Influence of Animal Heating on PET Imaging Quantification and Kinetics: Biodistribution of ^sup 18^F-Tetrafluoroborate and ^sup 18^F-FDG in Mice

Different environmental conditions under anesthesia may lead to unstable homeostatic conditions in rodents and therefore may alter kinetics. In this study, the impact of different heating conditions on PET imaging quantification was evaluated. Methods: Two groups of 6 adult female BALB/c nude mice with subcutaneously implanted tumors underwent microPET imaging after injection of 18F-labeled tetrafluoroborate or 18F-FDG. Dynamic scans were acquired under optimal and suboptimal heating conditions. Time-activity curves were analyzed to calculate uptake and washout time constants. Results: With 18F-labeled tetrafluoroborate, optimal animal heating led to a stable heart rate during acquisition (515 ± 35 [mean ± SD] beats/min), whereas suboptimal heating led to a lower heart rate and a higher SD (470 ± 84 beats/min). Both uptake and washout time constants were faster (P < 0.01) in animals maintained with optimal heating. Conclusion: Although the difference in heart rates was slight, optimal heating yielded significantly faster uptake and washout kinetics than suboptimal heating in all organs for both tracers.