Over the last a few decades, the field of imaging science witnessed exponential growth on many imaging techniques including Computed Tomography (CT), Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), bioluminescence, fluorescence, and Magnetic Resonance Imaging (MRI). With the ability to image specific biological pathways at the molecular and cellular level in vivo, molecular imaging techniques are widely used in diagnostic and therapeutic field. It also successfully accelerates the drug discovery and development process, especially for personalized medicine development. Generally, each molecular imaging technique has its own advantages and limitations in spatial and temporal resolution, depth penetration, sensitivity and cost. It is possible that synergistic effect could be obtained by the fusion of two or more in vivo imaging techniques. In particular, PET is a powerful imaging technique closely related to clinical translation in oncology.