Images demonstrating the effect of respiratory misregistration between CT and PET scans. On the left is a PET scan to which CT data were applied for attenuation correction. On the right is the same PET scan without attenuation correction. The lesions are on the dome of the liver, but they appear to be in the lungs on the attenuation-corrected PET scan because the lung volume was greater during acquisition of the CT scan. Courtesy of Henry Ford Hospital, Detroit, Michigan.