X-RAY APERTURE FOR X-RAY CT DEVICE

PURPOSE:To limit a visual field of an X-ray fan beam going through a cut hole in an X-ray shield, by providing a cut hole in an X-ray shielding plate, by rotating the plate around the hole region and by adjusting an apparent slit width made by the cut hole. CONSTITUTION:An X-ray fan beam 19 is emitted from an X-ray source 15 and irradiates an irradiation surface 21 through a cut hole 13. In this case, a plate 9 is placed so that the cut hole 13 may have the maximum width against the X-ray source 15. Then, for example, the plate 9 is rotated around a rotation axis O along a direction of an arrow I or J, thereby the plate 9 is rotated to the position shown by a dotted line 14. In this situation, the beam 19 emitted from the source 15 goes through an apparent width K' of the cut hole 13. Through this way, the irradiation beam 19 is limited as shown by a dotted line 20.