Improved Quantification of 18F-FDG PET during 131I-Rituximab Therapy on Mouse Lymphoma Models after 131I Prompt Emission Correction

18F-FDG Positron Emission Tomography (PET) is used to monitor tumor response to 131I-therapy, but is confounded by prompt emissions (284, 364, 637, and 723 keV) from 131I, particularly in animal PET imaging. We propose a method for correcting this emission in 18F-FDG PET. The 131I prompt emission effect was assessed within various energy windows and various activities. We applied a single gamma correction method to a phantom and in vivo mouse model. The 131I prompt emission fraction was 12% when 300 µCi of 131I and 100 µCi of FDG were administered, and increased exponentially with escalating 131I activity for all energy windows. The difference in spill-over ratio was reduced to