"Medical imaging is a multidisciplinary research field that has a direct application to the improvement of human health. Instrumentation development in this area is an essential step in the search for high performance imaging devices that can help to provide an early and accurate diagnosis of the diseases. The novel photodetectors known as silicon photomultipliers or multicell Geiger-mode avalanche photodiodes are an alternative to the traditional photomultiplier tubes that can overcome some of the limitations of the existing instrumentation. In the last years they have reached a performance level that can make their application to medical imaging highly advantageous. The use of these photodetectors makes possible the construction of high resolution and efficiency detector blocks that can lead to a significant improvement in the performance of detectors for Positron Emission Tomography (PET).The proposed project aims to contribute to the development of this technology and to assess its benefits in medical imaging through their employ in the construction of detector heads for two different applications: a small animal PET scanner with expected submillimeter spatial resolution and a clinical high resolution intra-operative PET probe. The project will greatly help the applicant in her reintegration process in the host institution, to continue her training as a scientist and further improve her management and leadership abilities, and also to get established and consolidate her research career. Furthermore, it will serve to reinforce the collaboration with the host institution of her previous Marie Curie Intra-European fellowship, and will also contribute to introduce this novel and promising technology in the host institution."