Assessing the absolute quantitative accuracy of Positron Emission Tomography for Cu-64 using traceable calibrated phantoms

Using uniform cylindrical phantoms containing calibrated solutions of 18F and 64Cu, we evaluated for the first time the accuracy with which the activity concentration of 64Cu can be quantified on an absolute basis using Positron Emission Tomography (with X-ray Computed Tomography, PET-CT). The scanner was first calibrated for 18F using the manufacturer's calibration protocol and a phantom with an activity concentration value traceable to the U.S. National standard. By using a similarly calibrated 18F solution phantom, we were able to determine a correction factor that can be applied to the 64Cu imaging data that gave a result that is consistent with 100% recovery with a combined standard uncertainty of 2%. We also demonstrate how a calibrated, solid phantom containing 68Ge as a long-lived 18F surrogate can be used to monitor and transfer the correction factor to other studies.