In this article, we propose a novel image reconstruction technique for three-gamma (3-<inline-formula> <tex-math notation="LaTeX"> {\gamma } </tex-math></inline-formula>) imaging systems that aims at ...reaching high image quality with a low statistics. The proposed approach is based on the utilization of a (<inline-formula> <tex-math notation="LaTeX"> {\beta +} </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">{\gamma } </tex-math></inline-formula>) emitter and a liquid xenon (LXe) camera, the Xenon Medical Imaging System 2 (XEMIS2), that is currently being manufactured. The third gamma emitted is more energetic than the two 511-keV photons and interacts mostly through Compton scattering in LXE; therefore, we utilize the interactions' position and the deposited energy to define a Compton cone that gives the direction from where the third gamma was emitted. The intersection point between the cone and the two coincidence photons' lines of response (LOR) is the center of the probability distribution function (PDF), a resolution model similar to that of time-of-flight (TOF)-positron emission tomography (PET). The third gamma's information is used to narrow the LOR portion employed during reconstruction. In this article, we show reconstruction results from simulation using highly realistic Geant4 Application for Emission Tomography (GATE) Monte Carlo simulation of the imaging device and a NEMA-like phantom.
Operation results are presented of a UV-sensitive gaseous photomultiplier (GPM) coupled through a MgF sub(2) window to a liquid-xenon scintillator. It consisted of a reflective CsI photocathode ...deposited on top of a THick Gaseous Electron Multiplier (THGEM); further multiplication stages were either a second THGEM or a Parallel Ionization Multiplier (PIM) followed by a MICROMEsh GAseous Structure (MICROMEGAS). The GPM operated in gas-flow mode with noncondensable gas mixtures. Gains of 10 sub(4) were measured with a CsI-coated double-THGEM detector in Ne/CH sub(4) (95:5), Ne/CF4 (95:5) and Ne/CH sub(4)/CF sub(4) (90:5:5), with soft X-rays at 173 K. Scintillation signals induced by alpha particles in liquid xenon were measured here for the first time with a double-THGEM GPM in He/CH sub(4) (92.5:7.5) and a triple-structure THGEM/PIM/MICROMEGAS GPM in Ne/CH sub(4) (90:10) with a fast-current preamplifier.
Radio detection of cosmic ray air showers by the CODALEMA experiment Ravel, O.; Dallier, R.; Denis, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
The possibilities of measuring Extremely High Energy Cosmic Rays by radio detection of electromagnetic pulses radiated during the development of extensive air showers in the atmosphere are ...investigated. We present the demonstrative CODALEMA experiment, set up at Nançay Radio-Observatory (France). The radio-decametric array has been adapted to measure radio transients in time coincidence between antennas.
We report the studies and optimization of scintillation light measurements in an updated version of the XEMIS1 prototype for the development of the XEMIS2 camera. A novel monolithic liquid xenon ...Compton camera, named XEMIS2 (XEnon Medical Imaging System), attempts to achieve low-activity small-animal imaging using the 3-gamma imaging technique. This emerging detector relies on the time projection chamber technique: it will be able to perform a simultaneous detection of the three γ-rays emitted by a specific radionuclide, such as scandium-44, and to produce a good quality image with a remarkable diminution of radiopharmaceutical activity at the same time. Vacuum Ultraviolet (VUV) scintillation light and ionization charge carriers generated from the recoiling particles within the detector are detected and used to reconstruct the interaction position and deposited energy. A cost-effective self-triggering scintillation signal read-out and data acquisition (DAQ) system has been developed to achieve a continuous data read-out with negligible electronics dead time. The DAQ prototype has been installed and qualified in an updated version of the XEMIS1 detector. It reaches the performance specifications in scintillation light measurements. Moreover, scintillation signals can also be used for the virtual segmentation of the monolithic detection volume through the matching algorithm of the scintillation and ionization signals based on the Light Collection Map (LCM). This spatial pre-localization of the physical events, called the virtual fiducialization of the active volume, is used to lower the detector occupancy rate when the administered activity is increased to lessen the examination time. The XEMIS1 experimental LCMs indicate that each PMT owns an individual field of view so as to segment the active volume virtually. The preparation work for the XEMIS2 camera operation has been completed in the updated XEMIS1 detector while the XEMIS2 scintillation light measurement system is under commissioning in Nantes Centre Hospitalier Universitaire.
•The XEMIS2 camera oriented to the whole-body small animal 3-gamma medical imaging is presented.•The XEMIS2 system is a monolithic liquid xenon Compton camera with a 24 cm axial field of view.•A cost-effective 16-channel self-triggering scintillation signal front-end read-out electronics named XSRETOT is reported.•The XEMIS1 experimental light collection maps can be used for the virtual segmentation of the monolithic detection volume.
A polarization-based extrinsic fibre Fabry - Perot interferometric sensor for the measurement of velocity and displacement of a vibrating target is demonstrated. It operates on the principle of dual ...interference within a single interferometric or "sensing" arm which also provides a sense of direction of the moving target. This is made possible by a retarding film positioned along the optical path between the sensing fibre end and the intended target. 2 sets of interference signals are thus propagated and detected along 1 fibre arm to give robust, repeatable displacement - velocity information which is relatively insensitive to external effects such as minor temperature changes. The sensor is capable of measuring the desired velocity information of an inclined target. Experimental results are presented from a sensor configuration employing a polarization maintaining (PANDA type) fibre as the sensing arm and operated at 1310 nm.
XEMIS2: A liquid xenon detector for small animal medical imaging Gallego Manzano, L.; Abaline, J.M.; Acounis, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2018, Letnik:
912
Journal Article
Recenzirano
Odprti dostop
We report a new liquid xenon Compton camera, called XEMIS2 (XEnon Medical Imaging System), developed to image for the first time small animals using 3γ 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.
•The first 3 gamma whole-body small animal scanner is presented.•The XEMIS2 camera is a single-phase liquid xenon detector with a 24 cm axial field of view.•A dedicated 32-channels low power circuit called XTRACT is described.•ReStoX is an advanced cryogenic system developed to liquefy, recover and store the xenon.•A reconstructed image using the innovative 3 gamma reconstruction algorithm is reported.
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