Multi-Radionuclide in Vivo Imaging of Solid Tumors in Small Laboratory Animals for Experimental Oncology

Abstract

Purpose: To show the feasibility of the simultaneous trimodal PET/SPECT/CT with 18F-FDG and 177Lu-DOTATATE for characterization of syngeneic subcutaneous mouse tumor model.
 Material and methods: Female C57Bl/6 mice with transplanted subcutaneous melanoma B16F10 were
 used for the study. Preclinical trimodal PET/SPECT/CT imaging system MiLabs VECTor 6 (Netherlands) was used. Mice from the first control group were intravenously injected with 177Lu-DOTATATE
 and underwent SPECT/CT. Mice from the second control group were intravenously injected with 18F-FDG and underwent PET/CT. Mice from the experimental group were intravenously injected with 18F-FDG and 177Lu-DOTATATE in one syringe and underwent simultaneous PET/SPECT/CT imaging.
 Results: Distribution pattern of each radiopharmaceutical 18F-FDG and 177Lu-DOTATATE in the tumor
 of mice from experimental group was similar to the pattern, observed in control groups. 177Lu-DOTATATE was detected in the tumor periphery, and its concentration decreased with time. 18F-FDG
 was detected in the tumor as a large homogeneous focus of hyperfixation and its concentration increased with time. Biodistribution of both tracers in the mouse organism, according to PET/SPECT/CT
 after single injection, was similar to the distribution of the tracers individually in PET and SPECT.
 Conclusion: The obtained results of the study confirm that neither physical or physiological interference nor chemical reaction between two tracers occurred. The tracers had no pharmacological influence on each other. The decrease of 177Lu-DOTATATE in experimental tumor indicated low level of SSTR
 expression, the increase of 18F-FDG revealed high level of metabolic activity in the tumor.