Development of Activity Concentration Detector Used for Positron Emission Nuclide in Air

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Manufacturing and the use of the positron-emitting radionuclide keep expanding as the number of domestic PET facilities increases. On the other hand, it was difficult to measure accurately such a gassy short half-life nuclide as 15O whose half-life is 2.037 minutes. Then a detector using GSO scintillator for activity concentration in air was developed from the view point of the characteristic of the positron-emitting radionuclide. The detector has cubic structure, four planes of which consist of a cubic scintillator and the other planes are open. This detects two annihilation photons emitted in the opposite direction simultaneously by facing two scintillators with energy discrimination. The number of coincidence signals from each detector pair is counted in a moment. Consequently, only the positron-emitting radionuclide that exists in the space (125 mL in case of this detector) becomes detectable, and the radioactive concentration of the unit volume can be measured in real time. Postulating 15O2, it was confirmed that 5.2×10-2 Bq/cm3 was detectable in 60 seconds by using and evaluating 511 keV photon from 22Na.
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