Patent Number: 054935997
Section: abstract

A toroidal x-ray tube (I) is supported and selectively positioned by a gantry (II). The x-ray tube includes a toroidal housing (A) in which a rotor (20) is rotatably mounted. One or more cathodes (C) are mounted on the rotor for generating an electron beam which strikes an anode (B) to generate a beam of x-rays which pass through a patient aperture (62) to strike a detector (60). The x-ray tube includes pre-collimators (70, 74) having slots (72, 76) for passage of the x-ray subsequent to generation thereof and prior to being collimated by the collimator (90). A ring collimator (90) collimates an x-rays formed into a fan shaped beam. The collimator (90) includes a first ring (92) and a second ring (94) which are concentric. The distance between the first and second rings (92, 94) is adjustable to adjust the slice thickness of the final image. The x-ray tube provides improved final images in that reduction of off-focal radiation occurs due to the utilization of pre-collimators and the collimation of x-rays is flexible due to adjustability of slice thickness.