Reference Sources for Small Instruments
| Radionuclide | Half-life | Principal x- or γ-ray energy | Surrogate for… | Common uses |
| 137Cs | 30 y | 662 keV | Dose calibrator constancy, accuracy | |
| Scintillation detector calibration, energy resolution | ||||
| 68Ge | 287 d | 511 keV (from 68Ga daughter) | Positron-emitting radionuclides | Well counter constancy, accuracy |
| Dose calibrator constancy | ||||
| 133Ba | 10.7 y | 356 keV | 131I | Dose calibrator constancy |
| Scintillation detector efficiency | ||||
| 57Co | 272 d | 122 keV | 99mTc | Dose calibrator constancy |
| Scintillation detector energy resolution | ||||
| Semiconductor probe constancy |
Adapted from Zanzonico (8).