Figure 4: In-vivo fibered confocal fluorescence microscopy. The optical probe was placed on the surface of the MCF-7 xenografted tumors by means of a minimal skin incision which preserved the integrity of the tissue. Control tumor immediately after FITC-dextran injection 5.105 g/mol (100 μL of 20 mg/ mL solution) of an untreated mouse (a). Typical time-resolved viewing of tumors carried by mice treated weekly with Rho-PE labelled RU-MFLs (4.3mg/week/ kg) 4 hours after the seventh injection and exposition to a 0.44 T magnet (155 T/m magnetic field gradient) (b-d). Images b to d show rhodamine signal due to the injected liposomes as obtained every two seconds and 10 min after magnet removal. Arrows indicate circulating RU-MFLs.