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

F-FDG Positron Emission Tomography (PET) is used to monitor tumor response to I-therapy, but is confounded by prompt emissions (284, 364, 637, and 723 keV) from I, particularly in animal PET imaging. We propose a method for correcting this emission in F-FDG PET. The I 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 I prompt emission fraction was 12% when 300 µCi of I and 100 µCi of FDG were administered, and increased exponentially with escalating I activity for all energy windows. The difference in spill-over ratio was reduced to <5% after I prompt emission correction. In the mouse model, the standard uptake value (SUV) did not differ significantly between FDG PET only (gold standard) and FDG PET after I prompt emission-correction, whereas it was overestimated by 38% before correction. Contrast was improved by 18% after I prompt emission correction. We first found that count contamination on F-FDG follow-up scans due to I spilled-over count after I rituximab tumor targeted therapy. Our developed I prompt emission-correction method increased accuracy during measurement of standard uptake values on F-FDG PET.