The main objective for this project is to develop dual-modality PET-MR for molecular biology and medicine which will allow for the combined and simultaneous use of positron emission tomography (PET) and magnetic resonance (MR). In such a combined machine the PET provides information from molecular targets with very high sensitivity, while the MR system provides versatile information such as high-resolution anatomical images, as well as bio-chemical and structural information. PET and MR alone, have alread y advanced the knowledge in cell biology and neuronal science and thereby accelerated new drug developments, and helped to understand cancer and to develop treatments. The simultaneous use of PET-MR would be a significant breakthrough for molecular imagin g technology which would lead to new methods and generate new knowledge in molecular biology and medicine. The reason why PET and MR are used independently, is purely technical and due to the photomultiplier tubes in the PET which do not work in the magne tic field of the MR system. The project will focus on the technical development of a PET machine that works in magnetic fields of MR. We will integrate the PET machine with an existing MR system at our collaborators site at the FUGE Molecular Imaging Cent er in Trondheim (NTNU). The FUGE technology platform, MIC Trondheim will cooperate closely with the new MI Lab ("Medical Imaging Laboratory for Innovative Future Healthcare") which is an SFI led by Prof. Olav Haraldseth. For the PET we will use new detect ors which can operate in the MR magnetic field, and which will not harm the performance of the MR system. The project will focus on the development of the PET technology for compatibility with MR systems. The result of the project will be a PET machine wh ich is compatible with MR and integrated with an existing MR system.