Experimental study on in vivo optical and radionuclide imaging in small animals

We report on tests of a combined fluorescence and radionuclide planar imaging system for in vivo investigation on small animals. Combined images of anaesthetized mice bearing a solid tumor are presented. The fluorescent marker is hematoporphyrin imaged with a standard CCD camera. The gamma-ray pinhole imaging system is a hybrid pixel detector obtained by hybridising a silicon or a CdTe pixel detector to the Medipix1 or Medipix2 integrated circuits. The acquisition of combined images shows that the tumor area can be imaged in a few minutes, with few millimeter resolution, radioactively (/sup 99m/Tc MIBI, 74 MBq), and with the optical system. Fluorescence spectroscopy and film auto radiography of the histological tumor sections have been used as control tests of tumor captation. Imaging revealed also a different captation of the two types of tumor cells with different malignancy, ascribed to the presence of necrosis in one the tumors.