A system and method for cross-calibrating a radionuclide at two separate locations (A and B) includes the use of a portable ion chamber configured to fit within a dose calibrator, which ion chamber receives a syringe containing a known volume of a sample of a radionuclide. The portable ion chamber and dose calibrator with the syringe is transported to another location, where a second syringe, identical to the first containing a second sample of the same volume of the same radionuclide is measured in a second dose calibrator.