Conventional X-ray Source Research Articles

A COMPARISON OF CONTEMPORARY PORTABLE X-RAY SYSTEMS

<h3>Background</h3> There is substantial evidence for a cumulative dose-related response to ionizing radiation in the form of cancer development years after initial exposure. Therefore, this study focused on effective dose (E), a quantity with direct correlations to biologic risk from dental x-ray exposures. <h3>Objectives</h3> The purpose of this study was to measure doses and calculate (E) from adult full-mouth examinations (FMXs) by using handheld and conventional wall-mounted x-ray sources with both circular and rectangular collimation (RC). <h3>Materials and Methods</h3> A human tissue-equivalent phantom and optically stimulated luminescent dosimeters were used to measure dose from simulated FMXs (n = 18) at 24 head/neck tissue sites. The parameters were 70 kV/7 mA (0.84 mAs and 1.34 mAs) for Conventional Circular and RC handheld device; 60 kV/2.5 mA (2.16 mAs) for NOMAD Circular and RC handheld device; and 60 kV/2.0 mA (1.98 mAs) for Xray2 Go Circular (XTG) handheld device. Analysis of variance (ANOVA) and Tukey's HSD ("honest significant difference") statistics demonstrated significant relationships. <h3>Results</h3> The FMX E (µSv) values were: NOMAD RC (6.9); XTG (16.7); NOMAD Circular (17.4); and Conventional Circular (26.3). For circular techniques, the handheld device E was significantly lower than the conventional unit for both devices (<i>P</i> < .0001). With RC, E was significantly lower than all circular techniques (<i>P</i> < .0001). Significant differences in E were found for all modality combinations except NOMAD Circular and XTG (<i>P</i> = .8329). Operator groin exposure was significantly higher (60%–90%) than thyroid, chest, and trigger hand exposures, which were indistinguishable from ambient background levels, for all handheld modalities (<i>P</i> < .0001). <h3>Discussion</h3> Handheld device E was at least 34% less than conventional circular and as much as 74% less with the use of RC. Operator exposure to the groin can increase significantly from overangulating the handheld sources; however, the addition of RC can reduce this exposure by as much as 76%.

Application of Synchrotron Radiation X-ray Scattering and Spectroscopy to Soft Matter

Light produced by synchrotron radiation (SR) is much brighter than that produced by conventional laboratory X-ray sources. The photon energy of SR X-ray ranges from soft and tender X-rays to hard X-rays. Moreover, X-rays become element sensitive with decreasing photon energy. By using a wide energy range and high-quality light of SR, different scattering and spectroscopic methods were applied to various soft matters. We present five of our recent studies performed using specific light properties of a synchrotron facility, which are as follows: (1) In situ USAXS study to understand the deformation behavior of colloidal crystals during uniaxial stretching; (2) structure characterization of semiconducting polymer thin films along the film thickness direction by grazing-incidence wide-angle X-ray scattering using tender X-rays; (3) X-ray absorption fine structure (XAFS) analysis of the formation mechanism of poly(3-hexylthiophene) (P3HT); (4) soft X-ray absorption and emission spectroscopic analysis of water structure in polyelectrolyte brushes; and (5) X-ray photon correlation spectroscopic analysis of the diffusion behavior of polystyrene-grafted nanoparticles dispersed in a polystyrene matrix.

Deep learning for high-resolution and high-sensitivity interferometric phase contrast imaging

In Talbot-Lau interferometry, the sample position yielding the highest phase sensitivity suffers from strong geometric blur. This trade-off between phase-sensitivity and spatial resolution is a fundamental challenge in such interferometric imaging applications with either neutron or conventional x-ray sources due to their relatively large beam-defining apertures or focal spots. In this study, a deep learning method is introduced to estimate a high phase-sensitive and high spatial resolution image from a trained neural network to attempt to avoid the trade-off for both high phase-sensitivity and high resolution. To realize this, the training data sets of the differential phase contrast images at a pair of sample positions, one of which is close to the phase grating and the other close to the detector, are numerically generated and are used as the inputs for the training data set of a generative adversarial network. The trained network has been applied to the real experimental data sets from a neutron grating interferometer and we have obtained improved images both in phase-sensitivity and spatial resolution.

Modeling of beam hardening effects in a dual-phase X-ray grating interferometer for quantitative dark-field imaging.

X-ray grating interferometry (XGI) can provide access to unresolved sub-pixel information by utilizing the so-called dark-field or visibility reduction contrast. A recently developed variant of conventional XGI named dual-phase grating interferometer, based only on phase-shifting structures, has allowed for straightforward micro-structural investigations over multiple length scales with conventional X-ray sources. Nonetheless, the theoretical framework of the image formation for the dark-field signal has not been fully developed yet, thus hindering the quantification of unresolved micro-structures. In this work, we expand the current theoretical formulation of dual-phase grating interferometers taking into account polychromatic sources and beam hardening effects. We propose a model that considers the contribution of beam hardening to the visibility reduction and accounts for it. Finally, the method is applied to previously acquired and new experimental data showing that discrimination between actual micro-structures and beam hardening effects can be achieved.

Imaging evaluation of the cartilage in rheumatoid arthritis patients with an x-ray phase imaging apparatus based on Talbot-Lau interferometry

X-ray Talbot-Lau interferometry is one of the x-ray phase imaging methods that has high sensitivity in depicting soft tissues. Unlike earlier x-ray phase imaging methods that required particular types of x-ray sources, such as a synchrotron or a micro-focus x-ray tube, x-ray Talbot-Lau interferometry enables to perform clinical x-ray phase imaging using a conventional x-ray source with a relatively compact configuration. We developed an apparatus to depict cartilage in the metacarpophalangeal joints of the hands. In addition, we examined the apparatus performance by applying it to healthy volunteers and patients with rheumatoid arthritis (RA). Cartilage deformation, which is thought to be a precursor of destruction of the joints, was successfully depicted by the apparatus, suggesting a potential early diagnosis of RA.

Grating-based phase-contrast CT (PCCT): histopathological correlation of human liver cirrhosis and hepatocellular carcinoma specimen

AimsTo correlate signal intensities in grating-based phase-contrast CT (PCCT) images obtained at a synchrotron light source and a conventional X-ray source with tissue components in human liver cirrhosis and hepatocellular...

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste.

In this study the first in situ high-pressure single-crystal X-ray diffraction experiments at Xpress, the Indo-Italian beamline of the Elettra synchrotron, Trieste (Italy), are reported. A description of the beamline experimental setup and of the procedures for single-crystal centring, data collection and processing, using diamond anvil cells, are provided. High-pressure experiments on a synthetic crystal of clinoenstatite (MgSiO3), CaCO3 polymorphs and a natural sample of leucophoenicite [Mn7Si3O12(OH)2] validated the suitability of the beamline experimental setup to: (i) locate and characterize pressure-induced phase transitions; (ii) solve ab initio the crystal structure of high-pressure polymorphs; (iii)perform fine structural analyses at the atomic scale as a function of pressure; (iv) disclose complex symmetry and structural features undetected using conventional X-ray sources.

Characterisation of pixelated CdZnTe sensors using MAXIPIX

In order to maximise the absoprtion efficiency of X-ray detectors for high energy photons above 20 keV, compound semiconductor sensors with high atomic number (Z) are under investigation. A promising material for future detector systems is Cadmium Zinc Telluride (CdZnTe). Redlen Technologies developed a novel CdZnTe material, optimised for applications with high photon fluxes. Such a material was used to fabricate pixelated CdZnTe sensors with a pitch of 55 μm and 110 μm. The sensors were flip-chip bonded to Timepix ASICs and their performance was characterised at the European Synchrotron Radiation Facility (ESRF) with conventional X-ray sources and monochromatic sychrotron beams using the MAXIPIX readout system. We present results concerning the uniformity, the stability and the spatial resolution of the sensors, obtained with X-ray energies up to 60 keV.

Focusing Properties of Bent Micro-Channel Plates in the X-Ray Range

Compact and flexible Micro-Channel Plate (MCP) devices are versatile optical systems suitable to condense and shape intense X-ray beams. Studies on propagation of both soft and hard X-ray radiations through these devices are of continuous interests because of increasing demand of synchrotron radiation X‑ray sources, in particular, to enhance the spot stability and to optimize the beam for specific experiments. In this work synchrotron radiation sources as well as a conventional X-ray tube coupled to polycapillary lenses have been used to characterize the transmission and the angular distribution of thin flat or spherically bent MCPs with different curvature radii. It is shown that the radiation beam from both synchrotron radiation and conventional X-ray sources can be efficiently condensed by thin spherically bent MCPs.

A Multi-Source CT Architecture with Three Imaging Modes for SBRT Image Guidance

Stereotactic ablative radiotherapy of oligometastatic disease is an emerging paradigm. Current image guidance via CBCT is limited by respiratory motion, scatter, and the requirement of fiducials for some sites. We investigate an alternative to CBCT that can surmount these limitations. Our proposed CT architecture has three imaging modes. These modes are (1) localization of high-contrast lung tumors in a 10 x 2 cm FOV in 100 milliseconds; (2) visualization of low-contrast liver tumors in a 10 x 2 cm FOV in 1 second; (3) daily setup imaging of a 50 cm by 15 cm volume in two minutes. Our proposed design includes a ring detector, an array of compact x-ray sources on an adjacent ring, and a movable collimator that switches between narrow and wide FOV modes. Narrow and wide FOVs are used for motion tracking and daily alignment, respectively. The ring detector is 4 cm wide, with total active area comparable to a flat panel detector. In the narrow FOV mode, 15 sources activate simultaneously and illuminate non-overlapping arcs of the detector. In lung imaging, each source is activated only once. In liver imaging, sources are re-activated many times over 1 second as the source ring rotates to sample more projection angles. Finally, in wide FOV mode, the sources activate sequentially to reduce scatter and distribute heat. The ring is mounted adjacent to the MV beam to avoid collision, or could be mounted at an angle if imaging during treatment is desired. We assessed the feasibility of this design in terms of number of sources required, impact of truncation artifacts, compatibility with existing x-ray source technology, and radiation dose. Visibility was assessed qualitatively using two patient datasets in simulation. For sufficient visibility of lung tumors, at least 30 x-ray sources are needed. Dose for lung imaging can be 100x less than CBCT, and imaging would require only 2 detector readouts of 15 sources each (<70 milliseconds), enabling cine reconstruction of lung tumor motion without data rebinning. For a 25 mm liver tumor with 15 HU contrast, 300 mAs was needed for adequate visualization. These requirements are compatible with the heat loading limitations of conventional fixed-anode x-ray sources, which are also inexpensive and compact (3 pounds, 6.5 cm wide) and therefore a practical choice for this design. Radiation dose for liver imaging is 10 times less than CBCT because of the small FOV. Acquisition with a wide field of view (250 mAs, 14 cm in z) requires about 100 seconds but would have reduced scatter compared to CBCT. A multi-source CT architecture with three imaging modes could enable fast image guidance tailored towards lung and liver lesions, while still maintaining adequate performance for daily alignment. This architecture could make intrafraction motion monitoring practical and could eliminate fiducial implantation in abdominal SBRT for tumors is visible in noncontrast CT.

Stress-dependent fracture porosity and permeability of fractured coal: An in-situ X-ray tomography study

Coal porosity and permeability are highly stress-sensitive. Although the stress-dependent permeability behaviour of coal has been well documented in the literature, few studies are available which directly observe the dependency of fracture aperture, porosity and connectivity on effective stress. In this study, in-situ X-ray tomography was conducted using a novel X-ray transparent tri-axial core holder to provide a detailed characterization of coal fracture network evolution due to increased effective stress. Both conventional and synchrotron X-ray sources were used to image two fractured anthracite coals (named sample A and sample B) at resolutions of 38.7 and 18.1 μm, respectively. Permeability was measured at effective stresses from 0.5 to 6 MPa for sample A and from 0.5 to 11.0 MPa for sample B. Results show that the permeability for both samples decreased by one order of magnitude following an exponential function. X-ray CT images indicate that large fractures were quickly compressed and isolated to small fractures, which accordingly caused dramatic porosity reduction by a power law. The fracture contact area increases in response to increased stresses, resulting in a decrease of fracture compressibility. Both an exponential decreasing trend and a linear decreasing trend were observed. When the fracture contact area increases, the tortuosity and spatial connectivity of the fractures become important, because these attributes significantly affect permeability. Preliminary studies on the correlation between permeability and CT-resolved porosity and that between permeability and CT-resolved aperture are not consistent with the cubic law. This may indicate that the fractures cannot be adequately represented as smooth parallel plates. A mixture of tube and plate model is proposed to better describe fracture geometry considering its rough nature.

Optimized EDXRF system for simultaneous detection of gold and silver nanoparticles in tumor phantom

An energy-dispersive X-ray fluorescence system (EDXRF) was optimized for simultaneous detection of gold and silver nanoparticles inside water-equivalent phantoms applied to theranostics. The optimization process was carried out in order to maximize the fluorescence detection, keeping dose levels as low as possible. Gold and silver fluorescent emissions were simultaneously detected emerging from phantom's volume, allowing the future development of multi-parametric imaging associated to specific tumor characteristics. For fluorescence detection, gold LIII-edge and silver K-edge emission lines were used, exited with a conventional X-ray source with a tungsten target. Several combinations of filters of different thickness were used to hardening the Bremsstrahlung spectrum, thus producing energetically narrow beams with central energy according to both excitation edges. In the case of gold, incident spectrum was optimized by means of strontium (Sr) and yttrium (Y) filters to relatively incrementing photons capable of exciting gold LIII-edge, while silver K-edge excitation was improved using a tin (Sn) filter. Filtering combinations made of 212.0 μm Sr with 94.5 μm Sn, and 130.2 μm Y with 94.5 μm Sn maximized fluorescence detection sensitivity and minimized delivered dose, resulting in doses 2.24 and 2.36 times lower than individual gold or silver fluorescent detection. Furthermore, when dual gold and silver fluorescent detection was performed, the minimum detectable concentration was lower than single element detection: 0.042 ± 0.002 mg/mL of Au and 0.024 ± 0.005 mg/mL of Ag in dual detection against 0.058 ± 0.003 mg/mL of Au and 0.124 ± 0.007 mg/mL of Ag when measured independently.

In-house setup for laboratory-based x-ray absorption fine structure spectroscopy measurements.

We report on a laboratory-based facility for in-house x-ray absorption fine structure (XAFS) measurements. The device consists of a conventional x-ray source for the production of the incident polychromatic radiation and a von Hamos bent crystal spectrometer for the analysis of the incoming and transmitted radiation. The reliability of the laboratory-based setup was evaluated by comparing the Cu K-edge and Ta L3-edge XAFS spectra obtained in-house with the corresponding spectra measured at a synchrotron radiation facility. To check the accuracy of the device, the K- and L-edge energies and the attenuation coefficients below and above the edges of several 3d, 4d, and 5d elements were determined and compared with the existing experimental and theoretical data. The dependence of the XAFS spectrum shape on the oxidation state of the sample was also probed by measuring inhouse the absorption spectra of metallic Fe and two Fe oxides (Fe2O3 and Fe3O4).

Study of Sulfur-Based Electrodes By in Situ Characterization Techniques

The Lithium-Sulfur (Li/S) battery system is one of the most promising candidates to become the successor of the current Li-ion battery. However, in spite of its high theoretical specific capacity (1675 mAh.g-1) and energy density (up to 500 Wh kg-1), it still suffers from a shortened cycle life resulting from the numerous complex processes occurring upon cycling. Hence the constant need for understanding of those mechanisms drives the use of innovative in situ characterization techniques. In the present study, the acoustic emission technique (AE), in situ Synchrotron X-ray tomography and diffraction are used to help better understand the optimization of sulphur-based electrodes for Li/S batteries. The acoustic emission (AE) technique has been widely used since the 70’s for detecting anomalies such as leakages and cracks on large structure (e.g. bridges, pressure containers, and pipe lines). The analysis of the AE signals (transient elastic waves) can also be used to characterize the degradation mechanisms (crack growth, friction, delamination, matrix cracking, corrosion, etc) of various materials subjected to a stress by mechanical, pressure or thermal means. Recently, AE technique has also been used to evaluate the degradation of metal hydride electrodes for Ni-MH [1] and Si-based electrodes for Li-ion batteries [2,3]. Cracking of the active material and gas evolution are the main sources of AE signals identified in these studies. On the other hand, X-Ray computed tomography (XRCT) is certainly one of the most powerful analytical tools enabling non-destructive 3D imaging of objects with complex and porous morphologies. Using appropriate image processing, segmentation and analysis procedures, quantitative parameters can be extracted such as the volume fraction, the size distribution, the connectivity and the geometrical tortuosity of the constitutive phases of the Li/S electrodes. A spatial resolution of a few tens of nm can be reached with a synchrotron X-ray source compared to a few µm with a conventional laboratory X-ray source. This technique, coupled with in situ synchrotron X-ray Diffraction, enables to follow in great details the evolution of the different species inside the tested Li/S batteries and get invaluable information on their behavior and degradation mechanisms. Recently, in situ XRCT and XRD has been used to characterize Si-based anodes [4]. In the present study, the AE technique is used for studying upon cycling the mechanical degradation of S-based electrodes for Li/S batteries. The AE signals were recorded by a piezoelectric transducer fixed on the back of the working electrode. S-based electrodes made with two different binders (PVdF vs. CMC) and two different current collectors (standard Al foil vs. porous 3D carbon paper) were studied. In all cases, AE signals were mainly detected during the first plateau of the first discharge, suggesting that the electrode degradation mostly occurs during the initial dissolution of the S8 particles. AE signals were also detected during a few subsequent cycles when CMC binder is used. This is attributed to a better propagation of the AE signals through the electrode thanks to an improved adhesion of the electrode to the current collector in comparison to PVdF binder. This is confirmed by further mechanical resistance testing (peel and scratch tests). The use of a carbon paper as a current collector combined to CMC binder greatly improves the electrochemical performance of the S electrode by preventing the collapse of the electrode upon cycling. This electrode also presents an increased amount of AE signals, suggesting that the carbon fibres of the C paper act as an AE waveguide. This study demonstrated that AE could be used as an efficient tool to monitor the morphological degradation of S-based electrodes upon their cycling and offers relevant information for optimizing their formulation and architecture. Further electrode optimization was investigated with the use of a poly-electrolyte binder (PEB) enhancing the performances of S-based electrodes by creating a ionic layer at the surface of the electrode which confines the polysulfide chains and prevents sulfur loss over cycling. In situ synchrotron X-ray tomography and diffraction was used at ESRF in France to study the behavior of those electrodes in comparison to classic CMC-binder based electrodes. Coupled with in situ X-Ray diffraction, the aim of this study was to get a better global understanding at the reduced capacity loss of PEB-based electrodes, especially on Aluminum current collector. To do so, the morphology of the electrodes were compared, as well as the evolution of the different sulfur and lithiated species throughout the electrode and the electrolyte upon cycling. Batteries were studied again after 10 cycles to compare the evolution of their internal degradation. Figure 1

Numerical simulation of novel concept 4D cardiac microtomography for small rodents based on all-optical Thomson scattering X-ray sources

Accurate dynamic three-dimensional (4D) imaging of the heart of small rodents is required for the preclinical study of cardiac biomechanics and their modification under pathological conditions, but technological challenges are met in laboratory practice due to the very small size and high pulse rate of the heart of mice and rats as compared to humans. In 4D X-ray microtomography (4D μCT), the achievable spatio-temporal resolution is hampered by limitations in conventional X-ray sources and detectors. Here, we propose a proof-of-principle 4D μCT platform, exploiting the unique spatial and temporal features of novel concept, all-optical X-ray sources based on Thomson scattering (TS). The main spatial and spectral properties of the photon source are investigated using a TS simulation code. The entire data acquisition workflow has been also simulated, using a novel 4D numerical phantom of a mouse chest with realistic intra- and inter-cycle motion. The image quality of a typical single 3D time frame has been studied using Monte Carlo simulations, taking into account the effects of the typical structure of the TS X-ray beam. Finally, we discuss the perspectives and shortcomings of the proposed platform.

Experimental 3D coherent diffractive imaging from photon-sparse random projections.

The routine atomic resolution structure determination of single particles is expected to have profound implications for probing structure-function relationships in systems ranging from energy-storage materials to biological molecules. Extremely bright ultrashort-pulse X-ray sources - X-ray free-electron lasers (XFELs) - provide X-rays that can be used to probe ensembles of nearly identical nanoscale particles. When combined with coherent diffractive imaging, these objects can be imaged; however, as the resolution of the images approaches the atomic scale, the measured data are increasingly difficult to obtain and, during an X-ray pulse, the number of photons incident on the 2D detector is much smaller than the number of pixels. This latter concern, the signal 'sparsity', materially impedes the application of the method. An experimental analog using a conventional X-ray source is demonstrated and yields signal levels comparable with those expected from single biomolecules illuminated by focused XFEL pulses. The analog experiment provides an invaluable cross check on the fidelity of the reconstructed data that is not available during XFEL experiments. Using these experimental data, it is established that a sparsity of order 1.3 × 10-3 photons per pixel per frame can be overcome, lending vital insight to the solution of the atomic resolution XFEL single-particle imaging problem by experimentally demonstrating 3D coherent diffractive imaging from photon-sparse random projections.

Electron Density Measurement Using Multi-Energy X-Rays from a Conventional Laboratory X-Ray Source

We have proposed a method to obtain the electron density and effective atomic number from the attenuation coefficients of multi-energy X-rays. The simulations were performed using NIST’s database and demonstrate that our approach can facilitate electron density measurements within accuracy of 1% in a human body. The proposed method exhibited an improvement in the accuracy of electron density measurements, which were obtained from experimental linear attenuation coefficients using a conventional laboratory X-ray source with energy spectrum.

Assessment of intraductal carcinoma in situ (DCIS) using grating-based X-ray phase-contrast CT at conventional X-ray sources: An experimental ex-vivo study.

BackgroundThe extent of intraductal carcinoma in situ (DCIS) is commonly underestimated due to the discontinuous growth and lack of microcalcifications. Specimen radiography has been established to reduce the rate of re-excision. However, the predictive value for margin assessment with conventional specimen radiography for DCIS is low. In this study we assessed the potential of grating-based phase-contrast computed tomography (GBPC-CT) at conventional X-ray sources for specimen tomography of DCIS containing samples.Materials and methodsGBPC-CT was performed on four ex-vivo breast specimens containing DCIS and invasive carcinoma of non-specific type. Phase-contrast and absorption-based datasets were manually matched with corresponding histological slices as the standard of reference.ResultsMatching of CT images and histology was successful. GBPC-CT showed an improved soft tissue contrast compared to absorption-based images revealing more histological details in the same sections. Non-calcifying DCIS exceeding the invasive tumor could be correlated to areas of dilated bright ducts around the tumor.ConclusionsGBPC-CT imaging at conventional X-ray sources offers improved depiction quality for the imaging of breast tissue samples compared to absorption-based imaging, allows the identification of diagnostically relevant tissue details, and provides full three-dimensional assessment of sample margins.

Elemental Concentration and Sulfur Chemical Speciation in the Amazonian Plant Andira surinamensis Using Synchrotron Radiation Techniques (SR-XRF, XANES), RBS and WD-XRF

The inorganic composition of the bark and leaf of a plant from the Amazon rainforest, Andira surinamensis, was determined using two non-destructive, multi-element techniques: X-ray fluorescence (XRF) and Rutherford backscattering spectrometry (RBS). XRF measurements were made using both a conventional X-ray source and synchrotron radiation. It was observed that although magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, and potassium are present in higher concentrations in the leaf, calcium is about three times more concentrated in the bark. Manganese, iron, copper, zinc, strontium and barium were also detected, with barium showing a concentration above the minimum toxicity level for plants. Chemical speciation of sulfur, performed using the X-ray absorption near edge structure (XANES) technique, showed that sulfur is present in several oxidation states, with a much larger contribution from the inorganic sulfate in the leaves. The article evidences that the combined use of synchrotron radiation and non-destructive multi-element techniques allows for an efficient and accurate determination of the inorganic composition and chemical speciation in plants.

A Fully Closed Nano-Focus X-Ray Source With Carbon Nanotube Field Emitters

We developed a fully closed nano-focus X-ray source using carbon nanotube (CNT) field emitters. The nano-focus X-ray source includes a fully vacuum-sealed CNT Electron-gun (E-gun) tube and E-beam-focusing modules consisting of electrostatic and magnetic lenses, facilitating very compact and high-resolution X-ray imaging. The paste-printed CNT emitters were prepared in a small pattern as an electron source, and the entire components, including the CNT emitter module, Cu tubes, collimators, and transmissive anode target, were specially brazed at an elevated temperature, resulting in a very compact E-gun tube. The CNT emitter showed a stable and reliable emission current with its density of over 300 mA/cm2 even in the vacuum-sealed E-gun tube. With the anode grounded and the CNT emitter module biased to negative high voltages, we achieved a considerably magnified x-ray image of a several hundred nanometer resolution. The fully vacuum-sealed CNT E-gun tube along with the magnetic lens module can offer much more compact, easily maintainable, high-resolution X-ray imaging compared with conventional open-type thermionic X-ray sources.