2,558 research outputs found

    Reduction of cone‚Äźbeam CT artifacts in a robotic CBCT device using saddle trajectories with integrated infrared tracking

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    International audienceAbstract Background Cone beam computed tomography (CBCT) is widely used in many medical fields. However, conventional CBCT circular scans suffer from cone beam (CB) artifacts that limit the quality and reliability of the reconstructed images due to incomplete data. Purpose Saddle trajectories in theory might be able to improve the CBCT image quality by providing a larger region with complete data. Therefore, we investigated the feasibility and performance of saddle trajectory CBCT scans and compared them to circular trajectory¬†scans. Methods We performed circular and saddle trajectory scans using a novel robotic CBCT scanner (Mobile ImagingRing (IRm); medPhoton, Salzburg, Austria). For the saddle trajectory, the gantry executed yaw motion up to using motorized wheels driving on the floor. An infrared (IR) tracking device with reflective markers was used for online geometric calibration correction (mainly floor unevenness). All images were reconstructed using penalized least‚Äźsquares minimization with the conjugate gradient algorithm from RTK with voxel size. A disk phantom and an Alderson phantom were scanned to assess the image quality. Results were correlated with the local incompleteness value represented by , which was calculated at each voxel as a function of the source trajectory and the voxel's 3D coordinates. We assessed the magnitude of CB artifacts using the full width half maximum (FWHM) of each disk profile in the axial center of the reconstructed images. Spatial resolution was also quantified by the modulation transfer function at 10% (MTF10). Results When using the saddle trajectory, the region without CB artifacts was increased from 43 to 190¬†mm in the SI direction compared to the circular trajectory. This region coincided with low values for . When was larger than 0.02, we found there was a linear relationship between the FWHM and . For the saddle, IR tracking allowed the increase of MTF10 from 0.37 to 0.98 lp/mm. Conclusions We achieved saddle trajectory CBCT scans with a novel CBCT system combined with IR tracking. The results show that the saddle trajectory provides a larger region with reliable reconstruction compared to the circular trajectory. The proposed method can be used to evaluate other non‚Äźcircular¬†trajectories

    Objective and subjective evaluation of speech enhancement methods in the UDASE task of the 7th CHiME challenge

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    Supervised models for speech enhancement are trained using artificially generated mixtures of clean speech and noise signals. However, the synthetic training conditions may not accurately reflect real-world conditions encountered during testing. This discrepancy can result in poor performance when the test domain significantly differs from the synthetic training domain. To tackle this issue, the UDASE task of the 7th CHiME challenge aimed to leverage real-world noisy speech recordings from the test domain for unsupervised domain adaptation of speech enhancement models. Specifically, this test domain corresponds to the CHiME-5 dataset, characterized by real multi-speaker and conversational speech recordings made in noisy and reverberant domestic environments, for which ground-truth clean speech signals are not available. In this paper, we present the objective and subjective evaluations of the systems that were submitted to the CHiME-7 UDASE task, and we provide an analysis of the results. This analysis reveals a limited correlation between subjective ratings and several supervised nonintrusive performance metrics recently proposed for speech enhancement. Conversely, the results suggest that more traditional intrusive objective metrics can be used for in-domain performance evaluation using the reverberant LibriCHiME-5 dataset developed for the challenge. The subjective evaluation indicates that all systems successfully reduced the background noise, but always at the expense of increased distortion. Out of the four speech enhancement methods evaluated subjectively, only one demonstrated an improvement in overall quality compared to the unprocessed noisy speech, highlighting the difficulty of the task. The tools and audio material created for the CHiME-7 UDASE task are shared with the community

    High fusion and cytopathy of SARS-CoV-2 variant B.1.640.1

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    International audienceABSTRACT SARS-CoV-2 variants with undetermined properties have emerged intermittently throughout the COVID-19 pandemic. Some variants possess unique phenotypes and mutations which allow further characterization of viral evolution and Spike functions. Around 1,100 cases of the B.1.640.1 variant were reported in Africa and Europe between 2021 and 2022, before the expansion of Omicron. Here, we analyzed the biological properties of a B.1.640.1 isolate and its Spike. Compared to the ancestral Spike, B.1.640.1 carried 14 amino acid substitutions and deletions. B.1.640.1 escaped binding by some anti-N-terminal domain and anti-receptor-binding domain monoclonal antibodies, and neutralization by sera from convalescent and vaccinated individuals. In cell lines, infection generated large syncytia and a high cytopathic effect. In primary airway cells, B.1.640.1 replicated less than Omicron BA.1 and triggered more syncytia and cell death than other variants. The B.1.640.1 Spike was highly fusogenic when expressed alone. This was mediated by two poorly characterized and infrequent mutations located in the Spike S2 domain, T859N and D936H. Altogether, our results highlight the cytopathy of a hyper-fusogenic SARS-CoV-2 variant, supplanted upon the emergence of Omicron BA.1. (This study has been registered at ClinicalTrials.gov under registration no. NCT04750720.) IMPORTANCE Our results highlight the plasticity of SARS-CoV-2 Spike to generate highly fusogenic and cytopathic strains with the causative mutations being uncharacterized in previous variants. We describe mechanisms regulating the formation of syncytia and the subsequent consequences in a primary culture model, which are poorly understood

    Measurement of the prompt D0D^0 nuclear modification factor in ppPb collisions at sNN=8.16\sqrt{s_\mathrm{NN}} = 8.16 TeV

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    International audienceThe production of prompt D0D^0 mesons in proton-lead collisions in the forward and backward configurations at a center-of-mass energy per nucleon pair of sNN=8.16¬†TeV\sqrt{s_\mathrm{NN}} = 8.16~\mathrm{TeV} is measured by the LHCb experiment. The nuclear modification factor of prompt D0D^0 mesons is determined as a function of the transverse momentum pTp_\mathrm{T}, and rapidity in the nucleon-nucleon center-of-mass frame y‚ąóy^*. In the forward rapidity region, significantly suppressed production with respect to pppp collisions is measured, which provides significant constraints of nuclear parton distributions and hadron production down to the very low Bjorken-xx region of ‚ąľ10‚ąí5\sim 10^{-5}. In the backward rapidity region, a suppression with a significance of 2.0 - 3.8 standard deviations compared to nPDF expectations is found in the kinematic region of pT>6¬†GeV/cp_\mathrm{T}>6~\mathrm{GeV}/c and ‚ąí3.25<y‚ąó<‚ąí2.5-3.25<y^*<-2.5, corresponding to x‚ąľ0.01x\sim 0.01

    The LHCb upgrade I

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    International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

    Respiratory multiplex PCR and procalcitonin to reduce antibiotic exposure in severe SARS-CoV-2 pneumonia: a multicenter randomised controlled trial

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    International audienceObjectives: We aimed at assessing the efficacy and safety on antibiotics exposure of a strategy combining a respiratory multiplex PCR (mPCR) with enlarged panel and daily procalcitonin (PCT) measurements, as compared with a conventional strategy, in critically ill adult patients with laboratory-confirmed SARS-CoV-2 pneumonia.Methods: This multicentre, parallel-group, open-label, randomised controlled trial enrolled patients admitted to 13 intensive care units (ICU) in France. Patients were assigned (1:1) to the control strategy, where antibiotic streamlining remained at the discretion of the physicians, or interventional strategy, consisting of using mPCR and daily PCT measurements within the first seven days of randomisation to streamline initial antibiotic therapy, with antibiotic continuation encouraged when PCT was > 1 ng/mL and discouraged if < 1 ng/mL or decreased by 80% from baseline. All patients underwent conventional microbiological tests and cultures. The primary end-point was antibiotic-free days at day 28.Results: Between April 20st and November 23st 2020, 194 patients were randomised, of whom 191 were retained in the intention-to-treat analysis. Respiratory bacterial coinfection was detected in 48.4% (45/93) and 21.4% (21/98) in the interventional and control group, respectively. The number of antibiotic-free days was 12.0 (0.0; 25.0) and 14.0 (0.0; 24.0) days, respectively (difference -2.0, (95% CI -10.6 to 6.6), P=0.89). Superinfection rates were high (51.6% and 48.5%, respectively). Mortality rates and ICU lengths of stay did not differ between groups.Conclusion: In severe SARS-CoV-2 pneumonia, the mPCR/PCT algorithm strategy did not affect 28-day antibiotics exposure nor the major clinical outcomes, as compared with routine practice
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