Validation of an Animal FDG PET Imaging System for Study of Glioblastoma Xenografted Mouse and Rat Models

Introduction: Because of the high incidence and poor prognosis of gliomas, the development of pre-clinically effective diagnostic tools is of great importance. The objective of this study is to validate the use of FDG PET imaging system for monitoring glioma proliferation in two rodent models. Methods: Two kinds of glioblastoma cells (human DBTRG-O5MG and rat RG2 tumor cells) were implanted intracerebrally to SCID mice and Wistar rats, respectively. To characterize the optimal scanning time required for effective detection of brain tumors, dynamic animal PET were acquired for 1 and 2 h immediately after intravenous injection of the FDG radiotracer to mice and rats, respectively. Test animals were then subjected to serial animal PET scans at day 7, 10, 14, and 17 after tumor cell implantation. Results: Mouse and rat brain tumors were first detected by FDG micro PET imaging at day 7 and 10 after tumor implantation, respectively. The smallest tumor size detectable was 2.5 mm in diameter. The peak tumor-to-background ratio was observed at 40 mm post-injection in the mouse model and at 90 mm post- injection in the rat study. Both the peak standard uptake value of FDG and the tumor-to-background ratios were found to increase as the tumors grew over time. Conclusion: A FDG PET scan protocol was validated for detecting and monitoring glioma tumor growth in both mouse and rat models. Optimal FDG uptake period required and optimal scanning times for experimental tests were hence established for future systematic studies in relevant animal models.