Abstract: The present invention relates to nuclear medicine using fluorescent silica nanoparticle and detecting method of optical dual imaging, and more particularly to radioisotope labeled fluorescent silica nanoparticles which are used for PET (positron emission tomography) and fluorescence detecting, and detecting method of PET and fluorescent dual imaging using thereof. Functionalized silica nanoparticles of this invention have promising potential as a role for organic lymphatic tracer in biomedical imaging such as pre- and intra-operative surgical guidance.