Computer tomography apparatus for conducting a spiral scan of an examination subject

Claim 1

A computer tomography apparatus comprising: examination means, including a radiation source and a radiation detector, for conducting a spiral scan of an examination subject by rotating said radiation source and said radiation detector around a longitudinal axis through a plurality of projections, each projection generating output signals at said radiation detector corresponding to radiation incident on said detector attenuated by said examination subject, all of said output signals for a single slice of said examination subject comprising a data set; computer means for calculating a new image I lr+1 (x), using only a data set from a single slice, from an initial image I lr (x) in the plane of a referenced projection l r at a defined location along said longitudinal axis from an auxiliary image I d lr+1 (x) at a distance d/N 2 π from said initial image I lr (x) according to the equation: I.sub.lr+1 (x)=I.sub.lr (x)-I.sup.d.sub.lr+1 (x) and means for calculating said auxiliary image I d lr+1 (x) from its predecessor I lr (x), wherein d is the slice thickness and N 2 π is the number of projections on the circumferential angle; and means for displaying said image.