X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
1999-09-03
2004-04-06
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S004000, C378S019000, C378S021000, C378S210000
Reexamination Certificate
active
06718003
ABSTRACT:
BACKGROUND OF THE INVENTION
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.
BRIEF SUMMARY OF THE INVENTION
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.
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Bruce David V.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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