[ 18 F]F-AraG PET Imaging of Immunometabolic Activity in Individuals Without Malignancy

[18F]F-AraG is a clinical-stage PET tracer in immuno-oncology that accumulates in activated T cells and tissues with high mitochondrial biogenesis. Characterizing its distribution in individuals without malignancy is essential for interpreting immunometabolic states relevant to cancer biology. Methods: Twenty adults without active malignancy underwent a single [18F]F-AraG PET/CT scan, with tracer uptake assessed in relation to clinical history, medications, and demographic and physiologic factors. Results: Bilateral brown adipose tissue activation was identified in 3 participants receiving potentially brown adipose tissue–activating medications, in the absence of cold exposure or fasting. One showed elevated vertebral bone marrow uptake, previously linked to poor survival in immune checkpoint inhibitor–treated lung cancer. One of 2 participants with breast implants showed asymmetric periimplant uptake. Posterior pulmonary uptake occurred in a subset of participants, often with prior respiratory conditions and thoracic lymph node uptake. Conclusion: Whole-body [18F]F-AraG PET captures diverse immunometabolic activity in individuals without malignancy, reflecting systemic processes that may influence cancer and treatment outcomes.