Comparison of retro-orbital, intraperitoneal, intravenous and per-oral routes for F-18 FDG administration in mouse tumor models

Objectives Although intravenous injection via mouse tail vein during small-animal PET studies has been widely used, it is not an easy task to repeat the injections even for experienced researchers. The aim of this study is to compare alternative routes for FDG administration such as retro-orbital (RO), intraperitoneal (IP) injections, and per-oral (PO) administration with intravenous (IV) injection by assessing the FDG uptake in normal tissues and tumors.

Methods CRL-1642 (ATCC) was cultured with RPMI. 8×10⁷ CRL-1642 cells were prepared and inoculated in anesthetized female BALB/c-nu/nu mice 6 to 10 weeks old. When the tumor grew and reached to about 9 mm in diameter, PET scans were performed from 10 minutes to 180 minutes after the FDG administration via RO, IP, PO or IV route. Additional serial PET scans were performed using the RO, IV, or IP route alternatively from 5 to 29 days after the tumor cell injection.

Results There was no significant difference of the FDG uptake in the liver, lung, brain, heart, kidneys, and joint region at 60 minutes after the FDG administration via RO, IP, IV routes. PO administration, however, showed delayed distribution and unwanted high gastrointestinal uptake. Tumoral uptake of FDG showed a similar temporal pattern and increased until 60 minutes after the FDG administration in the RO, IP, IV injection groups. In the PO administration group, tumoral uptake was delayed and reduced. There was no statistical difference among the RO, IP, IV administration groups for additional serial PET scans.

Conclusions Administration routes did not affect normal distribution and tumoral uptake of FDG. RO and IP injections can be effective alternative routes for FDG administration in mouse tumor models. Researchers should select an administration route for deemed most appropriate under the circumstances or needs

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Relative tumoral uptake at 60 minutes after the FDG administration