Dysprosium-159 for transmission imaging and bone mineral analysis.

PubMed

Rao, D V; Govelitz, G F; Sastry, K S

1977-01-01

The suitability of the intense Kalpha x rays of terbium emitted in the electron-capture decay of 159Dy for use in transmission imaging and bone mineral analysis is investigated. It is found that this radionuclide offers all the advantages of radiations from 210 Pb and none of the disadvantages inherent in the use of the latter. Yields of the Kalpha and Kbeta x rays of terbium and the 58-keV gamma rays emitted in 159 Dy decay are determined using a high-resolution Si(Li) photon spectrometer. Attenuation coefficients for these photons in gadolinium (critical) absorber are measured in a narrow-beam geometry. For Tb Kbeta x rays, whose average energy is only about 0.4 keV above the K edge or Gd, our experimental attenuation coefficient is about 10% less than the theoretical value given by Storm and Israel. Transmission images of regular and irregular bones obtained using 159Dy are presented.

Segmentation-free statistical image reconstruction for polyenergetic x-ray computed tomography with experimental validation.

PubMed

Idris A, Elbakri; Fessler, Jeffrey A

2003-08-07

This paper describes a statistical image reconstruction method for x-ray CT that is based on a physical model that accounts for the polyenergetic x-ray source spectrum and the measurement nonlinearities caused by energy-dependent attenuation. Unlike our earlier work, the proposed algorithm does not require pre-segmentation of the object into the various tissue classes (e.g., bone and soft tissue) and allows mixed pixels. The attenuation coefficient of each voxel is modelled as the product of its unknown density and a weighted sum of energy-dependent mass attenuation coefficients. We formulate a penalized-likelihood function for this polyenergetic model and develop an iterative algorithm for estimating the unknown density of each voxel. Applying this method to simulated x-ray CT measurements of objects containing both bone and soft tissue yields images with significantly reduced beam hardening artefacts relative to conventional beam hardening correction methods. We also apply the method to real data acquired from a phantom containing various concentrations of potassium phosphate solution. The algorithm reconstructs an image with accurate density values for the different concentrations, demonstrating its potential for quantitative CT applications.

Attenuation properties and percentage depth dose of tannin-based Rhizophora spp. particleboard phantoms using computed tomography (CT) and treatment planning system (TPS) at high energy x-ray beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yusof, M. F. Mohd, E-mail: mfahmi@usm.my; School of Health Sciences, Universiti Sains Malaysia, 16150 Kota Bharu, Kelantan; Abdullah, R.

A set of tannin-based Rhizophora spp. particleboard phantoms with dimension of 30 cm x 30 cm was fabricated at target density of 1.0 g/cm{sup 3}. The mass attenuation coefficient of the phantom was measured using {sup 60}Co gamma source. The phantoms were scanned using Computed Tomography (CT) scanner and the percentage depth dose (PDD) of the phantom was calculated using treatment planning system (TPS) at 6 MV and 10 MV x-ray and compared to that in solid water phantoms. The result showed that the mass attenuation coefficient of tannin-based Rhizohora spp. phantoms was near to the value of water with χ{sup 2} valuemore » of 1.2. The measured PDD also showed good agreement with solid water phantom at both 6 MV and 10 MV x-ray with percentage deviation below 8% at depth beyond the maximum dose, Z{sub max}.« less

Effective Atomic Number, Mass Attenuation Coefficient Parameterization, and Implications for High-Energy X-Ray Cargo Inspection Systems

NASA Astrophysics Data System (ADS)

Langeveld, Willem G. J.

The most widely used technology for the non-intrusive active inspection of cargo containers and trucks is x-ray radiography at high energies (4-9 MeV). Technologies such as dual-energy imaging, spectroscopy, and statistical waveform analysis can be used to estimate the effective atomic number (Zeff) of the cargo from the x-ray transmission data, because the mass attenuation coefficient depends on energy as well as atomic number Z. The estimated effective atomic number, Zeff, of the cargo then leads to improved detection capability of contraband and threats, including special nuclear materials (SNM) and shielding. In this context, the exact meaning of effective atomic number (for mixtures and compounds) is generally not well-defined. Physics-based parameterizations of the mass attenuation coefficient have been given in the past, but usually for a limited low-energy range. Definitions of Zeff have been based, in part, on such parameterizations. Here, we give an improved parameterization at low energies (20-1000 keV) which leads to a well-defined Zeff. We then extend this parameterization up to energies relevant for cargo inspection (10 MeV), and examine what happens to the Zeff definition at these higher energies.

Quality control tool of electrode coating for lithium-ion batteries based on X-ray radiography

NASA Astrophysics Data System (ADS)

Etiemble, A.; Besnard, N.; Adrien, J.; Tran-Van, P.; Gautier, L.; Lestriez, B.; Maire, E.

2015-12-01

A simple and efficient method, based on X-ray radiography, is developed to check the quality (homogeneity of the thickness, presence of defects) of NMC-, LFP- and NMC/LFP-based electrode coating for Li-ion batteries at the scale of several cm2 with a resolution of 20 μm. As a first step, the attenuation coefficient of NMC- and LFP-based coating is experimentally determined according to the Beer-Lambert law. Then, the attenuation coefficient of each active material is estimated from these experimental results and X-ray attenuation databases, which allows establishing an attenuation law for any coating composition. Finally, thanks to this relationship, the thickness can be evaluated in each spot of the film and the defects, such as pinholes or broad edges with gradual decrease of the thickness coating, can be detected. The analysis of NMC-, LFP- and NMC/LFP-based electrodes shows that the coating quality decreases as coating thickness increases and as the nanometric vs. micrometric material content increases in the coating composition. This reveals detrimental aspects of nanomaterials with respect to their use in composite electrode manufactured through conventional slot-die or casting process.

Mass attenuation coefficients in the range 3.8⩽E⩽11 keV, K fluorescence yield and Kβ/Kα relative X-ray emission rate for Ti, V, Fe, Co, Ni, Cu and Zn measured with a tunable monochromatic X-ray source

NASA Astrophysics Data System (ADS)

Ménesguen, Y.; Lépy, M.-C.

2010-08-01

This work presents new measurements of mass attenuation coefficients in the range 3.8⩽E⩽11 keV, K-absorption jump-ratios, Kα and Kβ fluorescence yields for Ti, V, Fe, Co, Ni, Cu and Zn. We use the experimental facility SOLEX, a tunable monochromatic X-ray source combined with an energy-dispersive high-purity germanium detector. The results are compared with theoretical values as well as with other experimental data and show a relatively good agreement. However, the derived K-jump-ratios appear larger than those widely used in the XCOM database. The Kα and Kβ fluorescence yields and the corresponding relative emission rates Kβ/Kα are also derived, which was made possible by the use of energy-dispersive detectors with good spectral resolution.

Reduce beam hardening artifacts of polychromatic X-ray computed tomography by an iterative approximation approach.

PubMed

Shi, Hongli; Yang, Zhi; Luo, Shuqian

2017-01-01

The beam hardening artifact is one of most important modalities of metal artifact for polychromatic X-ray computed tomography (CT), which can impair the image quality seriously. An iterative approach is proposed to reduce beam hardening artifact caused by metallic components in polychromatic X-ray CT. According to Lambert-Beer law, the (detected) projections can be expressed as monotonic nonlinear functions of element geometry projections, which are the theoretical projections produced only by the pixel intensities (image grayscale) of certain element (component). With help of a prior knowledge on spectrum distribution of X-ray beam source and energy-dependent attenuation coefficients, the functions have explicit expressions. Newton-Raphson algorithm is employed to solve the functions. The solutions are named as the synthetical geometry projections, which are the nearly linear weighted sum of element geometry projections with respect to mean of each attenuation coefficient. In this process, the attenuation coefficients are modified to make Newton-Raphson iterative functions satisfy the convergence conditions of fixed pointed iteration(FPI) so that the solutions will approach the true synthetical geometry projections stably. The underlying images are obtained using the projections by general reconstruction algorithms such as the filtered back projection (FBP). The image gray values are adjusted according to the attenuation coefficient means to obtain proper CT numbers. Several examples demonstrate the proposed approach is efficient in reducing beam hardening artifacts and has satisfactory performance in the term of some general criteria. In a simulation example, the normalized root mean square difference (NRMSD) can be reduced 17.52% compared to a newest algorithm. Since the element geometry projections are free from the effect of beam hardening, the nearly linear weighted sum of them, the synthetical geometry projections, are almost free from the effect of beam hardening. By working out the synthetical geometry projections, the proposed approach becomes quite efficient in reducing beam hardening artifacts.

Electron density and effective atomic number (Zeff) determination through x-ray Moiré deflectometry

NASA Astrophysics Data System (ADS)

Valdivia Leiva, Maria Pia; Stutman, Dan; Finkenthal, Michael

2014-10-01

Talbot-Lau based Moiré deflectometry is a powerful density diagnostic capable of delivering refraction information and attenuation from a single image, through the accurate detection of X-ray phase-shift and intensity. The technique is able to accurately measure both the real part of the index of refraction δ (directly related to electron density) and the attenuation coefficient μ of an object placed in the x-ray beam. Since the atomic number Z (or Zeff for a composite sample) is proportional to these quantities, an elemental map of the effective atomic number can be obtained with the ratio of the phase and the absorption image. The determination of Zeff from refraction and attenuation measurements with Moiré deflectometry could be of high interest in various fields of HED research such as shocked materials and ICF experiments as Zeff is linked, by definition, to the x-ray absorption properties of a specific material. This work is supported by U.S. DoE/NNSA Grant No. 435 DENA0001835.

Single-shot Z(eff) dense plasma diagnostic through simultaneous refraction and attenuation measurements with a Talbot-Lau x-ray moiré deflectometer.

PubMed

Valdivia, M P; Stutman, D; Finkenthal, M

2015-04-01

The Talbot-Lau x-ray moiré deflectometer is a powerful plasma diagnostic capable of delivering simultaneous refraction and attenuation information through the accurate detection of x-ray phase shift and intensity. The diagnostic can provide the index of refraction n=1-δ+iβ of an object (dense plasma, for example) placed in the x-ray beam by independently measuring both δ and β, which are directly related to the electron density n(e) and the attenuation coefficient μ, respectively. Since δ and β depend on the effective atomic number Z(eff), a map can be obtained from the ratio between phase and absorption images acquired in a single shot. The Talbot-Lau x-ray moiré deflectometer and its corresponding data acquisition and processing are briefly described to illustrate how the above is achieved; Z(eff) values of test objects within the 4-12 range were obtained experimentally through simultaneous refraction and attenuation measurements. We show that Z(eff) mapping of objects does not require previous knowledge of sample length or shape. The determination of Z(eff) from refraction and attenuation measurements with moiré deflectometry could be of high interest to various domains of high energy density research, such as shocked materials and inertial confinement fusion experiments, as well as material science and nondestructive testing.

Study of mass attenuation coefficients and effective atomic numbers of bismuth-ground granulated blast furnace slag concretes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Sandeep, E-mail: sandeep0078monu@gmail.com; Singh, Sukhpal, E-mail: sukhpal-78@rediffmail.com

2016-05-06

Five samples of Bismuth-Ground granulated blast furnace slag (Bi-GGBFS) concretes were prepared using composition (0.6 cement + x Bi{sub 2}O{sub 3} + (0.4-x) GGBFS, x = 0.05, 0.10, 0.15, 0.20 and 0.25) by keeping constant water (W) cement (C) ratio. Mass attenuation coefficients (μ{sub m}) of these prepared samples were calculated using a computer program winXCOM at different gamma ray energies, whereas effective atomic numbers (Z{sub eff}) is calculated using mathematical formulas. The radiation shielding properties of Bi-GGBFS concrete has been compared with standard radiation shielding concretes.

X-ray attenuation coefficients of high-atomic-number, hexanuclear transition metal cluster compounds: a new paradigm for radiographic contrast agents.

PubMed

Mullan, B F; Madsen, M T; Messerle, L; Kolesnichenko, V; Kruger, J

2000-04-01

The purpose of this study was to examine the radiologic attenuation properties of the parent cluster compounds, particularly attenuation as a function of discrete photon energy, before investigating ligand substitutions, which are necessary to improve cluster biocompatibility and to impart desirable physicochemical properties. The linear attenuation coefficients for solutions of the cluster compounds Ta6Br14, K8Ta6O19, and (H3O)2W6Cl14 were determined at 60, 80, 103, 122, and 140 keV from gamma-ray transmission measurements with americium-241, xenon-133, gadolinium-153, cobalt-57, and technetium-99m radioactive sources. Transmission measurements were obtained for a fixed time interval that ensured a statistically accurate count distribution exceeding 20,000 counts through the sample for each trial. On a strictly mole per liter basis, a 0.075 mol/L aqueous solution of K8Ta6O19 showed 1.08 times the attenuation of 0.063 mol/L aqueous iohexol at 60 keV and 3.30 times the attenuation at 80 keV. Similarly, a 0.05 mol/L methanolic solution of (H3O)2W6Cl4 showed 0.96 times (96%) the attenuation of 0.063 mol/L aqueous iohexol at 60 keV but 3.09 times the attenuation of the iohexol solution at 80 keV. Attenuations of 0.063 mol/L aqueous iohexol and 0.0125 mol/L Ta6Br14 (ie, at approximately one-fifth the iohexol concentration) were comparable at greater than 60 keV. These results confirm the theoretic potential for use of early transition metal cluster compounds as radiographic contrast agents. At higher x-ray energies, cluster compounds demonstrate multiplied x-ray attenuation relative to iodinated contrast agents.

Mass attenuation coefficients of several bio-adhesive based oil palm particleboards at 16.59-25.26 keV photon energies

NASA Astrophysics Data System (ADS)

Abdu Mustapa, U. A.; Yusof, M. F. Mohd; Hamid, P. N. K. Abd; Hashim, R.; Ahmad, M. Z.; Aziz, M. Z. Abd

2018-01-01

Particleboards made of oil palm with addition of polylactic acid (PLA), starch, and fish oil were fabricated with target density of 1.0 g/cm3. The mass attenuation coefficients of the particleboards were measured using x-ray fluorescence (XRF) configuration in conjunction with niobium, molybdenum, palladium and tin metal plates that provided Kα1 photon energies between 16.59 and 25.26 keV. The results were compared to the calculated value of water using XCOM. The results showed that all particleboards having mass attenuation coefficients near to the value of water with the mass attenuation coefficient different less than 0.25. The method of fabrication did not give significant different to the mass attenuation coefficients of the particleboards. The results had indicated the potential of bio-adhesive based palm oil particleboards to be developed as phantoms for low energy photons.

Linear attenuation coefficients of tissues from 1 keV to 150 keV

NASA Astrophysics Data System (ADS)

Böke, Aysun

2014-09-01

The linear attenuation coefficients and three interaction processes have been computed for liver, kidney, muscle, fat and for a range of x-ray energies from 1 keV to 150 keV. Molecular photoelectric absorption cross sections were calculated from atomic cross section data. Total coherent (Rayleigh) and incoherent (Compton) scattering cross sections were obtained by numerical integration over combinations of F2m(x) with the Thomson formula and Sm(x) with the Klein-Nishina formula, respectively. For the coherent (Rayleigh) scattering cross section calculations, molecular form factors were obtained from recent experimental data in the literature for values of x<1 Å-1 and from the relativistic modified atomic form factors for values of x≥1 Å-1. With the inclusion of molecular interference effects in the coherent (Rayleigh) scattering, more accurate knowledge of the scatter from these tissues will be provided. The number of elements involved in tissue composition is 5 for liver, 47 for kidney, 44 for muscle and 3 for fat. The results are compared with previously published experimental and theoretical linear attenuation coefficients. In general, good agreement is obtained. The molecular form factors and scattering functions and cross sections are incorporated into a Monte Carlo program. The energy distributions of x-ray photons scattered from tissues have been simulated and the results are presented.

X-ray CT core imaging of Oman Drilling Project on D/V CHIKYU

NASA Astrophysics Data System (ADS)

Michibayashi, K.; Okazaki, K.; Leong, J. A. M.; Kelemen, P. B.; Johnson, K. T. M.; Greenberger, R. N.; Manning, C. E.; Harris, M.; de Obeso, J. C.; Abe, N.; Hatakeyama, K.; Ildefonse, B.; Takazawa, E.; Teagle, D. A. H.; Coggon, J. A.

2017-12-01

We obtained X-ray computed tomography (X-ray CT) images for all cores (GT1A, GT2A, GT3A and BT1A) in Oman Drilling Project Phase 1 (OmanDP cores), since X-ray CT scanning is a routine measurement of the IODP measurement plan onboard Chikyu, which enables the non-destructive observation of the internal structure of core samples. X-ray CT images provide information about chemical compositions and densities of the cores and is useful for assessing sample locations and the quality of the whole-round samples. The X-ray CT scanner (Discovery CT 750HD, GE Medical Systems) on Chikyu scans and reconstructs the image of a 1.4 m section in 10 minutes and produces a series of scan images, each 0.625 mm thick. The X-ray tube (as an X-ray source) and the X-ray detector are installed inside of the gantry at an opposing position to each other. The core sample is scanned in the gantry with the scanning rate of 20 mm/sec. The distribution of attenuation values mapped to an individual slice comprises the raw data that are used for subsequent image processing. Successive two-dimensional (2-D) slices of 512 x 512 pixels yield a representation of attenuation values in three-dimensional (3-D) voxels of 512 x 512 by 1600 in length. Data generated for each core consist of core-axis-normal planes (XY planes) of X-ray attenuation values with dimensions of 512 × 512 pixels in 9 cm × 9 cm cross-section, meaning at the dimensions of a core section, the resolution is 0.176 mm/pixel. X-ray intensity varies as a function of X-ray path length and the linear attenuation coefficient (LAC) of the target material is a function of the chemical composition and density of the target material. The basic measure of attenuation, or radiodensity, is the CT number given in Hounsfield units (HU). CT numbers of air and water are -1000 and 0, respectively. Our preliminary results show that CT numbers of OmanDP cores are well correlated to gamma ray attenuation density (GRA density) as a function of chemical composition and mineral density, so that their profiles with respect to the core depth provide quick lithological information such as mineral identification and phase boundary etc. Moreover, X-ray CT images can be used for 3-D fabric analyses of the whole core even after core cutting into halves for individual analyses.

Feasibility study of a low-energy gamma ray system for measuring quantity and flow rate of slush hydrogen

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Shen, Chih-Ping; Sprinkle, Danny R.

1992-01-01

As part of a study to demonstrate the suitability of an X-ray or gamma ray probe for monitoring the quality and flow rate of slush hydrogen, mass attenuation coefficients for Cd-109 X- and gamma radiation in five chemical compounds were measured. The Ag-109 K rays were used for water and acetic acid, whereas E3 transition from the first excited state at 87.7 keV in Ag-109 provided the probe radiation for bromobenzene, alpha (exp 2) chloroisodurene, and cetyl bromide. Measurements were made for a single phase (gas, liquid, solid) as well as mixed phases (liquid plus solid) in all cases. It was shown that the mass attenuation coefficient for the selected radiations is independent of the phase of the test fluids or phase ratios in the case of mixed phase fluids. Described here are the procedure and the results for the five fluid systems investigated.

Investigations of some building materials for γ-rays shielding effectiveness

NASA Astrophysics Data System (ADS)

Mann, Kulwinder Singh; Kaur, Baljit; Sidhu, Gurdeep Singh; Kumar, Ajay

2013-06-01

For construction of residential and non-residential buildings bricks are used as building blocks. Bricks are made from mixtures of sand, clay, cement, fly ash, gypsum, red mud and lime. Shielding effectiveness of five soil samples and two fly ash samples have been investigated using some energy absorption parameters (Mass attenuation coefficients, mass energy absorption coefficients, KERMA (kinetic energy released per unit mass), HVL, equivalent atomic number and electron densities) firstly at 14 different energies from 81-1332 keV then extended to wide energy range 0.015-15 MeV. The soil sample with maximum shielding effectiveness has been used for making eight fly ash bricks [(Lime)0.15 (Gypsum)0.05 (Fly Ash)x (Soil)0.8-x, where values of x are from 0.4-0.7]. High Purity Germanium (HPGe) detector has been used for gamma-ray spectroscopy. The elemental compositions of samples were analysed using an energy dispersive X-ray fluorescence (EDXRF) spectrometer. The agreements of theoretical and experimental values of mass attenuation coefficient have been found to be quite satisfactory. It has been verified that common brick possess the maximum shielding effectiveness for wide energy range 0.015-15 MeV. The results have been shown graphically with some useful conclusions for making radiation safe buildings.

Single-shot Z eff dense plasma diagnostic through simultaneous refraction and attenuation measurements with a Talbot–Lau x-ray moiré deflectometer

DOE PAGES

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

2015-03-23

The Talbot–Lau x-ray moiré deflectometer is a powerful plasma diagnostic capable of delivering simultaneous refraction and attenuation information through the accurate detection of x-ray phase shift and intensity. The diagnostic can provide the index of refraction n=1₋δ + iβ of an object (dense plasma, for example) placed in the x-ray beam by independently measuring both δ and β, which are directly related to the electron density n e and the attenuation coefficient μ respectively. Since δ and β depend on the effective atomic number Z eff, a map can be obtained from the ratio between phase and absorption images acquiredmore » in a single shot. The Talbot–Lau x-ray moiré deflectometer and its corresponding data acquisition and processing are briefly described to illustrate how the above is achieved; Z eff values of test objects within the 4₋12 range were obtained experimentally through simultaneous refraction and attenuation measurements. We show that Z eff mapping of objects does not require previous knowledge of sample length or shape. In conclusion, the determination of Z eff from refraction and attenuation measurements with moiré deflectometry could be of high interest to various domains of high energy density research, such as shocked materials and inertial confinement fusion experiments, as well as material science and nondestructive testing.« less

Single-shot Z eff dense plasma diagnostic through simultaneous refraction and attenuation measurements with a Talbot–Lau x-ray moiré deflectometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

The Talbot–Lau x-ray moiré deflectometer is a powerful plasma diagnostic capable of delivering simultaneous refraction and attenuation information through the accurate detection of x-ray phase shift and intensity. The diagnostic can provide the index of refraction n=1₋δ + iβ of an object (dense plasma, for example) placed in the x-ray beam by independently measuring both δ and β, which are directly related to the electron density n e and the attenuation coefficient μ respectively. Since δ and β depend on the effective atomic number Z eff, a map can be obtained from the ratio between phase and absorption images acquiredmore » in a single shot. The Talbot–Lau x-ray moiré deflectometer and its corresponding data acquisition and processing are briefly described to illustrate how the above is achieved; Z eff values of test objects within the 4₋12 range were obtained experimentally through simultaneous refraction and attenuation measurements. We show that Z eff mapping of objects does not require previous knowledge of sample length or shape. In conclusion, the determination of Z eff from refraction and attenuation measurements with moiré deflectometry could be of high interest to various domains of high energy density research, such as shocked materials and inertial confinement fusion experiments, as well as material science and nondestructive testing.« less

Bismuth-Silicon and Bismuth-Polyurethane Composite Shields for Breast Protection in Chest Computed Tomography Examinations

PubMed Central

Mehnati, Parinaz; Arash, Mehran; Akhlaghi, Parisa

2018-01-01

The article aims at constructing protective composite shields for breasts in chest computed tomography and investigating the effects of applying these new bismuth composites on dose and image quality. Polyurethane and silicon with 5% of bismuth were fabricated as a protective shield. At first, their efficiency in attenuating the X-ray beam was investigated by calculating the total attenuation coefficients at diagnostic energy range. Then, a physical chest phantom was scanned without and with these shields at tube voltage of 120 kVp, and image parameters together with dose values were studied. The results showed that these two shields have great effects on attenuating the X-ray beam, especially for lower energies (<40 kV), and in average, the attenuation coefficients of bismuth-polyurethane composite are higher in this energy range. The maximum relative differences between the average Hounsfield units (HUs) and noises of images without and with shield for both composites in 13 regions of interest were 4.5% and 15.7%, respectively. Moreover, primary investigation confirmed the ability of both shields (especially polyurethane-bismuth composite) in dose reduction. Comparing these two composites regarding the amount of dose reduction, the changes in HU and noise, and attenuation coefficients in diagnostic energy range, it seems that polyurethane composite is more useful for dose reduction, especially for higher tube voltages. PMID:29628636

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

NASA Technical Reports Server (NTRS)

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

2002-01-01

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.

Finite element Compton tomography

NASA Astrophysics Data System (ADS)

Jannson, Tomasz; Amouzou, Pauline; Menon, Naresh; Gertsenshteyn, Michael

2007-09-01

In this paper a new approach to 3D Compton imaging is presented, based on a kind of finite element (FE) analysis. A window for X-ray incoherent scattering (or Compton scattering) attenuation coefficients is identified for breast cancer diagnosis, for hard X-ray photon energy of 100-300 keV. The point-by-point power/energy budget is computed, based on a 2D array of X-ray pencil beams, scanned vertically. The acceptable medical doses are also computed. The proposed finite element tomography (FET) can be an alternative to X-ray mammography, tomography, and tomosynthesis. In experiments, 100 keV (on average) X-ray photons are applied, and a new type of pencil beam collimation, based on a Lobster-Eye Lens (LEL), is proposed.

Image reconstruction of x-ray tomography by using image J platform

NASA Astrophysics Data System (ADS)

Zain, R. M.; Razali, A. M.; Salleh, K. A. M.; Yahya, R.

2017-01-01

A tomogram is a technical term for a CT image. It is also called a slice because it corresponds to what the object being scanned would look like if it were sliced open along a plane. A CT slice corresponds to a certain thickness of the object being scanned. So, while a typical digital image is composed of pixels, a CT slice image is composed of voxels (volume elements). In the case of x-ray tomography, similar to x-ray Radiography, the quantity being imaged is the distribution of the attenuation coefficient μ(x) within the object of interest. The different is only on the technique to produce the tomogram. The image of x-ray radiography can be produced straight foward after exposed to x-ray, while the image of tomography produces by combination of radiography images in every angle of projection. A number of image reconstruction methods by converting x-ray attenuation data into a tomography image have been produced by researchers. In this work, Ramp filter in "filtered back projection" has been applied. The linear data acquired at each angular orientation are convolved with a specially designed filter and then back projected across a pixel field at the same angle. This paper describe the step of using Image J software to produce image reconstruction of x-ray tomography.

Studies on effective atomic numbers, electron densities from mass attenuation coefficients near the K edge in some samarium compounds.

PubMed

Akman, F; Durak, R; Turhan, M F; Kaçal, M R

2015-07-01

The effective atomic numbers and electron densities of some samarium compounds were determined using the experimental total mass attenuation coefficient values near the K edge in the X-ray energy range from 36.847 up to 57.142 keV. The measurements, in the region from 36.847 to 57.142 keV, were done in a transmission geometry utilizing the Kα2, Kα1, Kβ1 and Kβ2 X-rays from different secondary source targets excited by the 59.54 keV gamma-photons from an Am-241 annular source. This paper presents the first measurement of the effective atomic numbers and electron densities for some samarium compounds near the K edge. The results of the study showed that the measured values were in good agreement with the theoretically calculated ones. Copyright © 2015 Elsevier Ltd. All rights reserved.

Utilization of barite/cement composites for gamma rays attenuation

NASA Astrophysics Data System (ADS)

Sakr, Khaled; Ramadan, Wageeh; Sayed, Magda; El-Zakla, Tarek; El-Desouqy, Mohamed; El-Faramawy, Nabil

2018-04-01

The present work is directed to investigate the contribution of adding barite aggregates to cement as a shielding material for radioactive wastes disposal facilities. The percentages of barite from 5% up to 20% mixed with cement with different grain sizes were examined. Mechanical and physical properties such as compressive strength, wet and dry densities, water absorption, and porosity have been investigated. The thermogravimetric analysis and X-ray diffraction were used to examine the thermal stability and the characterizations of studied samples, respectively. The linear attenuation coefficient, mean free path, half value layer, and transmission fraction were evaluated. All the nuclear shielding parameters revealed the uppermost values for cement mixed with 5% barite of size range 250-600 µm. The attenuation coefficient of the investigated samples displayed an increase by more than 125% than that of neat cement.

Gamma ray shielding characteristic of BiZnBo-SLS and PbZnBo-SLS glass

NASA Astrophysics Data System (ADS)

Syuhada Ahmad, Nor; Shahrim Mustafa, Iskandar; Mansor, Ishak; Malik, Muhammad Fadhirul Izwan bin Abdul; Ain Nabilah Razali, Nur; Nordin, Sufiniza

2018-05-01

The radiation shielding and optical properties of x [RmOn] (0.5‑x) [ZnO] 0.2 [B2O3] 0.3 [SLS], where RmOn are Bi2O3 and PbO with x = 0.05, 0.10, 0.20, 0.30, 0.40, and 0.45 have been prepared by using the melt-quenching method at 1200 °C and was investigated on their physical, structural and gamma ray shielding properties. Field-emission scanning electron microscope (FESEM) data revealed that the particle morphologies is aggregated and irregular in shapes and size. Energy dispersive x-ray spectroscopy (EDS) elemental mapping data confirmed that all mentioned element all present on the prepared glass. Soda Lime Silica (SLS) that is mainly composed of SiO2 has been utilized in this study as the source of SiO2 for fabrication of glass system. From the result, the density and molar volume of both glass samples increased as Bi2O3 and PbO content increased. The gamma ray shielding properties, such as linear attenuation and mass attenuation coefficient, were increased while half value layer (HVL) and mean free path (MFP) were decreased as the increased in Bi2O3 and PbO concentrations. It is recognized that the mass attenuation coefficient value of Bi2O3 and PbO glass are slightly different. From this study, it can be concluded that from the non-toxicity and shielding point of view, the bismuth glass is a good shield to gamma radiation as compared to lead glass.

Tomography using monochromatic thermal neutrons with attenuation and phase contrast

NASA Astrophysics Data System (ADS)

Dubus, Francois; Bonse, Ulrich; Biermann, Theodor; Baron, Matthias; Beckmann, Felix; Zawisky, Michael

2002-01-01

Attenuation-contrast tomography with monochromatic thermal neutrons was developed and operated at guide station S18 of the institute Laue-Langevin in Grenoble. From the S18 spectrum the neutron wavelength (lambda) equals 0.18 nm was selected by employing a fore crystal with the silicon 220 reflection at a Bragg angle (Theta) equals 30 degrees. Projections were registered by a position sensitive detector (PSD) consisting of a neutron-to-visible-light converter coupled to a CCD detector. Neutron tomography and its comparison with X-ray tomography is studied. This is of special interest since the cross section for neutron attenuation ((sigma) atom) and the cross section for neutron phase shift (bc) are isotope specific and, in addition, by no means mostly monotonous functions of atomic number Z as are attenuation coefficient ((mu) x) and atomic scattering amplitude (f) in the case of X-rays. Results obtained with n-attenuation tomography will be presented. Possibilities and the setup of an instrument for neutron phase-contrast tomography based on single-crystal neutron interferometry will be described.

Effective atomic numbers and electron density of dosimetric material

PubMed Central

Kaginelli, S. B.; Rajeshwari, T.; Sharanabasappa; Kerur, B. R.; Kumar, Anil S.

2009-01-01

A novel method for determination of mass attenuation coefficient of x-rays employing NaI (Tl) detector system and radioactive sources is described.in this paper. A rigid geometry arrangement and gating of the spectrometer at FWHM position and selection of absorber foils are all done following detailed investigation, to minimize the effect of small angle scattering and multiple scattering on the mass attenuation coefficient, μ/ρ, value. Firstly, for standardization purposes the mass attenuation coefficients of elemental foils such as Aluminum, Copper, Molybdenum, Tantalum and Lead are measured and then, this method is utilized for dosimetric interested material (sulfates). The experimental mass attenuation coefficient values are compared with the theoretical values to find good agreement between the theory and experiment within one to two per cent. The effective atomic numbers of the biological substitute material are calculated by sum rule and from the graph. The electron density of dosimetric material is calculated using the effective atomic number. The study has discussed in detail the attenuation coefficient, effective atomic number and electron density of dosimetric material/biological substitutes. PMID:20098566

Dual-energy X-ray analysis using synchrotron computed tomography at 35 and 60 keV for the estimation of photon interaction coefficients describing attenuation and energy absorption.

PubMed

Midgley, Stewart; Schleich, Nanette

2015-05-01

A novel method for dual-energy X-ray analysis (DEXA) is tested using measurements of the X-ray linear attenuation coefficient μ. The key is a mathematical model that describes elemental cross sections using a polynomial in atomic number. The model is combined with the mixture rule to describe μ for materials, using the same polynomial coefficients. Materials are characterized by their electron density Ne and statistical moments Rk describing their distribution of elements, analogous to the concept of effective atomic number. In an experiment with materials of known density and composition, measurements of μ are written as a system of linear simultaneous equations, which is solved for the polynomial coefficients. DEXA itself involves computed tomography (CT) scans at two energies to provide a system of non-linear simultaneous equations that are solved for Ne and the fourth statistical moment R4. Results are presented for phantoms containing dilute salt solutions and for a biological specimen. The experiment identifies 1% systematic errors in the CT measurements, arising from third-harmonic radiation, and 20-30% noise, which is reduced to 3-5% by pre-processing with the median filter and careful choice of reconstruction parameters. DEXA accuracy is quantified for the phantom as the mean absolute differences for Ne and R4: 0.8% and 1.0% for soft tissue and 1.2% and 0.8% for bone-like samples, respectively. The DEXA results for the biological specimen are combined with model coefficients obtained from the tabulations to predict μ and the mass energy absorption coefficient at energies of 10 keV to 20 MeV.

Application of micron X-ray CT based on micro-PIXE to investigate the distribution of Cs in silt particles for environmental remediation in Fukushima Prefecture

NASA Astrophysics Data System (ADS)

Ishii, Keizo; Hatakeyama, Taisuke; Itoh, Shin; Sata, Daichi; Ohnuma, Tohru; Yamaguchi, Toshiro; Arai, Hiromu; Arai, Hirotsugu; Matsuyama, Shigeo; Terakawa, Atsuki; Kim, Seong-Yun

2016-03-01

We used X-ray computed tomography (CT) using characteristic X-rays produced in micro-particle-induced X-ray emission (PIXE) to investigate the internal structure of silt particles and develop new methods to decontaminate soil containing radioactive cesium. We obtained 3D attenuation coefficient images of silt particles with a diameter of approximately 100 μm for V K and Cr K X-rays. Owing to the absorption edges of the Cs L-shell, the differences between the V K and Cr K X-ray images revealed the spatial distribution of Cs atoms in the silt particles. Cs atoms were distributed over the surfaces of the silt particles to a thickness of approximately 10 μm. This information is useful for the decontamination of silt contaminated by radiation from the Fukushima Daiichi nuclear disaster.

Explicit Filtering Based Low-Dose Differential Phase Reconstruction Algorithm with the Grating Interferometry.

PubMed

Jiang, Xiaolei; Zhang, Li; Zhang, Ran; Yin, Hongxia; Wang, Zhenchang

2015-01-01

X-ray grating interferometry offers a novel framework for the study of weakly absorbing samples. Three kinds of information, that is, the attenuation, differential phase contrast (DPC), and dark-field images, can be obtained after a single scanning, providing additional and complementary information to the conventional attenuation image. Phase shifts of X-rays are measured by the DPC method; hence, DPC-CT reconstructs refraction indexes rather than attenuation coefficients. In this work, we propose an explicit filtering based low-dose differential phase reconstruction algorithm, which enables reconstruction from reduced scanning without artifacts. The algorithm adopts a differential algebraic reconstruction technique (DART) with the explicit filtering based sparse regularization rather than the commonly used total variation (TV) method. Both the numerical simulation and the biological sample experiment demonstrate the feasibility of the proposed algorithm.

Explicit Filtering Based Low-Dose Differential Phase Reconstruction Algorithm with the Grating Interferometry

PubMed Central

Zhang, Li; Zhang, Ran; Yin, Hongxia; Wang, Zhenchang

2015-01-01

X-ray grating interferometry offers a novel framework for the study of weakly absorbing samples. Three kinds of information, that is, the attenuation, differential phase contrast (DPC), and dark-field images, can be obtained after a single scanning, providing additional and complementary information to the conventional attenuation image. Phase shifts of X-rays are measured by the DPC method; hence, DPC-CT reconstructs refraction indexes rather than attenuation coefficients. In this work, we propose an explicit filtering based low-dose differential phase reconstruction algorithm, which enables reconstruction from reduced scanning without artifacts. The algorithm adopts a differential algebraic reconstruction technique (DART) with the explicit filtering based sparse regularization rather than the commonly used total variation (TV) method. Both the numerical simulation and the biological sample experiment demonstrate the feasibility of the proposed algorithm. PMID:26089971

Gamma rays shielding parameters for white metal alloys

NASA Astrophysics Data System (ADS)

Kaur, Taranjot; Sharma, Jeewan; Singh, Tejbir

2018-05-01

In the present study, an attempt has been made to check the feasibility of white metal alloys as gamma rays shielding materials. Different combinations of cadmium, lead, tin and zinc were used to prepare quaternary alloys Pb60Sn20ZnxCd20-x (where x = 5, 10, 15) using melt quench technique. These alloys were also known as white metal alloys because of its shining appearance. The density of prepared alloys has been measured using Archimedes Principle. Gamma rays shielding parameters viz. mass attenuation coefficient (µm), effective atomic number (Zeff), electron density (Nel), Mean free path (mfp), Half value layer (HVL) and Tenth value layer (TVL) has been evaluated for these alloys in the wide energy range from 1 keV to 100 GeV. The WinXCom software has been used for obtaining mass attenuation coefficient values for the prepared alloys in the given energy range. The effective atomic number (Zeff) has been assigned to prepared alloys using atomic to electronic cross section ratio method. Further, the variation of various shielding parameters with photon energy has been investigated for the prepared white metal alloys.

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

NASA Astrophysics Data System (ADS)

Çevik, U.; Baltaş, H.

2007-03-01

The mass attenuation coefficients for Bi, Pb, Sr, Ca, Cu metals, Bi2O3, PbO, SrCO3, CaO, CuO compounds and solid-state forms of Bi1.7Pb0.3Sr2Ca2Cu3O10 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 γ-ray energies. The X-ray energies were obtained using secondary targets such as Ta, Bi2O3 and (CH3COO)2UO22H2O. The γ- 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.

High-resolution proxies for wood density variations in Terminalia superba

PubMed Central

De Ridder, Maaike; Van den Bulcke, Jan; Vansteenkiste, Dries; Van Loo, Denis; Dierick, Manuel; Masschaele, Bert; De Witte, Yoni; Mannes, David; Lehmann, Eberhard; Beeckman, Hans; Van Hoorebeke, Luc; Van Acker, Joris

2011-01-01

Background and Aims Density is a crucial variable in forest and wood science and is evaluated by a multitude of methods. Direct gravimetric methods are mostly destructive and time-consuming. Therefore, faster and semi- to non-destructive indirect methods have been developed. Methods Profiles of wood density variations with a resolution of approx. 50 µm were derived from one-dimensional resistance drillings, two-dimensional neutron scans, and three-dimensional neutron and X-ray scans. All methods were applied on Terminalia superba Engl. & Diels, an African pioneer species which sometimes exhibits a brown heart (limba noir). Key Results The use of X-ray tomography combined with a reference material permitted direct estimates of wood density. These X-ray-derived densities overestimated gravimetrically determined densities non-significantly and showed high correlation (linear regression, R2 = 0·995). When comparing X-ray densities with the attenuation coefficients of neutron scans and the amplitude of drilling resistance, a significant linear relation was found with the neutron attenuation coefficient (R2 = 0·986) yet a weak relation with drilling resistance (R2 = 0·243). When density patterns are compared, all three methods are capable of revealing the same trends. Differences are mainly due to the orientation of tree rings and the different characteristics of the indirect methods. Conclusions High-resolution X-ray computed tomography is a promising technique for research on wood cores and will be explored further on other temperate and tropical species. Further study on limba noir is necessary to reveal the causes of density variations and to determine how resistance drillings can be further refined. PMID:21131386

Radiography simulation on single-shot dual-spectrum X-ray for cargo inspection system.

PubMed

Gil, Youngmi; Oh, Youngdo; Cho, Moohyun; Namkung, Won

2011-02-01

We propose a method to identify materials in the dual energy X-ray (DeX) inspection system. This method identifies materials by combining information on the relative proportions T of high-energy and low-energy X-rays transmitted through the material, and the ratio R of the attenuation coefficient of the material when high-energy are used to that when low energy X-rays are used. In Monte Carlo N-Particle Transport Code (MCNPX) simulations using the same geometry as that of the real container inspection system, this T vs. R method successfully identified tissue-equivalent plastic and several metals. In further simulations, the single-shot mode of operating the accelerator led to better distinguishing of materials than the dual-shot system. Copyright © 2010 Elsevier Ltd. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Xiaolan; Meier, Dirk; Taguchi, Katsuyuki

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 experimentsmore » 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.« less

Infrared Radiography: Modeling X-ray Imaging Without Harmful Radiation

NASA Astrophysics Data System (ADS)

Zietz, Otto; Mylott, Elliot; Widenhorn, Ralf

2015-01-01

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.

Measurements of the hard-x-ray reflectivity of iridium

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2007-01-10

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.

Measurements of the hard-x-ray reflectivity of iridium.

PubMed

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

2007-01-10

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.

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

NASA Astrophysics Data System (ADS)

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

2014-09-01

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.

Effects of 160 keV electron irradiation on the optical properties and microstructure of "Panda" type Polarization-Maintaining optical fibers

NASA Astrophysics Data System (ADS)

Hong-Chen, Zhang; Hai, Liu; Hui-Jie, Xue; Wen-Qiang, Qiao; Shi-Yu, He

2012-11-01

In this paper, effects of 160 keV electron irradiated "Panda" type Polarization-Maintaining optical fiber at 1310 nm are investigated by us. Attenuation coefficient induced in optical fiber by electron beams at 1310 nm increases with increase in electron fluence. Electron irradiation-induced damage mechanism are studied by means of CASINO simulation program, the X-ray photoelectron spectroscopy (XPS), electron spin resonance spectrometer (EPR) and Fourier transform infrared spectroscopy (FTIR). The results show that Si-OH impurity defect concentration is the main reason of increasing attenuation coefficient at 1310 nm.

The Physics Analysis of a Gas Attenuator with Argon as a Working Gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryutov,, D.D.

2010-12-07

A gas attenuator is an important element of the LCLS facility. The attenuator must operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10{sup 4} with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. S. Shen has recently carried out a detailed design study of the attenuator based on the use of nitrogen as a working gas. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues, not the design features.

Mass attenuation coefficient of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using 16.59 - 25.26 keV photon energy range

NASA Astrophysics Data System (ADS)

Mohd Yusof, Mohd Fahmi; Hamid, Puteri Nor Khatijah Abdul; Bauk, Sabar; Hashim, Rokiah; Tajuddin, Abdul Aziz

2015-04-01

The Rhizophora spp. particleboards were fabricated using ≤ 104 µm particle size at three different fabrication methods; binderless, steam pre-treated and tannin-added. The mass attenuation coefficient of Rhizophora spp. particleboards were measured using x-ray fluorescent (XRF) photon from niobium, molybdenum, palladium, silver and tin metal plates that provided photon energy between 16.59 to 25.26 keV. The results were compared to theoretical values for water calculated using photon cross-section database (XCOM).The results showed that all Rhizophora spp. particleboards having mass attenuation coefficient close to calculated XCOM for water. Tannin-added Rizophora spp. particleboard was nearest to calculated XCOM for water with χ2 value of 13.008 followed by binderless Rizophora spp. (25.859) and pre-treated Rizophora spp. (91.941).

Na0.3WO3 nanorods: a multifunctional agent for in vivo dual-model imaging and photothermal therapy of cancer cells.

PubMed

Zhang, Yuxin; Li, Bo; Cao, Yunjiu; Qin, Jinbao; Peng, Zhiyou; Xiao, Zhiyin; Huang, Xiaojuan; Zou, Rujia; Hu, Junqing

2015-02-14

The combination of imaging diagnosis and photothermal ablation (PTA) therapy has become a potential treatment for cancer. In particular, tungsten bronzes have a number of unique properties such as broad near-infrared (NIR) absorption and a large X-ray attenuation coefficient. However, these materials have seldom been reported as an X-ray computed tomography (CT) contrast agent and a photothermal agent. Herein, we synthesized PEGylated Na(0.3)WO(3) nanorods (mean size ∼39 nm × 5 nm) by a simple one-pot solvothermal route. As we expected, the prepared PEGylated Na(0.3)WO(3) nanorods exhibit intense NIR absorption, derived from the outer d-electron of W(5+). These PEGylated Na(0.3)WO(3) nanorods also show an excellent CT imaging effect and a high HU value of 29.95 HU g L(-1) (much higher than the figure of iopamidol (19.35 HU g L(-1))), due to the intrinsic property of tungsten of large atomic number and X-ray attenuation coefficient. Furthermore, the temperature elevation and the in vivo photothermal experiment reveal that as-synthesized Na(0.3)WO(3) nanorods could be an effective photothermal agent, as they have low toxicity, high effectiveness and good photostability.

Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV-28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum.

PubMed

Tantau, L J; Chantler, C T; Bourke, J D; Islam, M T; Payne, A T; Rae, N A; Tran, C Q

2015-07-08

We use the x-ray extended range technique (XERT) to experimentally determine the mass attenuation coefficient of silver in the x-ray energy range 11 kev-28 kev including the silver K absorption edge. The results are accurate to better than 0.1%, permitting critical tests of atomic and solid state theory. This is one of the most accurate demonstrations of cross-platform accuracy in synchrotron studies thus far. We derive the mass absorption coefficients and the imaginary component of the form factor over this range. We apply conventional XAFS analytic techniques, extended to include error propagation and uncertainty, yielding bond lengths accurate to approximately 0.24% and thermal Debye-Waller parameters accurate to 30%. We then introduce the FDMX technique for accurate analysis of such data across the full XAFS spectrum, built on full-potential theory, yielding a bond length accuracy of order 0.1% and the demonstration that a single Debye parameter is inadequate and inconsistent across the XAFS range. Two effective Debye-Waller parameters are determined: a high-energy value based on the highly-correlated motion of bonded atoms (σ(DW) = 0.1413(21) Å), and an uncorrelated bulk value (σ(DW) = 0.1766(9) Å) in good agreement with that derived from (room-temperature) crystallography.

Observation of glassy state relaxation during annealing of frozen sugar solutions by X-ray computed tomography.

PubMed

Nakagawa, Kyuya; Tamiya, Shinri; Do, Gabsoo; Kono, Shinji; Ochiai, Takaaki

2018-06-01

Glassy phase formation in a frozen product determines various properties of the freeze-dried products. When an aqueous solution is subjected to freezing, a glassy phase forms as a consequence of freeze-concentration. During post-freezing annealing, the relaxation of the glassy phase and the ripening of ice crystals (i.e. Ostwald ripening) spontaneously occur, where the kinetics are controlled by the annealing and glass transition temperatures. This study was motivated to observe the progress of glassy state relaxation separate from ice coarsening during annealing. X-ray computed tomography (CT) was used to observe a frozen and post-freezing annealed solutions by using monochromatized X-ray from the synchrotron radiation. CT images were successfully obtained, and the frozen matrix were analyzed based on the gray level values that were equivalent to the linear X-ray attenuation coefficients of the observed matters. The CT images obtained from rapidly frozen sucrose and dextrin solutions with different concentrations gave clear linear relationships between the linear X-ray attenuation coefficients values and the solute concentrations. It was confirmed that the glassy state relaxation progressed as increasing annealing time, and this trend was larger in the order of the glass transition temperature of the maximally freeze-concentrated phase. The sucrose-water system required nearly 20 h of annealing time at -5 °C for the completion of the glassy phase relaxation, whereas dextrin-water systems required much longer periods because of their higher glass transition temperatures. The trends of ice coarsening, however, did not perfectly correspond to the trends of the relaxation, suggesting that the glassy phase relaxation and Ostwald ripening would jointly control the ice crystal growth/ripening kinetics, and the dominant mechanism differed by the annealing stage. Copyright © 2018 Elsevier B.V. All rights reserved.

X-ray fluorescence at nanoscale resolution for multicomponent layered structures: A solar cell case study

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, Bradley M.; Stuckelberger, Michael; Jeffries, April

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer–Lambert's law, formulae are presented in a general integral formmore » and numerically applicable framework. Here, the procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se 2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically.« less

X-ray fluorescence at nanoscale resolution for multicomponent layered structures: A solar cell case study

DOE PAGES

West, Bradley M.; Stuckelberger, Michael; Jeffries, April; ...

2017-01-01

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer–Lambert's law, formulae are presented in a general integral formmore » and numerically applicable framework. Here, the procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se 2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically.« less

In situ liquid water visualization in polymer electrolyte membrane fuel cells with high resolution synchrotron x-ray radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chevalier, S.; Banerjee, R.; Lee, J.

In this work, we investigated the dominating properties of the porous materials that impact water dynamics in a polymer electrolyte membrane fuel cell (PEMFC). Visualizations of liquid water in an operating PEMFC were performed at the Canadian Light Source. A miniature fuel cell was specifically designed for X-ray imaging investigations, and an in-house image processing algorithm based on the Beer-Lambert law was developed to extract quantities of liquid water thicknesses (cm) from raw X-ray radiographs. The X-ray attenuation coefficient of water at 24 keV was measured with a calibration device to ensure accurate measurements of the liquid water thicknesses. Frommore » this experiment, the through plane distribution of the liquid water in the fuel cell was obtained.« less

Mass attenuation coefficient of binderless, pre-treated and tannin-based Rhizophora spp. particleboards using 16.59 – 25.26 keV photon energy range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohd Yusof, Mohd Fahmi, E-mail: mfahmi@usm.my; Hamid, Puteri Nor Khatijah Abdul; Tajuddin, Abdul Aziz

2015-04-29

The Rhizophora spp. particleboards were fabricated using ≤ 104 µm particle size at three different fabrication methods; binderless, steam pre-treated and tannin-added. The mass attenuation coefficient of Rhizophora spp. particleboards were measured using x-ray fluorescent (XRF) photon from niobium, molybdenum, palladium, silver and tin metal plates that provided photon energy between 16.59 to 25.26 keV. The results were compared to theoretical values for water calculated using photon cross-section database (XCOM).The results showed that all Rhizophora spp. particleboards having mass attenuation coefficient close to calculated XCOM for water. Tannin-added Rizophora spp. particleboard was nearest to calculated XCOM for water with χ2 valuemore » of 13.008 followed by binderless Rizophora spp. (25.859) and pre-treated Rizophora spp. (91.941)« less

In-Line Phase-Contrast X-ray Imaging and Tomography for Materials Science

PubMed Central

Mayo, Sheridan C.; Stevenson, Andrew W.; Wilkins, Stephen W.

2012-01-01

X-ray phase-contrast imaging and tomography make use of the refraction of X-rays by the sample in image formation. This provides considerable additional information in the image compared to conventional X-ray imaging methods, which rely solely on X-ray absorption by the sample. Phase-contrast imaging highlights edges and internal boundaries of a sample and is thus complementary to absorption contrast, which is more sensitive to the bulk of the sample. Phase-contrast can also be used to image low-density materials, which do not absorb X-rays sufficiently to form a conventional X-ray image. In the context of materials science, X-ray phase-contrast imaging and tomography have particular value in the 2D and 3D characterization of low-density materials, the detection of cracks and voids and the analysis of composites and multiphase materials where the different components have similar X-ray attenuation coefficients. Here we review the use of phase-contrast imaging and tomography for a wide variety of materials science characterization problems using both synchrotron and laboratory sources and further demonstrate the particular benefits of phase contrast in the laboratory setting with a series of case studies. PMID:28817018

In-Line Phase-Contrast X-ray Imaging and Tomography for Materials Science.

PubMed

Mayo, Sheridan C; Stevenson, Andrew W; Wilkins, Stephen W

2012-05-24

X-ray phase-contrast imaging and tomography make use of the refraction of X-rays by the sample in image formation. This provides considerable additional information in the image compared to conventional X-ray imaging methods, which rely solely on X-ray absorption by the sample. Phase-contrast imaging highlights edges and internal boundaries of a sample and is thus complementary to absorption contrast, which is more sensitive to the bulk of the sample. Phase-contrast can also be used to image low-density materials, which do not absorb X-rays sufficiently to form a conventional X-ray image. In the context of materials science, X-ray phase-contrast imaging and tomography have particular value in the 2D and 3D characterization of low-density materials, the detection of cracks and voids and the analysis of composites and multiphase materials where the different components have similar X-ray attenuation coefficients. Here we review the use of phase-contrast imaging and tomography for a wide variety of materials science characterization problems using both synchrotron and laboratory sources and further demonstrate the particular benefits of phase contrast in the laboratory setting with a series of case studies.

Attenuation characteristics of fiberoptic plates for digital mammography and other X-ray imaging applications.

PubMed

Vedantham, S; Karellas, A; Suryanarayanan, S

2003-01-01

Spatially coherent fiberoptic plates are important components of some charge-coupled device (CCD)-based x-ray imaging systems. These plates efficiently transmit scintillations from the phosphor, and also filter out x-rays not absorbed by the phosphor, thus protecting the CCD from direct x-ray interaction. The thickness of the fiberoptic plate and the CCD package present a significant challenge in the design of a digital x-ray cassette capable of insertion into the existing film-screen cassette holders of digital mammography systems. This study was performed with an aim to optimize fiberoptic plate thickness. Attenuation measurements were performed on nine fiberoptic plates varying in material composition that exhibit desirable optical characteristics such as good coupling efficiency. Mammographic spectra from a clinical mammographic system and an Americium-241 (Am-241) source (59.54 KeV) were used. The spectra were recorded with a high-resolution cadmium zinc telluride (CZT)-based spectrometer and corrected for dead time and pile-up. The linear attenuation coefficients varied by a factor of 3 in the set of tested fiberoptic plates at both mammographic energies and 59.54 keV. Our results suggest that a 3-mm thick high-absorption plate might provide adequate for shielding at mammographic energies. A thickness of 2-mm is feasible for mammographic applications with further optimization of the fiberoptic plate composition by incorporating non-scintillating, high-atomic number material. This would allow more space for cooling components of the cassette and for a more compact device, which is critical for clinical implementation of the technology.

X-ray and gamma-ray computed tomography for industrial nondestructive testing and evaluation

NASA Astrophysics Data System (ADS)

Costello, Ian; Wells, Peter; Davis, John R.; Benci, Nino; Skerrett, David; Davies, D. R.

1994-03-01

This paper presents an overview of two recently constructed computed tomography (CT) scanners that have been designed to provide structural information for industrially relevant materials and components. CT enables cross-sectional slices of an object to be nondestructively imaged and represented as a map of linear attenuation coefficient. As linear attenuation is the product of mass attenuation and density, this usually enables a straightforward interpretation of the image in terms of density. The two instruments are a transportable scanner using a 160 kV(peak) powered x-ray tube for the inspection of wooden power poles up to 450 mm in diameter, and an industrial scanning system designed around an Ir-192 gamma-ray source for materials characterization and the testing and evaluation of castings, ceramics, and composites. The images presented in this paper have generally been reconstructed using the summation convolution back-projection (SCBP) method, and this technique is outlined. Direct Fourier reconstruction is also used and compared with the SCBP method. A brief discussion is offered on incorporating edge detection methods into the image reconstruction process for the improved identification of defects such as cracks and voids.

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)

Kaya, Necati; Tıraşoğlu, Engin; Apaydın, Gökhan; Aylıkcı, Volkan; Cengiz, Erhan

2007-08-01

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 α1 , K α2 , K β1 and K β2 X- rays from different secondary source targets (Yb, Ta, Os, W, Re and Ir, etc.) excited by the 123.6 keV γ-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.

[Development of a digital chest phantom for studies on energy subtraction techniques].

PubMed

Hayashi, Norio; Taniguchi, Anna; Noto, Kimiya; Shimosegawa, Masayuki; Ogura, Toshihiro; Doi, Kunio

2014-03-01

Digital chest phantoms continue to play a significant role in optimizing imaging parameters for chest X-ray examinations. The purpose of this study was to develop a digital chest phantom for studies on energy subtraction techniques under ideal conditions without image noise. Computed tomography (CT) images from the LIDC (Lung Image Database Consortium) were employed to develop a digital chest phantom. The method consisted of the following four steps: 1) segmentation of the lung and bone regions on CT images; 2) creation of simulated nodules; 3) transformation to attenuation coefficient maps from the segmented images; and 4) projection from attenuation coefficient maps. To evaluate the usefulness of digital chest phantoms, we determined the contrast of the simulated nodules in projection images of the digital chest phantom using high and low X-ray energies, soft tissue images obtained by energy subtraction, and "gold standard" images of the soft tissues. Using our method, the lung and bone regions were segmented on the original CT images. The contrast of simulated nodules in soft tissue images obtained by energy subtraction closely matched that obtained using the gold standard images. We thus conclude that it is possible to carry out simulation studies based on energy subtraction techniques using the created digital chest phantoms. Our method is potentially useful for performing simulation studies for optimizing the imaging parameters in chest X-ray examinations.

Evaluation of size, morphology, concentration, and surface effect of gold nanoparticles on X-ray attenuation in computed tomography.

PubMed

Khademi, Sara; Sarkar, Saeed; Kharrazi, Sharmin; Amini, Seyed Mohammad; Shakeri-Zadeh, Ali; Ay, Mohammad Reza; Ghadiri, Hossein

2018-01-01

Increasing attention has been focused on the use of nanostructures as contrast enhancement agents in medical imaging, especially in computed tomography (CT). To date, gold nanoparticles (GNPs) have been demonstrated to have great potential as contrast agents for CT imaging. This study was designed to evaluate any effect on X-ray attenuation that might result from employing GNPs with a variety of shapes, sizes, surface chemistries, and concentrations. Gold nanorods (GNRs) and spherical GNPs were synthesized for this application. X-ray attenuation was quantified by Hounsfield unit (HU) in CT. Our findings indicated that smaller spherical GNPs (13 nm) had higher X-ray attenuation than larger ones (60 nm) and GNRs with larger aspect ratio exhibited great effect on X-ray attenuation. Moreover, poly ethylene glycol (PEG) coating on GNRs declined X-ray attenuation as a result of limiting the aggregation of GNRs. We observed X-ray attenuation increased when mass concentration of GNPs was elevated. Overall, smaller spherical GNPs can be suggested as a better alternative to Omnipaque, a good contrast agent for CT imaging. This data can be also considered for the application of gold nanostructures in radiation dose enhancement where nanoparticles with high X-ray attenuation are applied. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Dimensionality and noise in energy selective x-ray imaging

PubMed Central

Alvarez, Robert E.

2013-01-01

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

Complex dark-field contrast and its retrieval in x-ray phase contrast imaging implemented with Talbot interferometry.

PubMed

Yang, Yi; Tang, Xiangyang

2014-10-01

Under the existing theoretical framework of x-ray phase contrast imaging methods implemented with Talbot interferometry, the dark-field contrast refers to the reduction in interference fringe visibility due to small-angle x-ray scattering of the subpixel microstructures of an object to be imaged. This study investigates how an object's subpixel microstructures can also affect the phase of the intensity oscillations. Instead of assuming that the object's subpixel microstructures distribute in space randomly, the authors' theoretical derivation starts by assuming that an object's attenuation projection and phase shift vary at a characteristic size that is not smaller than the period of analyzer grating G₂ and a characteristic length dc. Based on the paraxial Fresnel-Kirchhoff theory, the analytic formulae to characterize the zeroth- and first-order Fourier coefficients of the x-ray irradiance recorded at each detector cell are derived. Then the concept of complex dark-field contrast is introduced to quantify the influence of the object's microstructures on both the interference fringe visibility and the phase of intensity oscillations. A method based on the phase-attenuation duality that holds for soft tissues and high x-ray energies is proposed to retrieve the imaginary part of the complex dark-field contrast for imaging. Through computer simulation study with a specially designed numerical phantom, they evaluate and validate the derived analytic formulae and the proposed retrieval method. Both theoretical analysis and computer simulation study show that the effect of an object's subpixel microstructures on x-ray phase contrast imaging method implemented with Talbot interferometry can be fully characterized by a complex dark-field contrast. The imaginary part of complex dark-field contrast quantifies the influence of the object's subpixel microstructures on the phase of intensity oscillations. Furthermore, at relatively high energies, for soft tissues it can be retrieved for imaging with a method based on the phase-attenuation duality. The analytic formulae derived in this work to characterize the complex dark-field contrast in x-ray phase contrast imaging method implemented with Talbot interferometry are of significance, which may initiate more activities in the research and development of x-ray differential phase contrast imaging for extensive biomedical applications.

Tunable synthesis and acetylation of dendrimer-entrapped or dendrimer-stabilized gold-silver alloy nanoparticles.

PubMed

Liu, Hui; Shen, Mingwu; Zhao, Jinglong; Guo, Rui; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-06-01

In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates or stabilizers to synthesize dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy nanoparticles (NPs) with different gold atom/silver atom/dendrimer molar ratios with the assistance of sodium borohydride reduction chemistry. Following a one-step acetylation reaction to transform the dendrimer terminal amines to acetyl groups, a series of dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs with terminal acetyl groups were formed. The formed Au-Ag alloy NPs before and after acetylation reaction were characterized using different techniques. We showed that the optical property and the size of the bimetallic NPs were greatly affected by the metal composition. At the constant total metal atom/dendrimer molar ratio, the size of the alloy NPs decreased with the gold content. The formed Au-Ag alloy NPs were stable at different pH (pH 5-8) and temperature (4-50°C) conditions. X-ray absorption coefficient measurements showed that the attenuation of the binary NPs was dependent on both the gold content and the surface modification. With the increase of gold content in the binary NPs, their X-ray attenuation intensity was significantly enhanced. At a given metal composition, the X-ray attenuation intensity of the binary NPs was enhanced after acetylation. Cytotoxicity assays showed that after acetylation, the cytocompatibility of Au-Ag alloy NPs was significantly improved. With the controllable particle size and optical property, metal composition-dependent X-ray attenuation characteristics, and improved cytocompatibility after acetylation, these dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs should have a promising potential for CT imaging and other biomedical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Determination of K shell absorption jump factors and jump ratios in the elements between Tm( Z = 69) and Os( Z = 76) by measuring K shell fluorescence parameters

NASA Astrophysics Data System (ADS)

Kaya, N.; Tıraşoğlu, E.; Apaydın, G.

2008-04-01

The K shell absorption jump factors and jump ratios have been measured in the elements between Tm ( Z = 69) and Os( Z = 76) without having any mass attenuation coefficient at the upper and lower energy branch of the K absorption edge. The jump factors and jump ratios for these elements have been determined by measuring K shell fluorescence parameters such as the total atomic absorption cross-sections, the K α X-ray production cross-sections, the intensity ratio of the K β and K α X-rays and the K shell fluorescence yields. We have performed the measurements for the calculations of these values in attenuation and direct excitation experimental geometry. The K X-ray photons are excited in the target using 123.6 keV gamma-rays from a strong 57Co source, and detected with an Ultra-LEGe solid state detector with a resolution 0.15 keV at 5.9 keV. The measured values have been compared with theoretical and others' experimental values. The results have been plotted versus atomic number.

Determination of 210Pb concentration in NORM waste - An application of the transmission method for self-attenuation corrections for gamma-ray spectrometry

NASA Astrophysics Data System (ADS)

Bonczyk, Michal

2018-07-01

This article deals with the problem of the self-attenuation of low-energy gamma-rays from the isotope of lead 210Pb (46.5 keV) in industrial waste. The 167 samples of industrial waste, belonging to nine categories, were tested by means of gamma spectrometry in order to determine 210Pb activity concentration. The experimental method for self-attenuation corrections for gamma rays emitted by lead isotope was applied. Mass attenuation coefficients were determined for energy of 46.5 keV. Correction factors were calculated based on mass attenuation coefficients, sample density and thickness. A mathematical formula for correction calculation was evaluated. The 210Pb activity concentration obtained varied in the range from several Bq·kg-1 up to 19,810 Bq kg-1. The mass attenuation coefficients varied across the range of 0.19-4.42 cm2·g-1. However, the variation of mass attenuation coefficient within some categories of waste was relatively small. The calculated corrections for self-attenuation were 0.98 - 6.97. The high value of correction factors must not be neglect in radiation risk assessment.

Measurements of K shell absorption jump factors and jump ratios using EDXRF technique

NASA Astrophysics Data System (ADS)

Kacal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

2015-04-01

In the present work, the K-shell absorption jump factors and jump ratios for 30 elements between Ti ( Z = 22) and Er ( Z = 68) were measured by energy dispersive X-ray fluorescence (EDXRF) technique. The jump factors and jump ratios for these elements were determined by measuring the K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to- Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using an Am-241 radioactive point source and a Si (Li) detector in direct excitation and transmission experimental geometry. The results for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature.

Gamma-rays attenuation of zircons from Cambodia and South Africa at different energies: A new technique for identifying the origin of gemstone

NASA Astrophysics Data System (ADS)

Limkitjaroenporn, P.; Kaewkhao, J.

2014-10-01

In this work, the gamma-rays interaction properties of zircons from Cambodia and South Africa have been studied. The densities of Cambodian and South African's zircons are 4.6716±0.0040 g/cm3 and 4.5505±0.0018 g/cm3, respectively. The mass attenuation coefficient and the effective atomic number of gemstones were measured with the gamma-ray in energies range 223-662 keV using the Compton scattering technique. The mass attenuation coefficients of both zircons decreased with the increasing of gamma-rays energies. The different mass attenuation coefficients between the two zircons observed at gamma-ray energies below 400 keV are attributed to the differences in the photoelectric interaction. The effective atomic number of zircons was decreased with the increasing of gamma-ray energies and showed totally different values between the Cambodia and South Africa sources. The origins of the two zircons could be successfully identified by the method based on gamma-rays interaction with matter with advantage of being a non-destructive testing.

Investigation of photon attenuation coefficient of some building materials used in Turkey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dogan, B.; Altinsoy, N.

In this study, some building materials regularly used in Turkey, such as concrete, gas concrete, pumice and brick have been investigated in terms of mass attenuation coefficient at different gamma-ray energies. Measurements were carried out by gamma spectrometry containing NaI(Tl) detector. Narrow beam gamma-ray transmission geometry was used for the attenuation measurements. The results are in good agreement with the theoretical calculation of XCOM code.

Determination of K shell absorption jump factors and jump ratios of 3d transition metals by measuring K shell fluorescence parameters.

PubMed

Kaçal, Mustafa Recep; Han, İbrahim; Akman, Ferdi

2015-01-01

Energy dispersive X-ray fluorescence technique (EDXRF) has been employed for measuring K-shell absorption jump factors and jump ratios for Ti, Cr, Fe, Co, Ni and Cu elements. The jump factors and jump ratios for these elements were determined by measuring K shell fluorescence parameters such as the Kα X-ray production cross-sections, K shell fluorescence yields, Kβ-to-Kα X-rays intensity ratios, total atomic absorption cross sections and mass attenuation coefficients. The measurements were performed using a Cd-109 radioactive point source and an Si(Li) detector in direct excitation and transmission experimental geometry. The measured values for jump factors and jump ratios were compared with theoretically calculated and the ones available in the literature. Copyright © 2014 Elsevier Ltd. All rights reserved.

Characterization and analysis of Porous, Brittle solid structures by X-ray micro computed tomography

NASA Astrophysics Data System (ADS)

Lin, C. L.; Videla, A. R.; Yu, Q.; Miller, J. D.

2010-12-01

The internal structure of porous, brittle solid structures, such as porous rock, foam metal and wallboard, is extremely complex. For example, in the case of wallboard, the air bubble size and the thickness/composition of the wall structure are spatial parameters that vary significantly and influence mechanical, thermal, and acoustical properties. In this regard, the complex geometry and the internal texture of material, such as wallboard, is characterized and analyzed in 3-D using cone beam x-ray micro computed tomography. Geometrical features of the porous brittle structure are quantitatively analyzed based on calibration of the x-ray linear attenuation coefficient, use of a 3-D watershed algorithm, and use of a 3-D skeletonization procedure. Several examples of the 3-D analysis for porous, wallboard structures are presented and the results discussed.

Phase contrast imaging using a micro focus x-ray source

NASA Astrophysics Data System (ADS)

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

2014-09-01

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 Kα1 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.

Phantom evaluation of a cardiac SPECT/VCT system that uses a common set of solid-state detectors for both emission and transmission scans.

PubMed

Bai, Chuanyong; Conwell, Richard; Kindem, Joel; Babla, Hetal; Gurley, Mike; De Los Santos, Romer; Old, Rex; Weatherhead, Randy; Arram, Samia; Maddahi, Jamshid

2010-06-01

We developed a cardiac SPECT system (X-ACT) with low dose volume CT transmission-based attenuation correction (AC). Three solid-state detectors are configured to form a triple-head system for emission scans and reconfigured to form a 69-cm field-of-view detector arc for transmission scans. A near mono-energetic transmission line source is produced from the collimated fluorescence x-ray emitted from a lead target when the target is illuminated by a narrow polychromatic x-ray beam from an x-ray tube. Transmission scans can be completed in 1 min with insignificant patient dose (deep dose equivalent <5 muSv). We used phantom studies to evaluate (1) the accuracy of the reconstructed attenuation maps, (2) the effect of AC on image uniformity, and (3) the effect of AC on defect contrast (DC). The phantoms we used included an ACR phantom, an anthropomorphic phantom with a uniform cardiac insert, and an anthropomorphic phantom with two defects in the cardiac insert. The reconstructed attenuation coefficient of water at 140 keV was .150 +/- .003/cm in the uniform region of the ACR phantom, .151 +/- .003/cm and .151 +/- .002/cm in the liver and cardiac regions of the anthropomorphic phantom. The ACR phantom images with AC showed correction of the bowing effect due to attenuation in the images without AC (NC). The 17-segment scores of the images of the uniform cardiac insert were 78.3 +/- 6.5 before and 87.9 +/- 3.3 after AC (average +/- standard deviation). The inferior-to-anterior wall ratio and the septal-to-lateral wall ratio were .99 and 1.16 before and 1.02 and 1.00 after AC. The DC of the two defects was .528 and .156 before and .628 and .173 after AC. The X-ACT system generated accurate attenuation maps with 1-minute transmission scans. AC improved image quality and uniformity over NC.

Dimensionality and noise in energy selective x-ray imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alvarez, Robert E.

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 measurementmore » 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 × 10{sup 3}. With the soft tissue component, it is 2.7 × 10{sup 4}. 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.« less

Determining paediatric patient thickness from a single digital radiograph-a proof of principle.

PubMed

Worrall, Mark; Vinnicombe, Sarah; Sutton, David G

2018-04-05

This work presents a proof of principle for a method of estimating the thickness of an attenuator from a single radiograph using the image, the exposure factors with which it was acquired and a priori knowledge of the characteristics of the X-ray unit and detector used for the exposure. It is intended this could be developed into a clinical tool to assist with paediatric patient dose audit, for which a measurement of patient size is required. The proof of principle used measured pixel value and effective linear attenuation coefficient to estimate the thickness of a Solid Water attenuator. The kerma at the detector was estimated using a measurement of pixel value on the image and measured detector calibrations. The initial kerma was estimated using a lookup table of measured output values. The effective linear attenuation coefficient was measured for Solid Water at varying kV p . 11 test images of known and varying thicknesses of Solid Water were acquired at 60, 70 and 81 kV p . Estimates of attenuator thickness were made using the model and the results compared to the known thickness. Estimates of attenuator thickness made using the model differed from the known thickness by 3.8 mm (3.2%) on average, with a range of 0.5-10.8 mm (0.5-9%). A proof of principle is presented for a method of estimating the thickness of an attenuator using a single radiograph of the attenuator. The method has been shown to be accurate using a Solid Water attenuator, with a maximum difference between estimated and known attenuator thickness of 10.8 mm (9%). The method shows promise as a clinical tool for estimating abdominal paediatric patient thickness for paediatric patient dose audit, and is only contingent on the type of data routinely collected by Medical Physics departments. Advances in knowledge: A computational model has been created that is capable of accurately estimating the thickness of a uniform attenuator using only the radiographic image, the exposure factors with which it was acquired and a priori knowledge of the characteristics of the X-ray unit and detector used for the exposure.

Europium- and lithium-doped yttrium oxide nanocrystals that provide a linear emissive response with X-ray radiation exposure

NASA Astrophysics Data System (ADS)

Stanton, Ian N.; Belley, Matthew D.; Nguyen, Giao; Rodrigues, Anna; Li, Yifan; Kirsch, David G.; Yoshizumi, Terry T.; Therien, Michael J.

2014-04-01

Eu- and Li-doped yttrium oxide nanocrystals [Y2-xO3 Eux, Liy], in which Eu and Li dopant ion concentrations were systematically varied, were developed and characterized (TEM, XRD, Raman spectroscopic, UV-excited lifetime, and ICP-AES data) in order to define the most emissive compositions under specific X-ray excitation conditions. These optimized [Y2-xO3 Eux, Liy] compositions display scintillation responses that: (i) correlate linearly with incident radiation exposure at X-ray energies spanning from 40-220 kVp, and (ii) manifest no evidence of scintillation intensity saturation at the highest evaluated radiation exposures [up to 4 Roentgen per second]. For the most emissive nanoscale scintillator composition, [Y1.9O3; Eu0.1, Li0.16], excitation energies of 40, 120, and 220 kVp were chosen to probe the dependence of the integrated emission intensity upon X-ray exposure-rate in energy regimes having different mass-attenuation coefficients and where either the photoelectric or the Compton effect governs the scintillation mechanism. These experiments demonstrate for the first time for that for comparable radiation exposures, when the scintillation mechanism is governed by the photoelectric effect and a comparably larger mass-attenuation coefficient (120 kVp excitation), greater integrated emission intensities are recorded relative to excitation energies where the Compton effect regulates scintillation (220 kVp) in nanoscale [Y2-xO3 Eux] crystals. Nanoscale [Y1.9O3; Eu0.1, Li0.16] (70 +/- 20 nm) was further exploited as a detector material in a prototype fiber-optic radiation sensor. The scintillation intensity from the [Y1.9O3; Eu0.1, Li0.16]-modified, 400 μm sized optical fiber tip, recorded using a CCD-photodetector and integrated over the 605-617 nm wavelength domain, was correlated with radiation exposure using a Precision XRAD 225Cx small-animal image guided radiation therapy (IGRT) system. For both 80 and 225 kVp energies, this radiotransparent device recorded scintillation intensities that tracked linearly with total radiation exposure, highlighting its capability to provide alternately accurate dosimetry measurements for both diagnostic imaging (80 kVp) and radiation therapy treatment (225 kVp).Eu- and Li-doped yttrium oxide nanocrystals [Y2-xO3 Eux, Liy], in which Eu and Li dopant ion concentrations were systematically varied, were developed and characterized (TEM, XRD, Raman spectroscopic, UV-excited lifetime, and ICP-AES data) in order to define the most emissive compositions under specific X-ray excitation conditions. These optimized [Y2-xO3 Eux, Liy] compositions display scintillation responses that: (i) correlate linearly with incident radiation exposure at X-ray energies spanning from 40-220 kVp, and (ii) manifest no evidence of scintillation intensity saturation at the highest evaluated radiation exposures [up to 4 Roentgen per second]. For the most emissive nanoscale scintillator composition, [Y1.9O3; Eu0.1, Li0.16], excitation energies of 40, 120, and 220 kVp were chosen to probe the dependence of the integrated emission intensity upon X-ray exposure-rate in energy regimes having different mass-attenuation coefficients and where either the photoelectric or the Compton effect governs the scintillation mechanism. These experiments demonstrate for the first time for that for comparable radiation exposures, when the scintillation mechanism is governed by the photoelectric effect and a comparably larger mass-attenuation coefficient (120 kVp excitation), greater integrated emission intensities are recorded relative to excitation energies where the Compton effect regulates scintillation (220 kVp) in nanoscale [Y2-xO3 Eux] crystals. Nanoscale [Y1.9O3; Eu0.1, Li0.16] (70 +/- 20 nm) was further exploited as a detector material in a prototype fiber-optic radiation sensor. The scintillation intensity from the [Y1.9O3; Eu0.1, Li0.16]-modified, 400 μm sized optical fiber tip, recorded using a CCD-photodetector and integrated over the 605-617 nm wavelength domain, was correlated with radiation exposure using a Precision XRAD 225Cx small-animal image guided radiation therapy (IGRT) system. For both 80 and 225 kVp energies, this radiotransparent device recorded scintillation intensities that tracked linearly with total radiation exposure, highlighting its capability to provide alternately accurate dosimetry measurements for both diagnostic imaging (80 kVp) and radiation therapy treatment (225 kVp). Electronic supplementary information (ESI) available: Material synthesis; experimental details; X-ray diffraction (XRD), UV-excited lifetimes, ICP-AES, and additional TEM data. See DOI: 10.1039/c4nr00497c

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

PubMed

Okunade, Akintunde A

2007-07-01

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.

Hybrid modelling of a high-power X-ray attenuator plasma.

PubMed

Martín Ortega, Álvaro; Lacoste, Ana; Minea, Tiberiu

2018-05-01

X-ray gas attenuators act as stress-free high-pass filters for synchrotron and free-electron laser beamlines to reduce the heat load in downstream optical elements without affecting other properties of the X-ray beam. The absorption of the X-ray beam triggers a cascade of processes that ionize and heat up the gas locally, changing its density and therefore the X-ray absorption. Aiming to understand and predict the behaviour of the gas attenuator in terms of efficiency versus gas pressure, a hybrid model has been developed, combining three approaches: an analytical description of the X-ray absorption; Monte Carlo for the electron thermalization; and a fluid treatment for the electron diffusion, recombination and excited-states relaxation. The model was applied to an argon-filled attenuator prototype built and tested at the European Synchrotron Radiation Facility, at a pressure of 200 mbar and assuming stationary conditions. The results of the model showed that the electron population thermalizes within a few nanoseconds after the X-ray pulse arrival and it occurs just around the X-ray beam path, recombining in the bulk of the gas rather than diffusing to the attenuator walls. The gas temperature along the beam path reached 850 K for 770 W of incident power and 182 W m -1 of absorbed power. Around 70% of the absorbed power is released as visible and UV radiation rather than as heat to the gas. Comparison of the power absorption with the experiment showed an overall agreement both with the plasma radial profile and power absorption trend, the latter within an error smaller than 20%. This model can be used for the design and operation of synchrotron gas attenuators and as a base for a time-dependent model for free-electron laser attenuators.

Effect of an external magnetic field on the mass attenuation coefficients of p-Si and n-Si

NASA Astrophysics Data System (ADS)

Yılmaz, D.; Önder, P.

2018-05-01

In this study, the mass attenuation coefficients of p-Si and n-Si semiconductor samples have been determined in an external magnetic field. The semiconductor samples were located to the external magnetic field of intensities 0.2 T, 0.4 T, 0.6 T and 0.8 T. The samples were bombarded by 59.5 keV, 80.1 keV, 121.8 keV and 244.7 keV gamma-rays emitted from Am241, Ba133 and Eu152 radioactive sources. The transmitted photons were detected by a CdTe detector. It was observed that the mass attenuation coefficients of p-Si and n-Si semiconductor samples decrease with increasing gamma-ray energy. Also, the mass attenuation coefficients of the samples increase with applying magnetic field intensity.

X-ray transmissive debris shield

DOEpatents

Spielman, R.B.

1996-05-21

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.

X-ray transmissive debris shield

DOEpatents

Spielman, Rick B.

1996-01-01

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.

Effect of molybdenum on gamma ray shielding and structural properties of PbO-B2O3 glasses

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder

2018-04-01

The present study is aimed at developing new shielding materials for gamma ray shielding applications. Transparent glasses of the composition xMoO3-0.7PbO-(0.3-x)B2O3 where x= 0.03 to 0. 06 (mole fraction) have been prepared by using melt-quenchingtechnique. Gamma ray shielding properties have been evaluated in terms of mass attenuation coefficient and half value layer parameter at photon energies 662 and 1173 keV. These shielding parameters are also compared with standard shielding material`concretes'. It has been found that prepared glass system shows better shielding properties than barite and ordinary concretes proving the possibility of its usage as an alternate to conventional concrete for gamma ray shielding applications. The density, molar volume, X-Ray Diffraction, Fourier Transform InfraRed and Raman studies have been performed to study the structural properties of the glass system. It has been analyzed from FTIR and Raman studies that bridging oxygens increase with the decrease of MoO3 content in the glass composition.

Calibrating the X-ray attenuation of liquid water and correcting sample movement artefacts during in operando synchrotron X-ray radiographic imaging of polymer electrolyte membrane fuel cells.

PubMed

Ge, Nan; Chevalier, Stéphane; Hinebaugh, James; Yip, Ronnie; Lee, Jongmin; Antonacci, Patrick; Kotaka, Toshikazu; Tabuchi, Yuichiro; Bazylak, Aimy

2016-03-01

Synchrotron X-ray radiography, due to its high temporal and spatial resolutions, provides a valuable means for understanding the in operando water transport behaviour in polymer electrolyte membrane fuel cells. The purpose of this study is to address the specific artefact of imaging sample movement, which poses a significant challenge to synchrotron-based imaging for fuel cell diagnostics. Specifically, the impact of the micrometer-scale movement of the sample was determined, and a correction methodology was developed. At a photon energy level of 20 keV, a maximum movement of 7.5 µm resulted in a false water thickness of 0.93 cm (9% higher than the maximum amount of water that the experimental apparatus could physically contain). This artefact was corrected by image translations based on the relationship between the false water thickness value and the distance moved by the sample. The implementation of this correction method led to a significant reduction in false water thickness (to ∼0.04 cm). Furthermore, to account for inaccuracies in pixel intensities due to the scattering effect and higher harmonics, a calibration technique was introduced for the liquid water X-ray attenuation coefficient, which was found to be 0.657 ± 0.023 cm(-1) at 20 keV. The work presented in this paper provides valuable tools for artefact compensation and accuracy improvements for dynamic synchrotron X-ray imaging of fuel cells.

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

PubMed

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

2002-07-01

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 (calcite, Ca(1-x)Mg(x)CO(3)) cannot account for all of the linear attenuation coefficient decrease in the two zones: this suggested that soft tissue is localized there. Transmission diffraction mapping (synchrotron X-radiation, 80.8 keV, 0.1 x 0.1mm(2) beam area, 0.1mm translation grid, image plate area detector) simultaneously probed variations in 3-D and showed that the crystal elements of the "T"-shaped tooth were very highly aligned. Diffraction patterns from the keel (adaxial web) and from the abaxial flange (containing primary plates and the stone part) differed markedly. The flange contained two populations of identically oriented crystal elements with lattice parameters corresponding to x=0.13 and x=0.32. The keel produced one set of diffraction spots corresponding to the lower x. The compositions were more or less equivalent to those determined by others for camarodont teeth, and the high Mg phase is expected to be disks of secondary mineral epitaxially related to the underlying primary mineral element. Lattice parameter gradients were not noted in the keel or flange. Taken together, the microCT and diffraction results indicated that there was a band of relatively high protein content, of up to approximately 0.25 volume fraction, in the central part of the flange and paralleling its adaxial and abaxial faces. X-ray microCT and microdiffraction data used in conjunction with protein distribution data will be crucial for understanding the properties of various biocomposites and their mechanical functions.

Experimental determination of the x-ray atomic fundamental parameters of nickel

NASA Astrophysics Data System (ADS)

Ménesguen, Y.; Lépy, M.-C.; Hönicke, P.; Müller, M.; Unterumsberger, R.; Beckhoff, B.; Hoszowska, J.; Dousse, J.-Cl; Błachucki, W.; Ito, Y.; Yamashita, M.; Fukushima, S.

2018-02-01

The x-ray atomic properties of nickel (Ni) were investigated in a unique approach combining different experimental techniques to obtain new, useful and reliable values of atomic fundamental parameters for x-ray spectrometric purposes and for comparison with theoretical predictions. We determined the mass attenuation coefficients in an energy range covering the L- and K-absorption edges, the K-shell fluorescence yield and the Kβ/Kα and Kβ1, 3/Kα1, 2 transition probability ratios. The obtained line profiles and linewidths of the Kα and Kβ transitions in Ni can be considered as the contribution of the satellite lines arising from the [KM] shake processes suggested by Deutsch et al (1995 Phys. Rev. A 51 283) and Ito et al (2016 Phys. Rev. A 94 042506). Comparison of the new data with several databases showed good agreement, but also discrepancies were found with existing tabulated values.

Characterizing X-ray Attenuation of Containerized Cargo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birrer, N.; Divin, C.; Glenn, S.

X-ray inspection systems can be used to detect radiological and nuclear threats in imported cargo. In order to better understand performance of these systems, the attenuation characteristics of imported cargo need to be determined. This project focused on developing image processing algorithms for segmenting cargo and using x-ray attenuation to quantify equivalent steel thickness to determine cargo density. These algorithms were applied to over 450 cargo radiographs. The results are summarized in this report.

Experimental study of some shielding parameters for composite shields

NASA Astrophysics Data System (ADS)

Mkhaiber, Ahmed F.; Dheyaa, Abdulraheem

2018-05-01

In this study radiation protection shields have been prepared consist of composite materials have epoxy as a basis material and different reinforcing materials C Ni PbO and Bi with various reinforcing ratios 10 20 30 40 50 % and dimensions 1 × 10 × 10 cm. For examination the suitability of using this shields to protect from gamma ray some shielding parameters were calculated like: Linear attenuation coefficient μ, effective atomic number Zeffe, heaviness and half value thickness X1/2 for energy rang 1218 – 1480 KeV. These parameters have been measured by using sodium iodide system NaITI with deferent radiation sources 152Eu 60Co and 137Cs. The results show that these parameters are effected by the reinforcing ratio and gamma ray energy, it is found that the linear attenuation coefficient and atomic effective number increases with reinforcing ratio increases and decreased with energy increasing especially with high concentrations 40 50 % and at low energies Eγ < 0662 MeV with certain energy while the values of X1/2 decrease with reinforcing ratio increases. Heaviness was calculated too for all shields, with respect to lead from its values we found that this shields lighter than lead, which make it preferable to traditional material such as lead and concrete.

X-ray attenuation properties of stainless steel (u)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lily L; Berry, Phillip C

2009-01-01

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 stainlessmore » 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.« less

Measuring partial fluorescence yield using filtered detectors.

PubMed

Boyko, T D; Green, R J; Moewes, A; Regier, T Z

2014-07-01

Typically, X-ray absorption near-edge structure measurements aim to probe the linear attenuation coefficient. These measurements are often carried out using partial fluorescence yield techniques that rely on detectors having photon energy discrimination improving the sensitivity and the signal-to-background ratio of the measured spectra. However, measuring the partial fluorescence yield in the soft X-ray regime with reasonable efficiency requires solid-state detectors, which have limitations due to the inherent dead-time while measuring. Alternatively, many of the available detectors that are not energy dispersive do not suffer from photon count rate limitations. A filter placed in front of one of these detectors will make the energy-dependent efficiency non-linear, thereby changing the responsivity of the detector. It is shown that using an array of filtered X-ray detectors is a viable method for measuring soft X-ray partial fluorescence yield spectra without dead-time. The feasibility of this technique is further demonstrated using α-Fe2O3 as an example and it is shown that this detector technology could vastly improve the photon collection efficiency at synchrotrons and that these detectors will allow experiments to be completed with a much lower photon flux reducing X-ray-induced damage.

Towards a nanoscale mammographic contrast agent: development of a modular pre-clinical dual optical/x-ray agent

NASA Astrophysics Data System (ADS)

Hill, Melissa L.; Gorelikov, Ivan; Niroui, Farnaz; Levitin, Ronald B.; Mainprize, James G.; Yaffe, Martin J.; Rowlands, J. A.; Matsuura, Naomi

2013-08-01

Contrast-enhanced digital mammography (CEDM) can provide improved breast cancer detection and characterization compared to conventional mammography by imaging the effects of tumour angiogenesis. Current small-molecule contrast agents used for CEDM are limited by a short plasma half-life and rapid extravasation into tissue interstitial space. To address these limitations, nanoscale agents that can remain intravascular except at sites of tumour angiogenesis can be used. For CEDM, this agent must be both biocompatible and strongly attenuate mammographic energy x-rays. Nanoscale perfluorooctylbromide (PFOB) droplets have good x-ray attenuation and have been used in patients for other applications. However, the macroscopic scale of x-ray imaging (50-100 µm) is inadequate for direct verification that PFOB droplets localize at sites of breast tumour angiogenesis. For efficient pre-clinical optimization for CEDM, we integrated an optical marker into PFOB droplets for microscopic assessment (≪50 µm). To develop PFOB droplets as a new nanoscale mammographic contrast agent, PFOB droplets were labelled with fluorescent quantum dots (QDs). The droplets had mean diameters of 160 nm, fluoresced at 635 nm and attenuated x-ray spectra at 30.5 keV mean energy with a relative attenuation of 5.6 ± 0.3 Hounsfield units (HU) mg-1 mL-1 QD-PFOB. With the agent loaded into tissue phantoms, good correlation between x-ray attenuation and optical fluorescence was found (R2 = 0.96), confirming co-localization of the QDs with PFOB for quantitative assessment using x-ray or optical methods. Furthermore, the QDs can be removed from the PFOB agent without affecting its x-ray attenuation or structural properties for expedited translation of optimized PFOB droplet formulations into patients.

Measurement of breast-tissue x-ray attenuation by spectral mammography: solid lesions

NASA Astrophysics Data System (ADS)

Fredenberg, Erik; Kilburn-Toppin, Fleur; Willsher, Paula; Moa, Elin; Danielsson, Mats; Dance, David R.; Young, Kenneth C.; Wallis, Matthew G.

2016-04-01

Knowledge of x-ray attenuation is essential for developing and evaluating x-ray imaging technologies. For instance, techniques to distinguish between cysts and solid tumours at mammography screening would be highly desirable to reduce recalls, but the development requires knowledge of the x-ray attenuation for cysts and tumours. We have previously measured the attenuation of cyst fluid using photon-counting spectral mammography. Data on x-ray attenuation for solid breast lesions are available in the literature, but cover a relatively wide range, likely caused by natural spread between samples, random measurement errors, and different experimental conditions. In this study, we have adapted a previously developed spectral method to measure the linear attenuation of solid breast lesions. A total of 56 malignant and 5 benign lesions were included in the study. The samples were placed in a holder that allowed for thickness measurement. Spectral (energy-resolved) images of the samples were acquired and the image signal was mapped to equivalent thicknesses of two known reference materials, which can be used to derive the x-ray attenuation as a function of energy. The spread in equivalent material thicknesses was relatively large between samples, which is likely to be caused mainly by natural variation and only to a minor extent by random measurement errors and sample inhomogeneity. No significant difference in attenuation was found between benign and malignant solid lesions. The separation between cyst-fluid and tumour attenuation was, however, significant, which suggests it may be possible to distinguish cystic from solid breast lesions, and the results lay the groundwork for a clinical trial. In addition, the study adds a relatively large sample set to the published data and may contribute to a reduction in the overall uncertainty in the literature.

Coupling multiscale X-ray physics and micromechanics for bone tissue composition and elasticity determination from micro-CT data, by example of femora from OVX and sham rats

NASA Astrophysics Data System (ADS)

Hasslinger, Patricia; Vass, Viktoria; Dejaco, Alexander; Blanchard, Romane; Örlygsson, Gissur; Gargiulo, Paolo; Hellmich, Christian

2016-05-01

Due to its high resolution, micro-CT (Computed Tomograph) scanning is the key to assess bone quality of sham and OVX (ovariectomized) rats. Combination of basic X-ray physics, such as the energy- and chemistry-dependence of attenuation coefficients, with results from ashing tests on rat bones, delivers mineral, organic, and water volume fractions within the voxels. Additional use of a microelastic model for bone provides voxel-specific elastic properties. The new method delivers realistic bone mass densities, and reveals that OVX protocols may indeed induce some bone mass loss, while the average composition of the bone tissue remains largely unaltered.

Phantom evaluation of a cardiac SPECT/VCT system that uses a common set of solid-state detectors for both emission and transmission scans

PubMed Central

Conwell, Richard; Kindem, Joel; Babla, Hetal; Gurley, Mike; De Los Santos, Romer; Old, Rex; Weatherhead, Randy; Arram, Samia; Maddahi, Jamshid

2010-01-01

Background We developed a cardiac SPECT system (X-ACT) with low dose volume CT transmission-based attenuation correction (AC). Three solid-state detectors are configured to form a triple-head system for emission scans and reconfigured to form a 69-cm field-of-view detector arc for transmission scans. A near mono-energetic transmission line source is produced from the collimated fluorescence x-ray emitted from a lead target when the target is illuminated by a narrow polychromatic x-ray beam from an x-ray tube. Transmission scans can be completed in 1 min with insignificant patient dose (deep dose equivalent <5 μSv). Methods We used phantom studies to evaluate (1) the accuracy of the reconstructed attenuation maps, (2) the effect of AC on image uniformity, and (3) the effect of AC on defect contrast (DC). The phantoms we used included an ACR phantom, an anthropomorphic phantom with a uniform cardiac insert, and an anthropomorphic phantom with two defects in the cardiac insert. Results The reconstructed attenuation coefficient of water at 140 keV was .150 ± .003/cm in the uniform region of the ACR phantom, .151 ± .003/cm and .151 ± .002/cm in the liver and cardiac regions of the anthropomorphic phantom. The ACR phantom images with AC showed correction of the bowing effect due to attenuation in the images without AC (NC). The 17-segment scores of the images of the uniform cardiac insert were 78.3 ± 6.5 before and 87.9 ± 3.3 after AC (average ± standard deviation). The inferior-to-anterior wall ratio and the septal-to-lateral wall ratio were .99 and 1.16 before and 1.02 and 1.00 after AC. The DC of the two defects was .528 and .156 before and .628 and .173 after AC. Conclusion The X-ACT system generated accurate attenuation maps with 1-minute transmission scans. AC improved image quality and uniformity over NC. PMID:20169476

X-ray microscopy using reflection targets based on SEM with tungsten filament

NASA Astrophysics Data System (ADS)

Liu, Junbiao; Ma, Yutian; Zhao, Weixia; Niu, Geng; Chu, Mingzhang; Yin, Bohua; Han, Li; Liu, Baodong

2016-10-01

X-ray MicroandNano imaging is developed based on the conventional x-ray tomography, it can not only provide nondestructive testing with higher resolution measurement, but also be used to examine the material or the structure with low atomic number and low density. The source with micro-focal spot size is one of the key components of x-ray MicroandNano imaging. The focused electron beam from SEM bombarding the metal target can generate x-ray with ultra-small size. It is convenient to set up x-ray microscopy based on SEM for laboratory use. This paper describes a new x-ray microscopy using reflection targets based on FEI Quanta600 SEM with tungsten filament. The flat panel detector is placed outside of the vacuum chamber with 300μm thickness Be-window to isolate vacuum from the air. A stage with 3 DOFs is added to adjust the positions of the target, the SEM's sample stage is used to move sample. And the shape of target is designed as cone with 60° half cone angle to get the maximum x-ray dosage. The attenuation coefficient of Bewindow for x-ray is about 25%. Finally, the line pair card is used to evaluate the resolution and the result shows that the resolution of the system can receive less than 750nm, when the acceleration voltage is 30keV, the beam current is 160nA, the SEM working distance is 5mm and the acquisition time of the detector is 60s.

Correction of nonuniform attenuation and image fusion in SPECT imaging by means of separate X-ray CT.

PubMed

Kashiwagi, Toru; Yutani, Kenji; Fukuchi, Minoru; Naruse, Hitoshi; Iwasaki, Tadaaki; Yokozuka, Koichi; Inoue, Shinichi; Kondo, Shoji

2002-06-01

Improvements in image quality and quantitation measurement, and the addition of detailed anatomical structures are important topics for single-photon emission tomography (SPECT). The goal of this study was to develop a practical system enabling both nonuniform attenuation correction and image fusion of SPECT images by means of high-performance X-ray computed tomography (CT). A SPECT system and a helical X-ray CT system were placed next to each other and linked with Ethernet. To avoid positional differences between the SPECT and X-ray CT studies, identical flat patient tables were used for both scans; body distortion was minimized with laser beams from the upper and lateral directions to detect the position of the skin surface. For the raw projection data of SPECT, a scatter correction was performed with the triple energy window method. Image fusion of the X-ray CT and SPECT images was performed automatically by auto-registration of fiducial markers attached to the skin surface. After registration of the X-ray CT and SPECT images, an X-ray CT-derived attenuation map was created with the calibration curve for 99mTc. The SPECT images were then reconstructed with scatter and attenuation correction by means of a maximum likelihood expectation maximization algorithm. This system was evaluated in torso and cylindlical phantoms and in 4 patients referred for myocardial SPECT imaging with Tc-99m tetrofosmin. In the torso phantom study, the SPECT and X-ray CT images overlapped exactly on the computer display. After scatter and attenuation correction, the artifactual activity reduction in the inferior wall of the myocardium improved. Conversely, the incresed activity around the torso surface and the lungs was reduced. In the abdomen, the liver activity, which was originally uniform, had recovered after scatter and attenuation correction processing. The clinical study also showed good overlapping of cardiac and skin surface outlines on the fused SPECT and X-ray CT images. The effectiveness of the scatter and attenuation correction process was similar to that observed in the phantom study. Because the total time required for computer processing was less than 10 minutes, this method of attenuation correction and image fusion for SPECT images is expected to become popular in clinical practice.

Preparation, characterization and X-ray attenuation property of Gd2O3-based nanocomposites

NASA Astrophysics Data System (ADS)

Jayakumar, Sangeetha; Saravanan, T.; Philip, John

2017-11-01

In an attempt to develop an alternate to lead-based X-ray shielding material, we describe the X-ray attenuation property of nanocomposites containing Gd2O3 as nanofiller and silicone resin as matrix, prepared by a simple solution-casting technique. Gd2O3 nanoparticles of size 30 and 56 nm are used at concentrations of 25 and 2.5 wt%. The nanoparticles and the nanocomposites are characterized using X-ray diffraction (XRD) studies, small angle X-ray spectroscopy (SAXS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The X-ray attenuation property of nanocomposites, studied using an industrial X-ray unit, shows that nanocomposites containing nanoparticles of size 56 nm (G2) exhibit better attenuation than nanocomposites containing nanoparticles of size 30 nm (G1), which is attributed to the greater interfacial interaction between the G2 nanofillers and silicone matrix. In the case of nanocomposites containing G1 nanoparticles, the interfacial interaction between the nanofiller and the matrix is so weak that it results in pulling out of nanofillers, causing voids in the matrix, which act as X-ray transparent region, thereby reducing the overall X-ray attenuation property of G1 nanocomposites. This is further corroborated from the AFM images of the nanocomposites. The weight loss and heat flow curves of pure silicone matrix and the nanocomposites containing Gd2O3 nanoparticles of size 30 and 56 nm show the degradation of silicone resin, due to chain scission, between 403 and 622 °C. The same onset temperature (403 °C) of degradation of matrix with and without nanoparticles shows that the addition of nanofillers to the matrix does not deteriorate the thermal stability of the matrix. This confirms the thermal stability of nanocomposites. Therefore, our study shows that nanocomposites containing G2 nanoparticles are potential candidates for the development of X-ray opaque fabric material.

Theoretical study of depth profiling with gamma- and X-ray spectrometry based on measurements of intensity ratios

NASA Astrophysics Data System (ADS)

Bártová, H.; Trojek, T.; Johnová, K.

2017-11-01

This article describes the method for the estimation of depth distribution of radionuclides in a material with gamma-ray spectrometry, and the identification of a layered structure of a material with X-ray fluorescence analysis. This method is based on the measurement of a ratio of two gamma or X-ray lines of a radionuclide or a chemical element, respectively. Its principle consists in different attenuation coefficient for these two lines in a measured material. The main aim of this investigation was to show how the detected ratio of these two lines depends on depth distribution of an analyte and mainly how this ratio depends on density and chemical composition of measured materials. Several different calculation arrangements were made and a lot of Monte Carlo simulation with the code MCNP - Monte Carlo N-Particle (Briesmeister, 2000) was performed to answer these questions. For X-ray spectrometry, the calculated Kα/Kβ diagrams were found to be almost independent upon matrix density and composition. Thanks to this phenomenon it would be possible to draw only one Kα/Kβ diagram for an element whose depth distribution is examined.

Lithium-doped hydroxyapatite nano-composites: Synthesis, characterization, gamma attenuation coefficient and dielectric properties

NASA Astrophysics Data System (ADS)

Badran, H.; Yahia, I. S.; Hamdy, Mohamed S.; Awwad, N. S.

2017-01-01

Lithium-hydroxyapatite (0, 1, 5, 10, 20, 30 and 40 wt% Li-HAp) nano-composites were synthesized by sol-gel technique followed by microwave-hydrothermal treatment. The composites were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman techniques. Gamma attenuation coefficient and the dielectric properties for all composites were investigated. The crystallinity degree of Li-doped HAp was higher than that of un-doped HAp. Gamma attenuation coefficient values increased from 0.562 cm-1 for 0 wt% Li-HAp to 2.190 cm-1 for 40 wt% Li-HAp. The alternating current conductivity increased with increasing frequency. The concentration of Li affect the values of dielectric constant where Li doped HAp of low dielectric constant can have an advantage for healing in bone fractures. The calcium to phosphorus ratio decreased from 1.43 to 1.37 with the addition of lithium indicating the Ca deficiency in the studied composites. Our findings lead to the conclusion that Li-HAp is a new nano-composite useful for medical applications and could be doped with gamma shield materials.

Monte Carlo simulations for 20 MV X-ray spectrum reconstruction of a linear induction accelerator

NASA Astrophysics Data System (ADS)

Wang, Yi; Li, Qin; Jiang, Xiao-Guo

2012-09-01

To study the spectrum reconstruction of the 20 MV X-ray generated by the Dragon-I linear induction accelerator, the Monte Carlo method is applied to simulate the attenuations of the X-ray in the attenuators of different thicknesses and thus provide the transmission data. As is known, the spectrum estimation from transmission data is an ill-conditioned problem. The method based on iterative perturbations is employed to derive the X-ray spectra, where initial guesses are used to start the process. This algorithm takes into account not only the minimization of the differences between the measured and the calculated transmissions but also the smoothness feature of the spectrum function. In this work, various filter materials are put to use as the attenuator, and the condition for an accurate and robust solution of the X-ray spectrum calculation is demonstrated. The influences of the scattering photons within different intervals of emergence angle on the X-ray spectrum reconstruction are also analyzed.

Effects of Shielding on Gamma Rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karpius, Peter Joseph

2017-03-13

The interaction of gamma rays with matter results in an effect we call attenuation (i.e. ‘shielding’). Attenuation can dramatically alter the appearance of a spectrum. Attenuating materials may actually create features in a spectrum via x-ray fluorescence

Spectral CT Reconstruction with Image Sparsity and Spectral Mean

PubMed Central

Zhang, Yi; Xi, Yan; Yang, Qingsong; Cong, Wenxiang; Zhou, Jiliu

2017-01-01

Photon-counting detectors can acquire x-ray intensity data in different energy bins. The signal to noise ratio of resultant raw data in each energy bin is generally low due to the narrow bin width and quantum noise. To address this problem, here we propose an image reconstruction approach for spectral CT to simultaneously reconstructs x-ray attenuation coefficients in all the energy bins. Because the measured spectral data are highly correlated among the x-ray energy bins, the intra-image sparsity and inter-image similarity are important prior acknowledge for image reconstruction. Inspired by this observation, the total variation (TV) and spectral mean (SM) measures are combined to improve the quality of reconstructed images. For this purpose, a linear mapping function is used to minimalize image differences between energy bins. The split Bregman technique is applied to perform image reconstruction. Our numerical and experimental results show that the proposed algorithms outperform competing iterative algorithms in this context. PMID:29034267

Iodine imaging using spectral analysis. [radiography for visualization of small blood vessels

NASA Technical Reports Server (NTRS)

Macovski, A.

1978-01-01

Existing radiographic imaging systems provide images which represent an integration or averaging over the energy spectrum. In order to provide noninvasive angiography it is necessary to image the relatively small amounts of iodine which are available following an intravenous administration. This is accomplished by making use of the special spectral characteristics of iodine. Two methods will be presented. One involves a special grating for encoding the iodine information in the form of a fine line pattern. This is subsequently decoded to provide images of iodinated structures which are otherwise almost invisible. The second method utilizes a scanned X-ray beam which is rapidly switched in the high energy region. In this region, iodine experiences significant variations in the attenuation coefficient while bone and soft tissue do not. An efficient and accurate X-ray detector can be used with scanned X-ray beams. This provides a high degree of sensitivity enabling the visualization of small vessels containing relatively dilute iodine.

MCNP6 simulation of radiographs generated from megaelectron volt X-rays for characterizing a computed tomography system

NASA Astrophysics Data System (ADS)

Dooraghi, Alex A.; Tringe, Joseph W.

2018-04-01

To evaluate conventional munition, we simulated an x-ray computed tomography (CT) system for generating radiographs from nominal x-ray energies of 6 or 9 megaelectron volts (MeV). CT simulations, informed by measured data, allow for optimization of both system design and acquisition techniques necessary to enhance image quality. MCNP6 radiographic simulation tools were used to model ideal detector responses (DR) that assume either (1) a detector response proportional to photon flux (N) or (2) a detector response proportional to energy flux (E). As scatter may become significant with MeV x-ray systems, simulations were performed with and without the inclusion of object scatter. Simulations were compared against measurements of a cylindrical munition component principally composed of HMX, tungsten and aluminum encased in carbon fiber. Simulations and measurements used a 6 MeV peak energy x-ray spectrum filtered with 3.175 mm of tantalum. A detector response proportional to energy which includes object scatter agrees to within 0.6 % of the measured line integral of the linear attenuation coefficient. Exclusion of scatter increases the difference between measurement and simulation to 5 %. A detector response proportional to photon flux agrees to within 20 % when object scatter is included in the simulation and 27 % when object scatter is excluded.

Effect of interstitial low level laser therapy on tibial defect

NASA Astrophysics Data System (ADS)

Lee, Sangyeob; Ha, Myungjin; Hwang, Donghyun; Yu, Sungkon; Jang, Seulki; Park, Jihoon; Radfar, Edalat; Kim, Hansung; Jung, Byungjo

2016-03-01

Tibial defect is very common musculoskeletal disorder which makes patient painful and uncomfortable. Many studies about bone regeneration tried to figure out fast bone healing on early phase. It is already known that low level laser therapy (LLLT) is very convenient and good for beginning of bone disorder. However, light scattering and absorption obstruct musculoskeletal therapy which need optimal photon energy delivery. This study has used an interstitial laser probe (ILP) to overcome the limitations of light penetration depth and scattering. Animals (mouse, C57BL/6) were divided into three groups: laser treated test group 1 (660 nm; power 10 mW; total energy 5 J) and test group 2 (660 nm; power 20 mW; total energy 10 J); and untreated control group. All animals were taken surgical operation to make tibial defect on right crest of tibia. The test groups were treated every 48 hours with ILP. Bone volume and X-ray attenuation coefficient were measured on 0, 14th and 28th day with u-CT after treatment and were used to evaluate effect of LLLT. Results show that bone volume of test groups has been improved more than control group. X-ray attenuation coefficients of each groups have slightly different. The results suggest that LLLT combined with ILP may affect on early phase of bone regeneration and may be used in various musculoskeletal disease in deep tissue layer.

Teflon Examination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dooraghi, A. A.; Seetho, I.; Smith, J.. A.

2017-04-27

In this document, we outline an experiment performed at LLNL to evaluate the radiation sensitivity of polytetrafluoroethylene (PTFE) and a PTFE isomer, fluorinated ethylene propylene (FEP). We demonstrate that PTFE, a material currently used for assessing MicroCT system stability, shows higher radiation-dependent change in x-ray attenuation than FEP. Specifically, for a dose of approximately 1.44 x 10 3 Gy, the linear attenuation coefficient (LAC) of PTFE changes by 0.8 ± 0.1 %. During the same irradiation period, the LAC for FEP changes by 0.02 ± 0.1 %, which is within the statistical uncertainty of the measurement. Due to its highermore » resistance to radiation damage, we recommend that LLNL and partner labs operating under the Department of Homeland Security’s Explosives Division (DHS EXD) transition to the use of FEP as a reference material in place of PTFE.« less

Robust x-ray based material identification using multi-energy sinogram decomposition

NASA Astrophysics Data System (ADS)

Yuan, Yaoshen; Tracey, Brian; Miller, Eric

2016-05-01

There is growing interest in developing X-ray computed tomography (CT) imaging systems with improved ability to discriminate material types, going beyond the attenuation imaging provided by most current systems. Dual- energy CT (DECT) systems can partially address this problem by estimating Compton and photoelectric (PE) coefficients of the materials being imaged, but DECT is greatly degraded by the presence of metal or other materials with high attenuation. Here we explore the advantages of multi-energy CT (MECT) systems based on photon-counting detectors. The utility of MECT has been demonstrated in medical applications where photon- counting detectors allow for the resolution of absorption K-edges. Our primary concern is aviation security applications where K-edges are rare. We simulate phantoms with differing amounts of metal (high, medium and low attenuation), both for switched-source DECT and for MECT systems, and include a realistic model of detector energy 0 resolution. We extend the DECT sinogram decomposition method of Ying et al. to MECT, allowing estimation of separate Compton and photoelectric sinograms. We furthermore introduce a weighting based on a quadratic approximation to the Poisson likelihood function that deemphasizes energy bins with low signal. Simulation results show that the proposed approach succeeds in estimating material properties even in high-attenuation scenarios where the DECT method fails, improving the signal to noise ratio of reconstructions by over 20 dB for the high-attenuation phantom. Our work demonstrates the potential of using photon counting detectors for stably recovering material properties even when high attenuation is present, thus enabling the development of improved scanning systems.

Correction of energy-dependent systematic errors in dual-energy X-ray CT using a basis material coefficients transformation method

NASA Astrophysics Data System (ADS)

Goh, K. L.; Liew, S. C.; Hasegawa, B. H.

1997-12-01

Computer simulation results from our previous studies showed that energy dependent systematic errors exist in the values of attenuation coefficient synthesized using the basis material decomposition technique with acrylic and aluminum as the basis materials, especially when a high atomic number element (e.g., iodine from radiographic contrast media) was present in the body. The errors were reduced when a basis set was chosen from materials mimicking those found in the phantom. In the present study, we employed a basis material coefficients transformation method to correct for the energy-dependent systematic errors. In this method, the basis material coefficients were first reconstructed using the conventional basis materials (acrylic and aluminum) as the calibration basis set. The coefficients were then numerically transformed to those for a more desirable set materials. The transformation was done at the energies of the low and high energy windows of the X-ray spectrum. With this correction method using acrylic and an iodine-water mixture as our desired basis set, computer simulation results showed that accuracy of better than 2% could be achieved even when iodine was present in the body at a concentration as high as 10% by mass. Simulation work had also been carried out on a more inhomogeneous 2D thorax phantom of the 3D MCAT phantom. The results of the accuracy of quantitation were presented here.

Ion Storage Ring Measurements of Low Temperature Dielectronic Recombination Rate Coefficients for Modeling X-Ray Photoionized Cosmic Plasmas

NASA Technical Reports Server (NTRS)

Savin, D. W.; Gwinner, G.; Schwalm, D.; Wolf, A.; Mueller, A.; Schippers, S.

2002-01-01

Low temperature dielectronic recombination (DR) is the dominant recombination mechanism for most ions in X-ray photoionized cosmic plasmas. Reliably modeling and interpreting spectra from these plasmas requires accurate low temperature DR rate Coefficients. Of particular importance are the DR rate coefficients for the iron L-shell ions (Fe XVII-Fe XXIV). These ions are predicted to play an important role in determining the thermal structure and line emission of X-ray photoionized plasmas, which form in the media surrounding accretion powered sources such as X-ray binaries (XRBs), active galactic nuclei (AGN), and cataclysmic variables (Savin et al., 2000). The need for reliable DR data of iron L-shell ions has become particularly urgent after the launches of Chandra and XMM-Newton. These satellites are now providing high-resolution X-ray spectra from a wide range of X-ray photoionized sources. Interpreting the spectra from these sources requires reliable DR rate coefficients. However, at the temperatures relevant, for X-ray photoionized plasmas, existing theoretical DR rate coefficients can differ from one another by factors of two to orders of magnitudes.

Europium- and lithium-doped yttrium oxide nanocrystals that provide a linear emissive response with X-ray radiation exposure.

PubMed

Stanton, Ian N; Belley, Matthew D; Nguyen, Giao; Rodrigues, Anna; Li, Yifan; Kirsch, David G; Yoshizumi, Terry T; Therien, Michael J

2014-05-21

Eu- and Li-doped yttrium oxide nanocrystals [Y2-xO3; Eux, Liy], in which Eu and Li dopant ion concentrations were systematically varied, were developed and characterized (TEM, XRD, Raman spectroscopic, UV-excited lifetime, and ICP-AES data) in order to define the most emissive compositions under specific X-ray excitation conditions. These optimized [Y2-xO3; Eux, Liy] compositions display scintillation responses that: (i) correlate linearly with incident radiation exposure at X-ray energies spanning from 40-220 kVp, and (ii) manifest no evidence of scintillation intensity saturation at the highest evaluated radiation exposures [up to 4 Roentgen per second]. For the most emissive nanoscale scintillator composition, [Y1.9O3; Eu0.1, Li0.16], excitation energies of 40, 120, and 220 kVp were chosen to probe the dependence of the integrated emission intensity upon X-ray exposure-rate in energy regimes having different mass-attenuation coefficients and where either the photoelectric or the Compton effect governs the scintillation mechanism. These experiments demonstrate for the first time for that for comparable radiation exposures, when the scintillation mechanism is governed by the photoelectric effect and a comparably larger mass-attenuation coefficient (120 kVp excitation), greater integrated emission intensities are recorded relative to excitation energies where the Compton effect regulates scintillation (220 kVp) in nanoscale [Y2-xO3; Eux] crystals. Nanoscale [Y1.9O3; Eu0.1, Li0.16] (70 ± 20 nm) was further exploited as a detector material in a prototype fiber-optic radiation sensor. The scintillation intensity from the [Y1.9O3; Eu0.1, Li0.16]-modified, 400 μm sized optical fiber tip, recorded using a CCD-photodetector and integrated over the 605-617 nm wavelength domain, was correlated with radiation exposure using a Precision XRAD 225Cx small-animal image guided radiation therapy (IGRT) system. For both 80 and 225 kVp energies, this radiotransparent device recorded scintillation intensities that tracked linearly with total radiation exposure, highlighting its capability to provide alternately accurate dosimetry measurements for both diagnostic imaging (80 kVp) and radiation therapy treatment (225 kVp).

Europium- and lithium-doped yttrium oxide nanocrystals that provide a linear emissive response with X-ray radiation exposure†

PubMed Central

Stanton, Ian N.; Belley, Matthew D.; Nguyen, Giao; Rodrigues, Anna; Li, Yifan; Kirsch, David G.; Yoshizumi, Terry T.

2015-01-01

Eu- and Li-doped yttrium oxide nanocrystals [Y2−xO3; Eux, Liy], in which Eu and Li dopant ion concentrations were systematically varied, were developed and characterized (TEM, XRD, Raman spectroscopic, UV-excited lifetime, and ICP-AES data) in order to define the most emissive compositions under specific X-ray excitation conditions. These optimized [Y2−xO3; Eux, Liy] compositions display scintillation responses that: (i) correlate linearly with incident radiation exposure at X-ray energies spanning from 40–220 kVp, and (ii) manifest no evidence of scintillation intensity saturation at the highest evaluated radiation exposures [up to 4 Roentgen per second]. For the most emissive nanoscale scintillator composition, [Y1.9O3; Eu0.1, Li0.16], excitation energies of 40, 120, and 220 kVp were chosen to probe the dependence of the integrated emission intensity upon X-ray exposure-rate in energy regimes having different mass-attenuation coefficients and where either the photoelectric or the Compton effect governs the scintillation mechanism. These experiments demonstrate for the first time for that for comparable radiation exposures, when the scintillation mechanism is governed by the photoelectric effect and a comparably larger mass-attenuation coefficient (120 kVp excitation), greater integrated emission intensities are recorded relative to excitation energies where the Compton effect regulates scintillation (220 kVp) in nanoscale [Y2−xO3; Eux] crystals. Nanoscale [Y1.9O3; Eu0.1, Li0.16] (70 ± 20 nm) was further exploited as a detector material in a prototype fiber-optic radiation sensor. The scintillation intensity from the [Y1.9O3; Eu0.1, Li0.16]-modified, 400 μm sized optical fiber tip, recorded using a CCD-photodetector and integrated over the 605–617 nm wavelength domain, was correlated with radiation exposure using a Precision XRAD 225Cx small-animal image guided radiation therapy (IGRT) system. For both 80 and 225 kVp energies, this radio transparent device recorded scintillation intensities that tracked linearly with total radiation exposure, highlighting its capability to provide alternately accurate dosimetry measurements for both diagnostic imaging (80 kVp) and radiation therapy treatment (225 kVp). PMID:24696056

Patient-specific fracture risk assessment of vertebrae: A multiscale approach coupling X-ray physics and continuum micromechanics.

PubMed

Blanchard, Romane; Morin, Claire; Malandrino, Andrea; Vella, Alain; Sant, Zdenka; Hellmich, Christian

2016-09-01

While in clinical settings, bone mineral density measured by computed tomography (CT) remains the key indicator for bone fracture risk, there is an ongoing quest for more engineering mechanics-based approaches for safety analyses of the skeleton. This calls for determination of suitable material properties from respective CT data, where the traditional approach consists of regression analyses between attenuation-related grey values and mechanical properties. We here present a physics-oriented approach, considering that elasticity and strength of bone tissue originate from the material microstructure and the mechanical properties of its elementary components. Firstly, we reconstruct the linear relation between the clinically accessible grey values making up a CT, and the X-ray attenuation coefficients quantifying the intensity losses from which the image is actually reconstructed. Therefore, we combine X-ray attenuation averaging at different length scales and over different tissues, with recently identified 'universal' composition characteristics of the latter. This gives access to both the normally non-disclosed X-ray energy employed in the CT-device and to in vivo patient-specific and location-specific bone composition variables, such as voxel-specific mass density, as well as collagen and mineral contents. The latter feed an experimentally validated multiscale elastoplastic model based on the hierarchical organization of bone. Corresponding elasticity maps across the organ enter a finite element simulation of a typical load case, and the resulting stress states are increased in a proportional fashion, so as to check the safety against ultimate material failure. In the young patient investigated, even normal physiological loading is probable to already imply plastic events associated with the hydrated mineral crystals in the bone ultrastructure, while the safety factor against failure is still as high as five. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Sensitivity of photon-counting based K-edge imaging in X-ray computed tomography.

PubMed

Roessl, Ewald; Brendel, Bernhard; Engel, Klaus-Jürgen; Schlomka, Jens-Peter; Thran, Axel; Proksa, Roland

2011-09-01

The feasibility of K-edge imaging using energy-resolved, photon-counting transmission measurements in X-ray computed tomography (CT) has been demonstrated by simulations and experiments. The method is based on probing the discontinuities of the attenuation coefficient of heavy elements above and below the K-edge energy by using energy-sensitive, photon counting X-ray detectors. In this paper, we investigate the dependence of the sensitivity of K-edge imaging on the atomic number Z of the contrast material, on the object diameter D , on the spectral response of the X-ray detector and on the X-ray tube voltage. We assume a photon-counting detector equipped with six adjustable energy thresholds. Physical effects leading to a degradation of the energy resolution of the detector are taken into account using the concept of a spectral response function R(E,U) for which we assume four different models. As a validation of our analytical considerations and in order to investigate the influence of elliptically shaped phantoms, we provide CT simulations of an anthropomorphic Forbild-Abdomen phantom containing a gold-contrast agent. The dependence on the values of the energy thresholds is taken into account by optimizing the achievable signal-to-noise ratios (SNR) with respect to the threshold values. We find that for a given X-ray spectrum and object size the SNR in the heavy element's basis material image peaks for a certain atomic number Z. The dependence of the SNR in the high- Z basis-material image on the object diameter is the natural, exponential decrease with particularly deteriorating effects in the case where the attenuation from the object itself causes a total signal loss below the K-edge. The influence of the energy-response of the detector is very important. We observed that the optimal SNR values obtained with an ideal detector and with a CdTe pixel detector whose response, showing significant tailing, has been determined at a synchrotron differ by factors of about two to three. The potentially very important impact of scattered X-ray radiation and pulse pile-up occurring at high photon rates on the sensitivity of the technique is qualitatively discussed.

Investigation of gamma ray shielding, structural and dissolution rate properties of Bi2O3-BaO-B2O3-Na2O glass system

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder; Anand, Vikas; Kaur, Parminder; Singh, Prabhjot; Bajwa, B. S.

2018-03-01

In the present study, quaternary system of the composition (0.45 + x) Bi2O3-(0.25 - x) BaO-0.15 B2O3-0.15 Na2O (where 0 ≤ x ≤ 0.2 mol fraction) has been prepared by using melt-quenching technique for investigation of gamma ray shielding properties. Mass attenuation coefficients and half value layer parameters have been determined experimentally at 662 keV by using 137Cs source. It has been found that experimental results of these parameters hold good agreement with theoretical values. The density, molar volume, XRD, FTIR, Raman and UV-visible studies have been used to determine structural properties of the prepared glass samples. Dissolution rate of the samples has also been measured to check their utility as long term durable glasses.

Water equivalence of NIPAM based polymer gel dosimeters with enhanced sensitivity for x-ray CT

NASA Astrophysics Data System (ADS)

Gorjiara, Tina; Hill, Robin; Bosi, Stephen; Kuncic, Zdenka; Baldock, Clive

2013-10-01

Two new formulations of N-isopropylacrylamide (NIPAM) based three dimensional (3D) gel dosimeters have recently been developed with improved sensitivity to x-ray CT readout, one without any co-solvent and the other one with isopropanol co-solvent. The water equivalence of the NIPAM gel dosimeters was investigated using different methods to calculate their radiological properties including: density, electron density, number of electrons per grams, effective atomic number, photon interaction probabilities, mass attenuation and energy absorption coefficients, electron collisional, radiative and total mass stopping powers and electron mass scattering power. Monte Carlo modelling was also used to compare the dose response of these gel dosimeters with water for kilovoltage and megavoltage x-ray beams and for megavoltage electron beams. We found that the density and electron density of the co-solvent free gel dosimeter are more water equivalent with less than a 2.6% difference compared to a 5.7% difference for the isopropanol gel dosimeter. Both the co-solvent free and isopropanol solvent gel dosimeters have lower effective atomic numbers than water, differing by 2.2% and 6.5%, respectively. As a result, their photoelectric absorption interaction probabilities are up to 6% and 19% different from water, respectively. Compton scattering and pair production interaction probabilities of NIPAM gel with isopropanol differ by up to 10% from water while for the co-solvent free gel, the differences are 3%. Mass attenuation and energy absorption coefficients of the co-solvent free gel dosimeter and the isopropanol gel dosimeter are up to 7% and 19% lower than water, respectively. Collisional and total mass stopping powers of both gel dosimeters differ by less than 2% from those of water. The dose response of the co-solvent free gel dosimeter is water equivalent (with <1% discrepancy) for dosimetry of x-rays with energies <100 keV while the discrepancy increases (up to 5%) for the isopropanol gel dosimeter over the same energy range. For x-ray beams over the energy range 180 keV-18 MV, both gel dosimeters have less than 2% discrepancy with water. For megavoltage electron beams, the dose differences with water reach 7% and 14% for the co-solvent free gel dosimeter and the isopropanol gel dosimeter, respectively. Our results demonstrate that for x-ray beam dosimetry with photon energies higher than 100 keV and megavoltage electron beams, correction factors are needed for both NIPAM gels to be used as water equivalent dosimeters.

Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates

NASA Astrophysics Data System (ADS)

Ladhaf, Bibifatima M.; Pawar, Pravina P.

2015-04-01

We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), D-Galactose (C6H12O6), Inositol (C6H12O6), D-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

3D map of theranostic nanoparticles distribution in mice brain and liver by means of X-ray Phase Contrast Tomography

NASA Astrophysics Data System (ADS)

Longo, E.; Bravin, A.; Brun, F.; Bukreeva, I.; Cedola, A.; Fratini, M.; Le Guevel, X.; Massimi, L.; Sancey, L.; Tillement, O.; Zeitoun, P.; de La Rochefoucauld, O.

2018-01-01

The word "theranostic" derives from the fusion of two terms: therapeutic and diagnostic. It is a promising research field that aims to develop innovative therapies with high target specificity by exploiting the therapeutic and diagnostic properties, in particular for metal-based nanoparticles (NPs) developed to erase cancer. In the framework of a combined research program on low dose X-ray imaging and theranostic nanoparticles (NPs), high resolution Phase-Contrast Tomography images of mice organs injected with gadolinium and gold-NPs were acquired at the European Synchrotron Radiation Facility (ESRF). Both compounds are good X-ray contrast agents due to their high attenuation coefficient with respect to biological tissues, especially immediately above K-edge energy. X-ray tomography is a powerful non-invasive technique to image the 3D vasculature network in order to detect abnormalities. Phase contrast methods provide more detailed anatomical information with higher discrimination among soft tissues. We present the images of mice liver and brain injected with gold and gadolinium NPs, respectively. We discuss different image processing methods used aiming at enhancing the accuracy on localizing nanoparticles.

Evaluation of gamma-ray attenuation properties of bismuth borate glass systems using Monte Carlo method

NASA Astrophysics Data System (ADS)

Tarim, Urkiye Akar; Ozmutlu, Emin N.; Yalcin, Sezai; Gundogdu, Ozcan; Bradley, D. A.; Gurler, Orhan

2017-11-01

A Monte Carlo method was developed to investigate radiation shielding properties of bismuth borate glass. The mass attenuation coefficients and half-value layer parameters were determined for different fractional amounts of Bi2O3 in the glass samples for the 356, 662, 1173 and 1332 keV photon energies. A comparison of the theoretical and experimental attenuation coefficients is presented.

Microstructure and physical properties of bismuth-lead-tin ternary eutectic alloy

NASA Astrophysics Data System (ADS)

Kamal, M.; Moharram, B. M.; Farag, H.; El-Bediwi, A.; Abosheiasha, H. F.

2006-07-01

Using different experimental techniques, microstructure, electrical resistivity, attenuation coefficient, and mechanical and thermal properties of the quenched Bi-Pb-Sn ternary eutectic alloy have been investigated. From the X-ray analysis, Bi3Pb7 and Bi-Sn meta-stable phases are detected, in addition to rhombohedral bismuth and Sn body-centered tetragonal phases. This study also compared the physical properties of the Bi-Sn-Pb ternary eutectic alloys with the base binary Bi-Sn and Bi-Pb eutectic alloys.

Imaging of Rabbit VX-2 Hepatic Cancer by Cold and Thermal Neutron Radiography

NASA Astrophysics Data System (ADS)

Tsuchiya, Yoshinori; Matsubayashi, Masahito; Takeda, Tohoru; Lwin, Thet Thet; Wu, Jin; Yoneyama, Akio; Matsumura, Akira; Hori, Tomiei; Itai, Yuji

2003-11-01

Neutron radiography is based on differences in neutron mass attenuation coefficients among the elements and is a non-destructive imaging method. To investigate biomedical applications of neutron radiography, imaging of rabbit VX-2 liver cancer was performed using thermal and cold neutron radiography with a neutron imaging plate. Hepatic vessels and VX-2 tumor were clearly observed by neutron radiography, especially by cold neutron imaging. The image contrast of this modality was better than that of absorption-contrast X-ray radiography.

A new approach for reducing beam hardening artifacts in polychromatic X-ray computed tomography using more accurate prior image.

PubMed

Wang, Hui; Xu, Yanan; Shi, Hongli

2018-03-15

Metal artifacts severely degrade CT image quality in clinical diagnosis, which are difficult to removed, especially for the beam hardening artifacts. The metal artifact reduction (MAR) based on prior images are the most frequently-used methods. However, there exists a lot misclassification in most prior images caused by absence of prior information such as spectrum distribution of X-ray beam source, especially when multiple or big metal are included. This work aims is to identify a more accurate prior image to improve image quality. The proposed method includes four steps. First, the metal image is segmented by thresholding an initial image, where the metal traces are identified in the initial projection data using the forward projection of the metal image. Second, the accurate absorbent model of certain metal image is calculated according to the spectrum distribution of certain X-ray beam source and energy-dependent attenuation coefficients of metal. Third, a new metal image is reconstructed by the general analytical reconstruction algorithm such as filtered back projection (FPB). The prior image is obtained by segmenting the difference image between the initial image and the new metal image into air, tissue and bone. Fourth, the initial projection data are normalized by dividing the projection data of prior image pixel to pixel. The final corrected image is obtained by interpolation, denormalization and reconstruction. Several clinical images with dental fillings and knee prostheses were used to evaluate the proposed algorithm and normalized metal artifact reduction (NMAR) and linear interpolation (LI) method. The results demonstrate the artifacts were reduced efficiently by the proposed method. The proposed method could obtain an exact prior image using the prior information about X-ray beam source and energy-dependent attenuation coefficients of metal. As a result, better performance of reducing beam hardening artifacts can be achieved. Moreover, the process of the proposed method is rather simple and little extra calculation burden is necessary. It has superiorities over other algorithms when include multiple and/or big implants.

X-ray computed tomography of wood-adhesive bondlines: Attenuation and phase-contrast effects

DOE PAGES

Paris, Jesse L.; Kamke, Frederick A.; Xiao, Xianghui

2015-07-29

Microscale X-ray computed tomography (XCT) is discussed as a technique for identifying 3D adhesive distribution in wood-adhesive bondlines. Visualization and material segmentation of the adhesives from the surrounding cellular structures require sufficient gray-scale contrast in the reconstructed XCT data. Commercial wood-adhesive polymers have similar chemical characteristics and density to wood cell wall polymers and therefore do not provide good XCT attenuation contrast in their native form. Here, three different adhesive types, namely phenol formaldehyde, polymeric diphenylmethane diisocyanate, and a hybrid polyvinyl acetate, are tagged with iodine such that they yield sufficient X-ray attenuation contrast. However, phase-contrast effects at material edgesmore » complicate image quality and segmentation in XCT data reconstructed with conventional filtered backprojection absorption contrast algorithms. A quantitative phase retrieval algorithm, which isolates and removes the phase-contrast effect, was demonstrated. The paper discusses and illustrates the balance between material X-ray attenuation and phase-contrast effects in all quantitative XCT analyses of wood-adhesive bondlines.« less

X-ray computed tomography of wood-adhesive bondlines: Attenuation and phase-contrast effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paris, Jesse L.; Kamke, Frederick A.; Xiao, Xianghui

Microscale X-ray computed tomography (XCT) is discussed as a technique for identifying 3D adhesive distribution in wood-adhesive bondlines. Visualization and material segmentation of the adhesives from the surrounding cellular structures require sufficient gray-scale contrast in the reconstructed XCT data. Commercial wood-adhesive polymers have similar chemical characteristics and density to wood cell wall polymers and therefore do not provide good XCT attenuation contrast in their native form. Here, three different adhesive types, namely phenol formaldehyde, polymeric diphenylmethane diisocyanate, and a hybrid polyvinyl acetate, are tagged with iodine such that they yield sufficient X-ray attenuation contrast. However, phase-contrast effects at material edgesmore » complicate image quality and segmentation in XCT data reconstructed with conventional filtered backprojection absorption contrast algorithms. A quantitative phase retrieval algorithm, which isolates and removes the phase-contrast effect, was demonstrated. The paper discusses and illustrates the balance between material X-ray attenuation and phase-contrast effects in all quantitative XCT analyses of wood-adhesive bondlines.« less

Spectral reconstruction of dental X-ray tubes using laplace inverse transform of the attenuation curve

NASA Astrophysics Data System (ADS)

Malezan, A.; Tomal, A.; Antoniassi, M.; Watanabe, P. C. A.; Albino, L. D.; Poletti, M. E.

2015-11-01

In this work, a spectral reconstruction methodology for diagnostic X-ray, using Laplace inverse transform of the attenuation, was successfully applied to dental X-ray equipments. The attenuation curves of 8 commercially available dental X-ray equipment, from 3 different manufactures (Siemens, Gnatus and Dabi Atlante), were obtained by using an ionization chamber and high purity aluminium filters, while the kVp was obtained with a specific meter. A computational routine was implemented in order to adjust a model function, whose inverse Laplace transform is analytically known, to the attenuation curve. This methodology was validated by comparing the reconstructed and the measured (using semiconductor detector of cadmium telluride) spectra of a given dental X-ray unit. The spectral reconstruction showed the Dabi Atlante equipments generating similar shape spectra. This is a desirable feature from clinic standpoint because it produces similar levels of image quality and dose. We observed that equipments from Siemens and Gnatus generate significantly different spectra, suggesting that, for a given operating protocol, these units will present different levels of image quality and dose. This fact claims for the necessity of individualized operating protocols that maximize image quality and dose. The proposed methodology is suitable to perform a spectral reconstruction of dental X-ray equipments from the simple measurements of attenuation curve and kVp. The simplified experimental apparatus and the low level of technical difficulty make this methodology accessible to a broad range of users. The knowledge of the spectral distribution can help in the development of operating protocols that maximize image quality and dose.

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)

Sitko, Rafał

2008-11-01

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).

Examination of forensic entomology evidence using computed tomography scanning: case studies and refinement of techniques for estimating maggot mass volumes in bodies.

PubMed

Johnson, Aidan; Archer, Melanie; Leigh-Shaw, Lyndie; Pais, Mike; O'Donnell, Chris; Wallman, James

2012-09-01

A new technique has recently been developed for estimating the volume of maggot masses on deceased persons using post-mortem CT scans. This allows volume to be measured non-invasively and factored into maggot mass temperature calculations for both casework and research. Examination of admission scans also allows exploration of entomological evidence in anatomical areas not usually exposed by autopsy (e.g. nasal cavities and facial sinuses), and before autopsy disrupts the maggot distribution on a body. This paper expands on work already completed by providing the x-ray attenuation coefficient by way of Hounsfield unit (HU) values for various maggot species, maggot masses and human tissue adjacent to masses. Specifically, this study looked at the HU values for four forensically important blowfly larvae: Lucilia cuprina, L. sericata, Calliphora stygia and C. vicina. The Calliphora species had significantly lower HU values than the Lucilia species. This might be explained by histological analysis, which revealed a non-significant trend, suggesting that Calliphora maggots have a higher fat content than the Lucilia maggots. It is apparent that the variation in the x-ray attenuation coefficient usually precludes its use as a tool for delineating the maggot mass from human tissue and that morphology is the dominant method for delineating a mass. This paper also includes three case studies, which reveal different applications for interpreting entomological evidence using post-mortem CT scans.

Shielding properties of 80TeO2-5TiO2-(15-x) WO3-xAnOm glasses using WinXCom and MCNP5 code

NASA Astrophysics Data System (ADS)

Dong, M. G.; El-Mallawany, R.; Sayyed, M. I.; Tekin, H. O.

2017-12-01

Gamma ray shielding properties of 80TeO2-5TiO2-(15-x) WO3-xAnOm glasses, where AnOm is Nb2O5 = 0.01, 5, Nd2O3 = 3, 5 and Er2O3 = 5 mol% have been achieved. Shielding parameters; mass attenuation coefficients, half value layers, and macroscopic effective removal cross section for fast neutrons have been computed by using WinXCom program and MCNP5 Monte Carlo code. In addition, by using Geometric Progression method (G-P), exposure buildup factor values were also calculated. Variations of shielding parameters are discussed for the effect of REO addition into the glasses and photon energy.

Comparison of x-ray cross sections for diagnostic and therapeutic medical physics.

PubMed

Boone, J M; Chavez, A E

1996-12-01

The purpose of this technical report is to make available an up-to-date source of attenuation coefficient data to the medical physics community, and to compare these data with other more familiar sources. Data files from Lawrence Livermore National Laboratory (in Livermore, CA) were truncated to match the needs of the medical physics community, and an interpolation routine was written to calculate a continuous set of cross sections spanning energies from 1 keV to 50 MeV. Coefficient data are available for elements Z = 1 through Z = 100. Values for mass attenuation coefficients, mass-energy-transfer coefficients, and mass-energy absorption coefficients are produced by a single computer subroutine. In addition to total interaction cross sections, the cross sections for photoelectric, Rayleigh, Compton, pair, and some triplet interactions are also produced by this single program. The coefficients were compared to the 1970 data of Storm and Israel over the energy interval from 1 to 1000 keV; for elements 10, 20, 30, 40, 50, 60, 70, and 80, the average positive difference between the Storm and Israel coefficients and the coefficients reported here are 1.4%, 2.7%, and 2.6%, for the mass attenuation, mass energy-transfer, and mass-energy absorption coefficients, respectively. The 1969 data compilation of mass attenuation coefficients from McMaster et al. were also compared with the newer LLNL data. Over the energy region from 10 keV to 1000 keV, and from elements Z = 1 to Z = 82 (inclusive), the overall average difference was 1.53% (sigma = 0.85%). While the overall average difference was small, there was larger variation (> 5%) between cross sections for some elements. In addition to coefficient data, other useful data such as the density, atomic weight, K, L1, L2, L3, M, and N edges, and numerous characteristic emission energies are output by the program, depending on a single input variable. The computer source code, written in C, can be accessed and downloaded from the World Wide Web at: http:@www.aip.org/epaps/epaps.html [E-MPHSA-23-1977].

Comparative imaging study in ultrasound, MRI, CT, and DSA using a multimodality renal artery phantom

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, Deirdre M.; Fagan, Andrew J.; Moran, Carmel M.

2011-02-15

Purpose: A range of anatomically realistic multimodality renal artery phantoms consisting of vessels with varying degrees of stenosis was developed and evaluated using four imaging techniques currently used to detect renal artery stenosis (RAS). The spatial resolution required to visualize vascular geometry and the velocity detection performance required to adequately characterize blood flow in patients suffering from RAS are currently ill-defined, with the result that no one imaging modality has emerged as a gold standard technique for screening for this disease. Methods: The phantoms, which contained a range of stenosis values (0%, 30%, 50%, 70%, and 85%), were designed formore » use with ultrasound, magnetic resonance imaging, x-ray computed tomography, and x-ray digital subtraction angiography. The construction materials used were optimized with respect to their ultrasonic speed of sound and attenuation coefficient, MR relaxometry (T{sub 1},T{sub 2}) properties, and Hounsfield number/x-ray attenuation coefficient, with a design capable of tolerating high-pressure pulsatile flow. Fiducial targets, incorporated into the phantoms to allow for registration of images among modalities, were chosen to minimize geometric distortions. Results: High quality distortion-free images of the phantoms with good contrast between vessel lumen, fiducial markers, and background tissue to visualize all stenoses were obtained with each modality. Quantitative assessments of the grade of stenosis revealed significant discrepancies between modalities, with each underestimating the stenosis severity for the higher-stenosed phantoms (70% and 85%) by up to 14%, with the greatest discrepancy attributable to DSA. Conclusions: The design and construction of a range of anatomically realistic renal artery phantoms containing varying degrees of stenosis is described. Images obtained using the main four diagnostic techniques used to detect RAS were free from artifacts and exhibited adequate contrast to allow for quantitative measurements of the degree of stenosis in each phantom. Such multimodality phantoms may prove useful in evaluating current and emerging US, MRI, CT, and DSA technology.« less

The calculation of mass attenuation coefficients of well-known thermoluminescent dosimetric compounds at wide energy range

NASA Astrophysics Data System (ADS)

Ermis, Elif Ebru

2017-02-01

The photon mass attenuation coefficients of LiF, BaSO4, CaCO3 and CaSO4 thermoluminescent dosimetric compounds at 100; 300; 500; 600; 800; 1,000; 1,500; 2,000; 3,000 and 5,000 keV gamma-ray energies were calculated. For this purpose, FLUKA Monte Carlo (MC) program which is one of the well-known MC codes was used in this study. Furthermore, obtained results were analyzed by means of ROOT program. National Institute of Standards and Technology (NIST) values were also used to compare the obtained theoretical values because the mass attenuation values of the used compounds could not found in the literature. Calculated mass attenuation coefficients were highly in accordance with the NIST values. As a consequence, FLUKA was successful in calculating the mass attenuation coefficients of the most used thermoluminescent compound.

Method for non-intrusively identifying a contained material utilizing uncollided nuclear transmission measurements

DOEpatents

Morrison, John L.; Stephens, Alan G.; Grover, S. Blaine

2001-11-20

An improved nuclear diagnostic method identifies a contained target material by measuring on-axis, mono-energetic uncollided particle radiation transmitted through a target material for two penetrating radiation beam energies, and applying specially developed algorithms to estimate a ratio of macroscopic neutron cross-sections for the uncollided particle radiation at the two energies, where the penetrating radiation is a neutron beam, or a ratio of linear attenuation coefficients for the uncollided particle radiation at the two energies, where the penetrating radiation is a gamma-ray beam. Alternatively, the measurements are used to derive a minimization formula based on the macroscopic neutron cross-sections for the uncollided particle radiation at the two neutron beam energies, or the linear attenuation coefficients for the uncollided particle radiation at the two gamma-ray beam energies. A candidate target material database, including known macroscopic neutron cross-sections or linear attenuation coefficients for target materials at the selected neutron or gamma-ray beam energies, is used to approximate the estimated ratio or to solve the minimization formula, such that the identity of the contained target material is discovered.

Emergence of Uranium as a Distinct Metal Center for Building Intrinsic X-ray Scintillators.

PubMed

Wang, Yaxing; Yin, Xuemiao; Liu, Wei; Xie, Jian; Chen, Junfeng; Silver, Mark A; Sheng, Daopeng; Chen, Lanhua; Diwu, Juan; Liu, Ning; Chai, Zhifang; Albrecht-Schmitt, Thomas E; Wang, Shuao

2018-06-25

The combination of high atomic number and high oxidation state in U VI materials gives rise to both high X-ray attenuation efficiency and intense green luminescence originating from ligand-to-metal charge transfer. These two features suggest that U VI materials might act as superior X-ray scintillators, but this postulate has remained substantially untested. Now the first observation of intense X-ray scintillation in a uranyl-organic framework (SCU-9) that is observable by the naked eye is reported. Combining the advantage in minimizing the non-radiative relaxation during the X-ray excitation process over those of inorganic salts of uranium, SCU-9 exhibits a very efficient X-ray to green light luminescence conversion. The luminescence intensity shows an essentially linear correlation with the received X-ray intensity, and is comparable with that of commercially available CsI:Tl. SCU-9 possesses an improved X-ray attenuation efficiency (E>20 keV) as well as enhanced radiation resistance and decreased hygroscopy compared to CsI:Tl. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gamma ray detection with long NaI/Tl/ scintillator bars

NASA Technical Reports Server (NTRS)

Zych, A. D.; Tumer, O. T.; Dayton, B.

1983-01-01

Test measurements with a prototype NaI(Tl) scintillator for energy, position, and timing measurements in gamma ray astronomy are reported. The scintillator bar is 100 x 5 x 5 cu cm in size, and allows detection of the arrival times and pulse heights of signals from two photomultiplier tubes, one at each end of the bar. Data is gathered on the energy loss, linear position, and time-of-flight of gamma ray interactions within the bar over an energy range of 0.5-20 MeV. A mean attenuation coefficient of 0.015/cm has been determined, as have a FWHM resolution of 5 cm, 9.4%, and 10 nsec at an energy of 0.662 MeV. At 1.25 MeV the timing resolution was 6 nsec, and at 6.13 MeV the spatial resolution was 2.2 cm. The instrument is a prototype of a Compton scatter telescope being constructed for two balloon flights, one each in the Northern and Southern Hemispheres, in 1984.

THE ABSORPTION PROPERTIES OF LEAD-FREE GARMENTS FOR USE IN RADIATION PROTECTION.

PubMed

Çetin, Hüseyin; Yurt, Aysegül; Yüksel, Serra Haznaci

2017-04-15

In this study, the absorption capability and the weight of various radiation-shielding materials were evaluated, for applications as alternatives to lead garments. Toxicity, atomic number, density, K-edge absorption energy and availability of elements that can serve as an alternative to lead, including tin, antimony, bismuth and tungsten, were considered. The attenuation coefficients of these elements were determined using the XCOM software package, and these metals were mixed with polymers at 50, 70, 80 and 85 % mass ratios. It can be concluded that all of the new shielding materials used in the study can be used for a diagnostic range of X-rays. However, they were compared with the commercial lead garments in terms of weight and attenuation coefficient; the 85 % samples were lighter than a 0.5-mm lead garment and provided superior radiation protection, which demonstrates its potential for commercial applications. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Blind beam-hardening correction from Poisson measurements

NASA Astrophysics Data System (ADS)

Gu, Renliang; Dogandžić, Aleksandar

2016-02-01

We develop a sparse image reconstruction method for Poisson-distributed polychromatic X-ray computed tomography (CT) measurements under the blind scenario where the material of the inspected object and the incident energy spectrum are unknown. We employ our mass-attenuation spectrum parameterization of the noiseless measurements and express the mass- attenuation spectrum as a linear combination of B-spline basis functions of order one. A block coordinate-descent algorithm is developed for constrained minimization of a penalized Poisson negative log-likelihood (NLL) cost function, where constraints and penalty terms ensure nonnegativity of the spline coefficients and nonnegativity and sparsity of the density map image; the image sparsity is imposed using a convex total-variation (TV) norm penalty term. This algorithm alternates between a Nesterov's proximal-gradient (NPG) step for estimating the density map image and a limited-memory Broyden-Fletcher-Goldfarb-Shanno with box constraints (L-BFGS-B) step for estimating the incident-spectrum parameters. To accelerate convergence of the density- map NPG steps, we apply function restart and a step-size selection scheme that accounts for varying local Lipschitz constants of the Poisson NLL. Real X-ray CT reconstruction examples demonstrate the performance of the proposed scheme.

Novel experimental technique for 3D investigation of high-speed cavitating diesel fuel flows by X-ray micro computed tomography

NASA Astrophysics Data System (ADS)

Lorenzi, M.; Mitroglou, N.; Santini, M.; Gavaises, M.

2017-03-01

An experimental technique for the estimation of the temporal-averaged vapour volume fraction within high-speed cavitating flow orifices is presented. The scientific instrument is designed to employ X-ray micro computed tomography (microCT) as a quantitative 3D measuring technique applied to custom designed, large-scale, orifice-type flow channels made from Polyether-ether-ketone (PEEK). The attenuation of the ionising electromagnetic radiation by the fluid under examination depends on its local density; the transmitted radiation through the cavitation volume is compared to the incident radiation, and combination of radiographies from sufficient number of angles leads to the reconstruction of attenuation coefficients versus the spatial position. This results to a 3D volume fraction distribution measurement of the developing multiphase flow. The experimental results obtained are compared against the high speed shadowgraph visualisation images obtained in an optically transparent nozzle with identical injection geometry; comparison between the temporal mean image and the microCT reconstruction shows excellent agreement. At the same time, the real 3D internal channel geometry (possibly eroded) has been measured and compared to the nominal manufacturing CAD drawing of the test nozzle.

Novel experimental technique for 3D investigation of high-speed cavitating diesel fuel flows by X-ray micro computed tomography.

PubMed

Lorenzi, M; Mitroglou, N; Santini, M; Gavaises, M

2017-03-01

An experimental technique for the estimation of the temporal-averaged vapour volume fraction within high-speed cavitating flow orifices is presented. The scientific instrument is designed to employ X-ray micro computed tomography (microCT) as a quantitative 3D measuring technique applied to custom designed, large-scale, orifice-type flow channels made from Polyether-ether-ketone (PEEK). The attenuation of the ionising electromagnetic radiation by the fluid under examination depends on its local density; the transmitted radiation through the cavitation volume is compared to the incident radiation, and combination of radiographies from sufficient number of angles leads to the reconstruction of attenuation coefficients versus the spatial position. This results to a 3D volume fraction distribution measurement of the developing multiphase flow. The experimental results obtained are compared against the high speed shadowgraph visualisation images obtained in an optically transparent nozzle with identical injection geometry; comparison between the temporal mean image and the microCT reconstruction shows excellent agreement. At the same time, the real 3D internal channel geometry (possibly eroded) has been measured and compared to the nominal manufacturing CAD drawing of the test nozzle.

SU-F-I-14: 3D Breast Digital Phantom for XACT Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, S; Laaroussi, R; Chen, J

Purpose: The X-ray induced acoustic computed tomography (XACT) is a new imaging modality which combines X-ray contrast and high ultrasonic resolution in a single modality. Using XACT in breast imaging, a 3D breast volume can be imaged by only one pulsed X-ray radiation, which could dramatically reduce the imaging dose for patients undergoing breast cancer screening and diagnosis. A 3D digital phantom that contains both X-ray properties and acoustic properties of different tissue types is indeed needed for developing and optimizing the XACT system. The purpose of this study is to offer a realistic breast digital phantom as a valuablemore » tool for improving breast XACT imaging techniques and potentially leading to better diagnostic outcomes. Methods: A series of breast CT images along the coronal plane from a patient who has breast calcifications are used as the source images. A HU value based segmentation algorithm is employed to identify breast tissues in five categories, namely the skin tissue, fat tissue, glandular tissue, chest bone and calcifications. For each pixel, the dose related parameters, such as material components and density, and acoustic related parameters, such as frequency-dependent acoustic attenuation coefficient and bandwidth, are assigned based on tissue types. Meanwhile, other parameters which are used in sound propagation, including the sound speed, thermal expansion coefficient, and heat capacity are also assigned to each tissue. Results: A series of 2D tissue type image is acquired first and the 3D digital breast phantom is obtained by using commercial 3D reconstruction software. When giving specific settings including dose depositions and ultrasound center frequency, the X-ray induced initial pressure rise can be calculated accordingly. Conclusion: The proposed 3D breast digital phantom represents a realistic breast anatomic structure and provides a valuable tool for developing and evaluating the system performance for XACT.« less

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

PubMed

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

2015-04-01

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.

Thermal Stability and X-ray Attenuation Studies on α-Bi₂O₃, β-Bi₂O₃ and Bi Based Nanocomposites for Radiopaque Fabrics.

PubMed

Jayakumar, Sangeetha; Saravanan, T; Philip, John

2018-06-01

Nanocomposites containing α-Bi2O3, β-Bi2O3 and Bi nanoparticles as nanofillers in vulcanized silicone resin as a matrix are prepared and their diagnostic X-ray attenuation property is studied. The nanocomposites are prepared using a simple solution casting technique, with nanofiller concentration varying from 2-50 wt%. Thermogravimetric analysis and differential scanning calorimetry are performed to study the thermal stability of the nanocomposites. The attenuation property is studied by exposing the nanocomposites containing α-Bi2O3, β-Bi2O3 and Bi nanoparticles to X-rays of energy 30-60 keV. Nanocomposites containing β-Bi2O3 nanoparticles are found to exhibit the highest attenuation than nanocomposites of α-Bi2O3 and Bi nanoparticles of similar concentration. Nanocomposites containing 50 wt% of β-Bi2O3 nanoparticles exhibit an X-ray attenuation of 93, 86, 71, 45 and 10% at an X-ray photon energy of 40, 45, 50, 55 and 59 keV, respectively. Further increase in photon energy is found to saturate the flat panel detector owing to the lower thickness of the nanocomposites. Analysis of high resolution X-ray radiographs of the nanocomposites confirms the uniform distribution of nanofillers in the matrix. Thermal analysis confirms the structural integrity and thermal stability of the nanocomposites. Heat flow curves also confirm the interaction of nanofillers with the matrix, corroborated by a change in the peak position and its endothermic/exothermic nature, corresponding to the phase transition of the nanofillers. It is also interpreted from thermal analysis of nanocomposites that the nanofillers interact with the matrix either by intercalating in the bridging polymer chain of silicone resin network structure or by occupying the interchain space. Thermal analysis of X-ray exposed nanocomposites shows no significant change in heat flow rates, thus, confirming the stability of the nanocomposites. Our study shows that nanocomposites containing β-Bi2O3 nanofiller are potential candidates for radiopaque fabrics which can find application in diagnostic X-ray shielding in mammography, dental scan, etc.

Beam tracking phase tomography with laboratory sources

NASA Astrophysics Data System (ADS)

Vittoria, F. A.; Endrizzi, M.; Kallon, G. K. N.; Hagen, C. K.; Diemoz, P. C.; Zamir, A.; Olivo, A.

2018-04-01

An X-ray phase-contrast laboratory system is presented, based on the beam-tracking method. Beam-tracking relies on creating micro-beamlets of radiation by placing a structured mask before the sample, and analysing them by using a detector with sufficient resolution. The system is used in tomographic configuration to measure the three dimensional distribution of the linear attenuation coefficient, difference from unity of the real part of the refractive index, and of the local scattering power of specimens. The complementarity of the three signals is investigated, together with their potential use for material discrimination.

Comparison of radioactive transmission and mechanical properties of Portland cement and a modified cement with trommel sieve waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boncukcuoglu, Recep; Icelli, Orhan; Erzeneoglu, Salih

2005-06-01

In this study, it was aimed to stabilize trommel sieve waste (TSW) occurring during manufacture of borax from tincal. The effects of TSW added on the mechanical properties and radioactive transmission of modified cement prepared by adding TSW to clinker was investigated. The properties which TSW as additive caused the cement to gain were tested and compared with normal Portland cement. Measurements have been made to determine variation of mass attenuation coefficients of TSW and cement by using an extremely narrow-collimated-beam transmission method in the energy range 15.746-40.930 keV with X-ray transmission method. The characteristic K{alpha} and K{beta} X-rays ofmore » the different elements (Zr, Mo, Ag, In, Sb, Ba and Pr) passed through TSW and cement were detected with a high-resolution Si(Li) detector. Results are presented and discussed in this paper.« less

Monte Carlo Approach for Estimating Density and Atomic Number From Dual-Energy Computed Tomography Images of Carbonate Rocks

NASA Astrophysics Data System (ADS)

Victor, Rodolfo A.; Prodanović, Maša.; Torres-Verdín, Carlos

2017-12-01

We develop a new Monte Carlo-based inversion method for estimating electron density and effective atomic number from 3-D dual-energy computed tomography (CT) core scans. The method accounts for uncertainties in X-ray attenuation coefficients resulting from the polychromatic nature of X-ray beam sources of medical and industrial scanners, in addition to delivering uncertainty estimates of inversion products. Estimation of electron density and effective atomic number from CT core scans enables direct deterministic or statistical correlations with salient rock properties for improved petrophysical evaluation; this condition is specifically important in media such as vuggy carbonates where CT resolution better captures core heterogeneity that dominates fluid flow properties. Verification tests of the inversion method performed on a set of highly heterogeneous carbonate cores yield very good agreement with in situ borehole measurements of density and photoelectric factor.

Quantitative radiographic analysis of fiber reinforced polymer composites.

PubMed

Baidya, K P; Ramakrishna, S; Rahman, M; Ritchie, A

2001-01-01

X-ray radiographic examination of the bone fracture healing process is a widely used method in the treatment and management of patients. Medical devices made of metallic alloys reportedly produce considerable artifacts that make the interpretation of radiographs difficult. Fiber reinforced polymer composite materials have been proposed to replace metallic alloys in certain medical devices because of their radiolucency, light weight, and tailorable mechanical properties. The primary objective of this paper is to provide a comparable radiographic analysis of different fiber reinforced polymer composites that are considered suitable for biomedical applications. Composite materials investigated consist of glass, aramid (Kevlar-29), and carbon reinforcement fibers, and epoxy and polyether-ether-ketone (PEEK) matrices. The total mass attenuation coefficient of each material was measured using clinical X-rays (50 kev). The carbon fiber reinforced composites were found to be more radiolucent than the glass and kevlar fiber reinforced composites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fontainha, C.C.P.; Nolasco, A.V.; Santos, A.P.

Radiation dosimetry is commonly used to prevent deterministic radiation effects in high dose medical procedures. Radiochromic films find nowadays widely application in radiotherapy, interventional procedures and CT exams for isodose and maximum skin dose measurements. Moreover the size of the irradiated area and its distribution can be performed through the reading of the individual components in the RGB-spectrum. Particularly, radiochromic film has multiple advantages over alternative dosimeters for low-kV X-rays dosimetry. Concerned to spatial resolution it is far superior to that of ionization chambers and thermoluminescent dosimeters. For high energy photon fields (keV to MeV) the most used radiochromic filmmore » commercially available belongs to the EBT Gafchromic{sup R} series. On the other hand, for low energy photon fields in the x-ray range (20 kVp to 200 kVp) the best choice belongs to the XR-QA Gafchromic{sup R} film series. In this work we demonstrate the possibility of generating 2D images of thin polymeric composites films using EBT3 and XR-QA2 Gafchromic{sup R} films exposed to 6 MeV and 40 keV x-ray photons, respectively, using the digital filtering tools of the ImageJ{sup R} free software. In this context, EBT3 films were placed on the surface of a rigid anthropomorphic phantom. Then, they were covered with a thermoplastic mask made of PCL polymer. This setup was then exposed to 2.0 Gy absorbed dose in the Linear Accelerator beam. The EBT3 films were then scanned in the high resolution mode in a commercial scanner and the images subsequently treated with digital filters. It is somehow possible to see the image of the thermoplastic mask in the scanned image. However, in the treated image it is easy to observe the mask arrangement. The unexpected phenomenon here is the EB3 film ability to detect the attenuation of high energy photons by a plastic material, which in turn has a very low mass-energy attenuation coefficient, producing a very clear 2D image. This result is discussed in terms of the high Z halides added to the sensitive layer of EB3 film, once the main components are C (42.3%), H (39.7%) and O (16.0%)1-2. Based on the above results, we have speculated about the abilities of XR-AQ films in the detection of the distribution of nano-sized particles that has high mass-energy attenuation coefficients for low energy x-rays, in polymer composites. In another investigation we tested the ability of XR-QA2 Gafchromic{sup R} films to evaluate the dispersion of ZrO{sub 2} nano-sized grain clusters in protective composites. The P(VDFTrFE)/ ZrO{sub 2} film was sandwiched between two XR-QA2 radiochromic films. In this setup, one radiochromic film is directly exposed to 100 mGy of the x-rays beam and another one measures the attenuated beam. After storage for 24 hours at room temperature under no light conditions, the irradiated radiochromic films were scanned under the same conditions in order to obtain a more reliable result. All films were scanned using the same size ROI in high resolution mode and saved as tagged image file format (TIFF). The untreated scanned image of the XR-AQ2 film directed exposed to the X-ray beam and the correspondent treated image with digital filters are shown. The untreated and treated image of the XR-AQ2 film that was exposed to the attenuated x-ray beam is shown. The image treated with digital filters seems to reproduce the dispersion of ZrO{sub 2} nano-sized grain clusters in the P(VDF-TrFE) copolymer matrix. This result is also discussed in terms of the high Z halides added to the sensitive layer of XR-AQ2 film and compared to the MEV images obtained from the P(VDF-TrFE)/ZrO{sub 2} composites. The results indicate a clear correlation between the 2D radiochromic image and the MEV photography.« less

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

DOEpatents

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

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.

Lead oxide-decorated graphene oxide/epoxy composite towards X-Ray radiation shielding

NASA Astrophysics Data System (ADS)

Hashemi, Seyyed Alireza; Mousavi, Seyyed Mojtaba; Faghihi, Reza; Arjmand, Mohammad; Sina, Sedigheh; Amani, Ali Mohammad

2018-05-01

In this study, employing modified Hummers method coupled with a multi-stage manufacturing procedure, graphene oxide (GO) decorated with Pb3O4 (GO-Pb3O4) at different weight ratios was synthesized. Thereupon, via the vacuum shock technique, composites holding GO-Pb3O4 at different filler loadings (5 and 10 wt%) and thicknesses (4 and 6 mm) were fabricated. Successful decoration of GO with Pb3O4 was confirmed via FTIR analysis. Moreover, particle size distribution of the produced fillers was examined using particle size analyzer. X-ray attenuation examination revealed that reinforcement of epoxy-based composites with GO-Pb3O4 led to a significant improvement in the overall attenuation rate of X-ray beam. For instance, composites containing 10 wt% GO-Pb3O4 with 6 mm thickness showed 4.06, 4.83 and 3.91 mm equivalent aluminum thickness at 40, 60 and 80 kVp energies, denoting 124.3, 124.6 and 103.6% improvement in the X-ray attenuation rate compared to a sample holding neat epoxy resin, respectively. Simulation results revealed that the effect of GO-Pb3O4 loading on the X-ray shielding performance undermined with increase in the voltage of the applied X-ray beam.

Recent developments in the MuCAT microtomography facility

NASA Astrophysics Data System (ADS)

Davis, Graham R.; Evershed, Anthony N. Z.; Mills, David

2012-10-01

The goal of the MuCAT scanner development at Queen Mary University of London is to provide highly accurate maps of a specimen's X-ray linear attenuation coefficient; speed of data acquisition and spatial resolution having a lower priority. The reason for this approach is that the primary application is to accurately map the mineral concentration in teeth. Synchrotron tomography would generally be considered more appropriate for such a task, but many of the dental applications involve repeated scans with long intervening periods (from hours to weeks) and the management of synchrotron facilities does not readily allow such research. Development work is concentrated in two areas: beam hardening correction algorithms and novel scanning methodology. Beam hardening correction is combined with calibration, such that the raw X-ray projection data is corrected for beam hardening prior to reconstruction. Recent developments include the design of a multi-element calibration carousel. This has nine calibration pieces, five aluminium, three titanium and one copper. Development of the modelling algorithm is also yielding improved accuracy. A time-delay integration CCD camera is used to avoid ring artefacts. The original prototype averaged out inhomogeneities in both the detector array and the X-ray field; later designs used only software correction for the latter. However, at lower X-ray energies, the effect of deposits on the X-ray window (for example) becomes more conspicuous and so a new scanning methodology has been designed whereby the specimen moves in an arc about the source and equiangular data is acquired, thus overcoming this problem.

Accurate Modeling of X-ray Extinction by Interstellar Grains

NASA Astrophysics Data System (ADS)

Hoffman, John; Draine, B. T.

2016-02-01

Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must be taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.

WE-E-18C-01: Multi-Energy CT: Current Status and Recent Innovations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelc, N; McCollough, C; Yu, L

2014-06-15

Conventional computed tomography (CT) uses a single polychromatic x-ray spectrum and energy integrating detectors, and produces images whose contrast depends on the effective attenuation coefficient of the broad spectrum beam. This can introduce errors from beam hardening and does not produce the optimal contrast-to-noise ratio. In addition, multiple materials can have the same effective attenuation coefficient, causing different materials to be indistinguishable in conventional CT images. If transmission measurements at two or more energies are obtained, even with polychromatic beams, more specific information about the object can be obtained. If the object does not contain materials with k-edges in themore » spectrum, the x-ray attenuation can be well-approximated by a linear combination of two processes (photoelectric absorption and Compton scattering) or, equivalently, two basis materials. For such cases, two spectral measurements suffice, although additional measurements can provide higher precision. If K-edge materials are present, additional spectral measurements can allow these materials to be isolated. Current commercial implementations use varied approaches, including two sources operating a different kVp, one source whose kVp is rapidly switched in a single scan, and a dual layer detector that can provide spectral information in every reading. Processing of the spectral information can be performed in the raw data domain or in the image domain. The process of calculating the amount of the two basis functions implicitly corrects for beam hardening and therefore can lead to improvements in quantitative accuracy. Information can be extracted to provide material specific information beyond that of conventional CT. This additional information has been shown to be important in several clinical applications, and can also lead to more efficient clinical protocols. Recent innovations in x-ray sources, detectors, and systems have made multi-energy CT much more practical and improved its performance. In addition, this is a very active area of research and further improvements are expected through further technological improvements. Learning Objectives: Basic principles of multi-energy CT Current implementations of mutli-energy CT Data and image analysis methods in multi-energy CT Current clinical applications of dual energy CT5. recent innovations and anticipated advances in multi-energy CT.« less

[Accuracy of attenuation coefficient obtained by 137Cs single-transmission scanning in PET: comparison with conventional germanium line source].

PubMed

Matsumoto, Keiichi; Kitamura, Keishi; Mizuta, Tetsuro; Shimizu, Keiji; Murase, Kenya; Senda, Michio

2006-02-20

Transmission scanning can be successfully performed with a Cs-137 single-photon-emitting point source for three-dimensional PET imaging. This method was effective for postinjection transmission scanning because of differences in physical energy. However, scatter contamination in the transmission data lowers measured attenuation coefficients. The purpose of this study was to investigate the accuracy of the influence of object scattering by measuring the attenuation coefficients on the transmission images. We also compared the results with the conventional germanium line source method. Two different types of PET scanner, the SET-3000 G/X (Shimadzu Corp.) and ECAT EXACT HR(+) (Siemens/CTI) , were used. For the transmission scanning, the SET-3000 G/X and ECAT HR(+) were the Cs-137 point source and Ge-68/Ga-68 line source, respectively. With the SET-3000 G/X, we performed transmission measurement at two energy gate settings, the standard 600-800 keV as well as 500-800 keV. The energy gate setting of the ECAT HR(+) was 350-650 keV. The effects of scattering in a uniform phantom with different cross-sectional areas ranging from 201 cm(2) to 314 cm(2) to 628 cm(2) (apposition of the two 20 cm diameter phantoms) and 943 cm(2) (stacking of the three 20 cm diameter phantoms) were acquired without emission activity. First, we evaluated the attenuation coefficients of the two different types of transmission scanning using region of interest (ROI) analysis. In addition, we evaluated the attenuation coefficients with and without segmentation for Cs-137 transmission images using the same analysis. The segmentation method was a histogram-based soft-tissue segmentation process that can also be applied to reconstructed transmission images. In the Cs-137 experiment, the maximum underestimation was 3% without segmentation, which was reduced to less than 1% with segmentation at the center of the largest phantom. In the Ge-68/Ga-68 experiment, the difference in mean attenuation coefficients was stable with all phantoms. We evaluated the accuracy of attenuation coefficients of Cs-137 single-transmission scans. The results for Cs-137 suggest that scattered photons depend on object size. Although Cs-137 single-transmission scans contained scattered photons, attenuation coefficient error could be reduced using by the segmentation method.

Phase Imaging using Focusing Polycapillary Optics

NASA Astrophysics Data System (ADS)

Bashir, Sajid

The interaction of X rays in diagnostic energy range with soft tissues can be described by Compton scattering and by the complex refractive index, which together characterize the attenuation properties of the tissue and the phase imparted to X rays passing through it. Many soft tissues exhibit extremely similar attenuation, so that their discrimination using conventional radiography, which generates contrast in an image through differential attenuation, is challenging. However, these tissues will impart phase differences significantly greater than attenuation differences to the X rays passing through them, so that phase-contrast imaging techniques can enable their discrimination. A major limitation to the widespread adoption of phase-contrast techniques is that phase contrast requires significant spatial coherence of the X-ray beam, which in turn requires specialized sources. For tabletop sources, this often requires a small (usually in the range of 10-50 micron) X-ray source. In this work, polycapillary optics were employed to create a small secondary source from a large spot rotating anode. Polycapillary optics consist of arrays of small hollow glass tubes through which X rays can be guided by total internal reflection from the tube walls. By tapering the tubes to guide the X rays to a point, they can be focused to a small spot which can be used as a secondary source. The polycapillary optic was first aligned with the X-ray source. The spot size was measured using a computed radiography image plate. Images were taken at a variety of optic-to-object and object-to-detector distances and phase-contrast edge enhancement was observed. Conventional absorption images were also acquired at a small object-to detector distances for comparison. Background division was performed to remove strong non-uniformity due to the optics. Differential phase contrast reconstruction demonstrates promising preliminary results. This manuscript is divided into six chapters. The second chapter describes the limitations of conventional imaging methods and benefits of the phase imaging. Chapter three covers different types of X-ray photon interactions with matter. Chapter four describes the experimental set-up and different types of images acquired along with their analysis. Chapter five summarizes the findings in this project and describes future work as well.

Photon interaction studies using 241Am g-rays

NASA Astrophysics Data System (ADS)

Ramachandran, N.; Karunakaran Nair, K.; Abdullah, K. K.; Varier, K. M.

2006-09-01

We have carried out some photon interaction measurements using 59.54 keV γ-rays from a ^{241}Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes as well as pellets and aqueous solutions of rare earth compounds. In the case of the leaf and wood samples, we have used the γ-ray attenuation technique for the determination of the water content in fresh and dried samples. The variation of the attenuation coefficient with particle size has been investigated for sand and sugar samples. The attenuation studies as well as the photoelectric studies in the case of rare earth elements have been carried out on samples containing such elements whose K-absorption edge energies lie below and close to the γ-energy used. Suitable compounds of the rare earth elements have been chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. A well-shielded scattering geometry was used for the photoelectric measurements. The mixture rule was invoked to extract the values of the mass attenuation coefficients for the elements from those of the corresponding compounds. The results are consistent with theoretical values derived from the XCOM package.

Development of optimized segmentation map in dual energy computed tomography

NASA Astrophysics Data System (ADS)

Yamakawa, Keisuke; Ueki, Hironori

2012-03-01

Dual energy computed tomography (DECT) has been widely used in clinical practice and has been particularly effective for tissue diagnosis. In DECT the difference of two attenuation coefficients acquired by two kinds of X-ray energy enables tissue segmentation. One problem in conventional DECT is that the segmentation deteriorates in some cases, such as bone removal. This is due to two reasons. Firstly, the segmentation map is optimized without considering the Xray condition (tube voltage and current). If we consider the tube voltage, it is possible to create an optimized map, but unfortunately we cannot consider the tube current. Secondly, the X-ray condition is not optimized. The condition can be set empirically, but this means that the optimized condition is not used correctly. To solve these problems, we have developed methods for optimizing the map (Method-1) and the condition (Method-2). In Method-1, the map is optimized to minimize segmentation errors. The distribution of the attenuation coefficient is modeled by considering the tube current. In Method-2, the optimized condition is decided to minimize segmentation errors depending on tube voltagecurrent combinations while keeping the total exposure constant. We evaluated the effectiveness of Method-1 by performing a phantom experiment under the fixed condition and of Method-2 by performing a phantom experiment under different combinations calculated from the total exposure constant. When Method-1 was followed with Method-2, the segmentation error was reduced from 37.8 to 13.5 %. These results demonstrate that our developed methods can achieve highly accurate segmentation while keeping the total exposure constant.

ITAR: A modified TAR method to determine depth dose distribution for an ophthalmic device that performs kilovoltage x-ray pencil-beam stereotaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanlon, Justin, E-mail: jhanlon@orayainc.com; Chell, Erik; Firpo, Michael

2014-02-15

Purpose: New technology has been developed to treat age-related macular degeneration (AMD) using 100 kVp pencil-beams that enter the patient through the radio-resistant sclera with a depth of interest between 1.6 and 2.6 cm. Measurement of reference and relative dose in a kilovoltage x-ray beam with a 0.42 cm diameter field size and a 15 cm source to axis distance (SAD) is a challenge that is not fully addressed in current guidelines to medical physicists. AAPM's TG-61 gives dosimetry recommendations for low and medium energy x-rays, but not all of them are feasible to follow for this modality. Methods: Anmore » investigation was conducted to select appropriate equipment for the application. PTW's Type 34013 Soft X-Ray Chamber (Freiburg, Germany) and CIRS's Plastic Water LR (Norfolk, VA) were found to be the best available options. Attenuation curves were measured with minimal scatter contribution and thus called Low Scatter Tissue Air Ratio (LSTAR). A scatter conversion coefficient (C{sub scat}) was derived through Monte Carlo radiation transport simulation using MCNPX (LANL, Los Alamos, NM) to quantify the difference between a traditional TAR curve and the LSTAR curve. A material conversion coefficient (C{sub mat}) was determined through experimentation to evaluate the difference in attenuation properties between water and Plastic Water LR. Validity of performing direct dosimetry measurements with a source to detector distance other than the treatment distance, and therefore a different field size due to a fixed collimator, was explored. A method—Integrated Tissue Air Ratio (ITAR)—has been developed that isolates each of the three main radiological effects (distance from source, attenuation, and scatter) during measurement, and integrates them to determine the dose rate to the macula during treatment. Results: LSTAR curves were determined to be field size independent within the range explored, indicating that direct dosimetry measurements may be performed with a source to detector distance of 20 cm even though the SAD is 15 cm during treatment. C{sub scat} varied from 1.102 to 1.106 within the range of depths of interest. The experimental variance among repeated measurements of C{sub mat} was larger than depth dependence, so C{sub mat} was estimated as1.019 for all depths of interest. Conclusions: Equipment selection, measurement techniques, and formalism for the determination of dose rate to the macula during stereotaxy for AMD have been determined and are strongly recommended by the authors of this paper to be used by clinical medical physicists.« less

Characterization of imaging performance in differential phase contrast CT compared with the conventional CT: Spectrum of noise equivalent quanta NEQ(k)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang Xiangyang; Yang Yi; Tang Shaojie

Purpose: Differential phase contrast CT (DPC-CT) is emerging as a new technology to improve the contrast sensitivity of conventional attenuation-based CT. The noise equivalent quanta as a function over spatial frequency, i.e., the spectrum of noise equivalent quanta NEQ(k), is a decisive indicator of the signal and noise transfer properties of an imaging system. In this work, we derive the functional form of NEQ(k) in DPC-CT. Via system modeling, analysis, and computer simulation, we evaluate and verify the derived NEQ(k) and compare it with that of the conventional attenuation-based CT. Methods: The DPC-CT is implemented with x-ray tube and gratings.more » The x-ray propagation and data acquisition are modeled and simulated through Fresnel and Fourier analysis. A monochromatic x-ray source (30 keV) is assumed to exclude any system imperfection and interference caused by scatter and beam hardening, while a 360 Degree-Sign full scan is carried out in data acquisition to avoid any weighting scheme that may disrupt noise randomness. Adequate upsampling is implemented to simulate the x-ray beam's propagation through the gratings G{sub 1} and G{sub 2} with periods 8 and 4 {mu}m, respectively, while the intergrating distance is 193.6 mm (1/16 of the Talbot distance). The dimensions of the detector cell for data acquisition are 32 Multiplication-Sign 32, 64 Multiplication-Sign 64, 96 Multiplication-Sign 96, and 128 Multiplication-Sign 128 {mu}m{sup 2}, respectively, corresponding to a 40.96 Multiplication-Sign 40.96 mm{sup 2} field of view in data acquisition. An air phantom is employed to obtain the noise power spectrum NPS(k), spectrum of noise equivalent quanta NEQ(k), and detective quantum efficiency DQE(k). A cylindrical water phantom at 5.1 mm diameter and complex refraction coefficient n= 1 -{delta}+i{beta}= 1 -2.5604 Multiplication-Sign 10{sup -7}+i1.2353 Multiplication-Sign 10{sup -10} is placed in air to measure the edge transfer function, line spread function and then modulation transfer function MTF(k), of both DPC-CT and the conventional attenuation-based CT. The x-ray flux is set at 5 Multiplication-Sign 10{sup 6} photon/cm{sup 2} per projection and observes the Poisson distribution, which is consistent with that of a micro-CT for preclinical applications. Approximately 360 regions, each at 128 Multiplication-Sign 128 matrix, are used to calculate the NPS(k) via 2D Fourier transform, in which adequate zero padding is carried out to avoid aliasing in noise. Results: The preliminary data show that the DPC-CT possesses a signal transfer property [MTF(k)] comparable to that of the conventional attenuation-based CT. Meanwhile, though there exists a radical difference in their noise power spectrum NPS(k) (trait 1/|k| in DPC-CT but |k| in the conventional attenuation-based CT) the NEQ(k) and DQE(k) of DPC-CT and the conventional attenuation-based CT are in principle identical. Conclusions: Under the framework of ideal observer study, the joint signal and noise transfer property NEQ(k) and detective quantum efficiency DQE(k) of DPC-CT are essentially the same as those of the conventional attenuation-based CT. The findings reported in this paper may provide insightful guidelines on the research, development, and performance optimization of DPC-CT for extensive preclinical and clinical applications in the future.« less

On the response of Y 3Al 5O 12: Ce (YAG: Ce) powder scintillating screens to medical imaging X-rays

NASA Astrophysics Data System (ADS)

Kandarakis, I.; Cavouras, D.; Sianoudis, I.; Nikolopoulos, D.; Episkopakis, A.; Linardatos, D.; Margetis, D.; Nirgianaki, E.; Roussou, M.; Melissaropoulos, P.; Kalivas, N.; Kalatzis, I.; Kourkoutas, K.; Dimitropoulos, N.; Louizi, A.; Nomicos, C.; Panayiotakis, G.

2005-02-01

The aim of this study was to examine Y 3Al 5O 12:Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166 mg/cm 2 were prepared in our laboratory by sedimentation of Y 3Al 5O 12: Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80-120 kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (η≈0.03-0.05) and light attenuation coefficients (σ≈26.5 cm/g) were derived through this fitting. Y 3Al 5O 12:Ce showed peak emission in the wavelength range 530-550 nm. The light emission efficiency was found to be maximum for the 107 mg/cm 2 layer. Due to its "green" emission spectrum, Y 3Al 5O 12:Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y 3Al 5O 12:Ce could be considered for application in X-ray imaging especially in various digital detectors.

ImaSim, a software tool for basic education of medical x-ray imaging in radiotherapy and radiology

NASA Astrophysics Data System (ADS)

Landry, Guillaume; deBlois, François; Verhaegen, Frank

2013-11-01

Introduction: X-ray imaging is an important part of medicine and plays a crucial role in radiotherapy. Education in this field is mostly limited to textbook teaching due to equipment restrictions. A novel simulation tool, ImaSim, for teaching the fundamentals of the x-ray imaging process based on ray-tracing is presented in this work. ImaSim is used interactively via a graphical user interface (GUI). Materials and methods: The software package covers the main x-ray based medical modalities: planar kilo voltage (kV), planar (portal) mega voltage (MV), fan beam computed tomography (CT) and cone beam CT (CBCT) imaging. The user can modify the photon source, object to be imaged and imaging setup with three-dimensional editors. Objects are currently obtained by combining blocks with variable shapes. The imaging of three-dimensional voxelized geometries is currently not implemented, but can be added in a later release. The program follows a ray-tracing approach, ignoring photon scatter in its current implementation. Simulations of a phantom CT scan were generated in ImaSim and were compared to measured data in terms of CT number accuracy. Spatial variations in the photon fluence and mean energy from an x-ray tube caused by the heel effect were estimated from ImaSim and Monte Carlo simulations and compared. Results: In this paper we describe ImaSim and provide two examples of its capabilities. CT numbers were found to agree within 36 Hounsfield Units (HU) for bone, which corresponds to a 2% attenuation coefficient difference. ImaSim reproduced the heel effect reasonably well when compared to Monte Carlo simulations. Discussion: An x-ray imaging simulation tool is made available for teaching and research purposes. ImaSim provides a means to facilitate the teaching of medical x-ray imaging.

Comparison of lead attenuation and lead hardening equivalence of materials used in respect of diagnostic X-ray shielding.

PubMed

Okunade, Akintunde Akangbe

2002-12-01

Present interest is in the shielding of diagnostic X-ray units. Numerical comparison has been made of the attenuation and hardening properties of lead and some particular alternative materials: steel, plate glass and gypsum wallboard. Results show, for particular choices of thickness, that lead and steel can be made to provide closely similar attenuation and spectral hardening, values of lead attenuation equivalent (LAE) and lead hardening equivalent (LHE) thicknesses being nearly the same. Significant differences in the attenuation and hardening properties of lead are found in comparison with plate glass and gypsum wallboard. LAE produces better matching of exposure for lead-plate glass and lead-gypsum wallboard than LHE.

Gamma dosimetric parameters in some skeletal muscle relaxants

NASA Astrophysics Data System (ADS)

Manjunatha, H. C.

2017-09-01

We have studied the attenuation of gamma radiation of energy ranging from 84 keV to 1330 keV (^{170}Tm, ^{22}Na,^{137}Cs, and ^{60}Co) in some commonly used skeletal muscle relaxants such as tubocurarine chloride, gallamine triethiodide, pancuronium bromide, suxamethonium bromide and mephenesin. The mass attenuation coefficient is measured from the attenuation experiment. In the present work, we have also proposed the direct relation between mass attenuation coefficient (μ /ρ ) and mass energy absorption coefficient (μ _{en}/ρ ) based on the nonlinear fitting procedure. The gamma dosimetric parameters such as mass energy absorption coefficient (μ _{en}/ρ ), effective atomic number (Z_{eff}), effective electron density (N_{el}), specific γ-ray constant, air kerma strength and dose rate are evaluated from the measured mass attentuation coefficient. These measured gamma dosimetric parameters are compared with the theoretical values. The measured values agree with the theoretical values. The studied gamma dosimetric values for the relaxants are useful in medical physics and radiation medicine.

MicroCT with energy-resolved photon-counting detectors

PubMed Central

Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, BMW; Patt, B E; Frey, E C

2011-01-01

The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with Kabsorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences. PMID:21464527

MicroCT with energy-resolved photon-counting detectors.

PubMed

Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, B M W; Patt, B E; Frey, E C

2011-05-07

The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with K-absorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences.

A summary of Selected Data: DSDP Legs 20-44,

DTIC Science & Technology

1980-09-01

water X 100 minerals may be applied in the future density water when the mineralogy and attenuation wt. wate r \\+ wt r ed. + salIt coefficients...in the future when densities of some common minerals are the exact quantitative mineralogy and listed in Harms and Choquette (1965), attenuation...different attenuation coefficient than were used to get a " ball park" answer that of calcite. for a particular sediment type, or for drilling

First experiences with in-vivo x-ray dark-field imaging of lung cancer in mice

NASA Astrophysics Data System (ADS)

Gromann, Lukas B.; Scherer, Kai; Yaroshenko, Andre; Bölükbas, Deniz A.; Hellbach, Katharina; Meinel, Felix G.; Braunagel, Margarita; Eickelberg, Oliver; Reiser, Maximilian F.; Pfeiffer, Franz; Meiners, Silke; Herzen, Julia

2017-03-01

Purpose: The purpose of the present study was to evaluate if x-ray dark-field imaging can help to visualize lung cancer in mice. Materials and Methods: The experiments were performed using mutant mice with high-grade adenocarcinomas. Eight animals with pulmonary carcinoma and eight control animals were imaged in radiography mode using a prototype small-animal x-ray dark-field scanner and three of the cancerous ones additionally in CT mode. After imaging, the lungs were harvested for histological analysis. To determine their diagnostic value, x-ray dark-field and conventional attenuation images were analyzed by three experienced readers in a blind assessment. Results radiographic imaging: The lung nodules were much clearer visualized on the dark-field radiographs compared to conventional radiographs. The loss of air-tissue interfaces in the tumor leads to a significant loss of x-ray scattering, reflected in a strong dark-field signal change. The difference between tumor and healthy tissue in terms of x-ray attenuation is significantly less pronounced. Furthermore, the signal from the overlaying structures on conventional radiographs complicates the detection of pulmonary carcinoma. Results CT imaging: The very first in-vivo CT-imaging results are quite promising as smaller tumors are often better visible in the dark-field images. However the imaging quality is still quite low, especially in the attenuation images due to un-optimized scanning parameters. Conclusion: We found a superior diagnostic performance of dark-field imaging compared to conventional attenuation based imaging, especially when it comes to the detection of small lung nodules. These results support the motivation to further develop this technique and translate it towards a clinical environment.

2D beam hardening correction for micro-CT of immersed hard tissue

NASA Astrophysics Data System (ADS)

Davis, Graham; Mills, David

2016-10-01

Beam hardening artefacts arise in tomography and microtomography with polychromatic sources. Typically, specimens appear to be less dense in the center of reconstructions because as the path length through the specimen increases, so the X-ray spectrum is shifted towards higher energies due to the preferential absorption of low energy photons. Various approaches have been taken to reduce or correct for these artefacts. Pre-filtering the X-ray beam with a thin metal sheet will reduce soft energy X-rays and thus narrow the spectrum. Correction curves can be applied to the projections prior to reconstruction which transform measured attenuation with polychromatic radiation to predicted attenuation with monochromatic radiation. These correction curves can be manually selected, iteratively derived from reconstructions (this generally works where density is assumed to be constant) or derived from a priori information about the X-ray spectrum and specimen composition. For hard tissue specimens, the latter approach works well if the composition is reasonably homogeneous. In the case of an immersed or embedded specimen (e.g., tooth or bone) the relative proportions of mineral and "organic" (including medium and plastic container) species varies considerably for different ray paths and simple beam hardening correction does not give accurate results. By performing an initial reconstruction, the total path length through the container can be determined. By modelling the X-ray properties of the specimen, a 2D correction transform can then be created such that the predicted monochromatic attenuation can be derived as a function of both the measured polychromatic attenuation and the container path length.

Attenuation properties of diagnostic x-ray shielding materials.

PubMed

Archer, B R; Fewell, T R; Conway, B J; Quinn, P W

1994-09-01

Single- and three-phase broad-beam x-ray attenuation data have been obtained using lead, steel, plate glass, gypsum wallboard, lead acrylic, and wood. Tube voltages of 50, 70, 100, 125, and 150 kVp were employed and the resulting curves were compared to transmission data found in the literature. To simplify computation of barrier requirements, all data sets were parametrized by nonlinear least-squares fit to a previously described mathematical model. High attenuation half value layers and the lead equivalence of the alternate materials were also determined.

MUSCLE EQUIVALENT MATERIAL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawashima, K.; Takaku, Y.; Inada, T.

1961-01-01

A tissue-equivalent material was constructed from the following components: polyethylene (CH/sub 2/)/sub n/, 71.4% (by weight), NaNO/sub 3/ 21.3%, Al/sub 2/O/sub 3/ 5.5%, and TiC/sub 2/ 1.8%. The attenuation coefficients of this solid compound, Mix. p in x or gamma rays (40kev --1.25 Mev), were shown to be equal to those of a section of pork loin (m. longissimus dorsi). Thus, Mix. p is concluded to be good phantom material for depth dose measuremeat and suitable material for walls of ionizatlon chambers. (Abstr. Japan Med., 2: No. 3, March 1962)

Element-specific spectral imaging of multiple contrast agents: a phantom study

NASA Astrophysics Data System (ADS)

Panta, R. K.; Bell, S. T.; Healy, J. L.; Aamir, R.; Bateman, C. J.; Moghiseh, M.; Butler, A. P. H.; Anderson, N. G.

2018-02-01

This work demonstrates the feasibility of simultaneous discrimination of multiple contrast agents based on their element-specific and energy-dependent X-ray attenuation properties using a pre-clinical photon-counting spectral CT. We used a photon-counting based pre-clinical spectral CT scanner with four energy thresholds to measure the X-ray attenuation properties of various concentrations of iodine (9, 18 and 36 mg/ml), gadolinium (2, 4 and 8 mg/ml) and gold (2, 4 and 8 mg/ml) based contrast agents, calcium chloride (140 and 280 mg/ml) and water. We evaluated the spectral imaging performances of different energy threshold schemes between 25 to 82 keV at 118 kVp, based on K-factor and signal-to-noise ratio and ranked them. K-factor was defined as the X-ray attenuation in the K-edge containing energy range divided by the X-ray attenuation in the preceding energy range, expressed as a percentage. We evaluated the effectiveness of the optimised energy selection to discriminate all three contrast agents in a phantom of 33 mm diameter. A photon-counting spectral CT using four energy thresholds of 27, 33, 49 and 81 keV at 118 kVp simultaneously discriminated three contrast agents based on iodine, gadolinium and gold at various concentrations using their K-edge and energy-dependent X-ray attenuation features in a single scan. A ranking method to evaluate spectral imaging performance enabled energy thresholds to be optimised to discriminate iodine, gadolinium and gold contrast agents in a single spectral CT scan. Simultaneous discrimination of multiple contrast agents in a single scan is likely to open up new possibilities of improving the accuracy of disease diagnosis by simultaneously imaging multiple bio-markers each labelled with a nano-contrast agent.

Low-energy gamma ray attenuation characteristics of aviation fuels

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Shen, Chih-Ping; Sprinkle, Danny R.

1990-01-01

Am241 (59.5 keV) gamma ray attenuation characteristics were investigated in 270 aviation fuel (Jet A and Jet A-1) samples from 76 airports around the world as a part of world wide study to measure the variability of aviation fuel properties as a function of season and geographical origin. All measurements were made at room temperature which varied from 20 to 27 C. Fuel densities (rho) were measured concurrently with their linear attenuation coefficients (mu), thus providing a measure of mass attenuation coefficient (mu/rho) for the test samples. In 43 fuel samples, rho and mu values were measured at more than one room temperature, thus providing mu/rho values for them at several temperatures. The results were found to be independent of the temperature at which mu and rho values were measured. It is noted that whereas the individual mu and rho values vary considerably from airport to airport as well as season to season, the mu/rho values for all samples are constant at 0.1843 + or - 0.0013 cu cm/gm. This constancy of mu/rho value for aviation fuels is significant since a nuclear fuel quantity gauging system based on low energy gamma ray attenuation will be viable throughout the world.

X-ray radiography for container inspection

DOEpatents

Katz, Jonathan I [Clayton, MO; Morris, Christopher L [Los Alamos, NM

2011-06-07

Arrangements of X-ray inspection systems are described for inspecting high-z materials in voluminous objects such as containers. Inspection methods may involve generating a radiographic image based on detected attenuation corresponding to a pulsed beams of radiation transmitted through a voluminous object. The pulsed beams of radiation are generated by a high-energy source and transmitted substantially downward along an incident angle, of approximately 1.degree. to 30.degree., to a vertical axis extending through the voluminous object. The generated radiographic image may be analyzed to detect on localized high attenuation representative of high-z materials and to discriminate high-z materials from lower and intermediate-z materials on the basis of the high density and greater attenuation of high-z material for higher energy (3-10 MeV) X-rays, and the compact nature of threatening masses of fissionable materials.

ACCURATE MODELING OF X-RAY EXTINCTION BY INTERSTELLAR GRAINS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoffman, John; Draine, B. T., E-mail: jah5@astro.princeton.edu, E-mail: draine@astro.princeton.edu

Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must bemore » taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.« less

Characterization of the external and internal flow structure of an aerated-liquid injector using X-ray radiography and fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peltier, Scott J.; Lin, Kuo-Cheng; Carter, Campbell D.

In the present study, the internal flowfield of aerated-liquid fuel injectors is examined through x-ray radiography and x-ray fluorescence. An inside-out injector, consisting of a perforated aerating tube within an annular liquid stream, sprays into a quiescent environment at a fixed mass flow rate of water and nitrogen gas. The liquid is doped with bromine (in the form of NaBr) to create an x-ray fluorescence signal. This allows for reasonable absorption and fluorescence signals, and one or both diagnostics can be used to track the liquid distribution. The injector housing is fabricated from beryllium (Be), which allows the internal flowfieldmore » to be examined (as Be has relatively low x-ray attenuation coefficient). Two injector geometries are compared, illustrating the effects of aerating orifice size and location on the flow evolution. Time-averaged equivalent pathlength (EPL) and line-of-sight averaged density ρ(y) reveal the formation of the two-phase mixture, showing that the liquid film thickness along the injector walls is a function of the aerating tube geometry, though only upstream of the nozzle. These differences in gas and liquid distribution (between injectors with different aerating tube designs) are suppressed as the mixture traverses the nozzle contraction. The averaged liquid velocity (computed from the density and liquid mass flow rate) reveal a similar trend. This suggests that at least for the current configurations, the plume width, liquid mass distribution, and averaged liquid velocity for the time-averaged external spray are insensitive to the aerating tube geometry.« less

Ancient administrative handwritten documents: X-ray analysis and imaging

PubMed Central

Albertin, F.; Astolfo, A.; Stampanoni, M.; Peccenini, Eva; Hwu, Y.; Kaplan, F.; Margaritondo, G.

2015-01-01

Handwritten characters in administrative antique documents from three centuries have been detected using different synchrotron X-ray imaging techniques. Heavy elements in ancient inks, present even for everyday administrative manuscripts as shown by X-ray fluorescence spectra, produce attenuation contrast. In most cases the image quality is good enough for tomography reconstruction in view of future applications to virtual page-by-page ‘reading’. When attenuation is too low, differential phase contrast imaging can reveal the characters from refractive index effects. The results are potentially important for new information harvesting strategies, for example from the huge Archivio di Stato collection, objective of the Venice Time Machine project. PMID:25723946

Ancient administrative handwritten documents: X-ray analysis and imaging.

PubMed

Albertin, F; Astolfo, A; Stampanoni, M; Peccenini, Eva; Hwu, Y; Kaplan, F; Margaritondo, G

2015-03-01

Handwritten characters in administrative antique documents from three centuries have been detected using different synchrotron X-ray imaging techniques. Heavy elements in ancient inks, present even for everyday administrative manuscripts as shown by X-ray fluorescence spectra, produce attenuation contrast. In most cases the image quality is good enough for tomography reconstruction in view of future applications to virtual page-by-page `reading'. When attenuation is too low, differential phase contrast imaging can reveal the characters from refractive index effects. The results are potentially important for new information harvesting strategies, for example from the huge Archivio di Stato collection, objective of the Venice Time Machine project.

Mammographic x-ray unit kilovoltage test tool based on k-edge absorption effect.

PubMed

Napolitano, Mary E; Trueblood, Jon H; Hertel, Nolan E; David, George

2002-09-01

A simple tool to determine the peak kilovoltage (kVp) of a mammographic x-ray unit has been designed. Tool design is based on comparing the effect of k-edge discontinuity of the attenuation coefficient for a series of element filters. Compatibility with the mammography accreditation phantom (MAP) to obtain a single quality control film is a second design objective. When the attenuation of a series of sequential elements is studied simultaneously, differences in the absorption characteristics due to the k-edge discontinuities are more evident. Specifically, when the incident photon energy is higher than the k-edge energy of a number of the elements and lower than the remainder, an inflection may be seen in the resulting attenuation data. The maximum energy of the incident photon spectra may be determined based on this inflection point for a series of element filters. Monte Carlo photon transport analysis was used to estimate the photon transmission probabilities for each of the sequential k-edge filter elements. The photon transmission corresponds directly to optical density recorded on mammographic x-ray film. To observe the inflection, the element filters chosen must have k-edge energies that span a range greater than the expected range of the end point energies to be determined. For the design, incident x-ray spectra ranging from 25 to 40 kVp were assumed to be from a molybdenum target. Over this range, the k-edge energy changes by approximately 1.5 keV between sequential elements. For this design 21 elements spanning an energy range from 20 to 50 keV were chosen. Optimum filter element thicknesses were calculated to maximize attenuation differences at the k-edge while maintaining optical densities between 0.10 and 3.00. Calculated relative transmission data show that the kVp could be determined to within +/-1 kV. To obtain experimental data, a phantom was constructed containing 21 different elements placed in an acrylic holder. MAP images were used to determine appropriate exposure techniques for a series of end point energies from 25 to 35 kVp. The average difference between the kVp determination and the calibrated dial setting was 0.8 and 1.0 kV for a Senographe 600 T and a Senographe DMR, respectively. Since the k-edge absorption energies of the filter materials are well known, independent calibration or a series of calibration curves is not required.

Effective atomic numbers in some food materials and medicines for γ -ray attenuation using ^{137}Cs γ -ray

NASA Astrophysics Data System (ADS)

Revathy, J. S.; Anooja, J.; Krishnaveni, R. B.; Gangadathan, M. P.; Varier, K. M.

2018-06-01

A light-weight multichannel analyser (MCA)-based γ -ray spectrometer, developed earlier at the Inter University Accelerator Centre, New Delhi, has been used as part of the PG curriculum, to determine the effective atomic numbers for γ attenuation of ^{137}Cs γ -ray in different types of samples. The samples used are mixtures of graphite, aluminum and selenium powders in different proportions, commercial and home-made edible powders, fruit and vegetable juices as well as certain allopathic and ayurvedic medications. A narrow beam good geometry set-up has been used in the experiments. The measured attenuation coefficients have been used to extract effective atomic numbers in the samples. The results are consistent with XCOM values wherever available. The present results suggest that the γ attenuation technique can be used as an effective non-destructive method for finding adulteration of food materials.

High-energy x-ray grating-based phase-contrast radiography of human anatomy

NASA Astrophysics Data System (ADS)

Horn, Florian; Hauke, Christian; Lachner, Sebastian; Ludwig, Veronika; Pelzer, Georg; Rieger, Jens; Schuster, Max; Seifert, Maria; Wandner, Johannes; Wolf, Andreas; Michel, Thilo; Anton, Gisela

2016-03-01

X-ray grating-based phase-contrast Talbot-Lau interferometry is a promising imaging technology that has the potential to raise soft tissue contrast in comparison to conventional attenuation-based imaging. Additionally, it is sensitive to attenuation, refraction and scattering of the radiation and thus provides complementary and otherwise inaccessible information due to the dark-field image, which shows the sub-pixel size granularity of the measured object. Until recent progress the method has been mainly limited to photon energies below 40 keV. Scaling the method to photon energies that are sufficient to pass large and spacious objects represents a challenging task. This is caused by increasing demands regarding the fabrication process of the gratings and the broad spectra that come along with the use of polychromatic X-ray sources operated at high acceleration voltages. We designed a setup that is capable to reach high visibilities in the range from 50 to 120 kV. Therefore, spacious and dense parts of the human body with high attenuation can be measured, such as a human knee. The authors will show investigations on the resulting attenuation, differential phase-contrast and dark-field images. The images experimentally show that X-ray grating-based phase-contrast radiography is feasible with highly absorbing parts of the human body containing massive bones.

Flash-Bang Detector to Model the Attenuation of High-Energy Photons

NASA Astrophysics Data System (ADS)

Pagsanjan, N., III; Kelley, N. A.; Smith, D. M.; Sample, J. G.

2015-12-01

It has been known for years that lightning and thunderstorms produce gamma rays and x-rays. Terrestrial gamma-ray flashes (TGFs) are extremely bright bursts of gamma rays originating from thunderstorms. X-ray stepped leaders are bursts of x-rays coming from the lightning channel. It is known that the attenuation of these high-energy photons is a function of distance, losing energy and intensity at larger distances. To complement gamma-ray detectors on the ground it would be useful to measure the distance to the flash. Knowing the distance would allow for the true source fluence of gamma rays or x-rays to be modeled. A flash-bang detector, which uses a micro-controller, a photodiode, a microphone and temperature sensor will be able to detect the times at which lightning and thunder occurs. Knowing the speed of sound as function of temperature and the time difference between the flash and the thunder, the range to the lightning can be calculated. We will present the design of our detector as well as some preliminary laboratory test results.

Antibiofouling polymer-coated gold nanoparticles as a contrast agent for in vivo X-ray computed tomography imaging.

PubMed

Kim, Dongkyu; Park, Sangjin; Lee, Jae Hyuk; Jeong, Yong Yeon; Jon, Sangyong

2007-06-20

Current computed tomography (CT) contrast agents such as iodine-based compounds have several limitations, including short imaging times due to rapid renal clearance, renal toxicity, and vascular permeation. Here, we describe a new CT contrast agent based on gold nanoparticles (GNPs) that overcomes these limitations. Because gold has a higher atomic number and X-ray absorption coefficient than iodine, we expected that GNPs can be used as CT contrast agents. We prepared uniform GNPs ( approximately 30 nm in diameter) by general reduction of HAuCl4 by boiling with sodium citrate. The resulting GNPs were coated with polyethylene glycol (PEG) to impart antibiofouling properties, which extends their lifetime in the bloodstream. Measurement of the X-ray absorption coefficient in vitro revealed that the attenuation of PEG-coated GNPs is 5.7 times higher than that of the current iodine-based CT contrast agent, Ultravist. Furthermore, when injected intravenously into rats, the PEG-coated GNPs had a much longer blood circulation time (>4 h) than Ultravist (<10 min). Consequently, CT images of rats using PEG-coated GNPs showed a clear delineation of cardiac ventricles and great vessels. On the other hand, relatively high levels of GNPs accumulated in the spleen and liver, which contain phagocytic cells. Intravenous injection of PEG-coated GNPs into hepatoma-bearing rats resulted in a high contrast ( approximately 2-fold) between hepatoma and normal liver tissue on CT images. These results suggest that PEG-coated GNPs can be useful as a CT contrast agent for a blood pool and hepatoma imaging.

Structural and optical properties of Bi2O3-B2O3-CdO-Na2O glass system for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Dogra, Mridula; Singh, K. J.; Kaur, Kulwinder

2018-05-01

Quaternary system of the composition (0.15+x) Bi2O3-(0.55-x) B2O3-0.15CdO-0.15Na2O (where x=0, 0.1, 0.3 and 0.5 mole fraction) has been synthesized using melt-quenching technique. Gamma ray shielding properties are measured in terms of mass attenuation coefficient and half value layer at photon energies 662, 1173 and 1332 keV. These parameters are compared with standard nuclear radiation shielding `barite and ferrite' concretes. The results reflect better radiation shielding properties as compared to barite and ferrite concretes. Effective atomic number is calculated at photon energies 662 and 1173 keV. Density, molar volume and XRD studies are analyzed to know physical and structural properties of the glass system. Optical band gap, refractive index and molar refraction are calculated from UV-Visible measurements. Decrease in optical band gap and increase in molar refraction have been observed indicating the increase of non-bridging oxygens in the structure.

Single-Shot X-Ray Phase-Contrast Computed Tomography with Nonmicrofocal Laboratory Sources

NASA Astrophysics Data System (ADS)

Diemoz, P. C.; Hagen, C. K.; Endrizzi, M.; Minuti, M.; Bellazzini, R.; Urbani, L.; De Coppi, P.; Olivo, A.

2017-04-01

We present a method that enables performing x-ray phase-contrast imaging (XPCI) computed tomography with a laboratory setup using a single image per projection angle, eliminating the need to move optical elements during acquisition. Theoretical derivation of the method is presented, and its validity conditions are provided. The object is assumed to be quasihomogeneous, i.e., to feature a ratio between the refractive index and the linear attenuation coefficient that is approximately constant across the field of view. The method is experimentally demonstrated on a plastics phantom and on biological samples using a continuous rotation acquisition scheme achieving scan times of a few minutes. Moreover, we show that such acquisition times can be further reduced with the use of a high-efficiency photon-counting detector. Thanks to its ability to substantially simplify the image-acquisition procedure and greatly reduce collection times, we believe this method represents a very important step towards the application of XPCI to real-world problems.

Non-isothermal two-phase transport in the polymer electrolyte membrane fuel cell microporous layer

NASA Astrophysics Data System (ADS)

Ge, Nan

This thesis investigates the water transport mechanisms in the crack-free microporous layer (MPL) of a polymer electrolyte membrane (PEM) fuel cell. Synchrotron X-ray radiography was used to visualize and quantify the in situ liquid water in the gas diffusion layers (GDLs) of an operating fuel cell. A methodology was developed to correct the artefact of imaging sample movement. Furthermore, to address inaccuracies due to the scattering effect and higher harmonics at the synchrotron beamline, a calibration technique was introduced in order to experimentally determine the liquid water X-ray attenuation coefficient. Through in situ radiography, liquid water breakthrough events were observed in the MPL, and measured water thicknesses were used as inputs into a one-dimensional (1D) heat and mass transport model. The 1D model was used to describe the coupled relationship between liquid and vapour transport through the cathode MPL and the temperature distributions in the operating fuel cell.

Classification of materials using nuclear magnetic resonance dispersion and/or x-ray absorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Espy, Michelle A.; Matlashov, Andrei N.; Schultz, Larry J.

Methods for determining the identity of a substance are provided. A classification parameter set is defined to allow identification of substances that previously could not be identified or to allow identification of substances with a higher degree of confidence. The classification parameter set may include at least one of relative nuclear susceptibility (RNS) or an x-ray linear attenuation coefficient (LAC). RNS represents the density of hydrogen nuclei present in a substance relative to the density of hydrogen nuclei present in water. The extended classification parameter set may include T.sub.1, T.sub.2, and/or T.sub.1.rho. as well as at least one additional classificationmore » parameter comprising one of RNS or LAC. Values obtained for additional classification parameters as well as values obtained for T.sub.1, T.sub.2, and T.sub.1.rho. can be compared to known classification parameter values to determine whether a particular substance is a known material.« less

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

PubMed Central

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

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

Preparation and characterisation of Isophthalic-Bi2O3 polymer composite gamma radiation shields

NASA Astrophysics Data System (ADS)

Ambika, M. R.; Nagaiah, N.; Harish, V.; Lokanath, N. K.; Sridhar, M. A.; Renukappa, N. M.; Suman, S. K.

2017-01-01

Bi2O3 filled Isophthalic resin based polymer composites of different weight % (0, 5, 10, 20, 30, 40, 50 & 60) were fabricated by open mould cast technique. Gamma attenuation study was carried out using NaI (Tl) gamma ray spectrometer for Cs-137. The shielding parameters such as attenuation coefficient, HVL & λ were investigated. The distribution of the filler within the matrix was studied using Scanning Electron Microscopy. X ray diffractometer and Fourier Transform Infrared Spectroscopy were employed to study the structural changes if any. The thermal stability and mechanical strength of the composites were investigated using TGA & UTM respectively. Dielectric properties and AC conductivity were also studied using LCR meter. The composites are found to be thermally stable upto 200 °C. There were no such structural changes observed and all the composites show very low conductivity. The mechanical strength of the composites was found to increase upon adding the bismuth oxide with a slight decrease when the concentration of the filler exceeds 40 wt%. Attenuation results reveal that, the shielding efficiency increases with the increase of the filler wt% and are comparable to those of the conventional shielding materials. Hence, Bi2O3 filled composites can be used for gamma shielding applications.

Reconstruction of limited-angle dual-energy CT using mutual learning and cross-estimation (MLCE)

NASA Astrophysics Data System (ADS)

Zhang, Huayu; Xing, Yuxiang

2016-03-01

Dual-energy CT (DECT) imaging has gained a lot of attenuation because of its capability to discriminate materials. We proposes a flexible DECT scan strategy which can be realized on a system with general X-ray sources and detectors. In order to lower dose and scanning time, our DECT acquires two projections data sets on two arcs of limited-angular coverage (one for each energy) respectively. Meanwhile, a certain number of rays from two data sets form conjugate sampling pairs. Our reconstruction method for such a DECT scan mainly tackles the consequent limited-angle problem. Using the idea of artificial neural network, we excavate the connection between projections at two different energies by constructing a relationship between the linear attenuation coefficient of the high energy and that of the low one. We use this relationship to cross-estimate missing projections and reconstruct attenuation images from an augmented data set including projections at views covered by itself (projections collected in scanning) and by the other energy (projections estimated) for each energy respectively. Validated by our numerical experiment on a dental phantom with rather complex structures, our DECT is effective in recovering small structures in severe limited-angle situations. This DECT scanning strategy can much broaden DECT design in reality.

Wavelet-based adaptive thresholding method for image segmentation

NASA Astrophysics Data System (ADS)

Chen, Zikuan; Tao, Yang; Chen, Xin; Griffis, Carl

2001-05-01

A nonuniform background distribution may cause a global thresholding method to fail to segment objects. One solution is using a local thresholding method that adapts to local surroundings. In this paper, we propose a novel local thresholding method for image segmentation, using multiscale threshold functions obtained by wavelet synthesis with weighted detail coefficients. In particular, the coarse-to- fine synthesis with attenuated detail coefficients produces a threshold function corresponding to a high-frequency- reduced signal. This wavelet-based local thresholding method adapts to both local size and local surroundings, and its implementation can take advantage of the fast wavelet algorithm. We applied this technique to physical contaminant detection for poultry meat inspection using x-ray imaging. Experiments showed that inclusion objects in deboned poultry could be extracted at multiple resolutions despite their irregular sizes and uneven backgrounds.

Investigation of attenuation coefficients of some stainless steel and aluminum alloys

NASA Astrophysics Data System (ADS)

Caner, Zafer; Tufan, Mustafa ćaǧatay

2018-02-01

In this study, attenuation coefficients of two different stainless steel alloys (AISI 304 and AISI 310), which have a wide range of applications from home appliances to the automotive sector, and two different aluminum alloys (6013 and 5083), which have a high mechanical strength and a light weight structure and are used in many fields from aviation to military vehicles, has been determined. For this purpose, we used gamma spectrometer system with NaI(Tl) detector. In our measurements, we used Eu-152, Ra-226 and Co-60 as gamma ray sources. To narrow the beam of gamma rays, we designed the new steel based collimator. We also investigated the effect of using collimator. Obtained results were compared with the NIST XCOM values.

3D investigation of inclusions in diamonds using X-ray micro-tomography

NASA Astrophysics Data System (ADS)

Parisatto, M.; Nestola, F.; Artioli, G.; Nimis, P.; Harris, J. W.; Kopylova, M.; Pearson, G. D.

2012-04-01

The study of mineral inclusions in diamonds is providing invaluable insights into the geochemistry, geodynamics and geophysics of the Earth's mantle. Over the last two decades, the identification of different inclusion assemblages allowed to recognize diamonds deriving from the deep upper mantle, the transition zone and even the lower mantle. In such research field the in-situ investigation of inclusions using non-destructive techniques is often essential but still remains a challenging task. In particular, conventional 2D imaging techniques (e.g. SEM) are limited to the investigation of surfaces and the lack of access to the third dimension represents a major limitation when trying to extract quantitative information. Another critical aspect is related to sample preparation (cutting, polishing) which is typically very invasive. Nowadays, X-ray computed micro-tomography (X-μCT) allows to overcome such limitations, enabling the internal microstructure of totally undisturbed samples to be visualized in a three-dimensional (3D) manner at the sub-micrometric scale. The final output of a micro-tomography experiment is a greyvalue 3D map of the variations of the X-ray attenuation coefficient (µ) within the studied object. The high X-ray absorption contrast between diamond (almost transparent to X-rays) and the typical inclusion-forming minerals (olivines, garnets, pyroxenes, oxides and sulphides) makes X-μCT a straightforward method for the 3D visualization of inclusions and for the study of their spatial relationships with the diamond host. In this work we applied microfocus X-μCT to investigate silicate inclusions still trapped in diamonds, in order to obtain in-situ information on their exact position, crystal size, shape and X-ray absorption coefficient (which is related to their composition). We selected diamond samples from different deposits containing mainly olivine and garnet inclusions. The investigated samples derived from the Udachnaya pipe (Siberia, Russia), the Jericho Kimberlite (Slave Craton, Canada) and São Luiz-Juina (Brazil). The information obtained by tomographic experiments were combined with X-ray single-crystal diffraction data (see Nestola et al 2011) in order to identify the inclusion parageneses (peridotitic, eclogitic or websteritic) and to finally determine the origin of the studied diamonds. Our results showed that, by combining X-μCT with X-ray diffraction data, it is possible to exactly determine the 3D position of each inclusion together with their crystal size, even though they cannot be detected by using an optical microscope. In addition, such method could have strong crystallographic implications for inclusions still trapped in diamonds as it enables the application of a reliable numerical absorption correction to the 3D intensity data collections. REF. Nestola, F., Nimis, P., Ziberna, L., Longo, M., Marzoli, A., Harris, J.W., Manghnani, M.H., Fedortchouk, Y. (2011): First crystal-structure determination of olivine in diamond: composition and implications for provenance in the Earth's mantle. Earth Planet. Sci. Lett., 305, 249-255.

A new technique to characterize CT scanner bow-tie filter attenuation and applications in human cadaver dosimetry simulations

PubMed Central

Li, Xinhua; Shi, Jim Q.; Zhang, Da; Singh, Sarabjeet; Padole, Atul; Otrakji, Alexi; Kalra, Mannudeep K.; Xu, X. George; Liu, Bob

2015-01-01

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. PMID:26520720

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

DOEpatents

Gleason, Shaun S [Knoxville, TN; Paulus, Michael J [Knoxville, TN; Mullens, James A [Knoxville, TN

2002-04-09

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.

Theory and preliminary experimental verification of quantitative edge illumination x-ray phase contrast tomography.

PubMed

Hagen, C K; Diemoz, P C; Endrizzi, M; Rigon, L; Dreossi, D; Arfelli, F; Lopez, F C M; Longo, R; Olivo, A

2014-04-07

X-ray phase contrast imaging (XPCi) methods are sensitive to phase in addition to attenuation effects and, therefore, can achieve improved image contrast for weakly attenuating materials, such as often encountered in biomedical applications. Several XPCi methods exist, most of which have already been implemented in computed tomographic (CT) modality, thus allowing volumetric imaging. The Edge Illumination (EI) XPCi method had, until now, not been implemented as a CT modality. This article provides indications that quantitative 3D maps of an object's phase and attenuation can be reconstructed from EI XPCi measurements. Moreover, a theory for the reconstruction of combined phase and attenuation maps is presented. Both reconstruction strategies find applications in tissue characterisation and the identification of faint, weakly attenuating details. Experimental results for wires of known materials and for a biological object validate the theory and confirm the superiority of the phase over conventional, attenuation-based image contrast.

Characterization and attenuation study on tannin-added Rhizophora spp. particleboard at high energy photon and electron

NASA Astrophysics Data System (ADS)

Yusof, Mohd Fahmi Mohd; Hamid, Puteri Nor Khatijah Abd; Tajuddin, Abd Aziz; Abdullah, Reduan; Hashim, Rokiah; Bauk, Sabar; Isa, Norriza Mohd; Isa, Muhammad Jamal Md

2017-01-01

The effective atomic number of tannin-added Rhizophora spp. particleboards was determined based on elemental composition using Energy Dispersive X-ray Analysis (EDXA). The value of mass attenuation coefficients were measured using 137Cs and 60Co gamma energies. The attenuation properties of PDD curves and beam profile of tannin-added Rhizophora spp. particleboards were investigated using Gafchromic EBT2 film at 6 MV photon and 6 MeV electrons and compared to the value in water and solid water phantoms. The results showed that tannin-added Rhizophora spp. particleboards having effective atomic number close to the value of water. The mass attenuation coefficients were near to the value of water with χ2 values of 0.018 and 0.357 to 137Cs and 60Co gamma energies respectively. The PDD of tannin-added Rhizophora spp. particleboards at 6 MV photons showed good agreement within 3.21 and 5.91% to that in solid water phantoms and water respectively. The PDD at 6 MeV electrons showed a good agreement within 3.32 and 3.12% to that in solid water phantoms and water respectively. The depth of R50 and R90 in tannin-added Rhizophora spp. also showed a good agreement to that in water and solid water pahtoms. Lower surface dose was observed in tannin-added Rhizophora spp. particleboards at electron beams in comparison to solid water phantoms and water.

Monte Carlo study on the imaging performance of powder Lu2SiO5:Ce phosphor screens under x-ray excitation: comparison with Gd2O2S:Tb screens.

PubMed

Liaparinos, Panagiotis F; Kandarakis, Ioannis S; Cavouras, Dionisis A; Delis, Harry B; Panayiotakis, George S

2007-05-01

Lu2SiO5: Ce (LSO) scintillator is a relatively new luminescent material which has been successfully applied in positron emission tomography systems. Since it has been recently commercially available in powder form, it could be of value to investigate its performance for use in x-ray projection imaging as both physical and scintillating properties indicate a promising material for such applications. In the present study, a custom and validated Monte Carlo simulation code was used in order to examine the performance of LSO, under diagnostic radiology (mammography and general radiography) conditions. The Monte Carlo code was based on a model using Mie scattering theory for the description of light attenuation. Imaging characteristics, related to image brightness, spatial resolution and noise of LSO screens were predicted using only physical parameters of the phosphor. The overall performance of LSO powder phosphor screens was investigated in terms of the: (i) quantum detection efficiency (ii) emitted K-characteristic radiation (iii) luminescence efficiency (iv) modulation transfer function (v) Swank factor and (vi) zero-frequency detective quantum efficiency [DQE(0)]. Results were compared to the traditional rare-earth Gd2O2S:Tb (GOS) phosphor material. The relative luminescence efficiency of LSO phosphor was found inferior to that of GOS. This is due to the lower intrinsic conversion efficiency of LSO (0.08 instead of 0.15 of GOS) and the relatively high light extinction coefficient mext of this phosphor (0.239 mircom(-1) instead of 0.218 /microm(-1) for GOS). However, the property of increased light extinction combined with the rather sharp angular distribution of scattered light photons (anisotropy factor g=0.624 for LSO instead of 0.494 for GOS) reduce lateral light spreading and improve spatial resolution. In addition, LSO screens were found to exhibit better x-ray absorption as well as higher signal to noise transfer properties in the energy range from 18 keV up to 50.2 keV (e.g. DQE(0)=0.62 at 18 keV and for 34 mg/cm2, instead of 0.58 for GOS). The results indicate that certain optical properties of LSO (optical extinction coefficient, scattering anisotropy factor) combined with the relatively high x-ray coefficients, make this material a promising phosphor which, under appropriate conditions, could be considered for use in x-ray projection imaging detectors.

Identification of High-Z Materials With Photoneutrons Driven by a Low-Energy Electron Linear Accelerator

NASA Astrophysics Data System (ADS)

Yang, Yigang; Zhang, Zhi; Chen, Huaibi; Li, Yulan; Li, Yuanjing

2017-07-01

Contraband-detection systems can use X-rays and photoneutrons delivered from the same 7-MeV electron linear accelerator (e-LINAC) to stimulate and extract information from inspected materials. The X-ray attenuation information is used to measure the mass thickness, which is combined with the photoneutron attenuation information to categorize inspected materials as common organic materials, metals, and heavy metals. Once a heavy metal is found, the beta-delayed neutrons stimulated by the (γ,fission) reaction are measured by a polyethylene-moderated 3He counter to clarify if the material is fissile. The presence of neutron events 2000 μs after the X-ray pulse confirms the existence of the fissile material. The isotopes in the material are then identified using the time-of-flight method to analyze the resonant attenuation of the fissile material to the 10-1-102 eV photoneutrons emitted from and thermalized by the D2O photonto-neutron convertor, which converts X-rays to photoneutrons. Eight high-Z simulants are tested to confirm the feasibility of identifying the isotopes from the photoneutron resonance. The underlying principles and experimental results are discussed.

Engine materials characterization and damage monitoring by using x ray technologies

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1993-01-01

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.

Structural studies of liquid Co–Sn alloys

PubMed Central

Yakymovych, A.; Shtablavyi, I.; Mudry, S.

2014-01-01

An analysis of the structure features of liquid Co–Sn alloys has been performed by means of X-ray diffraction method, viscosity coefficient analysis and computer simulation method. The X-ray diffraction investigations were carried out over a wide concentration range at the temperature 1473 K. It was found that the structure of these alloys can be described in the frame of independent X-ray scattering model. The viscosity coefficient was calculated by an excess entropy scaling and compared with experimental data. PMID:25328282

Hypothesis-driven classification of materials using nuclear magnetic resonance relaxometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Espy, Michelle A.; Matlashov, Andrei N.; Schultz, Larry J.

Technologies related to identification of a substance in an optimized manner are provided. A reference group of known materials is identified. Each known material has known values for several classification parameters. The classification parameters comprise at least one of T.sub.1, T.sub.2, T.sub.1.rho., a relative nuclear susceptibility (RNS) of the substance, and an x-ray linear attenuation coefficient (LAC) of the substance. A measurement sequence is optimized based on at least one of a measurement cost of each of the classification parameters and an initial probability of each of the known materials in the reference group.

X-ray grid-detector apparatus

DOEpatents

Boone, John M.; Lane, Stephen M.

1998-01-27

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.

Comparison Between the NIST and the KEBS for the Determination of Air Kerma Calibration Coefficients for Narrow X-Ray Spectra and 137Cs Gamma-Ray Beams

PubMed Central

O’Brien, Michelle; Minniti, Ronaldo; Masinza, Stanslaus Alwyn

2010-01-01

Air kerma calibration coefficients for a reference class ionization chamber from narrow x-ray spectra and cesium 137 gamma-ray beams were compared between the National Institute of Standards and Technology (NIST) and the Kenya Bureau of Standards (KEBS). A NIST reference-class transfer ionization chamber was calibrated by each laboratory in terms of the quantity air kerma in four x-ray reference radiation beams of energies between 80 kV and 150 kV and in a cesium 137 gamma-ray beam. The reference radiation qualities used for this comparison are described in detail in the ISO 4037 publication.[1] The comparison began in September 2008 and was completed in March 2009. The results reveal the degree to which the participating calibration facility can demonstrate proficiency in transferring air kerma calibrations under the conditions of the said facility at the time of the measurements. The comparison of the calibration coefficients is based on the average ratios of calibration coefficients. PMID:27134777

Comparison Between the NIST and the KEBS for the Determination of Air Kerma Calibration Coefficients for Narrow X-Ray Spectra and (137)Cs Gamma-Ray Beams.

PubMed

O'Brien, Michelle; Minniti, Ronaldo; Masinza, Stanslaus Alwyn

2010-01-01

Air kerma calibration coefficients for a reference class ionization chamber from narrow x-ray spectra and cesium 137 gamma-ray beams were compared between the National Institute of Standards and Technology (NIST) and the Kenya Bureau of Standards (KEBS). A NIST reference-class transfer ionization chamber was calibrated by each laboratory in terms of the quantity air kerma in four x-ray reference radiation beams of energies between 80 kV and 150 kV and in a cesium 137 gamma-ray beam. The reference radiation qualities used for this comparison are described in detail in the ISO 4037 publication.[1] The comparison began in September 2008 and was completed in March 2009. The results reveal the degree to which the participating calibration facility can demonstrate proficiency in transferring air kerma calibrations under the conditions of the said facility at the time of the measurements. The comparison of the calibration coefficients is based on the average ratios of calibration coefficients.

Relationship between Hounsfield unit in CT scan and gray scale in CBCT

NASA Astrophysics Data System (ADS)

Kamaruddin, Noorshaida; Rajion, Zainul Ahmad; Yusof, Asilah; Aziz, Mohd Ezane

2016-12-01

Cone-beam computed tomography (CBCT) is an imaging system which has advantages over computed tomography (CT). Recently, CBCT has become widely used for oral and maxillofacial imaging. In CT scan, Hounsfield Unit (HU) is proportional to the degree of x-ray attenuation by the tissue. In CBCT, the degree of x-ray attenuation is shown by gray scale (voxel value). The aim of the present (in vitro) study was to investigate the relationship between gray scale in CBCT and HU in CT scan. In this descriptive study, the anthropomorphic head phantom was scanned with CBCT and CT scanner. Gray scales and HUs were detected on images at the crown of the teeth, trabecular and cortical bone of mandible. The images were analyzed to obtain the gray scale value and HU value. The obtained value then used to investigate the relationship between CBCT gray scales and HUs. For the statistical analysis, t-test, Pearson's correlation and regression analysis were used. The differences between the gray scale of CBCT and HU of CT were statistically not significant, whereas the Pearson's correlation coefficients demonstrated a statistically significant correlation between gray scale of CBCT and HU of CT values. Considering the fact that gray scale in CBCT is important in pre assessment evaluation of bone density before implant treatments, it is recommended because of the lower dose and cost compared to CT scan.

Thermal expansion behavior study of Co nanowire array with in situ x-ray diffraction and x-ray absorption fine structure techniques

NASA Astrophysics Data System (ADS)

Mo, Guang; Cai, Quan; Jiang, Longsheng; Wang, Wei; Zhang, Kunhao; Cheng, Weidong; Xing, Xueqing; Chen, Zhongjun; Wu, Zhonghua

2008-10-01

In situ x-ray diffraction and x-ray absorption fine structure techniques were used to study the structural change of ordered Co nanowire array with temperature. The results show that the Co nanowires are polycrystalline with hexagonal close packed structure without phase change up until 700 °C. A nonlinear thermal expansion behavior has been found and can be well described by a quadratic equation with the first-order thermal expansion coefficient of 4.3×10-6/°C and the second-order thermal expansion coefficient of 5.9×10-9/°C. The mechanism of this nonlinear thermal expansion behavior is discussed.

Mass energy-absorption coefficients and average atomic energy-absorption cross-sections for amino acids in the energy range 0.122-1.330 MeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

More, Chaitali V., E-mail: chaitalimore89@gmail.com; Lokhande, Rajkumar M.; Pawar, Pravina P., E-mail: pravinapawar4@gmail.com

Mass attenuation coefficients of amino acids such as n-acetyl-l-tryptophan, n-acetyl-l-tyrosine and d-tryptophan were measured in the energy range 0.122-1.330 MeV. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The measured attenuation coefficient values were then used to determine the mass energy-absorption coefficients (σ{sub a,en}) and average atomic energy-absorption cross sections (μ{sub en}/ρ) of the amino acids. Theoretical values were calculated based on XCOM data. Theoretical and experimental values are found to be in good agreement.

Evaluation of Radiation Shielding Properties of the Polyvinyl Alcohol/Iron Oxide Polymer Composite

PubMed Central

Srinivasan, K.; Samuel, E. James Jabaseelan

2017-01-01

Context: Lead is the conventional shielding material against gamma/X-rays. It has some limitations such as toxic, high density, nonflexibility, and also bremsstrahlung production during electron interaction. It may affect the accuracy of radiotherapy outcome. Aims: To theoretically analyze the radiation shielding properties of flexible polyvinyl alcohol/iron oxide polymer composite with five different concentrations of magnetite over the energy range of 15 KeV–20 MeV. Subjects and Methods: Radiological properties were calculated based on the published literature. Attenuation coefficients of pure elements are generated with the help of WinXCOM database. Results: Effective atomic numbers and electron density are increased with the concentration of magnetite. On the other hand, the number of electrons per gram decreased. Mass attenuation coefficient (μ/ϼ) and linear attenuation coefficients (μ) are higher in the lower energy <100 KeV, and their values decreased when the energy increased. Computed tomography numbers (CT) show the significant variation between the concentrations in <60 KeV. Half-value layer and tenth-value layers are directly proportional to the energy and indirectly proportional to the concentration of magnetite. Transmission curve, relaxation length (ƛ), kinetic energy released in the matter, and elemental weight fraction are also calculated and the results are discussed. Conclusions: 0.5% of the magnetite gives superior shielding properties compared with other concentrations. It may be due to the presence of 0.3617% of Fe. Elemental weight fraction, atomic number, photon energy, and mass densities are the important parameters to understand the shielding behavior of any material. PMID:29296043

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xinhua; Shi, Jim Q.; Zhang, Da

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at themore » isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the GEANT4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization.« less

In Vitro Validation of an Artefact Suppression Algorithm in X-Ray Phase-Contrast Computed Tomography.

PubMed

Sunaguchi, Naoki; Yuasa, Tetsuya; Hirano, Shin-Ichi; Gupta, Rajiv; Ando, Masami

2015-01-01

X-ray phase-contrast tomography can significantly increase the contrast-resolution of conventional attenuation-contrast imaging, especially for soft-tissue structures that have very similar attenuation. Just as in attenuation-based tomography, phase contrast tomography requires a linear dependence of aggregate beam direction on the incremental direction alteration caused by individual voxels along the path of the X-ray beam. Dense objects such as calcifications in biological specimens violate this condition. There are extensive beam deflection artefacts in the vicinity of such structures because they result in large distortion of wave front due to the large difference of refractive index; for such large changes in beam direction, the transmittance of the silicon analyzer crystal saturates and is no longer linearly dependent on the angle of refraction. This paper describes a method by which these effects can be overcome and excellent soft-tissue contrast of phase tomography can be preserved in the vicinity of such artefact-producing structures.

Representative Elementary Length to Measure Soil Mass Attenuation Coefficient

PubMed Central

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

2014-01-01

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 (μ s) is an important parameter for CT and GAT analysis. When experimentally determined (μ 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 μ 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 μ 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 (ρ s). As a consequence, ρ s might be under- or overestimated, generating inaccurate conclusions about the physical quality of the soil under study. PMID:24672338

Testing for characterization of the materials from radiological point of view

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bercea, Sorin; Iliescu, Elena; Dudu, Dorin

2013-12-16

The nuclear techniques and materials are now used in a large number of applications, both in medicine and industry. Due to this fact, new materials are needed in order to assure the radiological protection of the personnel involved in these activities. But, finally, all these materials have to be tested for some specific parameters, in order to prove that they are adequate for the purposed for which they were created. One of the important parameters of the materials used for the radiological protection is the attenuation coefficient. The attenuation coefficient of the ionizing radiation composed by particles without electrical chargemore » (X,γ-ray and neutron) is the most important parameter for the materials used for the shielding of these ionizing radiation. This paper deals with the experimental methods developed for the determination of the attenuation of fast and thermal neutrons. These experimental methods, involved the use of Am-Be source and U-120 Cyclotron of IFIN-HH. For the tests which were done at the U-120 Cyclotron, a number of experiments had to be performed, in order to establish the irradiation geometry and the dose equivalent rates in front of and behind the material samples. The experimental results obtained for samples of several materials, confirmed the methods as adequate for the aim of the test.« less

A Head and Neck Simulator for Radiology and Radiotherapy

NASA Astrophysics Data System (ADS)

Thompson, Larissa; Campos, Tarcísio P. R.

2013-06-01

Phantoms are suitable tools to simulate body tissues and organs in radiology and radiation therapy. This study presents the development of a physical head and neck phantom and its radiological response for simulating brain pathology. The following features on the phantom are addressed and compared to human data: mass density, chemical composition, anatomical shape, computerized tomography images and Hounsfield Units. Mass attenuation and kerma coefficients of the synthetic phantom and normal tissues, as well as their deviations, were also investigated. Radiological experiments were performed, including brain tumors and subarachnoid hemorrhage simulations. Computerized tomography images of such pathologies in phantom and human were obtained. The anthropometric dimensions of the phantom present anatomical conformation similar to a human head and neck. Elemental weight percentages of the equivalent tissues match the human ones. Hounsfield Unit values of the main developed structures are presented, approaching human data. Kerma and mass attenuation coefficients spectra from human and phantom are presented, demonstrating smaller deviations in the radiological X-ray spectral domain. In conclusion, the phantom presented suitable normal and pathological radiological responses relative to those observed in humans. It may improve radiological protocols and education in medical imaging.

Reconstruction algorithm for polychromatic CT imaging: application to beam hardening correction

NASA Technical Reports Server (NTRS)

Yan, C. H.; Whalen, R. T.; Beaupre, G. S.; Yen, S. Y.; Napel, S.

2000-01-01

This paper presents a new reconstruction algorithm for both single- and dual-energy computed tomography (CT) imaging. By incorporating the polychromatic characteristics of the X-ray beam into the reconstruction process, the algorithm is capable of eliminating beam hardening artifacts. The single energy version of the algorithm assumes that each voxel in the scan field can be expressed as a mixture of two known substances, for example, a mixture of trabecular bone and marrow, or a mixture of fat and flesh. These assumptions are easily satisfied in a quantitative computed tomography (QCT) setting. We have compared our algorithm to three commonly used single-energy correction techniques. Experimental results show that our algorithm is much more robust and accurate. We have also shown that QCT measurements obtained using our algorithm are five times more accurate than that from current QCT systems (using calibration). The dual-energy mode does not require any prior knowledge of the object in the scan field, and can be used to estimate the attenuation coefficient function of unknown materials. We have tested the dual-energy setup to obtain an accurate estimate for the attenuation coefficient function of K2 HPO4 solution.

Determination of tissue equivalent materials of a physical 8-year-old phantom for use in computed tomography

NASA Astrophysics Data System (ADS)

Akhlaghi, Parisa; Miri Hakimabad, Hashem; Rafat Motavalli, Laleh

2015-07-01

This paper reports on the methodology applied to select suitable tissue equivalent materials of an 8-year phantom for use in computed tomography (CT) examinations. To find the appropriate tissue substitutes, first physical properties (physical density, electronic density, effective atomic number, mass attenuation coefficient and CT number) of different materials were studied. Results showed that, the physical properties of water and polyurethane (as soft tissue), B-100 and polyvinyl chloride (PVC) (as bone) and polyurethane foam (as lung) agree more with those of original tissues. Then in the next step, the absorbed doses in the location of 25 thermoluminescent dosimeters (TLDs) as well as dose distribution in one slice of phantom were calculated for original and these proposed materials by Monte Carlo simulation at different tube voltages. The comparisons suggested that at tube voltages of 80 and 100 kVp using B-100 as bone, water as soft tissue and polyurethane foam as lung is suitable for dosimetric study in pediatric CT examinations. In addition, it was concluded that by considering just the mass attenuation coefficient of different materials, the appropriate tissue equivalent substitutes in each desired X-ray energy range could be found.

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

NASA Astrophysics Data System (ADS)

Kore, Prashant S.; Pawar, Pravina P.

2014-05-01

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.

Laser microbeam CT scanning of dosimetry gels

NASA Astrophysics Data System (ADS)

Maryanski, Marek J.; Ranade, Manisha K.

2001-06-01

A novel design of an optical tomographic scanner is described that can be used for 3D mapping of optical attenuation coefficient within translucent cylindrical objects with spatial resolution on the order of 100 microns. Our scanner design utilizes the cylindrical geometry of the imaged object to obtain the desired paths of the scanning light rays. A rotating mirror and a photodetector are placed at two opposite foci of the translucent cylinder that acts as a cylindrical lens. A He-Ne laser beam passes first through a focusing lens and then is reflected by the rotating mirror, so as to scan the interior of the cylinder with focused and parallel paraxial rays that are subsequently collected by the photodetector to produce the projection data, as the cylinder rotates in small angle increments between projections. Filtered backprojection is then used to reconstruct planar distributions of optical attenuation coefficient in the cylinder. Multiplanar scans are used to obtain a complete 3D tomographic reconstruction. Among other applications, the scanner can be used in radiation therapy dosimetry and quality assurance for mapping 3D radiation dose distributions in various types of tissue-equivalent gel phantoms that change their optical attenuation coefficients in proportion to the absorbed radiation dose.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sisniega, A.; Vaquero, J. J., E-mail: juanjose.vaquero@uc3m.es; Instituto de Investigación Sanitaria Gregorio Marañón, Madrid ES28007

2014-01-15

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, modifiedmore » 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.« less

Preliminary Mechanical Characterization of Thermal Filters for the X-IFU Instrument on Athena

NASA Astrophysics Data System (ADS)

Barbera, Marco; Lo Cicero, Ugo; Sciortino, Luisa; Parodi, Giancarlo; D'Anca, Fabio; Giglio, Paolo; Ferruggia Bonura, Salvatore; Nuzzo, Flavio; Jimenez Escobar, Antonio; Ciaravella, Angela; Collura, Alfonso; Varisco, Salvatore; Samain, Valerie

2018-05-01

The X-ray Integral Field Unit (X-IFU) is one of the two instruments of the Athena astrophysics space mission approved by ESA in the Cosmic Vision Science Program. The X-IFU consists of a large array of TES microcalorimeters that will operate at 50 mK inside a sophisticated cryostat. A set of thin filters, highly transparent to X-rays, will be mounted on the cryostat thermal shields in order to attenuate the IR radiative load, to attenuate RF electromagnetic interferences, and to protect the detector from contamination. In this paper, we present the current thermal filters design, describe the filter samples developed/procured so far, and present preliminary results from the ongoing characterization tests.

New contrasts for x-ray imaging and synergy with optical imaging

NASA Astrophysics Data System (ADS)

Wang, Ge

2017-02-01

Due to its penetrating power, fine resolution, unique contrast, high-speed, and cost-effectiveness, x-ray imaging is one of the earliest and most popular imaging modalities in biomedical applications. Current x-ray radiographs and CT images are mostly on gray-scale, since they reflect overall energy attenuation. Recent advances in x-ray detection, contrast agent, and image reconstruction technologies have changed our perception and expectation of x-ray imaging capabilities, and generated an increasing interest in imaging biological soft tissues in terms of energy-sensitive material decomposition, phase-contrast, small angle scattering (also referred to as dark-field), x-ray fluorescence and luminescence properties. These are especially relevant to preclinical and mesoscopic studies, and potentially mendable for hybridization with optical molecular tomography. In this article, we review new x-ray imaging techniques as related to optical imaging, suggest some combined x-ray and optical imaging schemes, and discuss our ideas on micro-modulated x-ray luminescence tomography (MXLT) and x-ray modulated opto-genetics (X-Optogenetics).

Vertical intensity modulation for improved radiographic penetration and reduced exclusion zone

NASA Astrophysics Data System (ADS)

Bendahan, J.; Langeveld, W. G. J.; Bharadwaj, V.; Amann, J.; Limborg, C.; Nosochkov, Y.

2016-09-01

In the present work, a method to direct the X-ray beam in real time to the desired locations in the cargo to increase penetration and reduce exclusion zone is presented. Cargo scanners employ high energy X-rays to produce radiographic images of the cargo. Most new scanners employ dual-energy to produce, in addition to attenuation maps, atomic number information in order to facilitate the detection of contraband. The electron beam producing the bremsstrahlung X-ray beam is usually directed approximately to the center of the container, concentrating the highest X-ray intensity to that area. Other parts of the container are exposed to lower radiation levels due to the large drop-off of the bremsstrahlung radiation intensity as a function of angle, especially for high energies (>6 MV). This results in lower penetration in these areas, requiring higher power sources that increase the dose and exclusion zone. The capability to modulate the X-ray source intensity on a pulse-by-pulse basis to deliver only as much radiation as required to the cargo has been reported previously. This method is, however, controlled by the most attenuating part of the inspected slice, resulting in excessive radiation to other areas of the cargo. A method to direct a dual-energy beam has been developed to provide a more precisely controlled level of required radiation to highly attenuating areas. The present method is based on steering the dual-energy electron beam using magnetic components on a pulse-to-pulse basis to a fixed location on the X-ray production target, but incident at different angles so as to direct the maximum intensity of the produced bremsstrahlung to the desired locations. The details of the technique and subsystem and simulation results are presented.

Gamma ray shielding properties of PbO-Li2O-B2O3 glasses

NASA Astrophysics Data System (ADS)

Kumar, Ashok

2017-07-01

The mass attenuation coefficients have been measured in (0.6-x) PbO-x Li2O-0.40 B2O3 (where 0≤ x≤0.25 mol%) glasses for photon energies of 356, 662, 1173 and 1332 keV in a narrow beam geometry with an overall scatter acceptance angle of 2.31°. The experimental results are found to be within 3% of their theoretical values. These coefficients were then used to obtain the values of mean free path, effective atomic number and electron density. The shielding properties of these glasses have also been compared among themselves in terms of their mean free path and radiation protection efficiency. The shielding properties prepared glasses have also been compared with standard concretes as well as with the standard shielding glasses. It is found that the prepared glasses are the better shielding substitute to the conventional concretes as well as other standard shielding glasses. The Pb3B4O9 has been found to be the most effective shield.

Filamentation effect in a gas attenuator for high-repetition-rate X-ray FELs.

PubMed

Feng, Yiping; Krzywinski, Jacek; Schafer, Donald W; Ortiz, Eliazar; Rowen, Michael; Raubenheimer, Tor O

2016-01-01

A sustained filamentation or density depression phenomenon in an argon gas attenuator servicing a high-repetition femtosecond X-ray free-electron laser has been studied using a finite-difference method applied to the thermal diffusion equation for an ideal gas. A steady-state solution was obtained by assuming continuous-wave input of an equivalent time-averaged beam power and that the pressure of the entire gas volume has reached equilibrium. Both radial and axial temperature/density gradients were found and describable as filamentation or density depression previously reported for a femtosecond optical laser of similar attributes. The effect exhibits complex dependence on the input power, the desired attenuation, and the geometries of the beam and the attenuator. Time-dependent simulations were carried out to further elucidate the evolution of the temperature/density gradients in between pulses, from which the actual attenuation received by any given pulse can be properly calculated.

Tomography of atomic number and density of materials using dual-energy imaging and the Alvarez and Macovski attenuation model

NASA Astrophysics Data System (ADS)

Paziresh, M.; Kingston, A. M.; Latham, S. J.; Fullagar, W. K.; Myers, G. M.

2016-06-01

Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073-2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127-135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260-1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and atomic number (Z) reconstructions to a significant extent.

Reproducing 2D breast mammography images with 3D printed phantoms

NASA Astrophysics Data System (ADS)

Clark, Matthew; Ghammraoui, Bahaa; Badal, Andreu

2016-03-01

Mammography is currently the standard imaging modality used to screen women for breast abnormalities and, as a result, it is a tool of great importance for the early detection of breast cancer. Physical phantoms are commonly used as surrogates of breast tissue to evaluate some aspects of the performance of mammography systems. However, most phantoms do not reproduce the anatomic heterogeneity of real breasts. New fabrication technologies, such as 3D printing, have created the opportunity to build more complex, anatomically realistic breast phantoms that could potentially assist in the evaluation of mammography systems. The primary objective of this work is to present a simple, easily reproducible methodology to design and print 3D objects that replicate the attenuation profile observed in real 2D mammograms. The secondary objective is to evaluate the capabilities and limitations of the competing 3D printing technologies, and characterize the x-ray properties of the different materials they use. Printable phantoms can be created using the open-source code introduced in this work, which processes a raw mammography image to estimate the amount of x-ray attenuation at each pixel, and outputs a triangle mesh object that encodes the observed attenuation map. The conversion from the observed pixel gray value to a column of printed material with equivalent attenuation requires certain assumptions and knowledge of multiple imaging system parameters, such as x-ray energy spectrum, source-to-object distance, compressed breast thickness, and average breast material attenuation. A detailed description of the new software, a characterization of the printed materials using x-ray spectroscopy, and an evaluation of the realism of the sample printed phantoms are presented.

Quantitative measurement of binary liquid distributions using multiple-tracer x-ray fluorescence and radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halls, Benjamin R.; Meyer, Terrence R.; Kastengren, Alan L.

2015-01-01

The complex geometry and large index-of-refraction gradients that occur near the point of impingement of binary liquid jets present a challenging environment for optical interrogation. A simultaneous quadruple-tracer x-ray fluorescence and line-of-sight radiography technique is proposed as a means of distinguishing and quantifying individual liquid component distributions prior to, during, and after jet impact. Two different pairs of fluorescence tracers are seeded into each liquid stream to maximize their attenuation ratio for reabsorption correction and differentiation of the two fluids during mixing. This approach for instantaneous correction of x-ray fluorescence reabsorption is compared with a more time-intensive approach of usingmore » stereographic reconstruction of x-ray attenuation along multiple lines of sight. The proposed methodology addresses the need for a quantitative measurement technique capable of interrogating optically complex, near-field liquid distributions in many mixing systems of practical interest involving two or more liquid streams.« less

Engineering iodine-doped carbon dots as dual-modal probes for fluorescence and X-ray CT imaging.

PubMed

Zhang, Miaomiao; Ju, Huixiang; Zhang, Li; Sun, Mingzhong; Zhou, Zhongwei; Dai, Zhenyu; Zhang, Lirong; Gong, Aihua; Wu, Chaoyao; Du, Fengyi

2015-01-01

X-ray computed tomography (CT) is the most commonly used imaging technique for noninvasive diagnosis of disease. In order to improve tissue specificity and prevent adverse effects, we report the design and synthesis of iodine-doped carbon dots (I-doped CDs) as efficient CT contrast agents and fluorescence probe by a facile bottom-up hydrothermal carbonization process. The as-prepared I-doped CDs are monodispersed spherical nanoparticles (a diameter of ~2.7 nm) with favorable dispersibility and colloidal stability in water. The aqueous solution of I-doped CDs showed wavelength-dependent excitation and stable photoluminescence similar to traditional carbon quantum dots. Importantly, I-doped CDs displayed superior X-ray attenuation properties in vitro and excellent biocompatibility. After intravenous injection, I-doped CDs were distributed throughout the body and excreted by renal clearance. These findings validated that I-doped CDs with high X-ray attenuation potency and favorable photoluminescence show great promise for biomedical research and disease diagnosis.

Engineering iodine-doped carbon dots as dual-modal probes for fluorescence and X-ray CT imaging

PubMed Central

Zhang, Miaomiao; Ju, Huixiang; Zhang, Li; Sun, Mingzhong; Zhou, Zhongwei; Dai, Zhenyu; Zhang, Lirong; Gong, Aihua; Wu, Chaoyao; Du, Fengyi

2015-01-01

X-ray computed tomography (CT) is the most commonly used imaging technique for noninvasive diagnosis of disease. In order to improve tissue specificity and prevent adverse effects, we report the design and synthesis of iodine-doped carbon dots (I-doped CDs) as efficient CT contrast agents and fluorescence probe by a facile bottom-up hydrothermal carbonization process. The as-prepared I-doped CDs are monodispersed spherical nanoparticles (a diameter of ~2.7 nm) with favorable dispersibility and colloidal stability in water. The aqueous solution of I-doped CDs showed wavelength-dependent excitation and stable photoluminescence similar to traditional carbon quantum dots. Importantly, I-doped CDs displayed superior X-ray attenuation properties in vitro and excellent biocompatibility. After intravenous injection, I-doped CDs were distributed throughout the body and excreted by renal clearance. These findings validated that I-doped CDs with high X-ray attenuation potency and favorable photoluminescence show great promise for biomedical research and disease diagnosis. PMID:26609232

Quantitative measurement of binary liquid distributions using multiple-tracer x-ray fluorescence and radiography

DOE PAGES

Halls, Benjamin R.; Meyer, Terrence R.; Kastengren, Alan L.

2015-01-23

The complex geometry and large index-of-refraction gradients that occur near the point of impingement of binary liquid jets present a challenging environment for optical interrogation. A simultaneous quadruple-tracer x-ray fluorescence and line-of-sight radiography technique is proposed as a means of distinguishing and quantifying individual liquid component distributions prior to, during, and after jet impact. Two different pairs of fluorescence tracers are seeded into each liquid stream to maximize their attenuation ratio for reabsorption correction and differentiation of the two fluids during mixing. This approach for instantaneous correction of x-ray fluorescence reabsorption is compared with a more time-intensive approach of usingmore » stereographic reconstruction of x-ray attenuation along multiple lines of sight. The proposed methodology addresses the need for a quantitative measurement technique capable of interrogating optically complex, near-field liquid distributions in many mixing systems of practical interest involving two or more liquid streams.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langeveld, Willem G. J.; Gozani, Tsahi; Ryge, Peter

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 techniquesmore » 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.« less

Neutron attenuation characteristics of polyethylene, polyvinyl chloride, and heavy aggregate concrete and mortars.

PubMed

Abdul-Majid, S; Othman, F

1994-03-01

Polyethylene and polyvinyl chloride pellets were introduced into concrete to improve its neutron attenuation characteristics while several types of heavy coarse aggregates were used to improve its gamma ray attenuation properties. Neutron and gamma ray attenuation were studied in concrete samples containing coarse aggregates of barite, pyrite, basalt, hematite, and marble as well as polyethylene and polyvinyl chloride pellets in narrow-beam geometry. The highest neutron attenuation was shown by polyethylene mortar, followed by polyvinyl chloride mortar; barite and pyrite concrete showed higher gamma ray attenuation than ordinary concrete. Broad-beam and continuous (infinite) medium geometries were used to study the neutron attenuation of samples containing polymers at different concentrations with and without heavy aggregates, the fitting equations were established, and from these the neutron removal coefficients were deduced. In a radiation field of neutrons and gamma rays, the appropriate concentration of polymer and heavy aggregate can be selected to give the optimum total dose attenuation depending on the relative intensities of each type of radiation. This would give much better design flexibility over ordinary concrete. The compressive strength tests performed on mortar and concrete samples showed that their value, in general, decreases as polymer concentration increases and that the polyvinyl chloride mortar showed higher values than the polyethylene mortar. For general construction purposes, the compression strength was considered acceptable in these samples.

Combining operando synchrotron X-ray tomographic microscopy and scanning X-ray diffraction to study lithium ion batteries

PubMed Central

Pietsch, Patrick; Hess, Michael; Ludwig, Wolfgang; Eller, Jens; Wood, Vanessa

2016-01-01

We present an operando study of a lithium ion battery combining scanning X-ray diffraction (SXRD) and synchrotron radiation X-ray tomographic microscopy (SRXTM) simultaneously for the first time. This combination of techniques facilitates the investigation of dynamic processes in lithium ion batteries containing amorphous and/or weakly attenuating active materials. While amorphous materials pose a challenge for diffraction techniques, weakly attenuating material systems pose a challenge for attenuation-contrast tomography. Furthermore, combining SXRD and SRXTM can be used to correlate processes occurring at the atomic level in the crystal lattices of the active materials with those at the scale of electrode microstructure. To demonstrate the benefits of this approach, we investigate a silicon powder electrode in lithium metal half-cell configuration. Combining SXRD and SRXTM, we are able to (i) quantify the dissolution of the metallic lithium electrode and the expansion of the silicon electrode, (ii) better understand the formation of the Li15Si4 phase, and (iii) non-invasively probe kinetic limitations within the silicon electrode. A simple model based on the 1D diffusion equation allows us to qualitatively understand the observed kinetics and demonstrates why high-capacity electrodes are more prone to inhomogeneous lithiation reactions. PMID:27324109

Combining operando synchrotron X-ray tomographic microscopy and scanning X-ray diffraction to study lithium ion batteries

NASA Astrophysics Data System (ADS)

Pietsch, Patrick; Hess, Michael; Ludwig, Wolfgang; Eller, Jens; Wood, Vanessa

2016-06-01

We present an operando study of a lithium ion battery combining scanning X-ray diffraction (SXRD) and synchrotron radiation X-ray tomographic microscopy (SRXTM) simultaneously for the first time. This combination of techniques facilitates the investigation of dynamic processes in lithium ion batteries containing amorphous and/or weakly attenuating active materials. While amorphous materials pose a challenge for diffraction techniques, weakly attenuating material systems pose a challenge for attenuation-contrast tomography. Furthermore, combining SXRD and SRXTM can be used to correlate processes occurring at the atomic level in the crystal lattices of the active materials with those at the scale of electrode microstructure. To demonstrate the benefits of this approach, we investigate a silicon powder electrode in lithium metal half-cell configuration. Combining SXRD and SRXTM, we are able to (i) quantify the dissolution of the metallic lithium electrode and the expansion of the silicon electrode, (ii) better understand the formation of the Li15Si4 phase, and (iii) non-invasively probe kinetic limitations within the silicon electrode. A simple model based on the 1D diffusion equation allows us to qualitatively understand the observed kinetics and demonstrates why high-capacity electrodes are more prone to inhomogeneous lithiation reactions.

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

NASA Astrophysics Data System (ADS)

Theodorakou, C.; Farquharson, M. J.

2008-06-01

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.

X-ray data booklet. Revision

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaughan, D.

A compilation of data is presented. Included are properties of the elements, electron binding energies, characteristic x-ray energies, fluorescence yields for K and L shells, Auger energies, energy levels for hydrogen-, helium-, and neonlike ions, scattering factors and mass absorption coefficients, and transmission bands of selected filters. Also included are selected reprints on scattering processes, x-ray sources, optics, x-ray detectors, and synchrotron radiation facilities. (WRF)

Spatial Distribution of Trehalose Dihydrate Crystallization in Tablets by X-ray Diffractometry.

PubMed

Thakral, Naveen K; Yamada, Hiroyuki; Stephenson, Gregory A; Suryanarayanan, Raj

2015-10-05

Crystallization of trehalose dihydrate (C12H22O11·2H2O) was induced by storing tablets of amorphous anhydrous trehalose (C12H22O11) at 65% RH (RT). Our goal was to evaluate the advantages and limitations of two approaches of profiling spatial distribution of drug crystallization in tablets. The extent of crystallization, as a function of depth, was determined in tablets stored for different time-periods. The first approach was glancing angle X-ray diffractometry, where the penetration depth of X-rays was modulated by the incident angle. Based on the mass attenuation coefficient of the matrix, the depth of X-ray penetration was calculated as a function of incident angle, which in turn enabled us to "calculate" the extent of crystallization to different depths. In the second approach, the tablets were split into halves and the split surfaces were analyzed directly. Starting from the tablet surface and moving toward the midplane, XRD patterns were collected in 36 "regions", in increments of 0.05 mm. The results obtained by the two approaches were, in general, in good agreement. Additionally, the results obtained were validated by determining the "average" crystallization in the entire tablet by using synchrotron radiation in the transmission mode. The glancing angle method could detect crystallization up to ∼650 μm and had a "surface bias". Being a nondestructive technique, this method will permit repeated analyses of the same tablet at different time points, for example, during a stability study. However, split tablet analyses, while a "destructive" technique, provided comprehensive and unbiased depth profiling information.

Spherical grating based x-ray Talbot interferometry.

PubMed

Cong, Wenxiang; Xi, Yan; Wang, Ge

2015-11-01

Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh-Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and improves both signal visibility and dose utilization for pre-clinical and clinical applications.

Spherical grating based x-ray Talbot interferometry

PubMed Central

Cong, Wenxiang; Xi, Yan; Wang, Ge

2015-01-01

Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and improves both signal visibility and dose utilization for pre-clinical and clinical applications. PMID:26520741

Spherical grating based x-ray Talbot interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cong, Wenxiang, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu; Xi, Yan, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu; Wang, Ge, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu

2015-11-15

Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme formore » a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and improves both signal visibility and dose utilization for pre-clinical and clinical applications.« less

Luminescence and scintillation characteristics of (GdxY3-x)Al2Ga3O12:Ce (x = 1,2,3) single crystals

NASA Astrophysics Data System (ADS)

Chewpraditkul, Warut; Pattanaboonmee, Nakarin; Sakthong, Ongsa; Chewpraditkul, Weerapong; Szczesniak, Tomasz; Moszynski, Marek; Kamada, Kei; Yoshikawa, Akira; Nikl, Martin

2018-02-01

The luminescence and scintillation characteristics of Czochralski-grown (GdxY3-x)Al2Ga3O12:Ce (x = 1,2,3) single crystals are presented. With increasing Gd content in this garnet host, the 5d2 absorption band was blue-shifted while the 5d1 absorption and 5d1 → 4f emission bands were red-shifted due to an increase in the crystal field splitting of the 5d levels. In addition, the luminescence quenching temperature of the Ce3+emission and activation energy for thermal quenching decreased with increasing Gd content. The Gd3+ → Ce3+ energy transfer was evidenced by photoluminescence excitation spectra of Ce3+ emission. At 662 keV γ - rays, the light yield (LY) of 48,600 ph/MeV and energy resolution of 6.5% was measured for a Gd3Al2Ga3O12:Ce crystal. Scintillation decay measurements were performed using the time-correlated single photon counting technique. Superior time resolution of Gd3Al2Ga3O12:Ce is due to its high LY and fast scintillation response. The total mass attenuation coefficients at 60 and 662 keV γ - rays were also determined.

Method for beam hardening correction in quantitative computed X-ray tomography

NASA Technical Reports Server (NTRS)

Yan, Chye Hwang (Inventor); Whalen, Robert T. (Inventor); Napel, Sandy (Inventor)

2001-01-01

Each voxel is assumed to contain exactly two distinct materials, with the volume fraction of each material being iteratively calculated. According to the method, the spectrum of the X-ray beam must be known, and the attenuation spectra of the materials in the object must be known, and be monotonically decreasing with increasing X-ray photon energy. Then, a volume fraction is estimated for the voxel, and the spectrum is iteratively calculated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sisniega, A.; Vaquero, J. J., E-mail: juanjose.vaquero@uc3m.es; Instituto de Investigación Sanitaria Gregorio Marañón, Madrid ES28007

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, modifiedmore » 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.« less

X ray attenuation measurements for high-temperature materials characterization and in-situ monitoring of damage accumulation. Ph.D. Thesis - Cleveland State Univ., 1991

NASA Technical Reports Server (NTRS)

Baaklini, George Y.

1992-01-01

The scope of this dissertation is to develop and apply x ray attenuation measurement systems that are capable of: (1) characterizing density variations in high-temperature materials, e.g., monolithic ceramics, ceramic and intermetallic matrix composites, and (2) noninvasively monitoring damage accumulation and failure sequences in ceramic matrix composites under room temperature tensile testing. This dissertation results in the development of: (1) a point scan digital radiography system, and (2) an in-situ x ray material testing system. Radiographic evaluation before, during, and after loading shows the effect of preexisting volume flaws on the fracture behavior of composites. Results 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. Further in-situ 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 for greater understanding of ceramic matrix composite mechanical behavior.

21 CFR 1020.30 - Diagnostic x-ray systems and their major components.

Code of Federal Regulations, 2010 CFR

2010-04-01

.... Diagnostic x-ray system means an x-ray system designed for irradiation of any part of the human body for the... HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING... for the radiographic visualization and measurement of the dimensions of the human head. Coefficient of...

21 CFR 1020.30 - Diagnostic x-ray systems and their major components.

Code of Federal Regulations, 2011 CFR

2011-04-01

.... Diagnostic x-ray system means an x-ray system designed for irradiation of any part of the human body for the... HUMAN SERVICES (CONTINUED) RADIOLOGICAL HEALTH PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING... for the radiographic visualization and measurement of the dimensions of the human head. Coefficient of...

Estimation of effective x-ray tissue attenuation differences for volumetric breast density measurement

NASA Astrophysics Data System (ADS)

Chen, Biao; Ruth, Chris; Jing, Zhenxue; Ren, Baorui; Smith, Andrew; Kshirsagar, Ashwini

2014-03-01

Breast density has been identified to be a risk factor of developing breast cancer and an indicator of lesion diagnostic obstruction due to masking effect. Volumetric density measurement evaluates fibro-glandular volume, breast volume, and breast volume density measures that have potential advantages over area density measurement in risk assessment. One class of volume density computing methods is based on the finding of the relative fibro-glandular tissue attenuation with regards to the reference fat tissue, and the estimation of the effective x-ray tissue attenuation differences between the fibro-glandular and fat tissue is key to volumetric breast density computing. We have modeled the effective attenuation difference as a function of actual x-ray skin entrance spectrum, breast thickness, fibro-glandular tissue thickness distribution, and detector efficiency. Compared to other approaches, our method has threefold advantages: (1) avoids the system calibration-based creation of effective attenuation differences which may introduce tedious calibrations for each imaging system and may not reflect the spectrum change and scatter induced overestimation or underestimation of breast density; (2) obtains the system specific separate and differential attenuation values of fibroglandular and fat for each mammographic image; and (3) further reduces the impact of breast thickness accuracy to volumetric breast density. A quantitative breast volume phantom with a set of equivalent fibro-glandular thicknesses has been used to evaluate the volume breast density measurement with the proposed method. The experimental results have shown that the method has significantly improved the accuracy of estimating breast density.

Quantitative Electron Probe Microanalysis: State of the Art

NASA Technical Reports Server (NTRS)

Carpernter, P. K.

2005-01-01

Quantitative electron-probe microanalysis (EPMA) has improved due to better instrument design and X-ray correction methods. Design improvement of the electron column and X-ray spectrometer has resulted in measurement precision that exceeds analytical accuracy. Wavelength-dispersive spectrometer (WDS) have layered-dispersive diffraction crystals with improved light-element sensitivity. Newer energy-dispersive spectrometers (EDS) have Si-drift detector elements, thin window designs, and digital processing electronics with X-ray throughput approaching that of WDS Systems. Using these systems, digital X-ray mapping coupled with spectrum imaging is a powerful compositional mapping tool. Improvements in analytical accuracy are due to better X-ray correction algorithms, mass absorption coefficient data sets,and analysis method for complex geometries. ZAF algorithms have ban superceded by Phi(pz) algorithms that better model the depth distribution of primary X-ray production. Complex thin film and particle geometries are treated using Phi(pz) algorithms, end results agree well with Monte Carlo simulations. For geological materials, X-ray absorption dominates the corretions end depends on the accuracy of mass absorption coefficient (MAC) data sets. However, few MACs have been experimentally measured, and the use of fitted coefficients continues due to general success of the analytical technique. A polynomial formulation of the Bence-Albec alpha-factor technique, calibrated using Phi(pz) algorithms, is used to critically evaluate accuracy issues and can be also be used for high 2% relative and is limited by measurement precision for ideal cases, but for many elements the analytical accuracy is unproven. The EPMA technique has improved to the point where it is frequently used instead of the petrogaphic microscope for reconnaissance work. Examples of stagnant research areas are: WDS detector design characterization of calibration standards, and the need for more complete treatment of the continuum X-ray fluorescence correction.

Air slab-correction for Γ-ray attenuation measurements

NASA Astrophysics Data System (ADS)

Mann, Kulwinder Singh

2017-12-01

Gamma (γ)-ray shielding behaviour (GSB) of a material can be ascertained from its linear attenuation coefficient (μ, cm-1). Narrow-beam transmission geometry is required for μ-measurement. In such measurements, a thin slab of the material has to insert between point-isotropic γ-ray source and detector assembly. The accuracy in measurements requires that sample's optical thickness (OT) remain below 0.5 mean free path (mfp). Sometimes it is very difficult to produce thin slab of sample (absorber), on the other hand for thick absorber, i.e. OT >0.5 mfp, the influence of the air displaced by it cannot be ignored during μ-measurements. Thus, for a thick sample, correction factor has been suggested which compensates the air present in the transmission geometry. The correction factor has been named as an air slab-correction (ASC). Six samples of low-Z engineering materials (cement-black, clay, red-mud, lime-stone, cement-white and plaster-of-paris) have been selected for investigating the effect of ASC on μ-measurements at three γ-ray energies (661.66, 1173.24, 1332.50 keV). The measurements have been made using point-isotropic γ-ray sources (Cs-137 and Co-60), NaI(Tl) detector and multi-channel-analyser coupled with a personal computer. Theoretical values of μ have been computed using a GRIC2-toolkit (standardized computer programme). Elemental compositions of the samples were measured with Wavelength Dispersive X-ray Fluorescence (WDXRF) analyser. Inter-comparison of measured and computed μ-values, suggested that the application of ASC helps in precise μ-measurement for thick samples of low-Z materials. Thus, this hitherto widely ignored ASC factor is recommended to use in similar γ-ray measurements.

Assessment of natural enamel lesions with optical coherence tomography in comparison with microfocus x-ray computed tomography.

PubMed

Espigares, Jorge; Sadr, Alireza; Hamba, Hidenori; Shimada, Yasushi; Otsuki, Masayuki; Tagami, Junji; Sumi, Yasunori

2015-01-01

A technology to characterize early enamel lesions is needed in dentistry. Optical coherence tomography (OCT) is a noninvasive method that provides high-resolution cross-sectional images. The aim of this study is to compare OCT with microfocus x-ray computed tomography ([Formula: see text]) for assessment of natural enamel lesions in vitro. Ten human teeth with visible white spot-like changes on the enamel smooth surface and no cavitation (ICDAS code 2) were subjected to imaging by μCT (SMX-100CT, Shimadzu) and 1300-nm swept-source OCT (Dental SS-OCT, Panasonic Health Care). In [Formula: see text], the lesions appeared as radiolucent dark areas, while in SS-OCT, they appeared as areas of increased signal intensity beneath the surface. An SS-OCT attenuation coefficient based on Beer-Lambert law could discriminate lesions from sound enamel. Lesion depth ranged from 175 to [Formula: see text] in SS-OCT. A correlation between [Formula: see text] and SS-OCT was found regarding lesion depth ([Formula: see text], [Formula: see text]) and also surface layer thickness ([Formula: see text], [Formula: see text]). The images obtained clinically in real time using the dental SS-OCT system are suitable for the assessment of natural subsurface lesions and their surface layer, providing comparable images to a laboratory high-resolution [Formula: see text] without the use of x-ray.

Assessment of natural enamel lesions with optical coherence tomography in comparison with microfocus x-ray computed tomography

PubMed Central

Espigares, Jorge; Sadr, Alireza; Hamba, Hidenori; Shimada, Yasushi; Otsuki, Masayuki; Tagami, Junji; Sumi, Yasunori

2015-01-01

Abstract. A technology to characterize early enamel lesions is needed in dentistry. Optical coherence tomography (OCT) is a noninvasive method that provides high-resolution cross-sectional images. The aim of this study is to compare OCT with microfocus x-ray computed tomography (μCT) for assessment of natural enamel lesions in vitro. Ten human teeth with visible white spot-like changes on the enamel smooth surface and no cavitation (ICDAS code 2) were subjected to imaging by μCT (SMX-100CT, Shimadzu) and 1300-nm swept-source OCT (Dental SS-OCT, Panasonic Health Care). In μCT, the lesions appeared as radiolucent dark areas, while in SS-OCT, they appeared as areas of increased signal intensity beneath the surface. An SS-OCT attenuation coefficient based on Beer–Lambert law could discriminate lesions from sound enamel. Lesion depth ranged from 175 to 606  μm in SS-OCT. A correlation between μCT and SS-OCT was found regarding lesion depth (R=0.81, p<0.001) and also surface layer thickness (R=0.76, p<0.005). The images obtained clinically in real time using the dental SS-OCT system are suitable for the assessment of natural subsurface lesions and their surface layer, providing comparable images to a laboratory high-resolution μCT without the use of x-ray. PMID:26158079

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

PubMed

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

2015-03-01

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

A framelet-based iterative maximum-likelihood reconstruction algorithm for spectral CT

NASA Astrophysics Data System (ADS)

Wang, Yingmei; Wang, Ge; Mao, Shuwei; Cong, Wenxiang; Ji, Zhilong; Cai, Jian-Feng; Ye, Yangbo

2016-11-01

Standard computed tomography (CT) cannot reproduce spectral information of an object. Hardware solutions include dual-energy CT which scans the object twice in different x-ray energy levels, and energy-discriminative detectors which can separate lower and higher energy levels from a single x-ray scan. In this paper, we propose a software solution and give an iterative algorithm that reconstructs an image with spectral information from just one scan with a standard energy-integrating detector. The spectral information obtained can be used to produce color CT images, spectral curves of the attenuation coefficient μ (r,E) at points inside the object, and photoelectric images, which are all valuable imaging tools in cancerous diagnosis. Our software solution requires no change on hardware of a CT machine. With the Shepp-Logan phantom, we have found that although the photoelectric and Compton components were not perfectly reconstructed, their composite effect was very accurately reconstructed as compared to the ground truth and the dual-energy CT counterpart. This means that our proposed method has an intrinsic benefit in beam hardening correction and metal artifact reduction. The algorithm is based on a nonlinear polychromatic acquisition model for x-ray CT. The key technique is a sparse representation of iterations in a framelet system. Convergence of the algorithm is studied. This is believed to be the first application of framelet imaging tools to a nonlinear inverse problem.

Attenuation coefficients and exposure buildup factor of some rocks for gamma ray shielding applications

NASA Astrophysics Data System (ADS)

Obaid, Shamsan S.; Sayyed, M. I.; Gaikwad, D. K.; Pawar, Pravina. P.

2018-07-01

In the present work, the mass attenuation coefficient μ/ρ is investigated experimentally and theoretically for seven rocks (olivine basalt, green marble, jet black granite, telphone black granite, cuddapah limestone, white marble and pink marble). The rock samples were collected from different places of India. The mass attenuation coefficients of the samples were measured experimentally at photon energies of radioisotopes Co57 (122 keV), Ba133 (356 keV), 22Na (511 and 1275 keV), Cs137 (662 keV), Mn54 (840 keV), and Co60 (1330 keV). Theoretically, the simulation results of μ/ρ using both XCOM and MCNP5 codes were compared with experimental results and a satisfactory agreement was observed. Total atomic cross sections (σt,a) electronic cross sections (σt,e), effective atomic number (Zeff), electron density (Ne) and half value layer (HVL) were evaluated using the obtained μ/ρ values for investigated rocks. The HVL values for the selected rocks were compared with some common shielding concretes. Moreover, by Geometric Progression method (G-P) exposure buildup factor (EBF) and energy absorption buildup factor (EABF) values were calculated for incident photon energy 0.015-15 MeV up to penetration depths of 40 mean free paths. The results show that among the studied rocks pink marble possesses superior shielding properties for γ-ray. This work was carried out to explore the advantage of utilizing the selected rocks in engineering structures and building construction to shield gamma-rays.

Modeling Contamination Migration on the Chandra X-Ray Observatory - III

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexy A.; Tennant, Allyn F.; Dahmer, Matthew T.

2015-01-01

During its first 16 years of operation, the cold (about -60 C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity, in part to evaluate potential bake-out scenarios intended to reduce the level of contamination. Keywords: X-ray astronomy, CCDs, contamination, modeling and simulation, spacecraft operations

First centenary of Röntgen's discovery of X-rays

NASA Astrophysics Data System (ADS)

Valkovic, V.

1996-04-01

Usually it takes a decade or even several decades, from a discovery to its practical applications. This was not the case with X-rays; they were widely applied in medical and industrial radiography within a year of their discovery in 1895 by W.C. Röntgen. Today, X-ray analysis covers a wide range of techniques and fields of applications: from deduction of atomic arrangements by observation of diffraction phenomena to measurements of trace element concentration levels, distributions and maps by measuring fluorescence, X-ray attenuation or scattering. Although the contribution of analytical applications of X-rays to the present knowledge is difficult to surpass, modern application cover a wide range of activities from three-dimensional microfabrication using synchroton radiation to collecting information from the deep space by X-ray astronomy.

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)

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

2013-03-01

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.

Multiple image x-radiography for functional lung imaging

NASA Astrophysics Data System (ADS)

Aulakh, G. K.; Mann, A.; Belev, G.; Wiebe, S.; Kuebler, W. M.; Singh, B.; Chapman, D.

2018-01-01

Detection and visualization of lung tissue structures is impaired by predominance of air. However, by using synchrotron x-rays, refraction of x-rays at the interface of tissue and air can be utilized to generate contrast which may in turn enable quantification of lung optical properties. We utilized multiple image radiography, a variant of diffraction enhanced imaging, at the Canadian light source to quantify changes in unique x-ray optical properties of lungs, namely attenuation, refraction and ultra small-angle scatter (USAXS or width) contrast ratios as a function of lung orientation in free-breathing or respiratory-gated mice before and after intra-nasal bacterial endotoxin (lipopolysaccharide) instillation. The lung ultra small-angle scatter and attenuation contrast ratios were significantly higher 9 h post lipopolysaccharide instillation compared to saline treatment whereas the refraction contrast decreased in magnitude. In ventilated mice, end-expiratory pressures result in an increase in ultra small-angle scatter contrast ratio when compared to end-inspiratory pressures. There were no detectable changes in lung attenuation or refraction contrast ratio with change in lung pressure alone. In effect, multiple image radiography can be applied towards following optical properties of lung air-tissue barrier over time during pathologies such as acute lung injury.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silvani, M. I.; Almeida, G. L.; Lopes, R. T.

Radiographic images acquired with point-like gamma-ray sources exhibit a desirable low penumbra effects specially when positioned far away from the set object-detector. Such an arrangement frequently is not affordable due to the limited flux provided by a distant source. A closer source, however, has two main drawbacks, namely the degradation of the spatial resolution - as actual sources are only approximately punctual - and the non-homogeneity of the beam hitting the detector, which creates a false attenuation map of the object being inspected. This non-homogeneity is caused by the beam divergence itself and by the different thicknesses traversed the beammore » even if the object were an homogeneous flat plate. In this work, radiographic images of objects with different geometries, such as flat plates and pipes have undergone a correction of beam divergence and attenuation addressing the experimental verification of the capability and soundness of an algorithm formerly developed to generate and process synthetic images. The impact of other parameters, including source-detector gap, attenuation coefficient, ratio defective-to-main hull thickness and counting statistics have been assessed for specifically tailored test-objects aiming at the evaluation of the ability of the proposed method to deal with different boundary conditions. All experiments have been carried out with an X-ray sensitive Imaging Plate and reactor-produced {sup 198}Au and {sup 165}Dy sources. The results have been compared with other technique showing a better capability to correct the attenuation map of inspected objects unveiling their inner structure otherwise concealed by the poor contrast caused by the beam divergence and attenuation, in particular for those regions far apart from the vertical of the source.« less

Incoherent-scatter computed tomography with monochromatic synchrotron x ray: feasibility of multi-CT imaging system for simultaneous measurement-of fluorescent and incoherent scatter x rays

NASA Astrophysics Data System (ADS)

Yuasa, T.; Akiba, M.; Takeda, T.; Kazama, M.; Hoshino, A.; Watanabe, Y.; Hyodo, K.; Dilmanian, F. A.; Akatsuka, T.; Itai, Y.

1997-10-01

We describe a new system of incoherent scatter computed tomography (ISCT) using monochromatic synchrotron X rays, and we discuss its potential to be used in in vivo imaging for medical use. The system operates on the basis of computed tomography (CT) of the first generation. The reconstruction method for ISCT uses the least squares method with singular value decomposition. The research was carried out at the BLNE-5A bending magnet beam line of the Tristan Accumulation Ring in KEK, Japan. An acrylic cylindrical phantom of 20-mm diameter containing a cross-shaped channel was imaged. The channel was filled with a diluted iodine solution with a concentration of 200 /spl mu/gI/ml. Spectra obtained with the system's high purity germanium (HPGe) detector separated the incoherent X-ray line from the other notable peaks, i.e., the iK/sub /spl alpha// and K/sub /spl beta/1/ X-ray fluorescent lines and the coherent scattering peak. CT images were reconstructed from projections generated by integrating the counts In the energy window centering around the incoherent scattering peak and whose width was approximately 2 keV. The reconstruction routine employed an X-ray attenuation correction algorithm. The resulting image showed more homogeneity than one without the attenuation correction.

Radiation effects on beta /10.6/ of pure and europium doped KCl

NASA Technical Reports Server (NTRS)

Grimes, H. H.; Maisel, J. E.; Hartford, R. H.

1975-01-01

Changes in the optical absorption coefficient as the result of X-ray and electron bombardment of pure monocrystalline and polycrystalline KCl and of divalent europium doped polycrystalline KCl were determined. A constant heat flow calorimetric method was used to measure the optical absorption coefficients. Both 300 kV X-ray irradiation and 2 MeV electron irradiation produced increases in the optical absorption coefficient at room temperature. X-ray irradiation produced more significant changes in pure monocrystalline KCl than equivalent amounts of electron irradiation. Electron irradiation of pure and Eu-doped polycrystalline KCl produced increases in the absorption by as much as a factor of 20 over untreated material. Bleaching of the electron-irradiated doped KCl with 649 millimicron light produced a further increase.

Photon Interaction Parameters for Some Borate Glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mann, Nisha; Kaur, Updesh; Singh, Tejbir

2010-11-06

Some photon interaction parameters of dosimetric interest such as mass attenuation coefficients, effective atomic number, electron density and KERMA relative to air have been computed in the wide energy range from 1 keV to 100 GeV for some borate glasses viz. barium-lead borate, bismuth-borate, calcium-strontium borate, lead borate and zinc-borate glass. It has been observed that lead borate glass and barium-lead borate glass have maximum values of mass attenuation coefficient, effective atomic number and KERMA relative to air. Hence, these borate glasses are suitable as gamma ray shielding material, packing of radioactive sources etc.

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

PubMed

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

2013-05-01

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 × 10(6) 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.

Intrinsic light yield and light loss coefficient of Bi4Ge3O12 single crystals

NASA Astrophysics Data System (ADS)

Yawai, Nattasuda; Chewpraditkul, Weerapong; Wanarak, Chalerm; Nikl, Martin; Ratanatongchai, Wichian

2014-10-01

In this paper we present the scintillation properties of polished Bi4Ge3O12 (BGO) crystals grown by the Bridgman method. The light yield (LY) and energy resolution were measured using XP5200B photomultiplier. At 662 keV γ-rays, high LY of 9680 photons/MeV and good energy resolution of 8.6% were obtained for a 5 × 5 × 1 mm3 BGO sample. The intrinsic LY and light loss coefficient were evaluated. The photofraction in pulse height spectrum of 662 keV γ-rays and the mass attenuation coefficient at 59.5 and 662 keV γ-rays were also determined and compared with the theoretical ones calculated using the WinXCom program.

Microchannel plate streak camera

DOEpatents

Wang, Ching L.

1989-01-01

An improved streak camera in which a microchannel plate electron multiplier is used in place of or in combination with the photocathode used in prior streak cameras. The improved streak camera is far more sensitive to photons (UV to gamma-rays) than the conventional x-ray streak camera which uses a photocathode. The improved streak camera offers gamma-ray detection with high temporal resolution. It also offers low-energy x-ray detection without attenuation inside the cathode. Using the microchannel plate in the improved camera has resulted in a time resolution of about 150 ps, and has provided a sensitivity sufficient for 1000 KeV x-rays.

Development of a novel low-radiation-absorbent lok-bar to reduce X-ray scattering and absorption in RapidArc® treatment planning and dose delivery.

PubMed

Monzen, Hajime; Kubo, Kazuki; Tamura, Mikoto; Hayakawa, Masaru; Nishimura, Yasumasa

2017-05-01

We developed a novel low-radiation-absorbent lok-bar (HM-bar) that is used to secure the immobilizers to the couch. The aim of this study was to investigate the X-ray scattering and absorption properties of the HM-bar in computed tomography (CT) simulation and radiotherapy dose delivery using the Varian Exact™ lok-bar (VL-bar) as a benchmark. CT images were obtained with or without lok-bar, and then each image was visually evaluated for artifacts. The attenuation rates for each lok-bar were measured using a farmer-type ionization chamber (PTW30013) and the I'mRT phantom (IBA Dosimetry GmbH). Measurement points were between gantry angles of 110 and 180°. The treatment apparatus was a NovalisTx (Brainlab AG); X-ray energies were set at 6 MV and 10 MV. In the presence of each lok-bar, the radiation dose was measured in accordance with 10 volumetric modulated arc therapy-stereotactic body radiation therapy (VMAT-SBRT) plans for lung cancer. Artifacts were seldom observed in the CT scans of the HM-bar. The attenuation rate of each lok-bar was higher when the X-ray energy was set at 6 MV than at 10 MV. The highest attenuation rate in the VL-bar was observed at a gantry angle of 112°; the rates were 22.4% at 6 MV and 19.3% at 10 MV. Similarly, the highest attenuation rate for the HM-bar was also observed at a gantry angle of 112°; the rates were 12.2% and 10.1% at 6 MV and 10 MV, respectively. When the VL-bar was evaluated, the isocenter dose of the VMAT-SBRT plans was attenuated by 2.6% as a maximum case. In the case of the HM-bar, the maximum attenuation was 1.4%. In the measurements of each VMAT-SBRT plan, the difference of the dose attenuation rate between the VL-bar and HM-bar was approximately 1%. The HM-bar could be used to minimize the occurrence of artifacts and provide good images in CT scans regarding radiotherapy planning and dose calculation. It can be used for patient therapy at hospitals to provide accurate dose delivery because of its low X-ray scattering and absorption characteristics. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

A new approach for beam hardening correction based on the local spectrum distributions

NASA Astrophysics Data System (ADS)

Rasoulpour, Naser; Kamali-Asl, Alireza; Hemmati, Hamidreza

2015-09-01

Energy dependence of material absorption and polychromatic nature of x-ray beams in the Computed Tomography (CT) causes a phenomenon which called "beam hardening". The purpose of this study is to provide a novel approach for Beam Hardening (BH) correction. This approach is based on the linear attenuation coefficients of Local Spectrum Distributions (LSDs) in the various depths of a phantom. The proposed method includes two steps. Firstly, the hardened spectra in various depths of the phantom (or LSDs) are estimated based on the Expectation Maximization (EM) algorithm for arbitrary thickness interval of known materials in the phantom. The performance of LSD estimation technique is evaluated by applying random Gaussian noise to transmission data. Then, the linear attenuation coefficients with regarding to the mean energy of LSDs are obtained. Secondly, a correction function based on the calculated attenuation coefficients is derived in order to correct polychromatic raw data. Since a correction function has been used for the conversion of the polychromatic data to the monochromatic data, the effect of BH in proposed reconstruction must be reduced in comparison with polychromatic reconstruction. The proposed approach has been assessed in the phantoms which involve less than two materials, but the correction function has been extended for using in the constructed phantoms with more than two materials. The relative mean energy difference in the LSDs estimations based on the noise-free transmission data was less than 1.5%. Also, it shows an acceptable value when a random Gaussian noise is applied to the transmission data. The amount of cupping artifact in the proposed reconstruction method has been effectively reduced and proposed reconstruction profile is uniform more than polychromatic reconstruction profile.

Study of CT Scan Flooding System at High Temperature and Pressure

NASA Astrophysics Data System (ADS)

Chen, X. Y.

2017-12-01

CT scan flooding experiment can scan micro-pore in different flooding stages by the use of CT scan technology, without changing the external morphology and internal structure of the core, and observe the distribution characterization in pore medium of different flooding fluid under different pressure.thus,it can rebuilt the distribution images of oil-water distribution in different flooding stages. However,under extreme high pressure and temperature conditions,the CT scan system can not meet the requirements. Container of low density materials or thin shell can not resist high pressure,while high density materials or thick shell will cause attenuation and scattering of X-ray. The experiment uses a simple Ct scanning systems.X ray from a point light source passing trough a micro beryllium shell on High pressure stainless steal container,continuously irradiates the core holder that can continuously 360° rotate along the core axis. A rare earth intensifying screen behind the core holder emitting light when irradiated with X ray can show the core X ray section image. An optical camera record the core X ray images through a transparency high pressure glazing that placed on the High pressure stainless steal container.Thus,multiple core X ray section images can reconstruct the 3D core reconstruction after a series of data processing.The experiment shows that both the micro beryllium shell and rare earth intensifying screen can work in high temperature and high pressure environment in the stainless steal container. This way that X-ray passes through a thin layer of micro beryllium shell , not high pressure stainless steal shell,avoid the attenuation and scattering of X-ray from the container shell,while improving the high-pressure experiment requirements.

Investigation of ultra low-dose scans in the context of quantum-counting clinical CT

NASA Astrophysics Data System (ADS)

Weidinger, T.; Buzug, T. M.; Flohr, T.; Fung, G. S. K.; Kappler, S.; Stierstorfer, K.; Tsui, B. M. W.

2012-03-01

In clinical computed tomography (CT), images from patient examinations taken with conventional scanners exhibit noise characteristics governed by electronics noise, when scanning strongly attenuating obese patients or with an ultra-low X-ray dose. Unlike CT systems based on energy integrating detectors, a system with a quantum counting detector does not suffer from this drawback. Instead, the noise from the electronics mainly affects the spectral resolution of these detectors. Therefore, it does not contribute to the image noise in spectrally non-resolved CT images. This promises improved image quality due to image noise reduction in scans obtained from clinical CT examinations with lowest X-ray tube currents or obese patients. To quantify the benefits of quantum counting detectors in clinical CT we have carried out an extensive simulation study of the complete scanning and reconstruction process for both kinds of detectors. The simulation chain encompasses modeling of the X-ray source, beam attenuation in the patient, and calculation of the detector response. Moreover, in each case the subsequent image preprocessing and reconstruction is modeled as well. The simulation-based, theoretical evaluation is validated by experiments with a novel prototype quantum counting system and a Siemens Definition Flash scanner with a conventional energy integrating CT detector. We demonstrate and quantify the improvement from image noise reduction achievable with quantum counting techniques in CT examinations with ultra-low X-ray dose and strong attenuation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paziresh, M.; Kingston, A. M., E-mail: andrew.kingston@anu.edu.au; Latham, S. J.

Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski,more » Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073–2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127–135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260–1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and atomic number (Z) reconstructions to a significant extent.« less

Experimentally determined spectral optimization for dedicated breast computed tomography.

PubMed

Prionas, Nicolas D; Huang, Shih-Ying; Boone, John M

2011-02-01

The current study aimed to experimentally identify the optimal technique factors (x-ray tube potential and added filtration material/thickness) to maximize soft-tissue contrast, microcalcification contrast, and iodine contrast enhancement using cadaveric breast specimens imaged with dedicated breast computed tomography (bCT). Secondarily, the study aimed to evaluate the accuracy of phantom materials as tissue surrogates and to characterize the change in accuracy with varying bCT technique factors. A cadaveric breast specimen was acquired under appropriate approval and scanned using a prototype bCT scanner. Inserted into the specimen were cylindrical inserts of polyethylene, water, iodine contrast medium (iodixanol, 2.5 mg/ml), and calcium hydroxyapatite (100 mg/ml). Six x-ray tube potentials (50, 60, 70, 80, 90, and 100 kVp) and three different filters (0.2 mm Cu, 1.5 mm Al, and 0.2 mm Sn) were tested. For each set of technique factors, the intensity (linear attenuation coefficient) and noise were measured within six regions of interest (ROIs): Glandular tissue, adipose tissue, polyethylene, water, iodine contrast medium, and calcium hydroxyapatite. Dose-normalized contrast to noise ratio (CNRD) was measured for pairwise comparisons among the six ROIs. Regression models were used to estimate the effect of tube potential and added filtration on intensity, noise, and CNRD. Iodine contrast enhancement was maximized using 60 kVp and 0.2 mm Cu. Microcalcification contrast and soft-tissue contrast were maximized at 60 kVp. The 0.2 mm Cu filter achieved significantly higher CNRD for iodine contrast enhancement than the other two filters (p = 0.01), but microcalcification contrast and soft-tissue contrast were similar using the copper and aluminum filters. The average percent difference in linear attenuation coefficient, across all tube potentials, for polyethylene versus adipose tissue was 1.8%, 1.7%, and 1.3% for 0.2 mm Cu, 1.5 mm Al, and 0.2 mm Sn, respectively. For water versus glandular tissue, the average percent difference was 2.7%, 3.9%, and 4.2% for the three filter types. Contrast-enhanced bCT, using injected iodine contrast medium, may be optimized for maximum contrast of enhancing lesions at 60 kVp with 0.2 mm Cu filtration. Soft-tissue contrast and microcalcification contrast may also benefit from lower tube potentials (60 kVp). The linear attenuation coefficients of water and polyethylene slightly overestimate the values of their corresponding tissues, but the reported differences may serve as guidance for dosimetry and quality assurance using tissue equivalent phantoms.

Filamentation effect in a gas attenuator for high-repetition-rate X-ray FELs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Yiping; Krzywinski, Jacek; Schafer, Donald W.

A sustained filamentation or density depression phenomenon in an argon gas attenuator servicing a high-repetition femtosecond X-ray free-electron laser has been studied using a finite-difference method applied to the thermal diffusion equation for an ideal gas. A steady-state solution was obtained by assuming continuous-wave input of an equivalent time-averaged beam power and that the pressure of the entire gas volume has reached equilibrium. Both radial and axial temperature/density gradients were found and describable as filamentation or density depression previously reported for a femtosecond optical laser of similar attributes. The effect exhibits complex dependence on the input power, the desired attenuation,more » and the geometries of the beam and the attenuator. Time-dependent simulations were carried out to further elucidate the evolution of the temperature/density gradients in between pulses, from which the actual attenuation received by any given pulse can be properly calculated.« less

NBSGSC - a FORTRAN program for quantitative x-ray fluorescence analysis. Technical note (final)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, G.Y.; Pella, P.A.; Rousseau, R.M.

1985-04-01

A FORTRAN program (NBSGSC) was developed for performing quantitative analysis of bulk specimens by x-ray fluorescence spectrometry. This program corrects for x-ray absorption/enhancement phenomena using the comprehensive alpha coefficient algorithm proposed by Lachance (COLA). NBSGSC is a revision of the program ALPHA and CARECAL originally developed by R.M. Rousseau of the Geological Survey of Canada. Part one of the program (CALCO) performs the calculation of theoretical alpha coefficients, and part two (CALCOMP) computes the composition of the analyte specimens. The analysis of alloys, pressed minerals, and fused specimens can currently be treated by the program. In addition to using measuredmore » x-ray tube spectral distributions, spectra from seven commonly used x-ray tube targets could also be calculated with an NBS algorithm included in the program. NBSGSC is written in FORTRAN IV for a Digital Equipment Corporation (DEC PDP-11/23) minicomputer using RLO2 firm disks and an RSX 11M operating system.« less

Advanced Experiments in Nuclear Science, Volume I: Advanced Nuclear Physics and Chemistry Experiments.

ERIC Educational Resources Information Center

Duggan, Jerome L.; And Others

The experiments in this manual represent state-of-the-art techniques which should be within the budgetary constraints of a college physics or chemistry department. There are fourteen experiments divided into five modules. The modules are on X-ray fluorescence, charged particle detection, neutron activation analysis, X-ray attenuation, and…

Mass density images from the diffraction enhanced imaging technique.

PubMed

Hasnah, M O; Parham, C; Pisano, E D; Zhong, Z; Oltulu, O; Chapman, D

2005-02-01

Conventional x-ray radiography measures the projected x-ray attenuation of an object. It requires attenuation differences to obtain contrast of embedded features. In general, the best absorption contrast is obtained at x-ray energies where the absorption is high, meaning a high absorbed dose. Diffraction-enhanced imaging (DEI) derives contrast from absorption, refraction, and extinction. The refraction angle image of DEI visualizes the spatial gradient of the projected electron density of the object. The projected electron density often correlates well with the projected mass density and projected absorption in soft-tissue imaging, yet the mass density is not an "energy"-dependent property of the object, as is the case of absorption. This simple difference can lead to imaging with less x-ray exposure or dose. In addition, the mass density image can be directly compared (i.e., a signal-to-noise comparison) with conventional radiography. We present the method of obtaining the mass density image, the results of experiments in which comparisons are made with radiography, and an application of the method to breast cancer imaging.

A cascaded model of spectral distortions due to spectral response effects and pulse pileup effects in a photon-counting x-ray detector for CT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cammin, Jochen, E-mail: jcammin1@jhmi.edu, E-mail: ktaguchi@jhmi.edu; Taguchi, Katsuyuki, E-mail: jcammin1@jhmi.edu, E-mail: ktaguchi@jhmi.edu; Xu, Jennifer

Purpose: Energy discriminating, photon-counting detectors (PCDs) are an emerging technology for computed tomography (CT) with various potential benefits for clinical CT. The photon energies measured by PCDs can be distorted due to the interactions of a photon with the detector and the interaction of multiple coincident photons. These effects result in distorted recorded x-ray spectra which may lead to artifacts in reconstructed CT images and inaccuracies in tissue identification. Model-based compensation techniques have the potential to account for the distortion effects. This approach requires only a small number of parameters and is applicable to a wide range of spectra andmore » count rates, but it needs an accurate model of the spectral distortions occurring in PCDs. The purpose of this study was to develop a model of those spectral distortions and to evaluate the model using a PCD (model DXMCT-1; DxRay, Inc., Northridge, CA) and various x-ray spectra in a wide range of count rates. Methods: The authors hypothesize that the complex phenomena of spectral distortions can be modeled by: (1) separating them into count-rate independent factors that we call the spectral response effects (SRE), and count-rate dependent factors that we call the pulse pileup effects (PPE), (2) developing separate models for SRE and PPE, and (3) cascading the SRE and PPE models into a combined SRE+PPE model that describes PCD distortions at both low and high count rates. The SRE model describes the probability distribution of the recorded spectrum, with a photo peak and a continuum tail, given the incident photon energy. Model parameters were obtained from calibration measurements with three radioisotopes and then interpolated linearly for other energies. The PPE model used was developed in the authors’ previous work [K. Taguchi et al., “Modeling the performance of a photon counting x-ray detector for CT: Energy response and pulse pileup effects,” Med. Phys. 38(2), 1089–1102 (2011)]. The agreement between the x-ray spectra calculated by the cascaded SRE+PPE model and the measured spectra was evaluated for various levels of deadtime loss ratios (DLR) and incident spectral shapes, realized using different attenuators, in terms of the weighted coefficient of variation (COV{sub W}), i.e., the root mean square difference weighted by the statistical errors of the data and divided by the mean. Results: At low count rates, when DLR < 10%, the distorted spectra measured by the DXMCT-1 were in agreement with those calculated by SRE only, with COV{sub W}'s less than 4%. At higher count rates, the measured spectra were also in agreement with the ones calculated by the cascaded SRE+PPE model; with PMMA as attenuator, COV{sub W} was 5.6% at a DLR of 22% and as small as 6.7% for a DLR as high as 55%. Conclusions: The x-ray spectra calculated by the proposed model agreed with the measured spectra over a wide range of count rates and spectral shapes. The SRE model predicted the distorted, recorded spectra with low count rates over various types and thicknesses of attenuators. The study also validated the hypothesis that the complex spectral distortions in a PCD can be adequately modeled by cascading the count-rate independent SRE and the count-rate dependent PPE.« less

A cascaded model of spectral distortions due to spectral response effects and pulse pileup effects in a photon-counting x-ray detector for CT

PubMed Central

Cammin, Jochen; Xu, Jennifer; Barber, William C.; Iwanczyk, Jan S.; Hartsough, Neal E.; Taguchi, Katsuyuki

2014-01-01

Purpose: Energy discriminating, photon-counting detectors (PCDs) are an emerging technology for computed tomography (CT) with various potential benefits for clinical CT. The photon energies measured by PCDs can be distorted due to the interactions of a photon with the detector and the interaction of multiple coincident photons. These effects result in distorted recorded x-ray spectra which may lead to artifacts in reconstructed CT images and inaccuracies in tissue identification. Model-based compensation techniques have the potential to account for the distortion effects. This approach requires only a small number of parameters and is applicable to a wide range of spectra and count rates, but it needs an accurate model of the spectral distortions occurring in PCDs. The purpose of this study was to develop a model of those spectral distortions and to evaluate the model using a PCD (model DXMCT-1; DxRay, Inc., Northridge, CA) and various x-ray spectra in a wide range of count rates. Methods: The authors hypothesize that the complex phenomena of spectral distortions can be modeled by: (1) separating them into count-rate independent factors that we call the spectral response effects (SRE), and count-rate dependent factors that we call the pulse pileup effects (PPE), (2) developing separate models for SRE and PPE, and (3) cascading the SRE and PPE models into a combined SRE+PPE model that describes PCD distortions at both low and high count rates. The SRE model describes the probability distribution of the recorded spectrum, with a photo peak and a continuum tail, given the incident photon energy. Model parameters were obtained from calibration measurements with three radioisotopes and then interpolated linearly for other energies. The PPE model used was developed in the authors’ previous work [K. Taguchi , “Modeling the performance of a photon counting x-ray detector for CT: Energy response and pulse pileup effects,” Med. Phys. 38(2), 1089–1102 (2011)]. The agreement between the x-ray spectra calculated by the cascaded SRE+PPE model and the measured spectra was evaluated for various levels of deadtime loss ratios (DLR) and incident spectral shapes, realized using different attenuators, in terms of the weighted coefficient of variation (COVW), i.e., the root mean square difference weighted by the statistical errors of the data and divided by the mean. Results: At low count rates, when DLR < 10%, the distorted spectra measured by the DXMCT-1 were in agreement with those calculated by SRE only, with COVW's less than 4%. At higher count rates, the measured spectra were also in agreement with the ones calculated by the cascaded SRE+PPE model; with PMMA as attenuator, COVW was 5.6% at a DLR of 22% and as small as 6.7% for a DLR as high as 55%. Conclusions: The x-ray spectra calculated by the proposed model agreed with the measured spectra over a wide range of count rates and spectral shapes. The SRE model predicted the distorted, recorded spectra with low count rates over various types and thicknesses of attenuators. The study also validated the hypothesis that the complex spectral distortions in a PCD can be adequately modeled by cascading the count-rate independent SRE and the count-rate dependent PPE. PMID:24694136

Gamma-ray energy buildup factor calculations and shielding effects of some Jordanian building structures

NASA Astrophysics Data System (ADS)

Sharaf, J. M.; Saleh, H.

2015-05-01

The shielding properties of three different construction styles, and building materials, commonly used in Jordan, were evaluated using parameters such as attenuation coefficients, equivalent atomic number, penetration depth and energy buildup factor. Geometric progression (GP) method was used to calculate gamma-ray energy buildup factors of limestone, concrete, bricks, cement plaster and air for the energy range 0.05-3 MeV, and penetration depths up to 40 mfp. It has been observed that among the examined building materials, limestone offers highest value for equivalent atomic number and linear attenuation coefficient and the lowest values for penetration depth and energy buildup factor. The obtained buildup factors were used as basic data to establish the total equivalent energy buildup factors for three different multilayer construction styles using an iterative method. The three styles were then compared in terms of fractional transmission of photons at different incident photon energies. It is concluded that, in case of any nuclear accident, large multistory buildings with five layers exterior walls, style A, could effectively attenuate radiation more than small dwellings of any construction style.

UNCERTAINTY IN SCALING NUTRIENT EXPORT COEFFICIENTS

EPA Science Inventory

The Innov-X XT400 portable XRF analyzer features a miniature, rugged x-ray tube excitation source for analyzing a wide variety of elements and sample materials, including alloys, environmental solids, and other analytical samples. The x-ray tube source and Light Element Analysis...

X-ray attenuation of the liver and kidney in cats considered at varying risk of hepatic lipidosis.

PubMed

Lam, Richard; Niessen, Stijn J; Lamb, Christopher R

2014-01-01

X-ray attenuation of the liver has been measured using computed tomography (CT) and reported to decrease in cats with experimentally induced hepatic lipidosis. To assess the clinical utility of this technique, medical records and noncontrast CT scans of a series of cats were retrospectively reviewed. A total of 112 cats met inclusion criteria and were stratified into three hepatic lipidosis risk groups. Group 1 cats were considered low-risk based on no history of inappetence or weight loss, and normal serum chemistry values; Group 2 cats were considered intermediate risk based on weight loss, serum hepatic enzymes above normal limits, or reasonably controlled diabetes mellitus; and Group 3 cats were considered high risk based on poorly controlled diabetes mellitus due to hypersomatotropism. Mean CT attenuation values (Hounsfield units, HU) were measured using regions of interest placed within the liver and cranial pole of the right kidney. Hepatic and renal attenuation were weakly positively correlated with each other (r = 0.2, P = 0.03) and weakly negatively correlated with body weight (r = -0.21, P = 0.05, and r = -0.34, P = 0.001, respectively). Mean (SD) hepatic and renal cortical attenuation values were 70.7 (8.7) HU and 49.6 (9.2) HU for Group 1 cats, 71.4 (7.9) HU and 48.6 (9.1) HU for Group 2, and 68.9 (7.6) HU and 47.6 (7.2) HU for Group 3. There were no significant differences in hepatic or renal attenuation among groups. Findings indicated that CT measures of X-ray attenuation in the liver and kidney may not be accurate predictors of naturally occurring hepatic lipidosis in cats. © 2013 American College of Veterinary Radiology.

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry.

PubMed

Mathieu, Kelsey B; Kappadath, S Cheenu; White, R Allen; Atkinson, E Neely; Cody, Dianna D

2011-08-01

The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49-33.03 mm Al on a computed tomography (CT) scanner, 0.09-1.93 mm Al on two mammography systems, and 0.1-0.45 mm Cu and 0.49-14.87 mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semi-logarithmic (exponential) and linear interpolation]. The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R2 > 0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and/or QVL than the traditional methods of semilogarithmic and linear interpolation. The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry).

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry

PubMed Central

Mathieu, Kelsey B.; Kappadath, S. Cheenu; White, R. Allen; Atkinson, E. Neely; Cody, Dianna D.

2011-01-01

Purpose: The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. Methods: An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49–33.03 mm Al on a computed tomography (CT) scanner, 0.09–1.93 mm Al on two mammography systems, and 0.1–0.45 mm Cu and 0.49–14.87 mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semilogarithmic (exponential) and linear interpolation]. Results: The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R2 > 0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and∕or QVL than the traditional methods of semilogarithmic and linear interpolation. Conclusions: The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry). PMID:21928626

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathieu, Kelsey B.; Kappadath, S. Cheenu; White, R. Allen

2011-08-15

Purpose: The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. Methods: An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49-33.03 mm Al on a computed tomography (CT) scanner, 0.09-1.93 mm Al on two mammography systems, and 0.1-0.45 mm Cu and 0.49-14.87more » mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semilogarithmic (exponential) and linear interpolation]. Results: The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R{sup 2} > 0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and/or QVL than the traditional methods of semilogarithmic and linear interpolation. Conclusions: The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry).« less

Aspects of image recognition in Vivid Technologies' dual-energy x-ray system for explosives detection

NASA Astrophysics Data System (ADS)

Eilbert, Richard F.; Krug, Kristoph D.

1993-04-01

The Vivid Rapid Explosives Detection Systems is a true dual energy x-ray machine employing precision x-ray data acquisition in combination with unique algorithms and massive computation capability. Data from the system's 960 detectors is digitally stored and processed by powerful supermicro-computers organized as an expandable array of parallel processors. The algorithms operate on the dual energy attenuation image data to recognize and define objects in the milieu of the baggage contents. Each object is then systematically examined for a match to a specific effective atomic number, density, and mass threshold. Material properties are determined by comparing the relative attenuations of the 75 kVp and 150 kVp beams and electronically separating the object from its local background. Other heuristic algorithms search for specific configurations and provide additional information. The machine automatically detects explosive materials and identifies bomb components in luggage with high specificity and throughput, X-ray dose is comparable to that of current airport x-ray machines. The machine is also configured to find heroin, cocaine, and US currency by selecting appropriate settings on-site. Since January 1992, production units have been operationally deployed at U.S. and European airports for improved screening of checked baggage.

Experiment to Determine the Absorption Coefficient of Gamma Rays as a Function of Energy.

ERIC Educational Resources Information Center

Ouseph, P. J.; And Others

1982-01-01

Simpler than x-ray diffractometer experiments, the experiment described illustrates certain concepts regarding the interaction of electromagnetic rays with matter such as the exponential decrease in the intensity with absorber thickness, variation of the coefficient of absorption with energy, and the effect of the K-absorption edge on the…

A comparative study of gamma-ray interaction and absorption in some building materials using Zeff-toolkit

NASA Astrophysics Data System (ADS)

Mann, Kulwinder Singh; Heer, Manmohan Singh; Rani, Asha

2016-07-01

The gamma-ray shielding behaviour of a material can be investigated by determining its various interaction and energy-absorption parameters (such as mass attenuation coefficients, mass energy absorption coefficients, and corresponding effective atomic numbers and electron densities). Literature review indicates that the effective atomic number (Zeff) has been used as extensive parameters for evaluating the effects and defect in the chosen materials caused by ionising radiations (X-rays and gamma-rays). A computer program (Zeff-toolkit) has been designed for obtaining the mean value of effective atomic number calculated by three different methods. A good agreement between the results obtained with Zeff-toolkit, Auto_Zeff software and experimentally measured values of Zeff has been observed. Although the Zeff-toolkit is capable of computing effective atomic numbers for both photon interaction (Zeff,PI) and energy absorption (Zeff,En) using three methods in each. No similar computer program is available in the literature which simultaneously computes these parameters simultaneously. The computed parameters have been compared and correlated in the wide energy range (0.001-20 MeV) for 10 commonly used building materials. The prominent variations in these parameters with gamma-ray photon energy have been observed due to the dominance of various absorption and scattering phenomena. The mean values of two effective atomic numbers (Zeff,PI and Zeff,En) are equivalent at energies below 0.002 MeV and above 0.3 MeV, indicating the dominance of gamma-ray absorption (photoelectric and pair production) over scattering (Compton) at these energies. Conversely in the energy range 0.002-0.3 MeV, the Compton scattering of gamma-rays dominates the absorption. From the 10 chosen samples of building materials, 2 soils showed better shielding behaviour than did other 8 materials.

Investigation of ionizing radiation shielding effectiveness of decorative building materials used in Bangladeshi dwellings

NASA Astrophysics Data System (ADS)

Yesmin, Sabina; Sonker Barua, Bijoy; Uddin Khandaker, Mayeen; Tareque Chowdhury, Mohammed; Kamal, Masud; Rashid, M. A.; Miah, M. M. H.; Bradley, D. A.

2017-11-01

Following the rapid growing per capita income, a major portion of Bangladeshi dwellers is upgrading their non-brick houses by rod-cement-concrete materials and simultaneously curious to decorate the houses using luxurious marble stones. Present study was undertaken to investigate the gamma-ray attenuation co-efficient of decorative marble materials leading to their suitability as shielding of ionizing radiation. A number of commercial grades decorative marble stones were collected from home and abroad following their large-scale uses. A well-shielded HPGe γ-ray spectrometer combined with associated electronics was used to evaluate the mass attenuation coefficients of the studied materials for high energy photons. Some allied parameters such as half-value layer and radiation protection efficacy of the investigated marbles were calculated. The results showed that among the studied samples, the marble 'Carrara' imported from Italy is suitable to be used as radiation shielding material.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazalova, M; Ahmad, M; Fahrig, R

Purpose: To evaluate x-ray fluorescence computed tomography induced with proton beams (pXFCT) for imaging of gold contrast agent. Methods: Proton-induced x-ray fluorescence was studied by means of Monte Carlo (MC) simulations using TOPAS, a MC code based on GEANT4. First, proton-induced K-shell and L-shell fluorescence was studied as a function of proton beam energy and 1) depth in water and 2) size of contrast object. Second, pXFCT images of a 2-cm diameter cylindrical phantom with four 5- mm diameter contrast vials and of a 20-cm diameter phantom with 1-cm diameter vials were simulated. Contrast vials were filled with water andmore » water solutions with 1-5% gold per weight. Proton beam energies were varied from 70-250MeV. pXFCT sinograms were generated based on the net number of gold K-shell or L-shell x-rays determined by interpolations from the neighboring 0.5keV energy bins of spectra collected with an idealized 4π detector. pXFCT images were reconstructed with filtered-back projection, and no attenuation correction was applied. Results: Proton induced x-ray fluorescence spectra showed very low background compared to x-ray induced fluorescence. Proton induced L-shell fluorescence had a higher cross-section compared to K-shell fluorescence. Excitation of L-shell fluorescence was most efficient for low-energy protons, i.e. at the Bragg peak. K-shell fluorescence increased with increasing proton beam energy and object size. The 2% and 5% gold contrast vials were accurately reconstructed in K-shell pXFCT images of both the 2-cm and 20-cm diameter phantoms. Small phantom L-shell pXFCT image required attenuation correction and had a higher sensitivity for 70MeV protons compared to 250MeV protons. With attenuation correction, L-shell pXFCT might be a feasible option for imaging of small size (∼2cm) objects. Imaging doses for all simulations were 5-30cGy. Conclusion: Proton induced x-ray fluorescence CT promises to be an alternative quantitative imaging technique to the commonly considered XFCT imaging with x-ray beams.« less

The Columbia University proton-induced soft x-ray microbeam.

PubMed

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

2011-09-15

A soft x-ray microbeam using proton-induced x-ray emission (PIXE) of characteristic titanium (K(α) 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 μm × 50 μm 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 μm round x-ray generation spot into the vertical direction. The x-rays are focused to a spot size of 5 μm in diameter using a Fresnel zone plate. The x-rays have an attenuation length of (1/e length of ~145 μm) 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.

Effect of solar flares flux on the propagation and modal composition of VLF signal in the lower ionosphere

NASA Astrophysics Data System (ADS)

Bouderba, Yasmina; Nait Amor, Samir; Tribeche, Mouloud

2015-04-01

The VLF radio waves propagating in the Earth-Ionosphere waveguide are sensitive to the ionospheric disturbances due to X rays solar flux. In order to understand the VLF signal response to the solar flares, the LWPC code is used to simulate the signal perturbation parameters (amplitude and phase) at fixed solar zenith angle. In this work, we used the NRK-Algiers signal data and the study was done for different flares classes. The results show that the perturbed parameters increase with the increasing solar flares flux. This increases is due to the growth of the electron density resulting from the changes of the Wait's parameters. However, the behavior of the perturbation parameters as function of distance shows different forms of signal perturbations. It was also observed that the null points move towards the transmitter location when the flare flux increases which is related to the modal composition of the propagating signal. Effectively, for a given mode, the plot of the attenuation coefficient as function of the flare flux shows a decreases when the flux increases which is more significant for high modes. Thus, the solar flares effect is to amplify the VLF signal by reducing the attenuation coefficient.

Comparison of the x-ray attenuation properties of breast calcifications, aluminium, hydroxyapatite and calcium oxalate.

PubMed

Warren, L M; Mackenzie, A; Dance, D R; Young, K C

2013-04-07

Aluminium is often used as a substitute material for calcifications in phantom measurements in mammography. Additionally, calcium oxalate, hydroxyapatite and aluminium are used in simulation studies. This assumes that these materials have similar attenuation properties to calcification, and this assumption is examined in this work. Sliced mastectomy samples containing calcification were imaged at ×5 magnification using a digital specimen cabinet. Images of the individual calcifications were extracted, and the diameter and contrast of each calculated. The thicknesses of aluminium required to achieve the same contrast as each calcification when imaged under the same conditions were calculated using measurements of the contrast of aluminium foils. As hydroxyapatite and calcium oxalate are also used to simulate calcifications, the equivalent aluminium thicknesses of these materials were also calculated using tabulated attenuation coefficients. On average the equivalent aluminium thickness was 0.85 times the calcification diameter. For calcium oxalate and hydroxyapatite, the equivalent aluminium thicknesses were 1.01 and 2.19 times the thickness of these materials respectively. Aluminium and calcium oxalate are suitable substitute materials for calcifications. Hydroxyapatite is much more attenuating than the calcifications and aluminium. Using solid hydroxyapatite as a substitute for calcification of the same size would lead to excessive contrast in the mammographic image.

Soft X-ray observations of Centaurus X-3 from Copernicus

NASA Technical Reports Server (NTRS)

Margon, B.; Mason, K. O.; Hawkins, F. J.; Sanford, P. W.

1975-01-01

We have detected soft X-ray emission from Centaurus X-3 in the 0.6-1.9 keV band, using the focusing telescope aboard OAO Copernicus. The flux is compatible with an extrapolation of the harder X-ray spectrum, attenuated by (3-4) times 10 to the 22nd atoms per sq cm of interstellar and/or circumstellar matter. The data are consistent with the distance estimate of 5-10 kpc derived from the spectroscopic modulus of the optical component, and obviate the need to postulate the primary to be an anomalously subluminous hot star. There is currently no compelling evidence that such models must be invoked to explain any of the observed compact X-ray sources.

Optimization of SPECT-CT Hybrid Imaging Using Iterative Image Reconstruction for Low-Dose CT: A Phantom Study

PubMed Central

Grosser, Oliver S.; Kupitz, Dennis; Ruf, Juri; Czuczwara, Damian; Steffen, Ingo G.; Furth, Christian; Thormann, Markus; Loewenthal, David; Ricke, Jens; Amthauer, Holger

2015-01-01

Background Hybrid imaging combines nuclear medicine imaging such as single photon emission computed tomography (SPECT) or positron emission tomography (PET) with computed tomography (CT). Through this hybrid design, scanned patients accumulate radiation exposure from both applications. Imaging modalities have been the subject of long-term optimization efforts, focusing on diagnostic applications. It was the aim of this study to investigate the influence of an iterative CT image reconstruction algorithm (ASIR) on the image quality of the low-dose CT images. Methodology/Principal Findings Examinations were performed with a SPECT-CT scanner with standardized CT and SPECT-phantom geometries and CT protocols with systematically reduced X-ray tube currents. Analyses included image quality with respect to photon flux. Results were compared to the standard FBP reconstructed images. The general impact of the CT-based attenuation maps used during SPECT reconstruction was examined for two SPECT phantoms. Using ASIR for image reconstructions, image noise was reduced compared to FBP reconstructions for the same X-ray tube current. The Hounsfield unit (HU) values reconstructed by ASIR were correlated to the FBP HU values(R2 ≥ 0.88) and the contrast-to-noise ratio (CNR) was improved by ASIR. However, for a phantom with increased attenuation, the HU values shifted for low X-ray tube currents I ≤ 60 mA (p ≤ 0.04). In addition, the shift of the HU values was observed within the attenuation corrected SPECT images for very low X-ray tube currents (I ≤ 20 mA, p ≤ 0.001). Conclusion/Significance In general, the decrease in X-ray tube current up to 30 mA in combination with ASIR led to a reduction of CT-related radiation exposure without a significant decrease in image quality. PMID:26390216

Determination of the chemical composition of human renal stones with MDCT: influence of the surrounding media

NASA Astrophysics Data System (ADS)

Grosjean, Romain; Sauer, Benoît; Guerra, Rui; Kermarrec, Isabelle; Ponvianne, Yannick; Winninger, Daniel; Daudon, Michel; Blum, Alain; Felblinger, Jacques; Hubert, Jacques

2007-03-01

The selection of the optimal treatment method for urinary stones diseases depends on the chemical composition of the stone and its corresponding fragility. MDCT has become the most used modality to determine rapidly and accurately the presence of stones when evaluating urinary lithiasis treatment. That is why several studies have tempted to determine the chemical composition of the stones based on the stone X-ray attenuation in-vitro and invivo. However, in-vitro studies did not reproduce the normal abdominal wall and fat, making uncertain the standardization of the obtained values. The aim of this study is to obtain X-ray attenuation values (in Hounsfield Units) of the six more frequent types of human renal stones (n=217) and to analyze the influence of the surrounding media on these values. The stones were first placed in a jelly, which X-ray attenuation is similar to that of the human kidney (30 HU at 120 kV). They were then stuck on a grid, scanned in a water tank and finally scanned in the air. Significant differences in CT-attenuation values were obtained with the three different surrounding media (jelly, water, air). Furthermore there was an influence of the surrounding media and consequently discrepancies in determination of the chemical composition of the renal stones. Consequently, CT-attenuation values found in in-vitro studies cannot really be considered as a reference for the determination of the chemical composition except if the used phantom is an anthropomorphic one.

The Physics Analysis of a Gas Attenuator with Argon as a Working Gas (Rev. 1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryutov, D D; Bionta, R M; McKernan, M A

2006-01-03

A gas attenuator is an important element of the LCLS facility. The attenuator has to operate in a broad range of x-ray energies, provide attenuation coefficient between 1 and 10{sup 4} with the accuracy of 1% and, at the same time, be reliable and allow for many months of un-interrupted operation. A detailed design study of the attenuator based on the use of nitrogen as a working gas has been recently carried out by S. Shen [1]. In this note we assess the features of the attenuator based on the use of argon. We concentrate on the physics issues; themore » design features will probably be not that different from the aforementioned nitrogen attenuator. Although specific results obtained in our note pertain to argon, the general framework (and many equations obtained) are applicable also to the nitrogen attenuator. In the past, an analysis of the attenuator based on the use of a noble gas has already been carried out [2]. This analysis was performed for an extremely stringent set of specifications. In particular, a very large diameter for the unobstructed x-ray beam was set (1 cm) to accommodate the spontaneous radiation; the attenuator was supposed to cover the whole range of energies of the coherent radiation, from 800 eV to 8000 eV; the maximum attenuation was set at the level of 10{sup 4}; the use of solid attenuators was not allowed, as well as the use of rotating shutters. The need to reach a sufficient absorption at the high-energy end of the spectrum predetermined the choice of Xe as the working gas (in order to have a reasonable absorption at a not-too-high pressure). A sophisticated differential pumping system that included a Penning-type ion pump was suggested in order to minimize the gas leak into the undulator/accelerator part of the facility. A high cost of xenon meant also that an efficient (and expensive) gas-recovery system would have to be installed. The main parameter that determined the high cost and the complexity of the system was a large radius of the orifice. The present viewpoint allows for much smaller size of the orifice, a = 1.5 mm. The use of solid attenuators is also allowed for a higher-energy end of the spectrum. It is, therefore, worthwhile to reconsider various parameters of the gas attenuator for these much less stringent conditions. As a working gas we consider now the argon, which, on the one hand, provides reasonable absorption lengths and, on the other hand, is inexpensive enough to be exhausted into the atmosphere (no need for recovery). We concentrate on the processes in the main attenuation cell and just outside it, not touching upon a performance of the differential pumping system. The graphs presented in this report can serve for a general orientation only, not for getting exact numerical values of various parameters.« less

A wavelet-based Gaussian method for energy dispersive X-ray fluorescence spectrum.

PubMed

Liu, Pan; Deng, Xiaoyan; Tang, Xin; Shen, Shijian

2017-05-01

This paper presents a wavelet-based Gaussian method (WGM) for the peak intensity estimation of energy dispersive X-ray fluorescence (EDXRF). The relationship between the parameters of Gaussian curve and the wavelet coefficients of Gaussian peak point is firstly established based on the Mexican hat wavelet. It is found that the Gaussian parameters can be accurately calculated by any two wavelet coefficients at the peak point which has to be known. This fact leads to a local Gaussian estimation method for spectral peaks, which estimates the Gaussian parameters based on the detail wavelet coefficients of Gaussian peak point. The proposed method is tested via simulated and measured spectra from an energy X-ray spectrometer, and compared with some existing methods. The results prove that the proposed method can directly estimate the peak intensity of EDXRF free from the background information, and also effectively distinguish overlap peaks in EDXRF spectrum.

Application of Scanning-Imaging X-Ray Microscopy to Fluid Inclusion Candidates in Carbonates of Carbonaceous Chondrites

NASA Technical Reports Server (NTRS)

Tsuchiyama, Akira; Nakano, Tsukasa; Miyake, Akira; Akihisa, Takeuchi; Uesugi, Kentaro; Suzuki, Yoshio; Kitayama, Akira; Matsuno, Junya; Zolensky, Michael E.

2016-01-01

In order to search for such fluid inclusions in carbonaceous chondrites, a nondestructive technique using x-ray micro-absorption tomography combined with FIB sampling was developed and applied to a carbonaceous chondrite. They found fluid inclusion candidates in calcite grains, which were formed by aqueous alteration. However, they could not determine whether they are really aqueous fluids or merely voids. Phase and absorption contrast images can be simultaneously obtained in 3D by using scanning-imaging x-ray microscopy (SIXM). In refractive index, n=1-sigma+i(beta), in the real part, 1-sigma is the refractive index with decrement, sigma, which is nearly proportional to the density, and the imaginary part, beta, is the extinction coefficient, which is related to the liner attenuation coefficient, mu. Many phases, including water and organic materials as well as minerals, can be identified by SIXM, and this technique has potential availability for Hayabusa-2 sample analysis too. In this study, we examined quantitative performance of d and m values and the spatial resolution in SIXM by using standard materials, and applied this technique to carbonaceous chondrite samples. We used POM ([CH2O]n), silicon, quartz, forsterite, corundum, magnetite and nickel as standard materials for examining the sigma and mu values. A fluid inclusion in terrestrial quartz and bi-valve shell (Atrina vexillum), which are composed of calcite and organic layers with different thickness, were also used for examining the spatial resolution. The Ivuna (CI) and Sutter's Mill (CM) meteorites were used as carbonaceous chondrite samples. Rod- or cube-shaped samples 20-30 micron in size were extracted by using FIB from cross-sectional surfaces of the standard materials or polished thin sections of the chondrites, which was previously observed with SEM. Then, the sample was attached to a thin W-needle and imaged by SIXM system at beamline BL47XU, SPring-8, Japan. The slice thickness was 109.3 nm and the pixel size was mostly 100 nm.

Greek Participation to Solar Orbiter Development

NASA Astrophysics Data System (ADS)

Katsiyannis, A.

2012-01-01

Greece, via its PRODEX membership intends to meaningfully participate to the instrument development of a flagship ESA mission, the Solar Orbiter (SolO). This involvement pertains to hardware development for SolO's Spectrometer/Telescope for Imaging X-rays (STIX), namely, STIX's movable attenuator. SolO will allow close-up and high-latitude studies of our mother star, the Sun, based mostly on remote-sensing measurements (imaging). STIX is a critical SolO instrument, enabling one of its major science goals: understanding and acceleration of electrons at the Sun and their transport into interplanetary space. The attenuator, or shutter, that will be developed by the Greek team, is a critical component of the STIX instrument. Attenuators are dictated by the substantial dynamical range of incident X-ray fluxes from solar flares: the largest X-ray flares can give as many as 105 more count rates in X-ray photons compared to those of the smallest microflare that STIX can detect. It is proposed that two mechanisms are developed for a comparative study. First, a mechanism based on sensitive Shape Memory Alloy actuators and, second, one based on a piezoelectric actuator module. Both mechanisms will be designed and manufactured and then tested in vacuum and alternating high-low temperature conditions. Evaluation of reliability and accuracy in assembly and operation will follow. A vibrating table will be used for the dynamical analysis of the mechanism and independent strength tests of the various parts of the mechanism will follow.

Automated X-ray quality control of catalytic converters

NASA Astrophysics Data System (ADS)

Shashishekhar, N.; Veselitza, D.

2017-02-01

Catalytic converters are devices attached to the exhaust system of automobile or other engines to eliminate or substantially reduce polluting emissions. They consist of coated substrates enclosed in a stainless steel housing. The substrate is typically made of ceramic honeycombs; however stainless steel foil honeycombs are also used. The coating is usually a slurry of alumina, silica, rare earth oxides and platinum group metals. The slurry also known as the wash coat is applied to the substrate in two doses, one on each end of the substrate; in some cases multiple layers of coating are applied. X-ray imaging is used to inspect the applied coating depth on a substrate to confirm compliance with quality requirements. Automated image analysis techniques are employed to measure the coating depth from the X-ray image. Coating depth is assessed by analysis of attenuation line profiles in the image. Edge detection algorithms with noise reduction and outlier rejection are used to calculate the coating depth at a specified point along an attenuation line profile. Quality control of the product is accomplished using several attenuation line profile regions for coating depth measurements, with individual pass or fail criteria specified for each region.

On the X-ray temperature of hot gas in diffuse nebulae

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Arthur, S. J.

2018-05-01

X-ray emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3]× 106 K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae (PNe), Wolf-Rayet nebulae (WR) and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

On the X-ray temperature of hot gas in diffuse nebulae

NASA Astrophysics Data System (ADS)

Toalá, J. A.; Arthur, S. J.

2018-07-01

X-ray-emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3] × 106K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae, Wolf-Rayet (WR) nebulae, and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

A beam hardening and dispersion correction for x-ray dark-field radiography.

PubMed

Pelzer, Georg; Anton, Gisela; Horn, Florian; Rieger, Jens; Ritter, André; Wandner, Johannes; Weber, Thomas; Michel, Thilo

2016-06-01

X-ray dark-field imaging promises information on the small angle scattering properties even of large samples. However, the dark-field image is correlated with the object's attenuation and phase-shift if a polychromatic x-ray spectrum is used. A method to remove part of these correlations is proposed. The experimental setup for image acquisition was modeled in a wave-field simulation to quantify the dark-field signals originating solely from a material's attenuation and phase-shift. A calibration matrix was simulated for ICRU46 breast tissue. Using the simulated data, a dark-field image of a human mastectomy sample was corrected for the finger print of attenuation- and phase-image. Comparing the simulated, attenuation-based dark-field values to a phantom measurement, a good agreement was found. Applying the proposed method to mammographic dark-field data, a reduction of the dark-field background and anatomical noise was achieved. The contrast between microcalcifications and their surrounding background was increased. The authors show that the influence of and dispersion can be quantified by simulation and, thus, measured image data can be corrected. The simulation allows to determine the corresponding dark-field artifacts for a wide range of setup parameters, like tube-voltage and filtration. The application of the proposed method to mammographic dark-field data shows an increase in contrast compared to the original image, which might simplify a further image-based diagnosis.

Quantitative imaging of single-shot liquid distributions in sprays using broadband flash x-ray radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halls, B. R.; Roy, S.; Gord, J. R.

Flash x-ray radiography is used to capture quantitative, two-dimensional line-of-sight averaged, single-shot liquid distribution measurements in impinging jet sprays. The accuracy of utilizing broadband x-ray radiation from compact flash tube sources is investigated for a range of conditions by comparing the data with radiographic high-speed measurements from a narrowband, high-intensity synchrotron x-ray facility at the Advanced Photon Source (APS) of Argonne National Laboratory. The path length of the liquid jets is varied to evaluate the effects of energy dependent x-ray attenuation, also known as spectral beam hardening. The spatial liquid distributions from flash x-ray and synchrotron-based radiography are compared, alongmore » with spectral characteristics using Taylor’s hypothesis. The results indicate that quantitative, single-shot imaging of liquid distributions can be achieved using broadband x-ray sources with nanosecond temporal resolution. Practical considerations for optimizing the imaging system performance are discussed, including the coupled effects of x-ray bandwidth, contrast, sensitivity, spatial resolution, temporal resolution, and spectral beam hardening.« less

Preclinical x-ray dark-field imaging: foreign body detection

NASA Astrophysics Data System (ADS)

Braig, Eva-Maria; Muenzel, Daniela; Fingerle, Alexander; Herzen, Julia; Rummeny, Ernst; Pfeiffer, Franz; Noel, Peter

2017-03-01

The purpose of this study was to evaluate the performance of X-ray dark-field imaging for detection of retained foreign bodies in ex-vivo hands and feet. X-ray dark-field imaging, acquired with a three-grating Talbot-Lau interferometer, has proven to provide access to sub-resolution structures due to small-angle scattering. The study was institutional review board (IRB) approved. Foreign body parts included pieces of wood and metal which were placed in a formalin fixated human ex-vivo hand. The samples were imaged with a grating-based interferometer consisting of a standard microfocus X-ray tube (60 kVp, 100 W) and a Varian 2520-DX detector (pixel size: 127 μm). The attenuation and the dark-field signals provide complementary diagnostic information for this clinical task. With regard to detecting of wooden objects, which are clinically the most relevant, only the dark-field image revealed the locations. The signal is especially strong for dry wood which in comparison is poorly to non-visible in computed tomography. The detection of high atomic-number or dense material and wood-like or porous materials in a single X-ray scan is enabled by the simultaneous acquisition of the conventional attenuation and dark-field signal. Our results reveal that with this approach one can reach a significantly improved sensitivity for detection of foreign bodies, while an easy implementation into the clinical arena is becoming feasible.

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for High Energy Density plasmas at energies below 10 keV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

2014-07-15

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities.more » We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.« less

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for high energy density plasmas at energies below 10 keV.

PubMed

Valdivia, M P; Stutman, D; Finkenthal, M

2014-07-01

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

Influence of yttrium content on the location of rare earth ions in LYSO:Ce crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Dongzhou, E-mail: dongzhou_ding@mail.sic.ac.cn; R and D Center of Shanghai Institute of Ceramics, No. 588 Heshuo Road, Shanghai 201899; Weng, Linhong

2014-01-15

Single-crystal X-ray diffraction (SCD), X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray excited luminescence (XEL) measurements were performed to investigate structure details and segregation coefficients of (Lu{sub 1−x}Y{sub x}){sub 2}SiO{sub 5}:Ce (x=0 at%, 8.7 at%, 25.7 at%, 44.7 at%, 65.7 at%, 87.9 at% and 100 at%). Y{sup 3+} cations were found to have a preferential occupation for RE1 site (7-oxygen-coordinated) over RE2 site (6-oxygen-coordinated), which results in a greater increase of cell parameter c than that of a with increase in Y content due to LYSO's microstructure characteristics. Results presented here revealed that the less themore » difference in electronegativity and effective ionic radius between the two ions, the easier substitution of one ion by the other, and hence the higher segregation coefficients. Besides, the contribution of luminescence of Ce1 and Ce2 in the whole XEL was evaluated, and the location of Ce{sup 3+} ion was discussed. - Graphical abstract: Segregation coefficients of (Lu{sub 1−x}Y{sub x}){sub 2}SiO{sub 5}:Cce:italic> at RT/ce:italic>. Display Omitted.« less

The relationship between coefficient of restitution and state of charge of zinc alkaline primary LR6 batteries [Bouncing alkaline batteries: A basic solution

DOE PAGES

Bhadra, S.; Hertzberg, B. J.; Croft, M.; ...

2015-03-13

The coefficient of restitution of alkaline batteries had been shown to increase as a function of depth of discharge. In this work, using non-destructive mechanical testing, the change in coefficient of restitution is compared to in situ energy-dispersive x-ray diffraction data to determine the cause of the macroscopic change in coefficient of restitution. The increase in coefficient of restitution correlates to the formation of a percolation pathway of ZnO within the anode of the cell, and that the coefficient of restitution saturates at a value of 0.63 ± .05 at 50% state if charge when the anode has densified intomore » porous ZnO solid. Of note is the sensitivity of coefficient of restitution to the amount of ZnO formation that rivals the sensitivity on in situ energy-dispersive x-ray diffraction spectroscopy.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Hao, E-mail: hc000211@ohio.edu; Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701; Cummings, Marvin

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beammore » attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Hao; Cummings, Marvin L.; Shirato, Nozomi

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the requiredmore » beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less

[Basic concepts of radiology physics].

PubMed

Gambini, D-J

2010-11-01

An x-ray tube mainly emits low-energy X-rays, with few maximum energy E₀ (equal in keV to the voltage U in kV) x-rays. Aluminium filtration (mandatory minimum thickness of 1.5 to 2.5 mm based on tube voltage) reduces soft X-rays and provides a mean energy equal to 2/3 E₀. The half value layer of a reference material characterizes the spectrum. X-ray attenuation in tissues is due to secondary electron interactions: photoelectric effect at low-energy, especially in dense materials with high Z number; compton effect at intermediate-energy, proportional to density. The optimization of acquisition parameters of a medically necessary examination is based on appropriate selection of the highest voltage (U in kV) providing the best contrast and lowest tube current (Q in mAs) providing a diagnostic image.

Diagnostic X-ray sources-present and future

NASA Astrophysics Data System (ADS)

Behling, Rolf; Grüner, Florian

2018-01-01

This paper compares very different physical principles of X-ray production to spur ideation. Since more than 120 years, bremsstrahlung from X-ray tubes has been the workhorse of medical diagnostics. Generated by X-ray segments comprised of X-ray tubes and high-voltage generators in the various medical systems, X-ray photons in the spectral range between about 16 keV and 150 keV deliver information about anatomy and function of human patients and in pre-clinical animal studies. Despite of strides to employ the wave nature of X-rays as phase sensitive means, commercial diagnostic X-ray systems available until the time of writing still rely exclusively on measuring the attenuation and scattering of X-rays by matter. Significant activities in research aim at building highly brilliant short pulse X-ray sources, based on e.g. synchrotron radiation, free electron lasers and/or laser wake-field acceleration of electrons followed by wiggling with magnetic structures or Thomson scattering in bunches of light. While both approaches, non-brilliant and brilliant sources, have different scope of application, we speculate that a combination may expand the efficacy in medical application. At this point, however, severe technical and commercial difficulties hinder closing this gap. This article may inspire further development and spark innovation in this important field.

Measurement of the mass attenuation coefficient from 81 keV to 1333 keV for elemental materials Al, Cu and Pb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gjorgieva, Slavica, E-mail: slavicagjorgieva89@gmail.com; Institute of Physics, Faculty of Natural Sciences and Mathematics, Ss Cyril and Methodius University, POB 162, 1000 Skopje; Barandovski, Lambe, E-mail: lambe@pmf.ukim.mk

The mass attenuation coefficients (μ/ρ) for 3 high purity elemental materials Al, Cu and Pb were measured in the γ-ray energy range from 81 keV up to 1333 keV using {sup 22}Na, {sup 60}Co {sup 133}Ba and {sup 133}Cs as sources of gamma radiation. Well shielded detector (NaI (Tl) semiconductor detector) was used to measure the intensity of the transmitted beam. The measurements were made under condition of good geometry, assuring that any photon absorbed or deflected appreciably does not reach the detector. The measured values are compared with the theoretical ones obtained by Seltzer (1993).

Characterization of a spectroscopic detector for application in x-ray computed tomography

NASA Astrophysics Data System (ADS)

Dooraghi, Alex A.; Fix, Brian J.; Smith, Jerel A.; Brown, William D.; Azevedo, Stephen G.; Martz, Harry E.

2017-09-01

Recent advances in cadmium telluride (CdTe) energy-discriminating pixelated detectors have enabled the possibility of Multi-Spectral X-ray Computed Tomography (MSXCT) to incorporate spectroscopic information into CT. MultiX ME 100 V2 is a CdTe-based spectroscopic x-ray detector array capable of recording energies from 20 to 160 keV in 1.1 keV energy bin increments. Hardware and software have been designed to perform radiographic and computed tomography tasks with this spectroscopic detector. Energy calibration is examined using the end-point energy of a bremsstrahlung spectrum and radioisotope spectral lines. When measuring the spectrum from Am-241 across 500 detector elements, the standard deviation of the peak-location and FWHM measurements are +/- 0.4 and +/- 0.6 keV, respectively. As these values are within the energy bin size (1.1 keV), detector elements are consistent with each other. The count rate is characterized, using a nonparalyzable model with a dead time of 64 +/- 5 ns. This is consistent with the manufacturer's quoted per detector-element linear-deviation at 2 Mpps (million photons per sec) of 8.9 % (typical) and 12 % (max). When comparing measured and simulated spectra, a low-energy tail is visible in the measured data due to the spectral response of the detector. If no valid photon detections are expected in the low-energy tail, then a background subtraction may be applied to allow for a possible first-order correction. If photons are expected in the low-energy tail, a detailed model must be implemented. A radiograph of an aluminum step wedge with a maximum height of 20 mm shows an underestimation of attenuation by about 10 % at 60 keV. This error is due to partial energy deposition from higher energy (>60 keV) photons into a lower-energy ( 60 keV) bin, reducing the apparent attenuation. A radiograph of a polytetrafluoroethylene (PTFE) cylinder taken using a bremsstrahlung spectrum from an x-ray voltage of 100 kV filtered by 1.3 mm Cu is reconstructed using Abel inversion. As no counts are expected in the low energy tail, a first order background correction is applied to the spectrum. The measured linear attenuation coefficient (LAC) is within 10% of the expected value in the 60 to 100 keV range. Below 60 keV, low counts in the corrected spectrum and partial energy deposition from incident photons of energy greater than 60 keV into energy bins below 60 keV impact the LAC measurements. This report ends with a demonstration of the tomographic capability of the system. The quantitative understanding of the detector developed in this report will enable further study in evaluating the system for characterization of an object's chemical make-up for industrial and security purposes.

Characterization of a spectroscopic detector for application in x-ray computed tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dooraghi, A. A.; Fix, B. J.; Smith, J. A.

Recent advances in cadmium telluride (CdTe) energy-discriminating pixelated detectors have enabled the possibility of Multi-Spectral X-ray Computed Tomography (MSXCT) to incorporate spectroscopic information into CT. MultiX ME 100 V2 is a CdTe-based spectroscopic x-ray detector array capable of recording energies from 20 to 160 keV in 1.1 keV energy bin increments. Hardware and software have been designed to perform radiographic and computed tomography tasks with this spectroscopic detector. Energy calibration is examined using the end-point energy of a bremsstrahlung spectrum and radioisotope spectral lines. When measuring the spectrum from Am-241 across 500 detector elements, the standard deviation of the peak-locationmore » and FWHM measurements are ±0.4 and ±0.6 keV, respectively. As these values are within the energy bin size (1.1 keV), detector elements are consistent with each other. The count rate is characterized, using a nonparalyzable model with a dead time of 64 ± 5 ns. This is consistent with the manufacturer’s quoted per detector-element linear-deviation at 2 Mpps (million photons per sec) of 8.9% (typical) and 12% (max). When comparing measured and simulated spectra, a low-energy tail is visible in the measured data due to the spectral response of the detector. If no valid photon detections are expected in the low-energy tail, then a background subtraction may be applied to allow for a possible first-order correction. If photons are expected in the low-energy tail, a detailed model must be implemented. A radiograph of an aluminum step wedge with a maximum height of about 20 mm shows an underestimation of attenuation by about 10% at 60 keV. This error is due to partial energy deposition from higher-energy (> 60 keV) photons into a lower-energy (~60 keV) bin, reducing the apparent attenuation. A radiograph of a PTFE cylinder taken using a bremsstrahlung spectrum from an x-ray voltage of 100 kV filtered by 1.3 mm Cu is reconstructed using Abel inversion. As no counts are expected in the low energy tail, a first order background correction is applied to the spectrum. The measured linear attenuation coefficient (LAC) is within 10% of the expected value in the 60 to 100 keV range. Below 60 keV, low counts in the corrected spectrum and partial energy deposition from incident photons of energy greater than 60 keV into energy bins below 60 keV impact the LAC measurements. This report ends with a demonstration of the tomographic capability of the system. The quantitative understanding of the detector developed in this report will enable further study in evaluating the system for characterization of an object’s chemical make-up for industrial and security purposes.« less

Inter-satellites x-ray communication system

NASA Astrophysics Data System (ADS)

Mou, Huan; Li, Bao-quan

2017-02-01

An inter-satellite X-ray communication system is presented in this paper. X-ray has a strong penetrating power without almost attenuation for transmission in outer space when the energy of X-ray photons is more than 10KeV and the atmospheric pressure is lower than 10-1 Pa, so it is convincing of x-ray communication in inter-satellite communication and deep space exploration. Additionally, using X-ray photons as information carriers can be used in some communication applications that laser communication and radio frequency (RF) communication are not available, such as ionization blackout area communication. The inter-satellites X-ray communication system, including the grid modulated X-ray source, the high-sensitivity X-ray detector and the transmitting and receiving antenna, is described explicitly. As the X-ray transmitter, a vacuum-sealed miniature modulated X-ray source has been fabricated via the single-step brazing process in a vacuum furnace. Pulse modulation of X-rays, by means of controlling the voltage value of the grid electrode, is realized. Three focusing electrodes, meanwhile, are used to make the electron beam converge and finally 150μm focusing spot diameter is obtained. The X-ray detector based on silicon avalanche photodiodes (APDs) is chosen as the communication receiver on account of its high temporal resolution and non-vacuum operating environment. Furthermore, considering x-ray emission characteristic and communication distance of X-rays, the multilayer nested rotary parabolic optics is picked out as transmitting and receiving antenna. And as a new concept of the space communication, there will be more important scientific significance and application prospects, called "Next-Generation Communications".

CT artifact recognition for the nuclear technologist.

PubMed

Popilock, Robert; Sandrasagaren, Kumar; Harris, Lowell; Kaser, Keith A

2008-06-01

The goal of this article is to make the PET/CT and SPECT/CT operator aware of common artifacts found in CT. In diagnostic imaging, the ability to render an accurate diagnosis requires the technologist to take steps to optimize image quality and recognize when image quality has been compromised-that is, when there is an image artifact. One way these artifacts occur is through the inability of the CT linear attenuation image to precisely represent the linear attenuation map of a 2-dimensional section through the body. The reasons for this inability are multifold. First, CT is subject to the laws of x-ray quantum physics resulting in noise in all CT images. Moreover, all current CT x-ray systems generate a spectrum of energies. Also, CT scanners use detectors of finite dimension, as are the x-ray focal spots; reconstruct images from a finite number of samples distributed over a finite number of views; and acquire the data for each reconstruction over a finite period.

Determining the mass attenuation coefficient, effective atomic number, and electron density of raw wood and binderless particleboards of Rhizophora spp. by using Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Marashdeh, Mohammad W.; Al-Hamarneh, Ibrahim F.; Abdel Munem, Eid M.; Tajuddin, A. A.; Ariffin, Alawiah; Al-Omari, Saleh

Rhizophora spp. wood has the potential to serve as a solid water or tissue equivalent phantom for photon and electron beam dosimetry. In this study, the effective atomic number (Zeff) and effective electron density (Neff) of raw wood and binderless Rhizophora spp. particleboards in four different particle sizes were determined in the 10-60 keV energy region. The mass attenuation coefficients used in the calculations were obtained using the Monte Carlo N-Particle (MCNP5) simulation code. The MCNP5 calculations of the attenuation parameters for the Rhizophora spp. samples were plotted graphically against photon energy and discussed in terms of their relative differences compared with those of water and breast tissue. Moreover, the validity of the MCNP5 code was examined by comparing the calculated attenuation parameters with the theoretical values obtained by the XCOM program based on the mixture rule. The results indicated that the MCNP5 process can be followed to determine the attenuation of gamma rays with several photon energies in other materials.

Dual-energy x-ray image decomposition by independent component analysis

NASA Astrophysics Data System (ADS)

Jiang, Yifeng; Jiang, Dazong; Zhang, Feng; Zhang, Dengfu; Lin, Gang

2001-09-01

The spatial distributions of bone and soft tissue in human body are separated by independent component analysis (ICA) of dual-energy x-ray images. It is because of the dual energy imaging modelí-s conformity to the ICA model that we can apply this method: (1) the absorption in body is mainly caused by photoelectric absorption and Compton scattering; (2) they take place simultaneously but are mutually independent; and (3) for monochromatic x-ray sources the total attenuation is achieved by linear combination of these two absorption. Compared with the conventional method, the proposed one needs no priori information about the accurate x-ray energy magnitude for imaging, while the results of the separation agree well with the conventional one.

Methodological accuracy of image-based electron density assessment using dual-energy computed tomography.

PubMed

Möhler, Christian; Wohlfahrt, Patrick; Richter, Christian; Greilich, Steffen

2017-06-01

Electron density is the most important tissue property influencing photon and ion dose distributions in radiotherapy patients. Dual-energy computed tomography (DECT) enables the determination of electron density by combining the information on photon attenuation obtained at two different effective x-ray energy spectra. Most algorithms suggested so far use the CT numbers provided after image reconstruction as input parameters, i.e., are imaged-based. To explore the accuracy that can be achieved with these approaches, we quantify the intrinsic methodological and calibration uncertainty of the seemingly simplest approach. In the studied approach, electron density is calculated with a one-parametric linear superposition ('alpha blending') of the two DECT images, which is shown to be equivalent to an affine relation between the photon attenuation cross sections of the two x-ray energy spectra. We propose to use the latter relation for empirical calibration of the spectrum-dependent blending parameter. For a conclusive assessment of the electron density uncertainty, we chose to isolate the purely methodological uncertainty component from CT-related effects such as noise and beam hardening. Analyzing calculated spectrally weighted attenuation coefficients, we find universal applicability of the investigated approach to arbitrary mixtures of human tissue with an upper limit of the methodological uncertainty component of 0.2%, excluding high-Z elements such as iodine. The proposed calibration procedure is bias-free and straightforward to perform using standard equipment. Testing the calibration on five published data sets, we obtain very small differences in the calibration result in spite of different experimental setups and CT protocols used. Employing a general calibration per scanner type and voltage combination is thus conceivable. Given the high suitability for clinical application of the alpha-blending approach in combination with a very small methodological uncertainty, we conclude that further refinement of image-based DECT-algorithms for electron density assessment is not advisable. © 2017 American Association of Physicists in Medicine.

Dual-energy X-ray absorptiometry–based body volume measurement for 4-compartment body composition123

PubMed Central

Wilson, Joseph P; Mulligan, Kathleen; Fan, Bo; Sherman, Jennifer L; Murphy, Elizabeth J; Tai, Viva W; Powers, Cassidy L; Marquez, Lorena; Ruiz-Barros, Viviana

2012-01-01

Background: Total body volume (TBV), with the exclusion of internal air voids, is necessary to quantify body composition in Lohman's 4-compartment (4C) model. Objective: This investigation sought to derive a novel, TBV measure with the use of only dual-energy X-ray absorptiometry (DXA) attenuation values for use in Lohman's 4C body composition model. Design: Pixel-specific masses and volumes were calculated from low- and high-energy attenuation values with the use of first principle conversions of mass attenuation coefficients. Pixel masses and volumes were summed to derive body mass and total body volume. As proof of concept, 11 participants were recruited to have 4C measures taken: DXA, air-displacement plethysmography (ADP), and total body water (TBW). TBV measures with the use of only DXA (DXA-volume) and ADP-volume measures were compared for each participant. To see how body composition estimates were affected by these 2 methods, we used Lohman's 4C model to quantify percentage fat measures for each participant and compared them with conventional DXA measures. Results: DXA-volume and ADP-volume measures were highly correlated (R2 = 0.99) and showed no statistically significant bias. Percentage fat by DXA volume was highly correlated with ADP-volume percentage fat measures and DXA software-reported percentage fat measures (R2 = 0.96 and R2 = 0.98, respectively) but were slightly biased. Conclusions: A novel method to calculate TBV with the use of a clinical DXA system was developed, compared against ADP as proof of principle, and used in Lohman's 4C body composition model. The DXA-volume approach eliminates many of the inherent inaccuracies associated with displacement measures for volume and, if validated in larger groups of participants, would simplify the acquisition of 4C body composition to a single DXA scan and TBW measure. PMID:22134952

Imaging method based on attenuation, refraction and ultra-small-angle-scattering of x-rays

DOEpatents

Wernick, Miles N.; Chapman, Leroy Dean; Oltulu, Oral; Zhong, Zhong

2005-09-20

A method for detecting an image of an object by measuring the intensity at a plurality of positions of a transmitted beam of x-ray radiation emitted from the object as a function of angle within the transmitted beam. The intensity measurements of the transmitted beam are obtained by a crystal analyzer positioned at a plurality of angular positions. The plurality of intensity measurements are used to determine the angular intensity spectrum of the transmitted beam. One or more parameters, such as an attenuation property, a refraction property and a scatter property, can be obtained from the angular intensity spectrum and used to display an image of the object.

CORRELATION OF HARD X-RAY AND WHITE LIGHT EMISSION IN SOLAR FLARES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuhar, Matej; Krucker, Säm; Battaglia, Marina

A statistical study of the correlation between hard X-ray and white light emission in solar flares is performed in order to search for a link between flare-accelerated electrons and white light formation. We analyze 43 flares spanning GOES classes M and X using observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager and Helioseismic and Magnetic Imager. We calculate X-ray fluxes at 30 keV and white light fluxes at 6173 Å summed over the hard X-ray flare ribbons with an integration time of 45 s around the peak hard-X ray time. We find a good correlation between hard X-raymore » fluxes and excess white light fluxes, with a highest correlation coefficient of 0.68 for photons with energy of 30 keV. Assuming the thick target model, a similar correlation is found between the deposited power by flare-accelerated electrons and the white light fluxes. The correlation coefficient is found to be largest for energy deposition by electrons above ∼50 keV. At higher electron energies the correlation decreases gradually while a rapid decrease is seen if the energy provided by low-energy electrons is added. This suggests that flare-accelerated electrons of energy ∼50 keV are the main source for white light production.« less

Cooled window for X-rays or charged particles

DOEpatents

Logan, Clinton M.

1996-01-01

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.

Surface topography of 1€ coin measured by stereo-PIXE

NASA Astrophysics Data System (ADS)

Gholami-Hatam, E.; Lamehi-Rachti, M.; Vavpetič, P.; Grlj, N.; Pelicon, P.

2013-07-01

We demonstrate the stereo-PIXE method by measurement of surface topography of the relief details on 1€ coin. Two X-ray elemental maps were simultaneously recorded by two X-ray detectors positioned at the left and the right side of the proton microbeam. The asymmetry of the yields in the pixels of the two X-ray maps occurs due to different photon attenuation on the exit travel path of the characteristic X-rays from the point of emission through the sample into the X-ray detectors. In order to calibrate the inclination angle with respect to the X-ray asymmetry, a flat inclined surface model was at first applied for the sample in which the matrix composition and the depth elemental concentration profile is known. After that, the yield asymmetry in each image pixel was transferred into corresponding local inclination angle using calculated dependence of the asymmetry on the surface inclination. Finally, the quantitative topography profile was revealed by integrating the local inclination angle over the lateral displacement of the probing beam.

X-ray lithography using holographic images

DOEpatents

Howells, M.S.; Jacobsen, C.

1997-03-18

Methods for forming X-ray images having 0.25 {micro}m minimum line widths on X-ray sensitive material are presented. A holographic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required. 15 figs.

X-ray lithography using holographic images

DOEpatents

Howells, Malcolm S.; Jacobsen, Chris

1997-01-01

Methods for forming X-ray images having 0.25 .mu.m minimum line widths on X-ray sensitive material are presented. A holgraphic image of a desired circuit pattern is projected onto a wafer or other image-receiving substrate to allow recording of the desired image in photoresist material. In one embodiment, the method uses on-axis transmission and provides a high flux X-ray source having modest monochromaticity and coherence requirements. A layer of light-sensitive photoresist material on a wafer with a selected surface is provided to receive the image(s). The hologram has variable optical thickness and variable associated optical phase angle and amplitude attenuation for transmission of the X-rays. A second embodiment uses off-axis holography. The wafer receives the holographic image by grazing incidence reflection from a hologram printed on a flat metal or other highly reflecting surface or substrate. In this second embodiment, an X-ray beam with a high degree of monochromaticity and spatial coherence is required.

Coated x-ray filters

DOEpatents

Steinmeyer, P.A.

1992-11-24

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.

Coated x-ray filters

DOEpatents

Steinmeyer, Peter A.

1992-11-24

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.

High resolution projection X-ray microscope equipped with fluorescent X-ray analyzer and its applications

NASA Astrophysics Data System (ADS)

Minami, K.; Saito, Y.; Kai, H.; Shirota, K.; Yada, K.

2009-09-01

We have newly developed an open type fine-focus X-ray tube "TX-510" to realize a spatial resolution of 50nm and to radiate low energy characteristic X-rays for giving high absorption contrast to images of microscopic organisms. The "TX-510" employs a ZrO/W(100) Schottky emitter and an "In-Lens Field Emission Gun". The key points of the improvements are (1) reduced spherical aberration coefficient of magnetic objective lens, (2) easy and accurate focusing, (3) newly designed astigmatism compensator, (4) segmented thin film target for interchanging the target materials by electron beam shift and (5) fluorescent X-ray analysis system.

Radiomics-based differentiation of lung disease models generated by polluted air based on X-ray computed tomography data.

PubMed

Szigeti, Krisztián; Szabó, Tibor; Korom, Csaba; Czibak, Ilona; Horváth, Ildikó; Veres, Dániel S; Gyöngyi, Zoltán; Karlinger, Kinga; Bergmann, Ralf; Pócsik, Márta; Budán, Ferenc; Máthé, Domokos

2016-02-11

Lung diseases (resulting from air pollution) require a widely accessible method for risk estimation and early diagnosis to ensure proper and responsive treatment. Radiomics-based fractal dimension analysis of X-ray computed tomography attenuation patterns in chest voxels of mice exposed to different air polluting agents was performed to model early stages of disease and establish differential diagnosis. To model different types of air pollution, BALBc/ByJ mouse groups were exposed to cigarette smoke combined with ozone, sulphur dioxide gas and a control group was established. Two weeks after exposure, the frequency distributions of image voxel attenuation data were evaluated. Specific cut-off ranges were defined to group voxels by attenuation. Cut-off ranges were binarized and their spatial pattern was associated with calculated fractal dimension, then abstracted by the fractal dimension -- cut-off range mathematical function. Nonparametric Kruskal-Wallis (KW) and Mann-Whitney post hoc (MWph) tests were used. Each cut-off range versus fractal dimension function plot was found to contain two distinctive Gaussian curves. The ratios of the Gaussian curve parameters are considerably significant and are statistically distinguishable within the three exposure groups. A new radiomics evaluation method was established based on analysis of the fractal dimension of chest X-ray computed tomography data segments. The specific attenuation patterns calculated utilizing our method may diagnose and monitor certain lung diseases, such as chronic obstructive pulmonary disease (COPD), asthma, tuberculosis or lung carcinomas.

Development of BaO-ZnO-B2O3 glasses as a radiation shielding material

NASA Astrophysics Data System (ADS)

Chanthima, N.; Kaewkhao, J.; Limkitjaroenporn, P.; Tuscharoen, S.; Kothan, S.; Tungjai, M.; Kaewjaeng, S.; Sarachai, S.; Limsuwan, P.

2017-08-01

The effects of the BaO on the optical, physical and radiation shielding properties of the xBaO: 20ZnO: (80-x)B2O3, where x=5, 10, 15, 20 and 25 mol%, were investigated. The glasses were developed by the conventional melt-quenching technique at 1400 °C with high purity chemicals of H3BO3, ZnO, and BaSO4. The optical transparency of the glasses indicated that the glasses samples were high, as observed by visual inspections. The mass attenuation coefficients (μm), the effective atomic numbers (Zeff), and the effective electron densities (Ne) were increased with the increase of BaO concentrations, and the decrease of gamma-ray energy. The developed glass samples were investigated and compared with the shielding concretes and glasses in terms of half value layer (HVL). The overall results demonstrated that the developed glasses had good shielding properties, and highly practical potentials in the environmental friendly radiation shielding materials without an additional of Pb.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clayton, James; Shedlock, Daniel; Langeveld, Willem G.J.

In the security and inspection market, there is a push towards highly mobile, reduced-dose active interrogation scanning and imaging systems to allow operation in urban environments. To achieve these goals, the accelerator system design needs to be smaller than existing systems. A smaller radiation exclusion zone may be accomplished through better beam collimation and an integrated, x-ray-source/detector-array assembly to allow feedback and control of an intensity-modulated x-ray source. A shaped low-Z target in the x-ray source can be used to generate a more forward peaked x-ray beam. Electron-beam steering can then be applied to direct the forward-peaked x rays towardmore » areas in the cargo with high attenuation. This paper presents an exploratory study to identify components and upgrades that would be required to meet the desired specifications, as well as the best technical approach to design and build a prototype.« less

Biological soft X-ray tomography on beamline 2.1 at the Advanced Light Source.

PubMed

Le Gros, Mark A; McDermott, Gerry; Cinquin, Bertrand P; Smith, Elizabeth A; Do, Myan; Chao, Weilun L; Naulleau, Patrick P; Larabell, Carolyn A

2014-11-01

Beamline 2.1 (XM-2) is a transmission soft X-ray microscope in sector 2 of the Advanced Light Source at Lawrence Berkeley National Laboratory. XM-2 was designed, built and is now operated by the National Center for X-ray Tomography as a National Institutes of Health Biomedical Technology Research Resource. XM-2 is equipped with a cryogenic rotation stage to enable tomographic data collection from cryo-preserved cells, including large mammalian cells. During data collection the specimen is illuminated with `water window' X-rays (284-543 eV). Illuminating photons are attenuated an order of magnitude more strongly by biomolecules than by water. Consequently, differences in molecular composition generate quantitative contrast in images of the specimen. Soft X-ray tomography is an information-rich three-dimensional imaging method that can be applied either as a standalone technique or as a component modality in correlative imaging studies.

Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation**

PubMed Central

Schomakers, Jasmin; Zehetner, Franz; Mentler, Axel; Ottner, Franz; Mayer, Herwig

2016-01-01

It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested high-accuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm−3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (< 10 J cm−3), which previous studies have largely neglected. This shows that low ultrasonic energies are required to capture the full range of aggregate stability and release of soil organic matter upon aggregate breakdown. PMID:27099408

Priors for X-ray in-line phase tomography of heterogeneous objects.

PubMed

Langer, Max; Cloetens, Peter; Hesse, Bernhard; Suhonen, Heikki; Pacureanu, Alexandra; Raum, Kay; Peyrin, Françoise

2014-03-06

We present a new prior for phase retrieval from X-ray Fresnel diffraction patterns. Fresnel diffraction patterns are achieved by letting a highly coherent X-ray beam propagate in free space after interaction with an object. Previously, either homogeneous or multi-material object assumptions have been used. The advantage of the homogeneous object assumption is that the prior can be introduced in the Radon domain. Heterogeneous object priors, on the other hand, have to be applied in the object domain. Here, we let the relationship between attenuation and refractive index vary as a function of the measured attenuation index. The method is evaluated using images acquired at beamline ID19 (ESRF, Grenoble, France) of a phantom where the prior is calculated by linear interpolation and of a healing bone obtained from a rat osteotomy model. It is shown that the ratio between attenuation and refractive index in bone for different levels of mineralization follows a power law. Reconstruction was performed using the mixed approach but is compatible with other, more advanced models. We achieve more precise reconstructions than previously reported in literature. We believe that the proposed method will find application in biomedical imaging problems where the object is strongly heterogeneous, such as bone healing and biomaterials engineering.

Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation

NASA Astrophysics Data System (ADS)

Schomakers, Jasmin; Zehetner, Franz; Mentler, Axel; Ottner, Franz; Mayer, Herwig

2015-10-01

It has been increasingly recognized that soil organic matter stabilization is strongly controlled by physical binding within soil aggregates. It is therefore essential to measure soil aggregate stability reliably over a wide range of disruptive energies and different aggregate sizes. To this end, we tested highaccuracy ultrasonic dispersion in combination with subsequent sedimentation and X-ray attenuation. Three arable topsoils (notillage) from Central Europe were subjected to ultrasound at four different specific energy levels: 0.5, 6.7, 100 and 500 J cm-3, and the resulting suspensions were analyzed for aggregate size distribution by wet sieving (2 000-63 μm) and sedimentation/X-ray attenuation (63-2 μm). The combination of wet sieving and sedimentation technique allowed for a continuous analysis, at high resolution, of soil aggregate breakdown dynamics after defined energy inputs. Our results show that aggregate size distribution strongly varied with sonication energy input and soil type. The strongest effects were observed in the range of low specific energies (< 10 J cm-3), which previous studies have largely neglected. This shows that low ultrasonic energies are required to capture the full range of aggregate stability and release of soil organic matter upon aggregate breakdown.

On the Design of Wide-Field X-ray Telescopes

NASA Technical Reports Server (NTRS)

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

2009-01-01

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.

Quantitative in vivo CT arthrography of the human osteoarthritic knee to estimate cartilage sulphated glycosaminoglycan content: correlation with ex-vivo reference standards.

PubMed

van Tiel, J; Siebelt, M; Reijman, M; Bos, P K; Waarsing, J H; Zuurmond, A-M; Nasserinejad, K; van Osch, G J V M; Verhaar, J A N; Krestin, G P; Weinans, H; Oei, E H G

2016-06-01

Recently, computed tomography arthrography (CTa) was introduced as quantitative imaging biomarker to estimate cartilage sulphated glycosaminoglycan (sGAG) content in human cadaveric knees. Our aim was to assess the correlation between in vivo CTa in human osteoarthritis (OA) knees and ex vivo reference standards for sGAG and collagen content. In this prospective observational study 11 knee OA patients underwent CTa before total knee replacement (TKR). Cartilage X-ray attenuation was determined in six cartilage regions. Femoral and tibial cartilage specimens harvested during TKR were re-scanned using equilibrium partitioning of an ionic contrast agent with micro-CT (EPIC-μCT), which served as reference standard for sGAG. Next, cartilage sGAG and collagen content were determined using dimethylmethylene blue (DMMB) and hydroxyproline assays. The correlation between CTa X-ray attenuation, EPIC-μCT X-ray attenuation, sGAG content and collagen content was assessed. CTa X-ray attenuation correlated well with EPIC-μCT (r = 0.76, 95% credibility interval (95%CI) 0.64 to 0.85). CTa correlated moderately with the DMMB assay (sGAG content) (r = -0.66, 95%CI -0.87 to -0.49) and to lesser extent with the hydroxyproline assay (collagen content) (r = -0.56, 95%CI -0.70 to -0.36). Outcomes of in vivo CTa in human OA knees correlate well with sGAG content. Outcomes of CTa also slightly correlate with cartilage collagen content. Since outcomes of CTa are mainly sGAG dependent and despite the fact that further validation using hyaline cartilage of other joints with different biochemical composition should be conducted, CTa may be suitable as quantitative imaging biomarker to estimate cartilage sGAG content in future clinical OA research. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Optical coefficient measurements using bulk living tissue by an optical fiber puncture with FOV change

NASA Astrophysics Data System (ADS)

Nakazawa, Haruna; Doi, Marika; Ogawa, Emiyu; Arai, Tsunenori

2018-02-01

To avoid an instability of the optical coefficient measurement using sliced tissue preparation, we proposed the combination of light intensity measurement through an optical fiber puncturing into a bulk tissue varying field of view (FOV) and ray tracing calculation using Monte-Carlo method. The optical coefficients of myocardium such as absorption coefficient μa, scattering coefficient μs, and anisotropic parameter g are used in the myocardium optical propagation. Since optical coefficients obtained using thin sliced tissue could be instable because they are affected by dehydration and intracellular fluid effusion on the sample surface, variety of coefficients have been reported over individual optical differences of living samples. The proposed method which combined the experiment using the bulk tissue with ray tracing calculation were performed. In this method, a 200 μmΦ high-NA silica fiber installed in a 21G needle was punctured up to the bottom of the myocardial bulk tissue over 3 cm in thickness to measure light intensity changing the fiber-tip depth and FOV. We found that the measured attenuation coefficients decreased as the FOV increased. The ray trace calculation represented the same FOV dependence in above mentioned experimental result. We think our particular fiber punctured measurement using bulk tissue varying FOV with Inverse Monte-Carlo method might be useful to obtain the optical coefficients to avoid sample preparation instabilities.

Multi-species beam hardening calibration device for x-ray microtomography

NASA Astrophysics Data System (ADS)

Evershed, Anthony N. Z.; Mills, David; Davis, Graham

2012-10-01

Impact-source X-ray microtomography (XMT) is a widely-used benchtop alternative to synchrotron radiation microtomography. Since X-rays from a tube are polychromatic, however, greyscale `beam hardening' artefacts are produced by the preferential absorption of low-energy photons in the beam path. A multi-material `carousel' test piece was developed to offer a wider range of X-ray attenuations from well-characterised filters than single-material step wedges can produce practically, and optimization software was developed to produce a beam hardening correction by use of the Nelder-Mead optimization method, tuned for specimens composed of other materials (such as hydroxyapatite [HA] or barium for dental applications.) The carousel test piece produced calibration polynomials reliably and with a significantly smaller discrepancy between the calculated and measured attenuations than the calibration step wedge previously in use. An immersion tank was constructed and used to simplify multi-material samples in order to negate the beam hardening effect of low atomic number materials within the specimen when measuring mineral concentration of higher-Z regions. When scanned in water at an acceleration voltage of 90 kV a Scanco AG hydroxyapatite / poly(methyl methacrylate) calibration phantom closely approximates a single-material system, producing accurate hydroxyapatite concentration measurements. This system can then be corrected for beam hardening for the material of interest.

Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited).

PubMed

Valdivia, M P; Stutman, D; Stoeckl, C; Mileham, C; Begishev, I A; Theobald, W; Bromage, J; Regan, S P; Klein, S R; Muñoz-Cordovez, G; Vescovi, M; Valenzuela-Villaseca, V; Veloso, F

2016-11-01

Talbot-Lau X-ray deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping were demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moiré pattern formation and grating survival were also observed using a copper x-pinch driven at 400 kA, ∼1 kA/ns. These results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

An upper limit on ultraviolet shot noise from Cygnus X-1

NASA Technical Reports Server (NTRS)

Duthie, J. G.; Mcmillan, R. S.

1979-01-01

Rapid photometry of Cygnus X-1 through an ultraviolet filter centered on 0.35 micron has been obtained at 100-ms sampling intervals. The autocorrelation function of these data has been examined for shot noise analogous to the behavior of the X-ray light curve. The ultraviolet data are entirely consistent with white noise. Considering randomly occurring ultraviolet shots with the same duration (0.5 s) and average rate (1 per sec) as the X-ray shots, a 3-sigma upper limit on the ratio of optical to X-ray energies per shot is estimated to be 0.13, before the ultraviolet light is attenuated by interstellar dust. This limit is then generalized for shots of arbitrary duration and rate.

Talbot-Lau X-ray Deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments

DOE PAGES

Valdivia, M. P.; Stutman, D.; Stoeckl, C.; ...

2016-04-21

Talbot-Lau X-ray Deflectometry has been developed as an electron density diagnostic for High Energy Density plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping was demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moire pattern formation and grating survival was also observed using a copper x-pinch driven at 400 kA, ~1 kA/ns. Lastly, these results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

Area beam equalization: optimization and performance of an automated prototype system for chest radiography.

PubMed

Xu, Tong; Shikhaliev, Polad M; Berenji, Gholam R; Tehranzadeh, Jamshid; Saremi, Farhood; Molloi, Sabee

2004-04-01

To evaluate the feasibility and performance of an x-ray beam equalization system for chest radiography using anthropomorphic phantoms. Area beam equalization involves the process of the initial unequalized image acquisition, attenuator thickness calculation, mask generation using a 16 x 16 piston array, and final equalized image acquisition. Chest radiographs of three different anthropomorphic phantoms were acquired with no beam equalization and equalization levels of 4.8, 11.3, and 21. Six radiologists evaluated the images by scoring them from 1-5 using 13 different criteria. The dose was calculated using the known attenuator material thickness and the mAs of the x-ray tube. The visibility of anatomic structures in the under-penetrated regions of the chest radiographs was shown to be significantly (P < .01) improved after beam equalization. An equalization level of 4.8 provided most of the improvements with moderate increases in patient dose and tube loading. Higher levels of beam equalization did not show much improvement in the visibility of anatomic structures in the under-penetrated regions. A moderate level of x-ray beam equalization in chest radiography is superior to both conventional radiographs and radiographs with high levels of beam equalization. X-ray beam equalization can significantly improve the visibility of anatomic structures in the under-penetrated regions while maintaining good image quality in the lung region.

Patient size and x-ray transmission in body CT.

PubMed

Ogden, Kent; Huda, Walter; Scalzetti, Ernest M; Roskopf, Marsha L

2004-04-01

Physical characteristics were obtained for 196 patients undergoing chest and abdomen computed tomography (CT) examinations. Computed tomography sections for these patients having no evident pathology were analyzed to determine patient dimensions (AP and lateral), together with the average attenuation coefficient. Patient weights ranged from approximately 3 kg to about 120 kg. For chest CT, the mean Hounsfield unit (HU) fell from about -120 HU for newborns to about -300 HU for adults. For abdominal CT, the mean HU for children and normal-sized adults was about 20 HU, but decreased to below -50 HU for adults weighing more than 100 kg. The effective photon energy and percent energy fluence transmitted through a given patient size and composition was calculated for representative x-ray spectra at 80, 100, 120, and 140 kV tube potentials. A 70-kg adult scanned at 120 kVp transmits 2.6% of the energy fluence for chest and 0.7% for abdomen CT examinations. Reducing the patient size to 10 kg increases transmission by an order of magnitude. For 70 kg patients, effective energies in body CT range from approximately 50 keV at 80 kVp to approximately 67 keV at 140 kVp; increasing patient size from 10 to 120 kg resulted in an increase in effective photon energy of approximately 4 keV. The x-ray transmission data and effective photon energy data can be used to determine CT image noise and image contrast, respectively, and information on patient size and composition can be used to determine patient doses.

Electron Effective-Attenuation-Length Database

National Institute of Standards and Technology Data Gateway

SRD 82 NIST Electron Effective-Attenuation-Length Database (PC database, no charge)   This database provides values of electron effective attenuation lengths (EALs) in solid elements and compounds at selected electron energies between 50 eV and 2,000 eV. The database was designed mainly to provide EALs (to account for effects of elastic-eletron scattering) for applications in surface analysis by Auger-electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

Modeling Contamination Migration on the Chandra X-ray Observatory II

NASA Technical Reports Server (NTRS)

O'Dell, Steve; Swartz, Doug; Tice, Neil; Plucinsky, Paul; Grant, Catherine; Marshall, Herman; Vikhlinin, Alexey

2013-01-01

During its first 14 years of operation, the cold (about -60degC) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition may have changed, perhaps partially related to changes in the operating temperature of the ACIS housing. This evolution of the accumulation of the molecular contamination has motivated further analysis of contamination migration on the Chandra X-ray Observatory, particularly within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon monitored temperature data, and an accordingly refined model of the molecular transport.

Edge-illumination x-ray phase contrast imaging with Pt-based metallic glass masks

NASA Astrophysics Data System (ADS)

Saghamanesh, Somayeh; Aghamiri, Seyed Mahmoud-Reza; Olivo, Alessandro; Sadeghilarijani, Maryam; Kato, Hidemi; Kamali-Asl, Alireza; Yashiro, Wataru

2017-06-01

Edge-illumination x-ray phase contrast imaging (EI XPCI) is a non-interferometric phase-sensitive method where two absorption masks are employed. These masks are fabricated through a photolithography process followed by electroplating which is challenging in terms of yield as well as time- and cost-effectiveness. We report on the first implementation of EI XPCI with Pt-based metallic glass masks fabricated by an imprinting method. The new tested alloy exhibits good characteristics including high workability beside high x-ray attenuation. The fabrication process is easy and cheap, and can produce large-size masks for high x-ray energies within minutes. Imaging experiments show a good quality phase image, which confirms the potential of these masks to make the EI XPCI technique widely available and affordable.

Asymmetric masks for laboratory-based X-ray phase-contrast imaging with edge illumination.

PubMed

Endrizzi, Marco; Astolfo, Alberto; Vittoria, Fabio A; Millard, Thomas P; Olivo, Alessandro

2016-05-05

We report on an asymmetric mask concept that enables X-ray phase-contrast imaging without requiring any movement in the system during data acquisition. The method is compatible with laboratory equipment, namely a commercial detector and a rotating anode tube. The only motion required is that of the object under investigation which is scanned through the imaging system. Two proof-of-principle optical elements were designed, fabricated and experimentally tested. Quantitative measurements on samples of known shape and composition were compared to theory with good agreement. The method is capable of measuring the attenuation, refraction and (ultra-small-angle) X-ray scattering, does not have coherence requirements and naturally adapts to all those situations in which the X-ray image is obtained by scanning a sample through the imaging system.

Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301.

PubMed

Mathur; Green; Arav; Brotherton; Crenshaw; deKool; Elvis; Goodrich; Hamann; Hines; Kashyap; Korista; Peterson; Shields; Shlosman; van Breugel W; Voit

2000-04-20

We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (NH greater, similar1024 cm-2) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.

Energy determination in industrial X-ray processing facilities

NASA Astrophysics Data System (ADS)

Cleland, M. R.; Gregoire, O.; Stichelbaut, F.; Gomola, I.; Galloway, R. A.; Schlecht, J.

2005-12-01

In industrial irradiation facilities, the determination of maximum photon or electron energy is important for regulated processes, such as food irradiation, and for assurance of treatment reproducibility. With electron beam irradiators, this has been done by measuring the depth-dose distribution in a homogeneous material. For X-ray irradiators, an analogous method has not yet been recommended. This paper describes a procedure suitable for typical industrial irradiation processes, which is based on common practice in the field of therapeutic X-ray treatment. It utilizes a measurement of the slope of the exponential attenuation curve of X-rays in a thick stack of polyethylene plates. Monte Carlo simulations and experimental tests have been performed to verify the suitability and accuracy of the method between 3 MeV and 8 MeV.

X-ray emission from a plasma mirror of a neodymium glass laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalal, M.; Pina, L.; Vrbova, M.

1984-11-01

An investigation was made of the optical and x-ray characteristics of the radiation emitted by a plasma mirror in a neodymium glass laser. The optical reflection coefficient of the mirror was found to be nonlinear and the plasma temperature was about 300 eV.

Imaging subtle microstructural variations in ceramics with precision ultrasonic velocity and attenuation measurements

NASA Technical Reports Server (NTRS)

Generazio, Edward R.; Roth, Don J.; Baaklini, George Y.

1987-01-01

Acoustic images of a silicon carbide ceramic disk were obtained using a precision scanning contact pulse echo technique. Phase and cross-correlation velocity, and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with X-ray radiography.

Analytical transmission cross-coefficients for pink beam X-ray microscopy based on compound refractive lenses.

PubMed

Falch, Ken Vidar; Detlefs, Carsten; Snigirev, Anatoly; Mathiesen, Ragnvald H

2018-01-01

Analytical expressions for the transmission cross-coefficients for x-ray microscopes based on compound refractive lenses are derived based on Gaussian approximations of the source shape and energy spectrum. The effects of partial coherence, defocus, beam convergence, as well as lateral and longitudinal chromatic aberrations are accounted for and discussed. Taking the incoherent limit of the transmission cross-coefficients, a compact analytical expression for the modulation transfer function of the system is obtained, and the resulting point, line and edge spread functions are presented. Finally, analytical expressions for optimal numerical aperture, coherence ratio, and bandwidth are given. Copyright © 2017 Elsevier B.V. All rights reserved.

A nonintrusive nuclear monitor for measuring liquid contents in sealed vessels

NASA Technical Reports Server (NTRS)

Singh, J. J.; Mall, G. H.

1984-01-01

A nonintrusive nuclear technique for monitoring fluid contents in sealed vessels, regardless of the fluid distribution inside the vessels is described. The technique is applicable to all-g environments. It is based on the differences in Cesium-137 gamma ray attenuation coefficients in air and the test liquids.

Measurement of Attenuation with Airborne and Ground-Based Radar in Convective Storms Over Land Its Microphysical Implications

NASA Technical Reports Server (NTRS)

Tian, Lin; Heymsfield, G. M.; Srivastava, R. C.; O'C.Starr, D. (Technical Monitor)

2001-01-01

Observations by the airborne X-band Doppler radar (EDOP) and the NCAR S-band polarimetric (S-Pol) radar from two field experiments are used to evaluate the surface reference technique (SRT) for measuring the path integrated attenuation (PIA) and to study attenuation in deep convective storms. The EDOP, flying at an altitude of 20 km, uses a nadir beam and a forward pointing beam. It is found that over land, the surface scattering cross-section is highly variable at nadir incidence but relatively stable at forward incidence. It is concluded that measurement by the forward beam provides a viable technique for measuring PIA using the SRT. Vertical profiles of peak attenuation coefficient are derived in two deep convective storms by the dual-wavelength method. Using the measured Doppler velocity, the reflectivities at the two wavelengths, the differential reflectivity and the estimated attenuation coefficients, it is shown that: supercooled drops and (dry) ice particles probably co-existed above the melting level in regions of updraft, that water-coated partially melted ice particles probably contributed to high attenuation below the melting level.

Taking into Account Interelement Interference in X-Ray Fluorescence Analysis of Thin Two-Layer Ti/V Systems

NASA Astrophysics Data System (ADS)

Mashin, N. I.; Razuvaev, A. G.; Cherniaeva, E. A.; Gafarova, L. M.; Ershov, A. V.

2018-03-01

We propose a new method for determining the thickness of layers in x-ray fluorescence analysis of two-layer Ti/V systems, using easily fabricated standardized film layers obtained by sputter deposition of titanium on a polymer film substrate. We have calculated correction factors taking into account the level of attenuation for the intensity of the primary emission from the x-ray tube and the analytical line for the element of the bottom layer in the top layer, and the enhancement of the fluorescence intensity for the top layer by the emission of atoms in the bottom layer.

Modeling Contamination Migration on the Chandra X-ray Observatory - II

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Grant, Catherine E.; Marshall, Herman L.; Vikhlinin, Alexey A.; Tennant, Allyn F.

2013-01-01

During its first 14 years of operation, the cold (about -60C) optical blocking filter of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination that attenuates low-energy x rays. Over the past few years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity. To this end, the current study employs a higher-fidelity geometric model of the ACIS cavity, detailed thermal modeling based upon temperature data, and a refined model of the molecular transport.

Measurement of small lesions near metallic implants with mega-voltage cone beam CT

NASA Astrophysics Data System (ADS)

Grigorescu, Violeta; Prevrhal, Sven; Pouliot, Jean

2008-03-01

Metallic objects severely limit diagnostic CT imaging because of their high X-ray attenuation in the diagnostic energy range. In contrast, radiation therapy linear accelerators now offer CT imaging with X-ray energies in the megavolt range, where the attenuation coefficients of metals are significantly lower. We hypothesized that Mega electron-Voltage Cone-Beam CT (MVCT) implemented on a radiation therapy linear accelerator can detect and quantify small features in the vicinity of metallic implants with accuracy comparable to clinical Kilo electron-Voltage CT (KVCT) for imaging. Our test application was detection of osteolytic lesions formed near the metallic stem of a hip prosthesis, a condition of severe concern in hip replacement surgery. Both MVCT and KVCT were used to image a phantom containing simulated osteolytic bone lesions centered around a Chrome-Cobalt hip prosthesis stem with hemispherical lesions with sizes and densities ranging from 0.5 to 4 mm radius and 0 to 500 mg•cm -3, respectively. Images for both modalities were visually graded to establish lower limits of lesion visibility as a function of their size. Lesion volumes and mean density were determined and compared to reference values. Volume determination errors were reduced from 34%, on KVCT, to 20% for all lesions on MVCT, and density determination errors were reduced from 71% on KVCT to 10% on MVCT. Localization and quantification of lesions was improved with MVCT imaging. MVCT offers a viable alternative to clinical CT in cases where accurate 3D imaging of small features near metallic hardware is critical. These results need to be extended to other metallic objects of different composition and geometry.

Beam hardening and partial beam hardening of the bowtie filter: Effects on dosimetric applications in CT

NASA Astrophysics Data System (ADS)

Lopez-Rendon, X.; Zhang, G.; Bosmans, H.; Oyen, R.; Zanca, F.

2014-03-01

Purpose: To estimate the consequences on dosimetric applications when a CT bowtie filter is modeled by means of full beam hardening versus partial beam hardening. Method: A model of source and filtration for a CT scanner as developed by Turner et. al. [1] was implemented. Specific exposures were measured with the stationary CT X-ray tube in order to assess the equivalent thickness of Al of the bowtie filter as a function of the fan angle. Using these thicknesses, the primary beam attenuation factors were calculated from the energy dependent photon mass attenuation coefficients and used to include beam hardening in the spectrum. This was compared to a potentially less computationally intensive approach, which accounts only partially for beam hardening, by giving the photon spectrum a global (energy independent) fan angle specific weighting factor. Percentage differences between the two methods were quantified by calculating the dose in air after passing several water equivalent thicknesses representative for patients having different BMI. Specifically, the maximum water equivalent thickness of the lateral and anterior-posterior dimension and of the corresponding (half) effective diameter were assessed. Results: The largest percentage differences were found for the thickest part of the bowtie filter and they increased with patient size. For a normal size patient they ranged from 5.5% at half effective diameter to 16.1% for the lateral dimension; for the most obese patient they ranged from 7.7% to 19.3%, respectively. For a complete simulation of one rotation of the x-ray tube, the proposed method was 12% faster than the complete simulation of the bowtie filter. Conclusion: The need for simulating the beam hardening of the bow tie filter in Monte Carlo platforms for CT dosimetry will depend on the required accuracy.

Dendrimer-stabilized bismuth sulfide nanoparticles: synthesis, characterization, and potential computed tomography imaging applications.

PubMed

Fang, Yi; Peng, Chen; Guo, Rui; Zheng, Linfeng; Qin, Jinbao; Zhou, Benqing; Shen, Mingwu; Lu, Xinwu; Zhang, Guixiang; Shi, Xiangyang

2013-06-07

We report here a general approach to synthesizing dendrimer-stabilized bismuth sulfide nanoparticles (Bi2S3 DSNPs) for potential computed tomography (CT) imaging applications. In this study, ethylenediamine core glycidol hydroxyl-terminated generation 4 poly(amidoamine) dendrimers (G4.NGlyOH) were used as stabilizers to first complex the Bi(III) ions, followed by reaction with hydrogen sulfide to generate Bi2S3 DSNPs. By varying the molar ratio of Bi atom to dendrimer, stable Bi2S3 DSNPs with an average size range of 5.2-5.7 nm were formed. The formed Bi2S3 DSNPs were characterized via different techniques. X-ray absorption coefficient measurements show that the attenuation of Bi2S3 DSNPs is much higher than that of iodine-based CT contrast agent at the same molar concentration of the active element (Bi versus iodine). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay and hemolysis assay reveal that the formed Bi2S3 DSNPs are noncytotoxic and have a negligible hemolysis effect in the studied concentration range. Furthermore, we show that cells incubated with the Bi2S3 DSNPs are able to be imaged using CT, a prominent enhancement at the point of rabbit injected subcutaneously with the Bi2S3 DSNPs is able to be visualized via CT scanning, and the mouse's pulmonary vein can be visualized via CT after intravenous injection of the Bi2S3 DSNPs. With the good biocompatibility, enhanced X-ray attenuation property, and tunable dendrimer chemistry, the designed Bi2S3 DSNPs should be able to be further functionalized, allowing them to be used as a highly efficient contrast agent for CT imaging of different biological systems.

Fabrication, characterization and gamma rays shielding properties of nano and micro lead oxide-dispersed-high density polyethylene composites

NASA Astrophysics Data System (ADS)

Mahmoud, Mohamed E.; El-Khatib, Ahmed M.; Badawi, Mohamed S.; Rashad, Amal R.; El-Sharkawy, Rehab M.; Thabet, Abouzeid A.

2018-04-01

Polymer composites of high-density polyethylene (HD-PE) filled with powdered lead oxide nanoparticles (PbO NPs) and bulk lead oxide (PbO Blk) were prepared with filler weight fraction [10% and 50%]. These polymer composites were investigated for radiation-shielding of gamma-rays emitted from radioactive point sources [241Am, 133Ba, 137Cs, and 60Co]. The polymer was found to decrease the heaviness of the shielding material and increase the flexibility while the metal oxide fillers acted as principle radiation attenuators in the polymer composite. The prepared composites were characterized by Fourier transform infrared spectrophotometer (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), Brunauer-Emmett-Teller surface area (BET) and field emission transmission electron microscope (FE-TEM). The morphological analysis of the assembled composites showed that, PbO NPs and PbO Blk materials exhibited homogenous dispersion in the polymer-matrix. Thermogravimetric analysis (TGA) demonstrated that the thermal-stability of HD-PE was enhanced in the presence of both PbO Blk and PbO NPs. The results declared that, the density of polymer composites was increase with the percentage of filler contents. The highest density value was identified as 1.652 g cm-3 for 50 wt% of PbO NPs. Linear attenuation coefficients (μ) have been estimated from the use of XCOM code and measured results. Reasonable agreement was attended between theoretical and experimental results. These composites were also found to display excellent percentage of heaviness with respect to other conventional materials.

Gold nanoparticle contrast agents in advanced X-ray imaging technologies.

PubMed

Ahn, Sungsook; Jung, Sung Yong; Lee, Sang Joon

2013-05-17

Recently, there has been significant progress in the field of soft- and hard-X-ray imaging for a wide range of applications, both technically and scientifically, via developments in sources, optics and imaging methodologies. While one community is pursuing extensive applications of available X-ray tools, others are investigating improvements in techniques, including new optics, higher spatial resolutions and brighter compact sources. For increased image quality and more exquisite investigation on characteristic biological phenomena, contrast agents have been employed extensively in imaging technologies. Heavy metal nanoparticles are excellent absorbers of X-rays and can offer excellent improvements in medical diagnosis and X-ray imaging. In this context, the role of gold (Au) is important for advanced X-ray imaging applications. Au has a long-history in a wide range of medical applications and exhibits characteristic interactions with X-rays. Therefore, Au can offer a particular advantage as a tracer and a contrast enhancer in X-ray imaging technologies by sensing the variation in X-ray attenuation in a given sample volume. This review summarizes basic understanding on X-ray imaging from device set-up to technologies. Then this review covers recent studies in the development of X-ray imaging techniques utilizing gold nanoparticles (AuNPs) and their relevant applications, including two- and three-dimensional biological imaging, dynamical processes in a living system, single cell-based imaging and quantitative analysis of circulatory systems and so on. In addition to conventional medical applications, various novel research areas have been developed and are expected to be further developed through AuNP-based X-ray imaging technologies.

Gold nanoclusters as contrast agents for fluorescent and X-ray dual-modality imaging.

PubMed

Zhang, Aili; Tu, Yu; Qin, Songbing; Li, Yan; Zhou, Juying; Chen, Na; Lu, Qiang; Zhang, Bingbo

2012-04-15

Multimodal imaging technique is an alternative approach to improve sensitivity of early cancer diagnosis. In this study, highly fluorescent and strong X-ray absorption coefficient gold nanoclusters (Au NCs) are synthesized as dual-modality imaging contrast agents (CAs) for fluorescent and X-ray dual-modality imaging. The experimental results show that the as-prepared Au NCs are well constructed with ultrasmall sizes, reliable fluorescent emission, high computed tomography (CT) value and fine biocompatibility. In vivo imaging results indicate that the obtained Au NCs are capable of fluorescent and X-ray enhanced imaging. Copyright © 2012 Elsevier Inc. All rights reserved.

A synchrotron radiation microtomography system for the analysis of trabecular bone samples.

PubMed

Salomé, M; Peyrin, F; Cloetens, P; Odet, C; Laval-Jeantet, A M; Baruchel, J; Spanne, P

1999-10-01

X-ray computed microtomography is particularly well suited for studying trabecular bone architecture, which requires three-dimensional (3-D) images with high spatial resolution. For this purpose, we describe a three-dimensional computed microtomography (microCT) system using synchrotron radiation, developed at ESRF. Since synchrotron radiation provides a monochromatic and high photon flux x-ray beam, it allows high resolution and a high signal-to-noise ratio imaging. The principle of the system is based on truly three-dimensional parallel tomographic acquisition. It uses a two-dimensional (2-D) CCD-based detector to record 2-D radiographs of the transmitted beam through the sample under different angles of view. The 3-D tomographic reconstruction, performed by an exact 3-D filtered backprojection algorithm, yields 3-D images with cubic voxels. The spatial resolution of the detector was experimentally measured. For the application to bone investigation, the voxel size was set to 6.65 microm, and the experimental spatial resolution was found to be 11 microm. The reconstructed linear attenuation coefficient was calibrated from hydroxyapatite phantoms. Image processing tools are being developed to extract structural parameters quantifying trabecular bone architecture from the 3-D microCT images. First results on human trabecular bone samples are presented.

Efficient material decomposition method for dual-energy X-ray cargo inspection system

NASA Astrophysics Data System (ADS)

Lee, Donghyeon; Lee, Jiseoc; Min, Jonghwan; Lee, Byungcheol; Lee, Byeongno; Oh, Kyungmin; Kim, Jaehyun; Cho, Seungryong

2018-03-01

Dual-energy X-ray inspection systems are widely used today for it provides X-ray attenuation contrast of the imaged object and also its material information. Material decomposition capability allows a higher detection sensitivity of potential targets including purposely loaded impurities in agricultural product inspections and threats in security scans for example. Dual-energy X-ray transmission data can be transformed into two basis material thickness data, and its transformation accuracy heavily relies on a calibration of material decomposition process. The calibration process in general can be laborious and time consuming. Moreover, a conventional calibration method is often challenged by the nonuniform spectral characteristics of the X-ray beam in the entire field-of-view (FOV). In this work, we developed an efficient material decomposition calibration process for a linear accelerator (LINAC) based high-energy X-ray cargo inspection system. We also proposed a multi-spot calibration method to improve the decomposition performance throughout the entire FOV. Experimental validation of the proposed method has been demonstrated by use of a cargo inspection system that supports 6 MV and 9 MV dual-energy imaging.

A laboratory system for element specific hyperspectral X-ray imaging.

PubMed

Jacques, Simon D M; Egan, Christopher K; Wilson, Matthew D; Veale, Matthew C; Seller, Paul; Cernik, Robert J

2013-02-21

X-ray tomography is a ubiquitous tool used, for example, in medical diagnosis, explosives detection or to check structural integrity of complex engineered components. Conventional tomographic images are formed by measuring many transmitted X-rays and later mathematically reconstructing the object, however the structural and chemical information carried by scattered X-rays of different wavelengths is not utilised in any way. We show how a very simple; laboratory-based; high energy X-ray system can capture these scattered X-rays to deliver 3D images with structural or chemical information in each voxel. This type of imaging can be used to separate and identify chemical species in bulk objects with no special sample preparation. We demonstrate the capability of hyperspectral imaging by examining an electronic device where we can clearly distinguish the atomic composition of the circuit board components in both fluorescence and transmission geometries. We are not only able to obtain attenuation contrast but also to image chemical variations in the object, potentially opening up a very wide range of applications from security to medical diagnostics.

Varying-energy CT imaging method based on EM-TV

NASA Astrophysics Data System (ADS)

Chen, Ping; Han, Yan

2016-11-01

For complicated structural components with wide x-ray attenuation ranges, conventional fixed-energy computed tomography (CT) imaging cannot obtain all the structural information. This limitation results in a shortage of CT information because the effective thickness of the components along the direction of x-ray penetration exceeds the limit of the dynamic range of the x-ray imaging system. To address this problem, a varying-energy x-ray CT imaging method is proposed. In this new method, the tube voltage is adjusted several times with the fixed lesser interval. Next, the fusion of grey consistency and logarithm demodulation are applied to obtain full and lower noise projection with a high dynamic range (HDR). In addition, for the noise suppression problem of the analytical method, EM-TV (expectation maximization-total Jvariation) iteration reconstruction is used. In the process of iteration, the reconstruction result obtained at one x-ray energy is used as the initial condition of the next iteration. An accompanying experiment demonstrates that this EM-TV reconstruction can also extend the dynamic range of x-ray imaging systems and provide a higher reconstruction quality relative to the fusion reconstruction method.

Radiation protection for an intra-operative X-ray device

PubMed Central

Eaton, D J; Gonzalez, R; Duck, S; Keshtgar, M

2011-01-01

Objectives Therapeutic partial breast irradiation can be delivered intra-operatively using the Intrabeam 50 kVp compact X-ray device. Spherical applicators are added to the source to give an isotropic radiation dose. The low energy of this unit leads to rapid attenuation with distance, but dose rates are much greater than for diagnostic procedures. Methods To investigate the shielding requirements for this unit, attenuation measurements were carried out with manufacturer-provided tungsten–rubber sheets, lead, plasterboard and bricks. A prospective environmental dose rate survey was also conducted in the designated theatre. Results As a result of isotropic geometry, the scattered dose around shielding can be 1% of primary and thus often dominates measured dose rates compared with transmission. The absorbed dose rate of the unshielded source at 1 m was 11.6 mGy h−1 but this was reduced by 95% with the shielding sheets. Measured values for the common shielding materials were similar to reference data for the attenuation of a 50 kVp diagnostic X-ray beam. Two lead screens were constructed to shield operators remaining in the theatre and an air vent into a service corridor. A lead apron would also provide suitable attenuation, although a screen allows greater flexibility for treatment operators. With these measures, staff doses were reduced to negligible quantities. Survey measurements taken during patient treatments confirmed no additional measures were required, but the theatre should be a controlled area and access restricted. Conclusion Results from this study and reference data can be used for planning other facilities. PMID:21304003

Study of the solar flares effect on VLF radio signal propagating along NRK-ALG path using LWPC code

NASA Astrophysics Data System (ADS)

Bouderba, Y.; NaitAmor, S.; Tribeche, M.

2016-07-01

The X-ray solar flare emissions penetrate down into the D region of the ionosphere (60-90 km of altitude) and affect the propagating very low frequency (VLF) radio signal. In this paper, we will present the effect of the solar flares on the signal mode composition of the NRK-ALG path during the period from 2007 to 2013. In the Long Wave Propagating Capability (LWPC) code theory, the VLF signal is a sum of discrete modes that propagate to the receiver with different attenuation coefficients. Therefore, an interest is given to the behavior of these coefficients under solar flares. Effectively, from the simulation, we give more explanations about the role of the signal mode composition on the fading displacement since this later is a consequence of the destructive modes interferences. Thus, the sign (positive or negative) of the perturbed signal parameters (amplitude and phase) is found to be depending on the distance between the transmitter and the receiver. Finally, we give the Wait parameters and the electron density variations as a function of solar flares.

Attenuation of encrustation by self-assembled inorganic fullerene-like nanoparticles.

PubMed

Ron, Racheli; Zbaida, David; Kafka, Ilan Z; Rosentsveig, Rita; Leibovitch, Ilan; Tenne, Reshef

2014-05-21

Ureteral stents and urethral catheters are commonly used medical devices for maintaining urinary flow. However, long-term placement (>30 days) of these devices in the urinary tracts is limited by the development of encrustation, a phenomenon that holds a prevalence of 50% within this patient population, resulting in a great deal of morbidity to the patients. Here we report the influence of surface coating of an all-silicone catheter with rhenium-doped fullerene-like molybdenum disulfide (Re:IF-MoS2) nanoparticles on the growth and attachment of in vitro encrustation stones. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) analyses indicated a remarkable attenuation in encrustation occupation on the Re:IF-MoS2-coated catheter surfaces compared to neat catheters. The doped nanoparticles displayed a unique tendency to self-assemble into mosaic-like arrangements, modifying the surface to be encrustation-repellent. The mechanism of encrustation retardation on the surface coated catheters is discussed in some detail. The ramification of these results for the clogging of other body indwelling devices is briefly discussed.

Edge Extraction by an Exponential Function Considering X-ray Transmission Characteristics

NASA Astrophysics Data System (ADS)

Kim, Jong Hyeong; Youp Synn, Sang; Cho, Sung Man; Jong Joo, Won

2011-04-01

3-D radiographic methodology has been into the spotlight for quality inspection of mass product or in-service inspection of aging product. To locate a target object in 3-D space, its characteristic contours such as edge length, edge angle, and vertices are very important. In spite of a simple geometry product, it is very difficult to get clear shape contours from a single radiographic image. The image contains scattering noise at the edges and ambiguity coming from X-Ray absorption within the body. This article suggests a concise method to extract whole edges from a single X-ray image. At the edge point of the object, the intensity of the X-ray decays exponentially as the X-ray penetrates the object. Considering this X-Ray decaying property, edges are extracted by using the least square fitting with the control of Coefficient of Determination.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability

NASA Astrophysics Data System (ADS)

Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.

2016-11-01

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability.

PubMed

Khong, J C; Daisenberger, D; Burca, G; Kockelmann, W; Tremsin, A S; Mi, J

2016-11-16

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe 48 Cr 15 Mo 14 C 15 B 6 Gd 2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications.

Development and evaluation of multi-energy PbO dosimeter for quality assurance of image-guide radiation therapy devices

NASA Astrophysics Data System (ADS)

Kim, Kyo-Tae; Heo, Ye-Ji; Han, Moo-Jae; Oh, Kyung-Min; Lee, Young-Kyu; Kim, Shin-Wook; Park, Sung-Kwang

2017-04-01

In radiation therapy, accurate radiotherapy treatment plan (RTP) reproduction is necessary to optimize the clinical results. Thus, attempts have recently been made to ensure high RTP reproducibility using image-guide radiation therapy (IGRT) technology. However, the clinical use of digital X-ray equipment requires extended quality assurance (QA) for those devices, since the IGRT device quality determines the precision of intensity-modulated radiation therapy. The study described in this paper was focused on developing a multi-energy PbO dosimeter for IGRT device QA. The Schottky-type polycrystalline PbO dosimeter with a Au/PbO/ITO structure was evaluated by comparing its response coincidence, dose linearity, measurement reproducibility, linear attenuation coefficient, and percent depth dose with those of Si diode and standard ionization chamber dosimeters.

Low dose reconstruction algorithm for differential phase contrast imaging.

PubMed

Wang, Zhentian; Huang, Zhifeng; Zhang, Li; Chen, Zhiqiang; Kang, Kejun; Yin, Hongxia; Wang, Zhenchang; Marco, Stampanoni

2011-01-01

Differential phase contrast imaging computed tomography (DPCI-CT) is a novel x-ray inspection method to reconstruct the distribution of refraction index rather than the attenuation coefficient in weakly absorbing samples. In this paper, we propose an iterative reconstruction algorithm for DPCI-CT which benefits from the new compressed sensing theory. We first realize a differential algebraic reconstruction technique (DART) by discretizing the projection process of the differential phase contrast imaging into a linear partial derivative matrix. In this way the compressed sensing reconstruction problem of DPCI reconstruction can be transformed to a resolved problem in the transmission imaging CT. Our algorithm has the potential to reconstruct the refraction index distribution of the sample from highly undersampled projection data. Thus it can significantly reduce the dose and inspection time. The proposed algorithm has been validated by numerical simulations and actual experiments.

Studying the spatial organization of membrane proteins by means of tritium stratigraphy: bacteriorhodopsin in purple membrane.

PubMed

Shishkov, A V; Ksenofontov, A L; Bogacheva, E N; Kordyukova, L V; Badun, G A; Alekseevsky, A V; Tsetlin, V I; Baratova, L A

2002-05-15

The topography of bacteriorhodopsin (bR) in situ was earlier studied by using the tritium bombardment approach [Eur. J. Biochem. 178 (1988) 123]. Now, having the X-ray crystallography data of bR at atom resolution [Proc. Natl. Acad. Sci. 95 (1998) 11673], we estimated the influence of membrane environment (lipid and protein) on tritium incorporation into amino acid residues forming transmembrane helices. We have determined the tritium flux attenuation coefficients for residues 10-29 of helix A. They turned out to be low (0.04+/-0.02 A(-1)) for residues adjacent to the lipid matrix, and almost fourfold higher (0.15+/-0.05 A(-1)) for those oriented to the neighboring transmembrane helices. We believe that tritium incorporation data could help modeling transmembrane segment arrangement in the membrane.

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

PubMed Central

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

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

Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P., E-mail: mpvaldivia@pha.jhu.edu; Stutman, D.; Stoeckl, C.

2016-11-15

Talbot-Lau X-ray deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping were demonstrated for 25–29 J, 8–30 ps laser pulses using copper foil targets. Moiré pattern formation and grating survival were also observed using a copper x-pinch driven at 400 kA, ∼1 kA/ns. These results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

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

PubMed Central

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

2011-01-01

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

Studies on absorption coefficient near edge of multi elements

NASA Astrophysics Data System (ADS)

Eisa, M. H.; Shen, H.; Yao, H. Y.; Mi, Y.; Zhou, Z. Y.; Hu, T. D.; Xie, Y. N.

2005-12-01

X-ray absorption near edge structure (XANES) was used to study the near edge mass-absorption coefficients of seven elements, such as, Ti, V, Fe, Co, Ni, Cu and Zn. It is well known that, on the near edge absorption of element, when incident X-ray a few eV change can make the absorption coefficient an order magnitude alteration. So that, there are only a few points mass-absorption coefficient at the near edge absorption and that always average value in published table. Our results showed a wide range of data, the total measured data of mass-absorption coefficient of the seven elements was about 505. The investigation confirmed that XANES is useful technique for multi-element absorption coefficient measurement. Details of experimental methods and results are given and discussed. The experimental work has been performed at Beijing Synchrotron Radiation Facility. The measured values were compared with the published data. Good agreement between experimental results and published data is obtained.

Correction factors for on-line microprobe analysis of multielement alloy systems

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.; Brewer, W. D.

1977-01-01

An on-line correction technique was developed for the conversion of electron probe X-ray intensities into concentrations of emitting elements. This technique consisted of off-line calculation and representation of binary interaction data which were read into an on-line minicomputer to calculate variable correction coefficients. These coefficients were used to correct the X-ray data without significantly increasing computer core requirements. The binary interaction data were obtained by running Colby's MAGIC 4 program in the reverse mode. The data for each binary interaction were represented by polynomial coefficients obtained by least-squares fitting a third-order polynomial. Polynomial coefficients were generated for most of the common binary interactions at different accelerating potentials and are included. Results are presented for the analyses of several alloy standards to demonstrate the applicability of this correction procedure.

The diagnostic X-ray protection characteristics of Panelcrete, Aquapanel, Betopan and Gypsoplak Superboard.

PubMed

Tsalafoutas, I A; Yakoumakis, E; Sandilos, P; Vlahos, L; Proukakis, C

2001-04-01

Panelcrete, Aquapanel and Betopan are cement-based building materials with uses similar to those of gypsum wallboard, whose properties as a diagnostic X-ray shielding material have been extensively studied. The X-ray attenuation characteristics of these cement-based boards as well as those of a gypsum wallboard, Gypsoplak Superboard, are investigated for broad beam geometry conditions and for tube potentials of 50 kVp, 70 kVp, 100 kVp, 125 kVp and 140 kVp. Comparisons between these materials as well as with published data for gypsum wallboard are made. An example of their use as secondary barriers is given. Furthermore, it is confirmed that when building materials are considered for diagnostic X-ray shielding, calculations based on data for similar materials and corrected for density differences can be used only as an approximation.

Quantifying Electromigration Processes in Sn-0.7Cu Solder with Lab-Scale X-Ray Computed Micro-Tomography

NASA Astrophysics Data System (ADS)

Mertens, James Charles Edwin

For decades, microelectronics manufacturing has been concerned with failures related to electromigration phenomena in conductors experiencing high current densities. The influence of interconnect microstructure on device failures related to electromigration in BGA and flip chip solder interconnects has become a significant interest with reduced individual solder interconnect volumes. A survey indicates that x-ray computed micro-tomography (muXCT) is an emerging, novel means for characterizing the microstructures' role in governing electromigration failures. This work details the design and construction of a lab-scale muXCT system to characterize electromigration in the Sn-0.7Cu lead-free solder system by leveraging in situ imaging. In order to enhance the attenuation contrast observed in multi-phase material systems, a modeling approach has been developed to predict settings for the controllable imaging parameters which yield relatively high detection rates over the range of x-ray energies for which maximum attenuation contrast is expected in the polychromatic x-ray imaging system. In order to develop this predictive tool, a model has been constructed for the Bremsstrahlung spectrum of an x-ray tube, and calculations for the detector's efficiency over the relevant range of x-ray energies have been made, and the product of emitted and detected spectra has been used to calculate the effective x-ray imaging spectrum. An approach has also been established for filtering 'zinger' noise in x-ray radiographs, which has proven problematic at high x-ray energies used for solder imaging. The performance of this filter has been compared with a known existing method and the results indicate a significant increase in the accuracy of zinger filtered radiographs. The obtained results indicate the conception of a powerful means for the study of failure causing processes in solder systems used as interconnects in microelectronic packaging devices. These results include the volumetric quantification of parameters which are indicative of both electromigration tolerance of solders and the dominant mechanisms for atomic migration in response to current stressing. This work is aimed to further the community's understanding of failure-causing electromigration processes in industrially relevant material systems for microelectronic interconnect applications and to advance the capability of available characterization techniques for their interrogation.

Improving gross count gamma-ray logging in uranium mining with the NGRS probe

NASA Astrophysics Data System (ADS)

Carasco, C.; Pérot, B.; Ma, J.-L.; Toubon, H.; Dubille-Auchère, A.

2018-01-01

AREVA Mines and the Nuclear Measurement Laboratory of CEA Cadarache are collaborating to improve the sensitivity and precision of uranium concentration measurement by means of gamma ray logging. The determination of uranium concentration in boreholes is performed with the Natural Gamma Ray Sonde (NGRS) based on a NaI(Tl) scintillation detector. The total gamma count rate is converted into uranium concentration using a calibration coefficient measured in concrete blocks with known uranium concentration in the AREVA Mines calibration facility located in Bessines, France. Until now, to take into account gamma attenuation in a variety of boreholes diameters, tubing materials, diameters and thicknesses, filling fluid densities and compositions, a semi-empirical formula was used to correct the calibration coefficient measured in Bessines facility. In this work, we propose to use Monte Carlo simulations to improve gamma attenuation corrections. To this purpose, the NGRS probe and the calibration measurements in the standard concrete blocks have been modeled with MCNP computer code. The calibration coefficient determined by simulation, 5.3 s-1.ppmU-1 ± 10%, is in good agreement with the one measured in Bessines, 5.2 s-1.ppmU-1. Based on the validated MCNP model, several parametric studies have been performed. For instance, the rock density and chemical composition proved to have a limited impact on the calibration coefficient. However, gamma self-absorption in uranium leads to a nonlinear relationship between count rate and uranium concentration beyond approximately 1% of uranium weight fraction, the underestimation of the uranium content reaching more than a factor 2.5 for a 50 % uranium weight fraction. Next steps will concern parametric studies with different tubing materials, diameters and thicknesses, as well as different borehole filling fluids representative of real measurement conditions.

Biological soft X-ray tomography on beamline 2.1 at the Advanced Light Source

PubMed Central

Le Gros, Mark A.; McDermott, Gerry; Cinquin, Bertrand P.; Smith, Elizabeth A.; Do, Myan; Chao, Weilun L.; Naulleau, Patrick P.; Larabell, Carolyn A.

2014-01-01

Beamline 2.1 (XM-2) is a transmission soft X-ray microscope in sector 2 of the Advanced Light Source at Lawrence Berkeley National Laboratory. XM-2 was designed, built and is now operated by the National Center for X-ray Tomography as a National Institutes of Health Biomedical Technology Research Resource. XM-2 is equipped with a cryogenic rotation stage to enable tomographic data collection from cryo-preserved cells, including large mammalian cells. During data collection the specimen is illuminated with ‘water window’ X-rays (284–543 eV). Illuminating photons are attenuated an order of magnitude more strongly by biomolecules than by water. Consequently, differences in molecular composition generate quantitative contrast in images of the specimen. Soft X-ray tomography is an information-rich three-dimensional imaging method that can be applied either as a standalone technique or as a component modality in correlative imaging studies. PMID:25343808

Attenuation of encrustation by self-assembled inorganic fullerene-like nanoparticles

NASA Astrophysics Data System (ADS)

Ron, Racheli; Zbaida, David; Kafka, Ilan Z.; Rosentsveig, Rita; Leibovitch, Ilan; Tenne, Reshef

2014-04-01

Ureteral stents and urethral catheters are commonly used medical devices for maintaining urinary flow. However, long-term placement (>30 days) of these devices in the urinary tracts is limited by the development of encrustation, a phenomenon that holds a prevalence of 50% within this patient population, resulting in a great deal of morbidity to the patients. Here we report the influence of surface coating of an all-silicone catheter with rhenium-doped fullerene-like molybdenum disulfide (Re:IF-MoS2) nanoparticles on the growth and attachment of in vitro encrustation stones. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) analyses indicated a remarkable attenuation in encrustation occupation on the Re:IF-MoS2-coated catheter surfaces compared to neat catheters. The doped nanoparticles displayed a unique tendency to self-assemble into mosaic-like arrangements, modifying the surface to be encrustation-repellent. The mechanism of encrustation retardation on the surface coated catheters is discussed in some detail. The ramification of these results for the clogging of other body indwelling devices is briefly discussed.Ureteral stents and urethral catheters are commonly used medical devices for maintaining urinary flow. However, long-term placement (>30 days) of these devices in the urinary tracts is limited by the development of encrustation, a phenomenon that holds a prevalence of 50% within this patient population, resulting in a great deal of morbidity to the patients. Here we report the influence of surface coating of an all-silicone catheter with rhenium-doped fullerene-like molybdenum disulfide (Re:IF-MoS2) nanoparticles on the growth and attachment of in vitro encrustation stones. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) analyses indicated a remarkable attenuation in encrustation occupation on the Re:IF-MoS2-coated catheter surfaces compared to neat catheters. The doped nanoparticles displayed a unique tendency to self-assemble into mosaic-like arrangements, modifying the surface to be encrustation-repellent. The mechanism of encrustation retardation on the surface coated catheters is discussed in some detail. The ramification of these results for the clogging of other body indwelling devices is briefly discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06231g

Reconstruction method for fluorescent X-ray computed tomography by least-squares method using singular value decomposition

NASA Astrophysics Data System (ADS)

Yuasa, T.; Akiba, M.; Takeda, T.; Kazama, M.; Hoshino, A.; Watanabe, Y.; Hyodo, K.; Dilmanian, F. A.; Akatsuka, T.; Itai, Y.

1997-02-01

We describe a new attenuation correction method for fluorescent X-ray computed tomography (FXCT) applied to image nonradioactive contrast materials in vivo. The principle of the FXCT imaging is that of computed tomography of the first generation. Using monochromatized synchrotron radiation from the BLNE-5A bending-magnet beam line of Tristan Accumulation Ring in KEK, Japan, we studied phantoms with the FXCT method, and we succeeded in delineating a 4-mm-diameter channel filled with a 500 /spl mu/g I/ml iodine solution in a 20-mm-diameter acrylic cylindrical phantom. However, to detect smaller iodine concentrations, attenuation correction is needed. We present a correction method based on the equation representing the measurement process. The discretized equation system is solved by the least-squares method using the singular value decomposition. The attenuation correction method is applied to the projections by the Monte Carlo simulation and the experiment to confirm its effectiveness.

THE ATTENUATION OF LATENT LESIONS CAUSED BY THE ACTION OF X RAYS ON RHIZOMES OF TOPINAMBOUR (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jonard, R.

1962-11-26

Tests on in vitro cultures of isolated rhizome fragments of Topinambour after x irradiation show that the changes caused by the irradiation can regress if the cultivation of the tissues is made several weeks after irradiation. (trauth)

High-temperature thermoelectric properties of the double-perovskite ruthenium oxide (Sr1-xLax)2ErRuO6

NASA Astrophysics Data System (ADS)

Takahashi, Ryohei; Okazaki, Ryuji; Yasui, Yukio; Terasaki, Ichiro; Sudayama, Takaaki; Nakao, Hironori; Yamasaki, Yuichi; Okamoto, Jun; Murakami, Youichi; Kitajima, Yoshinori

2012-10-01

We have prepared polycrystalline samples of (Sr1-xLax)2ErRuO6 and (Sr1-xLax)2YRuO6, and have measured the resistivity, Seebeck coefficient, thermal conductivity, susceptibility, and x-ray absorption in order to evaluate the electronic states and thermoelectric properties of the doped double-perovskite ruthenates. We have observed a large Seebeck coefficient of -160 μV/K and a low thermal conductivity of 7 mW/cmK for x = 0.1 at 800 K in air. These two values are suitable for efficient oxide thermoelectrics, although the resistivity is still as high as 1 Ω cm. From the susceptibility and x-ray absorption measurements, we find that the doped electrons exist as Ru4+ in the low spin state. On the basis of the measured results, the electronic states and the conduction mechanism are discussed.

Tomographic Neutron Imaging using SIRT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregor, Jens; FINNEY, Charles E A; Toops, Todd J

2013-01-01

Neutron imaging is complementary to x-ray imaging in that materials such as water and plastic are highly attenuating while material such as metal is nearly transparent. We showcase tomographic imaging of a diesel particulate filter. Reconstruction is done using a modified version of SIRT called PSIRT. We expand on previous work and introduce Tikhonov regularization. We show that near-optimal relaxation can still be achieved. The algorithmic ideas apply to cone beam x-ray CT and other inverse problems.

Ultrasonic attenuation measurements determine onset, degree, and completion of recrystallization

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1988-01-01

Ultrasonic attenuation was measured for cold worked Nickel 200 samples annealed at increasing temperatures. Localized dislocation density variations, crystalline order and volume percent of recrystallized phase were determined over the anneal temperature range using transmission electron microscopy, X-ray diffraction, and metallurgy. The exponent of the frequency dependence of the attenuation was found to be a key variable relating ultrasonic attenuation to the thermal kinetics of the recrystallization process. Identification of this key variable allows for the ultrasonic determination of onset, degree, and completion of recrystallization.

Experimental validation of a multi-energy x-ray adapted scatter separation method

NASA Astrophysics Data System (ADS)

Sossin, A.; Rebuffel, V.; Tabary, J.; Létang, J. M.; Freud, N.; Verger, L.

2016-12-01

Both in radiography and computed tomography (CT), recently emerged energy-resolved x-ray photon counting detectors enable the identification and quantification of individual materials comprising the inspected object. However, the approaches used for these operations require highly accurate x-ray images. The accuracy of the images is severely compromised by the presence of scattered radiation, which leads to a loss of spatial contrast and, more importantly, a bias in radiographic material imaging and artefacts in CT. The aim of the present study was to experimentally evaluate a recently introduced partial attenuation spectral scatter separation approach (PASSSA) adapted for multi-energy imaging. For this purpose, a prototype x-ray system was used. Several radiographic acquisitions of an anthropomorphic thorax phantom were performed. Reference primary images were obtained via the beam-stop (BS) approach. The attenuation images acquired from PASSSA-corrected data showed a substantial increase in local contrast and internal structure contour visibility when compared to uncorrected images. A substantial reduction of scatter induced bias was also achieved. Quantitatively, the developed method proved to be in relatively good agreement with the BS data. The application of the proposed scatter correction technique lowered the initial normalized root-mean-square error (NRMSE) of 45% between the uncorrected total and the reference primary spectral images by a factor of 9, thus reducing it to around 5%.

High-dynamic-range coherent diffractive imaging: ptychography using the mixed-mode pixel array detector

PubMed Central

Giewekemeyer, Klaus; Philipp, Hugh T.; Wilke, Robin N.; Aquila, Andrew; Osterhoff, Markus; Tate, Mark W.; Shanks, Katherine S.; Zozulya, Alexey V.; Salditt, Tim; Gruner, Sol M.; Mancuso, Adrian P.

2014-01-01

Coherent (X-ray) diffractive imaging (CDI) is an increasingly popular form of X-ray microscopy, mainly due to its potential to produce high-resolution images and the lack of an objective lens between the sample and its corresponding imaging detector. One challenge, however, is that very high dynamic range diffraction data must be collected to produce both quantitative and high-resolution images. In this work, hard X-ray ptychographic coherent diffractive imaging has been performed at the P10 beamline of the PETRA III synchrotron to demonstrate the potential of a very wide dynamic range imaging X-ray detector (the Mixed-Mode Pixel Array Detector, or MM-PAD). The detector is capable of single photon detection, detecting fluxes exceeding 1 × 108 8-keV photons pixel−1 s−1, and framing at 1 kHz. A ptychographic reconstruction was performed using a peak focal intensity on the order of 1 × 1010 photons µm−2 s−1 within an area of approximately 325 nm × 603 nm. This was done without need of a beam stop and with a very modest attenuation, while ‘still’ images of the empty beam far-field intensity were recorded without any attenuation. The treatment of the detector frames and CDI methodology for reconstruction of non-sensitive detector regions, partially also extending the active detector area, are described. PMID:25178008

High-dynamic-range coherent diffractive imaging: ptychography using the mixed-mode pixel array detector.

PubMed

Giewekemeyer, Klaus; Philipp, Hugh T; Wilke, Robin N; Aquila, Andrew; Osterhoff, Markus; Tate, Mark W; Shanks, Katherine S; Zozulya, Alexey V; Salditt, Tim; Gruner, Sol M; Mancuso, Adrian P

2014-09-01

Coherent (X-ray) diffractive imaging (CDI) is an increasingly popular form of X-ray microscopy, mainly due to its potential to produce high-resolution images and the lack of an objective lens between the sample and its corresponding imaging detector. One challenge, however, is that very high dynamic range diffraction data must be collected to produce both quantitative and high-resolution images. In this work, hard X-ray ptychographic coherent diffractive imaging has been performed at the P10 beamline of the PETRA III synchrotron to demonstrate the potential of a very wide dynamic range imaging X-ray detector (the Mixed-Mode Pixel Array Detector, or MM-PAD). The detector is capable of single photon detection, detecting fluxes exceeding 1 × 10(8) 8-keV photons pixel(-1) s(-1), and framing at 1 kHz. A ptychographic reconstruction was performed using a peak focal intensity on the order of 1 × 10(10) photons µm(-2) s(-1) within an area of approximately 325 nm × 603 nm. This was done without need of a beam stop and with a very modest attenuation, while `still' images of the empty beam far-field intensity were recorded without any attenuation. The treatment of the detector frames and CDI methodology for reconstruction of non-sensitive detector regions, partially also extending the active detector area, are described.

White matter segmentation by estimating tissue optical attenuation from volumetric OCT massive histology of whole rodent brains

NASA Astrophysics Data System (ADS)

Lefebvre, Joël.; Castonguay, Alexandre; Lesage, Frédéric

2017-02-01

A whole rodent brain was imaged using an automated massive histology setup and an Optical Coherence Tomography (OCT) microscope. Thousands of OCT volumetric tiles were acquired, each covering a size of about 2.5x2.5x0.8 mm3 with a sampling resolution of 4.9x4.9x6.5 microns. This paper shows the techniques for reconstruction, attenuation compensation and segmentation of the sliced brains. The tile positions within the mosaic were evaluated using a displacement model of the motorized stage and pairwise coregistration. Volume blending was then performed by solving the 3D Laplace equation, and consecutive slices were assembled using the cross-correlation of their 2D image gradient. This reconstruction algorithm resulted in a 3D map of optical reflectivity for the whole brain at micrometric resolution. OCT tissue slices were then used to estimate the local attenuation coefficient based on a single scattering photon model. The attenuation map obtained exhibits a high contrast for all white matter fibres, regardless of their orientation. The tissue optical attenuation from the intrinsic OCT reflectivity contributes to better white matter tissue segmentation. The combined 3D maps of reflectivity and attenuation is a step toward the study of white matter at a microscopic scale for the whole brain in small animals.

Borman effect in resonant diffraction of X-rays

NASA Astrophysics Data System (ADS)

Oreshko, A. P.

2013-08-01

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.

Development of a nuclear technique for monitoring water levels in pressurized vehicles

NASA Technical Reports Server (NTRS)

Singh, J. J.; Davis, W. T.; Mall, G. H.

1983-01-01

A new technique for monitoring water levels in pressurized stainless steel cylinders was developed. It is based on differences in attenuation coefficients of water and air for Cs137 (662 keV) gamma rays. Experimentally observed gamma ray counting rates with and without water in model reservoir cylinder were compared with corresponding calculated values for two different gamma ray detection theshold energies. Calculated values include the effects of multiple scattering and attendant gamma ray energy reductions. The agreement between the measured and calculated values is reasonably good. Computer programs for calculating angular and spectral distributions of scattered radition in various media are included.

Image-based spectral distortion correction for photon-counting x-ray detectors

PubMed Central

Ding, Huanjun; Molloi, Sabee

2012-01-01

Purpose: To investigate the feasibility of using an image-based method to correct for distortions induced by various artifacts in the x-ray spectrum recorded with photon-counting detectors for their application in breast computed tomography (CT). Methods: The polyenergetic incident spectrum was simulated with the tungsten anode spectral model using the interpolating polynomials (TASMIP) code and carefully calibrated to match the x-ray tube in this study. Experiments were performed on a Cadmium-Zinc-Telluride (CZT) photon-counting detector with five energy thresholds. Energy bins were adjusted to evenly distribute the recorded counts above the noise floor. BR12 phantoms of various thicknesses were used for calibration. A nonlinear function was selected to fit the count correlation between the simulated and the measured spectra in the calibration process. To evaluate the proposed spectral distortion correction method, an empirical fitting derived from the calibration process was applied on the raw images recorded for polymethyl methacrylate (PMMA) phantoms of 8.7, 48.8, and 100.0 mm. Both the corrected counts and the effective attenuation coefficient were compared to the simulated values for each of the five energy bins. The feasibility of applying the proposed method to quantitative material decomposition was tested using a dual-energy imaging technique with a three-material phantom that consisted of water, lipid, and protein. The performance of the spectral distortion correction method was quantified using the relative root-mean-square (RMS) error with respect to the expected values from simulations or areal analysis of the decomposition phantom. Results: The implementation of the proposed method reduced the relative RMS error of the output counts in the five energy bins with respect to the simulated incident counts from 23.0%, 33.0%, and 54.0% to 1.2%, 1.8%, and 7.7% for 8.7, 48.8, and 100.0 mm PMMA phantoms, respectively. The accuracy of the effective attenuation coefficient of PMMA estimate was also improved with the proposed spectral distortion correction. Finally, the relative RMS error of water, lipid, and protein decompositions in dual-energy imaging was significantly reduced from 53.4% to 6.8% after correction was applied. Conclusions: The study demonstrated that dramatic distortions in the recorded raw image yielded from a photon-counting detector could be expected, which presents great challenges for applying the quantitative material decomposition method in spectral CT. The proposed semi-empirical correction method can effectively reduce these errors caused by various artifacts, including pulse pileup and charge sharing effects. Furthermore, rather than detector-specific simulation packages, the method requires a relatively simple calibration process and knowledge about the incident spectrum. Therefore, it may be used as a generalized procedure for the spectral distortion correction of different photon-counting detectors in clinical breast CT systems. PMID:22482608

Modeling Contamination Migration on the Chandra X-Ray Observatory - IV

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil William; Plucinsky, Paul P.; Marshall, Herman L.; Bogdan, Akos; Grant, Catherine E.; Tennant, Allyn F.; Dahmer, Matthew

2017-01-01

During its first 18 years of operation, the cold (about -60degC) optical blocking filters of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination, which attenuates low-energy x rays. Over the past several years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity, in part to evaluate potential bake-out scenarios intended to reduce the level of contamination. This paper, the fourth on this topic, reports the results of recent contamination-migration simulations and their relevance to a decision whether to bake-out the ACIS instrument.

Modeling contamination migration on the Chandra X-ray Observatory IV

NASA Astrophysics Data System (ADS)

O'Dell, Stephen L.; Swartz, Douglas A.; Tice, Neil W.; Plucinsky, Paul P.; Marshall, Herman L.; Bogdan, Akos; Grant, Catherine E.; Tennant, Allyn F.; Dahmer, Matthew

2017-08-01

During its first 18 years of operation, the cold (about -60°C) optical blocking filters of the Advanced CCD Imaging Spectrometer (ACIS), aboard the Chandra X-ray Observatory, has accumulated a growing layer of molecular contamination, which attenuates low-energy x rays. Over the past several years, the accumulation rate, spatial distribution, and composition have changed. This evolution has motivated further analysis of contamination migration within and near the ACIS cavity, in part to evaluate potential bake-out scenarios intended to reduce the level of contamination. This paper, the fourth on this topic, reports the results of recent contamination-migration simulations and their relevance to a decision whether to bake-out the ACIS instrument.

Using Combined X-ray Computed Tomography and Acoustic Resonance to Understand Supercritical CO2 Behavior in Fractured Sandstone

NASA Astrophysics Data System (ADS)

Kneafsey, T. J.; Nakagawa, S.

2015-12-01

Distribution of supercritical (sc) CO2 has a large impact on its flow behavior as well as on the properties of seismic waves used for monitoring. Simultaneous imaging of scCO2 distribution in a rock core using X-ray computed tomography (CT) and measurements of seismic waves in the laboratory can help understand how the distribution evolves as scCO2 invades through rock, and the resulting seismic signatures. To this end, we performed a series of laboratory scCO2 core-flood experiments in intact and fractured anisotropic Carbon Tan sandstone samples. In these experiments, we monitored changes in the CO2 saturation distribution and sonic-frequency acoustic resonances (yielding both seismic velocity and attenuation) over the course of the floods. A short-core resonant bar test system (Split-Hopkinson Resonant Bar Apparatus) custom fit into a long X-ray transparent pressure vessel was used for the seismic measurements, and a modified General Electric medical CT scanner was used to acquire X-ray CT data from which scCO2 saturation distributions were determined. The focus of the experiments was on the impact of single fractures on the scCO2 distribution and the seismic properties. For this reason, we examined several cases including 1. intact, 2. a closely mated fracture along the core axis, 3. a sheared fracture along the core axis (both vertical and horizontal for examining the buoyancy effect), and 4. a sheared fracture perpendicular to the core axis. For the intact and closely mated fractured cores, Young's modulus declined with increasing CO2 saturation, and attenuation increased up to about 15% CO2 saturation after which attenuation declined. For cores having wide axial fractures, the Young's modulus was lower than for the intact and closely mated cases, however did not change much with CO2 pore saturation. Much lower CO2 pore saturations were achieved in these cases. Attenuation increased more rapidly however than for the intact sample. For the core-perpendicular fracture, the Young's modulus decreased quickly with increasing CO2 saturation. Attenuation increased with increasing CO2 saturation until the CO2 front reached the fracture, after which it fell to below that for the brine-saturated case, increasing again as the CO2 invaded the downstream core region.

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

NASA Astrophysics Data System (ADS)

Liu, Y.; Andrews, J. C.; Meirer, F.; Mehta, A.; Gil, S. Carrasco; Sciau, P.; Mester, Z.; Pianetta, P.

2011-09-01

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).

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

ERIC Educational Resources Information Center

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

2007-01-01

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…

Gamma-ray shielding effect of Gd3+ doped lead barium borate glasses

NASA Astrophysics Data System (ADS)

Kummathi, Harshitha; Naveen Kumar, P.; Vedavathi T., C.; Abhiram, J.; Rajaramakrishna, R.

2018-05-01

The glasses of the batch xPbO: 10BaO: (90-x)B2O3: 0.2Gd2O3 (x = 40,45,50 mol %) were prepared by melt-quench technique. The work emphasizes on gamma ray shielding effect on doped lead glasses. The role of Boron is significant as it acts as better neutron attenuator as compared with any other materials, as the thermal neutron cross-sections are high for Gadolinium, 0.2 mol% is chosen as the optimum concentration for this matrix, as higher the concentration may lead to further increase as it produces secondary γ rays due to inelastic neutron scattering. Shielding effects were studied using Sodium Iodide (NaI) - Scintillation Gamma ray spectrometer. It was found that at higher concentration of lead oxide (PbO) in the matrix, higher the attenuation which can be co-related with density. Infra-red (I.R.) spectra reveals that the conversion of Lose triangles to tight tetrahedral structure results in enhancement of shielding properties. The Differential Scanning Calorimeter (D.S.C.) study also reveals that the increase in glass forming range increases the stability which in-turn results in inter-conversion of BO3 to BO4 units such that the density of glass increases with increase in PbO content, resulting in much stable and efficient gamma ray shielding glasses.

Imaging and characterizing cells using tomography

PubMed Central

Do, Myan; Isaacson, Samuel A.; McDermott, Gerry; Le Gros, Mark A.; Larabell, Carolyn A.

2015-01-01

We can learn much about cell function by imaging and quantifying sub-cellular structures, especially if this is done non-destructively without altering said structures. Soft x-ray tomography (SXT) is a high-resolution imaging technique for visualizing cells and their interior structure in 3D. A tomogram of the cell, reconstructed from a series of 2D projection images, can be easily segmented and analyzed. SXT has a very high specimen throughput compared to other high-resolution structure imaging modalities; for example, tomographic data for reconstructing an entire eukaryotic cell is acquired in a matter of minutes. SXT visualizes cells without the need for chemical fixation, dehydration, or staining of the specimen. As a result, the SXT reconstructions are close representations of cells in their native state. SXT is applicable to most cell types. The deep penetration of soft x-rays allows cells, even mammalian cells, to be imaged without being sectioned. Image contrast in SXT is generated by the differential attenuation soft x-ray illumination as it passes through the specimen. Accordingly, each voxel in the tomographic reconstruction has a measured linear absorption coefficient (LAC) value. LAC values are quantitative and give rise to each sub-cellular component having a characteristic LAC profile, allowing organelles to be identified and segmented from the milieu of other cell contents. In this chapter, we describe the fundamentals of SXT imaging and how this technique can answer real world questions in the study of the nucleus. We also describe the development of correlative methods for the localization of specific molecules in a SXT reconstruction. The combination of fluorescence and SXT data acquired from the same specimen produces composite 3D images, rich with detailed information on the inner workings of cells. PMID:25602704

X-ray photoelectron spectroscopy and friction studies of nickel-zinc and manganese-zinc ferrites in contact with metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1983-01-01

X-ray photoelectron spectroscopy analysis and sliding friction experiments were conducted with hot-pressed, polycrystalline Ni-Zn and Mn-Zn ferrites in sliding contact with various transition metals at room temperature in a vacuum of 30 nPa. The results indicate that the coefficients of friction for Ni-Zn and Mn-Zn ferrites in contact with metals are related to the relative chemical activity in these metals: the more active the metal, the higher is the coefficient of friction. The coefficients of friction for the ferrites correlate with the free energy of formation of the lowest metal oxide. The interfacial bond can be regarded as a chemical bond between the metal atoms and the oxygen anions in the ferrite surfaces. The adsorption of oxygen on clean metal and ferrite surfaces increases the coefficients of friction for the Ni-Zn and Mn-Zn ferrite-metal interfaces.

Performance summary on a high power dense plasma focus x-ray lithography point source producing 70 nm line features in AlGaAs microcircuits

NASA Astrophysics Data System (ADS)

Petr, Rodney; Bykanov, Alexander; Freshman, Jay; Reilly, Dennis; Mangano, Joseph; Roche, Maureen; Dickenson, Jason; Burte, Mitchell; Heaton, John

2004-08-01

A high average power dense plasma focus (DPF), x-ray point source has been used to produce ˜70 nm line features in AlGaAs-based monolithic millimeter-wave integrated circuits (MMICs). The DPF source has produced up to 12 J per pulse of x-ray energy into 4π steradians at ˜1 keV effective wavelength in ˜2 Torr neon at pulse repetition rates up to 60 Hz, with an effective x-ray yield efficiency of ˜0.8%. Plasma temperature and electron concentration are estimated from the x-ray spectrum to be ˜170 eV and ˜5.1019 cm-3, respectively. The x-ray point source utilizes solid-state pulse power technology to extend the operating lifetime of electrodes and insulators in the DPF discharge. By eliminating current reversals in the DPF head, an anode electrode has demonstrated a lifetime of more than 5 million shots. The x-ray point source has also been operated continuously for 8 h run times at 27 Hz average pulse recurrent frequency. Measurements of shock waves produced by the plasma discharge indicate that overpressure pulses must be attenuated before a collimator can be integrated with the DPF point source.

Method and apparatus for measuring enrichment of UF6

DOEpatents

Hill, Thomas Roy [Santa Fe, NM; Ianakiev, Kiril Dimitrov [Los Alamos, NM

2011-06-07

A system and method are disclosed for determining the enrichment of .sup.235U in Uranium Hexafluoride (UF6) utilizing synthesized X-rays which are directed at a container test zone containing a sample of UF6. A detector placed behind the container test zone then detects and counts the X-rays which pass through the container and the UF6. In order to determine the portion of the attenuation due to the UF6 gas alone, this count rate may then be compared to a calibration count rate of X-rays passing through a calibration test zone which contains a vacuum, the test zone having experienced substantially similar environmental conditions as the actual test zone. Alternatively, X-rays of two differing energy levels may be alternately directed at the container, where either the container or the UF6 has a high sensitivity to the difference in the energy levels, and the other having a low sensitivity.

Improvement of the radiographic method for measurement of effective energy of pulsed X-ray emission from a PF device for different anode's insert materials.

PubMed

Miremad, Seyed Milad; Shirani, Babak

2018-06-01

In this paper, effective energy of pulsed X-Ray emitted from a Mather-type plasma focus device in stored energy of 2.5 kJ with six different anode's insert materials was measured using radiographic method with attenuation filters. Since intensity and energy of X-ray beam were considerably changed with changing the insert material, the method was improved by using different filters simultaneously in all the experiments and selection of the best filter in each experiment according to the appropriate criteria. Effective energy of pulsed X-ray beam was measured 16, 28, 50, 51, 34 and 44 keV when aluminum, copper, zinc, tin, tungsten and lead were used as insert materials, and aluminum, copper, silver, silver, copper and lead were used as filters, respectively. Copyright © 2018 Elsevier Ltd. All rights reserved.

X-ray phase-contrast imaging at 100 keV on a conventional source

PubMed Central

Thüring, T.; Abis, M.; Wang, Z.; David, C.; Stampanoni, M.

2014-01-01

X-ray grating interferometry is a promising imaging technique sensitive to attenuation, refraction and scattering of the radiation. Applications of this technique in the energy range between 80 and 150 keV pose severe technical challenges, and are still mostly unexplored. Phase-contrast X-ray imaging at such high energies is of relevant scientific and industrial interest, in particular for the investigation of strongly absorbing or thick materials as well as for medical imaging. Here we show the successful implementation of a Talbot-Lau interferometer operated at 100 keV using a conventional X-ray tube and a compact geometry, with a total length of 54 cm. We present the edge-on illumination of the gratings in order to overcome the current fabrication limits. Finally, the curved structures match the beam divergence and allow a large field of view on a short and efficient setup. PMID:24903579

Compact double-bunch x-ray free electron lasers for fresh bunch self-seeding and harmonic lasing

DOE PAGES

Emma, C.; Feng, Y.; Nguyen, D. C.; ...

2017-03-03

This study presents a novel method to improve the longitudinal coherence, efficiency and maximum photon energy of x-ray free electron lasers (XFELs). The method is equivalent to having two separate concatenated XFELs. The first uses one bunch of electrons to reach the saturation regime, generating a high power self-amplified spontaneous emission x-ray pulse at the fundamental and third harmonic. The x-ray pulse is filtered through an attenuator/monochromator and seeds a different electron bunch in the second FEL, using the fundamental and/or third harmonic as an input signal. In our method we combine the two XFELs operating with two bunches, separatedmore » by one or more rf cycles, in the same linear accelerator. We discuss the advantages and applications of the proposed system for present and future XFELs.« less

Quantitative CT characterization of pediatric lung development using routine clinical imaging

PubMed Central

Stein, Jill M.; Walkup, Laura L.; Brody, Alan S.; Fleck, Robert J.

2016-01-01

Background The use of quantitative CT analysis in children is limited by lack of normal values of lung parenchymal attenuation. These characteristics are important because normal lung development yields significant parenchymal attenuation changes as children age. Objective To perform quantitative characterization of normal pediatric lung parenchymal X-ray CT attenuation under routine clinical conditions in order to establish a baseline comparison to that seen in pathological lung conditions. Materials and methods We conducted a retrospective query of normal CT chest examinations in children ages 0–7 years from 2004 to 2014 using standard clinical protocol. During these examinations semi-automated lung parenchymal segmentation was performed to measure lung volume and mean lung attenuation. Results We analyzed 42 CT examinations in 39 children, ages 3 days to 83 months (mean ± standard deviation [SD] = 42±27 months). Lung volume ranged 0.10–1.72 liters (L). Mean lung attenuation was much higher in children younger than 12 months, with values as high as −380 Hounsfield units (HU) in neonates (lung volume 0.10 L). Lung volume decreased to approximately −650 HU by age 2 years (lung volume 0.47 L), with subsequently slower exponential decrease toward a relatively constant value of −860 HU as age and lung volume increased. Conclusion Normal lung parenchymal X-ray CT attenuation decreases with increasing lung volume and age; lung attenuation decreases rapidly in the first 2 years of age and more slowly thereafter. This change in normal lung attenuation should be taken into account as quantitative CT methods are translated to pediatric pulmonary imaging. PMID:27576458

Non-invasive localization of organic matter in soil aggregates using SR-μCT

NASA Astrophysics Data System (ADS)

Peth, Stephan; Mordhorst, Anneka; Chenu, Claire; Uteau Puschmann, Daniel; Garnier, Patricia; Nunan, Naoise; Pot, Valerie; Beckmann, Felix; Ogurreck, Malte

2014-05-01

Knowledge of the location of soil organic matter (SOM) and its spatial association to soil structure is an important step in improving modeling approaches for simulating organic matter turnover processes. Advanced models for carbon mineralization are able to account for the 3D distribution of SOM which is assumed to influence mineralisation. However, their application is still limited by the fact that no method exists to non-invasively determine the 3D spatial distribution of SOM in structured soils. SR-based X-ray microtomography (SR-µCT) is an advanced and promising tool in gaining knowledge on the 3-dimensional organization of soil phases (minerals, organic matter, water, air) which on a voxel level could be implemented into spatially explicit models. However, since the contrast of linear attenuation coefficients of soil organic matter on the one hand and mineral components and water on the other hand are relatively low, especially when materials are finely dispersed, organic matter within the soil pore space is often not resolved in ordinary X-ray absorption contrast imaging. To circumvent this problem we have developed a staining procedure for organic matter using Osmium-tetroxide since Osmium is an element with an absorption edge at a higher X-ray energy level. Osmium is known from transmission electron microscopy analysis (TEM) to stain organic matter specifically and irreversibly while having an absorption edge at approximately 74 keV. We report on the application of a novel Osmium vapor staining method to analyze differences in organic matter content and identify small scale spatial distribution of SOM in soil aggregates. To achieve this we have taken soil aggregate samples (6-8 mm across) obtained from arable soils differing in soil management. Aggregate samples were investigated by synchrotron-based X-ray microtomography (SR-µCT) after staining the sample with Osmium-tetroxide (OsO4) vapor. We utilized the monochromatic X-ray beam to locate osmium bound to SOM in the stained soil aggregate samples by scanning the aggregates at different photon energies: 30 keV at which the attenuation contrast is optimal for distinguishing other soil constituents, 70 keV (below the absorption of osmium) and 78 keV (above the absorption edge of osmium). The results suggest that particulate organic matter, which was not visibly by scanning samples at energy levels optimal for resolving soil structure (30 keV), was identified after osmium staining and scanning the samples at energy levels just below (70 keV) and above (78 keV) the absorption edge of Osmium. Subtracting the images below from the images above the osmium edged we were able to isolate stained particulate organic matter which otherwise would have been wrongly interpreted as pore space without staining. Combining both pore space and organic matter distribution we are able to investigate the association of SOM with soil structure.

Superior Volumetic Modulated Arc Therapy Planning Solution for Prostate Patients

DTIC Science & Technology

2014-07-01

narrow; it was selected to enhance the visibility of the small low-contrast tumors. The width of this window corresponds to about 13.5 Hounsfield units ...1R01EB013118-01 from the National Institute of Health. In order to obtain relative stopping power (RSP), Hounsfield units (i.e. units of x-ray...attenuation used in x-ray CT) are trans- formed using a calibration curve. However, there is no unique relationship between Hounsfield units and RSP, especially

Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: Performance and advantages for in situ analysis

NASA Astrophysics Data System (ADS)

Chou, I.-Ming; Bassett, William A.; Anderson, Alan J.; Mayanovic, Robert A.; Shang, Linbo

2008-11-01

Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 μm in diameter and ˜50 μm deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 °C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 °C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90° angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 μm, a pressure of 76 MPa at 500 °C was maintained for 2 h with no change in the original fluid density.

Radiopaque Resists for Two-Photon Lithography To Enable Submicron 3D Imaging of Polymer Parts via X-ray Computed Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saha, Sourabh K.; Oakdale, James S.; Cuadra, Jefferson A.

Two-photon lithography (TPL) is a high-resolution additive manufacturing (AM) technique capable of producing arbitrarily complex three-dimensional (3D) microstructures with features 2–3 orders of magnitude finer than human hair. This process finds numerous applications as a direct route toward the fabrication of novel optical and mechanical metamaterials, miniaturized optics, microfluidics, biological scaffolds, and various other intricate 3D parts. As TPL matures, metrology and inspection become a crucial step in the manufacturing process to ensure that the geometric form of the end product meets design specifications. X-ray-based computed tomography (CT) is a nondestructive technique that can provide this inspection capability for themore » evaluation of complex internal 3D structure. However, polymeric photoresists commonly used for TPL, as well as other forms of stereolithography, poorly attenuate X-rays due to the low atomic number (Z) of their constituent elements and therefore appear relatively transparent during imaging. We present the development of optically clear yet radiopaque photoresists for enhanced contrast under X-ray CT. We have synthesized iodinated acrylate monomers to formulate high-Z photoresist materials that are capable of forming 3D microstructures with sub-150 nm features. In addition, we have developed a formulation protocol to match the refractive index of the photoresists to the immersion medium of the objective lens so as to enable dip-in laser lithography, a direct laser writing technique for producing millimeter-tall structures. Our radiopaque photopolymer then resists increase X-ray attenuation by a factor of more than 10 times without sacrificing the sub-150 nm feature resolution or the millimeter-scale part height. Thus, our resists can successfully replace existing photopolymers to generate AM parts that are suitable for inspection via X-ray CT. By providing the “feedstock” for radiopaque AM parts, our resist formulation is expected to play a critical role in enabling fabrication of functional polymer parts to tight design tolerances.« less

Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: Performance and advantages for in situ analysis

USGS Publications Warehouse

Chou, I.-Ming; Bassett, William A.; Anderson, Alan J.; Mayanovic, Robert A.; Shang, L.

2008-01-01

Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 ??m in diameter and ???50 ??m deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 ??C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 ??C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90?? angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 ??m, a pressure of 76 MPa at 500 ??C was maintained for 2 h with no change in the original fluid density. ?? 2008 American Institute of Physics.

Time Resolved X-Ray Diffraction Study of Acoustoelectrically Amplified Phonons.

NASA Astrophysics Data System (ADS)

Chapman, Leroy Dean

X-rays diffracted by nearly perfect crystals of n-type InSb have been investigated in the presence of intense acoustoelectrically (A.E.) amplified phonons. The fact that these phonons are nearly monochromatic and have a well defined propagation and polarization direction presents an excellent opportunity to investigate the nature of x -ray photon-phonon scattering in a diffracting crystal. The Debye-Waller factor which accounts for the attenuation of diffracted x-ray intensities due to thermal phonons is reflection dependent owing to its sin (theta)/(lamda) dependence. We have performed experiments comparing the (004) and (008) anomalously transmitted intensities as a function of A.E. amplified flux. The attenuation of both reflections due to the amplified phonons was the same in direct contradiction to an expected sin (theta)/(lamda) dependence. Some possible reasons for this failure are discussed. In a Bragg reflection scattering geometry, the intense monochromatic amplified phonons give rise to satellite peaks symmetrically located about the central elastic Brag peak in a rocking profile. We report in this thesis on the first observation of satellites in a thin crystal Laue transmission geometry. We have theoretically simulated the rocking profiles with some success. The A.E. amplification process in InSb is strongly favored for {110} propagation fast transverse (FT) phonons. In earlier experiments it was found that non-{110} FT phonons were also produced during the amplification process. We have developed a time resolved x-ray counting system which, in conjunction with a spatially resolved x-ray beam and a localized, traveling A.E. phonon distribution, allow the time evolution of the amplified distribution to be followed. We report on time resolved measurements for both the symmetric Bragg and Laue geometries from which we can determine when and where non-{110 } FT flux is generated and restrict the possible mechanisms for its generation.

Containment of fluid samples in the hydrothermal diamond-anvil cell without the use of metal gaskets: performance and advantages for in situ analysis.

PubMed

Chou, I-Ming; Bassett, William A; Anderson, Alan J; Mayanovic, Robert A; Shang, Linbo

2008-11-01

Metal gaskets (Re, Ir, Inconel, or stainless steel) normally used to contain fluid samples in the hydrothermal diamond-anvil cell (HDAC) are sometimes undesirable due to possible contamination and to gasket deformation at high pressures and temperatures resulting in nonisochoric behavior. Furthermore, in x-ray spectroscopic experiments, metal gaskets may attenuate the incident x-ray beam and emitted fluorescence x-rays, and the interaction of scattered radiation with the gasket may produce fluorescence that interferes with the x-ray spectrum of the sample. New arrangements and procedures were tested for the operation of the HDAC without using the metal gaskets. Distilled, de-ionized water was loaded into the sample chamber, a laser-milled recess 300 microm in diameter and approximately 50 microm deep centered in the 1.0 mm face of the lower diamond anvil, and sealed by pressing the top diamond anvil face directly against the lower one without a metal gasket in between. A maximum sample pressure of 202 MPa at 617 degrees C was maintained for a duration of 10 min without evidence of leakage. A small change in fluid density was observed in one experiment where the sample was held at 266 MPa at 708 degrees C for 10 min. The gasketless HDAC was also employed in x-ray absorption spectroscopy experiments, where, in addition to the sample chamber in the lower diamond, two grooves were milled at a 90 degrees angle to each other around the sample chamber to minimize the attenuation of incident and fluorescent x rays. With a minimum distance between the sample chamber and the grooves of 80 microm, a pressure of 76 MPa at 500 degrees C was maintained for 2 h with no change in the original fluid density.

Radiopaque Resists for Two-Photon Lithography To Enable Submicron 3D Imaging of Polymer Parts via X-ray Computed Tomography

DOE PAGES

Saha, Sourabh K.; Oakdale, James S.; Cuadra, Jefferson A.; ...

2017-11-24

Two-photon lithography (TPL) is a high-resolution additive manufacturing (AM) technique capable of producing arbitrarily complex three-dimensional (3D) microstructures with features 2–3 orders of magnitude finer than human hair. This process finds numerous applications as a direct route toward the fabrication of novel optical and mechanical metamaterials, miniaturized optics, microfluidics, biological scaffolds, and various other intricate 3D parts. As TPL matures, metrology and inspection become a crucial step in the manufacturing process to ensure that the geometric form of the end product meets design specifications. X-ray-based computed tomography (CT) is a nondestructive technique that can provide this inspection capability for themore » evaluation of complex internal 3D structure. However, polymeric photoresists commonly used for TPL, as well as other forms of stereolithography, poorly attenuate X-rays due to the low atomic number (Z) of their constituent elements and therefore appear relatively transparent during imaging. We present the development of optically clear yet radiopaque photoresists for enhanced contrast under X-ray CT. We have synthesized iodinated acrylate monomers to formulate high-Z photoresist materials that are capable of forming 3D microstructures with sub-150 nm features. In addition, we have developed a formulation protocol to match the refractive index of the photoresists to the immersion medium of the objective lens so as to enable dip-in laser lithography, a direct laser writing technique for producing millimeter-tall structures. Our radiopaque photopolymer then resists increase X-ray attenuation by a factor of more than 10 times without sacrificing the sub-150 nm feature resolution or the millimeter-scale part height. Thus, our resists can successfully replace existing photopolymers to generate AM parts that are suitable for inspection via X-ray CT. By providing the “feedstock” for radiopaque AM parts, our resist formulation is expected to play a critical role in enabling fabrication of functional polymer parts to tight design tolerances.« less

Ultrasonic determination of recrystallization

NASA Technical Reports Server (NTRS)

Generazio, E. R.

1986-01-01

Ultrasonic attenuation was measured for cold worked Nickel 200 samples annealed at increasing temperatures. Localized dislocation density variations, crystalline order and colume percent of recrystallized phase were determined over the anneal temperature range using transmission electron microscopy, X-ray diffraction, and metallurgy. The exponent of the frequency dependence of the attenuation was found to be a key variable relating ultrasonic attenuation to the thermal kinetics of the recrystallization process. Identification of this key variable allows for the ultrasonic determination of onset, degree, and completion of recrystallization.

Model and reconstruction of a K-edge contrast agent distribution with an X-ray photon-counting detector

PubMed Central

Meng, Bo; Cong, Wenxiang; Xi, Yan; De Man, Bruno; Yang, Jian; Wang, Ge

2017-01-01

Contrast-enhanced computed tomography (CECT) helps enhance the visibility for tumor imaging. When a high-Z contrast agent interacts with X-rays across its K-edge, X-ray photoelectric absorption would experience a sudden increment, resulting in a significant difference of the X-ray transmission intensity between the left and right energy windows of the K-edge. Using photon-counting detectors, the X-ray intensity data in the left and right windows of the K-edge can be measured simultaneously. The differential information of the two kinds of intensity data reflects the contrast-agent concentration distribution. K-edge differences between various matters allow opportunities for the identification of contrast agents in biomedical applications. In this paper, a general radon transform is established to link the contrast-agent concentration to X-ray intensity measurement data. An iterative algorithm is proposed to reconstruct a contrast-agent distribution and tissue attenuation background simultaneously. Comprehensive numerical simulations are performed to demonstrate the merits of the proposed method over the existing K-edge imaging methods. Our results show that the proposed method accurately quantifies a distribution of a contrast agent, optimizing the contrast-to-noise ratio at a high dose efficiency. PMID:28437900

SU-E-I-42: Some New Aspects of the Energy Weighting Technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ganezer, K; Krmar, M; Josipovic, I

2015-06-15

Purpose: The development in the last few years of photon-counting pixel detectors creates an important and significant opportunity for x-ray spectroscopy to be applied in diagnostics. The energy weighting technique was originally developed to obtain the maximum benefit from the spectroscopic information. In all previous published papers the concept of an energy weighting function was tested on relatively simple test objects having only two materials with different absorption coefficients. Methods: In this study the shape of the energy weighting function was investigated with a set of ten trabecular bone test objects each with a similar geometry and structure but withmore » different attenuation properties. In previous publications it was determined that the function E-3 was a very good choice for the weighting function (wi). Results: The most important Result from this study was the discovery that a single function of the form E-b was not sufficient to explain the energy dependence of the different types of materials that might be used to describe common bodily tissues such as trabecular bone. It was also determined from the data contained in this paper that the exponent b is often significantly dependent upon the attenuation properties of the materials that were used to make the test objects. Conclusion: Studies of the attenuation properties will be useful in further studies involving energy weighting.« less

Using measured 30-150 kVp polychromatic tungsten x-ray spectra to determine ion chamber calibration factors, Nx (Gy C(-1)).

PubMed

Mercier, J R; Kopp, D T; McDavid, W D; Dove, S B; Lancaster, J L; Tucker, D M

2000-10-01

Two methods for determining ion chamber calibration factors (Nx) are presented for polychromatic tungsten x-ray beams whose spectra differ from beams with known Nx. Both methods take advantage of known x-ray fluence and kerma spectral distributions. In the first method, the x-ray tube potential is unchanged and spectra of differing filtration are measured. A primary standard ion chamber with known Nx for one beam is used to calculate the x-ray fluence spectrum of a second beam. Accurate air energy absorption coefficients are applied to the x-ray fluence spectra of the second beam to calculate actual air kerma and Nx. In the second method, two beams of differing tube potential and filtration with known Nx are used to bracket a beam of unknown Nx. A heuristically derived Nx interpolation scheme based on spectral characteristics of all three beams is described. Both methods are validated. Both methods improve accuracy over the current half value layer Nx estimating technique.

Novel paint design based on nanopowder to protection against X and gamma rays

PubMed Central

Movahedi, Mohammad Mehdi; Abdi, Adibe; Mehdizadeh, Alireza; Dehghan, Naser; Heidari, Emad; Masumi, Yusef; Abbaszadeh, Mojtaba

2014-01-01

Background: Lead-based shields are the standard method of intraoperative radiation protection in the radiology and nuclear medicine department. Human lead toxicity is well documented. The lead used is heavy, lacks durability, is difficult to launder, and its disposal is associated with environmental hazards. The aim of this study was to design a lead free paint for protection against X and gamma rays. Materials and Methods: In this pilot st we evaluated several types of nano metal powder that seemed to have good absorption. The Monte Carlo code, MCNP4C, was used to model the attenuation of X-ray photons in paints with different designs. Experimental measurements were carried out to assess the attenuation properties of each paint design. Results: Among the different nano metal powder, nano tungsten trioxide and nano tin dioxide were the two most appropriate candidates for making paint in diagnostic photon energy range. Nano tungsten trioxide (15%) and nano tin dioxide (85%) provided the best protection in both simulation and experiments. After this step, attempts were made to produce appropriate nano tungsten trioxide-nano tin dioxide paints. The density of this nano tungsten trioxide-nano tin dioxide paint was 4.2 g/cm3. The MCNP simulation and experimental measurements for HVL (Half-Value Layer) values of this shield at 100 kVp were 0.25 and 0.23 mm, respectively. Conclusions: The results showed the cost-effective lead-free paint can be a great power in absorbing the X-rays and gamma rays and it can be used instead of lead. PMID:24591777

Effective atomic number and electron density of amino acids within the energy range of 0.122-1.330 MeV

NASA Astrophysics Data System (ADS)

More, Chaitali V.; Lokhande, Rajkumar M.; Pawar, Pravina P.

2016-08-01

Photon attenuation coefficient calculation methods have been widely used to accurately study the properties of amino acids such as n-acetyl-L-tryptophan, n-acetyl-L-tyrosine, D-tryptophan, n-acetyl-L-glutamic acid, D-phenylalanine, and D-threonine. In this study, mass attenuation coefficients (μm) of these amino acids for 0.122-, 0.356-, 0.511-, 0.662-, 0.884-, 1.170, 1.275-, 1.330-MeV photons are determined using the radio-nuclides Co57, Ba133, Cs137, Na22, Mn54, and Co60. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The calculated attenuation coefficient values were then used to determine total atomic cross sections (σt), molar extinction coefficients (ε), electronic cross sections (σe), effective atomic numbers (Zeff), and effective electron densities (Neff) of the amino acids. Theoretical values were calculated based on the XCOM data. Theoretical and experimental values are found to be in a good agreement (error<5%). The variations of μm, σt, ε, σe, Zeff, and Neff with energy are shown graphically. The values of μm, σt, ε, σe are higher at lower energies, and they decrease sharply as energy increases; by contrast, Zeff and Neff were found to be almost constant.

Effects of gamma-ray irradiation on the optical properties of amorphous Se100-xHgx thin films

NASA Astrophysics Data System (ADS)

Ahmad, Shabir; Islam, Shama; Nasir, Mohd.; Asokan, K.; Zulfequar, M.

2018-06-01

In this study, the thermal quenching technique was employed to prepare bulk samples of Se100-xHgx (x = 0, 5, 10, 15). Thin films with a thickness of ∼250 nm were deposited on glass substrates using the thermal evaporation technique. These films were irradiated with gamma rays at doses of 25-100 kGy. The elemental compositions of the as-deposited thin films were confirmed by energy dispersive X-ray analysis and Rutherford backscattering spectrometry. X-ray diffraction analysis confirmed the crystalline nature of these thin films upto the dose of 75 kGy. Fourier transform-infrared spectroscopy showed that the concentration of defects decreased after gamma irradiation. Microstructural analysis by field emission scanning electron microscopy indicated that the grain size increases after irradiation. Optical study based on spectrophotometry showed that the optical band gap values of these films increase after the addition of Hg whereas they decrease after gamma irradiation. We found that the absorption coefficient increases with doses up to 75 kGy but decreases at higher doses. These remarkable shifts in the optical band gap and absorption coefficient values are interpreted in terms of the creation and annihilation of defects, which are the main effects produced by gamma irradiation.

A sequential solution for anisotropic total variation image denoising with interval constraints

NASA Astrophysics Data System (ADS)

Xu, Jingyan; Noo, Frédéric

2017-09-01

We show that two problems involving the anisotropic total variation (TV) and interval constraints on the unknown variables admit, under some conditions, a simple sequential solution. Problem 1 is a constrained TV penalized image denoising problem; problem 2 is a constrained fused lasso signal approximator. The sequential solution entails finding first the solution to the unconstrained problem, and then applying a thresholding to satisfy the constraints. If the interval constraints are uniform, this sequential solution solves problem 1. If the interval constraints furthermore contain zero, the sequential solution solves problem 2. Here uniform interval constraints refer to all unknowns being constrained to the same interval. A typical example of application is image denoising in x-ray CT, where the image intensities are non-negative as they physically represent linear attenuation coefficient in the patient body. Our results are simple yet seem unknown; we establish them using the Karush-Kuhn-Tucker conditions for constrained convex optimization.

Acoustic dynamics of supercooled indomethacin probed by Brillouin light scattering.

PubMed

De Panfilis, S; Pogna, E A A; Virga, A; Scopigno, T

2014-07-21

Acoustics dynamics of the molecular glass-former indomethacin (IMC) have been investigated by Brillouin light scattering (BLS) at GHz frequencies. Elastic response of the system has been tracked from the melting temperature down to the glass transition through the supercooled liquid. Both the structural arrest and the vibrational dynamics are described by modeling the experimentally determined dynamic structure factor within the framework of the Langevin equation, through a simplified choice of memory function which allows one to determine sound velocity and the acoustic attenuation coefficient as a function of temperature. The density fluctuation spectra in the glassy phase, as probed by BLS, are compared with time-domain results from photoacoustics experiments. The arising scenario is discussed in the context of current literature reporting inelastic X-ray scattering and BLS in platelet geometry. The link between the probed elastic properties and the non-ergodicity factor of the glass phase is finally scrutinized.

Design and Characterisation of Metallic Glassy Alloys of High Neutron Shielding Capability

PubMed Central

Khong, J. C.; Daisenberger, D.; Burca, G.; Kockelmann, W.; Tremsin, A. S.; Mi, J.

2016-01-01

This paper reports the design, making and characterisation of a series of Fe-based bulk metallic glass alloys with the aim of achieving the combined properties of high neutron absorption capability and sufficient glass forming ability. Synchrotron X-ray diffraction and pair distribution function methods were used to characterise the crystalline or amorphous states of the samples. Neutron transmission and macroscopic attenuation coefficients of the designed alloys were measured using energy resolved neutron imaging method and the very recently developed microchannel plate detector. The study found that the newly designed alloy (Fe48Cr15Mo14C15B6Gd2 with a glass forming ability of Ø5.8 mm) has the highest neutron absorption capability among all Fe-based bulk metallic glasses so far reported. It is a promising material for neutron shielding applications. PMID:27848991

Examination for optimization of synchrotron radiation spectrum for the x ray depth lithography

NASA Astrophysics Data System (ADS)

Dany, Raimund

1992-06-01

The effect of reducing the vertical distribution of synchrotron radiation on its spectral distribution is examined through resin irradiation. The resulting filter effect is compared to that of absorption filters. Transmission coefficients of titanium, gold, and polyamide were calculated from linear absorption coefficients with the Beer law. The use of a diaphragm in X-ray depth lithography, which is the first step of the LIGA (Lithography Galvanoforming Molding) process, is discussed. A calorimetric device for determining the synchrotron radiation power and distribution was developed and tested. Measurements at the ELSA storage ring show a strong dependence of the vertical emittance on the electron current.

Poisson-Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain.

PubMed

Lee, Sangyoon; Lee, Min Seok; Kang, Moon Gi

2018-03-29

The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson-Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson-Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods.

Poisson–Gaussian Noise Analysis and Estimation for Low-Dose X-ray Images in the NSCT Domain

PubMed Central

Lee, Sangyoon; Lee, Min Seok; Kang, Moon Gi

2018-01-01

The noise distribution of images obtained by X-ray sensors in low-dosage situations can be analyzed using the Poisson and Gaussian mixture model. Multiscale conversion is one of the most popular noise reduction methods used in recent years. Estimation of the noise distribution of each subband in the multiscale domain is the most important factor in performing noise reduction, with non-subsampled contourlet transform (NSCT) representing an effective method for scale and direction decomposition. In this study, we use artificially generated noise to analyze and estimate the Poisson–Gaussian noise of low-dose X-ray images in the NSCT domain. The noise distribution of the subband coefficients is analyzed using the noiseless low-band coefficients and the variance of the noisy subband coefficients. The noise-after-transform also follows a Poisson–Gaussian distribution, and the relationship between the noise parameters of the subband and the full-band image is identified. We then analyze noise of actual images to validate the theoretical analysis. Comparison of the proposed noise estimation method with an existing noise reduction method confirms that the proposed method outperforms traditional methods. PMID:29596335

Modeling contamination migration on the Chandra X-Ray Observatory

NASA Technical Reports Server (NTRS)

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

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.

X-ray microanalytical surveys of minor element concentrations in unsectioned biological samples

NASA Astrophysics Data System (ADS)

Schofield, R. M. S.; Lefevre, H. W.; Overley, J. C.; Macdonald, J. D.

1988-03-01

Approximate concentration maps of small unsectioned biological samples are made using the pixel by pixel ratio of PIXE images to areal density images. Areal density images are derived from scanning transmission ion microscopy (STIM) proton energy-loss images. Corrections for X-ray production cross section variations, X-ray attenuation, and depth averaging are approximated or ignored. Estimates of the magnitude of the resulting error are made. Approximate calcium concentrations within the head of a fruit fly are reported. Concentrations in the retinula cell region of the eye average about 1 mg/g dry weight. Concentrations of zinc in the mandible of several ant species average about 40 mg/g. Zinc concentrations in the stomachs of these ants are at least 1 mg/g.

First experience with x-ray dark-field radiography for human chest imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Noel, Peter B.; Willer, Konstantin; Fingerle, Alexander A.; Gromann, Lukas B.; De Marco, Fabio; Scherer, Kai H.; Herzen, Julia; Achterhold, Klaus; Gleich, Bernhard; Münzel, Daniela; Renz, Martin; Renger, Bernhard C.; Fischer, Florian; Braun, Christian; Auweter, Sigrid; Hellbach, Katharina; Reiser, Maximilian F.; Schröter, Tobias; Mohr, Jürgen; Yaroshenko, Andre; Maack, Hanns-Ingo; Pralow, Thomas; van der Heijden, Hendrik; Proksa, Roland; Köhler, Thomas; Wieberneit, Nataly; Rindt, Karsten; Rummeny, Ernst J.; Pfeiffer, Franz

2017-03-01

Purpose: To evaluate the performance of an experimental X-ray dark-field radiography system for chest imaging in humans and to compare with conventional diagnostic imaging. Materials and Methods: The study was institutional review board (IRB) approved. A single human cadaver (52 years, female, height: 173 cm, weight: 84 kg, chest circumference: 97 cm) was imaged within 24 hours post mortem on the experimental x-ray dark-field system. In addition, the cadaver was imaged on a clinical CT system to obtain a reference scan. The grating-based dark-field radiography setup was equipped with a set of three gratings to enable grating-based dark-field contrast x-ray imaging. The prototype operates at an acceleration voltage of up to 70 kVp and with a field-of-view large enough for clinical chest x-ray (>35 x 35 cm2). Results: It was feasible to extract x-ray dark-field signal of the whole human thorax, clearly demonstrating that human x-ray dark-field chest radiography is feasible. Lung tissue produced strong scattering, reflected in a pronounced x-ray dark-field signal. The ribcage and the backbone are less prominent than the lung but are also distinguishable. Finally, the soft tissue is not present in the dark-field radiography. The regions of the lungs affected by edema, as verified by CT, showed less dark-field signal compared to healthy lung tissue. Conclusion: Our results reveal the current status of translating dark-field imaging from a micro (small animal) scale to a macro (patient) scale. The performance of the experimental x-ray dark-field radiography setup offers, for the first time, obtaining multi-contrast chest x-ray images (attenuation and dark-field signal) from a human cadaver.

Microwave photonic filters using low-cost sources featuring tunability, reconfigurability and negative coefficients.

PubMed

Capmany, José; Mora, José; Ortega, Beatriz; Pastor, Daniel

2005-03-07

We propose and experimentally demonstrate two configurations of photonic filters for the processing of microwave signals featuring tunability, reconfigurability and negative coefficients based on the use of low cost optical sources. The first option is a low power configuration based on spectral slicing of a broadband source. The second is a high power configuration based on fixed lasers. Tunability, reconfigurability and negative coefficients are achieved by means of a MEMS cross-connect, a variable optical attenuator array and simple 2x2 switches respectively.

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

PubMed

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

2012-02-01

The aim of the study was to validate dual-energy X-ray absorptiometry (DXA) as a method to assess bone age in children. 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. 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. 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.

Electron temperature from x-ray continuum measurements on the NIF

NASA Astrophysics Data System (ADS)

Jarrott, Leonard; Bachmann, Benjamin; Benedetti, Robin; Izumi, Nobuhiko; Khan, Shahab; Landen, Otto; Ma, Tammy; Nagel, Sabrina; Pak, Arthur; Patel, Prav; Schneider, Marilyn; Springer, Paul; LLNL Collaboration

2017-10-01

We report on measurements of the electron temperature within the hot spot of inertially confined, layered implosions on the NIF using a titanium differential filtering x-ray diagnostic. The electron temperature from x-ray emission is insensitive to non-thermal velocity flows as is the case with ion temperature measurements and is thus a critical parameter in interpreting stagnated hot spot conditions. Here we discuss measurements using titanium filters ranging from 10 μm to 1mm in thickness with a sensitivity band of 10-30keV coupled with penumbral pinholes. The use of larger pinhole diameters increases x-ray fluence improving sensitivity of photon energies with minimal attenuation from the compressed fuel/shell. This diagnostic has been fielded on a series of cryogenic shots with DT ion temperatures ranging from 2-5keV. Analysis of the measurement will be presented along with a comparison against simulated electron temperatures and x-ray spectra as well as a comparison to DT ion temperature measurements. This work was performed under the auspices of U.S. DoE by LLNL under Contract No. DE-AC52-07NA27344.

SU-E-J-66: Evaluation of a Real-Time Positioning Assistance Simulator System for Skull Radiography Using the Microsoft Kinect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurata, T; Ono, M; Kozono, K

2014-06-01

Purpose: The purpose of this study is to investigate the feasibility of a low cost, small size positioning assistance simulator system for skull radiography using the Microsoft Kinect sensor. A conventional radiographic simulator system can only measure the three-dimensional coordinates of an x-ray tube using angle sensors, but not measure the movement of the subject. Therefore, in this study, we developed a real-time simulator system using the Microsoft Kinect to measure both the x-ray tube and the subject, and evaluated its accuracy and feasibility by comparing the simulated and the measured x-ray images. Methods: This system can track a headmore » phantom by using Face Tracking, which is one of the functions of the Kinect. The relative relationship between the Kinect and the head phantom was measured and the projection image was calculated by using the ray casting method, and by using three-dimensional CT head data with 220 slices at 512 × 512 pixels. X-ray images were thus obtained by using a computed radiography (CR) system. We could then compare the simulated projection images with the measured x-ray images from 0 degrees to 45 degrees at increments of 15 degrees by calculating the cross correlation coefficient C. Results: The calculation time of the simulated projection images was almost real-time (within 1 second) by using the Graphics Processing Unit(GPU). The cross-correlation coefficients C are: 0.916; 0.909; 0.891; and, 0.886 at 0, 15, 30, and 45 degrees, respectively. As a result, there were strong correlations between the simulated and measured images. Conclusion: This system can be used to perform head positioning more easily and accurately. It is expected that this system will be useful for learning radiographic techniques by students. Moreover, it could also be used for predicting the actual x-ray image prior to x-ray exposure in clinical environments.« less

Improving accuracy of simultaneously reconstructed activity and attenuation maps using deep learning.

PubMed

Hwang, Donghwi; Kim, Kyeong Yun; Kang, Seung Kwan; Seo, Seongho; Paeng, Jin Chul; Lee, Dong Soo; Lee, Jae Sung

2018-02-15

Simultaneous reconstruction of activity and attenuation using the maximum likelihood reconstruction of activity and attenuation (MLAA) augmented by time-of-flight (TOF) information is a promising method for positron emission tomography (PET) attenuation correction. However, it still suffers from several problems, including crosstalk artifacts, slow convergence speed, and noisy attenuation maps (μ-maps). In this work, we developed deep convolutional neural networks (CNNs) to overcome these MLAA limitations, and we verified their feasibility using a clinical brain PET data set. Methods: We applied the proposed method to one of the most challenging PET cases for simultaneous image reconstruction ( 18 F-FP-CIT PET scans with highly specific binding to striatum of the brain). Three different CNN architectures (convolutional autoencoder (CAE), U-net, hybrid of CAE and U-net) were designed and trained to learn x-ray computed tomography (CT) derived μ-map (μ-CT) from the MLAA-generated activity distribution and μ-map (μ-MLAA). PET/CT data of 40 patients with suspected Parkinson's disease were employed for five-fold cross-validation. For the training of CNNs, 800,000 transverse PET slices and CTs augmented from 32 patient data sets were used. The similarity to μ-CT of the CNN-generated μ-maps (μ-CAE, μ-Unet, and μ-Hybrid) and μ-MLAA was compared using Dice similarity coefficients. In addition, we compared the activity concentration of specific (striatum) and non-specific binding regions (cerebellum and occipital cortex) and the binding ratios in the striatum in the PET activity images reconstructed using those μ-maps. Results: The CNNs generated less noisy and more uniform μ-maps than original μ-MLAA. Moreover, the air cavities and bones were better resolved in the proposed CNN outputs. In addition, the proposed deep learning approach was useful for mitigating the crosstalk problem in the MLAA reconstruction. The hybrid network of CAE and U-net yielded the most similar μ-maps to μ-CT (Dice similarity coefficient in the whole head = 0.79 in the bone and 0.72 in air cavities), resulting in only approximately 5% errors in activity and biding ratio quantification. Conclusion: The proposed deep learning approach is promising for accurate attenuation correction of activity distribution in TOF PET systems. Copyright © 2018 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Poly(acrylic acid) Bridged Gadolinium Metal-Organic Framework-Gold Nanoparticle Composites as Contrast Agents for Computed Tomography and Magnetic Resonance Bimodal Imaging.

PubMed

Tian, Chixia; Zhu, Liping; Lin, Feng; Boyes, Stephen G

2015-08-19

Imaging contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT) have received significant attention in the development of techniques for early stage cancer diagnosis. Gadolinium (Gd)(III), which has seven unpaired electrons and a large magnetic moment, can dramatically influence the water proton relaxation and hence exhibits excellent MRI contrast. On the other hand, gold (Au), which has a high atomic number and high X-ray attenuation coefficient, is an ideal contrast agent candidate for X-ray-based CT imaging. Gd metal-organic framework (MOF) nanoparticles with tunable size, high Gd(III) loading and multivalency can potentially overcome the limitations of clinically utilized Gd chelate contrast agents. In this work, we report for the first time the integration of GdMOF nanoparticles with gold nanoparticles (AuNPs) for the preparation of a MRI/CT bimodal imaging agent. Highly stable hybrid GdMOF/AuNPs composites have been prepared by using poly(acrylic acid) as a bridge between the GdMOF nanoparticles and AuNPs. The hybrid nanocomposites were then evaluated in MRI and CT imaging. The results revealed high longitudinal relaxivity in MRI and excellent CT imaging performance. Therefore, these GdMOF/AuNPs hybrid nanocomposites potentially provide a new platform for the development of multimodal imaging probes.

Poly(acrylic acid) Bridged Gadolinium Metal-Organic Framework-Gold Nanoparticle Composites as Contrast Agents for Computed Tomography and Magnetic Resonance Bimodal Imaging

PubMed Central

Tian, Chixia; Zhu, Liping; Lin, Feng; Boyes, Stephen G.

2015-01-01

Imaging contrast agents for magnetic resonance imaging (MRI) and computed tomography (CT) have received significant attention in the development of techniques for early-stage cancer diagnosis. Gadolinium (Gd) (III), which has seven unpaired electrons and a large magnetic moment, can dramatically influence the water proton relaxation and hence exhibits excellent MRI contrast. On the other hand, gold (Au), which has a high atomic number and high x-ray attenuation coefficient, is an ideal contrast agent candidate for x-ray based CT imaging. Gd metal organic framework (MOF) nanoparticles with tunable size, high Gd (III) loading and multivalency can potentially overcome the limitations of clinically utilized Gd chelate contrast agents. In this work, we report for the first time the integration of GdMOF nanoparticles with gold nanoparticles (AuNPs) for the preparation of a MRI/CT bimodal imaging agent. Highly stable hybrid GdMOF/AuNPs composites have been prepared by using poly(acrylic acid) as a bridge between the GdMOF nanoparticles and AuNPs. The hybrid nanocomposites were then evaluated in MRI and CT imaging. The results revealed high longitudinal relaxivity in MRI and excellent CT imaging performance. Therefore, these GdMOF/AuNPs hybrid nanocomposites potentially provide a new platform for the development of multi-modal imaging probes. PMID:26147906

Characterization of adsorption sites on aggregate soil samples using synchrotron X-ray computerized microtomography.

PubMed

Altman, Susan J; Rivers, Mark L; Reno, Marissa D; Cygan, Randall T; McLain, Angela A

2005-04-15

Synchrotron-source X-ray computerized microtomography (CMT) was used to evaluate the adsorptive properties of aggregate soil samples. A linear relationship between measured mean mass attenuation coefficient (sigma) and mass fraction iron was generated by imaging mineral standards with known iron contents. On the basis of reported stoichiometries of the clay minerals and identifications of iron oxyhydroxides (1), we calculated the mass fraction iron and iron oxyhydroxide in the intergranular material. The mass fractions of iron were estimated to range from 0.17 to 0.22 for measurements made at 18 keV and from 0.18 to 0.21 for measurements made at 26 keV. One aggregate sample also contained regions within the intergranular material with mass fraction iron ranging from 0.29 to 0.31 and from 0.33 to 0.36 for the 18 and 26 keV measurements, respectively. The mass fraction iron oxyhydroxide ranged from 0.18 to 0.35 for the low-iron intergranular material and from 0.40 to 0.59 for the high-iron intergranular material. Using absorption edge difference imaging with CMT, we visualized cesium on the intergranular material, presumably because of adsorption and possible exchange reactions. By characterizing the mass fraction iron, the mass fraction iron oxyhydroxide, and the adsorptive capacity of these soil mineral aggregates, we provide information useful for conceptualization, development, and parametrization of transport models.

Surface applicator of a miniature X-ray tube for superficial electronic brachytherapy of skin cancer.

PubMed

Kim, Hyun Nam; Lee, Ju Hyuk; Park, Han Beom; Kim, Hyun Jin; Cho, Sung Oh

2018-01-01

We designed and fabricated a surface applicator of a novel carbon nanotube (CNT)-based miniature X-ray tube for the use in superficial electronic brachytherapy of skin cancer. To investigate the effectiveness of the surface applicator, the performance of the applicator was numerically and experimentally analyzed. The surface applicator consists of a graphite flattening filter and an X-ray shield. A Monte Carlo radiation transport code, MCNP6, was used to optimize the geometries of both the flattening filter and the shield so that X-rays are generated uniformly over the desired region. The performance of the graphite filter was compared with that of conventional aluminum (Al) filters of different geometries using the numerical simulations. After fabricating a surface applicator, the X-ray spatial distribution was measured to evaluate the performance of the applicator. The graphite filter shows better spatial dose uniformity and less dose distortion than Al filters. Moreover, graphite allows easy fabrication of the flattening filter due to its low X-ray attenuation property, which is particularly important for low-energy electronic brachytherapy. The applicator also shows that no further X-ray shielding is required for the application because unwanted X-rays are completely protected. As a result, highly uniform X-ray dose distribution was achieved from the miniature X-ray tube mounted with the surface applicators. The measured values of both flatness and symmetry were less than 5% and the measured penumbra values were less than 1 mm. All these values satisfy the currently accepted tolerance criteria for radiation therapy. The surface applicator exhibits sufficient performance capability for their application in electronic brachytherapy of skin cancers. © 2017 American Association of Physicists in Medicine.

Synchrotron x-ray spectroscopy of EuHN O3 aqueous solutions at high temperatures and pressures and Nb-bearing silicate melt phases coexisting with hydrothermal fluids using a modified hydrothermal diamond anvil cell and rail assembly

USGS Publications Warehouse

Mayanovic, Robert A.; Anderson, Alan J.; Bassett, William A.; Chou, I.-Ming

2007-01-01

A modified hydrothermal diamond anvil cell (HDAC) rail assembly has been constructed for making synchrotron x-ray absorption spectroscopy, x-ray fluorescence, and x-ray mapping measurements on fluids or solid phases in contact with hydrothermal fluids up to ???900??C and 700 MPa. The diamond anvils of the HDAC are modified by laser milling grooves or holes, for the reduction of attenuation of incident and fluorescent x rays and sample cavities. The modified HDAC rail assembly has flexibility in design for measurement of light elements at low concentrations or heavy elements at trace levels in the sample and the capability to probe minute individual phases of a multiphase fluid-based system using focused x-ray microbeam. The supporting rail allows for uniform translation of the HDAC, rotation and tilt stages, and a focusing mirror, which is used to illuminate the sample for visual observation using a microscope, relative to the direction of the incident x-ray beam. A structure study of Eu(III) aqua ion behavior in high-temperature aqueous solutions and a study of Nb partitioning and coordination in a silicate melt in contact with a hydrothermal fluid are described as applications utilizing the modified HDAC rail assembly. ?? 2007 American Institute of Physics.

Spectral correction algorithm for multispectral CdTe x-ray detectors

NASA Astrophysics Data System (ADS)

Christensen, Erik D.; Kehres, Jan; Gu, Yun; Feidenhans'l, Robert; Olsen, Ulrik L.

2017-09-01

Compared to the dual energy scintillator detectors widely used today, pixelated multispectral X-ray detectors show the potential to improve material identification in various radiography and tomography applications used for industrial and security purposes. However, detector effects, such as charge sharing and photon pileup, distort the measured spectra in high flux pixelated multispectral detectors. These effects significantly reduce the detectors' capabilities to be used for material identification, which requires accurate spectral measurements. We have developed a semi analytical computational algorithm for multispectral CdTe X-ray detectors which corrects the measured spectra for severe spectral distortions caused by the detector. The algorithm is developed for the Multix ME100 CdTe X-ray detector, but could potentially be adapted for any pixelated multispectral CdTe detector. The calibration of the algorithm is based on simple attenuation measurements of commercially available materials using standard laboratory sources, making the algorithm applicable in any X-ray setup. The validation of the algorithm has been done using experimental data acquired with both standard lab equipment and synchrotron radiation. The experiments show that the algorithm is fast, reliable even at X-ray flux up to 5 Mph/s/mm2, and greatly improves the accuracy of the measured X-ray spectra, making the algorithm very useful for both security and industrial applications where multispectral detectors are used.

Linear thermal expansion coefficient determination using in situ curvature and temperature dependent X-ray diffraction measurements applied to metalorganic vapor phase epitaxy-grown AlGaAs

NASA Astrophysics Data System (ADS)

Maaßdorf, A.; Zeimer, U.; Grenzer, J.; Weyers, M.

2013-07-01

AlxGa1-xAs grown on GaAs is known to be almost perfectly lattice matched with a maximum lattice mismatch of 0.14% at room temperature and even less at temperatures of 700 °C-800 °C. However, as layer structures for edge-emitting diode lasers exhibit an increasing overall thickness of several microns of AlxGa1-xAs, e.g., diode lasers comprising a super-large optical cavity, the accumulated elastic strain energy increases as well. Depending on the growth temperature the formation energy of dislocations can be reached, which is limiting the pseudomorphic growth. In this regard, the thermal expansion coefficient difference between layer and substrate is an important parameter. We utilize in situ curvature measurements during growth of AlxGa1-xAs by metal-organic vapour phase epitaxy to determine the thermal expansion coefficient α. The curvature change with increasing layer thickness, as well as with wafer temperature at constant layer thickness is used to assess α. This is compared to ex situ temperature dependent X-ray diffraction measurements to obtain α. All determined values for α are in good agreement, yielding αAlAs=4.1×10-6 K-1 for a given GaAs linear thermal expansion coefficient of αGaAs=5.73×10-6 K-1.

Insulating epoxy/barite and polyester/barite composites for radiation attenuation.

PubMed

El-Sarraf, M A; El-Sayed Abdo, A

2013-09-01

A trial has been made to create insulating Epoxy/Barite (EP/Brt) (ρ=2.85 g cm(-3)) and Crosslinked Unsaturated Polyester/Barite (CUP/Brt) (ρ=3.25 g cm(-3)) composites with radiation attenuation and shielding capabilities. Experimental work regarding mechanical and physical properties was performed to study the composites integrity for practical applications. The properties were found to be reasonable. Radiation attenuation properties have been carried out using emitted collimated beam from a fission (252)Cf (100 µg) neutron source, and the neutron-gamma spectrometer with stilbene scintillator. The pulse shape discriminating (P.S.D) technique based on the zero cross-over method was used to discriminate between neutron and gamma-ray pulses. Thermal neutron fluxes, measured using the BF3 detector and thermal neutron detection system, were used to plot the attenuation relations. The fast neutron macroscopic effective removal cross-section ΣR, gamma ray total attenuation coefficient µ and thermal neutron macroscopic cross-section Σ have been evaluated. Theoretical calculations have been achieved using MCNP-4C2 code to calculate ΣR, µ and Σ. Also, MERCSF-N program was used to calculate macroscopic effective removal cross-section ΣR. Measured and calculated results have been compared and were found to be in reasonable agreement. Copyright © 2013 Elsevier Ltd. All rights reserved.

Fast polyenergetic forward projection for image formation using OpenCL on a heterogeneous parallel computing platform.

PubMed

Zhou, Lili; Clifford Chao, K S; Chang, Jenghwa

2012-11-01

Simulated projection images of digital phantoms constructed from CT scans have been widely used for clinical and research applications but their quality and computation speed are not optimal for real-time comparison with the radiography acquired with an x-ray source of different energies. In this paper, the authors performed polyenergetic forward projections using open computing language (OpenCL) in a parallel computing ecosystem consisting of CPU and general purpose graphics processing unit (GPGPU) for fast and realistic image formation. The proposed polyenergetic forward projection uses a lookup table containing the NIST published mass attenuation coefficients (μ∕ρ) for different tissue types and photon energies ranging from 1 keV to 20 MeV. The CT images of interested sites are first segmented into different tissue types based on the CT numbers and converted to a three-dimensional attenuation phantom by linking each voxel to the corresponding tissue type in the lookup table. The x-ray source can be a radioisotope or an x-ray generator with a known spectrum described as weight w(n) for energy bin E(n). The Siddon method is used to compute the x-ray transmission line integral for E(n) and the x-ray fluence is the weighted sum of the exponential of line integral for all energy bins with added Poisson noise. To validate this method, a digital head and neck phantom constructed from the CT scan of a Rando head phantom was segmented into three (air, gray∕white matter, and bone) regions for calculating the polyenergetic projection images for the Mohan 4 MV energy spectrum. To accelerate the calculation, the authors partitioned the workloads using the task parallelism and data parallelism and scheduled them in a parallel computing ecosystem consisting of CPU and GPGPU (NVIDIA Tesla C2050) using OpenCL only. The authors explored the task overlapping strategy and the sequential method for generating the first and subsequent DRRs. A dispatcher was designed to drive the high-degree parallelism of the task overlapping strategy. Numerical experiments were conducted to compare the performance of the OpenCL∕GPGPU-based implementation with the CPU-based implementation. The projection images were similar to typical portal images obtained with a 4 or 6 MV x-ray source. For a phantom size of 512 × 512 × 223, the time for calculating the line integrals for a 512 × 512 image panel was 16.2 ms on GPGPU for one energy bin in comparison to 8.83 s on CPU. The total computation time for generating one polyenergetic projection image of 512 × 512 was 0.3 s (141 s for CPU). The relative difference between the projection images obtained with the CPU-based and OpenCL∕GPGPU-based implementations was on the order of 10(-6) and was virtually indistinguishable. The task overlapping strategy was 5.84 and 1.16 times faster than the sequential method for the first and the subsequent digitally reconstruction radiographies, respectively. The authors have successfully built digital phantoms using anatomic CT images and NIST μ∕ρ tables for simulating realistic polyenergetic projection images and optimized the processing speed with parallel computing using GPGPU∕OpenCL-based implementation. The computation time was fast (0.3 s per projection image) enough for real-time IGRT (image-guided radiotherapy) applications.

The Design, Implementation, and Performance of the Astro-H SXS Aperture Assembly and Blocking Filters

NASA Technical Reports Server (NTRS)

Kilbourne, C. A.; Adams, J. S.; Arsenovic, P.; Ayers, T.; Chiao, M. P.; DiPirro, M. J.; Eckart, M. E.; Fujimoto, R.; Kazeva, J. D.; Kelley, R. L.;

[Stature estimation for Sichuan Han nationality female based on X-ray technology with measurement of lumbar vertebrae].

PubMed

Qing, Si-han; Chang, Yun-feng; Dong, Xiao-ai; Li, Yuan; Chen, Xiao-gang; Shu, Yong-kang; Deng, Zhen-hua

2013-10-01

To establish the mathematical models of stature estimation for Sichuan Han female with measurement of lumbar vertebrae by X-ray to provide essential data for forensic anthropology research. The samples, 206 Sichuan Han females, were divided into three groups including group A, B and C according to the ages. Group A (206 samples) consisted of all ages, group B (116 samples) were 20-45 years old and 90 samples over 45 years old were group C. All the samples were examined lumbar vertebrae through CR technology, including the parameters of five centrums (L1-L5) as anterior border, posterior border and central heights (x1-x15), total central height of lumbar spine (x16), and the real height of every sample. The linear regression analysis was produced using the parameters to establish the mathematical models of stature estimation. Sixty-two trained subjects were tested to verify the accuracy of the mathematical models. The established mathematical models by hypothesis test of linear regression equation model were statistically significant (P<0.05). The standard errors of the equation were 2.982-5.004 cm, while correlation coefficients were 0.370-0.779 and multiple correlation coefficients were 0.533-0.834. The return tests of the highest correlation coefficient and multiple correlation coefficient of each group showed that the highest accuracy of the multiple regression equation, y = 100.33 + 1.489 x3 - 0.548 x6 + 0.772 x9 + 0.058 x12 + 0.645 x15, in group A were 80.6% (+/- lSE) and 100% (+/- 2SE). The established mathematical models in this study could be applied for the stature estimation for Sichuan Han females.

Energy dependence of radiation interaction parameters of some organic compounds

NASA Astrophysics Data System (ADS)

Singh, Mohinder; Tondon, Akash; Sandhu, B. S.; Singh, Bhajan

2018-04-01

Gamma rays interact with a material through photoelectric absorption, Compton scattering, Rayleigh scattering and Pair production in the intermediate energy range. The probability of occurrence of a particular type of process depends on the energy of incident gamma rays, atomic number of the material, scattering angle and geometrical conditions. Various radiological parameters for organic compounds, namely ethylene glycol (C2H6O2), propylene glycol (C3H8O2), glycerin (C3H8O3), isoamyl alcohol (C5H12O), butanone (C4H8O), acetophenone (C8H8O2), cyclohexanone (C6H10O), furfural (C5H4O2), benzaldehyde (C7H6O), cinnamaldehyde (C9H8O), glutaraldehyde (C5H8O2), aniline (C6H7N), benzyl amine (C6H7N), nitrobenzene (C6H5NO2), ethyl benzene (C8H10), ethyl formate (C3H6O2) and water (H2O) are presented at 81, 122, 356 and 511 keV energies employing NaI(Tl) scintillation detector in narrow-beam transmission geometry. The radiation interaction parameters such as mass attenuation, molar extinction and mass energy absorption coefficients, half value layer, total atomic and effective electronic cross-sections and CT number have been evaluated for these organic compounds. The general trend of values of mass attenuation coefficients, half value layer, molar extinction coefficients, total atomic and effective electronic cross-sections and mass energy absorption coefficients shows a decrease with increase in incident gamma photon energy. The values of CT number are found to increases linearly with increase of effective atomic number (Zeff). The variation in CT number around Zeff ≈ 3.3 shows the peak like structure with respect to water and the correlation between CT number and linear attenuation coefficient is about 0.99. Appropriate equations are fitted to these experimentally determined parameters for the organic compounds at incident photon energy ranging from 81 keV to 511 keV used in the present study. Experimental values are compared with the theoretical data obtained using WinXcom software package, and are found in good agreement.

A novel high-pressure vessel for simultaneous observations of seismic velocity and in situ CO2 distribution in a porous rock using a medical X-ray CT scanner

NASA Astrophysics Data System (ADS)

Jiang, Lanlan; Nishizawa, Osamu; Zhang, Yi; Park, Hyuck; Xue, Ziqiu

2016-12-01

Understanding the relationship between seismic wave velocity or attenuation and CO2 saturation is essential for CO2 storage in deep saline formations. In the present study, we describe a novel upright high-pressure vessel that is designed to keep a rock sample under reservoir conditions and simultaneously image the entire sample using a medical X-ray CT scanner. The pressure vessel is composed of low X-ray absorption materials: a carbon-fibre-enhanced polyetheretherketone (PEEK) cylinder and PEEK vessel closures supported by carbon-fibre-reinforced plastic (CFRP) joists. The temperature was controlled by a carbon-coated film heater and an aramid fibre thermal insulator. The assembled sample cell allows us to obtain high-resolution images of rock samples during CO2 drainage and brine imbibition under reservoir conditions. The rock sample was oriented vertical to the rotation axis of the CT scanner, and seismic wave paths were aligned parallel to the rotation axis to avoid shadows from the acoustic transducers. The reconstructed CO2 distribution images allow us to calculate the CO2 saturation in the first Fresnel zone along the ray path between transducers. A robust relationship between the seismic wave velocity or attenuation and the CO2 saturation in porous rock was obtained from experiments using this pressure vessel.

Application of a New Grain-Based Reconstruction Algorithm to Microtomography Images for Quantitative Characterization and Flow Modeling

DTIC Science & Technology

2008-06-01

mapping the X-ray absorption through the sample. The amount of absorption depends on the chemical composition and structure of the material and the X...obtained by measuring the X-ray attenua- tion coefficients of the sample at different angles as the sample is rotated about the vertical axis. These... McMaster University, Hamilton, Ontario, Canada. Allen H. Reed is a geologist with the Naval Research Laboratory. His research interests are in marine

PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511-keV attenuation coefficients.

PubMed

Burger, C; Goerres, G; Schoenes, S; Buck, A; Lonn, A H R; Von Schulthess, G K

2002-07-01

The CT data acquired in combined PET/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40-140 keV must be transformed into linear attenuation coefficients at the PET energy of 511 keV. As attenuation depends on photon energy and the absorbing material, an accurate theoretical relation cannot be devised. The transformation implemented in the Discovery LS PET/CT scanner (GE Medical Systems, Milwaukee, Wis.) uses a bilinear function based on the attenuation of water and cortical bone at the CT and PET energies. The purpose of this study was to compare this transformation with experimental CT values and corresponding PET attenuation coefficients. In 14 patients, quantitative PET attenuation maps were calculated from germanium-68 transmission scans, and resolution-matched CT images were generated. A total of 114 volumes of interest were defined and the average PET attenuation coefficients and CT values measured. From the CT values the predicted PET attenuation coefficients were calculated using the bilinear transformation. When the transformation was based on the narrow-beam attenuation coefficient of water at 511 keV (0.096 cm(-1)), the predicted attenuation coefficients were higher in soft tissue than the measured values. This bias was reduced by replacing 0.096 cm(-1) in the transformation by the linear attenuation coefficient of 0.093 cm(-1) obtained from germanium-68 transmission scans. An analysis of the corrected emission activities shows that the resulting transformation is essentially equivalent to the transmission-based attenuation correction for human tissue. For non-human material, however, it may assign inaccurate attenuation coefficients which will also affect the correction in neighbouring tissue.

Image enhancement by spectral-error correction for dual-energy computed tomography.

PubMed

Park, Kyung-Kook; Oh, Chang-Hyun; Akay, Metin

2011-01-01

Dual-energy CT (DECT) was reintroduced recently to use the additional spectral information of X-ray attenuation and aims for accurate density measurement and material differentiation. However, the spectral information lies in the difference between low and high energy images or measurements, so that it is difficult to acquire accurate spectral information due to amplification of high pixel noise in the resulting difference image. In this work, an image enhancement technique for DECT is proposed, based on the fact that the attenuation of a higher density material decreases more rapidly as X-ray energy increases. We define as spectral error the case when a pixel pair of low and high energy images deviates far from the expected attenuation trend. After analyzing the spectral-error sources of DECT images, we propose a DECT image enhancement method, which consists of three steps: water-reference offset correction, spectral-error correction, and anti-correlated noise reduction. It is the main idea of this work that makes spectral errors distributed like random noise over the true attenuation and suppressed by the well-known anti-correlated noise reduction. The proposed method suppressed noise of liver lesions and improved contrast between liver lesions and liver parenchyma in DECT contrast-enhanced abdominal images and their two-material decomposition.

Dark-field imaging in coronary atherosclerosis.

PubMed

Hetterich, Holger; Webber, Nicole; Willner, Marian; Herzen, Julia; Birnbacher, Lorenz; Auweter, Sigrid; Schüller, Ulrich; Bamberg, Fabian; Notohamiprodjo, Susan; Bartsch, Harald; Wolf, Johannes; Marschner, Mathias; Pfeiffer, Franz; Reiser, Maximilian; Saam, Tobias

2017-09-01

Dark-field imaging based on small angle X-ray scattering has been shown to be highly sensitive for microcalcifications, e.g. in breast tissue. We hypothesized (i) that high signal areas in dark-field imaging of atherosclerotic plaque are associated with microcalcifications and (ii) that dark-field imaging is more sensitive for microcalcifications than attenuation-based imaging. Fifteen coronary artery specimens were examined at an experimental set-up consisting of X-ray tube (40kV), grating-interferometer and detector. Tomographic dark-field-, attenuation-, and phase-contrast data were simultaneously acquired. Histopathology served as standard of reference. To explore the potential of dark field imaging in a full-body CT system, simulations were carried out with spherical calcifications of different sizes to simulate small and intermediate microcalcifications. Microcalcifications were present in 10/10 (100%) cross-sections with high dark-field signal and without evidence of calcifications in attenuation- or phase contrast. In positive controls with high signal areas in all three modalities, 10/10 (100%) cross-sections showed macrocalcifications. In negative controls without high signal areas, no calcifications were detected. Simulations showed that the microcalcifications generate substantially higher dark-field than attenuation signal. Dark-field imaging is highly sensitive for microcalcifications in coronary atherosclerotic plaque and might provide complementary information in the assessment of plaque instability. Copyright © 2017 Elsevier B.V. All rights reserved.

Transmission properties and physical mechanisms of X-ray communication for blackout mitigation during spacecraft reentry

NASA Astrophysics Data System (ADS)

Liu, Yunpeng; Li, Huan; Li, Yanlong; Hang, Shuang; Tang, Xiaobin

2017-11-01

Recent advances in X-ray science have witnessed the X-ray communication (XCOM), a new revolutionary technology first proposed by NASA since 2007. In combination with the advanced modulated X-ray source, XCOM shows a promising prospect for helping to alleviate the occurrence of inevitable blackout communication by using the regular radio frequency (RF) signal, paving the way towards realizing real-time communication during spacecraft reentry into atmosphere. Here, we acquired the detailed information of electron density distribution of plasma sheath encountered during vehicle reentry through Computational Fluid Dynamics simulation. Based on these derived parameters, Finite-difference Time-domain method was employed to investigate the transmission properties of X-rays through the plasma sheath, and the results indicated that X-ray transmission was not influenced by the reentry plasma sheath at different reentry altitudes and spacecraft surface positions compared with RF signal. In addition, 2D Particle-In-Cell simulation was also adopted to provide deeper insight into the transmission properties and physical mechanisms of X-ray carrier propagating through the plasma sheath, and results showed that the transmission coefficient was over 0.994 and the observation of plasma channel effect was also an important signature, which was of great importance to X-ray propagating through the plasma sheath.

Measurement of Attenuation with Airborne and Ground-Based Radar in Convective Storms Over Land and Its Microphysical Implications

NASA Technical Reports Server (NTRS)

Tian, Lin; Heymsfield, G. M.; Srivastava, R. C.; Starr, D. OC. (Technical Monitor)

2001-01-01

Observations by the airborne X-band Doppler radar (EDOP) and the NCAR S-band polarimetric (S-POL) radar from two field experiments are used to evaluate the Surface ref'ercnce technique (SRT) for measuring the path integrated attenuation (PIA) and to study attenuation in deep convective storms. The EDOP, flying at an altitude of 20 km, uses a nadir beam and a forward pointing beam. It is found that over land, the surface scattering cross-section is highly variable at nadir incidence but relatively stable at forward incidence. It is concluded that measurement by the forward beam provides a viable technique for measuring PIA using the SRT. Vertical profiles of peak attenuation coefficient are derived in vxo deep convective storms by the dual-wavelength method. Using the measured Doppler velocity, the reflectivities at. the two wavelengths, the differential reflectivity and the estimated attenuation coefficients, it is shown that: supercooled drops and dry ice particles probably co-existed above the melting level in regions of updraft, that water-coated partially melted ice particles probably contributed to high attenuation below the melting level, and that the data are not readil explained in terms of a gamma function raindrop size distribution.

Methods of Optimizing X-Ray Optical Prescriptions for Wide-Field Applications

NASA Technical Reports Server (NTRS)

Elsner, R. F.; O'Dell, S. L.; Ramsey, B. D.; Weisskopf, M. C.

2010-01-01

We are working on the development of a method for optimizing wide-field x-ray telescope mirror prescriptions, including polynomial coefficients, mirror shell relative displacements, and (assuming 4 focal plane detectors) detector placement and tilt that does not require a search through the multi-dimensional parameter space. Under the assumption that the parameters are small enough that second order expansions are valid, we show that the performance at the detector surface can be expressed as a quadratic function of the parameters with numerical coefficients derived from a ray trace through the underlying Wolter I optic. The best values for the parameters are found by solving the linear system of equations creating by setting derivatives of this function with respect to each parameter to zero. We describe the present status of this development effort.

Quantitative X-ray mapping, scatter diagrams and the generation of correction maps to obtain more information about your material

NASA Astrophysics Data System (ADS)

Wuhrer, R.; Moran, K.

2014-03-01

Quantitative X-ray mapping with silicon drift detectors and multi-EDS detector systems have become an invaluable analysis technique and one of the most useful methods of X-ray microanalysis today. The time to perform an X-ray map has reduced considerably with the ability to map minor and trace elements very accurately due to the larger detector area and higher count rate detectors. Live X-ray imaging can now be performed with a significant amount of data collected in a matter of minutes. A great deal of information can be obtained from X-ray maps. This includes; elemental relationship or scatter diagram creation, elemental ratio mapping, chemical phase mapping (CPM) and quantitative X-ray maps. In obtaining quantitative x-ray maps, we are able to easily generate atomic number (Z), absorption (A), fluorescence (F), theoretical back scatter coefficient (η), and quantitative total maps from each pixel in the image. This allows us to generate an image corresponding to each factor (for each element present). These images allow the user to predict and verify where they are likely to have problems in our images, and are especially helpful to look at possible interface artefacts. The post-processing techniques to improve the quantitation of X-ray map data and the development of post processing techniques for improved characterisation are covered in this paper.

'Taking X-ray phase contrast imaging into mainstream applications' and its satellite workshop 'Real and reciprocal space X-ray imaging'.

PubMed

Olivo, Alessandro; Robinson, Ian

2014-03-06

A double event, supported as part of the Royal Society scientific meetings, was organized in February 2013 in London and at Chicheley Hall in Buckinghamshire by Dr A. Olivo and Prof. I. Robinson. The theme that joined the two events was the use of X-ray phase in novel imaging approaches, as opposed to conventional methods based on X-ray attenuation. The event in London, led by Olivo, addressed the main roadblocks that X-ray phase contrast imaging (XPCI) is encountering in terms of commercial translation, for clinical and industrial applications. The main driver behind this is the development of new approaches that enable XPCI, traditionally a synchrotron method, to be performed with conventional laboratory sources, thus opening the way to its deployment in clinics and industrial settings. The satellite meeting at Chicheley Hall, led by Robinson, focused on the new scientific developments that have recently emerged at specialized facilities such as third-generation synchrotrons and free-electron lasers, which enable the direct measurement of the phase shift induced by a sample from intensity measurements, typically in the far field. The two events were therefore highly complementary, in terms of covering both the more applied/translational and the blue-sky aspects of the use of phase in X-ray research. 

Estimating pediatric entrance skin dose from digital radiography examination using DICOM metadata: A quality assurance tool.

PubMed

Brady, S L; Kaufman, R A

2015-05-01

To develop an automated methodology to estimate patient examination dose in digital radiography (DR) imaging using DICOM metadata as a quality assurance (QA) tool. Patient examination and demographical information were gathered from metadata analysis of DICOM header data. The x-ray system radiation output (i.e., air KERMA) was characterized for all filter combinations used for patient examinations. Average patient thicknesses were measured for head, chest, abdomen, knees, and hands using volumetric images from CT. Backscatter factors (BSFs) were calculated from examination kVp. Patient entrance skin air KERMA (ESAK) was calculated by (1) looking up examination technique factors taken from DICOM header metadata (i.e., kVp and mA s) to derive an air KERMA (k air) value based on an x-ray characteristic radiation output curve; (2) scaling k air with a BSF value; and (3) correcting k air for patient thickness. Finally, patient entrance skin dose (ESD) was calculated by multiplying a mass-energy attenuation coefficient ratio by ESAK. Patient ESD calculations were computed for common DR examinations at our institution: dual view chest, anteroposterior (AP) abdomen, lateral (LAT) skull, dual view knee, and bone age (left hand only) examinations. ESD was calculated for a total of 3794 patients; mean age was 11 ± 8 yr (range: 2 months to 55 yr). The mean ESD range was 0.19-0.42 mGy for dual view chest, 0.28-1.2 mGy for AP abdomen, 0.18-0.65 mGy for LAT view skull, 0.15-0.63 mGy for dual view knee, and 0.10-0.12 mGy for bone age (left hand) examinations. A methodology combining DICOM header metadata and basic x-ray tube characterization curves was demonstrated. In a regulatory era where patient dose reporting has become increasingly in demand, this methodology will allow a knowledgeable user the means to establish an automatable dose reporting program for DR and perform patient dose related QA testing for digital x-ray imaging.

Estimating pediatric entrance skin dose from digital radiography examination using DICOM metadata: A quality assurance tool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brady, S. L., E-mail: samuel.brady@stjude.org; Kaufman, R. A., E-mail: robert.kaufman@stjude.org

Purpose: To develop an automated methodology to estimate patient examination dose in digital radiography (DR) imaging using DICOM metadata as a quality assurance (QA) tool. Methods: Patient examination and demographical information were gathered from metadata analysis of DICOM header data. The x-ray system radiation output (i.e., air KERMA) was characterized for all filter combinations used for patient examinations. Average patient thicknesses were measured for head, chest, abdomen, knees, and hands using volumetric images from CT. Backscatter factors (BSFs) were calculated from examination kVp. Patient entrance skin air KERMA (ESAK) was calculated by (1) looking up examination technique factors taken frommore » DICOM header metadata (i.e., kVp and mA s) to derive an air KERMA (k{sub air}) value based on an x-ray characteristic radiation output curve; (2) scaling k{sub air} with a BSF value; and (3) correcting k{sub air} for patient thickness. Finally, patient entrance skin dose (ESD) was calculated by multiplying a mass–energy attenuation coefficient ratio by ESAK. Patient ESD calculations were computed for common DR examinations at our institution: dual view chest, anteroposterior (AP) abdomen, lateral (LAT) skull, dual view knee, and bone age (left hand only) examinations. Results: ESD was calculated for a total of 3794 patients; mean age was 11 ± 8 yr (range: 2 months to 55 yr). The mean ESD range was 0.19–0.42 mGy for dual view chest, 0.28–1.2 mGy for AP abdomen, 0.18–0.65 mGy for LAT view skull, 0.15–0.63 mGy for dual view knee, and 0.10–0.12 mGy for bone age (left hand) examinations. Conclusions: A methodology combining DICOM header metadata and basic x-ray tube characterization curves was demonstrated. In a regulatory era where patient dose reporting has become increasingly in demand, this methodology will allow a knowledgeable user the means to establish an automatable dose reporting program for DR and perform patient dose related QA testing for digital x-ray imaging.« less

Novel applications of X-ray photoelectron spectroscopy on unsupported nanoparticles

NASA Astrophysics Data System (ADS)

Kostko, Oleg; Xu, Bo; Jacobs, Michael I.; Ahmed, Musahid

X-ray photoelectron spectroscopy (XPS) is a powerful technique for chemical analysis of surfaces. We will present novel results of XPS on unsupported, gas-phase nanoparticles using a velocity-map imaging (VMI) spectrometer. This technique allows for probes of both the surfaces of nanoparticles via XPS as well as their interiors via near edge X-ray absorption fine structure (NEXAFS) spectroscopy. A recent application of this technique has confirmed that arginine's guanidinium group exists in a protonated state even in strongly basic solution. Moreover, the core-level photoelectron spectroscopy can provide information on the effective attenuation length (EAL) of low kinetic energy electrons. This contradictory value is important for determining the probing depth of XPS and in photolithography. A new method for determining EALs will be presented.

Radiation Detection and Dual-Energy X-Ray Imaging for Port Security

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pashby, J.; Glenn, S.; Divin, C.

Millions of cargo containers are transported across the United States border annually and are inspected for illicit radioactive material and contraband using a combination of passive radiation portal monitors (RPM) and high energy X-ray non-intrusive inspection (NII) systems. As detection performance is expected to vary with the material composition of cargo, characterizing the types of material present in cargo is important to national security. This work analyzes the passive radiation and dual energy radiography signatures from on RPM and two NII system, respectively. First, the cargos were analyzed to determine their ability to attenuate emissions from an embedded radioactive source.more » Secondly, dual-energy X-ray discrimination was used to determine the material composition and density of the cargos.« less

Noise properties and task-based evaluation of diffraction-enhanced imaging

PubMed Central

Brankov, Jovan G.; Saiz-Herranz, Alejandro; Wernick, Miles N.

2014-01-01

Abstract. Diffraction-enhanced imaging (DEI) is an emerging x-ray imaging method that simultaneously yields x-ray attenuation and refraction images and holds great promise for soft-tissue imaging. The DEI has been mainly studied using synchrotron sources, but efforts have been made to transition the technology to more practical implementations using conventional x-ray sources. The main technical challenge of this transition lies in the relatively lower x-ray flux obtained from conventional sources, leading to photon-limited data contaminated by Poisson noise. Several issues that must be understood in order to design and optimize DEI imaging systems with respect to noise performance are addressed. Specifically, we: (a) develop equations describing the noise properties of DEI images, (b) derive the conditions under which the DEI algorithm is statistically optimal, (c) characterize the imaging performance that can be obtained as measured by task-based metrics, and (d) consider image-processing steps that may be employed to mitigate noise effects. PMID:26158056

Colliding winds from early-type stars in binary systems

NASA Technical Reports Server (NTRS)

Stevens, Ian R.; Blondin, John M.; Pollock, A. M. T.

1992-01-01

The dynamics of the wind and shock structure formed by the wind collision in early-type binary systems is examined by means of a 2D hydrodynamics code, which self-consistently accounts for radiative cooling, and represents a significant improvement over previous attempts to model these systems. The X-ray luminosity and spectra of the shock-heated region, accounting for wind attenuation and the influence of different abundances on the resultant level and spectra of X-ray emission are calculated. A variety of dynamical instabilities that are found to dominate the intershock region is examined. These instabilities are found to be particularly important when postshock material is able to cool. These instabilities disrupt the postshock flow and add a time variability of order 10 percent to the X-ray luminosity. The X-ray spectrum of these systems is found to vary with the nuclear abundances of winds. These theoretical models are used to study several massive binary systems, in particular V444 Cyg and HD 193793.

Fourier domain image fusion for differential X-ray phase-contrast breast imaging.

PubMed

Coello, Eduardo; Sperl, Jonathan I; Bequé, Dirk; Benz, Tobias; Scherer, Kai; Herzen, Julia; Sztrókay-Gaul, Anikó; Hellerhoff, Karin; Pfeiffer, Franz; Cozzini, Cristina; Grandl, Susanne

2017-04-01

X-Ray Phase-Contrast (XPC) imaging is a novel technology with a great potential for applications in clinical practice, with breast imaging being of special interest. This work introduces an intuitive methodology to combine and visualize relevant diagnostic features, present in the X-ray attenuation, phase shift and scattering information retrieved in XPC imaging, using a Fourier domain fusion algorithm. The method allows to present complementary information from the three acquired signals in one single image, minimizing the noise component and maintaining visual similarity to a conventional X-ray image, but with noticeable enhancement in diagnostic features, details and resolution. Radiologists experienced in mammography applied the image fusion method to XPC measurements of mastectomy samples and evaluated the feature content of each input and the fused image. This assessment validated that the combination of all the relevant diagnostic features, contained in the XPC images, was present in the fused image as well. Copyright © 2017 Elsevier B.V. All rights reserved.

Optimization-Based Approach for Joint X-Ray Fluorescence and Transmission Tomographic Inversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di, Zichao; Leyffer, Sven; Wild, Stefan M.

2016-01-01

Fluorescence tomographic reconstruction, based on the detection of photons coming from fluorescent emission, can be used for revealing the internal elemental composition of a sample. On the other hand, conventional X-ray transmission tomography can be used for reconstructing the spatial distribution of the absorption coefficient inside a sample. In this work, we integrate both X-ray fluorescence and X-ray transmission data modalities and formulate a nonlinear optimization-based approach for reconstruction of the elemental composition of a given object. This model provides a simultaneous reconstruction of both the quantitative spatial distribution of all elements and the absorption effect in the sample. Mathematicallymore » speaking, we show that compared with the single-modality inversion (i.e., the X-ray transmission or fluorescence alone), the joint inversion provides a better-posed problem, which implies a better recovery. Therefore, the challenges in X-ray fluorescence tomography arising mainly from the effects of self-absorption in the sample are partially mitigated. The use of this technique is demonstrated on the reconstruction of several synthetic samples.« less

An upgraded x-ray spectroscopy diagnostic on MST.

PubMed

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

2010-10-01

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).

Comparison of Monte Carlo simulation of gamma ray attenuation coefficients of amino acids with XCOM program and experimental data

NASA Astrophysics Data System (ADS)

Elbashir, B. O.; Dong, M. G.; Sayyed, M. I.; Issa, Shams A. M.; Matori, K. A.; Zaid, M. H. M.

2018-06-01

The mass attenuation coefficients (μ/ρ), effective atomic numbers (Zeff) and electron densities (Ne) of some amino acids obtained experimentally by the other researchers have been calculated using MCNP5 simulations in the energy range 0.122-1.330 MeV. The simulated values of μ/ρ, Zeff, and Ne were compared with the previous experimental work for the amino acids samples and a good agreement was noticed. Moreover, the values of mean free path (MFP) for the samples were calculated using MCNP5 program and compared with the theoretical results obtained by XCOM. The investigation of μ/ρ, Zeff, Ne and MFP values of amino acids using MCNP5 simulations at various photon energies when compared with the XCOM values and previous experimental data for the amino acids samples revealed that MCNP5 code provides accurate photon interaction parameters for amino acids.

A relation between the short time variations of cosmic rays and geomagnetic field change

NASA Technical Reports Server (NTRS)

Saki, T.; Kato, M.

1985-01-01

An event is reported of approx. 37 min periodicity in cosmic ray intensity observed at Akeno(38 deg 47 N, 138 deg 30 E. 900m above s.l., cutoff 10.4 GV) during 1300 approx. 1900 UT on April 25th, 1984, just a day before Forbush decrease of April 26th. This event seemed to be followed by the periodic variations of the geomagnetic field observed at Kakioka (36 deg 23 N, 140 deg 18 E). The regression coefficient between them was obtained approx. 0.07%/10nT. It is shown that in general the power spectral density of cosmic rays in the frequency of 0.0001 approx. 0.001Hz correlates positively with the fluctuations of geomagnetic field (Dst field) around approx. 1.2x0.0001Hz. From the analysis of 47 days data (April 14th to June 13th, 1984) the regression curve was obtained as y=0.275x sup 0.343 with the correlation coefficient of 0.48, where x and y mean Fourier components of Dst field summed over 1.04 approx. 1.39x0.001Hz and cosmic ray power spectral density averaged over 0.0001 approx. 0.001Hz.

Dimensional Measurements of Three Tubes by Computed Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneberk, D J; Martz, Jr., H E; Brown, W D

2004-10-05

Low density polyethylene (LDPE), copper (Cu), and gold (Au) tubes were scanned on KCAT to identify and evaluate the impact of phase effects on quantitative object recovery. These tubes are phantoms for high energy density capsules.[Logan, et al. 2004] Digital radiographs for each tube are shown in Figure 1. The LDPE tube was scanned at 60 kV, while the Cu and the Au tubes were scanned at 140 kV. All tubes were scanned at a magnification of 3, with approximately 100-mm distance between the exit plane of the tube and the scintillator. Notice the prominence of the outer bright andmore » inner dark edges for the LDPE tube DR, and their absence from the Cu and Au tube DRs. The bright and dark edges are a result of change in phase of the x-rays. The x-ray fluence is partly attenuated and partly refracted. The location near the outer edge of the tube appears to be more attenuating since those x-rays have refracted to locations just outside the tube. Alternatively, the added counts from the refraction result in intensities that are greater than the incident intensity effectively representing a ''negative attenuation''. This results in more counts in that location than in the incident intensity image violating the ''positive-definite'' requirement for standard CT reconstruction methodologies. One aspect of our CT processing techniques remove some of this signal on the outside of the object. The goal of this paper is to evaluate the accuracy of our dimensional measurement methods for mesoscale object inspection.« less

Linear Electrooptic Effect In Sputtered Polycrystalline LiNbO3 Films

NASA Astrophysics Data System (ADS)

Griffel, G.; Ruschin, Shlomo; Croitoru, Nathan I.

1989-02-01

Light guiding and modulation was demonstrated in sputtered LiNbO3 films deposited on glass substrates. The films exhibit exceptionally low attenuation (< 2dB/cm) and the highest electrooptical coefficient reported so far for this kind of films (1.34 x 10-12 m/V).

Visualization of soil particulate organic matter by means of X-ray CT?

NASA Astrophysics Data System (ADS)

Sleutel, Steven; Van Loo, Denis; Maenhout, Peter; Van Hoorebeke, Luc; Cnudde, Veerle; De Neve, Stefaan

2014-05-01

The role of soil structure in organic matter (OM) stabilization has been primarily investigated through physical fractionation studies operative at the scale of aggregates and smaller organo-mineral particles. By narrowing down soil structure to an arrangement of mineral and organic particles, the majority of studies did not explore the spatial organization of the soil pore network, the actual habitat of microorganisms. The pore structure of soil can have a significant impact on soil processes like OM decomposition by excluding OM from micro-organisms in small pores, by regulating the diffusion of substrates and metabolites and by regulating aeration and presence of moisture. Because of its ability to visualize the 3D architecture of soil non-destructively, X-ray Computed Tomography (CT) is becoming a widespread tool for studying soil pore network structure. However, phase determination of pore space, soil OM, soil mineral matter (MM) and water is often limited even with the latest technological and software advances, allowing high resolution and better quality imaging. Contrast agents commonly used in histology enable enhancement of X-ray attenuation of targeted structures or compounds. Here we report on the first systematic investigation of the use of such X-ray contrast agents for soil research. An evaluation procedure as well as a method to apply the agents to soil samples was developed and applied on reference soil samples. The effectiveness and selectivity of the contrast agents was evaluated for soil organic matter (SOM), MM and water. Several products were found to selectively increase the attenuation of water or SOM. The four agents with the best OM-staining capabilities (Phosphomolybdenic acid (PMA), silver nitrate, lead nitrate and lead acetate) were further tested on an OM-MM mixture. Observed differences in reactivity of the staining agents with MM components were apparent, suggesting that contrasting agents may have to be selected for the specific composition of the soil mineral matrix. Furthermore, techniques such as multiple-energy scanning and K-edge imaging, even in the future perhaps in combination with spectral resolving detectors or spectroscopic techniques can could further enhance the potential benefit from this study of X-ray CT staining agents. The high Z elements of the staining agents have unique and characteristic traits that can be detected or quantified with the abovementioned techniques and methods. We conclude that, given resolution limits and inherent presence of partial volume effects staining, X-ray CT-based localization of discrete SOM particles will be limited to a lower limit of 20-50 µm. Still, the improved 3D visualization of OM and soil pore space opens up possibilities for tailored lab experiments with measures of microbial activity, which could generate new insights in carbon cycling at small scales. In addition, we report on a lab incubation experiment in which CO2 respiration from soil cores was monitored (headspace GC analysis) and an X-ray CT approach yielded soil pore size distributions. We incubated a sandy loam soil (with application of ground grass or sawdust) in 18 small aluminium rings (Ø 1 cm, h 1 cm). Bulk density was adjusted to 1.1 or 1.3 Mg m-3 (compaction) and 6 rings were filled at a coarser Coarse Sand:Fine Sand:Silt+Clay ratio. While compaction induced a strong reduction in the cumulative C mineralization for both grass and sawdust substrates, artificial change to a coarser soil texture only reduced net C mineralization from the added sawdust. There thus appears to be a strong interaction effect between soil pore structure and substrate type on substrate decomposition. Correlation coefficients between the C mineralization rates and volumes of 7 pore size classes (from the X-ray CT data) also showed an increasing positive correlation with increasing pore size. Since any particulate organic matter initially present in the soil was removed prior to the experiment (sieving, ashing the >53µm fraction and recombining with the <53µm fraction), the added OM can be localized by means of X-ray CT. Through on-going image analysis the surrounding porosity of the added grass or sawdust particles is being quantified to further study the interaction between the soil pore structure and substrate decomposition.

SU-F-I-75: Half-Value Layer Thicknesses and Homogeneity Coefficients for Fluoroscopic X-Ray Beam Spectra Incorporating Spectral Filtration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wunderle, K; Wayne State University School of Medicine, Detroit, MI; Godley, A

Purpose: The purpose of this investigation is to quantify various first half-value-layers (HVLs), second HVLs and homogeneity coefficients (HCs) for a state-of-the-art fluoroscope utilizing spectral (copper) filtration. Methods: A Radcal (Monrovia, Ca) AccuPro dosimeter with a 10×6-6 calibrated ionization chamber was used to measure air kerma for radiographic x-ray exposures made on a Siemens (Erlangen, Germany) Artis ZeeGo fluoroscope operated in the service mode. The ionization chamber was centered in the x-ray beam at 72 cm from the focal spot with a source-to-image-distance of 120 cm. The collimators were introduced to limit the x-ray field to approximately 5 cm ×more » 5 cm at the ionization chamber plane. Type-1100 aluminum filters, in 0.5 mm increments, were used to determine the HVL. Two HVL calculation methods were used, log-linear interpolation and Lambert-W interpolation as described by Mathieu [Med Phys, 38(8), 4546 (2011)]. Multiple measurements were made at 60, 80, 100, 120 kVp at spectral filtration thicknesses of 0, 0.1, 0.3, 0.6 and 0.9 mm. Results: First HVL, second HVL, and HCs are presented for the fluoroscopic x-ray beam spectra indicated above, with nearly identical results from the two interpolation methods. Accuracy of the set kVp was also determined and deviated less than 2%. First HVLs for fluoroscopic x-ray beam spectra without spectral filtration determined in our study were 7%–16% greater than previously published data by Fetterly et al. [Med Phys, 28, 205 (2001)]. However, the FDA minimum HVL requirements changed since that publication, requiring larger HVLs as of 2006. Additionally, x-ray tube and generator architecture have substantially changed over the last 15 years providing different beam spectra. Conclusion: X-ray beam quality characteristics for state-of-the-art fluoroscopes with spectral filtration have not been published. This study provides reference data which will be useful for defining beam qualities encountered on fluoroscopes using spectral filtration.« less

Theoretical consideration of the energy resolution in planar HPGe detectors for low energy X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samedov, Victor V.

In this work, theoretical consideration of the processes in planar High Purity Ge (HPGe) detectors for low energy X-rays using the random stochastic processes formalism was carried out. Using the random stochastic processes formalism, the generating function of the processes of X-rays registration in a planar HPGe detector was derived. The power serial expansions of the detector amplitude and the variance in terms of the inverse bias voltage were derived. The coefficients of these expansions allow determining the Fano factor, electron mobility lifetime product, nonuniformity of the trap density, and other characteristics of the semiconductor material. (authors)

High-rate x-ray spectroscopy in mammography with a CdTe detector: a digital pulse processing approach.

PubMed

Abbene, L; Gerardi, G; Principato, F; Del Sordo, S; Ienzi, R; Raso, G

2010-12-01

Direct measurement of mammographic x-ray spectra under clinical conditions is a difficult task due to the high fluence rate of the x-ray beams as well as the limits in the development of high resolution detection systems in a high counting rate environment. In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate x-ray spectroscopy in mammography. The DPP system performs a digital pile-up inspection and a digital pulse height analysis of the detector signals, digitized through a 14-bit, 100 MHz digitizer, for x-ray spectroscopy even at high photon counting rates. We investigated on the response of the digital detection system both at low (150 cps) and at high photon counting rates (up to 500 kcps) by using monoenergetic x-ray sources and a nonclinical molybdenum anode x-ray tube. Clinical molybdenum x-ray spectrum measurements were also performed by using a pinhole collimator and a custom alignment device. The detection system shows excellent performance up to 512 kcps with an energy resolution of 4.08% FWHM at 22.1 keV. Despite the high photon counting rate (up to 453 kcps), the molybdenum x-ray spectra, measured under clinical conditions, are characterized by a low number of pile-up events. The agreement between the attenuation curves and the half value layer values, obtained from the measured spectra, simulated spectra, and from the exposure values directly measured with an ionization chamber, also shows the accuracy of the measurements. These results make the proposed detection system a very attractive tool for both laboratory research and advanced quality controls in mammography.

Antioxidant protects blood-testis barrier against synchrotron radiation X-ray-induced disruption

PubMed Central

Zhang, Tingting; Liu, Tengyuan; Shao, Jiaxiang; Sheng, Caibin; Hong, Yunyi; Ying, Weihai; Xia, Weiliang

2015-01-01

Synchrotron radiation (SR) X-ray has wide biomedical applications including high resolution imaging and brain tumor therapy due to its special properties of high coherence, monochromaticity and high intensity. However, its interaction with biological tissues remains poorly understood. In this study, we used the rat testis as a model to investigate how SR X-ray would induce tissue responses, especially the blood-testis barrier (BTB) because BTB dynamics are critical for spermatogenesis. We irradiated the male gonad with increasing doses of SR X-ray and obtained the testicles 1, 10 and 20 d after the exposures. The testicle weight and seminiferous tubule diameter reduced in a dose- and time-dependent manner. Cryosections of testes were stained with tight junction (TJ) component proteins such as occludin, claudin-11, JAM-A and ZO-1. Morphologically, increasing doses of SR X-ray consistently induced developing germ cell sloughing from the seminiferous tubules, accompanied by shrinkage of the tubules. Interestingly, TJ constituent proteins appeared to be induced by the increasing doses of SR X-ray. Up to 20 d after SR X-ray irradiation, there also appeared to be time-dependent changes on the steady-state level of these protein exhibiting differential patterns at 20-day after exposure, with JAM-A/claudin-11 still being up-regulated whereas occludin/ZO-1 being down-regulated. More importantly, the BTB damage induced by 40 Gy of SR X-ray could be significantly attenuated by antioxidant N-Acetyl-L-Cysteine (NAC) at a dose of 125 mg/kg. Taken together, our studies characterized the changes of TJ component proteins after SR X-ray irradiation, illustrating the possible protective effects of antioxidant NAC to BTB integrity. PMID:26413412

Brillouin function characteristics for La-Co substituted barium hexaferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Chuanjian, E-mail: wcjuestc2005@gmail.com, E-mail: ksun@uestc.edu.cn; Yu, Zhong; Sun, Ke, E-mail: wcjuestc2005@gmail.com, E-mail: ksun@uestc.edu.cn

2015-09-14

La-Co substituted barium hexaferrites with the chemical formula of Ba{sub 1−x}La{sub x}Fe{sub 12−x}Co{sub x}O{sub 19} (x = 0.0, 0.1, 0.3, and 0.5), prepared by a conventional ceramic method, were systematically investigated by Raman spectra, X-ray photoelectron spectroscopy, Rietveld refinement of X-ray diffraction patterns, and vibrating sample magnetometer. The result manifests that all the compounds are crystallized in magnetoplumbite hexagonal structure. Trivalent cobalt ions prevailingly occupy the 2a, 4f{sub 1}, and 12k sites. According to Néel model of collinear-spin ferrimagnetism, the molecular-field coefficients ω{sub bf2}, ω{sub kf1}, ω{sub af1}, ω{sub kf2}, and ω{sub bk} of La-Co substituted barium hexaferrites have been calculated usingmore » the nonlinear fitting method, and the magnetic moment of five sublattices (2a, 2b, 4f{sub 1}, 4f{sub 2}, and 12k) versus temperature T has been also investigated. The fitting results are coincided well with the experimental data. Moreover, with the increase of La-Co substitution amount x, the molecular-field coefficients ω{sub bf2} and ω{sub af1} decrease constantly, while the molecular-field coefficients ω{sub kf1}, ω{sub kf2}, and ω{sub bk} show a slight change.« less

Comparison of photon attenuation coefficients (2-150 KeV) for diagnostic imaging simulations

NASA Astrophysics Data System (ADS)

Dodge, Charles W., III; Flynn, Michael J.

2004-05-01

The Radiology Research Laboratory at the Henry Ford Hospital has been involved in modeling x-ray units in order to predict image quality. A critical part of that modeling process is the accurate choice of interaction coefficients. This paper serves as a review and comparison of existing interaction models. Our objective was to obtain accurate and easily calculated interaction coefficients, at diagnostically relevant energies. We obtained data from: McMaster, Lawrence Berkeley Lab data (LBL), XCOM and FFAST Data from NIST, and the EPDL-97 database via LLNL. Our studies involve low energy photons; therefore, comparisons were limited to Coherent (Rayleigh), Incoherent (Compton) and Photoelectric effects, which were summed to determine a total interaction cross section. Without measured data, it becomes difficult to definitively choose the most accurate method. However, known limitations in the McMaster data and smoothing of photo-edge transitions can be used as a guide to establish more valid approaches. Each method was compared to one another graphically and at individual points. We found that agreement between all methods was excellent when away from photo-edges. Near photo-edges and at low energies, most methods were less accurate. Only the Chanter (FFAST) data seems to have consistently and accurately predicted the placement of edges (through M-shell), while minimizing smoothing errors. The EPDL-97 data by LLNL was the best over method in predicting coherent and incoherent cross sections.

Facile formation of dendrimer-stabilized gold nanoparticles modified with diatrizoic acid for enhanced computed tomography imaging applications.

PubMed

Peng, Chen; Li, Kangan; Cao, Xueyan; Xiao, Tingting; Hou, Wenxiu; Zheng, Linfeng; Guo, Rui; Shen, Mingwu; Zhang, Guixiang; Shi, Xiangyang

2012-11-07

We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid (G5.NH(2)-DTA) as stabilizers for enhanced computed tomography (CT) imaging applications. In this study, by simply mixing G5.NH(2)-DTA dendrimers with gold salt in aqueous solution at room temperature, dendrimer-entrapped gold nanoparticles (Au DENPs) with a mean core size of 2.5 nm were able to be spontaneously formed. Followed by an acetylation reaction to neutralize the dendrimer remaining terminal amines, Au DSNPs with a mean size of 6 nm were formed. The formed DTA-containing [(Au(0))(50)-G5.NHAc-DTA] DSNPs were characterized via different techniques. We show that the Au DSNPs are colloid stable in aqueous solution under different pH and temperature conditions. In vitro hemolytic assay, cytotoxicity assay, flow cytometry analysis, and cell morphology observation reveal that the formed Au DSNPs have good hemocompatibility and are non-cytotoxic at a concentration up to 3.0 μM. X-ray absorption coefficient measurements show that the DTA-containing Au DSNPs have enhanced attenuation intensity, much higher than that of [(Au(0))(50)-G5.NHAc] DENPs without DTA or Omnipaque at the same molar concentration of the active element (Au or iodine). The formed DTA-containing Au DSNPs can be used for CT imaging of cancer cells in vitro as well as for blood pool CT imaging of mice in vivo with significantly improved signal enhancement. With the two radiodense elements of Au and iodine incorporated within one particle, the formed DTA-containing Au DSNPs may be applicable for CT imaging of various biological systems with enhanced X-ray attenuation property and detection sensitivity.

The coefficient of bond thermal expansion measured by extended x-ray absorption fine structure.

PubMed

Fornasini, P; Grisenti, R

2014-10-28

The bond thermal expansion is in principle different from the lattice expansion and can be measured by correlation sensitive probes such as extended x-ray absorption fine structure (EXAFS) and diffuse scattering. The temperature dependence of the coefficient α(bond)(T) of bond thermal expansion has been obtained from EXAFS for CdTe and for Cu. A coefficient α(tens)(T) of negative expansion due to tension effects has been calculated from the comparison of bond and lattice expansions. Negative lattice expansion is present in temperature intervals where α(bond) prevails over α(tens); this real-space approach is complementary but not equivalent to the Grüneisen theory. The relevance of taking into account the asymmetry of the nearest-neighbours distribution of distances in order to get reliable bond expansion values and the physical meaning of the third cumulant are thoroughly discussed.

Calculation of x-ray spectra emerging from an x-ray tube. Part I. electron penetration characteristics in x-ray targets.

PubMed

Poludniowski, Gavin G; Evans, Philip M

2007-06-01

The penetration characteristics of electron beams into x-ray targets are investigated for incident electron kinetic energies in the range 50-150 keV. The frequency densities of electrons penetrating to a depth x in a target, with a fraction of initial kinetic energy, u, are calculated using Monte Carlo methods for beam energies of 50, 80, 100, 120 and 150 keV in a tungsten target. The frequency densities for 100 keV electrons in Al, Mo and Re targets are also calculated. A mixture of simple modeling with equations and interpolation from data is used to generalize the calculations in tungsten. Where possible, parameters derived from the Monte Carlo data are compared to experimental measurements. Previous electron transport approximations in the semiempirical models of other authors are discussed and related to this work. In particular, the crudity of the use of the Thomson-Whiddington law to describe electron penetration and energy loss is highlighted. The results presented here may be used towards calculating the target self-attenuation correction for bremsstrahlung photons emitted within a tungsten target.

Physically corrected forward operators for induced emission tomography: a simulation study

NASA Astrophysics Data System (ADS)

Viganò, Nicola Roberto; Solé, Vicente Armando

2018-03-01

X-ray emission tomography techniques over non-radioactive materials allow one to investigate different and important aspects of the matter that are usually not addressable with the standard x-ray transmission tomography, such as density, chemical composition and crystallographic information. However, the quantitative reconstruction of these investigated properties is hindered by additional problems, including the self-attenuation of the emitted radiation. Work has been done in the past, especially concerning x-ray fluorescence tomography, but this has always focused on solving very specific problems. The novelty of this work resides in addressing the problem of induced emission tomography from a much wider perspective, introducing a unified discrete representation that can be used to modify existing algorithms to reconstruct the data of the different types of experiments. The direct outcome is a clear and easy mathematical description of the implementation details of such algorithms, despite small differences in geometry and other practical aspects, but also the possibility to express the reconstruction as a minimization problem, allowing the use of variational methods, and a more flexible modeling of the noise involved in the detection process. In addition, we look at the results of a few selected simulated data reconstructions that describe the effect of physical corrections like the self-attenuation, and the response to noise of the adapted reconstruction algorithms.