Fig. 6

CT based attenuation correction of PET images. Low dose attenuation correction CT exams are not generally used for routine diagnostic interpretation. The AC CT accounts for differences in location/depth from which the 511 keV PET photons are emitted, and can be used to correct for differences in surrounding tissue density (HU density) and the degree to which those tissues absorb or attenuate the PET photons [5]. a shows the fused, uncorrected PET data, with increased signal at the periphery of the image and poor signal from middle of the torso and adjacent to the vertebral column. The attenuation corrected image of the same PET data (b) provides a more accurate representation of the ¹⁸F-FDG uptake