XEMIS2 Liquid Xenon Compton Camera for Small Animal 3γ Medical Imaging: Scintillation Light Measurement

An innovative XEnon Medical Imaging System, named XEMIS2, consisting of a liquid xenon (LXe) Compton camera, is developed to image small animal with 3γ imaging technique. The main objective of XEMIS2 involves the 3D localization of a radiopharmaceutical labeled with a specific radionuclide 44Sc and the lessening of the administered radiotracer activity while preserving the image quality in oncology diagnosis. XEMIS2 is a monolithic single-phase detector with a large axial Field Of View (FOV), handling up to nearly 200 kg of ultra-high-purity liquid xenon. The XEMIS2 facility has been successfully conceived and developed at the SUBATECH laboratory. In XEMIS2, the scintillation signals provide the γ-rays interaction time. Furthermore, it is possible to pre-localize the γ-rays interactions spatially and then achieve the virtual fiducialization of the active volume by matching the scintillation signals with the ionization signals. In order to measure scintillation light, we distribute a set of PhotoMultiplier Tubes (PMTs) around the surface of the active area. Besides, a self-triggered scintillation light detection chain has been specially developed for XEMIS2 to carry out continuous data taking with negligible electronics dead-time. It is currently calibrated in the prototype XEMIS1. The calibration results indicate that the dedicated detection chain has a good performance in scintillation light measurement. XEMIS2 is recently under construction in a small animal medical imaging center CIMA, for further preclinical studies.