The present invention relates to a gantry for acquiring projection data, which is an important component of an X-ray computer tomography apparatus.
FIG. 1 shows external appearance of a conventional gantry. The gantry 100 has a box-like shape having a cylindrical hole (hereinafter referred to as a view field) 121 in the central portion thereof. A subject is inserted in the view field 121, when photographed. The cover 111 of the gantry 100 has an air intake 115 and an air outlet 116 to cool the interior of the gantry.
FIGS. 2 and 3 are front and side views of the interior of the gantry, respectively. The gantry has a rotation ring 101, on which an X-ray tube and an X-ray detector are mounted in an arrangement such that they are opposite to each other with the subject lying therebetween. The rotation ring 101 is rotatably supported by a ring frame 103. A motor 104 for rotating the rotation ring 101 is mounted on the ring frame 103. The ring frame 103 is supported by two main posts 106 via tilt mechanisms 110. The main post 106 is mounted on a stand base 107 at right angles, as shown in FIG. 4. The gantry 100 contains electric members 105, for example, a control board and a power source.
As well known, the standard scan time at present is a second for a rotation. In the near future, a direct drive system, which directly drives the rotation ring (rotor) 101 by a stator coil, will be the mainstream of the driver of a gantry.
Such high-speed rotations of the unbalanced rotation ring 101 cause the main posts 106 to vibrate violently. To suppress the vibration, the main posts 106 must be thick. For this reason, the gantry is inevitably large and heavy. Further, if the top end of the main post 106 is displaced 0.5 mm, a tumor or a bone smaller than 0.5 mm cannot be observed, and a ring-like artifact may be produced.
An object of the present invention is to provide a gantry of a compact X-ray computer tomography apparatus having a high damping property.
A gantry of an X-ray computer tomography apparatus comprises a base, two main posts mounted on the base at right angles, a ring frame tiltably supported by the two main posts, a rotation ring rotatably supported by the ring frame, an X-ray tube mounted on the rotation ring, and an X-ray detector mounted on the rotation ring, opposing to the X-ray tube. The props obliquely abut on the main posts to reinforce them. Since the main posts are reinforced by the props, the vibration due to high-speed rotations of the rotation ring can be effectively suppressed. Moreover, since the main posts need not be thick, the gantry can be compact.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.