Advanced optical imaging for surgical vision

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UV sensitivity of planktonic net community production in ocean surface waters

The net plankton community metabolism of oceanic surface waters is particularly important as it more directly affects the partial pressure of CO2 in surface waters and thus the air-sea fluxes of CO2. Plankton communities in surface waters are exposed to high irradiance that includes significant ultraviolet blue (UVB, 280-315 nm) radiation. UVB radiation affects both photosynthetic and respiration rates, increase plankton mortality rates, and other metabolic and chemical processes. Here we test the sensitivity of net community production (NCP) to UVB of planktonic communities in surface waters across contrasting regions of the ocean. We observed here that UVB radiation affects net plankton community production at the ocean surface, imposing a shift in NCP by, on average, 50% relative to the values measured when excluding partly UVB. Our results show that under full solar radiation, the metabolic balance shows the prevalence of net heterotrophic community production. The demonstration of an important effect of UVB radiation on NCP in surface waters presented here is of particular relevance in relation to the increased UVB radiation derived from the erosion of the stratospheric ozone layer. Our results encourage design future research to further our understanding of UVB effects on the metabolic balance of plankton communities. Key Points UV sensitivity of planktonic NCP ©2014. American Geophysical Union. All Rights Reserved.This research was funded by the projects RODA (CTM-2004-06842-CO3-O2) and ATOS (POL2006-00550/CTM), Humboldt-2009 project (CTM2008-02497-E), MEDEICG (CTM2009-07013), and the Malaspina-2010 expedition project funded by the CONSOLIDER Ingenio-2010 program (CSD2008-00077), all funded by the National Plan of R + D of the Spanish Ministry of Science and Innovation. A.R.d.G. was supported by the EU Marie Curie EST project Metaoceans (MEST-CT-2005-019678)Peer Reviewe

Effect of properties of metallic foams on stiffness and strength of sandwich beams

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.Includes bibliographical references (leaves 92-93).by Gaël Gioux.S.M

Making sense in surgery using Near-Infrared Optical Imaging

There is a pressing clinical need to provide image guidance during surgery. Currently, assessment of tissue that needs to be resected or avoided is performed subjectively leading to a large number of failures, patient morbidity and increased healthcare cost. Because near-infrared (NIR) light propagates deeply within living tissues and interacts with molecular constituents, it offers unparalleled capabilities for objectively identifying healthy and diseased tissue intraoperatively. These capabilities are well illustrated through the ongoing clinical translation of fluorescence imaging during oncologic surgery. In this presentation, we will review our efforts to provide real-time & wide-field image-guidance during surgery using NIR diffuse optical imaging. We will present our latest results in fluorescence and endogenous imaging towards real-time monitoring and image-guided surgical intervention

Background fluorescence reduction and absorption correction for fluorescence reflectance imaging

International audienceIntraoperative fluorescence imaging in reflectance geometry (FRI) is an attractive imaging modality as it allows to noninvasively monitor the fluorescence targeted tumors located below the tissue surface. Some drawbacks of this technique are the background fluorescence decreasing the contrast and absorption heterogeneities leading to misinterpretations concerning fluorescence concentrations. We presented a FRI technique relying on a laser line scanning instead of a uniform illumination. Here, we propose a correction technique based on this illumination scheme. We scan the medium with the laser line and acquire at each position of the line both fluorescence and excitation images. We then use the finding that there is a relationship between the excitation intensity pro le and the background fluorescence one. This allows us to predict the amount of signal to subtract to the fluorescence images to get a better contrast. As the light absorption information is contained both in fluorescence and excitation images, this method also permits us to correct the eff ects of absorption heterogeneities, leading to a better accuracy for the detection. This technique has been validated on simulations (with a Monte-Carlo code and with the di usion approximation using NIRFAST) and experimentally with tissue-like liquid phantoms with di erent levels of background fluorescence. Fluorescent inclusions are observed in several con gurations at depths ranging from 1 mm to 1 cm. Results obtained with this technique are compared to those obtained with a more classical wide- field detection scheme for the contrast enhancement and to the fluorescence to excitation ratio approach for the absorption correction

Poor correlation between phytoplankton community growth rates and nutrient concentration in the sea

Nutrient availability is one of the major factors regulating marine productivity and phytoplankton community structure. While the response of phytoplankton species to nutrient variation is relatively well known, that of phytoplankton community remains unclear. We question whether phytoplankton community growth rates respond to nutrient concentration in a similar manner to phytoplankton species composing the community, that is, following Monod's model. Data on in situ marine community growth rates in relation to nutrient concentration and the behaviour of a simple multi-species community model suggest that community growth rate does not respond to nutrient concentration according to the Monod equation. Through a simulation study we show this can be explained as a consequence of changes in size structure. Marine biogeochemical models must not parameterize phytoplankton community growth rate response to nutrient concentration using a single Monod equation but rather involve different phytoplankton functional groups each with different equation parameters.Versión del editor3,859

SPAD based imaging of Cherenkov light in radiation therapy

During radiotherapy, X-ray beams induce Cherenkov light emission in tissue as part of the dose delivery. This light can be used for dosimetry, in order to track and image the dose as it happens. The Cherenkov light levels are in the range of 10−6 to 10−9 W∕cm2, which makes it challenging to detect in a clinical environment. However, because the radiation is pulsed in 4 microsecond bursts, time-gated acquisition of the signal allows for robust detection, even in the presence of ambient room lighting. Thus, imaging sensors for this application must be highly sensitive and must be able to time gate faster than a microsecond. In this study, the use of a solid-state detector composed of 64x32 single photon avalanche diodes (SPAD) was examined. The advantages of this technology were intra-chip amplification, superior X-ray noise rejection, and fast temporal gating of the acquisition. The results show that the SPAD camera was sensitive enough to detect Cherenkov radiation despite the 3% fill factor. 2D oversampling (x25) was also used to increase final image resolution to 320x160. In this work we demonstrate the SPAD camera performance in imaging Cherenkov emission from a tissue optical phantom and one patient undergoing radiotherapy. The SPAD camera sensors could be a viable alternative for Cherenkov imaging, as compared to current imaging methods that are mostly focused around image intensifier-based cameras and so have a range of non-linearities and instabilities which could be solved by an all solid-state camera sensor. Please click Additional Files below to see the full abstract

Pancreas-Targeted NIR Fluorophores for Dual-Channel Image-Guided Abdominal Surgery

Objective: Pancreas-related complications are some of the most serious ones in abdominal surgery. The goal of this study was to develop and validate novel near-infrared (NIR) fluorophores that would enable real-time pancreas imaging to avoid the intraoperative pancreatic injury. Design: After initial screening of a large NIR fluorophore library, the performance of 3 selected pancreas-targeted 700 nm NIR fluorophores, T700-H, T700-F, and MB, were quantified in mice, rats, and pigs. Dose ranging using 25 and 100 nmol, and 2.5 μmol of T700-F, and its imaging kinetics over a 4 h period were tested in each species. Three different 800 nm NIR fluorophores were employed for dual-channel FLARE™ imaging in pigs: 2 μmol of ZW800-1 for vessels and kidney, 1 μmol of ZW800-3C for lymph nodes, and 2 μmol of ESNF31 for adrenal glands. Results: T700-F demonstrated the highest signal to background ratio (SBR), with peak SBR at 4 h postinjection in mice. In pigs, T700-F produced an SBR ≥ 2 against muscle, spleen, and lymph nodes for up to 8 h after a single intravenous injection. The combination of T700-F with each 800 nm NIR fluorophore provided simultaneous dual-channel intraoperative imaging of pancreas with surrounding organs in real time. Conclusion: Pancreas-targeted NIR fluorophores combined with the FLARE dual-channel imaging system enable the real-time intraoperative pancreas imaging which helps surgeons perform safer and more curative abdominal surgeries

O impacto do upwelling de Cabo Frio sobre os processos metabólicos do plâncton: revisão bibliográfica

Núcleo de Pesquisa em Biodiversidade Marinha da Universidade de São Paulo (NP-BioMar/USP