1. A method for acquiring PET and CT images, comprising the steps of: placing a patient on a patient support; moving said patient support to position the patient within a CT scanner patient gantry such that a selected region of said patient to be imaged is within a field of view of a CT scanner associated with said CT scanner patient gantry; acquiring CT image data of the selected region of the patient; moving said patient support to position the patient within a PET scanner patient gantry such that said selected region to be imaged is within a field of view of a PET scanner associated with said PET scanner patient gantry; acquiring PET image data of the selected region of the patient; correcting said CT image data for artifacts due to field of view truncation, correcting said CT image data further comprising: obtaining non-corrected PET image data; determining a boundary of a truncated portion of the selected region of the patient using a non-corrected PET image reconstructed from said non-corrected PET image data; estimating a volume within said boundary of the truncated portion of the selected region using an average linear attenuation coefficient for the truncated portion of the selected region; and adding said volume to said CT image data; reconstructing a CT image from said corrected CT image data; and reconstructing a PET image from said acquired PET image data and using said corrected CT image data in the reconstruction of said PET image, to achieve a reconstructed PET image.