X-ray Fluorescence Microtomography Research Articles

Benchtop X-ray Fluorescence Microtomography Based Polycapillary

Benchtop X-ray Fluorescence Microtomography Based Polycapillary

X-ray fluorescence microtomography based on polycapillary-focused X-rays from laboratory source

X-ray fluorescence microtomography (mu XFCT) is a nondestructive analytical technique and has been widely used to nondestructively detect and quantify the elemental composition and distributions in samples. Usually, synchrotron radiation X-rays are used for mu XFCT, due to its high flux density. In this paper, a laboratory-sourcebased mu XFCT system was developed, in which a polycapillary lens is employed to focus the X-ray beam and improve the flux density. The maximum likelihood expectation maximization algorithm was used to reconstruct the computed tomography slices at a limited number of projections. The experimental results demonstrated that the developed system could reveal the elemental distribution inside the test sample, with an elemental sensitivity of 1000 ppm.

MicroXRF tomographic visualization of zinc and iron in the zebrafish embryo at the onset of the hatching period.

Transition metals such as zinc, copper, and iron play key roles in cellular proliferation, cell differentiation, growth, and development. Over the past decade, advances in synchrotron X-ray fluorescence instrumentation presented new opportunities for the three-dimensional mapping of trace metal distributions within intact specimens. Taking advantage of microXRF tomography, we visualized the 3D distribution of zinc and iron in a zebrafish embryo at the onset of the hatching period. The reconstructed volumetric data revealed distinct differences in the elemental distributions, with zinc predominantly localized to the yolk and yolk extension, and iron to various regions of the brain as well as the myotome extending along the dorsal side of the embryo. The data set complements an earlier tomographic study of an embryo at the pharyngula stage (24 hpf), thus offering new insights into the trace metal distribution at key stages of embryonic development.

Synchrotron X-ray Fluorescence Microtomography Profiling of Malus xiaojinensis Provides Insights into Mechanisms of Divalent Metals Transport Subjected to Iron Deficiency

Grafting has been widely used in orchard management because the rootstock can make the tree more tolerant to environmental stresses. Iron deficiency is one of the major limiting environmental factor in apple production worldwide. Systematic research has been made about iron-deficiency adaptive responses in the level of organs, cells, and subcells, whereas the interactions between Fe and other divalent cations in tissue level are little known. Synchrotron radiation X-ray fluorescence (SR-μXRF) was used to map the location of selected elements Fe, Zn, Mn, Ni, and Co in the longitudinal and latitudinal root samples of Malus xiaojinensis. Iron deficiency induced a significant increase in the relative contents of five micronutrients in epidermis and cortex. The ratio of element contents of roots under Fe-deficient condition and Fe-sufficient condition at same position increased obviously in the section of 1000- to 2000-μm distance from the root tip in xylem. Expression analysis of iron absorption- and transport-related genes in roots showed that MdNramp3 and MxCS1 increased significantly. These results indicated that iron deficiency promoted the long-distance transport of micronutrients in xylem, and MdNramp3 and MxCS1 might play an important role in this process. Importantly, this study directly provides visual divalent metals distribution in tissue level for an improved understanding of metal absorption process in apple rootstock.

3D imaging of transition metals in the zebrafish embryo by X-ray fluorescence microtomography.

Synchrotron X-ray fluorescence (SXRF) microtomography has emerged as a powerful technique for the 3D visualization of the elemental distribution in biological samples. The mechanical stability, both of the instrument and the specimen, is paramount when acquiring tomographic projection series. By combining the progressive lowering of temperature method (PLT) with femtosecond laser sectioning, we were able to embed, excise, and preserve a zebrafish embryo at 24 hours post fertilization in an X-ray compatible, transparent resin for tomographic elemental imaging. Based on a data set comprised of 60 projections, acquired with a step size of 2 μm during 100 hours of beam time, we reconstructed the 3D distribution of zinc, iron, and copper using the iterative maximum likelihood expectation maximization (MLEM) reconstruction algorithm. The volumetric elemental maps, which entail over 124 million individual voxels for each transition metal, revealed distinct elemental distributions that could be correlated with characteristic anatomical features at this stage of embryonic development.

Grain Accumulation of Selenium Species in Rice (Oryza sativa L.)

Efficient Se biofortification programs require a thorough understanding of the accumulation and distribution of Se species within the rice grain. Therefore, the translocation of Se species to the filling grain and their spatial unloading were investigated. Se species were supplied via cut flag leaves of intact plants and excised panicle stems subjected to a ± stem-girdling treatment during grain fill. Total Se concentrations in the flag leaves and grain were quantified by inductively coupled plasma mass spectrometry. Spatial accumulation was investigated using synchrotron X-ray fluorescence microtomography. Selenomethionine (SeMet) and selenomethylcysteine (SeMeSeCys) were transported to the grain more efficiently than selenite and selenate. SeMet and SeMeSeCys were translocated exclusively via the phloem, while inorganic Se was transported via both the phloem and xylem. For SeMet- and SeMeSeCys-fed grain, Se dispersed throughout the external grain layers and into the endosperm and, for SeMeSeCys, into the embryo. Selenite was retained at the point of grain entry. These results demonstrate that the organic Se species SeMet and SeMeSeCys are rapidly loaded into the phloem and transported to the grain far more efficiently than inorganic species. Organic Se species are distributed more readily, and extensively, throughout the grain than selenite.

Elemental distribution images in prostate samples by X-ray fluorescence microtomography

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFμCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), in order to determine the elemental distribution in prostate samples aiming at establishing a correlation between the concentration of some elements and the characteristics and pathology of the tissues.The CT images were reconstructed using a filtered-back projection algorithm and the XRFμCT images were reconstructed using a filtered-back projection algorithm with absorption corrections.

Internal elemental imaging by scanning X-ray fluorescence microtomography at the hard X-ray microprobe beamline of the SSRF: Preliminary experimental results

Synchrotron-based X-ray micro-fluorescence (μ-SXRF) is a non-destructive analytical technique and has been widely used to detect and quantify the elemental composition of samples in their natural state. To determine the internal elemental distributions within samples, X-ray fluorescence microtomography has been developed based on the hard X-ray microprobe at beamline BL15U1 of the Shanghai Synchrotron Radiation Facility (SSRF) in Shanghai, China. This technique was applied to image the cross-sectional distributions of multiple elements within a single human hair, and its validity was evaluated by comparing the results with the elemental maps of a thin hair section obtained using the well-established μ-SXRF mapping method. Elemental images of S, Ca, Mn, Fe, Cu, and Zn within a virtual slice of the hair were reconstructed after the tomographic measurements. The tomographic images of heavy elements like Fe, Cu, and Zn were found to be in good agreement with the corresponding μ-SXRF maps. Light elements, such as S, however, represented different patterns due to non-negligible self-absorption in the sample, and sophisticated correction algorithms accounting for such effects are required for obtaining qualitatively and quantitatively more accurate images. Compared to μ-SXRF mapping, X-ray fluorescence microtomography reduces the sample preparation requirements and has been demonstrated in this work as being a more ideal and effective imaging modality to non-destructively mapping out the internal distribution of heavy elements within samples at the micrometer scale at the SSRF.

Phloem transport of arsenic species from flag leaf to grain during grain filling

• Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was investigated. • Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analog) on grain As accumulation in arsenite-treated panicles was examined. • Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently retranslocated from flag leaves to rice grain; arsenate was poorly retranslocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no retranslocation. Within grains, DMA rapidly dispersed while MMA and inorganic As remained close to the entry point. Germanic acid addition did not affect grain As in arsenite-treated panicles. Three-dimensional SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains. • These results demonstrate that inorganic As is poorly remobilized, while organic species are readily remobilized, from leaves to grain. Stem translocation of inorganic As may not rely solely on silicic acid transporters.

Fast x-ray fluorescence microtomography of hydrated biological samples.

Metals and metalloids play a key role in plant and other biological systems as some of them are essential to living organisms and all can be toxic at high concentrations. It is therefore important to understand how they are accumulated, complexed and transported within plants. In situ imaging of metal distribution at physiological relevant concentrations in highly hydrated biological systems is technically challenging. In the case of roots, this is mainly due to the possibility of artifacts arising during sample preparation such as cross sectioning. Synchrotron x-ray fluorescence microtomography has been used to obtain virtual cross sections of elemental distributions. However, traditionally this technique requires long data acquisition times. This has prohibited its application to highly hydrated biological samples which suffer both radiation damage and dehydration during extended analysis. However, recent advances in fast detectors coupled with powerful data acquisition approaches and suitable sample preparation methods can circumvent this problem. We demonstrate the heightened potential of this technique by imaging the distribution of nickel and zinc in hydrated plant roots. Although 3D tomography was still impeded by radiation damage, we successfully collected 2D tomograms of hydrated plant roots exposed to environmentally relevant metal concentrations for short periods of time. To our knowledge, this is the first published example of the possibilities offered by a new generation of fast fluorescence detectors to investigate metal and metalloid distribution in radiation-sensitive, biological samples.

3D elemental distribution images in biological samples by XRFµCT

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFµCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The aim of this work was to determine the elemental distribution in biological samples (breast, prostate and lung samples) in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-ray fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high-precision goniometer and translation stages that allow rotating as well as translating it perpendicularly to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam path. The CT images were reconstructed using a filtered-back projection algorithm and the XRFµCT images were reconstructed using a filtered-back projection algorithm with absorption corrections. The 3D images were reconstructed using the 3D-DOCTOR software. Results from the 3D visualization showed that the distribution of iron, copper and zinc is different and heterogeneous from the analyzed samples. Copyright © 2011 John Wiley & Sons, Ltd.

Synchrotron radiation X-ray microfluorescence techniques and biological applications

Synchrotron X-ray imaging systems with fluorescence techniques was developed for biomedical researches in Brazilian Synchrotron Laboratory. An X-ray fluorescence microtomography system was implemented to analyse human prostate and breast samples and an X-ray microfluorescence system was implemented to study bone sites of human and animal samples with and without bone disorders.

3D elemental distribution images by XRFμCT at LNLS—Brazil

An X-ray Transmission Microtomography (CT) system combined with an X-ray Fluorescence Microtomography (XRFμCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The main objective of this work is to determine the elemental distribution in biological samples (breast, prostate and lung samples) in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high precision goniometer and translation stages that allow its rotation as well as translation perpendicular to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam direction. The CT images were reconstructed using a filtered back-projection algorithm and the XRFμCT were reconstructed using a filtered back-projection algorithm with absorption corrections. The 3D images were reconstructed using the 3D-DOCTOR software.

Grain Unloading of Arsenic Species in Rice

Rice (Oryza sativa) is the staple food for over half the world's population yet may represent a significant dietary source of inorganic arsenic (As), a nonthreshold, class 1 human carcinogen. Rice grain As is dominated by the inorganic species, and the organic species dimethylarsinic acid (DMA). To investigate how As species are unloaded into grain rice, panicles were excised during grain filling and hydroponically pulsed with arsenite, arsenate, glutathione-complexed As, or DMA. Total As concentrations in flag leaf, grain, and husk, were quantified by inductively coupled plasma mass spectroscopy and As speciation in the fresh grain was determined by x-ray absorption near-edge spectroscopy. The roles of phloem and xylem transport were investigated by applying a +/- stem-girdling treatment to a second set of panicles, limiting phloem transport to the grain in panicles pulsed with arsenite or DMA. The results demonstrate that DMA is translocated to the rice grain with over an order magnitude greater efficiency than inorganic species and is more mobile than arsenite in both the phloem and the xylem. Phloem transport accounted for 90% of arsenite, and 55% of DMA, transport to the grain. Synchrotron x-ray fluorescence mapping and fluorescence microtomography revealed marked differences in the pattern of As unloading into the grain between DMA and arsenite-challenged grain. Arsenite was retained in the ovular vascular trace and DMA dispersed throughout the external grain parts and into the endosperm. This study also demonstrates that DMA speciation is altered in planta, potentially through complexation with thiols.

X-ray fluorescence micro-tomography and laminography using an x-ray scanning microscope

Using a scanning microscope with a zone plate, x-ray fluorescence micro-tomography was investigated at SPring-8 BL20XU. A 120 nm-thick zinc layer could be resolved in the reconstructed section image. A frozen phytoplankton and a iron impurity of a diamond could be also reconstructed. X-ray fluorescence laminography was tested at SPring-8 BL47XU. A tantalum line pattern of 3 μm line width could be reconstructed.

Observation of iodine in oceanic plankton by scanning x-ray fluorescence micro-tomography

3-dimensional distribution of iodine of the female oceanic zooplankton, Paracalanus parves s.l., was observed by using scanning x-ray fluorescence micro-tomography. The distribution of iodine along the ventral border of the zooplankton was observed to be concentrated in seven regions between the head and the bases of the swimming legs. Then, 3-dimensional distributions of iron and zinc were also observed.

Imaging System for XRF Microtomography at LNLS-Brazil

An X-ray transmission microtomography (CT) system combined with an X-ray fluorescence microtomography (XRFCT) system was implemented in the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. The main of this work is to determine the elemental distribution map in reference samples and breast tissue samples in order to verify the concentration of some elements correlated with characteristics and pathology of each tissue observed by the transmission CT. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Laboratory, Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The sample was placed on a high precision goniometer and translation stages that allow rotating as well as translating it perpendicularly to the beam. The fluorescence photons were collected with an energy dispersive HPGe detector placed at 90deg to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter placed behind the sample on the beam direction. The CT images were reconstructed using a filtered-back projection algorithm and the XRFCT were reconstructed using a filtered-back projection algorithm with absorption corrections.

X‐Ray fluorescence microtomography under various excitation conditions

AbstractThe main goal of this work is two‐fold: (1) to compare three different excitation conditions in x‐ray fluorescence microtomography (XRFCT) in the analysis of reference samples, and (2) to determine the elemental distribution map for breast tissue samples, in order to verify concentrations of certain elements correlated with characteristics and pathology, using x‐ray transmission microtomography (CT).The experiments were performed at the X‐Ray Fluorescence Facility (D09B‐XRF) of the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. In this work, a multilayer monochromator with photon energies near 12 keV, a monochromatic beam at 9.8 keV using a Si (111) crystal, and the white beam were used for elements excitation of elements inside the sample. The sample was placed on a high‐precision goniometer and translation stages, which allowed for rotation as well as translation perpendicular to the beam. Fluorescence photons were collected by means of an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter, placed behind the sample, in the direction of the incoming beam. Transmission CT images were reconstructed using a filtered back‐projection algorithm, and XRFCT images were reconstructed using a filtered back‐projection algorithm with absorption correction. Copyright © 2009 John Wiley & Sons, Ltd.

Elemental Tomography of Cancer-Cell Spheroids Reveals Incomplete Uptake of Both Platinum(II) and Platinum(IV) Complexes

The limited penetration of cytotoxic drugs into tumors is a significant contributing factor to the limited effectiveness of cancer chemotherapy. Here we have shown that X-ray fluorescence microtomography is a suitable technique for imaging the distribution of Pt drugs within multicellular tumor spheroids, models of solid tumors. This has revealed that there is no significant difference between the distributions of the range of Pt(II) and Pt(IV) complexes investigated, suggesting that complexes that are more resistant to cellular uptake may be needed to ensure more complete distribution throughout a tumor.

X-ray fluorescence and X-ray transmission microtomography imaging system

An X-ray Transmission Microtomography (CT) system combined with an X-ray Fluorescence Microtomography (XRFCT) system was implemented in the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. The main aim of this work is to determine the elemental and absorption distribution map in breast tissue samples. The experiments were performed at the X-Ray Fluorescence beamline (D09B-XRF) of the Brazilian Synchrotron Light Source (LNLS), Campinas, Brazil. A quasi-monochromatic beam produced by a multilayer monochromator was used as an incident beam. The fluorescence photons were acquired with an energy dispersive HPGe detector (CANBERRA Industries Inc.) placed at 90 ∘ to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter (CYBERSTAR Oxford Danfysik) placed behind the sample in the beam direction. All the tomographic images were reconstructed using a filtered-back projection algorithm.