Establishment of preliminary diagnostic reference levels for 18F-FDG PET/CT in adult lymphoma in Costa Rica.

Diagnostic reference levels (DRLs) for positron emission tomography (PET/CT) examinations have not previously been established in Costa Rica, and data from Central America remain limited due to the restricted availability of PET/CT systems in the region. This study established local DRLs for administered 18F-FDG activity and CT dose metrics in 393 adult lymphoma patients undergoing PET/CT at the Cyclotron-PET/CT Laboratory (Centro de Investigación en Ciencias Atómicas, Nucleares y Moleculares), University of Costa Rica. DRLs were defined as the 75th percentile (P75), and the influence of patient body mass was assessed. The DRL for administered activity was 388.5 MBq (4.8 MBq kg-1). Whole-body CT DRLs were 12.1 mGy for Volume Computed Tomography Dose Index and 1250.2 mGy cm for dose-length product, while thorax CT DRLs were 8.5 mGy and 325.6 mGy cm, respectively. Dose metrics increased with patient body mass, whereas normalized activity values remained consistent with international practice. These findings provide the first PET/CT-specific DRLs for Costa Rica and support future national dose optimization and monitoring efforts.