XEMIS: Liquid Xenon Compton Camera for 3γ Imaging

International audienceAn innovative liquid xenon Compton camera project, XEMIS (XEnon Medical Imaging System) has been proposed by SUBATECH laboratory, for a new functional medical 3γ imaging technique based on the detection in coincidence of 3 γ-rays. The purpose of this 3γ imaging modality is to obtain a 3D image using 100 times less activity than in current PET systems. The combination of a liquid xenon time projection chamber (LXe TPC) and a specific (β$^{+}$, γ) radionuclide emitter$^{44}$Sc is investigated in this concept. In order to provide an experimental demonstration for the use of a LXe Compton camera for 3γ imaging, a succession of R&D programs, XEMIS1 and XEMIS2, have been carried out using innovative technologies. The first prototype XEMIS1 has been successfully validated showing very promising results for energy, spatial and angular resolutions with an ultra-low noise front-end electronics. The second phase dedicated to a 3D imaging of small animals, XEMIS2, is now under installation and qualification, while the characterizations of ionization signal using Monte Carlo simulation has shown preliminary good performances for energy measurement

Scintillation Signal in XEMIS2, a Liquid Xenon Compton Camera with 3γ Imaging Technique

International audienceThe XEMIS project (XEnon Medical Imaging System), which makes use of 3γ imaging technique and liquid xenon Compton camera, aims to make a precise 3D localization of a specific radioactive emitter and to reduce drastically (100 times less) the injected activity to the patient in cancer diagnosis. The 3γ imaging is characterized by the simultaneous detection of 3 γ-rays emitted by$^{44}$Sc which is a (β+, γ) emitter. The second prototype XEMIS2 is a liquid xenon cylindrical camera for small animal imaging. The active volume of XEMIS2 is surrounded by a set of VUV-sensitive Hamamatsu photomultipliers, for the scintillation signals detection. A pulse-shaping amplifier was tested in XEMIS1 for the readout of the scintillation signal of the PMT. The typical output pulse shows a relatively good performance of the pulse-shaping amplifier providing a possible solution for XEMIS2 scintillation DAQ. Meanwhile, the pulse-shaping amplifier and the constant fraction discriminator (CFD) have lay the foundation of the preliminary design of XEMIS2 scintillation signal detection chain

3gamma medical imaging with a liquid xenon Compton Camera and 44Sc radionuclide

International audienceThe development of a liquid xenon Compton camera called XEMIS2 (XEnon Medical Imaging System) is a step forward to a new type of medical imaging based on the use of 44Sc radionuclide emitting two annihilation rays and a third high energy ray simultaneously. The single phase TPC (Time Projection Chamber) under construction, containing nearly 200 kg of xenon, is designed to measure most of the Compton interactions in the active area with a sub-millimetre position resolution and a good energy resolution of 4% on 511 keV photopeak. The intersection of the Compton cone surface from the third ray with the line of response from the two annihilation rays allows to localize the radionuclide with a precision (FWHM) of about 1 cm along this line. The large field of view of such a liquid xenon camera combined with the 3 imaging technique will provide a good quality image while keeping the injected activity at a very low level. XEMIS2 will be installed in the Nantes University Hospital in order to demonstrate its capability to image small animals injected with a low activity of only 20 kBq in 20 mn acquisition time. To achieve this goal, a precise measurement of the ionization signal is provided by a pixelized anode, shielded by a Frisch Grid and read out by a low noise front-end electronics. In addition, new cryogenic and purification subsystems have been tested, allowing safe recovery of xenon in liquid phase at flow rates of about 1 ton per hour

XEMIS2: A liquid xenon detector for small animal medical imaging

International audienceWe report a new liquid xenon Compton camera, called XEMIS2 (XEnon Medical Imaging System), developed to image for the first time small animals using 3 γ imaging. This technique proposes an alternative to reduce the administered radiopharmaceutical activity while preserving diagnostic image quality using liquid xenon as detection medium. Given the success of its predecessor, a small dimension liquid xenon time projection chamber called XEMIS1, we are currently building a larger scale detector for preclinical applications. This second prototype, XEMIS2, is a single phase liquid xenon cylindrical camera with a large axial field of view for full-body small animal imaging. XEMIS2 holds around 200 kg of xenon and it has been designed to enable high-efficiency and simultaneous detection of the three γ -rays emitted by a 44Sc radionuclide. The innovative geometry of XEMIS2 will allow to discriminate and measure the position and deposited energy of most Compton interactions inside the detector. In order to manage such a large quantity of xenon, an innovative high-pressure subsystem known as ReStoX has been developed and successfully qualified. ReStoX allows to maintain the xenon in liquid state at the desired temperature and pressure, transfer the xenon into XEMIS2 and store it during long term periods. XEMIS2 will be installed at a non controlled radioactive area of Nantes Hospital. The goal is to evaluate image quality of a 20 min whole-body preclinical exam with an injected activity of 20 kBq