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A novel near-field imaging system is proposed and simulated. It is seen that a significant improvement in performance in the presence of noise is possible without loss of resolution.

Molecular contrast in optical coherence tomography (OCT) is demonstrated by use of coherent anti-Stokes Raman scattering (CARS) for molecular sensitivity. Femtosecond laser pulses are focused into a sample by use of a low-numerical-aperture lens to generate CARS photons, and the backreflected CARS signal is interferometrically measured. With the chemical selectivity provided by CARS and the advanced imaging capabilities of OCT, this technique may be useful for molecular contrast imaging in biological tissues. CARS can be generated and interferometrically measured over at least 600 microm of the depth of field of a low-numerical-aperture objective.

Optics has played a key role in the rapidly developing field of molecular imaging. The spectroscopic nature and high-resolution imaging capabilities of light provide a means for probing biological morphology and function at the cellular and molecular levels. While the use of bioluminescent and fluorescent probes has become a mainstay in optical molecular imaging, a large number of other optical imaging modalities exist that can be included in this emerging field. In vivo imaging technologies such as optical coherence tomography and reflectance confocal microscopy have had limited use of molecular probes. In the last few years, novel nonfluorescent and nonbioluminescent molecular imaging probes have been developed that will initiate new directions in coherent optical molecular imaging. Classes of probes reviewed in this work include those that alter the local optical scattering or absorption properties of the tissue, those that modulate these local optical properties in a predictable manner, and those that are detected utilizing spectroscopic optical coherence tomography (OCT) principles. In addition to spectroscopic OCT, novel nonlinear interferometric imaging techniques have recently been developed to detect endogenous molecules. Probes and techniques designed for coherent molecular imaging are likely to improve the detection and diagnostic capabilities of OCT.

Cachexia is a condition marked by decreased appetite and loss of lean body mass that occurs in many states of chronic inflammation. One area of the brain that is likely to be involved in producing the appetite changes associated with cachexia is the brainstem, which receives neural afferent input from the gastro-intestinal tract and sends efferent signals producing responses such as gastroperesis. Because peripheral injection of cytokines produces an anorexic response similar to that seen in cachexia, we set out to investigate whether neurons in brainstem nuclei co-express cytokine receptors and Cocaine and Amphetamine Related Transcript (CART), a potently anorexigenic peptide which is up-regulated during inflammation in other appetite-regulating centers. We performed a double-label in situ hybridization on sections of a single rat brainstem using a digoxinen-labeled probe to CART and a 33P radioactively-labeled probe to the receptor for Leukemic Inhibitory Factor (LIF-R), a cytokine which has been shown to produce a cachexic response. We then analyzed fluorescent cells (CART-labeled) for the number of silver grains that had been exposed inside the cell compared to non-cellular background silver grain levels. We used this information to generate a signal-to background ratio (SBR) for each of the cells. A SBR of greater than 2.5 is generally considered to be good evidence of co-expression. We found that CART and LIF-R were moderately co-expressed in the Area Postrema (AP), which is an important site of afferent synapsing, with 34% of CART-expressing cells having a SBR of 2.5 or greater and 17% of cells having a SBR of 10 or greater. In the lateral reticular nucleus, cells co-expressed to a greater degree to that seen in the AP with 63% of cells having an SBR ≥2.5 and 16% ≥10 SBR. The most striking difference in expression levels were seen between rostral and caudal inferior olivary (IO) nuclei with 87% of cells ≥2.5 SBR and 48% ≥10 SBR in the rostral IO while in the caudal IO only 24% of cells showed co-expression ≥ 2.5 SBR and 0% ≥ 10 SBR. Though the role of CART and LIF-R expression in the IO is unclear, the co-expression in the AP may reflect one way that cytokines can directly stimulate the production of CART, leading to a decrease in feeding response. Experiments are currently underway to analyze the extent of CART and LIF-R co-expression between groups of rats pre-treated with peripheral injections of either saline or lipopolysaccharide to induce cytokine storm. This will help confirm the findings in this abstract and determine whether LIF-R expression increases in response to LPS-induced cytokine cascade.

We present a new interferometric technique for measuring Coherent Anti-Stokes Raman Scattering (CARS) and Second Harmonic Generation (SHG) signals. Heterodyne detection is employed to increase the sensitivity in both CARS and SHG signal detection, which can also be extended to different coherent processes. The exploitation of the mentioned optical nonlinearities for molecular contrast enhancement in Optical Coherence Tomography (OCT) is presented. Numerical simulations for both coherent nonlinear processes are performed in order to determine the properties of the signal expected at the exit of the described nonlinear interferometer., 13 pages, Latex, 10 Postscript figures, uses opex3 style, submitted

Often in imaging systems, the bandpass of the system is not uniform. In temporal coherence imaging methods such as optical coherence tomography, one would like to achieve the most spatially confined impulse response possible with a given source spectrum, minimizing sidelobes that blur adjacent features together. Typically the spectrum of the source is controlled in order to remove sidelobes from the measured interferogram. However, the measured interferogram is not necessarily the best estimate of the scattering density of the object. In this work, a sidelobe supression method is proposed and demonstrated to achieve low sidelobes even with highly nonuniform, non-Gaussian spectra.

We demonstrate in vivo optical coherence tomography using a Fourier-domain optical delay line constructed with a commercially available polygonal scanner. The 20-faceted polygonal mirror array, capable of scanning at rates up to 15 kHz, is implemented at 4 kHz to acquire 500 500 pixel images at 8 framess with a signal-to-noise ratio of 80 dB. Features of this delay line include scalability to high repetition rates, 98.6% linearity in group delay over 2 mm, and bandwidth support exceeding 150 nm. Images are obtained in an animal model Xenopus laevis, and limitations due to phase-delay nonlinearity and polygon asymmetry are discussed. © 2003 Optical Society of America OCIS codes: 110.4500, 120.3180, 120.5800, 170.4500.

The resolution of optical coherence tomography (OCT) often suffers from blurring caused by material dispersion. We present a numerical algorithm for computationally correcting the effect of material dispersion on OCT reflectance data for homogeneous and stratified media. This is experimentally demonstrated by correcting the image of a polydimethyl siloxane microfludic structure and of glass slides. The algorithm can be implemented using the fast Fourier transform. With broad spectral bandwidths and highly dispersive media or thick objects, dispersion correction becomes increasingly important.

We present a simple reconstruction algorithm for three-dimensional (3D) incoherent source distributions imaged by a laterally scanned pinhole camera. We consider digital sampling of multiple pinhole images for 3D reconstruction and implement an experimental demonstration with lateral resolution of 2x10(-3) rad and longitudinal resolution of approximately 0.14z(2) m , where z is the object-to-pinhole distance in meters.

Skeletal muscle mitochondrial dysfunction and insulin resistance occur in chronic kidney disease. Ghrelin is a gastric hormone previously shown to enhance muscle mitochondrial enzyme activities and AKT-mediated insulin signaling independent of food intake in healthy rats. Here we determined the impact of ghrelin treatment on anorexia, skeletal muscle mitochondrial oxidative capacity, AKT phosphorylation as a measure of insulin signaling, and lean body mass in a rat model of chronic kidney disease. Ghrelin infusion promoted higher food intake and lean body mass. Further, although muscle mitochondrial enzyme activities were low in the rats with CKD (chronic kidney disease), they normalized with ghrelin treatment, a change that was consistent with the increase in the transcript levels of regulators of mitochondrial biogenesis and lipid metabolism. This was associated with a lower muscle triglyceride content and higher AKT phosphorylation. Pair-feeding showed that mitochondrial effects of ghrelin are independent of changes in food intake, whereas combined ghrelin treatment and higher food intake were needed to enhance AKT phosphorylation. Thus, ghrelin-induced muscle mitochondrial changes and lower tissue triglycerides could favor insulin action and muscle anabolism in the presence of improvement in food intake. Our study shows that combined effects of ghrelin on appetite and muscle mitochondria improve muscle metabolic and nutritional alterations in chronic kidney disease. This could have potential beneficial impact on patient morbidity and survival.

We developed a theoretical and experimental approach that allows for solving the 3D scattering inverse problem via quantitative phase imaging with broadband fields.

Summary from only given. The advancement of microfabrication techniques has led to increasingly complex microfluidic and bioMEM (biological micro electromechanical) systems. Three-dimensional microstructures such as microfluidic mixing systems, valves, and separation channels have been developed for biological and medical applications including low-level environmental microbial detection, high throughput drug screening, and point-of-care bedside monitoring of bacterial and viral infections.

The 4-D cross spectral density function is recovered using 2-D rotational shear interferometer measurements and a matrix completion algorithm for low rank matrices. Imaging of point sources through turbulence is demonstrated.

We describe how Fourier analysis in projective coordinates allows inversion in the Fresnel zone. Since the longitudinal resolution of 3D coherence imaging falls inversely in the square of range in both the Fresnel and Fraunhofer zones, extension to the Fresnel zone dramatically improves longitudinal resolution by removing far-field range constraints in Michelson rotational shear interferometry.

Relatively low cost focal arrays and the availability of high performance digital processing enable computational holographic imaging on unprecedented scale. This talk describes recent progress in registration and optimization algorithm.

Contrast in optical coherence tomography (OCT) images is often limited, particularly when pathological tissue is morphologically or optically similar to normal tissue. We present novel contrast enhancing methods designed to selectively identify tissues of interest.