Intramuscular 18F-sodium fluoride is a viable alternative to intravenous injection for positron emission tomography detection of atherosclerosis in Amazon parrots.

Abstract

OBJECTIVE: To compare IM and IV administration of 18F-sodium fluoride (18F-NaF) for PET-CT imaging of atherosclerosis in orange-winged Amazon parrots (Amazona amazonica) and to evaluate the effects of uptake time and acquisition duration on image quality using a reduced radiotracer dose. METHODS: From June to July 2025, parrots underwent 2 18F-NaF micro-PET-micro-CT scans at the University of California-Davis, each in a cross-over design (IM vs IV). A 0.1-mCi dose was used with a 30-minute uptake period and 30-minute dynamic acquisition. Images were reconstructed into 5-, 10-, and 15-minute frames to assess the effects of acquisition duration and uptake time. Standardized uptake values and target-to-background ratios were calculated in arterial lesions and control tissues. RESULTS: Eight older parrots were scanned. Atherosclerotic lesions were identified in 6 of 8 parrots. Both image noise and background activity were higher in IM than IV scans, particularly at shorter acquisition durations. Lesion conspicuity and quantitative stability improved at longer uptake times (≥ 45 minutes) and acquisitions (≥ 10 minutes). The IM administration produced slower equilibration but comparable or higher late-phase lesion uptake, consistent with gradual tracer release. CONCLUSIONS: The IM 18F-NaF administration provides diagnostic-quality PET images with lesion detectability approaching that of the IV administration, while being technically simpler and safer for parrots. CLINICAL RELEVANCE: An optimized protocol for PET imaging in psittacine birds using a similar scanner is proposed with the administration of approximately 0.3 mCi 18F-NaF IM or IV, a 1-hour uptake period, and a 10- to 15-minute acquisition to balance image quality, diagnostic sensitivity, procedural simplicity, and radiation safety.