To provide a computer tomography system which enables four fold improvement in the stability of both of short-time and long-time beam positions.
A beam position detector 30 is arranged at the peripheral edge of a primary fan beam and is relatively fixed on a primary detector 24 so as to indicate the position of the beam on the primary detector 24. In the beam position detector 30, the maximum sensitivity to the movement of the beam is turned to exist in the direction of the movement of the beam as caused by the drifting of the focus attributed to a temperature effect and gravity. The short-time focus drift is detected by a secondary beam 21 emitted from the primary fan beam to be corrected in real time by adjusting a collimator for the primary beam. Long-time changes at the focus position are corrected by re-calibration of a data set of a focus-beam collimator using information from the beam position detector 30.
DEYCH RUVIN
BOWERS JAMES
