A method of determining the location of an ingested capsule comprising the steps of providing an ingestible capsule (15) having a shell (16) and a flexible fluid retaining sleeve (17) affixed to the sleeve and defining a chamber (19) between the shell and the sleeve, the fluid retaining sleeve having a fill port (30), providing a radioactive material (22) contained in a filling device (31) having an output port (32) adapted to engage the fill port of the sleeve, engaging the output port of the filling device with the fill port of the sleeve, moving the radioactive material through the output port and into the chamber of the sleeve through the sleeve fill port, sealing the fill port to provide a radio-labeled ingestible capsule, having a subject ingest the radio-labeled capsule, and screening the subject by gamma imagining to determine location of the radio-labeled capsule within the subject.