TY - JOUR T1 - Lessons learned from post-COVID-19 vaccination PET/CT studies JF - Journal of Nuclear Medicine JO - J Nucl Med DO - 10.2967/jnumed.121.262348 SP - jnumed.121.262348 AU - Marina Orevi AU - Alexandre Chicheportiche AU - Simona Ben-Haim Y1 - 2021/07/01 UR - http://jnm.snmjournals.org/content/early/2021/07/22/jnumed.121.262348.abstract N2 - Anti-COVID-19 vaccination has created new challenges. Lymphadenopathy (LA) with increased uptake in patients undergoing PET/CT may mislead to unnecessary further evaluation. We have analyzed routinely performed PET/CT studies following Pfizer-BioNTech vaccination to familiarize with PET/CT appearances with various PET tracers and to prevent consequences of misinterpretation. Methods: 1281 PET/CT studies performed between January 01 2021 and February 15 2021 were analyzed. Information about dates and site of vaccination was collected. Visual and semi-quantitative analysis of axillary - neck LA and arm uptake was correlated with immunization data. Results: Increased uptake in unilateral axillary LA was observed in 66% vaccinated patients, in 55% vaccinated once and in 69% vaccinated twice. Intensity of uptake decreased over time. 64/315 patients (20%) had simultaneous increased activity in the posterior arm and ipsilateral axillary LA (“double sign” [DS]). Sensitivity, specificity, PPV and NPV of axillary LA and DS were 55.4%, 83.6%, 86.7%, 49.2% and 38.6%, 100%, 100% and 66.1%, respectively. No DS was observed later than 10 and 21 days after first and the second vaccinations, respectively. None of the non-vaccinated patients had arm uptake or DS. Conclusion: Anti-COVID-19 vaccination frequently causes non-specific axillary LA with increased PET tracer activity. In one fifth of our study population this was associated with increased uptake at the vaccination site, DS. DS was 100% specific with 100% PPV for p/vaccination LA hence enabling to avoid misinterpretation of PET/CT studies and further unnecessary evaluation. ER -