X-ray tubes for CT scanners.

摘要

A toroidal x-ray tube (I) is supported and selectively positioned by a CT gantry (II). The x-ray tube includes a toroidal housing (A) in which a rotor (30) 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 passes through a window (20) and strikes an annular ring of detectors (160). A grid bias control circuit (100) selectively applies a continuously adjustable bias to a grid (32) for regulating the electron current, and hence the intensity of the x-ray beam. A scintillating optical fibre (110) extends around the exterior of the window. The scintillation optical fibre includes fluorescent dopant (116) which converts a very small fraction of the x-rays into light which is transmitted along the fibre to an optoelectric transducer (118). The opto-electric transducer is connected with the grid bias control circuit. The opto-electrical transducer (118) can also be connected with an intensity compensator (162) for adjusting the signals from the detector ring before they are reconstructed (164) into an image representation.