JP4613901B2 - Radiation imaging device - Google Patents

Description

  The present invention relates to a radiation imaging apparatus that performs radiation imaging by obtaining a radiation image based on detected radiation, and more particularly to a technique for obtaining a tomographic image by performing reconstruction processing.

  X-ray CT (computed tomography) apparatuses and X-ray tomography apparatuses are examples of radiation imaging apparatuses that perform tomographic images by performing reconstruction processing. In an X-ray CT apparatus, an X-ray tube (radiation irradiation means) and an X-ray detector (radiation detection means) rotate around an axis of a body axis that is the longitudinal direction of a subject to obtain a tomographic image. In the X-ray tomography apparatus, for example, as shown in FIG. 10, the X-ray tube 101 and the X-ray detector 102 translate in opposite directions along the body axis z direction of the subject M to obtain a tomographic image. Compared with the X-ray CT apparatus, the X-ray tomography apparatus has an advantage that a tomographic image can be obtained only by translation, although the resolution of the obtained tomographic image is inferior. An imaging method performed by such an X-ray CT apparatus or an X-ray tomography apparatus is an imaging method effective in many parts such as a chest, a joint, and a digestive organ (see, for example, Patent Document 1).

When the subject is placed in a standing posture and applied to an X-ray tomographic imaging apparatus that performs imaging in the standing posture, as shown in FIG. 11, X along the body axis z direction of the subject M The ray tube 101 and the X-ray detector 102 are translated in opposite directions to obtain a tomographic image. Since the subject M is in a standing posture, the body axis z direction is the vertical direction. Therefore, the X-ray tube 101 and the X-ray detector 102 are moved up and down. Tomographic imaging in a standing posture is effective for parts such as the chest.
Japanese Patent Laying-Open No. 2005-237518 (Pages 2, 4, 5, 7, 8 and FIGS. 1, 5, 7, 8)

  However, when tomography is performed in a standing posture as shown in FIG. 11, the X-ray tube 101 and the X-ray detector 102 must be moved up and down as described above. In particular, regardless of the linkage of the X-ray detector 102, tomography must be performed while moving up and down while swinging the X-ray tube 101 and moving up and down. In this way, when performing tomography in a standing posture, the manual operation is mostly performed in the vertical direction, and even when one (for example, the X-ray detector 102) is electrically operated, the other (for example, the other) (for example, the X-ray detector 102) is operated. The X-ray tube 101) must also be performed manually. As shown in FIG. 10, when the subject is in a horizontal posture, the X-ray tube 101 and the X-ray detector 102 move in the horizontal direction as in the direction of the body axis z, and thus can be controlled electrically. However, it is desirable to configure the tomography apparatus using an imaging method other than that shown in FIG. 10 even when the subject is in a horizontal posture, not limited to the standing posture.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a radiation imaging apparatus capable of performing tomography with a new imaging method.

As a result of intensive studies to solve the above problems, the inventors have obtained the following knowledge.
That is, we focused on whether tomography can be obtained by movement other than vertical movement while the subject is in a standing posture. The horizontal direction is the easiest to control the movement other than the vertical movement. In other words, tomography can be performed even when the robot is moved horizontally in a standing posture. In this case, since the body axis direction is the vertical direction as described above, the direction perpendicular to the body axis direction which is the longitudinal direction of the subject is the horizontal direction. That is, tomographic imaging is possible if the X-ray tube 101 and the X-ray detector 102 are translated in opposite directions as shown in FIGS. 10 and 11 in the short direction of the subject.

  However, when the X-ray tube 101 and the X-ray detector 102 are translated in opposite directions along the direction of the body axis z, which is the longitudinal direction of the subject, the X-ray tube is within the range of the subject in the longitudinal direction. Since the moving range of the 101 and the X-ray detector 102 fits, there is no problem as a moving space, but the X-ray tube 101 and the X-ray detector 102 are translated in opposite directions along the short direction of the subject. Since the movement range of the X-ray tube 101 and the X-ray detector 102 is considerably wider than the range of the subject in the short direction, the movement space is expanded relative to the range of the subject.

  As a result, the radiation irradiation means typified by the X-ray tube 101 and the radiation detection means typified by the X-ray detector 102 are along the short direction (ie, the direction perpendicular to the longitudinal direction of the subject). If they are configured to move in parallel in the same direction, the moving range of the radiation irradiating means and the radiation detecting means in the short direction is narrower than in the prior art, so there is no problem as a moving space. On the other hand, since the images obtained by parallel translation in the same direction as described above are projection images, a further imaging method and a configuration for obtaining a tomographic image are necessary.

  Therefore, as a further imaging method of the former, the radiation that is intermittently irradiated from the radiation irradiation means every time the radiation irradiation means and the radiation detection means move every predetermined distance, and transmitted through the intermittently irradiated subject. Is detected by the radiation detection means. As a configuration for obtaining the latter tomographic image, the radiographic image is decomposed at every predetermined distance described above, and the decomposed images are synthesized at the same projection angle to obtain a projection image at each projection angle. In other words, it has been found that by performing reconstruction processing based on the synthesized projection image, it is possible to obtain a tomographic image without greatly expanding the moving space with respect to the range of the subject.

  More preferably, if the radiation detecting means is fixed to the subject and only the radiation irradiating means is translated in the short direction, the movement range of the radiation detecting means becomes “0”. A moving space for the radiation detection means is not required. Then, at least the radiation irradiating means is configured to translate in the lateral direction, and at least every time the radiation irradiating means moves every predetermined distance, the radiation irradiating means intermittently irradiates and intermittently It was found that the tomographic image can be obtained by configuring the radiation detection means to detect the radiation that has passed through the subject that has been irradiated, and similarly performing the decomposition and synthesis of the radiation image.

  Even when the tomography is performed in a general posture including a horizontal posture and the like without being limited to the standing posture, the tomography is performed by a new imaging method by imaging in such a direction. I got the knowledge that I can do it.

The present invention based on such knowledge has the following configuration.
That is, the invention according to claim 1 is provided with radiation irradiating means for irradiating the subject with radiation and radiation detecting means for detecting the radiation transmitted through the subject, and radiation based on the detected radiation. A radiation imaging apparatus that performs radiation imaging by obtaining an image, wherein at least the radiation irradiating means is configured to relatively translate along a direction perpendicular to the longitudinal direction of the subject, and at least Each time the radiation irradiation means moves relative to the subject at a predetermined distance, the radiation detection means irradiates the radiation intermittently from the radiation irradiation means, and the radiation detection means detects the radiation transmitted through the intermittently irradiated subject. The apparatus comprises: an image decomposing unit that decomposes the radiographic image at each predetermined distance; and the image obtained by synthesizing the decomposed image at the same projection angle. An image synthesizing means for obtaining a projected image of each time and is characterized in that it comprises a reconstruction processing means for obtaining a tomographic image by performing a reconstruction process based on the combined projected image.

  [Operation / Effect] According to the invention described in claim 1, at least the radiation irradiating means is configured to relatively translate along a direction perpendicular to the longitudinal direction of the subject. Data can be obtained from the radiation detection means in a state where the movement range of the radiation irradiation means in the short direction, which is a direction perpendicular to the longitudinal direction of the specimen, is narrower than before. On the other hand, at least every time the radiation irradiating means moves relative to the subject at a predetermined distance, the radiation irradiating means intermittently emits radiation, and the radiation that has passed through the intermittently irradiated subject is detected by the radiation detecting means. Configure to detect. Then, the image decomposing unit decomposes the radiographic image at every predetermined distance described above, and the image synthesizing unit synthesizes the decomposed image at the same projection angle to obtain a projection image at each projection angle. Therefore, the reconstruction processing means performs reconstruction processing based on the synthesized projection image, so that tomography can be performed with a new imaging method.

  The above-described invention may be applied to a case where the subject is in a standing posture and imaging is performed in the standing posture (the invention according to claim 2). In this case, since the subject is in a standing posture, the direction of the body axis that is the longitudinal direction is the vertical direction, and at least the direction in which the radiation irradiation means is moved relative to the subject, that is, the direction perpendicular to the longitudinal direction ( (Short direction) is a horizontal direction perpendicular to the vertical direction. Accordingly, at least the radiation irradiating means is configured to translate relatively in the horizontal direction with respect to the subject in the standing posture in the standing posture state.

  In the above-described invention, the radiation irradiating means is configured to translate relatively along a direction perpendicular to the longitudinal direction of the subject and to fix the radiation detecting means relative to the subject. In addition, the radiation irradiating means intermittently emits radiation every time the radiation irradiating means moves relative to the subject at a predetermined distance with the radiation detecting means fixed relative to the subject. It is preferable to constitute (the invention according to claim 3). With this configuration, the movement range of the radiation detection unit becomes “0” relative to the subject, so that the relative movement space of the radiation detection unit with respect to the subject becomes unnecessary.

  Even when the radiation detection means is fixed relative to the subject as described above, the subject is placed in a standing posture and imaging is performed in the standing posture, as in the second aspect of the invention. It may be applied to the case (the invention according to claim 4). Also in this case, since the subject is in a standing posture, the direction of the body axis that is the longitudinal direction is the vertical direction, and the direction in which the radiation irradiation means is moved relative to the subject, that is, the direction that is perpendicular to the longitudinal direction (short (Hand direction) is a horizontal direction perpendicular to the vertical direction. Therefore, in a state of standing posture and with the radiation detecting means fixed relative to the subject, the radiation irradiating means is relatively relative to the subject in the standing posture along the horizontal direction. It will be configured to move in parallel.

  In this invention, at least each time the radiation irradiating means moves relatively parallel along the direction perpendicular to the longitudinal direction of the subject, and at least every time the radiation irradiating means moves relative to the subject every predetermined distance. Since radiation only needs to be intermittently emitted from the radiation irradiating means, the radiation detecting means may be fixed relative to the subject as in the third and fourth aspects of the invention, or the radiation irradiating means. At the same time, the radiation detection means may be relatively moved. That is, the radiation irradiating means and the radiation detecting means are configured to relatively translate in the same direction along the direction perpendicular to the longitudinal direction of the subject, and the radiation irradiating means and the radiation detecting means are You may comprise so that radiation may be intermittently irradiated from a radiation irradiation means, whenever it carries out relative movement with respect to a specimen for every predetermined distance (invention of Claim 5).

  According to the fifth aspect of the present invention, the radiation irradiating means and the radiation detecting means are configured to relatively translate in the same direction along a direction perpendicular to the longitudinal direction of the subject. The data can be obtained from the radiation detection means in a state where the movement range of the radiation irradiation means and the radiation detection means in the short direction, which is a direction perpendicular to the longitudinal direction of the subject, is narrower than before.

  In the above-described invention according to claim 5, it is preferable that the radiation irradiating means and the radiation detecting means are relatively translated with respect to the subject at the same speed (the invention according to claim 6). Since the radiation irradiation means and the radiation detection means move relative to each other at the same speed relative to each other, the projection angle can be maintained at the same angle, and the radiation irradiation means and the radiation detection means can be moved relatively longer. Can be made. As a result, a long-field tomographic image can be obtained.

  Even when the radiation detection means and the radiation detection means are moved relative to each other in the same direction as in the invention described in claim 5 or claim 6 described above, as in the inventions described in claims 2 and 4, The present invention may be applied to a case where imaging is performed in a standing posture and in the standing posture (invention according to claim 7). Also in this case, since the subject is in a standing posture, the direction of the body axis, which is the longitudinal direction, is the vertical direction, and the direction in which the radiation irradiating means and the radiation detecting means are moved relative to the subject, that is, perpendicular to the longitudinal direction. The direction (short direction) is a horizontal direction perpendicular to the vertical direction. Accordingly, the radiation irradiating means and the radiation detecting means are configured to relatively translate in the same direction along the horizontal direction with respect to the subject in the standing posture in the standing posture state.

  An example of these inventions described above includes an output means for outputting a tomographic image obtained by the reconstruction processing means (the invention according to claim 8). By providing an output means, it can be used for browsing the output. The output means may be a display means typified by a monitor for display output or a printing means typified by a printer for print output.

  According to the radiation imaging apparatus of the present invention, at least the radiation irradiating means is configured to relatively translate along a direction perpendicular to the longitudinal direction of the subject, and at least the radiation irradiating means is the subject. The radiation detector is configured to detect the radiation transmitted through the intermittently irradiated subject by intermittently irradiating the radiation from the radiation irradiating means each time the relative movement is performed at a predetermined distance with respect to the radiation. The image decomposing unit decomposes the image at the predetermined distances described above, and the image synthesizing unit synthesizes the decomposed image at the same projection angle to obtain a projection image at each projection angle. Therefore, the reconstruction processing means performs reconstruction processing based on the synthesized projection image, so that tomography can be performed with a new imaging method.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of the X-ray tomography apparatus according to the embodiment, FIG. 2 is a schematic diagram showing a schematic configuration of an X-ray tube driving unit related to driving of the X-ray tube, and FIG. It is a schematic diagram which shows the parallel displacement of the horizontal direction (short direction) of the X-ray tube by a tube drive part. In this embodiment, a flat panel X-ray detector (hereinafter abbreviated as “FPD”) is taken as an example of radiation detection means, and an X-ray tomography apparatus is taken as an example of a radiation imaging apparatus.

  The X-ray tomography apparatus places the subject M in a standing posture, and X-ray tube 2 that irradiates the subject M with X-rays in the standing posture, and X-rays transmitted through the subject M FPD3 to detect. The X-ray tube 2 corresponds to the radiation irradiating means in the present invention, and the FPD 3 corresponds to the radiation detecting means in the present invention.

  In addition, the X-ray tomography apparatus digitally transmits an X-ray detection signal which is a charge signal from the X-ray tube control unit 7 having the high voltage generation unit 6 for generating the tube voltage and tube current of the X-ray tube 2 and the FPD 3. An A / D converter 8 that is converted into an image, an image processing unit 9 that performs various processes based on an X-ray detection signal output from the A / D converter 8, a controller 10 that supervises these components, A memory unit 11 for storing processed images, an input unit 12 for an operator to make input settings, a monitor 13 for displaying processed images, and the like. The monitor 13 corresponds to the output means in this invention.

  The high voltage generator 6 generates a tube voltage and a tube current for irradiating X-rays, and gives them to the X-ray tube 2. The X-ray tube control unit 7 performs control to translate the X-ray tube 2 along a direction (that is, a horizontal direction and a short direction) perpendicular to the body axis z direction that is the longitudinal direction of the subject M. . As shown in FIG. 2, this control is performed by controlling an X-ray tube driving unit 15 including a column 15a, a screw rod 15b, a motor 15c, an encoder 15d, and the like. Specifically, the support column 15a mounts and supports the X-ray tube 2 on the upper end side, and is screwed to the screw rod 15b on the lower end side. The screw rod 15b extends along the horizontal direction, which is a direction perpendicular to the body axis z direction of the subject M, and rotates by the rotation of the motor 15c. For example, when the motor 15c is rotated forward, the X-ray tube 2 is translated along with the column 15a to the right side of the subject M as shown by the one-dot chain line in FIGS. 2 and 3, and when the motor 15c is reversed, FIG. As shown by the two-dot chain line in FIG. 3, the X-ray tube 2 moves in parallel with the support 15a to the left side of the subject M (however, the subject M faces the FPD 3 side). The encoder 15d detects the rotation direction and the rotation amount of the motor 15c corresponding to the movement direction and the movement amount (movement distance) of the X-ray tube 2. The detection result by the encoder 15d is sent to the X-ray tube control unit 7. It should be noted that FIG. 1 is a view from the side, FIG. 2 and FIG. 3 (a) are views from the front, and FIG. 3 (b) is a view from the plane. .

  The X-ray tube control unit 7 controls the setting of the irradiation field of the collimator 2a on the X-ray tube 2 side. In the present embodiment, the collimator is irradiated so as to irradiate fan beam-shaped X-rays extending in the longitudinal direction (body axis z direction) and the lateral direction (direction perpendicular to the body axis z in the horizontal plane) of the subject M. Control and set the illumination field. Further, the X-ray tube control unit 7 controls so that X-rays (in the form of a fan beam) are intermittently emitted from the X-ray tube 2 every time the X-ray tube 2 moves every pitch (predetermined distance) described later. . And FPD3 detects the X-ray which permeate | transmitted the subject M irradiated intermittently. In this embodiment, the X-ray tube controller 7 also sets the irradiation field shown in FIG. 6 to be described later by the collimator 2a.

  The controller 10 is configured by a central processing unit (CPU) and the like, and the memory unit 11 is configured by a storage medium represented by ROM (Read-only Memory), RAM (Random-Access Memory), and the like. Yes. The input unit 12 includes a pointing device represented by a mouse, a keyboard, a joystick, a trackball, a touch panel, and the like.

  The image processing unit 9 performs lag correction, gain correction, and the like on the X-ray detection signal and outputs an X-ray image projected on the detection surface of the FPD 3, and the corrected X-ray image is pitched An image decomposing unit 9b for decomposing every time, an image synthesizing unit 9c for synthesizing the decomposed image for each same projection angle to obtain a projection image for each projection angle, and reconstruction based on the synthesized projection image A reconstruction processing unit 9d that performs processing to obtain a tomographic image. The image decomposition unit 9b corresponds to the image decomposition unit in the present invention, the image composition unit 9c corresponds to the image composition unit in the present invention, and the reconstruction processing unit 9d corresponds to the reconstruction processing unit in the present invention. Specific functions of the image decomposition unit 9b, the image composition unit 9c, and the reconstruction processing unit 9d will be described later with reference to FIGS.

  The memory unit 11 is configured to write and store each image processed by the image processing unit 9. Similarly to the controller 10, the X-ray tube control unit 7 is also composed of a CPU or the like.

  Next, the structure of the flat panel X-ray detector (FPD) 3 will be described with reference to FIGS. 4 is an equivalent circuit of a flat panel X-ray detector (FPD) viewed from the side, and FIG. 5 is an equivalent circuit of the flat panel X-ray detector (FPD) viewed from above.

  As shown in FIG. 4, the FPD 3 includes a glass substrate 31 and a thin film transistor TFT formed on the glass substrate 31. As for the thin film transistor TFT, as shown in FIGS. 4 and 5, a large number of switching elements 32 (for example, 1024 × 1024) are formed in a vertical / horizontal two-dimensional matrix arrangement. The switching elements 32 are formed separately from each other. That is, the FPD 3 is also a two-dimensional array radiation detector.

  As shown in FIG. 4, an X-ray sensitive semiconductor 34 is laminated on the carrier collection electrode 33, and the carrier collection electrode 33 is connected to the source S of the switching element 32 as shown in FIGS. 4 and 5. Has been. A plurality of gate bus lines 36 are connected from the gate driver 35, and each gate bus line 36 is connected to the gate G of the switching element 32. On the other hand, as shown in FIG. 5, a plurality of data bus lines 39 are connected to a multiplexer 37 that collects charge signals and outputs them to one through an amplifier 38, as shown in FIGS. Thus, each data bus line 39 is connected to the drain D of the switching element 32.

  With the bias voltage applied to the common electrode (not shown), the gate of the switching element 32 is turned on by applying the voltage of the gate bus line 36 (or 0 V), and the carrier collection electrode 33 is on the detection surface side. The charge signal (carrier) converted from the incident X-ray through the X-ray sensitive semiconductor 34 is read out to the data bus line 39 via the source S and drain D of the switching element 32. Until the switching element is turned on, the charge signal is temporarily accumulated and stored in a capacitor (not shown). The charge signals read to the respective data bus lines 39 are amplified by the amplifiers 38 and are collectively output as one charge signal by the multiplexer 37. The output charge signal is digitized by the A / D converter 8 and output as an X-ray detection signal.

  Next, specific setting of the illumination field by the collimator 2a will be described with reference to FIG. 6, and specific functions of the image decomposition unit 9b, the image composition unit 9c, and the reconstruction processing unit 9d will be described with reference to FIGS. This will be described with reference to FIG. FIG. 6 is a schematic diagram showing the specific setting of the illumination field by the collimator for each pitch (predetermined distance). FIG. 7 shows the imaging principle by the X-ray tube and the flat panel X-ray detector (FPD). FIG. 8 and FIG. 9 are schematic diagrams showing image separation and composition into a projected image. The X-ray image projected on the detection surface of the FPD 3 will be described on the assumption that processing such as lag correction and gain correction has already been completed by the correction unit 9a.

  In this embodiment, as shown in FIGS. 6A to 6E, the X-ray tube 2 is a direction that is perpendicular to the body axis z direction of the subject M (horizontal direction). And the FPD 3 is fixed to the subject M. At this time, the X-ray tube control unit 7 (see FIG. 1) controls the setting of the irradiation field of the collimator 2a so that the X-ray is not irradiated outside the FPD 3 every time the X-ray tube 2 moves for each pitch. Do. For example, as shown in FIG. 6A, when the X-ray tube 2 is moved from the right end of the subject M, the collimator 2a is also moved so that X-rays are not irradiated outside the FPD 3. When the subject M is translated in the left direction, the movement positions of the X-ray tube 2 and the collimator 2a are set in the order of FIGS. 6B to 6E, respectively. Also in FIGS. 6B to 6E, the collimator 2a is moved to a position where the outside of the FPD 3 is not irradiated with X-rays. Note that the width of the illumination field of the collimator 2a may be changed.

Each time the X-ray tube 2 moves for each pitch d, the X-ray image projected on the detection surface of the FPD 3 is shown in FIGS. 7 (h), O ₁ , O ₂ ,..., O _I ,..., O _M (1 ≦ I ≦ M). Each time the X-ray tube 2 moves at every pitch d, the X-ray tube 2 emits X-rays intermittently. That is, X-rays are irradiated with a pulse every time it moves every pitch d. In FIG. 7, the limitation of the X-ray irradiation field by the collimator 2a (see FIGS. 1, 3B, and 6) is ignored and the horizontal length of the FPD 3 is extended. .

More specifically, when the X-ray tube 2 first irradiates X-rays at the position shown in FIG. 7A, the X-ray tube 2 is moved at the position shown in FIG. Irradiate the line. The X-ray image O ₁ (see FIG. 7E) is obtained by the FPD 3 detecting the X-ray in FIG. 7A, and the X-ray is detected by the FPD 3 detecting the X-ray in FIG. 7B. An image O ₂ (see FIG. 7F) is obtained. Similarly, when the X-ray tube 2 moves at every pitch d, X-rays are irradiated at the position shown in FIG. 7C to the (I-1) th, and the X-rays are converted into FPD3 in FIG. 7C. Is detected, an X-ray image O _I (see FIG. 7G) is obtained. Finally, the (M-1) th, 7 irradiated with X-rays at the position (d), the 7 X-rays (d) by FPD3 to detect X-ray image _O M ( FIG. 7 (h) is obtained. In this embodiment, the imaging start position in FIG. 7A is the right end of the subject M, the imaging end position in FIG. 7D is the left end of the subject M, and FIG. 7A to FIG. As the X-ray tube 2 moves, it moves sequentially from the right side to the left side (however, the subject M faces the FPD 3 side).

By X-ray tube 2 is moved for each pitch d, the X-ray image _{O 1, O 2, ...,} O I, ..., the image decomposing unit 9b to _{O M} for each pitch d can be decomposed. Specifically, as shown in the enlarged view of FIG. 7 (i), an irradiation axis connecting the X-ray tube 2 to the FPD 3 and a short axis of the subject (a horizontal axis orthogonal to the body axis z) and the projection angle is an angle of each pitch _{d, θ 1, θ 2,} ..., θ J, ..., θ N-1, and _{θ N (1 ≦ J ≦ N} ). Then, the image decomposed for each pitch d coincides with the images divided into the same projection angles θ ₁ , θ ₂ ,..., Θ _J ,..., Θ _N−1 , θ _N.

As shown in FIG. 7E, the X-ray image O ₁ is decomposed into O ₁₁ , O ₁₂ ,..., O _1J ,..., O _{1 (N−1)} , O _1N for each pitch d and decomposed. The image O ₁₁ is an image obtained by irradiation at the projection angle θ ₁ , and the decomposed image O ₁₂ is an image obtained by irradiation at the projection angle θ _2. Hereinafter, the decomposed image O _1J is similarly expressed as The image obtained by irradiation with the projection angle θ _J is obtained, and the finally decomposed image O _1N becomes an image obtained by irradiation with the projection angle θ _N.

Similarly, the X-ray image O ₂ is decomposed into O ₂₁ , O ₂₂ ,..., O _2J ,..., O _{2 (N−1)} , O _2N for each pitch d, as shown in FIG. The decomposed image O ₂₁ becomes an image obtained by irradiation with the projection angle θ ₁ , and the decomposed image O ₂₂ becomes an image obtained by irradiation with the projection angle θ _2. O _2J is an image obtained by irradiation with the projection angle θ _J , and the finally decomposed image O _2N is an image obtained by irradiation with the projection angle θ _N.

The (I1) th, X-rays image _{O I} as shown in FIG. 7 (g) _{are, O} I1, _{O I2} for each pitch _{d, ..., O IJ, ...} , O I (N-1), O _IN is decomposed and decomposed image O _I1 is an image obtained by irradiation at projection angle θ ₁ , and decomposed image O _I2 is an image obtained by irradiation at projection angle θ ₂ . Similarly, the decomposed image O _IJ becomes an image obtained by irradiation with the projection angle θ _J , and the finally decomposed image O _IN becomes an image obtained by irradiation with the projection angle θ _N.

Eventually, the th (M1), the X-ray image _{O M} shown in FIG. 7 (h), _O M1 every pitch _{d, O M2, ..., O} MJ, ..., O M ( _N-1) , O _MN and the decomposed image O _M1 is an image obtained by irradiation with the projection angle θ ₁ , and the decomposed image O _M2 is obtained by irradiation with the projection angle θ ₂ Hereinafter, similarly, the decomposed image O _MJ is an image obtained by irradiation at the projection angle θ _J , and the finally decomposed image O _MN is an image obtained by irradiation at the projection angle θ _N. It becomes.

Such resolved each image was, 8, the same projection angle theta ₁ as shown in FIG. _{9, θ 2, ..., θ} J, ..., θ N-1, respectively the image combining unit 9c for each theta _N Is synthesized. As described above, each X-ray image O ₁ , O ₂ ,..., O _I ,..., O _M is decomposed for each pit d (that is, each projection angle θ ₁ , θ ₂ ,..., Θ _J ,. , Θ _N−1 , θ _N ) images are divided into FIGS. 8 (a) to 8 (d), FIGS. 8 (f) to 8 (i), and FIGS. 9 (a) to 9 ( d) As shown in FIGS. 9 (f) to 9 (i).

For example, in the case of the projection angle θ ₁ , an image O ₁₁ in the X-ray image O ₁ shown in FIG. 8A, an image O ₂₁ in the X-ray image O ₂ shown in FIG. 8C is synthesized with the image O _I1 in the X-ray image O _I shown in FIG. 8C and the image O _M1 in the X-ray image O _M shown in FIG. obtaining a projection image P ₁ in the projection angle theta ₁ as shown in).

Similarly, in the case of the projection angle θ ₂ , the image O ₁₂ in the X-ray image O ₁ shown in FIG. 8 (f), the image O ₂₂ in the X-ray image O ₂ shown in FIG. 8 (g), ..., and image _{O I2} of X-ray in the image _{O I} shown in FIG. 8 (h), ..., it synthesizes the image _{O M2} of X-ray in the image _{O M} shown in FIG. 8 (i), 8 ( obtaining a projection image P ₂ of the projection angle theta ₂ as shown in j).

(J-1) First, in the case of the projection angle θ _J , the image O _1J in the X-ray image O ₁ shown in FIG. 9A and the X-ray image O ₂ shown in FIG. 9B. to the image _{O 2J} of, ..., and image _{O IJ} in X-ray image _{O I} shown in FIG. 9 (c), ..., and an image _{O MJ} of X-ray in the image _{O M} shown in FIG. 9 (d) synthesis it is to obtain a projection image P _J at the projection angle theta _J as shown in FIG. 9 (e).

Finally, (N-1) th, in the case of the projection angle θ _N , the image O _1N in the X-ray image O ₁ shown in FIG. _9F and the X shown in FIG. image _{O 2N} in line image _{O 2,} ..., and image _{O iN} in X-ray image _{O I} shown in FIG. 9 (h), ..., image O of the X-ray in the image _{O M} that shown in FIG. 9 (i) by combining the _MN, to obtain a projection image P _N in the projection angle theta _N as shown in FIG. 9 (j).

In summary, the image combining unit 9c, the same projection angle theta ₁ of each image is _{decomposed, θ 2, ..., θ J} , ..., θ N-1, by combining each theta _N, 8 ( e), projection images for each projection angle θ ₁ , θ ₂ ,..., θ _J ,..., θ _N−1 , θ _N as shown in FIGS. _{P 1, P 2, ...,} P J, ..., obtaining _{P N.}

Reconstruction processing unit 9d, the synthetic projection images _{P 1, P 2, ...,} P J, ..., to obtain a tomographic image by performing a reconstruction process based on the _{P N.} The reconstruction process may be performed using a well-known filtered back projection (FBP) (also called “filtered back projection method”).

The number of projection images P ₁ , P ₂ ,..., P _J ,... _PN is N [Frame], the moving speed of the video system of the X-ray tube 2 is v [mm / sec], and the field of view of the FPD 3 When the size is V [mm] and the imaging cycle (also called “pulse time width”) is T [sec / Frame], the moving speed v [mm / sec] is v [mm / sec] = V [mm] / N [Frame] × 1 / T [sec / Frame]. The reciprocal of the imaging cycle is the imaging speed. If the imaging speed is F [Frame / sec], the moving speed v [mm / sec] is v [mm / sec] = V [mm] / N [Frame]. × F [Frame / sec] is also expressed. The pitch d [mm] is represented by d [mm] = V [mm] / N [Frame].

For example, the field size V used in this embodiment as 17 inches (= 430 [mm]), the projected image _{P 1, P 2, ...,} P J, ..., the number N of _{P N} and 50 [Frame], When the imaging speed F is 15 [Frame / sec], the moving speed v is v [mm / sec] = 430 [mm] / 50 [Frame] × 15 [Frame / sec] = 129 [mm / sec], and the pitch d is 430 [mm] / 50 [Frame] = 8.6 [mm / Frame]. Therefore, the X-ray tube 2 is translated at 129 [mm / sec], and the X-ray tube 2 is irradiated with X-rays intermittently at the imaging speed of 15 [Frame / sec], so that the X-ray tube 2 has a pitch of 8.6 [ X-rays are irradiated intermittently from the X-ray tube 2 every time the movement is made every [mm / Frame]. Then, 50 sheets projection images _{P 1, P 2, ...,} P J, ..., can be obtained _{P 50.} Further, for example, the length of the FPD 3 in the horizontal direction is increased, or the FPD 3 is also translated in the same direction together with the X-ray tube 2, and as the distance that the X-ray tube 2 moves increases, FIGS. each projection images _{P 1,} P 2, as shown in _..., P _{J, ...,} region of _{P N} also becomes elongated.

  According to the X-ray tomography apparatus according to the present embodiment, the X-ray tube 2 is configured to translate in a direction perpendicular to the direction of the body axis z, which is the longitudinal direction of the subject M. Thus, data can be obtained from the FPD 3 in a state in which the movement range of the X-ray tube 2 in the short direction, which is a direction perpendicular to the longitudinal direction, is narrower than in the past. On the other hand, every time the X-ray tube 2 moves at every pitch (predetermined distance), the X-ray tube 2 intermittently irradiates X-rays, and the FPD 3 transmits X-rays transmitted through the subject M irradiated intermittently. Configure to detect. Then, the image decomposing unit 9b decomposes the X-ray image for each pitch described above, and the image synthesizing unit 9c synthesizes the decomposed image for each same projection angle to obtain a projection image for each projection angle. Therefore, the reconstruction processing unit 9d performs reconstruction processing based on the synthesized projection image, so that tomography can be performed with a new imaging method.

  In this embodiment, the X-ray tube 2 is translated along a horizontal direction (short direction) that is a direction perpendicular to the body axis z direction of the subject M, and the FPD 3 is moved with respect to the subject M. The X-ray tube 2 is configured to be intermittently irradiated with X-rays every time the X-ray tube 2 moves for each pitch while the FPD 3 is fixed to the subject M. ing. With this configuration, the movement range of the FPD 3 becomes “0” with respect to the subject M, so that the movement space of the FPD 3 with respect to the subject M becomes unnecessary.

  Further, the present embodiment is applied to the case where the subject M is in a standing posture and imaging is performed in the standing posture. In this case, since the subject M is in a standing posture, the direction of the body axis z, which is the longitudinal direction, becomes a vertical direction as shown in FIG. 1, and is perpendicular to the direction in which the X-ray tube 2 is moved, that is, the longitudinal direction. The direction (short direction) is a horizontal direction perpendicular to the vertical direction. Therefore, the X-ray tube 2 is configured to translate in parallel with the subject M in the standing posture in the standing posture.

  Further, even when tomography is performed while the subject M is in a standing posture, it is not necessary to move the X-ray tube 2 and the FPD 3 up and down as in the prior art, and the X-ray tube 2 is parallel along the horizontal direction. Just move it. Conventionally, when tomography is performed in a standing posture, the vertical movement is manually moved up and down. However, in this embodiment, it is possible to realize tomography by horizontal movement, so it can be controlled electrically. Also has the effect of.

  In this embodiment, a monitor 13 for displaying and outputting a tomographic image obtained by the reconstruction processing unit 9d is provided. By providing such a monitor 13, the display can be browsed. Note that the display unit is not limited to the monitor 13, and a printing unit represented by a printer may be provided. In this case, the printing unit corresponds to the output unit in the present invention, and the printing unit prints out the tomographic image, so that the printing can be browsed. Note that both the monitor 13 and the printer may be provided.

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

  (1) In the above-described embodiment, the X-ray tomography apparatus is taken as an example of the radiation imaging apparatus. However, an ECT (typical of PET (Positron Emission Tomography) apparatus, SPECT (Single Photon Emission CT) apparatus, etc.) A radiation imaging apparatus that performs radiation imaging by detecting radiation other than X-rays (gamma rays in the case of a PET apparatus) and obtaining a radiation image based on the detected radiation, such as an Emission Computed Tomography apparatus You may apply.

  (2) In the above-described embodiment, the flat panel X-ray detector has been described as an example of the radiation detection means. However, the X-ray detection means normally used as in the image intensifier (II). If it is, it will not specifically limit. Moreover, as long as it is a radiation detection means used normally like the case where it applies to an ECT apparatus like the modification (1) mentioned above, it will not specifically limit.

  (3) In the above-described embodiment, the output unit represented by the monitor 13 is provided, but the output unit is not necessarily provided.

  (4) In the above-described embodiment, only the radiation irradiation means represented by the X-ray tube 2 translates along the direction perpendicular to the longitudinal direction of the subject M, and the radiation represented by the FPD 3 The detection means is configured to be fixed with respect to the subject M, and radiation is intermittently emitted from the radiation irradiation means every time the radiation irradiation means moves for each pitch while the radiation detection means is fixed to the subject M. However, at least the radiation irradiating means relatively translates in a direction perpendicular to the longitudinal direction of the subject M, and at least the radiation irradiating means is relative to the subject M. If the radiation is intermittently emitted from the radiation irradiating means every time it moves relative to each pitch (predetermined distance), only the radiation irradiating means represented by the X-ray tube 2 is relatively moved as in the embodiment. The And to the radiation detecting device represented by FPD3 may be fixed relative to the object M, the radiation detecting means may be moved relative with radioactive radiation means.

  (5) As described in the modification (4) above, when the radiation detecting means is relatively moved together with the radiation irradiating means, the radiation irradiating means and the radiation detecting means may be translated at the same speed. The radiation irradiating means and the radiation detecting means are relatively translated in the same direction along the direction perpendicular to the longitudinal direction of the subject M, and one of them is moved fast and the other is moved slowly. You may let them. Since the radiation irradiating means and the radiation detecting means move relative to each other at the same speed relative to the subject M, the projection angle can be maintained at the same angle, and the radiation irradiating means and the radiation detecting means are relatively longer. Can be moved. As a result, a long-field tomographic image can be obtained.

  (6) In the above-described embodiment, only the radiation irradiation means represented by the X-ray tube 2 is moved, and the radiation detection means represented by the FPD 3 is fixed to the subject M, so that the radiation irradiation means is The radiation detection unit is configured to move relative to the subject M and to be fixed relative to the subject M, but at least the radiation irradiating unit is perpendicular to the longitudinal direction of the subject M. The specific movement is not limited as long as the movement is relatively parallel.

  For example, the radiation irradiation means represented by the X-ray tube 2 is fixed, and the radiation detection means represented by the FPD 3 and the top plate on which the subject M is placed are perpendicular to the longitudinal direction of the subject M. The radiation irradiating means may move relative to the subject M by parallel translation at the same speed along the direction, and the radiation detecting means may be fixed relative to the subject M. . Further, the radiation irradiation means represented by the X-ray tube 2 is moved along a direction perpendicular to the longitudinal direction of the subject M, and the radiation detection means represented by the FPD 3 and the subject M are placed. By moving the top plate parallel to each other at the same speed along the direction perpendicular to the longitudinal direction of the subject M, the radiation irradiating means moves relative to the subject M, and the radiation detecting means is moved to the subject. You may comprise so that it may fix relatively with respect to M.

  In addition, the radiation irradiation means and the radiation detection means are fixed, and only the top plate on which the subject M is placed is moved along the direction perpendicular to the longitudinal direction of the subject M. The means and the radiation detection means may be configured to relatively translate in the same direction along a direction perpendicular to the longitudinal direction of the subject M. Further, the radiation irradiation means and the radiation detection means are relatively translated in the same direction along the direction perpendicular to the longitudinal direction of the subject M, and the subject M is fixed or the subject M is placed. The top plate is also translated along the direction perpendicular to the longitudinal direction of the subject M, so that the radiation irradiating means and the radiation detecting means are mutually aligned along the direction perpendicular to the longitudinal direction of the subject M. You may comprise so that it may translate relatively in the same direction.

  (7) In the above-described embodiment, the subject M is placed in a standing posture and imaging is performed in the standing posture, and the radiation irradiation means represented by the X-ray tube 2 is used as the subject M. The radiation detection means represented by FPD3 is fixed to the subject M in parallel along a direction perpendicular to the longitudinal direction of the subject. However, the subject M is in a standing posture. As described above, when the imaging is performed in the standing posture, and at least the radiation irradiating means relatively translates in a direction perpendicular to the longitudinal direction of the subject M, The present invention may be applied to the modified examples (4) and (5), in which the subject M is placed in a standing posture and imaging is performed in the standing posture.

  (8) In the above-described embodiment, the present invention is applied to the case where the subject M is in the standing posture and the imaging is performed in the standing posture. However, the present invention can be applied even when the subject M is in the horizontal posture. In this case, the direction perpendicular to the longitudinal direction of the subject M is the vertical direction. Therefore, it is only necessary to relatively translate the radiation irradiation means represented by at least the X-ray tube 2 along the vertical direction. Further, the present invention is not limited to the standing posture and the horizontal posture, and can also be applied to the case where the subject M performs imaging in an oblique posture with respect to the horizontal plane.

It is a block diagram of the X-ray tomography apparatus which concerns on an Example. It is a schematic diagram which shows schematic structure of the X-ray tube drive part regarding the drive of an X-ray tube. It is a schematic diagram which shows the parallel movement of the X-ray tube by the X-ray tube drive part in the horizontal direction (short direction), (a) is the figure seen from the front, (b) is the figure seen from the top. . 2 is an equivalent circuit of a flat panel X-ray detector (FPD) viewed from the side. 2 is an equivalent circuit of a flat panel X-ray detector (FPD) in plan view. (A)-(e) is the schematic diagram which planarly represented the specific setting of the irradiation visual field by a collimator for every pitch (predetermined distance). (A)-(i) is the schematic diagram which represented the imaging principle with an X-ray tube and a flat panel X-ray detector (FPD) for every pitch (predetermined distance). (A)-(j) is a schematic diagram showing separation of an image and composition to a projection image. (A)-(j) is a schematic diagram showing separation of an image and composition to a projection image. It is the side view which showed schematic structure of the conventional X-ray tomography apparatus. It is the side view which showed schematic structure of the conventional X-ray tomography apparatus in the case of imaging in the state of a standing posture.

Explanation of symbols

2 ... X-ray tube 3 ... Flat panel X-ray detector (FPD)
DESCRIPTION OF SYMBOLS 13 ... Monitor 9b ... Image decomposition part 9c ... Image composition part 9d ... Reconstruction process part d ... Pitch z ... Body axis M ... Subject

Claims (8)

  Radiation imaging comprising radiation irradiating means for irradiating radiation toward a subject and radiation detecting means for detecting radiation transmitted through the subject, and performing radiation imaging by obtaining a radiation image based on the detected radiation The apparatus is configured such that at least the radiation irradiating means relatively translates along a direction perpendicular to the longitudinal direction of the subject, and at least the radiation irradiating means has a predetermined distance from the subject. The radiation detector is configured to detect the radiation transmitted through the intermittently irradiated subject by intermittently irradiating the radiation from the radiation irradiating means every time it moves relative to each other. Image decomposing means for decomposing a radiographic image at each predetermined distance, and image synthesizing means for synthesizing the decomposed images at the same projection angle to obtain a projection image at each projection angle Radiation imaging apparatus characterized by comprising a reconstruction processing means for obtaining a tomographic image by performing a reconstruction process based on the combined projected image.   The radiation imaging apparatus according to claim 1, wherein the subject is in a standing posture, and in the standing posture, at least the radiation irradiating unit is relatively relative to the subject in the standing posture along the horizontal direction. A radiation imaging apparatus characterized by being configured to translate in parallel.   2. The radiation imaging apparatus according to claim 1, wherein the radiation irradiating means is relatively translated along a direction perpendicular to the longitudinal direction of the subject, and the radiation detecting means is relative to the subject. Each time the radiation irradiating means moves relative to the subject at a predetermined distance with the radiation detecting means fixed relative to the subject. A radiation imaging apparatus characterized by being configured to intermittently irradiate.   4. The radiation imaging apparatus according to claim 3, wherein the subject is placed in a standing posture, and the radiation irradiating unit is in the standing posture and the radiation detecting unit is fixed relative to the subject. A radiation imaging apparatus configured to translate in a horizontal direction relative to a subject in a standing posture.   2. The radiation imaging apparatus according to claim 1, wherein the radiation irradiating means and the radiation detecting means are configured to relatively translate in the same direction along a direction perpendicular to the longitudinal direction of the subject. A radiation imaging apparatus configured to intermittently irradiate radiation from the radiation irradiating means each time the radiation irradiating means and the radiation detecting means move relative to the subject at predetermined distances.   6. The radiation imaging apparatus according to claim 5, wherein the radiation irradiating means and the radiation detecting means are relatively translated with respect to the subject at the same speed.   7. The radiation imaging apparatus according to claim 5, wherein the subject is placed in a standing posture, and the radiation irradiating unit and the radiation detecting unit are in a standing posture in the standing posture. A radiation imaging apparatus configured to relatively translate in the same direction along a horizontal direction.   8. The radiation imaging apparatus according to claim 1, further comprising an output unit that outputs a tomographic image obtained by the reconstruction processing unit.

Images