Proposed Changes to the ACR Phantom Filling Procedure for More Accurate and Consistent Activity Concentrations

Objectives: The phantom filling procedures currently specified by the American College of Radiology (ACR) for its PET accreditation program unnecessarily limit how tight the tolerances can be made on the accuracy requirements for the concentrations measured in the resultant images.

Methods: New procedures are proposed to improve the accuracy and consistency of the concentrations within the phantom at the time of imaging. These improvements are gained by exchanging the difficult process of accurately measuring a dose with the more easily achieved accurate measurements of time and liquid volume to control final radioactivity concentrations. A comparison of the results when following the two filling procedures is made.

Results: The variability in metrics specified by the ACR was approximately halved by following the new procedures.

Conclusion: These improvements allow tighter thresholds to be applied when evaluating image quality and quantitative accuracy of the PET images. These changes also render this phantom data more suitable for inter-PET-scanner harmonization and improve its utility for comparing image reconstruction methods.