Two .gamma.-rays accompanying position annihilation are incident into .gamma.-ray detectors in detector arrays set with a measured object inbetween. Electric pulse signals output from the .gamma.-ray detectors are supplied to an annihilation presuming unit, which obtains a presumable event of positron...http://www.google.fr/patents/US5532489?utm_source=gb-gplus-shareBrevet US5532489 - Positron imaging apparatus
