JP3607321B2 - X-ray computed tomography equipment - Google Patents

Description

ベアリング７が受ける回転数、つまり固定部４に対する中間回転リング５の相対的な回転数（差動回転数）ｎ_ＢＡ、ベアリング１２が受ける回転数、つまり中間回転リング５に対する回転リング１１の相対的な回転数（差動回転数）ｎ_ＢＢは、それぞれ次の（３）式、（４）式で表される。
【００１４】

常に、Ｄ_Ｓ ＞Ｄ_Ａ であるので、ｎ_ＢＢ＞ｎ_ｂ が成り立ち、回転リング１１は中間回転リング５より速い回転角速度で回転することになる。
【００１５】
したがって、ｎ_ＢＢとｎ_Ａ との回転比は次の（５）式で表される。

常に、Ｄ_Ｓ ＞Ｄ_Ａ であるので、Ｄ_Ｓ ／Ｄ_Ａ ＞１が成り立つ。これにより、次の（６）式が成立する。
【００１６】
１／２＜ｎ_ＢＢ／ｎ_Ａ ＜１ …（６）
したがって、ベアリング７及びベアリング１２各々が受ける回転数を最小にするような理想的な状態では、ベアリング７が受ける回転数ｎ_ＢＡ及びベアリング１２が受ける回転数ｎ_ＢＢを、固定部４に対する回転リング１１の相対的な回転数ｎ_Ａ の１／２にすることができ、ベアリングの耐久特性を示すＤＮ値が許容値を越えることなく、回転リング１１の高速回転が可能になる。つまり、ベアリング７、１２を従来の中間回転リングの無いもののベアリングと同じＤＮ値のものを採用しても、回転リング１１の最高回転数を略２倍に高めることができる。したがって、スキャン時間が短縮されて被検体の１回の息止め時間中に広い範囲の投影データを収集することができるようになると共に、被検体の拘束時間の短縮、患者スループットの向上、態動アーチファクトの抑制の課題が根本的に解決される。
【００１７】
次に第２実施例について説明する。
図４は第２実施例に係る差動回転駆動機構３の構造図であり、図５は図４のＢ−Ｂ´断面図である。２０は固定部である。この固定部２０にはベアリング２３を介して中間回転リング２１が回転中心０に関して回転自在に支持されている。この中間回転リング２１の一部に設けられたプーリと、固定部２０に設けられた回転駆動手段としての原動機２６の回転軸に装着された駆動プーリ２７との間には、無端ベルト２８が掛け渡されている。原動機２６の回転運動は、無端ベルト２８により中間回転リング２１に伝達され、中間回転リング２１が回転駆動される。
【００１８】
Ｘ線管１と多チャンネル型のＸ線検出器２とを開口部を挟んで対向した状態で保持する回転リング２４は、ベアリング２５を介して中間回転リング２１と同軸、つまり同じ回転中心０に関して回転自在に中間回転リング２１に支持されている。回転リング２４の一部に設けられたプーリと、回転中心０に関して公転するように中間回転リング２１に設けられた回転駆動手段としての原動機２９の回転駆動軸に装着された駆動プーリ３０との間には、無端ベルト３１が掛け渡されている。原動機２９の回転運動は、無端ベルト３１により回転リング２４に伝達され、回転リング２４が回転駆動される。
【００１９】
原動機２６と原動機２９には図示しないが各々独立した駆動回路が接続され、両駆動回路には図示しないが共通の制御回路が接続されている。制御回路が各駆動回路を個々に制御することにより、原動機２６と原動機２９の各回転数は同じ又は各別に制御される。
【００２０】
このような構成において、原動機２６の単位時間当たりの回転数をｎ_Ａ とし、原動機２９の単位時間当たりの回転数を_Ｂ とし、また原動機２６による中間回転リング２１の固定部２０に対する単位時間当たりの回転数をｎ_ＢＢとし、原動機２９による回転リング２４の中間回転リング２１に対する相対的な単位時間当たりの回転数（中間回転リング２１の単位時間当たりの回転数ｎ_ＢＢで回転する回転座標系における回転数）をｎ_ＢＡと仮定する。原動機２９は中間回転リング２１上に設けられ、中間回転リング２１と共に回転中心Ｏの回りを回転（公転）するので、回転リング２４は中間回転リング２１より速い回転角速度で回転し、具体的には回転リング２４の固定部２０に対する単位時間当たりの回転数ｎは、次の（７）式で表される。
【００２１】
ｎ＝ｎ_ＢＡ＋ｎ_ＢＢ …（７）
したがって、ｎ_ＢＡ＝ｎ_ＢＢ＝１／２×ｎとなる理想的な状態では、ベアリング２３，２５が受ける回転数は、中間回転リング２１が無い場合の半分に抑えられ、ベアリングの耐久特性を示すＤＮ値が許容値を越えることなく、回転リング２４の高速回転が可能になる。つまり、ベアリング２３、２５を従来の中間回転リングの無いもののベアリングと同じＤＮ値のものを採用しても、回転リング２４の最高回転数を略２倍に高めることができる。したがって、スキャン時間が短縮されて被検体の１回の息止め時間中に広い範囲の投影データを収集することができるようになると共に、被検体の拘束時間の短縮、患者スループットの向上、態動アーチファクトの抑制の課題が根本的に解決される。
【００２２】
また、原動機２６と原動機２９の回転数を、中間回転リング２１が無い場合の半分に抑えることができ、原動機２６と原動機２９の負担が軽減される。
次に第３実施例について説明する。
【００２３】
図６は第３実施例に係る差動回転駆動機構３の構造図であり、図７は図６のＣ−Ｃ´断面図である。４０は固定部である。この固定部４０にはベアリング４１を介して中間回転リング４２が回転中心０に関して回転自在に支持されている。また、Ｘ線管１と多チャンネル型のＸ線検出器２とを開口部を挟んで対向した状態で保持する回転リング４４は、ベアリング４３を介して中間回転リング４２と同軸、つまり同じ回転中心０に関して回転自在に中間回転リング４２に支持されている。中間回転リング４２と回転リング４４にはそれぞれ後述する無端ベルトを掛けるための同径のプーリが設けられている。
【００２４】
固定部４０に設置された回転駆動手段としての原動機５１の回転軸に設けられた歯車５２には、固定部４０に設置されたベアリング５４により回転自在に支持されたシャフト４８に設けられた歯車５３が噛み合わされている。原動機５１の回転運動は、歯車５２，５３を介してシャフト４８に伝達される。
【００２５】
シャフト４８には、径の異なる大小２つのプーリ４９，５０が設けられる。径の小さなプーリ４９と、中間回転リング４２との間には無端ベルト４７が掛け渡されている。シャフト４８の回転運動は、無端ベルト４７を介して中間回転リング４２に伝達される。径の大きなプーリ５０と、回転リング４４との間には無端ベルト４６が掛け渡されている。シャフト４８の回転運動は、無端ベルト４６を介して回転リング４４に伝達される。したがって、回転リング２４は中間回転リング２１より速い回転角速度で回転することになる。勿論、回転リング４４が中間回転リング４２より速い回転角速度で回転すれば、プーリ４９，５０の各径を同じにして、中間回転リング４２に設けられたプーリより回転リング４４に設けられたプーリの径を小さくしてもよい。その他、回転リング４４が中間回転リング４２より速い回転角速度で回転する限りにおいて、プーリ４９，５０、中間回転リング４２に設けられたプーリ、回転リング４４に設けられたプーリの各径は、任意に調整することができる。
【００２６】
回転リング４４の単位時間当たりの回転数をｎ_Ａ 、中間回転リング４２の単位時間当たりの回転数をｎ_Ｂ （ｎ_Ｂ ＜ｎ_Ａ ）とすると、ベアリング４１が受ける回転数、つまり固定部４０に対する中間回転リング４２の相対的な回転数（差動回転数）ｎ_ＢＢ、ベアリング４３が受ける回転数、つまり中間回転リング４２に対する回転リング４４の相対的な回転数（差動回転数）ｎ_ＢＡは、それぞれ次の（８）式、（９）式で表される。
【００２７】
ｎ_ＢＢ＝ｎ_Ｂ …（８）
ｎ_ＢＡ＝ｎ_Ａ −ｎ_Ｂ …（９）
ここで、ｎ_ＢＢとｎ_ＢＡとを共に最小にするには、プーリ４９，５０、中間回転リング４２に設けられたプーリ、回転リング４４に設けられたプーリの各径を調整して、中間回転リング４２の回転数ｎ_Ｂ を、回転リング４４の回転数ｎ_Ａ の１／２にすればよい。したがって、ベアリング４１、４３を従来の中間回転リングの無いもののベアリングと同じＤＮ値のものを採用しても、回転リング４４の最高回転数を略２倍に高めることができる。したがって、スキャン時間が短縮されて被検体の１回の息止め時間中に広い範囲の投影データを収集することができるようになると共に、被検体の拘束時間の短縮、患者スループットの向上、態動アーチファクトの抑制の課題が根本的に解決される。
【００２８】
本発明は上述した実施例に限定されず、種々変形して実施可能である。上述の説明では、中間回転リングは１つとして説明したが、複数（ｎ個）の中間回転リングが多断層に組み合わされていてもよい。この場合、固定部と最端の中間回転リングとの間のベアリング、各中間回転リング間のベアリング、中間回転リングと回転リングとの間のベアリングの各々が受ける回転数は、回転リングの回転数の１／ｎでよく、これに伴って回転リングの最高回転数を従来の中間回転リングの無いものに比べて略ｎ倍に高めることができる。
【００２９】
【発明の効果】
本発明によれば、回転リングと固定部との間には中間回転リングが介挿され、固定部に対する回転リングの回転が固定部に対する中間回転リングの回転と中間回転リングに対する回転リングの回転とに分担され、固定部に対する中間回転リングの回転と中間回転リングに対する回転リングの回転との各回転数が固定部に対する回転リングの回転数より理想的には１／２になり、高速回転に対する構造上の耐久性の制限が実質的に拡大されて、回転リングの高速回転が可能になるＸ線コンピュータ断層撮影装置を提供できる。
【図面の簡単な説明】
【図１】ガントリ内部の概略構造図。
【図２】第１実施例による差動回転駆動機構の構造図。
【図３】図２のＡ−Ａ´断面図。
【図４】第２実施例による差動回転駆動機構の構造図。
【図５】図４のＢ−Ｂ´断面図。
【図６】第３実施例による差動回転駆動機構の構造図。
【図７】図６のＣ−Ｃ´断面図。
【符号の説明】
１…Ｘ線管、２…多チャンネル型Ｘ線検出器、
３…差動回転駆動機構、４…固定部、
５…中間回転リング、６…遊星歯車、
７…ベアリング、８…駆動プーリ、
９…無端ベツト、１０…原動機、
１１…回転リング、１２…ベアリング。[0001]
[Industrial application fields]
The present invention provides an X-ray computed tomography in which at least one of an X-ray tube and an X-ray detector collects projection data at all angles while rotating around the subject at high speed, and reconstructs a tomographic image from these projection data. The present invention relates to a photographing apparatus.
[0002]
[Prior art]
Conventionally, in this type of X-ray computed tomography apparatus, in the case of the third-generation R / R system, a fixed part is provided with a rotating ring that is rotatably held via a bearing. The tube and the X-ray detector are arranged to face each other. At the time of imaging, the subject is inserted into the central opening of the rotating ring, and the rotating ring is rotated at high speed by receiving the rotational force of the low tension motor. During this rotation, the X-ray exposure and transmission X-ray detection operations are repeated continuously or at every minute angle, and projection data relating to a slice plane of the subject is collected at all angles. These projection data are sent to a computer system, where they are subjected to reconstruction processing, and a tomographic image is reconstructed.
[0003]
By the way, in order to fundamentally solve the problems such as shortening the restraint time of the subject, improving the patient throughput, and suppressing the movement artifact, it is effective to shorten the imaging time. Rotation is desired. This high speed rotation has various obstacles to be solved such as a method of transmitting tube power, one of which relates to the durability characteristics of the bearing. The durability value of the bearing is based on the DN value derived from the multiplication result of the bearing diameter and the rotation speed. When the DN value exceeds the allowable value, the life of the bearing is extremely reduced. Therefore, the rotation number per unit time of the rotating ring is suppressed within a range where the DN value is less than or equal to an allowable value.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an X-ray computed tomography apparatus that allows high-speed rotation of a rotating ring.
[0005]
[Means for Solving the Problems]
According to a first aspect of the present invention , at least one of an X-ray tube and an X-ray detector collects projection data from all angles while rotating around the subject, and reconstructs a tomographic image from these projection data. In the X-ray computed tomography apparatus, a fixed portion, an intermediate rotation ring rotatably held by the fixed portion, and the intermediate rotation ring rotatably held coaxially with the intermediate rotation ring, the X-ray tube, a rotary ring for holding at least one of said X-ray detector, a rotation driving means for the rotating ring to said intermediate rotary order to rotary drive by the faster rotational angular velocity ring, for rotating the intermediate rotating ring, The intermediate rotating ring is rotatably supported and is fitted between the fixed portion and the rotating ring, and the rotating ring is driven to rotate by rotation and revolution associated with the rotation of the intermediate rotating ring. And a rotation driving means comprising a planetary rotating body .
According to a second aspect of the present invention, projection data is collected at all angles while at least one of an X-ray tube and an X-ray detector rotates around the subject, and a tomographic image is reconstructed from these projection data. In the X-ray computed tomography apparatus, a fixed portion, an intermediate rotation ring rotatably held by the fixed portion, and the intermediate rotation ring rotatably held coaxially with the intermediate rotation ring, the X-ray tube, A rotating ring that holds at least one of the X-ray detectors, and a first rotation driving means that rotationally drives the intermediate rotating ring to rotationally drive the rotating ring at a rotational angular velocity faster than the intermediate rotating ring; Rotation drive means comprising second rotation drive means for rotating the rotation ring at a rotational angular velocity faster than that of the intermediate rotation ring.
[0006]
[Action]
According to the present invention, the intermediate rotation ring is interposed between the rotation ring and the fixed portion, and the rotation of the rotation ring with respect to the fixed portion is the rotation of the intermediate rotation ring with respect to the fixed portion and the rotation of the rotation ring with respect to the intermediate rotation ring. The number of rotations of the rotation of the intermediate rotation ring with respect to the fixed part and the rotation of the rotation ring with respect to the intermediate rotation ring is ideally ½ of the rotation number of the rotation ring with respect to the fixed part. The upper durability limit is substantially expanded to allow high speed rotation of the rotating ring.
[0007]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
The X-ray computed tomography apparatus calculates an X-ray absorption coefficient at each point by applying a reconstruction processing method such as a successive approximation method or a Fourier calculation method to X-ray projection data (projection integral value) from multiple directions, This device gives a tomogram according to the X-ray absorption coefficient, and obtains a tomographic image. A fan beam X-ray that expands in a fan shape from an X-ray tube through a diaphragm device is emitted toward a subject, and is slightly applied to a living tissue. After being absorbed and attenuated, X-ray intensities with different paths are individually detected by the X-ray detection elements of the multi-channel X-ray detector, and these detection signals are amplified to a predetermined level by the data acquisition unit and digital signals Then, the computer system calculates a CT value corresponding to the X-ray absorption coefficient of each point in the imaging region by applying a reconstruction processing method such as a successive approximation method or a Fourier calculation method. Distributed faults It is intended to generate a.
[0008]
Such an X-ray computed tomography apparatus includes a type in which a multi-channel X-ray detector is fixed and projection data is collected at all angles while only the X-ray tube rotates around the subject. And X-ray computed tomography apparatus according to the present invention include various types such as a type that collects projection data from all angles while rotating around the subject together with a multi-channel X-ray detector. Any type may be used as long as at least one of the tube and the multi-channel X-ray detector rotates around the subject. Here, an example will be described in which the X-ray tube and the multi-channel X-ray detector both collect projection data from all angles while rotating around the subject.
[0009]
FIG. 1 shows a schematic structure inside a gantry which is a main structure of an X-ray computed tomography apparatus according to the present invention. The X-ray tube 1 and the multi-channel X-ray detector 2 can be rotated by a differential rotation driving mechanism 3 as a differential rotation driving means while facing each other with an opening at the center of the gantry. Supported. A subject is inserted into the opening during imaging.
[0010]
FIG. 2 is a structural diagram of the differential rotation drive mechanism 3 according to the first embodiment, and FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. 4 is a fixed part.
Although not shown, the fixed portion 4 is provided with an internal gear in a ring shape. An intermediate rotating ring 5 is supported on the fixed portion 4 via a bearing 7 so as to be rotatable about the rotation center 0. An endless belt 9 is disposed between a pulley provided in a part of the intermediate rotating ring 5 and a driving pulley 8 mounted on a rotation driving shaft of a prime mover 10 as a rotation driving means provided in the fixed portion 4. It is being handed over. The rotational motion of the prime mover 10 is transmitted to the intermediate rotating ring 5 through the driving pulley 8 and the endless belt 9, and the intermediate rotating ring 5 is rotationally driven. A plurality of planetary gears 6 as planetary rotating bodies are discretely supported on the intermediate rotating ring 5, and here, four planetary gears 6 are rotatably supported (rotated) at positions shifted by 90 °.
[0011]
The rotating ring 11 that holds the X-ray tube 1 and the multi-channel X-ray detector 2 facing each other across the opening is coaxial with the intermediate rotating ring 5 via the bearing 12, that is, with respect to the same rotation center 0. The intermediate rotation ring 5 is rotatably supported. Although not shown, a gear (hereinafter referred to as “external gear”) is formed on the outer periphery of the rotating ring 11. The external gear and the internal gear of the fixed portion 4 are arranged to face each other, and a planetary gear 6 is engaged with both gears. When the intermediate rotation ring 5 rotates, the planetary gear 6 revolves around the rotation center 0 while rotating. The rotating ring 11 rotates in conjunction with the rotation and revolution of the planetary gear 6.
[0012]
Here, inner diameter D _S of the internal gear of the fixed portion _4, the diameter of the planetary gear 6 d, the diameter of the external gear of the rotating ring 11 as D _A, per a unit time intermediate rotary ring 5 (e.g., per second) rotational speed Assume a case where _nb is rotationally driven. At this time, the rotation speed n _p per unit time of rotation of the planetary gear 6 is expressed by the following equation (1).
[0013]
n _p = (D _S / d) × n _b (1)
The rotation speed n _A of the rotating ring 11 is expressed by the following equation (2).

The rotational speed received by the bearing 7, that is, the relative rotational speed (differential rotational speed) n _BA of the intermediate rotating ring 5 with respect to the fixed portion 4, and the rotational speed received by the bearing 12, that is, the relative rotation of the rotating ring 11 with respect to the intermediate rotating ring 5. Rotational speed (differential rotational speed) n _BB is expressed by the following formulas (3) and (4), respectively.
[0014]

Since D _S > D _A always holds, n _BB > n _b holds, and the rotating ring 11 rotates at a rotational angular velocity faster than that of the intermediate rotating ring 5.
[0015]
Therefore, the rotation ratio between n _BB and n _A is expressed by the following equation (5).

Since D _S > D _A is always satisfied, D _S / D _A > 1 holds. As a result, the following equation (6) is established.
[0016]
1/2 <n _BB / n _A <1 (6)
Therefore, in an ideal state in which the number of rotations received by each of the bearing 7 and the bearing 12 is minimized, the number of rotations n _BA received by the bearing 7 and the number of rotations n _BB received by the bearing 12 are set to the rotation ring 11 for the fixed portion 4. can be half of the relative rotational speed n _a, DN value indicating the durability of the bearing without exceeding the allowable value, it becomes possible to high-speed rotation of the rotary ring 11. That is, even if the bearings 7 and 12 have the same DN value as that of the bearing without the conventional intermediate rotating ring, the maximum rotational speed of the rotating ring 11 can be increased approximately twice. Therefore, the scan time is shortened, and a wide range of projection data can be collected during one breath holding time of the subject, while the restraint time of the subject is shortened, the patient throughput is improved, and the behavior is increased. The problem of artifact suppression is fundamentally solved.
[0017]
Next, a second embodiment will be described.
FIG. 4 is a structural diagram of the differential rotation driving mechanism 3 according to the second embodiment, and FIG. 5 is a sectional view taken along the line BB ′ of FIG. Reference numeral 20 denotes a fixed portion. An intermediate rotating ring 21 is supported on the fixed portion 20 via a bearing 23 so as to be rotatable about the rotation center 0. An endless belt 28 is hung between a pulley provided in a part of the intermediate rotating ring 21 and a driving pulley 27 mounted on a rotating shaft of a prime mover 26 as a rotational driving means provided in the fixed portion 20. Has been passed. The rotational motion of the prime mover 26 is transmitted to the intermediate rotating ring 21 by the endless belt 28, and the intermediate rotating ring 21 is rotationally driven.
[0018]
The rotating ring 24 that holds the X-ray tube 1 and the multi-channel X-ray detector 2 facing each other across the opening is coaxial with the intermediate rotating ring 21 via the bearing 25, that is, with respect to the same rotation center 0. The intermediate rotation ring 21 is rotatably supported. Between a pulley provided in a part of the rotary ring 24 and a drive pulley 30 mounted on a rotary drive shaft of a prime mover 29 as a rotary drive means provided in the intermediate rotary ring 21 so as to revolve about the rotation center 0. An endless belt 31 is stretched over the belt. The rotational motion of the prime mover 29 is transmitted to the rotating ring 24 by the endless belt 31, and the rotating ring 24 is rotationally driven.
[0019]
Although not shown, independent driving circuits are connected to the prime mover 26 and the prime mover 29, and a common control circuit (not shown) is connected to both the drive circuits. When the control circuit individually controls each drive circuit, the rotational speeds of the prime mover 26 and the prime mover 29 are controlled to be the same or different.
[0020]
In such a configuration, the rotational speed per unit time of the prime mover 26 is n _A , the rotational speed per unit time of the prime mover 29 is _B, and the rotational speed per unit time of the intermediate rotational ring 21 by the prime mover 26 is fixed per unit time. The number of rotations is n _BB, and the number of rotations per unit time relative to the intermediate rotation ring 21 of the rotation ring 24 by the prime mover 29 (the rotation in the rotation coordinate system rotating at the number of rotations n _BB of the intermediate rotation ring 21 per unit time). suppose the number) and _{n BA.} Since the prime mover 29 is provided on the intermediate rotation ring 21 and rotates (revolves) around the rotation center O together with the intermediate rotation ring 21, the rotation ring 24 rotates at a rotational angular velocity faster than the intermediate rotation ring 21, specifically, The number of rotations n per unit time for the fixed portion 20 of the rotating ring 24 is expressed by the following equation (7).
[0021]
n = n _BA + n _BB (7)
Therefore, in an ideal state where n _BA = n _BB = 1/2 × n, the number of rotations received by the bearings 23 and 25 is reduced to half that when the intermediate rotation ring 21 is not provided, and the durability characteristics of the bearing are exhibited. The rotating ring 24 can be rotated at high speed without the DN value exceeding the allowable value. That is, even if the bearings 23 and 25 have the same DN value as that of the bearing without the conventional intermediate rotating ring, the maximum rotational speed of the rotating ring 24 can be increased approximately twice. Therefore, the scan time is shortened, and a wide range of projection data can be collected during one breath holding time of the subject, while the restraint time of the subject is shortened, the patient throughput is improved, and the behavior is improved. The problem of artifact suppression is fundamentally solved.
[0022]
Further, the rotational speed of the prime mover 26 and prime mover 29 can be reduced to half of the case where the intermediate rotation ring 21 is not provided, and the burden on the prime mover 26 and the prime mover 29 is reduced.
Next, a third embodiment will be described.
[0023]
FIG. 6 is a structural diagram of the differential rotation driving mechanism 3 according to the third embodiment, and FIG. 7 is a cross-sectional view taken along the line CC ′ of FIG. Reference numeral 40 denotes a fixed portion. An intermediate rotation ring 42 is supported on the fixed portion 40 via a bearing 41 so as to be rotatable about the rotation center 0. The rotating ring 44 that holds the X-ray tube 1 and the multi-channel X-ray detector 2 facing each other across the opening is coaxial with the intermediate rotating ring 42 via the bearing 43, that is, the same center of rotation. The intermediate rotating ring 42 is supported so as to be rotatable with respect to zero. Each of the intermediate rotation ring 42 and the rotation ring 44 is provided with a pulley having the same diameter for hooking an endless belt described later.
[0024]
A gear 52 provided on a rotation shaft of a prime mover 51 serving as a rotational drive means installed in the fixed portion 40 is provided with a gear 53 provided on a shaft 48 that is rotatably supported by a bearing 54 provided on the fixed portion 40. Are engaged. The rotational motion of the prime mover 51 is transmitted to the shaft 48 through gears 52 and 53.
[0025]
The shaft 48 is provided with two large and small pulleys 49 and 50 having different diameters. An endless belt 47 is stretched between the pulley 49 having a small diameter and the intermediate rotation ring 42. The rotational movement of the shaft 48 is transmitted to the intermediate rotation ring 42 via the endless belt 47. An endless belt 46 is stretched between the pulley 50 having a large diameter and the rotating ring 44. The rotational movement of the shaft 48 is transmitted to the rotating ring 44 via the endless belt 46. Therefore, the rotating ring 24 rotates at a rotation angular velocity faster than that of the intermediate rotating ring 21. Of course, if the rotating ring 44 rotates at a rotational angular velocity faster than that of the intermediate rotating ring 42, the pulleys 49 and 50 have the same diameter, and the pulley provided on the rotating ring 44 has the same diameter as the pulley provided on the intermediate rotating ring 42. The diameter may be reduced. In addition, as long as the rotating ring 44 rotates at a rotational angular velocity faster than that of the intermediate rotating ring 42, the diameters of the pulleys 49 and 50, the pulley provided in the intermediate rotating ring 42, and the pulley provided in the rotating ring 44 are arbitrarily set. Can be adjusted.
[0026]
Assuming that the rotational speed per unit time of the rotating ring 44 is n _A and the rotational speed per unit time of the intermediate rotating ring 42 is n _B (n _B <n _A ), the rotational speed received by the bearing 41, that is, relative to the fixed portion 40 The relative rotation speed (differential rotation speed) n _{BB of} the intermediate rotation ring 42, the rotation speed received by the bearing 43, that is, the relative rotation speed (differential rotation speed) n _BA of the rotation ring 44 with respect to the intermediate rotation ring 42 is Are expressed by the following equations (8) and (9), respectively.
[0027]
n _BB = n _B (8)
n _BA = n _A −n _B (9)
Here, in order to minimize both n _BB and n _BA , the pulleys 49 and 50, the pulleys provided in the intermediate rotating ring 42, and the diameters of the pulleys provided in the rotating ring 44 are adjusted to perform intermediate rotation. The rotation speed n _B of the ring 42 may be set to ½ of the rotation speed n _A of the rotation ring 44. Therefore, even if the bearings 41 and 43 have the same DN value as that of the bearing without the conventional intermediate rotating ring, the maximum rotational speed of the rotating ring 44 can be increased approximately twice. Therefore, the scan time is shortened, and a wide range of projection data can be collected during one breath holding time of the subject, while the restraint time of the subject is shortened, the patient throughput is improved, and the behavior is improved. The problem of artifact suppression is fundamentally solved.
[0028]
The present invention is not limited to the above-described embodiments, and various modifications can be made. In the above description, the number of intermediate rotation rings is one. However, a plurality (n) of intermediate rotation rings may be combined into multiple faults. In this case, the number of rotations received by each of the bearings between the fixed portion and the outermost intermediate rotation ring, the bearings between the intermediate rotation rings, and the bearings between the intermediate rotation ring and the rotation ring is the rotation number of the rotation ring. Accordingly, the maximum number of rotations of the rotating ring can be increased to approximately n times that of a conventional rotating ring without an intermediate rotating ring.
[0029]
【The invention's effect】
According to the present invention, the intermediate rotation ring is inserted between the rotation ring and the fixed portion, and the rotation of the rotation ring with respect to the fixed portion is the rotation of the intermediate rotation ring with respect to the fixed portion and the rotation of the rotation ring with respect to the intermediate rotation ring. The number of rotations of the rotation of the intermediate rotation ring with respect to the fixed part and the rotation of the rotation ring with respect to the intermediate rotation ring is ideally ½ of the rotation number of the rotation ring with respect to the fixed part. The upper endurance limit can be substantially expanded to provide an X-ray computed tomography apparatus that enables high speed rotation of the rotating ring.
[Brief description of the drawings]
FIG. 1 is a schematic structural diagram inside a gantry.
FIG. 2 is a structural diagram of a differential rotation driving mechanism according to a first embodiment.
3 is a cross-sectional view taken along line AA ′ of FIG.
FIG. 4 is a structural diagram of a differential rotation driving mechanism according to a second embodiment.
FIG. 5 is a cross-sectional view taken along the line BB ′ of FIG.
FIG. 6 is a structural diagram of a differential rotation drive mechanism according to a third embodiment.
7 is a cross-sectional view taken along the line CC ′ of FIG.
[Explanation of symbols]
1 ... X-ray tube, 2 ... Multi-channel X-ray detector,
3 ... Differential rotation drive mechanism, 4 ... Fixed part,
5 ... Intermediate rotating ring, 6 ... Planetary gear,
7 ... Bearing, 8 ... Drive pulley,
9 ... endless bet, 10 ... prime mover,
11 ... rotating ring, 12 ... bearing.

Claims (3)

In an X-ray computed tomography apparatus in which at least one of an X-ray tube and an X-ray detector collects projection data at all angles while rotating around the subject, and reconstructs a tomogram from these projection data,
A fixed part;
An intermediate rotating ring rotatably held by the fixed part;
A rotating ring that is coaxially rotatable with the intermediate rotating ring and is held by the intermediate rotating ring and holds at least one of the X-ray tube and the X-ray detector;
It said rotating ring in order to the intermediate rotary ring rotating driven at a faster rotational angular velocity, and rotation driving means for rotationally driving the intermediate rotating ring, and said is capable of rotating held at an intermediate rotating ring and the fixed portion the An X-ray computer, comprising: a planetary rotator which is inserted between the rotation ring and which rotates and revolves with the rotation of the intermediate rotation ring to drive the rotation ring. Tomography equipment. In an X-ray computed tomography apparatus in which at least one of an X-ray tube and an X-ray detector collects projection data at all angles while rotating around the subject, and reconstructs a tomogram from these projection data,
A fixed part;
An intermediate rotating ring rotatably held by the fixed part;
A rotating ring that is coaxially rotatable with the intermediate rotating ring and is held by the intermediate rotating ring, and holds at least one of the X-ray tube and the X-ray detector;
In order to rotationally drive the rotating ring at a rotational angular speed faster than that of the intermediate rotating ring, first rotational driving means for rotationally driving the intermediate rotating ring, and rotational driving of the rotating ring at a rotational angular speed faster than that of the intermediate rotating ring. An X-ray computed tomography apparatus comprising: a rotation driving unit including a second rotation driving unit. The rotation drive means is equipped with a rotation drive means, a rotation shaft of the rotation drive means, a first pulley for transmitting the rotation motion of the rotation drive means to the intermediate rotation ring, and the rotation drive means. 3. A second pulley mounted on a rotary shaft and having a diameter larger than that of the first pulley and transmitting a rotary motion of the rotary drive means to the rotary ring. X-ray computed tomography equipment.

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