A compact data acquisition system for TOHR multidetectors: time encoding for both time and energy measurements

IP

PIXSIC: a Pixellated Radiosensitive Intracerebral Beta Microprobe Allowing the Kinetics Measurements of Radiotracer on Awake and Fully Freely Moving Small Animals

The emergence of new animal models that mimic human disorders enables new fundamental and therapeutical approaches of these diseases. The increasing number of studies on animal models implies the development of new imaging tools adapted to the particular constraints of small animal studies. To that aim, the past few years have seen the development of numerous high resolution PET systems having a sensitivity and a spatial resolution well suited to the small animal imaging. Nevertheless, although these systems have already and extensively demonstrated their interest in the biomedical imaging field, they suffer from a few drawbacks (low temporal resolution, animal immobilization, high cost) that have stimulated the development of complementary approaches. In that particular context, our objective is to develop a beta radiosensitive probe surgically implantable in an animal brain that can measure autonomously the variation of injected radioactivity in a small tissue volume (typically a few mm3) on awake and freely moving animals. To reach that aim, the detector and its acquisition system must be entirely worn by the animal without wires except on the animal itself. This means to design a beta sensitive detector of very small size based on a technology that allows to produce a numerical signal compatible with the use of a telemetric system. This also means to develop a detector compact enough to be fixed on the rodent head without altering the animal movements. Moreover, the whole system must be allow the implantation of at least two probes in order to be able to measure on same animal, specific and non-specific binding rates of a radiotracer. Theoretical and experimental investigations carried out to demonstrate the feasibility of such a detector will be presented. On this basis, first architecture of the detector based on pixellated Si sensor technology will be proposed and detailed

PIXSIC: A Pixellated Beta-Microprobe for Kinetic Measurements of Radiotracers on Awake and Freely Moving Small Animals

We present a design study of PIXSIC, a new B^+ radiosensitive microprobe implantable in rodent brain dedicated to in vivo and autonomous measurements of local time activitycurves of beta radiotracers in a small (a few mm^3 ) volume of brain tissue. This project follows the initial β microprobe previously developed at IMNC, which has been validated in several neurobiological experiments. This first prototype has been extensively used on anesthetized animals, but presents some critical limits for utilization on awake and freely moving animals. Consequently, we propose to develop a wireless setup that can be worn by an animal without constraints upon its movements. To that aim, we have chosen a Silicon-based detector, highly β sensitive, which allows for the development of a compact pixellated probe (typically 600 X 200 X1000 μm^3), read out with miniaturized wireless electronics. Using Monte-Carlo simulations, we show that high resistive Silicon pixels are appropriate for this purpose, assuming that the pixel dimensions are adapted to our specific signals. More precisely, a tradeoff has to be found between the sensitivity to β^+ particles and to the 511 keV γ background resulting from annihilations of β^+ with electrons. We demonstrate that pixels with maximized surface and minimized thickness can lead to an optimization of their β^+ sensitivity with a relative transparency to the annihilation backgroun

Radio-imageurs a haute et tres haute resolution pour la biologie moleculaire

SIGLEINIST AR 13562 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

In vivo quantification of localized neuronal activation and inhibition in the rat brain using a dedicated high temporal-resolution β(+)-sensitive microprobe

Understanding brain disorders, the neural processes implicated in cognitive functions and their alterations in neurodegenerative pathologies, or testing new therapies for these diseases would benefit greatly from combined use of an increasing number of rodent models and neuroimaging methods specifically adapted to the rodent brain. Besides magnetic resonance (MR) imaging and functional MR, positron-emission tomography (PET) remains a unique methodology to study in vivo brain processes. However, current high spatial-resolution tomographs suffer from several technical limitations such as high cost, low sensitivity, and the need of restraining the animal during image acquisition. We have developed a β(+)-sensitive high temporal-resolution system that overcomes these problems and allows the in vivo quantification of cerebral biochemical processes in rodents. This β-MICROPROBE is an in situ technique involving the insertion of a fine probe into brain tissue in a way very similar to that used for microdialysis and cell electrode recordings. In this respect, it provides information on molecular interactions and pathways, which is complementary to that produced by these technologies as well as other modalities such as MR or fluorescence imaging. This study describes two experiments that provide a proof of concept to substantiate the potential of this technique and demonstrate the feasibility of quantifying brain activation or metabolic depression in individual living rats with 2-[(18)F]fluoro-2-deoxy-d-glucose and standard compartmental modeling techniques. Furthermore, it was possible to identify correctly the origin of variations in glucose consumption at the hexokinase level, which demonstrate the strength of the method and its adequacy for in vivo quantitative metabolic studies in small animals

Determinants of SARS-CoV-2 infection in Italian healthcare workers: a multicenter study

Healthcare workers (HCWs) are at increased risk of being infected with SARS-CoV-2, yet limited information is available on risk factors of infection. We pooled data on occupational surveillance of 10,654 HCW who were tested for SARS-CoV-2 infection in six Italian centers. Information was available on demographics, job title, department of employment, source of exposure, use of personal protective equipment (PPEs), and COVID-19-related symptoms. We fitted multivariable logistic regression models to calculate odds ratios and 95% confidence intervals of infection. The prevalence of infection ranged from 3.0 to 22.0%, and was correlated with that of the respective areas. Women were at lower risk of infection compared to men. Fever, cough, dyspnea and malaise were the symptoms most strongly associated with infection, together with anosmia and ageusia. No differences in the risk of infection were detected according to job title, or working in a COVID-19 designated department. Reported contact with a patient inside or outside the workplace was a risk factor. Use of a mask was strongly protective against risk of infection as was use of gloves. The use of a mask by the source of exposure (patient or colleague) had an independent effect in reducing infection risk