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1

Apparent Linear Attenuation Coefficients in Phase Contrast X-Ray Tomography  

PubMed Central

In the inline phase contrast x-ray tomography the reconstructed apparent linear attenuation coefficient values may be greatly larger than sample’s linear attenuation coefficients or even be negative. In this work we present a general formula to quantitatively relate the apparent linear attenuation coefficient values in cone-beam phase contrast tomography to sample’s linear attenuation coefficients and refractive indices. This formula overcomes the gross inaccuracy of the existing formula in the literature in analyzing high-resolution phase contrast tomography, and it will be useful for correctly interpreting and quantifying the apparent linear attenuation coefficients in cone-beam x-ray phase contrast tomography. PMID:21691420

Yan, Aimin; Wu, Xizeng

2011-01-01

2

Parameterization of X-ray mass attenuation coefficients in the energy range of 1-150 keV  

Microsoft Academic Search

Knowledge of X-ray mass attenuation coefficients is necessary when the thick target PIXE method is applied for quantitative elemental analysis of materials. For this purpose, the X-ray mass attenuation coefficients of Veigele [Atom. Data Tables 5 (1973) 51] ave been parameterized in the photon energy range of 1-150 keV for all elements from hydrogen to plutonium (Z = 1-94), taking

J. Braziewicz; E. Braziewicz; M. Pajek

1993-01-01

3

Exploring mediated reality to approximate x-ray attenuation coefficients from radiographs  

NASA Astrophysics Data System (ADS)

Estimation of the x-ray attenuation properties of an object with respect to the energy emitted from the source is a challenging task for traditional Bremsstrahlung sources. This exploratory work attempts to estimate the x-ray attenuation profile for the energy range of a given Bremsstrahlung profile. Previous work has shown that calculating a single effective attenuation value for a polychromatic source is not accurate due to the non-linearities associated with the image formation process. Instead, we completely characterize the imaging system virtually and utilize an iterative search method/constrained optimization technique to approximate the attenuation profile of the object of interest. This work presents preliminary results from various approaches that were investigated. The early results illustrate the challenges associated with these techniques and the potential for obtaining an accurate estimate of the attenuation profile for objects composed of homogeneous materials.

Jimenez, Edward S.; Orr, Laurel J.; Morgan, Megan L.; Thompson, Kyle R.

2014-09-01

4

Theoretical explanation of the relationship between backscattered electron and x-ray linear attenuation coefficients in calcified tissues.  

PubMed

X-ray absorption and backscattered electron (BSE) microscopies are two commonly used techniques for estimating mineral contents in calcified tissues. The resolution in BSE images is usually higher than in x-ray images, but due to the previous lack of good standards to quantify the grey levels in BSE images of bones and teeth, x-ray microtomography (XMT) images of the same specimens have been used for calibration. However, the physics of these two techniques is different: for a specimen with a given composition, the x-ray linear attenuation coefficient is proportional to density, but there is no such relation with the BSE coefficient. To understand the reason that this calibration appears to be valid, the behaviour of simulated bone samples was investigated. In this, the bone samples were modelled as having three phases: hydroxyapatite (Ca10(PO4)6(OH)2), protein, and void (either empty or completely filled with polymethylmethacrylate (PMMA), a resin which is usually used for embedding bones and teeth in microscopic studies). The x-ray linear attenuation coefficients (calculated using published data) and the BSE coefficients (calculated using Monte Carlo simulation) were compared for samples of various phase proportions. It was found that the BSE coefficient correlated only with the x-ray attenuation coefficient for samples with PMMA infiltration. This was attributed to the properties of PMMA (density and mean atomic number) being very similar to those of the protein; therefore, the sample behaves like a two-phase system which allows the establishment of a monotonic relation between density and BSE coefficient. With the newly developed standards (brominated and iodinated dimethacrylate esters) for BSE microscopy of bone, grey levels can be converted to absolute BSE coefficients by linear interpolation, from which equivalent densities can be determined. PMID:9418207

Wong, F S; Elliott, J C

1997-11-01

5

Determination of the mass attenuation coefficients for X-ray fluorescence measurements correction by the Rayleigh to Compton scattering ratio  

NASA Astrophysics Data System (ADS)

X-ray fluorescence technique plays an important role in nondestructive analysis nowadays. The development of equipment, including portable ones, enables a wide assortment of possibilities for analysis of stable elements, even in trace concentrations. Nevertheless, despite of the advantages, one important drawback is radiation self-attenuation in the sample being measured, which needs to be considered in the calculation for the proper determination of elemental concentration. The mass attenuation coefficient can be determined by transmission measurement, but, in this case, the sample must be in slab shape geometry and demands two different setups and measurements. The Rayleigh to Compton scattering ratio, determined from the X-ray fluorescence spectrum, provides a link to the mass attenuation coefficient by means of a polynomial type equation. This work presents a way to construct a Rayleigh to Compton scattering ratio versus mass attenuation coefficient curve by using the MCNP5 Monte Carlo computer code. The comparison between the calculated and literature values of the mass attenuation coefficient for some known samples showed to be within 15%. This calculation procedure is available on-line at www.macx.net.br.

Conti, C. C.; Anjos, M. J.; Salgado, C. M.

2014-09-01

6

Measurement of X-ray mass attenuation coefficients in biological and geological samples in the energy range of 7-12keV.  

PubMed

Information about X-ray mass attenuation coefficients in different materials is necessary for accurate X-ray fluorescent analysis. The X-ray mass attenuation coefficients for energy of 7-12keV were measured in biological (Mussel and Oyster tissues, blood, hair, liver, and Cabbage leaves) and geological (Baikal sludge, soil, and Alaskite granite) samples. The measurements were carried out at the EXAFS Station of Siberian Synchrotron Radiation Center (VEPP-3). Obtained experimental mass attenuation coefficients were compared with theoretical values calculated for some samples. PMID:25464176

Trunova, Valentina; Sidorina, Anna; Kriventsov, Vladimir

2014-10-17

7

Measurement of x-ray attenuation coefficients of aqueous solutions of indocyanine green and glycated chitosan  

E-print Network

and glycated chitosan Fang Xu and Hong Liua) Department of Radiology and Biomedical Engineering, University of a light absorbing dye, indocyanine green, and an immunoadjuvant, glycated chitosan. In the treatment results show that glycated chitosan has a higher attenuation coefficient compared to indocyanine green

Jiang, Hangyi

8

Determination of Linear X-Ray Attenuation Coefficients of Pathological Brain Tissues and Use of Filters in Tissue Contrast Enhancement in Computed Tomography  

PubMed Central

Objective: X-ray attenuation coefficients are used in common radiological, pathological and spectroscopic examinations and in the determination of the radiation dose distribution in biological tissues. In radiology, these coefficients enable diagnosis by differentiating the abnormal tissues from the normal ones using their morphological structure and contrast differences. In this study, our aim is to precisely determine the linear x-ray attenuation coefficients of pathological brain tissues and to use x-ray beam filters to enhance the tissue contrast in computed tomography. Materials and Methods: To directly measure the relative linear attenuation coefficients, an energy dispersive x-ray spectroscopy system (EDXRS-Canberra, Si(Li) with DSA-1000 spectrum analyzer 1998; CT, USA) was used with collimators and a medical-purpose x-ray tube (Siemens, Siremobil, 1985; Erlangen, Germany) in a linear geometry. Results: Using a Mo filter with Computed Tomography CT and photon energies from 15 to 25 keV, EDXRS acquisitions were found to significantly distinguish grades of brain tumors (p<0.05). For the data acquired from CT systems with the decreasing filtered photon mean energy, the x-ray attenuation coefficients (i.e., the Hounsfield units) show that the ratio of EDXRS to CT for water’s attenuation coefficient are increased. With our suggested x-ray filters, the tissue contrast has been found to be increased in ex vivo brain tumor slices compared with slices scanned in conventional CT scanners. Conclusion: X-ray attenuations measured with the EDXRS are found to be statistically more reliable because of the length of acquisition times in this study.

Sagsoz, M. Erdem; Erdogan, Fazl?; Erzeneoglu, Salih Z.; Yuce, ?hsan

2010-01-01

9

Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32-66 and 140 keV  

NASA Astrophysics Data System (ADS)

The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32- 66 keV were produced by X-ray fluorescence using a secondary target system, and 140 keV gamma rays were obtained from an unsealed 99 mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish between measurements with K ? and K ? characteristic X-rays, and the gamma ray measurements used a sodium iodide detector. Samples were selected on the basis of having known composition and mass densities were measured using a pycnometer. The samples comprised six plastics, seven crystalline materials, three tissue substitute materials, three liquids and six salt solutions. Our results have an uncertainty of less than 2% and are a few percent lower than values predicted by the tabulations.

Midgley, S. M.

2005-03-01

10

Chemical effects on K?/K? X-ray intensity ratios of Mo, Ag, Cd, Ba, La, Ce compounds and total mass attenuation coefficients of Fe and Cu  

NASA Astrophysics Data System (ADS)

The K?/K? intensity ratios for pure Mo, Ag, Cd, Ba, La and Ce elements and for some of their compounds were investigated. The vacancies in the K shell were created by 59.5-keV ?-rays from a heavily filtered 241Am radioactive source. K X-rays were measured using a Si(Li) detector with a resolution of 155 eV at 5.9 keV. We observed chemical effects on K?/K? intensity ratios of Mo, Ag, Cd, Ba, La and Ce compounds. Detailed interpretation of data obtained from X-ray transmission measurements usually depends on the assumption that the contribution of each element is additive. This assumption yields the mixture rule for X-ray attenuation coefficients which is valid if molecular and chemical effects are negligible. We measured the total mass attenuation coefficients of Fe and Cu in various compounds. Self-absorption corrections were carried out on data for ligands in the different compounds. Our values were compared with the theoretical values for pure elements.

Sögüt, Ö.; Seven, S.; Baydas, E.; Büyükkasap, E.; Küçükönder, A.

2001-08-01

11

Effective x-ray attenuation coefficient measurements from two full field digital mammography systems for data calibration applications  

Microsoft Academic Search

BACKGROUND: Breast density is a significant breast cancer risk factor. Currently, there is no standard method for measuring this important factor. Work presented here represents an essential component of an ongoing project that seeks to determine the appropriate method for calibrating (standardizing) mammography image data to account for the x-ray image acquisition influences. Longer term goals of this project are

John J Heine; Jerry A Thomas

2008-01-01

12

Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form-factor of tin over the energy range of 29 keV-60 keV.  

SciTech Connect

We use the x-ray extended-range technique (XERT) [C. T. Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of tin in the x-ray energy range of 29-60 keV to 0.04-3 % accuracy, and typically in the range 0.1-0.2 %. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct a number of potential experimental systematic errors. These results represent the most extensive experimental data set for tin and include absolute mass attenuation coefficients in the regions of x-ray absorption fine structure, extended x-ray absorption fine structure, and x-ray absorption near-edge structure. The imaginary component of the atomic form factor f{sub 2} is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-2 % persist between calculated and observed values.

de Jonge, M. D.; Tran, C. Q.; Chantler, C. T.; Barnea, Z.; Dhal, B. P.; Paterson, D.; Kanter, E. P.; Southworth, S. H.; Young, L.; Beno, M. A.; Linton, J. A.; Jennings, G.; Univ. of Melbourne; Australian Synchrotron Project

2007-01-01

13

X-ray mass attenuation coefficients and imaginary components of the atomic form factor of zinc over the energy range of 7.2-15.2 keV  

SciTech Connect

The x-ray mass attenuation coefficients of zinc are measured in a high-accuracy experiment between 7.2 and 15.2 keV with an absolute accuracy of 0.044% and 0.197%. This is the most accurate determination of any attenuation coefficient on a bending-magnet beamline and reduces the absolute uncertainty by a factor of 3 compared to earlier work by advances in integrated column density determination and the full-foil mapping technique described herein. We define a relative accuracy of 0.006%, which is not the same as either the precision or the absolute accuracy. Relative accuracy is the appropriate parameter for standard implementation of analysis of near-edge spectra. Values of the imaginary components f'' of the x-ray form factor of zinc are derived. Observed differences between the measured mass attenuation coefficients and various theoretical calculations reach a maximum of about 5% at the absorption edge and up to 2% further than 1 keV away from the edge. The measurements invite improvements in the theoretical calculations of mass attenuation coefficients of zinc.

Rae, Nicholas A.; Chantler, Christopher T.; Barnea, Zwi; Jonge, Martin D. de; Tran, Chanh Q.; Hester, James R. [School of Physics, University of Melbourne, Victoria 3010 (Australia); Australian Synchrotron, Victoria 3168 (Australia); La Trobe University, Victoria 3086 (Australia); Australian Nuclear Science and Technology Organisation, New South Wales 2234 (Australia)

2010-02-15

14

X-ray attenuation properties of stainless steel (u)  

SciTech Connect

Stainless steel vessels are used to enclose solid materials for studying x-ray radiolysis that involves gas release from the materials. Commercially available stainless steel components are easily adapted to form a static or a dynamic condition to monitor the gas evolved from the solid materials during and after the x-ray irradiation. Experimental data published on the x-ray attenuation properties of stainless steel, however, are very scarce, especially over a wide range of x-ray energies. The objective of this work was to obtain experimental data that will be used to determine how a poly-energetic x-ray beam is attenuated by the stainless steel container wall. The data will also be used in conjunction with MCNP (Monte Carlos Nuclear Particle) modeling to develop an accurate method for determining energy absorbed in known solid samples contained in stainless steel vessels. In this study, experiments to measure the attenuation properties of stainless steel were performed for a range of bremsstrahlung x-ray beams with a maximum energy ranging from 150 keV to 10 MeV. Bremsstrahlung x-ray beams of these energies are commonly used in radiography of engineering and weapon components. The weapon surveillance community has a great interest in understanding how the x-rays in radiography affect short-term and long-term properties of weapon materials.

Wang, Lily L [Los Alamos National Laboratory; Berry, Phillip C [Los Alamos National Laboratory

2009-01-01

15

Measurement of mass attenuation coefficients of Rhizophora spp. binderless particleboards in the 16.59-25.26 keV photon energy range and their density profile using x-ray computed tomography.  

PubMed

The mass attenuation coefficients of Rhizophora spp. binderless particleboard with four different particle sizes (samples A, B, C and D) and natural raw Rhizophora spp. wood (sample E) were determined using single-beam photon transmission in the energy range between 16.59 and 25.26 keV. This was done by determining the attenuation of K(?1) X-ray fluorescent (XRF) photons from niobium, molybdenum, palladium, silver and tin targets. The results were compared with theoretical values of young-age breast (Breast 1) and water calculated using a XCOM computer program. It was found that the mass attenuation coefficient of Rhizophora spp. binderless particleboards to be close to the calculated XCOM values in water than natural Rhizophora spp. wood. Computed tomography (CT) scans were then used to determine the density profile of the samples. The CT scan results showed that the Rhizophora spp. binderless particleboard has uniform density compared to natural Rhizophora spp. wood. In general, the differences in the variability of the profile density decrease as the particle size of the pellet samples decreases. PMID:22304963

Marashdeh, M W; Bauk, S; Tajuddin, A A; Hashim, R

2012-04-01

16

Determination of total x-ray absorption coefficient using non-resonant x-ray emission  

PubMed Central

An alternative measure of x-ray absorption spectroscopy (XAS) called inverse partial fluorescence yield (IPFY) has recently been developed that is both bulk sensitive and free of saturation effects. Here we show that the angle dependence of IPFY can provide a measure directly proportional to the total x-ray absorption coefficient, µ(E). In contrast, fluorescence yield (FY) and electron yield (EY) spectra are offset and/or distorted from µ(E) by an unknown and difficult to measure amount. Moreover, our measurement can determine µ(E) in absolute units with no free parameters by scaling to µ(E) at the non-resonant emission energy. We demonstrate this technique with measurements on NiO and NdGaO3. Determining µ(E) across edge-steps enables the use of XAS as a non-destructive measure of material composition. In NdGaO3, we also demonstrate the utility of IPFY for insulating samples, where neither EY or FY provide reliable spectra due to sample charging and self-absorption effects, respectively. PMID:22355697

Achkar, A. J.; Regier, T. Z.; Monkman, E. J.; Shen, K. M.; Hawthorn, D. G.

2011-01-01

17

Sparse signal reconstruction from polychromatic X-ray CT measurements via mass attenuation discretization  

NASA Astrophysics Data System (ADS)

We propose a method for reconstructing sparse images from polychromatic x-ray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the Lambert-Beer's law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained least-squares optimization approach for reconstructing the underlying object from log-domain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negative-energy and smooth ?1-norm penalty terms. We propose a two-step scheme for refining the mass attenuation discretization grid by using higher sampling rate over the range with higher photon energy, and eliminating the discretization points that have little effect on accuracy of the forward projection model. This refinement allows us to successfully handle the characteristic lines (Dirac impulses) in the incident energy density spectrum. We compare the proposed method with the standard filtered backprojection, which ignores the polychromatic nature of the measurements and sparsity of the image density map. Numerical simulations using both realistic simulated and real x-ray ct data are presented.

Gu, Renliang; Dogandži?, Aleksandar

2014-02-01

18

Sparse signal reconstruction from polychromatic X-ray CT measurements via mass attenuation discretization  

SciTech Connect

We propose a method for reconstructing sparse images from polychromatic x-ray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the Lambert-Beer’s law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained least-squares optimization approach for reconstructing the underlying object from log-domain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negative-energy and smooth ?{sub 1}-norm penalty terms. We propose a two-step scheme for refining the mass attenuation discretization grid by using higher sampling rate over the range with higher photon energy, and eliminating the discretization points that have little effect on accuracy of the forward projection model. This refinement allows us to successfully handle the characteristic lines (Dirac impulses) in the incident energy density spectrum. We compare the proposed method with the standard filtered backprojection, which ignores the polychromatic nature of the measurements and sparsity of the image density map. Numerical simulations using both realistic simulated and real x-ray ct data are presented.

Gu, Renliang; Dogandži?, Aleksandar [Iowa State University, Center for Nondestructive Evaluation, 1915 Scholl Road, Ames, IA 50011 (United States)

2014-02-18

19

Density and atomic number measurements with spectral x-ray attenuation method  

NASA Astrophysics Data System (ADS)

X-ray attenuation measurements are widely used in medical and industrial applications. The usual results are one- to three-dimensional representations of the attenuation coefficient ?(r). In this paper, we present the ?Z projection algorithm for obtaining the density ?(r) and atomic number Z(r) with an energy-resolving x-ray method. As input data the algorithm uses at least two measurements ?1,?2,… with different spectral weightings of the source spectrum S(E) and/or detector sensitivity D(E). Analytically, ? is a function of ?1-c?2, c=const, and Z is a function of ?1/?2. The full numerical treatment yields ?(?1,?2) and Z(?1,?2) with S(E) and D(E) as commutative parametric functions. We tested the method with dual-energy computed tomography measurements of an organic sample and a set of chemical solutions with predefined ? and Z. The resulting images show ? and Z as complementary information: The density ? reflects the morphology of the objects, whereas the atomic number Z=number of electrons/atom describes the material distribution. For our experimental setup we obtain an absolute precision of 0.1 for Z and 20 mg/cm3 for ?. The ?Z projection can potentially lead to these classes of quantitative information for various scientific, industrial, and medical applications.

Heismann, B. J.; Leppert, J.; Stierstorfer, K.

2003-08-01

20

X-ray emission computed tomography with attenuation correction for ICF research  

NASA Astrophysics Data System (ADS)

An attenuation correction method was proposed for laser-produced plasma emission computed tomography (ECT), which is based on relation of attenuation coefficient and emission coefficient in plasma. Simulation results show that the reconstructed images are dramatically improved in comparison to reconstructions without attenuation correction.

Chen, Yen-Wei

1996-05-01

21

The X-ray attenuation characteristics and density of human calcaneal marrow do not change significantly during adulthood  

NASA Technical Reports Server (NTRS)

Changes in the material characteristics of bone marrow with aging can be a significant source of error in measurements of bone density when using X-ray and ultrasound imaging modalities. In the context of computed tomography, dual-energy computed techniques have been used to correct for changes in marrow composition. However, dual-energy quantitative computed tomography (DE-QCT) protocols, while increasing the accuracy of the measurement, reduce the precision and increase the radiation dose to the patient in comparison to single-energy quantitative computed tomography (SE-QCT) protocols. If the attenuation properties of the marrow for a particular bone can be shown to be relatively constant with age, it should be possible to use single-energy techniques without experiencing errors caused by unknown marrow composition. Marrow was extracted by centrifugation from 10 mm thick frontal sections of 34 adult cadaver calcanei (28 males, 6 females, ages 17-65 years). The density and energy-dependent linear X-ray attenuation coefficient of each marrow sample were determined. For purposes of comparing our results, we then computed an effective CT number at two GE CT/i scan voltages (80 and 120 kVp) for each specimen. The coefficients of variation for the density, CT number at 80 kVp and CT number at 120 kVp were each less than 1%, and the parameters did not change significantly with age (p > 0.2, r2 < 0.02, power > 0.8 where the minimum acceptable r2 = 0.216). We could demonstrate no significant gender-associated differences in these relationships. These data suggest that calcaneal bone marrow X-ray attenuation properties and marrow density are essentially constant from the third through sixth decades of life.

Les, C. M.; Whalen, R. T.; Beaupre, G. S.; Yan, C. H.; Cleek, T. M.; Wills, J. S.

2002-01-01

22

The criteria for measuring average density by x-ray attenuation: The role of spatial resolution  

SciTech Connect

It is well known that the attenuation of X-rays as they pass through a material can be used to quantify the amount of matter in their path. This is the basis for the gamma ray densitometer which can measure the amount of material on a moving conveyor belt. It is also the rationale for using X-rays for medical imaging as the attenuation can discriminate between tissue of different density and composition, yielding images of great diagnostic utility. Spatial resolution is obviously important with regard to detecting small features. However, it is less obvious that it plays an important role in obtaining quantitative information from the X-ray transmission data since the spatial resolution of the instrument can affect the accuracy of those measurements. This problem is particularly severe in the case of computed tomography where the accuracy of the reconstruction is dependent on the accuracy of the initial projection data. It should be noted that spatial resolution is not a concern for the case where the material is uniform. Here uniform is defined by small variations related to either the scale size of the resolution element in the detector, or to the size of a collimated X-ray beam. However, if the material has non-homogeneous composition or changes in density on the scale size of the systems spatial resolution, then there can be effects that will compromise the transmission data before it is acquired and these errors can not be corrected by any subsequent data processing. A method is presented for computing the density measurement error which parameterizes the effect in terms of the actual modulation on the face of the detector and the attenuation in the material. For cases like stacks of lead plates the errors can exceed 80%.

Friedman, W.

1999-07-29

23

NAD+ administration significantly attenuates synchrotron radiation X-ray-induced DNA damage and structural alterations of rodent testes  

PubMed Central

Synchrotron radiation (SR) X-ray has great potential for its applications in medical imaging and cancer treatment. In order to apply SR X-ray in clinical settings, it is necessary to elucidate the mechanisms underlying the damaging effects of SR X-ray on normal tissues, and to search for the strategies to reduce the detrimental effects of SR X-ray on normal tissues. However, so far there has been little information on these topics. In this study we used the testes of rats as a model to characterize SR X-ray-induced tissue damage, and to test our hypothesis that NAD+ administration can prevent SR X-ray-induced injury of the testes. We first determined the effects of SR X-ray at the doses of 0, 0.5, 1.3, 4 and 40 Gy on the biochemical and structural properties of the testes one day after SR X-ray exposures. We found that 40 Gy of SR X-ray induced a massive increase in double-strand DNA damage, as assessed by both immunostaining and Western blot of phosphorylated H2AX levels, which was significantly decreased by intraperitoneally (i.p.) administered NAD+ at doses of 125 and 625 mg/kg. Forty Gy of SR X-ray can also induce marked increases in abnormal cell nuclei as well as significant decreases in the cell layers of the seminiferous tubules one day after SR X-ray exposures, which were also ameliorated by the NAD+ administration. In summary, our study has shown that SR X-ray can produce both molecular and structural alterations of the testes, which can be significantly attenuated by NAD+ administration. These results have provided not only the first evidence that SR X-ray-induced tissue damage can be ameliorated by certain approaches, but also a valuable basis for elucidating the mechanisms underlying SR X-ray-induced tissue injury. PMID:22518270

Sheng, Caibin; Chen, Heyu; Wang, Ban; Liu, Tengyuan; Hong, Yunyi; Shao, Jiaxiang; He, Xin; Ma, Yingxin; Nie, Hui; Liu, Na; Xia, Weiliang; Ying, Weihai

2012-01-01

24

Resonant Raman scattering contribution to attenuation of x rays at energies in lower vicinity of the K-shell ionization threshold of some elements  

NASA Astrophysics Data System (ADS)

Attenuation of the x rays and ? rays in the T22i, N41b, T69m, Y70b, and L71u elements have been measured with special emphasis for the x ray energies (Ein) in lower vicinity of the K shell ionization threshold (BK) of the element. The incident photon beam is obtained from decay of the F55e, A241m, and C57o radioisotopes, and fluorescence of the V23, Y70b, L71u, W74, O76s, and T90h targets excited by the x rays and ? rays from the radioisotopes. The measurements were performed using energy dispersive setups involving Ge detectors. The measured attenuation coefficients agree with the available theoretical values except at the photon energies with (BK-Ein) less than or nearly equal to the K-shell width (?K), where significant positive deviations as large as factor of 2 have been observed. In view of reliability of the available theoretical cross sections for the photoionization and the photon scattering processes, the magnitude of positive alteration at the photon energy in lower vicinity of the ionization threshold is attributed to the K shell resonant Raman scattering (RRS) process and the corresponding cross sections have been deduced. Possible matrix effects in the energy dispersive x ray spectrometry due to RRS are also discussed.

Kumar, Sanjeev; Sharma, Veena; Kumar, Sunil; Alrakabi, Muhanad; Mehta, D.; Singh, Nirmal

2009-05-01

25

Attenuation correction for small animal SPECT imaging using x-ray CT data  

SciTech Connect

Photon attenuation in small animal nuclear medicine scans can be significant when using isotopes that emit lower energy photons such as iodine-125. We have developed a method to use microCT data to perform attenuation corrected small animal single-photon emission computed tomography (SPECT). A microCT calibration phantom was first imaged, and the resulting calibration curve was used to convert microCT image values to linear attenuation coefficient values that were then used in an iterative SPECT reconstruction algorithm. This method was applied to reconstruct a SPECT image of a uniform phantom filled with {sup 125}I-NaI. Without attenuation correction, the image suffered a 30% decrease in intensity in the center of the image, which was removed with the addition of attenuation correction. This reduced the relative standard deviation in the region of interest from 10% to 6%.

Hwang, Andrew B.; Hasegawa, Bruce H. [Bioengineering Graduate Group, University of California at Berkeley and University of California, San Francisco, Berkeley, California 94720 (United States); Bioengineering Graduate Group, University of California at Berkeley and University of California, San Francisco, Berkeley, California 94720 and Department of Radiology, University of California, 185 Berry Street, Suite 350, San Francisco, San Francisco, California 94143-0943 (United States)

2005-09-15

26

Numerical comparison of X-ray differential phase contrast and attenuation contrast  

PubMed Central

We present a numerical tool to compare directly the contrast-to-noise-ratio (CNR) of the attenuation- and differential phase-contrast signals available from grating-based X-ray imaging for single radiographs. The attenuation projection is differentiated to bring it into a modality comparable to the differential phase projection using a Gaussian derivative filter. A Relative Contrast Gain (RCG) is then defined as the ratio of the CNR of image values in a region of interest (ROI) in the differential phase projection to the CNR of image values in the same ROI in the differential attenuation projection. We apply the method on experimental data of human breast tissue acquired using a grating interferometer to compare the two contrast modes for two regions of interest differing in the type of tissue. Our results indicate that the proposed method can be used as a local estimate of the spatial distribution of the ratio ?/?, i.e., real and imaginary part of the complex refractive index, across a sample. PMID:22741063

Hahn, Dieter; Thibault, Pierre; Bech, Martin; Stockmar, Marco; Schleede, Simone; Zanette, Irene; Rack, Alexander; Weitkamp, Timm; Sztrókay, Aniko; Schlossbauer, Thomas; Bamberg, Fabian; Reiser, Maximilian; Pfeiffer, Franz

2012-01-01

27

Flat panel X-ray detector with reduced internal scattering for improved attenuation accuracy and dynamic range  

DOEpatents

An x-ray detector is disclosed that has had all unnecessary material removed from the x-ray beam path, and all of the remaining material in the beam path made as light and as low in atomic number as possible. The resulting detector is essentially transparent to x-rays and, thus, has greatly reduced internal scatter. The result of this is that x-ray attenuation data measured for the object under examination are much more accurate and have an increased dynamic range. The benefits of this improvement are that beam hardening corrections can be made accurately, that computed tomography reconstructions can be used for quantitative determination of material properties including density and atomic number, and that lower exposures may be possible as a result of the increased dynamic range.

Smith, Peter D. (Santa Fe, NM); Claytor, Thomas N. (White Rock, NM); Berry, Phillip C. (Albuquerque, NM); Hills, Charles R. (Los Alamos, NM)

2010-10-12

28

Calculation of the X-Ray Bremsstrahlung Transmission Coefficient of Test Filter  

Microsoft Academic Search

The qualitative composition of the Xray brems? strahlung is characterized by parameters of Xray radia? tion attenuation during its transmission through absorb? ing material. One parameter is effective radiation energy determined using exposure radiation dose extinction (or exposure dose power) of a test filter (1). Effective energy is determined indirectly from transmission coefficient K of the test filter using a

M. G. Petrushanskii

2008-01-01

29

Attenuation coefficients for water quality trading.  

PubMed

Water quality trading has been proposed as a cost-effective approach for reducing nutrient loads through credit generation from agricultural or point source reductions sold to buyers facing costly options. We present a systematic approach to determine attenuation coefficients and their uncertainty. Using a process-based model, we determine attenuation with safety margins at many watersheds for total nitrogen (TN) and total phosphorus (TP) loads as they transport from point of load reduction to the credit buyer. TN and TP in-stream attenuation generally increases with decreasing mean river flow; smaller rivers in the modeled region of the Ohio River Basin had TN attenuation factors per km, including safety margins, of 0.19-1.6%, medium rivers of 0.14-1.2%, large rivers of 0.13-1.1%, and very large rivers of 0.04-0.42%. Attenuation in ditches transporting nutrients from farms to receiving rivers is 0.4%/km for TN, while for TP attenuation in ditches can be up to 2%/km. A 95 percentile safety margin of 30-40% for TN and 6-10% for TP, applied to the attenuation per km factors, was determined from the in-stream sensitivity of load reductions to watershed model parameters. For perspective, over 50 km a 1% per km factor would result in 50% attenuation = 2:1 trading ratio. PMID:24866482

Keller, Arturo A; Chen, Xiaoli; Fox, Jessica; Fulda, Matt; Dorsey, Rebecca; Seapy, Briana; Glenday, Julia; Bray, Erin

2014-06-17

30

FREQUENCY DEPENDENT ULTRASONIC ATTENUATION COEFFICIENT ASSESSMENT IN FRESH  

E-print Network

dependency of the ultrasonic attenuation coefficient ranges from f * e to fl.3 6 and its magnitude at 1 MHzFREQUENCY DEPENDENT ULTRASONIC ATTENUATION COEFFICIENT ASSESSMENT IN FRESH TISSUE Laurie A . Segal 61801 Abstract Ultrasonic attenuation coefficient measurements were made at 1.4, 4.2, 7.0 and 9.8 MHz

Illinois at Urbana-Champaign, University of

31

Measurement of atomic number and mass attenuation coefficient in magnesium ferrite  

NASA Astrophysics Data System (ADS)

Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (?), mass attenuation coefficient (?/?), total atomic cross-section (?_{tot}), total electronic cross-section (?_{ele}) and the effective atomic number (Z_{eff}) were calculated for pure magnesium ferrite (MgFe_{2}O_{4}). The values of ?-ray mass attenuation coefficient were obtained using a NaI energy selective scintillation counter with radioactive ?-ray sources having energy 0.36, 0.511, 0.662, 1.17 and 1.28 MeV. The experimentally obtained values of ?/? and Z_{eff} agreed fairly well with those obtained theoretically.

Kadam, R. H.; Alone, S. T.; Bichile, G. K.; Jadhav, K. M.

2007-05-01

32

Study on the influence of X-ray tube spectral distribution on the analysis of bulk samples and thin films: Fundamental parameters method and theoretical coefficient algorithms  

NASA Astrophysics Data System (ADS)

Knowledge of X-ray tube spectral distribution is necessary in theoretical methods of matrix correction, i.e. in both fundamental parameter (FP) methods and theoretical influence coefficient algorithms. Thus, the influence of X-ray tube distribution on the accuracy of the analysis of thin films and bulk samples is presented. The calculations are performed using experimental X-ray tube spectra taken from the literature and theoretical X-ray tube spectra evaluated by three different algorithms proposed by Pella et al. (X-Ray Spectrom. 14 (1985) 125-135), Ebel (X-Ray Spectrom. 28 (1999) 255-266), and Finkelshtein and Pavlova (X-Ray Spectrom. 28 (1999) 27-32). In this study, Fe-Cr-Ni system is selected as an example and the calculations are performed for X-ray tubes commonly applied in X-ray fluorescence analysis (XRF), i.e., Cr, Mo, Rh and W. The influence of X-ray tube spectra on FP analysis is evaluated when quantification is performed using various types of calibration samples. FP analysis of bulk samples is performed using pure-element bulk standards and multielement bulk standards similar to the analyzed material, whereas for FP analysis of thin films, the bulk and thin pure-element standards are used. For the evaluation of the influence of X-ray tube spectra on XRF analysis performed by theoretical influence coefficient methods, two algorithms for bulk samples are selected, i.e. Claisse-Quintin (Can. Spectrosc. 12 (1967) 129-134) and COLA algorithms (G.R. Lachance, Paper Presented at the International Conference on Industrial Inorganic Elemental Analysis, Metz, France, June 3, 1981) and two algorithms (constant and linear coefficients) for thin films recently proposed by Sitko (X-Ray Spectrom. 37 (2008) 265-272).

Sitko, Rafa?

2008-11-01

33

Infrared Radiography: Modeling X-ray Imaging without Harmful Radiation  

ERIC Educational Resources Information Center

Planar x-ray imaging is a ubiquitous diagnostic tool and is routinely performed to diagnose conditions as varied as bone fractures and pneumonia. The underlying principle is that the varying attenuation coefficients of air, water, tissue, bone, or metal implants within the body result in non-uniform transmission of x-ray radiation. Through the…

Zietz, Otto; Mylott, Elliot; Widenhorn, Ralf

2015-01-01

34

Selection of stopping-power and mass energy-absorption coefficient ratios for high-energy x-ray dosimetry  

Microsoft Academic Search

A method for the selection of average stopping-power (L-bar\\/rho)\\/sup med\\/\\/sub air\\/ and energy-absorption coefficient ( mu-bar\\/sub en\\/\\/rho)\\/sup med\\/\\/sub air\\/ ratios has been developed. The quality of the x-ray beam is characterized by the ratio of ionization chamber readings at depths of 20 and 10 cm in water (TMR)²°ââ. For convenience, a relationship is established between experimental (TMR)²°ââ and the nominal

John R. Cunningham; R. J. Schulz

1984-01-01

35

A generalized method of converting CT image to PET linear attenuation coefficient distribution in PET/CT imaging  

NASA Astrophysics Data System (ADS)

The accuracy of attenuation correction in positron emission tomography scanners depends mainly on deriving the reliable 511-keV linear attenuation coefficient distribution in the scanned objects. In the PET/CT system, the linear attenuation distribution is usually obtained from the intensities of the CT image. However, the intensities of the CT image relate to the attenuation of photons in an energy range of 40 keV-140 keV. Before implementing PET attenuation correction, the intensities of CT images must be transformed into the PET 511-keV linear attenuation coefficients. However, the CT scan parameters can affect the effective energy of CT X-ray photons and thus affect the intensities of the CT image. Therefore, for PET/CT attenuation correction, it is crucial to determine the conversion curve with a given set of CT scan parameters and convert the CT image into a PET linear attenuation coefficient distribution. A generalized method is proposed for converting a CT image into a PET linear attenuation coefficient distribution. Instead of some parameter-dependent phantom calibration experiments, the conversion curve is calculated directly by employing the consistency conditions to yield the most consistent attenuation map with the measured PET data. The method is evaluated with phantom experiments and small animal experiments. In phantom studies, the estimated conversion curve fits the true attenuation coefficients accurately, and accurate PET attenuation maps are obtained by the estimated conversion curves and provide nearly the same correction results as the true attenuation map. In small animal studies, a more complicated attenuation distribution of the mouse is obtained successfully to remove the attenuation artifact and improve the PET image contrast efficiently.

Wang, Lu; Wu, Li-Wei; Wei, Le; Gao, Juan; Sun, Cui-Li; Chai, Pei; Li, Dao-Wu

2014-02-01

36

A technique for estimating one-dimensional diffusion coefficients in low-permeability sedimentary rock using X-ray radiography: Comparison with through-diffusion measurements  

NASA Astrophysics Data System (ADS)

The measurement of diffusive properties of low-permeability rocks is of interest to the nuclear power industry, which is considering the option of deep geologic repositories for management of radioactive waste. We present a simple, non-destructive, constant source in-diffusion method for estimating one-dimensional pore diffusion coefficients ( Dp) in geologic materials based on X-ray radiography. Changes in X-ray absorption coefficient (? ?) are used to quantify changes in relative concentration ( C/ C0) of an X-ray attenuating iodide tracer as the tracer solution diffuses through the rock pores. Estimated values of Dp are then obtained by fitting an analytical solution to the measured concentration profiles over time. Measurements on samples before and after saturation with iodide can also be used to determine iodide-accessible porosity (? I). To evaluate the radiography method, results were compared with traditional steady-state through-diffusion measurements on two rock types: shale and limestone. Values of Dp of (4.8 ± 2.5) × 10 - 11 m 2·s - 1 (mean ± standard deviation) were measured for samples of Queenston Formation shale and (2.6 ± 1.0) × 10 - 11 m 2·s - 1 for samples of Cobourg Formation limestone using the radiography method. The range of results for each rock type agree well with Dp values of (4.6 ± 2.0) × 10 - 11 m 2·s - 1 for shale and (3.5 ± 1.8) × 10 - 11 m 2·s - 1 for limestone, calculated from through-diffusion experiments on adjacent rock samples. Low porosity (0.01 to 0.03) and heterogeneous distribution of porosity in the Cobourg Formation may be responsible for the slightly poorer agreement between radiography and through-diffusion results for limestones. Mean values of ? I for shales (0.060) and limestones (0.028) were close to mean porosity measurements made on bulk samples by the independent water loss technique (0.062 and 0.020 for shales and limestones, respectively). Radiography measurements offer the advantage of time-saving for diffusion experiments because the experiment does not require steady-state conditions and also allows for visualization of the small-scale heterogeneities in diffusive properties within rocks at the mm to cm scale.

Cavé, Lisa; Al, Tom; Xiang, Yan; Vilks, Peter

2009-01-01

37

Calculation of radiation attenuation coefficients, effective atomic numbers and electron densities for some building materials.  

PubMed

Some building materials, regularly used in Turkey, such as sand, cement, gas concrete (lightweight, aerated concrete), tile and brick, have been investigated in terms of mass attenuation coefficient (?/?), effective atomic, numbers (Z(eff)), effective electron densities (N(e)) and photon interaction cross section (?(a)) at 14 different energies from 81- to 1332-keV gamma-ray energies. The gamma rays were detected by using gamma-ray spectroscopy, a High Purity Germanium (HPGe) detector. The elemental compositions of samples were analysed using an energy dispersive X-ray fluorescence spectrometer. Mass attenuation coefficients of these samples have been compared with tabulations based upon the results of WinXcom. The theoretical mass attenuation coefficients were estimated using the mixture rule and the experimental values of investigated parameters were compared with the calculated values. The agreement of measured values of mass attenuation coefficient, effective atomic numbers, effective electron densities and photon interaction cross section with the theory has been found to be quite satisfactory. PMID:22128356

Damla, N; Baltas, H; Celik, A; Kiris, E; Cevik, U

2012-07-01

38

Dual energy CT-based characterization of x-ray attenuation properties of breast equivalent material plates  

NASA Astrophysics Data System (ADS)

Breast density is more and more considered as an important risk factor for breast cancer and several quantitative breast density evaluation methods have been proposed. The reference material for simulation of the breast attenuation properties of glandular and adipose breast tissues is manufactured by a single provider. In order to characterize the attenuation properties of these materials, measurements in Hounsfield Units (HU) have been performed using a CT-scanner. Breastequivalent plates have been imaged in different configurations (plates in and orthogonal to image planes), providing consistent results (+/- 1.3 HU). Breast density equivalent plates of different nominal breast density equivalences and sizes were measured, demonstrating both a good homogeneity within the plates (+/- 1.8 HU) and a good consistency between plates of the same nominal breast density equivalence (+/- 1.5 HU). In addition, dual energy CT provided mono-energetic HU from which mono-energetic linear attenuation coefficients of water and glandular and adipose equivalent materials were computed. The values for these coefficients were found in good agreement with results from literature, respectively direct mono-energetic measurements of breast samples, and computation by combining published breast tissue atomic compositions and linear attenuation coefficient tables. In conclusion, CT was found effective for the verification of the breast equivalent material, and the homogeneity and consistency of the plates were found satisfactory. Furthermore, the most recent spectral CT technology allowed demonstrating a good agreement of the attenuation properties of breastequivalent material plates with state-of-the-art knowledge of real breast tissue attenuation.

Geeraert, N.; Klausz, R.; Giudici, P.; Muller, S.; Cockmartin, L.; Bosmans, H.

2012-03-01

39

Radiographic least-squares fitting technique accurately measures dimensions and x-ray attenuation  

SciTech Connect

In support of stockpile stewardship and other important nondestructive test (NDT) applications, the authors seek improved methods for rapid evaluation of materials to detect degradation, warping, and shrinkage. Typically, such tests involve manual measurements of dimensions on radiographs. The authors seek to speed the process and reduce the costs of performing NDT by analyzing radiographic data using a least-squares fitting technique for rapid evaluation of industrial parts. In 1985, Whitman, Hanson, and Mueller demonstrated a least-squares fitting technique that very accurately locates the edges of cylindrically symmetrical objects in radiographs. To test the feasibility of applying this technique to a large number of parts, the authors examine whether an automated least squares algorithm can be routinely used for measuring the dimensions and attenuations of materials in two nested cylinders. The proposed technique involves making digital radiographs of the cylinders and analyzing the images. In the authors` preliminary study, however, they use computer simulations of radiographs.

Kelley, T.A.; Stupin, D.M.

1997-10-01

40

Dose reduction technique using a combination of a region of interest (ROI) material x-ray attenuator and spatially different temporal filtering for fluoroscopic interventions  

NASA Astrophysics Data System (ADS)

We demonstrate a novel approach for achieving patient dose savings during image-guided neurovascular interventions, involving a combination of a material x-ray region of interest (ROI) attenuator and a spatially different ROI temporal filtering technique. The part of the image under the attenuator is reduced in dose but noisy and less bright due to fewer x-ray quanta reaching the detector, as compared to the non-attenuating (or less attenuating) region. First the brightness is equalized throughout the image by post processing and then a temporal filter with higher weights is applied to the high attenuating region to reduce the noise, at the cost of increased lag; however, in the regions where less attenuation is present, a lower temporal weight is needed and is applied to preserve temporal resolution. A simulation of the technique is first presented on an actual image sequence obtained from an endovascular image guided interventional (EIGI) procedure. Then the actual implementation of the technique with a physical ROI attenuator is presented. Quantitative analysis including noise analysis and integral dose calculations are presented to validate the proposed technique.

Swetadri Vasan, S. N.; Panse, A.; Jain, A.; Sharma, P.; Ionita, Ciprian N.; Titus, A. H.; Cartwright, A. N.; Bednarek, D. R.; Rudin, S.

2012-03-01

41

Development of in vivo characterization of breast tissues through absolute attenuation coefficients using dedicated cone-beam CT  

NASA Astrophysics Data System (ADS)

With advances in 3D in vivo imaging technology, non-invasive procedures can be used to characterize tissues to identify tumors and monitor changes over time. Using a dedicated breast CT system with a quasi-monochromatic cone-beam x-ray source and flat-panel digital detector, this study was performed in an effort to directly characterize different materials in vivo based on their absolute attenuation coefficients. CT acquisitions were first acquired using a multi-material rod phantom with acrylic, delrin, polyethylene, fat-equivalent, and glandular-equivalent plastic rods, and also with a human cadaver breast. Projections were collected with and without a beam stop array for scatter correction. For each projection, the 2D scatter was estimated with cubic spline interpolation of the average values behind the shadow of each beam stop overlapping the object. Scatter-corrected projections were subsequently calculated by subtracting the scatter images containing only the region of the object from corresponding projections (consisting of primary and scatter x-rays) without the beam stop array. Iterative OSTR was used to reconstruct the data and estimate the non-uniform attenuation distribution. Preliminary results show that with reduced beam hardening from the x-ray beam, scatter correction further reduces the cupping artifact, improves image contrast, and yields attenuation coefficients < 8% of narrow-beam values of the known materials (range 1.2 - 7.8%). Peaks in the histogram showed clear separation between the different material attenuation coefficients. These findings indicate that minimizing beam hardening and applying scatter correction make it practical to directly characterize different tissues in vivo using absolute attenuation coefficients.

Madhav, Priti; Li, Christina M.; Tornai, Martin P.

2010-04-01

42

Gamma ray attenuation coefficient measurement for neutron-absorbent materials  

NASA Astrophysics Data System (ADS)

The compounds Na 2B 4O 7, H 3BO 3, CdCl 2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the ? rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H 3BO 3 with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.

Jalali, Majid; Mohammadi, Ali

2008-05-01

43

Attenuation coefficients of body tissues using principal-components analysis  

Microsoft Academic Search

Principal-components analysis is used to obtain a set of parameters for dual-energy radiography that completely describes the attenuation coefficient of any tissue over a given energy range. These parameters are the weighted averages of the densities of the elements present in a substance. Principal-components (PC) parameters are calculated for several soft tissues from measured attenuation coefficients published by Phelps et

J. B. Weaver; A. L. Huddleston

2009-01-01

44

Measurements of spectral attenuation coefficients in the lower Chesapeake Bay  

NASA Technical Reports Server (NTRS)

The spectral transmission was measured for water samples taken in the lower Chesapeake Bay to allow characterization of several optical properties. The coefficients of total attenuation, particle attenuation, and absorption by dissolved organic matter were determined over a wavelength range from 3500 A to 8000 A. The data were taken over a 3 year period and at a number of sites so that an indication of spatial and temporal variations could be obtained. The attenuations determined in this work are, on the average, 10 times greater than those obtained by Hulburt in 1944, which are commonly accepted in the literature for Chesapeake Bay attenuation.

Houghton, W. M.

1983-01-01

45

Dose reduction in fluoroscopic interventions using a combination of a region of interest (ROI) x-ray attenuator and spatially different, temporally variable temporal filtering  

NASA Astrophysics Data System (ADS)

A novel dose reduction technique for fluoroscopic interventions involving a combination of a material x-ray region of interest (ROI) attenuator and spatially different, temporally variable ROI temporal recursive filter, was used to guide the catheter to the ROI in three live animal studies, two involving rabbits and one involving a sheep. In the two rabbit studies presented , a catheter was guided to the entrance of the carotid artery. With the added ROI attenuator the image under the high attenuation region is very noisy. By using temporal filtering with a filter weight of 0.6 on previous frames, the noise is reduced. In the sheep study the catheter was guided to the descending aorta of the animal. The sheep offered a relatively higher attenuation to the incident x-rays and thus a higher temporal filter weight of 0.8 on previous frames was used during the procedure to reduce the noise to levels acceptable by the interventionalist. The image sequences from both studies show that significant dose reduction of 5-6 times can be achieved with acceptable image quality outside the ROI by using the above mentioned technique. Even though the temporal filter weighting outside the ROI is higher, the consequent lag does not prevent perception of catheter movement.

Swetadri Vasan, S. N.; Pope, Liza; Ionita, Ciprian N.; Titus, A. H.; Bednarek, D. R.; Rudin, S.

2013-03-01

46

Hygrothermal degradation of 3-glycidoxypropyltrimethoxysilane films studied by neutron and X-ray reflectivity and attenuated total reflection infrared spectroscopy.  

SciTech Connect

Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D{sub 2}O or H{sub 2}O at 80 C. For NR and XR, ultrathin ({approx}100 {angstrom}) films were prepared by spin-coating. Both D{sub 2}O and H{sub 2}O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H{sub 2}O or D{sub 2}O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H{sub 2}O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D{sub 2}O at 80 C for 1 month. This indicates that hydrolysis of Si-O-Si is much slower with D{sub 2}O than with H{sub 2}O.

Tallant, David Robert; Garcia, Manuel Joseph; Majewski, Jaroslaw (Los Alamos National Lab, Los Alamos, NM); Kent, Michael Stuart; Yim, Hyun

2005-05-01

47

X-ray scalpel—a new device for targeted x-ray brachytherapy and stereotactic radiosurgery  

NASA Astrophysics Data System (ADS)

The basic design and performance of a novel x-ray scalpel device for interstitial radiosurgery are reported. The x-ray scalpel is comprised of a capillary optics collimator conjugated with a high brilliance microfocus x-ray tube and a thin hollow needle (tip) attached to the collimator. The device is capable of producing a high dose rate (about 140 Gy min-1 in water-like absorber at the exit window), 0.7 mm diameter, quasi-parallel beam that can be delivered to a targeted site by a minimally invasive procedure. Contrary to insertable x-ray tubes or radionuclides used in brachytherapy and complying with the 1/r2 radiation attenuation law, the dose rate for a quasi-parallel beam decreases with distance as ? exp(-?r), where ? is the energy-dependent linear attenuation coefficient in the exposed medium. Moreover, the shape, energy and the dose attenuation curve of the x-ray beam can be adjusted. Two versions of the x-ray scalpel device (5.4 keV and 20.2 keV) are described. We present results from our first test of the x-ray scalpel as a controllable source of focal radiation for producing radiation necrosis in rat brain tissue. Irradiation was transdurally delivered to the rat cerebral cortex for 10 min at a dose rate of 20 Gy min-1.

Gutman, George; Strumban, Emil; Sozontov, Evgeny; Jenrow, Kenneth

2007-03-01

48

Determination of mass attenuation coefficients for threshold contrast evaluation in digital mammography  

NASA Astrophysics Data System (ADS)

According to the 'European protocol for the quality control of the physical and technical aspects of mammography screening' (EPQC) image quality digital mammography units has to be evaluated at different breast thicknesses. At the standard thickness of 50 mm polymethyl methacrylate (PMMA) image quality is determined by the analysis of CDMAM contrast detail phantom images where threshold contrasts are calculated for different gold disc diameters. To extend these results to other breast thicknesses contrast-to-noise ratios (CNR) and threshold contrast (TC) visibilities have to be calculated for all required thicknesses. To calculate the latter the mass attenuation coefficient (MAC) of gold has to be known for all possible beam qualities in the tube voltage range between 26 and 32 kV. In this paper we first determined the threshold contrast visibility using the CDMAM phantom with the same beam quality at different current-time products (mAs). We can derive from Rose theory that CNR • CT • ? = const, where ? is the diameter of the gold cylinder. From this the corresponding attenuation coefficients can be calculated. This procedure was repeated for four different beam qualities (Mo/Mo 27kV, Rh/Rh 29kV, Rh/Rh 31 kV, and W/Rh 29 kV)). Next, we measured the aluminium half value layer (HVL) of all x-ray spectra relevant for mammography. Using a first order Taylor expansion of MAC as a function of HVL, all other desired MAC can be calculated. The MAC as a function of the HVL was derived to MAChvl = -286.97 * hvl+186.03 with R2 = 0.997, where MAChvl indicates the MAC for all specific x-ray spectrum defined by its aluminium half value layer. Based on this function all necessary MACs needed for quality assurance (QA) were calculated. The results were in good agreement with the data found in the protocol.

Hummel, Johann; Semturs, Friedrich; Menhart, Susanne; Figl, Michael

2010-04-01

49

Dual-energy attenuation coefficient decomposition with differential filtration and application to a microCT scanner  

NASA Astrophysics Data System (ADS)

Dual-energy x-ray computed tomography (DECT) has the capability to decompose attenuation coefficients using two basis functions and has proved its potential in reducing beam-hardening artifacts from reconstructed images. The method typically involves two successive scans with different x-ray tube voltage settings. This work proposes an approach to dual-energy imaging through x-ray beam filtration that requires only one scan and a single tube voltage setting. It has been implemented in a preclinical microCT tomograph with minor modifications. Retrofitting of the microCT scanner involved the addition of an automated filter wheel and modifications to the acquisition and reconstruction software. Results show that beam-hardening artifacts are reduced to noise level. Acquisition of a ?-Compton image is well suited for attenuation-correction of PET images while dynamic energy selection (4D viewing) offers flexibility in image viewing by adjusting contrast and noise levels to suit the task at hand. All dual-energy and single energy reference scans were acquired at the same soft tissue dose level of 50 mGy.

Taschereau, R.; Silverman, R. W.; Chatziioannou, A. F.

2010-02-01

50

Dual-energy attenuation coefficient decomposition with differential filtration and application to a microCT scanner  

PubMed Central

Dual-energy x-ray computed tomography (DECT) has the capability to decompose attenuation coefficients using two basis functions and has proved its potential in reducing beam-hardening artifacts from reconstructed images. The method typically involves two successive scans with different x-ray tube voltage settings. This work proposes an approach to dual-energy imaging through x-ray beam filtration that requires only one scan and a single tube voltage setting. It has been implemented in a preclinical microCT tomograph with minor modifications. Retrofitting of the microCT scanner involved the addition of an automated filter wheel and modifications to the acquisition and reconstruction software. Results show that beam-hardening artifacts are reduced to noise level. Acquisition of a ?-Compton image is well suited for attenuation-correction of PET images while dynamic energy selection (4D viewing) offers flexibility in image viewing by adjusting contrast and noise levels to suit the task at hand. All dual-energy and single energy reference scans were acquired at the same soft tissue dose level of 50 mGy. PMID:20107245

Taschereau, R; Silverman, R W; Chatziioannou, A F

2010-01-01

51

Using Variable Temperature Powder X-Ray Diffraction to Determine the Thermal Expansion Coefficient of Solid MgO  

ERIC Educational Resources Information Center

A laboratory exercise was developed by using variable temperature powder X-ray diffraction (XRD) to determine [alpha] for MgO (periclase)and was tested in the Applied Physical Chemistry and Materials Characterization Laboratories at James Madison University. The experiment which was originally designed to provide undergraduate students with a…

Corsepius, Nicholas C.; DeVore, Thomas C.; Reisner, Barbara A.; Warnaar, Deborah L.

2007-01-01

52

The X-ray attenuation characteristics and density of human calcaneal marrow do not change significantly during adulthood  

Microsoft Academic Search

Changes in the material characteristics of bone marrow with aging can be a significant source of error in measurements of bone density when using X-ray and ultrasound imaging modalities. In the context of computed tomography, dual-energy computed techniques have been used to correct for changes in marrow composition. However, dual-energy quantitative computed tomography (DE-QCT) protocols, while increasing the accuracy of

C. M. Les; R. T. Whalen; G. S. Beaupré; C. H. Yan; T. M. Cleek; J. S. Wills

2002-01-01

53

Temporal Variations of Seismic Coda: Attenuation-Coefficient View  

NASA Astrophysics Data System (ADS)

When monitoring spatial or temporal variations of the subsurface, it is important to use properties that objectively exist and are insensitive to observational uncertainties. Although the frequency-dependent seismic coda quality factor, Qc is often found to change prior and following relation to major earthquakes and volcanic eruptions, it does not represent such a property. Qc is strongly dependent on the assumed theoretical models, which are usually insufficiently accurate for constraining the actual relationships between the geometrical spreading, anelastic dissipation, and scattering of seismic waves. This inaccuracy often leads to significant exaggeration of attenuation effects, and particularly to interpretations of temporal variations in Qc as related to changes in lithospheric scattering. To overcome this bias, we use an approach based on the temporal attenuation-coefficient, ?(f), instead of Q(f) for describing coda attenuation. Several attenuation case studies suggest that ?(f) typically linearly depends on f, with both the intercept ? = ?(0) and slope d?(f)/df = ?Qe-1 being sensitive to the physical state of the subsurface. Two published examples of temporal variations of local-earthquake coda Q are revisited: non-volcanic (near Stone Canyon in central California) and volcanic (Mt. St. Helens, Washington). In both cases, linear ?(f) patterns are found, with the effects of geometrical spreading (?) on coda attenuation being significantly stronger than those of Qe-1. At Stone Canyon, ? values ranged from 0.035 to 0.06 s-1 and Qe varies from 3000 to 10000, with ? increasing and Qe decreasing during the winter season. At Mt. St. Helens, ? ? 0.18 s-1, and Qe changed from 400 before the eruption to 750 after it. The observed temporal variations are explained by near-surface effects (seasonal variations in the non-volcanic case and gas-, magma-, and geothermal-system related in the volcanic case),which mostly affect the geometrical spreading and anelastic attenuation. Scattering does not appear to be a significant attenuation factor in these areas, or otherwise it may be indistinguishable from the intrinsic attenuation in the data.

Morozov, I. B.

2010-12-01

54

X-ray transmissive debris shield  

DOEpatents

An X-ray debris shield for use in X-ray lithography that is comprised of an X-ray window having a layer of low density foam exhibits increased longevity without a substantial increase in exposure time. The low density foam layer serves to absorb the debris emitted from the X-ray source and attenuate the shock to the window so as to reduce the chance of breakage. Because the foam is low density, the X-rays are hardly attenuated by the foam and thus the exposure time is not substantially increased.

Spielman, R.B.

1996-05-21

55

X-ray transmissive debris shield  

DOEpatents

An X-ray debris shield for use in X-ray lithography that is comprised of an X-ray window having a layer of low density foam exhibits increased longevity without a substantial increase in exposure time. The low density foam layer serves to absorb the debris emitted from the X-ray source and attenuate the shock to the window so as to reduce the chance of breakage. Because the foam is low density, the X-rays are hardly attenuated by the foam and thus the exposure time is not substantially increased.

Spielman, Rick B. (Albuquerque, NM)

1996-01-01

56

X-ray Interactions with Matter  

NSDL National Science Digital Library

The Center for X-ray Optics offers a concise discussion and many graphs illustrating the primary interactions of low-energy X-rays within matter. Users can find a database of atomic scattering factors which are used to characterize the interactions between X-rays and matter. The website provides the electron level widths, electron binding energies, atomic properties, and material properties for the elements. Visitors can generate plots of refraction indices, attenuation length of a solid, X-ray transmissions for solids and gases, X-ray reflectivity, bend magnet spectrum, and transmission grating efficiency. This website offers an effective means for visualizing X-ray data.

57

X-Ray Data Booklet  

NSDL National Science Digital Library

The X-Ray Data Booklet is provided by the Center for X-ray Optics and Advanced Light Source of the Lawrence Berkeley National Laboratory, which is funded by the US Department of Energy. The online publication contains topics such as x-ray properties of elements, mass absorption coefficients, synchrotron radiation, scattering processes, low-energy electron ranges in matter, optics and detectors, specular reflectivities for grazing-incidence mirrors, and other practical information that has been produced and gathered as a result of research at the center. Additional features of the informative site include an interactive periodic table of X-Ray properties and free deliverable hardcopies of the document.

Attwood, David.

2000-01-01

58

Synthesis and characterisation of ion-implanted epoxy composites for X-ray shielding  

NASA Astrophysics Data System (ADS)

The epoxy samples were implanted with heavy ions such as tungsten (W), gold (Au) and lead (Pb) to investigate the attenuation characteristics of these composites. Near-surface composition depth profiling of ion-implanted epoxy systems was studied using Rutherford Backscattering Spectroscopy (RBS). The effect of implanted ions on the X-ray attenuation was studied with a general diagnostic X-ray machine with X-ray tube voltages from 40 to 100 kV at constant exposure 10 mAs. Results show that the threshold of implanted ions above which X-ray mass attenuation coefficient, ?m of the ion-implanted epoxy composite is distinguishably higher than the ?m of the pure epoxy sample is different for W, Au and Pb.

Noor Azman, N. Z.; Siddiqui, S. A.; Ionescu, M.; Low, I. M.

2012-09-01

59

X-ray microtomography at high pressure  

NASA Astrophysics Data System (ADS)

X-ray microtomography at high pressure is now possible with the rotating anvil apparatus (RAA) on the 13-BM- D beamline at the Advanced Photon Source (Argonne National Lab). The high-pressure X-ray tomography microscope (HPXTM) can be used to determine densities of amorphous materials (glasses and melts) and in situ characterization of 3D microstructure of multiphase materials subject to temperature and shear deformation [1, 2]. Densities may be obtained directly by volume rendering or from X-ray absorption. The rotating anvil apparatus is compressed by a 250-ton hydraulic press between concentric thrust bearings. Toroidal and truncated cylindrical (Drickamer) anvils can be accommodated. The latter anvils perform well up to 11.5 GPa and 1873K, using boron epoxy/diamond epoxy gaskets and X-ray transparent aluminum or polytherimide plastic containment rings. Differential rotation allows for controlled sample deformation. Pressure is determined by energy dispersive diffraction of an internal standard by convenient switching from monochromatic and polychromatic radiation. In-situ calibrations of linear attenuation coefficient permit bracketing of natural basalt density to better than 1 percent relative, while [2] used volume rendering to determine the compressibility of magnesium silicate glasses and supercooled liquid. The utility of the RRA to characterize microstructural evolution will be discussed. [1] Wang et al., Rev. Sci. Instrum., 76, 073709, 2005. [2] Lesher et al., PEPI, in press, DOI: 10.1016/j.pepi.2008.10.023, 2009

Lesher, C. E.; Wang, Y.; Gaudio, S.; Clark, A.; Yamada, A.; Sanehira, T.; Rivers, M.

2009-05-01

60

Measurements of the hard-x-ray reflectivity of iridium  

SciTech Connect

In connection with the design of a hard-x-ray telescope for the Constellation X-Ray Observatory we measured the reflectivity of an iridium-coated zerodur substrate as a function of angle at 55, 60, 70, and 80 keV at the National Synchrotron Light Source of Brookhaven National Laboratory. The optical constants were derived from the reflectivity data. The real component of the index of refraction is in excellent agreement with theoretical values at all four energies. However, the imaginary component, which is related to the mass attenuation coefficient, is 50% to 70% larger at 55, 60, and 70 keV than theoretical values.

Romaine, S.; Bruni, R.; Gorenstein, P.; Zhong, Z

2007-01-10

61

Infrared Radiography: Modeling X-ray Imaging Without Harmful Radiation  

NASA Astrophysics Data System (ADS)

Planar x-ray imaging is a ubiquitous diagnostic tool and is routinely performed to diagnose conditions as varied as bone fractures and pneumonia. The underlying principle is that the varying attenuation coefficients of air, water, tissue, bone, or metal implants within the body result in non-uniform transmission of x-ray radiation. Through the detection of transmitted radiation, the spatial organization and composition of materials in the body can be ascertained. In this paper, we describe an original apparatus that teaches these concepts by utilizing near infrared radiation and an up-converting phosphorescent screen to safely probe the contents of an opaque enclosure.

Zietz, Otto; Mylott, Elliot; Widenhorn, Ralf

2015-01-01

62

Quantitative 3D petrography using x-ray tomography: Application to Bishop Tuff pumice clasts  

Microsoft Academic Search

Textures are traditionally studied using the petrographic microscope, which limits observations to 2D sections of 3D objects. Given the difficulty in retrieving information on shapes, sizes and spatial distribution of objects in 3D from random sections, a method that can yield observations in 3D is highly desirable.X-ray tomography yields a 3D map of the linear X-ray attenuation coefficient, which is

Guilherme A. R. Gualda; Mark Rivers

2006-01-01

63

Dual-energy X-ray radiography for automatic high- Z material detection  

NASA Astrophysics Data System (ADS)

There is an urgent need for high- Z material detection in cargo. Materials with Z > 74 can indicate the presence of fissile materials or radiation shielding. Dual (high) energy X-ray material discrimination is based on the fact that different materials have different energy dependence in X-ray attenuation coefficients. This paper introduces the basic physics and analyzes the factors that affect dual-energy material discrimination performance. A detection algorithm is also discussed.

Chen, Gongyin; Bennett, Gordon; Perticone, David

2007-08-01

64

Measurement of mass attenuation coefficients for YBaCuO superconductor at different energies  

NASA Astrophysics Data System (ADS)

The mass attenuation coefficients for Y2O3, BaCO3, CuO compounds, and solid-state forms of YBa2Cu3O7 superconductor were determined at energies of 57.5, 59.5, 65.2, 74.8, 77.1, 87.3, 94.6, 98.4, 122, and 136 keV. The samples were irradiated using a 241Am point source emitting 59.5 keV photon energies and a 57Co point source emitting 122 and 136 keV photon energies. The other energies were obtained using secondary targets such as Ta, Bi2O3, and (CH3COO)2UO22H2O. The gamma- and x-rays were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Samples were selected on the basis of known composition and mass densities were measured using a densitometer. The experimental results obtained in this study are compared with theoretical values.

Çevik, U.; Baltas, H.; Çelik, S.; Karaca, I.; Kopya, I.

2005-01-01

65

Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr1-xMnxO3 negative temperature coefficient ceramics  

NASA Astrophysics Data System (ADS)

Electrical conductivity anomaly of perovskite-type YCr1-xMnxO3 negative temperature coefficient (NTC) ceramics produced by spark plasma sintering (SPS) has been investigated by using defect chemistry theory combination with X-ray photoelectron spectroscopy (XPS) analysis. From the results of the ln?-1/T curves and the XPS analysis, it can be considered that YCr1-xMnxO3 ceramics exhibit the hopping conductivity. The major carriers in YCrO3 are holes, which are compensated by the oxygen vacancies produced due to the introduction of Mn ions. The Mn4+ ion contents increase monotonically in the range of 0.2 ? x ? 0.5. The resistivity increases at first and then decreases with increasing Mn contents, which has the same varying tendency with activation energy. The electrical conductivity anomaly appearing in these ceramics may be due to the variation of Cr4+ and Mn4+ ions concentration as Mn content changes.

Zhang, Bo; Zhao, Qing; Chang, Aimin; Li, Yiyu; Liu, Yin; Wu, Yiquan

2014-03-01

66

Representative Elementary Length to Measure Soil Mass Attenuation Coefficient  

PubMed Central

With increasing demand for better yield in agricultural areas, soil physical property representative measurements are more and more essential. Nuclear techniques such as computerized tomography (CT) and gamma-ray attenuation (GAT) have been widely employed with this purpose. The soil mass attenuation coefficient (?s) is an important parameter for CT and GAT analysis. When experimentally determined (?es), the use of suitable sized samples enable to evaluate it precisely, as well as to reduce measurement time and costs. This study investigated the representative elementary length (REL) of sandy and clayey soils for ?es measurements. Two radioactive sources were employed (241Am and 137Cs), three collimators (2–4?mm diameters), and 14 thickness (x) samples (2–15?cm). Results indicated ideal thickness intervals of 12–15 and 2–4?cm for the sources 137Cs and 241Am, respectively. The application of such results in representative elementary area (REA) evaluations in clayey soil clods via CT indicated that ?es average values obtained for x?>?4?cm and source 241Am might induce to the use of samples which are not large enough for soil bulk density evaluations (?s). As a consequence, ?s might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study. PMID:24672338

Borges, J. A. R.; Pires, L. F.; Costa, J. C.

2014-01-01

67

Material Identification from X-ray Images Made by Energy-Differentiation Type X-ray Line Sensor  

Microsoft Academic Search

\\u000a It was confirmed that linear attenuation coefficient and effective atomic number of objects could be identified by X-ray 2D\\u000a and CT images discriminated by different energy. The differences between theoretical and experimental values of linear attenuation\\u000a coefficient of each object from Xray images were 0.01-22.6% for carbon, 0.01%-23.1% for acrylic resin, and 0.07-22.1% for\\u000a aluminum. The effective atomic number of

Masao Matsumoto; Naoki Takayama

68

Quantitative x-ray microtomography with a conventional source  

NASA Astrophysics Data System (ADS)

In 1981, Elliott and Dover designed an X-ray microtomography scanner as a means of measuring the local mineral concentration in teeth. Although slow, this first generation system gave accurate measurements of the X-ray linear attenuation coefficient (LAC) due to its use of energy dispersive photon counting apparatus. Attaining such accuracy with integrating detectors in third generation scanners is difficult, but has been the goal of our ongoing development. The current "MuCat 2" system uses a 6cm square CCD chip with a parallel fibre-optic faceplate coupled to a CsI scintillator. Time delay integration readout (with sliding camera) is used to eliminate ring artefacts and enable high dynamic range X-ray projections to be acquired. The beam is collimated with a moving aperture (tracking the camera) to reduce X-ray scatter. Beam hardening is reduced by the use of filtering and corrected using data from an aluminium step wedge to optimise a model of polychromatic X-ray generation, attenuation and detection. Adjustments can be made to the model to allow for known specimen composition. Projections are corrected for distortion and repeatable wobble in the rotation stage. Where high absolute accuracy of the LAC is required, a pure aluminium wire is included in the scan and used to "fine-tune" the grey level after reconstruction.

Davis, Graham; Evershed, Anthony; Elliott, James; Mills, David

2010-09-01

69

[Problems of the effective energy used as a quality expression of diagnostic X-ray].  

PubMed

The effective energy has been generally used as a method of handily expressing an X-ray quality by one numerical value. The effective energy is a concept derived from "Half Value Layer (HVL)" that is the expressing parameter of beam quality based on the attenuation of the primary X-ray by a material. When beam quality is expressed by using HVL and / or the effective energy, it is necessary to describe the tube potential, the rectification method, and the homogeneity coefficient, etc. in parallel. However, recently feelings are that the effective energy should be handled like an absolute numerical value to physical characteristics of X-rays. In this paper, it was theoretically clarified that the effective energy had a different value depending on the absorber material used for the HVL measurement. In addition, the errors when physical characteristics of the X-rays were evaluated using the effective energy was also examined. Physical characteristics, such as interactions to the material of mono-energetic X-ray, are not equal to that of X-rays with a wide energy spectrum. It is not an easy comparison to express the quality of the diagnostic X-rays, and to calculate physical characteristics of the X-rays by using the effective energy. It is necessary to design a new method of expressing the quality of X-rays that takes the place of the "effective energy." PMID:22026986

Kato, Hideki; Hayashi, Naoki; Suzuki, Shoichi; Ando, Sho; Miyamoto, Mami; Wakasugi, Nao; Suzuki, Shizuma

2011-01-01

70

Skull x-ray  

MedlinePLUS

X-ray - head; X-ray - skull; Skull radiography; Head x-ray ... will be asked to lie on the x-ray table or sit in a chair. Your head ... is little or no discomfort during an x-ray. If there is a head injury , positioning the ...

71

Joint x-ray  

MedlinePLUS

X-ray - joint; Arthrography; Arthrogram ... x-ray technologist will help you position the joint to be x-rayed on the table. Once in place, pictures are taken. The joint may be moved into other positions for more ...

72

X-Rays  

MedlinePLUS

X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of ... different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white. Fat ...

73

A realistic projection simulator for laboratory based X-ray micro-CT  

NASA Astrophysics Data System (ADS)

In X-ray computed tomography (CT) each voxel of the reconstructed image contains a calculated grey value which represents the linear attenuation coefficient for the materials in that voxel. Conventional laboratory based CT scanners use polychromatic X-ray sources and integrating detectors with an energy dependent efficiency. Consequently the reconstructed attenuation coefficients will depend on the spectrum of the source and the spectral sensitivity of the detector. Beam hardening will alter the spectrum significantly as the beam propagates through the sample. Therefore, sample composition and shape will affect the reconstructed attenuation coefficients as well. A polychromatic projection simulator has been developed at the "Centre for X-ray Tomography" of the Ghent University (UGCT) which takes into account the aforementioned variables, allowing for complete and realistic simulations of CT scans for a wide range of geometrical setups. Monte Carlo simulations of the X-ray tubes and detectors were performed to model their spectral behaviour. In this paper, the implementation and features of the program are discussed. Simulated and real CT scans are compared to demonstrate the quantitative correctness of the simulations. Experiments performed at two different UGCT scanners yield a maximum deviation of 3.9% and 6.5% respectively, between the measured and simulated reconstructed attenuation coefficients.

Dhaene, Jelle; Pauwels, Elin; De Schryver, Thomas; De Muynck, Amelie; Dierick, Manuel; Van Hoorebeke, Luc

2015-01-01

74

Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr{sub 1?x}Mn{sub x}O{sub 3} negative temperature coefficient ceramics  

SciTech Connect

Electrical conductivity anomaly of perovskite-type YCr{sub 1?x}Mn{sub x}O{sub 3} negative temperature coefficient (NTC) ceramics produced by spark plasma sintering (SPS) has been investigated by using defect chemistry theory combination with X-ray photoelectron spectroscopy (XPS) analysis. From the results of the ln?-1/T curves and the XPS analysis, it can be considered that YCr{sub 1?x}Mn{sub x}O{sub 3} ceramics exhibit the hopping conductivity. The major carriers in YCrO{sub 3} are holes, which are compensated by the oxygen vacancies produced due to the introduction of Mn ions. The Mn{sup 4+} ion contents increase monotonically in the range of 0.2???x???0.5. The resistivity increases at first and then decreases with increasing Mn contents, which has the same varying tendency with activation energy. The electrical conductivity anomaly appearing in these ceramics may be due to the variation of Cr{sup 4+} and Mn{sup 4+} ions concentration as Mn content changes.

Zhang, Bo [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China) [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, Qing; Chang, Aimin, E-mail: changam@ms.xjb.ac.cn, E-mail: wuy@alfred.edu [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China)] [Key Laboratory of Functional Materials and Devices for Special Environments of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry of CAS, Urumqi 830011 (China); Li, Yiyu; Liu, Yin; Wu, Yiquan, E-mail: changam@ms.xjb.ac.cn, E-mail: wuy@alfred.edu [Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University, Alfred, New York 14802 (United States)] [Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University, Alfred, New York 14802 (United States)

2014-03-10

75

Chest x-ray  

MedlinePLUS

Chest radiography; Serial chest x-ray; X-ray - chest ... You stand in front of the x-ray machine. You will be told to hold your breath when the x-ray is taken. Two images are usually taken. You will need ...

76

X-Ray Imaging  

Cancer.gov

X-ray imaging is perhaps the most familiar type of imaging. Images produced by X-rays are due to the different absorption rates of different tissues. Calcium in bones absorbs X-rays the most, so bones look white on a film recording of the X-ray image,

77

Effect of atmospheric environment on the attenuation coefficient of light in water  

E-print Network

The attenuation coefficient of 532 nm light in water under different atmospheric conditions was investigated. Measurements were made over a two-year period at the same location and show that the attenuation coefficient is significantly influenced by the atmospheric environment. It is lowest when the atmospheric pressure is high and temperature is low, and is highest when the atmospheric pressure is low and temperature is high. The maximum attenuation coefficient of pure water in these studies was about three times the minimum value. The mechanism of the phenomena is discussed. These results are also important in underwater acoustics.

Liu, Juan; Tang, Yijun; Zhu, Kaixing; Ge, Yuan; Chen, Xuegang; He, Xingdao; Liu, Dahe

2014-01-01

78

Monitoring changes of optical attenuation coefficients of acupuncture points during laser acupuncture by optical coherence tomography  

NASA Astrophysics Data System (ADS)

The physical properties of acupuncture point were important to discover the mechanism of acupuncture meridian. In this paper, we used an optical coherence tomography to monitor in vivo the changes of optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point during laser irradiation on Yangxi acupuncture point. The optical attenuation coefficients of Hegu acupuncture point and non-acupuncture point were obtained by fitting the raw data according to the Beer-Lambert's law. The experimental results showed that the optical attenuation coefficient of Hegu acupuncture point decreased during the laser acupuncture, in contrast to a barely changed result in that of non-acupuncture point. The significant change of optical attenuation coefficient of Hegu acupuncture point indicated that there was a correlation between Hegu and Yangxi acupuncture points to some extent.

Huang, Yimei; Yang, Hongqin; Wang, Yuhua; Zheng, Liqin; Xie, Shusen

2010-11-01

79

NXcom – A program for calculating attenuation coefficients of fast neutrons and gamma-rays  

Microsoft Academic Search

This work is concerned with a construction and use of NXcom computer program for calculating the removal and attenuation coefficients of transmitted fast neutrons and ?-rays, respectively, through mixtures, composites, concretes and compounds. The program uses only one input data file for neutrons and ?-rays calculations. For ?-ray attenuation, the program predictions were tested by comparing them with the well-known

A. M. El-Khayatt

2011-01-01

80

Ultrasonic computed tomography reconstruction of the attenuation coefficient using a linear array.  

PubMed

The attenuation coefficient distribution and sound velocity distribution in the breast can be used to complement B-mode ultrasound imaging in the detection of breast cancer. This study investigated an approach for reconstructing the attenuation coefficient distribution in the breast using a linear array. The imaging setup was identical to that for conventional B-mode breast imaging, and the same setup has been used for reconstruction of sound velocity distributions in previous studies. In this study, we further developed a reconstruction method for the attenuation coefficient distribution. In particular, the proposed method incorporates the segmentation information from B-mode images and uses the sound velocity distribution to compensate for refraction effects. Experiments were conducted with a setup consisting of a 5-MHz, 128-channel linear array, a programmable digital array system, a phantom, and a computer. The constructed phantom contained materials mimicking the following breast tissues: glandular tissue, fat, cysts, high-attenuation tumors, and irregular tumors. Application of the proposed technique resulted in all the cysts and tumors (including high-attenuation and irregular tumors) being distinguished by thresholding the reconstructed attenuation coefficients. We have demonstrated that it is possible to use the same imaging setup to acquire data for B-mode image, sound velocity distribution, and attenuation coefficient distribution simultaneously. Moreover, the experimental data indicate its potential in improving the detection of breast cancer. PMID:16422413

Huang, Sheng-Wen; Li, Pai-Chi

2005-11-01

81

Measurements of linear attenuation coefficients of irregular shaped samples by two media method  

NASA Astrophysics Data System (ADS)

The linear attenuation coefficient values of regular and irregular shaped flyash materials have been measured without knowing the thickness of a sample using a new technique namely "two media method". These values have also been measured with a standard gamma ray transmission method and obtained theoretically with winXCOM computer code. From the comparison it is reported that the two media method has given accurate results of attenuation coefficients of flyash materials.

Singh, Sukhpal; Kumar, Ashok; Thind, Kulwant Singh; Mudahar, Gurmel S.

2008-04-01

82

X-ray properties of an anthropomorphic breast phantom for MRI and x-ray imaging  

NASA Astrophysics Data System (ADS)

The purpose of this study is to characterize the x-ray properties of a dual-modality, anthropomorphic breast phantom whose MRI properties have been previously evaluated. The goal of this phantom is to provide a platform for optimization and standardization of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and discrimination. The phantom is constructed using a mixture of lard and egg whites, resulting in a variable, tissue-mimicking structure with separate adipose- and glandular-mimicking components. The phantom can be produced with either a compressed or uncompressed shape. Mass attenuation coefficients of the phantom materials were estimated using elemental compositions from the USDA National Nutrient Database for Standard Reference and the atomic interaction models from the Monte Carlo code PENELOPE and compared with human values from the literature. The image structure was examined quantitatively by calculating and comparing spatial covariance matrices of the phantom and patient mammography images. Finally, a computerized version of the phantom was created by segmenting a computed tomography scan and used to simulate x-ray scatter of the phantom in a mammography geometry. Mass attenuation coefficients of the phantom materials were within 20% and 15% of the values for adipose and glandular tissues, respectively, which is within the estimation error of these values. Matching was improved at higher energies (>20 keV). Tissue structures in the phantom have a size similar to those in the patient data, but are slightly larger on average. Correlations in the patient data appear to be longer than those in the phantom data in the anterior-posterior direction; however, they are within the error bars of the measurement. Simulated scatter-to-primary ratio values of the phantom images were as high as 85% in some areas and were strongly affected by the heterogeneous nature of the phantom. Key physical x-ray properties of the phantom have been quantitatively evaluated and shown to be comparable to those of breast tissue. Since the MRI properties of the phantom have been previously evaluated, we believe it is a useful tool for quantitative evaluation of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and characterization.

Freed, Melanie; Badal, Andreu; Jennings, Robert J.; de las Heras, Hugo; Myers, Kyle J.; Badano, Aldo

2011-06-01

83

Parameters and computer software for the evaluation of mass attenuation and mass energy-absorption coefficients for body tissues and substitutes  

PubMed Central

The mass attenuation and energy-absorption coefficients (radiation interaction data), which are widely used in the shielding and dosimetry of X-rays used for medical diagnostic and orthovoltage therapeutic procedures, are strongly dependent on the energy of photons, elements and percentage by weight of elements in body tissues and substitutes. Significant disparities exist in the values of percentage by weight of elements reported in literature for body tissues and substitutes for individuals of different ages, genders and states of health. Often, interested parties are in need of these radiation interaction data for body tissues or substitutes with percentage by weight of elements and intermediate energies that are not tabulated in literature. To provide for the use of more precise values of these radiation interaction data, parameters and computer programs, MUA_T and MUEN_T are presented for the computation of mass attenuation and energy-absorption coefficients for body tissues and substitutes of arbitrary percentage-by-weight elemental composition and photon energy ranging between 1 keV (or k-edge) and 400 keV. Results are presented, which show that the values of mass attenuation and energy-absorption coefficients obtained from computer programs are in good agreement with those reported in literature. PMID:21157532

Okunade, Akintunde A.

2007-01-01

84

X-ray (image)  

MedlinePLUS

X-rays are a form of ionizing radiation that can penetrate the body to form an image on ... will be shades of gray depending on density. X-rays can provide information about obstructions, tumors, and other ...

85

A Generalised Porosity Formalism for Isotropic and Anisotropic Effective Opacity and Its Effects on X-ray Line Attenuation in Clumped O Star Winds  

NASA Technical Reports Server (NTRS)

We present a generalised formalism for treating the porosity-associated reduction in continuum opacity that occurs when individual clumps in a stochastic medium become optically thick. As in previous work, we concentrate on developing bridging laws between the limits of optically thin and thick clumps. We consider geometries resulting in either isotropic or anisotropic effective opacity, and, in addition to an idealised model in which all clumps have the same local overdensity and scale, we also treat an ensemble of clumps with optical depths set by Markovian statistics. This formalism is then applied to the specific case of bound-free absorption of X- rays in hot star winds, a process not directly affected by clumping in the optically thin limit. We find that the Markov model gives surprisingly similar results to those found previously for the single clump model, suggesting that porous opacity is not very sensitive to details of the assumed clump distribution function. Further, an anisotropic effective opacity favours escape of X-rays emitted in the tangential direction (the venetian blind effect), resulting in a bump of higher flux close to line centre as compared to profiles computed from isotropic porosity models. We demonstrate how this characteristic line shape may be used to diagnose the clump geometry, and we confirm previous results that for optically thick clumping to significantly influence X-ray line profiles, very large porosity lengths, defined as the mean free path between clumps, are required. Moreover, we present the first X-ray line profiles computed directly from line-driven instability simulations using a 3-D patch method, and find that porosity effects from such models also are very small. This further supports the view that porosity has, at most, a marginal effect on X-ray line diagnostics in O stars, and therefore that these diagnostics do indeed provide a good clumping insensitive method for deriving O star mass-loss rates.

Sundqvist, Jon O.; Owocki, Stanley P.; Cohen, David H.; Leutenegger, Maurice A.; Townsend, Richard H. D.

2002-01-01

86

X-Rays  

MedlinePLUS

... X-Rays htmProcedureXray X-rays are waves of electromagnetic radiation that are used to form images of structures ... What Is It? X-rays are waves of electromagnetic radiation that are used to create images of organs ...

87

Hand x-ray  

MedlinePLUS

X-ray - hand ... A hand x-ray is taken in a hospital radiology department or your health care provider's office by an ... technician. You will be asked to place your hand on the x-ray table, and keep it ...

88

Sinus x-ray  

MedlinePLUS

Paranasal sinus radiography; X-ray - sinuses ... sinus x-ray is taken in a hospital radiology department. Or the x-ray may be taken ... Anslow P. Ear, nose and throat radiology. In: Adam A, Dixon AK, ... Radiology: A Textbook of Medical Imaging . 5th ed. Philadelphia, ...

89

Microionization chamber air-kerma calibration coefficients as a function of photon energy for x-ray spectra in the range of 20-250 kVp relative to {sup 60}Co  

SciTech Connect

Purpose: To investigate the applicability of a wide range of microionization chambers for reference dosimetry measurements in low- and medium-energy x-ray beams. Methods: Measurements were performed with six cylindrical microchamber models, as well as one scanning chamber and two Farmer-type chambers for comparison purposes. Air-kerma calibration coefficients were determined at the University of Wisconsin Accredited Dosimetry Calibration Laboratory for each chamber for a range of low- and medium-energy x-ray beams (20-250 kVp), with effective energies ranging from 11.5 keV to 145 keV, and a {sup 60}Co beam. A low-Z proof-of-concept microchamber was developed and calibrated with and without a high-Z silver epoxy on the collecting electrode. Results: All chambers composed of low-Z materials (Z{<=} 13), including the Farmer-type chambers, the scanning chamber, and the PTW TN31014 and the proof-of-concept microchambers, exhibited air-kerma calibration coefficients with little dependence on the quality of the beam. These chambers typically exhibited variations in calibration coefficients of less than 3% with the beam quality, for medium energy beams. However, variations in air-kerma calibration coefficients of greater than 50% were measured over the range of medium-energy x-ray beams for each of the microchambers containing high-Z collecting electrodes (Z > 13). For these high-Z chambers, which include the Exradin A14SL and A16 chambers, the PTW TN31006 chamber, the IBA CC01 chamber, and the proof-of-concept chamber containing silver, the average variation in air-kerma calibration coefficients between any two calibration beams was nearly 25% over the entire range of beam qualities investigated. Conclusions: Due to the strong energy dependence observed with microchambers containing high-Z components, these chambers may not be suitable dosimeters for kilovoltage x-ray applications, as they do not meet the TG-61 requirements. It is recommended that only microchambers containing low-Z materials (Z{<=} 13) be considered for air-kerma calibrations for reference dosimetry in low- and medium-energy x-ray beams.

Snow, J. R.; Micka, J. A.; DeWerd, L. A. [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)

2013-04-15

90

The role of the reflection coefficient in precision measurement of ultrasonic attenuation  

NASA Technical Reports Server (NTRS)

Ultrasonic attenuation measurements using contact, pulse-echo techniques are sensitive to surface roughness and couplant thickness variations. This can reduce considerable inaccuracies in the measurement of the attenuation coefficient for broadband pulses. Inaccuracies arise from variations in the reflection coefficient at the buffer-couplant-sample interface. The reflection coefficient is examined as a function of the surface roughness and corresponding couplant thickness variations. Interrelations with ultrasonic frequency are illustrated. Reliable attenuation measurements are obtained only when the frequency dependence of the reflection coefficient is incorporated in signal analysis. Data are given for nickel 200 samples and a silicon nitride ceramic bar having surface roughness variations in the 0.3 to 3.0 microns range for signal bandwidths in the 50 to 100 MHz range.

Generazio, E. R.

1984-01-01

91

X-Ray Spectra  

NSDL National Science Digital Library

In this activity, learners use simple materials to simulate the effect of X-rays in a safe way. Learners place a piece of window screen over a box and a cardboard pattern on top of the screen. They sprinkle sand over the area of the box. The sand simulates X-rays passing through the screen to the bottom of the box, except where they are blocked by the cardboard. Use this activity to demonstrate how X-rays create an image, including "soft" and shorter wavelength X-rays as well as X-rays from space.

Neil Fetter

2007-01-01

92

Determination of Body Fat Distribution by Dual-Energy X-ray Absorptiometry and Attenuation of Visceral Fat Vasoconstriction by Enalapril  

Microsoft Academic Search

Use of dual-energy X-ray absorptiometry (DEXA) data to calculate the percent of body fat in the visceral (%VF) and subcutaneous\\u000a (%SF) compartments and the mechanism of visceral fat vasoconstriction when intestinal mucosal afferent nerves are stimulated\\u000a has not been reported. The aim of this sudy was to compare visceral fat weight determined by DEXA and direct weighing and\\u000a determine whether

Felix W. Leung; Samuel Murray; Elsa Murray; Vay Liang Go

2008-01-01

93

XOP v2.4: recent developments of the x-ray optics software toolkit  

NASA Astrophysics Data System (ADS)

XOP v2.4 consists of a collection of computer programs for calculation of radiation characteristics of X-ray sources and their interaction with matter. Many of the programs calculate radiation from undulators and wigglers, but others, such as X-ray tube codes, are also available. The computation of the index of refraction and attenuation coefficients of optical elements using user-selectable databases containing optical constants is an important part of the package for calculation of beam propagation. Coupled computations are thus feasible where the output from one program serves as the input to another program. Recent developments including enhancements to existing programs are described.

Sánchez del Río, Manuel; Dejus, Roger J.

2011-09-01

94

X-Ray Data Booklet X-RAY DATA BOOKLET  

E-print Network

X-Ray Data Booklet X-RAY DATA BOOKLET Center for X-ray Optics and Advanced Light Source Lawrence Berkeley National Laboratory Introduction X-Ray Properties of Elements Electron Binding Energies X-Ray Levels of Few Electron Ions Now Available Order X-Ray Data Booklet http://xdb.lbl.gov/ (1 of 3) [2

Meagher, Mary

95

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m? 1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light

D. Palandro; C. Hu; S. Andréfouët; F. E. Muller-Karger

2004-01-01

96

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m–1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light absorption

D. Palandro; C. Hu; S. Andréfouët; F. E. Muller-Karger

97

X-ray Polarimetry  

NASA Astrophysics Data System (ADS)

1. X-ray polarimetry: historical remarks and other considerations; Part I. Polarimetry Techniques: 2. Scattering polarimetry in high energy astronomy; 3. Photoelectric polarimeters; 4. Bragg crystal polarimeters; 5. X-ray polarimetry with the photon counting pixel detector timepix; 6. HE polarized photon interactions with matter: simulations with geant4; 7. The GPD as a polarimeter: theory and facts; 8. Ideal gas electron multipliers (GEMs) for x-ray polarimeters; 9. Broad-band soft x-ray polarimetry; 10. Feasibility of x-ray photoelectric polarimeters with large field of view; 11. Angular resolution of a photoelectric polarimeter; 12. Development of a Thomson x-ray polarimeter; 13. Hard x / soft gamma ray polarimetry using a Laue lens; Part II. Polarized Emission in X-ray Sources: 14. Probing strong gravity effects with x-ray polarimetry; 15. X-ray polarization from black holes in the thermal state; 16. Strong-gravity effects acting on polarization from orbiting spots; 17. Polarization of thermal emission from accreting black holes; 18. X-ray polarimetry and radio-quiet AGN; 19. The soft x-ray polarization in obscured AGN; 20. The polarization of complex x-ray sources; 21. Polarization of Compton x-rays from jets in AGN; 22. Polarization of x-ray lines from galaxy clusters and elliptical galaxies; 23. Polarization characteristics of rotation-powered pulsars; 24. Polarized x-rays from magnetized neutron stars; 25. Polarization properties of x-ray millisecond pulsars; 26. X-ray polarization signatures of neutron stars; 27. Polarization from the oscillating magnetized accretion torus; 28. X-ray polarization from accreting white dwarfs and associated systems; 29. Polarization of pulsar wind nebulae; 30. X-ray polarization of gamma-ray bursts; 31. Central engine afterglow from GRBs and the polarization signature; 32. GRB afterglow polarimetry. Past, present and future; 33. Gamma-ray polarimetry with SPI; 34. INTEGRAL/IBIS observations of the Crab Nebula and GRB 041219A; 35. Fermi results on the origin of high energy emission in pulsars; 36. Diagnostics of the evolution of spiral galaxies in a cluster environment; Part III. Future Missions: 37. Gravity and extreme magnetism SMEX (GEMS); 38. Programs of x-ray polarimetry in Italy; 39. A polarimeter for IXO; 40. Polarimetry with ASTRO-H soft gamma-ray detector; 41. EXIST and its polarization sensitivity; 42. PoGOLite: a balloon-borne soft gamma-ray polarimeter; 43. Studies of neutron background rejection in the PoGOLite polarimeter; 44. Observing polarized x-rays with PoGOLite; 45. Pre-flight qualification tests of the PoGOLite detector system; 46. The gamma-ray polarimeter experiment (GRAPE) Balloon Payload; 47. POLAR: an instrument dedicated to GRB polarization measurement; 48. Polarisation detection capability of GRIPS; 49. X-ray and y-ray polarimetry small satellite mission polaris; 50. GAP aboard the solar powered sail mission; 51. Hard x-ray polarimeter for small satellite missions; 52. Performance of hard x-ray polarimeter: PHENEX; 53. GRB polarimetry with POET; Index.

Bellazzini, Ronaldo; Costa, Enrico; Matt, Giorgio; Tagliaferri, Gianpiero

2010-07-01

98

Total photon attenuation coefficients in some rare earth elements using selective excitation method  

NASA Astrophysics Data System (ADS)

The total mass attenuation coefficients were measured in the elements La, Nd, Sm, Gd and Dy belonging to rare earth region in the energy range 30-55 keV by employing the selective excitation method. This method facilitates selection of excitation energies near the K edge. The present experimental results were compared with the theoretical values due to Chantler and XCOM.

SitaMahalakshmi, N. V.; Kareem, M. A.; Premachand, K.

2015-01-01

99

X-Rays  

NSDL National Science Digital Library

This problem set is designed to test students' understanding of x-rays. Students are given wavelengths and asked to calculate minimum potential energy, radiation frequency, and whether or not the mineral can be used as a radiation filter. They are also asked to determine the 2-theta for different crystal face x-ray diffractions given cell edge length and radiation wavelength.

100

X-ray binaries  

Microsoft Academic Search

We review the nuclear astrophysics aspects of accreting neutron stars in\\u000aX-ray binaries. We summarize open astrophysical questions in light of recent\\u000aobservations and their relation to the underlying nuclear physics. Recent\\u000aprogress in the understanding of the nuclear physics, especially of X-ray\\u000abursts, is also discussed.

H. Schatz; K. E. Rehm

2006-01-01

101

X-ray beamsplitter  

DOEpatents

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5--50 pairs of alternate Mo/Si layers with a period of 20--250 A. The support membrane is 10--200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window. 6 figs.

Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.W. Jr.

1987-08-07

102

X-ray beamsplitter  

DOEpatents

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5-50 pairs of alternate Mo/Si layers with a period of 20-250 A. The support membrane is 10-200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window.

Ceglio, Natale M. (Livermore, CA); Stearns, Daniel S. (Mountain View, CA); Hawryluk, Andrew M. (Modesto, CA); Barbee, Jr., Troy W. (Palo Alto, CA)

1989-01-01

103

K-shell absorption jump factors and jump ratios in elements between Tm ( Z = 69) and Os ( Z = 76) derived from new mass attenuation coefficient measurements  

NASA Astrophysics Data System (ADS)

The K-shell absorption jump factors and jump ratios were derived from new mass attenuation coefficients measured using an energy dispersive X-ray fluorescence (EDXRF) spectrometer for Tm, Yb elements being Tm 2O 3, Yb 2O 3 compounds and pure Lu, Hf, Ta, W, Re and Os. The measurements, in the region 56-77 keV, were done in a transmission geometry utilizing the K ?1 , K ?2 , K ?1 and K ?2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV ?-photons from an 57Co annular source and detected by an Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values. The measured values of Tm, Yb, Lu, Hf, Ta, W, Re and Os are reported here for the first time.

Kaya, Necati; T?ra?o?lu, Engin; Apayd?n, Gökhan; Ayl?kc?, Volkan; Cengiz, Erhan

2007-08-01

104

Measurement of the mass attenuation coefficients and electron densities for BiPbSrCaCuO superconductor at different energies  

NASA Astrophysics Data System (ADS)

The mass attenuation coefficients for Bi, Pb, Sr, Ca, Cu metals, Bi 2O 3, PbO, SrCO 3, CaO, CuO compounds and solid-state forms of Bi 1.7Pb 0.3Sr 2Ca 2Cu 3O 10 superconductor were determined at 57.5, 65.2, 77.1, 87.3, 94.6, 122 and 136 keV energies. The samples were irradiated using a 57Co point source emitted 122 and 136 keV ?-ray energies. The X-ray energies were obtained using secondary targets such as Ta, Bi 2O 3 and (CH 3COO) 2UO 22H 2O. The ?- and X-rays were counted by a Si(Li) detector with a resolution of 0.16 keV at 5.9 keV. The effect of absorption edges on electron density, effective atomic numbers and their variation with photon energy in composite superconductor samples was discussed. Obtained values were compared with theoretical values.

Çevik, U.; Balta?, H.

2007-03-01

105

X-ray grid-detector apparatus  

DOEpatents

A hybrid grid-detector apparatus for x-ray systems wherein a microchannel plate structure has an air-interspaced grid portion and a phosphor/optical fluid-filled grid portion. The grids are defined by multiple adjacent channels separated by lead-glass septa. X-rays entering the air-interspaced grid portion at an angle of impingement upon the septa are attenuated, while non-impinging x-rays pass through to the phosphor/fluid filled portion. X-ray energy is converted to luminescent energy in the phosphor/fluid filled portion and the resultant beams of light are directed out of the phosphor/optical fluid filled portion to an imaging device.

Boone, John M. (Folsom, CA); Lane, Stephen M. (Oakland, CA)

1998-01-27

106

The attenuation coefficient of ammonium chloride for 662 keV gamma radiation, measured for dilute solutions  

NASA Astrophysics Data System (ADS)

The technique developed for the direct measurement of linear attenuation and mass attenuation (or absorption) coefficients of dilute solutions of salts has been applied to the attenuation of 662 keV gamma rays from 137Cs in dilute NH 4Cl solution.

Teli, M. T.; Chaudhari, L. M.

1996-04-01

107

Development of a model of an x-ray tube transmission source  

SciTech Connect

In support of the development of an x-ray tube based source for transmission measurements of UF6 gas, we have developed a one-dimensional, spreadsheet-based model of the source. Starting with the spectrum produced by an x-ray tube we apply the linear attenuation coefficients for various notch filters, the aluminum pipe, and UF6 gas. This model allows calculation of the transmitted spectrum based on the type of filter, the thickness of the filter, the x-ray tube high voltage, the Al pipe thickness, and the UF6 gas pressure. The sensitivity of the magnitude of the transmission peak produced by the notch filter to any of these variables can be explored quickly and easily to narrow the choices for experimental measurements. To validate the spreadsheet based model, comparisons have been made to various experimental data.

Goda, Joetta M [Los Alamos National Laboratory; Ianakiev, Kiril D [Los Alamos National Laboratory; Moss, Cal E [Los Alamos National Laboratory

2009-01-01

108

Thoracic spine x-ray  

MedlinePLUS

Vertebral radiography; X-ray - spine; Thoracic x-ray; Spine x-ray; Thoracic spine films; Back films ... The test is done in a hospital radiology department or in the health care provider's office. You will lie on the x-ray table in different positions. If the x-ray ...

109

Lumbosacral spine x-ray  

MedlinePLUS

X-ray - lumbosacral spine; X-ray - lower spine ... The test is done in a hospital x-ray department or your health care provider's office by an x-ray technician. You will be asked to lie on the x-ray ...

110

Parametric imaging of the local attenuation coefficient in human axillary lymph nodes assessed using optical coherence tomography  

PubMed Central

We report the use of optical coherence tomography (OCT) to determine spatially localized optical attenuation coefficients of human axillary lymph nodes and their use to generate parametric images of lymphoid tissue. 3D-OCT images were obtained from excised lymph nodes and optical attenuation coefficients were extracted assuming a single scattering model of OCT. We present the measured attenuation coefficients for several tissue regions in benign and reactive lymph nodes, as identified by histopathology. We show parametric images of the measured attenuation coefficients as well as segmented images of tissue type based on thresholding of the attenuation coefficient values. Comparison to histology demonstrates the enhancement of contrast in parametric images relative to OCT images. This enhancement is a step towards the use of OCT for in situ assessment of lymph nodes. PMID:22312589

Scolaro, Loretta; McLaughlin, Robert A.; Klyen, Blake R.; Wood, Benjamin A.; Robbins, Peter D.; Saunders, Christobel M.; Jacques, Steven L.; Sampson, David D.

2012-01-01

111

X-ray laser  

DOEpatents

An X-ray laser (10) that lases between the K edges of carbon and oxygen, i.e. between 44 and 23 Angstroms, is provided. The laser comprises a silicon (12) and dysprosium (14) foil combination (16) that is driven by two beams (18, 20) of intense line focused (22, 24) optical laser radiation. Ground state nickel-like dysprosium ions (34) are resonantly photo-pumped to their upper X-ray laser state by line emission from hydrogen-like silicon ions (32). The novel X-ray laser should prove especially useful for the microscopy of biological specimens.

Nilsen, Joseph (Livermore, CA)

1991-01-01

112

X-Ray Diffraction  

NSDL National Science Digital Library

This site from the University of London presents a tutorial on several methods of X-ray diffraction, including the powder, rotating crystal, and Laue methods Each section includes interactive Java applets, exercises, and links to a glossary of terms.

Matter.org

113

X-Ray Diffraction.  

ERIC Educational Resources Information Center

Reviews applications in research and analytical characterization of compounds and materials in the field of X-ray diffraction, emphasizing new developments in applications and instrumentation in both single crystal and powder diffraction. Cites 414 references. (CS)

Smith, D. K.; Smith, K. L.

1980-01-01

114

Cosmic x ray physics  

NASA Technical Reports Server (NTRS)

This final report covers the period 1 January 1985 - 31 March 1992. It is divided into the following sections: the soft x-ray background; proportional counter and filter calibrations; sounding rocket flight preparations; new sounding rocket payload: x-ray calorimeter; and theoretical studies. Staff, publications, conference proceedings, invited talks, contributed talks, colloquia and seminars, public service lectures, and Ph. D. theses are listed.

Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

1992-01-01

115

Total attenuation coefficient of intralipid dilutions for discrete laser wavelengths between 405 and 1315 nm  

NASA Astrophysics Data System (ADS)

The experimental investigations on different aspects of optical tomography require the knowledge of the optical parameters of tissues and tissue-like phantoms in order to unambiguously interpret the experimental data and specify characteristic inhomogeneities in tissue diagnostics. The main optical parameters of interest are the absorption coefficient, the scattering, backscattering, and reduced-scattering coefficients, the total attenuation (extinction) coefficient and the anisotropy factor. In this work, we extend our investigations of the optical properties of tissuemimicking phantoms, such as Intralipid-20% fat emulsion, using an approach we have developed recently based on the peculiarities of laser radiation beams propagating through semi-infinite turbid media. The dependence of the total attenuation coefficient on the Intralipid concentration, for laser radiation wavelengths ?=405, 672, 850, and 1314 nm, is studied, by using a set of phantoms consisting of different dilutions of Intralipid in distilled water. The experimental results for the extinction are in agreement with our previous results and with empiric formulae found by other authors concerning the wavelength dependence of the scattering coefficient of Intralipid -10% and Intralipid - 20%. They are also in agreement with known data of the water absorptance. As a whole, the results obtained in this work confirm the consideration of the experimental phantoms as semi-infinite media. They also confirm and extend theoretical and experimental results obtained previously, and reveal advantages of using longer wavelengths for deeper diagnostics of tissues and mimic turbid media.

Dreischuh, Tanja N.; Gurdev, Ljuan L.; Vankov, Orlin I.; Avramov, Lachezar A.; Stoyanov, Dimitar V.

2015-01-01

116

Diffuse attenuation coefficient of downwelling irradiance: An evaluation of remote sensing methods  

Microsoft Academic Search

The propagation of downwelling irradiance at wavelength ? from surface to a depth (z) in the ocean is governed by the diffuse attenuation coefficient, $\\\\bar{K}_{d}$(?). There are two standard methods for the derivation of $\\\\bar{K}_{d}$(?) in remote sensing, which both are based on empirical relationships involving the blue-to-green ratio of ocean color. Recently, a semianalytical method to derive $\\\\bar{K}_{d}$(?) from

Zhong-Ping Lee; Miroslaw Darecki; Kendall L. Carder; Curtiss O. Davis; Dariusz Stramski; W. Joseph Rhea

2005-01-01

117

Measurement of photon mass attenuation coefficients of plutonium from 60 to 2615 keV  

NASA Astrophysics Data System (ADS)

Measurements have been made to determine plutonium photon mass attenuation coefficients by using a collimated-beam transmission method in the energy range from 60 to 2615 keV. These experimental results were compared with previous experimental and theoretical data. Good agreements are observed in the 240-800 keV energy range, whereas differences up to maximum 10% are observed out of these limits.

Rettschlag, M.; Berndt, R.; Mortreau, P.

2007-11-01

118

Obtaining flat x-ray images from round objects  

Technology Transfer Automated Retrieval System (TEKTRAN)

A technique to correct deficiencies in x-ray images of cylindrical or spherical objects that are a consequence of the geometry of the sample is derived, for both two-dimensional (2D) and linescan imaging. The methods described involve the use of attenuators specifically shaped to equalize the x-ray ...

119

Magnified hard x-ray image in one dimension  

SciTech Connect

The possibility of magnified x-ray imaging is explored, by the near-field attenuation of a sample intercepting a spherical wave-front, plus the beam profile modulation by Borrmann pyramid based on dynamic x-ray scattering. It is verified by experiments in one dimension as well as numerical simulation.

Britten, James [Department of Chemistry, McMaster University, Hamilton, Ontario L8S4L8 (Canada); Feng Zhechuan [Department of Electrical Engineering, National Taiwan University, Taipei 106-17, Taiwan (China); Xu Gu [Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S4L7 (Canada)

2010-06-28

120

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares  

NASA Astrophysics Data System (ADS)

Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (DeltaA) and amplitude time delay (Deltat) (vis- ´a-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22(°) 27'N, 87(°) 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient (alpha_{eff}) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (Deltat). For the C-class flares we find that there is a direct correspondence between Deltat of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the Deltat for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux phi_{max} independent of these time slots, the goodness of fit, as measured by reduced-chi(2) , actually worsens as the day progresses. The variation of the Z dependence of reduced-chi(2) seems to follow the variation of standard deviation of Z along the T_x-R_x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between Deltat and phi_{max} was observed.

Basak, Tamal; Chakrabarti, Sandip Kumar

121

Effective recombination coefficient and solar zenith angle effects on low-latitude D-region ionosphere evaluated from VLF signal amplitude and its time delay during X-ray solar flares  

NASA Astrophysics Data System (ADS)

Excess solar X-ray radiation during solar flares causes an enhancement of ionization in the ionospheric D-region and hence affects sub-ionospherically propagating VLF signal amplitude and phase. VLF signal amplitude perturbation (? A) and amplitude time delay (? t) (vis-á-vis corresponding X-ray light curve as measured by GOES-15) of NWC/19.8 kHz signal have been computed for solar flares which is detected by us during Jan-Sep 2011. The signal is recorded by SoftPAL facility of IERC/ICSP, Sitapur (22? 27'N, 87? 45'E), West Bengal, India. In first part of the work, using the well known LWPC technique, we simulated the flare induced excess lower ionospheric electron density by amplitude perturbation method. Unperturbed D-region electron density is also obtained from simulation and compared with IRI-model results. Using these simulation results and time delay as key parameters, we calculate the effective electron recombination coefficient ( ? eff ) at solar flare peak region. Our results match with the same obtained by other established models. In the second part, we dealt with the solar zenith angle effect on D-region during flares. We relate this VLF data with the solar X-ray data. We find that the peak of the VLF amplitude occurs later than the time of the X-ray peak for each flare. We investigate this so-called time delay (? t). For the C-class flares we find that there is a direct correspondence between ? t of a solar flare and the average solar zenith angle Z over the signal propagation path at flare occurrence time. Now for deeper analysis, we compute the ? t for different local diurnal time slots DT. We find that while the time delay is anti-correlated with the flare peak energy flux ? max independent of these time slots, the goodness of fit, as measured by reduced- ? 2, actually worsens as the day progresses. The variation of the Z dependence of reduced- ? 2 seems to follow the variation of standard deviation of Z along the T x - R x propagation path. In other words, for the flares having almost constant Z over the path a tighter anti-correlation between ? t and ? max was observed.

Basak, Tamal; Chakrabarti, Sandip K.

2013-12-01

122

Total mass attenuation coefficient evaluation of ten materials commonly used to simulate human tissue  

NASA Astrophysics Data System (ADS)

To study the doses received by patient submitted to ionizing radiation, several materials are used to simulate the human tissue and organs. The total mass attenuation coefficient is a reasonable way for evaluating the usage in dosimetry of these materials. The total mass attenuation coefficient is determined by photon energy and constituent elements of the material. Currently, the human phantoms are composed by a unique material that presents characteristics similar to the mean proprieties of the different tissues within the region. Therefore, the phantoms are usually homogeneous and filled with a material similar to soft tissue. We studied ten materials used as soft tissue-simulating. These materials were named: bolus, nylon®, orange articulation wax, red articulation wax, PMMA, modelling clay, bee wax, paraffin 1, paraffin 2 and pitch. The objective of this study was to verify the best material to simulate the human cerebral tissue. We determined the elementary composition, mass density and, therefore, calculated the total mass attenuation coefficient of each material. The results were compared to the values established by the International Commission on Radiation Units and Measurements - ICRU, report n° 44, and by the International Commission on Radiation Protection - ICRP, report n° 89, to determine the best material for this energy interval. These results indicate that new head phantoms can be constructed with nylon®.

Ferreira, C. C.; Ximenes, R. E.; Garcia, C. A. B.; Vieira, J. W.; Maia, A. F.

2010-11-01

123

CdZnTe detector in mammographic x-ray spectroscopy.  

PubMed

A CdZnTe (CZT) detector was utilized in mammographic x-ray spectroscopy under clinical conditions. First, the detector response was investigated using y-rays from 241Am. The escape of secondary (Compton scattered and K fluorescent) x-rays and tailing due to carrier trapping were minor in the mammographic energy range. In addition, the transmission of primary x-rays was minimal from the results calculated using the mass attenuation coefficients of CZT. Therefore, spectral distortion in this energy range was expected to be negligible. Secondly, x-ray spectroscopy was carried out with the CZT detector. The measured spectra were in good agreement with the spectra obtained with the Compton-scatter method with a high-purity germanium detector. Moreover, the half-value layers (HVLs) calculated from the CZT spectra were consistent with the HVLs measured with an ionization chamber. The results indicate that a CZT detector can be utilized in mammographic x-ray spectroscopy without any corrections. PMID:12476976

Miyajima, Satoshi; Imagawa, Kotaro

2002-11-21

124

Phase contrast imaging using a micro focus x-ray source  

NASA Astrophysics Data System (ADS)

Phase contrast x-ray imaging, a new technique to increase the imaging contrast for the tissues with close attenuation coefficients, has been studied since mid 1990s. This technique reveals the possibility to show the clear details of the soft tissues and tumors in small scale resolution. A compact and low cost phase contrast imaging system using a conventional x-ray source is described in this paper. Using the conventional x-ray source is of great importance, because it provides the possibility to use the method in hospitals and clinical offices. Simple materials and components are used in the setup to keep the cost in a reasonable and affordable range.Tungsten K?1 line with the photon energy 59.3 keV was used for imaging. Some of the system design details are discussed. The method that was used to stabilize the system is introduced. A chicken thigh bone tissue sample was used for imaging followed by the image quality, image acquisition time and the potential clinical application discussion. High energy x-ray beam can be used in phase contrast imaging. Therefore the radiation dose to the patients can be greatly decreased compared to the traditional x-ray radiography.

Zhou, Wei; Majidi, Keivan; Brankov, Jovan G.

2014-09-01

125

Simultaneous reconstruction of emission activity and attenuation coefficient distribution from TOF data, acquired with external transmission source  

NASA Astrophysics Data System (ADS)

The simultaneous PET data reconstruction of emission activity and attenuation coefficient distribution is presented, where the attenuation image is constrained by exploiting an external transmission source. Data are acquired in time-of-flight (TOF) mode, allowing in principle for separation of emission and transmission data. Nevertheless, here all data are reconstructed at once, eliminating the need to trace the position of the transmission source in sinogram space. Contamination of emission data by the transmission source and vice versa is naturally modeled. Attenuated emission activity data also provide additional information about object attenuation coefficient values. The algorithm alternates between attenuation and emission activity image updates. We also proposed a method of estimation of spatial scatter distribution from the transmission source by incorporating knowledge about the expected range of attenuation map values. The reconstruction of experimental data from the Siemens mCT scanner suggests that simultaneous reconstruction improves attenuation map image quality, as compared to when data are separated. In the presented example, the attenuation map image noise was reduced and non-uniformity artifacts that occurred due to scatter estimation were suppressed. On the other hand, the use of transmission data stabilizes attenuation coefficient distribution reconstruction from TOF emission data alone. The example of improving emission images by refining a CT-based patient attenuation map is presented, revealing potential benefits of simultaneous CT and PET data reconstruction.

Panin, V. Y.; Aykac, M.; Casey, M. E.

2013-06-01

126

X-Rays for Children  

MedlinePLUS

... your child, depending on the goal: Bitewing X-rays (also called cavity-detecting X-rays) — These X-rays are used to view the ... the 6-year molar) has erupted. Periapical X-rays — These are used to view the entire crowns ...

127

X-ray Crystallography  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students are introduced to the fundamental principles of X-ray crystallography and "guides students through a series of activities for learning how structural information can be derived from X-ray diffraction patterns." Upon completion of this activity students should be able to describe what can be detected with X-ray crystallography (proteins in particular) and explain the impact of temperature, atom size, and impurities in the test. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In the activity, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity, a test and rubric, central concepts, and their correlation to AAAS standards.

128

Ultrafast X-ray diffraction  

Microsoft Academic Search

This study presents recent developments and applications of ultrafast X-ray diffraction. These include optical pump\\/X-ray probe experiments for performing ultrafast X-ray spectroscopy, time-resolved X-ray diffraction for the investigation of electronically induced solid-liquid phase transformations in semiconductors, and time-resolved X-ray diffraction for monitoring the rapid changes of the atomic configuration associated with the lattice waves.

D. von der Linde; K. Sokolowski-Tinten

2003-01-01

129

X-ray beam finder  

DOEpatents

An X-ray beam finder for locating a focal spot of an X-ray tube includes a mass of X-ray opaque material having first and second axially-aligned, parallel-opposed faces connected by a plurality of substantially identical parallel holes perpendicular to the faces and a film holder for holding X-ray sensitive film tightly against one face while the other face is placed in contact with the window of an X-ray head.

Gilbert, H.W.

1983-06-16

130

X-ray microtomography  

SciTech Connect

In this tutorial, we describe X-ray microtomography as a technique to nondestructively characterize material microstructure in three dimensions at a micron level spatial resolution. While commercially available laboratory scale instrumentation is available, we focus our attention on synchrotron-based systems, where we can exploit a high flux, monochromatic X-ray beam to produce high fidelity three-dimensional images. A brief description of the physics and the mathematical analysis behind the technique is followed by example applications to specific materials characterization problems, with a particular focus on the utilization of three-dimensional image processing that can be used to extract a wide range of useful information.

Landis, Eric N., E-mail: landis@maine.edu [Department of Civil and Environmental Engineering, University of Maine, 5711 Boardman Hall, Orono, Maine 04469 (United States); Keane, Denis T., E-mail: dtkeane@northwestern.edu [Department of Materials Science and Engineering, Northwestern University (United States); DND-CAT, Advanced Photon Source, Argonne National Laboratory, Bldg. 432/A002, 9700 S. Cass Ave, Argonne, Illinois 60439 (United States)

2010-12-15

131

X-ray Reflection  

NASA Astrophysics Data System (ADS)

Material irradiated by X-rays produces backscattered radiation which is commonly known as the Reflection Spectrum. It consists of a structured continuum, due at high energies to the competition between photoelectric absorption and electron scattering enhanced at low energies by emission from the material itself, together with a complex line spectrum. We briefly review the history of X-ray reflection in astronomy and discuss various methods for computing the reflection spectrum from cold and ionized gas, illustrated with results from our own work reflionx. We discuss how the reflection spectrum can be used to obtain the geometry of the accretion flow, particularly the inner regions around black holes and neutron stars.

Fabian, A. C.; Ross, R. R.

2010-12-01

132

Measurement of the mass energy-absorption coefficient of air for x-rays in the range from 3 to 60 keV.  

PubMed

For the first time the absolute photon mass energy-absorption coefficient of air in the energy range of 10 to 60 keV has been measured with relative standard uncertainties below 1%, considerably smaller than those of up to 2% assumed for calculated data. For monochromatized synchrotron radiation from the electron storage ring BESSY II both the radiant power and the fraction of power deposited in dry air were measured using a cryogenic electrical substitution radiometer and a free air ionization chamber, respectively. The measured absorption coefficients were compared with state-of-the art calculations and showed an average deviation of 2% from calculations by Seltzer. However, they agree within 1% with data calculated earlier by Hubbell. In the course of this work, an improvement of the data analysis of a previous experimental determination of the mass energy-absorption coefficient of air in the range of 3 to 10 keV was found to be possible and corrected values of this preceding study are given. PMID:23192280

Buhr, H; Büermann, L; Gerlach, M; Krumrey, M; Rabus, H

2012-12-21

133

Attenuation coefficients of soils and some building materials of Bangladesh in the energy range 276-1332 keV.  

PubMed

The linear and mass attenuation coefficients of different types of soil, sand, building materials and heavy beach mineral samples from the Chittagong and Cox's Bazar area of Bangladesh were measured using a high-resolution HPGe detector and the gamma-ray energies 276.1, 302.8, 356.0, 383.8, 661.6 and 1173.2 and 1332.5 keV emitted from point sources of 133Ba, 137Cs and 60Co, respectively. The linear attenuation coefficients show a linear relationship with the corresponding densities of the samples studied. The variations of the mass attenuation coefficient with gamma-ray energy were exponential in nature. The measured mass attenuation coefficient values were compared with measurements made in other countries for similar kinds of materials. The values are in good agreement with each other in most cases. PMID:11300413

Alam, M N; Miah, M M; Chowdhury, M I; Kamal, M; Ghose, S; Rahman, R

2001-06-01

134

X-ray laser driven gold targets  

SciTech Connect

The femtosecond population dynamics of gold irradiated by a coherent high-intensity (>10{sup 17}?W/cm{sup 2}) x-ray laser pulse is investigated theoretically. There are two aspects to the assembled model. One is the construction of a detailed model of platinum-like gold inclusive of all inner-shell states that are created by photoionization of atomic gold and decay either by radiative or Auger processes. Second is the computation of the population dynamics that ensues when an x-ray pulse is absorbed in gold. The hole state generation depends on the intensity and wavelength of the driving x-ray pulse. The excited state populations reached during a few femtosecond timescales are high enough to generate population inversions, whose gain coefficients are calculated. These amplified lines in the emitted x-ray spectrum provide important diagnostics of the radiation dynamics and also suggest a nonlinear way to increase the frequency of the coherent output x-ray pulses relative to the frequency of the driver input x-ray pulse.

Petrova, Tz. B., E-mail: lina.petrova@nrl.navy.mil; Whitney, K. G.; Davis, J. [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)] [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States)

2014-03-15

135

Retrieval of diffuse attenuation coefficient in the Chesapeake Bay and turbid ocean regions for satellite ocean color applications  

Microsoft Academic Search

There are several empirical and semianalytical models for the satellite-based estimation of the diffuse attenuation coefficient for the downwelling spectral irradiance at the wavelength 490 nm, Kd(490), or the diffuse attenuation coefficient for the downwelling photosynthetically available radiation (PAR), Kd(PAR). An empirical algorithm has been used to routinely produce NASA standard Kd(490) product from the Moderate Resolution Imaging Spectroradiometer (MODIS).

Menghua Wang; SeungHyun Son; Lawrence W. Harding Jr

2009-01-01

136

Modeling X-Ray Photoionized Plasmas: Ion Storage Ring Measurements of Low Temperature Dielectronic Recombination Rate Coefficients for L-Shell Iron  

NASA Technical Reports Server (NTRS)

Iron L-shell ions (Fe XVII to Fe XXIV) play an important role in determining the line emission and thermal and ionization structures of photoionized gases. Existing uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affects our ability to model and interpret observations of photoionized plasmas. To help address this issue, we have initiated a laboratory program to produce reliable low temperature DR rates. Here, we present some of our recent results and discuss some of their astrophysical implications.

Savin, D. W.; Badnell, N. R.; Bartsch, T.; Brandau, C.; Chen, M. H.; Grieser, M.; Gwinner, G.; Hoffknecht, A.; Kahn, S. M.; Linkemann, J.

2000-01-01

137

X-Ray Spacing  

NSDL National Science Digital Library

This site features a collection of single-phase X-ray powder diffraction patterns for the three most intense D values of an extensive list of minerals. The information is presented in the form of tables of interplanar spacings (D), relative intensities, hkl plane. There are also links to more information about each mineral, such as chemical formula, composition, environment, and name origin.

David Barthelmy

138

X-ray Diffraction  

NSDL National Science Digital Library

A series of laboratory activities on x-ray diffraction physics using the Teltron Tel-X-Ometer System. Detailed explanations on the production and delivery of the beam is included, as well as a very complete safety protocol for conducting the experiments.

Langan, Shawn

2012-03-08

139

Estimating dynamic changes of tissue attenuation coefficient during high-intensity focused ultrasound treatment  

PubMed Central

Background This study investigated the dynamic changes of tissue attenuation coefficients before, during, and after high-intensity focused ultrasound (HIFU) treatment at different total acoustic powers (TAP) in ex vivo porcine muscle tissue. It further assessed the reliability of employing changes in tissue attenuation coefficient parameters as potential indicators of tissue thermal damage. Methods Two-dimensional pulse-echo radio frequency (RF) data were acquired before, during, and after HIFU exposure to estimate changes in least squares attenuation coefficient slope (??) and attenuation coefficient intercept (??0). Using the acquired RF data, ?? and ??0 images, along with conventional B-mode ultrasound images, were constructed. The dynamic changes of ?? and ??0, averaged in the region of interest, were correlated with B-mode images obtained during the HIFU treatment process. Results At a HIFU exposure duration of 40 s and various HIFU intensities (737–1,068 W/cm2), ?? and ??0 increased rapidly to values in the ranges 1.5–2.5 dB/(MHz.cm) and 4–5 dB/cm, respectively. This rapid increase was accompanied with the appearance of bubble clouds in the B-mode images. Bubble activities appeared as strong hyperechoic regions in the B-mode images and caused fluctuations in the estimated ?? and ??0 values. After the treatment, ?? and ??0 values gradually decreased, accompanied by fade-out of hyperechoic spots in the B-mode images. At 10 min after the treatment, they reached values in ranges 0.75–1 dB/(MHz.cm) and 1–1.5 dB/cm, respectively, and remained stable within those ranges. At a long HIFU exposure duration of around 10 min and low HIFU intensity (117 W/cm2), ?? and ??0 gradually increased to values of 2.2 dB/(MHz.cm) and 2.2 dB/cm, respectively. This increase was not accompanied with the appearance of bubble clouds in the B-mode images. After HIFU treatment, ?? and ??0 gradually decreased to values of 1.8 dB/(MHz.cm) and 1.5 dB/cm, respectively, and remained stable at those values. Conclusions ?? and ??0 estimations were both potentially reliable indicators of tissue thermal damage. In addition, ?? and ??0 images both had significantly higher contrast-to-speckle ratios compared to the conventional B-mode images and outperformed the B-mode images in detecting HIFU thermal lesions at all investigated TAPs and exposure durations. PMID:25516802

2013-01-01

140

Measurements of mass attenuation coefficient, effective atomic number and electron density of some amino acids  

NASA Astrophysics Data System (ADS)

The mass attenuation coefficients of some amino acids, such as DL-aspartic acid-LR(C4H7NO4), L-glutamine (C4H10N2O3), creatine monohydrate LR(C4H9N3O2H2O), creatinine hydrochloride (C4H7N3O·HCl) L-asparagine monohydrate(C4H9N3O2H2O), L-methionine LR(C5H11NO2S), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma-rays were detected using NaI (Tl) scintillation detection system with a resolution of 0.101785 at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical values with less than 1% error for amino acids.

Kore, Prashant S.; Pawar, Pravina P.

2014-05-01

141

Dimensionality and noise in energy selective x-ray imaging  

PubMed Central

Purpose: To develop and test a method to quantify the effect of dimensionality on the noise in energy selective x-ray imaging. Methods: The Cramèr-Rao lower bound (CRLB), a universal lower limit of the covariance of any unbiased estimator, is used to quantify the noise. It is shown that increasing dimensionality always increases, or at best leaves the same, the variance. An analytic formula for the increase in variance in an energy selective x-ray system is derived. The formula is used to gain insight into the dependence of the increase in variance on the properties of the additional basis functions, the measurement noise covariance, and the source spectrum. The formula is also used with computer simulations to quantify the dependence of the additional variance on these factors. Simulated images of an object with three materials are used to demonstrate the trade-off of increased information with dimensionality and noise. The images are computed from energy selective data with a maximum likelihood estimator. Results: The increase in variance depends most importantly on the dimension and on the properties of the additional basis functions. With the attenuation coefficients of cortical bone, soft tissue, and adipose tissue as the basis functions, the increase in variance of the bone component from two to three dimensions is 1.4 × 103. With the soft tissue component, it is 2.7 × 104. If the attenuation coefficient of a high atomic number contrast agent is used as the third basis function, there is only a slight increase in the variance from two to three basis functions, 1.03 and 7.4 for the bone and soft tissue components, respectively. The changes in spectrum shape with beam hardening also have a substantial effect. They increase the variance by a factor of approximately 200 for the bone component and 220 for the soft tissue component as the soft tissue object thickness increases from 1 to 30 cm. Decreasing the energy resolution of the detectors increases the variance of the bone component markedly with three dimension processing, approximately a factor of 25 as the resolution decreases from 100 to 3 bins. The increase with two dimension processing for adipose tissue is a factor of two and with the contrast agent as the third material for two or three dimensions is also a factor of two for both components. The simulated images show that a maximum likelihood estimator can be used to process energy selective x-ray data to produce images with noise close to the CRLB. Conclusions: The method presented can be used to compute the effects of the object attenuation coefficients and the x-ray system properties on the relationship of dimensionality and noise in energy selective x-ray imaging systems. PMID:24320442

Alvarez, Robert E.

2013-01-01

142

X-ray Dinosaurs  

NSDL National Science Digital Library

In this activity, learners explore dinosaur fossils and skeletons. First, learners listen to "Tyrannosaurus Rex" by Daniel Cohen to learn about T. rex dinosaurs specifically. Then, learners make dinosaur tracings and drawings similar to x-rays. Learners can repeat the activity using pictures of other dinosaurs to compare and contrast various dinosaurs. This activity is featured on page 38 of the "Dinosphere" unit of study for K-2 learners.

2014-04-14

143

Fluctuation X-Ray Scattering  

SciTech Connect

The work supported by the grant was aimed at developing novel methods of finding the structures of biomolecules using x-rays from novel sources such as the x-ray free electron laser and modern synchrotrons

Saldin, PI: D. K.; Co-I's: J. C. H. Spence and P. Fromme

2013-01-25

144

Soft X-ray Imaging  

SciTech Connect

The contents of this report cover the following: (1) design of the soft x-ray telescope; (2) fabrication and characterization of the soft x-ray telescope; and (3) experimental implementation at the OMEGA laser facility.

Seely, John

1999-05-20

145

Direct three-dimensional coherently scattered x-ray microtomography  

PubMed Central

Purpose: It has been shown that coherently scattered x rays can be used to discriminate and identify specific components in a mixture of low atomic weight materials. The authors demonstrated a new method of doing coherently scattered x-ray tomography with a thin sheet of x ray. Methods: A collimated x-ray fan-beam, a parallel polycapillary collimator, and a phantom consisting of several biocompatible materials of low attenuation-based contrast were used to investigate the feasibility of the method. Because of the particular experimental setup, only the phantom translation perpendicular to the x-ray beam is needed and, thus, there is no need of Radon-type tomographic reconstruction, except for the correction of the attenuation to the primary and scattered x rays, which was performed by using a conventional attenuation-based tomographic image data set. The coherent scatter image contrast changes with momentum transfer among component materials in the specimen were investigated with multiple x-ray sources with narrow bandwidth spectra generated with anode and filter combinations of Cu?Ni (8 keV), Mo?Zr (18 keV), and Ag?Pd (22 keV) and at multiple scatter angles by orienting the detector and polycapillary collimator at different angles to the illuminating x ray. Results: The contrast among different materials changes with the x-ray source energy and the angle at which the image was measured. The coherent scatter profiles obtained from the coherent scatter images are consistent with the published results. Conclusions: This method can be used to directly generate the three-dimensional coherent scatter images of small animal, biopsies, or other small objects with low atomic weight biological or similar synthetic materials with low attenuation contrast. With equipment optimized, submillimeter spatial resolution may be achieved. PMID:21302788

Cui, Congwu; Jorgensen, Steven M.; Eaker, Diane R.; Ritman, Erik L.

2010-01-01

146

X-Ray Vision  

NASA Technical Reports Server (NTRS)

We are fabricating optics for the hard-x-ray region using electroless nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently stable and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics (nickel has a relatively high density of 8.9 g/cu cm), and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength nickel alloys that permit very thin shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these and other hard-x-ray optics will be reviewed.

Ramsey, B. D.; Elsner, R. F.; Engelhaupt, D.; Kolodziejczak, J. J.; ODell, S. L.; Speegle, C. O.; Weisskopf, M. C.

2004-01-01

147

Refractive Optics for Hard X-ray Transmission Microscopy  

SciTech Connect

For hard x-ray transmission microscopy at photon energies higher than 15 keV we design refractive condenser and imaging elements to be used with synchrotron light sources as well as with x-ray tube sources. The condenser lenses are optimized for low x-ray attenuation--resulting in apertures greater than 1 mm--and homogeneous intensity distribution on the detector plane, whereas the imaging enables high-resolution (<100 nm) full-field imaging. To obtain high image quality at reasonable exposure times, custom-tailored matched pairs of condenser and imaging lenses are being developed. The imaging lenses (compound refractive lenses, CRLs) are made of SU-8 negative resist by deep x-ray lithography. SU-8 shows high radiation stability. The fabrication technique enables high-quality lens structures regarding surface roughness and arrangement precision with arbitrary 2D geometry. To provide point foci, crossed pairs of lenses are used. Condenser lenses have been made utilizing deep x-ray lithographic patterning of thick SU-8 layers, too, whereas in this case, the aperture is limited due to process restrictions. Thus, in terms of large apertures, condenser lenses made of structured and rolled polyimide film are more attractive. Both condenser types, x-ray mosaic lenses and rolled x-ray prism lenses (RXPLs), are considered to be implemented into a microscope setup. The x-ray optical elements mentioned above are characterized with synchrotron radiation and x-ray laboratory sources, respectively.

Simon, M.; Last, A.; Mohr, J.; Nazmov, V.; Reznikova, E. [Institute for Microstructure Technology, Karlsruhe Institute of Technology Kaiserstrasse 12, 76131 Karlsruhe (Germany); Ahrens, G.; Voigt, A. [Microresist Technology, Koepenikerstrasse 325, 12555 Berlin (Germany)

2011-09-09

148

Multiwavelength Anomalous Diffraction at High X-Ray Intensity  

NASA Astrophysics Data System (ADS)

The multiwavelength anomalous diffraction (MAD) method is used to determine phase information in x-ray crystallography by employing anomalous scattering from heavy atoms. X-ray free-electron lasers (FELs) show promise for revealing the structure of single molecules or nanocrystals, but the phase problem remains largely unsolved. Because of the ultrabrightness of x-ray FEL, samples experience severe electronic radiation damage, especially to heavy atoms, which hinders direct implementation of MAD with x-ray FELs. Here, we propose a generalized version of MAD phasing at high x-ray intensity. We demonstrate the existence of a Karle-Hendrickson-type equation in the high-intensity regime and calculate relevant coefficients with detailed electronic damage dynamics of heavy atoms. The present method offers a potential for ab initio structural determination in femtosecond x-ray nanocrystallography.

Son, Sang-Kil; Chapman, Henry N.; Santra, Robin

2011-11-01

149

Panoramic Dental X-Ray  

MedlinePLUS

... Unlike a traditional intraoral x-ray where the film is placed inside of the mouth, the film for a panoramic x-ray is contained inside ... tube mounted on a horizontal arm. X-ray film or a detector are mounted on another horizontal ...

150

X-ray lithography source  

DOEpatents

A high-intensity, inexpensive X-ray source for X-ray lithography for the production of integrated circuits is disclosed. Foil stacks are bombarded with a high-energy electron beam of 25 to 250 MeV to produce a flux of soft X-rays of 500 eV to 3 keV. Methods of increasing the total X-ray power and making the cross section of the X-ray beam uniform are described. Methods of obtaining the desired X-ray-beam field size, optimum frequency spectrum and eliminating the neutron flux are all described. A method of obtaining a plurality of station operation is also described which makes the process more efficient and economical. The satisfying of these issues makes transition radiation an excellent moderate-priced X-ray source for lithography. 26 figures.

Piestrup, M.A.; Boyers, D.G.; Pincus, C.

1991-12-31

151

SMM x ray polychromator  

NASA Technical Reports Server (NTRS)

The objective of the X-ray Polychromator (XRP) experiment was to study the physical properties of solar flare plasma and its relation to the parent active region to understand better the flare mechanism and related solar activity. Observations were made to determine the temperature, density, and dynamic structure of the pre-flare and flare plasma as a function of wavelength, space and time, the extent to which the flare plasma departs from thermal equilibrium, and the variation of this departure with time. The experiment also determines the temperature and density structure of active regions and flare-induced changes in the regions.

Saba, J. L. R.

1993-01-01

152

X-ray satellite  

NASA Technical Reports Server (NTRS)

An overview of the second quarter 1985 development of the X-ray satellite project is presented. It is shown that the project is proceeding according to plan and that the projected launch date of September 9, 1987 is on schedule. An overview of the work completed and underway on the systems, subsystems, payload, assembly, ground equipment and interfaces is presented. Problem areas shown include cost increases in the area of focal instrumentation, the star sensor light scattering requirements, and postponements in the data transmission subsystems.

1985-01-01

153

Dependence of optical attenuation coefficient and mechanical tension of irradiated human cartilage measured by optical coherence tomography.  

PubMed

As banked human tissues are not widely available, the development of new non-destructive and contactless techniques to evaluate the quality of allografts before distribution for transplantation is very important. Also, tissues will be processed accordingly to standard procedures and to minimize disease transmission most tissue banks will include a decontamination or sterilization step such as ionizing radiation. In this work, we present a new method to evaluate the internal structure of frozen or glycerol processed human cartilages, submitted to various dosis of irradiation, using the total optical attenuation coefficient retrieved from optical coherence tomography (OCT) images. Our results show a close relationship between tensile properties and the total optical attenuation coefficient of cartilages. Therefore, OCT associated with the total optical attenuation coefficient open a new window to evaluate quantitatively biological changes in processed tissues. PMID:23887800

Martinho, A C; Freitas, A Z; Raele, M P; Santin, S P; Soares, F A N; Herson, M R; Mathor, M B

2014-09-01

154

Noninvasive monitoring of photodynamic therapy on skin neoplastic lesions using the optical attenuation coefficient measured by optical coherence tomography.  

PubMed

Photodynamic therapy (PDT) has become a promising alternative for treatment of skin lesions such as squamous cell carcinoma. We propose a method to monitor the effects of PDT in a noninvasive way by using the optical attenuation coefficient (OAC) calculated from optical coherence tomography (OCT) images. We conducted a study on mice with chemically induced neoplastic lesions and performed PDT on these lesions using homemade photosensitizers. The response of neoplastic lesions to therapy was monitored using, at the same time, macroscopic clinical visualization, histopathological analysis, OCT imaging, and OCT-based attenuation coefficient measurement. Results with all four modalities demonstrated a positive response to treatment. The attenuation coefficient was found to be 1.4 higher in skin lesions than in healthy tissue and it decreased after therapy. This study shows that the OAC is a potential tool to noninvasively assess the evolution of skin neoplastic lesions with time after treatment. PMID:25415566

Goulart, Viviane P; dos Santos, Moisés O; Latrive, Anne; Freitas, Anderson Z; Correa, Luciana; Zezell, Denise M

2015-05-01

155

The determination of the effective attenuation coefficient from effective organ depth and modulation transfer function in gamma camera imaging.  

PubMed

Absolute measurement of activity implies a determination of effective depths and effective attenuation coefficients. In order to define restoration filters, it is necessary to measure the transfer function, i.e. position a line source at an effective depth for the specific measurement situation. A phantom was designed which can simulate an organ with a certain thickness at a certain depth. The phantom was used to measure transfer functions and a comparison was made with transfer functions from a line source to determine effective depths. Effective attenuation coefficients were calculated for 99mTc, 111In and 201Tl for different organ thicknesses and depths of simulated organs. The effective attenuation coefficient for 99mTc was found to be 0.124 +/- 0.006 cm-1, in good agreement with previously published values. For 111In, the attenuation coefficient decreased with the depth of an organ due to the use of two energy windows in the measurements and a corresponding change in mean photon energy by depth. For 201Tl, the attenuation coefficient decreased with increasing organ thickness due to the increasing fraction of scattered radiation in the 40% energy window used. Using attenuation coefficients of 0.124, 0.184 and 0.11 cm-1 for 99mTc, 201Tl and 111In respectively, the derived equations can be used to calculate the position of a conventional line source for measurements of transfer functions for a specific organ with a certain thickness at a certain depth for definition of different types of restoration filter. PMID:9364591

Starck, S A; Carlsson, S

1997-10-01

156

Numerical simulation of electron-impact x-ray sources  

NASA Astrophysics Data System (ADS)

Electron-impact x-ray sources will be used to calibrate the Advanced X-Ray Astrophysics Facility (AXAF), and models of the source x-ray spectra are necessary in forecasting the calibration performance. We simulate the spectra of x-ray lines and continuum (0.1 - 13 keV) arising from electron impact on solid targets. We use simple models for electron transport, line and continuum emissivities, and radiative transport through the target. The electrons are attenuated in energy in the target but are unscattered in direction. The continuum x-ray emission is modeled as bremsstrahlung, and the characteristic x-ray line emission is modeled by electron collisional ionization followed by radiative decay to form the lines. X-ray attenuation is also included in the radiative transfer through the target. Multilayer or compound targets can be easily treated. We compare the spectra produced by this model to the model of Pella et al. and data from metal targets.

Sulkanen, Martin E.; Kolodziejczak, Jeffery J.; Chartas, George

1995-06-01

157

Image reconstruction for x-ray K-edge imaging with a photon counting detector  

NASA Astrophysics Data System (ADS)

Contrast agents with high-Z elements have K-absorption edges which significantly change X-ray attenuation coefficients. The K-edge characteristics is different for various kinds of contrast agents, which offers opportunities for material decomposition in biomedical applications. In this paper, we propose a new K-edge imaging method, which not only quantifies a distribution of a contrast agent but also provides an optimized contrast ratio. Our numerical simulation tests demonstrate the feasibility and merits of the proposed methodology.

Meng, Bo; Cong, Wenxiang; Xi, Yan; Wang, Ge

2014-09-01

158

Rayleigh to Compton ratio with monochromatic radiation from an X-ray tube (preliminary results)  

NASA Astrophysics Data System (ADS)

Results on the Rayleigh to Compton ratio ( R/ C) for elements and compounds with low atomic number (5 ? Z ? 12) are presented. These materials are difficult to identify and characterize with other radiological techniques because of their very close linear attenuation coefficients. A transportable setup for R/ C measurements was assembled and tested. This comprises an X-ray tube, in which the output radiation is partially "converted" to monochromatic radiation emitted by a secondary target. The experimental results are compared with theory, determined through coherent and incoherent scattering cross sections.

Donativi, M.; Quarta, S.; Cesareo, R.; Castellano, A.

2007-11-01

159

Attenuation coefficients and absorbed gamma radiation energy of different varieties of potato, mango and prawn at different storage time and physiological condition.  

PubMed

Attenuation coefficients of different varieties of gamma irradiated potato (Kufri Chandramukhi, Kufri Jyoti, and Kufri Sindhuri), mango (Himsagar, Langra, Dashehri and Fazli) and prawn (Tiger prawn and Fresh water prawn) of different storage time and physiological stages were determined. After six months storage attenuation coefficient of Kufri Chandramukhi was decreased by 30.8% with decrease of density and moisture content. Decreasing trend of attenuation coefficient during storage was more prominent (almost 50%) in other two varieties of potato. On the other hand in all four varieties, unripe mango consisted of significantly less (p ? 0.05) attenuation coefficient (around 11-14%) than the ripe one due to changes in physiological properties and density. Different varieties of prawn had different attenuation coefficients due to subtle differences in their proximate composition. Due to having different attenuation coefficients, different food components, even different varieties of same food component absorbed different gamma radiation energy though exposed to same radiation dose. PMID:24128533

Ghosh, Sayanti; Das, M K

2014-02-15

160

PXAMS -- Projectile X ray AMS: X ray yields and applications  

SciTech Connect

Characteristic x rays have recently been explored as a method for the detection and identification of ions in accelerator mass spectrometry (AMS). After analysis in the AMS spectrometer, the ions stop in an appropriately chosen target and the induced x rays identify the ions by atomic number. For the application of AMS to higher mass isotopes, characteristic x rays allow significantly better discrimination of competing atomic isobars than is possible using energy loss detectors. Characteristic x rays also show promise as a convenient component in hybrid detection systems. Measurements of x ray yields are presented for Si, Fe, Ni, Se, Mo, and Pd ions of 0.5--2 MeV/AMU. The yields rise by more than a factor of 10 over this energy range, and approach 1 x-ray per incident ion at 2 MeV/AMU for the lighter ions. Preliminary work on the application of PXAMS to the detection of {sup 79}Se is described.

McAninch, J.E.; Bench, G.S.; Freeman, S.P.H.T.; Roberts, M.L.; Southon, J.R.; Vogel, J.S.; Proctor, I.D. [Lawrence Livermore National Lab., CA (United States). Center for Accelerator Mass Spectrometry

1994-10-07

161

X-Ray Spectrum Model  

NSDL National Science Digital Library

TheX-Ray Spectrum Model shows the effect of varying the high voltage (kVp), added filtration and ripple in the high voltage supply to the X-ray tube. The physical mechanisms by which X-rays are produced are Bremsstrahlung (in which collisions of the cathode electrons convert some of their energy into X-ray photons) and characteristic X-rays (in which the cathode electrons kick an inner shell electron out of an atom, and an X-ray photon is release when one of the atom's outer shell electron transitions to the inner shell). Changing the accelerating voltage of the cathode electrons (i.e. changing kVp) affects both mechanisms of X-ray production. Adding filtration to the X-ray beam reduces its intensity, but does not reduce all energy X-rays equally. The X-Ray Spectrum Model was created by Michael Gallis using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. You can examine and modify this compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open Ejs Model" from the pop-up menu. You must, of course, have EJS installed on your computer. 

Gallis, Michael R.

2014-04-16

162

Diel variability of the beam attenuation and backscattering coefficients in the northwestern Mediterranean Sea (BOUSSOLE site)  

NASA Astrophysics Data System (ADS)

diel variability of the particulate beam attenuation coefficient, cp, and of the particulate backscattering coefficient, bbp, were investigated during five seasonal cycles at an oceanic site in the northwestern Mediterranean Sea, covering contrasting physical and trophic situations. We observed a diel cycle in cp and bbp, related to changes in phytoplankton properties (i.e., size and refractive index) induced by the accumulation of carbon within phytoplankton cells associated with photosynthetic processes, during the winter mixing of the water column, the development of the spring phytoplankton bloom, its decline, and during the summer oligotrophy. The relative amplitude of the cp diel variability was much larger during the spring bloom (20-50%) than during other seasons (10-20%), whereas that of bbp is steadily around 20% and does not show significant seasonal variability. The minimal cp and bbp occurred at sunrise and are synchronized, whereas maximum bbp values are often reached 3-6 h before those for cp (except during bloom conditions), which occur near sunset. These different amplitudes and timing are tentatively explained using Mie computations, which allow discerning the respective roles of changes in the particle size distribution and refractive index. The differences observed here in the diel cycles of cp and bbp show that they cannot be used interchangeably to determine the daily increase of the particle pool. This result has implications on the feasibility to determine net community production from the bbp diel changes, when only bbp is measured in situ or available from ocean color observations.

Kheireddine, Malika; Antoine, David

2014-08-01

163

Generation of first hard X-ray pulse at Tsinghua Thomson Scattering X-ray Source  

NASA Astrophysics Data System (ADS)

Tsinghua Thomson Scattering X-ray Source (TTX) is the first-of-its-kind dedicated hard X-ray source in China based on the Thomson scattering between a terawatt ultrashort laser and relativistic electron beams. In this paper, we report the experimental generation and characterization of the first hard X-ray pulses (51.7 keV) via head-on collision of an 800 nm laser and 46.7 MeV electron beams. The measured yield is 1.0 × 106 per pulse with an electron bunch charge of 200 pC and laser pulse energy of 300 mJ. The angular intensity distribution and energy spectra of the X-ray pulse are measured with an electron-multiplying charge-coupled device using a CsI scintillator and silicon attenuators. These measurements agree well with theoretical and simulation predictions. An imaging test using the X-ray pulse at the TTX is also presented.

Du, Yingchao; Yan, Lixin; Hua, Jianfei; Du, Qiang; Zhang, Zhen; Li, Renkai; Qian, Houjun; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

2013-05-01

164

Miniature x-ray source  

DOEpatents

A miniature x-ray source capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature x-ray source comprises a compact vacuum tube assembly containing a cathode, an anode, a high voltage feedthru for delivering high voltage to the anode, a getter for maintaining high vacuum, a connection for an initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is highly x-ray transparent and made, for example, from boron nitride. The compact size and potential for remote operation allows the x-ray source, for example, to be placed adjacent to a material sample undergoing analysis or in proximity to the region to be treated for medical applications.

Trebes, James E. (Livermore, CA); Stone, Gary F. (Livermore, CA); Bell, Perry M. (Tracy, CA); Robinson, Ronald B. (Modesto, CA); Chornenky, Victor I. (Minnetonka, MN)

2002-01-01

165

Solar X-ray physics  

SciTech Connect

Research on solar X-ray phenomena performed by American scientists during 1987-1990 is reviewed. Major topics discussed include solar images observed during quiescent times, the processes observed during solar flares, and the coronal, interplanetary, and terrestrial phenomena associated with solar X-ray flares. Particular attention is given to the hard X-ray emission observed at the start of the flare, the energy transfer to the soft X-ray emitting plasma, the late resolution of the flare as observed in soft X-ray, and the rate of occurrence of solar flares as a function of time and latitude. Pertinent aspects of nonflaring, coronal X-ray emission and stellar flares are also discussed. 175 refs.

Bornmann, P.L. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

166

Topological X-Rays Revisited  

ERIC Educational Resources Information Center

We continue our study of topological X-rays begun in Lynch ["Topological X-rays and MRI's," iJMEST 33(3) (2002), pp. 389-392]. We modify our definition of a topological magnetic resonance imaging and give an affirmative answer to the question posed there: Can we identify a closed set in a box by defining X-rays to probe the interior and without…

Lynch, Mark

2012-01-01

167

Saturated x-ray lasers  

Microsoft Academic Search

Saturated operation of an X-ray laser is desirable as a high output irradiance is obtained with reduced shot-to-short variation. The potential of saturated X-ray laser output in probing plasma samples is first investigated. The laser pumping requirements to scale Ni-like saturated X-ray laser output to shorter wavelengths is then analyzed using published atomic physics data and a simple 4-level laser

Gregory J. Tallents; G. Eker; F. Strati; S. J. Pestehe; J. Lin; R. Smith; Sandrine Dobosz; Andrew G. MacPhee; Ciaran L. Lewis; R. M. N. O'Rourke; R. Keenan; Geoffrey J. Pert; Simon P. McCabe; David Neely; Ric M. Allott

1999-01-01

168

X-ray diagnostics for TFTR  

SciTech Connect

A short description of the x-ray diagnostic preparation for the TFTR tokamak is given. The x-ray equipment consists of the limiter x-ray monitoring system, the soft x-ray pulse-height-analysis-system, the soft x-ray imaging system and the x-ray crystal spectrometer. Particular attention is given to the radiation protection of the x-ray systems from the neutron environment.

von Goeler, S.; Hill, K.W.; Bitter, M.

1982-12-01

169

Bragg reflection x ray optics  

Microsoft Academic Search

After a brief summary of the properties of x rays and of materials in the x ray frequency range, the ray optics and microscopic wavefield optics of Bragg reflection in perfect crystals are reviewed. Particular attention is given to the phase relationships between fields, to the spatial modulation of wavefields and to the role of the structure amplitude in determining

M. Hart

1971-01-01

170

X-ray beam pointer  

NASA Technical Reports Server (NTRS)

Inexpensive, readily assembled pointer aims X-ray machine for welded assembly radiographs. Plumb bob used for vertical alinement and yardstick used to visualize X-ray paths were inconvenient and inaccurate. Pointer cuts alinement time by one-half and eliminates necessity of retakes. For 3,000 weld radiographs, pointer will save 300 worker-hours and significant materials costs.

Nelson, C. W.

1980-01-01

171

X-Ray Exam: Finger  

MedlinePLUS

What It Is A finger X-ray is a safe and painless test that uses a small amount of radiation to take a picture of one or more fingers. During the examination, an X-ray machine sends a beam of radiation through the ...

172

X-Ray Exam: Forearm  

MedlinePLUS

... performed by an X-ray technician in the radiology department of a hospital, a radiology center, or a health care provider's office. Two ... and can't easily be brought to the radiology department, a portable X-ray machine can be ...

173

X-Ray Exam: Wrist  

MedlinePLUS

What It Is A wrist X-ray is a safe and painless test that uses a small amount of radiation to make an image of a person's wrist. During the examination, an X-ray machine sends a beam of radiation through ...

174

X-Ray Exam: Foot  

MedlinePLUS

What It Is A foot X-ray is a safe and painless test that uses a small amount of radiation to make an image of a person's foot. During the examination, an X-ray machine sends a beam of radiation through ...

175

X-Ray Exam: Ankle  

MedlinePLUS

What It Is An ankle X-ray is a safe and painless test that uses a small amount of radiation to make an image of the ankle. ... back part of the foot (tarsal bones). An X-ray machine sends a beam of radiation through ...

176

X-ray shearing interferometer  

DOEpatents

An x-ray interferometer for analyzing high density plasmas and optically opaque materials includes a point-like x-ray source for providing a broadband x-ray source. The x-rays are directed through a target material and then are reflected by a high-quality ellipsoidally-bent imaging crystal to a diffraction grating disposed at 1.times. magnification. A spherically-bent imaging crystal is employed when the x-rays that are incident on the crystal surface are normal to that surface. The diffraction grating produces multiple beams which interfere with one another to produce an interference pattern which contains information about the target. A detector is disposed at the position of the image of the target produced by the interfering beams.

Koch, Jeffrey A. (Livermore, CA)

2003-07-08

177

X-Ray Diffraction Apparatus  

NASA Technical Reports Server (NTRS)

An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)

1996-01-01

178

Order of magnitude reduction of fluoroscopic x-ray dose  

NASA Astrophysics Data System (ADS)

The role of fluoroscopic imaging is critical for diagnostic and image guided therapy. However, fluoroscopic imaging can require significant radiation leading to increased cancer risk and non-stochastic effects such as radiation burns. Our purpose is to reduce the exposure and dose to the patient by an order of magnitude in these procedures by use of the region of interest method. Method and Materials: Region of interest fluoroscopy (ROIF) uses a partial attenuator. The central region of the image has full exposure while the image periphery, there to provide context only, has a reduced exposure rate. ROIF using a static partial attenuator has been shown in our previous studies to reduce the dose area product (DAP) to the patient by at least 2.5 times. Significantly greater reductions in DAP would require improvements in flat panel detectors performance at low x-ray exposures or a different x-ray attenuation strategy. Thus we have investigated a second, dynamic, approach. We have constructed an x-ray shutter system allowing a normal x-ray exposure in the region of interest while reducing the number of x-ray exposures in the periphery through the rapid introduction, positioning and removal of an x-ray attenuating shutter to block radiation only for selected frames. This dynamic approach eliminates the DQE(0) loss associated with the use of static partial attenuator applied to every frame thus permitting a greater reduction in DAP. Results: We have compared the two methods by modeling and determined their fundamental limits.

Bal, Abhinav; Robert, Normand; Machan, Lindsay; Deutsch, Meir; Kisselgoff, David; Babyn, Paul; Rowlands, John A.

2012-03-01

179

Bone age assessment by dual-energy X-ray absorptiometry in children: an alternative for X-ray?  

PubMed Central

Objective The aim of the study was to validate dual-energy X-ray absorptiometry (DXA) as a method to assess bone age in children. Methods Paired dual-energy X-ray absorptiometry (DXA) scans and X-rays of the left hand were performed in 95 children who attended the paediatric endocrinology outpatient clinic of University Hospital Rotterdam, the Netherlands. We compared bone age assessments by DXA scan with those performed by X-ray. Bone age assessment was performed by two blinded observers according to the reference method of Greulich and Pyle. Intra-observer and interobserver reproducibility were investigated using the intraclass correlation coefficient (ICC), and agreement was tested using Bland and Altman plots. Results The intra-observer ICCs for both observers were 0.997 and 0.991 for X-ray and 0.993 and 0.987 for DXA assessments. The interobserver ICC was 0.993 and 0.991 for X-ray and DXA assessments, respectively. The mean difference between bone age assessed by X-ray and DXA was 0.11 years. The limits of agreement ranged from ?0.82 to 1.05 years, which means that 95% of all differences between the methods were covered by this range. Conclusions Results of bone age assessment by DXA scan are similar to those obtained by X-ray. The DXA method seems to be an alternative for assessing bone age in a paediatric hospital-based population. PMID:21586503

Heppe, D H M; Taal, H R; Ernst, G D S; Van Den Akker, E L T; Lequin, M M H; Hokken-Koelega, A C S; Geelhoed, J J M; Jaddoe, V W V

2012-01-01

180

X-ray computerized tomography analysis and density estimation using a sediment core from the Challenger Mound area in the Porcupine Seabight, off Western Ireland  

NASA Astrophysics Data System (ADS)

X-ray computerized tomography (CT) analysis was used to image a half-round core sample of 50 cm long recovered from near Challenger Mound in the Porcupine Seabight, off western Ireland during the Integrated Ocean Drilling Program Expedition 307. This allowed three-dimensional examination of complex shapes of pebbles and ice-rafted debris in sedimentary sequences. X-ray CT analysis was also used for the determination of physical properties; a comparison between bulk density by the mass-volume method and estimated density based on linear attenuation coefficients of X-ray CT images provides insight into a spatially detailed and precise map of density variation in samples through the distribution of CT numbers.

Tanaka, A.; Nakano, T.; Ikehara, K.

2011-02-01

181

The precise measurement of the attenuation coefficients of various IR optical materials applicable to immersion grating  

NASA Astrophysics Data System (ADS)

Immersion grating is a next-generation diffraction grating which has the immersed the diffraction surface in an optical material with high refractive index of n > 2, and can provide higher spectral resolution than a classical reflective grating. Our group is developing various immersion gratings from the near- to mid-infrared region (Ikeda et al.1, 2, 3, 4, Sarugaku et al.5, and Sukegawa et al.6). The internal attenuation ?att of the candidate materials is especially very important to achieve the high efficiency immersion gratings used for astronomical applications. Nevertheless, because there are few available data as ?att < 0.01cm-1 in the infrared region, except for measurements of CVD-ZnSe, CVD-ZnS, and single-crystal Si in the short near-infrared region reported by Ikeda et al.7, we cannot select suitable materials as an immersion grating in an aimed wavelength range. Therefore, we measure the attenuation coefficients of CdTe, CdZnTe, Ge, Si, ZnSe, and ZnS that could be applicable to immersion gratings. We used an originally developed optical unit attached to a commercial FTIR which covers the wide wavelength range from 1.3?m to 28?m. This measurement system achieves the high accuracy of (triangle)?att ~ 0.01cm-1. As a result, high-resistivity single-crystal CdZnTe, single-crystal Ge, single-crystal Si, CVD-ZnSe, and CVD-ZnS show ?att < 0.01cm-1 at the wavelength range of 5.5 - 19.0?m, 2.0 - 10.5?m, 1.3 - 5.4?m, 1.7 - 13.2?m, and 1.9 - 9.2?m, respectively. This indicates that these materials are good candidates for high efficiency immersion grating covering those wavelength ranges. We plan to make similar measurement under the cryogenic condition as T <= 10K for the infrared, especially mid-infrared applications.

Kaji, Sayumi; Sarugaku, Yuki; Ikeda, Yuji; Kobayashi, Naoto; Nakanishi, Kenshi; Kondo, Sohei; Yasui, Chikako; Kawakita, Hideyo

2014-07-01

182

X-ray coherent scattering form factors of tissues, water and plastics using energy dispersion  

NASA Astrophysics Data System (ADS)

A key requirement for the development of the field of medical x-ray scatter imaging is accurate characterization of the differential scattering cross sections of tissues and phantom materials. The coherent x-ray scattering form factors of five tissues (fat, muscle, liver, kidney, and bone) obtained from butcher shops, four plastics (polyethylene, polystyrene, lexan (polycarbonate), nylon), and water have been measured using an energy-dispersive technique. The energy-dispersive technique has several improvements over traditional diffractometer measurements. Most notably, the form factor is measured on an absolute scale with no need for scaling factors. Form factors are reported in terms of the quantity x = ?-1sin (?/2) over the range 0.363-9.25 nm-1. The coherent form factors of muscle, liver, and kidney resemble those of water, while fat has a narrower peak at lower x, and bone is more structured. The linear attenuation coefficients of the ten materials have also been measured over the range 30-110 keV and parameterized using the dual-material approach with the basis functions being the linear attenuation coefficients of polymethylmethacrylate and aluminum.

King, B. W.; Landheer, K. A.; Johns, P. C.

2011-07-01

183

X-Ray Imaging March 28, 2012  

E-print Network

-electron atoms!! Eelectron = EXRay - EBinding Wednesday, March 28, 2012 #12;X-Ray Imaging Any atom that blocks X-RaysX-Ray Imaging P. Chandra March 28, 2012 Wednesday, March 28, 2012 #12;What are X-Rays ?? Discovered Called X-Rays because WR did not know nature of radiation Only later identified as Short Wavelength (High

Chandra, Premi

184

Chest X-Ray (Chest Radiography)  

MedlinePLUS

X-ray (Radiography) - Chest • Overview The chest x-ray is the most commonly performed diagnostic x-ray examination. A ... pregnancy and x-rays. A Word About Minimizing Radiation Exposure Special care is taken during x-ray ...

185

X-ray observations of ultraluminous X-ray sources  

E-print Network

Ultraluminous X-ray sources (ULXs) are amongst the most intriguing of X-ray source classes. Their extreme luminosities - greater than 10^39 erg/s in the 0.3 - 10 keV band alone - suggest either the presence of black holes larger than those regularly encountered in our own Galaxy (the Galactic centre excepted), or sources apparently radiating well above the Eddington limit. We review the insights afforded us by studies of their X-ray emission, focussing on what this reveals about the underlying compact object. In particular, we discuss recent deep observations of ULXs by the XMM-Newton observatory, and how the unprecedented data quality provided by this mission is starting to discriminate between the different physical models for these extraordinary X-ray emitters.

T. P. Roberts

2007-06-18

186

Auger Electrons via K? X-Ray Lines of Platinum Compounds for Nanotechnological Applications  

NASA Astrophysics Data System (ADS)

We will report study on the K? X-ray lines of platinum. Pt compounds, such as cisplatin, are common in biomedical applications. The active element Pt can emit or absorb hard X-rays. We have obtained the photoionization cross sections from the oscillator strengths of 1s-2p (K?) transitions in Pt ions. We find that these transitions appear as resonances in photoionization in the hard X-ray energy range of 64 - 71 keV (0.18 - 0.17 Å) below the K-shell ionization and with a strength orders of magnitude higher compared to that at the K-shell ionization. This is the focus of our study for possible initiation of an emission cascade of Auger electrons at the resonant energy. We will present the oscillator strengths and attenuation coefficients per unit mass for all the K? transitions in the event platinum cascades through various, namely from fluorine-like to hydrogen like, ionic states. The study is motivated by uur proposed method, Resonant Theranosticsb,C (RT) for biomedical appliations, which aims to find narrow band X-ray energy that corresponds to resonant photo-absorption and leads to emission of Auger electrons. As the next step of the RT method we will also report on experimental results on producing monochromatic X-rays, targeted to the resonant energy, from the wide band Bremstruhlung radiation of a conventional X-ray source. Partially support: DOE, Computational Facility: Ohio Supercomputer Center, Columbus, Ohio. "Resonant X-Ray Enhancement of the Auger Effect in High-Z atoms, molecules, and Nanoparticles: Biomedical Applications", A.K. Pradhan, S.N. Nahar, M. Montenegro, Yan Yu, H.L. Zhang, C. Sur, M. Mrozik, R.M. Pitzer, J. of Phys. Chem. A, 113 (2009), 12356. "Monte Carlo Simulations and Atomic Calculations for Auger Processes in Biomedical Nanotheranostics", M. Montenegro, S. N. Nahar, A. K. Pradhan, Ke Huang, Yan Yu, J. of Phys. Chem. A, 113 (2009), 12364.

Nahar, Sultana N.; Lim, Sara; Pradhan, A. K.; Pitzer, R. M.

2011-06-01

187

X-Ray Imaging System  

NASA Astrophysics Data System (ADS)

The FluoroScan Imaging System is a high resolution, low radiation device for viewing stationary or moving objects. It resulted from NASA technology developed for x-ray astronomy and Goddard application to a low intensity x-ray imaging scope. FlouroScan Imaging Systems, Inc, (formerly HealthMate, Inc.), a NASA licensee, further refined the FluoroScan System. It is used for examining fractures, placement of catheters, and in veterinary medicine. Its major components include an x-ray generator, scintillator, visible light image intensifier and video display. It is small, light and maneuverable.

1986-01-01

188

Automatic detection of bone fragments in poultry using multi-energy x-rays  

DOEpatents

At least two linear arrays of x-ray detectors are placed below a conveyor belt in a poultry processing plant. Multiple-energy x-ray sources illuminate the poultry and are detected by the detectors. Laser profilometry is used to measure the poultry thickness as the x-ray data is acquired. The detector readout is processed in real time to detect the presence of small highly attenuating fragments in the poultry, i.e., bone, metal, and cartilage.

Gleason, Shaun S. (Knoxville, TN); Paulus, Michael J. (Knoxville, TN); Mullens, James A. (Knoxville, TN)

2002-04-09

189

Optimization of system parameters for modulator design in x-ray scatter correction using primary modulation  

Microsoft Academic Search

The impact of the system parameters of the modulator on X-ray scatter correction using primary modulation is studied and an optimization of the modulator design is presented. Recently, a promising scatter correction method for X-ray computed tomography (CT) that uses a checkerboard pattern of attenuating blockers (primary modulator) placed between the X-ray source and the object has been developed and

Hewei Gao; Lei Zhu; Rebecca Fahrig

2010-01-01

190

Analysis of trace Co in synthetic diamonds using synchrotron radiation excited X-ray fluorescence analysis  

Microsoft Academic Search

Synchrotron radiation excited X-ray fluorescence analysis was utilized for characterization of trace impurities in synthetic diamonds. Advantage of the energy tunability was fully utilized to evaluate the attenuation of X-rays through the sample, and the absorption corrected X-ray fluorescence yield was utilized for quantitative analysis. Diamonds grown with several types of metallic solvents were investigated, and quantitative analysis of trace

Shinjiro Hayakawa; Xiao-Peng Jia; Masao Wakatsuki; Yohichi Gohshi; Takeshi Hirokawa

2000-01-01

191

Cross-Disciplinary Geological Research Using High-Resolution X-ray Computed Tomography  

Microsoft Academic Search

High-resolution X-ray computed tomography (CT) generates three-dimensional imagery of solid objects depicting X-ray attenuation, which is a function of density and atomic number. It is thus ideal for studying many features and quantities that are best observed, understood, and characterized in 3D, in objects from millimeter to decimeter scale. The High-resolution X-ray CT Facility at the University of Texas at

R. A. Ketcham; W. D. Carlson; T. B. Rowe

2002-01-01

192

The X-ray transfrom and the Radon transform  

E-print Network

The Euclidean X-ray transform of tensor fields of order two. 44. 9. The attenuated ...... Abel type which can be inverted explicitly. This was first ...... the estimate (3.2) in Theorem 3.1 to hold for all s without some modifications, at least. The same ...

193

Calibration of a turbidity meter for making estimates of total suspended solids concentrations and beam attenuation coefficients in field experiments  

NASA Technical Reports Server (NTRS)

Management of water resources such as a reservoir requires using analytical models which describe such parameters as the suspended sediment field. To select or develop an appropriate model requires making many measurements to describe the distribution of this parameter in the water column. One potential method for making those measurements expeditiously is to measure light transmission or turbidity and relate that parameter to total suspended solids concentrations. An instrument which may be used for this purpose was calibrated by generating curves of transmission measurements plotted against measured values of total suspended solids concentrations and beam attenuation coefficients. Results of these experiments indicate that field measurements made with this instrument using curves generated in this study should correlate with total suspended solids concentrations and beam attenuation coefficients in the water column within 20 percent.

Usry, J. W.; Whitlock, C. H.

1981-01-01

194

Measurement of attenuation coefficients for bone, muscle, fat and water at 140, 364 and 662 keV ?-ray energies  

NASA Astrophysics Data System (ADS)

The half-value thicknesses, linear and mass attenuation coefficients of biological samples such as bone, muscle, fat and water have been measured at 140, 364 and 662 keV ?-ray energies by using the ATOMLABTM-930 medical spectrometer. The ?-rays were obtained from 99mTc, 131I and 137Cs ?-ray point sources. Also theoretical calculations have been performed in order to obtain the half-value thicknesses and, mass and linear attenuation coefficients at photon energies 0.001 keV 20 MeV for bone, muscle and water samples. The calculated value and the experimental results of this work and the other results in literature are found to be in good agreement.

Akar, A.; Balta?, H.; Çevik, U.; Korkmaz, F.; Okumu?o?lu, N. T.

2006-11-01

195

Why Do I Need X-Rays?  

MedlinePLUS

... your desktop! more... Why Do I Need X-Rays? Article Chapters Why Do I Need X-Rays? ... tooth decay. Updated: January 2012 Related Articles: X-Rays The Academy of General Dentistry (AGD) Sets the ...

196

Miniature x-ray source  

DOEpatents

A miniature x-ray source utilizing a hot filament cathode. The source has a millimeter scale size and is capable of producing broad spectrum x-ray emission over a wide range of x-ray energies. The miniature source consists of a compact vacuum tube assembly containing the hot filament cathode, an anode, a high voltage feedthru for delivering high voltage to the cathode, a getter for maintaining high vacuum, a connector for initial vacuum pump down and crimp-off, and a high voltage connection for attaching a compact high voltage cable to the high voltage feedthru. At least a portion of the vacuum tube wall is fabricated from highly x-ray transparent materials, such as sapphire, diamond, or boron nitride.

Trebes, James E. (Livermore, CA); Bell, Perry M. (Tracy, CA); Robinson, Ronald B. (Modesto, CA)

2000-01-01

197

X-ray planetary nebulae  

NASA Technical Reports Server (NTRS)

A study of IUE archival low-dispersion spectra was conducted in an attempt to correlate the C IV/He II and C III)/C IV emission line ratios as indicators of X-ray emission in planetary nebulae. The presence of P Cygni lines revealed a strong correlation for planetaries known to exhibit X-ray emission. Of the twelve planetaries definitely known to emit X-rays, eleven have been observed with IUE and all but one show ultraviolet lines with very strong P Cygni profiles for at least one, and sometimes all, of the N V, O V, or C IV lines which are indicative of strong stellar winds. Twenty planetary nebulae are identified as likely candidates for X-ray sources, based on their high IUE emission line flux ratios for C IV/He II as well as prevalence of P Cygni lines. Some misconceptions based on outdated IUE data are corrected.

Feibelman, Walter A.

1994-01-01

198

Desktop x-ray microtomography  

NASA Astrophysics Data System (ADS)

An X-ray microtomography (or micro-CT) is an instrument for high-resolution 3D reconstruction of objects internal microstructure without destruction or time consuming specimen preparation. By using modern technology in x-ray sources and detectors several micro-CT systems were created as a simply usable desktop instrument. First micro-CT system is a laboratory instrument, giving true spatial resolution over a ten million times more detailed (in the term of volume parts) than the medical CT-scanners. The instrument contains a sealed microfocus X-ray source, a cooled X-ray digital CCD-camera and a Dual Pentium computer for system control and 3D-reconstructions running under Windows NT.

Sasov, Alexander; Ceulemans, Tom; Van Dyck, Dirk

2001-06-01

199

X-ray fluorescence microscopy  

SciTech Connect

Synchrotron x-ray fluorescence microscopy is used to quantitatively measure and image the distribution of trace elements in biological, geological and materials science specimens. The design and performance of the x-ray fluorescence (XFR) microprobe at the NSLS are discussed and compared with other XRF microprobe design. An example of a trace element image obtained with this instrument if presented. 6 refs., 5 figs.

Rivers, M.L.; Sutton, S.R. (Chicago Univ., IL (USA). Dept. of Geophysical Sciences); Jones, K.W. (Brookhaven National Lab., Upton, NY (USA))

1990-10-01

200

Nanoscale X-ray imaging  

Microsoft Academic Search

Recent years have seen significant progress in the field of soft- and hard-X-ray microscopy, both technically, through developments in source, optics and imaging methodologies, and also scientifically, through a wide range of applications. While an ever-growing community is pursuing the extensive applications of today's available X-ray tools, other groups are investigating improvements in techniques, including new optics, higher spatial resolutions,

Anne Sakdinawat; David Attwood

2010-01-01

201

X-ray computed tomography for structural ceramic applications: Beam hardening corrections  

Microsoft Academic Search

Beam hardening (BH), caused by the energy dependence of x-ray attenuation in materials, reduces the reliability of images generated by computed tomographic (CT) when polychromatic x-ray sources are used. The magnitude of the BH effect was calculated, and four different approaches to BH correction for CT imaging of ceramics were investigated: the ''water bag'' approach, prehardening of the beam by

W. A. Ellingson; E. Segal; M. W. Vannier

1987-01-01

202

Efficiency of Lu 2SiO 5:Ce (LSO) powder phosphor as X-ray to light converter under mammographic imaging conditions  

NASA Astrophysics Data System (ADS)

The aim of the present study was to examine the light emission efficiency of Lu 2SiO 5:Ce (LSO) powder scintillator under X-ray mammographic imaging conditions. Powder LSO scintillator has never been used in X-ray imaging. For the purposes of the present study, a 25 mg/cm 2 thick scintillating screen was prepared in our laboratory, by sedimentation of Lu 2SiO 5:Ce powder. Absolute luminescence efficiency measurements were performed within the range of X-ray tube voltages (22-49 kVp) used in mammographic applications. Parameters related to X-ray detection, i.e. the energy absorption efficiency (EAE) and the quantum detection efficiency (QDE) were calculated. A theoretical model, describing radiation and light transfer, was employed to fit experimental data and to estimate values of the intrinsic conversion efficiency and the light attenuation coefficients of the screen. The spectral compatibility of the LSO powder scintillator to mammographic X-ray films and to various electronic optical detectors was determined by performing light emission spectrum measurements and by taking into account the spectral sensitivity of the optical detectors. Results in the voltage range used in mammography showed that Lu 2SiO 5:Ce powder scintillator has approximately 10% higher values of QDE and 4.5% higher values of EAE than Gd 2O 2S:Tb.

David, S.; Michail, C.; Valais, I.; Nikolopoulos, D.; Liaparinos, P.; Kalivas, N.; Kalatzis, I.; Toutountzis, A.; Efthimiou, N.; Loudos, G.; Sianoudis, I.; Cavouras, D.; Dimitropoulos, N.; Nomicos, C. D.; Kandarakis, I.; Panayiotakis, G. S.

2007-02-01

203

Cooled window for X-rays or charged particles  

DOEpatents

A window that provides good structural integrity and a very high capacity for removal of the heat deposited by x-rays, electrons, or ions, with minimum attenuation of the desired beam. The window is cooled by providing microchannels therein through which a coolant is pumped. For example, the window may be made of silicon with etched microchannels therein and covered by a silicon member. A window made of silicon with a total thickness of 520 .mu.m transmits 96% of the x-rays at an energy of 60 keV, and the transmission is higher than 90% for higher energy photons.

Logan, Clinton M. (Pleasanton, CA)

1996-01-01

204

The Physics of the Gas Attenuator for the Linac Coherent Light Source (LCLS)  

SciTech Connect

A systematic assessment of a variety of physics issues affecting the performance of the LCLS X-ray beam attenuator is presented. Detailed analysis of the gas flow in the gas attenuator and in the apertures is performed. A lot of attention is directed towards the gas ionization and heating by intense X-ray pulses. The role of these phenomena in possible deviations of the attenuation coefficient from its 'dialed in' value is evaluated and found small in most cases. Other sources of systematic and statistical errors are also discussed. The regimes where the errors may reach a few percent correspond to the lower X-ray energies (less than 2 keV) and highest beam intensities. Other effects discussed include chemical interaction of the gas with apertures, shock formation in the transonic flow in the apertures of the attenuator, generation of electromagnetic wakes in the gas, and head-to-tail variation of the attenuation caused by the ionization of gas or solid. Possible experimental tests of the consistency of the physics assumptions used in the concept of the gas attenuator are discussed. Interaction of X-rays with the solid attenuator (that will be used at higher X-ray energies, from 2.5 to 8 keV) is considered and thermo-mechanical effects caused by the beam heating are evaluated. Wave-front distortions induced by non-uniform heating of both the solid and the gas are found to be small. An overall conclusion drawn from the analysis presented is that the attenuator will be a reliable and highly versatile device, provided that some caution is exercised in its use for highest beam intensities at lowest X-ray energies.

Ryutov, D.D.; Bionta, R.M.; Hau-Riege, S.P.; Kishiyama, K.I.; McMahon, D.; Roeben, M.D.; Shen, S.; /LLNL, Livermore; Stefan, P.M.; /SLAC; ,

2011-02-07

205

X-ray angiography systems.  

PubMed

Despite the emergence of several alternative angiographic imaging techniques (i.e., magnetic resonance imaging, computed tomography, and ultrasound angiography), x-ray angiography remains the predominant vascular imaging modality, generating over $4 billion in revenue a year in U.S. hospitals. In this issue, we provide a brief overview of the various angiographic imaging techniques, comparing them with x-ray angiography, and discuss the clinical aspects of x-ray vascular imaging, including catheterization and clinical applications. Clinical, cost, usage, and legal issues related to contrast media are discussed in "Contrast Media: Ionic versus Nonionic and Low-osmolality Agents." We also provide a technical overview and selection guidance for a basic x-ray angiography imaging system, including the gantry and table system, x-ray generator, x-ray tube, image intensifier, video camera and display monitors, image-recording devices, and digital acquisition and processing systems. This issue also contains our Evaluation of the GE Advantx L/C cardiac angiography system and the GE Advantx AFM general-purpose angiography system; the AFM can be used for peripheral, pulmonary, and cerebral vascular studied, among others, and can also be configured for cardiac angiography. Many features of the Advantx L/C system, including generator characteristics and ease of use, also apply to the Advantx AFM as configured for cardiac angiography. Our ratings are based on the systems' ability to provide the best possible image quality for diagnosis and therapy while minimizing patient and personnel exposure to radiation, as well as its ability to minimize operator effort and inconvenience. Both units are rated Acceptable. In the Guidance Section, "Radiation Safety and Protection," we discuss the importance of keeping patient and personnel exposures to radiation as low as reasonably possible, especially in procedures such as cardiac catheterization, angiographic imaging for special procedures, and interventional radiology, which produce among the highest radiation exposure of all x-ray imaging techniques. We also provide recommendations for minimizing personnel and patient exposures to radiation. For more information about x-ray angiography systems and similar devices, as well as for additional perspectives on which we based this study, see the following Health Devices Evaluations: "Mobile C-arm Units" (19[8], August 1990) and "Noninvasive Electronic Quality Control Devices for X-ray Generator Testing" (21[6-7], June-July 1992).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8119801

1993-11-01

206

X-rays surgical revolution.  

PubMed

Wilhelm Roentgen (1845-1923) created a surgical revolution with the discovery of the X-rays in late 1895 and the subsequent introduction of this technique for the management of surgical patients. No other physician or scientist had ever imagined such a powerful and worthwhile discovery. Other scientists paved the way for Roentgen to approach the use of these new X-rays for medical purposes. In this way, initially, and prior to Roentgen, Thompson, Hertz, and Lenard applied themselves to the early developments of this technology. They made good advances but never reached the clearly defined understanding brought about by Roentgen. The use of a Crookes tube, a barium platinocyanide screen, with fluorescent light and the generation of energy to propagate the cathode rays were the necessary elements for the conception of an X-ray picture. On November 8, 1895, Roentgen began his experiments on X-ray technology when he found that some kind of rays were being produced by the glass of the tube opposite to the cathode. The development of a photograph successfully completed this early imaging process. After six intense weeks of research, on December 22, he obtained a photograph of the hand of his wife, the first X-ray ever made. This would be a major contribution to the world of medicine and surgery. PMID:19842886

Toledo-Pereyra, Luis H

2009-01-01

207

Roentgen's Discovery of the x-ray  

NSDL National Science Digital Library

The text in this site describes how Roentgen's discovered x-rays, how he created the first x-ray image, and how he investigated x-ray properties. Early medical applications are explained. Also, the site contains a link to a small gallery of historical x-ray images.

2013-06-26

208

X-ray Emission from Massive Stars  

E-print Network

X-ray Emission from Massive Stars David Cohen Department of Physics and Astronomy Swarthmore be related to the production of X-rays on massive stars. If so, massive stars' X-rays are much different than those found our own Sun and other cooler stars like the Sun that produce X-rays via magnetic activity

Cohen, David

209

X-ray tensor tomography  

NASA Astrophysics Data System (ADS)

Here we introduce a new concept for x-ray computed tomography that yields information about the local micro-morphology and its orientation in each voxel of the reconstructed 3D tomogram. Contrary to conventional x-ray CT, which only reconstructs a single scalar value for each point in the 3D image, our approach provides a full scattering tensor with multiple independent structural parameters in each volume element. In the application example shown in this study, we highlight that our method can visualize sub-pixel fiber orientations in a carbon composite sample, hence demonstrating its value for non-destructive testing applications. Moreover, as the method is based on the use of a conventional x-ray tube, we believe that it will also have a great impact in the wider range of material science investigations and in future medical diagnostics. The authors declare no competing financial interests.

Malecki, A.; Potdevin, G.; Biernath, T.; Eggl, E.; Willer, K.; Lasser, T.; Maisenbacher, J.; Gibmeier, J.; Wanner, A.; Pfeiffer, F.

2014-02-01

210

Photoionized X-ray Emission  

NASA Astrophysics Data System (ADS)

Spectra in the 0.1 -- 10 keV energy range reveal that absorption by partially ionized gas is common in active galaxies and X-ray binaries. Modeling is key for understanding the implications of such spectra for the configuration of gas in these systems, and current models have been successfully applied to spectra from many objects. Photoionized X-ray emission spectra have been studied less thoroughly. These spectra are of interest partly because they must inevitably affect the absorption spectra and also as tests of the geometrical distribution of gas near compact objects. The modeling code xstar can be applied to both types of spectra, although an efficient treatment of emission associated with bound-bound radiative excitation was not included until recently.In this poster I will describe these recent changes and illustrate application of xstar to sample X-ray spectra.

Kallman, Timothy R.

2013-04-01

211

Photon attenuation coefficients of Heavy-Metal Oxide glasses by MCNP code, XCOM program and experimental data: A comparison study  

NASA Astrophysics Data System (ADS)

The mass attenuation coefficients, ?/?, total interaction cross-section, ?t, and mean free path (MFP) of some Heavy Metal Oxides (HMO) glasses, with potential applications as gamma ray shielding materials, have been investigated using the MCNP-4C code. Appreciable variations are noted for all parameters by changing the photon energy and the chemical composition of HMO glasses. The numerical simulations parameters are compared with experimental data wherever possible. Comparisons are also made with predictions from the XCOM program in the energy region from 1 keV to 100 MeV. Good agreement noticed indicates that the chosen Monte Carlo method may be employed to make additional calculations on the photon attenuation characteristics of different glass systems, a capability particularly useful in cases where no analogous experimental data exist.

El-Khayatt, A. M.; Ali, A. M.; Singh, Vishwanath P.

2014-01-01

212

The X-Ray Observatory Suzaku  

Microsoft Academic Search

High-sensitivity wide-band X-ray spectroscopy is the key feature of the Suzaku X-ray observatory, launched on 2005 July 10. This paper summarizes the spacecraft, in-orbit performance, operations, and data processing that are related to observations. The scientific instruments, the high-throughput X-ray telescopes, X-ray CCD cameras, non-imaging hard X-ray detector are also described.

Kazuhisa Mitsuda; Mark Bautz; Hajime Inoue; Richard L. Kelley; Katsuji Koyama; Hideyo Kunieda; Kazuo Makishima; Yoshiaki Ogawara; Robert Petre; Tadayuki Takahashi; Hiroshi Tsunemi; Nicholas E. White; Naohisa Anabuki; Lorella Angelini; Keith Arnaud; Hisamitsu Awaki; Aya Bamba; Kevin Boyce; Gregory V. Brown; Kai-Wing Chan; Jean Cottam; Tadayasu Dotanli; John Doty; Ken Ebisawa; Yuichiro Ezoe; Andrew C. Fabian; Enectali Figueroa; Ryuichi Fujimoto; Yasushi Fukazawa; Tae Furusho; Akihiro Furuzawa; Keith Gendreau; Richard E. Griffiths; Yoshito Haba; Kenji Hamaguchi; Ilana Harrus; Günther Hasinger; Isamu Hatsukade; Kiyoshi Hayashida; Patrick J. Henry; Junko S. Hiraga; Stephen S. Holt; Ann Hornschemeier; John P. Hughes; Una Hwang; Manabu Ishida; Yoshitaka Ishisaki; Naoki Isobe; Masayuki Itoh; Naoko Iyomoto; Steven M. Kahn; Tuneyoshi Kamae; Hideaki Katagiri; Jun Kataoka; Haruyoshi Katayama; Nobuyuki Kawai; Caroline Kilbourne; Kenzo Kinugasa; Steve Kissel; Shunji Kitamoto; Mitsuhiro Kohama; Takayoshi Kohmura; Motohide Kokubun; Taro Kotani; Jun'ichi Kotoku; Aya Kubota; Greg M. Madejski; Yoshitomo Maeda; Fumiyoshi Makino; Alex Markowitz; Chiho Matsumoto; Hironori Matsumoto; Masaru Matsuoka; Kyoko Matsushita; Dan McCammon; Tatehiko Mihara; Kazutami Misaki; Emi Miyata; Tsunefumi Mizuno; Koji Mori; Hideyuki Mori; Mikio Morii; Harvey Moseley; Koji Mukai; Hiroshi Murakami; Toshio Murakami; Richard Mushotzky; Fumiaki Nagase; Masaaki Namiki; Hitoshi Negoro; Kazuhiro Nakazawa; John A. Nousek; Takashi Okajima; Yasushi Ogasaka; Takaya Ohashi; Tai Oshima; Naomi Ota; Masanobu Ozaki; Hideki Ozawa; Arvind N. Parmar; William D. Pence; F. Scott Porter; James N. Reeves; George R. Ricker; Ikuya Sakurai; Wilton T. Sanders; Atsushi Senda; Peter Serlemitsos; Ryo Shibata; Yang Soong; Randall Smith; Motoko Suzuki; Andrew E. Szymkowiak; Hiromitsu Takahashi; Toru Tamagawa; Keisuke Tamura; Takayuki Tamura; Yasuo Tanaka; Makoto Tashiro; Yuzuru Tawara; Yukikatsu Terada; Yuichi Terashima; Hiroshi Tomida; Ken'ichi Torii; Yohko Tsuboi; Masahiro Tsujimoto; Takeshi Go Tsuru; Martin J. L.. Turner; Yoshihiro Ueda; Shiro Ueno; Masaru Ueno; Shin'ichiro Uno; Yuji Urata; Shin Watanabe; Norimasa Yamamoto; Kazutaka Yamashita; Noriko Y. Yamasaki; Koujun Yamashita; Makoto Yamauchi; Shigeo Yamauchi; Tahir Yaqoob; Daisuke Yonetoku; Atsumasa Yoshida

2007-01-01

213

Portable X-Ray Device  

NASA Technical Reports Server (NTRS)

Portable x-ray instrument developed by NASA now being produced commercially as an industrial tool may soon find further utility as a medical system. The instrument is Lixiscope - Low Intensity X-Ray Imaging Scope -- a self-contained, battery-powered fluoroscope that produces an instant image through use of a small amount of radioactive isotope. Originally developed by Goddard Space Flight Center, Lixiscope is now being produced by Lixi, Inc. which has an exclusive NASA license for one version of the device.

1983-01-01

214

Deriving attenuation coefficients from 3D CT data for SPECT Monte Carlo simulations  

Microsoft Academic Search

Quantitation of nuclear medicine data is a major goal in medical imaging. It implies that photon attenuation, scatter and depth dependent spatial resolution be corrected for. Realistic, anthropomorphic numerical phantoms are needed to understand how these phenomena degrade nuclear medicine images, and to validate correction methods. We developed a Monte Carlo simulator which simulates photon transport in an anthropomorphic phantom.

Veronique Baccarne; A. Turzo; Y. Bizais; M. Farine

1997-01-01

215

Dark-field X-ray imaging of unsaturated water transport in porous materials  

NASA Astrophysics Data System (ADS)

We introduce in this Letter an approach to X-ray imaging of unsaturated water transport in porous materials based upon the intrinsic X-ray scattering produced by the material microstructural heterogeneity at a length scale below the imaging system spatial resolution. The basic principle for image contrast creation consists in a reduction of such scattering by permeation of the porosity by water. The implementation of the approach is based upon X-ray dark-field imaging via Talbot-Lau interferometry. The proof-of-concept is provided by performing laboratory-scale dark-field X-ray radiography of mortar samples during a water capillary uptake experiment. The results suggest that the proposed approach to visualizing unsaturated water transport in porous materials is complementary to neutron and magnetic resonance imaging and alternative to standard X-ray imaging, the latter requiring the use of contrast agents because based upon X-ray attenuation only.

Yang, F.; Prade, F.; Griffa, M.; Jerjen, I.; Di Bella, C.; Herzen, J.; Sarapata, A.; Pfeiffer, F.; Lura, P.

2014-10-01

216

TOPICAL REVIEW: Human soft tissue analysis using x-ray or gamma-ray techniques  

NASA Astrophysics Data System (ADS)

This topical review is intended to describe the x-ray techniques used for human soft tissue analysis. X-ray techniques have been applied to human soft tissue characterization and interesting results have been presented over the last few decades. The motivation behind such studies is to provide improved patient outcome by using the data obtained to better understand a disease process and improve diagnosis. An overview of theoretical background as well as a complete set of references is presented. For each study, a brief summary of the methodology and results is given. The x-ray techniques include x-ray diffraction, x-ray fluorescence, Compton scattering, Compton to coherent scattering ratio and attenuation measurements. The soft tissues that have been classified using x-rays or gamma rays include brain, breast, colon, fat, kidney, liver, lung, muscle, prostate, skin, thyroid and uterus.

Theodorakou, C.; Farquharson, M. J.

2008-06-01

217

Compact x-ray source and panel  

DOEpatents

A compact, self-contained x-ray source, and a compact x-ray source panel having a plurality of such x-ray sources arranged in a preferably broad-area pixelized array. Each x-ray source includes an electron source for producing an electron beam, an x-ray conversion target, and a multilayer insulator separating the electron source and the x-ray conversion target from each other. The multi-layer insulator preferably has a cylindrical configuration with a plurality of alternating insulator and conductor layers surrounding an acceleration channel leading from the electron source to the x-ray conversion target. A power source is connected to each x-ray source of the array to produce an accelerating gradient between the electron source and x-ray conversion target in any one or more of the x-ray sources independent of other x-ray sources in the array, so as to accelerate an electron beam towards the x-ray conversion target. The multilayer insulator enables relatively short separation distances between the electron source and the x-ray conversion target so that a thin panel is possible for compactness. This is due to the ability of the plurality of alternating insulator and conductor layers of the multilayer insulators to resist surface flashover when sufficiently high acceleration energies necessary for x-ray generation are supplied by the power source to the x-ray sources.

Sampayon, Stephen E. (Manteca, CA)

2008-02-12

218

Applications of Hard X-ray Full-Field Transmission X-ray Microscopy at SSRL  

SciTech Connect

State-of-the-art hard x-ray full-field transmission x-ray microscopy (TXM) at beamline 6-2C of Stanford Synchrotron Radiation Lightsource has been applied to various research fields including biological, environmental, and material studies. With the capability of imaging a 32-micron field-of-view at 30-nm resolution using both absorption mode and Zernike phase contrast, the 3D morphology of yeast cells grown in gold-rich media was investigated. Quantitative evaluation of the absorption coefficient was performed for mercury nanoparticles in alfalfa roots exposed to mercury. Combining XANES and TXM, we also performed XANES-imaging on an ancient pottery sample from the Roman pottery workshop at LaGraufesenque (Aveyron).

Liu, Y.; Andrews, J. C.; Mehta, A.; Pianetta, P. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, CA 94025 (United States); Meirer, F. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, CA 94025 (United States); MiNALab, CMM-Irst, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo, Trento (Italy); Gil, S. Carrasco [CIEMAT, Avda Complutense 22, MADRID 28040 (Spain); Sciau, P. [CEMES (UPR 8011 CNRS), 29 rue J. Marvig, 31055 Toulouse Cedex 4 (France); Mester, Z. [Institute for National Measurement Standards, National Research Council, Ottawa ON K1A0R6 (Canada)

2011-09-09

219

Multi-frequency characterization of the speed of sound and attenuation coefficient for longitudinal transmission of freshly excised human skulls  

NASA Astrophysics Data System (ADS)

For medical applications of ultrasound inside the brain, it is necessary to understand the relationship between the apparent density of skull bone and its corresponding speed of sound and attenuation coefficient. Although there have been previous studies exploring this phenomenon, there is still a need to extend the measurements to cover more of the clinically relevant frequency range. The results of measurements of the longitudinal speed of sound and attenuation coefficient are presented for specimens of human calvaria. The study was performed for the frequencies of 0.27, 0.836, 1.402, 1.965 and 2.525 MHz. Specimens were obtained from fresh cadavers through a protocol with the Division of Anatomy of the University of Toronto. The protocol was approved by the Research Ethics Board of Sunnybrook Health Sciences Centre. The specimens were mounted in polycarbonate supports that were marked for stereoscopic positioning. Computer tomography (CT) scans of the skulls mounted on their supports were performed, and a three-dimensional skull surface was reconstructed. This surface was used to guide a positioning system to ensure the normal sound incidence of an acoustic signal. This signal was produced by a focused device with a diameter of 5 cm and a focal length of 10 cm. Measurements of delay in time of flight were carried out using a needle hydrophone. Measurements of effective transmitted energy were carried out using a radiation force method with a 10 µg resolution scale. Preliminary functions of speed of sound and attenuation coefficient, both of which are related to apparent density, were established using a multi-layer propagation model that takes into account speed of sound, density and thickness of the layer. An optimization process was executed from a large set of random functions and the best functions were chosen for those ones that closest reproduced the experimental observations. The final functions were obtained after a second pass of the optimization process was executed, but this time using a finite-difference time-difference solution of the Westervelt equation, which is more precise than the multi-layer model but much more time consuming for computation. For six of seven specimens, measurements were carried out on five locations on the calvaria, and for the other specimen three measurements were made. In total, measurements were carried out on 33 locations. Results indicated the presence of dispersion effects and that these effects are different according to the type of bone in the skull (cortical and trabecular). Additionally, both the speed of sound and attenuation showed dependence on the skull density that varied with the frequency. Using the optimal functions and the information of density from the CT scans, the average values (±s.d.) of the speed of sound for cortical bone were estimated to be 2384(± 130), 2471(± 90), 2504(± 120), 2327(± 90) and 2053(± 40) m s-1 for the frequencies of 270, 836, 1402, 1965 and 2526 kHz, respectively. For trabecular bone, and in the same order of frequency values, the speeds of sound were 2140(± 130), 2300(± 100), 2219(± 200), 2133(± 130) and 1937(± 40) m s-1, respectively. The average values of the attenuation coefficient for cortical bone were 33(± 9), 240(± 9) and 307(± 30) Np m-1 for the frequencies of 270, 836, and 1402, respectively. For trabecular bone, and in the same order of frequency values, the average values of the attenuation coefficient were 34(± 13), 216(± 16) and 375(± 30) Np m-1, respectively. For frequencies of 1.965 and 2.525 MHz, no measurable radiation force was detected with the setup used.

Pichardo, Samuel; Sin, Vivian W.; Hynynen, Kullervo

2011-01-01

220

Material separation in x-ray CT with energy resolved photon-counting detectors  

PubMed Central

Purpose: The objective of the study was to demonstrate that, in x-ray computed tomography (CT), more than two types of materials can be effectively separated with the use of an energy resolved photon-counting detector and classification methodology. Specifically, this applies to the case when contrast agents that contain K-absorption edges in the energy range of interest are present in the object. This separation is enabled via the use of recently developed energy resolved photon-counting detectors with multiple thresholds, which allow simultaneous measurements of the x-ray attenuation at multiple energies. Methods: To demonstrate this capability, we performed simulations and physical experiments using a six-threshold energy resolved photon-counting detector. We imaged mouse-sized cylindrical phantoms filled with several soft-tissue-like and bone-like materials and with iodine-based and gadolinium-based contrast agents. The linear attenuation coefficients were reconstructed for each material in each energy window and were visualized as scatter plots between pairs of energy windows. For comparison, a dual-kVp CT was also simulated using the same phantom materials. In this case, the linear attenuation coefficients at the lower kVp were plotted against those at the higher kVp. Results: In both the simulations and the physical experiments, the contrast agents were easily separable from other soft-tissue-like and bone-like materials, thanks to the availability of the attenuation coefficient measurements at more than two energies provided by the energy resolved photon-counting detector. In the simulations, the amount of separation was observed to be proportional to the concentration of the contrast agents; however, this was not observed in the physical experiments due to limitations of the real detector system. We used the angle between pairs of attenuation coefficient vectors in either the 5-D space (for non-contrast-agent materials using energy resolved photon-counting acquisition) or a 2-D space (for contrast agents using energy resolved photon-counting acquisition and all materials using dual-kVp acquisition) as a measure of the degree of separation. Compared to dual-kVp techniques, an energy resolved detector provided a larger separation and the ability to separate different target materials using measurements acquired in different energy window pairs with a single x-ray exposure. Conclusions: We concluded that x-ray CT with an energy resolved photon-counting detector with more than two energy windows allows the separation of more than two types of materials, e.g., soft-tissue-like, bone-like, and one or more materials with K-edges in the energy range of interest. Separating material types using energy resolved photon-counting detectors has a number of advantages over dual-kVp CT in terms of the degree of separation and the number of materials that can be separated simultaneously. PMID:21520865

Wang, Xiaolan; Meier, Dirk; Taguchi, Katsuyuki; Wagenaar, Douglas J.; Patt, Bradley E.; Frey, Eric C.

2011-01-01

221

Modeling Electron-Impact X-Ray Spectra for the AXAF Calibration  

NASA Astrophysics Data System (ADS)

The Advanced X-ray Astrophysics Facility (AXAF) will provide high-resolution imaging and spectroscopy of astrophysical x-ray sources. A precision calibration of the AXAF telescope and science instruments will be performed by the AXAF Team, using x-ray sources at NASA's X-Ray Calibration Facility (XRCF), located at Marshall Space Flight Center. A tool to model the spectra from electron-impact x-ray sources for a variety of targets is necessary to predict the detected spectra and count rates for various combinations of telescope-detector calibrations. We model the spectra of x-ray lines and continuum (0.1 - 13 keV) arising from electron impact on solid targets. We use simple models for electron transport, line and continuum emissivities, and radiative transport through the target. The electrons are attenuated in energy but not scattered in direction. The continuum x-ray emission is modeled as bremsstrahlung, and the characteristic x-ray line emission is modeled as electron-collisional ionization followed by radiative decay to form the lines. X-ray attenuation is included in the radiative transfer, and multilayer or compound targets can be handled. The x-ray spectra produced by this model are compared to those of the Pella et al./ model, and experimental data from metal targets. A WWW catalog is available of the x-ray source spectra for twenty-one targets, with atomic numbers 4 <= Z <= 79, for various target voltages. Also compiled are the x-ray spectra at the telescope focal plane after passage through the AXAF HRMA, and the detected-photon spectra for the ACIS and HRC.

Sulkanen, M. E.; Elsner, R. F.; Kolodziejczak, J. J.

1995-12-01

222

X-Ray Exam: Hip  

MedlinePLUS

... your child on the table, then step behind a wall or into an adjoining room to operate the machine. Two X-rays are usually taken, one with the legs straight (AP view) and one with the knees apart and feet ...

223

X-ray conversion physics  

SciTech Connect

We have performed a series of experiments to study the physics of the conversion of 0.35-..mu..m laser light to soft x-rays in high-Z materials. The efficiency of soft x-ray and M-band radiation production as a function of laser intensity (5 /times/ 10/sup 13/ to 3 /times/ 10/sup 15/ W/cm/sup 2/) was measured. At fixed intensity 5 /times/ 10/sup 14/ W/cm/sup 2/, the time-resolved and time-integrated thermal x-ray (E < 1.5 keV) conversion efficiency increased with the laser pulse length for up to 4-ns-long pulses on gold targets. The effects of material opacity were examined by making targets of mixtures of gold and beryllium to vary the density of the strongly radiating gold in the target. These experiments demonstrate the effects of material opacity on both thermal and M-band x-ray production. These experiments were performed with large laser spots and greater than 1 kj of 0.35-..mu..m laser light using the Nova laser. These experiments have expanded our understanding of our ability to computer model the interaction of high intensity laser light with high-Z plasmas. 5 refs., 4 figs

Kauffman, R.L.; Kania, D.R.; Langer, S.; Kornblum, H.; Ze, F.

1988-10-01

224

Alpha proton x ray spectrometer  

NASA Technical Reports Server (NTRS)

Mars Pathfinder will carry an alpha-proton x ray spectrometer (APX) for the determination of the elemental chemical composition of Martian rocks and soils. The instrument will measure the concentration of all major and some minor elements, including C, N, and O at levels above typically 1 percent.

Rieder, Rudi; Waeke, H.; Economou, T.

1994-01-01

225

Synchrotron X-ray Measurements  

E-print Network

binding energy spectra as a function of annealing temperature for Al2 O3 /SiO2 /Si gate stacks. An Al2 O3 that we employ include: (1) near-edge X-ray absorption fine structure (NEXAFS) spectroscopy; (2) extended

226

Prospects for in vivo estimation of photon linear attenuation coefficients using postprocessing dual-energy CT imaging on a commercial scanner: Comparison of analytic and polyenergetic statistical reconstruction algorithms  

PubMed Central

Purpose: Accurate patient-specific photon cross-section information is needed to support more accurate model-based dose calculation for low energy photon-emitting modalities in medicine such as brachytherapy and kilovoltage x-ray imaging procedures. A postprocessing dual-energy CT (pDECT) technique for noninvasive in vivo estimation of photon linear attenuation coefficients has been experimentally implemented on a commercial CT scanner and its accuracy assessed in idealized phantom geometries. Methods: Eight test materials of known composition and density were used to compare pDECT-estimated linear attenuation coefficients to NIST reference values over an energy range from 10 keV to 1 MeV. As statistical image reconstruction (SIR) has been shown to reconstruct images with less random and systematic error than conventional filtered backprojection (FBP), the pDECT technique was implemented with both an in-house polyenergetic SIR algorithm, alternating minimization (AM), as well as a conventional FBP reconstruction algorithm. Improvement from increased spectral separation was also investigated by filtering the high-energy beam with an additional 0.5 mm of tin. The law of propagated uncertainty was employed to assess the sensitivity of the pDECT process to errors in reconstructed images. Results: Mean pDECT-estimated linear attenuation coefficients for the eight test materials agreed within 1% of NIST reference values for energies from 1 MeV down to 30 keV, with mean errors rising to between 3% and 6% at 10 keV, indicating that the method is unbiased when measurement and calibration phantom geometries are matched. Reconstruction with FBP and AM algorithms conferred similar mean pDECT accuracy. However, single-voxel pDECT estimates reconstructed on a 1 × 1 × 3 mm3 grid are shown to be highly sensitive to reconstructed image uncertainty; in some cases pDECT attenuation coefficient estimates exhibited standard deviations on the order of 20% around the mean. Reconstruction with the statistical AM algorithm led to standard deviations roughly 40% to 60% less than FBP reconstruction. Additional tin filtration of the high energy beam exhibits similar pDECT estimation accuracy as the unfiltered beam, even when scanning with only 25% of the dose. Using the law of propagated uncertainty, low Z materials are found to be more sensitive to image reconstruction errors than high Z materials. Furthermore, it is estimated that reconstructed CT image uncertainty must be limited to less than 0.25% to achieve a target linear-attenuation coefficient estimation uncertainty of 3% at 28 keV. Conclusions: That pDECT supports mean linear attenuation coefficient measurement accuracies of 1% of reference values for energies greater than 30 keV is encouraging. However, the sensitivity of the pDECT measurements to noise and systematic errors in reconstructed CT images warrants further investigation in more complex phantom geometries. The investigated statistical reconstruction algorithm, AM, reduced random measurement uncertainty relative to FBP owing to improved noise performance. These early results also support efforts to increase DE spectral separation, which can further reduce the pDECT sensitivity to measurement uncertainty. PMID:24320525

Evans, Joshua D.; Whiting, Bruce R.; O’Sullivan, Joseph A.; Politte, David G.; Klahr, Paul H.; Yu, Yaduo; Williamson, Jeffrey F.

2013-01-01

227

Prospects for in vivo estimation of photon linear attenuation coefficients using postprocessing dual-energy CT imaging on a commercial scanner: Comparison of analytic and polyenergetic statistical reconstruction algorithms  

SciTech Connect

Purpose: Accurate patient-specific photon cross-section information is needed to support more accurate model-based dose calculation for low energy photon-emitting modalities in medicine such as brachytherapy and kilovoltage x-ray imaging procedures. A postprocessing dual-energy CT (pDECT) technique for noninvasivein vivo estimation of photon linear attenuation coefficients has been experimentally implemented on a commercial CT scanner and its accuracy assessed in idealized phantom geometries. Methods: Eight test materials of known composition and density were used to compare pDECT-estimated linear attenuation coefficients to NIST reference values over an energy range from 10 keV to 1 MeV. As statistical image reconstruction (SIR) has been shown to reconstruct images with less random and systematic error than conventional filtered backprojection (FBP), the pDECT technique was implemented with both an in-house polyenergetic SIR algorithm, alternating minimization (AM), as well as a conventional FBP reconstruction algorithm. Improvement from increased spectral separation was also investigated by filtering the high-energy beam with an additional 0.5 mm of tin. The law of propagated uncertainty was employed to assess the sensitivity of the pDECT process to errors in reconstructed images. Results: Mean pDECT-estimated linear attenuation coefficients for the eight test materials agreed within 1% of NIST reference values for energies from 1 MeV down to 30 keV, with mean errors rising to between 3% and 6% at 10 keV, indicating that the method is unbiased when measurement and calibration phantom geometries are matched. Reconstruction with FBP and AM algorithms conferred similar mean pDECT accuracy. However, single-voxel pDECT estimates reconstructed on a 1 × 1 × 3 mm{sup 3} grid are shown to be highly sensitive to reconstructed image uncertainty; in some cases pDECT attenuation coefficient estimates exhibited standard deviations on the order of 20% around the mean. Reconstruction with the statistical AM algorithm led to standard deviations roughly 40% to 60% less than FBP reconstruction. Additional tin filtration of the high energy beam exhibits similar pDECT estimation accuracy as the unfiltered beam, even when scanning with only 25% of the dose. Using the law of propagated uncertainty, low Z materials are found to be more sensitive to image reconstruction errors than high Z materials. Furthermore, it is estimated that reconstructed CT image uncertainty must be limited to less than 0.25% to achieve a target linear-attenuation coefficient estimation uncertainty of 3% at 28 keV. Conclusions: That pDECT supports mean linear attenuation coefficient measurement accuracies of 1% of reference values for energies greater than 30 keV is encouraging. However, the sensitivity of the pDECT measurements to noise and systematic errors in reconstructed CT images warrants further investigation in more complex phantom geometries. The investigated statistical reconstruction algorithm, AM, reduced random measurement uncertainty relative to FBP owing to improved noise performance. These early results also support efforts to increase DE spectral separation, which can further reduce the pDECT sensitivity to measurement uncertainty.

Evans, Joshua D., E-mail: jevans2@mcvh-vcu.edu; Yu, Yaduo; Williamson, Jeffrey F. [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)] [Department of Radiation Oncology, Virginia Commonwealth University, Richmond, Virginia 23298 (United States); Whiting, Bruce R. [Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 (United States)] [Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 (United States); O’Sullivan, Joseph A. [Department of Electrical and Systems Engineering, Washington University, St. Louis, Missouri 63130 (United States)] [Department of Electrical and Systems Engineering, Washington University, St. Louis, Missouri 63130 (United States); Politte, David G. [Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110 (United States)] [Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110 (United States); Klahr, Paul H. [Philips Healthcare, 595 Miner Rd., Highland Hts., Ohio 44143 (United States)] [Philips Healthcare, 595 Miner Rd., Highland Hts., Ohio 44143 (United States)

2013-12-15

228

Energy-resolved interferometric x-ray imaging  

NASA Astrophysics Data System (ADS)

Interferometric X-ray imaging becomes more and more attractive for applications such as medical imaging or non-destructive testing, where a compact setup is needed. Therefore a so-called Talbot-Lau interferometer in combination with a conventional X-ray tube is used. Thereby, three different kinds of images can be obtained. An attenuation image like in conventional X-ray imaging, an image of the differential phase-shifts caused by the object and the so-called dark-field image. The dark-field image shows information about the object's granularity even in sub-pixel dimensions what especially seems very promising for applications like mammography. With respect to optimizing the output of interferometric X-ray imaging in any application, it is inevitable to know the energy response of the interferometer as well as the energy dependence of the interactions of X- rays with matter. In this contribution, simulations and measurements using a Medipix 2 and a Timepix detector are presented.

Pelzer, Georg; Bayer, Florian; Gödel, Karl; Haas, Wilhelm; Horn, Florian; Rieger, Jens; Ritter, André; Sievers, Peter; Weber, Thomas; Zang, Andrea; Durst, Jürgen; Michel, Thilo; Anton, Gisela

2013-03-01

229

Modification of the TASMIP x-ray spectral model for the simulation of microfocus x-ray sources  

SciTech Connect

Purpose: The availability of accurate and simple models for the estimation of x-ray spectra is of great importance for system simulation, optimization, or inclusion of photon energy information into data processing. There is a variety of publicly available tools for estimation of x-ray spectra in radiology and mammography. However, most of these models cannot be used directly for modeling microfocus x-ray sources due to differences in inherent filtration, energy range and/or anode material. For this reason the authors propose in this work a new model for the simulation of microfocus spectra based on existing models for mammography and radiology, modified to compensate for the effects of inherent filtration and energy range. Methods: The authors used the radiology and mammography versions of an existing empirical model [tungsten anode spectral model interpolating polynomials (TASMIP)] as the basis of the microfocus model. First, the authors estimated the inherent filtration included in the radiology model by comparing the shape of the spectra with spectra from the mammography model. Afterwards, the authors built a unified spectra dataset by combining both models and, finally, they estimated the parameters of the new version of TASMIP for microfocus sources by calibrating against experimental exposure data from a microfocus x-ray source. The model was validated by comparing estimated and experimental exposure and attenuation data for different attenuating materials and x-ray beam peak energy values, using two different x-ray tubes. Results: Inherent filtration for the radiology spectra from TASMIP was found to be equivalent to 1.68 mm Al, as compared to spectra obtained from the mammography model. To match the experimentally measured exposure data the combined dataset required to apply a negative filtration of about 0.21 mm Al and an anode roughness of 0.003 mm W. The validation of the model against real acquired data showed errors in exposure and attenuation in line with those reported for other models for radiology or mammography. Conclusions: A new version of the TASMIP model for the estimation of x-ray spectra in microfocus x-ray sources has been developed and validated experimentally. Similarly to other versions of TASMIP, the estimation of spectra is very simple, involving only the evaluation of polynomial expressions.

Sisniega, A.; Vaquero, J. J., E-mail: juanjose.vaquero@uc3m.es [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain); Instituto de Investigación Sanitaria Gregorio Marañón, Madrid ES28007 (Spain); Desco, M. [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain) [Departamento de Bioingeniería e Ingeniería Aeroespacial, Universidad Carlos III de Madrid, Madrid ES28911 (Spain); Instituto de Investigación Sanitaria Gregorio Marañón, Madrid ES28007 (Spain); Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), Madrid ES28029 (Spain)

2014-01-15

230

X-ray microdiffraction of biominerals.  

PubMed

Biominerals have complex and heterogeneous architectures, hence diffraction experiments with spatial resolutions between 500 nm and 10 ?m are extremely useful to characterize them. X-ray beams in this size range are now routinely produced at many synchrotrons. This chapter provides a review of the different hard X-ray diffraction and scattering techniques, used in conjunction with efficient, state-of-the-art X-ray focusing optics. These include monochromatic X-ray microdiffraction, polychromatic (Laue) X-ray microdiffraction, and microbeam small-angle X-ray scattering. We present some of the most relevant discoveries made in the field of biomineralization using these approaches. PMID:24188780

Tamura, Nobumichi; Gilbert, Pupa U P A

2013-01-01

231

Microgap x-ray detector  

DOEpatents

An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.

Wuest, Craig R. (Danville, CA); Bionta, Richard M. (Livermore, CA); Ables, Elden (Livermore, CA)

1994-01-01

232

Microgap x-ray detector  

DOEpatents

An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.

Wuest, C.R.; Bionta, R.M.; Ables, E.

1994-05-03

233

A whole-system approach to x-ray spectroscopy in cargo inspection systems  

SciTech Connect

The bremsstrahlung x-ray spectrum used in high-energy, high-intensity x-ray cargo inspection systems is attenuated and modified by the materials in the cargo in a Z-dependent way. Therefore, spectroscopy of the detected x rays yields information about the Z of the x-rayed cargo material. It has previously been shown that such ZSpectroscopy (Z-SPEC) is possible under certain circumstances. A statistical approach, Z-SCAN (Z-determination by Statistical Count-rate ANalysis), has also been shown to be effective, and it can be used either by itself or in conjunction with Z-SPEC when the x-ray count rate is too high for individual x-ray spectroscopy. Both techniques require fast x-ray detectors and fast digitization electronics. It is desirable (and possible) to combine all techniques, including x-ray imaging of the cargo, in a single detector array, to reduce costs, weight, and overall complexity. In this paper, we take a whole-system approach to x-ray spectroscopy in x-ray cargo inspection systems, and show how the various parts interact with one another. Faster detectors and read-out electronics are beneficial for both techniques. A higher duty-factor x-ray source allows lower instantaneous count rates at the same overall x-ray intensity, improving the range of applicability of Z-SPEC in particular. Using an intensity-modulated advanced x-ray source (IMAXS) allows reducing the x-ray count rate for cargoes with higher transmission, and a stacked-detector approach may help material discrimination for the lowest attenuations. Image processing and segmentation allow derivation of results for entire objects, and subtraction of backgrounds. We discuss R and D performed under a number of different programs, showing progress made in each of the interacting subsystems. We discuss results of studies into faster scintillation detectors, including ZnO, BaF{sub 2} and PbWO{sub 4}, as well as suitable photo-detectors, read-out and digitization electronics. We discuss high-duty-factor linear-accelerator x-ray sources and their associated requirements, and how such sources improve spectroscopic techniques. We further discuss how image processing techniques help in correcting for backgrounds and overlapping materials. In sum, we present an integrated picture of how to optimize a cargo inspection system for x-ray spectroscopy.

Langeveld, Willem G. J.; Gozani, Tsahi; Ryge, Peter; Sinha, Shrabani; Shaw, Tim; Strellis, Dan [Rapiscan Laboratories, Inc. 520 Almanor Ave. Sunnyvale, CA 94085 (United States)

2013-04-19

234

MATHEMATICAL TECHNIQUES FOR X-RAY ANALYZERS  

EPA Science Inventory

Mathematical techniques and subsequent computer software were developed to process energy-dispersive x-ray fluorescence spectra for elemental analysis of airborne particulate matter collected on filters. The research concerned two areas: (1) determination of characteristic x-ray ...

235

X-Ray Exam: Cervical Spine  

MedlinePLUS

... Doctors & Hospitals > Medical Tests & Exams > X-Ray Exam: Cervical Spine Print A A A Text Size What's in ... If You Have Questions What It Is A cervical spine X-ray is a safe and painless test ...

236

Spectral analysis of X-ray binaries  

E-print Network

In this thesis, I present work from three separate research projects associated with observations of X-ray binaries. Two of those revolve around spectral characteristics of neutron star low-mass X-ray binaries (NS-LMXBs), ...

Fridriksson, Joel Karl

2011-01-01

237

Aspergillosis - chest x-ray (image)  

MedlinePLUS

... usually occurs in immunocompromised individuals. Here, a chest x-ray shows that the fungus has invaded the lung ... are usually seen as black areas on an x-ray. The cloudiness on the left side of this ...

238

Producing X-rays at the APS  

SciTech Connect

An introduction and overview of the Advanced Photon Source at Argonne National Laboratory, the technology that produces the brightest X-ray beams in the Western Hemisphere, and the research carried out by scientists using those X-rays.

None

2011-01-01

239

X-Ray Crystallography Reagent  

NASA Technical Reports Server (NTRS)

Microcapsules prepared by encapsulating an aqueous solution of a protein, drug or other bioactive substance inside a semi-permeable membrane by are disclosed. The microcapsules are formed by interfacial coacervation under conditions where the shear forces are limited to 0-100 dynes per square centimeter at the interface. By placing the microcapsules in a high osmotic dewatering solution. the protein solution is gradually made saturated and then supersaturated. and the controlled nucleation and crystallization of the protein is achieved. The crystal-filled microcapsules prepared by this method can be conveniently harvested and stored while keeping the encapsulated crystals in essentially pristine condition due to the rugged. protective membrane. Because the membrane components themselves are x-ray transparent, large crystal-containing microcapsules can be individually selected, mounted in x-ray capillary tubes and subjected to high energy x-ray diffraction studies to determine the 3-D smucture of the protein molecules. Certain embodiments of the microcapsules of the invention have composite polymeric outer membranes which are somewhat elastic, water insoluble, permeable only to water, salts, and low molecular weight molecules and are structurally stable in fluid shear forces typically encountered in the human vascular system.

Morrison, Dennis R. (Inventor); Mosier, Benjamin (Inventor)

2003-01-01

240

Supersoft X-ray sources  

NASA Astrophysics Data System (ADS)

More than 100 supersoft X-ray sources (SSS) are reported in ˜20 external galaxies, the Magellanic Clouds (MCs) and our Galaxy. The effective temperatures of the brighter SSS are ˜20-100 eV. SSS with luminosities below ?3 × 10 38 erg s -1 are consistent with accreting white dwarfs (WDs) with steady nuclear burning or post-novae. Optical identifications exist for SSS in our Galaxy and the MCs (including orbital period determinations) and for SSS in M31 (with novae and symbiotic stars, SySs). High resolution X-ray spectra of the brightest SSS in our Galaxy and the MCs reveal the existence of spectral features due to high gravity WDs. Timing studies in X-rays (combined with the optical) of the stable nuclear burning phase in steady nuclear burning sources and in post-novae allow to constrain the mass accretion rate onto and the mass of the nuclear burning WD. The nature of a few SSS with luminosities ?10 39 erg s -1 remains unclear.

Kahabka, Peter

2006-01-01

241

Combined SPECT and x-ray CT medical imaging system  

NASA Astrophysics Data System (ADS)

We have designed and built a system for correlated x ray CT transmission and SPECT emission imaging with an array of photon counting detectors. The scanner operates in a third generation fan beam geometry by translating a 23 element high purity germanium detector across the fan to image phantoms and small animals. The x ray CT image is used to obtain an object specific, i.e., anatomically accurate, attenuation map for the reconstruction of the SPECT image. SPECT images are reconstructed with an MLEM code and the pixel values are scaled in physical units by determining a scaling factor from a uniform water phantom with homogeneous and known attenuation. Single myocardial slices of several pigs were imaged with a 99mTc sestamibi imaging agent which is taken up in proportion to regional myocardial blood flow. The results show that 99mTc uptake and regional myocardial blood flow, determined in vivo from reconstructed SPECT images, correlate with the measured in vitro data. Furthermore, the correlation is markedly improved by reconstructing the images with an object specific attenuation map obtained from the coregistered x ray CT image. We were also able to restore the 99mTc sestamibi uptake from the reconstructed images to an accuracy between 40% and 90% of the true in vitro value, depending on the selection of maximum or mean pixel values in the regions of interest.

Kalki, Kathrin; Brown, J. Keenan; Blankespoor, Stephen C.; Heanue, Joseph A.; Wu, Xiang; Cann, Christopher E.; Hasegawa, Bruce H.; Chin, Michael; Stillson, Carol A.; Dae, Michael W.; Carver, James M.

1995-05-01

242

The Electromagnetic Spectrum: X-Rays  

NSDL National Science Digital Library

This site provided by NASA contains an introduction to X-rays and their uses in medicine and astronomy. Descriptions of the first X-ray observations, how they are used to visualize parts of the body, and results from X-ray astronomy are provided. The site contains striking astronomical images made with X-rays. Also provided are links to similar sites on the other electromagnetic spectrum regions.

2006-11-25

243

Advanced x-ray imaging spectrometer  

NASA Technical Reports Server (NTRS)

An x-ray spectrometer that also provides images of an x-ray source. Coded aperture imaging techniques are used to provide high resolution images. Imaging position-sensitive x-ray sensors with good energy resolution are utilized to provide excellent spectroscopic performance. The system produces high resolution spectral images of the x-ray source which can be viewed in any one of a number of specific energy bands.

Callas, John L. (Inventor); Soli, George A. (Inventor)

1998-01-01

244

Student X-Ray Fluorescence Experiments  

ERIC Educational Resources Information Center

Describes the experimental arrangement for x-ray analysis of samples which involves the following: the radioisotopic x-ray disk source; a student-built fluorescence chamber; the energy dispersive x-ray detector, linear amplifier and bias supply; and a multichannel pulse height analyzer. (GS)

Fetzer, Homer D.; And Others

1975-01-01

245

X-raying clumped stellar winds  

E-print Network

X-ray spectroscopy is a sensitive probe of stellar winds. X-rays originate from optically thin shock-heated plasma deep inside the wind and propagate outwards throughout absorbing cool material. Recent analyses of the line ratios from He-like ions in the X-ray spectra of O-stars highlighted problems with this general paradigm: the measured line ratios of highest ions are consistent with the location of the hottest X-ray emitting plasma very close to the base of the wind, perhaps indicating the presence of a corona, while measurements from lower ions conform with the wind-embedded shock model. Generally, to correctly model the emerging X-ray spectra, a detailed knowledge of the cool wind opacities based on stellar atmosphere models is prerequisite. A nearly grey stellar wind opacity for the X-rays is deduced from the analyses of high-resolution X-ray spectra. This indicates that the stellar winds are strongly clumped. Furthermore, the nearly symmetric shape of X-ray emission line profiles can be explained if the wind clumps are radially compressed. In massive binaries the orbital variations of X-ray emission allow to probe the opacity of the stellar wind; results support the picture of strong wind clumping. In high-mass X-ray binaries, the stochastic X-ray variability and the extend of the stellar-wind part photoionized by X-rays provide further strong evidence that stellar winds consist of dense clumps.

L. M. Oskinova; W. -R. Hamann; A. Feldmeier

2008-06-13

246

Cryotomography x-ray microscopy state  

DOEpatents

An x-ray microscope stage enables alignment of a sample about a rotation axis to enable three dimensional tomographic imaging of the sample using an x-ray microscope. A heat exchanger assembly provides cooled gas to a sample during x-ray microscopic imaging.

Le Gros, Mark (Berkeley, CA); Larabell, Carolyn A. (Berkeley, CA)

2010-10-26

247

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu Four Supernova Remnants: NASA's Chandra X-ray Observatory's Chandra X-ray Observatory, four newly processed images of supernova remnants dramatically illustrate

248

The Chandra X-ray Observatory (CXO)  

E-print Network

The Chandra X-ray Observatory (CXO) Research Program Call for Proposals Cycle 16 Due Date: 13 March 2014, 6 p.m. EDT Prepared by: Chandra X-ray Center 60 Garden Street, Cambridge, MA 02138 12 December 2013 The Chandra X-ray Center is operated for NASA by the Smithsonian Astrophysical Observatory #12;ii

249

X-Ray Absorption Spectroscopy of Metallobiomolecules  

E-print Network

9/6/09 1 X-Ray Absorption Spectroscopy of Metallobiomolecules The Outskirts of Structural Biology 6, 09] This is a tutorial about the use of X-ray Absorption Spectroscopy (XAS) in biology, RG; Eisenberger, P; Kincaid, BM "X-ray Absorption Spectroscopy of Biological Molecules" Annu. Rev

Scott, Robert A.

250

X-Ray Absorption Spectroscopy of Metallobiomolecules  

E-print Network

2/9/07 1 X-Ray Absorption Spectroscopy of Metallobiomolecules The Outskirts of Structural Biology 9, 07] This is a tutorial about the use of X-ray Absorption Spectroscopy (XAS) in biology, RG; Eisenberger, P; Kincaid, BM "X-ray Absorption Spectroscopy of Biological Molecules" Annu. Rev

Scott, Robert A.

251

Are X-Rays Safe during Pregnancy?  

MedlinePLUS

... And most of these deformities are minor, like skin tags or an extra finger or toe. Could I have another test instead of an X-ray? You might be able to have an ultrasound exam instead of an X-ray. Ultrasound, which is also called sonography, is the best alternative to an X-ray. ...

252

X-ray microbeam technology and applications  

SciTech Connect

This meeting was divided into the following sessions: x-ray microbeam focusing optics; techniques and imaging systems (such as x-ray microscopy and x-ray diffraction); applications; and poster session. Separate abstracts were prepared for 24 papers in this volume.

Yun, W. [ed.] [Argonne National Lab., IL (United States). Advanced Photon Source

1995-12-31

253

X-ray absorption microtomography (microCT) and small beam diffraction mapping of sea urchin teeth  

Microsoft Academic Search

Two noninvasive X-ray techniques, laboratory X-ray absorption microtomography (microCT) and X-ray diffraction mapping, were used to study teeth of the sea urchin Lytechinus variegatus. MicroCT revealed low attenuation regions at near the tooth’s stone part and along the carinar process—central prism boundary; this latter observation appears to be novel. The expected variation of Mg fraction x in the mineral phase

S. R. Stock; J. Barss; T. Dahl; A. Veis; J. D. Almer

2002-01-01

254

Bioabsorbable bone fixation plates for X-ray imaging diagnosis by a radiopaque layer of barium sulfate and poly(lactic-co-glycolic acid).  

PubMed

Bone fixation systems made of biodegradable polymers are radiolucent, making post-operative diagnosis with X-ray imaging a challenge. In this study, to allow X-ray visibility, we separately prepared a radiopaque layer and attached it to a bioabsorbable bone plate approved for clinical use (Inion, Finland). We employed barium sulfate as a radiopaque material due to the high X-ray attenuation coefficient of barium (2.196 cm(2) /g). The radiopaque layer was composed of a fine powder of barium sulfate bound to a biodegradable material, poly(lactic-co-glycolic acid) (PLGA), to allow layer degradation similar to the original Inion bone plate. In this study, we varied the mass ratio of barium sulfate and PLGA in the layer between 3:1 w/w and 10:1 w/w to modulate the degree and longevity of X-ray visibility. All radiopaque plates herein were visible via X-ray, both in vitro and in vivo, for up to 40 days. For all layer types, the radio-opacity decreased with time due to the swelling and degradation of PLGA, and the change in the layer shape was more apparent for layers with a higher PLGA content. The radiopaque plates released, at most, 0.5 mg of barium sulfate every 2 days in a simulated in vitro environment, which did not appear to affect the cytotoxicity. The radiopaque plates also exhibited good biocompatibility, similar to that of the Inion plate. Therefore, we concluded that the barium sulfate-based, biodegradable plate prepared in this work has the potential to be used as a fixation device with both X-ray visibility and biocompatibility. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2014. PMID:24964903

Choi, Sung Yoon; Hur, Woojune; Kim, Byeung Kyu; Shasteen, Catherine; Kim, Myung Hun; Choi, La Mee; Lee, Seung Ho; Park, Chun Gwon; Park, Min; Min, Hye Sook; Kim, Sukwha; Choi, Tae Hyun; Choy, Young Bin

2014-06-26

255

An upgraded x-ray spectroscopy diagnostic on MST.  

PubMed

An upgraded x-ray spectroscopy diagnostic is used to measure the distribution of fast electrons in MST and to determine Z(eff) and the particle diffusion coefficient D(r). A radial array of 12 CdZnTe hard-x-ray detectors measures 10-150 keV Bremsstrahlung from fast electrons, a signature of reduced stochasticity and improved confinement in the plasma. A new Si soft-x-ray detector measures 2-10 keV Bremsstrahlung from thermal and fast electrons. The shaped output pulses from both detector types are digitized and the resulting waveforms are fit with Gaussians to resolve pileup and provide good time and energy resolution. Lead apertures prevent detector saturation and provide a well-known etendue, while lead shielding prevents pickup from stray x-rays. New Be vacuum windows transmit >2?keV x-rays, and additional Al and Be filters are sometimes used to reduce low energy flux for better resolution at higher energies. Measured spectra are compared to those predicted by the Fokker-Planck code CQL3D to deduce Z(eff) and D(r). PMID:21034007

Clayton, D J; Almagri, A F; Burke, D R; Forest, C B; Goetz, J A; Kaufman, M C; O'Connell, R

2010-10-01

256

Roles of oxidative stress in synchrotron radiation X-ray-induced testicular damage of rodents  

PubMed Central

Synchrotron radiation (SR) X-ray has characteristic properties such as coherence and high photon flux, which has excellent potential for its applications in medical imaging and cancer treatment. However, there is little information regarding the mechanisms underlying the damaging effects of SR X-ray on biological tissues. Oxidative stress plays an important role in the tissue damage induced by conventional X-ray, while the role of oxidative stress in the tissue injury induced by SR X-ray remains unknown. In this study we used the male gonads of rats as a model to study the roles of oxidative stress in SR X-ray-induced tissue damage. Exposures of the testes to SR X-ray at various radiation doses did not significantly increase the lipid peroxidation of the tissues, assessed at one day after the irradiation. No significant decreases in the levels of GSH or total antioxidation capacity were found in the SR X-ray-irradiated testes. However, the SR X-ray at 40 Gy induced a marked increase in phosphorylated H2AX – a marker of double-strand DNA damage, which was significantly decreased by the antioxidant N-acetyl cysteine (NAC). NAC also attenuated the SR X-ray-induced decreases in the cell layer number of seminiferous tubules. Collectively, our observations have provided the first characterization of SR X-ray-induced oxidative damage of biological tissues: SR X-ray at high doses can induce DNA damage and certain tissue damage during the acute phase of the irradiation, at least partially by generating oxidative stress. However, SR X-ray of various radiation doses did not increase lipid peroxidation. PMID:22837810

Ma, Yingxin; Nie, Hui; Sheng, Caibin; Chen, Heyu; Wang, Ban; Liu, Tengyuan; Shao, Jiaxiang; He, Xin; Zhang, Tingting; Zheng, Chaobo; Xia, Weiliang; Ying, Weihai

2012-01-01

257

Coated x-ray filters  

DOEpatents

A radiation filter for filtering radiation beams of wavelengths within a preselected range of wavelengths comprises a radiation transmissive substrate and an attenuating layer deposited on the substrate. The attenuating layer may be deposited by a sputtering process or a vacuum process. Beryllium may be used as the radiation transmissive substrate. In addition, a second radiation filter comprises an attenuating layer interposed between a pair of radiation transmissive layers. 4 figs.

Steinmeyer, P.A.

1992-11-24

258

Coated x-ray filters  

DOEpatents

A radiation filter for filtering radiation beams of wavelengths within a preselected range of wavelengths comprises a radiation transmissive substrate and an attenuating layer deposited on the substrate. The attenuating layer may be deposited by a sputtering process or a vacuum process. Beryllium may be used as the radiation transmissive substrate. In addition, a second radiation filter comprises an attenuating layer interposed between a pair of radiation transmissive layers.

Steinmeyer, Peter A. (Farmington, NM)

1992-11-24

259

The effective attenuation coefficient of soft tissue in the presence of Compton scattering from bone: experiments on models.  

PubMed

Calibration methods are investigated for the determination of bone density by the Compton scattering method. The scattered radiation from materials of different densities and dimensions is measured for this purpose. A function for the dependence of the intensity on these parameters is derived and compared with the experimental results. The influence of the surrounding soft tissue is studied by simulation experiments with water. It is found that the 'effective attenuation coefficient' of water for the incident and scattered radiation depends on the thickness of the surrounding water layer itself, as well as on the density of the scattering material. The implications of these findings for the evaluation of bone density measurements are discussed. PMID:7454760

Leichter, I; Weinreb, A; Hazan, G

1980-07-01

260

X-ray Stacking 2008-Apr-22 Astrostats X-ray Stacking  

E-print Network

X-ray Stacking 2008-Apr-22 Astrostats X-ray Stacking Tom Aldcroft SAO/CXC #12;X-ray Stacking 2008 to gamma rays Detection efficiency of a source class (e.g. obscured active galactic nuclei) is often best analysis for a sample Stacking ­ mean properties of sample Chandra X-ray data (faint point sources

Wolfe, Patrick J.

261

Monte Carlo simulation of x-ray scatter based on patient model from digital breast tomosynthesis  

NASA Astrophysics Data System (ADS)

We are developing a breast specific scatter correction method for digital beast tomosynthesis (DBT). The 3D breast volume was initially reconstructed from 15 projection images acquired from a GE prototype tomosynthesis system without correction of scatter. The voxel values were mapped to the tissue compositions using various segmentation schemes. This voxelized digital breast model was entered into a Monte Carlo package simulating the prototype tomosynthesis system. One billion photons were generated from the x-ray source for each projection in the simulation and images of scattered photons were obtained. A primary only projection image was then produced by subtracting the scatter image from the corresponding original projection image which contains contributions from the both primary photons and scatter photons. The scatter free projection images were then used to reconstruct the 3D breast using the same algorithm. Compared with the uncorrected 3D image, the x-ray attenuation coefficients represented by the scatter-corrected 3D image are closer to those derived from the measurement data.

Liu, Bob; Wu, Tao; Moore, Richard H.; Kopans, Daniel B.

2006-03-01

262

Calibration-free quantification of interior properties of porous media with x-ray computed tomography.  

PubMed

A method is presented for interpreting the values of x-ray attenuation coefficients reconstructed in computed tomography of porous media, while overcoming the ambiguity caused by the multichromatic nature of x-rays, dilution by void, and material heterogeneity. The method enables determination of porosity without relying on calibration or image segmentation or thresholding to discriminate pores from solid material. It distinguishes between solution-accessible and inaccessible pores, and provides the spatial and frequency distributions of solid-matrix material in a heterogeneous medium. This is accomplished by matching an image of a sample saturated with a contrast solution with that saturated with a transparent solution. Voxels occupied with solid-material and inaccessible pores are identified by the fact that they maintain the same location and image attributes in both images, with voxels containing inaccessible pores appearing empty in both images. Fully porous and accessible voxels exhibit the maximum contrast, while the rest are porous voxels containing mixtures of pore solutions and solid. This matching process is performed with an image registration computer code, and image processing software that requires only simple subtraction and multiplication (scaling) processes. The process is demonstrated in dolomite (non-uniform void distribution, homogeneous solid matrix) and sandstone (nearly uniform void distribution, heterogeneous solid matrix) samples, and its overall performance is shown to compare favorably with a method based on calibration and thresholding. PMID:25576734

Hussein, Esam M A; Agbogun, H M D; Al, Tom A

2015-03-01

263

Improving chemical mapping algorithm and visualization in full-field hard x-ray spectroscopic imaging  

NASA Astrophysics Data System (ADS)

X-ray Absorption Near Edge Structure (XANES) imaging, an advanced absorption spectroscopy technique, at the Transmission X-ray Microscopy (TXM) Beamline X8C of NSLS enables high-resolution chemical mapping (a.k.a. chemical composition identification or chemical spectra fitting). Two-Dimensional (2D) chemical mapping has been successfully applied to study many functional materials to decide the percentages of chemical components at each pixel position of the material images. In chemical mapping, the attenuation coefficient spectrum of the material (sample) can be fitted with the weighted sum of standard spectra of individual chemical compositions, where the weights are the percentages to be calculated. In this paper, we first implemented and compared two fitting approaches: (i) a brute force enumeration method, and (ii) a constrained least square minimization algorithm proposed by us. Next, as 2D spectra fitting can be conducted pixel by pixel, so theoretically, both methods can be implemented in parallel. In order to demonstrate the feasibility of parallel computing in the chemical mapping problem and investigate how much efficiency improvement can be achieved, we used the second approach as an example and implemented a parallel version for a multi-core computer cluster. Finally we used a novel way to visualize the calculated chemical compositions, by which domain scientists could grasp the percentage difference easily without looking into the real data.

Chang, Cheng; Xu, Wei; Chen-Wiegart, Yu-chen Karen; Wang, Jun; Yu, Dantong

2013-12-01

264

Optical coherence tomography can assess skeletal muscle tissue from mouse models of muscular dystrophy by parametric imaging of the attenuation coefficient  

PubMed Central

We present the assessment of ex vivo mouse muscle tissue by quantitative parametric imaging of the near-infrared attenuation coefficient µt using optical coherence tomography. The resulting values of the local total attenuation coefficient µt (mean ± standard error) from necrotic lesions in the dystrophic skeletal muscle tissue of mdx mice are higher (9.6 ± 0.3 mm?1) than regions from the same tissue containing only necrotic myofibers (7.0 ± 0.6 mm?1), and significantly higher than values from intact myofibers, whether from an adjacent region of the same sample (4.8 ± 0.3 mm?1) or from healthy tissue of the wild-type C57 mouse (3.9 ± 0.2 mm?1) used as a control. Our results suggest that the attenuation coefficient could be used as a quantitative means to identify necrotic lesions and assess skeletal muscle tissue in mouse models of human Duchenne muscular dystrophy. PMID:24761302

Klyen, Blake R.; Scolaro, Loretta; Shavlakadze, Tea; Grounds, Miranda D.; Sampson, David D.

2014-01-01

265

X-ray crystal-optics  

NASA Astrophysics Data System (ADS)

Dynamic X-ray diffraction in ideal crystals and crystals with constant deformation gradients is described. X-ray diffraction theory is elaborated for transparent and absorbing crystals, with attention given to the incidence of plane monochromatic waves as well as wave packets. Particular consideration is given to Laue diffraction in transparent and absorbing crystals; Poynting vectors and the propagation of X-ray energy; the Bragg reflection of X-rays; and X-ray interferometry (including the moiretechnique). The generalized dynamic theory of diffraction in ideal and deformed crystals is also discussed.

Pinsker, Z. G.

266

X-ray holography of biological specimens  

SciTech Connect

The author reviews the reasons for x-ray imaging of biological specimens and the techniques presently being used for x-ray microscopy. The author points out the advantages of x-ray holography and the difficulties of obtaining the requisite coherence with conventional sources. The author discusses the problems of radiation damage and the remarkable fact that short pulse x-ray sources circumvent these problems and obtain high-resolution images of specimens in the living state. Finally, the author reviews some of the efforts underway to develop high-intensity coherent x-ray sources for the laboratory. 14 references, 5 figures, 2 tables.

Solem, J.C.

1984-01-01

267

X-ray lithography using holographic images  

DOEpatents

A non-contact X-ray projection lithography method for producing a desired X-ray image on a selected surface of an X-ray-sensitive material, such as photoresist material on a wafer, the desired X-ray image having image minimum linewidths as small as 0.063 .mu.m, or even smaller. A hologram and its position are determined that will produce the desired image on the selected surface when the hologram is irradiated with X-rays from a suitably monochromatic X-ray source of a selected wavelength .lambda.. On-axis X-ray transmission through, or off-axis X-ray reflection from, a hologram may be used here, with very different requirements for monochromaticity, flux and brightness of the X-ray source. For reasonable penetration of photoresist materials by X-rays produced by the X-ray source, the wavelength X, is preferably chosen to be no more than 13.5 nm in one embodiment and more preferably is chosen in the range 1-5 nm in the other embodiment. A lower limit on linewidth is set by the linewidth of available microstructure writing devices, such as an electron beam.

Howells, Malcolm R. (Berkeley, CA); Jacobsen, Chris (Sound Beach, NY)

1995-01-01

268

Near optimal energy selective x-ray imaging system performance with simple detectors  

SciTech Connect

Purpose: This article describes a method to achieve near optimal performance with low energy resolution detectors. Tapiovaara and Wagner [Phys. Med. Biol. 30, 519-529 (1985)] showed that an energy selective x-ray system using a broad spectrum source can produce images with a larger signal to noise ratio (SNR) than conventional systems using energy integrating or photon counting detectors. They showed that there is an upper limit to the SNR and that it can be achieved by measuring full spectrum information and then using an optimal energy dependent weighting. Methods: A performance measure is derived by applying statistical detection theory to an abstract vector space of the line integrals of the basis set coefficients of the two function approximation to the x-ray attenuation coefficient. The approach produces optimal results that utilize all the available energy dependent data. The method can be used with any energy selective detector and is applied not only to detectors using pulse height analysis (PHA) but also to a detector that simultaneously measures the total photon number and integrated energy, as discussed by Roessl et al. [Med. Phys. 34, 959-966 (2007)]. A generalization of this detector that improves the performance is introduced. A method is described to compute images with the optimal SNR using projections in a ''whitened'' vector space transformed so the noise is uncorrelated and has unit variance in both coordinates. Material canceled images with optimal SNR can also be computed by projections in this space. Results: The performance measure is validated by showing that it provides the Tapiovaara-Wagner optimal results for a detector with full energy information and also a conventional detector. The performance with different types of detectors is compared to the ideal SNR as a function of x-ray tube voltage and subject thickness. A detector that combines two bin PHA with a simultaneous measurement of integrated photon energy provides near ideal performance across a wide range of operating conditions. Conclusions: Low energy resolution detectors can be used in energy selective x-ray imaging systems to produce images with near optimal performance.

Alvarez, Robert E. [Aprend Technology, Mountain View, California 94043 (United States)

2010-02-15

269

Near optimal energy selective x-ray imaging system performance with simple detectors  

PubMed Central

Purpose: This article describes a method to achieve near optimal performance with low energy resolution detectors. Tapiovaara and Wagner [Phys. Med. Biol. 30, 519–529 (1985)] showed that an energy selective x-ray system using a broad spectrum source can produce images with a larger signal to noise ratio (SNR) than conventional systems using energy integrating or photon counting detectors. They showed that there is an upper limit to the SNR and that it can be achieved by measuring full spectrum information and then using an optimal energy dependent weighting. Methods: A performance measure is derived by applying statistical detection theory to an abstract vector space of the line integrals of the basis set coefficients of the two function approximation to the x-ray attenuation coefficient. The approach produces optimal results that utilize all the available energy dependent data. The method can be used with any energy selective detector and is applied not only to detectors using pulse height analysis (PHA) but also to a detector that simultaneously measures the total photon number and integrated energy, as discussed by Roessl et al. [Med. Phys. 34, 959–966 (2007)]. A generalization of this detector that improves the performance is introduced. A method is described to compute images with the optimal SNR using projections in a “whitened” vector space transformed so the noise is uncorrelated and has unit variance in both coordinates. Material canceled images with optimal SNR can also be computed by projections in this space. Results: The performance measure is validated by showing that it provides the Tapiovaara–Wagner optimal results for a detector with full energy information and also a conventional detector. The performance with different types of detectors is compared to the ideal SNR as a function of x-ray tube voltage and subject thickness. A detector that combines two bin PHA with a simultaneous measurement of integrated photon energy provides near ideal performance across a wide range of operating conditions. Conclusions: Low energy resolution detectors can be used in energy selective x-ray imaging systems to produce images with near optimal performance. PMID:20229892

Alvarez, Robert E.

2010-01-01

270

Evolution of X-ray astronomy  

NASA Technical Reports Server (NTRS)

The evolution of X-ray astronomy up to the launching of the Einstein observatory is presented. The evaluation proceeded through the following major steps: (1) discovery of an extrasolar X-ray source, Sco X-1, orders of magnitude stronger than astronomers believed might exist; (2) identification of a strong X-ray source with the Crab Nebula; (3) identification of Sco X-1 with a faint, peculiar optical object; (4) demonstration that X-ray stars are binary systems, each consisting of a collapsed object accreting matter from an ordinary star; (5) discovery of X-ray bursts; (6) discovery of exceedingly strong X-ray emission from active galaxies, quasars and clusters of galaxies; (7) demonstration that the principal X-ray source is a hot gas filling the space between galaxies.

Rossj, B.

1981-01-01

271

X ray imaging microscope for cancer research  

NASA Technical Reports Server (NTRS)

The NASA technology employed during the Stanford MSFC LLNL Rocket X Ray Spectroheliograph flight established that doubly reflecting, normal incidence multilayer optics can be designed, fabricated, and used for high resolution x ray imaging of the Sun. Technology developed as part of the MSFC X Ray Microscope program, showed that high quality, high resolution multilayer x ray imaging microscopes are feasible. Using technology developed at Stanford University and at the DOE Lawrence Livermore National Laboratory (LLNL), Troy W. Barbee, Jr. has fabricated multilayer coatings with near theoretical reflectivities and perfect bandpass matching for a new rocket borne solar observatory, the Multi-Spectral Solar Telescope Array (MSSTA). Advanced Flow Polishing has provided multilayer mirror substrates with sub-angstrom (rms) smoothnesss for the astronomical x ray telescopes and x ray microscopes. The combination of these important technological advancements has paved the way for the development of a Water Window Imaging X Ray Microscope for cancer research.

Hoover, Richard B.; Shealy, David L.; Brinkley, B. R.; Baker, Phillip C.; Barbee, Troy W., Jr.; Walker, Arthur B. C., Jr.

1991-01-01

272

On stellar X-ray emission  

NASA Technical Reports Server (NTRS)

Stellar X-ray astronomy represents an entirely new astronomical discipline which has emerged during the past five years. It lies at the crossroads of solar physics, stellar physics, and general astrophysics. The present review is concerned with the main physical problems which arise in connection with a study of the stellar X-ray data. A central issue is the extent to which the extrapolation from solar physics is justified and the definition (if possible) of the limits to such extrapolation. The observational properties of X-ray emission from stars are considered along with the solar analogy and the modeling of X-ray emission from late-type stars, the modeling of X-ray emission from early-type stars, the physics of stellar X-ray emission, stellar X-ray emission in the more general astrophysical context, and future prospects.

Rosner, R.; Golub, L.; Vaiana, G. S.

1985-01-01

273

Spectral slicing X-ray telescope  

NASA Astrophysics Data System (ADS)

Layered synthetic microstructure (LSM) X-ray optics is investigated as a system for coupling a conventional glancing incidence X-ray mirror to a high sensitivity X-ray detector. It is shown that, by the use of figured LSM optics, it is possible to magnify the X-ray image produced by the primary mirrors so as to maintain their high inherent spatial resolution. The results of theoretical and design analyses of several spectral slicing X-ray telescope systems that utilize LSM mirrors of hyperboloidal, spherical, ellipsoidal, and constant optical path aspheric configurations are presented. It is shown that the spherical LSM optics are the preferred configuration, yielding subarcsecond performance over the entire field. The Stanford/Marshall Space Flight Center Rocket X-ray Telescope, which will utilize normal incidence LSM optics to couple a Wolter-Schwarzschild primary mirror to high resolution detectors for solar X-ray/EUV studies, is discussed. Design diagrams are included.

Hoover, R. B.; Shealy, D.; Chao, S.-H.

1986-08-01

274

Developments of x-ray grating imaging and trying of multiple information fusion  

NASA Astrophysics Data System (ADS)

The present paper reviews the X-ray grating imaging systems at home and abroad from the aspects of technological characterizations and the newest researching focus. First, not only the imaging principles and the frameworks of the typical X-ray grating imaging system based on Talbot-Lau interferometry method, but also the algorithms of retrieving the signals of attenuation, refraction and small-angle scattering are introduced. Second, the system optimizing methods are discussed, which involves mainly the relaxing the requirement of high positioning resolution and strict circumstances for gratings and designing large field of view with high resolution. Third, two and four-dimensional grating-based X-ray imaging techniques are introduced. Moreover, the trends of X-ray grating based imaging technology are discussed, especially the multiple information fusions are tried with attenuation, refraction and scattering obtained synchronously.

Han, Yueping; Li, Ruihong; Jiang, Xiaolei

2014-09-01

275

Polychromatic x-ray source for diffraction apparatus using polychromatic x-rays  

Microsoft Academic Search

A polychromatic x-ray source used in a polychromatic x-ray diffraction apparatus is described. The polychromatic x-rays are cast upon a sample to be analyzed, the energies of the x-rays diffracted from the crystallographic planes of the sample are measured and the physical properties of the sample are detected on the basis of the measured energies. The polychromatic x-ray source has

Y. Fukuda; S. Kusumoto; S. Nemoto; N. Sakurama

1981-01-01

276

Observations of Compact X-Ray Binaries with the Chandra X-Ray Observatory  

NASA Technical Reports Server (NTRS)

The Chandra X-Ray Observatory Launched on July 23, 1999. The first X-ray photons were detected on August 12 of that same year. Subsequently observations with the Observatory, which features sub-arcsecond angular resolution, have revolutionized our understanding of the X-ray emitting sky providing hosts of spectacular energy-resolved images and high-resolution spectra. Here we present a brief overview of Chandra X-Ray Observatory observations of compact X-ray binaries.

Weisskopf, Martin C.

2006-01-01

277

X-ray Anomalous Scattering  

NSDL National Science Digital Library

This University of Washington Web site "is intended to serve both as an introductory tutorial to anomalous scattering and as a general tool for designing experiments based on anomalous scattering." Visitors can find a periodic table and a chart supplying X-ray absorption edge data. Students needing assistance with the concept of anomalous scattering will find the tutorial explaining the interactions of incident photons having relatively high and low energy with scattering electrons very instructive. The site also supplies users with information about Friedel's Law and MAD experiments.

278

Deriving effective atomic numbers from DECT based on a parameterization of the ratio of high and low linear attenuation coefficients  

NASA Astrophysics Data System (ADS)

Dual energy computed tomography (DECT) can provide simultaneous estimation of relative electron density ?e and effective atomic number Zeff. The ability to obtain these quantities (?e, Zeff) has been shown to benefit selected radiotherapy applications where tissue characterization is required. The conventional analysis method (spectral method) relies on knowledge of the CT scanner photon spectra which may be difficult to obtain accurately. Furthermore an approximate empirical attenuation correction of the photon spectrum through the patient is necessary. We present an alternative approach based on a parameterization of the measured ratio of low and high kVp linear attenuation coefficients for deriving Zeff which does not require the estimation of the CT scanner spectra. In a first approach, the tissue substitute method (TSM), the Rutherford parameterization of the linear attenuation coefficients was employed to derive a relation between Zeff and the ratio of the linear attenuation coefficients measured at the low and high kVp of the CT scanner. A phantom containing 16 tissue mimicking inserts was scanned with a dual source DECT scanner at 80 and 140 kVp. The data from the 16 inserts phantom was used to obtain model parameters for the relation between Zeff and \\mu \\big|_{140kVp}^{80kVp}. The accuracy of the method was evaluated with a second phantom containing 4 tissue mimicking inserts. The TSM was compared to a more complex approach, the reference tissue method (RTM), which requires the derivation of stoichiometric fit parameters. These were derived from the 16 inserts phantom scans and used to calculate CT numbers at 80 and 140 kVp for a set of tabulated reference human tissues. Model parameters for the parameterization of \\mu \\big|_{140\\;kVp}^{80\\;kVp} were estimated for this reference tissue dataset and compared to the results of the TSM. Residuals on Zeff for the reference tissue dataset for both TSM and RTM were compared to those obtained from the spectral method. The tissue substitutes were well fitted by the TSM with R2 = 0.9930. Residuals on Zeff for the phantoms were similar between the TSM and spectral methods for Zeff < 8 while they were improved by the TSM for higher Zeff. The RTM fitted the reference tissue dataset well with R2 = 0.9999. Comparing the Zeff extracted from TSM and the more complex RTM to the known values from the reference tissue dataset yielded errors of up to 0.3 and 0.15 units of Zeff respectively. The parameterization approach yielded standard deviations which were up to 0.3 units of Zeff higher than those observed with the spectral method for Zeff around 7.5. Procedures for the DECT estimation of Zeff removing the need for estimates of the CT scanner spectra have been presented. Both the TSM and the more complex RTM performed better than the spectral method. The RTM yielded the best results for the reference human tissue dataset reducing errors from up to 0.3 to 0.15 units of Zeff compared to the simpler TSM. Both TSM and RTM are simpler to implement than the spectral method which requires estimates of the CT scanner spectra.

Landry, Guillaume; Seco, Joao; Gaudreault, Mathieu; Verhaegen, Frank

2013-10-01

279

Deriving effective atomic numbers from DECT based on a parameterization of the ratio of high and low linear attenuation coefficients.  

PubMed

Dual energy computed tomography (DECT) can provide simultaneous estimation of relative electron density ?e and effective atomic number Zeff. The ability to obtain these quantities (?e, Zeff) has been shown to benefit selected radiotherapy applications where tissue characterization is required. The conventional analysis method (spectral method) relies on knowledge of the CT scanner photon spectra which may be difficult to obtain accurately. Furthermore an approximate empirical attenuation correction of the photon spectrum through the patient is necessary. We present an alternative approach based on a parameterization of the measured ratio of low and high kVp linear attenuation coefficients for deriving Zeff which does not require the estimation of the CT scanner spectra. In a first approach, the tissue substitute method (TSM), the Rutherford parameterization of the linear attenuation coefficients was employed to derive a relation between Zeff and the ratio of the linear attenuation coefficients measured at the low and high kVp of the CT scanner. A phantom containing 16 tissue mimicking inserts was scanned with a dual source DECT scanner at 80 and 140 kVp. The data from the 16 inserts phantom was used to obtain model parameters for the relation between Zeff and [Formula: see text]. The accuracy of the method was evaluated with a second phantom containing 4 tissue mimicking inserts. The TSM was compared to a more complex approach, the reference tissue method (RTM), which requires the derivation of stoichiometric fit parameters. These were derived from the 16 inserts phantom scans and used to calculate CT numbers at 80 and 140 kVp for a set of tabulated reference human tissues. Model parameters for the parameterization of [Formula: see text] were estimated for this reference tissue dataset and compared to the results of the TSM. Residuals on Zeff for the reference tissue dataset for both TSM and RTM were compared to those obtained from the spectral method. The tissue substitutes were well fitted by the TSM with R(2) = 0.9930. Residuals on Zeff for the phantoms were similar between the TSM and spectral methods for Zeff < 8 while they were improved by the TSM for higher Zeff. The RTM fitted the reference tissue dataset well with R(2) = 0.9999. Comparing the Zeff extracted from TSM and the more complex RTM to the known values from the reference tissue dataset yielded errors of up to 0.3 and 0.15 units of Zeff respectively. The parameterization approach yielded standard deviations which were up to 0.3 units of Zeff higher than those observed with the spectral method for Zeff around 7.5. Procedures for the DECT estimation of Zeff removing the need for estimates of the CT scanner spectra have been presented. Both the TSM and the more complex RTM performed better than the spectral method. The RTM yielded the best results for the reference human tissue dataset reducing errors from up to 0.3 to 0.15 units of Zeff compared to the simpler TSM. Both TSM and RTM are simpler to implement than the spectral method which requires estimates of the CT scanner spectra. PMID:24025623

Landry, Guillaume; Seco, Joao; Gaudreault, Mathieu; Verhaegen, Frank

2013-10-01

280

Fabrication of High Aspect Ratio X-ray Grating Using X-ray Lithography  

NASA Astrophysics Data System (ADS)

X-ray radiographic imaging technique has found applications in various fields. However, it is not enough to get clear X-ray images of samples with low absorbance, such as biological soft tissues. To resolve this problem, we proposed a method using an X-ray Talbot interferometer of X-ray phase imaging. In this X-ray Talbot interferometer, X-ray gratings were required to have a fine, high accuracy, high aspect ratio structure. Then, we have developed and succeeded high aspect ratio X-ray gratings with a pitch of 5.3 ?m and a height of 30 ?m using X-ray lithography technique. We discuss that the X-ray gratings having a large effective area in order to obtain imaging size of practical use in medical application. In currently study, we have fabricated the X-ray gratings with a large effective area of 60 mm×60 mm. And, we conducted X-ray phase tomography of mouse at the chest and abdominal using X-ray Talbot interferometer. As a result, we successfully observed soft tissues and high density tissues. With the aim of broadening a field of view, we try to fabricate X-ray gratings that have a pitch of below 5.3 ?m and larger area of 100 mm square. This result suggests that X-ray Talbot interferometer is a novel and simple method for phase sensitive X-ray radiography.

Noda, Daiji; Tsujii, Hiroshi; Shimada, Kazuma; Yashiro, Wataru; Momose, Atsushi; Hattori, Tadashi

281

Three-dimensional characterization of electrodeposited lithium microstructures using synchrotron X-ray phase contrast imaging.  

PubMed

The electrodeposition of metallic lithium is a major cause of failure in lithium batteries. The 3D microstructure of electrodeposited lithium 'moss' in liquid electrolytes has been characterised at sub-micron resolution for the first time. Using synchrotron X-ray phase contrast imaging we distinguish mossy metallic lithium microstructures from high surface area lithium salt formations by their contrasting X-ray attenuation. PMID:24898258

Eastwood, David S; Bayley, Paul M; Chang, Hee Jung; Taiwo, Oluwadamilola O; Vila-Comamala, Joan; Brett, Daniel J L; Rau, Christoph; Withers, Philip J; Shearing, Paul R; Grey, Clare P; Lee, Peter D

2015-01-01

282

Transportable X-ray cart  

SciTech Connect

The main body of the report summarizes the project scope, project milestones, highlights any unresolved problems encountered during the project and includes a summary of the financial information. The purpose of this CRADA was to assist Digiray Corporation in the development and evaluation of a Transportable Reverse Geometry X-Ray 0 (RGX-T) cart for aircraft inspection Scope: LLNL was to provide a review of the RGX-T engineering drawing package supplied by Digiray, suggest and incorporate design modifications, fabricate, assemble and provide performance evaluation testing of the RGX-T prototype. Major deliverables were (a) engineering design analysis and evaluation (b) cart prototype hardware, and (c) performance evaluation. Schedule: Procurement and technical delays extended the project twelve months past than the original four month project duration estimate. LLNL reviewed engineering drawings of the RGX-T prototype provided by Digiray, performed a engineering design analysis and evaluation, suggested and incorporated modifications to improve design safety factors, fabricated and assembled the prototype system, and evaluated the motion and positioning capabilities of the assembled system. The RGX-T provides a limited set of positioning orientations for the Digiray x-ray tube head that do not meet the overall Digiray requirements for aircraft inspection. In addition, mechanical stability concerns remain for positioning the tube head with the mechanical arm and for rolling the assembly with arbitrary orientation of the mechanical arm.

NONE

1995-12-01

283

Controlling X-rays With Light  

SciTech Connect

Ultrafast x-ray science is an exciting frontier that promises the visualization of electronic, atomic and molecular dynamics on atomic time and length scales. A largelyunexplored area of ultrafast x-ray science is the use of light to control how x-rays interact with matter. In order to extend control concepts established for long wavelengthprobes to the x-ray regime, the optical control field must drive a coherent electronic response on a timescale comparable to femtosecond core-hole lifetimes. An intense field is required to achieve this rapid response. Here an intense optical control pulse isobserved to efficiently modulate photoelectric absorption for x-rays and to create an ultrafast transparency window. We demonstrate an application of x-ray transparencyrelevant to ultrafast x-ray sources: an all-photonic temporal cross-correlation measurement of a femtosecond x-ray pulse. The ability to control x-ray/matterinteractions with light will create new opportunities at current and next-generation x-ray light sources.

Glover, Ernie; Hertlein, Marcus; Southworth, Steve; Allison, Tom; van Tilborg, Jeroen; Kanter, Elliot; Krassig, B.; Varma, H.; Rude, Bruce; Santra, Robin; Belkacem, Ali; Young, Linda

2010-08-02

284

Collimator for an x-ray mammography apparatus  

Microsoft Academic Search

A device for generating collimated X-ray beams is described, the device comprising: an X-ray source for emitting an input X-ray beam; a cone arranged in the input X-ray beam to receive the entire input X-ray beam, the cone blocking a portion of the input X-ray beam such that a limited output X-ray beam emerges from the cone, the output X-ray

1989-01-01

285

The Columbia University proton-induced soft x-ray microbeam  

PubMed Central

A soft x-ray microbeam using proton-induced x-ray emission (PIXE) of characteristic titanium (K? 4.5 keV) as the x-ray source has been developed at the Radiological Research Accelerator Facility (RARAF) at Columbia University. The proton beam is focused to a 120 ?m × 50 ?m spot on the titanium target using an electrostatic quadrupole quadruplet previously used for the charged particle microbeam studies at RARAF. The proton induced x-rays from this spot project a 50 ?m round x-ray generation spot into the vertical direction. The x-rays are focused to a spot size of 5 ?m in diameter using a Fresnel zone plate. The x-rays have an attenuation length of (1/e length of ~145 ?m) allowing more consistent dose delivery across the depth of a single cell layer and penetration into tissue samples than previous ultra soft x-ray systems. The irradiation end station is based on our previous design to allow quick comparison to charged particle experiments and for mixed irradiation experiments. PMID:21811347

Harken, Andrew D.; Randers-Pehrson, Gerhard; Johnson, Gary W.; Brenner, David J.

2011-01-01

286

Towards a quantitative, measurement-based estimate of the uncertainty in photon mass attenuation coefficients at radiation therapy energies.  

PubMed

In this study, a quantitative estimate is derived for the uncertainty in the XCOM photon mass attenuation coefficients in the energy range of interest to external beam radiation therapy-i.e. 100 keV (orthovoltage) to 25 MeV-using direct comparisons of experimental data against Monte Carlo models and theoretical XCOM data. Two independent datasets are used. The first dataset is from our recent transmission measurements and the corresponding EGSnrc calculations (Ali et al 2012 Med. Phys. 39 5990-6003) for 10-30 MV photon beams from the research linac at the National Research Council Canada. The attenuators are graphite and lead, with a total of 140 data points and an experimental uncertainty of ?0.5% (k = 1). An optimum energy-independent cross section scaling factor that minimizes the discrepancies between measurements and calculations is used to deduce cross section uncertainty. The second dataset is from the aggregate of cross section measurements in the literature for graphite and lead (49 experiments, 288 data points). The dataset is compared to the sum of the XCOM data plus the IAEA photonuclear data. Again, an optimum energy-independent cross section scaling factor is used to deduce the cross section uncertainty. Using the average result from the two datasets, the energy-independent cross section uncertainty estimate is 0.5% (68% confidence) and 0.7% (95% confidence). The potential for energy-dependent errors is discussed. Photon cross section uncertainty is shown to be smaller than the current qualitative 'envelope of uncertainty' of the order of 1-2%, as given by Hubbell (1999 Phys. Med. Biol 44 R1-22). PMID:25622289

Ali, E S M; Spencer, B; McEwen, M R; Rogers, D W O

2015-02-21

287

Towards a quantitative, measurement-based estimate of the uncertainty in photon mass attenuation coefficients at radiation therapy energies  

NASA Astrophysics Data System (ADS)

In this study, a quantitative estimate is derived for the uncertainty in the XCOM photon mass attenuation coefficients in the energy range of interest to external beam radiation therapy—i.e. 100 keV (orthovoltage) to 25 MeV—using direct comparisons of experimental data against Monte Carlo models and theoretical XCOM data. Two independent datasets are used. The first dataset is from our recent transmission measurements and the corresponding EGSnrc calculations (Ali et al 2012 Med. Phys. 39 5990–6003) for 10–30 MV photon beams from the research linac at the National Research Council Canada. The attenuators are graphite and lead, with a total of 140 data points and an experimental uncertainty of ?0.5% (k = 1). An optimum energy-independent cross section scaling factor that minimizes the discrepancies between measurements and calculations is used to deduce cross section uncertainty. The second dataset is from the aggregate of cross section measurements in the literature for graphite and lead (49 experiments, 288 data points). The dataset is compared to the sum of the XCOM data plus the IAEA photonuclear data. Again, an optimum energy-independent cross section scaling factor is used to deduce the cross section uncertainty. Using the average result from the two datasets, the energy-independent cross section uncertainty estimate is 0.5% (68% confidence) and 0.7% (95% confidence). The potential for energy-dependent errors is discussed. Photon cross section uncertainty is shown to be smaller than the current qualitative ‘envelope of uncertainty’ of the order of 1–2%, as given by Hubbell (1999 Phys. Med. Biol 44 R1–22).

Ali, E. S. M.; Spencer, B.; McEwen, M. R.; Rogers, D. W. O.

2015-02-01

288

Modeling contamination migration on the Chandra X-Ray Observatory  

NASA Technical Reports Server (NTRS)

During its first 5 years of operation, the cold (-60 C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), on board the Chandra X-ray Observatory, has accumulated a contaminating layer that attenuates the low-energy x rays. To assist in assessing the likelihood of successfully baking off the contaminant, members of the Chandra Team developed contamination-migration simulation software. The simulation follows deposition onto and (temperature-dependent) vaporization from surfaces comprising a geometrical model of the Observatory. A separate thermal analysis, augmented by on-board temperature monitoring, provides temperatures for each surface of the same geometrical model. This paper describes the physical basis for the simulations, the methodologies, and the predicted migration of the contaminant for various bake-out scenarios and assumptions.

O'Dell, Stephen L.; Swartz, Douglas A.; Anderson, Scot K.; Chen, Kenny C.; Giordano, Rino J.; Knollenberg, Perry J.; Morris, Peter A.; Plucinsky, Paul P.; Tice, Neil W.; Tran, Hien

2005-01-01

289

Silicon Refractive optics for hard X-rays  

NASA Astrophysics Data System (ADS)

X-rays refractive optics has made a real success in a hard radiation domain promising for many applications. An analysis made of refractive materials properties, which are most suitable for this new kind of X-ray focusing optics shows that in silicon refraction effects prevail on attenuation. A wide variety of technologies dedicated to microstructure formation on Si make it as a most suitable one. Using electron beam lithography and deep plasma etching planar parabolic profiles are produced with the focal distance 1 m on 17.4 keV radiation. They are tested on synchrotron radiation at beamline X47 SPRING-8. Experiments carried out open the way to construct kinoform refracting profiles, which exceed simple parabolas in gain and aperture. A number of kinoform profiles on silicon is created for energies up to 50 keV, which at apertures 2 mm have calculated gain up to 5000. Some focusing properties of such planar refracting profiles are discussed.

Aristov, V.; Firsov, A.; Grigoriev, M.; Ishikawa, T.; Kikuta, S.; Kohmura, Y.; Kuznetsov, S.; Shabelnikov, L.; Yunkin, V.

2000-05-01

290

Determination of photon attenuation coefficient, porosity and field capacity of soil by gamma-ray transmission for 60, 356 and 662 keV gamma rays.  

PubMed

Gamma-ray transmission methods have been used accurately for the study of the properties of soil in the agricultural purposes. In this study, photon attenuation coefficient, porosity and field capacity of soil are determined by using gamma-ray transmission method. To this end, the soil sample was collected from Erzurum and a 2 x 2 in NaI (Tl) scintillation detector measured the attenuation of strongly collimated monoenergetic gamma beam through soil sample. The radioactive sources used in the experiment were (241)Am, (133)Ba and (137)Cs. The mass attenuation coefficients of dry soil samples were calculated from the transmission measurements. The soil samples were irrigated by adding known quantities of water and the soil-water properties were examined. It was observed that gamma-ray transmission method for determination of the soil parameters has advantages such as practical, inexpensive, non-destructive and fast analysis. PMID:18554919

Demir, D; Un, A; Ozgül, M; Sahin, Y

2008-12-01

291

Surface sensitive X-ray scattering  

SciTech Connect

This paper explores the application of x-ray scattering to the study of surface structures. While there are several approaches to this problem, the most successful use some variant of the grazing incidence x-ray scattering approach (GIXS). In the GIXS approach x-rays impinge on the sample at a small grazing angle ({phi}) and are detected at a combination of an in-plane scattering angle (2 {theta}) and a second grazing angle ({phi}). We begin with a summary of x-ray scattering theory with particular emphasis on the modifications required for surface sensitive measurements. Second, we cover the experimental aspects of surface sensitive x-ray scattering, particularly the x-ray sources and experimental equipment. Finally, we describe the application of these ideas and concepts to the study of a few, illustrative experiments. We note that this chapter is not intended to be a comprehensive review of the literature.

Fuoss, P.H. (AT and T Bell Lab., Holmdel, NJ (US)); Brennan, S. (Stanford Synchrotron Radiation Lab., Stanford, CA (US))

1990-01-01

292

X-ray FE line studies  

NASA Technical Reports Server (NTRS)

We present the first broadband, moderate-resolution X-ray spectral observations of the Seyfert galaxies NGC 4151 and NGC 1068. The Seyfert 1 galaxy NGC 4151 is shown to have a complex X-ray spectrum with multiple components and a strong, intrinsically narrow Fe K emission line. The characteristics of the scattering medium of the Seyfert 2 galaxy NGC 1068 are determined using the very strong Fe line emission and the lack of features due to oxygen in the X-ray spectrum. The soft X-ray flux from Mrk 3 and Mrk 348 are consistent with that expected from electron scattered X-rays from an obscured Seyfert 1 nucleus. A survey of the X-ray properties of Seyfert 2 galaxies indicates that a substantial fraction may have column densities of about 10 exp 23, suggesting that NGC 1068 has an unusually thick obscuring torus.

Marshall, F. E.; Arnaud, K.; Boldt, E. A.; Holt, S. S.; Jahoda, K. M.; Kelley, R.; Mushotzky, R. F.; Netzer, H.; Petre, R.; Serlemitsos, P. J.

1992-01-01

293

Synchrotron x-ray microbeam characteristics for x-ray fluorescence analysis  

SciTech Connect

X-ray fluorescence analysis using a synchrotron x-ray microprobe has become an indispensable technique for non-destructive micro-analysis. One of the most important parameters that characterize the x-ray microbeam system for x-ray fluorescence analysis is the beam size. For practical analysis, however, the photon flux, the energy resolution and the available energy range are also crucial. Three types of x-ray microbeam systems, including monochromatic and continuum excitation systems, were compared with reference to the sensitivity, the minimum detection limit and the applicability to various types of x-ray spectroscopic analysis. 16 refs., 5 figs.

Iida, Atsuo; Noma, Takashi [National Laboratory for High Energy Physics, Ibaraki (Japan)

1995-12-31

294

Industrial X-Ray Imaging  

NASA Technical Reports Server (NTRS)

In 1990, Lewis Research Center jointly sponsored a conference with the U.S. Air Force Wright Laboratory focused on high speed imaging. This conference, and early funding by Lewis Research Center, helped to spur work by Silicon Mountain Design, Inc. to break the performance barriers of imaging speed, resolution, and sensitivity through innovative technology. Later, under a Small Business Innovation Research contract with the Jet Propulsion Laboratory, the company designed a real-time image enhancing camera that yields superb, high quality images in 1/30th of a second while limiting distortion. The result is a rapidly available, enhanced image showing significantly greater detail compared to image processing executed on digital computers. Current applications include radiographic and pathology-based medicine, industrial imaging, x-ray inspection devices, and automated semiconductor inspection equipment.

1997-01-01

295

X-ray microlaminography with polycapillary optics  

SciTech Connect

We demonstrate layer-by-layer x-ray microimaging using polycapillary optics. The depth resolution is achieved without sample or source rotation and in a way similar to classical tomography or laminography. The method takes advantage from large angular apertures of polycapillary optics and from their specific microstructure, which is treated as a coded aperture. The imaging geometry is compatible with polychromatic x-ray sources and with scanning and confocal x-ray fluorescence setups.

Dabrowski, K. M.; Dul, D. T.; Wrobel, A.; Korecki, P. [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)] [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

2013-06-03

296

The X-ray Polarimeter Experiment (XPE)  

Microsoft Academic Search

Polarimetric studies will provide a new probe of cosmic x-ray sources, supplying important clues to source geometries and emission mechanisms. However, at the present time there is only one measurement of x-ray polarization from a cosmic source, the OSO-8 detection of 19% linear polarization from the Crab Nebula. We propose a new low cost x-ray polarimeter experiment (XPE), ideally sized

R. F. Elsner; B. D. Ramsey; S. L. O'dell; M. Sulkanen; A. F. Tennant; M. C. Weisskopf; S. Gunji; T. Minamitani; R. A. Austin; J. Kolodziejczak; D. Swartz; G. Garmire; P. Meszaros; G. G. Pavlov

1997-01-01

297

Lobster-Eye X-Ray Astronomy  

NASA Astrophysics Data System (ADS)

We report on technical and astrophysical aspects of Lobster-Eye wide-field X-ray telescopes expected to monitor the sky with high sensitivity and angular resolution of order of 1 arcmin. They will contribute essentially to study of various astrophysical objects such as AGN, SNe, Gamma-ray bursts (GRBs), X-ray flashes (XRFs), galactic binary sources, stars, CVs, X-ray novae, various transient sources, etc.

Hudec, R.; Pina, L.; Marsikova, V.; Inneman, A.

2010-07-01

298

X-ray transmissive debris shield  

DOEpatents

A composite window structure is described for transmitting x-ray radiation and for shielding radiation generated debris. In particular, separate layers of different x-ray transmissive materials are laminated together to form a high strength, x-ray transmissive debris shield which is particularly suited for use in high energy fluences. In one embodiment, the composite window comprises alternating layers of beryllium and a thermoset polymer.

Spielman, Rick B. (Albuquerque, NM)

1994-01-01

299

Lobster-Eye X-Ray Astronomy  

SciTech Connect

We report on technical and astrophysical aspects of Lobster-Eye wide-field X-ray telescopes expected to monitor the sky with high sensitivity and angular resolution of order of 1 arcmin. They will contribute essentially to study of various astrophysical objects such as AGN, SNe, Gamma-ray bursts (GRBs), X-ray flashes (XRFs), galactic binary sources, stars, CVs, X-ray novae, various transient sources, etc.

Hudec, R. [Astronomical Institute, AS CR, 25165 Ondrejov (Czech Republic); Czech Technical University in Prague, Faculty of Electrical Engineering (Czech Republic); Pina, L. [Czech Technical Universiry in Prague, Faculty of Nuclear Science, Prague (Czech Republic); Rigaku Innovative Technologies Europe, Prague (Czech Republic); Marsikova, V.; Inneman, A. [Rigaku Innovative Technologies Europe, Prague (Czech Republic)

2010-07-15

300

Topological X-Rays and MRIs  

ERIC Educational Resources Information Center

Let K be a compact subset of the interior of the unit disk D in the plane and suppose one can't see through the boundary of D and identify K. However, assume that one can take "topological X-rays" of D which measure the "density" of K along the lines of the X-rays. By taking these X-rays from all directions, a "topological MRI" is generated for…

Lynch, Mark

2002-01-01

301

A Plethora of X-ray Telescopes  

NSDL National Science Digital Library

This explanation describes the observatories we are currently using to study X-rays from space. Chandra, named for Nobel prize winner Subrahmanyan Chandrasekhar, was launched from the space shuttle in 1999. Current X-ray observatories include The Rossi X-ray Timing Explorer (RXTE), named after astronomer Bruno Rossi, and The Advanced Satellite for Cosmology and Astrophysics (ASCA). The site also discusses what observatories we will use in the coming years to explore the structure and evolution of the Universe.

302

MICROQUASARS AND X-RAY NOVAE  

E-print Network

Part I MICROQUASARS AND X-RAY NOVAE allbook.tex; 15/11/2000; 21:23; p.1 #12; 2 allbook.tex; 15/11/2000; 21:23; p.2 #12; Recent results on X-ray novae and microquasars at radio and infrared wavelengths and infrared wavelengths have provided a sig- ni#12;cant contribution to our knowledge of X-ray novae

Greiner, Jochen

303

X-Ray and Particle Emission Techniques  

Microsoft Academic Search

\\u000a The short wavelengths and high energy of X-rays make them a highly versatile form of electromagnetic radiation. Several analytical\\u000a techniques utilize the interaction of X-rays with a substance, or their emission from excited atoms, to gain information about\\u000a sample composition. This chapter describes the production of X-rays and analytical techniques that in some way employ the\\u000a use or analysis of

Mary E. Malainey

304

X-raying clumped stellar winds  

Microsoft Academic Search

X-ray spectroscopy is a sensitive probe of stellar winds. X-rays originate from optically thin shock-heated plasma deep inside the wind and propagate outwards throughout absorbing cool material. Recent analyses of the line ratios from He-like ions in the X-ray spectra of O-stars highlighted problems with this general paradigm: the measured line ratios of highest ions are consistent with the location

Lidia M. Oskinova; Wolf-Rainer Hamann; Achim Feldmeier

2008-01-01

305

Novel space communication technology based on modulated x-ray source  

NASA Astrophysics Data System (ADS)

A novel space communication method is presented in this paper based on X-ray photons. As a result of its short wavelength and great penetrability, X-ray has no attenuation for transmission in space when its photon energy is more than 10keV (?<0.1nm). Thus a communication technology of long distance signal transmission in space can be achieved with smaller volume, lower weight and lower power. Therefore, X-ray communication (XCOM) is especially valuable to the deep space missions, which will be able to realize higher data rates, smaller SWAP than with RF and laser communications. Using X-ray photons as information carrier will not only be a good complement to laser and RF communications, but will also have unique applications when RF and laser signals are not available like the spacecraft's re-entering to the earth. High-speed modulation and high-sensitivity detection of X-rays are two major technical issues which should be addressed in order for the X-ray communication to take place. A Grid-controlled Modulated X-ray tube (GMXT) is proposed and developed as X-ray transmitter. One or more specially designed grid electrodes are added to the traditional X-ray tube to modulate the electrons. The communication signal is coded and applied to the modulated grid electrode, and then the corresponding X-ray signals are generated and sent out. X-ray detector based on micro-channel plate(MCP) is used as communication receiver because of its high temporal resolution. An audio communication experiment system based on XCOM is setup in laboratory including the X-ray transmitter and the receiver. X-ray communication is successfully demonstrated and the communication speed reaches 64 kilobits per second in a vacuum tube of 6 meters long. As a new concept of space communication, X-ray communication will have more important scientific significance and application prospects when technologies for X-ray modulation and detection are further developed.

Sheng, Li-zhi; Zhao, Bao-sheng; Liu, Yong-an

2014-09-01

306

X-rays from Massive StarsX-rays from Massive Stars David CohenDavid Cohen  

E-print Network

X-rays from Massive StarsX-rays from Massive Stars David CohenDavid Cohen Swarthmore CollegeSwarthmore College #12;X-ray spectroscopy of hot plasmasX-ray spectroscopy of hot plasmas temperature, density: shock-heating and X-ray emissionshock-heating and X-ray emission with Stan Owocki (U. Del.)with Stan

Cohen, David

307

X-ray laser frequency near-doubling and generation of tunable coherent x rays in plasma  

E-print Network

X-ray laser frequency near-doubling and generation of tunable coherent x rays in plasma P. L plasmas in which efficient x-ray laser frequency near-doubling is expected for a number of available x-ray of coherent x rays and tunable optical radiation may result in tunable coherent x-ray radiation powerful

Kaplan, Alexander

308

Ultrashort X-ray pulse science  

SciTech Connect

A variety of phenomena involves atomic motion on the femtosecond time-scale. These phenomena have been studied using ultrashort optical pulses, which indirectly probe atomic positions through changes in optical properties. Because x-rays can more directly probe atomic positions, ultrashort x-ray pulses are better suited for the study of ultrafast structural dynamics. One approach towards generating ultrashort x-ray pulses is by 90{sup o} Thomson scattering between terawatt laser pulses and relativistic electrons. Using this technique, the author generated {approx} 300 fs, 30 keV (0.4 {angstrom}) x-ray pulses. These x-ray pulses are absolutely synchronized with ultrashort laser pulses, allowing femtosecond optical pump/x-ray probe experiments to be performed. Using the right-angle Thomson scattering x-ray source, the author performed time-resolved x-ray diffraction studies of laser-perturbated InSb. These experiments revealed a delayed onset of lattice expansion. This delay is due to the energy relaxation from a dense electron-hole plasma to the lattice. The dense electron-hole plasma first undergoes Auger recombination, which reduces the carrier concentration while maintaining energy content. Longitudinal-optic (LO) phonon emission then couples energy to the lattice. LO phonon decay into acoustic phonons, and acoustic phonon propagation then causes the growth of a thermally expanded layer. Source characterization is instrumental in utilizing ultrashort x-ray pulses in time-resolved x-ray spectroscopies. By measurement of the electron beam diameter at the generation point, the pulse duration of the Thomson scattered x-rays is determined. Analysis of the Thomson scattered x-ray beam properties also provides a novel means of electron bunch characterization. Although the pulse duration is inferred for the Thomson scattering x-ray source, direct measurement is required for other x-ray pulse sources. A method based on the laser-assisted photoelectric effect (LAPE) has been demonstrated as a means of measuring ultrashort x-ray pulse durations. LAPE may also serve as the basis for a gated x-ray detector.

Chin, A.H. [Univ. of California, Berkeley, CA (US). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (US). Materials Science Div.

1998-05-01

309

Bent crystal X-ray topography  

NASA Technical Reports Server (NTRS)

A television X-ray topographic camera system was constructed. The system differs from the previous system in that it incorporates the X-ray TV imaging system and has a semi-automatic wafer loading system. Also the X-ray diffraction is in a vertical plane. This feature makes wafer loading easier and makes the system compatible with any commercial X-ray generating system. Topographs and results obtained from a study of the diffraction contrast variation with impurity concentration for both boron implanted and boron diffused silicon are included.

Parker, D. L.

1978-01-01

310

Compound refractive X-ray lens  

DOEpatents

An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

Nygren, David R. (Berkeley, CA); Cahn, Robert (Walnut Creek, CA); Cederstrom, Bjorn (Traellborg, SE); Danielsson, Mats (Stocksund, SE); Vestlund, Jonas (Stockholm, SE)

2000-01-01

311

X-ray laser microscope apparatus  

DOEpatents

A microscope consisting of an x-ray contact microscope and an optical microscope. The optical, phase contrast, microscope is used to align a target with respect to a source of soft x-rays. The source of soft x-rays preferably comprises an x-ray laser but could comprise a synchrotron or other pulse source of x-rays. Transparent resist material is used to support the target. The optical microscope is located on the opposite side of the transparent resist material from the target and is employed to align the target with respect to the anticipated soft x-ray laser beam. After alignment with the use of the optical microscope, the target is exposed to the soft x-ray laser beam. The x-ray sensitive transparent resist material whose chemical bonds are altered by the x-ray beam passing through the target mater GOVERNMENT LICENSE RIGHTS This invention was made with government support under Contract No. De-FG02-86ER13609 awarded by the Department of Energy. The Government has certain rights in this invention.

Suckewer, Szymon (Princeton, NJ); DiCicco, Darrell S. (Plainsboro, NJ); Hirschberg, Joseph G. (Coral Gables, FL); Meixler, Lewis D. (East Windsor, NJ); Sathre, Robert (Princeton, NJ); Skinner, Charles H. (Lawrenceville, NJ)

1990-01-01

312

X-rays from supernova 1987A  

NASA Technical Reports Server (NTRS)

Detailed calculations of the development of the X-ray spectrum of 1987A are presented using more realistic models for the supernova composition and density structure provided by Woosley. It is shown how the emergence of the X-ray spectrum depends on the parameters of the model and the nature of its central energy source. It is shown that the soft X-ray spectrum should be dominated by a 6.4 keV Fe K(alpha) emission line that could be observed by a sensitive X-ray telescope.

Xu, Yueming; Sutherland, Peter; Mccray, Richard; Ross, Randy R.

1988-01-01

313

An Imaging X-Ray Polarimetry Mission  

NASA Technical Reports Server (NTRS)

Technical progress both in x-ray optics and in polarization-sensitive x-ray detectors, which our groups have pioneered, enables a scientifically powerful---yet inexpensive---dedicated mission for imaging x-ray polarimetry. Such a mission is sufficiently sensitive to measure x-ray (linear) polarization for a broad range of cosmic sources --particularly those involving neutron stars, stellar black holes, and supermassive black holes (active galactic nuclei). We describe the technical elements, discuss a mission concept, and synopsize the important physical and astrophysical questions such a mission would address.

Weisskopf, Martin C.; Bellazini, Ronaldo; Costa, Enrico; Ramsey, Brian; O'Dell, Steve; Elsner, Ronald; Pavlov, George; Matt, Giorgio; Kaspi, Victoria; Tennant, Allyn; Coppi, Paolo; Wu, Kinwah; Siegmund, Oswald

2008-01-01

314

An Imaging X-Ray Polarimetry Mission  

NASA Technical Reports Server (NTRS)

Technical progress both in x-ray optics and in polarization-sensitive x-ray detectors, which our groups have pioneered, enables a scientifically powerful - yet inexpensive - dedicated mission for imaging x-ray polarimetry. Such a mission is sufficiently sensitive to measure x-ray (linear) polarization for a broad range of cosmic sources --- particularly those involving neutron stars, stellar black holes, and supermassive black holes (active galactic nuclei). We describe the technical elements, discuss a mission concept, and synopsiz:e the important physical and astrophysical questions such as mission would address.

Weisskopf, Martin C.; Bellazini, Ronaldo; Costa, Enrico; Ramsey, Brian; O'Dell, Steve; Tennant, Allyn; Elsner, Ronald; Pavlov, George; Matt, Girogio; Kaspi, Vicky; Coppi, Paolo; Wu, Kinwah; Siegmund, Oswald

2008-01-01

315

MODIS-based retrieval of suspended sediment concentration and diffuse attenuation coefficient in Chinese estuarine and coastal waters  

NASA Astrophysics Data System (ADS)

Radiative transfer modelling in atmosphere, water, and on the air-water surface was used to create an algorithm and computer code for satellite monitoring Chinese estuarine and coastal waters. The atmospheric part of the algorithm is based on the Reference Evaluation of Solar Transmittance (REST) model for calculation of optical properties of the atmosphere from the top of the atmosphere to the target; for modelling optical properties from target towards satellite's sensor, an optical reciprocity principle has been used. An algorithm uses estimates derived from three different sources: 1) the MODIS-based software; 2) radiative transfer equations, and 3) well-known empirical relationships between measured parameters and optical depths and transmittances for such atmospheric components as molecules, aerosols, ozone, nitrogen dioxide, precipitable water vapor and uniformly mixed gases. Using this model allowed us to derive a reliable relationship relating an important parameter, the diffuse-to-global solar incoming irradiance ratio, to the aerosol optical thickness, solar zenith angle and wavelength. The surface and underwater parts of the algorithm contained theoretical and semi-empirical relationships between inherent (such as absorption, scattering and backscattering coefficients) and apparent (remote-sensing reflectance and diffuse attenuation coefficient, Kd) optical properties, and suspended sediment concentration (SSC) measured in the Yangtze River Estuary and its adjacent coastal area. The first false colour maps of SSC and Kd demonstrated a well accordance with the multi-year field observations in the region, and suggest promise for use of this algorithm for the regular monitoring of Chinese and worldwide natural waters.

Sokoletsky, Leonid; Yang, Xianping; Shen, Fang

2014-11-01

316

X-ray induced reduction effects at CeO sub 2 surfaces: An x-ray photoelectron spectroscopy study  

SciTech Connect

XPS techniques are used to study the effects of Al {ital K}{alpha} x-rays on the surface chemical composition of CeO{sub 2}. We find that prolonged exposures cause the formation of some Ce{sup 3+} oxidic species at the surface. We have studied the Ce 3{ital p}, Ce 3{ital d}, O 1{ital s}, Ce 4{ital p}, Ce 4{ital d}, and valence band regions in an attempt to localize the depth of damage. Consideration of published formulations for electron attenuation lengths and electron inelastic mean free paths indicates that the chemical reduction occurs mainly in the first 15--20 A from the surface. Our results show that some of the XPS features, usually referred to as excited electronic states of ceria, are in fact induced by prolonged exposures to the x rays.

Paparazzo, E. (Istituto di Struttura della Materia del CNR, Via E. Fermi 38, 00044 Frascati, Italy (IT)); Ingo, G.M. (Istituto di Teoria e Struttura Elettronica, Area della Ricerca di Roma del CNR, Via Salaria km 29.500, 00016 Monterotondo, Italy (IT)); Zacchetti, N. (Centro Sviluppo Materiali S.p.A., Casella Postale 10747, Roma-Eur, Roma, Italy (IT))

1991-05-01

317

Statistical data of X-ray emission from laboratory sparks  

NASA Astrophysics Data System (ADS)

In this study we present a summary of the data of 1331 long laboratory sparks in atmospheric pressure intended for a statistical analysis. A 2 MV, 17kJ Marx generator were used to generate 1.2/52?s shape pulses positive and negative polarity. The generator was connected to a spark gap with cone-shaped electrodes. The distance between high-voltage and grounded electrodes was 1.08 meters. Breakdown voltage between electrodes was about 1MV. X-rays have been detected during the development of the discharge channel. The currents through the grounded electrode and through the high-voltage electrode were recorded separately and simultaneously with the voltage and the X-ray signal. X-rays were registered by two LaBr3(Ce+) scintillation detectors in different positions with respect to the forming discharge channel. Detector D1 was placed immediately under the grounded electrode at 15cm distance. Detector D2 was placed at horizontal distances of 143cm and 210cm, at mid-gap height. We also used lead shields of 1.5, 3, and 4 mm thickness for radiation attenuation measurements. For detector collimation we used shields up to 2 cm thickness. Also no metallic objects with pointed surfaces were present within 2 m from the spark gap. Typical plot of positive discharge presented in Figure 1a. Table 1 shows the summary of the X-ray registrations. Signal detection occurred significantly more for positive polarity discharges than for negative. This dependence was observed for both detectors. For detector D2 the probability of X-ray registration decreased proportional to 1/d2 with increasing the distance d to the breakdown gap from 1m43 to 2m10. Detailed energy spectra and time distribution of X-ray emission were obtained; see for example Fig. 1b. For both polarities of the high voltage, the X-rays only occurred when there was a current at the cathode.

Kochkin, P.; Deursen, D. V.

2011-12-01

318

A New Technique for In Situ X-ray Microtomography Under High Pressure  

NASA Astrophysics Data System (ADS)

We have developed a new technique for in situ synchrotron microtomography to study texture evolution in multi-phase specimens under high pressure and temperature. Two critical issues in performing tomography experiments under pressure are (1) the limited X-ray access to the sample because of the highly absorbing materials, such as tungsten carbide and tool steel, typically used in the pressure vessel and (2) a high pressure compatible rotation mechanism to collect projections of the sample continuously from 0 to 180° . We addressed these issues by (1) employing an opposed-anvil high pressure cell, known as the Drickamer cell, with an X-ray transparent containment ring, to allow panoramic X-ray access, and (2) rotating the Dricakmer cell by Harmonic DriveTM gear reducers, with thrust bearings supporting the hydraulic load. The design of the rotation mechanism benefited from the rotational deformation apparatus developed by Yamazaki and Karato (Rev. Sci. Instrum., 72, 4207, 2001). We report results obtained from a test run performed under pressure with monochromatic synchrotron radiation. A sapphire sphere (1.0 mm dia.) was embedded in a powdered mixture of Fe and 9 wt.% S alloy. The diameter of the sample chamber was 2 mm. Under pressure, the entire Drickamer cell was rotated to collect radiographs of the sample at various angles from 0 to 179.5° in 0.5° step size. Computational reconstruction of these projections provided three dimensional (3D) distribution of linear attenuation coefficient of the sample with a spatial resolution of 6 microns. The shape change in the sapphire sphere during compression was clearly observed. Using the program Blob3d, reconstructed 3D images of the sphere were separated from the surrounding Fe-S alloy. Volumes of the sphere were then accurately determined from the extracted images, by carefully defining the image intensity threshold. The errors in the volume measurement are about 0.3 to 0.7%, mostly due to shadowing by anvil deformation. The results, although performed using a solid sample, demonstrate the potential of measuring melt volume. Previous density measurements using X-ray radiography with only one dimensional data assumed that the shape of the sample remained unchanged throughout the experiment. In our new technique, this assumption is no longer required and density of melts can be inferred directly from the sample volume even when the molten sample is distorted. Other applications of this apparatus will be also discussed.

Uchida, T.; Wang, Y.; Westferro, F.; Gebhardt, J.; Rivers, M. L.; Sutton, S. R.

2004-12-01

319

X-rays from Saturn Pose Puzzles  

NASA Astrophysics Data System (ADS)

The first clear detection of X-rays from the giant, gaseous planet Saturn has been made with NASA's Chandra X-ray Observatory. Chandra's image shows that the X-rays are concentrated near Saturn's equator, a surprising result since Jupiter's X-ray emission is mainly concentrated near the poles. Existing theories cannot easily explain the intensity or distribution of Saturn's X-rays. Chandra observed Saturn for about 20 hours in April of 2003. The spectrum, or distribution with energy of the X-rays, was found to be very similar to that of X-rays from the Sun. "This indicates that Saturn's X-ray emission is due to the scattering of solar X-rays by Saturn's atmosphere," said Jan-Uwe Ness, of the University of Hamburg in Germany and lead author of a paper discussing the Saturn results in an upcoming issue of Astronomy & Astrophysics. "It's a puzzle, since the intensity of Saturn's X-rays requires that Saturn reflects X-rays fifty times more efficiently than the Moon." The observed 90 megawatts of X-ray power from Saturn's equatorial region is roughly consistent with previous observations of the X-radiation from Jupiter's equatorial region. This suggests that both giant, gaseous planets reflect solar X-rays at unexpectedly high rates. Further observations of Jupiter will be needed to test this possibility. The weak X-radiation from Saturn's south-polar region presents another puzzle (the north pole was blocked by Saturn's rings during this observation). Saturn's magnetic field, like that of Jupiter, is strongest near the poles. X-radiation from Jupiter is brightest at the poles because of auroral activity due to the enhanced interaction of high-energy particles from the Sun with its magnetic field. Since spectacular ultraviolet polar auroras have been observed to occur on Saturn, Ness and colleagues expected that Saturn's south pole might be bright in X-rays. It is not clear whether the auroral mechanism does not produce X-rays on Saturn, or for some reason concentrates the X-rays at the north pole. "Another interesting result of the observation is that Saturn's rings were not detected in X-rays," noted Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, a coauthor of the paper. "This requires Saturn's rings to be less efficient at scattering X-rays than the planet itself." The same team detected X-radiation from Saturn using the European Space Agency's XMM-Newton Observatory. Although these observations could not locate the X-rays on Saturn's disk, the intensity of the observed X-rays was very similar to what was found with Chandra and consistent with a marginal detection of X-rays from Saturn reported in 2000 using the German Roentgensatellite (ROSAT). The research team, which used Chandra's ACIS instrument to observed Saturn, also included J. Schmitt (Univ. of Hamburg) as well as Konrad Dennerl and Vadim Burwitz (Max Planck Institute, Garching Germany). NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

2004-03-01

320

Wide field x-ray telescopes: Detecting x-ray transients/afterglows related to GRBs  

SciTech Connect

The recent discovery of X-ray afterglows of GRBs opens the possibility of analyses of GRBs by their X-ray detections. However, imaging X-ray telescopes in current use mostly have limited fields of view. Alternative X-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70's but not constructed and used so far. We review the geometries and basic properties of the wide-field X-ray optical systems based on one- and two-dimensional lobster-eye geometry and suggest technologies for their development and construction. First results of the development of double replicated X-ray reflecting flats for use in one-dimensional X-ray optics of lobster-eye type are presented and discussed. The optimum strategy for locating GRBs upon their X-ray counterparts is also presented and discussed.

Hudec, Rene [Astronomical Institute of Czech Academy of Science, Observatory Ondrejov, 251 65 Ondrejov (Czech Republic); Pina, Ladislav [Faculty of Nuclear Engineering, Czech Technical University, Prague (Czech Republic); Inneman, Adolf [Department of Precision Mechanics and Optics, Faculty of Mechanical Engineering, Czech Technical University, Prague (Czech Republic); Gorenstein, Paul [Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts (United States)

1998-05-16

321

Chandra X-Ray Observatory Computer Rendering  

NASA Technical Reports Server (NTRS)

This is a computer rendering of the fully developed Chandra X-Ray Observatory (CXO), formerly Advanced X-Ray Astrophysics Facility (AXAF). In 1999, the AXAF was renamed the CXO in honor of the late Indian-American Novel Laureate Subrahmanyan Chandrasekhar. The CXO is the most sophisticated and the world's most powerful x-ray telescope ever built. It is designed to observe x-rays from high energy regions of the Universe, such as hot gas in the renmants of exploded stars. It produces picture-like images of x-ray emissions analogous to those made in visible light, as well as gathers data on the chemical composition of x-ray radiating objects. The CXO helps astronomers world-wide better understand the structure and evolution of the universe by studying powerful sources of x-ray such as exploding stars, matter falling into black holes, and other exotic celestial objects. The Observatory has three major parts: (1) the x-ray telescope, whose mirrors will focus x-rays from celestial objects; (2) the science instruments that record the x-rays so that x-ray images can be produced and analyzed; and (3) the spacecraft, which provides the environment necessary for the telescope and the instruments to work. TRW, Inc. was the prime contractor for the development of the CXO and NASA's Marshall Space Flight Center was responsible for its project management. The Smithsonian Astrophysical Observatory controls science and flight operations of the CXO for NASA from Cambridge, Massachusetts. The Observatory was launched July 22, 1999 aboard the Space Shuttle Columbia, STS-93 mission. (Image courtesy of TRW).

1998-01-01

322

X-ray Diffraction (XRD) 1.0 What is X-ray Diffraction  

E-print Network

X-ray Diffraction (XRD) · 1.0 What is X-ray Diffraction · 2.0 Basics of Crystallography · 3.0 Production of X-rays · 4.0 Applications of XRD · 5.0 Instrumental Sources of Error · 6.0 Conclusions #12 why the cleavage faces of crystals appear to reflect X-ray beams at certain angles of incidence (theta

Moeck, Peter

323

Quantification and normalization of x-ray mammograms  

NASA Astrophysics Data System (ADS)

The analysis of (x-ray) mammograms remains qualitative, relying on the judgement of clinicians. We present a novel method to compute a quantitative, normalized measure of tissue radiodensity traversed by the primary beam incident on each pixel of a mammogram, a measure we term the standard attenuation rate (SAR). SAR enables: the estimation of breast density which is linked to cancer risk; direct comparison between images; the full potential of computer aided diagnosis to be utilized; and a basis for digital breast tomosynthesis reconstruction. It does this by removing the effects of the imaging conditions under which the mammogram is acquired. First, the x-ray spectrum incident upon the breast is calculated, and from this, the energy exiting the breast is calculated. The contribution of scattered radiation is calculated and subtracted. The SAR measure is the scaling factor that must be applied to the reference material in order to match the primary attenuation of the breast. Specifically, this is the scaled reference material attenuation which when traversed by an identical beam to that traversing the breast, and when subsequently detected, results in the primary component of the pixel intensity observed in the breast image. We present results using two tissue equivalent phantoms, as well as a sensitivity analysis to detector response changes over time and possible errors in compressed thickness measurement.

Tromans, Christopher E.; Cocker, Mary R.; Brady, Michael, Sir

2012-10-01

324

X-Ray Imaging Study  

NASA Technical Reports Server (NTRS)

The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the currently estimated integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 1O(exp 10) electrons/sq cm/day and the proton integral fluence is above 1 x 10(exp 9) protons/sq cm/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionally less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of this combined environment is the issue which needs to be understood for the long term exposure of structures in space. At the same time, there will be substantial potential for collisions between the space platforms and space debris. The current NASA catalogue contains over 4500 objects floating in space which are not considered payloads. This debris can have significant effects on collision with orbiting spacecraft. In order to better understand the effect of these hostile phenomena on spacecraft, several types of studies are being performed to simulate at some level the effect of the environment. In particular the study of debris clouds produced by hypervelocity impact on the various surfaces anticipated on the Space Station is very important at this point in time. The need to assess the threat of such debris clouds on space structures is an on-going activity. The Space Debris Impact facility in Building 4612 provides a test facility to monitor the types of damage produced with hypervelocity impact. These facilities are used to simulate space environmental effects from energetic particles. Flash radiography or x-ray imaging has traditionally provided such information and as such has been an important tool for recording damage in situ with the event. The proper operation of the system can provide much useful information with respect to parametric analysis of the hypervelocity experiment. The following report outlines the procedures developed to optimize the operation of the x-ray imaging system and its operational characteristics.

OBrien, Susan K.; Workman, Gary L.

1996-01-01

325

Small x-ray telescope based on lobster eye x-ray optics and pixel detector  

NASA Astrophysics Data System (ADS)

Two experimental modules of small X-ray telescopes based on the Lobster eye X-ray optics are presented. These modules are regarded to use for x-ray astronomy applications in space. At this time, the optical tests of these modules have been performed. Results of these tests are presented.

Tichý, Vladimír; Hrom?ík, Martin; Hudec, René; Inneman, Adolf; Jakubek, Jan; Maršík, Ji?í; Pína, Ladislav; Semencová, Veronika; Švéda, Libor

2009-05-01

326

The Advanced X-ray Astrophysics Facility. Observing the universe in X-rays  

NASA Technical Reports Server (NTRS)

An overview of the Advanced X ray Astronophysics Facility (AXAF) program is presented. Beginning with a brief introduction to X ray astrophysics, the AXAF observatory is described including the onboard instrumentation and system capabilities. Possible X ray sources suitable for AXAF observation are identified and defined.

Neal, V.

1984-01-01

327

X-Ray Exam: Scoliosis (For Parents)  

MedlinePLUS

What It Is A scoliosis X-ray is a relatively safe and painless test that uses a small amount of radiation to create detailed images ... recorded on a computer or special film. The scoliosis X-ray includes the thoracic spine (upper back) ...

328

X-ray imaging: Status and trends  

Microsoft Academic Search

There is a veritable renaissance occurring in x-ray imaging. X-ray imaging by radiography has been a highly developed technology in medicine and industry for many years. However, high resolution imaging has not generally been practical because sources have been relatively dim and diffuse, optical elements have been nonexistent for most applications, and detectors have been slow and of low resolution.

R. W. Ryon; H. E. Martz; J. M. Hernandez; J. J. Haskins; R. A. Day; J. M. Brase; B. Cross; D. Wherry

1987-01-01

329

Nearly Anastigmatic X-Ray Telescope  

NASA Technical Reports Server (NTRS)

Proposed X-ray telescope made of many concentric reflecting rings, each of which consists of two portions of cone. Proposed design is variation on conventional grazing incidence X-ray telescope, which has just one twosegment reflecting element but suffers from excessive astigmatism and field curvature. Using many short elements instead of single long element, new design gives nearly anastigmatic image.

Korsch, D.

1985-01-01

330

Coccidioidomycosis - chest x-ray (image)  

MedlinePLUS

This chest x-ray shows the affects of a fungal infection, coccidioidomycosis. In the middle of the left lung (seen on the ... defined borders. Other diseases that may explain these x-ray findings include lung abscesses, chronic pulmonary tuberculosis, chronic ...

331

Adenocarcinoma - chest x-ray (image)  

MedlinePLUS

This chest x-ray shows adenocarcinoma of the lung. There is a rounded light spot in the right upper lung (left side ... density. Diseases that may cause this type of x-ray result would be tuberculous or fungal granuloma, and ...

332

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu ESO 137-001: A spiral galaxy in the Norma cluster over, & the Hubble Heritage Team (STScI/AURA) Caption: This composite image from the Chandra X-ray Observatory (blue

333

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu IGR J11014-6103: A pulsar moving at supersonic speeds is seen in this composite image that contains X-ray data from Chandra (purple), radio data from the ACTA

334

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu Flame Nebula: A star cluster in the center of the Flame 2024, in X-rays from Chandra (purple) and infrared data from Spitzer Space Telescope (red, green

335

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu NGC 2392: A Sun-like star in its end phase of life about. This composite image of NGC 2392 contains X-ray data from Chandra in pink showing the location of million

336

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu NGC 4258 (M106): A spiral galaxy, also known as M106 shows the galaxy in X-rays from Chandra (blue), radio waves from the VLA (purple), optical data from

337

Chandra X-ray Observatory Center  

E-print Network

Chandra X-ray Observatory Center Harvard-Smithsonian Center for Astrophysics 60 Garden St. Cambridge, MA 02138 USA http://chandra.harvard.edu Coma Cluster: A collection of thousands of galaxies about's Chandra X-ray Observatory and ESA's XMM-Newton. A specially processed Chandra image (pink) has been

338

Subpicosecond Coherent Manipulation of X-Rays  

SciTech Connect

The Takagi-Taupin theory is synthesized with the eikonal theory in a unified space-time approach, based upon microscopic electromagnetism. It is designed specifically to address x-ray diffraction in crystal structures being modified within down to a few femtosconds. Possible applications in the subpicosecond coherent manipulation of x-rays are given.

Adams, Bernhard W. [Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439 (United States)

2004-05-12

339

X-ray Analysis of Unknown Minerals  

NSDL National Science Digital Library

In this exercise, students use X-ray analysis to identify unknown minerals. They are given two samples to grind up and X-ray, using Jade to identify them. Once the minerals are identified, students make a spreadsheet and do a series of calculations.

Dexter Perkins

340

Aortic rupture, chest x-ray (image)  

MedlinePLUS

... from the heart) can be seen on a chest x-ray. In this case, it was caused by a ... of the thoracic aorta. This is how the x-ray appears when the chest is full of blood (right-sided hemothorax) seen ...

341

X-ray Emission from Massive Stars  

E-print Network

the Sun - magnetic activity, x-ray spectra b. Hot stars c. Radiation-driven winds and the Doppler shift d #12;Spectra: continuum vs. line Visible solar spectrum: continuum, from surface X-ray/EUV solar spectrum: emission lines from hot, thin gas above the surface #12;This hot plasma is related to magnetic

Cohen, David

342

X-ray determination of parts alignment  

NASA Technical Reports Server (NTRS)

A method for determining the alignment of adjoining metal objects is provided. The method comprises producing an X-ray image of adjoining surfaces of the two metal objects. The X-ray beam is tangential to the point the surfaces are joined. The method is particularly applicable where the alignment of the two metal objects is not readily susceptible to visual inspection.

Nelson, C. W.

1985-01-01

343

Compact flash X-ray units  

Microsoft Academic Search

Flash X-ray units are used to diagnose pulsed power driven experiments on the Pegasus machine at Los Alamos. Several unique designs of Marx powered flash X-ray units have been developed to meet the requirements of the Pegasus experiments. All of these units are compact, battery powered, fiber optically controlled, and EMP shielded. Some of these units are operated with a

D. Platts; M. P. Hockaday; D. Beck; W. Coulter; R. C. Smith

1995-01-01

344

A calculation model for primary intensity distributions from cylindrically symmetric x-ray lenses.  

PubMed

A calculation model for the quantitative prediction of primary intensity fluence distributions obtained by the Bragg diffraction focusing of kilovoltage radiation by cylindrical x-ray lenses is presented. The mathematical formalism describes primary intensity distributions from cylindrically-symmetric x-ray lenses, with a planar isotropic radiation source located in a plane perpendicular to the lens axis. The presence of attenuating medium inserted between the lens and the lens focus is accounted for by energy-dependent attenuation. The influence of radiation scattered within the media is ignored. Intensity patterns are modeled under the assumption that photons that are not interacting with the lens are blocked out at any point of interest. The main characteristics of the proposed calculation procedure are that (i) the application of vector formalism allows universal treatment of all cylindrical lenses without the need of explicit geometric constructs; (ii) intensity distributions resulting from x-ray diffraction are described by a 3D generalization of the mosaic spread concept; (iii) the calculation model can be immediately coupled to x-ray diffraction simulation packages such as XOP and Shadow. Numerical simulations based on this model are to facilitate the design of focused orthovoltage treatment (FOT) systems employing cylindrical x-ray lenses, by providing insight about the influence of the x-ray source and lens parameters on quantities of dosimetric interest to radiation therapy. PMID:18199899

Hristov, Dimitre; Maltz, Jonathan

2008-02-01

345

A calculation model for primary intensity distributions from cylindrically symmetric x-ray lenses  

NASA Astrophysics Data System (ADS)

A calculation model for the quantitative prediction of primary intensity fluence distributions obtained by the Bragg diffraction focusing of kilovoltage radiation by cylindrical x-ray lenses is presented. The mathematical formalism describes primary intensity distributions from cylindrically-symmetric x-ray lenses, with a planar isotropic radiation source located in a plane perpendicular to the lens axis. The presence of attenuating medium inserted between the lens and the lens focus is accounted for by energy-dependent attenuation. The influence of radiation scattered within the media is ignored. Intensity patterns are modeled under the assumption that photons that are not interacting with the lens are blocked out at any point of interest. The main characteristics of the proposed calculation procedure are that (i) the application of vector formalism allows universal treatment of all cylindrical lenses without the need of explicit geometric constructs; (ii) intensity distributions resulting from x-ray diffraction are described by a 3D generalization of the mosaic spread concept; (iii) the calculation model can be immediately coupled to x-ray diffraction simulation packages such as XOP and Shadow. Numerical simulations based on this model are to facilitate the design of focused orthovoltage treatment (FOT) systems employing cylindrical x-ray lenses, by providing insight about the influence of the x-ray source and lens parameters on quantities of dosimetric interest to radiation therapy.

Hristov, Dimitre; Maltz, Jonathan

2008-02-01

346

Differential X-ray phase-contrast imaging with a grating interferometer using a laboratory X-ray micro-focus tube  

NASA Astrophysics Data System (ADS)

X-ray phase-contrast imaging can provide images with much greater soft-tissue contrast than conventional absorption-based images. In this paper, we describe differential X-ray phase-contrast images of insect specimens that were obtained using a grating-based Talbot interferometer and a laboratory X-ray source with a spot size of a few tens of micrometers. We developed the interferometer on the basis of the wavelength, periods, and height of the gratings; the field of view depends on the size of the grating, considering the refractive index of the specimen. The phase-contrast images were acquired using phase-stepping methods. The phase contrast imaging provided a significantly enhanced soft-tissue contrast compared with the attenuation data. The contour of the sample was clearly visible because the refraction from the edges of the object was strong in the differential phase-contrast image. Our results demonstrate that a grating-based Talbot interferometer with a conventional X-ray tube may be attractive as an X-ray imaging system for generating phase images. X-ray phase imaging obviously has sufficient potential and is expected to soon be a great tool for medical diagnostics.

Yoon, Kwon-Ha; Ryu, Jong Hyun; Jung, Chang Won; Ryu, Cheol Woo; Kim, Young Jo; Kwon, Young Man; Park, Miran; Cho, Seungryong; Chon, Kwon Su

2014-12-01

347

Borman effect in resonant diffraction of X-rays  

SciTech Connect

A dynamic theory of resonant diffraction (occurring when the energy of incident radiation is close to the energy of the absorption edge of an element in the composition of a given substance) of synchronous X-rays is developed in the two-wave approximation in the coplanar Laue geometry for large grazing angles in perfect crystals. A sharp decrease in the absorption coefficient in the substance with simultaneously satisfied diffraction conditions (Borman effect) is demonstrated, and the theoretical and first experimental results are compared. The calculations reveal the possibility of applying this approach in analyzing the quadrupole-quadrupole contribution to the absorption coefficient.

Oreshko, A. P., E-mail: ap.oreshko@physics.msu.ru [Moscow State University (Russian Federation)

2013-08-15

348

Instrument Development for X-Ray Astronomy  

NASA Technical Reports Server (NTRS)

Current x-ray observatories such as Chandra and XMM-Newton have delivered spectacular results at soft-x-ray energies thanks to their grazing incidence mirrors. To continue these advances necessitates the development of mirrors with even larger collecting areas, yet within manageable weights and budgets, and focal detectors with improved energy resolution. At higher energies where x-ray critical-grazing angles become very small, x-ray optics have typically not been employed and thus this region remains relatively unexplored at high sensitivity levels and fine angular resolutions. This situation is changing with the development of hard-x-ray optics carried aloft by high-altitude balloons, which promise to bring about dramatic advances. This presentation will review developments in all these areas.

Ramsey, Brian; Whitaker, Ann F. (Technical Monitor)

2001-01-01

349

Solar x ray astronomy rocket program  

NASA Technical Reports Server (NTRS)

The dynamics were studied of the solar corona through the imaging of large scale coronal structures with AS&E High Resolution Soft X ray Imaging Solar Sounding Rocket Payload. The proposal for this program outlined a plan of research based on the construction of a high sensitivity X ray telescope from the optical and electronic components of the previous flight of this payload (36.038CS). Specifically, the X ray sensitive CCD camera was to be placed in the prime focus of the grazing incidence X ray mirror. The improved quantum efficiency of the CCD detector (over the film which had previously been used) allows quantitative measurements of temperature and emission measure in regions of low x ray emission such as helmet streamers beyond 1.2 solar radii or coronal holes. Furthermore, the improved sensitivity of the CCD allows short exposures of bright objects to study unexplored temporal regimes of active region loop evolution.

1990-01-01

350

SMM X-ray polychromator  

NASA Technical Reports Server (NTRS)

The range of observing and analysis programs accomplished with the X-Ray Polychromator (XRP) instruments during the decline of solar cycle 21 and the rise of the solar cycle 22 is summarized. Section 2 describes XRP operations and current status. This is meant as a guide on how the instrument is used to obtain data and what its capabilities are for potential users. The science section contains a series of representative abstracts from recently published papers on major XRP science topics. It is not meant to be a complete list but illustrates the type of science that can come from the analysis of the XRP data. There then follows a series of appendixes that summarize the major data bases that are available. Appendix A is a complete bibliography of papers and presentations produced using XRP data. Appendix B lists all the spectroscopic data accumulated by the Flat Crystal Spectrometer (FCS). Appendix C is a compilation of the XRP flare catalogue for events equivalent to a GOES C-level flare or greater. It lists the start, peak and end times as well as the peak Ca XIX flux.

Strong, Keith T.; Haisch, Bernhard M. (compiler); Lemen, James R. (compiler); Acton, L. W.; Bawa, H. S.; Claflin, E. S.; Freeland, S. L.; Slater, G. L.; Kemp, D. L.; Linford, G. A.

1988-01-01

351

SN X-ray Progenitor?  

NASA Technical Reports Server (NTRS)

Identifying stars that explode, right before they explode, is a tricky proposition since the end of starlife comes swiftly: in thermonuclear deflagrations, in nuclear exhaustion, or maybe in a rapid swirling merger of two dead stellar cores. On the right in the image above is an image of the galaxy NGC 1404 taken by the UV/optical Telescope (UVOT) on the Swift observatory. The circle surrounds SN 2007on, a supernova of Type Ia produced by the explosion of a white dwarf star in a binary system. These types of supernovae are important since they are believed to be 'standard candles', events which have the same intrinsic brightness which can serve as an important yardstick to measure cosmic distances. On the left is an image of the same galaxy taken by the Chandra X-ray observatory four years before the supernova. Conspicuous in the SN source circle is a bright source in the Chandra image, believed to be emission from a compact object+normal star companion: a similar system to the supposed precursor of SN 2007on. If true this would be the first time a Type Ia supernova precursor has ever been seen. But astronomers are still debating whether the Chandra source really is the precursor or not; it seems there's a slight but significant difference in the location of the Chandra source and the supernova. Stay tuned for more developments.

2008-01-01

352

X-ray satellite (Rosat)  

NASA Technical Reports Server (NTRS)

An overview of the current status of the ROSAT X-Ray satellite project is given. Areas discussed include an overview of problem areas, systems and mechanical subsystems, the electrical subsystem, power supply, data processing and transmission, the wide field camera, ground support equipment and the production scheduling. It is shown that the project is proceeding according to schedule, including the hardware production and costs. However, it is stated that estimated additional costs will exceed the plan. The previous schedule for production of the flight model will no longer be met. A modified milestone plan has been worked out with Dornier Systems. The current working schedule calls for a launch data of December 21, 1987; however, this does not take into account a 4-week buffer prior to transporting the flight model to the launch site. As of the date of this report, milestone M5 has been met. Previous problems with the gold vapor deposition on the flight model mirror due to contamination have been eliminated.

1986-01-01

353

JOURNAL DE PHYSIQUE CoZZoque C7, supptdment a u n07, Tome 40, JuiZZet 1979, page C7-853 RAYLnGH AND COMPTON XATTEFUNGCROSS SECTIOUS OF X-RAYS BY OXYGENIONS  

E-print Network

scattering are widely used in plasma diagnostic [I) .The X-rays and gamma rays attenuation and energy cross sections for X-rays absorption at energies above 1 keV can be written as the sum of all partial cross sections for the photoelec- tric effect, for Rayleigh and Compton scattering. X-rays and gamma

Boyer, Edmond

354

Computed tomography of x-ray index of refraction using the diffraction enhanced imaging method.  

PubMed

Diffraction enhanced imaging (DEI) is a new, synchrotron-based, x-ray radiography method that uses monochromatic, fan-shaped beams, with an analyser crystal positioned between the subject and the detector. The analyser allows the detection of only those x-rays transmitted by the subject that fall into the acceptance angle (central part of the rocking curve) of the monochromator/analyser system. As shown by Chapman et al, in addition to the x-ray attenuation, the method provides information on the out-of-plane angular deviation of x-rays. New images result in which the image contrast depends on the x-ray index of refraction and on the yield of small-angle scattering, respectively. We implemented DEI in the tomography mode at the National Synchrotron Light Source using 22 keV x-rays, and imaged a cylindrical acrylic phantom that included oil-filled, slanted channels. The resulting 'refraction CT image' shows the pure image of the out-of-plane gradient of the x-ray index of refraction. No image artefacts were present, indicating that the CT projection data were a consistent set. The 'refraction CT image' signal is linear with the gradient of the refractive index, and its value is equal to that expected. The method, at the energy used or higher, has the potential for use in clinical radiography and in industry. PMID:10795982

Dilmanian, F A; Zhong, Z; Ren, B; Wu, X Y; Chapman, L D; Orion, I; Thomlinson, W C

2000-04-01

355

Quantitative Measurements of X-ray Intensity  

SciTech Connect

This chapter describes the characterization of several X-ray sources and their use in calibrating different types of X-ray cameras at National Security Technologies, LLC (NSTec). The cameras are employed in experimental plasma studies at Lawrence Livermore National Laboratory (LLNL), including the National Ignition Facility (NIF). The sources provide X-rays in the energy range from several hundred eV to 110 keV. The key to this effort is measuring the X-ray beam intensity accurately and traceable to international standards. This is accomplished using photodiodes of several types that are calibrated using radioactive sources and a synchrotron source using methods and materials that are traceable to the U.S. National Institute of Standards and Technology (NIST). The accreditation procedures are described. The chapter begins with an introduction to the fundamental concepts of X-ray physics. The types of X-ray sources that are used for device calibration are described. The next section describes the photodiode types that are used for measuring X-ray intensity: power measuring photodiodes, energy dispersive photodiodes, and cameras comprising photodiodes as pixel elements. Following their description, the methods used to calibrate the primary detectors, the power measuring photodiodes and the energy dispersive photodiodes, as well as the method used to get traceability to international standards are described. The X-ray source beams can then be measured using the primary detectors. The final section then describes the use of the calibrated X-ray beams to calibrate X-ray cameras. Many of the references are web sites that provide databases, explanations of the data and how it was generated, and data calculations for specific cases. Several general reference books related to the major topics are included. Papers expanding some subjects are cited.

Haugh, M. J., Schneider, M.

2011-09-01

356

Multimodal hard X-ray imaging of a mammography phantom at a compact synchrotron light source  

PubMed Central

The Compact Light Source is a miniature synchrotron producing X-rays at the interaction point of a counter-propagating laser pulse and electron bunch through the process of inverse Compton scattering. The small transverse size of the luminous region yields a highly coherent beam with an angular divergence of a few milliradians. The intrinsic monochromaticity and coherence of the produced X-rays can be exploited in high-sensitivity differential phase-contrast imaging with a grating-based interferometer. Here, the first multimodal X-ray imaging experiments at the Compact Light Source at a clinically compatible X-ray energy of 21?keV are reported. Dose-compatible measurements of a mammography phantom clearly demonstrate an increase in contrast attainable through differential phase and dark-field imaging over conventional attenuation-based projections. PMID:22713884

Schleede, Simone; Bech, Martin; Achterhold, Klaus; Potdevin, Guillaume; Gifford, Martin; Loewen, Rod; Limborg, Cecile; Ruth, Ronald; Pfeiffer, Franz

2012-01-01

357

Diffraction-Enhanced Imaging of Musculoskeletal Tissues Using a Conventional X-Ray Tube  

SciTech Connect

DEI based on a conventional x-ray tube allows the visualization of skeletal and soft tissues simultaneously. Although more in-depth testing and optimization of the DEI setup must be carried out, these data demonstrate a proof of principle for further development of the technology for future clinical imaging. In conventional projection radiography, cartilage and other soft tissues do not produce enough radiographic contrast to be distinguishable from each other. Diffraction-enhanced imaging (DEI) uses a monochromatic x-ray beam and a silicon crystal analyzer to produce images in which attenuation contrast is greatly enhanced and x-ray refraction at tissue boundaries can be detected. The aim of this study was to test the efficacy of conventional x-ray tube-based DEI for the detection of soft tissues in experimental samples.

Muehleman, C.; Li, J; Connor, D; Parham, C; Pisano, E; Zhong, Z

2009-01-01

358

Large area soft x-ray collimator to facilitate x-ray optics testing  

NASA Technical Reports Server (NTRS)

The first objective of this program is to design a nested conical foil x-ray optic which will collimate x-rays diverging from a point source. The collimator could then be employed in a small, inexpensive x-ray test stand which would be used to test various x-ray optics and detector systems. The second objective is to demonstrate the fabrication of the x-ray reflectors for this optic using lacquer-smoothing and zero-stress electroforming techniques.

Espy, Samuel L.

1994-01-01

359

Time-resolved x-ray diffraction with subpicosecond x-ray pulses  

Microsoft Academic Search

The emission from plasmas created with fs-lasers provides sub-picosecond x-ray pulses in the keV-range. Intense emission of K(alpha) lines as well as quasi continuum x-rays can be used for time-resolved diffraction and spectroscopy, i.e. to study lattice or atomic dynamics with sub-picosecond resolution by using a laser pump x-ray probe technique. The x-ray yield and x-ray pulse duration of the

Ingo Uschmann; Eckhart Foerster; Paul Gibbon; Christian Reich; Thomas Feurer; Andreas Morak; Roland A. Sauerbrey; Antoine Rousse; Patrick Audebert; Jean-Paul Geindre; Jean-Claude J. Gauthier

2001-01-01

360

Modeling Broadband X-ray Absorption of Massive Star Winds  

NASA Astrophysics Data System (ADS)

We present a method for computing the net transmission of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming that the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes that all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength-dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral interstellar medium (ISM) tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype can largely be understood as a wind absorption effect.

Leutenegger, Maurice A.; Cohen, David H.; Zsargó, Janos; Martell, Erin M.; MacArthur, James P.; Owocki, Stanley P.; Gagné, Marc; Hillier, D. John

2010-08-01

361

Bulk sensitive hard x-ray photoemission electron microscopy  

NASA Astrophysics Data System (ADS)

Hard x-ray photoelectron spectroscopy (HAXPES) has now matured into a well-established technique as a bulk sensitive probe of the electronic structure due to the larger escape depth of the highly energetic electrons. In order to enable HAXPES studies with high lateral resolution, we have set up a dedicated energy-filtered hard x-ray photoemission electron microscope (HAXPEEM) working with electron kinetic energies up to 10 keV. It is based on the NanoESCA design and also preserves the performance of the instrument in the low and medium energy range. In this way, spectromicroscopy can be performed from threshold to hard x-ray photoemission. The high potential of the HAXPEEM approach for the investigation of buried layers and structures has been shown already on a layered and structured SrTiO3 sample. Here, we present results of experiments with test structures to elaborate the imaging and spectroscopic performance of the instrument and show the capabilities of the method to image bulk properties. Additionally, we introduce a method to determine the effective attenuation length of photoelectrons in a direct photoemission experiment.

Patt, M.; Wiemann, C.; Weber, N.; Escher, M.; Gloskovskii, A.; Drube, W.; Merkel, M.; Schneider, C. M.

2014-11-01

362

On the Design of Wide-Field X-ray Telescopes  

NASA Technical Reports Server (NTRS)

X-ray telescopes having a relatively wide field-of-view and spatial resolution vs. polar off-axis angle curves much flatter than the parabolic dependence characteristic of Wolter I designs are of great interest for surveys of the X-ray sky and potentially for study of the Sun s X-ray emission. We discuss the various considerations affecting the design of such telescopes, including the possible use of polynomial mirror surface prescriptions, a method of optimizing the polynomial coefficients, scaling laws for mirror segment length vs. intersection radius, the loss of on-axis spatial resolution, and the positioning of focal plane detectors.

Elsner, Ronald F.; O'Dell, Stephen L.; Ramsey, Brian D.; Weiskopf, Martin C.

2009-01-01

363

Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size  

SciTech Connect

Lawrence Livermore National Laboratory (LLNL) is currently investigating various approaches to minimize the x-ray source size on the Flash X-Ray (FXR) linear induction accelerator in order to improve x-ray flux and increase resolution for hydrodynamic radiography experiments. In order to effectively gauge improvements to final x-ray source size, a fast, robust, and accurate system for measuring the spot size is required. Timely feedback on x-ray source size allows new and improved accelerator tunes to be deployed and optimized within the limited run-time constraints of a production facility with a busy experimental schedule; in addition, time-resolved measurement capability allows the investigation of not only the time-averaged source size, but also the evolution of the source size, centroid position, and x-ray dose throughout the 70 ns beam pulse. Combined with time-resolved measurements of electron beam parameters such as emittance, energy, and current, key limiting factors can be identified, modeled, and optimized for the best possible spot size. Roll-bar techniques are a widely used method for x-ray source size measurement, and have been the method of choice at FXR for many years. A thick bar of tungsten or other dense metal with a sharp edge is inserted into the path of the x-ray beam so as to heavily attenuate the lower half of the beam, resulting in a half-light, half-dark image as seen downstream of the roll-bar; by measuring the width of the transition from light to dark across the edge of the roll-bar, the source size can be deduced. For many years, film has been the imaging medium of choice for roll-bar measurements thanks to its high resolution, linear response, and excellent contrast ratio. Film measurements, however, are fairly cumbersome and require considerable setup and analysis time; moreover, with the continuing trend towards all-electronic measurement systems, film is becoming increasingly difficult and expensive to procure. Here, we shall discuss an x-ray source size measurement system which utilizes a traditional roll-bar setup combined with a high resolution gated CCD camera, fast-response organic plastic scintillator, and image processing and analysis software, which is executable on a standard PC running which is executable on a standard PC running LabVIEW and Matlab. Analysis time is reduced from several hours to several minutes, while our experimental results demonstrate good agreement with both traditional film-based roll-bar measurements as well as the entirely unrelated technique of x-ray pinhole camera measurements; in addition, our time-resolved measurements show a significant variation in source size throughout the 70 ns beam pulse, a phenomenon which requires further investigation and indicates the possibility of greatly improving final spot size.

Jacob, J; Ong, M; Wargo, P

2005-07-21

364

X-ray/EUV optics for astronomy and microscopy  

SciTech Connect

The proceedings of this book are organized under the following headings: X-Ray/EUV zone plates, filters, and windows; X-Ray/EUV microscopes, telescopes, and monochromators; Design, characterization and test of multilayer optics; Fabrication of x-ray/EUV multilayer optics; Design, characterization, and test of grazing incidence x-ray optics; Fabrication of grazing incidence x-ray optics; X-ray/EUV space observations and missions; Test and calibration of x-ray/EUV instruments; X-ray polarimetry; X-ray/EUV spectroscopy and instruments.

Hoover, R.B.

1989-01-01

365

Scintillating ribbon x-ray detector  

SciTech Connect

A patent in the early 1970`s by Aerojet Corporation in Sacramento, CA put forth the idea of using an array of scintillating fibers for x-ray detection and imaging. In about 1975, Pratt and Whitney Aircraft in East Hartford, CT designed and manufactured an imaging system based on the patent. The device was 1.75 in thick in the direction of the x-ray beam and about 4 in. by 4 in. square. The device was used with a 8 MeV x-ray source to image and measure internal clearances within operating aircraft, gas turbines engines. There are significant advantages of fiber optic detectors in x-ray detection. However, the advantages are often outweighed by the disadvantages. Two of the advantages of scintillating fiber optic x-ray detectors are: (1) high limiting spatial frequency -- between 20 and 25 lp/mm; and (2) excellent x-ray stopping power -- they can be made thick and retain spatial resolution. In traditional fiber optic detectors the x-rays are oriented parallel to the long axis of the fiber. For the scintillating ribbon x-ray sensor, the x-rays are oriented normal to the fiber long axis. This ribbon sensor technique has a number of advantages over the two current radiographic techniques digital x-radiography and x-ray film: The main advantage the ribbon has is size and shape. It can be as thin as 0.05 in., virtually any width or length, and flexible. Once positioned in a given location, 20 to 100 square inches of the object being inspected can be imaged with a single x-ray beam sweep. It is clear that conventional digital cameras do not lend themselves to placement between walls of aircraft structures or similar items requiring x-ray inspections. A prototype scintillating ribbon x-ray sensor has been fabricated and tested by Synergistic Detector Designs. Images were acquired on corrosion test panels of aluminum fabricated by Iowa State University.

Kinchen, B.E. [BK Science and Engineering, Fremont, CA (United States); Rogers, A. [Synergistic Detector Designs, Sunnyvale, CA (United States)

1995-12-31

366

X-ray scatter tomography using coded apertures  

NASA Astrophysics Data System (ADS)

This work proposes and studies a new field of x-ray tomography which combines the principles of scatter imaging and coded apertures, termed "coded aperture x-ray scatter imaging" (CAXSI). Conventional x-ray tomography reconstructs an object's electron density distribution by measuring a set of line integrals known as the x-ray transform, based physically on the attenuation of incident rays. More recently, scatter imaging has emerged as an alternative to attenuation imaging by measuring radiation from coherent and incoherent scattering. The information-rich scatter signal may be used to infer density as well as molecular structure throughout a volume. Some scatter modalities use collimators at the source and detector, resulting in long scan times due to the low efficiency of scattering mechanisms combined with a high degree of spatial filtering. CAXSI comes to the rescue by employing coded apertures. Coded apertures transmit a larger fraction of the scattered rays than collimators while also imposing structure to the scatter signal. In a coded aperture system each detector is sensitive to multiple ray paths, producing multiplexed measurements. The coding problem is then to design an aperture which enables de-multiplexing to reconstruct the desired physical properties and spatial distribution of the target. In this work, a number of CAXSI systems are proposed, analyzed, and demonstrated. One-dimensional "pencil" beams, two-dimensional "fan" beams, and three-dimensional "cone" beams are considered for the illumination. Pencil beam and fan beam CAXSI systems are demonstrated experimentally. The utility of energy-integrating (scintillation) detectors and energy-sensitive (photon counting) detectors are evaluated theoretically, and new coded aperture designs are presented for each beam geometry. Physical models are developed for each coded aperture system, from which resolution metrics are derived. Systems employing different combinations of beam geometry, coded apertures, and detectors are analyzed by constructing linear measurement operators and comparing their singular value decompositions. Since x-ray measurements are typically dominated by photon "shot" noise, iterative algorithms based on Poisson statistics are used to perform the reconstructions. This dissertation includes previously published and unpublished co-authored material.

MacCabe, Kenneth P.

367

Recent X-ray Variability of Eta Car Approaching The X-ray Eclipse  

NASA Technical Reports Server (NTRS)

We discuss recent X-ray spectral variability of the supermassive star Eta Car in the interval since the last X-ray eclipse in 1998. We concentrate on the interval just prior to the next X-ray eclipse which is expected to occur in June 2003. We compare the X-ray behavior during the 2001-2003 cycle with the previous cycle (1996-1998) and note similarities and differences in the temporal X-ray behavior. We also compare a recent X-ray observation of Eta Car obtained with the Chandra high energy transmission grating in October 2002 with an earlier observation from Nov 2002, and interpret these results in terms of the proposed colliding wind binary model for the star. In addition we discuss planned observations for the upcoming X-ray eclipse.

Corcoran, M.; Swank, J. H.; Ishibashi, K.; Gull, T.; Humphreys, R.; Damineli, A.; Walborn, N.; Hillier, D. J.; Davidson, K.; White, S. M.

2002-01-01

368

Measurement of piezoelectric constants of lanthanum-gallium tantalate crystal by X-ray diffraction methods  

SciTech Connect

A method for measuring piezoelectric constants of crystals of intermediate systems by X-ray quasi-multiple-wave diffraction is proposed and implemented. This technique makes it possible to determine the piezoelectric coefficient by measuring variations in the lattice parameter under an external electric field. This method has been approved, its potential is evaluated, and a comparison with high-resolution X-ray diffraction data is performed.

Blagov, A. E.; Marchenkov, N. V., E-mail: marchenkov@ns.crys.ras.ru; Pisarevsky, Yu. V.; Prosekov, P. A.; Kovalchuk, M. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)] [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2013-01-15

369

Suzaku Overview and X-ray Binaries  

NASA Astrophysics Data System (ADS)

High resolution X-ray spectroscopy and high-sensitivity wide-band imaging spectroscopy are expected to provide new insights in study of high energy universe. The Suzaku observatory developed by major international collaboration with JAXA and ISAS was put in orbit on July 10, 2005. It carries five X-ray mirrors, an X-ray microcalorimeter array (XRS), four X-ray CCD cameras, and a hard X-ray detector. The XRS and its accompanying X-ray telescope was supposed to provide high energy resolution spectroscopy of FWHM < 10 eV in 0.3 to 10 keV energy band. However, the functionality was lost about a month after the launch due to failure in the cryogenic system. The remaining instruments started observation successfully to provide a high-sensitivity wide band (0.3 - 700 keV) spectroscopy. Low background, hence high sensitivity, and good energy resolution have been confirmed in orbit. In this paper we will present the general view, the in-orbit perfomrance and the present status of Suzaku mission, and the some initial results on X-ray binaries.

Mitsuda, Kazu; Kunieda, H.; Takahashi, T.; Kelly, R.; White, N.

2006-06-01

370

GEMS x-ray polarimeter performance simulations  

NASA Astrophysics Data System (ADS)

The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarization of astrophysical X-rays in the 2-10 keV band by sensing the direction of the track of the primary photoelectron excited by the incident X-ray. We have simulated the expected sensitivity of the polarimeter to polarized X-rays. We use the simulation package Penelope to model the physics of the interaction of the initial photoelectron with the detector gas and to determine the distribution of charge deposited in the detector volume. We then model the charge diffusion in the detector, and produce simulated track images. Within the track reconstruction algorithm we apply cuts on the track shape and focus on the initial photoelectron direction in order to maximize the overall sensitivity of the instrument. Using this technique we have predicted instrument modulation factors ?100 for 100% polarized X-rays ranging from 10% to over 60% across the 2-10 keV X-ray band. We also discuss the simulation program used to develop and model some of the algorithms used for triggering, and energy measurement of events in the polarimeter.

Baumgartner, Wayne H.; Strohmayer, Tod; Kallman, Tim; Black, J. Kevin; Hill, Joanne E.; Swank, Jean H.; Jahoda, Keith M.

2012-09-01

371

GEMS X-ray Polarimeter Performance Simulations  

NASA Technical Reports Server (NTRS)

The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarization of astrophysical X-rays in the 2-10 keV band by sensing the direction of the track of the primary photoelectron excited by the incident X-ray. We have simulated the expected sensitivity of the polarimeter to polarized X-rays. We use the simulation package Penelope to model the physics of the interaction of the initial photoelectron with the detector gas and to determine the distribution of charge deposited in the detector volume. We then model the charge diffusion in the detector,and produce simulated track images. Within the track reconstruction algorithm we apply cuts on the track shape and focus on the initial photoelectron direction in order to maximize the overall sensitivity of the instrument, using this technique we have predicted instrument modulation factors nu(sub 100) for 100% polarized X-rays ranging from 10% to over 60% across the 2-10 keV X-ray band. We also discuss the simulation program used to develop and model some of the algorithms used for triggering, and energy measurement of events in the polarimeter.

Baumgartner, Wayne H.; Strohmayer, Tod; Kallman, Tim; Black, J. Kevin; Hill, Joanne; Swank, Jean

2012-01-01

372

Toward Active X-ray Telescopes II  

NASA Technical Reports Server (NTRS)

In the half century since the initial discovery of an astronomical (non-solar) x-ray source, the sensitivity for detection of cosmic x-ray sources has improved by ten orders of magnitude. Largely responsible for this dramatic progress has been the refinement of the (grazing-incidence) focusing x-ray telescope. The future of x-ray astronomy relies upon the development of x-ray telescopes with larger aperture areas (greater than 1 m2) and finer angular resolution (less than 1.). Combined with the special requirements of grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically challenging.requiring precision fabrication, alignment, and assembly of large areas (greater than 100 m2) of lightweight (approximately 1 kg m2 areal density) mirrors. Achieving precise and stable alignment and figure control may entail active (in-space adjustable) x-ray optics. This paper discusses relevant programmatic and technological issues and summarizes progress toward active x-ray telescopes.

O'Dell, Stephen L.; Aldroft, Thomas L.; Atkins, Carolyn; Button, Timothy W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peter; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Johnson-Wilke, Raegan L.; Kolodziejczak, Jeffery J.; Lillie, Charles F.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Sanmartin, Daniel Rodriguez; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan E.; Ulmer, Melville P.; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.

2012-01-01

373

Toward Adaptive X-Ray Telescopes  

NASA Technical Reports Server (NTRS)

Future x-ray observatories will require high-resolution (less than 1 inch) optics with very-large-aperture (greater than 25 square meter) areas. Even with the next generation of heavy-lift launch vehicles, launch-mass constraints and aperture-area requirements will limit the surface areal density of the grazing-incidence mirrors to about 1 kilogram per square meter or less. Achieving sub-arcsecond x-ray imaging with such lightweight mirrors will require excellent mirror surfaces, precise and stable alignment, and exceptional stiffness or deformation compensation. Attaining and maintaining alignment and figure control will likely involve adaptive (in-space adjustable) x-ray optics. In contrast with infrared and visible astronomy, adaptive optics for x-ray astronomy is in its infancy. In the middle of the past decade, two efforts began to advance technologies for adaptive x-ray telescopes: The Generation-X (Gen-X) concept studies in the United States, and the Smart X-ray Optics (SXO) Basic Technology project in the United Kingdom. This paper discusses relevant technological issues and summarizes progress toward adaptive x-ray telescopes.

O'Dell, Stephen L.; Atkins, Carolyn; Button, Tim W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peer; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Kolodziejczak, Jeffrey J.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Rodriguez Sanmartin, Daniel; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.

2011-01-01

374

Toward active x-ray telescopes II  

NASA Astrophysics Data System (ADS)

In the half century since the initial discovery of an astronomical (non-solar) x-ray source, the observation time required to achieve a given sensitivity has decreased by eight orders of magnitude. Largely responsible for this dramatic progress has been the refinement of the (grazing-incidence) focusing x-ray telescope, culminating with the exquisite subarcsecond imaging performance of the Chandra X-ray Observatory. The future of x-ray astronomy relies upon the development of x-ray telescopes with larger aperture areas (< 1 m2) and comparable or finer angular resolution (< 1?). Combined with the special requirements of grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically challenging—requiring precision fabrication, alignment, and assembly of large areas (< 200 m2) of lightweight (? 1 kg m-2 areal density) mirrors. Achieving precise and stable alignment and figure control may entail active (in-space adjustable) x-ray optics. This paper discusses relevant programmatic and technological issues and summarizes current progress toward active x-ray telescopes.

O'Dell, Stephen L.; Aldcroft, Thomas L.; Atkins, Carolyn; Button, Timothy W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peter; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Johnson-Wilke, Raegan L.; Kolodziejczak, Jeffery J.; Lillie, Charles F.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Rodriguez Sanmartin, Daniel; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan E.; Ulmer, Melville P.; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.

2012-10-01

375

Supergiant X-Ray Binaries Observed by Suzaku  

NASA Technical Reports Server (NTRS)

Suzaku observations are presented for the high-mass X-ray binaries IGR 116207-5129 and IGR 117391-3021. For IGR 116207-5129, we provide the first X-ray broadband (0.5-60 keV) spectrum from which we confirm a large intrinsic column density (N(sub H) = 1.6 x 10(exp 23)/sq cm), and we constrain the cutoff energy for the first time (E(sub cut) = 19 keV). A prolonged (> 30 ks) attenuation of the X-ray flux was observed which we tentatively attribute to an eclipse of the probable neutron star by its massive companion, in a binary system with an orbital period between 4 and 9 days, and inclination angles> 50 degrees. For IGRJ17391-3021, we witnessed a transition from quiescence to a low-activity phase punctuated by weak flares whose peak luminosities in the 0.5-10keV band are only a factor of 5 times that of the pre-flare emission. These micro flares are accompanied by an increase in NH which suggests the accretion of obscuring clumps of wind. We now recognize that these low-activity epochs constitute the most common emission phase for this system, and perhaps in other supergiant fast X-ray transients (SFXTs) as well. We close with an overview of our upcoming program in which Suzaku will provide the first ever observation of an SFXT (IGRJ16479-4514) during a binary orbit enabling us to probe the accretion wind at every phase.

Bodaghee, A.; Tomsick, J. A.; Rodriquez, J.; Chaty, S.; Pottschmidt, K.; Walter, R.; Romano, P.

2011-01-01

376

Globular cluster x-ray sources  

PubMed Central

Globular clusters and x-ray astronomy have a long and fruitful history. Uhuru and OSO-7 revealed highly luminous (> 1036 ergs-1) x-ray sources in globular clusters, and Einstein and ROSAT revealed a larger population of low-luminosity (< 1033 ergs-1) x-ray sources. It was realized early on that the high-luminosity sources were low-mass x-ray binaries in outburst and that they were orders of magnitude more abundant per unit mass in globular clusters than in the rest of the galaxy. However, the low-luminosity sources proved difficult to classify. Many ideas were put forth—low-mass x-ray binaries in quiescence (qLMXBs), cataclysmic variables (CVs), active main-sequence binaries (ABs), and millisecond pulsars (MSPs)—but secure identifications were scarce. In ROSAT observations of 55 clusters, about 25 low-luminosity sources were found. Chandra has now observed over 80 Galactic globular clusters, and these observations have revealed over 1,500 x-ray sources. The superb angular resolution has allowed for many counterpart identifications, providing clues to the nature of this population. It is a heterogeneous mix of qLMXBs, CVs, ABs, and MSPs, and it has been shown that the qLMXBs and CVs are both, in part, overabundant like the luminous LMXBs. The number of x-ray sources in a cluster correlates very well with its encounter frequency. This points to dynamical formation scenarios for the x-ray sources and shows them to be excellent tracers of the complicated internal dynamics. The relation between the encounter frequency and the number of x-ray sources has been used to suggest that we have misunderstood the dynamical states of globular clusters. PMID:20404204

Pooley, David

2010-01-01

377

Calibration of x-ray densitometry for the measurement of coral skeletal density  

NASA Astrophysics Data System (ADS)

A new method is proposed for the measurement of coral skeletal density by x-radiography. X-radiographs were made of sections cut from skeletons of massive corals of the genus Porites. Included on the x-ray film with each specimen were an aluminium step-wedge, a set of aragonite standards and several aluminium bars, all of measured thickness and density. The images on the developed x-ray film were scanned with a microdensitometer. Semilogarithmic plots of microdensitometer output voltage vs. thickness of the aluminium and aragonite standards provided characteristic curves, with initial linear slopes which were defined as relative linear absorption coefficients. These coefficients varied with the x-ray exposure and microdensitometer measurement conditions; however, they were consistent within one set of conditions. The relative linear absorption coefficients and densities of the standards, together with data for thickness of standard vs. film exposure, can be used to determine the density of coral specimens at points along microdensitometer traverses of their x-ray images. The bars of aluminium can be used to correct for the non-uniform irradiation of the x-ray film which is characteristic of x-ray machines.

Chalker, Bruce; Barnes, David; Isdale, Peter

1985-09-01

378

Identification of X-ray Point Sources and Study on the Nature of 62 X-ray Globular Cluster Candidates in M31  

E-print Network

This paper includes two parts. The first is to present the spectral energy distributions (SEDs) of 49 globular cluster (GC) X-ray sources in the BATC 13 intermediate-band filters from 3800 to 10000 A, and identify 8 unidentified X-ray sources in M31. Using the X-ray data of Einstein observation from 1979 to 1980, ROSAT HRI observation in 1990, Chandra HRC and ACIS-I observations from 1999 to 2001, and the BATC optical survey from 1995 to 1999, we find 49 GC X-ray sources and 8 new unidentified X-ray sources in the BATC M31 field. By analyzing SEDs and FWHMs, 4 of the 8 X-ray sources may be GC candidates. The second is to present some statistical relationships about 62 GC X-ray sources, of which 58 are already known, and 4 are identified in this paper. The distribution of M31 GC X-ray sources' V mags is bimodal, with peaks at m_v = 15.65 and m_v = 17.89, which is different from the distribution of GC candidates. The distribution of B-V color shows that,the GC X-ray sources seem to be associated preferentially with the redder GCs, in agreement with the previous results. Kolmogorov-Smirnov test shows that the maximum value of the absolute difference of B-V distributions of GC X-ray sources and GCs is D_{max}=0.181, and the probability P=0.068 which means we can reject the hypothesis that the two distributions are the same at the 90.0% confidence level. In the end, we study the correlation between X-ray luminosity (0.3-10 keV) and the optical luminosity (in V band) of the GC X-ray sources in M31, and find that there exits a weak relationship with the linear correlation coefficient r = 0.36 at the confidence level of 98.0%.

Zhou Fan; Jun Ma; Xu Zhou; Jiansheng Chen; Zhaoji Jiang; Zhenyu Wu

2005-07-20

379

3D Reconstruction from X-ray Fluoroscopy for Clinical Veterinary Medicine using Differential Volume Rendering  

NASA Astrophysics Data System (ADS)

3D reconstruction from ordinary X-ray equipment which is not CT or MRI is required in clinical veterinary medicine. Authors have already proposed a 3D reconstruction technique from X-ray photograph to present bone structure. Although the reconstruction is useful for veterinary medicine, the thechnique has two problems. One is about exposure of X-ray and the other is about data acquisition process. An x-ray equipment which is not special one but can solve the problems is X-ray fluoroscopy. Therefore, in this paper, we propose a method for 3D-reconstruction from X-ray fluoroscopy for clinical veterinary medicine. Fluoroscopy is usually used to observe a movement of organ or to identify a position of organ for surgery by weak X-ray intensity. Since fluoroscopy can output a observed result as movie, the previous two problems which are caused by use of X-ray photograph can be solved. However, a new problem arises due to weak X-ray intensity. Although fluoroscopy can present information of not only bone structure but soft tissues, the contrast is very low and it is very difficult to recognize some soft tissues. It is very useful to be able to observe not only bone structure but soft tissues clearly by ordinary X-ray equipment in the field of clinical veterinary medicine. To solve this problem, this paper proposes a new method to determine opacity in volume rendering process. The opacity is determined according to 3D differential coefficient of 3D reconstruction. This differential volume rendering can present a 3D structure image of multiple organs volumetrically and clearly for clinical veterinary medicine. This paper shows results of simulation and experimental investigation of small dog and evaluation by veterinarians.

Khongsomboon, Khamphong; Hamamoto, Kazuhiko; Kondo, Shozo

380

X-ray phase-contrast methods  

NASA Astrophysics Data System (ADS)

This review is devoted to a comparative description of the methods for forming X-ray phase-contrast images of weakly absorbing (phase) objects. These include the crystal interferometer method, the Talbot interferometer method, diffraction-enhanced X-ray imaging, and the in-line method. The potential of their practical application in various fields of science and technology is discussed. The publications on the development and optimization of X-ray phase-contrast methods and the experimental study of phase objects are analyzed.

Lider, V. V.; Kovalchuk, M. V.

2013-11-01

381

X-ray transmission microscope development  

NASA Technical Reports Server (NTRS)

We are developing a hard x-ray microscope for direct observation of solidification dynamics in metal alloys and metal matrix composites. The Fein-Focus Inc. x-ray source was delivered in September and found to perform better than expected. Confirmed resolution of better than 2 micrometers was obtained and magnifications up to 800X were measured. Nickel beads of 30 micrometer diameter were easily detected through 6mm of aluminum. X-ray metallography was performed on several specimens showing high resolution and clear definition of 3-dimensional structures. Prototype furnace installed and tested.

Kaukler, William F.; Rosenberger, Franz E.

1995-01-01

382

Streaked, x-ray-transmission-grating spectrometer  

SciTech Connect

A free standing x-ray transmission grating has been coupled with a soft x-ray streak camera to produce a time resolved x-ray spectrometer. The instrument has a temporal resolution of approx. 20 psec, is capable of covering a broad spectral range, 2 to 120 A, has high sensitivity, and is simple to use requiring no complex alignment procedure. In recent laser fusion experiments the spectrometer successfully recorded time resolved spectra over the range 10 to 120 A with a spectral resolving power, lambda/..delta..lambda of 4 to 50, limited primarily by source size and collimation effects.

Ceglio, N.M.; Roth, M.; Hawryluk, A.M.

1981-08-01

383

Subnanosecond piezoelectric x-ray switch  

SciTech Connect

We report an ultrafast piezoelectric switch for synchrotron x rays. A thin epitaxial film of piezoelectric Pb(Zr,Ti)O{sub 3} works as a diffractive optical switch at frequencies from dc to >1 GHz. The broad frequency range allows single bunches of synchrotron x rays to be selected in an arbitrary sequence. The piezoelectric effect introduces mechanical strains of a fraction of 1% in the Pb(Zr,Ti)O{sub 3} film, which can be used for blocking or passing diffracted x rays.

Grigoriev, Alexei; Do, Dal-Hyun; Kim, Dong Min; Eom, Chang-Beom; Evans, Paul G.; Adams, Bernhard; Dufresne, Eric M. [Department of Materials Science and Engineering, University of Wisconsin Madison, Madison, Wisconsin 53706 (United States); Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2006-07-10

384

Large Area X-Ray Spectroscopy Mission  

NASA Technical Reports Server (NTRS)

The Large Area X-ray Spectroscopy (LAXS) mission concept study continues to evolve strongly following the merging of the LAXS mission with the Next Generation X-ray Observatory (NGXO, PI: Nick White) into the re-named High Throughput X-ray Spectroscopy (HTXS) Mission. HTXS retains key elements of the LAXS proposal, including the use of multiple satellites for risk-reduction and cost savings. A key achievement of the program has been the recommendation by the Structure and Evolution of the Universe (SEUS) (April 1997) for a new start for the HTXS mission in the 2000-2004 timeframe.

Tananbaum, H.

1997-01-01

385

Experimental investigation of beam heating in a soft X-ray scanning transmission X-ray microscope  

E-print Network

Experimental investigation of beam heating in a soft X-ray scanning transmission X-ray microscope and an accuracy of �1 C has been fabricated for scanning transmission X-ray microscopes (STXM). Here we describe the current generation of soft X-ray (60­2500 eV) scan- ning transmission X-ray microscopes (STXM) to focus

Hitchcock, Adam P.

386

Studies on mass attenuation coefficient, effective atomic number and electron density of some amino acids in the energy range 0.122-1.330 MeV  

NASA Astrophysics Data System (ADS)

The total mass attenuation coefficients of some amino acids, such as Glycine (C2H5NO2), DL-Alanine (C3H7NO2), Proline (C5H9NO2), L-Leucine (C6H13NO2 ), L-Arginine (C6H14N4O2) and L-Arginine Monohydrochloride (C6H15ClN4O2), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma rays were detected using NaI (Tl) scintillation detection system with a resolution of 10.2% at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff) and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) tend to be almost constant as a function of gamma-ray energy. The results show that, the experimental values of mass attenuation coefficients, effective atomic numbers and effective electron densities are in good agreement with the theoretical values with less than 1% error.

Pawar, Pravina P.; Bichile, Govind K.

2013-11-01

387

"X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"  

NASA Technical Reports Server (NTRS)

This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.

Halpern, Jules P.; Kaaret, Philip

1999-01-01

388

Exploring X-Ray Phase-Contrast Imaging using Photon Counting Detectors for Early Breast Cancer Detection  

NASA Astrophysics Data System (ADS)

X-ray attenuation-contrast (AC) imaging in the form of digital mammography (DM) is the current gold standard of screening for deep-set cancers like breast cancer. DM creates images based on the attenuation differences between normal and malignant breast tissue, but the extremely low attenuation contrast poses severe challenges for early cancer detection. In order to overcome these limitations posed by AC imaging, there is a growing interest in exploring phase changes in x-rays as they propagate through the tissue. Theoretical estimations show that the x-ray phase difference between normal and malignant breast tissue is three orders of magnitude higher than the corresponding absorption contrast. While x-ray attenuation is determined by the atomic number of the elements forming the tissue, the phase change is determined by the density or refractive index. Due to high energy of x-rays, absolute measurement of phase change is challenging. We will present our efforts to understand x-ray phase contrast in biological tissue using a photon counting detector (TIMEPIX), which is capable of energy and time resolved measurements with very high spatial resolution (about 50 microns). We are exploring novel methods, which will also be clinically feasible to extract phase information using a combination of PCDs and phase retrieval techniques. Phase changes and contrast details of various breast cancer types will also be investigated using the energy resolved measurements obtained using PCDs.

Das, Mini

2012-02-01

389

Engine materials characterization and damage monitoring by using x ray technologies  

NASA Astrophysics Data System (ADS)

X ray attenuation measurement systems that are capable of characterizing density variations in monolithic ceramics and damage due to processing and/or mechanical testing in ceramic and intermetallic matrix composites are developed and applied. Noninvasive monitoring of damage accumulation and failure sequences in ceramic matrix composites is used during room-temperature tensile testing. This work resulted in the development of a point-scan digital radiography system and an in situ x ray material testing system. The former is used to characterize silicon carbide and silicon nitride specimens, and the latter is used to image the failure behavior of silicon-carbide-fiber-reinforced, reaction-bonded silicon nitride matrix composites. State-of-the-art x ray computed tomography is investigated to determine its capabilities and limitations in characterizing density variations of subscale engine components (e.g., a silicon carbide rotor, a silicon nitride blade, and a silicon-carbide-fiber-reinforced beta titanium matrix rod, rotor, and ring). Microfocus radiography, conventional radiography, scanning acoustic microscopy, and metallography are used to substantiate the x ray computed tomography findings. Point-scan digital radiography is a viable technique for characterizing density variations in monolithic ceramic specimens. But it is very limited and time consuming in characterizing ceramic matrix composites. Precise x ray attenuation measurements, reflecting minute density variations, are achieved by photon counting and by using microcollimators at the source and the detector. X ray computed tomography is found to be a unique x ray attenuation measurement technique capable of providing cross-sectional spatial density information in monolithic ceramics and metal matrix composites. X ray computed tomography is proven to accelerate generic composite component development. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results from one-, three-, five-, and eight-ply ceramic composite specimens show that x ray film radiography can monitor damage accumulation during tensile loading. Matrix cracking, fiber-matrix debonding, fiber bridging, and fiber pullout are imaged throughout the tensile loading of the specimens. In situ film radiography is found to be a practical technique for estimating interfacial shear strength between the silicon carbide fibers and the reaction-bonded silicon nitride matrix. It is concluded that pretest, in situ, and post-test x ray imaging can provide greater understanding of ceramic matrix composite mechanical behavior.

Baaklini, George Y.

1993-10-01

390

Calculation of 10 MV x-ray spectra emitted by a medical linear accelerator using the BFGS quasi-Newton method  

NASA Astrophysics Data System (ADS)

To calculate photon spectra for a 10 MV x-ray beam emitted by a medical linear accelerator, we performed numerical analysis using the aluminium transmission data obtained along the central axis of the beam under the narrow beam condition corresponding to a 3 × 3 cm2 field at a 100 cm distance from the source. We used the BFGS quasi-Newton method based on a general nonlinear optimization technique for the numerical analysis. The attenuation coefficients, aluminium thicknesses and measured transmission data are necessary inputs for the numerical analysis. The calculated x-ray spectrum shape was smooth in the lower to higher energy regions without any angular components. The x-ray spectrum acquired by the employed method was evaluated by comparing the measurements along the central axis percentage depth dose in a water phantom and by a Monte Carlo simulation code, the electron gamma shower code. The values of the calculated percentage depth doses for a 10 × 10 cm2 field at a 100 cm source-to-surface distance in a water phantom were obtained using the same geometry settings as those of the water phantom measurement. The differences in the measured and calculated values were less than ±1.0% for a broad region from the shallow part near the surface to deep parts of up to 25 cm in the water phantom.

Shimozato, T.; Tabushi, K.; Kitoh, S.; Shiota, Y.; Hirayama, C.; Suzuki, S.

2007-01-01

391

Fourier X-ray Scattering Radiography Yields Bone Structural Information  

PubMed Central

Purpose: To characterize certain aspects of the microscopic structures of cortical and trabecular bone by using Fourier x-ray scattering imaging. Materials and Methods: Protocols approved by the National Institutes of Health Animal Care and Use Committee were used to examine ex vivo the hind limb of a rat and the toe of a pig. The Fourier x-ray scattering imaging technique involves the use of a grid mask to modulate the cone beam and Fourier spectral filters to isolate the harmonic images. The technique yields attenuation, scattering, and phase-contrast (PC) images from a single exposure. In the rat tibia cortical bone, the scattering signals from two orthogonal grid orientations were compared by using Wilcoxon signed rank tests. In the pig toe, the heterogeneity of scattering and PC signals was compared between trabecular and compact bone regions of uniform attenuation by using F tests. Results: In cortical bone, the scattering signal was significantly higher (P < 10?15) when the grid was parallel to the periosteal surface. Trabecular bone, as compared with cortical bone, appeared highly heterogeneous on the scattering (P < 10?34) and PC (P < 10?27) images. Conclusion: The ordered alignment of the mineralized collagen fibrils in compact bone was reflected in the anisotropic scattering signal in this bone. In trabecular bone, the porosity of the mineralized matrix accounted for the granular pattern seen on the scattering and PC images. © RSNA, 2009 PMID:19403849

Wen, Han; Bennett, Eric E.; Hegedus, Monica M.; Rapacchi, Stanislas

2009-01-01

392

21 CFR 892.1730 - Photofluorographic x-ray system.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Photofluorographic x-ray system. 892.1730 Section 892.1730...Devices § 892.1730 Photofluorographic x-ray system. (a) Identification. A photofluorographic x-ray system is a device that includes a...

2013-04-01

393

21 CFR 892.1730 - Photofluorographic x-ray system.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Photofluorographic x-ray system. 892.1730 Section 892.1730...Devices § 892.1730 Photofluorographic x-ray system. (a) Identification. A photofluorographic x-ray system is a device that includes a...

2010-04-01

394

21 CFR 892.1730 - Photofluorographic x-ray system.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Photofluorographic x-ray system. 892.1730 Section 892.1730...Devices § 892.1730 Photofluorographic x-ray system. (a) Identification. A photofluorographic x-ray system is a device that includes a...

2012-04-01

395

21 CFR 892.1730 - Photofluorographic x-ray system.  

...2014-04-01 false Photofluorographic x-ray system. 892.1730 Section 892.1730...Devices § 892.1730 Photofluorographic x-ray system. (a) Identification. A photofluorographic x-ray system is a device that includes a...

2014-04-01

396

21 CFR 892.1730 - Photofluorographic x-ray system.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Photofluorographic x-ray system. 892.1730 Section 892.1730...Devices § 892.1730 Photofluorographic x-ray system. (a) Identification. A photofluorographic x-ray system is a device that includes a...

2011-04-01

397

Upper Gastrointestinal (GI) Tract X-Ray (Radiography)  

MedlinePLUS

X-ray (Radiography) - Upper GI Tract • Overview Upper gastrointestinal tract radiography, also called an upper GI, is an x- ... pregnancy and x-rays. A Word About Minimizing Radiation Exposure Special care is taken during x-ray ...

398

Lower Gastrointestinal (GI) Tract X-Ray (Radiography)  

MedlinePLUS

X-ray (Radiography) - Lower GI Tract • Overview View larger with caption Lower gastrointestinal (GI) tract radiography, also called a ... pregnancy and x-rays. A Word About Minimizing Radiation Exposure Special care is taken during x-ray ...

399

The analysis of densitometry image of bone tissue based on computer simulation of X-ray radiation propagation through plate model.  

PubMed

In this work, we have presented an attempt at the computer modelling of the attenuation effect of X-ray radiation which occurs in the densitometry test. The purpose of the modelling is to examine the extent to which the parameters of the plate model of bone tissue affect bone mineral density (BMD) parameter. In the modelling the fundamental functions realised by a densitometry device have been taken into consideration. Certain necessary assumptions simplifying the computation of the complex physical processes that occur during the transition of X-ray radiation through an object have been made. In order to compute the image produced by interaction of radiation the attenuation law is applied. The modelling of an object consists in defining its dimensions and its material characteristics. In the presented simulation the material characteristics of the object are limited to its attenuation coefficient. A different value of the coefficient can be defined for each voxel. The result image is produced by the calculation of partial attenuation in the individual voxels. The levels of grey in the image represent the value of the computed radiation intensity which is recorded in the "detector" after transition through the object. The simulation has been performed for the plate model representing trabecular bone tissue with 0.1mm porosity compartments. The results of the simulation of the plate model are presented. It can be observed that for certain modelled porosity compartments the size, structure and spatial arrangement are not properly recorded in the two-dimensional "detector". The recorded simulation results may be found useful for explaining difference that has been noticed between the BMD obtained from the densitometry test and the bone susceptibility to fracture. PMID:16643881

Binkowski, Marcin; Dyszkiewicz, Andrzej; Wróbel, Zygmunt

2007-02-01

400

Design and measurement of a Cu L-edge x-ray filter for free electron laser pumped x-ray laser experiments.  

PubMed

An inner-shell photoionized x-ray laser pumped by the Linac Coherent Light Source (LCLS) free electron laser has been proposed recently. The measurement of the on-axis 849 eV Ne?K? laser and protection of the x-ray spectrometer from damage require attenuation of the 1 keV LCLS beam. An Al/Cu foil combination is well suited, serving as a low energy bandpass filter below the Cu L-edge at 933 eV. A high resolution grating spectrometer is used to measure the transmission of a candidate filter with an intense laser-produced x-ray backlighter developed at the Lawrence Livermore National Laboratory Jupiter Laser Facility Janus. The methodology and discussion of the observed fine structure above the Cu L-edge will be presented. PMID:21034028

Dunn, J; London, R A; Cone, K V; Rocca, J J; Rohringer, N

2010-10-01

401

Design and measurement of a Cu L-edge x-ray filter for free electron laser pumped x-ray laser experimentsa)  

NASA Astrophysics Data System (ADS)

An inner-shell photoionized x-ray laser pumped by the Linac Coherent Light Source (LCLS) free electron laser has been proposed recently. The measurement of the on-axis 849 eV Ne K? laser and protection of the x-ray spectrometer from damage require attenuation of the 1 keV LCLS beam. An Al/Cu foil combination is well suited, serving as a low energy bandpass filter below the Cu L-edge at 933 eV. A high resolution grating spectrometer is used to measure the transmission of a candidate filter with an intense laser-produced x-ray backlighter developed at the Lawrence Livermore National Laboratory Jupiter Laser Facility Janus. The methodology and discussion of the observed fine structure above the Cu L-edge will be presented.

Dunn, J.; London, R. A.; Cone, K. V.; Rocca, J. J.; Rohringer, N.

2010-10-01

402

Design and measurement of a Cu L-edge x-ray filter for free electron laser pumped x-ray laser experiments  

SciTech Connect

An inner-shell photoionized x-ray laser pumped by the Linac Coherent Light Source (LCLS) free electron laser has been proposed recently. The measurement of the on-axis 849 eV Ne K{alpha} laser and protection of the x-ray spectrometer from damage require attenuation of the 1 keV LCLS beam. An Al/Cu foil combination is well suited, serving as a low energy bandpass filter below the Cu L-edge at 933 eV. A high resolution grating spectrometer is used to measure the transmission of a candidate filter with an intense laser-produced x-ray backlighter developed at the Lawrence Livermore National Laboratory Jupiter Laser Facility Janus. The methodology and discussion of the observed fine structure above the Cu L-edge will be presented.

Dunn, J.; London, R. A.; Rohringer, N. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Cone, K. V. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); Department of Applied Sciences, University of California, Davis, California 95616 (United States); Rocca, J. J. [NSF Center for Extreme Ultraviolet Science and Technology, Colorado State University, Fort Collins, Colorado 80523 (United States)

2010-10-15

403

Talbot phase-contrast x-ray imaging for the small joints of the hand  

NASA Astrophysics Data System (ADS)

A high-resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of rheumatoid arthritis (RA) and osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 µm resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast (DPC) or refraction-based x-ray imaging with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and can be implemented with conventional x-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that, due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high-resolution bench-top interferometer using 10 µm period gratings, a W anode tube and a CCD-based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ~25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging thus comes mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ~2 m long 'symmetric' interferometer operated in a high Talbot order.

Stutman, Dan; Beck, Thomas J.; Carrino, John A.; Bingham, Clifton O.

2011-09-01

404

Talbot phase-contrast x-ray imaging for the small joints of the hand.  

PubMed

A high-resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of rheumatoid arthritis (RA) and osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 µm resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast (DPC) or refraction-based x-ray imaging with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and can be implemented with conventional x-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that, due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high-resolution bench-top interferometer using 10 µm period gratings, a W anode tube and a CCD-based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ?25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging thus comes mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ?2 m long 'symmetric' interferometer operated in a high Talbot order. PMID:21841214

Stutman, Dan; Beck, Thomas J; Carrino, John A; Bingham, Clifton O

2011-09-01

405

Talbot phase-contrast X-ray imaging for the small joints of the hand  

PubMed Central

A high resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of Rheumatoid Arthritis (RA) and Osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 ?m resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast or refraction based X-ray imaging (DPC) with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and it can be implemented with conventional X-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high resolution bench-top interferometer using 10 ?m period gratings, a W anode tube and a CCD based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ~25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging comes thus mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ~2 m long ‘symmetric’ interferometer operated in a high Talbot order. PMID:21841214

Stutman, Dan; Beck, Thomas J; Carrino, John A; Bingham, Clifton O

2011-01-01

406

Density of BCR-2 basalt glass at high pressure by X-ray Absorption Microtomography  

NASA Astrophysics Data System (ADS)

Improved understanding of compressibility and thermal expansion and their integral properties, density and volume, of basaltic liquids are important for modeling the thermodynamics of partial melting and crystallization, and melt migration in the Earth’s crust and mantle. We are using X-ray absorption in conjunction with microtomography to determine density of basalt glass/melt at high pressures from the linear attenuation coefficient of voxels calibrated using internal calibration standards at monochromatic energy. Experiments are conducted with the rotating anvil apparatus on the 13-BM-D beamline at the Advanced Photon Source, Argonne National Laboratory in an opposing anvil (Drickamer) assembly with 4 mm truncations and 20o taper. The sample and standards are contained within a single crystal diamond sleeve capped with Mo lids inserted into a graphite box-type heater with Mo leads and surrounded by pyrophillite, zirconia and a composite boron epoxy-diamond epoxy--pyrophillite gasket. Pressure is determined by using energy dispersive X-ray diffraction of MgO and Au contained within the capsule. Temperature is controlled to within ±25 oC by regulating power to the heater based on prior calibration. The density of USGS standard BCR-2 (Columbia River Basalt) glass is determined by this technique up to 3 GPa at room temperature giving a compressibility (Ko) for the glass of 70 ±5 GPa, assuming K’= 4. The cell was successfully heated to 900 oC at 1 GPa with tomographic data sets collected at 200 oC temperature intervals. The variation in density with temperature gives a thermal expansion for BCR-2 glass of 3x10-5 K-1. Success in performing microtomography under simultaneous high pressure-temperature conditions will enable this technique to be extended to the melting interval for basalt at elevated pressures in the near future.

Clark, A. N.; Lesher, C. E.; Gaudio, S. J.; Yamada, A.; Wang, Y.

2009-12-01

407

X-ray transients in quiescence  

E-print Network

Transient X-ray binaries remain in their quiescent state for a long time (months to hundred years) and then bright up as the most powerful sources of the X-ray sky. While it is clear that, when in outbursts, transient binaries are powered by accretion, the origin of the low luminosity X-ray emission that has been detected in the quiescent state has different interpretations and provides the unique opportunity for testing different accretion regimes. In this paper we concentrate on the various aspects of the accretion physics at low rates onto compact objects. We describe the observational panorama of quiescent emission for the three classes of X-ray transients and try to interpret these data in light of the different regimes accessible at such low mass inflow rates.

Sergio Campana

2000-12-04

408

VETA-I x ray test analysis  

NASA Technical Reports Server (NTRS)

This interim report presents some definitive results from our analysis of the VETA-I x-ray testing data. It also provides a description of the hardware and software used in the conduct of the VETA-I x-ray test program performed at the MSFC x-ray Calibration Facility (XRCF). These test results also serve to supply data and information to include in the TRW final report required by DPD 692, DR XC04. To provide an authoritative compendium of results, we have taken nine papers as published in the SPIE Symposium, 'Grazing Incidence X-ray/EUV Optics for Astronomy and Projection Lithography' and have reproduced them as the content of this report.

Brissenden, R. J. V.; Chartas, G.; Freeman, M. D.; Hughes, J. P.; Kellogg, E. M.; Podgorski, W. A.; Schwartz, D. A.; Zhao, P.

1992-01-01

409

Laboratory Data for X-Ray Astronomy  

NASA Technical Reports Server (NTRS)

Laboratory facilities have made great strides in producing large sets of reliable data for X-ray astronomy, which include ionization and recombination cross sections needed for charge balance calculations as well as the atomic data needed for interpreting X-ray line formation. We discuss data from the new generation sources and pay special attention to the LLNL electron beam ion trap experiment, which is unique in its ability to provide direct laboratory access to spectral data under precisely controlled conditions that simulate those found in many astrophysical plasmas. Examples of spectral data obtained in the 1-160 A wavelength range are given illustrating the type of laboratory X-ray data produced in support of such missions as Chandra, X-Ray Multi-Mirror telescope (XMM), Advanced Satellite for Cosmology and Astrophysics (ASCA) and Extreme Ultraviolet Explorer Satellite (EUVE).

Beiersdorfer, P.; Brown, G. V.; Chen, H.; Gu, M.-F.; Kahn, S. M.; Lepson, J. K.; Savin, D. W.; Utter, S. B.

2000-01-01

410

X-rays from supernova explosions  

NASA Astrophysics Data System (ADS)

The X-ray emission to be expected from SN 1987A is calculated using a model developed by Beall (1979), wherein a thermal distribution of photons from the supernova photosphere is inverse Compton scattered by relativistic electrons within or near the surface of the star. Such a model has been corroborated with the X-ray emission detected from SN 1980K (Canizares, et al., 1982). The relationship between the radio and X-ray fluxes, the total energy in relativistic electrons produced in the explosion, and the ambient medium near the precursor star is considered. Finally, the X-ray flux expected from thermal bremsstrahlung (Chevalier and Fransson, 1987; Chevalier, 1984) is compared with that produced by the inverse Compton process, and the regimes where each mechanism dominates are discussed.

Beall, J. H.; Wood, K. S.

411

Tuberculosis, advanced - chest x-rays (image)  

MedlinePLUS

Tuberculosis is an infectious disease that causes inflammation, the formation of tubercules and other growths within tissue, ... death. These chest x-rays show advanced pulmonary tuberculosis. There are multiple light areas (opacities) of varying ...

412

X-Rays, Pregnancy and You  

MedlinePLUS

... Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco Products Radiation-Emitting Products Print this page Share this page ... Dental Cone-beam Computed Tomography Fluoroscopy Mammography X-Rays, Pregnancy and You Pregnancy is a time to ...

413

X-RAY MICROBEAM SPEECH PRODUCTION DATABASE  

E-print Network

X-RAY MICROBEAM SPEECH PRODUCTION DATABASE USER'S HANDBOOK Version 1.0 (June 1994) prepared by John . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Chapter Three: Speech & Task Sample) Physiology of Speech Production, the now-classic cineradiographic account of thirteen disyllables spoken

414

X-ray Outburst in Mira A  

E-print Network

We report here the Chandra ACIS-S detection of a bright soft X-ray transient in the Mira AB interacting symbiotic-like binary. We resolved the system for the first time in the X-rays. Using Chandra and HST images we determined that the unprecedented outburst is likely associated with the cool AGB star (Mira A), the prototype of Mira-type variables. X-rays have never before been detected from an AGB star, and the recent activity signals that the system is undergoing dramatic changes. The total X-ray luminosity of the system is several times higher than the luminosity estimated using previous XMM and ROSAT observations. The outburst may be caused by a giant flare in Mira A associated with a mass ejection or a jet, and may have long term consequences on the system.

M. Karovska; E. Schlegel; W. Hack; B. Wood

2005-03-02

415

Small Angle X-Ray Scattering Detector  

DOEpatents

A detector for time-resolved small-angle x-ray scattering includes a nearly constant diameter, evacuated linear tube having an end plate detector with a first fluorescent screen and concentric rings of first fiber optic bundles for low angle scattering detection and an annular detector having a second fluorescent screen and second fiber optic bundles concentrically disposed about the tube for higher angle scattering detection. With the scattering source, i.e., the specimen under investigation, located outside of the evacuated tube on the tube's longitudinal axis, scattered x-rays are detected by the fiber optic bundles, to each of which is coupled a respective photodetector, to provide a measurement resolution, i.e., dq/q, where q is the momentum transferred from an incident x-ray to an x-ray scattering specimen, of 2% over two (2) orders of magnitude in reciprocal space, i.e., qmax/qmin approx=lO0.

Hessler, Jan P.

2004-06-15

416

X-Ray Exam: Femur (Upper Leg)  

MedlinePLUS

KidsHealth > Parents > Doctors & Hospitals > Medical Tests & Exams > X-Ray Exam: Femur (Upper Leg) Print A A A Text Size What's in this article? What It Is Why It's Done Preparation Procedure What ...

417

X-ray source for mammography  

DOEpatents

An x-ray source utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum would be in the 20-35 keV region. Thus, the anode material of this invention provides for imaging of breasts with higher than average x-ray opacity without increase of the radiation dose, and thus reduces the risk of induced breast cancer due to the radiation dose administered for mammograms.

Logan, Clinton M. (Pleasanton, CA)

1994-01-01

418

X-ray source for mammography  

DOEpatents

An x-ray source is described utilizing anode material which shifts the output spectrum to higher energy and thereby obtains higher penetrating ability for screening mammography application, than the currently utilized anode material. The currently used anode material (molybdenum) produces an energy x-ray spectrum of 17.5/19.6 keV, which using the anode material of this invention (e.g. silver, rhodium, and tungsten) the x-ray spectrum would be in the 20-35 keV region. Thus, the anode material of this invention provides for imaging of breasts with higher than average x-ray opacity without increase of the radiation dose, and thus reduces the risk of induced breast cancer due to the radiation dose administered for mammograms. 6 figures.

Logan, C.M.

1994-12-20

419

Chandra X-Ray Observatory Center  

NSDL National Science Digital Library

This week, Space Shuttle mission STS-93 deployed the Chandra X-Ray Observatory, the world's most powerful X-Ray telescope. The third of NASA's "Great Observatories," the Chandra X-Ray Observatory will study X-Rays rather than visible light (the Hubble Space Telescope) or gamma rays (the Compton Gamma Ray Observatory). This site offers overviews and news of the Observatory and its mission. Operated for NASA by the Harvard-Smithsonian Center for Astrophysics, this site provides resources for students, scientists, the press, and general users. In the Public Information and Education section, users will find photos, a field guide, and educational materials. The Scientific User Support Section includes detailed target information, various documents, newsletters, and information on the Emission Line Project (ELP). In addition, the site provides breaking mission news, links to live video feeds, telemetry diagrams, and a timeline.

420

X-Ray Background Survey Spectrometer (XBSS)  

NASA Technical Reports Server (NTRS)

The objective of this investigation was to perform a spectral survey of the low energy diffuse X-ray background using the X-ray Background Survey Spectrometer (XBSS) on board the Space Station Freedom (SSF). XBSS obtains spectra of the X-ray diffuse background in the 11-24 A and 44-84 A wavelength intervals over the entire sky with 15 deg spatial resolution. These X-rays are almost certainly from a very hot (10(exp 6) K) component of the interstellar medium that is contained in regions occupying a large fraction of the interstellar volume near the Sun. Astrophysical plasmas near 10(exp 6) K are rich in emission lines, and the relative strengths of these lines, besides providing information about the physical conditions of the emitting gas, also provide information about its history and heating mechanisms.

Sanders, W. T. (Principal Investigator); Paulos, R. J.

1996-01-01

421

X-ray induced optical reflectivity  

The change in optical reflectivity induced by intense x-ray pulses can now be used to study ultrafast many body responses in solids in the femtosecond time domain. X-ray absorption creates photoelectrons and core level holes subsequently filled by Auger or fluorescence processes, and these excitations ultimately add conduction and valence band carriers that perturb optical reflectivity.Optical absorption associated with band filling and band gap narrowing is shown to explain the basic features found in recent measurements on an insulator (silicon nitride, Si3N4), a semiconductor(gallium arsenide,GaAs), and a metal (gold,Au), obtained with ?100 fs x-ray pulses at 500-2000 eV and probed with 800 nm laser pulses. In particular GaAs exhibits an abrupt drop in reflectivity, persisting only for a time comparable to the x-ray excitation pulse duration, consistent with prompt band gap narrowing.

Durbin, Stephen M.

2012-01-01

422

Isolating Supports for X-Ray Mirrors  

NASA Technical Reports Server (NTRS)

Simple concept reduces effects of gravity, temperature and magnetism. Single circumferential ring supports fused-quartz mirror in high-resolution x-ray telescope. Adaptable to such terrestrial instruments as imaging devices and spectroscopes.

Cohen, L. M.

1984-01-01

423

X-ray fluorescence with synchrotron radiation  

SciTech Connect

X-ray fluorescence (XRF) has long been used to make measurements of trace element concentrations in biological materials with very high sensitivity. It has not been previously possible to work with micrometer spatial resolutions because of the relatively low brightness of x-ray tubes. This situation is much improved by using synchrotron storage ring x-ray sources since the brightness of the synchrotron source is many orders of magnitude higher than is obtained with the most intense tube sources. These intense sources open the possibility of using the XRF technique for measurements with resolutions of approximately cellular dimensions. A description of a current research project at Brookhaven which uses synchrotron radiation induced x-ray emission (SRIXE) is presented to illustrate a specific application of the method in biology. 1 ref., 4 figs.

Jones, K.W.; Gordon, B.M.; Hanson, A.L.; Pounds, J.G.; Schidlovsky, G.

1986-03-01

424

X-rays from colliding stellar winds  

NASA Technical Reports Server (NTRS)

A stellar wind from a massive OB or Wolf-Rayet star in a binary system will strike the surface or stellar wind of its companion, forming shocked gas that can radiate X-rays. The X-ray spectrum from the shocked winds will vary in a predictable way with orbital phase, owing to photoelectric absorption by the stellar winds. Detailed models are calculated for the hydrodynamics and X-ray emission from two such systems. In one of these systems (HD 165052), the winds are nearly identical in strength. In the other (V444 Cygni), the wind of the Wolf-Rayet star overwhelms and crushes that of its companion. The calculated X-ray luminosities agree fairly well with the observed values for HD 165052 and for V444 Cygni. These results can be scaled to other such systems.

Luo, Ding; Mccray, Richard; Mac Low, Mordecai-Mark

1990-01-01

425

Low-mass X-ray binaries  

NASA Astrophysics Data System (ADS)

A review is given of current understanding of low-mass X-ray binaries (LMXBs), which are luminous X-ray sources composed of a late-type optical companion (mass less than about 1 solar mass) and a neutron star (or possibly a black hole). Thirty-two LMXBs have been identified with optical counterparts in the Galaxy and one in the Large Magellanic Cloud (Brad and McClintock, 1983). It is unlikely that there are more than about 100 active LMXBs in the Galaxy, compared with about 200,000 cataclysmic variables. Topics covered in the review are: typical X-ray and optical properties; orbital periods; the nature of the compact source; accretion disks; formation; mass transfer mechanisms; and globular clusters and bright bulge X-ray sources.

McClintock, J. E.; Rappaport, S. A.

426

X-Ray Methods to Estimate Breast Density Content in Breast Tissue  

NASA Astrophysics Data System (ADS)

This work focuses on analyzing x-ray methods to estimate the fat and fibroglandular contents in breast biopsies and in breasts. The knowledge of fat in the biopsies could aid in their wide-angle x-ray scatter analyses. A higher mammographic density (fibrous content) in breasts is an indicator of higher cancer risk. Simulations for 5 mm thick breast biopsies composed of fibrous, cancer, and fat and for 4.2 cm thick breast fat/fibrous phantoms were done. Data from experimental studies using plastic biopsies were analyzed. The 5 mm diameter 5 mm thick plastic samples consisted of layers of polycarbonate (lexan), polymethyl methacrylate (PMMA-lucite) and polyethylene (polyet). In terms of the total linear attenuation coefficients, lexan ? fibrous, lucite ? cancer and polyet ? fat. The detectors were of two types, photon counting (CdTe) and energy integrating (CCD). For biopsies, three photon counting methods were performed to estimate the fat (polyet) using simulation and experimental data, respectively. The two basis function method that assumed the biopsies were composed of two materials, fat and a 50:50 mixture of fibrous (lexan) and cancer (lucite) appears to be the most promising method. Discrepancies were observed between the results obtained via simulation and experiment. Potential causes are the spectrum and the attenuation coefficient values used for simulations. An energy integrating method was compared to the two basis function method using experimental and simulation data. A slight advantage was observed for photon counting whereas both detectors gave similar results for the 4.2 cm thick breast phantom simulations. The percentage of fibrous within a 9 cm diameter circular phantom of fibrous/fat tissue was estimated via a fan beam geometry simulation. Both methods yielded good results. Computed tomography (CT) images of the circular phantom were obtained using both detector types. The radon transforms were estimated via four energy integrating techniques and one photon counting technique. Contrast, signal to noise ratio (SNR) and pixel values between different regions of interest were analyzed. The two basis function method and two of the energy integrating methods (calibration, beam hardening correction) gave the highest and more linear curves for contrast and SNR.

Maraghechi, Borna

427

Real-Time X-Ray Inspection  

NASA Technical Reports Server (NTRS)

X-ray imaging instrument adapted to continuous scanning. Modern version of fluoroscope enables rapid x-ray inspection of parts. Developed for detection of buckling in insulated ducts. Uses radiation from radioactive gadolinium or thallium source. Instrument weighs only 6 1/2 lb. Quickly scanned by hand along duct surface, providing real-time image. Based on Lixiscope, developed at Goddard Space Flight Center.

Bulthuis, Ronald V.

1988-01-01

428

Bomb Detection Using Backscattered X-Rays  

Microsoft Academic Search

Bomb Detection Using Backscattered X-rays*;\\u000a;\\u000aCurrently the most common method to determine the contents of a package suspected of containing an;\\u000aexplosive device is to use transmission radiography. This technique requires that an x-ray source and film;\\u000abe placed on opposite sides of the package. This poses a problem if the pachge is placed so that only one;\\u000aside

J. Jacobs; G. Lockwood; M Selph; S. Shope; J. Wehlburg

1998-01-01

429

Next-Generation X-Ray Astronomy  

NASA Astrophysics Data System (ADS)

This review of future timing capabilities in X-ray astronomy includes missions in implementation (astro-h, gems, srg and astrosat), those under study (currently nicer, athena and loft), and new technologies that may be the seeds for future missions, such as lobster-eye optics. Those missions and technologies will offer exciting new capabilities that will take X-ray Astronomy into a new generation of achievements.

White, Nicholas E.

2012-04-01

430

The high energy X-ray universe.  

PubMed

Since its beginning in the early 1960s, the field of X-ray astronomy has exploded, experiencing a ten-billion-fold increase in sensitivity, which brought it on par with the most advanced facilities at all wavelengths. I will briefly describe the revolutionary first discoveries prior to the launch of the Chandra and XMM-Newton X-ray observatories, present some of the current achievements, and offer some thoughts about the future of this field. PMID:20404148

Giacconi, Riccardo

2010-04-20

431

X-ray elastography: A feasibility study  

Microsoft Academic Search

We propose a new elastography method based on x-ray imaging. After taking two x-ray tomographic images of the breast-mimicking phantom with applying different compressing pressure to it, we calculated displacement and strain maps from the two images using a non-rigid body image registration. The strain maps showed elasticity characteristics of the phantom medium. We expect that the proposed elastography method

Gyu W. Kim; Byung H. Han; Min H. Cho; Soo Y. Lee

2009-01-01

432

Advances in X-ray analysis  

Microsoft Academic Search

Various aspects of X-ray fluorescence are presented in these proceedings of the 13th Annual Conference on Applications of X-Ray Analysis (Denver, Colorado, August 3-7, 1981). The papers are concerned with XRF detectors and XRF instrumentation, XRF applications (mineral and geological), XRF applications (metals, catalysts, oils), XRF environmental applications, XRF search\\/match procedures and automation, XRD methods and instrumentation, and XRD applications.

J. C. Russ; C. S. Barrett; D. C. Leyden; P. K. Predecki

1982-01-01

433

The Constellation X-ray Mission  

Microsoft Academic Search

Constellation-X will obtain for the first time high quality X-ray spectra for all classes of X-ray sources, over a wide range of luminosity and distance. It is the second priority major space initiative in the National Academy of Sciences Decadal survey (after JWST). Over the past few years, NASA budgets for SMD have been significantly reduced relative to earlier projections.

Harvey Tananbaum

2006-01-01

434

Positioning X-Ray Film By Balloon  

NASA Technical Reports Server (NTRS)

Film rolled around deflated balloon before being inserted in duct. Clamped at end of segmented flexible cable and fed with balloon into duct to predetermined point where inspection made, as indicated by length of cable paid out. Inflated balloon holds x-ray film against inside wall of duct for radiographic inspection. Ensures film positioned in contact with welded joint far along duct from opening through which inserted, so clear x-ray image of joint obtained.

Windbiel, Frederich; Guirguis, Kamal

1990-01-01

435

Searching for X-ray luminous  

Microsoft Academic Search

Aims.We cross-correlated the Chandra XASSIST and XMM-Newton Serendipitous Source Catalogues with the 2 degree Field Galaxy Redshift Survey (2dFGRS) database. Our aim was to identify the most X-ray luminous (LX > 1042 erg s-1) examples of galaxies in the local Universe whose X-ray emission is dominated by stellar processes rather than AGN activity (\\

P. Tzanavaris; I. Georgantopoulos; A. Georgakakis

2006-01-01

436

X-Ray Metrology for Quality Assurance  

Microsoft Academic Search

Abstract: There is considerable currentinterest in derivingaccurate dimensional measurements of the internal geometryof complex manufactured parts, particularlycastings. This paper describes an approachtothereconstructionof 3D part geometry from multiple digitalX-ray images. A novel method for radiographicstereo is described whichtakes into accountthespecialimaging geometry of the digital X-ray sensor modeledby a linear moving array, or pushbroom, camera.The 3D reconstruction algorithm employs ...

A. Noble; Richard I. Hartley; Joseph L. Mundy; J. Farley

1994-01-01

437

X-Ray Fluorescent Recovers Ancient Text  

NSDL National Science Digital Library

This article from Cornell University News Service presents an interdisciplinary effort among physicists and classicists to read a weathered 2000-year-old inscription on stone with x-ray fluorescence. The article describes how a powerful x-ray light source at Cornell produced fluorescence in trace elements in the inscribed stone and includes images showing the original inscription. The article is written for the general public.

2008-10-27

438

High speed gated x-ray imagers  

SciTech Connect

Single and multi-frame gated x-ray images with time-resolution as fast as 150 psec are described. These systems are based on the gating of microchannel plates in a stripline configuration. The gating voltage comes from the avalanche breakdown of reverse biased p-n junction producing high power voltage pulses as short as 70 psec. Results from single and four frame x-ray cameras used on Nova are described. 8 refs., 9 figs.

Kilkenny, J.D.; Bell, P.; Hanks, R.; Power, G.; Turner, R.E.; Wiedwald, J.

1988-01-01

439

The high energy X-ray universe  

PubMed Central

Since its beginning in the early 1960s, the field of X-ray astronomy has exploded, experiencing a ten-billion-fold increase in sensitivity, which brought it on par with the most advanced facilities at all wavelengths. I will briefly describe the revolutionary first discoveries prior to the launch of the Chandra and XMM-Newton X-ray observatories, present some of the current achievements, and offer some thoughts about the future of this field. PMID:20404148

Giacconi, Riccardo

2010-01-01

440

Compton backscattered collimated x-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source is disclosed for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications. 4 figs.

Ruth, R.D.; Huang, Z.

1998-10-20

441

Compton backscattered collmated X-ray source  

DOEpatents

A high-intensity, inexpensive and collimated x-ray source for applications such as x-ray lithography is disclosed. An intense pulse from a high power laser, stored in a high-finesse resonator, repetitively collides nearly head-on with and Compton backscatters off a bunched electron beam, having relatively low energy and circulating in a compact storage ring. Both the laser and the electron beams are tightly focused and matched at the interaction region inside the optical resonator. The laser-electron interaction not only gives rise to x-rays at the desired wavelength, but also cools and stabilizes the electrons against intrabeam scattering and Coulomb repulsion with each other in the storage ring. This cooling provides a compact, intense bunch of electrons suitable for many applications. In particular, a sufficient amount of x-rays can be generated by this device to make it an excellent and flexible Compton backscattered x-ray (CBX) source for high throughput x-ray lithography and many other applications.

Ruth, Ronald D. (Woodside, CA); Huang, Zhirong (Stanford, CA)

2000-01-01

442

Echoes in X-ray binaries  

NASA Astrophysics Data System (ADS)

We present a method of analysing the correlated X-ray and optical/UV variability in X-ray binaries, using the observed time delays between the X-ray driving light curves and their reprocessed optical echoes. This allows us to determine the distribution of reprocessing sites within the binary. We model the time-delay transfer functions by simulating the distribution of reprocessing regions, using geometrical and binary parameters. We construct best-fitting time-delay transfer functions, showing the regions in the binary responsible for the reprocessing of X-rays. We have applied this model to observations of the soft X-ray transient GRO J1655-40. We find that the optical variability lags the X-ray variability with a mean time delay of 19.3+/-2.2s. This means that the outer regions of the accretion disc are the dominant reprocessing site in this system. On fitting the data to a simple geometric model, we derive a best-fitting disc half-opening angle of 13.5+2.1-2.8\\circ, which is similar to that observed after the previous outburst by Orosz & Bailyn. This disc thickening has the effect of almost entirely shielding the companion star from irradiation at this stage of the outburst.

O'Brien, K.; Horne, Keith; Hynes, R. I.; Chen, W.; Haswell, C. A.; Still, M. D.

2002-08-01

443

Optics Developments for X-Ray Astronomy  

NASA Technical Reports Server (NTRS)

X-ray optics has revolutionized x-ray astronomy. The degree of background suppression that these afford, have led to a tremendous increase in sensitivity. The current Chandra observatory has the same collecting area (approx. 10(exp 3)sq cm) as the non-imaging UHURU observatory, the first x-ray observatory which launched in 1970, but has 5 orders of magnitude more sensitivity due to its focusing optics. In addition, its 0.5 arcsec angular resolution has revealed a wealth of structure in many cosmic x-ray sources. The Chandra observatory achieved its resolution by using relatively thick pieces of Zerodur glass, which were meticulously figured and polished to form the four-shell nested array. The resulting optical assembly weighed around 1600 kg, and cost approximately $0.5B. The challenge for future x-ray astronomy missions is to greatly increase the collecting area (by one or more orders of magnitude) while maintaining high angular resolution, and all within realistic mass and budget constraints. A review of the current status of US optics for x-ray astronomy will be provided along with the challenges for future developments.

Ramsey, Brian

2014-01-01

444

Differential X-Ray Absorption Model  

NSDL National Science Digital Library

The Differential X-Ray Absorption Model provides a qualitative exploration of how X-rays interact with varying material properties and how this difference can produce contrast in the x-ray image. For a typical medical diagnostic, images are created when X-rays from a source penetrate an object and then expose a film. This simulation shows how different materials in the X-rays beam produce the contrast that generates the detail of the image. The Differential X-Ray Absorption Model was created by Michael Gallis using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. You can examine and modify this compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open Ejs Model" from the pop-up menu. You must, of course, have EJS installed on your computer. 

Gallis, Michael R.

2014-04-16