Two determinations of the Ge-68 half-life.

In nuclear medicine, 68 Ge is used to generate 68 Ga for imaging by positron emission tomography (PET) and sealed sources containing 68 Ge/68 Ga in equilibrium have been adopted as long-lived calibration surrogates for the more common PET nuclide, 18 F. We prepared several 68 Ge sources for measurement on a NaI(Tl) well counter and a pressurized ionization chamber, following their decay for 110 weeks (≈ 2.8 half-lives). We determined values for the 68 Ge half-life of T1/2 = 271.14(15) d and T1/2 = 271.07(12) d from the NaI(Tl) well counter and ionization chamber measurements, respectively. These are in accord with the current Decay Data Evaluation Project (DDEP) recommended value of T1/2 = 270.95(26) d and we discuss the expected impact of our measurements on this value.