Calibration of PET scanners with a new traceable point-like Ge 68 /Ga 68 source

We have been developing reliable and convenient calibration methods based on the use of point-like radioactive sources. In the present study, we used a newly developed traceable point-like Ge 68 /Ga 68 radioactive source for determining calibration factors of a PET scanner. The point-like Ge 68 /Ga 68 radioactive source consists of a spherical aluminum absorber with an outer diameter of 8 mm and a small radioactive bead in it. The physical characteristics of the source were evaluated with a Monte Carlo simulation code based on Geant4. The source radioactivity was calibrated at an accredited calibration facility. The point-like source was placed in the field-of-view of a clinical PET scanner, SET-2400W (Shimadzu Co.). The calibration factors determined with the point-like source were consistent with those determined by a conventional standard calibration method within a reasonable uncertainty. In conclusion, the proposed method with newly developed traceable point-like sources is useful for calibrating PET scanners.