Development of the XEMIS2 Liquid Xenon Compton Camera for 3-gamma Imaging: Studies and Optimization of Scintillation Light Measurements

The work described in this thesis is focused on the studies and optimization of scintillation light measurements in an innovative Xenon Medical Imaging System, named XEMIS2, consisting of a liquid xenon Compton camera, designed for low activity small animal 3-gamma imaging. The main objective of XEMIS2 involves the 3D localization of a radiopharmaceutical labeled with a specific radio-nuclide, such as Scandium-44, and the reduction of the administered activity while preserving the image quality. In XEMIS2, the scintillation light mainly provides the gamma-rays interaction time. A set of photomultiplier tubes are distributed around the active volume to measure it. Besides, a self-triggered scintillation light measurement system has been specially developed for XEMIS2 to carry out. The data acquisition prototype has been implemented and qualified in the XEMIS1 under the XEMIS2 operation conditions. The experimental results indicate that the dedicated detection system has a good performance in scintillation light measurement. Furthermore, it is possible to spatially pre-localize the gamma-rays interactions and achieve the virtual fiducialization of the active volume by matching the scintillation signals with the ionization signals through an algorithm on the basis of the light collection map, which contributes to reducing the occupancy of the TPC (Time Projection Chamber) in the context of increasing the injected activity to shorten the exposure time. (author)