Resume L'objectif du travail etait la caracterisation de deux installations TEP/TDM, basees sur des technologies differentes, sur la base du protocole propose dans la norme NEMA NU 2-2001. Les deux systemes ont ete qualifies en mode d'acquisition 3D en utilisant les fantomes de la National Electric Manufacturers Association (NEMA). Les resultats obtenus montrent que la norme NEMA permet de mettre en evidence des differences entre la resolution spatiale, la sensibilite, la fraction de diffuse et les performances en taux de comptage des deux systemes, differences attribuables a la geometrie et aux materiaux des detecteurs utilises. Ainsi, l'utilisation de la norme permet d'etablir de veritables points de reference des systemes. Les tests de qualite d'image, obtenus dans des conditions plus proches des applications cliniques montrent que les deux installations, en depit de leurs differences de technologies, produisent, dans des temps d'acquisition courts, des images suffisamment contrastees pour permettre la detection de petites lesions. Ce test devrait d'ailleurs faire partie des tests de stabilite pour assurer la comparaison des examens, lorsque les aspects quantitatifs sont d'importance. The goal of work is the characterization of two PET/CT units that are based on different technologies, using the methodology proposed in the NEMA NU 2-2001 standard. The two systems were qualified in the 3D acquisition mode by means of the National Electric Manufacturers Association (NEMA) phantoms. The results obtained showed that the NEMA standard allows to highlight differences in terms of spatial resolution, sensitivity, scatter fraction and counting rate performances between the two systems ; differences that can be explained by the geometry of the units and the materials of the detectors used. Thus, the use of the standard makes it possible to benchmark PET units and establish reference values that can be used to follow the stability of the system over the time. The tests of image quality, obtained under conditions closer to the clinical applications, showed nevertheless that the two units give, in spite of different technologies, images with sufficient contrast, within short acquisition times, allowing the detection of small lesions. This test should be part of the constancy tests to enable the comparison of examinations performed on different units when the quantitative aspects are of importance.