Fusion of [(18)F]FDG PET with Fluorescence Diffuse Optical Tomography to Improve Validation of Probes and Tumor Imaging

PURPOSE: Given the progress of fluorescence diffuse optical tomography (fDOT) technology, here, we study the additional benefits provided by multimodal PET/fDOT imaging by comparing the biodistribution of 2-deoxy-2-[(18)F]fluoro-d-glucose ([(18)F]FDG) in tumors with three fluorescent probes: a glucose analog, a protease activatable optical probe, and a ligand of αvβ3 integrin. PROCEDURES: Sequential fDOT/PET/computed tomography (CT) imaging of mice was performed with a custom multimodal mouse support that allows the subject to be transferred between the fDOT and the PET/CT scanners. Experiments were performed in xenografted tumor models derived from the human breast cancer line MDA-MB 231 and compared to ex vivo analysis. RESULTS: The three-dimensional signals showed that the fluorescent glucose analog is not colocalized with [(18)F]FDG, raising questions about its use as a surrogate probe of the PET tracer. Fusion of [(18)F]FDG with the other fluorescent probes showed evidence of high variability both for the protease activity and the αvβ3 integrin expression during tumor growth. CONCLUSION: The added value of hybrid PET/fDOT over the two modalities was demonstrated for cross-validation of probes and for better characterization of tumor models.