2.2 Positron Emission Tomography (PET). Positron Emission Tomography combined with Computerized Tomography (PET/CT) is a well-established tool in diagnosing and staging of several types of cancer . PET is an imaging technique where pairs of gamma rays emitted by positron-emitting radionuclide tracer are detected, producing a three-dimensional image of tracer concentration based on the amount of gamma rays emitted. The radioactive tracer is coupled to a biologically active molecule depending on the organ or metabolic process of interest . These images can then be fused with CT to create a combined functional and high-resolution anatomical image. Several tracers have been developed for use in cancer diagnostics and staging. As of now, PET/CT has no generally accepted role in the diagnosing or staging of PCa neither in Europe nor in the US .