Physiological ¹⁸F-Fluciclovine Biodistribution in the Head: A PET/CT Study

Objective Anti-1-amino-3-[18F] fluorocyclobutane-1-carboxylic acid (18F-fluciclovine; anti-3-[18F] FACBC) is an amino acid positron emission tomography (PET) tracer used for the evaluation of brain tumors in cases of suspected or diagnosed glioma. However, reports on the physiological biodistribution of 18F-fluciclovine in the head, are limited. This study analyzed the physiological biodistribution of 18F-fluciclovine PET in the head. Methods 18F-fluciclovine PET/CT images from 20 patients with suspected malignant glioma were retrospectively reviewed. Standardized uptake values (SUVs) were measured in 24 predefined head regions, and inter-regional differences were assessed using one-way ANOVA. Time–activity curves were generated for dynamic evaluation in 15 patients to assess temporal uptake patterns. Among these patients, 8 also underwent 11C-methionine PET/CT, enabling direct comparison of SUVs between the two tracers using paired t-tests. Statistical significance was set at P < 0.05. Results All values are reported as SUVmean. Intracerebral uptake of 18F-fluciclovine was low (white matter 0.2, cerebral cortex 0.3, other brain regions 0.4). Extracerebral uptake was highest in the parotid glands (3.4), followed by pharynx (2.5), pituitary gland and nasal cavity (2.3), muscle (2.2), bone marrow (2.0), and skin (1.9). Dynamic analysis showed that brain uptake remained low and stable, whereas the pituitary and parotid glands peaked early with gradual washout. In paired comparison, 11C-methionine showed significantly higher uptake in all brain regions, whereas 18F-fluciclovine was significantly higher in the venous sinus, cavernous sinus, muscle, and nasal cavity. Conclusion This study establishes a detailed baseline of physiological 18F-fluciclovine distribution in the head. These findings may contribute to distinguishing physiological from pathological uptake and suggest the potential usefulness of 18F-fluciclovine PET for tumor margin delineation and preoperative diagnostic assessment in brain tumors.