A method for calibration and a calibrator source standard calibrated by the method are provided. The calibration method includes providing mock syringes, or other simulated dose container. A first of the mock syringes is filled with a short half life positron emitter. A second of the mock syringes is filled with a longer half life radionuclide set in a matrix material such as an epoxy. The activities of the two syringes can be determined, ideally in the same ion chamber, for example, against a radioactive source standard having a half life greater than the first and second radionuclides. This allows a conversion factor to be determined which can be used for a calibrator source standard formed as for the second mock syringe (i.e., with the same type of container containing the longer half life radionuclide set in a matrix material), when the calibrator source standard is used as a proxy for calibrating a calibrator for use in determining the activity of a dose container of the same configuration containing a dose of the short lived radionuclide.