54 research outputs found

    Multi-modal image fusion for small animal studies in in-line PET /3T MRI

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    Congrès sous l’égide de la Société Française de Génie Biologique et Médical (SFGBM).National audienceIn the framework of small animal multi-modal imaging, the current progression of the IMAPPI project is illustrated by the design of an in-line PET/MRI prototype, coupled to a dedicated multi-resolution registration method allowing the robust fusion of data coming from both modalities. The first results show a good alignment of the data from tumor imaging at the level of the abdomen

    Temperature dependence of plankton community metabolism in the subtropical and tropical oceans

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    Here we assess the temperature dependence of the metabolic rates (gross primary production (GPP), community respiration (CR), and the ratio GPP/CR) of oceanic plankton communities. We compile data from 133 stations of the Malaspina 2010 Expedition, distributed among the subtropical and tropical Atlantic, Pacific, and Indian oceans. We used the in vitro technique to measured metabolic rates during 24 h incubations at three different sampled depths: surface, 20%, and 1% of the photosynthetically active radiation measured at surface. We also measured the % of ultraviolet B radiation (UVB) penetrating at surface waters. GPP and CR rates increased with warming, albeit different responses were observed for each sampled depth. The overall GPP/CR ratio declined with warming. Higher activation energies (Ea) were derived for both processes (GPPChla = 0.97; CRChla = 1.26; CRHPA = 0.95 eV) compared to those previously reported. The Indian Ocean showed the highest Ea (GPPChla = 1.70; CRChla = 1.48; CRHPA = 0.57 eV), while the Atlantic Ocean showed the lowest (GPPChla = 0.86; CRChla = 0.77; CRHPA = 0.13 eV). We believe that the difference between previous assessments and the ones presented here can be explained by the overrepresentation of Atlantic communities in the previous data sets. We found that UVB radiation also affects the temperature dependence of surface GPP, which decreased rather than increased under high levels of UVB. Ocean warming, which causes stratification and oligotrophication of the subtropical and tropical oceans, may lead to reduced surface GPP as a result of increased penetration of UVB radiation.En prens

    Left-Ventricle Segmentation of SPECT Images of Rats

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    Left-Ventricle Segmentation of SPECT Images of Rats

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    Site-Specific Dual Labeling of Proteins on Cysteine Residues with Chlorotetrazines

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    International audienceDual-labeled biomolecules constitute a new generation of bioconjugates with promising applications in therapy and diagnosis. Unfortunately, the development of these new families of biologics is hampered by the technical difficulties associated with their construction. In particular, the site specificity of the conjugation is critical as the number and position of payloads can have a dramatic impact on the pharmacokinetics of the bioconjugate. Herein, we introduce dichlorotetrazine as a trivalent platform for the selective double modification of proteins on cysteine residues. This strategy is applied to the dual labeling of albumin with a macrocyclic chelator for nuclear imaging and a fluorescent probe for fluorescence imaging

    Performance evaluation of the PET component of a sequential APD-based micro-PET/MR imaging system

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    International audienceThe LabPET/MR imaging system is a new preclinical prototype with sequentially-acquired PET/MR scan capabilities. The dual modality system is composed of a modified APD-based LabPET4 subsystem, coupled with a cryogen-free superconducting 3.0T MRI subsystem. The objective of the study was to characterize the imaging performance of the PET subsystem and identify the change in PET performance due to the presence of the magnetic field. NEMA NU-4-2008 performance characteristics were conducted with the MR subsystem switched ON and OFF. Influence of the temperature was also investigated by repeating selected performance tests. In the ON configuration, the radial/tangential FBP spatial resolution ranged from 1.62 ± 0.08 /1.88 ± 0.08 mm to 2.83 ± 0.11/2.03 ± 0.03 mm at the axial center field of view. The peak absolute sensitivity for an energy window of 250-650 keV was 0.87%. The maximum noise equivalent counting rates were 133 kcps at 3.8 MBq/mL and 25 kcps at 0.4 MBq/mL for the mouse- and rat- like phantoms, respectively. The corresponding scatter fractions were 13% and 23%. No differences could be identified between the ON and OFF configuration, except for a mean loss in peak absolute sensitivity of 5.1 ± 0.5% which was attributed to a mean rise in temperature of 1.2°C when the magnet was ON. Compared with the LabPET standalone scanner, the LabPET/MR imaging prototype is working in a warmer environment and this impacts on the sensitivity of the APD-based LabPET scanner
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