Investigation of factors affecting a potential worldwide network of medical PET scanners to monitor the decay rate of Lu-176 and detect global radiation events

Medical PET scanners now exist in relatively large numbers around the world suggesting that certain physics experiments might be carried out during off-hours with these machines if organized into a global array of interlinked devices. Workers at Purdue, for example, have claimed to detect a possibly neutrino-induced annual periodicity in the decay rate of Cl-36 as the Earth traverses its elliptical orbit around the Sun but these claims remain controversial. A subset array of Lu-based PET scanners might help resolve this matter by measuring for an extended period (years) the decay rate of Lu-176 (38 billion year half life), a radioactive contaminant (2.6% abundance) present in the scintillation crystals of these machines. Night-side PET scanners in time synchrony might also detect and directionally locate other previously unrecognized global radiation events of astronomical origin. The present work identifies several sources of error that could affect such measurements.