Abstract: The disclosed CT scanner includes a tomography system for generating data during a scan. The tomography system includes a detector characterized by at least one afterglow amplitude and at least one afterglow time constant, and a sampling device for generating a plurality of samples x.sub.i for all i from zero to MAX minus one of the detector output signal. The scanner also includes a set of N sub-processors for processing the samples x.sub.i, each of the sub-processors being represented by a unique integer q selected from zero to N minus one and receiving only the samples X.sub.iN+q. Each sub-processor includes a device for generating a compensated signal according to a function of at least a portion of the received samples and parameters representative of the afterglow amplitude and the afterglow time constant.

Abstract: An apparatus for compensating for drift of the focal spot of an X-ray radiation source used in a tomography system is disclosed so as to maintain a primary collimated beam of radiation emanating from the focal spot aligned with target detectors of the tomography system. A second collimated beam of radiation is produced from the same focal spot and directed along a different axis from the first beam. An array of detectors track the movement of the second collimated beam and produce signals which are used to reposition the collimator used to collimate the primary beam so as to maintain the primary beam substantially aligned with the target detectors.