JP2004121297A - X-ray ct system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a change in the scale factor in an X-ray CT measurement. <P>SOLUTION: An X-ray generator 52 is provided on one side of a rotation axis O, and an X-ray detector 60 is provided on the other side. A distance between them is fixed, however, the positions of them to the rotation axis O can be changed by a displacing mechanism 62. The scale factor of a CT image can be changed by such a change. A gantry rotating mechanism 66 rotates the whole of a movable unit 50. In an effective visual field 58, a container housing, e.g., a small animal is arranged. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray CT apparatus, and more particularly, to an X-ray CT apparatus having a magnification changing function.
[0002]
[Prior art]
An X-ray CT apparatus is an apparatus that rotates an X-ray beam transmitted through a subject, and reconstructs a tomographic image or a three-dimensional image of the subject based on data obtained thereby. The X-ray CT apparatus is used not only for diagnosing diseases of the human body but also for measuring animals and other objects other than the human body for research and experiments. For example, in a pharmaceutical company, an X-ray CT apparatus is used for verification of an animal experiment. In this case, examples of the subject include small animals such as guinea pigs, rats, mice, hamsters, and the like. Conventionally, when performing X-ray diagnosis of a small animal using an X-ray CT apparatus, for example, a subject is simply placed on a horizontal bed.
[0003]
Patent Document 1 below discloses a veterinary X-ray imaging apparatus (a so-called X-ray imaging apparatus) including a base having a simple V-shaped groove on which an animal such as a dog is placed. In this device, the front and back of the small animal are open. Patent Literature 2 below discloses an industrial X-ray CT apparatus. According to this document, an enlarged projection image is obtained by rotating the sample side and changing the distance between the X-ray generator and the sample. In this device, the sample to be measured is an industrial product. In addition, the sample is measured in a bare state.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-299786 [Patent Document 2]
JP-A-5-322802 [0005]
[Problems to be solved by the invention]
In a general X-ray CT apparatus, an X-ray generation unit and an X-ray detection unit are rotationally driven in a gantry, and the distance between them is constant. On the premise of such a configuration, a configuration capable of changing the magnification of an image is required.
[0006]
An object of the present invention is to make it possible to mechanically change magnification in an X-ray CT apparatus in which a measurement unit is rotated.
[0007]
Another object of the present invention is to provide a highly practical X-ray CT apparatus particularly suitable for small animals.
[0008]
[Means for Solving the Problems]
(1) In order to achieve the above object, the present invention provides a measurement unit comprising: an X-ray generator that generates an X-ray beam having a divergent shape; and an X-ray detector that detects the X-ray beam. Means for holding the subject at a position where the X-ray beam transmits, a rotation mechanism for rotating the measurement unit around a rotation center axis intersecting the X-ray beam, the X-ray generator, the X-ray And a displacement mechanism that displaces at least one of the detection unit and the rotation center axis in the X-ray beam direction, thereby changing the magnification of the image.
[0009]
According to the above configuration, the subject is held by the holding means for holding the subject, and the rotating mechanism includes the X-ray generation unit and the X-ray detection unit around the rotation center axis set on the subject around the subject. To rotate. Thus, the X-ray beam is rotationally scanned. The holding means for holding the subject is for positioning the subject, and may be a bed or the like, but is particularly preferably a container for containing the subject. The subject may be an animal, a human body, a non-living object, or the like, and is particularly preferably a small mouse.
[0010]
The displacement mechanism is one of a distance between the rotation center axis and the X-ray generation unit and a distance between the rotation center axis and the X-ray detection unit in the X-ray beam direction (X-ray beam center axis direction). Or change both. As a result, the width of the X-ray beam passing through the subject changes due to the nature of the X-ray beam having the divergent shape, and the magnification when a CT image of the subject is formed can be changed. In this case, the spatial resolution also varies. Normally, the magnification is changed so that the entire cross section of the subject is covered. However, the magnification may be changed so that a part of the cross section is magnified and observed. In this case, it is desirable to position the holding means or the subject such that the center of the part is coincident with the rotation center axis. The concept of the divergent shape includes a fan beam shape that spreads two-dimensionally.
[0011]
Preferably, the displacement mechanism holds the measurement unit, and the rotation mechanism rotates the measurement unit by rotating the displacement mechanism. According to this configuration, when the rotation mechanism drives the displacement mechanism to rotate, the measurement unit held by the displacement mechanism rotates. Assuming that the rotation center axis is not changed, the same magnification can be maintained at each rotation angle by rotating the measurement unit by the displacement mechanism in a desired displacement state and performing rotation driving.
[0012]
Preferably, the displacement mechanism displaces the measurement unit with respect to the rotation center axis set on the subject while maintaining a distance between the X-ray generation unit and the X-ray detection unit.
[0013]
Preferably, the displacement mechanism is provided on one side of a frame on which the measurement unit is mounted, and a first mechanism that guides the displacement movement of the frame, and is provided on the other side of the frame, and controls the displacement movement of the frame. And a second mechanism for guiding. If the displacement motion is guided on both sides of the frame, a smooth displacement motion can be ensured, and the positioning accuracy can be improved.
[0014]
(2) The present invention also provides an X-ray CT apparatus for small animals, comprising: an X-ray generation unit that generates an X-ray beam having a fan beam shape; and an X-ray detection unit that detects the X-ray beam. A measuring unit provided, provided at a position where the X-ray beam is transmitted, and a container for accommodating the small animal, and the container relative to the measuring unit in a rotation center axis direction crossing the X-ray beam. A moving mechanism for moving, a rotating mechanism for rotating the measurement unit around the rotation center axis, and a displacement mechanism for displacing the measurement unit in the X-ray beam direction, thereby changing the magnification of the image. Features.
[0015]
According to the above configuration, the small animal as the subject is accommodated in the container, and the measurement unit is driven to rotate around the container. Further, the container is relatively moved in the direction of the rotation center axis by the moving mechanism as needed. In this case, the container may be moved with respect to the measurement unit, or the measurement unit may be moved with respect to the container. Although the movement is performed automatically, artificial force may be used. When the measurement unit is displaced by the displacement mechanism, the magnification of the image is changed.
[0016]
Preferably, the container has a hollow cylindrical shape, and the container is disposed in a horizontal state. Preferably, a plurality of types of containers having different sizes are selectively used as the containers. Preferably, a means for setting the magnification according to the size of the container to be used is included. In this case, size information input by the user or automatically detected size information may be used. Preferably, a means for variably setting the magnification by a user is included.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
FIG. 1 shows an example of an X-ray CT apparatus. This X-ray CT apparatus is an apparatus for performing CT measurement of mice, such as mice, rats, rats, guinea pigs, and hamsters. This X-ray CT apparatus is roughly composed of a measurement unit 10 and a calculation control unit 12.
[0019]
The measuring unit 10 has a main body 16 having a gantry 18. An opening is formed in the upper surface 16A of the main body 16, and the arm 26 projects upward from the opening. The arm 26 forms a part of a slide mechanism described later. The arm 26 is connected to a container 24 described later, and slides in the direction of the central axis.
[0020]
On the other hand, a measurement unit (X-ray generator, X-ray detector) to be described later is housed in the gantry 18, and they rotate around a rotation center axis. A hollow portion 18A is formed in the center of the gantry 18 in the direction of the rotation center axis.
[0021]
The container 24 is a capsule for accommodating a small animal as a subject, and the container 24 has a substantially cylindrical shape in the present embodiment, and is arranged in a state where the center axis of the container coincides with the center axis of rotation. Specifically, the base end 76 of the container 24 is detachably attached to the upper end of the arm 26 described above. In this case, examples of the attachment / detachment mechanism include various types of engagement mechanisms or screwing mechanisms. As described above, the container 24 has a hollow cylindrical shape, and a small animal is disposed inside the container 24. Such a configuration prevents the hair of the small animal from directly contacting the gantry 18. Can be prevented. Further, it is possible to prevent a problem that excrement and detached body hair of the small animal are released to the outside. Furthermore, as described later, since it becomes possible to restrain small animals, it is possible to prevent problems such as image blurring when reconstructing a CT image. It is desirable that a plurality of types of containers having different sizes and shapes be prepared and selectively used.
[0022]
After the container 24 is mounted on the arm 26, the arm 26 is driven forward along the rotation center axis direction, whereby the container 24 is inserted into the cavity 18A of the gantry 18. At this time, the container 24 is positioned so that the X-ray beam is set with respect to a cross section at a predetermined position in the subject. Also, such measurement positions may be changed continuously or stepwise as needed.
[0023]
An operation panel 20 is provided on the upper surface 16A of the main body 16, and the operation panel 20 has a plurality of switches, a display, and the like. Using this operation panel 20, the user can operate the operation of the device at the measurement site. A plurality of casters 22 are provided below the main body 16. Incidentally, the height of the measuring unit 10 is, for example, 100 cm.
[0024]
Next, the arithmetic control unit 12 will be described. The arithmetic and control unit 12 is electrically connected to the measuring unit 10 by a cable 14. The measurement unit 10 and the arithmetic and control unit 12 may be provided in the same room, or may be installed in different places. The arithmetic control unit 12 is configured by a general computer system or the like, and specifically includes a processor 30, a display 32, a keyboard 36, a mouse 38, a storage device 34, a printer 40, and the like. The operation of the measuring unit 10 is controlled by the arithmetic control unit 12, and a CT image is formed based on the data transmitted from the measuring unit 10. Although this CT image usually corresponds to a two-dimensional tomographic image, a three-dimensional image may be constructed. Incidentally, in the apparatus of the present embodiment, the rotation speed of the measurement unit in the gantry 18 is, for example, 10 rotations per minute. Of course, such a rotation speed can be appropriately set according to the application.
[0025]
FIG. 2 is a block diagram showing each configuration of the X-ray CT apparatus shown in FIG. An X-ray generator 52 is provided on one side and an X-ray detector 60 is provided on the other side with the rotation center axis O therebetween. A collimator 54 is provided on the irradiation side of the X-ray generator 52. The X-ray generator 52 generates a divergent or fan-shaped (here, fan-beam shaped) X-ray beam 56 as shown. On the other hand, the X-ray detector 60 is configured by arranging a plurality of (for example, 100) X-ray sensors in a line, and the X-ray receiving aperture is set according to the opening angle of the X-ray beam 56. Incidentally, the arrangement of the plurality of X-ray sensors may be linear or arcuate.
[0026]
In FIG. 2, a high-voltage source used with the X-ray generator 52 and a data processing circuit used with the X-ray detector 60 are not shown.
[0027]
In FIG. 2, reference numeral 58 indicates an effective field of view. This is a circular area where a CT image can be formed when the X-ray beam 56 is rotated and scanned. Incidentally, the effective field of view 58 is determined according to the positional relationship between the X-ray generator 52 and the X-ray detector 60 and the subject or the rotation center axis. In the present embodiment, since the displacement mechanism 62 described below is provided, it is possible to mechanically change the magnification of the CT image by changing their positional relationship.
[0028]
That is, the X-ray generator 52 and the X-ray detector 60 are connected to the displacement mechanism 62, and the displacement mechanism 62 maintains the distance between the X-ray generator 52 and the X-ray detector 60 while maintaining the distance therebetween. (Ie, a measurement unit) is displaced in the beam axis direction of the X-ray beam 56. In this case, the rotation center axis O is unchanged, that is, the magnification can be changed by moving the measuring unit side without moving the above-mentioned container at all. This will be described later in detail with reference to FIGS. The displacement mechanism 62 has a motor 62A for generating a displacement force.
[0029]
The gantry rotation mechanism 66 is a mechanism that rotates a rotation base, which will be described later, to thereby rotationally drive all components including the displacement mechanism mounted thereon. Since the measurement mechanism is mounted on the displacement mechanism 62, the measurement unit positioned at a desired position by the displacement mechanism 62 is driven to rotate while maintaining the position. The gantry rotation mechanism 66 has a motor 66A for generating the driving force.
[0030]
The slide mechanism 68 is a moving mechanism that slides the arm 26 shown in FIG. 1, and its driving force is generated by a motor 68A. The operation panel 20 is provided on the upper surface of the main body as described above. The operation panel 20 may be connected to a local controller (not shown) provided on the measurement unit 10 side, and the local controller and the arithmetic control unit 12 may communicate with each other.
[0031]
Incidentally, FIG. 2 shows various mechanisms 62, 66, 68 and the like, but it is desirable to provide a sensor for detecting a position or a change due to those mechanisms. It is desirable that the arithmetic and control unit 12 performs so-called feedback control based on the output signals of those sensors. Further, the magnification change by the displacement mechanism 62 may be performed by a user input, for example, by automatically detecting the subject size or the size of the container, and automatically setting the magnification based on the detected data. Is also good. Furthermore, when the type of the container is registered in advance, the magnification may be set using the registered information. Further, in the example shown in FIG. 2, the slide mechanism 68 has the motor 68A as a drive source, but the slide force may be artificially generated.
[0032]
Next, the operation control unit 12 will be described. As described above, the processor 30 is connected to the display 32, the storage device 34, the keyboard 36, the mouse 38, the printer 40, and the like. A communication unit 42 for performing communication with an external device via a network is connected.
[0033]
The processor 30 includes a CPU, an operation control program, an image processing program, and the like. FIG. 2 shows a representative function thereof, and the processor 30 has an operation control unit 44 and a reconstruction operation unit 46. The operation control unit 44 controls the entire operation of the measurement unit 10. The reconstruction operation unit 46 executes an operation for constructing a CT image based on a large amount of data obtained by rotational scanning of the X-ray beam. In this case, a three-dimensional image may be constructed. Various known methods can be used for the reconstruction operation. In changing the magnification, the calculation formula used in the reconstruction calculation can be basically used as it is. However, when a special variable magnification method is applied, a part of the reconstruction arithmetic expression may be changed as necessary.
[0034]
The display unit 32 displays the CT image as a tomographic image or the like. In this case, it is desirable to display a numerical value or a scale representing a magnification (magnification). According to this configuration, it is possible to evaluate the size of the object when visually determining the image. That is, it is possible to quantitatively determine, for example, the amount of fat and the size of a tumor.
[0035]
FIG. 3 shows a cross section of the container 24 shown in FIG. The container 24 is roughly composed of a container body 70 and a lid 72. A distal end portion 74 is provided on the distal end side of the container body 70, and the distal end portion 74 has a conical shape protruding forward. A through hole 78 is formed at the center of the tip 74.
[0036]
A base end portion 76 is provided on the base end side of the container body 70. As described above, the base end portion 76 is a portion to be mounted on the slide mechanism, but the mounting mechanism is not shown. The interior 70 </ b> B of the container body 70 is partitioned by a distal end portion 74 on the distal end side and is partitioned by a partition wall 80 on the proximal end side. A through hole 82 is formed in the center of the partition 80.
[0037]
The through holes 78 and 82 are holes into which a tube or the like for introducing an anesthetic gas, for example, is inserted. Of course, the through holes 78 and 82 may function as air holes. Even when such through holes 78 and 82 are formed, when the container 24 is arranged in a horizontal state, dirt and the like excreted from small animals are stored in the inside 70B of the container body 70, and Can be prevented. The detached hairs are hardly released to the outside because the through holes 78 and 82 are small holes.
[0038]
An opening 70A is formed in the container body 70, and the above-described lid 72 is provided in the opening 70A. The lid 72 may be opened and closed by, for example, a hinge or the like, may be simply attached to one side of the container body 70 with an adhesive tape or the like, or may be completely attached to the container body 70. A configuration in which the lid 72 is separated may be used. In any case, it is desirable that the lid 72 be closed after the small animal is stored inside the container body 70.
[0039]
Incidentally, the container 24 is constituted by a transparent X-ray transmitting member as a whole. Examples of the material include resins such as acrylic and ABS.
[0040]
In the example shown in FIG. 3, the container 24 has a hollow substantially cylindrical shape as a whole, but other shapes may be employed. For example, a rotationally symmetrical shape around the central axis can be mentioned, and further, an elliptical shape, a D-shaped shape, or a square shape can be given. Considering that the effective field of view 58 shown in FIG. 2 is circular, the cross section of the container 24 is desirably circular, and in that sense, it is desirable to adopt a cylindrical shape or a rotationally symmetric shape.
[0041]
Incidentally, in the example shown in FIG. 1, the container 24 is set in a horizontal state, but in an example described later with reference to FIG. 24, for example, the container 24 is set in an upright state. In this case, if the lower side of the container 24 is the tip 74, it is better not to form a through hole in the tip 74. The reason is that it is possible to prevent the waste and the like excreted from the small animal from flowing out.
[0042]
In the example shown in FIG. 3, the length of the container 24 is, for example, 400 mm, and its diameter (outer diameter) is, for example, 120 mm. For example, one small animal or two small animals is stored in the interior 70B of the container body 70. Even in such a case, the tail of the small animal is not pulled out, and can be stored in the container 24. In exceptional cases, such a tail-extracting hole may be formed in the partition wall 80.
[0043]
Next, an example of use of the container 24 will be described with reference to FIGS.
[0044]
As shown in FIG. 4, a small animal 84 is accommodated in the inside 70B of the container 24. In that case, as shown in FIG. 5, the lid 72 is opened with respect to the container body 70, and the small animal 84 is stored. Then, as shown in FIG. 6, by closing the lid 72, the small animal 84 is held in the container 24. In this case, even if hairs, beards, and the like are present, they are securely held in the container 24. That is, for example, it is possible to prevent a problem that the subject protrudes from the effective visual field 58 illustrated in FIG. In the examples shown in FIGS. 4 and 5 described above, the small animal 84 is simply stored in the container 24. In such a case, the CT measurement can be performed, but the small animal 84 is securely restrained. For this purpose, a fixing member as described below may be used.
[0045]
In FIG. 7, sponge bodies 86 and 88 that are elastically deformed are provided in the container 24A. That is, as shown in FIG. 8, a sponge body 86 is provided on the container body 70 side, and a sponge body 88 is provided on the lid 72 side. Then, as shown in FIG. 9, by closing the lid 72 with respect to the container body 70, the entire periphery of the small animal 84 is wrapped by the sponge bodies 86 and 88, and the movement of the small animal 84 is suppressed, and It is possible to reliably prevent a problem such as occurrence of displacement of the position.
[0046]
In this case, for example, air packing may be used as the fixing member, or an adhesive fixing member may be provided. Further, for simplicity, the small animal 84 may be wrapped with a gauze or other eye-opening member to fix its movement.
[0047]
According to the above configuration, since the movement of the subject 80 can be prevented and the surface of the small animal 84 can be separated from the inner surface of the container, an advantage in data calculation can be obtained. That is, when the container material has an X-ray absorption coefficient equivalent to the fat and muscle of the small animal 84, if the small animal 84 is in contact with the inner surface of the container, the container itself is a part of the small animal. As described above, there is a risk of being mistaken in data operation. On the other hand, by inserting a material having an X-ray absorption coefficient different from that between the small animal 84 and the container, the two can be discriminated on the image, and the above-described misperception can be prevented.
[0048]
In the examples shown in FIGS. 7 to 9, the fixing member is divided into two parts on the container main body 70 side and the lid 72 side, but various methods other than the above may be adopted as a method for arranging the fixing member.
[0049]
10 to 12 show other examples. As shown in FIG. 10, a plurality of through holes 90 are formed in the container body 70 and the lid 72 in the container 24B, and a linear member 92 such as a string having an elastic action is formed in the through holes 90. Has been passed over. For example, the linear member 92 is rubber or the like.
[0050]
As shown in FIG. 11, when the lid 72 is opened, the small animal 84 is placed on a plurality of linear members 92 which are hung in parallel with each other, and then the lid 72 is closed, as shown in FIG. As described above, the small animal 84 is sandwiched between the plurality of linear members 96 provided on the side of the lid 72 and the plurality of linear members 92, thereby achieving the pressing and fixing.
[0051]
The example shown in FIGS. 11 to 12 is merely an example, and a pair of sheet-like members having an elastic force may be provided, and the small animal 84 may be sandwiched from both sides thereof. Also in the examples shown in FIGS. 10 to 12, the body surface of the small animal 84 can be separated from the inner surface of the container.
[0052]
Therefore, if a CT measurement is performed on a small animal using the above-described container, the small animal can be confined within a certain circular area on the CT scanning plane, and a part of the small animal comes into contact with the device, Alternatively, it is possible to prevent wastes released from the small animal from being released or hygiene problems from occurring. Further, since the movement of the small animal can be suppressed by the fixing member, it is possible to prevent a problem caused by the movement of the object during the measurement, and it is also possible to separate the body surface of the small animal from the inner surface of the container. In that case, there is an advantage that image processing can be easily performed. Further, in the above-described example, the state of the small animal can be observed from outside even during the CT measurement because the container is formed of the transparent member. In the present embodiment, the entire container is made of a transparent member, but it is sufficient that at least a part of the container is transparent as long as observation can be performed.
[0053]
Next, variable magnification by the above-described displacement mechanism will be described with reference to schematic diagrams of FIGS.
[0054]
In FIG. 13, reference numeral 100 denotes a rotation center axis. In the X-ray CT apparatus, the X-ray generator 52 and the X-ray detector 60 perform a rotational movement around the rotation center axis 100. In this case, the effective field of view 102 is defined by an inscribed circle when the X-ray beam 101 is rotationally scanned. This effective field of view 102 corresponds to a photographing range. The X-ray beam 101 has a divergent shape, that is, it is a fan beam.
[0055]
FIG. 14 shows the positional relationship between the components. Here, the distance from the rotation center axis 100 to the X-ray generator 52 is defined as R, and the distance from the X-ray generator 52 to the X-ray detector 60 is defined as L. Incidentally, the distance from the rotation center axis 100 to the X-ray detector 60 is represented by T. Assuming the X-ray beam 101 having the above fan beam shape, the magnification of the image is determined by L / R, and the larger the fraction value, the larger the magnification, that is, the magnification. What can be said from this is that the magnification can be changed by moving at least one of the X-ray generator 52, the rotation center axis, and the X-ray detector 60.
[0056]
In FIG. 15, a relatively large object (subject) 104 exists in the effective visual field 102. When the object 104 is imaged in the geometric relationship as shown in FIG. 15, the object 104 becomes as shown by reference numeral 104A. That is, the object is displayed in a considerably large size on the screen. Note that, in this example, the center of the object 104 coincides with the rotation center axis, so that the center of the image also coincides with the center of the object 104A.
[0057]
On the other hand, as shown in FIG. 16, when an object 106 that is relatively small with respect to the effective field of view 102 is present, the size of the object on the screen is very small as indicated by reference numeral 106A. As a result, there arises a problem that the diagnosis of the object cannot be performed accurately. Therefore, as shown in FIG. 17, for example, by reducing R while keeping L constant (in other words, by increasing T), even a small object 106 is displayed on the screen as indicated by reference numeral 106B. It is possible to express it in large scale. That is, zoom-up can be realized. In this example, similarly to the above, the center of the object 106 coincides with the center axis of rotation, whereby the center of the image coincides with the center of the object 106A.
[0058]
Of course, in the case shown in FIG. 16, it is possible to enlarge the obtained data by image processing, but it is not possible to improve the spatial resolution itself. However, according to the method as shown in FIG. 17, since the spatial resolution itself can be increased, there is an advantage that a high-accuracy enlarged image can be obtained.
[0059]
Here, considering the method of changing the magnification, at least one of the X-ray generator 52, the rotation center axis (coincident with the center of the object 106 in this example), and the X-ray detector 60 is moved in the X-ray beam axis direction. It is understood that it is necessary to move. Incidentally, in the case where the distance L between the X-ray generator 52 and the X-ray detector 60 is variable, it is desirable that the opening of the X-ray detector 60 should be set to be spacious.
[0060]
The principle described above will be further described with reference to FIGS. 18 and 19. In the case shown in FIG. 18, the distance between the X-ray generator 52 and the object 108 is R1, and in this case, the X-ray beam Only the portion indicated by reference numeral 110 in 101 passes through the object 108. In this case, the X-ray intensity observed by the X-ray detector 60 is as illustrated. That is, only a central sensor among many X-ray sensors (elements) acquires valid data.
[0061]
On the other hand, as shown in FIG. 19, assuming that the object 108 is brought closer to the X-ray generator 52 and the distance between the two is R2 (R1> R2), the range of the X-ray beam 101 passing through the object 108 (symbol 112), the X-ray sensor in a large part of the full aperture in the X-ray detector 60 acquires valid data. What is understood from this is that the spatial resolution is improved. Of course, even when the distance between the X-ray generator 52 and the X-ray detector 60 is not constant, the advantage of improving the spatial resolution can be obtained.
[0062]
Incidentally, when acquiring a CT image of a small animal, the CT image may be formed so as to cover the entire abdomen of the small animal, or an enlarged image of some organs in the abdomen may be acquired. May be set to the magnification. That is, instead of aligning the rotation center axis with the center of the object, for example, the rotation center axis may be aligned with the center of the portion to be enlarged. For this purpose, a mechanism for moving the object not only in the X-ray beam direction but also in a direction orthogonal to both the X-ray beam and the rotation center axis may be provided.
[0063]
The principle described above is not limited to an X-ray CT apparatus, but can be applied to, for example, a bone mineral amount measurement apparatus using X-rays, an X-ray imaging apparatus, and the like.
[0064]
Next, a specific configuration and operation of the measurement unit 10 illustrated in FIG. 1 will be described with reference to FIGS. First, the configuration of the measurement unit 10 will be described with reference to FIG. As described above, the X-ray generator 52 is provided on one side with respect to the rotation center axis, and the X-ray detector 60 is provided on the other side. Reference numeral 101 denotes an X-ray beam having a fan beam shape, and reference numeral 102 denotes the above-described effective field of view. Reference numeral 120 represents the shape of the cavity in the gantry.
[0065]
A belt 122 is wound around the motor 66 </ b> A, and the rotational force of the belt 122 is transmitted by rotating the belt 122 by rotating the movable unit 50. The movable section 50 is configured by various mechanisms mounted on the rotation base 123. Specifically, a displacement mechanism 62 is provided on the rotation base 123, and the displacement mechanism 62 is shown as a first mechanism 62L and a second mechanism 62R in FIG. Each of the first mechanism 62L and the second mechanism 62R has a member 134 fixed on the rotation base 123, and the member 134 is provided with a guide 132 for slidably receiving the rail 130 fixed to the frame 124. ing. Incidentally, the rail 130 and the guide 132 are not shown in the drawing for the first mechanism 62L.
[0066]
The rails 130 are provided on both sides of the frame 124, that is, the frame 124 is slidably held on both sides. The X-ray generator 52 and the X-ray detector 60 are mounted on the frame 124.
[0067]
The first mechanism 62L has a motor 62A, and its rotational force is transmitted to the feed screw 126. A bearing 128 is engaged with the feed screw 126. The bearing 128 is fixed to the rotation base 123. Therefore, when the feed screw 126 is rotated, the frame 124 moves forward or backward depending on the engagement relationship between the feed screw 126 and the bearing 128. That is, the measurement unit including the X-ray generator 52 and the X-ray detector 60 can be displaced with respect to the rotation center axis.
[0068]
FIG. 21 shows a state where the movable unit 50 is rotated from the state shown in FIG.
[0069]
On the other hand, FIG. 22 shows a state in which the feed screw 126 is rotated as described above, and the frame 124 is pulled upward due to the engagement between the feed screw 126 and the bearing 128. Since the X-ray beam 101 has a divergent shape, the effective field of view 102 is extremely small in the state shown in FIG. That is, this means that the magnification has been increased. FIG. 23 illustrates a state where the movable unit 50 is rotated from the state illustrated in FIG. 22. During the rotation, the once set displacement state of the measurement unit is maintained.
[0070]
In the above-described embodiment, the driving force for varying the magnification is generated by the motor 62A, but the driving force may be performed by an artificial force. Even in that case, a mechanism for sliding the measurement unit in the direction of the beam axis of the X-ray beam and maintaining the once set displacement state is necessary.
[0071]
FIG. 24 shows another example of the X-ray CT apparatus. In the example shown in FIG. 1, the container moves only in the direction of the center axis of rotation, but in the example shown in FIG. 24, the container itself is driven to rotate and its position is changed to change the magnification.
[0072]
In FIG. 24, an X-ray generator 204 and an X-ray detector 206 are fixedly arranged on a base 202. A container 208 is set between them as described below. The container 208 has, for example, a form similar to that of the container 24 shown in FIG. 3, except that the through hole 78 shown in FIG. 3 does not exist because the container 202 is set upright. That is, it is to prevent outflow of dirt and the like from the inside of the container 208. Except for the absence of the through-hole 78, the specific configuration of the container 208 is the same as the example shown in FIGS. 3 to 12, and a description thereof will be omitted.
[0073]
On the base 202, plates 212, 214, and 216 are arranged in an upright state. The displacement mechanism 210 is held by the plates 212, 214, and 216. Hereinafter, the displacement mechanism 210 will be described in detail.
[0074]
Two poles 218 and 220 are arranged between the plate 214 and the plate 216 in parallel with each other at a certain interval vertically. A slider 222 is provided for the poles 218 and 220 so as to be slidable in the X direction in the drawing. A pulley 226 is connected to the X motor 230, and a wire 228 extends between the pulley 226 and the other pulley 224. A slider 222 is coupled in the middle of the wire 228, that is, when the X motor 230 is driven, the wire 228 rotates, and as a result, the slider 222 slides in the X direction according to the rotation of the wire 228. This sliding movement causes the entire movable section 300 including the displacement mechanism 210 to move in the X direction, and makes it possible to change the magnification as described later. That is, as shown in FIG. 14, R can be varied while L is kept constant.
[0075]
The slider 222 is provided with a Z motor 232, and the screw 234 is driven to rotate by the Z motor 232. A bearing 236 is engaged with the screw 234, and the bearing 236 is fixed to the vertical plate 238. Therefore, when the Z motor 232 is rotationally driven, the screw 234 rotates, and the bearing 236 engaged with the screw 234 moves in the Z direction in the drawing. As a result, the vertical plate 238 also moves.
[0076]
The vertical plate 238 is provided with a horizontal plate 240 on the lower side and a horizontal plate 241 on the upper side. On the upper surface of the horizontal plate 240, a circular rotating plate 244 is provided. The rotating plate 244 is hollow at the center, that is, has a funnel-like shape, and is itself capable of rotational movement.
[0077]
On the other hand, the horizontal plate 241 is provided with a ring-shaped rotary holder 242. The rotation holder 242 has a structure for holding the base end of the container 208. A motor 246 is provided at the upper end of the vertical plate 238, and a roller 248 is connected to a shaft of the motor 246. The roller 248 is in contact with the outer peripheral surface 242A of the rotary holder 242. Therefore, when the motor 246 is driven, the rotary holder 242 is rotationally driven due to the contact relationship between the roller 248 and the outer surface 242A. That is, the container 208 rotates.
[0078]
In this case, the tip or lower end of the container 208 has a conical shape as described above, which matches the funnel-like shape of the rotating plate 244. That is, the rotation of the container 208 is performed without the center axis being shifted left and right. Therefore, when the container 208 is rotated with the slider 222 set at a position in the X direction, a CT image of the subject housed in the container 208 is formed at a magnification corresponding to the position of the slider 222. The rotation speed is, for example, 0.2 rotations per second.
[0079]
The image thus formed is displayed on a display provided in an arithmetic control unit (not shown) (see FIGS. 1 and 2).
[0080]
On the other hand, when it is desired to change the magnification, the slider 222 is moved in the X direction to set a desired magnification. Then, the X-ray CT image can be obtained by continuously irradiating the X-ray beam 201 while rotating the container 208 at a constant speed in the same manner as described above.
[0081]
The above embodiment differs from the configuration shown in FIG. 1 in that the container 208 is disposed in an upright state and the container 208 itself is driven to rotate. However, a CT image can be obtained by any of the methods, and it is desirable to select one of the methods according to the contents of the subject or the purpose of measurement.
[0082]
The example shown in FIG. 24 has an advantage that a large-scale mechanism is not required to rotate the container 208 itself. As shown in FIG. 24, when the container 208 is set up and rotated to perform a rotational motion, the container 208 is arranged in a horizontal state and rotated, in combination with the above-described operation of the fixing member in the container. The displacement of the subject is less likely to occur than in the case.
[0083]
Incidentally, when obtaining a tomographic image of a certain part of the subject and forming a tomographic image of the next part, the container 208 is moved in the Z direction by the Z motor 232 as described above. In this case, such a vertical movement may be performed using an artificial force, and the same applies to the movement in the X direction.
[0084]
FIG. 25 shows two types of containers 208 and 250. The container 208 shown in (B) is the same as the container shown in FIG. 24, and is the same as that shown in FIG. 3 except that the through hole 78 provided at the tip is not formed.
[0085]
On the other hand, the container 250 shown in (A) has a smaller diameter at its main part than the container 208 shown in (B), while the outer shape of the proximal portion 250A matches the outer shape of the proximal portion 208A of the container 208. ing. Further, the distal end portion 250B of the container 250 has a conical shape as described above. According to the configuration as shown in FIG. 25, since the distal end of each container has a conical shape, any type of container can be engaged with the rotating plate 244. Even in the case of the type container, the outer diameter of the base end portion matches, so that the container can be reliably held by the rotary holder 242.
[0086]
FIG. 26 shows a case where the container 250 shown in FIG. 25A is set. In a case where such a small-sized container 250 is used, the container 250 is displaced by the displacement mechanism 210, for example. The X-ray is measured at a position close to the X-ray generator 204, that is, with the magnification increased.
[0087]
The container shown in FIG. 25 is an example, and a container having another shape can be used. In any case, if the measurement is performed with the object stored, that is, in a state where the object is wrapped, the above-described various advantages can be obtained.
[0088]
Incidentally, the above-mentioned container is not limited to the X-ray CT apparatus, but can be used, for example, in a bone mineral amount measuring apparatus using X-rays, an X-ray imaging apparatus, and the like, and the same advantages as above can be obtained.
[0089]
【The invention's effect】
According to the present invention, the magnification can be mechanically changed in the X-ray CT apparatus in which the measurement unit is rotated.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an overall configuration of an X-ray CT apparatus related to the present invention.
FIG. 2 is a block diagram showing an overall configuration of the X-ray CT apparatus shown in FIG.
FIG. 3 is a cross-sectional view of a container that stores a subject.
FIG. 4 is a perspective view showing a usage example of the container.
FIG. 5 is a sectional view showing an example of use of the container.
FIG. 6 is a sectional view showing an example of use of the container.
FIG. 7 is a perspective view showing a usage example of the container.
FIG. 8 is a sectional view showing an example of use of the container.
FIG. 9 is a cross-sectional view showing a usage example of the container.
FIG. 10 is a perspective view showing a usage example of the container.
FIG. 11 is a cross-sectional view showing a usage example of the container.
FIG. 12 is a cross-sectional view showing a usage example of the container.
FIG. 13 is a diagram for explaining an effective field of view.
FIG. 14 is a diagram for explaining a positional relationship between members.
FIG. 15 is a diagram showing a relationship between an effective field of view and a relatively large object.
FIG. 16 is a diagram illustrating a relationship between an effective visual field and a relatively small object.
FIG. 17 is a diagram for explaining formation of an enlarged image of an object.
FIG. 18 is a diagram for explaining an X-ray transmitted through an object.
FIG. 19 is a diagram for explaining an X-ray transmitted through an object.
FIG. 20 is a diagram illustrating the operation of the measurement unit when the magnification is small.
FIG. 21 is a diagram illustrating the operation of the measurement unit when the magnification is small.
FIG. 22 is a diagram illustrating the operation of the measurement unit when the magnification is large.
FIG. 23 is a diagram illustrating the operation of the measurement unit when the magnification is large.
FIG. 24 is a perspective view showing a main configuration of an X-ray CT apparatus related to the present invention.
FIG. 25 is a view showing various containers.
26 is a diagram showing an example in which a small-sized container is used in the X-ray CT apparatus shown in FIG.
[Explanation of symbols]
Reference Signs List 10 measurement unit, 12 operation control unit, 16 main body, 18 gantry, 20 operation panel, 24 containers, 30 processor, 44 operation control unit, 46 reconstruction operation unit, 50 movable unit, 52 X-ray generator, 60 X-ray detection Vessel, 62 displacement mechanism, 66 gantry rotation mechanism, 68 slide mechanism, 200 measuring section, 204 X-ray generator, 206 X-ray detector, 208 container, 210 displacement mechanism, 300 movable section.

Claims (10)

A measurement unit including: an X-ray generation unit that generates an X-ray beam having a divergent shape; and an X-ray detection unit that detects the X-ray beam.
Holding means for holding the subject at a position where the X-ray beam is transmitted;
A rotation mechanism for rotating the measurement unit around a rotation center axis intersecting the X-ray beam,
A displacement mechanism that displaces at least one of the X-ray generation unit, the X-ray detection unit, and the rotation center axis in an X-ray beam direction, thereby changing a magnification of an image;
An X-ray CT apparatus comprising: The device of claim 1,
The X-ray CT apparatus, wherein the holding unit is a container that contains the subject. The device of claim 1,
The displacement mechanism holds the measurement unit,
An X-ray CT apparatus, wherein the rotation mechanism rotates the measurement unit by rotating the displacement mechanism. The device according to claim 3,
The displacement mechanism displaces the measurement unit with respect to the rotation center axis set on the subject while maintaining a distance between the X-ray generation unit and the X-ray detection unit. X-ray CT apparatus. The device according to claim 4,
The displacement mechanism,
A first mechanism provided on one side of a frame on which the measurement unit is mounted, for guiding displacement movement of the frame;
A second mechanism provided on the other side of the frame to guide a displacement movement of the frame;
An X-ray CT apparatus comprising: In an X-ray CT apparatus for small animals,
A measurement unit including: an X-ray generation unit that generates an X-ray beam having a fan beam shape; and an X-ray detection unit that detects the X-ray beam.
A container that is provided at a position where the X-ray beam transmits and that accommodates the small animal;
A moving mechanism that relatively moves the container with respect to the measurement unit in a rotation center axis direction crossing the X-ray beam;
A rotation mechanism for rotating the measurement unit around the rotation center axis,
A displacement mechanism for displacing the measurement unit in the X-ray beam direction, thereby changing the magnification of the image,
An X-ray CT apparatus comprising: The device according to claim 6,
The said container has a hollow substantially cylindrical shape, The said container was arrange | positioned in the horizontal state, The X-ray CT apparatus characterized by the above-mentioned. The device according to claim 6,
An X-ray CT apparatus, wherein a plurality of types of containers having different sizes are selectively used as the containers. The device according to claim 8,
An X-ray CT apparatus comprising means for setting the magnification according to the size of a container to be used. The device according to claim 6,
An X-ray CT apparatus comprising means for allowing a user to variably set the magnification.

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