Kinetic Modelling of Infection Tracers [(18)F]FDG, [(68)Ga]Ga-Citrate, [(11)C]Methionine, and [(11)C]Donepezil in a Porcine Osteomyelitis Model

Jødal, Lars; Jensen, Svend B.; Nielsen, Ole L.; Afzelius, Pia; Borghammer, Per; Alstrup, Aage K. O.; Hansen, Søren B.

INTRODUCTION: Positron emission tomography (PET) is increasingly applied for infection imaging using [(18)F]FDG as tracer, but uptake is unspecific. The present study compares the kinetics of [(18)F]FDG and three other PET tracers with relevance for infection imaging. METHODS: A juvenile porcine osteomyelitis model was used. Eleven pigs underwent PET/CT with 60-minute dynamic PET imaging of [(18)F]FDG, [(68)Ga]Ga-citrate, [(11)C]methionine, and/or [(11)C]donepezil, along with blood sampling. For infectious lesions, kinetic modelling with one- and two-tissue-compartment models was conducted for each tracer. RESULTS: Irreversible uptake was found for [(18)F]FDG and [(68)Ga]Ga-citrate; reversible uptake was found for [(11)C]methionine (two-tissue model) and [(11)C]donepezil (one-tissue model). The uptake rate for [(68)Ga]Ga-citrate was slow and diffusion-limited. For the other tracers, the uptake rate was primarily determined by perfusion (flow-limited uptake). Net uptake rate for [(18)F]FDG and distribution volume for [(11)C]methionine were significantly higher for infectious lesions than for correspondingly noninfected tissue. For [(11)C]donepezil in pigs, labelled metabolite products appeared to be important for the analysis. CONCLUSIONS: The kinetics of the four studied tracers in infection was characterized. For clinical applications, [(18)F]FDG remains the first-choice PET tracer. [(11)C]methionine may have a potential for detecting soft tissue infections. [(68)Ga]Ga-citrate and [(11)C]donepezil were not found useful for imaging of osteomyelitis.