JP6048343B2 - Radiation tomography equipment - Google Patents

Description

  The present invention relates to a radiation tomography apparatus for imaging a tomographic image of a subject, and more particularly to a radiation tomography apparatus capable of capturing both a morphological image and a functional image and displaying these images superimposed.

  Conventionally, PET (positron emission tomography) apparatuses that image the distribution of radiopharmaceuticals administered to a subject have been developed. A PET image obtained with such a PET apparatus is a tomographic image of the subject, and is a functional image representing the activity in the subject. That is, if a circular image is reflected in the PET image, the circular portion is in a state where the radiopharmaceutical is distributed at a high concentration in the subject. Just because a circular image appears in the PET image does not mean that a structure having the same shape as this image exists in the subject. That is, the PET image is not an image representing the form of the organ of the subject.

  Such a situation becomes a problem when using diagnosis using a PET image. That is, it is not possible to accurately know which part of which organ of the subject the dense portion of the radiopharmaceutical is from just by looking at the PET image.

  Thus, a configuration has been devised conventionally in which a CT image (MR image) is superimposed and displayed on a PET image. CT images are imaging using X-rays and are called morphological images. That is, if a circular image is reflected in the CT image, a structure having the same shape as the image is present in the subject. If the subject is cut at a certain cut surface, the cut end is the same as the CT image formed by the cut surface. If the PET image and the CT image are superimposed and displayed, it is possible to know in which part of which organ of the subject the radiopharmaceutical is distributed at a high concentration.

  PET images and CT images cannot be taken with a common apparatus. Therefore, alignment when both images are superimposed becomes a problem. If the cut surface related to the PET image and the cut surface related to the CT image to be superimposed on the PET image are not the same, there will be a discrepancy between the image on the PET image and the image on the CT image. . Such a situation should be avoided for accurate diagnosis.

  An apparatus that displays a PET image and a CT image in an overlapping manner is an apparatus in which a PET apparatus and a CT apparatus are integrated. In the case of such an apparatus, since the positional relationship between both apparatuses is known in advance, it is easy to acquire a CT image having the same cut surface as that of the PET image. The cut surface related to the CT image photographed by such an apparatus and the cut surface related to the PET image are merely separated by a distance between the two apparatuses.

  Further, as another method for displaying the PET image and the CT image in a superimposed manner, there is a method using a PET apparatus and a CT apparatus that are in separate rooms. In such a method, calibration photography relating to correction of the cutting position is performed in advance on both apparatuses. When superimposing images, the calibration position is corrected using the result of the calibration photographing to prevent the discrepancy between the images (for example, see Patent Document 1).

International Patent Publication WO2007 / 03730

However, the conventional radiation tomography apparatus has the following problems.
That is, the conventional radiation tomography apparatus does not assume a configuration in which one apparatus is movable with respect to the other apparatus.

  Currently, a radiation tomography apparatus having a configuration in which one of a PET apparatus and a CT apparatus is fixed and one of them is movable has been developed. According to such a configuration, since the apparatus can be rearranged and removed in accordance with the purpose of the inspection, the apparatus can be operated with a higher degree of freedom.

  In such a partially movable radiation tomography apparatus, it is difficult to obtain a CT image having the same cut surface as that of the PET image, and an image discrepancy tends to occur between the two images. This is because the distance between the two devices is not determined. This point is different from a radiation tomography apparatus in which a CT apparatus and a PET apparatus are integrated.

  In addition, a correction method for correcting an imaging position between a PET apparatus and a CT apparatus in separate rooms according to the conventional configuration cannot be used as it is for a partially movable radiation tomography apparatus. The correction method in this case is based on the premise that the PET apparatus and the CT apparatus have different bets, and the above-described calibration imaging is performed with the marker placed on the bet. At this time, the positional relationship between the imaging field of view and the bed that the PET apparatus has is known, and the positional relationship between the imaging field of view and the bed that the CT apparatus has is also known. However, in a partially movable radiation tomography apparatus, for example, even if the positional relationship between the PET apparatus fixed to the floor and the bed fixed to the floor is known, the movable CT apparatus and the bed The positional relationship of is not determined. Therefore, if the positional relationship between the CT apparatus and the PET apparatus changes, the correction method obtained by calibration imaging cannot be used.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a partially movable radiation tomography apparatus capable of overlapping a morphological image and a functional image without discrepancy. is there.

The present invention has the following configuration in order to solve the above-described problems.
That is, the radiation tomography apparatus according to the present invention includes a first gantry having an opening for introducing a subject, a top plate for placing a subject attached to the first gantry, and a top plate. A top plate moving means for moving in the direction in which the opening extends with respect to one gantry, and a first plate having an opening for introducing the top plate on which the subject is placed, which can be attached to and detached from the device related to the first gantry. Two gantry, and a correction unit that corrects the alignment of the subject image captured by the apparatus related to the first gantry and the subject image captured by the apparatus related to the second gantry. It is characterized in that the alignment correction of the subject image is performed based on a calibration image obtained by placing the marker attached to the first gantry and the marker attached to the second gantry within a single visual field. is there.

  [Operation / Effect] According to the present invention, the top plate includes the attached first gantry device and the second gantry device, and the second gantry device corresponds to the first gantry device. In the radiation tomography apparatus which can be attached and detached, the positional discrepancy of the image image | photographed with each apparatus can be suppressed. According to the present invention, the first gantry is photographed by the apparatus according to the first gantry on the basis of the calibration image photographed by placing the marker attached to the first gantry and the marker attached to the second gantry within a single visual field. The alignment of the subject image and the subject image photographed by the apparatus related to the second gantry is corrected. With such a configuration, it is possible to align the subject image in consideration of the positional deviation of the second gantry relative to the first gantry, and the subject image captured by the first gantry and the second gantry There is no positional discrepancy between the subject image captured by the gantry-related apparatus.

  In the above-described radiation tomography apparatus, one of the first gantry and the second gantry is an apparatus for imaging the form of the subject, and the other is a drug in the subject. It is more desirable if it is an apparatus for imaging the distribution of.

  Moreover, in the above-mentioned radiation tomography apparatus, it is more desirable that one of the first gantry and the second gantry is a radiotherapy apparatus.

  [Operation / Effect] The above-mentioned radiation tomography apparatus represents a specific configuration of the present invention. That is, one of the device related to the first gantry and the device related to the second gantry is a device that images the form of the subject, and the other is a device that images the distribution of the drug in the subject. Thus, it becomes possible to accurately align the morphological image and the functional image. The present invention can also be applied to a radiation tomography apparatus in which one of the apparatus according to the first gantry and the apparatus according to the second gantry is a radiation therapy apparatus.

  In the above-described radiation tomography apparatus, it is more desirable that a holding member that holds the positions of a plurality of markers attached to the first gantry is provided in the first gantry.

  In the above-described radiation tomography apparatus, it is more desirable that a holding member for holding the positions of a plurality of markers attached to the second gantry is provided on the second gantry.

  [Operation / Effect] The above-mentioned radiation tomography apparatus represents a specific configuration of the present invention. If the marker attached to the gantry is held by the holding member, the positional relationship between the markers held by the holding member will not change, so the positional relationship between the gantry can be known more accurately. It becomes like this.

  In the above-described radiation tomography apparatus, it is more preferable that the correction unit executes the alignment correction by combining the correction for moving the subject image in parallel with the correction for rotating the subject image.

  [Operation / Effect] The above-mentioned radiation tomography apparatus represents a specific configuration of the present invention. The correction operation can be completed more reliably by performing the alignment correction by combining the correction means for correcting the object image in parallel with the correction for rotating the subject image.

  In the above-described radiation tomography apparatus, it is more desirable to include an optical tracking unit that captures a calibration image.

  [Operation / Effect] The above-mentioned radiation tomography apparatus represents a specific configuration of the present invention. If an optical tracking unit that captures a calibration image is provided, a radiation tomography apparatus that can reliably acquire a calibration image can be provided.

  In the above-described radiation tomography apparatus, it is more desirable to include an image superimposing unit that generates a superposed image by superimposing the subject images corrected for alignment.

  [Operation / Effect] The above-mentioned radiation tomography apparatus represents a specific configuration of the present invention. A radiation tomography apparatus capable of generating a superposed image that is easy to diagnose can be provided by providing an image superimposing unit that generates a superposed image by superimposing the subject images corrected for alignment.

  According to the present invention, the top plate includes the attached first gantry device and the second gantry device, and the second gantry device can be attached to and detached from the first gantry device. In the radiation tomography apparatus, the positional discrepancy of the images photographed by each apparatus can be suppressed. According to the present invention, the correction of the alignment of the subject images photographed by the apparatus related to each gantry is performed based on the calibration image in which the marker attached to each gantry is photographed. With such a configuration, it is possible to align the subject image in consideration of the positional deviation of each gantry, and there is a positional discrepancy with the subject image photographed by the apparatus related to each gantry. Does not occur.

1 is a functional block diagram illustrating an overall configuration of a radiation tomography apparatus according to Embodiment 1. FIG. 1 is a cross-sectional view illustrating a configuration of a PET apparatus according to Example 1. FIG. 1 is a cross-sectional view illustrating a configuration of a CT apparatus according to a first embodiment. 1 is a perspective view illustrating a configuration of a PET apparatus according to Example 1. FIG. FIG. 3 is a plan view for explaining a configuration of a marker according to the first embodiment. It is a perspective view explaining the structure of the marker which concerns on Example 1. FIG. It is a top view explaining attachment of the marker concerning Example 1. FIG. FIG. 6 is a perspective view for describing marker imaging according to the first embodiment. 6 is a schematic diagram illustrating calculation of correction conditions according to Embodiment 1. FIG. 6 is a schematic diagram illustrating calculation of correction conditions according to Embodiment 1. FIG. 6 is a schematic diagram illustrating calculation of correction conditions according to Embodiment 1. FIG. 6 is a schematic diagram illustrating calculation of correction conditions according to Embodiment 1. FIG. FIG. 3 is a schematic diagram for explaining a positional shift between apparatuses according to the first embodiment. FIG. 3 is a schematic diagram for explaining a positional shift between apparatuses according to the first embodiment. FIG. 6 is a schematic diagram for explaining a positional shift between images according to the first embodiment. FIG. 6 is a schematic diagram for explaining a positional shift between images according to the first embodiment. 6 is a schematic diagram illustrating image processing according to Embodiment 1. FIG.

<Configuration of radiation tomography system>
Embodiments of a radiation tomography apparatus according to the present invention will be described below with reference to the drawings. The gamma rays and X-rays in Example 1 are an example of the radiation of the present invention. FIG. 1 is a functional block diagram illustrating the configuration of the radiation tomography apparatus according to the first embodiment. The radiation tomography apparatus according to the first embodiment is a PET / CT apparatus including a CT apparatus 9b and a PET apparatus 9a.

  The PET / CT apparatus according to the first embodiment can be imaged only by the CT apparatus 9b. That is, the PET apparatus 9a constituting the PET / CT apparatus can be moved from the CT apparatus 9b and can be imaged only by the CT apparatus, or can be imaged by combining the PET apparatus 9a and the CT apparatus 9b. it can. FIG. 2 shows a state in which the PET apparatus 9a is detached from the CT apparatus 9b. The CT apparatus 9b is fixed to the floor surface of the examination room. The top plate 10 is an accessory of the CT apparatus 9b. If imaging is performed with an apparatus as shown in FIG. 2, the PET apparatus 9a does not hinder CT imaging, and a smooth imaging operation can be realized. The PET gantry 11 can be attached to and detached from the apparatus related to the CT gantry 45. The PET device 9a is a device that images the distribution of the drug in the subject, and the CT device 9b is a device that images the form of the subject M.

  FIG. 3 shows a state where the PET apparatus 9a is about to be mounted on the CT apparatus 9b. The PET apparatus 9a includes a caster so as to be able to move on the floor surface of the examination room. When performing imaging, the caster of the PET apparatus 9a is locked, and the positional relationship between the CT apparatus 9b and the PET apparatus 9a is constant. If the PET apparatus 9a is brought closer to the CT apparatus 9b as shown by the arrow in FIG. 3, imaging as a PET / CT apparatus capable of both PET imaging and CT imaging becomes possible. If imaging is performed with an apparatus as shown in FIG. 3, an imaging operation capable of acquiring both a morphological image captured by the CT apparatus 9b and a functional image captured by the PET apparatus 9a can be realized.

  For convenience of explanation, it is assumed that the PET gantry 11 included in the PET apparatus 9a and the CT gantry 45 included in the CT apparatus have the same size and shape when viewed from the z direction. The CT gantry 45 corresponds to the first gantry of the present invention, and the PET gantry 11 corresponds to the second gantry of the present invention.

<Configuration of CT device>
Next, the configuration of the CT apparatus 9b according to the first embodiment will be described. As shown in FIG. 1, the CT apparatus 9b has a CT gantry 45 having a top plate 10 on which the subject M is placed and an opening through which the top plate 10 and the subject M are introduced from the longitudinal direction (z direction). doing. The CT gantry 45 is provided with an opening extending in the z direction, and the top 10 and the subject M are introduced into this opening. Thus, the top plate 10 is a configuration attached to the CT apparatus 9b. The base 10a that supports the top plate 10 is also a configuration attached to the CT apparatus 9b. The base 10a is fixed to the floor surface of the examination room.

  Inside the CT gantry 45, an X-ray tube 43 that irradiates X-rays toward the subject M, an X-ray detector 44 that detects X-rays transmitted through the subject M, and the X-ray tubes 43 and X A support 47 that supports the line detector 44 is provided. The support 47 has a ring shape and is rotatable around the z axis. The rotation of the support 47 is performed by a rotation mechanism 39 including a power generation unit such as a motor and a power transmission unit such as a gear. The rotation control unit 40 controls the rotation mechanism 39. The central axis in the rotation of the support 47 (X-ray tube 43 and X-ray detector 44) coincides with the central axis of the detector ring 12 in the later-described PET apparatus 9a. That is, the CT apparatus 9b is provided adjacent to the PET apparatus from the z direction while sharing the central axis with the central axis of the detector ring 12. The X-ray tube 43 corresponds to the radiation source of the present invention, and the X-ray detector 44 corresponds to the radiation detection means of the present invention.

  The CT image generation unit 48 generates an X-ray form tomographic image (CT image Pb) of the subject M based on the X-ray detection data output from the X-ray detector 44. This CT image Pb is a three-dimensional image of the subject M, and the ease of transmission of X-rays inside the subject M is imaged. The CT image generation unit 48 corresponds to the tomographic image generation means of the present invention.

  The top plate 10 is provided so as to penetrate the opening of the CT gantry 45 from the z direction, and can be moved forward and backward along the z direction. Such sliding of the top plate 10 is realized by the top plate moving mechanism 15. The top plate moving mechanism 15 is controlled by the top plate movement control unit 16. The top board movement control unit 16 is a top board movement control means for controlling the top board movement mechanism 15. The top plate movement control unit 16 is configured to move the top plate 10 with respect to the CT gantry 45 in the direction in which the opening extends. The top plate 10 slides from a position where the entire area is located outside the CT gantry 45 and is introduced into the opening of the CT gantry 45 from one side thereof, and penetrates the inside of the CT gantry 45, The CT gantry 45 can protrude from the other side of the opening.

<Configuration of PET apparatus>
First, the configuration of the PET apparatus 9a will be described. A PET gantry 11 having an opening for introducing the subject M from the longitudinal direction (z direction) and a ring-shaped detector ring 12 provided inside the PET gantry 11 are provided. The opening provided in the detector ring 12 has a cylindrical shape extending in the z direction (the longitudinal direction of the top 10 and the body axis direction of the subject M). The detector ring 12 corresponds to the detector of the present invention. The PET apparatus 9a is adjacent to the CT apparatus 9b from the z direction. The PET gantry 11 of the PET apparatus 9a and the CT gantry 45 of the CT apparatus 9b are arranged so that their openings are connected in the z direction. Thereby, it is possible to continuously capture the CT image Pb and the PET image Pa without changing the position of the subject M on the top 10 as much as possible. The detector ring 12 detects pair annihilation gamma rays generated in the subject. In addition, the positional relationship between the top plate moving mechanism 15 and the PET gantry 11 and the CT gantry 45 configured in the first embodiment is merely an example of an aspect that can be adopted. Therefore, the configuration of the present invention is not limited to this.

  Inside the PET gantry 11, a detector ring 12 that detects pair annihilation γ-rays emitted from the subject M is provided. The detector ring 12 has a cylindrical shape extending in the body axis direction of the subject M, and the length in the z direction is about 15 to 30 cm. The clock 19 is input to the detector ring 12. The detection data output from the detector ring 12 is given time information indicating when the γ rays based on the clock 19 were acquired, and is input to the coincidence counting unit 20 described later.

  The coincidence counting unit 20 performs simultaneous event determination of the detection data output from the detector ring 12. Note that the simultaneous event determination of the detection data by the coincidence unit 20 uses time information given to the detection data by the clock 19. Assuming that the two γ-rays determined to be simultaneously incident on the detector ring 12 are pair annihilation γ-rays caused by the radiopharmaceutical in the subject, the detection data of the two γ-rays are sent to the PET image generation unit 21. To do.

  The PET image generation unit 21 generates a PET image Pa based on the detection data output from the detector ring 12 through the coincidence counting unit 20. This PET image Pa is a three-dimensional image of the subject M, and the generation intensity of pair annihilation γ rays is imaged. The image superimposing unit 23 is provided for the purpose of generating a superposed image P1.

  The configuration of the detector ring 12 will be described. According to the first embodiment, one unit ring is formed by arranging around 100 radiation detectors 1 in a virtual circle on a plane perpendicular to the z direction. The unit rings are arranged in the z direction to form the detector ring 12.

  The configuration of the radiation detector 1 will be briefly described. FIG. 4 is a perspective view illustrating the configuration of the radiation detector according to the first embodiment. As shown in FIG. 4, the radiation detector 1 includes a scintillator 2 that converts γ rays into fluorescence, and a photodetector 3 that detects fluorescence. A light guide 4 for transmitting and receiving fluorescence is provided at a position where the scintillator 2 and the photodetector 3 are interposed.

The scintillator 2 is configured by scintillator crystals arranged three-dimensionally. The scintillator crystal is composed of Lu _{2 (1-X)} Y _2X SiO ₅ (hereinafter referred to as LYSO ₎ in which Ce is diffused. The photodetector 3 can specify the fluorescence generation position indicating which scintillator crystal emits fluorescence, and can also specify the intensity of fluorescence and the time when the fluorescence is generated. it can. The scintillator 2 having the configuration of the first embodiment is merely an example of an aspect that can be adopted. Therefore, the configuration of the present invention is not limited to this.

  The PET apparatus 9a includes a main control unit 41 that comprehensively controls each unit and a display unit 36 that displays morphological tomographic images and the like. The main control unit 41 is constituted by a CPU, and realizes the above-described units 16, 20, 21, 22, 23, and 24 and units 25 and 26 described later by executing various programs. In addition, each above-mentioned part may be divided | segmented and implement | achieved by the control apparatus which takes charge of them.

  The set value storage unit 37 stores various parameters relating to the examination, and the console 35 allows the operator to input various operations. The console 35 corresponds to the input means of the present invention.

  The PET image Pa generated by the PET image generation unit 21 and the CT image Pb generated by the CT image generation unit 48 represent three-dimensional images of the same part at the same cutting position in the subject M at the same magnification. It has become. The difference is that the CT image Pb represents the internal structure of the subject M, whereas the PET image Pa represents the distribution of the radiopharmaceutical.

  The main control unit 41 implements a rotation control unit 40, a CT image generation unit 48, and an X-ray tube control unit 46 in addition to the respective units related to the PET apparatus 9a by executing various programs. In addition, each above-mentioned part may be divided | segmented and implement | achieved by the control apparatus which takes charge of them. The X-ray tube control unit 46 is provided for the purpose of controlling the tube current, tube voltage, pulse width, and the like of the X-ray tube 43.

<About markers>
The radiation tomography apparatus according to the present invention includes a marker m used when specifying the relative position of the PET apparatus 9a with respect to the CT apparatus 9b. As shown in FIG. 5, the marker m has a circular shape, and is attached to an elongated holding member H. Three markers m are attached to the holding member H, and the three markers m attached to the holding member H are arranged in series in the direction in which the holding member H extends. Further, the marker m may be a seal-like structure as shown on the left side of FIG. 6 or may have a spherical structure as shown on the right side of FIG. Further, the shape of the marker m does not have to be circular or spherical, and may be a cross shape, for example. The number of markers m attached to the holding member H may not be three, but may be three or more or two. The positional relationship between these markers m does not change as long as they are attached to the holding member H.

  FIG. 7 shows a state where the marker m is attached to the gantry of the apparatus. As shown in FIG. 7, the holding member H is fixed to the upper part of the side surface of the gantry 11, 45. In the holding member H, the direction in which the marker m is arranged in the portion of the gantry 11, 45 where the subject introduction opening is provided, which corresponds to the vertical upper side of the opening, is the upper side of the gantry 11, 45. It is pasted to be parallel. The upper side of the side surface of the gantry 11, 45 is the side farthest from the floor surface among the sides of the side surface of the gantry 11, 45. The side surfaces of the gantry 11, 45 have the same shape, but the holding member H is fixed at the same position of the gantry 11, 45. The holding member H fixed to the gantry 11, 45 is the same. Accordingly, three markers m are pasted on each of the gantry 11 and 45. That is, the holding member H that holds the positions of the plurality of markers m attached to the PET gantry 11 is provided in the PET gantry 11 and the holding member that holds the positions of the plurality of markers m attached to the CT gantry 45. H is provided in the CT gantry 45.

<About optical tracking device>
The radiation tomography apparatus according to the present invention includes an optical tracking device 13 that images a marker m using visible light. As shown in FIG. 8, the optical tracking device 13 is provided on the top of the gantry 11, 45, and includes three markers m attached to the PET gantry 11 and three markers m attached to the CT gantry 45. The six markers m are photographed using visible light so that they fall within the same field of view. When shooting with the optical tracking device 13, shooting data output by the optical tracking device 13 is sent to the calibration image generating unit 25. The calibration image generation unit 25 generates a calibration image based on the shooting data. The optical tracking device 13 has a configuration in which two cameras with different viewpoints synchronized in shooting timing are integrated, and can acquire two images for stereoscopic viewing. Therefore, when the optical tracking device 13 captures six markers m, the optical tracking device 13 outputs photographing data derived from the first camera and photographing data derived from the second camera. . The calibration image generation unit 25 generates two calibration images corresponding to two types of shooting data. The optical tracking device 13 corresponds to the optical tracking means of the present invention.

  Therefore, when the marker m is affixed to the side surfaces of the gantry 11, 45, it is necessary to allow the optical tracking device 13 to capture all of the marker m. That is, the marker m is attached to the gantry 11, 45 so as not to be located behind the gantry 11, 45 or hidden behind the gantry 11, 45 when viewed from the optical tracking device 13. Attached. When the PET gantry 11 is affixed to the side surface on the base 10 a side that supports the top plate 10, the marker m is also affixed to the CT gantry 45 on the side surface on the base 10 a side. When the side surface is affixed to the side surface far from the base 10a, the marker m is also pasted to the CT gantry 45 on the side surface far from the base 10a.

<About the correction condition calculation unit>
The generated two calibration images are sent to the correction condition calculation unit 26. The correction condition calculation unit 26 calculates a correction condition indicating how to specifically perform the alignment when the PET image Pa and the CT image Pb are superimposed based on the two calibration images. Hereinafter, details of the operation of the correction condition calculation unit 26 will be described.

  The correction condition calculation unit 26 includes a line segment La connecting three markers ma pasted on the CT gantry 45 from two calibration images obtained from different viewpoints, and three markers pasted on the PET gantry 11. The three-dimensional positional relationship with the line segment Lb connecting mb is grasped. FIG. 9 schematically shows two line segments La and Lb grasped by the correction condition calculation unit 26. As shown in FIG. 9, a direction from one line segment Lb to the other line segment La is defined as a direction d1, and a direction perpendicular to a plane including the line segments La and Lb is defined as a direction d2. The correction condition calculation unit 26 holds the grasped positional relationship between the line segments La and Lb as a three-dimensional map. The line segments La and Lb are line segments formed by connecting the centers of gravity of the markers ma and mb on the three-dimensional map.

  The line segments La and Lb do not intersect or overlap each other. Since the line segment La represents the installation direction and position of the CT gantry 45, and the line segment Lb represents the installation direction and position of the PET gantry 11, the line segments La and Lb are always separated from each other. Because. Then, it is not so whether the line segment Lb is completely parallel to the line segment La. This is because it is difficult to precisely move the PET gantry 11 to a fixed position with respect to the CT gantry 45. The actual line segment Lb rotates about a central axis parallel to the direction d1 with respect to the line segment La, or rotates about a central axis parallel to the direction d2 with respect to the line segment La. FIG. 10 shows the rotation of the line segment Lb in the direction d1, and FIG. 11 shows the rotation of the line segment Lb in the direction d2.

  Further, the line segment La and the line segment Lb are shifted in the direction d1. As shown in FIG. 1, the deviation is considerably large because it is derived from arranging the CT gantry 45 and the PET gantry 11 side by side in the z direction. The amount of deviation is not always constant every time the PET gantry 11 is installed with respect to the CT gantry 45. This is because it is difficult to precisely move the PET gantry 11 to a fixed position with respect to the CT gantry 45.

  And line segment La and line segment Lb have shifted | deviated with respect to the direction orthogonal to the direction d1 and the direction d2. This deviation is a positional deviation in the depth direction of the paper surface in FIG. The displacement of the gantry in this direction is slight compared to the displacement in the direction d1 described above. However, it is difficult to eliminate this gap completely. This is because it is difficult to precisely move the PET gantry 11 to a fixed position with respect to the CT gantry 45.

  The correction condition calculation unit 26 calculates the degree of rotation and the degree of translation of the line segment Lb relative to the line segment La based on the three-dimensional map showing the positional relationship between the line segments La and Lb. The correction condition calculation unit 26 determines the positional relationship between the line segments La and Lb as the rotation component described in FIG. 10, the rotation component described in FIG. 11, the movement component in the direction d1, and the orthogonal direction of the directions d1 and d2. Is divided into four components of movement components, and the respective rotation amounts and movement amounts are calculated. FIG. 12 schematically shows how the correction condition calculation unit 26 decomposes the positional relationship between the line segments La and Lb into four components.

  When the correction condition calculation unit 26 obtains the rotation amount in the direction d1, the line segments La and Lb are projected onto a plane orthogonal to the direction d1, and an image in which the line segments La and Lb intersect as shown in FIG. And the angle formed by the line segments La and Lb is calculated. The angle formed by this is the amount of rotation in the direction d1. Similarly, when the correction condition calculation unit 26 obtains the rotation amount in the direction d2, the line segments La and Lb are projected onto a plane orthogonal to the direction d2 to generate an image as shown in FIG. , Lb, the angle formed by two straight lines is calculated. The angle formed by this is the amount of rotation in the direction d2.

  When the correction condition calculation unit 26 obtains the movement component in the direction d1 and the movement component in the direction orthogonal to the directions d1 and d2, first, the line segment Lb is calculated with respect to the line segment La based on the rotation amount described above. Then, after making the line segments La and Lb parallel to each other, the degree of movement of the center of gravity of the line segments La and Lb is calculated. The component of the movement amount calculated at this time in the direction d1 is the component of movement in the direction d1 described above. Further, the component of movement in the orthogonal direction of the directions d1 and d2 calculated at this time is the component of movement in the orthogonal direction of the directions d1 and d2.

  The correction condition calculation unit 26 sends the calculated rotation amount and movement amount to the set value storage unit 37 for storage. The rotation amount and the movement amount are parameters necessary for the alignment of the images when the PET image Pa and the CT image Pb are overlapped.

  For example, the rotation amount in the direction d1 calculated by the correction condition calculation unit 26 indicates how much the PET gantry 11 is rotated with respect to the CT gantry 45 about the axis extending in the z direction as shown in FIG. Show. The CT gantry 45 and the PET gantry 11 are preferably arranged so as to overlap each other when viewed from the z direction. However, when the PET gantry 11 is placed on the CT gantry 45, it is difficult to arrange the PET gantry 11 in this ideal manner.

  The rotation amount in the direction d1 calculated by the correction condition calculation unit 26 indicates how much the PET gantry 11 is inclined with respect to the CT gantry 45 with the axis extending in the vertical direction as the rotation axis. FIG. 14 schematically shows the inclination in this case. The CT gantry 45 and the PET gantry 11 are desirably arranged so as to be parallel to each other when viewed from the vertical direction. However, when the PET gantry 11 is placed on the CT gantry 45, it is difficult to arrange the PET gantry 11 in this ideal manner.

  The movement amount calculated by the correction condition calculation unit 26 indicates how much the PET gantry 11 is shifted with respect to the CT gantry 45. That is, the movement component in the direction d1 calculated by the correction condition calculation unit 26 represents how far the gantry 11, 45 is in the z direction, and the direction d1, d2 calculated by the correction condition calculation unit 26 The component of movement in the orthogonal direction represents how much the gantry 11, 45 is displaced in the direction orthogonal to the z direction and the vertical direction. As shown in FIG. 15, the PET gantry 11 is ideally separated from the CT gantry 45 by a predetermined shift width w in the z direction. The PET gantry 11 is separated from the CT gantry 45 in the depth direction of the paper surface of FIG. Ideally, no deviation occurs in the body side direction of the specimen M. However, when the PET gantry 11 is placed on the CT gantry 45, it is difficult to arrange the PET gantry 11 in this ideal manner.

  The shift width w is a distance between the centers determined in the gantry 11 and 45. The center of the gantry means the position of the center point of the visual field range of the apparatus.

  As described above, the correction condition calculation unit 26 calculates the positional deviation of the PET gantry 11 with respect to the CT gantry 45 by analyzing the three-dimensional map in which the marker m is reflected. The calculation result of the correction condition calculation unit 26 is referred to as a correction condition. The correction conditions include two types of rotation amount conditions and two types of parallel movement amount conditions as shown in FIG.

<About image correction unit>
The correction conditions calculated by the correction condition calculation unit 26 are sent to the image correction unit 22. The image correction unit 22 corrects the position according to the correction condition for the PET image Pa obtained from the PET apparatus 9a. The image correction unit 22 corresponds to the correction unit of the present invention.

  The CT image Pb is voxel data in which a three-dimensional image of the subject M is reflected as described above. This CT image Pb is acquired while moving the top 10 in the z direction. The subject M placed on the top 10 is too long to fit in the field of view of the CT apparatus 9b. Therefore, the CT apparatus 9b continuously captures images while moving the subject M in the z direction, and obtains a three-dimensional image of the whole subject by joining the imaging results. That is, the top plate 10 needs to be moved in order to capture the CT image Pb. When the CT image Pb is generated, the amount of movement of the top 10 is taken into account. That is, at the time of CT imaging, data relating to the amount of movement of the top board 10 is sent from the top board movement control unit 16 to the CT apparatus 9b, and the CT apparatus 9b receives the data from the top board movement control unit 16 at the time of imaging. Based on this, a three-dimensional image is generated while distinguishing the position of the subject M in the z direction. If there is no data from the top board movement control unit 16, the CT apparatus 9b cannot recognize the movement of the subject M in the z direction during imaging, so that the head of the subject M is in the imaging field of view. It is possible to acquire only images in which the head, chest, abdomen, and legs overlap each other.

  Such a situation is the same for the PET image Pa which is voxel data. Even in the PET apparatus 9a, by continuously moving the subject M while moving in the z direction by moving the top plate 10 during imaging, a three-dimensional image of the whole body of the subject is obtained by connecting the imaging results. I have to. That is, at the time of PET imaging, data related to the amount of movement of the top board 10 is sent from the top board movement control unit 16 to the PET apparatus 9a. The PET apparatus 9a receives the data from the top board movement control unit 16 at the time of imaging. Based on this, a three-dimensional image is generated while distinguishing the position of the subject M in the z direction.

  Hereinafter, movement of the subject M when acquiring an image will be described. A subject M indicated by a solid line in FIG. 16 represents the position of the subject M at the time when imaging of the PET image Pa is started. As PET imaging progresses, the subject M is gradually moved to the left side of the figure as indicated by the arrow. Then, the PET imaging is completed when the imaging of the toe of the subject M is completed.

  When the PET apparatus 9a captures the PET image Pa for the whole body of the subject M and then the CT apparatus 9b captures the CT image Pb for the entire body of the subject M, the top 10 is moved prior to the imaging. . A subject M indicated by a broken line in FIG. 16 represents the position of the subject M at the time when imaging of the CT image Pb is started. As CT imaging progresses, the subject M is gradually moved to the left side of the figure as shown by the arrows. Then, CT imaging is completed when imaging of the toe of the subject M is completed.

  Therefore, the position of the subject M in CT imaging is moved in the direction from the PET apparatus 9a toward the CT apparatus 9b by the shift width w shown in FIG. 15 relative to the position of the subject M in PET imaging. By shifting the position of the subject M in CT imaging by the shift width w, the whole body of the subject M can be reliably imaged by the CT apparatus.

  If there is a difference in the field of view of the imaging between the PET apparatus 9a and the CT apparatus 9b, the subject M in CT imaging does not necessarily have to be moved by the shift width w than the subject M in PET imaging. Even in such a case, the position of the subject M at the time of CT imaging can be determined based on the position of the subject M at the time of PET imaging and the shift width w between the two devices 9a and 9b. There is no difference. That is, the CT imaging at this time is performed after moving the subject M to a position moved by a predetermined distance from the shift width w from the position at the time of PET imaging. Hereinafter, the description will be continued on the assumption that the imaging field of view is the same between the PET apparatus and the CT apparatus, and the subject M in CT imaging is moved by the shift width w from the subject M in PET imaging.

  From the above description, it can be seen that the position of the subject M during CT imaging and the position of the subject M during PET imaging are shifted by a shift width w. Therefore, if image processing that moves the subject M of the PET image Pa to the CT apparatus 9b side by the shift width w is performed on the PET image Pa, the subject M that appears in the CT image Pb and the subject that appears in the PET image Pa. It should be in a positional relationship that just overlaps with the sample M. But that is not the case. This is because the positional relationship between the CT image Pb and the PET apparatus 9a at the time of imaging is not ideal. The PET apparatus 9a at the time of imaging may be inclined with respect to the CT apparatus 9b as described with reference to FIGS. 13 and 14, or the PET apparatus 9a may be located at a position translated from the ideal position. unknown.

  Therefore, the image correction unit 22 performs image correction so as to cancel the displacement of the position of the subject image caused by the positional deviation between the apparatuses from the PET image Pa. That is, the image correction unit 22 is placed at an ideal position with respect to the CT apparatus 9b by rotating and translating the subject image of the PET image Pa based on the correction condition calculated by the correction condition calculation unit 26. The subject image obtained by the PET apparatus 9a is acquired. The PET image Pa at the ideal position is not inclined with respect to the CT apparatus 9b, is separated by a shift width w in the z direction, and is shifted in the depth direction (the body side direction of the subject M) in FIG. There is no PET image Pa. The image correction unit 22 executes alignment correction by combining correction for moving the subject image in parallel with correction for rotating the subject image.

  As described above, the image correction unit 22 corrects the alignment between the subject image photographed by the apparatus related to the PET gantry 11 and the subject image photographed by the apparatus related to the CT gantry 45. The image correction unit 22 then positions the subject image based on a calibration image that is captured with the marker m attached to the PET gantry 11 and the marker m attached to the CT gantry 45 within a single field of view. Perform alignment correction. The PET image corrected by the image correction unit 22 is referred to as a PET image PA.

<About the image superposition part>
The image superimposing unit 23 superimposes the CT image Pb and the corrected PET image PA to obtain the superimposed image P1. At this time, the subject image reflected in the corrected PET image PA is an image in which the subject image reflected in the CT image Pb is moved by a shift width w in the direction from the CT apparatus 9b to the PET apparatus 9a. It has become. Therefore, the image superimposing unit 23 performs an image process such that the PET image PA is moved by the shift width w before overlapping the images, and executes the alignment between the CT image Pb and the PET image PA in advance. It has a configuration. In this way, the image superimposing unit 23 generates a superposed image P1 by superimposing the subject images. The image superimposing unit 23 corresponds to the image superimposing means of the present invention.

  FIG. 17 schematically illustrates processing performed by the image correction unit 22 and the image superimposing unit 23. The PET image Pa is superposed on the CT image Pb after the image correction unit 22 removes the influence of the positional deviation of the imaging apparatus. In this way, a superimposed image P1 is generated.

<Operation of radiation tomography system>
Next, the operation of the radiation tomography apparatus according to Embodiment 1 will be described. First, the subject M is placed on the top board 10. When the surgeon gives an instruction to acquire the PET image Pa through the console 35, the top 10 moves and the subject M is introduced into the PET gantry 11. A radiopharmaceutical is injected into the subject M in advance, and the radiopharmaceutical generates annihilation gamma rays. Thus, the pair annihilation gamma rays generated in the body of the subject M are detected by the detector ring 12. The detector ring 12 sends detection data to the coincidence counting unit 20, and the coincidence counting unit 20 performs simultaneous event determination of the detection data. The detection data is a data set in which the incident time, energy, and incident time are related.

  The detection data determined as a simultaneous event by the coincidence counting unit 20 is sent to the PET image generating unit 21. The PET image generation unit 21 is a tomographic image when the subject M is cut at each of the planes arranged with a predetermined width, and the PET image in which the generation state of pair annihilation γ-rays is three-dimensionally imaged. Pa is generated. The image correction unit 22 corrects the position of the PET image Pa according to correction conditions acquired in advance before shooting. In this way, a corrected PET image PA is generated.

  After the acquisition of the PET image Pa, when the operator gives an instruction to start acquiring the CT image Pb through the console 35, the top 10 moves and the subject M is introduced into the CT gantry 45. Then, the X-ray tube 43 and the X-ray detector 44 rotate around the z-axis while maintaining their relative positions.

  When the surgeon instructs the start of X-ray irradiation through the console 35, the X-ray tube 43 intermittently irradiates the subject M with X-rays, and each time the CT image generation unit 48 performs X-ray irradiation. A perspective image is generated. The plurality of fluoroscopic images are assembled into a single CT image Pb in the CT image generation unit 48 using, for example, an existing back projection method.

  The PET image PA and the CT image Pb are input to the image superimposing unit 23. The tomographic image of the superimposed image P1 generated by the image superimposing unit 23 is displayed on the display unit 36, and the inspection is completed. At this time, a tomographic image of the PET image PA and the CT image Pb before the polymerization process may be displayed on the display unit 36.

  As described above, according to the present invention, the top plate 10 includes the attached CT gantry 45 device and the PET gantry 11 device, and the PET gantry 11 device corresponds to the CT gantry 45 device. In the radiation tomography apparatus that can be attached and detached in this way, it is possible to suppress a positional discrepancy between images captured by each apparatus. According to the present invention, the apparatus according to the PET gantry 11 is based on a calibration image obtained by placing the marker m attached to the PET gantry 11 and the marker m attached to the CT gantry 45 within a single field of view. Correction of alignment between the photographed subject image and the subject image photographed by the apparatus related to the CT gantry 45 is performed. With such a configuration, it is possible to align the subject image in consideration of the positional deviation of the CT gantry 45 with respect to the PET gantry 11, and the subject image captured by the apparatus related to the PET gantry 11 and the CT gantry No positional discrepancy occurs between the subject image photographed by the apparatus according to No. 45.

  In the above-described radiation tomography apparatus, one of the apparatus related to the PET gantry 11 and the apparatus related to the CT gantry 45 is an apparatus that images the form of the subject M, and the other is an apparatus for the medicine in the subject. It is a device for imaging the distribution. As a result, the morphological image and the functional image can be accurately aligned.

  Further, if the marker m attached to the gantry is held by the holding member H as described above, the positional relationship between the markers m held by the holding member H does not change with each other. It becomes possible to know the positional relationship between gantry.

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

  (1) According to the above-described embodiment, the PET apparatus can be attached to and detached from the fixed CT apparatus, but the present invention is not limited to this configuration. The CT apparatus may be detachable from the fixed PET apparatus. In the present invention, another apparatus such as an MRI apparatus may be applied instead of the CT apparatus. Moreover, you may apply the radiotherapy apparatus which has a gantry instead of CT apparatus or PET apparatus of this invention. That is, the radiotherapy apparatus may be detachable from the fixed CT apparatus / PET apparatus / MRI apparatus, or the CT apparatus / PET with respect to the fixed radiotherapy apparatus. The apparatus / MRI apparatus may be configured to be detachable.

  (2) According to the above-described embodiment, the PET gantry 11 and the CT gantry 45 have the same shape, but the present invention is not limited to this configuration. The gantry 11, 45 when viewed from the z direction can also have different shapes. At that time, the correction condition calculation unit 26 performs a prior conversion process on the three-dimensional map indicating the positional relationship between the line segments La and Lb before calculating the correction condition. That is, the correction condition calculation unit 26 derives from the CT gantry 45 in the three-dimensional map based on a deformation mode in which the CT gantry 45 when viewed from the z direction becomes the shape of the PET gantry 11 when viewed from the z direction. The line segment Lb is deformed. By making such a modification, the line segments La and Lb on the three-dimensional map have a positional relationship obtained when a gantry having the same shape as shown in FIG. 9 is photographed. The correction condition calculation unit 26 calculates the correction conditions described in FIG. 9 and subsequent drawings on the three-dimensional map subjected to this conversion process.

  (3) According to the above-described embodiment, the image correcting unit 22 is configured to correct the PET image Pa. Instead, the image correcting unit 22 applies the CT image Pb to the CT image Pb. It is good also as a structure which correct | amends.

  (4) The above correction condition may be expressed by a rotation matrix and a translation vector.

m Marker H Holding member 11 PET gantry (first gantry)
13 Optical tracking means (optical tracking means)
16 Top plate movement controller (top plate moving means)
45 CT gantry (second gantry)
22 Image correction unit (correction means)
23 Image superposition part (Image superposition means)

Claims (8)

A first gantry having an opening for introducing a subject;
A top plate for placing a subject attached to the apparatus according to the first gantry;
A top plate moving means for moving the top plate in a direction in which the opening extends with respect to the first gantry;
A second gantry that is attachable to and detachable from the apparatus related to the first gantry and has an opening for introducing the top plate on which the subject is placed;
Correction means for correcting the alignment between the subject image photographed by the apparatus related to the first gantry and the subject image photographed by the apparatus related to the second gantry;
The correction means corrects the alignment of the subject image based on a calibration image captured by placing the marker attached to the first gantry and the marker attached to the second gantry within a single field of view. Radiation tomography apparatus characterized by performing. The radiation tomography apparatus according to claim 1,
One of the device related to the first gantry and the device related to the second gantry is a device that images the form of the subject, and the other is a device that images the distribution of the drug in the subject. A radiation tomography apparatus characterized by that. The radiation tomography apparatus according to claim 1,
One of the apparatus concerning the 1st gantry and the apparatus concerning the 2nd gantry is a radiotherapy apparatus, The radiation tomography apparatus characterized by the above-mentioned. The radiation tomography apparatus according to any one of claims 1 to 3,
A radiation tomography apparatus, wherein a holding member for holding positions of a plurality of markers attached to the first gantry is provided on the first gantry. The radiation tomography apparatus according to any one of claims 1 to 4,
A radiation tomography apparatus, wherein a holding member for holding positions of a plurality of markers attached to the second gantry is provided in the second gantry. The radiation tomography apparatus according to any one of claims 1 to 5,
The radiation tomography apparatus according to claim 1, wherein the correction unit executes alignment correction by combining correction for moving the subject image in parallel with correction for rotating the subject image. The radiation tomography apparatus according to any one of claims 1 to 6,
A radiation tomography apparatus comprising optical tracking means for photographing the calibration image. The radiation tomography apparatus according to any one of claims 1 to 7,
A radiation tomography apparatus comprising: an image superimposing unit that generates a superposed image by superimposing the subject images corrected for alignment.

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