A third generation CT scanner includes a rotating x ray source (18) and a detector array (16). Each sampling of the detector array generates a source fan data line of data values that are converted (34) to attenuation values in a logarithmic domain and subject to preliminary corrections (36). Attenuation values from a plurality of adjoining source fans are converted (94) back to a non logarithmic domain as intensity values. A corresponding deconvolution function (88) from a deconvolution function look-up table (90) corresponding to the detector whose intensity value is being corrected is deconvolved with a line (84) of the intensity values which spans a plurality of adjoining source fan data lines to remove the intensity attributable to off-focal radiation (30). The intensity data is converted (102) back into attenuation values in the logarithmic domain and reconstructed (106) into an image representation for display on a monitor (112).
