Feasibility of a PET/MR Imaging Workflow in Adult Zebrafish Using Intracardiac FDG Injection

Abstract Purpose In vivo imaging of adult zebrafish remains technically challenging due to loss of optical transparency and the lack of standardized molecular imaging protocols. The development of reliable radiotracer delivery and acquisition parameters is essential for improving imaging reproducibility and translational relevance. Methods Adult zebrafish with hepatobiliary tumor models were imaged using an integrated PET/MR system following intracardiac injection of F-18 FDG. Animals were assigned to four groups based primarily on uptake time, ranging from approximately 40 to 90 min, with injected activity maintained within a narrow range. A standardized imaging workflow, including anesthesia, positioning, PET acquisition, and MRI co-registration, was implemented. Image quality, tracer distribution, and tumor visualization were qualitatively compared across groups. Results Intracardiac injection provided reliable systemic tracer delivery across all groups. Short uptake times resulted in high background activity, particularly in the gastrointestinal tract, while prolonged uptake times led to signal decay. An intermediate uptake time (~ 60 min) appeared to provide the most favorable balance between signal intensity and background suppression under the current experimental setting. MRI consistently delineated hepatic lesions, while PET signal quality varied depending on protocol parameters. Semi-quantitative analysis indicated higher tracer uptake in lesion regions relative to adjacent background tissue. Conclusion This study establishes the first feasible PET/MR imaging workflow and identifies preliminary imaging conditions for adult zebrafish, demonstrating that uptake time is a critical determinant of imaging quality. The proposed workflow provides a reproducible platform for longitudinal in vivo imaging and may serve as a practical intermediate platform for preclinical molecular imaging prior to rodent studies.