X-ray CT scanners and scanning procedures

Abstract

X-ray CT scanner with: a rotating device (3) with an X-ray generator (1) and an X-ray detector (2) which are opposite each other and which are arranged so that an object (O) can be inserted between them; a rotation mechanism for rotating the rotation device (3) about a rotation axis (3a); a movement mechanism (31) for moving the rotating device (3) in a plane that intersects the axis of rotation (3a); and a control device which is designed to control the rotation mechanism and the movement mechanism (31) in such a way that a combined movement of the rotation device (3) is performed during the taking of X-ray images; wherein the combined motion of the rotating device (3) is a combination of a motion of the rotating mechanism controlled by the control device with a motion by the motion mechanism (31) controlled by the control device; wherein, during the movement of the rotating device (3) by the motion mechanism (31) controlled by the control device, the axis of rotation (3a) is arranged such that it is moved along a circular path (LC1, LC2, LC3) whose center lies in a center (3X) of an area of ​​interest in the object (O), such that the axis of rotation (3a) and the center (3X) of the area of ​​interest in the object (O) are kept at a constant distance from each other.

Description

Field of invention

[0001] The invention relates to X-ray computed tomography for reconstructing an image in a three-dimensional area. Background image technology

[0002] In an X-ray computed tomography (CT) scanner, an object is placed between an X-ray generator and an X-ray detector. The X-ray generator and detector are rotated around the object, which is then exposed to the X-ray beam generated by the X-ray generator from multiple directions. The X-ray intensity distribution passing through the object (or a projection thereof) is measured by the X-ray detector. Based on the X-ray projection data acquired during rotation, a distribution of linear absorption coefficients (or an image) within the object is reconstructed two-dimensionally to generate a cross-sectional image. This reconstruction calculation is performed in multiple planes orthogonal to the axis of rotation to create a three-dimensional image based on the cross-sectional images.

[0003] If the magnification of an image in a CT scan can be changed, the field of view (the size of an area of ​​interest) can be altered, and the image resolution can be changed. In an X-ray CT scanner with an X-ray generator and an X-ray detector mounted on a rotating arm or gantry, the X-ray generator and the X-ray detector are rotated around an object while the distances between the X-ray generator, the object, and the X-ray detector are kept constant. The magnification of an image can be increased or decreased according to the relative distance between the X-ray generator or the X-ray detector within the object.

[0004] As will be explained later, the invention allows the distance between the X-ray generator and a rotation center for a CT scan and / or the distance between the X-ray detector and the rotation center to be changed. This is relevant with regard to some prior art documents. In a CT scanner as described in Japanese patent publication JP 2004 - 329 293 A, still images (so-called pilot images) with a dual positional relationship between the X-ray generator and the X-ray detector are transmitted before a CT scan is started in order to determine a three-dimensional position of an area to be scanned.

[0005] When the size of a pilot image is changed, the position of a chair relative to the X-ray detector is adjusted. However, although the size of a pilot image can be changed, no design for changing the magnification of an image is described. In a CT scanner as described in Japanese patent publication JP H05-322802A, intended for use on an object in an industrial setting, the positions of the X-ray generator and the X-ray detector are fixed. On the other hand, an object is placed on a table, and a projection image of it is captured while the table is rotated. The magnification of the image is changed according to the positions of the X-ray generator and the X-ray detector relative to the rotating table. However, the rotation of the object is possible because it is a stationary object.If the object is a person, problems arise such as artifacts due to their movement and dizziness caused by the rotation. Therefore, this method is not practical for CT scans of people, especially in medical settings. Furthermore, even if the object is an object, the CT scanner cannot be used if the object has a structure so precise that it cannot be subjected to continuous rotation. In an X-ray CT scanner, as described in Japanese patent publication JP 2001-37747A, a rotating arm has an X-ray generator and a planar X-ray detector positioned opposite each other, with an object placed between them.The planar X-ray detector is mounted on a ring arm with an extendable arm, and the detector can be positioned closer to or further away from the object, thus changing the magnification of the image. However, changing the magnification requires a mechanism to adjust the X-ray detector relative to the rotating device or to adjust the rotating device relative to the X-ray device. Medical devices are widely used for panoramic X-ray imaging or X-ray CT scans, where an X-ray generator and an X-ray detector are located at opposite ends of a rotating arm, and modifications to these devices are desirable.

[0006] From DE 10 2004 020 668 A1, an X-ray CT scanner is known in which the rotation device is rotated during a projection, but the center of rotation is fixed to prevent the center of rotation from drifting out of the area of ​​interest of the object. Summary of the invention

[0007] One object of the invention is to make it easier to change the field of view in a CT scan (or the size of an area of ​​interest).

[0008] This problem is solved by an X-ray CT scanner according to claim 1. Further embodiments can be found in the dependent claims.

[0009] A first X-ray CT scanner according to the invention has a rotating device with an X-ray generator and an X-ray detector, which are positioned opposite each other and between which an object is inserted, a rotation mechanism for rotating the adjusting device about an axis of rotation, a mechanism for adjusting the axis of rotation of the rotating mechanism in two-dimensional directions intersecting the axis of rotation, and a control device that controls the rotation mechanism and the mechanism for adjusting the axis of rotation in order to rotate the rotating device such that the center of an area of ​​interest in the object always remains at the center of rotation, at a CT scan viewing point, due to a combined movement of the rotation of the rotating device by the rotation mechanism and the movement of the axis of rotation by the mechanism for adjusting the axis of rotation.The distance between the X-ray detector and the center of rotation and / or the distance between the X-ray detector and the center of rotation can be changed, so that the magnification can be changed.

[0010] With the first X-ray CT scanner, and with the second and third X-ray CT scanners, as well as with an X-ray CT scanning method that will be explained later, the field of view (or the magnification of an area of ​​interest) can be easily changed using the X-ray generator and the X-ray detector in a relative position relationship during a CT scan. In particular, if the X-ray detector has a detection area of ​​limited size, and if the area of ​​interest to be magnified is too large for the detection area, or if the entire area of ​​interest cannot be imaged, the magnification can be reduced so that the entire area of ​​interest fits within the detection area.

[0011] Furthermore, the magnification can be changed without using a mechanism to adjust the X-ray detector or the X-ray generator relative to the rotating device.

[0012] Furthermore, if the rotating device is moved around the axis of rotation, even if a deviation in the position of the axis occurs due to a mechanical malfunction, this can easily be corrected by setting the center of rotation differently from the axis of rotation.

[0013] Preferably, in this X-ray CT scanner, the mechanism for adjusting the rotation axis comprises a first adjustment device that adjusts the rotation axis of the rotation mechanism in a first direction different from the rotation axis, and a second adjustment device that adjusts the rotation axis in a second direction different from the first direction and the rotation axis. This allows for easy control of two-dimensional movement of the object.

[0014] Preferably, in this X-ray CT scanner, the mechanism for adjusting the rotation axis and the rotation device are mounted in the same housing. This allows the rotation mechanism to be accommodated in a relatively large two-dimensional space. Furthermore, since the rotation mechanism does not need to be housed within the rotation device, the design of the adjustment device can be simplified.

[0015] Preferably, in this X-ray CT scanner, the mechanism for adjusting the axis of rotation has one or more connecting elements linked together in series and connected to the bearing of the rotation mechanism, whereby the center of rotation can be adjusted in two-dimensional directions intersecting the axis of rotation. The two-dimensional movement of the axis of rotation can then be controlled by a simple design.

[0016] A second X-ray CT scanner according to the invention has a rotation device with an X-ray generator and an X-ray detector, which are opposite each other and between which an object is inserted, a rotation mechanism for rotating the rotation device about an axis of rotation, a mechanism for adjusting the object in two-dimensional directions intersecting the axis of rotation about the axis of rotation, and a control device that controls the rotation mechanism and the mechanism for adjusting the object in order to rotate the rotation device such that a point in an area of ​​interest of the object is always located at the center of rotation, at a CT scan viewing point, due to a combined movement of the rotation of the adjustment device by the rotation mechanism and the movement of the object.This allows the distance between the X-ray generator and the center of rotation and / or the distance between the X-ray detector and the object to be changed, so that the magnification can be changed.

[0017] Preferably, in the second X-ray CT scanner, the mechanism for adjusting the object comprises a first adjustment device that moves the object in a first direction different from the axis of rotation, and a second adjustment device that moves the object in a second direction different from both the first direction and the axis of rotation. This allows for easy control of the object's two-dimensional movement.

[0018] Preferably, in the second X-ray CT scanner, the rotation axis of the rotation mechanism extends vertically. This allows the subject, if a human body is being scanned, to be positioned standing or sitting, and the scanner to be installed in a small space.

[0019] Preferably, the rotation axis of the first and second X-ray CT scanners is a rotating arm. This allows the rotation axis to be provided by a mechanically simple design.

[0020] A third X-ray CT scanner according to the invention has a rotating device with an X-ray generator and an X-ray detector, which are positioned opposite each other and between which an object is inserted, a rotation mechanism for rotating the adjusting device about an axis of rotation, a mechanism for adjusting the axis of rotation of the rotating mechanism and / or the object in two-dimensional directions intersecting the axis of rotation, and a control device that controls the rotation mechanism and the mechanism for adjusting the axis of rotation and / or the object in order to rotate the adjusting device such that a point in an area of ​​interest in the object is always located at the center of rotation, at a CT scan viewing point,due to a combined movement of the rotation of the rotating device by the rotation mechanism and the movement of the rotation axis and / or the object by the mechanism for adjusting the rotation axis and / or the object.

[0021] In an X-ray CT scanning method according to the invention, the distance between the X-ray generator and the center of rotation and / or the distance between the X-ray detector and the center of rotation are changed to alter the magnification in an X-ray CT scanner by means of the following: a rotating device with an X-ray generator and an X-ray detector that are positioned opposite each other and between which an object is inserted, a rotation mechanism for rotating the rotating device about an axis of rotation, a mechanism for adjusting the axis of rotation of the rotating mechanism in two-dimensional directions intersecting the axis of rotation, and a control device that controls the rotation mechanism and the mechanism for adjusting the axis of rotation such that the rotating device is rotated so that a point in an area of ​​interest in the object is always located at the center of rotation, at a CT scan viewing point.due to a combined movement of the rotation of the rotating device by the rotation mechanism and the movement of the rotation axis by the mechanism for moving the rotation axis. Brief description of the drawings

[0022] These and other tasks and features of the invention will become clear from the following description in conjunction with the preferred embodiments thereof with reference to the accompanying drawings, in which the following is illustrated: Fig. 1A, Fig. 1B and Fig. Figure 1C shows sectional views illustrating the structure of a recording medium in one embodiment of the invention. Fig. Figure 2 is a schematic diagram to illustrate a situation in which magnification is changed while a rotating device is rotated in a circular motion. Fig. Figure 3 is a schematic diagram to illustrate a situation where the magnification is changed while an object is rotated in a circle. Fig. 4A and Fig. Figure 4B shows schematic diagrams for a first X-ray CT scanner (a) and a second X-ray CT scanner (b), Fig. 5A and Fig. 5B are diagrams to explain the first X-ray scanner for magnification and reduction, Fig. 6A and Fig. 6B are diagrams to explain the second X-ray scanner for magnification and reduction, Fig. 7A and Fig. Figure 7B shows diagrams of a basic setup of the first X-ray CT scanner. Fig. Figure 8 is a diagram of a control system of the first X-ray CT scanner, Fig. Figure 9 is a diagram of a rotation system of the first X-ray CT scanner, Fig. Figure 10 is a diagram of a part relating to the up-down control of the rotary arm, Fig. Figure 11 is a diagram of a part relating to the control of the position of the rotary arm and the rotation, Fig. 12 is a flowchart of a rotary control system, Fig. Figure 13 is a diagram of a modified example of a rotation system, Fig. 14A and Fig. Figure 14B shows diagrams of the basic structure of the second X-ray CT scanner. Fig. Figure 15 is a diagram of a control system of the second X-ray CT scanner, Fig. Figure 16 is a diagram of a modified example of the two-dimensional adjustment mechanism, and Fig. Figure 17 is a diagram of another, modified example of the two-dimensional adjustment mechanism. Description of preferred embodiments

[0023] Embodiments of the invention are explained below with reference to the accompanying drawings, wherein identical reference numerals denote identical or corresponding parts in all of the different views.

[0024] In an X-ray CT scanner, an adjustment device, such as a rotating arm, has an X-ray generator 1 and an X-ray detector 2 positioned opposite each other, with an object inserted between them. The distance between the X-ray generator 1 and the X-ray detector 2 is constant. A rotation mechanism holds the adjustment device so that it can be rotated about an axis of rotation within the mechanism. This axis of rotation is referred to as the "mechanical axis of rotation" or simply the "rotation axis." The mechanical axis of rotation, or rotation axis, can be set, for example, using a rotating shaft, as a rotating shaft with the axis of rotation is used for rotation by the mechanism. Any suitable rotation mechanism can be used to rotate at least one X-ray generator 1 and one X-ray detector 2.Even if the rotation mechanism does not have a mechanical shaft, it has an axis of rotation about which the X-ray generator 1 and the X-ray detector 2 are rotated. For example, a ring-shaped rotating device with an X-ray generator 1 and an X-ray detector 2 facing each other and driven by a motor via a rotor or gears can be used without having an axis of rotation, and this device does have an axis of rotation. When the rotating device is rotated about the mechanical axis of rotation, the X-ray generator 1 and the X-ray detector 2 are rotated around the object. It is preferred that the mechanical axis of rotation is orthogonal or substantially orthogonal to the centerline of the X-ray beam emitted by the X-ray generator 1.If the object in this case is a human body, it can be in a standing or sitting position and the scanner can be installed in a small space.

[0025] Now, the magnification (or magnification factor) of an image captured in an X-ray CT scan will be explained. In the Fig. 1 is F the position of the X-ray generator 1 (more precisely, the position of the focal point of the X-ray beam in the X-ray generator 1), S is the position of the X-ray detector 2 (more precisely, the position of an X-ray detection plane in the X-ray detector 2), B is the position of the rotating shaft 3a in the rotation mechanism, and C is the position of the object O (more precisely, the position of a point in an area of ​​interest in the object).

[0026] In the cases listed below, a cylindrical or nearly cylindrical area, which is always irradiated by the cone-shaped X-ray beam, is considered the area of ​​interest (the cylindrical or nearly cylindrical area is, for example, area B in the Fig. 5A or area A in the Fig. 5B, which can be scanned during a CT scan by rotating the cone-shaped X-ray beam.) The position of the center of rotation of the cone-shaped X-ray beam can be considered the center of the area of ​​interest, viewed in the direction of rotation, and position C can be any point, namely the center of the area of ​​interest. However, there is a case where the shape of the area of ​​interest is not defined. In this case, any point of undefined shape within the area of ​​interest can be chosen as position C. In another case, where the size of the area to be scanned is so small that it is sufficiently enclosed within the aforementioned cylindrical or nearly cylindrical area, the area that can at least encompass the area to be scanned can be considered the area of ​​interest.In this case, the position of the center of rotation of the cone-shaped X-ray beam can be chosen as position C, and of course, the position of the center of rotation of the cone-shaped X-ray beam can be chosen as position C.

[0027] As it is in the Fig. As shown in Figure 1C, if the position B of the rotating shaft 3a in the rotation mechanism coincides with the position C of the point in the area of ​​interest in the object O, the magnification of the object in an image acquisition plane of the X-ray detector 2 can be expressed as FS / FB (= FS / FC) using the distance Fs between the X-ray generator 1 and the X-ray detector 2 and the distance FB between the X-ray generator 1 and that of the rotating shaft 3a. (In the Fig. 1C applies distance FB = distance FC between the X-ray detector 1 and the object O)

[0028] The magnification can be changed by altering the distance FC between the X-ray generator 1 and the object O and / or the distance CS between the object O and the X-ray detector 2. For example, as described in the Fig. As shown in Figure 1A, when the position C of object O relative to the rotating shaft 3a in the rotation mechanism towards the X-ray detector 2 is changed, the magnification decreases, and a larger area can be imaged. In this situation, object O is moved by a distance α (> 0) relative to the X-ray detector 2 in front of an X-ray CT scan. Next, as will be explained later with reference to the Fig. 2 is explained, the rotation device 3 is rotated while the center of rotation of the rotation mechanism or the rotation shaft 3a is moved along a circular path with a radius α, the center of which lies at point 3X in the area of ​​interest in object 1 (more precisely, the position of the center of rotation in the Fig. 1A). Alternatively, as will be explained later with reference to the Fig. As explained in section 3, the object O moves along a circular path with radius α, the center of which lies at the center of rotation of the rotation mechanism. The center of rotation of the rotation mechanism lies on the rotation shaft 3a, and the magnification of the object O imaged in the X-ray detector 2 is FS / (FB + α) (= FS / FC).

[0029] If, on the other hand, as it is in the Fig. As shown in Figure 1B, when the position C in object O relative to the rotational shaft 3a in the rotational mechanism towards the X-ray generator 1 is changed, the magnification increases, and an image of a smaller area can be acquired. In this situation, object O is moved a distance α (> 0) towards the X-ray generator 1 before an X-ray CT scan. Next, as will be explained later with reference to the Fig. 2 is explained, the rotation device 3 is rotated and the center of rotation of the rotation mechanism or the rotation shaft 3a is moved along the circular path with a radius α, the center of which lies at the point in the area of ​​interest in the object O, or, as will be explained later with reference to the Fig. As explained in section 3, the object O moves along a circular path with radius α, the center of which lies at the center of rotation of the rotation mechanism. The center of rotation of the rotation mechanism lies on the rotation shaft 3a, and the magnification of the object O imaged in the X-ray detector 2 is FS / (FB - α) (= FS / FC).

[0030] In the Fig. 1A and Fig. In the situations shown in Figure 1B, the rotating shaft 3a in the rotation mechanism (position B) does not coincide with the point in the area of ​​interest in the object O (position C). Therefore, if the rotation mechanism causes the rotating device 3 to rotate around the rotating shaft 3a, the position of the rotating shaft 3a in the rotation mechanism, or the object O, must be moved in a circle according to the rotation angle of the rotation mechanism. When this circular movement is achieved, the magnification of a CT scan can be changed. Then, the entire rotation mechanism should be subjected to a circular rotation according to the rotation angle of the rotation mechanism. In this way, the relative position relationship between the X-ray generator 1, the orbit O, and the X-ray detector 2 is kept constant. Such a CT scan offers the following advantages.Using the X-ray generator 1 and the X-ray detector 2 in a relative position relationship, the field of view or the magnification of an area of ​​interest can be easily changed. In particular, if the X-ray detector 2 has a detection area of ​​limited size and the area of ​​interest is too large for the detection volume or the entire area of ​​interest to be imaged at a given magnification, the magnification can be reduced so that the entire area of ​​interest falls within the detection area. Furthermore, the magnification can be changed without using a mechanism to move the X-ray detector 2 or the X-ray generator 1 relative to the rotating device.Even if a positional deviation of the rotation axis occurs due to a mechanical malfunction or similar cause when the rotating device is moved around the rotating shaft, this can be easily corrected by setting the center of rotation at a CT scan viewing point differently from the mechanical rotation axis. The CT scan viewing point can also be referred to as the viewing point when taking a photograph of an object by detector 2, and the center of rotation at the viewing point when taking a photograph is, as stated above, different from the mechanical rotation axis. The center of rotation at the CT scan viewing point will be explained in more detail later.

[0031] First, a first X-ray CT scanner is explained. The first X-ray CT scanner has a mechanism 31, which will be explained in detail later, to adjust the rotational shaft 3a of the rotational mechanism in two-dimensional directions that intersect the rotational shaft 3a. Fig. Figure 2 shows a situation for the control process. This mechanism 31 adjusts the rotating shaft 3a. The rotating device 3 rotates the X-ray generator 1 and the X-ray detector 2 around the rotating shaft 3a, while the latter is moved by the mechanism 31. The two types of movement are synchronized so that the distance FC between the X-ray generator 1 and point 3X in the area of ​​interest, as well as the distance CS between the X-ray generator 2 and the center 3X, are always kept constant. In the combined movement resulting from the two types of movement, the center of rotation 3X is located at a CT scan viewing point at point 3X in the area of ​​interest in object O, and the X-ray generator 1 and the X-ray detector 2 are rotated around the center 3X to keep the distance to it constant.If the X-ray generator 1 and the X-ray detector 2 are rotated around the rotating shaft 3a by an angle, the shaft is also rotated around point 3X in the area of ​​interest by the same angle. Then, viewed from point 3X in the area of ​​interest, the X-ray generator 1 and the X-ray detector 2 are rotated around center 3X, similar to a rotation in the... Fig. 1C shows a conventional CT scan, except that the position of the object differs from that of the rotating shaft. Thus, even if the rotating shaft 3a of the rotation mechanism assumes a position other than point 3X in the area of ​​interest in object O, a rotation center 3X different from the rotating shaft 3a is always set to point 3X of the area of ​​interest, and the rotation device 3 is always rotated about point 3X in the area of ​​interest in object O, due to the combined motion that couples the rotation of the rotation device 3a of the rotation mechanism with the movement of the rotating shaft by the mechanism 31 for moving it.

[0032] The aforementioned “rotation center 3X in a CT scan viewpoint, which is different from the rotation wave 3a” represents a rotation center that is defined independently of the rotation wave 3a in a CT scan viewpoint, and this is realized by the mechanism 31, which adjusts the position of the rotation wave 3a. The rotation center 3X in a CT scan viewpoint can coincide with the position of the rotation wave.The rotating device 3, comprising the X-ray generator 1 and the X-ray detector 2, which are positioned opposite each other, is rotated by the rotation mechanism by a rotation angle β around the rotating shaft 3a, while the center of the rotation mechanism or the rotating shaft 3a is rotated relative to point 3X in the area of ​​interest (corresponding to the initial rotation center) according to the rotation angle β of the circular rotation, so that the relative position relationship between the X-ray generator 1, the object O, and the X-ray detector 2 is kept constant. Fig. 2 and Fig. Figure 3 shows situations where the magnification is set lower; however, when the magnification is set higher, point 3X in the area of ​​interest is closer to X-ray generator 1.

[0033] On the other hand, in a second X-ray CT scanner, where an object is moved in a circle according to a rotation angle of the rotation mechanism, a holding mechanism is provided to hold an object O between the X-ray generator 1 and the X-ray detector 2, and an adjustment mechanism, which will be explained in detail later, moves the holding mechanism in two-dimensional directions that intersect the rotational shaft 3a in the rotation mechanism. Fig. Figure 3 illustrates this control process. Even if the position of the rotating shaft 3a differs from point 3X in the area of ​​interest within object O, the distance between point 3X in the area of ​​interest and the X-ray generator 1, as well as the distance between the center 3X and the X-ray generator 1, are always kept constant due to the combined movement achieved by synchronizing the rotation of the rotating device 3 with the rotation of the object via the adjustment mechanism 5. This means that the center of rotation 3X at a CT scan viewing point is set differently from the rotating shaft 3a, and the rotating device 3 is always rotated around point 3X in the area of ​​interest within object O.

[0034] The aforementioned “rotation center 3X, which is different from the rotational axis 3a” means a rotation center at a CT scan viewpoint that is defined independently of the mechanical rotational axis 3a, similar to the one in the Fig. In the case shown in Figure 2, this is achieved by the mechanism for rotating the object. The center of rotation 3X can coincide with the position of the rotating shaft 3a (or the mechanical axis of rotation). The rotating device 3 is rotated by the rotating mechanism, while point 3X in the area of ​​interest within the object is rotated according to the rotation angle of the rotating device relative to the center of rotation of the rotating mechanism (the rotating shaft 3a), while the relative position relationship between the X-ray generator 1, the object, and the X-ray detector 2 is kept constant.

[0035] The in the Fig. 2 and Fig. The three illustrated embodiments are explained in detail below.

[0036] The Fig. 4A schematically shows the [unclear] in the Fig. Figure 2 shows the first X-ray CT scanner. In this embodiment, the rotation device 3 is a rotating arm with an X-ray generator 1 and an X-ray detector 2, positioned opposite each other, with an object inserted between them. Using the rotating arm, a rotating shaft 3a with a mechanically simple construction is constructed. The rotation device 3 is rotated around the rotating shaft 3a by a motor 33 to control its rotation. The rotating shaft 3a extends along the vertical direction. The rotating shaft 3a and the motor 33 are components of the rotation mechanism. An XY table 31 is a mechanism for adjusting the rotating shaft 3a in two dimensions that intersect it, or, in this example, in a plane orthogonal to the rotating shaft 3a.The XY table, as a mechanism for adjusting the object, has devices for adjusting the object in two intersecting directions, and the two-dimensional adjustment of the object is controlled in a simple manner. The object O is fixed in the mechanism and has a region B at and around its center, as well as a region A excluding region B.

[0037] The Fig. 4B schematically shows the [unclear] in the Fig. Figure 3 shows the second X-ray CT scanner. In this embodiment, the rotating device 3 is a rotating arm with an X-ray generator 1 and an X-ray detector 2, which are positioned opposite each other, with an object O inserted between them. The rotating device 3 is operated similarly to the second X-ray CT scanner shown in Figure 3. Fig. In the example shown in Figure 4A, the object O is rotated around the rotating shaft 3a. The object O is fixed in the mechanism and has a region B around its center and a region A excluding region B. It is moved by the device 5 (not shown) to adjust the object in the directions forwards and backwards, left and right, and up and down. The device 5 is a mechanism for adjusting the object O in two directions intersecting the rotating shaft 3a, or, in this example, in a plane orthogonal to the rotating shaft 3a.

[0038] The one in Fig. The mechanism shown in Figure 4A for moving the rotating shaft is a mechanism for moving the rotating shaft 3a in two intersecting directions, while the one in the Fig. The mechanism shown in Figure 4B for moving object O is one for moving it in two directions that intersect the rotating wave 3a. One of the two mechanisms can be configured to move either the rotating wave 3a or the object O. Alternatively, both mechanisms can be present to move the rotating wave 3a and the object O simultaneously.

[0039] The Fig. 5A and Fig. 5B shows the ones in the Fig. The embodiment shown in 4A is in a plane. In the embodiment shown in the Fig. In the embodiment shown in 5A, an image of the object O is generated by moving it a distance α from the rotating shaft 3a to the X-ray generator 1, whereas in the embodiment shown in the Fig. In the embodiment shown in Figure 5B, an image of object O is generated by moving it a distance α from the rotating shaft 3a to the X-ray detector 2. The rotating device 3 is rotated by the mechanism described above, while the rotating shaft 3a is adjusted synchronously according to the rotation angle of the rotating device 3. Due to the combined motion of the rotating device 3 and the rotating shaft 3a, the rotating shaft 3a is rotated and adjusted relative to point 3X in the area of ​​interest, and the relative position between the X-ray generator 1, the object O, and the X-ray detector 2 is kept constant. The rotating device 3 is rotated while the center of rotation 3X, at a CT scan viewing point, is always held at point 3X in the area of ​​interest within the object, unlike the rotating shaft 3a in the rotation mechanism.

[0040] In the Fig. 5A, the rotating shaft 3a is rotated and moved along a circle with radius α (or along positions LC1 → LC2 → LC3) relative to point 3X in the area of ​​interest, by a distance α from the rotating shaft 3a, towards the X-ray generator 1. The object O is moved a distance α away from the X-ray detector 2, and the X-ray detector 2 only detects area B in order to reconstruct it. Area A is located outside the detectable area. On the other hand, in the Fig. 5B, the rotating shaft 3a is rotated and moved along a circle with radius α (or along positions LC1' → LC2' → LC3') relative to point 3X in the area of ​​interest, at a distance α from the rotating shaft 3a, towards the X-ray detector 2. The object O is moved a distance α away from the X-ray detector 2, and the X-ray detector 2 detects not only area B but also the entire area A. Thus, the images of areas A and B can be reconstructed. As is described with reference to the Fig. 5A and Fig. As can be seen in Figure 5B, the magnification can be changed by altering the distance between X-ray generator 1 and the rotation center 3X and / or the distance between X-ray detector 2 and the rotation center 3X relative to the distance between X-ray generator 1 and X-ray detector 2. It is important to note that... Fig. 5A and Fig. 5B, a rotation center 3x in the CT scan viewing point set to point 3X.

[0041] Because only the rotation device is adjusted without moving an object, it is possible to change the magnification for a scan from one value to another. For example, at the start, the rotation shaft 3a is set so that it coincides with the point in the area of ​​interest, and a scan is performed. If it is then desired to increase the magnification, the rotation shaft 3a is moved to the position shown in the Fig. The position LC1 shown in 5A is adjusted, and a scan is performed in which it is rotated relative to the center of the image acquisition area 3 times from position LC1 along a circular path, following positions LC1, LC2, and LC3 as explained above. If it is desired to reduce the magnification, the rotation shaft 3a is moved to the position shown in the Fig. The position LC1' shown in Figure 5B is adjusted, and a scan is performed in which it is rotated relative to the center of the image acquisition area 3 times from position LC1' along a circular path, following positions LC1', LC2', and LC3' as explained above. This allows the magnification for a scan to be freely changed without moving the object.

[0042] The Fig. 6A and Fig. 6B shows the ones in the Fig. The examples shown in 4B are top views. Fig. 6A, the object O is moved by the rotational shaft of the rotational mechanism by the distance α to the X-ray generator 1, while it is in the Fig. 6B is moved by the rotation shaft of the rotation mechanism by a distance α towards the X-ray detector 2. The rotation device 3 is rotated about the rotation shaft 3a, and the object O is moved synchronously according to the rotation angle by the mechanism 5. Due to the combined movement of the rotation device 3 and the object O, the relative position between the X-ray detector, the object, and the X-ray generator 2 is kept constant. Thus, the rotation mechanism rotates the rotation device, while the center of rotation 3x, different from the rotation shaft 3a in the rotation mechanism, is always located at point 3X in the area of ​​interest within the object.

[0043] In the Fig. 6A, point 3X in the area of ​​interest, located a distance α from the X-ray generator 1 and away from the rotating shaft 3a, is moved relative to the rotating shaft 3a along a circular path of radius α, following positions LC10, LC20, and LC30. The object is rotated by the mechanism 5 for adjusting it, but the orientation of the object's front is not changed during a scan. For example, if the object is a human head, the head is rotated along positions LC10, LC20, and LC30 while facing the same direction. The object O is moved by the distance α in such a direction that it moves away from the X-ray detector 2, and the X-ray detector 2 only detects area B to reconstruct an image within it. Area A lies outside the detectable area of ​​the X-ray detector 2.

[0044] In the Fig. In step 6B, point 3X in the area of ​​interest, located at a distance α from the rotating wave 3a towards the X-ray detector 2, is moved along a circular path with radius α, following the positions LC10', LC20', and LC30', relative to the rotating wave 3a. The object O is moved a distance α towards the X-ray detector 2, which detects not only area B but also area A. Thus, an image of the two areas A and B can be reconstructed. Here, in the Fig. 6A and Fig. 6B, a rotation center 3x in the CT scan viewing point set to point 3X.

[0045] In the Fig. 6A and Fig. In the examples shown in Figure 6B, the center of rotation 3x at a CT scan viewing point is controlled so that it is always located at point 3X in the area of ​​interest. This means that the first and second X-ray CT scanners, via the rotating device 3 with the X-ray generator 1 and the X-ray detector 2 facing each other, have a rotation mechanism for rotating the rotating device 3 around the rotating shaft 3a, which extends vertically to an X-ray beam generated by the X-ray generator 1, and a mechanism for adjusting the rotating shaft 3a and / or the object O in a plane orthogonal to the rotating shaft 3a. The mechanism for adjusting the rotating shaft 3a and / or the object O is either the mechanism 3a for adjusting the rotating shaft in the first X-ray CT scanner or the mechanism 5 for adjusting the object in the second X-ray CT scanner.A control device, which will be explained later, performs such control that the center of rotation is set 3x differently from the rotating shaft 3a and the distances of the X-ray generator 1 and the X-ray detector 2 relative to the point in the area of ​​interest in the object O are always kept constant, which is done according to the combined and synchronized movement of the rotation of the rotating device 3 and the movement of the rotating shaft 3a and / or the object O.

[0046] As explained above, the magnification can be easily adjusted, allowing a user to set it according to the scan purpose. For example, if a volumetric image of a person's entire jaw is needed with a dental X-ray CT scanner, the magnification is reduced to image a larger area. Conversely, if a detailed image of just a few teeth is required, the magnification is increased to image a smaller area in detail.

[0047] Next, an example of the first X-ray CT scanner will be explained in detail. Fig. 7 and Fig. 8 show an example of the in the Fig. 2, Fig. Figures 4A, 5A, and 5B show the first X-ray CT scanner. A base frame 10 has a very stable, gate-shaped structure that supports the entire scanner. The base frame 10 consists of an upper frame 10a for rotatably holding the X-ray beam 3, a pair of crossbeams 10b for holding the ends of the upper frame 10a, a pair of vertical supports 10c that support the crossbeams 10b, and a base 10d for mounting the vertical supports 10c as a base for the entire scanner. The mechanism 5 for adjusting the object is mounted on the base 10d, and it includes a chair 4d as a device 4 for receiving the object. An operating console 10e is provided on one of the vertical supports 10c.

[0048] The rotation device 3 is a U-shaped rotating arm with an X-ray generator for emitting a cone-shaped X-ray beam and an X-ray detector 2 (a two-dimensional X-ray image sensor) positioned opposite each other. During a CT scan, while the rotation device 3 is rotated around an object, the object is exposed to the cone-shaped X-ray beam, and the X-rays passing through the object are captured as projection data by the X-ray detector 2. A three-dimensional image of the object is then reconstructed from this projection data.

[0049] The XY table 31 is mounted on the upper frame 10a, with a rotatable bearing for the rotating device 3. The XY table 31 is an example of the mechanism for adjusting the vertically extending rotating shaft 3a in a plane orthogonal to it. As will be explained later, the XY table 31 can be adjusted in a horizontal plane in mutually orthogonal directions. The XY table 31 has a Y table for adjustment in a Y direction as the first direction, and an X table, which is mounted orthogonal to the Y direction through the Y table for movement in an X direction as the second direction. (The X direction is in the Fig. 7A the left-right direction, and the Y-direction is a direction orthogonal to the X-direction.) Furthermore, for the XY table 31, there is a motor 31a for adjusting it in the X-direction, a motor 31b for adjusting the XY table 31 in the Y-direction, and no motor 32 for adjusting the rotation device in a direction orthogonal to the XY table 31 (up-down direction in the Fig. 7A) and a motor 33 for rotating the rotary device 3 are provided. The motor 33 rotates the rotating shaft (center of rotation) 3a located in a cavity 3b within the rotary device 3. By controlling the motors 31a and 31b for movements in the X and Y axes, the rotating shaft 3a of the rotary device 3 can be moved up and down, and by driving the motor 32, the rotary device 3 can be moved up and down. When an object is scanned, the motor 33 is operated at a constant speed to rotate the rotary device 3 around the object. In this example, the XY stage 31 is used to adjust the rotating shaft 3a in the first direction (e.g., the X direction), which is different from the axis of rotation, and in the second direction (e.g., the Y direction), which is orthogonal to the first direction.Generally speaking, the second direction need not be orthogonal to the first direction, or the rotational wave 3a is distorted in the first direction and the second direction, which differs from the first. Furthermore, in this example, the rotational wave 3a extends vertically. However, the rotational wave 3a can also extend horizontally. For example, an image can be taken of a patient lying in a horizontal position.

[0050] The Fig. Figure 9 shows part of the CT scanner for controlling the position and rotation of the rotary arm 3. The upper frame 10a has the table 54Y (Y-table) for forward and backward adjustment (Y-direction), the other table 54X (X-table) which is mounted for transverse movement (X-direction) by the table 54Y, the Y-axis control motor 31a for adjusting the Y-table in the Y-direction, the X-axis control motor 31b (not shown) for adjusting the X-table in the X-direction, and the motor 33 for rotating the rotary arm 3 about a vertically extending axis of rotation 62 of the rotating shaft 3a to connect the X-table 54X to the rotary arm 3. The rotary arm 3 has a bearing 3c. The motor 33 is mounted inside the rotary arm 3, and it drives the bearing 3c through a belt 34 to rotate the rotary shaft 3a.The rotary shaft 3a, the bearing 3c, the belt 34 and the motor 33 are components of an example of the rotation mechanism for rotating the rotary device 3. By controlling the three motors according to a predetermined program, the XY table can be moved forwards and backwards (Y-direction) and left and right (X-direction) while the rotary arm 3 is rotated.

[0051] The Fig. Figure 10 shows an example of a part of the CT scanner relating to the up-down control of the rotary arm 3. The crossbeam 10b can be adjusted up and down relative to the vertical support 10c. Extending from one end of the crossbeam 10b is a projection 10b1, which engages in a hole 10c1 in the vertical support 10c. The projection 10b1 has a threaded hole (not shown), and a threaded shaft 32a of the motor attached to the vertical support 10c engages in the threaded hole of the projection 10b. The threaded shaft 32a extends in a direction orthogonal to both the X and Y directions. The projection 10b1, the hole 10c1, the threaded hole, the motor 32, and the threaded shaft 32a are present at both ends of the crossbeam 10a and the vertical support 10c. The threaded shaft 32a is rotated by the motor 32 to move the projection 10b1 up and down.Thus, the entire crossbeam 10b is moved upwards or downwards, so that the rotary arm 3 is also moved upwards or downwards.

[0052] The Fig. Figure 11 shows a top view of a portion of the CT scanner used to control the position and rotation of the rotary arm 3, with the table 54Y (Y-table) for forward and backward movement, the table 54X (X-table) supported by the table 54Y for a transverse direction, the motor 31a for moving the Y-table in the Y-direction, and the motor 31b for adjusting the X-table in the X-direction. The table 54X is an example of a first adjustment device that moves the rotary shaft 3a in a first direction, and the table 54Y is an example of a second adjustment device that moves the rotary shaft 3a in a second direction, different from the first. In the example above, the X-direction is orthogonal to the Y-direction to simplify the calculation of the coordinates. However, the first and second directions can intersect at any angle, provided that two-dimensional control is possible.

[0053] Next, the rotation control by the control device 7 for changing the magnification in a CT scan control is explained. A case is described in which the center of rotation is moved along a circular path. First, an operator sets a magnification using a magnification-changing device 12 located in the operating device 11, and the magnification is adjusted accordingly. Fig. The control process illustrated in Figure 12 is called up. First, the adjustment path for the center of rotation is calculated according to the magnification (S10), and motors 31b and 31a for adjustment in the X-axis and Y-axis are activated to move the rotation shaft 3a by the calculated path (S12). Next, the circular path of the center of rotation is calculated (S14). During a CT scan, motor 33 is activated to rotate the X-ray beam 3, while motors 31b and 31a are activated to move the rotation shaft 3a along a circle with radius α, the center of which lies within an object (S16). This means that in CT scan control, the rotation conditions for motor 33 for rotation as well as the movement path of motors 31b and 31a in the directions X and Y are calculated according to the magnification, and motors 33, 31b and 31a are controlled according to the rotation conditions and the calculated path.Thus, according to the combined movement due to the rotation and the adjustment, the rotation arm 3 is rotated by setting the point in the area of ​​interest in the object O as the center of rotation 3x in a CT scan viewing point, different from the rotation shaft 3a.

[0054] During the Fig. In example 9, the motor 33 is arranged in the rotary arm 3 to control the rotation. However, as shown in the Fig. As shown in Figure 13, a motor 33' for controlling the rotation is present in the same housing as the upper frame 10a. In the Fig. In the example shown in 13, the motor 33 is not present in the rotary arm 3, unlike in the Fig. In the example shown in Figure 9, the motor 33' is mounted on a table 54X (X-table) within a housing of the upper frame 10a. The rotating shaft 3a' of the rotating arm 3, which is rotatably mounted in the table 54X by a bearing 3c', is driven by the motor 33'. Since the XY-table (or a mechanism for adjusting the rotating shaft) is located in the same housing as the motor 33' for controlling the rotation (or a rotation mechanism), a rotation mechanism can be accommodated in a space that is relatively large in two dimensions for the mechanism for adjusting the rotating shaft. Furthermore, because they are installed in the same housing, the rotation mechanism does not need to be located within the rotating device, and the design of the rotating device can be simplified.

[0055] When the position of the center of rotation is changed to alter the magnification, as explained above, for example, when an object is moved a distance α (> 0) relative to the X-ray detector 2, motors 31b and 31a are activated to move the X-stage 54X and the Y-stage 54Y a distance α to bring the X-ray detector 2 closer to the object O. During a CT scan, motor 33 is activated to rotate the rotary arm 3, while motors 31b and 31a are activated to move the rotary shaft 3a along a circular path of radius α around the object. The scanning principle was described above with reference to the Fig. 5 explained.

[0056] Next, an example of the second X-ray CT scanner will be explained in detail. Fig. 14 and Fig. 15 show an example of the in the Fig. 3, Fig. 4A, Fig. 6A and Fig. The second X-ray CT scanner shown in 6B. Its basic design is that of the one described in the Fig. 7 and Fig. The first X-ray CT scanner shown in Figure 8 is similar, except that the device 5 for moving the object in the X and Y directions is used instead of the XY table as the mechanism for adjusting the rotational shaft. The device 5 for adjusting the object is mounted on the base 10d of the base frame 10, and a chair 4b is mounted on it to hold the object (or a patient) in a seated position. A mechanism 4 for holding the object comprises a chair 4b and a head fixation device 4a located at the rear of the chair 4b. The mechanism 4 for holding the object is not limited to the aforementioned chair 4b and head fixation device 4a. For example, it could be any device for holding an object, such as a chin rest for resting the object's chin or ear sticks for fixing the position of the patient's ears.The device for adjusting the object's position can adjust chair 4b in the X, Y, and Z directions, or forward and backward, left and right, and up and down. The device for adjusting the object's position in the X direction is the first adjustment device, and the device for adjusting the object's position in the Y direction is the second adjustment device.

[0057] The device 5 for adjusting the object has a motor 51 for adjusting the chair 4b in the X direction, a motor 52 for adjusting the chair 4b in the Y direction, and a motor 53 for adjusting the chair 4b in the Z direction, providing adjustment in the upward and downward directions. The movement of the tables in the X, Y, and Z axes by the motors 51, 52, and 53 can be achieved using a rack and pinion, a ball screw, or a conventional thread. Accurate positioning is desirable. The device 5 for moving the object is an example of a mechanism for moving the object in a plane orthogonal to the rotating shaft 3a of the above, with reference to the Fig. Figure 4B describes the rotation mechanism. In this embodiment, the mechanism 5 moves the chair 4b in a first direction (for example, the X-direction) and a second direction, orthogonal to the first direction (for example, the Y-direction). However, the chair 4b can also be moved in a second direction that is not orthogonal to the first direction but different from it.

[0058] When the position of an object O is changed to adjust the magnification, as explained above—for example, when object O is moved by the distance α (> 0) relative to the X-ray detector 2—motors 51 and 52 are activated to adjust chair 4b by the distances corresponding to distance α in the X and Y directions, bringing object O closer to the X-ray detector 2. During a CT scan, motor 33 is activated to rotate the rotary arm 3, while motors 31b and 31a are activated to move the rotary shaft 3a along a circular path of radius α around the object. The scanning principle was described above with reference to the Fig. 6A and Fig. 6B explained.

[0059] Next, the CT scan control of the X-ray CT scanner will be explained. As described in the Fig. As shown in Figure 8, the X-ray CT scanner 20, as an example of the first X-ray CT scanner, has a control unit 7 with a computer. The control unit 7 has a computer with a central processing unit (CPU), a storage device, and an input / output interface, and it is connected to a data processor with a coprocessor, a keyboard 8, a mouse 9, a display monitor 10 such as a liquid crystal display, and an operating device with an operator console 10b. The operating device 7 has a magnification adjustment device 12 with which an operator can set a magnification value. The control unit 7 is also connected to the X-ray generator 1 and the X-ray detector 2, and it controls the motors 31a, 31b, 32, and 33.The storage device has a control program for a CT scan process as well as a processing program for calculating three-dimensional CT data from the projection data.

[0060] As it is in the Fig. As shown in Figure 15, the X-ray CT scanner 20, as an example of the second X-ray CT scanner, has a control unit 7 with a computer. The control unit 7 has the computer with a central processing unit (CPU), a storage device and an input / output interface, and it is connected to a data processor with a coprocessor, a keyboard 8, a mouse 9, a display monitor 10 such as a liquid crystal display and an operating device with an operator console 10b.

[0061] The operating device 7 has a magnification adjustment device 12 with which an operator can set a magnification value. The control device 7 is connected to the X-ray generator 1 and the X-ray detector 2, and it controls the operation of the motors 51, 52, and 53 for adjusting the position of the object. The storage device has a control program for a CT scan operation and a processing program for calculating three-dimensional CT data from the projection data. As described in the Fig. As shown in Figure 15, the second X-ray CT scanner can have an XY table 31, as used in the first X-ray CT scanner mentioned above.

[0062] If the object is in the Fig. 14 and Fig. As the second X-ray CT scanner shown in section 15 is moved along a circular path, the rotation control for changing the magnification is similar to the one described above. Fig. The counterpart to the first X-ray CT scanner is described in section 12. However, since the chair is moved in the second X-ray CT scanner, whereas the rotation shaft is moved in the first X-ray CT scanner, the rotation control differs in this respect. In step S10, the adjustment path for chair 4b is calculated, and the path is calculated according to the magnification. In step S12, motors 51 and 52 are activated to move chair B by the calculated path. Furthermore, in step S14, the circular path of chair 4b is calculated. During a CT scan, in step S16, motor 33 is activated to rotate the rotation arm 3, while motors 51 and 52 are activated to move chair 4b along a circle with radius α around the center of rotation.

[0063] In the aforementioned first X-ray CT scanner, the XY table 31 is used as a mechanism for adjusting the rotational shaft 3a in a plane orthogonal to it. For example, as described in the Fig. As shown schematically in Figure 16, the position of the rotating arm can be changed using connecting elements that are rotatably linked to one another. In the case of a Fig. In the example shown in Figure 16, two connecting elements 80 and 81 are connected in series. The first connecting element 80 is rotatably connected to the upper frame 10a by an axis 82, and the second connecting element 81 is rotatably connected to the first connecting element 80 by an axis 83. Furthermore, the second connecting element 81 is rotatably connected to a bearing of the rotating shaft 3a. The axes 82, 83 and the rotating shaft 3a are moved by the motors 84, 85 and 86. The control device 7 controls the motors 84, 85 and 86 to move the position of the rotating shaft 3a orthogonally to it in a two-dimensional plane.

[0064] The Fig. Figure 17 shows another, modified example of the mechanism for moving the rotating shaft. In this example, an extendable element 90 is used as a connecting device. One end of the extendable element 90 is rotatably connected to an axis 91 of the upper frame 10a, while its other end is rotatably connected to a bearing of the rotating shaft 3a of the rotating arm 3. The extendable element 90 and the rotating shaft 3a are moved to their respective drives by motors 92 and 93. The control device 7 controls the extendable element 90 and the motors 92 and 93 to move the position of the rotating shaft 3a in a two-dimensional plane orthogonal to it. Since the mechanisms for adjusting the rotating shaft, as described in the Fig. 16 and Fig. As shown in Figure 17, which are constructed with one or more connecting elements connected in series, the movement of the rotating shaft in a two-dimensional plane can be controlled by a simple construction.

[0065] In the embodiments described above, an X-ray CT scanner has either a mechanism for moving the rotating shaft or a mechanism for moving an object. However, if an X-ray CT scanner has both the mechanism for moving the rotating shaft and the mechanism for moving the object, as described above with reference to the Fig.As mentioned in section 15, the rotation can be controlled using various combinations of the two mechanisms. In this case, it is possible to select either the mechanism for moving the rotating shaft or the mechanism for moving an object. It is also possible to use both mechanisms simultaneously, so that the center of rotation at the CT scan viewing point, different from the mechanical axis of rotation, is always kept at the point in the area of ​​interest within the object. Thus, the magnification can be changed according to the distance between the X-ray generator and the center of rotation and / or the distance between the X-ray detector and the center of rotation, relative to the distance between the X-ray generator and the center of rotation.

[0066] Examples of different patterns of movement of the rotating wave or object are listed below. (a) Control in all directions X, Y and Z for use of the mechanism to move the axis of rotation. (b) Control in all directions X, Y and Z using the mechanism to move the object. (c) Control in the X and Y directions using the mechanism for moving the axis of rotation, and control in the Z direction using the mechanism for moving an object. (d) Control in the X and Y directions using the mechanism for moving an object, and control in the Z direction using the mechanism for moving the axis of rotation. (e) Control in the X and Y directions using both the mechanism for moving the axis of rotation and the mechanism for moving an object. (f) Control in all directions X, Y and Z using both the mechanism for moving the axis of rotation and the mechanism for moving an object.

[0067] Using patterns (e) and (f) advantageously reduces the deflections of both the rotating device 3 and the mechanism for holding the object.

[0068] In the embodiments described above, the magnification can be changed. However, even if the magnification is fixed or cannot be changed, an X-ray CT scan is possible by changing the position of the rotation shaft of the rotation mechanism and the position of the center of rotation at a CT scan viewing point, and by rotating the rotation device around the point in the area of ​​interest in an object as the center of rotation, always different from the axis of rotation of the rotation mechanism, according to the synthesis of the rotation of the rotation device 3 and the movement of the rotation shaft 3a and / or the object O.

[0069] The rotation device 3 can be the aforementioned U-shaped rotation arm, but it can also be a familiar gantry such as those used for scanning a patient lying on a bed. Furthermore, any construction capable of rotating an X-ray generator and an X-ray detector positioned opposite each other can be used.

[0070] The applicant of this invention has already disclosed an X-ray imaging device that can be used for both CT and panoramic modes, as disclosed in Japanese patent publication JP H10-225455A. It is possible to incorporate this X-ray imaging device into the design of this invention. Thus, a panoramic tomographic image can be acquired using an X-ray CT scanner according to the invention.

[0071] Although the invention can be applied to a dental X-ray CT scanner, it can also be applied to an X-ray CT scanner for otolaryngology, where the object is, for example, a very small part such as the stapes or a large part of a head.

[0072] Although embodiments have been disclosed and described, it is evident that other embodiments and modifications of the invention are possible.

Claims

[1] X-ray CT scanner with: a rotating device (3) with an X-ray generator (1) and an X-ray detector (2) which are opposite each other and which are arranged so that an object (O) can be inserted between them; a rotation mechanism for rotating the rotation device (3) about a rotation axis (3a); a movement mechanism (31) for moving the rotating device (3) in a plane that intersects the axis of rotation (3a); and a control device which is designed to control the rotation mechanism and the movement mechanism (31) in such a way that a combined movement of the rotation device (3) is performed during the taking of X-ray images; wherein the combined motion of the rotating device (3) is a combination of a motion of the rotating mechanism controlled by the control device with a motion by the motion mechanism (31) controlled by the control device; wherein, during the movement of the rotating device (3) by the motion mechanism (31) controlled by the control device, the axis of rotation (3a) is arranged such that it is moved along a circular path (LC1, LC2, LC3) whose center lies in a center (3X) of an area of ​​interest in the object (O), such that the axis of rotation (3a) and the center (3X) of the area of ​​interest in the object (O) are kept at a constant distance from each other. [2] X-ray CT scanner according to claim 1, wherein the movement mechanism (31) comprises: a first adjusting device (54X) that adjusts the rotating device (3) in a first direction; and a second adjusting device (54Y) which adjusts the rotating device (3) in a second direction which is different from the first. [3] X-ray CT scanner according to claim 1 or 2, wherein the movement mechanism (31) and the rotation mechanism are mounted in the same housing. [4] X-ray CT scanner according to one of claims 1 to 3, wherein the movement mechanism (31) has a connecting element or several connecting elements (80, 81) connected in series which are connected to a bearing, whereby the rotation device (3) can be adjusted in the plane intersecting the axis of rotation (3a). [5] X-ray CT scanner according to one of claims 1 to 4, wherein the control device is configured to allow the magnification to be changed by adjusting the distance between the X-ray generator (1) and the center (3X) of the area of ​​interest and / or the distance between the X-ray detector (2) and the center (3X) of the area of ​​interest. [6] X-ray CT scanner according to any one of claims 1 to 5, wherein the axis of rotation (3a) extends vertically. [7] X-ray CT scanner according to any one of claims 1 to 6, wherein the rotation device (3) consists of a rotation arm.

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