Optimisation of Animal Handing and Timing of 2-deoxy-2-[¹⁸F]fluoro-D-glucose PET Tumour Imaging in Mice

In humans, 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) tumour-to-background contrast continues to increase long after a typical uptake period of 45 - 60 min. Similar studies have not been performed in mice and the static imaging time point for most studies is arbitrarily set at 30 - 60 min post-injection of [¹⁸F]FDG. Ideally, static PET imaging should be performed after the initial period of rapid uptake but this period has not been defined in mice, with previous dynamic studies in mice being limited to 60 min. This study aimed to define the kinetics of [¹⁸F]FDG biodistribution over periods of 3 - 4 h in different murine tumour models, both subcutaneous and autochthonous, and to further refine fasting and warming protocols used prior to imaging.

Dynamic [¹⁸F]FDG PET-CT scans lasting 3 or 4 h were performed with C57BL/6 J and Balb/c nude mice bearing subcutaneous EL4 murine T-cell lymphoma and Colo205 human colorectal tumours, respectively, and with transgenic Eμ-Myc lymphoma mice. Prior to [¹⁸F]FDG injection, four combinations of different animal handling conditions were used: warming for 1 h at 31 °C; maintenance at room temperature (20 - 24 °C), fasting for 6 - 10 h and a fed state.

Tumour mean standardised uptake value (SUV_mean) peaked at 147 ± 48 min post injection in subcutaneous tumours and 74 ± 31 min in autochthonous Eμ-Myc lymphomas. The tumour-to-blood ratio (TBR) peaked at 171 ± 57 and 83 ± 33 min in subcutaneous and autochthonous Eμ-Myc tumours, respectively. Fasting increased tumour [¹⁸F]FDG uptake and suppressed myocardial uptake in EL4 tumour-bearing mice. There was a good correlation between tumour SUV_mean and K_i calculated using an input function (IDIF) derived from the inferior vena cava.

Delayed static [¹⁸F]FDG-PET imaging (> 60 min) in both autochthonous and subcutaneous tumours in improved tumour-to-background contrast and increased reproducibility.