[¹⁸F]Fluoride uptake in various bone types and soft tissues in rat

Area of Science:

• Nuclear medicine
• Radiochemistry
• Pharmacokinetics

Background:

• ¹⁸F-labelled PET tracers can release [¹⁸F]fluoride via defluorination during scans.
• Comprehensive pharmacokinetic data for [¹⁸F]fluoride in rat bones and soft tissues are lacking.
• Understanding [¹⁸F]fluoride biodistribution is vital for assessing the reliability of ¹⁸F-labelled tracers.

Purpose of the Study:

• To investigate the pharmacokinetics of [¹⁸F]fluoride in Sprague Dawley rats.
• To determine the biodistribution of [¹⁸F]fluoride released from defluorinated ¹⁸F-labelled tracers.
• To provide a comprehensive understanding of [¹⁸F]fluoride uptake in various rat bones and soft tissues.

Main Methods:

• In vivo PET/CT imaging over 60 minutes to assess [¹⁸F]fluoride uptake in rat bones.
• Calculation of kinetic parameters (K₁, K_i, K_i/K₁, k₃) using a three-compartment model.
• Ex vivo bone and soft tissue harvesting with gamma counting over 6 hours in separate male and female rat groups.

Main Results:

• [¹⁸F]fluoride perfusion and uptake demonstrated variability across different bone types.
• Higher [¹⁸F]fluoride uptake was observed in trabecular bones compared to cortical bones, attributed to perfusion and osteoblastic activity.
• Soft tissues, including eyes, lungs, brain, testes, and ovaries, showed increasing organ-to-blood uptake ratios over the 6-hour study period.

Conclusions:

• Knowledge of [¹⁸F]fluoride pharmacokinetics in bones and soft tissues is essential for evaluating ¹⁸F-labelled radiotracers.
• The study provides critical data for interpreting PET scans involving tracers prone to defluorination.