Structured illumination microscopy using micro-pixellated light-emitting diodes

Structured illumination is a flexible and economical method of obtaining optical sectioning in wide-field microscopy [1]. In this technique the illumination system is modified to project a single-spatial frequency grid pattern onto the sample [2, 3]. The pattern can only be resolved in the focal plane and by recording images for different transverse grid positions (or phases) an image of the in-focus parts of the object can be calculated. Light emitting diodes (LEDs) are becoming increasingly popular for lighting and illumination systems due to their low cost, small dimensions, low coherence, uniform illumination, high efficiency and long lifetime. These properties, together with recent developments in high brightness, ultraviolet operation and microstructured emitter design offer great potential for LEDs as light sources for microscopy. In this paper we demonstrate a novel structured illumination microscope using a blue micro-structured light emitting diode as the illumination source. The system is potentially very compact and has no-moving-parts

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

Phytochemicals as novel agents for the induction of browning in white adipose tissue

Obesity and its associated metabolic syndrome continue to be a health epidemic in westernized societies and is catching up in the developing world. Despite such increases, little headway has been made to reverse adverse weight gain in the global population. Few medical options exist for the treatment of obesity which points to the necessity for exploration of anti-obesity therapies including pharmaceutical and nutraceutical compounds. Defects in brown adipose tissue, a major energy dissipating organ, has been identified in the obese and is hypothesized to contribute to the overall metabolic deficit observed in obesity. Not surprisingly, considerable attention has been placed on the discovery of methods to activate brown adipose tissue. A variety of plant-derived, natural compounds have shown promise to regulate brown adipose tissue activity and enhance the lipolytic and catabolic potential of white adipose tissue. Through activation of the sympathetic nervous system, thyroid hormone signaling, and transcriptional regulation of metabolism, natural compounds such as capsaicin and resveratrol may provide a relatively safe and effective option to upregulate energy expenditure. Through utilizing the energy dissipating potential of such nutraceutical compounds, the possibility exists to provide a therapeutic solution to correct the energy imbalance that underlines obesity

D-dimer Quantification from Autologous Red Blood Cells Agglutination by a Lens-free Imaging Device

International audienceQuantification of biomarkers closest to the patient remains an impressive challenge for the development of personalized medicine. The detection of D-dimer, a fibrin degradation product, indicative of deep vein thrombosis, pulmonary embolism or stroke is a particular biomarker of interest. In this study, we developed a quantitative assay based on the measurement of autologous red blood cells agglutination by a lens-free device. An indicator, obtained from the shape of the gray level histogram of the images, allows us for a linear quantification of D-dimer opening the door for a Point-of-Care device

Laser line scanning illumination scheme for the enhancement of contrast and resolution for fluorescence reflectance imaging

International audienceIntraoperative fluorescence imaging in reflectance geometry is an attractive imaging modality as it allows to noninvasively monitor fluorescence targeted tumors located below the tissue surface. The drawbacks of this technique are the poor resolution in the axial and lateral directions due to multiple light scattering and background fluorescence decreasing the contrast. We propose a novel fluorescence imaging method based on laser line illumination in reflectance geometry. We scan the medium with the laser line and acquire images at each position of the line. We then detect only single stripes of each image located on the excitation line or farther from it. We can also subtract the surrounding signal to the detected stripe, the optimal detection scheme depending on the depth of the object of interest. This allows us to reduce the contribution of parasite signals such as background fluorescence or excitation leaks and also enhances the resolution. These operations on the images can either be digitally done in post-processing or can directly be hardware implemented, allowing our method to be integrated in a handheld device for real-time use. This technique has been validated with tissue-like liquid phantoms with different levels of background fluorescence. Fluorescent inclusions are observed in several configurations at depths ranging from 1 mm to 1 cm. Our results are compared to those obtained with a more classical wide-field detection scheme. Finally, we propose a setup to optically implement the masking detection that will dramatically fasten the detection scheme and optimize the fluorescence light throughput of the system

Masked detection of structured illumination (MDSI): depth sensitive fluorescence measurement

International audienceCurrent methodologies for obtaining depth-sensitive contrast information from an optically diffusive medium involve complex hardware and software implementations. In turn, such methods typically lead to long acquisition and long reconstruction times, rendering them impractical for real-time use. In this work, we report preliminary proof-of-concept for a hardware-only method capable of providing depth sensitive contrast information without requiring post acquisition image reconstruction and with rapid acquisition. This method, termed Masked Detection of Structured Illumination (MDSI), relies on physically masking, in the detection arm, the point spread function from a collimated beam illuminating a diffusive medium, to isolate the contribution of the photon path lengths of interest. By continuously scanning and integrating the obtained images, MDSI allows, for the first time, optical depth sectioning of a diffusive medium without any processing

Lecture des tests intradermiques de la tuberculinique par spectroscopie: résultats cliniques

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