Abstract: A method, system and kit for calibrating a PET scanner is disclosed. A first aliquot (10) containing a quantity of a radionuclide dispersed in a solid matrix material is provided, wherein the first aliquot is sized and configured to be received for measurement by a conventional dose calibrator. A second aliquot (200) containing a quantity of the radionuclide dispersed in the solid matrix material is sized configured to be scanned in a PET scanner. The radionuclide/matrix materials in the first and second aliquots are obtained from the same batch of material, such that the two quantities have the same radioactivity density, or are obtained from different cross-calibrated batches of material. In a method, the first aliquot is placed in a does calibrator (36) and the radioactivity is measured. The second aliquot is scanned in the PET scanner (190) and the intensity of the image is correlated with the known radioactivity measured by the dose calibrator and used to calibrate the PET scanner.