth oblique plane image.

  Next, as shown in FIG. 9, the image reconstruction of the axial image is performed (S122).

  Here, both the first subject region in which the first scan is performed and the second subject region in which the second scan is performed are surfaces having the column direction j and the body axis direction z as perpendicular lines. The image reconstruction unit 303 reconstructs an axial image corresponding to the axial plane including the image based on a plurality of oblique plane images obtained by image reconstruction as described above.

  FIG. 11 is a side view showing an oblique plane corresponding to an oblique plane image reconstructed by the image reconstruction unit 303 and an axial plane corresponding to an axial plane image reconstructed from the oblique plane image in the present embodiment. FIG. In FIG. 11, FIG. 11A shows the first oblique plane T1, the second oblique plane T2, the third oblique plane T3, the fourth oblique plane T4, and the fifth, in which the oblique plane image is reconstructed as described above. FIG. 6 is a side view showing an oblique plane T5, a sixth oblique plane T6, a seventh oblique plane T7, and an eighth oblique plane T8 with the x direction as a line of sight. In FIG. 11A, for the fifth oblique plane T5, the sixth oblique plane T6, the seventh oblique plane T7, and the eighth oblique plane T8, the center line in the x direction is indicated by a dotted line in order to simplify the drawing. However, it is actually inclined in the x direction.

  As shown in FIGS. 11 (a) and 11 (b), in this embodiment, oblique planes T1, T2, T3, T4, T5 intersecting a plurality of axial surfaces A1, A2, A3, A4 of the subject. , T6, T7, and T8, the image reconstructing unit 303 reconstructs the axial images of the plurality of axial planes A1, A2, A3, and A4. Specifically, a plurality of oblique plane images corresponding to the plurality of oblique planes T1, T2, T3, T4, T5, T6, T7, and T8 are subjected to weighted addition processing to perform cross-sectional conversion, and along the column direction j. For each of the first axial plane A1, the second axial plane A2, the third axial plane A3, and the fourth axial plane A4 that are sequentially arranged, the image reconstruction unit 303 performs the first axial image, the second axial image, the third axial image, The fourth axial image is reconstructed. For example, as shown in FIG. 11B, the second axial image corresponding to the second axial surface A2 located between the first axial surface A1 and the third axial surface A3 is shown in FIG. As shown, the first oblique plane image and the third oblique plane for the first oblique plane T1, the third oblique plane T3, the fifth oblique plane T5, and the seventh oblique plane T7 that are close to and intersect the second axial plane A2. Each pixel value of the image, the fifth oblique plane image, and the seventh oblique plane image is reconstructed by performing weighted addition processing according to the pixel position.

  Next, as shown in FIG. 9, an axial image is displayed (S131).

  Here, as described above, the display device 51 displays a plurality of axial images reconstructed by the image reconstruction unit 303 on the display surface.

  As described above, in the present embodiment, the first scan in which the first subject region of the subject is scanned by the axial scan method at the first position J1 in the column direction j, and the first position in the column direction j. The scanning gantry 2 performs a second scan in which the second subject region of the subject is scanned by the axial scan method at a second position J2 different from J1. Here, the scanning gantry 2 performs the first scan and the second scan so that the first subject region and the second subject region are adjacent to each other in the column direction j. Thereafter, the first subject region and the second subject region correspond to a plurality of oblique planes in which the axial plane is inclined within the range of the elevation angle of the X-rays emitted in the column direction j by the scanning gantry 2. In addition, the image reconstruction unit 303 reconstructs a plurality of oblique plane images. Here, in the column direction j, the image reconstruction unit 303 reconstructs a plurality of oblique plane images using the oblique plane along the radiation direction in which the scanning gantry 2 emits X-rays as an image reconstruction plane. Then, based on the plurality of oblique plane images, the image reconstruction unit 303 reconstructs an axial image corresponding to the axial plane. Here, the image reconstruction unit uses an oblique plane image corresponding to an oblique plane intersecting the axial plane as an axial image corresponding to the axial plane including both the first subject area and the second subject area. 303 reconstructs an image. Therefore, according to the present embodiment, in the projection data facing each other, the path through which X-rays are emitted when each projection data is acquired is the same, and thus an artifact is generated in the reconstructed axial image. Can be prevented, and the image quality can be improved.

<Embodiment 3>
The third embodiment of the present invention will be described below.

  In the present embodiment, the operations of the scanning gantry 2 and the image reconstruction unit 303 are different from those in the first embodiment. Except for this point, the present embodiment is the same as the first embodiment. For this reason, description is omitted about the overlapping part.

  FIG. 12 is a flowchart showing the operation of the X-ray CT apparatus 1 in this embodiment.

  First, as shown in FIG. 12, a helical scan is performed (S211).

  Here, based on the control signal CTL 30a from the operation console 3, the subject moved to the imaging space 29 by the subject transport unit 4 is scanned by the scanning gantry 2 with an X-ray by the helical scan method, and the subject's Obtain projection data. For example, the scanning gantry 2 performs a helical scan type scan in which the helical pitch is 1.5 and the subject is rotated once.

  Next, as shown in FIG. 12, image reconstruction of the oblique plane image is performed (S21).

  Here, the image reconstruction unit 303 reconstructs a slice image of the slice of the subject based on the projection data obtained by the above scan.

  FIG. 13 is a side view showing the relationship between the oblique plane reconstructed by the image reconstruction unit 303 and the scanning gantry 2 in this embodiment, with the y direction as the line of sight. FIG. 13 shows the relationship between the scanning gantry 2 and the oblique plane when the view angle is 90 ° and 270 ° in the helical scan method.

  In the present embodiment, as shown in FIG. 13, the center value of the rotation angle (360 ° in the present embodiment) at which the X-ray tube 20 rotates around the subject when performing the scan in the helical scan method. Scan S90 at a view angle (90 ° in the present embodiment) at −90 ° with respect to (180 ° in the present embodiment) and scan at a view angle (270 ° in the present embodiment) at + 90 °. In S270, the image reconstructing unit 303 displays an oblique plane T in which the axial plane is inclined within the range of the elevation angle θ of the X-rays radiated in the column direction j by the X-ray tube 20 during each scan S90 and S270. An oblique plane image is reconstructed as a reconstruction plane. For example, in each of the scans S90 and S270, the projection data obtained in the scan S90 having a view angle of 90 ° and the projection data obtained in the scan S270 at 270 ° that is the view angle facing the scan S90 are used. The image reconstruction unit 303 reconstructs an oblique plane image of the oblique plane T with which the paths of the emitted X-rays coincide with each other by the cone beam reconstruction method. That is, the image reconstruction unit 303 performs weighted addition processing corresponding to the oblique plane T on the projection data obtained at mutually opposing view angles, and reconstructs the oblique plane image.

  Next, as shown in FIG. 12, an oblique plane image is displayed (S31).

  Here, as described above, the display device 51 displays the oblique plane image reconstructed by the image reconstruction unit 303 on the display surface.

  As described above, in this embodiment, the X-ray tube 20 rotates around the subject around the column direction j, emits X-rays from the periphery of the subject to the subject, and passes through the subject. The scanning gantry 2 obtains the projection data of the subject by performing the scan for detecting the X-rays by the helical scan method. Then, based on the projection data obtained by the scanning gantry 2, the image reconstruction unit 303 reconstructs an image of the slice of the subject by the cone beam back projection method. Here, the image reconstruction unit 303 is axial in the region where X-rays are emitted from the scanning gantry 2 in the subject and within the range of the elevation angle θ of the X-rays emitted from the scanning gantry 2 in the column direction j. The oblique plane image of the subject is reconstructed so that the plane corresponds to the oblique plane T inclined in the column direction j. Specifically, the image reconstruction unit 303 performs oblique plane images on the oblique plane T along the radial direction radiated in the scans S90 and S270 having mutually opposite view angles, such as 90 ° and 270 °, An image is reconstructed by performing weighted addition processing so that the projection data obtained in the scans S90 and S270 at the opposite view angles correspond to the oblique plane T. That is, the image reconstruction unit 303 reconstructs an oblique plane image using the oblique plane T along the spiral orbit in the helical scan method as an image reconstruction plane. Therefore, in the present embodiment, in the projection data facing each other, the path through which X-rays are emitted when each projection data is acquired is the same, and thus an artifact is generated in the oblique plane image that has been reconstructed. This can be prevented and the image quality can be improved.

<Embodiment 4>
Hereinafter, Embodiment 4 of the present invention will be described.

  In the present embodiment, the operation of the image reconstruction unit 303 is different from that in the third embodiment. Except for this point, the present embodiment is the same as the third embodiment. For this reason, description is omitted about the overlapping part.

  FIG. 14 is a flowchart showing the operation of the X-ray CT apparatus 1 in the present embodiment.

  First, as shown in FIG. 14, a helical scan is performed (S311).

  Here, as in the third embodiment, the scanning gantry 2 performs scanning in the helical scan method.

  Next, as shown in FIG. 14, image reconstruction of the oblique plane image is performed (S321).

  FIG. 15 is a side view showing an oblique plane on which the image reconstruction unit 303 reconstructs an image in the present embodiment. 15A is a side view with the x direction as the line of sight, and FIG. 15B is a side view with the y direction as the line of sight.

  Here, as shown in FIG. 15, a plurality of oblique planes T11 along the radiation direction of X-rays radiated at mutually opposing view angles during the scan in the helical scan system performed by the scanning gantry 2 are provided. Similar to the first embodiment, the image reconstruction unit 303 generates a plurality of oblique plane images corresponding to T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, and T23. Reconfigure.

  Next, as shown in FIG. 14, the image reconstruction of the axial image is performed (S322).

  FIG. 16 is a side view showing an axial plane on which the image reconstruction unit 303 reconstructs an image in the present embodiment. 16A is a side view with the x direction as the line of sight, and FIG. 16B is a side view with the y direction as the line of sight.

  Here, as shown in FIG. 16, the axial images corresponding to the plurality of axial surfaces A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, A23 are as described above. An image reconstruction unit based on a plurality of oblique plane images reconstructed to correspond to a plurality of oblique planes T11, T12, T13, T14, T15, T16, T17, T18, T19, T20, T21, T22, and T23. 303 reconstructs an image. For example, as shown in FIG. 16, for the second axial image corresponding to the second axial surface A2 located between the first axial surface A1 and the third axial surface A3, as shown in FIG. The image reconstruction is performed by weighting and adding the pixel values of the oblique plane image for the plurality of oblique planes T11, T12, and T13 adjacent to the 2-axial plane A2 according to the pixel position.

  Next, as shown in FIG. 14, an axial image is displayed (S331).

  Here, as described above, the display device 51 displays a plurality of axial images reconstructed by the image reconstruction unit 303 on the display surface.

  As described above, the present embodiment corresponds to a plurality of oblique planes along the radiation direction of the radiation emitted at the mutually opposing view angles during the scan in the helical scan system performed by the scanning gantry 2. As described above, the image reconstruction unit 303 reconstructs a plurality of oblique plane images. In other words, the image reconstruction unit 303 reconstructs a plurality of oblique plane images using the plurality of oblique planes T along the spiral trajectory in the scan by the helical scan method as an image reconstruction plane. Thereafter, based on the plurality of oblique plane images reconstructed, the image reconstruction unit 303 reconstructs a plurality of axial images corresponding to the plurality of axial surfaces of the subject. Therefore, the present embodiment prevents the occurrence of artifacts in the axial image because the paths in which X-rays are emitted when the projection data are acquired are the same in the projection data facing each other. Image quality can be improved.

  In the above embodiment, the X-ray CT apparatus 1 corresponds to the radiation imaging apparatus of the present invention. In the above embodiment, the scanning gantry 2 corresponds to the scanning unit of the present invention. In the above embodiment, the X-ray tube 20 corresponds to the radiation source of the present invention. In the above embodiment, the X-ray detector 23 corresponds to the detection unit of the present invention. Moreover, in said embodiment, the rotation part 27 is corresponded to the rotation part of this invention. In the above embodiment, the image reconstruction unit 303 corresponds to the image reconstruction unit of the present invention. The “elevation angle of the X-ray” is based on the plane where the X-ray emitted from the focal point of the X-ray tube 20 connects the focal point of the X-ray tube 20 and the center of the X-ray detector 23 in the column direction j. This corresponds to the angle emitted in the column direction j.

  In implementing the present invention, the present invention is not limited to the above-described embodiment, and various modifications can be employed.

  For example, in the above embodiment, an example in which X-rays are used as radiation has been described, but the present invention is not limited to this. For example, radiation such as gamma rays may be used.

  Further, for example, in the above-described embodiment, an example in which an oblique plane image of an oblique plane along the radiation direction of X-rays radiated in the column direction j is described is described, but the present invention is not limited to this. . FIG. 17 is a side view showing an oblique plane in which the image reconstruction unit 303 reconstructs an image from projection data obtained by scanning using the axial scan method in a modification of the embodiment according to the present invention. FIG. 18 is a side view showing an oblique plane in which the image reconstruction unit 303 reconstructs an image from projection data obtained by scanning using the helical scan scan method in a modification of the embodiment according to the present invention. . As shown in FIGS. 17 and 18, for example, an image corresponding to a surface T in which a plurality of oblique planes are connected so as to draw a curved surface may be reconstructed.

  For example, in the above-described embodiment, an example in which the helical scan is performed with a helical pitch of 1.5 has been described. However, the present invention is not limited to this. FIG. 19 shows an oblique plane that the image reconstruction unit 303 reconstructs when a helical scan is performed at a helical pitch of 1.0 in a modification of the embodiment according to the present invention, and a scanning gantry. 2 is a side view showing the relationship with FIG. FIG. 20 shows an oblique plane in which the image reconstruction unit 303 reconstructs an image when a helical scan is performed at a helical pitch of 0.5 in a modification of the embodiment of the present invention. It is a side view which shows the relationship with the scanning gantry 2 by making a y direction a line of sight. As shown in FIG. 19 and FIG. 20, the present invention may be applied when a helical scan type scan is performed at an arbitrary helical pitch.

FIG. 1 is a block diagram showing an overall configuration of an X-ray CT apparatus 1 in Embodiment 1 according to the present invention. FIG. 2 is a configuration diagram illustrating a main part of the X-ray CT apparatus 1 according to the first embodiment of the present invention. FIG. 3 is a block diagram showing a configuration of the central processing unit 30 in the first embodiment according to the present invention. FIG. 4 is a perspective view showing a configuration of the subject transport unit 4 in the first embodiment according to the present invention. FIG. 5 is a flowchart showing the operation of the X-ray CT apparatus 1 according to the first embodiment of the present invention. FIG. 6 is a side view showing the scanning gantry 2 when performing scanning in the first embodiment of the present invention. FIG. 7 is a side view showing an oblique plane on which the image reconstruction unit 303 reconstructs an image according to the first embodiment of the present invention. FIG. 8 is a diagram illustrating a geometric relationship on the yz plane when performing image reconstruction. FIG. 9 is a flowchart showing the operation of the X-ray CT apparatus 1 according to the second embodiment of the present invention. FIG. 10 is a side view showing an oblique plane on which the image reconstruction unit 303 reconstructs an image according to the second embodiment of the present invention. FIG. 11 shows an oblique plane corresponding to an oblique plane image reconstructed by the image reconstruction unit 303 and an axial plane corresponding to an axial plane image reconstructed from the oblique plane image in Embodiment 2 according to the present invention. FIG. FIG. 12 is a flowchart showing the operation of the X-ray CT apparatus 1 according to the third embodiment of the present invention. FIG. 13 is a side view showing the relationship between the oblique plane reconstructed by the image reconstruction unit 303 and the scanning gantry 2 in the third embodiment according to the present invention, with the y direction as the line of sight. FIG. 14 is a flowchart showing the operation of the X-ray CT apparatus 1 in Embodiment 4 according to the present invention. FIG. 15 is a side view showing an oblique plane on which the image reconstruction unit 303 reconstructs an image according to the fourth embodiment of the present invention. FIG. 16 is a side view showing an axial plane on which the image reconstruction unit 303 reconstructs an image according to the fourth embodiment of the present invention. FIG. 17 is a side view showing an oblique plane in which the image reconstruction unit 303 reconstructs an image from projection data obtained by scanning using the axial scan method in a modification of the embodiment according to the present invention. FIG. 18 is a side view showing an oblique plane in which the image reconstruction unit 303 reconstructs an image from projection data obtained by scanning using the helical scan scan method in a modification of the embodiment according to the present invention. FIG. 19 shows an oblique plane that the image reconstruction unit 303 reconstructs when a helical scan is performed at a helical pitch of 1.0 in a modification of the embodiment according to the present invention, and a scanning gantry. 2 is a side view showing the relationship with FIG. FIG. 20 shows an oblique plane that the image reconstruction unit 303 reconstructs when a helical scan is performed at a helical pitch of 0.5 in a modification of the embodiment according to the present invention, and a scanning gantry. 2 is a side view showing the relationship with FIG.

Explanation of symbols

1 ... X-ray CT apparatus (radiation imaging apparatus),
2. Scanning gantry (scanning part)
3. Operation console,
4 ... Subject transport section,
20 ... X-ray tube (radiation source),
21 ... X-ray tube moving part,
22 ... Collimator,
23 ... X-ray detector (detector),
23a ... detecting element,
24 ... Data collection unit,
241 ... Selection / addition switching circuit,
242 ... Analog-to-digital converter,
25 ... X-ray controller,
26 ... Collimator controller,
27: Rotating part (rotating part),
28 ... Gantry controller,
29 ... Shooting space,
30 ... Central processing unit,
41 ... input device,
51. Display device,
61 ... Storage device,
301 ... control unit,
302: Scan condition setting unit,
303 ... Image reconstruction unit (image reconstruction unit)
401 ... table part,
402: Table moving unit

Claims (20)

A scan unit that emits radiation to the subject so as to rotate around the subject, and obtains projection data of the subject by performing a scan that detects the radiation transmitted through the subject; and
An image reconstruction unit that reconstructs an image of the subject based on the projection data obtained by the scan unit, and
The image reconstruction unit reconstructs an image of the subject so as to correspond to an oblique plane with a plane perpendicular to a rotation axis direction in which the scanning unit rotates the radiation around the subject. Radiography equipment. In the image reconstruction unit, a surface having a perpendicular to a rotation axis direction in which the scanning unit rotates the radiation around the subject is in a region where the radiation is emitted from the scanning unit in the subject. The image of the subject is reconstructed so as to correspond to an oblique plane inclined in the rotation axis direction within an elevation angle range of the radiation emitted in the rotation axis direction. Radiography equipment. The image reconstruction unit reconstructs an image of the subject so as to correspond to the oblique plane along the radiation direction in which the scanning unit emits the radiation in the rotation axis direction. Radiography equipment. The radiographic apparatus according to claim 1, wherein the scan unit performs the scan by an axial scan method. The scan unit performs the scan by a helical scan method,
The image reconstruction unit
During the helical scan method performed by the scanning unit, the image of the subject is re-imaged so as to correspond to the oblique plane along the radiation direction of the radiation emitted at mutually opposing view angles. The radiation imaging apparatus according to any one of claims 1 to 4. The image reconstruction unit reconstructs a plurality of oblique plane images so as to correspond to the plurality of oblique planes having different positions in the rotation axis direction, and then performs the rotation based on the plurality of oblique plane images. The radiation imaging apparatus according to claim 5, wherein an image of the subject corresponding to a plane having a perpendicular axis is reconstructed. The scanning unit
A radiation source emitting the radiation;
A detector that detects the radiation emitted from the radiation source and transmitted through the subject;
A rotation unit that rotates the radiation source and the detection unit around the subject around the rotation axis direction;
The radiation source radiates the radiation so as to spread radially in the rotation direction rotated by the rotating unit and the rotation axis direction,
The radiation imaging apparatus according to claim 1, wherein the detection unit includes a plurality of detection elements that detect the radiation along the rotation direction and the rotation axis direction. The radiation imaging apparatus according to claim 7, wherein the radiation source emits X-rays as the radiation. The radiation imaging apparatus according to claim 1, further comprising: a display unit configured to display an image of the subject reconstructed by the image reconstruction unit on a display surface. A scan unit that emits radiation to the subject so as to rotate around the subject, and obtains projection data of the subject by performing a scan that detects the radiation transmitted through the subject; and
An image reconstruction unit that reconstructs an image of the subject based on the projection data obtained by the scan unit, and
The scan unit scans a first subject region of the subject at a first position in a rotation axis direction that rotates the radiation around the subject, and the first scan in the rotation axis direction. Performing a second scan for scanning a second subject region of the subject at a second position different from the first position;
The image reconstructing unit includes a plurality of oblique planes corresponding to a plurality of oblique planes, the first subject area and the second subject area being inclined with a surface perpendicular to the rotation axis direction. A radiographic apparatus that reconstructs an image of the subject corresponding to a plane with the rotation axis direction as a normal after reconstructing a planar image based on the plurality of oblique planar images. The image reconstruction unit includes the first subject region and the second subject region, and the direction of the rotation axis is within the range of the elevation angle of the radiation emitted in the direction of the rotation axis by the scanning unit. The radiation imaging apparatus according to claim 10, wherein the plurality of oblique plane images are reconstructed so that a plane having a perpendicular line corresponds to a plurality of oblique planes inclined in the rotation axis direction. The radiation imaging apparatus according to claim 10, wherein the image reconstruction unit reconstructs the plurality of oblique plane images in a projection data space. The radiation imaging apparatus according to claim 10, wherein the image reconstruction unit reconstructs the plurality of oblique plane images in an image space. The radiation imaging apparatus according to claim 10, wherein the scan unit performs the first scan and the second scan by an axial scan method. The radiation according to claim 14, wherein the scan unit performs the first scan and the second scan so that the first subject region and the second subject region are adjacent to each other in the rotation axis direction. Shooting device. The image reconstruction unit is configured to display an image of the subject corresponding to a surface including both the first subject region and the second subject region on a surface having the rotation axis direction as a perpendicular line. The radiation imaging apparatus according to claim 15, wherein the image is reconstructed based on the oblique plane image. The image reconstruction unit reconstructs the plurality of oblique plane images so as to include the oblique plane along the radial direction in which the scanning unit emits the radiation in the rotation axis direction. The radiation imaging apparatus according to any one of the above. The image reconstruction unit uses the oblique plane image corresponding to the oblique plane intersecting the plane having the rotation axis direction as a perpendicular line, and the image of the subject corresponding to the plane having the rotation axis direction as a perpendicular line. The radiation imaging apparatus according to claim 14, wherein the image is reconstructed. The scanning unit
A radiation source emitting the radiation;
A detector that detects the radiation emitted from the radiation source and transmitted through the subject;
A rotation unit that rotates the radiation source and the detection unit around the subject around the rotation axis direction;
The radiation source emits the radiation so as to spread radially in a rotation direction rotated by the rotating unit and in the rotation axis direction,
The radiation imaging apparatus according to claim 10, wherein the detection unit includes a plurality of detection elements that detect the radiation along the rotation direction and the rotation axis direction. The radiation imaging apparatus according to claim 10, further comprising: a display unit configured to display an image of the subject reconstructed by the image reconstruction unit on a display surface.

Images