A method for generating transmission information in a time-of-flight positron emission tomography (PET) scanner having a patient tunnel and a plurality of PET detector rings. The PET scanner uses continuous bed motion to move a patient bed and patient through the patient tunnel. The patient receives a positron-emitting radioisotope dose prior to undergoing a PET scan. The method includes storing a positron-emitting radioisotope in a radiation shielded container. The method also includes moving the radioisotope into a stationary vessel located adjacent to the PET detectors and within a field of view of the PET scanner at substantially the same time that the patient receives the radioisotope dose to form a stationary transmission source wherein transmission information is generated while the bed undergoes continuous bed motion. Further, the method includes withdrawing the radioisotope from the vessel when the PET scan is complete and storing the radioisotope in the container.