Local Diagnostic Reference Levels for Pediatric Whole-body and Brain [18F]FDG PET/CT

Background: PET/CT scanners allow anatomical and metabolic imaging but expose patients to ionizing radiation, requiring dose optimization according to the ALARA principle, especially in children. Diagnostic Reference Levels are a possibility, yet no pediatric [ 18 F]FDG PET/CT DRLs exist in Europe. This study reports typical doses for pediatric whole-body and brain [ 18 F]FDG PET/CT. Methods: A retrospective study included all PET/CT scans performed at our center in patients under 18 y (2014–2018). Patients were grouped by body weight (whole-body: 15≤30 kg, 30≤50 kg, 50≤80 kg) and age (brain: 1≤6 y, 6≤18 y), according to the ICRP 135 classification. DRLs are defined as the 75th percentile (P75) of observed values. Results: For whole-body PET, P75 (median) administered activities were 4.5 (4.4), 4.5 (4.1), and 4.7 (4.3) MBq kg -1 across weight groups. Brain PET P75 (median) values were 5.1 (4.5) MBq kg -1 (1≤6 y) and 4.0 (3.1) MBq kg -1 (6≤18 y). Whole-body CT metrics P75 (median) were: CTDI vol of 2.5 (1.6), 3.1 (2.2), and 3.9 (3.1) mGy; DLP of 211.9 (145.5), 331.0 (230.9), and 464.8 (342.6) mGy·cm. Brain CT showed a P75 CTDI vol of 3.5 mGy for both age groups, with DLPs of 75.8 and 76.2 (median: 75.8) mGy·cm. Conclusion: The values reported in this article, by comparison with existing literature, show that it is possible to reduce the administered activity for certain patient categories. Local, national, or international DRLs are expected to change over time and results need to be updated in an iterative way, particularly when new technologies are implemented.