This project will facilitate the development of a powerful, ultra high resolution whole body Positron Emission Tomographic (PET) scanner which is envisioned to have 2.5 mm in-plane resolution 7.5 mm axial resolution, a 6 cm axial filed-of-view, 3-dimensional volume sampling and a system sensitivity of at least 200,000 counts/sec/micoroCi/cc. An imaging system of this type will have improved clinical applications in the areas of cardiology., neurology and oncology. The specific aims of this project are to design the detection system physics which will support the above performance specifications, to focus on the design of the fundamental modularized detector unit, to evaluate two candidate innovative detector encoding schemes of functionality and producibility, to build two prototype detector modules and to fully project goals will be achieved in five phases: 1) conceptual design, 2) computer modeling and design refinement, 3) generation of a comprehensive mechanical and assembly specification, 4) prototype implementation and 5) extensive bench testing. the results of this research will be immediately applied toward a new commercial PET scanner.