Examination of iatrogenic FDG accumulation after COVID-19 vaccination

Abstract

Purpose This study aimed to investigate the frequency of COVID-19 vaccine-induced reactive change and potential factors correlated with increased FDG uptake on positron emission tomography (PET)/computed tomography (CT). Materials and methods We evaluated 285 patients who underwent PET/CT between June and September 2021 and had a known history of COVID-19 vaccination. Information on the injection site, vaccine type, and adverse reactions was obtained. We visually assessed the presence or absence of accumulation in the axillary and supraclavicular lymph nodes and the deltoid muscles. We measured the maximum standardized uptake value (SUVmax) using semi-quantitative analysis. Results Our study included 158 males and 127 females aged 16 to 94 years. The median time between vaccination and PET/CT was nine and 42 days for patients who had received their first and second doses, respectively. We observed axillary lymph node accumulation, supraclavicular lymph node accumulation, and deltoid muscle accumulation in 99 (SUVmax 1.07–25.1), nine (SUVmax 2.28–14.5), and 33 cases (SUVmax 0.93–7.42), respectively. In cases with axillary lymph node (P = 0.0066) or deltoid muscle (P = 0.047) accumulation, the shorter the time since vaccination, the higher the FDG accumulation. Patients with axillary lymph node accumulation were significantly younger (P < 0.0001) and had a significantly higher frequency of adverse reactions such as fever (P < 0.0001) and myalgia (P = 0.001). Logistic regression analysis also showed that age, sex, days since vaccination, and adverse reactions such as fever and myalgia were important factors for axillary lymph node accumulation. Conclusion Our study found that FDG accumulation in the axillary lymph nodes and deltoid muscle was higher within a shorter time after vaccination, and axillary lymph node accumulation was higher in young patients, females, and those with adverse reactions of fever and myalgia. Confirming the vaccination status, time since vaccination, and the presence of adverse reactions before PET may reduce false positives.