X-ray Fluorescence Screening Research Articles

Laboratory μ-X-ray fluorescence elemental mapping of herbarium specimens for hyperaccumulator studies

Background and aimsAn innovative approach “Herbarium Ionomics” used a handheld X-ray fluorescence (XRF) device to non-destructively extract quantitative elemental data (i.e., the metallome) from herbarium specimens. This has led to the discovery of numerous hyperaccumulator plants. Once a new hyperaccumulator is identified through XRF screening, the next step is to verify whether this is in fact ‘real’ as there are numerous causes for anomalous measurements caused by artefacts. MethodsHere we report on the use of a scanning μ-XRF for herbarium specimens to answer the question whether the abnormal concentrations of a particular element truly represent hyperaccumulation as well as reveal broad patterns of elemental distribution to provide the first hints at the ecophysiology of the hyperaccumulated element.Results and conclusionsThe use of μ-XRF analysis of herbarium specimens can form the starting point for further studies using specimens properly prepared for micro-analytical investigations.

The X-ray fluorescence screening of multiple elements in herbarium specimens from the Neotropical region reveals new records of metal accumulation in plants.

Plants have developed a diversity of strategies to take up and store essential metals in order to colonize various types of soils including mineralized soils. Yet, our knowledge of the capacity of plant species to accumulate metals is still fragmentary across the plant kingdom. In this study, we have used the X-ray fluorescence technology to analyze metal concentration in a wide diversity of species of the Neotropical flora that was not extensively investigated so far. In total, we screened more than 11000 specimens representing about 5000 species from herbaria in Paris and Cuba. Our study provides a large overview of the accumulation of metals such as manganese, zinc, and nickel in the Neotropical flora. We report 30 new nickel hyperaccumulating species from Cuba, including the first records in the families Connaraceae, Melastomataceae, Polygonaceae, Santalaceae, and Urticaceae. We also identified the first species from this region of the world that can be considered as manganese hyperaccumulators in the genera Lomatia (Proteaceae), Calycogonium (Melastomataceae), Ilex (Aquifoliaceae), Morella (Myricaceae), and Pimenta (Myrtaceae). Finally, we report the first zinc hyperaccumulator, Rinorea multivenosa (Violaceae), from the Amazonas region. The identification of species able to accumulate high amounts of metals will become instrumental to support the development of phytotechnologies in order to limit the impact of soil metal pollution in this region of the world.

Herbarium X-ray fluorescence screening for nickel, cobalt and manganese hyperaccumulator plants in the flora of Sabah (Malaysia, Borneo Island)

Sabah (Malaysia) on the Island of Borneo has a high plant diversity (>8000 species) occurring on a wide range of soils, including ultramafic soils which are known to host hyperaccumulator plants. In this study a new approach (“Herbarium X-ray Fluorescence Ionomics”) was used to obtain elemental data from herbarium specimens using non-destructive X-ray Fluorescence spectroscopy analysis. In total ~7300 specimens were thus analysed for nickel, cobalt, and manganese concentrations at the Herbarium of the Forest Research Centre (FRC) in Sepilok, Sabah. The measurements led to recording a total of 759 specimens (originating from 17 families in 30 genera and 74 species) as trace element hyperaccumulators, including 28 nickel hyperaccumulator species (in 10 families, 17 genera), 12 cobalt hyperaccumulator species (in 3 families, 7 genera), and 51 manganese hyperaccumulator species (in 12 families, 24 genera). The outcomes of this research demonstrate that X-ray Fluorescence scanning is highly useful approach for hyperaccumulator plant discovery in herbarium collections that has the potential to add vast numbers of hyperaccumulating taxa to the global inventory.

Spatial variability of trace elements in allotment gardens of four European cities: assessments at city, garden, and plot scale

Urban allotment gardens (UAGs) are expanding worldwide, especially in large cities. Environmental pressures (direct and diffuse pollution, gardener practice, geogenic contamination) often result in the accumulation of potentially harmful trace elements in garden soils. The objectives of this study were to assess the spatial variability of trace element distribution in UAGs from city, garden, and plot scale in four European cities; to provide a baseline understanding and identify abnormal values under environmental pressures; and to evaluate the potential of portable X-ray fluorescence screening as a useful tool in soil management. The four cities (Ayr and Greenock (Scotland), Lisbon (Portugal), Nantes (France)) provided a wide range of environmental pressures on soils. The locations of the 14 allotment gardens were identified in consultation with the local municipality in each city to reflect various land uses or according to previous evaluation of soil quality. Soil sampling was carried out in 66 plots in total, from which 3 datasets were produced: (i) basic soil properties and trace element concentrations from a composite sample of topsoil for each plot (trace elements quantified by inductively coupled plasma–optical emission spectrometry/mass spectrometry (ICP-OES/MS) or using in-lab portable X-ray fluorescence (PXRF); (ii) in situ PXRF measurement on composite samples (263 plots in Nantes); and (iii) composite samples from 32 small areas within 4 plots in one garden of Nantes. The results were analyzed to assess the spatial variability of soil properties. At city and garden scale, the variability observed for basic soil properties and major elements is dominated by local geology/parent material (pH, CaCO3, Fe) and gardening practice (OM, CaCO3), which vary between each country. The range of trace element concentrations is similar between each city except for Greenock. Extreme values are observed for Cu, Pb, and Zn reflecting human disruption. In most situations, the trace element contamination was explained through the historical and environmental situations of the site. The PXRF screening method proved useful in providing detailed mapping for hot spot detection or delineation, providing support for soil management at plot and garden scale. As anticipated, basic soil properties appear to be controlled by the parent material. At plot and garden scale, the trace element variability shows the influence of land use history and background and strong inputs from external factors (e.g., by industrial activity or traffic emission). The PXRF screening method appears to be an efficient solution for soil management as it can be used to discriminate zones which may require restriction on cultivation.

Leather Contains Cobalt and Poses a Risk of Allergic Contact Dermatitis: Cobalt Indicator Solution and X-ray Florescence Spectrometry as Screening Tests.

Cobalt was recently identified in a leather couch responsible for dermatitis. Cobalt content/release in leather in the United States is unknown. We evaluated leather for cobalt content/release and investigated screening methods for identifying cobalt in leather. One hundred thirty-one leather swatches were screened for cobalt content/release with X-ray fluorescence (XRF) spectrometry and cobalt indicator solution (CIS). Samples with positive screens and 1 negative control were analyzed using inductively-coupled plasma mass spectrometry (ICPMS). CIS showed that 5 of 131 samples contained cobalt, subsequently found to be between 1 and 190 parts per million (ppm) when evaluated with ICPMS. The XRF analysis showed that 6 samples contained >5% cobalt, subsequently found to contain greater than 300 ppm cobalt by ICPMS. 7 of 12 tested swatches contained cobalt in excess of 100 ppm. One sample contained greater than 1000 ppm cobalt. The prevalence of swatches containing cobalt at levels in excess of 190 ppm was at least 5% (n = 7; total, N = 131). Some leather consumer goods contain and release cobalt. Cobalt indicator solution is a poor screening test for cobalt in leather while XRF screening may be effective. Leather is a new source of cobalt exposure. Exposures to metal allergens are changing in ways that impact clinical decision making.

Evaluation of a novel portable x-ray fluorescence screening tool for detection of arsenic exposure

A new portable x-ray fluorescence (XRF) screening tool was evaluated for its effectiveness in arsenic (As) quantification in human finger and toe nails (). Nail samples were measured for total As concentration by XRF and inductively coupled plasma-mass spectrometry (ICP-MS). Using concordance correlation coefficient (CCC), kappa, diagnostic sensitivity (Sn) and specificity (Sp), and linear regression analyses, the concentration of As measured by XRF was compared to ICP-MS. The CCC peaked for scaled values of fingernail samples, at 0.424 (95% CI: 0.065–0.784). The largest kappa value, 0.400 (95% CI: −0.282–1.000), was found at a 1.3 μg g−1 cut-off concentration, for fingernails only, and the largest kappa at a clinically relevant cut-off concentration of 1.0 μg g−1 was 0.237 (95% CI: −0.068–0.543), again in fingernails. Analyses generally showed excellent XRF Sn (up to 100%, 95% CI: 48–100%), but low Sp (up to 30% for the same analysis, 95% CI: 14–50%). Portable XRF shows some potential for use as a screening tool with fingernail samples. The difference between XRF and ICP-MS measurements decreased as sample mass increased to 30 mg. While this novel method of As detection in nails has shown relatively high agreement in some scenarios, this portable XRF is not currently considered suitable as a substitute for ICP-MS.

A waveguide electron cyclotron resonance source of X-ray emission for low-dose introscopy

It is shown that a “point” target in a conventional evacuated waveguide in the magnetic field of a mirror trap formed by two disk magnets axially magnetized in the direction perpendicular to the electric field vector represents a source of X-ray bremsstrahlung of electrons accelerated in an ECR discharge with a broad range of photon energies up to 0.8 MeV. The dosage rate of the source is ∼1 R/h. The source fed from a conventional microwave oven has small dimensions and a low weight. It is easy-to-use and is suitable as a laboratory tool, in particular, in radiobiology and introscopy. After passing through the object, X-ray emission is recorded by a digital camera with the help of a highly sensitive X-ray fluorescent screen, which converts it into an optical image.

SU-GG-I-124: The Effect of Oblique X-Ray Incidence on the Design of X-Ray Detectors for Digital Tomosynthesis

Purpose: Digital breast tomosynthesis (DBT) is an emerging imaging modality in which tomographic sections of the breast are generated from x-ray projections taken over a limited range of angles. One drawback of DBT is resolution loss in the oblique projection images. The purpose of this work is to extend Swank's formulation of the transfer functions of x-ray fluorescent screens to oblique x-ray incidence. This analysis generates a platform for optimizing the design of detectors used in DBT. Method and Materials: We model a non-structured turbid granular phosphor such as Gd2O2S:Tb which is commonly used in breast imaging and which can reasonably approximate other detector materials. From first principles, the optical transfer function (OTF), noise power spectra (NPS), and detective quantum efficiency (DQE) are derived using the diffusion approximation to the Boltzmann transport equation. We use this analysis to investigate the effect of oblique x-ray incidence on DQE. The DQE is calculated using the Nishikawa formulation, where the DQE is written as the product of the x-ray quantum detection efficiency (QDE), the Swank information factor, and the Lubberts factor. Results: As expected, the modulation transfer function (MTF) is shown to decrease with increasing projection angle regardless of frequency. By contrast, the dependence of the DQE on projection angle is found to be frequency dependent. At low frequencies DQE increases with projection angle, but at high frequencies DQE decreases with projection angle. Furthermore, the x-ray QDE yielding maximal DQE at high frequencies is found to be projection angle dependent, shifting to lower QDE values (thinner phosphors) at higher projection angles. Conclusion: This work develops analytical models of OTF, NPS, and DQE for a turbid granular phosphor irradiated at oblique incidence. The models have applications in the design of optimal DBT detectors.

Equipment for investigations of biological nanostructures by diffraction methods using synchrotron radiation

This paper reports on the experimental and methodical developments intended for the small-angle time-resolved station DICSI (“diffraction movie“) at the K1.3a beamline of the Siberia-2 storage ring at the Russian Research Centre “Kurchatov Institute.“ The principles of operation of the optical geometric and detecting systems, as well as the control and recording system, as applied to the investigation of the dynamics of biological nanostructures, have been considered in detail. A new version of the two-coordinate detecting system based on the designed highly effective fluorescent screen (Gd2O2S: Tb) and a CSDU-429 digital camera has been developed. The advantage of this recording system over the Image Plate detecting system in phenomenological investigations is that the optical images obtained on X-ray fluorescent screens with the use of cooled CCD/CMOS arrays can be directly entered into a computer. The detecting system has been tested on different samples by small- and wide-angle X-ray diffraction methods with the use of synchrotron radiation of the VEPP-3 storage ring at the Siberian Synchrotron Center (Novosibirsk, Russia) and the Siberia-2 storage ring at the Kurchatov Center for Synchrotron Radiation and Nanotechnology (Moscow, Russia). Different modifications of original two-coordinate recording systems have been used in systematic studies of the structural dynamics of biological tissues.

Image information transfer properties of x-ray intensifying screens in the energy range from 17 to 320 keV.

The image information transfer properties of a number of x-ray fluorescent screens have been measured for x-ray energies from 17 to 320 keV. The detective quantum efficiency of the screens at each x-ray energy has been determined by separate measurements of the x-ray absorption efficiency and the statistical factor associated with the emission of optical photons upon absorption of an incident x-ray. Data have been recorded for both rare-earth phosphor screens and calcium tungstate screens. The value of the statistical factor for optical photon emission tends toward a constant value as the incident energy increases. Comparisons of the image information transfer properties are presented for several screens, which have been measured over a ten year interval. The utility of the screens for high-energy radiography is discussed.

A thermoluminescent image storage panel

A thermoluminescent imaging device is described in which the phosphor layer and the heated layer are fully integrated into a single panel. The performance of this image storage panel is compared with that obtained from a commercially available luminescent imaging panel, and with an X-ray fluorescent screen.

Evaluation of Gd2O2S:Tb as a Phosphor for the Input Screen of X-Ray Image Intensifier

X-ray fluorescent screens consisting of a powder embedded in a silicone resin matrix and deposited on an aluminum plate have been prepared with the phosphors Gd2O2S:Tb and (ZnCd)S:Ag(P-20) at a series of different screen thicknesses. The x-ray conversion efficiency of the screens was measured using both radioisotopes and a dental radiography unit as x-ray sources. To simulate screen performance in an x-ray image intensifier tube, the screens were optically coupled to the photomultiplier which served as the detector. We found that Gd2O2S:Tb screens were substantially superior to P-20 screens in both x-ray conversion efficiency and x-ray energy absorption efficiency. Experimental screen efficiencies agree with those derived from theory by an analysis in which the efficiency of the conversion of absorbed x-ray energy to light is assumed equal to the energy efficiency of the phosphor under cathode ray excitation and optical parameters of the screens are used to estimate the efficiency with which the generated light is transmitted to the detector.

Recent Developments in the Use of High-Gain Optical Image Intensifiers for High-Speed Photography of Dynamic X-ray Diffraction Patterns

With advancing technology, the possibility of monitoring in real time the continuous changes in an x-ray diffraction pattern produced by dynamic events has drawn the interest of many investigators. Progress has been slow, largely because of strict limitations on available intensity and required resolution. Also, not only the apparatus but the technique of application to research must be developed in order to make the equipment compatible with rather specific scientific interests. One new system uses a very fine grained fluorescent screen to display the x-ray patterns as optical light images. Those images are transferred via standard lenses to a low noise, high gain optical image intensifier. The intensified image is then viewed from the rear of the image tube with a high-resolution vidicon and the final image displayed on a TV monitor. Time exposure photographs, commonly 12 seconds in duration, were made of the TV screen while the x-ray device scanned a 5-mm specimen. The most recent system also uses a low-noise, high-gain optical image intensifier, but the image tube is fiber optically coupled to the x-ray fluorescent screen increasing the sensitivity of the system by eliminating optical lens absorption. The theoretical resolution of this system is 35 1p/mm. Cine-recording of changing x-ray diffraction patterns during deformation has been achieved with this system.

Random Noise Produced by X-Ray Fluorescent Screens*

A theory is presented concerning the spatial light-energy fluctuation in a photographic emulsion placed in intimate contact with a fluorescent screen that is excited by x rays. For simplicity, the fluorescent screen is assumed to be irradiated with monoenergetic x rays. Formulas have been developed for the average light energy received by the emulsion, the autocorrelation function, and the Wiener spectral density associated with the fluctuation of light energy about the average value.For a linear, time-invariant electrical network, the transfer function can be determined by means of a white-noise input. Theoretical considerations indicate that an analogous method is not valid for fluorescent-screen–film systems. This point is illustrated only analytically for a homogeneous fluorescent screen which consists of a thin, but large, macrocrystal of calcium tungstate.The recording of the fluctuations of light energy as variations of optical density by the photographic film is discussed quantitatively.

Microsecond Measurement of the Phosphorescence of X-Ray Fluorescent Screens

Microsecond square-wave x-ray pulses, repeated a thousand times a second, were obtained by operating an x-ray tube directly from a radar pulser. The phosphorescent build-up and decay of light emitted by fluorescent materials when irradiated by the x-ray pulses was observed with a multiplier phototube connected to an oscilloscope. Oscillograms of CaWO4 (radiographic intensifying screen) and BaSO4 indicate simple exponential response, with decay to 1/eth intensity in 6 and 0.8 microseconds, respectively. MgWO4 and Patterson B (fluoroscopic) and D (photofluorographic) screens were found to complete their main response to microsecond excitation in 10 to 100 microseconds, but their decay is not exponential.