X-ray Computed Tomography (CT) method is an integral part of hydraulic-fracture imaging, but its application to micro-fractures in cores is limited. This paper documents the visualization of fractured cores via an accessorial PET-CT approach to improve both spatial resolution and image contrast. PET-CT approach combines X-ray Computed Tomography (CT) and positron emission tomography (PET) method. CT technique provides information of core structure and accurate location of fractures based on density variations. PET is a nuclear imaging technique through inducing radionuclide into fractures, offering the potential to overcome CT limitations by providing information of micro-fractures. Combined PET-CT approach has been demonstrated as a technical advancement for imaging fractured cores better than simply CT or PET method. Comprehensive information of core structure, micro-fractures and connected fractures could be provided by PET-CT method. The applicability of each visualization technique was evaluated, the favorable implementation of combined PET-CT for laboratory core analysis was discussed.