JP2012148143A - Radiation imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation imaging apparatus stably obtaining a long radiation image according to a situation of a test subject.SOLUTION: When performing imaging (slot imaging) performed in a state that an irradiation visual field is narrowed down by a collimator, setting of a slot width of a prescribed distance is changed based on a subject thickness of the test subject, so that even setting of a movement velocity of an imaging system is changed based on the subject thickness of the test subject. An X-ray image can be obtained in a state that a prescribed X-ray irradiation amount is secured without depending on the body thickness of the test subject, and a rectangular X-ray image (a slot image) and the long X-ray image can be stably obtained according to the situation of the test subject.

Description

  The present invention relates to a radiation imaging apparatus that performs radiation imaging by obtaining a radiation image based on detected radiation, and in particular, imaging while moving by a predetermined distance (slot width) in a state of being narrowed narrower than an irradiation field ( The present invention relates to a technique of slot radiography for performing slot imaging.

  In slot radiography, a collimator (irradiation field control means) for controlling an irradiation field irradiated from an X-ray tube (radiation irradiation means) is disposed on the irradiation side of the X-ray tube, and an X-ray detector ( The X-ray tube and the X-ray detector are parallel to the top plate along the longitudinal direction of the subject by a predetermined distance (that is, slot width) in a state of being narrowed narrower than the irradiation field projected onto the radiation detection means). Imaging is performed by intermittently irradiating slot-shaped X-rays narrowed down from the X-ray tube while being moved. Such imaging is defined as “slot imaging” in this specification.

  By combining a plurality of strip-shaped X-ray images for each slot width detected with the collimator narrowing the irradiation field of view into one long X-ray image, the so-called imaging range is longer than before. Long imaging is performed (for example, refer to Patent Document 1). The slot width is fixed.

JP 2004-236929 A (page 1-10, FIGS. 1, 6 and 8)

  However, the imaging system (X-ray tube / X-ray detector pair) preferably scans (moves) the subject in as short a time as possible. Therefore, it is essential to move the imaging system continuously instead of stepwise (scanning only at the time of imaging and stopping at other times). However, if X-ray irradiation is performed while continuously moving, blurring due to movement occurs, so the irradiation interval is limited. For example, when the body thickness of the subject is thick, it is necessary to increase the irradiation interval for each intermittent irradiation in order to ensure the X-ray dose. However, as described above, if the effective slot width is fixed, the imaging time is reduced. It can't be long. If the body thickness is large, and imaging is performed at a limited irradiation interval, only a coarse image with a small X-ray dose and granularity can be obtained.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a radiation imaging apparatus capable of stably obtaining a long radiation image according to the condition of a subject. .

In order to achieve such an object, the present invention has the following configuration.
That is, the invention according to claim 1 is disposed in the radiation irradiating means for irradiating the subject with radiation, the radiation detecting means for detecting the radiation transmitted through the subject, and the radiation irradiating means, and An irradiation field control means for controlling the irradiation field irradiated from the radiation irradiation means to be narrower than the irradiation field projected onto the radiation detection means, and obtaining a radiation image based on the detected radiation. A radiation imaging apparatus that performs radiation imaging, wherein the radiation irradiation means and the radiation detection means are in the same direction and in the same direction along the longitudinal direction of the subject in a state where the irradiation field control means narrows the irradiation field. It is configured to move relatively in parallel with the speed, and each time the radiation irradiation means and the radiation detection means move relative to the subject at a predetermined distance, the radiation irradiation is performed. The radiation detector is configured to intermittently irradiate radiation from the stage and detect the radiation transmitted through the intermittently irradiated subject, and the apparatus can detect the irradiation field by the irradiation field control unit. An image composition means for synthesizing a plurality of strip-shaped radiographic images for each predetermined distance detected in a narrowed state into one long radiographic image, and the predetermined distance is set based on the body thickness of the subject. A predetermined distance setting changing means for changing, and an irradiation interval for each intermittent irradiation, which is a time for intermittently irradiating radiation from the radiation irradiating means, is fixed, and the predetermined distance setting changing means By changing the setting of the predetermined distance based on the body thickness, the predetermined distance is a value obtained by dividing the predetermined distance by the irradiation interval for each fixed intermittent irradiation. The Do moving speed, and is characterized in that to change settings based on the body thickness of the subject.

  [Operation / Effect] According to the invention described in claim 1, the irradiation field control unit controls the irradiation field irradiated from the radiation irradiation unit to be narrower than the irradiation field projected onto the radiation detection unit. While the irradiation field is narrowed down by the visual field control means, the radiation irradiation means and the radiation detection means are moved from the radiation irradiation means while moving in parallel in the same direction and at the same speed along the longitudinal direction of the subject. , And the radiation detection means detects the radiation that has passed through the intermittently irradiated subject, and performs radiation imaging (that is, slot imaging). By performing such slot imaging, a plurality of strip-shaped radiation images for each predetermined distance (that is, slot width) detected with the irradiation field narrowed by the irradiation field control means are obtained. The image synthesizing unit synthesizes these strip-shaped radiographic images into one long radiographic image, thereby obtaining a long radiographic image. When such slot imaging is performed, a predetermined distance setting changing unit that changes the predetermined distance (slot width) described above based on the body thickness of the subject is provided, so that it does not depend on the body thickness of the subject. A radiation image can be obtained by securing a certain radiation dose. As a result, a long radiation image can be stably obtained according to the condition of the subject.

  Usually, the irradiation interval for each intermittent irradiation, which is the time for intermittently irradiating radiation from the radiation irradiation means, is fixed. Therefore, the predetermined distance setting changing means described above changes the setting of the predetermined distance based on the body thickness of the subject, so that the relative moving speed of the radiation irradiating means and the radiation detecting means with respect to the subject (that is, the predetermined distance is described above). The value divided by the irradiation interval for each fixed intermittent irradiation) is also changed based on the body thickness of the subject.

  Also, the predetermined distance setting changing means shortens the predetermined distance and slows the moving speed if the subject's body thickness is thick, and increases and changes the moving speed by increasing the predetermined distance if the body thickness is thin. Thus, it is preferable that the illumination field control means changes the illumination field according to the predetermined distance (the invention according to claim 2). It is possible to prevent the irradiation dose from being excessive or insufficient with respect to the predetermined distance (slot width) that is caused by changing the predetermined distance, and to change the setting of the irradiation field with an appropriate irradiation dose according to the predetermined distance.

According to the radiation imaging apparatus of the present invention, the predetermined distance setting changing means is based on the body thickness of the subject when imaging (slot imaging) is performed with the illumination field narrowed by the illumination field control means. By changing the setting of the predetermined distance (slot width), it is possible to obtain a radiation image by securing a certain radiation dose regardless of the body thickness of the subject. The radiation image can be obtained stably.
Further, the irradiation interval for each intermittent irradiation, which is the time for intermittently irradiating the radiation from the radiation irradiating means, is fixed, and the predetermined distance setting changing means changes the predetermined distance based on the body thickness of the subject. Thus, the relative moving speed of the radiation irradiating means and the radiation detecting means with respect to the subject (that is, the value obtained by dividing the predetermined distance by the irradiation interval for each fixed intermittent irradiation described above) is also changed based on the body thickness of the subject. Will be.

1 is a block diagram of an X-ray imaging apparatus according to an embodiment. It is a schematic diagram which shows schematic structure of the FPD drive mechanism regarding the drive of a flat panel type X-ray detector (FPD). It is a schematic diagram which shows schematic structure of the X-ray tube drive part regarding the drive of an X-ray tube. 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. It is the flowchart which showed the flow of a series of X-ray imaging. It is the flowchart which showed the flow of slot imaging during X-ray imaging. It is a schematic diagram for explaining the body thickness of a subject. It is the graph which modeled the relationship between the body thickness of a subject, and moving speed. It is a timing chart of irradiation used for explanation showing the relation between effective slot width, moving speed, and irradiation interval (exposure interval). It is the schematic of the synthesis | combination of a strip-shaped X-ray image, (a) is the schematic of the synthesis | combination of the image in an Example, (b) is the schematic of the synthesis | combination of the image in the past. It is a timing chart of each signal at the time of image composition.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of the X-ray imaging apparatus according to the embodiment, FIG. 2 is a schematic diagram showing a schematic configuration of an FPD driving mechanism related to driving of a flat panel X-ray detector, and FIG. It is a schematic diagram which shows schematic structure of the X-ray tube drive part regarding the drive of a tube. 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 imaging device is taken as an example of a radiation imaging device.

  As shown in FIG. 1, the X-ray imaging apparatus includes a top plate 1 on which a subject M is placed, an X-ray tube 2 that irradiates the subject M with X-rays, and an X transmitted through the subject M. FPD3 which detects a line is provided. A collimator 2 a that controls the irradiation field irradiated from the X-ray tube 2 is disposed on the irradiation side of the X-ray tube 2. The X-ray tube 2 corresponds to the radiation irradiation means in the present invention, the collimator 2a corresponds to the irradiation field control means in the present invention, and the FPD 3 corresponds to the radiation detection means in the present invention.

  In addition, the X-ray imaging apparatus also includes the top panel control unit 4 that controls the elevation and horizontal movement of the top panel 1, the FPD control unit 5 that controls the scanning of the FPD 3, and the tube voltage and tube current of the X-ray tube 2. An X-ray tube control unit 7 having a high voltage generation unit 6 to be generated, an A / D converter 8 that digitizes and extracts an X-ray detection signal that is a charge signal from the FPD 3, and an A / D converter 8 An image processing unit 9 that performs various processes based on the X-ray detection signal, a controller 10 that controls each of these components, a memory unit 11 that stores processed images, and an input that is input by an operator And a monitor 13 for displaying the processed image and the like.

  The top board control unit 4 horizontally moves the top board 1 to accommodate the subject M up to the imaging position, moves the top and bottom, rotates and horizontally moves the subject M to a desired position, or horizontally moves the subject M. Then, the image is picked up, or the image is moved horizontally after the image pickup is finished, and the control is performed to retract from the image pickup position. These controls are performed by controlling a top plate drive mechanism (not shown) including a motor and an encoder (not shown).

  The FPD control unit 5 performs control to translate the FPD 3 along 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 FPD drive mechanism 14 including a rack 14a, a pinion 14b, a motor 14c, an encoder 14d, and the like. Specifically, the rack 14 a extends along the body axis z direction of the subject M. The pinion 14b supports the FPD 3, and a part of the pinion 14b is fitted to the rack 14a and is rotated by the rotation of the motor 14c. For example, when the motor 14c is rotated forward, the FPD 3 is translated along the rack 14a toward the feet of the subject M as shown by the one-dot chain line in FIG. 2, and when the motor 14c is rotated reversely, the two in FIG. As indicated by the chain line, the FPD 3 moves in parallel to the head side of the subject M along the rack 14a. The encoder 14d detects the rotation direction and the rotation amount of the motor 14c corresponding to the movement direction and the movement amount (movement distance) of the FPD 3. The detection result by the encoder 14d is sent to the FPD control unit 5.

  In the present embodiment, the FPD control unit 5 changes the setting of the slot width and the moving speed based on the body thickness of the subject M stored in the body thickness memory unit 11a of the memory unit 11 described later. Specific setting changes by the FPD control unit 5 will be described later with reference to FIGS. The FPD control unit 5 corresponds to the predetermined distance setting change 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 the body axis z direction of the subject M. As shown in FIG. 3, 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 body axis z direction of the subject M, and is rotated 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 support 15a to the foot side of the subject M as shown by the one-dot chain line in FIG. As indicated by the two-dot chain line, the X-ray tube 2 moves in parallel to the head side of the subject M together with the support column 15a. 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.

  As shown in FIG. 1, in order to configure the X-ray tube 2 and the FPD 3 to translate in the same direction and at the same speed along the body axis z direction of the subject M, the motor 14c in FIG. The FPD control unit 5 and the X-ray tube control unit 7 perform control so that the rotation direction of the motor 15c in FIG. That is, the FPD control unit 5 controls the rotation amount of the motor 14c so that the movement amount of the X-ray tube 2 and the movement amount of the FPD 3 are the same, and the X-ray tube control unit 7 controls the rotation amount of the motor 15c. Control.

  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 this embodiment, slot-shaped X-rays are irradiated in the longitudinal direction (body axis z direction) of the subject M in a state of being narrowed narrower than the irradiation field projected onto the FPD 3, and the short direction (body axis z). The collimator 2a is controlled so as to irradiate fan beam-shaped X-rays extending in a direction perpendicular to the horizontal plane. Further, every time the X-ray tube 2 and the FPD 3 move for every slot width (predetermined distance) described later, X-rays are intermittently emitted from the X-ray tube 2 (slot shape in the longitudinal direction and fan beam shape in the short direction). The X-ray tube control unit 7 controls to irradiate the light. The FPD controller 5 controls the FPD 3 to detect X-rays transmitted through the subject M irradiated intermittently.

  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 each corrected X-ray image Are combined with one long X-ray image. The image composition unit 9b corresponds to image composition means. Specific functions of the image composition unit 9b 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. In the present embodiment, the memory unit 11 includes a body thickness memory unit 11a, and the body thickness memory unit 11a stores in advance the body thickness of the subject M obtained by fluoroscopic imaging according to the site of the subject M. It is remembered. Similarly to the controller 10, the FPD control unit 5 and the X-ray tube control unit 7 are also configured with 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 changes by the FPD control unit 5 and specific functions of the image composition unit 9b will be described with reference to FIGS. FIG. 6 is a flowchart showing a flow of a series of X-ray imaging, FIG. 7 is a flowchart showing a flow of slot imaging during X-ray imaging, and FIG. 8 is a description of the body thickness of the subject. FIG. 9 is a graph schematically illustrating the relationship between the body thickness of the subject and the moving speed, and FIG. 10 is a relationship between the effective slot width, the moving speed, and the irradiation interval (exposure interval). FIG. 11 is a schematic diagram of composition of strip-shaped X-ray images, and FIG. 12 is a timing chart of signals at the time of image composition.

(Step S1) Perspective Imaging Before performing actual slot imaging, first, fluoroscopic imaging is performed. The imaging system (X-ray tube 2 / FPD 3 pair) scans (moves) the subject M under fluoroscopic conditions to perform fluoroscopic imaging, and obtains the body thickness of the subject M according to the site of the subject M. The body thickness of the subject M corresponding to the site of the subject M is written and stored in the body thickness memory unit 11a. For example, as shown in FIG. 8, becomes h ₁ is the body thickness of the region of the neck of the subject M, the body thickness of the region of the chest becomes h _2. By reading out information on the body thickness h including the body thicknesses h ₁ and h ₂ at these parts from the body thickness memory unit 11a, a certain amount of X is obtained without depending on the body thickness of the subject M in the next slot imaging. Control X-ray conditions (in this case, slot width setting change) in the next slot imaging so that a dose (X-ray irradiation amount) and a certain amount of X-ray detection signal (image signal) can be obtained. . That is, fluoroscopy for automatic brightness control is performed in step S1. If the body thickness h of the subject M is already stored in the memory unit 11a and the information of the same body thickness h of the subject M is always used in each slot imaging, the fluoroscopic imaging in this step S1. It is not always necessary to do. Of course, if the latest information on the body thickness h of the subject M is always used, the fluoroscopic imaging in step S1 is performed before each slot imaging.

(Step S2) Slot Imaging When fluoroscopic imaging is performed in step S1 and the body thickness h of the subject M is written and stored in the body thickness memory unit 11a, slot imaging is performed. Step S2 includes the following steps T1 to T3.

(Step T1) Setting Change of Slot Width (Movement Speed) First, the FPD control unit 5 changes the setting of the slot width based on the body thickness of the subject M stored in the body thickness memory unit 11a. Usually, the irradiation interval for each intermittent irradiation, which is the time for intermittently irradiating the X-rays from the X-ray tube 2, is fixed. Therefore, the FPD control unit 5 changes the setting of the slot width that is a predetermined distance based on the body thickness h of the subject M, thereby moving the imaging system (X-ray tube 2 / FPD 3 pair) relative to the subject M ( In other words, the value obtained by dividing the slot width (predetermined distance) by the irradiation interval for each fixed intermittent irradiation described above is also changed based on the body thickness h of the subject M. Therefore, in this embodiment, changing the setting of the slot width will be described as synonymous with changing the setting of the moving speed.

When the moving speed is V, when the body thickness h of the subject M is thick, the slot width (moving speed V) is shortened as shown in FIG. (Slow) Conversely, when the body thickness h of the subject M is thin, the slot width (moving speed V) is increased as shown in FIG. 9 (faster at the moving speed V) in order to ensure a constant X-ray dose. When the body thickness h ₁ of the neck region of the subject is thicker than the body thickness h ₂ of the chest region (that is, h ₁ > h ₂ ), the imaging system (X-ray tube 2 and FPD 3 pair) is the neck region. when scanning a is faster the movement speed as V _1, when the imaging system (X-ray tube 2 · FPD 3 pairs) scans the site of the chest to slow its movement speed as V _2. In the graph of FIG. 9, the function is represented by a linear function, but is not limited thereto, and may be a quadratic function or another curved function. Further, since the transmittance and absorption rate of X-rays differ depending on the region of the subject M, even if the relationship between the body thickness h and the moving speed V of the subject M is graphed in consideration of the transmittance and the absorption rate. Good.

  The actual slot width is defined as “effective slot width”, and as shown in FIG. 10, the effective slot width is d, and the irradiation interval (that is, the exposure interval) that is the time interval from intermittent irradiation to the next intermittent irradiation. ) Is t, d = V × t. If a portion (fixed width) necessary for image composition is Δd and a width obtained by adding the fixed width Δd to the effective slot width d is d ′, d ′ = d + Δd. Therefore, when the effective slot width d is changed by the FPD control unit 5, the collimator 2a preferably changes the setting of the illumination field according to the effective slot width d. Of course, the collimator 2a may change the setting of the illumination field according to the width d ′ obtained by adding the fixed width Δd to the effective slot width d, and the target of the setting change is limited particularly to the effective slot width d and the width d ′. Not.

(Step T2) Acquisition of a strip-shaped X-ray image The (valid) slot width d based on the body thickness h of the subject M, the setting of which is changed by the FPD control unit 5 in Step T1, and the illumination corresponding to the slot width d In the field of view, the imaging system (X-ray tube 2 / FPD 3 pair) scans each part of the subject M and acquires a strip-shaped X-ray image (also referred to as a “slot image”). Specifically, the imaging system (X-ray tube 2 and FPD 3 pair) is in the same direction and at the same speed along the body axis z, which is the longitudinal direction of the subject M, with the irradiation field narrowed by the collimator 2a. The X-ray detection signal is obtained by intermittently irradiating X-rays from the X-ray tube 2 while the FPD 3 detects X-rays transmitted through the subject M irradiated intermittently. . In the illumination fields P ₁ , P ₂ ,..., P _N projected onto the FPD 3 by the correction unit 9a performing lag correction, gain correction, and the like on the X-ray detection signal. A strip-shaped X-ray image (slot image) having an effective slot width d is obtained as P _S1 , P _{S2 ,.}

Since the effective slot width d is changed according to the region of the subject M, for example, as shown in FIG. In the conventional case, since the effective slot width d is fixed without changing the setting, it is as shown in FIG. If the effective slot width d in the slot images P _S1 , P _S2 ,..., P _SN is as shown in FIG. 11 (a), the next slot image P is defined based on the first slot image P _{S1. In S2} , the body thickness h of the subject M is thinner than that in the slot image _PS1 , so the moving speed V is increased to increase the effective slot width d. Conversely, in the last slot image _PSN , the body thickness h of the subject M is thicker than that in the slot image _PS1 , so the moving speed is slowed down to shorten the effective slot width d.

(Step T3) Is there a site?
For each intermittent irradiation, slot images P _S1 , P _S2 ,..., _PSN as shown in FIG. 11A are obtained in order to determine whether or not there is a site to be scanned. If there is a part to be scanned, the process returns to step T2, and steps T2 and T3 are repeated until there is no part to be scanned. If there is no part to be scanned, it is assumed that the slot imaging consisting of the above steps T1 to T3 is completed.

(Step S3) Image Composition The image composition unit 9b composes a plurality of N slot images P _S1 , P _S2 ,..., _PSN as shown in FIG. . In this synthesis, considering the X-ray transmittance and absorption rate according to the region of the subject M, as shown in FIG. 12, each slot image P _S1 , P _{S2 ,.} It is preferable that weighting is performed for the synthesis. “Weight 1” in FIG. 12 is a value weighted for “slot image 1” in FIG. 12, “Weight 2” is a value weighted for “slot image 2”, “3” is a value weighted for “slot image 3”, and “weight 4” is a value weighted for “slot image 4”. Therefore, in the case of FIG. 12, the composite image is expressed as composite image = slot image 1 × weight 1 + slot image 2 × weight 2 + slot image 3 × weight 3 + slot image 4 × weight 4+.

  In FIG. 12, since it is represented by a timing chart, the time corresponding to the effective slot width d is d / V, and the time corresponding to the width d ′ is d ′ / V. Further, since the above-described fixed width Δd is divided into two in time series, the time corresponding to Δd / 2 is added before and after the time (d / V) corresponding to the effective slot width d. The time corresponding to Δd / 2 is Δd / 2V.

  According to the X-ray imaging apparatus according to the present embodiment, the collimator 2a is configured such that the irradiation field irradiated from the X-ray tube 2 is narrower than the irradiation field projected onto the flat panel X-ray detector (FPD) 3. The X-ray tube 2 and the FPD 3 are translated in the same direction and at the same speed along the body axis z, which is the longitudinal direction of the subject M, with the irradiation field narrowed by the collimator 2a. X-rays are intermittently irradiated from the tube 2, the FPD 3 detects X-rays transmitted through the subject M irradiated intermittently, and X-ray imaging (that is, slot imaging) is performed. By performing such slot imaging, a plurality of strip-shaped X-ray images (that is, slot images) for each predetermined distance (that is, slot width d) detected with the irradiation field narrowed by the collimator 2a are obtained. . The image combining unit 9b combines these strip-shaped X-ray images (slot images) into one long X-ray image, thereby obtaining a long X-ray image.

  When such a slot imaging is performed, the FPD control unit 5 that changes the setting of the predetermined distance (slot width d) described above based on the body thickness h of the subject M is provided, thereby reducing the body thickness h of the subject M. An X-ray image can be obtained by ensuring a constant X-ray irradiation dose (X-ray dose) without depending on the X-ray image. As a result, a long X-ray image can be stably obtained according to the condition of the subject M.

  When the subject M is applied to a human body and this X-ray imaging is applied to a diagnostic apparatus such as an orthopedic surgeon, only the bone components of the entire spinal column required by the orthopedic surgeon are extracted in the body axis direction of the human body. It is possible to extract a specific tissue in a long field of view. As a result, an X-ray dose is ensured and an image with good graininess can be obtained, and the diagnostic ability can be improved.

  In the present embodiment, the FPD control unit 5 shortens the predetermined distance (slot width d) if the body thickness h of the subject M is thick, and decreases the predetermined distance (slot width d) if the body thickness h is thin. By changing the setting long (wide), preferably, the collimator 2a changes the setting of the irradiation field according to the predetermined distance. It is possible to prevent an excess or deficiency of the X-ray irradiation amount with respect to the predetermined distance (slot width) caused by changing the predetermined distance, and to change the setting of the irradiation field with an appropriate X-ray irradiation amount according to the predetermined distance.

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

  (1) In the above-described embodiments, an X-ray imaging apparatus has been described as an example of a radiation imaging apparatus. However, an ECT (Emission) represented by a PET (Positron Emission Tomography) apparatus, a SPECT (Single Photon Emission CT) apparatus, or the like. Applied to radiation imaging devices that perform radiation imaging by detecting radiation other than X-rays (γ rays in the case of PET devices) and obtaining radiation images based on the detected radiation, such as computed tomography devices May be.

  (2) In the above-described embodiment, the X-ray imaging apparatus as shown in FIG. 1 has been described as an example. However, the present invention is also applied to, for example, an X-ray imaging apparatus disposed on a C-arm. Also good. The present invention may also be applied to an X-ray CT apparatus.

  (3) In the above-described embodiment, the flat panel X-ray detector is taken as an example of the radiation detection means. However, the X-ray detection means normally used like 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.

  (4) In the above-described embodiment, only the radiation irradiation means represented by the X-ray tube 2 and the radiation detection means represented by the FPD 3 are moved to fix the top plate 1 on which the subject M is placed. The radiation irradiating means and the radiation detecting means are relatively translated in the same direction and at the same speed along the longitudinal direction of the subject, but the radiation irradiating means and the radiation detecting means are mutually moved along the longitudinal direction of the subject. The specific movement is not limited as long as it moves in parallel in the same direction and at the same speed. For example, the radiation irradiation means represented by the X-ray tube 2 and the radiation detection means represented by the FPD 3 are fixed, and only the top plate 1 on which the subject M is placed is moved in the longitudinal direction. In addition, the radiation detection means may be relatively translated in the same direction and at the same speed along the longitudinal direction of the subject. In addition, the radiation irradiation means represented by the X-ray tube 2 and the radiation detection means represented by the FPD 3 are moved, and the top plate 1 on which the subject M is placed is also moved in the longitudinal direction. The radiation detection means may be relatively translated in the same direction and at the same speed along the longitudinal direction of the subject.

  (5) In the above-described embodiment, the collimator 2a has been described as an example of the illumination field control means in the present invention. However, any means for controlling the illumination field is particularly limited as illustrated by a simple slit. Not.

  (6) In the embodiment described above, all the strip-shaped images (slot images) are combined and then combined, but may be combined each time each slot image is acquired.

2 ... X-ray tube 2a ... Collimator 3 ... Flat panel X-ray detector (FPD)
5 ... FPD control part 9b ... Image composition part d ... (Effective) Slot width V ... Movement speed h ... Body thickness P _S1 , P _S2 , ..., P _SN ... Strip-shaped X-ray image (slot image)
Q ... Long X-ray image z ... Body axis M ... Subject

Claims (2)

A radiation irradiating means for irradiating the subject with radiation; a radiation detecting means for detecting radiation transmitted through the subject; and an irradiation field disposed on the radiation irradiating means and irradiated from the radiation irradiating means. An irradiation field control unit that controls the irradiation field narrower than the irradiation field projected onto the radiation detection unit, and a radiation imaging apparatus that performs radiation imaging by obtaining a radiation image based on the detected radiation, The radiation irradiating means and the radiation detecting means are configured to relatively translate in the same direction and at the same speed along the longitudinal direction of the subject while the irradiation field control means narrows the irradiation field. In addition, every time the radiation irradiating means and the radiation detecting means move relative to the subject at a predetermined distance, the radiation irradiating means intermittently irradiates the radiation, The radiation detection means is configured to detect radiation that has passed through a partially irradiated subject, and the apparatus detects the predetermined distance detected with the irradiation field control means narrowing the irradiation field. Image synthesizing means for synthesizing a plurality of strip-shaped radiographic images for each elongate radiographic image, and predetermined distance setting changing means for changing the predetermined distance based on the body thickness of the subject,
The irradiation interval for each intermittent irradiation, which is the time for intermittently irradiating the radiation from the radiation irradiating means, is fixed, and the predetermined distance setting changing means changes the predetermined distance based on the body thickness of the subject. Thus, the relative movement speed of the radiation irradiation means and the radiation detection means relative to the subject, which is a value obtained by dividing the predetermined distance by the irradiation interval for each fixed intermittent irradiation, is based on the body thickness of the subject. A radiation imaging apparatus characterized in that the setting is changed.   2. The radiation imaging apparatus according to claim 1, wherein the predetermined distance setting change unit shortens the predetermined distance and slows the moving speed if the subject has a large body thickness, and if the body thickness is thin. The radiation imaging apparatus according to claim 1, wherein the irradiation field control means changes the setting of the irradiation field according to the predetermined distance by increasing the predetermined distance and changing the moving speed faster.

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