a third generation ct scanner includes a rotating x - ray source and a detector array . each sampling of the detector array generates a source fan data line of data values that are converted to attenuation values in a logarithmic domain and subject to preliminary corrections . attenuation values from a plurality of adjoining source fans are converted back to a non - logarithmic domain as intensity values . a corresponding deconvolution function from a deconvolution function look - up table corresponding to the detector whose intensity value is being corrected is deconvolved with a line of the intensity values which spans a plurality of adjoining source fan data lines to remove the intensity attributable to off - focal radiation . the intensity data is converted back into attenuation values in the logarithmic domain and reconstructed into an image representation for display on a monitor .