Development of a calibration methodology for large-volume, solid 68Ge phantoms for traceable measurements in positron emission tomography

• Large (9 L) solid Ge-68 epoxy phantom was designed and calibrated.
• Activity concentration was calibrated with standard uncertainty of about 1.1%.
• Inhomogeneity of Ge-68 activity distribution was estimated at about 0.3%.
• Data from PET–CT scans of phantoms were consistent with data from calibration.

We have developed a methodology to calibrate the 68Ge activity concentration in large (9 L) cylindrical epoxy phantoms in a way that is traceable to national standards. The method was tested on two prototype cylindrical phantoms that are being used in a clinical trial and gave 68Ge activity concentration values with combined standard uncertainties of about 1.1%. Imaging data from the phantoms using a calibrated PET–CT scanner gave values consistent with the calibrated activity concentrations within experimental uncertainties.