Contributions to the instrumental developments of the XEMIS2 camera, on-board ionization and scintillation measurements

The work described in this thesis focuses on the evolution of nuclear medical imaging, from fundamental imaging techniques to current innovations, with a particular focus on the XEMIS2 camera. This liquid xenon Compton camera is designed for 3-gamma imaging of small, low-activity animals. The main objective of XEMIS2 is to localize in three dimensions a radiopharmaceutical labeled with a specific radionuclide, such as Scandium-44, while reducing the administered activity without compromising image quality. The thesis then focuses on the development and performance of the XEMIS2 camera. It covers the operational principles of the liquid xenon time projection chambers (LXeTPCs), the use of the Frisch grid to improve the performance of the ionization chambers, and the complex process of calibrating the scintillation signals in XEMIS2 using the Time over Threshold (TOT) method. Efforts to optimize calibration results are also discussed. By summarizing these technological and methodological advances, the thesis provides a historical perspective and a prospective analysis of the potential impact of these technologies on medical diagnostics and research. (author)