Multimodal imaging for the detection and characterization of liver lesions in a mouse model of neuroendocrine tumor.
Résumé
BACKGROUND: The aim of this study was to compare in vivo magnetic resonance imaging (MRI) and ex vivo autoradiography with histopathological results for the detection and characterization of liver lesions in an experimental model of human neuroendocrine tumors. MATERIAL AND METHODS: Intestinal STC-1 endocrine tumor cells were injected into 30 nude mice to achieve hepatic dissemination. Seven to 30 days after injection, T2-weighted in vivo images covering the entire liver were acquired with a 7-T system. Autoradiographs were also obtained in 28 mice after injection of fluorodeoxyglucose (18F-FDG). The autoradiographic liver samples were then stained with an antichromogranin antibody before histological analysis. Tumor size and the hepatic tumor fraction were measured using the three imaging modalities. RESULTS: Metastatic tumors visualized on the histological liver sections ranged in size from 50 microm (day 7) to 3 mm (day 30). The hepatic tumor fraction increased with time, reaching 30% of the hepatic surface area on day 30. Visual analysis revealed variable tumor distribution and type (solid and/or cystic). On MRI, lesions were identified from day 12 (about 100 icrom in diameter) and the hepatic tumor fraction was up to 48% at day 30. The smallest lesions (350 microm in diameter) were also detected at day 12 on the autoradiographs. There was good correlation between tumor fractions determined from autoradiographic and histological data. CONCLUSION: In vivo, MRI appears to be well suited to the follow-up of liver lesions in a mouse model of neuroendocrine tumor. Preliminary results using 18F-FDG in this animal model are promising, showing differences in FDG uptake.