Enhanced X-ray absorption for micro-CT analysis of low density polymers

Micro-computed tomography (micro-CT) facilitates the visualization and quantification of contrast-enhanced microvessels within intact tissue specimens, but conventional preclinical vascular contrast agents may be inadequate near dense tissue (such as bone). Typical lead-based contrast agents do not exhibit optimal X-ray absorption properties when used with X-ray tube potentials below 90 kilo-electron volts (keV). We have developed a high-atomic number lanthanide (erbium) contrast agent, with a K-edge at 57.5 keV. This approach optimizes X-ray absorption in the output spectral band of conventional microfocal spot X-ray tubes. Erbium oxide nanoparticles (nominal diameter < 50 nm) suspended in a two-part silicone elastomer produce a perfusable fluid with viscosity of 19.2 mPa-s. Ultrasonic cavitation was used to reduce aggregate sizes to <70 nm. Postmortem intact mice were perfused to investigate the efficacy of contrast agent. The observed vessel contrast was >4000 Hounsfield units, and perfusion of vessels < 10 μm in diameter was demonstrated in kidney glomeruli. The described new contrast agent facilitated the visualization and quantification of vessel density and microarchitecture, even adjacent to dense bone. Erbium’s K-edge makes this contrast agent ideally suited for both single- and dual-energy micro-CT, expanding potential preclinical research applications in models of musculoskeletal, oncological, cardiovascular, and neurovascular diseases.

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Three-dimensional imaging and morphometric analysis of alveolar tissue from microfocal X-ray-computed tomography

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00088.2005 ◽

2006 ◽

Vol 291 (3) ◽

pp. L535-L545 ◽

Cited By ~ 42

Author(s):

Horst Detlef Litzlbauer ◽

Christoph Neuhaeuser ◽

Alexander Moell ◽

Susanne Greschus ◽

Andreas Breithecker ◽

...

Keyword(s):

Computed Tomography ◽

Three Dimensional ◽

Ct Scans ◽

Micro Ct ◽

Tissue Samples ◽

X Ray ◽

Ct Analysis ◽

X Ray Computed ◽

Mean Linear Intercept ◽

Alveolar Surface

We evaluated microfocal X-ray-computed tomography (micro-CT) as a method to visualize lung architecture two and three dimensionally and to obtain morphometric data. Inflated porcine lungs were fixed by formaldehyde ventilation. Tissue samples (8-mm diameter, 10-mm height) were stained with osmium tetroxide, and 400 projection images (1,024 × 1,024 pixel) were obtained. Continuous isometric micro-CT scans (voxel size 9 μm) were acquired to reconstruct two- and three-dimensional images. Tissue samples were sectioned (8-μm thickness) for histological analysis. Alveolar surface density and mean linear intercept were assessed by stereology-based morphometry in micro-CT scans and corresponding histological sections. Furthermore, stereology-based morphometry was compared with morphometric semi-automated micro-CT analysis within the same micro-CT scan. Agreement of methods was assessed by regression and Bland-Altman analysis. Comparing histology with micro-CT, alveolar surface densities (35.4 ± 2.4 vs. 33.4 ± 1.9/mm, P < 0.05) showed a correlation ( r = 0.72; P = 0.018) with an agreement of 2 ± 1.6/mm; the mean linear intercept (135.7 ± 14.5 vs. 135.8 ± 15 μm) correlated well ( r = 0.97; P < 0.0001) with an agreement of −0.1 ± 3.4 μm. Semi-automated micro-CT analysis resulted in smaller alveolar surface densities (33.4 ± 1.9 vs. 30.5 ± 1/mm; P < 0.01) with a correlation ( r = 0.70; P = 0.023) and agreement of 2.9 ± 1.4/mm. Non-destructive micro-CT scanning offers the advantage to visualize the spatial tissue architecture of small lung samples two and three dimensionally.

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Mechanical and Microscopic Characteristics of Polyurethane-Based Pervious Pavement Composites

Materials ◽

10.3390/ma14164365 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4365

Author(s):

Hongdong Cho ◽

Hongsu Bae ◽

Chanho Park ◽

Hyeong Min Park ◽

Seo-Eun Oh ◽

...

Keyword(s):

Morphological Characteristics ◽

Element Model ◽

Micro Ct ◽

Micro Computed Tomography ◽

X Ray ◽

Pavement Materials ◽

Pervious Pavement ◽

Brittle Behavior ◽

Internal Structures ◽

Ct Analysis

Conventional pervious pavement materials (PPM) that consist of cement and aggregate materials are known for poor durability due to their brittle behavior. Thus, to enhance the durability, we fabricated polymeric PPMs from durable and abundant polyurethane (PU) and undertook mechanical and microscopic characterizations. PU-based PPM samples with varying aggregate sizes were produced and examined to test their compressive strength and water permeability. Furthermore, X-ray micro-computed tomography (micro-CT) was implemented to analyze the samples’ pore and tortuosity characteristics. Through the micro-CT analysis, the morphological characteristics of PPM’s internal structures were identified and quantitively analyzed the correlations between the pore size distribution, connectivity, and tortuosity within the samples. Finally, the microstructures derived from micro-CT were generated as a finite element model and also numerically determined the stress distribution generated inside.

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Mechanical and Microscopic Characteristics of Polyurethane-Based Pervious Pavement Composites

10.20944/preprints202107.0234.v1 ◽

2021 ◽

Author(s):

Hongdong Cho ◽

Hongsu Bae ◽

Changho Park ◽

Hyeong Min Park ◽

Seo-Eun Oh ◽

...

Keyword(s):

Morphological Characteristics ◽

Element Model ◽

Micro Ct ◽

Micro Computed Tomography ◽

X Ray ◽

Pavement Materials ◽

Pervious Pavement ◽

Brittle Behavior ◽

Internal Structures ◽

Ct Analysis

Conventional pervious pavement materials (PPM) consist of cement and aggregate materials and are known for poor durability due to their brittle behavior. Herein, we fabricated polymeric PPMs from durable and abundant polyurethane (PU) to enhance the durability of the material and undertook mechanical and microscopic characterizations. PU-based PPM samples with varying aggregate sizes were produced and the compressive strength and water permeability of each were examined. The pore and tortuosity characteristics of the specimens were analyzed using X-ray micro-computed tomography (micro-CT). Through the micro-CT analysis, the morphological characteristics of the internal structures of PPM were identified and the correlations between the pore size distribution, connectivity, and tortuosity within the specimen were quantitatively analyzed. The microstructures derived from micro-CT were generated as a finite element model and the stress distribution generated inside was numerically determined.

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X-ray microanalysis of thin specimens in the transmission electron microscope at voltages up to 1000 Kv.

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109847 ◽

1978 ◽

Vol 36 (1) ◽

pp. 540-541

Author(s):

G. Cliff ◽

M.J. Nasir ◽

G.W. Lorimer ◽

N. Ridley

Keyword(s):

Electron Microscope ◽

Transmission Electron Microscope ◽

Weight Fraction ◽

Present Series ◽

Constant Independent ◽

X Ray ◽

Transmission Electron ◽

Series Of Experiments ◽

Image Position ◽

X Ray Absorption

In a specimen which is transmission thin to 100 kV electrons - a sample in which X-ray absorption is so insignificant that it can be neglected and where fluorescence effects can generally be ignored (1,2) - a ratio of characteristic X-ray intensities, I1/I2 can be converted into a weight fraction ratio, C1/C2, using the equationwhere k12 is, at a given voltage, a constant independent of composition or thickness, k12 values can be determined experimentally from thin standards (3) or calculated (4,6). Both experimental and calculated k12 values have been obtained for K(11<Z>19),kα(Z>19) and some Lα radiation (3,6) at 100 kV. The object of the present series of experiments was to experimentally determine k12 values at voltages between 200 and 1000 kV and to compare these with calculated values.The experiments were carried out on an AEI-EM7 HVEM fitted with an energy dispersive X-ray detector.

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SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100097600 ◽

1981 ◽

Vol 39 ◽

pp. 198-199 ◽

Cited By ~ 3

Author(s):

R.F. Egerton

Keyword(s):

Cross Sections ◽

Fortran Program ◽

Absorption Data ◽

X Ray ◽

Atomic Electrons ◽

Energy Dependent ◽

Hydrogenic Model ◽

Electron Energy Loss ◽

X Ray Absorption ◽

Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

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point-Analysis Using the Extrapolation Method in the Analytical Electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135757 ◽

1990 ◽

Vol 48 (2) ◽

pp. 430-431

Author(s):

Zenji Horita ◽

Ryuzo Nishimachi ◽

Takeshi Sano ◽

Minoru Nemoto

Keyword(s):

Electron Microscope ◽

Extrapolation Method ◽

X Ray ◽

Absorption Correction ◽

Point Analysis ◽

Analytical Electron ◽

Analytical Electron Microscope ◽

Data Points ◽

Identical Composition ◽

X Ray Absorption

Absorption correction is often required in quantitative x-ray microanalysis of thin specimens using the analytical electron microscope. For such correction, it is convenient to use the extrapolation method[l] because the thickness, density and mass absorption coefficient are not necessary in the method. The characteristic x-ray intensities measured for the analysis are only requirement for the absorption correction. However, to achieve extrapolation, it is imperative to obtain data points more than two at different thicknesses in the identical composition. Thus, the method encounters difficulty in analyzing a region equivalent to beam size or the specimen with uniform thickness. The purpose of this study is to modify the method so that extrapolation becomes feasible in such limited conditions. Applicability of the new form is examined by using a standard sample and then it is applied to quantification of phases in a Ni-Al-W ternary alloy.The earlier equation for the extrapolation method was formulated based on the facts that the magnitude of x-ray absorption increases with increasing thickness and that the intensity of a characteristic x-ray exhibiting negligible absorption in the specimen is used as a measure of thickness.

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EXELFS Studies of Carbon Fibers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133953 ◽

1990 ◽

Vol 48 (2) ◽

pp. 72-73

Author(s):

V. Serin ◽

K. Hssein ◽

G. Zanchi ◽

J. Sévely

Keyword(s):

Carbon Fibers ◽

Energy Analysis ◽

Electron Excitation ◽

Complex Structures ◽

High Modulus ◽

Promising Technique ◽

X Ray ◽

Fine Structures ◽

X Ray Absorption

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

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Improving soil remediation through characterization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138300 ◽

1995 ◽

Vol 53 ◽

pp. 386-387

Author(s):

E. C. Buck ◽

N. L. Dietz ◽

J. K. Bates

Keyword(s):

Dust Particles ◽

Radiochemical Analysis ◽

Solid Product ◽

Uranium Contamination ◽

Physical Separation ◽

X Ray ◽

Rocky Flats ◽

Remediation Strategies ◽

Bearing Materials ◽

X Ray Absorption

Operations at former weapons processing facilities in the U. S. have resulted in a large volume of radionuclidecontaminated soils and residues. In an effort to improve remediation strategies and meet environmental regulations, radionuclide-bearing particles in contaminant soils from Fernald in Ohio and the Rocky Flats Plant (RFP) in Colorado have been characterized by electron microscopy. The object of these studies was to determine the form of the contaminant radionuclide, so that it properties could be established [1]. Physical separation and radiochemical analysis determined that uranium contamination at Fernald was not present exclusively in any one size/density fraction [2]. The uranium-contamination resulted from aqueous and solid product spills, air-borne dust particles, and from the operation of an incinerator on site. At RFP the contamination was from the incineration of Pu-bearing materials. Further analysis by x-ray absorption spectroscopy indicated that the majority of the uranium was in the 6+ oxidation state [3].

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