Time-dependent contrast functions for quantitative imaging in time-resolved transillumination experiments

We have developed a methodology that can be used in reconstruction algorithms to quantify the optical coefficients and the geometrical cross section of a weakly abnormal optical target embedded in an otherwise homogeneous medium. This novel procedure uses differenttime-dependent point-spread functions to analyze the diffusive and absorptive contrasts obtained from time-of-flight measurements. Data obtained from time-resolved transillumination of a tissuelike phantom are used to test the accuracy of this new deconvolution methodology.     

In vivo quantitative three-dimensional localization of tumor labeled with exogenous specific fluorescence markers

We introduce a diffused optical detection system based on the administration of a fluorophore-antibody conjugate to diseased tissue. The conjugate interacts with the antigens expressed by the diseased tissue, resulting in fluorescent labeling of the antigen. By combining an optical detection system with a reconstruction algorithm developed on the basis of the random-walk model, we were able to determine the position of the fluorophore (and, thus, of the diseased cells) in the tissue. We present three-dimensional reconstructions of the location of a fluorophore (FITC-fluorescein isothiocyanate) in the tongues of mice. Measurements were performed with the fluorophore embedded at various simulated depths. The simulations were performed with agarose-based gel slabs applied to the tongue as tissuelike phantoms. Reconstructed fluorophore locations agree well with the actual values.     

Effects of anisotropy of the turbid media on the photon penetration depth

Biomedical applications of near infrared radiation (NIR) techniques (i.e. based on light wavelengths roughly between 400 and 1100?nm) require that a preliminary estimate of the tissue volume being investigated be found. One possible estimate is the depth to which a photon penetrates a tissue before eventually emerging at a separating plane at a given time. A simple model for this problem can be based on a lattice random walk and was initially analyzed when the associated optical coefficients are isotropic with respect to the geometrical configuration. Here we include the effects of anisotropy in the optical coefficients, finding that at long times the statistical properties of the depth of penetration can be accounted for by very simple scaling factors while at short times the anisotropy effects can be quite noticeable.     

Inverse method 3-D reconstruction of localized in vivofluorescence-application to Sjogren syndrome

The development of specific fluorescently labeled cell surface markers have opened the possibility of specific and quantitative noninvasive diagnosis of tissue changes. We are developing a fluorescence scanning imaging system that can perform a “noninvasive optical biopsy” of the Sjogren syndrome (SS) which may replace the currently used histological biopsy. The diagnosis of SS is based on the quantification of the number of topical preadministered fluorescent antibodies which specifically bind to the lymphocytes infiltrating the minor salivary glands. We intend to scan the lower lip, and for each position of the scan, generate a two-dimensional (2-D) image of fluorescence using a charge-coupled device (CCD) camera. We have shown previously that our diffuse fluorescent photon migration theory predicts adequately the positions and strengths of one and two fluorescent targets embedded at different depths in tissue-like phantoms. An inverse reconstruction algorithm based on our theoretical findings has been written in C⁺⁺ and uses 2-D images to predict the strength and location of embedded fluorophores. However, due to large numbers of variables, which include the optical properties of the tissue at the excitation and emission wavelengths, and the positions and strengths of an unknown number of fluorophore targets, the validity of the final result depends on assumptions (such as the number of targets) and the input values for the optical parameters. Our results show that the number of fluorophore targets reconstructed for each scan is limited to two, and at least the scattering coefficient at the excitation wavelength is needed a priori to obtain good results. The latter can be obtained by measurements of spatially resolved diffuse reflectance at the excitation wavelength that provides the product of the absorption and scattering coefficients     

A gear-type vacuum press for forming thin-walled parts of complex configuration

Conclusions The gear-type vacuum press of the design developed, in which the feeder and the pressing device are made in the form of gears in contact engagement, is suitable for operation with mixtures of reduced moisture content and for production of thin walled parts of complex profile.Tests showed the operating reliability of the gear-type vacuum press and the possibility of its effective use in the refractory, ceramic, and other industries.Translated from Ogneupory, No. 1, pp. 44–45, January, 1984.     

A method of forming of ceramic parts

Conclusions For the first time in domestic practice the proposed method of forming of ceramic parts made it possible to obtain parts on standard presses with a height 1.5–2.0 times greater than those shown in the characteristics of existing equipment.The introduction of the prepressing chamber improves the quality of standard production parts.Translated from Ogneupory, No. 6, pp. 33–35, June, 1986.     

High-Rate Deposition of Amorphous Silicon

A method for rapid deposition of amorphous silicon (a-Si) films in a low-frequency (55 kHz) glow discharge plasma is suggested. The structure and electrophysical properties of the films were investigated. It is shown that the use of the low-frequency discharge makes it possible to independently control the stability and concentration of recombination centers in a-Si. This fact, along with the possibility of fabricating heterostructures with a low density of surface states, makes this method promising for mass production of a-Si-based electron devices.