WorldWideScience

Sample records for space images flat

  1. Flat-space singletons

    Fronsdal, C.

    1987-01-01

    Singletons exist, as particles and as local fields, only in 3+2 de Sitter space. Their kinematical properties make them natural candidates for constituents of massless fields, and perhaps for quarks. It is interesting to find out how to describe this type of compositeness in flat space. A theory of interacting singleton fields in de Sitter space is now available, and in this paper we study the flat-space limit of the Green's functions of that theory. The flat-space limit is an autonomous theory of Green's functions, but is not an operator field theory. The three-point function is calculated and its flat-space limit is found to reveal glimpses of a physical interpretation. Causal and spectral properties are in accord with the tenets of axiomatic field theory. The theory is a generalization of local field theory, in which photons appear as composite objects although the physical S matrix is the same as in conventional QED

  2. Flat slices in Minkowski space

    Murchadha, Niall Ó.; Xie, Naqing

    2015-03-01

    Minkowski space, flat spacetime, with a distance measure in natural units of d{{s}2}=-d{{t}2}+d{{x}2}+d{{y}2}+d{{z}2}, or equivalently, with spacetime metric diag(-1, +1, +1, +1), is recognized as a fundamental arena for physics. The Poincaré group, the set of all rigid spacetime rotations and translations, is the symmetry group of Minkowski space. The action of this group preserves the form of the spacetime metric. Each t = constant slice of each preferred coordinate system is flat. We show that there are also nontrivial non-singular representations of Minkowski space with complete flat slices. If the embedding of the flat slices decays appropriately at infinity, the only flat slices are the standard ones. However, if we remove the decay condition, we find non-trivial flat slices with non-vanishing extrinsic curvature. We write out explicitly the coordinate transformation to a frame with such slices.

  3. Flat space physics from holography

    Bousso, Raphael

    2004-01-01

    We point out that aspects of quantum mechanics can be derived from the holographic principle, using only a perturbative limit of classical general relativity. In flat space, the covariant entropy bound reduces to the Bekenstein bound. The latter does not contain Newton's constant and cannot operate via gravitational back reaction. Instead, it is protected by - and in this sense, predicts - the Heisenberg uncertainty principle. (author)

  4. Instability of flat space at finite temperature

    Gross, D.J.; Perry, M.J.; Yaffe, L.G.

    1982-01-01

    The instabilities of quantum gravity are investigated using the path-integral formulation of Einstein's theory. A brief review is given of the classical gravitational instabilities, as well as the stability of flat space. The Euclidean path-integral representation of the partition function is employed to discuss the instability of flat space at finite temperature. Semiclassical, or saddle-point, approximations are utilized. We show how the Jeans instability arises as a tachyon in the graviton propagator when small perturbations about hot flat space are considered. The effect due to the Schwarzschild instanton is studied. The small fluctuations about this instanton are analyzed and a negative mode is discovered. This produces, in the semiclassical approximation, an imaginary part of the free energy. This is interpreted as being due to the metastability of hot flat space to nucleate black holes. These then evolve by evaporation or by accretion of thermal gravitons, leading to the instability of hot flat space. The nucleation rate of black holes is calculated as a function of temperature

  5. Flat tori in three-dimensional space and convex integration.

    Borrelli, Vincent; Jabrane, Saïd; Lazarus, Francis; Thibert, Boris

    2012-05-08

    It is well-known that the curvature tensor is an isometric invariant of C(2) Riemannian manifolds. This invariant is at the origin of the rigidity observed in Riemannian geometry. In the mid 1950s, Nash amazed the world mathematical community by showing that this rigidity breaks down in regularity C(1). This unexpected flexibility has many paradoxical consequences, one of them is the existence of C(1) isometric embeddings of flat tori into Euclidean three-dimensional space. In the 1970s and 1980s, M. Gromov, revisiting Nash's results introduced convex integration theory offering a general framework to solve this type of geometric problems. In this research, we convert convex integration theory into an algorithm that produces isometric maps of flat tori. We provide an implementation of a convex integration process leading to images of an embedding of a flat torus. The resulting surface reveals a C(1) fractal structure: Although the tangent plane is defined everywhere, the normal vector exhibits a fractal behavior. Isometric embeddings of flat tori may thus appear as a geometric occurrence of a structure that is simultaneously C(1) and fractal. Beyond these results, our implementation demonstrates that convex integration, a theory still confined to specialists, can produce computationally tractable solutions of partial differential relations.

  6. Rigidity of generalized Bach-flat vacuum static spaces

    Yun, Gabjin; Hwang, Seungsu

    2017-11-01

    In this paper, we study the structure of generalized Bach-flat vacuum static spaces. Generalized Bach-flat metrics are considered as extensions of both Einstein and Bach-flat metrics. First, we prove that a compact Riemannian n-manifold with n ≥ 4 which is a generalized Bach-flat vacuum static space is Einstein. A generalized Bach-flat vacuum static space with the potential function f having compact level sets is either Ricci-flat or a warped product with zero scalar curvature when n ≥ 5, and when n = 4, it is Einstein if f has its minimum. Secondly, we consider critical metrics for another quadratic curvature functional involving the Ricci tensor, and prove similar results. Lastly, by applying the technique developed above, we prove Besse conjecture when the manifold is generalized Bach-flat.

  7. Loop quantum gravity in asymptotically flat spaces

    Arnsdorf, M.

    2000-01-01

    This thesis describes applications and extensions of the loop variable approach to non-perturbative quantum gravity. The common theme of the work presented, is the need to generalise loop quantum gravity to be applicable in cases where space is asymptotically flat, and no longer compact as is usually assumed. This is important for the study of isolated gravitational systems. It also presents a natural context in which to search for the semi-classical limit, one of the main outstanding problems in loop quantum gravity. In the first part of the thesis we study how isolated gravitational systems can be attributed particle-like properties. In particular, we show how spinorial states can arise in pure loop quantum gravity if spatial topology is non-trivial, thus confirming an old conjecture of Friedman and Sorkin. Heuristically, this corresponds to the idea that we can rotate isolated regions of spatial topology relative to the environment at infinity, and that only a 4π-rotation will take us back to the original configuration. To do this we extend the standard loop quantum gravity formalism by introducing a compactification of our non-compact spatial manifold, and study the knotting of embedded graphs. The second part of the thesis takes a more systematic approach to the study of loop quantum gravity on non-compact spaces. We look for new representations of the loop algebra, which give rise to quantum theories that are inequivalent to the standard one. These theories naturally describe excitations of a fiducial background state, which is specified via the choice of its vacuum expectation values. In particular, we can choose background states that describe the geometries of non-compact manifolds. We also discuss how suitable background states can be constructed that can approximate classical phase space data, in our case holonomies along embedded paths and geometrical quantities related to areas and volumes. These states extend the notion of the weave and provide a

  8. Flat synchronizations in spherically symmetric space-times

    Herrero, Alicia; Morales-Lladosa, Juan Antonio

    2010-01-01

    It is well known that the Schwarzschild space-time admits a spacelike slicing by flat instants and that the metric is regular at the horizon in the associated adapted coordinates (Painleve-Gullstrand metric form). We consider this type of flat slicings in an arbitrary spherically symmetric space-time. The condition ensuring its existence is analyzed, and then, we prove that, for any spherically symmetric flat slicing, the densities of the Weinberg momenta vanish. Finally, we deduce the Schwarzschild solution in the extended Painleve-Gullstrand-LemaItre metric form by considering the coordinate decomposition of the vacuum Einstein equations with respect to a flat spacelike slicing.

  9. An efficient direct method for image registration of flat objects

    Nikolaev, Dmitry; Tihonkih, Dmitrii; Makovetskii, Artyom; Voronin, Sergei

    2017-09-01

    Image alignment of rigid surfaces is a rapidly developing area of research and has many practical applications. Alignment methods can be roughly divided into two types: feature-based methods and direct methods. Known SURF and SIFT algorithms are examples of the feature-based methods. Direct methods refer to those that exploit the pixel intensities without resorting to image features and image-based deformations are general direct method to align images of deformable objects in 3D space. Nevertheless, it is not good for the registration of images of 3D rigid objects since the underlying structure cannot be directly evaluated. In the article, we propose a model that is suitable for image alignment of rigid flat objects under various illumination models. The brightness consistency assumptions used for reconstruction of optimal geometrical transformation. Computer simulation results are provided to illustrate the performance of the proposed algorithm for computing of an accordance between pixels of two images.

  10. Unitarity in three-dimensional flat space higher spin theories

    Grumiller, D.; Riegler, M.; Rosseel, J.

    2014-01-01

    We investigate generic flat-space higher spin theories in three dimensions and find a no-go result, given certain assumptions that we spell out. Namely, it is only possible to have at most two out of the following three properties: unitarity, flat space, non-trivial higher spin states. Interestingly, unitarity provides an (algebra-dependent) upper bound on the central charge, like c=42 for the Galilean W_4"("2"−"1"−"1") algebra. We extend this no-go result to rule out unitary “multi-graviton” theories in flat space. We also provide an example circumventing the no-go result: Vasiliev-type flat space higher spin theory based on hs(1) can be unitary and simultaneously allow for non-trivial higher-spin states in the dual field theory.

  11. On maximal surfaces in asymptotically flat space-times

    Bartnik, R.; Chrusciel, P.T.; O Murchadha, N.

    1990-01-01

    Existence of maximal and 'almost maximal' hypersurfaces in asymptotically flat space-times is established under boundary conditions weaker than those considered previously. We show in particular that every vacuum evolution of asymptotically flat data for Einstein equations can be foliated by slices maximal outside a spatially compact set and that every (strictly) stationary asymptotically flat space-time can be foliated by maximal hypersurfaces. Amongst other uniqueness results, we show that maximal hypersurface can be used to 'partially fix' an asymptotic Poincare group. (orig.)

  12. Higher-spin flat space cosmologies with soft hair

    Ammon, Martin [Theoretisch-Physikalisches Institut, Friedrich-Schiller University of Jena, Max-Wien-Platz 1, D-07743 Jena (Germany); Grumiller, Daniel [Institute for Theoretical Physics, TU Wien, Wiedner Hauptstrasse 8-10/136, A-1040 Vienna (Austria); CMCC-Universidade Federal do ABC,Santo André, S.P. (Brazil); Prohazka, Stefan [Institute for Theoretical Physics, TU Wien, Wiedner Hauptstrasse 8-10/136, A-1040 Vienna (Austria); Riegler, Max [Université libre de Bruxelles, Boulevard du Triomphe, Campus de la Plaine,1050 Bruxelles (Belgium); Wutte, Raphaela [Institute for Theoretical Physics, TU Wien, Wiedner Hauptstrasse 8-10/136, A-1040 Vienna (Austria)

    2017-05-08

    We present and discuss near horizon boundary conditions for flat space higher-spin gravity in three dimensions. As in related work our boundary conditions ensure regularity of the solutions independently of the charges. The asymptotic symmetry algebra is given by a set of û(1) current algebras. The associated charges generate higher-spin soft hair. We derive the entropy for solutions that are continuously connected to flat space cosmologies and find the same result as in the spin-2 case: the entropy is linear in the spin-2 zero-mode charges and independent from the spin-3 charges. Using twisted Sugawara-like constructions of higher-spin currents we show that our simple result for entropy of higher-spin flat space cosmologies coincides precisely with the complicated earlier results expressed in terms of higher-spin zero mode charges.

  13. Cosmic microwave background anisotropies in multiconnected flat spaces

    Riazuelo, Alain; Weeks, Jeffrey; Uzan, Jean-Philippe; Lehoucq, Roland; Luminet, Jean-Pierre

    2004-01-01

    This article investigates the signature of the seventeen multiconnected flat spaces in cosmic microwave background (CMB) maps. For each such space it recalls a fundamental domain and a set of generating matrices, and then goes on to find an orthonormal basis for the set of eigenmodes of the Laplace operator on that space. The basis eigenmodes are expressed as linear combinations of eigenmodes of the simply connected Euclidean space. A preceding work, which provides a general method for implementing multiconnected topologies in standard CMB codes, is then applied to simulate CMB maps and angular power spectra for each space. Unlike in the 3-torus, the results in most multiconnected flat spaces depend on the location of the observer. This effect is discussed in detail. In particular, it is shown that the correlated circles on a CMB map are generically not back to back, so that negative search of back-to-back circles in the Wilkinson Microwave Anisotropy Probe data does not exclude a vast majority of flat or nearly flat topologies

  14. A flat array large telescope concept for use on the moon, earth, and in space

    Woodgate, Bruce E.

    1991-01-01

    An astronomical optical telescope concept is described which can provide very large collecting areas, of order 1000 sq m. This is an order of magnitude larger than the new generation of telescopes now being designed and built. Multiple gimballed flat mirrors direct the beams from a celestial source into a single telescope of the same aperture as each flat mirror. Multiple images of the same source are formed at the telescope focal plane. A beam combiner collects these images and superimposes them into a single image, onto a detector or spectrograph aperture. This telescope could be used on the earth, the moon, or in space.

  15. Two theorems on flat space-time gravitational theories

    Castagnino, M.; Chimento, L.

    1980-01-01

    The first theorem states that all flat space-time gravitational theories must have a Lagrangian with a first term that is an homogeneous (degree-1) function of the 4-velocity usup(i), plus a functional of nsub(ij)usup(i)usup(j). The second theorem states that all gravitational theories that satisfy the strong equivalence principle have a Lagrangian with a first term gsub(ij)(x)usup(i)usup(j) plus an irrelevant term. In both cases the theories must issue from a unique variational principle. Therefore, under this condition it is impossible to find a flat space-time theory that satisfies the strong equivalence principle. (author)

  16. Blackbody radiation from light cone in flat space time

    Gerlach, U.H.

    1983-01-01

    Blackbody radiation in flat space-time is not necessarily associated with the flat event horizon of a single accelerated observer. The author considers a spherical bubble which expands in a uniformly accelerating fashion. Its history traces out a time-like hyperboloid. Suppose the bubble membrane has a spatially isotropic and homogeneous (surface) stress energy tensor i.e. the membrane is made out of the stiffest possible material permitted by causality considerations. It follows that this bubble membrane is in equilibrium even though it is expanding. Such an expanding bubble membrane may serve as a detector of electromagnetic radiation if the membrane can interact with the electromagnetic field. (Auth.)

  17. Higher-spin algebras, holography and flat space

    Sleight, C. [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, D-80805 Munich (Germany); Université Libre de Bruxelles and International Solvay Institutes,ULB-Campus Plaine CP231, 1050 Brussels (Belgium); Taronna, M. [Université Libre de Bruxelles and International Solvay Institutes,ULB-Campus Plaine CP231, 1050 Brussels (Belgium)

    2017-02-20

    In this article we study the higher-spin algebra behind the type-A cubic couplings recently extracted from the free O(N) model in generic dimensions, demonstrating that they coincide with the known structure constants for the unique higher-spin algebra in generic dimensions. This provides an explicit check of the holographic reconstruction and of the duality between higher-spin theories and the free O(N) model in generic dimensions, generalising the result of Giombi and Yin in AdS{sub 4}. For completeness, we also address the same problem in the flat space for the cubic couplings derived by Metsaev in 1991, which are recovered from the flat limit of the AdS type-A cubic couplings. We observe that both flat and AdS{sub 4} higher-spin Lorentz subalgebras coincide, hinting towards the existence of a full higher-spin symmetry behind the flat-space cubic couplings of Metsaev.

  18. Null geodesic deviation II. Conformally flat space--times

    Peters, P.C.

    1975-01-01

    The equation of geodesic deviation is solved in conformally flat space--time in a covariant manner. The solution is given as an integral equation for general geodesics. The solution is then used to evaluate second derivatives of the world function and derivatives of the parallel propagator, which need to be known in order to find the Green's function for wave equations in curved space--time. A method of null geodesic limits of two-point functions is discussed, and used to find the scalar Green's function as an iterative series

  19. Extracting flat-field images from scene-based image sequences using phase correlation

    Caron, James N., E-mail: Caron@RSImd.com [Research Support Instruments, 4325-B Forbes Boulevard, Lanham, Maryland 20706 (United States); Montes, Marcos J. [Naval Research Laboratory, Code 7231, 4555 Overlook Avenue, SW, Washington, DC 20375 (United States); Obermark, Jerome L. [Naval Research Laboratory, Code 8231, 4555 Overlook Avenue, SW, Washington, DC 20375 (United States)

    2016-06-15

    Flat-field image processing is an essential step in producing high-quality and radiometrically calibrated images. Flat-fielding corrects for variations in the gain of focal plane array electronics and unequal illumination from the system optics. Typically, a flat-field image is captured by imaging a radiometrically uniform surface. The flat-field image is normalized and removed from the images. There are circumstances, such as with remote sensing, where a flat-field image cannot be acquired in this manner. For these cases, we developed a phase-correlation method that allows the extraction of an effective flat-field image from a sequence of scene-based displaced images. The method uses sub-pixel phase correlation image registration to align the sequence to estimate the static scene. The scene is removed from sequence producing a sequence of misaligned flat-field images. An average flat-field image is derived from the realigned flat-field sequence.

  20. Nonlocality and Multipartite Entanglement in Asymptotically Flat Space-Times

    Moradi, Shahpoor; Amiri, Firouz

    2016-01-01

    We study the Bell's inequality and multipartite entanglement generation for initially maximally entangled states of free Dirac field in a non inertial frame and asymptotically flat Robertson–Walker space-time. For two qubit case, we show that the Bell's inequality always is violated as measured by the accelerated observers which are in the causally connected regions. On the other hand, for those observers in the causally disconnected regions inequality is not violated for any values of acceleration. The generated three qubit state from two qubit state due to acceleration of one parties has a zero 3-tangle. For a three qubit state, the inequality violated for measurements done by both causally connected and disconnected observers. Initially GHZ state with non zero 3-tangle, in accelerated frame, transformed to a four qubit state with vanishing 4-tangle value. On the other hand, for a W-state with zero 3-tangle, in non inertial frame, transformed to a four qubit state with a non-zero 4-tangle acceleration dependent. In an expanding space-time with asymptotically flat regions, for an initially maximally entangled state, the maximum value of violation of Bell's inequality in the far past decreased in the far future due to cosmological particle creation. For some initially maximally entangled states, the generated four qubit state due to expansion of space-time, has non vanishing 4-tangle. (paper)

  1. Flat dielectric metasurface lens array for three dimensional integral imaging

    Zhang, Jianlei; Wang, Xiaorui; Yang, Yi; Yuan, Ying; Wu, Xiongxiong

    2018-05-01

    In conventional integral imaging, the singlet refractive lens array limits the imaging performance due to its prominent aberrations. Different from the refractive lens array relying on phase modulation via phase change accumulated along the optical paths, metasurfaces composed of nano-scatters can produce phase abrupt over the scale of wavelength. In this letter, we propose a novel lens array consisting of two neighboring flat dielectric metasurfaces for integral imaging system. The aspherical phase profiles of the metasurfaces are optimized to improve imaging performance. The simulation results show that our designed 5 × 5 metasurface-based lens array exhibits high image quality at designed wavelength 865 nm.

  2. Re-examination of globally flat space-time.

    Michael R Feldman

    Full Text Available In the following, we offer a novel approach to modeling the observed effects currently attributed to the theoretical concepts of "dark energy," "dark matter," and "dark flow." Instead of assuming the existence of these theoretical concepts, we take an alternative route and choose to redefine what we consider to be inertial motion as well as what constitutes an inertial frame of reference in flat space-time. We adopt none of the features of our current cosmological models except for the requirement that special and general relativity be local approximations within our revised definition of inertial systems. Implicit in our ideas is the assumption that at "large enough" scales one can treat objects within these inertial systems as point-particles having an insignificant effect on the curvature of space-time. We then proceed under the assumption that time and space are fundamentally intertwined such that time- and spatial-translational invariance are not inherent symmetries of flat space-time (i.e., observable clock rates depend upon both relative velocity and spatial position within these inertial systems and take the geodesics of this theory in the radial Rindler chart as the proper characterization of inertial motion. With this commitment, we are able to model solely with inertial motion the observed effects expected to be the result of "dark energy," "dark matter," and "dark flow." In addition, we examine the potential observable implications of our theory in a gravitational system located within a confined region of an inertial reference frame, subsequently interpreting the Pioneer anomaly as support for our redefinition of inertial motion. As well, we extend our analysis into quantum mechanics by quantizing for a real scalar field and find a possible explanation for the asymmetry between matter and antimatter within the framework of these redefined inertial systems.

  3. ACS/WFC Sky Flats from Frontier Fields Imaging

    Mack, J.; Lucas, R. A.; Grogin, N. A.; Bohlin, R. C.; Koekemoer, A. M.

    2018-04-01

    Parallel imaging data from the HST Frontier Fields campaign (Lotz et al. 2017) have been used to compute sky flats for the ACS/WFC detector in order to verify the accuracy of the current set of flat field reference files. By masking sources and then co-adding many deep frames, the F606W and F814W filters have enough combined background signal that from Poisson statistics are efficiency tracks the thickness of the two WFC chips. Observations of blue and red calibration standards measured at various positions on the detector (Bohlin et al. 2017) confirm the fidelity of the F814W flat, with aperture photometry consistent to 1% across the FOV, regardless of spectral type. At bluer wavelengths, the total sky background is substantially lower, and the F435W sky flat shows a combination of both flat errors and detector artifacts. Aperture photometry of the red standard star shows a maximum deviation of 1.4% across the array in this filter. Larger residuals up to 2.5% are found for the blue standard, suggesting that the spatial sensitivity in F435W depends on spectral type.

  4. Light-front higher-spin theories in flat space

    Ponomarev, Dmitry; Skvortsov, Evgeny

    2017-03-01

    We revisit the problem of interactions of higher-spin fields in flat space. We argue that all no-go theorems can be avoided by the light-cone approach, which results in more interaction vertices as compared to the usual covariant approaches. It is stressed that there exist two-derivative gravitational couplings of higher-spin fields. We show that some reincarnation of the equivalence principle still holds for higher-spin fields—the strength of gravitational interaction does not depend on spin. Moreover, it follows from the results by Metsaev that there exists a complete chiral higher-spin theory in four dimensions. We give a simple derivation of this theory and show that the four-point scattering amplitude vanishes. Also, we reconstruct the quartic vertex of the scalar field in the unitary higher-spin theory, which turns out to be perturbatively local.

  5. Light-front higher-spin theories in flat space

    Ponomarev, Dmitry; Skvortsov, Evgeny

    2017-01-01

    We revisit the problem of interactions of higher-spin fields in flat space. We argue that all no-go theorems can be avoided by the light-cone approach, which results in more interaction vertices as compared to the usual covariant approaches. It is stressed that there exist two-derivative gravitational couplings of higher-spin fields. We show that some reincarnation of the equivalence principle still holds for higher-spin fields—the strength of gravitational interaction does not depend on spin. Moreover, it follows from the results by Metsaev that there exists a complete chiral higher-spin theory in four dimensions. We give a simple derivation of this theory and show that the four-point scattering amplitude vanishes. Also, we reconstruct the quartic vertex of the scalar field in the unitary higher-spin theory, which turns out to be perturbatively local. (paper)

  6. Field-theoretic approach to gravity in the flat space-time

    Cavalleri, G [Centro Informazioni Studi Esperienze, Milan (Italy); Milan Univ. (Italy). Ist. di Fisica); Spinelli, G [Istituto di Matematica del Politecnico di Milano, Milano (Italy)

    1980-01-01

    In this paper it is discussed how the field-theoretical approach to gravity starting from the flat space-time is wider than the Einstein approach. The flat approach is able to predict the structure of the observable space as a consequence of the behaviour of the particle proper masses. The field equations are formally equal to Einstein's equations without the cosmological term.

  7. Evaluation of flat panel PMT for gamma ray imaging

    Pani, R.; Cinti, M.N.; Pellegrini, R.; Trotta, C.; Trotta, G.; Montani, L.; Ridolfi, S.; Garibaldi, F.; Scafe, R.; Belcari, N.; Del Guerra, A.

    2003-01-01

    The first position sensitive PMT, Hamamatsu R2486, developed in 1985, represented a strong technological advance for gamma-ray imaging. Hamamatsu H8500 Flat Panel PMT is the last generation position sensitive PMT: extremely compact with 2 in. active area. Its main features are: minimum peripheral dead zone (1 mm) and height of 12 mm. It was designed to be assembled in array to cover large detection area. It can represent a technical revolution for many applications in the field of gamma-ray imaging as for example nuclear medicine. This tube is based on metal channel dynode for charge multiplication and 8x8 anodes for charge collection and position calculation. In this paper we present a preliminary evaluation of the imaging performances addressed to nuclear medicine application. To this aim we have taken into account two different electronic readouts: resistive chain with Anger Camera principle and multianode readout. Flat panel PMT was coupled to CsI(Tl) and NaI(Tl) scintillation arrays. The results were also compared with the first generation PSPMT

  8. European Space Imaging & Skybox Imaging

    Clark, J.; Schichor, P.

    2015-01-01

    Skybox and European Space Imaging have partnered to bring timely, Very High-Resolution imagery to customers in Europe and North Africa. Leveraging Silicon Valley ingenuity and world-class aerospace expertise, Skybox designs, builds, and operates a fleet of imaging satellites. With two satellites currently on-orbit, Skybox is quickly advancing towards a planned constellation of 24+ satellites with the potential for daily or sub-daily imaging at 70-90 cm resolution. With consistent, high-resolution imagery and video, European customers can monitor the dynamic units of human activity - cars, trucks, shipping containers, ships, aircraft, etc. - and derive valuable insights about the global economy. With multiple imaging opportunities per day, the Skybox constellation provides unprecedented access to imagery and information about critical targets that require rapid analysis. Skybox's unique capability to deliver high-definition video from space enables European customers to monitor a network of globally distributed assets with full-motion snapshots, without the need to deploy an aircraft or field team. The movement captured in these 30-90 second video windows yield unique insights that improve operational decisions. Skybox and EUSI are excited to offer a unique data source that can drive a better understanding of our world through supply chain monitoring, natural resource management, infrastructure monitoring, and crisis response. (author)

  9. Image quality analysis of vibration effects In C-arm-flat panel X-ray imaging

    Snoeren, R.M.; Kroon, J.N.; With, de P.H.N.

    2011-01-01

    The motion of C-arm scanning X-ray systems may result in vibrations of the imaging sub-system. In this paper, we connect C-arm system vibrations to Image Quality (IQ) deterioration for 2D angiography and 3D cone beam X-ray imaging, using large Flat Panel detectors. Vibrations will affect the

  10. A flat space-time relativistic explanation for the perihelion advance of Mercury

    Behera, Harihar; Naik, P. C.

    2003-01-01

    Starting with the flat space-time relativistic versions of Maxwell-Heaviside's toy model vector theory of gravity and introducing the gravitational analogues for the electromagnetic Lienard-Wiechert potentials together with the notion of a gravitational Thomas Precession; the observed anomalous perihelion advance of Mercury's orbit is here explained as a relativistic effect in flat (Minkowski) space-time, unlike Einstein's curved space-time relativistic explanation. In this new explanation fo...

  11. Inevitable ambiguity in perturbation around flat space-time

    Ichinose, S.; Kaminaga, Y.

    1989-01-01

    Perturbation of general-relativistic predictions around flat geometry, in general, introduces inevitable ambiguity. The ambiguity reflects the geometrical nature of general relativity and is never a difficulty of it. We explain it by taking a concrete example of the radar-echo experiment

  12. Implementation of a program of quality assurance of image in an imaging system of flat panel portal

    Gomez Barrado, A.; Sanchez Jimenez, E.; Benitez, J. A.; Sanchez-Reyes, A.

    2013-01-01

    (IGRT) image-guided radiation therapy is the one in which images are used to locate the area of treatment. Modern irradiation systems are equipped with different modalities for obtaining images, such as flat panel systems, systems conebeam, tomoimagen, etc. This paper describes the start-up and the experience of a quality assurance program based on a flat panel portal Imaging System. (Author)

  13. Discrete space charge affected field emission: Flat and hemisphere emitters

    Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil [Code 6854, Naval Research Laboratory, Washington, DC 20375 (United States); Shiffler, Donald A.; Tang, Wilkin [Air Force Research Laboratory, Kirtland AFB, New Mexico 87117 (United States); Rittersdorf, Ian M. [Code 6770, Naval Research Laboratory, Washington, DC 20375 (United States); Lebowitz, Joel L. [Department of Mathematics and Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States); Harris, John R. [U.S. Navy Reserve, New Orleans, Louisiana 70143 (United States); Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Petillo, John J. [Leidos, Billerica, Massachusetts 01821 (United States); Luginsland, John W. [Physics and Electronics Directorate, AFOSR, Arlington, Virginia 22203 (United States)

    2015-05-21

    Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.

  14. Solution of the stationary vacuum equations of relativity for conformally flat 3-spaces

    Perjes, Z.; Lukacs, B.; Sebestyen, A.; Valentini, A.; Sparling, G.A.J.

    1983-08-01

    The solution of Einstein's vacuum gravitational equations for stationary space-times with a conformally flat 3-space is presented. There is no other solution of this problem than the Ehlers-rotation generalizations of the three conformastat space-times including the Schwarzschild metric. (author)

  15. Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality

    Vano, E.; Geiger, B.; Schreiner, A.; Back, C.; Beissel, J.

    2005-12-01

    The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 µGy/frame (cine) and 5 and 95 mGy min-1 (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

  16. On black holes in multidimensional theory with Ricci-flat internal spaces

    Fadeev, S. B.; Ivashchuk, V. D.; Melnikov, V. N.

    2010-01-01

    A generalization of the Tangherlini solution for the case of n internal Ricci-flat spaces is obtained. It is shown that in the (2+d)-dimensional section a horizon exists only in the trivial case when the internal-space factors are constant. The p-adic analog of the solution is also considered.

  17. Bohr-Sommerfeld orbits in the moduli space of flat connections and the Verlinde dimension formula

    Jeffrey, L.C.; Weitsman, J.

    1992-01-01

    We show how the moduli space of flat SU(2) connections on a two-manifold can be quantized. The dimension of the quantization, given by the number of integral fibres of the polarization, matches the Verlinde formula, which is known to give the dimension of the quantization of this space in a Kaehler polarization. (orig./HSI)

  18. Tracking brachytherapy sources using emission imaging with one flat panel detector

    Song Haijun; Bowsher, James; Das, Shiva; Yin Fangfang

    2009-01-01

    This work proposes to use the radiation from brachytherapy sources to track their dwell positions in three-dimensional (3D) space. The prototype device uses a single flat panel detector and a BB tray. The BBs are arranged in a defined pattern. The shadow of the BBs on the flat panel is analyzed to derive the 3D coordinates of the illumination source, i.e., the dwell position of the brachytherapy source. A kilovoltage x-ray source located 3.3 m away was used to align the center BB with the center pixel on the flat panel detector. For a test plan of 11 dwell positions, with an Ir-192 high dose rate unit, one projection was taken for each dwell point, and locations of the BB shadows were manually identified on the projection images. The 3D coordinates for the 11 dwell positions were reconstructed based on two BBs. The distances between dwell points were compared with the expected values. The average difference was 0.07 cm with a standard deviation of 0.15 cm. With automated BB shadow recognition in the future, this technique possesses the potential of tracking the 3D trajectory and the dwell times of a brachytherapy source in real time, enabling real time source position verification.

  19. Consistent Lorentz violation in flat and curved space

    Dvali, Gia; Pujolas, Oriol; Redi, Michele

    2007-01-01

    Motivated by the severity of the bounds on Lorentz violation in the presence of ordinary gravity, we study frameworks in which Lorentz violation does not affect the spacetime geometry. We show that there are at least two inequivalent classes of spontaneous Lorentz breaking that even in the presence of gravity result in Minkowski space. The first one generically corresponds to the condensation of tensor fields with tachyonic mass, which in turn is related to ghost condensation. In the second class, realized by the Dvali-Gabadadze-Porrati model or theories of massive gravitons, spontaneous Lorentz breaking is induced by the expectation value of sources. The generalization to de Sitter space is also discussed

  20. Conformally flat spaces and solutions to Yang-Mills equations

    Chaohao, G.

    1980-01-01

    Using the conformal invariance of Yang-Mills equations in four-dimensional manifolds, it is proved that in a simply connected space of negative constant curvature Yang-Mills equations admit solutions with any real number as their Pontryagin number. It is also shown that the space S 3 x S 1 which is the regular counterpart of the meron solution is one example of a class of solutions to Yang-Mills equations on compact manifolds that are neither self-dual nor anti-self-dual

  1. Noncommutative spaces and matrix embeddings on flat ℝ{sup 2n+1}

    Karczmarek, Joanna L.; Yeh, Ken Huai-Che [Department of Physics and Astronomy, University of British Columbia,6224 Agricultural Road, Vancouver (Canada)

    2015-11-23

    We conjecture an embedding operator which assigns, to any 2n+1 hermitian matrices, a 2n-dimensional hypersurface in flat (2n+1)-dimensional Euclidean space. This corresponds to precisely defining a fuzzy D(2n)-brane corresponding to N D0-branes. Points on the emergent hypersurface correspond to zero eigenstates of the embedding operator, which have an interpretation as coherent states underlying the emergent noncommutative geometry. Using this correspondence, all physical properties of the emergent D(2n)-brane can be computed. We apply our conjecture to noncommutative flat and spherical spaces. As a by-product, we obtain a construction of a rotationally symmetric flat noncommutative space in 4 dimensions.

  2. A Grassmann path from AdS3 to flat space

    Krishnan, Chethan; Raju, Avinash; Roy, Shubho

    2014-01-01

    We show that interpreting the inverse AdS 3 radius 1/l as a Grassmann variable results in a formal map from gravity in AdS 3 to gravity in flat space. The underlying reason for this is the fact that ISO(2,1) is the Inonu-Wigner contraction of SO(2,2). We show how this works for the Chern-Simons actions, demonstrate how the general (Banados) solution in AdS 3 maps to the general flat space solution, and how the Killing vectors, charges and the Virasoro algebra in the Brown-Henneaux case map to the corresponding quantities in the BMS 3 case. Our results straightforwardly generalize to the higher spin case: the recently constructed flat space higher spin theories emerge automatically in this approach from their AdS counterparts. We conclude with a discussion of singularity resolution in the BMS gauge as an application

  3. On integral formulation of the Mach principle in a conformally flat space

    Mal'tsev, V.K.

    1976-01-01

    The integral formulation of the Mach principle represents a rather complicated mathematical formalism in which many aspects of the physical content of theory are not clear. Below an attempt is made to consider the integral representation for the most simple case of conformally flat spaces. The fact that this formalism there is only one scalar function makes it possible to analyse in more detail many physical peculiarities of this representation of the Mach principle: the absence of asymptotically flat spaces, problems of inertia and gravity, constraints on state equations, etc

  4. Ghost Imaging of Space Objects

    National Aeronautics and Space Administration — Ghost imaging is an optical imaging technique that utilizes the correlations between optical fields in two channels. One of the channels contains the object, however...

  5. Thinking in z-space: flatness and spatial narrativity

    Zone, Ray

    2012-03-01

    Now that digital technology has accessed the Z-space in cinema, narrative artistry is at a loss. Motion picture professionals no longer can readily resort to familiar tools. A new language and new linguistics for Z-axis storytelling are necessary. After first examining the roots of monocular thinking in painting, prior modes of visual narrative in twodimensional cinema obviating true binocular stereopsis can be explored, particularly montage, camera motion and depth of field, with historic examples. Special attention is paid to the manner in which monocular cues for depth have been exploited to infer depth on a planar screen. Both the artistic potential and visual limitations of actual stereoscopic depth as a filmmaking language are interrogated. After an examination of the historic basis of monocular thinking in visual culture, a context for artistic exploration of the use of the z-axis as a heightened means of creating dramatic and emotional impact upon the viewer is illustrated.

  6. Space-Time Quantum Imaging

    Ronald E. Meyers

    2015-03-01

    Full Text Available We report on an experimental and theoretical investigation of quantum imaging where the images are stored in both space and time. Ghost images of remote objects are produced with either one or two beams of chaotic laser light generated by a rotating ground glass and two sensors measuring the reference field and bucket field at different space-time points. We further observe that the ghost images translate depending on the time delay between the sensor measurements. The ghost imaging experiments are performed both with and without turbulence. A discussion of the physics of the space-time imaging is presented in terms of quantum nonlocal two-photon analysis to support the experimental results. The theoretical model includes certain phase factors of the rotating ground glass. These experiments demonstrated a means to investigate the time and space aspects of ghost imaging and showed that ghost imaging contains more information per measured photon than was previously recognized where multiple ghost images are stored within the same ghost imaging data sets. This suggests new pathways to explore quantum information stored not only in multi-photon coincidence information but also in time delayed multi-photon interference. The research is applicable to making enhanced space-time quantum images and videos of moving objects where the images are stored in both space and time.

  7. Fuzzy topological digital space and their properties of flat electroencephalography in epilepsy disease

    Muzafar Shah, Mazlina; Fatah Wahab, Abdul

    2017-09-01

    There are an abnormal electric activities or irregular interference in brain of epilepsy patient. Then a sensor will be put in patient’s scalp to measure and records all electric activities in brain. The result of the records known as Electroencephalography (EEG). The EEG has been transfer to flat EEG because it’s easier to analyze. In this study, the uncertainty in flat EEG data will be considered as fuzzy digital space. The purpose of this research is to show that the flat EEG is fuzzy topological digital space. Therefore, the main focus for this research is to introduce fuzzy topological digital space concepts with their properties such as neighbourhood, interior and closure by using fuzzy set digital concept and Chang’s fuzzy topology approach. The product fuzzy topology digital also will be shown. By introduce this concept, the data in flat EEG can considering having fuzzy topology digital properties and can identify the area in fuzzy digital space that has been affected by epilepsy seizure in epileptic patient’s brain.

  8. Christoffel symbols and inertia in flat space-time theory. [Curvilinear coordinate systems

    Krause, J [Universidad Central de Venezuela, Caracas

    1976-11-01

    A necessary and sufficient criterion of inertia is presented, for the flat space-time theory of general frames of reference, in terms of the vanishing of some typical components of the affine connection pertaining to curvilinear coordinate systems. The physical identification of inertial forces thus arises in the context of the special theory of relativity.

  9. Lectures on strings in flat space and plane waves from N = 4 super Yang Mills

    Maldacena, J.

    2003-01-01

    In these lecture notes we explain how the string spectrum in flat space and plane waves arises from the large N limit of U(N) N = 4 super Yang Mills. We reproduce the spectrum by summing a subset of the planar Feynman diagrams. We also describe some other aspects of string propagation on plane wave backgrounds. (author)

  10. Comparison of dose and image quality of a Flat-panel detector and an image intensifier

    Lazzaro, M.; Friedrich, B.Q.; Luz, R.M. da; Silva, A.M.M. da

    2016-01-01

    With the development of new technologies, have emerged new conversion methods of X-ray image, such as flat panel detectors. The aim of this work is the comparison of entrance surface air kerma (ESAK) and image quality between an image intensifier type of detector (A) and a flat panel (B). The ESAK was obtained by placing a ionization chamber under PMMA simulators of 10, 20 and 30 cm and the image quality was obtained by using the TOR "1"8FG simulator. The ESAK to the equipment A is higher when compared to the equipment B. The high contrast resolution is better for the equipment A for all thicknesses of simulators. The equipment A has low contrast resolution with a better viewing threshold for thicknesses of 10 and 20 cm, and a worse performance for 30 cm. It is concluded that the equipment B has ESAK smaller and despite having lower resolution, in almost all cases, have appropriate image quality for diagnosis. (author)

  11. Stationary vacuum fields with a conformally flat three-space Pt. 1

    Lukacs, B.; Perjes, Z.; Sebestyen, A.; Sparling, G.A.J.

    1982-01-01

    A generalized notion of conformastat space-times is introduced in relativity theory. In this sense, the conformastat space-time is stationary with the three-space of time-like Killing trajectories being conformally flat. A 3+1 decomposition of the field equations is given, and two classes of nonstatic conformastat vacuum fields are exhaustively investigated. The resulting three metrics form a NUT-type extension of the solution of the static conformastat vacuum problem. The authors conjecture that all conformastat vacuum space-times are axially symmetric. (author)

  12. Seismic Imager Space Telescope

    Sidick, Erkin; Coste, Keith; Cunningham, J.; Sievers,Michael W.; Agnes, Gregory S.; Polanco, Otto R.; Green, Joseph J.; Cameron, Bruce A.; Redding, David C.; Avouac, Jean Philippe; hide

    2012-01-01

    A concept has been developed for a geostationary seismic imager (GSI), a space telescope in geostationary orbit above the Pacific coast of the Americas that would provide movies of many large earthquakes occurring in the area from Southern Chile to Southern Alaska. The GSI movies would cover a field of view as long as 300 km, at a spatial resolution of 3 to 15 m and a temporal resolution of 1 to 2 Hz, which is sufficient for accurate measurement of surface displacements and photometric changes induced by seismic waves. Computer processing of the movie images would exploit these dynamic changes to accurately measure the rapidly evolving surface waves and surface ruptures as they happen. These measurements would provide key information to advance the understanding of the mechanisms governing earthquake ruptures, and the propagation and arrest of damaging seismic waves. GSI operational strategy is to react to earthquakes detected by ground seismometers, slewing the satellite to point at the epicenters of earthquakes above a certain magnitude. Some of these earthquakes will be foreshocks of larger earthquakes; these will be observed, as the spacecraft would have been pointed in the right direction. This strategy was tested against the historical record for the Pacific coast of the Americas, from 1973 until the present. Based on the seismicity recorded during this time period, a GSI mission with a lifetime of 10 years could have been in position to observe at least 13 (22 on average) earthquakes of magnitude larger than 6, and at least one (2 on average) earthquake of magnitude larger than 7. A GSI would provide data unprecedented in its extent and temporal and spatial resolution. It would provide this data for some of the world's most seismically active regions, and do so better and at a lower cost than could be done with ground-based instrumentation. A GSI would revolutionize the understanding of earthquake dynamics, perhaps leading ultimately to effective warning

  13. Flat-space holography and stress tensor of Kerr black hole

    Baghchesaraei, Omid, E-mail: omidbaghchesaraei@gmail.com [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Fareghbal, Reza, E-mail: r_fareghbal@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Izadi, Yousef, E-mail: yizadi2015@fau.edu [Department of Physics, Florida Atlantic University, Boca Raton, FL 33431 (United States)

    2016-09-10

    We propose a stress tensor for the Kerr black hole written in the Boyer–Lindquist coordinate. To achieve this, we use the dictionary of the Flat/CCFT correspondence and take the flat-space limit from the quasi-local stress tensor of the four-dimensional Kerr–AdS black hole. The proposed stress tensor yields the correct values for the mass and angular momentum of the Kerr black hole at spatial infinity. We also calculate some components of the energy momentum tensor of the three dimensional CCFT and show that they are consistent with the holographic calculation of the Kerr black hole. The calculation we present in this paper is another confirmation for the Flat/CCFT proposal.

  14. Equivalence of meson scattering amplitudes in strong coupling lattice and flat space string theory

    Adi Armoni

    2018-03-01

    Full Text Available We consider meson scattering in the framework of the lattice strong coupling expansion. In particular we derive an expression for the 4-point function of meson operators in the planar limit of scalar Chromodynamics. Interestingly, in the naive continuum limit the expression coincides with an independently known result, that of the worldline formalism. Moreover, it was argued by Makeenko and Olesen that (assuming confinement the resulting scattering amplitude in momentum space is the celebrated expression proposed by Veneziano several decades ago. This motivates us to also use holography in order to argue that the continuum expression for the scattering amplitude is related to the result obtained from flat space string theory. Our results hint that at strong coupling and large-Nc the naive continuum limit of the lattice formalism can be related to a flat space string theory.

  15. Equivalence of meson scattering amplitudes in strong coupling lattice and flat space string theory

    Armoni, Adi; Ireson, Edwin; Vadacchino, Davide

    2018-03-01

    We consider meson scattering in the framework of the lattice strong coupling expansion. In particular we derive an expression for the 4-point function of meson operators in the planar limit of scalar Chromodynamics. Interestingly, in the naive continuum limit the expression coincides with an independently known result, that of the worldline formalism. Moreover, it was argued by Makeenko and Olesen that (assuming confinement) the resulting scattering amplitude in momentum space is the celebrated expression proposed by Veneziano several decades ago. This motivates us to also use holography in order to argue that the continuum expression for the scattering amplitude is related to the result obtained from flat space string theory. Our results hint that at strong coupling and large-Nc the naive continuum limit of the lattice formalism can be related to a flat space string theory.

  16. Imaging of the perivertebral space.

    Mills, Megan K; Shah, Lubdha M

    2015-01-01

    The perivertebral space extends from the skull base to the mediastinum and is delineated by the deep layer of the deep cervical fascia. The different tissue types, including muscles, bones, nerves, and vascular structures, give rise to the various disorders that can be seen in this space. This article defines the anatomy of the perivertebral space, guides lesion localization, discusses different disease processes arising within this space, and reviews the best imaging approaches. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Space Radar Image of Central Sumatra, Indonesia

    1994-01-01

    This is a radar image of the central part of the island of Sumatra in Indonesia that shows how the tropical rainforest typical of this country is being impacted by human activity. Native forest appears in green in this image, while prominent pink areas represent places where the native forest has been cleared. The large rectangular areas have been cleared for palm oil plantations. The bright pink zones are areas that have been cleared since 1989, while the dark pink zones are areas that were cleared before 1989. These radar data were processed as part of an effort to assist oil and gas companies working in the area to assess the environmental impact of both their drilling operations and the activities of the local population. Radar images are useful in these areas because heavy cloud cover and the persistent smoke and haze associated with deforestation have prevented usable visible-light imagery from being acquired since 1989. The dark shapes in the upper right (northeast) corner of the image are a chain of lakes in flat coastal marshes. This image was acquired in October 1994 by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour. Environmental changes can be easily documented by comparing this image with visible-light data that were acquired in previous years by the Landsat satellite. The image is centered at 0.9 degrees north latitude and 101.3 degrees east longitude. The area shown is 50 kilometers by 100 kilometers (31 miles by 62 miles). The colors in the image are assigned to different frequencies and polarizations of the radar as follows: red is L-band horizontally transmitted, horizontally received; green is L-band horizontally transmitted, vertically received; blue is L-band vertically transmitted, vertically received. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's Mission to Planet Earth program.

  18. Plutonium contamination in soils in open space and residential areas near Rocky Flats, Colorado

    Litaor, M.I.

    1999-01-01

    Spatial analysis of the 240 Pu: 239 Pu isotopic ratio of 42 soil samples collected around Rocky Flats Plant near Golden, Colorado, was conducted to assess the effect of Rocky Flats Plant activity on the soil environment. Two probability maps that quantified the uncertainty of the spatial distribution of plutonium isotopic ratios were constructed using the sequential Gaussian simulation technique (sGs). Assuming a plutonium isotopic ratio range of 0.152 ± 0.003 to 0.169 ± 0.009 is characteristic to global fallout in Colorado, and a mean value of 0.155 is representative for the Rocky Flats Plant area, the main findings of the current work were (1) the areas northwest and southwest of Rocky Flats Plant exhibited a plutonium ratio ≥0.155, this were minimally impacted by the plant activity; (2) he study area east of Rocky Flats Plant exhibited a plutonium isotopic ratio ≤0.155, which is a definitive indicator of Rocky Flats Plant-derived plutonium; and (3) inventory calculations across the study area exhibited large standard error of estimates. These errors were originated from the high variability in plutonium activity over a small sampling scale and the uncertainty in the global fallout isotopic ratio. Using the mean simulated estimates of plutonium isotopic ratio, coupled with plutonium activity measured at 11 soil pits and additional plutonium information published elsewhere, the plutonium loading on the open space and residential areas amounted to 111.2 GBq, with a standard error of estimate of 50.8 GBq

  19. MO-AB-BRA-07: Low Dose Imaging with Avalanche Amorphous Selenium Flat Panel Imager

    Scheuermann, J; Howansky, A; Goldan, A; Tanioka, K; Zhao, W [Stony Brook University, Stony Brook, New York (United States); Leveille, S; Tousignant, O [2Analogic Canada, Saint-laurent, Quebec (Canada)

    2016-06-15

    Purpose: We present the first active matrix flat panel imager (AMFPI) capable of producing x-ray quantum noise limited images at low doses by overcoming the electronic noise through signal amplification by photoconductive avalanche gain (gav). The indirect detector fabricated uses an optical sensing layer of amorphous selenium (a-Se) known as High-Gain Avalanche Rushing Photoconductor (HARP). The detector design is called Scintillator HARP (SHARP)-AMFPI. This is the first image sensor to utilize solid-state HARP technology. Methods: The detector’s electronic readout is a 24 × 30 cm{sup 2} array of thin film transistors (TFT) with a pixel pitch of 85 µm. The HARP structure consists of a 15 µm layer of a-Se isolated from the high voltage (HV) and signal electrode by a 2 µm thick hole blocking layer and electron blocking layer, respectively, to reduce dark current. A 150 µm thick structured CsI scintillator with reflective backing and a fiber optic faceplate (FOP) was coupled to the semi-transparent HV bias electrode of the HARP structure. Images were acquired using a 30 kVp Mo/Mo spectrum typically used in mammography. Results: Optical sensitivity measurements demonstrate that gav = 76 ± 5 can be achieved over the entire active area of the detector. At a constant dose to the detector of 6.67 µGy, image quality increases with gav until the effective electronic noise is negligible. Quantum noise limited images can be obtained with doses as low as 0.18 µGy. Conclusion: We demonstrate the feasibility of utilizing avalanche gain to overcome electronic noise. The indirect detector fabricated is the first solid-state imaging sensor to use HARP, and the largest active area HARP sensor to date. Our future work is to improve charge transport within the HARP structure and utilize a transparent HV electrode.

  20. Non-Abelian bosonization as a nonholonomic transformation from a flat to a curved field space

    Kleinert, H.

    1997-01-01

    There exists a simple rule by which path integrals for the motion of a point particle in a flat space can be transformed correctly into those in a curved space. This rule arose from well-established methods in the theory of plastic deformations, where crystals with defects are described mathematically by applying active nonholonomic coordinate transformations to ideal crystals. In the context of time-sliced path integrals, this has given rise to a quantum equivalence principle which determines the short-time action and functional integration measure of fluctuating orbits in spaces with curvature and torsion. The nonholonomic transformations have a nontrivial Jacobian which in curved spaces produces an additional energy proportional to the curvature scalar, thereby canceling an equal term found earlier by DeWitt in his formulation of Feynman close-quote s time-sliced path integral in curved space. The importance of this cancelation has been documented in various systems (H-atom, particle on the surface of a sphere, spinning top). Here we point out its relevance to the bosonization of a non-Abelian one-dimensional quantum field theory, whose fields live in a flat field space. The bosonized version is a quantum-mechanical path integral of a point particle moving in a space with constant curvature. The additional term introduced by the Jacobian is crucial for the identity between original and bosonized theory. A useful bosonization tool is the so-called Hubbard endash Stratonovich formula for which we find a nonabelian version. copyright 1997 Academic Press, Inc

  1. Human Visual Performance and Flat Panel Display Image Quality

    1980-07-01

    visible light energy can be described in electro- magnetic energy space as that portion of the electromagnetic wavelength (or frequency) domain to...temporal frequency domain much as one analyzes spatial information in the spatial frequency domain. As the content of a complex but periodic sound ...briefly with the more intepretive aspects of information display, those pertaining to information encoding and the design problems and parame- ters

  2. CMOS Flat-Panel CBCT for Dental Imaging

    Youn, Han Bean; Cho, Min Kook; Kim, Jee Young; Lee, Hyun Ji; Cho, Bong Hye; Heo, Sung Kyn

    2009-01-01

    Computed tomography (CT) has become one of the most frequently used imaging modalities for the preoperative evaluation of the jaw for dental implants. Sometimes dental Implant surgery needs histologic information of the regeneration of bone structure However conventional dental CT cannot serve these information because of its resolution limit. Hence we suggest dental CT which has micro scale resolution with high magnification factor. In these regards, We investigated micro dental CT with optimal magnification factor about our hardware system and evaluated along the 2D and 3D performance experimentally

  3. Evaluation of a flat panel digital radiographic system for low-dose portable imaging of neonates

    Samei, Ehsan; Hill, Jeanne G.; Frey, G. Donald; Southgate, W. Michael; Mah, Eugene; Delong, David

    2003-01-01

    The purpose of this study was to evaluate the clinical utility of an investigational flat-panel digital radiography system for low-dose portable neonatal imaging. Thirty image-pairs from neonatal intensive care unit patients were acquired with a commercial Computed Radiography system (Agfa, ADC 70), and with the investigational system (Varian, Paxscan 2520) at one-quarter of the exposure. The images were evaluated for conspicuity and localization of the endings of ancillary catheters and tubes in two observer performance experiments with three pediatric radiologists and three neonatologists serving as observers. The results indicated no statistically significant difference in diagnostic quality between the images from the investigational system and from CR. Given the investigational system's superior resolution and noise characteristics, observer results suggest that the high detective quantum efficiency of flat-panel digital radiography systems can be utilized to decrease the radiation dose/exposure to neonatal patients, although post-processing of the images remains to be optimized. The rapid availability of flat-panel images in portable imaging was found to be an added advantage for timely clinical decision-making

  4. Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

    Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

    2007-09-25

    The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

  5. Local differential geometry of null curves in conformally flat space-time

    Urbantke, H.

    1989-01-01

    The conformally invariant differential geometry of null curves in conformally flat space-times is given, using the six-vector formalism which has generalizations to higher dimensions. This is then paralleled by a twistor description, with a twofold merit: firstly, sometimes the description is easier in twistor terms, sometimes in six-vector terms, which leads to a mutual enlightenment of both; and secondly, the case of null curves in timelike pseudospheres or 2+1 Minkowski space we were only able to treat twistorially, making use of an invariant differential found by Fubini and Cech. The result is the expected one: apart from stated exceptional cases there is a conformally invariant parameter and two conformally invariant curvatures which, when specified in terms of this parameter, serve to characterize the curve up to conformal transformations. 12 refs. (Author)

  6. Attenuation of multiples in image space

    Alvarez, Gabriel F.

    In complex subsurface areas, attenuation of 3D specular and diffracted multiples in data space is difficult and inaccurate. In those areas, image space is an attractive alternative. There are several reasons: (1) migration increases the signal-to-noise ratio of the data; (2) primaries are mapped to coherent events in Subsurface Offset Domain Common Image Gathers (SODCIGs) or Angle Domain Common Image Gathers (ADCIGs); (3) image space is regular and smaller; (4) attenuating the multiples in data space leaves holes in the frequency-Wavenumber space that generate artifacts after migration. I develop a new equation for the residual moveout of specular multiples in ADCIGs and use it for the kernel of an apex-shifted Radon transform to focus and separate the primaries from specular and diffracted multiples. Because of small amplitude, phase and kinematic errors in the multiple estimate, we need adaptive matching and subtraction to estimate the primaries. I pose this problem as an iterative least-squares inversion that simultaneously matches the estimates of primaries and multiples to the data. Standard methods match only the estimate of the multiples. I demonstrate with real and synthetic data that the method produces primaries and multiples with little cross-talk. In 3D, the multiples exhibit residual moveout in SODCIGs in in-line and cross-line offsets. They map away from zero subsurface offsets when migrated with the faster velocity of the primaries. In ADCIGs the residual moveout of the primaries as a function of the aperture angle, for a given azimuth, is flat for those angles that illuminate the reflector. The multiples have residual moveout towards increasing depth for increasing aperture angles at all azimuths. As a function of azimuth, the primaries have better azimuth resolution than the multiples at larger aperture angles. I show, with a real 3D dataset, that even below salt, where illumination is poor, the multiples are well attenuated in ADCIGs with the new

  7. Multiband super-resolution imaging of graded-index photonic crystal flat lens

    Xie, Jianlan; Wang, Junzhong; Ge, Rui; Yan, Bei; Liu, Exian; Tan, Wei; Liu, Jianjun

    2018-05-01

    Multiband super-resolution imaging of point source is achieved by a graded-index photonic crystal flat lens. With the calculations of six bands in common photonic crystal (CPC) constructed with scatterers of different refractive indices, it can be found that the super-resolution imaging of point source can be realized by different physical mechanisms in three different bands. In the first band, the imaging of point source is based on far-field condition of spherical wave while in the second band, it is based on the negative effective refractive index and exhibiting higher imaging quality than that of the CPC. However, in the fifth band, the imaging of point source is mainly based on negative refraction of anisotropic equi-frequency surfaces. The novel method of employing different physical mechanisms to achieve multiband super-resolution imaging of point source is highly meaningful for the field of imaging.

  8. FLAT TIME-LIKE SUBMANIFOLDS IN ANTI-DE SITTER SPACE H12n-1(-1)

    ZUO DAFENG; CHEN QING; CHENG YI

    2005-01-01

    By using dressing actions of the Gn-1 1,1,n-1-system, the authors study geometric transformations for flat time-like n-submanifolds with flat, non-degenerate normal bun dle in anti-de Sitter space H1 2n-1(-1), where G1,1 n-1,n-1= O(2n - 2, 2)/O(n - 1, 1) ×O(n - 1, 1).

  9. A camac based data acquisition system for flat-panel image array readout

    Morton, E.J.; Antonuk, L.E.; Berry, J.E.; Huang, W.; Mody, P.; Yorkston, J.; Longo, M.J.

    1993-01-01

    A readout system has been developed to facilitate the digitization and subsequent display of image data from two-dimensional, pixellated, flat-panel, amorphous silicon imaging arrays. These arrays have been designed specifically for medical x-ray imaging applications. The readout system is based on hardware and software developed for various experiments at CERN and Fermi National Accelerator Laboratory. Additional analog signal processing and digital control electronics were constructed specifically for this application. The authors report on the form of the resulting data acquisition system, discuss aspects of its performance, and consider the compromises which were involved in its design

  10. Ghost Imaging of Space Objects

    Strekalov, Dmitry V; Erkmen, Baris I; Yu Nan

    2013-01-01

    The term 'ghost imaging' was coined in 1995 when an optical correlation measurement in combination with an entangled photon-pair source was used to image a mask placed in one optical channel by raster-scanning a detector in the other, empty, optical channel. Later, it was shown that the entangled photon source could be replaced with thermal sources of light, which are abundantly available as natural illumination sources. It was also shown that the bucket detector could be replaced with a remote point-like detector, opening the possibility to remote-sensing imaging applications. In this paper, we discuss the application of ghost-imaging-like techniques to astronomy, with the objective of detecting intensity-correlation signatures resulting from space objects of interest, such as exo-planets, gas clouds, and gravitational lenses. An important aspect of being able to utilize ghost imaging in astronomy, is the recognition that in interstellar imaging geometries the object of interest can act as an effective beam splitter, yielding detectable variations in the intensity-correlation signature.

  11. Progress toward clinical implementation of the first flat-panel amorphous silicon imager

    Antonuk, Larry E.; El-Mohri, Youcef; Weidong, Huang; Sandler, Howard; Siewerdsen, Jeffrey H.; Yorkston, John

    1995-01-01

    Purpose: Approximately 7 years after the development of the general concept, megavoltage imagers based on thin-film, flat-panel electronics will likely enter routine clinical use within the next few years. In this paper, current capabilities and anticipated development of this imaging technology as pertains to clinical use will be presented. The results of the first use of this technology with an early prototype imager in a clinical setting are reported. The development of a more advanced clinical prototype imager designed for routine clinical use is described and the clinically-relevant capabilities, advantages, and limitations of this device are described. Materials and Methods: Flat-panel amorphous silicon imagers consist of an imaging array, an x-ray converter, external data acquisition electronics, along with appropriate software and a host workstation. The array consists of a two-dimensional grid of imaging pixels with each pixel consisting of a transistor coupled to a photodiode. An initial study of patient imaging has been performed with an early prototype imager which incorporates a 512x560 array with 450 μm pixels giving an imaging surface of 23x25 cm 2 . Portal images acquired with this prototype imager and with film under similar geometric and irradiation conditions were acquired and compared. In addition, a clinical prototype imager based upon a 26x26 cm 2 array with 508 μm pixels (512x512 pixels) is under development. This prototype incorporates advanced analog and digital external electronics which will improve imaging performance thereby increasing clinical utility of the device. The imagers are interfaced to the operation of a treatment machine so as to allow both radiographic and fluoroscopic operation. Results: The image quality is limited by the presence of pixel and line defects in the array and by the presence of correlated and uncorrelated noise sources in the acquisition system. Nevertheless, the contrast and spatial resolution offered by

  12. Space Radar Image of Chernobyl

    1994-01-01

    This is an image of the Chernobyl nuclear power plant and its surroundings, centered at 51.17 north latitude and 30.15 west longitude. The image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar aboard the space shuttle Endeavour on its 16th orbit on October 1, 1994. The area is located on the northern border of the Ukraine Republic and was produced by using the L-band (horizontally transmitted and received) polarization. The differences in the intensity are due to differences in vegetation cover, with brighter areas being indicative of more vegetation. These data were acquired as part of a collaboration between NASA and the National Space Agency of Ukraine in Remote Sensing and Earth Sciences. NASA has included several sites provided by the Ukrainian space agency as targets of opportunity during the second flight of SIR-C/X-SAR. The Ukrainian space agency also plans to conduct airborne surveys of these sites during the mission. The Chernobyl nuclear power plant is located toward the top of the image near the Pripyat River. The 12-kilometer (7.44-mile)-long cooling pond is easily distinguishable as an elongated dark shape in the center near the top of the image. The reactor complex is visible as the bright area to the extreme left of the cooling pond and the city of Chernobyl is the bright area just below the cooling pond next to the Pripyat River. The large dark area in the bottom right of the image is the Kiev Reservoir just north of Kiev. Also visible is the Dnieper River, which feeds into the Kiev Reservoir from the top of the image. The Soviet government evacuated 116,000 people within 30 kilometers (18.6 miles) of the Chernobyl reactor after the explosion and fire on April 26, 1986. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight

  13. Automatic analysis of quality of images from X-ray digital flat detectors

    Le Meur, Y.

    2009-04-01

    Since last decade, medical imaging has grown up with the development of new digital imaging techniques. In the field of X-ray radiography, new detectors replace progressively older techniques, based on film or x-ray intensifiers. These digital detectors offer a higher sensibility and reduced overall dimensions. This work has been prepared with Trixell, the world leading company in flat detectors for medical radiography. It deals with quality control on digital images stemming from these detectors. High quality standards of medical imaging impose a close analysis of the defects that can appear on the images. This work describes a complete process for quality analysis of such images. A particular focus is given on the detection task of the defects, thanks to methods well adapted to our context of spatially correlated defects in noise background. (author)

  14. On the non-local obstruction to interacting higher spins in flat space

    Taronna, Massimo [Physique Théorique et Mathématique,Université Libre de Bruxelles and International Solvay Institutes,ULB-Campus Plaine CP231, 1050 Brussels (Belgium)

    2017-05-04

    Owing to a renewed interest in flat space higher spin gauge theories, in this note we provide further details and clarifications on the results presented in arXiv:1107.5843 and arXiv: 1209.5755, which investigated their locality properties. Focusing, for simplicity, on quartic couplings with one of the external legs having non-zero integer spin (which can be considered as a prototype for Weinberg-type arguments), we review the appearance of 1/◻ non-localities. In particular, we emphasise that it appears to be not possible to eliminate all of the aforementioned non-localities in the general quartic Noether procedure solution with a judicious choice of coupling constants and spectrum. We also discuss the light-cone gauge fixing in d=4, and argue that the non-local obstruction discussed in the covariant language cannot be avoided using light-cone gauge formalism.

  15. Space Radar Image of Flevoland, Netherlands

    1999-01-01

    This is a three-frequency false color image of Flevoland, The Netherlands, centered at 52.4 degrees north latitude, 5.4 degrees east longitude. This image was acquired by the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard space shuttle Endeavour on April 14, 1994. It was produced by combining data from the X-band, C-band and L-band radars. The area shown is approximately 25 kilometers by 28 kilometers (15-1/2 by 17-1/2 miles). Flevoland, which fills the lower two-thirds of the image, is a very flat area that is made up of reclaimed land that is used for agriculture and forestry. At the top of the image, across the canal from Flevoland, is an older forest shown in red; the city of Harderwijk is shown in white on the shore of the canal. At this time of the year, the agricultural fields are bare soil, and they show up in this image in blue. The changes in the brightness of the blue areas are equal to the changes in roughness. The dark blue areas are water and the small dots in the canal are boats. This SIR-C/X-SAR supersite is being used for both calibration and agricultural studies. Several soil and crop ground-truth studies will be conducted during the shuttle flight. In addition, about 10calibration devices and 10 corner reflectors have been deployed to calibrate and monitor the radar signal. One of these transponders can be seen as a bright star in the lower right quadrant of the image. This false-color image was made using L-band total power in the red channel, C-band total power in the green channel, and X-band VV polarization in the blue channel. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by

  16. Continuous imaging space in three-dimensional integral imaging

    Zhang Lei; Yang Yong; Wang Jin-Gang; Zhao Xing; Fang Zhi-Liang; Yuan Xiao-Cong

    2013-01-01

    We report an integral imaging method with continuous imaging space. This method simultaneously reconstructs real and virtual images in the virtual mode, with a minimum gap that separates the entire imaging space into real and virtual space. Experimental results show that the gap is reduced to 45% of that in a conventional integral imaging system with the same parameters. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  17. An asynchronous, pipelined, electronic acquisition system for Active Matrix Flat-Panel Imagers (AMFPIs)

    Huang, W; Berry, J; Maolinbay, M; Martelli, C; Mody, P; Nassif, S; Yeakey, M

    1999-01-01

    The development of a full-custom electronic acquisition system designed for readout of large-area active matrix flat-panel imaging arrays is reported. The arrays, which comprise two-dimensional matrices of pixels utilizing amorphous silicon thin-film transistors, are themselves under development for a wide variety of X-ray imaging applications. The acquisition system was specifically designed to facilitate detailed, quantitative investigations of the properties of these novel imaging arrays and contains significant enhancements compared to a previously developed acquisition system. These enhancements include pipelined preamplifier circuits to allow faster readout speed, expanded addressing capabilities allowing a maximum of 4096 array data lines, and on-board summing of image frames. The values of many acquisition system parameters, including timings and voltages, may be specified and downloaded from a host computer. Once acquisition is enabled, the system operates asynchronously of its host computer. The sys...

  18. Paediatric interventional cardiology: flat detector versus image intensifier using a test object

    Vano, E.; Ubeda, C.; Martinez, L. C.; Leyton, F.; Miranda, P.

    2010-12-01

    Entrance surface air kerma (ESAK) values and image quality parameters were measured and compared for two biplane angiography x-ray systems dedicated to paediatric interventional cardiology, one equipped with image intensifiers (II) and the other one with dynamic flat detectors (FDs). Polymethyl methacrylate phantoms of different thicknesses, ranging from 8 to 16 cm, and a Leeds TOR 18-FG test object were used. The parameters of the image quality evaluated were noise, signal-difference-to-noise ratio (SdNR), high contrast spatial resolution (HCSR) and three figures of merit combining entrance doses and signal-to-noise ratios or HCSR. The comparisons showed a better behaviour of the II-based system in the low contrast region over the whole interval of thicknesses. The FD-based system showed a better performance in HCSR. The FD system evaluated would need around two times more dose than the II system evaluated to reach a given value of SdNR; moreover, a better spatial resolution was measured (and perceived in conventional monitors) for the system equipped with flat detectors. According to the results of this paper, the use of dynamic FD systems does not lead to an automatic reduction in ESAK or to an automatic improvement in image quality by comparison with II systems. Any improvement also depends on the setting of the x-ray systems and it should still be possible to refine these settings for some of the dynamic FDs used in paediatric cardiology.

  19. Paediatric interventional cardiology: flat detector versus image intensifier using a test object

    Vano, E [Radiology Department, Medicine School, Complutense University and San Carlos University Hospital, 28040 Madrid (Spain); Ubeda, C [Clinical Sciences Department, Faculty of the Science of Health and CIHDE, Tarapaca University, 18 de Septiembre 2222, Arica (Chile); Martinez, L C [Medical Physics and Radiation Protection Service, 12 de Octubre University Hospital, Madrid (Spain); Leyton, F [Institute of Public Health of Chile, Marathon 1000, Nunoa, Santiago (Chile); Miranda, P, E-mail: eliseov@med.ucm.e [Hemodynamic Department, Cardiovascular Service, Luis Calvo Mackenna Hospital, Avenida Antonio Varaas 360, Providencia, Santiago (Chile)

    2010-12-07

    Entrance surface air kerma (ESAK) values and image quality parameters were measured and compared for two biplane angiography x-ray systems dedicated to paediatric interventional cardiology, one equipped with image intensifiers (II) and the other one with dynamic flat detectors (FDs). Polymethyl methacrylate phantoms of different thicknesses, ranging from 8 to 16 cm, and a Leeds TOR 18-FG test object were used. The parameters of the image quality evaluated were noise, signal-difference-to-noise ratio (SdNR), high contrast spatial resolution (HCSR) and three figures of merit combining entrance doses and signal-to-noise ratios or HCSR. The comparisons showed a better behaviour of the II-based system in the low contrast region over the whole interval of thicknesses. The FD-based system showed a better performance in HCSR. The FD system evaluated would need around two times more dose than the II system evaluated to reach a given value of SdNR; moreover, a better spatial resolution was measured (and perceived in conventional monitors) for the system equipped with flat detectors. According to the results of this paper, the use of dynamic FD systems does not lead to an automatic reduction in ESAK or to an automatic improvement in image quality by comparison with II systems. Any improvement also depends on the setting of the x-ray systems and it should still be possible to refine these settings for some of the dynamic FDs used in paediatric cardiology.

  20. Space Radar Image of Bahia

    1994-01-01

    This is a color composite image of southern Bahia, Brazil, centered at 15.22 degree south latitude and 39.07 degrees west longitude. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar aboard the space shuttle Endeavour on its 38th orbit of Earth on October 2, 1994. The image covers an area centered over the Una Biological Reserve, one the largest protected areas in northeastern Brazil. The 7,000-hectare reserve is administered by the Brazilian Institute for the Environment and is part of the larger Atlantic coastal forest, a narrow band of rain forest extending along the eastern coast of Brazil. The Atlantic coastal forest of southern Bahia is one of the world's most threatened and diverse ecosystems. Due to widespread settlement, only 2 to 5 percent of the original forest cover remains. Yet the region still contains an astounding variety of plants and animals, including a large number of endemic species. More than half of the region's tree species and 80 percent of its animal species are indigenous and found nowhere else on Earth. The Una Reserve is also the only federally protected habitat for the golden-headed lion tamarin, the yellow-breasted capuchin monkey and many other endangered species. In the past few years, scientists from Brazilian and international conservation organizations have coordinated efforts to study the biological diversity of this region and to develop practical and economically viable options for preserving the remaining primary forests in southern Bahia. The shuttle imaging radar is used in this study to identify various land uses and vegetation types, including remaining patches of primary forest, cabruca forest (cacao planted in the understory of the native forest), secondary forest, pasture and coastal mangrove. Standard remote-sensing technology that relies on light reflected from the forest canopy cannot accurately distinguish between cabruca and undisturbed forest. Optical remote sensing is also

  1. Space Images for NASA/JPL

    Boggs, Karen; Gutheinz, Sandy C.; Watanabe, Susan M.; Oks, Boris; Arca, Jeremy M.; Stanboli, Alice; Peez, Martin; Whatmore, Rebecca; Kang, Minliang; Espinoza, Luis A.

    2010-01-01

    Space Images for NASA/JPL is an Apple iPhone application that allows the general public to access featured images from the Jet Propulsion Laboratory (JPL). A back-end infrastructure stores, tracks, and retrieves space images from the JPL Photojournal Web server, and catalogs the information into a streamlined rating infrastructure.

  2. An asynchronous, pipelined, electronic acquisition system for Active Matrix Flat-Panel Imagers (AMFPIs)

    Huang, W.; Antonuk, L.E. E-mail: antonuk@umich.edu; Berry, J.; Maolinbay, M.; Martelli, C.; Mody, P.; Nassif, S.; Yeakey, M

    1999-07-11

    The development of a full-custom electronic acquisition system designed for readout of large-area active matrix flat-panel imaging arrays is reported. The arrays, which comprise two-dimensional matrices of pixels utilizing amorphous silicon thin-film transistors, are themselves under development for a wide variety of X-ray imaging applications. The acquisition system was specifically designed to facilitate detailed, quantitative investigations of the properties of these novel imaging arrays and contains significant enhancements compared to a previously developed acquisition system. These enhancements include pipelined preamplifier circuits to allow faster readout speed, expanded addressing capabilities allowing a maximum of 4096 array data lines, and on-board summing of image frames. The values of many acquisition system parameters, including timings and voltages, may be specified and downloaded from a host computer. Once acquisition is enabled, the system operates asynchronously of its host computer. The system allows image capture in both radiographic mode (corresponding to the capture of individual X-ray images), and fluoroscopic mode (corresponding to the capture of a continual series of X-ray images). A detailed description of the system architecture and the underlying motivations for the design is reported in this paper. (author)

  3. Mid-space-independent deformable image registration.

    Aganj, Iman; Iglesias, Juan Eugenio; Reuter, Martin; Sabuncu, Mert Rory; Fischl, Bruce

    2017-05-15

    Aligning images in a mid-space is a common approach to ensuring that deformable image registration is symmetric - that it does not depend on the arbitrary ordering of the input images. The results are, however, generally dependent on the mathematical definition of the mid-space. In particular, the set of possible solutions is typically restricted by the constraints that are enforced on the transformations to prevent the mid-space from drifting too far from the native image spaces. The use of an implicit atlas has been proposed as an approach to mid-space image registration. In this work, we show that when the atlas is aligned to each image in the native image space, the data term of implicit-atlas-based deformable registration is inherently independent of the mid-space. In addition, we show that the regularization term can be reformulated independently of the mid-space as well. We derive a new symmetric cost function that only depends on the transformation morphing the images to each other, rather than to the atlas. This eliminates the need for anti-drift constraints, thereby expanding the space of allowable deformations. We provide an implementation scheme for the proposed framework, and validate it through diffeomorphic registration experiments on brain magnetic resonance images. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Auto-calibration of GF-1 WFV images using flat terrain

    Zhang, Guo; Xu, Kai; Huang, Wenchao

    2017-12-01

    Four wide field view (WFV) cameras with 16-m multispectral medium-resolution and a combined swath of 800 km are onboard the Gaofen-1 (GF-1) satellite, which can increase the revisit frequency to less than 4 days and enable large-scale land monitoring. The detection and elimination of WFV camera distortions is key for subsequent applications. Due to the wide swath of WFV images, geometric calibration using either conventional methods based on the ground control field (GCF) or GCF independent methods is problematic. This is predominantly because current GCFs in China fail to cover the whole WFV image and most GCF independent methods are used for close-range photogrammetry or computer vision fields. This study proposes an auto-calibration method using flat terrain to detect nonlinear distortions of GF-1 WFV images. First, a classic geometric calibration model is built for the GF1 WFV camera, and at least two images with an overlap area that cover flat terrain are collected, then the elevation residuals between the real elevation and that calculated by forward intersection are used to solve nonlinear distortion parameters in WFV images. Experiments demonstrate that the orientation accuracy of the proposed method evaluated by GCF CPs is within 0.6 pixel, and residual errors manifest as random errors. Validation using Google Earth CPs further proves the effectiveness of auto-calibration, and the whole scene is undistorted compared to not using calibration parameters. The orientation accuracy of the proposed method and the GCF method is compared. The maximum difference is approximately 0.3 pixel, and the factors behind this discrepancy are analyzed. Generally, this method can effectively compensate for distortions in the GF-1 WFV camera.

  5. Cerebral blood volume imaging by flat detector computed tomography in comparison to conventional multislice perfusion CT

    Struffert, Tobias; Kloska, Stephan; Engelhorn, Tobias; Doerfler, Arnd; Deuerling-Zheng, Yu; Boese, Jan; Zellerhoff, Michael; Schwab, Stefan

    2011-01-01

    We tested the hypothesis that Flat Detector computed tomography (FD-CT) with intravenous contrast medium would allow the calculation of whole brain cerebral blood volume (CBV) mapping (FD-CBV) and would correlate with multislice Perfusion CT (PCT). Twenty five patients were investigated with FD-CBV and PCT. Correlation of the CBV maps of both techniques was carried out with measurements from six anatomical regions from both sides of the brain. Mean values of each region and the correlation coefficient were calculated. Bland-Altman analysis was performed to compare the two different imaging techniques. The image and data quality of both PCT and FD-CBV were suitable for evaluation in all patients. The mean CBV values of FD-CBV and PCT showed only minimal differences with overlapping standard deviation. The correlation coefficient was 0.79 (p < 0.01). Bland-Altman analysis showed a mean difference of -0.077 ± 0.48 ml/100 g between FD-CBV and PCT CBV measurements, indicating that FD-CBV values were only slightly lower than those of PCT. CBV mapping with intravenous contrast medium using Flat Detector CT compared favourably with multislice PCT. The ability to assess cerebral perfusion within the angiographic suite may improve the management of ischaemic stroke and evaluation of the efficacy of dedicated therapies. (orig.)

  6. Cone-beam CT with a flat-panel detector: From image science to image-guided surgery

    Siewerdsen, Jeffrey H.

    2011-01-01

    The development of large-area flat-panel X-ray detectors (FPDs) has spurred investigation in a spectrum of advanced medical imaging applications, including tomosynthesis and cone-beam CT (CBCT). Recent research has extended image quality metrics and theoretical models to such applications, providing a quantitative foundation for the assessment of imaging performance as well as a general framework for the design, optimization, and translation of such technologies to new applications. For example, cascaded systems models of the Fourier domain metrics, such as noise-equivalent quanta (NEQ), have been extended to these modalities to describe the propagation of signal and noise through the image acquisition and reconstruction chain and to quantify the factors that govern spatial resolution, image noise, and detectability. Moreover, such models have demonstrated basic agreement with human observer performance for a broad range of imaging conditions and imaging tasks. These developments in image science have formed a foundation for the knowledgeable development and translation of CBCT to new applications in image-guided interventions-for example, CBCT implemented on a mobile surgical C-arm for intraoperative 3D imaging. The ability to acquire high-quality 3D images on demand during surgical intervention overcomes conventional limitations of surgical guidance in the context of preoperative images alone. A prototype mobile C-arm developed in academic-industry partnership demonstrates CBCT with low radiation dose, sub-mm spatial resolution, and soft-tissue visibility potentially approaching that of diagnostic CT. Integration of the 3D imaging system with real-time tracking, deformable registration, endoscopic video, and 3D visualization offers a promising addition to the surgical arsenal in interventions ranging from head-and-neck/skull base surgery to spine, orthopaedic, thoracic, and abdominal surgeries. Cadaver studies show the potential for significant boosts in surgical

  7. Cone-beam CT with a flat-panel detector: From image science to image-guided surgery

    Siewerdsen, Jeffrey H., E-mail: jeff.siewerdsen@jhu.edu [Department of Biomedical Engineering, Johns Hopkins University, Traylor Building, Room 718, 720 Rutland Avenue, Baltimore, MD 21205 (United States)

    2011-08-21

    The development of large-area flat-panel X-ray detectors (FPDs) has spurred investigation in a spectrum of advanced medical imaging applications, including tomosynthesis and cone-beam CT (CBCT). Recent research has extended image quality metrics and theoretical models to such applications, providing a quantitative foundation for the assessment of imaging performance as well as a general framework for the design, optimization, and translation of such technologies to new applications. For example, cascaded systems models of the Fourier domain metrics, such as noise-equivalent quanta (NEQ), have been extended to these modalities to describe the propagation of signal and noise through the image acquisition and reconstruction chain and to quantify the factors that govern spatial resolution, image noise, and detectability. Moreover, such models have demonstrated basic agreement with human observer performance for a broad range of imaging conditions and imaging tasks. These developments in image science have formed a foundation for the knowledgeable development and translation of CBCT to new applications in image-guided interventions-for example, CBCT implemented on a mobile surgical C-arm for intraoperative 3D imaging. The ability to acquire high-quality 3D images on demand during surgical intervention overcomes conventional limitations of surgical guidance in the context of preoperative images alone. A prototype mobile C-arm developed in academic-industry partnership demonstrates CBCT with low radiation dose, sub-mm spatial resolution, and soft-tissue visibility potentially approaching that of diagnostic CT. Integration of the 3D imaging system with real-time tracking, deformable registration, endoscopic video, and 3D visualization offers a promising addition to the surgical arsenal in interventions ranging from head-and-neck/skull base surgery to spine, orthopaedic, thoracic, and abdominal surgeries. Cadaver studies show the potential for significant boosts in surgical

  8. Generalized probabilistic scale space for image restoration.

    Wong, Alexander; Mishra, Akshaya K

    2010-10-01

    A novel generalized sampling-based probabilistic scale space theory is proposed for image restoration. We explore extending the definition of scale space to better account for both noise and observation models, which is important for producing accurately restored images. A new class of scale-space realizations based on sampling and probability theory is introduced to realize this extended definition in the context of image restoration. Experimental results using 2-D images show that generalized sampling-based probabilistic scale-space theory can be used to produce more accurate restored images when compared with state-of-the-art scale-space formulations, particularly under situations characterized by low signal-to-noise ratios and image degradation.

  9. Sensitivity of imaging properties of metal-dielectric layered flat lens to fabrication inaccuracies

    Kotynski, R.; Baghdasaryan, H.; Stefaniuk, T.

    2010-01-01

    We characterize the sensitivity of imaging properties of a layered silver-TiO2 flat lens to fabrication inaccuracies. The lens is designed for approximately diffraction-free imaging with subwavelength resolution at distances in the order of a wavelength. Its operation may be attributed to self......-collimation with a secondary role of Fabry-Perot resonant transmission, even though the first order effective medium description of the structure is inaccurate. Super-resolution is maintained for a broad range of overall thicknesses and the total thickness of the multilayer is limited by absorption. The tolerance analysis...... indicates that the resolution and transmission efficiency are highly sensitive to small changes of layer thicknesses....

  10. Solid-state, flat-panel, digital radiography detectors and their physical imaging characteristics

    Cowen, A.R. [LXi Research, Academic Unit of Medical Physics, University of Leeds, West Yorkshire (United Kingdom)], E-mail: a.r.cowen@leeds.ac.uk; Kengyelics, S.M.; Davies, A.G. [LXi Research, Academic Unit of Medical Physics, University of Leeds, West Yorkshire (United Kingdom)

    2008-05-15

    Solid-state, digital radiography (DR) detectors, designed specifically for standard projection radiography, emerged just before the turn of the millennium. This new generation of digital image detector comprises a thin layer of x-ray absorptive material combined with an electronic active matrix array fabricated in a thin film of hydrogenated amorphous silicon (a-Si:H). DR detectors can offer both efficient (low-dose) x-ray image acquisition plus on-line readout of the latent image as electronic data. To date, solid-state, flat-panel, DR detectors have come in two principal designs, the indirect-conversion (x-ray scintillator-based) and the direct-conversion (x-ray photoconductor-based) types. This review describes the underlying principles and enabling technologies exploited by these designs of detector, and evaluates their physical imaging characteristics, comparing performance both against each other and computed radiography (CR). In standard projection radiography indirect conversion DR detectors currently offer superior physical image quality and dose efficiency compared with direct conversion DR and modern point-scan CR. These conclusions have been confirmed in the findings of clinical evaluations of DR detectors. Future trends in solid-state DR detector technologies are also briefly considered. Salient innovations include WiFi-enabled, portable DR detectors, improvements in x-ray absorber layers and developments in alternative electronic media to a-Si:H.

  11. Potential Applications of Flat-Panel Volumetric CT in Morphologic, Functional Small Animal Imaging

    Susanne Greschus

    2005-08-01

    Full Text Available Noninvasive radiologic imaging has recently gained considerable interest in basic, preclinical research for monitoring disease progression, therapeutic efficacy. In this report, we introduce flat-panel volumetric computed tomography (fpVCT as a powerful new tool for noninvasive imaging of different organ systems in preclinical research. The three-dimensional visualization that is achieved by isotropic high-resolution datasets is illustrated for the skeleton, chest, abdominal organs, brain of mice. The high image quality of chest scans enables the visualization of small lung nodules in an orthotopic lung cancer model, the reliable imaging of therapy side effects such as lung fibrosis. Using contrast-enhanced scans, fpVCT displayed the vascular trees of the brain, liver, kidney down to the subsegmental level. Functional application of fpVCT in dynamic contrast-enhanced scans of the rat brain delivered physiologically reliable data of perfusion, tissue blood volume. Beyond scanning of small animal models as demonstrated here, fpVCT provides the ability to image animals up to the size of primates.

  12. Dynamic chest radiography: flat-panel detector (FPD) based functional X-ray imaging.

    Tanaka, Rie

    2016-07-01

    Dynamic chest radiography is a flat-panel detector (FPD)-based functional X-ray imaging, which is performed as an additional examination in chest radiography. The large field of view (FOV) of FPDs permits real-time observation of the entire lungs and simultaneous right-and-left evaluation of diaphragm kinetics. Most importantly, dynamic chest radiography provides pulmonary ventilation and circulation findings as slight changes in pixel value even without the use of contrast media; the interpretation is challenging and crucial for a better understanding of pulmonary function. The basic concept was proposed in the 1980s; however, it was not realized until the 2010s because of technical limitations. Dynamic FPDs and advanced digital image processing played a key role for clinical application of dynamic chest radiography. Pulmonary ventilation and circulation can be quantified and visualized for the diagnosis of pulmonary diseases. Dynamic chest radiography can be deployed as a simple and rapid means of functional imaging in both routine and emergency medicine. Here, we focus on the evaluation of pulmonary ventilation and circulation. This review article describes the basic mechanism of imaging findings according to pulmonary/circulation physiology, followed by imaging procedures, analysis method, and diagnostic performance of dynamic chest radiography.

  13. Three-dimensional imaging of flat natural and cultural heritage objects by a Compton scattering modality

    Guerrero Prado, Patricio; Nguyen, Mai K.; Dumas, Laurent; Cohen, Serge X.

    2017-01-01

    Characterization and interpretation of flat ancient material objects, such as those found in archaeology, paleoenvironments, paleontology, and cultural heritage, have remained a challenging task to perform by means of conventional x-ray tomography methods due to their anisotropic morphology and flattened geometry. To overcome the limitations of the mentioned methodologies for such samples, an imaging modality based on Compton scattering is proposed in this work. Classical x-ray tomography treats Compton scattering data as noise in the image formation process, while in Compton scattering tomography the conditions are set such that Compton data become the principal image contrasting agent. Under these conditions, we are able, first, to avoid relative rotations between the sample and the imaging setup, and second, to obtain three-dimensional data even when the object is supported by a dense material by exploiting backscattered photons. Mathematically this problem is addressed by means of a conical Radon transform and its inversion. The image formation process and object reconstruction model are presented. The feasibility of this methodology is supported by numerical simulations.

  14. Megavoltage imaging with a large-area, flat-panel, amorphous silicon imager

    Antonuk, Larry E.; Yorkston, John; Huang Weidong; Sandler, Howard; Siewerdsen, Jeffrey H.; El-Mohri, Youcef

    1996-01-01

    Purpose: The creation of the first large-area, amorphous silicon megavoltage imager is reported. The imager is an engineering prototype built to serve as a stepping stone toward the creation of a future clinical prototype. The engineering prototype is described and various images demonstrating its properties are shown including the first reported patient image acquired with such an amorphous silicon imaging device. Specific limitations in the engineering prototype are reviewed and potential advantages of future, more optimized imagers of this type are presented. Methods and Materials: The imager is based on a two-dimensional, pixelated array containing amorphous silicon field-effect transistors and photodiode sensors which are deposited on a thin glass substrate. The array has a 512 x 560-pixel format and a pixel pitch of 450 μm giving an imaging area of ∼23 x 25 cm 2 . The array is used in conjunction with an overlying metal plate/phosphor screen converter as well as an electronic acquisition system. Images were acquired fluoroscopically using a megavoltage treatment machine. Results: Array and digitized film images of a variety of anthropomorphic phantoms and of a human subject are presented and compared. The information content of the array images generally appears to be at least as great as that of the digitized film images. Conclusion: Despite a variety of severe limitations in the engineering prototype, including many array defects, a relatively slow and noisy acquisition system, and the lack of a means to generate images in a radiographic manner, the prototype nevertheless generated clinically useful information. The general properties of these amorphous silicon arrays, along with the quality of the images provided by the engineering prototype, strongly suggest that such arrays could eventually form the basis of a new imaging technology for radiotherapy localization and verification. The development of a clinically useful prototype offering high

  15. Performance quantification of a flat-panel imager in industrial mega-voltage X-ray imaging systems

    Stritt, Carina; Plamondon, Mathieu; Hofmann, Jürgen; Flisch, Alexander; Sennhauser, Urs

    2017-01-01

    Active matrix flat-panel detectors have gained popularity amongst X-ray imaging systems due to their speed, resolution and high dynamic range. With appropriate shielding modern flat-panel imagers can even be used in high energy Computed Tomography (CT) systems of energies up to several mega-electronvolt (MeV). However, the performance of a digital detector is not independent of the rest of the radiographic system but depends on all other components of the system. Signal and noise transfer properties highly depend on all parameters of an imaging chain. This work focuses on quantifying the resolution capabilities and the noise in the signals of a MeV X-ray imaging system. The performance quantification is done by computing the modulation transfer function (MTF) using the standard edge method as well as the noise power spectrum (NPS) of the imaging system. We performed Monte Carlo (MC) simulations in order to understand the influence of scattered radiation on the measurements. A comparison of the horizontal and vertical MTF showed that the imaging behaviour of the detector is isotropic. Moreover, an additional investigation of the noise performance of the system showed that there is no measurable noise correlation present in the system. It was shown that the thickness of the edge device does not have a significant influence on the resulting system MTF. A rapid drop in the visibility could be observed resulting in a value of 1.2 line pairs per mm at 50% MTF. The visibility limit of line pair patterns was found to be at 2.3 line pairs per mm given by the 10% MTF value.

  16. Performance quantification of a flat-panel imager in industrial mega-voltage X-ray imaging systems

    Stritt, Carina, E-mail: carina.stritt@empa.ch [Empa, Swiss Federal Laboratories for Material Science and Technology, Center for X-ray Analytics, Ueberlandstrasse 129, 8600 Dübendorf (Switzerland); Plamondon, Mathieu; Hofmann, Jürgen; Flisch, Alexander [Empa, Swiss Federal Laboratories for Material Science and Technology, Center for X-ray Analytics, Ueberlandstrasse 129, 8600 Dübendorf (Switzerland); Sennhauser, Urs [Empa, Swiss Federal Laboratories for Material Science and Technology, Reliability Science and Technology Laboratory, Ueberlandstrasse 129, 8600 Dübendorf (Switzerland)

    2017-03-11

    Active matrix flat-panel detectors have gained popularity amongst X-ray imaging systems due to their speed, resolution and high dynamic range. With appropriate shielding modern flat-panel imagers can even be used in high energy Computed Tomography (CT) systems of energies up to several mega-electronvolt (MeV). However, the performance of a digital detector is not independent of the rest of the radiographic system but depends on all other components of the system. Signal and noise transfer properties highly depend on all parameters of an imaging chain. This work focuses on quantifying the resolution capabilities and the noise in the signals of a MeV X-ray imaging system. The performance quantification is done by computing the modulation transfer function (MTF) using the standard edge method as well as the noise power spectrum (NPS) of the imaging system. We performed Monte Carlo (MC) simulations in order to understand the influence of scattered radiation on the measurements. A comparison of the horizontal and vertical MTF showed that the imaging behaviour of the detector is isotropic. Moreover, an additional investigation of the noise performance of the system showed that there is no measurable noise correlation present in the system. It was shown that the thickness of the edge device does not have a significant influence on the resulting system MTF. A rapid drop in the visibility could be observed resulting in a value of 1.2 line pairs per mm at 50% MTF. The visibility limit of line pair patterns was found to be at 2.3 line pairs per mm given by the 10% MTF value.

  17. Existential space understanding through digital image

    Susana Iñarra Abad

    2013-10-01

    Full Text Available The logical way to learn from the architectural space and then be able to design and represent it is, undoubtedly, that of experiencing it through all the sensitive channels that the space wakes up us.  But since the last 30 years, much of our learning about space comes from images of architecture and not from the space itself. The art of architecture is drifting towards a visual art and moving away from its existential side. In digital images that have flooded the architectural media, digital photographs of existing spaces intermingle with non-existent space renderings (photographs with a virtual camera. The first ones represent existing places but can be altered to change the perception that  the observer of the image will have, the second ones speak to us about places that do not exist yet but they present reality portions through extracts from digital photography (textures, trees, people... that compose the image.

  18. Effect of electromagnetic fields on the creation of scalar particles in a flat Robertson-Walker space-time

    Haouat, S.; Chekireb, R.

    2012-01-01

    The influence of electromagnetic fields on the creation of scalar particles from vacuum in a flat Robertson-Walker space-time is studied. The Klein-Gordon equation with varying electric field and constant magnetic one is solved. The Bogoliubov transformation method is applied to calculate the pair creation probability and the number density of created particles. It is shown that the electric field amplifies the creation of scalar particles while the magnetic field minimizes it. (orig.)

  19. Particle creation by a black hole as a consequence of quantum-field effects in flat space-time

    Nugayev, R.M.

    1985-01-01

    The application of quantum-field flat-space-time results to a black hole reveals the domain and the mechanism of particle creation. The Hawking radiation is ''squeezed out'' by the tail of gravitational-field potential barrier in the [1.5 Rg, infinity] region. Its black-body spectrum is due to the interaction of virtual particles with the ''cavity'' formed by the potential barrier

  20. Indirect flat-panel detector with avalanche gain: Fundamental feasibility investigation for SHARP-AMFPI (scintillator HARP active matrix flat panel imager)

    Zhao Wei; Li Dan; Reznik, Alla; Lui, B.J.M.; Hunt, D.C.; Rowlands, J.A.; Ohkawa, Yuji; Tanioka, Kenkichi

    2005-01-01

    An indirect flat-panel imager (FPI) with avalanche gain is being investigated for low-dose x-ray imaging. It is made by optically coupling a structured x-ray scintillator CsI(Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The final electronic image is read out using an active matrix array of thin film transistors (TFT). We call the proposed detector SHARP-AMFPI (scintillator HARP active matrix flat panel imager). The advantage of the SHARP-AMFPI is its programmable gain, which can be turned on during low dose fluoroscopy to overcome electronic noise, and turned off during high dose radiography to avoid pixel saturation. The purpose of this paper is to investigate the important design considerations for SHARP-AMFPI such as avalanche gain, which depends on both the thickness d Se and the applied electric field E Se of the HARP layer. To determine the optimal design parameter and operational conditions for HARP, we measured the E Se dependence of both avalanche gain and optical quantum efficiency of an 8 μm HARP layer. The results were used in a physical model of HARP as well as a linear cascaded model of the FPI to determine the following x-ray imaging properties in both the avalanche and nonavalanche modes as a function of E Se : (1) total gain (which is the product of avalanche gain and optical quantum efficiency); (2) linearity; (3) dynamic range; (4) gain nonuniformity resulting from thickness nonuniformity; and (5) effects of direct x-ray interaction in HARP. Our results showed that a HARP layer thickness of 8 μm can provide adequate avalanche gain and sufficient dynamic range for x-ray imaging applications to permit quantum limited operation over the range of exposures needed for radiography and fluoroscopy

  1. Beyond the limits of present active matrix flat-panel imagers (AMFPIs) for diagnostic radiology

    Antonuk, Larry E.; El-Mohri, Youcef; Jee, Kyung-Wook; Maolinbay, Manat; Nassif, Samer C.; Rong, Xiujiang; Siewerdsen, Jeffrey H.; Zhao, Qihua; Street, Robert A.

    1999-05-01

    A theoretical cascaded systems analysis of the performance limits of x-ray imagers based on thin-film, active matrix flat-panel technology is presented. This analysis specifically focuses upon an examination of the functional dependence of the detective quantum efficiency on exposure. While the DQE of AMFPI systems is relatively high at the large exposure levels associated with radiographic x-ray imaging, there is a significant decline in DQE with decreasing exposure over the medium and lower end of the exposure range associated with fluoroscopic imaging. This fall-off in DQE originates from the relatively large size of the additive noise of AMFPI systems compared to their overall system gain. Therefore, strategies to diminish additive noise and increase system gain should significantly improve performance. Potential strategies for noise reduction include the use of charge compensation lines while strategies for gain enhancement include continuous photodiodes, pixel amplification structures, or higher gain converters. The effect of the implementation of such strategies is examined for a variety for hypothetical imager configurations. Through the modeling of these configurations, such enhancements are shown to hold the potential of making low frequency DQE response large and essentially independent of exposure while greatly reducing the fall-off in DQE at higher spatial frequencies.

  2. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    Abu Anas, Emran Mohammad; Kim, Jae Gon; Lee, Soo Yeol; Kamrul Hasan, Md

    2011-10-01

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  3. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    Anas, Emran Mohammad Abu; Hasan, Md Kamrul; Kim, Jae Gon; Lee, Soo Yeol

    2011-01-01

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  4. Normalized glandular dose (DgN) coefficients for flat-panel CT breast imaging

    Thacker, Samta C; Glick, Stephen J

    2004-01-01

    The development of new digital mammography techniques such as dual-energy imaging, tomosynthesis and CT breast imaging will require investigation of optimal camera design parameters and optimal imaging acquisition parameters. In optimizing these acquisition protocols and imaging systems it is important to have knowledge of the radiation dose to the breast. This study presents a methodology for estimating the normalized glandular dose to the uncompressed breast using the geometry proposed for flat-panel CT breast imaging. The simulation uses the GEANT 3 Monte Carlo code to model x-ray transport and absorption within the breast phantom. The Monte Carlo software was validated for breast dosimetry by comparing results of the normalized glandular dose (DgN) values of the compressed breast to those reported in the literature. The normalized glandular dose was then estimated for a range of breast diameters from 10 cm to 18 cm using an uncompressed breast model with a homogeneous composition of adipose and glandular tissue, and for monoenergetic x-rays from 10 keV to 120 keV. These data were fit providing expressions for the normalized glandular dose. Using these expressions for the DgN coefficients and input variables such as the diameter, height and composition of the breast phantom, the mean glandular dose for any spectra can be estimated. A computer program to provide normalized glandular dose values has been made available online. In addition, figures displaying energy deposition maps are presented to better understand the spatial distribution of dose in CT breast imaging

  5. Imaging the Surfaces of Stars from Space

    Carpenter, Kenneth; Rau, Gioia

    2018-04-01

    Imaging of Stellar Surfacess has been dominated to-date by ground-based observations, but space-based facilities offer tremendous potential for extending the wavelength coverage and ultimately the resolution of such efforts. We review the imaging accomplished so far from space and then talk about exciting future prospects. The earliest attempts from space indirectly produced surface maps via the Doppler Imaging Technique, using UV spectra obtained with the International Ultraviolet Explorer (IUE). Later, the first direct UV images were obtained with the Hubble Space Telescope (HST), of Mira and Betelgeuse, using the Faint Object Camera (FOC). We will show this work and then investigate prospects for IR imaging with the James Webb Space Telescope (JWST). The real potential of space-based Imaging of Stellar Surfacess, however, lies in the future, when large-baseline Fizeau interferometers, such as the UV-optical Stellar Imager (SI) Vision Mission, with a 30-element array and 500m max baseline, are flown. We describe SI and its science goals, which include 0.1 milli-arcsec spectral Imaging of Stellar Surfacess and the probing of internal structure and flows via asteroseismology.

  6. Measurement of Flat Slab Deformations by the Multi-Image Photogrammetry Method

    Marčiš, Marián; Fraštia, Marek; Augustín, Tomáš

    2017-12-01

    The use of photogrammetry during load tests of building components is a common practise all over the world. It is very effective thanks to its contactless approach, 3D measurement, fast data collection, and partial or full automation of image processing; it can deliver very accurate results. Multi-image convergent photogrammetry supported by artificial coded targets is the most accurate photogrammetric method when the targets are detected in an image with a higher degree of accuracy than a 0.1 pixel. It is possible to achieve an accuracy of 0.03 mm for all the points measured on the object observed if the camera is close enough to the object, and the positions of the camera and the number of shots are precisely planned. This contribution deals with the design of a special hanging frame for a DSLR camera used during the photogrammetric measurement of the deformation of flat concrete slab. The results of the photogrammetric measurements are compared to the results from traditional contact measurement techniques during load tests.

  7. Measurement of Flat Slab Deformations by the Multi-Image Photogrammetry Method

    Marčiš Marián

    2017-12-01

    Full Text Available The use of photogrammetry during load tests of building components is a common practise all over the world. It is very effective thanks to its contactless approach, 3D measurement, fast data collection, and partial or full automation of image processing; it can deliver very accurate results. Multi-image convergent photogrammetry supported by artificial coded targets is the most accurate photogrammetric method when the targets are detected in an image with a higher degree of accuracy than a 0.1 pixel. It is possible to achieve an accuracy of 0.03 mm for all the points measured on the object observed if the camera is close enough to the object, and the positions of the camera and the number of shots are precisely planned. This contribution deals with the design of a special hanging frame for a DSLR camera used during the photogrammetric measurement of the deformation of flat concrete slab. The results of the photogrammetric measurements are compared to the results from traditional contact measurement techniques during load tests.

  8. Quantization vial real polarization of the moduli space of flat connections and Chern-Simons gauge theory in genus one

    Weitsman, J.; Harvard Univ., Cambridge, MA

    1991-01-01

    We study the quantization of the moduli space of flat connections on a surface of genus one, using the real polarization of this space. The quantum wave functions in this formalism are exponential functions supported along the integral fibres of the polarization. The space of wave functions obtained in this way is isomorphic to a space of theta functions. We use our construction to cunstruct part of what may be a topological field theory in genus one, and to compute the associated invariants of some three manifolds. These computations agree with those of Witten, but the invariants are expressed as sums of quantities computed at a discrete set of connections with curvature concentrated on a link in the three manifold. A similar prescription is used to produce knot invariants. (orig.)

  9. Leaf trajectory verification during dynamic intensity modulated radiotherapy using an amorphous silicon flat panel imager

    Sonke, Jan-Jakob; Ploeger, Lennert S.; Brand, Bob; Smitsmans, Monique H.P.; Herk, Marcel van

    2004-01-01

    An independent verification of the leaf trajectories during each treatment fraction improves the safety of IMRT delivery. In order to verify dynamic IMRT with an electronic portal imaging device (EPID), the EPID response should be accurate and fast such that the effect of motion blurring on the detected moving field edge position is limited. In the past, it was shown that the errors in the detected position of a moving field edge determined by a scanning liquid-filled ionization chamber (SLIC) EPID are negligible in clinical practice. Furthermore, a method for leaf trajectory verification during dynamic IMRT was successfully applied using such an EPID. EPIDs based on amorphous silicon (a-Si) arrays are now widely available. Such a-Si flat panel imagers (FPIs) produce portal images with superior image quality compared to other portal imaging systems, but they have not yet been used for leaf trajectory verification during dynamic IMRT. The aim of this study is to quantify the effect of motion distortion and motion blurring on the detection accuracy of a moving field edge for an Elekta iViewGT a-Si FPI and to investigate its applicability for the leaf trajectory verification during dynamic IMRT. We found that the detection error for a moving field edge to be smaller than 0.025 cm at a speed of 0.8 cm/s. Hence, the effect of motion blurring on the detection accuracy of a moving field edge is negligible in clinical practice. Furthermore, the a-Si FPI was successfully applied for the verification of dynamic IMRT. The verification method revealed a delay in the control system of the experimental DMLC that was also found using a SLIC EPID, resulting in leaf positional errors of 0.7 cm at a leaf speed of 0.8 cm/s

  10. Optimization of a flat-panel based real time dual-energy system for cardiac imaging

    Ducote, Justin L.; Xu Tong; Molloi, Sabee

    2006-01-01

    A simulation study was conducted to evaluate the effects of high-energy beam filtration, dual-gain operation and noise reduction on dual-energy images using a digital flat-panel detector. High-energy beam filtration increases image contrast through greater beam separation and tends to reduce total radiation exposure and dose per image pair. It is also possible to reduce dual-energy image noise by acquiring low and high-energy images at two different detector gains. In addition, dual-energy noise reduction algorithms can further reduce image noise. The cumulative effect of these techniques applied in series was investigated in this study. The contrast from a small thickness of calcium was simulated over a step phantom of tissue equivalent material with a CsI phosphor as the image detector. The dual-energy contrast-to-noise ratio was calculated using values of energy absorption and energy variance. A figure-of-merit (FOM) was calculated from dual-energy contrast-to-noise ratio (CNR) and patient effective dose estimated from values of entrance exposure. Filter atomic numbers in the range of 1-100 were considered with thicknesses ranging from 0-2500 mg/cm 2 . The simulation examined combinations of the above techniques which maximized the FOM. The application of a filter increased image contrast by as much as 45%. Near maximal increases were seen for filter atomic numbers in the range of 40-60 and 85-100 with masses above 750 mg/cm 2 . Increasing filter thickness beyond 1000 mg/cm 2 increased tube loading without further significant contrast enhancement. No additional FOM improvements were seen with dual gain before or after the application of any noise reduction algorithm. Narrow beam experiments were carried out to verify predictions. The measured FOM increased by more than a factor of 3.5 for a silver filter thickness of 800 μm, equal energy weighting and application of a noise clipping algorithm. The main limitation of dynamic high-energy filtration is increased

  11. A performance comparison of direct- and indirect-detection flat-panel imagers

    Partridge, M; Müller, L

    2002-01-01

    A comparison of the performance of a direct- and an indirect-detection amorphous silicon flat-panel X-ray imager is presented for a 6 MV beam. Experimental measurements of the noise characteristics, image lag, spectral response, spatial resolution and quantum efficiency are described, compared and discussed. The two systems are comprised of 512x512 pixel, 400 mu m pitch, arrays of a-Si:H p-i-n photodiodes and thin-film transistors. In the direct-detection system, X-rays interact to produce electron/hole pairs directly in the silicon photodiodes. For the indirect-detection system, a phosphor screen converts energy from the incident X-rays into visible light, which is then detected by the photodiodes. Both systems are shown to be quantum noise limited, with the total electronic noise in the detector 10-15 times smaller than the Poisson noise level in detected signal. The measured lag for both systems is 1.0+-0.1% or less in the first frame with subsequent signals decaying exponentially with frame read-out, with...

  12. Stress tensor correlators of CCFT{sub 2} using flat-space holography

    Asadi, Mohammad; Baghchesaraei, Omid; Fareghbal, Reza [Shahid Beheshti University, Department of Physics, Tehran (Iran, Islamic Republic of)

    2017-11-15

    We use the correspondence between three-dimensional asymptotically flat spacetimes and two-dimensional contracted conformal field theories (CCFTs) to derive the stress tensor correlators of CCFT{sub 2}. On the gravity side we use the metric formulation instead of the Chern-Simons formulation of three-dimensional gravity. This method can also be used for the four-dimensional case, where there is no Chern-Simons formulation for the bulk theory. (orig.)

  13. Bianchi like classification of cosmologies in conformally flat space-times

    Tauber, G.E.

    1989-01-01

    Solutions of Killing's equations for a conformally flat line element have been found, which are seen to correspond to the conformal group of transformations consisting of the pure conformal group, the Lorentz group, translation and dilation. A classification of the line element has been carried out, singly and combining several of them. Upon comparison with expanding universes it has been found that the Friedmann universes are a subclass with other cosmologies resulting in wider subclasses. (orig.)

  14. IMAGE QUALITY FORECASTING FOR SPACE OBJECTS

    A. I. Altukhov

    2013-05-01

    Full Text Available The article deals with an approach to quality predicting of the space objects images, which can be used to plan optoelectronic systems of remote sensing satellites work programs. The proposed approach is based on evaluation of the optoelectronic equipment transfer properties and calculation of indexes images quality considering the influence of the orbital shooting conditions.

  15. Improved space bandwidth product in image upconversion

    Dam, Jeppe Seidelin; Pedersen, Christian; Tidemand-Lichtenberg, Peter

    2012-01-01

    We present a technique increasing the space bandwidth product of a nonlinear image upconversion process used for spectral imaging. The technique exploits the strong dependency of the phase-matching condition in sum frequency generation (SFG) on the angle of propagation of the interacting fields...

  16. Line operators in theories of class S, quantized moduli space of flat connections, and Toda field theory

    Coman, Ioana; Teschner, Joerg

    2015-05-01

    Non-perturbative aspects of N=2 supersymmetric gauge theories of class S are deeply encoded in the algebra of functions on the moduli space M flat of at SL(N)-connections on Riemann surfaces. Expectation values of Wilson and 't Hooft line operators are related to holonomies of flat connections, and expectation values of line operators in the low-energy effective theory are related to Fock-Goncharov coordinates on M flat . Via the decomposition of UV line operators into IR line operators, we determine their noncommutative algebra from the quantization of Fock-Goncharov Laurent polynomials, and find that it coincides with the skein algebra studied in the context of Chern-Simons theory. Another realization of the skein algebra is generated by Verlinde network operators in Toda field theory. Comparing the spectra of these two realizations provides non-trivial support for their equivalence. Our results can be viewed as evidence for the generalization of the AGT correspondence to higher-rank class S theories.

  17. Image features for misalignment correction in medical flat-detector CT

    Wicklein, Julia; Kunze, Holger; Kalender, Willi A.; Kyriakou, Yiannis

    2012-01-01

    Purpose: Misalignment artifacts are a serious problem in medical flat-detector computed tomography. Generally, the geometrical parameters, which are essential for reconstruction, are provided by preceding calibration routines. These procedures are time consuming and the later use of stored parameters is sensitive toward external impacts or patient movement. The method of choice in a clinical environment would be a markerless online-calibration procedure that allows flexible scan trajectories and simultaneously corrects misalignment and motion artifacts during the reconstruction process. Therefore, different image features were evaluated according to their capability of quantifying misalignment. Methods: Projections of the FORBILD head and thorax phantoms were simulated. Additionally, acquisitions of a head phantom and patient data were used for evaluation. For the reconstruction different sources and magnitudes of misalignment were introduced in the geometry description. The resulting volumes were analyzed by entropy (based on the gray-level histogram), total variation, Gabor filter texture features, Haralick co-occurrence features, and Tamura texture features. The feature results were compared to the back-projection mismatch of the disturbed geometry. Results: The evaluations demonstrate the ability of several well-established image features to classify misalignment. The authors elaborated the particular suitability of the gray-level histogram-based entropy on identifying misalignment artifacts, after applying an appropriate window level (bone window). Conclusions: Some of the proposed feature extraction algorithms show a strong correlation with the misalignment level. Especially, entropy-based methods showed very good correspondence, with the best of these being the type that uses the gray-level histogram for calculation. This makes it a suitable image feature for online-calibration.

  18. Implementation of a program of quality assurance of image in an imaging system of flat panel portal; Puesta en marcha de un programa de garantia de calidad de imagen en un sistema de imagen portal de panel plano

    Gomez Barrado, A.; Sanchez Jimenez, E.; Benitez, J. A.; Sanchez-Reyes, A.

    2013-07-01

    (IGRT) image-guided radiation therapy is the one in which images are used to locate the area of treatment. Modern irradiation systems are equipped with different modalities for obtaining images, such as flat panel systems, systems conebeam, tomoimagen, etc. This paper describes the start-up and the experience of a quality assurance program based on a flat panel portal Imaging System. (Author)

  19. Feasibility study of an image slicer for future space application

    Calcines, A.; Ichimoto, K.

    2014-08-01

    This communication presents the feasibility study of an image slicer for future space missions, especially for the integral field unit (IFU) of the SUVIT (Solar UV-Visible-IR telescope) spectro-polarimeter on board the Japanese-led solar space mission Solar-C as a backup option. The MuSICa (Multi-Slit Image slicer based on collimator-Camera) image slicer concept, originally developed for the European Solar Telescope, has been adapted to the SUVIT requirements. The IFU will reorganizes a 2-D field of view of 10 x 10 arcsec2 into three slits of 0.18 arcsec width by 185.12 arcsec length using flat slicer mirrors of 100 μm width. The layout of MuSICa for Solar-C is telecentric and offers an optical quality limited by diffraction. The entrance for the SUVIT spectro-polarimeter is composed by the three IFU slits and one ordinal long slit to study, using high resolution spectro-polarimetry, the solar atmosphere (Photosphere and Chromosphere) within a spectral range between 520 nm (optionally 280 nm) and 1,100 nm.

  20. Kaluza-Klein Multidimensional Models with Ricci-Flat Internal Spaces: The Absence of the KK Particles

    Alexey Chopovsky

    2013-01-01

    Full Text Available We consider a multidimensional Kaluza-Klein (KK model with a Ricci-flat internal space, for example, a Calabi-Yau manifold. We perturb this background metrics by a system of gravitating masses, for example, astrophysical objects such as our Sun. We suppose that these masses are pressureless in the external space but they have relativistic pressure in the internal space. We show that metric perturbations do not depend on coordinates of the internal space and gravitating masses should be uniformly smeared over the internal space. This means, first, that KK modes corresponding to the metric fluctuations are absent and, second, particles should be only in the ground quantum state with respect to the internal space. In our opinion, these results look very unnatural. According to statistical physics, any nonzero temperature should result in fluctuations, that is, in KK modes. We also get formulae for the metric correction terms which enable us to calculate the gravitational tests: the deflection of light, the time-delay of the radar echoes, and the perihelion advance.

  1. Measurement of parapharyngeal space using CT images

    Ichimura, Keiichi; Kase, Yasuhiro; Iinuma, Toshitaka

    1991-01-01

    Parapharyngeal space can be defined as a potential space surrounded by deglutitional and masticator muscles and their covering, superficial and middle layer of deep cervical fascia. Parapharyngeal space has traditionally been divided by styloid process and fascia of tensor veli palatini muscle (nasopharyngeal level) or fascia of stylopharyngeus muscle (oropharyngeal level) into two compartments, prestyloid and poststyloid spaces. The latter is often called as carotid space. Prestyloid portion exclusively contains fat tissue, which yields hypoabsorption area in CT films and high density area in MRI. In most of papers in radiological journals, the term of parapharyngeal space is regarded as its prestyloid portion which is clearly identified. Axial CT images of 144 patients without any naso- or oropharyngeal lesions were analyzed. Two reference levels of nasopharynx were adopted for the study. The upper level passes through the plane of fossa of Rosenmuller, and the lower reference level transects soft palate. The following parameters of the space were measured; Length and width of the whole space, length and width of prestyloid fatty space, and furthermore, width of pre- and poststyloid space, that were divided by a imaginary line pararell to the axis of the whole space (the upper level); Length and width of the whole space, length of base and height of a triangle of the prestyloid part (the lower level). While parapharyngeal space was symmmetrical in the upper level, the rate of asymmetry amounted to a fourth in the lower level. Prestyloid space was broader than poststyloid one in the upper level. Men were dominant in length of the space in both the upper and the lower level and in length of the base of fatty space in the lower level. There was no difference between any age groups other than in fatty area in the lower level. Teens tended to be narrow, while 60's and older were wide. (author)

  2. Calibration model of a dual gain flat panel detector for 2D and 3D x-ray imaging

    Schmidgunst, C.; Ritter, D.; Lang, E.

    2007-01-01

    The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology

  3. Amorphous and Polycrystalline Photoconductors for Direct Conversion Flat Panel X-Ray Image Sensors

    Karim S. Karim

    2011-05-01

    Full Text Available In the last ten to fifteen years there has been much research in using amorphous and polycrystalline semiconductors as x-ray photoconductors in various x-ray image sensor applications, most notably in flat panel x-ray imagers (FPXIs. We first outline the essential requirements for an ideal large area photoconductor for use in a FPXI, and discuss how some of the current amorphous and polycrystalline semiconductors fulfill these requirements. At present, only stabilized amorphous selenium (doped and alloyed a-Se has been commercialized, and FPXIs based on a-Se are particularly suitable for mammography, operating at the ideal limit of high detective quantum efficiency (DQE. Further, these FPXIs can also be used in real-time, and have already been used in such applications as tomosynthesis. We discuss some of the important attributes of amorphous and polycrystalline x-ray photoconductors such as their large area deposition ability, charge collection efficiency, x-ray sensitivity, DQE, modulation transfer function (MTF and the importance of the dark current. We show the importance of charge trapping in limiting not only the sensitivity but also the resolution of these detectors. Limitations on the maximum acceptable dark current and the corresponding charge collection efficiency jointly impose a practical constraint that many photoconductors fail to satisfy. We discuss the case of a-Se in which the dark current was brought down by three orders of magnitude by the use of special blocking layers to satisfy the dark current constraint. There are also a number of polycrystalline photoconductors, HgI2 and PbO being good examples, that show potential for commercialization in the same way that multilayer stabilized a-Se x-ray photoconductors were developed for commercial applications. We highlight the unique nature of avalanche multiplication in a-Se and how it has led to the development of the commercial HARP video-tube. An all solid state version of the

  4. Evaluation the image obtained from X-ray flat-panel detectors utilizing a polycrystalline CdZnTe film as the conversion layer

    Tokuda, S.; Kishihara, H.; Kaino, M.; Sato, T.

    2006-01-01

    We can expect that fluoroscopic images with a high sensitivity and excellent detective efficiency can be obtained by using a semiconductor with a small W factor for the conversion layer of X-ray flat-panel detectors, which have experienced a rapid gain inpopularity for medical and non-destructive industrial inspection uses in recent years. We believe that polycrystalline CdZnTe film formed by the closed spaced sublimation (CSS) method is a promising conversion material for next-generation high efficiency X-ray flat-panel detectors, and have previously reported the results of feasibility studies. In this paper, we present an overview of X-ray flat-panel detectors and the features of CdZnTe film, then we describe the CSS method of deposition and evaluation of the physical characteristics of CdZnTe film, and finally we present the results of our fabrication and testing of proto-type detectors utilizing CdZnTe film. (author)

  5. An investigation of flat panel equipment variables on image quality with a dedicated cardiac phantom

    Dragusin, O; Bosmans, H; Pappas, C; Desmet, W

    2008-01-01

    Image quality (IQ) evaluation plays a key role in the process of optimization of new x-ray systems. Ideally, this process should be supported by real clinical images, but ethical issues and differences in anatomy and pathology of patients make it impossible. Phantom studies might overcome these issues. This paper presents the IQ evaluation of 30 cineangiographic films acquired with a cardiac flat panel system. The phantom used simulates the anatomy of the heart and allows the circulation of contrast agent boluses through coronary arteries. Variables investigated with influence on IQ and radiation dose are: tube potential, detector dose, added Copper filters, dynamic density optimization (DDO) and viewing angle. The IQ evaluation consisted of scoring 4 simulated calcified lesions located on different coronary artery segments in terms of degree of visualization. Eight cardiologists rated the lesions using a five-point scale ((1) lesion not visible to (5) very good visibility). Radiation doses associated to the angiograms are expressed in terms of incident air kerma (IAK) and effective dose that has been calculated with PCXMX software (STUK, Finland) from the exposure settings assuming a standard sized patient of 70 Kg. Mean IQ scores ranged from 1.68 to 4.88. The highest IQ scores were obtained for the angiograms acquired with tube potential 80 kVp, no added Cu filters, DDO 60%, RAO and LAO views and the highest entrance detector dose that has been used in the present study, namely 0.17 μGy/im. Radiation doses (IAK ∼40 mGy and effective dose of 1 mSv) were estimated for angiograms acquired at 15 frames s -1 , detector field-of-view 20 cm, and a length of 5 s. The following parameters improved the IQ factor significantly: a change in tube potential from 96 to 80 kVp, detector dose from 0.10 μGy/im to 0.17 μGy/im, the absence of Copper filtration. DDO variable which is a post-processing parameter should be carefully evaluated because it alters the quality of the

  6. An investigation of flat panel equipment variables on image quality with a dedicated cardiac phantom

    Dragusin, O; Bosmans, H [Department of Radiology, University Hospital Gasthuisberg, 49, Herestraat, 3000-Leuven (Belgium); Pappas, C; Desmet, W [Department of Cardiology, University Hospital Gasthuisberg, 49, Herestraat, 3000-Leuven (Belgium)], E-mail: odragusin@yahoo.com

    2008-09-21

    Image quality (IQ) evaluation plays a key role in the process of optimization of new x-ray systems. Ideally, this process should be supported by real clinical images, but ethical issues and differences in anatomy and pathology of patients make it impossible. Phantom studies might overcome these issues. This paper presents the IQ evaluation of 30 cineangiographic films acquired with a cardiac flat panel system. The phantom used simulates the anatomy of the heart and allows the circulation of contrast agent boluses through coronary arteries. Variables investigated with influence on IQ and radiation dose are: tube potential, detector dose, added Copper filters, dynamic density optimization (DDO) and viewing angle. The IQ evaluation consisted of scoring 4 simulated calcified lesions located on different coronary artery segments in terms of degree of visualization. Eight cardiologists rated the lesions using a five-point scale ((1) lesion not visible to (5) very good visibility). Radiation doses associated to the angiograms are expressed in terms of incident air kerma (IAK) and effective dose that has been calculated with PCXMX software (STUK, Finland) from the exposure settings assuming a standard sized patient of 70 Kg. Mean IQ scores ranged from 1.68 to 4.88. The highest IQ scores were obtained for the angiograms acquired with tube potential 80 kVp, no added Cu filters, DDO 60%, RAO and LAO views and the highest entrance detector dose that has been used in the present study, namely 0.17 {mu}Gy/im. Radiation doses (IAK {approx}40 mGy and effective dose of 1 mSv) were estimated for angiograms acquired at 15 frames s{sup -1}, detector field-of-view 20 cm, and a length of 5 s. The following parameters improved the IQ factor significantly: a change in tube potential from 96 to 80 kVp, detector dose from 0.10 {mu}Gy/im to 0.17 {mu}Gy/im, the absence of Copper filtration. DDO variable which is a post-processing parameter should be carefully evaluated because it alters the

  7. Space Images for NASA JPL Android Version

    Nelson, Jon D.; Gutheinz, Sandy C.; Strom, Joshua R.; Arca, Jeremy M.; Perez, Martin; Boggs, Karen; Stanboli, Alice

    2013-01-01

    This software addresses the demand for easily accessible NASA JPL images and videos by providing a user friendly and simple graphical user interface that can be run via the Android platform from any location where Internet connection is available. This app is complementary to the iPhone version of the application. A backend infrastructure stores, tracks, and retrieves space images from the JPL Photojournal and Institutional Communications Web server, and catalogs the information into a streamlined rating infrastructure. This system consists of four distinguishing components: image repository, database, server-side logic, and Android mobile application. The image repository contains images from various JPL flight projects. The database stores the image information as well as the user rating. The server-side logic retrieves the image information from the database and categorizes each image for display. The Android mobile application is an interfacing delivery system that retrieves the image information from the server for each Android mobile device user. Also created is a reporting and tracking system for charting and monitoring usage. Unlike other Android mobile image applications, this system uses the latest emerging technologies to produce image listings based directly on user input. This allows for countless combinations of images returned. The backend infrastructure uses industry-standard coding and database methods, enabling future software improvement and technology updates. The flexibility of the system design framework permits multiple levels of display possibilities and provides integration capabilities. Unique features of the software include image/video retrieval from a selected set of categories, image Web links that can be shared among e-mail users, sharing to Facebook/Twitter, marking as user's favorites, and image metadata searchable for instant results.

  8. Projection x-space magnetic particle imaging.

    Goodwill, Patrick W; Konkle, Justin J; Zheng, Bo; Saritas, Emine U; Conolly, Steven M

    2012-05-01

    Projection magnetic particle imaging (MPI) can improve imaging speed by over 100-fold over traditional 3-D MPI. In this work, we derive the 2-D x-space signal equation, 2-D image equation, and introduce the concept of signal fading and resolution loss for a projection MPI imager. We then describe the design and construction of an x-space projection MPI scanner with a field gradient of 2.35 T/m across a 10 cm magnet free bore. The system has an expected resolution of 3.5 × 8.0 mm using Resovist tracer, and an experimental resolution of 3.8 × 8.4 mm resolution. The system images 2.5 cm × 5.0 cm partial field-of views (FOVs) at 10 frames/s, and acquires a full field-of-view of 10 cm × 5.0 cm in 4 s. We conclude by imaging a resolution phantom, a complex "Cal" phantom, mice injected with Resovist tracer, and experimentally confirm the theoretically predicted x-space spatial resolution.

  9. Momentum and angular momentum in the H-space of asymptotically flat, Einstein-Maxwell space-time

    Hallidy, W.; Ludvigsen, M.

    1979-01-01

    New definitions are proposed for the momentum and angular momentum of Einstein-Maxwell fields that overcome the deficiencies of earlier definitions of these terms and are appropriate to the new H-space formulations of space-time. Definitions are made in terms of the Winicour-Tamburino linkages applied to the good cuts of Cj + . The transformations between good cuts then correspond to the translations and Lorentz transformations at points in H-space. For the special case of Robinson-Trautman type II space-times, it is shown that the definitions of momentum and angular momentum yield previously published results. (author)

  10. X-ray performance of a wafer-scale CMOS flat panel imager for applications in medical imaging and nondestructive testing

    Cha, Bo Kyung; Jeon, Seongchae; Seo, Chang-Woo

    2016-01-01

    This paper presents a wafer-scale complementary metal-oxide semiconductor (CMOS)-based X-ray flat panel detector for medical imaging and nondestructive testing applications. In this study, our proposed X-ray CMOS flat panel imager has been fabricated by using a 0.35 µm 1-poly/4-metal CMOS process. The pixel size is 100 µm×100 µm and the pixel array format is 1200×1200 pixels, which provide a field-of-view (FOV) of 120mm×120 mm. The 14.3-bit extended counting analog-to digital converter (ADC) with built-in binning mode was used to reduce the area and simultaneously improve the image resolution. The different screens such as thallium-doped CsI (CsI:Tl) and terbium gadolinium oxysulfide (Gd_2O_2S:Tb) scintillators were used as conversion materials for X-rays to visible light photons. The X-ray imaging performance such as X-ray sensitivity as a function of X-ray exposure dose, spatial resolution, image lag and X-ray images of various objects were measured under practical medical and industrial application conditions. This paper results demonstrate that our prototype CMOS-based X-ray flat panel imager has the significant potential for medical imaging and non-destructive testing (NDT) applications with high-resolution and high speed rate.

  11. X-ray performance of a wafer-scale CMOS flat panel imager for applications in medical imaging and nondestructive testing

    Cha, Bo Kyung, E-mail: goldrain99@kaist.ac.kr [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Jeon, Seongchae [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Seo, Chang-Woo [Department of Radiological Science, Yonsei University, Gangwon-do 220-710 (Korea, Republic of)

    2016-09-21

    This paper presents a wafer-scale complementary metal-oxide semiconductor (CMOS)-based X-ray flat panel detector for medical imaging and nondestructive testing applications. In this study, our proposed X-ray CMOS flat panel imager has been fabricated by using a 0.35 µm 1-poly/4-metal CMOS process. The pixel size is 100 µm×100 µm and the pixel array format is 1200×1200 pixels, which provide a field-of-view (FOV) of 120mm×120 mm. The 14.3-bit extended counting analog-to digital converter (ADC) with built-in binning mode was used to reduce the area and simultaneously improve the image resolution. The different screens such as thallium-doped CsI (CsI:Tl) and terbium gadolinium oxysulfide (Gd{sub 2}O{sub 2}S:Tb) scintillators were used as conversion materials for X-rays to visible light photons. The X-ray imaging performance such as X-ray sensitivity as a function of X-ray exposure dose, spatial resolution, image lag and X-ray images of various objects were measured under practical medical and industrial application conditions. This paper results demonstrate that our prototype CMOS-based X-ray flat panel imager has the significant potential for medical imaging and non-destructive testing (NDT) applications with high-resolution and high speed rate.

  12. Use and imaging performance of CMOS flat panel imager with LiF/ZnS(Ag) and Gadox scintillation screens for neutron radiography

    Cha, B. K.; kim, J. Y.; Kim, T. J.; Sim, C.; Cho, G.; Lee, D. H.; Seo, C.-W.; Jeon, S.; Huh, Y.

    2011-01-01

    In digital neutron radiography system, a thermal neutron imaging detector based on neutron-sensitive scintillating screens with CMOS(complementary metal oxide semiconductor) flat panel imager is introduced for non-destructive testing (NDT) application. Recently, large area CMOS APS (active-pixel sensor) in conjunction with scintillation films has been widely used in many digital X-ray imaging applications. Instead of typical imaging detectors such as image plates, cooled-CCD cameras and amorphous silicon flat panel detectors in combination with scintillation screens, we tried to apply a scintillator-based CMOS APS to neutron imaging detection systems for high resolution neutron radiography. In this work, two major Gd2O2S:Tb and 6LiF/ZnS:Ag scintillation screens with various thickness were fabricated by a screen printing method. These neutron converter screens consist of a dispersion of Gd2O2S:Tb and 6LiF/ZnS:Ag scintillating particles in acrylic binder. These scintillating screens coupled-CMOS flat panel imager with 25x50mm2 active area and 48μm pixel pitch was used for neutron radiography. Thermal neutron flux with 6x106n/cm2/s was utilized at the NRF facility of HANARO in KAERI. The neutron imaging characterization of the used detector was investigated in terms of relative light output, linearity and spatial resolution in detail. The experimental results of scintillating screen-based CMOS flat panel detectors demonstrate possibility of high sensitive and high spatial resolution imaging in neutron radiography system.

  13. A performance comparison of direct- and indirect-detection flat-panel imagers

    Partridge, M.; Hesse, B.-M.; Mueller, L.

    2002-01-01

    A comparison of the performance of a direct- and an indirect-detection amorphous silicon flat-panel X-ray imager is presented for a 6 MV beam. Experimental measurements of the noise characteristics, image lag, spectral response, spatial resolution and quantum efficiency are described, compared and discussed. The two systems are comprised of 512x512 pixel, 400 μm pitch, arrays of a-Si:H p-i-n photodiodes and thin-film transistors. In the direct-detection system, X-rays interact to produce electron/hole pairs directly in the silicon photodiodes. For the indirect-detection system, a phosphor screen converts energy from the incident X-rays into visible light, which is then detected by the photodiodes. Both systems are shown to be quantum noise limited, with the total electronic noise in the detector 10-15 times smaller than the Poisson noise level in detected signal. The measured lag for both systems is 1.0±0.1% or less in the first frame with subsequent signals decaying exponentially with frame read-out, with a half-life of between 3.3 and 3.8 frames. Both systems are demonstrated to have a pronounced sensitivity to low-energy multiply scattered photons, although this is shown to be effectively filtered out using a 2 mm copper build-up plate. The direct-detection system, with the 2 mm Cu build-up, shows greater sensitivity to scattered radiation than the indirect system. The spatial resolutions of both systems were effectively equal with an f 50 of 0.25 mm -1 when pixels are binned 2x2, although a slight contribution from optical scattering in the phosphor screen is seen for the indirect-detection system. The quantum efficiency of the direct-detection system is a factor of 0.45 lower than that of the indirect-detection system. The application of these detectors to megavoltage CT is discussed, with the conclusion that the indirect-detection system is to be preferred

  14. Efficient Mosaicking of Spitzer Space Telescope Images

    Jacob, Joseph; Makovoz, David; Eisenhardt, Peter

    2007-01-01

    A parallel version of the MOPEX software, which generates mosaics of infrared astronomical images acquired by the Spitzer Space Telescope, extends the capabilities of the prior serial version. In the parallel version, both the input image space and the output mosaic space are divided among the available parallel processors. This is the only software that performs the point-source detection and the rejection of spurious imaging effects of cosmic rays required by Spitzer scientists. This software includes components that implement outlier-detection algorithms that can be fine-tuned for a particular set of image data by use of a number of adjustable parameters. This software has been used to construct a mosaic of the Spitzer Infrared Array Camera Shallow Survey, which comprises more than 17,000 exposures in four wavelength bands from 3.6 to 8 m and spans a solid angle of about 9 square degrees. When this software was executed on 32 nodes of the 1,024-processor Cosmos cluster computer at NASA s Jet Propulsion Laboratory, a speedup of 8.3 was achieved over the serial version of MOPEX. The performance is expected to improve dramatically once a true parallel file system is installed on Cosmos.

  15. MR imaging of masticator space infection

    Seong, Chang Kyu; Han, Moon Hee; Kim, Hong Dae; Park, Byung Kwan; Lee, In Hee; Chang, Kee Hyun; Kim, Sam Soo

    1998-01-01

    To identify the characteristic appearances of masticator space infection, as seen on magnetic resonance(MR) imaging. We retrospectively reviewed the MR images of 23 patients with clinically and bacteriologically proven masticator space infection, with attention to the involved structures, spread pattern, abscess formation, mandibular involvement, and etiology. The masseter muscle was involved in 21 of 23 cases, while the cases, medial pterygoid, lateral pterygoid, and temporalis muscles were involved in 14, 12 , and 13 cases, respectively. All muscles in the masticator space were involved in eight cases and only a single muscle in five. In all but one case, extension through the muscle plane was noted, and in 10 cases, transfascial extension was seen. Abscess formation was noted in seven cases. Mandibular involvement was seen in 16 cases, half of which showed focal cortical disruption. The source of infection was odontogenous in 15 cases, with frequent involvement of the mandible and masseter. Masticator space infection frequently originated from an odontogenous source. the characteristic MR appearances of this infection included extension through the muscle plane and frequent transfascial spread to adjacent deep cervical spaces, as well as common mandibular involvement with or without cortical disruption of focal pattern.=20

  16. Space Radar Image of Harvard Forest

    1999-01-01

    This is a radar image of the area surrounding the Harvard Forest in north-central Massachusetts that has been operated as a ecological research facility by Harvard University since 1907. At the center of the image is the Quabbin Reservoir, and the Connecticut River is at the lower left of the image. The Harvard Forest itself is just above the reservoir. Researchers are comparing the naturally occurring physical disturbances in the forest and the recent and projected chemical disturbances and their effects on the forest ecosystem. Agricultural land appears dark blue/purple, along with low shrub vegetation and some wetlands. Urban development is bright pink; the yellow to green tints are conifer-dominated vegetation with the pitch pine sand plain at the middle left edge of the image appearing very distinctive. The green tint may indicate pure pine plantation stands, and deciduous broadleaf trees appear gray/pink with perhaps wetter sites being pinker. This image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour. SIR-C/X-SAR, a joint mission of the German, Italian and the United States space agencies, is part of NASA's Mission to Planet Earth. The image is centered at 42.50 degrees North latitude and 72.33 degrees West longitude and covers an area of 53 kilometers 63 by kilometers (33 miles by 39 miles). The colors in the image are assigned to different frequencies and polarizations of the radar as follows: red is L-band horizontally transmitted and horizontally received; green is L-band horizontally transmitted and vertically received; and blue is C-band horizontally transmitted and horizontally received.

  17. Quantum field theory in flat Robertson-Walker space-time functional Schrodinger picture

    Pi, S.Y.

    1990-01-01

    Quantum field theory in Robertson-Walker space-time is intrinsically time-dependent and the functional Schrodinger picture provides a useful description. This paper discusses free and self-interacting bosonic quantum field theories: Schrodinger picture quantization, time-dependent Gaussian approximations based on variational principles describing time evolution of pure and mixed states, and renormalizability of the Schrodinger picture. The technique introduced can be used to study various dynamical questions in early universe processes

  18. Quantum field theory in flat Robertson-Walker space-time functional Schroedinger picture

    Pi, S.Y.

    1989-01-01

    Quantum field theory in Robertson-Walker space-time is intrinsically time-dependent and the functional Schroedinger picture provides a useful description. We discuss free and self-interacting bosonic quantum field theories: Schroedinger picture quantization, time-dependent Gaussian approximations based on variational principles describing time evolution of pure and mixed states, and renormalizability of the Schroedinger picture. The techniques introduced can be used to study various dynamical questions in early universe processes. (author)

  19. SU-E-J-45: The Correlation Between CBCT Flat Panel Misalignment and 3D Image Guidance Accuracy

    Kenton, O; Valdes, G; Yin, L; Teo, B; Brousmiche, S; Wikler, D

    2015-01-01

    Purpose To simulate the impact of CBCT flat panel misalignment on the image quality, the calculated correction vectors in 3D image guided proton therapy and to determine if these calibration errors can be caught in our QA process. Methods The X-ray source and detector geometrical calibration (flexmap) file of the CBCT system in the AdaPTinsight software (IBA proton therapy) was edited to induce known changes in the rotational and translational calibrations of the imaging panel. Translations of up to ±10 mm in the x, y and z directions (see supplemental) and rotational errors of up to ±3° were induced. The calibration files were then used to reconstruct the CBCT image of a pancreatic patient and CatPhan phantom. Correction vectors were calculated for the patient using the software’s auto match system and compared to baseline values. The CatPhan CBCT images were used for quantitative evaluation of image quality for each type of induced error. Results Translations of 1 to 3 mm in the x and y calibration resulted in corresponding correction vector errors of equal magnitude. Similar 10mm shifts were seen in the y-direction; however, in the x-direction, the image quality was too degraded for a match. These translational errors can be identified through differences in isocenter from orthogonal kV images taken during routine QA. Errors in the z-direction had no effect on the correction vector and image quality.Rotations of the imaging panel calibration resulted in corresponding correction vector rotations of the patient images. These rotations also resulted in degraded image quality which can be identified through quantitative image quality metrics. Conclusion Misalignment of CBCT geometry can lead to incorrect translational and rotational patient correction vectors. These errors can be identified through QA of the imaging isocenter as compared to orthogonal images combined with monitoring of CBCT image quality

  20. Quantum mechanics in curved space-time and its consequences for the theory on the flat space-time

    Tagirov, E.A.

    1997-01-01

    Thus, the structure is extracted from the initial general-relativistic setting of the quantum theory of the scalar field φ that can be considered as quantum mechanics in V 1,3 in the Schroedinger picture, which includes relativistic corrections not only in the Hamiltonian of the Schroedinger equation but also in the operators of primary observables. In the terms pertaining to these corrections the operators differ from their counterparts resulting from quantization of a classical spinless particle. In general, they do not commute at all and thus the quantum phase space loses the feature that half its coordinates retain a manifold structure, which Biedenharn called 'a miracle of quantization'. This non-commutativity expands up to the exact (in the sense 'non-asymptotic in c -2 ') quantum mechanics of a free motion in the Minkowski space-time if curvilinear coordinates are taken as observables, which are necessary if non-inertial frames of references are considered

  1. Space Radar Image of Manaus, Brazil

    1999-01-01

    These two images were created using data from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR). On the left is a false-color image of Manaus, Brazil acquired April 12, 1994, onboard space shuttle Endeavour. In the center of this image is the Solimoes River just west of Manaus before it combines with the Rio Negro to form the Amazon River. The scene is around 8 by 8 kilometers (5 by 5 miles) with north toward the top. The radar image was produced in L-band where red areas correspond to high backscatter at HH polarization, while green areas exhibit high backscatter at HV polarization. Blue areas show low backscatter at VV polarization. The image on the right is a classification map showing the extent of flooding beneath the forest canopy. The classification map was developed by SIR-C/X-SAR science team members at the University of California,Santa Barbara. The map uses the L-HH, L-HV, and L-VV images to classify the radar image into six categories: Red flooded forest Green unflooded tropical rain forest Blue open water, Amazon river Yellow unflooded fields, some floating grasses Gray flooded shrubs Black floating and flooded grasses Data like these help scientists evaluate flood damage on a global scale. Floods are highly episodic and much of the area inundated is often tree-covered. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those

  2. Space Radar Image of Wenatchee, Washington

    1994-01-01

    This spaceborne radar image shows a segment of the Columbia River as it passes through the area of Wenatchee, Washington, about 220 kilometers (136 miles) east of Seattle. The Wenatchee Mountains, part of the Cascade Range, are shown in green at the lower left of the image. The Cascades create a 'rain shadow' for the region, limiting rainfall east of the range to less than 26 centimeters (10 inches) per year. The radar's ability to see different types of vegetation is highlighted in the contrast between the pine forests, that appear in green and the dry valley plain that shows up as dark purple. The cities of Wenatchee and East Wenatchee are the grid-like areas straddling the Columbia River in the left center of the image. With a population of about 60,000, the region produces about half of Washington state's lucrative apple crop. Several orchard areas appear as green rectangular patches to the right of the river in the lower right center. Radar images such as these can be used to monitor land use patterns in areas such as Wenatchee, that have diverse and rapidly changing urban, agricultural and wild land pressures. This image was acquired by Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour on October 10, 1994. The image is 38 kilometers by 45 kilometers (24 miles by 30 miles) and is centered at 47.3 degrees North latitude, 120.1 degrees West longitude. North is toward the upper left. The colors are assigned to different radar frequencies and polarizations of the radar as follows: red is L-band, horizontally transmitted and received; green is L-band, horizontally transmitted, vertically received; and blue is C-band, horizontally transmitted, vertically received. SIR-C/X-SAR, a joint mission of the German, Italian, and United States space agencies, is part of NASA's Mission to Planet Earth.

  3. A perceptual space of local image statistics.

    Victor, Jonathan D; Thengone, Daniel J; Rizvi, Syed M; Conte, Mary M

    2015-12-01

    Local image statistics are important for visual analysis of textures, surfaces, and form. There are many kinds of local statistics, including those that capture luminance distributions, spatial contrast, oriented segments, and corners. While sensitivity to each of these kinds of statistics have been well-studied, much less is known about visual processing when multiple kinds of statistics are relevant, in large part because the dimensionality of the problem is high and different kinds of statistics interact. To approach this problem, we focused on binary images on a square lattice - a reduced set of stimuli which nevertheless taps many kinds of local statistics. In this 10-parameter space, we determined psychophysical thresholds to each kind of statistic (16 observers) and all of their pairwise combinations (4 observers). Sensitivities and isodiscrimination contours were consistent across observers. Isodiscrimination contours were elliptical, implying a quadratic interaction rule, which in turn determined ellipsoidal isodiscrimination surfaces in the full 10-dimensional space, and made predictions for sensitivities to complex combinations of statistics. These predictions, including the prediction of a combination of statistics that was metameric to random, were verified experimentally. Finally, check size had only a mild effect on sensitivities over the range from 2.8 to 14min, but sensitivities to second- and higher-order statistics was substantially lower at 1.4min. In sum, local image statistics form a perceptual space that is highly stereotyped across observers, in which different kinds of statistics interact according to simple rules. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Space Radar Image of Sydney, Australia

    1994-01-01

    This spaceborne radar image is dominated by the metropolitan area of Australia's largest city, Sydney. Sydney Harbour, with numerous coves and inlets, is seen in the upper center of the image, and the roughly circular Botany Bay is shown in the lower right. The downtown business district of Sydney appears as a bright white area just above the center of the image. The Sydney Harbour Bridge is a white line adjacent to the downtown district. The well-known Sydney Opera House is the small, white dot to the right of the bridge. Urban areas appear yellow, blue and brown. The purple areas are undeveloped areas and park lands. Manly, the famous surfing beach, is shown in yellow at the top center of the image. Runways from the Sydney Airport are the dark features that extend into Botany Bay in the lower right. Botany Bay is the site where Captain James Cook first landed his ship, Endeavour, in 1770. The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on April 20, 1994, onboard the space shuttle Endeavour. The area shown is 33 kilometers by 38kilometers (20 miles by 23 miles) and is centered at 33.9 degrees south latitude, 151.2 degrees east longitude. North is toward the upper left. The colors are assigned to different radar frequenciesand polarizations as follows: red is L-band, vertically transmittedand horizontally received; green is C-band, vertically transmitted and horizontally received; and blue is C-band, vertically transmittedand received. SIR-C/X-SAR, a joint mission of the German, Italianand United States space agencies, is part of NASA's Mission to Planet Earth. #####

  5. Space Radar Image of County Kerry, Ireland

    1994-01-01

    The Iveragh Peninsula, one of the four peninsulas in southwestern Ireland, is shown in this spaceborne radar image. The lakes of Killarney National Park are the green patches on the left side of the image. The mountains to the right of the lakes include the highest peaks (1,036 meters or 3,400 feet) in Ireland. The patchwork patterns between the mountains are areas of farming and grazing. The delicate patterns in the water are caused by refraction of ocean waves around the peninsula edges and islands, including Skellig Rocks at the right edge of the image. The Skelligs are home to a 15th century monastery and flocks of puffins. The region is part of County Kerry and includes a road called the 'Ring of Kerry' that is one of the most famous tourist routes in Ireland. This image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the Space Shuttle Endeavour on April 12, 1994. The image is 82 kilometers by 42 kilometers (51 miles by 26 miles) and is centered at 52.0 degrees north latitude, 9.9 degrees west longitude. North is toward the lower left. The colors are assigned to different radar frequencies and polarizations of the radar as follows: red is L-band, horizontally transmitted and received; green is L-band, vertically transmitted and received; and blue is C-band, vertically transmitted and received. SIR-C/X-SAR, a joint mission of the German, Italian and United States space agencies, is part of NASA's Mission to Planet Earth program.

  6. Evaluation of imaging quality for flat-panel detector based low dose C-arm CT system

    Seo, Chang-Woo; Cha, Bo Kyung; Jeon, Sungchae; Huh, Young

    2015-01-01

    The image quality associated with the extent of the angle of gantry rotation, the number of projection views, and the dose of X-ray radiation was investigated in flat-panel detector (FPD) based C-arm cone-beam computed tomography (CBCT) system for medical applications. A prototype CBCT system for the projection acquisition used the X-ray tube (A-132, Varian inc.) having rhenium-tungsten molybdenum target and flat panel a-Si X-ray detector (PaxScan 4030CB, Varian inc.) having a 397 x 298 mm active area with 388 μm pixel pitch and 1024 x 768 pixels in 2 by 2 binning mode. The performance comparison of X-ray imaging quality was carried out using the Feldkamp, Davis, and Kress (FDK) reconstruction algorithm between different conditions of projection acquisition. In this work, head-and-dental (75 kVp/20 mA) and chest (90 kVp/25 mA) phantoms were used to evaluate the image quality. The 361 (30 fps x 12 s) projection data during 360 deg. gantry rotation with 1 deg. interval for the 3D reconstruction were acquired. Parke weighting function were applied to handle redundant data and improve the reconstructed image quality in a mobile C-arm system with limited rotation angles. The reconstructed 3D images were investigated for comparison of qualitative image quality in terms of scan protocols (projection views, rotation angles and exposure dose). Furthermore, the performance evaluation in image quality will be investigated regarding X-ray dose and limited projection data for a FPD based mobile C-arm CBCT system. (authors)

  7. Positioning in a flat two-dimensional space-time: The delay master equation

    Coll, Bartolome; Ferrando, Joan Josep; Morales-Lladosa, Juan Antonio

    2010-01-01

    The basic theory on relativistic positioning systems in a two-dimensional space-time has been presented in two previous papers [B. Coll, J. J. Ferrando, and J. A. Morales, Phys. Rev. D 73, 084017 (2006); ibid.74, 104003 (2006)], where the possibility of making relativistic gravimetry with these systems has been analyzed by considering specific examples. Here, generic relativistic positioning systems in the Minkowski plane are studied. The information that can be obtained from the data received by a user of the positioning system is analyzed in detail. In particular, it is shown that the accelerations of the emitters and of the user along their trajectories are determined by the sole knowledge of the emitter positioning data and of the acceleration of only one of the emitters. Moreover, as a consequence of the so-called master delay equation, the knowledge of this acceleration is only required during an echo interval, i.e., the interval between the emission time of a signal by an emitter and its reception time after being reflected by the other emitter. These results are illustrated with the obtention of the dynamics of the emitters and of the user from specific sets of data received by the user.

  8. Aging of imaging properties of a CMOS flat-panel detector for dental cone-beam computed tomography

    Kim, D. W.; Han, J. C.; Yun, S.; Kim, H. K.

    2017-01-01

    We have experimentally investigated the long-term stability of imaging properties of a flat-panel detector in conditions used for dental x-ray imaging. The detector consists of a CsI:Tl layer and CMOS photodiode pixel arrays. Aging simulations were carried out using an 80-kVp x-ray beam at an air-kerma rate of approximately 5 mGy s-1 at the entrance surface of the detector with a total air kerma of up to 0.6 kGy. Dark and flood-field images were periodically obtained during irradiation, and the mean signal and noise levels were evaluated for each image. We also evaluated the modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). The aging simulation showed a decrease in both the signal and noise of the gain-offset-corrected images, but there was negligible change in the signal-to-noise performance as a function of the accumulated dose. The gain-offset correction for analyzing images resulted in negligible changes in MTF, NPS, and DQE results over the total dose. Continuous x-ray exposure to a detector can cause degradation in the physical performance factors such the detector sensitivity, but linear analysis of the gain-offset-corrected images can assure integrity of the imaging properties of a detector during its lifetime.

  9. Image slicer manufacturing: from space application to mass production

    Bonneville, Christophe; Cagnat, Jean-François; Laurent, Florence; Prieto, Eric; Ancourt, Gérard

    2004-09-01

    This presentation aims to show technical and industrial inputs to be taking into account for Image Slicer systems design and development for different types of projects from space application to mass production for multi-IFU instruments. Cybernétix has a strong experience of precision optics assembled thanks to molecular adhesion and have already manufactured 6 prototypes of image slicer subsystem (prototypes of NIRSPEC-IFU, IFS for JWST, MUSE ...) in collaboration with the Laboratoire d"Astrophysique de Marseille (LAM) and the Centre de Recherche Astronomique de Lyon (CRAL). After a brief presentation of the principle of manufacturing and assembly, we will focus on the different performances achieved in our prototypes of slicer mirrors, pupil and slit mirrors lines: an accuracy on centre of curvature position better than 15 arsec has been obtained for a stack of 30 slices. The contribution of the slice stacking to this error is lower than 4 arcsec. In spite of very thin surfaces (~ 0.9 x 40 mm for instance), a special process allows to guarantee a surface roughness about 5 nm and very few digs on the slice borders. The WFE of the mini-mirror can also be measured at a stage of the manufacturing. Different environmental tests have shown the withstanding of these assemblies to cryogenic temperature (30 K). Then, we will describe the different solutions (spherical, flat, cylindrical surfaces) and characteristics of an image slicer that can influence difficulties of manufacturing and metrology, cost, schedule and risks with regard to fabrication. Finally, the study of a mass production plan for MUSE (CRAL) composed of 24 Image Slicers of 38 slices, that"s to say 912 slices, will be exposed as an example of what can be do for multi-module instruments.

  10. The Earth isn't flat: The (large) influence of topography on geodetic fault slip imaging.

    Thompson, T. B.; Meade, B. J.

    2017-12-01

    While earthquakes both occur near and generate steep topography, most geodetic slip inversions assume that the Earth's surface is flat. We have developed a new boundary element tool, Tectosaur, with the capability to study fault and earthquake problems including complex fault system geometries, topography, material property contrasts, and millions of elements. Using Tectosaur, we study the model error induced by neglecting topography in both idealized synthetic fault models and for the cases of the MW=7.3 Landers and MW=8.0 Wenchuan earthquakes. Near the steepest topography, we find the use of flat Earth dislocation models may induce errors of more than 100% in the inferred slip magnitude and rake. In particular, neglecting topographic effects leads to an inferred shallow slip deficit. Thus, we propose that the shallow slip deficit observed in several earthquakes may be an artefact resulting from the systematic use of elastic dislocation models assuming a flat Earth. Finally, using this study as an example, we emphasize the dangerous potential for forward model errors to be amplified by an order of magnitude in inverse problems.

  11. High resolution X-ray imaging of bone-implant interface by large area flat-panel detector

    Kytyr, D; Jirousek, O; Dammer, J

    2011-01-01

    The aim of the research was to investigate the cemented bone-implant interface behavior (cement layer degradation and bone-cement interface debonding) with emphasis on imaging techniques suitable to detect the early defects in the cement layer. To simulate in vivo conditions a human pelvic bone was implanted with polyurethane acetabular cup using commercial acrylic bone cement. The implanted cup was then loaded in a custom hip simulator to initiate fatigue crack propagation in the bone cement. The pelvic bone was then repetitively scanned in a micro-tomography device. Reconstructed tomography images showed failure processes that occurred in the cement layer during the first 250,000 cycles. A failure in cemented acetabular implant - debonding, crumbling and smeared cracks - has been found to be at the bone-cement interface. Use of micro-focus source and high resolution flat panel detector of large physical dimensions allowed to reconstruct the micro-structural models suitable for investigation of migration, micro-motions and consecutive loosening of the implant. The large area flat panel detector with physical dimensions 120 x 120mm with 50μm pixel size provided a superior image quality compared to clinical CT systems with 300-150μm pixel size.

  12. Space radar image of Mauna Loa, Hawaii

    1995-01-01

    This image of the Mauna Loa volcano on the Big Island of Hawaii shows the capability of imaging radar to map lava flows and other volcanic structures. Mauna Loa has erupted more than 35 times since the island was first visited by westerners in the early 1800s. The large summit crater, called Mokuaweoweo Caldera, is clearly visible near the center of the image. Leading away from the caldera (towards top right and lower center) are the two main rift zones shown here in orange. Rift zones are areas of weakness within the upper part of the volcano that are often ripped open as new magma (molten rock) approaches the surface at the start of an eruption. The most recent eruption of Mauna Loa was in March and April 1984, when segments of the northeast rift zones were active. If the height of the volcano was measured from its base on the ocean floor instead of from sea level, Mauna Loa would be the tallest mountain on Earth. Its peak (center of the image) rises more than 8 kilometers (5 miles) above the ocean floor. The South Kona District, known for cultivation of macadamia nuts and coffee, can be seen in the lower left as white and blue areas along the coast. North is toward the upper left. The area shown is 41.5 by 75 kilometers (25.7 by 46.5 miles), centered at 19.5 degrees north latitude and 155.6 degrees west longitude. The image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/ X-SAR) aboard the space shuttle Endeavour on its 36th orbit on October 2, 1994. The radar illumination is from the left of the image. The colors in this image were obtained using the following radar channels: red represents the L-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted, vertically received); blue represents the C-band (horizontally transmitted, vertically received). The resulting color combinations in this radar image are caused by differences in surface roughness of the lava flows. Smoother flows

  13. Space Radar Image of Kilauea Volcano, Hawaii

    1994-01-01

    This is a deformation map of the south flank of Kilauea volcano on the big island of Hawaii, centered at 19.5 degrees north latitude and 155.25 degrees west longitude. The map was created by combining interferometric radar data -- that is data acquired on different passes of the space shuttle which are then overlayed to obtain elevation information -- acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar during its first flight in April 1994 and its second flight in October 1994. The area shown is approximately 40 kilometers by 80 kilometers (25 miles by 50 miles). North is toward the upper left of the image. The colors indicate the displacement of the surface in the direction that the radar instrument was pointed (toward the right of the image) in the six months between images. The analysis of ground movement is preliminary, but appears consistent with the motions detected by the Global Positioning System ground receivers that have been used over the past five years. The south flank of the Kilauea volcano is among the most rapidly deforming terrains on Earth. Several regions show motions over the six-month time period. Most obvious is at the base of Hilina Pali, where 10 centimeters (4 inches) or more of crustal deformation can be seen in a concentrated area near the coastline. On a more localized scale, the currently active Pu'u O'o summit also shows about 10 centimeters (4 inches) of change near the vent area. Finally, there are indications of additional movement along the upper southwest rift zone, just below the Kilauea caldera in the image. Deformation of the south flank is believed to be the result of movements along faults deep beneath the surface of the volcano, as well as injections of magma, or molten rock, into the volcano's 'plumbing' system. Detection of ground motions from space has proven to be a unique capability of imaging radar technology. Scientists hope to use deformation data acquired by SIR-C/X-SAR and future imaging

  14. Small space object imaging : LDRD final report.

    Ackermann, Mark R.; Valley, Michael T.; Kearney, Sean Patrick

    2009-10-01

    We report the results of an LDRD effort to investigate new technologies for the identification of small-sized (mm to cm) debris in low-earth orbit. This small-yet-energetic debris presents a threat to the integrity of space-assets worldwide and represents significant security challenge to the international community. We present a nonexhaustive review of recent US and Russian efforts to meet the challenges of debris identification and removal and then provide a detailed description of joint US-Russian plans for sensitive, laser-based imaging of small debris at distances of hundreds of kilometers and relative velocities of several kilometers per second. Plans for the upcoming experimental testing of these imaging schemes are presented and a preliminary path toward system integration is identified.

  15. Hubble Space Telescope Image of Omega Nebula

    2002-01-01

    This sturning image, taken by the newly installed Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST), is an image of the center of the Omega Nebula. It is a hotbed of newly born stars wrapped in colorful blankets of glowing gas and cradled in an enormous cold, dark hydrogen cloud. The region of nebula shown in this photograph is about 3,500 times wider than our solar system. The nebula, also called M17 and the Swan Nebula, resides 5,500 light-years away in the constellation Sagittarius. The Swan Nebula is illuminated by ultraviolet radiation from young, massive stars, located just beyond the upper-right corner of the image. The powerful radiation from these stars evaporates and erodes the dense cloud of cold gas within which the stars formed. The blistered walls of the hollow cloud shine primarily in the blue, green, and red light emitted by excited atoms of hydrogen, nitrogen, oxygen, and sulfur. Particularly striking is the rose-like feature, seen to the right of center, which glows in the red light emitted by hydrogen and sulfur. As the infant stars evaporate the surrounding cloud, they expose dense pockets of gas that may contain developing stars. One isolated pocket is seen at the center of the brightest region of the nebula. Other dense pockets of gas have formed the remarkable feature jutting inward from the left edge of the image. The color image is constructed from four separate images taken in these filters: blue, near infrared, hydrogen alpha, and doubly ionized oxygen. Credit: NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

  16. Space Radar Image of Colombian Volcano

    1999-01-01

    This is a radar image of a little known volcano in northern Colombia. The image was acquired on orbit 80 of space shuttle Endeavour on April 14, 1994, by the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR). The volcano near the center of the image is located at 5.6 degrees north latitude, 75.0 degrees west longitude, about 100 kilometers (65 miles) southeast of Medellin, Colombia. The conspicuous dark spot is a lake at the bottom of an approximately 3-kilometer-wide (1.9-mile) volcanic collapse depression or caldera. A cone-shaped peak on the bottom left (northeast rim) of the caldera appears to have been the source for a flow of material into the caldera. This is the northern-most known volcano in South America and because of its youthful appearance, should be considered dormant rather than extinct. The volcano's existence confirms a fracture zone proposed in 1985 as the northern boundary of volcanism in the Andes. The SIR-C/X-SAR image reveals another, older caldera further south in Colombia, along another proposed fracture zone. Although relatively conspicuous, these volcanoes have escaped widespread recognition because of frequent cloud cover that hinders remote sensing imaging in visible wavelengths. Four separate volcanoes in the Northern Andes nations ofColombia and Ecuador have been active during the last 10 years, killing more than 25,000 people, including scientists who were monitoring the volcanic activity. Detection and monitoring of volcanoes from space provides a safe way to investigate volcanism. The recognition of previously unknown volcanoes is important for hazard evaluations because a number of major eruptions this century have occurred at mountains that were not previously recognized as volcanoes. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of

  17. Space Radar Image of Maui, Hawaii

    1994-01-01

    This spaceborne radar image shows the 'Valley Island' of Maui, Hawaii. The cloud-penetrating capabilities of radar provide a rare view of many parts of the island, since the higher elevations are frequently shrouded in clouds. The light blue and yellow areas in the lowlands near the center are sugar cane fields. The three major population centers, Lahaina on the left at the western tip of island, Wailuku left of center, and Kihei in the lower center appear as small yellow, white or purple mottled areas. West Maui volcano, in the lower left, is 1800 meters high (5900 feet) and is considered extinct. The entire eastern half of the island consists of East Maui volcano, which rises to an elevation of 3200 meters (10,500 feet) and features a spectacular crater called Haleakala at its summit. Haleakala Crater was produced by erosion during previous ice ages rather than by volcanic activity, although relatively recent small eruptions have produced the numerous volcanic cones and lava flows that can be seen on the floor of the crater. The most recent eruption took place near the coast at the southwestern end of East Maui volcano in the late 1700s. Such a time frame indicates that East Maui should be considered a dormant, rather than an extinct volcano. A new eruption is therefore possible in the next few hundred years. The multi-wavelength capability of the SIR-C radar also permits differences in the vegetation cover on the middle flanks of East Maui to be identified. Rain forests appear in yellow, while grassland is shown in dark green, pink and blue. Radar images such as this one are being used by scientists to understand volcanic processes and to assess potential threats that future activity may pose to local populations. This image was acquired by Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour on April 16, 1994. The image is 73.7 kilometers by 48.7 kilometers (45.7 miles by 30.2 miles) and is centered at 20

  18. Space Radar Image of Bebedauro, Brazil, seasonal

    1994-01-01

    This is an X-band image showing seasonal changes at the hydrological test site of Bebedouro in Brazil. The image is centered at 9 degrees south latitude and 40.2 degrees west longitude. This image was acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour on April 10, 1994, during the first flight of the radar system, and on October 1, 1994, during the second mission. The swath width is approximately 16.5 kilometers (10.5 miles) wide. The image channels have the following color assignments: red represents data acquired on April 10; green represents data acquired on October 1; blue corresponds to the ratio of the two data sets. Agriculture plays an important economic and social role in Brazil. One of the major problems related to Brazilian agriculture is estimating the size of planting areas and their productivity. Due to cloud cover and the rainy season, which occurs from November through April, optical and infrared Earth observations are seldom used to survey the region. An additional goal of monitoring this region is to watch the floodplains of rivers like Rio Sao Francisco in order to determine suitable locations for additional agricultural fields. This area belongs to the semi-arid northeastern region of Brazil, where estimates have suggested that about 10 times more land could be used for agriculture, including some locations which could be used for irrigation projects. Monitoring of soil moisture during the important summer crop season is of high priority for the future development and productivity of this region. In April the area was covered with vegetation because of the moisture of the soil and only small differences could be seen in X-band data. In October the run-off channels of this hilly region stand out quite clearly because the greenish areas indicated much less soil moisture and water content in plants. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR

  19. Properties of Brownian Image Models in Scale-Space

    Pedersen, Kim Steenstrup

    2003-01-01

    Brownian images) will be discussed in relation to linear scale-space theory, and it will be shown empirically that the second order statistics of natural images mapped into jet space may, within some scale interval, be modeled by the Brownian image model. This is consistent with the 1/f 2 power spectrum...... law that apparently governs natural images. Furthermore, the distribution of Brownian images mapped into jet space is Gaussian and an analytical expression can be derived for the covariance matrix of Brownian images in jet space. This matrix is also a good approximation of the covariance matrix......In this paper it is argued that the Brownian image model is the least committed, scale invariant, statistical image model which describes the second order statistics of natural images. Various properties of three different types of Gaussian image models (white noise, Brownian and fractional...

  20. Comparison of imaging properties of direct-type and indirect-type of flat-panel detector

    Matsumoto, Masao; Suekane, Koji; Ichimaru, Yasunobu; Ogata, Yuji; Inamura, Kiyonari; Kanai, Kouzou; Kanamori, Hitoshi

    2002-01-01

    A Flat-Panel Detector (FPD) has many advantages such as eliminating cassette handling and being able to display a preview image immediately in addition to the digital image processing and the networking. Thus, the FPD has ability to innovate the radiology department. We measured and evaluated the digital and over-all imaging properties (characteristic curves, modulation Transfer Functions, Wiener spectra and Noise Equivalent Quanta (NEQ) for the direct-type and indirect-type of FPD. The pre-sampling and overall NEQ of the indirect-type of FPD were better than the NEQ of the direct-type of FPD at lower spatial frequencies, but were worse at higher spatial frequencies. The FPD can take image data at real-time and be easy to digitalize. From these results, Screen/Film system and Computed Radiography system will be replaced by the FPD system, together with diffusion of CAD, cone beam Computed Tomography (CT) system and open-type Magnetic Resonance Imagining (MRI) system. (T. Tanaka)

  1. A performance comparison of flat-panel imager-based MV and kV cone-beam CT

    Groh, B.A.; Siewerdsen, J.H.; Drake, D.G.; Wong, J.W.; Jaffray, D.A.

    2002-01-01

    The use of cone-beam computed tomography (CBCT) has been proposed for guiding the delivery of radiation therapy, and investigators have examined the use of both kilovoltage (kV) and megavoltage (MV) x-ray beams in the development of such CBCT systems. In this paper, the inherent contrast and signal-to-noise ratio (SNR) performance for a variety of existing and hypothetical detectors for CBCT are investigated analytically as a function of imaging dose and object size. Theoretical predictions are compared to the results of experimental investigations employing large-area flat-panel imagers (FPIs) at kV and MV energies. Measurements were performed on two different FPI-based CBCT systems: a bench-top prototype incorporating an FPI and kV x-ray source (100 kVp x rays), and a system incorporating an FPI mounted on the gantry of a medical linear accelerator (6 MV x rays). The SNR in volume reconstructions was measured as a function of dose and found to agree reasonably with theoretical predictions. These results confirm the theoretically predicted advantages of employing kV energy x rays in imaging soft-tissue structures found in the human body. While MV CBCT may provide a valuable means of correcting 3D setup errors and may offer an advantage in terms of simplicity of mechanical integration with a linear accelerator (e.g., implementation in place of a portal imager), kV CBCT offers significant performance advantages in terms of image contrast and SNR per unit dose for visualization of soft-tissue structures. The relatively poor SNR performance at MV energies is primarily a result of the low x-ray quantum efficiencies (∼a few percent or less) that are currently achieved with FPIs at high energies. Furthermore, kV CBCT with an FPI offers the potential of combined volumetric and radiographic/fluoroscopic imaging using the same device

  2. Physics-based optimization of image quality in 3D X-ray flat-panel cone-beam imaging

    Snoeren, R.M.

    2012-01-01

    This thesis describes the techniques for modeling and control of 3D X-ray cardiovascular systems in terms of Image Quality and patient dose, aiming at optimizing the diagnostic quality. When aiming at maximum Image Quality (IQ), a cascaded system constituted from inter-dependent imaging components,

  3. Reconstruction of quasimonochromatic images for multispectral x-ray imaging with a pinhole array and a flat Bragg mirror

    Izumi, N.; Barbee, T. W.; Koch, J. A.; Mancini, R. C.; Welser, L. A.

    2006-01-01

    We have developed a software package for reconstruction of quasimonochromatic images from a multiple monochromatic x-ray imager for inertial confinement fusion implosions. The instrument consists of a pinhole array, a multilayer Bragg mirror, and an image detector. The pinhole array projects hundreds of images onto the detector after reflection off the multilayer Bragg mirror, which introduces spectral dispersion along the reflection axis. The quasimonochromatic images of line emissions and continuum emissions can be used for measurement of temperature and density maps of implosion plasmas. In this article, we describe a computer-aided processing technique for systematic reconstruction of quasimonochromatic images from raw data. This technique provides flexible spectral bandwidth selection and allows systematic subtraction of continuum emission from line emission images

  4. Space-Ready Advanced Imaging System, Phase II

    National Aeronautics and Space Administration — In this Phase II effort Toyon will increase the state-of-the-art for video/image systems. This will include digital image compression algorithms as well as system...

  5. The performance of an amorphous silicon flat panel for neutron imaging at the PSI NEUTRA facility

    Estermann, Mirko; Frei, Gabriel; Lehmann, Eberhard; Vontobel, Peter

    2005-01-01

    Commonly applied imaging methods in neutron radiography use a CCD camera in conjunction with a scintillator or imaging plates. CCDs and imaging plates have desirable properties concerning resolution, linearity, dynamic range and signal-to-noise ratio (S/N) but both techniques have the disadvantage of a slow read out and for the CCD camera, an additional disadvantage is the loss of light through the optical system. Amorphous silicon detectors, originally developed for medical and industrial X-ray imaging, generally do not have the above-mentioned disadvantages. These detectors have a much faster readout and, in comparison to the generally used crystalline silicon, can be put directly in the X-ray or neutron beam without being damaged. This type of detector also does not require any optical interface, minimizing possible light loss. The detector is operated at room temperature, which has some influence on the noise. Using the whole dynamic range with a low gain, results in a S/N of up to 30, for normal applications, however, a S/N of about 15-20 is typical. The main drawback of this imaging device is the dynamic range of only 12 bits and the relatively complicated operating system in which different operation modes can be chosen. In 2003, successful experiments were performed with this new device, but it is still in its fledgling stages and improvements from the manufacturer as well as the experience from the NEUTRA team will help to advance this technique for neutron imaging in a most efficient way

  6. Determination of point spread function for a flat-panel X-ray imager and its application in image restoration

    Jeon, Sungchae; Cho, Gyuseong; Huh, Young; Jin, Seungoh; Park, Jongduk

    2006-01-01

    We investigate the image blur estimation methods, namely modified the Richardson-Lucy (R-L) estimator and the Wiener estimator. Based on the empirical model of the PSF, an image restoration is applied to radiological images. The accuracy of the PSF estimation under the Poisson noise and readout electronic noise is significantly better for the R-L estimator than the Wiener estimator. In the image restoration using the 2-D PSF from the R-L estimator, the result shows a good improvement in the low and middle range of spatial frequency

  7. Investigation on effect of image lag in fluoroscopic images obtained with a dynamic flat-panel detector (FPD) on accuracy of target tracking in radiotherapy

    Tanaka, Rie; Ichikawa, Katsuhiro; Sanada, Sigeru; Mori, Shinichiro; Dobashi, Suguru; Kumagai, Motoki; Minohara, Shinichi; Kawashima, Hiroki

    2010-01-01

    Real-time tumor tracking in external radiotherapy can be achieved by diagnostic (kV) X-ray imaging with a dynamic flat-panel detector (FPD). The purpose of this study was to address image lag in target tracking and its influence on the accuracy of tumor tracking. Fluoroscopic images were obtained using a direct type of dynamic FPD. Image lag properties were measured without test devices according to IEC 62220-1. Modulation transfer function (MTF) and profile curves were measured on the edges of a moving tungsten plate at movement rate of 10 and 20 mm/s, covering lung tumor movement of normal breathing. A lung tumor and metal sphere with blurred edge due to image lag was simulated using the results and then superimposed on breathing chest radiographs of a patient. The moving target with and without image lag was traced using a template-matching technique. In the results, the image lag for the first frame after X-ray cutoff was 2.0% and decreased to less than 0.1% in the fifth frame. In the measurement of profile curves on the edges of static and moving tungsten material plates, the effect of image lag was seen as blurred edges of the plate. The blurred edges of a moving target were indicated as reduction of MTF. However, the target could be traced within an error of ±5 mm. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation. (author)

  8. Quality control beam of radiation through imaging system using a flat panel (ILD)

    Benitez Serrano, J. A.; Gomez Barrado, A.; Sanchez-Reyes, A.

    2013-01-01

    The daily quality checks of the accelerator include, among others, checks of the daily calibration, symmetry and uniformity of the radiation beam. Usually verification systems daily are used for this purpose, which employ arrays of detectors of solid-state or ionization chambers. This paper intends to carry out the control of quality through the irradiation of a number of fields in the portal imaging system and its subsequent analysis in software's own creation, as well as the comparison of results with the daily verification system. (Author)

  9. Quantitative image quality evaluation of pixel-binning in a flat-panel detector for x-ray fluoroscopy

    Srinivas, Yogesh; Wilson, David L.

    2004-01-01

    X-ray fluoroscopy places stringent design requirements on new flat-panel (FP) detectors, requiring both low-noise electronics and high data transfer rates. Pixel-binning, wherein data from more that one detector pixel are collected simultaneously, not only lowers the data transfer rate but also increases x-ray counts and pixel signal-to-noise ratio (SNR). In this study, we quantitatively assessed image quality of image sequences from four acquisition methods; no-binning and three types of binning; in synthetic images using a clinically relevant task of detecting an extended guidewire in a four-alternative forced-choice paradigm. Binning methods were conventional data-line (D) and gate-line (G) binning, and a novel method in which alternate frames in an image sequence used D and G binning. Two detector orientations placed the data lines either parallel or perpendicular to the guide wire. At a low exposure of 0.6 μR (1.548x10 -10 C/kg) per frame, irrespective of detector orientation, D binning with its reduced electronic noise was significantly (p -10 C/kg) per frame, with data lines parallel to the guidewire, detection with D binning was significantly (p<0.1) better than G binning. However, with data lines perpendicular to the guidewire, G binning was significantly (p<0.1) better than D binning because the partial area effect was reduced. Alternate binning was the best binning method when results were averaged over both orientations, and it was as good as the best binning method at either orientation. In addition, at low and high exposures, alternate binning gave a temporally fused image with a smooth guidewire, an important image quality feature not assessed in a detection experiment. While at high exposure, detection with no binning was as good, or better, than the best binning method, it might be impractical at fluoroscopy imaging rates. A computational observer model based on signal detection theory successfully fit data and was used to predict effects of

  10. Imaging findings and significance of deep neck space infection

    Zhuang Qixin; Gu Yifeng; Du Lianjun; Zhu Lili; Pan Yuping; Li Minghua; Yang Shixun; Shang Kezhong; Yin Shankai

    2004-01-01

    Objective: To study the imaging appearance of deep neck space cellulitis and abscess and to evaluate the diagnostic criteria of deep neck space infection. Methods: CT and MRI findings of 28 cases with deep neck space infection proved by clinical manifestation and pathology were analyzed, including 11 cases of retropharyngeal space, 5 cases of parapharyngeal space infection, 4 cases of masticator space infection, and 8 cases of multi-space infection. Results: CT and MRI could display the swelling of the soft tissues and displacement, reduction, or disappearance of lipoid space in the cellulitis. In inflammatory tissues, MRI imaging demonstrated hypointense or isointense signal on T 1 WI, and hyperintense signal changes on T 2 WI. In abscess, CT could display hypodensity in the center and boundary enhancement of the abscess. MRI could display obvious hyperintense signal on T 2 WI and boundary enhancement. Conclusion: CT and MRI could provide useful information for deep neck space cellulitis and abscess

  11. A Learning State-Space Model for Image Retrieval

    Lee Greg C

    2007-01-01

    Full Text Available This paper proposes an approach based on a state-space model for learning the user concepts in image retrieval. We first design a scheme of region-based image representation based on concept units, which are integrated with different types of feature spaces and with different region scales of image segmentation. The design of the concept units aims at describing similar characteristics at a certain perspective among relevant images. We present the details of our proposed approach based on a state-space model for interactive image retrieval, including likelihood and transition models, and we also describe some experiments that show the efficacy of our proposed model. This work demonstrates the feasibility of using a state-space model to estimate the user intuition in image retrieval.

  12. Relationship between x-ray illumination field size and flat field intensity and its impacts on x-ray imaging

    Dong Xue; Niu Tianye; Jia Xun; Zhu Lei

    2012-01-01

    Purpose: X-ray cone-beam CT (CBCT) is being increasingly used for various clinical applications, while its performance is still hindered by image artifacts. This work investigates a new source of reconstruction error, which is often overlooked in the current CBCT imaging. The authors find that the x-ray flat field intensity (I 0 ) varies significantly as the illumination volume size changes at different collimator settings. A wrong I 0 value leads to inaccurate CT numbers of reconstructed images as well as wrong scatter measurements in the CBCT research. Methods: The authors argue that the finite size of x-ray focal spot together with the detector glare effect cause the I 0 variation at different illumination sizes. Although the focal spot of commercial x-ray tubes typically has a nominal size of less than 1 mm, the off-focal-spot radiation covers an area of several millimeters on the tungsten target. Due to the large magnification factor from the field collimator to the detector, the penumbra effects of the collimator blades result in different I 0 values for different illumination field sizes. Detector glare further increases the variation, since one pencil beam of incident x-ray is scattered into an area of several centimeters on the detector. In this paper, the authors study these two effects by measuring the focal spot distribution with a pinhole assembly and the detector point spread function (PSF) with an edge-spread function method. The authors then derive a formula to estimate the I 0 value for different illumination field sizes, using the measured focal spot distribution and the detector PSF. Phantom studies are carried out to investigate the accuracy of scatter measurements and CT images with and without considering the I 0 variation effects. Results: On our tabletop system with a Varian Paxscan 4030CB flat-panel detector and a Varian RAD-94 x-ray tube as used on a clinical CBCT system, the focal spot distribution has a measured full

  13. UVIS Flat Field Uniformity

    Quijano, Jessica Kim

    2009-07-01

    The stability and uniformity of the low-frequency flat fields {L-flat} of the UVIS detector will be assessed by using multiple-pointing observations of the globular clusters 47 Tucanae {NGC104} and Omega Centauri {NGC5139}, thus imaging moderately dense stellar fields. By placing the same star over different portions of the detector and measuring relative changes in its brightness, it will be possible to determine local variations in the response of the UVIS detector. Based on previous experience with STIS and ACS, it is deemed that a total of 9 different pointings will suffice to provide adequate characterization of the flat field stability in any given band. For each filter to be tested, the baseline consists of 9 pointings in a 3X3 box pattern with dither steps of about 25% of the FOV, or 40.5", in either the x or y direction {useful also for CTE measurements, if needed in the future}. During SMOV, the complement of filters to be tested is limited to the following 6 filters: F225W, F275W, F336W, for Omega Cen, and F438W, F606W, and F814W for 47 Tuc. Three long exposures for each target are arranged such that the initial dither position is observed with the appropriate filters for that target within one orbit at a single pointing, so that filter-to-filter differences in the observed star positions can be checked. In addition to the 9 baseline exposures, two sets of short exposures will be taken:a} one short exposure will be taken of OmegaCen with each of the visible filters {F438W, F606W and F814W} in order to check the geometric distortion solution to be obtained with the data from proposal 11444;b} for each target, a single short exposure will be taken with each filter to facilitate the study of the PSF as a function of position on the detector by providing unsaturated images of sparsely-spaced bright stars.This proposal corresponds to Activity Description ID WF39. It should execute only after the following proposal has executed:WF21 - 11434

  14. Image Segmentation and Processing for Efficient Parking Space Analysis

    Tutika, Chetan Sai; Vallapaneni, Charan; R, Karthik; KP, Bharath; Muthu, N Ruban Rajesh Kumar

    2018-01-01

    In this paper, we develop a method to detect vacant parking spaces in an environment with unclear segments and contours with the help of MATLAB image processing capabilities. Due to the anomalies present in the parking spaces, such as uneven illumination, distorted slot lines and overlapping of cars. The present-day conventional algorithms have difficulties processing the image for accurate results. The algorithm proposed uses a combination of image pre-processing and false contour detection ...

  15. Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.

    Pierre Gueriau

    Full Text Available The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies.

  16. Trace elemental imaging of rare earth elements discriminates tissues at microscale in flat fossils.

    Gueriau, Pierre; Mocuta, Cristian; Dutheil, Didier B; Cohen, Serge X; Thiaudière, Dominique; Charbonnier, Sylvain; Clément, Gaël; Bertrand, Loïc

    2014-01-01

    The interpretation of flattened fossils remains a major challenge due to compression of their complex anatomies during fossilization, making critical anatomical features invisible or hardly discernible. Key features are often hidden under greatly preserved decay prone tissues, or an unpreparable sedimentary matrix. A method offering access to such anatomical features is of paramount interest to resolve taxonomic affinities and to study fossils after a least possible invasive preparation. Unfortunately, the widely-used X-ray micro-computed tomography, for visualizing hidden or internal structures of a broad range of fossils, is generally inapplicable to flattened specimens, due to the very high differential absorbance in distinct directions. Here we show that synchrotron X-ray fluorescence spectral raster-scanning coupled to spectral decomposition or a much faster Kullback-Leibler divergence based statistical analysis provides microscale visualization of tissues. We imaged exceptionally well-preserved fossils from the Late Cretaceous without needing any prior delicate preparation. The contrasting elemental distributions greatly improved the discrimination of skeletal elements material from both the sedimentary matrix and fossilized soft tissues. Aside content in alkaline earth elements and phosphorus, a critical parameter for tissue discrimination is the distinct amounts of rare earth elements. Local quantification of rare earths may open new avenues for fossil description but also in paleoenvironmental and taphonomical studies.

  17. Flat-port connectors

    Alrashed, Mohammed

    2017-05-26

    Disclosed are various embodiments for connectors used with electronic devices, such as input and/or output ports to connect peripheral equipment or accessories. More specifically, various flat-port are provided that can be used in place of standard connectors including, but not limited to, audio jacks and Universal Serial Bus (USB) ports. The flat-port connectors are an alternate connection design to replace the traditional receptacle port (female-port), making the device more sealed creation more dust and water resistant. It is unique in the way of using the outer surfaces of the device for the electrical connection between the ports. Flat-port design can allow the manufacture of extremely thin devices by eliminating the side ports slots that take a lot of space and contribute to the increase thickness of the device. The flat-port receptacle improves the overall appearance of the device and makes it more resistant to dust and water.

  18. The design and imaging characteristics of dynamic, solid-state, flat-panel x-ray image detectors for digital fluoroscopy and fluorography

    Cowen, A.R.; Davies, A.G.; Sivananthan, M.U.

    2008-01-01

    Dynamic, flat-panel, solid-state, x-ray image detectors for use in digital fluoroscopy and fluorography emerged at the turn of the millennium. This new generation of dynamic detectors utilize a thin layer of x-ray absorptive material superimposed upon an electronic active matrix array fabricated in a film of hydrogenated amorphous silicon (a-Si:H). Dynamic solid-state detectors come in two basic designs, the indirect-conversion (x-ray scintillator based) and the direct-conversion (x-ray photoconductor based). This review explains the underlying principles and enabling technologies associated with these detector designs, and evaluates their physical imaging characteristics, comparing their performance against the long established x-ray image intensifier television (TV) system. Solid-state detectors afford a number of physical imaging benefits compared with the latter. These include zero geometrical distortion and vignetting, immunity from blooming at exposure highlights and negligible contrast loss (due to internal scatter). They also exhibit a wider dynamic range and maintain higher spatial resolution when imaging over larger fields of view. The detective quantum efficiency of indirect-conversion, dynamic, solid-state detectors is superior to that of both x-ray image intensifier TV systems and direct-conversion detectors. Dynamic solid-state detectors are playing a burgeoning role in fluoroscopy-guided diagnosis and intervention, leading to the displacement of x-ray image intensifier TV-based systems. Future trends in dynamic, solid-state, digital fluoroscopy detectors are also briefly considered. These include the growth in associated three-dimensional (3D) visualization techniques and potential improvements in dynamic detector design

  19. Image Enhancement In HSI Space Using Wavelet Transform

    Bansal, Sonia; Malhotra, Deepti

    2010-11-01

    Image processing modifies images to improve them (enhancement, restoration), extract information (analysis, recognition), and change their structure (composition, image editing). Image Enhancement is simple and most appealing area among all the digital image processing techniques. The main purpose of image enhancement is to bring out detail that is hidden in an image or to increase contrast in a low contrast image [1]. The color restoration functions of some real color image enhancement algorithms are greatly at random and not proved , and the real color images enhanced which are based on illumination-reflectance model have the loss of details and the `halos', we proposed a new algorithm to overcome these disadvantages. Firstly, we transform the real color image from RGB space to HSI space which is approximately orthonormal system. Secondly, the illumination and the reflectance of value are separated by homomorphic filtering based on illumination-reflectance model. We have discovered that the high dynamic range of image including high bright lights is mainly caused by the reflectance. Thirdly, the details of reflectance are preserved by wavelet transform. Fourthly, the dynamic range of reflectance is compressed by Butterworth filtering. Lastly, the energy of the saturation of real color image in HSI space is attenuated according to the spectral sensitivity of most human vision.

  20. METHOD OF IMAGE QUALITY ENHANCEMENT FOR SPACE OBJECTS

    D. S. Korshunov

    2014-07-01

    Full Text Available The paper deals with an approach for image quality improvement of the space objects in the visible range of electromagnetic wave spectrum. The proposed method is based on the joint taking into account of both the motion velocity of the space supervisory apparatus and a space object observed in the near-earth space when the time of photo-detector exposure is chosen. The timing of exposure is carried out by light-signal characteristics, which determines the optimal value of the charge package formed in the charge-coupled device being irradiated. Thus, the parameters of onboard observation equipment can be selected, which provides space images suitable for interpretation. The linear resolving capacity is used as quality indicator for space images, giving a complete picture for the image contrast and geometric properties of the object on the photo. Observation scenario modeling of the space object, done by sputnik-inspector, has shown the possibility of increasing the linear resolution up to10% - 20% or up to 40% - 50% depending on the non-complanarity angle at the movement along orbits. The proposed approach to the increase of photographs quality provides getting sharp and highcontrast images of space objects by the optical-electronic equipment of the space-based remote sensing. The usage of these images makes it possible to detect in time the space technology failures, which are the result of its exploitation in the nearearth space. The proposed method can be also applied at the stage of space systems design for optical-electronic surveillance in computer models used for facilities assessment of the shooting equipment information tract.

  1. On the reduction of symmetry for static flat space-time in some general cylindrical-like coordinates

    Bokhari, A.H.; Bokhari, N.A.

    1987-09-01

    Flat static metric in terms of general cylindrical-like coordinates is considered and symmetry is reduced step by step. It turns out that the maximal and the minimal symmetry remains the same as that of the Minkowski or the Schwarzschild type. As soon as the dimensions of the metric are reduced, the symmetry turns out to be 6 or 3 in terms of independent Killing vector fields, respectively, not yet filling all the gaps between 10 to 8 to 4 or from 10 to 8 to 6 to 4 to 3 to 1. (author). 8 refs

  2. Imaging of the meninges and the extra-axial spaces.

    Kirmi, Olga; Sheerin, Fintan; Patel, Neel

    2009-12-01

    The separate meningeal layers and extraaxial spaces are complex and can only be differentiated by pathologic processes on imaging. Differentiation of the location of such processes can be achieved using different imaging modalities. In this pictorial review we address the imaging techniques, enhancement and location patterns, and disease spread that will promote accurate localization of the pathology, thus improving accuracy of diagnosis. Typical and unusual magnetic resonance (MR), computed tomography (CT), and ultrasound imaging findings of many conditions affecting these layers and spaces are described.

  3. Signal Space Separation Method for a Biomagnetic Sensor Array Arranged on a Flat Plane for Magnetocardiographic Applications: A Computer Simulation Study

    2018-01-01

    Although the signal space separation (SSS) method can successfully suppress interference/artifacts overlapped onto magnetoencephalography (MEG) signals, the method is considered inapplicable to data from nonhelmet-type sensor arrays, such as the flat sensor arrays typically used in magnetocardiographic (MCG) applications. This paper shows that the SSS method is still effective for data measured from a (nonhelmet-type) array of sensors arranged on a flat plane. By using computer simulations, it is shown that the optimum location of the origin can be determined by assessing the dependence of signal and noise gains of the SSS extractor on the origin location. The optimum values of the parameters LC and LD, which, respectively, indicate the truncation values of the multipole-order ℓ of the internal and external subspaces, are also determined by evaluating dependences of the signal, noise, and interference gains (i.e., the shield factor) on these parameters. The shield factor exceeds 104 for interferences originating from fairly distant sources. However, the shield factor drops to approximately 100 when calibration errors of 0.1% exist and to 30 when calibration errors of 1% exist. The shielding capability can be significantly improved using vector sensors, which measure the x, y, and z components of the magnetic field. With 1% calibration errors, a vector sensor array still maintains a shield factor of approximately 500. It is found that the SSS application to data from flat sensor arrays causes a distortion in the signal magnetic field, but it is shown that the distortion can be corrected by using an SSS-modified sensor lead field in the voxel space analysis. PMID:29854364

  4. Signal Space Separation Method for a Biomagnetic Sensor Array Arranged on a Flat Plane for Magnetocardiographic Applications: A Computer Simulation Study

    Kensuke Sekihara

    2018-01-01

    Full Text Available Although the signal space separation (SSS method can successfully suppress interference/artifacts overlapped onto magnetoencephalography (MEG signals, the method is considered inapplicable to data from nonhelmet-type sensor arrays, such as the flat sensor arrays typically used in magnetocardiographic (MCG applications. This paper shows that the SSS method is still effective for data measured from a (nonhelmet-type array of sensors arranged on a flat plane. By using computer simulations, it is shown that the optimum location of the origin can be determined by assessing the dependence of signal and noise gains of the SSS extractor on the origin location. The optimum values of the parameters LC and LD, which, respectively, indicate the truncation values of the multipole-order ℓ of the internal and external subspaces, are also determined by evaluating dependences of the signal, noise, and interference gains (i.e., the shield factor on these parameters. The shield factor exceeds 104 for interferences originating from fairly distant sources. However, the shield factor drops to approximately 100 when calibration errors of 0.1% exist and to 30 when calibration errors of 1% exist. The shielding capability can be significantly improved using vector sensors, which measure the x, y, and z components of the magnetic field. With 1% calibration errors, a vector sensor array still maintains a shield factor of approximately 500. It is found that the SSS application to data from flat sensor arrays causes a distortion in the signal magnetic field, but it is shown that the distortion can be corrected by using an SSS-modified sensor lead field in the voxel space analysis.

  5. Psychophysical evaluation of the image quality of a dynamic flat-panel digital x-ray image detector using the threshold contrast detail detectability (TCDD) technique

    Davies, Andrew G.; Cowen, Arnold R.; Bruijns, Tom J. C.

    1999-05-01

    We are currently in an era of active development of the digital X-ray imaging detectors that will serve the radiological communities in the new millennium. The rigorous comparative physical evaluations of such devices are therefore becoming increasingly important from both the technical and clinical perspectives. The authors have been actively involved in the evaluation of a clinical demonstration version of a flat-panel dynamic digital X-ray image detector (or FDXD). Results of objective physical evaluation of this device have been presented elsewhere at this conference. The imaging performance of FDXD under radiographic exposure conditions have been previously reported, and in this paper a psychophysical evaluation of the FDXD detector operating under continuous fluoroscopic conditions is presented. The evaluation technique employed was the threshold contrast detail detectability (TCDD) technique, which enables image quality to be measured on devices operating in the clinical environment. This approach addresses image quality in the context of both the image acquisition and display processes, and uses human observers to measure performance. The Leeds test objects TO[10] and TO[10+] were used to obtain comparative measurements of performance on the FDXD and two digital spot fluorography (DSF) systems, one utilizing a Plumbicon camera and the other a state of the art CCD camera. Measurements were taken at a range of detector entrance exposure rates, namely 6, 12, 25 and 50 (mu) R/s. In order to facilitate comparisons between the systems, all fluoroscopic image processing such as noise reduction algorithms, were disabled during the experiments. At the highest dose rate FDXD significantly outperformed the DSF comparison systems in the TCDD comparisons. At 25 and 12 (mu) R/s all three-systems performed in an equivalent manner and at the lowest exposure rate FDXD was inferior to the two DSF systems. At standard fluoroscopic exposures, FDXD performed in an equivalent

  6. Flat-Panel Computed Tomography (DYNA-CT) in Neuroradiology. From High-Resolution Imaging of Implants to One-Stop-Shopping for Acute Stroke.

    Doerfler, A; Gölitz, P; Engelhorn, T; Kloska, S; Struffert, T

    2015-10-01

    Originally aimed at improving standard radiography by providing higher absorption efficiency and a wider dynamic range, flat-panel detector technology has meanwhile got widely accepted in the neuroradiological community. Especially flat-panel detector computed tomography (FD-CT) using rotational C-arm mounted flat-panel detector technology is capable of volumetric imaging with a high spatial resolution. By providing CT-like images of the brain within the angio suite, FD-CT is able to rapidly visualize hemorrhage and may thus improve complication management without the need of patient transfer. As "Angiographic CT" FD-CT may be helpful during many diagnostic and neurointerventional procedures and for noninvasive monitoring and follow-up. In addition, spinal interventions and high-resolution imaging of the temporal bone might also benefit from FD-CT. Finally, using novel dynamic perfusion and angiographic protocols, FD-CT may provide functional information on brain perfusion and vasculature with the potential to replace standard imaging in selected acute stroke patients.

  7. Processing of space images and geologic interpretation

    Yudin, V S

    1981-01-01

    Using data for standard sections, a correlation was established between natural formations in geologic/geophysical dimensions and the form they take in the imaging. With computer processing, important data can be derived from the image. Use of the above correlations has allowed to make a number of preliminary classifications of tectonic structures, and to determine certain ongoing processes in the given section. The derived data may be used for search of useful minerals.

  8. TU-F-18C-02: Increasing Amorphous Selenium Thickness in Direct Conversion Flat-Panel Imagers for Contrast-Enhanced Dual-Energy Breast Imaging

    Scaduto, DA; Hu, Y-H; Zhao, W

    2014-01-01

    Purpose: Contrast-enhanced (CE) breast imaging using iodinated contrast agents requires imaging with x-ray spectra at energies greater than those used in mammography. Optimizing amorphous selenium (a-Se) flat panel imagers (FPI) for this higher energy range may increase lesion conspicuity. Methods: We compare imaging performance of a conventional FPI with 200 μm a-Se conversion layer to a prototype FPI with 300 μm a-Se layer. Both detectors are evaluated in a Siemens MAMMOMAT Inspiration prototype digital breast tomosynthesis (DBT) system using low-energy (W/Rh 28 kVp) and high-energy (W/Cu 49 kVp) x-ray spectra. Detectability of iodinated lesions in dual-energy images is evaluated using an iodine contrast phantom. Effects of beam obliquity are investigated in projection and reconstructed images using different reconstruction methods. The ideal observer signal-to-noise ratio is used as a figure-of-merit to predict the optimal a-Se thickness for CE lesion detectability without compromising conventional full-field digital mammography (FFDM) and DBT performance. Results: Increasing a-Se thickness from 200 μm to 300 μm preserves imaging performance at typical mammographic energies (e.g. W/Rh 28 kVp), and improves the detective quantum efficiency (DQE) for high energy (W/Cu 49 kVp) by 30%. While the more penetrating high-energy x-ray photons increase geometric blur due to beam obliquity in the FPI with thicker a-Se layer, the effect on lesion detectability in FBP reconstructions is negligible due to the reconstruction filters employed. Ideal observer SNR for CE objects shows improvements in in-plane detectability with increasing a-Se thicknesses, though small lesion detectability begins to degrade in oblique projections for a-Se thickness above 500 μm. Conclusion: Increasing a-Se thickness in direct conversion FPI from 200 μm to 300 μm improves lesion detectability in CE breast imaging with virtually no cost to conventional FFDM and DBT. This work was partially

  9. Use of discrete chromatic space to tune the image tone in a color image mosaic

    Zhang, Zuxun; Li, Zhijiang; Zhang, Jianqing; Zheng, Li

    2003-09-01

    Color image process is a very important problem. However, the main approach presently of them is to transfer RGB colour space into another colour space, such as HIS (Hue, Intensity and Saturation). YIQ, LUV and so on. Virutally, it may not be a valid way to process colour airborne image just in one colour space. Because the electromagnetic wave is physically altered in every wave band, while the color image is perceived based on psychology vision. Therefore, it's necessary to propose an approach accord with physical transformation and psychological perception. Then, an analysis on how to use relative colour spaces to process colour airborne photo is discussed and an application on how to tune the image tone in colour airborne image mosaic is introduced. As a practice, a complete approach to perform the mosaic on color airborne images via taking full advantage of relative color spaces is discussed in the application.

  10. Design and analysis of the trapeziform and flat acoustic cloaks with controllable invisibility performance in a quasi-space

    Jian Zhu

    2015-07-01

    Full Text Available We present the design, implementation and detailed performance analysis for a class of trapeziform and flat acoustic cloaks. An effective large invisible area is obtained compared with the traditional carpet cloak. The cloaks are realized with homogeneous metamaterials which are made of periodic arrangements of subwavelength unit cells composed of steel embedded in air. The microstructures and its effective parameters of the cloaks are determined quickly and precisely in a broadband frequency range by using the effective medium theory and the proposed parameters optimization method. The invisibility capability of the cloaks can be controlled by the variation of the key design parameters and scale factor which are proved to have more influence on the performance in the near field than that in the far field. Different designs are suitable for different application situations. Good cloaking performance demonstrates that such a device can be physically realized with natural materials which will greatly promote the real applications of invisibility cloak.

  11. CT image registration in sinogram space.

    Mao, Weihua; Li, Tianfang; Wink, Nicole; Xing, Lei

    2007-09-01

    Object displacement in a CT scan is generally reflected in CT projection data or sinogram. In this work, the direct relationship between object motion and the change of CT projection data (sinogram) is investigated and this knowledge is applied to create a novel algorithm for sinogram registration. Calculated and experimental results demonstrate that the registration technique works well for registering rigid 2D or 3D motion in parallel and fan beam samplings. Problem and solution for 3D sinogram-based registration of metallic fiducials are also addressed. Since the motion is registered before image reconstruction, the presented algorithm is particularly useful when registering images with metal or truncation artifacts. In addition, this algorithm is valuable for dealing with situations where only limited projection data are available, making it appealing for various applications in image guided radiation therapy.

  12. CT image registration in sinogram space

    Mao Weihua; Li Tianfang; Wink, Nicole; Xing Lei

    2007-01-01

    Object displacement in a CT scan is generally reflected in CT projection data or sinogram. In this work, the direct relationship between object motion and the change of CT projection data (sinogram) is investigated and this knowledge is applied to create a novel algorithm for sinogram registration. Calculated and experimental results demonstrate that the registration technique works well for registering rigid 2D or 3D motion in parallel and fan beam samplings. Problem and solution for 3D sinogram-based registration of metallic fiducials are also addressed. Since the motion is registered before image reconstruction, the presented algorithm is particularly useful when registering images with metal or truncation artifacts. In addition, this algorithm is valuable for dealing with situations where only limited projection data are available, making it appealing for various applications in image guided radiation therapy

  13. Digital chest radiography with an amorphous silicon flat-panel-detector versus a storage-phosphor system: comparison of soft-copy images

    Lee, Hyun Ju; Im, Jung Gi; Goo, Jin Mo; Lee, Chang Hyun

    2006-01-01

    We compared the soft-copy images produced by an amorphous silicon flat-panel-detector system with the images produced by a storage-phosphor radiography system for their ability to visualize anatomic regions of the chest. Two chest radiologists independently analyzed 234 posteroanterior chest radiographs obtained from 78 patients on high-resolution liquid crystal display monitors (2560 x 2048 x 8 bits). In each patient, one radiograph was obtained with a storage-phosphor system, and two radiographs were obtained via amorphous silicon flat-panel-detector radiography with and without spatial frequency filtering. After randomizing the 234 images, the interpreters rated the visibility and radiographic quality of 11 different anatomic regions. Each image was ranked on a five-point scale (1 = not visualized, 2 = poor visualization, 3 = fair visualization, 4 = good visualization, and 5 = excellent visualization). The statistical difference between each system was determined using the Wilcoxon's signed rank test. The visibility of three anatomic regions (hilum, heart border and ribs), as determined by the chest radiologist with 14 years experience (ρ < 0.05) and the visibility of the thoracic spine, as determined by the chest radiologist with 8 years experience (ρ = 0.036), on the amorphous silicon flat-panel-detector radiography prior to spatial frequency filtering were significantly superior to that on the storage-phosphor radiography. The visibility of 11 anatomic regions, as determined by the chest radiologist with 14 years experience (ρ < 0.0001) and the visibility of five anatomic regions (unobscured lung, rib, proximal airway, thoracic spine and overall appearance), as determined by the chest radiologist with 8 years experience (ρ < 0.05), on the amorphous silicon flat-panel-detector radiography after spatial frequency filtering were significantly superior to that on the storage-phosphor radiography. The amorphous silicon flat-panel-detector system depicted the

  14. Performance Study of an aSi Flat Panel Detector for Fast Neutron Imaging of Nuclear Waste

    Schumann, M.; Mauerhofer, E. [Institute of Energy and Climate Research - Nuclear Waste Management and Reactor Safety, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Engels, R.; Kemmerling, G. [Central Institute for Engineering, Electronics and Analytics - Electronic Systems, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Frank, M. [MATHCCES - Department of Mathematics, RWTH Aachen University, 52062 Aachen (Germany); Havenith, A.; Kettler, J.; Klapdor-Kleingrothaus, T. [Institute of Nuclear Engineering and Technology Transfer, RWTH Aachen University, 52062 Aachen (Germany); Schitthelm, O. [Corporate Technology, Siemens AG, 91058 Erlangen (Germany)

    2015-07-01

    Radioactive waste must be characterized to check its conformance for intermediate storage and final disposal according to national regulations. For the determination of radio-toxic and chemo-toxic contents of radioactive waste packages non-destructive analytical techniques are preferentially used. Fast neutron imaging is a promising technique to assay large and dense items providing, in complementarity to photon imaging, additional information on the presence of structures in radioactive waste packages. Therefore the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons is studied in a cooperation framework of Forschungszentrum Juelich GmbH, RWTH Aachen University and Siemens AG. However due to the low neutron emission of neutron generators in comparison to research reactors the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose. The setup is composed of a commercial D-T neutron generator (Genie16GT, Sodern) with a surrounding shielding made of polyethylene, which acts as a collimator and an amorphous silicon flat panel detector (aSi, 40 x 40 cm{sup 2}, XRD-1642, Perkin Elmer). Neutron detection is achieved using a general propose plastic scintillator (EJ-260, Eljen Technology) linked to the detector. The thermal noise of the photodiodes is reduced by employing an entrance window made of aluminium. Optimal gain and integration time for data acquisition are set by measuring the response of the detector to the radiation of a 500 MBq {sup 241}Am-source. Detector performance was studied by recording neutron radiography images of materials with various, but well known, chemical compositions, densities and dimensions (Al, C, Fe, Pb, W, concrete, polyethylene, 5 x 8 x 10 cm{sup 3}). To simulate gamma-ray emitting waste radiographs in presence of a gamma-ray sources ({sup 60}Co, {sup 137}Cs, {sup 241

  15. Space-based infrared sensors of space target imaging effect analysis

    Dai, Huayu; Zhang, Yasheng; Zhou, Haijun; Zhao, Shuang

    2018-02-01

    Target identification problem is one of the core problem of ballistic missile defense system, infrared imaging simulation is an important means of target detection and recognition. This paper first established the space-based infrared sensors ballistic target imaging model of point source on the planet's atmosphere; then from two aspects of space-based sensors camera parameters and target characteristics simulated atmosphere ballistic target of infrared imaging effect, analyzed the camera line of sight jitter, camera system noise and different imaging effects of wave on the target.

  16. The effect of dose reduction on image quality in digital radiography using a flat-panel detector: experimental study in rabbits

    Jung, Sung Il; Goo, Jin Mo; Lee, Hyun Ju; Moon, Woo Kyung; Lim, Kun Young; Cho, Gyung Goo; Kim, Ji Hoon; Im, Jung Gi; Choi, Jang Yong; Nam, Sang Hee

    2005-01-01

    To evaluate the effect of dose reduction on image quality in digital radiography using a flat-panel detector. Digital radiographs of 30 rabbits were obtained at two different dose levels (33.23 μGY for the standard dose group and 20.09 μGY for the reduced dose group). The amorphous selenium-based flat-panel detector system had a panel size of 7 x 8.5 inches, a matrix of 1280 x 1536 (pixels?), and a pixel pitch of 138 μm. Four observers evaluated the soft-copy images on a high-resolution video monitor (2560 x 2048 x 8 bits) in random order. The observers rated the visibility of 13 different anatomic structures on a 5-point scale, viz, the retrocardiac lung, subdiaphragmatic lung, heart border, diaphragmatic border, proximal airway, unobscured lung, liver border, kidney border, bowel gas, flank stripe, ribs, and vertebrae in the mediastinal and abdominal regions. Statistical significance was determined using Wilcoxon's signed rank test. There was no statistically significant difference in the visibility of the anatomic structures on digital radiography between the standard and reduced dose groups. Digital radiography using an amorphous selenium-based flat-panel detector can preserve the image quality, though the dose is reduced to 40% of the standard level

  17. The effect of dose reduction on image quality in digital radiography using a flat-panel detector: experimental study in rabbits

    Jung, Sung Il; Goo, Jin Mo; Lee, Hyun Ju; Moon, Woo Kyung; Lim, Kun Young; Cho, Gyung Goo; Kim, Ji Hoon; Im, Jung Gi [Seoul National College of Medicine, Seoul (Korea, Republic of); Choi, Jang Yong; Nam, Sang Hee [Inje University, Seoul (Korea, Republic of)

    2005-07-15

    To evaluate the effect of dose reduction on image quality in digital radiography using a flat-panel detector. Digital radiographs of 30 rabbits were obtained at two different dose levels (33.23 {mu}GY for the standard dose group and 20.09 {mu}GY for the reduced dose group). The amorphous selenium-based flat-panel detector system had a panel size of 7 x 8.5 inches, a matrix of 1280 x 1536 (pixels?), and a pixel pitch of 138 {mu}m. Four observers evaluated the soft-copy images on a high-resolution video monitor (2560 x 2048 x 8 bits) in random order. The observers rated the visibility of 13 different anatomic structures on a 5-point scale, viz, the retrocardiac lung, subdiaphragmatic lung, heart border, diaphragmatic border, proximal airway, unobscured lung, liver border, kidney border, bowel gas, flank stripe, ribs, and vertebrae in the mediastinal and abdominal regions. Statistical significance was determined using Wilcoxon's signed rank test. There was no statistically significant difference in the visibility of the anatomic structures on digital radiography between the standard and reduced dose groups. Digital radiography using an amorphous selenium-based flat-panel detector can preserve the image quality, though the dose is reduced to 40% of the standard level.

  18. Preliminary performance of image quality for a low-dose C-arm CT system with a flat-panel detector

    Kyung Cha, Bo [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Seo, Chang-Woo [Department of Radiation Convergence Engineering, College of Health Science, Yonsei University, Wonju (Korea, Republic of); Yang, Keedong [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Jeon, Seongchae, E-mail: sarim@keri.re.kr [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of); Huh, Young [Advanced Medical Device Research Center, Korea Electrotechnology Research Institute, Ansan (Korea, Republic of)

    2015-06-01

    Digital flat panel imager (FPI)-based cone-beam computed tomography (CBCT) has been widely used in C-arm imaging for spine surgery and interventional procedures. The system provides real-time fluoroscopy with high spatial resolution and three-dimensional (3D) visualization of anatomical structure without the need for patient transportation in interventional suite. In this work, a prototype CBCT imaging platform with continuous single rotation about the gantry was developed by using a large-area flat-panel detector with amorphous Si-based thin film transistor matrix. The different 2D projection images were acquired during constant gantry velocity for reconstructed images at a tube voltage of 80–120 kVp, and different current (10–50 mA) conditions. Various scan protocols were applied to a chest phantom human by changing the number of projection images and scanning angles. The projections were then reconstructed into a volumetric data of sections by using a 3D reconstruction algorithm (e.g., filtered back projection). The preliminary quantitative X-ray performance of our CBCT system was investigated by using the American Association of Physicists in Medicine CT phantom in terms of spatial resolution, contrast resolution, and CT number linearity for mobile or fixed C-arm based CBCT application with limited rotational geometry. The novel results of the projection data with different scanning angles and angular increments in the orbital gantry platform were acquired and evaluated experimentally.

  19. Preliminary performance of image quality for a low-dose C-arm CT system with a flat-panel detector

    Kyung Cha, Bo; Seo, Chang-Woo; Yang, Keedong; Jeon, Seongchae; Huh, Young

    2015-01-01

    Digital flat panel imager (FPI)-based cone-beam computed tomography (CBCT) has been widely used in C-arm imaging for spine surgery and interventional procedures. The system provides real-time fluoroscopy with high spatial resolution and three-dimensional (3D) visualization of anatomical structure without the need for patient transportation in interventional suite. In this work, a prototype CBCT imaging platform with continuous single rotation about the gantry was developed by using a large-area flat-panel detector with amorphous Si-based thin film transistor matrix. The different 2D projection images were acquired during constant gantry velocity for reconstructed images at a tube voltage of 80–120 kVp, and different current (10–50 mA) conditions. Various scan protocols were applied to a chest phantom human by changing the number of projection images and scanning angles. The projections were then reconstructed into a volumetric data of sections by using a 3D reconstruction algorithm (e.g., filtered back projection). The preliminary quantitative X-ray performance of our CBCT system was investigated by using the American Association of Physicists in Medicine CT phantom in terms of spatial resolution, contrast resolution, and CT number linearity for mobile or fixed C-arm based CBCT application with limited rotational geometry. The novel results of the projection data with different scanning angles and angular increments in the orbital gantry platform were acquired and evaluated experimentally

  20. Relaxation in x-space magnetic particle imaging.

    Croft, Laura R; Goodwill, Patrick W; Conolly, Steven M

    2012-12-01

    Magnetic particle imaging (MPI) is a new imaging modality that noninvasively images the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIOs). MPI has demonstrated high contrast and zero attenuation with depth, and MPI promises superior safety compared to current angiography methods, X-ray, computed tomography, and magnetic resonance imaging angiography. Nanoparticle relaxation can delay the SPIO magnetization, and in this work we investigate the open problem of the role relaxation plays in MPI scanning and its effect on the image. We begin by amending the x-space theory of MPI to include nanoparticle relaxation effects. We then validate the amended theory with experiments from a Berkeley x-space relaxometer and a Berkeley x-space projection MPI scanner. Our theory and experimental data indicate that relaxation reduces SNR and asymmetrically blurs the image in the scanning direction. While relaxation effects can have deleterious effects on the MPI scan, we show theoretically and experimentally that x-space reconstruction remains robust in the presence of relaxation. Furthermore, the role of relaxation in x-space theory provides guidance as we develop methods to minimize relaxation-induced blurring. This will be an important future area of research for the MPI community.

  1. THE FLAT TRANSMISSION SPECTRUM OF THE SUPER-EARTH GJ1214b FROM WIDE FIELD CAMERA 3 ON THE HUBBLE SPACE TELESCOPE

    Berta, Zachory K.; Charbonneau, David; Désert, Jean-Michel; Irwin, Jonathan; Miller-Ricci Kempton, Eliza; Fortney, Jonathan J.; Nutzman, Philip; McCullough, Peter R.; Burke, Christopher J.; Homeier, Derek

    2012-01-01

    Capitalizing on the observational advantage offered by its tiny M dwarf host, we present Hubble Space Telescope/Wide Field Camera 3 (WFC3) grism measurements of the transmission spectrum of the super-Earth exoplanet GJ1214b. These are the first published WFC3 observations of a transiting exoplanet atmosphere. After correcting for a ramp-like instrumental systematic, we achieve nearly photon-limited precision in these observations, finding the transmission spectrum of GJ1214b to be flat between 1.1 and 1.7 μm. Inconsistent with a cloud-free solar composition atmosphere at 8.2σ, the measured achromatic transit depth most likely implies a large mean molecular weight for GJ1214b's outer envelope. A dense atmosphere rules out bulk compositions for GJ1214b that explain its large radius by the presence of a very low density gas layer surrounding the planet. High-altitude clouds can alternatively explain the flat transmission spectrum, but they would need to be optically thick up to 10 mbar or consist of particles with a range of sizes approaching 1 μm in diameter.

  2. Image correlation spectroscopy: mapping correlations in space, time, and reciprocal space.

    Wiseman, Paul W

    2013-01-01

    This chapter presents an overview of two recent implementations of image correlation spectroscopy (ICS). The background theory is presented for spatiotemporal image correlation spectroscopy and image cross-correlation spectroscopy (STICS and STICCS, respectively) as well as k-(reciprocal) space image correlation spectroscopy (kICS). An introduction to the background theory is followed by sections outlining procedural aspects for properly implementing STICS, STICCS, and kICS. These include microscopy image collection, sampling in space and time, sample and fluorescent probe requirements, signal to noise, and background considerations that are all required to properly implement the ICS methods. Finally, procedural steps for immobile population removal and actual implementation of the ICS analysis programs to fluorescence microscopy image time stacks are described. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Studies of a general flat space/boson star transition model in a box through a language similar to holographic superconductors

    Peng, Yan

    2017-07-01

    We study a general flat space/boson star transition model in quasi-local ensemble through approaches familiar from holographic superconductor theories. We manage to find a parameter ψ 2, which is proved to be useful in disclosing properties of phase transitions. In this work, we explore effects of the scalar mass, scalar charge and Stückelberg mechanism on the critical phase transition points and the order of transitions mainly from behaviors of the parameter ψ 2. We mention that properties of transitions in quasi-local gravity are strikingly similar to those in holographic superconductor models. We also obtain an analytical relation ψ 2 ∝ ( μ - μ c )1/2, which also holds for the condensed scalar operator in the holographic insulator/superconductor system in accordance with mean field theories.

  4. X-space MPI: magnetic nanoparticles for safe medical imaging.

    Goodwill, Patrick William; Saritas, Emine Ulku; Croft, Laura Rose; Kim, Tyson N; Krishnan, Kannan M; Schaffer, David V; Conolly, Steven M

    2012-07-24

    One quarter of all iodinated contrast X-ray clinical imaging studies are now performed on Chronic Kidney Disease (CKD) patients. Unfortunately, the iodine contrast agent used in X-ray is often toxic to CKD patients' weak kidneys, leading to significant morbidity and mortality. Hence, we are pioneering a new medical imaging method, called Magnetic Particle Imaging (MPI), to replace X-ray and CT iodinated angiography, especially for CKD patients. MPI uses magnetic nanoparticle contrast agents that are much safer than iodine for CKD patients. MPI already offers superb contrast and extraordinary sensitivity. The iron oxide nanoparticle tracers required for MPI are also used in MRI, and some are already approved for human use, but the contrast agents are far more effective at illuminating blood vessels when used in the MPI modality. We have recently developed a systems theoretic framework for MPI called x-space MPI, which has already dramatically improved the speed and robustness of MPI image reconstruction. X-space MPI has allowed us to optimize the hardware for fi ve MPI scanners. Moreover, x-space MPI provides a powerful framework for optimizing the size and magnetic properties of the iron oxide nanoparticle tracers used in MPI. Currently MPI nanoparticles have diameters in the 10-20 nanometer range, enabling millimeter-scale resolution in small animals. X-space MPI theory predicts that larger nanoparticles could enable up to 250 micrometer resolution imaging, which would represent a major breakthrough in safe imaging for CKD patients.

  5. Exploring Sustainability Using images from Space

    Chen, Loris; Salmon, Jennifer; Burns, Courtney

    2016-04-01

    , laptops, iPads). As a result, web-based resources are incorporated into student learning on a daily basis. This has created a truly global classroom for students who, via the Internet, can and do access materials from any country in the world. Students work collaboratively using Google Classroom and a suite of Google apps. Teacher-created websites serve as the textbook with text, video, static images, interactive images, and external links designed to stimulate student growth in scientific literacy, language arts, and mathematics. Images of Earth's systems generated from data collected by Earth orbiting spacecraft are essential tools for understanding sustainability concepts at global, national, regional, and local scales. Images and supporting data from NASA (U.S.), ESA (Europe), and JAXA (Japan) are used to explore Earth's atmosphere, hydrosphere, and geosphere. Simulations, time-lapses, and graphical representations of historical and real-time, remote-sensing data stimulate student questions and engage students in learning as they design and test models to explain complex interactions of Earth's systems and feedback loops between natural and human-made environments. As students make meaning of observations and communicate their perceptions and understandings to a variety of audiences, they gain mastery of scientific literacy, language arts skills, and mathematics skills.

  6. Source-space ICA for MEG source imaging.

    Jonmohamadi, Yaqub; Jones, Richard D

    2016-02-01

    One of the most widely used approaches in electroencephalography/magnetoencephalography (MEG) source imaging is application of an inverse technique (such as dipole modelling or sLORETA) on the component extracted by independent component analysis (ICA) (sensor-space ICA + inverse technique). The advantage of this approach over an inverse technique alone is that it can identify and localize multiple concurrent sources. Among inverse techniques, the minimum-variance beamformers offer a high spatial resolution. However, in order to have both high spatial resolution of beamformer and be able to take on multiple concurrent sources, sensor-space ICA + beamformer is not an ideal combination. We propose source-space ICA for MEG as a powerful alternative approach which can provide the high spatial resolution of the beamformer and handle multiple concurrent sources. The concept of source-space ICA for MEG is to apply the beamformer first and then singular value decomposition + ICA. In this paper we have compared source-space ICA with sensor-space ICA both in simulation and real MEG. The simulations included two challenging scenarios of correlated/concurrent cluster sources. Source-space ICA provided superior performance in spatial reconstruction of source maps, even though both techniques performed equally from a temporal perspective. Real MEG from two healthy subjects with visual stimuli were also used to compare performance of sensor-space ICA and source-space ICA. We have also proposed a new variant of minimum-variance beamformer called weight-normalized linearly-constrained minimum-variance with orthonormal lead-field. As sensor-space ICA-based source reconstruction is popular in EEG and MEG imaging, and given that source-space ICA has superior spatial performance, it is expected that source-space ICA will supersede its predecessor in many applications.

  7. Electrostatic images for underwater anisotropic conductive half spaces

    Flykt, M.; Lindell, I.; Eloranta, E.

    1998-01-01

    A static image principle makes it possible to derive analytical solutions to some basic geometries for DC fields. The underwater environment is especially difficult both from the theoretical and practical point of view. However, there are increasing demands that also the underwater geological formations should be studied in detail. The traditional image of a point source lies at the mirror point of the original. When anisotropic media is involved, however, the image location can change and the image source may be a continues, sector-like distribution. In this paper some theoretical considerations are carried out in the case where the lower half space can have a very general anisotropy in terms of electrical conductivity, while the upper half space is assumed isotropic. The reflection potential field is calculated for different values of electrical conductivity. (orig.)

  8. Research-grade CMOS image sensors for demanding space applications

    Saint-Pé, Olivier; Tulet, Michel; Davancens, Robert; Larnaudie, Franck; Magnan, Pierre; Corbière, Franck; Martin-Gonthier, Philippe; Belliot, Pierre

    2017-11-01

    Imaging detectors are key elements for optical instruments and sensors on board space missions dedicated to Earth observation (high resolution imaging, atmosphere spectroscopy...), Solar System exploration (micro cameras, guidance for autonomous vehicle...) and Universe observation (space telescope focal planes, guiding sensors...). This market has been dominated by CCD technology for long. Since the mid- 90s, CMOS Image Sensors (CIS) have been competing with CCDs for more and more consumer domains (webcams, cell phones, digital cameras...). Featuring significant advantages over CCD sensors for space applications (lower power consumption, smaller system size, better radiations behaviour...), CMOS technology is also expanding in this field, justifying specific R&D and development programs funded by national and European space agencies (mainly CNES, DGA, and ESA). All along the 90s and thanks to their increasingly improving performances, CIS have started to be successfully used for more and more demanding applications, from vision and control functions requiring low-level performances to guidance applications requiring medium-level performances. Recent technology improvements have made possible the manufacturing of research-grade CIS that are able to compete with CCDs in the high-performances arena. After an introduction outlining the growing interest of optical instruments designers for CMOS image sensors, this talk will present the existing and foreseen ways to reach high-level electro-optics performances for CIS. The developments of CIS prototypes built using an imaging CMOS process and of devices based on improved designs will be presented.

  9. Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: An experimental study of a single-pixel prototype

    Mei, X.; Pang, G.

    2005-01-01

    Our overall goal is to develop a new generation of electronic portal imaging devices (EPIDs) with a quantum efficiency (QE) more than an order of magnitude higher and a spatial resolution equivalent to that of EPIDs currently used for portal imaging. A novel design of such a high QE flat-panel based EPID was introduced recently and its feasibility was investigated theoretically [see Pang and Rowlands, Med. Phys. 31, 3004 (2004)]. In this work, we constructed a prototype single-pixel detector based on the novel design. Some fundamental imaging properties including the QE, spatial resolution, and sensitivity of the prototype detector were measured with a 6 MV beam. It has been shown that the experimental results agree well with theoretical predictions and further development based on the novel design including the construction of a prototype area detector is warranted

  10. Gauge constructs and immersions of four-dimensional spacetimes in (4 + k)-dimensional flat spaces: algebraic evaluation of gravity fields

    Edelen, Dominic G B

    2003-01-01

    Local action of the fundamental group SO(a, 4 + k - a) is used to show that any solution of an algebraically closed differential system, that is generated from matrix Lie algebra valued 1-forms on a four-dimensional parameter space, will generate families of immersions of four-dimensional spacetimes R 4 in flat (4 + k)-dimensional spaces M 4+k with compatible signature. The algorithm is shown to work with local action of SO(a, 4 + k - a) replaced by local action of GL(4 + k). Immersions generated by local action of the Poincare group on the target spacetime are also obtained. Evaluations of the line elements, immersion loci and connection and curvature forms of these immersions are algebraic. Families of immersions that depend on one or more arbitrary functions are calculated for 1 ≤ k ≤ 4. Appropriate sections of graphs of the conformal factor for two and three interacting line singularities immersed in M 6 are given in appendix A. The local immersion theorem given in appendix B shows that all local solutions of the immersion problem are obtained by use of this method and an algebraic extension in exceptional cases

  11. OBJECT-SPACE MULTI-IMAGE MATCHING OF MOBILE-MAPPING-SYSTEM IMAGE SEQUENCES

    Y. C. Chen

    2012-07-01

    Full Text Available This paper proposes an object-space multi-image matching procedure of terrestrial MMS (Mobile Mapping System image sequences to determine the coordinates of an object point automatically and reliably. This image matching procedure can be applied to find conjugate points of MMS image sequences efficiently. Conventional area-based image matching methods are not reliable to deliver accurate matching results for this application due to image scale variations, viewing angle variations, and object occlusions. In order to deal with these three matching problems, an object space multi-image matching is proposed. A modified NCC (Normalized Cross Correlation coefficient is proposed to measure the similarity of image patches. A modified multi-window matching procedure will also be introduced to solve the problem of object occlusion. A coarse-to-fine procedure with a combination of object-space multi-image matching and multi-window matching is adopted. The proposed procedure has been implemented for the purpose of matching terrestrial MMS image sequences. The ratio of correct matches of this experiment was about 80 %. By providing an approximate conjugate point in an overlapping image manually, most of the incorrect matches could be fixed properly and the ratio of correct matches was improved up to 98 %.

  12. Color image segmentation using perceptual spaces through applets ...

    Color image segmentation using perceptual spaces through applets for determining and preventing diseases in chili peppers. JL González-Pérez, MC Espino-Gudiño, J Gudiño-Bazaldúa, JL Rojas-Rentería, V Rodríguez-Hernández, VM Castaño ...

  13. Subjective assessment of impairment in scale-space-coded images

    Ridder, de H.; Majoor, G.M.M.

    1988-01-01

    Direct category scaling and a scaling procedure in accordance with Functional Measurement Theory (Anderson, 1982) have been used to assess impairment in scale-space-coded illlages, displayed on a black-and-white TV monitor. The image of a complex scene was passed through a Gaussian filter of limited

  14. Color quality management in advanced flat panel display engines

    Lebowsky, Fritz; Neugebauer, Charles F.; Marnatti, David M.

    2003-01-01

    During recent years color reproduction systems for consumer needs have experienced various difficulties. In particular, flat panels and printers could not reach a satisfactory color match. The RGB image stored on an Internet server of a retailer did not show the desired colors on a consumer display device or printer device. STMicroelectronics addresses this important color reproduction issue inside their advanced display engines using novel algorithms targeted for low cost consumer flat panels. Using a new and genuine RGB color space transformation, which combines a gamma correction Look-Up-Table, tetrahedrization, and linear interpolation, we satisfy market demands.

  15. Concept of a selective tumour therapy and its evaluation by near-infrared fluorescence imaging and flat-panel volume computed tomography in mice.

    Alves, Frauke; Dullin, Christian; Napp, Joanna; Missbach-Guentner, Jeannine; Jannasch, Katharina; Mathejczyk, Julia; Pardo, Luis A; Stühmer, Walter; Tietze, Lutz-F

    2009-05-01

    Conventional chemotherapy of cancer has its limitations, especially in advanced and disseminated disease and suffers from lack of specificity. This results in a poor therapeutic index and considerable toxicity to normal organs. Therefore, many efforts are made to develop novel therapeutic tools against cancer with the aim of selectively targeting the drug to the tumour site. Drug delivery strategies fundamentally rely on the identification of good-quality biomarkers, allowing unequivocal discrimination between cancer and healthy tissue. At present, antibodies or antibody fragments have clearly proven their value as carrier molecules specific for a tumour-associated molecular marker. This present review draws attention to the use of near-infrared fluorescence (NIRF) imaging to investigate binding specificity and kinetics of carrier molecules such as monoclonal antibodies. In addition, flat-panel volume computed tomography (fpVCT) will be presented to monitor anatomical structures in tumour mouse models over time in a non-invasive manner. Each imaging device sheds light on a different aspect; functional imaging is applied to optimise the dose schedule and the concept of selective tumour therapies, whereas anatomical imaging assesses preclinically the efficacy of novel tumour therapies. Both imaging techniques in combination allow the visualisation of functional information obtained by NIRF imaging within an adequate anatomic framework.

  16. Space Radar Image of Central African Gorilla Habitat

    1999-01-01

    This is a false-color radar image of Central Africa, showing the Virunga Volcano chain along the borders of Rwanda, Zaire and Uganda. This area is home to the endangered mountain gorillas. This C-band L-band image was acquired on April 12, 1994, on orbit 58 of space shuttle Endeavour by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR). The area is centered at about 1.75 degrees south latitude and 29.5 degrees east longitude. The image covers an area 58 kilometers by 178 kilometers (48 miles by 178 miles). The false-color composite is created by displaying the L-band HH return in red, the L-band HV return in green and the C-band HH return in blue. The dark area in the bottom of the image is Lake Kivu, which forms the border between Zaire (to the left) and Rwanda (to the right). The airport at Goma, Zaire is shown as a dark line just above the lake in the bottom left corner of the image. Volcanic flows from the 1977 eruption of Mt. Nyiragongo are shown just north of the airport. Mt. Nyiragongo is not visible in this image because it is located just to the left of the image swath. Very fluid lava flows from the 1977 eruption killed 70 people. Mt. Nyiragongo is currently erupting (August 1994) and will be a target of observation during the second flight of SIR-C/X-SAR. The large volcano in the center of the image is Mt. Karisimbi (4,500 meters or 14,800 feet). This radar image highlights subtle differences in the vegetation and volcanic flows of the region. The faint lines shown in the purple regions are believed to be the result of agriculture terracing by the people who live in the region. The vegetation types are an important factor in the habitat of the endangered mountain gorillas. Researchers at Rutgers University in New Jersey and the Dian Fossey Gorilla Fund in London will use this data to produce vegetation maps of the area to aid in their study of the remaining 650 gorillas in the region. SIR-C was developed by NASA's Jet

  17. Space Radar Image of West Texas - SAR scan

    1999-01-01

    This radar image of the Midland/Odessa region of West Texas, demonstrates an experimental technique, called ScanSAR, that allows scientists to rapidly image large areas of the Earth's surface. The large image covers an area 245 kilometers by 225 kilometers (152 miles by 139 miles). It was obtained by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) flying aboard the space shuttle Endeavour on October 5, 1994. The smaller inset image is a standard SIR-C image showing a portion of the same area, 100 kilometers by 57 kilometers (62 miles by 35 miles) and was taken during the first flight of SIR-C on April 14, 1994. The bright spots on the right side of the image are the cities of Odessa (left) and Midland (right), Texas. The Pecos River runs from the top center to the bottom center of the image. Along the left side of the image are, from top to bottom, parts of the Guadalupe, Davis and Santiago Mountains. North is toward the upper right. Unlike conventional radar imaging, in which a radar continuously illuminates a single ground swath as the space shuttle passes over the terrain, a Scansar radar illuminates several adjacent ground swaths almost simultaneously, by 'scanning' the radar beam across a large area in a rapid sequence. The adjacent swaths, typically about 50 km (31 miles) wide, are then merged during ground processing to produce a single large scene. Illumination for this L-band scene is from the top of the image. The beams were scanned from the top of the scene to the bottom, as the shuttle flew from left to right. This scene was acquired in about 30 seconds. A normal SIR-C image is acquired in about 13 seconds. The ScanSAR mode will likely be used on future radar sensors to construct regional and possibly global radar images and topographic maps. The ScanSAR processor is being designed for 1996 implementation at NASA's Alaska SAR Facility, located at the University of Alaska Fairbanks, and will produce digital images from the

  18. Space imaging infrared optical guidance for autonomous ground vehicle

    Akiyama, Akira; Kobayashi, Nobuaki; Mutoh, Eiichiro; Kumagai, Hideo; Yamada, Hirofumi; Ishii, Hiromitsu

    2008-08-01

    We have developed the Space Imaging Infrared Optical Guidance for Autonomous Ground Vehicle based on the uncooled infrared camera and focusing technique to detect the objects to be evaded and to set the drive path. For this purpose we made servomotor drive system to control the focus function of the infrared camera lens. To determine the best focus position we use the auto focus image processing of Daubechies wavelet transform technique with 4 terms. From the determined best focus position we transformed it to the distance of the object. We made the aluminum frame ground vehicle to mount the auto focus infrared unit. Its size is 900mm long and 800mm wide. This vehicle mounted Ackerman front steering system and the rear motor drive system. To confirm the guidance ability of the Space Imaging Infrared Optical Guidance for Autonomous Ground Vehicle we had the experiments for the detection ability of the infrared auto focus unit to the actual car on the road and the roadside wall. As a result the auto focus image processing based on the Daubechies wavelet transform technique detects the best focus image clearly and give the depth of the object from the infrared camera unit.

  19. Uniform color space analysis of LACIE image products

    Nalepka, R. F. (Principal Investigator); Balon, R. J.; Cicone, R. C.

    1979-01-01

    The author has identified the following significant results. Analysis and comparison of image products generated by different algorithms show that the scaling and biasing of data channels for control of PFC primaries lead to loss of information (in a probability-of misclassification sense) by two major processes. In order of importance they are: neglecting the input of one channel of data in any one image, and failing to provide sufficient color resolution of the data. The scaling and biasing approach tends to distort distance relationships in data space and provides less than desirable resolution when the data variation is typical of a developed, nonhazy agricultural scene.

  20. Topology of digital images visual pattern discovery in proximity spaces

    Peters, James F

    2014-01-01

    This book carries forward recent work on visual patterns and structures in digital images and introduces a near set-based a topology of digital images. Visual patterns arise naturally in digital images viewed as sets of non-abstract points endowed with some form of proximity (nearness) relation. Proximity relations make it possible to construct uniform topolo- gies on the sets of points that constitute a digital image. In keeping with an interest in gaining an understanding of digital images themselves as a rich source of patterns, this book introduces the basics of digital images from a computer vision perspective. In parallel with a computer vision perspective on digital images, this book also introduces the basics of prox- imity spaces. Not only the traditional view of spatial proximity relations but also the more recent descriptive proximity relations are considered. The beauty of the descriptive proximity approach is that it is possible to discover visual set patterns among sets that are non-overlapping ...

  1. Space Radar Image of Manaus region of Brazil

    1994-01-01

    These L-band images of the Manaus region of Brazil were acquired by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle Endeavour. The left image was acquired on April 12, 1994, and the middle image was acquired on October 3, 1994. The area shown is approximately 8 kilometers by 40 kilometers (5 miles by 25 miles). The two large rivers in this image, the Rio Negro (top) and the Rio Solimoes (bottom), combine at Manaus (west of the image) to form the Amazon River. The image is centered at about 3 degrees south latitude and 61 degrees west longitude. North is toward the top left of the images. The differences in brightness between the images reflect changes in the scattering of the radar channel. In this case, the changes are indicative of flooding. A flooded forest has a higher backscatter at L-band (horizontally transmitted and received) than an unflooded river. The extent of the flooding is much greater in the April image than in the October image, and corresponds to the annual, 10-meter (33-foot) rise and fall of the Amazon River. A third image at right shows the change in the April and October images and was created by determining which areas had significant decreases in the intensity of radar returns. These areas, which appear blue on the third image at right, show the dramatic decrease in the extent of flooded forest, as the level of the Amazon River falls. The flooded forest is a vital habitat for fish and floating meadows are an important source of atmospheric methane. This demonstrates the capability of SIR-C/X-SAR to study important environmental changes that are impossible to see with optical sensors over regions such as the Amazon, where frequent cloud cover and dense forest canopies obscure monitoring of floods. Field studies by boat, on foot and in low-flying aircraft by the University of California at Santa Barbara, in collaboration with Brazil's Instituto Nacional de Pesguisas Estaciais, during

  2. Restoration of retinal images with space-variant blur

    Marrugo, A.; Millán, M. S.; Šorel, Michal; Šroubek, Filip

    2014-01-01

    Roč. 19, č. 1 (2014), 016023-1-016023-12 ISSN 1083-3668 R&D Projects: GA ČR GA13-29225S Institutional support: RVO:67985556 Keywords : blind deconvolution * space-variant restoration * retinal image Subject RIV: JD - Computer Applications, Robotics Impact factor: 2.859, year: 2014 http://library.utia.cas.cz/separaty/2014/ZOI/sorel-0424586.pdf

  3. Multiplexed phase-space imaging for 3D fluorescence microscopy.

    Liu, Hsiou-Yuan; Zhong, Jingshan; Waller, Laura

    2017-06-26

    Optical phase-space functions describe spatial and angular information simultaneously; examples of optical phase-space functions include light fields in ray optics and Wigner functions in wave optics. Measurement of phase-space enables digital refocusing, aberration removal and 3D reconstruction. High-resolution capture of 4D phase-space datasets is, however, challenging. Previous scanning approaches are slow, light inefficient and do not achieve diffraction-limited resolution. Here, we propose a multiplexed method that solves these problems. We use a spatial light modulator (SLM) in the pupil plane of a microscope in order to sequentially pattern multiplexed coded apertures while capturing images in real space. Then, we reconstruct the 3D fluorescence distribution of our sample by solving an inverse problem via regularized least squares with a proximal accelerated gradient descent solver. We experimentally reconstruct a 101 Megavoxel 3D volume (1010×510×500µm with NA 0.4), demonstrating improved acquisition time, light throughput and resolution compared to scanning aperture methods. Our flexible patterning scheme further allows sparsity in the sample to be exploited for reduced data capture.

  4. Image reconstruction in k-space from MR data encoded with ambiguous gradient fields.

    Schultz, Gerrit; Gallichan, Daniel; Weber, Hans; Witschey, Walter R T; Honal, Matthias; Hennig, Jürgen; Zaitsev, Maxim

    2015-02-01

    In this work, the limits of image reconstruction in k-space are explored when non-bijective gradient fields are used for spatial encoding. The image space analogy between parallel imaging and imaging with non-bijective encoding fields is partially broken in k-space. As a consequence, it is hypothesized and proven that ambiguities can only be resolved partially in k-space, and not completely as is the case in image space. Image-space and k-space based reconstruction algorithms for multi-channel radiofrequency data acquisitions are programmed and tested using numerical simulations as well as in vivo measurement data. The hypothesis is verified based on an analysis of reconstructed images. It is found that non-bijective gradient fields have the effect that densely sampled autocalibration data, used for k-space reconstruction, provide less information than a separate scan of the receiver coil sensitivity maps, used for image space reconstruction. Consequently, in k-space only the undersampling artifact can be unfolded, whereas in image space, it is also possible to resolve aliasing that is caused by the non-bijectivity of the gradient fields. For standard imaging, reconstruction in image space and in k-space is nearly equivalent, whereas there is a fundamental difference with practical consequences for the selection of image reconstruction algorithms when non-bijective encoding fields are involved. © 2014 Wiley Periodicals, Inc.

  5. Owhership of flats

    Přibil, Jan

    2012-01-01

    Ownership of Flats Summary In his diploma thesis "Ownership of Flats", the author focuses on applicable law of flat ownership in the Czech Republic, especially the Flat Ownership Act 72/1994 Sb. The author puts the contemporary regulation in historical context; he describes the theoretical principles underlining the current applicable law and defines in detail the basic legal terms used by the Flat Ownership Act. Original and derivative forms of flat ownership acquisition are explained, namel...

  6. Design of a space-based infrared imaging interferometer

    Hart, Michael; Hope, Douglas; Romeo, Robert

    2017-07-01

    Present space-based optical imaging sensors are expensive. Launch costs are dictated by weight and size, and system design must take into account the low fault tolerance of a system that cannot be readily accessed once deployed. We describe the design and first prototype of the space-based infrared imaging interferometer (SIRII) that aims to mitigate several aspects of the cost challenge. SIRII is a six-element Fizeau interferometer intended to operate in the short-wave and midwave IR spectral regions over a 6×6 mrad field of view. The volume is smaller by a factor of three than a filled-aperture telescope with equivalent resolving power. The structure and primary optics are fabricated from light-weight space-qualified carbon fiber reinforced polymer; they are easy to replicate and inexpensive. The design is intended to permit one-time alignment during assembly, with no need for further adjustment once on orbit. A three-element prototype of the SIRII imager has been constructed with a unit telescope primary mirror diameter of 165 mm and edge-to-edge baseline of 540 mm. The optics, structure, and interferometric signal processing principles draw on experience developed in ground-based astronomical applications designed to yield the highest sensitivity and resolution with cost-effective optical solutions. The initial motivation for the development of SIRII was the long-term collection of technical intelligence from geosynchronous orbit, but the scalable nature of the design will likely make it suitable for a range of IR imaging scenarios.

  7. Comparison of dose and image quality of a Flat-panel detector and an image intensifier; Comparacao da dose e qualidade da imagem de um detector Flatpanel e um intensificador de imagem

    Lazzaro, M.; Friedrich, B.Q.; Luz, R.M. da; Silva, A.M.M. da, E-mail: marcos.lazzaro@acad.pucrs.br [Pontificia Universidade Catolica do Rio Grande do Sul (PUC-RS), Porto Alegre, RS (Brazil)

    2016-07-01

    With the development of new technologies, have emerged new conversion methods of X-ray image, such as flat panel detectors. The aim of this work is the comparison of entrance surface air kerma (ESAK) and image quality between an image intensifier type of detector (A) and a flat panel (B). The ESAK was obtained by placing a ionization chamber under PMMA simulators of 10, 20 and 30 cm and the image quality was obtained by using the TOR {sup 18}FG simulator. The ESAK to the equipment A is higher when compared to the equipment B. The high contrast resolution is better for the equipment A for all thicknesses of simulators. The equipment A has low contrast resolution with a better viewing threshold for thicknesses of 10 and 20 cm, and a worse performance for 30 cm. It is concluded that the equipment B has ESAK smaller and despite having lower resolution, in almost all cases, have appropriate image quality for diagnosis. (author)

  8. Usefulness of DICOM headers in the analysis of two biplane X-ray systems setting (image intensifier and flat panel) used in pediatric interventional cardiology in Chile

    Ubeda, C.; Vergara, F.

    2009-01-01

    The setting of two biplane X ray systems were evaluated (image intensifier (II) and flat panel (PP)), through DICOM tags from 32 images created during the characterization of both systems. The technical parameters adjusted for systems were: 63,8 to 80,0 kV and 15,0 to 388,0 mA, for the system with II and 52,0 to 77,0 kV and 25,0 to 476,0 mA, for the system with PP detector. Both equipment presented a different mA adjustment, when moving from fluoroscopy modes low dose (FL), medium dose (FM) and high dose (FH) to cine mode (CI). Two dosimetric quantities were evaluated, the first one was the dose-area product (DAP) which gave as a result for FB mode, between 0,03 to 0,35 uGycm 2 /image (II) and from 0,05 a 0,69 uGycm 2 /image (PP), when the polymethyl methacrylate (PMMA) thickness was incremented from 4 to 16 cm. In cine mode the DAP quantity showed, percentage values from 24 to -1 % for the same PMMA increment. Skin cumulative dose was the second quantity evaluated and showed an increment of incident air kerma (KAI)/image in factors from 17 to 35 (II) and 15 to 28 (PP) when used in CI mode instead of FB mode, to the different PMMA thicknesses used. This dose increment for CI mode must be considered by cardiologists, to use the fluoroscopic run as an alternative to document part of the procedures when there is no need to use a high quality image (author)

  9. Imaging analyses of odontogenic infection involving the maxillofacial fascial spaces, with special emphasis on the parapharyngeal space

    Ariji, Yoshiko; Gotoh, Masakazu; Izumi, Masahiro; Naitoh, Munetaka; Kurita, Kenichi; Natsume, Nagato; Ariji, Eiichiro [Aichi-Gakuin Univ., Nisshin (Japan). School of Dentistry

    2002-01-01

    The purpose of this study was to investigate odontogenic infection pathways into the maxillofacial fascial spaces, especially into the parapharyngeal space, in relation to causal tooth and clinical symptoms. CT and MR images were retrospectively investigated in 47 patients with spread of odontogenic infection into the maxillofacial spaces. The involvement of spaces was evaluated based on lateral asymmetry of their shapes and density on CT images or intensity on MR images. Involvement on images was observed in 70%, 49%, and 30% of the submandibular, the masticator, and the parapharyngeal spaces, respectively. Patients with submandibular space involvement often had spontaneous pain. Of 14 patients with parapharyngeal space involvement, 8 patients showed dysphagia and/or fever, and 13 patients showed involvement of the mandibular molar as a cause of infection. All of these 14 patients also had submandibular space involvement, while only 7 patients (50%) showed changes in the medial pterygoid muscle. The fat layer between the medial pterygoid muscle and parapharyngeal space was maintained in 11 of 14 (79%) patients with parapharyngeal involvement. CT and MR images clearly demonstrated the spread of odontogenic infection into the maxillofacial spaces. Involvement of the parapharyngeal space was mostly caused by infection originating in the mandibular molar, and was considered to be secondary spread from the submandibular space and/or medial pterygoid muscle. (author)

  10. Mapping from Speech to Images Using Continuous State Space Models

    Lehn-Schiøler, Tue; Hansen, Lars Kai; Larsen, Jan

    2005-01-01

    In this paper a system that transforms speech waveforms to animated faces are proposed. The system relies on continuous state space models to perform the mapping, this makes it possible to ensure video with no sudden jumps and allows continuous control of the parameters in 'face space...... a subjective point of view the model is able to construct an image sequence from an unknown noisy speech sequence even though the number of training examples are limited.......'. The performance of the system is critically dependent on the number of hidden variables, with too few variables the model cannot represent data, and with too many overfitting is noticed. Simulations are performed on recordings of 3-5 sec.\\$\\backslash\\$ video sequences with sentences from the Timit database. From...

  11. Flat-Panel Detector—Based Volume Computed Tomography: A Novel 3D Imaging Technique to Monitor Osteolytic Bone Lesions in a Mouse Tumor Metastasis Model

    Jeannine Missbach-Guentner

    2007-09-01

    Full Text Available Skeletal metastasis is an important cause of mortality in patients with breast cancer. Hence, animal models, in combination with various imaging techniques, are in high demand for preclinical assessment of novel therapies. We evaluated the applicability of flat-panel volume computed tomography (fpVCT to noninvasive detection of osteolytic bone metastases that develop in severe immunodeficient mice after intracardial injection of MDA-MB-231 breast cancer cells. A single fpVCT scan at 200-wm isotropic resolution was employed to detect osteolysis within the entire skeleton. Osteolytic lesions identified by fpVCT correlated with Faxitron X-ray analysis and were subsequently confirmed by histopathological examination. Isotropic three-dimensional image data sets obtained by fpVCT were the basis for the precise visualization of the extent of the lesion within the cortical bone and for the measurement of bone loss. Furthermore, fpVCT imaging allows continuous monitoring of growth kinetics for each metastatic site and visualization of lesions in more complex regions of the skeleton, such as the skull. Our findings suggest that fpVCT is a powerful tool that can be used to monitor the occurrence and progression of osteolytic lesions in vivo and can be further developed to monitor responses to antimetastatic therapies over the course of the disease.

  12. Complex Pupil Masks for Aberrated Imaging of Closely Spaced Objects

    Reddy, A. N. K.; Sagar, D. K.; Khonina, S. N.

    2017-12-01

    Current approach demonstrates the suppression of optical side-lobes and the contraction of the main lobe in the composite image of two object points of the optical system under the influence of defocusing effect when an asymmetric phase edges are imposed over the apodized circular aperture. The resolution of two point sources having different intensity ratio is discussed in terms of the modified Sparrow criterion, functions of the degree of coherence of the illumination, the intensity difference and the degree of asymmetric phase masking. Here we have introduced and explored the effects of focus aberration (defect-of-focus) on the two-point resolution of the optical systems. Results on the aberrated composite image of closely spaced objects with amplitude mask and asymmetric phase masks forms a significant contribution in astronomical and microscopic observations.

  13. Evaluation of an Experimental Model for Flat-Fan Nozzles Drift in Wind Tunnel by Image Processing

    S.H Fattahi

    2014-09-01

    Full Text Available Each year, millions of liters of toxic liquid, are used to combat with pests and plant diseases in farms. The wide spread use of chemical pesticides causes great environmental hazards. Particles drift is one of the main problems in spraying which results in the contamination of farm lands, humans and animals. Management of particle size is regarded as the main factor in drift control. In this study, the effect of some parameters on the size of deposited particles on non-target areas was studied using statistical method. The effects of nozzle type (orifice size, spraying pressure, spraying boom height and wind speed as effective factors on drift were examined. A horizontal wind tunnel with working section of 0.47 m wide, 0.75 m height and 5.5 m long was used for testing. Experiment was performed in the form of factorial split-plot based on randomized complete block design with two replications. Droplets were measured in the treatment combinations of the type of flat-fan nozzle with three orifice area (11003- 0.87 mm2, 11004-1.18 mm2 and 11006- 1.8 mm2, spraying pressure (150, 275 and 400 kpa, wind speed (1, 2 and 3 m s-1 and the boom height of (0.35, 0.55 and 0.75 m. Water-sensitive papers were used at intervals of 0.8, 1.6 and 2.4 m from the tip of nozzles for detecting droplets size. The factors of pressure, speed and height had positive effects on the droplet size at the desired distance, but the effect of nozzle size on droplet size was negative. In the regression model the coefficients of speed was higher than the others.

  14. Ricci-flat branes

    Brecher, D.; Perry, M.J.

    2000-01-01

    Up to overall harmonic factors, the D8-brane solution of the massive type IIA supergravity theory is the product of nine-dimensional Minkowski space (the world-volume) with the real line (the transverse space). We show that the equations of motion allow for the world-volume metric to be generalised to an arbitrary Ricci-flat one. If this nine-dimensional Ricci-flat manifold admits Killing spinors, then the resulting solutions are supersymmetric and satisfy the usual Bogomol'nyi bound, although they preserve fewer than the usual one half of the supersymmetries. We describe the possible choices of such manifolds, elaborating on the connection between the existence of Killing spinors and the self-duality condition on the curvature two-form. Since the D8-brane is a domain wall in ten dimensions, we are led to consider the general case: domain walls in any supergravity theory. Similar considerations hold here also. Moreover, it is shown that the world-volume of any magnetic brane - of which the domain walls are a specific example - can be generalised in precisely the same way. The general class of supersymmetric solutions have gravitational instantons as their spatial sections. Some mention is made of the world-volume solitons of such branes

  15. Application of ultrasound processed images in space: assessing diffuse affectations

    Pérez-Poch, A.; Bru, C.; Nicolau, C.

    The purpose of this study was to evaluate diffuse affectations in the liver using texture image processing techniques. Ultrasound diagnose equipments are the election of choice to be used in space environments as they are free from hazardous effects on health. However, due to the need for highly trained radiologists to assess the images, this imaging method is mainly applied on focal lesions rather than on non-focal ones. We have conducted a clinical study on 72 patients with different degrees of chronic hepatopaties and a group of control of 18 individuals. All subjects' clinical reports and results of biopsies were compared to the degree of affectation calculated by our computer system , thus validating the method. Full statistical results are given in the present paper showing a good correlation (r=0.61) between pathologist's report and analysis of the heterogenicity of the processed images from the liver. This computer system to analyze diffuse affectations may be used in-situ or via telemedicine to the ground.

  16. Astronomers Make First Images With Space Radio Telescope

    1997-07-01

    Marking an important new milestone in radio astronomy history, scientists at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, have made the first images using a radio telescope antenna in space. The images, more than a million times more detailed than those produced by the human eye, used the new Japanese HALCA satellite, working in conjunction with the National Science Foundation's (NSF) Very Long Baseline Array (VLBA) and Very Large Array (VLA) ground-based radio telescopes. The landmark images are the result of a long-term NRAO effort supported by the National Aeronautics and Space Administration (NASA). "This success means that our ability to make detailed radio images of objects in the universe is no longer limited by the size of the Earth," said NRAO Director Paul Vanden Bout. "Astronomy's vision has just become much sharper." HALCA, launched on Feb. 11 by Japan's Institute of Space and Astronautical Science (ISAS), is the first satellite designed for radio astronomy imaging. It is part of an international collaboration led by ISAS and backed by NRAO; Japan's National Astronomical Observatory; NASA's Jet Propulsion Laboratory (JPL); the Canadian Space Agency; the Australia Telescope National Facility; the European VLBI Network and the Joint Institute for Very Long Baseline Interferometry in Europe. On May 22, HALCA observed a distant active galaxy called PKS 1519-273, while the VLBA and VLA also observed it. Data from the satellite was received by a tracking station at the NRAO facility in Green Bank, West Virginia. Tape-recorded data from the satellite and from the radio telescopes on the ground were sent to NRAO's Array Operations Center (AOC) in Socorro, NM. In Socorro, astronomers and computer scientists used a special-purpose computer to digitally combine the signals from the satellite and the ground telescopes to make them all work together as a single, giant radio telescope. This dedicated machine, the VLBA Correlator, built as

  17. Imaging responses of on-site CsI and Gd2O2S flat-panel detectors: Dependence on the tube voltage

    Jeon, Hosang; Chung, Myung Jin; Youn, Seungman; Nam, Jiho; Lee, Jayoung; Park, Dahl; Kim, Wontaek; Ki, Yongkan; Kim, Ho Kyung

    2015-07-01

    One of the emerging issues in radiography is low-dose imaging to minimize patient's exposure. The scintillating materials employed in most indirect flat-panel detectors show a drastic change of X-ray photon absorption efficiency around their K-edge energies that consequently affects image quality. Using various tube voltages, we investigated the imaging performance of most popular scintillators: cesium iodide (CsI) and gadolinium oxysulfide (Gd2O2S). The integrated detective quantum efficiencies (iDQE) of four detectors installed in the same hospital were evaluated according to the standardized procedure IEC 62220-1 at tube voltages of 40 - 120 kVp. The iDQE values of the Gd2O2S detectors were normalized by those of CsI detectors to exclude the effects of image postprocessing. The contrast-to-noise ratios (CNR) were also evaluated by using an anthropomorphic chest phantom. The iDQE of the CsI detector outperformed that of the Gd2O2S detector over all tube voltages. Moreover, we noted that the iDQE of the Gd2O2S detectors quickly rolled off with decreasing tube voltage under 70 kVp. The CNRs of the two scintillators were similar at 120 kVp. At 60 kVp, however, the CNR of Gd2O2S was about half that of CsI. Compared to the Gd2O2S detectors, variations in the DQE performance of the CsI detectors were relatively immune to variations in the applied tube voltages. Therefore, we claim that Gd2O2S detectors are inappropriate for use in low-tube-voltage imaging (e.g., extremities and pediatrics) with low patient exposure.

  18. Binary-space-partitioned images for resolving image-based visibility.

    Fu, Chi-Wing; Wong, Tien-Tsin; Tong, Wai-Shun; Tang, Chi-Keung; Hanson, Andrew J

    2004-01-01

    We propose a novel 2D representation for 3D visibility sorting, the Binary-Space-Partitioned Image (BSPI), to accelerate real-time image-based rendering. BSPI is an efficient 2D realization of a 3D BSP tree, which is commonly used in computer graphics for time-critical visibility sorting. Since the overall structure of a BSP tree is encoded in a BSPI, traversing a BSPI is comparable to traversing the corresponding BSP tree. BSPI performs visibility sorting efficiently and accurately in the 2D image space by warping the reference image triangle-by-triangle instead of pixel-by-pixel. Multiple BSPIs can be combined to solve "disocclusion," when an occluded portion of the scene becomes visible at a novel viewpoint. Our method is highly automatic, including a tensor voting preprocessing step that generates candidate image partition lines for BSPIs, filters the noisy input data by rejecting outliers, and interpolates missing information. Our system has been applied to a variety of real data, including stereo, motion, and range images.

  19. Evaluation of automatic dose rate control for flat panel imaging using a spatial frequency domain figure of merit

    Dehairs, M.; Bosmans, H.; Desmet, W.; Marshall, N. W.

    2017-08-01

    Current automatic dose rate controls (ADRCs) of dynamic x-ray imaging systems adjust their acquisition parameters in response to changes in patient thickness in order to achieve a constant signal level in the image receptor. This work compares a 3 parameter (3P) ADRC control to a more flexible 5-parameter (5P) method to meet this goal. A phantom composed of 15 composite poly(methyl) methacrylate (PMMA)/aluminium (Al) plates was imaged on a Siemens Artis Q dynamic system using standard 3P and 5P ADRC techniques. Phantom thickness covered a water equivalent thickness (WET) range of 2.5 cm to 37.5 cm. Acquisition parameter settings (tube potential, tube current, pulse length, copper filtration and focus size) and phantom entrance air kerma rate (EAKR) were recorded as the thickness changed. Signal difference to noise ratio (SDNR) was measured using a 0.3 mm iron insert centred in the PMMA stack, positioned at the system isocentre. SDNR was then multiplied by modulation transfer function (MTF) based correction factors for focal spot penumbral blurring and motion blurring, to give a spatial frequency dependent parameter, SDNR(u). These MTF correction factors were evaluated for an object motion of 25 mm s-1 and at a spatial frequency of 1.4 mm-1 in the object plane, typical for cardiac imaging. The figure of merit (FOM) was calculated as SDNR(u)²/EAKR for the two ADRC regimes. Using 5P versus 3P technique showed clear improvements over all thicknesses. Averaged over clinically relevant adult WET values (20 cm-37.5 cm), EAKR was reduced by 13% and 27% for fluoroscopy and acquisition modes, respectively, while the SDNR(u) based FOM increased by 16% and 34% for fluoroscopy and acquisition. In conclusion, the generalized FOM, taking into account the influence of focus size and object motion, showed benefit in terms of image quality and patient dose for the 5-parameter control over 3-parameter method for the ADRC programming of dynamic x-ray imaging systems.

  20. High resolution X-ray imaging of bone-implant interface by large area flat-panel detector

    Kytýř, Daniel; Jiroušek, Ondřej; Dammer, J.

    2011-01-01

    Roč. 6, č. 1 (2011), s. 1038-1043 ISSN 1748-0221 R&D Projects: GA ČR(CZ) GAP105/10/2305 Institutional research plan: CEZ:AV0Z20710524 Keywords : computed radiography * computerized tomography * medical-image reconstruction Subject RIV: JJ - Other Materials Impact factor: 1.869, year: 2011 http://iopscience.iop.org/1748-0221/6/01/C01038

  1. Performance of a static-anode/flat-panel x-ray fluoroscopy system in a diagnostic strength magnetic field: a truly hybrid x-ray/MR imaging system.

    Fahrig, R; Wen, Z; Ganguly, A; DeCrescenzo, G; Rowlands, J A; Stevens, G M; Saunders, R F; Pelc, N J

    2005-06-01

    Minimally invasive procedures are increasing in variety and frequency, facilitated by advances in imaging technology. Our hybrid imaging system (GE Apollo flat panel, custom Brand x-ray static anode x-ray tube, GE Lunar high-frequency power supply and 0.5 T Signa SP) provides both x-ray and MR imaging capability to guide complex procedures without requiring motion of the patient between two distant gantries. The performance of the x-ray tube in this closely integrated system was evaluated by modeling and measuring both the response of the filament to an externally applied field and the behavior of the electron beam for field strengths and geometries of interest. The performance of the detector was assessed by measuring the slanted-edge modulation transfer function (MTF) and when placed at zero field and at 0.5 T. Measured resonant frequencies of filaments can be approximated using a modified vibrating beam model, and were at frequencies well below the 25 kHz frequency of our generator for our filament geometry. The amplitude of vibration was not sufficient to cause shorting of the filament during operation within the magnetic field. A simple model of electrons in uniform electric and magnetic fields can be used to estimate the deflection of the electron beam on the anode for the fields of interest between 0.2 and 0.5 T. The MTF measured at the detector and the DQE showed no significant difference inside and outside of the magnetic field. With the proper modifications, an x-ray system can be fully integrated with a MR system, with minimal loss of image quality. Any x-ray tube can be assessed for compatibility when placed at a particular location within the field using the models. We have also concluded that a-Si electronics are robust against magnetic fields. Detailed knowledge of the x-ray system installation is required to provide estimates of system operation.

  2. Performance of a static-anode/flat-panel x-ray fluoroscopy system in a diagnostic strength magnetic field: A truly hybrid x-ray/MR imaging system

    Fahrig, R.; Wen, Z.; Ganguly, A.; DeCrescenzo, G.; Rowlands, J.A.; Stevens, G.M.; Saunders, R.F.; Pelc, N.J.

    2005-01-01

    Minimally invasive procedures are increasing in variety and frequency, facilitated by advances in imaging technology. Our hybrid imaging system (GE Apollo TM flat panel, custom Brand x-ray static anode x-ray tube, GE Lunar high-frequency power supply and 0.5 T Signa SP TM ) provides both x-ray and MR imaging capability to guide complex procedures without requiring motion of the patient between two distant gantries. The performance of the x-ray tube in this closely integrated system was evaluated by modeling and measuring both the response of the filament to an externally applied field and the behavior of the electron beam for field strengths and geometries of interest. The performance of the detector was assessed by measuring the slanted-edge modulation transfer function (MTF) and when placed at zero field and at 0.5 T. Measured resonant frequencies of filaments can be approximated using a modified vibrating beam model, and were at frequencies well below the 25 kHz frequency of our generator for our filament geometry. The amplitude of vibration was not sufficient to cause shorting of the filament during operation within the magnetic field. A simple model of electrons in uniform electric and magnetic fields can be used to estimate the deflection of the electron beam on the anode for the fields of interest between 0.2 and 0.5 T. The MTF measured at the detector and the DQE showed no significant difference inside and outside of the magnetic field. With the proper modifications, an x-ray system can be fully integrated with a MR system, with minimal loss of image quality. Any x-ray tube can be assessed for compatibility when placed at a particular location within the field using the models. We have also concluded that a-Si electronics are robust against magnetic fields. Detailed knowledge of the x-ray system installation is required to provide estimates of system operation

  3. Update on the Status of the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope

    Hernandez, Svea; Aloisi, A.; Bostroem, K. A.; Cox, C.; Debes, J. H.; DiFelice, A.; Roman-Duval, J.; Hodge, P.; Holland, S.; Lindsay, K.; Lockwood, S. A.; Mason, E.; Oliveira, C. M.; Penton, S. V.; Proffitt, C. R.; Sonnentrucker, P.; Taylor, J. M.; Wheeler, T.

    2013-06-01

    The Space Telescope Imaging Spectrograph (STIS) has been on orbit for approximately 16 years as one of the 2nd generation instruments on the Hubble Space Telescope (HST). Its operations were interrupted by an electronics failure in 2004, but STIS was successfully repaired in May 2009 during Service Mission 4 (SM4) allowing it to resume science observations. The Instrument team continues to monitor its performance and work towards improving the quality of its products. Here we present updated information on the status of the FUV and NUV MAMA and the CCD detectors onboard STIS and describe recent changes to the STIS calibration pipeline. We also discuss the status of efforts to apply a pixel-based correction for charge transfer inefficiency (CTI) effects to STIS CCD data. These techniques show promise for ameliorating the effects of ongoing radiation damage on the quality of STIS CCD data.

  4. q-Space imaging using small magnetic field gradient

    Umezawa, Eizou; Yamaguchi, Kojiro; Yoshikawa, Mayo; Ueoku, Sachiko; Tanaka, Eiji

    2006-01-01

    q-space diffusion analysis is a method to obtain the probability density function of the translational displacement of diffusing water molecules. Several quantities can be extracted from the function that indicate a characteristic of the water diffusion in tissue, e.g., the mean displacement of the diffusion, probability for zero displacement, and kurtosis of the function. These quantities are expected to give information about the microstructure of tissues in addition to that obtained from the apparent diffusion coefficient (ADC); however, this method requires high q (i.e., high b) values, which are undesirable in practical applications of the method using clinical magnetic resonance (MR) imaging equipment. We propose a method to obtain certain quantities that indicate a characteristic of the diffusion and that uses low q-value measurements. The quantities we can obtain are the moments of translational displacement, R; the n-th order moment is defined as the average of R n (n: integer). Kurtosis can also be calculated from the second and fourth moments. We tried to map the moments and kurtosis using clinical MR imaging equipment. We also estimated the inherent errors of the moments obtained. Our method requires precision in measuring spin echo signals and setting q values rather than using high q-value measurements. Although our results show that further error reductions are desired, our method is workable using ordinary clinical MR imaging equipment. (author)

  5. Self-calibrated correlation imaging with k-space variant correlation functions.

    Li, Yu; Edalati, Masoud; Du, Xingfu; Wang, Hui; Cao, Jie J

    2018-03-01

    Correlation imaging is a previously developed high-speed MRI framework that converts parallel imaging reconstruction into the estimate of correlation functions. The presented work aims to demonstrate this framework can provide a speed gain over parallel imaging by estimating k-space variant correlation functions. Because of Fourier encoding with gradients, outer k-space data contain higher spatial-frequency image components arising primarily from tissue boundaries. As a result of tissue-boundary sparsity in the human anatomy, neighboring k-space data correlation varies from the central to the outer k-space. By estimating k-space variant correlation functions with an iterative self-calibration method, correlation imaging can benefit from neighboring k-space data correlation associated with both coil sensitivity encoding and tissue-boundary sparsity, thereby providing a speed gain over parallel imaging that relies only on coil sensitivity encoding. This new approach is investigated in brain imaging and free-breathing neonatal cardiac imaging. Correlation imaging performs better than existing parallel imaging techniques in simulated brain imaging acceleration experiments. The higher speed enables real-time data acquisition for neonatal cardiac imaging in which physiological motion is fast and non-periodic. With k-space variant correlation functions, correlation imaging gives a higher speed than parallel imaging and offers the potential to image physiological motion in real-time. Magn Reson Med 79:1483-1494, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  6. The x-ray time of flight method for investigation of ghosting in amorphous selenium-based flat panel medical x-ray imagers

    Rau, A.W.; Bakueva, L.; Rowlands, J.A.

    2005-01-01

    Amorphous selenium (a-Se) based real-time flat-panel imagers (FPIs) are finding their way into the digital radiology department because they offer the practical advantages of digital x-ray imaging combined with an image quality that equals or outperforms that of conventional systems. The temporal imaging characteristics of FPIs can be affected by ghosting (i.e., radiation-induced changes of sensitivity) when the dose to the detector is high (e.g., portal imaging and mammography) or the images are acquired at a high frame rate (e.g., fluoroscopy). In this paper, the x-ray time-of-flight (TOF) method is introduced as a tool for the investigation of ghosting in a-Se photoconductor layers. The method consists of irradiating layers of a-Se with short x-ray pulses. From the current generated in the a-Se layer, ghosting is quantified and the ghosting parameters (charge carrier generation rate and carrier lifetimes and mobilities) are assessed. The x-ray TOF method is novel in that (1) x-ray sensitivity (S) and ghosting parameters can be measured simultaneously (2) the transport of both holes and electrons can be isolated, and (3) the method is applicable to the practical a-Se layer structure with blocking contacts used in FPIs. The x-ray TOF method was applied to an analysis of ghosting in a-Se photoconductor layers under portal imaging conditions, i.e., 1 mm thick a-Se layers, biased at 5 V/μm, were irradiated using a 6 MV LINAC x-ray beam to a total dose (ghosting dose) of 30 Gy. The initial sensitivity (S 0 ) of the a-Se layers was 63±2 nC cm -2 cGy -1 . It was found that S decreases to 30% of S 0 after a ghosting dose of 5 Gy and to 21% after 30 Gy at which point no further change in S occurs. At an x-ray intensity of 22 Gy/s (instantaneous dose rate during a LINAC x-ray pulse), the charge carrier generation rate was 1.25±0.1x10 22 ehp m -3 s -1 and, to a first approximation, independent of the ghosting dose. However, both hole and electron transport showed a

  7. Batman flies: a compact spectro-imager for space observation

    Zamkotsian, Frederic; Ilbert, Olivier; Zoubian, Julien; Delsanti, Audrey; Boissier, Samuel; Lancon, Ariane

    2017-11-01

    from the sky background is blocked. To get more than 2 millions independent micromirrors, the only available component is a Digital Micromirror Device (DMD) chip from Texas Instruments (TI) that features 2048 x 1080 mirrors and a 13.68μm pixel pitch. DMDs have been tested in space environment (-40°C, vacuum, radiations) by LAM and no showstopper has been revealed [7]. We are presenting in this paper a DMD-based spectrograph called BATMAN, including two arms, one spectroscopic channel and one imaging channel. This instrument is designed for getting breakthrough results in several science cases, from high-z galaxies to nearby galaxies and Trans-Neptunian Objects of Kuiper Belt.

  8. Assessment of flatness and symmetry of megavoltage x-ray beam with an electronic portal imaging device

    Liu, G; Bezak, E

    2002-01-01

    The input/output characteristics of the Wellhofer BIS 710 electronic portal imaging device (EPID) have been investigated to establish its efficacy for periodic quality assurance (QA) applications. Calibration curves have been determined for the energy fluence incident on the detector versus the pixel values. The effect of the charge coupled device (CCD) camera sampling time and beam parameters (such as beam field size, dose rate, photon energy) on the calibration have been investigated for a region of interest (ROI) around the central beam axis. The results demonstrate that the pixel output is a linear function of the incident exposure, as expected for a video-based electronic portal imaging system. The field size effects of the BIS 710 are similar to that of an ion chamber for smaller field sizes up to 10 x 10 cm sup 2. However, for larger field sizes the pixel value increases more rapidly. Furthermore, the system is slightly sensitive to dose rate and is also energy dependent. The BIS 710 has been used in t...

  9. A three-dimensional radiation image display on a real space image created via photogrammetry

    Sato, Y.; Ozawa, S.; Tanifuji, Y.; Torii, T.

    2018-03-01

    The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown after the occurrence of a large tsunami caused by the Great East Japan Earthquake of March 11, 2011. The radiation distribution measurements inside the FDNPS buildings are indispensable to execute decommissioning tasks in the reactor buildings. We have developed a three-dimensional (3D) image reconstruction method for radioactive substances using a compact Compton camera. Moreover, we succeeded in visually recognizing the position of radioactive substances in real space by the integration of 3D radiation images and the 3D photo-model created using photogrammetry.

  10. Pixel detectors for x-ray imaging spectroscopy in space

    Treis, J; Andritschke, R; Hartmann, R; Herrmann, S; Holl, P; Lauf, T; Lechner, P; Lutz, G; Meidinger, N; Porro, M; Richter, R H; Schopper, F; Soltau, H; Strueder, L

    2009-01-01

    Pixelated semiconductor detectors for X-ray imaging spectroscopy are foreseen as key components of the payload of various future space missions exploring the x-ray sky. Located on the platform of the new Spectrum-Roentgen-Gamma satellite, the eROSITA (extended Roentgen Survey with an Imaging Telescope Array) instrument will perform an imaging all-sky survey up to an X-ray energy of 10 keV with unprecedented spectral and angular resolution. The instrument will consist of seven parallel oriented mirror modules each having its own pnCCD camera in the focus. The satellite born X-ray observatory SIMBOL-X will be the first mission to use formation-flying techniques to implement an X-ray telescope with an unprecedented focal length of around 20 m. The detector instrumentation consists of separate high- and low energy detectors, a monolithic 128 x 128 DEPFET macropixel array and a pixellated CdZTe detector respectively, making energy band between 0.5 to 80 keV accessible. A similar concept is proposed for the next generation X-ray observatory IXO. Finally, the MIXS (Mercury Imaging X-ray Spectrometer) instrument on the European Mercury exploration mission BepiColombo will use DEPFET macropixel arrays together with a small X-ray telescope to perform a spatially resolved planetary XRF analysis of Mercury's crust. Here, the mission concepts and their scientific targets are briefly discussed, and the resulting requirements on the detector devices together with the implementation strategies are shown.

  11. Pixel detectors for x-ray imaging spectroscopy in space

    Treis, J.; Andritschke, R.; Hartmann, R.; Herrmann, S.; Holl, P.; Lauf, T.; Lechner, P.; Lutz, G.; Meidinger, N.; Porro, M.; Richter, R. H.; Schopper, F.; Soltau, H.; Strüder, L.

    2009-03-01

    Pixelated semiconductor detectors for X-ray imaging spectroscopy are foreseen as key components of the payload of various future space missions exploring the x-ray sky. Located on the platform of the new Spectrum-Roentgen-Gamma satellite, the eROSITA (extended Roentgen Survey with an Imaging Telescope Array) instrument will perform an imaging all-sky survey up to an X-ray energy of 10 keV with unprecedented spectral and angular resolution. The instrument will consist of seven parallel oriented mirror modules each having its own pnCCD camera in the focus. The satellite born X-ray observatory SIMBOL-X will be the first mission to use formation-flying techniques to implement an X-ray telescope with an unprecedented focal length of around 20 m. The detector instrumentation consists of separate high- and low energy detectors, a monolithic 128 × 128 DEPFET macropixel array and a pixellated CdZTe detector respectively, making energy band between 0.5 to 80 keV accessible. A similar concept is proposed for the next generation X-ray observatory IXO. Finally, the MIXS (Mercury Imaging X-ray Spectrometer) instrument on the European Mercury exploration mission BepiColombo will use DEPFET macropixel arrays together with a small X-ray telescope to perform a spatially resolved planetary XRF analysis of Mercury's crust. Here, the mission concepts and their scientific targets are briefly discussed, and the resulting requirements on the detector devices together with the implementation strategies are shown.

  12. Pixel detectors for x-ray imaging spectroscopy in space

    Treis, J; Andritschke, R; Hartmann, R; Herrmann, S; Holl, P; Lauf, T; Lechner, P; Lutz, G; Meidinger, N; Porro, M; Richter, R H; Schopper, F; Soltau, H; Strueder, L [MPI Semiconductor Laboratory, Otto-Hahn-Ring 6, D-81739 Munich (Germany)], E-mail: jft@hll.mpg.de

    2009-03-15

    Pixelated semiconductor detectors for X-ray imaging spectroscopy are foreseen as key components of the payload of various future space missions exploring the x-ray sky. Located on the platform of the new Spectrum-Roentgen-Gamma satellite, the eROSITA (extended Roentgen Survey with an Imaging Telescope Array) instrument will perform an imaging all-sky survey up to an X-ray energy of 10 keV with unprecedented spectral and angular resolution. The instrument will consist of seven parallel oriented mirror modules each having its own pnCCD camera in the focus. The satellite born X-ray observatory SIMBOL-X will be the first mission to use formation-flying techniques to implement an X-ray telescope with an unprecedented focal length of around 20 m. The detector instrumentation consists of separate high- and low energy detectors, a monolithic 128 x 128 DEPFET macropixel array and a pixellated CdZTe detector respectively, making energy band between 0.5 to 80 keV accessible. A similar concept is proposed for the next generation X-ray observatory IXO. Finally, the MIXS (Mercury Imaging X-ray Spectrometer) instrument on the European Mercury exploration mission BepiColombo will use DEPFET macropixel arrays together with a small X-ray telescope to perform a spatially resolved planetary XRF analysis of Mercury's crust. Here, the mission concepts and their scientific targets are briefly discussed, and the resulting requirements on the detector devices together with the implementation strategies are shown.

  13. Hubble Space Telescope Image, Supernova Remnant Cassiopeia A

    2000-01-01

    The colorful streamers that float across the sky in this photo taken by NASA's Hubble Space Telescope (HST) were created by the universe's biggest firecracker, the titanic supernova explosion of a massive star. The light from the exploding star reached Earth 320 years ago, nearly a century before the United States celebrated its birth with a bang. The dead star's shredded remains are called Cassiopeia A, or 'Cas A' for short. Cas A is the youngest known supernova remnant in our Milky Way Galaxy and resides 10,000 light-years away in the constellation Cassiopeia, so the star actually blew up 10,000 years before the light reached Earth in the late 1600s. This HST image of Cas A shows for the first time that the debris is arranged into thousands of small, cooling knots of gas. This material eventually will be recycled into building new generations of stars and planets. Our own Sun and planets are constructed from the debris of supernovae that exploded billions of years ago. This photo shows the upper rim of the super nova remnant's expanding shell. Near the top of the image are dozens of tiny clumps of matter. Each small clump, originally just a small fragment of the star, is tens of times larger than the diameter of our solar system. The colors highlight parts of the debris where chemical elements are glowing. The dark blue fragments, for example, are richest in oxygen; the red material is rich in sulfur. The images were taken with the Wide Field and Planetary Camera 2 in January 2000 and January 2002. Image Credit: NASA and HST team (Stoics/AURA). Acknowledgment: R. Fesen (Darmouth) and J. Morse ( Univ. of Colorado).

  14. Flat plate collector. Solarflachkollektor

    Raab, N

    1979-03-29

    The invention refers to a flat solar collector with an absorber plate, which is arranged on a support and is covered by a transparent window, between which and the plate there is an air space. The previously known structures of this type had the disadvantage that the thermal expansion of the enclosed air caused considerable difficulties. The purpose of the invention is therefore to create a collector, which can be used on the modular system, retains its properties and is safe in spite of the great temperature variations. According to the invention this problem is solved by providing a compensating space in the collector, which is separated by a diaphragm from the airspace between the plate and the covering window. The airspace therefore remains sealed against the atmosphere, so that no dirt, corrosion of the inside and no condensation can reduce the efficiency of the collector. A rise in pressure due to an increase in temperature is immediately reduced by expansion of the diaphragm, which enters the compensation space. In order to increase the pressure in the airspace above the plate for increases in temperature, the compensation space is connected to the atmosphere. The diaphragm can be mirrored on the side towards the absorber, which makes the diaphragm into an insulating element, as it reflects radiated heat from the absorber.

  15. Predictors of underestimation of malignancy after image-guided core needle biopsy diagnosis of flat epithelial atypia or atypical ductal hyperplasia.

    Yu, Chi-Chang; Ueng, Shir-Hwa; Cheung, Yun-Chung; Shen, Shih-Che; Kuo, Wen-Lin; Tsai, Hsiu-Pei; Lo, Yung-Feng; Chen, Shin-Cheh

    2015-01-01

    Flat epithelial atypia (FEA) and atypical ductal hyperplasia (ADH) are precursors of breast malignancy. Management of FEA or ADH after image-guided core needle biopsy (CNB) remains controversial. The aim of this study was to evaluate malignancy underestimation rates after FEA or ADH diagnosis using image-guided CNB and to identify clinical characteristics and imaging features associated with malignancy as well as identify cases with low underestimation rates that may be treatable by observation only. We retrospectively reviewed 2,875 consecutive image-guided CNBs recorded in an electronic data base from January 2010 to December 2011 and identified 128 (4.5%) FEA and 83 (2.9%) ADH diagnoses (211 total cases). Of these, 64 (30.3%) were echo-guided CNB procedures and 147 (69.7%) mammography-guided CNBs. Twenty patients (9.5%) were upgraded to malignancy. Multivariate analysis indicated that age (OR = 1.123, p = 0.002, increase of 1 year), mass-type lesion with calcifications (OR = 8.213, p = 0.006), and ADH in CNB specimens (OR = 8.071, p = 0.003) were independent predictors of underestimation. In univariate analysis of echo-guided CNB (n = 64), mass with calcifications had the highest underestimation rate (p < 0.001). Multivariate analysis of 147 mammography-guided CNBs revealed that age (OR = 1.122, p = 0.040, increase of 1 year) and calcification distribution were significant independent predictors of underestimation. No FEA case in which, complete calcification retrieval was recorded after CNB was upgraded to malignancy. Older age at diagnosis on image-guided CNB was a predictor of malignancy underestimation. Mass with calcifications was more likely to be associated with malignancy, and in cases presenting as calcifications only, segmental distribution or linear shapes were significantly associated with upgrading. Excision after FEA or ADH diagnosis by image-guided CNB is warranted except for FEA diagnosed using mammography-guided CNB with complete calcification

  16. Efficient and compact hyperspectral imager for space-borne applications

    Pisani, Marco; Zucco, Massimo

    2017-11-01

    In the last decades Hyperspectral Imager (HI) have become irreplaceable space-borne instruments for an increasing number of applications. A number of HIs are now operative onboard (e.g. CHRIS on PROBA), others are going to be launched (e.g. PRISMA, EnMAP, HyspIRI), many others are at the breadboard level. The researchers goal is to realize HI with high spatial and spectral resolution, having low weight and contained dimensions. The most common HI technique is based on the use of a dispersive mean (a grating or a prism) or on the use of band pass filters (tunable or linear variable). These approaches have the advantages of allowing compact devices. Another approach is based on the use of interferometer based spectrometers (Michelson or Sagnac type). The advantage of the latter is a very high efficiency in light collection because of the well-known Felgett and Jaquinot principles.

  17. Real-space imaging of fractional quantum Hall liquids

    Hayakawa, Junichiro; Muraki, Koji; Yusa, Go

    2013-01-01

    Electrons in semiconductors usually behave like a gas--as independent particles. However, when confined to two dimensions under a perpendicular magnetic field at low temperatures, they condense into an incompressible quantum liquid. This phenomenon, known as the fractional quantum Hall (FQH) effect, is a quantum-mechanical manifestation of the macroscopic behaviour of correlated electrons that arises when the Landau-level filling factor is a rational fraction. However, the diverse microscopic interactions responsible for its emergence have been hidden by its universality and macroscopic nature. Here, we report real-space imaging of FQH liquids, achieved with polarization-sensitive scanning optical microscopy using trions (charged excitons) as a local probe for electron spin polarization. When the FQH ground state is spin-polarized, the triplet/singlet intensity map exhibits a spatial pattern that mirrors the intrinsic disorder potential, which is interpreted as a mapping of compressible and incompressible electron liquids. In contrast, when FQH ground states with different spin polarization coexist, domain structures with spontaneous quasi-long-range order emerge, which can be reproduced remarkably well from the disorder patterns using a two-dimensional random-field Ising model. Our results constitute the first reported real-space observation of quantum liquids in a class of broken symmetry state known as the quantum Hall ferromagnet.

  18. Fast MR image reconstruction for partially parallel imaging with arbitrary k-space trajectories.

    Ye, Xiaojing; Chen, Yunmei; Lin, Wei; Huang, Feng

    2011-03-01

    Both acquisition and reconstruction speed are crucial for magnetic resonance (MR) imaging in clinical applications. In this paper, we present a fast reconstruction algorithm for SENSE in partially parallel MR imaging with arbitrary k-space trajectories. The proposed method is a combination of variable splitting, the classical penalty technique and the optimal gradient method. Variable splitting and the penalty technique reformulate the SENSE model with sparsity regularization as an unconstrained minimization problem, which can be solved by alternating two simple minimizations: One is the total variation and wavelet based denoising that can be quickly solved by several recent numerical methods, whereas the other one involves a linear inversion which is solved by the optimal first order gradient method in our algorithm to significantly improve the performance. Comparisons with several recent parallel imaging algorithms indicate that the proposed method significantly improves the computation efficiency and achieves state-of-the-art reconstruction quality.

  19. Resliced image space construction for coronary artery collagen fibers.

    Luo, Tong; Chen, Huan; Kassab, Ghassan S

    2017-01-01

    Collagen fibers play an important role in the biomechanics of the blood vessel wall. The objective of this study was to determine the 3D microstructure of collagen fibers in the media and adventitia of coronary arteries. We present a novel optimal angle consistence algorithm to reform image slices in the visualization and analysis of 3D collagen images. 3D geometry was reconstructed from resliced image space where the 3D skeleton was extracted as the primary feature for accurate reconstruction of geometrical parameters. Collagen fibers (range 80-200) were reconstructed from the porcine coronary artery wall for the measurement of various morphological parameters. Collagen waviness and diameters were 1.37 ± 0.19 and 2.61 ± 0.89 μm, respectively. The biaxial distributions of orientation had two different peaks at 110.7 ± 25.2° and 18.4 ± 19.3°. Results for width, waviness, and orientation were found to be in good agreement with manual measurements. In addition to accurately measuring 2D features more efficiently than the manual approach, the present method produced 3D features that could not be measured in the 2D manual approach. These additional parameters included the tilt angle (5.10 ± 2.95°) and cross-sectional area (CSA; 5.98 ± 3.79 μm2) of collagen fibers. These 3D collagen reconstructions provide accurate and reliable microstructure for biomechanical modeling of vessel wall mechanics.

  20. A singular K-space model for fast reconstruction of magnetic resonance images from undersampled data.

    Luo, Jianhua; Mou, Zhiying; Qin, Binjie; Li, Wanqing; Ogunbona, Philip; Robini, Marc C; Zhu, Yuemin

    2017-12-09

    Reconstructing magnetic resonance images from undersampled k-space data is a challenging problem. This paper introduces a novel method of image reconstruction from undersampled k-space data based on the concept of singularizing operators and a novel singular k-space model. Exploring the sparsity of an image in the k-space, the singular k-space model (SKM) is proposed in terms of the k-space functions of a singularizing operator. The singularizing operator is constructed by combining basic difference operators. An algorithm is developed to reliably estimate the model parameters from undersampled k-space data. The estimated parameters are then used to recover the missing k-space data through the model, subsequently achieving high-quality reconstruction of the image using inverse Fourier transform. Experiments on physical phantom and real brain MR images have shown that the proposed SKM method constantly outperforms the popular total variation (TV) and the classical zero-filling (ZF) methods regardless of the undersampling rates, the noise levels, and the image structures. For the same objective quality of the reconstructed images, the proposed method requires much less k-space data than the TV method. The SKM method is an effective method for fast MRI reconstruction from the undersampled k-space data. Graphical abstract Two Real Images and their sparsified images by singularizing operator.

  1. NRT Lightning Imaging Sensor (LIS) on International Space Station (ISS) Science Data Vb0

    National Aeronautics and Space Administration — The NRT Lightning Imaging Sensor (LIS) on International Space Station (ISS) Science Data were collected by the LIS instrument on the ISS used to detect the...

  2. NRT Lightning Imaging Sensor (LIS) on International Space Station (ISS) Provisional Science Data Vp0

    National Aeronautics and Space Administration — The International Space Station (ISS) Lightning Imaging Sensor (LIS) datasets were collected by the LIS instrument on the ISS used to detect the distribution and...

  3. Integrated radiotherapy imaging system (IRIS): design considerations of tumour tracking with linac gantry-mounted diagnostic x-ray systems with flat-panel detectors.

    Berbeco, Ross I; Jiang, Steve B; Sharp, Gregory C; Chen, George T; Mostafavi, Hassan; Shirato, Hiroki

    2004-01-21

    The design of an integrated radiotherapy imaging system (IRIS), consisting of gantry mounted diagnostic (kV) x-ray tubes and fast read-out flat-panel amorphous-silicon detectors, has been studied. The system is meant to be capable of three main functions: radiographs for three-dimensional (3D) patient set-up, cone-beam CT and real-time tumour/marker tracking. The goal of the current study is to determine whether one source/panel pair is sufficient for real-time tumour/marker tracking and, if two are needed, the optimal position of each relative to other components and the isocentre. A single gantry-mounted source/imager pair is certainly capable of the first two of the three functions listed above and may also be useful for the third, if combined with prior knowledge of the target's trajectory. This would be necessary because only motion in two dimensions is visible with a single imager/source system. However, with previously collected information about the trajectory, the third coordinate may be derived from the other two with sufficient accuracy to facilitate tracking. This deduction of the third coordinate can only be made if the 3D tumour/marker trajectory is consistent from fraction to fraction. The feasibility of tumour tracking with one source/imager pair has been theoretically examined here using measured lung marker trajectory data for seven patients from multiple treatment fractions. The patients' selection criteria include minimum mean amplitudes of the tumour motions greater than 1 cm peak-to-peak. The marker trajectory for each patient was modelled using the first fraction data. Then for the rest of the data, marker positions were derived from the imager projections at various gantry angles and compared with the measured tumour positions. Our results show that, due to the three dimensionality and irregular trajectory characteristics of tumour motion, on a fraction-to-fraction basis, a 'monoscopic' system (single source/imager) is inadequate for

  4. Comparison between radiation exposure levels using an image intensifier and a flat-panel detector-based system in image-guided central venous catheter placement in children weighing less than 10 kg

    Miraglia, Roberto; Maruzzelli, Luigi; Cortis, Kelvin; Gerasia, Roberta; Maggio, Simona; Luca, Angelo [Diagnostic and Therapeutic Services, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (ISMETT), Palermo (Italy); Piazza, Marcello [Department of Anesthesia, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (ISMETT), Palermo (Italy); Tuzzolino, Fabio [Department of Information Technology, Mediterranean Institute for Transplantation and Advanced Specialized Therapies (ISMETT), Palermo (Italy)

    2014-09-10

    Ultrasound-guided central venous puncture and fluoroscopic guidance during central venous catheter (CVC) positioning optimizes technical success and lowers the complication rates in children, and is therefore considered standard practice. The purpose of this study was to compare the radiation exposure levels recorded during CVC placement in children weighing less than 10 kg in procedures performed using an image intensifier-based angiographic system (IIDS) to those performed in a flat-panel detector-based interventional suite (FPDS). A retrospective review of 96 image-guided CVC placements, between January 2008 and October 2013, in 49 children weighing less than 10 kg was performed. Mean age was 8.2 ± 4.4 months (range: 1-22 months). Mean weight was 7.1 ± 2.7 kg (range: 2.5-9.8 kg). The procedures were classified into two categories: non-tunneled and tunneled CVC placement. Thirty-five procedures were performed with the IIDS (21 non-tunneled CVC, 14 tunneled CVC); 61 procedures were performed with the FPDS (47 non-tunneled CVC, 14 tunneled CVC). For non-tunneled CVC, mean DAP was 113.5 ± 126.7 cGy cm{sup 2} with the IIDS and 15.9 ± 44.6 cGy . cm{sup 2} with the FPDS (P < 0.001). For tunneled CVC, mean DAP was 84.6 ± 81.2 cGy . cm{sup 2} with the IIDS and 37.1 ± 33.5 cGy cm{sup 2} with the FPDS (P = 0.02). The use of flat-panel angiographic equipment reduces radiation exposure in small children undergoing image-guided CVC placement. (orig.)

  5. Origins Space Telescope: The Far Infrared Imager and Polarimeter FIP

    Staguhn, Johannes G.; Chuss, David; Howard, Joseph; Meixner, Margaret; Vieira, Joaquin; Amatucci, Edward; Bradley, Damon; Carter, Ruth; Cooray, Asantha; Flores, Anel; Leisawitz, David; Moseley, Samuel Harvey; Wollack, Edward; Origins Space Telescope Study Team

    2018-01-01

    The Origins Space Telescope (OST)* is the mission concept for the Far-Infrared Surveyor, one of the four science and technology definition studies of NASA Headquarters for the 2020 Astronomy and Astrophysics Decadal survey. The current "concept 1", which envisions a cold (4K) 9m space telescope, includes 5 instruments, providing a wavelength coverage ranging from 6um and 667um. The achievable sensitivity of the observatory will provide three to four orders of magnitude of improvement in sensitivity over current observational capabilities, allowing to address a wide range of new and so far inaccessible scientific questions, ranging from bio-signatures on exo-planets to mapping primordial H_2 from the "dark ages" before the universe went through the phase of re-ionization.Here we present the Far Infrared Imager and Polarimeter (FIP) for OST. The cameral will cover four bands, 40um, 80um, 120um, and 240um. It will allow for differential polarimetry in those bands with the ability to observe two colors in polarimtery mode simultaneously, while all four bands can be observed simultaneously in total power mode. While the confusion limit will be reached in only 32ms at 240um, at 40um the source density on the sky is so low, that at the angular resolution of 1" of OST at this wavelength there will be no source confusion, even for the longest integration times. Science topics that can be addressed by FIP include but are not limited to galactic and extragalactic magnetic field studies, Deep Galaxy Surveys, and Outer Solar System objects..*Origins will enable flagship-quality general observing programs led by the astronomical community in the 2030s. We welcome you to contact the Science and Technology Definition Team (STDT) with your science needs and ideas by emailing us at ost_info@lists.ipac.caltech.edu

  6. Wavelet-space correlation imaging for high-speed MRI without motion monitoring or data segmentation.

    Li, Yu; Wang, Hui; Tkach, Jean; Roach, David; Woods, Jason; Dumoulin, Charles

    2015-12-01

    This study aims to (i) develop a new high-speed MRI approach by implementing correlation imaging in wavelet-space, and (ii) demonstrate the ability of wavelet-space correlation imaging to image human anatomy with involuntary or physiological motion. Correlation imaging is a high-speed MRI framework in which image reconstruction relies on quantification of data correlation. The presented work integrates correlation imaging with a wavelet transform technique developed originally in the field of signal and image processing. This provides a new high-speed MRI approach to motion-free data collection without motion monitoring or data segmentation. The new approach, called "wavelet-space correlation imaging", is investigated in brain imaging with involuntary motion and chest imaging with free-breathing. Wavelet-space correlation imaging can exceed the speed limit of conventional parallel imaging methods. Using this approach with high acceleration factors (6 for brain MRI, 16 for cardiac MRI, and 8 for lung MRI), motion-free images can be generated in static brain MRI with involuntary motion and nonsegmented dynamic cardiac/lung MRI with free-breathing. Wavelet-space correlation imaging enables high-speed MRI in the presence of involuntary motion or physiological dynamics without motion monitoring or data segmentation. © 2014 Wiley Periodicals, Inc.

  7. General classification of a normally flat Ric- semi symmetric submanifolds

    Mirzoyan, V.A.

    2012-01-01

    It has been proved that a normally flat submanifold M in Euclidean space En satisfies the condition R(X,Y)Ricci =0 if and only if it is the open part of one of the following submanifolds: (1) normally flat two-dimensional submanifold, (2) normally flat Einstein submanifold (in particular Ricci-flat or locally Euclidean), (3) normally flat semi- Einstein submanifold, (4) normally flat interlacing product of semi-Einstein submanifolds and locally Euclidean submanifold (may be of zero dimension), (5) direct product of the above enumerated classes of submanifolds

  8. Real-space imaging of interfacial water with submolecular resolution

    Jiang, Ying; Peking University Team

    2014-03-01

    Water/solid interfaces are vital to our daily lives and also a central theme across an incredibly wide range of scientific disciplines. Resolving the internal structure, i.e. the O-H directionality, of water molecules adsorbed on solid surfaces has been one of the key issues of water science yet remains challenging. Using a low-temperature scanning tunneling microscope (STM), we report the submolecular-resolution imaging of individual water monomers and tetramers on NaCl(001) films supported by a Au(111) substrate at 5 K. The frontier molecular orbitals of adsorbed water were directly visualized, which allowed discriminating the orientation of the monomers and the H-bond directionality of the tetramers in real space. Comparison with ab initio density functional theory calculations reveals that the ability to access the orbital structures of water stems from the electronic decoupling effect provided by the NaCl films and the precisely tunable tip-water coupling. Supported by National Basic Research Programs of China and National Science Foundation of China.

  9. The Sun Radio Imaging Space Experiment (SunRISE) Mission

    Kasper, J. C.; Lazio, J.; Alibay, F.; Amiri, N.; Bastian, T.; Cohen, C.; Landi, E.; Hegedus, A. M.; Maksimovic, M.; Manchester, W.; Reinard, A.; Schwadron, N.; Cecconi, B.; Hallinan, G.; Krupar, V.

    2017-12-01

    Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 R_S. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (nu > 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  10. Performance evaluation of a direct-conversion flat-panel detector system in imaging and quality assurance for a high-dose-rate 192Ir source

    Miyahara, Yoshinori; Hara, Yuki; Nakashima, Hiroto; Nishimura, Tomonori; Itakura, Kanae; Inomata, Taisuke; Kitagaki, Hajime

    2018-03-01

    In high-dose-rate (HDR) brachytherapy, a direct-conversion flat-panel detector (d-FPD) clearly depicts a 192Ir source without image halation, even under the emission of high-energy gamma rays. However, it was unknown why iridium is visible when using a d-FPD. The purpose of this study was to clarify the reasons for visibility of the source core based on physical imaging characteristics, including the modulation transfer functions (MTF), noise power spectral (NPS), contrast transfer functions, and linearity of d-FPD to high-energy gamma rays. The acquired data included: x-rays, [X]; gamma rays, [γ] dual rays (X  +  γ), [D], and subtracted data for depicting the source ([D]  -  [γ]). In the quality assurance (QA) test for the positional accuracy of a source core, the coordinates of each dwelling point were compared between the planned and actual source core positions using a CT/MR-compatible ovoid applicator and a Fletcher-Williamson applicator. The profile curves of [X] and ([D]  -  [γ]) matched well on MTF and NPS. The contrast resolutions of [D] and [X] were equivalent. A strongly positive linear correlation was found between the output data of [γ] and source strength (r 2  >  0.99). With regard to the accuracy of the source core position, the largest coordinate difference (3D distance) was noted at the maximum curvature of the CT/MR-compatible ovoid and Fletcher-Williamson applicators, showing 1.74  ±  0.02 mm and 1.01  ±  0.01 mm, respectively. A d-FPD system provides high-quality images of a source, even when high-energy gamma rays are emitted to the detector, and positional accuracy tests with clinical applicators are useful in identifying source positions (source movements) within the applicator for QA.

  11. Visual properties and memorising scenes: Effects of image-space sparseness and uniformity.

    Lukavský, Jiří; Děchtěrenko, Filip

    2017-10-01

    Previous studies have demonstrated that humans have a remarkable capacity to memorise a large number of scenes. The research on memorability has shown that memory performance can be predicted by the content of an image. We explored how remembering an image is affected by the image properties within the context of the reference set, including the extent to which it is different from its neighbours (image-space sparseness) and if it belongs to the same category as its neighbours (uniformity). We used a reference set of 2,048 scenes (64 categories), evaluated pairwise scene similarity using deep features from a pretrained convolutional neural network (CNN), and calculated the image-space sparseness and uniformity for each image. We ran three memory experiments, varying the memory workload with experiment length and colour/greyscale presentation. We measured the sensitivity and criterion value changes as a function of image-space sparseness and uniformity. Across all three experiments, we found separate effects of 1) sparseness on memory sensitivity, and 2) uniformity on the recognition criterion. People better remembered (and correctly rejected) images that were more separated from others. People tended to make more false alarms and fewer miss errors in images from categorically uniform portions of the image-space. We propose that both image-space properties affect human decisions when recognising images. Additionally, we found that colour presentation did not yield better memory performance over grayscale images.

  12. A Convex Formulation for Magnetic Particle Imaging X-Space Reconstruction.

    Konkle, Justin J; Goodwill, Patrick W; Hensley, Daniel W; Orendorff, Ryan D; Lustig, Michael; Conolly, Steven M

    2015-01-01

    Magnetic Particle Imaging (mpi) is an emerging imaging modality with exceptional promise for clinical applications in rapid angiography, cell therapy tracking, cancer imaging, and inflammation imaging. Recent publications have demonstrated quantitative mpi across rat sized fields of view with x-space reconstruction methods. Critical to any medical imaging technology is the reliability and accuracy of image reconstruction. Because the average value of the mpi signal is lost during direct-feedthrough signal filtering, mpi reconstruction algorithms must recover this zero-frequency value. Prior x-space mpi recovery techniques were limited to 1d approaches which could introduce artifacts when reconstructing a 3d image. In this paper, we formulate x-space reconstruction as a 3d convex optimization problem and apply robust a priori knowledge of image smoothness and non-negativity to reduce non-physical banding and haze artifacts. We conclude with a discussion of the powerful extensibility of the presented formulation for future applications.

  13. SU-E-I-11: Cascaded Linear System Model for Columnar CsI Flat Panel Imagers with Depth Dependent Gain and Blur

    Peng, B; Lubinsky, A; Zheng, H; Zhao, W; Teymurazyan, A

    2014-01-01

    Purpose: To implement a depth dependent gain and blur cascaded linear system model (CLSM) for optimizing columnar structured CsI indirect conversion flat panel imager (FPI) for advanced imaging applications. Methods: For experimental validation, depth dependent escape efficiency, e(z), was extracted from PHS measurement of different CsI scintillators (thickness, substrate and light output). The inherent MTF and DQE of CsI was measured using high resolution CMOS sensor. For CLSM, e(z) and the depth dependent MTF(f,z), were estimated using Monte Carlo simulation (Geant4) of optical photon transport through columnar CsI. Previous work showed that Monte Carlo simulation for CsI was hindered by the non-ideality of its columnar structure. In the present work we allowed variation in columnar width with depth, and assumed diffusive reflective backing and columns. Monte Carlo simulation was performed using an optical point source placed at different depth of the CsI layer, from which MTF(z,f) and e(z) were computed. The resulting e(z) with excellent matching with experimental measurements were then applied to the CLSM, Monte Carlo simulation was repeated until the modeled MTF, DQE(f) also match experimental measurement. Results: For a 150 micron FOS HL type CsI, e(z) varies between 0.56 to 0.45, and the MTF at 14 cycles/mm varies between 62.1% to 3.9%, from the front to the back of the scintillator. The overall MTF and DQE(f) at all frequencies are in excellent agreement with experimental measurements at all frequencies. Conclusion: We have developed a CLSM for columnar CsI scintillators with depth dependent gain and MTF, which were estimated from Monte Carlo simulation with novel optical simulation settings. Preliminary results showed excellent agreement between simulation results and experimental measurements. Future work is aimed at extending this approach to optimize CsI screen optic design and sensor structure for achieving higher DQE(f) in cone-beam CT, which uses

  14. Creating flat design websites

    Pratas, Antonio

    2014-01-01

    This book contains practical, step-by-step tutorials along with plenty of explanation about designing your flat website. Each section is introduced sequentially, building up your web design skills and completing your website.Creating Flat Design Websites is ideal for you if you are starting on your web development journey, but this book will also benefit seasoned developers wanting to start developing in flat.

  15. Landscape in Cinema: Images to Think Time through Space

    Filipa Rosário

    2017-01-01

    Full Text Available This text is an introduction to the special issue on ‘Landscape and Cinema’ published by Aniki. Portuguese Journal of the Moving Image. It is composed of a brief state of the art, which anchors this work within the bibliography on the subject, and a synthetic description of the discourses developed by the six papers included in the issue: the first one addresses the historical and aesthetic evolution of the background in the Russian and Soviet cinema of the first decades of the twentieth century; the second discusses the representation of the Portuguese landscape in Manuel Guimarães’ films; the third identifies a few cinematic techniques that work as conventions of psychological landscape film, such as juxtaposition and superimposition; the fourth interprets the meaning of Brazilian urban landscapes showed in the feature film A Vida Provisória (Maurício Gomes Leite, 1968; the fifth deals with the corporeal and conceptual relations between body, memory and landscape through a sensory reading of the films Ten Skies (James Benning, 2004 and Sin Peso (Cao Guimarães, 2007; and finally, the sixth undertakes a comparative analysis of three South American non-fiction works that show several waterscapes as places of memory: El botón de nácar (Patricio Guzmán, 2015, Los durmientes (Enrique Ramírez, 2015 and Las aguas del olvido (Jonathan Perel, 2013. The aim of this preliminary text is therefore to introduce the main contents of the issue and some of its conclusions. In this sense, it is necessary to emphasise the open and polysemic nature of landscape, which works, inside and outside cinema, as a palimpsest in which multiple meanings come together. For this reason, those films that depict, create and intervene in landscape allow to perceive, among other things, the overlapping of historical and subjective times that takes place in certain spaces.

  16. Distance determinations to shield galaxies from Hubble space telescope imaging

    McQuinn, Kristen B. W.; Skillman, Evan D. [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church Street, S.E., Minneapolis, MN 55455 (United States); Cannon, John M.; Cave, Ian [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Salzer, John J. [Department of Astronomy, Indiana University, 727 East 3rd Street, Bloomington, IN 47405 (United States); Haynes, Martha P.; Adams, Elizabeth; Giovanelli, Riccardo [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Elson, Ed C. [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Ott, Juërgen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Saintonge, Amélie, E-mail: kmcquinn@astro.umn.edu [Max-Planck-Institute for Astrophysics, D-85741 Garching (Germany)

    2014-04-10

    The Survey of H I in Extremely Low-mass Dwarf (SHIELD) galaxies is an ongoing multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies. The galaxies were selected from the first ∼10% of the H I Arecibo Legacy Fast ALFA (ALFALFA) survey based on their inferred low H I mass and low baryonic mass, and all systems have recent star formation. Thus, the SHIELD sample probes the faint end of the galaxy luminosity function for star-forming galaxies. Here, we measure the distances to the 12 SHIELD galaxies to be between 5 and 12 Mpc by applying the tip of the red giant method to the resolved stellar populations imaged by the Hubble Space Telescope. Based on these distances, the H I masses in the sample range from 4 × 10{sup 6} to 6 × 10{sup 7} M {sub ☉}, with a median H I mass of 1 × 10{sup 7} M {sub ☉}. The tip of the red giant branch distances are up to 73% farther than flow-model estimates in the ALFALFA catalog. Because of the relatively large uncertainties of flow-model distances, we are biased toward selecting galaxies from the ALFALFA catalog where the flow model underestimates the true distances. The measured distances allow for an assessment of the native environments around the sample members. Five of the galaxies are part of the NGC 672 and NGC 784 groups, which together constitute a single structure. One galaxy is part of a larger linear ensemble of nine systems that stretches 1.6 Mpc from end to end. Three galaxies reside in regions with 1-9 neighbors, and four galaxies are truly isolated with no known system identified within a radius of 1 Mpc.

  17. Space imaging measurement system based on fixed lens and moving detector

    Akiyama, Akira; Doshida, Minoru; Mutoh, Eiichiro; Kumagai, Hideo; Yamada, Hirofumi; Ishii, Hiromitsu

    2006-08-01

    We have developed the Space Imaging Measurement System based on the fixed lens and fast moving detector to the control of the autonomous ground vehicle. The space measurement is the most important task in the development of the autonomous ground vehicle. In this study we move the detector back and forth along the optical axis at the fast rate to measure the three-dimensional image data. This system is just appropriate to the autonomous ground vehicle because this system does not send out any optical energy to measure the distance and keep the safety. And we use the digital camera of the visible ray range. Therefore it gives us the cost reduction of the three-dimensional image data acquisition with respect to the imaging laser system. We can combine many pieces of the narrow space imaging measurement data to construct the wide range three-dimensional data. This gives us the improvement of the image recognition with respect to the object space. To develop the fast movement of the detector, we build the counter mass balance in the mechanical crank system of the Space Imaging Measurement System. And then we set up the duct to prevent the optical noise due to the ray not coming through lens. The object distance is derived from the focus distance which related to the best focused image data. The best focused image data is selected from the image of the maximum standard deviation in the standard deviations of series images.

  18. The chinese space program as the image instrument of the great China

    Daniel Lemus Delgado

    2012-10-01

    Full Text Available This article analyzes the Chinese space program and how the bureaucratic elite acts to convert China as a leading nation in international arena. This article assumes that, beyond the scientific advances that space exploration has in multiple fields of knowledge, the support to the space program depicts a way to project a positive image of China. This image is a China rising in the international community. The author discusses how space missions and the discourse around the space program strengthen national pride. Thus, China’s space program projects the image of a Greater China. The article concludes that the space program shows that China is modernizing rapidly and is able to be a world power.

  19. Scintillator high-gain avalanche rushing photoconductor active-matrix flat panel imager: zero-spatial frequency x-ray imaging properties of the solid-state SHARP sensor structure.

    Wronski, M; Zhao, W; Tanioka, K; Decrescenzo, G; Rowlands, J A

    2012-11-01

    The authors are investigating the feasibility of a new type of solid-state x-ray imaging sensor with programmable avalanche gain: scintillator high-gain avalanche rushing photoconductor active matrix flat panel imager (SHARP-AMFPI). The purpose of the present work is to investigate the inherent x-ray detection properties of SHARP and demonstrate its wide dynamic range through programmable gain. A distributed resistive layer (DRL) was developed to maintain stable avalanche gain operation in a solid-state HARP. The signal and noise properties of the HARP-DRL for optical photon detection were investigated as a function of avalanche gain both theoretically and experimentally, and the results were compared with HARP tube (with electron beam readout) used in previous investigations of zero spatial frequency performance of SHARP. For this new investigation, a solid-state SHARP x-ray image sensor was formed by direct optical coupling of the HARP-DRL with a structured cesium iodide (CsI) scintillator. The x-ray sensitivity of this sensor was measured as a function of avalanche gain and the results were compared with the sensitivity of HARP-DRL measured optically. The dynamic range of HARP-DRL with variable avalanche gain was investigated for the entire exposure range encountered in radiography∕fluoroscopy (R∕F) applications. The signal from HARP-DRL as a function of electric field showed stable avalanche gain, and the noise associated with the avalanche process agrees well with theory and previous measurements from a HARP tube. This result indicates that when coupled with CsI for x-ray detection, the additional noise associated with avalanche gain in HARP-DRL is negligible. The x-ray sensitivity measurements using the SHARP sensor produced identical avalanche gain dependence on electric field as the optical measurements with HARP-DRL. Adjusting the avalanche multiplication gain in HARP-DRL enabled a very wide dynamic range which encompassed all clinically relevant

  20. Scintillator high-gain avalanche rushing photoconductor active-matrix flat panel imager: Zero-spatial frequency x-ray imaging properties of the solid-state SHARP sensor structure

    Wronski, M.; Zhao, W.; Tanioka, K.; DeCrescenzo, G.; Rowlands, J. A.

    2012-01-01

    Purpose: The authors are investigating the feasibility of a new type of solid-state x-ray imaging sensor with programmable avalanche gain: scintillator high-gain avalanche rushing photoconductor active matrix flat panel imager (SHARP-AMFPI). The purpose of the present work is to investigate the inherent x-ray detection properties of SHARP and demonstrate its wide dynamic range through programmable gain. Methods: A distributed resistive layer (DRL) was developed to maintain stable avalanche gain operation in a solid-state HARP. The signal and noise properties of the HARP-DRL for optical photon detection were investigated as a function of avalanche gain both theoretically and experimentally, and the results were compared with HARP tube (with electron beam readout) used in previous investigations of zero spatial frequency performance of SHARP. For this new investigation, a solid-state SHARP x-ray image sensor was formed by direct optical coupling of the HARP-DRL with a structured cesium iodide (CsI) scintillator. The x-ray sensitivity of this sensor was measured as a function of avalanche gain and the results were compared with the sensitivity of HARP-DRL measured optically. The dynamic range of HARP-DRL with variable avalanche gain was investigated for the entire exposure range encountered in radiography/fluoroscopy (R/F) applications. Results: The signal from HARP-DRL as a function of electric field showed stable avalanche gain, and the noise associated with the avalanche process agrees well with theory and previous measurements from a HARP tube. This result indicates that when coupled with CsI for x-ray detection, the additional noise associated with avalanche gain in HARP-DRL is negligible. The x-ray sensitivity measurements using the SHARP sensor produced identical avalanche gain dependence on electric field as the optical measurements with HARP-DRL. Adjusting the avalanche multiplication gain in HARP-DRL enabled a very wide dynamic range which encompassed all

  1. Space situational awareness satellites and ground based radiation counting and imaging detector technology

    Jansen, Frank; Behrens, Joerg; Pospisil, Stanislav; Kudela, Karel

    2011-01-01

    We review the current status from the scientific and technological point of view of solar energetic particles, solar and galactic cosmic ray measurements as well as high energy UV-, X- and gamma-ray imaging of the Sun. These particles and electromagnetic data are an important tool for space situational awareness (SSA) aspects like space weather storm predictions to avoid failures in space, air and ground based technological systems. Real time data acquisition, position and energy sensitive imaging are demanded by the international space weather forecast services. We present how newly developed, highly miniaturized radiation detectors can find application in space in view of future SSA related satellites as a novel space application due to their counting and imaging capabilities.

  2. Space situational awareness satellites and ground based radiation counting and imaging detector technology

    Jansen, Frank, E-mail: frank.jansen@dlr.de [DLR Institute of Space Systems, Robert-Hooke-Str. 7, 28359 Bremen (Germany); Behrens, Joerg [DLR Institute of Space Systems, Robert-Hooke-Str. 7, 28359 Bremen (Germany); Pospisil, Stanislav [Czech Technical University, IEAP, 12800 Prague 2, Horska 3a/22 (Czech Republic); Kudela, Karel [Slovak Academy of Sciences, IEP, 04001 Kosice, Watsonova 47 (Slovakia)

    2011-05-15

    We review the current status from the scientific and technological point of view of solar energetic particles, solar and galactic cosmic ray measurements as well as high energy UV-, X- and gamma-ray imaging of the Sun. These particles and electromagnetic data are an important tool for space situational awareness (SSA) aspects like space weather storm predictions to avoid failures in space, air and ground based technological systems. Real time data acquisition, position and energy sensitive imaging are demanded by the international space weather forecast services. We present how newly developed, highly miniaturized radiation detectors can find application in space in view of future SSA related satellites as a novel space application due to their counting and imaging capabilities.

  3. Image Analysis Based on Soft Computing and Applied on Space Shuttle During the Liftoff Process

    Dominquez, Jesus A.; Klinko, Steve J.

    2007-01-01

    Imaging techniques based on Soft Computing (SC) and developed at Kennedy Space Center (KSC) have been implemented on a variety of prototype applications related to the safety operation of the Space Shuttle during the liftoff process. These SC-based prototype applications include detection and tracking of moving Foreign Objects Debris (FOD) during the Space Shuttle liftoff, visual anomaly detection on slidewires used in the emergency egress system for the Space Shuttle at the laJlIlch pad, and visual detection of distant birds approaching the Space Shuttle launch pad. This SC-based image analysis capability developed at KSC was also used to analyze images acquired during the accident of the Space Shuttle Columbia and estimate the trajectory and velocity of the foam that caused the accident.

  4. Space-time encoding for high frame rate ultrasound imaging

    Misaridis, Thanssis; Jensen, Jørgen Arendt

    2002-01-01

    dynamically focused in both transmit and receive with only two firings. This reduces the problem of motion artifacts. The method has been tested with extensive simulations using Field II. Resolution and SNR are compared with uncoded STA imaging and conventional phased-array imaging. The range resolution...... remains the same for coded STA imaging with four emissions and is slightly degraded for STA imaging with two emissions due to the −55 dB cross-talk between the signals. The additional proposed temporal encoding adds more than 15 dB on the SNR gain, yielding a SNR at the same order as in phased-array...

  5. Sampling in image space for vision based SLAM

    Booij, O.; Zivkovic, Z.; Kröse, B.

    2008-01-01

    Loop closing in vision based SLAM applications is a difficult task. Comparing new image data with all previous image data acquired for the map is practically impossible because of the high computational costs. This problem is part of the bigger problem to acquire local geometric constraints from

  6. Conservative image transformations with restoration and scale-space properties

    Weickert, J.A.; Haar Romenij, ter B.M.; Viergever, M.A.; Delogne, P.

    1996-01-01

    Many image processing applications require to solve problems such as denoising with edge enhancement, preprocessing for segmentation, or the completion of interrupted lines. This may be accomplished by applying a suitable nonlinear anisotropic diffusion process to the image. Its diffusion tensor is

  7. Flat detectors and their clinical applications

    Spahn, Martin

    2005-01-01

    Diagnostic and interventional flat detector X-ray systems are penetrating the market in all application segments. First introduced in radiography and mammography, they have conquered cardiac and general angiography and are getting increasing attention in fluoroscopy. Two flat detector technologies prevail. The dominating method is based on an indirect X-ray conversion process, using cesium iodide scintillators. It offers considerable advantages in radiography, angiography and fluoroscopy. The other method employs a direct converter such as selenium which is particularly suitable for mammography. Both flat detector technologies are based on amorphous silicon active pixel matrices. Flat detectors facilitate the clinical workflow in radiographic rooms, foster improved image quality and provide the potential to reduce dose. This added value is based on their large dynamic range, their high sensitivity to X-rays and the instant availability of the image. Advanced image processing is instrumental in these improvements and expand the range of conventional diagnostic methods. In angiography and fluoroscopy the transition from image intensifiers to flat detectors is facilitated by ample advantages they offer, such as distortion-free images, excellent coarse contrast, large dynamic range and high X-ray sensitivity. These characteristics and their compatibility with strong magnetic fields are the basis for improved diagnostic methods and innovative interventional applications. (orig.)

  8. Color Image Evaluation for Small Space Based on FA and GEP

    Li Deng

    2014-01-01

    Full Text Available Aiming at the problem that color image is difficult to quantify, this paper proposes an evaluation method of color image for small space based on factor analysis (FA and gene expression programming (GEP and constructs a correlation model between color image factors and comprehensive color image. The basic color samples of small space and color images are evaluated by semantic differential method (SD method, color image factors are selected via dimension reduction in FA, factor score function is established, and by combining the entropy weight method to determine each factor weights then the comprehensive color image score is calculated finally. The best fitting function between color image factors and comprehensive color image is obtained by GEP algorithm, which can predict the users’ color image values. A color image evaluation system for small space is developed based on this model. The color evaluation of a control room on AC frequency conversion rig is taken as an example, verifying the effectiveness of the proposed method. It also can assist the designers in other color designs and provide a fast evaluation tool for testing users’ color image.

  9. The dimensions of urban public space in user’s mental image

    Matej Nikšič

    2006-01-01

    Full Text Available The article presents a method for recognising qualitative and quantitative dimensions of open urban space in the user’s perceptual image. It stems from the hypothesis that the open urban space in mental perception isn’t a uniform continuum, which in general applies to its physical phenomenon. It discloses where and how users experience the limits of real open public space that they occupy and what they perceive as the neighbourhood of such a place. Therefore it researches rules applied by the user to mentally structure physically continuous space into smaller units and then reassemble these into a network. Knowledge of such rules enables expansion of open urban public spaces, which user’s experience as positive, into the wider area, thus revitalising those neighbouring spaces that are perceived as negative or are completely absent in the mental image and consequentially unused. The presence of people is in fact the essential component of quality public spaces.

  10. Optimal Electric Field Estimation for Exoplanet Imaging Observatories in Space

    National Aeronautics and Space Administration — The discovery and characterization of Earth-like planets around other stars is a high priority in modern astronomy. While over 900 confirmed exoplanets have been...

  11. Adaptive removal of background and white space from document images using seam categorization

    Fillion, Claude; Fan, Zhigang; Monga, Vishal

    2011-03-01

    Document images are obtained regularly by rasterization of document content and as scans of printed documents. Resizing via background and white space removal is often desired for better consumption of these images, whether on displays or in print. While white space and background are easy to identify in images, existing methods such as naïve removal and content aware resizing (seam carving) each have limitations that can lead to undesirable artifacts, such as uneven spacing between lines of text or poor arrangement of content. An adaptive method based on image content is hence needed. In this paper we propose an adaptive method to intelligently remove white space and background content from document images. Document images are different from pictorial images in structure. They typically contain objects (text letters, pictures and graphics) separated by uniform background, which include both white paper space and other uniform color background. Pixels in uniform background regions are excellent candidates for deletion if resizing is required, as they introduce less change in document content and style, compared with deletion of object pixels. We propose a background deletion method that exploits both local and global context. The method aims to retain the document structural information and image quality.

  12. Detecting areal changes in tidal flats after sea dike construction ...

    The main objective of this study was to estimate changes in the area of tidal flats that occurred after sea dike construction on the western coast of South Korea using Landsat-TM images. Applying the ISODATA method of unsupervised classification for Landsat-TM images, the tidal flats were identified, and the resulting areas ...

  13. Geometric shapes inversion method of space targets by ISAR image segmentation

    Huo, Chao-ying; Xing, Xiao-yu; Yin, Hong-cheng; Li, Chen-guang; Zeng, Xiang-yun; Xu, Gao-gui

    2017-11-01

    The geometric shape of target is an effective characteristic in the process of space targets recognition. This paper proposed a method of shape inversion of space target based on components segmentation from ISAR image. The Radon transformation, Hough transformation, K-means clustering, triangulation will be introduced into ISAR image processing. Firstly, we use Radon transformation and edge detection to extract space target's main body spindle and solar panel spindle from ISAR image. Then the targets' main body, solar panel, rectangular and circular antenna are segmented from ISAR image based on image detection theory. Finally, the sizes of every structural component are computed. The effectiveness of this method is verified using typical targets' simulation data.

  14. Phase space imaging of a beam of charged particles by frictional forces

    Daniel, H.

    1977-01-01

    In the case of frictional forces, defined by always acting opposite to the particle motion, Liouville's theorem does not apply. The effect of such forces on a beam of charged particles is calculated in closed form. Emphasis is given to the phase space imaging by a moderator. Conditions for an increase in phase space density are discussed. (Auth.)

  15. The SAFARI imaging spectrometer for the SPICA space observatory

    Roelfsema, Pieter; Giard, Martin; Najarro, Francisco; Wafelbakker, Kees; Jellema, Willem; Jackson, Brian; Swinyard, Bruce; Audard, Marc; Doi, Yasuo; Griffin, Matt; Helmich, Frank; Kerschbaum, Franz; Meyer, Michael; Naylor, David; Nielsen, Hans; Olofsson, Göran; Poglitsch, Albrecht; Spinoglio, Luigi; Vandenbussche, Bart; Isaak, Kate; Goicoechea, Javier R.

    The Japanese SPace Infrared telescope for Cosmology and Astrophysics, SPICA, will provide astronomers with a long awaited new window on the universe. Having a large cold telescope cooled to only 6K above absolute zero, SPICA will provide a unique environment where instruments are limited only by the

  16. Second Harmonic Imaging improves Echocardiograph Quality on board the International Space Station

    Garcia, Kathleen; Sargsyan, Ashot; Hamilton, Douglas; Martin, David; Ebert, Douglas; Melton, Shannon; Dulchavsky, Scott

    2008-01-01

    Ultrasound (US) capabilities have been part of the Human Research Facility (HRF) on board the International Space Station (ISS) since 2001. The US equipment on board the ISS includes a first-generation Tissue Harmonic Imaging (THI) option. Harmonic imaging (HI) is the second harmonic response of the tissue to the ultrasound beam and produces robust tissue detail and signal. Since this is a first-generation THI, there are inherent limitations in tissue penetration. As a breakthrough technology, HI extensively advanced the field of ultrasound. In cardiac applications, it drastically improves endocardial border detection and has become a common imaging modality. U.S. images were captured and stored as JPEG stills from the ISS video downlink. US images with and without harmonic imaging option were randomized and provided to volunteers without medical education or US skills for identification of endocardial border. The results were processed and analyzed using applicable statistical calculations. The measurements in US images using HI improved measurement consistency and reproducibility among observers when compared to fundamental imaging. HI has been embraced by the imaging community at large as it improves the quality and data validity of US studies, especially in difficult-to-image cases. Even with the limitations of the first generation THI, HI improved the quality and measurability of many of the downlinked images from the ISS and should be an option utilized with cardiac imaging on board the ISS in all future space missions.

  17. Phase-space evolution of x-ray coherence in phase-sensitive imaging.

    Wu, Xizeng; Liu, Hong

    2008-08-01

    X-ray coherence evolution in the imaging process plays a key role for x-ray phase-sensitive imaging. In this work we present a phase-space formulation for the phase-sensitive imaging. The theory is reformulated in terms of the cross-spectral density and associated Wigner distribution. The phase-space formulation enables an explicit and quantitative account of partial coherence effects on phase-sensitive imaging. The presented formulas for x-ray spectral density at the detector can be used for performing accurate phase retrieval and optimizing the phase-contrast visibility. The concept of phase-space shearing length derived from this phase-space formulation clarifies the spatial coherence requirement for phase-sensitive imaging with incoherent sources. The theory has been applied to x-ray Talbot interferometric imaging as well. The peak coherence condition derived reveals new insights into three-grating-based Talbot-interferometric imaging and gratings-based x-ray dark-field imaging.

  18. Islet grafting and imaging in a bioengineered intramuscular space.

    Witkowski, Piotr; Sondermeijer, Hugo; Hardy, Mark A; Woodland, David C; Lee, Keagan; Bhagat, Govind; Witkowski, Kajetan; See, Fiona; Rana, Abbas; Maffei, Antonella; Itescu, Silviu; Harris, Paul E

    2009-11-15

    Because the hepatic portal system may not be the optimal site for islet transplantation, several extrahepatic sites have been studied. Here, we examine an intramuscular transplantation site, bioengineered to better support islet neovascularization, engraftment, and survival, and we demonstrate that at this novel site, grafted beta cell mass may be quantitated in a real-time noninvasive manner by positron emission tomography (PET) imaging. Streptozotocin-induced rats were pretreated intramuscularly with a biocompatible angiogenic scaffold received syngeneic islet transplants 2 weeks later. The recipients were monitored serially by blood glucose and glucose tolerance measurements and by PET imaging of the transplant site with [11C] dihydrotetrabenazine. Parallel histopathologic evaluation of the grafts was performed using insulin staining and evaluation of microvasularity. Reversal of hyperglycemia by islet transplantation was most successful in recipients pretreated with bioscaffolds containing angiogenic factors when compared with those who received no bioscaffolds or bioscaffolds not treated with angiogenic factors. PET imaging with [11C] dihydrotetrabenazine, insulin staining, and microvascular density patterns were consistent with islet survival, increased levels of angiogenesis, and with reversal of hyperglycemia. Induction of increased neovascularization at an intramuscular site significantly improves islet transplant engraftment and survival compared with controls. The use of a nonhepatic transplant site may avoid intrahepatic complications and permit the use of PET imaging to measure and follow transplanted beta cell mass in real time. These findings have important implications for effective islet implantation outside of the liver and offer promising possibilities for improving islet survival, monitoring, and even prevention of islet loss.

  19. Double-theodolite measurement system used in the image calibration of space photographic instrument

    LI Yan; QIAO Yan-feng; SU Wan-xin; LIU Ze-xun

    2005-01-01

    The purpose of characterizing the image of space photographic instrument is to gain the space included angles from three coordinate axes in the three-dimensional coordinate of the image and the directionality of the three axes of coordinate in the frame of axes of the instrument. The two reference frames will keep in the same direction finally by adjusting according to space angles. This problem was solved by a new high-precision measurement system composed of a double-theodolite and a set of communication system. In the survey system, two TDA5005 total stations from Leica Company will be selected as the double-theodolite and the interdependence of both coordinate systems can be achieved by moving the stations only at one time. Therefore, this measurement system provides a highly efficient and high-precision surveying method to the image calibration of the space photographic instrument. According to the experiment, its measuring accuracy can reach arc-second level.

  20. An alternative to scale-space representation for extracting local features in image recognition

    Andersen, Hans Jørgen; Nguyen, Phuong Giang

    2012-01-01

    In image recognition, the common approach for extracting local features using a scale-space representation has usually three main steps; first interest points are extracted at different scales, next from a patch around each interest point the rotation is calculated with corresponding orientation...... and compensation, and finally a descriptor is computed for the derived patch (i.e. feature of the patch). To avoid the memory and computational intensive process of constructing the scale-space, we use a method where no scale-space is required This is done by dividing the given image into a number of triangles...... with sizes dependent on the content of the image, at the location of each triangle. In this paper, we will demonstrate that by rotation of the interest regions at the triangles it is possible in grey scale images to achieve a recognition precision comparable with that of MOPS. The test of the proposed method...

  1. Rocky Flats Compliance Program

    1994-02-01

    The Department of Energy (DOE) established the Office of Technology Development (EM-50) (OTD) as an element of Environmental Restoration and Waste Management (EM) in November 1989. The primary objective of the Office of Technology Development, Rocky Flats Compliance Program (RFCP), is to develop altemative treatment technologies for mixed low-level waste (wastes containing both hazardous and radioactive components) to use in bringing the Rocky Flats Plant (RFP) into compliance with Federal and state regulations and agreements. Approximately 48,000 cubic feet of untreated low-level mixed waste, for which treatment has not been specified, are stored at the RFP. The cleanup of the Rocky Flats site is driven by agreements between DOE, the Environmental Protection Agency (EPA), and the Colorado Department of Health (CDH). Under these agreements, a Comprehensive Treatment and Management Plan (CTMP) was drafted to outline the mechanisms by which RFP will achieve compliance with the regulations and agreements. This document describes DOE's strategy to treat low-level mixed waste to meet Land Disposal Restrictions and sets specific milestones related to the regulatory aspects of technology development. These milestones detail schedules for the development of technologies to treat all of the mixed wastes at the RFP. Under the Federal Facilities Compliance Act (FFCA), the CTMP has been incorporated into Rocky Flats Plant Conceptual Site Treatment Plan (CSTP). The CSTP will become the Rocky Flats Plant site Treatment Plan in 1995 and will supersede the CTMP

  2. Decomposition of Space-Variant Blur in Image Deconvolution

    Šroubek, Filip; Kamenický, Jan; Lu, Y. M.

    2016-01-01

    Roč. 23, č. 3 (2016), s. 346-350 ISSN 1070-9908 R&D Projects: GA ČR GA13-29225S; GA MŠk 7H14004 Grant - others:GA AV ČR(CZ) M100751201 Institutional support: RVO:67985556 Keywords : space-variant convolution * singular value decomposition * alternating direction method of multipliers Subject RIV: JD - Computer Applications, Robotics Impact factor: 2.528, year: 2016 http://library.utia.cas.cz/separaty/2016/ZOI/sroubek-0456182.pdf

  3. Differentiation of posterior pararenal space infection from psoas abscess by gallium imaging

    Bose, A.; Mishkin, F.; Delgado, J.

    1983-01-01

    Three of four patients whose cases fit the clinical description of psoas abscess proved on gallium imaging to have infection in the posterior pararenal space sparing the psoas muscle. This space provides a route for spread of infection connecting the spine, the anterior abdominal wall, the scrotum, the anterior thigh, and the gluteal region as demonstrated by the cases presented. Clinical differentiation between posterior pararenal space infection and psoas abscesses is difficult and CT studies may not demonstrate the process when the psoas space is not involved.

  4. The structure and properties of color spaces and the representation of color images

    Dubois, Eric

    2009-01-01

    This lecture describes the author's approach to the representation of color spaces and their use for color image processing. The lecture starts with a precise formulation of the space of physical stimuli (light). The model includes both continuous spectra and monochromatic spectra in the form of Dirac deltas. The spectral densities are considered to be functions of a continuous wavelength variable. This leads into the formulation of color space as a three-dimensional vector space, with all the associated structure. The approach is to start with the axioms of color matching for normal human vie

  5. Differentiation of posterior pararenal space infection from psoas abscess by gallium imaging

    Bose, A.; Mishkin, F.; Delgado, J.

    1983-01-01

    Three of four patients whose cases fit the clinical description of psoas abscess proved on gallium imaging to have infection in the posterior pararenal space sparing the psoas muscle. This space provides a route for spread of infection connecting the spine, the anterior abdominal wall, the scrotum, the anterior thigh, and the gluteal region as demonstrated by the cases presented. Clinical differentiation between posterior pararenal space infection and psoas abscesses is difficult and CT studies may not demonstrate the process when the psoas space is not involved

  6. Static dosimetry space image in which urology diagnostics are performed

    Banduka, M.S.; Vasic, D.D.

    2002-01-01

    Background. The effects of the dispersed radiation described theoretically imply complex picture of interaction of the photon beam with the patient's body, as well as its dispersion on other structures. Basic theoretical laws of this phenomenon are highlighted, thus giving the opportunity to model the effect in total. Material and methods. The measurements of the absorbed dose in the air give isodose curves that show distribution of the radiation dose. For the urological procedures standard urological diagnostic methods were being used. Results. Through a large series of measuring, we got the distribution of the radiation dose in space, where urology diagnostics is being made using the X-ray. The parameters determining this picture are the most frequent ones in the total number of 20 random cases taken in General Hospital in Doboj, Bosnia and Herzegovina. Conclusions. Static dosimetric picture of the space (radiation zone) in the general sense is useful before all for organisation of the diagnostic procedures utilising ionised radiation. Obtained in any way, this picture enables an insight into the three-dimensional distribution of the dosage on the basis of which it is possible to correct the organisation of the diagnostics being performed under these conditions. The values of the radiation dosage show it is necessary to use the protecting means prescribed by law. For more frequent exposure, it would be useful to make a dynamic dosimetric picture for professional exposure and assessment of the radiation risk of these persons. (author)

  7. Landscape in Cinema: Images to Think Time through Space

    Filipa Rosário; Iván Villarmea Álvarez

    2017-01-01

    This text is an introduction to the special issue on ‘Landscape and Cinema’ published by Aniki. Portuguese Journal of the Moving Image. It is composed of a brief state of the art, which anchors this work within the bibliography on the subject, and a synthetic description of the discourses developed by the six papers included in the issue: the first one addresses the historical and aesthetic evolution of the background in the Russian and Soviet cinema of the first decades of the twentieth cent...

  8. Total variation regularization in measurement and image space for PET reconstruction

    Burger, M

    2014-09-18

    © 2014 IOP Publishing Ltd. The aim of this paper is to test and analyse a novel technique for image reconstruction in positron emission tomography, which is based on (total variation) regularization on both the image space and the projection space. We formulate our variational problem considering both total variation penalty terms on the image and on an idealized sinogram to be reconstructed from a given Poisson distributed noisy sinogram. We prove existence, uniqueness and stability results for the proposed model and provide some analytical insight into the structures favoured by joint regularization. For the numerical solution of the corresponding discretized problem we employ the split Bregman algorithm and extensively test the approach in comparison to standard total variation regularization on the image. The numerical results show that an additional penalty on the sinogram performs better on reconstructing images with thin structures.

  9. 8. Asymptotically Flat and Regular Cauchy Data

    Dain, Sergio

    I describe the construction of a large class of asymptotically flat initial data with non-vanishing mass and angular momentum for which the metric and the extrinsic curvature have asymptotic expansions at space-like infinity in terms of powers of a radial coordinate. I emphasize the motivations and the main ideas behind the proofs.

  10. The research of Digital Holographic Object Wave Field Reconstruction in Image and Object Space

    LI Jun-Chang; PENG Zu-Jie; FU Yun-Chang

    2011-01-01

    @@ For conveniently detecting objects of different sizes using digital holography, usual measurements employ the object wave transformed by an optical system with different magnifications to fit charge coupled devices (CCDs), then the object field reconstruction involves the diffraction calculation of the optic wave passing through the optical system.We propose two methods to reconstruct the object field.The one is that, when the object is imaging in an image space in which we reconstruct the image of the object field, the object field can be expressed according to the object-image relationship.The other is that, when the object field reaching CCD is imaged in an object space in which we reconstruct the object field, the optical system is described by introducing matrix optics in this paper.The reconstruction formulae which easily use classic diffraction integral are derived.Finally, experimental verifications are also accomplished.%For conveniently detecting objects of different sizes using digital holography, usual measurements employ the object wave transformed by an optical system with different magnifications to fit charge coupled devices (CCDs), then the object Reid reconstruction involves the diffraction calculation of the optic wave passing through the optical system. We propose two methods to reconstruct the object field. The one is that, when the object is imaging in an image space in which we reconstruct the image of the object field, the object field can be expressed according to the object-image relationship. The other is that, when the object field reaching CCD is imaged in an object space in which we reconstruct the object field, the optical system is described by introducing matrix optics in this paper. The reconstruction formulae which easily use classic diffraction integral are derived. Finally, experimental verifications are also accomplished.

  11. Parallel magnetic resonance imaging as approximation in a reproducing kernel Hilbert space

    Athalye, Vivek; Lustig, Michael; Martin Uecker

    2015-01-01

    In magnetic resonance imaging data samples are collected in the spatial frequency domain (k-space), typically by time-consuming line-by-line scanning on a Cartesian grid. Scans can be accelerated by simultaneous acquisition of data using multiple receivers (parallel imaging), and by using more efficient non-Cartesian sampling schemes. To understand and design k-space sampling patterns, a theoretical framework is needed to analyze how well arbitrary sampling patterns reconstruct unsampled k-space using receive coil information. As shown here, reconstruction from samples at arbitrary locations can be understood as approximation of vector-valued functions from the acquired samples and formulated using a reproducing kernel Hilbert space with a matrix-valued kernel defined by the spatial sensitivities of the receive coils. This establishes a formal connection between approximation theory and parallel imaging. Theoretical tools from approximation theory can then be used to understand reconstruction in k-space and to extend the analysis of the effects of samples selection beyond the traditional image-domain g-factor noise analysis to both noise amplification and approximation errors in k-space. This is demonstrated with numerical examples. (paper)

  12. Near-field flat focusing mirrors

    Cheng, Yu-Chieh; Staliunas, Kestutis

    2018-03-01

    This article reviews recent progress towards the design of near-field flat focusing mirrors, focusing/imaging light patterns in reflection. An important feature of such flat focusing mirrors is their transverse invariance, as they do not possess any optical axis. We start with a review of the physical background to the different focusing mechanisms of near- and far-field focusing. These near-field focusing devices like flat lenses and the reviewed near-field focusing mirrors can implement planar focusing devices without any optical axis. In contrast, various types of far-field planar focusing devices, such as high-contrast gratings and metasurfaces, unavoidably break the transverse invariance due to their radially symmetrical structures. The particular realizations of near-field flat focusing mirrors including Bragg-like dielectric mirrors and dielectric subwavelength gratings are the main subjects of the review. The first flat focusing mirror was demonstrated with a chirped mirror and was shown to manage an angular dispersion for beam focusing, similar to the management of chromatic dispersion for pulse compression. Furthermore, the reviewed optimized chirped mirror demonstrated a long near-field focal length, hardly achieved by a flat lens or a planar hyperlens. Two more different configurations of dielectric subwavelength gratings that focus a light beam at normal or oblique incidence are also reviewed. We also summarize and compare focusing performance, limitations, and future perspectives between the reviewed flat focusing mirrors and other planar focusing devices including a flat lens with a negative-index material, a planar hyperlens, a high-contrast grating, and a metasurface.

  13. Efficient and automatic image reduction framework for space debris detection based on GPU technology

    Diprima, Francesco; Santoni, Fabio; Piergentili, Fabrizio; Fortunato, Vito; Abbattista, Cristoforo; Amoruso, Leonardo

    2018-04-01

    In the last years, the increasing number of space debris has triggered the need of a distributed monitoring system for the prevention of possible space collisions. Space surveillance based on ground telescope allows the monitoring of the traffic of the Resident Space Objects (RSOs) in the Earth orbit. This space debris surveillance has several applications such as orbit prediction and conjunction assessment. In this paper is proposed an optimized and performance-oriented pipeline for sources extraction intended to the automatic detection of space debris in optical data. The detection method is based on the morphological operations and Hough Transform for lines. Near real-time detection is obtained using General Purpose computing on Graphics Processing Units (GPGPU). The high degree of processing parallelism provided by GPGPU allows to split data analysis over thousands of threads in order to process big datasets with a limited computational time. The implementation has been tested on a large and heterogeneous images data set, containing both imaging satellites from different orbit ranges and multiple observation modes (i.e. sidereal and object tracking). These images were taken during an observation campaign performed from the EQUO (EQUatorial Observatory) observatory settled at the Broglio Space Center (BSC) in Kenya, which is part of the ASI-Sapienza Agreement.

  14. Many-core computing for space-based stereoscopic imaging

    McCall, Paul; Torres, Gildo; LeGrand, Keith; Adjouadi, Malek; Liu, Chen; Darling, Jacob; Pernicka, Henry

    The potential benefits of using parallel computing in real-time visual-based satellite proximity operations missions are investigated. Improvements in performance and relative navigation solutions over single thread systems can be achieved through multi- and many-core computing. Stochastic relative orbit determination methods benefit from the higher measurement frequencies, allowing them to more accurately determine the associated statistical properties of the relative orbital elements. More accurate orbit determination can lead to reduced fuel consumption and extended mission capabilities and duration. Inherent to the process of stereoscopic image processing is the difficulty of loading, managing, parsing, and evaluating large amounts of data efficiently, which may result in delays or highly time consuming processes for single (or few) processor systems or platforms. In this research we utilize the Single-Chip Cloud Computer (SCC), a fully programmable 48-core experimental processor, created by Intel Labs as a platform for many-core software research, provided with a high-speed on-chip network for sharing information along with advanced power management technologies and support for message-passing. The results from utilizing the SCC platform for the stereoscopic image processing application are presented in the form of Performance, Power, Energy, and Energy-Delay-Product (EDP) metrics. Also, a comparison between the SCC results and those obtained from executing the same application on a commercial PC are presented, showing the potential benefits of utilizing the SCC in particular, and any many-core platforms in general for real-time processing of visual-based satellite proximity operations missions.

  15. T2-weighted MR imaging of the liver: Qualitative and quantitative comparison of SPACE MR imaging with turbo spin-echo MR imaging

    Dohan, Anthony, E-mail: anthony.dohan@lrb.aphp.fr [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Université Paris-Diderot, Sorbonne Paris Cité, 10 Rue de Verdun, 75010 Paris (France); UMR INSERM 965, Hôpital Lariboisière, 2 Rue Amboise Paré, 75010 Paris (France); Gavini, Jean-Philippe, E-mail: jpgavini@gmail.com [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Université Paris-Diderot, Sorbonne Paris Cité, 10 Rue de Verdun, 75010 Paris (France); Placé, Vinciane, E-mail: vinciane.place@gmail.com [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Sebbag, Delphine, E-mail: delphinesebbag@gmail.com [Department of Body and Interventional Imaging, Hôpital Lariboisière, AP-HP, 2 Rue Ambroise Paré, 75475 Paris Cedex 10 (France); Université Paris-Diderot, Sorbonne Paris Cité, 10 Rue de Verdun, 75010 Paris (France); Vignaud, Alexandre, E-mail: alexandre.vignaud@cea.fr [LRMN, Neurospin, CEA-SACLAY, Bâtiment 145, 91 191 Gif-sur-Yvette Cedex (France); and others

    2013-11-01

    Objective: To qualitatively and quantitatively compare T2-weighted MR imaging of the liver using volumetric spin-echo with sampling perfection with application-optimized contrast using different flip angle evolutions (SPACE) with conventional turbo spin-echo (TSE) sequence for fat-suppressed T2-weighted MR imaging of the liver. Materials and methods: Thirty-three patients with suspected focal liver lesions had SPACE MR imaging and conventional fat-suppressed TSE MR imaging. Images were analyzed quantitatively by measuring the lesion-to-liver contrast-to-noise ratio (CNR), and the signal-to-noise ratio (SNR) of main focal hepatic lesions, hepatic and splenic parenchyma and qualitatively by evaluating the presence of vascular, respiratory motion and cardiac artifacts. Wilcoxon signed rank test was used to search for differences between the two sequences. Results: SPACE MR imaging showed significantly greater CNR for focal liver lesions (median = 22.82) than TSE MR imaging (median = 14.15) (P < .001). No differences were found for SNR of hepatic parenchyma (P = .097), main focal hepatic lesions (P = .35), and splenic parenchyma (P = .25). SPACE sequence showed less artifacts than TSE sequence (vascular, P < .001; respiratory motion, P < .001; cardiac, P < .001) but needed a longer acquisition time (228.4 vs. 162.1 s; P < .001). Conclusion: SPACE MR imaging provides a significantly increased CNR for focal liver lesions and less artifacts by comparison with the conventional TSE sequence. These results should stimulate further clinical studies with a surgical standard of reference to compare the two techniques in terms of sensitivity for malignant lesions.

  16. C-arm flat detector computed tomography parenchymal blood volume imaging: the nature of parenchymal blood volume parameter and the feasibility of parenchymal blood volume imaging in aneurysmal subarachnoid haemorrhage patients

    Kamran, Mudassar; Byrne, James V.

    2015-01-01

    C-arm flat detector computed tomography (FDCT) parenchymal blood volume (PBV) measurements allow assessment of cerebral haemodynamics in the neurointerventional suite. This paper explores the feasibility of C-arm computed tomography (CT) PBV imaging and the relationship between the C-arm CT PBV and the MR-PWI-derived cerebral blood volume (CBV) and cerebral blood flow (CBF) parameters in aneurysmal subarachnoid haemorrhage (SAH) patients developing delayed cerebral ischemia (DCI). Twenty-six patients with DCI following aneurysmal SAH underwent a research C-arm CT PBV scan using a biplane angiography system and contemporaneous MR-PWI scan as part of a prospective study. Quantitative whole-brain atlas-based volume-of-interest analysis in conjunction with Pearson correlation and Bland-Altman tests was performed to explore the agreement between C-arm CT PBV and MR-derived CBV and CBF measurements. All patients received medical management, while eight patients (31 %) underwent selective intra-arterial chemical angioplasty. Colour-coded C-arm CT PBV maps were 91 % sensitive and 100 % specific in detecting the perfusion abnormalities. C-arm CT rPBV demonstrated good agreement and strong correlation with both MR-rCBV and MR-rCBF measurements; the agreement and correlation were stronger for MR-rCBF relative to MR-rCBV and improved for C-arm CT PBV versus the geometric mean of MR-rCBV and MR-rCBF. Analysis of weighted means showed that the C-arm CT PBV has a preferential blood flow weighting (∼60 % blood flow and ∼40 % blood volume weighting). C-arm CT PBV imaging is feasible in DCI following aneurysmal SAH. PBV is a composite perfusion parameter incorporating both blood flow and blood volume weightings. That PBV has preferential (∼60 %) blood flow weighting is an important finding, which is of clinical significance when interpreting the C-arm CT PBV maps, particularly in the setting of acute brain ischemia. (orig.)

  17. C-arm flat detector computed tomography parenchymal blood volume imaging: the nature of parenchymal blood volume parameter and the feasibility of parenchymal blood volume imaging in aneurysmal subarachnoid haemorrhage patients

    Kamran, Mudassar; Byrne, James V. [University of Oxford, Nuffield Department of Surgical Sciences, Oxford (United Kingdom)

    2015-09-15

    C-arm flat detector computed tomography (FDCT) parenchymal blood volume (PBV) measurements allow assessment of cerebral haemodynamics in the neurointerventional suite. This paper explores the feasibility of C-arm computed tomography (CT) PBV imaging and the relationship between the C-arm CT PBV and the MR-PWI-derived cerebral blood volume (CBV) and cerebral blood flow (CBF) parameters in aneurysmal subarachnoid haemorrhage (SAH) patients developing delayed cerebral ischemia (DCI). Twenty-six patients with DCI following aneurysmal SAH underwent a research C-arm CT PBV scan using a biplane angiography system and contemporaneous MR-PWI scan as part of a prospective study. Quantitative whole-brain atlas-based volume-of-interest analysis in conjunction with Pearson correlation and Bland-Altman tests was performed to explore the agreement between C-arm CT PBV and MR-derived CBV and CBF measurements. All patients received medical management, while eight patients (31 %) underwent selective intra-arterial chemical angioplasty. Colour-coded C-arm CT PBV maps were 91 % sensitive and 100 % specific in detecting the perfusion abnormalities. C-arm CT rPBV demonstrated good agreement and strong correlation with both MR-rCBV and MR-rCBF measurements; the agreement and correlation were stronger for MR-rCBF relative to MR-rCBV and improved for C-arm CT PBV versus the geometric mean of MR-rCBV and MR-rCBF. Analysis of weighted means showed that the C-arm CT PBV has a preferential blood flow weighting (∼60 % blood flow and ∼40 % blood volume weighting). C-arm CT PBV imaging is feasible in DCI following aneurysmal SAH. PBV is a composite perfusion parameter incorporating both blood flow and blood volume weightings. That PBV has preferential (∼60 %) blood flow weighting is an important finding, which is of clinical significance when interpreting the C-arm CT PBV maps, particularly in the setting of acute brain ischemia. (orig.)

  18. Flat-port connectors

    Alrashed, Mohammed

    2017-01-01

    and water resistant. It is unique in the way of using the outer surfaces of the device for the electrical connection between the ports. Flat-port design can allow the manufacture of extremely thin devices by eliminating the side ports slots that take a lot

  19. Piecewise flat gravitational waves

    van de Meent, M.

    2011-01-01

    We examine the continuum limit of the piecewise flat locally finite gravity model introduced by ’t Hooft. In the linear weak field limit, we find the energy–momentum tensor and metric perturbation of an arbitrary configuration of defects. The energy–momentum turns out to be restricted to satisfy

  20. Flat out and bluesome

    Wilson, Mark; Snaebjornsdottir, Bryndis; Byatt, Lucy

    2008-01-01

    ‘Nanoq: flat out and bluesome’ is the story of polar bears, the largest land predators on earth, and their journey from the arctic wilderness to the museums and stately homes of the UK. The work documents the histories of each of these bears, the legacies of the hunters who shot them and the skills and expertise of the taxidermists who stuffed them.

  1. Rapid characterization of a nanomaterial structure using X-ray reciprocal-lattice-space imaging

    Sakata, Osami; Yoshimoto, Mamoru; Miki, Kazushi

    2006-01-01

    The X-ray reciprocal-lattice-space imaging method is able to record the reciprocal-lattice-space of nanostructure by sample-and-detector fixed geometry. This method was developed by the surface structure analysis beam line BL13XU of SPring-8. Outline of the X-ray diffraction method and basic principles of the X-ray reciprocal-lattice-space imaging method, and application examples are stated. The method is able to find out the Bragg conditions of nanostructure of surface in the atmosphere. The reciprocal-lattice of the embedded trace atomic wires was observed. The trace atoms of Bi atomic wires embedded in silicone showed the diffraction signal and image by a short exposure time. This method is useful at rapid non-destructive measurement of nanostructure. (S.Y.)

  2. CT and MR imaging of the buccal space: Normal anatomy and abnormalities

    Kim, Hyo Cheol; Han, Moon Hee; Moon, Min Hoan; Kim, Ji Hoon; Kim, In One; Chang, Kee Hyun

    2005-01-01

    The buccal space is an anatomical compartment lying anterior to the masticator space and lateral to the buccinator muscle. Since the major purpose of imaging is to define the likely anatomic origin and also the extent of a given lesion, thorough knowledge of the normal anatomy of the buccal space is essential, and this knowledge can aid the physician in narrowing down the list of possible maladies on the differential diagnosis. We illustrate here in this paper the important anatomic landmarks and typical pathologic conditions of the buccal space such as the developmental lesions and the neoplastic lesions. Knowledge of the expected pathologic conditions is useful for the radiologist when interpreting facial CT and MR images

  3. Possible application of an imaging plate to space radiation dosimetry

    Ohuchi, Hiroko; Yamadera, Akira

    2002-01-01

    Fading correction plays an important role in the application of commercially available BaBrF:Eu 2+ phosphors: imaging plates (IP) to dosimetry. We successfully determined a fading correction equation, which is a function of elapsed time and absolute temperature, as the sum of several exponentially decaying components having different half-lives. In this work, a new method was developed to eliminate a short half-life component by annealing the IP and estimating the radiation dose with the long half-life components. Annealing decreases the effect of fading on the estimated dose, however, it also causes the loss of photo-stimulated luminescence (PSL). Considering an IP as an integral detector for a specific period of up to one month, the practically optimum conditions for quantitative measurement with two types of IP (BAS-TR and BAS-MS) were evaluated by using the fading correction equation, which was obtained after irradiation with a 244 Cm source as the alpha-ray source having a specific radioactivity of 1,638.5 Bq/cm 2 including beta and gamma-ray (alpha energy of 5.763 and 5.805 MeV). Annealing at 80 deg C for 24 hours after irradiation for one month using BAS-MS should minimize the effect of the elapsed time, resulting in sufficient sensitivity. The results demonstrate new possibilities for radiation dosimetry offered by the use of an IP. (author)

  4. Holography and Entanglement in Flat Spacetime

    Li Wei; Takayanagi, Tadashi

    2011-01-01

    We propose a holographic correspondence of the flat spacetime based on the behavior of the entanglement entropy and the correlation functions. The holographic dual theory turns out to be highly nonlocal. We argue that after most part of the space is traced out, the reduced density matrix gives the maximal entropy and the correlation functions become trivial. We present a toy model for this holographic dual using a nonlocal scalar field theory that reproduces the same property of the entanglement entropy. Our conjecture is consistent with the entropy of Schwarzschild black holes in asymptotically flat spacetimes.

  5. First Space VLBI Observations and Images Using the VLBA and VSOP

    Romney, J. D.; Benson, J. M.; Claussen, M. J.; Desai, K. M.; Flatters, C.; Mioduszewski, A. J.; Ulvestad, J. S.

    1997-12-01

    The National Radio Astronomy Observatory (NRAO) is a participant in the VSOP Space VLBI mission, an international collaboration led by Japan's Institute of Space and Astronautical Science. NRAO has committed up to 30% of scheduled observing time on the Very Long Baseline Array (VLBA), and corresponding correlation resources, to Space VLBI observations. The NRAO Space VLBI Project, funded by NASA, has been working for several years to complete the necessary enhancements to the VLBA correlator and the AIPS image processing system. These developments were completed by the time of the successful launch of the VSOP mission's Halca spacecraft on 1997 February 12. As part of the in-orbit checkout phase, the first Space VLBI fringes from a VLBA observation were detected on 1997 June 12, and the VSOP mission's first images, in both the 1.6- and 5-GHz bands, were obtained shortly thereafter. In-orbit test observations continued through early September, with the first General Observing Time (GOT) scientific observations beginning in July. Through mid-October, a total of 20 Space VLBI observations, comprising 190 hours, had been completed at the VLBA correlator. This paper reviews the unique features of correlation and imaging of Space VLBI observations. These include, for correlation, the ephemeris for an orbiting VLBI ``station'' which is not fixed on the surface of the earth, and the requirement to close the loop on the phase-transfer process from a frequency standard on the ground to the spacecraft. Images from a number of early tests and scientific observations are presented. NRAO's user-support program, providing expert assistance in data analysis to Space VLBI observers, is also described.

  6. Color Image Segmentation Based on Different Color Space Models Using Automatic GrabCut

    Dina Khattab

    2014-01-01

    Full Text Available This paper presents a comparative study using different color spaces to evaluate the performance of color image segmentation using the automatic GrabCut technique. GrabCut is considered as one of the semiautomatic image segmentation techniques, since it requires user interaction for the initialization of the segmentation process. The automation of the GrabCut technique is proposed as a modification of the original semiautomatic one in order to eliminate the user interaction. The automatic GrabCut utilizes the unsupervised Orchard and Bouman clustering technique for the initialization phase. Comparisons with the original GrabCut show the efficiency of the proposed automatic technique in terms of segmentation, quality, and accuracy. As no explicit color space is recommended for every segmentation problem, automatic GrabCut is applied with RGB, HSV, CMY, XYZ, and YUV color spaces. The comparative study and experimental results using different color images show that RGB color space is the best color space representation for the set of the images used.

  7. The application of heliospheric imaging to space weather operations: Lessons learned from published studies

    Harrison, Richard A.; Davies, Jackie A.; Biesecker, Doug; Gibbs, Mark

    2017-08-01

    The field of heliospheric imaging has matured significantly over the last 10 years—corresponding, in particular, to the launch of NASA's STEREO mission and the successful operation of the heliospheric imager (HI) instruments thereon. In parallel, this decade has borne witness to a marked increase in concern over the potentially damaging effects of space weather on space and ground-based technological assets, and the corresponding potential threat to human health, such that it is now under serious consideration at governmental level in many countries worldwide. Hence, in a political climate that recognizes the pressing need for enhanced operational space weather monitoring capabilities most appropriately stationed, it is widely accepted, at the Lagrangian L1 and L5 points, it is timely to assess the value of heliospheric imaging observations in the context of space weather operations. To this end, we review a cross section of the scientific analyses that have exploited heliospheric imagery—particularly from STEREO/HI—and discuss their relevance to operational predictions of, in particular, coronal mass ejection (CME) arrival at Earth and elsewhere. We believe that the potential benefit of heliospheric images to the provision of accurate CME arrival predictions on an operational basis, although as yet not fully realized, is significant and we assert that heliospheric imagery is central to any credible space weather mission, particularly one located at a vantage point off the Sun-Earth line.

  8. Improving the Calibration of Image Sensors Based on IOFBs, Using Differential Gray-Code Space Encoding

    Carlos Luna Vázquez

    2012-07-01

    Full Text Available This paper presents a fast calibration method to determine the transfer function for spatial correspondences in image transmission devices with Incoherent Optical Fiber Bundles (IOFBs, by performing a scan of the input, using differential patterns generated from a Gray code (Differential Gray-Code Space Encoding, DGSE. The results demonstrate that this technique provides a noticeable reduction in processing time and better quality of the reconstructed image compared to other, previously employed techniques, such as point or fringe scanning, or even other known space encoding techniques.

  9. Image processing improvement for optical observations of space debris with the TAROT telescopes

    Thiebaut, C.; Theron, S.; Richard, P.; Blanchet, G.; Klotz, A.; Boër, M.

    2016-07-01

    CNES is involved in the Inter-Agency Space Debris Coordination Committee (IADC) and is observing space debris with two robotic ground based fully automated telescopes called TAROT and operated by the CNRS. An image processing algorithm devoted to debris detection in geostationary orbit is implemented in the standard pipeline. Nevertheless, this algorithm is unable to deal with debris tracking mode images, this mode being the preferred one for debris detectability. We present an algorithm improvement for this mode and give results in terms of false detection rate.

  10. Edema in the retropharyngeal space associated with head and neck tumors: CT imaging characteristics

    Kurihara, Noriko; Nakamura, Mamoru; Tsuda, Masashi; Saito, Haruo; Takahashi, Shoki; Higano, Shuichi

    2005-01-01

    To determine computed tomographic (CT) imaging characteristics of retropharygeal edema, we reviewed CT images in 18 patients with head and neck tumors. Retropharyngeal edema spread craniocaudally between soft palate and upper half of thyroid cartilage in all patients. No edema fluid extended above soft palate and below thyroid cartilage. Horizontally, it spread symmetrically in ten and asymmetrically in eight patients. Predominance in asymmetrical retropharyngeal edema was found on the same side as that of unilateral predominance both in lymph nodes enlargement and jugular vein stenosis/occlusion. All patients had edema also in other cervical spaces. Edema of retropharyngeal and other spaces fluctuated synchronously. In 14 patients, as primary lesion and/or cervical lymph nodes regressed, retropharyngeal edema disappeared or decreased. Retropharyngeal edema had some imaging characteristics. With knowledge of that, we could avoid diagnostic confusion when evaluating head and neck CT images. (orig.)

  11. 3D flat holography: entropy and logarithmic corrections

    Bagchi, Arjun; Basu, Rudranil

    2014-01-01

    We compute the leading corrections to the Bekenstein-Hawking entropy of the Flat Space Cosmological (FSC) solutions in 3D flat spacetimes, which are the flat analogues of the BTZ black holes in AdS 3 . The analysis is done by a computation of density of states in the dual 2D Galilean Conformal Field Theory and the answer obtained by this matches with the limiting value of the expected result for the BTZ inner horizon entropy as well as what is expected for a generic thermodynamic system. Along the way, we also develop other aspects of holography of 3D flat spacetimes

  12. Flat Files - JSNP | LSDB Archive [Life Science Database Archive metadata

    Full Text Available switchLanguage; BLAST Search Image Search Home About Archive Update History Data ... Data file File name: jsnp_flat_files File URL: ftp://ftp.biosciencedbc.jp/archiv...his Database Database Description Download License Update History of This Database Site Policy | Contact Us Flat Files - JSNP | LSDB Archive ...

  13. Determining Plane-Sweep Sampling Points in Image Space Using the Cross-Ratio for Image-Based Depth Estimation

    Ruf, B.; Erdnuess, B.; Weinmann, M.

    2017-08-01

    With the emergence of small consumer Unmanned Aerial Vehicles (UAVs), the importance and interest of image-based depth estimation and model generation from aerial images has greatly increased in the photogrammetric society. In our work, we focus on algorithms that allow an online image-based dense depth estimation from video sequences, which enables the direct and live structural analysis of the depicted scene. Therefore, we use a multi-view plane-sweep algorithm with a semi-global matching (SGM) optimization which is parallelized for general purpose computation on a GPU (GPGPU), reaching sufficient performance to keep up with the key-frames of input sequences. One important aspect to reach good performance is the way to sample the scene space, creating plane hypotheses. A small step size between consecutive planes, which is needed to reconstruct details in the near vicinity of the camera may lead to ambiguities in distant regions, due to the perspective projection of the camera. Furthermore, an equidistant sampling with a small step size produces a large number of plane hypotheses, leading to high computational effort. To overcome these problems, we present a novel methodology to directly determine the sampling points of plane-sweep algorithms in image space. The use of the perspective invariant cross-ratio allows us to derive the location of the sampling planes directly from the image data. With this, we efficiently sample the scene space, achieving higher sampling density in areas which are close to the camera and a lower density in distant regions. We evaluate our approach on a synthetic benchmark dataset for quantitative evaluation and on a real-image dataset consisting of aerial imagery. The experiments reveal that an inverse sampling achieves equal and better results than a linear sampling, with less sampling points and thus less runtime. Our algorithm allows an online computation of depth maps for subsequences of five frames, provided that the relative

  14. DETERMINING PLANE-SWEEP SAMPLING POINTS IN IMAGE SPACE USING THE CROSS-RATIO FOR IMAGE-BASED DEPTH ESTIMATION

    B. Ruf

    2017-08-01

    Full Text Available With the emergence of small consumer Unmanned Aerial Vehicles (UAVs, the importance and interest of image-based depth estimation and model generation from aerial images has greatly increased in the photogrammetric society. In our work, we focus on algorithms that allow an online image-based dense depth estimation from video sequences, which enables the direct and live structural analysis of the depicted scene. Therefore, we use a multi-view plane-sweep algorithm with a semi-global matching (SGM optimization which is parallelized for general purpose computation on a GPU (GPGPU, reaching sufficient performance to keep up with the key-frames of input sequences. One important aspect to reach good performance is the way to sample the scene space, creating plane hypotheses. A small step size between consecutive planes, which is needed to reconstruct details in the near vicinity of the camera may lead to ambiguities in distant regions, due to the perspective projection of the camera. Furthermore, an equidistant sampling with a small step size produces a large number of plane hypotheses, leading to high computational effort. To overcome these problems, we present a novel methodology to directly determine the sampling points of plane-sweep algorithms in image space. The use of the perspective invariant cross-ratio allows us to derive the location of the sampling planes directly from the image data. With this, we efficiently sample the scene space, achieving higher sampling density in areas which are close to the camera and a lower density in distant regions. We evaluate our approach on a synthetic benchmark dataset for quantitative evaluation and on a real-image dataset consisting of aerial imagery. The experiments reveal that an inverse sampling achieves equal and better results than a linear sampling, with less sampling points and thus less runtime. Our algorithm allows an online computation of depth maps for subsequences of five frames, provided that

  15. PSF Estimation of Space-Variant Ultra-Wide Field of View Imaging Systems

    Petr Janout

    2017-02-01

    Full Text Available Ultra-wide-field of view (UWFOV imaging systems are affected by various aberrations, most of which are highly angle-dependent. A description of UWFOV imaging systems, such as microscopy optics, security camera systems and other special space-variant imaging systems, is a difficult task that can be achieved by estimating the Point Spread Function (PSF of the system. This paper proposes a novel method for modeling the space-variant PSF of an imaging system using the Zernike polynomials wavefront description. The PSF estimation algorithm is based on obtaining field-dependent expansion coefficients of the Zernike polynomials by fitting real image data of the analyzed imaging system using an iterative approach in an initial estimate of the fitting parameters to ensure convergence robustness. The method is promising as an alternative to the standard approach based on Shack–Hartmann interferometry, since the estimate of the aberration coefficients is processed directly in the image plane. This approach is tested on simulated and laboratory-acquired image data that generally show good agreement. The resulting data are compared with the results of other modeling methods. The proposed PSF estimation method provides around 5% accuracy of the optical system model.

  16. A Space-Time Periodic Task Model for Recommendation of Remote Sensing Images

    Xiuhong Zhang

    2018-01-01

    Full Text Available With the rapid development of remote sensing technology, the quantity and variety of remote sensing images are growing so quickly that proactive and personalized access to data has become an inevitable trend. One of the active approaches is remote sensing image recommendation, which can offer related image products to users according to their preference. Although multiple studies on remote sensing retrieval and recommendation have been performed, most of these studies model the user profiles only from the perspective of spatial area or image features. In this paper, we propose a spatiotemporal recommendation method for remote sensing data based on the probabilistic latent topic model, which is named the Space-Time Periodic Task model (STPT. User retrieval behaviors of remote sensing images are represented as mixtures of latent tasks, which act as links between users and images. Each task is associated with the joint probability distribution of space, time and image characteristics. Meanwhile, the von Mises distribution is introduced to fit the distribution of tasks over time. Then, we adopt Gibbs sampling to learn the random variables and parameters and present the inference algorithm for our model. Experiments show that the proposed STPT model can improve the capability and efficiency of remote sensing image data services.

  17. Non-Quality Controlled Lightning Imaging Sensor (LIS) on International Space Station (ISS) Science Data Vb0

    National Aeronautics and Space Administration — The Non-Quality Controlled Lightning Imaging Sensor (LIS) on International Space Station (ISS) Science Data were collected by the LIS instrument on the ISS used to...

  18. Non-Quality Controlled Lightning Imaging Sensor (LIS) on International Space Station (ISS) Provisional Science Data Vp0

    National Aeronautics and Space Administration — The International Space Station (ISS) Lightning Imaging Sensor (LIS) datasets were collected by the LIS instrument on the ISS used to detect the distribution and...

  19. High-Sensitivity Semiconductor Photocathodes for Space-Born UV Photon-Counting and Imaging, Phase I

    National Aeronautics and Space Administration — Many UV photon-counting and imaging applications, including space-borne astronomy, missile tracking and guidance, UV spectroscopy for chemical/biological...

  20. CT and MR imaging anatomy of the fascia in the pelvic extraperitoneal space

    Nagayoshi, Kensuke

    1993-01-01

    CT and MRI anatomy of the fascia in the pelvic extraperitoneal space has not been established. CT and some MR imagings of nine patients who received irradiation to the pelvis and of eleven patients who received transarterial infusion for urinary bladder carcinoma were studied about the anterior and posterior attachment sites of the coccygeus muscle, the sacrouterine ligament and the lateral ligament. Observing the course of the inferior gluteal artery, the author set up three axial levels: (a), (b) and (c) levels, where the artery passes in front of the piriformis muscle, just gets over the coccygeus muscle and over the sacrospinous ligament, respectively. At (b) and (c) levels, the posterior attachment site of the sacrouterine ligament was the coccygeus muscle and the posterior attachment site of the lateral ligament was the sacrouterine ligament. By these ligaments, the pelvic extraperitoneal space was divided into three compartments; the prevesical, the perivesical and the perirectal spaces. The prevesical space was limited by the coccygeus muscle and the sacrouterine ligament posteriorly, the perivesical space was limited by the sacrouterine ligament and the lateral ligament posteriorly, and the perirectal space was surrounded by the sacrouterine ligament and the coccygeus muscle. On the coronal image through the level slightly posterior to the anus, the sacrouterine ligament attached to the levator ani muscle at the lateral third like a screen. On the basis of these results, new axial and coronal models of the pelvic extraperitoneal space are presented, which are useful for understanding the location and spread of the lesion. (author)

  1. Application of a Near Infrared Imaging System for Thermographic Imaging of the Space Shuttle during Hypersonic Re-Entry

    Zalameda, Joseph N.; Tietjen, Alan B.; Horvath, Thomas J.; Tomek, Deborah M.; Gibson, David M.; Taylor, Jeff C.; Tack, Steve; Bush, Brett C.; Mercer, C. David; Shea, Edward J.

    2010-01-01

    High resolution calibrated near infrared (NIR) imagery was obtained of the Space Shuttle s reentry during STS-119, STS-125, and STS-128 missions. The infrared imagery was collected using a US Navy NP-3D Orion aircraft using a long-range infrared optical package referred to as Cast Glance. The slant ranges between the Space Shuttle and Cast Glance were approximately 26-41 nautical miles at point of closest approach. The Hypersonic Thermodynamic Infrared Measurements (HYTHIRM) project was a NASA Langley led endeavor sponsored by the NASA Engineering Safety Center, the Space Shuttle Program Office and the NASA Aeronautics Research Mission Directorate to demonstrate a quantitative thermal imaging capability. HYTHIRM required several mission tools to acquire the imagery. These tools include pre-mission acquisition simulations of the Shuttle trajectory in relationship to the Cast Glance aircraft flight path, radiance modeling to predict the infrared response of the Shuttle, and post mission analysis tools to process the infrared imagery to quantitative temperature maps. The spatially resolved global thermal measurements made during the Shuttle s hypersonic reentry provides valuable flight data for reducing the uncertainty associated with present day ground-to-flight extrapolation techniques and current state-of-the-art empirical boundary-layer transition or turbulent heating prediction methods. Laminar and turbulent flight data is considered critical for the development of turbulence models supporting NASA s next-generation spacecraft. This paper will provide the motivation and details behind the use of an upgraded NIR imaging system used onboard a Navy Cast Glance aircraft and describe the characterizations and procedures performed to obtain quantitative temperature maps. A brief description and assessment will be provided of the previously used analog NIR camera along with image examples from Shuttle missions STS-121, STS-115, and solar tower test. These thermal

  2. MR imaging findings of leiomyoma in the prevesical space: case report

    Whang, In Yong; Jung, Seung Eun; Lee, Jae Mun; Hahn, Seong Tai

    2003-01-01

    Leiomyomas most frequently occur in the genitourinary and gastrointestinal system. This report describes the clinical and imaging findings of a leiomyoma originating in the prevesical space, a rare location. The mass abutted the fundus of the uterus, but after the correct identification of feeding vessels from the right iliac artery, prevesical leiomyoma was diagnosed radiologically

  3. MR imaging findings of leiomyoma in the prevesical space: case report

    Whang, In Yong; Jung, Seung Eun; Lee, Jae Mun; Hahn, Seong Tai [College of Medicine, Catholic Univ., Seoul (Korea, Republic of)

    2003-10-01

    Leiomyomas most frequently occur in the genitourinary and gastrointestinal system. This report describes the clinical and imaging findings of a leiomyoma originating in the prevesical space, a rare location. The mass abutted the fundus of the uterus, but after the correct identification of feeding vessels from the right iliac artery, prevesical leiomyoma was diagnosed radiologically.

  4. Perceptual quality of color images of natural scenes transformed in CIELUV color space

    Fedorovskaya, E.A.; Blommaert, F.J.J.; Ridder, de H.; Eschbach, R.; Braun, K.

    1997-01-01

    Transformations of digitized color images in perceptually-uniform CIELUV color space and their perceptual relevance were investigated. Chroma veriation was chosen as the first step of a series of investigations into possible transformations (including lightness, hue-angle, chroma, ect.) To obtain

  5. Perceptual quality of color images of natural scenes transformed in CIELUV color space

    Fedorovskaya, E.A.; Blommaert, F.J.J.; Ridder, de H.

    1993-01-01

    Transformations of digitized color images in perceptually-uniform CIELUV color space and their perceptual relevance were investigated. Chroma variation was chosen as the first step of a series of investigations into possible transformations (including lightness, hue-angle, chroma, etc.). To obtain

  6. Micro-digital sun sensor: an imaging sensor for space applications

    Xie, N.; Theuwissen, A.J.P.; Büttgen, B.; Hakkesteegt, H.C.; Jasen, H.; Leijtens, J.A.P.

    2010-01-01

    Micro-Digital Sun Sensor is an attitude sensor which senses relative position of micro-satellites to the sun in space. It is composed of a solar cell power supply, a RF communication block and an imaging chip which is called APS+. The APS+ integrates a CMOS Active Pixel Sensor (APS) of 512×512

  7. The OMERACT-RAMRIS Rheumatoid Arthritis Magnetic Resonance Imaging Joint Space Narrowing Score

    Møller Døhn, Uffe; Conaghan, Philip G; Eshed, Iris

    2014-01-01

    To test the intrareader and interreader reliability of assessment of joint space narrowing (JSN) in rheumatoid arthritis (RA) wrist and metacarpophalangeal (MCP) joints on magnetic resonance imaging (MRI) and computed tomography (CT) using the newly proposed OMERACT-RAMRIS JSN scoring method...

  8. CT with a CMOS flat panel detector integrated on the YAP-(S)PET scanner for in vivo small animal imaging

    Di Domenico, Giovanni; Cesca, Nicola; Zavattini, Guido; Auricchio, Natalia; Gambaccini, Mauro

    2007-01-01

    Several research groups are pursuing multimodality simultaneous functional and morphological imaging. In this line of research the high resolution YAP-(S)PET small animal integrated PET-SPECT imaging system, constructed by our group of medical physics at the University of Ferrara, is being upgraded with a computed tomography (CT). In this way it will be possible to perform in vivo molecular and genomic imaging studies on small animals (such as mice and rats) and at the same time obtain morphological information necessary for both attenuation correction and accurate localization of the region under investigation. We have take simultaneous PET-CT and SPECT-CT images of phantoms obtained with a single scanner

  9. Scale-space for empty catheter segmentation in PCI fluoroscopic images.

    Bacchuwar, Ketan; Cousty, Jean; Vaillant, Régis; Najman, Laurent

    2017-07-01

    In this article, we present a method for empty guiding catheter segmentation in fluoroscopic X-ray images. The guiding catheter, being a commonly visible landmark, its segmentation is an important and a difficult brick for Percutaneous Coronary Intervention (PCI) procedure modeling. In number of clinical situations, the catheter is empty and appears as a low contrasted structure with two parallel and partially disconnected edges. To segment it, we work on the level-set scale-space of image, the min tree, to extract curve blobs. We then propose a novel structural scale-space, a hierarchy built on these curve blobs. The deep connected component, i.e. the cluster of curve blobs on this hierarchy, that maximizes the likelihood to be an empty catheter is retained as final segmentation. We evaluate the performance of the algorithm on a database of 1250 fluoroscopic images from 6 patients. As a result, we obtain very good qualitative and quantitative segmentation performance, with mean precision and recall of 80.48 and 63.04% respectively. We develop a novel structural scale-space to segment a structured object, the empty catheter, in challenging situations where the information content is very sparse in the images. Fully-automatic empty catheter segmentation in X-ray fluoroscopic images is an important and preliminary step in PCI procedure modeling, as it aids in tagging the arrival and removal location of other interventional tools.

  10. STEP: Self-supporting tailored k-space estimation for parallel imaging reconstruction.

    Zhou, Zechen; Wang, Jinnan; Balu, Niranjan; Li, Rui; Yuan, Chun

    2016-02-01

    A new subspace-based iterative reconstruction method, termed Self-supporting Tailored k-space Estimation for Parallel imaging reconstruction (STEP), is presented and evaluated in comparison to the existing autocalibrating method SPIRiT and calibrationless method SAKE. In STEP, two tailored schemes including k-space partition and basis selection are proposed to promote spatially variant signal subspace and incorporated into a self-supporting structured low rank model to enforce properties of locality, sparsity, and rank deficiency, which can be formulated into a constrained optimization problem and solved by an iterative algorithm. Simulated and in vivo datasets were used to investigate the performance of STEP in terms of overall image quality and detail structure preservation. The advantage of STEP on image quality is demonstrated by retrospectively undersampled multichannel Cartesian data with various patterns. Compared with SPIRiT and SAKE, STEP can provide more accurate reconstruction images with less residual aliasing artifacts and reduced noise amplification in simulation and in vivo experiments. In addition, STEP has the capability of combining compressed sensing with arbitrary sampling trajectory. Using k-space partition and basis selection can further improve the performance of parallel imaging reconstruction with or without calibration signals. © 2015 Wiley Periodicals, Inc.

  11. Software Simulates Sight: Flat Panel Mura Detection

    2008-01-01

    In the increasingly sophisticated world of high-definition flat screen monitors and television screens, image clarity and the elimination of distortion are paramount concerns. As the devices that reproduce images become more and more sophisticated, so do the technologies that verify their accuracy. By simulating the manner in which a human eye perceives and interprets a visual stimulus, NASA scientists have found ways to automatically and accurately test new monitors and displays. The Spatial Standard Observer (SSO) software metric, developed by Dr. Andrew B. Watson at Ames Research Center, measures visibility and defects in screens, displays, and interfaces. In the design of such a software tool, a central challenge is determining which aspects of visual function to include while accuracy and generality are important, relative simplicity of the software module is also a key virtue. Based on data collected in ModelFest, a large cooperative multi-lab project hosted by the Optical Society of America, the SSO simulates a simplified model of human spatial vision, operating on a pair of images that are viewed at a specific viewing distance with pixels having a known relation to luminance. The SSO measures the visibility of foveal spatial patterns, or the discriminability of two patterns, by incorporating only a few essential components of vision. These components include local contrast transformation, a contrast sensitivity function, local masking, and local pooling. By this construction, the SSO provides output in units of "just noticeable differences" (JND) a unit of measure based on the assumed smallest difference of sensory input detectable by a human being. Herein is the truly amazing ability of the SSO, while conventional methods can manipulate images, the SSO models human perception. This set of equations actually defines a mathematical way of working with an image that accurately reflects the way in which the human eye and mind behold a stimulus. The SSO is

  12. PETRA, MSVAT-SPACE and SEMAC sequences for metal artefact reduction in dental MR imaging

    Hilgenfeld, Tim; Heil, Alexander; Bendszus, Martin; Prager, Marcel; Heiland, Sabine; Schwindling, Franz Sebastian; Rammelsberg, Peter; Nittka, Mathias; Grodzki, David

    2017-01-01

    Dental MRI is often impaired by artefacts due to metallic dental materials. Several sequences were developed to reduce susceptibility artefacts. Here, we evaluated a set of sequences for artefact reduction for dental MRI for the first time. Artefact volume, signal-to-noise ratio (SNR) and image quality were assessed on a 3-T MRI for pointwise encoding time reduction with radial acquisition (PETRA), multiple-slab acquisition with view angle tilting gradient, based on a sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) sequence (MSVAT-SPACE), slice-encoding for metal-artefact correction (SEMAC) and compared to a standard SPACE and a standard turbo-spin-echo (TSE) sequence. Field-of-view and acquisition times were chosen to enable in vivo application. Two implant-supported prostheses were tested (porcelain fused to metal non-precious alloy and monolithic zirconia). Smallest artefact was measured for TSE sequences with no difference between the standard TSE and the SEMAC. MSVAT-SPACE reduced artefacts about 56% compared to the standard SPACE. Effect of the PETRA was dependent on sample used. Image quality and SNR were comparable for all sequences except PETRA, which yielded poor results. There is no benefit in terms of artefact reduction for SEMAC compared to standard TSE. Usage of MSVAT-SPACE is advantageous since artefacts are reduced and higher resolution is achieved. (orig.)

  13. PETRA, MSVAT-SPACE and SEMAC sequences for metal artefact reduction in dental MR imaging

    Hilgenfeld, Tim; Heil, Alexander; Bendszus, Martin [Heidelberg University Hospital, Department of Neuroradiology, Heidelberg (Germany); Prager, Marcel; Heiland, Sabine [Heidelberg University Hospital, Department of Neuroradiology, Heidelberg (Germany); Heidelberg University Hospital, Section of Experimental Radiology, Heidelberg (Germany); Schwindling, Franz Sebastian; Rammelsberg, Peter [Heidelberg University Hospital, Department of Prosthodontics, Heidelberg (Germany); Nittka, Mathias; Grodzki, David [Siemens Healthcare GmbH, Erlangen (Germany)

    2017-12-15

    Dental MRI is often impaired by artefacts due to metallic dental materials. Several sequences were developed to reduce susceptibility artefacts. Here, we evaluated a set of sequences for artefact reduction for dental MRI for the first time. Artefact volume, signal-to-noise ratio (SNR) and image quality were assessed on a 3-T MRI for pointwise encoding time reduction with radial acquisition (PETRA), multiple-slab acquisition with view angle tilting gradient, based on a sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) sequence (MSVAT-SPACE), slice-encoding for metal-artefact correction (SEMAC) and compared to a standard SPACE and a standard turbo-spin-echo (TSE) sequence. Field-of-view and acquisition times were chosen to enable in vivo application. Two implant-supported prostheses were tested (porcelain fused to metal non-precious alloy and monolithic zirconia). Smallest artefact was measured for TSE sequences with no difference between the standard TSE and the SEMAC. MSVAT-SPACE reduced artefacts about 56% compared to the standard SPACE. Effect of the PETRA was dependent on sample used. Image quality and SNR were comparable for all sequences except PETRA, which yielded poor results. There is no benefit in terms of artefact reduction for SEMAC compared to standard TSE. Usage of MSVAT-SPACE is advantageous since artefacts are reduced and higher resolution is achieved. (orig.)

  14. Space-borne observation of mesospheric bore by Visible and near Infrared Spectral Imager onboard the International Space Station

    Hozumi, Y.; Saito, A.; Sakanoi, T.; Yamazaki, A.; Hosokawa, K.

    2017-12-01

    Mesospheric bores were observed by Visible and near Infrared Spectral Imager (VISI) of the ISS-IMAP mission (Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere mapping mission from the International Space Station) in O2 airglow at 762 nm wavelength. The mesospheric bore is moving front of sharp jump followed by undulations or turbulence in the mesopause region. Since previous studies of mesospheric bore were mainly based on ground-based airglow imaging that is limited in field-of-view and observing site, little is known about its horizontal extent and global behavior. Space-borne imaging by ISS-IMAP/VISI provides an opportunity to study the mesospheric bore with a wide field-of-view and global coverage. A mesospheric bore was captured by VISI in two consecutive paths on 9 July 2015 over the south of African continent (48ºS - 54ºS and 15ºE). The wave front aligned with south-north direction and propagated to west. The phase velocity and wave length of the following undulation were estimated to 100 m/s and 30 km, respectively. Those parameters are similar to those reported by previous studies. 30º anti-clockwise rotation of the wave front was recognized in 100 min. Another mesospheric bore was captured on 9 May 2013 over the south Atlantic ocean (35ºS - 43ºS and 24ºW - 1ºE) with more than 2,200 km horizontal extent of wave front. The wave front aligned with southeast-northwest direction. Because the following undulation is recognized in the southwest side of the wave front, it is estimated to propagate to northeast direction. The wave front was modulated with 1,000 km wave length. This modulation implies inhomogeneity of the phase velocity.

  15. Detection of cold gas releases in space via low energy neutral atom imaging

    McComas, D.J.; Funsten, H.O.; Moore, K.R.; Scime, E.E.; Thomsen, M.F.

    1993-01-01

    Low energy neutral atoms (LENAs) are produced in space plasmas by charge exchange between the ambient magnetospheric plasma ions and cold neutral atoms. Under normal conditions these cold neutrals come from the terrestrial geocorona, a shroud of few-eV hydrogen atoms surrounding the Earth. As a consequence of this charge exchange, it has become possible to remotely image many regions of the magnetosphere for the first time utilizing recently developed LENA imaging technology. In addition to the natural hydrogen geocorona, conventional explosions and maneuvering thruster firings can also introduce large amounts of cold gas into the space environment. In this paper the authors examine whether such potentially clandestine activities could also be remotely observed for the first time via LENA imaging. First, they examine the fluxes of LENAs produced in the space environment from a conventional explosion. Then they review the present state of the art in the emerging field of LENA detection and imaging. Recent work has shown that LENAs can be imaged by first converting the neutrals to ions with ultra-thin (10s of angstrom) foils and then electrostatically analyzing these newly created ions to reject the large (> 10 10 cm -2 s -1 ) UV background to which the low energy detectors are sensitive. They conclude that the sensitivities for present LENA imager designs may be just adequate for detecting some man-made releases. With additional improvements in LENA detection capabilities, this technique could become an important new method for monitoring for conventional explosions, as well as other man-made neutral releases, in the space environment

  16. Streak detection and analysis pipeline for space-debris optical images

    Virtanen, Jenni; Poikonen, Jonne; Säntti, Tero; Komulainen, Tuomo; Torppa, Johanna; Granvik, Mikael; Muinonen, Karri; Pentikäinen, Hanna; Martikainen, Julia; Näränen, Jyri; Lehti, Jussi; Flohrer, Tim

    2016-04-01

    We describe a novel data-processing and analysis pipeline for optical observations of moving objects, either of natural (asteroids, meteors) or artificial origin (satellites, space debris). The monitoring of the space object populations requires reliable acquisition of observational data, to support the development and validation of population models and to build and maintain catalogues of orbital elements. The orbital catalogues are, in turn, needed for the assessment of close approaches (for asteroids, with the Earth; for satellites, with each other) and for the support of contingency situations or launches. For both types of populations, there is also increasing interest to detect fainter objects corresponding to the small end of the size distribution. The ESA-funded StreakDet (streak detection and astrometric reduction) activity has aimed at formulating and discussing suitable approaches for the detection and astrometric reduction of object trails, or streaks, in optical observations. Our two main focuses are objects in lower altitudes and space-based observations (i.e., high angular velocities), resulting in long (potentially curved) and faint streaks in the optical images. In particular, we concentrate on single-image (as compared to consecutive frames of the same field) and low-SNR detection of objects. Particular attention has been paid to the process of extraction of all necessary information from one image (segmentation), and subsequently, to efficient reduction of the extracted data (classification). We have developed an automated streak detection and processing pipeline and demonstrated its performance with an extensive database of semisynthetic images simulating streak observations both from ground-based and space-based observing platforms. The average processing time per image is about 13 s for a typical 2k-by-2k image. For long streaks (length >100 pixels), primary targets of the pipeline, the detection sensitivity (true positives) is about 90% for

  17. Image to physical space registration of supine breast MRI for image guided breast surgery

    Conley, Rebekah H.; Meszoely, Ingrid M.; Pheiffer, Thomas S.; Weis, Jared A.; Yankeelov, Thomas E.; Miga, Michael I.

    2014-03-01

    Breast conservation therapy (BCT) is a desirable option for many women diagnosed with early stage breast cancer and involves a lumpectomy followed by radiotherapy. However, approximately 50% of eligible women will elect for mastectomy over BCT despite equal survival benefit (provided margins of excised tissue are cancer free) due to uncertainty in outcome with regards to complete excision of cancerous cells, risk of local recurrence, and cosmesis. Determining surgical margins intraoperatively is difficult and achieving negative margins is not as robust as it needs to be, resulting in high re-operation rates and often mastectomy. Magnetic resonance images (MRI) can provide detailed information about tumor margin extents, however diagnostic images are acquired in a fundamentally different patient presentation than that used in surgery. Therefore, the high quality diagnostic MRIs taken in the prone position with pendant breast are not optimal for use in surgical planning/guidance due to the drastic shape change between preoperative images and the common supine surgical position. This work proposes to investigate the value of supine MRI in an effort to localize tumors intraoperatively using image-guidance. Mock intraoperative setups (realistic patient positioning in non-sterile environment) and preoperative imaging data were collected from a patient scheduled for a lumpectomy. The mock intraoperative data included a tracked laser range scan of the patient's breast surface, tracked center points of MR visible fiducials on the patient's breast, and tracked B-mode ultrasound and strain images. The preoperative data included a supine MRI with visible fiducial markers. Fiducial markers localized in the MRI were rigidly registered to their mock intraoperative counterparts using an optically tracked stylus. The root mean square (RMS) fiducial registration error using the tracked markers was 3.4mm. Following registration, the average closest point distance between the MR

  18. An image compression method for space multispectral time delay and integration charge coupled device camera

    Li Jin; Jin Long-Xu; Zhang Ran-Feng

    2013-01-01

    Multispectral time delay and integration charge coupled device (TDICCD) image compression requires a low-complexity encoder because it is usually completed on board where the energy and memory are limited. The Consultative Committee for Space Data Systems (CCSDS) has proposed an image data compression (CCSDS-IDC) algorithm which is so far most widely implemented in hardware. However, it cannot reduce spectral redundancy in multispectral images. In this paper, we propose a low-complexity improved CCSDS-IDC (ICCSDS-IDC)-based distributed source coding (DSC) scheme for multispectral TDICCD image consisting of a few bands. Our scheme is based on an ICCSDS-IDC approach that uses a bit plane extractor to parse the differences in the original image and its wavelet transformed coefficient. The output of bit plane extractor will be encoded by a first order entropy coder. Low-density parity-check-based Slepian—Wolf (SW) coder is adopted to implement the DSC strategy. Experimental results on space multispectral TDICCD images show that the proposed scheme significantly outperforms the CCSDS-IDC-based coder in each band

  19. Imaging system for obtaining space- and time-resolved plasma images on TMX

    Koehler, H.A.; Frerking, C.E.

    1980-01-01

    A Reticon 50 x 50 photodiode array camera has been placed on Livermore's Tandem Mirror Experiment to view a 56-cm diameter plasma source of visible, vacuum-ultraviolet, and x-ray photons. The compact camera views the source through a pinhole, filters, a fiber optic coupler, a microchannel plate intensifier (MCPI), and a reducer. The images are digitized (at 3.3 MHz) and stored in a large, high-speed memory that has a capacity of 45 images. A local LSI-11 microprocessor provides immediate processing and display of the data. The data are also stored on floppy disks that can be further processed on the large Livermore Computer System. The temporal resolution is limited by the fastest MCPI gate. The number of images recorded is determined by the read-out time of the Reticon camera (minimum 0.9 msec). The spatial resolution of approximately 1.4 cm is fixed by the geometry and the pinhole of 0.025 cm. Typical high-quality color representation of some plasma images are included

  20. Research on spatial-variant property of bistatic ISAR imaging plane of space target

    Guo Bao-Feng; Wang Jun-Ling; Gao Mei-Guo

    2015-01-01

    The imaging plane of inverse synthetic aperture radar (ISAR) is the projection plane of the target. When taking an image using the range-Doppler theory, the imaging plane may have a spatial-variant property, which causes the change of scatter’s projection position and results in migration through resolution cells. In this study, we focus on the spatial-variant property of the imaging plane of a three-axis-stabilized space target. The innovative contributions are as follows. 1) The target motion model in orbit is provided based on a two-body model. 2) The instantaneous imaging plane is determined by the method of vector analysis. 3) Three Euler angles are introduced to describe the spatial-variant property of the imaging plane, and the image quality is analyzed. The simulation results confirm the analysis of the spatial-variant property. The research in this study is significant for the selection of the imaging segment, and provides the evidence for the following data processing and compensation algorithm. (paper)

  1. Interferometric and nonlinear-optical spectral-imaging techniques for outer space and live cells

    Itoh, Kazuyoshi

    2015-12-01

    Multidimensional signals such as the spectral images allow us to have deeper insights into the natures of objects. In this paper the spectral imaging techniques that are based on optical interferometry and nonlinear optics are presented. The interferometric imaging technique is based on the unified theory of Van Cittert-Zernike and Wiener-Khintchine theorems and allows us to retrieve a spectral image of an object in the far zone from the 3D spatial coherence function. The retrieval principle is explained using a very simple object. The promising applications to space interferometers for astronomy that are currently in progress will also be briefly touched on. An interesting extension of interferometric spectral imaging is a 3D and spectral imaging technique that records 4D information of objects where the 3D and spectral information is retrieved from the cross-spectral density function of optical field. The 3D imaging is realized via the numerical inverse propagation of the cross-spectral density. A few techniques suggested recently are introduced. The nonlinear optical technique that utilizes stimulated Raman scattering (SRS) for spectral imaging of biomedical targets is presented lastly. The strong signals of SRS permit us to get vibrational information of molecules in the live cell or tissue in real time. The vibrational information of unstained or unlabeled molecules is crucial especially for medical applications. The 3D information due to the optical nonlinearity is also the attractive feature of SRS spectral microscopy.

  2. Multiscale characterization of pore spaces using multifractals analysis of scanning electronic microscopy images of carbonates

    M. S. Jouini

    2011-12-01

    Full Text Available Pore spaces heterogeneity in carbonates rocks has long been identified as an important factor impacting reservoir productivity. In this paper, we study the heterogeneity of carbonate rocks pore spaces based on the image analysis of scanning electron microscopy (SEM data acquired at various magnifications. Sixty images of twelve carbonate samples from a reservoir in the Middle East were analyzed. First, pore spaces were extracted from SEM images using a segmentation technique based on watershed algorithm. Pores geometries revealed a multifractal behavior at various magnifications from 800x to 12 000x. In addition, the singularity spectrum provided quantitative values that describe the degree of heterogeneity in the carbonates samples. Moreover, for the majority of the analyzed samples, we found low variations (around 5% in the multifractal dimensions for magnifications between 1700x and 12 000x. Finally, these results demonstrate that multifractal analysis could be an appropriate tool for characterizing quantitatively the heterogeneity of carbonate pore spaces geometries. However, our findings show that magnification has an impact on multifractal dimensions, revealing the limit of applicability of multifractal descriptions for these natural structures.

  3. Fundamentals and applications of neutron imaging. Application part 3. Application of neutron imaging in aircraft, space rocket, car and gunpowder industries

    Ikeda, Yasushi

    2007-01-01

    Neutron imaging is applied to nondestructive test. Four neutron imaging facilities are used in Japan. The application examples of industries are listed in the table: space rocket, aircraft, car, liquid metal, and works of art. Neutron imaging of transportation equipments are illustrated as an application to industry. X-ray radiography testing (XRT) image and neutron radiography testing (NRT) image of turbine blade of aircraft engine, honeycomb structure of aircraft, helicopter rotor blade, trigger tube, separation nut of space rocket, carburetor of car, BMW engine, fireworks and ammunitions are illustrated. (S.Y.)

  4. Flat feet in children

    Vukašinović Zoran

    2009-01-01

    Full Text Available The authors describe flatfoot, as one of very frequent deformities in everyday medical practice. A special condition of the deformity associated with a calcaneal valgus position and complicated by a knee valgus position (as a consequence of non-treatment is described. Also, the precise anatomy of the longitudinal foot arches (medial and lateral, definition and classification of the deformity, clinical findings and therapeutic protocols are proposed. The authors especially emphasise that the need for having extensive knowledge on the differences between a flexible and rigid flatfoot, having in mind that the treatment of flexible flat foot is usually not necessary, while the treatment of rigid flatfoot is usually unavoidable.

  5. Neutron μstiX. Micrometer structure investigation with real space and reciprocal space crossover using neutron imaging detectors

    Muehlbauer, Martin Johann

    2013-07-19

    This work is concerned with the investigation of inhomogeneities in materials with length scales of the order of micrometers by means of neutrons. In real space this is done by neutron imaging methods measuring the transmitted signal while for Ultra Small Angle Neutron Scattering (USANS) the signal of the scattered neutrons is assigned to a spatial frequency distribution in reciprocal space. The part about neutron imaging is focused on time-resolved neutron radiography on an injection nozzle similar to the ones used for modern diesel truck engines. The associated experiments have been carried out at the neutron imaging facility ANTARES at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) of the Technische Universitaet Muenchen in Garching near Munich. Especially the demands on the detector system were high. Therefore different detection methods and detector configurations have been tested. On the one hand the detector should allow for a time resolution high enough to record the injection process lasting about 900 μs. On the other hand it needed to offer a spatial resolution sufficient to resolve the test oil inside the spray hole of a maximum diameter of less than 200 μm. An advanced aim of this work is the visualization of cavitation phenomena which may occur during the injection process inside of the spray hole. In order to operate the injector at conditions as close to reality as possible a high pressure pump supplying the injector with test oil at a pressure of 1600 bar was needed in addition to the specially developed control electronics, the recuperation tank and the exhaust gas equipment for the escaping atomized spray. A second part of the work describes USANS experiments based on the idea of Dr. Roland Gaehler and carried out at the instrument D11 at the Institut Laue-Langevin in Grenoble. For this purpose a specific multi-beam geometry was applied, where a multi-slit aperture replaced the standard source aperture and the sample aperture was

  6. Neutron μstiX. Micrometer structure investigation with real space and reciprocal space crossover using neutron imaging detectors

    Muehlbauer, Martin Johann

    2013-01-01

    This work is concerned with the investigation of inhomogeneities in materials with length scales of the order of micrometers by means of neutrons. In real space this is done by neutron imaging methods measuring the transmitted signal while for Ultra Small Angle Neutron Scattering (USANS) the signal of the scattered neutrons is assigned to a spatial frequency distribution in reciprocal space. The part about neutron imaging is focused on time-resolved neutron radiography on an injection nozzle similar to the ones used for modern diesel truck engines. The associated experiments have been carried out at the neutron imaging facility ANTARES at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) of the Technische Universitaet Muenchen in Garching near Munich. Especially the demands on the detector system were high. Therefore different detection methods and detector configurations have been tested. On the one hand the detector should allow for a time resolution high enough to record the injection process lasting about 900 μs. On the other hand it needed to offer a spatial resolution sufficient to resolve the test oil inside the spray hole of a maximum diameter of less than 200 μm. An advanced aim of this work is the visualization of cavitation phenomena which may occur during the injection process inside of the spray hole. In order to operate the injector at conditions as close to reality as possible a high pressure pump supplying the injector with test oil at a pressure of 1600 bar was needed in addition to the specially developed control electronics, the recuperation tank and the exhaust gas equipment for the escaping atomized spray. A second part of the work describes USANS experiments based on the idea of Dr. Roland Gaehler and carried out at the instrument D11 at the Institut Laue-Langevin in Grenoble. For this purpose a specific multi-beam geometry was applied, where a multi-slit aperture replaced the standard source aperture and the sample aperture was

  7. The image of public space on planned housing based on environmental and behavior cognition mapping (case study: Cemara Asri Estate)

    Nirfalini Aulia, Dwira; Zahara, Aina

    2018-03-01

    Public spaces in a planned housing is a place of social interaction for every visitor of public space. The research on public space image uses four public spaces that meet the criteria of public space such as pedestrian sidewalks, public park, water front and worship place. Research on the perception of public space is interesting to investigate because housing development is part of the forming of a society that should design with proper architectural considerations. The purpose of this research is to know the image of public space on the planned housing in Medan City based on the mapping of environmental and behavior cognition and to know the difference between the image that happened to four group respondent. The research method of architecture used in this research is a descriptive qualitative method with case study approach (most similar case). Analysis of data used using mental maps and questionnaires. Then the image of public space is formed based on the elements of public space, wayfinding, route choice, and movement. The image difference that occurs to the housing residents and architecture students, design and planning are outstanding, visitors to the public housing space is good, people who have never visited the public space is inadequate.

  8. On birecurrent spaces

    Rahman, M.S.

    1991-10-01

    A birecurrent space is defined with its classification and studied with involvement of Einstein, conformally flat, conformally symmetric and conformally recurrent spaces. A necessary and sufficient condition that a birecurrent space be recurrent is found. (author). 6 refs

  9. The architecture of a video image processor for the space station

    Yalamanchili, S.; Lee, D.; Fritze, K.; Carpenter, T.; Hoyme, K.; Murray, N.

    1987-01-01

    The architecture of a video image processor for space station applications is described. The architecture was derived from a study of the requirements of algorithms that are necessary to produce the desired functionality of many of these applications. Architectural options were selected based on a simulation of the execution of these algorithms on various architectural organizations. A great deal of emphasis was placed on the ability of the system to evolve and grow over the lifetime of the space station. The result is a hierarchical parallel architecture that is characterized by high level language programmability, modularity, extensibility and can meet the required performance goals.

  10. Flat Engineered Multichannel Reflectors

    V. S. Asadchy

    2017-09-01

    Full Text Available Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here, we introduce a concept of multichannel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions simultaneously. In particular, we reveal a possibility to engineer multichannel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three basic functionalities of such reflectors: specular, anomalous, and retroreflections. Multichannel response of a general flat reflector can be described by a combination of these functionalities. To demonstrate the potential of the introduced concept, we design and experimentally test three different multichannel reflectors: three- and five-channel retroreflectors and a three-channel power splitter. Furthermore, by extending the concept to reflectors supporting higher-order Floquet harmonics, we forecast the emergence of other multichannel flat devices, such as isolating mirrors, complex splitters, and multi-functional gratings.

  11. Flat Engineered Multichannel Reflectors

    Asadchy, V. S.; Díaz-Rubio, A.; Tcvetkova, S. N.; Kwon, D.-H.; Elsakka, A.; Albooyeh, M.; Tretyakov, S. A.

    2017-07-01

    Recent advances in engineered gradient metasurfaces have enabled unprecedented opportunities for light manipulation using optically thin sheets, such as anomalous refraction, reflection, or focusing of an incident beam. Here, we introduce a concept of multichannel functional metasurfaces, which are able to control incoming and outgoing waves in a number of propagation directions simultaneously. In particular, we reveal a possibility to engineer multichannel reflectors. Under the assumption of reciprocity and energy conservation, we find that there exist three basic functionalities of such reflectors: specular, anomalous, and retroreflections. Multichannel response of a general flat reflector can be described by a combination of these functionalities. To demonstrate the potential of the introduced concept, we design and experimentally test three different multichannel reflectors: three- and five-channel retroreflectors and a three-channel power splitter. Furthermore, by extending the concept to reflectors supporting higher-order Floquet harmonics, we forecast the emergence of other multichannel flat devices, such as isolating mirrors, complex splitters, and multi-functional gratings.

  12. Ex vivo imaging of early dental caries within the interproximal space

    Choo-Smith, Lin-P'ing; Hewko, Mark D.; Dufour, Marc L.; Fulton, Crystal; Qiu, Pingli; Gauthier, Bruno; Padioleau, Christian; Bisaillon, Charles-Etienne; Dong, Cecilia; Cleghorn, Blaine M.; Lamouche, Guy; Sowa, Michael G.

    2009-02-01

    Optical coherence tomography (OCT) is emerging as a technology that can potentially be used for the detection and monitoring of early dental enamel caries since it can provide high-resolution depth imaging of early lesions. To date, most caries detection optical technologies are well suited for examining caries at facial, lingual, incisal and occlusal surfaces. The approximal surfaces between adjacent teeth are difficult to examine due to lack of visual access and limited space for these new caries detection tools. Using a catheter-style probe developed at the NRC-Industrial Materials Institute, the probe was inserted into the interproximal space to examine the approximal surfaces with OCT imaging at 1310 nm. The probe was rotated continuously and translated axially to generate depth images in a spiral fashion. The probe was used in a mock tooth arch model consisting of extracted human teeth mounted with dental rope wax in their anatomically correct positions. With this ex vivo model, the probe provided images of the approximal surfaces revealing morphological structural details, regions of calculus, and especially regions of early dental caries (white spot lesions). Results were compared with those obtained from OCT imaging of individual samples where the approximal surfaces of extracted teeth are accessible on a lab-bench. Issues regarding access, regions of interest, and factors to be considered in an in vivo setting will be discussed. Future studies are aimed at using the probe in vivo with patient volunteers.

  13. Imaging in real and reciprocal space at the Diamond beamline I13

    Rau, C.; Wagner, U. H.; Vila-Comamala, J.; Bodey, A.; Parson, A.; García-Fernández, M.; Pešić, Z.; De Fanis, A.

    2016-01-01

    The Diamond Imaging and Coherence beamline I13 consists of two independent branchlines for imaging in real and reciprocal space. Different microscopies are available providing a range of spatial resolution from 5µm to potentially 5nm. The beamline operates in the energy range of 6-35keV covering different scientific areas such as biomedicine, materials science and geophysics. Several original devices have been developed at the beamline, such as the EXCALIBUR photon counting detector and the combined robot arms for coherent X-ray diffraction

  14. Artificial neural network for the determination of Hubble Space Telescope aberration from stellar images

    Barrett, Todd K.; Sandler, David G.

    1993-01-01

    An artificial-neural-network method, first developed for the measurement and control of atmospheric phase distortion, using stellar images, was used to estimate the optical aberration of the Hubble Space Telescope. A total of 26 estimates of distortion was obtained from 23 stellar images acquired at several secondary-mirror axial positions. The results were expressed as coefficients of eight orthogonal Zernike polynomials: focus through third-order spherical. For all modes other than spherical the measured aberration was small. The average spherical aberration of the estimates was -0.299 micron rms, which is in good agreement with predictions obtained when iterative phase-retrieval algorithms were used.

  15. Imaging in real and reciprocal space at the Diamond beamline I13

    Rau, C., E-mail: Christoph.rau@diamond.ac.uk [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, OX 11 0DE (United Kingdom); University of Manchester, School of Materials Grosvenor St., Manchester, M1 7HS (United Kingdom); Northwestern University School of Medicine, 303 E. Chicago Avenue, Chicago, IL 60611-3008 (United States); Wagner, U. H.; Vila-Comamala, J.; Bodey, A.; Parson, A.; García-Fernández, M.; Pešić, Z. [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, OX 11 0DE (United Kingdom); De Fanis, A. [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, OX 11 0DE (United Kingdom); European XFEL GmbH, Notkestraße 85, 22607 Hamburg (Germany)

    2016-01-28

    The Diamond Imaging and Coherence beamline I13 consists of two independent branchlines for imaging in real and reciprocal space. Different microscopies are available providing a range of spatial resolution from 5µm to potentially 5nm. The beamline operates in the energy range of 6-35keV covering different scientific areas such as biomedicine, materials science and geophysics. Several original devices have been developed at the beamline, such as the EXCALIBUR photon counting detector and the combined robot arms for coherent X-ray diffraction.

  16. Research on lossless compression of true color RGB image with low time and space complexity

    Pan, ShuLin; Xie, ChengJun; Xu, Lin

    2008-12-01

    Eliminating correlated redundancy of space and energy by using a DWT lifting scheme and reducing the complexity of the image by using an algebraic transform among the RGB components. An improved Rice Coding algorithm, in which presents an enumerating DWT lifting scheme that fits any size images by image renormalization has been proposed in this paper. This algorithm has a coding and decoding process without backtracking for dealing with the pixels of an image. It support LOCO-I and it can also be applied to Coder / Decoder. Simulation analysis indicates that the proposed method can achieve a high image compression. Compare with Lossless-JPG, PNG(Microsoft), PNG(Rene), PNG(Photoshop), PNG(Anix PicViewer), PNG(ACDSee), PNG(Ulead photo Explorer), JPEG2000, PNG(KoDa Inc), SPIHT and JPEG-LS, the lossless image compression ratio improved 45%, 29%, 25%, 21%, 19%, 17%, 16%, 15%, 11%, 10.5%, 10% separately with 24 pieces of RGB image provided by KoDa Inc. Accessing the main memory in Pentium IV,CPU2.20GHZ and 256MRAM, the coding speed of the proposed coder can be increased about 21 times than the SPIHT and the efficiency of the performance can be increased 166% or so, the decoder's coding speed can be increased about 17 times than the SPIHT and the efficiency of the performance can be increased 128% or so.

  17. SuperAGILE: The hard X-ray imager for the AGILE space mission

    Feroci, M.; Costa, E.; Soffitta, P.; Del Monte, E.; Di Persio, G.; Donnarumma, I.; Evangelista, Y.; Frutti, M.; Lapshov, I.; Lazzarotto, F.; Mastropietro, M.; Morelli, E.; Pacciani, L.; Porrovecchio, G.; Rapisarda, M.; Rubini, A.; Tavani, M.; Argan, A.

    2007-01-01

    SuperAGILE is a coded mask experiment based on silicon microstrip detectors. It operates in the 15-45 keV nominal energy range, providing crossed one-dimensional images of the X-ray sky with an on-axis angular resolution of 6 arcmin, over a field of view in excess of 1 sr. It was designed as the hard X-ray monitor of the AGILE space mission, a small satellite of the Italian Space Agency devoted to image the gamma-ray sky in the 30 MeV-50 GeV energy band. The AGILE mission was launched in a low-earth orbit on 23rd April 2007. In this paper we describe the SuperAGILE experiment, its construction and test processes, and its performance before flight, based on the on-ground test and calibrations

  18. Photometric Calibration of the Barium Cloud Image in a Space Active Experiment: Determining the Release Efficiency

    Xie Liang-Hai; Li Lei; Wang Jing-Dong; Tao Ran; Cheng Bing-Jun; Zhang Yi-Teng

    2014-01-01

    The barium release experiment is an effective method to explore the near-earth environment and to study all kinds of space physics processes. The first space barium release experiment in China was successfully carried out by a sounding rocket on April 5, 2013. This work is devoted to calculating the release efficiency of the barium release by analyzing the optical image observed during the experiment. First, we present a method to calibrate the images grey value of barium cloud with the reference stars to obtain the radiant fluxes at different moments. Then the release efficiency is obtained by a curve fitting with the theoretical evolution model of barium cloud. The calculated result is basically consistent with the test value on ground

  19. Flat-panel detectors in x-ray diagnosis

    Spahn, M.; Heer, V.; Freytag, R.

    2003-01-01

    For all application segments X-ray systems with flat-panel detectors increasingly enter the market. In digital radiography, mammography and cardiologic angiography flat-panel detectors are already well established while they are made ready for market introduction in general angiography and fluoroscopy. Two flat-panel detector technologies are available. One technology is based on an indirect conversion process of X-rays while the other one uses a direct conversion method.For radiography and dynamic applications the indirect method provides substantial advantages, while the direct method has some benefits for mammography. In radiography and mammography flat-panel detectors lead to clear improvements with respect to workflow, image quality and dose reduction potentials. These improvements are fostered by the immediate availability of the image, the large dynamic range and the high sensitivity to X-rays. New applications and the use of complex image processing algorithms have the potential to enlarge the present diagnostic range of applications.Up to now, image intensifiers are still the well-established technology for angiography and fluoroscopy. Nevertheless flat-panel detectors begin to enter this field, especially in cardiologic angiography.Characteristics of flat-panel detectors such as the availability of distortion-free images, the excellent contrast resolution, the large dynamic range, the high sensitivity to X-rays and the usability in magnetic fields provide the basis for improved and new diagnostic and interventional methods. (orig.) [de

  20. Large anterior temporal Virchow-Robin spaces: unique MR imaging features

    Lim, Anthony T. [Monash University, Neuroradiology Service, Monash Imaging, Monash Health, Melbourne, Victoria (Australia); Chandra, Ronil V. [Monash University, Neuroradiology Service, Monash Imaging, Monash Health, Melbourne, Victoria (Australia); Monash University, Department of Surgery, Faculty of Medicine, Nursing and Health Sciences, Melbourne (Australia); Trost, Nicholas M. [St Vincent' s Hospital, Neuroradiology Service, Melbourne (Australia); McKelvie, Penelope A. [St Vincent' s Hospital, Anatomical Pathology, Melbourne (Australia); Stuckey, Stephen L. [Monash University, Neuroradiology Service, Monash Imaging, Monash Health, Melbourne, Victoria (Australia); Monash University, Southern Clinical School, Faculty of Medicine, Nursing and Health Sciences, Melbourne (Australia)

    2015-05-01

    Large Virchow-Robin (VR) spaces may mimic cystic tumor. The anterior temporal subcortical white matter is a recently described preferential location, with only 18 reported cases. Our aim was to identify unique MR features that could increase prospective diagnostic confidence. Thirty-nine cases were identified between November 2003 and February 2014. Demographic, clinical data and the initial radiological report were retrospectively reviewed. Two neuroradiologists reviewed all MR imaging; a neuropathologist reviewed histological data. Median age was 58 years (range 24-86 years); the majority (69 %) was female. There were no clinical symptoms that could be directly referable to the lesion. Two thirds were considered to be VR spaces on the initial radiological report. Mean maximal size was 9 mm (range 5-17 mm); majority (79 %) had perilesional T2 or fluid-attenuated inversion recovery (FLAIR) hyperintensity. The following were identified as potential unique MR features: focal cortical distortion by an adjacent branch of the middle cerebral artery (92 %), smaller adjacent VR spaces (26 %), and a contiguous cerebrospinal fluid (CSF) intensity tract (21 %). Surgery was performed in three asymptomatic patients; histopathology confirmed VR spaces. Unique MR features were retrospectively identified in all three patients. Large anterior temporal lobe VR spaces commonly demonstrate perilesional T2 or FLAIR signal and can be misdiagnosed as cystic tumor. Potential unique MR features that could increase prospective diagnostic confidence include focal cortical distortion by an adjacent branch of the middle cerebral artery, smaller adjacent VR spaces, and a contiguous CSF intensity tract. (orig.)

  1. EUV imager and spectrometer for LYOT and solar orbiter space missions

    Millard, Anne; Lemaire, Philippe; Vial, Jean-Claude

    2017-11-01

    In the 2010 horizon, solar space missions such as LYOT and Solar Orbiter will allow high cadence UV observations of the Sun at spatial and spectral resolution never obtained before. To reach these goals, the two missions could take advantage of spectro-imagers. A reflective only optical solution for such an instrument is described in this paper and the first results of the mock-up being built at IAS are shown.

  2. The Physics of Imaging with Remote Sensors : Photon State Space & Radiative Transfer

    Davis, Anthony B.

    2012-01-01

    Standard (mono-pixel/steady-source) retrieval methodology is reaching its fundamental limit with access to multi-angle/multi-spectral photo- polarimetry. Next... Two emerging new classes of retrieval algorithm worth nurturing: multi-pixel time-domain Wave-radiometry transition regimes, and more... Cross-fertilization with bio-medical imaging. Physics-based remote sensing: - What is "photon state space?" - What is "radiative transfer?" - Is "the end" in sight? Two wide-open frontiers! center dot Examples (with variations.

  3. Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images

    Yothers, Mitchell P.; Browder, Aaron E.; Bumm, Lloyd A.

    2017-01-01

    We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

  4. Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images.

    Yothers, Mitchell P; Browder, Aaron E; Bumm, Lloyd A

    2017-01-01

    We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

  5. Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. IV. Measurement for Sculptor

    Piatek, Slawomir; Pryor, Carlton; Bristow, Paul; Olszewski, Edward W.; Harris, Hugh C.; Mateo, Mario; Minniti, Dante; Tinney, Christopher G.

    2006-03-01

    This article presents a measurement of the proper motion of the Sculptor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope using the Space Telescope Imaging Spectrograph in the imaging mode. Each of two distinct fields contains a quasi-stellar object that serves as the ``reference point.'' The measured proper motion of Sculptor, expressed in the equatorial coordinate system, is (μα, μδ)=(9+/-13, 2+/-13) mas century-1. Removing the contributions from the motion of the Sun and the motion of the local standard of rest produces the proper motion in the Galactic rest frame: (μGrfα, μGrfδ)=(-23+/-13, 45+/-13) mas century-1. The implied space velocity with respect to the Galactic center has a radial component of Vr=79+/-6 km s-1 and a tangential component of Vt=198+/-50 km s-1. Integrating the motion of Sculptor in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 68 (31, 83) and 122 (97, 313) kpc, respectively, where the values in the parentheses represent the 95% confidence interval derived from Monte Carlo experiments. The eccentricity of the orbit is 0.29 (0.26, 0.60), and the orbital period is 2.2 (1.5, 4.9) Gyr. Sculptor is on a polar orbit around the Milky Way: the angle of inclination is 86° (83°, 90°). Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  6. Approaches to automatic parameter fitting in a microscopy image segmentation pipeline: An exploratory parameter space analysis.

    Held, Christian; Nattkemper, Tim; Palmisano, Ralf; Wittenberg, Thomas

    2013-01-01

    Research and diagnosis in medicine and biology often require the assessment of a large amount of microscopy image data. Although on the one hand, digital pathology and new bioimaging technologies find their way into clinical practice and pharmaceutical research, some general methodological issues in automated image analysis are still open. In this study, we address the problem of fitting the parameters in a microscopy image segmentation pipeline. We propose to fit the parameters of the pipeline's modules with optimization algorithms, such as, genetic algorithms or coordinate descents, and show how visual exploration of the parameter space can help to identify sub-optimal parameter settings that need to be avoided. This is of significant help in the design of our automatic parameter fitting framework, which enables us to tune the pipeline for large sets of micrographs. The underlying parameter spaces pose a challenge for manual as well as automated parameter optimization, as the parameter spaces can show several local performance maxima. Hence, optimization strategies that are not able to jump out of local performance maxima, like the hill climbing algorithm, often result in a local maximum.

  7. Approaches to automatic parameter fitting in a microscopy image segmentation pipeline: An exploratory parameter space analysis

    Christian Held

    2013-01-01

    Full Text Available Introduction: Research and diagnosis in medicine and biology often require the assessment of a large amount of microscopy image data. Although on the one hand, digital pathology and new bioimaging technologies find their way into clinical practice and pharmaceutical research, some general methodological issues in automated image analysis are still open. Methods: In this study, we address the problem of fitting the parameters in a microscopy image segmentation pipeline. We propose to fit the parameters of the pipeline′s modules with optimization algorithms, such as, genetic algorithms or coordinate descents, and show how visual exploration of the parameter space can help to identify sub-optimal parameter settings that need to be avoided. Results: This is of significant help in the design of our automatic parameter fitting framework, which enables us to tune the pipeline for large sets of micrographs. Conclusion: The underlying parameter spaces pose a challenge for manual as well as automated parameter optimization, as the parameter spaces can show several local performance maxima. Hence, optimization strategies that are not able to jump out of local performance maxima, like the hill climbing algorithm, often result in a local maximum.

  8. Controllable Fabrication of Au Nanocups by Confined-Space Thermal Dewetting for OCT Imaging.

    Gao, Aiqin; Xu, Wenjing; Ponce de León, Yenisey; Bai, Yaocai; Gong, Mingfu; Xie, Kongliang; Park, Boris Hyle; Yin, Yadong

    2017-07-01

    Here, this study reports a novel confined-space thermal dewetting strategy for the fabrication of Au nanocups with tunable diameter, height, and size of cup opening. The nanocup morphology is defined by the cup-shaped void space created by a yolk-shell silica template that spontaneously takes an eccentric configuration during annealing. Thermal dewetting of Au, which is sandwiched between the yolk and shell, leads to the desired nanocup morphology. With strong scattering in near infrared, the Au nanocups exhibit superior efficiency as contrast agents for spectral-domain optical coherence tomography imaging. This confined-space thermal dewetting strategy is scalable and general, and can be potentially extended to the synthesis of novel anisotropic nanostructures of various compositions that are difficult to produce by conventional wet chemical or physical methods, thus opening up opportunities for many new applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Multiscale registration of medical images based on edge preserving scale space with application in image-guided radiation therapy

    Li, Dengwang; Li, Hongsheng; Wan, Honglin; Chen, Jinhu; Gong, Guanzhong; Wang, Hongjun; Wang, Liming; Yin, Yong

    2012-08-01

    Mutual information (MI) is a well-accepted similarity measure for image registration in medical systems. However, MI-based registration faces the challenges of high computational complexity and a high likelihood of being trapped into local optima due to an absence of spatial information. In order to solve these problems, multi-scale frameworks can be used to accelerate registration and improve robustness. Traditional Gaussian pyramid representation is one such technique but it suffers from contour diffusion at coarse levels which may lead to unsatisfactory registration results. In this work, a new multi-scale registration framework called edge preserving multiscale registration (EPMR) was proposed based upon an edge preserving total variation L1 norm (TV-L1) scale space representation. TV-L1 scale space is constructed by selecting edges and contours of images according to their size rather than the intensity values of the image features. This ensures more meaningful spatial information with an EPMR framework for MI-based registration. Furthermore, we design an optimal estimation of the TV-L1 parameter in the EPMR framework by training and minimizing the transformation offset between the registered pairs for automated registration in medical systems. We validated our EPMR method on both simulated mono- and multi-modal medical datasets with ground truth and clinical studies from a combined positron emission tomography/computed tomography (PET/CT) scanner. We compared our registration framework with other traditional registration approaches. Our experimental results demonstrated that our method outperformed other methods in terms of the accuracy and robustness for medical images. EPMR can always achieve a small offset value, which is closer to the ground truth both for mono-modality and multi-modality, and the speed can be increased 5-8% for mono-modality and 10-14% for multi-modality registration under the same condition. Furthermore, clinical application by adaptive

  10. Multiscale registration of medical images based on edge preserving scale space with application in image-guided radiation therapy

    Li Dengwang; Wan Honglin; Li Hongsheng; Chen Jinhu; Gong Guanzhong; Yin Yong; Wang Hongjun; Wang Liming

    2012-01-01

    Mutual information (MI) is a well-accepted similarity measure for image registration in medical systems. However, MI-based registration faces the challenges of high computational complexity and a high likelihood of being trapped into local optima due to an absence of spatial information. In order to solve these problems, multi-scale frameworks can be used to accelerate registration and improve robustness. Traditional Gaussian pyramid representation is one such technique but it suffers from contour diffusion at coarse levels which may lead to unsatisfactory registration results. In this work, a new multi-scale registration framework called edge preserving multiscale registration (EPMR) was proposed based upon an edge preserving total variation L1 norm (TV-L1) scale space representation. TV-L1 scale space is constructed by selecting edges and contours of images according to their size rather than the intensity values of the image features. This ensures more meaningful spatial information with an EPMR framework for MI-based registration. Furthermore, we design an optimal estimation of the TV-L1 parameter in the EPMR framework by training and minimizing the transformation offset between the registered pairs for automated registration in medical systems. We validated our EPMR method on both simulated mono- and multi-modal medical datasets with ground truth and clinical studies from a combined positron emission tomography/computed tomography (PET/CT) scanner. We compared our registration framework with other traditional registration approaches. Our experimental results demonstrated that our method outperformed other methods in terms of the accuracy and robustness for medical images. EPMR can always achieve a small offset value, which is closer to the ground truth both for mono-modality and multi-modality, and the speed can be increased 5–8% for mono-modality and 10–14% for multi-modality registration under the same condition. Furthermore, clinical application by

  11. Scanless nonlinear optical microscope for image reconstruction and space-time correlation analysis

    Ceffa, N. G.; Radaelli, F.; Pozzi, P.; Collini, M.; Sironi, L.; D'alfonso, L.; Chirico, G.

    2017-06-01

    Optical Microscopy has been applied to life science from its birth and reached widespread application due to its major advantages: limited perturbation of the biological tissue and the easy accessibility of the light sources. However, as the spatial and time resolution requirements and the time stability of the microscopes increase, researchers are struggling against some of its limitations: limited transparency and the refractivity of the living tissue to light and the field perturbations induced by the path in the tissue. We have developed a compact stand-alone, completely scan-less, optical setup that allows to acquire non-linear excitation images and to measure the sample dynamics simultaneously on an ensemble of arbitrary chosen regions of interests. The image is obtained by shining a square array of spots on the sample obtained by a spatial light modulator and by shifting it (10 ms refresh time) on the sample. The final image is computed from the superposition of (100-1000) images. Filtering procedures can be applied to the raw images of the excitation array before building the image. We discuss results that show how this setup can be used for the correction of wave front aberrations induced by turbid samples (such as living tissues) and for the computation of space-time cross-correlations in complex networks.

  12. PLANE MATCHING WITH OBJECT-SPACE SEARCHING USING INDEPENDENTLY RECTIFIED IMAGES

    H. Takeda

    2012-07-01

    Full Text Available In recent years, the social situation in cities has changed significantly such as redevelopment due to the massive earthquake and large-scale urban development. For example, numerical simulations can be used to study this phenomenon. Such simulations require the construction of high-definition three-dimensional city models that accurately reflect the real world. Progress in sensor technology allows us to easily obtain multi-view images. However, the existing multi-image matching techniques are inadequate. In this paper, we propose a new technique for multi-image matching. Since the existing method of feature searching is complicated, we have developed a rectification method that can be processed independently for each image does not depend on the stereo-pair. The object-space searching method that produces mismatches due to the occlusion or distortion of wall textures on images is the focus of our study. Our proposed technique can also match the building wall surface. The proposed technique has several advantages, and its usefulness is clarified through an experiment using actual images.

  13. A robust state-space kinetics-guided framework for dynamic PET image reconstruction

    Tong, S; Alessio, A M; Kinahan, P E; Liu, H; Shi, P

    2011-01-01

    Dynamic PET image reconstruction is a challenging issue due to the low SNR and the large quantity of spatio-temporal data. We propose a robust state-space image reconstruction (SSIR) framework for activity reconstruction in dynamic PET. Unlike statistically-based frame-by-frame methods, tracer kinetic modeling is incorporated to provide physiological guidance for the reconstruction, harnessing the temporal information of the dynamic data. Dynamic reconstruction is formulated in a state-space representation, where a compartmental model describes the kinetic processes in a continuous-time system equation, and the imaging data are expressed in a discrete measurement equation. Tracer activity concentrations are treated as the state variables, and are estimated from the dynamic data. Sampled-data H ∞ filtering is adopted for robust estimation. H ∞ filtering makes no assumptions on the system and measurement statistics, and guarantees bounded estimation error for finite-energy disturbances, leading to robust performance for dynamic data with low SNR and/or errors. This alternative reconstruction approach could help us to deal with unpredictable situations in imaging (e.g. data corruption from failed detector blocks) or inaccurate noise models. Experiments on synthetic phantom and patient PET data are performed to demonstrate feasibility of the SSIR framework, and to explore its potential advantages over frame-by-frame statistical reconstruction approaches.

  14. Ultrasound Imaging of Spine: State of the Art and Utility for Space Flight

    Sargsyan, Ashot E.; Bouffard, Antonio J.; Garcia, Kathleen; Hamilton, Douglas R.; Van Holsbeeck, Marnix; Ebert, Douglas J. W.; Dulchavsky, Scott A.

    2010-01-01

    Introduction: Ultrasound imaging (sonography) has been increasingly used for both primary diagnosis and monitoring of musculoskeletal injury, including fractures. In certain injuries, sonography has been shown to equal or surpass Magnetic Resonance Imaging in accuracy. Long-term exposure to reduced gravity may be expected to cause physiological and anatomical changes of the musculoskeletal system, which are not fully described or understood. In a limited-resource environment like space flight, sonography will likely remain the only imaging modality; therefore, further attention to its potential is warranted, including its ability to image anatomical deviations as well as irregularities of vertebrae and the spinal column. Methods: A thorough review of literature was conducted on the subject. A multipurpose ultrasound system was used to identify specific vertebrae, intervertebral disks, and other structures of the cervical spine in healthy volunteers, selected to represent various age, gender, and Body Mass Index (BMI) groups. Sonographic views were sought that would parallel radiographic views and signs used in the diagnosis of cervical spine injuries. Results: While using widely accepted radiographic signs of cervical spine injury, this sonographic protocol development effort resulted in successful identification of scanning planes and imaging protocols that could serve as alternatives for radiography. Some of these views are also applicable to diagnosing degenerative disk and bone disease, and other non-traumatic spine pathology. Strong, preliminary correlation has been demonstrated in a number of clinical cases between sonography and other imaging modalities. Conclusion: In the absence of radiography, sonography can be used to diagnose or rule out certain common types of cervical spine conditions including injury. Clinical validation of the findings appears to be realistic and would facilitate establishment of new sonographic protocols for special environments

  15. NIAC Phase II Orbiting Rainbows: Future Space Imaging with Granular Systems

    Quadrelli, Marco B.; Basinger, Scott; Arumugam, Darmindra; Swartzlander, Grover

    2017-01-01

    Inspired by the light scattering and focusing properties of distributed optical assemblies in Nature, such as rainbows and aerosols, and by recent laboratory successes in optical trapping and manipulation, we propose a unique combination of space optics and autonomous robotic system technology, to enable a new vision of space system architecture with applications to ultra-lightweight space optics and, ultimately, in-situ space system fabrication. Typically, the cost of an optical system is driven by the size and mass of the primary aperture. The ideal system is a cloud of spatially disordered dust-like objects that can be optically manipulated: it is highly reconfigurable, fault-tolerant, and allows very large aperture sizes at low cost. This new concept is based on recent understandings in the physics of optical manipulation of small particles in the laboratory and the engineering of distributed ensembles of spacecraft swarms to shape an orbiting cloud of micron-sized objects. In the same way that optical tweezers have revolutionized micro- and nano-manipulation of objects, our breakthrough concept will enable new large scale NASA mission applications and develop new technology in the areas of Astrophysical Imaging Systems and Remote Sensing because the cloud can operate as an adaptive optical imaging sensor. While achieving the feasibility of constructing one single aperture out of the cloud is the main topic of this work, it is clear that multiple orbiting aerosol lenses could also combine their power to synthesize a much larger aperture in space to enable challenging goals such as exo-planet detection. Furthermore, this effort could establish feasibility of key issues related to material properties, remote manipulation, and autonomy characteristics of cloud in orbit. There are several types of endeavors (science missions) that could be enabled by this type of approach, i.e. it can enable new astrophysical imaging systems, exo-planet search, large apertures

  16. Using the phase-space imager to analyze partially coherent imaging systems: bright-field, phase contrast, differential interference contrast, differential phase contrast, and spiral phase contrast

    Mehta, Shalin B.; Sheppard, Colin J. R.

    2010-05-01

    Various methods that use large illumination aperture (i.e. partially coherent illumination) have been developed for making transparent (i.e. phase) specimens visible. These methods were developed to provide qualitative contrast rather than quantitative measurement-coherent illumination has been relied upon for quantitative phase analysis. Partially coherent illumination has some important advantages over coherent illumination and can be used for measurement of the specimen's phase distribution. However, quantitative analysis and image computation in partially coherent systems have not been explored fully due to the lack of a general, physically insightful and computationally efficient model of image formation. We have developed a phase-space model that satisfies these requirements. In this paper, we employ this model (called the phase-space imager) to elucidate five different partially coherent systems mentioned in the title. We compute images of an optical fiber under these systems and verify some of them with experimental images. These results and simulated images of a general phase profile are used to compare the contrast and the resolution of the imaging systems. We show that, for quantitative phase imaging of a thin specimen with matched illumination, differential phase contrast offers linear transfer of specimen information to the image. We also show that the edge enhancement properties of spiral phase contrast are compromised significantly as the coherence of illumination is reduced. The results demonstrate that the phase-space imager model provides a useful framework for analysis, calibration, and design of partially coherent imaging methods.

  17. Projective flatness in the quantisation of bosons and fermions

    Wu, Siye

    2015-07-01

    We compare the quantisation of linear systems of bosons and fermions. We recall the appearance of projectively flat connection and results on parallel transport in the quantisation of bosons. We then discuss pre-quantisation and quantisation of fermions using the calculus of fermionic variables. We define a natural connection on the bundle of Hilbert spaces and show that it is projectively flat. This identifies, up to a phase, equivalent spinor representations constructed by various polarisations. We introduce the concept of metaplectic correction for fermions and show that the bundle of corrected Hilbert spaces is naturally flat. We then show that the parallel transport in the bundle of Hilbert spaces along a geodesic is a rescaled projection provided that the geodesic lies within the complement of a cut locus. Finally, we study the bundle of Hilbert spaces when there is a symmetry.

  18. Vacuum energy in asymptotically flat 2 + 1 gravity

    Miskovic, Olivera, E-mail: olivera.miskovic@pucv.cl [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile); Olea, Rodrigo, E-mail: rodrigo.olea@unab.cl [Departamento de Ciencias Físicas, Universidad Andres Bello, Sazié 2212, Piso 7, Santiago (Chile); Roy, Debraj, E-mail: roy.debraj@pucv.cl [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile)

    2017-04-10

    We compute the vacuum energy of three-dimensional asymptotically flat space based on a Chern–Simons formulation for the Poincaré group. The equivalent action is nothing but the Einstein–Hilbert term in the bulk plus half of the Gibbons–Hawking term at the boundary. The derivation is based on the evaluation of the Noether charges in the vacuum. We obtain that the vacuum energy of this space has the same value as the one of the asymptotically flat limit of three-dimensional anti-de Sitter space.

  19. Vacuum energy in asymptotically flat 2 + 1 gravity

    Miskovic, Olivera; Olea, Rodrigo; Roy, Debraj

    2017-01-01

    We compute the vacuum energy of three-dimensional asymptotically flat space based on a Chern–Simons formulation for the Poincaré group. The equivalent action is nothing but the Einstein–Hilbert term in the bulk plus half of the Gibbons–Hawking term at the boundary. The derivation is based on the evaluation of the Noether charges in the vacuum. We obtain that the vacuum energy of this space has the same value as the one of the asymptotically flat limit of three-dimensional anti-de Sitter space.

  20. Mapping of Geographically Isolated Wetlands of Western Siberia Using High Resolution Space Images

    Dyukarev, E.; Pologova, N.; Dyukarev, A.; Lane, C.; Autrey, B. C.

    2014-12-01

    Using the remote sensing data for integrated study of natural objects is actual for investigation of difficult to access areas of West Siberia. The research of this study focuses on determining the extent and spectral signatures of isolated wetlands within Ob-Tom Interfluve area using Landsat and Quickbird space images. High-resolution space images were carefully examined and wetlands were manually delineated. Wetlands have clear visible signs at the high resolution space images. 567 wetlands were recognized as isolated wetlands with the area about 10 000 ha (of 2.5% of the study area). Isolated wetlands with area less 2 ha are the most frequent. Half of the total amount of wetlands has area less than 6.4 ha. The largest isolated wetland occupies 797 ha, and only 5% have area more than 50 ha. The Landsat 7 ETM+ data were used for analysis of vegetation structure and spectral characteristics of wetlands. The masked isolated wetlands image was classified into 12 land cover classes using ISODATA unsupervised classification. The attribution of unsupervised classification results allowed us to clearly recognize 7 types of wetlands: tall, low and sparse ryams (Pine-Shrub-Sphagnum community), open wetlands with shrub, moss or sedge cover, and open water objects. Analysis of spectral profiles for all classes has shown that Landsat spectral bands 4 and 5 have higher variability. These bands allow to separate wetland classed definitely. Accuracy assessment of isolated wetland map shows a good agreement with expert field data. The work was supported by grants ISTC № 4079.

  1. IoSiS: a radar system for imaging of satellites in space

    Jirousek, M.; Anger, S.; Dill, S.; Schreiber, E.; Peichl, M.

    2017-05-01

    Space debris nowadays is one of the main threats for satellite systems especially in low earth orbit (LEO). More than 700,000 debris objects with potential to destroy or damage a satellite are estimated. The effects of an impact often are not identifiable directly from ground. High-resolution radar images are helpful in analyzing a possible damage. Therefor DLR is currently developing a radar system called IoSiS (Imaging of Satellites in Space), being based on an existing steering antenna structure and our multi-purpose high-performance radar system GigaRad for experimental investigations. GigaRad is a multi-channel system operating at X band and using a bandwidth of up to 4.4 GHz in the IoSiS configuration, providing fully separated transmit (TX) and receive (RX) channels, and separated antennas. For the observation of small satellites or space debris a highpower traveling-wave-tube amplifier (TWTA) is mounted close to the TX antenna feed. For the experimental phase IoSiS uses a 9 m TX and a 1 m RX antenna mounted on a common steerable positioner. High-resolution radar images are obtained by using Inverse Synthetic Aperture Radar (ISAR) techniques. The guided tracking of known objects during overpass allows here wide azimuth observation angles. Thus high azimuth resolution comparable to the range resolution can be achieved. This paper outlines technical main characteristics of the IoSiS radar system including the basic setup of the antenna, the radar instrument with the RF error correction, and the measurement strategy. Also a short description about a simulation tool for the whole instrument and expected images is shown.

  2. Flat flexible polymer heat pipes

    Oshman, Christopher; Li, Qian; Liew, Li-Anne; Yang, Ronggui; Bright, Victor M; Lee, Y C

    2013-01-01

    Flat, flexible, lightweight, polymer heat pipes (FPHP) were fabricated. The overall geometry of the heat pipe was 130 mm × 70 mm × 1.31 mm. A commercially available low-cost film composed of laminated sheets of low-density polyethylene terephthalate, aluminum and polyethylene layers was used as the casing. A triple-layer sintered copper woven mesh served as a liquid wicking structure, and water was the working fluid. A coarse nylon woven mesh provided space for vapor transport and mechanical rigidity. Thermal power ranging from 5 to 30 W was supplied to the evaporator while the device was flexed at 0°, 45° and 90°. The thermal resistance of the FPHP ranged from 1.2 to 3.0 K W −1 depending on the operating conditions while the thermal resistance for a similar-sized solid copper reference was a constant at 4.6 K W −1 . With 25 W power input, the thermal resistance of the liquid–vapor core of the FPHP was 23% of a copper reference sample with identical laminated polymer material. This work shows a promising combination of technologies that has the potential to usher in a new generation of highly flexible, lightweight, low-cost, high-performance thermal management solutions. (paper)

  3. Medical Image Segmentation using the HSI color space and Fuzzy Mathematical Morphology

    Gasparri, J P; Bouchet, A; Abras, G; Ballarin, V; Pastore, J I

    2011-01-01

    Diabetic retinopathy is the most common cause of blindness among the active population in developed countries. An early ophthalmologic examination followed by proper treatment can prevent blindness. The purpose of this work is develop an automated method for segmentation the vasculature in retinal images in order to assist the expert in the evolution of a specific treatment or in the diagnosis of a potential pathology. Since the HSI space has the ability to separate the intensity of the intrinsic color information, its use is recommended for the digital processing images when they are affected by lighting changes, characteristic of the images under study. By the application of color filters, is achieved artificially change the tone of blood vessels, to better distinguish them from the bottom. This technique, combined with the application of fuzzy mathematical morphology tools as the Top-Hat transformation, creates images of the retina, where vascular branches are markedly enhanced over the original. These images provide the visualization of blood vessels by the specialist.

  4. Medical Image Segmentation using the HSI color space and Fuzzy Mathematical Morphology

    Gasparri, J. P.; Bouchet, A.; Abras, G.; Ballarin, V.; Pastore, J. I.

    2011-12-01

    Diabetic retinopathy is the most common cause of blindness among the active population in developed countries. An early ophthalmologic examination followed by proper treatment can prevent blindness. The purpose of this work is develop an automated method for segmentation the vasculature in retinal images in order to assist the expert in the evolution of a specific treatment or in the diagnosis of a potential pathology. Since the HSI space has the ability to separate the intensity of the intrinsic color information, its use is recommended for the digital processing images when they are affected by lighting changes, characteristic of the images under study. By the application of color filters, is achieved artificially change the tone of blood vessels, to better distinguish them from the bottom. This technique, combined with the application of fuzzy mathematical morphology tools as the Top-Hat transformation, creates images of the retina, where vascular branches are markedly enhanced over the original. These images provide the visualization of blood vessels by the specialist.

  5. Planetary Radar Imaging with the Deep-Space Network's 34 Meter Uplink Array

    Vilnrotter, Victor; Tsao, P.; Lee, D.; Cornish, T.; Jao, J.; Slade, M.

    2011-01-01

    A coherent Uplink Array consisting of two or three 34-meter antennas of NASA's Deep Space Network has been developed for the primary purpose of increasing EIRP at the spacecraft. Greater EIRP ensures greater reach, higher uplink data rates for command and configuration control, as well as improved search and recovery capabilities during spacecraft emergencies. It has been conjectured that Doppler-delay radar imaging of lunar targets can be extended to planetary imaging, where the long baseline of the uplink array can provide greater resolution than a single antenna, as well as potentially higher EIRP. However, due to the well known R4 loss in radar links, imaging of distant planets is a very challenging endeavor, requiring accurate phasing of the Uplink Array antennas, cryogenically cooled low-noise receiver amplifiers, and sophisticated processing of the received data to extract the weak echoes characteristic of planetary radar. This article describes experiments currently under way to image the planets Mercury and Venus, highlights improvements in equipment and techniques, and presents planetary images obtained to date with two 34 meter antennas configured as a coherently phased Uplink Array.

  6. Exact piecewise flat gravitational waves

    van de Meent, M.

    2011-01-01

    We generalize our previous linear result (van de Meent 2011 Class. Quantum Grav 28 075005) in obtaining gravitational waves from our piecewise flat model for gravity in 3+1 dimensions to exact piecewise flat configurations describing exact planar gravitational waves. We show explicitly how to

  7. Optimized image acquisition for breast tomosynthesis in projection and reconstruction space

    Chawla, Amarpreet S.; Lo, Joseph Y.; Baker, Jay A.; Samei, Ehsan

    2009-01-01

    Breast tomosynthesis has been an exciting new development in the field of breast imaging. While the diagnostic improvement via tomosynthesis is notable, the full potential of tomosynthesis has not yet been realized. This may be attributed to the dependency of the diagnostic quality of tomosynthesis on multiple variables, each of which needs to be optimized. Those include dose, number of angular projections, and the total angular span of those projections. In this study, the authors investigated the effects of these acquisition parameters on the overall diagnostic image quality of breast tomosynthesis in both the projection and reconstruction space. Five mastectomy specimens were imaged using a prototype tomosynthesis system. 25 angular projections of each specimen were acquired at 6.2 times typical single-view clinical dose level. Images at lower dose levels were then simulated using a noise modification routine. Each projection image was supplemented with 84 simulated 3 mm 3D lesions embedded at the center of 84 nonoverlapping ROIs. The projection images were then reconstructed using a filtered backprojection algorithm at different combinations of acquisition parameters to investigate which of the many possible combinations maximizes the performance. Performance was evaluated in terms of a Laguerre-Gauss channelized Hotelling observer model-based measure of lesion detectability. The analysis was also performed without reconstruction by combining the model results from projection images using Bayesian decision fusion algorithm. The effect of acquisition parameters on projection images and reconstructed slices were then compared to derive an optimization rule for tomosynthesis. The results indicated that projection images yield comparable but higher performance than reconstructed images. Both modes, however, offered similar trends: Performance improved with an increase in the total acquisition dose level and the angular span. Using a constant dose level and angular

  8. History of Rocky Flats waste streams

    Luckett, L.L.; Dickman, A.A.; Wells, C.R.; Vickery, D.J.

    1982-01-01

    An analysis of the waste streams at Rocky Flats was done to provide information for the Waste Certification program. This program has involved studying the types and amounts of retrievable transuranic (TRU) waste from Rocky Flats that is stored at the Idaho National Engineering Laboratory (INEL). The information can be used to estimate the types and amounts of waste that will need to be permanently stored in the Waste Isolation Pilot Plant (WIPP). The study covered mostly the eight-year period from June 1971 to June 1979. The types, amounts, and plutonium content of TRU waste and the areas or operations responsible for generating the waste are summarized in this waste stream history report. From the period studied, a total of 24,546,153 lbs of waste containing 211,148 g of plutonium currently occupies 709,497 cu ft of storage space at INEL

  9. Standardized performance tests of collectors of solar thermal energy: A selectively coated, flat-plate copper collector with one transparent cover and a tube-to-tube spacing of 5 5/8 inches

    1976-01-01

    This preliminary data report gives basic test results of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator. The collector was tested over ranges of inlet temperatures, fluxes and coolant flow rates. Collector efficiency is correlated in terms of inlet temperature and flux level.

  10. Standard performance tests of collectors of solar thermal energy: A selectively coated, flat-plate copper collector with one transparent cover and a tube-to-tube spacing of 3-7/8 inches

    1976-01-01

    Basic test results are given of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator. The collector was tested over ranges of inlet temperatures, fluxes, and coolant flow rates. Collector efficiency is correlated in terms of inlet temperature and flux level.

  11. Environmental crimes at the Rocky Flats Nuclear Weapons Facility. Hearings before the Subcommittee on Investigations and Oversight of the Committee on Science, Space and Technology, US House of Representatives, One Hundred Second Congress, Second Session, Volume I

    Anon.

    1992-01-01

    Documented here are the executive session: September 10, 11, 17, 18, 23 [11:00 a.m.], 24, 25, 30, 1992 and the public session: September 23 [2:15 p.m.]; October 2, 5, 1992 of the hearings on the Environmental Crimes at the Rocky Flats Nuclear Weapons Facility. This document is Volume I of the hearings

  12. Four dimensional magnetic resonance imaging with retrospective k-space reordering: A feasibility study

    Liu, Yilin; Yin, Fang-Fang; Cai, Jing; Chen, Nan-kuei; Chu, Mei-Lan

    2015-01-01

    Purpose: Current four dimensional magnetic resonance imaging (4D-MRI) techniques lack sufficient temporal/spatial resolution and consistent tumor contrast. To overcome these limitations, this study presents the development and initial evaluation of a new strategy for 4D-MRI which is based on retrospective k-space reordering. Methods: We simulated a k-space reordered 4D-MRI on a 4D digital extended cardiac-torso (XCAT) human phantom. A 2D echo planar imaging MRI sequence [frame rate (F) = 0.448 Hz; image resolution (R) = 256 × 256; number of k-space segments (N KS ) = 4] with sequential image acquisition mode was assumed for the simulation. Image quality of the simulated “4D-MRI” acquired from the XCAT phantom was qualitatively evaluated, and tumor motion trajectories were compared to input signals. In particular, mean absolute amplitude differences (D) and cross correlation coefficients (CC) were calculated. Furthermore, to evaluate the data sufficient condition for the new 4D-MRI technique, a comprehensive simulation study was performed using 30 cancer patients’ respiratory profiles to study the relationships between data completeness (C p ) and a number of impacting factors: the number of repeated scans (N R ), number of slices (N S ), number of respiratory phase bins (N P ), N KS , F, R, and initial respiratory phase at image acquisition (P 0 ). As a proof-of-concept, we implemented the proposed k-space reordering 4D-MRI technique on a T2-weighted fast spin echo MR sequence and tested it on a healthy volunteer. Results: The simulated 4D-MRI acquired from the XCAT phantom matched closely to the original XCAT images. Tumor motion trajectories measured from the simulated 4D-MRI matched well with input signals (D = 0.83 and 0.83 mm, and CC = 0.998 and 0.992 in superior–inferior and anterior–posterior directions, respectively). The relationship between C p and N R was found best represented by an exponential function (C P =100(1−e −0.18N R ), when N S

  13. CT and MR imaging of primary tumors of the masticator space

    Aspestrand, F.; Boysen, M.

    1992-01-01

    A retrospective study of CT and MR examinations in 14 patients with benign and malignant tumors originating in the masticator space is presented. At presentation, 12 patients revealed tumor extension to adjacent regions and spaces. Perineutral tumor spread along trigeminal nerve branches to the cavernous sinus and orbits was combined with facial pain, and/or numbness, ophthalmoplegia, and exophthalmus. Detailed analysis of tumor growth and spread, enhancement and signal features at CT and MR imaging indicated that tumor histology was, with a few exceptions, nonspecific. More extensive growth and bone destruction was noted only among malignant tumors. MR imaging was found superior to CT in delineating tumor extension due to better soft tissue contrast resolution and multiplanar imaging. Posttreatment examinations were available in 11 patients and showed long-standing regional edema of the adjacent temporal lobe and masticator muscles in 4 out of 5 patients without clinical evidence of tumor. In 6 patients, CT and MR features were found almost unchanged with only small size differences after various forms of treatment. (orig.)

  14. Multiband CCD Image Compression for Space Camera with Large Field of View

    Jin Li

    2014-01-01

    Full Text Available Space multiband CCD camera compression encoder requires low-complexity, high-robustness, and high-performance because of its captured images information being very precious and also because it is usually working on the satellite where the resources, such as power, memory, and processing capacity, are limited. However, the traditional compression approaches, such as JPEG2000, 3D transforms, and PCA, have the high-complexity. The Consultative Committee for Space Data Systems-Image Data Compression (CCSDS-IDC algorithm decreases the average PSNR by 2 dB compared with JPEG2000. In this paper, we proposed a low-complexity compression algorithm based on deep coupling algorithm among posttransform in wavelet domain, compressive sensing, and distributed source coding. In our algorithm, we integrate three low-complexity and high-performance approaches in a deeply coupled manner to remove the spatial redundant, spectral redundant, and bit information redundancy. Experimental results on multiband CCD images show that the proposed algorithm significantly outperforms the traditional approaches.

  15. Real-space imaging of non-collinear antiferromagnetic order with a single-spin magnetometer

    Gross, I.; Akhtar, W.; Garcia, V.; Martínez, L. J.; Chouaieb, S.; Garcia, K.; Carrétéro, C.; Barthélémy, A.; Appel, P.; Maletinsky, P.; Kim, J.-V.; Chauleau, J. Y.; Jaouen, N.; Viret, M.; Bibes, M.; Fusil, S.; Jacques, V.

    2017-09-01

    Although ferromagnets have many applications, their large magnetization and the resulting energy cost for switching magnetic moments bring into question their suitability for reliable low-power spintronic devices. Non-collinear antiferromagnetic systems do not suffer from this problem, and often have extra functionalities: non-collinear spin order may break space-inversion symmetry and thus allow electric-field control of magnetism, or may produce emergent spin-orbit effects that enable efficient spin-charge interconversion. To harness these traits for next-generation spintronics, the nanoscale control and imaging capabilities that are now routine for ferromagnets must be developed for antiferromagnetic systems. Here, using a non-invasive, scanning single-spin magnetometer based on a nitrogen-vacancy defect in diamond, we demonstrate real-space visualization of non-collinear antiferromagnetic order in a magnetic thin film at room temperature. We image the spin cycloid of a multiferroic bismuth ferrite (BiFeO3) thin film and extract a period of about 70 nanometres, consistent with values determined by macroscopic diffraction. In addition, we take advantage of the magnetoelectric coupling present in BiFeO3 to manipulate the cycloid propagation direction by an electric field. Besides highlighting the potential of nitrogen-vacancy magnetometry for imaging complex antiferromagnetic orders at the nanoscale, these results demonstrate how BiFeO3 can be used in the design of reconfigurable nanoscale spin textures.

  16. Overview of CMOS process and design options for image sensor dedicated to space applications

    Martin-Gonthier, P.; Magnan, P.; Corbiere, F.

    2005-10-01

    With the growth of huge volume markets (mobile phones, digital cameras...) CMOS technologies for image sensor improve significantly. New process flows appear in order to optimize some parameters such as quantum efficiency, dark current, and conversion gain. Space applications can of course benefit from these improvements. To illustrate this evolution, this paper reports results from three technologies that have been evaluated with test vehicles composed of several sub arrays designed with some space applications as target. These three technologies are CMOS standard, improved and sensor optimized process in 0.35μm generation. Measurements are focussed on quantum efficiency, dark current, conversion gain and noise. Other measurements such as Modulation Transfer Function (MTF) and crosstalk are depicted in [1]. A comparison between results has been done and three categories of CMOS process for image sensors have been listed. Radiation tolerance has been also studied for the CMOS improved process in the way of hardening the imager by design. Results at 4, 15, 25 and 50 krad prove a good ionizing dose radiation tolerance applying specific techniques.

  17. Calibration Efforts and Unique Capabilities of the HST Space Telescope Imaging Spectrograph

    Monroe, TalaWanda R.; Proffitt, Charles R.; Welty, Daniel; Branton, Doug; Carlberg, Joleen K.; debes, John Henry; Lockwood, Sean; Riley, Allyssa; Sohn, Sangmo Tony; Sonnentrucker, Paule G.; Walborn, Nolan R.; Jedrzejewski, Robert I.

    2018-01-01

    The Space Telescope Imaging Spectrograph (STIS) continues to offer the astronomy community the ability to carry out innovative UV and optical spectroscopic and imaging studies, two decades after its deployment on the Hubble Space Telescope (HST). Most notably, STIS provides spectroscopy in the FUV and NUV, including high spectral resolution echelle modes, imaging in the FUV, optical spectroscopy, and coronagraphic capabilities. Additionally, spatial scanning on the CCD with the long-slits is now possible to enable very high S/N spectroscopic observations without saturation while mitigating telluric and fringing concerns in the far red and near-IR. This new mode may especially benefit the diffuse interstellar bands and exoplanet transiting communities. We present recent calibration efforts for the instrument, including work to optimize the calibration of the echelle spectroscopic modes by improving the flux agreement of overlapping spectral orders affected by changes in the grating blaze function since HST Servicing Mission 4. We also discuss considerations to maintain the wavelength precision of the spectroscopic modes, and the current capabilities of CCD spectroscopic spatial trails.

  18. Developmental Research in Space: Predicting Adult Neurobehavioral Phenotypes via Metabolomic Imaging

    Schorn, Julia M.; Moyer, Eric L.; Lowe, Moniece M.; Morgan, Jonathan; Tulbert, Christina D.; Olson, John; Olson, John; Horita, David A.; Kleven, Gale A.

    2017-01-01

    As human habitation and eventual colonization of space becomes an inevitable reality, there is a necessity to understand how organisms develop over the life span in the space environment. Microgravity, altered CO2, radiation and psychological stress are some of the key factors that could affect mammalian reproduction and development in space, however there is a paucity of information on this topic. Here we combine early (neonatal) in vivo spectroscopic imaging with an adult emotionality assay following a common obstetric complication (prenatal asphyxia) likely to occur during gestation in space. The neural metabolome is sensitive to alteration by degenerative changes and developmental disorders, thus we hypothesized that that early neonatal neurometabolite profiles can predict adult response to novelty. Late gestation fetal rats were exposed to moderate asphyxia by occluding the blood supply feeding one of the rats pair uterine horns for 15min. Blood supply to the opposite horn was not occluded (within-litter cesarean control). Further comparisons were made with vaginal (natural) birth controls. In one-week old neonates, we measured neurometabolites in three brain areas (i.e., striatum, prefrontal cortex, and hippocampus). Adult perinatally-asphyxiated offspring exhibited greater anxiety-like behavioral phenotypes (as measured the composite neurobehavioral assay involving open field activity, responses to novel object, quantification of fecal droppings, and resident-intruder tests of social behavior). Further, early neurometabolite profiles predicted adult responses. Non-invasive MRS screening of mammalian offspring is likely to advance ground-based space analogue studies informing mammalian reproduction in space, and achieving high-priority.

  19. High resolution inverse synthetic aperture radar imaging of three-axis-stabilized space target by exploiting orbital and sparse priors

    Ma Jun-Tao; Gao Mei-Guo; Xiong Di; Feng Qi; Guo Bao-Feng; Dong Jian

    2017-01-01

    The development of inverse synthetic aperture radar (ISAR) imaging techniques is of notable significance for monitoring, tracking and identifying space targets in orbit. Usually, a well-focused ISAR image of a space target can be obtained in a deliberately selected imaging segment in which the target moves with only uniform planar rotation. However, in some imaging segments, the nonlinear range migration through resolution cells (MTRCs) and time-varying Doppler caused by the three-dimensional rotation of the target would degrade the ISAR imaging performance, and it is troublesome to realize accurate motion compensation with conventional methods. Especially in the case of low signal-to-noise ratio (SNR), the estimation of motion parameters is more difficult. In this paper, a novel algorithm for high-resolution ISAR imaging of a space target by using its precise ephemeris and orbital motion model is proposed. The innovative contributions are as follows. 1) The change of a scatterer projection position is described with the spatial-variant angles of imaging plane calculated based on the orbital motion model of the three-axis-stabilized space target. 2) A correction method of MTRC in slant- and cross-range dimensions for arbitrarily imaging segment is proposed. 3) Coarse compensation for translational motion using the precise ephemeris and the fine compensation for residual phase errors by using sparsity-driven autofocus method are introduced to achieve a high-resolution ISAR image. Simulation results confirm the effectiveness of the proposed method. (paper)

  20. Lightning Imaging Sensor (LIS) on the International Space Station (ISS): Launch, Installation, Activation, and First Results

    Blakeslee, R. J.; Christian, H. J., Jr.; Mach, D. M.; Buechler, D. E.; Koshak, W. J.; Walker, T. D.; Bateman, M. G.; Stewart, M. F.; O'Brien, S.; Wilson, T. O.; Pavelitz, S. D.; Coker, C.

    2016-12-01

    Over the past 20 years, the NASA Marshall Space Flight Center, the University of Alabama in Huntsville, and their partners developed and demonstrated the effectiveness and value of space-based lightning observations as a remote sensing tool for Earth science research and applications, and, in the process, established a robust global lightning climatology. The observations included measurements from the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) and its Optical Transient Detector (OTD) predecessor that acquired global observations of total lightning (i.e., intracloud and cloud-to-ground discharges) spanning a period from May 1995 through April 2015. As an exciting follow-on to these prior missions, a space-qualified LIS built as a flight-spare for TRMM will be delivered to the International Space Station (ISS) for a 2 year or longer mission, flown as a hosted payload on the Department of Defense (DoD) Space Test Program-Houston 5 (STP-H5) mission. The STP-H5 payload containing LIS is scheduled launch from NASA's Kennedy Space Center to the ISS in November 2016, aboard the SpaceX Cargo Resupply Services-10 (SpaceX-10) mission, installed in the unpressurized "trunk" of the Dragon spacecraft. After the Dragon is berth to ISS Node 2, the payload will be removed from the trunk and robotically installed in a nadir-viewing location on the external truss of the ISS. Following installation on the ISS, the LIS Operations Team will work with the STP-H5 and ISS Operations Teams to power-on LIS and begin instrument checkout and commissioning. Following successful activation, LIS orbital operations will commence, managed from the newly established LIS Payload Operations Control Center (POCC) located at the National Space Science Technology Center (NSSTC) in Huntsville, AL. The well-established and robust processing, archival, and distribution infrastructure used for TRMM was easily adapted to the ISS mission, assuring that lightning

  1. Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy

    Chen, Qian Nataly; Li, Jiangyu; Adler, Stuart B.

    2014-01-01

    Nanocrystalline ceria exhibits a total conductivity several orders of magnitude higher than microcrystalline ceria in air at high temperature. The most widely accepted theory for this enhancement (based on fitting of conductivity data to various transport and kinetic models) is that relatively immobile positively charged defects and/or impurities accumulate at the grain boundary core, leading to a counterbalancing increase in the number of mobile electrons (small polarons) within a diffuse space charge region adjacent to each grain boundary. In an effort to validate this model, we have applied electrochemical strain microscopy to image the location and relative population of mobile electrons near grain boundaries in polycrystalline Sm-doped ceria in air at 20–200 °C. Our results show the first direct (spatially resolved) evidence that such a diffuse space charge region does exist in ceria, and is localized to both grain boundaries and the gas-exposed surface

  2. Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy

    Chen, Qian Nataly; Li, Jiangyu, E-mail: jjli@uw.edu [Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195 (United States); Adler, Stuart B., E-mail: stuadler@uw.edu [Department of Chemical Engineering, University of Washington, Seattle, Washington 98195 (United States)

    2014-11-17

    Nanocrystalline ceria exhibits a total conductivity several orders of magnitude higher than microcrystalline ceria in air at high temperature. The most widely accepted theory for this enhancement (based on fitting of conductivity data to various transport and kinetic models) is that relatively immobile positively charged defects and/or impurities accumulate at the grain boundary core, leading to a counterbalancing increase in the number of mobile electrons (small polarons) within a diffuse space charge region adjacent to each grain boundary. In an effort to validate this model, we have applied electrochemical strain microscopy to image the location and relative population of mobile electrons near grain boundaries in polycrystalline Sm-doped ceria in air at 20–200 °C. Our results show the first direct (spatially resolved) evidence that such a diffuse space charge region does exist in ceria, and is localized to both grain boundaries and the gas-exposed surface.

  3. 3D Reconfigurable NoC Multiprocessor Imaging Interferometer for Space Climate

    Dekoulis, George

    2016-07-01

    This paper describes the development of an imaging interferometer for long-term observations of solar activity related events. Heliospheric physics phenomena are responsible for causing irregularities to the ionospheric-magnetospheric plasmasphere. Distinct signatures of these events are captured and studied over long periods of time deducting crucial conclusions about the short-term Space Weather and in the long run about Space Climate. The new prototype features an eight-channel implementation. The available hardware resources permit a 256- channel configuration for accurate beam scanning of the Earth's plasmasphere. A dual-polarization scheme has been implemented for obtaining accurate measurements. The system is based on state-of-the-art three-dimensional reconfigurable logic and exhibits a performance increase in the range of 70% compared to similar instruments in operation. Special circuits allow measurements of the most intense heliospheric physics events to be fully captured and analyzed.

  4. Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space

    Hernando, Moises Fernandez; Cerezal, Luis; Perez-Carro, Luis; Abascal, Faustino; Canga, Ana

    2015-01-01

    Deep gluteal syndrome (DGS) is an underdiagnosed entity characterized by pain and/or dysesthesias in the buttock area, hip or posterior thigh and/or radicular pain due to a non-discogenic sciatic nerve entrapment in the subgluteal space. Multiple pathologies have been incorporated in this all-included ''piriformis syndrome,'' a term that has nothing to do with the presence of fibrous bands, obturator internus/gemellus syndrome, quadratus femoris/ischiofemoral pathology, hamstring conditions, gluteal disorders and orthopedic causes. The concept of fibrous bands playing a role in causing symptoms related to sciatic nerve mobility and entrapment represents a radical change in the current diagnosis of and therapeutic approach to DGS. The development of periarticular hip endoscopy has led to an understanding of the pathophysiological mechanisms underlying piriformis syndrome, which has supported its further classification. A broad spectrum of known pathologies may be located nonspecifically in the subgluteal space and can therefore also trigger DGS. These can be classified as traumatic, iatrogenic, inflammatory/infectious, vascular, gynecologic and tumors/pseudo-tumors. Because of the ever-increasing use of advanced magnetic resonance neurography (MRN) techniques and the excellent outcomes of the new endoscopic treatment, radiologists must be aware of the anatomy and pathologic conditions of this space. MR imaging is the diagnostic procedure of choice for assessing DGS and may substantially influence the management of these patients. The infiltration test not only has a high diagnostic but also a therapeutic value. This article describes the subgluteal space anatomy, reviews known and new etiologies of DGS, and assesses the role of the radiologist in the diagnosis, treatment and postoperative evaluation of sciatic nerve entrapments, with emphasis on MR imaging and endoscopic correlation. (orig.)

  5. Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space

    Hernando, Moises Fernandez; Cerezal, Luis; Perez-Carro, Luis; Abascal, Faustino; Canga, Ana [Diagnostico Medico Cantabria (DMC), Department of Radiology, Santander, Cantabria (Spain); Valdecilla University Hospital, Orthopedic Surgery Department Clinica Mompia (L.P.C.), Santander, Cantabria (Spain); Valdecilla University Hospital, Department of Radiology, Santander, Cantabria (Spain)

    2015-03-05

    Deep gluteal syndrome (DGS) is an underdiagnosed entity characterized by pain and/or dysesthesias in the buttock area, hip or posterior thigh and/or radicular pain due to a non-discogenic sciatic nerve entrapment in the subgluteal space. Multiple pathologies have been incorporated in this all-included ''piriformis syndrome,'' a term that has nothing to do with the presence of fibrous bands, obturator internus/gemellus syndrome, quadratus femoris/ischiofemoral pathology, hamstring conditions, gluteal disorders and orthopedic causes. The concept of fibrous bands playing a role in causing symptoms related to sciatic nerve mobility and entrapment represents a radical change in the current diagnosis of and therapeutic approach to DGS. The development of periarticular hip endoscopy has led to an understanding of the pathophysiological mechanisms underlying piriformis syndrome, which has supported its further classification. A broad spectrum of known pathologies may be located nonspecifically in the subgluteal space and can therefore also trigger DGS. These can be classified as traumatic, iatrogenic, inflammatory/infectious, vascular, gynecologic and tumors/pseudo-tumors. Because of the ever-increasing use of advanced magnetic resonance neurography (MRN) techniques and the excellent outcomes of the new endoscopic treatment, radiologists must be aware of the anatomy and pathologic conditions of this space. MR imaging is the diagnostic procedure of choice for assessing DGS and may substantially influence the management of these patients. The infiltration test not only has a high diagnostic but also a therapeutic value. This article describes the subgluteal space anatomy, reviews known and new etiologies of DGS, and assesses the role of the radiologist in the diagnosis, treatment and postoperative evaluation of sciatic nerve entrapments, with emphasis on MR imaging and endoscopic correlation. (orig.)

  6. 40 CFR 230.42 - Mud flats.

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Mud flats. 230.42 Section 230.42... Aquatic Sites § 230.42 Mud flats. (a) Mud flats are broad flat areas along the sea coast and in coastal rivers to the head of tidal influence and in inland lakes, ponds, and riverine systems. When mud flats...

  7. Restoration of color images degraded by space-variant motion blur

    Šorel, Michal; Flusser, Jan

    2007-01-01

    Roč. 2007, č. 4673 (2007), s. 450-457 ISSN 0302-9743. [Computer Analysis of Images and Patterns. Vienna, 27.08.2007-29.08.2007] R&D Projects: GA MŠk 1M0572 Institutional research plan: CEZ:AV0Z10750506 Keywords : deblurring * space-variant restoration * motion blur * color Subject RIV: JD - Computer Applications, Robotics Impact factor: 0.402, year: 2005 http://dx.doi.org/10.1007/978-3-540-74272-2_56

  8. Estimation of the depth of the thoracic epidural space in children using magnetic resonance imaging

    Wani TM

    2017-03-01

    Full Text Available Tariq M Wani,1,2 Mahmood Rafiq,1 Arif Nazir,1 Hatem A Azzam,1 Usama Al Zuraigi,1 Joseph D Tobias2 1Department of Anesthesia, King Fahad Medical City, Riyadh, Saudi Arabia; 2Department of Anesthesiology and Pain Medicine, Nationwide Children’s Hospital, Columbus, OH, USA Background: The estimation of the distance from the skin to the thoracic epidural space or skin to epidural depth (SED may increase the success rate and decrease the incidence of complications during placement of a thoracic epidural catheter. Magnetic resonance imaging (MRI is the most comprehensive imaging modality of the spine, allowing for the accurate determination of tissue spaces and distances. The present study uses MRI-derived measurements to measure the SED and define the ratio between the straight and inclined SEDs at two thoracic levels (T6–7 and T9–10 in children.Methods: The T2-weighed sagittal MRI images of 109 children, ranging in age from 1 month to 8 years, undergoing radiological evaluation unrelated to spine pathology were assessed. The SEDs (inclined and straight were determined, and a comparison between the SEDs at two thoracic levels (T6–7 and T9–10 was made. Univariate and multivariate linear regression models were used to assess the relationship of the inclined thoracic T6–7 and T9–10 SED measurements with age, height, and weight.Results: Body weight demonstrated a stronger association with the SED than did the age or height with R2 values of 0.6 for T6–7 and 0.5 for T9–10. The formulae describing the relationship between the weight and the inclined SED were T6–7 inclined (mm = 7 + 0.9 × kg and T9–10 inclined (mm = 7 + 0.8 × kg.Conclusion: The depth of the pediatric thoracic epidural space shows a stronger correlation with weight than with age or height. Based on the MRI data, the predictive weight-based formulas can serve as guide to clinicians for placement of thoracic epidural catheters. Keywords: thoracic epidural space

  9. The development of a specialized processor for a space-based multispectral earth imager

    Khedr, Mostafa E.

    2008-10-01

    This work was done in the Department of Computer Engineering, Lvov Polytechnic National University, Lvov, Ukraine, as a thesis entitled "Space Imager Computer System for Raw Video Data Processing" [1]. This work describes the synthesis and practical implementation of a specialized computer system for raw data control and processing onboard a satellite MultiSpectral earth imager. This computer system is intended for satellites with resolution in the range of one meter with 12-bit precession. The design is based mostly on general off-the-shelf components such as (FPGAs) plus custom designed software for interfacing with PC and test equipment. The designed system was successfully manufactured and now fully functioning in orbit.

  10. Anatomy of the retroperitoneal space as shown by magnetic resonance imaging

    Zilch, H.G.; Hammersen, F.

    1989-01-01

    More than 300 NMR examinations form the basis of the survey presented of the anatomy and topography of the retroperitoneal space. The examinations were done with the Siemens supraconducting magnet system 'Magnetom' (1.0 Tesla), with different planes of imaging chosen, according to clinical approaches (axial, sagittal, frontal). Sectional thicknesses varied between 5 and 10 mm. The spin-echo technique was applied, with repetition times between 0.3 and 2.0s, echo times between 30 and 150 ms. In addition, special means such as high-resolution coils and respiratory gating were applied, and also a contrast medium (gadolinium-DTPA). The possibilities of imaging are explained, referring to the pancreas, kidneys, adrenal glands, lymph nodes, aorta abdominalis, and vena cava inferior. (orig./MG) [de

  11. Space telescope design to directly image the habitable zone of Alpha Centauri

    Bendek, Eduardo A.; Belikov, Ruslan; Lozi, Julien; Thomas, Sandrine; Males, Jared; Weston, Sasha; McElwain, Michael

    2015-09-01

    The scientific interest in directly imaging and identifying Earth-like planets within the Habitable Zone (HZ) around nearby stars is driving the design of specialized direct imaging missions such as ACESAT, EXO-C, EXO-S and AFTA-C. The inner edge of Alpha Cen A and B Habitable Zone is found at exceptionally large angular separations of 0.7" and 0.4" respectively. This enables direct imaging of the system with a 0.3m class telescope. Contrast ratios on the order of 1010 are needed to image Earth-brightness planets. Low-resolution (5-band) spectra of all planets may allow establishing the presence and amount of an atmosphere. This star system configuration is optimal for a specialized small, and stable space telescope that can achieve high-contrast but has limited resolution. This paper describes an innovative instrument design and a mission concept based on a full Silicon Carbide off-axis telescope, which has a Phase Induced Amplitude Apodization coronagraph embedded in the telescope. This architecture maximizes stability and throughput. A Multi-Star Wave Front algorithm is implemented to drive a deformable mirror controlling simultaneously diffracted light from the on-axis and binary companion star. The instrument has a Focal Plane Occulter to reject starlight into a highprecision pointing control camera. Finally we utilize a Orbital Differential Imaging (ODI) post-processing method that takes advantage of a highly stable environment (Earth-trailing orbit) and a continuous sequence of images spanning 2 years, to reduce the final noise floor in post processing to ~2e-11 levels, enabling high confidence and at least 90% completeness detections of Earth-like planets.

  12. Semiautomated digital analysis of knee joint space width using MR images

    Agnesi, Filippo; Amrami, Kimberly K.; Frigo, Carlo A.; Kaufman, Kenton R.

    2007-01-01

    The goal of this study was to (a) develop a semiautomated computer algorithm to measure knee joint space width (JSW) from magnetic resonance (MR) images using standard imaging techniques and (b) evaluate the reproducibility of the algorithm. Using a standard clinical imaging protocol, bilateral knee MR images were obtained twice within a 2-week period from 17 asymptomatic research participants. Images were analyzed to determine the variability of the measurements performed by the program compared with the variability of manual measurements. Measurement variability of the computer algorithm was considerably smaller than the variability of manual measurements. The average difference between two measurements of the same slice performed with the computer algorithm by the same user was 0.004 ± 0.07 mm for the tibiofemoral joint (TF) and 0.009 ± 0.11 mm for the patellofemoral joint (PF) compared with an average of 0.12 ± 0.22 mm TF and 0.13 ± 0.29 mm PF, respectively, for the manual method. Interuser variability of the computer algorithm was also considerably smaller, with an average difference of 0.004 ± 0.1 mm TF and 0.0006 ± 0.1 mm PF compared with 0.38 ± 0.59 mm TF and 0.31 ± 0.66 mm PF obtained using a manual method. The between-day reproducibility was larger but still within acceptable limits at 0.09 ± 0.39 mm TF and 0.09 ± 0.51 mm PF. This technique has proven consistently reproducible on a same slice base,while the reproducibility comparing different acquisitions of the same subject was larger. Longitudinal reproducibility improvement needs to be addressed through acquisition protocol improvements. A semiautomated method for measuring knee JSW from MR images has been successfully developed. (orig.)

  13. Semiautomated digital analysis of knee joint space width using MR images

    Agnesi, Filippo [Mayo Clinic, Motion Analysis Laboratory, Division of Orthopedic Research, Rochester, MN (United States); Polytechnic of Milan, Department of Bioengineering, Milan (Italy); Amrami, Kimberly K. [Mayo Clinic, Department of Radiology, Rochester, MN (United States); Frigo, Carlo A. [Polytechnic of Milan, Department of Bioengineering, Milan (Italy); Kaufman, Kenton R. [Mayo Clinic, Motion Analysis Laboratory, Division of Orthopedic Research, Rochester, MN (United States); Mayo Clinic, Mayo Foundation, Motion Analysis Laboratory, Department of Orthopedic Surgery, Rochester, MN (United States)

    2007-05-15

    The goal of this study was to (a) develop a semiautomated computer algorithm to measure knee joint space width (JSW) from magnetic resonance (MR) images using standard imaging techniques and (b) evaluate the reproducibility of the algorithm. Using a standard clinical imaging protocol, bilateral knee MR images were obtained twice within a 2-week period from 17 asymptomatic research participants. Images were analyzed to determine the variability of the measurements performed by the program compared with the variability of manual measurements. Measurement variability of the computer algorithm was considerably smaller than the variability of manual measurements. The average difference between two measurements of the same slice performed with the computer algorithm by the same user was 0.004 {+-} 0.07 mm for the tibiofemoral joint (TF) and 0.009 {+-} 0.11 mm for the patellofemoral joint (PF) compared with an average of 0.12 {+-} 0.22 mm TF and 0.13 {+-} 0.29 mm PF, respectively, for the manual method. Interuser variability of the computer algorithm was also considerably smaller, with an average difference of 0.004 {+-} 0.1 mm TF and 0.0006 {+-} 0.1 mm PF compared with 0.38 {+-} 0.59 mm TF and 0.31 {+-} 0.66 mm PF obtained using a manual method. The between-day reproducibility was larger but still within acceptable limits at 0.09 {+-} 0.39 mm TF and 0.09 {+-} 0.51 mm PF. This technique has proven consistently reproducible on a same slice base,while the reproducibility comparing different acquisitions of the same subject was larger. Longitudinal reproducibility improvement needs to be addressed through acquisition protocol improvements. A semiautomated method for measuring knee JSW from MR images has been successfully developed. (orig.)

  14. Medical X-ray Image Hierarchical Classification Using a Merging and Splitting Scheme in Feature Space.

    Fesharaki, Nooshin Jafari; Pourghassem, Hossein

    2013-07-01

    Due to the daily mass production and the widespread variation of medical X-ray images, it is necessary to classify these for searching and retrieving proposes, especially for content-based medical image retrieval systems. In this paper, a medical X-ray image hierarchical classification structure based on a novel merging and splitting scheme and using shape and texture features is proposed. In the first level of the proposed structure, to improve the classification performance, similar classes with regard to shape contents are grouped based on merging measures and shape features into the general overlapped classes. In the next levels of this structure, the overlapped classes split in smaller classes based on the classification performance of combination of shape and texture features or texture features only. Ultimately, in the last levels, this procedure is also continued forming all the classes, separately. Moreover, to optimize the feature vector in the proposed structure, we use orthogonal forward selection algorithm according to Mahalanobis class separability measure as a feature selection and reduction algorithm. In other words, according to the complexity and inter-class distance of each class, a sub-space of the feature space is selected in each level and then a supervised merging and splitting scheme is applied to form the hierarchical classification. The proposed structure is evaluated on a database consisting of 2158 medical X-ray images of 18 classes (IMAGECLEF 2005 database) and accuracy rate of 93.6% in the last level of the hierarchical structure for an 18-class classification problem is obtained.

  15. Application of ultrasound processed images in space: Quanitative assessment of diffuse affectations

    Pérez-Poch, A.; Bru, C.; Nicolau, C.

    The purpose of this study was to evaluate diffuse affectations in the liver using texture image processing techniques. Ultrasound diagnose equipments are the election of choice to be used in space environments as they are free from hazardous effects on health. However, due to the need for highly trained radiologists to assess the images, this imaging method is mainly applied on focal lesions rather than on non-focal ones. We have conducted a clinical study on 72 patients with different degrees of chronic hepatopaties and a group of control of 18 individuals. All subjects' clinical reports and results of biopsies were compared to the degree of affectation calculated by our computer system , thus validating the method. Full statistical results are given in the present paper showing a good correlation (r=0.61) between pathologist's report and analysis of the heterogenicity of the processed images from the liver. This computer system to analyze diffuse affectations may be used in-situ or via telemedicine to the ground.

  16. Design of free space optical omnidirectional transceivers for indoor applications using non-imaging optical devices

    Agrawal, Navik; Davis, Christopher C.

    2008-08-01

    Omnidirectional free space optical communication receivers can employ multiple non-imaging collectors, such as compound parabolic concentrators (CPCs), in an array-like fashion to increase the amount of possible light collection. CPCs can effectively channel light collected over a large aperture to a small area photodiode. The aperture to length ratio of such devices can increase the overall size of the transceiver unit, which may limit the practicality of such systems, especially when small size is desired. New non-imaging collector designs with smaller sizes, larger field of view (FOV), and comparable transmission curves to CPCs, offer alternative transceiver designs. This paper examines how transceiver performance is affected by the use of different non-imaging collector shapes that are designed for wide FOV with reduced efficiency compared with shapes such as the CPC that are designed for small FOV with optimal efficiency. Theoretical results provide evidence indicating that array-like transceiver designs using various non-imaging collector shapes with less efficient transmission curves, but a larger FOV will be an effective means for the design of omnidirectional optical transceiver units. The results also incorporate the effects of Fresnel loss at the collector exit aperture-photodiode interface, which is an important consideration for indoor omnidirectional FSO systems.

  17. Statistical inference and visualization in scale-space for spatially dependent images

    Vaughan, Amy

    2012-03-01

    SiZer (SIgnificant ZERo crossing of the derivatives) is a graphical scale-space visualization tool that allows for statistical inferences. In this paper we develop a spatial SiZer for finding significant features and conducting goodness-of-fit tests for spatially dependent images. The spatial SiZer utilizes a family of kernel estimates of the image and provides not only exploratory data analysis but also statistical inference with spatial correlation taken into account. It is also capable of comparing the observed image with a specific null model being tested by adjusting the statistical inference using an assumed covariance structure. Pixel locations having statistically significant differences between the image and a given null model are highlighted by arrows. The spatial SiZer is compared with the existing independent SiZer via the analysis of simulated data with and without signal on both planar and spherical domains. We apply the spatial SiZer method to the decadal temperature change over some regions of the Earth. © 2011 The Korean Statistical Society.

  18. Hubble Space Telescope Imaging of the Mass-losing Supergiant VY Canis Majoris

    Kastner, Joel H.; Weintraub, David A.

    1998-04-01

    The highly luminous M supergiant VY CMa is a massive star that appears to be in its final death throes, losing mass at high rate en route to exploding as a supernova. Subarcsecond-resolution optical images of VY CMa, obtained with the Faint Object Camera (FOC) aboard the Hubble Space Telescope, vividly demonstrate that mass loss from VY CMa is highly anisotropic. In the FOC images, the optical ``star'' VY CMa constitutes the bright, well-resolved core of an elongated reflection nebula. The imaged nebula is ~3" (~4500 AU) in extent and is clumpy and highly asymmetric. The images indicate that the bright core, which lies near one edge of the nebula, is pure scattered starlight. We conclude that at optical wavelengths VY CMa is obscured from view along our line of sight by its own dusty envelope. The presence of the extended reflection nebula then suggests that this envelope is highly flattened and/or that the star is surrounded by a massive circumstellar disk. Such axisymmetric circumstellar density structure should have profound effects on post-red supergiant mass loss from VY CMa and, ultimately, on the shaping of the remnant of the supernova that will terminate its post-main-sequence evolution.

  19. Papaya Tree Detection with UAV Images Using a GPU-Accelerated Scale-Space Filtering Method

    Hao Jiang

    2017-07-01

    Full Text Available The use of unmanned aerial vehicles (UAV can allow individual tree detection for forest inventories in a cost-effective way. The scale-space filtering (SSF algorithm is commonly used and has the capability of detecting trees of different crown sizes. In this study, we made two improvements with regard to the existing method and implementations. First, we incorporated SSF with a Lab color transformation to reduce over-detection problems associated with the original luminance image. Second, we ported four of the most time-consuming processes to the graphics processing unit (GPU to improve computational efficiency. The proposed method was implemented using PyCUDA, which enabled access to NVIDIA’s compute unified device architecture (CUDA through high-level scripting of the Python language. Our experiments were conducted using two images captured by the DJI Phantom 3 Professional and a most recent NVIDIA GPU GTX1080. The resulting accuracy was high, with an F-measure larger than 0.94. The speedup achieved by our parallel implementation was 44.77 and 28.54 for the first and second test image, respectively. For each 4000 × 3000 image, the total runtime was less than 1 s, which was sufficient for real-time performance and interactive application.

  20. A rationalized approach to the imaging of space-occupying lesions in the liver

    Engelbrecht, H.E.

    1985-01-01

    A rational approach to the imaging of mass lesions within the liver has been presented. An attempt has been made to advocate a philosophy which emphasizes the importance of considering pathological, biochemical, clinical and likely management criteria in each case before selecting a first-line imaging procedure. The subject is presented under three headings: i) What That is, clinical and pathological criteria for assesing the nature of a suspected space-occupying lesion in the liver; ii) Why That is a projection of the likely practical value of the result; iii) How That is determination of a logical imaging program depending on the assesment of criteria under the first two headings. The following examples of active treatment are discussed: partial hepotectomy, highly vascular lesions, toxaemia and pyrexia. The following factors influence the decision of the imaging procedure to be used: the accuracy of the modality in relation to the suspected lesion, local availability of equipment and expentise, invasive versus non-invasive aspects and cost-effectiveness

  1. Alterations of the cytoskeleton in human cells in space proved by life-cell imaging

    Corydon, Thomas J.; Kopp, Sascha; Wehland, Markus; Braun, Markus; Schütte, Andreas; Mayer, Tobias; Hülsing, Thomas; Oltmann, Hergen; Schmitz, Burkhard; Hemmersbach, Ruth; Grimm, Daniela

    2016-01-01

    Microgravity induces changes in the cytoskeleton. This might have an impact on cells and organs of humans in space. Unfortunately, studies of cytoskeletal changes in microgravity reported so far are obligatorily based on the analysis of fixed cells exposed to microgravity during a parabolic flight campaign (PFC). This study focuses on the development of a compact fluorescence microscope (FLUMIAS) for fast live-cell imaging under real microgravity. It demonstrates the application of the instrument for on-board analysis of cytoskeletal changes in FTC-133 cancer cells expressing the Lifeact-GFP marker protein for the visualization of F-actin during the 24th DLR PFC and TEXUS 52 rocket mission. Although vibration is an inevitable part of parabolic flight maneuvers, we successfully for the first time report life-cell cytoskeleton imaging during microgravity, and gene expression analysis after the 31st parabola showing a clear up-regulation of cytoskeletal genes. Notably, during the rocket flight the FLUMIAS microscope reveals significant alterations of the cytoskeleton related to microgravity. Our findings clearly demonstrate the applicability of the FLUMIAS microscope for life-cell imaging during microgravity, rendering it an important technological advance in live-cell imaging when dissecting protein localization. PMID:26818711

  2. Accelerated whole brain intracranial vessel wall imaging using black blood fast spin echo with compressed sensing (CS-SPACE).

    Zhu, Chengcheng; Tian, Bing; Chen, Luguang; Eisenmenger, Laura; Raithel, Esther; Forman, Christoph; Ahn, Sinyeob; Laub, Gerhard; Liu, Qi; Lu, Jianping; Liu, Jing; Hess, Christopher; Saloner, David

    2018-06-01

    Develop and optimize an accelerated, high-resolution (0.5 mm isotropic) 3D black blood MRI technique to reduce scan time for whole-brain intracranial vessel wall imaging. A 3D accelerated T 1 -weighted fast-spin-echo prototype sequence using compressed sensing (CS-SPACE) was developed at 3T. Both the acquisition [echo train length (ETL), under-sampling factor] and reconstruction parameters (regularization parameter, number of iterations) were first optimized in 5 healthy volunteers. Ten patients with a variety of intracranial vascular disease presentations (aneurysm, atherosclerosis, dissection, vasculitis) were imaged with SPACE and optimized CS-SPACE, pre and post Gd contrast. Lumen/wall area, wall-to-lumen contrast ratio (CR), enhancement ratio (ER), sharpness, and qualitative scores (1-4) by two radiologists were recorded. The optimized CS-SPACE protocol has ETL 60, 20% k-space under-sampling, 0.002 regularization factor with 20 iterations. In patient studies, CS-SPACE and conventional SPACE had comparable image scores both pre- (3.35 ± 0.85 vs. 3.54 ± 0.65, p = 0.13) and post-contrast (3.72 ± 0.58 vs. 3.53 ± 0.57, p = 0.15), but the CS-SPACE acquisition was 37% faster (6:48 vs. 10:50). CS-SPACE agreed with SPACE for lumen/wall area, ER measurements and sharpness, but marginally reduced the CR. In the evaluation of intracranial vascular disease, CS-SPACE provides a substantial reduction in scan time compared to conventional T 1 -weighted SPACE while maintaining good image quality.

  3. Lightning Imaging Sensor (LIS) on the International Space Station (ISS): Launch, Installation, Activation, and First Results

    Blakeslee, R. J.; Christian, H. J., Jr.; Mach, D. M.; Buechler, D. E.; Wharton, N. A.; Stewart, M. F.; Ellett, W. T.; Koshak, W. J.; Walker, T. D.

    2017-12-01

    Over two decades, the NASA Marshall Space Flight Center, the University of Alabama in Huntsville, and their partners developed and demonstrated the effectiveness and value of space-based lightning observations as a remote sensing tool for Earth science research and applications, and, in the process, established a robust global lightning climatology. The Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) provided global observations of tropical lightning for an impressive 17 years before that mission came to a close in April 2015. Now a space-qualified LIS, built as the flight spare for TRMM, has been installed on the International Space Station (ISS) for a minimum two year mission following its SpaceX launch on February 19, 2017. The LIS, flown as a hosted payload on the Department of Defense Space Test Program-Houston 5 (STP-H5) mission, was robotically installed in an Earth-viewing position on the outside of the ISS, providing a great opportunity to not only extend the 17-year TRMM LIS record of tropical lightning measurements but also to expand that coverage to higher latitudes missed by the TRMM mission. Since its activation, LIS has continuously observed the amount, rate, and radiant energy lightning within its field-of-view as it orbits the Earth. A major focus of this mission is to better understand the processes which cause lightning, as well as the connections between lightning and subsequent severe weather events. This understanding is a key to improving weather predictions and saving lives and property here in the United States and around the world. The LIS measurements will also help cross-validate observations from the new Geostationary Lightning Mapper (GLM) operating on NOAA's newest weather satellite GOES-16. An especially unique contribution from the ISS platform will be the availability of real-time lightning data, especially valuable for operational forecasting and warning applications over data sparse regions such

  4. The bifurcations of nearly flat origami

    Santangelo, Christian

    Self-folding origami structures provide one means of fabricating complex, three-dimensional structures from a flat, two-dimensional sheet. Self-folding origami structures have been fabricated on scales ranging from macroscopic to microscopic and can have quite complicated structures with hundreds of folds arranged in complex patterns. I will describe our efforts to understand the mechanics and energetics of self-folding origami structures. Though the dimension of the configuration space of an origami structure scales with the size of the boundary and not with the number of vertices in the interior of the structure, a typical origami structure is also floppy in the sense that there are many possible ways to assign fold angles consistently. I will discuss our theoretical progress in understanding the geometry of the configuration space of origami. For random origami, the number of possible bifurcations grows surprisingly quickly even when the dimension of the configuration space is small. EFRI ODISSEI-1240441, DMR-0846582.

  5. High resolution time- and 2-dimensional space-resolved x-ray imaging of plasmas at NOVA

    Landen, O.L.

    1992-01-01

    A streaked multiple pinhole camera technique, first used by P. Choi et al. to record time- and 2-D space-resolved soft X-ray images of plasma pinches, has been implemented on laser plasmas at NOVA. The instrument is particularly useful for time-resolved imaging of small sources ( 2.5 key imaging, complementing the existing 1--3 key streaked X-ray microscope capabilities at NOVA

  6. All-sky-imaging capabilities for ionospheric space weather research using geomagnetic conjugate point observing sites

    Martinis, C.; Baumgardner, J.; Wroten, J.; Mendillo, M.

    2018-04-01

    Optical signatures of ionospheric disturbances exist at all latitudes on Earth-the most well known case being visible aurora at high latitudes. Sub-visual emissions occur equatorward of the auroral zones that also indicate periods and locations of severe Space Weather effects. These fall into three magnetic latitude domains in each hemisphere: (1) sub-auroral latitudes ∼40-60°, (2) mid-latitudes (20-40°) and (3) equatorial-to-low latitudes (0-20°). Boston University has established a network of all-sky-imagers (ASIs) with sites at opposite ends of the same geomagnetic field lines in each hemisphere-called geomagnetic conjugate points. Our ASIs are autonomous instruments that operate in mini-observatories situated at four conjugate pairs in North and South America, plus one pair linking Europe and South Africa. In this paper, we describe instrument design, data-taking protocols, data transfer and archiving issues, image processing, science objectives and early results for each latitude domain. This unique capability addresses how a single source of disturbance is transformed into similar or different effects based on the unique "receptor" conditions (seasonal effects) found in each hemisphere. Applying optical conjugate point observations to Space Weather problems offers a new diagnostic approach for understanding the global system response functions operating in the Earth's upper atmosphere.

  7. Stationary closed strings in five-dimensional flat spacetime

    Igata, Takahisa; Ishihara, Hideki; Nishiwaki, Keisuke

    2012-11-01

    We investigate stationary rotating closed Nambu-Goto strings in five-dimensional flat spacetime. The stationary string is defined as a world sheet that is tangent to a timelike Killing vector. The Nambu-Goto equation of motion for the stationary string is reduced to the geodesic equation on the orbit space of the isometry group action generated by the Killing vector. We take a linear combination of a time-translation vector and space-rotation vectors as the Killing vector, and explicitly construct general solutions of stationary rotating closed strings in five-dimensional flat spacetime. We show a variety of their configurations and properties.

  8. NASA Space Imaging is a Great Resource to Teach Science Topics in Professional Development Courses

    Verner, E.; Bruhweiler, F. C.; Long, T.; Edwards, S.; Ofman, L.; Brosius, J. W.; Gordon, D.; St Cyr, O. C.; Krotkov, N. A.; Fatoyinbo, T. E.

    2013-12-01

    Our multi- component project aims to develop and test NASA educational resource materials, provide training for pre- and in-service elementary school teachers in STEM disciplines needed in Washington DC area. We use physics and math in a hands-on enquiry based setting and make extensive use of imagery from NASA space missions (SDO, SOHO, STEREO) to develop instructional modules focusing on grades, PK-8. Our two years of effort culminated in developing three modules: The Sun - the nearest star Students learn about the Sun as the nearest star. Students make outdoor observations during the day and all year round. At night, they observe and record the motion of the moon and stars. Students learn these bodies move in regular and predictable ways. Electricity & Magnetism - From your classroom to the Sun Students investigate electricity and magnetism in the classroom and see large scale examples of these concepts on the Sun's surface, interplanetary space, and the Earth's magnetosphere as revealed from NASA space missions. Solar Energy The Sun is the primary source of energy for Earth's climate system. Students learn about wavelength and frequency and develop skills to do scientific inquiry, including how to use math as a tool. They use optical, UV, EUV, and X-ray images to trace out the energetic processes of the Sun. Each module includes at least one lesson plan, vocabulary, activities and children book for each grade range PK-3; 4-5; 6-8

  9. Validation of Ultrasound Imaging to Rule-out Thoracic Trauma on the International Space Station

    Hamilton, Douglas R.; Sargsyan, Ashot E.; Melton, Shannon; Martin, David; Dulchavsky, Scott A.

    2006-01-01

    Introduction: Aboard the International Space Station (ISS) an intra-thoracic injury may be disastrous to the crew member if the diagnosis is missed or even delayed. Pneumothorax and hemothorax commonly seen in trauma patients; the diagnosis is usually confirmed by chest X-ray or computed tomography. In this study, the ability of ultrasound to rule out pneumothorax by the presence "lung sliding" and hemothorax by the absence of pleural fluid was validated. Methods: The research activities were approved by the NASA Johnson Space Center Committee for the Protection of Human Subjects, and the participating crewmembers signed informed consent prior to the activity. ISS crewmembers received 2-hours of "hands on" ultrasound training 8 months prior to the on-orbit ultrasound exam. Baseline ultrasound images of the thorax were acquired on the crewmebers of Increment 8 and 9 prior to launch from Bakonur, Russia. Ultrasound examination of the thorax were performed on crewmembers at 30 day intervals (n=??) throughout their flight. Post flight images were acquired on or about landing day 10. Ultrasound images were acquired using the ISS Health Research Facility ultrasound system and examined by experts on the ground to rule out the presence of pneumothorax and hemothorax. Results: The presence of "lung sliding" which excludes pneumothorax, was seen in all subjects. The absence of pleural fluid, which excludes hemothorax was seen in all subjects. The optimal position between sonographer and patient under microgravity conditions and the amount and type of training for a non-physician crew medical officer for these procedures was also established for this procedure. Conclusion: Ultrasound can be performed on orbit under microgravity condition to rule thoracic trauma, such as pneumothorax and hemothorax.

  10. Flat H Frangible Joint Evolution

    Diegelman, Thomas E.; Hinkel, Todd J.; Benjamin, Andrew; Rochon, Brian V.; Brown, Christopher W.

    2016-01-01

    Space vehicle staging and separation events require pyrotechnic devices. They are single-use mechanisms that cannot be tested, nor can failure-tolerant performance be demonstrated in actual flight articles prior to flight use. This necessitates the implementation of a robust design and test approach coupled with a fully redundant, failure-tolerant explosive mechanism to ensure that the system functions even in the event of a single failure. Historically, NASA has followed the single failure-tolerant (SFT) design philosophy for all human-rated spacecraft, including the Space Shuttle Program. Following the end of this program, aerospace companies proposed building the next generation human-rated vehicles with off-the-shelf, non-redundant, zero-failure-tolerant (ZFT) separation systems. Currently, spacecraft and launch vehicle providers for both the Orion and Commercial Crew Programs (CCPs) plan to deviate from the heritage safety approach and NASA's SFT human rating requirements. Both programs' partners have base-lined ZFT frangible joints for vehicle staging and fairing separation. These joints are commercially available from pyrotechnic vendors. Non-human-rated missions have flown them numerous times. The joints are relatively easy to integrate structurally within the spacecraft. In addition, the separation event is debris free, and the resultant pyro shock is lower than that of other design solutions. It is, however, a serious deficiency to lack failure tolerance. When used for critical applications on human-rated vehicles, a single failure could potentially lead to loss of crew (LOC) or loss of mission (LOM)). The Engineering and Safety & Mission Assurance directorates within the NASA Johnson Space Center took action to address this safety issue by initiating a project to develop a fully redundant, SFT frangible joint design, known as the Flat H. Critical to the ability to retrofit on launch vehicles being developed, the SFT mechanisms must fit within the same

  11. Mapping Palaeohydrography in Deserts: Contribution from Space-Borne Imaging Radar

    Philippe Paillou

    2017-03-01

    Full Text Available Space-borne Synthetic Aperture Radar (SAR has the capability to image subsurface features down to several meters in arid regions. A first demonstration of this capability was performed in the Egyptian desert during the early eighties, thanks to the first Shuttle Imaging Radar mission. Global coverage provided by recent SARs, such as the Japanese ALOS/PALSAR sensor, allowed the mapping of vast ancient hydrographic systems in Northern Africa. We present a summary of palaeohydrography results obtained using PALSAR data over large deserts such as the Sahara and the Gobi. An ancient river system was discovered in eastern Lybia, connecting in the past the Kufrah oasis to the Mediterranean Sea, and the terminal part of the Tamanrasett river was mapped in western Mauritania, ending with a large submarine canyon. In southern Mongolia, PALSAR images combined with topography analysis allowed the mapping of the ancient Ulaan Nuur lake. We finally show the potentials of future low frequency SAR sensors by comparing L-band (1.25 GHz and P-band (435 MHz airborne SAR acquisitions over a desert site in southern Tunisia.

  12. Ultracompact Blue Dwarf Galaxies: Hubble Space Telescope Imaging and Stellar Population Analysis

    Corbin, Michael R.; Vacca, William D.; Cid Fernandes, Roberto; Hibbard, John E.; Somerville, Rachel S.; Windhorst, Rogier A.

    2006-11-01

    We present deep Hubble Space Telescope (HST) Advanced Camera for Surveys/High Resolution Channel U-, narrow-V-, and I-band images of nine ``ultracompact'' blue dwarf galaxies (UCBDs) selected from the Sloan Digital Sky Survey (SDSS). We define UCBDs as local (zPOX 186, but the structure of several of them suggests that their current star formation has been triggered by the collisions/mergers of smaller clumps of stars. In one case, HS 0822+3542, the images resolve what may be two small (~100 pc) components that have recently collided, supporting this interpretation. In six of the objects much of the star formation is concentrated in young massive clusters, contributing to their compactness in ground-based images. The evidence that the galaxies consist mainly of ~10 Gyr old stars establishes that they are not protogalaxies, forming their first generation of stars. Their low metallicities are more likely to be the result of the escape of supernova ejecta, rather than youth.

  13. Semi-automated digital image analysis of patellofemoral joint space width from lateral knee radiographs

    Grochowski, S.J. [Mayo Clinic, Department of Orthopedic Surgery, Rochester (United States); Amrami, K.K. [Mayo Clinic, Department of Radiology, Rochester (United States); Kaufman, K. [Mayo Clinic, Department of Orthopedic Surgery, Rochester (United States); Mayo Clinic/Foundation, Biomechanics Laboratory, Department of Orthopedic Surgery, Charlton North L-110L, Rochester (United States)

    2005-10-01

    To design a semi-automated program to measure minimum patellofemoral joint space width (JSW) using standing lateral view radiographs. Lateral patellofemoral knee radiographs were obtained from 35 asymptomatic subjects. The radiographs were analyzed to report both the repeatability of the image analysis program and the reproducibility of JSW measurements within a 2 week period. The results were also compared with manual measurements done by an experienced musculoskeletal radiologist. The image analysis program was shown to have an excellent coefficient of repeatability of 0.18 and 0.23 mm for intra- and inter-observer measurements respectively. The manual method measured a greater minimum JSW than the automated method. Reproducibility between days was comparable to other published results, but was less satisfactory for both manual and semi-automated measurements. The image analysis program had an inter-day coefficient of repeatability of 1.24 mm, which was lower than 1.66 mm for the manual method. A repeatable semi-automated method for measurement of the patellofemoral JSW from radiographs has been developed. The method is more accurate than manual measurements. However, the between-day reproducibility is higher than the intra-day reproducibility. Further investigation of the protocol for obtaining sequential lateral knee radiographs is needed in order to reduce the between-day variability. (orig.)

  14. A statistically harmonized alignment-classification in image space enables accurate and robust alignment of noisy images in single particle analysis.

    Kawata, Masaaki; Sato, Chikara

    2007-06-01

    In determining the three-dimensional (3D) structure of macromolecular assemblies in single particle analysis, a large representative dataset of two-dimensional (2D) average images from huge number of raw images is a key for high resolution. Because alignments prior to averaging are computationally intensive, currently available multireference alignment (MRA) software does not survey every possible alignment. This leads to misaligned images, creating blurred averages and reducing the quality of the final 3D reconstruction. We present a new method, in which multireference alignment is harmonized with classification (multireference multiple alignment: MRMA). This method enables a statistical comparison of multiple alignment peaks, reflecting the similarities between each raw image and a set of reference images. Among the selected alignment candidates for each raw image, misaligned images are statistically excluded, based on the principle that aligned raw images of similar projections have a dense distribution around the correctly aligned coordinates in image space. This newly developed method was examined for accuracy and speed using model image sets with various signal-to-noise ratios, and with electron microscope images of the Transient Receptor Potential C3 and the sodium channel. In every data set, the newly developed method outperformed conventional methods in robustness against noise and in speed, creating 2D average images of higher quality. This statistically harmonized alignment-classification combination should greatly improve the quality of single particle analysis.

  15. Lightning Imaging Sensor (LIS) for the International Space Station (ISS): Mission Description and Science Goals

    Blakeslee, R. J.; Christian, H. J.; Mach, D. M.; Buechler, D. E.; Koshak, W. J.; Walker, T. D.; Bateman, M.; Stewart, M. F.; O'Brien, S.; Wilson, T.; hide

    2015-01-01

    In recent years, the NASA Marshall Space Flight Center, the University of Alabama in Huntsville, and their partners have developed and demonstrated space-based lightning observations as an effective remote sensing tool for Earth science research and applications. The Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) continues to acquire global observations of total (i.e., intracloud and cloud-to-ground) lightning after 17 years on-orbit. However, TRMM is now low on fuel, so this mission will soon be completed. As a follow on to this mission, a space-qualified LIS built as the flight spare for TRMM has been selected for flight as a science mission on the International Space Station (ISS). The ISS LIS will be flown as a hosted payload on the Department of Defense Space Test Program (STP) H5 mission, which has a January 2016 baseline launch date aboard a SpaceX launch vehicle for a 2-4 year or longer mission. The LIS measures the amount, rate, and radiant energy of total lightning over the Earth. More specifically, it measures lightning during both day and night, with storm scale resolution (approx. 4 km), millisecond timing, and high, uniform detection efficiency, without any land-ocean bias. Lightning is a direct and most impressive response to intense atmospheric convection. It has been found that lightning measured by LIS can be quantitatively related to thunderstorm and other geophysical processes. Therefore, the ISS LIS lightning observations will continue to provide important gap-filling inputs to pressing Earth system science issues across a broad range of disciplines, including weather, climate, atmospheric chemistry, and lightning physics. A unique contribution from the ISS platform will be the availability of real-time lightning data, especially valuable for operational applications over data sparse regions such as the oceans. The ISS platform will also uniquely enable LIS to provide simultaneous and complementary observations

  16. Measuring the Flatness of Focal Plane for Very Large Mosaic CCD Camera

    Hao, Jiangang; Estrada, Juan; Cease, Herman; Diehl, H.Thomas; Flaugher, Brenna L.; Kubik, Donna; Kuk, Keivin; Kuropatkine, Nickolai; Lin, Huan; Montes, Jorge; Scarpine, Vic; /Fermilab

    2010-06-08

    Large mosaic multiCCD camera is the key instrument for modern digital sky survey. DECam is an extremely red sensitive 520 Megapixel camera designed for the incoming Dark Energy Survey (DES). It is consist of sixty two 4k x 2k and twelve 2k x 2k 250-micron thick fully-depleted CCDs, with a focal plane of 44 cm in diameter and a field of view of 2.2 square degree. It will be attached to the Blanco 4-meter telescope at CTIO. The DES will cover 5000 square-degrees of the southern galactic cap in 5 color bands (g, r, i, z, Y) in 5 years starting from 2011. To achieve the science goal of constraining the Dark Energy evolution, stringent requirements are laid down for the design of DECam. Among them, the flatness of the focal plane needs to be controlled within a 60-micron envelope in order to achieve the specified PSF variation limit. It is very challenging to measure the flatness of the focal plane to such precision when it is placed in a high vacuum dewar at 173 K. We developed two image based techniques to measure the flatness of the focal plane. By imaging a regular grid of dots on the focal plane, the CCD offset along the optical axis is converted to the variation the grid spacings at different positions on the focal plane. After extracting the patterns and comparing the change in spacings, we can measure the flatness to high precision. In method 1, the regular dots are kept in high sub micron precision and cover the whole focal plane. In method 2, no high precision for the grid is required. Instead, we use a precise XY stage moves the pattern across the whole focal plane and comparing the variations of the spacing when it is imaged by different CCDs. Simulation and real measurements show that the two methods work very well for our purpose, and are in good agreement with the direct optical measurements.

  17. A Novel Multi-View-Angle Range Images Generation Method for Measurement of Complicated Polyhedron in 3D Space

    Deming Kong

    2017-01-01

    Full Text Available A new kind of generation method is proposed in this paper to acquire range images for complicated polyhedron in 3D space from a series of view angles. In the proposed generation method, concept of three-view drawing in mechanical cartography is introduced into the range image generation procedure. Negative and positive directions of x-, y-, and z-axes are selected as the view angles to generate the range images for complicated polyhedron in 3D space. Furthermore, a novel iterative operation of mathematical morphology is proposed to ensure that satisfactory range images can be generated for the polyhedron from all the selected view angles. Compared with the existing method based on single view angle and interpolation operation, structure features contained in surface of the complicated polyhedron can be represented more consistently with the reality by using the proposed multi-view-angle range images generation method. The proposed generation method is validated by using an experiment.

  18. Weyl-Euler-Lagrange Equations of Motion on Flat Manifold

    Zeki Kasap

    2015-01-01

    Full Text Available This paper deals with Weyl-Euler-Lagrange equations of motion on flat manifold. It is well known that a Riemannian manifold is said to be flat if its curvature is everywhere zero. Furthermore, a flat manifold is one Euclidean space in terms of distances. Weyl introduced a metric with a conformal transformation for unified theory in 1918. Classical mechanics is one of the major subfields of mechanics. Also, one way of solving problems in classical mechanics occurs with the help of the Euler-Lagrange equations. In this study, partial differential equations have been obtained for movement of objects in space and solutions of these equations have been generated by using the symbolic Algebra software. Additionally, the improvements, obtained in this study, will be presented.

  19. Quantitative in vivo HR-pQCT imaging of 3D wrist and metacarpophalangeal joint space width in rheumatoid arthritis.

    Burghardt, Andrew J; Lee, Chan Hee; Kuo, Daniel; Majumdar, Sharmila; Imboden, John B; Link, Thomas M; Li, Xiaojuan

    2013-12-01

    In this technique development study, high-resolution peripheral quantitative computed tomography (HR-pQCT) was applied to non-invasively image and quantify 3D joint space morphology of the wrist and metacarpophalangeal (MCP) joints of patients with rheumatoid arthritis (RA). HR-pQCT imaging (82 μm voxel-size) of the dominant hand was performed in patients with diagnosed rheumatoid arthritis (RA, N = 16, age: 52.6 ± 12.8) and healthy controls (CTRL, N = 7, age: 50.1 ± 15.0). An automated computer algorithm was developed to segment wrist and MCP joint spaces. The 3D distance transformation method was applied to spatially map joint space width, and summarized by the mean joint space width (JSW), minimal and maximal JSW (JSW.MIN, JSW.MAX), asymmetry (JSW.AS), and distribution (JSW.SD)-a measure of joint space heterogeneity. In vivo precision was determined for each measure by calculating the smallest detectable difference (SDD) and root mean square coefficient of variation (RMSCV%) of repeat scans. Qualitatively, HR-pQCT images and pseudo-color JSW maps showed global joint space narrowing, as well as regional and focal abnormalities in RA patients. In patients with radiographic JSN at an MCP, JSW.SD was two-fold greater vs. CTRL (p 3D joint space morphology from HR-pQCT, could improve early detection of joint damage in rheumatological diseases.

  20. Optical Performance of Breadboard Amon-Ra Imaging Channel Instrument for Deep Space Albedo Measurement

    Won Hyun Park

    2007-03-01

    Full Text Available The AmonRa instrument, the primary payload of the international EARTHSHINE mission, is designed for measurement of deep space albedo from L1 halo orbit. We report the optical design, tolerance analysis and the optical performance of the breadborad AmonRa imaging channel instrument optimized for the mission science requirements. In particular, an advanced wavefront feedback process control technique was used for the instrumentation process including part fabrication, system alignment and integration. The measured performances for the complete breadboard system are the RMS 0.091 wave(test wavelength: 632.8 nm in wavefront error, the ensquared energy of 61.7%(in 14 μ m and the MTF of 35.3%(Nyquist frequency: 35.7 mm^{-1} at the center field. These resulting optical system performances prove that the breadboard AmonRa instrument, as built, satisfies the science requirements of the EARTHSHINE mission.

  1. Correction of defective pixels for medical and space imagers based on Ising Theory

    Cohen, Eliahu; Shnitser, Moriel; Avraham, Tsvika; Hadar, Ofer

    2014-09-01

    We propose novel models for image restoration based on statistical physics. We investigate the affinity between these fields and describe a framework from which interesting denoising algorithms can be derived: Ising-like models and simulated annealing techniques. When combined with known predictors such as Median and LOCO-I, these models become even more effective. In order to further examine the proposed models we apply them to two important problems: (i) Digital Cameras in space damaged from cosmic radiation. (ii) Ultrasonic medical devices damaged from speckle noise. The results, as well as benchmark and comparisons, suggest in most of the cases a significant gain in PSNR and SSIM in comparison to other filters.

  2. Characterizing the Evolution of Circumstellar Systems with the Hubble Space Telescope and the Gemini Planet Imager

    Wolff, Schuyler; Schuyler G. Wolff

    2018-01-01

    The study of circumstellar disks at a variety of evolutionary stages is essential to understand the physical processes leading to planet formation. The recent development of high contrast instruments designed to directly image the structures surrounding nearby stars, such as the Gemini Planet Imager (GPI) and coronagraphic data from the Hubble Space Telescope (HST) have made detailed studies of circumstellar systems possible. In my thesis work I detail the observation and characterization of three systems. GPI polarization data for the transition disk, PDS 66 shows a double ring and gap structure with a temporally variable azimuthal asymmetry. This evolved morphology could indicate shadowing from some feature in the innermost regions of the disk, a gap-clearing planet, or a localized change in the dust properties of the disk. Millimeter continuum data of the DH Tau system places limits on the dust mass that is contributing to the strong accretion signature on the wide-separation planetary mass companion, DH Tau b. The lower than expected dust mass constrains the possible formation mechanism, with core accretion followed by dynamical scattering being the most likely. Finally, I present HST scattered light observations of the flared, edge-on protoplanetary disk ESO H$\\alpha$ 569. I combine these data with a spectral energy distribution to model the key structural parameters such as the geometry (disk outer radius, vertical scale height, radial flaring profile), total mass, and dust grain properties in the disk using the radiative transfer code MCFOST. In order to conduct this work, I developed a new tool set to optimize the fitting of disk parameters using the MCMC code \\texttt{emcee} to efficiently explore the high dimensional parameter space. This approach allows us to self-consistently and simultaneously fit a wide variety of observables in order to place constraints on the physical properties of a given disk, while also rigorously assessing the uncertainties in

  3. New Frontiers for Massive Star Winds: Imaging and Spectroscopy with the James Webb Space Telescope

    Sonneborn, George

    2007-01-01

    The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2013. JWST will find the first stars and galaxies that formed in the early universe, connecting the Big Bang to our own Milky Way galaxy. JWST will peer through dusty clouds to see stars forming planetary systems, connecting the Milky Way to our own Solar System. JWST's instruments are designed to work primarily in the infrared range of 1 - 28 microns, with some capability in the visible range. JWST will have a large mirror, 6.5 meters in diameter, and will be diffraction-limited at 2 microns (0.1 arcsec resolution). JWST will be placed in an L2 orbit about 1.5 million km from the Earth. The instruments will provide imaging, coronography, and multi-object and integral-field spectroscopy across the full 1 - 28 micron wavelength range. The breakthrough capabilities of JWST will enable new studies of massive star winds from the Milky Way to the early universe.

  4. Technical aspects of the Space Telescope Imaging Spectrograph Repair (STIS-R)

    Rinehart, S. A.; Domber, J.; Faulkner, T.; Gull, T.; Kimble, R.; Klappenberger, M.; Leckrone, D.; Niedner, M.; Proffitt, C.; Smith, H.; Woodgate, B.

    2008-07-01

    In August 2004, the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) ceased operation due to a failure of the 5V mechanism power converter in the Side 2 Low Voltage Power Supply (LVPS2). The failure precluded movement of any STIS mechanism and, because of the earlier (2001) loss of the Side 1 electronics chain, left the instrument shuttered and in safe mode after 7.5 years of science operations. A team was assembled to analyze the fault and to determine if STIS repair (STIS-R) was feasible. The team conclusively pinpointed the Side 2 failure to the 5V mechanism converter, and began studying EVA techniques for opening STIS during Servicing Mission 4 (SM4) to replace the failed LVPS2 board. The restoration of STIS functionality via surgical repair by astronauts has by now reached a mature and final design state, and will, along with a similar repair procedure for the Advanced Camera for Surveys (ACS), represent a first for Hubble servicing. STIS-R will restore full scientific functionality of the spectrograph on Side 2, while Side 1 will remain inoperative. Because of the high degree of complementarity between STIS and the new Cosmic Origins Spectrograph (COS, to be installed during SM4)), successful repair of the older spectrograph is an important scientific objective. In this presentation, we focus on the technical aspects associated with STIS-R.

  5. Estimation of the temperature spatial variability in confined spaces based on thermal imaging

    Augustyn, Grzegorz; Jurasz, Jakub; Jurczyk, Krzysztof; Korbiel, Tomasz; Mikulik, Jerzy; Pawlik, Marcin; Rumin, Rafał

    2017-11-01

    In developed countries the salaries of office workers are several times higher than the total cost of maintaining and operating the building. Therefore even a small improvement in human work productivity and performance as a result of enhancing the quality of their work environment may lead to a meaningful economic benefits. The air temperature is the most commonly used indicator in assessing the indoor environment quality. What is more, it is well known that thermal comfort has the biggest impact on employees performance and their ability to work efficiently. In majority of office buildings, indoor temperature is managed by heating, ventilation and air conditioning (HVAC) appliances. However the way how they are currently managed and controlled leads to the nonhomogeneous distribution of temperature in certain space. An approach to determining the spatial variability of temperature in confined spaces was introduced based on thermal imaging temperature measurements. The conducted research and obtained results enabled positive verification of the method and creation of surface plot illustrating the temperature variability.

  6. Estimation of the temperature spatial variability in confined spaces based on thermal imaging

    Augustyn Grzegorz

    2017-01-01

    Full Text Available In developed countries the salaries of office workers are several times higher than the total cost of maintaining and operating the building. Therefore even a small improvement in human work productivity and performance as a result of enhancing the quality of their work environment may lead to a meaningful economic benefits. The air temperature is the most commonly used indicator in assessing the indoor environment quality. What is more, it is well known that thermal comfort has the biggest impact on employees performance and their ability to work efficiently. In majority of office buildings, indoor temperature is managed by heating, ventilation and air conditioning (HVAC appliances. However the way how they are currently managed and controlled leads to the nonhomogeneous distribution of temperature in certain space. An approach to determining the spatial variability of temperature in confined spaces was introduced based on thermal imaging temperature measurements. The conducted research and obtained results enabled positive verification of the method and creation of surface plot illustrating the temperature variability.

  7. Thermal-hydraulic characteristics of double flat core HCLWR

    Sugimoto, Jun; Iwamura, Takamichi; Okubo, Tsutomu; Murao, Yoshio

    1989-02-01

    A thermal-hydraulic characteristics of double flat core high conversion light water reactor (HCLWR) is described. The concept of flat core proposed by Ishiguro et al. is to achieve negative void reactivity coefficient in tight lattice core, and at the same time, high conversion ratio and high burnup can be obtainable. The proposed double flat core HCLWR, based on these physical advantages and the consideration of safety assurance, aims at efficient use of the pressure vessel space to produce comparable thermal output as current 3-loop PWRs. The present work revealed the following items concerning the thermalhydraulic feasibility of the double flat core HCLWR: (1) Main thermal-hydraulic parameters of the plant can be almost the same as current PWRs, showing the use of PWR standard components without major modifications except in core region. (2) Heat removal from the fuel rod in a steady operational condition has enough margin to the critical heat flux (CHF) limit, which is evaluated with the existing CHF correlations. (3) The calculation by REFLA code shows that the maximum cladding temperature in LOCA-reflood is estimated to be far lower than the licensing criteria. It is therefore considered that the proposed double flat core HCLWR is feasible from the point of thermal-hydraulics. Since the available data base has certain applicational limit to the very short core as the present double flat core HCLWR, further detailed assessment is required. (author)

  8. A Possible Technology Development Path to Direct Imaging of Exo-Earths from Space

    Siegler, Nicholas

    2018-01-01

    We describe a possible roadmap to achieving the technological capability to search for biosignatures on an Earth-like exoplanet from a future space telescope. The detection of Earth-like exoplanets in the habitable zone of their stars, and their spectroscopic characterization in a search for biosignatures, requires starlight suppression that exceeds the current best ground-based performance by orders of magnitude. The required planet/star brightness ratio of order 1e-10 at visible wavelengths can be obtained by blocking stellar photons with an occulter, either externally (a starshade) or internally (a coronagraph) to the telescope system, and managing diffracted starlight, so as to directly image the exoplanet in reflected starlight. Coronagraph instruments require advancement in telescope aperture (either monolithic or segmented), aperture obscurations (obscured by secondary mirror and its support struts), and wavefront error sensitivity (e.g. line-of-sight jitter, telescope vibration, polarization). The starshade, which has never been used in a science application, benefits a mission by being decoupled from the telescope, allowing a loosening of telescope stability requirements. In doing so, it transfers the difficult technology from the telescope system to a large deployable structure (tens of meters to greater than ~ 100 m in diameter) that must be positioned precisely at a distance of tens of thousands of kilometers from the telescope. Two ongoing mission concept studies, HabEx and LUVOIR, include the direct imaging of Earth-sized habitable exoplanets as a central science theme.

  9. Real space channelization for generic DBT system image quality evaluation with channelized Hotelling observer

    Petrov, Dimitar; Cockmartin, Lesley; Marshall, Nicholas; Vancoillie, Liesbeth; Young, Kenneth; Bosmans, Hilde

    2017-03-01

    Digital breast tomosynthesis (DBT) is a relatively new 3D mammography technique that promises better detection of low contrast masses than conventional 2D mammography. The parameter space for DBT is large however and finding an optimal balance between dose and image quality remains challenging. Given the large number of conditions and images required in optimization studies, the use of human observers (HO) is time consuming and certainly not feasible for the tuning of all degrees of freedom. Our goal was to develop a model observer (MO) that could predict human detectability for clinically relevant details embedded within a newly developed structured phantom for DBT applications. DBT series were acquired on GE SenoClaire 3D, Giotto Class, Fujifilm AMULET Innovality and Philips MicroDose systems at different dose levels, Siemens Inspiration DBT acquisitions were reconstructed with different algorithms, while a larger set of DBT series was acquired on Hologic Dimensions system for first reproducibility testing. A channelized Hotelling observer (CHO) with Gabor channels was developed The parameters of the Gabor channels were tuned on all systems at standard scanning conditions and the candidate that produced the best fit for all systems was chosen. After tuning, the MO was applied to all systems and conditions. Linear regression lines between MO and HO scores were calculated, giving correlation coefficients between 0.87 and 0.99 for all tested conditions.

  10. CdTe Based Hard X-ray Imager Technology For Space Borne Missions

    Limousin, Olivier; Delagnes, E.; Laurent, P.; Lugiez, F.; Gevin, O.; Meuris, A.

    2009-01-01

    CEA Saclay has recently developed an innovative technology for CdTe based Pixelated Hard X-Ray Imagers with high spectral performance and high timing resolution for efficient background rejection when the camera is coupled to an active veto shield. This development has been done in a R&D program supported by CNES (French National Space Agency) and has been optimized towards the Simbol-X mission requirements. In the latter telescope, the hard X-Ray imager is 64 cm² and is equipped with 625µm pitch pixels (16384 independent channels) operating at -40°C in the range of 4 to 80 keV. The camera we demonstrate in this paper consists of a mosaic of 64 independent cameras, divided in 8 independent sectors. Each elementary detection unit, called Caliste, is the hybridization of a 256-pixel Cadmium Telluride (CdTe) detector with full custom front-end electronics into a unique 1 cm² component, juxtaposable on its four sides. Recently, promising results have been obtained from the first micro-camera prototypes called Caliste 64 and will be presented to illustrate the capabilities of the device as well as the expected performance of an instrument based on it. The modular design of Caliste enables to consider extended developments toward IXO type mission, according to its specific scientific requirements.

  11. Eyjafjallajokull Volcano Plume Particle-Type Characterization from Space-Based Multi-angle Imaging

    Kahn, Ralph A.; Limbacher, James

    2012-01-01

    The Multi-angle Imaging SpectroRadiometer (MISR) Research Aerosol algorithm makes it possible to study individual aerosol plumes in considerable detail. From the MISR data for two optically thick, near-source plumes from the spring 2010 eruption of the Eyjafjallaj kull volcano, we map aerosol optical depth (AOD) gradients and changing aerosol particle types with this algorithm; several days downwind, we identify the occurrence of volcanic ash particles and retrieve AOD, demonstrating the extent and the limits of ash detection and mapping capability with the multi-angle, multi-spectral imaging data. Retrieved volcanic plume AOD and particle microphysical properties are distinct from background values near-source, as well as for overwater cases several days downwind. The results also provide some indication that as they evolve, plume particles brighten, and average particle size decreases. Such detailed mapping offers context for suborbital plume observations having much more limited sampling. The MISR Standard aerosol product identified similar trends in plume properties as the Research algorithm, though with much smaller differences compared to background, and it does not resolve plume structure. Better optical analogs of non-spherical volcanic ash, and coincident suborbital data to validate the satellite retrieval results, are the factors most important for further advancing the remote sensing of volcanic ash plumes from space.

  12. Dark current spectroscopy of space and nuclear environment induced displacement damage defects in pinned photodiode based CMOS image sensors

    Belloir, Jean-Marc

    2016-01-01

    CMOS image sensors are envisioned for an increasing number of high-end scientific imaging applications such as space imaging or nuclear experiments. Indeed, the performance of high-end CMOS image sensors has dramatically increased in the past years thanks to the unceasing improvements of microelectronics, and these image sensors have substantial advantages over CCDs which make them great candidates to replace CCDs in future space missions. However, in space and nuclear environments, CMOS image sensors must face harsh radiation which can rapidly degrade their electro-optical performances. In particular, the protons, electrons and ions travelling in space or the fusion neutrons from nuclear experiments can displace silicon atoms in the pixels and break the crystalline structure. These displacement damage effects lead to the formation of stable defects and to the introduction of states in the forbidden bandgap of silicon, which can allow the thermal generation of electron-hole pairs. Consequently, non ionizing radiation leads to a permanent increase of the dark current of the pixels and thus a decrease of the image sensor sensitivity and dynamic range. The aim of the present work is to extend the understanding of the effect of displacement damage on the dark current increase of CMOS image sensors. In particular, this work focuses on the shape of the dark current distribution depending on the particle type, energy and fluence but also on the image sensor physical parameters. Thanks to the many conditions tested, an empirical model for the prediction of the dark current distribution induced by displacement damage in nuclear or space environments is experimentally validated and physically justified. Another central part of this work consists in using the dark current spectroscopy technique for the first time on irradiated CMOS image sensors to detect and characterize radiation-induced silicon bulk defects. Many types of defects are detected and two of them are identified

  13. Wetting of flat gradient surfaces.

    Bormashenko, Edward

    2018-04-01

    Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions. The linear approximation of the problem is considered. It is demonstrated that the contact angle hysteresis is inevitable on gradient surfaces. Electrowetting of gradient surfaces is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

  14. Development of flat panel X-ray detector utilizing a CdZnTe film as conversion layer

    Tokuda, Satoshi; Kishihara, Hiroyuki; Kaino, Masatomo; Sato, Toshiyuki

    2006-01-01

    A polycrystalline CdZnTe film formed by the CSS (closed-spaced sublimation) method is one of the most promising materials as a conversion layer of next-generation highly efficient flat-panel X-ray detectors. Therefore, we have developed a prototype of a new flat-panel X-ray detector (a sensing region of 3 inches by 3 inches) with the film and evaluated its commercial feasibility. This paper describes evaluation of the physical and imaging properties of the prototype and explains the features of the CdZnTe film and the construction, specifications, and fabrication procedures of the prototype. Also included in this paper are formation of a semiconductor thin film barrier layer by the CBD (chemical bath deposition) method and conjunction of a sensor substrate and a TFT array substrate with the bump electrodes formed by screen printing, both of which we have developed during the course of the development of the prototype. (author)

  15. A Hubble Space Telescope imaging study of four FeLoBAL quasar host galaxies

    Lawther, D.; Vestergaard, M.; Fan, X.

    2018-04-01

    We study the host galaxies of four Iron Low-Ionization Broad Absorption-line Quasars (FeLoBALs), using Hubble Space Telescope imaging data, investigating the possibility that they represent a transition between an obscured active galactic nucleus (AGN) and an ordinary optical quasar. In this scenario, the FeLoBALs represent the early stage of merger-triggered accretion, in which case their host galaxies are expected to show signs of an ongoing or recent merger. Using PSF subtraction techniques, we decompose the images into host galaxy and AGN components at rest-frame ultraviolet and optical wavelengths. The ultraviolet is sensitive to young stars, while the optical probes stellar mass. In the ultraviolet we image at the BAL absorption trough wavelengths so as to decrease the contrast between the quasar and host galaxy emission. We securely detect an extended source for two of the four FeLoBALs in the rest-frame optical; a third host galaxy is marginally detected. In the rest-frame UV we detect no host emission; this constrains the level of unobscured star formation. Thus, the host galaxies have observed properties that are consistent with those of non-BAL quasars with the same nuclear luminosity, i.e. quiescent or moderately star-forming elliptical galaxies. However, we cannot exclude starbursting hosts that have the stellar UV emission obscured by modest amounts of dust reddening. Thus, our findings also allow the merger-induced young quasar scenario. For three objects, we identify possible close companion galaxies that may be gravitationally interacting with the quasar hosts.

  16. HUBBLE SPACE TELESCOPE IMAGING OF Lyα EMISSION AT z ∼ 4.4

    Finkelstein, Steven L.; Finkelstein, Keely D.; Cohen, Seth H.; Windhorst, Rogier A.; Malhotra, Sangeeta; Rhoads, James E.; Ryan, Russell E.; Hathi, Nimish P.; McCarthy, Patrick J.; Anderson, Jay; Grogin, Norman A.; Koekemoer, Anton M.; Mutchler, Max; Bond, Howard E.; O'Connell, Robert W.; Balick, Bruce; Calzetti, Daniela; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.

    2011-01-01

    We present the highest redshift detections of resolved Lyα emission, using Hubble Space Telescope (HST)/Advanced Camera for Surveys F658N narrowband-imaging data taken in parallel with the Wide Field Camera 3 Early Release Science program in the GOODS Chandra Deep Field-South. We detect Lyα emission from three spectroscopically confirmed z = 4.4 Lyα emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Lyα emission. Comparing the light distribution between the rest-frame ultraviolet continuum and narrowband images, we investigate the escape of Lyα photons at high redshift. While our data do not support a positional offset between the Lyα and rest-frame ultraviolet (UV) continuum emission, the half-light radius in one out of the three galaxies is significantly (>1σ) larger in Lyα than in the rest-frame UV continuum. Stacking the three LAEs in both the narrowband and UV continuum images, we find that the Lyα light appears larger than the rest-frame UV at 4.2σ significance. This Lyα flux detected with HST is a factor of 4-10 less than observed in similar filters from the ground. These results together imply that the Lyα emission is not strictly confined to its indigenous star-forming regions. Rather, for at least one object the Lyα emission is more extended, with the missing HST flux possibly existing in a diffuse outer halo. This suggests that the radiative transfer of Lyα photons in high-redshift LAEs is complicated, with the interstellar-medium geometry and/or outflows playing a significant role in galaxies at these redshifts.

  17. Conformally flat tilted Bianchi Type-V cosmological models in ...

    the complete determination of these quantities, we assume two extra conditions. First we assume that the space-time is conformally flat which leads to. 1008 .... Discussions. The model starts expanding with a big-bang at М = 0 and the expansion in the model stops at М = ∞ and = -2(Т + 2)¬. The model in general represents.

  18. Advanced Photon Counting Imaging Detectors with 100ps Timing for Astronomical and Space Sensing Applications

    Siegmund, O.; Vallerga, J.; Welsh, B.; Rabin, M.; Bloch, J.

    In recent years EAG has implemented a variety of high-resolution, large format, photon-counting MCP detectors in space instrumentation for satellite FUSE, GALEX, IMAGE, SOHO, HST-COS, rocket, and shuttle payloads. Our scheme of choice has been delay line readouts encoding photon event position centroids, by determination of the difference in arrival time of the event charge at the two ends of a distributed resistive-capacitive (RC) delay line. Our most commonly used delay line configuration is the cross delay line (XDL). In its simplest form the delay-line encoding electronics consists of a fast amplifier for each end of the delay line, followed by time-to-digital converters (TDC's). We have achieved resolutions of Pulsar with a telescope as small as 1m. Although microchannel plate delay line detectors meet many of the imaging and timing demands of various applications, they have limitations. The relatively high gain (107) reduces lifetime and local counting rate, and the fixed delay (10's of ns) makes multiple simultaneous event recording problematic. To overcome these limitations we have begun development of cross strip readout anodes for microchannel plate detectors. The cross strip (XS) anode is a coarse (~0.5 mm) multi-layer metal and ceramic pattern of crossed fingers on an alumina substrate. The charge cloud is matched to the anode period so that it is collected on several neighboring fingers to ensure an accurate event charge centroid can be determined. Each finger of the anode is connected to a low noise charge sensitive amplifier and followed by subsequent A/D conversion of individual strip charge values and a hardware centroid determination of better than 1/100 of a strip are possible. Recently we have commissioned a full 32 x 32 mm XS open face laboratory detector and demonstrated excellent resolution (Los Alamos National Laboratory, NASA and NSF we are developing high rate (>107 Hz) XS encoding electronics that will encode temporally simultaneous

  19. Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. III. Measurement for Ursa Minor

    Piatek, Slawomir; Pryor, Carlton; Bristow, Paul; Olszewski, Edward W.; Harris, Hugh C.; Mateo, Mario; Minniti, Dante; Tinney, Christopher G.

    2005-07-01

    This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. Each field contains a quasi-stellar object that serves as the ``reference point.'' The measured proper motion for Ursa Minor, expressed in the equatorial coordinate system, is (μα,μδ)=(-50+/-17,22+/-16) mas century-1. Removing the contributions of the solar motion and the motion of the local standard of rest yields the proper motion in the Galactic rest frame: (μGrfα,μGrfδ)=(-8+/-17,38+/-16) mas century-1. The implied space velocity with respect to the Galactic center has a radial component of Vr=-75+/-44 km s-1 and a tangential component of Vt=144+/-50 km s-1. Integrating the motion of Ursa Minor in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 40 (10, 76) and 89 (78, 160) kpc, respectively, where the values in the parentheses represent the 95% confidence intervals derived from Monte Carlo experiments. The eccentricity of the orbit is 0.39 (0.09, 0.79), and the orbital period is 1.5 (1.1, 2.7) Gyr. The orbit is retrograde and inclined by 124° (94°, 136°) to the Galactic plane. Ursa Minor is not a likely member of a proposed stream of galaxies on similar orbits around the Milky Way, nor is the plane of its orbit coincident with a recently proposed planar alignment of galaxies around the Milky Way. Comparing the orbits of Ursa Minor and Carina shows no reason for the different star formation histories of these two galaxies. Ursa Minor must contain dark matter to have a high probability of having survived disruption by the Galactic tidal force until the present. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  20. What is the public's role in 'space' policymaking? Images of the public by practitioners of 'space' communication in the United Kingdom.

    Entradas, Marta

    2016-07-01

    Studies on experts' understanding of the public have mainly focused on the views of scientists. We add to the literature on constructions of the public by analyzing the views of decision-makers, professional science communicators and scientists involved in 'space' communication on the public and public participation in policy. Findings show that contextual situations and roles determine the way the public is conceptualised: the public is sophisticated and knowledgeable to participate in space activities/citizen science, but in matters of policy, a gullible image of the public is brought up. Despite the democratic talk on participation, practitioners delimited public involvement in policy in some way or other to protect their own power and decision-making capabilities. This conception of the public competes with the stated aims of scientific and political institutions for public engagement and the substantive value of public participation, leaving a limited role for the public in space policymaking. © The Author(s) 2015.

  1. Near-Space TOPSAR Large-Scene Full-Aperture Imaging Scheme Based on Two-Step Processing

    Qianghui Zhang

    2016-07-01

    Full Text Available Free of the constraints of orbit mechanisms, weather conditions and minimum antenna area, synthetic aperture radar (SAR equipped on near-space platform is more suitable for sustained large-scene imaging compared with the spaceborne and airborne counterparts. Terrain observation by progressive scans (TOPS, which is a novel wide-swath imaging mode and allows the beam of SAR to scan along the azimuth, can reduce the time of echo acquisition for large scene. Thus, near-space TOPS-mode SAR (NS-TOPSAR provides a new opportunity for sustained large-scene imaging. An efficient full-aperture imaging scheme for NS-TOPSAR is proposed in this paper. In this scheme, firstly, two-step processing (TSP is adopted to eliminate the Doppler aliasing of the echo. Then, the data is focused in two-dimensional frequency domain (FD based on Stolt interpolation. Finally, a modified TSP (MTSP is performed to remove the azimuth aliasing. Simulations are presented to demonstrate the validity of the proposed imaging scheme for near-space large-scene imaging application.

  2. A Miniature Multimodal Imaging System for Medical Diagnostics and Interventions in Space

    National Aeronautics and Space Administration — Long-term health of astronauts in space relies on effective in-situ diagnoses, management and interventions. However, clinicians are not always present during space...

  3. Urban Space Innovation - “10+” Principles through Designing the New Image of the Existing Shopping Mall in Csepel, Hungary

    Gyergyak, Janos

    2017-10-01

    The first part of the paper is about to introduce the principles of “placemaking” as an innovation and important tool of the cities in the 21st century. The process helps designers to transform the spaces of “nobody” to a community-based space for supporting the connection among humans. The second part of the paper shows the process of the used principles by the author for designing the new image of the existing shopping mall in Csepel, Hungary. This work was selected as one of the best design ideas for renewing the existing underutilized space.

  4. Global Monitoring of Mountain Glaciers Using High-Resolution Spotlight Imaging from the International Space Station

    Donnellan, A.; Green, J. J.; Bills, B. G.; Goguen, J.; Ansar, A.; Knight, R. L.; Hallet, B.; Scambos, T. A.; Thompson, L. G.; Morin, P. J.

    2013-12-01

    Mountain glaciers around the world are retreating rapidly, contributing about 20% to present-day sea level rise. Numerous studies have shown that mountain glaciers are sensitive to global environmental change. Temperate-latitude glaciers and snowpack provide water for over 1 billion people. Glaciers are a resource for irrigation and hydroelectric power, but also pose flood and avalanche hazards. Accurate mass balance assessments have been made for only 280 glaciers, yet there are over 130,000 in the World Glacier Inventory. The rate of glacier retreat or advance can be highly variable, is poorly sampled, and inadequately understood. Liquid water from ice front lakes, rain, melt, or sea water and debris from rocks, dust, or pollution interact with glacier ice often leading to an amplification of warming and further melting. Many mountain glaciers undergo rapid and episodic events that greatly change their mass balance or extent but are sparsely documented. Events include calving, outburst floods, opening of crevasses, or iceberg motion. Spaceborne high-resolution spotlight optical imaging provides a means of clarifying the relationship between the health of mountain glaciers and global environmental change. Digital elevation models (DEMs) can be constructed from a series of images from a range of perspectives collected by staring at a target during a satellite overpass. It is possible to collect imagery for 1800 targets per month in the ×56° latitude range, construct high-resolution DEMs, and monitor changes in high detail over time with a high-resolution optical telescope mounted on the International Space Station (ISS). Snow and ice type, age, and maturity can be inferred from different color bands as well as distribution of liquid water. Texture, roughness, albedo, and debris distribution can be estimated by measuring bidirectional reflectance distribution functions (BRDF) and reflectance intensity as a function of viewing angle. The non-sun-synchronous orbit

  5. 78 FR 40196 - National Environmental Policy Act; Sounding Rockets Program; Poker Flat Research Range

    2013-07-03

    ...; Sounding Rockets Program; Poker Flat Research Range AGENCY: National Aeronautics and Space Administration... Sounding Rockets Program (SRP) at Poker Flat Research Range (PFRR), Alaska. SUMMARY: Pursuant to the... government agencies, and educational institutions have conducted suborbital rocket launches from the PFRR...

  6. 76 FR 20715 - National Environmental Policy Act; Sounding Rockets Program; Poker Flat Research Range

    2011-04-13

    ...; Sounding Rockets Program; Poker Flat Research Range AGENCY: National Aeronautics and Space Administration... continuing sounding rocket operations at Poker Flat Research Range (PFRR), Alaska. SUMMARY: Pursuant to the... information about NASA's Sounding Rocket Program (SRP) and the University of Alaska-Fairbanks' PFRR may be...

  7. Soil decontamination at Rocky Flats

    Olsen, R.L.; Hayden, J.A.; Alford, C.E.; Kochen, R.L.; Stevens, J.R.

    1979-01-01

    A soils decontamination project was initiated, to remove actinides from soils at Rocky Flats. Wet screening, attrition scrubbing with Calgon at high pH, attrition scrubbing at low pH, and cationic flotation were investigated. Pilot plant studies were carried out. Conceptual designs have been generated for mounting the process in semi-trailers

  8. The formation of music-scenes in Manchester and their relation to urban space and the image of the city

    Nielsen, Tom

    2013-01-01

    and the image of the city. This image has later been utilised in the branding of Manchester as a creative city. The case is interesting in relation to the current ideals of planning ‘creative cities’ and local cultural scenes. The music scenes cannot be seen as participatory projects and has developed in more......The formation of music-scenes in Manchester and their relation to urban space and the image of the city The paper I would like to present derives from a study of the relation between the atmospheric qualities of a city and the formation of music scenes. I have studied Manchester which is a known...

  9. Hubble Space Telescope STIS observations of GRB 000301C: CCD imaging and near-ultraviolet MAMA spectroscopy

    Smette, A.; Fruchter, A.S.; Gull, T.R.

    2001-01-01

    We present Space Telescope Imaging Spectrograph observations of the optical transient (OT) counterpart of the c-ray burster GRB 000301C obtained 5 days after the burst, on 2000 March 6. CCD clear-aperture imaging reveals a R similar or equal to 21.50 +/- 0.15 source with no apparent host galaxy...... Telescope images appear to lie on the stellar field of a host galaxy, and as the large H I column density measured here and in later ground-based observations is unlikely on a random line of sight, we believe we are probably seeing absorption from H I in the host galaxy. In any case, this represents...

  10. The Lyman alpha reference sample. II. Hubble space telescope imaging results, integrated properties, and trends

    Hayes, Matthew; Östlin, Göran; Duval, Florent; Sandberg, Andreas; Guaita, Lucia; Melinder, Jens; Rivera-Thorsen, Thøger [Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm (Sweden); Adamo, Angela [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Schaerer, Daniel [Université de Toulouse, UPS-OMP, IRAP, F-31000 Toulouse (France); Verhamme, Anne; Orlitová, Ivana [Geneva Observatory, University of Geneva, 51 Chemin des Maillettes, CH-1290 Versoix (Switzerland); Mas-Hesse, J. Miguel; Otí-Floranes, Héctor [Centro de Astrobiología (CSIC-INTA), Departamento de Astrofísica, P.O. Box 78, E-28691 Villanueva de la Cañada (Spain); Cannon, John M.; Pardy, Stephen [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Atek, Hakim [Laboratoire dAstrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, CH-1290 Sauverny (Switzerland); Kunth, Daniel [Institut d' Astrophysique de Paris, UMR 7095, CNRS and UPMC, 98 bis Bd Arago, F-75014 Paris (France); Laursen, Peter [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Herenz, E. Christian, E-mail: matthew@astro.su.se [Leibniz-Institut für Astrophysik (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    2014-02-10

    We report new results regarding the Lyα output of galaxies, derived from the Lyman Alpha Reference Sample, and focused on Hubble Space Telescope imaging. For 14 galaxies we present intensity images in Lyα, Hα, and UV, and maps of Hα/Hβ, Lyα equivalent width (EW), and Lyα/Hα. We present Lyα and UV radial light profiles and show they are well-fitted by Sérsic profiles, but Lyα profiles show indices systematically lower than those of the UV (n ≈ 1-2 instead of ≳ 4). This reveals a general lack of the central concentration in Lyα that is ubiquitous in the UV. Photometric growth curves increase more slowly for Lyα than the far ultraviolet, showing that small apertures may underestimate the EW. For most galaxies, however, flux and EW curves flatten by radii ≈10 kpc, suggesting that if placed at high-z only a few of our galaxies would suffer from large flux losses. We compute global properties of the sample in large apertures, and show total Lyα luminosities to be independent of all other quantities. Normalized Lyα throughput, however, shows significant correlations: escape is found to be higher in galaxies of lower star formation rate, dust content, mass, and nebular quantities that suggest harder ionizing continuum and lower metallicity. Six galaxies would be selected as high-z Lyα emitters, based upon their luminosity and EW. We discuss the results in the context of high-z Lyα and UV samples. A few galaxies have EWs above 50 Å, and one shows f{sub esc}{sup Lyα} of 80%; such objects have not previously been reported at low-z.

  11. Comparison of air space measurement imaged by CT, small-animal CT, and hyperpolarized Xe MRI

    Madani, Aniseh; White, Steven; Santyr, Giles; Cunningham, Ian

    2005-04-01

    Lung disease is the third leading cause of death in the western world. Lung air volume measurements are thought to be early indicators of lung disease and markers in pharmaceutical research. The purpose of this work is to develop a lung phantom for assessing and comparing the quantitative accuracy of hyperpolarized xenon 129 magnetic resonance imaging (HP 129Xe MRI), conventional computed tomography (HRCT), and highresolution small-animal CT (μCT) in measuring lung gas volumes. We developed a lung phantom consisting of solid cellulose acetate spheres (1, 2, 3, 4 and 5 mm diameter) uniformly packed in circulated air or HP 129Xe gas. Air volume is estimated based on simple thresholding algorithm. Truth is calculated from the sphere diameters and validated using μCT. While this phantom is not anthropomorphic, it enables us to directly measure air space volume and compare these imaging methods as a function of sphere diameter for the first time. HP 129Xe MRI requires partial volume analysis to distinguish regions with and without 129Xe gas and results are within %5 of truth but settling of the heavy 129Xe gas complicates this analysis. Conventional CT demonstrated partial-volume artifacts for the 1mm spheres. μCT gives the most accurate air-volume results. Conventional CT and HP 129Xe MRI give similar results although non-uniform densities of 129Xe require more sophisticated algorithms than simple thresholding. The threshold required to give the true air volume in both HRCT and μCT, varies with sphere diameters calling into question the validity of thresholding method.

  12. The Lyman alpha reference sample. II. Hubble space telescope imaging results, integrated properties, and trends

    Hayes, Matthew; Östlin, Göran; Duval, Florent; Sandberg, Andreas; Guaita, Lucia; Melinder, Jens; Rivera-Thorsen, Thøger; Adamo, Angela; Schaerer, Daniel; Verhamme, Anne; Orlitová, Ivana; Mas-Hesse, J. Miguel; Otí-Floranes, Héctor; Cannon, John M.; Pardy, Stephen; Atek, Hakim; Kunth, Daniel; Laursen, Peter; Herenz, E. Christian

    2014-01-01

    We report new results regarding the Lyα output of galaxies, derived from the Lyman Alpha Reference Sample, and focused on Hubble Space Telescope imaging. For 14 galaxies we present intensity images in Lyα, Hα, and UV, and maps of Hα/Hβ, Lyα equivalent width (EW), and Lyα/Hα. We present Lyα and UV radial light profiles and show they are well-fitted by Sérsic profiles, but Lyα profiles show indices systematically lower than those of the UV (n ≈ 1-2 instead of ≳ 4). This reveals a general lack of the central concentration in Lyα that is ubiquitous in the UV. Photometric growth curves increase more slowly for Lyα than the far ultraviolet, showing that small apertures may underestimate the EW. For most galaxies, however, flux and EW curves flatten by radii ≈10 kpc, suggesting that if placed at high-z only a few of our galaxies would suffer from large flux losses. We compute global properties of the sample in large apertures, and show total Lyα luminosities to be independent of all other quantities. Normalized Lyα throughput, however, shows significant correlations: escape is found to be higher in galaxies of lower star formation rate, dust content, mass, and nebular quantities that suggest harder ionizing continuum and lower metallicity. Six galaxies would be selected as high-z Lyα emitters, based upon their luminosity and EW. We discuss the results in the context of high-z Lyα and UV samples. A few galaxies have EWs above 50 Å, and one shows f esc Lyα of 80%; such objects have not previously been reported at low-z.

  13. Behind the Photos and the Tears: Media Images, Neoliberal Discourses, Racialized Constructions of Space and School Closings in Chicago

    Allweiss, Alexandra; Grant, Carl A.; Manning, Karla

    2015-01-01

    This critical article provides insights into how media frames influence our understandings of school reform in urban spaces by examining images of students during the 2013 school closings in Chicago. Using visual framing analysis and informed by framing theory and critiques of neoliberalism we seek to explore two questions: (1) What role do media…

  14. Vascular lesions of the lumbar epidural space: magnetic resonance imaging features of epidural cavernous hemangioma and epidural hematoma

    Basile Júnior Roberto

    1999-01-01

    Full Text Available The authors report the magnetic resonance imaging diagnostic features in two cases with respectively lumbar epidural hematoma and cavernous hemangioma of the lumbar epidural space. Enhanced MRI T1-weighted scans show a hyperintense signal rim surrounding the vascular lesion. Non-enhanced T2-weighted scans showed hyperintense signal.

  15. Comprehensive quantification of signal-to-noise ratio and g-factor for image-based and k-space-based parallel imaging reconstructions.

    Robson, Philip M; Grant, Aaron K; Madhuranthakam, Ananth J; Lattanzi, Riccardo; Sodickson, Daniel K; McKenzie, Charles A

    2008-10-01

    Parallel imaging reconstructions result in spatially varying noise amplification characterized by the g-factor, precluding conventional measurements of noise from the final image. A simple Monte Carlo based method is proposed for all linear image reconstruction algorithms, which allows measurement of signal-to-noise ratio and g-factor and is demonstrated for SENSE and GRAPPA reconstructions for accelerated acquisitions that have not previously been amenable to such assessment. Only a simple "prescan" measurement of noise amplitude and correlation in the phased-array receiver, and a single accelerated image acquisition are required, allowing robust assessment of signal-to-noise ratio and g-factor. The "pseudo multiple replica" method has been rigorously validated in phantoms and in vivo, showing excellent agreement with true multiple replica and analytical methods. This method is universally applicable to the parallel imaging reconstruction techniques used in clinical applications and will allow pixel-by-pixel image noise measurements for all parallel imaging strategies, allowing quantitative comparison between arbitrary k-space trajectories, image reconstruction, or noise conditioning techniques. (c) 2008 Wiley-Liss, Inc.

  16. Future space-based direct imaging platforms: high fidelity simulations and instrument testbed development

    Hicks, Brian A.; Eberhardt, Andrew; SAINT, VNC, LUVOIR

    2017-06-01

    The direct detection and characterization of habitable zone (HZ) Earth-like exoplanets is predicated on light gathering power of a large telescope operating with tens of millicarcsecond angular resolution, and at contrast scales on the order of 0.1 ppb. Accessing a statistically significant sample of planets to search for habitable worlds will likely build on the knowledge and insfrastructure gained through JWST, later advancing to assembly in space or formation flying approaches that may eventually be used to achieve even greater photometric sensitivity or resolution. in order to address contrast, a means of starlight suppression is needed that contends with complex aperture diffraction. The Visible Nulling Coronagraph (VNC) is one such approach that destructively interferes starlight to enable detection and characterization of extrasolar objects.The VNC is being incorporated into an end-to-end telescope-coronagraph system demonstrator called the Segmented Aperture Interferometric Nulling Testbed (SAINT). Development of the VNC has a rich legacy, and successfully demonstrating its capability with SAINT will mark milestones towards meeting the high-contrast direct imaging needs of future large space telescopes. SAINT merges the VNC with an actively-controlled segmented aperture telescope via a fine pointing system and aims to demonstrate 1e-8 contrast nulling of a segmented aperture at an inner working angle of four diffraction radii over a 20 nm visible bandpass. The system comprises four detectors for wavefront sensing, one of which is the high-contrast focal plane. The detectors provide feedback to control the segmented telescope primary mirror, a fast steering mirror, a segmented deformable mirror, and a delay stage. All of these components must work in concert with passive optical elements that are designed, fabricated, and aligned pairwise to achieve the requisite wavefront symmetry needed to push the state of the art in broadband destructive interferometric

  17. Individual energy savings for individual flats in blocks of flats

    Nielsen, Anker; Rose, Jørgen

    2014-01-01

    and 1980. Normally, we expect the reduction in energy consumption to be around 20% for a 2 °C lower temperature, but for an inner flat the reduction can be up to 71%. The owners of the adjoining flats get an increase in energy demand of 10 to 20% each. They will not be able to figure out whether...... this is because the neighbour maintains a low temperature or the fact that they maintain a higher temperature. The best solution is to keep your own indoor temperature low. We can also turn the problem around: if you maintain a higher temperature than your neighbours, then you will pay part of their heating bill....

  18. Application of Fourier-wavelet regularized deconvolution for improving image quality of free space propagation x-ray phase contrast imaging.

    Zhou, Zhongxing; Gao, Feng; Zhao, Huijuan; Zhang, Lixin

    2012-11-21

    New x-ray phase contrast imaging techniques without using synchrotron radiation confront a common problem from the negative effects of finite source size and limited spatial resolution. These negative effects swamp the fine phase contrast fringes and make them almost undetectable. In order to alleviate this problem, deconvolution procedures should be applied to the blurred x-ray phase contrast images. In this study, three different deconvolution techniques, including Wiener filtering, Tikhonov regularization and Fourier-wavelet regularized deconvolution (ForWaRD), were applied to the simulated and experimental free space propagation x-ray phase contrast images of simple geometric phantoms. These algorithms were evaluated in terms of phase contrast improvement and signal-to-noise ratio. The results demonstrate that the ForWaRD algorithm is most appropriate for phase contrast image restoration among above-mentioned methods; it can effectively restore the lost information of phase contrast fringes while reduce the amplified noise during Fourier regularization.

  19. YOUNG PLANETARY NEBULAE: HUBBLE SPACE TELESCOPE IMAGING AND A NEW MORPHOLOGICAL CLASSIFICATION SYSTEM

    Sahai, Raghvendra; Villar, Gregory G.; Morris, Mark R.

    2011-01-01

    Using Hubble Space Telescope images of 119 young planetary nebulae (PNs), most of which have not previously been published, we have devised a comprehensive morphological classification system for these objects. This system generalizes a recently devised system for pre-planetary nebulae, which are the immediate progenitors of PNs. Unlike previous classification studies, we have focused primarily on young PNs rather than all PNs, because the former best show the influences or symmetries imposed on them by the dominant physical processes operating at the first and primary stage of the shaping process. Older PNs develop instabilities, interact with the ambient interstellar medium, and are subject to the passage of photoionization fronts, all of which obscure the underlying symmetries and geometries imposed early on. Our classification system is designed to suffer minimal prejudice regarding the underlying physical causes of the different shapes and structures seen in our PN sample, however, in many cases, physical causes are readily suggested by the geometry, along with the kinematics that have been measured in some systems. Secondary characteristics in our system, such as ansae, indicate the impact of a jet upon a slower-moving, prior wind; a waist is the signature of a strong equatorial concentration of matter, whether it be outflowing or in a bound Keplerian disk, and point symmetry indicates a secular trend, presumably precession, in the orientation of the central driver of a rapid, collimated outflow.

  20. Rigidity of complete noncompact bach-flat n-manifolds

    Chu, Yawei; Feng, Pinghua

    2012-11-01

    Let (Mn,g) be a complete noncompact Bach-flat n-manifold with the positive Yamabe constant and constant scalar curvature. Assume that the L2-norm of the trace-free Riemannian curvature tensor R∘m is finite. In this paper, we prove that (Mn,g) is a constant curvature space if the L-norm of R∘m is sufficiently small. Moreover, we get a gap theorem for (Mn,g) with positive scalar curvature. This can be viewed as a generalization of our earlier results of 4-dimensional Bach-flat manifolds with constant scalar curvature R≥0 [Y.W. Chu, A rigidity theorem for complete noncompact Bach-flat manifolds, J. Geom. Phys. 61 (2011) 516-521]. Furthermore, when n>9, we derive a rigidity result for R<0.