The correlation of molecular neuroimaging and behavior studies in preclinical PET imaging is of major interest to unlock progress in the understanding of brain processes and assess the validity of ...preclinical studies in drug development. However, fully achieving this ambition requires performing molecular images of awake and freely moving animals, whereas most of the preclinical imaging procedures are currently performed under anesthesia. To overcome this issue, the MAPSSIC project aims to develop a pixelated intracerebral probe to be implanted into awake and freely moving rats. The aforementioned probe relies on IMIC (Imageur Moléculaire Intra Cérébral), a Monolithic Active Pixel Sensor (MAPS) prototype set to directly detect positrons. The IMIC sensors were produced in 5 different configurations. Measurements using a 204Tl source showed that the sensor parameters can be optimized to boost its performance allowing to increase the sensitivity and reduce the average cluster size. In addition, comparisons between sensor configurations show a clear gain provided by the introduction of CMOS process modifications. Finally, the choice of the optimal sensor configuration will depend on the expected in vivo conditions.
Molecular radiotherapy is a treatment modality that requires personalized dosimetry for efficient treatment and reduced toxicity. Current clinical imaging systems and miniaturized gamma-cameras lack ...the necessary features for this task. In this article, we present the design and optimization of a mobile gamma-camera with a <inline-formula> <tex-math notation="LaTeX">10\times 10 </tex-math></inline-formula> cm2 field of view tailored for quantitative imaging during <inline-formula> <tex-math notation="LaTeX">^{131}\text{I} </tex-math></inline-formula> therapy of thyroid diseases. The camera uses a monolithic <inline-formula> <tex-math notation="LaTeX">10\times 10\times 1 </tex-math></inline-formula> cm3 CeBr3 scintillator coupled to a <inline-formula> <tex-math notation="LaTeX">16\times 16 </tex-math></inline-formula> SiPMs array and commercial electronics. It exhibits high imaging performance with an intrinsic spatial resolution (SR) of 1.15-mm FWHM, an energy resolution of 8% FWHM at 356 keV and negligible deadtime up to 150 kcps. Images are reconstructed in real time using a convolutional neural network. The manufacturing method of tungsten collimators and shielding was optimized using laser 3-D printing to achieve an effective density of 97% that of bulk tungsten. Their geometry was adjusted with Monte-Carlo simulations in order to reduce septal penetration and scattering and optimize the signal-to-noise ratio at short times after treatment administration. Two high-energy parallel-hole collimators with high sensitivity or very high SR were designed for treatment planning and post-treatment control. The fully operational gamma-camera will soon be clinically assessed.
Aims/hypothesis Inflammation is associated with obesity and has been implicated in the development of diabetes and atherosclerosis. During gram-negative bacterial infection, lipopolysaccharide causes ...an inflammatory reaction via toll-like receptor 4 (TLR4), which has an essential function in the induction of innate and adaptative immunity. Our aim was to determine what role TLR4 plays in the development of metabolic phenotypes during high-fat feeding. Materials and methods We evaluated metabolic consequences of a high-fat diet in TLR4 mutant mice (C3H/HeJ) and their respective controls. Results TLR4 inactivation reduced food intake without significant modification of body weight, but with higher epididymal adipose tissue mass and adipocyte hypertrophy. It also attenuated the inflammatory response and increased glucose transport and the expression levels of adiponectin and lipogenic markers in white adipose tissue. In addition, TLR4 inactivation blunted insulin resistance induced by lipopolysaccharide in differentiated adipocytes. Increased feeding efficiency in TLR4 mutant mice was associated with lower mass and lower expression of uncoupling protein 1 gene in brown adipose tissue. Finally, TLR4 inactivation slowed the development of hepatic steatosis, reducing the liver triacylglycerol content and also expression levels of lipogenic and fibrosis markers. Conclusions/interpretation TLR4 influences white adipose tissue inflammation and insulin sensitivity, as well as liver fat storage, and is important in the regulation of metabolic phenotype during a fat-enriched diet.
We developed a positron intraoperative probe with high sensitivity dedicated to real-time assessment of the resection margins of tumors and control of the surgical cavity. Its main limitation comes ...from the annihilation photon background generated by distal non-specific radiotracer uptakes. This study is a proof of concept for a dual-scintillator intraoperative probe with background subtraction capability. It associates a highly p-terphenyl β-sensitive scintillator and a highly γ-sensitive LYSO:Ce. Both scintillator are readout by a single pixelated photodetector based on SiPMs and the shape and intensity of the light distribution is used to identify in which scintillator the interactions occurred to allow further discrimination of the signals and subsequent quantification of this background can be utilized to have it subtracted from the raw images. We describe in this study the design of the probe and the analysis to achieve this identification with a good accuracy. An average efficiency of events identification of 97.90 ± 0.06% is reported on the whole field of view.
•Intraoperative positron imaging probe with gamma-ray background subtraction.•Subtraction based on the stack of two scintillators readout by a single photodetector.•Scintillator discrimination based on the light distribution.
Vectorized internal radiotherapy is an efficient modality for cancer treatment but requires a personalized dosimetry to adapt the administered dose for each patient, in order to limit the toxicity to ...organs-at-risk and maximize therapeutic effects. This can be done by performing quantitative imaging of the target organ with high resolution γ-imaging devices in order to evaluate the uptake and biokinetics of the radiotracer. We developed a high-resolution portable γ-camera with a 10 × 10 cm2 field of view dedicated to thyroid imaging during diseases treatments with 131I. In addition to the optimization of the detection elements, the quality of the images also depends on the implementation of efficient methods to reconstruct the interaction position of gamma rays in the monolithic scintillator from the measurement of the scintillation light distribution. We present here the results obtained with two different machine learning methods based on experimental data for reconstruction of the γ-rays interaction position. Those methods reach high spatial performances such as millimeter spatial resolution and submillimeter distortion in the center of the field of view.
Prompted by intriguing events observed in certain particle-physics searches for rare events, we study light and acoustic emission simultaneously in some inorganic scintillators subject to mechanical ...stress. We observe mechanoluminescence in Bi4Ge3O12, CdWO4, and ZnWO4, in various mechanical configurations at room temperature and ambient pressure. We analyze the temporal and amplitude correlations between the light emission and the acoustic emission during fracture. A novel application of the precise energy calibration of Bi4Ge3O12 provided by radioactive sources allows us to deduce that the fraction of elastic energy converted to light is at least 3×10(-5).
Implantable CMOS pixel sensor for positron imaging in rat brain Heymes, J.; Ammour, L.; Bautista, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2018, Letnik:
911
Journal Article
Recenzirano
Odprti dostop
IMIC is a Monolithic Active Pixel Sensor prototype designed for the MAPSSIC project, which aims at developing wireless intracerebral probes dedicated to image positron-emitting source activity in the ...brain of awake and freely moving rats. Former experiments with the PIXSIC positron probe based on a passive sensor have validated the proof of concept, but have also shown limitations with regards to the probe robustness and to its transparency to annihilation photons. The IMIC circuit features a matrix of 16 × 128 active pixels of 30 × 50 µm2 size and targets to overcome the PIXSIC probe drawbacks by exploiting a thin sensitive layer of 18 µm, still featuring an overall thickness close to 300 µm. Additionally, by using a low power (55 nW/pixel) in-pixel front-end architecture providing binary output, IMIC solves the challenge of implanting an active sensor in tissues where overheating is forbidden.
The needle-shaped sensor 610 µm × 12000 µm was fabricated and tested in laboratory. The whole sensor dissipates 160 µW and its imaging capabilities were asserted with various sources: 55Fe, 90Sr and 18F. These tests also demonstrated robust count-rate measurement with IMIC in the range 10–1000 counts/matrix/s. Finally, a dedicated setup qualitatively confirmed excellent in-sensitivity to 511 keV γ-rays.
In this paper, we present the sensor requirements and its detailed design. We also discuss the first characterisation results and the outlook for the integration of IMIC into an implantable probe.
This article reports on the design and features of a very compact and light gamma camera based on SiPMarrays and miniaturized readout electronics dedicated to tumor localization during radio-guided ...cancersurgery. This gamma camera, called MAGICS, is composed of four (2x2) photo-detection elementarymodules coupled to an inorganic scintillator. The 256 channels photo-detection system covers a sensitivearea of 54x53 m^2. Each elementary module is based on four (2x2) SiPM monolithic arrays, each arrayconsisting of 16 SiPM photo-sensors (4x4) with3x3 mm^2 sensitive area, coupled to a miniaturizedreadout electronics and a dedicated ASIC. The overall dimensions of the electronics fit the size of thedetector, enabling to assemble side-by-side several elementary modules in a close-packed arrangement.The preliminary performances of the system are very encouraging, showing an energy resolution of 9.8%and a spatial resolution of less than 1 mm at 122 keV.
A new design of a cryogenic germanium detector for dark matter search is presented, taking advantage of the coplanar grid technique of event localisation for improved background discrimination. ...Experiments performed with prototype devices in the EDELWEISS II setup at the Modane underground facility demonstrate the remarkably high efficiency of these devices for the rejection of low-energy β, approaching 105. This opens the road to investigate the range beyond 10−8 pb in the WIMP–nucleon collision cross-sections, as proposed in the EURECA project of a one-ton cryogenic detector mass.
The EDELWEISS-II Collaboration has performed a direct search for WIMP dark matter with an array of ten 400 g heat-and-ionization cryogenic detectors equipped with interleaved electrodes for the ...rejection of near-surface events. Six months of continuous operation at the Laboratoire Souterrain de Modane have been achieved. The observation of one nuclear recoil candidate above 20 keV in an effective exposure of 144 kg d is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 1.0×10−7 pb is excluded at 90% CL for a WIMP mass of 80 GeV/c2. This result demonstrates for the first time the very high background rejection capabilities of these simple and robust detectors in an actual WIMP search experiment.
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