JP5415885B2 - Radiation CT apparatus and image processing apparatus - Google Patents

Description

  The present invention provides an image acquired by a radiation CT apparatus that captures a radiation image of a subject placed on a rotation axis while rotating an imaging unit in which a radiation source and a detection panel are opposed to each other with the rotation axis interposed therebetween. The present invention relates to a radiation CT apparatus and an image processing apparatus for correcting deformation of a subject shape on an image represented by the image signal.

  Conventionally, a radiation CT (Computed Tomography) apparatus for performing radiography is known. As such a radiation CT apparatus, a subject is placed on a rotation axis while rotating a radiographic source that emits radiation in a conical shape and an imaging unit in which a two-dimensional detection panel is disposed opposite to the rotation axis. There is known one that obtains a three-dimensional radiation CT image by continuously capturing radiation images and further performing image reconstruction calculation based on image signals obtained by continuous imaging (for example, Patent Document 1).

  Such a radiation CT apparatus is generally an apparatus that shoots a subject on a bed and rotates an imaging unit around a horizontal axis. In addition, the imaging unit is held by a movable arm. The position and angle of the imaging unit can be adjusted freely, and the imaging unit can be used in a state where the subject is standing upright as well as a mode in which imaging is performed while rotating the imaging unit around the horizontal axis with the subject lying down. There has also been proposed an apparatus capable of performing various photographing such as an aspect of photographing while rotating around a vertical axis.

  When imaging is performed while rotating the imaging unit as in the radiation CT apparatus as described above, an accurate three-dimensional radiation CT image cannot be constructed unless the positional relationship between the radiation source and the detection panel with respect to the rotation axis is always constant. However, when a heavy object such as a radiation source or a detection panel is rotated, the positional relationship between the radiation source and the detection panel with respect to the rotation axis is kept constant by deformation of the C arm, vibration of the device, mechanical rattling of the drive unit, and the like. It is very difficult to keep.

  Therefore, for example, a phantom of a known shape is photographed in advance, subject shape correction information is acquired based on the image captured at this time, and the shape of the image obtained by actual photographing is determined based on the correction information. It is conceivable to perform some correction such as correction. (For example, patent documents 1-3 etc.)

JP 09-173330 A Japanese Patent No. 399389 JP 2005-058309 A

  Here, the positional relationship between the radiation source and the detection panel in the radiation CT apparatus will be described in detail with reference to the drawings. 2A is a schematic perspective view of the radiation source and detection panel of the radiation CT apparatus, FIG. 2B is a top view of the radiation source and detection panel shown in FIG. 2A, and FIG. 2C is FIG. It is a side view of the radiation source and detection panel which are shown to (A).

  As shown in FIG. 2A, the radiation source 10 and the detection panel 11 normally detect the radiation irradiation axis from the radiation source 10 (more precisely, the radiation focal point in the radiation source 10) through the rotation axis Z. Although it arrange | positions so that it may hit the center of the panel 11, it may remove | deviate from this arrangement | positioning at the time of imaging | photography for the above reasons.

  As shown in FIGS. 2B and 2C, this shift is caused by the fact that the detection panel 11 is shifted in the horizontal direction (U-axis direction) with respect to the radiation irradiation axis from the radiation focus 10. A deviation of the detection panel 11 in the vertical direction (V-axis direction) with respect to the radiation irradiation axis from the focal point 10 is a V-axis offset, a rotation of the detection panel 11 about the horizontal direction is a U-tilt, and the detection panel 11 is vertical. Rotation about the direction is called V tilt, and rotation of the detection panel 11 with respect to the radiation irradiation axis from the radiation focus 10 is called a pivot angle.

  In order to construct an accurate three-dimensional radiation CT image, correction must be made so as to reduce all the effects of these errors. However, in Patent Document 1, only the U-axis offset, the V-axis offset, and the pivot angle are used. In Patent Document 2, correction is performed only for the U-axis offset, and in Patent Document 3, correction is performed only for the U-axis offset and the pivot angle.

  That is, various correction methods have been proposed for correcting the U-axis offset, V-axis offset, and pivot angle, but no effective method has been proposed for U-tilt and V-tilt.

  An object of the present invention is to provide a radiation CT apparatus and an image processing apparatus capable of correcting the V tilt among them.

  The applicant of the present application photographs a phantom of a known shape in consideration of the subject extending so as to include a horizontal component on a three-dimensional radiation CT image when a V tilt occurs in the radiation detection means. In the three-dimensional radiation CT image obtained by this, the influence of the V tilt of the radiation detecting means is obtained based on the horizontal extent of the phantom shape, and the image signal is corrected so as to reduce the influence of the V tilt. It was found that V tilt can be corrected by doing so.

  This point will be described in detail with reference to the drawings. FIG. 3 is a diagram showing a state of phantom imaging when a V-tilt is generated in the radiation detecting means, and FIG. 4 is a three-dimensional radiation CT acquired by phantom imaging when a V-tilt is generated in the radiation detecting means. FIG. 5 is a detailed tomogram of a three-dimensional radiation CT image acquired by phantom imaging, FIG. 5A is an image in a state where no V tilt occurs, and FIG. 5C is an image in a state where V tilt is generated, FIG. 5C is an image obtained by binarizing the images of FIGS. 5A and 5B, and FIG. 6 is an image of FIGS. 5A and 5B. This is an image profile.

  The left part of FIG. 3 shows a state in which the rotation axis Z is viewed from above. As shown here, since the radiation source emits conical radiation (cone beam), V-tilt is applied to the radiation detection means. If this occurs, the reconstructed position of the micro phantom A is shifted in the horizontal direction from the position where it is originally reconstructed.

  In addition, the right part of FIG. 3 shows the state of the rotation axis Z as viewed from the side. As shown here, since the radiation source emits conical radiation (cone beam), When the V tilt is generated, if the position of the microsphere phantom A is shifted from the midplane (the rotational orbital plane of the radiation focal point about the rotation axis Z), the reconstruction position is originally reconstructed. A different amount of deviation occurs in each of the photographing directions in the vertical direction from the position where the image is applied.

As a result of combining these, as shown in FIG. 4, on the three-dimensional radiation CT image, the microsphere phantoms A, B, and C having the same shape are stretched in different directions depending on the height. CT images A ′, B ′, and C ′ are reconstructed. (A, B, and C in the figure show CT images when no V tilt occurs in the radiation detection means.)
The phantom CT images A ′, B ′, and C ′ are each stretched from the origin (image center) onto a line that connects the centers of the phantoms A, B, and C. The vertical component can be decomposed according to the height at which the microsphere phantoms A, B, and C are arranged. Specifically, the phantom on the midplane has V The vertical component of the tilt influence amount does not appear, and the vertical component of the V tilt influence amount appears as the phantom moves away from the midplane in the vertical direction.

  Regarding the horizontal direction component W, the horizontal direction component W of the V tilt influence amount does not appear in the phantom on the rotation axis Z, and the horizontal direction component W of the V tilt influence amount increases as the phantom moves away from the rotation axis Z in the horizontal direction. In addition, the effect of V tilt appears uniformly according to the distance from the rotation axis Z in the horizontal direction regardless of the height from the midplane.

  That is, since the CT image of the phantom extends on a line connecting the origin (image center) to the center of the phantom, the V tilt amount may be calculated based on the length in the extending direction. The V tilt amount may be calculated based on the length of the horizontal component of the CT image of the phantom, but in any case, the V tilt amount can be grasped by paying attention to the horizontal extent of the phantom shape. It becomes possible to do.

  Here, as a method for determining the extent of the phantom shape in the horizontal direction, as shown in FIG. 5A, an image in a state where no V tilt is generated or as shown in FIG. A method of binarizing an image in a state where V tilt is generated as shown in FIG. 5C and comparing the lengths in a direction including a horizontal component such as a stretching direction or a horizontal direction, or as shown in FIG. Thus, any method such as a method of comparing the half-value width in the direction profile including the horizontal direction component of the image shown in FIG. 5A or FIG. 5B, a method of comparing indexes such as contrast and sharpness, etc. But it doesn't matter.

  The first radiation CT apparatus of the present invention is made on the basis of the above knowledge, and a radiation source for emitting radiation in a conical shape and a radiation detecting means for detecting radiation are arranged opposite to each other with a rotation axis in between. An imaging unit, a driving unit that rotates the imaging unit around a rotation axis, a reading unit that reads an image signal recorded in the radiation detection unit, and a radiation image of a subject arranged on the rotation axis while rotating the imaging unit CT apparatus comprising: control means for controlling to continuously take images, and image processing means for obtaining a three-dimensional radiation CT image of a subject by performing image reconstruction calculation based on image signals obtained by continuous photography In the three-dimensional radiation CT image obtained by photographing a phantom of a known shape, the V-shaped detector of the radiation detecting means is based on the horizontal extent of the phantom shape. Seeking effect of bets, is characterized in that it comprises a correction means for correcting an image signal so as to reduce the effect of V tilt.

  Here, “the extent of the phantom shape in the horizontal direction” means a direction including the horizontal direction component of the phantom in the vertical sectional view of the three-dimensional radiation CT image including the origin of the three-dimensional radiation CT image and the center position of the phantom. Measure not only the length but also the spread of the half width in the profile including the horizontal component of the phantom in the above cross-sectional view, the extent of the direction including the horizontal component of the phantom shape, such as contrast and sharpness. Any index can be used as long as it is possible.

  The applicant of the present application has found that not only the V tilt amount but also the V axis offset amount can be easily grasped when grasping the deviation amount of the radiation detecting means from the three-dimensional radiation CT image as described above. This point will be described in detail with reference to the drawings. FIG. 7 is a diagram showing a state of phantom imaging when a V-axis offset is generated in the radiation detection means, and FIG. 8 is a three-dimensional image acquired by phantom imaging when a V-axis offset is generated in the radiation detection means. It is a tomogram of a radiation CT image.

  As shown in FIG. 7, when a V-axis offset occurs in the radiation detection means and the radiation detection means is displaced upward, the projection position of the phantom on the detection surface of the radiation detection means moves relatively downward, and as a result The reconstruction position of the minute phantom A moves downward from the position where it is originally reconstructed. On the contrary, when the radiation detection means is shifted downward, the projection position of the phantom on the detection surface of the radiation detection means moves relatively upward, and as a result, the reconstruction position of the micro phantom A is originally reconstructed. Will move upwards.

  Further, since cone-shaped radiation (cone beam) is emitted from the radiation source, if the V-axis offset is generated in the radiation detection means, the reconstruction position of the micro phantom A is perpendicular to the position where it is originally reconstructed. In the direction, a different amount of deviation occurs for each photographing direction.

  As a result of combining these, as shown in FIG. 8, on the three-dimensional radiation CT image, the CT images A ′, B ′, and C ′ of the phantoms are displayed regardless of the arrangement positions of the microsphere phantoms A, B, and C. The center position moves in the direction opposite to the direction of the V-axis offset, and extends in the vertical direction depending on the amount of V-axis offset. Therefore, it is possible to grasp the V-axis offset by paying attention to the position of the phantom and the vertical spread of the phantom shape.

  In addition, as a method for determining the vertical extent of the phantom shape, similarly to the above-described V tilt, a method of binarizing the captured image and comparing the length in the direction including the vertical component, Any method may be used such as a method of comparing indices such as the length of the half-value width in the direction profile including the vertical direction component, contrast, and sharpness.

  The second radiation CT apparatus of the present invention has been made based on the above knowledge, and a radiation source that emits radiation in a conical shape and a radiation detection means that detects radiation are disposed opposite to each other with a rotation axis in between. An imaging unit, a driving unit that rotates the imaging unit around a rotation axis, a reading unit that reads an image signal recorded in the radiation detection unit, and a radiation image of a subject arranged on the rotation axis while rotating the imaging unit CT apparatus comprising: control means for controlling to continuously take images, and image processing means for obtaining a three-dimensional radiation CT image of a subject by performing image reconstruction calculation based on image signals obtained by continuous photography In a three-dimensional radiation CT image obtained by photographing a phantom of a known shape, based on the position of the phantom and the vertical spread of the phantom shape Seeking effect of V-axis offset of the radiation detecting means, it is characterized in that it comprises a correction means for correcting an image signal so as to reduce the effects of V-axis offset.

  Here, “the extent of the phantom shape in the vertical direction” means a direction including the vertical component of the phantom in the vertical sectional view of the three-dimensional radiation CT image including the origin of the three-dimensional radiation CT image and the center position of the phantom. Measure not only the length but also the width of the half-value width in the profile including the vertical component of the phantom in the above cross-sectional view, the degree of spread in the direction including the vertical component of the phantom shape, such as contrast and sharpness. Any index can be used as long as it is possible.

  In the radiation CT apparatus of the present invention, an apparatus that acquires an image signal and an image processing apparatus that performs image processing on the image signal may be configured separately. In the first image processing apparatus according to the present invention, a radiation source that emits radiation in a conical shape and a radiation detection means that detects radiation are disposed opposite to each other with a rotation axis therebetween. An imaging unit, a driving unit that rotates the imaging unit around a rotation axis, a reading unit that reads an image signal recorded in the radiation detection unit, and a radiation of a subject arranged on the rotation axis while rotating the imaging unit Radiation CT comprising control means for controlling to continuously take images, and image processing means for obtaining a three-dimensional radiation CT image of a subject by performing image reconstruction calculation based on image signals obtained by continuous photography By equipment An image processing apparatus that performs image processing on an acquired image signal, based on a horizontal spread of a phantom shape in a three-dimensional radiation CT image obtained by photographing a phantom of a known shape And a correction means for correcting the image signal so as to reduce the influence of the V tilt by obtaining the influence of the V tilt of the radiation detection means.

  Further, the second image processing apparatus of the present invention includes an imaging unit in which a radiation source that emits radiation in a conical shape and a radiation detection unit that detects radiation are disposed opposite to each other with a rotation axis interposed therebetween, and the imaging unit is configured with the rotation axis Driving means for rotating the image center, reading means for reading out image signals recorded in the radiation detection means, and control for continuously taking radiographic images of the subject arranged on the rotation axis while rotating the imaging unit An image signal obtained by a radiation CT apparatus comprising: means and an image processing means for obtaining a three-dimensional radiation CT image of a subject by performing image reconstruction calculation based on an image signal obtained by continuous imaging An image processing apparatus that performs image processing, and in a three-dimensional radiation CT image obtained by photographing a phantom of a known shape, the phantom position and the phantom shape are perpendicular to each other. Seeking effect of V-axis offset of the radiation detector based on the spatial spread of direction, it is characterized in that it comprises a correction means for correcting an image signal so as to reduce the effects of V-axis offset.

  According to the first radiation CT apparatus and image processing apparatus of the present invention, when a V tilt occurs in the radiation detection means, the subject extends so as to include a horizontal component on the three-dimensional radiation CT image. In consideration, in a three-dimensional radiation CT image obtained by imaging a phantom of a known shape, the influence of the V tilt of the radiation detection means is obtained based on the horizontal extent of the phantom shape, and the V tilt Since the image signal is corrected so as to reduce the influence of the above, it is possible to correct the V tilt which has been difficult in the past.

  Further, according to the second radiation CT apparatus and image processing apparatus of the present invention, it is considered that the subject extends in the vertical direction on the three-dimensional radiation CT image when a V-axis offset is generated in the radiation detection means. Then, in the three-dimensional radiation CT image obtained by imaging a phantom of a known shape, the influence of the V-axis offset of the radiation detection means is obtained based on the position of the phantom and the vertical spread of the phantom shape. Thus, since the image signal is corrected so as to reduce the influence of the V-axis offset, the V-axis offset can be easily corrected based on the three-dimensional radiation CT image.

1 is a schematic configuration diagram of a radiation CT apparatus according to an embodiment of the present invention. Schematic perspective view of radiation source and detection panel of radiation CT apparatus Top view of the radiation source and detection panel shown in FIG. Side view of radiation source and detection panel shown in FIG. The figure which shows the state of the phantom imaging | photography when V tilt has generate | occur | produced in the radiation detection means A tomographic view of a three-dimensional radiation CT image acquired by phantom imaging when a V tilt occurs in the radiation detection means It is a detailed tomogram of a three-dimensional radiation CT image acquired by phantom imaging, and an image in a state where no V tilt occurs An image with V-tilt occurring, An image obtained by binarizing the images of FIGS. 5 (A) and 5 (B) Profiles of images in FIGS. 5 (A) and 5 (B) The figure which shows the state of the phantom imaging when the V-axis offset has generate | occur | produced in the radiation detection means A tomogram of a three-dimensional radiation CT image acquired by phantom imaging when a V-axis offset occurs in the radiation detection means

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a radiation CT apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the radiation CT apparatus 1 is connected to an imaging apparatus that captures a radiographic image, a bed 22 that is a support base for supporting the subject P, and the imaging apparatus, and controls and captures the imaging apparatus. The computer 30 which processes the image obtained by this, and the monitor 31 connected to this computer 30 are comprised.

  The imaging apparatus includes a radiation source 10 that emits conical radiation (hereinafter also referred to as conical radiation), a detection panel 11 that detects radiation emitted from the radiation source 10, and a C-arm that holds the radiation source 10 and the detection panel 11. The imaging unit 2 includes 12, a driving unit 15 that rotates the imaging unit 2, and an arm 20 that holds the driving unit 15.

  The imaging unit 2 can rotate 360 ° around the rotation axis C. In addition, the arm 20 including the movable portion 20a is held by a base 21 that is movably attached to the ceiling, and can be moved to a wide range of positions in the photographing room, and the rotation direction of the photographing portion 2 ( The rotation axis angle) can also be changed.

  The radiation source 10 and the detection panel 11 are arranged to face each other with the rotation axis C interposed therebetween. When performing radiation CT imaging with the radiation CT apparatus 1, the rotation axis C, the radiation source 10, and the detection panel 11 are positioned relative to each other. The relationship is fixed. The detection surface on which the detection pixels constituting the detection panel 11 are arranged may be a flat surface or a curved surface.

  The computer 30 includes a central processing unit (CPU) (not shown) as control means, a storage device (not shown) such as HDD and SSD, and operation input means such as a mouse and keyboard (not shown).

  The CPU functions as a correction unit that performs correction processing on the image signal acquired from the detection panel 11 or an image processing unit that obtains a three-dimensional radiation CT image of the subject by performing image reconstruction calculation based on the image signal. As control means for controlling the functions of the radiation source 10, the detection operation of the detection panel 11 and the control of the image signal reading operation, the rotation control of the imaging unit 2 by the drive unit 15, and the drive control of the arm 20 and the base unit 21. It has the function of.

  Hereinafter, the operation of the radiation CT apparatus 1 will be described.

  First, the subject P is laid on the bed 22, and the radiation source 10 and the detection panel 11 are arranged at symmetrical positions with the rotational axis C being the approximate center of the subject P's body. Then, the photographing unit 2 is positioned. The photographing unit 2 is moved based on the operation of the computer 30 by the photographer.

  After positioning the photographing unit 2 in this way, when the photographer operates the computer 30 to input the angular velocity and photographing start instruction of the photographing unit 2, the CPU rotates the photographing unit 2 to rotate the subject. Imaging is performed while the radiation source 10 and the detection panel 11 are rotated integrally around a rotation axis C passing through P.

  While rotating the imaging unit 2, the exposure of the conical radiation emitted from the radiation source 10 and passing through the subject P to the detection panel 11 and the reading of the image signal recorded on the detection panel 11 are repeated a plurality of times at predetermined angles. Thus, radiographic images representing the subject P are continuously acquired. That is, for each shooting in the continuous shooting, the image signal recorded on the detection panel 11 is read out, input to the computer 30, and stored in the storage device.

  The above process is repeatedly executed, and the continuous shooting with the subject P as the subject is completed.

  After completion of the continuous imaging, the CPU generates a three-dimensional radiation CT image by performing an image reconstruction calculation based on a plurality of image signals stored in the storage device, and displays it on the monitor 31.

  Note that, when imaging is performed while rotating the imaging unit 2, it is difficult to obtain an accurate three-dimensional radiation CT image due to the overlap of various factors as described above. A microsphere phantom is arranged around the subject P, and the subject P and the microsphere phantom are photographed simultaneously.

  Here, the V tilt and V axis offset correction processing performed in the present embodiment will be described in detail.

  First, regarding the V tilt correction process, as described above, on the three-dimensional radiation CT image of the phantom obtained by photographing the phantom of a known shape, attention is paid to the horizontal component in the extending direction of the phantom CT image. Thus, the V tilt amount can be grasped, and the V tilt amount is obtained based on these pieces of information. Then, the image signal is corrected so as to reduce the influence of the V tilt obtained above on a plurality of image signals (signals representing the projection image) before the image reconstruction calculation.

  As shown in FIG. 2B, the correction process is performed with reference to the radiation source 10 (more precisely, the radiation focus in the radiation source 10) when the detection panel 11 has a V tilt. The projected image appears smaller in the portion closer to the position, and the projected image appears larger in the portion farther than the original position with respect to the radiation focal point 10. What is necessary is just to process.

  Next, regarding the V-axis offset correction process, as described above, the V-axis offset is calculated from the vertical length of the phantom on the three-dimensional radiation CT image of the phantom obtained by photographing the phantom having a known shape. It is possible to grasp the influence direction of the V-axis offset depending on whether the CT image of the phantom is shifted up or down with respect to the position where the phantom CT image is originally reconstructed. Based on this information, the amount of V-axis offset and the moving direction are obtained. Then, the image signal is corrected so as to reduce the influence of the V-axis offset obtained as described above on a plurality of image signals (signals representing a projection image) before the image reconstruction calculation.

  As for this correction processing, as shown in FIG. 2C, when the V-axis offset is generated in the detection panel 11, the detection panel 11 is moved above the original position with respect to the radiation focus 10. The projected image is projected downward, and when the detection panel 11 is moved below the original position with respect to the radiation focal point 10, the projected image is projected upward. Can be done.

  Then, by performing image reconstruction calculation again based on the plurality of image signals that have been subjected to the V tilt and V axis offset correction processing as described above, the three-dimensional radiation CT in which the influence of the V tilt and the V axis offset is reduced. An image can be acquired.

  As for the phantom arrangement position, as described above, the horizontal component of the V tilt influence amount does not appear in the phantom on the rotation axis Z, and the V tilt influence amount increases as the phantom moves away from the rotation axis Z in the horizontal direction. Since many horizontal components appear and it becomes easy to detect the amount of V tilt influence, it is preferable to dispose the phantom away from the rotation axis Z in the horizontal direction.

  The shape of the phantom to be photographed is preferably a microsphere, but it is not always necessary to have this shape, and various shapes of phantoms can be used.

  Although the radiation CT apparatus of the present invention has been described in detail above, the present invention is not limited to the above embodiment.

  For example, it is not always necessary to photograph the phantom at the same time as the subject. When only the phantom is photographed first, information on the V tilt and the V-axis offset obtained at this time is stored, and the actual photographing is performed later. In addition, the correction process may be performed on the image signal at the time of the main photographing based on the information about the V tilt and the V axis offset acquired in advance.

  Further, the correction process for the image signal is not limited to the enlargement / reduction process and the movement process, and various image processes capable of achieving the object such as a pixel value conversion process can be applied.

  In addition, the correction processing for the image signal is not limited to both V tilt and V axis offset, and only one of them may be performed. On the contrary, in addition to V tilt and V axis offset, U axis offset, U tilt, pivot angle, and the like may be corrected.

  Furthermore, the apparatus configuration of the above embodiment is a relatively large apparatus capable of imaging the subject's chest and limbs, but is not limited to such a mode, for example, imaging while the imaging unit rotates around the breast. Any device configuration may be used, such as a relatively small device that performs the above.

  In addition to the above, it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Radiation CT apparatus 2 Imaging part 10 Radiation source (radiation focus)
11 Detection Panel 12 C Arm 15 Drive Unit 20 Arm 21 Base 22 Bed 30 Computer 31 Monitor C Rotating Axis P Subject

Claims (2)

An imaging unit in which a radiation source that emits radiation in a conical shape and a radiation detection means that detects the radiation are disposed opposite to each other with a rotation axis in between,
Driving means for rotating the imaging unit around the rotation axis;
Reading means for reading out the image signal recorded in the radiation detection means;
Control means for controlling to continuously take a radiographic image of a subject arranged on the rotation axis while rotating the imaging unit;
A radiation CT apparatus comprising image processing means for obtaining a three-dimensional radiation CT image of the subject by performing image reconstruction calculation based on image signals obtained by the continuous imaging,
In the three-dimensional radiation CT image obtained by photographing a phantom of a known shape, the influence of the V tilt of the radiation detection means is obtained based on the horizontal extent of the phantom shape, and the V tilt A radiation CT apparatus comprising correction means for correcting the image signal so as to reduce the influence. A radiation source that emits radiation in a conical shape and a radiation detection unit that detects the radiation is disposed opposite to each other with a rotation axis in between, a drive unit that rotates the imaging unit around the rotation axis, and A reading means for reading out an image signal recorded in the radiation detecting means, a control means for controlling to continuously take a radiographic image of a subject arranged on the rotation axis while rotating the photographing section; and by the continuous photographing. An image for performing image processing on an image signal acquired by a radiation CT apparatus provided with image processing means for obtaining a three-dimensional radiation CT image of the subject by performing image reconstruction calculation based on the obtained image signal A processing device comprising:
In the three-dimensional radiation CT image obtained by photographing a phantom of a known shape, the influence of the V tilt of the radiation detection means is obtained based on the horizontal extent of the phantom shape, and the V tilt An image processing apparatus comprising correction means for correcting the image signal so as to reduce the influence.

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