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131دورية أكاديمية
المؤلفون: Daed El Safadi, Grégorie Lebeau, Alisé Lagrave, Julien Mélade, Lauriane Grondin, Sarah Rosanaly, Floran Begue, Mathilde Hoareau, Bryan Veeren, Marjolaine Roche, Jean-Jacques Hoarau, Olivier Meilhac, Patrick Mavingui, Philippe Desprès, Wildriss Viranaïcken, Pascale Krejbich-Trotot
المصدر: Viruses, Vol 15, Iss 2, p 364 (2023)
مصطلحات موضوعية: flavivirus, Dengue, Zika, NS1, exosome, viral toxin vectorization, Microbiology, QR1-502
الوصف: Extracellular vesicles (EVs), produced during viral infections, are of emerging interest in understanding infectious processes and host–pathogen interactions. EVs and exosomes in particular have the natural ability to transport nucleic acids, proteins, and other components of cellular or viral origin. Thus, they participate in intercellular communication, immune responses, and infectious and pathophysiological processes. Some viruses are known to hijack the cell production and content of EVs for their benefit. Here, we investigate whether two pathogenic flaviviruses i.e., Zika Virus (ZIKV) and Dengue virus (DENV2) could have an impact on the features of EVs. The analysis of EVs produced by infected cells allowed us to identify that the non-structural protein 1 (NS1), described as a viral toxin, is associated with exosomes. This observation could be confirmed under conditions of overexpression of recombinant NS1 from each flavivirus. Using different isolation methods (i.e., exosome isolation kit, size exclusion chromatography, Polyethylene Glycol enrichment, and ELISA capture), we showed that NS1 was present as a dimer at the surface of excreted exosomes, and that this association could occur in the extracellular compartment. This finding could be of major importance in a physiological context. Indeed, this capacity of NS1 to address EVs and its implication in the pathophysiology during Dengue or Zika diseases should be explored. Furthermore, exosomes that have demonstrated a natural capacity to vectorize NS1 could serve as useful tools for vaccine development.
وصف الملف: electronic resource
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132دورية أكاديمية
المؤلفون: Oumar Ndiaye, Cheikh Tidiane Diagne, Ahmed Abd El Wahed, Fatou Dia, Moussa Dia, Adama Faye, Silvania Da Veiga Leal, Menilita dos Santos, Maria da Luz de Lima Mendonça, Carolina Cardoso da Silva Leite, Cheikh Saad Bouh Boye, Juliet E. Bryant, Philippe Desprès, Ousmane Faye, Amadou Alpha Sall, Oumar Faye
المصدر: Diagnostics, Vol 13, Iss 3, p 462 (2023)
مصطلحات موضوعية: Zika, diagnostics, ELISA, recombinant, antigen, envelope, Medicine (General), R5-920
الوصف: Zika virus (ZIKV) diagnostics are crucial for proper antenatal and postnatal care and also for surveillance and serosurvey studies. Since the viremia during ZIKV infection is fleeting, serological testing is highly valuable to inform diagnosis. However, current serology tests using whole virus antigens frequently suffer from cross reactivity issues, delays, and technical complexity, especially in low and middle income countries (LMICs) and endemic countries. Here, we describe an indirect ELISA to detect specific IgG antibodies using the ZIKV envelope domain III (EDIII) protein expressed in Drosophila S2 cells as an immunogen. Using a total of 367 clinical samples, we showed that the EDIII-ELISA was able to detect IgG antibodies against ZIKV with high sensitivity of 100.0% and specificity of 94.7% when compared to plaque reduction neutralization tests (PRNTs) as the gold standard and using 0.208 as the cut-off OD value. These results show the usefulness of the recombinant envelope domain III as an alternative to standard whole virus proteins for ZIKV diagnostics as it improves the sensitivity and specificity of IgG ELISA assay when used as an immunogen. This method should, therefore, be extended to serological diagnostic techniques for other members of the flavivirus genus and for use in IgM diagnostic testing.
وصف الملف: electronic resource
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133
المؤلفون: Philippe Després, Bruce H. Hasegawa, Mingshan Sun, Sven Prevrhal
المصدر: SPIE Proceedings.
مصطلحات موضوعية: Tomographic reconstruction, business.industry, Computer science, Graphics hardware, Fast Fourier transform, Computer programming, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, Parallel computing, Application-specific integrated circuit, Computer data storage, Graphics, Field-programmable gate array, business, ComputingMethodologies_COMPUTERGRAPHICS
الوصف: Graphics processing units (GPUs) are increasingly used for general purpose calculations. Their pipelined architecture can be exploited to accelerate various parallelizable algorithms. Medical imaging applications are inherently well suited to benefit from the development of GPU-based computational platforms. We evaluate in this work the potential of GPUs to improve the execution speed of two common medical imaging tasks, namely Fourier transforms and tomographic reconstructions. A two-dimensional fast Fourier transform (FFT) algorithm was GPU-implemented and compared, in terms of execution speed, to two popular CPU-based FFT routines. Similarly, the Feldkamp, David and Kress (FDK) algorithm for cone-beam tomographic reconstruction was implemented on the GPU and its performance compared to a CPU version. Different reconstruction strategies were employed to assess the performance of various GPU memory layouts. For the specific hardware used, GPU implementations of the FFT were up to 20 times faster than their CPU counterparts, but slower than highly optimized CPU versions of the algorithm. Tomographic reconstructions were faster on the GPU by a factor up to 30, allowing 256 3 voxel reconstructions of 256 projections in about 20 seconds. Overall, GPUs are an attractive alternative to other imaging-dedicated computing hardware like application-specific integrated circuits (ASICs) and field programmable gate arrays (FPGAs) in terms of cost, simplicity and versatility. With the development of simpler language extensions and programming interfaces, GPUs are likely to become essential tools in medical imaging.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::0639fd5a7033db2f2c8b72575f15e12a
https://doi.org/10.1117/12.709994 -
134
المؤلفون: Philippe Després, Bruce H. Hasegawa, E.W. Izaguirre, Kanai S. Shah, M.F. Wendland, Leonard J. Cirignano, Hadong Kim, Siyuan Liu
المصدر: 2007 IEEE Nuclear Science Symposium Conference Record.
مصطلحات موضوعية: Physics, Photomultiplier, medicine.diagnostic_test, business.industry, Preamplifier, Detector, Magnetic resonance imaging, Single-photon emission computed tomography, equipment and supplies, Particle detector, Optics, Nuclear magnetic resonance, Positron emission tomography, medicine, business, Image resolution
الوصف: Multimodality imaging is increasingly relevant in many clinical and preclinical fields. PET/CT and SPECT/CT studies, for instance, generally provide more information than the same imaging modalities taken separately. This synergistic effect, obtained by combining anatomical and functional information, also would be desirable for magnetic resonance imaging (MRI), a nonionizing modality that provides excellent spatial resolution and soft-tissue contrast. The development of a PET/MRI or SPECT/MRI system however represents a significant technological challenge, in part due to the effect of the strong MRI magnetic field on the PET/SPECT detection subsystem. This environment complicates the use of photomultiplier tubes (PMTs) and rather favors solid-state detection technologies. As a proof of principle, we have studied the behavior of a MR-compatible CdZnTe (CZT) detector, a room-temperature semiconductor already used in some SPECT systems. The detector, made from a single 5x5x2 mm3 CZT crystal, was coupled to a Cremat CR-110 preamplifier with nonmagnetic connectors. The whole detector/preamplifier assembly was tested within a static magnetic field while the radiation detector electronics remained outside the magnet room. We measured the energy resolution of the detector from 57Co spectra both inside and outside the magnet. The results suggest that the static magnetic field does not affect the energy resolution of the CZT detector, making it a good candidate for the development of a MRI device combining a nuclear medicine imaging subsystem.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::92551974ffd8a3770d7994ca5d8f251b
https://doi.org/10.1109/nssmic.2007.4437072 -
135دورية أكاديمية
المؤلفون: Fenia D. Ramiharimanana, Juliano G. Haddad, Maminiaina A. Andrianavalonirina, Cécile Apel, Florent Olivon, Nicolas Diotel, Philippe Desprès, Voahangy Vestalys Ramanandraibe, Chaker El Kalamouni
المصدر: Pharmaceuticals, Vol 15, Iss 12, p 1500 (2022)
مصطلحات موضوعية: Stenocline ericoides, Stenocline inuloides, dengue virus, zika virus, antiviral activity, molecular networking, Medicine, Pharmacy and materia medica, RS1-441
الوصف: Dengue and Zika viruses are identified as the most medically important arthropod-borne viral pathogens. Over the past 20 years, the global dengue incidence has dramatically increased with epidemics of severe dengue where the case fatality rate can reach up to 20% in untreated patients. The association between Zika virus infection and severe congenital anomalies was first reported in 2015. Today no specific antiviral therapies are available for dengue and Zika virus infections, accentuating the need of adapted antiviral strategies based on medicinal plant drug discovery. Plants are a potential source of antiviral phytocompounds which act primarily by blocking virus entry in the host-cell. In the present study, we evaluated whether crude extracts from Stenocline ericoides DC. and Stenocline inuloides DC., two endemic plants from Madagascar, may have antiviral effects against dengue and Zika viruses. We showed that S. ericoides has virucidal action whereas S. inuloides inhibits the early steps of virus infection with a non-cytotoxic effect in human cells. The administration of S. ericoides and S. inuloides extracts in zebrafish had no effect on the behavior of animals at the active doses against dengue and Zika viruses, suggesting the absence of adverse effects at these doses. LC-HRMS2 and molecular networking analyses revealed the richness of these two plants in polyphenols and flavonoid with the presence of clusters of phytocompounds specific to each Stenocline species. Consequently, S. ericoides and S. inuloides represent potential sources for natural and safe antiviral phytocompounds against flaviviruses of medical concern.
وصف الملف: electronic resource
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136
المصدر: Medical physics. 33(5)
مصطلحات موضوعية: Equipment Failure Analysis, Tomography, Emission-Computed, Single-Photon, Phantoms, Imaging, Animals, Computer-Aided Design, Reproducibility of Results, Equipment Design, Image Enhancement, Sensitivity and Specificity
الوصف: Single photon emission computed tomography (SPECT) is an important technology for molecular imaging studies of small animals. In this arena, there is an increasing demand for high performance imaging systems that offer improved spatial resolution and detection efficiency. We have designed a multipinhole small animal imaging system based on position sensitive avalanche photodiode (PSAPD) detectors with the goal of submillimeter spatial resolution and high detection efficiency, which will allow us to minimize the radiation dose to the animal and to shorten the time needed for the imaging study. Our design will use 8 x 24 mm2 PSAPD detector modules coupled to thallium-doped cesium iodide [CsI(Tl)] scintillators, which can achieve an intrinsic spatial resolution of 0.5 mm at 140 keV. These detectors will be arranged in rings of 24 modules each; the animal is positioned in the center of the 9 stationary detector rings which capture projection data from the animal with a cylindrical tungsten multipinhole collimator. The animal is supported on a bed which can be rocked about the central axis to increase angular sampling of the object. In contrast to conventional SPECT pinhole systems, in our design each pinhole views only a portion of the object. However, the ensemble of projection data from all of the multipinhole detectors provide angular sampling that is sufficient to reconstruct tomographic data from the object. The performance of this multipinhole PSAPD imaging system was simulated using a ray tracing program that models the appropriate point spread functions and then was compared against the performance of a dual-headed pinhole SPECT system. The detection efficiency of both systems was simulated and projection data of a hot rod phantom were generated and reconstructed to assess spatial resolution. Appropriate Poisson noise was added to the data to simulate an acquisition time of 15 min and an activity of 18.5 MBq distributed in the phantom. Both sets of data were reconstructed with an ML-EM reconstruction algorithm. In addition, the imaging performance of both systems was evaluated with a uniformity phantom and a realistic digital mouse phantom. Simulations show that our proposed system produces a spatial resolution of 0.8 mm and an average detection efficiency of 630 cps/MBq. In contrast, simulations of the dual-headed pinhole SPECT system produce a spatial resolution of 1.1 mm and an average detection efficiency of 53 cps/MBq. These results suggest that our novel design will achieve high spatial resolution and will improve the detection efficiency by more than an order of magnitude compared to a dual-headed pinhole SPECT system. We expect that this system can perform SPECT with submillimeter spatial resolution, high throughput, and low radiation dose suitable for in vivo imaging of small animals.
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137
المؤلفون: Philippe Després, Jacques A. de Guise, Gilles Beaudoin, Pierre Gravel
المصدر: Physics in medicine and biology. 51(10)
مصطلحات موضوعية: Computer science, Information Storage and Retrieval, Image processing, Sensitivity and Specificity, Imaging phantom, Signal-to-noise ratio, Contrast-to-noise ratio, Region of interest, Humans, Radiology, Nuclear Medicine and imaging, Computer vision, Image resolution, Image restoration, Radiological and Ultrasound Technology, business.industry, Phantoms, Imaging, Detector, Reproducibility of Results, Signal Processing, Computer-Assisted, Filter (signal processing), Radiographic Image Enhancement, Radiographic Image Interpretation, Computer-Assisted, Deconvolution, Artificial intelligence, business, Algorithms
الوصف: We have developed a restoration method for radiographs that enhances image sharpness and reveals bone microstructures that were initially hidden in the soft-tissue glare. The method is two fold: the image is first deconvolved using the Richardson-Lucy algorithm and is then divided with a signal modelling the soft-tissue distribution to increase the overall contrast. Each step has its own merits but the power of the restoration method lies in their combination. The originality of the method is its reliance on a priori information at each step in the processing. We have measured and modelled analytically the point-spread function of a low-dose gas microstrip x-ray detector at several beam energies. We measured the relationship between the local image intensity and the noise variance for these images. The soft-tissue signal was also modelled using a minimum-curvature filtering technique. These results were then combined into an image deconvolution procedure that uses wavelet filtering to reduce restoration noise while keeping the enhanced small-scale features. The method was applied successfully to images of a human-torso phantom and improved the contrast of small details on the bones and in the soft tissues. We measured a mean 54% increase in signal to noise ratio and a mean 105% increase in contrast to noise ratio in the 70 and 140 kVp images we analysed. The method was designed to facilitate the analysis of radiographs by relying on two levels of visual inspection. The contrast of the full image is first enhanced by division with the signal modelling the soft-tissue distribution. Based on the result, a radiologist might decide to zoom in on a given image section. The full restoration method is then applied to that region of interest. Indeed, full image deconvolution is often unnecessary since enhanced small-scale details are not visible at large scale; only the section of interest is processed which is more efficient.
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138
المؤلفون: Kanai S. Shah, Tobias Funk, Philippe Després, Bruce H. Hasegawa, William C. Barber, M. McClish
المصدر: IEEE Nuclear Science Symposium Conference Record, 2005.
مصطلحات موضوعية: Physics, Photomultiplier, medicine.diagnostic_test, business.industry, Amplifier, Detector, Scintillator, Single-photon emission computed tomography, Avalanche photodiode, Optics, Medical imaging, medicine, business, Image resolution
الوصف: Single photon emission computed tomography (SPECT) is a widely used medical imaging technique, both for clinical (human) and preclinical (small animal) use to obtain in vivo functional information. Recently, effort has been devoted to the development of solid state detectors for scintillation cameras because they are lighter, smaller, and more reliable than the photomultiplier tubes (PMTs) commonly used. However, a significant disadvantage of most solid state detectors is that they require pixellization to produce position resolution, which greatly increases the number of amplifier channels and the cost of a detector with a large enough area for medical imaging. New position sensitive avalanche photodiodes (PSAPDs) can produce submillimeter position resolution over a relatively wide area with a small number of amplifier channels and therefore have the potential to replace PMTs in scintillator based gamma-ray detectors for medical imaging. PSAPDs have recently demonstrated good properties for clinical SPECT applications however submillimeter spatial resolution is desirable for preclinical use. We therefore have built and tested a detector constructed with a finely segmented cesium-iodide scintillator coupled to a PSAPD. The PSAPD detector uses only five amplifier channels and yet demonstrated 0.74 mm spatial resolution over a 64 mm/sup 2/ active area, with good efficiency, for /sup 99m/Tc imaging. These measurements indicate that PSAPDs coupled to segmented scintillators offer excellent performance for preclinical SPECT applications.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::5065a917cc38494a45a092da35962414
https://doi.org/10.1109/nssmic.2005.1596810 -
139
المؤلفون: Philippe Després, Bruce H. Hasegawa, William C. Barber, Kanai S. Shah, Tobias Funk, M. McClish
المصدر: IEEE Nuclear Science Symposium Conference Record, 2005.
مصطلحات موضوعية: Physics, Resistive touchscreen, Photomultiplier, Physics::Instrumentation and Detectors, business.industry, Distortion (optics), Avalanche photodiode, Multiplexing, law.invention, Charge sharing, Optics, law, Resistor, business, Gamma camera
الوصف: Position-sensitive avalanche photodiodes (PSAPDs) are a promising alternative to photomultiplier tubes for the development of a new generation of gamma-ray imagers. They are compact solid-state devices that provide high quantum efficiency and gain, and they can achieve precise positioning over relatively large surfaces with few readout channels. This key feature is obtained by Anger-logic event positioning from the signals of four corner anodes printed on a resistive layer covering one of the PSAPD surface. This readout scheme provides high degree of multiplexing for reading position and energy information from the device, but leads to pincushion distortion in the spatial information due to the nonlinear charge sharing pattern associated with the potential across the resistive layer. We have developed a method to reproduce and correct this distortion based on finite-element simulations of the readout configuration. The resistive layer and the anodes are represented by a two-dimensional array of resistors and this circuit is numerically solved to obtain the signal on the four anodes for different current injection nodes. The relation between the injection positions and the resulting Anger positions is modeled and then used to correct nonlinearities in events positions obtained experimentally. The algorithm was tested on 99mTc flood images of a 16times16 array of 0.4times0.4times4 mm3 CsI(TI) crystals and successfully restored the regular pattern. The correction procedure is fast and robust, and constitutes a step toward the realization of a low-cost, high-resolution gamma camera based on PSAPDs
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::007956114b63dc6d090b10a4b03838b3
https://doi.org/10.1109/nssmic.2005.1596732 -
140
المؤلفون: Philippe Després, Bruce H. Hasegawa, Junqiang Li, Tobias Funk, B.E. Pratt, Yong Huang, E.W. Izaguirre, Mingshan Sun, K.B. Parnham, T. Vandehei
المصدر: 2006 IEEE Nuclear Science Symposium Conference Record.
مصطلحات موضوعية: Physics, Pixel, business.industry, Detector, Imaging phantom, law.invention, Cadmium zinc telluride, chemistry.chemical_compound, Optics, chemistry, law, Pinhole camera, Pinhole (optics), business, Image resolution, Gamma camera
الوصف: Small animal microSPECT systems require high resolution and efficiency to faithfully image biodistributions of molecular reporters and radiopharmaceuticals in a short time. Because of their variable magnification, pinhole and multipinhole cameras are particularly well suited for small animal imaging systems. These cameras nonetheless require a high degree of sampling to achieve high resolution in tomographic images. In order to construct a high resolution pinhole and multipinhole gamma camera for small animal imaging, we developed a large cadmium zinc telluride (CZT) detector array. This detector, having 128times128 1.5times1.5 mm2 pixels, is one of the largest of its kind in terms of number of pixels and readout channels. The CZT detector crystal array and application-specific integrate circuits (ASICs) are embedded in an aluminum enclosure to form a compact cassette unit. The signals generated by gamma interactions in the CZT crystal are amplified, shaped and multiplexed within the detector unit, and thereafter read by a computer-based data acquisition system. A high-energy keel edge pinhole collimator was coupled to this detector and used to image photons with energies up to 250 keV. This new CZT gamma detector was characterized using Tc-99m (140 keV) and In-111 (171 keV and 245 keV). Specifically, we measured the dead pixel fraction, the uniformity, the intrinsic spatial resolution, and the energy resolution of this detector. Furthermore, we assessed the sensitivity of the pinhole camera. The detector was shown to have fewer than 1% of dead pixels, and also demonstrated energy resolutions of 6.8 % at 140keV (Tc-99m), 6.2 % at 171 keV, and 6.0 % at 245 keV (In-111). Using a microsphere phantom at 3 cm from a 0.5 mm pinhole, a sensitivity of 20 cps/MBq (Tc-99m) was achieved. This new detector will be integrated into our recently developed microSPECT/microCT small animal scanner to increase the overall system sensitivity and image resolution.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::75e1a23c98b950e6d5650b47dac3f478
https://doi.org/10.1109/nssmic.2006.353823
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