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 (^99mTc 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.