Helical scanning computed tomography apparatus with constrained tracking of the x-ray source

摘要

A CT apparatus reduces errors in projection data acquired in helical scanning. The imaged object moves concurrently along a translation axis and the x-ray beam is periodically translated with the imaged object so as to subtend a single predetermined volume element during the acquisition of one projection set of data for a first slice. The x-ray beam then returns to its starting position and tracks a second predetermined volume element within a next slice. The x-ray beam may be translated by moving the focal point or a collimator or a combination of both. Helical scans with a pitch requiring sweeping of the x-ray beam beyond the detector limits are accommodated by limiting the sweep to a lessor compliance distance. The angular rate of the sweep is held constant within this compliance distance during the sweep.